potential ap models: Topics by Science.gov

Sample records for potential ap models

Nonlinear Dynamic Modeling of Neuron Action Potential Threshold During Synaptically Driven Broadband Intracellular Activity

PubMed Central

Roach, Shane M.; Song, Dong; Berger, Theodore W.

2012-01-01

Activity-dependent variation of neuronal thresholds for action potential (AP) generation is one of the key determinants of spike-train temporal-pattern transformations from presynaptic to postsynaptic spike trains. In this study, we model the nonlinear dynamics of the threshold variation during synaptically driven broadband intracellular activity. First, membrane potentials of single CA1 pyramidal cells were recorded under physiologically plausible broadband stimulation conditions. Second, a method was developed to measure AP thresholds from the continuous recordings of membrane potentials. It involves measuring the turning points of APs by analyzing the third-order derivatives of the membrane potentials. Four stimulation paradigms with different temporal patterns were applied to validate this method by comparing the measured AP turning points and the actual AP thresholds estimated with varying stimulation intensities. Results show that the AP turning points provide consistent measurement of the AP thresholds, except for a constant offset. It indicates that 1) the variation of AP turning points represents the nonlinearities of threshold dynamics; and 2) an optimization of the constant offset is required to achieve accurate spike prediction. Third, a nonlinear dynamical third-order Volterra model was built to describe the relations between the threshold dynamics and the AP activities. Results show that the model can predict threshold accurately based on the preceding APs. Finally, the dynamic threshold model was integrated into a previously developed single neuron model and resulted in a 33% improvement in spike prediction. PMID:22156947
Contribution of the Axon Initial Segment to Action Potentials Recorded Extracellularly.

PubMed

Teleńczuk, Maria; Brette, Romain; Destexhe, Alain; Teleńczuk, Bartosz

2018-01-01

Action potentials (APs) are electric phenomena that are recorded both intracellularly and extracellularly. APs are usually initiated in the short segment of the axon called the axon initial segment (AIS). It was recently proposed that at the onset of an AP the soma and the AIS form a dipole. We study the extracellular signature [the extracellular AP (EAP)] generated by such a dipole. First, we demonstrate the formation of the dipole and its extracellular signature in detailed morphological models of a reconstructed pyramidal neuron. Then, we study the EAP waveform and its spatial dependence in models with axonal AP initiation and contrast it with the EAP obtained in models with somatic AP initiation. We show that in the models with axonal AP initiation the dipole forms between somatodendritic compartments and the AIS, and not between soma and dendrites as in the classical models. The soma-dendrites dipole is present only in models with somatic AP initiation. Our study has consequences for interpreting extracellular recordings of single-neuron activity and determining electrophysiological neuron types, but also for better understanding the origins of the high-frequency macroscopic extracellular potentials recorded in the brain.
A four-component model of the action potential in mouse detrusor smooth muscle cell

PubMed Central

Brain, Keith L.; Young, John S.; Manchanda, Rohit

2018-01-01

Background and hypothesis Detrusor smooth muscle cells (DSMCs) of the urinary bladder are electrically connected to one another via gap junctions and form a three dimensional syncytium. DSMCs exhibit spontaneous electrical activity, including passive depolarizations and action potentials. The shapes of spontaneous action potentials (sAPs) observed from a single DSM cell can vary widely. The biophysical origins of this variability, and the precise components which contribute to the complex shapes observed are not known. To address these questions, the basic components which constitute the sAPs were investigated. We hypothesized that linear combinations of scaled versions of these basic components can produce sAP shapes observed in the syncytium. Methods and results The basic components were identified as spontaneous evoked junction potentials (sEJP), native AP (nAP), slow after hyperpolarization (sAHP) and very slow after hyperpolarization (vsAHP). The experimental recordings were grouped into two sets: a training data set and a testing data set. A training set was used to estimate the components, and a test set to evaluate the efficiency of the estimated components. We found that a linear combination of the identified components when appropriately amplified and time shifted replicated various AP shapes to a high degree of similarity, as quantified by the root mean square error (RMSE) measure. Conclusions We conclude that the four basic components—sEJP, nAP, sAHP, and vsAHP—identified and isolated in this work are necessary and sufficient to replicate all varieties of the sAPs recorded experimentally in DSMCs. This model has the potential to generate testable hypotheses that can help identify the physiological processes underlying various features of the sAPs. Further, this model also provides a means to classify the sAPs into various shape classes. PMID:29351282
A four-component model of the action potential in mouse detrusor smooth muscle cell.

PubMed

Padmakumar, Mithun; Brain, Keith L; Young, John S; Manchanda, Rohit

2018-01-01

Detrusor smooth muscle cells (DSMCs) of the urinary bladder are electrically connected to one another via gap junctions and form a three dimensional syncytium. DSMCs exhibit spontaneous electrical activity, including passive depolarizations and action potentials. The shapes of spontaneous action potentials (sAPs) observed from a single DSM cell can vary widely. The biophysical origins of this variability, and the precise components which contribute to the complex shapes observed are not known. To address these questions, the basic components which constitute the sAPs were investigated. We hypothesized that linear combinations of scaled versions of these basic components can produce sAP shapes observed in the syncytium. The basic components were identified as spontaneous evoked junction potentials (sEJP), native AP (nAP), slow after hyperpolarization (sAHP) and very slow after hyperpolarization (vsAHP). The experimental recordings were grouped into two sets: a training data set and a testing data set. A training set was used to estimate the components, and a test set to evaluate the efficiency of the estimated components. We found that a linear combination of the identified components when appropriately amplified and time shifted replicated various AP shapes to a high degree of similarity, as quantified by the root mean square error (RMSE) measure. We conclude that the four basic components-sEJP, nAP, sAHP, and vsAHP-identified and isolated in this work are necessary and sufficient to replicate all varieties of the sAPs recorded experimentally in DSMCs. This model has the potential to generate testable hypotheses that can help identify the physiological processes underlying various features of the sAPs. Further, this model also provides a means to classify the sAPs into various shape classes.
Fitting membrane resistance along with action potential shape in cardiac myocytes improves convergence: application of a multi-objective parallel genetic algorithm.

PubMed

Kaur, Jaspreet; Nygren, Anders; Vigmond, Edward J

2014-01-01

Fitting parameter sets of non-linear equations in cardiac single cell ionic models to reproduce experimental behavior is a time consuming process. The standard procedure is to adjust maximum channel conductances in ionic models to reproduce action potentials (APs) recorded in isolated cells. However, vastly different sets of parameters can produce similar APs. Furthermore, even with an excellent AP match in case of single cell, tissue behaviour may be very different. We hypothesize that this uncertainty can be reduced by additionally fitting membrane resistance (Rm). To investigate the importance of Rm, we developed a genetic algorithm approach which incorporated Rm data calculated at a few points in the cycle, in addition to AP morphology. Performance was compared to a genetic algorithm using only AP morphology data. The optimal parameter sets and goodness of fit as computed by the different methods were compared. First, we fit an ionic model to itself, starting from a random parameter set. Next, we fit the AP of one ionic model to that of another. Finally, we fit an ionic model to experimentally recorded rabbit action potentials. Adding the extra objective (Rm, at a few voltages) to the AP fit, lead to much better convergence. Typically, a smaller MSE (mean square error, defined as the average of the squared error between the target AP and AP that is to be fitted) was achieved in one fifth of the number of generations compared to using only AP data. Importantly, the variability in fit parameters was also greatly reduced, with many parameters showing an order of magnitude decrease in variability. Adding Rm to the objective function improves the robustness of fitting, better preserving tissue level behavior, and should be incorporated.
Computational Modeling Reveals Key Contributions of KCNQ and hERG Currents to the Malleability of Uterine Action Potentials Underpinning Labor

PubMed Central

Tong, Wing-Chiu; Tribe, Rachel M.; Smith, Roger; Taggart, Michael J.

2014-01-01

The electrical excitability of uterine smooth muscle cells is a key determinant of the contraction of the organ during labor and is manifested by spontaneous, periodic action potentials (APs). Near the end of term, APs vary in shape and size reflecting an ability to change the frequency, duration and amplitude of uterine contractions. A recent mathematical model quantified several ionic features of the electrical excitability in uterine smooth muscle cells. It replicated many of the experimentally recorded uterine AP configurations but its limitations were evident when trying to simulate the long-duration bursting APs characteristic of labor. A computational parameter search suggested that delayed rectifying K+ currents could be a key model component requiring improvement to produce the longer-lasting bursting APs. Of the delayed rectifying K+ currents family it is of interest that KCNQ and hERG channels have been reported to be gestationally regulated in the uterus. These currents exhibit features similar to the broadly defined uterine I K1 of the original mathematical model. We thus formulated new quantitative descriptions for several I KCNQ and I hERG. Incorporation of these currents into the uterine cell model enabled simulations of the long-lasting bursting APs. Moreover, we used this modified model to simulate the effects of different contributions of I KCNQ and I hERG on AP form. Our findings suggest that the alterations in expression of hERG and KCNQ channels can potentially provide a mechanism for fine tuning of AP forms that lends a malleability for changing between plateau-like and long-lasting bursting-type APs as uterine cells prepare for parturition. PMID:25474527
The augmented anticancer potential of AP9-cd loaded solid lipid nanoparticles in human leukemia Molt-4 cells and experimental tumor.

PubMed

Bhushan, Shashi; Kakkar, Vandita; Pal, Harish Chandra; Mondhe, D M; Kaur, Indu Pal

2016-01-25

AP9-cd, a novel lignan composition from Cedrus deodara has significant anticancer potential, and to further enhance its activity, it was lucratively encumbered into solid lipid nanoparticles (SLNs). These nanoparticles were formulated by micro-emulsion technique with 70% drug trap competence. AP9-cd-SLNs were regular, solid, globular particles in the range of 100-200 nm, which were confirmed by electron microscopic studies. Moreover, AP9-cd-SLNs were found to be stable for up to six months in terms of color, particle size, zeta potential, drug content and entrapment. AP9-cd-SLNs have 30-50% higher cytotoxic and apoptotic potential than the AP9-cd alone. The augmented anticancer potential of AP9-cd-SLNs was observed in cytotoxic IC50 value, apoptosis signaling cascade and in Ehrlich ascites tumor (EAT) model. AP9-cd-SLNs induce apoptosis in Molt-4 cells via both intrinsic and extrinsic pathway. Moreover, the dummy nanoparticles (SLNs without AP9-cd) did not have any cytotoxic effect in cancer as well as in normal cells. Consequently, SLNs of AP9-cd significantly augment the apoptotic and antitumor potential of AP9-cd. The present study provides a podium for ornamental the remedial latent via novel delivery systems like solid lipid nanoparticles. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
Action Potential Energy Efficiency Varies Among Neuron Types in Vertebrates and Invertebrates

PubMed Central

Sengupta, Biswa; Stemmler, Martin; Laughlin, Simon B.; Niven, Jeremy E.

2010-01-01

The initiation and propagation of action potentials (APs) places high demands on the energetic resources of neural tissue. Each AP forces ATP-driven ion pumps to work harder to restore the ionic concentration gradients, thus consuming more energy. Here, we ask whether the ionic currents underlying the AP can be predicted theoretically from the principle of minimum energy consumption. A long-held supposition that APs are energetically wasteful, based on theoretical analysis of the squid giant axon AP, has recently been overturned by studies that measured the currents contributing to the AP in several mammalian neurons. In the single compartment models studied here, AP energy consumption varies greatly among vertebrate and invertebrate neurons, with several mammalian neuron models using close to the capacitive minimum of energy needed. Strikingly, energy consumption can increase by more than ten-fold simply by changing the overlap of the Na+ and K+ currents during the AP without changing the APs shape. As a consequence, the height and width of the AP are poor predictors of energy consumption. In the Hodgkin–Huxley model of the squid axon, optimizing the kinetics or number of Na+ and K+ channels can whittle down the number of ATP molecules needed for each AP by a factor of four. In contrast to the squid AP, the temporal profile of the currents underlying APs of some mammalian neurons are nearly perfectly matched to the optimized properties of ionic conductances so as to minimize the ATP cost. PMID:20617202
Action potential energy efficiency varies among neuron types in vertebrates and invertebrates.

PubMed

Sengupta, Biswa; Stemmler, Martin; Laughlin, Simon B; Niven, Jeremy E

2010-07-01

The initiation and propagation of action potentials (APs) places high demands on the energetic resources of neural tissue. Each AP forces ATP-driven ion pumps to work harder to restore the ionic concentration gradients, thus consuming more energy. Here, we ask whether the ionic currents underlying the AP can be predicted theoretically from the principle of minimum energy consumption. A long-held supposition that APs are energetically wasteful, based on theoretical analysis of the squid giant axon AP, has recently been overturned by studies that measured the currents contributing to the AP in several mammalian neurons. In the single compartment models studied here, AP energy consumption varies greatly among vertebrate and invertebrate neurons, with several mammalian neuron models using close to the capacitive minimum of energy needed. Strikingly, energy consumption can increase by more than ten-fold simply by changing the overlap of the Na(+) and K(+) currents during the AP without changing the APs shape. As a consequence, the height and width of the AP are poor predictors of energy consumption. In the Hodgkin-Huxley model of the squid axon, optimizing the kinetics or number of Na(+) and K(+) channels can whittle down the number of ATP molecules needed for each AP by a factor of four. In contrast to the squid AP, the temporal profile of the currents underlying APs of some mammalian neurons are nearly perfectly matched to the optimized properties of ionic conductances so as to minimize the ATP cost.
Computational modeling of inhibition of voltage-gated Ca channels: identification of different effects on uterine and cardiac action potentials.

PubMed

Tong, Wing-Chiu; Ghouri, Iffath; Taggart, Michael J

2014-01-01

The uterus and heart share the important physiological feature whereby contractile activation of the muscle tissue is regulated by the generation of periodic, spontaneous electrical action potentials (APs). Preterm birth arising from premature uterine contractions is a major complication of pregnancy and there remains a need to pursue avenues of research that facilitate the use of drugs, tocolytics, to limit these inappropriate contractions without deleterious actions on cardiac electrical excitation. A novel approach is to make use of mathematical models of uterine and cardiac APs, which incorporate many ionic currents contributing to the AP forms, and test the cell-specific responses to interventions. We have used three such models-of uterine smooth muscle cells (USMC), cardiac sinoatrial node cells (SAN), and ventricular cells-to investigate the relative effects of reducing two important voltage-gated Ca currents-the L-type (ICaL) and T-type (ICaT) Ca currents. Reduction of ICaL (10%) alone, or ICaT (40%) alone, blunted USMC APs with little effect on ventricular APs and only mild effects on SAN activity. Larger reductions in either current further attenuated the USMC APs but with also greater effects on SAN APs. Encouragingly, a combination of ICaL and ICaT reduction did blunt USMC APs as intended with little detriment to APs of either cardiac cell type. Subsequent overlapping maps of ICaL and ICaT inhibition profiles from each model revealed a range of combined reductions of ICaL and ICaT over which an appreciable diminution of USMC APs could be achieved with no deleterious action on cardiac SAN or ventricular APs. This novel approach illustrates the potential for computational biology to inform us of possible uterine and cardiac cell-specific mechanisms. Incorporating such computational approaches in future studies directed at designing new, or repurposing existing, tocolytics will be beneficial for establishing a desired uterine specificity of action.
Computational modeling of inhibition of voltage-gated Ca channels: identification of different effects on uterine and cardiac action potentials

PubMed Central

Tong, Wing-Chiu; Ghouri, Iffath; Taggart, Michael J.

2014-01-01

The uterus and heart share the important physiological feature whereby contractile activation of the muscle tissue is regulated by the generation of periodic, spontaneous electrical action potentials (APs). Preterm birth arising from premature uterine contractions is a major complication of pregnancy and there remains a need to pursue avenues of research that facilitate the use of drugs, tocolytics, to limit these inappropriate contractions without deleterious actions on cardiac electrical excitation. A novel approach is to make use of mathematical models of uterine and cardiac APs, which incorporate many ionic currents contributing to the AP forms, and test the cell-specific responses to interventions. We have used three such models—of uterine smooth muscle cells (USMC), cardiac sinoatrial node cells (SAN), and ventricular cells—to investigate the relative effects of reducing two important voltage-gated Ca currents—the L-type (ICaL) and T-type (ICaT) Ca currents. Reduction of ICaL (10%) alone, or ICaT (40%) alone, blunted USMC APs with little effect on ventricular APs and only mild effects on SAN activity. Larger reductions in either current further attenuated the USMC APs but with also greater effects on SAN APs. Encouragingly, a combination of ICaL and ICaT reduction did blunt USMC APs as intended with little detriment to APs of either cardiac cell type. Subsequent overlapping maps of ICaL and ICaT inhibition profiles from each model revealed a range of combined reductions of ICaL and ICaT over which an appreciable diminution of USMC APs could be achieved with no deleterious action on cardiac SAN or ventricular APs. This novel approach illustrates the potential for computational biology to inform us of possible uterine and cardiac cell-specific mechanisms. Incorporating such computational approaches in future studies directed at designing new, or repurposing existing, tocolytics will be beneficial for establishing a desired uterine specificity of action. PMID:25360118
Relationships between resting conductances, excitability, and t-system ionic homeostasis in skeletal muscle.

PubMed

Fraser, James A; Huang, Christopher L-H; Pedersen, Thomas H

2011-07-01

Activation of skeletal muscle fibers requires rapid sarcolemmal action potential (AP) conduction to ensure uniform excitation along the fiber length, as well as successful tubular excitation to initiate excitation-contraction coupling. In our companion paper in this issue, Pedersen et al. (2011. J. Gen. Physiol. doi:10.1085/jgp.201010510) quantify, for subthreshold stimuli, the influence upon both surface conduction velocity and tubular (t)-system excitation of the large changes in resting membrane conductance (G(M)) that occur during repetitive AP firing. The present work extends the analysis by developing a multi-compartment modification of the charge-difference model of Fraser and Huang to provide a quantitative description of the conduction velocity of actively propagated APs; the influence of voltage-gated ion channels within the t-system; the influence of t-system APs on ionic homeostasis within the t-system; the influence of t-system ion concentration changes on membrane potentials; and the influence of Phase I and Phase II G(M) changes on these relationships. Passive conduction properties of the novel model agreed with established linear circuit analysis and previous experimental results, while key simulations of AP firing were tested against focused experimental microelectrode measurements of membrane potential. This study thereby first quantified the effects of the t-system luminal resistance and voltage-gated Na(+) channel density on surface AP propagation and the resultant electrical response of the t-system. Second, it demonstrated the influence of G(M) changes during repetitive AP firing upon surface and t-system excitability. Third, it showed that significant K(+) accumulation occurs within the t-system during repetitive AP firing and produces a baseline depolarization of the surface membrane potential. Finally, it indicated that G(M) changes during repetitive AP firing significantly influence both t-system K(+) accumulation and its influence on the resting membrane potential. Thus, the present study emerges with a quantitative description of the changes in membrane potential, excitability, and t-system ionic homeostasis that occur during repetitive AP firing in skeletal muscle.
Tracking individual action potentials throughout mammalian axonal arbors.

PubMed

Radivojevic, Milos; Franke, Felix; Altermatt, Michael; Müller, Jan; Hierlemann, Andreas; Bakkum, Douglas J

2017-10-09

Axons are neuronal processes specialized for conduction of action potentials (APs). The timing and temporal precision of APs when they reach each of the synapses are fundamentally important for information processing in the brain. Due to small diameters of axons, direct recording of single AP transmission is challenging. Consequently, most knowledge about axonal conductance derives from modeling studies or indirect measurements. We demonstrate a method to noninvasively and directly record individual APs propagating along millimeter-length axonal arbors in cortical cultures with hundreds of microelectrodes at microsecond temporal resolution. We find that cortical axons conduct single APs with high temporal precision (~100 µs arrival time jitter per mm length) and reliability: in more than 8,000,000 recorded APs, we did not observe any conduction or branch-point failures. Upon high-frequency stimulation at 100 Hz, successive became slower, and their arrival time precision decreased by 20% and 12% for the 100th AP, respectively.
The Role of Potassium Channels in Arabidopsis thaliana Long Distance Electrical Signalling: AKT2 Modulates Tissue Excitability While GORK Shapes Action Potentials.

PubMed

Cuin, Tracey Ann; Dreyer, Ingo; Michard, Erwan

2018-03-21

Fast responses to an external threat depend on the rapid transmission of signals through a plant. Action potentials (APs) are proposed as such signals. Plant APs share similarities with their animal counterparts; they are proposed to depend on the activity of voltage-gated ion channels. Nonetheless, despite their demonstrated role in (a)biotic stress responses, the identities of the associated voltage-gated channels and transporters remain undefined in higher plants. By demonstrating the role of two potassium-selective channels in Arabidopsis thaliana in AP generation and shaping, we show that the plant AP does depend on similar Kv -like transport systems to those of the animal signal. We demonstrate that the outward-rectifying potassium-selective channel GORK limits the AP amplitude and duration, while the weakly-rectifying channel AKT2 affects membrane excitability. By computational modelling of plant APs, we reveal that the GORK activity not only determines the length of an AP but also the steepness of its rise and the maximal amplitude. Thus, outward-rectifying potassium channels contribute to both the repolarisation phase and the initial depolarisation phase of the signal. Additionally, from modelling considerations we provide indications that plant APs might be accompanied by potassium waves, which prime the excitability of the green cable.
Comprehensive Analyses of Ventricular Myocyte Models Identify Targets Exhibiting Favorable Rate Dependence

PubMed Central

Bugana, Marco; Severi, Stefano; Sobie, Eric A.

2014-01-01

Reverse rate dependence is a problematic property of antiarrhythmic drugs that prolong the cardiac action potential (AP). The prolongation caused by reverse rate dependent agents is greater at slow heart rates, resulting in both reduced arrhythmia suppression at fast rates and increased arrhythmia risk at slow rates. The opposite property, forward rate dependence, would theoretically overcome these parallel problems, yet forward rate dependent (FRD) antiarrhythmics remain elusive. Moreover, there is evidence that reverse rate dependence is an intrinsic property of perturbations to the AP. We have addressed the possibility of forward rate dependence by performing a comprehensive analysis of 13 ventricular myocyte models. By simulating populations of myocytes with varying properties and analyzing population results statistically, we simultaneously predicted the rate-dependent effects of changes in multiple model parameters. An average of 40 parameters were tested in each model, and effects on AP duration were assessed at slow (0.2 Hz) and fast (2 Hz) rates. The analysis identified a variety of FRD ionic current perturbations and generated specific predictions regarding their mechanisms. For instance, an increase in L-type calcium current is FRD when this is accompanied by indirect, rate-dependent changes in slow delayed rectifier potassium current. A comparison of predictions across models identified inward rectifier potassium current and the sodium-potassium pump as the two targets most likely to produce FRD AP prolongation. Finally, a statistical analysis of results from the 13 models demonstrated that models displaying minimal rate-dependent changes in AP shape have little capacity for FRD perturbations, whereas models with large shape changes have considerable FRD potential. This can explain differences between species and between ventricular cell types. Overall, this study provides new insights, both specific and general, into the determinants of AP duration rate dependence, and illustrates a strategy for the design of potentially beneficial antiarrhythmic drugs. PMID:24675446
Comprehensive analyses of ventricular myocyte models identify targets exhibiting favorable rate dependence.

PubMed

Cummins, Megan A; Dalal, Pavan J; Bugana, Marco; Severi, Stefano; Sobie, Eric A

2014-03-01

Reverse rate dependence is a problematic property of antiarrhythmic drugs that prolong the cardiac action potential (AP). The prolongation caused by reverse rate dependent agents is greater at slow heart rates, resulting in both reduced arrhythmia suppression at fast rates and increased arrhythmia risk at slow rates. The opposite property, forward rate dependence, would theoretically overcome these parallel problems, yet forward rate dependent (FRD) antiarrhythmics remain elusive. Moreover, there is evidence that reverse rate dependence is an intrinsic property of perturbations to the AP. We have addressed the possibility of forward rate dependence by performing a comprehensive analysis of 13 ventricular myocyte models. By simulating populations of myocytes with varying properties and analyzing population results statistically, we simultaneously predicted the rate-dependent effects of changes in multiple model parameters. An average of 40 parameters were tested in each model, and effects on AP duration were assessed at slow (0.2 Hz) and fast (2 Hz) rates. The analysis identified a variety of FRD ionic current perturbations and generated specific predictions regarding their mechanisms. For instance, an increase in L-type calcium current is FRD when this is accompanied by indirect, rate-dependent changes in slow delayed rectifier potassium current. A comparison of predictions across models identified inward rectifier potassium current and the sodium-potassium pump as the two targets most likely to produce FRD AP prolongation. Finally, a statistical analysis of results from the 13 models demonstrated that models displaying minimal rate-dependent changes in AP shape have little capacity for FRD perturbations, whereas models with large shape changes have considerable FRD potential. This can explain differences between species and between ventricular cell types. Overall, this study provides new insights, both specific and general, into the determinants of AP duration rate dependence, and illustrates a strategy for the design of potentially beneficial antiarrhythmic drugs.
A nonlinear autoregressive Volterra model of the Hodgkin-Huxley equations.

PubMed

Eikenberry, Steffen E; Marmarelis, Vasilis Z

2013-02-01

We propose a new variant of Volterra-type model with a nonlinear auto-regressive (NAR) component that is a suitable framework for describing the process of AP generation by the neuron membrane potential, and we apply it to input-output data generated by the Hodgkin-Huxley (H-H) equations. Volterra models use a functional series expansion to describe the input-output relation for most nonlinear dynamic systems, and are applicable to a wide range of physiologic systems. It is difficult, however, to apply the Volterra methodology to the H-H model because is characterized by distinct subthreshold and suprathreshold dynamics. When threshold is crossed, an autonomous action potential (AP) is generated, the output becomes temporarily decoupled from the input, and the standard Volterra model fails. Therefore, in our framework, whenever membrane potential exceeds some threshold, it is taken as a second input to a dual-input Volterra model. This model correctly predicts membrane voltage deflection both within the subthreshold region and during APs. Moreover, the model naturally generates a post-AP afterpotential and refractory period. It is known that the H-H model converges to a limit cycle in response to a constant current injection. This behavior is correctly predicted by the proposed model, while the standard Volterra model is incapable of generating such limit cycle behavior. The inclusion of cross-kernels, which describe the nonlinear interactions between the exogenous and autoregressive inputs, is found to be absolutely necessary. The proposed model is general, non-parametric, and data-derived.
Dendritic mechanisms underlying the coupling of the dendritic with the axonal action potential initiation zone of adult rat layer 5 pyramidal neurons

PubMed Central

Larkum, M E; Zhu, J J; Sakmann, B

2001-01-01

Double, triple and quadruple whole-cell voltage recordings were made simultaneously from different parts of the apical dendritic arbor and the soma of adult layer 5 (L5) pyramidal neurons. We investigated the membrane mechanisms that support the conduction of dendritic action potentials (APs) between the dendritic and axonal AP initiation zones and their influence on the subsequent AP pattern. The duration of the current injection to the distal dendritic initiation zone controlled the degree of coupling with the axonal initiation zone and the AP pattern. Two components of the distally evoked regenerative potential were pharmacologically distinguished: a rapidly rising peak potential that was TTX sensitive and a slowly rising plateau-like potential that was Cd2+ and Ni2+ sensitive and present only with longer-duration current injection. The amplitude of the faster forward-propagating Na+-dependent component and the amplitude of the back-propagating AP fell into two classes (more distinctly in the forward-propagating case). Current injection into the dendrite altered propagation in both directions. Somatic current injections that elicited single Na+ APs evoked bursts of Na+ APs when current was injected simultaneously into the proximal apical dendrite. The mechanism did not depend on dendritic Na+–Ca2+ APs. A three-compartment model of a L5 pyramidal neuron is proposed. It comprises the distal dendritic and axonal AP initiation zones and the proximal apical dendrite. Each compartment contributes to the initiation and to the pattern of AP discharge in a distinct manner. Input to the three main dendritic arbors (tuft dendrites, apical oblique dendrites and basal dendrites) has a dominant influence on only one of these compartments. Thus, the AP pattern of L5 pyramids reflects the laminar distribution of synaptic activity in a cortical column. PMID:11389204
A model for studying the energetics of sustained high frequency firing

PubMed Central

Morris, Catherine E.

2018-01-01

Regulating membrane potential and synaptic function contributes significantly to the energetic costs of brain signaling, but the relative costs of action potentials (APs) and synaptic transmission during high-frequency firing are unknown. The continuous high-frequency (200-600Hz) electric organ discharge (EOD) of Eigenmannia, a weakly electric fish, underlies its electrosensing and communication. EODs reflect APs fired by the muscle-derived electrocytes of the electric organ (EO). Cholinergic synapses at the excitable posterior membranes of the elongated electrocytes control AP frequency. Based on whole-fish O2 consumption, ATP demand per EOD-linked AP increases exponentially with AP frequency. Continual EOD-AP generation implies first, that ion homeostatic processes reliably counteract any dissipation of posterior membrane ENa and EK and second that high frequency synaptic activation is reliably supported. Both of these processes require energy. To facilitate an exploration of the expected energy demands of each, we modify a previous excitability model and include synaptic currents able to drive APs at frequencies as high as 600 Hz. Synaptic stimuli are modeled as pulsatile cation conductance changes, with or without a small (sustained) background conductance. Over the full species range of EOD frequencies (200–600 Hz) we calculate frequency-dependent “Na+-entry budgets” for an electrocyte AP as a surrogate for required 3Na+/2K+-ATPase activity. We find that the cost per AP of maintaining constant-amplitude APs increases nonlinearly with frequency, whereas the cost per AP for synaptic input current is essentially constant. This predicts that Na+ channel density should correlate positively with EOD frequency, whereas AChR density should be the same across fish. Importantly, calculated costs (inferred from Na+-entry through Nav and ACh channels) for electrocyte APs as frequencies rise are much less than expected from published whole-fish EOD-linked O2 consumption. For APs at increasingly high frequencies, we suggest that EOD-related costs external to electrocytes (including packaging of synaptic transmitter) substantially exceed the direct cost of electrocyte ion homeostasis. PMID:29708986
Effects of a human recombinant alkaline phosphatase on renal hemodynamics, oxygenation and inflammation in two models of acute kidney injury

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peters, Esther, E-mail: esther.peters@radboudumc.n

Two small clinical trials indicated that administration of bovine intestinal alkaline phosphatase (AP) improves renal function in critically ill patients with sepsis-associated acute kidney injury (AKI), for which the mechanism of action is not completely understood. Here, we investigated the effects of a newly developed human recombinant AP (recAP) on renal oxygenation and hemodynamics and prevention of kidney damage and inflammation in two in vivo AKI models. To induce AKI, male Wistar rats (n = 18) were subjected to renal ischemia (30 min) and reperfusion (I/R), or sham-operated. In a second model, rats (n = 18) received a 30 minmore » infusion of lipopolysaccharide (LPS; 2.5 mg/kg), or saline, and fluid resuscitation. In both models, recAP (1000 U/kg) was administered intravenously (15 min before reperfusion, or 90 min after LPS). Following recAP treatment, I/R-induced changes in renal blood flow, renal vascular resistance and oxygen delivery at early, and cortical microvascular oxygen tension at late reperfusion were no longer significantly affected. RecAP did not influence I/R-induced effects on mean arterial pressure. During endotoxemia, recAP treatment did not modulate the LPS-induced changes in systemic hemodynamics and renal oxygenation. In both models, recAP did exert a clear renal protective anti-inflammatory effect, demonstrated by attenuated immunostaining of inflammatory, tubular injury and pro-apoptosis markers. Whether this renal protective effect is sufficient to improve outcome of patients suffering from sepsis-associated AKI is being investigated in a large clinical trial. - Highlights: • Human recombinant alkaline phosphatase (recAP) is a potential new therapy for sepsis-associated acute kidney injury (AKI). • RecAP can modulate renal oxygenation and hemodynamics immediately following I/R-induced AKI. • RecAP did not modulate endotoxemia-induced changes in systemic hemodynamics and renal oxygenation. • RecAP did exert a clear renal protective anti-inflammatory effect in both models.« less

High-performance space shuttle auxiliary propellant valve system

NASA Technical Reports Server (NTRS)

Smith, G. M.

1973-01-01

Several potential valve closures for the space shuttle auxiliary propulsion system (SS/APS) were investigated analytically and experimentally in a modeling program. The most promising of these were analyzed and experimentally evaluated in a full-size functional valve test fixture of novel design. The engineering investigations conducted for both model and scale evaluations of the SS/APS valve closures and functional valve fixture are described. Preliminary designs, laboratory tests, and overall valve test fixture designs are presented, and a final recommended flightweight SS/APS valve design is presented.
MRP2 mediated drug-drug interaction: indomethacin increases sulfasalazine absorption in the small intestine, potentially decreasing its colonic targeting.

PubMed

Dahan, Arik; Amidon, Gordon L

2010-02-15

We have recently shown that efflux transport, mediated by multidrug resistance-associated protein 2 (MRP2) and breast cancer resistance protein (BCRP), is responsible for sulfasalazine low-permeability in the small intestine, thereby enabling its colonic targeting and therapeutic action. The purpose of the present study was to evaluate the potential pharmacokinetic interaction between indomethacin and sulfasalazine, in the mechanism of efflux transporter competition. The concentration-dependent effects of indomethacin on sulfasalazine intestinal epithelial transport were investigated across Caco-2 cell monolayers, in both apical to basolateral (AP-BL) and BL-AP directions. The interaction was then investigated in the in situ single-pass rat jejunal perfusion model. Sulfasalazine displayed 30-fold higher BL-AP than AP-BL Caco-2 permeability, indicative of net mucosal secretion. Indomethacin significantly increased AP-BL and decreased BL-AP sulfasalazine Caco-2 transport, in a concentration-dependent manner, with IC(50) values of 75 and 196 microM respectively. In the rat model, higher sulfasalazine concentrations resulted in higher intestinal permeability, consistent with saturation of efflux transporter. Without indomethacin, sulfasalazine demonstrated low rat jejunal permeability (vs. metoprolol). Indomethacin significantly increased sulfasalazine P(eff), effectively shifting it from BCS (biopharmaceutics classification system) Class IV to II. In conclusion, the data indicate that concomitant intake of indomethacin and sulfasalazine may lead to increased absorption of sulfasalazine in the small intestine, thereby reducing its colonic concentration and potentially altering its therapeutic effect. Copyright 2009 Elsevier B.V. All rights reserved.
Irregularity, volatility, risk, and financial market time series

PubMed Central

Pincus, Steve; Kalman, Rudolf E.

2004-01-01

The need to assess subtle, potentially exploitable changes in serial structure is paramount in the analysis of financial data. Herein, we demonstrate the utility of approximate entropy (ApEn), a model-independent measure of sequential irregularity, toward this goal, by several distinct applications. We consider both empirical data and models, including composite indices (Standard and Poor's 500 and Hang Seng), individual stock prices, the random-walk hypothesis, and the Black–Scholes and fractional Brownian motion models. Notably, ApEn appears to be a potentially useful marker of system stability, with rapid increases possibly foreshadowing significant changes in a financial variable. PMID:15358860
Three-dimensional mapping and regulation of action potential propagation in nanoelectronics-innervated tissues.

PubMed

Dai, Xiaochuan; Zhou, Wei; Gao, Teng; Liu, Jia; Lieber, Charles M

2016-09-01

Real-time mapping and manipulation of electrophysiology in three-dimensional (3D) tissues could have important impacts on fundamental scientific and clinical studies, yet realization is hampered by a lack of effective methods. Here we introduce tissue-scaffold-mimicking 3D nanoelectronic arrays consisting of 64 addressable devices with subcellular dimensions and a submillisecond temporal resolution. Real-time extracellular action potential (AP) recordings reveal quantitative maps of AP propagation in 3D cardiac tissues, enable in situ tracing of the evolving topology of 3D conducting pathways in developing cardiac tissues and probe the dynamics of AP conduction characteristics in a transient arrhythmia disease model and subsequent tissue self-adaptation. We further demonstrate simultaneous multisite stimulation and mapping to actively manipulate the frequency and direction of AP propagation. These results establish new methodologies for 3D spatiotemporal tissue recording and control, and demonstrate the potential to impact regenerative medicine, pharmacology and electronic therapeutics.
Three-dimensional mapping and regulation of action potential propagation in nanoelectronics innervated tissues

PubMed Central

Dai, Xiaochuan; Zhou, Wei; Gao, Teng; Liu, Jia; Lieber, Charles M.

2016-01-01

Real-time mapping and manipulation of electrophysiology in three-dimensional (3D) tissues could impact broadly fundamental scientific and clinical studies, yet realization lacks effective methods. Here we introduce tissue-scaffold-mimicking 3D nanoelectronic arrays consisting of 64 addressable devices with subcellular dimensions and sub-millisecond time-resolution. Real-time extracellular action potential (AP) recordings reveal quantitative maps of AP propagation in 3D cardiac tissues, enable in situ tracing of the evolving topology of 3D conducting pathways in developing cardiac tissues, and probe the dynamics of AP conduction characteristics in a transient arrhythmia disease model and subsequent tissue self-adaptation. We further demonstrate simultaneous multi-site stimulation and mapping to manipulate actively the frequency and direction of AP propagation. These results establish new methodologies for 3D spatiotemporal tissue recording and control, and demonstrate the potential to impact regenerative medicine, pharmacology and electronic therapeutics. PMID:27347837
Realising their potential? Exploring interprofessional perceptions and potential of the advanced practitioner role: a qualitative analysis

PubMed Central

Powell, Tom; Watkins, Dianne; Kelly, Daniel

2015-01-01

Objectives To explore perceptions of the current practice and future potential of advanced practitioners (APs) from the perspectives of different professional groups in Wales UK. Design A qualitative study consisting of nine focus group interviews. Methods Initially verbatim transcriptions of each focus group interviews were analysed thematically before themes were merged to represent perceptions for the whole data set. Participants Data were gathered from a total of 67 stakeholders—including APs from a variety of professional groups (eg, nursing, physiotherapy, paramedics) as well as managers, workforce developers, educators and medical staff who have a role developing and supporting APs in practice. Results The results are presented in four themes: (1) demand, policy context and future priorities, (2) role clarity and standardisation, (3) agreement and understanding of the role and (4) interprofessional working. The context within which current and future AP roles were considered was influenced by inexorable demands for healthcare and the requirements to meet health policy priorities. Developing AP roles were hampered currently by a lack of shared understanding and ‘joined-up’ working between different groups such as medical practitioners, managers, commissioners and educators. Conclusions For the AP role to flourish more ‘joined-up’ thinking, support and development opportunities are required between APs, managers, senior clinicians, commissioners and educators. Working together to plan and deliver education, innovation and service delivery is of prime importance to meeting ever increasing complex health needs. This will ensure that future APs are adequately prepared and supported to reach their full potential and help deliver necessary innovations in current models of care delivery. PMID:26656024
Dynamics of action potential backpropagation in basal dendrites of prefrontal cortical pyramidal neurons.

PubMed

Zhou, Wen-Liang; Yan, Ping; Wuskell, Joseph P; Loew, Leslie M; Antic, Srdjan D

2008-02-01

Basal dendrites of neocortical pyramidal neurons are relatively short and directly attached to the cell body. This allows electrical signals arising in basal dendrites to strongly influence the neuronal output. Likewise, somatic action potentials (APs) should readily propagate back into the basilar dendritic tree to influence synaptic plasticity. Two recent studies, however, determined that sodium APs are severely attenuated in basal dendrites of cortical pyramidal cells, so that they completely fail in distal dendritic segments. Here we used the latest improvements in the voltage-sensitive dye imaging technique (Zhou et al., 2007) to study AP backpropagation in basal dendrites of layer 5 pyramidal neurons of the rat prefrontal cortex. With a signal-to-noise ratio of > 15 and minimal temporal averaging (only four sweeps) we were able to sample AP waveforms from the very last segments of individual dendritic branches (dendritic tips). We found that in short- (< 150 microm) and medium (150-200 microm in length)-range basal dendrites APs backpropagated with modest changes in AP half-width or AP rise-time. The lack of substantial changes in AP shape and dynamics of rise is inconsistent with the AP-failure model. The lack of substantial amplitude boosting of the third AP in the high-frequency burst also suggests that in short- and medium-range basal dendrites backpropagating APs were not severely attenuated. Our results show that the AP-failure concept does not apply in all basal dendrites of the rat prefrontal cortex. The majority of synaptic contacts in the basilar dendritic tree actually received significant AP-associated electrical and calcium transients.
Period doubling cascades of limit cycles in cardiac action potential models as precursors to chaotic early Afterdepolarizations.

PubMed

Kügler, Philipp; Bulelzai, M A K; Erhardt, André H

2017-04-04

Early afterdepolarizations (EADs) are pathological voltage oscillations during the repolarization phase of cardiac action potentials (APs). EADs are caused by drugs, oxidative stress or ion channel disease, and they are considered as potential precursors to cardiac arrhythmias in recent attempts to redefine the cardiac drug safety paradigm. The irregular behaviour of EADs observed in experiments has been previously attributed to chaotic EAD dynamics under periodic pacing, made possible by a homoclinic bifurcation in the fast subsystem of the deterministic AP system of differential equations. In this article we demonstrate that a homoclinic bifurcation in the fast subsystem of the action potential model is neither a necessary nor a sufficient condition for the genesis of chaotic EADs. We rather argue that a cascade of period doubling (PD) bifurcations of limit cycles in the full AP system paves the way to chaotic EAD dynamics across a variety of models including a) periodically paced and spontaneously active cardiomyocytes, b) periodically paced and non-active cardiomyocytes as well as c) unpaced and spontaneously active cardiomyocytes. Furthermore, our bifurcation analysis reveals that chaotic EAD dynamics may coexist in a stable manner with fully regular AP dynamics, where only the initial conditions decide which type of dynamics is displayed. EADs are a potential source of cardiac arrhythmias and hence are of relevance both from the viewpoint of drug cardiotoxicity testing and the treatment of cardiomyopathies. The model-independent association of chaotic EADs with period doubling cascades of limit cycles introduced in this article opens novel opportunities to study chaotic EADs by means of bifurcation control theory and inverse bifurcation analysis. Furthermore, our results may shed new light on the synchronization and propagation of chaotic EADs in homogeneous and heterogeneous multicellular and cardiac tissue preparations.
Dendritic Properties Control Energy Efficiency of Action Potentials in Cortical Pyramidal Cells

PubMed Central

Yi, Guosheng; Wang, Jiang; Wei, Xile; Deng, Bin

2017-01-01

Neural computation is performed by transforming input signals into sequences of action potentials (APs), which is metabolically expensive and limited by the energy available to the brain. The metabolic efficiency of single AP has important consequences for the computational power of the cell, which is determined by its biophysical properties and morphologies. Here we adopt biophysically-based two-compartment models to investigate how dendrites affect energy efficiency of APs in cortical pyramidal neurons. We measure the Na+ entry during the spike and examine how it is efficiently used for generating AP depolarization. We show that increasing the proportion of dendritic area or coupling conductance between two chambers decreases Na+ entry efficiency of somatic AP. Activating inward Ca2+ current in dendrites results in dendritic spike, which increases AP efficiency. Activating Ca2+-activated outward K+ current in dendrites, however, decreases Na+ entry efficiency. We demonstrate that the active and passive dendrites take effects by altering the overlap between Na+ influx and internal current flowing from soma to dendrite. We explain a fundamental link between dendritic properties and AP efficiency, which is essential to interpret how neural computation consumes metabolic energy and how biophysics and morphologies contribute to such consumption. PMID:28919852
Dendritic Properties Control Energy Efficiency of Action Potentials in Cortical Pyramidal Cells.

PubMed

Yi, Guosheng; Wang, Jiang; Wei, Xile; Deng, Bin

2017-01-01

Neural computation is performed by transforming input signals into sequences of action potentials (APs), which is metabolically expensive and limited by the energy available to the brain. The metabolic efficiency of single AP has important consequences for the computational power of the cell, which is determined by its biophysical properties and morphologies. Here we adopt biophysically-based two-compartment models to investigate how dendrites affect energy efficiency of APs in cortical pyramidal neurons. We measure the Na + entry during the spike and examine how it is efficiently used for generating AP depolarization. We show that increasing the proportion of dendritic area or coupling conductance between two chambers decreases Na + entry efficiency of somatic AP. Activating inward Ca 2+ current in dendrites results in dendritic spike, which increases AP efficiency. Activating Ca 2+ -activated outward K + current in dendrites, however, decreases Na + entry efficiency. We demonstrate that the active and passive dendrites take effects by altering the overlap between Na + influx and internal current flowing from soma to dendrite. We explain a fundamental link between dendritic properties and AP efficiency, which is essential to interpret how neural computation consumes metabolic energy and how biophysics and morphologies contribute to such consumption.
ParamAP: Standardized Parameterization of Sinoatrial Node Myocyte Action Potentials.

PubMed

Rickert, Christian; Proenza, Catherine

2017-08-22

Sinoatrial node myocytes act as cardiac pacemaker cells by generating spontaneous action potentials (APs). Much information is encoded in sinoatrial AP waveforms, but both the analysis and the comparison of AP parameters between studies is hindered by the lack of standardized parameter definitions and the absence of automated analysis tools. Here we introduce ParamAP, a standalone cross-platform computational tool that uses a template-free detection algorithm to automatically identify and parameterize APs from text input files. ParamAP employs a graphic user interface with automatic and user-customizable input modes, and it outputs data files in text and PDF formats. ParamAP returns a total of 16 AP waveform parameters including time intervals such as the AP duration, membrane potentials such as the maximum diastolic potential, and rates of change of the membrane potential such as the diastolic depolarization rate. ParamAP provides a robust AP detection algorithm in combination with a standardized AP parameter analysis over a wide range of AP waveforms and firing rates, owing in part to the use of an iterative algorithm for the determination of the threshold potential and the diastolic depolarization rate that is independent of the maximum upstroke velocity, a parameter that can vary significantly among sinoatrial APs. Because ParamAP is implemented in Python 3, it is also highly customizable and extensible. In conclusion, ParamAP is a powerful computational tool that facilitates quantitative analysis and enables comparison of sinoatrial APs by standardizing parameter definitions and providing an automated work flow. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.
Anodal sensory nerve action potentials: From physiological understanding to potential clinical applicability.

PubMed

Leote, Joao; Pereira, Pedro; Cabib, Christopher; Cipullo, Federica; Valls-Sole, Josep

2016-06-01

Low-intensity electrical stimuli of digital nerves may generate a double peak potential (DPp), composed of a cathodal (caAP) and an anodal (anAP) potential in orthodromic recordings. We studied the effects on caAP and anAP of stimuli of variable intensity, duration, and frequency. We also applied a conditioning stimulus to study potential differences in recovery time. The anAP was obtained in 33 of 40 healthy subjects (82.5%) and 4 of 20 patients with various types of sensory neuropathies (20%). Changes in stimulus duration and intensity had reciprocal effects on the amplitude of the anAP and the caAP. There were significant differences in recovery time between caAP and anAP after a conditioning stimulus. The caAP and anAP are 2 interdependent waveforms generated by different effects of the same stimulus over axons at the verge of depolarization. Muscle Nerve 53: 897-905, 2016. © 2015 Wiley Periodicals, Inc.
Intrinsic neurophysiological properties of hilar ectopic and normotopic dentate granule cells in human temporal lobe epilepsy and a rat model.

PubMed

Althaus, A L; Sagher, O; Parent, J M; Murphy, G G

2015-02-15

Hilar ectopic dentate granule cells (DGCs) are a salient feature of aberrant plasticity in human temporal lobe epilepsy (TLE) and most rodent models of the disease. Recent evidence from rodent TLE models suggests that hilar ectopic DGCs contribute to hyperexcitability within the epileptic hippocampal network. Here we investigate the intrinsic excitability of DGCs from humans with TLE and the rat pilocarpine TLE model with the objective of comparing the neurophysiology of hilar ectopic DGCs to their normotopic counterparts in the granule cell layer (GCL). We recorded from 36 GCL and 7 hilar DGCs from human TLE tissue. Compared with GCL DGCs, hilar DGCs in patient tissue exhibited lower action potential (AP) firing rates, more depolarized AP threshold, and differed in single AP waveform, consistent with an overall decrease in excitability. To evaluate the intrinsic neurophysiology of hilar ectopic DGCs, we made recordings from retrovirus-birthdated, adult-born DGCs 2-4 mo after pilocarpine-induced status epilepticus or sham treatment in rats. Hilar DGCs from epileptic rats exhibited higher AP firing rates than normotopic DGCs from epileptic or control animals. They also displayed more depolarized resting membrane potential and wider AP waveforms, indicating an overall increase in excitability. The contrasting findings between disease and disease model may reflect differences between the late-stage disease tissue available from human surgical specimens and the earlier disease stage examined in the rat TLE model. These data represent the first neurophysiological characterization of ectopic DGCs from human hippocampus and prospectively birthdated ectopic DGCs in a rodent TLE model. Copyright © 2015 the American Physiological Society.
Developing an undue influence screening tool for Adult Protective Services.

PubMed

Quinn, Mary Joy; Nerenberg, Lisa; Navarro, Adria E; Wilber, Kathleen H

2017-03-01

The study purpose was to develop and pilot an undue influence screening tool for California's Adult Protective Services (APS) personnel based on the definition of undue influence enacted into California law January 1, 2014. Methods included four focus groups with APS providers (n = 33), piloting the preliminary tool by APS personnel (n = 15), and interviews with four elder abuse experts and two APS administrators. Social service literature-including existing undue influence models-was reviewed, as were existing screening and assessment tools. Using the information from these various sources, the California Undue Influence Screening Tool (CUIST) was developed. It can be applied to APS cases and potentially adapted for use by other professionals and for use in other states. Implementation of the tool into APS practice, policy, procedures, and training of personnel will depend on the initiative of APS management. Future work will need to address the reliability and validity of CUIST.
A Parsimonious Model of the Rabbit Action Potential Elucidates the Minimal Physiological Requirements for Alternans and Spiral Wave Breakup

PubMed Central

2016-01-01

Elucidating the underlying mechanisms of fatal cardiac arrhythmias requires a tight integration of electrophysiological experiments, models, and theory. Existing models of transmembrane action potential (AP) are complex (resulting in over parameterization) and varied (leading to dissimilar predictions). Thus, simpler models are needed to elucidate the “minimal physiological requirements” to reproduce significant observable phenomena using as few parameters as possible. Moreover, models have been derived from experimental studies from a variety of species under a range of environmental conditions (for example, all existing rabbit AP models incorporate a formulation of the rapid sodium current, INa, based on 30 year old data from chick embryo cell aggregates). Here we develop a simple “parsimonious” rabbit AP model that is mathematically identifiable (i.e., not over parameterized) by combining a novel Hodgkin-Huxley formulation of INa with a phenomenological model of repolarization similar to the voltage dependent, time-independent rectifying outward potassium current (IK). The model was calibrated using the following experimental data sets measured from the same species (rabbit) under physiological conditions: dynamic current-voltage (I-V) relationships during the AP upstroke; rapid recovery of AP excitability during the relative refractory period; and steady-state INa inactivation via voltage clamp. Simulations reproduced several important “emergent” phenomena including cellular alternans at rates > 250 bpm as observed in rabbit myocytes, reentrant spiral waves as observed on the surface of the rabbit heart, and spiral wave breakup. Model variants were studied which elucidated the minimal requirements for alternans and spiral wave break up, namely the kinetics of INa inactivation and the non-linear rectification of IK.The simplicity of the model, and the fact that its parameters have physiological meaning, make it ideal for engendering generalizable mechanistic insight and should provide a solid “building-block” to generate more detailed ionic models to represent complex rabbit electrophysiology. PMID:27749895
A Parsimonious Model of the Rabbit Action Potential Elucidates the Minimal Physiological Requirements for Alternans and Spiral Wave Breakup.

PubMed

Gray, Richard A; Pathmanathan, Pras

2016-10-01

Elucidating the underlying mechanisms of fatal cardiac arrhythmias requires a tight integration of electrophysiological experiments, models, and theory. Existing models of transmembrane action potential (AP) are complex (resulting in over parameterization) and varied (leading to dissimilar predictions). Thus, simpler models are needed to elucidate the "minimal physiological requirements" to reproduce significant observable phenomena using as few parameters as possible. Moreover, models have been derived from experimental studies from a variety of species under a range of environmental conditions (for example, all existing rabbit AP models incorporate a formulation of the rapid sodium current, INa, based on 30 year old data from chick embryo cell aggregates). Here we develop a simple "parsimonious" rabbit AP model that is mathematically identifiable (i.e., not over parameterized) by combining a novel Hodgkin-Huxley formulation of INa with a phenomenological model of repolarization similar to the voltage dependent, time-independent rectifying outward potassium current (IK). The model was calibrated using the following experimental data sets measured from the same species (rabbit) under physiological conditions: dynamic current-voltage (I-V) relationships during the AP upstroke; rapid recovery of AP excitability during the relative refractory period; and steady-state INa inactivation via voltage clamp. Simulations reproduced several important "emergent" phenomena including cellular alternans at rates > 250 bpm as observed in rabbit myocytes, reentrant spiral waves as observed on the surface of the rabbit heart, and spiral wave breakup. Model variants were studied which elucidated the minimal requirements for alternans and spiral wave break up, namely the kinetics of INa inactivation and the non-linear rectification of IK.The simplicity of the model, and the fact that its parameters have physiological meaning, make it ideal for engendering generalizable mechanistic insight and should provide a solid "building-block" to generate more detailed ionic models to represent complex rabbit electrophysiology.
Antifouling Activity of Synthetic Alkylpyridinium Polymers Using the Barnacle Model

PubMed Central

Piazza, Veronica; Dragić, Ivanka; Sepčić, Kristina; Faimali, Marco; Garaventa, Francesca; Turk, Tom; Berne, Sabina

2014-01-01

Polymeric alkylpyridinium salts (poly-APS) isolated from the Mediterranean marine sponge, Haliclona (Rhizoniera) sarai, effectively inhibit barnacle larva settlement and natural marine biofilm formation through a non-toxic and reversible mechanism. Potential use of poly-APS-like compounds as antifouling agents led to the chemical synthesis of monomeric and oligomeric 3-alkylpyridinium analogues. However, these are less efficient in settlement assays and have greater toxicity than the natural polymers. Recently, a new chemical synthesis method enabled the production of poly-APS analogues with antibacterial, antifungal and anti-acetylcholinesterase activities. The present study examines the antifouling properties and toxicity of six of these synthetic poly-APS using the barnacle (Amphibalanus amphitrite) as a model (cyprids and II stage nauplii larvae) in settlement, acute and sub-acute toxicity assays. Two compounds, APS8 and APS12-3, show antifouling effects very similar to natural poly-APS, with an anti-settlement effective concentration that inhibits 50% of the cyprid population settlement (EC50) after 24 h of 0.32 mg/L and 0.89 mg/L, respectively. The toxicity of APS8 is negligible, while APS12-3 is three-fold more toxic (24-h LC50: nauplii, 11.60 mg/L; cyprids, 61.13 mg/L) than natural poly-APS. This toxicity of APS12-3 towards nauplii is, however, 60-fold and 1200-fold lower than that of the common co-biocides, Zn- and Cu-pyrithione, respectively. Additionally, exposure to APS12-3 for 24 and 48 h inhibits the naupliar swimming ability with respective IC50 of 4.83 and 1.86 mg/L. PMID:24699112
Dynamic modulation of spike timing-dependent calcium influx during corticostriatal upstates

PubMed Central

Evans, R. C.; Maniar, Y. M.

2013-01-01

The striatum of the basal ganglia demonstrates distinctive upstate and downstate membrane potential oscillations during slow-wave sleep and under anesthetic. The upstates generate calcium transients in the dendrites, and the amplitude of these calcium transients depends strongly on the timing of the action potential (AP) within the upstate. Calcium is essential for synaptic plasticity in the striatum, and these large calcium transients during the upstates may control which synapses undergo plastic changes. To investigate the mechanisms that underlie the relationship between calcium and AP timing, we have developed a realistic biophysical model of a medium spiny neuron (MSN). We have implemented sophisticated calcium dynamics including calcium diffusion, buffering, and pump extrusion, which accurately replicate published data. Using this model, we found that either the slow inactivation of dendritic sodium channels (NaSI) or the calcium inactivation of voltage-gated calcium channels (CDI) can cause high calcium corresponding to early APs and lower calcium corresponding to later APs. We found that only CDI can account for the experimental observation that sensitivity to AP timing is dependent on NMDA receptors. Additional simulations demonstrated a mechanism by which MSNs can dynamically modulate their sensitivity to AP timing and show that sensitivity to specifically timed pre- and postsynaptic pairings (as in spike timing-dependent plasticity protocols) is altered by the timing of the pairing within the upstate. These findings have implications for synaptic plasticity in vivo during sleep when the upstate-downstate pattern is prominent in the striatum. PMID:23843436
A novel framework for feature extraction in multi-sensor action potential sorting.

PubMed

Wu, Shun-Chi; Swindlehurst, A Lee; Nenadic, Zoran

2015-09-30

Extracellular recordings of multi-unit neural activity have become indispensable in neuroscience research. The analysis of the recordings begins with the detection of the action potentials (APs), followed by a classification step where each AP is associated with a given neural source. A feature extraction step is required prior to classification in order to reduce the dimensionality of the data and the impact of noise, allowing source clustering algorithms to work more efficiently. In this paper, we propose a novel framework for multi-sensor AP feature extraction based on the so-called Matched Subspace Detector (MSD), which is shown to be a natural generalization of standard single-sensor algorithms. Clustering using both simulated data and real AP recordings taken in the locust antennal lobe demonstrates that the proposed approach yields features that are discriminatory and lead to promising results. Unlike existing methods, the proposed algorithm finds joint spatio-temporal feature vectors that match the dominant subspace observed in the two-dimensional data without needs for a forward propagation model and AP templates. The proposed MSD approach provides more discriminatory features for unsupervised AP sorting applications. Copyright © 2015 Elsevier B.V. All rights reserved.
NS5806 partially restores action potential duration but fails to ameliorate calcium transient dysfunction in a computational model of canine heart failure.

PubMed

Maleckar, Mary M; Lines, Glenn T; Koivumäki, Jussi T; Cordeiro, Jonathan M; Calloe, Kirstine

2014-11-01

The study investigates how increased Ito, as mediated by the activator NS5806, affects excitation-contraction coupling in chronic heart failure (HF). We hypothesized that restoring spike-and-dome morphology of the action potential (AP) to a healthy phenotype would be insufficient to restore the intracellular Ca(2) (+) transient (CaT), due to HF-induced remodelling of Ca(2+) handling. An existing mathematical model of the canine ventricular myocyte was modified to incorporate recent experimental data from healthy and failing myocytes, resulting in models of both healthy and HF epicardial, midmyocardial, and endocardial cell variants. Affects of NS5806 were also included in HF models through its direct interaction with Kv4.3 and Kv1.4. Single-cell simulations performed in all models (control, HF, and HF + drug) and variants (epi, mid, and endo) assessed AP morphology and underlying ionic processes with a focus on calcium transients (CaT), how these were altered in HF across the ventricular wall, and the subsequent effects of varying compound concentration in HF. Heart failure model variants recapitulated a characteristic increase in AP duration (APD) in the disease. The qualitative effects of application of half-maximal effective concentration (EC50) of NS5806 on APs and CaT are heterogeneous and non-linear. Deepening in the AP notch with drug is a direct effect of the activation of Ito; both Ito and consequent alteration of IK1 kinetics cause decrease in AP plateau potential. Decreased APD50 and APD90 are both due to altered IK1. Analysis revealed that drug effects depend on transmurality. Ca(2+) transient morphology changes-increased amplitude and shorter time to peak-are due to direct increase in ICa,L and indirect larger SR Ca(2+) release subsequent to Ito activation. Downstream effects of a compound acting exclusively on sarcolemmal ion channels are difficult to predict. Remediation of APD to pre-failing state does not ameliorate dysfunction in CaT; however, restoration of notch depth appears to impart modest benefit and a likelihood of therapeutic value in modulating early repolarization. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2014. For permissions please email: journals.permissions@oup.com.

Clinical significance of the summating potential-action potential ratio and the action potential latency difference for condensation and rarefaction clicks in Meniere's disease.

PubMed

Ohashi, Toru; Nishino, Hirohito; Arai, Yoko; Hyodo, Makoto; Takatsu, Mitsuharu

2009-04-01

This study was aimed to elucidate the diagnostic significance of the summating potential (SP)-action potential (AP) ratio and the AP latency difference between condensation and rarefaction clicks (AP con-rar difference) in Meniere's disease. The AP and SP were recorded transtympanically in 67 patients with definite Meniere's disease. The SP/AP ratio and the AP con-rar difference were assessed in terms of 1) their interrelationship, 2) their relationship to hearing level, and 3) the rate of occurrence of abnormal values according to the stages of Meniere's disease. No correlation was found between the SP/AP ratio and the AP con-rar difference. Neither the SP/AP ratio in general nor the AP con-rar difference was correlated with the hearing level. However, enhanced values of the SP/AP ratio (0.35 or higher) were moderately correlated with the hearing level (r = 0.51), and their occurrence rate was 55.2%. An increased AP con-rar difference (0.13 ms or longer) was not correlated with the hearing level, and its occurrence rate was 50.2%; it appeared most frequently at stage 3 (p <0.05). An enhanced SP/AP ratio might not always indicate the presence of endolymphatic hydrops associated with an increase in endolymphatic pressure. An increased AP con-rar difference might reflect the presence of a biased basilar membrane resulting from an increased endolymphatic pressure, and hence it is diagnostically essential to simultaneously evaluate the SP/AP ratio and the AP con-rar difference.
Collision of two action potentials in a single excitable cell.

PubMed

Fillafer, Christian; Paeger, Anne; Schneider, Matthias F

2017-12-01

It is a common incident in nature, that two waves or pulses run into each other head-on. The outcome of such an event is of special interest, because it allows conclusions about the underlying physical nature of the pulses. The present experimental study dealt with the head-on meeting of two action potentials (AP) in a single excitable plant cell (Chara braunii internode). The membrane potential was monitored with multiple sensors along a single excitable cell. In control experiments, an AP was excited electrically at either end of the cell cylinder. Subsequently, stimuli were applied simultaneously at both ends of the cell in order to generate two APs that met each other head-on. When two action potentials propagated into each other, the pulses did not penetrate but annihilated (N=26 experiments in n=10 cells). APs in excitable plant cells did not penetrate upon meeting head-on. In the classical electrical model, this behavior is specifically attributed to relaxation of ion channel proteins. From an acoustic point of view, annihilation can be viewed as a result of nonlinear material properties (e.g. a phase change). The present results suggest that APs in excitable animal and plant cells belong to a similar class of nonlinear phenomena. Intriguingly, other excitation waves in biology (intracellular waves, cortical spreading depression, etc.) also annihilate upon collision and are thus expected to follow the same underlying principles as the observed action potentials. Copyright © 2017 Elsevier B.V. All rights reserved.
The ionic bases of the action potential in isolated mouse cardiac Purkinje cell.

PubMed

Vaidyanathan, Ravi; O'Connell, Ryan P; Deo, Makarand; Milstein, Michelle L; Furspan, Philip; Herron, Todd J; Pandit, Sandeep V; Musa, Hassan; Berenfeld, Omer; Jalife, José; Anumonwo, Justus M B

2013-01-01

Collecting electrophysiological and molecular data from the murine conduction system presents technical challenges. Thus, only little advantage has been taken of numerous genetically engineered murine models to study excitation through the cardiac conduction system of the mouse. To develop an approach for isolating murine cardiac Purkinje cells (PCs), to characterize major ionic currents and to use the data to simulate action potentials (APs) recorded from PCs. Light microscopy was used to isolate and identify PCs from apical and septal cells. Current and voltage clamp techniques were used to record APs and whole cell currents. We then simulated a PC AP on the basis of our experimental data. APs recorded from PCs were significantly longer than those recorded from ventricular cells. The prominent plateau phase of the PC AP was very negative (≈-40 mV). Spontaneous activity was observed only in PCs. The inward rectifier current demonstrated no significant differences compared to ventricular myocytes (VMs). However, sodium current density was larger, and the voltage-gated potassium current density was significantly less in PCs compared with myocytes. T-type Ca(2+) currents (I(Ca,T)) were present in PCs but not VMs. Computer simulations suggest that I(Ca,T) and cytosolic calcium diffusion significantly modulate AP profile recorded in PCs, as compared to VMs. Our study provides the first comprehensive ionic profile of murine PCs. The data show unique features of PC ionic mechanisms that govern its excitation process. Experimental data and numerical modeling results suggest that a smaller voltage-gated potassium current and the presence of I(Ca,T) are important determinants of the longer and relatively negative plateau phase of the APs. Copyright © 2013 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.
Physiological time-series analysis: what does regularity quantify?

NASA Technical Reports Server (NTRS)

Pincus, S. M.; Goldberger, A. L.

1994-01-01

Approximate entropy (ApEn) is a recently developed statistic quantifying regularity and complexity that appears to have potential application to a wide variety of physiological and clinical time-series data. The focus here is to provide a better understanding of ApEn to facilitate its proper utilization, application, and interpretation. After giving the formal mathematical description of ApEn, we provide a multistep description of the algorithm as applied to two contrasting clinical heart rate data sets. We discuss algorithm implementation and interpretation and introduce a general mathematical hypothesis of the dynamics of a wide class of diseases, indicating the utility of ApEn to test this hypothesis. We indicate the relationship of ApEn to variability measures, the Fourier spectrum, and algorithms motivated by study of chaotic dynamics. We discuss further mathematical properties of ApEn, including the choice of input parameters, statistical issues, and modeling considerations, and we conclude with a section on caveats to ensure correct ApEn utilization.
Mechanism for Amplitude Alternans in Electrocardiograms and the Initiation of Spatiotemporal Chaos

NASA Astrophysics Data System (ADS)

Chen, Diandian Diana; Gray, Richard A.; Uzelac, Ilija; Herndon, Conner; Fenton, Flavio H.

2017-04-01

It is widely believed that one major life-threatening transition to chaotic fibrillation occurs via spiral-wave breakup that is preceded by spatiotemporal dispersion of refractoriness due to alternations in the duration of the cardiac action potential (AP). However, recent clinical and experimental evidence suggests that other characteristics of the AP may contribute to, and perhaps drive, this dangerous dynamical instability. To identify the relative roles of AP characteristics, we performed experiments in rabbit hearts under conditions to minimize AP duration dynamics which unmasked pronounced AP amplitude alternans just before the onset of fibrillation. We used a simplified ionic cell model to derive a return map and a stability condition that elucidates a novel underlying mechanism for AP alternans and spiral breakup. We found that inactivation of the sodium current is key to developing amplitude alternans and is directly connected to conduction block and initiation of arrhythmias. Simulations in 2D where AP amplitude alternation led to turbulence confirm our hypothesis.
Phytoextraction potential of water fern (Azolla pinnata) in the removal of a hazardous dye, methyl violet 2B: Artificial neural network modelling.

PubMed

Kooh, Muhammad Raziq Rahimi; Lim, Linda B L; Lim, Lee-Hoon; Malik, Owais Ahmed

2018-04-16

This study investigated the potential of Azolla pinnata (AP) in the removal of toxic methyl violet 2B (MV) dye wastewater using the phytoextraction approach with the inclusion of an Artificial Neural Network (ANN) modelling. Parameters examined included the effects of dye concentration, pH and plant dosage. The highest removal efficiency was 93% which was achieved at a plant dosage of 0.8 g (dye volume = 200 mL, initial pH = 6.0, initial dye concentration = 10 mg L -1 ). A significant decrease in relative frond number (RFN), a growth rate estimator, observed at a dye concentration of 20 mg L -1 MV indicated some toxicity, which coincided with the plant pigments studies where the chlorophyll a content was lower than the control. There were little differences in the plant pigment contents between the control and those in the presence of dye (5 to 15 mg L -1 ) indicating the tolerance of AP to MV at lower concentrations. A three-layer ANN model was optimized (6 neurons in the hidden layer) and successfully predicted the phytoextraction of MV (R = 0.9989, RMSE = 0.0098). In conclusion, AP proved to be a suitable plant that could be used for the phytoextraction of MV while the ANN modelling has shown to be a reliable method for the modelling of phytoextraction of MV using AP.
Patch-Clamp Recording from Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes: Improving Action Potential Characteristics through Dynamic Clamp

PubMed Central

Veerman, Christiaan C.; Zegers, Jan G.; Mengarelli, Isabella; Bezzina, Connie R.

2017-01-01

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) hold great promise for studying inherited cardiac arrhythmias and developing drug therapies to treat such arrhythmias. Unfortunately, until now, action potential (AP) measurements in hiPSC-CMs have been hampered by the virtual absence of the inward rectifier potassium current (IK1) in hiPSC-CMs, resulting in spontaneous activity and altered function of various depolarising and repolarising membrane currents. We assessed whether AP measurements in “ventricular-like” and “atrial-like” hiPSC-CMs could be improved through a simple, highly reproducible dynamic clamp approach to provide these cells with a substantial IK1 (computed in real time according to the actual membrane potential and injected through the patch-clamp pipette). APs were measured at 1 Hz using perforated patch-clamp methodology, both in control cells and in cells treated with all-trans retinoic acid (RA) during the differentiation process to increase the number of cells with atrial-like APs. RA-treated hiPSC-CMs displayed shorter APs than control hiPSC-CMs and this phenotype became more prominent upon addition of synthetic IK1 through dynamic clamp. Furthermore, the variability of several AP parameters decreased upon IK1 injection. Computer simulations with models of ventricular-like and atrial-like hiPSC-CMs demonstrated the importance of selecting an appropriate synthetic IK1. In conclusion, the dynamic clamp-based approach of IK1 injection has broad applicability for detailed AP measurements in hiPSC-CMs. PMID:28867785
Changes in intrinsic excitability of ganglion cells in degenerated retinas of RCS rats.

PubMed

Ren, Yi-Ming; Weng, Chuan-Huang; Zhao, Cong-Jian; Yin, Zheng-Qin

2018-01-01

To evaluate the intrinsic excitability of retinal ganglion cells (RGCs) in degenerated retinas. The intrinsic excitability of various morphologically defined RGC types using a combination of patch-clamp recording and the Lucifer yellow tracer in retinal whole-mount preparations harvested from Royal College of Surgeons (RCS) rats, a common retinitis pigmentosa (RP) model, in a relatively late stage of retinal degeneration (P90) were investigated. Several parameters of RGC morphologies and action potentials (APs) were measured and compared to those of non-dystrophic control rats, including dendritic stratification, dendritic field diameter, peak amplitude, half width, resting membrane potential, AP threshold, depolarization to threshold, and firing rates. Compared with non-dystrophic control RGCs, more depolarizations were required to reach the AP threshold in RCS RGCs with low spontaneous spike rates and in RCS OFF cells (especially A2o cells), and RCS RGCs maintained their dendritic morphologies, resting membrane potentials and capabilities to generate APs. RGCs are relatively well preserved morphologically and functionally, and some cells are more susceptible to decreased excitability during retinal degeneration. These findings provide valuable considerations for optimizing RP therapeutic strategies.
Ion channel mechanisms underlying frequency-firing patterns of the avian nucleus magnocellularis: A computational model

PubMed Central

Lu, Ting; Wade, Kirstie; Sanchez, Jason Tait

2017-01-01

ABSTRACT We have previously shown that late-developing avian nucleus magnocellularis (NM) neurons (embryonic [E] days 19–21) fire action potentials (APs) that resembles a band-pass filter in response to sinusoidal current injections of varying frequencies. NM neurons located in the mid- to high-frequency regions of the nucleus fire preferentially at 75 Hz, but only fire a single onset AP to frequency inputs greater than 200 Hz. Surprisingly, NM neurons do not fire APs to sinusoidal inputs less than 20 Hz regardless of the strength of the current injection. In the present study we evaluated intrinsic mechanisms that prevent AP generation to low frequency inputs. We constructed a computational model to simulate the frequency-firing patterns of NM neurons based on experimental data at both room and near physiologic temperatures. The results from our model confirm that the interaction among low- and high-voltage activated potassium channels (KLVA and KHVA, respectively) and voltage dependent sodium channels (NaV) give rise to the frequency-firing patterns observed in vitro. In particular, we evaluated the regulatory role of KLVA during low frequency sinusoidal stimulation. The model shows that, in response to low frequency stimuli, activation of large KLVA current counterbalances the slow-depolarizing current injection, likely permitting NaV closed-state inactivation and preventing the generation of APs. When the KLVA current density was reduced, the model neuron fired multiple APs per sinusoidal cycle, indicating that KLVA channels regulate low frequency AP firing of NM neurons. This intrinsic property of NM neurons may assist in optimizing response to different rates of synaptic inputs. PMID:28481659
Contributions of adaptation currents to dynamic spike threshold on slow timescales: Biophysical insights from conductance-based models

NASA Astrophysics Data System (ADS)

Yi, Guosheng; Wang, Jiang; Wei, Xile; Deng, Bin; Li, Huiyan; Che, Yanqiu

2017-06-01

Spike-frequency adaptation (SFA) mediated by various adaptation currents, such as voltage-gated K+ current (IM), Ca2+-gated K+ current (IAHP), or Na+-activated K+ current (IKNa), exists in many types of neurons, which has been shown to effectively shape their information transmission properties on slow timescales. Here we use conductance-based models to investigate how the activation of three adaptation currents regulates the threshold voltage for action potential (AP) initiation during the course of SFA. It is observed that the spike threshold gets depolarized and the rate of membrane depolarization (dV/dt) preceding AP is reduced as adaptation currents reduce firing rate. It is indicated that the presence of inhibitory adaptation currents enables the neuron to generate a dynamic threshold inversely correlated with preceding dV/dt on slower timescales than fast dynamics of AP generation. By analyzing the interactions of ionic currents at subthreshold potentials, we find that the activation of adaptation currents increase the outward level of net membrane current prior to AP initiation, which antagonizes inward Na+ to result in a depolarized threshold and lower dV/dt from one AP to the next. Our simulations demonstrate that the threshold dynamics on slow timescales is a secondary effect caused by the activation of adaptation currents. These findings have provided a biophysical interpretation of the relationship between adaptation currents and spike threshold.
Rethinking the evaluation and measurement of Health in all policies.

PubMed

Bauman, Adrian E; King, Lesley; Nutbeam, Don

2014-06-01

Current international attention to Health in all policies (HiAP) has its origins in a more sophisticated understanding of the impact of public policies on health, and a recognition that policies across government have an impact on the social and environmental determinants of health and related inequalities in health. As an emerging field, there has been limited attention focused on comprehensive approaches to the evaluation of HiAP to date, and the research focus around HiAP has mainly examined the processes of cross-sectoral policy development, rather than their health-related impacts or outcomes. The purpose of this paper is to explore issues in assessing the implementation of HiAP and describe an expanded evaluation framework for assessing the potential intermediate and end-point effects of HiAP actions, using a planning logic model for 'complex programs'. This meets the needs of public sector policy-makers who express an interest in understanding the relationship between HiAP and health-related and social outcomes. The paper proposes applying a contribution analysis method to estimate and model the anticipated impacts of HiAP policies on intermediate and longer term outcomes, in advance of empirical studies of these outcomes, and as an innovative input into HiAP and evaluation planning. A broader long-term evaluation framework will enhance the political saliency of HiAP initiatives, especially from governments considering HiAP approaches in financially constrained environments. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
New method for estimating clustering of DNA lesions induced by physical/chemical mutagens using fluorescence anisotropy.

PubMed

Akamatsu, Ken; Shikazono, Naoya; Saito, Takeshi

2017-11-01

We have developed a new method for estimating the localization of DNA damage such as apurinic/apyrimidinic sites (APs) on DNA using fluorescence anisotropy. This method is aimed at characterizing clustered DNA damage produced by DNA-damaging agents such as ionizing radiation and genotoxic chemicals. A fluorescent probe with an aminooxy group (AlexaFluor488) was used to label APs. We prepared a pUC19 plasmid with APs by heating under acidic conditions as a model for damaged DNA, and subsequently labeled the APs. We found that the observed fluorescence anisotropy (r obs ) decreases as averaged AP density (λ AP : number of APs per base pair) increases due to homo-FRET, and that the APs were randomly distributed. We applied this method to three DNA-damaging agents, 60 Co γ-rays, methyl methanesulfonate (MMS), and neocarzinostatin (NCS). We found that r obs -λ AP relationships differed significantly between MMS and NCS. At low AP density (λ AP < 0.001), the APs induced by MMS seemed to not be closely distributed, whereas those induced by NCS were remarkably clustered. In contrast, the AP clustering induced by 60 Co γ-rays was similar to, but potentially more likely to occur than, random distribution. This simple method can be used to estimate mutagenicity of ionizing radiation and genotoxic chemicals. Copyright © 2017 Elsevier Inc. All rights reserved.
Molecular dynamics simulations of theoretical cellulose nanotube models.

PubMed

Uto, Takuya; Kodama, Yuta; Miyata, Tatsuhiko; Yui, Toshifumi

2018-06-15

Nanotubes are remarkable nanoscale architectures for a wide range of potential applications. In the present paper, we report a molecular dynamics (MD) study of the theoretical cellulose nanotube (CelNT) models to evaluate their dynamic behavior in solution (either chloroform or benzene). Based on the one-quarter chain staggering relationship, we constructed six CelNT models by combining the two chain polarities (parallel (P) and antiparallel (AP)) and three symmetry operations (helical right (H R ), helical left (H L ), and rotation (R)) to generate a circular arrangement of molecular chains. Among the four models that retained the tubular form (P-H R , P-H L , P-R, and AP-R), the P-R and AP-R models have the lowest steric energies in benzene and chloroform, respectively. The structural features of the CelNT models were characterized in terms of the hydroxymethyl group conformation and intermolecular hydrogen bonds. Solvent structuring more clearly occurred with benzene than chloroform, suggesting that the CelNT models may disperse in benzene. Copyright © 2018 Elsevier Ltd. All rights reserved.
Adiponectin attenuates kidney injury and fibrosis in deoxycorticosterone acetate-salt and angiotensin II induced CKD mice.

PubMed

Tian, Mi; Tang, Li; Wu, Yuanyuan; Beddhu, Srinivasan; Huang, Yufeng

2018-06-06

Adiponectin (ApN) is a multifunctional adipokine. However high, rather than low, concentrations of ApN are unexpectedly found in patients with chronic kidney disease (CKD) via an as yet unknown mechanism and the role of ApN in CKD is unclear. We, herein, investigated the effect of ApN overexpression on the progressive renal injury resulted from deoxycorticosterone acetate-salt (DOCA) and angiotensin II (Ang-II) infusion using a transgenic, inducible ApN-overexpressing mouse model. Three groups of mice (wild type receiving no infusion (WT), WT and cyp1a1 ApN transgenic mice (ApN-Tg) receiving DOCA+Ang-II infusion (WT/DOCA+Ang-II and ApN-Tg/DOCA+Ang-II)) were assigned to receive a normal food containing 0.15% of the transgene inducer indol-3-carbinol (I3C) for 3 weeks. The I3C-induced ApN-Tg/DOCA+Ang-II mice, not the WT or WT/DOCA+Ang-II mice, overexpressing ApN in liver resulted in 3.15-fold increases in circulating ApN than non-transgenic controls. Of note, these transgenic mice receiving DOCA+Ang-II infusion were still hypertensive but had much less albuminuria and glomerular and tubulointerstitial fibrosis, which were associated with ameliorated podocyte injury determined by ameliorated podocyte loss and foot process effacement; and alleviated tubular injury determined by ameliorated mRNA overexpression of KIM-1 and NGAL and mRNA decreases of cubilin and megalin in tubular cells, compared with WT/DOCA+Ang-II mice. In addition, renal production of NF-kB-p65, NAPDH oxidase-2 and p47phox, and MAPK-related cellular proliferation, which were induced in WT/DOCA+Ang-II mice, were markedly reduced in ApN-Tg/DOCA+Ang-II mice. These results indicate that elevated ApN in CKD mouse model is renal protective. Enhancing adiponectin production or signaling may have therapeutic potential for CKD.
Systematic characterization of the ionic basis of rabbit cellular electrophysiology using two ventricular models.

PubMed

Romero, Lucía; Carbonell, Beatriz; Trenor, Beatriz; Rodríguez, Blanca; Saiz, Javier; Ferrero, José M

2011-10-01

Several mathematical models of rabbit ventricular action potential (AP) have been proposed to investigate mechanisms of arrhythmias and excitation-contraction coupling. Our study aims at systematically characterizing how ionic current properties modulate the main cellular biomarkers of arrhythmic risk using two widely-used rabbit ventricular models, and comparing simulation results using the two models with experimental data available for rabbit. A sensitivity analysis of AP properties, Ca²⁺ and Na⁺ dynamics, and their rate dependence to variations (±15% and ±30%) in the main transmembrane current conductances and kinetics was performed using the Shannon et al. (2004) and the Mahajan et al. (2008a,b) AP rabbit models. The effects of severe transmembrane current blocks (up to 100%) on steady-state AP and calcium transients, and AP duration (APD) restitution curves were also simulated using both models. Our simulations show that, in both virtual rabbit cardiomyocytes, APD is significantly modified by most repolarization currents, AP triangulation is regulated mostly by the inward rectifier K⁺ current (I(K1)) whereas APD rate adaptation as well as [Na⁺](i) rate dependence is influenced by the Na⁺/K⁺ pump current (I(NaK)). In addition, steady-state [Ca²⁺](i) levels, APD restitution properties and [Ca²⁺](i) rate dependence are strongly dependent on I(NaK), the L-Type Ca²⁺ current (I(CaL)) and the Na⁺/Ca²⁺ exchanger current (I(NaCa)), although the relative role of these currents is markedly model dependent. Furthermore, our results show that simulations using both models agree with many experimentally-reported electrophysiological characteristics. However, our study shows that the Shannon et al. model mimics rabbit electrophysiology more accurately at normal pacing rates, whereas Mahajan et al. model behaves more appropriately at faster rates. Our results reinforce the usefulness of sensitivity analysis for further understanding of cellular electrophysiology and validation of cardiac AP models. Copyright © 2011 Elsevier Ltd. All rights reserved.
Deformations of the Almheiri-Polchinski model

NASA Astrophysics Data System (ADS)

Kyono, Hideki; Okumura, Suguru; Yoshida, Kentaroh

2017-03-01

We study deformations of the Almheiri-Polchinski (AP) model by employing the Yang-Baxter deformation technique. The general deformed AdS2 metric becomes a solution of a deformed AP model. In particular, the dilaton potential is deformed from a simple quadratic form to a hyperbolic function-type potential similarly to integrable deformations. A specific solution is a deformed black hole solution. Because the deformation makes the spacetime structure around the boundary change drastically and a new naked singularity appears, the holographic interpretation is far from trivial. The Hawking temperature is the same as the undeformed case but the Bekenstein-Hawking entropy is modified due to the deformation. This entropy can also be reproduced by evaluating the renormalized stress tensor with an appropriate counter-term on the regularized screen close to the singularity.
Human induced pluripotent stem cell‐derived versus adult cardiomyocytes: an in silico electrophysiological study on effects of ionic current block

PubMed Central

Paci, M; Hyttinen, J; Rodriguez, B

2015-01-01

Background and Purpose Two new technologies are likely to revolutionize cardiac safety and drug development: in vitro experiments on human‐induced pluripotent stem cell‐derived cardiomyocytes (hiPSC‐CMs) and in silico human adult ventricular cardiomyocyte (hAdultV‐CM) models. Their combination was recently proposed as a potential replacement for the present hERG‐based QT study for pharmacological safety assessments. Here, we systematically compared in silico the effects of selective ionic current block on hiPSC‐CM and hAdultV‐CM action potentials (APs), to identify similarities/differences and to illustrate the potential of computational models as supportive tools for evaluating new in vitro technologies. Experimental Approach In silico AP models of ventricular‐like and atrial‐like hiPSC‐CMs and hAdultV‐CM were used to simulate the main effects of four degrees of block of the main cardiac transmembrane currents. Key Results Qualitatively, hiPSC‐CM and hAdultV‐CM APs showed similar responses to current block, consistent with results from experiments. However, quantitatively, hiPSC‐CMs were more sensitive to block of (i) L‐type Ca2+ currents due to the overexpression of the Na+/Ca2+ exchanger (leading to shorter APs) and (ii) the inward rectifier K+ current due to reduced repolarization reserve (inducing diastolic potential depolarization and repolarization failure). Conclusions and Implications In silico hiPSC‐CMs and hAdultV‐CMs exhibit a similar response to selective current blocks. However, overall hiPSC‐CMs show greater sensitivity to block, which may facilitate in vitro identification of drug‐induced effects. Extrapolation of drug effects from hiPSC‐CM to hAdultV‐CM and pro‐arrhythmic risk assessment can be facilitated by in silico predictions using biophysically‐based computational models. PMID:26276951
Andrographis Paniculata shows anti-nociceptive effects in an animal model of sensory hypersensitivity associated with migraine

PubMed Central

Greco, Rosaria; Siani, Francesca; Demartini, Chiara; Zanaboni, Annamaria; Nappi, Giuseppe; Davinelli, Sergio; Scapagnini, Giovanni; Tassorelli, Cristina

2016-01-01

Administration of nitroglycerin (NTG) to rats induces a hyperalgesic condition and neuronal activation of central structures involved in migraine pain. In order to identify therapeutic strategies for migraine pain, we evaluated the anti-nociceptive activity of Andrographis Paniculata (AP), a herbaceous plant, in the hyperalgesia induced by NTG administration in the formalin test. We also analyzed mRNA expression of cytokines in specific brain areas after AP treatment. Male Sprague-Dawley rats were pre-treated with AP extract 30 minutes before NTG or vehicle injection. The data show that AP extract significantly reduced NTG-induced hyperalgesia in phase II of the test, 4 hours after NTG injection. In addition, AP extract reduced IL-6 mRNA expression in the medulla and mesencephalon and also mRNA levels of TNF-alpha in the mesencephalic region. These findings suggest that AP extract may be a potential therapeutic approach in the treatment of general pain, and possibly of migraine. PMID:27027895
Andrographis Paniculata shows anti-nociceptive effects in an animal model of sensory hypersensitivity associated with migraine.

PubMed

Greco, Rosaria; Siani, Francesca; Demartini, Chiara; Zanaboni, Annamaria; Nappi, Giuseppe; Davinelli, Sergio; Scapagnini, Giovanni; Tassorelli, Cristina

2016-01-01

Administration of nitroglycerin (NTG) to rats induces a hyperalgesic condition and neuronal activation of central structures involved in migraine pain. In order to identify therapeutic strategies for migraine pain, we evaluated the anti-nociceptive activity of Andrographis Paniculata (AP), a herbaceous plant, in the hyperalgesia induced by NTG administration in the formalin test. We also analyzed mRNA expression of cytokines in specific brain areas after AP treatment. Male Sprague-Dawley rats were pre-treated with AP extract 30 minutes before NTG or vehicle injection. The data show that AP extract significantly reduced NTG-induced hyperalgesia in phase II of the test, 4 hours after NTG injection. In addition, AP extract reduced IL-6 mRNA expression in the medulla and mesencephalon and also mRNA levels of TNFalpha in the mesencephalic region. These findings suggest that AP extract may be a potential therapeutic approach in the treatment of general pain, and possibly of migraine.
Rickettsia prowazekii methionine aminopeptidase as a promising target for the development of antibacterial agents

DOE PAGES

Helgren, Travis R.; Chen, Congling; Wangtrakuldee, Phumvadee; ...

2016-11-10

Methionine aminopeptidase (MetAP) is a class of ubiquitous enzymes essential for the survival of numerous bacterial species. These enzymes are responsible for the cleavage of N-terminal formyl-methionine initiators from nascent proteins to initiate post-translational modifications that are often essential to proper protein function. Thus, inhibition of MetAP activity has been implicated as a novel antibacterial target. In this study, we tested this idea in the present study by targeting the MetAP enzyme in the obligate intracellular pathogen Rickettsia prowazekii. We first identified potent RpMetAP inhibitory species by employing an in vitro enzymatic activity assay. The molecular docking program AutoDock wasmore » then utilized to compare published crystal structures of inhibited MetAP species to docked poses of RpMetAP. Based on these in silico and in vitro screens, a subset of 17 compounds was tested for inhibition of R. prowazekii growth in a pulmonary vascular endothelial cell (EC) culture infection model system. All compounds were tested over concentration ranges that were determined to be non-toxic to the ECs and 8 of the 17 compounds displayed substantial inhibition of R. prowazekii growth. Lastly, these data highlight the therapeutic potential for inhibiting RpMetAP as a novel antimicrobial strategy and set the stage for future studies in pre-clinical animal models of infection.« less

Rickettsia prowazekii methionine aminopeptidase as a promising target for the development of antibacterial agents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Helgren, Travis R.; Chen, Congling; Wangtrakuldee, Phumvadee

Methionine aminopeptidase (MetAP) is a class of ubiquitous enzymes essential for the survival of numerous bacterial species. These enzymes are responsible for the cleavage of N-terminal formyl-methionine initiators from nascent proteins to initiate post-translational modifications that are often essential to proper protein function. Thus, inhibition of MetAP activity has been implicated as a novel antibacterial target. In this study, we tested this idea in the present study by targeting the MetAP enzyme in the obligate intracellular pathogen Rickettsia prowazekii. We first identified potent RpMetAP inhibitory species by employing an in vitro enzymatic activity assay. The molecular docking program AutoDock wasmore » then utilized to compare published crystal structures of inhibited MetAP species to docked poses of RpMetAP. Based on these in silico and in vitro screens, a subset of 17 compounds was tested for inhibition of R. prowazekii growth in a pulmonary vascular endothelial cell (EC) culture infection model system. All compounds were tested over concentration ranges that were determined to be non-toxic to the ECs and 8 of the 17 compounds displayed substantial inhibition of R. prowazekii growth. Lastly, these data highlight the therapeutic potential for inhibiting RpMetAP as a novel antimicrobial strategy and set the stage for future studies in pre-clinical animal models of infection.« less
Environmental risk assessment of alkylphenols from offshore produced water on fish reproduction.

PubMed

Beyer, Jonny; Myhre, Lars Petter; Sundt, Rolf C; Meier, Sonnich; Tollefsen, Knut-Erik; Vabø, Rune; Klungsøyr, Jarle; Sanni, Steinar

2012-04-01

Concern has been raised over whether environmental release of alkylphenols (AP) in produced water (PW) discharges from the offshore oil industry could impose a risk to the reproduction of fish stocks in the North Sea. An environmental risk assessment (ERA) was performed to determine if environmental exposure to PW APs in North Sea fish populations is likely to be high enough to give effects on reproduction endpoints. The DREAM (Dose related Risk and Effect Assessment Model) software was used in the study and the inputs to the ERA model included PW discharge data, fate information of PW plumes, fish distribution information, as well as uptake and elimination information of PW APs. Toxicodynamic data from effect studies with Atlantic cod (Gadus morhua) exposed to APs were used to establish a conservative environmental risk threshold value for AP concentration in seawater. By using the DREAM software to 1) identify the areas of highest potential risk and 2) integrate fish movement and uptake/elimination rates of APs for the chosen areas we found that the environmental exposure of fish to APs from PW is most likely too low to affect reproduction in wild populations of fish in the North Sea. The implications related to risk management of offshore PW and uncertainties in the risk assessment performed are discussed. Copyright Â© 2011 Elsevier Ltd. All rights reserved.
On the Perceptual Subprocess of Absolute Pitch.

PubMed

Kim, Seung-Goo; Knösche, Thomas R

2017-01-01

Absolute pitch (AP) is the rare ability of musicians to identify the pitch of tonal sound without external reference. While there have been behavioral and neuroimaging studies on the characteristics of AP, how the AP is implemented in human brains remains largely unknown. AP can be viewed as comprising of two subprocesses: perceptual (processing auditory input to extract a pitch chroma) and associative (linking an auditory representation of pitch chroma with a verbal/non-verbal label). In this review, we focus on the nature of the perceptual subprocess of AP. Two different models on how the perceptual subprocess works have been proposed: either via absolute pitch categorization (APC) or based on absolute pitch memory (APM). A major distinction between the two views is that whether the AP uses unique auditory processing (i.e., APC) that exists only in musicians with AP or it is rooted in a common phenomenon (i.e., APM), only with heightened efficiency. We review relevant behavioral and neuroimaging evidence that supports each notion. Lastly, we list open questions and potential ideas to address them.
On the Perceptual Subprocess of Absolute Pitch

PubMed Central

Kim, Seung-Goo; Knösche, Thomas R.

2017-01-01

Absolute pitch (AP) is the rare ability of musicians to identify the pitch of tonal sound without external reference. While there have been behavioral and neuroimaging studies on the characteristics of AP, how the AP is implemented in human brains remains largely unknown. AP can be viewed as comprising of two subprocesses: perceptual (processing auditory input to extract a pitch chroma) and associative (linking an auditory representation of pitch chroma with a verbal/non-verbal label). In this review, we focus on the nature of the perceptual subprocess of AP. Two different models on how the perceptual subprocess works have been proposed: either via absolute pitch categorization (APC) or based on absolute pitch memory (APM). A major distinction between the two views is that whether the AP uses unique auditory processing (i.e., APC) that exists only in musicians with AP or it is rooted in a common phenomenon (i.e., APM), only with heightened efficiency. We review relevant behavioral and neuroimaging evidence that supports each notion. Lastly, we list open questions and potential ideas to address them. PMID:29085275
A novel hypothesis for an alkaline phosphatase 'rescue' mechanism in the hepatic acute phase immune response.

PubMed

Pike, Adrianne F; Kramer, Nynke I; Blaauboer, Bas J; Seinen, Willem; Brands, Ruud

2013-12-01

The liver isoform of the enzyme alkaline phosphatase (AP) has been used classically as a serum biomarker for hepatic disease states such as hepatitis, steatosis, cirrhosis, drug-induced liver injury, and hepatocellular carcinoma. Recent studies have demonstrated a more general anti-inflammatory role for AP, as it is capable of dephosphorylating potentially deleterious molecules such as nucleotide phosphates, the pathogenic endotoxin lipopolysaccharide (LPS), and the contact clotting pathway activator polyphosphate (polyP), thereby reducing inflammation and coagulopathy systemically. Yet the mechanism underlying the observed increase in liver AP levels in circulation during inflammatory insults is largely unknown. This paper hypothesizes an immunological role for AP in the liver and the potential of this system for damping generalized inflammation along with a wide range of ancillary pathologies. Based on the provided framework, a mechanism is proposed in which AP undergoes transcytosis in hepatocytes from the canalicular membrane to the sinusoidal membrane during inflammation and the enzyme's expression is upregulated as a result. Through a tightly controlled, nucleotide-stimulated negative feedback process, AP is transported in this model as an immune complex with immunoglobulin G by the asialoglycoprotein receptor through the cell and secreted into the serum, likely using the receptor's State 1 pathway. The subsequent dephosphorylation of inflammatory stimuli by AP and uptake of the circulating immune complex by endothelial cells and macrophages may lead to decreased inflammation and coagulopathy while providing an early upstream signal for the induction of a number of anti-inflammatory gene products, including AP itself. © 2013.
Evaluation of 99mTc labeled diadenosine tetraphosphate as an atherosclerotic plaque imaging agent in experimental models.

PubMed

Cao, Wei; Zhang, Yongxue; An, Rui

2006-01-01

The potential of 99mTc labeled P1, P4-di (adenosine-5')-tetraphosphate (Ap4A) for imaging experimental atherosclerotic plaques was evaluated in New Zealand white (NZW) rabbits. To label the 99mTc to Ap4A, stannous tartrate solution was used. 99mTc-Ap4A was purified on a Sephadex G-25 column. The radiochemistry purities of 99mTc-Ap4A were 85% to 91%. Biodistribution study revealed 99mTc-Ap4A cleared from blood rapidly. Thirty min after 99mTc-Ap4A administrated on NZW atherosclerotic rabbits, lesion to blood (target/blood, T/B) ratio was 3.17 +/- 1.27, and lesions to normal (target/non-target, T/NT) ratio was 5.23 +/- 1.87. Shadows of atherosclerotic plaques were clearly visible on radioautographic film. Aortas with atherosclerotic plaques also could be seen on ex vivo gamma camera images. Atherosclerotic abdominal aortas were clearly visible on in vivo images 15 min to 3 h after 99mTc-Ap4A administration. 99mTc-labeled Ap4A can be used for rapid noninvasive detection of experimental atherosclerotic plaque.
Changes in intrinsic excitability of ganglion cells in degenerated retinas of RCS rats

PubMed Central

Ren, Yi-Ming; Weng, Chuan-Huang; Zhao, Cong-Jian; Yin, Zheng-Qin

2018-01-01

AIM To evaluate the intrinsic excitability of retinal ganglion cells (RGCs) in degenerated retinas. METHODS The intrinsic excitability of various morphologically defined RGC types using a combination of patch-clamp recording and the Lucifer yellow tracer in retinal whole-mount preparations harvested from Royal College of Surgeons (RCS) rats, a common retinitis pigmentosa (RP) model, in a relatively late stage of retinal degeneration (P90) were investigated. Several parameters of RGC morphologies and action potentials (APs) were measured and compared to those of non-dystrophic control rats, including dendritic stratification, dendritic field diameter, peak amplitude, half width, resting membrane potential, AP threshold, depolarization to threshold, and firing rates. RESULTS Compared with non-dystrophic control RGCs, more depolarizations were required to reach the AP threshold in RCS RGCs with low spontaneous spike rates and in RCS OFF cells (especially A2o cells), and RCS RGCs maintained their dendritic morphologies, resting membrane potentials and capabilities to generate APs. CONCLUSION RGCs are relatively well preserved morphologically and functionally, and some cells are more susceptible to decreased excitability during retinal degeneration. These findings provide valuable considerations for optimizing RP therapeutic strategies. PMID:29862172
Mannose-coated gadolinium liposomes for improved magnetic resonance imaging in acute pancreatitis.

PubMed

Tian, Bing; Liu, Ri; Chen, Shiyue; Chen, Luguang; Liu, Fang; Jia, Guorong; Dong, Yinmei; Li, Jing; Chen, Huaiwen; Lu, Jianping

2017-01-01

Acute pancreatitis (AP) is an acute inflammatory condition of the pancreas. The symptoms, treatment, and prognosis of mild and severe AP are different, and severe AP is a potentially life-threatening disease with a high incidence of complications and high mortality rate. Thus, it is urgent to develop an effective approach to reliably discriminate between mild and severe AP. We have developed novel gadolinium-diethylenetriaminepentaacetic (Gd-DTPA)-loaded mannosylated liposomes (named thereafter M-Gd-NL) that preferably target macrophages in AP. The targeting ability of M-Gd-NL toward macrophages in AP and its ability to discriminate between mild and severe AP were evaluated. The liposomes were of desired particle size (~100 nm), Gd-DTPA encapsulation efficiency (~85%), and stability. M-Gd-NL and non-targeted Gd-DTPA-loaded liposomes (Gd-NL) exhibited increased relaxivity compared with Gd-DTPA. Compared with Gd-NL and Gd-DTPA, M-Gd-NL showed increased uptake in macrophages, resulting in increased T 1 imaging ability both in vitro (macrophage cell line) and in vivo (severe AP model). Importantly, M-Gd-NL had the ability to discriminate between mild and severe AP, as reflected by a significantly higher T 1 magnetic resonance imaging signal in severe AP than in mild AP. M-Gd-NL did not show severe organ toxicity in rats. Our data suggest that M-Gd-NL had enhanced magnetic resonance imaging ability by targeting macrophages in AP and good ability to discriminate between mild and severe AP. We believe that M-Gd-NL could shed new light on the diagnosis of AP in the near future.
Long-term Treatment with Oriental Medicinal Herb Artemisia princeps Alters Neuroplasticity in a Rat Model of Ovarian Hormone Deficiency.

PubMed

Kim, Hyun-Bum; Kwon, Byeong-Jae; Cho, Hyun-Ji; Kim, Ji-Won; Chon, Jeong-Woo; Do, Moon-Ho; Park, Sang-Yong; Kim, Sun-Yeou; Maeng, Sung-Ho; Park, Yoo-Kyoung; Park, Ji-Ho

2015-03-01

Artemisia princeps (AP) is a flowering perennial used as a traditional medicine and dietary supplement across East Asia. No study has yet assessed its effects on synaptic plasticity in hippocampus and much less in a model of ovarian hormone deficiency. We examined the influence of chronic oral AP ethanol extract treatment in ovariectomized rats on the induction of long-term depression in a representative synapse (CA3-CA1) of the hippocampus. Ovariectomized rats demonstrated lower trabecular mean bone mineral densities than sham, validating the establishment of pathology. Against this background of pathology, AP-treated ovariectomized rats exhibited attenuated long-term depression (LTD) in CA1 relative to water-treated controls as measured by increased field excitatory post-synaptic potentials (fEPSP) activation averages over the post-stimulation period. While pathological significance of long-term depression (LTD) in ovariectomized rats is conflicting, that AP treatment significantly affected its induction offers justification for further study of its influences on plasticity and its related disorders.
A mathematical model of action potential heterogeneity in adult rat left ventricular myocytes.

