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Sample records for amphibia forms voltage-dependent

  1. Amphibia Kupffer cells.

    PubMed

    Sichel, Giovanni; Scalia, Marina; Corsaro, Concetta

    2002-06-15

    Amphibia Kupffer cells (i.e., liver resident macrophages) show many common characteristics when compared with Mammalia Kupffer cells: filopodia, microvillous-like structures, lamellipodia, fuzzy coat, coated vesicles, bristled vacuoles, nonspecific esterase activity, and pinocytotic and phagocytic activity are present both in Amphibia and Mammalia Kupffer cells. On the other hand, some differences are present between Kupffer cells of both zoological classes: phagocytosed red cells and their derivatives, iron-protein complexes, and lipofuscin bodies are normally present in Amphibia Kupffer cells, but absent in the same cells of healthy mammals. Worm-like structures are not seen in Amphibia and endogenous peroxidase activity is very weak in these animals compared with Mammalia. The most important difference lies in the ability of Amphibia Kupffer cells to produce melanins: in fact the tyrosinase gene is expressed, "melanosome centers" are present, and dopa oxidase activity is demonstrable.

  2. Voltage Dependence of a Neuromodulator-Activated Ionic Current123

    PubMed Central

    2016-01-01

    Abstract The neuromodulatory inward current (IMI) generated by crab Cancer borealis stomatogastric ganglion neurons is an inward current whose voltage dependence has been shown to be crucial in the activation of oscillatory activity of the pyloric network of this system. It has been previously shown that IMI loses its voltage dependence in conditions of low extracellular calcium, but that this effect appears to be regulated by intracellular calmodulin. Voltage dependence is only rarely regulated by intracellular signaling mechanisms. Here we address the hypothesis that the voltage dependence of IMI is mediated by intracellular signaling pathways activated by extracellular calcium. We demonstrate that calmodulin inhibitors and a ryanodine antagonist can reduce IMI voltage dependence in normal Ca2+, but that, in conditions of low Ca2+, calmodulin activators do not restore IMI voltage dependence. Further, we show evidence that CaMKII alters IMI voltage dependence. These results suggest that calmodulin is necessary but not sufficient for IMI voltage dependence. We therefore hypothesize that the Ca2+/calmodulin requirement for IMI voltage dependence is due to an active sensing of extracellular calcium by a GPCR family calcium-sensing receptor (CaSR) and that the reduction in IMI voltage dependence by a calmodulin inhibitor is due to CaSR endocytosis. Supporting this, preincubation with an endocytosis inhibitor prevented W7 (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride)-induced loss of IMI voltage dependence, and a CaSR antagonist reduced IMI voltage dependence. Additionally, myosin light chain kinase, which is known to act downstream of the CaSR, seems to play a role in regulating IMI voltage dependence. Finally, a Gβγ-subunit inhibitor also affects IMI voltage dependence, in support of the hypothesis that this process is regulated by a G-protein-coupled CaSR. PMID:27257619

  3. A voltage-dependent gap junction in Drosophila melanogaster.

    PubMed Central

    Verselis, V K; Bennett, M V; Bargiello, T A

    1991-01-01

    -junction channels are capable of two distinct, but interactive forms of voltage dependence. Images FIGURE 2 PMID:1901743

  4. Osteological Variation among Extreme Morphological Forms in the Mexican Salamander Genus Chiropterotriton (Amphibia: Plethodontidae): Morphological Evolution And Homoplasy

    PubMed Central

    Darda, David M.; Wake, David B.

    2015-01-01

    Osteological variation is recorded among and within four of the most distinctive species of the Mexican salamander genus Chiropterotriton. Analysis of the data is consistent with the monophyletic status of the genus and documents previously unrecorded intraspecific and interspecific variation. Most of the recorded variation involves qualitative and quantitative proportional differences, but four fixed differences constitute autapomorphic states that affirm and diagnose some species (C. dimidiatus, C. magnipes). Osteological variation in 15 characters is analyzed with respect to predictions generated from four hypotheses: 1) phylogeny, 2) adaptation to specific habitats (the four species include cave-dwelling, terrestrial, and arboreal forms), 3) size-free shape, and 4) size. High levels of intraspecific variation suggest that the characters studied are not subject to rigid functional constraints in salamanders, regardless of size. The pattern predicted by the hypothesis based on size differences seen among these four Chiropterotriton species matches most closely the observed pattern of relative skull robustness. Since size change and heterochrony are often associated in plethodontid evolution, it is likely that changes in developmental timing play a role in the morphological transitions among these morphologically diverse taxa. Webbed feet, miniaturization, body shape, and an unusual tarsal arrangement are morphologies exhibited in species of Chiropterotrition that are shown to be homoplastic with other clades of tropical plethodontids. Although extensive homoplasy in salamanders might be seen as a roadblock to unraveling phylogenetic hypotheses, the homologous developmental systems that appear to underlie such homoplasy may reveal common and consistent evolutionary processes at work. PMID:26060996

  5. Osteological Variation among Extreme Morphological Forms in the Mexican Salamander Genus Chiropterotriton (Amphibia: Plethodontidae): Morphological Evolution And Homoplasy.

    PubMed

    Darda, David M; Wake, David B

    2015-01-01

    Osteological variation is recorded among and within four of the most distinctive species of the Mexican salamander genus Chiropterotriton. Analysis of the data is consistent with the monophyletic status of the genus and documents previously unrecorded intraspecific and interspecific variation. Most of the recorded variation involves qualitative and quantitative proportional differences, but four fixed differences constitute autapomorphic states that affirm and diagnose some species (C. dimidiatus, C. magnipes). Osteological variation in 15 characters is analyzed with respect to predictions generated from four hypotheses: 1) phylogeny, 2) adaptation to specific habitats (the four species include cave-dwelling, terrestrial, and arboreal forms), 3) size-free shape, and 4) size. High levels of intraspecific variation suggest that the characters studied are not subject to rigid functional constraints in salamanders, regardless of size. The pattern predicted by the hypothesis based on size differences seen among these four Chiropterotriton species matches most closely the observed pattern of relative skull robustness. Since size change and heterochrony are often associated in plethodontid evolution, it is likely that changes in developmental timing play a role in the morphological transitions among these morphologically diverse taxa. Webbed feet, miniaturization, body shape, and an unusual tarsal arrangement are morphologies exhibited in species of Chiropterotrition that are shown to be homoplastic with other clades of tropical plethodontids. Although extensive homoplasy in salamanders might be seen as a roadblock to unraveling phylogenetic hypotheses, the homologous developmental systems that appear to underlie such homoplasy may reveal common and consistent evolutionary processes at work.

  6. Voltage-dependent conductances in Limulus ventral photoreceptors

    PubMed Central

    1982-01-01

    The voltage-dependent conductances of Limulus ventral photoreceptors have been investigated using a voltage-clamp technique. Depolarization in the dark induces inward and outward currents. The inward current is reduced by removing Na+ or Ca2+ and is abolished by removing both ions. These results suggest that both Na+ and Ca2+ carry voltage-dependent inward current. Inward current is insensitive to tetrodotoxin but is blocked by external Ni2+. The outward current has a large transient component that is followed by a smaller maintained component. Intracellular tetraethylammonium preferentially reduces the maintained component, and extracellular 4-amino pyridine preferentially reduces the transient component. Neither component is strongly affected by removal of extracellular Ca2+ or by intracellular injection of EGTA. It is concluded that the photoreceptors contain at least three separate voltage-dependent conductances: 1) a conductance giving rise to inward currents; 2) a delayed rectifier giving rise to maintained outward K+ current; and 3) a rapidly inactivating K+ conductance similar to the A current of molluscan neurons. PMID:7057161

  7. Voltage-dependent amplification of synaptic inputs in respiratory motoneurones.

    PubMed

    Enríquez Denton, M; Wienecke, J; Zhang, M; Hultborn, H; Kirkwood, P A

    2012-07-01

    The role of persistent inward currents (PICs) in cat respiratory motoneurones (phrenic inspiratory and thoracic expiratory) was investigated by studying the voltage-dependent amplification of central respiratory drive potentials (CRDPs), recorded intracellularly, with action potentials blocked with the local anaesthetic derivative, QX-314. Decerebrate unanaesthetized or barbiturate-anaesthetized preparations were used. In expiratory motoneurones, plateau potentials were observed in the decerebrates, but not under anaesthesia. For phrenic motoneurones, no plateau potentials were observed in either state (except in one motoneurone after the abolition of the respiratory drive by means of a medullary lesion), but all motoneurones showed voltage-dependent amplification of the CRDPs, over a wide range of membrane potentials, too wide to result mainly from PIC activation. The measurements of the amplification were restricted to the phase of excitation, thus excluding the inhibitory phase. Amplification was found to be greatest for the smallest CRDPs in the lowest resistance motoneurones and was reduced or abolished following intracellular injection of the NMDA channel blocker, MK-801. Plateau potentials were readily evoked in non-phrenic cervical motoneurones in the same (decerebrate) preparations. We conclude that the voltage-dependent amplification of synaptic excitation in phrenic motoneurones is mainly the result of NMDA channel modulation rather than the activation of Ca2+ channel mediated PICs, despite phrenic motoneurones being strongly immunohistochemically labelled for CaV1.3 channels. The differential PIC activation in different motoneurones, all of which are CaV1.3 positive, leads us to postulate that the descending modulation of PICs is more selective than has hitherto been believed. PMID:22495582

  8. Cytoplasmic Domains and Voltage-Dependent Potassium Channel Gating

    PubMed Central

    Barros, Francisco; Domínguez, Pedro; de la Peña, Pilar

    2012-01-01

    The basic architecture of the voltage-dependent K+ channels (Kv channels) corresponds to a transmembrane protein core in which the permeation pore, the voltage-sensing components and the gating machinery (cytoplasmic facing gate and sensor–gate coupler) reside. Usually, large protein tails are attached to this core, hanging toward the inside of the cell. These cytoplasmic regions are essential for normal channel function and, due to their accessibility to the cytoplasmic environment, constitute obvious targets for cell-physiological control of channel behavior. Here we review the present knowledge about the molecular organization of these intracellular channel regions and their role in both setting and controlling Kv voltage-dependent gating properties. This includes the influence that they exert on Kv rapid/N-type inactivation and on activation/deactivation gating of Shaker-like and eag-type Kv channels. Some illustrative examples about the relevance of these cytoplasmic domains determining the possibilities for modulation of Kv channel gating by cellular components are also considered. PMID:22470342

  9. Cumulative Activation of Voltage-Dependent KVS-1 Potassium Channels

    PubMed Central

    Rojas, Patricio; Garst-Orozco, Jonathan; Baban, Beravan; de Santiago-Castillo, Jose Antonio; Covarrubias, Manuel; Salkoff, Lawrence

    2008-01-01

    In this study, we reveal the existence of a novel use-dependent phenomenon in potassium channels, which we refer to as cumulative activation (CA). CA consists of an increase in current amplitude in response to repetitive depolarizing step pulses to the same potential. CA persists for up to 20 s and is similar to a phenomenon called “voltage-dependent facilitation” observed in some calcium channels. The KVS-1 K+ channel, which exhibits CA, is a rapidly activating and inactivating voltage-dependent potassium channel expressed in chemosensory and other neurons of Caenorhabditis elegans. It is unusual in being most closely related to the Shab (Kv2) family of potassium channels, which typically behave like delayed rectifier K+ channels in other species. The magnitude of CA depends on the frequency, voltage, and duration of the depolarizing step pulse. CA also radically changes the activation and inactivation kinetics of the channel, suggesting that the channel may undergo a physical modification in a use-dependent manner; thus, a model that closely simulates the behavior of the channel postulates the existence of two populations of channels, unmodified and modified. Use-dependent changes in the behavior of potassium channels, such as CA observed in KVS-1, could be involved in functional mechanisms of cellular plasticity such as synaptic depression that represent the cellular basis of learning and memory. PMID:18199775

  10. Charged Residues at the First Transmembrane Region Contribute to the Voltage Dependence of the Slow Gate of Connexins.

    PubMed

    Pinto, Bernardo I; García, Isaac E; Pupo, Amaury; Retamal, Mauricio A; Martínez, Agustín D; Latorre, Ramón; González, Carlos

    2016-07-22

    Connexins (Cxs) are a family of membrane-spanning proteins that form gap junction channels and hemichannels. Connexin-based channels exhibit two distinct voltage-dependent gating mechanisms termed slow and fast gating. Residues located at the C terminus of the first transmembrane segment (TM-1) are important structural components of the slow gate. Here, we determined the role of the charged residues at the end of TM-1 in voltage sensing in Cx26, Cx46, and Cx50. Conductance/voltage curves obtained from tail currents together with kinetics analysis reveal that the fast and slow gates of Cx26 involves the movement of two and four charges across the electric field, respectively. Primary sequence alignment of different Cxs shows the presence of well conserved glutamate residues in the C terminus of TM-1; only Cx26 contains a lysine in that position (lysine 41). Neutralization of lysine 41 in Cx26 increases the voltage dependence of the slow gate. Swapping of lysine 41 with glutamate 42 maintains the voltage dependence. In Cx46, neutralization of negative charges or addition of a positive charge in the Cx26 equivalent region reduced the slow gate voltage dependence. In Cx50, the addition of a glutamate in the same region decreased the voltage dependence, and the neutralization of a negative charge increased it. These results indicate that the charges at the end of TM-1 are part of the slow gate voltage sensor in Cxs. The fact that Cx42, which has no charge in this region, still presents voltage-dependent slow gating suggests that charges still unidentified also contribute to the slow gate voltage sensitivity.

  11. Purification and Characterization of Two Voltage-Dependent Anion Channel Isoforms from Plant Seeds1

    PubMed Central

    Abrecht, Helge; Wattiez, Ruddy; Ruysschaert, Jean-Marie; Homblé, Fabrice

    2000-01-01

    Mitochondria were isolated from imbibed seeds of lentil (Lens culinaris) and Phaseolus vulgaris. We copurified two voltage-dependent anion channel from detergent solubilized mitochondria in a single purification step using hydroxyapatite. The two isoforms from P. vulgaris were separated by chromatofocusing chromatography in 4 m urea without any loss of channel activity. Channel activity of each isoform was characterized upon reconstitution into diphytanoyl phosphatidylcholine planar lipid bilayers. Both isoforms form large conductance channels that are slightly anion selective and display cation selective substates. PMID:11080295

  12. Purification and characterization of two voltage-dependent anion channel isoforms from plant seeds.

    PubMed

    Abrecht, H; Wattiez, R; Ruysschaert, J M; Homblé, F

    2000-11-01

    Mitochondria were isolated from imbibed seeds of lentil (Lens culinaris) and Phaseolus vulgaris. We copurified two voltage-dependent anion channel from detergent solubilized mitochondria in a single purification step using hydroxyapatite. The two isoforms from P. vulgaris were separated by chromatofocusing chromatography in 4 M urea without any loss of channel activity. Channel activity of each isoform was characterized upon reconstitution into diphytanoyl phosphatidylcholine planar lipid bilayers. Both isoforms form large conductance channels that are slightly anion selective and display cation selective substates.

  13. Voltage Dependent Charge Storage Modes and Capacity in Subnanometer Pores

    SciTech Connect

    Qiao, Rui; Meunier, V.; Huang, Jingsong; Wu, Peng; Sumpter, Bobby G

    2012-01-01

    Using molecular dynamics simulations, we show that charge storage in subnanometer pores follows a distinct voltage-dependent behavior. Specifically, at lower voltages, charge storage is achieved by swapping co-ions in the pore with counterions in the bulk electrolyte. As voltage increases, further charge storage is due mainly to the removal of co-ions from the pore, leading to a capacitance increase. The capacitance eventually reaches a maximum when all co-ions are expelled from the pore. At even higher electrode voltages, additional charge storage is realized by counterion insertion into the pore, accompanied by a reduction of capacitance. The molecular mechanisms of these observations are elucidated and provide useful insight for optimizing energy storage based on supercapacitors.

  14. Voltage-dependent membrane displacements measured by atomic force microscopy.

    PubMed

    Mosbacher, J; Langer, M; Hörber, J K; Sachs, F

    1998-01-01

    Cells use polar molecules in the membrane to sense changes in the transmembrane potential. The opening of voltage-gated ion channels and membrane bending due to the inverse flexoelectric effect are two examples of such electromechanical coupling. We have looked for membrane motions in an electric field using atomic (or scanning) force microscopy (AFM) with the intent of studying voltage-dependent conformational changes of ion channels. Voltage-clamped HEK293 cells were either untransfected controls or transfected with Shaker K+ channels. Using a +/- 10-mV peak-peak AC carrier stimulus, untransfected cells moved 0.5-15 nm normal to the plane of the membrane. These movements tracked the voltage at frequencies >1 kHz with a phase lead of 60-120 degrees, as expected of a displacement current. The movement was outward with depolarization, but the holding potential only weakly influenced the amplitude of the movement. In contrast, cells transfected with a noninactivating mutant of Shaker K+channels showed similar movements, but these were sensitive to the holding potential; decreasing with depolarization between -80 and 0 mV. Searching for artifactual origins of these movements, we used open or sealed pipettes and AFM cantilever placements just above the cells. These results were negative, suggesting that the observed movements were produced by the cell membrane rather than by movement of the patch pipette, or by acoustic or electrical interactions of the membrane with the AFM tip. In control cells, the electrical motor may arise from the flexoelectric effect, where changes in potential induce changes in curvature. In transfected cells, it appears that channel-specific movements also occurred. These experiments demonstrate that the AFM may be able to exploit voltage-dependent movements as a source of contrast for imaging membrane components. The electrically induced motility will cause twitching during action potentials, and may have physiological consequences. PMID

  15. Voltage-Dependent Gating of hERG Potassium Channels

    PubMed Central

    Cheng, Yen May; Claydon, Tom W.

    2012-01-01

    The mechanisms by which voltage-gated channels sense changes in membrane voltage and energetically couple this with opening of the ion conducting pore has been the source of significant interest. In voltage-gated potassium (Kv) channels, much of our knowledge in this area comes from Shaker-type channels, for which voltage-dependent gating is quite rapid. In these channels, activation and deactivation are associated with rapid reconfiguration of the voltage-sensing domain unit that is electromechanically coupled, via the S4–S5 linker helix, to the rate-limiting opening of an intracellular pore gate. However, fast voltage-dependent gating kinetics are not typical of all Kv channels, such as Kv11.1 (human ether-à-go-go related gene, hERG), which activates and deactivates very slowly. Compared to Shaker channels, our understanding of the mechanisms underlying slow hERG gating is much poorer. Here, we present a comparative review of the structure–function relationships underlying activation and deactivation gating in Shaker and hERG channels, with a focus on the roles of the voltage-sensing domain and the S4–S5 linker that couples voltage sensor movements to the pore. Measurements of gating current kinetics and fluorimetric analysis of voltage sensor movement are consistent with models suggesting that the hERG activation pathway contains a voltage independent step, which limits voltage sensor transitions. Constraints upon hERG voltage sensor movement may result from loose packing of the S4 helices and additional intra-voltage sensor counter-charge interactions. More recent data suggest that key amino acid differences in the hERG voltage-sensing unit and S4–S5 linker, relative to fast activating Shaker-type Kv channels, may also contribute to the increased stability of the resting state of the voltage sensor. PMID:22586397

  16. Selected emerging diseases of amphibia.

    PubMed

    Latney, La'Toya V; Klaphake, Eric

    2013-05-01

    This review summarizes the most recent updates on emerging infectious diseases of amphibia. A brief summary of Batrachochytrium dendrobatidis history, epidemiology, pathogenesis, life cycle, diagnosis, treatment, and biosecurity is provided. Ambystoma tigrinum virus, common midwife toad virus, frog virus 3, Rana grylio virus, Rana catesbeiana ranavirus, Mahaffey Road virus, Rana esculenta virus, Bohle iridovirus, and tiger frog virus ranaviruses are extensively reviewed. Emerging bacterial pathogens are discussed, including Flavobacter sp, Aeromonas sp, Citrobacter freundii, Chlamydophila sp, Mycobacterium liflandii, Elizabethkingia meningoseptica, and Ochrobactrum anthropi. Rhabdias sp, Ribeiroia sp, and Spirometra erinacei are among several of the parasitic infections overviewed in this article.

  17. Conductance hysteresis in the voltage dependent anion-selective channel

    PubMed Central

    Hoogerheide, David P.; Rostovtseva, Tatiana K.; Berezhkovskii, Alexander M.; Bezrukov, Sergey M.

    2015-01-01

    When the transmembrane voltage is periodically varied with time, the conductance of voltage-sensitive ion channels shows hysteretic behavior. Although this phenomenon has been used in studies of gating of the voltage-dependent anion channel, VDAC, from the outer mitochondrial membrane for nearly four decades, full hysteresis curves have never been reported, since the focus was only on the channel opening branches of the hysteresis loops. Here we study hysteretic response of a multichannel VDAC system to a triangular voltage ramp whose frequency varies within three orders of magnitude, ranging from 0.5 mHz to 0.2 Hz. We find that in this wide frequency range the area encircled by the hysteresis curves changes by less than a factor of three, thus suggesting a broad distribution of the characteristic times and strongly non-equilibrium behavior. At the same time, hysteresis branches corresponding to VDAC opening show quasi-equilibrium two-state behavior. This allows calculating usual equilibrium gating parameters, the gating charge and voltage of equipartitioning, which turn out to be virtually insensitive to the ramp frequency. To rationalize this peculiarity, we hypothesize that during voltage-induced closure and opening the system explores different regions of the complex free energy landscape, where, in the opening branch, it follows quasi-equilibrium paths. PMID:26094068

  18. Conductance hysteresis in the voltage-dependent anion channel.

    PubMed

    Rappaport, Shay M; Teijido, Oscar; Hoogerheide, David P; Rostovtseva, Tatiana K; Berezhkovskii, Alexander M; Bezrukov, Sergey M

    2015-09-01

    Hysteresis in the conductance of voltage-sensitive ion channels is observed when the transmembrane voltage is periodically varied with time. Although this phenomenon has been used in studies of gating of the voltage-dependent anion channel, VDAC, from the outer mitochondrial membrane for nearly four decades, full hysteresis curves have never been reported, because the focus was solely on the channel opening branches of the hysteresis loops. We studied the hysteretic response of a multichannel VDAC system to a triangular voltage ramp the frequency of which was varied over three orders of magnitude, from 0.5 mHz to 0.2 Hz. We found that in this wide frequency range the area encircled by the hysteresis curves changes by less than a factor of three, suggesting broad distribution of the characteristic times and strongly non-equilibrium behavior. At the same time, quasi-equilibrium two-state behavior is observed for hysteresis branches corresponding to VDAC opening. This enables calculation of the usual equilibrium gating parameters, gating charge and voltage of equipartitioning, which were found to be almost insensitive to the ramp frequency. To rationalize this peculiarity, we hypothesize that during voltage-induced closure and opening the system explores different regions of the complex free energy landscape, and, in the opening branch, follows quasi-equilibrium paths.

  19. Voltage-dependent capacitance of human embryonic kidney cells

    NASA Astrophysics Data System (ADS)

    Farrell, Brenda; Do Shope, Cythnia; Brownell, William E.

    2006-04-01

    We determine membrane capacitance, C as a function of dc voltage for the human embryonic kidney (HEK) cell. C was calculated from the admittance, Y , obtained during a voltage ramp when the HEK cell was held in whole-cell patch-clamp configuration. Y was determined at frequencies of 390.625 and 781.25Hz from the measured current, i obtained with a dual-sinusoidal stimulus. We find that the fractional increase in the capacitance, C is small (<1%) and grows with the square of the voltage, Ψ . C can be described by: C=C(0)(1+α(Ψ+ψs)2) [where C(0) : Capacitance at 0volts , ψs : Difference in surface potential between cytoplasmic and extracellular leaflets and α : Proportionality constant]. We find that α and ψs are 0.120 (±0.01)V-2 and -0.073 (±0.017)V in solutions that contain ion channel blockers and 0.108 (±0.29)V-2 and -0.023 (±0.009)V when 10mM sodium salicylate was added to the extracellular solution. This suggests that salicylate does not affect the rate at which C grows with Ψ , but reduces the charge asymmetry of the membrane. We also observe an additional linear differential capacitance of about (-46fFV-1) in about 60% of the cells, this additional component acts simultaneously with the quadratic component and was not observed when salicylate was added to the solution. We suggest that the voltage dependent capacitance originates from electromechanical coupling either by electrostriction and/or Maxwell stress effects and estimate that a small electromechanical force (≈1pN) acts at physiological potentials. These results are relevant to understand the electromechanical coupling in outer hair cells (OHCs) of the mammalian cochlea, where an asymmetric bell-shaped C versus Ψ relationship is observed upon application of a similar field. Prestin, a membrane protein expressed in OHCs is required to observe this function. When we compare the total charge contributions from HEK cell membrane ( 7×104 electrons, 10pF cell) with that determined for

  20. Precipitation-Induced Voltage-Dependent Ion Current Fluctuations in Conical Nanopores

    SciTech Connect

    Vlassiouk, Ivan V

    2010-01-01

    Single conically shaped nanopores produce stable ion current fluctuations when in contact with weakly soluble salts, such as calcium hydrogen phosphate (CaHPO{sub 4}) and cobalt hydrogen phosphate (CoHPO{sub 4}). The pore spontaneously switches between high and low conductance states, called open and closed states, respectively. Pore opening and closing are linked to the dynamic formation of the calcium and cobalt precipitates at the small opening of the pore. The probabilities of pore opening and closing are voltage-dependent, and this characteristic of ion current signal is known for biological voltage-gated channels. We show that new types of ion current fluctuations are obtained in conditions at which precipitates of CaHPO{sub 4} and CoHPO{sub 4} can form in the pore at the same time.

  1. AmphibiaChina: an online database of Chinese Amphibians.

    PubMed

    Che, Jing; Wang, Kai

    2016-01-18

    AmphibiaChina, an open-access, web-based database, is designed to provide comprehensive and up-to-date information on Chinese amphibians. It offers an integrated module with six major sections. Compared to other known databases including AmphibiaWeb and Amphibian Species of the World, AmphibiaChina has the following new functions: (1) online species identification based on DNA barcode sequences; (2) comparisons and discussions of different major taxonomic systems; and (3) phylogenetic progress on Chinese amphibians. This database offers a window for the world to access available information of Chinese amphibians. AmphibiaChina with its Chinese version can be accessed at http://www.amphibiachina.org.

  2. The spleen pigment cells in some amphibia.

    PubMed

    Scalia, Marina; Di Pietro, Cinzia; Poma, Mariangela; Ragusa, Marco; Sichel, Giovanni; Corsaro, Concetta

    2004-04-01

    It was demonstrated that the spleen pigment cells of Amphibia are macrophages: they show an ultrastructurally distinctive morphology, are able to phagocytose and react positively for non-specific esterases. These pigmented macrophages express mRNA for tyrosinase and also they show dopa oxidase activity; therefore they are able to synthesize melanins, as Kupffer cells do.

  3. Functional significance of voltage-dependent conductances in Limulus ventral photoreceptors

    PubMed Central

    1982-01-01

    The influence of voltage-dependent conductances on the receptor potential of Limulus ventral photoreceptors was investigated. During prolonged, bright illumination, the receptor potential consists of an initial transient phase followed by a smaller plateau phase. Generally, a spike appears on the rising edge of the transient phase, and often a dip occurs between the transient and plateau. Block of the rapidly inactivating outward current, iA, by 4-aminopyridine eliminates the dip under some conditions. Block of maintained outward current by internal tetraethylammonium increases the height of the plateau phase, but does not eliminate the dip. Block of the voltage-dependent Na+ and Ca2+ current by external Ni2+ eliminates the spike. The voltage-dependent Ca2+ conductance also influences the sensitivity of the photoreceptor to light as indicated by the following evidence: depolarizing voltage- clamp pulses reduce sensitivity to light. This reduction is blocked by removal of external Ca2+ or by block of inward Ca2+ current with Ni2+. The reduction of sensitivity depends on the amplitude of the pulse, reaching a maximum at or approximately +15 mV. The voltage dependence is consistent with the hypothesis that the desensitization results from passive Ca2+ entry through a voltage-dependent conductance. PMID:7057162

  4. Anomalous voltage dependence of channel blockade at a crustacean glutamate-mediated synapse.

    PubMed Central

    Lingle, C J

    1989-01-01

    1. The voltage dependence and concentration dependence of blockade of glutamate-activated currents by the diquaternary amine, chlorisondamine, were examined in a marine crustacean muscle. 2. Chlorisondamine results in the splitting of focally recorded synaptic current decays into two exponential components. The fast component becomes faster with increases in drug concentration and with hyperpolarization. The slow decay rate is unchanged or faster with hyperpolarization and the relative amplitude of the slow component is increased with hyperpolarization. 3. The alteration of synaptic current decay rates by chlorisondamine over the range of 5 to 100 microM and -80 to -140 mV is quantitatively consistent with a simple channel blockade model with a zero-voltage blocking rate of 6 x 10(5) M-1 s-1 at 12 degrees C with a voltage dependence of about 40 mV per e-fold change. The unblocking rate is about 5 s-1 at 0 mV and increases with hyperpolarization with a voltage dependence of about 30 mV per e-fold change. 4. The dose dependence and voltage dependence of blockade of ionophoretically activated glutamate currents by chlorisondamine are qualitatively consistent with the kinetic estimates. 5. The anomalous voltage dependence of the unblocking process is considered in terms of the possibility that the relief from blockade by chlorisondamine occurs by transit of chlorisondamine through the ion channel opened by glutamate. PMID:2479739

  5. Vector spin modeling for magnetic tunnel junctions with voltage dependent effects

    SciTech Connect

    Manipatruni, Sasikanth Nikonov, Dmitri E.; Young, Ian A.

    2014-05-07

    Integration and co-design of CMOS and spin transfer devices requires accurate vector spin conduction modeling of magnetic tunnel junction (MTJ) devices. A physically realistic model of the MTJ should comprehend the spin torque dynamics of nanomagnet interacting with an injected vector spin current and the voltage dependent spin torque. Vector spin modeling allows for calculation of 3 component spin currents and potentials along with the charge currents/potentials in non-collinear magnetic systems. Here, we show 4-component vector spin conduction modeling of magnetic tunnel junction devices coupled with spin transfer torque in the nanomagnet. Nanomagnet dynamics, voltage dependent spin transport, and thermal noise are comprehended in a self-consistent fashion. We show comparison of the model with experimental magnetoresistance (MR) of MTJs and voltage degradation of MR with voltage. Proposed model enables MTJ circuit design that comprehends voltage dependent spin torque effects, switching error rates, spin degradation, and back hopping effects.

  6. Voltage-Dependent K+-Channel in Protoplasmic Droplets of Chara corallina1

    PubMed Central

    Homblé, Fabrice; Ferrier, Jack M.; Dainty, Jack

    1987-01-01

    Passive transport of potassium through the plasma membrane of a protoplasmic droplet isolated from large internodal cells of Chara corallina Klein ex Willd., em, R.D.W. has been investigated using the patchclamp technique. When the membrane is hyperpolarized the conductance of a single K+-channel is of the order of magnitude of 100 picoSiemens and is reduced by tetraethylammonium chloride. Its open time is voltage dependent. This voltage-dependent K+-channel displays rectifying properties. The channel density is about 0.1 channel per square micrometer of membrane. When the membrane is depolarized the conductance of a single channel is of the order of magnitude of 30 picoSiemens and is insensitive to tetraethylammonium chloride. These results suggest that K+-channels are incorporated in the plasma membrane during membranogenesis of a protoplasmic droplet. They constitute further evidence for the existence of voltage-dependent K+-channels in plant cells. PMID:16665215

  7. Models of Voltage-Dependent Conformational Changes in NaChBac Channels

    PubMed Central

    Shafrir, Yinon; Durell, Stewart R.; Guy, H. Robert

    2008-01-01

    Models of the transmembrane region of the NaChBac channel were developed in two open/inactivated and several closed conformations. Homology models of NaChBac were developed using crystal structures of Kv1.2 and a Kv1.2/2.1 chimera as templates for open conformations, and MlotiK and KcsA channels as templates for closed conformations. Multiple molecular-dynamic simulations were performed to refine and evaluate these models. A striking difference between the S4 structures of the Kv1.2-like open models and MlotiK-like closed models is the secondary structure. In the open model, the first part of S4 forms an α-helix, and the last part forms a 310 helix, whereas in the closed model, the first part of S4 forms a 310 helix, and the last part forms an α-helix. A conformational change that involves this type of transition in secondary structure should be voltage-dependent. However, this transition alone is not sufficient to account for the large gating charge movement reported for NaChBac channels and for experimental results in other voltage-gated channels. To increase the magnitude of the motion of S4, we developed another model of an open/inactivated conformation, in which S4 is displaced farther outward, and a number of closed models in which S4 is displaced farther inward. A helical screw motion for the α-helical part of S4 and a simple axial translation for the 310 portion were used to develop models of these additional conformations. In our models, four positively charged residues of S4 moved outwardly during activation, across a transition barrier formed by highly conserved hydrophobic residues on S1, S2, and S3. The S4 movement was coupled to an opening of the activation gate formed by S6 through interactions with the segment linking S4 to S5. Consistencies of our models with experimental studies of NaChBac and Kv channels are discussed. PMID:18641074

  8. Eugenol dilates rat cerebral arteries by inhibiting smooth muscle cell voltage-dependent calcium channels.

    PubMed

    Peixoto-Neves, Dieniffer; Leal-Cardoso, Jose Henrique; Jaggar, Jonathan H

    2014-11-01

    Plants high in eugenol, a phenylpropanoid compound, are used as folk medicines to alleviate diseases including hypertension. Eugenol has been demonstrated to relax conduit and ear arteries and reduce systemic blood pressure, but mechanisms involved are unclear. Here, we studied eugenol regulation of resistance-size cerebral arteries that control regional brain blood pressure and flow and investigated mechanisms involved. We demonstrate that eugenol dilates arteries constricted by either pressure or membrane depolarization (60 mM K) in a concentration-dependent manner. Experiments performed using patch-clamp electrophysiology demonstrated that eugenol inhibited voltage-dependent calcium (Ca) currents, when using Ba as a charge carrier, in isolated cerebral artery smooth muscle cells. Eugenol inhibition of voltage-dependent Ca currents involved pore block, a hyperpolarizing shift (∼-10 mV) in voltage-dependent inactivation, an increase in the proportion of steady-state inactivating current, and acceleration of inactivation rate. In summary, our data indicate that eugenol dilates cerebral arteries by means of multimodal inhibition of voltage-dependent Ca channels.

  9. Eugenol dilates rat cerebral arteries by inhibiting smooth muscle cell voltage-dependent calcium channels

    PubMed Central

    Peixoto-Neves, Dieniffer; Leal-Cardoso, Jose Henrique; Jaggar, Jonathan H.

    2014-01-01

    Plants high in eugenol, a phenylpropanoid compound, are used as folk medicines to alleviate diseases including hypertension. Eugenol has been demonstrated to relax conduit and ear arteries and reduce systemic blood pressure, but mechanisms involved are unclear. Here, we studied eugenol regulation of resistance-size cerebral arteries that control regional brain blood pressure and flow and investigated mechanisms involved. We demonstrate that eugenol dilates arteries constricted by either pressure or membrane depolarization (60 mM K+) in a concentration-dependent manner. Experiments performed using patch-clamp electrophysiology demonstrated that eugenol inhibited voltage-dependent calcium (Ca2+) currents, when using Ba2+ as a charge carrier, in isolated cerebral artery smooth muscle cells. Eugenol inhibition of voltage-dependent Ca2+ currents involved pore block, a hyperpolarizing shift ( ~−10 mV) in voltage-dependent inactivation, an increase in the proportion of steady-state inactivating current, and acceleration of inactivaiton rate. In summary, our data indicate that eugenol dilates cerebral arteries via multi-modal inhibition of voltage-dependent Ca2+ channels. PMID:24921632

  10. Eugenol dilates rat cerebral arteries by inhibiting smooth muscle cell voltage-dependent calcium channels.

    PubMed

    Peixoto-Neves, Dieniffer; Leal-Cardoso, Jose Henrique; Jaggar, Jonathan H

    2014-11-01

    Plants high in eugenol, a phenylpropanoid compound, are used as folk medicines to alleviate diseases including hypertension. Eugenol has been demonstrated to relax conduit and ear arteries and reduce systemic blood pressure, but mechanisms involved are unclear. Here, we studied eugenol regulation of resistance-size cerebral arteries that control regional brain blood pressure and flow and investigated mechanisms involved. We demonstrate that eugenol dilates arteries constricted by either pressure or membrane depolarization (60 mM K) in a concentration-dependent manner. Experiments performed using patch-clamp electrophysiology demonstrated that eugenol inhibited voltage-dependent calcium (Ca) currents, when using Ba as a charge carrier, in isolated cerebral artery smooth muscle cells. Eugenol inhibition of voltage-dependent Ca currents involved pore block, a hyperpolarizing shift (∼-10 mV) in voltage-dependent inactivation, an increase in the proportion of steady-state inactivating current, and acceleration of inactivation rate. In summary, our data indicate that eugenol dilates cerebral arteries by means of multimodal inhibition of voltage-dependent Ca channels. PMID:24921632

  11. Expression of voltage dependent potassium currents in freshly dissociated rat articular chondrocytes.

    PubMed

    Ponce, Arturo

    2006-01-01

    The electrophysiological properties of voltage dependent potassium channels from freshly dissociated rat articular chondrocytes were studied. The resting membrane potential (-42.7+/-2.0 mV) was significantly depolarized by increasing concentrations of external potassium. No change was observed when external chloride concentration was varied. Addition of TEA, 4AP, alpha-Dendrotoxin and charybdotoxin depolarized resting membrane potential. Whole cell patch clamp studies revealed the presence of outwardly rectifying currents whose kinetic and pharmacological properties suggest the expression of voltage dependent potassium channels. Two kinds of currents were observed under the same experimental conditions. The first one, most frequently observed (80%), starts activating near -50 mV, with V(1/2)=-18 mV, G(max)=0.30 pS/pF. The second kind was observed in only 10% of cases; It activates near -40 mV, with(1/2)=+28.35 mV, G(max)=0.28 pS/pF pA/pF and does not inactivates. Inactivating currents were significantly inhibited by TEA (IC(50)=1.45 mM), 4AP (IC(50)=0.64 mM), CTX (IC(50) = 10 nM), alpha-Dendrotoxin (IC(50) < 100 nM) and Margatoxin (IC(50)=28.5 nM). These results show that rat chondrocytes express voltage dependent potassium currents and suggest a role of voltage-dependent potassium channels in regulating membrane potential of rat chondrocytes.

  12. Calmodulin and calcium differentially regulate the neuronal Nav1.1 voltage-dependent sodium channel

    SciTech Connect

    Gaudioso, Christelle; Carlier, Edmond; Youssouf, Fahamoe; Clare, Jeffrey J.; Debanne, Dominique; Alcaraz, Gisele

    2011-07-29

    Highlights: {yields} Both Ca{sup ++}-Calmodulin (CaM) and Ca{sup ++}-free CaM bind to the C-terminal region of Nav1.1. {yields} Ca{sup ++} and CaM have both opposite and convergent effects on I{sub Nav1.1}. {yields} Ca{sup ++}-CaM modulates I{sub Nav1.1} amplitude. {yields} CaM hyperpolarizes the voltage-dependence of activation, and increases the inactivation rate. {yields} Ca{sup ++} alone antagonizes CaM for both effects, and depolarizes the voltage-dependence of inactivation. -- Abstract: Mutations in the neuronal Nav1.1 voltage-gated sodium channel are responsible for mild to severe epileptic syndromes. The ubiquitous calcium sensor calmodulin (CaM) bound to rat brain Nav1.1 and to the human Nav1.1 channel expressed by a stably transfected HEK-293 cell line. The C-terminal region of the channel, as a fusion protein or in the yeast two-hybrid system, interacted with CaM via a consensus C-terminal motif, the IQ domain. Patch clamp experiments on HEK1.1 cells showed that CaM overexpression increased peak current in a calcium-dependent way. CaM had no effect on the voltage-dependence of fast inactivation, and accelerated the inactivation kinetics. Elevating Ca{sup ++} depolarized the voltage-dependence of fast inactivation and slowed down the fast inactivation kinetics, and for high concentrations this effect competed with the acceleration induced by CaM alone. Similarly, the depolarizing action of calcium antagonized the hyperpolarizing shift of the voltage-dependence of activation due to CaM overexpression. Fluorescence spectroscopy measurements suggested that Ca{sup ++} could bind the Nav1.1 C-terminal region with micromolar affinity.

  13. Voltage-dependent ion channels in small-cell lung cancer cells.

    PubMed

    Pancrazio, J J; Viglione, M P; Tabbara, I A; Kim, Y I

    1989-11-01

    Small-cell carcinoma of the lung is a highly lethal form of cancer associated with a wide variety of paraneoplastic syndromes. Using the patch-clamp technique, we have directly demonstrated the presence of voltage-gated K+, Na+, and Ca2+ channels in three cell lines of human small-cell carcinoma, NCI-H128, NCI-H69, and NCI-H146. Whole-cell currents were measured from the tumor cells held at -80 mV and depolarized to -60 to +120 mV. Outward K+ current (IK), which was found in every cell tested, reached 1.58 +/- 0.12 nA (mean +/- SE, n = 24 cells) for H128 cells and 2.14 +/- 0.18 nA (n = 41) for H69 cells in response to a test potential of +80 mV. Unlike H69 and H128 tumor cells, IK from H146 cells occasionally exhibited partial inactivation during the 60-ms pulse length and reached 0.94 +/- 0.15 nA (n = 18) in response to a +80 mV test potential. IK from each of the cell lines was significantly reduced by 4-aminopyridine and tetraethylammonium. The rapidly inactivating inward Na+ current (INa), recorded in H146 cells and about 30% of the H69 and H128 cells tested, demonstrated a peak amplitude of 58 +/- 6 pA (n = 11) at 0 mV and a reversal potential of 47 +/- 2 mV (n = 11). Externally applied tetrodotoxin quickly suppressed INa. For the H128 and H69 tumor cells, inward Ca2+ current (ICa), observed in about 25% of the cells exposed to 10 mM [Ca2+]o, peaked at 5.1 +/- 0.4 ms (n = 5) with an amplitude of 46 +/- 14 pA (n = 5) at +20 mV and partially inactivated over the 40-ms depolarization. In H128 cells exposed to isotonic Ba2+ (110 mM), inward currents with time courses similar to those of ICa were recorded. Nearly all H146 tumor cells demonstrated a significant inward Ca2+ current which peaked with an amplitude of 93 +/- 16 pA (n = 26) at +30 to +40 mV in the presence of 10 mM [Ca2+]o. Application of test potentials 2 s in duration revealed that H146 ICa inactivated in a voltage-dependent manner with a time constant on the order of seconds. Adjustment of the holding

  14. Characterization and functional analysis of voltage-dependent anion channel 1 (VDAC1) from orange-spotted grouper (Epinephelus coioides).

    PubMed

    Shi, Yan; Zhao, Zhe; Hong, Xiaoyou; Chen, Kunci; Zhu, Xinping

    2014-07-01

    The voltage-dependent anion channel (VDAC) is a highly conserved integral protein of mitochondria in different eukaryotic species. It forms a selective channel in the mitochondrial outer membrane that serves as the controlled pathway for small metabolites and ions. In this study, a VDAC gene, EcVDAC1, was isolated from orange-spotted grouper (Epinephelus coioides). The EcVDAC1 exhibits ubiquitous expression in various tissues of orange-spotted grouper and is upregulated in liver, gill, and spleen after stimulation with lipopolysaccharides (LPS). Subcellular localization analysis shows that the EcVDAC1 protein colocalized with the mitochondria. A caspase-3 assay demonstrates that overexpression of the EcVDAC1 induced apoptotic cell death in fathead minnow cells. The data presented in this study provide new information regarding the relationship between LPS and the EcVDAC1 gene, suggesting that the fish VDAC1 gene may play an important role in antibacterial immune response. PMID:24891093

  15. Characterization and functional analysis of voltage-dependent anion channel 1 (VDAC1) from orange-spotted grouper (Epinephelus coioides).

    PubMed

    Shi, Yan; Zhao, Zhe; Hong, Xiaoyou; Chen, Kunci; Zhu, Xinping

    2014-07-01

    The voltage-dependent anion channel (VDAC) is a highly conserved integral protein of mitochondria in different eukaryotic species. It forms a selective channel in the mitochondrial outer membrane that serves as the controlled pathway for small metabolites and ions. In this study, a VDAC gene, EcVDAC1, was isolated from orange-spotted grouper (Epinephelus coioides). The EcVDAC1 exhibits ubiquitous expression in various tissues of orange-spotted grouper and is upregulated in liver, gill, and spleen after stimulation with lipopolysaccharides (LPS). Subcellular localization analysis shows that the EcVDAC1 protein colocalized with the mitochondria. A caspase-3 assay demonstrates that overexpression of the EcVDAC1 induced apoptotic cell death in fathead minnow cells. The data presented in this study provide new information regarding the relationship between LPS and the EcVDAC1 gene, suggesting that the fish VDAC1 gene may play an important role in antibacterial immune response.

  16. Relaxation of Isolated Ventricular Cardiomyocytes by a Voltage-Dependent Process

    NASA Astrophysics Data System (ADS)

    Bridge, John H. B.; Spitzer, Kenneth W.; Ershler, Philip R.

    1988-08-01

    Cell contraction and relaxation were measured in single voltage-clamped guinea pig cardiomyocytes to investigate the contribution of sarcolemmal Na+-Ca2+ exchange to mechanical relaxation. Cells clamped from -80 to 0 millivolts displayed initial phasic and subsequent tonic contractions; caffeine reduced or abolished the phasic and enlarged the tonic contraction. The rate of relaxation from tonic contractions was steeply voltage-dependent and was significantly slowed in the absence of a sarcolemmal Na+ gradient. Tonic contractions elicited in the absence of a Na+ gradient promptly relaxed when external Na+ was applied, reflecting activation of Na+-Ca2+ exchange. It appears that a voltage-dependent Na+-Ca2+ exchange can rapidly mechanically relax mammalian heart muscle.

  17. Identification of two voltage-dependent anion channel-like protein sequences conserved in Kinetoplastida

    PubMed Central

    Flinner, Nadine; Schleiff, Enrico; Mirus, Oliver

    2012-01-01

    The eukaryotic porin superfamily consists of two families, voltage-dependent anion channel (VDAC) and Tom40, which are both located in the mitochondrial outer membrane. In Trypanosoma brucei, only a single member of the VDAC family has been described. We report the detection of two additional eukaryotic porin-like sequences in T. brucei. By bioinformatic means, we classify both as putative VDAC isoforms. PMID:22219392

  18. Voltage-dependent drug blockade of L-glutamate activated channels of the crayfish.

    PubMed Central

    Dekin, M S; Edwards, C

    1983-01-01

    The actions of d-tubocurarine (d-TC) and local anaesthetics on the L-glutamate activated channel at the voltage-clamped crayfish neuromuscular junction were studied. The effect of d-TC and local anaesthetics on the dose-response relationship between ionophoretically applied L-glutamate and synaptic current suggested that both acted as non-competitive inhibitors. The amount of inhibition was voltage dependent, and increased as the membrane potential was hyperpolarized. This voltage-dependent block was also manifest in a flattening of the I-V relationship between L-glutamate induced current and membrane potential in the presence of d-TC. However, the reversal potential for the L-glutamate activated channel was not affected; it was about +7 mV in both the presence and absence of d-TC. The neurally evoked excitatory post-synaptic current (e.p.s.c.) was depressed in the presence of these drugs and this effect was also voltage dependent. The time course of the e.p.s.c. was affected, but less so than expected if the L-glutamate activated channel were identical to the channel opened by acetylcholine at the vertebrate neuromuscular junction. Possible reasons for this discrepancy are discussed. PMID:6312026

  19. Voltage Dependence of Conformational Dynamics and Subconducting States of VDAC-1.

    PubMed

    Briones, Rodolfo; Weichbrodt, Conrad; Paltrinieri, Licia; Mey, Ingo; Villinger, Saskia; Giller, Karin; Lange, Adam; Zweckstetter, Markus; Griesinger, Christian; Becker, Stefan; Steinem, Claudia; de Groot, Bert L

    2016-09-20

    The voltage-dependent anion channel 1 (VDAC-1) is an important protein of the outer mitochondrial membrane that transports energy metabolites and is involved in apoptosis. The available structures of VDAC proteins show a wide β-stranded barrel pore, with its N-terminal α-helix (N-α) bound to its interior. Electrophysiology experiments revealed that voltage, its polarity, and membrane composition modulate VDAC currents. Experiments with VDAC-1 mutants identified amino acids that regulate the gating process. However, the mechanisms for how these factors regulate VDAC-1, and which changes they trigger in the channel, are still unknown. In this study, molecular dynamics simulations and single-channel experiments of VDAC-1 show agreement for the current-voltage relationships of an "open" channel and they also show several subconducting transient states that are more cation selective in the simulations. We observed voltage-dependent asymmetric distortions of the VDAC-1 barrel and the displacement of particular charged amino acids. We constructed conformational models of the protein voltage response and the pore changes that consistently explain the protein conformations observed at opposite voltage polarities, either in phosphatidylethanolamine or phosphatidylcholine membranes. The submicrosecond VDAC-1 voltage response shows intrinsic structural changes that explain the role of key gating amino acids and support some of the current gating hypotheses. These voltage-dependent protein changes include asymmetric barrel distortion, its interaction with the membrane, and significant displacement of N-α amino acids. PMID:27653481

  20. Voltage dependence of Hodgkin-Huxley rate functions for a multistage K+ channel voltage sensor within a membrane

    NASA Astrophysics Data System (ADS)

    Vaccaro, S. R.

    2014-11-01

    The activation of a K+channel sensor in two sequential stages during a voltage clamp may be described as the translocation of a Brownian particle in an energy landscape with two large barriers between states. A solution of the Smoluchowski equation for a square-well approximation to the potential function of the S4 voltage sensor satisfies a master equation and has two frequencies that may be determined from the forward and backward rate functions. When the higher-frequency terms have small amplitude, the solution reduces to the relaxation of a rate equation, where the derived two-state rate functions are dependent on the relative magnitude of the forward rates (α and γ ) and the backward rates (β and δ ) for each stage. In particular, the voltage dependence of the Hodgkin-Huxley rate functions for a K+channel may be derived by assuming that the rate functions of the first stage are large relative to those of the second stage—α ≫γ and β ≫δ . For a Shaker IR K+ channel, the first forward and backward transitions are rate limiting (α <γ and δ ≪β ), and for an activation process with either two or three stages, the derived two-state rate functions also have a voltage dependence that is of a similar form to that determined for the squid axon. The potential variation generated by the interaction between a two-stage K+ ion channel and a noninactivating Na+ ion channel is determined by the master equation for K+channel activation and the ionic current equation when the Na+channel activation time is small, and if β ≪δ and α ≪γ , the system may exhibit a small amplitude oscillation between spikes, or mixed-mode oscillation, in which the slow closed state modulates the K+ ion channel conductance in the membrane.

  1. Voltage dependence of the Ca(2+)-activated K(+) channel K(Ca)3.1 in human erythroleukemia cells.

    PubMed

    Stoneking, Colin J; Shivakumar, Oshini; Thomas, David Nicholson; Colledge, William H; Mason, Michael J

    2013-05-01

    We have isolated a K(+)-selective, Ca(2+)-dependent whole cell current and single-channel correlate in the human erythroleukemia (HEL) cell line. The whole cell current was inhibited by the intermediate-conductance KCa3.1 inhibitors clotrimazole, TRAM-34, and charybdotoxin, unaffected by the small-conductance KCa2 family inhibitor apamin and the large-conductance KCa1.1 inhibitors paxilline and iberiotoxin, and augmented by NS309. The single-channel correlate of the whole cell current was blocked by TRAM-34 and clotrimazole, insensitive to paxilline, and augmented by NS309 and had a single-channel conductance in physiological K(+) gradients of ~9 pS. RT-PCR revealed that the KCa3.1 gene, but not the KCa1.1 gene, was expressed in HEL cells. The KCa3.1 current, isolated in HEL cells under whole cell patch-clamp conditions, displayed an activated current component during depolarizing voltage steps from hyperpolarized holding potentials and tail currents upon repolarization, consistent with voltage-dependent modulation. This activated current increased with increasing voltage steps above -40 mV and was sensitive to inhibition by clotrimazole, TRAM-34, and charybdotoxin and insensitive to apamin, paxilline, and iberiotoxin. In single-channel experiments, depolarization resulted in an increase in open channel probability (Po) of KCa3.1, with no increase in channel number. The voltage modulation of Po was an increasing monotonic function of voltage. In the absence of elevated Ca(2+), voltage was ineffective at inducing channel activity in whole cell and single-channel experiments. These data indicate that KCa3.1 in HEL cells displays a unique form of voltage dependence modulating Po.

  2. Voltage dependence of the Ca(2+)-activated K(+) channel K(Ca)3.1 in human erythroleukemia cells.

    PubMed

    Stoneking, Colin J; Shivakumar, Oshini; Thomas, David Nicholson; Colledge, William H; Mason, Michael J

    2013-05-01

    We have isolated a K(+)-selective, Ca(2+)-dependent whole cell current and single-channel correlate in the human erythroleukemia (HEL) cell line. The whole cell current was inhibited by the intermediate-conductance KCa3.1 inhibitors clotrimazole, TRAM-34, and charybdotoxin, unaffected by the small-conductance KCa2 family inhibitor apamin and the large-conductance KCa1.1 inhibitors paxilline and iberiotoxin, and augmented by NS309. The single-channel correlate of the whole cell current was blocked by TRAM-34 and clotrimazole, insensitive to paxilline, and augmented by NS309 and had a single-channel conductance in physiological K(+) gradients of ~9 pS. RT-PCR revealed that the KCa3.1 gene, but not the KCa1.1 gene, was expressed in HEL cells. The KCa3.1 current, isolated in HEL cells under whole cell patch-clamp conditions, displayed an activated current component during depolarizing voltage steps from hyperpolarized holding potentials and tail currents upon repolarization, consistent with voltage-dependent modulation. This activated current increased with increasing voltage steps above -40 mV and was sensitive to inhibition by clotrimazole, TRAM-34, and charybdotoxin and insensitive to apamin, paxilline, and iberiotoxin. In single-channel experiments, depolarization resulted in an increase in open channel probability (Po) of KCa3.1, with no increase in channel number. The voltage modulation of Po was an increasing monotonic function of voltage. In the absence of elevated Ca(2+), voltage was ineffective at inducing channel activity in whole cell and single-channel experiments. These data indicate that KCa3.1 in HEL cells displays a unique form of voltage dependence modulating Po. PMID:23407879

  3. KCNQ1 channels voltage dependence through a voltage-dependent binding of the S4-S5 linker to the pore domain.

    PubMed

    Choveau, Frank S; Rodriguez, Nicolas; Abderemane Ali, Fayal; Labro, Alain J; Rose, Thierry; Dahimène, Shehrazade; Boudin, Hélène; Le Hénaff, Carole; Escande, Denis; Snyders, Dirk J; Charpentier, Flavien; Mérot, Jean; Baró, Isabelle; Loussouarn, Gildas

    2011-01-01

    Voltage-dependent potassium (Kv) channels are tetramers of six transmembrane domain (S1-S6) proteins. Crystallographic data demonstrate that the tetrameric pore (S5-S6) is surrounded by four voltage sensor domains (S1-S4). One key question remains: how do voltage sensors (S4) regulate pore gating? Previous mutagenesis data obtained on the Kv channel KCNQ1 highlighted the critical role of specific residues in both the S4-S5 linker (S4S5(L)) and S6 C terminus (S6(T)). From these data, we hypothesized that S4S5(L) behaves like a ligand specifically interacting with S6(T) and stabilizing the closed state. To test this hypothesis, we designed plasmid-encoded peptides corresponding to portions of S4S5(L) and S6(T) of the voltage-gated potassium channel KCNQ1 and evaluated their effects on the channel activity in the presence and absence of the ancillary subunit KCNE1. We showed that S4S5(L) peptides inhibit KCNQ1, in a reversible and state-dependent manner. S4S5(L) peptides also inhibited a voltage-independent KCNQ1 mutant. This inhibition was competitively prevented by a peptide mimicking S6(T), consistent with S4S5(L) binding to S6(T). Val(254) in S4S5(L) is known to contact Leu(353) in S6(T) when the channel is closed, and mutations of these residues alter the coupling between the two regions. The same mutations introduced in peptides altered their effects, further confirming S4S5(L) binding to S6(T). Our results suggest a mechanistic model in which S4S5(L) acts as a voltage-dependent ligand bound to its receptor on S6 at rest. This interaction locks the channel in a closed state. Upon plasma membrane depolarization, S4 pulls S4S5(L) away from S6(T), allowing channel opening.