PubMed Central

Pandit, S V; Clark, R B; Giles, W R; Demir, S S

2001-01-01

Mathematical models were developed to reconstruct the action potentials (AP) recorded in epicardial and endocardial myocytes isolated from the adult rat left ventricle. The main goal was to obtain additional insight into the ionic mechanisms responsible for the transmural AP heterogeneity. The simulation results support the hypothesis that the smaller density and the slower reactivation kinetics of the Ca(2+)-independent transient outward K(+) current (I(t)) in the endocardial myocytes can account for the longer action potential duration (APD), and more prominent rate dependence in that cell type. The larger density of the Na(+) current (I(Na)) in the endocardial myocytes results in a faster upstroke (dV/dt(max)). This, in addition to the smaller magnitude of I(t), is responsible for the larger peak overshoot of the simulated endocardial AP. The prolonged APD in the endocardial cell also leads to an enhanced amplitude of the sustained K(+) current (I(ss)), and a larger influx of Ca(2+) ions via the L-type Ca(2+) current (I(CaL)). The latter results in an increased sarcoplasmic reticulum (SR) load, which is mainly responsible for the higher peak systolic value of the Ca(2+) transient [Ca(2+)](i), and the resultant increase in the Na(+)-Ca(2+) exchanger (I(NaCa)) activity, associated with the simulated endocardial AP. In combination, these calculations provide novel, quantitative insights into the repolarization process and its naturally occurring transmural variations in the rat left ventricle. PMID:11720973
An updated computational model of rabbit sinoatrial action potential to investigate the mechanisms of heart rate modulation

PubMed Central

Severi, Stefano; Fantini, Matteo; Charawi, Lara A; DiFrancesco, Dario

2012-01-01

The cellular basis of cardiac pacemaking is still debated. Reliable computational models of the sinoatrial node (SAN) action potential (AP) may help gain a deeper understanding of the phenomenon. Recently, novel models incorporating detailed Ca2+-handling dynamics have been proposed, but they fail to reproduce a number of experimental data, and more specifically effects of ‘funny’ (If) current modifications. We therefore developed a SAN AP model, based on available experimental data, in an attempt to reproduce physiological and pharmacological heart rate modulation. Cell compartmentalization and intracellular Ca2+-handling mechanisms were formulated as in the Maltsev–Lakatta model, focusing on Ca2+-cycling processes. Membrane current equations were revised on the basis of published experimental data. Modifications of the formulation of currents/pumps/exchangers to simulate If blockers, autonomic modulators and Ca2+-dependent mechanisms (ivabradine, caesium, acetylcholine, isoprenaline, BAPTA) were derived from experimental data. The model generates AP waveforms typical of rabbit SAN cells, whose parameters fall within the experimental ranges: 352 ms cycle length, 80 mV AP amplitude, −58 mV maximum diastolic potential (MDP), 108 ms APD50, and 7.1 V s−1 maximum upstroke velocity. Rate modulation by If-blocking drugs agrees with experimental findings: 20% and 22% caesium-induced (5 mm) and ivabradine-induced (3 μm) rate reductions, respectively, due to changes in diastolic depolarization (DD) slope, with no changes in either MDP or take-off potential (TOP). The model consistently reproduces the effects of autonomic modulation: 20% rate decrease with 10 nm acetylcholine and 28% increase with 1 μm isoprenaline, again entirely due to increase in the DD slope, with no changes in either MDP or TOP. Model testing of BAPTA effects showed slowing of rate, −26%, without cessation of beating. Our up-to-date model describes satisfactorily experimental data concerning autonomic stimulation, funny-channel blockade and inhibition of the Ca2+-related system by BAPTA, making it a useful tool for further investigation. Simulation results suggest that a detailed description of the intracellular Ca2+ fluxes is fully compatible with the observation that If is a major component of pacemaking and rate modulation. PMID:22711956
Electronic neuron within a ganglion of a leech (Hirudo medicinalis).

PubMed

Aliaga, J; Busca, N; Minces, V; Mindlin, G B; Pando, B; Salles, A; Sczcupak, L

2003-06-01

We report the construction of an electronic device that models and replaces a neuron in a midbody ganglion of the leech Hirudo medicinalis. In order to test the behavior of our device, we used a well-characterized synaptic interaction between the mechanosensory, sensitive to pressure, (P) cell and the anteropagoda (because of the action potential shape) (AP) neuron. We alternatively stimulated a P neuron and our device connected to the AP neuron, and studied the response of the latter. The number and timing of the AP spikes were the same when the electronic parameters were properly adjusted. Moreover, after changes in the depolarization of the AP cell, the responses under the stimulation of both the biological neuron and the electronic device vary in a similar manner.
IK1-enhanced human-induced pluripotent stem cell-derived cardiomyocytes: an improved cardiomyocyte model to investigate inherited arrhythmia syndromes

PubMed Central

Vaidyanathan, Ravi; Markandeya, Yogananda S.; Kamp, Timothy J.; Makielski, Jonathan C.; January, Craig T.

2016-01-01

Currently available induced pluripotent stem cell-derived cardiomyocytes (iPS-CMs) do not ideally model cellular mechanisms of human arrhythmic disease due to lack of a mature action potential (AP) phenotype. In this study, we create and characterize iPS-CMs with an electrically mature AP induced by potassium inward rectifier (IK1) enhancement. The advantages of IK1-enhanced iPS-CMs include the absence of spontaneous beating, stable resting membrane potentials at approximately −80 mV and capability for electrical pacing. Compared with unenhanced, IK1-enhanced iPS-CMs calcium transient amplitudes were larger (P < 0.05) with a typical staircase pattern. IK1-enhanced iPS-CMs demonstrated a twofold increase in cell size and membrane capacitance and increased DNA synthesis compared with control iPS-CMs (P < 0.05). Furthermore, IK1-enhanced iPS-CMs expressing the F97C-CAV3 long QT9 mutation compared with wild-type CAV3 demonstrated an increase in AP duration and late sodium current. IK1-enhanced iPS-CMs represent a more mature cardiomyocyte model to study arrhythmia mechanisms. PMID:27059077
New Insights into the Methodology of L-Arginine-Induced Acute Pancreatitis

PubMed Central

Kui, Balázs; Balla, Zsolt; Vasas, Béla; Végh, Eszter T.; Pallagi, Petra; Kormányos, Eszter S.; Venglovecz, Viktória; Iványi, Béla; Takács, Tamás; Hegyi, Péter; Rakonczay, Zoltán

2015-01-01

Animal models are ideal to study the pathomechanism and therapy of acute pancreatitis (AP). The use of L-arginine-induced AP model is nowadays becoming increasingly popular in mice. However, carefully looking through the literature, marked differences in disease severity could be observed. In fact, while setting up the L-arginine (2×4 g/kg i.p.)-induced AP model in BALB/c mice, we found a relatively low rate (around 15%) of pancreatic necrosis, whereas others have detected much higher rates (up to 55%). We suspected that this may be due to differences between mouse strains. We administered various concentrations (5–30%, pH = 7.4) and doses (2×4, 3×3, or 4×2.5 g/kg) of L-arginine-HCl in BALB/c, FVB/n and C57BL/6 mice. The potential gender-specific effect of L-arginine was investigated in C57BL/6 mice. The fate of mice in response to the i.p. injections of L arginine followed one of three courses. Some mice (1) developed severe AP or (2) remained AP-free by 72 h, whereas others (3) had to be euthanized (to avoid their death, which was caused by the high dose of L-arginine and not AP) within 12 h., In FVB/n and C57BL/6 mice, the pancreatic necrosis rate (about 50%) was significantly higher than that observed in BALB/c mice using 2×4 g/kg 10% L–arginine, but euthanasia was necessary in a large proportion of animals, The i.p. injection of lower L-arginine concentrations (e.g. 5–8%) in case of the 2×4 g/kg dose, or other L-arginine doses (3×3 or 4×2.5 g/kg, 10%) were better for inducing AP. We could not detect any significant differences between the AP severity of male and female mice. Taken together, when setting up the L-arginine-induced AP model, there are several important factors that are worth consideration such as the dose and concentration of the administered L arginine-HCl solution and also the strain of mice. PMID:25688985
Risk Factor Differences in Calcified and Non-Calcified Aortic Plaque: The Framingham Heart Study

PubMed Central

Chuang, Michael L.; Gona, Philimon; Oyama-Manabe, Noriko; Manders, Emily S.; Salton, Carol J.; Hoffmann, Udo; Manning, Warren J.; O'Donnell, Christopher J.

2014-01-01

Objective Determine the prevalence and risk factor (RF) correlates of aortic plaque (AP) detected by cardiovascular magnetic resonance (CMR), which mainly shows noncalcified plaques, and by noncontrast computed tomography (CT), which best depicts calcified plaques, in community-dwelling adults. Approach and Results 1016 Framingham Offspring cohort members (64±9y, 474 men) underwent CMR and CT of the aorta. Potential RFs for AP (age; sex; BMI; blood pressure; LDL and HDL cholesterol; fasting glucose; C-reactive protein; prevalent hypertension, diabetes, smoking; use of antihypertensive, diabetes or lipid-lowering drugs) were compared between participants with zero versus nonzero AP by CMR and by CT. Candidate RFs attaining p<0.05 for difference with either imaging modality were entered into multivariable logistic regression models adjusting for age, sex and other RFs. Odds ratios were calculated for modality-specific prevalence of AP. Associations between RFs and continuous measures of AP were assessed using Tobit regression. Prevalences of CMR and CT AP were 49% and 82% respectively. AP burdens by CMR and CT were correlated, r=0.28, p<0.0001. Increasing age and smoking were associated with prevalent AP by both CMR and CT. Additionally, prevalent AP by CMR was associated with female sex and fasting glucose, prevalent AP by CT with hypertension treatment and with adverse lipid profile. Conclusions AP by CMR and CT are both associated with smoking and increasing age, but other risk factors differ between calcified and noncalcified AP. The relative predictive value of AP detected by CMR versus by CT for incident cardiovascular events remains to be determined. PMID:24833796
A Comparison of Van Allen Belt Radiation Environment Modeling Programs: AE8/AP8 Legacy, AE9/AP9, and SPENVIS

NASA Technical Reports Server (NTRS)

Reed, Evan; Pellish, Jonathan

2016-01-01

In the space surrounding Earth there exists an active radiation environment consisting mostly of electrons and protons that have been trapped by Earths magnetic field. This radiation, also known as the Van Allen Belts, has the potential to damage man-made satellites in orbit; thus, proper precautions must be taken to shield NASA assets from this phenomenon. Data on the Van Allen Belts has been collected continuously by a multitude of space-based instruments since the beginning of space exploration. Subsequently, using theory to fill in the gaps in the collected data, computer models have been developed that take in the orbital information of a hypothetical mission and output the expected particle fluence and flux for that orbit. However, as new versions of the modeling system are released, users are left wondering how the new version differs from the old. Therefore, we performed a comparison of three different editions of the modeling system: AE8/AP8 (legacy), which is included in the model 9 graphical user interface as an option for ones calculations, AE9/AP9, and the Space Environment Information System (SPENVIS), which is an online-based form of AE8/AP8 developed by NASA and the European Space Agency that changed the code to allow the program to extrapolate data to predict fluence and flux at higher energies. Although this evaluation is still ongoing, it is predicted that the model 8 (legacy) and SPENVIS version will have identical outputs with the exception of the extended energy levels from SPENVIS, while model 9 will provide different fluences than model 8 based on additional magnetic field descriptions and on-orbit data.
Human ex-vivo action potential model for pro-arrhythmia risk assessment.

PubMed

Page, Guy; Ratchada, Phachareeya; Miron, Yannick; Steiner, Guido; Ghetti, Andre; Miller, Paul E; Reynolds, Jack A; Wang, Ken; Greiter-Wilke, Andrea; Polonchuk, Liudmila; Traebert, Martin; Gintant, Gary A; Abi-Gerges, Najah

2016-01-01

While current S7B/E14 guidelines have succeeded in protecting patients from QT-prolonging drugs, the absence of a predictive paradigm identifying pro-arrhythmic risks has limited the development of valuable drug programs. We investigated if a human ex-vivo action potential (AP)-based model could provide a more predictive approach for assessing pro-arrhythmic risk in man. Human ventricular trabeculae from ethically consented organ donors were used to evaluate the effects of dofetilide, d,l-sotalol, quinidine, paracetamol and verapamil on AP duration (APD) and recognized pro-arrhythmia predictors (short-term variability of APD at 90% repolarization (STV(APD90)), triangulation (ADP90-APD30) and incidence of early afterdepolarizations at 1 and 2Hz to quantitatively identify the pro-arrhythmic risk. Each drug was blinded and tested separately with 3 concentrations in triplicate trabeculae from 5 hearts, with one vehicle time control per heart. Electrophysiological stability of the model was not affected by sequential applications of vehicle (0.1% dimethyl sulfoxide). Paracetamol and verapamil did not significantly alter anyone of the AP parameters and were classified as devoid of pro-arrhythmic risk. Dofetilide, d,l-sotalol and quinidine exhibited an increase in the manifestation of pro-arrhythmia markers. The model provided quantitative and actionable activity flags and the relatively low total variability in tissue response allowed for the identification of pro-arrhythmic signals. Power analysis indicated that a total of 6 trabeculae derived from 2 hearts are sufficient to identify drug-induced pro-arrhythmia. Thus, the human ex-vivo AP-based model provides an integrative translational assay assisting in shaping clinical development plans that could be used in conjunction with the new CiPA-proposed approach. Copyright © 2016 Elsevier Inc. All rights reserved.
Human ex-vivo action potential model for pro-arrhythmia risk assessment

PubMed Central

Page, Guy; Ratchada, Phachareeya; Miron, Yannick; Steiner, Guido; Ghetti, Andre; Miller, Paul E; Reynolds, Jack A; Wang, Ken; Greiter-Wilke, Andrea; Polonchuk, Liudmila; Traebert, Martin; Gintant, Gary A; Abi-Gerges, Najah

2016-01-01

While current S7B/E14 guidelines have succeeded in protecting patients from QT-prolonging drugs, the absence of a predictive paradigm identifying pro-arrhythmic risks has limited the development of valuable drug programs. We investigated if a human ex-vivo action potential (AP)-based model could provide a more predictive approach for assessing pro-arrhythmic risk in man. Human ventricular trabeculae from ethically consented organ donors were used to evaluate the effects of dofetilide, d,l-sotalol, quinidine, paracetamol and verapamil on AP duration (APD) and recognized pro-arrhythmia predictors (short-term variability of APD at 90% repolarization (STV(APD90)), triangulation (ADP90-APD30) and incidence of early afterdepolarizations at 1 and 2 Hz to quantitatively identify the pro-arrhythmic risk. Each drug was blinded and tested separately with 3 concentrations in triplicate trabeculae from 5 hearts, with one vehicle time control per heart. Electrophysiological stability of the model was not affected by sequential applications of vehicle (0.1% dimethyl sulfoxide). Paracetamol and verapamil did not significantly alter anyone of the AP parameters and were classified as devoid of pro-arrhythmic risk. Dofetilide, d,l-sotalol and quinidine exhibited an increase in the manifestation of pro-arrhythmia markers. The model provided quantitative and actionable activity flags and the relatively low total variability in tissue response allowed for the identification of pro-arrhythmic signals. Power analysis indicated that a total of 6 trabeculae derived from 2 hearts are sufficient to identify drug-induced pro-arrhythmia. Thus, the human ex-vivo AP-based model provides an integrative translational assay assisting in shaping clinical development plans that could be used in conjunction with the new CiPA-proposed approach. PMID:27235787
Grapefruit juice and its constituents augment colchicine intestinal absorption: potential hazardous interaction and the role of p-glycoprotein.

PubMed

Dahan, Arik; Amidon, Gordon L

2009-04-01

To investigate the potential interaction between grapefruit juice (GFJ) and the oral microtubule polymerization inhibitor colchicine, a P-gp and CYP3A4 substrate. Colchicine intestinal epithelial transport was investigated across Caco-2 cell monolayers in both AP-BL and BL-AP directions, in the absence/presence of known P-gp inhibitors (verapamil and quinidine). The concentration-dependent effects of GFJ and its major constituents (6'-7'-dihydroxybergamottin, naringin and naringenin) on colchicine Caco-2 mucosal secretion were examined. The effect of GFJ on colchicine intestinal-permeability was then investigated in-situ in the rat perfusion model, in both jejunum and ileum. Colchicine exhibited 20-fold higher BL-AP than AP-BL Caco-2 permeability, indicative of net mucosal secretion, which was reduced by verapamil/quinidine. Colchicine AP-BL permeability was increased and BL-AP was decreased by GFJ in a concentration-dependent manner (IC(50) values of 0.75% and 0.46% respectively), suggesting inhibition of efflux transport, rather than metabolizing enzyme. Similar effects obtained following pre-experiment incubation with GFJ, even though the juice was not present throughout the transepithelial study. 6'-7'-Dihydroxybergamottin, naringin and naringenin displayed concentration-dependent inhibition on colchicine BL-AP secretion (IC(50) values of 90, 592 and 11.6 microM respectively). Ten percent GFJ doubled colchicine rat in-situ ileal permeability, and increased 1.5-fold jejunal permeability. The data suggest that GFJ may augment colchicine oral bioavailability. Due to colchicine narrow therapeutic-index and severely toxic side-effects, awareness of this interaction is prudent.
Understanding and treating amotivation in people with psychosis: An experimental study of the role of guided imagery.

PubMed

Cox, Charlotte; Jolley, Suzanne; Johns, Louise

2016-12-30

Psychological models propose that the amotivational negative symptoms (ANS) of psychosis are influenced by expectations of future events; both anticipatory success (believing one can achieve something, AS) and anticipatory pleasure (mentally pre-creating potential future experiences of enjoyment, AP). Mental imagery manipulations have been shown to change expectations across a range of settings, and may therefore enhance psychological interventions for ANS in people with psychosis. We set out to investigate the impact of a guided imagery manipulation on AS and AP in this group. Forty-two participants with psychosis and ANS completed measures of ANS severity, before random allocation to either a positive or neutral imagery manipulation. AS and AP towards a dart-throwing task were measured before and after the manipulation. Greater ANS severity was associated with lower levels of AS, but not of AP, irrespective of task performance. AS, but not AP, improved during both positive and neutral imagery manipulations, with no effect of imagery type. Anticipatory success is a candidate psychological factor influencing the severity of ANS in psychosis that may be changed by guided imagery manipulation. Imagery interventions are feasible and acceptable for this group: further investigation is needed of their mechanism of action and potential to improve functioning. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Covariation of axon initial segment location and dendritic tree normalizes the somatic action potential

PubMed Central

Hamada, Mustafa S.; Goethals, Sarah; de Vries, Sharon I.; Brette, Romain

2016-01-01

In mammalian neurons, the axon initial segment (AIS) electrically connects the somatodendritic compartment with the axon and converts the incoming synaptic voltage changes into a temporally precise action potential (AP) output code. Although axons often emanate directly from the soma, they may also originate more distally from a dendrite, the implications of which are not well-understood. Here, we show that one-third of the thick-tufted layer 5 pyramidal neurons have an axon originating from a dendrite and are characterized by a reduced dendritic complexity and thinner main apical dendrite. Unexpectedly, the rising phase of somatic APs is electrically indistinguishable between neurons with a somatic or a dendritic axon origin. Cable analysis of the neurons indicated that the axonal axial current is inversely proportional to the AIS distance, denoting the path length between the soma and the start of the AIS, and to produce invariant somatic APs, it must scale with the local somatodendritic capacitance. In agreement, AIS distance inversely correlates with the apical dendrite diameter, and model simulations confirmed that the covariation suffices to normalize the somatic AP waveform. Therefore, in pyramidal neurons, the AIS location is finely tuned with the somatodendritic capacitive load, serving as a homeostatic regulation of the somatic AP in the face of diverse neuronal morphologies. PMID:27930291
Lecithin-based microemulsions for targeted delivery of ceramide AP into the stratum corneum: formulation, characterizations, and in vitro release and penetration studies.

PubMed

Sahle, Fitsum F; Metz, Hendrik; Wohlrab, Johannes; Neubert, Reinhard H H

2013-02-01

To improve the solubility and penetration of Ceramide AP (CER [AP]) into the stratum corneum that potentially restores the barrier function of aged and affected skin. CER [AP] microemulsions (MEs) were formulated using lecithin, Miglyol® 812 (miglyol) and water-1,2 pentandiol (PeG) mixture as amphiphilic, oily and hydrophilic components, respectively. The nanostructure of the MEs was revealed using electrical conductivity, differential scanning calorimeter (DSC) and electron paramagnetic resonance (EPR) techniques. Photon correlation spectroscopy (PCS) was used to measure the sizes and shape of ME droplets. The release and penetration of the CER into the stratum corneum was investigated in vitro using a multi-layer membrane model. The MEs exhibited excellent thermodynamic stability (>2 years) and loading capacity (0.5% CER [AP]). The pseudo-ternary phase diagrams of the MEs were obtained and PCS results showed that the droplets are spherical in shape and bigger in size. In vitro investigations showed that the MEs exhibited excellent rate and extent of release and penetration. Stable lecithin-based CER [AP] MEs that significantly enhance the solubility and penetration of CER [AP] into the stratum corneum were developed. The MEs also have better properties than the previously reported polyglycerol fatty acid surfactant-based CER [AP] MEs.
In vitro and in vivo antioxidant activities of polysaccharide purified from aloe vera (Aloe barbadensis) gel.

PubMed

Kang, Min-Cheol; Kim, Seo Young; Kim, Yoon Taek; Kim, Eun-A; Lee, Seung-Hong; Ko, Seok-Chun; Wijesinghe, W A J P; Samarakoon, Kalpa W; Kim, Young-Sun; Cho, Jin Hun; Jang, Hyeang-Su; Jeon, You-Jin

2014-01-01

The in vitro and in vivo antioxidant potentials of a polysaccharide isolated from aloe vera gel were investigated. Enzymatic extracts were prepared from aloe vera gel by using ten digestive enzymes including five carbohydrases and five proteases. Among them, the highest yield was obtained with the Viscozyme extract and the same extract showed the best radical scavenging activity. An active polysaccharide was purified from the Viscozyme extract using ethanol-added separation and anion exchange chromatography. Purified aloe vera polysaccharide (APS) strongly scavenged radicals including DPPH, hydroxyl and alkyl radicals. In addition, APS showed a protective effect against AAPH-induced oxidative stress and cell death in Vero cells as well as in the in vivo zebrafish model. In this study, it is proved that both the in vitro and in vivo antioxidant potentials of APS could be further utilized in relevant industrial applications. Copyright © 2013 Elsevier Ltd. All rights reserved.
Numerical Test of the Additivity Principle in Anomalous Transport

NASA Astrophysics Data System (ADS)

Tamaki, Shuji

2017-10-01

The additivity principle (AP) is one of the remarkable predictions that systematically generates all information on current fluctuations once the value of average current in the linear response regime is input. However, conditions to justify the AP are still ambiguous. We hence consider three tractable models, and discuss possible conditions. The models include the harmonic chain (HC), momentum exchange (ME) model, and momentum flip (MF) model, which respectively show ballistic, anomalous, and diffusive transport. We compare the heat current cumulants predicted by the AP with exact numerical data obtained for these models. The HC does not show the AP, whereas the MF model satisfies it, as expected, since the AP was originally proposed for diffusive systems. Surprisingly, the ME model also shows the AP. The ME model is known to show the anomalous transport similar to that shown in nonlinear systems such as the Fermi-Pasta-Ulam model. Our finding indicates that general nonlinear systems may satisfy the AP. Possible conditions for satisfying the AP are discussed.
Chinese Herbal Medicines Attenuate Acute Pancreatitis: Pharmacological Activities and Mechanisms

PubMed Central

Xiang, Hong; Zhang, Qingkai; Qi, Bing; Tao, Xufeng; Xia, Shilin; Song, Huiyi; Qu, Jialin; Shang, Dong

2017-01-01

Acute pancreatitis (AP) is a commonly occurring gastrointestinal disorder. An increase in the annual incidence of AP has been observed, and it causes acute hospitalization and high mortality. The diagnosis and treatment guidelines for AP recommend conservative medical treatments focused on reducing pancreatic secretion and secondary injury, as a primary therapeutic approach. Unfortunately, the existing treatment options have limited impact on the incidence and severity of AP due to the complex and multifaceted pathological process of this disease. In recent decades, Chinese herbal medicines (CHMs) have been used as efficient therapeutic agents to attenuate AP in Asian countries. Despite early cell culture, animal models, and clinical trials, CHMs are capable of interacting with numerous molecular targets participating in the pathogenesis of AP; however, comprehensive, up-to-date communication in this field is not yet available. This review focuses on the pharmacological activities of CHMs against AP in vitro and in vivo and the underlying mechanisms. A computational prediction of few selected and promising plant-derived molecules (emodin, baicalin, resveratrol, curcumin, ligustrazine, and honokiol) to target numerous proteins or networks involved in AP was initially established based on a network pharmacology simulation. Moreover, we also summarized some potential toxic natural products for pancreas in order to more safe and reasonable medication. These breakthrough findings may have important implications for innovative drug research and the future development of treatments for AP. PMID:28487653
Kinase activation through dimerization by human SH2-B.

PubMed

Nishi, Masahiro; Werner, Eric D; Oh, Byung-Chul; Frantz, J Daniel; Dhe-Paganon, Sirano; Hansen, Lone; Lee, Jongsoon; Shoelson, Steven E

2005-04-01

The isoforms of SH2-B, APS, and Lnk form a family of signaling proteins that have been described as activators, mediators, or inhibitors of cytokine and growth factor signaling. We now show that the three alternatively spliced isoforms of human SH2-B readily homodimerize in yeast two-hybrid and cellular transfections assays, and this is mediated specifically by a unique domain in its amino terminus. Consistent with previous reports, we further show that the SH2 domains of SH2-B and APS bind JAK2 at Tyr813. These findings suggested a model in which two molecules of SH2-B or APS homodimerize with their SH2 domains bound to two JAK2 molecules, creating heterotetrameric JAK2-(SH2-B)2-JAK2 or JAK2-(APS)2-JAK2 complexes. We further show that APS and SH2-B isoforms heterodimerize. At lower levels of SH2-B or APS expression, dimerization approximates two JAK2 molecules to induce transactivation. At higher relative concentrations of SH2-B or APS, kinase activation is blocked. SH2-B or APS homodimerization and SH2-B/APS heterodimerization thus provide direct mechanisms for activating and inhibiting JAK2 and other kinases from the inside of the cell and for potentiating or attenuating cytokine and growth factor receptor signaling when ligands are present.
Factor Xa Mediates Calcium Flux in Endothelial Cells and is Potentiated by Igg From Patients With Lupus and/or Antiphospholipid Syndrome.

PubMed

Artim-Esen, Bahar; Smoktunowicz, Natalia; McDonnell, Thomas; Ripoll, Vera M; Pericleous, Charis; Mackie, Ian; Robinson, Eifion; Isenberg, David; Rahman, Anisur; Ioannou, Yiannis; Chambers, Rachel C; Giles, Ian

2017-09-07

Factor (F) Xa reactive IgG isolated from patients with antiphospholipid syndrome (APS) display higher avidity binding to FXa with greater coagulant effects compared to systemic lupus erythematosus (SLE) non APS IgG. FXa signalling via activation of protease-activated receptors (PAR) leads to increased intracellular calcium (Ca 2+ ). Therefore, we measured alterations in Ca 2+ levels in human umbilical vein endothelial cells (HUVEC) following FXa-mediated PAR activation and investigated whether FXa reactive IgG from patients with APS or SLE/APS- alter these responses. We observed concentration-dependent induction of Ca 2+ release by FXa that was potentiated by APS-IgG and SLE/APS- IgG compared to healthy control subjects' IgG, and FXa alone. APS-IgG and SLE/APS- IgG increased FXa mediated NFκB signalling and this effect was fully-retained in the affinity purified anti-FXa IgG sub-fraction. Antagonism of PAR-1 and PAR-2 reduced FXa-induced Ca 2+ release. Treatment with a specific FXa inhibitor, hydroxychloroquine or fluvastatin significantly reduced FXa-induced and IgG-potentiated Ca 2+ release. In conclusion, PAR-1 and PAR-2 are involved in FXa-mediated intracellular Ca 2+ release in HUVEC and FXa reactive IgG from patients with APS and/or SLE potentiate this effect. Further work is required to explore the potential use of IgG FXa reactivity as a novel biomarker to stratify treatment with FXa inhibitors in these patients.
An ecological systems examination of elder abuse: a week in the life of adult protective services.

PubMed

Wangmo, Tenzin; Teaster, Pamela B; Grace, James; Wong, Wilson; Mendiondo, Marta S; Blandford, Caitlin; Fisher, Steve; Fardo, David W

2014-01-01

Using Bronfenbrenner's ecological systems model, this study examined allegations of elder abuse made to Kentucky Adult Protective Services (APS) and the investigation that followed, in order to understand how APS addressed the needs of abused elders. Elder abuse allegations made to APS during the study week were collected using 3 study tools. Allegations and resulting investigations were analyzed. During the study week, APS received 1,002 calls alleging elder abuse. Of these, 483 were categorized as reports needing protective services, with 177 reports screened in for investigation and 167 actually investigated. Results describe characteristics of abuse calls, investigations, victims, perpetrators, and total investigation times. Substantiation ratio, recidivism, and whether investigation increased or decreased the risk of abuse were also assessed. An examination of APS casework through the lens of nested systems frames the study findings and discussion. Such an examination has the potential to improve the quality of services provided to older adults.
Risk factor differences in calcified and noncalcified aortic plaque: the Framingham Heart Study.

PubMed

Chuang, Michael L; Gona, Philimon; Oyama-Manabe, Noriko; Manders, Emily S; Salton, Carol J; Hoffmann, Udo; Manning, Warren J; O'Donnell, Christopher J

2014-07-01

The objective of this study was to determine the prevalence and risk factor (RF) correlates of aortic plaque (AP) detected by cardiovascular magnetic resonance (CMR), which mainly shows noncalcified plaques, and by noncontrast computed tomography (CT), which best depicts calcified plaques, in community-dwelling adults. A total of 1016 Framingham Heart Study Offspring cohort members (64 ± 9 years; 474 men) underwent CMR and CT of the aorta. Potential RFs for AP (age; sex; body mass index; blood pressure; low-density lipoprotein and high-density lipoprotein cholesterol; fasting glucose; C-reactive protein; prevalent hypertension, diabetes mellitus, smoking; use of antihypertensive, diabetes mellitus, or lipid-lowering drugs) were compared between participants, with zero versus nonzero AP by CMR and by CT. Candidate RFs attaining P<0.05 for difference with either imaging modality were entered into multivariable logistic regression models adjusting for age, sex, and other RFs. Odds ratios were calculated for modality-specific prevalence of AP. Associations between RFs and continuous measures of AP were assessed using Tobit regression. Prevalence of CMR and CT AP was 49% and 82%, respectively. AP burdens by CMR and CT were correlated, r=0.28, P<0.0001. Increasing age and smoking were associated with prevalent AP by both CMR and CT. Additionally, prevalent AP by CMR was associated with female sex and fasting glucose and prevalent AP by CT with hypertension treatment and adverse lipid profile. AP by CMR and CT are both associated with smoking and increasing age, but other RFs differ between calcified and noncalcified AP. The relative predictive value of AP detected by CMR versus by CT for incident cardiovascular events remains to be determined. © 2014 American Heart Association, Inc.
Health in All Policies in South Australia: what has supported early implementation?

PubMed

Delany, Toni; Lawless, Angela; Baum, Frances; Popay, Jennie; Jones, Laura; McDermott, Dennis; Harris, Elizabeth; Broderick, Danny; Marmot, Michael

2016-12-01

Health in All Policies (HiAP) is a policy development approach that facilitates intersectoral responses to addressing the social determinants of health and health equity whilst, at the same time, contributing to policy priorities across the various sectors of government. Given that different models of HiAP have been implemented in at least 16 countries, there is increasing interest in how its effectiveness can be optimized. Much of the existing literature on HiAP remains descriptive, however, and lacks critical, empirically informed analyses of the elements that support implementation. Furthermore, literature on HiAP, and intersectoral action more generally, provides little detail on the practical workings of policy collaborations. This paper contributes empirical findings from a multi-method study of HiAP implementation in South Australia (SA) between 2007 and 2013. It considers the views of public servants and presents analysis of elements that have supported, and impeded, implementation of HiAP in SA. We found that HiAP has been implemented in SA using a combination of interrelated elements. The operation of these elements has provided a strong foundation, which suggests the potential for HiAP to extend beyond being an isolated strategy, to form a more integrated and systemic mechanism of policy-making. We conclude with learnings from the SA experience of HiAP implementation to inform the ongoing development and implementation of HiAP in SA and internationally. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Changes in extracellular pH and myocardial ischaemia alter the cardiac effects of diadenosine tetraphosphate and pentaphosphate

PubMed Central

Stavrou, Brigitte M; Beck, Caroline; Flores, Nicholas A

2001-01-01

The structural conformation of diadenosine tetraphosphate (Ap4A) and pentaphosphate (Ap5A) has been reported to alter as pH is reduced. As such, it is possible that the cardiac effects of Ap4A and Ap5A vary during acidosis and myocardial ischaemia due to changes in ligand structure, receptor proteins or intracellular signalling. We investigated whether the cardiac electrophysiological and coronary vasomotor effects of Ap4A and Ap5A are preserved under conditions of extracellular acidosis (pH 6.5) and alkalosis (pH 8.5) and whether Ap4A has any electrophysiological or antiarrhythmic effects during ischaemia. Transmembrane right ventricular action potentials, refractory periods and coronary perfusion pressure were recorded from isolated, Langendorff-perfused guinea-pig hearts under constant flow conditions. The effects of 1 nM and 1 μM Ap4A and Ap5A were studied at pH 7.4, 6.5 and 8.5. The effects of 1 μM Ap4A were studied during global low-flow ischaemia and reperfusion. At pH 7.4, Ap4A and Ap5A increased action potential duration (APD95) and refractory period (RP) and reduced coronary perfusion pressure. The electrophysiological effects were absent at pH 6.5 while the reductions in perfusion pressure were attenuated. At pH 8.5, Ap4A increased RP but the effects of Ap4A and Ap5A on perfusion pressure were attenuated. During ischaemia, Ap4A had no antiarrhythmic or electrophysiological effects. These data demonstrate the importance of extracellular pH in influencing the effects of Ap4A and Ap5A on the heart and indicate that any potentially cardioprotective effects of these compounds during normal perfusion at physiological pH are absent during ischaemia. PMID:11588119
Long-term Treatment with Oriental Medicinal Herb Artemisia princeps Alters Neuroplasticity in a Rat Model of Ovarian Hormone Deficiency

PubMed Central

Kim, Hyun-Bum; Kwon, Byeong-Jae; Cho, Hyun-Ji; Kim, Ji-Won; Chon, Jeong-Woo; Do, Moon-Ho; Park, Sang-Yong; Kim, Sun-Yeou; Maeng, Sung-Ho; Park, Yoo-Kyoung

2015-01-01

Artemisia princeps (AP) is a flowering perennial used as a traditional medicine and dietary supplement across East Asia. No study has yet assessed its effects on synaptic plasticity in hippocampus and much less in a model of ovarian hormone deficiency. We examined the influence of chronic oral AP ethanol extract treatment in ovariectomized rats on the induction of long-term depression in a representative synapse (CA3-CA1) of the hippocampus. Ovariectomized rats demonstrated lower trabecular mean bone mineral densities than sham, validating the establishment of pathology. Against this background of pathology, AP-treated ovariectomized rats exhibited attenuated long-term depression (LTD) in CA1 relative to water-treated controls as measured by increased field excitatory post-synaptic potentials (fEPSP) activation averages over the post-stimulation period. While pathological significance of long-term depression (LTD) in ovariectomized rats is conflicting, that AP treatment significantly affected its induction offers justification for further study of its influences on plasticity and its related disorders. PMID:25792871
Genetic dissection of ion currents underlying all-or-none action potentials in C. elegans body-wall muscle cells

PubMed Central

Liu, Ping; Ge, Qian; Chen, Bojun; Salkoff, Lawrence; Kotlikoff, Michael I; Wang, Zhao-Wen

2011-01-01

Although the neuromuscular system of C. elegans has been studied intensively, little is known about the properties of muscle action potentials (APs). By combining mutant analyses with in vivo electrophysiological recording techniques and Ca2+ imaging, we have established the fundamental properties and molecular determinants of body-wall muscle APs. We show that, unlike mammalian skeletal muscle APs, C. elegans muscle APs occur in spontaneous trains, do not require the function of postsynaptic receptors, and are all-or-none overshooting events, rather than graded potentials as has been previously reported. Furthermore, we show that muscle APs depend on Ca2+ entry through the L-type Ca2+ channel EGL-19 with a contribution from the T-type Ca2+ channel CCA-1. Both the Shaker K+ channel SHK-1 and the Ca2+/Cl−-gated K+ channel SLO-2 play important roles in controlling the speed of membrane repolarization, the amplitude of afterhyperpolarization (AHP) and the pattern of AP firing; SLO-2 is also important in setting the resting membrane potential. Finally, AP-elicited elevations of [Ca2+]i require both EGL-19 and the ryanodine receptor UNC-68. Thus, like mammalian skeletal muscle, C. elegans body-wall myocytes generate all-or-none APs, which evoke Ca2+ release from the sarcoplasmic reticulum (SR), although the specific ion channels used for AP upstroke and repolarization differ. PMID:21059759
Loss of AP-5 results in accumulation of aberrant endolysosomes: defining a new type of lysosomal storage disease

PubMed Central

Hirst, Jennifer; Edgar, James R.; Esteves, Typhaine; Darios, Frédéric; Madeo, Marianna; Chang, Jaerak; Roda, Ricardo H.; Dürr, Alexandra; Anheim, Mathieu; Gellera, Cinzia; Li, Jun; Züchner, Stephan; Mariotti, Caterina; Stevanin, Giovanni; Blackstone, Craig; Kruer, Michael C.; Robinson, Margaret S.

2015-01-01

Adaptor proteins (AP 1–5) are heterotetrameric complexes that facilitate specialized cargo sorting in vesicular-mediated trafficking. Mutations in AP5Z1, encoding a subunit of the AP-5 complex, have been reported to cause hereditary spastic paraplegia (HSP), although their impact at the cellular level has not been assessed. Here we characterize three independent fibroblast lines derived from skin biopsies of patients harbouring nonsense mutations in AP5Z1 and presenting with spastic paraplegia accompanied by neuropathy, parkinsonism and/or cognitive impairment. In all three patient-derived lines, we show that there is complete loss of AP-5 ζ protein and a reduction in the associated AP-5 µ5 protein. Using ultrastructural analysis, we show that these patient-derived lines consistently exhibit abundant multilamellar structures that are positive for markers of endolysosomes and are filled with aberrant storage material organized as exaggerated multilamellar whorls, striated belts and ‘fingerprint bodies’. This phenotype can be replicated in a HeLa cell culture model by siRNA knockdown of AP-5 ζ. The cellular phenotype bears striking resemblance to features described in a number of lysosomal storage diseases (LSDs). Collectively, these findings reveal an emerging picture of the role of AP-5 in endosomal and lysosomal homeostasis, illuminates a potential pathomechanism that is relevant to the role of AP-5 in neurons and expands the understanding of recessive HSPs. Moreover, the resulting accumulation of storage material in endolysosomes leads us to propose that AP-5 deficiency represents a new type of LSDs. PMID:26085577
Human In Silico Drug Trials Demonstrate Higher Accuracy than Animal Models in Predicting Clinical Pro-Arrhythmic Cardiotoxicity.

PubMed

Passini, Elisa; Britton, Oliver J; Lu, Hua Rong; Rohrbacher, Jutta; Hermans, An N; Gallacher, David J; Greig, Robert J H; Bueno-Orovio, Alfonso; Rodriguez, Blanca

2017-01-01

Early prediction of cardiotoxicity is critical for drug development. Current animal models raise ethical and translational questions, and have limited accuracy in clinical risk prediction. Human-based computer models constitute a fast, cheap and potentially effective alternative to experimental assays, also facilitating translation to human. Key challenges include consideration of inter-cellular variability in drug responses and integration of computational and experimental methods in safety pharmacology. Our aim is to evaluate the ability of in silico drug trials in populations of human action potential (AP) models to predict clinical risk of drug-induced arrhythmias based on ion channel information, and to compare simulation results against experimental assays commonly used for drug testing. A control population of 1,213 human ventricular AP models in agreement with experimental recordings was constructed. In silico drug trials were performed for 62 reference compounds at multiple concentrations, using pore-block drug models (IC 50 /Hill coefficient). Drug-induced changes in AP biomarkers were quantified, together with occurrence of repolarization/depolarization abnormalities. Simulation results were used to predict clinical risk based on reports of Torsade de Pointes arrhythmias, and further evaluated in a subset of compounds through comparison with electrocardiograms from rabbit wedge preparations and Ca 2+ -transient recordings in human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs). Drug-induced changes in silico vary in magnitude depending on the specific ionic profile of each model in the population, thus allowing to identify cell sub-populations at higher risk of developing abnormal AP phenotypes. Models with low repolarization reserve (increased Ca 2+ /late Na + currents and Na + /Ca 2+ -exchanger, reduced Na + /K + -pump) are highly vulnerable to drug-induced repolarization abnormalities, while those with reduced inward current density (fast/late Na + and Ca 2+ currents) exhibit high susceptibility to depolarization abnormalities. Repolarization abnormalities in silico predict clinical risk for all compounds with 89% accuracy. Drug-induced changes in biomarkers are in overall agreement across different assays: in silico AP duration changes reflect the ones observed in rabbit QT interval and hiPS-CMs Ca 2+ -transient, and simulated upstroke velocity captures variations in rabbit QRS complex. Our results demonstrate that human in silico drug trials constitute a powerful methodology for prediction of clinical pro-arrhythmic cardiotoxicity, ready for integration in the existing drug safety assessment pipelines.
AP® Potential Predicted by PSAT/NMSQT® Scores Using Logistic Regression. Statistical Report 2014-1

ERIC Educational Resources Information Center

Zhang, Xiuyuan; Patel, Priyank; Ewing, Maureen

2014-01-01

AP Potential™ is an educational guidance tool that uses PSAT/NMSQT® scores to identify students who have the potential to do well on one or more Advanced Placement® (AP®) Exams. Students identified as having AP potential, perhaps students who would not have been otherwise identified, should consider enrolling in the corresponding AP course if they…
A non-inactivating high-voltage-activated two-pore Na+ channel that supports ultra-long action potentials and membrane bistability

NASA Astrophysics Data System (ADS)

Cang, Chunlei; Aranda, Kimberly; Ren, Dejian

2014-09-01

Action potentials (APs) are fundamental cellular electrical signals. The genesis of short APs lasting milliseconds is well understood. Ultra-long APs (ulAPs) lasting seconds to minutes also occur in eukaryotic organisms, but their biological functions and mechanisms of generation are largely unknown. Here, we identify TPC3, a previously uncharacterized member of the two-pore channel protein family, as a new voltage-gated Na+ channel (NaV) that generates ulAPs, and that establishes membrane potential bistability. Unlike the rapidly inactivating NaVs that generate short APs in neurons, TPC3 has a high activation threshold, activates slowly and does not inactivate—three properties that help generate long-lasting APs and guard the membrane against unintended perturbation. In amphibian oocytes, TPC3 forms a channel similar to channels induced by depolarization and sperm entry into eggs. TPC3 homologues are present in plants and animals, and they may be important for cellular processes and behaviours associated with prolonged membrane depolarization.
Role of suppression of the inward rectifier current in terminal action potential repolarization in the failing heart.

PubMed

Klein, Michael G; Shou, Matie; Stohlman, Jayna; Solhjoo, Soroosh; Haigney, Myles; Tidwell, Richard R; Goldstein, Robert E; Flagg, Thomas P; Haigney, Mark C

2017-08-01

The failing heart exhibits an increased arrhythmia susceptibility that is often attributed to action potential (AP) prolongation due to significant ion channel remodeling. The inwardly rectifying K + current (I K1 ) has been reported to be reduced, but its contribution to shaping the AP waveform and cell excitability in the failing heart remains unclear. The purpose of this study was to define the effect of I K1 suppression on the cardiac AP and excitability in the normal and failing hearts. We used electrophysiological and pharmacological approaches to investigate I K1 function in a swine tachy-pacing model of heart failure (HF). Terminal repolarization of the AP (TRAP; the time constant of the exponential fit to terminal repolarization) was markedly prolonged in both myocytes and arterially perfused wedges from animals with HF. TRAP was increased by 54.1% in HF myocytes (P < .001) and 26.2% in HF wedges (P = .014). The increase in TRAP was recapitulated by the potent and specific I K1 inhibitor, PA-6 (pentamidine analog 6), indicating that I K1 is the primary determinant of the final phase of repolarization. Moreover, we find that I K1 suppression reduced the ratio of effective refractory period to AP duration at 90% of repolarization, permitting re-excitation before full repolarization, reduction of AP upstroke velocity, and likely promotion of slow conduction. Using an objective measure of terminal repolarization, we conclude that I K1 is the major determinant of the terminal repolarization time course. Moreover, suppression of I K1 prolongs repolarization and reduces postrepolarization refractoriness without marked effects on the overall AP duration. Collectively, these findings demonstrate how I K1 suppression may contribute to arrhythmogenesis in the failing heart. Published by Elsevier Inc.
Brugada syndrome and ischemia-induced ST-segment elevation. Similarities and differences#

PubMed Central

Di Diego, José M.; Fish, Jeffrey M.; Antzelevitch, Charles

2006-01-01

Introduction ST-Segment elevation is a common electrocardiogram (ECG) manifestation of acute transmural myocardial ischemia in leads facing the injury. Acute myocardial ischemia involving the right-ventricular (RV) outflow tract is known to induce a Brugada-like ECG. In this paper, we examined the electrophysiological bases for the similarities between the ECG characteristics of the Brugada syndrome model induced by terfenadine (5 μmol/L) and the ECG manifestations of the acute transmural no-flow ischemia model. Methods For both experimental simulations, we used isolated arterially perfused canine RV wedge preparations to record transmembrane action potentials (AP) from endocardium and epicardium together with a transmural pseudo-ECG (ECG); basic cycle length = 400 to 2000 ms. Results In the presence of a prominent Ito-mediated AP notch, no-flow ischemia causes true ST-segment elevation because of selective depression and loss of the AP dome at some epicardial sites. In the absence of a prominent AP notch, ischemia ultimately produces an apparent ST-segment elevation, which is secondary to a prolongation of the R wave caused by marked transmural conduction delays. Similarly, in the Brugada syndrome model generated in preparations displaying a large epicardial Ito, ST-segment elevation was due to loss of the epicardial AP dome at some sites but not at others. Transmural conduction delay giving the appearance of ST-segment elevation is also observed in the Brugada model in preparations exhibiting smaller AP notch. In both models, propagation of the dome from the site at which it is maintained to a site at which it is lost may result in closely coupled phase 2 reentrant extrasystoles. Conclusion Our results suggest that Ito can modulate the electrocardiographic manifestation of acute ischemia as well as that of the Brugada syndrome, and that both clinical entities are the result of a similar electrophysiological substrate. PMID:16226068
A Novel Cell Wall Lipopeptide Is Important for Biofilm Formation and Pathogenicity of Mycobacterium avium subspecies paratuberculosis

PubMed Central

Wu, Chia-wei; Schmoller, Shelly K.; Bannantine, John P.; Eckstein, Torsten M.; Inamine, Julie M.; Livesey, Michael; Albrecht, Ralph; Talaat, Adel M.

2009-01-01

Biofilm formation by pathogenic bacteria plays a key role in their pathogenesis. Previously, the pstA gene was shown to be involved in the virulence of Mycobacterium avium subspecies paratuberculosis (M. ap), the causative agent of Johne's disease in cattle and a potential risk factor for Crohn's disease. Scanning electron microscopy and colonization levels of the M. ap mutant indicated that the pstA gene significantly contributes to the ability of M. ap to form biofilms. Digital measurements taken during electron microscopy identified a unique morphology for the ΔpstA mutant, which consisted of significantly shorter bacilli than the wild type. Analysis of the lipid profiles of the mycobacterial strains identified a novel lipopeptide that was present in the cell wall extracts of wild-type M. ap, but missing from the ΔpstA mutant. Interestingly, the calf infection model suggested that pstA contributes to intestinal invasion of M. ap. Furthermore, immunoblot analysis of peptides encoded by pstA identified a specific and significant level of immunogenicity. Taken together, our analysis revealed a novel cell wall component that could contribute to biofilm formation and to the virulence and immunogenicity of M. ap. Molecular tools to better control M. ap infections could be developed utilizing the presented findings. PMID:19490829

Self-propulsion against a moving membrane: Enhanced accumulation and drag force

NASA Astrophysics Data System (ADS)

Marini Bettolo Marconi, U.; Sarracino, A.; Maggi, C.; Puglisi, A.

2017-09-01

Self-propulsion (SP) is a main feature of active particles (AP), such as bacteria or biological micromotors, distinguishing them from passive colloids. A renowned consequence of SP is accumulation at static interfaces, even in the absence of hydrodynamic interactions. Here we address the role of SP in the interaction between AP and a moving semipermeable membrane. In particular, we implement a model of noninteracting AP in a channel crossed by a partially penetrable wall, moving at a constant velocity c . With respect to both the cases of passive colloids with c >0 and AP with c =0 , the AP with finite c show enhancement of accumulation in front of the obstacle and experience a largely increased drag force. This effect is understood in terms of an effective potential localised at the interface between particles and membrane, of height proportional to c τ /ξ , where τ is the AP's reorientation time and ξ the width characterizing the surface's smoothness (ξ →0 for hard core obstacles). An approximate analytical scheme is able to reproduce the observed density profiles and the measured drag force, in very good agreement with numerical simulations. The effects discussed here can be exploited for automatic selection and filtering of AP with desired parameters.
Natural Firing Patterns Imply Low Sensitivity of Synaptic Plasticity to Spike Timing Compared with Firing Rate

PubMed Central

Wallisch, Pascal; Ostojic, Srdjan

2016-01-01

Synaptic plasticity is sensitive to the rate and the timing of presynaptic and postsynaptic action potentials. In experimental protocols inducing plasticity, the imposed spike trains are typically regular and the relative timing between every presynaptic and postsynaptic spike is fixed. This is at odds with firing patterns observed in the cortex of intact animals, where cells fire irregularly and the timing between presynaptic and postsynaptic spikes varies. To investigate synaptic changes elicited by in vivo-like firing, we used numerical simulations and mathematical analysis of synaptic plasticity models. We found that the influence of spike timing on plasticity is weaker than expected from regular stimulation protocols. Moreover, when neurons fire irregularly, synaptic changes induced by precise spike timing can be equivalently induced by a modest firing rate variation. Our findings bridge the gap between existing results on synaptic plasticity and plasticity occurring in vivo, and challenge the dominant role of spike timing in plasticity. SIGNIFICANCE STATEMENT Synaptic plasticity, the change in efficacy of connections between neurons, is thought to underlie learning and memory. The dominant paradigm posits that the precise timing of neural action potentials (APs) is central for plasticity induction. This concept is based on experiments using highly regular and stereotyped patterns of APs, in stark contrast with natural neuronal activity. Using synaptic plasticity models, we investigated how irregular, in vivo-like activity shapes synaptic plasticity. We found that synaptic changes induced by precise timing of APs are much weaker than suggested by regular stimulation protocols, and can be equivalently induced by modest variations of the AP rate alone. Our results call into question the dominant role of precise AP timing for plasticity in natural conditions. PMID:27807166
A Computational Model of the Ionic Currents, Ca2+ Dynamics and Action Potentials Underlying Contraction of Isolated Uterine Smooth Muscle

PubMed Central

Tong, Wing-Chiu; Choi, Cecilia Y.; Karche, Sanjay; Holden, Arun V.; Zhang, Henggui; Taggart, Michael J.

2011-01-01

Uterine contractions during labor are discretely regulated by rhythmic action potentials (AP) of varying duration and form that serve to determine calcium-dependent force production. We have employed a computational biology approach to develop a fuller understanding of the complexity of excitation-contraction (E-C) coupling of uterine smooth muscle cells (USMC). Our overall aim is to establish a mathematical platform of sufficient biophysical detail to quantitatively describe known uterine E-C coupling parameters and thereby inform future empirical investigations of physiological and pathophysiological mechanisms governing normal and dysfunctional labors. From published and unpublished data we construct mathematical models for fourteen ionic currents of USMCs: currents (L- and T-type), current, an hyperpolarization-activated current, three voltage-gated currents, two -activated current, -activated current, non-specific cation current, - exchanger, - pump and background current. The magnitudes and kinetics of each current system in a spindle shaped single cell with a specified surface area∶volume ratio is described by differential equations, in terms of maximal conductances, electrochemical gradient, voltage-dependent activation/inactivation gating variables and temporal changes in intracellular computed from known fluxes. These quantifications are validated by the reconstruction of the individual experimental ionic currents obtained under voltage-clamp. Phasic contraction is modeled in relation to the time constant of changing . This integrated model is validated by its reconstruction of the different USMC AP configurations (spikes, plateau and bursts of spikes), the change from bursting to plateau type AP produced by estradiol and of simultaneous experimental recordings of spontaneous AP, and phasic force. In summary, our advanced mathematical model provides a powerful tool to investigate the physiological ionic mechanisms underlying the genesis of uterine electrical E-C coupling of labor and parturition. This will furnish the evolution of descriptive and predictive quantitative models of myometrial electrogenesis at the whole cell and tissue levels. PMID:21559514
Electrophysiological characteristics of IB4-negative TRPV1-expressing muscle afferent DRG neurons.

PubMed

Lin, Yi-Wen; Chen, Chih-Cheng

2015-01-01

Muscle afferent neurons that express transient receptor potential vanilloid type I (TRPV1) are responsible for muscle pain associated with tissue acidosis. We have previously found that TRPV1 of isolectin B4 (IB4)-negative muscle nociceptors plays an important role in the acid-induced hyperalgesic priming and the development of chronic hyperalgesia in a mouse model of fibromyalgia. To understand the electrophysiological properties of the TRPV1-expressing muscle afferent neurons, we used whole-cell patch clamp recording to study the acid responsiveness and action potential (AP) configuration of capsaicin-sensitive neurons innervating to gastrocnemius muscle. Here we showed that IB4-negative TRPV1-expressing muscle afferent neurons are heterogeneous in terms of cell size, resting membrane potential, AP configuration, tetrodotoxin (TTX)-resistance, and acid-induced current (I acid), as well as capsaicin-induced current (I cap). TRPV1-expressing neurons were all acid-sensitive and could be divided into two acid-sensitive groups depending on an acid-induced sustained current (type I) or an acid-induced biphasic ASIC3-like current (type II). Type I TRPV1-expressing neurons were distinguishable from type II TRPV1-expressing neurons in AP overshoot, after-hyperpolarization duration, and all I acid parameters, but not in AP threshold, TTX-resistance, resting membrane potential, and I cap parameters. These differential biophysical properties of TRPV1-expressing neurons might partially annotate their different roles involved in the development and maintenance of chronic muscle pain.
Identification and characterization of a transient outward K+ current in human induced pluripotent stem cell-derived cardiomyocytes

PubMed Central

Cordeiro, Jonathan M.; Nesterenko, Vladislav V.; Sicouri, Serge; Goodrow, Robert J.; Treat, Jacqueline A.; Desai, Mayurika; Wu, Yuesheng; Doss, Michael Xavier; Antzelevitch, Charles; Di Diego, José M.

2013-01-01

Background The ability to recapitulate mature adult phenotypes is critical to the development of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) as models of disease. The present study examines the characteristics of the transient outward current (Ito) and its contribution to the hiPSC-CM action potential (AP). Method Embryoid bodies were made from a hiPS cell line reprogrammed with Oct4, Nanog, Lin28 and Sox2. Sharp microelectrodes were used to record APs from beating-clusters (BC) and patch-clamp techniques were used to record Ito in single hiPSC-CM. mRNA levels of Kv1.4, KChIP2 and Kv4.3 were quantified from BCs. Results BCs exhibited spontaneous beating (60.5 ± 2.6 bpm) and maximum-diastolic-potential (MDP) of 67.8 ± 0.8 mV (n = 155). A small 4-aminopyridine-sensitive phase-1-repolarization was observed in only 6/155 BCs. A robust Ito was recorded in the majority of cells (13.7 ± 1.9 pA/pF at +40 mV; n = 14). Recovery of Ito from inactivation (at −80 mV) showed slow kinetics (τ1 = 200 ± 110 ms (12%) and τ2 = 2380 ± 240 ms (80%)) accounting for its minimal contribution to the AP. Transcript data revealed relatively high expression of Kv1.4 and low expression of KChIP2 compared to human native ventricular tissues. Mathematical modeling predicted that restoration of IK1 to normal levels would result in a more negative MDP and a prominent phase-1-repolarization. Conclusion The slow recovery kinetics of Ito coupled with a depolarized MDP account for the lack of an AP notch in the majority of hiPSC-CM. These characteristics reveal a deficiency for the development of in vitro models of inherited cardiac arrhythmia syndromes in which Ito-induced AP notch is central to the disease phenotype. PMID:23542310
A supercritical density of fast Na+ channels ensures rapid propagation of action potentials in GABAergic interneuron axons

PubMed Central

Hu, Hua; Jonas, Peter

2014-01-01

Fast-spiking, parvalbumin-expressing GABAergic interneurons/basket cells (BCs) play a key role in feedforward and feedback inhibition, gamma oscillations, and complex information processing. For these functions, fast propagation of action potentials (APs) from the soma to the presynaptic terminals is important. However, the functional properties of interneuron axons remain elusive. Here, we examined interneuron axons by confocally targeted subcellular patch-clamp recording in rat hippocampal slices. APs were initiated in the proximal axon ~20 μm from the soma, and propagated to the distal axon with high reliability and speed. Subcellular mapping revealed a stepwise increase of Na+ conductance density from the soma to the proximal axon, followed by a further gradual increase in the distal axon. Active cable modeling and experiments with partial channel block indicated that low axonal Na+ conductance density was sufficient for reliability, but high Na+ density was necessary for both speed of propagation and fast-spiking AP phenotype. Our results suggest that a supercritical density of Na+ channels compensates for the morphological properties of interneuron axons (small segmental diameter, extensive branching, and high bouton density), ensuring fast AP propagation and high-frequency repetitive firing. PMID:24657965
Can optical recordings of membrane potential be used to screen for drug-induced action potential prolongation in single cardiac myocytes?

PubMed

Hardy, M E L; Lawrence, C L; Standen, N B; Rodrigo, G C

2006-01-01

Potential-sensitive dyes have primarily been used to optically record action potentials (APs) in whole heart tissue. Using these dyes to record drug-induced changes in AP morphology of isolated cardiac myocytes could provide an opportunity to develop medium throughout assays for the pharmaceutical industry. Ideally, this requires that the dye has a consistent and rapid response to membrane potential, is insensitive to movement, and does not itself affect AP morphology. We recorded the AP from isolated adult guinea-pig ventricular myocytes optically using di-8-ANEPPS in a single-excitation dual-emission ratiometric system, either separately in electrically field stimulated myocytes, or simultaneously with an electrical AP recorded with a patch electrode in the whole-cell bridge mode. The ratio of di-8-ANEPPS fluorescence signal was calibrated against membrane potential using a switch-clamp to voltage clamp the myocyte. Our data show that the ratio of the optical signals emitted at 560/620 nm is linearly related to voltage over the voltage range of an AP, producing a change in ratio of 7.5% per 100 mV, is unaffected by cell movement and is identical to the AP recorded simultaneously with a patch electrode. However, the APD90 recorded optically in myocytes loaded with di-8-ANEPPS was significantly longer than in unloaded myocytes recorded with a patch electrode (355.6+/-13.5 vs. 296.2+/-16.2 ms; p<0.01). Despite this effect, the apparent IC50 for cisapride, which prolongs the AP by blocking IKr, was not significantly different whether determined optically or with a patch electrode (91+/-46 vs. 81+/-20 nM). These data show that the optical AP recorded ratiometrically using di-8-ANEPPS from a single ventricular myocyte accurately follows the action potential morphology. This technique can be used to estimate the AP prolonging effects of a compound, although di-8-ANEPPS itself prolongs APD90. Optical dyes require less technical skills and are less invasive than conventional electrophysiological techniques and, when coupled to ventricular myocytes, decreases animal usage and facilitates higher throughput assays.
A human ventricular cell model for investigation of cardiac arrhythmias under hyperkalaemic conditions.

PubMed

Carro, Jesús; Rodríguez, José Félix; Laguna, Pablo; Pueyo, Esther

2011-11-13

In this study, several modifications were introduced to a recently proposed human ventricular action potential (AP) model so as to render it suitable for the study of ventricular arrhythmias. These modifications were driven by new sets of experimental data available from the literature and the analysis of several well-established cellular arrhythmic risk biomarkers, namely AP duration at 90 per cent repolarization (APD(90)), AP triangulation, calcium dynamics, restitution properties, APD(90) adaptation to abrupt heart rate changes, and rate dependence of intracellular sodium and calcium concentrations. The proposed methodology represents a novel framework for the development of cardiac cell models. Five stimulation protocols were applied to the original model and the ventricular AP model developed here to compute the described arrhythmic risk biomarkers. In addition, those models were tested in a one-dimensional fibre in which hyperkalaemia was simulated by increasing the extracellular potassium concentration, [K(+)](o). The effective refractory period (ERP), conduction velocity (CV) and the occurrence of APD alternans were investigated. Results show that modifications improved model behaviour as verified by: (i) AP triangulation well within experimental limits (the difference between APD at 50 and 90 per cent repolarization being 78.1 ms); (ii) APD(90) rate adaptation dynamics characterized by fast and slow time constants within physiological ranges (10.1 and 105.9 s); and (iii) maximum S1S2 restitution slope in accordance with experimental data (S(S1S2)=1.0). In simulated tissues under hyperkalaemic conditions, APD(90) progressively shortened with the degree of hyperkalaemia, whereas ERP increased once a threshold in [K(+)](o) was reached ([K(+)](o)≈6 mM). CV decreased with [K(+)](o), and conduction was blocked for [K(+)](o)>10.4 mM. APD(90) alternans were observed for [K(+)](o)>9.8 mM. Those results adequately reproduce experimental observations. This study demonstrated the value of basing the development of AP models on the computation of arrhythmic risk biomarkers, as opposed to joining together independently derived ion channel descriptions to produce a whole-cell AP model, with the new framework providing a better picture of the model performance under a variety of stimulation conditions. On top of replicating experimental data at single-cell level, the model developed here was able to predict the occurrence of APD(90) alternans and areas of conduction block associated with high [K(+)](o) in tissue, which is of relevance for the investigation of the arrhythmogenic substrate in ischaemic hearts.
Tribology studies of the natural knee using an animal model in a new whole joint natural knee simulator.

PubMed

Liu, Aiqin; Jennings, Louise M; Ingham, Eileen; Fisher, John

2015-09-18

The successful development of early-stage cartilage and meniscus repair interventions in the knee requires biomechanical and biotribological understanding of the design of the therapeutic interventions and their tribological function in the natural joint. The aim of this study was to develop and validate a porcine knee model using a whole joint knee simulator for investigation of the tribological function and biomechanical properties of the natural knee, which could then be used to pre-clinically assess the tribological performance of cartilage and meniscal repair interventions prior to in vivo studies. The tribological performance of standard artificial bearings in terms of anterior-posterior (A/P) shear force was determined in a newly developed six degrees of freedom tribological joint simulator. The porcine knee model was then developed and the tribological properties in terms of shear force measurements were determined for the first time for three levels of biomechanical constraints including A/P constrained, spring force semi-constrained and A/P unconstrained conditions. The shear force measurements showed higher values under the A/P constrained condition (predominantly sliding motion) compared to the A/P unconstrained condition (predominantly rolling motion). This indicated that the shear force simulation model was able to differentiate between tribological behaviours when the femoral and tibial bearing was constrained to slide or/and roll. Therefore, this porcine knee model showed the potential capability to investigate the effect of knee structural, biomechanical and kinematic changes, as well as different cartilage substitution therapies on the tribological function of natural knee joints. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.
Andrographis paniculata Diterpenoids Protect against Radiation-Induced Transformation in BALB/3T3 Cells.

PubMed

Nantajit, Danupon; Jetawattana, Suwimol; Suriyo, Tawit; Grdina, David J; Satayavivad, Jutamaad

2017-07-01

One of the most concerning side effects of exposure to radiation are the carcinogenic risks. To reduce the negative effects of radiation, both cytoprotective and radioprotective agents have been developed. However, little is known regarding their potential for suppressing carcinogenesis. Andrographis paniculata , a plant, with multiple medicinal uses that is commonly used in traditional medicine, has three major constituents known to have cellular antioxidant activity: andrographolide (AP1); 14-deoxy-11,12-didehydroandrographolide (AP3); and neoandrographolide (AP4). In our study, we tested these elements for their radioprotective properties as well as their anti-neoplastic effects on transformation using the BALB/3T3 cell model. All three compounds were able to reduce radiation-induced DNA damage. However, AP4 appeared to have superior radioprotective properties compared to the other two compounds, presumably by protecting mitochondrial function. The compound was able to suppress radiation-induced cellular transformation through inhibition of STAT3. Treatment with AP4 also reduced expressions of MMP-2 and MMP-9. These results suggest that AP4 could be further studied and developed into an anti-transformation/carcinogenic drug as well as a radioprotective agent.
Clathrin and AP1 are required for apical sorting of glycosyl phosphatidyl inositol-anchored proteins in biosynthetic and recycling routes in Madin-Darby canine kidney cells.

PubMed

Castillon, Guillaume A; Burriat-Couleru, Patricia; Abegg, Daniel; Criado Santos, Nina; Watanabe, Reika

2018-03-01

Recently, studies in animal models demonstrate potential roles for clathrin and AP1 in apical protein sorting in epithelial tissue. However, the precise functions of these proteins in apical protein transport remain unclear. Here, we reveal mistargeting of endogenous glycosyl phosphatidyl inositol-anchored proteins (GPI-APs) and soluble secretory proteins in Madin-Darby canine kidney (MDCK) cells upon clathrin heavy chain or AP1 subunit knockdown (KD). Using a novel directional endocytosis and recycling assay, we found that these KD cells are not only affected for apical sorting of GPI-APs in biosynthetic pathway but also for their apical recycling and basal-to-apical transcytosis routes. The apical distribution of the t-SNARE syntaxin 3, which is known to be responsible for selective targeting of various apical-destined cargo proteins in both biosynthetic and endocytic routes, is compromised suggesting a molecular explanation for the phenotype in KD cells. Our results demonstrate the importance of biosynthetic and endocytic routes for establishment and maintenance of apical localization of GPI-APs in polarized MDCK cells. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
The aspartic proteinase family of three Phytophthora species

PubMed Central

2011-01-01

Background Phytophthora species are oomycete plant pathogens with such major social and economic impact that genome sequences have been determined for Phytophthora infestans, P. sojae and P. ramorum. Pepsin-like aspartic proteinases (APs) are produced in a wide variety of species (from bacteria to humans) and contain conserved motifs and landmark residues. APs fulfil critical roles in infectious organisms and their host cells. Annotation of Phytophthora APs would provide invaluable information for studies into their roles in the physiology of Phytophthora species and interactions with their hosts. Results Genomes of Phytophthora infestans, P. sojae and P. ramorum contain 11-12 genes encoding APs. Nine of the original gene models in the P. infestans database and several in P. sojae and P. ramorum (three and four, respectively) were erroneous. Gene models were corrected on the basis of EST data, consistent positioning of introns between orthologues and conservation of hallmark motifs. Phylogenetic analysis resolved the Phytophthora APs into 5 clades. Of the 12 sub-families, several contained an unconventional architecture, as they either lacked a signal peptide or a propart region. Remarkably, almost all APs are predicted to be membrane-bound. Conclusions One of the twelve Phytophthora APs is an unprecedented fusion protein with a putative G-protein coupled receptor as the C-terminal partner. The others appear to be related to well-documented enzymes from other species, including a vacuolar enzyme that is encoded in every fungal genome sequenced to date. Unexpectedly, however, the oomycetes were found to have both active and probably-inactive forms of an AP similar to vertebrate BACE, the enzyme responsible for initiating the processing cascade that generates the Aβ peptide central to Alzheimer's Disease. The oomycetes also encode enzymes similar to plasmepsin V, a membrane-bound AP that cleaves effector proteins of the malaria parasite Plasmodium falciparum during their translocation into the host red blood cell. Since the translocation of Phytophthora effector proteins is currently a topic of intense research activity, the identification in Phytophthora of potential functional homologues of plasmepsin V would appear worthy of investigation. Indeed, elucidation of the physiological roles of the APs identified here offers areas for future study. The significant revision of gene models and detailed annotation presented here should significantly facilitate experimental design. PMID:21599950
Conditional depletion of intellectual disability and Parkinsonism candidate gene ATP6AP2 in fly and mouse induces cognitive impairment and neurodegeneration

PubMed Central

Dubos, Aline; Castells-Nobau, Anna; Meziane, Hamid; Oortveld, Merel A.W.; Houbaert, Xander; Iacono, Giovanni; Martin, Christelle; Mittelhaeuser, Christophe; Lalanne, Valérie; Kramer, Jamie M.; Bhukel, Anuradha; Quentin, Christine; Slabbert, Jan; Verstreken, Patrik; Sigrist, Stefan J.; Messaddeq, Nadia; Birling, Marie-Christine; Selloum, Mohammed; Stunnenberg, Henk G.; Humeau, Yann; Schenck, Annette; Herault, Yann

2015-01-01

ATP6AP2, an essential accessory component of the vacuolar H+ ATPase (V-ATPase), has been associated with intellectual disability (ID) and Parkinsonism. ATP6AP2 has been implicated in several signalling pathways; however, little is known regarding its role in the nervous system. To decipher its function in behaviour and cognition, we generated and characterized conditional knockdowns of ATP6AP2 in the nervous system of Drosophila and mouse models. In Drosophila, ATP6AP2 knockdown induced defective phototaxis and vacuolated photoreceptor neurons and pigment cells when depleted in eyes and altered short- and long-term memory when depleted in the mushroom body. In mouse, conditional Atp6ap2 deletion in glutamatergic neurons (Atp6ap2Camk2aCre/0 mice) caused increased spontaneous locomotor activity and altered fear memory. Both Drosophila ATP6AP2 knockdown and Atp6ap2Camk2aCre/0 mice presented with presynaptic transmission defects, and with an abnormal number and morphology of synapses. In addition, Atp6ap2Camk2aCre/0 mice showed autophagy defects that led to axonal and neuronal degeneration in the cortex and hippocampus. Surprisingly, axon myelination was affected in our mutant mice, and axonal transport alterations were observed in Drosophila. In accordance with the identified phenotypes across species, genome-wide transcriptome profiling of Atp6ap2Camk2aCre/0 mouse hippocampi revealed dysregulation of genes involved in myelination, action potential, membrane-bound vesicles and motor behaviour. In summary, ATP6AP2 disruption in mouse and fly leads to cognitive impairment and neurodegeneration, mimicking aspects of the neuropathology associated with ATP6AP2 mutations in humans. Our results identify ATP6AP2 as an essential gene for the nervous system. PMID:26376863
Conditional depletion of intellectual disability and Parkinsonism candidate gene ATP6AP2 in fly and mouse induces cognitive impairment and neurodegeneration.

PubMed

Dubos, Aline; Castells-Nobau, Anna; Meziane, Hamid; Oortveld, Merel A W; Houbaert, Xander; Iacono, Giovanni; Martin, Christelle; Mittelhaeuser, Christophe; Lalanne, Valérie; Kramer, Jamie M; Bhukel, Anuradha; Quentin, Christine; Slabbert, Jan; Verstreken, Patrik; Sigrist, Stefan J; Messaddeq, Nadia; Birling, Marie-Christine; Selloum, Mohammed; Stunnenberg, Henk G; Humeau, Yann; Schenck, Annette; Herault, Yann

2015-12-01

ATP6AP2, an essential accessory component of the vacuolar H+ ATPase (V-ATPase), has been associated with intellectual disability (ID) and Parkinsonism. ATP6AP2 has been implicated in several signalling pathways; however, little is known regarding its role in the nervous system. To decipher its function in behaviour and cognition, we generated and characterized conditional knockdowns of ATP6AP2 in the nervous system of Drosophila and mouse models. In Drosophila, ATP6AP2 knockdown induced defective phototaxis and vacuolated photoreceptor neurons and pigment cells when depleted in eyes and altered short- and long-term memory when depleted in the mushroom body. In mouse, conditional Atp6ap2 deletion in glutamatergic neurons (Atp6ap2(Camk2aCre/0) mice) caused increased spontaneous locomotor activity and altered fear memory. Both Drosophila ATP6AP2 knockdown and Atp6ap2(Camk2aCre/0) mice presented with presynaptic transmission defects, and with an abnormal number and morphology of synapses. In addition, Atp6ap2(Camk2aCre/0) mice showed autophagy defects that led to axonal and neuronal degeneration in the cortex and hippocampus. Surprisingly, axon myelination was affected in our mutant mice, and axonal transport alterations were observed in Drosophila. In accordance with the identified phenotypes across species, genome-wide transcriptome profiling of Atp6ap2(Camk2aCre/0) mouse hippocampi revealed dysregulation of genes involved in myelination, action potential, membrane-bound vesicles and motor behaviour. In summary, ATP6AP2 disruption in mouse and fly leads to cognitive impairment and neurodegeneration, mimicking aspects of the neuropathology associated with ATP6AP2 mutations in humans. Our results identify ATP6AP2 as an essential gene for the nervous system. © The Author 2015. Published by Oxford University Press.
Neurotransmitter Release Can Be Stabilized by a Mechanism That Prevents Voltage Changes Near the End of Action Potentials from Affecting Calcium Currents

PubMed Central

Clarke, Stephen G.; Scarnati, Matthew S.

2016-01-01

At chemical synapses, presynaptic action potentials (APs) activate voltage-gated calcium channels, allowing calcium to enter and trigger neurotransmitter release. The duration, peak amplitude, and shape of the AP falling phase alter calcium entry, which can affect neurotransmitter release significantly. In many neurons, APs do not immediately return to the resting potential, but instead exhibit a period of depolarization or hyperpolarization referred to as an afterpotential. We hypothesized that presynaptic afterpotentials should alter neurotransmitter release by affecting the electrical driving force for calcium entry and calcium channel gating. In support of this, presynaptic calcium entry is affected by afterpotentials after standard instant voltage jumps. Here, we used the mouse calyx of Held synapse, which allows simultaneous presynaptic and postsynaptic patch-clamp recording, to show that the postsynaptic response is affected significantly by presynaptic afterpotentials after voltage jumps. We therefore tested the effects of presynaptic afterpotentials using simultaneous presynaptic and postsynaptic recordings and AP waveforms or real APs. Surprisingly, presynaptic afterpotentials after AP stimuli did not alter calcium channel responses or neurotransmitter release appreciably. We show that the AP repolarization time course causes afterpotential-induced changes in calcium driving force and changes in calcium channel gating to effectively cancel each other out. This mechanism, in which electrical driving force is balanced by channel gating, prevents changes in calcium influx from occurring at the end of the AP and therefore acts to stabilize synaptic transmission. In addition, this mechanism can act to stabilize neurotransmitter release when the presynaptic resting potential changes. SIGNIFICANCE STATEMENT The shape of presynaptic action potentials (APs), particularly the falling phase, affects calcium entry and small changes in calcium influx can produce large changes in postsynaptic responses. We hypothesized that afterpotentials, which often follow APs, affect calcium entry and neurotransmitter release. We tested this in calyx of Held nerve terminals, which allow simultaneous recording of presynaptic calcium currents and postsynaptic responses. Surprisingly, presynaptic afterpotentials did not alter calcium current or neurotransmitter release. We show that the AP falling phase causes afterpotential-induced changes in electrical driving force and calcium channel gating to cancel each other out. This mechanism regulates calcium entry at the end of APs and therefore stabilizes synaptic transmission. This also stabilizes responses when the presynaptic resting potential changes. PMID:27911759
Neurotransmitter Release Can Be Stabilized by a Mechanism That Prevents Voltage Changes Near the End of Action Potentials from Affecting Calcium Currents.

PubMed

Clarke, Stephen G; Scarnati, Matthew S; Paradiso, Kenneth G

2016-11-09

At chemical synapses, presynaptic action potentials (APs) activate voltage-gated calcium channels, allowing calcium to enter and trigger neurotransmitter release. The duration, peak amplitude, and shape of the AP falling phase alter calcium entry, which can affect neurotransmitter release significantly. In many neurons, APs do not immediately return to the resting potential, but instead exhibit a period of depolarization or hyperpolarization referred to as an afterpotential. We hypothesized that presynaptic afterpotentials should alter neurotransmitter release by affecting the electrical driving force for calcium entry and calcium channel gating. In support of this, presynaptic calcium entry is affected by afterpotentials after standard instant voltage jumps. Here, we used the mouse calyx of Held synapse, which allows simultaneous presynaptic and postsynaptic patch-clamp recording, to show that the postsynaptic response is affected significantly by presynaptic afterpotentials after voltage jumps. We therefore tested the effects of presynaptic afterpotentials using simultaneous presynaptic and postsynaptic recordings and AP waveforms or real APs. Surprisingly, presynaptic afterpotentials after AP stimuli did not alter calcium channel responses or neurotransmitter release appreciably. We show that the AP repolarization time course causes afterpotential-induced changes in calcium driving force and changes in calcium channel gating to effectively cancel each other out. This mechanism, in which electrical driving force is balanced by channel gating, prevents changes in calcium influx from occurring at the end of the AP and therefore acts to stabilize synaptic transmission. In addition, this mechanism can act to stabilize neurotransmitter release when the presynaptic resting potential changes. The shape of presynaptic action potentials (APs), particularly the falling phase, affects calcium entry and small changes in calcium influx can produce large changes in postsynaptic responses. We hypothesized that afterpotentials, which often follow APs, affect calcium entry and neurotransmitter release. We tested this in calyx of Held nerve terminals, which allow simultaneous recording of presynaptic calcium currents and postsynaptic responses. Surprisingly, presynaptic afterpotentials did not alter calcium current or neurotransmitter release. We show that the AP falling phase causes afterpotential-induced changes in electrical driving force and calcium channel gating to cancel each other out. This mechanism regulates calcium entry at the end of APs and therefore stabilizes synaptic transmission. This also stabilizes responses when the presynaptic resting potential changes. Copyright © 2016 the authors 0270-6474/16/3611559-14$15.00/0.
Angelica polysaccharides inhibit the growth and promote the apoptosis of U251 glioma cells in vitro and in vivo.

PubMed

Zhang, Wen-Feng; Yang, Yan; Li, Xin; Xu, Da-Yan; Yan, Yu-Li; Gao, Qiao; Jia, Ai-Ling; Duan, Ming-Hua

2017-09-15

Angelica sinensis (Oliv) Diels (Apiaceae) is a traditional medicine that has been used for more than 2000 years in China. It exhibits various therapeutic effects including neuroprotective, anti-oxidant, anti-inflammatory, and immunomodulatory activities. Angelica polysaccharides (APs), bioactive constituents of Angelica have been shown to be responsible for these effects; however, the utility of APs for the treatment of glioma and their mechanism of action remain to be elucidated. In this study, we investigated the inhibitory effects of APs on a glioma cell line and their molecular mechanism of action. U251 cells were utilized to confirm the effects of APs on glioma. The human glioblastoma cell line U251 was utilized for both in vitro and in vivo models, in which we tested the effects of APs. Flow cytometry, gene expression analysis, western blotting, and MTT assays were used to elucidate the effects of APs on cell proliferation, cell cycle, and apoptosis. The results demonstrated that APs significantly inhibited the growth and proliferation of U251 cells and induced their apoptosis. Furthermore, APs effectively reduced the expression of several cell cycle regulators: cyclins D1, B, and E. The apoptosis suppressor protein Bcl-2 was also downregulated, and the expression of pro-apoptotic proteins Bax and cleaved-caspase-3 increased. Additionally, APs inhibited the transforming growth factor (TGF)-β signaling pathway and stimulated the expression of E-cadherin, thus prohibiting cell growth. In conclusion, the results indicate that APs attenuate the tumorigenicity of glioma cells and promote their apoptosis by suppressing the TGF-β signaling pathway. The present study therefore provides evidence of the inhibitory effects of APs against glioma progression, and proposes their potential application as alternative therapeutic agents for glioma. Copyright © 2017 Elsevier GmbH. All rights reserved.
Superresolution imaging reveals activity-dependent plasticity of axon morphology linked to changes in action potential conduction velocity.

PubMed

Chéreau, Ronan; Saraceno, G Ezequiel; Angibaud, Julie; Cattaert, Daniel; Nägerl, U Valentin

2017-02-07

Axons convey information to nearby and distant cells, and the time it takes for action potentials (APs) to reach their targets governs the timing of information transfer in neural circuits. In the unmyelinated axons of hippocampus, the conduction speed of APs depends crucially on axon diameters, which vary widely. However, it is not known whether axon diameters are dynamic and regulated by activity-dependent mechanisms. Using time-lapse superresolution microscopy in brain slices, we report that axons grow wider after high-frequency AP firing: synaptic boutons undergo a rapid enlargement, which is mostly transient, whereas axon shafts show a more delayed and progressive increase in diameter. Simulations of AP propagation incorporating these morphological dynamics predicted bidirectional effects on AP conduction speed. The predictions were confirmed by electrophysiological experiments, revealing a phase of slowed down AP conduction, which is linked to the transient enlargement of the synaptic boutons, followed by a sustained increase in conduction speed that accompanies the axon shaft widening induced by high-frequency AP firing. Taken together, our study outlines a morphological plasticity mechanism for dynamically fine-tuning AP conduction velocity, which potentially has wide implications for the temporal transfer of information in the brain.
Calcium Signaling in Intact Dorsal Root Ganglia

PubMed Central

Gemes, Geza; Rigaud, Marcel; Koopmeiners, Andrew S.; Poroli, Mark J.; Zoga, Vasiliki; Hogan, Quinn H.

2013-01-01

Background Ca2+ is the dominant second messenger in primary sensory neurons. In addition, disrupted Ca2+ signaling is a prominent feature in pain models involving peripheral nerve injury. Standard cytoplasmic Ca2+ recording techniques use high K+ or field stimulation and dissociated neurons. To compare findings in intact dorsal root ganglia, we used a method of simultaneous electrophysiologic and microfluorimetric recording. Methods Dissociated neurons were loaded by bath-applied Fura-2-AM and subjected to field stimulation. Alternatively, we adapted a technique in which neuronal somata of intact ganglia were loaded with Fura-2 through an intracellular microelectrode that provided simultaneous membrane potential recording during activation by action potentials (APs) conducted from attached dorsal roots. Results Field stimulation at levels necessary to activate neurons generated bath pH changes through electrolysis and failed to predictably drive neurons with AP trains. In the intact ganglion technique, single APs produced measurable Ca2+ transients that were fourfold larger in presumed nociceptive C-type neurons than in nonnociceptive Aβ-type neurons. Unitary Ca2+ transients summated during AP trains, forming transients with amplitudes that were highly dependent on stimulation frequency. Each neuron was tuned to a preferred frequency at which transient amplitude was maximal. Transients predominantly exhibited monoexponential recovery and had sustained plateaus during recovery only with trains of more than 100 APs. Nerve injury decreased Ca2+ transients in C-type neurons, but increased transients in Aβ-type neurons. Conclusions Refined observation of Ca2+ signaling is possible through natural activation by conducted APs in undissociated sensory neurons and reveals features distinct to neuronal types and injury state. PMID:20526180
System modeling of the Thirty Meter Telescope alignment and phasing system

NASA Astrophysics Data System (ADS)

Dekens, Frank G.; Seo, Byoung-Joon; Troy, Mitchell

2014-08-01

We have developed a system model using the System Modeling Language (SysML) for the Alignment and Phasing System (APS) on the Thirty Meter Telescope (TMT). APS is a Shack-Hartmann wave-front sensor that will be used to measure the alignment and phasing of the primary mirror segments, and the alignment of the secondary and tertiary mirrors. The APS system model contains the ow-down of the Level 1 TMT requirements to APS (Level 2) requirements, and from there to the APS sub-systems (Level 3) requirements. The model also contains the operating modes and scenarios for various activities, such as maintenance alignment, post-segment exchange alignment, and calibration activities. The requirements ow-down is captured in SysML requirements diagrams, and we describe the process of maintaining the DOORS database as the single-source-of-truth for requirements, while using the SysML model to capture the logic and notes associated with the ow-down. We also use the system model to capture any needed communications from APS to other TMT systems, and between the APS sub-systems. The operations are modeled using SysML activity diagrams, and will be used to specify the APS interface documents. The modeling tool can simulate the top level activities to produce sequence diagrams, which contain all the communications between the system and subsystem needed for that activity. By adding time estimates for the lowest level APS activities, a robust estimate for the total time on-sky that APS requires to align and phase the telescope can be obtained. This estimate will be used to verify that the time APS requires on-sky meets the Level 1 TMT requirements.

Differential excitability and modulation of striatal medium spiny neuron dendrites

PubMed Central

Day, Michelle; Wokosin, David; Plotkin, Joshua L.; Tian, Xinyoung; Surmeier, D. James

2011-01-01

The loss of striatal dopamine (DA) in Parkinson's disease (PD) models triggers a cell-type specific reduction in the density of dendritic spines in D2 receptor-expressing striatopallidal medium spiny neurons (D2 MSNs). How the intrinsic properties of MSN dendrites, where the vast majority of DA receptors are found, contribute to this adaptation is not clear. To address this question, two-photon laser scanning microscopy (2PLSM) was performed in patch-clamped mouse MSNs identified in striatal slices by expression of green fluorescent protein (eGFP) controlled by DA receptor promoters. These studies revealed that single back-propagating action potentials (bAP) produced more reliable elevations in cytosolic Ca2+ concentration at distal dendritic locations in D2 MSNs than at similar locations in D1 receptor-expressing striatonigral MSNs (D1 MSNs). In both cell types, the dendritic Ca2+ entry elicited by bAPs was enhanced by pharmacological blockade of Kv4, but not Kv1 K+ channels. Local application of DA depressed dendritic bAP-evoked Ca2+ transients, whereas application of ACh increased these Ca2+ transients in D2 MSNs—but not in D1 MSNs. Following DA depletion, bAP-evoked Ca2+ transients were enhanced in distal dendrites and spines in D2 MSNs. Taken together, these results suggest that normally D2 MSN dendrites are more excitable than those of D1 MSNs and that DA depletion exaggerates this asymmetry, potentially contributing to adaptations in PD models. PMID:18987196
An analysis of the relationships between subthreshold electrical properties and excitability in skeletal muscle

PubMed Central

L.-H. Huang, Christopher; Fraser, James A.

2011-01-01

Skeletal muscle activation requires action potential (AP) initiation followed by its sarcolemmal propagation and tubular excitation to trigger Ca2+ release and contraction. Recent studies demonstrate that ion channels underlying the resting membrane conductance (GM) of fast-twitch mammalian muscle fibers are highly regulated during muscle activity. Thus, onset of activity reduces GM, whereas prolonged activity can markedly elevate GM. Although these observations implicate GM regulation in control of muscle excitability, classical theoretical studies in un-myelinated axons predict little influence of GM on membrane excitability. However, surface membrane morphologies differ markedly between un-myelinated axons and muscle fibers, predominantly because of the tubular (t)-system of muscle fibers. This study develops a linear circuit model of mammalian muscle fiber and uses this to assess the role of subthreshold electrical properties, including GM changes during muscle activity, for AP initiation, AP propagation, and t-system excitation. Experimental observations of frequency-dependent length constant and membrane-phase properties in fast-twitch rat fibers could only be replicated by models that included t-system luminal resistances. Having quantified these resistances, the resulting models showed enhanced conduction velocity of passive current flow also implicating elevated AP propagation velocity. Furthermore, the resistances filter passive currents such that higher frequency current components would determine sarcolemma AP conduction velocity, whereas lower frequency components excite t-system APs. Because GM modulation affects only the low-frequency membrane impedance, the GM changes in active muscle would predominantly affect neuromuscular transmission and low-frequency t-system excitation while exerting little influence on the high-frequency process of sarcolemmal AP propagation. This physiological role of GM regulation was increased by high Cl− permeability, as in muscle endplate regions, and by increased extracellular [K+], as observed in working muscle. Thus, reduced GM at the onset of exercise would enhance t-system excitation and neuromuscular transmission, whereas elevated GM after sustained activity would inhibit these processes and thereby accentuate muscle fatigue. PMID:21670208
Action potential propagation recorded from single axonal arbors using multi-electrode arrays.

PubMed

Tovar, Kenneth R; Bridges, Daniel C; Wu, Bian; Randall, Connor; Audouard, Morgane; Jang, Jiwon; Hansma, Paul K; Kosik, Kenneth S

2018-04-11

We report the presence of co-occurring extracellular action potentials (eAPs) from cultured mouse hippocampal neurons among groups of planar electrodes on multi-electrode arrays (MEAs). The invariant sequences of eAPs among co-active electrode groups, repeated co-occurrences and short inter-electrode latencies are consistent with action potential propagation in unmyelinated axons. Repeated eAP co-detection by multiple electrodes was widespread in all our data records. Co-detection of eAPs confirms they result from the same neuron and allows these eAPs to be isolated from all other spikes independently of spike sorting algorithms. We averaged co-occurring events and revealed additional electrodes with eAPs that would otherwise be below detection threshold. We used these eAP cohorts to explore the temperature sensitivity of action potential propagation and the relationship between voltage-gated sodium channel density and propagation velocity. The sequence of eAPs among co-active electrodes 'fingerprints' neurons giving rise to these events and identifies them within neuronal ensembles. We used this property and the non-invasive nature of extracellular recording to monitor changes in excitability at multiple points in single axonal arbors simultaneously over several hours, demonstrating independence of axonal segments. Over several weeks, we recorded changes in inter-electrode propagation latencies and ongoing changes in excitability in different regions of single axonal arbors. Our work illustrates how repeated eAP co-occurrences can be used to extract physiological data from single axons with low electrode density MEAs. However, repeated eAP co-occurrences leads to over-sampling spikes from single neurons and thus can confound traditional spike-train analysis.
Thrombopoietin as Early Biomarker of Disease Severity in Patients With Acute Pancreatitis.

PubMed

Lupia, Enrico; Pigozzi, Luca; Pivetta, Emanuele; Bosco, Ornella; Vizio, Barbara; Loiacono, Maria; Lucchiari, Manuela; Battista, Stefania; Morello, Fulvio; Moiraghi, Corrado; Mengozzi, Giulio; Montrucchio, Giuseppe

2017-02-01

To study the concentrations of thrombopoietin (TPO), a growth factor recently involved in the pathogenesis of experimental acute pancreatitis (AP), and its potential role as an early diagnostic and prognostic biomarker in patients with AP. Thrombopoietin was measured in 44 AP patients, 18 patients with nonpancreatic acute abdominal pain, and 18 healthy volunteers. Acute pancreatitis severity was classified on the basis of the 2012 International Atlanta Symposium on Acute Pancreatitis criteria. Thrombopoietin levels did not differ between AP patients and control subjects, whereas these were higher in patients with moderately severe or severe AP compared with those with mild AP. Receiver operating characteristic curve analysis of TPO for severe AP diagnosis showed an area under the curve of 0.80. A cutoff value of 31.48 pg/mL showed the highest sensitivity, allowing to rule out severe AP when TPO was lower, whereas TPO higher than 98.23 pg/mL was associated with severe AP with high specificity (93.5%). Furthermore, TPO levels were greater in AP patients developing organ dysfunction or sepsis and in nonsurvivors compared with survivors. Our data provide the first evidence for TPO as potential early prognostic biomarker in AP patients. High TPO levels at hospital admission may predict organ dysfunction, sepsis, and fatal outcome in AP patients.
Suppression of acute and anticipatory nausea by peripherally restricted fatty acid amide hydrolase inhibitor in animal models: role of PPARα and CB1 receptors.

PubMed

Rock, Erin M; Moreno-Sanz, Guillermo; Limebeer, Cheryl L; Petrie, Gavin N; Angelini, Roberto; Piomelli, Daniele; Parker, Linda A

2017-11-01

Effective treatments of nausea are limited. In this study we evaluated the ability of the peripherally restricted fatty acid amide hydrolase (FAAH) inhibitor, URB937, to suppress acute and anticipatory nausea in rats and examined the pharmacological mechanism of this effect. We investigated the potential of URB937 (administered i.p.) to reduce the establishment of lithium chloride-induced conditioned gaping (model of acute nausea) and to reduce the expression of contextually-elicited conditioned gaping (model of anticipatory nausea) in rats. The role of CB 1 receptors, CB 2 receptors and PPARα in the anti-nausea effect of URB937 was examined. The potential of URB937 to suppress FAAH activity in tissue collected from the area postrema (AP), prefrontal cortex (PFC), liver and duodenum and to elevate levels of FAAH substrates - anandamide (AEA), N-oleoylethanolamide (OEO) and N-palmitoylethanolamide (PEA) - in the AP was also evaluated. URB937 reduced acute nausea by a PPARα-dependent mechanism and reduced anticipatory nausea by a CB 1 receptor-dependent mechanism. The PPARα agonist, GW7647, similarly attenuated acute nausea. URB937 reduced FAAH activity in the liver and the duodenum but not in the PFC. In addition, URB937 reduced FAAH activity and elevated levels of fatty-acid ethanolamides in the AP, a brain region that is not protected by the blood-brain barrier. The anti-nausea action of URB937 may occur in the AP and may involve PPARα to suppress acute nausea and CB 1 receptors to suppress anticipatory nausea. © 2017 The British Pharmacological Society.
Theoretical studies on the electronic and optoelectronic properties of [A.2AP(w)/A*.2AP(WC)/C.2AP(w)/C*.2AP(WC)/C.A(w)/C*.A(WC)]-Au8 mismatch nucleobase complexes

NASA Astrophysics Data System (ADS)

Srivastava, Ruby

2018-01-01

The electronic and optoelectronic properties of [A.2AP(w)/A*.2AP(WC)/C.2AP(w)/C*.2AP(WC)/C.A(w)/ C*.A(WC)]-Au8 metal-mismatch nucleobase complexes are investigated by means of density functional theory and time-dependent methods. We selected these mispairs as 2-aminopurine (2AP) produces incorporation errors when binding with cytosine (C) into the wobble (w) C.2AP(w) mispair, and is tautomerised into Watson-Crick (WC)-like base mispair C*.2AP(WC) and less effectively produces A.2AP(w)/A*.2AP(WC) mispairs. The vertical ionisation potential, vertical electron affinity, hardness and electrophilicity index of these complexes have also been discussed. The modifications of energy levels and charge density distributions of the frontier orbitals are also analysed. The absorption spectra of these complexes lie in the visible region, which suggests their application in fluorescent-bio imaging. The mechanism of cooperativity effect is studied by molecular orbital potential (MEP), atoms-in-molecules (AIM) and natural bond orbital analyses. Most metalated pairs have smaller HOMO-LUMO band gaps than the isolated mismatch nucleobases which suggest interesting consequences for electron transfer through DNA duplexes.
Diadenosine tetra- and pentaphosphates affect contractility and bioelectrical activity in the rat heart via P2 purinergic receptors.

PubMed

Pustovit, Ksenia B; Kuzmin, Vladislav S; Abramochkin, Denis V

2016-03-01

Diadenosine polyphosphates (Ap(n)As) are endogenously produced molecules which have been identified in various tissues of mammalian organism, including myocardium. Ap(n)As contribute to the blood clotting and are also widely accepted as regulators of blood vascular tone. Physiological role of Ap(n)As in cardiac muscle has not been completely elucidated. The present study aimed to investigate the effects of diadenosine tetra- (Ap4A) and penta- (Ap5A) polyphosphates on contractile function and action potential (AP) waveform in rat supraventricular and ventricular myocardium. We have also demonstrated the effects of A4pA and Ap5A in myocardial sleeves of pulmonary veins (PVs), which play a crucial role in genesis of atrial fibrillation. APs were recorded with glass microelectrodes in multicellular myocardial preparations. Contractile activity was measured in isolated Langendorff-perfused rat hearts. Both Ap4A and Ap5A significantly reduced contractility of isolated Langendorff-perfused heart and produced significant reduction of AP duration in left and right auricle, interatrial septum, and especially in right ventricular wall myocardium. Ap(n)As also shortened APs in rat pulmonary veins and therefore may be considered as potential proarrhythmic factors. Cardiotropic effects of Ap4A and Ap5A were strongly antagonized by selective blockers of P2 purine receptors suramin and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), while P1 blocker DPCPX was not effective. We conclude that Ap(n)As may be considered as new class of endogenous cardioinhibitory compounds. P2 purine receptors play the central role in mediation of Ap4A and Ap5A inhibitory effects on electrical and contractile activity in different regions of the rat heart.
Empirical radiation belt models: Comparison with in situ data and implications for environment definition

NASA Astrophysics Data System (ADS)

de Soria-Santacruz Pich, Maria; Jun, Insoo; Evans, Robin

2017-09-01

The empirical AP8/AE8 model has been the de facto Earth's radiation belts engineering reference for decades. The need from the community for a better model incubated the development of AP9/AE9/SPM, which addresses several shortcomings of the old model. We provide additional validation of AP9/AE9 by comparing in situ electron and proton data from Jason-2, Polar Orbiting Environmental Satellites (POES), and the Van Allen Probes spacecraft with the 5th, 50th, and 95th percentiles from AE9/AP9 and with the model outputs from AE8/AP8. The relatively short duration of Van Allen Probes and Jason-2 missions means that their measurements are most certainly the result of specific climatological conditions. In low Earth orbit (LEO), the Jason-2 proton flux is better reproduced by AP8 compared to AP9, while the POES electron data are well enveloped by AE9 5th and 95th percentiles. The shape of the South Atlantic anomaly (SAA) from Jason-2 data is better captured by AP9 compared to AP8, while the peak SAA flux is better reproduced by AP8. The <1.5 MeV inner belt electrons from Magnetic Electron Ion Spectrometer (MagEIS) are well enveloped by AE9 5th and 95th percentiles, while AE8 overpredicts the measurements. In the outer radiation belt, MagEIS and Relativistic Electron and Proton Telescope (REPT) electrons closely follow the median estimate from AE9, while AP9 5th and 95th percentiles generally envelope REPT proton measurements in the inner belt and slot regions. While AE9/AP9 offer the flexibility to specify the environment with different confidence levels, the dose and trapped proton peak flux for POES and Jason-2 trajectories from the AE9/AP9 50th percentile and above are larger than the estimates from the AE8/AP8 models.
Action potential properties are gravity dependent

NASA Astrophysics Data System (ADS)

Meissner, Klaus; Hanke, Wolfgang

2005-06-01

The functional properties of neuronal tissue critically depend on cellular composition and intercellular comunication. A basic principle of such communication found in various types of neurons is the generation of action potentials (APs). These APs depend on the presence of voltage gated ion channels and propagate along cellular processes (e.g. axons) towards target neurons or other cells. It has already been shown that the properties of ion channels depend on gravity. To discover whether the properties of APs also depend on gravity, we examined the propagation of APs in earthworms (invertebrates) and isolated nerve fibres (i.e. bundles of axons) from earthworms under conditions of micro- and macro-gravity. In a second set of experiments we could verify our results on rat axons (vertebrates). Our experiments carried out during two parabolic flight campaigns revealed that microgravity slows AP propagation velocity and macrogravity accelerates the transmission of action potentials. The relevance for live-science related questions is considerable, taking into account that altered gravity conditions might affect AP velocity in man during space flight missions.
Antiphospholipid Syndrome Nephropathy: From Pathogenesis to Treatment.

PubMed

Tektonidou, Maria G

2018-01-01

Kidney damage is a well-recognized complication of the antiphospholipid syndrome (APS), either primary or systemic lupus erythematosus (SLE)-associated APS. Kidney involvement in APS involves a variety of manifestations, such as renal artery thrombosis or stenosis, renal vein thrombosis, allograft loss due to thrombosis after kidney transplantation, and injury to the renal microvasculature, also known as APS nephropathy. Biopsy in patients with APS nephropathy includes acute thrombotic microangiopathy lesions and chronic intrarenal vascular lesions such as interlobular fibrous intimal hyperplasia, arterial and arteriolar recanalizing thrombosis, fibrous arterial occlusion, and focal cortical atrophy. The most frequent clinical features are hypertension, microscopic hematuria, proteinuria (ranging from mild to nephritic levels), and renal insufficiency. It is uncertain whether antiphospholipid antibodies or other factors are implicated in the development of APS nephropathy, and whether it is driven mainly by thrombotic or by inflammatory processes. Experimental models and clinical studies of thrombotic microangiopathy lesions implicate activation of the complement cascade, tissue factor, and the mTORC pathway. Currently, the management of APS nephropathy relies on expert opinion, and consensus is lacking. There is limited evidence about the effect of anticoagulants, and their use remains controversial. Treatment approaches in patients with APS nephropathy lesions may include the use of heparin based on its role on complement activation pathway inhibition or the use of intravenous immunoglobulin and/or plasma exchange. Targeted therapies may also be considered based on potential APS nephropathy pathogenetic mechanisms such as B-cell directed therapies, complement inhibition, tissue factor inhibition, mTOR pathway inhibition, or anti-interferon antibodies, but prospective multicenter studies are needed to address their role.
AP-1 Oligodeoxynucleotides Reduce Aortic Elastolysis in a Murine Model of Marfan Syndrome.

PubMed

Arif, Rawa; Zaradzki, Marcin; Remes, Anca; Seppelt, Philipp; Kunze, Reiner; Schröder, Hannes; Schwill, Simon; Ensminger, Stephan M; Robinson, Peter N; Karck, Matthias; Müller, Oliver J; Hecker, Markus; Wagner, Andreas H; Kallenbach, Klaus

2017-12-15

Marfan syndrome is characterized by high expression of matrix metalloproteinases (MMPs) in aortic smooth muscle cells (AoSMCs) associated with medial elastolysis and aortic root aneurysm. We aimed to reduce aortic elastolysis through decrease of MMP expression with decoy oligodeoxynucleotides (dODNs) neutralizing the transcription factor activating factor-1 (AP-1). AP-1 abundance in nuclear extracts as well as MMP-2 and MMP-9 expression were significantly increased in isolated mAoSMC of mgR/mgR Marfan mice compared to wild-type cells. Exposure to AP-1 neutralizing dODNs resulted in a significant reduction of basal and interleukin-1β-stimulated MMP expression and activity in mAoSMCs. Moreover, increased migration and formation of superoxide radical anions was substantially decreased in mAoSMCs by AP-1 dODN treatment. Aortic grafts from donor Marfan mice were treated with AP-1- dODN ex vivo and implanted as infrarenal aortic interposition grafts in mgR/mgR mice. Pretreatment of aortic grafts with AP-1 dODN led to reduced elastolysis, macrophage infiltration, and MMP activity. Permeability of the endothelial monolayer was increased for dODN in mgR/mgR aortae with observed loss of tight junction proteins ZO-1 and occludin, enabling dODN to reach the tunica media. Targeting AP-1 activity offers a new potential strategy to treat the vascular phenotype associated with Marfan syndrome. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.
HIV-1 Nef-induced Down-Regulation of MHC Class I Requires AP-1 and Clathrin but Not PACS-1 and Is Impeded by AP-2

PubMed Central

Lubben, Nienke B.; Sahlender, Daniela A.; Motley, Alison M.; Lehner, Paul J.; Benaroch, Philippe

2007-01-01

Major histocompatibility complex class I is down-regulated from the surface of human immunodeficiency virus (HIV)-1-infected cells by Nef, a virally encoded protein that is thought to reroute MHC-I to the trans-Golgi network (TGN) in a phosphofurin acidic cluster sorting protein (PACS) 1, adaptor protein (AP)-1, and clathrin-dependent manner. More recently, an alternative model has been proposed, in which Nef uses AP-1 to direct MHC-I to endosomes and lysosomes. Here, we show that knocking down either AP-1 or clathrin with small interfering RNA inhibits the down-regulation of HLA-A2 (an MHC-I isotype) by Nef in HeLa cells. However, knocking down PACS-1 has no effect, not only on Nef-induced down-regulation of HLA-A2 but also on the localization of other proteins containing acidic cluster motifs. Surprisingly, knocking down AP-2 actually enhances Nef activity. Immuno-electron microscopy labeling of Nef-expressing cells indicates that HLA-A2 is rerouted not to the TGN, but to endosomes. In AP-2–depleted cells, more of the HLA-A2 localizes to the inner vesicles of multivesicular bodies. We propose that depleting AP-2 potentiates Nef activity by altering the membrane composition and dynamics of endosomes and causing increased delivery of HLA-A2 to a prelysosomal compartment. PMID:17581864
Distinct Physiological Effects of Dopamine D4 Receptors on Prefrontal Cortical Pyramidal Neurons and Fast-Spiking Interneurons

PubMed Central

Zhong, Ping; Yan, Zhen

2016-01-01

Dopamine D4 receptor (D4R), which is strongly linked to neuropsychiatric disorders, such as attention-deficit hyperactivity disorder and schizophrenia, is highly expressed in pyramidal neurons and GABAergic interneurons in prefrontal cortex (PFC). In this study, we examined the impact of D4R on the excitability of these 2 neuronal populations. We found that D4R activation decreased the frequency of spontaneous action potentials (sAPs) in PFC pyramidal neurons, whereas it induced a transient increase followed by a decrease of sAP frequency in PFC parvalbumin-positive (PV+) interneurons. D4R activation also induced distinct effects in both types of PFC neurons on spontaneous excitatory and inhibitory postsynaptic currents, which drive the generation of sAP. Moreover, dopamine substantially decreased sAP frequency in PFC pyramidal neurons, but markedly increased sAP frequency in PV+ interneurons, and both effects were partially mediated by D4R activation. In the phencyclidine model of schizophrenia, the decreasing effect of D4R on sAP frequency in both types of PFC neurons was attenuated, whereas the increasing effect of D4R on sAP in PV+ interneurons was intact. These results suggest that D4R activation elicits distinct effects on synaptically driven excitability in PFC projection neurons versus fast-spiking interneurons, which are differentially altered in neuropsychiatric disorder-related conditions. PMID:25146372
Effects of the Mitochondria-Targeted Antioxidant Mitoquinone in Murine Acute Pancreatitis

PubMed Central

Wen, Li; Szatmary, Peter; Mukherjee, Rajarshi; Armstrong, Jane; Chvanov, Michael; Tepikin, Alexei V.; Murphy, Michael P.; Sutton, Robert; Criddle, David N.

2015-01-01

Although oxidative stress has been strongly implicated in the development of acute pancreatitis (AP), antioxidant therapy in patients has so far been discouraging. The aim of this study was to assess potential protective effects of a mitochondria-targeted antioxidant, MitoQ, in experimental AP using in vitro and in vivo approaches. MitoQ blocked H2O2-induced intracellular ROS responses in murine pancreatic acinar cells, an action not shared by the control analogue dTPP. MitoQ did not reduce mitochondrial depolarisation induced by either cholecystokinin (CCK) or bile acid TLCS, and at 10 µM caused depolarisation per se. Both MitoQ and dTPP increased basal and CCK-induced cell death in a plate-reader assay. In a TLCS-induced AP model MitoQ treatment was not protective. In AP induced by caerulein hyperstimulation (CER-AP), MitoQ exerted mixed effects. Thus, partial amelioration of histopathology scores was observed, actions shared by dTPP, but without reduction of the biochemical markers pancreatic trypsin or serum amylase. Interestingly, lung myeloperoxidase and interleukin-6 were concurrently increased by MitoQ in CER-AP. MitoQ caused biphasic effects on ROS production in isolated polymorphonuclear leukocytes, inhibiting an acute increase but elevating later levels. Our results suggest that MitoQ would be inappropriate for AP therapy, consistent with prior antioxidant evaluations in this disease. PMID:25878403
Effects of the mitochondria-targeted antioxidant mitoquinone in murine acute pancreatitis.

PubMed

Huang, Wei; Cash, Nicole; Wen, Li; Szatmary, Peter; Mukherjee, Rajarshi; Armstrong, Jane; Chvanov, Michael; Tepikin, Alexei V; Murphy, Michael P; Sutton, Robert; Criddle, David N

2015-01-01

Although oxidative stress has been strongly implicated in the development of acute pancreatitis (AP), antioxidant therapy in patients has so far been discouraging. The aim of this study was to assess potential protective effects of a mitochondria-targeted antioxidant, MitoQ, in experimental AP using in vitro and in vivo approaches. MitoQ blocked H2O2-induced intracellular ROS responses in murine pancreatic acinar cells, an action not shared by the control analogue dTPP. MitoQ did not reduce mitochondrial depolarisation induced by either cholecystokinin (CCK) or bile acid TLCS, and at 10 µM caused depolarisation per se. Both MitoQ and dTPP increased basal and CCK-induced cell death in a plate-reader assay. In a TLCS-induced AP model MitoQ treatment was not protective. In AP induced by caerulein hyperstimulation (CER-AP), MitoQ exerted mixed effects. Thus, partial amelioration of histopathology scores was observed, actions shared by dTPP, but without reduction of the biochemical markers pancreatic trypsin or serum amylase. Interestingly, lung myeloperoxidase and interleukin-6 were concurrently increased by MitoQ in CER-AP. MitoQ caused biphasic effects on ROS production in isolated polymorphonuclear leukocytes, inhibiting an acute increase but elevating later levels. Our results suggest that MitoQ would be inappropriate for AP therapy, consistent with prior antioxidant evaluations in this disease.
In vivo fluorescence imaging of hepatocellular carcinoma using a novel GPC3-specific aptamer probe

PubMed Central

Zhao, Menglong; Dong, Lili; Liu, Zhuang; Yang, Shuohui

2018-01-01

Background Glypican-3 (GPC3) is highly expressed in most of the hepatocellular carcinomas (HCCs), even in small HCCs. It may be used as a potential biomarker for early detection of HCC. The aptamer is a promising targeting agent with unique advantages over antibody. This study was to introduce a novel GPC3 specific aptamer (AP613-1), to verify its specific binding property in vitro, and to evaluate its targeting efficiency in vivo by performing near-infrared (NIR) fluorescence imaging on an HCC xenograft model. Methods AP613-1 was generated from the systematic evolution of ligands by exponential enrichment. Flow cytometry and aptamer-based immunofluorescence imaging were performed to verify the binding affinity of AP613-1 to GPC3 in vitro. NIR Fluorescence images of nude mice with unilateral (n=12) and bilateral (n=4) subcutaneous xenograft tumors were obtained. Correlation between the tumor fluorescence intensities in vivo and ex vivo was analyzed. Results AP613-1 could specifically bind to GPC3 in vitro. In vivo and ex vivo tumors, fluorescence intensities were in excellent correlation (P<0.001, r=0.968). The fluorescence intensity is significantly higher in tumors given Alexa Fluor 750 (AF750) labeled AP613-1 than in those given AF750 labeled initial ssDNA library both in vivo (P<0.001) and ex vivo (P=0.022). In the mice with bilateral subcutaneous tumors injected with AF750 labeled AP613-1, Huh-7 tumors showed significantly higher fluorescence intensities than A549 tumors both in vivo (P=0.016) and ex vivo (P=0.004). Conclusions AP613-1 displays a specific binding affinity to GPC3 positive HCC. Fluorescently labeled AP613-1 could be used as an imaging probe to subcutaneous HCC in xenograft models. PMID:29675356
The effect of Astragalus polysaccharides on attenuation of diabetic cardiomyopathy through inhibiting the extrinsic and intrinsic apoptotic pathways in high glucose -stimulated H9C2 cells.

PubMed

Sun, Shuqin; Yang, Shuo; Dai, Min; Jia, Xiujuan; Wang, Qiyan; Zhang, Zheng; Mao, Yongjun

2017-06-13

Apoptosis plays a critical role in the progression of diabetic cardiomyopathy (DC). Astragalus polysaccharides (APS), an extract of astragalus membranaceus (AM), is an effective cardioprotectant. Currently, little is known about the detailed mechanisms underlying cardioprotective effects of APS. The aims of this study were to investigate the potential effects and mechanisms of APS on apoptosis employing a model of high glucose induction of apoptosis in H9C2 cells. A model of high glucose induction of H9C2 cell apoptosis was adopted in this research. The cell viabilities were analyzed by MTT assay, and the apoptotic response was quantified by flow cytometry. The expression levels of the apoptosis related proteins were determined by Real-time PCR and western blotting. Incubation of H9C2 cells with various concentrations of glucose (i.e., 5.5, 12.5, 25, 33 and 44 mmol/L) for 24 h revealed that cell viability was reduced by high glucose dose-dependently. Pretreatment of cells with APS could inhibit high glucose-induced H9C2 cell apoptosis by decreasing the expressions of caspases and the release of cytochrome C from mitochondria to cytoplasm. Further experiments also showed that APS could modulate the ratio of Bcl-2 to Bax in mitochondria. APS decreases high glucose-induced H9C2 cell apoptosis by inhibiting the expression of pro-apoptotic proteins of both the extrinsic and intrinsic pathways and modulating the ratio of Bcl-2 to Bax in mitochondria.
Electrophysiological and morphological features underlying neurotransmission efficacy at the splanchnic nerve-chromaffin cell synapse of bovine adrenal medulla.

PubMed

de Diego, Antonio M G

2010-02-01

The ability of adrenal chromaffin cells to fast-release catecholamines relies on their capacity to fire action potentials (APs). However, little attention has been paid to the requirements needed to evoke the controlled firing of APs. Few data are available in rodents and none on the bovine chromaffin cell, a model extensively used by researchers. The aim of this work was to clarify this issue. Short puffs of acetylcholine (ACh) were fast perifused to current-clamped chromaffin cells and produced the firing of single APs. Based on the currents generated by such ACh applications and previous literature, current waveforms that efficiently elicited APs at frequencies up to 20 Hz were generated. Complex waveforms were also generated by adding simple waveforms with different delays; these waveforms aimed at modeling the stimulation patterns that a chromaffin cell would conceivably undergo upon strong synaptic stimulation. Cholinergic innervation was assessed using the acetylcholinesterase staining technique on the supposition that the innervation pattern is a determinant of the kind of stimuli chromaffin cells can receive. It is concluded that 1) a reliable method to produce frequency-controlled APs by applying defined current injection waveforms is achieved; 2) the APs thus generated have essentially the same features as those spontaneously emitted by the cell and those elicited by fast-ACh perifusion; 3) the higher frequencies attainable peak at around 30 Hz; and 4) the bovine adrenal medulla shows abundant cholinergic innervation, and chromaffin cells show strong acetylcholinesterase staining, consistent with a tight cholinergic presynaptic control of firing frequency.
High Resolution Genomic Scans Reveal Genetic Architecture Controlling Alcohol Preference in Bidirectionally Selected Rat Model.

PubMed

Lo, Chiao-Ling; Lossie, Amy C; Liang, Tiebing; Liu, Yunlong; Xuei, Xiaoling; Lumeng, Lawrence; Zhou, Feng C; Muir, William M

2016-08-01

Investigations on the influence of nature vs. nurture on Alcoholism (Alcohol Use Disorder) in human have yet to provide a clear view on potential genomic etiologies. To address this issue, we sequenced a replicated animal model system bidirectionally-selected for alcohol preference (AP). This model is uniquely suited to map genetic effects with high reproducibility, and resolution. The origin of the rat lines (an 8-way cross) resulted in small haplotype blocks (HB) with a corresponding high level of resolution. We sequenced DNAs from 40 samples (10 per line of each replicate) to determine allele frequencies and HB. We achieved ~46X coverage per line and replicate. Excessive differentiation in the genomic architecture between lines, across replicates, termed signatures of selection (SS), were classified according to gene and region. We identified SS in 930 genes associated with AP. The majority (50%) of the SS were confined to single gene regions, the greatest numbers of which were in promoters (284) and intronic regions (169) with the least in exon's (4), suggesting that differences in AP were primarily due to alterations in regulatory regions. We confirmed previously identified genes and found many new genes associated with AP. Of those newly identified genes, several demonstrated neuronal function involved in synaptic memory and reward behavior, e.g. ion channels (Kcnf1, Kcnn3, Scn5a), excitatory receptors (Grin2a, Gria3, Grip1), neurotransmitters (Pomc), and synapses (Snap29). This study not only reveals the polygenic architecture of AP, but also emphasizes the importance of regulatory elements, consistent with other complex traits.
Spike-timing dependent inhibitory plasticity to learn a selective gating of backpropagating action potentials.

PubMed

Wilmes, Katharina Anna; Schleimer, Jan-Hendrik; Schreiber, Susanne

2017-04-01

Inhibition is known to influence the forward-directed flow of information within neurons. However, also regulation of backward-directed signals, such as backpropagating action potentials (bAPs), can enrich the functional repertoire of local circuits. Inhibitory control of bAP spread, for example, can provide a switch for the plasticity of excitatory synapses. Although such a mechanism is possible, it requires a precise timing of inhibition to annihilate bAPs without impairment of forward-directed excitatory information flow. Here, we propose a specific learning rule for inhibitory synapses to automatically generate the correct timing to gate bAPs in pyramidal cells when embedded in a local circuit of feedforward inhibition. Based on computational modeling of multi-compartmental neurons with physiological properties, we demonstrate that a learning rule with anti-Hebbian shape can establish the required temporal precision. In contrast to classical spike-timing dependent plasticity of excitatory synapses, the proposed inhibitory learning mechanism does not necessarily require the definition of an upper bound of synaptic weights because of its tendency to self-terminate once annihilation of bAPs has been reached. Our study provides a functional context in which one of the many time-dependent learning rules that have been observed experimentally - specifically, a learning rule with anti-Hebbian shape - is assigned a relevant role for inhibitory synapses. Moreover, the described mechanism is compatible with an upregulation of excitatory plasticity by disinhibition. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

A simplified protocol for differentiation of electrophysiologically mature neuronal networks from human induced pluripotent stem cells.

PubMed

Gunhanlar, N; Shpak, G; van der Kroeg, M; Gouty-Colomer, L A; Munshi, S T; Lendemeijer, B; Ghazvini, M; Dupont, C; Hoogendijk, W J G; Gribnau, J; de Vrij, F M S; Kushner, S A

2018-05-01

Progress in elucidating the molecular and cellular pathophysiology of neuropsychiatric disorders has been hindered by the limited availability of living human brain tissue. The emergence of induced pluripotent stem cells (iPSCs) has offered a unique alternative strategy using patient-derived functional neuronal networks. However, methods for reliably generating iPSC-derived neurons with mature electrophysiological characteristics have been difficult to develop. Here, we report a simplified differentiation protocol that yields electrophysiologically mature iPSC-derived cortical lineage neuronal networks without the need for astrocyte co-culture or specialized media. This protocol generates a consistent 60:40 ratio of neurons and astrocytes that arise from a common forebrain neural progenitor. Whole-cell patch-clamp recordings of 114 neurons derived from three independent iPSC lines confirmed their electrophysiological maturity, including resting membrane potential (-58.2±1.0 mV), capacitance (49.1±2.9 pF), action potential (AP) threshold (-50.9±0.5 mV) and AP amplitude (66.5±1.3 mV). Nearly 100% of neurons were capable of firing APs, of which 79% had sustained trains of mature APs with minimal accommodation (peak AP frequency: 11.9±0.5 Hz) and 74% exhibited spontaneous synaptic activity (amplitude, 16.03±0.82 pA; frequency, 1.09±0.17 Hz). We expect this protocol to be of broad applicability for implementing iPSC-based neuronal network models of neuropsychiatric disorders.
Unexpected Heterodivalent Recruitment of NOS1AP to nNOS Reveals Multiple Sites for Pharmacological Intervention in Neuronal Disease Models.

PubMed

Li, Li-Li; Melero-Fernandez de Mera, Raquel M; Chen, Jia; Ba, Wei; Kasri, Nael Nadif; Zhang, Mingjie; Courtney, Michael J

2015-05-13

The protein NOS1AP/CAPON mediates signaling from a protein complex of NMDA receptor, PSD95 and nNOS. The only stroke trial for neuroprotectants that showed benefit to patients targeted this ternary complex. NOS1AP/nNOS interaction regulates small GTPases, iron transport, p38MAPK-linked excitotoxicity, and anxiety. Moreover, the nos1ap gene is linked to disorders from schizophrenia, post-traumatic stress disorder, and autism to cardiovascular disorders and breast cancer. Understanding protein interactions required for NOS1AP function, therefore, has broad implications for numerous diseases. Here we show that the interaction of NOS1AP with nNOS differs radically from the classical PDZ docking assumed to be responsible. The NOS1AP PDZ motif does not bind nNOS as measured by multiple methods. In contrast, full-length NOS1AP forms an unusually stable interaction with nNOS. We mapped the discrepancy between full-length and C-terminal PDZ motif to a novel internal region we call the ExF motif. The C-terminal PDZ motif, although neither sufficient nor necessary for binding, nevertheless promotes the stability of the complex. It therefore potentially affects signal transduction and suggests that functional interaction of nNOS with NOS1AP might be targetable at two distinct sites. We demonstrate that excitotoxic pathways can be regulated, in cortical neuron and organotypic hippocampal slice cultures from rat, either by the previously described PDZ ligand TAT-GESV or by the ExF motif-bearing region of NOS1AP, even when lacking the critical PDZ residues as long as the ExF motif is intact and not mutated. This previously unrecognized heterodivalent interaction of nNOS with NOS1AP may therefore provide distinct opportunities for pharmacological intervention in NOS1AP-dependent signaling and excitotoxicity. Copyright © 2015 the authors 0270-6474/15/357349-16$15.00/0.
DL-2-amino-3-phosphonopropionic acid protects primary neurons from oxygen-glucose deprivation induced injury.

PubMed

Cui, Di; Xu, Jun; Xu, Quanyi; Zuo, Guokun

2017-02-21

Cerebral infarction is a type of ischemic stroke and is one of the main causes of irreversible brain damage. Although multiple neuroprotective agents have been investigated recently, the potential of DL-2-amino-3-phosphonopropionic acid (DL-AP3) in treating oxygen-glucose deprivation (OGD)-induced neuronal injury, has not been clarified yet. This study was aimed to explore the role of DL-AP3 in primary neuronal cell cultures. Primary neurons were divided into four groups: (1) a control group that was not treated; (2) DL-AP3 group treated with 10 μM of DL-AP3; (3) OGD group, in which neurons were cultured under OGD conditions; and (4) OGD + DL-AP3 group, in which OGD model was first established and then the cells were treated with 10 μM of DL-AP3. Neuronal viability and apoptosis were measured using Cell Counting Kit-8 and flow cytometry. Expressions of phospho-Akt1 (p-Akt1) and cytochrome c were detected using Western blot. The results showed that DL-AP3 did not affect neuronal viability and apoptosis in DL-AP3 group, nor it changed p-Akt1 and cytochrome c expression (p > 0.05). In OGD + DL-AP3 group, DL-AP3 significantly attenuated the inhibitory effects of OGD on neuronal viability (p < 0.001), and reduced OGD induced apoptosis (p < 0.01). Additionally, the down-regulation of p-Akt1 and up-regulation of cytochrome c, induced by OGD, were recovered to some extent after DL-AP3 treatment (p < 0.05 or p < 0.001). Overall, DL-AP3 could protect primary neurons from OGD-induced injury by affecting the viability and apoptosis of neurons, and by regulating the expressions of p-Akt1 and cytochrome c.
Models of Disability in Children's Pretend Play: Measurement of Cognitive Representations and Affective Expression Using the Affect in Play Scale.

PubMed

Federici, Stefano; Meloni, Fabio; Catarinella, Antonio; Mazzeschi, Claudia

2017-01-01

Play is a natural mode of children's expression and constitutes a fundamental aspect of their life. Cognitive, affective, and social aspects can be assessed through play, considered as a "window" to observe a child's functioning. According to Russ's model, cognitive and affective components and their reciprocal connections can be assessed through the Affect in Play Scale (APS). The aim of the present study was to investigate children's representations of the three main models of disability (medical, social, and biopsychosocial) and how these models affected cognitive and affective components of children's play. Sixty-three children, aged 6-10 years, were assessed by means of the APS. Participants were randomly assigned to one of two APS task orders: the standard APS task followed by the modified APS task (including a wheelchair toy), or vice versa. The standard and modified APS sessions were coded according to the APS system. The modified APS sessions were also coded for the model of disability expressed by children. A one-way ANOVA conducted on the APS affective and cognitive indexes revealed an effect of condition on the affective components of play and no effect on cognitive components and variety of affect as assessed by the APS. In addition, when children are involved in pretend play from which concepts of disability emerge, these concepts are almost exclusively related to the medical model of disability. Results suggested implications for intervention with children in educational contexts that aim to teach children about disability.
An Excel‐based implementation of the spectral method of action potential alternans analysis

PubMed Central

Pearman, Charles M.

2014-01-01

Abstract Action potential (AP) alternans has been well established as a mechanism of arrhythmogenesis and sudden cardiac death. Proper interpretation of AP alternans requires a robust method of alternans quantification. Traditional methods of alternans analysis neglect higher order periodicities that may have greater pro‐arrhythmic potential than classical 2:1 alternans. The spectral method of alternans analysis, already widely used in the related study of microvolt T‐wave alternans, has also been used to study AP alternans. Software to meet the specific needs of AP alternans analysis is not currently available in the public domain. An AP analysis tool is implemented here, written in Visual Basic for Applications and using Microsoft Excel as a shell. This performs a sophisticated analysis of alternans behavior allowing reliable distinction of alternans from random fluctuations, quantification of alternans magnitude, and identification of which phases of the AP are most affected. In addition, the spectral method has been adapted to allow detection and quantification of higher order regular oscillations. Analysis of action potential morphology is also performed. A simple user interface enables easy import, analysis, and export of collated results. PMID:25501439
The Effects of Different Purifying Methods on the Chemical Properties, in Vitro Anti-Tumor and Immunomodulatory Activities of Abrus cantoniensis Polysaccharide Fractions

PubMed Central

Wu, Shaowei; Fu, Xiong; Brennan, Margaret A.; Brennan, Charles S.; Chun, Chen

2016-01-01

Abrus cantoniensis (Hance) is a popular Chinese vegetable consumed as a beverage, soup or folk medicine. To fully exploit the potential of the polysaccharide in Abrus cantoniensis, nine polysaccharide fractions of Abrus cantoniensis were isolated and purified (AP-AOH30-1, AP-AOH30-2, AP-AOH80-1, AP-AOH80-2, AP-ACl-1, AP-ACl-2, AP-ACl-3, AP-H and AP-L). Fourier-transform infrared spectroscopy (FT-IR) and gas chromatography (GC) were used to characterize these Abrus polysaccharides fractions (APF). In vitro anti-tumor and immunomodulatory activities were also investigated and compared using the rank-sum ratio (RSR) method. Results demonstrated significant differences in the structure and bioactivities among APF, which were associated to the process used for their purification. Among the APF, AP-ACl-3 yield was 613.5 mg/kg of product and consisted of rhamnose (9.8%), arabinose (8.9%), fructose (3.0%), galactose (9.9%), glucose (4.3%), galacturonic acid (3.0%) and glucuronic acid (61.1%) with a molecular weight of 4.4 × 104 Da. Furthermore, AP-ACl-3 exhibited considerable bioactivities significantly preventing the migration of MCF-7 cells and stimulating lymphocyte proliferation along with nitric oxide (NO) production of peritoneal macrophages. AP-ACl-3 could be explored as a novel potential anti-tumor and immunomodulatory agent. PMID:27058538
Onset dynamics of action potentials in rat neocortical neurons and identified snail neurons: quantification of the difference.

PubMed

Volgushev, Maxim; Malyshev, Aleksey; Balaban, Pavel; Chistiakova, Marina; Volgushev, Stanislav; Wolf, Fred

2008-04-09

The generation of action potentials (APs) is a key process in the operation of nerve cells and the communication between neurons. Action potentials in mammalian central neurons are characterized by an exceptionally fast onset dynamics, which differs from the typically slow and gradual onset dynamics seen in identified snail neurons. Here we describe a novel method of analysis which provides a quantitative measure of the onset dynamics of action potentials. This method captures the difference between the fast, step-like onset of APs in rat neocortical neurons and the gradual, exponential-like AP onset in identified snail neurons. The quantitative measure of the AP onset dynamics, provided by the method, allows us to perform quantitative analyses of factors influencing the dynamics.
Onset Dynamics of Action Potentials in Rat Neocortical Neurons and Identified Snail Neurons: Quantification of the Difference

PubMed Central

Volgushev, Maxim; Malyshev, Aleksey; Balaban, Pavel; Chistiakova, Marina; Volgushev, Stanislav; Wolf, Fred

2008-01-01

The generation of action potentials (APs) is a key process in the operation of nerve cells and the communication between neurons. Action potentials in mammalian central neurons are characterized by an exceptionally fast onset dynamics, which differs from the typically slow and gradual onset dynamics seen in identified snail neurons. Here we describe a novel method of analysis which provides a quantitative measure of the onset dynamics of action potentials. This method captures the difference between the fast, step-like onset of APs in rat neocortical neurons and the gradual, exponential-like AP onset in identified snail neurons. The quantitative measure of the AP onset dynamics, provided by the method, allows us to perform quantitative analyses of factors influencing the dynamics. PMID:18398478
A Fungal P450 (CYP5136A3) Capable of Oxidizing Polycyclic Aromatic Hydrocarbons and Endocrine Disrupting Alkylphenols: Role of Trp129 and Leu324

PubMed Central

Syed, Khajamohiddin; Porollo, Aleksey; Lam, Ying Wai; Yadav, Jagjit S.

2011-01-01

The model white rot fungus Phanerochaete chrysosporium, which is known for its versatile pollutant-biodegradation ability, possesses an extraordinarily large repertoire of P450 monooxygenases in its genome. However, the majority of these P450s have hitherto unknown function. Our initial studies using a genome-wide gene induction strategy revealed multiple P450s responsive to individual classes of xenobiotics. Here we report functional characterization of a cytochrome P450 monooxygenase, CYP5136A3 that showed common responsiveness and catalytic versatility towards endocrine-disrupting alkylphenols (APs) and mutagenic/carcinogenic polycyclic aromatic hydrocarbons (PAHs). Using recombinant CYP5136A3, we demonstrated its oxidation activity towards APs with varying alkyl side-chain length (C3-C9), in addition to PAHs (3–4 ring size). AP oxidation involves hydroxylation at the terminal carbon of the alkyl side-chain (ω-oxidation). Structure-activity analysis based on a 3D model indicated a potential role of Trp129 and Leu324 in the oxidation mechanism of CYP5136A3. Replacing Trp129 with Leu (W129L) and Phe (W129F) significantly diminished oxidation of both PAHs and APs. The W129L mutation caused greater reduction in phenanthrene oxidation (80%) as compared to W129F which caused greater reduction in pyrene oxidation (88%). Almost complete loss of oxidation of C3-C8 APs (83–90%) was observed for the W129L mutation as compared to W129F (28–41%). However, the two mutations showed a comparable loss (60–67%) in C9-AP oxidation. Replacement of Leu324 with Gly (L324G) caused 42% and 54% decrease in oxidation activity towards phenanthrene and pyrene, respectively. This mutation also caused loss of activity towards C3-C8 APs (20–58%), and complete loss of activity toward nonylphenol (C9-AP). Collectively, the results suggest that Trp129 and Leu324 are critical in substrate recognition and/or regio-selective oxidation of PAHs and APs. To our knowledge, this is the first report on an AP-oxidizing P450 from fungi and on structure-activity relationship of a eukaryotic P450 for fused-ring PAHs (phenanthrene and pyrene) and AP substrates. PMID:22164262
Initial segment Kv2.2 channels mediate a slow delayed rectifier and maintain high frequency action potential firing in medial nucleus of the trapezoid body neurons

PubMed Central

Johnston, Jamie; Griffin, Sarah J; Baker, Claire; Skrzypiec, Anna; Chernova, Tatanya; Forsythe, Ian D

2008-01-01

The medial nucleus of the trapezoid body (MNTB) is specialized for high frequency firing by expression of Kv3 channels, which minimize action potential (AP) duration, and Kv1 channels, which suppress multiple AP firing, during each calyceal giant EPSC. However, the outward K+ current in MNTB neurons is dominated by another unidentified delayed rectifier. It has slow kinetics and a peak conductance of ∼37 nS; it is half-activated at −9.2 ± 2.1 mV and half-inactivated at −35.9 ± 1.5 mV. It is blocked by several non-specific potassium channel antagonists including quinine (100 μm) and high concentrations of extracellular tetraethylammonium (TEA; IC50 = 11.8 mm), but no specific antagonists were found. These characteristics are similar to recombinant Kv2-mediated currents. Quantitative RT-PCR showed that Kv2.2 mRNA was much more prevalent than Kv2.1 in the MNTB. A Kv2.2 antibody showed specific staining and Western blots confirmed that it recognized a protein ∼110 kDa which was absent in brainstem tissue from a Kv2.2 knockout mouse. Confocal imaging showed that Kv2.2 was highly expressed in axon initial segments of MNTB neurons. In the absence of a specific antagonist, Hodgkin–Huxley modelling of voltage-gated conductances showed that Kv2.2 has a minor role during single APs (due to its slow activation) but assists recovery of voltage-gated sodium channels (Nav) from inactivation by hyperpolarizing interspike potentials during repetitive AP firing. Current-clamp recordings during high frequency firing and characterization of Nav inactivation confirmed this hypothesis. We conclude that Kv2.2-containing channels have a distinctive initial segment location and crucial function in maintaining AP amplitude by regulating the interspike potential during high frequency firing. PMID:18511484
Separation of toxic rhodamine B from aqueous solution using an efficient low-cost material, Azolla pinnata, by adsorption method.

PubMed

Kooh, Muhammad Raziq Rahimi; Lim, Linda B L; Lim, Lee Hoon; Dahri, Muhammad Khairud

2016-02-01

This study investigated the potential of untreated Azolla pinnata (AP) to remove toxic rhodamine B (RB) dye. The effects of adsorbent dosage, pH, ionic strength, contact time, and concentration were studied. Experiments involving the effects of pH and ionic strength indicated that hydrophobic-hydrophobic interactions might be the dominant force of attraction for the RB-AP adsorption system. The kinetics modelling of the kinetics experiment showed that pseudo-second-order best represented the adsorption process. The Weber-Morris intraparticle diffusion model showed that intraparticle diffusion is not the rate-limiting step, while the Boyd model suggested that film diffusion might be rate-limiting. The adsorption isotherm model, Langmuir, best represented the adsorption process, and the maximum adsorption capacity was predicted to be 72.2 and 199.7 mg g(-1) at 25 and 65 °C, respectively. Thermodynamics study indicates spontaneity, endothermic and physisorption-dominant adsorption process. The adsorbents were regenerated to satisfactory level with distilled water, HNO3 and NaOH. Pre-treatment of adsorbent with oxalic acid, citric acid, NaOH, HCl and phosphoric acid was investigated but the adsorption capacity was less than the untreated AP.
The absorption and transport of magnolol in Caco-2 cell model.

PubMed

Wu, An-Guo; Zeng, Bao; Huang, Meng-Qiu; Li, Sheng-Mei; Chen, Jian-Nan; Lai, Xiao-Ping

2013-03-01

To investigate the absorption and transport mechanism of magnolol in Caco-2 cell model. A human intestinal epithelial cell model Caco-2 cell in vitro cultured was applied to study the absorption and transport of magnolol, the effects of time, donor concentration, P-gp inhibitor verapamil, pH and temperature on the absorption and transport of magnolol were investigated. The determination of magnolol was performed by high performance liquid chromatography, then the values of apparent permeability coefficient (P app ) and P ratio Basolateral-to-Apical (BL-to-AP)/Apical-to-Basolateral (AP-to-BL) were calculated. In Caco-2 cell model, comparing the amounts of transport of AP-to-BL and BL-to-AP, the latter was larger. At the same donor concentration, either the amounts of transport of AP-to-BL or BL-to-AP increased with increase in donor concentration and incubation time. Verapamil could significantly improve the amounts of transport of AP-to-BL. The transport of AP-to-BL and BL-to-AP depended on temperature, and there was no significant effect of pH on the transport of AP-to-BL. Magnolol could be transported through the intestinal mucosa via a passive diffusion mechanism primarily, coexisting with a carrier-mediated transport, at the same time, the efflux mechanism could be involved.
Treatment with pentylenetetrazole (PTZ) and 4-aminopyridine (4-AP) differently affects survival, locomotor activity, and biochemical markers in Drosophila melanogaster.

PubMed

Soares, Deividi C S; Portela, José L R; Roos, Daniel H; Rodrigues, Nathane R; Gomes, Karen K; Macedo, Giulianna E; Posser, Thais; Franco, Jeferson L; Hassan, Waseem; Puntel, Robson L

2018-05-01

PTZ is a convulsive agent that acts via selective blockage of GABA A receptor channels, whereas 4-AP leads to a convulsive episode via blockage of K + channels. However, the mechanism(s) by which pentylenetetrazole (PTZ) and 4-aminopyridine (4-AP) cause toxicity to Drosophila melanogaster needs to be properly explored, once it will help in establishing an alternative model for development of proper therapeutic strategies and also to counteract the changes associated with exposure to both epileptic drugs. For the purpose, we investigated the effects of exposure (48 h) to PTZ (60 mM) and/or 4-AP (20 mM) on survival, locomotor performance, and biochemical markers in the body and/or head of flies. 4-AP-fed flies presented a higher incidence of mortality and a worse performance in the open field test as compared to non-treated flies. 4-AP also caused a significant increase in the reactive species (RS) and protein carbonyl (PC) content in the body and head. Also a significant increase in catalase and acetylcholinesterase (AChE) activities was observed in the body. In the same vein, PTZ exposure resulted in a significant increase in RS, thiobarbituric acid reactive substances (TBARS), PC content, and catalase activity in the body. PTZ exposure also caused a significant increase in AChE activity both in body and head. It is important to note that PTZ-treated flies also down-regulated the NRF 2 expression. Moreover, both 4AP- and PTZ-fed flies presented a significant decrease in MTT reduction, down-regulation, and inhibition of SOD in body. However, SOD was significantly more active in the head of both 4-AP and PTZ-treated flies. Our findings provide evidence regarding the toxicological potential of both PTZ and/or 4-AP to flies. This model will help in decoding the underlying toxicological mechanisms of the stated drugs. It will also help to properly investigate the therapeutic strategies and to counteract the drastic changes associated with both epileptogenic drugs.
Alkaline Phosphatase, an Unconventional Immune Protein.

PubMed

Rader, Bethany A

2017-01-01

Recent years have seen an increase in the number of studies focusing on alkaline phosphatases (APs), revealing an expanding complexity of function of these enzymes. Of the four human AP (hAP) proteins, most is known about tissue non-specific AP (TNAP) and intestinal AP (IAP). This review highlights current understanding of TNAP and IAP in relation to human health and disease. TNAP plays a role in multiple processes, including bone mineralization, vitamin B6 metabolism, and neurogenesis, is the genetic cause of hypophosphatasia, influences inflammation through regulation of purinergic signaling, and has been implicated in Alzheimer's disease. IAP regulates fatty acid absorption and has been implicated in the regulation of diet-induced obesity and metabolic syndrome. IAP and TNAP can dephosphorylate bacterial-derived lipopolysaccharide, and IAP has been identified as a potential regulator of the composition of the intestinal microbiome, an evolutionarily conserved function. Endogenous and recombinant bovine APs and recombinant hAPs are currently being explored for their potential as pharmacological agents to treat AP-associated diseases and mitigate multiple sources of inflammation. Continued research on these versatile proteins will undoubtedly provide insight into human pathophysiology, biochemistry, and the human holobiont.
Diadenosine tetraphosphate protects against injuries induced by ischemia and 6-hydroxydopamine in rat brain.

PubMed

Wang, Yun; Chang, Chen-Fu; Morales, Marisela; Chiang, Yung-Hsiao; Harvey, Brandon K; Su, Tsung-Ping; Tsao, Li-I; Chen, Suyu; Thiemermann, Christoph

2003-08-27

Diadenosine tetraphosphate (AP4A), an endogenous diadenosine polyphosphate, reduces ischemic injury in the heart. In this study, we report the potent and protective effects of AP4A in rodent models of stroke and Parkinson's disease. AP4A, given intracerebroventricularly before middle cerebral artery (MCA) ligation, reduced cerebral infarction size and enhanced locomotor activity in adult rats. The intravenous administration of AP4A also induced protection when given early after MCA ligation. AP4A suppressed terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling (TUNEL) induced by hypoxia/reperfusion in primary cortical cultures, and reduced both ischemia-induced translocation of mitochondrial cytochrome c and the increase in cytoplasmic caspase-3 activity in vivo. The purinergic P2/P4 antagonist di-inosine pentaphosphate or P1-receptor antagonist sulfonylphenyl theophylline, but not the P2-receptor antagonist suramin, antagonized the effect of AP4A, suggesting that the observed protection is mediated through an anti-apoptotic mechanism and the activation of P1- and P4-purinergic receptors. AP4A also afforded protection from toxicity induced by unilateral medial forebrain bundle injection of 6-hydroxydopamine (6-OHDA). One month after lesioning, vehicle-treated rats exhibited amphetamine-induced rotation. Minimal tyrosine hydroxylase immunoreactivity was detected in the lesioned nigra or striatum. No KCl-induced dopamine release was found in the lesioned striatum. All of these indices of dopaminergic degeneration were attenuated by pretreatment with AP4A. In addition, AP4A reduced TUNEL in the lesioned nigra 2 d after 6-OHDA administration. Collectively, our data suggest that AP4A is protective against neuronal injuries induced by ischemia or 6-OHDA through the inhibition of apoptosis. We propose that AP4A may be a potentially useful target molecule in the therapy of stroke and Parkinson's disease.
Overview on Recent Developments of Bondcoats for Plasma-Sprayed Thermal Barrier Coatings

NASA Astrophysics Data System (ADS)

Naumenko, D.; Pillai, R.; Chyrkin, A.; Quadakkers, W. J.

2017-12-01

The performance of MCrAlY (M = Ni, Co) bondcoats for atmospheric plasma-sprayed thermal barrier coatings (APS-TBCs) is substantially affected by the contents of Co, Ni, Cr, and Al as well as minor additions of Y, Hf, Zr, etc., but also by manufacturing-related properties such as coating thickness, porosity, surface roughness, and oxygen content. The latter properties depend in turn on the exact technology and set of parameters used for bondcoat deposition. The well-established LPPS process competes nowadays with alternative technologies such as HVOF and APS. In addition, new technologies have been developed for bondcoats manufacturing such as high-velocity APS or a combination of HVOF and APS for application of a flashcoat. Future developments of the bondcoat systems will likely include optimization of thermal spraying methods for obtaining complex bondcoat roughness profiles required for extended APS-TBC lifetimes. Introduction of the newest generation single-crystal superalloys possessing low Cr and high Al and refractory metals (Re, Ru) contents will require definition of new bondcoat compositions and/or multilayered bondcoats to minimize interdiffusion issues. The developments of new bondcoat compositions may be substantially facilitated using thermodynamic-kinetic modeling, the vast potential of which has been demonstrated in recent years.
The New APS Topical Group on the Physics of Climate: History, Objectives and Panel Discussion

NASA Astrophysics Data System (ADS)

Brasseur, James; Behringer, Robert

2013-03-01

The GPC Chair will introduce the new APS Topical Group on the Physics of Climate (GPC), describe its history and objectives, and introduce the current GPC leadership before opening the floor to a panel discussion. The GPC resulted from two petitions that emerged from the controversy that followed the APS Statement on Climate Change (see APS website). The two proposals were merged and an organization committee formed by the APS leadership. After a long organizational period in 2011, the GPC bylaws were finalized with the following key objective: The objective of the GPC shall be to promote the advancement and diffusion of knowledge concerning the physics, measurement, and modeling of climate processes, within the domain of natural science and outside the domains of societal impact and policy, legislation and broader societal issues. The objective includes the integration of scientific knowledge and analysis methods across disciplines to address the dynamical complexities and uncertainties of climate physics. The GPC Invited and Focus Sessions at this March meeting are the inaugural GPC events. The Program Committee Chair will moderate a panel between the attending GPC leadership and audience to solicit suggestions for potential future GPC events that advance the GPC objectives.
Sodium Channel β2 Subunits Prevent Action Potential Propagation Failures at Axonal Branch Points.

PubMed

Cho, In Ha; Panzera, Lauren C; Chin, Morven; Hoppa, Michael B

2017-09-27

Neurotransmitter release depends on voltage-gated Na + channels (Na v s) to propagate an action potential (AP) successfully from the axon hillock to a synaptic terminal. Unmyelinated sections of axon are very diverse structures encompassing branch points and numerous presynaptic terminals with undefined molecular partners of Na + channels. Using optical recordings of Ca 2+ and membrane voltage, we demonstrate here that Na + channel β2 subunits (Na v β2s) are required to prevent AP propagation failures across the axonal arborization of cultured rat hippocampal neurons (mixed male and female). When Na v β2 expression was reduced, we identified two specific phenotypes: (1) membrane excitability and AP-evoked Ca 2+ entry were impaired at synapses and (2) AP propagation was severely compromised with >40% of axonal branches no longer responding to AP-stimulation. We went on to show that a great deal of electrical signaling heterogeneity exists in AP waveforms across the axonal arborization independent of axon morphology. Therefore, Na v β2 is a critical regulator of axonal excitability and synaptic function in unmyelinated axons. SIGNIFICANCE STATEMENT Voltage-gated Ca 2+ channels are fulcrums of neurotransmission that convert electrical inputs into chemical outputs in the form of vesicle fusion at synaptic terminals. However, the role of the electrical signal, the presynaptic action potential (AP), in modulating synaptic transmission is less clear. What is the fidelity of a propagating AP waveform in the axon and what molecules shape it throughout the axonal arborization? Our work identifies several new features of AP propagation in unmyelinated axons: (1) branches of a single axonal arborization have variable AP waveforms independent of morphology, (2) Na + channel β2 subunits modulate AP-evoked Ca 2+ -influx, and (3) β2 subunits maintain successful AP propagation across the axonal arbor. These findings are relevant to understanding the flow of excitation in the brain. Copyright © 2017 the authors 0270-6474/17/379519-15$15.00/0.
Differences in glucose-stimulated insulin secretion in vitro of islets from human, nonhuman primate, and porcine origin.

PubMed

Mueller, Kate R; Balamurugan, A N; Cline, Gary W; Pongratz, Rebecca L; Hooper, Rebecca L; Weegman, Bradley P; Kitzmann, Jennifer P; Taylor, Michael J; Graham, Melanie L; Schuurman, Henk-Jan; Papas, Klearchos K

2013-01-01

Porcine islet xenotransplantation is considered a potential cell-based therapy for type 1 diabetes. It is currently being evaluated in diabetic nonhuman primates (NHP) to assess safety and efficacy of the islet product. However, due to a variety of distinct differences between the respective species, including the insulin secretory characteristics of islets, the suitability and predictive value of the preclinical model in the extrapolation to the clinical setting remain a critical issue. Islets isolated from human (n = 3), NHP (n = 2), adult pig (AP, n = 3), and juvenile pig (JP, n = 4) pancreata were perifused with medium at basal glucose (2.5 mm) followed by high glucose (16.7 mm) concentrations. The total glucose-stimulated insulin secretion (GSIS) was calculated from generated insulin secretion profiles. Nonhuman primate islets exhibited GSIS 3-fold higher than AP islets, while AP and JP islets exhibited GSIS 1/3 and 1/30 of human islets, respectively. The insulin content of NHP and AP islets was similar to that of human islets, whereas that of JP islets was 1/5 of human islets. Despite the fact that human, NHP, and AP islets contain similar amounts of insulin, the much higher GSIS for NHP islets than for AP and JP islets suggests the need for increased dosing of islets from JP and AP in pig-to-NHP transplantation. Porcine islet xenotransplantation to humans may require significantly higher dosing given the lower GSIS of AP islets compared to human islets. © 2013 John Wiley & Sons A/S.
A computational model of the ionic currents, Ca2+ dynamics and action potentials underlying contraction of isolated uterine smooth muscle.

PubMed

Tong, Wing-Chiu; Choi, Cecilia Y; Kharche, Sanjay; Karche, Sanjay; Holden, Arun V; Zhang, Henggui; Taggart, Michael J

2011-04-29

Uterine contractions during labor are discretely regulated by rhythmic action potentials (AP) of varying duration and form that serve to determine calcium-dependent force production. We have employed a computational biology approach to develop a fuller understanding of the complexity of excitation-contraction (E-C) coupling of uterine smooth muscle cells (USMC). Our overall aim is to establish a mathematical platform of sufficient biophysical detail to quantitatively describe known uterine E-C coupling parameters and thereby inform future empirical investigations of physiological and pathophysiological mechanisms governing normal and dysfunctional labors. From published and unpublished data we construct mathematical models for fourteen ionic currents of USMCs: Ca2+ currents (L- and T-type), Na+ current, an hyperpolarization-activated current, three voltage-gated K+ currents, two Ca2+-activated K+ current, Ca2+-activated Cl current, non-specific cation current, Na+-Ca2+ exchanger, Na+-K+ pump and background current. The magnitudes and kinetics of each current system in a spindle shaped single cell with a specified surface area:volume ratio is described by differential equations, in terms of maximal conductances, electrochemical gradient, voltage-dependent activation/inactivation gating variables and temporal changes in intracellular Ca2+ computed from known Ca2+ fluxes. These quantifications are validated by the reconstruction of the individual experimental ionic currents obtained under voltage-clamp. Phasic contraction is modeled in relation to the time constant of changing [Ca2+]i. This integrated model is validated by its reconstruction of the different USMC AP configurations (spikes, plateau and bursts of spikes), the change from bursting to plateau type AP produced by estradiol and of simultaneous experimental recordings of spontaneous AP, [Ca2+]i and phasic force. In summary, our advanced mathematical model provides a powerful tool to investigate the physiological ionic mechanisms underlying the genesis of uterine electrical E-C coupling of labor and parturition. This will furnish the evolution of descriptive and predictive quantitative models of myometrial electrogenesis at the whole cell and tissue levels.

BDNF mRNA abundance regulated by antidromic action potentials and AP-LTD in hippocampus.

PubMed

Bukalo, Olena; Lee, Philip R; Fields, R Douglas

2016-12-02

Action-potential-induced LTD (AP-LTD) is a form of synaptic plasticity that reduces synaptic strength in CA1 hippocampal neurons firing antidromically during sharp-wave ripples. This firing occurs during slow-wave sleep and quiet moments of wakefulness, which are periods of offline replay of neural sequences learned during encoding sensory information. Here we report that rapid and persistent down-regulation of different mRNA transcripts of the BDNF gene accompanies AP-LTD, and that AP-LTD is abolished in mice with the BDNF gene knocked out in CA1 hippocampal neurons. These findings increase understanding of the mechanism of AP-LTD and the cellular mechanisms of memory consolidation. Published by Elsevier Ireland Ltd.
Large area CMOS active pixel sensor x-ray imager for digital breast tomosynthesis: Analysis, modeling, and characterization.

PubMed

Zhao, Chumin; Kanicki, Jerzy; Konstantinidis, Anastasios C; Patel, Tushita

2015-11-01

Large area x-ray imagers based on complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology have been proposed for various medical imaging applications including digital breast tomosynthesis (DBT). The low electronic noise (50-300 e-) of CMOS APS x-ray imagers provides a possible route to shrink the pixel pitch to smaller than 75 μm for microcalcification detection and possible reduction of the DBT mean glandular dose (MGD). In this study, imaging performance of a large area (29×23 cm2) CMOS APS x-ray imager [Dexela 2923 MAM (PerkinElmer, London)] with a pixel pitch of 75 μm was characterized and modeled. The authors developed a cascaded system model for CMOS APS x-ray imagers using both a broadband x-ray radiation and monochromatic synchrotron radiation. The experimental data including modulation transfer function, noise power spectrum, and detective quantum efficiency (DQE) were theoretically described using the proposed cascaded system model with satisfactory consistency to experimental results. Both high full well and low full well (LFW) modes of the Dexela 2923 MAM CMOS APS x-ray imager were characterized and modeled. The cascaded system analysis results were further used to extract the contrast-to-noise ratio (CNR) for microcalcifications with sizes of 165-400 μm at various MGDs. The impact of electronic noise on CNR was also evaluated. The LFW mode shows better DQE at low air kerma (Ka<10 μGy) and should be used for DBT. At current DBT applications, air kerma (Ka∼10 μGy, broadband radiation of 28 kVp), DQE of more than 0.7 and ∼0.3 was achieved using the LFW mode at spatial frequency of 0.5 line pairs per millimeter (lp/mm) and Nyquist frequency ∼6.7 lp/mm, respectively. It is shown that microcalcifications of 165-400 μm in size can be resolved using a MGD range of 0.3-1 mGy, respectively. In comparison to a General Electric GEN2 prototype DBT system (at MGD of 2.5 mGy), an increased CNR (by ∼10) for microcalcifications was observed using the Dexela 2923 MAM CMOS APS x-ray imager at a lower MGD (2.0 mGy). The Dexela 2923 MAM CMOS APS x-ray imager is capable to achieve a high imaging performance at spatial frequencies up to 6.7 lp/mm. Microcalcifications of 165 μm are distinguishable based on reported data and their modeling results due to the small pixel pitch of 75 μm. At the same time, potential dose reduction is expected using the studied CMOS APS x-ray imager.
Quantitative and Mechanistic Assessment of Model Lipophilic Drugs in Micellar Solutions in the Transport Kinetics Across MDR1-MDCK Cell Monolayers.

PubMed

Ho, Norman F H; Nielsen, James; Peterson, Michelle; Burton, Philip S

2016-02-01

An approach to characterizing P-glycoprotein (Pgp) interaction potential for sparingly water-soluble compounds was developed using bidirectional transport kinetics in MDR1-MDCK cell monolayers. Paclitaxel, solubilized in a dilute polysorbate 80 (PS80) micellar solution, was used as a practical example. Although the passage of paclitaxel across the cell monolayer was initially governed by the thermodynamic activity of the micelle-solubilized drug solution, Pgp inhibition was sustained by the thermodynamic activity (i.e., critical micelle concentration) of the PS80 micellar solution bathing the apical (ap) membrane. The mechanistic understanding of the experimental strategies and treatment of data was supported by a biophysical model expressed in the form of transport events occurring at the ap and basolateral (bl) membranes in series whereas the vectorial directions of the transcellular kinetics were accommodated. The derived equations permitted the stepwise quantitative delineation of the Pgp efflux activity (inhibited and uninhibited by PS80) and the passive permeability coefficient of the ap membrane, the passive permeability at the bl membrane and, finally, the distinct coupling of these with efflux pump activity to identify the rate-determining steps and mechanisms. The Jmax/KM(∗) for paclitaxel was in the order of 10(-4) cm/s and the ap- and bl-membrane passive permeability coefficients were asymmetric, with bl-membrane permeability significantly greater than ap. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.
Andrographolide Inhibits Ovariectomy-Induced Bone Loss via the Suppression of RANKL Signaling Pathways.

PubMed

Wang, Tao; Liu, Qian; Zhou, Lin; Yuan, Jin Bo; Lin, Xixi; Zeng, Rong; Liang, Xiaonan; Zhao, Jinmin; Xu, Jiake

2015-11-17

Osteoporosis is a debilitating skeletal disorder with an increased risk of low-energy fracture, which commonly occurs among postmenopausal women. Andrographolide (AP), a natural product isolated from Andrographis paniculata, has been found to have anti-inflammatory, anti-cancer, anti-asthmatic, and neuro-protective properties. However, its therapeutic effect on osteoporosis is unknown. In this study, an ovariectomy (OVX) mouse model was used to evaluate the therapeutic effects of AP on post-menopausal osteoporosis by using micro-computed tomography (micro-CT). Bone marrow-derived osteoclast culture was used to examine the inhibitory effect of AP on osteoclastogenesis. Real time PCR was employed to examine the effect of AP on the expression of osteoclast marker genes. The activities of transcriptional factors NF-κB and NFATc1 were evaluated using a luciferase reporter assay, and the IκBα protein level was analyzed by Western blot. We found that OVX mice treated with AP have greater bone volume (BV/TV), trabecular thickness (Tb.Th), and trabecular number (Tb.N) compared to vehicle-treated OVX mice. AP inhibited RANKL-induced osteoclastogenesis, the expression of osteoclast marker genes including cathepsin K (Ctsk), TRACP (Acp5), and NFATc1, as well as the transcriptional activities of NF-κB and NFATc1. In conclusion, our results suggest that AP inhibits estrogen deficiency-induced bone loss in mice via the suppression of RANKL-induced osteoclastogensis and NF-κB and NFATc1 activities and, thus, might have therapeutic potential for osteoporosis.
An Excel-based implementation of the spectral method of action potential alternans analysis.

PubMed

Pearman, Charles M

2014-12-01

Action potential (AP) alternans has been well established as a mechanism of arrhythmogenesis and sudden cardiac death. Proper interpretation of AP alternans requires a robust method of alternans quantification. Traditional methods of alternans analysis neglect higher order periodicities that may have greater pro-arrhythmic potential than classical 2:1 alternans. The spectral method of alternans analysis, already widely used in the related study of microvolt T-wave alternans, has also been used to study AP alternans. Software to meet the specific needs of AP alternans analysis is not currently available in the public domain. An AP analysis tool is implemented here, written in Visual Basic for Applications and using Microsoft Excel as a shell. This performs a sophisticated analysis of alternans behavior allowing reliable distinction of alternans from random fluctuations, quantification of alternans magnitude, and identification of which phases of the AP are most affected. In addition, the spectral method has been adapted to allow detection and quantification of higher order regular oscillations. Analysis of action potential morphology is also performed. A simple user interface enables easy import, analysis, and export of collated results. © 2014 The Author. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.
Effects of Nicotinamide Adenine Dinucleotide (NAD(+)) and Diadenosine Tetraphosphate (Ap4A) on Electrical Activity of Working and Pacemaker Atrial Myocardium in Guinea Pigs.

PubMed

Pustovit, K B; Abramochkin, D V

2016-04-01

Effects of nucleotide polyphosphate compounds (nicotinamide adenine dinucleotide, NAD(+); diadenosine tetraphosphate, Ap4A) on the confi guration of action potentials were studied in isolated preparations of guinea pig sinoatrial node and right atrial appendage (auricle). In the working myocardium, NAD(+) and Ap4A in concentrations of 10(-5) and 10(-4) M had no effect on resting potential, but significantly reduced the duration of action potentials; the most pronounced decrease was found at 25% repolarization. In the primary pacemaker of the sinoatrial node, both concentrations of NAD(+) and Ap4A induced hyperpolarization and reduction in the rate of slow diastolic depolarization, but significant slowing of the sinus rhythm was produced by these substances only in the concentration of 10(-4) M. Moreover, AP shortening and marked acceleration of AP upstroke were observed in the pacemaker myocardium after application of polyphosphates. Comparative analysis of the effects of NAD(+) and Ap4A in the working and pacemaker myocardium drove us to a hypothesis on inhibitory effects of these substances on L-type calcium current accompanied by stimulation of one or several potassium currents, which induce enhancement of repolarization and hyperpolarization of membranes probably mediated by the activation of purine receptors.
Role of cytosolic calcium diffusion in cardiac purkinje cells.

PubMed

Limbu, Bijay; Shah, Kushal; Deo, Makarand

2016-08-01

The Cardiac Purkinje cells (PCs) exhibit distinct calcium (Ca2+) homeostasis than that in ventricular myocytes (VMs). Due to lack of t-tubules in PCs, the Ca2+ ions entering the cell have to diffuse through the cytoplasm to reach the sarcoplasmic reticulum (SR) before triggering Ca2+-induced-Ca2+-release (CICR). In recent experimental studies PCs have been shown to be more susceptible to action potential (AP) abnormalities than the VMs, however the exact mechanisms are poorly understood. In this study, we utilize morphologically realistic detailed biophysical mathematical model of a murine PC to systematically examine the role intracellular Ca2+ diffusion in the APs of PCs. A biphasic spatiotemporal Ca2+ diffusion process, as observed experimentally, was implemented in the model which includes radial Ca2+ wavelets and cell wide longitudinal Ca2+ diffusion wave (CWW). The AP morphology, specifically plateau, is affected due to changes in intracellular Ca2+ dynamics. When Ca2+ concentration in sarcolemmal region is elevated, it activated inward sodium Ca2+ exchanger (NCX) current resulting into prolongation of the plateau at faster diffusion rates. Our results demonstrate that the cytosolic Ca2+ diffusion waves play a significant role in shaping APs of PCs and could provide mechanistic insights into the increased arrhythmogeneity of PCs.
Associations of long-term exposure to air pollution and road traffic noise with cognitive function-An analysis of effect measure modification.

PubMed

Tzivian, Lilian; Jokisch, Martha; Winkler, Angela; Weimar, Christian; Hennig, Frauke; Sugiri, Dorothea; Soppa, Vanessa J; Dragano, Nico; Erbel, Raimund; Jöckel, Karl-Heinz; Moebus, Susanne; Hoffmann, Barbara

2017-06-01

Adverse effects of traffic-related air pollution (AP) and noise on cognitive functions have been proposed, but little is known about their interactions and the combined effect of co-exposure. Cognitive assessment was completed by 4086 participants of the population-based Heinz Nixdorf Recall cohort study using five neuropsychological subtests and an additively calculated global cognitive score (GCS). We assessed long-term residential concentrations for size-fractioned particulate matter (PM) and nitrogen oxides with land use regression. Road traffic noise (weighted 24-h (L DEN ) and night-time (L NIGHT ) means) was assessed according to the EU directive 2002/49/EC. Linear regression models adjusted for individual-level characteristics were calculated to estimate effect modification of associations between AP and noise with cognitive function. We used multiplicative interaction terms and categories of single or double high exposure, dichotomizing the potential effect modifier at the median (AP) or at an a priori defined threshold (road traffic noise). In fully adjusted models, high noise exposure increased the association of AP with cognitive function. For example, for an interquartile range increase of PM 2.5 (IQR 1.43), association s with GCS were: estimate (β)=-0.16 [95% confidence interval: -0.33; 0.01] and β=-0.48 [-0.72; -0.23] for low and high L DEN , respectively. The association of noise with GCS was restricted to highly AP-exposed participants. We observed stronger negative associations in those participants with double exposure compared to the addition of effect estimates of each single exposure. Our study suggests that AP and road traffic noise might act synergistically on cognitive function in adults. Copyright © 2017 Elsevier Ltd. All rights reserved.
Radiographic cup anteversion measurement corrected from pelvic tilt.

PubMed

Wang, Liao; Thoreson, Andrew R; Trousdale, Robert T; Morrey, Bernard F; Dai, Kerong; An, Kai-Nan

2017-11-01

The purpose of this study was to develop a novel technique to improve the accuracy of radiographic cup anteversion measurement by correcting the influence of pelvic tilt. Ninety virtual total hip arthroplasties were simulated from computed tomography data of 6 patients with 15 predetermined cup orientations. For each simulated implantation, anteroposterior (AP) virtual pelvic radiographs were generated for 11 predetermined pelvic tilts. A linear regression model was created to capture the relationship between radiographic cup anteversion angle error measured on AP pelvic radiographs and pelvic tilt. Overall, nine hundred and ninety virtual AP pelvic radiographs were measured, and 90 linear regression models were created. Pearson's correlation analyses confirmed a strong correlation between the errors of conventional radiographic cup anteversion angle measured on AP pelvic radiographs and the magnitude of pelvic tilt (P < 0.001). The mean of 90 slopes and y-intercepts of the regression lines were -0.8 and -2.5°, which were applied as the general correction parameters for the proposed tool to correct conventional cup anteversion angle from the influence of pelvic tilt. The current method proposes to measure the pelvic tilt on a lateral radiograph, and to use it as a correction for the radiographic cup anteversion measurement on an AP pelvic radiograph. Thus, both AP and lateral pelvic radiographs are required for the measurement of pelvic posture-integrated cup anteversion. Compared with conventional radiographic cup anteversion, the errors of pelvic posture-integrated radiographic cup anteversion were reduced from 10.03 (SD = 5.13) degrees to 2.53 (SD = 1.33) degrees. Pelvic posture-integrated cup anteversion measurement improves the accuracy of radiographic cup anteversion measurement, which shows the potential of further clarifying the etiology of postoperative instability based on planar radiographs. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.
Modeling Instruction in AP Physics C: Mechanics and Electricity and Magnetism

NASA Astrophysics Data System (ADS)

Belcher, Nathan Tillman

This action research study used data from multiple assessments in Mechanics and Electricity and Magnetism to determine the viability of Modeling Instruction as a pedagogy for students in AP Physics C: Mechanics and Electricity and Magnetism. Modeling Instruction is a guided-inquiry approach to teaching science in which students progress through the Modeling Cycle to develop a fully-constructed model for a scientific concept. AP Physics C: Mechanics and Electricity and Magnetism are calculus-based physics courses, approximately equivalent to first-year calculus-based physics courses at the collegiate level. Using a one-group pretest-posttest design, students were assessed in Mechanics using the Force Concept Inventory, Mechanics Baseline Test, and 2015 AP Physics C: Mechanics Practice Exam. With the same design, students were assessed in Electricity and Magnetism on the Brief Electricity and Magnetism Assessment, Electricity and Magnetism Conceptual Assessment, and 2015 AP Physics C: Electricity and Magnetism Practice Exam. In a one-shot case study design, student scores were collected from the 2017 AP Physics C: Mechanics and Electricity and Magnetism Exams. Students performed moderately well on the assessments in Mechanics and Electricity and Magnetism, demonstrating that Modeling Instruction is a viable pedagogy in AP Physics C: Electricity and Magnetism.
Delayed onset of changes in soma action potential genesis in nociceptive A-beta DRG neurons in vivo in a rat model of osteoarthritis

PubMed Central

Wu, Qi; Henry, James L

2009-01-01

Background Clinical data on osteoarthritis (OA) suggest widespread changes in sensory function that vary during the progression of OA. In previous studies on a surgically-induced animal model of OA we have observed that changes in structure and gene expression follow a variable trajectory over the initial days and weeks. To investigate mechanisms underlying changes in sensory function in this model, the present electrophysiological study compared properties of primary sensory nociceptive neurons at one and two months after model induction with properties in naïve control animals. Pilot data indicated no difference in C- or Aδ-fiber associated neurons and therefore the focus is on Aβ-fiber nociceptive neurons. Results At one month after unilateral derangement of the knee by cutting the anterior cruciate ligament and removing the medial meniscus, the only changes observed in Aβ-fiber dorsal root ganglion (DRG) neurons were in nociceptor-like unresponsive neurons bearing a hump on the repolarization phase; these changes consisted of longer half width, reflecting slowed dynamics of AP genesis, a depolarized Vm and an increased AP amplitude. At two months, changes observed were in Aβ-fiber high threshold mechanoreceptors, which exhibited shorter AP duration at base and half width, shorter rise time and fall time, and faster maximum rising rate/maximum falling rate, reflecting accelerated dynamics of AP genesis. Conclusion These data indicate that Aβ nociceptive neurons undergo significant changes that vary in time and occur later than changes in structure and in nociceptive scores in this surgically induced OA model. Thus, if changes in Aβ-fiber nociceptive neurons in this model reflect a role in OA pain, they may relate to mechanisms underlying pain associated with advanced OA. PMID:19785765
Molecular motions that shape the cardiac action potential: Insights from voltage clamp fluorometry.

PubMed

Zhu, Wandi; Varga, Zoltan; Silva, Jonathan R

2016-01-01

Very recently, voltage-clamp fluorometry (VCF) protocols have been developed to observe the membrane proteins responsible for carrying the ventricular ionic currents that form the action potential (AP), including those carried by the cardiac Na(+) channel, NaV1.5, the L-type Ca(2+) channel, CaV1.2, the Na(+)/K(+) ATPase, and the rapid and slow components of the delayed rectifier, KV11.1 and KV7.1. This development is significant, because VCF enables simultaneous observation of ionic current kinetics with conformational changes occurring within specific channel domains. The ability gained from VCF, to connect nanoscale molecular movement to ion channel function has revealed how the voltage-sensing domains (VSDs) control ion flux through channel pores, mechanisms of post-translational regulation and the molecular pathology of inherited mutations. In the future, we expect that this data will be of great use for the creation of multi-scale computational AP models that explicitly represent ion channel conformations, connecting molecular, cell and tissue electrophysiology. Here, we review the VCF protocol, recent results, and discuss potential future developments, including potential use of these experimental findings to create novel computational models. Copyright © 2015 Elsevier Ltd. All rights reserved.
Mechanisms of pro-arrhythmic abnormalities in ventricular repolarisation and anti-arrhythmic therapies in human hypertrophic cardiomyopathy.

PubMed

Passini, Elisa; Mincholé, Ana; Coppini, Raffaele; Cerbai, Elisabetta; Rodriguez, Blanca; Severi, Stefano; Bueno-Orovio, Alfonso

2016-07-01

Hypertrophic cardiomyopathy (HCM) is a cause of sudden arrhythmic death, but the understanding of its pro-arrhythmic mechanisms and an effective pharmacological treatment are lacking. HCM electrophysiological remodelling includes both increased inward and reduced outward currents, but their role in promoting repolarisation abnormalities remains unknown. The goal of this study is to identify key ionic mechanisms driving repolarisation abnormalities in human HCM, and to evaluate anti-arrhythmic effects of single and multichannel inward current blocks. Experimental ionic current, action potential (AP) and Ca(2+)-transient (CaT) recordings were used to construct populations of human non-diseased and HCM AP models (n=9118), accounting for inter-subject variability. Simulations were conducted for several degrees of selective and combined inward current block. Simulated HCM cardiomyocytes exhibited prolonged AP and CaT, diastolic Ca(2+) overload and decreased CaT amplitude, in agreement with experiments. Repolarisation abnormalities in HCM models were consistently driven by L-type Ca(2+) current (ICaL) re-activation, and ICaL block was the most effective intervention to normalise repolarisation and diastolic Ca(2+), but compromised CaT amplitude. Late Na(+) current (INaL) block partially abolished repolarisation abnormalities, with small impact on CaT. Na(+)/Ca(2+) exchanger (INCX) block effectively restored repolarisation and CaT amplitude, but increased Ca(2+) overload. Multichannel block increased efficacy in normalising repolarisation, AP biomarkers and CaT amplitude compared to selective block. Experimentally-calibrated populations of human AP models identify ICaL re-activation as the key mechanism for repolarisation abnormalities in HCM, and combined INCX, INaL and ICaL block as effective anti-arrhythmic therapies also able to partially reverse the HCM electrophysiological phenotype. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.
Impact of ionic current variability on human ventricular cellular electrophysiology.

PubMed

Romero, Lucía; Pueyo, Esther; Fink, Martin; Rodríguez, Blanca

2009-10-01

Abnormalities in repolarization and its rate dependence are known to be related to increased proarrhythmic risk. A number of repolarization-related electrophysiological properties are commonly used as preclinical biomarkers of arrhythmic risk. However, the variability and complexity of repolarization mechanisms make the use of cellular biomarkers to predict arrhythmic risk preclinically challenging. Our goal is to investigate the role of ionic current properties and their variability in modulating cellular biomarkers of arrhythmic risk to improve risk stratification and identification in humans. A systematic investigation into the sensitivity of the main preclinical biomarkers of arrhythmic risk to changes in ionic current conductances and kinetics was performed using computer simulations. Four stimulation protocols were applied to the ten Tusscher and Panfilov human ventricular model to quantify the impact of +/-15 and +/-30% variations in key model parameters on action potential (AP) properties, Ca(2+) and Na(+) dynamics, and their rate dependence. Simulations show that, in humans, AP duration is moderately sensitive to changes in all repolarization current conductances and in L-type Ca(2+) current (I(CaL)) and slow component of the delayed rectifier current (I(Ks)) inactivation kinetics. AP triangulation, however, is strongly dependent only on inward rectifier K(+) current (I(K1)) and delayed rectifier current (I(Kr)) conductances. Furthermore, AP rate dependence (i.e., AP duration rate adaptation and restitution properties) and intracellular Ca(2+) and Na(+) levels are highly sensitive to both I(CaL) and Na(+)/K(+) pump current (I(NaK)) properties. This study provides quantitative insights into the sensitivity of preclinical biomarkers of arrhythmic risk to variations in ionic current properties in humans. The results show the importance of sensitivity analysis as a powerful method for the in-depth validation of mathematical models in cardiac electrophysiology.
Potassium Currents of Olfactory Bulb Juxtaglomerular Cells: Characterization, Simulation, and Implications for Plateau Potential Firing

PubMed Central

Masurkar, Arjun V.; Chen, Wei R.

2011-01-01

Odor identity is encoded by the activity of olfactory bulb glomeruli, which receive primary sensory input and transfer it to projection neurons. Juxtaglomerular cells (JGCs) may influence glomerular processing via firing of long lasting plateau potentials. Though inward currents have been investigated, little is known regarding potassium current contribution to JGC plateau potentials. We pursued study of these currents, with the overarching goal of creating components for a computational model of JGC plateau potential firing. In conditions minimizing calcium-activated potassium current (IK(Ca)), we used whole cell voltage clamp and in vitro slice preparations to characterize three potassium currents in rat JGCs. The prominent component Ikt1 displayed rapid kinetics (τ10%−90% rise 0.6–2ms, τinactivation 5–10ms) and was blocked by high concentration 4-AP (5mM) and TEA (40mM). It had half maximal activation at −10mV (V½max) and little inactivation at rest. Ikt2, with slower kinetics (τ10%−90% rise 11–15ms, τinactivation 100–300ms), was blocked by low concentration 4-AP (0.5mM) and TEA (5mM). The V½max was 0mV and inactivation was also minimal at rest. Sustained current Ikt3 showed sensitivity to low concentration 4-AP and TEA, and had V½max of +10mV. Further experiments, in conditions of physiologic calcium buffering, suggested that IK(Ca) contributed to Ikt3 with minimal effect on plateau potential evolution. We transformed these characterizations into Hodgkin-Huxley models that robustly mimicked experimental data. Further simulation demonstrated that Ikt1 would be most efficiently activated by plateau potential waveforms, predicting a critical role in shaping JGC firing. These studies demonstrated that JGCs possess a unique potassium current profile, with delayed rectifier (Ikt3), atypical A-current (Ikt1), and D-current (Ikt2) in accordance with known expression patterns in OB glomeruli. Our simulations also provide an initial framework for more integrative models of JGC plateau potential firing. PMID:21704678
Properties and ionic mechanisms of action potential adaptation, restitution, and accommodation in canine epicardium.

PubMed

Decker, Keith F; Heijman, Jordi; Silva, Jonathan R; Hund, Thomas J; Rudy, Yoram

2009-04-01

Computational models of cardiac myocytes are important tools for understanding ionic mechanisms of arrhythmia. This work presents a new model of the canine epicardial myocyte that reproduces a wide range of experimentally observed rate-dependent behaviors in cardiac cell and tissue, including action potential (AP) duration (APD) adaptation, restitution, and accommodation. Model behavior depends on updated formulations for the 4-aminopyridine-sensitive transient outward current (I(to1)), the slow component of the delayed rectifier K(+) current (I(Ks)), the L-type Ca(2+) channel current (I(Ca,L)), and the Na(+)-K(+) pump current (I(NaK)) fit to data from canine ventricular myocytes. We found that I(to1) plays a limited role in potentiating peak I(Ca,L) and sarcoplasmic reticulum Ca(2+) release for propagated APs but modulates the time course of APD restitution. I(Ks) plays an important role in APD shortening at short diastolic intervals, despite a limited role in AP repolarization at longer cycle lengths. In addition, we found that I(Ca,L) plays a critical role in APD accommodation and rate dependence of APD restitution. Ca(2+) entry via I(Ca,L) at fast rate drives increased Na(+)-Ca(2+) exchanger Ca(2+) extrusion and Na(+) entry, which in turn increases Na(+) extrusion via outward I(NaK). APD accommodation results from this increased outward I(NaK). Our simulation results provide valuable insight into the mechanistic basis of rate-dependent phenomena important for determining the heart's response to rapid and irregular pacing rates (e.g., arrhythmia). Accurate simulation of rate-dependent phenomena and increased understanding of their mechanistic basis will lead to more realistic multicellular simulations of arrhythmia and identification of molecular therapeutic targets.
The effects of anticonvulsants on 4-aminopyridine-induced bursting: in vitro studies on rat peripheral nerve and dorsal roots.

PubMed Central

Lees, G.

1996-01-01

1. Aminopyridines have been used as beneficial symptomatic treatments in a variety of neurological conditions including multiple sclerosis but have been associated with considerable toxicity in the form of abdominal pain, paraesthesias and (rarely) convulsions. 2. Extracellular and intracellular recording was used to characterize action potentials in rat sciatic nerves and dorsal roots and the effects of 4-aminopyridine (4-AP). 3. In sciatic nerve trunks, 1 mM 4-AP produced pronounced after potentials at room temperature secondary to regenerative firing in affected axons (5-10 spikes per stimulus). At physiological temperatures, after potentials (2-3 spikes) were greatly attenuated in peripheral axons. 4. 4-AP evoked more pronounced and prolonged after discharges in isolated dorsal roots at 37 degrees C (3-5.5 mV and 80-100 ms succeeded by a smaller inhibitory/depolarizing voltage shift) which were used to assess the effects of anticonvulsants. 5. Phenytoin, carbamazepine and lamotrigine dose-dependently reduced the area of 4-AP-induced after potentials at 100 and 320 microM but the amplitude of compound action potentials (evoked at 0.5 Hz) was depressed in parallel. 6. The tonic block of sensory action potentials by all three drugs (at 320 microM) was enhanced by high frequency stimulation (5-500 Hz). 7. The lack of selectivity of these frequency-dependent Na+ channel blockers for burst firing compared to low-frequency spikes, is discussed in contrast to their effects on 4-AP-induced seizures and paroxysmal activity in CNS tissue (which is associated with large and sustained depolarizing plateau potentials). 8. In conclusion, these in vitro results confirm the marked sensitivity of sensory axons to 4-AP (the presumptive basis for paraesthesias). Burst firing was not preferentially impaired at relatively high concentrations suggesting that anticonvulsants will not overcome the toxic peripheral actions of 4-AP in neurological patients. PMID:8821551
Benchmarking electrophysiological models of human atrial myocytes

PubMed Central

Wilhelms, Mathias; Hettmann, Hanne; Maleckar, Mary M.; Koivumäki, Jussi T.; Dössel, Olaf; Seemann, Gunnar

2013-01-01

Mathematical modeling of cardiac electrophysiology is an insightful method to investigate the underlying mechanisms responsible for arrhythmias such as atrial fibrillation (AF). In past years, five models of human atrial electrophysiology with different formulations of ionic currents, and consequently diverging properties, have been published. The aim of this work is to give an overview of strengths and weaknesses of these models depending on the purpose and the general requirements of simulations. Therefore, these models were systematically benchmarked with respect to general mathematical properties and their ability to reproduce certain electrophysiological phenomena, such as action potential (AP) alternans. To assess the models' ability to replicate modified properties of human myocytes and tissue in cardiac disease, electrical remodeling in chronic atrial fibrillation (cAF) was chosen as test case. The healthy and remodeled model variants were compared with experimental results in single-cell, 1D and 2D tissue simulations to investigate AP and restitution properties, as well as the initiation of reentrant circuits. PMID:23316167
AP233: An Information Model for Systems Engineering

NASA Technical Reports Server (NTRS)

Siebes, Georg

2009-01-01

In today's world, information is abundant. We have no problems generating it. But we are challenged to find, organize, and exchange information. center dot A standardized model of information can help. Such a model nearly completed its development for Systems Engineering. It is referred to as AP233 (AP = Application Protocol).
Antipsychotic Use in Pregnancy and the Risk for Congenital Malformations.

PubMed

Huybrechts, Krista F; Hernández-Díaz, Sonia; Patorno, Elisabetta; Desai, Rishi J; Mogun, Helen; Dejene, Sara Z; Cohen, Jacqueline M; Panchaud, Alice; Cohen, Lee; Bateman, Brian T

2016-09-01

The frequency of antipsychotic (AP) use during pregnancy has approximately doubled during the last decade. However, little is known about their safety for the developing fetus, and concerns have been raised about a potential association with congenital malformations. To examine the risk for congenital malformations overall and cardiac malformations associated with first-trimester exposure to APs. This nationwide sample of 1 360 101 pregnant women enrolled in Medicaid with a live-born infant constituted the pregnancy cohort nested in the Medicaid Analytic Extract database, which included data from January 1, 2000, to December 31, 2010. Participants were enrolled in Medicaid from 3 months before their last menstrual period through at least 1 month after delivery. Relative risks (RRs) were estimated using generalized linear models with fine stratification on the propensity score to control for the underlying psychiatric disorders and other potential confounders. Data were analyzed during 2015. Use of APs during the first trimester, the etiologically relevant period for organogenesis. Major congenital malformations overall and cardiac malformations identified during the first 90 days after delivery. Of the 1 341 715 pregnancies that met inclusion criteria (mean [SD] age of women, 24.02 [5.77] years), 9258 (0.69%) filled at least 1 prescription for an atypical AP and 733 (0.05%) filled at least 1 prescription for a typical AP during the first trimester. Overall, 32.7 (95% CI, 32.4-33.0) per 1000 births not exposed to APs were diagnosed with congenital malformations compared with 44.5 (95% CI, 40.5-48.9) per 1000 births exposed to atypical and 38.2 (95% CI, 26.6-54.7) per 1000 births exposed to typical APs. Unadjusted analyses suggested an increased risk for malformations overall for atypical APs (RR, 1.36; 95% CI, 1.24-1.50) but not for typical APs (RR, 1.17; 95% CI, 0.81-1.68). After confounding adjustment, the RR was reduced to 1.05 (95% CI, 0.96-1.16) for atypical APs and 0.90 (95% CI, 0.62-1.31) for typical APs. The findings for cardiac malformations were similar. For the individual agents examined, a small increased risk in overall malformations (RR, 1.26; 95% CI, 1.02-1.56) and cardiac malformations (RR, 1.26; 95% CI, 0.88-1.81) was found for risperidone that was independent of measured confounders. Evidence from this large study suggests that use of APs early in pregnancy generally does not meaningfully increase the risk for congenital malformations overall or cardiac malformations in particular. The small increase in the risk for malformations observed with risperidone requires additional study.

Na+ current in presynaptic terminals of the crayfish opener cannot initiate action potentials.

PubMed

Lin, Jen-Wei

2016-01-01

Action potential (AP) propagation in presynaptic axons of the crayfish opener neuromuscular junction (NMJ) was investigated by simultaneously recording from a terminal varicosity and a proximal branch. Although orthodromically conducting APs could be recorded in terminals with amplitudes up to 70 mV, depolarizing steps in terminals to -20 mV or higher failed to fire APs. Patch-clamp recordings did detect Na(+) current (INa) in most terminals. The INa exhibited a high threshold and fast activation rate. Local perfusion of Na(+)-free saline showed that terminal INa contributed to AP waveform by slightly accelerating the rising phase and increasing the peak amplitude. These findings suggest that terminal INa functions to "touch up" but not to generate APs. Copyright © 2016 the American Physiological Society.
An improved model for the combustion of AP composite propellants

NASA Technical Reports Server (NTRS)

Cohen, N. S.; Strand, L. D.

1981-01-01

This paper presents several improvements to the BDP model of steady-state burning of AP composite solid propellants. The Price-Boggs-Derr model of AP monopropellant burning is incorporated to represent the AP. A separate energy equation is written for the binder to permit a different surface temperature from the AP; this includes an analysis of the sharing of primary diffusion flame energy, and correction of a BDP model inconsistency in treating the binder regression rate. A method for assembling component contributions to calculate the burning rates of multimodal propellants is also presented. Results are shown in the form of representative burning rate curves, comparisons with data, and calculated internal details of interest. Ideas for future work are discussed in an Appendix.
In vitro and in vivo antioxidant potential of milks, yoghurts, fermented milks and cheeses: a narrative review of evidence.

PubMed

Fardet, Anthony; Rock, Edmond

2018-06-01

The antioxidant potential (AP) is an important nutritional property of foods, as increased oxidative stress is involved in most diet-related chronic diseases. In dairy products, the protein fraction contains antioxidant activity, especially casein. Other antioxidants include: antioxidant enzymes; lactoferrin; conjugated linoleic acid; coenzyme Q10; vitamins C, E, A and D3; equol; uric acid; carotenoids; and mineral activators of antioxidant enzymes. The AP of dairy products has been extensively studied in vitro, with few studies in animals and human subjects. Available in vivo studies greatly differ in their design and objectives. Overall, on a 100 g fresh weight-basis, AP of dairy products is close to that of grain-based foods and vegetable or fruit juices. Among dairy products, cheeses present the highest AP due to their higher protein content. AP of milk increases during digestion by up to 2·5 times because of released antioxidant peptides. AP of casein is linked to specific amino acids, whereas β-lactoglobulin thiol groups play a major role in the AP of whey. Thermal treatments such as ultra-high temperature processing have no clear effect on the AP of milk. Raw fat-rich milks have higher AP than less fat-rich milk, because of lipophilic antioxidants. Probiotic yoghurts and fermented milks have higher AP than conventional yoghurt and milk because proteolysis by probiotics releases antioxidant peptides. Among the probiotics, Lactobacillus casei/acidophilus leads to the highest AP. The data are insufficient for cheese, but fermentation-based changes appear to make a positive impact on AP. In conclusion, AP might participate in the reported dairy product-protective effects against some chronic diseases.
The high energy demand of neuronal cells caused by passive leak currents is not a waste of energy.

PubMed

Berndt, Nikolaus; Holzhütter, Hermann-Georg

2013-11-01

It is estimated that maintenance of the resting potential of neurons consumes between 15% (in gray matter) and 44% (in fully myelinated white matter) of the brain's total energy budget [1]. This poses the intriguing question why evolution has not strived to lower the permeability of passive ion channels to cut the high resting-state energy budget of the brain. Based on a conceptual mathematical model of neuronal ion currents and action potential (AP) firing we demonstrate that a neuron endowed with small leak currents and correspondingly low energy consumption by the Na(+)/K(+)-ATPase in the resting state may indeed recapitulate all features of normal AP firing. However, the activation and inactivation of such a "low-energy-cost neuron" turns out to be extremely sensitive to small fluctuation of Na(+) currents associated with Na(+)-dependent secondary-active transport that is indispensable for the metabolic integrity of the cell and neurotransmitter recycling. We provide evidence that sufficiently large leak currents function as important stabilizers of the membrane potential and thus are required to allow robust AP firing. Our simulations suggest that the energy demand of the Na(+)/K(+)-ATPase needed to counterbalance passive leak currents cannot be significantly dropped below observed values.
Resting state functional connectivity of the ventral auditory pathway in musicians with absolute pitch.

PubMed

Kim, Seung-Goo; Knösche, Thomas R

2017-08-01

Absolute pitch (AP) is the ability to recognize pitch chroma of tonal sound without external references, providing a unique model of the human auditory system (Zatorre: Nat Neurosci 6 () 692-695). In a previous study (Kim and Knösche: Hum Brain Mapp () 3486-3501), we identified enhanced intracortical myelination in the right planum polare (PP) in musicians with AP, which could be a potential site for perceptional processing of pitch chroma information. We speculated that this area, which initiates the ventral auditory pathway, might be crucially involved in the perceptual stage of the AP process in the context of the "dual pathway hypothesis" that suggests the role of the ventral pathway in processing nonspatial information related to the identity of an auditory object (Rauschecker: Eur J Neurosci 41 () 579-585). To test our conjecture on the ventral pathway, we investigated resting state functional connectivity (RSFC) using functional magnetic resonance imaging (fMRI) from musicians with varying degrees of AP. Should our hypothesis be correct, RSFC via the ventral pathway is expected to be stronger in musicians with AP, whereas such group effect is not predicted in the RSFC via the dorsal pathway. In the current data, we found greater RSFC between the right PP and bilateral anteroventral auditory cortices in musicians with AP. In contrast, we did not find any group difference in the RSFC of the planum temporale (PT) between musicians with and without AP. We believe that these findings support our conjecture on the critical role of the ventral pathway in AP recognition. Hum Brain Mapp 38:3899-3916, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.
Exogenous alkaline phosphatase treatment complements endogenous enzyme protection in colonic inflammation and reduces bacterial translocation in rats.

PubMed

Martínez-Moya, P; Ortega-González, M; González, R; Anzola, A; Ocón, B; Hernández-Chirlaque, C; López-Posadas, R; Suárez, M D; Zarzuelo, A; Martínez-Augustin, O; Sánchez de Medina, F

2012-08-01

Alkaline phosphatase (AP) inactivates bacterial lipopolysaccharide and may therefore be protective. The small intestine and colon express intestinal (IAP) and tissue nonspecific enzyme (TNAP), respectively. The aim of this study was to assess the therapeutic potential of exogenous AP and its complementarity with endogenous enzyme protection in the intestine, as evidenced recently. IAP was given to rats by the oral or intrarectal route (700U/kgday). Oral budesonide (1mg/kgday) was used as a reference treatment. Treatment with intrarectal AP resulted in a 54.5% and 38.0% lower colonic weight and damage score, respectively, and an almost complete normalization of the expression of S100A8, LCN2 and IL-1β (p<0.05). Oral AP was less efficacious, while budesonide had a more pronounced effect on most parameters. Both oral and intrarectal AP counteracted bacterial translocation effectively (78 and 100%, respectively, p<0.05 for the latter), while budesonide failed to exert a positive effect. AP activity was increased in the feces of TNBS colitic animals, associated with augmented sensitivity to the inhibitor levamisole, suggesting enhanced luminal release of this enzyme. This was also observed in the mouse lymphocyte transfer model of chronic colitis. In a separate time course study, TNAP was shown to increase 2-3 days after colitis induction, while dextran sulfate sodium was a much weaker inducer of this isoform. We conclude that exogenous AP exerts beneficial effects on experimental colitis, which includes protection against bacterial translocation. AP of the tissue-nonspecific isoform is shed in higher amounts to the intestinal lumen in experimental colitis, possibly aiding in intestinal protection. Copyright © 2012 Elsevier Ltd. All rights reserved.
Bridging of a substrate between cyclodextrin and an enzyme’s active site pocket triggers a unique mode of inhibition

PubMed Central

Sule, Nitesh V; Ugrinov, Angel; Mallik, Sanku; Srivastava, D. K.

2014-01-01

Background Methionyl-7-amino-4-methylcoumarin (MetAMC) serves as a substrate for the E. coli Methionine aminopeptidase (MetAP) catalyzed reaction, and is routinely used for screening compounds to identify potential antibiotic agents. In pursuit of screening the enzyme’s inhibitors, we observed that 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), utilized to solubilize hydrophobic inhibitors, inhibited the catalytic activity of the enzyme, and such inhibition was not solely due to sequestration of the substrate by HP-β-CD. Methods The mechanistic path for the HP-β-CD mediated inhibition of MetAP was probed by performing a detailed account of steady-state kinetics, ligand binding, X-ray crystallographic, and molecular modeling studies. Results X-ray crystallographic data of the β-cyclodextrin—substrate (β-CD—MetAMC) complex reveal that while the AMC moiety of the substrate is confined within the CD cavity, the methionine moiety protrudes outward. The steady-state kinetic data for inhibition of MetAP by HP-β-CD—MetAMC conform to a model mechanism in which the substrate is “bridged” between HP-β-CD and the enzyme’s active-site pocket, forming HP-β-CD—MetAMC—MetAP as the catalytically inactive ternary complex. Molecular modeling shows that the scissile bond of HP-β-CD-bound MetAMC substrate does not reach within the proximity of the enzyme’s catalytic metal center, and thus the substrate fails to undergo cleavage. Conclusions The data presented herein suggests that the bridging of the substrate between the enzyme and HP-β-CD cavities is facilitated by interaction of their surfaces, and the resulting complex inhibits the enzyme activity. General Significance Due to its potential interaction with physiological proteins via sequestered substrates, caution must be exercised in HP-β-CD mediated delivery of drugs under pathophysiological conditions. PMID:25450177
Variable Action Potential Backpropagation during Tonic Firing and Low-Threshold Spike Bursts in Thalamocortical But Not Thalamic Reticular Nucleus Neurons.

PubMed

Connelly, William M; Crunelli, Vincenzo; Errington, Adam C

2017-05-24

Backpropagating action potentials (bAPs) are indispensable in dendritic signaling. Conflicting Ca 2+ -imaging data and an absence of dendritic recording data means that the extent of backpropagation in thalamocortical (TC) and thalamic reticular nucleus (TRN) neurons remains unknown. Because TRN neurons signal electrically through dendrodendritic gap junctions and possibly via chemical dendritic GABAergic synapses, as well as classical axonal GABA release, this lack of knowledge is problematic. To address this issue, we made two-photon targeted patch-clamp recordings from rat TC and TRN neuron dendrites to measure bAPs directly. These recordings reveal that "tonic"' and low-threshold-spike (LTS) "burst" APs in both cell types are always recorded first at the soma before backpropagating into the dendrites while undergoing substantial distance-dependent dendritic amplitude attenuation. In TC neurons, bAP attenuation strength varies according to firing mode. During LTS bursts, somatic AP half-width increases progressively with increasing spike number, allowing late-burst spikes to propagate more efficiently into the dendritic tree compared with spikes occurring at burst onset. Tonic spikes have similar somatic half-widths to late burst spikes and undergo similar dendritic attenuation. In contrast, in TRN neurons, AP properties are unchanged between LTS bursts and tonic firing and, as a result, distance-dependent dendritic attenuation remains consistent across different firing modes. Therefore, unlike LTS-associated global electrical and calcium signals, the spatial influence of bAP signaling in TC and TRN neurons is more restricted, with potentially important behavioral-state-dependent consequences for synaptic integration and plasticity in thalamic neurons. SIGNIFICANCE STATEMENT In most neurons, action potentials (APs) initiate in the axosomatic region and propagate into the dendritic tree to provide a retrograde signal that conveys information about the level of cellular output to the locations that receive most input: the dendrites. In thalamocortical and thalamic reticular nucleus neurons, the site of AP generation and the true extent of backpropagation remain unknown. Using patch-clamp recordings, this study measures dendritic propagation of APs directly in these neurons. In either cell type, high-frequency low-threshold spike burst or lower-frequency tonic APs undergo substantial voltage attenuation as they spread into the dendritic tree. Therefore, backpropagating spikes in these cells can only influence signaling in the proximal part of the dendritic tree. Copyright © 2017 Connelly et al.
Antioxidants Inhibit Formation of 3-Monochloropropane-1,2-diol Esters in Model Reactions.

PubMed

Li, Chang; Jia, Hanbing; Shen, Mingyue; Wang, Yuting; Nie, Shaoping; Chen, Yi; Zhou, Yongqiang; Wang, Yuanxing; Xie, Mingyong

2015-11-11

The capacities of six antioxidants to inhibit the formation of 3-monochloropropane-1,2 diol (3-MCPD) esters were examined in this study. Inhibitory capacities of the antioxidants were investigated both in chemical models containing the precursors (tripalmitoyl glycerol, 1,2-dipalmitoyl-sn-glycerol, monopalmitoyl glycerol, and sodium chloride) of 3-MCPD esters and in oil models (rapeseed oil and sodium chloride). Six antioxidants, butylated hydroxytoluene (BHT), butylated hydroxy anisole (BHA), tert-butyl hydroquinone (TBHQ), propyl gallate (PG), L-ascorbyl palmitate (AP), and α-tocopherol (VE), were found to exhibit inhibiting capacities on 3-MCPD ester formation both in chemical models and in oil models. TBHQ provided the highest inhibitory capacity both in chemical models and in oil models; 44% of 3-MCPD ester formation was inhibited in the presence of TBHQ (66 mg/kg of oil) after heating of rapeseed oil at 230 °C for 30 min, followed by PG and AP. BHT, BHA, and VE appeared to have weaker inhibitory abilities in both models. VE exhibited the lowest inhibition rate; 22% of 3-MCPD esters were inhibited in the presence of VE (172 mg/kg of oil) after heating of rapeseed oil at 230 °C for 30 min. In addition, the inhibition rates of PG and VE decreased dramatically with an increase in temperature or heating time. The results suggested that some antioxidants, such as TBHQ, PG, and AP, could be the potential inhibitors of 3-MCPD esters in practice.
Dendritic small conductance calcium-activated potassium channels activated by action potentials suppress EPSPs and gate spike-timing dependent synaptic plasticity.

PubMed

Jones, Scott L; To, Minh-Son; Stuart, Greg J

2017-10-23

Small conductance calcium-activated potassium channels (SK channels) are present in spines and can be activated by backpropagating action potentials (APs). This suggests they may play a critical role in spike-timing dependent synaptic plasticity (STDP). Consistent with this idea, EPSPs in both cortical and hippocampal pyramidal neurons were suppressed by preceding APs in an SK-dependent manner. In cortical pyramidal neurons EPSP suppression by preceding APs depended on their precise timing as well as the distance of activated synapses from the soma, was dendritic in origin, and involved SK-dependent suppression of NMDA receptor activation. As a result SK channel activation by backpropagating APs gated STDP induction during low-frequency AP-EPSP pairing, with both LTP and LTD absent under control conditions but present after SK channel block. These findings indicate that activation of SK channels in spines by backpropagating APs plays a key role in regulating both EPSP amplitude and STDP induction.
Differences in glucose-stimulated insulin secretion in vitro of islets from human, nonhuman primate and porcine origin

PubMed Central

Mueller, Kate R; Balamurugan, A.N.; Cline, Gary W; Pongratz, Rebecca L; Hooper, Rebecca L; Weegman, Bradley P; Kitzmann, Jennifer P; Taylor, Michael J; Graham, Melanie L; Schuurman, Henk-Jan; Papas, Klearchos K

2014-01-01

Background Porcine islet xenotransplantation is considered a potential cell-based therapy for type 1 diabetes. It is currently being evaluated in diabetic nonhuman primates (NHP) to assess safety and efficacy of the islet product. However, due to a variety of distinct differences between the respective species, including the insulin secretory characteristics of islets, the suitability and predictive value of the preclinical model in the extrapolation to the clinical setting remains a critical issue. Methods Islets isolated from human (n=3), NHP (n=2), adult pig (AP, n=3) and juvenile pig (JP, n=3) pancreata were perifused with medium at basal glucose (2.5mM) followed by high glucose (16.7mM) concentrations. The total glucose-stimulated insulin secretion (GSIS) was calculated from generated insulin secretion profiles. Results NHP islets exhibited GSIS 3-fold higher than human islets, while AP and JP islets exhibited GSIS 1/3 and 1/16 of human islets, respectively. The insulin content of NHP and AP islets was similar to that of human islets, whereas that of JP islets was 1/3 of human islets. Conclusion Despite the fact that human, NHP, and AP islets contain similar amounts of insulin, the much higher GSIS for NHP islets than for human, AP and JP islets suggests the need for increased dosing of islets from JP and AP in pig-to-NHP transplantation which may be substantially higher than that required for humans. Finally, porcine islet xenotransplantation to humans may require significantly higher dosing given the lower GSIS of AP islets compared to human islets. PMID:23384163
Diadenosine tetraphosphate (Ap4A) and triphosphate (Ap3A) signaling of human sperm motility.

PubMed

Chan, P J; Su, B C; Tredway, D R

1991-01-01

The ubiquitous dinucleotide polyphosphate, diadenosine tetraphosphate (Ap4A), has been shown to be a signal molecule for DNA replication in mammalian cells. In this study, Ap4A and a related compound, diadenosine triphosphate (Ap3A), were tested for possible signaling functions in human spermatozoa. A computerized automated semen analyzer was used to detect changes in spermatozoa motility parameters. Cryopreserved-thawed donor spermatozoa were washed and incubated in 0.1 mM Ap4A, 0.1 mM Ap3A, or control medium. The data indicated that both Ap4A and Ap3A decreased the percentage of motile spermatozoa after 4 or more hours of incubation in vitro. The two dinucleotide polyphosphates caused an increase in the amplitude of lateral spermatozoa head displacement parameter only at the start of incubation. The other spermatozoa kinematic parameters were unaffected. No opposing ying-yang dual actions of Ap4A to Ap3A were seen. From the results, Ap4A and Ap3A were observed to be potential inhibitory signals of spermatozoa motility after prolonged exposure.
Electrophysiological mechanisms of sophocarpine as a potential antiarrhythmic agent.