  4. New index of pain triggered by spinal activation of voltage-dependent sodium channels.

    PubMed

    Enomoto, Ryugo; Tsukamoto, Mina; Shimoshige, Yukinori; Aoki, Toshiaki; Matsuoka, Nobuya

    2013-12-01

    Voltage-dependent sodium channels (VDSCs) are crucial for pain generation. Here, to develop a new behavioral index of pain induced by spinal VDSC activation, we examined whether intrathecal veratridine injection produced nociceptive behavior. Intrathecal injection of the VDSC opener veratridine in mice dose-dependently induced nociceptive responses, with response times subsequently reduced by administration of morphine or pregabalin. Systemic administration of lidocaine and mexiletine, but not amitriptyline, also decreased this response time. Taken together, these results demonstrated that response time of nociceptive behavior induced by intrathecal veratridine injection is a quantitative index of pain triggered by spinal VDSC activation. PMID:23760511

  5. Voltage-dependence of drug-induced conductance in frog neuromuscular junction.

    PubMed Central

    Neher, E; Sakmann, B

    1975-01-01

    Membrane currents from voltage-clamped frog muscle fibers were recorded during iontophoretic application of steady doses of carbachol, acetylcholine, and suberyldicholine to the endplate region. In the presence of these drugs, an exponentially relaxing current was observed after step changes of membrane potential. The time constant of relaxation was found to be voltage-dependent. It was equal to the time constant obtained from the autocorrelation function of drug-induced conductance fluctuations measured under similar conditions. Analysis of instantaneous current at the on- and offsets of voltageclamp pulses showed that there is no shift in equilibrium potential during the pulses. PMID:1079601

  6. Cloning and functional expression of a plant voltage-dependent chloride channel.

    PubMed Central

    Lurin, C; Geelen, D; Barbier-Brygoo, H; Guern, J; Maurel, C

    1996-01-01

    Plant cell membrane anion channels participate in basic physiological functions, such as cell volume regulation and signal transduction. However, nothing is known about their molecular structure. Using a polymerase chain reaction strategy, we have cloned a tobacco cDNA (CIC-Nt1) encoding a 780-amino acid protein with several putative transmembrane domains. CIC-Nt1 displays 24 to 32% amino acid identity with members of the animal voltage-dependent chloride channel (CIC) family, whose archetype is CIC-0 from the Torpedo marmorata electric organ. Injection of CIC-Nt1 complementary RNA into Xenopus oocytes elicited slowly activating inward currents upon membrane hyperpolarization more negative than -120 mV. These currents were carried mainly by anions, modulated by extracellular anions, and totally blocked by 10 mM extracellular calcium. The identification of CIC-Nt1 extends the CIC family to higher plants and provides a molecular probe for the study of voltage-dependent anion channels in plants. PMID:8624442

  7. Sodium channel from rat brain. Reconstitution of voltage-dependent scorpion toxin binding in vesicles of defined lipid composition

    SciTech Connect

    Feller, D.J.; Talvenheimo, J.A.; Catterall, W.A.

    1985-09-25

    Purified sodium channels incorporated into phosphatidylcholine (PC) vesicles mediate neurotoxin-activated SSNa influx but do not bind the alpha-scorpion toxin from Leiurus quinquestriatus (LqTx) with high affinity. Addition of phosphatidylethanolamine (PE) or phosphatidylserine to the reconstitution mixture restores high affinity LqTx binding with KD = 1.9 nM for PC/PE vesicles at -90 mV and 36 degrees C in sucrose-substituted medium. Other lipids tested were markedly less effective. The binding of LqTx in vesicles of PC/PE (65:35) is sensitive to both the membrane potential formed by sodium gradients across the reconstituted vesicle membrane and the cation concentration in the extravesicular medium. Binding of LqTx is reduced 3- to 4-fold upon depolarization to 0 mV from -50 to -60 mV in experiments in which (Na+)out/(Na+)in is varied by changing (Na+)in or (Na+)out at constant extravesicular ionic strength. It is concluded that the purified sodium channel contains the receptor site for LqTx in functional form and that restoration of high affinity, voltage-dependent binding of LqTx by the purified sodium channel requires an appropriate ratio of PC to PE and/or phosphatidylserine in the vesicle membrane.

  8. A vesicle-trafficking protein commandeers Kv channel voltage sensors for voltage-dependent secretion.

    PubMed

    Grefen, Christopher; Karnik, Rucha; Larson, Emily; Lefoulon, Cécile; Wang, Yizhou; Waghmare, Sakharam; Zhang, Ben; Hills, Adrian; Blatt, Michael R

    2015-01-01

    Growth in plants depends on ion transport for osmotic solute uptake and secretory membrane trafficking to deliver material for wall remodelling and cell expansion. The coordination of these processes lies at the heart of the question, unresolved for more than a century, of how plants regulate cell volume and turgor. Here we report that the SNARE protein SYP121 (SYR1/PEN1), which mediates vesicle fusion at the Arabidopsis plasma membrane, binds the voltage sensor domains (VSDs) of K(+) channels to confer a voltage dependence on secretory traffic in parallel with K(+) uptake. VSD binding enhances secretion in vivo subject to voltage, and mutations affecting VSD conformation alter binding and secretion in parallel with channel gating, net K(+) concentration, osmotic content and growth. These results demonstrate a new and unexpected mechanism for secretory control, in which a subset of plant SNAREs commandeer K(+) channel VSDs to coordinate membrane trafficking with K(+) uptake for growth.

  9. Frequency and voltage dependence of series resistance in a solar cell

    NASA Astrophysics Data System (ADS)

    Ogle, Alexander; Cox, Thaddeus; Heath, Jennifer

    While admittance measurements of solar cells are typically conducted in reverse or at zero bias, and analyzed using the depletion approximation, the operating point of the solar cell is in forward bias, and the series resistance is often estimated using IV curves with a high forward current. In this mode, the device is no longer in the depletion regime, and the large number of injected minority carriers alter the transport properties significantly. In our Cu(In,Ga)Se2 devices, we measure negative values of capacitance at high forward bias, which may be linked to injected minority carriers and carrier transport limitations, although our calculations of capacitance may also be influenced by series resistance. In this study, we compare ac and dc measurements of voltage dependent series resistance to try to better understand the negative capacitance signal.

  10. Identification of PN1, a Predominant Voltage-Dependent Sodium Channel Expressed Principally in Peripheral Neurons

    NASA Astrophysics Data System (ADS)

    Toledo-Aral, Juan J.; Moss, Brenda L.; He, Zhi-Jun; Koszowski, Adam G.; Whisenand, Teri; Levinson, Simon R.; Wolf, John J.; Silos-Santiago, Inmaculada; Halegoua, Simon; Mandel, Gail

    1997-02-01

    Membrane excitability in different tissues is due, in large part, to the selective expression of distinct genes encoding the voltage-dependent sodium channel. Although the predominant sodium channels in brain, skeletal muscle, and cardiac muscle have been identified, the major sodium channel types responsible for excitability within the peripheral nervous system have remained elusive. We now describe the deduced primary structure of a sodium channel, peripheral nerve type 1 (PN1), which is expressed at high levels throughout the peripheral nervous system and is targeted to nerve terminals of cultured dorsal root ganglion neurons. Studies using cultured PC12 cells indicate that both expression and targeting of PN1 is induced by treatment of the cells with nerve growth factor. The preferential localization suggests that the PN1 sodium channel plays a specific role in nerve excitability.

  11. Voltage-dependent K+ currents contribute to heterogeneity of olfactory ensheathing cells

    PubMed Central

    Rela, Lorena; Piantanida, Ana Paula; Bordey, Angelique; Greer, Charles A.

    2015-01-01

    The olfactory nerve is permissive for axon growth throughout life. This has been attributed in part to the olfactory ensheathing glial cells that encompass the olfactory sensory neuron fascicles. Olfactory ensheathing cells also promote axon growth in vitro and when transplanted in vivo to sites of injury. The mechanisms involved remain largely unidentified owing in part to the limited knowledge of the physiological properties of ensheathing cells. Glial cells rely for many functions on the properties of the potassium channels expressed; however, those expressed in ensheathing cells are unknown. Here we show that olfactory ensheathing cells express voltage-dependent potassium currents compatible with inward rectifier (Kir) and delayed rectifier (KDR) channels. Together with gap junction coupling, these contribute to the heterogeneity of membrane properties observed in olfactory ensheathing cells. The relevance of K+ currents expressed by ensheathing cells is discussed in relation to plasticity of the olfactory nerve. PMID:25856239

  12. A voltage-dependent chloride channel fine-tunes photosynthesis in plants

    PubMed Central

    Herdean, Andrei; Teardo, Enrico; Nilsson, Anders K.; Pfeil, Bernard E.; Johansson, Oskar N.; Ünnep, Renáta; Nagy, Gergely; Zsiros, Ottó; Dana, Somnath; Solymosi, Katalin; Garab, Győző; Szabó, Ildikó; Spetea, Cornelia; Lundin, Björn

    2016-01-01

    In natural habitats, plants frequently experience rapid changes in the intensity of sunlight. To cope with these changes and maximize growth, plants adjust photosynthetic light utilization in electron transport and photoprotective mechanisms. This involves a proton motive force (PMF) across the thylakoid membrane, postulated to be affected by unknown anion (Cl−) channels. Here we report that a bestrophin-like protein from Arabidopsis thaliana functions as a voltage-dependent Cl− channel in electrophysiological experiments. AtVCCN1 localizes to the thylakoid membrane, and fine-tunes PMF by anion influx into the lumen during illumination, adjusting electron transport and the photoprotective mechanisms. The activity of AtVCCN1 accelerates the activation of photoprotective mechanisms on sudden shifts to high light. Our results reveal that AtVCCN1, a member of a conserved anion channel family, acts as an early component in the rapid adjustment of photosynthesis in variable light environments. PMID:27216227

  13. Variable, voltage-dependent, blocking effects of nitrendipine, verapamil, diltiazem, cinnarizine and cadmium on adrenomedullary secretion.

    PubMed Central

    López, M. G.; Moro, M. A.; Castillo, C. F.; Artalejo, C. R.; García, A. G.

    1989-01-01

    1. Catecholamine release from cat adrenal glands perfused at a high rate (4 ml min-1) at 37 degrees C with modified Krebs solutions lacking Ca and containing 1.2 mM K (hyperpolarizing solution) or 118 mM K (depolarizing solution) was triggered by 10-s pulses of Ca (0.5 mM) in the presence of 118 mM K. Hyperpolarized glands released 1280 +/- 135 ng per pulse and depolarized glands 831 +/- 98 ng per pulse (n = 29). 2. While the dihydropyridine Ca channel blocker nitrendipine inhibited secretion in hyperpolarized glands with an IC50 of 214 nM, in depolarizing conditions the drug was much more potent (IC50 = 0.99 nM). In contrast, the inorganic Ca channel blocker cadmium inhibited secretion with the same potency both in hyperpolarized or depolarized glands. 3. Cinnarizine, diltiazem and verapamil exhibited intermediate degrees of voltage-dependence in blocking secretion. The IC50 ratios between hyperpolarized and depolarized glands were 215, 36, 19, 8 and 0.76 respectively for nitrendipine, cinnarizine, diltiazem, verapamil and cadmium. Because the experimental design (strong depolarization in the absence of Ca) favours the highest opening probability of Ca channels, it seems that these drugs bind preferentially to their receptors when these channels are in their open state. 4. Variable voltage-dependent effects of the five Ca channel blockers on adrenomedullary catecholamine release suggests different sites and mechanisms of action on, or near L-type Ca channels in chromaffin cells. In addition, these findings might help to explain why these drugs exhibit tissue selectivity and why they act differently in normal polarized as compared to ischaemic depolarized cells. PMID:2720300

  14. Immunomodulation of voltage-dependent K+ channels in macrophages: molecular and biophysical consequences.

    PubMed

    Villalonga, Núria; David, Miren; Bielanska, Joanna; Vicente, Rubén; Comes, Núria; Valenzuela, Carmen; Felipe, Antonio

    2010-02-01

    Voltage-dependent potassium (K(v)) channels play a pivotal role in the modulation of macrophage physiology. Macrophages are professional antigen-presenting cells and produce inflammatory and immunoactive substances that modulate the immune response. Blockage of K(v) channels by specific antagonists decreases macrophage cytokine production and inhibits proliferation. Numerous pharmacological agents exert their effects on specific target cells by modifying the activity of their plasma membrane ion channels. Investigation of the mechanisms involved in the regulation of potassium ion conduction is, therefore, essential to the understanding of potassium channel functions in the immune response to infection and inflammation. Here, we demonstrate that the biophysical properties of voltage-dependent K(+) currents are modified upon activation or immunosuppression in macrophages. This regulation is in accordance with changes in the molecular characteristics of the heterotetrameric K(v)1.3/K(v)1.5 channels, which generate the main K(v) in macrophages. An increase in K(+) current amplitude in lipopolysaccharide-activated macrophages is characterized by a faster C-type inactivation, a greater percentage of cumulative inactivation, and a more effective margatoxin (MgTx) inhibition than control cells. These biophysical parameters are related to an increase in K(v)1.3 subunits in the K(v)1.3/K(v)1.5 hybrid channel. In contrast, dexamethasone decreased the C-type inactivation, the cumulative inactivation, and the sensitivity to MgTx concomitantly with a decrease in K(v)1.3 expression. Neither of these treatments apparently altered the expression of K(v)1.5. Our results demonstrate that the immunomodulation of macrophages triggers molecular and biophysical consequences in K(v)1.3/K(v)1.5 hybrid channels by altering the subunit stoichiometry.

  15. Myosin light chain kinase controls voltage-dependent calcium channels in vascular smooth muscle.

    PubMed

    Martinsen, A; Schakman, O; Yerna, X; Dessy, C; Morel, N

    2014-07-01

    The Ca(2+)-dependent kinase myosin light chain kinase (MLCK) is the activator of smooth muscle contraction. In addition, it has been reported to be involved in Ca(2+) channel regulation in cultured cells, and we previously showed that the MLCK inhibitor ML-7 decreases arginine vasopressin (AVP)-induced Ca(2+) influx in rat aorta. This study was designed to investigate whether MLCK is involved in Ca(2+) regulation in resistance artery smooth muscle cell, which plays a major role in the control of blood pressure. As ML compounds were shown to have off-target effects, MLCK was downregulated by transfection with a small interfering RNA targeting MLCK (MLCK-siRNA) in rat small resistance mesenteric artery (RMA) and in the rat embryonic aortic cell line A7r5. Noradrenaline-induced contraction and Ca(2+) signal were significantly depressed in MLCK-siRNA compared to scramble-siRNA-transfected RMA. Contraction and Ca(2+) signal induced by high KCl and voltage-activated Ca(2+) current were also significantly decreased in MLCK-siRNA-transfected RMA, suggesting that MLCK depletion modifies voltage-operated Ca(2+) channels. KCl- and AVP-induced Ca(2+) signals and voltage-activated Ca(2+) current were decreased in MLCK-depleted A7r5 cells. Eventually, real-time quantitative PCR analysis indicated that in A7r5, MLCK controlled mRNA expression of CaV1.2 (L-type) and CaV3.1 (T-type) voltage-dependent Ca(2+) channels. Our results suggest that MLCK controls the transcription of voltage-dependent Ca(2+) channels in vascular smooth muscle cells. PMID:24162233

  16. Voltage Dependence of Proton Pumping by Bacteriorhodopsin Mutants with Altered Lifetime of the M Intermediate

    PubMed Central

    Geibel, Sven; Lörinczi, Èva; Bamberg, Ernst; Friedrich, Thomas

    2013-01-01

    The light-driven proton pump bacteriorhodopsin (BR) from Halobacterium salinarum is tightly regulated by the [H+] gradient and transmembrane potential. BR exhibits optoelectric properties, since spectral changes during the photocycle are kinetically controlled by voltage, which predestines BR for optical storage or processing devices. BR mutants with prolonged lifetime of the blue-shifted M intermediate would be advantageous, but the optoelectric properties of such mutants are still elusive. Using expression in Xenopus oocytes and two-electrode voltage-clamping, we analyzed photocurrents of BR mutants with kinetically destabilized (F171C, F219L) or stabilized (D96N, D96G) M intermediate in response to green light (to probe H+ pumping) and blue laser flashes (to probe accumulation/decay of M). These mutants have divergent M lifetimes. As for BR-WT, this strictly correlates with the voltage dependence of H+ pumping. BR-F171C and BR-F219L showed photocurrents similar to BR-WT. Yet, BR-F171C showed a weaker voltage dependence of proton pumping. For both mutants, blue laser flashes applied during and after green-light illumination showed reduced M accumulation and shorter M lifetime. In contrast, BR-D96G and BR-D96N exhibited small photocurrents, with nonlinear current-voltage curves, which increased strongly in the presence of azide. Blue laser flashes showed heavy M accumulation and prolonged M lifetime, which accounts for the strongly reduced H+ pumping rate. Hyperpolarizing potentials augmented these effects. The combination of M-stabilizing and -destabilizing mutations in BR-D96G/F171C/F219L (BR-tri) shows that disruption of the primary proton donor Asp-96 is fatal for BR as a proton pump. Mechanistically, M destabilizing mutations cannot compensate for the disruption of Asp-96. Accordingly, BR-tri and BR-D96G photocurrents were similar. However, BR-tri showed negative blue laser flash-induced currents even without actinic green light, indicating that Schiff base

  17. Sperm morphology of salamandrids (Amphibia, Urodela): implications for phylogeny and fertilization biology.

    PubMed

    Selmi, M G; Brizzi, R; Bigliardi, E

    1997-12-01

    Mature spermatozoa belonging to four salamander species, Salamandrina terdigitata, Triturus alpestris, Triturus carnifex and Triturus vulgaris, have been investigated by electron microscopy. The sperm ultrastructure of these species was compared with that of previously examined urodeles (36 species and 20 genera) and with that of anurans and caecilians. Many phylogenetic considerations may be inferred as a consequence of comparative spermatology. Urodela appears to be a monophyletic order characterized by three sperm synapomorphies: the acrosomal barb, nuclear ridge and marginal filament. Cryptobranchoidea are confirmed to form a monophyletic suborder having two synapomorphic characters: absence of mitochondria in the tail, and cylindrical shape of the tail axial rod. Within the family Salamandridae, sperm morphology confirms the phylogenetic distance between Salamandrina and Triturus, as already pointed out on the basis of molecular and morphological characters. The very complex ultrastructure of spermatozoa confirms a previous opinion that internal fertilization is the ancestral condition of the Amphibia. PMID:18627832

  18. Involvement of voltage-dependent anion channel (VDAC) in dengue infection

    PubMed Central

    Jitobaom, Kunlakanya; Tongluan, Natthida; Smith, Duncan R.

    2016-01-01

    During infection, dengue virus (DENV) proteins interact with host cellular constituents promoting the remodeling of the cell to facilitate virus production. While a number of interacting proteins have been identified for DENV non-structural proteins, far fewer interacting partners have been identified for the DENV structural proteins. One protein that has been identified as a DENV E protein interacting protein is the cellular chaperone GRP78. GRP78 has been shown to have a number of cellular interacting partners including the voltage-dependent anion channel (VDAC). In this study we confirmed the interactions between GRP78 and DENV E protein and between GRP78 and VDAC. VDAC was shown to be re-localized during DENV infection, with no change in levels of protein expression. VDAC is predominantly located on the outer membrane of mitochondria and our result is consistent with movement of the mitochondria towards the ER during DENV infection. Down regulation of VDAC through siRNA significantly reduced DENV protein expression, as well as the percentage infection and output virus titer. Our results suggest that VDAC plays an important role in DENV infection. PMID:27779201

  19. Current state of theoretical and experimental studies of the voltage-dependent anion channel (VDAC).

    PubMed

    Noskov, Sergei Yu; Rostovtseva, Tatiana K; Chamberlin, Adam C; Teijido, Oscar; Jiang, Wei; Bezrukov, Sergey M

    2016-07-01

    Voltage-dependent anion channel (VDAC), the major channel of the mitochondrial outer membrane provides a controlled pathway for respiratory metabolites in and out of the mitochondria. In spite of the wealth of experimental data from structural, biochemical, and biophysical investigations, the exact mechanisms governing selective ion and metabolite transport, especially the role of titratable charged residues and interactions with soluble cytosolic proteins, remain hotly debated in the field. The computational advances hold a promise to provide a much sought-after solution to many of the scientific disputes around solute and ion transport through VDAC and hence, across the mitochondrial outer membrane. In this review, we examine how Molecular Dynamics, Free Energy, and Brownian Dynamics simulations of the large β-barrel channel, VDAC, advanced our understanding. We will provide a short overview of non-conventional techniques and also discuss examples of how the modeling excursions into VDAC biophysics prospectively aid experimental efforts. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov. PMID:26940625

  20. Regulation of Mitochondrial Function by Voltage Dependent Anion Channels in Ethanol Metabolism and the Warburg Effect

    PubMed Central

    Lemasters, John J.; Holmuhamedov, Ekhson L.; Czerny, Christoph; Zhong, Zhi; Maldonado, Eduardo N.

    2012-01-01

    Voltage dependent anion channels (VDAC) are highly conserved proteins that are responsible for permeability of the mitochondrial outer membrane to hydrophilic metabolites like ATP, ADP and respiratory substrates. Although previously assumed to remain open, VDAC closure is emerging as an important mechanism for regulation of global mitochondrial metabolism in apoptotic cells and also in cells that are not dying. During hepatic ethanol oxidation to acetaldehyde, VDAC closure suppresses exchange of mitochondrial metabolites, resulting in inhibition of ureagenesis. In vivo, VDAC closure after ethanol occurs coordinately with mitochondrial uncoupling. Since acetaldehyde passes through membranes independently of channels and transporters, VDAC closure and uncoupling together foster selective and more rapid oxidative metabolism of toxic acetaldehyde to nontoxic acetate by mitochondrial aldehyde dehydrogenase. In single reconstituted VDAC, tubulin decreases VDAC conductance, and in HepG2 hepatoma cells, free tubulin negatively modulates mitochondrial membrane potential, an effect enhanced by protein kinase A. Tubulin-dependent closure of VDAC in cancer cells contributes to suppression of mitochondrial metabolism and may underlie the Warburg phenomenon of aerobic glycolysis. PMID:22172804

  1. Stochastic diffusion model of multistep activation in a voltage-dependent K channel

    NASA Astrophysics Data System (ADS)

    Vaccaro, S. R.

    2010-04-01

    The energy barrier to the activated state for the S4 voltage sensor of a K channel is dependent on the electrostatic force between positively charged S4 residues and negatively charged groups on neighboring segments, the potential difference across the membrane, and the dielectric boundary force on the charged residues near the interface between the solvent and the low dielectric region of the membrane gating pore. The variation of the potential function with transverse displacement and rotation of the S4 sensor across the membrane may be derived from a solution of Poisson's equation for the electrostatic potential. By approximating the energy of an S4 sensor along a path between stationary states by a piecewise linear function of the transverse displacement, the dynamics of slow activation, in the millisecond range, may be described by the lowest frequency component of an analytical solution of interacting diffusion equations of Fokker-Planck type for resting and barrier regions. The solution of the Smoluchowski equations for an S4 sensor in an energy landscape with several barriers is in accord with an empirical master equation for multistep activation in a voltage-dependent K channel.

  2. RAS-RAF-MEK-dependent oxidative cell death involving voltage-dependent anion channels.

    PubMed

    Yagoda, Nicholas; von Rechenberg, Moritz; Zaganjor, Elma; Bauer, Andras J; Yang, Wan Seok; Fridman, Daniel J; Wolpaw, Adam J; Smukste, Inese; Peltier, John M; Boniface, J Jay; Smith, Richard; Lessnick, Stephen L; Sahasrabudhe, Sudhir; Stockwell, Brent R

    2007-06-14

    Therapeutics that discriminate between the genetic makeup of normal cells and tumour cells are valuable for treating and understanding cancer. Small molecules with oncogene-selective lethality may reveal novel functions of oncoproteins and enable the creation of more selective drugs. Here we describe the mechanism of action of the selective anti-tumour agent erastin, involving the RAS-RAF-MEK signalling pathway functioning in cell proliferation, differentiation and survival. Erastin exhibits greater lethality in human tumour cells harbouring mutations in the oncogenes HRAS, KRAS or BRAF. Using affinity purification and mass spectrometry, we discovered that erastin acts through mitochondrial voltage-dependent anion channels (VDACs)--a novel target for anti-cancer drugs. We show that erastin treatment of cells harbouring oncogenic RAS causes the appearance of oxidative species and subsequent death through an oxidative, non-apoptotic mechanism. RNA-interference-mediated knockdown of VDAC2 or VDAC3 caused resistance to erastin, implicating these two VDAC isoforms in the mechanism of action of erastin. Moreover, using purified mitochondria expressing a single VDAC isoform, we found that erastin alters the permeability of the outer mitochondrial membrane. Finally, using a radiolabelled analogue and a filter-binding assay, we show that erastin binds directly to VDAC2. These results demonstrate that ligands to VDAC proteins can induce non-apoptotic cell death selectively in some tumour cells harbouring activating mutations in the RAS-RAF-MEK pathway.

  3. Hippocampal glucocorticoid receptor activation enhances voltage-dependent Ca2+ conductances: relevance to brain aging.

    PubMed Central

    Kerr, D S; Campbell, L W; Thibault, O; Landfield, P W

    1992-01-01

    Glucocorticoids (GCs) activate several biochemical/molecular processes in the hippocampus through two receptor types. In addition, GCs influence cognitive behaviors and hippocampal neural activity and can also increase the rate of aging-dependent cell loss in the hippocampus. However, the ionic mechanisms through which GCs modulate hippocampal neuronal function are not well understood. We report here direct evidence that activation of cytosolic steroid receptors, specifically of the type II GC receptor, can enhance voltage-dependent Ca2+ conductances in brain neurons. Ca2+ current was assessed by current-clamp measures of Ca2+ action potentials and by sharp electrode voltage-clamp analyses of voltage-sensitive currents in cesium-, tetrodotoxin-, and tetraethylammonium-treated CA1 neurons in hippocampal slices. Both Ca2+ action potentials and voltage-activated Ca2+ currents (N- and L-like) were increased by 2-hr exposure to the synthetic GC receptor agonist, RU 28362. This effect of RU 28362 was blocked by coincubation with cycloheximide, indicating that the GC receptor-Ca2+ channel interaction depends on de novo protein synthesis. Dysregulated calcium homeostasis is also viewed as a candidate mechanism in brain aging. Thus, present results are consistent with the hypothesis that excessive GC-receptor activation and resultant increased Ca2+ influx may be two sequential phases of a brain-aging process that results initially in impairment of function and eventually in neuronal loss. PMID:1528857

  4. A calcium- and voltage-dependent cation channel in the tonoplast of Saccharomyces cerevisiae

    SciTech Connect

    Bertl, A.; Slayman, C.L. )

    1990-05-01

    Ion channels have been studied in the tonoplast of Saccharomyces cerevisiae by means of patch-recording techniques. The main type of channel seen thus far in excised membrane patches is a cation channel having an open-channel conductance of {approx}120 pS (in 100 mM KCl) and relative permeabilities of 1:1:0.1, for K{sup +}:Na{sup +}:Cl{sup {minus}}. Channel open probability is strongly voltage-dependent, being highest at large negative voltages (i.e., >70 mV, cytoplasm negative to the vacuole). Current-voltage (I-V) curves obtained by averaging individual channel currents over a long time (1-2 min) show marked rectification and agree well with steady-state I-V curves from whole-vacuole records. Channel opening is also strongly regulated by cytoplasmic Ca{sup ++}: openings are rare at or below 0.1 {mu}M Ca{sup ++}, but increase sigmoidally with Ca{sup ++} concentrations above 1 {mu}M, to reach a maximal open probability of {approx}0.5 at 2-5 mM free Ca{sup ++}.

  5. Charged residues distribution modulates selectivity of the open state of human isoforms of the voltage dependent anion-selective channel.

    PubMed

    Amodeo, Giuseppe Federico; Scorciapino, Mariano Andrea; Messina, Angela; De Pinto, Vito; Ceccarelli, Matteo

    2014-01-01

    Voltage Dependent Anion-selective Channels (VDACs) are pore-forming proteins located in the outer mitochondrial membrane. They are responsible for the access of ions and energetic metabolites into the inner membrane transport systems. Three VDAC isoforms exist in mammalian, but their specific role is unknown. In this work we have performed extensive (overall ∼5 µs) Molecular Dynamics (MD) simulations of the human VDAC isoforms to detect structural and conformational variations among them, possibly related to specific functional roles of these proteins. Secondary structure analysis of the N-terminal domain shows a high similarity among the three human isoforms of VDAC but with a different plasticity. In particular, the N-terminal domain of the hVDAC1 is characterized by a higher plasticity, with a ∼20% occurrence for the 'unstructured' conformation throughout the folded segment, while hVDAC2, containing a peculiar extension of 11 amino acids at the N-terminal end, presents an additional 310-helical folded portion comprising residues 10' to 3, adhering to the barrel wall. The N-terminal sequences of hVDAC isoforms are predicted to have a low flexibility, with possible consequences in the dynamics of the human VDACs. Clear differences were found between hVDAC1 and hVDAC3 against hVDAC2: a significantly modified dynamics with possible important consequence on the voltage-gating mechanism. Charge distribution inside and at the mouth of the pore is responsible for a different preferential localization of ions with opposite charge and provide a valuable rationale for hVDAC1 and hVDAC3 having a Cl-/K+ selectivity ratio of 1.8, whereas hVDAC2 of 1.4. Our conclusion is that hVDAC isoforms, despite sharing a similar scaffold, have modified working features and a biological work is now requested to give evidence to the described dissimilarities. PMID:25084457

  6. The Voltage-dependent Anion Channel 1 Mediates Amyloid β Toxicity and Represents a Potential Target for Alzheimer Disease Therapy.