PubMed

Yang, Zhi-fang; Li, Ci-zhen; Wang, Wei; Chen, Ying-min; Zhang, Ying; Liu, Yuan-mou; Wang, Hong-wei

2011-03-01

To examine the electrophysiological effects of sophocarpine on action potentials (AP) and ionic currents of cardiac myocytes and to compare some of these effects with those of amiodarone. Langendorff perfusion set-up was used in isolated guinea pig heart, and responses to sophocarpine were monitored using electrocardiograph. Conventional microelectrode, voltage clamp technique and perforated patch were employed to record fast response AP (fAP), slow response AP (sAP) and ionic currents in guinea pig papillary muscle or rabbit sinus node cells. Tachyarrhythmia produced by isoprenaline (15 μmol/L) could be reversed by sophocarpine (300 μmol/L). Sophocarpine (10 μmol/L) decreased the amplitude by 4.0%, maximal depolarization velocity (V(max)) of the fAP by 24.4%, and Na(+) current (I(Na)) by 18.0%, while it prolonged the effective refractory period (ERP) by 21.1%. The same concentration of sophocarpine could also decrease the amplitude and V(max) of the sAP, by 26.8% and 25.7%, respectively, and attenuated the Ca(2+) current (I(CaL)) and the K(+) tail current substantially. Comparison of sophocarpine with amiodarone demonstrated that both prolonged the duration and the ERP of fAP and sAP, both decreased the amplitude and V(max) of the fAP and sAP, and both slowed the automatic heart rate. Sophocarpine could reverse isoprenaline-induced arrhythmia and inhibit I(Na), I(CaL), and I(Kr) currents. The electrophysiological effects of sophocarpine are similar to those of amiodarone, which might be regarded as a prospective antiarrhythmic agent.
AP-8 trapped proton environment for solar maximum and solar minimum. [Computer accessible models

NASA Technical Reports Server (NTRS)

Sawyer, D. M.; Vette, J. I.

1976-01-01

Data sets from Ov-3 and Azur indicate a need for improvement in models of the stably trapped proton flux with energies between 0.1 and 400 MeV. Two computer accessible models are described: AP8MAX and AP8MIN. The models are presented in the form of nomographs, B-L plots, R-lambda plots, and equatorial radial profiles. Nomographs of the orbit-integrated fluxes are also discussed. The models are compared with each other, with the data, and with previous AP models. Requirements for future improvements include more complete data coverage and periodic comparisons with new data sets as they become available. The machine-sensible format in which the models are available are described.
Patent foramen ovale and atrial septal aneurysm can cause ischemic stroke in patients with antiphospholipid syndrome.

PubMed

Tanaka, Yasutaka; Ueno, Yuji; Miyamoto, Nobukazu; Shimada, Yoshiaki; Tanaka, Ryota; Hattori, Nobutaka; Urabe, Takao

2013-01-01

The purpose of the present study was to evaluate the contributions of embolic etiologies, patent foramen ovale (PFO) and atrial septal aneurysm (ASA) to the pathogenesis of ischemic stroke in patients with antiphospholipid syndrome (APS). We performed transesophageal echocardiography (TEE) examination for consecutive stroke patients who had been diagnosed with APS (APS group) to detect potential embolic sources. APS was diagnosed based on the modified Sapporo criteria. The control stroke group comprised age- and sex-matched cryptogenic stroke patients undergoing TEE. We assessed and compared the clinical characteristics and TEE findings between stroke patients with APS and control stroke groups. Among 582 patients, nine patients (nine women; mean age, 50 ± 18 years) were classified into the APS group. In 137 patients undergoing TEE, 41 age-matched female stroke patients were recruited to the control stroke group. Prevalences of PFO and ASA were significantly higher in the APS group than in the control stroke group (89 vs. 41 %, p = 0.027; 67 vs. 20 %, p = 0.015, respectively). Multiple logistic regression analysis showed that PFO (odds ratio (OR), 13.71; 95 % confidence interval (CI), 1.01-185.62; p = 0.049) and ASA (OR, 8.06; 95 % CI, 1.17-55.59; p = 0.034) were independently associated with the APS group. PFO and ASA were strongly associated with the APS group, and could thus represent potential embolic sources in ischemic stroke patients with APS.
Computer-controlled closed-loop drug infusion system for automated hemodynamic resuscitation in endotoxin-induced shock.

PubMed

Uemura, Kazunori; Kawada, Toru; Zheng, Can; Li, Meihua; Sugimachi, Masaru

2017-10-23

Hemodynamic resuscitation in septic shock requires aggressive fluid replacement and appropriate use of vasopressors to optimize arterial pressure (AP) and cardiac output (CO). Because responses to these drugs vary between patients and within patient over time, strict monitoring of patient condition and repetitive adjustment of drug dose are required. This task is time and labor consuming, and is associated with poor adherence to resuscitation guidelines. To overcome this issue, we developed a computer-controlled closed-loop drug infusion system for automated hemodynamic resuscitation in septic shock, and evaluated the performance of the system in a canine model of endotoxin shock. Our system monitors AP, CO and central venous pressure, and computes arterial resistance (R), stressed blood volume (V) and Frank-Starling slope of left ventricle (S). The system controls R with noradrenaline (NA), and V with Ringer's acetate solution (RiA), thereby controlling AP and CO. In 4 dogs, AP and CO were measured invasively. In another 4 dogs, AP and CO were measured less invasively using clinically acceptable modalities, aiming to make the system clinically feasible. In all 8 dogs, endotoxin shock was induced by injecting Escherichia coli lipopolysaccharide, which significantly decreased AP from 95 (91-108) to 43 (39-45) mmHg, and CO from 112 (104-142) to 62 (51-73) ml·min -1 ·kg -1 . The system was then connected to the dogs, and activated. System performance was observed over a period of 4 h. Our system immediately started infusions of NA and RiA. Within 40 min, RiA increased V to target level, and NA maintained R at target level, while S was concomitantly increased. These resulted in restoration of AP to 70 (69-71) mmHg and CO to 130 (125-138) ml·min -1 ·kg -1 . Median of absolute performance error, an index of precision of control, was small in AP [2.5 (2.1-4.5) %] and CO [2.4 (1.4-5.5) %], which were not increased even when the variables were measured less invasively. In a canine model of endotoxin shock, our system automatically improved and maintained AP and CO at their target values with small performance error. Our system is potentially an attractive clinical tool for rescuing patients with septic shock.
Acute Pancreatitis and Use of Pancreatitis-Associated Drugs: A 10-Year Population-Based Cohort Study.

PubMed

Bertilsson, Sara; Kalaitzakis, Evangelos

2015-10-01

To assess the use of acute pancreatitis (AP)-associated drugs in patients with AP, the relation between sales of these drugs and the incidence of AP, and the potential impact on AP severity and recurrence. All patients with incident AP between 2003 and 2012, in a well-defined area, were retrospectively identified. Data regarding AP etiology, severity, and recurrence and use of AP-associated drugs were extracted from medical records. Drugs were classified according to an evidence-based classification system. Annual drug sales data were obtained from the Swedish drug administration service. Overall, 1457 cases of incident AP were identified. Acute pancreatitis-associated drug users increased from 32% in 2003 to 51% in 2012, reflecting increasing user rates in the general population. The incidence of AP increased during the study period but was not related to AP-associated drug user rates (P > 0.05). Recurrent AP occurred in 23% but was unrelated to AP-associated drug use (P > 0.05). In logistic regression analysis, after adjustment for comorbidity, AP-associated drug use was not related to AP severity (P > 0.05). Use of AP-associated drugs is increasingly frequent in patients with AP. However, it does not have any major impact on the observed epidemiological changes in occurrence, severity, or recurrence of AP.
Activation of the Arabidopsis B class homeotic genes by APETALA1.

PubMed

Ng, M; Yanofsky, M F

2001-04-01

Proper development of petals and stamens in Arabidopsis flowers requires the activities of APETALA3 (AP3) and PISTILLATA (PI), whose transcripts can be detected in the petal and stamen primordia. Localized expression of AP3 and PI requires the activities of at least three genes: APETALA1 (AP1), LEAFY (LFY), and UNUSUAL FLORAL ORGANS (UFO). It has been proposed that UFO provides spatial cues and that LFY specifies competence for AP3 and PI expression in the developing flower. To understand the epistatic relationship among AP1, LFY, and UFO in regulating AP3 and PI expression, we generated two versions of AP1 that have strong transcriptional activation potential. Genetic and molecular analyses of transgenic plants expressing these activated AP1 proteins show that the endogenous AP1 protein acts largely as a transcriptional activator in vivo and that AP1 specifies petals by regulating the spatial domains of AP3 and PI expression through UFO.
Advances in Bacterial Methionine Aminopeptidase Inhibition

PubMed Central

Helgren, Travis R.; Wangtrakuldee, Phumvadee; Staker, Bart L.; Hagen, Timothy J.

2016-01-01

Methionine aminopeptidases (MetAPs) are metalloenzymes that cleave the N-terminal methionine from newly synthesized peptides and proteins. These MetAP enzymes are present in bacteria, and knockout experiments have shown that MetAP activity is essential for cell life, suggesting that MetAPs are good antibacterial drug targets. MetAP enzymes are also present in the human host and selectivity is essential. There have been significant structural biology efforts and over 65 protein crystal structures of bacterial MetAPs are deposited into the PDB. This review highlights the available crystallographic data for bacterial MetAPs. Structural comparison of bacterial MetAPs with human MetAPs highlights differences that can lead to selectivity. In addition, this review includes the chemical diversity of molecules that bind and inhibit the bacterial MetAP enzymes. Analysis of the structural biology and chemical space of known bacterial MetAP inhibitors leads to a greater understanding of this antibacterial target and the likely development of potential antibacterial agents. PMID:26268344
Large area CMOS active pixel sensor x-ray imager for digital breast tomosynthesis: Analysis, modeling, and characterization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Chumin; Kanicki, Jerzy, E-mail: kanicki@eecs.umich.edu; Konstantinidis, Anastasios C.

Purpose: Large area x-ray imagers based on complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) technology have been proposed for various medical imaging applications including digital breast tomosynthesis (DBT). The low electronic noise (50–300 e{sup −}) of CMOS APS x-ray imagers provides a possible route to shrink the pixel pitch to smaller than 75 μm for microcalcification detection and possible reduction of the DBT mean glandular dose (MGD). Methods: In this study, imaging performance of a large area (29 × 23 cm{sup 2}) CMOS APS x-ray imager [Dexela 2923 MAM (PerkinElmer, London)] with a pixel pitch of 75 μm was characterizedmore » and modeled. The authors developed a cascaded system model for CMOS APS x-ray imagers using both a broadband x-ray radiation and monochromatic synchrotron radiation. The experimental data including modulation transfer function, noise power spectrum, and detective quantum efficiency (DQE) were theoretically described using the proposed cascaded system model with satisfactory consistency to experimental results. Both high full well and low full well (LFW) modes of the Dexela 2923 MAM CMOS APS x-ray imager were characterized and modeled. The cascaded system analysis results were further used to extract the contrast-to-noise ratio (CNR) for microcalcifications with sizes of 165–400 μm at various MGDs. The impact of electronic noise on CNR was also evaluated. Results: The LFW mode shows better DQE at low air kerma (K{sub a} < 10 μGy) and should be used for DBT. At current DBT applications, air kerma (K{sub a} ∼ 10 μGy, broadband radiation of 28 kVp), DQE of more than 0.7 and ∼0.3 was achieved using the LFW mode at spatial frequency of 0.5 line pairs per millimeter (lp/mm) and Nyquist frequency ∼6.7 lp/mm, respectively. It is shown that microcalcifications of 165–400 μm in size can be resolved using a MGD range of 0.3–1 mGy, respectively. In comparison to a General Electric GEN2 prototype DBT system (at MGD of 2.5 mGy), an increased CNR (by ∼10) for microcalcifications was observed using the Dexela 2923 MAM CMOS APS x-ray imager at a lower MGD (2.0 mGy). Conclusions: The Dexela 2923 MAM CMOS APS x-ray imager is capable to achieve a high imaging performance at spatial frequencies up to 6.7 lp/mm. Microcalcifications of 165 μm are distinguishable based on reported data and their modeling results due to the small pixel pitch of 75 μm. At the same time, potential dose reduction is expected using the studied CMOS APS x-ray imager.« less

The non-competitive acetylcholinesterase inhibitor APS12-2 is a potent antagonist of skeletal muscle nicotinic acetylcholine receptors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grandič, Marjana; Aráoz, Romulo; Molgó, Jordi

APS12-2, a non-competitive acetylcholinesterase inhibitor, is one of the synthetic analogs of polymeric alkylpyridinium salts (poly-APS) isolated from the marine sponge Reniera sarai. In the present work the effects of APS12-2 were studied on isolated mouse phrenic nerve–hemidiaphragm muscle preparations, using twitch tension measurements and electrophysiological recordings. APS12-2 in a concentration-dependent manner blocked nerve-evoked isometric muscle contraction (IC{sub 50} = 0.74 μM), without affecting directly-elicited twitch tension up to 2.72 μM. The compound (0.007–3.40 μM) decreased the amplitude of miniature endplate potentials until a complete block by concentrations higher than 0.68 μM, without affecting their frequency. Full size endplate potentials,more » recorded after blocking voltage-gated muscle sodium channels, were inhibited by APS12-2 in a concentration-dependent manner (IC{sub 50} = 0.36 μM) without significant change in the resting membrane potential of the muscle fibers up to 3.40 μM. The compound also blocked acetylcholine-evoked inward currents in Xenopus oocytes in which Torpedo (α1{sub 2}β1γδ) muscle-type nicotinic acetylcholine receptors (nAChRs) have been incorporated (IC{sub 50} = 0.0005 μM), indicating a higher affinity of the compound for Torpedo (α1{sub 2}β1γδ) than for the mouse (α1{sub 2}β1γε) nAChR. Our data show for the first time that APS12-2 blocks neuromuscular transmission by a non-depolarizing mechanism through an action on postsynaptic nAChRs of the skeletal neuromuscular junction. -- Highlights: ► APS12-2 produces concentration-dependent inhibition of nerve-evoked muscle contraction in vitro. ► APS12-2 blocks MEPPs and EPPs at the neuromuscular junction. APS12-2 blocks ACh-activated current in Xenopus oocytes incorporated with Torpedo nAChRs.« less
Tumor-targeting peptide conjugated pH-responsive micelles as a potential drug carrier for cancer therapy.

PubMed

Wu, Xiang Lan; Kim, Jong Ho; Koo, Heebeom; Bae, Sang Mun; Shin, Hyeri; Kim, Min Sang; Lee, Byung-Heon; Park, Rang-Woon; Kim, In-San; Choi, Kuiwon; Kwon, Ick Chan; Kim, Kwangmeyung; Lee, Doo Sung

2010-02-17

Herein, we prepared tumor-targeting peptide (AP peptide; CRKRLDRN) conjugated pH-responsive polymeric micelles (pH-PMs) in cancer therapy by active and pH-responsive tumor targeting delivery systems, simultaneously. The active tumor targeting and tumoral pH-responsive polymeric micelles were prepared by mixing AP peptide conjugated PEG-poly(d,l-lactic acid) block copolymer (AP-PEG-PLA) into the pH-responsive micelles of methyl ether poly(ethylene glycol) (MPEG)-poly(beta-amino ester) (PAE) block copolymer (MPEG-PAE). These mixed amphiphilic block copolymers were self-assembled to form stable AP peptide-conjugated and pH-responsive AP-PEG-PLA/MPEG-PAE micelles (AP-pH-PMs) with an average size of 150 nm. The AP-pH-PMs containing 10 wt % of AP-PEG-PLA showed a sharp pH-dependent micellization/demicellization transition at the tumoral acid pH. Also, they presented the pH-dependent drug release profile at the acidic pH of 6.4. The fluorescence dye, TRITC, encapsulated AP-pH-PMs (TRITC-AP-pH-PMs) presented the higher tumor-specific targeting ability in vitro cancer cell culture system and in vivo tumor-bearing mice, compared to control pH-responsive micelles of MPEG-PAE. For the cancer therapy, the anticancer drug, doxorubicin (DOX), was efficiently encapsulated into the AP-pH-PMs (DOX-AP-pH-PMs) with a higher loading efficiency. DOX-AP-pH-PMs efficiently deliver anticancer drugs in MDA-MB231 human breast tumor-bearing mice, resulted in excellent anticancer therapeutic efficacy, compared to free DOX and DOX encapsulated MEG-PAE micelles, indicating the excellent tumor targeting ability of AP-pH-PMs. Therefore, these tumor-targeting peptide-conjugated and pH-responsive polymeric micelles have great potential application in cancer therapy.
AP Potential Expectancy Tables Based on PSAT/NMSQT and SAT Scores on the 2015-16 Redesigned Scales Using Final Concordance Tables. Statistical Report

ERIC Educational Resources Information Center

Ewing, Maureen; Wyatt, Jeff

2017-01-01

Historically, AP Potential™ has used PSAT/NMSQT® scores to identify students who are likely to earn a 3 or higher on a specific AP Exam based on research showing moderate to strong relationships between PSAT/NMSQT scores and AP Exam scores (Camara & Millsap, 1998; Ewing, Camara, & Millsap, 2006; Zhang, Patel, & Ewing, 2014a). For most…
Combined soft and hard X-ray ambient pressure photoelectron spectroscopy studies of semiconductor/electrolyte interfaces

DOE PAGES

Starr, David E.; Favaro, Marco; Abdi, Fatwa F.; ...

2017-05-18

The development of solar fuel generating materials would greatly benefit from a molecular level understanding of the semiconductor/electrolyte interface and changes in the interface induced by an applied potential and illumination by solar light. Ambient pressure photoelectron spectroscopy techniques with both soft and hard X-rays, AP-XPS and AP-HAXPES respectively, have the potential to markedly contribute to this understanding. In this paper we initially provide two examples of current challenges in solar fuels material development that AP-XPS and AP-HAXPES can directly a ddress. This will be followed by a brief description of the distinguishing and complementary characteristics of soft and hardmore » X-ray AP-XPS and AP-HAXPES and best approaches to achieving monolayer sensitivity in solid/aqueous electrolyte studies. In particular we focus on the detection of surface adsorbed hydroxyl groups in the presence of aqueous hydroxide anions in the electrolyte, a common situation when investigating photoanodes for solar fuel generating applications. Finally, the article concludes by providing an example of a combined AP-XPS and AP-HAXPES study of a semiconductor/aqueous electrolyte interface currently used in water splitting devices specifically the BiVO 4/aqueous potassium phosphate electrolyte interface.« less
Timing and efficacy of Ca2+ channel activation in hippocampal mossy fiber boutons.

PubMed

Bischofberger, Josef; Geiger, Jörg R P; Jonas, Peter

2002-12-15

The presynaptic Ca2+ signal is a key determinant of transmitter release at chemical synapses. In cortical synaptic terminals, however, little is known about the kinetic properties of the presynaptic Ca2+ channels. To investigate the timing and magnitude of the presynaptic Ca2+ inflow, we performed whole-cell patch-clamp recordings from mossy fiber boutons (MFBs) in rat hippocampus. MFBs showed large high-voltage-activated Ca(2+) currents, with a maximal amplitude of approximately 100 pA at a membrane potential of 0 mV. Both activation and deactivation were fast, with time constants in the submillisecond range at a temperature of approximately 23 degrees C. An MFB action potential (AP) applied as a voltage-clamp command evoked a transient Ca2+ current with an average amplitude of approximately 170 pA and a half-duration of 580 microsec. A prepulse to +40 mV had only minimal effects on the AP-evoked Ca2+ current, indicating that presynaptic APs open the voltage-gated Ca2+ channels very effectively. On the basis of the experimental data, we developed a kinetic model with four closed states and one open state, linked by voltage-dependent rate constants. Simulations of the Ca2+ current could reproduce the experimental data, including the large amplitude and rapid time course of the current evoked by MFB APs. Furthermore, the simulations indicate that the shape of the presynaptic AP and the gating kinetics of the Ca2+ channels are tuned to produce a maximal Ca2+ influx during a minimal period of time. The precise timing and high efficacy of Ca2+ channel activation at this cortical glutamatergic synapse may be important for synchronous transmitter release and temporal information processing.
Perimenstrual-Like Hormonal Regulation of Extrasynaptic δ-Containing GABAA Receptors Mediating Tonic Inhibition and Neurosteroid Sensitivity

PubMed Central

Carver, Chase Matthew; Wu, Xin; Gangisetty, Omkaram

2014-01-01

Neurosteroids are endogenous regulators of neuronal excitability and seizure susceptibility. Neurosteroids, such as allopregnanolone (AP; 3α-hydroxy-5α-pregnan-20-one), exhibit enhanced anticonvulsant activity in perimenstrual catamenial epilepsy, a neuroendocrine condition in which seizures are clustered around the menstrual period associated with neurosteroid withdrawal (NSW). However, the molecular mechanisms underlying such enhanced neurosteroid sensitivity remain unclear. Neurosteroids are allosteric modulators of both synaptic (αβγ2-containing) and extrasynaptic (αβδ-containing) GABAA receptors, but they display greater sensitivity toward δ-subunit receptors in dentate gyrus granule cells (DGGCs). Here we report a novel plasticity of extrasynaptic δ-containing GABAA receptors in the dentate gyrus in a mouse perimenstrual-like model of NSW. In molecular and immunofluorescence studies, a significant increase occurred in δ subunits, but not α1, α2, β2, and γ2 subunits, in the dentate gyrus of NSW mice. Electrophysiological studies confirmed enhanced sensitivity to AP potentiation of GABA-gated currents in DGGCs, but not in CA1 pyramidal cells, in NSW animals. AP produced a greater potentiation of tonic currents in DGGCs of NSW animals, and such enhanced AP sensitivity was not evident in δ-subunit knock-out mice subjected to a similar withdrawal paradigm. In behavioral studies, mice undergoing NSW exhibited enhanced seizure susceptibility to hippocampus kindling. AP has enhanced anticonvulsant effects in fully kindled wild-type mice, but not δ-subunit knock-out mice, undergoing NSW-induced seizures, confirming δ-linked neurosteroid sensitivity. These results indicate that perimenstrual NSW is associated with striking upregulation of extrasynaptic, δ-containing GABAA receptors that mediate tonic inhibition and neurosteroid sensitivity in the dentate gyrus. These findings may represent a molecular rationale for neurosteroid therapy of catamenial epilepsy. PMID:25339733
Molecular Basis for Association of PIPKIγ-p90 with Clathrin Adaptor AP-2*

PubMed Central

Kahlfeldt, Nina; Vahedi-Faridi, Ardeschir; Koo, Seong Joo; Schäfer, Johannes G.; Krainer, Georg; Keller, Sandro; Saenger, Wolfram; Krauss, Michael; Haucke, Volker

2010-01-01

Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) is an essential determinant in clathrin-mediated endocytosis (CME). In mammals three type I phosphatidylinositol-4-phosphate 5-kinase (PIPK) enzymes are expressed, with the Iγ-p90 isoform being highly expressed in the brain where it regulates synaptic vesicle (SV) exo-/endocytosis at nerve terminals. How precisely PI(4,5)P2 metabolism is controlled spatially and temporally is still uncertain, but recent data indicate that direct interactions between type I PIPK and components of the endocytic machinery, in particular the AP-2 adaptor complex, are involved. Here we demonstrated that PIPKIγ-p90 associates with both the μ and β2 subunits of AP-2 via multiple sites. Crystallographic data show that a peptide derived from the splice insert of the human PIPKIγ-p90 tail binds to a cognate recognition site on the sandwich subdomain of the β2 appendage. Partly overlapping aromatic and hydrophobic residues within the same peptide also can engage the C-terminal sorting signal binding domain of AP-2μ, thereby potentially competing with the sorting of conventional YXXØ motif-containing cargo. Biochemical and structure-based mutagenesis analysis revealed that association of the tail domain of PIPKIγ-p90 with AP-2 involves both of these sites. Accordingly the ability of overexpressed PIPKIγ tail to impair endocytosis of SVs in primary neurons largely depends on its association with AP-2β and AP-2μ. Our data also suggest that interactions between AP-2 and the tail domain of PIPKIγ-p90 may serve to regulate complex formation and enzymatic activity. We postulate a model according to which multiple interactions between PIPKIγ-p90 and AP-2 lead to spatiotemporally controlled PI(4,5)P2 synthesis during clathrin-mediated SV endocytosis. PMID:19903820
Andrographis paniculata elicits anti-invasion activities by suppressing TM4SF3 gene expression and by anoikis-sensitization in esophageal cancer cells

PubMed Central

Yue, Grace Gar-Lee; Lee, Julia Kin-Ming; Li, Lin; Chan, Kar-Man; Wong, Eric Chun-Wai; Chan, Judy Yuet-Wah; Fung, Kwok-Pui; Lui, Vivian Wai Yan; Chiu, Philip Wai-Yan; Lau, Clara Bik-San

2015-01-01

Esophageal cancer is the sixth most common cancer in male causing death worldwide. It is usually diagnosed at advanced stage with high postoperative recurrence and systemic metastasis, which leads to poor prognosis. The potential inhibitory effect of herbal medicines on metastasis of esophageal cancer has drawn researchers’ great attention. In the present study, the anti-invasion activities of Andrographis paniculata (AP) have been evaluated in two esophageal cancer cell lines, EC-109 and KYSE-520, as well as human microvascular endothelial cells (HMEC-1). The anti-tumor and anti-metastatic activities of AP were also evaluated in human esophageal xenograft-bearing mouse models. Our results demonstrated for the first time that aqueous extract of AP inhibited the motility and invasion of esophageal cancer cells, which is the initial step of metastasis, without cytotoxicity. Anoikis resistance has also been reversed in AP-treated cancer cells. Besides, the expression of metastasis-related gene TM4SF3 in EC-109 cells was significantly decreased in AP extract-treated cells in a concentration-dependent manner. Furthermore, the anti-tumor and anti-metastatic efficacies in subcutaneous and intraperitoneal esophageal xenograft-bearing mice were demonstrated after oral administration of AP aqueous extract for 3 weeks. Last but not least, the active component, isoandrographolide, responsible for the anti-migratory activity was firstly revealed here. In conclusion, the AP aqueous extract exerted inhibitory activities on the migration and anoikis resistance of esophageal cancer cells EC-109 and KYSE-520, as well as suppressed the proliferation and motility of endothelial cells. Combining the mentioned effects may account for the anti-tumor and anti-metastasis effects of AP aqueous extract in xenograft-bearing mice. The findings in the present study further enhance the understanding of the therapeutic mechanisms of the herb AP, which may lead to clinical applications. PMID:26885447
Predicting and evaluation the severity in acute pancreatitis using a new modeling built on body mass index and intra-abdominal pressure.

PubMed

Fei, Yang; Gao, Kun; Tu, Jianfeng; Wang, Wei; Zong, Guang-Quan; Li, Wei-Qin

2017-06-03

Acute pancreatitis (AP) keeps as severe medical diagnosis and treatment problem. Early evaluation for severity and risk stratification in patients with AP is very important. Some scoring system such as acute physiology and chronic health evaluation-II (APACHE-II), the computed tomography severity index (CTSI), Ranson's score and the bedside index of severity of AP (BISAP) have been used, nevertheless, there're a few shortcomings in these methods. The aim of this study was to construct a new modeling including intra-abdominal pressure (IAP) and body mass index (BMI) to evaluate the severity in AP. The study comprised of two independent cohorts of patients with AP, one set was used to develop modeling from Jinling hospital in the period between January 2013 and October 2016, 1073 patients were included in it; another set was used to validate modeling from the 81st hospital in the period between January 2012 and December 2016, 326 patients were included in it. The association between risk factors and severity of AP were assessed by univariable analysis; multivariable modeling was explored through stepwise selection regression. The change in IAP and BMI were combined to generate a regression equation as the new modeling. Statistical indexes were used to evaluate the value of the prediction in the new modeling. Univariable analysis confirmed change in IAP and BMI to be significantly associated with severity of AP. The predict sensitivity, specificity, positive predictive value, negative predictive value and accuracy by the new modeling for severity of AP were 77.6%, 82.6%, 71.9%, 87.5% and 74.9% respectively in the developing dataset. There were significant differences between the new modeling and other scoring systems in these parameters (P < 0.05). In addition, a comparison of the area under receiver operating characteristic curves of them showed a statistically significant difference (P < 0.05). The same results could be found in the validating dataset. A new modeling based on IAP and BMI is more likely to predict the severity of AP. Copyright © 2017. Published by Elsevier Inc.
Isolation of a small molecule inhibitor of DNA base excision repair

PubMed Central

Madhusudan, Srinivasan; Smart, Fiona; Shrimpton, Paul; Parsons, Jason L.; Gardiner, Laurence; Houlbrook, Sue; Talbot, Denis C.; Hammonds, Timothy; Freemont, Paul A.; Sternberg, Michael J. E.; Dianov, Grigory L.; Hickson, Ian D.

2005-01-01

The base excision repair (BER) pathway is essential for the removal of DNA bases damaged by alkylation or oxidation. A key step in BER is the processing of an apurinic/apyrimidinic (AP) site intermediate by an AP endonuclease. The major AP endonuclease in human cells (APE1, also termed HAP1 and Ref-1) accounts for >95% of the total AP endonuclease activity, and is essential for the protection of cells against the toxic effects of several classes of DNA damaging agents. Moreover, APE1 overexpression has been linked to radio- and chemo-resistance in human tumors. Using a newly developed high-throughput screen, several chemical inhibitors of APE1 have been isolated. Amongst these, CRT0044876 was identified as a potent and selective APE1 inhibitor. CRT0044876 inhibits the AP endonuclease, 3′-phosphodiesterase and 3′-phosphatase activities of APE1 at low micromolar concentrations, and is a specific inhibitor of the exonuclease III family of enzymes to which APE1 belongs. At non-cytotoxic concentrations, CRT0044876 potentiates the cytotoxicity of several DNA base-targeting compounds. This enhancement of cytotoxicity is associated with an accumulation of unrepaired AP sites. In silico modeling studies suggest that CRT0044876 binds to the active site of APE1. These studies provide both a novel reagent for probing APE1 function in human cells, and a rational basis for the development of APE1-targeting drugs for antitumor therapy. PMID:16113242
Comment on "Penetration of Action Potentials During Collision in the Median and Lateral Giant Axons of Invertebrates"

NASA Astrophysics Data System (ADS)

Berg, Rune W.; Stauning, Marius Tving; Sørensen, Jakob Balslev; Jahnsen, Henrik

2017-04-01

The action potential (AP) is an electrical impulse elicited by depolarization of the neuronal membrane from the resting membrane potential (around -70 mV ). It propagates along the axon, allowing for rapid and distant communication. Recently, it was claimed that two APs traveling in opposite direction will pass unhindered through each other (penetrate) upon collision [Gonzalez-Perez et al.Phys. Rev. X 4, 031047 (2014), 10.1103/PhysRevX.4.031047]. We tested this claim under carefully controlled conditions and found that we cannot reproduce penetration. Instead, APs consistently annihilated upon collision. This is consistent with a vast body of literature.
Antipsychotic Use in Pregnancy and the Risk for Congenital Malformations

PubMed Central

Huybrechts, Krista F.; Hernández-Díaz, Sonia; Patorno, Elisabetta; Desai, Rishi J.; Mogun, Helen; Dejene, Sara Z.; Cohen, Jacqueline M.; Panchaud, Alice; Cohen, Lee; Bateman, Brian T.

2017-01-01

IMPORTANCE The frequency of antipsychotic (AP) use during pregnancy has approximately doubled during the last decade. However, little is known about their safety for the developing fetus, and concerns have been raised about a potential association with congenital malformations. OBJECTIVE To examine the risk for congenital malformations overall and cardiac malformations associated with first-trimester exposure to APs. DESIGN, SETTING, AND PARTICIPANTS This nationwide sample of 1 360 101 pregnant women enrolled in Medicaid with a live-born infant constituted the pregnancy cohort nested in the Medicaid Analytic Extract database, which included data from January 1, 2000, to December 31, 2010. Participants were enrolled in Medicaid from 3 months before their last menstrual period through at least 1 month after delivery. Relative risks (RRs) were estimated using generalized linear models with fine stratification on the propensity score to control for the underlying psychiatric disorders and other potential confounders. Data were analyzed during 2015. EXPOSURES Use of APs during the first trimester, the etiologically relevant period for organogenesis. MAIN OUTCOMES AND MEASURES Major congenital malformations overall and cardiac malformations identified during the first 90 days after delivery. RESULTS Of the 1 341 715 pregnancies that met inclusion criteria (mean [SD] age of women, 24.02 [5.77] years), 9258 (0.69%) filled at least 1 prescription for an atypical AP and 733 (0.05%) filled at least 1 prescription for a typical AP during the first trimester. Overall, 32.7 (95% CI, 32.4–33.0) per 1000 births not exposed to APs were diagnosed with congenital malformations compared with 44.5 (95% CI, 40.5–48.9) per 1000 births exposed to atypical and 38.2 (95% CI, 26.6–54.7) per 1000 births exposed to typical APs. Unadjusted analyses suggested an increased risk for malformations overall for atypical APs (RR, 1.36; 95% CI, 1.24–1.50) but not for typical APs (RR, 1.17; 95% CI, 0.81–1.68). After confounding adjustment, the RR was reduced to 1.05 (95% CI, 0.96–1.16) for atypical APs and 0.90 (95% CI, 0.62–1.31) for typical APs. The findings for cardiac malformations were similar. For the individual agents examined, a small increased risk in overall malformations (RR, 1.26; 95% CI, 1.02–1.56) and cardiac malformations (RR, 1.26; 95% CI, 0.88–1.81) was found for risperidone that was independent of measured confounders. CONCLUSIONS AND RELEVANCE Evidence from this large study suggests that use of APs early in pregnancy generally does not meaningfully increase the risk for congenital malformations overall or cardiac malformations in particular. The small increase in the risk for malformations observed with risperidone requires additional study. PMID:27540849
Building and verifying a severity prediction model of acute pancreatitis (AP) based on BISAP, MEWS and routine test indexes.

PubMed

Ye, Jiang-Feng; Zhao, Yu-Xin; Ju, Jian; Wang, Wei

2017-10-01

To discuss the value of the Bedside Index for Severity in Acute Pancreatitis (BISAP), Modified Early Warning Score (MEWS), serum Ca2+, similarly hereinafter, and red cell distribution width (RDW) for predicting the severity grade of acute pancreatitis and to develop and verify a more accurate scoring system to predict the severity of AP. In 302 patients with AP, we calculated BISAP and MEWS scores and conducted regression analyses on the relationships of BISAP scoring, RDW, MEWS, and serum Ca2+ with the severity of AP using single-factor logistics. The variables with statistical significance in the single-factor logistic regression were used in a multi-factor logistic regression model; forward stepwise regression was used to screen variables and build a multi-factor prediction model. A receiver operating characteristic curve (ROC curve) was constructed, and the significance of multi- and single-factor prediction models in predicting the severity of AP using the area under the ROC curve (AUC) was evaluated. The internal validity of the model was verified through bootstrapping. Among 302 patients with AP, 209 had mild acute pancreatitis (MAP) and 93 had severe acute pancreatitis (SAP). According to single-factor logistic regression analysis, we found that BISAP, MEWS and serum Ca2+ are prediction indexes of the severity of AP (P-value<0.001), whereas RDW is not a prediction index of AP severity (P-value>0.05). The multi-factor logistic regression analysis showed that BISAP and serum Ca2+ are independent prediction indexes of AP severity (P-value<0.001), and MEWS is not an independent prediction index of AP severity (P-value>0.05); BISAP is negatively related to serum Ca2+ (r=-0.330, P-value<0.001). The constructed model is as follows: ln()=7.306+1.151*BISAP-4.516*serum Ca2+. The predictive ability of each model for SAP follows the order of the combined BISAP and serum Ca2+ prediction model>Ca2+>BISAP. There is no statistical significance for the predictive ability of BISAP and serum Ca2+ (P-value>0.05); however, there is remarkable statistical significance for the predictive ability using the newly built prediction model as well as BISAP and serum Ca2+ individually (P-value<0.01). Verification of the internal validity of the models by bootstrapping is favorable. BISAP and serum Ca2+ have high predictive value for the severity of AP. However, the model built by combining BISAP and serum Ca2+ is remarkably superior to those of BISAP and serum Ca2+ individually. Furthermore, this model is simple, practical and appropriate for clinical use. Copyright © 2016. Published by Elsevier Masson SAS.
Structural modeling and molecular simulation analysis of HvAP2/EREBP from barley.

PubMed

Pandey, Bharati; Sharma, Pradeep; Tyagi, Chetna; Goyal, Sukriti; Grover, Abhinav; Sharma, Indu

2016-06-01

AP2/ERF transcription factors play a critical role in plant development and stress adaptation. This study reports the three-dimensional ab initio-based model of AP2/EREBP protein of barley and its interaction with DNA. Full-length coding sequence of HvAP2/EREBP gene isolated from two Indian barley cultivars, RD 2503 and RD 31, was used to model the protein. Of five protein models obtained, the one with lowest C-score was chosen for further analysis. The N- and C-terminal regions of HvAP2 protein were found to be highly disordered. The dynamic properties of AP2/EREBP and its interaction with DNA were investigated by molecular dynamics simulation. Analysis of trajectories from simulation yielded the equilibrated conformation between 2-10ns for protein and 7-15ns for protein-DNA complex. We established relationship between DNA having GCC box and DNA-binding domain of HvAP2/EREBP was established by modeling 11-base-pair-long nucleotide sequence and HvAP2/EREBP protein using ab initio method. Analysis of protein-DNA interaction showed that a β-sheet motif constituting amino acid residues THR105, ARG100, ARG93, and ARG83 seems to play important role in stabilizing the complex as they form strong hydrogen bond interactions with the DNA motif. Taken together, this study provides first-hand comprehensive information detailing structural conformation and interactions of HvAP2/EREBP proteins in barley. The study intensifies the role of computational approaches for preliminary examination of unknown proteins in the absence of experimental information. It also provides molecular insight into protein-DNA binding for understanding and enhancing abiotic stress resistance for improving the water use efficiency in crop plants.
Modulation of KCNQ1 alternative splicing regulates cardiac IKs and action potential repolarization.

PubMed

Lee, Hsiang-Chun; Rudy, Yoram; Po-Yuan, Phd; Sheu, Sheng-Hsiung; Chang, Jan-Gowth; Cui, Jianmin

2013-08-01

Slow delayed-rectifier potassium current (IKs) channels, made of the pore-forming KCNQ1 and auxiliary KCNE1 subunits, play a key role in determining action potential duration (APD) in cardiac myocytes. The consequences of drug-induced KCNQ1 splice alteration remain unknown. To study the modulation of KCNQ1 alternative splicing by amiloride and the consequent changes in IKs and action potentials (APs) in ventricular myocytes. Canine endocardial, midmyocardial, and epicardial ventricular myocytes were isolated. Levels of KCNQ1a and KCNQ1b as well as a series of splicing factors were quantified by using the reverse transcriptase-polymerase chain reaction and Western blot. The effect of amiloride-induced changes in the KCNQ1b/total KCNQ1 ratio on AP was measured by using whole-cell patch clamp with and without isoproterenol. With 50 μmol/L of amiloride for 6 hours, KCNQ1a at transcriptional and translational levels increased in midmyocardial myocytes but decreased in endo- and epicardial myocytes. Likewise, changes in splicing factors in midmyocardial were opposite to that in endo- and epicardial myocytes. In midmyocardial myocytes amiloride shortened APD and decreased isoproterenol-induced early afterdepolarizations significantly. The same amiloride-induced effects were demonstrated by using human ventricular myocyte model for AP simulations under beta-adrenergic stimulation. Moreover, amiloride reduced the transmural dispersion of repolarization in pseudo-electrocardiogram. Amiloride regulates IKs and APs with transmural differences and reduces arrhythmogenicity through the modulation of KCNQ1 splicing. We suggested that the modulation of KCNQ1 splicing may help prevent arrhythmia. Copyright © 2013 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.
Use and Characteristics of Antipsychotic/Methylphenidate Combination Therapy in Children and Adolescents with a Diagnosis of Attention-Deficit/Hyperactivity Disorder.

PubMed

Scholle, Oliver; Banaschewski, Tobias; Enders, Dirk; Garbe, Edeltraut; Riedel, Oliver

2018-05-16

Children and adolescents with attention-deficit/hyperactivity disorder (ADHD) frequently have comorbidities that are potential indications for antipsychotics (APs). Some studies have suggested that the combined use of methylphenidate (MPH) and APs is increasing in this population group. Longitudinal analyses and in-depth investigations on the substance level are lacking. This study aimed to estimate the cumulative proportion of concomitant AP/MPH use in children and adolescents with ADHD over a follow-up of up to 9 years and to describe patient characteristics stratified by specific AP drug. Based on claims data, concomitant AP/MPH use was identified among 67,595 children and adolescents with ADHD starting MPH treatment between 2005 and 2013. Characteristics and diagnoses-including those indicating appropriateness of AP use according to approved indications and/or guidelines-were examined at the time of first AP/MPH combination therapy. In addition, subsequent use of AP/MPH combination therapy was evaluated. The cumulative proportion of individuals with any AP/MPH combination therapy rose to over 6% within 9 years after initiating MPH. The most frequent APs first used in combination with MPH were risperidone (72%), pipamperone (15%), and tiapride (8%). Percentages of psychiatric hospitalization in the year preceding the first combination therapy with MPH were 33%, 43%, and 19%, respectively. The proportion of individuals with potentially appropriate use was high (>72%) in risperidone/MPH and tiapride/MPH and low (15%) in pipamperone/MPH combination users. Conduct disorders and tic disorders were frequent in users who were prescribed MPH with risperidone and tiapride, respectively. One-quarter of patients with AP/MPH combination therapy were one-time-only combination users. Our study suggests that a considerable proportion of children and adolescents with ADHD receive MPH in combination with APs and that this is a factor not only during the first years of MPH treatment. ADHD guidelines should specify algorithms concerning the use of AP medication.
Some properties of the action potentials conducted in the spines of the sea urchin Diadema antillarum.

PubMed

Berrios, A; Brink, D; del Castillo, J; Smith, D S

1985-01-01

Brief (2-5 msec) electrical pulses applied to the primary spines of the sea urchin Diadema antillarum elicit graded action potentials (ap's). These ap's can be attributed to the electrical activity of a set of 14-21 bundles of neurites, each comprising 1000 processes near the spine base and tapering towards the spine tip. The shape of the ap's varies from a simple diphasic deflection to a complex waveform with 6 or more components. Peak-to-peak amplitude is less than 1mV. The ap's are conducted at a uniform speed of ca. 27 cm/sec. The ap's are not affected by tetrodotoxin (1 microgram/ml) and continue to be produced in Na-free artificial sea water (ASW). The amplitude of the ap's is greatly reduced or totally abolished in Ca-free ASW. However, some electrical activity may continue in the absence of external Ca, due to release of Ca2+ ions from the calcium carbonate crystals of the spine shaft. Replacing the Ca content of ASW by barium ions causes an irreversible blockade of the ap's. Spines equilibrated with ASW containing Sr2+ ions instead of Ca2+ produce ap's of increased amplitude (up to X 2). The ap's are blocked by La3+, Co2+, Cd2+ (2-5 mM) and by the organic Ca channel blocker Bepridil (2 mM). We conclude that the spinal ap's are due to the summation of Ca spikes produced by the activation of Ca channels which are blocked by barium and have a high affinity for, or permeability to Sr vs Ca.
Altered Ca2+ signaling in skeletal muscle fibers of the R6/2 mouse, a model of Huntington’s disease

PubMed Central

Braubach, Peter; Orynbayev, Murat; Andronache, Zoita; Hering, Tanja; Landwehrmeyer, Georg Bernhard; Lindenberg, Katrin S.

2014-01-01

Huntington’s disease (HD) is caused by an expanded CAG trinucleotide repeat within the gene encoding the protein huntingtin. The resulting elongated glutamine (poly-Q) sequence of mutant huntingtin (mhtt) affects both central neurons and skeletal muscle. Recent reports suggest that ryanodine receptor–based Ca2+ signaling, which is crucial for skeletal muscle excitation–contraction coupling (ECC), is changed by mhtt in HD neurons. Consequently, we searched for alterations of ECC in muscle fibers of the R6/2 mouse, a mouse model of HD. We performed fluorometric recordings of action potentials (APs) and cellular Ca2+ transients on intact isolated toe muscle fibers (musculi interossei), and measured L-type Ca2+ inward currents on internally dialyzed fibers under voltage-clamp conditions. Both APs and AP-triggered Ca2+ transients showed slower kinetics in R6/2 fibers than in fibers from wild-type mice. Ca2+ removal from the myoplasm and Ca2+ release flux from the sarcoplasmic reticulum were characterized using a Ca2+ binding and transport model, which indicated a significant reduction in slow Ca2+ removal activity and Ca2+ release flux both after APs and under voltage-clamp conditions. In addition, the voltage-clamp experiments showed a highly significant decrease in L-type Ca2+ channel conductance. These results indicate profound changes of Ca2+ turnover in skeletal muscle of R6/2 mice and suggest that these changes may be associated with muscle pathology in HD. PMID:25348412
Biological substantiation of antipsychotic-associated pneumonia: Systematic literature review and computational analyses

PubMed Central

2017-01-01

Introduction Antipsychotic (AP) safety has been widely investigated. However, mechanisms underlying AP-associated pneumonia are not well-defined. Aim The aim of this study was to investigate the known mechanisms of AP-associated pneumonia through a systematic literature review, confirm these mechanisms using an independent data source on drug targets and attempt to identify novel AP drug targets potentially linked to pneumonia. Methods A search was conducted in Medline and Web of Science to identify studies exploring the association between pneumonia and antipsychotic use, from which information on hypothesized mechanism of action was extracted. All studies had to be in English and had to concern AP use as an intervention in persons of any age and for any indication, provided that the outcome was pneumonia. Information on the study design, population, exposure, outcome, risk estimate and mechanism of action was tabulated. Public repositories of pharmacology and drug safety data were used to identify the receptor binding profile and AP safety events. Cytoscape was then used to map biological pathways that could link AP targets and off-targets to pneumonia. Results The literature search yielded 200 articles; 41 were included in the review. Thirty studies reported a hypothesized mechanism of action, most commonly activation/inhibition of cholinergic, histaminergic and dopaminergic receptors. In vitro pharmacology data confirmed receptor affinities identified in the literature review. Two targets, thromboxane A2 receptor (TBXA2R) and platelet activating factor receptor (PTAFR) were found to be novel AP target receptors potentially associated with pneumonia. Biological pathways constructed using Cytoscape identified plausible biological links potentially leading to pneumonia downstream of TBXA2R and PTAFR. Conclusion Innovative approaches for biological substantiation of drug-adverse event associations may strengthen evidence on drug safety profiles and help to tailor pharmacological therapies to patient risk factors. PMID:29077727
Biological substantiation of antipsychotic-associated pneumonia: Systematic literature review and computational analyses.

PubMed

Sultana, Janet; Calabró, Marco; Garcia-Serna, Ricard; Ferrajolo, Carmen; Crisafulli, Concetta; Mestres, Jordi; Trifirò', Gianluca

2017-01-01

Antipsychotic (AP) safety has been widely investigated. However, mechanisms underlying AP-associated pneumonia are not well-defined. The aim of this study was to investigate the known mechanisms of AP-associated pneumonia through a systematic literature review, confirm these mechanisms using an independent data source on drug targets and attempt to identify novel AP drug targets potentially linked to pneumonia. A search was conducted in Medline and Web of Science to identify studies exploring the association between pneumonia and antipsychotic use, from which information on hypothesized mechanism of action was extracted. All studies had to be in English and had to concern AP use as an intervention in persons of any age and for any indication, provided that the outcome was pneumonia. Information on the study design, population, exposure, outcome, risk estimate and mechanism of action was tabulated. Public repositories of pharmacology and drug safety data were used to identify the receptor binding profile and AP safety events. Cytoscape was then used to map biological pathways that could link AP targets and off-targets to pneumonia. The literature search yielded 200 articles; 41 were included in the review. Thirty studies reported a hypothesized mechanism of action, most commonly activation/inhibition of cholinergic, histaminergic and dopaminergic receptors. In vitro pharmacology data confirmed receptor affinities identified in the literature review. Two targets, thromboxane A2 receptor (TBXA2R) and platelet activating factor receptor (PTAFR) were found to be novel AP target receptors potentially associated with pneumonia. Biological pathways constructed using Cytoscape identified plausible biological links potentially leading to pneumonia downstream of TBXA2R and PTAFR. Innovative approaches for biological substantiation of drug-adverse event associations may strengthen evidence on drug safety profiles and help to tailor pharmacological therapies to patient risk factors.

Efficient triple helix formation by oligodeoxyribonucleotides containing alpha- or beta-2-amino-5-(2-deoxy-D-ribofuranosyl) pyridine residues.

PubMed

Bates, P J; Laughton, C A; Jenkins, T C; Capaldi, D C; Roselt, P D; Reese, C B; Neidle, S

1996-11-01

Triple helices containing C+xGxC triplets are destabilised at physiological pH due to the requirement for base protonation of 2'-deoxycytidine (dC), which has a pKa of 4.3. The C nucleoside 2-amino-5-(2'-deoxy-beta-D-ribofuranosyl)pyridine (beta-AP) is structurally analogous to dC but is considerably more basic, with a pKa of 5.93. We have synthesised 5'-psoralen linked oligodeoxyribonucleotides (ODNs) containing thymidine (dT) and either beta-AP or its alpha-anomer (alpha-AP) and have assessed their ability to form triplexes with a double-stranded target derived from standard deoxynucleotides (i.e. beta-anomers). Third strand ODNs derived from dT and beta-AP were found to have considerably higher binding affinities for the target than the corresponding ODNs derived from dT and either dC or 5-methyl-2'-deoxycytidine (5-Me-dC). ODNs containing dT and alpha-AP also showed enhanced triplex formation with the duplex target and, in addition are more stable in serum-containing medium than standard oligopyrimidine-derived ODNs or ODNs derived from dT and beta-AP. Molecular modelling studies showed that an alpha-anomeric AP nucleotide can be accommodated within an otherwise beta-anomeric triplex with only minor perturbation of the triplex structure. Molecular dynamics (MD) simulations on triplexes containing either the alpha- or beta-anomer of (N1-protonated) AP showed that in both cases the base retained two standard hydrogen bonds to its associated guanine when the 'A-type' model of the triplex was used as the start-point for the simulation, but that bifurcated hydrogen bonds resulted when the alternative 'B-type' triplex model was used. The lack of a differential stability between alpha-AP- and beta-AP-containing triplexes at pH >7, predicted from the behaviour of the B-type models, suggests that the A-type models are more appropriate.
Transepithelial transport of rosuvastatin and effect of ursolic acid on its transport in Caco-2 monolayers.

PubMed

Hua, Wen Jin; Fang, Hu Jin; Hua, Wei Xiao

2012-09-01

The aim of this study was to determine transepithelial transport characteristics of rosuvastatin and effect of ursolic acid (P-gp potential inhibitor) and ko143 (ABC transporters selective inhibitor) on its transport in Caco-2 monolayers. A reliable Caco-2 cell monolayers model was established. The TEER value was used to inspect integrity of cell model. Apparent permeability coefficients (Papp(BL-AP) and Papp(AP-BL)) were used to analyze transepithelial transport of rosuvastatin. Uptake of rosuvastatin was time- and concentration-dependent in Caco-2 cell. The ko143 but not ursolic acid had effect on the uptake of rosuvastatin in Caco-2 cell monolayer model and affected apparent permeability coefficient and apparent permeability of rosuvastatin. Active transport and passive diffusion absorption existed in transepithelial transport of rosuvastatin in Caco-2 cell model. Ursolic acid had no effect on transport of rosuvastatin in Caco-2 cell monolayer. The result indicated that ursolic acid may not cause effect on intestinal absorption of rosuvastatin.
Predicting risk for portal vein thrombosis in acute pancreatitis patients: A comparison of radical basis function artificial neural network and logistic regression models.

PubMed

Fei, Yang; Hu, Jian; Gao, Kun; Tu, Jianfeng; Li, Wei-Qin; Wang, Wei

2017-06-01

To construct a radical basis function (RBF) artificial neural networks (ANNs) model to predict the incidence of acute pancreatitis (AP)-induced portal vein thrombosis. The analysis included 353 patients with AP who had admitted between January 2011 and December 2015. RBF ANNs model and logistic regression model were constructed based on eleven factors relevant to AP respectively. Statistical indexes were used to evaluate the value of the prediction in two models. The predict sensitivity, specificity, positive predictive value, negative predictive value and accuracy by RBF ANNs model for PVT were 73.3%, 91.4%, 68.8%, 93.0% and 87.7%, respectively. There were significant differences between the RBF ANNs and logistic regression models in these parameters (P<0.05). In addition, a comparison of the area under receiver operating characteristic curves of the two models showed a statistically significant difference (P<0.05). The RBF ANNs model is more likely to predict the occurrence of PVT induced by AP than logistic regression model. D-dimer, AMY, Hct and PT were important prediction factors of approval for AP-induced PVT. Copyright © 2017 Elsevier Inc. All rights reserved.
Mechanisms underlying subunit independence in pyramidal neuron dendrites

PubMed Central

Behabadi, Bardia F.; Mel, Bartlett W.

2014-01-01

Pyramidal neuron (PN) dendrites compartmentalize voltage signals and can generate local spikes, which has led to the proposal that their dendrites act as independent computational subunits within a multilayered processing scheme. However, when a PN is strongly activated, back-propagating action potentials (bAPs) sweeping outward from the soma synchronize dendritic membrane potentials many times per second. How PN dendrites maintain the independence of their voltage-dependent computations, despite these repeated voltage resets, remains unknown. Using a detailed compartmental model of a layer 5 PN, and an improved method for quantifying subunit independence that incorporates a more accurate model of dendritic integration, we first established that the output of each dendrite can be almost perfectly predicted by the intensity and spatial configuration of its own synaptic inputs, and is nearly invariant to the rate of bAP-mediated “cross-talk” from other dendrites over a 100-fold range. Then, through an analysis of conductance, voltage, and current waveforms within the model cell, we identify three biophysical mechanisms that together help make independent dendritic computation possible in a firing neuron, suggesting that a major subtype of neocortical neuron has been optimized for layered, compartmentalized processing under in-vivo–like spiking conditions. PMID:24357611
Prevention & treatment of obstetrical complications in APS: Is hydroxychloroquine the Holy Grail we are looking for?

PubMed

Meroni, Pier Luigi

2016-12-01

Pregnancy morbidity is part of the clinical spectrum of the anti-phospholipid syndrome (APS), with an important social and economical cost. Antiplatelet and anticoagulant agents are effective in preventing the clinical manifestations in the majority of the patients. However, a consistent proportion of the pregnant women present recurrences in spite of the standard therapy. Observational studies and anecdotal reports raised the issue of additional therapeutic strategies in these refractory cases. Among these, anti-malarials (AMs) and in particular hydroxychloroquine (HCQ) are becoming more and more popular in APS as well as in other systemic autoimmune rheumatic conditions. AMs display a pleiotropic activity spanning from immunomodulation effect to anti-inflammatory and anti-thrombotic activities, all of which potentially useful in APS. The well-known safety of HCQ in pregnancy encouraged its use in pregnant women with autoimmune rheumatic disorders including APS and observational reports suggested a protective effect on obstetrical recurrences. Since thrombosis does not seem to be the main pathogenic mechanism in obstetric APS, effectiveness of the treatment with HCQ should be related to other pharmacological effects rather than to the anti-platelet or anti-thrombotic activity of the molecule. Experimental models showed that HCQ may restore some defective biological functions induced by anti-phospholipid antibodies (aPL) on trophoblasts and a recent study reported a protective effect on in vivo aPL-mediated placental and foetal neurodevelopmental abnormalities. Although the rational behind the use of HCQ in obstetric APS is sound, the evidence from the real life is not conclusive and a critical appraisal through clinical trials is mandatory. Copyright © 2016. Published by Elsevier Ltd.
Simultaneous recording of t-tubular electrical activity and Ca2+-release in heart failure

NASA Astrophysics Data System (ADS)

Crocini, C.; Coppini, R.; Ferrantini, C.; Yan, P.; Loew, L.; Tesi, C.; Poggesi, C.; Cerbai, E.; Pavone, F. S.; Sacconi, L.

2014-05-01

T-tubules (TT) are invaginations of the surface sarcolemma (SS) that mediate the rapid propagation of the action potential (AP) to the cardiomyocyte core. We employed the advantages of an ultrafast random access multi-photon (RAMP) microscope (Sacconi et al., PNAS 2012) with a double staining approach to optically record t-tubular AP and, simultaneously, the corresponding local Ca2+-release in different positions across the cardiomyocytes. Despite a uniform AP between SS and TT at steady-state stimulation, in control cardiomyocytes we observed a non-negligible be variability of local Ca2+-transient amplitude and kinetics. This variability was significantly reduced by applying 0.1μM Isoproterenol, which increases the opening probability of Ca2+-release units. In the rat heart failure model (HF), we previously demonstrated that some tubular elements fail to propagate AP. We found that the tubules unable to propagate AP, displayed a reduced correspondent Ca2+-transient amplitude as well as a slower Ca2+ rise compared to electrically coupled tubules. Moreover variability of Ca2+-transient kinetics were increased in HF. Finally, TT that did not show AP, occasionally exhibited spontaneous depolarizations that were never accompanied by local Ca2+-release in the absence of any pro-arrhythmogenic stimulation. Simultaneous recording of AP and Ca2+-transient allows us to probe the spatio-temporal variability of Ca2+-release, whereas the investigation of Ca2+-transient in HF discloses an unexpected uncoupling between t-tubular depolarization and Ca2+-release in remodeled tubules. This work was funded by the European Union 7th Framework Program (FP7/2007- 2013) under grant agreement n° 284464, 241526, by the Italian Ministry of University and Research (NANOMAX), and by Telethon-Italy (GGP13162).
Effects of exogenous nicotinamide adenine dinucleotide (NAD+) in the rat heart are mediated by P2 purine receptors.

PubMed

Kuzmin, Vladislav S; Pustovit, Ksenia B; Abramochkin, Denis V

2016-06-27

Recently, NAD+ has been considered as an essential factor, participating in nerve control of physiological functions and intercellular communication. NAD+ also has been supposed as endogenous activator of P1 and P2 purinoreceptors. Effects of extracellular NAD+ remain poorly investigated in cardiac tissue. This study aims to investigate the effects of extracellular NAD+ in different types of supraventricular and ventricular working myocardium from rat and their potential mechanisms. The standard technique of sharp microelectrode action potential recording in cardiac multicellular preparations was used to study the effects of NAD+. Extracellular NAD+ induced significant changes in bioelectrical activity of left auricle (LA), right auricle (RA), pulmonary veins (PV) and right ventricular wall (RV) myocardial preparations. 10-100 μM NAD+ produced two opposite effects in LA and RA - quickly developing and transient prolongation of action potentials (AP) and delayed sustained AP shortening, which follows the initial positive effect. In PV and RV only AP shortening was observed in response to NAD+ application. In PV preparations AP shortening induced by NAD+ may be considered as a potential proarrhythmic effect. Revealed cardiotropic effects of NAD+ are likely to be mediated by P2 purine receptors, since P1 blocker DPCPX failed to affect them and P2 antagonist suramin abolished NAD + -induced alterations of electrical activity. P2X receptors may be responsible for NAD + -induced short-lasting AP prolongation, while P2Y receptors mediate persistent AP shortening. The latter effect is partially removed by PLC inhibitor U73122 showing the potential involvement of phosphoinositide signaling pathway in mediation of NAD+ cardiotropic effects. Extracellular NAD+ is supposed to be a novel regulator of cardiac electrical activity. P2 receptors represent the main target of NAD+ at least in the rat heart.
Symptomatic and neuroprotective effects following activation of nigral group III metabotropic glutamate receptors in rodent models of Parkinson's disease

PubMed Central

Austin, PJ; Betts, MJ; Broadstock, M; O'Neill, MJ; Mitchell, SN; Duty, S

2010-01-01

Background and purpose: Increased glutamatergic innervation of the substantia nigra pars reticulata (SNpr) and pars compacta (SNpc) may contribute to the motor deficits and neurodegeneration, respectively, in Parkinson's disease (PD). This study aimed to establish whether activation of pre-synaptic group III metabotropic glutamate (mGlu) receptors reduced glutamate release in the SN, and provided symptomatic or neuroprotective relief in animal models of PD. Experimental approach: Broad-spectrum group III mGlu receptor agonists, O-phospho-l-serine (l-SOP) and l-2-amino-4-phosphonobutyrate (l-AP4), were assessed for their ability to inhibit KCl-evoked [3H]-d-aspartate release in rat nigral prisms or inhibit KCl-evoked endogenous glutamate release in the SNpr in vivo using microdialysis. Reversal of akinesia in reserpine-treated rats was assessed following intranigral injection of l-SOP and l-AP4. Finally, the neuroprotective effect of 7 days' supra-nigral treatment with l-AP4 was examined in 6-hydroxydopamine (6-OHDA)-lesioned rats. Key results: l-SOP and l-AP4 inhibited [3H]-d-aspartate release by 33 and 44% respectively. These effects were blocked by the selective group III mGlu antagonist (RS)-α-cyclopropyl-4-phosphonophenylglycine (CPPG). l-SOP also reduced glutamate release in the SNpr in vivo by 48%. Injection of l-SOP and l-AP4 into the SNpr reversed reserpine-induced akinesia. Following administration above the SNpc, l-AP4 provided neurochemical, histological and functional protection against 6-OHDA lesion of the nigrostriatal tract. Pretreatment with CPPG inhibited these effects. Conclusions and implications: These findings highlight group III mGlu receptors in the SN as potential targets for providing both symptomatic and neuroprotective relief in PD, and indicate that inhibition of glutamate release in the SN may underlie these effects. PMID:20649576
DiAs User Interface: A Patient-Centric Interface for Mobile Artificial Pancreas Systems

PubMed Central

Keith-Hynes, Patrick; Guerlain, Stephanie; Mize, Benton; Hughes-Karvetski, Colleen; Khan, Momin; McElwee-Malloy, Molly; Kovatchev, Boris P.

2013-01-01

Background Recent in-hospital studies of artificial pancreas (AP) systems have shown promising results in improving glycemic control in patients with type 1 diabetes mellitus. The next logical step in AP development is to conduct transitional outpatient clinical trials with a mobile system that is controlled by the patient. In this article, we present the user interface (UI) of the Diabetes Assistant (DiAs), an experimental smartphone-based mobile AP system, and describe the reactions of a round of focus groups to the UI. This work is an initial inquiry involving a relatively small number of potential users, many of whom had never seen an AP system before, and the results should be understood in that light. Methods We began by considering how the UI of an AP system could be designed to make use of the familiar touch-based graphical UI of a consumer smartphone. After developing a working prototype UI, we enlisted a human factors specialist to perform a heuristic expert analysis. Next we conducted a formative evaluation of the UI through a series of three focus groups with N = 13 potential end users as participants. The UI was modified based upon the results of these studies, and the resulting DiAs system was used in transitional outpatient AP studies of adults in the United States and Europe. Results The DiAs UI was modified based on focus group feedback from potential users. The DiAs was subsequently used in JDRF- and AP@Home-sponsored transitional outpatient AP studies in the United States and Europe by 40 subjects for 2400 h with no adverse events. Conclusions Adult patients with type 1 diabetes mellitus are able to control an AP system successfully using a patient-centric UI on a commercial smartphone in a transitional outpatient environment. PMID:24351168
Effects of a human recombinant alkaline phosphatase on renal hemodynamics, oxygenation and inflammation in two models of acute kidney injury.

PubMed

Peters, Esther; Ergin, Bülent; Kandil, Asli; Gurel-Gurevin, Ebru; van Elsas, Andrea; Masereeuw, Rosalinde; Pickkers, Peter; Ince, Can

2016-12-15

Two small clinical trials indicated that administration of bovine intestinal alkaline phosphatase (AP) improves renal function in critically ill patients with sepsis-associated acute kidney injury (AKI), for which the mechanism of action is not completely understood. Here, we investigated the effects of a newly developed human recombinant AP (recAP) on renal oxygenation and hemodynamics and prevention of kidney damage and inflammation in two in vivo AKI models. To induce AKI, male Wistar rats (n=18) were subjected to renal ischemia (30min) and reperfusion (I/R), or sham-operated. In a second model, rats (n=18) received a 30min infusion of lipopolysaccharide (LPS; 2.5mg/kg), or saline, and fluid resuscitation. In both models, recAP (1000U/kg) was administered intravenously (15min before reperfusion, or 90min after LPS). Following recAP treatment, I/R-induced changes in renal blood flow, renal vascular resistance and oxygen delivery at early, and cortical microvascular oxygen tension at late reperfusion were no longer significantly affected. RecAP did not influence I/R-induced effects on mean arterial pressure. During endotoxemia, recAP treatment did not modulate the LPS-induced changes in systemic hemodynamics and renal oxygenation. In both models, recAP did exert a clear renal protective anti-inflammatory effect, demonstrated by attenuated immunostaining of inflammatory, tubular injury and pro-apoptosis markers. Whether this renal protective effect is sufficient to improve outcome of patients suffering from sepsis-associated AKI is being investigated in a large clinical trial. Copyright Â© 2016. Published by Elsevier Inc.
Regulation of rat mesangial cell growth by diadenosine phosphates.

PubMed Central

Heidenreich, S; Tepel, M; Schlüter, H; Harrach, B; Zidek, W

1995-01-01

The newly recognized human endogenous vasoconstrictive dinucleotides, diadenosine pentaphosphate (AP5A) and diadenosine hexaphosphate (AP6A), were tested for growth stimulatory effects in rat mesangial cells (MC). Both AP5A and AP6A stimulated growth in micromolar concentrations. The growth stimulatory effect exceeded that of ATP, alpha,beta-methylene ATP, adenosine 5'-O-(3-thio)triphosphate and UTP. Both diadenosine phosphates potentiated the growth response to platelet-derived growth factor, but not to insulin-like growth factor-1. To further elucidate the site of action in the cell cycle, RNA and protein synthesis were assessed. AP5 and AP6A stimulated protein synthesis, but not RNA formation. Furthermore, both agents increased cytosolic free Ca2+ concentration. It is concluded that AP5A and AP6A may play a regulatory role in MC growth as progression factors and possibly modify MC proliferation in glomerular disease. PMID:7769127
AP214, an analogue of α-melanocyte-stimulating hormone, ameliorates sepsis-induced acute kidney injury and mortality

PubMed Central

Doi, Kent; Hu, Xuzhen; Yuen, Peter S.T.; Leelahavanichkul, Asada; Yasuda, Hideo; Kim, Soo Mi; Schnermann, Jürgen; Jonassen, Thomas E.N.; Frøkiær, Jørgen; Nielsen, Søren; Star, Robert A.

2008-01-01

Sepsis remains a serious problem in critically ill patients with the mortality increasing to over half when there is attendant acute kidney injury. α-Melanocyte-stimulating hormone is a potent anti-inflammatory cytokine that inhibits many forms of inflammation including that with acute kidney injury. We tested whether a new α-melanocyte-stimulating hormone analogue (AP214), which has increased binding affinity to melanocortin receptors, improves sepsis-induced kidney injury and mortality using a cecal ligation and puncture mouse model. In the lethal cecal ligation-puncture model of sepsis, severe hypotension and bradycardia resulted and AP214 attenuated acute kidney injury of the lethal model with a bell-shaped dose-response curve. An optimum AP214 dose reduced acute kidney injury even when it was administered 6 hr after surgery and it significantly improved blood pressure and heart rate. AP214 reduced serum TNF-α and IL-10 levels with a bell-shaped dose-response curve. Additionally; NF-κB activation in the kidney and spleen, and splenocyte apoptosis were decreased by the treatment. AP214 significantly improved survival in both lethal and sublethal models. We have shown that AP214 improves hemodynamic failure, acute kidney injury, mortality and splenocyte apoptosis attenuating pro- and anti-inflammatory actions due to sepsis. PMID:18354376
Limitations in electrophysiological model development and validation caused by differences between simulations and experimental protocols.

PubMed

Carro, Jesús; Rodríguez-Matas, José F; Monasterio, Violeta; Pueyo, Esther

2017-10-01

Models of ion channel dynamics are usually built by fitting isolated cell experimental values of individual parameters while neglecting the interaction between them. Another shortcoming regards the estimation of ionic current conductances, which is often based on quantification of Action Potential (AP)-derived markers. Although this procedure reduces the uncertainty in the calculation of conductances, many studies evaluate electrophysiological AP-derived markers from single cell simulations, whereas experimental measurements are obtained from tissue preparations. In this work, we explore the limitations of these approaches to estimate ion channel dynamics and maximum current conductances and how they could be overcome by using multiscale simulations of experimental protocols. Four human ventricular cell models, namely ten Tusscher and Panfilov (2006), Grandi et al. (2010), O'Hara et al. (2011), and Carro et al. (2011), were used. Two problems involving scales from ion channels to tissue were investigated: 1) characterization of L-type calcium voltage-dependent inactivation I Ca,L ; 2) identification of major ionic conductance contributors to steady-state AP markers, including APD 90 , APD 75 , APD 50 , APD 25 , Triangulation and maximal and minimal values of V and dV/dt during the AP (V max , V min , dV/dt max , dV/dt min ). Our results show that: 1) I Ca,L inactivation characteristics differed significantly when calculated from model equations and from simulations reproducing the experimental protocols. 2) Large differences were found in the ionic currents contributors to APD 25 , Triangulation, V max , dV/dt max and dV/dt min between single cells and 1D-tissue. When proposing any new model formulation, or evaluating an existing model, consistency between simulated and experimental data should be verified considering all involved effects and scales. Copyright © 2016 Elsevier Ltd. All rights reserved.
Semi-analytical Model for Estimating Absorption Coefficients of Optically Active Constituents in Coastal Waters

NASA Astrophysics Data System (ADS)

Wang, D.; Cui, Y.

2015-12-01

The objectives of this paper are to validate the applicability of a multi-band quasi-analytical algorithm (QAA) in retrieval absorption coefficients of optically active constituents in turbid coastal waters, and to further improve the model using a proposed semi-analytical model (SAA). The ap(531) and ag(531) semi-analytically derived using SAA model are quite different from the retrievals procedures of QAA model that ap(531) and ag(531) are semi-analytically derived from the empirical retrievals results of a(531) and a(551). The two models are calibrated and evaluated against datasets taken from 19 independent cruises in West Florida Shelf in 1999-2003, provided by SeaBASS. The results indicate that the SAA model produces a superior performance to QAA model in absorption retrieval. Using of the SAA model in retrieving absorption coefficients of optically active constituents from West Florida Shelf decreases the random uncertainty of estimation by >23.05% from the QAA model. This study demonstrates the potential of the SAA model in absorption coefficients of optically active constituents estimating even in turbid coastal waters. Keywords: Remote sensing; Coastal Water; Absorption Coefficient; Semi-analytical Model
Development and evaluation of human AP endonuclease inhibitors in melanoma and glioma cell lines.

PubMed

Mohammed, M Z; Vyjayanti, V N; Laughton, C A; Dekker, L V; Fischer, P M; Wilson, D M; Abbotts, R; Shah, S; Patel, P M; Hickson, I D; Madhusudan, S

2011-02-15

Modulation of DNA base excision repair (BER) has the potential to enhance response to chemotherapy and improve outcomes in tumours such as melanoma and glioma. APE1, a critical protein in BER that processes potentially cytotoxic abasic sites (AP sites), is a promising new target in cancer. In the current study, we aimed to develop small molecule inhibitors of APE1 for cancer therapy. An industry-standard high throughput virtual screening strategy was adopted. The Sybyl8.0 (Tripos, St Louis, MO, USA) molecular modelling software suite was used to build inhibitor templates. Similarity searching strategies were then applied using ROCS 2.3 (Open Eye Scientific, Santa Fe, NM, USA) to extract pharmacophorically related subsets of compounds from a chemically diverse database of 2.6 million compounds. The compounds in these subsets were subjected to docking against the active site of the APE1 model, using the genetic algorithm-based programme GOLD2.7 (CCDC, Cambridge, UK). Predicted ligand poses were ranked on the basis of several scoring functions. The top virtual hits with promising pharmaceutical properties underwent detailed in vitro analyses using fluorescence-based APE1 cleavage assays and counter screened using endonuclease IV cleavage assays, fluorescence quenching assays and radiolabelled oligonucleotide assays. Biochemical APE1 inhibitors were then subjected to detailed cytotoxicity analyses. Several specific APE1 inhibitors were isolated by this approach. The IC(50) for APE1 inhibition ranged between 30 nM and 50 μM. We demonstrated that APE1 inhibitors lead to accumulation of AP sites in genomic DNA and potentiated the cytotoxicity of alkylating agents in melanoma and glioma cell lines. Our study provides evidence that APE1 is an emerging drug target and could have therapeutic application in patients with melanoma and glioma.
From two competing oscillators to one coupled-clock pacemaker cell system

PubMed Central

Yaniv, Yael; Lakatta, Edward G.; Maltsev, Victor A.

2015-01-01

At the beginning of this century, debates regarding “what are the main control mechanisms that ignite the action potential (AP) in heart pacemaker cells” dominated the electrophysiology field. The original theory which prevailed for over 50 years had advocated that the ensemble of surface membrane ion channels (i.e., “M-clock”) is sufficient to ignite rhythmic APs. However, more recent experimental evidence in a variety of mammals has shown that the sarcoplasmic reticulum (SR) acts as a “Ca2+-clock” rhythmically discharges diastolic local Ca2+ releases (LCRs) beneath the cell surface membrane. LCRs activate an inward current (likely that of the Na+/Ca2+ exchanger) that prompts the surface membrane “M-clock” to ignite an AP. Theoretical and experimental evidence has mounted to indicate that this clock “crosstalk” operates on a beat-to-beat basis and determines both the AP firing rate and rhythm. Our review is focused on the evolution of experimental definition and numerical modeling of the coupled-clock concept, on how mechanisms intrinsic to pacemaker cell determine both the heart rate and rhythm, and on future directions to develop further the coupled-clock pacemaker cell concept. PMID:25741284
GM2-activator protein: a new biomarker for lung cancer.

PubMed

Potprommanee, Laddawan; Ma, Haou-Tzong; Shank, Lalida; Juan, Yi-Hsiu; Liao, Wei-Yu; Chen, Shui-Tein; Yu, Chong-Jen

2015-01-01

Effective biomarkers for early diagnosis of lung cancer are needed. A recent study demonstrated that urinary GM2-activator protein (GM2AP) level was increased in lung cancer patients. This study aims to validate the potential application of GM2AP as a biomarker for diagnosis of lung cancer. Serum and urine samples were obtained from 189 participants (133 patients for treatment naive lung cancer, 26 healthy volunteers for urine, and 30 healthy volunteers for serum). GM2AP level was detected by Western blotting and quantified using enzyme-linked immunosorbent assay (ELISA). The GM2AP expression in tumors and nontumor parts of lung tissues from 143 nonsmall cell lung cancers was detected by immunohistochemical stains. There was an 8.11 ± 1.36 folds increase in urine and a 5.41 ± 0.73 folds increase in serum level of GM2AP in lung cancer patients compared with healthy volunteers (p < 0.0001), achieving a 0.89 AUC value in urine and 0.90 AUC value in serum for the receiver-operating characteristic curves. Both serum and urine levels of GM2AP correlated significantly with pathology stages (urine, p = 0.009; serum, p < 0.0001). Using immunohistochemical, positive expression of GM2AP was found at 83.9% of nonsmall cell lung cancers patients and none in normal tissue. The GM2AP expression was significantly correlated with pathology stage (p = 0.0001). Patients with higher GM2AP expression had shorter overall survival (p = 0.045) and disease-free survival (p = 0.049) than lower GM2AP expression. Moreover, the multivariate analysis suggested GM2AP as an independent predictors of disease-free survival and overall survival. Our study demonstrates that GM2AP might serve as potential diagnostic and prognostic biomarkers in patients with lung cancer.
Nutrient and Trace Metal Controls on Alkaline Phosphatase in the Subtropical Ocean: Insights from Bioassays and Gene Expression

NASA Astrophysics Data System (ADS)

Mahaffey, C.; Reynolds, S.; Davis, C. E.; Lohan, M. C.

2016-02-01

Phosphorus is an essential nutrient for all life on earth. In the ocean, the most bioavailable form of phosphorus is inorganic phosphate, but in the extensive subtropical gyres, phosphate concentrations can be chronically low in the surface ocean and limit biological activity. In response to phosphate limitation, organisms produce phosphohydrolytic enzymes, such as alkaline phosphatases (AP), that enable them to utilize the more replete dissolved organic phosphorus (DOP) pool to meet their cellular phosphorus demands. Synthesis of data from the surface ocean from 14 open ocean studies reveals an inverse hyperbolic relationship between phosphate and AP, where AP is significantly induced at phosphate concentrations below 50 nM and DOP concentrations decrease as AP increases. AP activity was significantly higher in the subtropical Atlantic compared to the subtropical Pacific Ocean, even over the same low phosphate concentration range (0 to 50 nM). While the phosphate concentration may have a first order control on the rates of AP, we demonstrate that other factors influence AP activity. AP are metalloenzymes and zinc and iron are co-factors of the AP proteins PhoA and PhoX, respectively. Using bioassay experiments, we show that the addition of Saharan dust and zinc significantly increases the rate of AP. To our knowledge, our results are the first direct field-based evidence that AP activity is limited by zinc in the subtropical ocean. In colonies of nitrogen fixer, Trichodesmium, we found enhanced expression of the phoA gene in a region of elevated zinc concentrations and enhanced expression of the phoX gene in a region of elevated iron concentrations around the intertropical convergence zone. Our study highlights the potential link between the phosphorus cycle and trace metals, specifically zinc and iron, and implies that there is potential for zinc-phosphorus and iron-phosphorus co-limitation in the ocean via AP.
Effects of Intravenous Administration of Human Umbilical Cord Blood Stem Cells in 3-Acetylpyridine-Lesioned Rats

PubMed Central

Calatrava-Ferreras, Lucía; Gonzalo-Gobernado, Rafael; Herranz, Antonio S.; Reimers, Diana; Montero Vega, Teresa; Jiménez-Escrig, Adriano; Richart López, Luis Alberto; Bazán, Eulalia

2012-01-01

Cerebellar ataxias include a heterogeneous group of infrequent diseases characterized by lack of motor coordination caused by disturbances in the cerebellum and its associated circuits. Current therapies are based on the use of drugs that correct some of the molecular processes involved in their pathogenesis. Although these treatments yielded promising results, there is not yet an effective therapy for these diseases. Cell replacement strategies using human umbilical cord blood mononuclear cells (HuUCBMCs) have emerged as a promising approach for restoration of function in neurodegenerative diseases. The aim of this work was to investigate the potential therapeutic activity of HuUCBMCs in the 3-acetylpyridine (3-AP) rat model of cerebellar ataxia. Intravenous administered HuUCBMCs reached the cerebellum and brain stem of 3-AP ataxic rats. Grafted cells reduced 3-AP-induced neuronal loss promoted the activation of microglia in the brain stem, and prevented the overexpression of GFAP elicited by 3-AP in the cerebellum. In addition, HuUCBMCs upregulated the expression of proteins that are critical for cell survival, such as phospho-Akt and Bcl-2, in the cerebellum and brain stem of 3-AP ataxic rats. As all these effects were accompanied by a temporal but significant improvement in motor coordination, HuUCBMCs grafts can be considered as an effective cell replacement therapy for cerebellar disorders. PMID:23150735
The stochastic nature of action potential backpropagation in apical tuft dendrites.

PubMed

Short, Shaina M; Oikonomou, Katerina D; Zhou, Wen-Liang; Acker, Corey D; Popovic, Marko A; Zecevic, Dejan; Antic, Srdjan D

2017-08-01

In cortical pyramidal neurons, backpropagating action potentials (bAPs) supply Ca 2+ to synaptic contacts on dendrites. To determine whether the efficacy of AP backpropagation into apical tuft dendrites is stable over time, we performed dendritic Ca 2+ and voltage imaging in rat brain slices. We found that the amplitude of bAP-Ca 2+ in apical tuft branches was unstable, given that it varied from trial to trial (termed "bAP-Ca 2+ flickering"). Small perturbations in dendritic physiology, such as spontaneous synaptic inputs, channel inactivation, or temperature-induced changes in channel kinetics, can cause bAP flickering. In the tuft branches, the density of Na + and K + channels was sufficient to support local initiation of fast spikelets by glutamate iontophoresis. We quantified the time delay between the somatic AP burst and the peak of dendritic Ca 2+ transient in the apical tuft, because this delay is important for induction of spike-timing dependent plasticity. Depending on the frequency of the somatic AP triplets, Ca 2+ signals peaked in the apical tuft 20-50 ms after the 1st AP in the soma. Interestingly, at low frequency (<20 Hz), the Ca 2+ peaked sooner than at high frequency, because only the 1st AP invaded tuft. Activation of dendritic voltage-gated Ca 2+ channels is sensitive to the duration of the dendritic voltage transient. In apical tuft branches, small changes in the duration of bAP voltage waveforms cause disproportionately large increases in dendritic Ca 2+ influx (bAP-Ca 2+ flickering). The stochastic nature of bAP-Ca 2+ adds a new perspective on the mechanisms by which pyramidal neurons combine inputs arriving at different cortical layers. NEW & NOTEWORTHY The bAP-Ca 2+ signal amplitudes in some apical tuft branches randomly vary from moment to moment. In repetitive measurements, successful AP invasions are followed by complete failures. Passive spread of voltage from the apical trunk into the tuft occasionally reaches the threshold for local Na + spike, resulting in stronger Ca 2+ influx. During a burst of three somatic APs, the peak of dendritic Ca 2+ in the apical tuft occurs with a delay of 20-50 ms depending on AP frequency. Copyright © 2017 the American Physiological Society.

PSAT Component Scores as a Predictor of Success on AP Exam Performance for Diverse Students

ERIC Educational Resources Information Center

Richardson, Cristianne C.; Gonzalez, Alejandro; Leal, Lonnie; Castillo, Mary Z.; Carman, Carol A.

2016-01-01

While studies have shown the positive effect of the Advanced Placement (AP) program on college readiness, there are still barriers preventing minority and low socioeconomic status (SES) students who possess high academic potential from participating in the opportunity that AP courses offer. One tool that could help identify students for…
Stimulus waveform determines the characteristics of sensory nerve action potentials.

PubMed

Pereira, Pedro; Leote, João; Cabib, Christopher; Casanova-Molla, Jordi; Valls-Sole, Josep

2016-03-01

In routine nerve conduction studies supramaximal electrical stimuli generate sensory nerve action potentials by depolarization of nerve fibers under the cathode. However, stimuli of submaximal intensity may give rise to action potentials generated under the anode. We tested if this phenomenon depends on the characteristics of stimulus ending. We added a circuit to our stimulation device that allowed us to modify the end of the stimulus by increasing the time constant of the decay phase. Increasing the fall time caused a reduction of anode action potential (anAP) amplitude, and eventually abolished it, in all tested subjects. We subsequently examined the stimulus waveform in a series of available electromyographs stimulators and found that the anAP could only be obtained with stimulators that issued stimuli ending sharply. Our results prove that the anAP is generated at stimulus end, and depends on the sharpness of current shut down. Electromyographs produce stimuli of varying characteristics, which limits the reproducibility of anAP results by interested researchers. The study of anodal action potentials might be a useful tool to have a quick appraisal of distal human sensory nerve excitability. Copyright © 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
Influence of apple pomace inclusion on the process of animal feed pelleting.

PubMed

Maslovarić, Marijana D; Vukmirović, Đuro; Pezo, Lato; Čolović, Radmilo; Jovanović, Rade; Spasevski, Nedeljka; Tolimir, Nataša

2017-08-01

Apple pomace (AP) is the main by-product of apple juice production. Large amounts of this material disposed into landfills can cause serious environmental problems. One of the solutions is to utilise AP as animal feed. The aim of this study was to investigate the impact of dried AP inclusion into model mixtures made from conventional feedstuffs on pellet quality and pellet press performance. Three model mixtures, with different ratios of maize, sunflower meal and AP, were pelleted. Response surface methodology (RSM) was applied when designing the experiment. The simultaneous and interactive effects of apple pomace share (APS) in the mixtures, die thickness (DT) of the pellet press and initial moisture content of the mixtures (M), on pellet quality and production parameters were investigated. Principal component analysis (PCA) and standard score (SS) analysis were applied for comprehensive analysis of the experimental data. The increase in APS led to an improvement of pellet quality parameters: pellet durability index (PDI), hardness (H) and proportion of fines in pellets. The increase in DT and M resulted in pellet quality improvement. The increase in DT and APS resulted in higher energy consumption of the pellet press. APS was the most influential variable for PDI and H calculation, while APS and DT were the most influential variables in the calculation of pellet press energy consumption. PCA showed that the first two principal components could be considered sufficient for data representation. In conclusion, addition of dried AP to feed model mixtures significantly improved the quality of the pellets.
Structure of a microsporidian methionine aminopeptidase type 2 complexed with fumagillin and TNP-470

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alvarado, J.; Nemkal, A; Sauder, J

2009-01-01

Microsporidia are protists that have been reported to cause infections in both vertebrates and invertebrates. They have emerged as human pathogens particularly in patients that are immunosuppressed and cases of gastrointestinal infection, encephalitis, keratitis, sinusitis, myositis and disseminated infection are well described in the literature. While benzimidazoles are active against many species of microsporidia, these drugs do not have significant activity against Enterocytozoon bieneusi. Fumagillin and its analogues have been demonstrated to have activity in vitro and in animal models of microsporidiosis and human infections due to E. bieneusi. Fumagillin and its analogues inhibit methionine aminopeptidase type 2. Encephalitozoon cuniculimore » MetAP2 (EcMetAP2) was cloned and expressed as an active enzyme using a baculovirus system. The crystal structure of EcMetAP2 was determined with and without the bound inhibitors fumagillin and TNP-470. This structure classifies EcMetAP2 as a member of the MetAP2c family. The EcMetAP2 structure was used to generate a homology model of the E. bieneusi MetAP2. Comparison of microsporidian MetAP2 structures with human MetAP2 provides insights into the design of inhibitors that might exhibit specificity for microsporidian MetAP2.« less
Improved solubility and oral bioavailability of apigenin via Soluplus/Pluronic F127 binary mixed micelles system.

PubMed

Zhang, Zhenhai; Cui, Changchang; Wei, Fang; Lv, Huixia

2017-08-01

The aim of this study was to develop a novel mix micelles system composing of two biocompatible copolymers of Soluplus ® and Pluronic F127 to improve the solubility, oral bioavailability of insoluble drug apigenin (AP) as model drug. The AP-loaded mixed micelles (AP-M) were prepared by ethanol thin-film hydration method. The formed optimal formulation of AP-M were provided with small size (178.5 nm) and spherical shape at ratio of 4:1 (Soluplus ® :Pluronic F127), as well as increasing solubility of to 5.61 mg/mL in water which was about 3442-fold compared to that of free AP. The entrapment efficiency and drug loading of AP-M were 95.72 and 5.32%, respectively, and a sustained release of AP-M was obtained as in vitro release study indicated. Transcellular transport study showed that the cell uptake of AP was increased in Caco-2 cell transport models. The oral bioavailability of AP-M was 4.03-fold of free AP in SD rats, indicating the mixed micelles of Soluplus ® and Pluronic F127 is an industrially feasible drug delivery system to promote insoluble drug oral absorption in the gastrointestinal tract.
The redox status of experimental hemorrhagic shock as measured by cyclic voltammetry.

PubMed

Mittal, Anubhav; Göke, Friederike; Flint, Richard; Loveday, Benjamin P T; Thompson, Nichola; Delahunt, Brett; Kilmartin, Paul A; Cooper, Garth J S; MacDonald, Julia; Hickey, Anthony; Windsor, John A; Phillips, Anthony R J

2010-05-01

Hemorrhagic shock (HS) leads to reactive oxygen species production. However, clinicians do not have access to bedside measurements of the redox status during HS. Cyclic voltammetry (CyV) is a simple electrochemical method of measuring redox status. The aims of this study were to 1) report the first application of cyclic voltammetry to measure the acute changes in serum redox status after HS, 2) to contrast it with another severe systemic disease with a different redox pathology (acute pancreatitis [AP]), and 3) to describe the response of CyV over time in a resolving model of AP. In the acute study, 24 male Wistar rats were randomized into three groups: groups 1 (control), 2 (AP), and 3 (HS). In the time-course study, 28 rats were randomized to a sham-control as well as 6 and 24 h post-AP cohorts, respectively.Cyclic voltammetry was performed using a three-electrode system. In the acute study, the first and second voltammetric peaks increased significantly in HS. In contrast, within the AP group, only the first voltammetric peak showed a significant increase. The first voltammetric peak correlated with plasma protein carbonyls (PCs) and with thiobarbituric acid-reactive substances, whereas the second voltammetric peak correlated positively with plasma protein carbonyls. In the second study, the first voltammetric peak correlated with physiological improvements. Here, we showed that serum CyV could respond to the serum redox change in HS and AP. Cyclic voltammetry warrants evaluation as a potential real-time beside measure of a patient's redox status during shock.
Identifying risk factors for progression to critical care admission and death among individuals with acute pancreatitis: a record linkage analysis of Scottish healthcare databases

PubMed Central

Mole, Damian J; Gungabissoon, Usha; Johnston, Philip; Cochrane, Lynda; Hopkins, Leanne; Wyper, Grant M A; Skouras, Christos; Dibben, Chris; Sullivan, Frank; Morris, Andrew; Ward, Hester J T; Lawton, Andrew M; Donnan, Peter T

2016-01-01

Objectives Acute pancreatitis (AP) can initiate systemic complications that require support in critical care (CC). Our objective was to use the unified national health record to define the epidemiology of AP in Scotland, with a specific focus on deterministic and prognostic factors for CC admission in AP. Setting Health boards in Scotland (n=4). Participants We included all individuals in a retrospective observational cohort with at least one episode of AP (ICD10 code K85) occurring in Scotland from 1 April 2009 to 31 March 2012. 3340 individuals were coded as AP. Methods Data from 16 sources, spanning general practice, community prescribing, Accident and Emergency attendances, hospital in-patient, CC and mortality registries, were linked by a unique patient identifier in a national safe haven. Logistic regression and gamma models were used to define independent predictive factors for severe AP (sAP) requiring CC admission or leading to death. Results 2053 individuals (61.5% (95% CI 59.8% to 63.2%)) met the definition for true AP (tAP). 368 patients (17.9% of tAP (95% CI 16.2% to 19.6%)) were admitted to CC. Predictors of sAP were pre-existing angina or hypertension, hypocalcaemia and age 30–39 years, if type 2 diabetes mellitus was present. The risk of sAP was lower in patients with multiple previous episodes of AP. In-hospital mortality in tAP was 5.0% (95% CI 4.1% to 5.9%) overall and 21.7% (95% CI 19.9% to 23.5%) in those with tAP necessitating CC admission. Conclusions National record-linkage analysis of routinely collected data constitutes a powerful resource to model CC admission and prognosticate death during AP. Mortality in patients with AP who require CC admission remains high. PMID:27311912
Dendritic Na+ spikes enable cortical input to drive action potential output from hippocampal CA2 pyramidal neurons

PubMed Central

Sun, Qian; Srinivas, Kalyan V; Sotayo, Alaba; Siegelbaum, Steven A

2014-01-01

Synaptic inputs from different brain areas are often targeted to distinct regions of neuronal dendritic arbors. Inputs to proximal dendrites usually produce large somatic EPSPs that efficiently trigger action potential (AP) output, whereas inputs to distal dendrites are greatly attenuated and may largely modulate AP output. In contrast to most other cortical and hippocampal neurons, hippocampal CA2 pyramidal neurons show unusually strong excitation by their distal dendritic inputs from entorhinal cortex (EC). In this study, we demonstrate that the ability of these EC inputs to drive CA2 AP output requires the firing of local dendritic Na+ spikes. Furthermore, we find that CA2 dendritic geometry contributes to the efficient coupling of dendritic Na+ spikes to AP output. These results provide a striking example of how dendritic spikes enable direct cortical inputs to overcome unfavorable distal synaptic locale to trigger axonal AP output and thereby enable efficient cortico-hippocampal information flow. DOI: http://dx.doi.org/10.7554/eLife.04551.001 PMID:25390033
Electrophysiological characteristics of hamster dorsal root ganglion cells and their response to axotomy.

PubMed

Gurtu, S; Smith, P A

1988-02-01

1. The active and passive membrane properties of neurons in the lower lumbar (L6, L7) or sacral (S1) dorsal root ganglia from golden hamsters were examined in vitro by means of conventional intracellular recording techniques. Data were collected from neurons exhibiting action potentials (AP) of 70 mV or more in amplitude. 2. Cells with axonal conduction velocities (CV) greater than 20 m/s were termed fast-A-cells, those with CVs between 2.5 and 20 m/s were termed A-delta-cells, and those with CVs less than 1 m/s were termed C-cells. 3. Fast-A-cells usually exhibited short-duration APs (2.51 +/- 0.41 ms, n = 19) followed by short (less than 50 ms) afterhyperpolarizations (AHPs). C-cells usually exhibited long-duration APs (10.5 +/- 0.69 ms, n = 18) followed by long-duration AHPs (much greater than 50 ms). The characteristics of APs in A-delta-cells (AP mean duration 3.34 +/- 0.42 ms, n = 32) were intermediate between those of fast-A- and C-cells. Long AHPs (duration much greater than 50 ms) were manifest in 43.8% of A-delta-cells. 4. A time-dependent sag in hyperpolarizing electrotonic potentials (rectification) was found in 68.8% of fast-A-cells, 45.5% of A-delta-cells, and 62.5% of C-cells. 5. To examine neuronal properties 1-6 wk after transection of the sciatic nerve (axotomy), cells were reclassified as SAP (short action potential) cells and LAP (long action potential) cells. Cells in the SAP category had AP durations less than 5 ms and included all fast-A-cells and the majority of A-delta-cells. The LAP category included cells with AP durations greater than 8 ms contained only C-cells. 6. Axotomy failed to decrease the CV of LAP cells or A-delta-cells in the SAP group. The CV of LAP cells may have increased (P less than 0.05), whereas that of SAP cells was unchanged. 7. The duration of the AP and AHP of SAP cells were slightly increased (0.1 greater than P greater than 0.05), whereas AP and AHP duration of LAP cells were unchanged after axotomy. AHP amplitudes of all cell types tended to be smaller (0.1 greater than P greater than 0.05). Axotomy did not alter the resting membrane potential or reduce the incidence of rectification in any cell type. 8. Invasion of the soma by axonally evoked APs was impeded in all cell types after axotomy even though a decrease (P less than 0.05) in rheobase of SAP cells occurred.(ABSTRACT TRUNCATED AT 400 WORDS)
Molecular dynamics simulation for the test of calibrated OPLS-AA force field for binary liquid mixture of tri-iso-amyl phosphate and n-dodecane.

PubMed

Das, Arya; Ali, Sk Musharaf

2018-02-21

Tri-isoamyl phosphate (TiAP) has been proposed to be an alternative for tri-butyl phosphate (TBP) in the Plutonium Uranium Extraction (PUREX) process. Recently, we have successfully calibrated and tested all-atom optimized potentials for liquid simulations using Mulliken partial charges for pure TiAP, TBP, and dodecane by performing molecular dynamics (MD) simulation. It is of immense importance to extend this potential for the various molecular properties of TiAP and TiAP/n-dodecane binary mixtures using MD simulation. Earlier, efforts were devoted to find out a suitable force field which can explain both structural and dynamical properties by empirical parameterization. Therefore, the present MD study reports the structural, dynamical, and thermodynamical properties with different mole fractions of TiAP-dodecane mixtures at the entire range of mole fraction of 0-1 employing our calibrated Mulliken embedded optimized potentials for liquid simulation (OPLS) force field. The calculated electric dipole moment of TiAP was seen to be almost unaffected by the TiAP concentration in the dodecane diluent. The calculated liquid densities of the TiAP-dodecane mixture are in good agreement with the experimental data. The mixture densities at different temperatures are also studied which was found to be reduced with temperature as expected. The plot of diffusivities for TiAP and dodecane against mole fraction in the binary mixture intersects at a composition in the range of 25%-30% of TiAP in dodecane, which is very much closer to the TBP/n-dodecane composition used in the PUREX process. The excess volume of mixing was found to be positive for the entire range of mole fraction and the excess enthalpy of mixing was shown to be endothermic for the TBP/n-dodecane mixture as well as TiAP/n-dodecane mixture as reported experimentally. The spatial pair correlation functions are evaluated between TiAP-TiAP and TiAP-dodecane molecules. Further, shear viscosity has been computed by performing the non-equilibrium molecular dynamics employing the periodic perturbation method. The calculated shear viscosity of the binary mixture is found to be in excellent agreement with the experimental values. The use of the newly calibrated OPLS force field embedding Mulliken charges is shown to be equally reliable in predicting the structural and dynamical properties for the mixture without incorporating any arbitrary scaling in the force field or Lennard-Jones parameters. Further, the present MD simulation results demonstrate that the Stokes-Einstein relation breaks down at the molecular level. The present methodology might be adopted to evaluate the liquid state properties of an aqueous-organic biphasic system, which is of great significance in the interfacial science and technology.
Molecular dynamics simulation for the test of calibrated OPLS-AA force field for binary liquid mixture of tri-iso-amyl phosphate and n-dodecane

NASA Astrophysics Data System (ADS)

Das, Arya; Ali, Sk. Musharaf

2018-02-01

Tri-isoamyl phosphate (TiAP) has been proposed to be an alternative for tri-butyl phosphate (TBP) in the Plutonium Uranium Extraction (PUREX) process. Recently, we have successfully calibrated and tested all-atom optimized potentials for liquid simulations using Mulliken partial charges for pure TiAP, TBP, and dodecane by performing molecular dynamics (MD) simulation. It is of immense importance to extend this potential for the various molecular properties of TiAP and TiAP/n-dodecane binary mixtures using MD simulation. Earlier, efforts were devoted to find out a suitable force field which can explain both structural and dynamical properties by empirical parameterization. Therefore, the present MD study reports the structural, dynamical, and thermodynamical properties with different mole fractions of TiAP-dodecane mixtures at the entire range of mole fraction of 0-1 employing our calibrated Mulliken embedded optimized potentials for liquid simulation (OPLS) force field. The calculated electric dipole moment of TiAP was seen to be almost unaffected by the TiAP concentration in the dodecane diluent. The calculated liquid densities of the TiAP-dodecane mixture are in good agreement with the experimental data. The mixture densities at different temperatures are also studied which was found to be reduced with temperature as expected. The plot of diffusivities for TiAP and dodecane against mole fraction in the binary mixture intersects at a composition in the range of 25%-30% of TiAP in dodecane, which is very much closer to the TBP/n-dodecane composition used in the PUREX process. The excess volume of mixing was found to be positive for the entire range of mole fraction and the excess enthalpy of mixing was shown to be endothermic for the TBP/n-dodecane mixture as well as TiAP/n-dodecane mixture as reported experimentally. The spatial pair correlation functions are evaluated between TiAP-TiAP and TiAP-dodecane molecules. Further, shear viscosity has been computed by performing the non-equilibrium molecular dynamics employing the periodic perturbation method. The calculated shear viscosity of the binary mixture is found to be in excellent agreement with the experimental values. The use of the newly calibrated OPLS force field embedding Mulliken charges is shown to be equally reliable in predicting the structural and dynamical properties for the mixture without incorporating any arbitrary scaling in the force field or Lennard-Jones parameters. Further, the present MD simulation results demonstrate that the Stokes-Einstein relation breaks down at the molecular level. The present methodology might be adopted to evaluate the liquid state properties of an aqueous-organic biphasic system, which is of great significance in the interfacial science and technology.
Variable Basal Melt Rates of Antarctic Peninsula Ice Shelves, 1994-2016

NASA Astrophysics Data System (ADS)

Adusumilli, Susheel; Fricker, Helen Amanda; Siegfried, Matthew R.; Padman, Laurie; Paolo, Fernando S.; Ligtenberg, Stefan R. M.

2018-05-01

We have constructed 23-year (1994-2016) time series of Antarctic Peninsula (AP) ice-shelf height change using data from four satellite radar altimeters (ERS-1, ERS-2, Envisat, and CryoSat-2). Combining these time series with output from atmospheric and firn models, we partitioned the total height-change signal into contributions from varying surface mass balance, firn state, ice dynamics, and basal mass balance. On the Bellingshausen coast of the AP, ice shelves lost 84 ± 34 Gt a-1 to basal melting, compared to contributions of 50 ± 7 Gt a-1 from surface mass balance and ice dynamics. Net basal melting on the Weddell coast was 51 ± 71 Gt a-1. Recent changes in ice-shelf height include increases over major AP ice shelves driven by changes in firn state. Basal melt rates near Bawden Ice Rise, a major pinning point of Larsen C Ice Shelf, showed large increases, potentially leading to substantial loss of buttressing if sustained.
Investigation of atmospheric pressure capillary non-thermal plasmas and their applications to the degradation of volatile organic compounds

NASA Astrophysics Data System (ADS)

Yin, Shu-Min

Atmospheric pressure capillary non-thermal plasma (AP-CNTP) has been investigated as a potential technology far the removal of volatile organic compounds (VOCs) in Advanced Life Support Systems (ALS). AP-CNTP is a destructive technology far the removal of VOCs from air streams by active plasma species, such as electrons, ions, and excited molecules. Complete VOC destruction ideally results in the formation of water, carbon dioxide (CO2), and other by-product's may also form, including ozone (O3), nitrous oxide (N2O), nitrogen dioxide (NO2), and decomposed hydrocarbons. Several organic compounds, such as BTEX, ethylene, n-heptane, isooctane, methanol and NH3, were tested in an AP-CNTP system. Parametric experiments were carried out by varying plasma discharge power, flowrates, and initial concentrations. The degradation efficiency varied depending on the chemical nature of the compounds. A plasmochemical kinetic model was derived for toluene, ethylbenzene, and m-xylene and n-heptane.
Melatonin potentiates tear secretion induced by diadenosine tetraphosphate in the rabbit.

PubMed

Hoyle, Charles H V; Peral, Assumpta; Pintor, Jesús

2006-12-15

Diadenosine tetraphosphate (Ap(4)A, 0.03 nmol) applied topically to the cornea of New Zealand white rabbits, evoked an increase in tear secretion of 9.7 +/- 2.60% (N=7). Melatonin (1 nmol) had no significant effect. Application of Ap(4)A in combination with melatonin, evoked a significantly greater increase in tear secretion of 34.2 +/- 5.8% (N=11). This potentiating effect of melatonin was blocked by pretreating the cornea with a topical application of the melatonin receptor antagonist, luzindole (240 nmol). Melatonin combined with Ap(4)A may be useful for treating dry eye conditions.
Analytical performance specifications for external quality assessment - definitions and descriptions.

PubMed

Jones, Graham R D; Albarede, Stephanie; Kesseler, Dagmar; MacKenzie, Finlay; Mammen, Joy; Pedersen, Morten; Stavelin, Anne; Thelen, Marc; Thomas, Annette; Twomey, Patrick J; Ventura, Emma; Panteghini, Mauro

2017-06-27

External Quality Assurance (EQA) is vital to ensure acceptable analytical quality in medical laboratories. A key component of an EQA scheme is an analytical performance specification (APS) for each measurand that a laboratory can use to assess the extent of deviation of the obtained results from the target value. A consensus conference held in Milan in 2014 has proposed three models to set APS and these can be applied to setting APS for EQA. A goal arising from this conference is the harmonisation of EQA APS between different schemes to deliver consistent quality messages to laboratories irrespective of location and the choice of EQA provider. At this time there are wide differences in the APS used in different EQA schemes for the same measurands. Contributing factors to this variation are that the APS in different schemes are established using different criteria, applied to different types of data (e.g. single data points, multiple data points), used for different goals (e.g. improvement of analytical quality; licensing), and with the aim of eliciting different responses from participants. This paper provides recommendations from the European Federation of Laboratory Medicine (EFLM) Task and Finish Group on Performance Specifications for External Quality Assurance Schemes (TFG-APSEQA) and on clear terminology for EQA APS. The recommended terminology covers six elements required to understand APS: 1) a statement on the EQA material matrix and its commutability; 2) the method used to assign the target value; 3) the data set to which APS are applied; 4) the applicable analytical property being assessed (i.e. total error, bias, imprecision, uncertainty); 5) the rationale for the selection of the APS; and 6) the type of the Milan model(s) used to set the APS. The terminology is required for EQA participants and other interested parties to understand the meaning of meeting or not meeting APS.
Deletion Of XIAP reduces the severity of acute pancreatitis via regulation of cell death and nuclear factor-κB activity

PubMed Central

Liu, Yong; Chen, Xiao-Dong; Yu, Jiang; Chi, Jun-Lin; Long, Fei-Wu; Yang, Hong-Wei; Chen, Ke-Ling; Lv, Zhao-Ying; Zhou, Bin; Peng, Zhi-Hai; Sun, Xiao-Feng; Li, Yuan; Zhou, Zong-Guang

2017-01-01

Severe acute pancreatitis (SAP) still remains a clinical challenge, not only for its high mortality but the uncontrolled inflammatory progression from acute pancreatitis (AP) to SAP. Cell death, including apoptosis and necrosis are critical pathology of AP, since the severity of pancreatitis correlates directly with necrosis and inversely with apoptosis Therefore, regulation of cell death from necrosis to apoptosis may have practicably therapeutic value. X-linked inhibitor of apoptosis protein (XIAP) is the best characterized member of the inhibitor of apoptosis proteins (IAP) family, but its function in AP remains unclear. In the present study, we investigated the potential role of XIAP in regulation of cell death and inflammation during acute pancreatitis. The in vivo pancreatitis model was induced by the administration of cerulein with or without lipopolysaccharide (LPS) or by the administration of l-arginine in wild-type or XIAP-deficient mice, and ex vivo model was induced by the administration of cerulein+LPS in AR42J cell line following XIAP inhibition. The severity of acute pancreatitis was determined by serum amylase activity and histological grading. XIAP deletion on cell apoptosis, necrosis and inflammatory response were examined. Caspases activities, nuclear factor-κB (NF-κB) activation and receptor-interacting protein kinase1 (RIP1) degradation were assessed by western blot. Deletion of XIAP resulted in the reduction of amylase activity, decrease of NF-κB activation and less release of TNF-α and IL-6, together with increased caspases activities and RIP1 degradation, leading to enhanced apoptosis and reduced necrosis in pancreatic acinar cells and ameliorated the severity of acute pancreatitis. Our results indicate that deletion of XIAP switches cell death away from necrosis to apoptosis and decreases the inflammatory response, effectively attenuating the severity of AP/SAP. The critical role of XIAP in cell death and inflammation suggests that inhibition of XIAP represents a potential therapeutic strategy for the treatment of acute pancreatitis. PMID:28300832
AE8/AP8 Implementations in AE9/AP9, IRBEM, and SPENVIS

DTIC Science & Technology

2014-02-18

period applies to orbit generation only; AE8/AP8 utilizes geomagnetic field models from other epochs as specified in the table below.) SHIELDOSE2 model...finite and semi- infinite slab data tables for Bremsstrahlung have been reversed [Heynderickx, private communication, May 2013]. This correction is...Cain, J. C., S. J. Hendricks, R. A. Langel, and W. V. Hudson (1967), A proposed model for the international geomagnetic reference field, 1965, J
Assimilation and implications of AE-9/AP-9 in the design process of JPL missions

NASA Astrophysics Data System (ADS)

de Soria-Santacruz Pich, M.; Jun, I.

2015-12-01

The NASA AE-8/AP-8 has been the standard geospace environment specification for decades. This model describes the energetic particle environment around the Earth and is currently the default model used in the design of space missions at the Jet Propulsion Laboratory (JPL). Moreover, the model plays a critical role in the determination of the shielding and survivability of the satellites orbiting our planet. A recent update supported by the Air Force Research Laboratory (AFRL) and the National Reconnaissance Office (NRO), the AE-9/AP-9 model, was released in September 2012 and included many improvements like increased spatial resolution and the specification of the uncertainty due to instrument errors or space weather variability. A current effort at JPL is in place with the objective of making a decision within the Laboratory on the transition from AE-8/AP-8 to the new AE-9/AP-9. In this study we present the results of this effort, which involves the comparison between both versions of the model for different satellite orbits, the comparison between AE-9/AP-9 and in-situ satellite data from the Van Allen Probes and the OSTM/Jason 2 satellite, and the implications of adopting the new model for spacecraft design in terms of survivability, shielding, single event effects, and spacecraft charging.
Catecholamine exocytosis during low frequency stimulation in mouse adrenal chromaffin cells is primarily asynchronous and controlled by the novel mechanism of Ca2+ syntilla suppression

PubMed Central

Lefkowitz, Jason J; DeCrescenzo, Valerie; Duan, Kailai; Bellve, Karl D; Fogarty, Kevin E; Walsh, John V; ZhuGe, Ronghua

2014-01-01

Adrenal chromaffin cells (ACCs), stimulated by the splanchnic nerve, generate action potentials (APs) at a frequency near 0.5 Hz in the resting physiological state, at times described as ‘rest and digest’. How such low frequency stimulation in turn elicits sufficient catecholamine exocytosis to set basal sympathetic tone is not readily explained by the classical mechanism of stimulus–secretion coupling, where exocytosis is synchronized to AP-induced Ca2+ influx. By using simulated action potentials (sAPs) at 0.5 Hz in isolated patch-clamped mouse ACCs, we show here that less than 10% of all catecholaminergic exocytosis, measured by carbon fibre amperometry, is synchronized to an AP. The asynchronous phase, the dominant phase, of exocytosis does not require Ca2+ influx. Furthermore, increased asynchronous exocytosis is accompanied by an AP-dependent decrease in frequency of Ca2+ syntillas (i.e. transient, focal Ca2+ release from internal stores) and is ryanodine sensitive. We propose a mechanism of disinhibition, wherein APs suppress Ca2+ syntillas, which themselves inhibit exocytosis as they do in the case of spontaneous catecholaminergic exocytosis. PMID:25128575
Stimulatory effect of exogenous diadenosine tetraphosphate on insulin and glucagon secretion in the perfused rat pancreas

PubMed Central

Silvestre, Ramona A; Rodríguez-Gallardo, Jovita; Egido, Eva M; Marco, José

1999-01-01

Diadenosine triphosphate (AP3A) and diadenosine tetraphosphate (AP4A) are released by various cells (e.g. platelets and chromaffin cells), and may act as extracellular messengers. In pancreatic B-cells, AP3A and AP4A are inhibitors of the ATP-regulated K+ channels, and glucose increases intracellular levels of both substances.We have studied the effect of exogenous AP3A and AP4A on insulin and glucagon secretion by the perfused rat pancreas.AP3A did not significantly modify insulin or glucagon release, whereas AP4A induced a prompt, short-lived insulin response (≈4 fold higher than basal value; P<0.05) in pancreases perfused at different glucose concentrations (3.2, 5.5 or 9 mM). AP4A-induced insulin release was abolished by somatostatin and by diazoxide. These two substances share the capacity to activate ATP-dependent K+ channels, suggesting that these channels are a potential target for AP4A in the B-cell.AP4A stimulated glucagon release at both 3.2 and 5.5 mM glucose. This effect was abolished by somatostatin.The results suggest that extracellular AP4A may play a physiological role in the control of insulin and glucagon secretion. PMID:10516664

Stimulatory effect of exogenous diadenosine tetraphosphate on insulin and glucagon secretion in the perfused rat pancreas.

PubMed

Silvestre, R A; Rodríguez-Gallardo, J; Egido, E M; Marco, J

1999-10-01

1. Diadenosine triphosphate (AP3A) and diadenosine tetraphosphate (AP4A) are released by various cells (e.g. platelets and chromaffin cells), and may act as extracellular messengers. In pancreatic B-cells, AP3A and AP4A are inhibitors of the ATP-regulated K+ channels, and glucose increases intracellular levels of both substances. 2. We have studied the effect of exogenous AP3A and AP4A on insulin and glucagon secretion by the perfused rat pancreas. 3. AP3A did not significantly modify insulin or glucagon release, whereas AP4A induced a prompt, short-lived insulin response ( approximately 4 fold higher than basal value; P<0.05) in pancreases perfused at different glucose concentrations (3.2, 5.5 or 9 mM). AP4A-induced insulin release was abolished by somatostatin and by diazoxide. These two substances share the capacity to activate ATP-dependent K+ channels, suggesting that these channels are a potential target for AP4A in the B-cell. 4. AP4A stimulated glucagon release at both 3.2 and 5.5 mM glucose. This effect was abolished by somatostatin. 5. The results suggest that extracellular AP4A may play a physiological role in the control of insulin and glucagon secretion.
Polysorbate 80-coated PLGA nanoparticles improve the permeability of acetylpuerarin and enhance its brain-protective effects in rats.

PubMed

Sun, Deqing; Xue, Aiying; Zhang, Bin; Lou, Haiyan; Shi, Huanying; Zhang, Xiumei

2015-12-01

Acetylpuerarin (AP) is an acetylated derivative of puerarin (PUE). The study aimed to prepare polysorbate 80-coated poly(lactic-co-glycolic acid) (PLGA) nanoparticles to improve the permeability of AP across the blood-brain barrier (BBB) and enhance its brain-protective effects. AP-loaded PLGA nanoparticles (AP-PLGA-NPs) were prepared using a solvent diffusion methodology. The NPs were characterized. The pharmacokinetics, tissue distributions and brain-protective effects of AP-PLGA-NPs were evaluated in animals. AP-PLGA-NPs were successfully prepared with a mean particle size of 145.0 nm and a zeta potential of -14.81 mV. The in-vitro release of AP from the PLGA-NPs showed a biphasic release profile. AP was metabolized into PUE in rats. The AUC0-∞ values of AP and PUE for AP-PLGA-NPs were 2.90- and 2.29-fold as great as those for AP solution, respectively. The values of the relative targeting efficiency in the brain were 2.40 and 2.58 for AP and PUE, and the ratios of peak concentration were 1.91 and 1.89 for AP and PUE, respectively. Compared with the crude drug, AP-PLGA-NPs showed better brain-protective effects in rats. Polysorbate 80-coated PLGA-NPs can improve the permeability of AP cross the BBB and enhance its brain-protective effects in rats. © 2015 Royal Pharmaceutical Society.
The Surface Mass Balance of the Antarctic Peninsula at 5.5 km horizontal resolution, as simulated by a regional atmospheric climate model

NASA Astrophysics Data System (ADS)

van Wessem, M.; Reijmer, C.; van den Broeke, M. R.; Ligtenberg, S.; Scambos, T. A.; Barrand, N. E.; Van De Berg, W. J.; Thomas, E. R.; Wuite, J.; van Meijgaard, E.; Turner, J.

2015-12-01

The Antarctic Peninsula (AP) is one of the most rapidly changing regions on earth, but limited detailed information is available about AP climate due to a lack of observational data. Here, we present a high-resolution (5.5 km) estimate of the surface mass balance (SMB) for the AP, from 1979 to 2014, calculated by the regional atmospheric climate model RACMO2.3, that is specifically adapted for use over the polar regions. Next to this, a firn densification model is used to calculate the processes in the snowpack, such as firn compaction and meltwater percolation, refreezing, and runoff. A comparison with the few available in-situ observations shows that the AP SMB is well modeled, but that discrepancies remain that are mainly related to the highly variable AP topography compared to the model resolution. Integrated over an ice sheet area of 4.1 105 km2, the climatological (1979-2014) SMB of the AP amounts to 351 Gt y-1 (with interannual variability = 58 Gt y-1), which mostly consists of snowfall (363 ± 56 Gt y-1). The other SMB components, sublimation, drifting snow erosion and meltwater runoff, are small (11, 0.5 and 4 Gt y-1, respectively). The AP mountains act as an important climate barrier, leading to distinct differences between the climate of the western AP (WAP) and the eastern AP (EAP). For instance, 77% of all AP snowfall falls over the WAP, where strong orographic forcing leads to snowfall rates >4 m w.e. y-1 on the northwestern slopes, while snowfall rates are <400 mm w.e. y-1 over the EAP ice shelves. These results, and further investigations of this sharp west-to-east climate distinction, clearly highlight the different forcing mechanisms of the SMB over the WAP and the EAP: over the WAP most snowfall is orographically induced, while over the EAP it is generated by depressions over the Weddell Sea. Furthermore, no significant trends are found in any of the SMB components, except for a slight decrease in snowmelt.
Fractional diffusion models of cardiac electrical propagation: role of structural heterogeneity in dispersion of repolarization

PubMed Central

Bueno-Orovio, Alfonso; Kay, David; Grau, Vicente; Rodriguez, Blanca; Burrage, Kevin

2014-01-01

Impulse propagation in biological tissues is known to be modulated by structural heterogeneity. In cardiac muscle, improved understanding on how this heterogeneity influences electrical spread is key to advancing our interpretation of dispersion of repolarization. We propose fractional diffusion models as a novel mathematical description of structurally heterogeneous excitable media, as a means of representing the modulation of the total electric field by the secondary electrical sources associated with tissue inhomogeneities. Our results, analysed against in vivo human recordings and experimental data of different animal species, indicate that structural heterogeneity underlies relevant characteristics of cardiac electrical propagation at tissue level. These include conduction effects on action potential (AP) morphology, the shortening of AP duration along the activation pathway and the progressive modulation by premature beats of spatial patterns of dispersion of repolarization. The proposed approach may also have important implications in other research fields involving excitable complex media. PMID:24920109
Cardiac arrhythmia mechanisms in rats with heart failure induced by pulmonary hypertension

PubMed Central

Benoist, David; Stones, Rachel; Drinkhill, Mark J.; Benson, Alan P.; Yang, Zhaokang; Cassan, Cecile; Gilbert, Stephen H.; Saint, David A.; Cazorla, Olivier; Steele, Derek S.; Bernus, Olivier

2012-01-01

Pulmonary hypertension provokes right heart failure and arrhythmias. Better understanding of the mechanisms underlying these arrhythmias is needed to facilitate new therapeutic approaches for the hypertensive, failing right ventricle (RV). The aim of our study was to identify the mechanisms generating arrhythmias in a model of RV failure induced by pulmonary hypertension. Rats were injected with monocrotaline to induce either RV hypertrophy or failure or with saline (control). ECGs were measured in conscious, unrestrained animals by telemetry. In isolated hearts, electrical activity was measured by optical mapping and myofiber orientation by diffusion tensor-MRI. Sarcoplasmic reticular Ca2+ handling was studied in single myocytes. Compared with control animals, the T-wave of the ECG was prolonged and in three of seven heart failure animals, prominent T-wave alternans occurred. Discordant action potential (AP) alternans occurred in isolated failing hearts and Ca2+ transient alternans in failing myocytes. In failing hearts, AP duration and dispersion were increased; conduction velocity and AP restitution were steeper. The latter was intrinsic to failing single myocytes. Failing hearts had greater fiber angle disarray; this correlated with AP duration. Failing myocytes had reduced sarco(endo)plasmic reticular Ca2+-ATPase activity, increased sarcoplasmic reticular Ca2+-release fraction, and increased Ca2+ spark leak. In hypertrophied hearts and myocytes, dysfunctional adaptation had begun, but alternans did not develop. We conclude that increased electrical and structural heterogeneity and dysfunctional sarcoplasmic reticular Ca2+ handling increased the probability of alternans, a proarrhythmic predictor of sudden cardiac death. These mechanisms are potential therapeutic targets for the correction of arrhythmias in hypertensive, failing RVs. PMID:22427523
Cardiac tissue slices: preparation, handling, and successful optical mapping.

PubMed

Wang, Ken; Lee, Peter; Mirams, Gary R; Sarathchandra, Padmini; Borg, Thomas K; Gavaghan, David J; Kohl, Peter; Bollensdorff, Christian

2015-05-01

Cardiac tissue slices are becoming increasingly popular as a model system for cardiac electrophysiology and pharmacology research and development. Here, we describe in detail the preparation, handling, and optical mapping of transmembrane potential and intracellular free calcium concentration transients (CaT) in ventricular tissue slices from guinea pigs and rabbits. Slices cut in the epicardium-tangential plane contained well-aligned in-slice myocardial cell strands ("fibers") in subepicardial and midmyocardial sections. Cut with a high-precision slow-advancing microtome at a thickness of 350 to 400 μm, tissue slices preserved essential action potential (AP) properties of the precutting Langendorff-perfused heart. We identified the need for a postcutting recovery period of 36 min (guinea pig) and 63 min (rabbit) to reach 97.5% of final steady-state values for AP duration (APD) (identified by exponential fitting). There was no significant difference between the postcutting recovery dynamics in slices obtained using 2,3-butanedione 2-monoxime or blebistatin as electromechanical uncouplers during the cutting process. A rapid increase in APD, seen after cutting, was caused by exposure to ice-cold solution during the slicing procedure, not by tissue injury, differences in uncouplers, or pH-buffers (bicarbonate; HEPES). To characterize intrinsic patterns of CaT, AP, and conduction, a combination of multipoint and field stimulation should be used to avoid misinterpretation based on source-sink effects. In summary, we describe in detail the preparation, mapping, and data analysis approaches for reproducible cardiac tissue slice-based investigations into AP and CaT dynamics. Copyright © 2015 the American Physiological Society.
Cardiac tissue slices: preparation, handling, and successful optical mapping

PubMed Central

Wang, Ken; Lee, Peter; Mirams, Gary R.; Sarathchandra, Padmini; Borg, Thomas K.; Gavaghan, David J.; Kohl, Peter

2015-01-01

Cardiac tissue slices are becoming increasingly popular as a model system for cardiac electrophysiology and pharmacology research and development. Here, we describe in detail the preparation, handling, and optical mapping of transmembrane potential and intracellular free calcium concentration transients (CaT) in ventricular tissue slices from guinea pigs and rabbits. Slices cut in the epicardium-tangential plane contained well-aligned in-slice myocardial cell strands (“fibers”) in subepicardial and midmyocardial sections. Cut with a high-precision slow-advancing microtome at a thickness of 350 to 400 μm, tissue slices preserved essential action potential (AP) properties of the precutting Langendorff-perfused heart. We identified the need for a postcutting recovery period of 36 min (guinea pig) and 63 min (rabbit) to reach 97.5% of final steady-state values for AP duration (APD) (identified by exponential fitting). There was no significant difference between the postcutting recovery dynamics in slices obtained using 2,3-butanedione 2-monoxime or blebistatin as electromechanical uncouplers during the cutting process. A rapid increase in APD, seen after cutting, was caused by exposure to ice-cold solution during the slicing procedure, not by tissue injury, differences in uncouplers, or pH-buffers (bicarbonate; HEPES). To characterize intrinsic patterns of CaT, AP, and conduction, a combination of multipoint and field stimulation should be used to avoid misinterpretation based on source-sink effects. In summary, we describe in detail the preparation, mapping, and data analysis approaches for reproducible cardiac tissue slice-based investigations into AP and CaT dynamics. PMID:25595366
Human bone marrow-derived clonal mesenchymal stem cells inhibit inflammation and reduce acute pancreatitis in rats.

PubMed

Jung, Kyung Hee; Song, Sun U; Yi, Tacghee; Jeon, Myung-Shin; Hong, Sang-Won; Zheng, Hong-Mei; Lee, Hee-Seung; Choi, Myung-Joo; Lee, Don-Haeng; Hong, Soon-Sun

2011-03-01

Acute pancreatitis (AP) has a high mortality rate; repetitive AP induces chronic AP and pancreatic adenocarcinoma. Mesenchymal stem cells (MSCs) have immunoregulatory effects and reduce inflammation. We developed a protocol to isolate human bone marrow-derived clonal MSCs (hcMSCs) from bone marrow aspirate and investigated the effects of these cells in rat models of mild and severe AP. Mild AP was induced in Sprague-Dawley rats by 3 intraperitoneal injections of cerulein (100 μg/kg), given at 2-hour intervals; severe AP was induced by intraparenchymal injection of 3% sodium taurocholate solution. hcMSCs were labeled with CM-1,1'-dioctadecyl-3,3,3'-tetramethylindo-carbocyanine perchloride and administered to rats through the tail vein. hcMSCs underwent self-renewal and had multipotent differentiation capacities and immunoregulatory functions. Greater numbers of infused hcMSCs were detected in pancreas of rats with mild and severe AP than of control rats. Infused hcMSCs reduced acinar-cell degeneration, pancreatic edema, and inflammatory cell infiltration in each model of pancreatitis. The hcMSCs reduced expression of inflammation mediators and cytokines in rats with mild and severe AP. hcMSCs suppressed the mixed lymphocyte reaction and increased expression of Foxp3(+) (a marker of regulatory T cells) in cultured rat lymph node cells. Rats with mild or severe AP that were given infusions of hcMSCs had reduced numbers of CD3(+) T cells and increased expression of Foxp3(+) in pancreas tissues. hcMSCs reduced inflammation and damage to pancreatic tissue in a rat model of AP; they reduced levels of cytokines and induced numbers of Foxp3(+) regulatory T cells. hcMSCs might be developed as a cell therapy for pancreatitis. Copyright © 2011 AGA Institute. Published by Elsevier Inc. All rights reserved.
Optical magnetic detection of single-neuron action potentials using quantum defects in diamond

PubMed Central

Barry, John F.; Turner, Matthew J.; Schloss, Jennifer M.; Glenn, David R.; Song, Yuyu; Lukin, Mikhail D.; Park, Hongkun; Walsworth, Ronald L.

2016-01-01

Magnetic fields from neuronal action potentials (APs) pass largely unperturbed through biological tissue, allowing magnetic measurements of AP dynamics to be performed extracellularly or even outside intact organisms. To date, however, magnetic techniques for sensing neuronal activity have either operated at the macroscale with coarse spatial and/or temporal resolution—e.g., magnetic resonance imaging methods and magnetoencephalography—or been restricted to biophysics studies of excised neurons probed with cryogenic or bulky detectors that do not provide single-neuron spatial resolution and are not scalable to functional networks or intact organisms. Here, we show that AP magnetic sensing can be realized with both single-neuron sensitivity and intact organism applicability using optically probed nitrogen-vacancy (NV) quantum defects in diamond, operated under ambient conditions and with the NV diamond sensor in close proximity (∼10 µm) to the biological sample. We demonstrate this method for excised single neurons from marine worm and squid, and then exterior to intact, optically opaque marine worms for extended periods and with no observed adverse effect on the animal. NV diamond magnetometry is noninvasive and label-free and does not cause photodamage. The method provides precise measurement of AP waveforms from individual neurons, as well as magnetic field correlates of the AP conduction velocity, and directly determines the AP propagation direction through the inherent sensitivity of NVs to the associated AP magnetic field vector. PMID:27911765
Optical magnetic detection of single-neuron action potentials using quantum defects in diamond.

PubMed

Barry, John F; Turner, Matthew J; Schloss, Jennifer M; Glenn, David R; Song, Yuyu; Lukin, Mikhail D; Park, Hongkun; Walsworth, Ronald L

2016-12-06

Magnetic fields from neuronal action potentials (APs) pass largely unperturbed through biological tissue, allowing magnetic measurements of AP dynamics to be performed extracellularly or even outside intact organisms. To date, however, magnetic techniques for sensing neuronal activity have either operated at the macroscale with coarse spatial and/or temporal resolution-e.g., magnetic resonance imaging methods and magnetoencephalography-or been restricted to biophysics studies of excised neurons probed with cryogenic or bulky detectors that do not provide single-neuron spatial resolution and are not scalable to functional networks or intact organisms. Here, we show that AP magnetic sensing can be realized with both single-neuron sensitivity and intact organism applicability using optically probed nitrogen-vacancy (NV) quantum defects in diamond, operated under ambient conditions and with the NV diamond sensor in close proximity (∼10 µm) to the biological sample. We demonstrate this method for excised single neurons from marine worm and squid, and then exterior to intact, optically opaque marine worms for extended periods and with no observed adverse effect on the animal. NV diamond magnetometry is noninvasive and label-free and does not cause photodamage. The method provides precise measurement of AP waveforms from individual neurons, as well as magnetic field correlates of the AP conduction velocity, and directly determines the AP propagation direction through the inherent sensitivity of NVs to the associated AP magnetic field vector.
Modeling and Simulation of Ceramic Arrays to Improve Ballaistic Performance

DTIC Science & Technology

2013-09-09

targets with .30cal AP M2 projectile using SPH elements. -Model validation runs were conducted based on the DoP experiments described in reference...effect of material properties on DoP 15. SUBJECT TERMS .30cal AP M2 Projectile, 762x39 PS Projectile, SPH , Aluminum 5083, SiC, DoP Expeminets...and ceramic-faced aluminum targets with „30cal AP M2 projectile using SPH elements. □ Model validation runs were conducted based on the DoP
Seasonal acclimatization of the cardiac action potential in the Arctic navaga cod (Eleginus navaga, Gadidae).

PubMed

Hassinen, Minna; Abramochkin, Denis V; Vornanen, Matti

2014-04-01

Freshwater fishes of north-temperate latitudes adjust electrical excitability of the heart to seasonal temperature changes by changing expression levels of ion channel isoforms. However, little is known about thermal responses of action potential (AP) in the hearts of marine polar fishes. To this end, we examined cardiac AP in the atrial myocardium of the Arctic navaga cod (Eleginus navaga) from the White Sea (Russia) acclimatized to winter (March) and summer (September) seasons. Acute increases in temperature from 4 to 10 °C were associated with increases in heart rate, maximum velocity of AP upstroke and negative resting membrane potential, while duration of AP was shortened in both winter-acclimatized and summer-acclimatized navaga hearts. In winter, there was a compensatory shortening (41.1%) of atrial AP duration and this was associated with a strong increase in transcript expression of Erg K(+) channels, known to produce the rapid component of the delayed rectifier K(+) current, I(Kr). Smaller increases were found in the expression of Kir2.1 channels that produce the inward rectifier K(+) current, I(K1). These findings indicate that the heart of navaga cod has a good acclimatory capacity in electrical excitation of cardiac myocytes, which enables cardiac function in the cold-eurythermal waters of the subarctic White Sea.
Iterative random vs. Kennard-Stone sampling for IR spectrum-based classification task using PLS2-DA

NASA Astrophysics Data System (ADS)

Lee, Loong Chuen; Liong, Choong-Yeun; Jemain, Abdul Aziz

2018-04-01

External testing (ET) is preferred over auto-prediction (AP) or k-fold-cross-validation in estimating more realistic predictive ability of a statistical model. With IR spectra, Kennard-stone (KS) sampling algorithm is often used to split the data into training and test sets, i.e. respectively for model construction and for model testing. On the other hand, iterative random sampling (IRS) has not been the favored choice though it is theoretically more likely to produce reliable estimation. The aim of this preliminary work is to compare performances of KS and IRS in sampling a representative training set from an attenuated total reflectance - Fourier transform infrared spectral dataset (of four varieties of blue gel pen inks) for PLS2-DA modeling. The `best' performance achievable from the dataset is estimated with AP on the full dataset (APF, error). Both IRS (n = 200) and KS were used to split the dataset in the ratio of 7:3. The classic decision rule (i.e. maximum value-based) is employed for new sample prediction via partial least squares - discriminant analysis (PLS2-DA). Error rate of each model was estimated repeatedly via: (a) AP on full data (APF, error); (b) AP on training set (APS, error); and (c) ET on the respective test set (ETS, error). A good PLS2-DA model is expected to produce APS, error and EVS, error that is similar to the APF, error. Bearing that in mind, the similarities between (a) APS, error vs. APF, error; (b) ETS, error vs. APF, error and; (c) APS, error vs. ETS, error were evaluated using correlation tests (i.e. Pearson and Spearman's rank test), using series of PLS2-DA models computed from KS-set and IRS-set, respectively. Overall, models constructed from IRS-set exhibits more similarities between the internal and external error rates than the respective KS-set, i.e. less risk of overfitting. In conclusion, IRS is more reliable than KS in sampling representative training set.
Cardiac action potential repolarization revisited: early repolarization shows all-or-none behaviour.

PubMed

Trenor, Beatriz; Cardona, Karen; Saiz, Javier; Noble, Denis; Giles, Wayne

2017-11-01

In healthy mammalian hearts the action potential (AP) waveform initiates and modulates each contraction, or heartbeat. As a result, AP height and duration are key physiological variables. In addition, rate-dependent changes in ventricular AP duration (APD), and variations in APD at a fixed heart rate are both reliable biomarkers of electrophysiological stability. Present guidelines for the likelihood that candidate drugs will increase arrhythmias rely on small changes in APD and Q-T intervals as criteria for safety pharmacology decisions. However, both of these measurements correspond to the final repolarization of the AP. Emerging clinical evidence draws attention to the early repolarization phase of the action potential (and the J-wave of the ECG) as an additional important biomarker for arrhythmogenesis. Here we provide a mechanistic background to this early repolarization syndrome by summarizing the evidence that both the initial depolarization and repolarization phases of the cardiac action potential can exhibit distinct time- and voltage-dependent thresholds, and also demonstrating that both can show regenerative all-or-none behaviour. An important consequence of this is that not all of the dynamics of action potential repolarization in human ventricle can be captured by data from single myocytes when these results are expressed as 'repolarization reserve'. For example, the complex pattern of cell-to-cell current flow that is responsible for AP conduction (propagation) within the mammalian myocardium can change APD and the Q-T interval of the electrocardiogram alter APD stability, and modulate responsiveness to pharmacological agents (such as Class III anti-arrhythmic drugs). © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.
Army and Marine Corps Active Protection System (APS) Efforts

DTIC Science & Technology

2016-08-30

safe enough for operational use, the benefits of MAPS relative to non-developmental efforts, MAPS’ impacts on NDI APS performance and costs, the Army’s...APSs Effective and Safe Enough for Operational Use? .............................. 24 What are the Benefits of MAPS Relative to Non-Developmental...corrosion—which will also factor into their eventual APS plans. Potential issues for Congress include whether current NDI APSs are effective and
Experimental and Numerical Study of Ammonium Perchlorate Counterflow Diffusion Flames

NASA Technical Reports Server (NTRS)

Smooke, M. D.; Yetter, R. A.; Parr, T. P.; Hanson-Parr, D. M.; Tanoff, M. A.

1999-01-01

Many solid rocket propellants are based on a composite mixture of ammonium perchlorate (AP) oxidizer and polymeric binder fuels. In these propellants, complex three-dimensional diffusion flame structures between the AP and binder decomposition products, dependent upon the length scales of the heterogeneous mixture, drive the combustion via heat transfer back to the surface. Changing the AP crystal size changes the burn rate of such propellants. Large AP crystals are governed by the cooler AP self-deflagration flame and burn slowly, while small AP crystals are governed more by the hot diffusion flame with the binder and burn faster. This allows control of composite propellant ballistic properties via particle size variation. Previous measurements on these diffusion flames in the planar two-dimensional sandwich configuration yielded insight into controlling flame structure, but there are several drawbacks that make comparison with modeling difficult. First, the flames are two-dimensional and this makes modeling much more complex computationally than with one-dimensional problems, such as RDX self- and laser-supported deflagration. In addition, little is known about the nature, concentration, and evolution rates of the gaseous chemical species produced by the various binders as they decompose. This makes comparison with models quite difficult. Alternatively, counterflow flames provide an excellent geometric configuration within which AP/binder diffusion flames can be studied both experimentally and computationally.
Development of a Series of Kynurenine 3-Monooxygenase Inhibitors Leading to a Clinical Candidate for the Treatment of Acute Pancreatitis.

PubMed

Walker, Ann L; Ancellin, Nicolas; Beaufils, Benjamin; Bergeal, Marylise; Binnie, Margaret; Bouillot, Anne; Clapham, David; Denis, Alexis; Haslam, Carl P; Holmes, Duncan S; Hutchinson, Jonathan P; Liddle, John; McBride, Andrew; Mirguet, Olivier; Mowat, Christopher G; Rowland, Paul; Tiberghien, Nathalie; Trottet, Lionel; Uings, Iain; Webster, Scott P; Zheng, Xiaozhong; Mole, Damian J

2017-04-27

Recently, we reported a novel role for KMO in the pathogenesis of acute pancreatitis (AP). A number of inhibitors of kynurenine 3-monooxygenase (KMO) have previously been described as potential treatments for neurodegenerative conditions and particularly for Huntington's disease. However, the inhibitors reported to date have insufficient aqueous solubility relative to their cellular potency to be compatible with the intravenous (iv) dosing route required in AP. We have identified and optimized a novel series of high affinity KMO inhibitors with favorable physicochemical properties. The leading example is exquisitely selective, has low clearance in two species, prevents lung and kidney damage in a rat model of acute pancreatitis, and is progressing into preclinical development.
Functions of Adaptor Protein (AP)-3 and AP-1 in Tyrosinase Sorting from Endosomes to MelanosomesD⃞

PubMed Central

Theos, Alexander C.; Tenza, Danièle; Martina, José A.; Hurbain, Ilse; Peden, Andrew A.; Sviderskaya, Elena V.; Stewart, Abigail; Robinson, Margaret S.; Bennett, Dorothy C.; Cutler, Daniel F.; Bonifacino, Juan S.; Marks, Michael S.; Raposo, Graça

2005-01-01

Specialized cells exploit adaptor protein complexes for unique post-Golgi sorting events, providing a unique model system to specify adaptor function. Here, we show that AP-3 and AP-1 function independently in sorting of the melanocyte-specific protein tyrosinase from endosomes to the melanosome, a specialized lysosome-related organelle distinguishable from lysosomes. AP-3 and AP-1 localize in melanocytes primarily to clathrin-coated buds on tubular early endosomes near melanosomes. Both adaptors recognize the tyrosinase dileucine-based melanosome sorting signal, and tyrosinase largely colocalizes with each adaptor on endosomes. In AP-3-deficient melanocytes, tyrosinase accumulates inappropriately in vacuolar and multivesicular endosomes. Nevertheless, a substantial fraction still accumulates on melanosomes, concomitant with increased association with endosomal AP-1. Our data indicate that AP-3 and AP-1 function in partially redundant pathways to transfer tyrosinase from distinct endosomal subdomains to melanosomes and that the AP-3 pathway ensures that tyrosinase averts entrapment on internal membranes of forming multivesicular bodies. PMID:16162817
Cardiac structural changes and electrical remodeling in a thiamine-deficiency model in rats.

PubMed

Roman-Campos, D; Campos, A C; Gioda, C R; Campos, P P; Medeiros, M A A; Cruz, J S

2009-06-05

Thiamine is an important cofactor present in many biochemical reactions, and its deprivation can lead to heart dysfunction. Little is known about the influence of thiamine deprivation on the electrophysiological behavior of the isolated heart cells and information about thiamine deficiency in heart morphology is controversial. Thus, we decided to investigate the major repolarizing conductances and their influence in the action potential (AP) waveform as well as the changes in the heart structure in a set of thiamine deficiency in rats. Using the patch-clamp technique, we investigated inward (I(K1)) and outward K(+) currents (I(to)), T-type and L-type Ca(2+) currents and APs. To evaluate heart morphology we used hematoxylin and eosin in transversal heart sections. Thiamine deficiency caused a marked decrease in left ventricle thickness, cardiomyocyte number, cell length and width, and membrane capacitance. When evaluating I(to) we did not find difference in current amplitude; however an acceleration of I(to) inactivation was observed. I(K1) showed a reduction in the amplitude and slope conductance, which implicated a less negative resting membrane potential in cardiac myocytes isolated from thiamine-deficient rats. We did not find any difference in L-type Ca(2+) current density. T-type Ca(2+) current was not observed. In addition, we did not observe significant changes in AP repolarization. Based on our study we can conclude that thiamine deficiency causes heart hypotrophy and not heart hypertrophy. Moreover, we provided evidence that there is no major electrical remodeling during thiamine deficiency, a feature of heart failure models.
Regulated Apoptosis of Genetically-Modified Hematopoietic Stem and Progenitor Cells via an Inducible Caspase-9 Suicide Gene in Rhesus Macaques

PubMed Central

Barese, Cecilia N.; Felizardo, Tania C.; Sellers, Stephanie E.; Keyvanfar, Keyvan; Di Stasi, Antonio; Metzger, Mark E.; Krouse, Allen E.; Donahue, Robert E.; Spencer, David M.; Dunbar, Cynthia E.

2014-01-01

The high risk of insertional oncogenesis reported in clinical trials utilizing integrating retroviral vectors to genetically-modify hematopoietic stem and progenitor cells (HSPC) requires the development of safety strategies to minimize risks associated with novel cell and gene therapies. The ability to ablate genetically modified cells in vivo is desirable, should an abnormal clone emerge. Inclusion of “suicide genes” in vectors to facilitate targeted ablation of vector-containing abnormal clones in vivo is one potential safety approach. We tested whether the inclusion of the “inducible Caspase-9” (iCasp9) suicide gene in a gamma-retroviral vector facilitated efficient elimination of vector-containing HSPCs and their hematopoietic progeny in vivo long-term, in an autologous non-human primate transplantation model. Following stable engraftment of iCasp9 expressing hematopoietic cells in rhesus macaques, administration of AP1903, a chemical inducer of dimerization able to activate iCasp9, specifically eliminated vector-containing cells in all hematopoietic lineages long-term, suggesting activity at the HSPC level. Between 75–94% of vector-containing cells were eliminated by well-tolerated AP1903 dosing, but lack of complete ablation was linked to lower iCasp9 expression in residual cells. Further investigation of resistance mechanisms demonstrated upregulation of Bcl-2 in hematopoietic cell lines transduced with the vector and resistant to AP1903 ablation. These results demonstrate both the potential and the limitations of safety approaches utilizing iCasp9 to HSPC-targeted gene therapy settings, in a model with great relevance to clinical development. PMID:25330775

Cannabinoids and schizophrenia: therapeutic prospects.

PubMed

Robson, P J; Guy, G W; Di Marzo, V

2014-01-01

Approximately one third of patients diagnosed with schizophrenia do not achieve adequate symptom control with standard antipsychotic drugs (APs). Some of these may prove responsive to clozapine, but non-response to APs remains an important clinical problem and cause of increased health care costs. In a significant proportion of patients, schizophrenia is associated with natural and iatrogenic metabolic abnormalities (obesity, dyslipidaemia, impaired glucose tolerance or type 2 diabetes mellitus), hyperadrenalism and an exaggerated HPA response to stress, and chronic systemic inflammation. The endocannabinoid system (ECS) in the brain plays an important role in maintaining normal mental health. ECS modulates emotion, reward processing, sleep regulation, aversive memory extinction and HPA axis regulation. ECS overactivity contributes to visceral fat accumulation, insulin resistance and impaired energy expenditure. The cannabis plant synthesises a large number of pharmacologically active compounds unique to it known as phytocannabinoids. In contrast to the euphoric and pro-psychotic effects of delta-9-tetrahydrocannabinol (THC), certain non-intoxicating phytocannabinoids have emerged in pre-clinical and clinical models as potential APs. Since the likely mechanism of action does not rely upon dopamine D2 receptor antagonism, synergistic combinations with existing APs are plausible. The anti-inflammatory and immunomodulatory effects of the non-intoxicating phytocannabinoid cannabidiol (CBD) are well established and are summarised below. Preliminary data reviewed in this paper suggest that CBD in combination with a CB1 receptor neutral antagonist could not only augment the effects of standard APs but also target the metabolic, inflammatory and stress-related components of the schizophrenia phenotype.
Using Computer Models to Identify Common Therapeutic Targets in Host Adapted Bacterial Threat Agents

DTIC Science & Technology

2011-08-01

tetraphosphatase[c] : ap4a + 2o -‐-‐> (2) adp + (2) hNucleo d Salvage Pathways Nucleo(deBMA_1991 ApaH EC...tetraphosphatase[c] : ap4a + h2o --> (2) adp + (2) h BPSL2687 ApaH AP5AH Ap5A hydrolase [c] : ap5a + h2o --> adp + atp + (2) h BPSL2687 ApaH CSND Cytosine deaminase
Selectivity and activity of adenine dinucleotides at recombinant P2X2 and P2Y1 purinoceptors.

PubMed Central

Pintor, J.; King, B. F.; Miras-Portugal, M. T.; Burnstock, G.

1996-01-01

1. Adenine dinucleotides (Ap3A, x = 2-6) are naturally-occurring polyphosphated nucleotidic substances which are found in the CNS and are known to be released in a calcium-dependent manner from storage vesicles in brain synaptosomes. The selectivity and activity of adenine dinucleotides for neuronally-derived recombinant P2 purinoceptors were studied using P2X2 and P2Y1 subtypes expressed in Xenopus oocytes. 2. For the P2Y1 subtype derived from chick brain, Ap3A was equipotent and as active as ATP (EC50 values: 375 +/- 86 nM and 334 +/- 25 nM, respectively). Ap4A was a weak partial agonist and other dinucleotides were inactive as agonists. None of the inactive dinucleotides were antagonists nor modulated the activity of Ap3A and ATP. 3. For the P2X2 subtype derived from rat PC12 cells, Ap4A was as active as ATP but less potent (EC50 values: 15.2 +/- 1 microM and 3.7 +/- 0.7 microM, respectively). Other adenosine dinucleotides were inactive as either agonists or antagonists. 4. Ap5A (1-100 nM) potentiated ATP-responses at the P2X2 subtype, showing an EC50 of 2.95 +/- 0.7 nM for this modulatory effect. Ap5A (10 nM) shifted the concentration-response curves for ATP to the left by one-half log10 unit but did not alter the Hill co-efficient for ATP (nH = 2.1 +/- 0.1). Ap5A (10 nM) failed to potentiate Ap4A-responses but did enhance the efficacy of the P2 purinoceptor antagonist, suramin, by 12 fold at the P2X2 subtype. 5. In conclusion, the results show that ionotropic (P2X2) and metabotropic (P2Y1) ATP receptors which occur in the CNS are activated selectively by naturally-occurring adenine dinucleotides which are known to be released with nucleotides from storage vesicles. The observed potentiation of P2X2-responses by Ap5A, where co-released with ATP by brain synaptosomes, may have a functional bearing in purinergic signalling in the CNS. PMID:8922753
The receptive function of hypothalamic and brainstem centres to hormonal and nutrient signals affecting energy balance.

PubMed

Riediger, Thomas

2012-11-01

The hypothalamic arcuate nucleus (ARC) and the area postrema (AP) represent targets for hormonal and metabolic signals involved in energy homoeostasis, e.g. glucose, amylin, insulin, leptin, peptide YY (PYY), glucagon-like peptide 1 (GLP-1) and ghrelin. Orexigenic neuropeptide Y expressing ARC neurons are activated by food deprivation and inhibited by feeding in a nutrient-dependent manner. PYY and leptin also reverse or prevent fasting-induced activation of the ARC. Interestingly, hypothalamic responses to fasting are blunted in different models of obesity (e.g. diet-induced obesity (DIO) or late-onset obesity). The AP also responds to feeding-related signals. The pancreatic hormone amylin acts via the AP to control energy intake. Amylin-sensitive AP neurons are also glucose-responsive. Furthermore, diet-derived protein attenuates amylin responsiveness suggesting a modulation of AP sensitivity by macronutrient supply. This review gives an overview of the receptive function of the ARC and the AP to hormonal and nutritional stimuli involved in the control of energy balance and the possible implications in the context of obesity. Collectively, there is consistency between the neurophysiological actions of these stimuli and their effects on energy homoeostasis under experimental conditions. However, surprisingly little progress has been made in the development of effective pharmacological approaches against obesity. A promising way to improve effectiveness involves combination treatments (e.g. amylin/leptin agonists). Hormonal alterations (e.g. GLP-1 and PYY) are also considered to mediate body weight loss observed in obese patients receiving bariatric surgery. The effects of hormonal and nutritional signals and their interactions might hold the potential to develop poly-mechanistic therapeutic strategies against obesity.
Neuroplasticity of A-type potassium channel complexes induced by chronic alcohol exposure enhances dendritic calcium transients in hippocampus.

PubMed

Mulholland, Patrick J; Spencer, Kathryn B; Hu, Wei; Kroener, Sven; Chandler, L Judson

2015-06-01

Chronic alcohol-induced cognitive impairments and maladaptive plasticity of glutamatergic synapses are well-documented. However, it is unknown if prolonged alcohol exposure affects dendritic signaling that may underlie hippocampal dysfunction in alcoholics. Back-propagation of action potentials (bAPs) into apical dendrites of hippocampal neurons provides distance-dependent signals that modulate dendritic and synaptic plasticity. The amplitude of bAPs decreases with distance from the soma that is thought to reflect an increase in the density of Kv4.2 channels toward distal dendrites. The aim of this study was to quantify changes in hippocampal Kv4.2 channel function and expression using electrophysiology, Ca(2+) imaging, and western blot analyses in a well-characterized in vitro model of chronic alcohol exposure. Chronic alcohol exposure significantly decreased expression of Kv4.2 channels and KChIP3 in hippocampus. This reduction was associated with an attenuation of macroscopic A-type K(+) currents in CA1 neurons. Chronic alcohol exposure increased bAP-evoked Ca(2+) transients in the distal apical dendrites of CA1 pyramidal neurons. The enhanced bAP-evoked Ca(2+) transients induced by chronic alcohol exposure were not related to synaptic targeting of N-methyl-D-aspartate (NMDA) receptors or morphological adaptations in apical dendritic arborization. These data suggest that chronic alcohol-induced decreases in Kv4.2 channel function possibly mediated by a downregulation of KChIP3 drive the elevated bAP-associated Ca(2+) transients in distal apical dendrites. Alcohol-induced enhancement of bAPs may affect metaplasticity and signal integration in apical dendrites of hippocampal neurons leading to alterations in hippocampal function.
Asymmetric segregation and self-renewal of hematopoietic stem and progenitor cells with endocytic Ap2a2.

PubMed

Ting, Stephen B; Deneault, Eric; Hope, Kristin; Cellot, Sonia; Chagraoui, Jalila; Mayotte, Nadine; Dorn, Jonas F; Laverdure, Jean-Philippe; Harvey, Michael; Hawkins, Edwin D; Russell, Sarah M; Maddox, Paul S; Iscove, Norman N; Sauvageau, Guy

2012-03-15

The stem cell-intrinsic model of self-renewal via asymmetric cell division (ACD) posits that fate determinants be partitioned unequally between daughter cells to either activate or suppress the stemness state. ACD is a purported mechanism by which hematopoietic stem cells (HSCs) self-renew, but definitive evidence for this cellular process remains open to conjecture. To address this issue, we chose 73 candidate genes that function within the cell polarity network to identify potential determinants that may concomitantly alter HSC fate while also exhibiting asymmetric segregation at cell division. Initial gene-expression profiles of polarity candidates showed high and differential expression in both HSCs and leukemia stem cells. Altered HSC fate was assessed by our established in vitro to in vivo screen on a subcohort of candidate polarity genes, which revealed 6 novel positive regulators of HSC function: Ap2a2, Gpsm2, Tmod1, Kif3a, Racgap1, and Ccnb1. Interestingly, live-cell videomicroscopy of the endocytic protein AP2A2 shows instances of asymmetric segregation during HSC/progenitor cell cytokinesis. These results contribute further evidence that ACD is functional in HSC self-renewal, suggest a role for Ap2a2 in HSC activity, and provide a unique opportunity to prospectively analyze progeny from HSC asymmetric divisions.
An integrative model of the cardiac ventricular myocyte incorporating local control of Ca2+ release.

PubMed Central

Greenstein, Joseph L; Winslow, Raimond L

2002-01-01

The local control theory of excitation-contraction (EC) coupling in cardiac muscle asserts that L-type Ca(2+) current tightly controls Ca(2+) release from the sarcoplasmic reticulum (SR) via local interaction of closely apposed L-type Ca(2+) channels (LCCs) and ryanodine receptors (RyRs). These local interactions give rise to smoothly graded Ca(2+)-induced Ca(2+) release (CICR), which exhibits high gain. In this study we present a biophysically detailed model of the normal canine ventricular myocyte that conforms to local control theory. The model formulation incorporates details of microscopic EC coupling properties in the form of Ca(2+) release units (CaRUs) in which individual sarcolemmal LCCs interact in a stochastic manner with nearby RyRs in localized regions where junctional SR membrane and transverse-tubular membrane are in close proximity. The CaRUs are embedded within and interact with the global systems of the myocyte describing ionic and membrane pump/exchanger currents, SR Ca(2+) uptake, and time-varying cytosolic ion concentrations to form a model of the cardiac action potential (AP). The model can reproduce both the detailed properties of EC coupling, such as variable gain and graded SR Ca(2+) release, and whole-cell phenomena, such as modulation of AP duration by SR Ca(2+) release. Simulations indicate that the local control paradigm predicts stable APs when the L-type Ca(2+) current is adjusted in accord with the balance between voltage- and Ca(2+)-dependent inactivation processes as measured experimentally, a scenario where common pool models become unstable. The local control myocyte model provides a means for studying the interrelationship between microscopic and macroscopic behaviors in a manner that would not be possible in experiments. PMID:12496068
Calcium Dynamics in Basal Dendrites of Layer 5A and 5B Pyramidal Neurons Is Tuned to the Cell-Type Specific Physiological Action Potential Discharge

PubMed Central

Krieger, Patrik; de Kock, Christiaan P. J.; Frick, Andreas

2017-01-01

Layer 5 (L5) is a major neocortical output layer containing L5A slender-tufted (L5A-st) and L5B thick-tufted (L5B-tt) pyramidal neurons. These neuron types differ in their in vivo firing patterns, connectivity and dendritic morphology amongst other features, reflecting their specific functional role within the neocortical circuits. Here, we asked whether the active properties of the basal dendrites that receive the great majority of synaptic inputs within L5 differ between these two pyramidal neuron classes. To quantify their active properties, we measured the efficacy with which action potential (AP) firing patterns backpropagate along the basal dendrites by measuring the accompanying calcium transients using two-photon laser scanning microscopy in rat somatosensory cortex slices. For these measurements we used both “artificial” three-AP patterns and more complex physiological AP patterns that were previously recorded in anesthetized rats in L5A-st and L5B-tt neurons in response to whisker stimulation. We show that AP patterns with relatively few APs (3APs) evoke a calcium response in L5B-tt, but not L5A-st, that is dependent on the temporal pattern of the three APs. With more complex in vivo recorded AP patterns, the average calcium response was similar in the proximal dendrites but with a decay along dendrites (measured up to 100 μm) of L5B-tt but not L5A-st neurons. Interestingly however, the whisker evoked AP patterns—although very different for the two cell types—evoke similar calcium responses. In conclusion, although the effectiveness with which different AP patterns evoke calcium transients vary between L5A-st and L5B-tt cell, the calcium influx appears to be tuned such that whisker-evoked calcium transients are within the same dynamic range for both cell types. PMID:28744201
Altered distribution of ATG9A and accumulation of axonal aggregates in neurons from a mouse model of AP-4 deficiency syndrome

PubMed Central

De Pace, Raffaella; Damme, Markus; Mattera, Rafael; Jarnik, Michal; Hoffmann, Victoria; Morris, H. Douglas; Han, Tae-Un; Mancini, Grazia M. S.; Buonanno, Andrés

2018-01-01

The hereditary spastic paraplegias (HSP) are a clinically and genetically heterogeneous group of disorders characterized by progressive lower limb spasticity. Mutations in subunits of the heterotetrameric (ε-β4-μ4-σ4) adaptor protein 4 (AP-4) complex cause an autosomal recessive form of complicated HSP referred to as “AP-4 deficiency syndrome”. In addition to lower limb spasticity, this syndrome features intellectual disability, microcephaly, seizures, thin corpus callosum and upper limb spasticity. The pathogenetic mechanism, however, remains poorly understood. Here we report the characterization of a knockout (KO) mouse for the AP4E1 gene encoding the ε subunit of AP-4. We find that AP-4 ε KO mice exhibit a range of neurological phenotypes, including hindlimb clasping, decreased motor coordination and weak grip strength. In addition, AP-4 ε KO mice display a thin corpus callosum and axonal swellings in various areas of the brain and spinal cord. Immunohistochemical analyses show that the transmembrane autophagy-related protein 9A (ATG9A) is more concentrated in the trans-Golgi network (TGN) and depleted from the peripheral cytoplasm both in skin fibroblasts from patients with mutations in the μ4 subunit of AP-4 and in various neuronal types in AP-4 ε KO mice. ATG9A mislocalization is associated with increased tendency to accumulate mutant huntingtin (HTT) aggregates in the axons of AP-4 ε KO neurons. These findings indicate that the AP-4 ε KO mouse is a suitable animal model for AP-4 deficiency syndrome, and that defective mobilization of ATG9A from the TGN and impaired autophagic degradation of protein aggregates might contribute to neuroaxonal dystrophy in this disorder. PMID:29698489
Characterization of Canna yellow mottle virus in a New Host, Alpinia purpurata, in Hawaii.

PubMed

Zhang, Jingxin; Dey, Kishore K; Lin, Birun; Borth, Wayne B; Melzer, Michael J; Sether, Diane; Wang, Yanan; Wang, I-Chin; Shen, Huifang; Pu, Xiaoming; Sun, Dayuan; Hu, John S

2017-06-01

Canna yellow mottle virus (CaYMV) is an important badnavirus infecting Canna spp. worldwide. This is the first report of CaYMV in flowering ginger (Alpinia purpurata) in Hawaii, where it is associated with yellow mottling and necrosis of leaves, vein streaking, and stunted plants. We have sequenced CaYMV in A. purpurata (CaYMV-Ap) using a combination of next-generation sequencing and traditional Sanger sequencing techniques. The complete genome of CaYMV-Ap was 7,120 bp with an organization typical of other Badnavirus species. Our results indicated that CaYMV-Ap was present in the episomal form in infected flowering ginger. We determined that this virus disease is prevalent in Hawaii and could potentially have significant economic impact on the marketing of A. purpurata as cut flowers. There is a potential concern that the host range of CaYMV-Ap may expand to include other important tropical plants.
Optimal size of stochastic Hodgkin-Huxley neuronal systems for maximal energy efficiency in coding pulse signals

NASA Astrophysics Data System (ADS)

Yu, Lianchun; Liu, Liwei

2014-03-01

The generation and conduction of action potentials (APs) represents a fundamental means of communication in the nervous system and is a metabolically expensive process. In this paper, we investigate the energy efficiency of neural systems in transferring pulse signals with APs. By analytically solving a bistable neuron model that mimics the AP generation with a particle crossing the barrier of a double well, we find the optimal number of ion channels that maximizes the energy efficiency of a neuron. We also investigate the energy efficiency of a neuron population in which the input pulse signals are represented with synchronized spikes and read out with a downstream coincidence detector neuron. We find an optimal number of neurons in neuron population, as well as the number of ion channels in each neuron that maximizes the energy efficiency. The energy efficiency also depends on the characters of the input signals, e.g., the pulse strength and the interpulse intervals. These results are confirmed by computer simulation of the stochastic Hodgkin-Huxley model with a detailed description of the ion channel random gating. We argue that the tradeoff between signal transmission reliability and energy cost may influence the size of the neural systems when energy use is constrained.
Optimal size of stochastic Hodgkin-Huxley neuronal systems for maximal energy efficiency in coding pulse signals.

PubMed

Yu, Lianchun; Liu, Liwei

2014-03-01

The generation and conduction of action potentials (APs) represents a fundamental means of communication in the nervous system and is a metabolically expensive process. In this paper, we investigate the energy efficiency of neural systems in transferring pulse signals with APs. By analytically solving a bistable neuron model that mimics the AP generation with a particle crossing the barrier of a double well, we find the optimal number of ion channels that maximizes the energy efficiency of a neuron. We also investigate the energy efficiency of a neuron population in which the input pulse signals are represented with synchronized spikes and read out with a downstream coincidence detector neuron. We find an optimal number of neurons in neuron population, as well as the number of ion channels in each neuron that maximizes the energy efficiency. The energy efficiency also depends on the characters of the input signals, e.g., the pulse strength and the interpulse intervals. These results are confirmed by computer simulation of the stochastic Hodgkin-Huxley model with a detailed description of the ion channel random gating. We argue that the tradeoff between signal transmission reliability and energy cost may influence the size of the neural systems when energy use is constrained.
Hepatoprotective effects of Auricularia cornea var. Li. polysaccharides against the alcoholic liver diseases through different metabolic pathways.

PubMed

Wang, Xiuxiu; Lan, Yufei; Zhu, Yongfa; Li, Shangshang; Liu, Min; Song, Xinling; Zhao, Huajie; Liu, Weiru; Zhang, Jianjun; Wang, Shouxian; Jia, Le

2018-05-15

The present work was designed to evaluate the antioxidation and hepatoprotective effects of Auricularia cornea var. Li. polysaccharides (APS) and enzymatic-extractable APS (EAPS) on the acute alcohol-induced alcoholic liver diseases (ALD). The in vitro antioxidant activities demonstrated that both APS and EAPS had strong reducing power and potential effects on scavenging reactive oxygen species. The in vivo mice experiments showed that the pretreatment with APS or EAPS showed potential hepatoprotective effects on the ALD possibly by increasing the antioxidant activities, reducing the lipid peroxidation, improving the alcohol metabolism, inhibiting the expression levels of inflammatory mediators and preventing the alcohol-induced histopathological alterations. In addition, the fourier-transform infrared (FT-IR), 1 H and 13 C nuclear magnetic resonance spectroscopy (NMR) and gas chromatography (GC) had been analyzed to obtained the primarily characteristics. The results indicated that abundant xylose and glucose contents probably had potential effects on possessing the bioactivities. The findings suggested that the A. cornea var. Li. might be considered as promising natural resource on exploring clinical drugs for the prevention and treatment with ALD and its complications.
Hydrogen-Rich Saline Inhibits NLRP3 Inflammasome Activation and Attenuates Experimental Acute Pancreatitis in Mice

PubMed Central

Ma, Jie; Jin, Wei-Hua; Wu, Juan; Fan, Kai-Hua

2014-01-01

Increasing evidence has demonstrated that reactive oxygen species (ROS) induces oxidative stress and plays a crucial role in the pathogenesis of acute pancreatitis (AP). Hydrogen-rich saline (HRS), a well-known ROS scavenger, has been shown to possess therapeutic benefit on AP in many animal experiments. Recent findings have indicated that the NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome, an intracellular multiprotein complex required for the maturation of interleukin- (IL-) 1β, may probably be a potential target of HRS in the treatment of AP. Therefore, in this study, we evaluated the activation of NLRP3 inflammasome and meanwhile assessed the degree of oxidative stress and inflammatory cascades, as well as the histological alterations in mice suffering from cerulein-induced AP after the treatment of HRS. The results showed that the activation of NLRP3 inflammasome in AP mice was substantially inhibited following the administration of HRS, which was paralleled with the decreased NF-κB activity and cytokines production, attenuated oxidative stress and the amelioration of pancreatic tissue damage. In conclusion, our study has, for the first time, revealed that inhibition of the activation of NLRP3 inflammasome probably contributed to the therapeutic potential of HRS in AP. PMID:25214720
Diadenosine tetraphosphate as a potential therapeutic nucleotide to treat glaucoma.

PubMed

Fonseca, Begoña; Martínez-Águila, Alejandro; de Lara, María J Pérez; Pintor, Jesús

2017-06-01

Glaucoma is a neurodegenerative disease that produces blindness. The main factor associated with this disease is an abnormally elevated intraocular pressure (IOP). To date, some attempts have been made to demonstrate the role of nucleotides modulating IOP, but never in a model of glaucoma. The DBA/2J mouse is an animal that develops the pathology spontaneously, starting from the typical rise in IOP at 9 months of age. Using this animal model, together with a control mouse, C57BL/6J, it has been possible to monitor the elevation in IOP in the glaucomatous mice and to check the ability of the dinucleotide diadenosine tetraphosphate AKA Ap 4 A to reduce IOP. The topical application of Ap 4 A when IOP is maximal (9-12 months) reduced IOP 30.6 ± 6.6% in the DBA/2J and 17.9 ± 4.0% in the C57BL/6J mice. Concentration response curves in both animal strains produced similar pD2 values; these being 4.9 ± 0.5 and 5.1 ± 0.4 for the normotensive C57BL/6J and the glaucomatous DBA/2J respectively. Antagonist studies showed differences between the control and the glaucomatous animals. In particular, the main receptor reducing IOP in the control animal was the P2Y 1 receptor and in the glaucomatous model the P2Y 6 , although the participation of other P2 receptors cannot be ruled out. The long-term effect of Ap 4 A applied three times a week for 3 months showed a clear stop in the elevation of IOP in the glaucomatous model, thus indicating the possibility of using Ap 4 A as an effective compound for the treatment of glaucoma.
The Effects of Tissue-Nonspecific Alkaline Phosphatase Gene Therapy on Craniosynostosis and Craniofacial Morphology in the FGFR2C342Y/+ Mouse Model of Crouzon Craniosynostosis

PubMed Central

Wang, E; Nam, HK; Liu, J; Hatch, NE

2015-01-01

Objectives Craniosynostosis, the premature fusion of cranial bones, has traditionally been described as a disease of increased bone mineralization. However, multiple mouse models of craniosynostosis display craniosynostosis simultaneously with diminished cranial bone volume and/or density. We propose an alternative hypothesis that craniosynostosis results from abnormal tissue mineralization through the downregulation of tissue-nonspecific alkaline phosphatase (TNAP) enzyme downstream of activating mutations in FGFRs. Material & Methods Neonatal Crouzon (FGFRC342Y/+) and wild type (FGFR+/+) mice were injected with lentivirus to deliver a recombinant form of TNAP. Mice were sacrificed at four weeks post-natal. Serum was collected to test for alkaline phosphatase (AP), phosphorus, and calcium levels. Craniofacial bone fusion and morphology was assessed by micro-computed tomography. Results Injection with the TNAP lentivirus significantly increased serum AP levels (increased serum AP levels are indicative of efficient transduction and production of the recombinant protein), but results were variable and dependent upon viral lot and the litter of mice injected. Morphologic analysis revealed craniofacial form differences for inferior surface (p=.023) and cranial height (p=.014) regions between TNAP lentivirus injected and vehicle-injected Crouzon mice. With each unit increase in AP level, the odds of lambdoid suture fusion decreased by 84.2% and these results came close to statistical significance (p=.068). Conclusion These results suggest that TNAP deficiency may mediate FGFR2-associated craniosynostosis. Future studies should incorporate injection of recombinant TNAP protein, to avoid potential side effects and variable efficacy of lentiviral gene delivery. PMID:25865549
Reducing motion artifacts in 4D MR images using principal component analysis (PCA) combined with linear polynomial fitting model

PubMed Central

Yang, Juan; Yin, Yong; Li, Dengwang

2015-01-01

We have previously developed a retrospective 4D‐MRI technique using body area as the respiratory surrogate, but generally, the reconstructed 4D MR images suffer from severe or mild artifacts mainly caused by irregular motion during image acquisition. Those image artifacts may potentially affect the accuracy of tumor target delineation or the shape representation of surrounding nontarget tissues and organs. So the purpose of this study is to propose an approach employing principal component analysis (PCA), combined with a linear polynomial fitting model, to remodel the displacement vector fields (DVFs) obtained from deformable image registration (DIR), with the main goal of reducing the motion artifacts in 4D MR images. Seven patients with hepatocellular carcinoma (2/7) or liver metastases (5/7) in the liver, as well as a patient with non‐small cell lung cancer (NSCLC), were enrolled in an IRB‐approved prospective study. Both CT and MR simulations were performed for each patient for treatment planning. Multiple‐slice, multiple‐phase, cine‐MRI images were acquired in the axial plane for 4D‐MRI reconstruction. Single‐slice 2D cine‐MR images were acquired across the center of the tumor in axial, coronal, and sagittal planes. For a 4D MR image dataset, the DVFs in three orthogonal direction (inferior–superior (SI), anterior–posterior (AP), and medial–lateral (ML)) relative to a specific reference phase were calculated using an in‐house DIR algorithm. The DVFs were preprocessed in three temporal and spatial dimensions using a polynomial fitting model, with the goal of correcting the potential registration errors introduced by three‐dimensional DIR. Then PCA was used to decompose each fitted DVF into a linear combination of three principal motion bases whose spanned subspaces combined with their projections had been validated to be sufficient to represent the regular respiratory motion. By wrapping the reference MR image using the remodeled DVFs, ‘synthetic’ MR images with reduced motion artifacts were generated at selected phase. Tumor motion trajectories derived from cine‐MRI, 4D CT, original 4D MRI, and ‘synthetic’ 4D MRI were analyzed in the SI, AP, and ML directions, respectively. Their correlation coefficient (CC) and difference (D) in motion amplitude were calculated for comparison. Of all the patients, the means and standard deviations (SDs) of CC comparing ‘synthetic’ 4D MRI and cine‐MRI were 0.98±0.01,0.98±0,01, and 0.99±0.01 in SI, AP, and ML directions, respectively. The mean±SD Ds were 0.59±0.09 mm,0.29±0.10 mm, and 0.15±0.05 mm in SI, AP and ML directions, respectively. The means and SDs of CC comparing ‘synthetic’ 4D MRI and 4D CT were 0.96±0.01,0.95±0.01, and 0.95±0.01 in SI, AP, and ML directions, respectively. The mean±SD Ds were 0.76±0.20 mm,0.33±0.14 mm, and 0.19±0.07 mm in SI, AP, and ML directions, respectively. The means and SDs of CC comparing ‘synthetic’ 4D MRI and original 4D MRI were 0.98±0.01,0.98±0.01, and 0.97±0.01 in SI, AP, and ML directions, respectively. The mean±SD Ds were 0.58±0.10 mm,0.30±0.09 mm, and 0.17±0.04 mm in SI, AP, and ML directions, respectively. In this study we have proposed an approach employing PCA combined with a linear polynomial fitting model to capture the regular respiratory motion from a 4D MR image dataset. And its potential usefulness in reducing motion artifacts and improving image quality has been demonstrated by the preliminary results in oncological patients. PACS numbers: 87.57.cp, 87.57.nj, 87.61.‐c PMID:26103185
Thermal and photo-stability of the antioxidant potential of Spirulina platensis powder.

PubMed

Colla, L M; Bertol, C D; Ferreira, D J; Bavaresco, J; Costa, J A V; Bertolin, T E

2017-01-01

This work aimed to evaluate the thermal and photo stability of the antioxidant potential (AP) of the Spirulina platensis biomass. Thermal stability was established at 25ºC, 40ºC and 50ºC for 60 days, in the dark, protected from light. Photo stability was evaluated using UV (15 W, λ = 265 nm) and fluorescent (20 W, 0.16 A, power factor FP > 0.5, 50/60 Hz, 60 lm/w, 1200 lm) light for 90 days in capsules, glass and Petri dishes, at room temperature. The AP of the biomass in these conditions was determined at intervals (every 7 and 30 days in the studies of thermal and photo stability, respectively) using the induction of the oxidation of a lipid system by heat and aeration. In this lipid system, the biomass submitted to degradation was used as an antioxidant. The kinetics of the reaction was determined by the Arrhenius method. Thermal degradation was found to follow zero order kinetics, whereas photo degradation followed first order kinetics. The AP decreased 50% after 50 days at 25°C. At 40°C and 50°C, the AP decreased more than 50% after 35 and 21 days of exposition, respectively. The decrease of the AP of Spirulina was more sensible to UV and fluorescence light. After 30 days of exposition, the AP decreased more than 50% in all storage conditions tested. The antioxidant potential of Spirulina platensis is easily degraded when the biomass is exposed to heat and light, indicating the need for care to be taken in its storage.
Antipathogen genes and the replacement of disease-vectoring mosquito populations: a model-based evaluation

PubMed Central

Robert, Michael A; Okamoto, Kenichi W; Gould, Fred; Lloyd, Alun L

2014-01-01

Recently, genetic strategies aimed at controlling populations of disease-vectoring mosquitoes have received considerable attention as alternatives to traditional measures. Theoretical studies have shown that female-killing (FK), antipathogen (AP), and reduce and replace (R&R) strategies can each decrease the number competent vectors. In this study, we utilize a mathematical model to evaluate impacts on competent Aedes aegypti populations of FK, AP, and R&R releases as well as hybrid strategies that result from combinations of these three approaches. We show that while the ordering of efficacy of these strategies depends upon population life history parameters, sex ratio of releases, and switch time in combination strategies, AP-only and R&R/AP releases typically lead to the greatest long-term reduction in competent vectors. R&R-only releases are often less effective at long-term reduction of competent vectors than AP-only releases or R&R/AP releases. Furthermore, the reduction in competent vectors caused by AP-only releases is easier to maintain than that caused by FK-only or R&R-only releases even when the AP gene confers a fitness cost. We discuss the roles that density dependence and inclusion of females play in the order of efficacy of the strategies. We anticipate that our results will provide added impetus to continue developing AP strategies. PMID:25558284
Diadenosine pentaphosphate affects electrical activity in guinea pig atrium via activation of potassium acetylcholine-dependent inward rectifier.

PubMed

Abramochkin, Denis V; Karimova, Viktoria M; Filatova, Tatiana S; Kamkin, Andre

2017-07-01

Diadenosine pentaphosphate (Ap5A) belongs to the family of diadenosine polyphosphates, endogenously produced compounds that affect vascular tone and cardiac performance when released from platelets. The previous findings indicate that Ap5A shortens action potentials (APs) in rat myocardium via activation of purine P2 receptors. The present study demonstrates alternative mechanism of Ap5A electrophysiological effects found in guinea pig myocardium. Ap5A (10 -4 M) shortens APs in guinea pig working atrial myocardium and slows down pacemaker activity in the sinoatrial node. P1 receptors antagonist DPCPX (10 -7 M) or selective GIRK channels blocker tertiapin (10 -6 M) completely abolished all Ap5A effects, while P2 blocker PPADS (10 -4 M) was ineffective. Patch-clamp experiments revealed potassium inward rectifier current activated by Ap5A in guinea pig atrial myocytes. The current was abolished by DPCPX or tertiapin and therefore was considered as potassium acetylcholine-dependent inward rectifier (I KACh ). Thus, unlike rat, in guinea pig atrium Ap5A produces activation of P1 receptors and subsequent opening of KACh channels leading to negative effects on cardiac electrical activity.

Synchronous inhibitory potentials precede seizure-like events in acute models of focal limbic seizures.

PubMed

Uva, Laura; Breschi, Gian Luca; Gnatkovsky, Vadym; Taverna, Stefano; de Curtis, Marco

2015-02-18

Interictal spikes in models of focal seizures and epilepsies are sustained by the synchronous activation of glutamatergic and GABAergic networks. The nature of population spikes associated with seizure initiation (pre-ictal spikes; PSs) is still undetermined. We analyzed the networks involved in the generation of both interictal and PSs in acute models of limbic cortex ictogenesis induced by pharmacological manipulations. Simultaneous extracellular and intracellular recordings from both principal cells and interneurons were performed in the medial entorhinal cortex of the in vitro isolated guinea pig brain during focal interictal and ictal discharges induced in the limbic network by intracortical and brief arterial infusions of either bicuculline methiodide (BMI) or 4-aminopyridine (4AP). Local application of BMI in the entorhinal cortex did not induce seizure-like events (SLEs), but did generate periodic interictal spikes sensitive to the glutamatergic non-NMDA receptor antagonist DNQX. Unlike local applications, arterial perfusion of either BMI or 4AP induced focal limbic SLEs. PSs just ahead of SLE were associated with hyperpolarizing potentials coupled with a complete blockade of firing in principal cells and burst discharges in putative interneurons. Interictal population spikes recorded from principal neurons between two SLEs correlated with a depolarizing potential. We demonstrate in two models of acute limbic SLE that PS events are different from interictal spikes and are sustained by synchronous activation of inhibitory networks. Our findings support a prominent role of synchronous network inhibition in the initiation of a focal seizure. Copyright © 2015 the authors 0270-6474/15/353048-08$15.00/0.
AP1S3 Mutations Are Associated with Pustular Psoriasis and Impaired Toll-like Receptor 3 Trafficking

PubMed Central

Setta-Kaffetzi, Niovi; Simpson, Michael A.; Navarini, Alexander A.; Patel, Varsha M.; Lu, Hui-Chun; Allen, Michael H.; Duckworth, Michael; Bachelez, Hervé; Burden, A. David; Choon, Siew-Eng; Griffiths, Christopher E.M.; Kirby, Brian; Kolios, Antonios; Seyger, Marieke M.B.; Prins, Christa; Smahi, Asma; Trembath, Richard C.; Fraternali, Franca; Smith, Catherine H.; Barker, Jonathan N.; Capon, Francesca

2014-01-01

Adaptor protein complex 1 (AP-1) is an evolutionary conserved heterotetramer that promotes vesicular trafficking between the trans-Golgi network and the endosomes. The knockout of most murine AP-1 complex subunits is embryonically lethal, so the identification of human disease-associated alleles has the unique potential to deliver insights into gene function. Here, we report two founder mutations (c.11T>G [p.Phe4Cys] and c.97C>T [p.Arg33Trp]) in AP1S3, the gene encoding AP-1 complex subunit σ1C, in 15 unrelated individuals with a severe autoinflammatory skin disorder known as pustular psoriasis. Because the variants are predicted to destabilize the 3D structure of the AP-1 complex, we generated AP1S3-knockdown cell lines to investigate the consequences of AP-1 deficiency in skin keratinocytes. We found that AP1S3 silencing disrupted the endosomal translocation of the innate pattern-recognition receptor TLR-3 (Toll-like receptor 3) and resulted in a marked inhibition of downstream signaling. These findings identify pustular psoriasis as an autoinflammatory phenotype caused by defects in vesicular trafficking and demonstrate a requirement of AP-1 for Toll-like receptor homeostasis. PMID:24791904
Acquired pellicle as a modulator for dental erosion.

PubMed

Vukosavljevic, Dusa; Custodio, William; Buzalaf, Marilia A R; Hara, Anderson T; Siqueira, Walter L

2014-06-01

Dental erosion is a multifactorial condition that can result in the loss of tooth structure and function, potentially increasing tooth sensitivity. The exposure of enamel to acids from non-bacterial sources is responsible for the progression of erosion. These erosive challenges are counteracted by the anti-erosive properties of the acquired pellicle (AP), an integument formed in vivo as a result of selective adsorption of salivary proteins on the tooth surface, containing also lipids and glycoproteins. This review provides an in-depth discussion regarding how the physical structure of the AP, along with its composition, contributes to AP anti-erosive properties. The physical properties that contribute to AP protective nature include pellicle thickness, maturation time, and site of development. The pellicle contains salivary proteins embedded within its structure that demonstrate anti-erosive properties; however, rather than individual proteins, protein-protein interactions play a fundamental role in the protective nature of the AP. In addition, dietary and synthetic proteins can modify the pellicle, enhancing its protective efficiency against dental erosion. The salivary composition of the AP and its corresponding protein-profile may be employed as a diagnostic tool, since it likely contains salivary biomarkers for oral diseases that initiate at the enamel surface, including dental erosion. Finally, by modifying the composition and structure of the AP, this protein integument has the potential to be used as a target-specific treatment option for oral diseases related to tooth demineralization. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.
Lipopolysaccharide potentiates the effect of hepatocyte growth factor on hepatocyte replication in rats by augmenting AP-1 activity.

PubMed

Gao, C; Jokerst, R; Gondipalli, P; Cai, S R; Kennedy, S; Flye, M W; Ponder, K P

1999-12-01

The liver regenerates by replication of differentiated hepatocytes after damage or removal of part of the liver. Although several growth factors and signaling pathways are activated during regeneration, it is unclear as to which of these are essential for hepatocyte replication. We show here that low- (1 mg/kg) and high- (10 mg/kg) dose hepatocyte growth factor (HGF) induced replication of 2.1% and 11.1% of hepatocytes in rats, respectively. Lipopolysaccharide (LPS), an inducer of the acute phase response, augmented hepatocyte replication in response to low- and high-dose HGF by 4- and 2-fold, respectively. HGF alone induced moderate levels of c-Jun-N-terminal kinase (JNK) and p44/p42 mitogen-activated protein kinase (MAPK), resulting in moderate levels of AP-1-DNA binding activity. The combination of LPS + HGF increased JNK and AP-1-DNA binding activity more than levels seen with LPS or HGF alone. The activation of Stat3 that was observed after administration of LPS + HGF, but not HGF alone, could contribute to increased transcription of AP-1 components. Because phosphorylation of the c-Jun component of AP-1 by JNK increases its ability to activate transcription, the AP-1 in hepatocytes from animals treated with LPS + HGF may be more active than in rats treated with LPS or HGF alone. LPS may contribute to hepatocyte replication by potentiating the effect of HGF on the activation of both AP-1-DNA binding and transcriptional activity.
Antimicrobial preservatives induce aggregation of interferon alpha-2a: The order in which preservatives induce protein aggregation is independent of the protein

PubMed Central

Bis, Regina L.; Mallela, Krishna M.G.

2014-01-01

Antimicrobial preservatives (APs) are included in liquid multi-dose protein formulations to combat the growth of microbes and bacteria. These compounds have been shown to cause protein aggregation, which leads to serious immunogenic and toxic side-effects in patients. Our earlier work on a model protein cytochrome c (Cyt c) demonstrated that APs cause protein aggregation in a specific manner. The aim of this study is to validate the conclusions obtained from our model protein studies on a pharmaceutical protein. Interferon α-2a (IFNA2) is available as a therapeutic treatment for numerous immune-compromised disorders including leukemia and hepatitis c, and APs have been used in its multi-dose formulation. Similar to Cyt c, APs induced IFNA2 aggregation, demonstrated by the loss of soluble monomer and increase in solution turbidity. The extent of IFNA2 aggregation increased with the increase in AP concentration. IFNA2 aggregation also depended on the nature of AP, and followed the order m-cresol > phenol > benzyl alcohol > phenoxyethanol. This specific order exactly matched with that observed for the model protein Cyt c. These and previously published results on antibodies and other recombinant proteins suggest that the general mechanism by which APs induce protein aggregation may be independent of the protein. PMID:24974985
Antimicrobial preservatives induce aggregation of interferon alpha-2a: the order in which preservatives induce protein aggregation is independent of the protein.

PubMed

Bis, Regina L; Mallela, Krishna M G

2014-09-10

Antimicrobial preservatives (APs) are included in liquid multi-dose protein formulations to combat the growth of microbes and bacteria. These compounds have been shown to cause protein aggregation, which leads to serious immunogenic and toxic side-effects in patients. Our earlier work on a model protein cytochrome c (Cyt c) demonstrated that APs cause protein aggregation in a specific manner. The aim of this study is to validate the conclusions obtained from our model protein studies on a pharmaceutical protein. Interferon α-2a (IFNA2) is available as a therapeutic treatment for numerous immune-compromised disorders including leukemia and hepatitis C, and APs have been used in its multi-dose formulation. Similar to Cyt c, APs induced IFNA2 aggregation, demonstrated by the loss of soluble monomer and increase in solution turbidity. The extent of IFNA2 aggregation increased with the increase in AP concentration. IFNA2 aggregation also depended on the nature of AP, and followed the order m-cresol>phenol>benzyl alcohol>phenoxyethanol. This specific order exactly matched with that observed for the model protein Cyt c. These and previously published results on antibodies and other recombinant proteins suggest that the general mechanism by which APs induce protein aggregation may be independent of the protein. Copyright © 2014 Elsevier B.V. All rights reserved.
Cytokine Autoantibody Screening in the Swedish Addison Registry Identifies Patients With Undiagnosed APS1.

PubMed

Eriksson, Daniel; Dalin, Frida; Eriksson, Gabriel Nordling; Landegren, Nils; Bianchi, Matteo; Hallgren, Åsa; Dahlqvist, Per; Wahlberg, Jeanette; Ekwall, Olov; Winqvist, Ola; Catrina, Sergiu-Bogdan; Rönnelid, Johan; Hulting, Anna-Lena; Lindblad-Toh, Kerstin; Alimohammadi, Mohammad; Husebye, Eystein S; Knappskog, Per Morten; Rosengren Pielberg, Gerli; Bensing, Sophie; Kämpe, Olle

2018-01-01

Autoimmune polyendocrine syndrome type 1 (APS1) is a monogenic disorder that features autoimmune Addison disease as a major component. Although APS1 accounts for only a small fraction of all patients with Addison disease, early identification of these individuals is vital to prevent the potentially lethal complications of APS1. To determine whether available serological and genetic markers are valuable screening tools for the identification of APS1 among patients diagnosed with Addison disease. We systematically screened 677 patients with Addison disease enrolled in the Swedish Addison Registry for autoantibodies against interleukin-22 and interferon-α4. Autoantibody-positive patients were investigated for clinical manifestations of APS1, additional APS1-specific autoantibodies, and DNA sequence and copy number variations of AIRE. In total, 17 patients (2.5%) displayed autoantibodies against interleukin-22 and/or interferon-α4, of which nine were known APS1 cases. Four patients previously undiagnosed with APS1 fulfilled clinical, genetic, and serological criteria. Hence, we identified four patients with undiagnosed APS1 with this screening procedure. We propose that patients with Addison disease should be routinely screened for cytokine autoantibodies. Clinical or serological support for APS1 should warrant DNA sequencing and copy number analysis of AIRE to enable early diagnosis and prevention of lethal complications. Copyright © 2017 Endocrine Society
Evaluation of nefazodone-induced cardiotoxicity in human induced pluripotent stem cell-derived cardiomyocytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Sujeong, E-mail: crystalee@gmail.com; Lee, Hyang-Ae, E-mail: hyangaelee@gmail.com; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul, 110-799

2016-04-01

The recent establishment of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), which express the major cardiac ion channels and recapitulate spontaneous mechanical and electrical activities, may provide a possible solution for the lack of in vitro human-based cardiotoxicity testing models. Cardiotoxicity induced by the antidepressant nefazodone was previously revealed to cause an acquired QT prolongation by hERG channel blockade. To elucidate the cellular mechanisms underlying the cardiotoxicity of nefazodone beyond hERG, its effects on cardiac action potentials (APs) and ion channels were investigated using hiPSC-CMs with whole-cell patch clamp techniques. In a proof of principle study, we examined the effectsmore » of cardioactive channel blockers on the electrophysiological profile of hiPSC-CMs in advance of the evaluation of nefazodone. Nefazodone dose-dependently prolonged the AP duration at 90% (APD{sub 90}) and 50% (APD{sub 50}) repolarization, reduced the maximum upstroke velocity (dV/dt{sub max}) and induced early after depolarizations. Voltage-clamp studies of hiPSC-CMs revealed that nefazodone inhibited various voltage-gated ion channel currents including I{sub Kr}, I{sub Ks}, I{sub Na}, and I{sub Ca}. Among them, I{sub Kr} and I{sub Na} showed relatively higher sensitivity to nefazodone, consistent with the changes in the AP parameters. In summary, hiPSC-CMs enabled an integrated approach to evaluate the complex interactions of nefazodone with cardiac ion channels. These results suggest that hiPSC-CMs can be an effective model for detecting drug-induced arrhythmogenicity beyond the current standard assay of heterologously expressed hERG K{sup +} channels. - Highlights: • Nefazodone prolonged APD and decreased upstroke velocity of APs in hiPSC-CMs. • Nefazodone inhibited cardiac ion channels, especially I{sub Kr} and I{sub Na}, in hiPSC-CMs. • Nefazodone-induced AP changes are mainly the result of I{sub Kr} and I{sub Na} inhibition. • hiPSC-CMs are sensitive model to validate nefazodone-induced cardiotoxicity. • hiPSC-CMs provide an integrated approach for evaluating mechanism of drug actions.« less
The Relationship of AP® Teacher Practices and Student AP Exam Performance. Research Report No. 2007-5. ETS RR-05-10

ERIC Educational Resources Information Center

Paek, Pamela L.; Braun, Henry; Trapani, Catherine; Ponte, Eva; Powers, Don

2008-01-01

This report analyzes the relationship of Advanced Placement Program® (AP®) teacher practices and student performance on AP Biology and AP U.S. History Exams. Using a national survey of AP teachers, the study developed four models for each subject with public school teachers only and both public and nonpublic school teachers, using two standards of…
Constraining Cometary Crystal Shapes from IR Spectral Features

NASA Astrophysics Data System (ADS)

Wooden, D. H.; Lindsay, S.; Harker, D. E.; Kelley, M. S.; Woodward, C. E.; Murphy, J. R.

2013-12-01

A major challenge in deriving the silicate mineralogy of comets is ascertaining how the anisotropic nature of forsterite crystals affects the spectral features' wavelength, relative intensity, and asymmetry. Forsterite features are identified in cometary comae near 10, 11.05-11.2, 16, 19, 23.5, 27.5 and 33 μm [1-10], so accurate models for forsterite's absorption efficiency (Qabs) are a primary requirement to compute IR spectral energy distributions (SEDs, λFλ vs. λ) and constrain the silicate mineralogy of comets. Forsterite is an anisotropic crystal, with three crystallographic axes with distinct indices of refraction for the a-, b-, and c-axis. The shape of a forsterite crystal significantly affects its spectral features [13-16]. We need models that account for crystal shape. The IR absorption efficiencies of forsterite are computed using the discrete dipole approximation (DDA) code DDSCAT [11,12]. Starting from a fiducial crystal shape of a cube, we systematically elongate/reduce one of the crystallographic axes. Also, we elongate/reduce one axis while the lengths of the other two axes are slightly asymmetric (0.8:1.2). The most significant grain shape characteristic that affects the crystalline spectral features is the relative lengths of the crystallographic axes. The second significant grain shape characteristic is breaking the symmetry of all three axes [17]. Synthetic spectral energy distributions using seven crystal shape classes [17] are fit to the observed SED of comet C/1995 O1 (Hale-Bopp). The Hale-Bopp crystalline residual better matches equant, b-platelets, c-platelets, and b-columns spectral shape classes, while a-platelets, a-columns and c-columns worsen the spectral fits. Forsterite condensation and partial evaporation experiments demonstrate that environmental temperature and grain shape are connected [18-20]. Thus, grain shape is a potential probe for protoplanetary disk temperatures where the cometary crystalline forsterite formed. The forsterite crystal shapes (equant, b-platelets, c-platelets, b-colums - excluding a- and c-columns) derived from our modeling [17] of comet Hale-Bopp, compared to laboratory synthesis experiments [18], suggests that these crystals are high temperature condensates. By observing and modeling the crystalline features in comet ISON, we may constrain forsterite crystal shape(s) and link to their formation temperature(s) and environment(s). References: [1] Campins, H., Ryan, E.V. 1989. ApJ, 341, 1059 [2] Crovisier, J., et al. 1997. Science, 275, 1904 [3] Wooden, D.H., et al. 1999. ApJ, 517, 1034 [4] Wooden, D.H., et al. 2004. ApJL, 612, L77 [5] Harker, D.E., et al. 2002. ApJ, 580, 579 [6] --. 2004, ApJ, 615, 1081 [7] Lisse, C.M., et al. 2006. Icarus 195, 941-944. [8] Lisse, C.M., et.al. 2007. Icarus 191, 223-240. [9] Kelley, M.S., et al. 2010, LPSC, 41, #2375 [10] Harker, D.E., et al. 2011, AJ, 141, 26 [11] Draine, B.T., & Flatau, P.J. 1994, J. Opt. Soc. Am. A, 11, 1491 [12] Draine, B.T., & Flatau, P.J. 2008, J. Opt. Soc. Am. A, 25, 2693 [13] Fabian, D., et al., 2001, A&A, 378, 228 [14] Tamanai, A., et al. 2006. ApJ, 648, L147 [15] Tamanai, A., et al. 2009. ASP Conf. Ser., 414, 438 [16] Koike, C., et al. 2010. ApJ, 709, 983 [17] Lindsay, S.S., et al. 2013, ApJ, 766, 54 [18] Tsuchiyama, A. 1998. Mineralogical J., 20, 59 [19] Kobatake, H., et al., 2008. Icarus, 198, 208 [20] Takigawa, A., et al.. 2009. ApJL, 707, L97
Trapped Radiation Model Uncertainties: Model-Data and Model-Model Comparisons

NASA Technical Reports Server (NTRS)

Armstrong, T. W.; Colborn, B. L.

2000-01-01

The standard AP8 and AE8 models for predicting trapped proton and electron environments have been compared with several sets of flight data to evaluate model uncertainties. Model comparisons are made with flux and dose measurements made on various U.S. low-Earth orbit satellites (APEX, CRRES, DMSP, LDEF, NOAA) and Space Shuttle flights, on Russian satellites (Photon-8, Cosmos-1887, Cosmos-2044), and on the Russian Mir Space Station. This report gives the details of the model-data comparisons-summary results in terms of empirical model uncertainty factors that can be applied for spacecraft design applications are given in a combination report. The results of model-model comparisons are also presented from standard AP8 and AE8 model predictions compared with the European Space Agency versions of AP8 and AE8 and with Russian-trapped radiation models.
Trapped Radiation Model Uncertainties: Model-Data and Model-Model Comparisons

NASA Technical Reports Server (NTRS)

Armstrong, T. W.; Colborn, B. L.

2000-01-01

The standard AP8 and AE8 models for predicting trapped proton and electron environments have been compared with several sets of flight data to evaluate model uncertainties. Model comparisons are made with flux and dose measurements made on various U.S. low-Earth orbit satellites (APEX, CRRES, DMSP. LDEF, NOAA) and Space Shuttle flights, on Russian satellites (Photon-8, Cosmos-1887, Cosmos-2044), and on the Russian Mir space station. This report gives the details of the model-data comparisons -- summary results in terms of empirical model uncertainty factors that can be applied for spacecraft design applications are given in a companion report. The results of model-model comparisons are also presented from standard AP8 and AE8 model predictions compared with the European Space Agency versions of AP8 and AE8 and with Russian trapped radiation models.
Fatty acid ethyl ester synthase inhibition ameliorates ethanol-induced Ca2+-dependent mitochondrial dysfunction and acute pancreatitis

PubMed Central

Huang, Wei; Booth, David M; Cane, Matthew C; Chvanov, Michael; Javed, Muhammad A; Elliott, Victoria L; Armstrong, Jane A; Dingsdale, Hayley; Cash, Nicole; Li, Yan; Greenhalf, William; Mukherjee, Rajarshi; Kaphalia, Bhupendra S; Jaffar, Mohammed; Petersen, Ole H; Tepikin, Alexei V; Sutton, Robert; Criddle, David N

2014-01-01

Objective Non-oxidative metabolism of ethanol (NOME) produces fatty acid ethyl esters (FAEEs) via carboxylester lipase (CEL) and other enzyme action implicated in mitochondrial injury and acute pancreatitis (AP). This study investigated the relative importance of oxidative and non-oxidative pathways in mitochondrial dysfunction, pancreatic damage and development of alcoholic AP, and whether deleterious effects of NOME are preventable. Design Intracellular calcium ([Ca2+]C), NAD(P)H, mitochondrial membrane potential and activation of apoptotic and necrotic cell death pathways were examined in isolated pancreatic acinar cells in response to ethanol and/or palmitoleic acid (POA) in the presence or absence of 4-methylpyrazole (4-MP) to inhibit oxidative metabolism. A novel in vivo model of alcoholic AP induced by intraperitoneal administration of ethanol and POA was developed to assess the effects of manipulating alcohol metabolism. Results Inhibition of OME with 4-MP converted predominantly transient [Ca2+]C rises induced by low ethanol/POA combination to sustained elevations, with concurrent mitochondrial depolarisation, fall of NAD(P)H and cellular necrosis in vitro. All effects were prevented by 3-benzyl-6-chloro-2-pyrone (3-BCP), a CEL inhibitor. 3-BCP also significantly inhibited rises of pancreatic FAEE in vivo and ameliorated acute pancreatic damage and inflammation induced by administration of ethanol and POA to mice. Conclusions A combination of low ethanol and fatty acid that did not exert deleterious effects per se became toxic when oxidative metabolism was inhibited. The in vitro and in vivo damage was markedly inhibited by blockade of CEL, indicating the potential for development of specific therapy for treatment of alcoholic AP via inhibition of FAEE generation. PMID:24162590
Activation of Toll-like receptor-9 promotes cellular migration via up-regulating MMP-2 expression in oral squamous cell carcinoma.

PubMed

Ruan, Min; Zhang, Zun; Li, Siyi; Yan, Min; Liu, Shengwen; Yang, Wenjun; Wang, Lizheng; Zhang, Chenping

2014-01-01

Activation of Toll like receptors (TLRs) signaling has been implicated in promoting malignant cell invasion and metastatic potential. Previously we demonstrated that increased TLR-9 expression predicted poor survival in oral cancer patients. The objective of this study is to further investigate the roles and potential molecular mechanisms of TLR-9 signaling in human oral cancer cell invasion. Cell migration, invasion and protein expression were detected by wound healing assay, Transwell chambers model and western blot. The secretion and activity levels of metalloproteinases-2/9 were quantified by ELISA and Gelatin zymography. EMSA and ChIP assays were employed to detect the activity of AP-1signal pathway. TLR-9 siRNA transfection was used to regulate the expression and activity of TLR-9 in oral cancer cell line HB cells. The results of both wound healing assay and in vitro Transwell assay revealed that activation of TLR-9 induced dose- and time- dependent migration and invasion of HB cells. An increased expression, secretion and activity of MMP-2 were observed upon the treatment of CpG-ODN. The TLR-9 signaling-mediated MMP-2 expression appeared to be a consequence of AP-1 activation, because that their DNA binding activity was enhanced by CpG-ODN treatment. All these influences were efficiently repressed by the knockdown of TLR-9 through siRNA or pretreatment of an AP-1 inhibitor. Activation of TLR-9 signaling could promote human oral cancer HB cells invasion with the induction of MMP-2 presentation by attenuating AP-1 binding activity, suggesting a novel anti-metastatic application for TLR-9 targeted therapy in oral cancer in the future.
Gateway-Assisted Retransmission for Lightweight and Reliable IoT Communications.

PubMed

Chang, Hui-Ling; Wang, Cheng-Gang; Wu, Mong-Ting; Tsai, Meng-Hsun; Lin, Chia-Ying

2016-09-22

Message Queuing Telemetry Transport for Sensor Networks (MQTT-SN) and Constrained Application Protocol (CoAP) are two protocols supporting publish/subscribe models for IoT devices to publish messages to interested subscribers. Retransmission mechanisms are introduced to compensate for the lack of data reliability. If the device does not receive the acknowledgement (ACK) before retransmission timeout (RTO) expires, the device will retransmit data. Setting an appropriate RTO is important because the delay may be large or retransmission may be too frequent when the RTO is inappropriate. We propose a Gateway-assisted CoAP (GaCoAP) to dynamically compute RTO for devices. Simulation models are proposed to investigate the performance of GaCoAP compared with four other methods. The experiment results show that GaCoAP is more suitable for IoT devices.
Gateway-Assisted Retransmission for Lightweight and Reliable IoT Communications

PubMed Central

Chang, Hui-Ling; Wang, Cheng-Gang; Wu, Mong-Ting; Tsai, Meng-Hsun; Lin, Chia-Ying

2016-01-01

Message Queuing Telemetry Transport for Sensor Networks (MQTT-SN) and Constrained Application Protocol (CoAP) are two protocols supporting publish/subscribe models for IoT devices to publish messages to interested subscribers. Retransmission mechanisms are introduced to compensate for the lack of data reliability. If the device does not receive the acknowledgement (ACK) before retransmission timeout (RTO) expires, the device will retransmit data. Setting an appropriate RTO is important because the delay may be large or retransmission may be too frequent when the RTO is inappropriate. We propose a Gateway-assisted CoAP (GaCoAP) to dynamically compute RTO for devices. Simulation models are proposed to investigate the performance of GaCoAP compared with four other methods. The experiment results show that GaCoAP is more suitable for IoT devices. PMID:27669243
In silico simulations of experimental protocols for cardiac modeling.