    PubMed

    Smilansky, Angela; Dangoor, Liron; Nakdimon, Itay; Ben-Hail, Danya; Mizrachi, Dario; Shoshan-Barmatz, Varda

    2015-12-25

    The voltage-dependent anion channel 1 (VDAC1), found in the mitochondrial outer membrane, forms the main interface between mitochondrial and cellular metabolisms, mediates the passage of a variety of molecules across the mitochondrial outer membrane, and is central to mitochondria-mediated apoptosis. VDAC1 is overexpressed in post-mortem brains of Alzheimer disease (AD) patients. The development and progress of AD are associated with mitochondrial dysfunction resulting from the cytotoxic effects of accumulated amyloid β (Aβ). In this study we demonstrate the involvement of VDAC1 and a VDAC1 N-terminal peptide (VDAC1-N-Ter) in Aβ cell penetration and cell death induction. Aβ directly interacted with VDAC1 and VDAC1-N-Ter, as monitored by VDAC1 channel conductance, surface plasmon resonance, and microscale thermophoresis. Preincubated Aβ interacted with bilayer-reconstituted VDAC1 and increased its conductance ∼ 2-fold. Incubation of cells with Aβ resulted in mitochondria-mediated apoptotic cell death. However, the presence of non-cell-penetrating VDAC1-N-Ter peptide prevented Aβ cellular entry and Aβ-induced mitochondria-mediated apoptosis. Likewise, silencing VDAC1 expression by specific siRNA prevented Aβ entry into the cytosol as well as Aβ-induced toxicity. Finally, the mode of Aβ-mediated action involves detachment of mitochondria-bound hexokinase, induction of VDAC1 oligomerization, and cytochrome c release, a sequence of events leading to apoptosis. As such, we suggest that Aβ-mediated toxicity involves mitochondrial and plasma membrane VDAC1, leading to mitochondrial dysfunction and apoptosis induction. The VDAC1-N-Ter peptide targeting Aβ cytotoxicity is thus a potential new therapeutic strategy for AD treatment.

  7. Blockade of voltage-dependent sup 42 K efflux from rat brain synaptosome by minaprine and tetrahydroaminoacridine

    SciTech Connect

    Chaki, Shigeyuki; Muramatsu, Makoto; Otomo, Susumu )

    1991-01-01

    The effect of minaprine (3-(2-morpholinoethylamino)-4-methyl-6-phenylpyridazine) on the K{sup +} channels was studied by means of {sup 42}K efflux from rat brain synaptosomes, comparing the effects of 4-aminopyridine and 9-amino-1,2,3,4-tetrahydroacridine (THA). {sup 42}K efflux from rat brain synaptosomes was classified into five components: a resting component (R), a rapidly inactivating, voltage-dependent component (T), a slowly inactivating, voltage-dependent component (S) and a voltage-dependent, Ca{sup 2+}-dependent component which is divided into a fast phase (C{sub T}) and a slower phase (C{sub S}). 4-Aminopyridine selectively inhibited {sup 42}K efflux of component T. THA blocked both S and T components. The inhibitory effect of THA on the {sup 42}K efflux of component S was quite pronounced compared with that of component T. Minaprine inhibited the {sup 42}K efflux of components S and T but the inhibitory effect on component S was observed with a lower dose of minaprine than that needed for the effect on component T. Minaprine had no effect on the Ca{sup 2+}-dependent component while THA blocked component C{sub T}. {sup 42}K efflux of the resting component was not changed by minaprine, THA or 4-aminopyridine. These results suggest that minaprine blocks Ca{sup 2+} independent voltage-dependent K{sup +} channel is involved in the pharmacological actions of minaprine.

  8. Inactivation of N-type calcium current in chick sensory neurons: calcium and voltage dependence.

    PubMed

    Cox, D H; Dunlap, K

    1994-08-01

    We have studied the inactivation of high-voltage-activated (HVA), omega-conotoxin-sensitive, N-type Ca2+ current in embryonic chick dorsal root ganglion (DRG) neurons. Voltage steps from -80 to 0 mV produced inward Ca2+ currents that inactivated in a biphasic manner and were fit well with the sum of two exponentials (with time constants of approximately 100 ms and > 1 s). As reported previously, upon depolarization of the holding potential to -40 mV, N current amplitude was significantly reduced and the rapid phase of inactivation all but eliminated (Nowycky, M. C., A. P. Fox, and R. W. Tsien. 1985. Nature. 316:440-443; Fox, A. P., M. C. Nowycky, and R. W. Tsien. 1987a. Journal of Physiology. 394:149-172; Swandulla, D., and C. M. Armstrong. 1988. Journal of General Physiology. 92:197-218; Plummer, M. R., D. E. Logothetis, and P. Hess. 1989. Neuron. 2:1453-1463; Regan, L. J., D. W. Sah, and B. P. Bean. 1991. Neuron. 6:269-280; Cox, D. H., and K. Dunlap. 1992. Journal of Neuroscience. 12:906-914). Such kinetic properties might be explained by a model in which N channels inactivate by both fast and slow voltage-dependent processes. Alternatively, kinetic models of Ca-dependent inactivation suggest that the biphasic kinetics and holding-potential-dependence of N current inactivation could be due to a combination of Ca-dependent and slow voltage-dependent inactivation mechanisms. To distinguish between these possibilities we have performed several experiments to test for the presence of Ca-dependent inactivation. Three lines of evidence suggest that N channels inactivate in a Ca-dependent manner. (a) The total extent of inactivation increased 50%, and the ratio of rapid to slow inactivation increased approximately twofold when the concentration of the Ca2+ buffer, EGTA, in the patch pipette was reduced from 10 to 0.1 mM. (b) With low intracellular EGTA concentrations (0.1 mM), the ratio of rapid to slow inactivation was additionally increased when the extracellular Ca2

  9. Inactivation of N-type calcium current in chick sensory neurons: calcium and voltage dependence.

    PubMed

    Cox, D H; Dunlap, K

    1994-08-01

    We have studied the inactivation of high-voltage-activated (HVA), omega-conotoxin-sensitive, N-type Ca2+ current in embryonic chick dorsal root ganglion (DRG) neurons. Voltage steps from -80 to 0 mV produced inward Ca2+ currents that inactivated in a biphasic manner and were fit well with the sum of two exponentials (with time constants of approximately 100 ms and > 1 s). As reported previously, upon depolarization of the holding potential to -40 mV, N current amplitude was significantly reduced and the rapid phase of inactivation all but eliminated (Nowycky, M. C., A. P. Fox, and R. W. Tsien. 1985. Nature. 316:440-443; Fox, A. P., M. C. Nowycky, and R. W. Tsien. 1987a. Journal of Physiology. 394:149-172; Swandulla, D., and C. M. Armstrong. 1988. Journal of General Physiology. 92:197-218; Plummer, M. R., D. E. Logothetis, and P. Hess. 1989. Neuron. 2:1453-1463; Regan, L. J., D. W. Sah, and B. P. Bean. 1991. Neuron. 6:269-280; Cox, D. H., and K. Dunlap. 1992. Journal of Neuroscience. 12:906-914). Such kinetic properties might be explained by a model in which N channels inactivate by both fast and slow voltage-dependent processes. Alternatively, kinetic models of Ca-dependent inactivation suggest that the biphasic kinetics and holding-potential-dependence of N current inactivation could be due to a combination of Ca-dependent and slow voltage-dependent inactivation mechanisms. To distinguish between these possibilities we have performed several experiments to test for the presence of Ca-dependent inactivation. Three lines of evidence suggest that N channels inactivate in a Ca-dependent manner. (a) The total extent of inactivation increased 50%, and the ratio of rapid to slow inactivation increased approximately twofold when the concentration of the Ca2+ buffer, EGTA, in the patch pipette was reduced from 10 to 0.1 mM. (b) With low intracellular EGTA concentrations (0.1 mM), the ratio of rapid to slow inactivation was additionally increased when the extracellular Ca2

  10. Stoichiometry and voltage dependence of the sodium pump in voltage- clamped, internally dialyzed squid giant axon

    PubMed Central

    1989-01-01

    The stoichiometry and voltage dependence of the Na/K pump were studied in internally dialyzed, voltage-clamped squid giant axons by simultaneously measuring, at various membrane potentials, the changes in Na efflux (delta phi Na) and holding current (delta I) induced by dihydrodigitoxigenin (H2DTG). H2DTG stops the Na/K pump without directly affecting other current pathways: (a) it causes no delta I when the pump lacks Na, K, Mg, or ATP, and (b) ouabain causes no delta I or delta phi Na in the presence of saturating H2DTG. External K (Ko) activates Na efflux with Michaelis-Menten kinetics (Km = 0.45 +/- 0.06 mM [SEM]) in Na-free seawater (SW), but with sigmoid kinetics in approximately 400 mM Na SW (Hill coefficient = 1.53 +/- 0.08, K1/2 = 3.92 +/- 0.29 mM). H2DTG inhibits less strongly (Ki = 6.1 +/- 0.3 microM) in 1 or 10 mM K Na-free SW than in 10 mM K, 390 mM Na SW (1.8 +/- 0.2 microM). Dialysis with 5 mM each ATP, phosphoenolpyruvate, and phosphoarginine reduced Na/Na exchange to at most 2% of the H2DTG- sensitive Na efflux. H2DTG sensitive but nonpump current caused by periaxonal K accumulation upon stopping the pump, was minimized by the K channel blockers 3,4-diaminopyridine (1 mM), tetraethylammonium (approximately 200 mM), and phenylpropyltriethylammonium (20-25 mM) whose adequacy was tested by varying [K]o (0-10 mM) with H2DTG present. Two ancillary clamp circuits suppressed stray current from the axon ends. Current and flux measured from the center pool derive from the same membrane area since, over the voltage range -60 to +20 mV, tetrodotoxin-sensitive current and Na efflux into Na-free SW, under K- free conditions, were equal. The stoichiometry and voltage dependence of pump Na/K exchange were examined at near-saturating [ATP], [K]o and [Na]i in both Na-free and 390 mM Na SW. The H2DTG-sensitive F delta phi Na/delta I ratio (F is Faraday's constant) of paired measurements corrected for membrane area match, was 2.86 +/- 0.09 (n = 8) at 0 mV and 3

  11. Voltage-dependent Gating of Single Wild-Type and S4 Mutant KAT1 Inward Rectifier Potassium Channels

    PubMed Central

    Zei, Paul C.; Aldrich, Richard W.

    1998-01-01

    The voltage-dependent gating mechanism of KAT1 inward rectifier potassium channels was studied using single channel current recordings from Xenopus oocytes injected with KAT1 mRNA. The inward rectification properties of KAT1 result from an intrinsic gating mechanism in the KAT1 channel protein, not from pore block by an extrinsic cation species. KAT1 channels activate with hyperpolarizing potentials from −110 through −190 mV with a slow voltage-dependent time course. Transitions before first opening are voltage dependent and account for much of the voltage dependence of activation, while transitions after first opening are only slightly voltage dependent. Using burst analysis, transitions near the open state were analyzed in detail. A kinetic model with multiple closed states before first opening, a single open state, a single closed state after first opening, and a closed-state inactivation pathway accurately describes the single channel and macroscopic data. Two mutations neutralizing charged residues in the S4 region (R177Q and R176L) were introduced, and their effects on single channel gating properties were examined. Both mutations resulted in depolarizing shifts in the steady state conductance–voltage relationship, shortened first latencies to opening, decreased probability of terminating bursts, and increased burst durations. These effects on gating were well described by changes in the rate constants in the kinetic model describing KAT1 channel gating. All transitions before the open state were affected by the mutations, while the transitions after the open state were unaffected, implying that the S4 region contributes to the early steps in gating for KAT1 channels. PMID:9834140

  12. EXPRESS: Voltage-dependent sodium (NaV) channels in group IV sensory afferents.

    PubMed

    Ramachandra, Renuka; Elmslie, Keith S

    2016-01-01

    Patients with intermittent claudication suffer from both muscle pain and an exacerbated exercise pressor reflex. Excitability of the group III and group IV afferent fibers mediating these functions is controlled in part by voltage-dependent sodium (NaV) channels. We previously found tetrodotoxin-resistant NaV1.8 channels to be the primary type in muscle afferent somata. However, action potentials in group III and IV afferent axons are blocked by TTX, supporting a minimal role of NaV1.8 channels. To address these apparent differences in NaV channel expression between axon and soma, we used immunohistochemistry to identify the NaV channels expressed in group IV axons within the gastrocnemius muscle and the dorsal root ganglia sections. Positive labeling by an antibody against the neurofilament protein peripherin was used to identify group IV neurons and axons. We show that >67% of group IV fibers express NaV1.8, NaV1.6, or NaV1.7. Interestingly, expression of NaV1.8 channels in group IV somata was significantly higher than in the fibers, whereas there were no significant differences for either NaV1.6 or NaV1.7. When combined with previous work, our results suggest that NaV1.8 channels are expressed in most group IV axons, but that, under normal conditions, NaV1.6 and/or NaV1.7 play a more important role in action potential generation to signal muscle pain and the exercise pressor reflex. PMID:27385723

  13. Voltage-Dependent Anion Channel-1, a Possible Ligand of Plasminogen Kringle 5

    PubMed Central

    Liang, Yin-ku; Bian, Liu-jiao

    2016-01-01

    Kringle 5, the fifth fragment of plasminogen, is known to be important for inhibiting the proliferation and migration of vascular endothelial cell (VEC), while not having any effects on normal endothelial cells. Therefore, it may be a potential tumor therapy candidate. However, the ligand of the Kringle 5 in VEC has not yet been identified. In this study, the possible ligand of Kringle 5 in vitro was screened and validated using Ph.D.-7 phage display peptide library with molecular docking, along with surface plasma resonance (SPR). After four rounds of panning, the specific clones of Kringle 5 were confirmed using enzyme-linked immunosorbent assay (ELISA). The gene sequence analysis showed that they expressed the common amino sequence IGNSNTL. Then, using a NCBI BLAST, 103 matching sequences were found. Following the molecular docking evaluation and considering the acting function and pathway of the plasminogen Kringle 5 in the human body, the most promising candidate was determined to be voltage-dependent anion channel-1 (VDAC-1), which was able to bind to Kringle 5 at -822.65 J·mol-1 of the binding energy at the residues of Lys12, Thr19, Ser57, Thr188, Arg139, Asn214, Ser240 and Lys274. A strong dose-dependent interaction occurred between the VDAC-1 and Kringle 5 (binding constant 2.43 × 103 L·mol-1) in SPR observation. Therefore, this study proposed that VDAC-1 was a potential ligand of plasminogen Kringle 5, and also demonstrated that the screening and validation of protein ligand using phage display peptide library with the molecular docking, along with SPR, was a practicable application. PMID:27749918

  14. THE CRITICAL ROLE OF VOLTAGE-DEPENDENT CALCIUM CHANNEL IN AXONAL REPAIR FOLLOWING MECHANICAL TRAUMA

    PubMed Central

    Nehrt, Ashley; Rodgers, Richard; Shapiro, Scott; Borgens, Richard; Shi, Riyi

    2009-01-01

    Membrane disruption following mechanical injury likely plays a critical role in the pathology of spinal cord trauma. It is known that intracellular calcium is a key factor that is essential to membrane resealing. However, the differential role of calcium influx through the injury site and through voltage dependent calcium channels (VDCC) has not been examined in detail. Using a well established ex vivo guinea pig spinal cord white matter preparation, we have found that axonal membrane resealing was significantly inhibited following transection or compression in the presence of cadmiun, a non-specific calcium channel blocker, or nimodipine, a specific L-type calcium channel blocker. Membrane resealing was assessed by the changes of membrane potential and compound action potential (CAP), and exclusion of horseradish peroxidase 60 minutes following trauma. Furthermore, 1 μM BayK 8644, a VDCC agonist, significantly enhanced membrane resealing. Interestingly, this effect was completely abolished when the concentration of BayK 8644 was increased to 30 μM. These data suggest that VDCC play a critical role in membrane resealing. Further, there is likely an appropriate range of calcium influx through VDCC which ensures effective axonal membrane resealing. Since elevated intracellular calcium has also been linked to axonal deterioration, blockage of VDCC is proposed to be a clinical treatment for various injuries. The knowledge gained in this study will likely help us better understand the role of calcium in various CNS trauma, which is critical for designing new approaches or perhaps optimizing the effectiveness of existing methods in the treatment of CNS trauma. PMID:17448606

  15. Wnt signalling suppresses voltage-dependent Na⁺ channel expression in postnatal rat cardiomyocytes.

    PubMed

    Liang, Wenbin; Cho, Hee Cheol; Marbán, Eduardo

    2015-03-01

    Wnt signalling plays crucial roles in heart development, but is normally suppressed postnatally. In arrhythmogenic conditions, such as cardiac hypertrophy and heart failure, Wnt signalling is reactivated. To explore the potential role of Wnt signalling in arrhythmogenic electrical remodelling, we examined voltage-dependent ion channels in cardiomyocytes. Treatment of neonatal rat ventricular myocytes with either recombinant Wnt3a protein or CHIR-99021 (CHIR, a glycogen synthase kinase-3β inhibitor) caused a dose-dependent increase in Wnt target gene expression (Axin2 and Lef1), indicating activation of the Wnt/β-catenin pathway. Cardiac Na(+) current (INa) density was reduced by Wnt3a (-20 ± 4 vs. control -59 ± 7 pA pF(-1) , at -30 mV) or CHIR (-22 ± 5 pA pF(-1) ), without changes in steady-state activation, inactivation or repriming kinetics. Wnt3a and CHIR also produced dose-dependent reductions in the mRNA level of Scn5a (the cardiac Na(+) channel α subunit gene), as well as a 56% reduction (by Wnt3a) in the Nav 1.5 protein level. Consistent with INa reduction, action potentials in Wnt3a-treated neonatal rat ventricular myocytes had a lower upstroke amplitude (91 ± 3 vs. control 137 ± 2 mV) and decreased maximum upstroke velocity (70 ± 10 vs. control 163 ± 15 V s(-1)). In contrast, inward rectifier K(+) current and L-type Ca(2+) channels were not affected by Wnt3a treatment. Taken together, our data indicate that the Wnt/β-catenin pathway suppresses INa in postnatal cardiomyocytes and may contribute to ion channel remodelling in heart disease.

  16. Voltage-dependent Gating of the Cystic Fibrosis Transmembrane Conductance Regulator Cl− Channel

    PubMed Central

    Cai, Zhiwei; Scott-Ward, Toby S.; Sheppard, David N.

    2003-01-01

    When excised inside-out membrane patches are bathed in symmetrical Cl−-rich solutions, the current-voltage (I-V) relationship of macroscopic cystic fibrosis transmembrane conductance regulator (CFTR) Cl− currents inwardly rectifies at large positive voltages. To investigate the mechanism of inward rectification, we studied CFTR Cl− channels in excised inside-out membrane patches from cells expressing wild-type human and murine CFTR using voltage-ramp and -step protocols. Using a voltage-ramp protocol, the magnitude of human CFTR Cl− current at +100 mV was 74 ± 2% (n = 10) of that at −100 mV. This rectification of macroscopic CFTR Cl− current was reproduced in full by ensemble currents generated by averaging single-channel currents elicited by an identical voltage-ramp protocol. However, using a voltage-step protocol the single-channel current amplitude (i) of human CFTR at +100 mV was 88 ± 2% (n = 10) of that at −100 mV. Based on these data, we hypothesized that voltage might alter the gating behavior of human CFTR. Using linear three-state kinetic schemes, we demonstrated that voltage has marked effects on channel gating. Membrane depolarization decreased both the duration of bursts and the interburst interval, but increased the duration of gaps within bursts. However, because the voltage dependencies of the different rate constants were in opposite directions, voltage was without large effect on the open probability (Po) of human CFTR. In contrast, the Po of murine CFTR was decreased markedly at positive voltages, suggesting that the rectification of murine CFTR is stronger than that of human CFTR. We conclude that inward rectification of CFTR is caused by a reduction in i and changes in gating kinetics. We suggest that inward rectification is an intrinsic property of the CFTR Cl− channel and not the result of pore block. PMID:14581585

  17. Ginger lowers blood pressure through blockade of voltage-dependent calcium channels.

    PubMed

    Ghayur, Muhammad Nabeel; Gilani, Anwarul Hassan

    2005-01-01

    Ginger (Zingiber officinale Roscoe), a well-known spice plant, has been used traditionally in a wide variety of ailments including hypertension. We report here the cardiovascular effects of ginger under controlled experimental conditions. The crude extract of ginger (Zo.Cr) induced a dose-dependent (0.3-3 mg/kg) fall in the arterial blood pressure of anesthetized rats. In guinea pig paired atria, Zo.Cr exhibited a cardiodepressant activity on the rate and force of spontaneous contractions. In rabbit thoracic aorta preparation, Zo.Cr relaxed the phenylephrine-induced vascular contraction at a dose 10 times higher than that required against K (80 mM)-induced contraction. Ca2+ channel-blocking (CCB) activity was confirmed when Zo.Cr shifted the Ca2+ dose-response curves to the right similar to the effect of verapamil. It also inhibited the phenylephrine (1 microM) control peaks in normal-Ca2+ and Ca2+-free solution, indicating that it acts at both the membrane-bound and the intracellular Ca2+ channels. When tested in endothelium-intact rat aorta, it again relaxed the K-induced contraction at a dose 14 times less than that required for relaxing the PE-induced contraction. The vasodilator effect of Zo.Cr was endothelium-independent because it was not blocked by L-NAME (0.1 mM) or atropine (1 microM) and also was reproduced in the endothelium-denuded preparations at the same dose range. These data indicate that the blood pressure-lowering effect of ginger is mediated through blockade of voltage-dependent calcium channels. PMID:15613983

  18. Voltage-dependent gating and gating charge measurements in the Kv1.2 potassium channel

    PubMed Central

    Ishida, Itzel G.; Rangel-Yescas, Gisela E.; Carrasco-Zanini, Julia

    2015-01-01

    Much has been learned about the voltage sensors of ion channels since the x-ray structure of the mammalian voltage-gated potassium channel Kv1.2 was published in 2005. High resolution structural data of a Kv channel enabled the structural interpretation of numerous electrophysiological findings collected in various ion channels, most notably Shaker, and permitted the development of meticulous computational simulations of the activation mechanism. The fundamental premise for the structural interpretation of functional measurements from Shaker is that this channel and Kv1.2 have the same characteristics, such that correlation of data from both channels would be a trivial task. We tested these assumptions by measuring Kv1.2 voltage-dependent gating and charge per channel. We found that the Kv1.2 gating charge is near 10 elementary charges (eo), ∼25% less than the well-established 13–14 eo in Shaker. Next, we neutralized positive residues in the Kv1.2 S4 transmembrane segment to investigate the cause of the reduction of the gating charge and found that, whereas replacing R1 with glutamine decreased voltage sensitivity to ∼50% of the wild-type channel value, mutation of the subsequent arginines had a much smaller effect. These data are in marked contrast to the effects of charge neutralization in Shaker, where removal of the first four basic residues reduces the gating charge by roughly the same amount. In light of these differences, we propose that the voltage-sensing domains (VSDs) of Kv1.2 and Shaker might undergo the same physical movement, but the septum that separates the aqueous crevices in the VSD of Kv1.2 might be thicker than Shaker’s, accounting for the smaller Kv1.2 gating charge. PMID:25779871

  19. Lavender oil-potent anxiolytic properties via modulating voltage dependent calcium channels.

    PubMed

    Schuwald, Anita M; Nöldner, Michael; Wilmes, Thomas; Klugbauer, Norbert; Leuner, Kristina; Müller, Walter E

    2013-01-01

    Recent clinical data support the clinical use of oral lavender oil in patients suffering from subsyndromal anxiety. We identified the molecular mechanism of action that will alter the perception of lavender oil as a nonspecific ingredient of aromatherapy to a potent anxiolytic inhibiting voltage dependent calcium channels (VOCCs) as highly selective drug target. In contrast to previous publications where exorbitant high concentrations were used, the effects of lavender oil in behavioral, biochemical, and electrophysiological experiments were investigated in physiological concentrations in the nanomolar range, which correlate to a single dosage of 80 mg/d in humans that was used in clinical trials. We show for the first time that lavender oil bears some similarities with the established anxiolytic pregabalin. Lavender oil inhibits VOCCs in synaptosomes, primary hippocampal neurons and stably overexpressing cell lines in the same range such as pregabalin. Interestingly, Silexan does not primarily bind to P/Q type calcium channels such as pregabalin and does not interact with the binding site of pregabalin, the α2δ subunit of VOCCs. Lavender oil reduces non-selectively the calcium influx through several different types of VOCCs such as the N-type, P/Q-type and T-type VOCCs. In the hippocampus, one brain region important for anxiety disorders, we show that inhibition by lavender oil is mainly mediated via N-type and P/Q-type VOCCs. Taken together, we provide a pharmacological and molecular rationale for the clinical use of the oral application of lavender oil in patients suffering from anxiety.

  20. Tubulin binding blocks mitochondrial voltage-dependent anion channel and regulates respiration.

    PubMed

    Rostovtseva, Tatiana K; Sheldon, Kely L; Hassanzadeh, Elnaz; Monge, Claire; Saks, Valdur; Bezrukov, Sergey M; Sackett, Dan L

    2008-12-01

    Regulation of mitochondrial outer membrane (MOM) permeability has dual importance: in normal metabolite and energy exchange between mitochondria and cytoplasm and thus in control of respiration, and in apoptosis by release of apoptogenic factors into the cytosol. However, the mechanism of this regulation, dependent on the voltage-dependent anion channel (VDAC), the major channel of MOM, remains controversial. A long-standing puzzle is that in permeabilized cells, adenine nucleotide translocase (ANT) is less accessible to cytosolic ADP than in isolated mitochondria. We solve this puzzle by finding a missing player in the regulation of MOM permeability: the cytoskeletal protein tubulin. We show that nanomolar concentrations of dimeric tubulin induce voltage-sensitive reversible closure of VDAC reconstituted into planar phospholipid membranes. Tubulin strikingly increases VDAC voltage sensitivity and at physiological salt conditions could induce VDAC closure at <10 mV transmembrane potentials. Experiments with isolated mitochondria confirm these findings. Tubulin added to isolated mitochondria decreases ADP availability to ANT, partially restoring the low MOM permeability (high apparent K(m) for ADP) found in permeabilized cells. Our findings suggest a previously unknown mechanism of regulation of mitochondrial energetics, governed by VDAC and tubulin at the mitochondria-cytosol interface. This tubulin-VDAC interaction requires tubulin anionic C-terminal tail (CTT) peptides. The significance of this interaction may be reflected in the evolutionary conservation of length and anionic charge in CTT throughout eukaryotes, despite wide changes in the exact sequence. Additionally, tubulins that have lost significant length or anionic character are only found in cells that do not have mitochondria. PMID:19033201

  1. Voltage-dependent sodium (NaV) channels in group IV sensory afferents

    PubMed Central

    Elmslie, Keith S

    2016-01-01

    Patients with intermittent claudication suffer from both muscle pain and an exacerbated exercise pressor reflex. Excitability of the group III and group IV afferent fibers mediating these functions is controlled in part by voltage-dependent sodium (NaV) channels. We previously found tetrodotoxin-resistant NaV1.8 channels to be the primary type in muscle afferent somata. However, action potentials in group III and IV afferent axons are blocked by TTX, supporting a minimal role of NaV1.8 channels. To address these apparent differences in NaV channel expression between axon and soma, we used immunohistochemistry to identify the NaV channels expressed in group IV axons within the gastrocnemius muscle and the dorsal root ganglia sections. Positive labeling by an antibody against the neurofilament protein peripherin was used to identify group IV neurons and axons. We show that >67% of group IV fibers express NaV1.8, NaV1.6, or NaV1.7. Interestingly, expression of NaV1.8 channels in group IV somata was significantly higher than in the fibers, whereas there were no significant differences for either NaV1.6 or NaV1.7. When combined with previous work, our results suggest that NaV1.8 channels are expressed in most group IV axons, but that, under normal conditions, NaV1.6 and/or NaV1.7 play a more important role in action potential generation to signal muscle pain and the exercise pressor reflex. PMID:27385723

  2. Voltage dependence of Na/K pump current in Xenopus oocytes.

    PubMed

    Rakowski, R F; Paxson, C L

    1988-12-01

    mV, it is not necessary to postulate the existence of more than one voltage-dependent step in the reaction cycle of the forward-going Na/K pump.

  3. Heparin/heparan sulfates bind to and modulate neuronal L-type (Cav1.2) voltage-dependent Ca(2+) channels.

    PubMed

    Garau, Gianpiero; Magotti, Paola; Heine, Martin; Korotchenko, Svetlana; Lievens, Patricia Marie-Jeanne; Berezin, Vladimir; Dityatev, Alexander

    2015-12-01

    Our previous studies revealed that L-type voltage-dependent Ca(2+) channels (Cav1.2 L-VDCCs) are modulated by the neural extracellular matrix backbone, polyanionic glycan hyaluronic acid. Here we used isothermal titration calorimetry and screened a set of peptides derived from the extracellular domains of Cav1.2α1 to identify putative binding sites between the channel and hyaluronic acid or another class of polyanionic glycans, such as heparin/heparan sulfates. None of the tested peptides showed detectable interaction with hyaluronic acid, but two peptides derived from the first pore-forming domain of Cav1.2α1 subunit bound to heparin. At 25 °C the binding of the peptide P7 (MGKMHKTCYN) was at ~50 μM, and that of the peptide P8 (GHGRQCQNGTVCKPGWDGPKHG) was at ~21 μM. The Cav1.2α1 first pore forming segment that contained both peptides maintained a high affinity for heparin (~23 μM), integrating their enthalpic and entropic binding contributions. Interaction between heparin and recombinant as well as native full-length neuronal Cav1.2α1 channels was confirmed using the heparin-agarose pull down assay. Whole cell patch clamp recordings in HEK293 cells transfected with neuronal Cav1.2 channels revealed that enzymatic digestion of highly sulfated heparan sulfates with heparinase 1 affects neither voltage-dependence of channel activation nor the level of steady state inactivation, but did speed up channel inactivation. Treatment of hippocampal cultures with heparinase 1 reduced the firing rate and led to appearance of long-lasting bursts in the same manner as treatment with the inhibitor of L-VDCC diltiazem. Thus, heparan sulfate proteoglycans may bind to and regulate L-VDCC inactivation and network activity.