PubMed

Carro, Jesus; Rodriguez, Jose Felix; Pueyo, Esther

2014-01-01

A mathematical model of the AP involves the sum of different transmembrane ionic currents and the balance of intracellular ionic concentrations. To each ionic current corresponds an equation involving several effects. There are a number of model parameters that must be identified using specific experimental protocols in which the effects are considered as independent. However, when the model complexity grows, the interaction between effects becomes increasingly important. Therefore, model parameters identified considering the different effects as independent might be misleading. In this work, a novel methodology consisting in performing in silico simulations of the experimental protocol and then comparing experimental and simulated outcomes is proposed for parameter model identification and validation. The potential of the methodology is demonstrated by validating voltage-dependent L-type calcium current (ICaL) inactivation in recently proposed human ventricular AP models with different formulations. Our results show large differences between ICaL inactivation as calculated from the model equation and ICaL inactivation from the in silico simulations due to the interaction between effects and/or to the experimental protocol. Our results suggest that, when proposing any new model formulation, consistency between such formulation and the corresponding experimental data that is aimed at being reproduced needs to be first verified considering all involved factors.
Aptamer-functionalized PEG-PLGA nanoparticles for enhanced anti-glioma drug delivery.

PubMed

Guo, Jianwei; Gao, Xiaoling; Su, Lina; Xia, Huimin; Gu, Guangzhi; Pang, Zhiqing; Jiang, Xinguo; Yao, Lei; Chen, Jun; Chen, Hongzhuan

2011-11-01

Targeted delivery of therapeutic nanoparticles in a disease-specific manner represents a potentially powerful technology especially when treating infiltrative brain tumors such as gliomas. We developed a nanoparticulate drug delivery system decorated with AS1411 (Ap), a DNA aptamer specifically binding to nucleolin which was highly expressed in the plasma membrane of both cancer cells and endothelial cells in angiogenic blood vessels, as the targeting ligand to facilitate anti-glioma delivery of paclitaxel (PTX). Ap was conjugated to the surface of PEG-PLGA nanoparticles (NP) via an EDC/NHS technique. With the conjugation confirmed by Urea PAGE and XPS, the resulting Ap-PTX-NP was uniformly round with particle size at 156.0 ± 54.8 nm and zeta potential at -32.93 ± 3.1 mV. Ap-nucleolin interaction significantly enhanced cellular association of nanoparticles in C6 glioma cells, and increased the cytotoxicity of its payload. Prolonged circulation and enhanced PTX accumulation at the tumor site was achieved for Ap-PTX-NP, which eventually obtained significantly higher tumor inhibition on mice bearing C6 glioma xenografts and prolonged animal survival on rats bearing intracranial C6 gliomas when compared with PTX-NP and Taxol(®). The results of this contribution demonstrated the potential utility of AS1411-functionalized nanoparticles for a therapeutic application in the treatment of gliomas. Copyright © 2011 Elsevier Ltd. All rights reserved.
Preparation, crystallization and preliminary X-ray crystallographic studies of diadenosine tetraphosphate hydrolase from Shigella flexneri 2a.

PubMed

Hu, Wenxin; Wang, Qihai; Bi, Ruchang

2005-12-01

Diadenosine tetraphosphate (Ap4A) hydrolase (EC 3.6.1.41) hydrolyzes Ap4A symmetrically in prokaryotes. It plays a potential role in organisms by regulating the concentration of Ap4A in vivo. To date, no three-dimensional structures of proteins with significant sequence homology to this protein have been determined. The 31.3 kDa Ap4A hydrolase from Shigella flexneri 2a has been cloned, expressed and purified using an Escherichia coli expression system. Crystals of Ap4A hydrolase have been obtained by the hanging-drop technique at 291 K using PEG 550 MME as precipitant. Ap4A hydrolase crystals diffract X-rays to 3.26 A and belong to space group P2(1), with unit-cell parameters a = 118.9, b = 54.6, c = 128.5 A, beta = 95.7 degrees.
A sampling framework for incorporating quantitative mass spectrometry data in protein interaction analysis.

PubMed

Tucker, George; Loh, Po-Ru; Berger, Bonnie

2013-10-04

Comprehensive protein-protein interaction (PPI) maps are a powerful resource for uncovering the molecular basis of genetic interactions and providing mechanistic insights. Over the past decade, high-throughput experimental techniques have been developed to generate PPI maps at proteome scale, first using yeast two-hybrid approaches and more recently via affinity purification combined with mass spectrometry (AP-MS). Unfortunately, data from both protocols are prone to both high false positive and false negative rates. To address these issues, many methods have been developed to post-process raw PPI data. However, with few exceptions, these methods only analyze binary experimental data (in which each potential interaction tested is deemed either observed or unobserved), neglecting quantitative information available from AP-MS such as spectral counts. We propose a novel method for incorporating quantitative information from AP-MS data into existing PPI inference methods that analyze binary interaction data. Our approach introduces a probabilistic framework that models the statistical noise inherent in observations of co-purifications. Using a sampling-based approach, we model the uncertainty of interactions with low spectral counts by generating an ensemble of possible alternative experimental outcomes. We then apply the existing method of choice to each alternative outcome and aggregate results over the ensemble. We validate our approach on three recent AP-MS data sets and demonstrate performance comparable to or better than state-of-the-art methods. Additionally, we provide an in-depth discussion comparing the theoretical bases of existing approaches and identify common aspects that may be key to their performance. Our sampling framework extends the existing body of work on PPI analysis using binary interaction data to apply to the richer quantitative data now commonly available through AP-MS assays. This framework is quite general, and many enhancements are likely possible. Fruitful future directions may include investigating more sophisticated schemes for converting spectral counts to probabilities and applying the framework to direct protein complex prediction methods.

Engagement with the auditory processing system during targeted auditory cognitive training mediates changes in cognitive outcomes in individuals with schizophrenia

PubMed Central

Biagianti, Bruno; Fisher, Melissa; Neilands, Torsten B.; Loewy, Rachel; Vinogradov, Sophia

2016-01-01

BACKGROUND Individuals with schizophrenia who engage in targeted cognitive training (TCT) of the auditory system show generalized cognitive improvements. The high degree of variability in cognitive gains maybe due to individual differences in the level of engagement of the underlying neural system target. METHODS 131 individuals with schizophrenia underwent 40 hours of TCT. We identified target engagement of auditory system processing efficiency by modeling subject-specific trajectories of auditory processing speed (APS) over time. Lowess analysis, mixed models repeated measures analysis, and latent growth curve modeling were used to examine whether APS trajectories were moderated by age and illness duration, and mediated improvements in cognitive outcome measures. RESULTS We observed signifcant improvements in APS from baseline to 20 hours of training (initial change), followed by a flat APS trajectory (plateau) at subsequent time-points. Participants showed inter-individual variability in the steepness of the initial APS change and in the APS plateau achieved and sustained between 20–40 hours. We found that participants who achieved the fastest APS plateau, showed the greatest transfer effects to untrained cognitive domains. CONCLUSIONS There is a significant association between an individual's ability to generate and sustain auditory processing efficiency and their degree of cognitive improvement after TCT, independent of baseline neurocognition. APS plateau may therefore represent a behavioral measure of target engagement mediating treatment response. Future studies should examine the optimal plateau of auditory processing efficiency required to induce significant cognitive improvements, in the context of inter-individual differences in neural plasticity and sensory system efficiency that characterize schizophrenia. PMID:27617637
Artificial pancreas (AP) clinical trial participants' acceptance of future AP technology.

PubMed

Bevier, Wendy C; Fuller, Serena M; Fuller, Ryan P; Rubin, Richard R; Dassau, Eyal; Doyle, Francis J; Jovanovič, Lois; Zisser, Howard C

2014-09-01

Artificial pancreas (AP) systems are currently an active field of diabetes research. This pilot study examined the attitudes of AP clinical trial participants toward future acceptance of the technology, having gained firsthand experience. After possible influencers of AP technology adoption were considered, a 34-question questionnaire was developed. The survey assessed current treatment satisfaction, dimensions of clinical trial participant motivation, and variables of the technology acceptance model (TAM). Forty-seven subjects were contacted to complete the survey. The reliability of the survey scales was tested using Cronbach's α. The relationship of the factors to the likelihood of AP technology adoption was explored using regression analysis. Thirty-six subjects (76.6%) completed the survey. Of the respondents, 86.1% were either highly likely or likely to adopt the technology once available. Reliability analysis of the survey dimensions revealed good internal consistency, with scores of >0.7 for current treatment satisfaction, convenience (motivation), personal health benefit (motivation), perceived ease of use (TAM), and perceived usefulness (TAM). Linear modeling showed that future acceptance of the AP was significantly associated with TAM and the motivation variables of convenience plus the individual item benefit to others (R(2)=0.26, P=0.05). When insulin pump and continuous glucose monitor use were added, the model significance improved (R(2)=0.37, P=0.02). This pilot study demonstrated that individuals with direct AP technology experience expressed high likelihood of future acceptance. Results support the factors of personal benefit, convenience, perceived usefulness, and perceived ease of use as reliable scales that suggest system adoption in this highly motivated patient population.
Glucose hydrogen breath test for small intestinal bacterial overgrowth in children with abdominal pain-related functional gastrointestinal disorders.

PubMed

Korterink, Judith J; Benninga, Marc A; van Wering, Herbert M; Deckers-Kocken, Judith M

2015-04-01

A potential link between small intestinal bacterial overgrowth (SIBO) and abdominal pain-related functional gastrointestinal disorders (AP-FGID) has been suggested by symptom similarities and by the reported prevalence of SIBO in children with irritable bowel syndrome (IBS) and functional AP. The aim of this study is to evaluate the prevalence of SIBO using the glucose hydrogen breath test (GHBT), in a cohort of Dutch children with AP-FGID fulfilling the Rome III criteria, and to identify potential predictors. Children ages 6 to 18 years with AP-FGID fulfilling the Rome III criteria were included. All of the children underwent a GHBT. SIBO was diagnosed if the fasting breath hydrogen concentration was ≥20 ppm or an increase in H2 levels of ≥12 ppm above the baseline value was measured after ingestion of glucose. Gastrointestinal symptoms were collected using a standardised AP questionnaire. A total of 161 Dutch children with AP-FGID were enrolled. Twenty-three patients (14.3%) were diagnosed as having SIBO, as assessed by GHBT; 78% of the children diagnosed as having SIBO had fasting hydrogen levels ≥20 ppm. IBS was significantly more found in children with SIBO compared with children without SIBO (P = 0.001). An altered defecation pattern (ie, change in frequency or form of stool) (P = 0.013), loss of appetite (P = 0.007), and belching (P = 0.023) were significantly more found in children with SIBO compared with those without SIBO. SIBO is present in 14.3% of children presenting with AP-FGID. IBS, altered defecation pattern, loss of appetite, and belching were predictors for SIBO in children with AP-FGID.
Roles of specific Kv channel types in repolarization of the action potential in genetically identified subclasses of pyramidal neurons in mouse neocortex

PubMed Central

Pathak, Dhruba; Guan, Dongxu

2016-01-01

The action potential (AP) is a fundamental feature of excitable cells that serves as the basis for long-distance signaling in the nervous system. There is considerable diversity in the appearance of APs and the underlying repolarization mechanisms in different neuronal types (reviewed in Bean BP. Nat Rev Neurosci 8: 451–465, 2007), including among pyramidal cell subtypes. In the present work, we used specific pharmacological blockers to test for contributions of Kv1, Kv2, or Kv4 channels to repolarization of single APs in two genetically defined subpopulations of pyramidal cells in layer 5 of mouse somatosensory cortex (etv1 and glt) as well as pyramidal cells from layer 2/3. These three subtypes differ in AP properties (Groh A, Meyer HS, Schmidt EF, Heintz N, Sakmann B, Krieger P. Cereb Cortex 20: 826–836, 2010; Guan D, Armstrong WE, Foehring RC. J Neurophysiol 113: 2014–2032, 2015) as well as laminar position, morphology, and projection targets. We asked what the roles of Kv1, Kv2, and Kv4 channels are in AP repolarization and whether the underlying mechanisms are pyramidal cell subtype dependent. We found that Kv4 channels are critically involved in repolarizing neocortical pyramidal cells. There are also pyramidal cell subtype-specific differences in the role for Kv1 channels. Only Kv4 channels were involved in repolarizing the narrow APs of glt cells. In contrast, in etv1 cells and layer 2/3 cells, the broader APs are partially repolarized by Kv1 channels in addition to Kv4 channels. Consistent with their activation in the subthreshold range, Kv1 channels also regulate AP voltage threshold in all pyramidal cell subtypes. PMID:26864770
Different role of TTX-sensitive voltage-gated sodium channel (NaV 1) subtypes in action potential initiation and conduction in vagal airway nociceptors.

PubMed

Kollarik, M; Sun, H; Herbstsomer, R A; Ru, F; Kocmalova, M; Meeker, S N; Undem, B J

2018-04-15

The action potential initiation in the nerve terminals and its subsequent conduction along the axons of afferent nerves are not necessarily dependent on the same voltage-gated sodium channel (Na V 1) subunits. The action potential initiation in jugular C-fibres within airway tissues is not blocked by TTX; nonetheless, conduction of action potentials along the vagal axons of these nerves is often dependent on TTX-sensitive channels. This is not the case for nodose airway Aδ-fibres and C-fibres, where both action potential initiation and conduction is abolished by TTX or selective Na V 1.7 blockers. The difference between the initiation of action potentials within the airways vs. conduction along the axons should be considered when developing Na V 1 blocking drugs for topical application to the respiratory tract. The action potential (AP) initiation in the nerve terminals and its subsequent AP conduction along the axons do not necessarily depend on the same subtypes of voltage-gated sodium channels (Na V 1s). We evaluated the role of TTX-sensitive and TTX-resistant Na V 1s in vagal afferent nociceptor nerves derived from jugular and nodose ganglia innervating the respiratory system. Single cell RT-PCR was performed on vagal afferent neurons retrogradely labelled from the guinea pig trachea. Almost all of the jugular neurons expressed the TTX-sensitive channel Na V 1.7 along with TTX-resistant Na V 1.8 and Na V 1.9. Tracheal nodose neurons also expressed Na V 1.7 but, less frequently, Na V 1.8 and Na V 1.9. Na V 1.6 were expressed in ∼40% of the jugular and 25% of nodose tracheal neurons. Other Na V 1 α subunits were only rarely expressed. Single fibre recordings were made from the vagal nodose and jugular nerve fibres innervating the trachea or lung in the isolated perfused vagally-innervated preparations that allowed for selective drug delivery to the nerve terminal compartment (AP initiation) or to the desheathed vagus nerve (AP conduction). AP initiation in jugular C-fibres was unaffected by TTX, although it was inhibited by Na V 1.8 blocker (PF-01247324) and abolished by combination of TTX and PF-01247324. However, AP conduction in the majority of jugular C-fibres was abolished by TTX. By contrast, both AP initiation and conduction in nodose nociceptors was abolished by TTX or selective Na V 1.7 blockers. Distinction between the effect of a drug with respect to inhibiting AP in the nerve terminals within the airways vs. at conduction sites along the vagus nerve is relevant to therapeutic strategies involving inhaled Na V 1 blocking drugs. © 2018 The Authors. The Journal of Physiology © 2018 The Physiological Society.
Materials Degradation in the Jovian Radiation Environment

NASA Technical Reports Server (NTRS)

Miloshevsky, Gennady; Caffrey, Jarvis A.; Jones, Jonathan E.; Zoladz, Thomas F.

2017-01-01

The radiation environment of Jupiter represents a significant hazard for Europa Lander deorbit stage components, and presents a significant potential mission risk. The radiolytic degradation of ammonium perchlorate (AP) oxidizer in solid propellants may affect its properties and performance. The Monte Carlo code MONSOL was used for modeling of laboratory experiments on the electron irradiation of propellant samples. An approach for flattening dose profiles along the depth of irradiated samples is proposed. Depth-dose distributions produced by Jovian electrons in multi-layer slabs of materials are calculated. It is found that the absorbed dose in a particular slab is significantly affected by backscattered electrons and photons from neighboring slabs. The dose and radiolytic decomposition of AP crystals are investigated and radiation-induced chemical yields and weight percent of radical products are reported.
Differential calcium sensitivity in NaV 1.5 mixed syndrome mutants.

PubMed

Abdelsayed, Mena; Baruteau, Alban-Elouen; Gibbs, Karen; Sanatani, Shubhayan; Krahn, Andrew D; Probst, Vincent; Ruben, Peter C

2017-09-15

SCN5a mutations may express gain-of-function (Long QT Syndrome-3), loss-of-function (Brugada Syndrome 1) or both (mixed syndromes), depending on the mutation and environmental triggers. One such trigger may be an increase in cytosolic calcium, accompanying exercise. Many mixed syndromes mutants, including ∆KPQ, E1784K, 1795insD and Q1909R, are found in calcium-sensitive regions. Elevated cytosolic calcium attenuates gain-of-function properties in ∆KPQ, 1795insD and Q1909R, but not in E1784K. By contrast, elevated cytosolic calcium further exacerbates gain-of-function in E1784K by destabilizing slow inactivation. Action potential modelling, using a modified O'Hara Rudy model, suggests that elevated heart rate rescues action potential duration in ∆KPQ, 1795insD and Q1909R, but not in E1784K. Action potential simulations suggest that E1784K carriers have an increased intracellular sodium-to-calcium ratio under bradycardia and tachycardia conditions. Elevated cytosolic calcium, which is common during high heart rates, ameliorates or exacerbates the mixed syndrome phenotype depending on the genetic signature. Inherited arrhythmias may arise from mutations in the gene for SCN5a, which encodes the cardiac voltage-gated sodium channel, Na V 1.5. Mutants in Na V 1.5 result in Brugada Syndrome (BrS1), Long-QT Syndrome (LQT3) or mixed syndromes (an overlap of BrS1/LQT3). Exercise is a potential arrhythmogenic trigger in mixed syndromes. We aimed to determine the effects of elevated cytosolic calcium, which is common during exercise, in mixed syndrome Na V 1.5 mutants. We used whole-cell patch clamp to assess the biophysical properties of Na V 1.5 wild-type (WT), ∆KPQ, E1784K, 1795insD and Q1909R mutants in human embryonic kidney 293 cells transiently transfected with the Na V 1.5 α subunit (WT or mutants), β1 subunit and enhanced green fluorescent protein. Voltage-dependence and kinetics were measured at cytosolic calcium levels of approximately 0, 500 and 2500 nm. In silico, action potential (AP) model simulations were performed using a modified O'Hara Rudy model. Elevated cytosolic calcium attenuates the late sodium current in ∆KPQ, 1795insD and Q1909R, but not in E1784K. Elevated cytosolic calcium restores steady-state slow inactivation (SSSI) to the WT-form in Q1909R, but depolarized SSSI in E1784K. Our AP simulations showed a frequency-dependent reduction of AP duration in ∆KPQ, 1795insD and Q1909R carriers. In E1784K, AP duration is relatively prolonged at both low and high heart rates, resulting in a sodium overload. Cellular perturbations during exercise may affect BrS1/LQT3 patients differently depending on their individual genetic signature. Thus, exercise may be therapeutic or may be an arrhythmogenic trigger in some SCN5a patients. © 2017 The Authors. The Journal of Physiology © 2017 The Physiological Society.
LaAP2L1, a heterosis-associated AP2/EREBP transcription factor of Larix, increases organ size and final biomass by affecting cell proliferation in Arabidopsis.

PubMed

Li, Ai; Zhou, Yanan; Jin, Chuan; Song, Wenqin; Chen, Chengbin; Wang, Chunguo

2013-11-01

In Larix and in some crops, heterosis is prevalent and has been widely used in breeding to produce excellent varieties. However, the molecular basis of heterosis in Larix remains ambiguous. LaAP2L1, a member of the AP2/EREBP transcription factor family, has been suggested to be involved in heterosis in Larix hybrids. Here, the function and regulation of LaAP2L1 were further explored. Overexpression of LaAP2L1 led to markedly enlarged organs and heterosis-like traits in Arabidopsis. Fresh weight of leaves was almost twice as great as in vector controls. Likewise, seed yield of 35S::LaAP2L1 individual plants was >200% greater than that of control plants. The enlarged organs and heterosis-like traits displayed by 35S::LaAP2L1 plants were mainly due to enhanced cell proliferation and prolonged growth duration. At the molecular level, LaAP2L1 upregulated the expression of ANT, EBP1, and CycD3;1 and inhibited the expression of ARGOS in 35S::LaAP2L1 plants, suggesting an important molecular role of LaAP2L1 in regulating plant organ development. These findings provide new insights into the formation of heterosis in woody plants and suggest that LaAP2L1 has potential applications in breeding high-yielding crops and energy plants. In addition, 50 AP2/EREBP transcription factors, including LaAP2L1, in Larix were identified by transcriptome sequencing, and phylogenetic analysis was conducted. This provided information that will be important in further revealing the functions of these transcription factors.
P alpha-chiral phosphorothioate analogues of bis(5'-adenosyl)tetraphosphate (Ap4A); their enzymatic synthesis and degradation.

PubMed Central

Lazewska, D; Guranowski, A

1990-01-01

Synthesis of Sp and Rp diastereomers of Ap4A alpha S has been characterized in two enzymatic systems, the lysyl-tRNA synthetase from Escherichia coli and the Ap4A alpha, beta-phosphorylase from Saccharomyces cerevisiae. The synthetase was able to use both (Sp)ATP alpha S and (Rp)ATP alpha S as acceptors of adenylate thus yielding corresponding monothioanalogues of Ap4A,(Sp) Ap4A alpha S and (Rp)Ap4A alpha S. No dithiophosphate analogue was formed. Relative synthetase velocities of the formation of Ap4A,(Sp) Ap4A alpha S and (Rp)Ap4A alpha S were 1:0.38:0.15, and the computed Km values for (Sp)ATP alpha S and (Rp)ATP alpha S were 0.48 and 1.34 mM, respectively. The yeast Ap4A phosphorylase synthesized (Sp)Ap4A alpha S and (Rp)Ap4A alpha S using adenosine 5'-phosphosulfate (APS) as source of adenylate. The adenylate was accepted by corresponding thioanalogues of ATP. In that system, relative velocities of Ap4A, (Sp)Ap4A alpha S and (Rp)Ap4A alpha S formation were 1:0.15:0.60. The two isomeric phosphorothioate analogues of Ap4A were tested as substrates for the following specific Ap4A-degrading enzymes: (asymmetrical) Ap4A hydrolase (EC 3.6.1.17) from yellow lupin (Lupinus luteus) seeds hydrolyzed each of the analogues to AMP and the corresponding isomer of ATP alpha S; (symmetrical) Ap4A hydrolase (EC 3.6.1.41) from E. coli produced ADP and the corresponding diastereomer of ADP alpha S; and Ap4A phosphorylase (EC 2.7.7.53) from S. cerevisiae cleaved the Rp isomer only at the unmodified end yielding ADP and (Rp)ATP alpha S whereas the Sp isomer was degraded non-specifically yielding a mixture of ADP, (Sp)ADP alpha S, ATP and (Sp)ATP alpha S. For all the Ap4A-degrading enzymes, the Rp isomer of Ap4A alpha S appeared to be a better substrate than its Sp counterpart; stereoselectivity of the three enzymes for the Ap4A alpha S diastereomers is 51, 6 and 2.5, respectively. Basic kinetic parameters of the degradation reactions are presented and structural requirements of the Ap4A-metabolizing enzymes with respect to the potential substrates modified at the Ap4A-P alpha are discussed. PMID:2172926
Accession-dependent action potentials in Arabidopsis.

PubMed

Favre, Patrick; Greppin, Hubert; Degli Agosti, Robert

2011-05-01

Plant excitability, as measured by the appearance and circulation of action potentials (APs) after biotic and abiotic stress treatments, is a far lesser and more versatile phenomenon than in animals. To examine the genetic basis of plant excitability we used different Arabidopsis thaliana accessions. APs were induced by wounding (W) with a subsequent deposition (D) of 5μL of 1M KCl onto adult leaves. This treatment elicited transient voltage responses (APs) that were detected by 2 extracellular electrodes placed at a distance from the wounding location over an experimental time of 150min. The first electrode (e1) was placed at the end of the petiole and the beginning of the leaf, and the second (e2) electrode was placed on the petiole near the center of the rosette. All accessions (Columbia (Col), Wassilewskija (Ws) and Landsberg erecta (Ler)) responded to the W & D treatment. After W & D treatment was performed on 100 plants for each accession, the number of APs ranged from 0 to 37 (median 8, total 940), 0 to 16 (median 5, total 528) and 0 to 18 (median 2, total 296) in Col, Ws and Ler, respectively. Responding plants (>0 APs) showed significantly different behaviors depending on their accessions of origin (i.e., Col 91, Ws 83 and Ler 76%). Some AP characteristics, such as amplitude and speed of propagation from e1 to e2 (1.28mms(-1)), were the same for all accessions, whereas the average duration of APs was similar in Col and Ws, but different in Ler. Self-sustained oscillations were observed more frequently in Col than Ws and least often in Ler, and the mean oscillation frequency was more rapid in Col, followed by Ws, and was slowest in Ler. In general, Col was the most excitable accession, followed by Ws, and Ler was the least excitable; this corresponded well with voltage elicited action potentials. In conclusion, part of Arabidopsis excitability in AP responses is genetically pre-determined. Copyright © 2010 Elsevier GmbH. All rights reserved.
The Role of Complement in Cnidarian-Dinoflagellate Symbiosis and Immune Challenge in the Sea Anemone Aiptasia pallida

PubMed Central

Poole, Angela Z.; Kitchen, Sheila A.; Weis, Virginia M.

2016-01-01

The complement system is an innate immune pathway that in vertebrates, is responsible for initial recognition and ultimately phagocytosis and destruction of microbes. Several complement molecules including C3, Factor B, and mannose binding lectin associated serine proteases (MASP) have been characterized in invertebrates and while most studies have focused on their conserved role in defense against pathogens, little is known about their role in managing beneficial microbes. The purpose of this study was to (1) characterize complement pathway genes in the symbiotic sea anemone Aiptasia pallida, (2) investigate the evolution of complement genes in invertebrates, and (3) examine the potential dual role of complement genes Factor B and MASP in the onset and maintenance of cnidarian-dinoflagellate symbiosis and immune challenge using qPCR based studies. The results demonstrate that A. pallida has multiple Factor B genes (Ap_Bf-1, Ap_Bf-2a, and Ap_Bf-2b) and one MASP gene (Ap_MASP). Phylogenetic analysis indicates that the evolutionary history of complement genes is complex, and there have been many gene duplications or gene loss events, even within members of the same phylum. Gene expression analyses revealed a potential role for complement in both onset and maintenance of cnidarian-dinoflagellate symbiosis and immune challenge. Specifically, Ap_Bf-1 and Ap_MASP are significantly upregulated in the light at the onset of symbiosis and in response to challenge with the pathogen Serratia marcescens suggesting that they play a role in the initial recognition of both beneficial and harmful microbes. Ap_Bf-2b in contrast, was generally downregulated during the onset and maintenance of symbiosis and in response to challenge with S. marcescens. Therefore, the exact role of Ap_Bf-2b in response to microbes remains unclear, but the results suggest that the presence of microbes leads to repressed expression. Together, these results indicate functional divergence between Ap_Bf-1 and Ap_Bf-2b, and that Ap_Bf-1 and Ap_MASP may be functioning together in an ancestral hybrid of the lectin and alternative complement pathways. Overall, this study provides information on the role of the complement system in a basal metazoan and its role in host-microbe interactions. PMID:27148208
The Role of Complement in Cnidarian-Dinoflagellate Symbiosis and Immune Challenge in the Sea Anemone Aiptasia pallida.

PubMed

Poole, Angela Z; Kitchen, Sheila A; Weis, Virginia M

2016-01-01

The complement system is an innate immune pathway that in vertebrates, is responsible for initial recognition and ultimately phagocytosis and destruction of microbes. Several complement molecules including C3, Factor B, and mannose binding lectin associated serine proteases (MASP) have been characterized in invertebrates and while most studies have focused on their conserved role in defense against pathogens, little is known about their role in managing beneficial microbes. The purpose of this study was to (1) characterize complement pathway genes in the symbiotic sea anemone Aiptasia pallida, (2) investigate the evolution of complement genes in invertebrates, and (3) examine the potential dual role of complement genes Factor B and MASP in the onset and maintenance of cnidarian-dinoflagellate symbiosis and immune challenge using qPCR based studies. The results demonstrate that A. pallida has multiple Factor B genes (Ap_Bf-1, Ap_Bf-2a, and Ap_Bf-2b) and one MASP gene (Ap_MASP). Phylogenetic analysis indicates that the evolutionary history of complement genes is complex, and there have been many gene duplications or gene loss events, even within members of the same phylum. Gene expression analyses revealed a potential role for complement in both onset and maintenance of cnidarian-dinoflagellate symbiosis and immune challenge. Specifically, Ap_Bf-1 and Ap_MASP are significantly upregulated in the light at the onset of symbiosis and in response to challenge with the pathogen Serratia marcescens suggesting that they play a role in the initial recognition of both beneficial and harmful microbes. Ap_Bf-2b in contrast, was generally downregulated during the onset and maintenance of symbiosis and in response to challenge with S. marcescens. Therefore, the exact role of Ap_Bf-2b in response to microbes remains unclear, but the results suggest that the presence of microbes leads to repressed expression. Together, these results indicate functional divergence between Ap_Bf-1 and Ap_Bf-2b, and that Ap_Bf-1 and Ap_MASP may be functioning together in an ancestral hybrid of the lectin and alternative complement pathways. Overall, this study provides information on the role of the complement system in a basal metazoan and its role in host-microbe interactions.
Osmotic and Salt Stresses Modulate Spontaneous and Glutamate-Induced Action Potentials and Distinguish between Growth and Circumnutation in Helianthus annuus Seedlings

PubMed Central

Stolarz, Maria; Dziubinska, Halina

2017-01-01

Action potentials (APs), i.e., long-distance electrical signals, and circumnutations (CN), i.e., endogenous plant organ movements, are shaped by ion fluxes and content in excitable and motor tissues. The appearance of APs and CN as well as growth parameters in seedlings and 3-week old plants of Helianthus annuus treated with osmotic and salt stress (0–500 mOsm) were studied. Time-lapse photography and extracellular measurements of electrical potential changes were performed. The hypocotyl length was strongly reduced by the osmotic and salt stress. CN intensity declined due to the osmotic but not salt stress. The period of CN in mild salt stress was similar to the control (~164 min) and increased to more than 200 min in osmotic stress. In sunflower seedlings growing in a hydroponic medium, spontaneous APs (SAPs) propagating basipetally and acropetally with a velocity of 12–20 cm min−1 were observed. The number of SAPs increased 2–3 times (7–10 SAPs 24 h−1plant−1) in the mild salt stress (160 mOsm NaCl and KCl), compared to the control and strong salt stress (3–4 SAPs 24 h−1 plant−1 in the control and 300 mOsm KCl and NaCl). Glutamate-induced series of APs were inhibited in the strong salt stress-treated seedlings but not at the mild salt stress and osmotic stress. Additionally, in 3-week old plants, the injection of the hypo- or hyperosmotic solution at the base of the sunflower stem evoked series of APs (3–24 APs) transmitted along the stem. It has been shown that osmotic and salt stresses modulate differently hypocotyl growth and CN and have an effect on spontaneous and evoked APs in sunflower seedlings. We suggested that potassium, sodium, and chloride ions at stress concentrations in the nutrient medium modulate sunflower excitability and CN. PMID:29093722
Analysis of the AP-42, supplement 5 emission model.

DOT National Transportation Integrated Search

1976-01-01

This report examines the performance of the source strength model presented in the U.S. Environmental Protection Agency publication AP-42, Supplement 5 relative to field data gathered during the AIRPOL project and relative to the previous source stre...
The influence of material anisotropy on vibration at onset in a three-dimensional vocal fold model

PubMed Central

Zhang, Zhaoyan

2014-01-01

Although vocal folds are known to be anisotropic, the influence of material anisotropy on vocal fold vibration remains largely unknown. Using a linear stability analysis, phonation onset characteristics were investigated in a three-dimensional anisotropic vocal fold model. The results showed that isotropic models had a tendency to vibrate in a swing-like motion, with vibration primarily along the superior-inferior direction. Anterior-posterior (AP) out-of-phase motion was also observed and large vocal fold vibration was confined to the middle third region along the AP length. In contrast, increasing anisotropy or increasing AP-transverse stiffness ratio suppressed this swing-like motion and allowed the vocal fold to vibrate in a more wave-like motion with strong medial-lateral motion over the entire medial surface. Increasing anisotropy also suppressed the AP out-of-phase motion, allowing the vocal fold to vibrate in phase along the entire AP length. Results also showed that such improvement in vibration pattern was the most effective with large anisotropy in the cover layer alone. These numerical predictions were consistent with previous experimental observations using self-oscillating physical models. It was further hypothesized that these differences may facilitate complete glottal closure in finite-amplitude vibration of anisotropic models as observed in recent experiments. PMID:24606284
Surfactant protein A (SP-A) inhibits agglomeration and macrophage uptake of toxic amine modified nanoparticles.

PubMed

McKenzie, Zofi; Kendall, Michaela; Mackay, Rose-Marie; Whitwell, Harry; Elgy, Christine; Ding, Ping; Mahajan, Sumeet; Morgan, Cliff; Griffiths, Mark; Clark, Howard; Madsen, Jens

2015-01-01

The lung provides the main route for nanomaterial exposure. Surfactant protein A (SP-A) is an important respiratory innate immune molecule with the ability to bind or opsonise pathogens to enhance phagocytic removal from the airways. We hypothesised that SP-A, like surfactant protein D, may interact with inhaled nanoparticulates, and that this interaction will be affected by nanoparticle (NP) surface characteristics. In this study, we characterise the interaction of SP-A with unmodified (U-PS) and amine-modified (A-PS) polystyrene particles of varying size and zeta potential using dynamic light scatter analysis. SP-A associated with both 100 nm U-PS and A-PS in a calcium-independent manner. SP-A induced significant calcium-dependent agglomeration of 100 nm U-PS NPs but resulted in calcium-independent inhibition of A-PS self agglomeration. SP-A enhanced uptake of 100 nm U-PS into macrophage-like RAW264.7 cells in a dose-dependent manner but in contrast inhibited A-PS uptake. Reduced association of A-PS particles in RAW264.7 cells following pre-incubation of SP-A was also observed with coherent anti-Stokes Raman spectroscopy. Consistent with these findings, alveolar macrophages (AMs) from SP-A(-/-) mice were more efficient at uptake of 100 nm A-PS compared with wild type C57Bl/6 macrophages. No difference in uptake was observed with 500 nm U-PS or A-PS particles. Pre-incubation with SP-A resulted in a significant decrease in uptake of 100 nm A-PS in macrophages isolated from both groups of mice. In contrast, increased uptake by AMs of U-PS was observed after pre-incubation with SP-A. Thus we have demonstrated that SP-A promotes uptake of non-toxic U-PS particles but inhibits the clearance of potentially toxic A-PS particles by blocking uptake into macrophages.
Interaction between the plant ApDef1 defensin and Saccharomyces cerevisiae results in yeast death through a cell cycle- and caspase-dependent process occurring via uncontrolled oxidative stress.

PubMed

Soares, Júlia Ribeiro; José Tenório de Melo, Edésio; da Cunha, Maura; Fernandes, Kátia Valevski Sales; Taveira, Gabriel Bonan; da Silva Pereira, Lidia; Pimenta, Samy; Trindade, Fernanda Gomes; Regente, Mariana; Pinedo, Marcela; de la Canal, Laura; Gomes, Valdirene Moreira; de Oliveira Carvalho, André

2017-01-01

Plant defensins were discovered at beginning of the 90s'; however, their precise mechanism of action is still unknown. Herein, we studied ApDef 1 -Saccharomyces cerevisiae interaction. ApDef 1 -S. cerevisiae interaction was studied by determining the MIC, viability and death kinetic assays. Viability assay was repeated with hydroxyurea synchronized-yeast and pretreated with CCCP. Plasma membrane permeabilization, ROS induction, chromatin condensation, and caspase activation analyses were assessed through Sytox green, DAB, DAPI and FITC-VAD-FMK, respectively. Viability assay was done in presence of ascorbic acid and Z-VAD-FMK. Ultrastructural analysis was done by electron microscopy. ApDef 1 caused S. cerevisiae cell death and MIC was 7.8μM. Whole cell population died after 18h of ApDef 1 interaction. After 3h, 98.76% of synchronized cell population died. Pretreatment with CCCP protected yeast from ApDef 1 induced death. ApDef 1 -S. cerevisiae interaction resulted in membrane permeabilization, H 2 O 2 increased production, chromatin condensation and caspase activation. Ascorbic acid prevented yeast cell death and membrane permeabilization. Z-VAD-FMK prevented yeast cell death. ApDef 1 -S. cerevisiae interaction caused cell death through cell cycle dependentprocess which requires preserved membrane potential. After interaction, yeast went through uncontrolled ROS production and accumulation, which led to plasma membrane permeabilization, chromatin condensation and, ultimately, cell death by activation of caspase-dependent apoptosis via. We show novel requirements for the interaction between plant defensin and fungi cells, i.e. cell cycle phase and membrane potential, and we indicate that membrane permeabilization is probably caused by ROS and therefore, it would be an indirect event of the ApDef 1 -S. cerevisiae interaction. Copyright Â© 2016 Elsevier B.V. All rights reserved.
Low Earth orbit assessment of proton anisotropy using AP8 and AP9 trapped proton models

NASA Astrophysics Data System (ADS)

Badavi, Francis F.; Walker, Steven A.; Santos Koos, Lindsey M.

2015-04-01

The completion of the International Space Station (ISS) in 2011 has provided the space research community with an ideal evaluation and testing facility for future long duration human activities in space. Ionized and secondary neutral particles radiation measurements inside ISS form the ideal tool for validation of radiation environmental models, nuclear reaction cross sections and transport codes. Studies using thermo-luminescent detectors (TLD), tissue equivalent proportional counter (TPEC), and computer aided design (CAD) models of early ISS configurations confirmed that, as input, computational dosimetry at low Earth orbit (LEO) requires an environmental model with directional (anisotropic) capability to properly describe the exposure of trapped protons within ISS. At LEO, ISS encounters exposure from trapped electrons, protons and geomagnetically attenuated galactic cosmic rays (GCR). For short duration studies at LEO, one can ignore trapped electrons and ever present GCR exposure contributions during quiet times. However, within the trapped proton field, a challenge arises from properly estimating the amount of proton exposure acquired. There exist a number of models to define the intensity of trapped particles. Among the established trapped models are the historic AE8/AP8, dating back to the 1980s and the recently released AE9/AP9/SPM. Since at LEO electrons have minimal exposure contribution to ISS, this work ignores the AE8 and AE9 components of the models and couples a measurement derived anisotropic trapped proton formalism to omnidirectional output from the AP8 and AP9 models, allowing the assessment of the differences between the two proton models. The assessment is done at a target point within the ISS-11A configuration (circa 2003) crew quarter (CQ) of Russian Zvezda service module (SM), during its ascending and descending nodes passes through the south Atlantic anomaly (SAA). The anisotropic formalism incorporates the contributions of proton narrow pitch angle (PA) and east-west (EW) effects. Within SAA, the EW anisotropy results in different level of exposure to each side of the ISS Zvezda SM, allowing angular evaluation of the anisotropic proton spectrum. While the combined magnitude of PA and EW effects at LEO depends on a multitude of factors such as trapped proton energy, orientation and altitude of the spacecraft along the velocity vector, this paper draws quantitative conclusions on the combined anisotropic magnitude differences within ISS SM target point between AP8 and AP9 models.
Low Earth orbit assessment of proton anisotropy using AP8 and AP9 trapped proton models.

PubMed

Badavi, Francis F; Walker, Steven A; Santos Koos, Lindsey M

2015-04-01

The completion of the International Space Station (ISS) in 2011 has provided the space research community with an ideal evaluation and testing facility for future long duration human activities in space. Ionized and secondary neutral particles radiation measurements inside ISS form the ideal tool for validation of radiation environmental models, nuclear reaction cross sections and transport codes. Studies using thermo-luminescent detectors (TLD), tissue equivalent proportional counter (TPEC), and computer aided design (CAD) models of early ISS configurations confirmed that, as input, computational dosimetry at low Earth orbit (LEO) requires an environmental model with directional (anisotropic) capability to properly describe the exposure of trapped protons within ISS. At LEO, ISS encounters exposure from trapped electrons, protons and geomagnetically attenuated galactic cosmic rays (GCR). For short duration studies at LEO, one can ignore trapped electrons and ever present GCR exposure contributions during quiet times. However, within the trapped proton field, a challenge arises from properly estimating the amount of proton exposure acquired. There exist a number of models to define the intensity of trapped particles. Among the established trapped models are the historic AE8/AP8, dating back to the 1980s and the recently released AE9/AP9/SPM. Since at LEO electrons have minimal exposure contribution to ISS, this work ignores the AE8 and AE9 components of the models and couples a measurement derived anisotropic trapped proton formalism to omnidirectional output from the AP8 and AP9 models, allowing the assessment of the differences between the two proton models. The assessment is done at a target point within the ISS-11A configuration (circa 2003) crew quarter (CQ) of Russian Zvezda service module (SM), during its ascending and descending nodes passes through the south Atlantic anomaly (SAA). The anisotropic formalism incorporates the contributions of proton narrow pitch angle (PA) and east-west (EW) effects. Within SAA, the EW anisotropy results in different level of exposure to each side of the ISS Zvezda SM, allowing angular evaluation of the anisotropic proton spectrum. While the combined magnitude of PA and EW effects at LEO depends on a multitude of factors such as trapped proton energy, orientation and altitude of the spacecraft along the velocity vector, this paper draws quantitative conclusions on the combined anisotropic magnitude differences within ISS SM target point between AP8 and AP9 models. Copyright © 2015 The Committee on Space Research (COSPAR). All rights reserved.
Taskmaster: A Prototype Graphical User-Interface to a Schedule Optimization Model

DTIC Science & Technology

1990-03-01

34Assimilation Paradox" .. ........................... 42 c. O nline H elp ......................................... 43 C. DIRECT MANIPULATION...advantage of these hardware capabilit’es. As a result of these changes, new markets are developing for a variety of computer apTIications that were once...the 1989 meeting of ORSATIMS. In that paper the authors make the following observation. 8 With traditionally developed systems, the potential market

Hepatoprotective effect of engineered silver nanoparticles coated bioactive compounds against diethylnitrosamine induced hepatocarcinogenesis in experimental mice.

PubMed

Prasannaraj, Govindaraj; Venkatachalam, Perumal

2017-02-01

Nanoparticle based drug delivery can rapidly improves the therapeutic potential of anti-cancer agents. The present study focused to evaluate the hepatoprotective activity of silver nanoparticles (AgNPs) synthesized using aqueous extracts of Andrographis paniculata leaves (ApAgNPs) and Semecarpus anacardium nuts (SaAgNPs) against diethylnitrosamine (DEN) induced liver cancer in mice model. The physico-chemical properties of synthesized AgNPs were characterized by Fourier transform infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), X-ray Diffraction (XRD), Energy Dispersive X-ray (EDX) spectrum, Zeta potential and Dynamic Light Scattering (DLS) analysis. The surface plasmon resonance (SPR) absorption spectrum revealed a strong peak at 420nm for both SaAgNPs and ApAgNPs. FTIR results exhibited the presence of possible functional groups in the synthesized AgNPs. TEM analysis determined the hexagonal, and spherical shape of the synthesized silver nanoparticles. The XRD and SAED pattern confirmed the crystalline nature and crystalline size of the AgNPs. EDX result clearly showed strong silver signals in the range between 2 and 4keV. Zeta potential measurements indicated a sharp peak at -3.93 and -13.8mV for ApAgNPs and SaAgNPs, respectively. DLS measurement expressed the particle size distribution was 70 and 60nm for ApAgNPs and SaAgNPs, respectively. DEN (20mg/kg b.wt.) was subjected to induce liver cancer in mice for 8weeks and treated with biosynthesized silver nanoparticles. Interestingly, ApAgNPs and SaAgNPs treated DEN induced animal groups show a decreased level of aspartate amino transferase (AST), alanine amino transferase (ALT), serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT) activity and elevated level of catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST) and superoxide dismutase (SOD) activity over untreated DEN control animals group. Histopathological investigation reveals decreased fat accumulation, appearance of binucleated cells in nanoparticle treated animals and showed mere normal cells induced by DEN. Argyrophilic nucleolar organiser region (AgNORs) had a significant decrease in number of acidic proteins and mast cells assay showed decrease of metachromatic cells in nanoparticles treated animal groups over control. Present results strongly suggest that biomolecule coated silver nanoparticles exposure showed potential hepatoprotective effect against DEN induced liver cancer and could be used as an effective anticancer nanodrug. Copyright © 2017. Published by Elsevier B.V.
Validation of the new trapped environment AE9/AP9/SPM at low Earth orbit

NASA Astrophysics Data System (ADS)

Badavi, Francis F.

2014-09-01

The completion of the international space station (ISS) in 2011 has provided the space research community an ideal proving ground for future long duration human activities in space. Ionizing radiation measurements in ISS form the ideal tool for the validation of radiation environmental models, nuclear transport codes and nuclear reaction cross sections. Indeed, prior measurements on the space transportation system (STS; shuttle) provided vital information impacting both the environmental models and the nuclear transport code developments by indicating the need for an improved dynamic model of the low Earth orbit (LEO) trapped environment. Additional studies using thermo-luminescent detector (TLD), tissue equivalent proportional counter (TEPC) area monitors, and computer aided design (CAD) model of earlier ISS configurations, confirmed STS observations that, as input, computational dosimetry requires an environmental model with dynamic and directional (anisotropic) behavior, as well as an accurate six degree of freedom (DOF) definition of the vehicle attitude and orientation along the orbit of ISS. At LEO, a vehicle encounters exposure from trapped particles and attenuated galactic cosmic rays (GCR). Within the trapped field, a challenge arises from properly estimating the amount of exposure acquired. There exist a number of models to define the intensities of the trapped particles during the solar quiet and active times. At active times, solar energetic particles (SEP) generated by solar flare or coronal mass ejection (CME) also contribute to the exposure at high northern and southern latitudes. Among the more established trapped models are the historic and popular AE8/AP8, dating back to the 1980s, the historic and less popular CRRES electron/proton, dating back to 1990s and the recently released AE9/AP9/SPM. The AE9/AP9/SPM model is a major improvement over the older AE8/AP8 and CRRES models. This model is derived from numerous measurements acquired over four solar cycles dating back to the 1970s, roughly representing 40 years of data collection. In contrast, the older AE8/AP8 and CRRES models were limited to only a few months of measurements taken during the prior solar minima and maxima. The dual goal of this paper is to first validate the AE8/AP8 and AE9/AP9/SPM trapped models against ISS dosemetric measurements for a silicon based detector, to assess the improvements in the AE9/AP9/SPM model as compared to AE8/AP8 model. The validation is done at selected target points within ISS-6A configuration during its passage through the south Atlantic anomaly (SAA). For such validation, only the isotropic spectrum of either model is needed. As a second goal, the isotropic spectra of both trapped models are re-casted into anisotropic spectra by modulating them with a measurement derived angular formalism which is applicable to trapped protons. Since at LEO electrons have minimal exposure contribution, the paper ignores the AE8 and AE9 component of the models and presents the angular validation of AP8 and AP9 against measurements from the compact environment anomaly sensor (CEASE) science instrument package, flown onboard the tri-service experiment-5 (TSX-5) satellite during the period of June 2000-July 2006. The spin stabilized satellite was flown in a 410 × 1710 km, 69° inclination orbit, allowing it to be exposed to a broad range of LEO regime. Particular emphasize is put on the validation of proton flux profiles at differential 40 MeV and integral >40 MeV, in the vicinity of SAA where protons exhibit east-west (EW) anisotropy and have a relatively narrow pitch angle distribution. Within SAA, the EW anisotropy results in different level of exposure to each side of CEASE instrument package, allowing the extraction of anisotropic proton spectra from the measurements. While the magnitude of the EW effect at LEO depends on a multitude of factors such as trapped proton energy, orientation of the spacecraft along the velocity vector and altitude of the spacecraft, for this part, the paper draws quantitative conclusions on the combined effect of proton pitch angle and EW anomaly.
A comparison of newborn stylized and tomographic models for dose assessment in paediatric radiology

NASA Astrophysics Data System (ADS)

Staton, R. J.; Pazik, F. D.; Nipper, J. C.; Williams, J. L.; Bolch, W. E.

2003-04-01

Establishment of organ doses from diagnostic and interventional examinations is a key component to quantifying the radiation risks from medical exposures and for formulating corresponding dose-reduction strategies. Radiation transport models of human anatomy provide a convenient method for simulating radiological examinations. At present, two classes of models exist: stylized mathematical models and tomographic voxel models. In the present study, organ dose comparisons are made for projection radiographs of both a stylized and a tomographic model of the newborn patient. Sixteen separate radiographs were simulated for each model at x-ray technique factors typical of newborn examinations: chest, abdomen, thorax and head views in the AP, PA, left LAT and right LAT projection orientation. For AP and PA radiographs of the torso (chest, abdomen and thorax views), the effective dose assessed for the tomographic model exceeds that for the stylized model with per cent differences ranging from 19% (AP abdominal view) to 43% AP chest view. In contrast, the effective dose for the stylized model exceeds that for the tomographic model for all eight lateral views including those of the head, with per cent differences ranging from 9% (LLAT chest view) to 51% (RLAT thorax view). While organ positioning differences do exist between the models, a major factor contributing to differences in effective dose is the models' exterior trunk shape. In the tomographic model, a more elliptical shape is seen thus providing for less tissue shielding for internal organs in the AP and PA directions, with corresponding increased tissue shielding in the lateral directions. This observation is opposite of that seen in comparisons of stylized and tomographic models of the adult.
Necroptosis: a potential, promising target and switch in acute pancreatitis.

PubMed

Wang, Gang; Qu, Feng-Zhi; Li, Le; Lv, Jia-Chen; Sun, Bei

2016-02-01

Pancreatic acinar cell death is the major pathophysiological change in early acute pancreatitis (AP), and the death modalities are important factors determining its progression and prognosis. During AP, acinar cells undergo two major modes of death, including necrosis and apoptosis. Acinar necrosis can lead to intensely local and systemic inflammatory responses, which both induce and aggravate the lesion. Necrosis has long been considered an unregulated, and passive cell death process. Since the effective interventions of necrosis are difficult to perform, its relevant studies have not received adequate attention. Necroptosis is a newly discovered cell death modality characterized by both necrosis and apoptosis, i.e., it is actively regulated by special genes, while has the typical morphological features of necrosis. Currently, necroptosis is gradually becoming an important topic in the fields of inflammatory diseases. The preliminary results from necroptosis in AP have confirmed the existence of acinar cell necroptosis, which may be a potential target for effectively regulating inflammatory injuries and improving its outcomes; however, the functional changes and mechanisms of necroptosis still require further investigation. This article reviewed the progress of necroptosis in AP to provide a reference for deeply understanding the pathogenic mechanisms of AP and identifying new therapeutic targets.
Intrinsic excitability changes induced by acute treatment of hippocampal CA1 pyramidal neurons with exogenous amyloid β peptide

PubMed Central

Scullion, Sarah; Brown, Jon T.; Randall, Andrew D.

2015-01-01

ABSTRACT Accumulation of beta‐amyloid (Aβ) peptides in the human brain is a canonical pathological hallmark of Alzheimer's disease (AD). Recent work in Aβ‐overexpressing transgenic mice indicates that increased brain Aβ levels can be associated with aberrant epileptiform activity. In line with this, such mice can also exhibit altered intrinsic excitability (IE) of cortical and hippocampal neurons: these observations may relate to the increased prevalence of seizures in AD patients. In this study, we examined what changes in IE are produced in hippocampal CA1 pyramidal cells after 2–5 h treatment with an oligomeric preparation of synthetic human Aβ 1–42 peptide. Whole cell current clamp recordings were compared between Aβ‐(500 nM) and vehicle‐(DMSO 0.05%) treated hippocampal slices obtained from mice. The soluble Aβ treatment did not produce alterations in sub‐threshold intrinsic properties, including membrane potential, input resistance, and hyperpolarization activated “sag”. Similarly, no changes were noted in the firing profile evoked by 500 ms square current supra‐threshold stimuli. However, Aβ 500 nM treatment resulted in the hyperpolarization of the action potential (AP) threshold. In addition, treatment with Aβ at 500 nM depressed the after‐hyperpolarization that followed both a single AP or 50 Hz trains of a number of APs between 5 and 25. These data suggest that acute exposure to soluble Aβ oligomers affects IE properties of CA1 pyramidal neurons differently from outcomes seen in transgenic models of amyloidopathy. However, in both chronic and acute models, the IE changes are toward hyperexcitability, reinforcing the idea that amyloidopathy and increased incidence in seizures might be causally related in AD patients. © 2014 The Authors Hippocampus Published by Wiley Periodicals, Inc. PMID:25515596
Influence of highly distinctive structural properties on the excitability of pyramidal neurons in monkey visual and prefrontal cortices

PubMed Central

Amatrudo, Joseph M.; Weaver, Christina M.; Crimins, Johanna L.; Hof, Patrick R.; Rosene, Douglas L.; Luebke, Jennifer I.

2012-01-01

Whole-cell patch-clamp recordings and high-resolution 3D morphometric analyses of layer 3 pyramidal neurons in in vitro slices of monkey primary visual cortex (V1) and dorsolateral granular prefrontal cortex (dlPFC) revealed that neurons in these two brain areas possess highly distinctive structural and functional properties. Area V1 pyramidal neurons are much smaller than dlPFC neurons, with significantly less extensive dendritic arbors and far fewer dendritic spines. Relative to dlPFC neurons, V1 neurons have a significantly higher input resistance, depolarized resting membrane potential and higher action potential (AP) firing rates. Most V1 neurons exhibit both phasic and regular-spiking tonic AP firing patterns, while dlPFC neurons exhibit only tonic firing. Spontaneous postsynaptic currents are lower in amplitude and have faster kinetics in V1 than in dlPFC neurons, but are no different in frequency. Three-dimensional reconstructions of V1 and dlPFC neurons were incorporated into computational models containing Hodgkin-Huxley and AMPA- and GABAA-receptor gated channels. Morphology alone largely accounted for observed passive physiological properties, but led to AP firing rates that differed more than observed empirically, and to synaptic responses that opposed empirical results. Accordingly, modeling predicts that active channel conductances differ between V1 and dlPFC neurons. The unique features of V1 and dlPFC neurons are likely fundamental determinants of area-specific network behavior. The compact electrotonic arbor and increased excitability of V1 neurons support the rapid signal integration required for early processing of visual information. The greater connectivity and dendritic complexity of dlPFC neurons likely support higher level cognitive functions including working memory and planning. PMID:23035077
Remodeling of repolarization and arrhythmia susceptibility in a myosin-binding protein C knockout mouse model.

PubMed

Toib, Amir; Zhang, Chen; Borghetti, Giulia; Zhang, Xiaoxiao; Wallner, Markus; Yang, Yijun; Troupes, Constantine D; Kubo, Hajime; Sharp, Thomas E; Feldsott, Eric; Berretta, Remus M; Zalavadia, Neil; Trappanese, Danielle M; Harper, Shavonn; Gross, Polina; Chen, Xiongwen; Mohsin, Sadia; Houser, Steven R

2017-09-01

Hypertrophic cardiomyopathy (HCM) is one of the most common genetic cardiac diseases and among the leading causes of sudden cardiac death (SCD) in the young. The cellular mechanisms leading to SCD in HCM are not well known. Prolongation of the action potential (AP) duration (APD) is a common feature predisposing hypertrophied hearts to SCD. Previous studies have explored the roles of inward Na + and Ca 2+ in the development of HCM, but the role of repolarizing K + currents has not been defined. The objective of this study was to characterize the arrhythmogenic phenotype and cellular electrophysiological properties of mice with HCM, induced by myosin-binding protein C (MyBPC) knockout (KO), and to test the hypothesis that remodeling of repolarizing K + currents causes APD prolongation in MyBPC KO myocytes. We demonstrated that MyBPC KO mice developed severe hypertrophy and cardiac dysfunction compared with wild-type (WT) control mice. Telemetric electrocardiographic recordings of awake mice revealed prolongation of the corrected QT interval in the KO compared with WT control mice, with overt ventricular arrhythmias. Whole cell current- and voltage-clamp experiments comparing KO with WT mice demonstrated ventricular myocyte hypertrophy, AP prolongation, and decreased repolarizing K + currents. Quantitative RT-PCR analysis revealed decreased mRNA levels of several key K + channel subunits. In conclusion, decrease in repolarizing K + currents in MyBPC KO ventricular myocytes contributes to AP and corrected QT interval prolongation and could account for the arrhythmia susceptibility. NEW & NOTEWORTHY Ventricular myocytes isolated from the myosin-binding protein C knockout hypertrophic cardiomyopathy mouse model demonstrate decreased repolarizing K + currents and action potential and QT interval prolongation, linking cellular repolarization abnormalities with arrhythmia susceptibility and the risk for sudden cardiac death in hypertrophic cardiomyopathy. Copyright © 2017 the American Physiological Society.
Frozen lattice and absorptive model for high angle annular dark field scanning transmission electron microscopy: A comparison study in terms of integrated intensity and atomic column position measurement.

PubMed

Alania, M; Lobato, I; Van Aert, S

2018-01-01

In this paper, both the frozen lattice (FL) and the absorptive potential (AP) approximation models are compared in terms of the integrated intensity and the precision with which atomic columns can be located from an image acquired using high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM). The comparison is made for atoms of Cu, Ag, and Au. The integrated intensity is computed for both an isolated atomic column and an atomic column inside an FCC structure. The precision has been computed using the so-called Cramér-Rao Lower Bound (CRLB), which provides a theoretical lower bound on the variance with which parameters can be estimated. It is shown that the AP model results into accurate measurements for the integrated intensity only for small detector ranges under relatively low angles and for small thicknesses. In terms of the attainable precision, both methods show similar results indicating picometer range precision under realistic experimental conditions. Copyright © 2017 Elsevier B.V. All rights reserved.
AP1S3 mutations are associated with pustular psoriasis and impaired Toll-like receptor 3 trafficking.

PubMed

Setta-Kaffetzi, Niovi; Simpson, Michael A; Navarini, Alexander A; Patel, Varsha M; Lu, Hui-Chun; Allen, Michael H; Duckworth, Michael; Bachelez, Hervé; Burden, A David; Choon, Siew-Eng; Griffiths, Christopher E M; Kirby, Brian; Kolios, Antonios; Seyger, Marieke M B; Prins, Christa; Smahi, Asma; Trembath, Richard C; Fraternali, Franca; Smith, Catherine H; Barker, Jonathan N; Capon, Francesca

2014-05-01

Adaptor protein complex 1 (AP-1) is an evolutionary conserved heterotetramer that promotes vesicular trafficking between the trans-Golgi network and the endosomes. The knockout of most murine AP-1 complex subunits is embryonically lethal, so the identification of human disease-associated alleles has the unique potential to deliver insights into gene function. Here, we report two founder mutations (c.11T>G [p.Phe4Cys] and c.97C>T [p.Arg33Trp]) in AP1S3, the gene encoding AP-1 complex subunit σ1C, in 15 unrelated individuals with a severe autoinflammatory skin disorder known as pustular psoriasis. Because the variants are predicted to destabilize the 3D structure of the AP-1 complex, we generated AP1S3-knockdown cell lines to investigate the consequences of AP-1 deficiency in skin keratinocytes. We found that AP1S3 silencing disrupted the endosomal translocation of the innate pattern-recognition receptor TLR-3 (Toll-like receptor 3) and resulted in a marked inhibition of downstream signaling. These findings identify pustular psoriasis as an autoinflammatory phenotype caused by defects in vesicular trafficking and demonstrate a requirement of AP-1 for Toll-like receptor homeostasis. Copyright © 2014 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.
Intestinal Fatty Acid Binding Protein as a Marker of Necrosis and Severity in Acute Pancreatitis.

PubMed

Kupčinskas, Juozas; Gedgaudas, Rolandas; Hartman, Hannes; Sippola, Tomi; Lindström, Outi; Johnson, Colin D; Regnér, Sara

2018-07-01

The aim of this study was to study intestinal fatty acid binding protein (i-FABP) as a potential biomarker in predicting severity of acute pancreatitis (AP). In a prospective multicenter cohort study, plasma levels of i-FABP were measured in 402 patients with AP. Severity of AP was determined based on the 1992 Atlanta Classification. Admission levels of plasma i-FABP were significantly higher in patients with pancreatic necrosis, in patients having systemic complications, in patients treated invasively, in patients treated in the intensive care unit, in patients with severe AP, and in deceased patients. Plasma i-FABP levels on admission yielded an area under curve (AUC) of 0.732 in discriminating patients with or without pancreatic necrosis and AUC of 0.669 in predicting severe AP. Combination of levels of i-FABP and venous lactate on the day of admission showed higher discriminative power in severe AP-AUC of 0.808. Higher i-FABP levels on admission were associated with pancreatic necrosis, systemic complications, and severe AP. Low levels of i-FABP had a high negative predictive value for pancreatic necrosis and severe AP. Combination of levels of i-FABP and venous lactates on admission were superior to either of markers used alone in predicting severe AP.
Amphioxus and lamprey AP-2 genes: implications for neural crest evolution and migration patterns

NASA Technical Reports Server (NTRS)

Meulemans, Daniel; Bronner-Fraser, Marianne

2002-01-01

The neural crest is a uniquely vertebrate cell type present in the most basal vertebrates, but not in cephalochordates. We have studied differences in regulation of the neural crest marker AP-2 across two evolutionary transitions: invertebrate to vertebrate, and agnathan to gnathostome. Isolation and comparison of amphioxus, lamprey and axolotl AP-2 reveals its extensive expansion in the vertebrate dorsal neural tube and pharyngeal arches, implying co-option of AP-2 genes by neural crest cells early in vertebrate evolution. Expression in non-neural ectoderm is a conserved feature in amphioxus and vertebrates, suggesting an ancient role for AP-2 genes in this tissue. There is also common expression in subsets of ventrolateral neurons in the anterior neural tube, consistent with a primitive role in brain development. Comparison of AP-2 expression in axolotl and lamprey suggests an elaboration of cranial neural crest patterning in gnathostomes. However, migration of AP-2-expressing neural crest cells medial to the pharyngeal arch mesoderm appears to be a primitive feature retained in all vertebrates. Because AP-2 has essential roles in cranial neural crest differentiation and proliferation, the co-option of AP-2 by neural crest cells in the vertebrate lineage was a potentially crucial event in vertebrate evolution.
A retrospective, longitudinal study of factors associated with new antipsychotic medication use among recently admitted long-term care residents.

PubMed

Foebel, Andrea; Ballokova, Anna; Wellens, Nathalie I H; Fialova, Daniela; Milisen, Koen; Liperoti, Rosa; Hirdes, John P

2015-10-19

Use of antipsychotic (AP) medications is high and often inappropriate among institutionalized populations. Little is known about the correlates of new AP drug use following admission to long-term care (LTC) settings. This study investigated the frequency and correlates of new AP drug use among newly admitted LTC residents. This longitudinal, retrospective study used data from the interRAI - Nursing Home Minimum Data Set version 2.0 (MDS 2.0) instrument. Data about demographic, clinical and social characteristics, and medication use, were collected in Ontario, Canada, from 2003-2011 by trained nurses. Residents with complete admission and 3-6 month follow-up data were included (N = 47,768). Multivariate logistic regression analyses, stratified by gender, explored correlates of new AP drug use upon admission to LTC. New AP drug users comprised 7 % of the final cohort. Severe cognitive impairment, dementia, and motor agitation were significantly associated with new AP drug use among both sexes. Additionally, behavioural problems, conflicts with staff and reduced social engagement were strong correlates of new AP drug use. Social factors were as strongly associated with new AP drug use after LTC admission as clinical factors. Strategies to prevent the potential misuse of AP drugs upon LTC admission should consider the social determinants of such prescribing.
Shape-selective recognition of DNA abasic sites by metallohelices: inhibition of human AP endonuclease 1

PubMed Central

Malina, Jaroslav; Scott, Peter; Brabec, Viktor

2015-01-01

Loss of a base in DNA leading to creation of an abasic (AP) site leaving a deoxyribose residue in the strand, is a frequent lesion that may occur spontaneously or under the action of various physical and chemical agents. Progress in the understanding of the chemistry and enzymology of abasic DNA largely relies upon the study of AP sites in synthetic duplexes. We report here on interactions of diastereomerically pure metallo–helical ‘flexicate’ complexes, bimetallic triple-stranded ferro-helicates [Fe2(NN-NN)3]4+ incorporating the common NN–NN bis(bidentate) helicand, with short DNA duplexes containing AP sites in different sequence contexts. The results show that the flexicates bind to AP sites in DNA duplexes in a shape-selective manner. They preferentially bind to AP sites flanked by purines on both sides and their binding is enhanced when a pyrimidine is placed in opposite orientation to the lesion. Notably, the Λ-enantiomer binds to all tested AP sites with higher affinity than the Δ-enantiomer. In addition, the binding of the flexicates to AP sites inhibits the activity of human AP endonuclease 1, which is as a valid anticancer drug target. Hence, this finding indicates the potential of utilizing well-defined metallo–helical complexes for cancer chemotherapy. PMID:25940617
Modeling Instruction in AP Physics C: Mechanics and Electricity and Magnetism

ERIC Educational Resources Information Center

Belcher, Nathan Tillman

2017-01-01

This action research study used data from multiple assessments in Mechanics and Electricity and Magnetism to determine the viability of Modeling Instruction as a pedagogy for students in AP Physics C: Mechanics and Electricity and Magnetism. Modeling Instruction is a guided-inquiry approach to teaching science in which students progress through…
Insights into Antimicrobial Peptides from Spiders and Scorpions

PubMed Central

Wang, Xiuqing; Wang, Guangshun

2015-01-01

The venoms of spiders and scorpions contain a variety of chemical compounds. Antimicrobial peptides (AMPs) from these organisms were first discovered in the 1990s. As of May 2015, there were 42 spider’s and 63 scorpion’s AMPs in the Antimicrobial Peptide Database (http://aps.unmc.edu/AP). These peptides have demonstrated broad or narrow-spectrum activities against bacteria, fungi, viruses, and parasites. In addition, they can be toxic to cancer cells, insects and erythrocytes. To provide insight into such an activity spectrum, this article discusses the discovery, classification, structure and activity relationships, bioinformatics analysis, and potential applications of spider and scorpion AMPs. Our analysis reveals that, in the case of linear peptides, spiders use both glycine-rich and helical peptide models for defense, whereas scorpions use two distinct helical peptide models with different amino acid compositions to exert the observed antimicrobial activities and hemolytic toxicity. Our structural bioinformatics study improves the knowledge in the field and can be used to design more selective peptides to combat tumors, parasites, and viruses. PMID:27165405
Characteristics of the isomeric flavonoids apigenin and genistein binding to hemoglobin by spectroscopic methods

NASA Astrophysics Data System (ADS)

Yuan, Jiang-Lan; Liu, Hui; Kang, Xu; Lv, Zhong; Zou, Guo-Lin

2008-11-01

Apigenin (Ap) and genistein (Ge), a couple of isomeric flavonoids with extensive bioactivities, are the most common dietary ingredients. They have been widely investigated due to their potential therapeutic actions for some diseases. In our work, binding characteristics of Ap and Ge to hemoglobin (Hb) were analyzed with fluorescence spectroscopy, circular dichroism (CD) and UV-vis absorption spectroscopy. The results indicated that Ap and Ge caused strong fluorescence quenching of Hb by static quenching mechanism, but their quenching efficiency and mechanisms were different. The binding site n suggested that there was a single binding site in Hb for Ap and Ge. The results of synchronous fluorescence showed that the microenvironment around Tyr residues of Hb had a slight trend of polarity decreasing, but the polarity around Trp residues increased by adding Ap. Results of CD indicated that the Ap and Ge did not changed the secondary structure of Hb. According to the theory of Förster resonance energy transfer, the binding distance r between Trp 37 and Ap/Ge was predicted to be 3.4 nm and 3.32 nm, respectively. The affinity of Ge toward Hb was higher than that of Ap.
Kynurenine–3–monooxygenase inhibition prevents multiple organ failure in rodent models of acute pancreatitis

PubMed Central

Mole, Damian J; Webster, Scott P; Uings, Iain; Zheng, Xiaozhong; Binnie, Margaret; Wilson, Kris; Hutchinson, Jonathan P; Mirguet, Olivier; Walker, Ann; Beaufils, Benjamin; Ancellin, Nicolas; Trottet, Lionel; Bénéton, Véronique; Mowat, Christopher G; Wilkinson, Martin; Rowland, Paul; Haslam, Carl; McBride, Andrew; Homer, Natalie ZM; Baily, James E; Sharp, Matthew GF; Garden, O James; Hughes, Jeremy; Howie, Sarah EM; Holmes, Duncan S; Liddle, John; Iredale, John P

2015-01-01

Acute pancreatitis (AP) is a common and devastating inflammatory condition of the pancreas that is considered to be a paradigm of sterile inflammation leading to systemic multiple organ dysfunction syndrome (MODS) and death1,2 Acute mortality from AP-MODS exceeds 20%3 and for those who survive the initial episode, their lifespan is typically shorter than the general population4. There are no specific therapies available that protect individuals against AP-MODS. Here, we show that kynurenine-3-monooxygenase (KMO), a key enzyme of tryptophan metabolism5, is central to the pathogenesis of AP-MODS. We created a mouse strain deficient for Kmo with a robust biochemical phenotype that protected against extrapancreatic tissue injury to lung, kidney and liver in experimental AP-MODS. A medicinal chemistry strategy based on modifications of the kynurenine substrate led to the discovery of GSK180 as a potent and specific inhibitor of KMO. The binding mode of the inhibitor in the active site was confirmed by X-ray co-crystallography at 3.2 Å resolution. Treatment with GSK180 resulted in rapid changes in levels of kynurenine pathway metabolites in vivo and afforded therapeutic protection against AP-MODS in a rat model of AP. Our findings establish KMO inhibition as a novel therapeutic strategy in the treatment of AP-MODS and open up a new area for drug discovery in critical illness. PMID:26752518
Acute Lipotoxicity Regulates Severity of Biliary Acute Pancreatitis without Affecting Its Initiation

PubMed Central

Durgampudi, Chandra; Noel, Pawan; Patel, Krutika; Cline, Rachel; Trivedi, Ram N.; DeLany, James P.; Yadav, Dhiraj; Papachristou, Georgios I.; Lee, Kenneth; Acharya, Chathur; Jaligama, Deepthi; Navina, Sarah; Murad, Faris; Singh, Vijay P.

2015-01-01

Obese patients have worse outcomes during acute pancreatitis (AP). Previous animal models of AP have found worse outcomes in obese rodents who may have a baseline proinflammatory state. Our aim was to study the role of acute lipolytic generation of fatty acids on local severity and systemic complications of AP. Human postpancreatitis necrotic collections were analyzed for unsaturated fatty acids (UFAs) and saturated fatty acids. A model of biliary AP was designed to replicate the human variables by intraductal injection of the triglyceride glyceryl trilinoleate alone or with the chemically distinct lipase inhibitors orlistat or cetilistat. Parameters of AP etiology and outcomes of local and systemic severity were measured. Patients with postpancreatitis necrotic collections were obese, and 13 of 15 had biliary AP. Postpancreatitis necrotic collections were enriched in UFAs. Intraductal glyceryl trilinoleate with or without the lipase inhibitors resulted in oil red O–positive areas, resembling intrapancreatic fat. Both lipase inhibitors reduced the glyceryl trilinoleate–induced increase in serum lipase, UFAs, pancreatic necrosis, serum inflammatory markers, systemic injury, and mortality but not serum alanine aminotransferase, bilirubin, or amylase. We conclude that UFAs are enriched in human necrotic collections and acute UFA generation via lipolysis worsens pancreatic necrosis, systemic inflammation, and injury associated with severe AP. Inhibition of lipolysis reduces UFA generation and improves these outcomes of AP without interfering with its induction. PMID:24854864
Mechanism underlying impaired cardiac pacemaking rhythm during ischemia: A simulation study

NASA Astrophysics Data System (ADS)

Bai, Xiangyun; Wang, Kuanquan; Yuan, Yongfeng; Li, Qince; Dobrzynski, Halina; Boyett, Mark R.; Hancox, Jules C.; Zhang, Henggui

2017-09-01

Ischemia in the heart impairs function of the cardiac pacemaker, the sinoatrial node (SAN). However, the ionic mechanisms underlying the ischemia-induced dysfunction of the SAN remain elusive. In order to investigate the ionic mechanisms by which ischemia causes SAN dysfunction, action potential models of rabbit SAN and atrial cells were modified to incorporate extant experimental data of ischemia-induced changes to membrane ion channels and intracellular ion homeostasis. The cell models were incorporated into an anatomically detailed 2D model of the intact SAN-atrium. Using the multi-scale models, the functional impact of ischemia-induced electrical alterations on cardiac pacemaking action potentials (APs) and their conduction was investigated. The effects of vagal tone activity on the regulation of cardiac pacemaker activity in control and ischemic conditions were also investigated. The simulation results showed that at the cellular level ischemia slowed the SAN pacemaking rate, which was mainly attributable to the altered Na+-Ca2+ exchange current and the ATP-sensitive potassium current. In the 2D SAN-atrium tissue model, ischemia slowed down both the pacemaking rate and the conduction velocity of APs into the surrounding atrial tissue. Simulated vagal nerve activity, including the actions of acetylcholine in the model, amplified the effects of ischemia, leading to possible SAN arrest and/or conduction exit block, which are major features of the sick sinus syndrome. In conclusion, this study provides novel insights into understanding the mechanisms by which ischemia alters SAN function, identifying specific conductances as contributors to bradycardia and conduction block.
Anticancer kinase inhibitors impair intracellular viral trafficking and exert broad-spectrum antiviral effects.

PubMed

Bekerman, Elena; Neveu, Gregory; Shulla, Ana; Brannan, Jennifer; Pu, Szu-Yuan; Wang, Stanley; Xiao, Fei; Barouch-Bentov, Rina; Bakken, Russell R; Mateo, Roberto; Govero, Jennifer; Nagamine, Claude M; Diamond, Michael S; De Jonghe, Steven; Herdewijn, Piet; Dye, John M; Randall, Glenn; Einav, Shirit

2017-04-03

Global health is threatened by emerging viral infections, which largely lack effective vaccines or therapies. Targeting host pathways that are exploited by multiple viruses could offer broad-spectrum solutions. We previously reported that AAK1 and GAK, kinase regulators of the host adaptor proteins AP1 and AP2, are essential for hepatitis C virus (HCV) infection, but the underlying mechanism and relevance to other viruses or in vivo infections remained unknown. Here, we have discovered that AP1 and AP2 cotraffic with HCV particles in live cells. Moreover, we found that multiple viruses, including dengue and Ebola, exploit AAK1 and GAK during entry and infectious virus production. In cultured cells, treatment with sunitinib and erlotinib, approved anticancer drugs that inhibit AAK1 or GAK activity, or with more selective compounds inhibited intracellular trafficking of HCV and multiple unrelated RNA viruses with a high barrier to resistance. In murine models of dengue and Ebola infection, sunitinib/erlotinib combination protected against morbidity and mortality. We validated sunitinib- and erlotinib-mediated inhibition of AAK1 and GAK activity as an important mechanism of antiviral action. Additionally, we revealed potential roles for additional kinase targets. These findings advance our understanding of virus-host interactions and establish a proof of principle for a repurposed, host-targeted approach to combat emerging viruses.

Anticancer kinase inhibitors impair intracellular viral trafficking and exert broad-spectrum antiviral effects

PubMed Central

Bekerman, Elena; Shulla, Ana; Brannan, Jennifer; Wang, Stanley; Barouch-Bentov, Rina; Bakken, Russell R.; Mateo, Roberto; Govero, Jennifer; Nagamine, Claude M.; Diamond, Michael S.; De Jonghe, Steven; Herdewijn, Piet; Dye, John M.; Randall, Glenn

2017-01-01

Global health is threatened by emerging viral infections, which largely lack effective vaccines or therapies. Targeting host pathways that are exploited by multiple viruses could offer broad-spectrum solutions. We previously reported that AAK1 and GAK, kinase regulators of the host adaptor proteins AP1 and AP2, are essential for hepatitis C virus (HCV) infection, but the underlying mechanism and relevance to other viruses or in vivo infections remained unknown. Here, we have discovered that AP1 and AP2 cotraffic with HCV particles in live cells. Moreover, we found that multiple viruses, including dengue and Ebola, exploit AAK1 and GAK during entry and infectious virus production. In cultured cells, treatment with sunitinib and erlotinib, approved anticancer drugs that inhibit AAK1 or GAK activity, or with more selective compounds inhibited intracellular trafficking of HCV and multiple unrelated RNA viruses with a high barrier to resistance. In murine models of dengue and Ebola infection, sunitinib/erlotinib combination protected against morbidity and mortality. We validated sunitinib- and erlotinib-mediated inhibition of AAK1 and GAK activity as an important mechanism of antiviral action. Additionally, we revealed potential roles for additional kinase targets. These findings advance our understanding of virus-host interactions and establish a proof of principle for a repurposed, host-targeted approach to combat emerging viruses. PMID:28240606
Acute pancreatitis with gradient echo T2*-weighted magnetic resonance imaging

PubMed Central

Tang, Meng Yue; Chen, Tian Wu; Huang, Xiao Hua; Li, Xing Hui; Wang, Si Yue; Liu, Nian

2016-01-01

Background To study gradient recalled echo (GRE) T2*-weighted imaging (T2*WI) for normal pancreas and acute pancreatitis (AP). Methods Fifty-one patients without any pancreatic disorders (control group) and 117 patients with AP were recruited. T2* values derived from T2*WI of the pancreas were measured for the two groups. The severity of AP was graded by the magnetic resonance severity index (MRSI) and the Acute Physiology and Chronic Healthy Evaluation II (APACHE II) scoring system. Logistic regression was used to analyze the relationship between the T2* values and AP severity. The usefulness of the T2* value for diagnosing AP and the relationship between the T2* values and the severity of AP were analyzed. Results On GRE-T2*WI, the normal pancreas showed a well-marinated and consistently homogeneous isointensity. Edematous AP, as well as the non-necrotic area in necrotizing AP, showed ill-defined but homogeneous signal intensity. AP with pancreatic hemorrhage showed a decreased T2* value and a signal loss on the signal decay curve. The T2* value of pancreas in the AP group was higher than that of the control group (t=−8.20, P<0.05). The T2* value tended to increase along with the increase in MRSI scores but not with the APACHE II scores (P>0.05). AP was associated with a one standard deviation increment in the T2* value (OR =1.37; 95% CI: 1.216–1.532). Conclusions T2*WI demonstrates a few characteristics of the normal pancreas and AP, which could potentially be helpful for detecting hemorrhage, and contributes to diagnosing AP and its severity. PMID:27190768
Engagement with the auditory processing system during targeted auditory cognitive training mediates changes in cognitive outcomes in individuals with schizophrenia.

PubMed

Biagianti, Bruno; Fisher, Melissa; Neilands, Torsten B; Loewy, Rachel; Vinogradov, Sophia

2016-11-01

Individuals with schizophrenia who engage in targeted cognitive training (TCT) of the auditory system show generalized cognitive improvements. The high degree of variability in cognitive gains maybe due to individual differences in the level of engagement of the underlying neural system target. 131 individuals with schizophrenia underwent 40 hours of TCT. We identified target engagement of auditory system processing efficiency by modeling subject-specific trajectories of auditory processing speed (APS) over time. Lowess analysis, mixed models repeated measures analysis, and latent growth curve modeling were used to examine whether APS trajectories were moderated by age and illness duration, and mediated improvements in cognitive outcome measures. We observed significant improvements in APS from baseline to 20 hours of training (initial change), followed by a flat APS trajectory (plateau) at subsequent time-points. Participants showed interindividual variability in the steepness of the initial APS change and in the APS plateau achieved and sustained between 20 and 40 hours. We found that participants who achieved the fastest APS plateau, showed the greatest transfer effects to untrained cognitive domains. There is a significant association between an individual's ability to generate and sustain auditory processing efficiency and their degree of cognitive improvement after TCT, independent of baseline neurocognition. APS plateau may therefore represent a behavioral measure of target engagement mediating treatment response. Future studies should examine the optimal plateau of auditory processing efficiency required to induce significant cognitive improvements, in the context of interindividual differences in neural plasticity and sensory system efficiency that characterize schizophrenia. (PsycINFO Database Record (c) 2016 APA, all rights reserved).
Proteinase-activated receptor-4 evoked colorectal analgesia in mice: an endogenously activated feed-back loop in visceral inflammatory pain.

PubMed

Annaházi, A; Dabek, M; Gecse, K; Salvador-Cartier, C; Polizzi, A; Rosztóczy, A; Róka, R; Theodorou, V; Wittmann, T; Bueno, L; Eutamene, H

2012-01-01

Activation of proteinase-activated receptor-4 (PAR-4) from the colonic lumen has an antinociceptive effect to colorectal distension (CRD) in mice in basal conditions. We aimed to determine the functional localization of the responsible receptors and to test their role in two different hyperalgesia models. Mice received PAR-4 activating peptide (PAR-4-AP, AYPGKF-NH(2)) or vehicle intraperitoneally (IP), and abdominal EMG response to CRD was measured. The next group received PAR-4-AP intracolonically (IC) with or without 2,4,6-triaminopyrimidine, a chemical tight junction blocker, before CRD. The SCID mice were used to test the role of lymphocytes in the antihyperalgesic effect. The effects of PAR-4-AP and PAR-4-antagonist (P4pal-10) were evaluated in water avoidance stress (WAS) model and low grade 2,4,6-trinitrobenzene sulfonic acid (TNBS) colitis. Spinal Fos protein expression was visualized by immunohistochemistry. The antinociceptive effect of PAR-4-AP disappeared when was administrered IP, or with the blockade of colonic epithelial tight junctions, suggesting that PAR-4-AP needs to reach directly the nerve terminals in the colon. The CRD-induced spinal Fos overexpression was reduced by 43% by PAR-4-AP. The PAR-4-AP was antihyperalgesic in both hyperalgesia models and in mice with impaired lymphocytes. The PAR-4-antagonist significantly increased the TNBS, but not the WAS-induced colonic hyperalgesia. The antinociceptive effect of PAR-4-AP depends on its penetration to the colonic mucosa. The PAR-4 activation is endogenously involved as a feedback loop to attenuate inflammatory colonic hyperalgesia to CRD. © 2011 Blackwell Publishing Ltd.
Advanced Placement Course Enrollment and School-Level Characteristics

ERIC Educational Resources Information Center

Barnard-Brak, Lucy; McGaha-Garnett, Valerie; Burley, Hansel

2011-01-01

The current study examined access to Advanced Placement (AP) courses as a function of these school characteristics (e.g., percentage of ethnic minority and lower socioeconomic status) and then examined AP course enrollment as a function of both access to AP courses and these school characteristics. Using structural equation modeling techniques,…
Pitch and Plasticity: Insights from the Pitch Matching of Chords by Musicians with Absolute and Relative Pitch

PubMed Central

McLachlan, Neil M.; Marco, David J. T.; Wilson, Sarah J.

2013-01-01

Absolute pitch (AP) is a form of sound recognition in which musical note names are associated with discrete musical pitch categories. The accuracy of pitch matching by non-AP musicians for chords has recently been shown to depend on stimulus familiarity, pointing to a role of spectral recognition mechanisms in the early stages of pitch processing. Here we show that pitch matching accuracy by AP musicians was also dependent on their familiarity with the chord stimulus. This suggests that the pitch matching abilities of both AP and non-AP musicians for concurrently presented pitches are dependent on initial recognition of the chord. The dual mechanism model of pitch perception previously proposed by the authors suggests that spectral processing associated with sound recognition primes waveform processing to extract stimulus periodicity and refine pitch perception. The findings presented in this paper are consistent with the dual mechanism model of pitch, and in the case of AP musicians, the formation of nominal pitch categories based on both spectral and periodicity information. PMID:24961624
[Inhibitory effect and the mechanism of Astragalus polysaccharide combined with cisplatin on growth of inplanted Lewis lung carcinoma in mice].

PubMed

Zhuang, Mengjie; Liu, Dan; Chen, Yanwen; Ming, Haixia; Li, Yang

2017-04-01

Objective To observe the effect of Astragalus polysaccharides (APS) combined with cisplatin (DDP) on the expressions of cytochrome C (CytC) and high temperature required serine protease A2 (Omi/HtrA2) in the mice with Lewis lung carcinoma (LLC) transplantated tumors. Methods Ninty C57BL/6J mice were randomly divided into normal control group, model group, and (50, 100, 200) μg/mL APS groups, 6 mg/kg DDP group, 3 mg/kg DDP combined with (50, 100, 200) μg/mL APS groups. Each group included 10 mice. Except the mice in the normal group, the rest mice were inoculated subcutaneously with LLC cells (1×10 7 mL) at the right fore axillary fossa to establish tumor-bearing mouse models. In the second day of building models, the mice in the treatment group were given intraperitoneal injection of 0.3 mL of the drug. DDP was given once a week, and the other drugs once a day. The mice in the normal group and the model group were administrated the same amount of saline injection for continuous 20 days. All mice were killed at the 21st day. The pathological changes of tumor tissues were observed by HE staining. The expressions and location of CytC and Omi/HtrA2 proteins in the transplanted tumor tissues were detected by immunohistochemical staining and image analysis. Results The mass of tumor decreased in the mice of (100, 200) μg/mL APS group and 3 mg/kg DDP combined with (100, 200) μg/mL APS group. Compared with the model group, the necrosis of tumor tissues in 200 μg/mL APS combined with 3 mg/kg DDP group was the most obvious. The expressions of CytC and Omi/HtrA2 increased in the treatment groups, and the increase was the most remarkable in 200 μg/mL APS combined with 3 mg/kg DDP group. Conclusion APS and APS combined with DDP can restrain the growth of Lewis Lung cancer in C57BL/6J mice, which may be related to the increased expressions of CytC and Omi/HtrA2.
The role of extracellular conductivity profiles in compartmental models for neurons: particulars for layer 5 pyramidal cells.

PubMed

Wang, Kai; Riera, Jorge; Enjieu-Kadji, Herve; Kawashima, Ryuta

2013-07-01

With the rapid increase in the number of technologies aimed at observing electric activity inside the brain, scientists have felt the urge to create proper links between intracellular- and extracellular-based experimental approaches. Biophysical models at both physical scales have been formalized under assumptions that impede the creation of such links. In this work, we address this issue by proposing a multicompartment model that allows the introduction of complex extracellular and intracellular resistivity profiles. This model accounts for the geometrical and electrotonic properties of any type of neuron through the combination of four devices: the integrator, the propagator, the 3D connector, and the collector. In particular, we applied this framework to model the tufted pyramidal cells of layer 5 (PCL5) in the neocortex. Our model was able to reproduce the decay and delay curves of backpropagating action potentials (APs) in this type of cell with better agreement with experimental data. We used the voltage drops of the extracellular resistances at each compartment to approximate the local field potentials generated by a PCL5 located in close proximity to linear microelectrode arrays. Based on the voltage drops produced by backpropagating APs, we were able to estimate the current multipolar moments generated by a PCL5. By adding external current sources in parallel to the extracellular resistances, we were able to create a sensitivity profile of PCL5 to electric current injections from nearby microelectrodes. In our model for PCL5, the kinetics and spatial profile of each ionic current were determined based on a literature survey, and the geometrical properties of these cells were evaluated experimentally. We concluded that the inclusion of the extracellular space in the compartmental models of neurons as an extra electrotonic medium is crucial for the accurate simulation of both the propagation of the electric potentials along the neuronal dendrites and the neuronal reactivity to an electrical stimulation using external microelectrodes.
The effects of tissue-non-specific alkaline phosphatase gene therapy on craniosynostosis and craniofacial morphology in the FGFR2C342Y/+ mouse model of Crouzon craniosynostosis.

PubMed

Wang, E; Nam, H K; Liu, J; Hatch, N E

2015-04-01

Craniosynostosis, the premature fusion of cranial bones, has traditionally been described as a disease of increased bone mineralization. However, multiple mouse models of craniosynostosis display craniosynostosis simultaneously with diminished cranial bone volume and/or density. We propose an alternative hypothesis that craniosynostosis results from abnormal tissue mineralization through the downregulation of tissue-non-specific alkaline phosphatase (TNAP) enzyme downstream of activating mutations in FGFRs. Neonatal Crouzon (FGFRC342Y/+) and wild-type (FGFR+/+) mice were injected with lentivirus to deliver a recombinant form of TNAP. Mice were sacrificed at 4 weeks postnatal. Serum was collected to test for alkaline phosphatase (AP), phosphorus, and calcium levels. Craniofacial bone fusion and morphology were assessed by micro-computed tomography. Injection with the TNAP lentivirus significantly increased serum AP levels (increased serum AP levels are indicative of efficient transduction and production of the recombinant protein), but results were variable and dependent upon viral lot and the litter of mice injected. Morphological analysis revealed craniofacial form differences for inferior surface (p=0.023) and cranial height (p=0.014) regions between TNAP lentivirus-injected and vehicle-injected Crouzon mice. With each unit increase in AP level, the odds of lambdoid suture fusion decreased by 84.2% and these results came close to statistical significance (p=0.068). These results suggest that TNAP deficiency may mediate FGFR2-associated craniosynostosis. Future studies should incorporate injection of recombinant TNAP protein, to avoid potential side effects and variable efficacy of lentiviral gene delivery. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
Simple Analytic Collisional Rates for non-LTE Vibrational Populations in Astrophysical Environments: the Cases of Circumstellar SiO Masers and Shocked H2

NASA Astrophysics Data System (ADS)

Bieniek, Ronald

2008-05-01

Rates for collisionally induced transitions between molecular vibrational levels are important in modeling a variety of non-LTE processes in astrophysical environments. Two examples are SiO masering in circumstellar envelopes in certain late-type stars [1] and the vibrational populations of molecular hydrogen in shocked interstellar medium [cf 2]. A simple exponential-potential model of molecular collisions leads to a two-parameter analytic expression for state-to-state and thermally averaged rates for collisionally induced vibrational-translational (VT) transitions in diatomic molecules [3,4]. The thermally averaged rates predicted by this formula have been shown to be in excellent numerical agreement with absolute experimental and quantum mechanical rates over large temperature ranges and initial vibrational excitation levels in a variety of species, e.g., OH, O2, N2 [3] and even for the rate of H2(v=1)+H2, which changes by five orders of magnitude in the temperature range 50-2000 K [4]. Analogous analytic rates will be reported for vibrational transitions in SiO due to collisions with H2 and compared to the numerical fit of quantum-mechanical rates calculated by Bieniek and Green [5]. [1] Palov, A.P., Gray, M.D., Field, D., & Balint-Kurti, G.G. 2006, ApJ, 639, 204. [2] Flower, D. 2007, Molecular Collisions in the Interstellar Medium (Cambridge: Cambridge Univ. Press) [3] Bieniek, R.J. & Lipson, S.J. 1996, Chem. Phys. Lett. 263, 276. [4] Bieniek, R.J. 2006, Proc. NASA LAW (Lab. Astrophys. Workshop) 2006, 299; http://www.physics.unlv.edu/labastro/nasalaw2006proceedings.pdf. [5] Bieniek, R.J., & Green, S. 1983, ApJ, 265, L29 and 1983, ApJ, 270, L101.
Cellular Mechanism Underlying Hypothermia-Induced VT/VF in the Setting of Early Repolarization and the Protective Effect of Quinidine, Cilostazol and Milrinone

PubMed Central

Gurabi, Zsolt; Koncz, István; Patocskai, Bence; Nesterenko, Vladislav V.; Antzelevitch, Charles

2014-01-01

Background Hypothermia has been reported to induce ventricular tachycardia and fibrillation (VT/VF) in patients with early repolarization (ER) pattern. This study examines the cellular mechanisms underlying VT/VF associated with hypothermia in an experimental model of ER syndrome (ERS) and examines the effectiveness of quinidine, cilostazol and milrinone to prevent hypothermia-induced arrhythmias. Method and Results Transmembrane action potentials (AP) were simultaneously recorded from 2 epicardial and 1 endocardial site of coronary-perfused canine left-ventricular wedge preparations, together with a pseudo-ECG. A combination of NS5806 (3–10 µM) and verapamil (1µM) was used to pharmacologically model the genetic mutations responsible for ERS. Acetylcholine (3µM) was used to simulate increased parasympathetic tone, which is known to promote ER. In control, lowering the temperature of the coronary perfusate to induce mild hypothermia (32°C-34°C) resulted in increased J wave area on the ECG and accentuated epicardial AP notch but no arrhythmic activity. In the setting of ER, hypothermia caused further accentuation of the epicardial AP notch, leading to loss of the AP dome at some sites but not others, thus creating the substrate for development of phase-2-reentry and VT/VF. Addition of the Ito antagonist quinidine (5 µM) or the phosphodiesterase III inhibitors cilostazol (10 µM) or milrinone (5 µM), diminished the ER manifestations and prevented the hypothermia-induced phase 2 reentry and VT/VF. Conclusions Hypothermia leads to VT/VF in the setting of ER by exaggerating repolarization abnormalities, leading to development of phase-2-reentry. Quinidine, cilostazol and milrinone suppress the hypothermia-induced VT/VF by reversing the repolarization abnormalities. PMID:24429494
Long-term exposure to transportation noise and air pollution in relation to incident diabetes in the SAPALDIA study

PubMed Central

Eze, Ikenna C; Foraster, Maria; Schaffner, Emmanuel; Vienneau, Danielle; Héritier, Harris; Rudzik, Franziska; Thiesse, Laurie; Pieren, Reto; Imboden, Medea; von Eckardstein, Arnold; Schindler, Christian; Brink, Mark; Cajochen, Christian; Wunderli, Jean-Marc; Röösli, Martin; Probst-Hensch, Nicole

2017-01-01

Abstract Background Epidemiological studies have inconsistently linked transportation noise and air pollution (AP) with diabetes risk. Most studies have considered single noise sources and/or AP, but none has investigated their mutually independent contributions to diabetes risk. Methods We investigated 2631 participants of the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA), without diabetes in 2002 and without change of residence between 2002 and 2011. Using questionnaire and biomarker data, incident diabetes cases were identified in 2011. Noise and AP exposures in 2001 were assigned to participants’ residences (annual average road, railway or aircraft noise level during day-evening-night (Lden), total night number of noise events, intermittency ratio (temporal variation as proportion of event-based noise level over total noise level) and nitrogen dioxide (NO2) levels. We applied mixed Poisson regression to estimate the relative risk (RR) of diabetes and their 95% confidence intervals (CI) in mutually-adjusted models. Results Diabetes incidence was 4.2%. Median [interquartile range (IQR)] road, railway, aircraft noise and NO2 were 54 (10) dB, 32 (11) dB, 30 (12) dB and 21 (15) μg/m3, respectively. Lden road and aircraft were associated with incident diabetes (respective RR: 1.35; 95% CI: 1.02–1.78 and 1.86; 95% CI: 0.96–3.59 per IQR) independently of Lden railway and NO2 (which were not associated with diabetes risk) in mutually adjusted models. We observed stronger effects of Lden road among participants reporting poor sleep quality or sleeping with open windows. Conclusions Transportation noise may be more relevant than AP in the development of diabetes, potentially acting through noise-induced sleep disturbances. PMID:28338949
Tolerogenic β2-glycoprotein I DNA vaccine and FK506 as an adjuvant attenuates experimental obstetric antiphospholipid syndrome.

PubMed

Chao, Ya-Hsuan; Chen, Der-Yuan; Lan, Joung-Liang; Tang, Kuo-Tung; Lin, Chi-Chien

2018-01-01

DNA vaccines have recently emerged as a therapeutic agent for treating autoimmune diseases, such as multiple sclerosis. Antiphospholipid antibody syndrome (APS) is an autoimmune disease characterized by β2-glycoprotein I (β2-GPI)-targeting antiphospholipid antibodies (APAs) and vascular thrombosis or obstetrical complications. To examine the therapeutic potential of a β2-GPI DNA vaccine, we administered a vaccine mixed with FK506 as an adjuvant to a mouse model of obstetric APS. First, the pCMV3-β2-GPI DNA vaccine, which encodes the full-length human β2-GPI gene, was constructed. Then, we administered the β2-GPI DNA vaccine in 0.1 ml of saline, mixed with or without 100 μg of FK506, intramuscularly to the mice on days 28, 35 and 42. Blood titers of the anti-β2-GPI antibody, platelet counts, activated partial thromboplastin times (aPTTs), and the percentage of fetal loss were measured. We also stimulated murine splenic T cells ex vivo with β2-GPI and determined the T helper cell proportion and cytokine secretion. The administration of the β2-GPI DNA vaccine mixed with FK506 reduced the blood IgG anti-β2-GPI antibody titers and suppressed APS manifestations in mice. The combination also suppressed interferon-γ and interleukin (IL)-17A secretion but increased the Treg cell proportion and IL-10 secretion in murine splenic T cells following ex vivo stimulation with β2-GPI. Our results demonstrated the therapeutic efficacy of a β2-GPI DNA vaccine and FK506 as an adjuvant in a murine model of obstetric APS. Possible mechanisms include the inhibition of Th1 and Th17 responses and the up-regulation of Treg cells.
Tolerogenic β2-glycoprotein I DNA vaccine and FK506 as an adjuvant attenuates experimental obstetric antiphospholipid syndrome

PubMed Central

Chen, Der-Yuan; Lan, Joung-Liang; Tang, Kuo-Tung; Lin, Chi-Chien

2018-01-01

DNA vaccines have recently emerged as a therapeutic agent for treating autoimmune diseases, such as multiple sclerosis. Antiphospholipid antibody syndrome (APS) is an autoimmune disease characterized by β2-glycoprotein I (β2-GPI)-targeting antiphospholipid antibodies (APAs) and vascular thrombosis or obstetrical complications. To examine the therapeutic potential of a β2-GPI DNA vaccine, we administered a vaccine mixed with FK506 as an adjuvant to a mouse model of obstetric APS. First, the pCMV3-β2-GPI DNA vaccine, which encodes the full-length human β2-GPI gene, was constructed. Then, we administered the β2-GPI DNA vaccine in 0.1 ml of saline, mixed with or without 100 μg of FK506, intramuscularly to the mice on days 28, 35 and 42. Blood titers of the anti-β2-GPI antibody, platelet counts, activated partial thromboplastin times (aPTTs), and the percentage of fetal loss were measured. We also stimulated murine splenic T cells ex vivo with β2-GPI and determined the T helper cell proportion and cytokine secretion. The administration of the β2-GPI DNA vaccine mixed with FK506 reduced the blood IgG anti-β2-GPI antibody titers and suppressed APS manifestations in mice. The combination also suppressed interferon-γ and interleukin (IL)-17A secretion but increased the Treg cell proportion and IL-10 secretion in murine splenic T cells following ex vivo stimulation with β2-GPI. Our results demonstrated the therapeutic efficacy of a β2-GPI DNA vaccine and FK506 as an adjuvant in a murine model of obstetric APS. Possible mechanisms include the inhibition of Th1 and Th17 responses and the up-regulation of Treg cells. PMID:29894515
Long-term exposure to transportation noise and air pollution in relation to incident diabetes in the SAPALDIA study.

PubMed

Eze, Ikenna C; Foraster, Maria; Schaffner, Emmanuel; Vienneau, Danielle; Héritier, Harris; Rudzik, Franziska; Thiesse, Laurie; Pieren, Reto; Imboden, Medea; von Eckardstein, Arnold; Schindler, Christian; Brink, Mark; Cajochen, Christian; Wunderli, Jean-Marc; Röösli, Martin; Probst-Hensch, Nicole

2017-08-01

Epidemiological studies have inconsistently linked transportation noise and air pollution (AP) with diabetes risk. Most studies have considered single noise sources and/or AP, but none has investigated their mutually independent contributions to diabetes risk. We investigated 2631 participants of the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA), without diabetes in 2002 and without change of residence between 2002 and 2011. Using questionnaire and biomarker data, incident diabetes cases were identified in 2011. Noise and AP exposures in 2001 were assigned to participants' residences (annual average road, railway or aircraft noise level during day-evening-night (Lden), total night number of noise events, intermittency ratio (temporal variation as proportion of event-based noise level over total noise level) and nitrogen dioxide (NO2) levels. We applied mixed Poisson regression to estimate the relative risk (RR) of diabetes and their 95% confidence intervals (CI) in mutually-adjusted models. Diabetes incidence was 4.2%. Median [interquartile range (IQR)] road, railway, aircraft noise and NO2 were 54 (10) dB, 32 (11) dB, 30 (12) dB and 21 (15) μg/m3, respectively. Lden road and aircraft were associated with incident diabetes (respective RR: 1.35; 95% CI: 1.02-1.78 and 1.86; 95% CI: 0.96-3.59 per IQR) independently of Lden railway and NO2 (which were not associated with diabetes risk) in mutually adjusted models. We observed stronger effects of Lden road among participants reporting poor sleep quality or sleeping with open windows. Transportation noise may be more relevant than AP in the development of diabetes, potentially acting through noise-induced sleep disturbances. © The Author 2017. Published by Oxford University Press on behalf of the International Epidemiological Association
Contribution of delayed rectifier potassium currents to the electrical activity of murine colonic smooth muscle

PubMed Central

Koh, S D; Ward, S M; Dick, G M; Epperson, A; Bonner, H P; Sanders, K M; Horowitz, B; Kenyon, J L

1999-01-01

We used intracellular microelectrodes to record the membrane potential (Vm) of intact murine colonic smooth muscle. Electrical activity consisted of spike complexes separated by quiescent periods (Vm≈−60 mV). The spike complexes consisted of about a dozen action potentials of approximately 30 mV amplitude. Tetraethylammonium (TEA, 1–10 mM) had little effect on the quiescent periods but increased the amplitude of the action potential spikes. 4-Aminopyridine (4-AP, ⋧ 5 mM) caused continuous spiking.Voltage clamp of isolated myocytes identified delayed rectifier K+ currents that activated rapidly (time to half-maximum current, 11.5 ms at 0 mV) and inactivated in two phases (τf = 96 ms, τs = 1.5 s at 0 mV). The half-activation voltage of the permeability was −27 mV, with significant activation at −50 mV.TEA (10 mM) reduced the outward current at potentials positive to 0 mV. 4-AP (5 mM) reduced the early current but increased outward current at later times (100–500 ms) consistent with block of resting channels relieved by depolarization. 4-AP inhibited outward current at potentials negative to −20 mV, potentials where TEA had no effect.Qualitative PCR amplification of mRNA identified transcripts encoding delayed rectifier K+ channel subunits Kv1.6, Kv4.1, Kv4.2, Kv4.3 and the Kvβ1.1 subunit in murine colon myocytes. mRNA encoding Kv 1.4 was not detected.We find that TEA-sensitive delayed rectifier currents are important determinants of action potential amplitude but not rhythmicity. Delayed rectifier currents sensitive to 4-AP are important determinants of rhythmicity but not action potential amplitude. PMID:10050014
Computer modeling of siRNA knockdown effects indicates an essential role of the Ca2+ channel alpha2delta-1 subunit in cardiac excitation-contraction coupling.

PubMed

Tuluc, Petronel; Kern, Georg; Obermair, Gerald J; Flucher, Bernhard E

2007-06-26

L-type Ca(2+) currents determine the shape of cardiac action potentials (AP) and the magnitude of the myoplasmic Ca(2+) signal, which regulates the contraction force. The auxiliary Ca(2+) channel subunits alpha(2)delta-1 and beta(2) are important regulators of membrane expression and current properties of the cardiac Ca(2+) channel (Ca(V)1.2). However, their role in cardiac excitation-contraction coupling is still elusive. Here we addressed this question by combining siRNA knockdown of the alpha(2)delta-1 subunit in a muscle expression system with simulation of APs and Ca(2+) transients by using a quantitative computer model of ventricular myocytes. Reconstitution of dysgenic muscle cells with Ca(V)1.2 (GFP-alpha(1C)) recapitulates key properties of cardiac excitation-contraction coupling. Concomitant depletion of the alpha(2)delta-1 subunit did not perturb membrane expression or targeting of the pore-forming GFP-alpha(1C) subunit into junctions between the outer membrane and the sarcoplasmic reticulum. However, alpha(2)delta-1 depletion shifted the voltage dependence of Ca(2+) current activation by 9 mV to more positive potentials, and it slowed down activation and inactivation kinetics approximately 2-fold. Computer modeling revealed that the altered voltage dependence and current kinetics exert opposing effects on the function of ventricular myocytes that in total cause a 60% prolongation of the AP and a 2-fold increase of the myoplasmic Ca(2+) concentration during each contraction. Thus, the Ca(2+) channel alpha(2)delta-1 subunit is not essential for normal Ca(2+) channel targeting in muscle but is a key determinant of normal excitation and contraction of cardiac muscle cells, and a reduction of alpha(2)delta-1 function is predicted to severely perturb normal heart function.
Evaluation of the new radiation belt AE9/AP9/SPM model for a cislunar mission

NASA Astrophysics Data System (ADS)

Badavi, Francis F.; Walker, Steven A.; Santos Koos, Lindsey M.

2014-09-01

Space mission planners continue to experience challenges associated with human space flight. Concerned with the omnipresence of harmful ionizing radiation in space, at the mission design stage, mission planners must evaluate the amount of exposure the crew of a spacecraft is subjected to during the transit trajectory from low Earth orbit (LEO) to geosynchronous orbit (GEO) and beyond (free space). The Earth's geomagnetic field is located within the domain of LEO-GEO and, depending on latitude, extends out some 40,000-60,000 km. This field contains the Van Allen trapped electrons, protons, and low-energy plasmas, such as the nuclei of hydrogen, helium, oxygen, and to a lesser degree other atoms. In addition, there exist the geomagnetically attenuated energetic galactic cosmic rays (GCR). These particles are potentially harmful to improperly shielded crew members and onboard subsystems. Mitigation strategies to limit the exposure due to free space GCR and sporadic solar energetic particles (SEP) such as flare and coronal mass ejection (CME) must also be exercised beyond the trapped field. Presented in this work is the exposure analysis for a multi-vehicle mission planned for the epoch of February 2020 from LEO to the Earth-moon Lagrange-point two (L2), located approximately 63,000 km beyond the orbit of the Earth-moon binary system. Space operation at L2 provides a gravitationally stable orbit for a vehicle and partially eliminates the need for periodic thrust-vectoring to maintain orbital stability. In the cislunar (Earth-moon) space of L2, the mission trajectory and timeline in this work call for a cargo vehicle to rendezvous with a crew vehicle. This is followed by 15 days of space activities at L2 while the cargo and crew vehicles are docked after which the crew returns to Earth. The mission epoch of 2020 is specifically chosen as it is anticipated that the next solar minimum (i.e. end of cycle 24) in the Sun's approximate 11 years cycle will take place around this time. From a mission planning point of view, this date is ideal as the predictable GCR exposure will be at a maximum, while the sporadic SEP will be at a minimum. In addition, it is anticipated that by 2020 a vehicle capable of launching a crew of four will be operationally ready. During the LEO-GEO transit, the crew and cargo vehicles will encounter exposure from trapped particles and attenuated GCR, followed by free space exposure due to GCR and SEP during solar active times. Within the trapped field, a challenge arises from properly calculating the amount of exposure acquired. Within this field, in the absence of SEP (i.e. solar quiet times), the vehicles will have to transit through an inner proton belt, an inner and outer electron belts, and an attenuated GCR field. There exist a number of models to define the intensities of the trapped particles during the quiet and active SEP. Among the more established trapped models are the historic and popular electron/proton AE8/AP8 model dating back to the 1980s, the historic and less popular electron/proton CRRES model dating back to 1990s, and the recently released electron/proton/space plasma AE9/AP9/SPM model. The AE9/AP9/SPM model is a major improvement over the older AE8/AP8 and CRRES models. This model is derived from numerous measurements acquired over four solar cycles dating back to the 1970s, roughly representing 40 years of data collection. In contrast, the older AE8/AP8 and CRRES models were limited to only a few months of measurements taken during the prior solar minima and maxima. In this work, within the trapped field, along the design trajectory of the crew vehicle, the AE9/AP9/SPM model is evaluated against the older AE8/AP8 model during solar quiet times. The analysis is then extended to the GCR dominated en-route, cislunar L2 space and return trajectories in order to provide cumulative exposure estimates to the crew vehicle for the duration of the entire mission.
Using the Rasch model as an objective and probabilistic technique to integrate different soil properties

NASA Astrophysics Data System (ADS)

Rebollo, Francisco J.; Jesús Moral García, Francisco

2016-04-01

Soil apparent electrical conductivity (ECa) is one of the simplest, least expensive soil measurements that integrates many soil properties affecting crop productivity, including, for instance, soil texture, water content, and cation exchange capacity. The ECa measurements obtained with a 3100 Veris sensor, operating in both shallow (0-30 cm), ECs, and deep (0-90 cm), ECd, mode, can be used as an additional and essential information to be included in a probabilistic model, the Rasch model, with the aim of quantifying the overall soil fertililty potential in an agricultural field. This quantification should integrate the main soil physical and chemical properties, with different units. In this work, the formulation of the Rasch model integrates 11 soil properties (clay, silt and sand content, organic matter -OM-, pH, total nitrogen -TN-, available phosphorus -AP- and potassium -AK-, cation exchange capacity -CEC-, ECd, and ECs) measured at 70 locations in a field. The main outputs of the model include a ranking of all soil samples according to their relative fertility potential and the unexpected behaviours of some soil samples and properties. In the case study, the considered soil variables fit the model reasonably, having an important influence on soil fertility, except pH, probably due to its homogeneity in the field. Moreover, ECd, ECs are the most influential properties on soil fertility and, on the other hand, AP and AK the less influential properties. The use of the Rasch model to estimate soil fertility potential (always in a relative way, taking into account the characteristics of the studied soil) constitutes a new application of great practical importance, enabling to rationally determine locations in a field where high soil fertility potential exists and establishing those soil samples or properties which have any anomaly; this information can be necessary to conduct site-specific treatments, leading to a more cost-effective and sustainable field management. Furthermore, from the measures of soil fertility potential at sampled locations, estimates can be computed using, for instance, a geostatistical algorithm, and these estimates can be utilized to map soil fertility potential and delineate with a rational basis the management zones in the field. Keywords: Rasch model; soil management; soil electrical conductivity; probabilistic algorithm.
MO-F-CAMPUS-J-02: Automatic Recognition of Patient Treatment Site in Portal Images Using Machine Learning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, X; Yang, D

Purpose: To investigate the method to automatically recognize the treatment site in the X-Ray portal images. It could be useful to detect potential treatment errors, and to provide guidance to sequential tasks, e.g. automatically verify the patient daily setup. Methods: The portal images were exported from MOSAIQ as DICOM files, and were 1) processed with a threshold based intensity transformation algorithm to enhance contrast, and 2) where then down-sampled (from 1024×768 to 128×96) by using bi-cubic interpolation algorithm. An appearance-based vector space model (VSM) was used to rearrange the images into vectors. A principal component analysis (PCA) method was usedmore » to reduce the vector dimensions. A multi-class support vector machine (SVM), with radial basis function kernel, was used to build the treatment site recognition models. These models were then used to recognize the treatment sites in the portal image. Portal images of 120 patients were included in the study. The images were selected to cover six treatment sites: brain, head and neck, breast, lung, abdomen and pelvis. Each site had images of the twenty patients. Cross-validation experiments were performed to evaluate the performance. Results: MATLAB image processing Toolbox and scikit-learn (a machine learning library in python) were used to implement the proposed method. The average accuracies using the AP and RT images separately were 95% and 94% respectively. The average accuracy using AP and RT images together was 98%. Computation time was ∼0.16 seconds per patient with AP or RT image, ∼0.33 seconds per patient with both of AP and RT images. Conclusion: The proposed method of treatment site recognition is efficient and accurate. It is not sensitive to the differences of image intensity, size and positions of patients in the portal images. It could be useful for the patient safety assurance. The work was partially supported by a research grant from Varian Medical System.« less

Fabrication and Physical Evaluation of Gelatin-Coated Carbonate Apatite Foam.

PubMed

Hara, Kanae; Fujisawa, Kenji; Nagai, Hirokazu; Takamaru, Natsumi; Ohe, Go; Tsuru, Kanji; Ishikawa, Kunio; Miyamoto, Youji

2016-08-23

Carbonate apatite (CO₃Ap) foam has gained much attention in recent years because of its ability to rapidly replace bone. However, its mechanical strength is extremely low for clinical use. In this study, to understand the potential of gelatin-reinforced CO₃Ap foam for bone replacement, CO₃Ap foam was reinforced with gelatin and the resulting physical characteristics were evaluated. The mechanical strength increased significantly with the gelatin reinforcement. The compressive strength of gelatin-free CO₃Ap foam was 74 kPa whereas that of the gelatin-reinforced CO₃Ap foam, fabricated using 30 mass % gelatin solution, was approximately 3 MPa. Heat treatment for crosslinking gelatin had little effect on the mechanical strength of the foam. The gelatin-reinforced foam did not maintain its shape when immersed in a saline solution as this promoted swelling of the gelatin; however, in the same conditions, the heat-treated gelatin-reinforced foam proved to be stable. It is concluded, therefore, that heat treatment is the key to the fabrication of stable gelatin-reinforced CO₃Ap foam.
Mitochondrial Dysfunction, Through Impaired Autophagy, Leads to Endoplasmic Reticulum Stress, Deregulated Lipid Metabolism, and Pancreatitis in Animal Models.

PubMed

Biczo, Gyorgy; Vegh, Eszter T; Shalbueva, Natalia; Mareninova, Olga A; Elperin, Jason; Lotshaw, Ethan; Gretler, Sophie; Lugea, Aurelia; Malla, Sudarshan R; Dawson, David; Ruchala, Piotr; Whitelegge, Julian; French, Samuel W; Wen, Li; Husain, Sohail Z; Gorelick, Fred S; Hegyi, Peter; Rakonczay, Zoltan; Gukovsky, Ilya; Gukovskaya, Anna S

2018-02-01

Little is known about the signaling pathways that initiate and promote acute pancreatitis (AP). The pathogenesis of AP has been associated with abnormal increases in cytosolic Ca 2+ , mitochondrial dysfunction, impaired autophagy, and endoplasmic reticulum (ER) stress. We analyzed the mechanisms of these dysfunctions and their relationships, and how these contribute to development of AP in mice and rats. Pancreatitis was induced in C57BL/6J mice (control) and mice deficient in peptidylprolyl isomerase D (cyclophilin D, encoded by Ppid) by administration of L-arginine (also in rats), caerulein, bile acid, or an AP-inducing diet. Parameters of pancreatitis, mitochondrial function, autophagy, ER stress, and lipid metabolism were measured in pancreatic tissue, acinar cells, and isolated mitochondria. Some mice with AP were given trehalose to enhance autophagic efficiency. Human pancreatitis tissues were analyzed by immunofluorescence. Mitochondrial dysfunction in pancreas of mice with AP was induced by either mitochondrial Ca 2+ overload or through a Ca 2+ overload-independent pathway that involved reduced activity of ATP synthase (80% inhibition in pancreatic mitochondria isolated from rats or mice given L-arginine). Both pathways were mediated by cyclophilin D and led to mitochondrial depolarization and fragmentation. Mitochondrial dysfunction caused pancreatic ER stress, impaired autophagy, and deregulation of lipid metabolism. These pathologic responses were abrogated in cyclophilin D-knockout mice. Administration of trehalose largely prevented trypsinogen activation, necrosis, and other parameters of pancreatic injury in mice with L-arginine AP. Tissues from patients with pancreatitis had markers of mitochondrial damage and impaired autophagy, compared with normal pancreas. In different animal models, we find a central role for mitochondrial dysfunction, and for impaired autophagy as its principal downstream effector, in development of AP. In particular, the pathway involving enhanced interaction of cyclophilin D with ATP synthase mediates L-arginine-induced pancreatitis, a model of severe AP the pathogenesis of which has remained unknown. Strategies to restore mitochondrial and/or autophagic function might be developed for treatment of AP. Copyright © 2018 AGA Institute. Published by Elsevier Inc. All rights reserved.
Predicting electromyographic signals under realistic conditions using a multiscale chemo-electro-mechanical finite element model.

PubMed

Mordhorst, Mylena; Heidlauf, Thomas; Röhrle, Oliver

2015-04-06

This paper presents a novel multiscale finite element-based framework for modelling electromyographic (EMG) signals. The framework combines (i) a biophysical description of the excitation-contraction coupling at the half-sarcomere level, (ii) a model of the action potential (AP) propagation along muscle fibres, (iii) a continuum-mechanical formulation of force generation and deformation of the muscle, and (iv) a model for predicting the intramuscular and surface EMG. Owing to the biophysical description of the half-sarcomere, the model inherently accounts for physiological properties of skeletal muscle. To demonstrate this, the influence of membrane fatigue on the EMG signal during sustained contractions is investigated. During a stimulation period of 500 ms at 100 Hz, the predicted EMG amplitude decreases by 40% and the AP propagation velocity decreases by 15%. Further, the model can take into account contraction-induced deformations of the muscle. This is demonstrated by simulating fixed-length contractions of an idealized geometry and a model of the human tibialis anterior muscle (TA). The model of the TA furthermore demonstrates that the proposed finite element model is capable of simulating realistic geometries, complex fibre architectures, and can include different types of heterogeneities. In addition, the TA model accounts for a distributed innervation zone, different fibre types and appeals to motor unit discharge times that are based on a biophysical description of the α motor neurons.
Predicting electromyographic signals under realistic conditions using a multiscale chemo–electro–mechanical finite element model

PubMed Central

Mordhorst, Mylena; Heidlauf, Thomas; Röhrle, Oliver

2015-01-01

This paper presents a novel multiscale finite element-based framework for modelling electromyographic (EMG) signals. The framework combines (i) a biophysical description of the excitation–contraction coupling at the half-sarcomere level, (ii) a model of the action potential (AP) propagation along muscle fibres, (iii) a continuum-mechanical formulation of force generation and deformation of the muscle, and (iv) a model for predicting the intramuscular and surface EMG. Owing to the biophysical description of the half-sarcomere, the model inherently accounts for physiological properties of skeletal muscle. To demonstrate this, the influence of membrane fatigue on the EMG signal during sustained contractions is investigated. During a stimulation period of 500 ms at 100 Hz, the predicted EMG amplitude decreases by 40% and the AP propagation velocity decreases by 15%. Further, the model can take into account contraction-induced deformations of the muscle. This is demonstrated by simulating fixed-length contractions of an idealized geometry and a model of the human tibialis anterior muscle (TA). The model of the TA furthermore demonstrates that the proposed finite element model is capable of simulating realistic geometries, complex fibre architectures, and can include different types of heterogeneities. In addition, the TA model accounts for a distributed innervation zone, different fibre types and appeals to motor unit discharge times that are based on a biophysical description of the α motor neurons. PMID:25844148
3D virtual human atria: A computational platform for studying clinical atrial fibrillation.

PubMed

Aslanidi, Oleg V; Colman, Michael A; Stott, Jonathan; Dobrzynski, Halina; Boyett, Mark R; Holden, Arun V; Zhang, Henggui

2011-10-01

Despite a vast amount of experimental and clinical data on the underlying ionic, cellular and tissue substrates, the mechanisms of common atrial arrhythmias (such as atrial fibrillation, AF) arising from the functional interactions at the whole atria level remain unclear. Computational modelling provides a quantitative framework for integrating such multi-scale data and understanding the arrhythmogenic behaviour that emerges from the collective spatio-temporal dynamics in all parts of the heart. In this study, we have developed a multi-scale hierarchy of biophysically detailed computational models for the human atria--the 3D virtual human atria. Primarily, diffusion tensor MRI reconstruction of the tissue geometry and fibre orientation in the human sinoatrial node (SAN) and surrounding atrial muscle was integrated into the 3D model of the whole atria dissected from the Visible Human dataset. The anatomical models were combined with the heterogeneous atrial action potential (AP) models, and used to simulate the AP conduction in the human atria under various conditions: SAN pacemaking and atrial activation in the normal rhythm, break-down of regular AP wave-fronts during rapid atrial pacing, and the genesis of multiple re-entrant wavelets characteristic of AF. Contributions of different properties of the tissue to mechanisms of the normal rhythm and arrhythmogenesis were investigated. Primarily, the simulations showed that tissue heterogeneity caused the break-down of the normal AP wave-fronts at rapid pacing rates, which initiated a pair of re-entrant spiral waves; and tissue anisotropy resulted in a further break-down of the spiral waves into multiple meandering wavelets characteristic of AF. The 3D virtual atria model itself was incorporated into the torso model to simulate the body surface ECG patterns in the normal and arrhythmic conditions. Therefore, a state-of-the-art computational platform has been developed, which can be used for studying multi-scale electrical phenomena during atrial conduction and AF arrhythmogenesis. Results of such simulations can be directly compared with electrophysiological and endocardial mapping data, as well as clinical ECG recordings. The virtual human atria can provide in-depth insights into 3D excitation propagation processes within atrial walls of a whole heart in vivo, which is beyond the current technical capabilities of experimental or clinical set-ups. Copyright © 2011 Elsevier Ltd. All rights reserved.
An Updated AP2 Beamline TURTLE Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gormley, M.; O'Day, S.

1991-08-23

This note describes a TURTLE model of the AP2 beamline. This model was created by D. Johnson and improved by J. Hangst. The authors of this note have made additional improvements which reflect recent element and magnet setting changes. The magnet characteristics measurements and survey data compiled to update the model will be presented. A printout of the actual TURTLE deck may be found in appendix A.
NECAPs are negative regulators of the AP2 clathrin adaptor complex.

PubMed

Beacham, Gwendolyn M; Partlow, Edward A; Lange, Jeffrey J; Hollopeter, Gunther

2018-01-18

Eukaryotic cells internalize transmembrane receptors via clathrin-mediated endocytosis, but it remains unclear how the machinery underpinning this process is regulated. We recently discovered that membrane-associated muniscin proteins such as FCHo and SGIP initiate endocytosis by converting the AP2 clathrin adaptor complex to an open, active conformation that is then phosphorylated (Hollopeter et al., 2014). Here we report that loss of ncap-1 , the sole C. elegans gene encoding an adaptiN Ear-binding Coat-Associated Protein (NECAP), bypasses the requirement for FCHO-1. Biochemical analyses reveal AP2 accumulates in an open, phosphorylated state in ncap-1 mutant worms, suggesting NECAPs promote the closed, inactive conformation of AP2. Consistent with this model, NECAPs preferentially bind open and phosphorylated forms of AP2 in vitro and localize with constitutively open AP2 mutants in vivo. NECAPs do not associate with phosphorylation-defective AP2 mutants, implying that phosphorylation precedes NECAP recruitment. We propose NECAPs function late in endocytosis to inactivate AP2. © 2018, Beacham et al.
NECAPs are negative regulators of the AP2 clathrin adaptor complex

PubMed Central

Beacham, Gwendolyn M; Partlow, Edward A; Lange, Jeffrey J

2018-01-01

Eukaryotic cells internalize transmembrane receptors via clathrin-mediated endocytosis, but it remains unclear how the machinery underpinning this process is regulated. We recently discovered that membrane-associated muniscin proteins such as FCHo and SGIP initiate endocytosis by converting the AP2 clathrin adaptor complex to an open, active conformation that is then phosphorylated (Hollopeter et al., 2014). Here we report that loss of ncap-1, the sole C. elegans gene encoding an adaptiN Ear-binding Coat-Associated Protein (NECAP), bypasses the requirement for FCHO-1. Biochemical analyses reveal AP2 accumulates in an open, phosphorylated state in ncap-1 mutant worms, suggesting NECAPs promote the closed, inactive conformation of AP2. Consistent with this model, NECAPs preferentially bind open and phosphorylated forms of AP2 in vitro and localize with constitutively open AP2 mutants in vivo. NECAPs do not associate with phosphorylation-defective AP2 mutants, implying that phosphorylation precedes NECAP recruitment. We propose NECAPs function late in endocytosis to inactivate AP2. PMID:29345618
Acute physiology and chronic health evaluation (APACHE II) and Medicare reimbursement

PubMed Central

Wagner, Douglas P.; Draper, Elizabeth A.

1984-01-01

This article describes the potential for the acute physiology score (APS) of acute physiology and chronic health evaluation (APACHE) II, to be used as a severity adjustment to diagnosis-related groups (DRG's) or other diagnostic classifications. The APS is defined by a relative value scale applied to 12 objective physiologic variables routinely measured on most hospitalized patients shortly after hospital admission. For intensive care patients, APS at admission is strongly related to subsequent resource costs of intensive care for 5,790 consecutive admissions to 13 large hospitals, across and within diagnoses. The APS could also be used to evaluate quality of care, medical technology, and the response to changing financial incentives. PMID:10311080
How the Chemistry Modeling Curriculum Engages Students in Seven Science Practices Outlined by the College Board

ERIC Educational Resources Information Center

Posthuma-Adams, Erica

2014-01-01

As advanced placement (AP) teachers strive to implement the changes outlined in the AP chemistry redesign, they will have the opportunity to reflect on and evaluate their current practices. For many AP teachers, the new focus on conceptual understanding, reasoning, inquiry, and critical thinking over memorization and algorithmic problem solving…
The APS SASE FEL : modeling and code comparison.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biedron, S. G.

A self-amplified spontaneous emission (SASE) free-electron laser (FEL) is under construction at the Advanced Photon Source (APS). Five FEL simulation codes were used in the design phase: GENESIS, GINGER, MEDUSA, RON, and TDA3D. Initial comparisons between each of these independent formulations show good agreement for the parameters of the APS SASE FEL.
The adipocyte fatty acid–binding protein aP2 is required in allergic airway inflammation

PubMed Central

Shum, Bennett O.V.; Mackay, Charles R.; Gorgun, Cem Z.; Frost, Melinda J.; Kumar, Rakesh K.; Hotamisligil, Gökhan S.; Rolph, Michael S.

2006-01-01

The adipocyte fatty acid–binding protein aP2 regulates systemic glucose and lipid metabolism. We report that aP2, in addition to being abundantly expressed by adipocytes, is also expressed by human airway epithelial cells and shows a striking upregulation following stimulation of epithelial cells with the Th2 cytokines IL-4 and IL-13. Regulation of aP2 mRNA expression by Th2 cytokines was highly dependent on STAT6, a transcription factor with a major regulatory role in allergic inflammation. We examined aP2-deficient mice in a model of allergic airway inflammation and found that infiltration of leukocytes, especially eosinophils, into the airways was highly dependent on aP2 function. T cell priming was unaffected by aP2 deficiency, suggesting that aP2 was acting locally within the lung, and analysis of bone marrow chimeras implicated non-hematopoietic cells, most likely bronchial epithelial cells, as the site of action of aP2 in allergic airway inflammation. Thus, aP2 regulates allergic airway inflammation and may provide a link between fatty acid metabolism and asthma. PMID:16841093
Endotoxin- and ATP-neutralizing activity of alkaline phosphatase as a strategy to limit neuroinflammation

PubMed Central

2012-01-01

Background Alkaline phosphatase (AP) is a ubiquitously expressed enzyme which can neutralize endotoxin as well as adenosine triphosphate (ATP), an endogenous danger signal released during brain injury. In this study we assessed a potential therapeutic role for AP in inhibiting neuroinflammation using three complementary approaches. Methods Mice were immunized to induce experimental autoimmune encephalomyelitis (EAE) and treated with AP for seven days during different phases of disease. In addition, serological assays to determine AP activity, endotoxin levels and endotoxin-reactive antibodies were performed in a cohort of multiple sclerosis (MS) patients and controls. Finally, the expression of AP and related enzymes CD39 and CD73 was investigated in brain tissue from MS patients and control subjects. Results AP administration during the priming phase, but not during later stages, of EAE significantly reduced neurological signs. This was accompanied by reduced proliferation of splenocytes to the immunogen, myelin oligodendrocyte glycoprotein peptide. In MS patients, AP activity and isoenzyme distribution were similar to controls. Although endotoxin-reactive IgM was reduced in primary-progressive MS patients, plasma endotoxin levels were not different between groups. Finally, unlike AP and CD73, CD39 was highly upregulated on microglia in white matter lesions of patients with MS. Conclusions Our findings demonstrate that: 1) pre-symptomatic AP treatment reduces neurological signs of EAE; 2) MS patients do not have altered circulating levels of AP or endotoxin; and 3) the expression of the AP-like enzyme CD39 is increased on microglia in white matter lesions of MS patients. PMID:23231745
P4-ATPase Requirement for AP-1/Clathrin Function in Protein Transport from the trans-Golgi Network and Early Endosomes

PubMed Central

Liu, Ke; Surendhran, Kavitha; Nothwehr, Steven F.

2008-01-01

Drs2p is a resident type 4 P-type ATPase (P4-ATPase) and potential phospholipid translocase of the trans-Golgi network (TGN) where it has been implicated in clathrin function. However, precise protein transport pathways requiring Drs2p and how it contributes to clathrin-coated vesicle budding remain unclear. Here we show a functional codependence between Drs2p and the AP-1 clathrin adaptor in protein sorting at the TGN and early endosomes of Saccharomyces cerevisiae. Genetic criteria indicate that Drs2p and AP-1 operate in the same pathway and that AP-1 requires Drs2p for function. In addition, we show that loss of AP-1 markedly increases Drs2p trafficking to the plasma membrane, but does not perturb retrieval of Drs2p from the early endosome back to the TGN. Thus AP-1 is required at the TGN to sort Drs2p out of the exocytic pathway, presumably for delivery to the early endosome. Moreover, a conditional allele that inactivates Drs2p phospholipid translocase (flippase) activity disrupts its own transport in this AP-1 pathway. Drs2p physically interacts with AP-1; however, AP-1 and clathrin are both recruited normally to the TGN in drs2Δ cells. These results imply that Drs2p acts independently of coat recruitment to facilitate AP-1/clathrin-coated vesicle budding from the TGN. PMID:18508916
The soil sulphate effect and maize plant (Zea mays L.) growth of sulphate reducing bacteria (SRB) inoculation in acid sulfate soils with the different soil water condition

NASA Astrophysics Data System (ADS)

Asmarlaili, S.; Rauf, A.; Hanafiah, D. S.; Sudarno, Y.; Abdi, P.

2018-02-01

The objective of the study was to determine the potential application of sulphate reducing bacteria on acid sulfate soil with different water content in the green house. The research was carried out in the Laboratory and Green House, Faculty of Agriculture, Universitas Sumatera Utara. This research used Randomized Block Design with two treatments factors, ie sulphate reducing bacteria (SRB) isolate (control, LK4, LK6, TSM4, TSM3, AP4, AP3, LK4 + TSM3, LK4 + AP4, LK4 + AP3, LK6 + TSM3, LK6 + AP4, LK6 + AP3, TSM4 + TSM3, TSM4 + AP4, TSM4 + AP3) and water condition (100% field capacity and 110% field capacity). The results showed that application of isolate LK4 + AP4 with water condition 110% field capacity decreased the soil sulphate content (27.38 ppm) significantly after 6 weeks. Application of isolate LK4 + AP3 with water condition 110% field capacity increased soil pH (5.58) after-week efficacy 6. Application of isolate LK4 with water condition 110% field capacity increased plant growth (140 cm; 25.74 g) significantly after week 6. The best treatment was application isolate LK4 with water condition 110% field Capacity (SRB population 2.5x108; soil sulphate content 29.10ppm; soil acidity 4.78; plant height 140cm; plant weight 25.74g).
Human stem cell-derived cardiomyocytes detect drug-mediated changes in action potentials and ion currents.

PubMed

Gibson, John K; Yue, Yimei; Bronson, Jared; Palmer, Cassie; Numann, Randy

2014-01-01

It has been proposed that proarrhythmia assessment for safety pharmacology testing includes the use of human pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) to detect drug-induced changes in cardiac electrophysiology. This study measured the actions of diverse agents on action potentials (AP) and ion currents recorded from hiPSC-CM. During AP experiments, the hiPSC-CM were paced at 1Hz during a baseline period, and when increasing concentrations of test compound were administered at 4-minute intervals. AP parameters, including duration (APD60 and APD90), resting membrane potential, rate of rise, and amplitude, were measured throughout the entire experiment. Voltage clamp experiments with E-4031 and nifedipine were similarly conducted. E-4031 produced a dose-dependent prolongation of cardiac action potential and blocked the hERG/IKr current with an IC50 of 17nM. At 3nM, dofetilide significantly increased APD90. Astemizole significantly increased APD60 and APD90 at 30nM. Terfenadine significantly increased APD90 at concentrations greater than 10nM. Fexofenadine, a metabolite of terfenadine, did not produce any electrophysiologic changes in cardiac action potentials. Flecainide produced a dose-dependent prolongation of the cardiac action potential at 1 and 3μM. Acute exposure to nifedipine significantly decreased APD60 and APD90 and produced a dose-dependent block of calcium current with an IC50 of 0.039μM. Verapamil first shortened APD60 and APD90 in a dose-dependent manner, until a compensating increase in APD90, presumably via hERG blockade, was observed at 1 and 3μM. Following a chronic exposure (20-24h) to clinically relevant levels of pentamidine, a significant increase in action potential duration was accompanied by early afterdepolarizations (EADs). These experiments show the ability of AP measured from hiPSC-CM to record the interactions of various ion channels via AP recording and avoid the limitations of using several single ion channel assays in a noncardiac tissue. Copyright © 2014 Elsevier Inc. All rights reserved.
Nonlinear identification of the total baroreflex arc: higher-order nonlinearity

PubMed Central

Moslehpour, Mohsen; Kawada, Toru; Sunagawa, Kenji; Sugimachi, Masaru

2016-01-01

The total baroreflex arc is the open-loop system relating carotid sinus pressure (CSP) to arterial pressure (AP). The nonlinear dynamics of this system were recently characterized. First, Gaussian white noise CSP stimulation was employed in open-loop conditions in normotensive and hypertensive rats with sectioned vagal and aortic depressor nerves. Nonparametric system identification was then applied to measured CSP and AP to establish a second-order nonlinear Uryson model. The aim in this study was to assess the importance of higher-order nonlinear dynamics via development and evaluation of a third-order nonlinear model of the total arc using the same experimental data. Third-order Volterra and Uryson models were developed by employing nonparametric and parametric identification methods. The R2 values between the AP predicted by the best third-order Volterra model and measured AP in response to Gaussian white noise CSP not utilized in developing the model were 0.69 ± 0.03 and 0.70 ± 0.03 for normotensive and hypertensive rats, respectively. The analogous R2 values for the best third-order Uryson model were 0.71 ± 0.03 and 0.73 ± 0.03. These R2 values were not statistically different from the corresponding values for the previously established second-order Uryson model, which were both 0.71 ± 0.03 (P > 0.1). Furthermore, none of the third-order models predicted well-known nonlinear behaviors including thresholding and saturation better than the second-order Uryson model. Additional experiments suggested that the unexplained AP variance was partly due to higher brain center activity. In conclusion, the second-order Uryson model sufficed to represent the sympathetically mediated total arc under the employed experimental conditions. PMID:27629885
Adenanthera pavonina trypsin inhibitor retard growth of Anagasta kuehniella (Lepidoptera: Pyralidae).

PubMed

Macedo, Maria Lígia Rodrigues; Durigan, Roberta Aparecida; da Silva, Desiree Soares; Marangoni, Sérgio; Freire, Maria das Graças Machado; Parra, José Roberto Postali

2010-04-01

Anagasta kuehniella is a polyphagous pest that feeds on a wide variety of stored products. The possible roles suggested for seed proteinase inhibitors include the function as a part of the plant defensive system against pest via inhibition of their proteolytic enzymes. In this study, a trypsin inhibitor (ApTI) was purified from Adenanthera pavonina seed and was tested for insect growth regulatory effect. The chronic ingestion of ApTI did result in a significant reduction in larval survival and weight. Larval and pupal developmental time of larvae fed on ApTI diet at 1% was significantly longer; the larval period was extended by 5 days and pupal period was 10 days longer, therefore delaying by up to 20 days and resulting in a prolonged period of development from larva to adult. As a result, the ApTI diet emergence rate was only 28% while the emergence rate of control larvae was 80%. The percentage of surviving adults (%S) decreased to 62%. The fourth instar larvae reared on a diet containing 1% ApTI showed a decrease in tryptic activity of gut and that no novel proteolytic form resistant to ApTI was induced. In addition, the tryptic activity in ApTI -fed larvae was sensitive to ApTI. These results suggest that ApTI have a potential antimetabolic effect when ingested by A. kuehniella. (c) 2010 Wiley Periodicals, Inc.
Shape-selective recognition of DNA abasic sites by metallohelices: inhibition of human AP endonuclease 1.

PubMed

Malina, Jaroslav; Scott, Peter; Brabec, Viktor

2015-06-23

Loss of a base in DNA leading to creation of an abasic (AP) site leaving a deoxyribose residue in the strand, is a frequent lesion that may occur spontaneously or under the action of various physical and chemical agents. Progress in the understanding of the chemistry and enzymology of abasic DNA largely relies upon the study of AP sites in synthetic duplexes. We report here on interactions of diastereomerically pure metallo-helical 'flexicate' complexes, bimetallic triple-stranded ferro-helicates [Fe2(NN-NN)3](4+) incorporating the common NN-NN bis(bidentate) helicand, with short DNA duplexes containing AP sites in different sequence contexts. The results show that the flexicates bind to AP sites in DNA duplexes in a shape-selective manner. They preferentially bind to AP sites flanked by purines on both sides and their binding is enhanced when a pyrimidine is placed in opposite orientation to the lesion. Notably, the Λ-enantiomer binds to all tested AP sites with higher affinity than the Δ-enantiomer. In addition, the binding of the flexicates to AP sites inhibits the activity of human AP endonuclease 1, which is as a valid anticancer drug target. Hence, this finding indicates the potential of utilizing well-defined metallo-helical complexes for cancer chemotherapy. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.
Alkaline Phosphatases in the Complex Chronic Kidney Disease-Mineral and Bone Disorders.

PubMed

Bover, Jordi; Ureña, Pablo; Aguilar, Armando; Mazzaferro, Sandro; Benito, Silvia; López-Báez, Víctor; Ramos, Alejandra; daSilva, Iara; Cozzolino, Mario

2018-02-14

Alkaline phosphatases (APs) remove the phosphate (dephosphorylation) needed in multiple metabolic processes (from many molecules such as proteins, nucleotides, or pyrophosphate). Therefore, APs are important for bone mineralization but paradoxically they can also be deleterious for other processes, such as vascular calcification and the increasingly known cross-talk between bone and vessels. A proper balance between beneficial and harmful activities is further complicated in the context of chronic kidney disease (CKD). In this narrative review, we will briefly update the complexity of the enzyme, including its different isoforms such as the bone-specific alkaline phosphatase or the most recently discovered B1x. We will also analyze the correlations and potential discrepancies with parathyroid hormone and bone turnover and, most importantly, the valuable recent associations of AP's with cardiovascular disease and/or vascular calcification, and survival. Finally, a basic knowledge of the synthetic and degradation pathways of APs promises to open new therapeutic strategies for the treatment of the CKD-Mineral and Bone Disorder (CKD-MBD) in the near future, as well as for other processes such as sepsis, acute kidney injury, inflammation, endothelial dysfunction, metabolic syndrome or, in diabetes, cardiovascular complications. However, no studies have been done using APs as a primary therapeutic target for clinical outcomes, and therefore, AP's levels cannot yet be used alone as an isolated primary target in the treatment of CKD-MBD. Nonetheless, its diagnostic and prognostic potential should be underlined.

Glutathione-S-transferase profiles in the emerald ash borer, Agrilus planipennis.

PubMed

Rajarapu, Swapna Priya; Mittapalli, Omprakash

2013-05-01

The emerald ash borer, Agrilus planipennis Fairmaire is a recently discovered invasive insect pest of ash, Fraxinus spp. in North America. Glutathione-S-transferases (GST) are a multifunctional superfamily of enzymes which function in conjugating toxic compounds to less toxic and excretable forms. In this study, we report the molecular characterization and expression patterns of different classes of GST genes in different tissues and developmental stages plus their specific activity. Multiple sequence alignment of all six A. planipennis GSTs (ApGST-E1, ApGST-E2, ApGST-E3, ApGST-O1, ApGST-S1 and ApGST-μ1) revealed conserved features of insect GSTs and a phylogenetic analysis grouped the GSTs within the epsilon, sigma, omega and microsomal classes of GSTs. Real time quantitative PCR was used to study field collected samples. In larval tissues high mRNA levels for ApGST-E1, ApGST-E3 and ApGST-O1 were obtained in the midgut and Malpighian tubules. On the other hand, ApGST-E2 and ApGST-S1 showed high mRNA levels in fat body and ApGST-μ1 showed constitutive levels in all the tissues assayed. During development, mRNA levels for ApGST-E2 were observed to be the highest in feeding instars, ApGST-S1 in prepupal instars; while the others showed constitutive patterns in all the developmental stages examined. At the enzyme level, total GST activity was similar in all the tissues and developmental stages assayed. Results obtained suggest that A. planipennis is potentially primed with GST-driven detoxification to metabolize ash allelochemicals. To our knowledge this study represents the first report of GSTs in A. planipennis and also in the family of wood boring beetles. Copyright © 2013 Elsevier Inc. All rights reserved.
All-Cause and Acute Pancreatitis Health Care Costs in Patients With Severe Hypertriglyceridemia.

PubMed

Rashid, Nazia; Sharma, Puza P; Scott, Ronald D; Lin, Kathy J; Toth, Peter P

2017-01-01

The aim of this study was to assess health care utilization and costs related to acute pancreatitis (AP) in patients with severe hypertriglyceridemia (sHTG) levels. Patients with sHTG levels 1000 mg/dL or higher were identified from January 1, 2007, to June 30, 2013. The first identified incident triglyceride level was labeled as index date. All-cause, AP-related health care visits, and mean total all-cause costs in patients with and without AP were compared during 12 months postindex. A generalized linear model regression was used to compare costs while controlling for patient characteristics and comorbidities. Five thousand five hundred fifty sHTG patients were identified, and 5.4% of these patients developed AP during postindex. Patients with AP had significantly (P < 0.05) more all-cause outpatient visits, hospitalizations, longer length of stays during the hospital visits, and emergency department visits versus patients without AP. Mean (SD) unadjusted all-cause health care costs in the 12 months postindex were $25,343 ($33,139) for patients with AP compared with $15,195 ($24,040) for patients with no AP. The regression showed annual all-cause costs were 49.9% higher (P < 0.01) for patients with AP versus without AP. Patients who developed AP were associated with higher costs; managing patients with sHTG at risk of developing AP may help reduce unnecessary costs.
Pharmacokinetics of aniracetam and its metabolites in rats.

PubMed

Ogiso, T; Iwaki, M; Tanino, T; Ikeda, K; Paku, T; Horibe, Y; Suzuki, H

1998-05-01

The pharmacokinetics of aniracetam (AP), a new cognitive performance enhancer, and its main metabolites was investigated after intravenous (iv) and oral administrations to rat. The plasma levels of AP, 4-p-anisamidobutyric acid (ABA), and p-anisic acid (AA) were determined simultaneously by the HPLC method. The plasma concentrations of the parent drug and ABA quickly declined in a biexponential manner, with rapid terminal decay and a small mean residence time. However, AA yielded nonlinearly high levels at the initial times and the plasma concentrations of 2-pyrrolidinone (PD) were sustained over a relatively long time. When AA was administered intravenously, nonlinearity of the plasma concentrations was also found at higher doses. To describe the time course of the plasma levels of AP and its metabolites after iv administration, a pharmacokinetic model with seven compartments was applied, which included 10 first-order rate constants and one Michaelis-Menten constant. An approximate fit was obtained between the observed and calculated curves based on the model, except for the plasma concentrations of ABA. The plasma concentration-time profiles of AP and its metabolites following oral administration of AP (50 and 100 mg/kg) were similar to those after iv dosing, with the exception of PD, which showed much lower plasma levels than those after iv administration. Elimination of AP and ABA was rapid after oral dosing, and the bioavailability of AP was extremely small (11.4 and 8.6%). As a result, AP was largely metabolized to ABA, AA, and PD in rat.
A species dependent response to the pro-epileptic drug pentylentetrazole in birds.

PubMed

Amin, Faiq; Dar, Asim H; Osama, Khan; Khan, Faezah; Mitha, Rida; Tharwani, Arsal; Haider, Ghulam; Chand, Prem; Arain, Fazal M

2017-09-01

Epilepsy is common disorder that affects over 50 million people worldwide. Birds remain a promising yet largely under-explored model of epilepsy. This study reports the comparison of the response of two species of birds, Australian Parrots (APs) and Sparrows (SPs), to a pro-epileptic drug, Pentylenetetrazole (PTZ). PTZ injections caused myoclonic jerks (MCJs) and tonic clonic seizures (TCSs) in both species. The frequency of MCJs in APs was greater at the dose of 75mg/kg compared to both 50mg/kg and 25mg/kg while it was not significantly different in SPs. The comparison of APs and SPs showed that the frequency of MCJs was greater in APs compared to SPs at 25mg/kg and 75mg/kg while its latency was reduced at 25mg/kg and 50mg/kg. Interestingly SPs had a reduced latency of TCSs compared to APs at 75mg/kg. Glutamatergic and Gabaergic cell count was conducted to determine an association with the epileptic response to PTZ. The Glutamatergic cell counts for SPs was significantly greater than APs and conversely the Gabaergic cell counts in APs was higher compared to SPs. The reason for this difference in findings needs to be further investigated. This study shows that birds, and APs and SPs in particular, are a valid, interesting and under-explored model of epilepsy that should be further explored in order to understand the mysteries of epilepsy. Copyright © 2017 Elsevier Inc. All rights reserved.
Mitochondrial Protection and Anti-aging Activity of Astragalus Polysaccharides and Their Potential Mechanism

PubMed Central

Li, Xing-Tai; Zhang, Ya-Kui; Kuang, Hai-Xue; Jin, Feng-Xin; Liu, De-Wen; Gao, Ming-Bo; Liu, Ze; Xin, Xiao-Juan

2012-01-01

The current study was performed to investigate mitochondrial protection and anti-aging activity of Astragalus polysaccharides (APS) and the potential underlying mechanism. Lipid peroxidation of liver and brain mitochondria was induced by Fe2+–Vit C in vitro. Thiobarbituric acid (TBA) colorimetry was used to measure the content of thiobarbituric acid reactive substances (TBARS). Mouse liver mitochondrial permeability transition (PT) was induced by calcium overload in vitro and spectrophotometry was used to measure it. The scavenging activities of APS on superoxide anion (O2•−) and hydroxyl radical (•OH), which were produced by reduced nicotinamide adenine dinucleotide (NADH)—N-Methylphenazonium methyl sulfate (PMS) and hydrogen peroxide (H2O2)–Fe2+ system respectively, were measured by 4-nitrobluetetrazolium chloride (NBT) reduction and Fenton reaction colorimetry respectively. The Na2S2O3 titration method was used to measure the scavenging activities of APS on H2O2. APS could inhibit TBARS production, protect mitochondria from PT, and scavenge O2•−, •OH and H2O2 significantly in a concentration-dependent manner respectively. The back of the neck of mice was injected subcutaneously with D-galactose to induce aging at a dose of 100 mg/kg/d for seven weeks. Moreover, the activities of catalase (CAT), surperoxide dismutase (SOD) and glutathione peroxidase (GPx) and anti-hydroxyl radical which were assayed by using commercial monitoring kits were increased significantly in vivo by APS. According to this research, APS protects mitochondria by scavenging reactive oxygen species (ROS), inhibiting mitochondrial PT and increasing the activities of antioxidases. Therefore, APS has the effect of promoting health. PMID:22408421
Joint geophysical and petrological models for the lithosphere structure of the Antarctic Peninsula continental margin

NASA Astrophysics Data System (ADS)

Yegorova, Tamara; Bakhmutov, Vladimir; Janik, Tomasz; Grad, Marek

2011-01-01

The Antarctic Peninsula (AP) is a composite magmatic arc terrane formed at the Pacific margin of Gondwana. Through the late Mesozoic and Cenozoic subduction has stopped progressively from southwest to northeast as a result of a series of ridge trench collisions. Subduction may be active today in the northern part of the AP adjacent to the South Shetland Islands. The subduction system is confined by the Shackleton and Hero fracture zones. The magmatic arc of the AP continental margin is marked by high-amplitude gravity and magnetic anomaly belts reaching highest amplitudes in the region of the South Shetland Islands and trench. The sources for these anomalies are highly magnetic and dense batholiths of mafic bulk composition, which were intruded in the Cretaceous, due to partial melting of upper-mantle and lower-crustal rocks. 2-D gravity and magnetic models provide new insights into crustal and upper-mantle structure of the active and passive margin segments of the northern AP. Our models incorporate seismic refraction constraints and physical property data. This enables us to better constrain both Moho geometry and petrological interpretations in the crust and upper mantle. Model along the DSS-12 profile crosses the AP margin near the Anvers Island and shows typical features of a passive continental margin. The second model along the DSS-17 profile extends from the Drake Passage through the South Shetland Trench/Islands system and Bransfield Strait to the AP and indicates an active continental margin linked to slow subduction and on-going continental rifting in the backarc region. Continental rifting beneath the Bransfield Strait is associated with an upward of hot upper mantle rocks and with extensive magmatic underplating.
TRPV1 antagonist capsazepine suppresses 4-AP-induced epileptiform activity in vitro and electrographic seizures in vivo.

PubMed

Gonzalez-Reyes, Luis E; Ladas, Thomas P; Chiang, Chia-Chu; Durand, Dominique M

2013-12-01

Transient receptor potential vanilloid 1 (TRPV1) is a cation-permeable ion channel found in the peripheral and central nervous systems. The membrane surface expression of TRPV1 is known to occur in neuronal cell bodies and sensory neuron axons. TRPV1 receptors are also expressed in the hippocampus, the main epileptogenic region in the brain. Although, previous studies implicate TRPV1 channels in the generation of epilepsy, suppression of ongoing seizures by TRPV1 antagonists has not yet been attempted. Here, we evaluate the role of TRPV1 channels in the modulation of epileptiform activity as well as the anti-convulsant properties of capsazepine (CZP), an established TRPV1 competitive antagonist, using in vitro and in vivo models. To this end, we used 4-aminopyridine (4-AP) to trigger seizure-like activity. We found that CZP suppressed 4-AP induced epileptiform activity in vitro (10-100μM) and in vivo (50mg/kg s.c.). In contrast, capsaicin enhanced 4-AP induced epileptiform activity in vitro (1-100μM) and triggered bursting activity in vivo (100μM dialysis perfusion), which was abolished by the TRPV1 antagonist CZP. To further investigate the mechanisms of TRPV1 modulation, we studied the effect of capsaicin and CZP on evoked potentials. Capsaicin (1-100μM) and CZP (10-100μM) increased and decreased, respectively, the amplitude of extracellular field evoked potentials in a concentration-dependent manner. Additional in vitro studies showed that the effect of the TRPV1 blocker on evoked potentials was similar whether the response was orthodromic or antidromic, suggesting that the effect involves interference with membrane depolarization on cell bodies and axons. The fact that CZP could act directly on axons was confirmed by decreased amplitude of the compound action potential and by an increased delay of both the antidromic potentials and the axonal response. Histological studies using transgenic mice also show that, in addition to the known neural expression, TRPV1 channels are widely expressed in alvear oligodendrocytes in the hippocampus. Taken together, these results indicate that activation of TRPV1 channels leads to enhanced excitability, while their inhibition can effectively suppress ongoing electrographic seizures. These results support a role for TRPV1 channels in the suppression of convulsive activity, indicating that antagonism of TRPV1 channels particularly in axons may possibly be a novel target for effective acute suppression of seizures. © 2013.
AP-1-mediated chromatin looping regulates ZEB2 transcription: new insights into TNFα-induced epithelial-mesenchymal transition in triple-negative breast cancer.

PubMed

Qiao, Yichun; Shiue, Chiou-Nan; Zhu, Jian; Zhuang, Ting; Jonsson, Philip; Wright, Anthony P H; Zhao, Chunyan; Dahlman-Wright, Karin

2015-04-10

The molecular determinants of malignant cell behaviour in triple-negative breast cancer (TNBC) are poorly understood. Recent studies have shown that regulators of epithelial-mesenchymal transition (EMT) are potential therapeutic targets for TNBC. In this study, we demonstrate that the inflammatory cytokine TNFα induces EMT in TNBC cells via activation of AP-1 signaling and subsequently induces expression of the EMT regulator ZEB2. We also show that TNFα activates both the PI3K/Akt and MAPK/ERK pathways, which act upstream of AP-1. We further investigated in detail AP-1 regulation of ZEB2 expression. We show that two ZEB2 transcripts derived from distinct promoters are both expressed in breast cancer cell lines and breast tumor samples. Using the chromosome conformation capture assay, we demonstrate that AP-1, when activated by TNFα, binds to a site in promoter 1b of the ZEB2 gene where it regulates the expression of both promoter 1b and 1a, the latter via mediating long range chromatin interactions. Overall, this work provides a plausible mechanism for inflammation-induced metastatic potential in TNBC, involving a novel regulatory mechanism governing ZEB2 isoform expression.
AP-1-mediated chromatin looping regulates ZEB2 transcription: new insights into TNFα-induced epithelial–mesenchymal transition in triple-negative breast cancer

PubMed Central

Qiao, Yichun; Shiue, Chiou-Nan; Zhu, Jian; Zhuang, Ting; Jonsson, Philip; Wright, Anthony P.H.; Zhao, Chunyan; Dahlman-Wright, Karin

2015-01-01

The molecular determinants of malignant cell behaviour in triple-negative breast cancer (TNBC) are poorly understood. Recent studies have shown that regulators of epithelial-mesenchymal transition (EMT) are potential therapeutic targets for TNBC. In this study, we demonstrate that the inflammatory cytokine TNFα induces EMT in TNBC cells via activation of AP-1 signaling and subsequently induces expression of the EMT regulator ZEB2. We also show that TNFα activates both the PI3K/Akt and MAPK/ERK pathways, which act upstream of AP-1. We further investigated in detail AP-1 regulation of ZEB2 expression. We show that two ZEB2 transcripts derived from distinct promoters are both expressed in breast cancer cell lines and breast tumor samples. Using the chromosome conformation capture assay, we demonstrate that AP-1, when activated by TNFα, binds to a site in promoter 1b of the ZEB2 gene where it regulates the expression of both promoter 1b and 1a, the latter via mediating long range chromatin interactions. Overall, this work provides a plausible mechanism for inflammation-induced metastatic potential in TNBC, involving a novel regulatory mechanism governing ZEB2 isoform expression. PMID:25762639
AP-1 Inhibition by SR 11302 Protects Human Hepatoma HepG2 Cells from Bile Acid-Induced Cytotoxicity by Restoring the NOS-3 Expression

PubMed Central

González-Rubio, Sandra; Linares, Clara I.; Aguilar-Melero, Patricia; Rodríguez-Perálvarez, Manuel; Montero-Álvarez, José L.

2016-01-01

The harmful effects of bile acid accumulation occurring during cholestatic liver diseases have been associated with oxidative stress increase and endothelial nitric oxide synthase (NOS-3) expression decrease in liver cells. We have previously reported that glycochenodeoxycholic acid (GCDCA) down-regulates gene expression by increasing SP1 binding to the NOS-3 promoter in an oxidative stress dependent manner. In the present study, we aimed to investigate the role of transcription factor (TF) AP-1 on the NOS-3 deregulation during GCDCA-induced cholestasis. The cytotoxic response to GCDCA was characterized by 1) the increased expression and activation of TFs cJun and c-Fos; 2) a higher binding capability of these at position -666 of the NOS-3 promoter; 3) a decrease of the transcriptional activity of the promoter and the expression and activity of NOS-3; and 4) the expression increase of cyclin D1. Specific inhibition of AP-1 by the retinoid SR 11302 counteracted the cytotoxic effects induced by GCDCA while promoting NOS-3 expression recovery and cyclin D1 reduction. NOS activity inhibition by L-NAME inhibited the protective effect of SR 11302. Inducible NOS isoform was no detected in this experimental model of cholestasis. Our data provide direct evidence for the involvement of AP-1 in the NOS-3 expression regulation during cholestasis and define a critical role for NOS-3 in regulating the expression of cyclin D1 during the cell damage induced by bile acids. AP-1 appears as a potential therapeutic target in cholestatic liver diseases given its role as a transcriptional repressor of NOS-3. PMID:27490694
Effect of knockout of α2δ-1 on action potentials in mouse sensory neurons.

PubMed

Margas, Wojciech; Ferron, Laurent; Nieto-Rostro, Manuela; Schwartz, Arnold; Dolphin, Annette C

2016-08-05

Gene deletion of the voltage-gated calcium channel auxiliary subunit α2δ-1 has been shown previously to have a cardiovascular phenotype, and a reduction in mechano- and cold sensitivity, coupled with delayed development of neuropathic allodynia. We have also previously shown that dorsal root ganglion (DRG) neuron calcium channel currents were significantly reduced in α2δ-1 knockout mice. To extend our findings in these sensory neurons, we have examined here the properties of action potentials (APs) in DRG neurons from α2δ-1 knockout mice in comparison to their wild-type (WT) littermates, in order to dissect how the calcium channels that are affected by α2δ-1 knockout are involved in setting the duration of individual APs and their firing frequency. Our main findings are that there is reduced Ca(2+) entry on single AP stimulation, particularly in the axon proximal segment, reduced AP duration and reduced firing frequency to a 400 ms stimulation in α2δ-1 knockout neurons, consistent with the expected role of voltage-gated calcium channels in these events. Furthermore, lower intracellular Ca(2+) buffering also resulted in reduced AP duration, and a lower frequency of AP firing in WT neurons, mimicking the effect of α2δ-1 knockout. By contrast, we did not obtain any consistent evidence for the involvement of Ca(2+)-activation of large conductance calcium-activated potassium (BK) and small conductance calcium-activated potassium (SK) channels in these events. In conclusion, the reduced Ca(2+) elevation as a result of single AP stimulation is likely to result from the reduced duration of the AP in α2δ-1 knockout sensory neurons.This article is part of the themed issue 'Evolution brings Ca(2+) and ATP together to control life and death'. © 2016 The Authors.
Transmural ultrasound imaging of thermal lesion and action potential changes in perfused canine cardiac wedge preparations by high intensity focused ultrasound ablation.

PubMed

Wu, Ziqi; Gudur, Madhu S R; Deng, Cheri X

2013-01-01

Intra-procedural imaging is important for guiding cardiac arrhythmia ablation. It is difficult to obtain intra-procedural correlation of thermal lesion formation with action potential (AP) changes in the transmural plane during ablation. This study tested parametric ultrasound imaging for transmural imaging of lesion and AP changes in high intensity focused ultrasound (HIFU) ablation using coronary perfused canine ventricular wedge preparations (n = 13). The preparations were paced from epi/endocardial surfaces and subjected to HIFU application (3.5 MHz, 11 Hz pulse-repetition-frequency, 70% duty cycle, duration 4 s, 3500 W/cm(2)), during which simultaneous optical mapping (1 kframes/s) using di-4-ANEPPS and ultrasound imaging (30 MHz) of the same transmural surface of the wedge were performed. Spatiotemporally correlated AP measurements and ultrasound imaging allowed quantification of the reduction of AP amplitude (APA), shortening of AP duration at 50% repolarization, AP triangulation, decrease of optical AP rise, and change of conduction velocity along tissue depth direction within and surrounding HIFU lesions. The threshold of irreversible change in APA correlating to lesions was determined to be 43 ± 1% with a receiver operating characteristic (ROC) area under curve (AUC) of 0.96 ± 0.01 (n = 13). Ultrasound imaging parameters such as integrated backscatter, Rayleigh (α) and log-normal (σ) parameters, cumulative extrema of σ were tested, with the cumulative extrema of σ performing the best in detecting lesion (ROC AUC 0.89 ± 0.01, n = 13) and change of APA (ROC AUC 0.79 ± 0.03, n = 13). In conclusion, characteristic tissue and AP changes in HIFU ablation were identified and spatiotemporally correlated using optical mapping and ultrasound imaging. Parametric ultrasound imaging using cumulative extrema of σ can detect HIFU lesion and APA reduction.
Transmural Ultrasound Imaging of Thermal Lesion and Action Potential Changes in Perfused Canine Cardiac Wedge Preparations by High Intensity Focused Ultrasound Ablation

PubMed Central

Wu, Ziqi; Gudur, Madhu S. R.; Deng, Cheri X.

2013-01-01

Intra-procedural imaging is important for guiding cardiac arrhythmia ablation. It is difficult to obtain intra-procedural correlation of thermal lesion formation with action potential (AP) changes in the transmural plane during ablation. This study tested parametric ultrasound imaging for transmural imaging of lesion and AP changes in high intensity focused ultrasound (HIFU) ablation using coronary perfused canine ventricular wedge preparations (n = 13). The preparations were paced from epi/endocardial surfaces and subjected to HIFU application (3.5 MHz, 11 Hz pulse-repetition-frequency, 70% duty cycle, duration 4 s, 3500 W/cm2), during which simultaneous optical mapping (1 kframes/s) using di-4-ANEPPS and ultrasound imaging (30 MHz) of the same transmural surface of the wedge were performed. Spatiotemporally correlated AP measurements and ultrasound imaging allowed quantification of the reduction of AP amplitude (APA), shortening of AP duration at 50% repolarization, AP triangulation, decrease of optical AP rise, and change of conduction velocity along tissue depth direction within and surrounding HIFU lesions. The threshold of irreversible change in APA correlating to lesions was determined to be 43±1% with a receiver operating characteristic (ROC) area under curve (AUC) of 0.96±0.01 (n = 13). Ultrasound imaging parameters such as integrated backscatter, Rayleigh (α) and log-normal (σ) parameters, cumulative extrema of σ were tested, with the cumulative extrema of σ performing the best in detecting lesion (ROC AUC 0.89±0.01, n = 13) and change of APA (ROC AUC 0.79±0.03, n = 13). In conclusion, characteristic tissue and AP changes in HIFU ablation were identified and spatiotemporally correlated using optical mapping and ultrasound imaging. Parametric ultrasound imaging using cumulative extrema of σ can detect HIFU lesion and APA reduction. PMID:24349337
Control of Phasic Firing by a Background Leak Current in Avian Forebrain Auditory Neurons

PubMed Central

Dagostin, André A.; Lovell, Peter V.; Hilscher, Markus M.; Mello, Claudio V.; Leão, Ricardo M.

2015-01-01

Central neurons express a variety of neuronal types and ion channels that promote firing heterogeneity among their distinct neuronal populations. Action potential (AP) phasic firing, produced by low-threshold voltage-activated potassium currents (VAKCs), is commonly observed in mammalian brainstem neurons involved in the processing of temporal properties of the acoustic information. The avian caudomedial nidopallium (NCM) is an auditory area analogous to portions of the mammalian auditory cortex that is involved in the perceptual discrimination and memorization of birdsong and shows complex responses to auditory stimuli We performed in vitro whole-cell patch-clamp recordings in brain slices from adult zebra finches (Taeniopygia guttata) and observed that half of NCM neurons fire APs phasically in response to membrane depolarizations, while the rest fire transiently or tonically. Phasic neurons fired APs faster and with more temporal precision than tonic and transient neurons. These neurons had similar membrane resting potentials, but phasic neurons had lower membrane input resistance and time constant. Surprisingly phasic neurons did not express low-threshold VAKCs, which curtailed firing in phasic mammalian brainstem neurons, having similar VAKCs to other NCM neurons. The phasic firing was determined not by VAKCs, but by the potassium background leak conductances, which was more prominently expressed in phasic neurons, a result corroborated by pharmacological, dynamic-clamp, and modeling experiments. These results reveal a new role for leak currents in generating firing diversity in central neurons. PMID:26696830
The modelled surface mass balance of the Antarctic Peninsula at 5.5 km horizontal resolution

NASA Astrophysics Data System (ADS)

van Wessem, J. M.; Ligtenberg, S. R. M.; Reijmer, C. H.; van de Berg, W. J.; van den Broeke, M. R.; Barrand, N. E.; Thomas, E. R.; Turner, J.; Wuite, J.; Scambos, T. A.; van Meijgaard, E.

2016-02-01

This study presents a high-resolution (˜ 5.5 km) estimate of surface mass balance (SMB) over the period 1979-2014 for the Antarctic Peninsula (AP), generated by the regional atmospheric climate model RACMO2.3 and a firn densification model (FDM). RACMO2.3 is used to force the FDM, which calculates processes in the snowpack, such as meltwater percolation, refreezing and runoff. We evaluate model output with 132 in situ SMB observations and discharge rates from six glacier drainage basins, and find that the model realistically simulates the strong spatial variability in precipitation, but that significant biases remain as a result of the highly complex topography of the AP. It is also clear that the observations significantly underrepresent the high-accumulation regimes, complicating a full model evaluation. The SMB map reveals large accumulation gradients, with precipitation values above 3000 mm we yr-1 in the western AP (WAP) and below 500 mm we yr-1 in the eastern AP (EAP), not resolved by coarser data sets such as ERA-Interim. The average AP ice-sheet-integrated SMB, including ice shelves (an area of 4.1 × 105 km2), is estimated at 351 Gt yr-1 with an interannual variability of 58 Gt yr-1, which is dominated by precipitation (PR) (365 ± 57 Gt yr-1). The WAP (2.4 × 105 km2) SMB (276 ± 47 Gt yr-1), where PR is large (276 ± 47 Gt yr-1), dominates over the EAP (1.7 × 105 km2) SMB (75 ± 11 Gt yr-1) and PR (84 ± 11 Gt yr-1). Total sublimation is 11 ± 2 Gt yr-1 and meltwater runoff into the ocean is 4 ± 4 Gt yr-1. There are no significant trends in any of the modelled AP SMB components, except for snowmelt that shows a significant decrease over the last 36 years (-0.36 Gt yr-2).
Post-Inhibitory Rebound Spikes in Rat Medial Entorhinal Layer II/III Principal Cells: In Vivo, In Vitro, and Computational Modeling Characterization

PubMed Central

Ferrante, Michele; Shay, Christopher F.; Tsuno, Yusuke; William Chapman, G.; Hasselmo, Michael E.

2017-01-01

Abstract Medial entorhinal cortex Layer-II stellate cells (mEC-LII-SCs) primarily interact via inhibitory interneurons. This suggests the presence of alternative mechanisms other than excitatory synaptic inputs for triggering action potentials (APs) in stellate cells during spatial navigation. Our intracellular recordings show that the hyperpolarization-activated cation current (Ih) allows post-inhibitory-rebound spikes (PIRS) in mEC-LII-SCs. In vivo, strong inhibitory-post-synaptic potentials immediately preceded most APs shortening their delay and enhancing excitability. In vitro experiments showed that inhibition initiated spikes more effectively than excitation and that more dorsal mEC-LII-SCs produced faster and more synchronous spikes. In contrast, PIRS in Layer-II/III pyramidal cells were harder to evoke, voltage-independent, and slower in dorsal mEC. In computational simulations, mEC-LII-SCs morphology and Ih homeostatically regulated the dorso-ventral differences in PIRS timing and most dendrites generated PIRS with a narrow range of stimulus amplitudes. These results suggest inhibitory inputs could mediate the emergence of grid cell firing in a neuronal network. PMID:26965902
Vaginal wall weakness in parous ewes: a potential preclinical model of pelvic organ prolapse.

PubMed

Young, Natharnia; Rosamilia, Anna; Arkwright, John; Lee, Joseph; Davies-Tuck, Miranda; Melendez, Joan; Werkmeister, Jerome; Gargett, Caroline E

2017-07-01

Ewes develop pelvic organ prolapse (POP) and may be a suitable model for preclinical studies evaluating cell-based therapies for POP. The aim of this study was to establish a clinical score of vaginal weakness and to compare POP Quantification System (POP-Q) values in conscious nulliparous and parous ewes and determine whether ewes are a suitable POP model. Ewes (n = 114) were examined while conscious, without sedation, and standing in a V conveyer by adapting the human POP-Q measurement. Ovine POP was defined as descent to the introitus from POP-Q points Aa 3 cm above the introitus on the anterior wall, Ap 3 cm above the introitus on the posterior wall, or increased Ba anterior wall descent above the urethra (≥0). A test-retest showed good inter- and intrarater reliability. There was no evidence of tissue mobility at Aa, Ap, Ba (all -3 cm) in nulliparous ewes (n = 14). In contrast, multiparous ewes had a median of -1 and interquartile range (IQR) (-2 to 0) for Aa, [0 (-1 to 0)] for Ap and [0 (-2.75 to 0)] for Ba (n = 33; P < 0.0001 in comparison with nulliparous) ewes. Ovine vaginal displacement was seen in 50.9 % of parous ewes and was strongly associated with parity (P = 0.003). A modified POP-Q in conscious ewes was established showing that the vaginal wall of parous animals has similar regions of weakness as do women and may be similarly related to parity. Ewes appear to be a representative preclinical model of human vaginal prolapse.
In silico assessment of drug safety in human heart applied to late sodium current blockers

PubMed Central

Trenor, Beatriz; Gomis-Tena, Julio; Cardona, Karen; Romero, Lucia; Rajamani, Sridharan; Belardinelli, Luiz; Giles, Wayne R; Saiz, Javier

2013-01-01

Drug-induced action potential (AP) prolongation leading to Torsade de Pointes is a major concern for the development of anti-arrhythmic drugs. Nevertheless the development of improved anti-arrhythmic agents, some of which may block different channels, remains an important opportunity. Partial block of the late sodium current (INaL) has emerged as a novel anti-arrhythmic mechanism. It can be effective in the settings of free radical challenge or hypoxia. In addition, this approach can attenuate pro-arrhythmic effects of blocking the rapid delayed rectifying K+ current (IKr). The main goal of our computational work was to develop an in-silico tool for preclinical anti-arrhythmic drug safety assessment, by illustrating the impact of IKr/INaL ratio of steady-state block of drug candidates on “torsadogenic” biomarkers. The O’Hara et al. AP model for human ventricular myocytes was used. Biomarkers for arrhythmic risk, i.e., AP duration, triangulation, reverse rate-dependence, transmural dispersion of repolarization and electrocardiogram QT intervals, were calculated using single myocyte and one-dimensional strand simulations. Predetermined amounts of block of INaL and IKr were evaluated. “Safety plots” were developed to illustrate the value of the specific biomarker for selected combinations of IC50s for IKr and INaL of potential drugs. The reference biomarkers at baseline changed depending on the “drug” specificity for these two ion channel targets. Ranolazine and GS967 (a novel potent inhibitor of INaL) yielded a biomarker data set that is considered safe by standard regulatory criteria. This novel in-silico approach is useful for evaluating pro-arrhythmic potential of drugs and drug candidates in the human ventricle. PMID:23696033
Activation of the chemosensing transient receptor potential channel A1 (TRPA1) by alkylating agents.

PubMed

Stenger, Bernhard; Zehfuss, Franziska; Mückter, Harald; Schmidt, Annette; Balszuweit, Frank; Schäfer, Eva; Büch, Thomas; Gudermann, Thomas; Thiermann, Horst; Steinritz, Dirk

2015-09-01

The transient receptor potential ankyrin 1 (TRPA1) cation channel is expressed in different tissues including skin, lung and neuronal tissue. Recent reports identified TRPA1 as a sensor for noxious substances, implicating a functional role in the molecular toxicology. TRPA1 is activated by various potentially harmful electrophilic substances. The chemical warfare agent sulfur mustard (SM) is a highly reactive alkylating agent that binds to numerous biological targets. Although SM is known for almost 200 years, detailed knowledge about the pathophysiology resulting from exposure is lacking. A specific therapy is not available. In this study, we investigated whether the alkylating agent 2-chloroethyl-ethylsulfide (CEES, a model substance for SM-promoted effects) and SM are able to activate TRPA1 channels. CEES induced a marked increase in the intracellular calcium concentration ([Ca(2+)]i) in TRPA1-expressing but not in TRPA1-negative cells. The TRP-channel blocker AP18 diminished the CEES-induced calcium influx. HEK293 cells permanently expressing TRPA1 were more sensitive toward cytotoxic effects of CEES compared with wild-type cells. At low CEES concentrations, CEES-induced cytotoxicity was prevented by AP18. Proof-of-concept experiments using SM resulted in a pronounced increase in [Ca(2+)]i in HEK293-A1-E cells. Human A549 lung epithelial cells, which express TRPA1 endogenously, reacted with a transient calcium influx in response to CEES exposure. The CEES-dependent calcium response was diminished by AP18. In summary, our results demonstrate that alkylating agents are able to activate TRPA1. Inhibition of TRPA1 counteracted cellular toxicity and could thus represent a feasible approach to mitigate SM-induced cell damage.
QUEST: Qualifying Environmentally Sustainable Technologies

NASA Technical Reports Server (NTRS)

2006-01-01

Over the years, pollution prevention has proven to be a means to comply with environmental regulations, improve product performance and reduce costs. The NASA Acquisition Pollution Prevention (AP2) Program was created to help individual NASA Centers and programs work together to evaluate and adopt environmentally preferable technologies and practices. The AP2 Program accomplishes its mission using a variety of tools such as networking, information/technology exchange and partnering. Due to its extensive network of contacts, the AP2 Program is an excellent resource for finding existing solutions to problems. If no solution is readily known, the AP2 Program works to identify potential solutions and partners for demonstration/ validation projects. Partnering to prevent pollution is a cornerstone of NASA's prime mission and the One NASA Initiative. This annual newsletter highlights some of our program's collaborative efforts. I believe you will discover how the AP2 Program is responsive in meeting the Agency's environmental management strategic plans.

Pro-arrhythmogenic effects of atrial fibrillation-induced electrical remodelling: insights from the three-dimensional virtual human atria

PubMed Central

Colman, Michael A; Aslanidi, Oleg V; Kharche, Sanjay; Boyett, Mark R; Garratt, Clifford; Hancox, Jules C; Zhang, Henggui

2013-01-01

Chronic atrial fibrillation (AF) is associated with structural and electrical remodelling in the atria, which are associated with a high recurrence of AF. Through biophysically detailed computer modelling, this study investigated mechanisms by which AF-induced electrical remodelling promotes and perpetuates AF. A family of Courtemanche–Ramirez–Nattel variant models of human atrial cell action potentials (APs), taking into account of intrinsic atrial electrophysiological properties, was modified to incorporate various experimental data sets on AF-induced changes of major ionic channel currents (ICaL, IKur, Ito, IK1, IKs, INaCa) and on intracellular Ca2+ handling. The single cell models for control and AF-remodelled conditions were incorporated into multicellular three-dimensional (3D) atrial tissue models. Effects of the AF-induced electrical remodelling were quantified as the changes of AP profile, AP duration (APD) and its dispersion across the atria, and the vulnerability of atrial tissue to the initiation of re-entry. The dynamic behaviour of re-entrant excitation waves in the 3D models was characterised. In our simulations, AF-induced electrical remodelling abbreviated atrial APD non-uniformly across the atria; this resulted in relatively short APDs co-existing with marked regional differences in the APD at junctions of the crista terminalis/pectinate muscle, pulmonary veins/left atrium. As a result, the measured tissue vulnerability to re-entry initiation at these tissue junctions was increased. The AF-induced electrical remodelling also stabilized and accelerated re-entrant excitation waves, leading to rapid and sustained re-entry. Under the AF-remodelled condition, re-entrant scroll waves in the 3D model degenerated into persistent and erratic wavelets, leading to fibrillation. In conclusion, realistic 3D atrial tissue models indicate that AF-induced electrical remodelling produces regionally heterogeneous and shortened APD; these respectively facilitate initiation and maintenance of re-entrant excitation waves. PMID:23732649
Pro-arrhythmogenic effects of atrial fibrillation-induced electrical remodelling: insights from the three-dimensional virtual human atria.

PubMed

Colman, Michael A; Aslanidi, Oleg V; Kharche, Sanjay; Boyett, Mark R; Garratt, Clifford; Hancox, Jules C; Zhang, Henggui

2013-09-01

Chronic atrial fibrillation (AF) is associated with structural and electrical remodelling in the atria, which are associated with a high recurrence of AF. Through biophysically detailed computer modelling, this study investigated mechanisms by which AF-induced electrical remodelling promotes and perpetuates AF. A family of Courtemanche-Ramirez-Nattel variant models of human atrial cell action potentials (APs), taking into account of intrinsic atrial electrophysiological properties, was modified to incorporate various experimental data sets on AF-induced changes of major ionic channel currents (ICaL, IKur, Ito, IK1, IKs, INaCa) and on intracellular Ca(2+) handling. The single cell models for control and AF-remodelled conditions were incorporated into multicellular three-dimensional (3D) atrial tissue models. Effects of the AF-induced electrical remodelling were quantified as the changes of AP profile, AP duration (APD) and its dispersion across the atria, and the vulnerability of atrial tissue to the initiation of re-entry. The dynamic behaviour of re-entrant excitation waves in the 3D models was characterised. In our simulations, AF-induced electrical remodelling abbreviated atrial APD non-uniformly across the atria; this resulted in relatively short APDs co-existing with marked regional differences in the APD at junctions of the crista terminalis/pectinate muscle, pulmonary veins/left atrium. As a result, the measured tissue vulnerability to re-entry initiation at these tissue junctions was increased. The AF-induced electrical remodelling also stabilized and accelerated re-entrant excitation waves, leading to rapid and sustained re-entry. Under the AF-remodelled condition, re-entrant scroll waves in the 3D model degenerated into persistent and erratic wavelets, leading to fibrillation. In conclusion, realistic 3D atrial tissue models indicate that AF-induced electrical remodelling produces regionally heterogeneous and shortened APD; these respectively facilitate initiation and maintenance of re-entrant excitation waves.
Diversity of layer 5 projection neurons in the mouse motor cortex

PubMed Central

Oswald, Manfred J.; Tantirigama, Malinda L. S.; Sonntag, Ivo; Hughes, Stephanie M.; Empson, Ruth M.

2013-01-01

In the primary motor cortex (M1), layer 5 projection neurons signal directly to distant motor structures to drive movement. Despite their pivotal position and acknowledged diversity these neurons are traditionally separated into broad commissural and corticofugal types, and until now no attempt has been made at resolving the basis for their diversity. We therefore probed the electrophysiological and morphological properties of retrogradely labeled M1 corticospinal (CSp), corticothalamic (CTh), and commissural projecting corticostriatal (CStr) and corticocortical (CC) neurons. An unsupervised cluster analysis established at least four phenotypes with additional differences between lumbar and cervical projecting CSp neurons. Distinguishing parameters included the action potential (AP) waveform, firing behavior, the hyperpolarisation-activated sag potential, sublayer position, and soma and dendrite size. CTh neurons differed from CSp neurons in showing spike frequency acceleration and a greater sag potential. CStr neurons had the lowest AP amplitude and maximum rise rate of all neurons. Temperature influenced spike train behavior in corticofugal neurons. At 26°C CTh neurons fired bursts of APs more often than CSp neurons, but at 36°C both groups fired regular APs. Our findings provide reliable phenotypic fingerprints to identify distinct M1 projection neuron classes as a tool to understand their unique contributions to motor function. PMID:24137110
The interaction of diadenosine polyphosphates with P2x-receptors in the guinea-pig isolated vas deferens.

PubMed

Westfall, T D; McIntyre, C A; Obeid, S; Bowes, J; Kennedy, C; Sneddon, P

1997-05-01

1. The site(s) at which diadenosine 5',5"'-P1,P4-tetraphosphate (AP4A) and diadenosine 5', 5"'-P1,P5-pentaphosphate (AP5A) act to evoke contraction of the guinea-pig isolated vas deferens was studied by use of a series of P2-receptor antagonists and the ecto-ATPase inhibitor 6-N,N-diethyl-D-beta,gamma-dibromomethyleneATP (ARL 67156). 2. Pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) (300 nM - 30 microM), suramin (3-100 microM) and pyridoxal-5'-phosphate (P-5-P) (3-1000 microM) inhibited contractions evoked by equi-effective concentrations of AP5A (3 microM), AP4A (30 microM) and alpha,beta-methyleneATP (alpha,beta-meATP) (1 microM), in a concentration-dependent manner and abolished them at the highest concentrations used. 3. PPADS was more potent than suramin, which in turn was more potent than P-5-P. PPADS inhibited AP5A, AP4A and alpha,beta-meATP with similar IC50 values. No significant difference was found between IC50 values for suramin against alpha,beta-meATP and AP5A or alpha,beta-meATP and AP4A, but suramin was more than 2.5 times more potent against AP4A than AP5A. P-5-P showed the same pattern of antagonism. 4. Desensitization of the P2xi-receptor by alpha,beta-meATP abolished contractions evoked by AP5A (3 microM) and AP4A (30 microM), but had no effect on those elicited by noradrenaline (100 microM). 5. ARL 67156 (100 microM) reversibly potentiated contractions evoked by AP4A (30 microM) by 61%, but caused a small, significant decrease in the mean response to AP5A (3 microM). 6. It is concluded that AP4A and AP5A act at the P2xi-receptor, or a site similar to the P2xi-receptor, to evoke contraction of the guinea-pig isolated vas deferens. Furthermore, the potency of AP4A, but not AP5A, appears to be inhibited by an ecto-enzyme which is sensitive to ARL 67156.
An Absolute Phase Space for the Physicality of Matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valentine, John S.

2010-12-22

We define an abstract and absolute phase space (''APS'') for sub-quantum intrinsic wave states, in three axes, each mapping directly to a duality having fundamental ontological basis. Many aspects of quantum physics emerge from the interaction algebra and a model deduced from principles of 'unique solvability' and 'identifiable entity', and we reconstruct previously abstract fundamental principles and phenomena from these new foundations. The physical model defines bosons as virtual continuous waves pairs in the APS, and fermions as real self-quantizing snapshots of those waves when simple conditions are met. The abstraction and physical model define a template for the constitutionmore » of all fermions, a template for all the standard fundamental bosons and their local interactions, in a common framework and compactified phase space for all forms of real matter and virtual vacuum energy, and a distinct algebra for observables and unobservables. To illustrate our scheme's potential, we provide examples of slit experiment variations (where the model finds theoretical basis for interference only occurring between two final sources), QCD (where we may model most attributes known to QCD, and a new view on entanglement), and we suggest approaches for other varied applications. We believe this is a viable candidate for further exploration as a foundational proposition for physics.« less
Molecular characterization and specific detection of Anaplasma species (AP-sd) in sika deer and its first detection in wild brown bears and rodents in Hokkaido, Japan.

PubMed

Moustafa, Mohamed Abdallah Mohamed; Lee, Kyunglee; Taylor, Kyle; Nakao, Ryo; Sashika, Mariko; Shimozuru, Michito; Tsubota, Toshio

2015-12-01

A previously undescribed Anaplasma species (herein referred to as AP-sd) has been detected in sika deer, cattle and ticks in Japan. Despite being highly similar to some strains of A. phagocytophilum, AP-sd has never been detected in humans. Its ambiguous epidemiology and the lack of tools for its specific detection make it difficult to understand and interpret the prevalence of this Anaplasma species. We developed a method for specific detection, and examined AP-sd prevalence in Hokkaido wildlife. Our study included 250 sika deer (Cervus nippon yesoensis), 13 brown bears (Ursus arctos yesoensis) and 252 rodents including 138 (Apodemus speciosus), 45 (Apodemus argenteus), 42 (Myodes rufocanus) and 27 (Myodes rutilus) were collected from Hokkaido island, northern Japan, collected during 2010 to 2015. A 770 bp and 382 bp segment of the 16S rRNA and gltA genes, respectively, were amplified by nested PCR. Results were confirmed by cloning and sequencing of the positive PCR products. A reverse line blot hybridization (RLB) based on the 16S rRNA gene was then developed for the specific detection of AP-sd. The prevalence of AP-sd by nested PCR in sika deer was 51% (128/250). We detected this Anaplasma sp. for the first time in wild brown bears and rodents with a prevalence of 15% (2/13) and 2.4% (6/252), respectively. The sequencing results of the 16S rRNA and gltA gene amplicons were divergent from the selected A. phagocytophilum sequences in GenBank. Using a newly designed AP-sd specific probe for RLB has enabled us to specifically detect this Anaplasma species. Besides sika deer and cattle, wild brown bears and rodents were identified as potential reservoir hosts for AP-sd. This study provided a high throughput molecular method that specifically detects AP-sd, and which can be used to investigate its ecology and its potential as a threat to humans in Japan. Copyright © 2015 Elsevier B.V. All rights reserved.
Experimental and clinical evidence of antioxidant therapy in acute pancreatitis

PubMed Central

Esrefoglu, Mukaddes

2012-01-01

Oxidative stress has been shown to play an important role in the pathogenesis of acute pancreatitis (AP). Antioxidants, alone or in combination with conventional therapy, should improve oxidative-stress-induced organ damage and therefore accelerate the rate of recovery. In recent years, substantial amounts of data about the efficiency of antioxidants against oxidative damage have been obtained from experiments with rodents. Some of these antioxidants have been found beneficial in the treatment of AP in humans; however, at present there is insufficient clinical data to support the benefits of antioxidants, alone or in combination with conventional therapy, in the management of AP in humans. Conflicting results obtained from experimental animals and humans may represent distinct pathophysiological mechanisms mediating tissue injury in different species. Further detailed studies should be done to clarify the exact mechanisms of tissue injury in human AP. Herein I tried to review the existing experimental and clinical studies on AP in order to determine the efficiency of antioxidants. The use of antioxidant enriched nutrition is a potential direction of clinical research in AP given the lack of clues about the efficiency and safety of antioxidant usage in patients with AP. PMID:23112545
Quantitative analysis of the Ca2+ -dependent regulation of delayed rectifier K+ current IKs in rabbit ventricular myocytes.

PubMed

Bartos, Daniel C; Morotti, Stefano; Ginsburg, Kenneth S; Grandi, Eleonora; Bers, Donald M

2017-04-01

[Ca 2+ ] i enhanced rabbit ventricular slowly activating delayed rectifier K + current (I Ks ) by negatively shifting the voltage dependence of activation and slowing deactivation, similar to perfusion of isoproterenol. Rabbit ventricular rapidly activating delayed rectifier K + current (I Kr ) amplitude and voltage dependence were unaffected by high [Ca 2+ ] i . When measuring or simulating I Ks during an action potential, I Ks was not different during a physiological Ca 2+ transient or when [Ca 2+ ] i was buffered to 500 nm. The slowly activating delayed rectifier K + current (I Ks ) contributes to repolarization of the cardiac action potential (AP). Intracellular Ca 2+ ([Ca 2+ ] i ) and β-adrenergic receptor (β-AR) stimulation modulate I Ks amplitude and kinetics, but details of these important I Ks regulators and their interaction are limited. We assessed the [Ca 2+ ] i dependence of I Ks in steady-state conditions and with dynamically changing membrane potential and [Ca 2+ ] i during an AP. I Ks was recorded from freshly isolated rabbit ventricular myocytes using whole-cell patch clamp. With intracellular pipette solutions that controlled free [Ca 2+ ] i , we found that raising [Ca 2+ ] i from 100 to 600 nm produced similar increases in I Ks as did β-AR activation, and the effects appeared additive. Both β-AR activation and high [Ca 2+ ] i increased maximally activated tail I Ks , negatively shifted the voltage dependence of activation, and slowed deactivation kinetics. These data informed changes in our well-established mathematical model of the rabbit myocyte. In both AP-clamp experiments and simulations, I Ks recorded during a normal physiological Ca 2+ transient was similar to I Ks measured with [Ca 2+ ] i clamped at 500-600 nm. Thus, our study provides novel quantitative data as to how physiological [Ca 2+ ] i regulates I Ks amplitude and kinetics during the normal rabbit AP. Our results suggest that micromolar [Ca 2+ ] i , in the submembrane or junctional cleft space, is not required to maximize [Ca 2+ ] i -dependent I Ks activation during normal Ca 2+ transients. © 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.
Biotransformation of potentially persistent alkylphenols in natural seawater.

PubMed

Lofthus, Synnøve; Almås, Inger K; Evans, Peter; Pelz, Oliver; Brakstad, Odd Gunnar

2016-08-01

Produced water (PW) discharged to the marine environment may contain both natural substances and industrial chemicals that are potentially persistent, bioaccumulating and toxic (PBT). Identification of substances as PBT is dependent upon accurate assessment of biodegradation rates, but these measurements can be impeded where substances exhibit inherently low solubility in water. Examples of substances of this kind include some alkylated phenols (APs). Biotransformation of three APs, suspected to be PBT compounds in PW, was investigated by adopting a new methodology in which they were immobilized to hydrophobic adsorbents submerged in natural seawater. These compounds were not ready biodegradable by conventional screening biochemical oxygen demand (BOD) methods at high concentrations (2 mg/L). However, potential biodegradability for two of the three APs were demonstrated by the immobilization method at low concentrations (appr. 100 μg/L), with biotransformation half-lives <50 days. Thus, standard screening tests should be supplemented by biodegradation methods suited for testing of poorly soluble substances before the persistence of potential PBT substances are defined. Copyright © 2016 Elsevier Ltd. All rights reserved.
Circulating microRNAs as biomarkers of disease and typification of the atherothrombotic status in antiphospholipid syndrome

PubMed Central

Pérez-Sánchez, Carlos; Arias-de la Rosa, Iván; Aguirre, María Ángeles; Luque-Tévar, María; Ruiz-Limón, Patricia; Barbarroja, Nuria; Jiménez-Gómez, Yolanda; Ábalos-Aguilera, María Carmen; Collantes-Estévez, Eduardo; Segui, Pedro; Velasco, Francisco; Herranz, María Teresa; Lozano-Herrero, Jesús; Hernandez-Vidal, María Julia; Martínez, Constantino; González-Conejero, Rocío; Radin, Massimo; Sciascia, Savino; Cecchi, Irene; Cuadrado, María José; López-Pedrera, Chary

2018-01-01

We aimed to identify the plasma miRNA profile of antiphospholipid syndrome (APS) patients and to investigate the potential role of specific circulating miRNAs as non-invasive disease biomarkers. Ninety APS patients and 42 healthy donors were recruited. Profiling of miRNAs by PCR-array in plasma of APS patients identified a set of miRNAs differentially expressed and collectively involved in clinical features. Logistic regression and ROC analysis identified a signature of 10 miRNA ratios as biomarkers of disease. In addition, miRNA signature was related to fetal loss, atherosclerosis, and type of thrombosis, and correlated with parameters linked to inflammation, thrombosis, and autoimmunity. Hard clustering analysis differentiated 3 clusters representing different thrombotic risk profile groups. Significant differences between groups for several miRNA ratios were found. Moreover, miRNA signature remained stable over time, demonstrated by their analysis three months after the first sample collection. Parallel analysis in two additional cohorts of patients, including thrombosis without autoimmune disease, and systemic lupus erythematosus without antiphospholipid antibodies, each displayed specific miRNA profiles that were distinct from those of APS patients. In vitro, antiphospholipid antibodies of IgG isotype promoted deregulation in selected miRNAs and their potential atherothrombotic protein targets in monocytes and endothelial cells. Taken together, differentially expressed circulating miRNAs in APS patients, modulated at least partially by antiphospholipid antibodies of IgG isotype, might have the potential to serve as novel biomarkers of disease features and to typify patients’ atherothrombotic status, thus constituting a useful tool in the management of the disease. PMID:29545345
A novel bradykinin potentiating peptide isolated from Bothrops jararacussu venom using catallytically inactive oligopeptidase EP24.15.

PubMed

Rioli, Vanessa; Prezoto, Benedito C; Konno, Katsuhiro; Melo, Robson L; Klitzke, Clécio F; Ferro, Emer S; Ferreira-Lopes, Mônica; Camargo, Antonio C M; Portaro, Fernanda C V

2008-05-01

Characterization of the peptide content of venoms has a number of potential benefits for basic research, clinical diagnosis, development of new therapeutic agents, and production of antiserum. Here, we use a substrate-capture assay that employs a catalytically inactive mutant of thimet oligopeptidase (EC 3.4.24.15; EP24.15) to identify novel bioactive peptides in Bothrops jararacussu venom. Of the peptides captured with inactive EP24.15 and identified by mass spectrometry, three were previously identified bradykinin-potentiating peptides (BPP),
Learning rules for spike timing-dependent plasticity depend on dendritic synapse location.

PubMed

Letzkus, Johannes J; Kampa, Björn M; Stuart, Greg J

2006-10-11

Previous studies focusing on the temporal rules governing changes in synaptic strength during spike timing-dependent synaptic plasticity (STDP) have paid little attention to the fact that synaptic inputs are distributed across complex dendritic trees. During STDP, propagation of action potentials (APs) back to the site of synaptic input is thought to trigger plasticity. However, in pyramidal neurons, backpropagation of single APs is decremental, whereas high-frequency bursts lead to generation of distal dendritic calcium spikes. This raises the question whether STDP learning rules depend on synapse location and firing mode. Here, we investigate this issue at synapses between layer 2/3 and layer 5 pyramidal neurons in somatosensory cortex. We find that low-frequency pairing of single APs at positive times leads to a distance-dependent shift to long-term depression (LTD) at distal inputs. At proximal sites, this LTD could be converted to long-term potentiation (LTP) by dendritic depolarizations suprathreshold for BAC-firing or by high-frequency AP bursts. During AP bursts, we observed a progressive, distance-dependent shift in the timing requirements for induction of LTP and LTD, such that distal synapses display novel timing rules: they potentiate when inputs are activated after burst onset (negative timing) but depress when activated before burst onset (positive timing). These findings could be explained by distance-dependent differences in the underlying dendritic voltage waveforms driving NMDA receptor activation during STDP induction. Our results suggest that synapse location within the dendritic tree is a crucial determinant of STDP, and that synapses undergo plasticity according to local rather than global learning rules.
Complementing the Mainstream: An Exploration of Partnership Work between Complementary Alternative Provisions and Mainstream Schools

ERIC Educational Resources Information Center

Pennacchia, Jodie; Thomson, Pat

2016-01-01

In the English context, complementary alternative provisions (APs) can make specific positive contributions for young people at risk of exclusion from mainstream school. Whilst recognising the potential value of all complementary AP that is carefully selected and of high quality, we problematise the "repair and return" rationale that…
[Role of CD2-associated protein in podocyte differentiation.].

PubMed

Jiang, Hua-Jun; Chang, Ying; Zhu, Zhong-Hua; Liu, Jian-She; Deng, An-Guo; Zhang, Chun

2008-02-25

To study the cellular changes and the potential role of CD2-associated protein (CD2AP) in podocyte differentiation, conditionally immortalized murine podocyte cell line was cultured in RPMI 1640 medium under permissive condition at 33 °C. After transfection with CD2AP small interfering RNA (siRNA) the cells were shifted to non-permissive condition at 37 °C. Simultaneously, untransfected cells were taken as differentiation control. The podocyte proliferation rate was determined by MTT method. The expressions of CD2AP, WT1, synaptopodin and nephrin mRNAs were examined by RT-PCR. CD2AP, WT1 and nephrin protein expressions were examined by Western blot. The distribution of CD2AP, nephrin, F-actin and tubulin in differentiated and undifferentiated podocytes was detected by laser scanning confocal microscopy. The results showed: (1) CD2AP, WT1 and nephrin were stably expressed in differentiated and undifferentiated podocytes while synaptopodin was only expressed in differentiated podocytes. (2) CD2AP and nephrin mRNA and protein expressions were up-regulated during podocyte differentiation (P<0.05). (3) CD2AP and tubulin were distributed in the cytoplasm and perinulcear region in undifferentiated podocytes, and F-actin was predominantly localized to a cortical belt and paralleled to the cell axis. Under differentiation condition, CD2AP distribution profile was presented as peripheral accumulation, tubulin took on fascicular style and F-actin extended into foot processes in podocytes. CD2AP colocalized with nephrin and F-actin in undifferentiated podocytes. (4) After transfection with CD2AP siRNA, the expression of CD2AP was partially inhibited and cell growth was arrested; Synaptopodin, the differentiation podocyte marker, was apparently down-regulated; The differentiation of podocytes was delayed. The results demonstrate that podocyte differentiation is accompanied by cytoskeleton rearrangement and cell morphology change. CD2AP might play an essential role in podocyte differentiation.
Genome-wide investigation and expression analysis of AP2-ERF gene family in salt tolerant common bean

PubMed Central

Kavas, Musa; Kizildogan, Aslihan; Gökdemir, Gökhan; Baloglu, Mehmet Cengiz

2015-01-01

Apetala2-ethylene-responsive element binding factor (AP2-ERF) superfamily with common AP2-DNA binding domain have developmentally and physiologically important roles in plants. Since common bean genome project has been completed recently, it is possible to identify all of the AP2-ERF genes in the common bean genome. In this study, a comprehensive genome-wide in silico analysis identified 180 AP2-ERF superfamily genes in common bean (Phaseolus vulgaris). Based on the amino acid alignment and phylogenetic analyses, superfamily members were classified into four subfamilies: DREB (54), ERF (95), AP2 (27) and RAV (3), as well as one soloist. The physical and chemical characteristics of amino acids, interaction between AP2-ERF proteins, cis elements of promoter region of AP2-ERF genes and phylogenetic trees were predicted and analyzed. Additionally, expression levels of AP2-ERF genes were evaluated by in silico and qRT-PCR analyses. In silico micro-RNA target transcript analyses identified nearly all PvAP2-ERF genes as targets of by 44 different plant species' miRNAs were identified in this study. The most abundant target genes were PvAP2/ERF-20-25-62-78-113-173. miR156, miR172 and miR838 were the most important miRNAs found in targeting and BLAST analyses. Interactome analysis revealed that the transcription factor PvAP2-ERF78, an ortholog of Arabidopsis At2G28550, was potentially interacted with at least 15 proteins, indicating that it was very important in transcriptional regulation. Here we present the first study to identify and characterize the AP2-ERF transcription factors in common bean using whole-genome analysis, and the findings may serve as a references for future functional research on the transcription factors in common bean. PMID:27152109
4-aminopyridine, a Kv channel antagonist, prevents apoptosis of rat cerebellar granule neurons.

PubMed

Hu, Chang-Long; Liu, Zheng; Zeng, Xi-Min; Liu, Zi-Qiang; Chen, Xian-Hua; Zhang, Zhi-Hong; Mei, Yan-Ai

2006-09-01

Compelling evidence indicates that excessive potassium (K+) efflux and intracellular K+ depletion are the key early steps in apoptosis. Previously, we reported that apoptosis of cerebellar granule neurons induced by incubation in low-K+ (5 mM) and serum-free medium was associated with an increase in A-type transient inactivation of K+ channel current (IA) amplitude and modulation of channels' gating properties. Here, we showed that a classic K+ channel blocker, 4-aminopyradine (4-AP), significantly inhibited IA amplitude in a concentration-dependent manner (reduction of current by 10 microM and 10 mM 4-AP was 11.4+/-1.3% and 72.2+/-3.3%, respectively). Moreover, 4-AP modified the steady-state activation and inactivation kinetics of IA channels, such that the activation and inactivation curves were shifted to the right about 20 mV and 17 mV, respectively. Fluorescence staining showed that 4-AP dramatically increased the viability of cells undergoing apoptosis in a dose-dependent manner. That is, while 5 mM 4-AP was present, cell viability was 84.9+/-5.2%. Consistent with the cell viability analysis, internucleosomal DNA fragmentation by gel electrophoresis analysis showed that 5 mM 4-AP also protected against neuronal apoptosis. Furthermore, 4-AP significantly inhibited cytochrome c release and caspase-3 activity induced by low-K+/serum-free incubation. Finally, current-clamp analysis indicated that 5 mM 4-AP did not significantly depolarize the membrane potential. These results suggest that 4-AP has robust neuroprotective effects on apoptotic granule cells. The neuroprotective effect of 4-AP is likely not due to membrane depolarization, but rather that 4-AP may modulate the gating properties of IA channels in an anti-apoptotic manner.
Assimilation of active and passive microwave observations for improved estimates of soil moisture and crop growth

USDA-ARS?s Scientific Manuscript database

An Ensemble Kalman Filter-based data assimilation framework that links a crop growth model with active and passive (AP) microwave models was developed to improve estimates of soil moisture (SM) and vegetation biomass over a growing season of soybean. Complementarities in AP observations were incorpo...
VizieR Online Data Catalog: K giant stars along Sagittarius streams (Ren+, 2017)

NASA Astrophysics Data System (ADS)

Ren, H.-B.; Shi, W.-B.; Zhang, X.; Tang, Y.-K.; Zhang, Y.; Hou, Y.-H.; Wang, Y.-F.