  4. A calcium- and voltage-dependent chloride current in developing chick skeletal muscle.

    PubMed Central

    Hume, R I; Thomas, S A

    1989-01-01

    1. Depolarization of embryonic chick myotubes from negative potentials elicits a rapid spike followed by a long-duration after-potential. The ionic basis of the long-duration after-potential was examined by making intracellular recordings from cultured myotubes, and by making whole-cell patch-clamp recordings from myoblasts and myoballs. 2. The peak potential of the long-duration after-potential varied with the chloride gradient, suggesting that a conductance increase to chloride is involved in generating the after-potential. However, a calcium current was also implicated, since lowering the extracellular calcium or replacing extracellular calcium with cobalt abolished the after-potential. 3. When extracellular calcium was replaced with strontium or barium, short-duration spikes similar to calcium spikes were observed, but only strontium was able to support activation of long-duration after-potentials. Intracellular injection of calcium or strontium into myotubes bathed in calcium-free extracellular solutions restored the ability of depolarization to evoke an after-potential. Intracellular injection of magnesium, barium, nickel or cobalt did not restore this ability. These experiments strongly suggested that the long-duration after-potential was due to a calcium- and voltage-activated chloride current. 4. Whole-cell voltage-clamp recordings from myoballs and myoblasts showed that a large chloride conductance could be activated by depolarization when the internal free calcium concentration was buffered at levels greater than 10(-7) M. At 2.5 x 10(-7) M-calcium, the voltage dependence of activation was steepest in the range of -30 to -20 mV and the activation kinetics varied with the membrane potential. The time to half-maximal activation ranged from 0.1 s at positive potentials to greater than 1 s at more negative potentials. The time constant for deactivation was approximately 1 s at -50 mV. No inactivation was observed. 5. The selectivity of the chloride current

  5. Phosphoinositide 5- and 3-phosphatase activities of a voltage-sensing phosphatase in living cells show identical voltage dependence.

    PubMed

    Keum, Dongil; Kruse, Martin; Kim, Dong-Il; Hille, Bertil; Suh, Byung-Chang

    2016-06-28

    Voltage-sensing phosphatases (VSPs) are homologs of phosphatase and tensin homolog (PTEN), a phosphatidylinositol 3,4-bisphosphate [PI(3,4)P2] and phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] 3-phosphatase. However, VSPs have a wider range of substrates, cleaving 3-phosphate from PI(3,4)P2 and probably PI(3,4,5)P3 as well as 5-phosphate from phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] and PI(3,4,5)P3 in response to membrane depolarization. Recent proposals say these reactions have differing voltage dependence. Using Förster resonance energy transfer probes specific for different PIs in living cells with zebrafish VSP, we quantitate both voltage-dependent 5- and 3-phosphatase subreactions against endogenous substrates. These activities become apparent with different voltage thresholds, voltage sensitivities, and catalytic rates. As an analytical tool, we refine a kinetic model that includes the endogenous pools of phosphoinositides, endogenous phosphatase and kinase reactions connecting them, and four exogenous voltage-dependent 5- and 3-phosphatase subreactions of VSP. We show that apparent voltage threshold differences for seeing effects of the 5- and 3-phosphatase activities in cells are not due to different intrinsic voltage dependence of these reactions. Rather, the reactions have a common voltage dependence, and apparent differences arise only because each VSP subreaction has a different absolute catalytic rate that begins to surpass the respective endogenous enzyme activities at different voltages. For zebrafish VSP, our modeling revealed that 3-phosphatase activity against PI(3,4,5)P3 is 55-fold slower than 5-phosphatase activity against PI(4,5)P2; thus, PI(4,5)P2 generated more slowly from dephosphorylating PI(3,4,5)P3 might never accumulate. When 5-phosphatase activity was counteracted by coexpression of a phosphatidylinositol 4-phosphate 5-kinase, there was accumulation of PI(4,5)P2 in parallel to PI(3,4,5)P3 dephosphorylation

  6. “Slow” Voltage-Dependent Inactivation of CaV2.2 Calcium Channels Is Modulated by the PKC Activator Phorbol 12-Myristate 13-Acetate (PMA)

    PubMed Central

    Zhu, Lei; McDavid, Sarah; Currie, Kevin P. M.

    2015-01-01

    CaV2.2 (N-type) voltage-gated calcium channels (Ca2+ channels) play key roles in neurons and neuroendocrine cells including the control of cellular excitability, neurotransmitter / hormone secretion, and gene expression. Calcium entry is precisely controlled by channel gating properties including multiple forms of inactivation. “Fast” voltage-dependent inactivation is relatively well-characterized and occurs over the tens-to- hundreds of milliseconds timeframe. Superimposed on this is the molecularly distinct, but poorly understood process of “slow” voltage-dependent inactivation, which develops / recovers over seconds-to-minutes. Protein kinases can modulate “slow” inactivation of sodium channels, but little is known about if/how second messengers control “slow” inactivation of Ca2+ channels. We investigated this using recombinant CaV2.2 channels expressed in HEK293 cells and native CaV2 channels endogenously expressed in adrenal chromaffin cells. The PKC activator phorbol 12-myristate 13-acetate (PMA) dramatically prolonged recovery from “slow” inactivation, but an inactive control (4α-PMA) had no effect. This effect of PMA was prevented by calphostin C, which targets the C1-domain on PKC, but only partially reduced by inhibitors that target the catalytic domain of PKC. The subtype of the channel β-subunit altered the kinetics of inactivation but not the magnitude of slowing produced by PMA. Intracellular GDP-β-S reduced the effect of PMA suggesting a role for G proteins in modulating “slow” inactivation. We postulate that the kinetics of recovery from “slow” inactivation could provide a molecular memory of recent cellular activity and help control CaV2 channel availability, electrical excitability, and neurotransmission in the seconds-to-minutes timeframe. PMID:26222492

  7. Estimating the voltage-dependent free energy change of ion channels using the median voltage for activation.

    PubMed

    Chowdhury, Sandipan; Chanda, Baron

    2012-01-01

    Voltage-gated ion channels are crucial for electrical activity and chemical signaling in a variety of cell types. Structure-activity studies involving electrophysiological characterization of mutants are widely used and allow us to quickly realize the energetic effects of a mutation by measuring macroscopic currents and fitting the observed voltage dependence of conductance to a Boltzmann equation. However, such an approach is somewhat limiting, principally because of the inherent assumption that the channel activation is a two-state process. In this analysis, we show that the area delineated by the gating charge displacement curve and its ordinate axis is related to the free energy of activation of a voltage-gated ion channel. We derive a parameter, the median voltage of charge transfer (V(m)), which is proportional to this area, and prove that the chemical component of free energy change of a system can be obtained from the knowledge of V(m) and the maximum number of charges transferred. Our method is not constrained by the number or connectivity of intermediate states and is applicable to instances in which the observed responses show a multiphasic behavior. We consider various models of ion channel gating with voltage-dependent steps, latent charge movement, inactivation, etc. and discuss the applicability of this approach in each case. Notably, our method estimates a net free energy change of approximately -14 kcal/mol associated with the full-scale activation of the Shaker potassium channel, in contrast to -2 to -3 kcal/mol estimated from a single Boltzmann fit. Our estimate of the net free energy change in the system is consistent with those derived from detailed kinetic models (Zagotta et al. 1994. J. Gen. Physiol. doi:10.1085/jgp.103.2.321). The median voltage method can reliably quantify the magnitude of free energy change associated with activation of a voltage-dependent system from macroscopic equilibrium measurements. This will be particularly useful

  8. Effect of angiotensin II-induced arterial hypertension on the voltage-dependent contractions of mouse arteries.

    PubMed

    Fransen, Paul; Van Hove, Cor E; Leloup, Arthur J A; Schrijvers, Dorien M; De Meyer, Guido R Y; De Keulenaer, Gilles W

    2016-02-01

    Arterial hypertension (AHT) affects the voltage dependency of L-type Ca(2+) channels in cardiomyocytes. We analyzed the effect of angiotensin II (AngII)-induced AHT on L-type Ca(2+) channel-mediated isometric contractions in conduit arteries. AHT was induced in C57Bl6 mice with AngII-filled osmotic mini-pumps (4 weeks). Normotensive mice treated with saline-filled osmotic mini-pumps were used for comparison. Voltage-dependent contractions mediated by L-type Ca(2+) channels were studied in vaso-reactive studies in vitro in isolated aortic and femoral arteries by using extracellular K(+) concentration-response (KDR) experiments. In aortic segments, AngII-induced AHT significantly sensitized isometric contractions induced by elevated extracellular K(+) and depolarization. This sensitization was partly prevented by normalizing blood pressure with hydralazine, suggesting that it was caused by AHT rather than by direct AngII effects on aortic smooth muscle cells. The EC50 for extracellular K(+) obtained in vitro correlated significantly with the rise in arterial blood pressure induced by AngII in vivo. The AHT-induced sensitization persisted when aortic segments were exposed to levcromakalim or to inhibitors of basal nitric oxide release. Consistent with these observations, AngII-treatment also sensitized the vaso-relaxing effects of the L-type Ca(2+) channel blocker diltiazem during K(+)-induced contractions. Unlike aorta, AngII-treatment desensitized the isometric contractions to depolarization in femoral arteries pointing to vascular bed specific responses of arteries to hypertension. AHT affects the voltage-dependent L-type Ca(2+) channel-mediated contraction of conduit arteries. This effect may contribute to the decreased vascular compliance in AHT and explain the efficacy of Ca(2+) channel blockers to reduce vascular stiffness and central blood pressure in AHT.

  9. Voltage-dependent conductance changes in the store-operated Ca2+ current ICRAC in rat basophilic leukaemia cells

    PubMed Central

    Bakowski, Daniel; Parekh, Anant B

    2000-01-01

    Tight-seal whole-cell patch-clamp experiments were carried out in order to investigate the effects of different holding potentials on the rate of development and amplitude of the Ca2+ release-activated Ca2+ current ICRAC in rat basophilic leukaemia (RBL-1) cells. ICRAC was monitored at −80 mV from fast voltage ramps, spanning 200 mV in 50 ms. At hyperpolarised potentials, the macroscopic CRAC conductance was lower than that seen at depolarised potentials. The conductance increased almost 5-fold over the voltage range −60 to +40 mV and was seen when the stores were depleted either by the combination of IP3 and thapsigargin in high Ca2+ buffer, or passively with 10 mm EGTA or BAPTA. The voltage-dependent conductance of the CRAC channels could not be fully accounted for by Ca2+-dependent fast inactivation, nor by other slower inhibitory mechanisms. It also did not seem to involve intracellular Mg2+ or the polycations spermine and spermidine. Voltage step relaxation experiments revealed that the voltage-dependent conductance changes developed and reversed slowly, with a time constant of several seconds at −60 mV. In the presence of physiological levels of intracellular Ca2+ buffers, ICRAC was barely detectable when cells were clamped at −60 mV and dialysed with IP3 and thapsigargin, but at 0 mV the current in low Ca2+ buffer was as large as that seen in high Ca2+ buffer. Our results suggest that CRAC channels exhibit slow voltage-dependent conductance changes which can triple the current amplitude over the physiological range of voltages normally encountered by these cells. The role of this conductance change and possible underlying mechanisms are discussed. PMID:11101641

  10. Faster voltage-dependent activation of Na+ channels in growth cones versus somata of neuroblastoma N1E-115 cells.

    PubMed Central

    Zhang, J; Loew, L M; Davidson, R M

    1996-01-01

    Kinetics of voltage-gated ionic channels fundamentally reflect the response of the channels to local electric fields. In this report cell-attached patch-clamp studies reveal that the voltage-dependent activation rate of sodium channels residing in the growth cone membrane differs from that of soma sodium channels in differentiating N1E-115 neuroblastoma cells. Because other electrophysiological properties of these channels do not differ, this finding may be a reflection of the difference in intramembrane electric field in these two regions of the cell. This represents a new mechanism for channels to attain a range of activities both within and between cells. PMID:8913589

  11. Inhibition of the voltage-dependent chloride channel of Torpedo electric organ by diisopropylfluorophosphate and its reversal by oximes

    SciTech Connect

    Abalis, I.M.; Chiang, P.K.; Wirtz, R.A.; Andre, R.G.

    1986-05-01

    Diisopropylfluorophosphate (DFP), a potent organophosphate inhibitor of cholinesterases, was found to inhibit the specific binding of (/sup 35/S)t-butylbicyclophosphorothionate (TBPS), specific chloride channels ligand, to the electric organ membranes of Torpedo, with a Ki of 21 +/- 3 ..mu..M. The binding sites of (/sup 35/S)TBPS in the Torpedo membranes were found not to be GABA receptors or nicotinic acetylcholine receptors as previously described. Interestingly, a stimulation of the binding of (/sup 35/S)TBPS was observed in the presence of atropine and three oximes, monopyridinium oxime 2-PAM, bispyridinium bis-oxime TMB-4 and H-oxime HI-6. The maximal stimulation was 300-500% of control, after which, the stimulation was reversed at higher concentrations. The three oximes protected by more than 95% the inhibition by 1 mM DFP of the binding of (/sup 35/S)TBPS to the voltage-dependent chloride channel. However, atropine protected only 20% of the inhibited channel. These results, thus, suggest that the protection against the toxic effects of DFP or other anticholinesterase agents by the tested oximes may not be solely a result of the reactivation of cholinesterases but also the protection of the voltage-dependent chloride channel.

  12. Multiple types of voltage-dependent Ca2+-activated K+ channels of large conductance in rat brain synaptosomal membranes.

    PubMed Central

    Farley, J.; Rudy, B.

    1988-01-01

    K+-selective ion channels from a mammalian brain synaptosomal membrane preparation were inserted into planar phospholipid bilayers on the tips of patch-clamp pipettes, and single-channel currents were measured. Multiple distinct classes of K+ channels were observed. We have characterized and described the properties of several types of voltage-dependent, Ca2+-activated K+ channels of large single-channel conductance (greater than 50 pS in symmetrical KCl solutions). One class of channels (Type I) has a 200-250-pS single-channel conductance. It is activated by internal calcium concentrations greater than 10(-7) M, and its probability of opening is increased by membrane depolarization. This channel is blocked by 1-3 mM internal concentrations of tetraethylammonium (TEA). These channels are similar to the BK channel described in a variety of tissues. A second novel group of voltage-dependent, Ca2+-activated K+ channels was also studied. These channels were more sensitive to internal calcium, but less sensitive to voltage than the large (Type I) channel. These channels were minimally affected by internal TEA concentrations of 10 mM, but were blocked by a 50 mM concentration. In this class of channels we found a wide range of relatively large unitary channel conductances (65-140 pS). Within this group we have characterized two types (75-80 pS and 120-125 pS) that also differ in gating kinetics. The various types of voltage-dependent, Ca2+-activated K+ channels described here were blocked by charybdotoxin added to the external side of the channel. The activity of these channels was increased by exposure to nanomolar concentrations of the catalytic subunit of cAMP-dependent protein kinase. These results indicate that voltage-dependent, charybdotoxin-sensitive Ca2+-activated K+ channels comprise a class of related, but distinguishable channel types. Although the Ca2+-activated (Type I and II) K+ channels can be distinguished by their single-channel properties, both could

  13. Voltage-dependent calcium signaling in rat cerebellar unipolar brush cells.

    PubMed

    Birnstiel, S; Slater, N T; McCrimmon, D R; Mugnaini, E; Hartell, N A

    2009-09-01

    Unipolar brush cells (UBCs) are a class of excitatory interneuron found in the granule cell layer of the vestibulocerebellum. Mossy fibers form excitatory inputs on to the paint brush shaped dendrioles in the form of giant, glutamatergic synapses, activation of which results in prolonged bursts of action potentials in the postsynaptic UBC. The axons of UBCs themselves form mossy fiber contacts with other UBCs and granule cells, forming an excitatory, intrinsic cerebellar network that has the capacity to synchronize and amplify mossy fiber inputs to potentially large populations of granule cells. In this paper, we demonstrate that UBCs in rat cerebellar slices express low voltage activated (LVA) fast-inactivating and high voltage activated (HVA) slowly inactivating calcium channels. LVA calcium currents are mediated by T-type calcium channels and they are associated with calcium increases in the dendrites and to a lesser extent the cell soma. HVA currents, mediated by L-type calcium channels, are slowly inactivating and they produce larger overall increases in intracellular calcium but with a similar distribution pattern. We review these observations alongside several recent papers that examine how intrinsic membrane properties influence UBCs firing patterns and we discuss how UBC signaling may affect downstream cerebellar processing. PMID:19409228

  14. Transient voltage-dependent potassium currents are reduced in NTS neurons isolated from renal wrap hypertensive rats.

    PubMed

    Belugin, Sergei; Mifflin, Steve

    2005-12-01

    Whole cell patch-clamp measurements were made in neurons enzymatically dispersed from the nucleus of the solitary tract (NTS) to determine if alterations occur in voltage-dependent potassium channels from rats made hypertensive (HT) by unilateral nephrectomy/renal wrap for 4 wk. Some rats had the fluorescent tracer DiA applied to the aortic nerve before the experiment to identify NTS neurons receiving monosynaptic baroreceptor afferent inputs. Mean arterial pressure (MAP) was greater in 4-wk HT (165 +/- 5 mmHg, n = 26, P < 0.001) rats compared with normotensive (NT) rats (109 +/- 3 mmHg measured in 10 of 69 rats). Transient outward currents (TOCs) were observed in 67-82% of NTS neurons from NT and HT rats. At activation voltages from -10 to +10 mV, TOCs were significantly less in HT neurons compared with those observed in NT neurons (P < 0.001). There were no differences in the voltage-dependent activation kinetics, the voltage dependence of steady-state inactivation, and the rise and decay time constants of the TOCs comparing neurons isolated from NT and HT rats. The 4-aminopyridine-sensitive component of the TOC was significantly less in neurons from HT compared with NT rats (P < 0.001), whereas steady-state outward currents, whether or not sensitive to 4-aminopyridine or tetraethylammonium, were not different. Delayed excitation, studied under current clamp, was observed in 60-80% of NTS neurons from NT and HT rats and was not different comparing neurons from NT and HT rats. However, examination of the subset of NTS neurons exhibiting somatic DiA fluorescence revealed that DiA-labeled neurons from HT rats had a significantly shorter duration delayed excitation (n = 8 cells, P = 0.022) than DiA-labeled neurons from NT rats (n = 7 cells). Neurons with delayed excitation from HT rats had a significantly broader first action potential (AP) and a slower maximal downstroke velocity of repolarization compared with NT neurons with delayed excitation (P = 0.016 and P = 0

  15. Selective modulation of cellular voltage-dependent calcium channels by hyperbaric pressure—a suggested HPNS partial mechanism

    PubMed Central

    Aviner, Ben; Gradwohl, Gideon; Mor Aviner, Merav; Levy, Shiri; Grossman, Yoram

    2014-01-01

    Professional deep sea divers experience motor and cognitive impairment, known as High Pressure Neurological Syndrome (HPNS), when exposed to pressures of 100 msw (1.1 MPa) and above, considered to be the result of synaptic transmission alteration. Previous studies have indicated modulation of presynaptic Ca2+ currents at high pressure. We directly measured for the first time pressure effects on the currents of voltage dependent Ca2+ channels (VDCCs) expressed in Xenopus oocytes. Pressure selectivity augmented the current in CaV1.2 and depressed it in CaV3.2 channels. Pressure application also affected the channels' kinetics, such as ƮRise, ƮDecay. Pressure modulation of VDCCs seems to play an important role in generation of HPNS signs and symptoms. PMID:24904281

  16. Peripheral benzodiazepine receptor regulates vascular endothelial activations via suppression of the voltage-dependent anion channel-1.

    PubMed

    Joo, Hee Kyoung; Lee, Yu Ran; Lim, Sun Young; Lee, Eun Ji; Choi, Sunga; Cho, Eun Jung; Park, Myoung Soo; Ryoo, Sungwoo; Park, Jin Bong; Jeon, Byeong Hwa

    2012-05-01

    Peripheral benzodiazepine receptor (PBR) is a multifunctional protein mainly found on the outer mitochondrial membrane. PBR expression is increased by tumor necrosis factor-α (TNF-α) in endothelial cells. Adenoviral overexpression of PBR inhibits monocyte adhesion, VCAM-1, and ICAM-1 expression in TNF-α-activated endothelial cells. Rotenone, cyclosporine A, and bongkrekic acid suppress TNF-α-induced VCAM-1 expression. Overexpression of PBR inhibits voltage-dependent anion channel-1 (VDAC-1) expression and the silencing of PBR increases VDAC-1 expression in endothelial cells. Moreover, TNF-α-induced VCAM-1 expression is suppressed by VDAC-1 gene silencing. PBR overexpression significantly decreases TNF-α-induced mitochondrial reactive oxygen species and MnSOD expression. These results suggest that PBR can inhibit endothelial activation and this action is related to the inhibition of mitochondrial ROS and/or VDAC-1 expression in endothelial cells.

  17. Functional coupling between sodium-activated potassium channels and voltage-dependent persistent sodium currents in cricket Kenyon cells

    PubMed Central

    Takahashi, Izumi

    2015-01-01

    In this study, we examined the functional coupling between Na+-activated potassium (KNa) channels and Na+ influx through voltage-dependent Na+ channels in Kenyon cells isolated from the mushroom body of the cricket Gryllus bimaculatus. Single-channel activity of KNa channels was recorded with the cell-attached patch configuration. The open probability (Po) of KNa channels increased with increasing Na+ concentration in a bath solution, whereas it decreased by the substitution of Na+ with an equimolar concentration of Li+. The Po of KNa channels was also found to be reduced by bath application of a high concentration of TTX (1 μM) and riluzole (100 μM), which inhibits both fast (INaf) and persistent (INaP) Na+ currents, whereas it was unaffected by a low concentration of TTX (10 nM), which selectively blocks INaf. Bath application of Cd2+ at a low concentration (50 μM), as an inhibitor of INaP, also decreased the Po of KNa channels. Conversely, bath application of the inorganic Ca2+-channel blockers Co2+ and Ni2+ at high concentrations (500 μM) had little effect on the Po of KNa channels, although Cd2+ (500 μM) reduced the Po of KNa channels. Perforated whole cell clamp analysis further indicated the presence of sustained outward currents for which amplitude was dependent on the amount of Na+ influx. Taken together, these results indicate that KNa channels could be activated by Na+ influx passing through voltage-dependent persistent Na+ channels. The functional significance of this coupling mechanism was discussed in relation to the membrane excitability of Kenyon cells and its possible role in the formation of long-term memory. PMID:26269549

  18. Differential expression of T- and L-type voltage-dependent calcium channels in renal resistance vessels.

    PubMed

    Hansen, P B; Jensen, B L; Andreasen, D; Skøtt, O

    2001-09-28

    The distribution of voltage-dependent calcium channels in kidney pre- and postglomerular resistance vessels was determined at the molecular and functional levels. Reverse transcription-polymerase chain reaction analysis of microdissected rat preglomerular vessels and cultured smooth muscle cells showed coexpression of mRNAs for T-type subunits (Ca(V)3.1, Ca(V)3.2) and for an L-type subunit (Ca(V)1.2). The same expression pattern was observed in juxtamedullary efferent arterioles and outer medullary vasa recta. No calcium channel messages were detected in cortical efferent arterioles. Ca(V)1.2 protein was demonstrated by immunochemical labeling of rat preglomerular vasculature and juxtamedullary efferent arterioles and vasa recta. Cortical efferent arterioles were not immunopositive. Recordings of intracellular calcium concentration with digital fluorescence imaging microscopy showed a significant increase of calcium in response to K(+) (100 mmol/L) in isolated afferent arterioles (140+/-25%) and in juxtamedullary efferent arterioles (118+/-21%). These calcium responses were attenuated by the L-type antagonist calciseptine and by the T-type antagonist mibefradil. Intracellular calcium increased in response to K(+) in cortical efferent arterioles (21+/-9%). Mibefradil and nickel concentration dependently blocked K(+)-induced contraction of perfused rabbit afferent arterioles. Calciseptine blocked the contraction mediated by K(+) (EC(50) 8x10(-14)). S-(-)-Bay K 8644 had no effect on vascular diameter in the afferent arteriole. We conclude that voltage-dependent L- and T-type calcium channels are expressed and of functional significance in renal cortical preglomerular vessels, in juxtamedullary efferent arterioles, and in outer medullary vasa recta, but not in cortical efferent arterioles.

  19. Voltage dependence of sodium-calcium exchange current in guinea-pig atrial myocytes determined by means of an inhibitor.

    PubMed Central

    Lipp, P; Pott, L

    1988-01-01

    1. Spontaneous transient inward currents (Iti) caused by cyclic release of Ca2+ ions from the sarcoplasmic reticulum were studied in cultured atrial myocytes from hearts of adult guinea-pigs. K+ channel currents were blocked by replacing K+ on both sides of the membrane by Cs+; the L-type Ca2+ current was inhibited by D600. 2. The voltage dependence of peak Iti and the background current displayed distinct outward-going rectification. The I-V curves for both currents approach each other at strongly positive membrane potentials but do not intersect. 3. 3'-4'Dichlorobenzamil (DCB) causes a concentration-dependent inhibition of peak Iti and a shift of the holding current (at -60 to -40 mV) in the inward direction. Inhibition of Iti is half-maximal at a concentration of 30 microM. 4. DCB reduces the outward-rectifying component of both peak Iti and the background current. The I-V curves of the control and DCB-inhibited currents intersect at ca. +10 mV (peak Iti) and negative to -75 mV (background current), suggesting the reversal potential of the DCB-inhibited current to be shifted by ca. 85 mV in the positive direction if Cai2+ rises following Ca2+ release. 5. The voltage dependence of the DCB-inhibited currents is highly compatible with the concept of Na+-Ca2+ exchange being the charge-carrying mechanism of the outward-rectifying background current. Ca2+ release from the SR alters the I-V curve of this current according to the shift of the thermodynamic driving force. PMID:2855345

  20. Amine blockers of the cytoplasmic mouth of sodium channels: a small structural change can abolish voltage dependence.

    PubMed Central

    Zamponi, G W; French, R J

    1994-01-01

    Many drugs block sodium channels from the cytoplasmic end (Moczydlowski, E., A. Uehara, X, Guo, and J. Heiny. 1986. Isochannels and blocking modes of voltage-dependent sodium channels. Ann. N.Y. Acad. Sci. 479:269-292.). Lidocaine, applied to either side of the membrane, induces two blocking modes, a rapid, voltage-dependent open-channel block, and a block of the inactivated channel that occurs on a 1000-fold slower timescale. Here we describe the actions of several lidocaine-related amines on batrachotoxin(BTX)-activated bovine cardiac sodium channels incorporated into planar lipid bilayers. We applied blocking amines from the intracellular side and examined the structural determinants of fast, open-channel block. Neither hydroxyl nor carbonyl groups, present in the aryl-amine link of lidocaine, were necessary, indicating that hydrogen bonding between structures in the aryl-amine link and the channel is not required. Block, however, was significantly enhanced by addition of an aromatic ring, or by the lengthening of aliphatic side chains, suggesting that a hydrophobic domain strengthens binding while the amine group blocks the pore. For most blockers, depolarizing potentials enhanced block, with the charged amine group apparently traversing 45-60% of the transmembrane voltage. By contrast, block by phenylhydrazine was essentially voltage-independent. The relatively rigid planar structure of phenylhydrazine may prevent the charged amino end from entering the electric field when the aromatic ring is bound. The relation between structural features of different blockers and their sensitivity to voltage suggests that the transmembrane voltage drops completely over less than 5 A. We raise the possibility that the proposed hydrophobic binding domain overlaps the endogenous receptor for the inactivation gate. If so, our data place limits on the distance between this receptor and the intrapore site at which charged amines bind. PMID:7811912

  1. Voltage-dependent dye coupling at a rectifying electrotonic synapse of the crayfish.

    PubMed Central

    Giaume, C; Korn, H

    1984-01-01

    At the crayfish giant motor synapse, the lateral giant axon (l.g.a.) and the giant motor fibre (g.m.f.) form an electrotonic junction which exhibits two states of ionic coupling (Furshpan & Potter, 1959a; Giaume & Korn, 1983). Junctional conductance is low at resting membrane potentials (i.e. with lateral axon more negative than the motor fibre) and high when the polarity of the voltage difference (delta V) across the synapse is reversed. For these two states of conductance, junctional permeability was investigated using the intercellular tracer Lucifer Yellow. The dye was ionophoretically injected into either the presynaptic (l.g.a.) or the post-synaptic (g.m.f.) cell. In the high conductance state (delta V greater than 0), fluorescence was detected in both neurones whether Lucifer Yellow had been injected pre- or post-synaptically. By contrast, at the resting junctional polarization (delta V less than 0) Lucifer Yellow spread from the giant axon to the g.m.f., but not from the g.m.f. to the giant axons. These data demonstrate that dye transfer at the giant motor synapse, like ionic coupling, is sensitive to junctional polarization and is more marked in the high conductance state. Possible explanations for the asymmetry observed in the low conductance state are discussed. Images PLATE 1 PLATE 2 PLATE 3 PMID:6097668

  2. Phosphorylation by Nek1 regulates opening and closing of voltage dependent anion channel 1

    SciTech Connect

    Chen, Yumay; Gaczynska, Maria; Osmulski, Pawel; Polci, Rosaria; Riley, Daniel J.

    2010-04-09

    VDAC1 is a key component of the mitochondrial permeability transition pore. To initiate apoptosis and certain other forms of cell death, mitochondria become permeable such that cytochrome c and other pre-apoptotic molecules resident inside the mitochondria enter the cytosol and activate apoptotic cascades. We have shown recently that VDAC1 interacts directly with never-in-mitosis A related kinase 1 (Nek1), and that Nek1 phosphorylates VDAC1 on Ser193 to prevent excessive cell death after injury. How this phosphorylation regulates the activity of VDAC1, however, has not yet been reported. Here, we use atomic force microscopy (AFM) and cytochrome c conductance studies to examine the configuration of VDAC1 before and after phosphorylation by Nek1. Wild-type VDAC1 assumes an open configuration, but closes and prevents cytochrome c efflux when phosphorylated by Nek1. A VDAC1-Ser193Ala mutant, which cannot be phosphorylated by Nek1 under identical conditions, remains open and constitutively allows cytochrome c efflux. Conversely, a VDAC1-Ser193Glu mutant, which mimics constitutive phosphorylation by Nek1, remains closed by AFM and prevents cytochrome c leakage in the same liposome assays. Our data provide a mechanism to explain how Nek1 regulates cell death by affecting the opening and closing of VDAC1.

  3. Biophysics of gating phenomena in voltage-dependent OmpC mutant porin channels (R74C and R37C) of Escherichia coli outer membranes.

    PubMed

    Mobasheri, Hamid; Lea, Edward J A

    2002-09-01

    The mechanism by which the membrane potential closes and opens voltage-dependent beta-barrel membrane channels is not fully understood. OmpC porins form trimeric water-filled channels when incorporated into artificial bilayers, each monomer having a conductance of approximately 510 pS in 1 M KCl. These channels are relatively insensitive to membrane potential difference (pd) and close only when the pd exceeds +/-250 mV. Another well-known trimer, OmpF, has a monomer conductance of approximately 780 pS in 1 M NaCl, is more sensitive to pd, and can be closed reversibly when a pd of more than +/-150 mV is applied to the channel-containing membranes. With the aid of the 3D atomic structure of these channels determined by X-ray crystallography, and using site-directed mutagenesis, specific amino acids can be substituted in desired locations in the channel lumen. In this study we have used mutants 37C and 74C and attached fluorescence probes to them to monitor polarity changes in the channel lumen during gating. From the observed changes in polarity, we conclude that conformational changes occur in the channel which interrupt the electrolyte conducting pathway. PMID:12202916

  4. Patch clamp combined with voltage/concentration clamp to determine the kinetics and voltage dependency of N-methyl-D-aspartate (NMDA) receptor open channel blockers.

    PubMed

    Parsons, Chris G; Gilling, Kate E

    2014-01-01

    Electrophysiological techniques can be used to great effect to help determine the mechanism of action of a compound. However, many factors can compromise the resulting data and their analysis, such as the speed of solution exchange, expression of additional ion channel populations including other ligand-gated receptors and voltage-gated channels, compounds having multiple binding sites, and current desensitization and rundown. In this chapter, such problems and their solutions are discussed and illustrated using data from experiments involving the uncompetitive NMDA receptor antagonist memantine. Memantine differs from many other NMDA receptor channel blockers in that it is well tolerated and does not cause psychotomimetic effects at therapeutic doses. Various electrophysiological parameters of NMDA-induced current blockade by memantine have been proposed to be important in determining therapeutic tolerability; potency, onset and offset kinetics, and voltage dependency. These were all measured using whole cell patch clamp techniques using hippocampal neurons. Full results are shown here for memantine, and these are summarized and compared to those from similar experiments with other NMDA channel blockers. The interpretation of these results is discussed, as are theories concerning the tolerability of NMDA channel blockers, with the aim of illustrating how electrophysiological data can be used to form and support a physiological hypothesis.

  5. Voltage-dependent gating of single gap junction channels in an insect cell line.

    PubMed Central

    Bukauskas, F F; Weingart, R

    1994-01-01

    De novo formation of cell pairs was used to examine the gating properties of single gap junction channels. Two separate cells of an insect cell line (clone C6/36, derived from the mosquito Aedes albopictus) were pushed against each other to provoke formation of gap junction channels. A dual voltage-clamp method was used to control the voltage gradient between the cells (Vj) and measure the intercellular current (Ij). The first sign of channel activity was apparent 4.7 min after cell contact. Steady-state coupling reached after 30 min revealed a conductance of 8.7 nS. Channel formation involved no leak between the intra- and extracellular space. The first opening of a newly formed channel was slow (25-28 ms). Each preparation passed through a phase with only one operational gap junction channel. This period was exploited to examine the single channel properties. We found that single channels exhibit several conductance states with different conductances gamma j; a fully open state (gamma j(main state)), several substates (gamma j(substates)), a residual state (gamma j(residual)) and a closed state (gamma j(closed)). The gamma j(main state) was 375 pS, and gamma j(residual) ranged from 30 to 90 pS. The transitions between adjacent substates were 1/7-1/4 of gamma j(main state). Vj had no effect on gamma j(main state), but slightly affected gamma j (residual). The lj transitions involving gamma j(closed) were slow (15-60 ms), whereas those not involving gamma j(closed) were fast (< 2 ms). An increase in Vj led to a decrease in open channel probability. Depolarization of the membrane potential (Vm) increased the incidence of slow transitions leading to gamma j(closed). We conclude that insect gap junctions possess two gates, a fast gate controlled by Vj and giving rise to gamma j(substates) and gamma j(residual), and a slow gate sensitive to Vm and able to close the channel completely. PMID:7524710

  6. General method to predict voltage-dependent ionic conduction in a solid electrolyte coating on electrodes

    NASA Astrophysics Data System (ADS)

    Pan, Jie; Cheng, Yang-Tse; Qi, Yue

    2015-04-01

    Understanding the ionic conduction in solid electrolytes in contact with electrodes is vitally important to many applications, such as lithium ion batteries. The problem is complex because both the internal properties of the materials (e.g., electronic structure) and the characteristics of the externally contacting phases (e.g., voltage of the electrode) affect defect formation and transport. In this paper, we developed a method based on density functional theory to study the physics of defects in a solid electrolyte in equilibrium with an external environment. This method was then applied to predict the ionic conduction in lithium fluoride (LiF), in contact with different electrodes which serve as reservoirs with adjustable Li chemical potential (μLi) for defect formation. LiF was chosen because it is a major component in the solid electrolyte interphase (SEI) formed on lithium ion battery electrodes. Seventeen possible native defects with their relevant charge states in LiF were investigated to determine the dominant defect types on various electrodes. The diffusion barrier of dominant defects was calculated by the climbed nudged elastic band method. The ionic conductivity was then obtained from the concentration and mobility of defects using the Nernst-Einstein relationship. Three regions for defect formation were identified as a function of μLi: (1) intrinsic, (2) transitional, and (3) p -type region. In the intrinsic region (high μLi, typical for LiF on the negative electrode), the main defects are Schottky pairs and in the p -type region (low μLi, typical for LiF on the positive electrode) are Li ion vacancies. The ionic conductivity is calculated to be approximately 10-31Scm-1 when LiF is in contact with a negative electrode but it can increase to 10-12Scm-1 on a positive electrode. This insight suggests that divalent cation (e.g., Mg2+) doping is necessary to improve Li ion transport through the engineered LiF coating, especially for LiF on negative

  7. Voltage-dependent inactivation of inward-rectifying single-channel currents in the guinea-pig heart cell membrane.

    PubMed Central

    Sakmann, B; Trube, G

    1984-01-01

    Inward currents through single K+ channels in isolated ventricular heart cells of the guinea-pig were recorded using the patch-clamp technique (Hamill, Marty, Neher, Sakmann & Sigworth, 1981). The voltage-dependent gating properties of the channels were examined in the potential range between 0 and -120 mV with 145 mM-KCl on the extracellular side of the membrane patch, i.e. with approximately symmetrical transmembrane K+ concentrations. When voltage pulses from 0 mV to negative test potentials were applied to patches containing several channels, more channels were open at the beginning of the pulses than in the steady state. Averages of many current responses showed inactivation of the mean current in response to the hyperpolarizing voltage pulses. The inactivation was stronger and faster at larger hyperpolarization. The lifetimes of the open and closed states of the channel and the probability of the open state p were estimated from records of the elementary currents at various constant potentials. As indicated by the inactivation of the averaged currents, the value of p was smaller at more negative potentials, approximately 0.15 at -50 mV and 0.02 at -110 mV. This caused a negative slope in the current-voltage relation of the time-averaged current at potentials more negative than -50 mV. The channel openings were grouped in complex bursts. At least three exponentials were needed to fit the frequency histogram of the lifetimes of all closed states (time constants at -50 mV: 1.1 ms, 16 ms and 3.2 s). The lifetimes of the individual openings were exponentially distributed (time constant: 70 ms). The kinetics of the channel were interpreted by two different models involving three states of a channel (closed-closed-open or closed-open-closed). The rate constants and their voltage dependence were estimated for both models. Both models describe the data equally well; the reason for this ambiguity is discussed. The channels are blocked by Cs+ or Ba2+. Cs+ (0.1 m

  8. Voltage-dependent block by internal Ca2+ ions of inwardly rectifying K+ channels in guinea-pig ventricular cells.

    PubMed Central

    Matsuda, H; Cruz, J dos S

    1993-01-01

    1. The block of the inwardly rectifying K+ channel by intracellular Ca2+ was studied in guinea-pig ventricular cells. 2. Single-channel currents through the inwardly rectifying K+ channel were recorded in the inside-out configuration at 150 mM external and internal K+. Internal Ca2+, at a concentration of 0.4-10 microM, induced subconductance levels with one-third and two-thirds of the unitary amplitude in the outward currents without affecting the inward currents. 3. Occupancy at each sublevel was estimated from the amplitude histogram which showed four equally spaced peaks in the presence of internal Ca2+. At different degrees of blockade, the distribution of the current levels showed a reasonable agreement with the binomial theorem. 4. The outward mean open-channel currents were measured at different Ca2+ concentrations and voltages. The current-voltage relation rectified inwardly in the presence of internal Ca2+ in a concentration-dependent manner. 5. The outward mean open-channel currents were normalized to unitary amplitudes in the absence of Ca2+. The normalized current-Ca2+ concentration curve was fitted by saturation kinetics with a Hill coefficient of 1 at each voltage. The voltage dependence of the dissociation constants gives the value for the fractional electrical distance of the Ca2+ binding site of 0.7. 6. The dwell times in each substrate were distributed exponentially. On the assumption that the inwardly rectifying K+ channel of cardiac cells is composed of three identical conducting subunits and each subunit is blocked by Ca2+ independently, the blocking (mu) and unblocking (lambda) rates were calculated. The value of mu increased with higher Ca2+ concentrations or larger depolarizations, while lambda was independent of Ca2+ and decreased with larger depolarization. 7. It is thus concluded that internal Ca2+ produces a voltage-dependent block of the channel to cause inward rectification although the blocking effect is less potent than that of Mg2

  9. Effects of proctolin on contractions, membrane resistance, and non-voltage-dependent sarcolemmal ion channels in crustacean muscle fibers.

    PubMed

    Erxleben, C F; deSantis, A; Rathmayer, W

    1995-06-01

    The neuropeptide proctolin in nanomolar concentrations enhances the contraction of crustacean muscle fibers manyfold. The cellular mechanisms underlying this potentiation were investigated in single, isolated, fast-contracting abdominal extensor muscle fibers of a small crustacean, the marine isopod Idotea baltica. Force measurements and current-clamp experiments revealed two actions of proctolin on the muscle fibers. In half of the preparations, proctolin (10(-9)-10(-6) M) increased the fiber's input resistance by up to 25%. In about one-fourth of the preparations, proctolin induced all-or-none action potentials in response to depolarizing current pulses in muscle fibers that showed graded electric responses under control conditions. In both cases, proctolin potentiated the peak force of muscle contractions (between 1.5- and 18-fold for 5 x 10(-9) M proctolin). Proctolin affected neither the membrane resting potential nor the threshold for excitation-contraction coupling. Using cell-attached patches on the sarcolemmal membrane, we identified non-voltage-dependent ion channels which contribute to the passive membrane properties of the muscle fibers. A 53 +/- 6 pS channel had its reversal potential near rest and carried outward current at depolarized potentials with physiological saline in the recording pipette. With isotonic K+ saline in the patch pipette, the reversal potential was +85 +/- 12 mV depolarized from the resting potential and single-channel conductances ranged from 36 to 166 pS. Proctolin modulated the activity of all these putative K+ channels by reducing the number of functionally active channels. The effects of proctolin on force of contraction, input resistance, and single-channel activity were mimicked by a membrane-permeating analog of cAMP. Conversely, a monothio analog of cAMP (Rp-cAMPS), a blocker of protein kinase A activity, substantially decreased the membrane input resistance of the muscle fibers. The results suggest that activation of the

  10. Wait or escape? Contrasting submergence tolerance strategies of Rorippa amphibia, Rorippa sylvestris and their hybrid

    PubMed Central

    Akman, Melis; Bhikharie, Amit V.; McLean, Elizabeth H.; Boonman, Alex; Visser, Eric J. W.; Schranz, M. Eric; van Tienderen, Peter H.

    2012-01-01

    Background and Aims Differential responses of closely related species to submergence can provide insight into the evolution and mechanisms of submergence tolerance. Several traits of two wetland species from habitats with contrasting flooding regimes, Rorippa amphibia and Rorippa sylvestris, as well as F1 hybrid Rorippa × anceps were analysed to unravel mechanisms underlying submergence tolerance. Methods In the first submergence experiment (lasting 20 d) we analysed biomass, stem elongation and carbohydrate content. In the second submergence experiment (lasting 3 months) we analysed survival and the effect of re-establishment of air contact on biomass and carbohydrate content. In a separate experiment we analysed expression of two carbohydrate catabolism genes, ADH1 and SUS1, upon re-establishment of air contact following submergence. Key Results All plants had low mortality even after 3 months of submergence. Rorippa sylvestris was characterized by 100 % survival and higher carbohydrate levels coupled with lower ADH1 gene expression as well as reduced growth compared with R. amphibia. Rorippa amphibia and the hybrid elongated their stems but this did not pay-off in higher survival when plants remained submerged. Only R. amphibia and the hybrid benefited in terms of increased biomass and carbohydrate accumulation upon re-establishing air contact. Conclusions Results demonstrate contrasting ‘escape’ and ‘quiescence’ strategies between Rorippa species. Being a close relative of arabidopsis, Rorippa is an excellent model for future studies on the molecular mechanism(s) controlling these strategies. PMID:22499857

  11. The human red cell voltage-dependent cation channel. Part III: Distribution homogeneity and pH dependence.

    PubMed

    Bennekou, P; Barksmann, T L; Christophersen, P; Kristensen, B I

    2006-01-01

    The homogeneity of the distribution of the non-selective voltage-dependent cation channel (the NSVDC channel) in the human erythrocyte, and the pH dependence was investigated. Activation of this channel caused a uniform cellular dehydration, which was characterized by the changes in the erythrocyte osmotic resistance profiles: after 1/2 h of activation, the osmolarity at 50% hemolysis changed from 73 mM (control) to 34 mM NaCl, corresponding to 0.48% and 0.21% NaCl respectively. Unchanging standard deviations show participation of the entire erythrocyte population, which implies an even distribution of the NSVDC channel among the cells. Inactivation of the NSVDC channel with N-ethyl-maleimide (NEM) or blocking of the Cl(-) conductance with NS1652 retarded the migration of the resistance profiles towards lower osmolarities. The NSVDC channel activation was blocked by a decrease of the intracellular -- but not the extracellular -- pH. The apparent pK(A) value for the effect was estimated to be 6.5, and the specific histidine reagent 2.4'-dibromoacetophenone (DBAB) inactivated the NSVDC channel. PMID:16376587

  12. The calmodulin inhibitor and antipsychotic drug trifluoperazine inhibits voltage-dependent K+ channels in rabbit coronary arterial smooth muscle cells.

    PubMed

    Hong, Da Hye; Son, Youn Kyoung; Li, Hongliang; Jung, In Duk; Park, Yeong-Min; Jung, Won-Kyo; Kim, Han Sol; Choi, Il-Whan; Park, Won Sun

    2014-01-01

    We investigated the effect of the calmodulin inhibitor and antipsychotic drug trifluoperazine on voltage-dependent K(+) (Kv) channels. Kv currents were recorded by whole-cell configuration of patch clamp in freshly isolated rabbit coronary arterial smooth muscle cells. The amplitudes of Kv currents were reduced by trifluoperazine in a concentration-dependent manner, with an apparent IC50 value of 1.58±0.48 μM. The rate constants of association and dissociation by trifluoperazine were 3.73±0.33 μM(-1) s(-1) and 5.84±1.41 s(-1), respectively. Application of trifluoperazine caused a positive shift in the activation curve but had no significant effect on the inactivation curve. Furthermore, trifluoperazine provoked use-dependent inhibition of the Kv current under train pulses (1 or 2 Hz). These findings suggest that trifluoperazine interacts with Kv current in a closed state and inhibits Kv current in the open state in a time- and use-dependent manner, regardless of its function as a calmodulin inhibitor and antipsychotic drug.

  13. Spexin Enhances Bowel Movement through Activating L-type Voltage-dependent Calcium Channel via Galanin Receptor 2 in Mice

    PubMed Central

    Lin, Cheng-yuan; Zhang, Man; Huang, Tao; Yang, Li-ling; Fu, Hai-bo; Zhao, Ling; Zhong, Linda LD; Mu, Huai-xue; Shi, Xiao-ke; Leung, Christina FP; Fan, Bao-min; Jiang, Miao; Lu, Ai-ping; Zhu, Li-xin; Bian, Zhao-xiang

    2015-01-01

    A novel neuropeptide spexin was found to be broadly expressed in various endocrine and nervous tissues while little is known about its functions. This study investigated the role of spexin in bowel movement and the underlying mechanisms. In functional constipation (FC) patients, serum spexin levels were significantly decreased. Consistently, in starved mice, the mRNA of spexin was significantly decreased in intestine and colon. Spexin injection increased the velocity of carbon powder propulsion in small intestine and decreased the glass beads expulsion time in distal colon in mice. Further, spexin dose-dependently stimulated the intestinal/colonic smooth muscle contraction. Galanin receptor 2 (GALR2) antagonist M871, but not Galanin receptor 3 (GALR3) antagonist SNAP37899, effectively suppressed the stimulatory effects of spexin on intestinal/colonic smooth muscle contraction, which could be eliminated by extracellular [Ca2+] removal and L-type voltage-dependentCa2+ channel (VDCC) inhibitor nifedipine. Besides, spexin dramatically increased the [Ca2+]i in isolated colonic smooth muscle cells. These data indicate that spexin can act on GALR2 receptor to regulate bowel motility by activating L-type VDCC. Our findings provide evidence for important physiological roles of spexin in GI functions. Selective action on spexin pathway might have therapeutic effects on GI diseases with motility disorders. PMID:26160593

  14. Voltage-dependent motion of the catalytic region of voltage-sensing phosphatase monitored by a fluorescent amino acid

    PubMed Central

    Sakata, Souhei; Jinno, Yuka; Kawanabe, Akira; Okamura, Yasushi

    2016-01-01

    The cytoplasmic region of voltage-sensing phosphatase (VSP) derives the voltage dependence of its catalytic activity from coupling to a voltage sensor homologous to that of voltage-gated ion channels. To assess the conformational changes in the cytoplasmic region upon activation of the voltage sensor, we genetically incorporated a fluorescent unnatural amino acid, 3-(6-acetylnaphthalen-2-ylamino)-2-aminopropanoic acid (Anap), into the catalytic region of Ciona intestinalis VSP (Ci-VSP). Measurements of Anap fluorescence under voltage clamp in Xenopus oocytes revealed that the catalytic region assumes distinct conformations dependent on the degree of voltage-sensor activation. FRET analysis showed that the catalytic region remains situated beneath the plasma membrane, irrespective of the voltage level. Moreover, Anap fluorescence from a membrane-facing loop in the C2 domain showed a pattern reflecting substrate turnover. These results indicate that the voltage sensor regulates Ci-VSP catalytic activity by causing conformational changes in the entire catalytic region, without changing their distance from the plasma membrane. PMID:27330112

  15. Ferulic Acid Suppresses Glutamate Release Through Inhibition of Voltage-Dependent Calcium Entry in Rat Cerebrocortical Nerve Terminals

    PubMed Central

    Lin, Tzu Yu; Lu, Cheng Wei; Huang, Shu-Kuei

    2013-01-01

    Abstract This study investigated the effects and possible mechanism of ferulic acid, a naturally occurring phenolic compound, on endogenous glutamate release in the nerve terminals of the cerebral cortex in rats. Results show that ferulic acid inhibited the release of glutamate evoked by the K+ channel blocker 4-aminopyridine (4-AP). The effect of ferulic acid on the evoked glutamate release was prevented by chelating the extracellular Ca2+ ions, but was insensitive to the glutamate transporter inhibitor DL-threo-beta-benzyl-oxyaspartate. Ferulic acid suppressed the depolarization-induced increase in a cytosolic-free Ca2+ concentration, but did not alter 4-AP–mediated depolarization. Furthermore, the effect of ferulic acid on evoked glutamate release was abolished by blocking the Cav2.2 (N-type) and Cav2.1 (P/Q-type) channels, but not by blocking ryanodine receptors or mitochondrial Na+/Ca2+ exchange. These results show that ferulic acid inhibits glutamate release from cortical synaptosomes in rats through the suppression of presynaptic voltage-dependent Ca2+ entry. PMID:23342970

  16. Clinical implication of voltage-dependent anion channel 1 in uterine cervical cancer and its action on cervical cancer cells

    PubMed Central

    Wu, Chih-Hsien; Lin, Yu-Wen; Wu, Tzu-Fan; Ko, Jiunn-Liang; Wang, Po-Hui

    2016-01-01

    Two-dimensional gel electrophoresis and liquid chromatography-tandem mass spectrometry were performed to investigate the influence of human nonmetastatic clone 23 type 1 (nm23-H1), a metastasis-associated gene on proteomic alterations in cancer cells of the uterine cervix. It was validated by RT-PCR and Western blot analysis. The expression of voltage-dependent anion channel 1 (VDAC1) was increased in nm23-H1 gene silenced SiHa or CaSki cervical cancer cells. The clinical implication was shown that cervical cancer tissues with positive VDAC1 immunoreactivity exhibited deep stromal invasion (>10 mm in depth) and large tumor size (> 4 cm in diameter). Cervical cancer patients with positive VDAC1 immunoreactivity displayed higher recurrence and poorer overall survival than those with negative VDAC1. Silencing of VDAC1 reduced cell proliferation and migratory ability. Mitochondrial membrane potential was decreased and reactive oxygen species generation was increased in the VDAC1 gene-silenced cervical cancer cells. Cell cycle progression and autophagy were not changed in VDAC1 silencing cells. The cytotoxicity of cisplatin was significantly enhanced by knockdown of cellular VDAC1 and the compounds that interfere with hexokinase binding to VDAC. Therapeutic strategies may be offered using VDAC1 as a target to reduce cell growth and migration, enhance the synergistic therapeutic efficacy of cisplatin and reduce cisplatin dose-limiting toxicity. PMID:26716410

  17. The voltage-dependent K+ channels Kv1.3 and Kv1.5 in human cancer

    PubMed Central

    Comes, Núria; Bielanska, Joanna; Vallejo-Gracia, Albert; Serrano-Albarrás, Antonio; Marruecos, Laura; Gómez, Diana; Soler, Concepció; Condom, Enric; Ramón y Cajal, Santiago; Hernández-Losa, Javier; Ferreres, Joan C.; Felipe, Antonio

    2013-01-01

    Voltage-dependent K+ channels (Kv) are involved in a number of physiological processes, including immunomodulation, cell volume regulation, apoptosis as well as differentiation. Some Kv channels participate in the proliferation and migration of normal and tumor cells, contributing to metastasis. Altered expression of Kv1.3 and Kv1.5 channels has been found in several types of tumors and cancer cells. In general, while the expression of Kv1.3 apparently exhibits no clear pattern, Kv1.5 is induced in many of the analyzed metastatic tissues. Interestingly, evidence indicates that Kv1.5 channel shows inversed correlation with malignancy in some gliomas and non-Hodgkin's lymphomas. However, Kv1.3 and Kv1.5 are similarly remodeled in some cancers. For instance, expression of Kv1.3 and Kv1.5 correlates with a certain grade of tumorigenicity in muscle sarcomas. Differential remodeling of Kv1.3 and Kv1.5 expression in human cancers may indicate their role in tumor growth and their importance as potential tumor markers. However, despite of this increasing body of information, which considers Kv1.3 and Kv1.5 as emerging tumoral markers, further research must be performed to reach any conclusion. In this review, we summarize what it has been lately documented about Kv1.3 and Kv1.5 channels in human cancer. PMID:24133455

  18. Voltage-dependent anion channel 2 modulates resting Ca²+ sparks, but not action potential-induced Ca²+ signaling in cardiac myocytes.

    PubMed

    Subedi, Krishna Prasad; Kim, Joon-Chul; Kang, Moonkyung; Son, Min-Jeong; Kim, Yeon-Soo; Woo, Sun-Hee

    2011-02-01

    Voltage-dependent anion channels (VDACs) are pore forming proteins predominantly found in the outer mitochondrial membrane and are thought to transport Ca(2+). In this study, we have investigated the possible role of type 2 VDAC (VDAC2) in cardiac Ca(2+) signaling and Ca(2+) sparks using a lentiviral knock-down (KD) technique and two-dimensional confocal Ca(2+) imaging in immortalized autorhythmic adult atrial cells, HL-1. We confirmed high expression of VDAC2 protein in ventricular, atrial, and HL-1 cells using Western blot analysis. Infection of HL-1 cells with VDAC2-targeting lentivirus reduced the level of VDAC2 protein to ∼10%. Comparisons of autorhythmic Ca(2+) transients between wild-type (WT) and VDAC2 KD cells showed no significant change in the magnitude, decay, and beating rate of the Ca(2+) transients. Caffeine (10mM)-induced Ca(2+) release, which indicates sarcoplasmic reticulum (SR) Ca(2+) content, was not altered by VDAC2 KD. Interestingly, however, the intensity, width, and duration of the individual Ca(2+) sparks were significantly increased by VDAC2 KD in resting conditions, with no change in the frequency of sparks. VDAC2 KD significantly delayed mitochondrial Ca(2+) uptake during artificial Ca(2+) pulses in permeabilized HL-1 cells. These results suggest that VDAC2 may facilitate mitochondrial Ca(2+) uptake and restrict Ca(2+) spark expansion without regulating activations of sparks under resting conditions, thereby providing evidence on the functional role of VDAC2 in cardiac local Ca(2+) signaling.

  19. A conserved threonine in the S1-S2 loop of KV7.2 and K V7.3 channels regulates voltage-dependent activation.

    PubMed

    Füll, Yvonne; Seebohm, Guiscard; Lerche, Holger; Maljevic, Snezana

    2013-06-01

    The voltage-gated potassium channels KV7.2 and KV7.3 (KCNQ2/3 genes) play an important role in regulating neuronal excitability. More than 50 KCNQ2/3 mutations have been identified to cause an inherited form of epilepsy in newborns. For two of those (E119G and S122L) found in the S1-S2 region of KV7.2, we previously showed a decreased channel availability mainly at action potential subthreshold voltages caused by a slight depolarizing shift of the activation curve. Interestingly, recent studies revealed that a threonine residue within the S1-S2 loop, highly conserved among different classes of KV channels, is crucial for both their function and surface expression. To investigate the functional role of the homologous threonine residues in KV7.2 (T114) and KV7.3 (T144) channels, we replaced them with alanine and examined the electrophysiological properties using heterologous expression in CHO cells and whole cell patch clamping. Channels comprising mutant subunits yielded decreased potassium currents with slowed activation and accelerated deactivation kinetics. However, the most striking effect was a depolarizing shift in the voltage dependence of activation reaching +30 mV upon co-expression of both mutant subunits. Potential interactions of T114 within the channel were analyzed by creating a 3D homology model of KV7.2 in an open state suggesting that this residue plays a central role in the formation of a stable interface between the S1-S2 and the S5 segment helices. This could be the explanation why substitution of the conserved threonine in KV7.2 and KV7.3 channels destabilizes the open and favors the closed state of these channels.