2017-08-01

Law & Majewski (2010ApJ...714..229L) provided a Sgr model that has 105 points with angular position, distance and radial velocity. By using the model of Law & Majewski (2010ApJ...714..229L), we selected K giant samples belonging to the leading Sgr stream. (1 data file).
75 FR 74608 - Airworthiness Directives; CENTRAIR Models 101, 101A, 101P, and 101AP Gliders

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-01

... Airworthiness Directives; CENTRAIR Models 101, 101A, 101P, and 101AP Gliders AGENCY: Federal Aviation...[eacute] Nouvelle (SN) Centrair. This tube had been reinforced in 1984 with a modification. Gliders...[eacute] Nouvelle (SN) Centrair. This tube had been reinforced in 1984 with a modification. Gliders...
Ranolazine inhibits shear sensitivity of endogenous Na+ current and spontaneous action potentials in HL-1 cells

PubMed Central

Strege, Peter; Beyder, Arthur; Bernard, Cheryl; Crespo-Diaz, Ruben; Behfar, Atta; Terzic, Andre; Ackerman, Michael; Farrugia, Gianrico

2012-01-01

NaV1.5 is a mechanosensitive voltage-gated Na+ channel encoded by the gene SCN5A, expressed in cardiac myocytes and required for phase 0 of the cardiac action potential (AP). In the cardiomyocyte, ranolazine inhibits depolarizing Na+ current and delayed rectifier (IKr) currents. Recently, ranolazine was also shown to be an inhibitor of NaV1.5 mechanosensitivity. Stretch also accelerates the firing frequency of the SA node, and fluid shear stress increases the beating rate of cultured cardiomyocytes in vitro. However, no cultured cell platform exists currently for examination of spontaneous electrical activity in response to mechanical stimulation. In the present study, flow of solution over atrial myocyte-derived HL-1 cultured cells was used to study shear stress mechanosensitivity of Na+ current and spontaneous, endogenous rhythmic action potentials. In voltage-clamped HL-1 cells, bath flow increased peak Na+ current by 14 ± 5%. In current-clamped cells, bath flow increased the frequency and decay rate of AP by 27 ± 12% and 18 ± 4%, respectively. Ranolazine blocked both responses to shear stress. This study suggests that cultured HL-1 cells are a viable in vitro model for detailed study of the effects of mechanical stimulation on spontaneous cardiac action potentials. Inhibition of the frequency and decay rate of action potentials in HL-1 cells are potential mechanisms behind the antiarrhythmic effect of ranolazine. PMID:23018927

A two-channel action-potential generator for testing neurophysiologic data acquisition/analysis systems.

PubMed

Lisiecki, R S; Voigt, H F

1995-08-01

A 2-channel action-potential generator system was designed for use in testing neurophysiologic data acquisition/analysis systems. The system consists of a personal computer controlling an external hardware unit. This system is capable of generating 2 channels of simulated action potential (AP) waveshapes. The AP waveforms are generated from the linear combination of 2 principal-component template functions. Each channel generates randomly occurring APs with a specified rate ranging from 1 to 200 events per second. The 2 trains may be independent of one another or the second channel may be made to be excited or inhibited by the events from the first channel with user-specified probabilities. A third internal channel may be made to excite or inhibit events in both of the 2 output channels with user-specified rate parameters and probabilities. The system produces voltage waveforms that may be used to test neurophysiologic data acquisition systems for recording from 2 spike trains simultaneously and for testing multispike-train analysis (e.g., cross-correlation) software.
Genome-wide analysis of the emerging infection with Mycobacterium avium subspecies paratuberculosis in the Arabian camels (Camelus dromedarius).

PubMed

Ghosh, Pallab; Hsu, Chungyi; Alyamani, Essam J; Shehata, Maher M; Al-Dubaib, Musaad A; Al-Naeem, Abdulmohsen; Hashad, Mahmoud; Mahmoud, Osama M; Alharbi, Khalid B J; Al-Busadah, Khalid; Al-Swailem, Abdulaziz M; Talaat, Adel M

2012-01-01

Mycobacterium avium subspecies paratuberculosis (M. ap) is the causative agent of paratuberculosis or Johne's disease (JD) in herbivores with potential involvement in cases of Crohn's disease in humans. JD is spread worldwide and is economically important for both beef and dairy industries. Generally, pathogenic ovine strains (M. ap-S) are mainly found in sheep while bovine strains (M. ap-C) infect other ruminants (e.g. cattle, goat, deer), as well as sheep. In an effort to characterize this emerging infection in dromedary/Arabian camels, we successfully cultured M. ap from several samples collected from infected camels suffering from chronic, intermittent diarrhea suggestive of JD. Gene-based typing of isolates indicated that all isolates belong to sheep lineage of strains of M. ap (M. ap-S), suggesting a putative transmission from infected sheep herds. Screening sheep and goat herds associated with camels identified the circulation of this type in sheep but not goats. The current genome-wide analysis recognizes these camel isolates as a sub-lineage of the sheep strain with a significant number of single nucleotide polymorphisms (SNPs) between sheep and camel isolates (∼1000 SNPs). Such polymorphism could represent geographical differences among isolates or host adaptation of M. ap during camel infection. To our knowledge, this is the first attempt to examine the genomic basis of this emerging infection in camels with implications on the evolution of this important pathogen. The sequenced genomes of M. ap isolates from camels will further assist our efforts to understand JD pathogenesis and the dynamic of disease transmission across animal species.
Genome-Wide Analysis of the Emerging Infection with Mycobacterium avium Subspecies paratuberculosis in the Arabian Camels (Camelus dromedarius)

PubMed Central

Ghosh, Pallab; Hsu, Chungyi; Alyamani, Essam J.; Shehata, Maher M.; Al-Dubaib, Musaad A.; Al-Naeem, Abdulmohsen; Hashad, Mahmoud; Mahmoud, Osama M.; Alharbi, Khalid B. J.; Al-Busadah, Khalid; Al-Swailem, Abdulaziz M.; Talaat, Adel M.

2012-01-01

Mycobacterium avium subspecies paratuberculosis (M. ap) is the causative agent of paratuberculosis or Johne's disease (JD) in herbivores with potential involvement in cases of Crohn's disease in humans. JD is spread worldwide and is economically important for both beef and dairy industries. Generally, pathogenic ovine strains (M. ap-S) are mainly found in sheep while bovine strains (M. ap-C) infect other ruminants (e.g. cattle, goat, deer), as well as sheep. In an effort to characterize this emerging infection in dromedary/Arabian camels, we successfully cultured M. ap from several samples collected from infected camels suffering from chronic, intermittent diarrhea suggestive of JD. Gene-based typing of isolates indicated that all isolates belong to sheep lineage of strains of M. ap (M. ap-S), suggesting a putative transmission from infected sheep herds. Screening sheep and goat herds associated with camels identified the circulation of this type in sheep but not goats. The current genome-wide analysis recognizes these camel isolates as a sub-lineage of the sheep strain with a significant number of single nucleotide polymorphisms (SNPs) between sheep and camel isolates (∼1000 SNPs). Such polymorphism could represent geographical differences among isolates or host adaptation of M. ap during camel infection. To our knowledge, this is the first attempt to examine the genomic basis of this emerging infection in camels with implications on the evolution of this important pathogen. The sequenced genomes of M. ap isolates from camels will further assist our efforts to understand JD pathogenesis and the dynamic of disease transmission across animal species. PMID:22393374
Cardiotoxicity screening with simultaneous optogenetic pacing, voltage imaging and calcium imaging.

PubMed

Dempsey, Graham T; Chaudhary, Khuram W; Atwater, Nicholas; Nguyen, Cuong; Brown, Barry S; McNeish, John D; Cohen, Adam E; Kralj, Joel M

2016-01-01

The Comprehensive in vitro Proarrhythmia Assay (CiPA) initiative seeks an in vitro test to accurately predict clinical Torsades de Pointes (TdP). We developed a cardiotoxicity assay incorporating simultaneous measurement of the action potential (AP) waveform and Ca(2+) transient (CT) in human iPSC-derived cardiomyocytes (CMs). Concurrent optogenetic pacing provided a well-controlled electrophysiological background. We used the Optopatch platform for all-optical electrophysiology (Hochbaum et al., 2014). In a monolayer culture, a subset of cells expressed a genetically encoded, calcium and voltage reporter, CaViar (Hou, Kralj, Douglass, Engert, & Cohen, 2014), while others expressed a channelrhodopsin variant, CheRiff. Optical pacing of CheRiff-expressing cells synchronized the syncytium. We screened 12 compounds (11 acute, 1 chronic) to identify electrophysiological (AP rise time, AP50, AP90, beat rate) and CT effects in spontaneously beating and paced cultures (1Hz, 2Hz). CaViar reported spontaneous and paced APs and CTs with high signal-to-noise ratio and low phototoxicity. Quinidine, flecainide, E-4031, digoxin and cisapride prolonged APs, while verapamil and nifedipine shortened APs. Early after depolarizations (EADs) were elicited by quinidine, flecainide and cisapride. All but four compounds (amiodarone, chromanol, nifedipine, verapamil) prolonged AP rise time. Nifedipine and verapamil decreased CT amplitude, while digoxin increased CT amplitude. Pentamidine prolonged APs after chronic exposure. The Optopatch platform provides a robust assay to measure APs and CTs in hiPSC-CMs. This addresses the CiPA mandate and will facilitate comparisons of cell-based assays to human clinical data. Copyright © 2016 Elsevier Inc. All rights reserved.
Framework for Smart Electronic Health Record- Linked Predictive Models to Optimize Care for Complex Digestive Diseases

DTIC Science & Technology

2015-03-01

data against previous published outcomes in AP and Chronic Pancreatitis (CP). This served as useful validation of our data set before entering the...These patients can develop multiple complications from their disease. In addition, the treatments for CD (both medical and surgical ) can impose...years of diagnosis. The treatment for CD can sometimes involve very expensive medications with potentially serious side effects, as well as surgical
Zebrafish CaV2.1 Calcium Channels Are Tailored for Fast Synchronous Neuromuscular Transmission

PubMed Central

Naranjo, David; Wen, Hua; Brehm, Paul

2015-01-01

The CaV2.2 (N-type) and CaV2.1 (P/Q-type) voltage-dependent calcium channels are prevalent throughout the nervous system where they mediate synaptic transmission, but the basis for the selective presence at individual synapses still remains an open question. The CaV2.1 channels have been proposed to respond more effectively to brief action potentials (APs), an idea supported by computational modeling. However, the side-by-side comparison of CaV2.1 and CaV2.2 kinetics in intact neurons failed to reveal differences. As an alternative means for direct functional comparison we expressed zebrafish CaV2.1 and CaV2.2 α-subunits, along with their accessory subunits, in HEK293 cells. HEK cells lack calcium currents, thereby circumventing the need for pharmacological inhibition of mixed calcium channel isoforms present in neurons. HEK cells also have a simplified morphology compared to neurons, which improves voltage control. Our measurements revealed faster kinetics and shallower voltage-dependence of activation and deactivation for CaV2.1. Additionally, recordings of calcium current in response to a command waveform based on the motorneuron AP show, directly, more effective activation of CaV2.1. Analysis of calcium currents associated with the AP waveform indicate an approximately fourfold greater open probability (PO) for CaV2.1. The efficient activation of CaV2.1 channels during APs may contribute to the highly reliable transmission at zebrafish neuromuscular junctions. PMID:25650925
Expression and characterization of recombinant bifunctional enzymes with glutathione peroxidase and superoxide dismutase activities.

PubMed

Guan, Tuchen; Song, Jian; Wang, Yanan; Guo, Liying; Yuan, Lin; Zhao, Yingding; Gao, Yuan; Lin, Liangru; Wang, Yali; Wei, Jingyan

2017-09-01

To balance the production and decomposition of reactive oxygen species, living organisms have generated antioxidant enzymes and non-enzymatic antioxidant defense systems. Glutathione peroxidase (GPx) and superoxide dismutase (SOD) are two important antioxidant enzymes. Apart from their catalytic functions, they protect each other, resulting in more efficient removal of reactive oxygen species, protection of cells against injury, and maintenance of the normal metabolism of reactive oxygen species. SOD catalyzes the dismutation of the superoxide anion (O 2 •- ) to oxygen (O 2 ) and hydrogen peroxide (H 2 O 2 ). H 2 O 2 is then detoxified to water by GPx. In this study, human GPx1 Ser and the Alvinella pompejana SOD (ApSOD) gene were used to design and generate several recombinant proteins with both GPx and SOD activities by combining traditional fusion protein technology, a cysteine auxotrophic expression system, and a single protein production (SPP) system. Among the fusion proteins, Se-hGPx1 Ser -L-ApSOD exhibited the highest SOD and GPx activities. Additional research was conducted to better understand the properties of Se-hGPx1 Ser -L-ApSOD. The synergism of Se-hGPx1 Ser -L-ApSOD was evaluated by using an in vitro model. This research may facilitate future studies on the cooperation and catalytic mechanisms of GPx and SOD. We believe that the bifunctional enzyme has potential applications as a potent antioxidant. Copyright © 2017 Elsevier Inc. All rights reserved.
Structural insights into abasic site for Fpg specific binding and catalysis: comparative high-resolution crystallographic studies of Fpg bound to various models of abasic site analogues-containing DNA

PubMed Central

de Jésus, Karine Pereira; Serre, Laurence; Zelwer, Charles; Castaing, Bertrand

2005-01-01

Fpg is a DNA glycosylase that recognizes and excises the mutagenic 8-oxoguanine (8-oxoG) and the potentially lethal formamidopyrimidic residues (Fapy). Fpg is also associated with an AP lyase activity which successively cleaves the abasic (AP) site at the 3′ and 5′ sides by βδ-elimination. Here, we present the high-resolution crystal structures of the wild-type and the P1G defective mutant of Fpg from Lactococcus lactis bound to 14mer DNA duplexes containing either a tetrahydrofuran (THF) or 1,3-propanediol (Pr) AP site analogues. Structures show that THF is less extrahelical than Pr and its backbone C5′–C4′–C3′ diverges significantly from those of Pr, rAP, 8-oxodG and FapydG. Clearly, the heterocyclic oxygen of THF is pushed back by the carboxylate of the strictly conserved E2 residue. We can propose that the ring-opened form of the damaged deoxyribose is the structure active form of the sugar for Fpg catalysis process. Both structural and functional data suggest that the first step of catalysis mediated by Fpg involves the expulsion of the O4′ leaving group facilitated by general acid catalysis (involving E2), rather than the immediate cleavage of the N-glycosic bond of the damaged nucleoside. PMID:16243784
The Na+/K+ pump is an important modulator of refractoriness and rotor dynamics in human atrial tissue.

PubMed

Sánchez, Carlos; Corrias, Alberto; Bueno-Orovio, Alfonso; Davies, Mark; Swinton, Jonathan; Jacobson, Ingemar; Laguna, Pablo; Pueyo, Esther; Rodríguez, Blanca

2012-03-01

Pharmacological treatment of atrial fibrillation (AF) exhibits limited efficacy. Further developments require a comprehensive characterization of ionic modulators of electrophysiology in human atria. Our aim is to systematically investigate the relative importance of ionic properties in modulating excitability, refractoriness, and rotor dynamics in human atria before and after AF-related electrical remodeling (AFER). Computer simulations of single cell and tissue atrial electrophysiology were conducted using two human atrial action potential (AP) models. Changes in AP, refractory period (RP), conduction velocity (CV), and rotor dynamics caused by alterations in key properties of all atrial ionic currents were characterized before and after AFER. Results show that the investigated human atrial electrophysiological properties are primarily modulated by maximal value of Na(+)/K(+) pump current (G(NaK)) as well as conductances of inward rectifier potassium current (G(K1)) and fast inward sodium current (G(Na)). G(NaK) plays a fundamental role through both electrogenic and homeostatic modulation of AP duration (APD), APD restitution, RP, and reentrant dominant frequency (DF). G(K1) controls DF through modulation of AP, APD restitution, RP, and CV. G(Na) is key in determining DF through alteration of CV and RP, particularly in AFER. Changes in ionic currents have qualitatively similar effects in control and AFER, but effects are smaller in AFER. The systematic analysis conducted in this study unravels the important role of the Na(+)/K(+) pump current in determining human atrial electrophysiology.
Eradication of Helicobacter pylori infection by the probiotic strains Lactobacillus johnsonii MH-68 and L. salivarius ssp. salicinius AP-32.

PubMed

Hsieh, Pei-Shan; Tsai, Yi-Chun; Chen, Yi-Chun; Teh, Su-Fen; Ou, Chung-Mou; King, V An-Erl

2012-12-01

The current therapy for Helicobacter pylori infection includes antimicrobial agents and proton pump inhibitors. We have examined the ability of Lactobacillus spp. to inhibit H. pylori infection. Probiotic strains isolated from samples of adult feces, infant feces, breast milk, and vaginal swab collected from healthy volunteers in Taiwan and commercially available strains were screened for antagonism toward H. pylori. Inhibition liquid culture assay was used to screen potential anti-H. pylori activity. Then, we performed agar plate inhibition assay, and assays to determine the capacity of probiotics for adhesion, and inhibition and killing of H. pylori, and measured the levels of IL-8 and IL-10. Using animal models, we studied regulation of gastric acid and histopathological changes accompanying anti-H. pylori activity. We found that six of the tested strains suppressed urease activity of H. pylori: Lactobacillus acidophilus TYCA08, L. acidophilus TYCA15, L. johnsonii MH-68, and L. salivarius subsp. salicinius AP-32 were more effective than the others. In vivo, L. johnsonii MH-68 and L. salivarius subsp. salicinius AP-32 alone or in combination, reduced the H. pylori load in the gastric mucosa, and also reduced inflammatory chemokine expression and lymphocyte infiltration. Lactobacillus johnsonii MH-68 and L. salivarius subsp. salicinius AP-32 effectively suppress H. pylori viability, and when used as probiotics, they may help decrease the occurrence of gastritis, and even reduce the risk of H. pylori infection. © 2012 Blackwell Publishing Ltd.
Myogenic progenitors contribute to open but not closed fracture repair.

PubMed

Liu, Renjing; Birke, Oliver; Morse, Alyson; Peacock, Lauren; Mikulec, Kathy; Little, David G; Schindeler, Aaron

2011-12-22

Bone repair is dependent on the presence of osteocompetent progenitors that are able to differentiate and generate new bone. Muscle is found in close association with orthopaedic injury, however its capacity to make a cellular contribution to bone repair remains ambiguous. We hypothesized that myogenic cells of the MyoD-lineage are able to contribute to bone repair. We employed a MyoD-Cre+:Z/AP+ conditional reporter mouse in which all cells of the MyoD-lineage are permanently labeled with a human alkaline phosphatase (hAP) reporter. We tracked the contribution of MyoD-lineage cells in mouse models of tibial bone healing. In the absence of musculoskeletal trauma, MyoD-expressing cells are limited to skeletal muscle and the presence of reporter-positive cells in non-muscle tissues is negligible. In a closed tibial fracture model, there was no significant contribution of hAP+ cells to the healing callus. In contrast, open tibial fractures featuring periosteal stripping and muscle fenestration had up to 50% of hAP+ cells detected in the open fracture callus. At early stages of repair, many hAP+ cells exhibited a chondrocyte morphology, with lesser numbers of osteoblast-like hAP+ cells present at the later stages. Serial sections stained for hAP and type II and type I collagen showed that MyoD-lineage cells were surrounded by cartilaginous or bony matrix, suggestive of a functional role in the repair process. To exclude the prospect that osteoprogenitors spontaneously express MyoD during bone repair, we created a metaphyseal drill hole defect in the tibia. No hAP+ staining was observed in this model suggesting that the expression of MyoD is not a normal event for endogenous osteoprogenitors. These data document for the first time that muscle cells can play a significant secondary role in bone repair and this knowledge may lead to important translational applications in orthopaedic surgery. Please see related article: http://www.biomedcentral.com/1741-7015/9/136.
Determination of the influence of C24 D/(2R)- and L/(2S)-isomers of the CER[AP] on the lamellar structure of stratum corneum model systems using neutron diffraction.

PubMed

Schmitt, Thomas; Lange, Stefan; Sonnenberger, Stefan; Dobner, Bodo; Demé, Bruno; Neubert, Reinhard H H; Gooris, Gert; Bouwstra, Joke A

2017-12-01

This study was able to investigate the different influence of the d- and l-ceramide [AP] on the lamellar as well as molecular nanostructure of stratum corneum simulating lipid model mixtures. In this case, neutron diffraction together with specifically deuterated ceramide was used as an effective tool to investigate the lamellar and the molecular nanostructure of the mixtures. It could clearly be demonstrated, that both isomers show distinctly different characteristics, even though the variation between both is only a single differently arranged OH-group. The l-ceramide [AP] promotes a crystalline like phase behaviour even if mixed with ceramide [NP], cholesterol and free fatty acids. The d-ceramide [AP] only shows crystalline-like features if mixed only with cholesterol and free fatty acids but adopts a native-like behaviour if additionally mixed with ceramide [NP]. It furthermore demonstrates that the l-ceramide [AP] should not be used for any applications concerning ceramide substitution. It could however possibly serve its own purpose, if this crystalline like behaviour has some kind of positive influence on the SC or can be utilized for any practical applications. The results obtained in this study demonstrate that the diastereomers of ceramide [AP] are an attractive target for further research because their influence on the lamellar as well as the nanostructure is exceptionally strong. Additionally, the results furthermore show a very strong influence on hydration of the model membrane. With these properties, the d-ceramide [AP] could be effectively used to simulate native like behaviour even in very simple mixtures and could also have a strong impact on the native stratum corneum as well as high relevance for dermal ceramide substitution. The unnatural l-ceramide [AP] on the other hand should be investigated further, to assess its applicability. Copyright © 2017 Elsevier B.V. All rights reserved.
Associations of udder-health indicators with cow factors and with intramammary infection in dairy cows.

PubMed

Nyman, A-K; Persson Waller, K; Bennedsgaard, T W; Larsen, T; Emanuelson, U

2014-09-01

The objective of this study was to investigate if and how cow factors and intramammary infection (IMI) are associated with 4 different udder-health indicators in dairy cows as a first step in investigating whether the diagnostic performance of these indicators can be improved. The investigated indicators were somatic cell count (SCC), lactate dehydrogenase (LDH), N-acetyl-β-d-glucosaminidase (NAGase), and alkaline phosphatase (AP) measured in milk. In this cross-sectional study, approximately 1,000 cows from 25 dairy herds were sampled for bacteriology (quarter milk samples) during 3 consecutive days: the day before test milking, at the day of test milking, and at the day after test milking. The whole-udder test milking sample was analyzed for milk composition, SCC, LDH, NAGase, and AP. Cow data (parity, breed, milk yield, percentage of milk fat and protein, milk urea concentration, and days in milk from the sampled test milking) were collected from the Swedish milk-recording scheme. Of the sampled cows 485 were considered IMI negative and were used in multivariable mixed-effect linear regression models to investigate associations between cow factors and the udder-health indicators. A second modeling including all cows, both IMI negative and IMI positive (256 cows), was also performed. The results showed that all udder-health indicators were affected by cow factors but that different cow factors were associated with different indicators. Intramammary-infection status was significantly associated with all udder-health indicators except AP. Parity and milk urea concentration were the only cow factors associated with all indicators in all models. The significant cow factors explained 23% of the variation in SCC and >30% of the variation in LDH, NAGase, and AP in IMI-negative cows, showing that LDH, NAGase, and AP are more affected than SCC by cow factors. The IMI status explained 23% of the variation in SCC in the model with all cows but only 7% of the variation in LDH and 2% of the variation in NAGase, indicating that SCC has the best potential as a diagnostic tool in finding cows with IMI. However, further studies are needed to investigate whether the diagnostic properties of these udder-health indicators will improve with adjustment according to their associations with different cow factors when used as a diagnostic tool for finding cows with IMI. Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.
Risk score to predict hospital-acquired pneumonia after spontaneous intracerebral hemorrhage.

PubMed

Ji, Ruijun; Shen, Haipeng; Pan, Yuesong; Du, Wanliang; Wang, Penglian; Liu, Gaifen; Wang, Yilong; Li, Hao; Zhao, Xingquan; Wang, Yongjun

2014-09-01

We aimed to develop a risk score (intracerebral hemorrhage-associated pneumonia score, ICH-APS) for predicting hospital-acquired stroke-associated pneumonia (SAP) after ICH. The ICH-APS was developed based on the China National Stroke Registry (CNSR), in which eligible patients were randomly divided into derivation (60%) and validation (40%) cohorts. Variables routinely collected at presentation were used for predicting SAP after ICH. For testing the added value of hematoma volume measure, we separately developed 2 models with (ICH-APS-B) and without (ICH-APS-A) hematoma volume included. Multivariable logistic regression was performed to identify independent predictors. The area under the receiver operating characteristic curve (AUROC), Hosmer-Lemeshow goodness-of-fit test, and integrated discrimination index were used to assess model discrimination, calibration, and reclassification, respectively. The SAP was 16.4% and 17.7% in the overall derivation (n=2998) and validation (n=2000) cohorts, respectively. A 23-point ICH-APS-A was developed based on a set of predictors and showed good discrimination in the overall derivation (AUROC, 0.75; 95% confidence interval, 0.72-0.77) and validation (AUROC, 0.76; 95% confidence interval, 0.71-0.79) cohorts. The ICH-APS-A was more sensitive for patients with length of stay >48 hours (AUROC, 0.78; 95% confidence interval, 0.75-0.81) than those with length of stay <48 hours (AUROC, 0.64; 95% confidence interval, 0.55-0.73). The ICH-APS-A was well calibrated (Hosmer-Lemeshow test) in the derivation (P=0.20) and validation (P=0.66) cohorts. Similarly, a 26-point ICH-APS-B was established. The ICH-APS-A and ICH-APS-B were not significantly different in discrimination and reclassification for SAP after ICH. The ICH-APSs are valid risk scores for predicting SAP after ICH, especially for patients with length of stay >48 hours. © 2014 American Heart Association, Inc.
Advanced APS impacts on vehicle payloads

NASA Technical Reports Server (NTRS)

Schneider, Steven J.; Reed, Brian D.

1989-01-01

Advanced auxiliary propulsion system (APS) technology has the potential to both, increase the payload capability of earth-to-orbit (ETO) vehicles by reducing APS propellant mass, and simplify ground operations and logistics by reducing the number of fluids on the vehicle and eliminating toxic, corrosive propellants. The impact of integrated cryogenic APS on vehicle payloads is addressed. In this system, launch propulsion system residuals are scavenged from integral launch propulsion tanks for use in the APS. Sufficient propellant is preloaded into the APS to return to earth with margin and noncomplete scavenging assumed. No propellant conditioning is required by the APS, but ambient heat soak is accommodated. High temperature rocket materials enable the use of the unconditioned hydrogen/oxygen in the APS and are estimated to give APS rockets specific impulse of up to about 444 sec. The payload benefits are quantified and compared with an uprated monomethylhydrazine/nitrogen tetroxide system in a conservative fashion, by assuming a 25.5 percent weight growth for the hydrogen/oxygen system and a 0 percent weight growth for the uprated system. The combination of scavenging and high performance gives payload impacts which are highly mission specific. A payload benefit of 861 kg (1898 lbm) was estimated for a Space Station Freedom rendezvous mission and 2099 kg (4626 lbm) for a sortie mission, with payload impacts varying with the amount of launch propulsion residual propellants. Missions without liquid propellant scavenging were estimated to have payload penalties, however, operational benefits were still possible.
Advanced APS Impacts on Vehicle Payloads

NASA Technical Reports Server (NTRS)

Schneider, Steven J.; Reed, Brian D.

1989-01-01

Advanced auxiliary propulsion system (APS) technology has the potential to both, increase the payload capability of earth-to-orbit (ETO) vehicles by reducing APS propellant mass, and simplify ground operations and logistics by reducing the number of fluids on the vehicle and eliminating toxic, corrosive propellants. The impact of integrated cryogenic APS on vehicle payloads is addressed. In this system, launch propulsion system residuals are scavenged from integral launch propulsion tanks for use in the APS. Sufficient propellant is preloaded into the APS to return to earth with margin and noncomplete scavenging assumed. No propellant conditioning is required by the APS, but ambient heat soak is accommodated. High temperature rocket materials enable the use of the unconditioned hydrogen/oxygen in the APS and are estimated to give APS rockets specific impulse of up to about 444 sec. The payload benefits are quantified and compared with an uprated monomethyl hydrazine/nitrogen tetroxide system in a conservative fashion, by assuming a 25.5 percent weight growth for the hydrogen/oxygen system and a 0 percent weight growth for the uprated system. The combination and scavenging and high performance gives payload impacts which are highly mission specific. A payload benefit of 861 kg (1898 lbm) was estimated for a Space Station Freedom rendezvous mission and 2099 kg (4626 lbm) for a sortie mission, with payload impacts varying with the amount of launch propulsion residual propellants. Missions without liquid propellant scavenging were estimated to have payload penalties, however, operational benefits were still possible.
TRO40303 Ameliorates Alcohol-Induced Pancreatitis Through Reduction of Fatty Acid Ethyl Ester–Induced Mitochondrial Injury and Necrotic Cell Death

PubMed Central

Javed, Muhammad Ahsan; Wen, Li; Awais, Muhammad; Latawiec, Diane; Huang, Wei; Chvanov, Michael; Schaller, Sophie; Bordet, Thierry; Michaud, Magali; Pruss, Rebecca; Tepikin, Alexei; Criddle, David; Sutton, Robert

2018-01-01

Objectives Mitochondrial permeability transition pore inhibition is a promising approach to treat acute pancreatitis (AP). We sought to determine (i) the effects of the mitochondrial permeability transition pore inhibitor 3,5-seco-4-nor-cholestan-5-one oxime-3-ol (TRO40303) on murine and human pancreatic acinar cell (PAC) injury induced by fatty acid ethyl esters (FAEEs) or taurolithocholic acid-3-sulfate and (ii) TRO40303 pharmacokinetics and efficacy in experimental alcoholic AP (FAEE-AP). Methods Changes in mitochondrial membrane potential (Δψm), cytosolic Ca2+ ([Ca2+]c), and cell fate were examined in freshly isolated murine or human PACs by confocal microscopy. TRO40303 pharmacokinetics were assessed in cerulein-induced AP and therapeutic efficacy in FAEE-AP induced with palmitoleic acid and ethanol. Severity of AP was assessed by standard biomarkers and blinded histopathology. Results TRO40303 prevented loss of Δψm and necrosis induced by 100 μM palmitoleic acid ethyl ester or 500 μM taurolithocholic acid-3-sulfate in murine and human PACs. Pharmacokinetic analysis found TRO40303 accumulated in the pancreas. A single dose of 3 mg/kg TRO40303 significantly reduced serum amylase (P = 0.043), pancreatic trypsin (P = 0.018), and histopathology scores (P = 0.0058) in FAEE-AP. Conclusions TRO40303 protects mitochondria and prevents necrotic cell death pathway activation in murine and human PACs, ameliorates the severity of FAEE-AP, and is a candidate drug for human AP. PMID:29200128
Insights into electrochemical reactions from ambient pressure photoelectron spectroscopy.

PubMed

Stoerzinger, Kelsey A; Hong, Wesley T; Crumlin, Ethan J; Bluhm, Hendrik; Shao-Horn, Yang

2015-11-17

The understanding of fundamental processes in the bulk and at the interfaces of electrochemical devices is a prerequisite for the development of new technologies with higher efficiency and improved performance. One energy storage scheme of great interest is splitting water to form hydrogen and oxygen gas and converting back to electrical energy by their subsequent recombination with only water as a byproduct. However, kinetic limitations to the rate of oxygen-based electrochemical reactions hamper the efficiency in technologies such as solar fuels, fuel cells, and electrolyzers. For these reactions, the use of metal oxides as electrocatalysts is prevalent due to their stability, low cost, and ability to store oxygen within the lattice. However, due to the inherently convoluted nature of electrochemical and chemical processes in electrochemical systems, it is difficult to isolate and study individual electrochemical processes in a complex system. Therefore, in situ characterization tools are required for observing related physical and chemical processes directly at the places where and while they occur and can help elucidate the mechanisms of charge separation and charge transfer at electrochemical interfaces. X-ray photoelectron spectroscopy (XPS), also known as ESCA (electron spectroscopy for chemical analysis), has been used as a quantitative spectroscopic technique that measures the elemental composition, as well as chemical and electronic state of a material. Building from extensive ex situ characterization of electrochemical systems, initial in situ studies were conducted at or near ultrahigh vacuum (UHV) conditions (≤10(-6) Torr) to probe solid-state electrochemical systems. However, through the integration of differential-pumping stages, XPS can now operate at pressures in the torr range, comprising a technique called ambient pressure XPS (AP-XPS). In this Account, we briefly review the working principles and current status of AP-XPS. We use several recent in situ studies on model electrochemical components as well as operando studies performed by our groups at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory to illustrate that AP-XPS is both a chemically and an electrically specific tool since photoelectrons carry information on both the local chemistry and electrical potentials. The applications of AP-XPS to oxygen electrocatalysis shown in this Account span well-defined studies of (1) the oxide/oxygen gas interface, (2) the oxide/water vapor interface, and (3) operando measurements of half and full electrochemical cells. Using specially designed model devices, we can expose and isolate the electrode or interface of interest to the incident X-ray beam and AP-XPS analyzer to relate the electrical potentials to the composition/chemical state of the key components and interfaces. We conclude with an outlook on new developments of AP-XPS end stations, which may provide significant improvement in the observation of dynamics over a wide range of time scales, higher spatial resolution, and improved characterization of boundary or interface layers (solid/solid and liquid/solid).
Brief Report: HIV Assisted Partner Services Among Those With and Without a History of Intimate Partner Violence in Kenya.

PubMed

Goyette, Marielle S; Mutiti, Peter M; Bukusi, David; Wamuti, Beatrice M; Otieno, Felix A; Cherutich, Peter; Golden, Matthew R; Spiegel, Hans; Richardson, Barbra A; Ngʼangʼa, Anne; Farquhar, Carey

2018-05-01

HIV assisted partner services (APS) are a notification and testing strategy for sex partners of HIV-infected index patients. This cluster-randomized controlled trial secondary data analysis investigated whether history of intimate partner violence (IPV) modified APS effectiveness and risk of relationship dissolution. Eighteen HIV testing and counseling sites in Kenya randomized to provide immediate APS (intervention) or APS delayed for 6 weeks (control). History of IPV was ascertained at study enrollment and defined as reporting ever experiencing physical or sexual IPV. Those reporting IPV in the month before enrollment were excluded. We tested whether history of IPV modified intervention effectiveness and risk of relationship dissolution using population-averaged Poisson and log-binomial generalized estimating equation models. Exploratory analyses investigated associations between history of IPV and events that occurred after HIV diagnosis using log-binomial generalized estimating equation models. The study enrolled 1119 index participants and 1286 partners. Among index participants, 81 (7%) had history of IPV. History of IPV did not modify APS effectiveness in testing, newly diagnosing, or linking partners to care. History of IPV did not modify the association between receiving immediate APS and relationship dissolution during the study. Among participants who had not experienced IPV in the last month but had experienced IPV in their lifetimes, our results suggest that APS is an effective and safe partner notification strategy in Kenya. As APS is scaled up in different contexts, these data support including those reporting past IPV and closely monitoring adverse events.
Spectrum of cisplatin-induced mutations in Escherichia coli

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burnouf, D.; Duane, M.; Fuchs, R.P.

1987-06-01

Using a forward-mutation assay based on the inactivation of the tetracycline-resistance gene located on plasmid pBR322, we have determined the mutation spectrum induced in Escherichia coli by cisplatin (cis-diamminedichloroplatinum(II)), a widely used antitumor drug. Cisplatin is known to form mainly intrastrand diadducts at ApG and GpG sites. We found that cisplatin efficiently induces mutations in an SOS-dependent way (i.e., dependent upon UV irradiation of the host bacteria). More than 90% of the mutations are single-base-pair substitutions occurring at the potential sites of cisplatin adducts (ApG and GpG). Taking into account the relative proportions of ApG and GpG adducts, we foundmore » that the ApG adducts are at least 5 times more mutagenic than the GpG adducts. Moreover, a strong mutation specificity was seen at the 5' side of the ApG adducts (A X T----T X A transversions). The observation that most mutations occur at the 5' end of the adduct at both ApG and GpG sites is discussed in relation to recent structural data.« less

Fabrication and Physical Evaluation of Gelatin-Coated Carbonate Apatite Foam

PubMed Central

Hara, Kanae; Fujisawa, Kenji; Nagai, Hirokazu; Takamaru, Natsumi; Ohe, Go; Tsuru, Kanji; Ishikawa, Kunio; Miyamoto, Youji

2016-01-01

Carbonate apatite (CO3Ap) foam has gained much attention in recent years because of its ability to rapidly replace bone. However, its mechanical strength is extremely low for clinical use. In this study, to understand the potential of gelatin-reinforced CO3Ap foam for bone replacement, CO3Ap foam was reinforced with gelatin and the resulting physical characteristics were evaluated. The mechanical strength increased significantly with the gelatin reinforcement. The compressive strength of gelatin-free CO3Ap foam was 74 kPa whereas that of the gelatin-reinforced CO3Ap foam, fabricated using 30 mass % gelatin solution, was approximately 3 MPa. Heat treatment for crosslinking gelatin had little effect on the mechanical strength of the foam. The gelatin-reinforced foam did not maintain its shape when immersed in a saline solution as this promoted swelling of the gelatin; however, in the same conditions, the heat-treated gelatin-reinforced foam proved to be stable. It is concluded, therefore, that heat treatment is the key to the fabrication of stable gelatin-reinforced CO3Ap foam. PMID:28773832
Efficacy and safety of novel antipsychotics: a critical review.

PubMed

Balestrieri, Matteo; Vampini, Claudio; Bellantuono, Cesario

2000-10-01

Efficacy and safety of novel antipsychotic (AP) drugs (amisulpride, olanzapine, quetiapine, ziprasidone and zotepine) have been reviewed. Data on their antipsychotic efficacy and side effects profile have been evaluated only on the basis of controlled trials so far published. Overall, all these drugs have shown an antipsychotic efficacy on positive symptoms of schizophrenia similar to that of the conventional AP drugs. On negative symptoms, all novel AP drugs, except quetiapine and ziprasidone, demonstrated a better efficacy than haloperidol. Long-term efficacy of these AP drugs in the maintenance treatment of schizophrenia needs to be explored by further, better-designed, epidemiological studies. The safety profile shows that the novel AP drugs are generally well-tolerated and induce significantly less acute extrapyramidal side effects in comparison with haloperidol. Some methodological flaws in the experimental design of the clinical trials analysed are discussed. Although these novel AP drugs have potential clinical advantages, a number of relevant questions still remain to be addressed, in order to establish the impact of these drugs in the overall treatment of schizophrenia. Copyright 2000 John Wiley & Sons, Ltd.
Network-specific mechanisms may explain the paradoxical effects of carbamazepine and phenytoin.

PubMed

Thomas, Evan A; Petrou, Steven

2013-07-01

A common notion of the mechanism by which the antiepileptic drugs (AEDs) carbamazepine and phenytoin act is that they block sodium channels by binding preferentially to the inactivated state, thereby allowing normal neuronal firing while blocking ictal activity. However, these drugs have unpredictable efficacy and, in some cases, may exacerbate seizures. Previous studies have suggested that reducing sodium channel availability in the dentate gyrus (DG) paradoxically increases excitability. We used a biophysically detailed computer model of the DG to test the hypothesis that AEDs increase excitability by disproportionately reducing negative feedback mechanisms. We built a Markov model of sodium channel gating that reproduces responses to voltage clamp experiments in the presence of carbamazepine and phenytoin. We incorporated this validated Markov model into a biophysically realistic computer model of DG neurons and networks. Simulated drug concentrations were similar to those measured in cerebral spinal fluid in medicated patients. Single neuron models were stimulated with current injections, and networks were stimulated with perforant path synaptic input. In the network model, environmental effects were studied by introducing mossy fiber sprouting. As expected, drugs reduced sodium channel availability, which in turn reduced action potential amplitude. This had only a small effect on action potential (AP) firing rate during brief (100 msec) current injections. Paradoxically, long current injections (2,500 msec) increased AP firing rates. This was caused by reduced calcium entry and consequently reduced activation of calcium activated potassium channels. It is important to note that the main determinant of drug effect was resting membrane potential (RMP) and not action potential firing rate. Binding of phenytoin and carbamazepine is slow and, thus drug effects are largely determined by the long term state of the RMP. This paradoxical AP firing increase was dependent on the unusually large calcium-activated potassium conductances expressed by DG granule cells. This predicts that drug efficacy in a given network will depend on the precise makeup of conductances in the network. RMP is expected to vary with the level of activity in the network. We simulated the effects of drugs on single shot stimulus responses in networks with mossy fiber sprouting and varied the RMP in all neurons as a model for network activity. For an RMP of -50 mV, representing an active network, drugs had no effect, or in some cases, increased excitability. Drugs had an increasingly larger inhibitory effect on network responses as RMP decreased. An important prediction is that drugs will be unable to block ictal activity invading an active network. Our key findings are that drug effects depend on both intrinsic properties of the network and its behavioral state. This may explain the paradoxical and unpredictable effects of some AEDs on seizure control in some patients. Wiley Periodicals, Inc. © 2013 International League Against Epilepsy.
[Spatial variation of soil phosphorus in flooded area of the Yellow River based on GIS and geo-statistical methods: A case study in Zhoukou City, Henan, China.

PubMed

Jia, Zhen Yu; Zhang, Jun Hua; Ding, Sheng Yan; Feng, Shu; Xiong, Xiao Bo; Liang, Guo Fu

2016-04-22

Soil phosphorus is an important indicator to measure the soil fertility, because the content of soil phosphorus has an important effect on physical and chemical properties of soil, plant growth, and microbial activity in soil. In this study, the soil samples collecting and indoor analysis were conducted in Zhoukou City located in the flooded area of the Yellow River. By using GIS combined with geo-statistics, we tried to analyze the spatial variability and content distribution of soil total phosphorus (TP) and soil available phosphorus (AP) in the study area. Results showed that TP and AP of both soil layers (0-20 cm and 20-40 cm) were rich, and the contents of TP and AP in surface layer (0-20 cm) were higher than in the second layer (20-40 cm). TP and AP of both soil layers exhibited variation at medium level, and AP had varied much higher than TP. TP of both layers showed medium degree of anisotropy which could be well modeled by the Gaussian model. TP in the surface layer showed strong spatial correlation, but that of the second layer had medium spatial correlation. AP of both layers had a weaker scope in anisotropy which could be simulated by linear model, and both soil layers showed weaker spatial correlations. TP of both soil layers showed a slowly rising change from southwest to northeast of the study area, while it gradually declined from northwest to southeast. AP in soil surface layer exhibited an increase tendency firstly and then decrease from southwest to the northeast, while it decreased firstly and then increased from southeast to the northwest. AP in the second soil layer had an opposite change in the southwest to the northeast, while it showed continuously increasing tendency from northwest to the southeast. The contents of TP and AP in the surface layer presented high grades and the second layer of TP belonged to medium grade, but the second layer of AP was in a lower grade. The artificial factors such as land use type, cropping system, irrigation and fertilization were the main factors influencing the distribution and spatial variation of soil phosphorus in this area.
Pro‐arrhythmic atrial phenotypes in incrementally paced murine Pgc1β −/− hearts: effects of age

PubMed Central

Valli, Haseeb; Ahmad, Shiraz; Fraser, James A.; Jeevaratnam, Kamalan

2017-01-01

New Findings What is the central question of this study? Can we experimentally replicate atrial pro‐arrhythmic phenotypes associated with important chronic clinical conditions, including physical inactivity, obesity, diabetes mellitus and metabolic syndrome, compromising mitochondrial function, and clarify their electrophysiological basis? What is the main finding and its importance? Electrocardiographic and intracellular cardiomyocyte recording at progressively incremented pacing rates demonstrated age‐dependent atrial arrhythmic phenotypes in Langendorff‐perfused murine Pgc1β −/− hearts for the first time. We attributed these to compromised action potential conduction and excitation wavefronts, whilst excluding alterations in recovery properties or temporal electrophysiological instabilities, clarifying these pro‐arrhythmic changes in chronic metabolic disease. Atrial arrhythmias, most commonly manifesting as atrial fibrillation, represent a major clinical problem. The incidence of atrial fibrillation increases with both age and conditions associated with energetic dysfunction. Atrial arrhythmic phenotypes were compared in young (12–16 week) and aged (>52 week) wild‐type (WT) and peroxisome proliferative activated receptor, gamma, coactivator 1 beta (Ppargc1b)‐deficient (Pgc1β −/−) Langendorff‐perfused hearts, previously used to model mitochondrial energetic disorder. Electrophysiological explorations were performed using simultaneous whole‐heart ECG and intracellular atrial action potential (AP) recordings. Two stimulation protocols were used: an S1S2 protocol, which imposed extrasystolic stimuli at successively decremented intervals following regular pulse trains; and a regular pacing protocol at successively incremented frequencies. Aged Pgc1β −/− hearts showed greater atrial arrhythmogenicity, presenting as atrial tachycardia and ectopic activity. Maximal rates of AP depolarization (dV/dt max) were reduced in Pgc1β −/− hearts. Action potential latencies were increased by the Pgc1β −/− genotype, with an added interactive effect of age. In contrast, AP durations to 90% recovery (APD90) were shorter in Pgc1β −/− hearts despite similar atrial effective recovery periods amongst the different groups. These findings accompanied paradoxical decreases in the incidence and duration of alternans in the aged and Pgc1β −/− hearts. Limiting slopes of restitution curves of APD90 against diastolic interval were correspondingly reduced interactively by Pgc1β −/− genotype and age. In contrast, reduced AP wavelengths were associated with Pgc1β −/− genotype, both independently and interacting with age, through the basic cycle lengths explored, with the aged Pgc1β −/− hearts showing the shortest wavelengths. These findings thus implicate AP wavelength in possible mechanisms for the atrial arrhythmic changes reported here. PMID:28960529
Quantification of circulating fetal DNA as a tool for potential monitoring of pregnant patients with antiphospholipid antibodies.

PubMed

Korabecna, Marie; Ulcova-Gallova, Zdenka; Horinek, Ales; Pazourková, Eva; Calda, Pavel

2014-11-01

Apoptosis of tissues of fetal origin is thought to be one of the main sources of cell-free fetal DNA (cffDNA) in maternal circulation, impaired apoptosis is also involved in the mechanisms contributing to recurrent spontaneous miscarriages (RSM) associated with antiphospholipid syndrome (APS). The APS increases the risk for preeclampsia nine times. In preeclampsia, the elevated levels of cffDNA were described by different authors. To our knowledge, cffDNA in pregnant patients with APS was never studied. In our pilot study, we focused on the levels of cffDNA in four pregnant patients with treated primary APS and compared them with values obtained in twenty-one healthy subjects of comparable gestation age (the third trimester of pregnancy). We supposed that the increase of cffDNA concentration in our treated patients would signalize the elevated apoptosis of fetal tissues as in other pathological changes of placentation. The aim of our pilot study was to determine cffDNA concentrations in patients with treated APS and to compare them with values detected in healthy pregnant women of comparable gestation age in order to discover potential non-physiological elevations in patients. The elevated values of cffDNA were not observed in our patients (p value = 0.4363, Mann-Whitney test). All patients delivered healthy children. The measurement of concentrations of cffDNA seems to be a promising tool for monitoring of therapy effectiveness in pregnant women with APS but evaluation of randomized controlled trials would be necessary to determine the specificity and the sensitivity of this test.
Shade-Induced Action Potentials in Helianthus annuus L. Originate Primarily from the Epicotyl

PubMed Central

Stephens, Nicholas R; Cleland, Robert E; Van Volkenburgh, Elizabeth

2006-01-01

Repeated observations that shading (a drastic reduction in illumination rate) increased the generation of spikes (rapidly reversed depolarizations) in leaves and stems of many cucumber and sunflower plants suggests a phenomenon widespread among plant organs and species. Although shaded leaves occasionally generate spikes and have been suggested to trigger systemic action potentials (APs) in sunflower stems, we never found leaf-generated spikes to propagate out of the leaf and into the stem. On the contrary, our data consistently implicate the epicotyl as the location where most spikes and APs (propagating spikes) originate. Microelectrode studies of light and shading responses in mesophyll cells of leaf strips and in epidermis/cortex cells of epicotyl segments confirm this conclusion and show that spike induction is not confined to intact plants. 90% of the epicotyl-generated APs undergo basipetal propagation to the lower epicotyl, hypocotyl and root. They propagate with an average rate of 2 ± 0.3 mm s−1 and always undergo a large decrement from the hypocotyl to the root. The few epicotyl-derived APs that can be tracked to leaf blades (< 10%) undergo either a large decrement or fail to be transmitted at all. Occasionally (5% of the observations) spikes were be generated in hypocotyl and lower epicotyl that moved towards the upper epicotyl unaltered, decremented, or amplified. This study confirms that plant APs arise to natural, nontraumatic changes. In simultaneous recordings with epicotyl growth, AP generation was found to parallel the acceleration of stem growth under shade. The possible relatedness of both processes must be further investigated. PMID:19521471
Recording temperature affects the excitability of mouse superficial dorsal horn neurons, in vitro.

PubMed

Graham, B A; Brichta, A M; Callister, R J

2008-05-01

Superficial dorsal horn (SDH) neurons in laminae I-II of the spinal cord play an important role in processing noxious stimuli. These neurons represent a heterogeneous population and are divided into various categories according to their action potential (AP) discharge during depolarizing current injection. We recently developed an in vivo mouse preparation to examine functional aspects of nociceptive processing and AP discharge in SDH neurons and to extend investigation of pain mechanisms to the genetic level of analysis. Not surprisingly, some in vivo data obtained at body temperature (37 degrees C) differed from those generated at room temperature (22 degrees C) in spinal cord slices. In the current study we examine how temperature influences SDH neuron properties by making recordings at 22 and 32 degrees C in transverse spinal cord slices prepared from L3-L5 segments of adult mice (C57Bl/6). Patch-clamp recordings (KCH(3)SO(4) internal) were made from visualized SDH neurons. At elevated temperature all SDH neurons had reduced input resistance and smaller, briefer APs. Resting membrane potential and AP afterhyperpolarization amplitude were temperature sensitive only in subsets of the SDH population. Notably, elevated temperature increased the prevalence of neurons that did not discharge APs during current injection. These reluctant firing neurons expressed a rapid A-type potassium current, which is enhanced at higher temperatures and thus restrains AP discharge. When compared with previously published whole cell recordings obtained in vivo (37 degrees C) our results suggest that, on balance, in vitro data collected at elevated temperature more closely resemble data collected under in vivo conditions.
Experience-dependent increase in spine calcium evoked by backpropagating action potentials in layer 2/3 pyramidal neurons in rat somatosensory cortex.

PubMed

Krieger, Patrik

2009-11-01

In spines on basal dendrites of layer 2/3 pyramidal neurons in somatosensory barrel cortex, calcium transients evoked by back-propagating action potentials (bAPs) were investigated (i) along the length of the basal dendrite, (ii) with postnatal development and (iii) with sensory deprivation during postnatal development. Layer 2/3 pyramidal neurons were investigated at three different ages. At all ages [postnatal day (P)8, P14, P21] the bAP-evoked calcium transient amplitude increased with distance from the soma with a peak at around 50 microm, followed by a gradual decline in amplitude. The effect of sensory deprivation on the bAP-evoked calcium was investigated using two different protocols. When all whiskers on one side of the rat snout were trimmed daily from P8 to P20-24 there was no difference in the bAP-evoked calcium transient between cells in the contralateral hemisphere, lacking sensory input from the whisker, and cells in the ipsilateral barrel cortex, with intact whisker activation. When, however, only the D-row whiskers on one side were trimmed the distribution of bAP-evoked calcium transients in spines was shifted towards larger amplitudes in cells located in the deprived D-column. In conclusion, (i) the bAP-evoked calcium transient gradient along the dendrite length is established at P8, (ii) the calcium transient increases in amplitude with age and (iii) this increase is enhanced in layer 2/3 pyramidal neurons located in a sensory-deprived barrel column that is bordered by non-deprived barrel columns.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Koenig, Xaver; Kovar, Michael; Rubi, Lena

The plant alkaloid ibogaine has promising anti-addictive properties. Albeit not licenced as a therapeutic drug, and despite hints that ibogaine may perturb the heart rhythm, this alkaloid is used to treat drug addicts. We have recently reported that ibogaine inhibits human ERG (hERG) potassium channels at concentrations similar to the drugs affinity for several of its known brain targets. Thereby the drug may disturb the heart's electrophysiology. Here, to assess the drug's cardiac ion channel profile in more detail, we studied the effects of ibogaine and its congener 18-Methoxycoronaridine (18-MC) on various cardiac voltage-gated ion channels. We confirmed that heterologouslymore » expressed hERG currents are reduced by ibogaine in low micromolar concentrations. Moreover, at higher concentrations, the drug also reduced human Na{sub v}1.5 sodium and Ca{sub v}1.2 calcium currents. Ion currents were as well reduced by 18-MC, yet with diminished potency. Unexpectedly, although blocking hERG channels, ibogaine did not prolong the action potential (AP) in guinea pig cardiomyocytes at low micromolar concentrations. Higher concentrations (≥ 10 μM) even shortened the AP. These findings can be explained by the drug's calcium channel inhibition, which counteracts the AP-prolonging effect generated by hERG blockade. Implementation of ibogaine's inhibitory effects on human ion channels in a computer model of a ventricular cardiomyocyte, on the other hand, suggested that ibogaine does prolong the AP in the human heart. We conclude that therapeutic concentrations of ibogaine have the propensity to prolong the QT interval of the electrocardiogram in humans. In some cases this may lead to cardiac arrhythmias. - Highlights: • We study effects of anti-addiction drug ibogaine on ionic currents in cardiomyocytes. • We assess the cardiac ion channel profile of ibogaine. • Ibogaine inhibits hERG potassium, sodium and calcium channels. • Ibogaine’s effects on ion channels are a potential source of cardiac arrhythmias. • 18-Methoxycoronaridine has a lower affinity for cardiac ion channels than ibogaine.« less
Microelectrode array measurement of potassium ion channel remodeling on the field action potential duration in rapid atrial pacing rabbits model.

PubMed

Sun, Juan; Yan, Huang; Wugeti, Najina; Guo, Yujun; Zhang, Ling; Ma, Mei; Guo, Xingui; Jiao, Changan; Xu, Wenli; Li, Tianqi

2015-01-01

Atrial fibrillation (AF) arises from abnormalities in atrial structure and electrical activity. Microelectrode arrays (MEA) is a real-time, nondestructive measurement of the resting and action potential signal, from myocardial cells, to the peripheral circuit of electrophysiological activity. This study examined the field action potential duration (fAPD) of the right atrial appendage (RAA) by MEA in rapid atrial pacing (RAP) in the right atrium of rabbits. In addition, this study also investigated the effect of potassium ion channel blockers on fAPD. 40 New Zealand white rabbits of either sex were randomly divided into 3 groups: 1) the control, 2) potassium ion channel blocker (TEA, 4-Ap and BaCl2), and 3) amiodarone groups. The hearts were quickly removed and right atrial appendage sectioned (slice thickness 500 μm). Each slice was perfused with Tyrode's solution and continuously stimulated for 30 minutes. Sections from the control group were superfused with Tyrode's solution for 10 minutes, while the blocker groups and amiodarone were both treated with their respective compounds for 10 minutes each. The fAPD of RAA and action field action potential morphology were measured using MEA. In non-pace (control) groups, fAPD was 188.33 ± 18.29 ms after Tyrode's solution superfusion, and 173.91 ± 6.83 ms after RAP. In pace/potassium ion channel groups, TEA and BaCl2 superfusion prolonged atrial field action potential (fAPD) (control vs blocker: 176.67 ± 8.66 ms vs 196.11 ± 10.76 ms, 182.22 ± 12.87 ms vs 191.11 ± 13.09 ms with TEA and BaCl2 superfusion, respectively, P < 0.05). 4-AP superfusion significantly prolonged FAPD. In pace/amiodarone groups, 4-Ap superfusion extended fAPD. MEA was a sensitive and stable reporter for the measurement of the tissue action potential in animal heart slices. After superfusing potassium ion channel blockers, fAPD was prolonged. These results suggest that Ito, IKur and IK1 remodel and mediate RAP-induced atrial electrical remodeling. Amiodarone alter potassium ion channel activity (Ito, IKur, IK1 and IKs), shortening fAPD.
Beam-driven acceleration in ultra-dense plasma media

DOE PAGES

Shin, Young-Min

2014-09-15

Accelerating parameters of beam-driven wakefield acceleration in an extremely dense plasma column has been analyzed with the dynamic framed particle-in-cell plasma simulator, and compared with analytic calculations. In the model, a witness beam undergoes a TeV/m scale alternating potential gradient excited by a micro-bunched drive beam in a 10 25 m -3 and 1.6 x 10 28 m -3 plasma column. The acceleration gradient, energy gain, and transformer ratio have been extensively studied in quasi-linear, linear-, and blowout-regimes. The simulation analysis indicated that in the beam-driven acceleration system a hollow plasma channel offers 20 % higher acceleration gradient by enlargingmore » the channel radius (r) from 0.2 Ap to 0.6 .Ap in a blowout regime. This paper suggests a feasibility of TeV/m scale acceleration with a hollow crystalline structure (e.g. nanotubes) of high electron plasma density.« less
Electromechanical feedback with reduced cellular connectivity alters electrical activity in an infarct injured left ventricle: a finite element model study

PubMed Central

Guccione, Julius M.; Ratcliffe, Mark B.; Sundnes, Joakim S.

2012-01-01

Myocardial infarction (MI) significantly alters the structure and function of the heart. As abnormal strain may drive heart failure and the generation of arrhythmias, we used computational methods to simulate a left ventricle with an MI over the course of a heartbeat to investigate strains and their potential implications to electrophysiology. We created a fully coupled finite element model of myocardial electromechanics consisting of a cellular physiological model, a bidomain electrical diffusion solver, and a nonlinear mechanics solver. A geometric mesh built from magnetic resonance imaging (MRI) measurements of an ovine left ventricle suffering from a surgically induced anteroapical infarct was used in the model, cycled through the cardiac loop of inflation, isovolumic contraction, ejection, and isovolumic relaxation. Stretch-activated currents were added as a mechanism of mechanoelectric feedback. Elevated fiber and cross fiber strains were observed in the area immediately adjacent to the aneurysm throughout the cardiac cycle, with a more dramatic increase in cross fiber strain than fiber strain. Stretch-activated channels decreased action potential (AP) dispersion in the remote myocardium while increasing it in the border zone. Decreases in electrical connectivity dramatically increased the changes in AP dispersion. The role of cross fiber strain in MI-injured hearts should be investigated more closely, since results indicate that these are more highly elevated than fiber strain in the border of the infarct. Decreases in connectivity may play an important role in the development of altered electrophysiology in the high-stretch regions of the heart. PMID:22058157
Increased levels of 3-hydroxykynurenine parallel disease severity in human acute pancreatitis.

PubMed

Skouras, Christos; Zheng, Xiaozhong; Binnie, Margaret; Homer, Natalie Z M; Murray, Toby B J; Robertson, Darren; Briody, Lesley; Paterson, Finny; Spence, Heather; Derr, Lisa; Hayes, Alastair J; Tsoumanis, Andreas; Lyster, Dawn; Parks, Rowan W; Garden, O James; Iredale, John P; Uings, Iain J; Liddle, John; Wright, Wayne L; Dukes, George; Webster, Scott P; Mole, Damian J

2016-09-27

Inhibition of kynurenine 3-monooxygenase (KMO) protects against multiple organ dysfunction (MODS) in experimental acute pancreatitis (AP). We aimed to precisely define the kynurenine pathway activation in relation to AP and AP-MODS in humans, by carrying out a prospective observational study of all persons presenting with a potential diagnosis of AP for 90 days. We sampled peripheral venous blood at 0, 3, 6, 12, 24, 48, 72 and 168 hours post-recruitment. We measured tryptophan metabolite concentrations and analysed these in the context of clinical data and disease severity indices, cytokine profiles and C-reactive protein (CRP) concentrations. 79 individuals were recruited (median age: 59.6 years; 47 males, 59.5%). 57 met the revised Atlanta definition of AP: 25 had mild, 23 moderate, and 9 severe AP. Plasma 3-hydroxykynurenine concentrations correlated with contemporaneous APACHE II scores (R 2 = 0.273; Spearman rho = 0.581; P < 0.001) and CRP (R 2 = 0.132; Spearman rho = 0.455, P < 0.001). Temporal profiling showed early tryptophan depletion and contemporaneous 3-hydroxykynurenine elevation. Furthermore, plasma concentrations of 3-hydroxykynurenine paralleled systemic inflammation and AP severity. These findings support the rationale for investigating early intervention with a KMO inhibitor, with the aim of reducing the incidence and severity of AP-associated organ dysfunction.
Increased levels of 3-hydroxykynurenine parallel disease severity in human acute pancreatitis

PubMed Central

Skouras, Christos; Zheng, Xiaozhong; Binnie, Margaret; Homer, Natalie Z. M.; Murray, Toby B. J.; Robertson, Darren; Briody, Lesley; Paterson, Finny; Spence, Heather; Derr, Lisa; Hayes, Alastair J.; Tsoumanis, Andreas; Lyster, Dawn; Parks, Rowan W.; Garden, O. James; Iredale, John P.; Uings, Iain J.; Liddle, John; Wright, Wayne L.; Dukes, George; Webster, Scott P.; Mole, Damian J.

2016-01-01

Inhibition of kynurenine 3-monooxygenase (KMO) protects against multiple organ dysfunction (MODS) in experimental acute pancreatitis (AP). We aimed to precisely define the kynurenine pathway activation in relation to AP and AP-MODS in humans, by carrying out a prospective observational study of all persons presenting with a potential diagnosis of AP for 90 days. We sampled peripheral venous blood at 0, 3, 6, 12, 24, 48, 72 and 168 hours post-recruitment. We measured tryptophan metabolite concentrations and analysed these in the context of clinical data and disease severity indices, cytokine profiles and C-reactive protein (CRP) concentrations. 79 individuals were recruited (median age: 59.6 years; 47 males, 59.5%). 57 met the revised Atlanta definition of AP: 25 had mild, 23 moderate, and 9 severe AP. Plasma 3-hydroxykynurenine concentrations correlated with contemporaneous APACHE II scores (R2 = 0.273; Spearman rho = 0.581; P < 0.001) and CRP (R2 = 0.132; Spearman rho = 0.455, P < 0.001). Temporal profiling showed early tryptophan depletion and contemporaneous 3-hydroxykynurenine elevation. Furthermore, plasma concentrations of 3-hydroxykynurenine paralleled systemic inflammation and AP severity. These findings support the rationale for investigating early intervention with a KMO inhibitor, with the aim of reducing the incidence and severity of AP-associated organ dysfunction. PMID:27669975
Adipocyte fatty acid-binding protein, aP2, alters late atherosclerotic lesion formation in severe hypercholesterolemia.

PubMed

Boord, Jeffrey B; Maeda, Kazuhisa; Makowski, Liza; Babaev, Vladimir R; Fazio, Sergio; Linton, MacRae F; Hotamisligil, Gökhan S

2002-10-01

The adipocyte fatty acid-binding protein, aP2, has important effects on insulin resistance, lipid metabolism, and atherosclerosis. Its expression in macrophages enhances early foam cell formation and atherosclerosis in vivo. This study was designed to determine whether aP2 deficiency has a similar effect in the setting of advanced atherosclerosis and severe hypercholesterolemia. Mice deficient in aP2 and apolipoprotein E (aP2(-/-)apoE(-/-) mice) and apolipoprotein E-deficient control mice (apoE(-/-) mice) were fed a Western diet for 14 weeks. No significant differences in fasting serum levels of cholesterol, triglycerides, or free fatty acids were found between groups for each sex. Compared with apoE(-/-) control mice, male and female aP2(-/-)apoE(-/-) mice had significant reductions in mean atherosclerotic lesion size in the proximal aorta, en face aorta, and innominate/right carotid artery. Feeding the Western diet in the apoE-deficient background did not cause a significant reduction in insulin sensitivity in vivo, as determined by steady-state serum glucose levels and insulin tolerance testing. These data demonstrate an important role for aP2 expression in the advanced stages of atherosclerotic lesion formation. Thus, aP2 provides an important physiological link between different features of the metabolic syndrome and is a potential target for therapy of atherosclerosis.
Modelling drug modulation of nystagmus.

PubMed

Glasauer, Stefan; Rössert, Christian

2008-01-01

A better understanding of the neural and functional mechanisms underlying drug-induced changes in pathological nystagmus is likely to improve medical treatment. A treatment option for downbeat nystagmus (DBN), a common form of acquired fixation nystagmus that often occurs with cerebellar degeneration, is low doses of the potassium channel blocker 4-aminopyridine (4-AP). The upward ocular drift in DBN has a spontaneous and a vertical gaze-evoked component. Detailed analysis of the effect of 4-AP in patients showed that the drug consistently improved the gaze-evoked component, but had less effect in reducing the spontaneous drift. We show by a combination of computational modelling at the systems level and at the neuronal level how this differential effect can be investigated. We have previously postulated that DBN is caused by damage to the floccular lobe (FL). 4-AP, which has been shown to increase the excitability of Purkinje cells (PCs) in slice experiments, may thus suppress DBN by partly restoring floccular function. We simulated the effect of low concentrations of 4-AP on the cellular level using a multicompartment model of a PC, in which we changed ion channel properties to simulate damage. The transition from the cellular level to the systems level was achieved by constructing a population response. Systems level modelling predicted that the effect of 4-AP on the PCs should reduce DBN, but the predicted effect on the gaze-dependent component was less than is observed in patients. Our results suggest that the beneficial effect of 4-AP on DBN cannot be solely explained by its effect at the neuronal level of PCs, and suggests added effects at the level of the population of neurons.
MAPK/AP-1-Targeted Anti-Inflammatory Activities of Xanthium strumarium.

PubMed

Hossen, Muhammad Jahangir; Kim, Mi-Yeon; Cho, Jae Youl

2016-01-01

Xanthium strumarium L. (Asteraceae), a traditional Chinese medicine, is prescribed to treat arthritis, bronchitis, and rhinitis. Although the plant has been used for many years, the mechanism by which it ameliorates various inflammatory diseases is not yet fully understood. To explore the anti-inflammatory mechanism of methanol extracts of X. strumarium (Xs-ME) and its therapeutic potential, we used lipopolysaccharide (LPS)-stimulated murine macrophage-like RAW264.7 cells and human monocyte-like U937 cells as well as a LPS/D-galactosamine (GalN)-induced acute hepatitis mouse model. To find the target inflammatory pathway, we used holistic immunoblotting analysis, reporter gene assays, and mRNA analysis. Xs-ME significantly suppressed the up-regulation of both the activator protein (AP)-1-mediated luciferase activity and the production of LPS-induced proinflammatory cytokines, including interleukin (IL)-1[Formula: see text], IL-6, and tumor necrosis factor (TNF)-[Formula: see text]. Moreover, Xs-ME strongly inhibited the phosphorylation of mitogen-activated protein kinase (MAPK) in LPS-stimulated RAW264.7 and U937 cells. Additionally, these results highlighted the hepatoprotective and curative effects of Xs-ME in a mouse model of LPS/D-GalN-induced acute liver injury, as assessed by elevated serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and histological damage. Therefore, our results strongly suggest that the ethnopharmacological roles of Xs-ME in hepatitis and other inflammatory diseases might result from its inhibitory activities on the inflammatory signaling of MAPK and AP-1.
Measuring and Understanding Authentic Youth Engagement: The Youth-Adult Partnership Rubric

ERIC Educational Resources Information Center

Wu, Heng-Chieh Jamie; Kornbluh, Mariah; Weiss, John; Roddy, Lori

2016-01-01

Commonly described as youth-led or youth-driven, the youth-adult partnership (Y-AP) model has gained increasing popularity in out-of-school time (OST) programs in the past two decades (Larson, Walker, & Pearce, 2005; Zeldin, Christens, & Powers, 2013). The Y-AP model is defined as "the practice of (a) multiple youth and multiple…
Genome-Wide Investigation and Expression Profiling of AP2/ERF Transcription Factor Superfamily in Foxtail Millet (Setaria italica L.)

PubMed Central

Lata, Charu; Mishra, Awdhesh Kumar; Muthamilarasan, Mehanathan; Bonthala, Venkata Suresh; Khan, Yusuf; Prasad, Manoj

2014-01-01

The APETALA2/ethylene-responsive element binding factor (AP2/ERF) family is one of the largest transcription factor (TF) families in plants that includes four major sub-families, namely AP2, DREB (dehydration responsive element binding), ERF (ethylene responsive factors) and RAV (Related to ABI3/VP). AP2/ERFs are known to play significant roles in various plant processes including growth and development and biotic and abiotic stress responses. Considering this, a comprehensive genome-wide study was conducted in foxtail millet (Setaria italica L.). A total of 171 AP2/ERF genes were identified by systematic sequence analysis and were physically mapped onto nine chromosomes. Phylogenetic analysis grouped AP2/ERF genes into six classes (I to VI). Duplication analysis revealed that 12 (∼7%) SiAP2/ERF genes were tandem repeated and 22 (∼13%) were segmentally duplicated. Comparative physical mapping between foxtail millet AP2/ERF genes and its orthologs of sorghum (18 genes), maize (14 genes), rice (9 genes) and Brachypodium (6 genes) showed the evolutionary insights of AP2/ERF gene family and also the decrease in orthology with increase in phylogenetic distance. The evolutionary significance in terms of gene-duplication and divergence was analyzed by estimating synonymous and non-synonymous substitution rates. Expression profiling of candidate AP2/ERF genes against drought, salt and phytohormones revealed insights into their precise and/or overlapping expression patterns which could be responsible for their functional divergence in foxtail millet. The study showed that the genes SiAP2/ERF-069, SiAP2/ERF-103 and SiAP2/ERF-120 may be considered as potential candidate genes for further functional validation as well for utilization in crop improvement programs for stress resistance since these genes were up-regulated under drought and salinity stresses in ABA dependent manner. Altogether the present study provides new insights into evolution, divergence and systematic functional analysis of AP2/ERF gene family at genome level in foxtail millet which may be utilized for improving stress adaptation and tolerance in millets, cereals and bioenergy grasses. PMID:25409524

Genome-wide investigation and expression profiling of AP2/ERF transcription factor superfamily in foxtail millet (Setaria italica L.).

PubMed

Lata, Charu; Mishra, Awdhesh Kumar; Muthamilarasan, Mehanathan; Bonthala, Venkata Suresh; Khan, Yusuf; Prasad, Manoj

2014-01-01

The APETALA2/ethylene-responsive element binding factor (AP2/ERF) family is one of the largest transcription factor (TF) families in plants that includes four major sub-families, namely AP2, DREB (dehydration responsive element binding), ERF (ethylene responsive factors) and RAV (Related to ABI3/VP). AP2/ERFs are known to play significant roles in various plant processes including growth and development and biotic and abiotic stress responses. Considering this, a comprehensive genome-wide study was conducted in foxtail millet (Setaria italica L.). A total of 171 AP2/ERF genes were identified by systematic sequence analysis and were physically mapped onto nine chromosomes. Phylogenetic analysis grouped AP2/ERF genes into six classes (I to VI). Duplication analysis revealed that 12 (∼7%) SiAP2/ERF genes were tandem repeated and 22 (∼13%) were segmentally duplicated. Comparative physical mapping between foxtail millet AP2/ERF genes and its orthologs of sorghum (18 genes), maize (14 genes), rice (9 genes) and Brachypodium (6 genes) showed the evolutionary insights of AP2/ERF gene family and also the decrease in orthology with increase in phylogenetic distance. The evolutionary significance in terms of gene-duplication and divergence was analyzed by estimating synonymous and non-synonymous substitution rates. Expression profiling of candidate AP2/ERF genes against drought, salt and phytohormones revealed insights into their precise and/or overlapping expression patterns which could be responsible for their functional divergence in foxtail millet. The study showed that the genes SiAP2/ERF-069, SiAP2/ERF-103 and SiAP2/ERF-120 may be considered as potential candidate genes for further functional validation as well for utilization in crop improvement programs for stress resistance since these genes were up-regulated under drought and salinity stresses in ABA dependent manner. Altogether the present study provides new insights into evolution, divergence and systematic functional analysis of AP2/ERF gene family at genome level in foxtail millet which may be utilized for improving stress adaptation and tolerance in millets, cereals and bioenergy grasses.
Easy Method to Examine Single Nerve Fiber Excitability and Conduction Parameters Using Intact Nonanesthetized Earthworms

ERIC Educational Resources Information Center

Bähring, Robert; Bauer, Christiane K.

2014-01-01

The generation and conduction of neuronal action potentials (APs) were the subjects of a cell physiology exercise for first-year medical students. In this activity, students demonstrated the all-or-none nature of AP generation, measured conduction velocity, and examined the dependence of the threshold stimulus amplitude on stimulus duration. For…
Oncology Advanced Practitioners Bring Advanced Community Oncology Care.

PubMed

Vogel, Wendy H

2016-01-01

Oncology care is becoming increasingly complex. The interprofessional team concept of care is necessary to meet projected oncology professional shortages, as well as to provide superior oncology care. The oncology advanced practitioner (AP) is a licensed health care professional who has completed advanced training in nursing or pharmacy or has completed training as a physician assistant. Oncology APs increase practice productivity and efficiency. Proven to be cost effective, APs may perform varied roles in an oncology practice. Integrating an AP into an oncology practice requires forethought given to the type of collaborative model desired, role expectations, scheduling, training, and mentoring.
Simultaneous mapping of membrane voltage and calcium in zebrafish heart in vivo reveals chamber-specific developmental transitions in ionic currents

PubMed Central

Hou, Jennifer H.; Kralj, Joel M.; Douglass, Adam D.; Engert, Florian; Cohen, Adam E.

2014-01-01

The cardiac action potential (AP) and the consequent cytosolic Ca2+ transient are key indicators of cardiac function. Natural developmental processes, as well as many drugs and pathologies change the waveform, propagation, or variability (between cells or over time) of these parameters. Here we apply a genetically encoded dual-function calcium and voltage reporter (CaViar) to study the development of the zebrafish heart in vivo between 1.5 and 4 days post fertilization (dpf). We developed a high-sensitivity spinning disk confocal microscope and associated software for simultaneous three-dimensional optical mapping of voltage and calcium. We produced a transgenic zebrafish line expressing CaViar under control of the heart-specific cmlc2 promoter, and applied ion channel blockers at a series of developmental stages to map the maturation of the action potential in vivo. Early in development, the AP initiated via a calcium current through L-type calcium channels. Between 90 and 102 h post fertilization (hpf), the ventricular AP switched to a sodium-driven upswing, while the atrial AP remained calcium driven. In the adult zebrafish heart, a sodium current drives the AP in both the atrium and ventricle. Simultaneous voltage and calcium imaging with genetically encoded reporters provides a new approach for monitoring cardiac development, and the effects of drugs on cardiac function. PMID:25309445
Simultaneous mapping of membrane voltage and calcium in zebrafish heart in vivo reveals chamber-specific developmental transitions in ionic currents.

PubMed

Hou, Jennifer H; Kralj, Joel M; Douglass, Adam D; Engert, Florian; Cohen, Adam E

2014-01-01

The cardiac action potential (AP) and the consequent cytosolic Ca(2+) transient are key indicators of cardiac function. Natural developmental processes, as well as many drugs and pathologies change the waveform, propagation, or variability (between cells or over time) of these parameters. Here we apply a genetically encoded dual-function calcium and voltage reporter (CaViar) to study the development of the zebrafish heart in vivo between 1.5 and 4 days post fertilization (dpf). We developed a high-sensitivity spinning disk confocal microscope and associated software for simultaneous three-dimensional optical mapping of voltage and calcium. We produced a transgenic zebrafish line expressing CaViar under control of the heart-specific cmlc2 promoter, and applied ion channel blockers at a series of developmental stages to map the maturation of the action potential in vivo. Early in development, the AP initiated via a calcium current through L-type calcium channels. Between 90 and 102 h post fertilization (hpf), the ventricular AP switched to a sodium-driven upswing, while the atrial AP remained calcium driven. In the adult zebrafish heart, a sodium current drives the AP in both the atrium and ventricle. Simultaneous voltage and calcium imaging with genetically encoded reporters provides a new approach for monitoring cardiac development, and the effects of drugs on cardiac function.
A mathematical method for precisely calculating the radiographic angles of the cup after total hip arthroplasty.

PubMed

Zhao, Jing-Xin; Su, Xiu-Yun; Xiao, Ruo-Xiu; Zhao, Zhe; Zhang, Li-Hai; Zhang, Li-Cheng; Tang, Pei-Fu

2016-11-01

We established a mathematical method to precisely calculate the radiographic anteversion (RA) and radiographic inclination (RI) angles of the acetabular cup based on anterior-posterior (AP) pelvic radiographs after total hip arthroplasty. Using Mathematica software, a mathematical model for an oblique cone was established to simulate how AP pelvic radiographs are obtained and to address the relationship between the two-dimensional and three-dimensional geometry of the opening circle of the cup. In this model, the vertex was the X-ray beam source, and the generatrix was the ellipse in radiographs projected from the opening circle of the acetabular cup. Using this model, we established a series of mathematical formulas to reveal the differences between the true RA and RI cup angles and the measurements results achieved using traditional methods and AP pelvic radiographs and to precisely calculate the RA and RI cup angles based on post-operative AP pelvic radiographs. Statistical analysis indicated that traditional methods should be used with caution if traditional measurements methods are used to calculate the RA and RI cup angles with AP pelvic radiograph. The entire calculation process could be performed by an orthopedic surgeon with mathematical knowledge of basic matrix and vector equations. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.
Protective effect of asiatic acid in an experimental cerulein-induced model of acute pancreatitis in mice

PubMed Central

Xiao, Wenqin; Jiang, Weiliang; Li, Kai; Hu, Yangyang; Li, Sisi; Zhou, Li; Wan, Rong

2017-01-01

Asiatic acid (AA), a triterpenoid derived from the medicinal plant Centella asiatica, is considered to have anti-inflammatory, anti-fibrotic and anti-tumor effects, but its effects in acute pancreatitis (AP) are unknown. Our purpose of this study was to investigate the effects of AA in a mouse model of cerulein-induced pancreatitis. We evaluated AA in an experimental model of AP induced in mice by six hourly intraperitoneal injections of cerulein 50 µg/kg. Mice were pretreated with vehicle or AA 50 mg/kg 2 h before the first cerulein injection. The severity of AP was evaluated histologically and by biochemistry, myeloperoxidase activity, proinflammatory cytokine production, and nuclear factor (NF)-κB activity. Administration of AA significantly reduced the severity of AP, and was associated with reduction of serum amylase and lipase levels, decreased pancreatic histological damage, and decreased myeloperoxidase activity. The serum levels and mRNA expression of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and NF-κB activity were reduced. AA also significantly improved the in vitro viability of pancreatic acinar cells induced by cholecystokinin (CCK) and suppressed NF-κB activity. AA protected against experimental AP, possibly by reducing production of proinflammatory cytokines via suppression NF-κB activation. PMID:28861174
AP39, a mitochondria‐targeting hydrogen sulfide (H2S) donor, protects against myocardial reperfusion injury independently of salvage kinase signalling

PubMed Central

Karwi, Qutuba G; Bornbaum, Julia; Boengler, Kerstin; Torregrossa, Roberta; Whiteman, Matthew; Wood, Mark E; Schulz, Rainer

2017-01-01

Background and Purpose H2S protects myocardium against ischaemia/reperfusion injury. This protection may involve the cytosolic reperfusion injury salvage kinase (RISK) pathway, but direct effects on mitochondrial function are possible. Here, we investigated the potential cardioprotective effect of a mitochondria‐specific H2S donor, AP39, at reperfusion against ischaemia/reperfusion injury. Experimental Approach Anaesthetized rats underwent myocardial ischaemia (30 min)/reperfusion (120 min) with randomization to receive interventions before reperfusion: vehicle, AP39 (0.01, 0.1, 1 μmol·kg−1), or control compounds AP219 and ADT‐OH (1 μmol·kg−1). LY294002, L‐NAME or ODQ were used to investigate the involvement of the RISK pathway. Myocardial samples harvested 5 min after reperfusion were analysed for RISK protein phosphorylation and isolated cardiac mitochondria were used to examine the direct mitochondrial effects of AP39. Key Results AP39, dose‐dependently, reduced infarct size. Inhibition of either PI3K/Akt, eNOS or sGC did not affect this effect of AP39. Western blot analysis confirmed that AP39 did not induce phosphorylation of Akt, eNOS, GSK‐3β or ERK1/2. In isolated subsarcolemmal and interfibrillar mitochondria, AP39 significantly attenuated mitochondrial ROS generation without affecting respiratory complexes I or II. Furthermore, AP39 inhibited mitochondrial permeability transition pore (PTP) opening and co‐incubation of mitochondria with AP39 and cyclosporine A induced an additive inhibitory effect on the PTP. Conclusion and Implications AP39 protects against reperfusion injury independently of the cytosolic RISK pathway. This cardioprotective effect could be mediated by inhibiting PTP via a cyclophilin D‐independent mechanism. Thus, selective delivery of H2S to mitochondria may be therapeutically applicable for employing the cardioprotective utility of H2S. PMID:27930802
Effect of the 3-halo substitution of the 2'-deoxy aminopyridinyl-pseudocytidine derivatives on the selectivity and stability of antiparallel triplex DNA with a CG inversion site.

PubMed

Wang, Lei; Taniguchi, Yosuke; Okamura, Hidenori; Sasaki, Shigeki

2017-07-15

Triplex formation against a target duplex DNA has the potential to become a tool for the genome research. However, there is an intrinsic restriction on the duplex DNA sequences capable of forming the triplex DNA. Recently, we demonstrated the selective formation of the stable antiparallel triplexes containing the CG inversion sites using the 2'-deoxy-1-methylpseudocytidine derivative (ΨdC), whose amino group was conjugated with the 2-aminopyridine at its 5-position as an additional hydrogen bonding unit (AP-ΨdC). The 1-N of 2-aminopyridine was supposed to be protonated to form the hydrogen bond with the guanine of the CG inversion site. In this study, to test the effect of the 3-substitution of the 2-aminopyridine unit of AP-ΨdC on the triplex stability, we synthesized the 3-halogenated 2-aminopyridine derivatives of AP-ΨdC. The pKa values 1-N of the 2-aminopyridine unit of AP-ΨdC as the monomer nucleoside were determined to be 6.3 for 3-CH 3 ( Me AP-ΨdC), 6.1 for 3-H (AP-ΨdC), 4.3 for 3-Cl ( Cl AP-ΨdC), 4.4 for 3-Br ( Br AP-ΨdC), and 4.7 for 3-I ( I AP-ΨdC), suggesting that all the halogenated AP-ΨdCs are not protonated under neutral conditions. Interestingly, although the recognition selectivity depends on the sequence context, the TFO having the sequence of the 3'-G-( I AP-ΨdC)-A-5' context showed the selective triplex formation with the CG inversion site. These results suggest that the protonation at the 1-N position plays an important role in the stable and selective triplex formation of AP-ΨdC derivatives in any sequences. Copyright © 2017 Elsevier Ltd. All rights reserved.
Effect of Potamogeton crispus L. on bioavailability and biodegradation activity of pyrene in aged and unaged sediments.

PubMed

Meng, Fanbo; Chi, Jie

2017-02-15

In order to clarify the effect of Potamogeton crispus L. (P. crispus) on bioavailability and biodegradation activity of pyrene in aged and unaged sediments, model calculation based on experimental results was carried out. During a 36-day experiment, the dissipation ratio of pyrene was increased by planting but decreased by aging. P. crispus improved the dissipation more significantly in aged sediments (45.9%) than in unaged sediments (17.6%). Results derived from a two-compartment desorption model showed that the decrease of rapidly desorbing fraction of pyrene was in the order of aged sediments without plant (A)>unaged sediments without plant (U)>unaged sediments with plant (UP)>aged sediments with plant (AP). Moreover, the results of biodegradation kinetic model showed that the first-order biodegradation coefficient was in the order of AP>UP>U and A, which was consistent with that of sediment redox potential. These modeling results indicated that planting could enhance the bioavailability (73.9%) and biodegradation activity (277%) of pyrene more significantly in aged sediments as compared to unaged sediments (13.1% and 150%, respectively), which should be the key reasons leading to more significant dissipation increment of pyrene in aged sediments by P. crispus. Copyright © 2016 Elsevier B.V. All rights reserved.
The interaction of diadenosine polyphosphates with P2X-receptors in the guinea-pig isolated vas deferens

PubMed Central

Westfall, T D; McIntyre, C A; Obeid, S; Bowes, J; Kennedy, C; Sneddon, P

1997-01-01

The site(s) at which diadenosine 5′,5′′′-P1,P4-tetraphosphate (AP4A) and diadenosine 5′, 5′′′-P1,P5-pentaphosphate (AP5A) act to evoke contraction of the guinea-pig isolated vas deferens was studied by use of a series of P2-receptor antagonists and the ecto-ATPase inhibitor 6-N,N-diethyl-D-β,γ-dibromomethyleneATP (ARL 67156). Pyridoxalphosphate-6-azophenyl-2′,4′-disulphonic acid (PPADS) (300 nM–30 μM), suramin (3–100 μM) and pyridoxal-5′-phosphate (P-5-P) (3–1000 μM) inhibited contractions evoked by equi-effective concentrations of AP5A (3 μM), AP4A (30 μM) and α,β-methyleneATP (α,β-meATP) (1 μM), in a concentration-dependent manner and abolished them at the highest concentrations used. PPADS was more potent than suramin, which in turn was more potent than P-5-P. PPADS inhibited AP5A, AP4A and α,β-meATP with similar IC50 values. No significant difference was found between IC50 values for suramin against α,β-meATP and AP5A or α,β-meATP and AP4A, but suramin was more than 2.5 times more potent against AP4A than AP5A. P-5-P showed the same pattern of antagonism. Desensitization of the P2X1-receptor by α,β-meATP abolished contractions evoked by AP5A (3 μM) and AP4A (30 μM), but had no effect on those elicited by noradrenaline (100 μM). ARL 67156 (100 μM) reversibly potentiated contractions evoked by AP4A (30 μM) by 61%, but caused a small, significant decrease in the mean response to AP5A (3 μM). It is concluded that AP4A and AP5A act at the P2X1-receptor, or a site similar to the P2X1-receptor, to evoke contraction of the guinea-pig isolated vas deferens. Furthermore, the potency of AP4A, but not AP5A, appears to be inhibited by an ecto-enzyme which is sensitive to ARL 67156. PMID:9146887
Subtype-specific differentiation of cardiac pacemaker cell clusters from human induced pluripotent stem cells.

PubMed

Schweizer, Patrick A; Darche, Fabrice F; Ullrich, Nina D; Geschwill, Pascal; Greber, Boris; Rivinius, Rasmus; Seyler, Claudia; Müller-Decker, Karin; Draguhn, Andreas; Utikal, Jochen; Koenen, Michael; Katus, Hugo A; Thomas, Dierk

2017-10-16

Human induced pluripotent stem cells (hiPSC) harbor the potential to differentiate into diverse cardiac cell types. Previous experimental efforts were primarily directed at the generation of hiPSC-derived cells with ventricular cardiomyocyte characteristics. Aiming at a straightforward approach for pacemaker cell modeling and replacement, we sought to selectively differentiate cells with nodal-type properties. hiPSC were differentiated into spontaneously beating clusters by co-culturing with visceral endoderm-like cells in a serum-free medium. Subsequent culturing in a specified fetal bovine serum (FBS)-enriched cell medium produced a pacemaker-type phenotype that was studied in detail using quantitative real-time polymerase chain reaction (qRT-PCR), immunocytochemistry, and patch-clamp electrophysiology. Further investigations comprised pharmacological stimulations and co-culturing with neonatal cardiomyocytes. hiPSC co-cultured in a serum-free medium with the visceral endoderm-like cell line END-2 produced spontaneously beating clusters after 10-12 days of culture. The pacemaker-specific genes HCN4, TBX3, and TBX18 were abundantly expressed at this early developmental stage, while levels of sarcomeric gene products remained low. We observed that working-type cardiomyogenic differentiation can be suppressed by transfer of early clusters into a FBS-enriched cell medium immediately after beating onset. After 6 weeks under these conditions, sinoatrial node (SAN) hallmark genes remained at high levels, while working-type myocardial transcripts (NKX2.5, TBX5) were low. Clusters were characterized by regular activity and robust beating rates (70-90 beats/min) and were triggered by spontaneous Ca 2+ transients recapitulating calcium clock properties of genuine pacemaker cells. They were responsive to adrenergic/cholinergic stimulation and able to pace neonatal rat ventricular myocytes in co-culture experiments. Action potential (AP) measurements of cells individualized from clusters exhibited nodal-type (63.4%) and atrial-type (36.6%) AP morphologies, while ventricular AP configurations were not observed. We provide a novel culture media-based, transgene-free approach for targeted generation of hiPSC-derived pacemaker-type cells that grow in clusters and offer the potential for disease modeling, drug testing, and individualized cell-based replacement therapy of the SAN.
Disease progression of acute pancreatitis in pediatric patients.

PubMed

Hao, Fabao; Guo, Hongjie; Luo, Qianfu; Guo, Chunbao

2016-05-15

Approximately 10% of patients with acute pancreatitis (AP) progress to chronic pancreatitis. Little is known about the factors that affect recurrence of pancreatitis after an initial episode. We retrospectively investigated patients with AP, focusing on their outcomes and the predictors for disease progression. Between July 2003 and June 2015, we retrospectively enrolled first-time AP patients with medical records on disease etiology, severity (according to the Atlanta classifications), and recurrence of AP. Independent predictors of recurrent AP (RAP) and chronic pancreatitis were identified using the logistic regression model. Of the total 159 patients, 45 (28.3%) developed RAP, including two episodes of RAP in 19 patients, and 9 (5.7%) developed chronic pancreatitis. The median duration from the time of AP to the onset of RAP was 5.6 ± 2.3 months. RAP patients were identified as more common among patients with idiopathic first-time AP. The presence of severe ascites, pancreatic necrosis, and systemic complications was independent predictors of RAP in pediatric patients. Experiencing over two RAP episodes was the predictor for developing chronic pancreatitis. No influence of age or number of AP episodes was found on the occurrence of abdominal pain, pain severity, and the prevalence of any pain. Severity of first-time AP and idiopathic first-time AP are related to RAP. Recurrence increases risk for progression to chronic pancreatitis. The risk of recurrence increased with increasing numbers of AP episodes. Copyright © 2016 Elsevier Inc. All rights reserved.
Formation of the imidazolides of dinucleotides under potentially prebiotic conditions

NASA Technical Reports Server (NTRS)

Sleeper, H. L.; Lohrmann, R.; Orgel, L. E.

1978-01-01

Imidazolides of dinucleotides such as ImpApA can be formed from the corresponding dinucleotides in a two-stage process, which gives up to 15% yields under potentially prebiotic conditions. First a solution of the dinucleotide and sodium trimetaphosphate is dried out at constant temperature and humidity. This produces polyphosphates such as p(n)ApA in excellent yield (greater than or equal to 80%). The products are dissolved in water, imidazole is added, and the solution is dried out again. This yields the 5'-phosphorimidazolides.
Decreased allopregnanolone levels in cerebrospinal fluid obtained during status epilepticus.

PubMed

Meletti, Stefano; Lucchi, Chiara; Monti, Giulia; Giovannini, Giada; Bedin, Roberta; Trenti, Tommaso; Rustichelli, Cecilia; Biagini, Giuseppe

2017-02-01

Neuroactive steroids are increasingly considered as relevant modulators of neuronal activity. Especially allopregnanolone (AP) and pregnenolone sulfate (PS) have been shown to possess, respectively, anticonvulsant or proconvulsant properties. In view of the potential role of these steroids, we aimed at evaluating AP and PS levels in cerebrospinal fluid (CSF) and blood samples obtained from patients with status epilepticus (SE). To this purpose, we enrolled 41 patients affected by SE and 41 subjects investigated for nonepileptic neurologic disorders. Liquid chromatographic procedures coupled with electrospray tandem mass spectrometry and routine laboratory investigations were performed. Significantly lower AP levels were found in the CSF of patients affected by SE (-30%; p < 0.05, Mann-Whitney test). Notably, AP was not detectable in 28 of 41 patients affected by SE (p < 0.01 vs. controls, Fisher's exact test). In serum, AP levels did not differ in the two considered groups. Conversely, PS was present at similar levels in the investigated groups. Finally, differences in AP levels could not be explained by a variation in CSF albumin content. These findings indicate that AP is defective in the CSF of patients affected by SE. This phenomenon was not dependent on carriers for steroids, such as albumin. Wiley Periodicals, Inc. © 2016 International League Against Epilepsy.
Effects of Artemisia Princeps Supplementation on Bone Metabolism in Ovariectomized Rats.

PubMed

Cho, H-J; Kim, J-W; Ju, S-Y; Park, Y-K

2016-01-01

The aim of this study was to investigate the effects of Artemisia princeps (AP) extract on bone metabolism and its potential role in the prevention of osteoporosis in ovariectomized rats. Twenty-six female Sprague-Dawley rats were divided into five groups and treated as follows: sham-operated control group (SHAM); ovariectomized control group (OVX), ovariectomized group treated by gavage with 10 mg/kg/day alendronate (ALEN); ovariectomized group treated by gavage with 100 mg/kg/day Artemisia princeps (AP100); ovariectomized group treated by gavage with 300 mg/kg/day Artemisia princeps (AP300). Treatment of ovariectomized rats with AP extracts for 15 weeks prevented the reduction in bone thickness and trabecular bone mineral density caused by urinary Ca and Cr excretion, and also prevented the increase in bone turnover by maintaining the serum Ca/P ratio. As a result, the microarchitecture of the trabecular bone and cortical bone after ovariectomy was markedly improved by administration of AP extracts. In conclusion, AP prevented bone loss and osteoclast activity associated with high bone turnover in ovariectomized rats by controlling the serum Ca/P ratio and through anti-inflammatory and anti-oxidant properties. Our data implicate AP as a promising therapeutic option for the improvement of postmenopausal osteoporosis.
Kynurenine-3-monooxygenase inhibition prevents multiple organ failure in rodent models of acute pancreatitis.

PubMed

Mole, Damian J; Webster, Scott P; Uings, Iain; Zheng, Xiaozhong; Binnie, Margaret; Wilson, Kris; Hutchinson, Jonathan P; Mirguet, Olivier; Walker, Ann; Beaufils, Benjamin; Ancellin, Nicolas; Trottet, Lionel; Bénéton, Véronique; Mowat, Christopher G; Wilkinson, Martin; Rowland, Paul; Haslam, Carl; McBride, Andrew; Homer, Natalie Z M; Baily, James E; Sharp, Matthew G F; Garden, O James; Hughes, Jeremy; Howie, Sarah E M; Holmes, Duncan S; Liddle, John; Iredale, John P

2016-02-01

Acute pancreatitis (AP) is a common and devastating inflammatory condition of the pancreas that is considered to be a paradigm of sterile inflammation leading to systemic multiple organ dysfunction syndrome (MODS) and death. Acute mortality from AP-MODS exceeds 20% (ref. 3), and the lifespans of those who survive the initial episode are typically shorter than those of the general population. There are no specific therapies available to protect individuals from AP-MODS. Here we show that kynurenine-3-monooxygenase (KMO), a key enzyme of tryptophan metabolism, is central to the pathogenesis of AP-MODS. We created a mouse strain that is deficient for Kmo (encoding KMO) and that has a robust biochemical phenotype that protects against extrapancreatic tissue injury to the lung, kidney and liver in experimental AP-MODS. A medicinal chemistry strategy based on modifications of the kynurenine substrate led to the discovery of the oxazolidinone GSK180 as a potent and specific inhibitor of KMO. The binding mode of the inhibitor in the active site was confirmed by X-ray co-crystallography at 3.2 Å resolution. Treatment with GSK180 resulted in rapid changes in the levels of kynurenine pathway metabolites in vivo, and it afforded therapeutic protection against MODS in a rat model of AP. Our findings establish KMO inhibition as a novel therapeutic strategy in the treatment of AP-MODS, and they open up a new area for drug discovery in critical illness.
Automated activity-aware prompting for activity initiation.

PubMed

Holder, Lawrence B; Cook, Diane J

2013-01-01

Performing daily activities without assistance is important to maintaining an independent functional lifestyle. As a result, automated activity prompting systems can potentially extend the period of time that adults can age in place. In this paper we introduce AP, an algorithm to automate activity prompting based on smart home technology. AP learns prompt rules based on the time when activities are typically performed as well as the relationship between activities that normally occur in a sequence. We evaluate the AP algorithm based on smart home datasets and demonstrate its ability to operate within a physical smart environment.
Involvement of an ent-copalyl diphosphate synthase in tissue-specific accumulation of specialized diterpenes in Andrographis paniculata.

PubMed

Misra, Rajesh Chandra; Garg, Anchal; Roy, Sudeep; Chanotiya, Chandan Singh; Vasudev, Prema G; Ghosh, Sumit

2015-11-01

Ent-labdane-related diterpene (ent-LRD) specialized (i.e. secondary) metabolites of the medicinal plant kalmegh (Andrographis paniculata) have long been known for several pharmacological activities. However, our understanding of the ent-LRD biosynthetic pathway has remained largely incomplete. Since ent-LRDs accumulate in leaves, we carried out a comparative transcriptional analysis using leaf and root tissues, and identified 389 differentially expressed transcripts, including 223 transcripts that were preferentially expressed in leaf tissue. Analysis of the transcripts revealed various specialized metabolic pathways, including transcripts of the ent-LRD biosynthetic pathway. Two class II diterpene synthases (ApCPS1 and ApCPS2) along with one (ApCPS1') and two (ApCPS2' and ApCPS2″) transcriptional variants that were the outcomes of alternative splicing of the precursor mRNA and alternative transcriptional termination, respectively, were identified. ApCPS1 and ApCPS2 encode for 832- and 817-amino acids proteins, respectively, and are phylogenetically related to the dicotyledons ent-copalyl diphosphate synthases (ent-CPSs). The spatio-temporal patterns of ent-LRD metabolites accumulation and gene expression suggested a likely role for ApCPS1 in general (i.e. primary) metabolism, perhaps by providing precursor for the biosynthesis of phytohormone gibberellin (GA). However, ApCPS2 is potentially involved in tissue-specific accumulation of ent-LRD specialized metabolites. Bacterially expressed recombinant ApCPS2 catalyzed the conversion of (E,E,E)-geranylgeranyl diphosphate (GGPP), the general precursor of diterpenes to ent-copalyl diphosphate (ent-CPP), the precursor of ent-LRDs. Taken together, these results advance our understanding of the tissue-specific accumulation of specialized ent-LRDs of medicinal importance. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
New Discriminant Method for Identifying the Aggressive Disease Phenotype of Non-alcoholic Fatty Liver Disease.

PubMed

Kawamura, Yusuke; Ikeda, Kenji; Arase, Yasuji; Fujiyama, Shunichiro; Hosaka, Tetsuya; Kobayashi, Masahiro; Saitoh, Satoshi; Sezaki, Hitomi; Akuta, Norio; Suzuki, Fumitaka; Suzuki, Yoshiyuki; Kumada, Hiromitsu

2017-01-01

Objective To detect the aggressive phenotype (AP) of non-alcoholic fatty liver disease (NAFLD) based on the initial laboratory data and clinical characteristics. Methods We enrolled 144 patients with histologically proven NAFLD. For the first analysis, 24 NAFLD patients underwent repeat biopsy to establish a discriminant formula for predicting the AP of NAFLD (D-APN). The AP was defined by NAFLD that had been maintained or progressed to a fibrotic stage beyond stage 2. In the second analysis, we analyzed the distribution of the AP in each stage of disease and the incidence of the PNPLA3 rs738409 GG genotype in AP in 120 other patients. Results After the analysis, the following function was found to discriminate the disease phenotype: z=0.150×body mass index (kg/m 2 )+0.085×age (years)+1.112×ln (AST) (IU/L)+0.127×ln (m-AST)-12.96. A positive result indicates the AP of NAFLD. The discriminant functions had a positive predictive value of 94% and a negative predictive value of 71%. The distribution of the AP and the incidence of the PNPLA3 GG genotype in the AP in each stage of the disease among the 120 patients were as follows: non-alcoholic fatty liver, 30%/33%; non-alcoholic steatohepatitis (NASH) stage 1, 53%/26%; stage 2, 71%/70%; stage 3, 92%/57%; and stage 4, 93%/64%; there was a significant increase in the incidence of the AP as the disease progressed (p<0.001). Conclusion The new discriminant formula was useful for predicting disease progression potential in NAFLD patients and the incidence of the PNPLA3 GG genotype was elevated according to the distribution of AP.

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