  20. Bias voltage dependence of the electron spin depolarization in quantum wires in the quantum Hall regime detected by the resistively detected NMR

    SciTech Connect

    Chida, K.; Yamauchi, Y.; Arakawa, T.; Kobayashi, K.; Ono, T.; Hashisaka, M.; Nakamura, S.; Machida, T.

    2013-12-04

    We performed the resistively-detected nuclear magnetic resonance (RDNMR) to study the electron spin polarization in the non-equilibrium quantum Hall regime. By measuring the Knight shift, we derive source-drain bias voltage dependence of the electron spin polarization in quantum wires. The electron spin polarization shows minimum value around the threshold voltage of the dynamic nuclear polarization.

  1. 4-Aminopyridine causes a voltage-dependent block of the transient outward K+ current in rat melanotrophs.

    PubMed Central

    Kehl, S J

    1990-01-01

    1. Whole-cell voltage-clamp recordings were made from acutely dissociated melanotrophs obtained from adult rats. 2. In the presence of external Na+ and Ca2+ channel blockers and 20 mM-tetraethylammonium (TEA) depolarizations to -40 mV or more evoked a fast-activating fast-inactivating outward K+ current (IK(f)). Double-pulse experiments showed that steady-state half-inactivation occurred near -37 mV; half-maximal activation of IK(f) occurred at -15 mV. Recovery from inactivation in most cells fitted a single exponential with a time constant of 40-50 ms. 3. When applied either internally or externally, 1-2.5 mM-4-aminopyridine (4-AP) substantially reduced IK(f) but the degree of block was affected by the intensity, duration and frequency of depolarizing commands. 4. Analysis of the steady-state voltage dependence of the block by 4-AP showed that half-maximal blocking occurred at approximately -31 mV. This implied that 4-AP binds to the resting state of the IK(f) channel. 5. Studies of the time dependence for the blocking or unblocking of IK(f) showed that both processes were exponential with mean time constants of 1942 ms (at -70 mV) and 726 ms (at 20 mV), respectively. Recovery from inactivation was apparently unaffected by 4-AP. 6. A four-state sequential model in which 4-AP reversibly binds to the resting state of the channel replicates the frequency dependence of the 4-AP blockade. PMID:2100315

  2. In self-defence: hexokinase promotes voltage-dependent anion channel closure and prevents mitochondria-mediated apoptotic cell death.

    PubMed Central

    Azoulay-Zohar, Heftsi; Israelson, Adrian; Abu-Hamad, Salah; Shoshan-Barmatz, Varda

    2004-01-01

    In tumour cells, elevated levels of mitochondria-bound isoforms of hexokinase (HK-I and HK-II) result in the evasion of apoptosis, thereby allowing the cells to continue proliferating. The molecular mechanisms by which bound HK promotes cell survival are not yet fully understood. Our studies relying on the purified mitochondrial outer membrane protein VDAC (voltage-dependent anion channel), isolated mitochondria or cells in culture suggested that the anti-apoptotic activity of HK-I occurs via modulation of the mitochondrial phase of apoptosis. In the present paper, a direct interaction of HK-I with bilayer-reconstituted purified VDAC, inducing channel closure, is demonstrated for the first time. Moreover, HK-I prevented the Ca(2+)-dependent opening of the mitochondrial PTP (permeability transition pore) and release of the pro-apoptotic protein cytochrome c. The effects of HK-I on VDAC activity and PTP opening were prevented by the HK reaction product glucose 6-phosphate, a metabolic intermediate in most biosynthetic pathways. Furthermore, glucose 6-phosphate re-opened both the VDAC and the PTP closed by HK-I. The HK-I-mediated effects on VDAC and PTP were not observed using either yeast HK or HK-I lacking the N-terminal hydrophobic peptide responsible for binding to mitochondria, or in the presence of an antibody specific for the N-terminus of HK-I. Finally, HK-I overexpression in leukaemia-derived U-937 or vascular smooth muscle cells protected against staurosporine-induced apoptosis, with a decrease of up to 70% in cell death. These results offer insight into the mechanisms by which bound HK promotes tumour cell survival, and suggests that its overexpression not only ensures supplies of energy and phosphometabolites, but also reflects an anti-apoptotic defence mechanism. PMID:14561215

  3. Tubulin tail sequences and post-translational modifications regulate closure of mitochondrial voltage-dependent anion channel (VDAC).

    PubMed

    Sheldon, Kely L; Gurnev, Philip A; Bezrukov, Sergey M; Sackett, Dan L

    2015-10-30

    It was previously shown that tubulin dimer interaction with the mitochondrial outer membrane protein voltage-dependent anion channel (VDAC) blocks traffic through the channel and reduces oxidative metabolism and that this requires the unstructured anionic C-terminal tail peptides found on both α- and β-tubulin subunits. It was unclear whether the α- and β-tubulin tails contribute equally to VDAC blockade and what effects might be due to sequence variations in these tail peptides or to tubulin post-translational modifications, which mostly occur on the tails. The nature of the contribution of the tubulin body beyond acting as an anchor for the tails had not been clarified either. Here we present peptide-protein chimeras to address these questions. These constructs allow us to easily combine a tail peptide with different proteins or combine different tail peptides with a particular protein. The results show that a single tail grafted to an inert protein is sufficient to produce channel closure similar to that observed with tubulin. We show that the β-tail is more than an order of magnitude more potent than the α-tail and that the lower α-tail activity is largely due to the presence of a terminal tyrosine. Detyrosination activates the α-tail, and activation is reversed by the removal of the glutamic acid penultimate to the tyrosine. Nitration of tyrosine reverses the tyrosine inhibition of binding and even induces prolonged VDAC closures. Our results demonstrate that small changes in sequence or post-translational modification of the unstructured tails of tubulin result in substantial changes in VDAC closure.

  4. Characterization of Oyster Voltage-Dependent Anion Channel 2 (VDAC2) Suggests Its Involvement in Apoptosis and Host Defense.

    PubMed

    Li, Yingxiang; Zhang, Linlin; Qu, Tao; Li, Li; Zhang, Guofan

    2016-01-01

    Genomic and transcriptomic studies have revealed a sophisticated and powerful apoptosis regulation network in oyster, highlighting its adaptation to sessile life in a highly stressful intertidal environment. However, the functional molecular basis of apoptosis remains largely unexplored in oysters. In this study, we focused on a representative apoptotic gene encoding voltage-dependent anion channel 2 (VDAC2), a porin that abounds at the mitochondrial outer membrane. This is the first report on the identification and characterization of a VDAC gene in the Pacific oyster, Crassostrea gigas (CgVDAC2). The full length of CgVDAC2 was 1,738 bp with an open reading frame of 843 bp that encoded a protein of 281 amino acids. A four-element eukaryotic porin signature motif, a conserved ATP binding motif, and a VKAKV-like sequence were identified in the predicted CgVDAC2. Expression pattern analysis in different tissues and developmental stages as well as upon infection by ostreid herpesvirus 1 revealed the energy supply-related and immunity-related expression of CgVDAC2. CgVDAC2 was co-localized with mitochondria when it was transiently transfected into HeLa cells. Overexpression of CgVDAC2 in HEK293T cells suppressed the UV irradiation-induced apoptosis by inhibiting the pro-apoptotic function of CgBak. RNA interference induced reduction in CgVDAC2 expression showed a promoted apoptosis level upon UV light irradiation in hemocytes. The yeast two-hybrid system and co-immunoprecipitation assay indicated a direct interaction between CgVDAC2 and the pro-apoptotic protein CgBak. This study revealed the function of VDAC2 in oyster and provided new insights into its involvement in apoptosis modulation and host defense in mollusks.

  5. Mild Alkalization Acutely Triggers the Warburg Effect by Enhancing Hexokinase Activity via Voltage-Dependent Anion Channel Binding.

    PubMed

    Quach, Cung Hoa Thien; Jung, Kyung-Ho; Lee, Jin Hee; Park, Jin Won; Moon, Seung Hwan; Cho, Young Seok; Choe, Yearn Seong; Lee, Kyung-Han

    2016-01-01

    To fully understand the glycolytic behavior of cancer cells, it is important to recognize how it is linked to pH dynamics. Here, we evaluated the acute effects of mild acidification and alkalization on cancer cell glucose uptake and glycolytic flux and investigated the role of hexokinase (HK). Cancer cells exposed to buffers with graded pH were measured for 18F-fluorodeoxyglucose (FDG) uptake, lactate production and HK activity. Subcellular localization of HK protein was assessed by western blots and confocal microscopy. The interior of T47D breast cancer cells was mildly alkalized to pH 7.5 by a buffer pH of 7.8, and this was accompanied by rapid increases of FDG uptake and lactate extrusion. This shift toward glycolytic flux led to the prompt recovery of a reversed pH gradient. In contrast, mild acidification rapidly reduced cellular FDG uptake and lactate production. Mild acidification decreased and mild alkalization increased mitochondrial HK translocation and enzyme activity. Cells transfected with specific siRNA against HK-1, HK-2 and voltage-dependent anion channel (VDAC)1 displayed significant attenuation of pH-induced changes in FDG uptake. Confocal microscopy showed increased co-localization of HK-1 and HK-2 with VDAC1 by alkaline treatment. In isolated mitochondria, acidic pH increased and alkaline pH decreased release of free HK-1 and HK-2 from the mitochondrial pellet into the supernatant. Furthermore, experiments using purified proteins showed that alkaline pH promoted co-immunoprecipitation of HK with VDAC protein. These findings demonstrate that mild alkalization is sufficient to acutely trigger cancer cell glycolytic flux through enhanced activity of HK by promoting its mitochondrial translocation and VDAC binding. This process might serve as a mechanism through which cancer cells trigger the Warburg effect to maintain a dysregulated pH. PMID:27479079

  6. Mild Alkalization Acutely Triggers the Warburg Effect by Enhancing Hexokinase Activity via Voltage-Dependent Anion Channel Binding

    PubMed Central

    Lee, Jin Hee; Park, Jin Won; Moon, Seung Hwan; Cho, Young Seok; Choe, Yearn Seong; Lee, Kyung-Han

    2016-01-01

    To fully understand the glycolytic behavior of cancer cells, it is important to recognize how it is linked to pH dynamics. Here, we evaluated the acute effects of mild acidification and alkalization on cancer cell glucose uptake and glycolytic flux and investigated the role of hexokinase (HK). Cancer cells exposed to buffers with graded pH were measured for 18F-fluorodeoxyglucose (FDG) uptake, lactate production and HK activity. Subcellular localization of HK protein was assessed by western blots and confocal microscopy. The interior of T47D breast cancer cells was mildly alkalized to pH 7.5 by a buffer pH of 7.8, and this was accompanied by rapid increases of FDG uptake and lactate extrusion. This shift toward glycolytic flux led to the prompt recovery of a reversed pH gradient. In contrast, mild acidification rapidly reduced cellular FDG uptake and lactate production. Mild acidification decreased and mild alkalization increased mitochondrial HK translocation and enzyme activity. Cells transfected with specific siRNA against HK-1, HK-2 and voltage-dependent anion channel (VDAC)1 displayed significant attenuation of pH-induced changes in FDG uptake. Confocal microscopy showed increased co-localization of HK-1 and HK-2 with VDAC1 by alkaline treatment. In isolated mitochondria, acidic pH increased and alkaline pH decreased release of free HK-1 and HK-2 from the mitochondrial pellet into the supernatant. Furthermore, experiments using purified proteins showed that alkaline pH promoted co-immunoprecipitation of HK with VDAC protein. These findings demonstrate that mild alkalization is sufficient to acutely trigger cancer cell glycolytic flux through enhanced activity of HK by promoting its mitochondrial translocation and VDAC binding. This process might serve as a mechanism through which cancer cells trigger the Warburg effect to maintain a dysregulated pH. PMID:27479079

  7. Tubulin tail sequences and post-translational modifications regulate closure of mitochondrial voltage-dependent anion channel (VDAC).

    PubMed

    Sheldon, Kely L; Gurnev, Philip A; Bezrukov, Sergey M; Sackett, Dan L

    2015-10-30

    It was previously shown that tubulin dimer interaction with the mitochondrial outer membrane protein voltage-dependent anion channel (VDAC) blocks traffic through the channel and reduces oxidative metabolism and that this requires the unstructured anionic C-terminal tail peptides found on both α- and β-tubulin subunits. It was unclear whether the α- and β-tubulin tails contribute equally to VDAC blockade and what effects might be due to sequence variations in these tail peptides or to tubulin post-translational modifications, which mostly occur on the tails. The nature of the contribution of the tubulin body beyond acting as an anchor for the tails had not been clarified either. Here we present peptide-protein chimeras to address these questions. These constructs allow us to easily combine a tail peptide with different proteins or combine different tail peptides with a particular protein. The results show that a single tail grafted to an inert protein is sufficient to produce channel closure similar to that observed with tubulin. We show that the β-tail is more than an order of magnitude more potent than the α-tail and that the lower α-tail activity is largely due to the presence of a terminal tyrosine. Detyrosination activates the α-tail, and activation is reversed by the removal of the glutamic acid penultimate to the tyrosine. Nitration of tyrosine reverses the tyrosine inhibition of binding and even induces prolonged VDAC closures. Our results demonstrate that small changes in sequence or post-translational modification of the unstructured tails of tubulin result in substantial changes in VDAC closure. PMID:26306046

  8. Biophysical and Pharmacological Characterization of Nav1.9 Voltage Dependent Sodium Channels Stably Expressed in HEK-293 Cells

    PubMed Central

    Santos, Sonia; Padilla, Karen; Printzenhoff, David; Castle, Neil A.

    2016-01-01

    The voltage dependent sodium channel Nav1.9, is expressed preferentially in peripheral sensory neurons and has been linked to human genetic pain disorders, which makes it target of interest for the development of new pain therapeutics. However, characterization of Nav1.9 pharmacology has been limited due in part to the historical difficulty of functionally expressing recombinant channels. Here we report the successful generation and characterization of human, mouse and rat Nav1.9 stably expressed in human HEK-293 cells. These cells exhibit slowly activating and inactivating inward sodium channel currents that have characteristics of native Nav1.9. Optimal functional expression was achieved by coexpression of Nav1.9 with β1/β2 subunits. While recombinantly expressed Nav1.9 was found to be sensitive to sodium channel inhibitors TC-N 1752 and tetracaine, potency was up to 100-fold less than reported for other Nav channel subtypes despite evidence to support an interaction with the canonical local anesthetic (LA) binding region on Domain 4 S6. Nav1.9 Domain 2 S6 pore domain contains a unique lysine residue (K799) which is predicted to be spatially near the local anesthetic interaction site. Mutation of this residue to the consensus asparagine (K799N) resulted in an increase in potency for tetracaine, but a decrease for TC-N 1752, suggesting that this residue can influence interaction of inhibitors with the Nav1.9 pore. In summary, we have shown that stable functional expression of Nav1.9 in the widely used HEK-293 cells is possible, which opens up opportunities to better understand channel properties and may potentially aid identification of novel Nav1.9 based pharmacotherapies. PMID:27556810

  9. Phosphorylation of Voltage-Dependent Anion Channel by Serine/Threonine Kinases Governs Its Interaction with Tubulin

    PubMed Central

    Sheldon, Kely L.; Maldonado, Eduardo N.; Lemasters, John J.; Rostovtseva, Tatiana K.; Bezrukov, Sergey M.

    2011-01-01

    Tubulin was recently found to be a uniquely potent regulator of the voltage-dependent anion channel (VDAC), the most abundant channel of the mitochondrial outer membrane, which constitutes a major pathway for ATP/ADP and other metabolites across this membrane. Dimeric tubulin induces reversible blockage of VDAC reconstituted into a planar lipid membrane and dramatically reduces respiration of isolated mitochondria. Here we show that VDAC phosphorylation is an important determinant of its interaction with dimeric tubulin. We demonstrate that in vitro phosphorylation of VDAC by either glycogen synthase kinase-3β (GSK3β) or cAMP-dependent protein kinase A (PKA), increases the on-rate of tubulin binding to the reconstituted channel by orders of magnitude, but only for tubulin at the cis side of the membrane. This and the fact the basic properties of VDAC, such as single-channel conductance and selectivity, remained unaltered by phosphorylation allowed us to suggest the phosphorylation regions positioned on the cytosolic loops of VDAC and establish channel orientation in our reconstitution experiments. Experiments on human hepatoma cells HepG2 support our conjecture that VDAC permeability for the mitochondrial respiratory substrates is regulated by dimeric tubulin and channel phosphorylation. Treatment of HepG2 cells with colchicine prevents microtubule polymerization, thus increasing dimeric tubulin availability in the cytosol. Accordingly, this leads to a decrease of mitochondrial potential measured by assessing mitochondrial tetramethylrhodamine methyester uptake with confocal microscopy. Inhibition of PKA activity blocks and reverses mitochondrial depolarization induced by colchicine. Our findings suggest a novel functional link between serine/threonine kinase signaling pathways, mitochondrial respiration, and the highly dynamic microtubule network which is characteristic of cancerogenesis and cell proliferation. PMID:22022409

  10. Immunomodulatory effects of diclofenac in leukocytes through the targeting of Kv1.3 voltage-dependent potassium channels.

    PubMed

    Villalonga, Núria; David, Miren; Bielańska, Joanna; González, Teresa; Parra, David; Soler, Concepció; Comes, Núria; Valenzuela, Carmen; Felipe, Antonio

    2010-09-15

    Kv1.3 plays a crucial role in the activation and proliferation of T-lymphocytes and macrophages. While Kv1.3 is responsible for the voltage-dependent potassium current in T-cells, in macrophages this K(+) current is generated by the association of Kv1.3 and Kv1.5. Patients with autoimmune diseases show a high number of effector memory T cells that are characterized by a high expression of Kv1.3 and Kv1.3 antagonists ameliorate autoimmune disorders in vivo. Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) used in patients who suffer from painful autoimmune diseases such as rheumatoid arthritis. In this study, we show that diclofenac impairs immune response via a mechanism that involves Kv1.3. While diclofenac inhibited Kv1.3 expression in activated macrophages and T-lymphocytes, Kv1.5 remained unaffected. Diclofenac also decreased iNOS levels in Raw 264.7 cells, impairing their activation in response to lipopolysaccharide (LPS). LPS-induced macrophage migration and IL-2 production in stimulated Jurkat T-cells were also blocked by pharmacological doses of diclofenac. These effects were mimicked by Margatoxin, a specific Kv1.3 inhibitor, and Charybdotoxin, which blocks both Kv1.3 and Ca(2+)-activated K(+) channels (K(Ca)3.1). Because Kv1.3 is a very good target for autoimmune therapies, the effects of diclofenac on Kv1.3 are of high pharmacological relevance.

  11. Characterization of Oyster Voltage-Dependent Anion Channel 2 (VDAC2) Suggests Its Involvement in Apoptosis and Host Defense.

    PubMed

    Li, Yingxiang; Zhang, Linlin; Qu, Tao; Li, Li; Zhang, Guofan

    2016-01-01

    Genomic and transcriptomic studies have revealed a sophisticated and powerful apoptosis regulation network in oyster, highlighting its adaptation to sessile life in a highly stressful intertidal environment. However, the functional molecular basis of apoptosis remains largely unexplored in oysters. In this study, we focused on a representative apoptotic gene encoding voltage-dependent anion channel 2 (VDAC2), a porin that abounds at the mitochondrial outer membrane. This is the first report on the identification and characterization of a VDAC gene in the Pacific oyster, Crassostrea gigas (CgVDAC2). The full length of CgVDAC2 was 1,738 bp with an open reading frame of 843 bp that encoded a protein of 281 amino acids. A four-element eukaryotic porin signature motif, a conserved ATP binding motif, and a VKAKV-like sequence were identified in the predicted CgVDAC2. Expression pattern analysis in different tissues and developmental stages as well as upon infection by ostreid herpesvirus 1 revealed the energy supply-related and immunity-related expression of CgVDAC2. CgVDAC2 was co-localized with mitochondria when it was transiently transfected into HeLa cells. Overexpression of CgVDAC2 in HEK293T cells suppressed the UV irradiation-induced apoptosis by inhibiting the pro-apoptotic function of CgBak. RNA interference induced reduction in CgVDAC2 expression showed a promoted apoptosis level upon UV light irradiation in hemocytes. The yeast two-hybrid system and co-immunoprecipitation assay indicated a direct interaction between CgVDAC2 and the pro-apoptotic protein CgBak. This study revealed the function of VDAC2 in oyster and provided new insights into its involvement in apoptosis modulation and host defense in mollusks. PMID:26727366

  12. Characterization of Oyster Voltage-Dependent Anion Channel 2 (VDAC2) Suggests Its Involvement in Apoptosis and Host Defense

    PubMed Central

    Li, Yingxiang; Zhang, Linlin; Qu, Tao; Li, Li; Zhang, Guofan

    2016-01-01

    Genomic and transcriptomic studies have revealed a sophisticated and powerful apoptosis regulation network in oyster, highlighting its adaptation to sessile life in a highly stressful intertidal environment. However, the functional molecular basis of apoptosis remains largely unexplored in oysters. In this study, we focused on a representative apoptotic gene encoding voltage-dependent anion channel 2 (VDAC2), a porin that abounds at the mitochondrial outer membrane. This is the first report on the identification and characterization of a VDAC gene in the Pacific oyster, Crassostrea gigas (CgVDAC2). The full length of CgVDAC2 was 1,738 bp with an open reading frame of 843 bp that encoded a protein of 281 amino acids. A four-element eukaryotic porin signature motif, a conserved ATP binding motif, and a VKAKV-like sequence were identified in the predicted CgVDAC2. Expression pattern analysis in different tissues and developmental stages as well as upon infection by ostreid herpesvirus 1 revealed the energy supply-related and immunity-related expression of CgVDAC2. CgVDAC2 was co-localized with mitochondria when it was transiently transfected into HeLa cells. Overexpression of CgVDAC2 in HEK293T cells suppressed the UV irradiation-induced apoptosis by inhibiting the pro-apoptotic function of CgBak. RNA interference induced reduction in CgVDAC2 expression showed a promoted apoptosis level upon UV light irradiation in hemocytes. The yeast two-hybrid system and co-immunoprecipitation assay indicated a direct interaction between CgVDAC2 and the pro-apoptotic protein CgBak. This study revealed the function of VDAC2 in oyster and provided new insights into its involvement in apoptosis modulation and host defense in mollusks. PMID:26727366

  13. Sodium-calcium exchange in regulation of cardiac contractility. Evidence for an electrogenic, voltage-dependent mechanism

    PubMed Central

    1979-01-01

    The origin and regulatory mechanisms of tonic tension (Ca current- independent component of contractility) were investigated in frog atrial muscle under voltage-clamp conditions. Tonic tension was elicited by depolarizing pulses of 160 mV (Em = +90 mV, i.e., close to E ca) and 400--600 ms long. An application of Na-free (LiCl) or Ca-free Ringer's solutions resulted in a fast (less than 120 s), almost complete abolition of tonic tension. When [Na]o was reduced (with LiCl or sucrose as the substitutes), the peak tonic tension increased transiently and then decreased below the control level. The transient changes in tonic tension were prevented by using low-Na, low-Ca solutions where the ratios [Ca]0/[Na]40 to [Ca]o/[Na]4o were kept constant (1.1 X 10(-8) mM-3 to 8.7 X 10(-13) mM-5). Na-free (LiCl) solution elicited contractures accompanied by a membrane hyperpolarization or by an outward current even when the Na-K pump was inhibited. 15 mM MnCl2 (or 3 mM LaCl3) inhibited the development of the Na-free contracture and the related part of hyperpolarization or the outward current. In conclusion, our results indicate that tonic tension is regulated by a Na-Ca exchange mechanism. Furthermore, they suggest that this exchange could be electrogenic (exchanging three or more Na ions for one Ca ion) and thus voltage dependent. The possible contribution of an electrogenic Na-Ca exchange in the maintenance of cardiac membrane potential is discussed. PMID:312914

  14. The structural organization of the kidney of Typhlonectes compressicaudus (Amphibia, Gymnophiona).

    PubMed

    Sakai, T; Billo, R; Kriz, W

    1986-01-01

    The structural organization of the kidney of Typhlonectes compressicaudus (Amphibia, Gymnophiona) was studied by light microscopic (LM) examination of serial paraffin and semithin Epon sections. The kidney is slender and quite long and has a mesonephric segmental construction; the excretory duct (Wolffian duct), running along the lateral side of the kidney, segmentally receives the terminal trunks of the collecting duct system. The nephron has the following parts: renal corpuscle, neck segment, proximal tubule, intermediate segment, distal tubule and connecting tubule. The distal tubule is located in a ventromedial (central) zone of the kidney; all other tubular segments lie in a dorsolateral (peripheral) zone. The renal corpuscles are found at the border between these two zones. The renal corpuscle is very large; its urinary pole faces the peripheral zone. A small proportion of neck segments receive either a nephrostomal duct or a blind branch. The proximal tubule is a thick, highly convoluted tubule. The intermediate segment is ciliated and makes a few coils. The distal tubule is composed of three portions: a highly convoluted part in the central zone, subsequently an attachment site with the renal corpuscle and a short postattachment-part. The connecting tubule and the collecting duct have a heterogeneous epithelium consisting of light and dark cells. The collecting duct is distinguished by dilated intercellular spaces. The Wolffian duct has a pseudostratified epithelium. The present study correlates the course and segmentation of the renal tubule of Typhlonectes. The tubule has three major convolutions. The first occurs in the proximal tubule in the peripheral zone; the second is established by the distal tubule and occurs in the central zone; the third is formed by the connecting tubule and is found in the peripheral zone. PMID:3740458

  15. The structural organization of the kidney of Typhlonectes compressicaudus (Amphibia, Gymnophiona).

    PubMed

    Sakai, T; Billo, R; Kriz, W

    1986-01-01

    The structural organization of the kidney of Typhlonectes compressicaudus (Amphibia, Gymnophiona) was studied by light microscopic (LM) examination of serial paraffin and semithin Epon sections. The kidney is slender and quite long and has a mesonephric segmental construction; the excretory duct (Wolffian duct), running along the lateral side of the kidney, segmentally receives the terminal trunks of the collecting duct system. The nephron has the following parts: renal corpuscle, neck segment, proximal tubule, intermediate segment, distal tubule and connecting tubule. The distal tubule is located in a ventromedial (central) zone of the kidney; all other tubular segments lie in a dorsolateral (peripheral) zone. The renal corpuscles are found at the border between these two zones. The renal corpuscle is very large; its urinary pole faces the peripheral zone. A small proportion of neck segments receive either a nephrostomal duct or a blind branch. The proximal tubule is a thick, highly convoluted tubule. The intermediate segment is ciliated and makes a few coils. The distal tubule is composed of three portions: a highly convoluted part in the central zone, subsequently an attachment site with the renal corpuscle and a short postattachment-part. The connecting tubule and the collecting duct have a heterogeneous epithelium consisting of light and dark cells. The collecting duct is distinguished by dilated intercellular spaces. The Wolffian duct has a pseudostratified epithelium. The present study correlates the course and segmentation of the renal tubule of Typhlonectes. The tubule has three major convolutions. The first occurs in the proximal tubule in the peripheral zone; the second is established by the distal tubule and occurs in the central zone; the third is formed by the connecting tubule and is found in the peripheral zone.

  16. Mitochondrial evidence on the phylogenetic position of caecilians (Amphibia: Gymnophiona).

    PubMed Central

    Zardoya, R; Meyer, A

    2000-01-01

    The complete nucleotide sequence (17,005 bp) of the mitochondrial genome of the caecilian Typhlonectes natans (Gymnophiona, Amphibia) was determined. This molecule is characterized by two distinctive genomic features: there are seven large 109-bp tandem repeats in the control region, and the sequence for the putative origin of replication of the L strand can potentially fold into two alternative secondary structures (one including part of the tRNA(Cys)). The new sequence data were used to assess the phylogenetic position of caecilians and to gain insights into the origin of living amphibians (frogs, salamanders, and caecilians). Phylogenetic analyses of two data sets-one combining protein-coding genes and the other combining tRNA genes-strongly supported a caecilian + frog clade and, hence, monophyly of modern amphibians. These two data sets could not further resolve relationships among the coelacanth, lungfishes, and tetrapods, but strongly supported diapsid affinities of turtles. Phylogenetic relationships among a larger set of species of frogs, salamanders, and caecilians were estimated with a mitochondrial rRNA data set. Maximum parsimony analysis of this latter data set also recovered monophyly of living amphibians and favored a frog + salamander (Batrachia) relationship. However, bootstrap support was only moderate at these nodes. This is likely due to an extensive among-site rate heterogeneity in the rRNA data set and the narrow window of time in which the three main groups of living amphibians were originated. PMID:10835397

  17. Ultrastructure of the mature spermatozoa of caecilians (Amphibia: Gymnophiona).

    PubMed

    Scheltinga, David M; Wilkinson, Mark; Jamieson, Barrie G M; Oommen, Oommen V

    2003-11-01

    The spermatozoa of Gymnophiona show the following autapomorphies: 1) penetration of the distal centriole by the axial fiber; 2) presence of an acrosomal baseplate; 3) presence of an acrosome seat (flattened apical end of nucleus); and 4) absence of juxta-axonemal fibers. The wide separation of the plasma membrane bounding the undulating membrane is here also considered to be apomorphic. Three plesiomorphic spermatozoal characters are recognized that are not seen in other Amphibia but occur in basal amniotes: 1) presence of mitochondria with a delicate array of concentric cristae (concentric cristae of salamander spermatozoa differ in lacking the delicate array); 2) presence of peripheral dense fibers associated with the triplets of the distal centriole; and 3) presence of a simple annulus (a highly modified, elongate annulus is present in salamander sperm). The presence of an endonuclear canal containing a perforatorium is a plesiomorphic feature of caecilian spermatozoa that is shared with urodeles, some basal anurans, sarcopterygian fish, and some amniotes. Spermatozoal synapomorphies are identified for 1) the Uraeotyphlidae and Ichthyophiidae, and 2) the Caeciliidae and Typhlonectidae, suggesting that the members of each pair of families are more closely related to each other than to other caecilians. Although caecilian spermatozoa exhibit the clear amphibian synapomorphy of the unilateral location of the undulating membrane and its axial fiber, they have no apomorphic characters that suggest a closer relationship to either the Urodela or Anura.

  18. Mitochondrial evidence on the phylogenetic position of caecilians (Amphibia: Gymnophiona).

    PubMed

    Zardoya, R; Meyer, A

    2000-06-01

    The complete nucleotide sequence (17,005 bp) of the mitochondrial genome of the caecilian Typhlonectes natans (Gymnophiona, Amphibia) was determined. This molecule is characterized by two distinctive genomic features: there are seven large 109-bp tandem repeats in the control region, and the sequence for the putative origin of replication of the L strand can potentially fold into two alternative secondary structures (one including part of the tRNA(Cys)). The new sequence data were used to assess the phylogenetic position of caecilians and to gain insights into the origin of living amphibians (frogs, salamanders, and caecilians). Phylogenetic analyses of two data sets-one combining protein-coding genes and the other combining tRNA genes-strongly supported a caecilian + frog clade and, hence, monophyly of modern amphibians. These two data sets could not further resolve relationships among the coelacanth, lungfishes, and tetrapods, but strongly supported diapsid affinities of turtles. Phylogenetic relationships among a larger set of species of frogs, salamanders, and caecilians were estimated with a mitochondrial rRNA data set. Maximum parsimony analysis of this latter data set also recovered monophyly of living amphibians and favored a frog + salamander (Batrachia) relationship. However, bootstrap support was only moderate at these nodes. This is likely due to an extensive among-site rate heterogeneity in the rRNA data set and the narrow window of time in which the three main groups of living amphibians were originated.

  19. Ultrastructure of the mature spermatozoa of caecilians (Amphibia: Gymnophiona).

    PubMed

    Scheltinga, David M; Wilkinson, Mark; Jamieson, Barrie G M; Oommen, Oommen V

    2003-11-01

    The spermatozoa of Gymnophiona show the following autapomorphies: 1) penetration of the distal centriole by the axial fiber; 2) presence of an acrosomal baseplate; 3) presence of an acrosome seat (flattened apical end of nucleus); and 4) absence of juxta-axonemal fibers. The wide separation of the plasma membrane bounding the undulating membrane is here also considered to be apomorphic. Three plesiomorphic spermatozoal characters are recognized that are not seen in other Amphibia but occur in basal amniotes: 1) presence of mitochondria with a delicate array of concentric cristae (concentric cristae of salamander spermatozoa differ in lacking the delicate array); 2) presence of peripheral dense fibers associated with the triplets of the distal centriole; and 3) presence of a simple annulus (a highly modified, elongate annulus is present in salamander sperm). The presence of an endonuclear canal containing a perforatorium is a plesiomorphic feature of caecilian spermatozoa that is shared with urodeles, some basal anurans, sarcopterygian fish, and some amniotes. Spermatozoal synapomorphies are identified for 1) the Uraeotyphlidae and Ichthyophiidae, and 2) the Caeciliidae and Typhlonectidae, suggesting that the members of each pair of families are more closely related to each other than to other caecilians. Although caecilian spermatozoa exhibit the clear amphibian synapomorphy of the unilateral location of the undulating membrane and its axial fiber, they have no apomorphic characters that suggest a closer relationship to either the Urodela or Anura. PMID:14518011

  20. Mitochondrial evidence on the phylogenetic position of caecilians (Amphibia: Gymnophiona).

    PubMed

    Zardoya, R; Meyer, A

    2000-06-01

    The complete nucleotide sequence (17,005 bp) of the mitochondrial genome of the caecilian Typhlonectes natans (Gymnophiona, Amphibia) was determined. This molecule is characterized by two distinctive genomic features: there are seven large 109-bp tandem repeats in the control region, and the sequence for the putative origin of replication of the L strand can potentially fold into two alternative secondary structures (one including part of the tRNA(Cys)). The new sequence data were used to assess the phylogenetic position of caecilians and to gain insights into the origin of living amphibians (frogs, salamanders, and caecilians). Phylogenetic analyses of two data sets-one combining protein-coding genes and the other combining tRNA genes-strongly supported a caecilian + frog clade and, hence, monophyly of modern amphibians. These two data sets could not further resolve relationships among the coelacanth, lungfishes, and tetrapods, but strongly supported diapsid affinities of turtles. Phylogenetic relationships among a larger set of species of frogs, salamanders, and caecilians were estimated with a mitochondrial rRNA data set. Maximum parsimony analysis of this latter data set also recovered monophyly of living amphibians and favored a frog + salamander (Batrachia) relationship. However, bootstrap support was only moderate at these nodes. This is likely due to an extensive among-site rate heterogeneity in the rRNA data set and the narrow window of time in which the three main groups of living amphibians were originated. PMID:10835397

  1. Voltage-dependent interaction of open-channel blocking molecules with gating of NMDA receptors in rat cortical neurons.

    PubMed Central

    Antonov, S M; Johnson, J W

    1996-01-01

    1. The mechanisms by which four adamantane derivatives (IEM-1857, -1592, -1460 and -1754) block the open NMDA-activated channel were studied at membrane voltages (Vm) from -170 to +30 mV. The rate constants of channel block (k+) and of channel unblock (k-) were measured from the fully resolvable flicker of single-channel currents induced by each compound. 2. The k+ of each compound exhibited a similar exponential dependence on voltage over the Vm range studied. 3. The k- of IEM-1857 and IEM-1592 over the Vm range studied, and of IEM-1754 and IEM-1460 from -30 to -90 mV, exhibited similar exponential dependencies on voltage. However, the k- of IEM-1754 and IEM-1460 at Vm values more hyperpolarized than -90 mV were much more steeply voltage dependent, suggesting that at these Vm values the two drugs can occupy a deeper binding site. 4. Each of the drugs induced a concentration-dependent prolongation of the mean burst length at -90 mV, suggesting that while blocking they can interfere with channel closure. 5. The prolongation of mean burst length induced by the largest drug (IEM-1857) increased with hyperpolarization. The increase was consistent at each Vm with the predictions of the sequential scheme of block, suggesting that channel closure is prevented when IEM-1857 is bound. The prolongation of burst length induced by the smallest drug (IEM-1754) was less than predicted by the sequential scheme and the deviation increased with hyperpolarization. 6. The IEM-1857 concentration-dependence of number of blockages per unit open time had a slope equal to k+ at -150 mV. The IEM-1754 concentration-dependence of number of blockages per unit open time revealed a slope about two times less than k+ for this compound at -150 mV. 7. The mean patch current was not significantly altered by 3 microM IEM-1857 at Vm values from -90 to -150 mV, as expected of a drug that prevents channel closure when blocking. Mean patch current significantly decreased with hyperpolarization beyond

  2. Time-resolved photoluminescence measurements for determining voltage-dependent charge-separation efficiencies of subcells in triple-junction solar cells

    SciTech Connect

    Tex, David M.; Ihara, Toshiyuki; Kanemitsu, Yoshihiko; Akiyama, Hidefumi; Imaizumi, Mitsuru

    2015-01-05

    Conventional external quantum-efficiency measurement of solar cells provides charge-collection efficiency for approximate short-circuit conditions. Because this differs from actual operating voltages, the optimization of high-quality tandem solar cells is especially complicated. Here, we propose a contactless method, which allows for the determination of the voltage dependence of charge-collection efficiency for each subcell independently. By investigating the power dependence of photoluminescence decays, charge-separation and recombination-loss time constants are obtained. The upper limit of the charge-collection efficiencies at the operating points is then obtained by applying the uniform field model. This technique may complement electrical characterization of the voltage dependence of charge collection, since subcells are directly accessible.

  3. Trimebutine maleate has inhibitory effects on the voltage-dependent Ca2+ inward current and other membrane currents in intestinal smooth muscle cells.

    PubMed

    Shimada, T; Kurachi, Y; Terano, A; Hamada, E; Sugimoto, T

    1990-04-01

    We examined effects of trimebutine maleate on the membrane currents of the intestinal smooth muscle cells by using the tight-seal whole cell clamp technique. Trimebutine suppressed the Ba2+ inward current through voltage-dependent Ca2+ channels in a dose-dependent manner. The inhibitory effect of trimebutine on the Ba2+ inward current was not use-dependent. It shifted the steady-state inactivation curve to the left along the voltage axis. Trimebutine also had inhibitory effects on the other membrane currents of the cells, such as the voltage-dependent K+ current, the Ca2(+)-activated oscillating K+ current and the acetylcholine-induced inward current. These relatively non-specific inhibitory effects of trimebutine on the membrane currents may explain, at least in part, the dual actions of the drug on the intestinal smooth muscle contractility, i.e. inhibitory as well as excitatory. PMID:2161373

  4. Voltage-dependent currents and modulation of calcium channel expression in zona fasciculata cells from rat adrenal gland.

    PubMed Central

    Barbara, J G; Takeda, K

    1995-01-01

    2+ current types was unaffected by pre-incubation with 8-bromo-cAMP or forskolin. The protein kinase A antagonist, H89, did not inhibit the ACTH-induced upregulation of T-type Ca2+ currents. 7. It is concluded that the main voltage-dependent currents involved in cell excitability and steroidogenesis in rat adrenal ZF cells are an A-type K+ current and a T-type Ca2+ current. The physiological role and control of expression of L-type Ca2+ channels in rat ZF cells remain less clear. PMID:8576852

  5. [Helminth fauna of amphibians (Vertebrata: Amphibia) in the Republic of Belarus].

    PubMed

    Shimalov, V V

    2009-01-01

    Historical review of the investigations of helminth fauna in amphibians from Belarus is presented. In 12 amphibian species examined by different authors 46 helminth species were found, including 29 Trematoda, 13 Nematoda, 1 Monogenea, 2 Cestoda, and 1 Acanthocephala. Original data on helminths parasitizing Amphibia in Byelorussian Polesie, by the results of long-term investigations in 1986-2004 are given. Distribution of 40 helminth species by hosts and respective infestation rates are reported.

  6. Voltage-dependent capacitance behavior and underlying mechanisms in metal-insulator-metal capacitors with Al2O3-ZrO2-SiO2 nano-laminates

    NASA Astrophysics Data System (ADS)

    Zhu, Bao; Liu, Wen-Jun; Wei, Lei; Ding, Shi-Jin

    2016-04-01

    Nano-laminates consisting of high-permittivity dielectrics and SiO2 have been extensively studied for radio frequency metal-insulator-metal (MIM) capacitors because of their superior voltage linearity and low leakage current. However, there are no reports on the capacitance-voltage (C-V) characteristics at a high sweep voltage range. In this work, an interesting variation in the voltage-dependent capacitance that forms a ‘ω’-like shape is demonstrated for the MIM capacitors with Al2O3/ZrO2/SiO2 nano-laminates. As the thickness ratio of the SiO2 film to the total insulator increases to around 0.15, the C-V curve changes from an upward parabolic shape to a ‘ω’ shape. This can be explained based on the competition between the orientation polarization from SiO2 and the electrode polarization from Al2O3 and ZrO2. When the SiO2 film is very thin, the electrode polarization dominates in the MIM capacitor, generating a positive curvature C-V curve. When the thickness of SiO2 is increased, the orientation polarization is enhanced and thus both polarizations are operating in the MIM capacitors. This leads to the appearance of a multiple domain C-V curve containing positive and negative curvatures. Therefore, good consistency between the experimental results and the theoretical simulations is demonstrated. Such voltage-dependent capacitance behavior is not determined by the stack structure of the insulator, measurement frequency and oscillator voltage, but by the thickness ratio of the SiO2 film to the whole insulator. These findings are helpful to engineer MIM capacitors with good voltage linearity.

  7. Gαi2- and Gαi3-Specific Regulation of Voltage-Dependent L-Type Calcium Channels in Cardiomyocytes

    PubMed Central

    Dizayee, Sara; Kaestner, Sonja; Kuck, Fabian; Hein, Peter; Klein, Christoph; Piekorz, Roland P.; Meszaros, Janos; Matthes, Jan; Nürnberg, Bernd; Herzig, Stefan

    2011-01-01

    Background Two pertussis toxin sensitive Gi proteins, Gi2 and Gi3, are expressed in cardiomyocytes and upregulated in heart failure. It has been proposed that the highly homologous Gi isoforms are functionally distinct. To test for isoform-specific functions of Gi proteins, we examined their role in the regulation of cardiac L-type voltage-dependent calcium channels (L-VDCC). Methods Ventricular tissues and isolated myocytes were obtained from mice with targeted deletion of either Gαi2 (Gαi2−/−) or Gαi3 (Gαi3−/−). mRNA levels of Gαi/o isoforms and L-VDCC subunits were quantified by real-time PCR. Gαi and Cavα1 protein levels as well as protein kinase B/Akt and extracellular signal-regulated kinases 1/2 (ERK1/2) phosphorylation levels were assessed by immunoblot analysis. L-VDCC function was assessed by whole-cell and single-channel current recordings. Results In cardiac tissue from Gαi2−/− mice, Gαi3 mRNA and protein expression was upregulated to 187±21% and 567±59%, respectively. In Gαi3−/− mouse hearts, Gαi2 mRNA (127±5%) and protein (131±10%) levels were slightly enhanced. Interestingly, L-VDCC current density in cardiomyocytes from Gαi2−/− mice was lowered (−7.9±0.6 pA/pF, n = 11, p<0.05) compared to wild-type cells (−10.7±0.5 pA/pF, n = 22), whereas it was increased in myocytes from Gαi3−/− mice (−14.3±0.8 pA/pF, n = 14, p<0.05). Steady-state inactivation was shifted to negative potentials, and recovery kinetics slowed in the absence of Gαi2 (but not of Gαi3) and following treatment with pertussis toxin in Gαi3−/−. The pore forming Cavα1 protein level was unchanged in all mouse models analyzed, similar to mRNA levels of Cavα1 and Cavβ2 subunits. Interestingly, at the cellular signalling level, phosphorylation assays revealed abolished carbachol-triggered activation of ERK1/2 in mice lacking Gαi2. Conclusion Our data provide novel evidence for an isoform-specific modulation of L-VDCC by G

  8. The Nitric Oxide Donor SNAP-Induced Amino Acid Neurotransmitter Release in Cortical Neurons. Effects of Blockers of Voltage-Dependent Sodium and Calcium Channels

    PubMed Central

    Merino, José Joaquín; Arce, Carmen; Naddaf, Ahmad; Bellver-Landete, Victor; Oset-Gasque, Maria Jesús; González, María Pilar

    2014-01-01

    Background The discovery that nitric oxide (NO) functions as a signalling molecule in the nervous system has radically changed the concept of neuronal communication. NO induces the release of amino acid neurotransmitters but the underlying mechanisms remain to be elucidated. Findings The aim of this work was to study the effect of NO on amino acid neurotransmitter release (Asp, Glu, Gly and GABA) in cortical neurons as well as the mechanism underlying the release of these neurotransmitters. Cortical neurons were stimulated with SNAP, a NO donor, and the release of different amino acid neurotransmitters was measured by HPLC. The involvement of voltage dependent Na+ and Ca2+ channels as well as cGMP in its mechanism of action was evaluated. Conclusions Our results indicate that NO induces release of aspartate, glutamate, glycine and GABA in cortical neurons and that this release is inhibited by ODQ, an inhibitor of soluble guanylate cyclase. Thus, the NO effect on amino acid neurotransmission could be mediated by cGMP formation in cortical neurons. Our data also demonstrate that the Na+ and Ca2+ voltage- dependent calcium channels are involved in the NO effects on cortical neurons. PMID:24598811

  9. Cosmocercoides himalayanus sp. nov. (Nematoda, Cosmocercidae) in Duttaphrynus himalayanus (Amphibia, Anura) from Dehradun (Uttarakhand), India.

    PubMed

    Rizvi, Anjum N; Bursey, Charles R

    2014-03-01

    Cosmocercoides himalayanus sp. nov. (Nematoda, Cosmocercidae) from the large intestine of Duttaphrynus himalayanus (Amphibia, Anura) from Dehradun, India is described and illustrated. Cosmocercoides himalayanus sp. nov. represents the 21st species assigned to the genus and the 9th species from the Oriental biogeographical region. Cosmocercoides himalayanus sp. nov. differs from the previously described Oriental species in number and position of rosette papillae; it is the only species possessing 24 or more rosette papillae to have 4 postcloacal papillae. In addition, a list of species assigned to Cosmocercoides is provided; however, C. fotedari Arya, 1992 is removed from the genus and until further study is considered a species inquirenda.

  10. The telencephalon of Ichthyophis paucisulcus (Amphibia, Gymnophiona (= Caecilia)). A quantitative cytoarchitectonic study.

    PubMed

    Zilles, K; Welsch, U; Schleicher, A

    1981-01-01

    A parcellation of the telencephalon of Ichthyophis paucisulcus (Amphibia, Gymnophiona (= Caecilia) has been performed with a quantitative cytoarchitectonic method. Ten different regions have been delineated and compared with earlier reports on telencephalic regions in anurans, urodeles and caecilians. The most striking difference between the brain of Ichthyophis and other amphibian brains is the high level of morphological differentiation of the accessory olfactory bulb in Ichthyophis and the large extension of this brain region. This feature may be a correlate of the advanced development and the particular structure of Jacobson's organ in this species. PMID:7336818

  11. A-887826 is a structurally novel, potent and voltage-dependent Na(v)1.8 sodium channel blocker that attenuates neuropathic tactile allodynia in rats.

    PubMed

    Zhang, Xu-Feng; Shieh, Char-Chang; Chapman, Mark L; Matulenko, Mark A; Hakeem, Ahmed H; Atkinson, Robert N; Kort, Michael E; Marron, Brian E; Joshi, Shailen; Honore, Prisca; Faltynek, Connie R; Krafte, Douglas S; Jarvis, Michael F

    2010-09-01

    Activation of sodium channels is essential to action potential generation and propagation. Recent genetic and pharmacological evidence indicates that activation of Na(v)1.8 channels contributes to chronic pain. Herein, we describe the identification of a novel series of structurally related pyridine derivatives as potent Na(v)1.8 channel blockers. A-887826 exemplifies this series and potently (IC(50)=11nM) blocked recombinant human Na(v)1.8 channels. A-887826 was approximately 3 fold less potent to block Na(v)1.2, approximately 10 fold less potent to block tetrodotoxin-sensitive sodium (TTX-S Na(+)) currents and was >30 fold less potent to block Na(V)1.5 channels. A-887826 potently blocked tetrodotoxin-resistant sodium (TTX-R Na(+)) currents (IC(50)=8nM) from small diameter rat dorsal root ganglion (DRG) neurons in a voltage-dependent fashion. A-887826 effectively suppressed evoked action potential firing when DRG neurons were held at depolarized potentials and reversibly suppressed spontaneous firing in small diameter DRG neurons from complete Freund's adjuvant inflamed rats. Following oral administration, A-887826 significantly attenuated tactile allodynia in a rat neuropathic pain model. Further characterization of TTX-R current block in rat DRG neurons demonstrated that A-887826 (100nM) shifted the mid-point of voltage-dependent inactivation of TTX-R currents by approximately 4mV without affecting voltage-dependent activation and did not exhibit frequency-dependent inhibition. The present data demonstrate that A-887826 is a structurally novel and potent Na(v)1.8 blocker that inhibits rat DRG TTX-R currents in a voltage-, but not frequency-dependent fashion. The ability of this structurally novel Na(v)1.8 blocker to effectively reduce tactile allodynia in neuropathic rats further supports the role of Na(v)1.8 sodium channels in pathological pain states. PMID:20566409

  12. Hydrogen sulfide-induced enhancement of gastric fundus smooth muscle tone is mediated by voltage-dependent potassium and calcium channels in mice

    PubMed Central

    Meng, Xiang-Min; Huang, Xu; Zhang, Chun-Mei; Liu, Dong-Hai; Lu, Hong-Li; Kim, Young-chul; Xu, Wen-Xie

    2015-01-01

    AIM: To investigate the effect of hydrogen sulfide (H2S) on smooth muscle motility in the gastric fundus. METHODS: The expression of cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) in cultured smooth muscle cells from the gastric fundus was examined by the immunocytochemistry technique. The tension of the gastric fundus smooth muscle was recorded by an isometric force transducer under the condition of isometric contraction with each end of the smooth muscle strip tied with a silk thread. Intracellular recording was used to identify whether hydrogen sulfide affects the resting membrane potential of the gastric fundus in vitro. Cells were freshly separated from the gastric fundus of mice using a variety of enzyme digestion methods and whole-cell patch-clamp technique was used to find the effects of hydrogen sulfide on voltage-dependent potassium channel and calcium channel. Calcium imaging with fura-3AM loading was used to investigate the mechanism by which hydrogen sulfide regulates gastric fundus motility in cultured smooth muscle cells. RESULTS: We found that both CBS and CSE were expressed in the cultured smooth muscle cells from the gastric fundus and that H2S increased the smooth muscle tension of the gastric fundus in mice at low concentrations. In addition, nicardipine and aminooxyacetic acid (AOAA), a CBS inhibitor, reduced the tension, whereas Nω-nitro-L-arginine methyl ester, a nonspecific nitric oxide synthase, increased the tension. The AOAA-induced relaxation was significantly recovered by H2S, and the NaHS-induced increase in tonic contraction was blocked by 5 mmol/L 4-aminopyridine and 1 μmol/L nicardipine. NaHS significantly depolarized the membrane potential and inhibited the voltage-dependent potassium currents. Moreover, NaHS increased L-type Ca2+ currents and caused an elevation in intracellular calcium ([Ca2+]i). CONCLUSION: These findings suggest that H2S may be an excitatory modulator in the gastric fundus in mice. The

  13. Calmodulin kinase II is involved in voltage-dependent facilitation of the L-type Cav1.2 calcium channel: Identification of the phosphorylation sites.

    PubMed

    Lee, Tae-Seong; Karl, Rosi; Moosmang, Sven; Lenhardt, Peter; Klugbauer, Norbert; Hofmann, Franz; Kleppisch, Thomas; Welling, Andrea

    2006-09-01

    Calcium-dependent facilitation of L-type calcium channels has been reported to depend on the function of calmodulin kinase II. In contrast, the mechanism for voltage-dependent facilitation is not clear. In HEK 293 cells expressing Ca(v)1.2, Ca(v)beta2a, and calmodulin kinase II, the calcium current measured at +30 mV was facilitated up to 1.5-fold by a 200-ms-long prepulse to +160 mV. This voltage-dependent facilitation was prevented by the calmodulin kinase II inhibitors KN93 and the autocamtide-2-related peptide. In cells expressing the Ca(v)1.2 mutation I1649E, a residue critical for the binding of Ca2+-bound calmodulin, facilitation was also abolished. Calmodulin kinase II was coimmunoprecipitated with the Ca(v)1.2 channel from murine heart and HEK 293 cells expressing Ca(v)1.2 and calmodulinkinase II. The precipitated Ca(v)1.2 channel was phosphorylated in the presence of calmodulin and Ca2+. Fifteen putative calmodulin kinase II phosphorylation sites were identified mostly in the carboxyl-terminal tail of Ca(v)1.2. Neither truncation at amino acid 1728 nor changing the II-III loop serines 808 and 888 to alanines affected facilitation of the calcium current. In contrast, facilitation was decreased by the single mutations S1512A and S1570A and abolished by the double mutation S1512A/S1570A. These serines flank the carboxyl-terminal EF-hand motif. Immunoprecipitation of calmodulin kinase II with the Ca(v)1.2 channel was not affected by the mutation S1512A/S1570A. The phosphorylation of the Ca(v)1.2 protein was strongly decreased in the S1512A/S1570A double mutant. These results suggest that voltage-dependent facilitation of the Ca(v)1.2 channel depends on the phosphorylation of Ser1512/Ser1570 by calmodulin kinase II. PMID:16820363

  14. Precocene II, a Trichothecene Production Inhibitor, Binds to Voltage-Dependent Anion Channel and Increases the Superoxide Level in Mitochondria of Fusarium graminearum.

    PubMed

    Furukawa, Tomohiro; Sakamoto, Naoko; Suzuki, Michio; Kimura, Makoto; Nagasawa, Hiromichi; Sakuda, Shohei

    2015-01-01

    Precocene II, a constituent of essential oils, shows antijuvenile hormone activity in insects and inhibits trichothecene production in fungi. We investigated the molecular mechanism by which precocene II inhibits trichothecene production in Fusarium graminearum, the main causal agent of Fusarium head blight and trichothecene contamination in grains. Voltage-dependent anion channel (VDAC), a mitochondrial outer membrane protein, was identified as the precocene II-binding protein by an affinity magnetic bead method. Precocene II increased the superoxide level in mitochondria as well as the amount of oxidized mitochondrial proteins. Ascorbic acid, glutathione, and α-tocopherol promoted trichothecene production by the fungus. These antioxidants compensated for the inhibitory activity of precocene II on trichothecene production. These results suggest that the binding of precocene II to VDAC may cause high superoxide levels in mitochondria, which leads to stopping of trichothecene production. PMID:26248339

  15. Physics-Based Compact Model for CIGS and CdTe Solar Cells: From Voltage-Dependent Carrier Collection to Light-Enhanced Reverse Breakdown: Preprint

    SciTech Connect

    Sun, Xingshu; Alam, Muhammad Ashraful; Raguse, John; Garris, Rebekah; Deline, Chris; Silverman, Timothy

    2015-10-15

    In this paper, we develop a physics-based compact model for copper indium gallium diselenide (CIGS) and cadmium telluride (CdTe) heterojunction solar cells that attributes the failure of superposition to voltage-dependent carrier collection in the absorber layer, and interprets light-enhanced reverse breakdown as a consequence of tunneling-assisted Poole-Frenkel conduction. The temperature dependence of the model is validated against both simulation and experimental data for the entire range of bias conditions. The model can be used to characterize device parameters, optimize new designs, and most importantly, predict performance and reliability of solar panels including the effects of self-heating and reverse breakdown due to partial-shading degradation.

  16. Noradrenaline activates a calcium-activated chloride conductance and increases the voltage-dependent calcium current in cultured single cells of rat portal vein.

    PubMed

    Pacaud, P; Loirand, G; Mironneau, C; Mironneau, J

    1989-05-01

    1. Membrane responses were recorded by a patch pipette technique in cultured cells isolated from rat portal vein. Using the whole-cell mode, pressure ejections of noradrenaline evoked depolarization (current clamp) and inward current (voltage clamp) at membrane potentials of -60 to -70 mV. The noradrenaline-induced response was reversibly blocked by prazosin indicating that the response was mediated by alpha 1-adrenoceptors. 2. The ionic mechanism of the noradrenaline-induced inward current was investigated in potassium-free caesium-containing solutions. Alteration of the chloride equilibrium potential produced similar changes in the reversal potential of the noradrenaline-induced current, indicating that noradrenaline opened chloride-selective channels. There was no evidence implicating sodium or calcium as the charge-carrying ion. 3. Caffeine applied in the bathing solution also induced a transient increase in chloride conductance but the noradrenaline-induced response was lost after application of caffeine. This is interpreted to mean that the increase in chloride conductance induced by noradrenaline and caffeine can occur as a consequence of a rise in intracellular calcium concentration depending on release of calcium from the same intracellular stores. 4. In the presence of caffeine, noradrenaline increased both the voltage-dependent calcium and chloride membrane conductances during application of repetitive depolarizing pulses. It is concluded that in isolated cells of the rat portal vein the depolarization in response to noradrenaline is mediated by an increase in chloride conductance depending on both the calcium release from intracellular stores and the increase of the voltage-dependent calcium current. PMID:2470458

  17. Voltage-Dependent Rhythmogenic Property of Respiratory Pre-Bötzinger Complex Glutamatergic, Dbx1-Derived, and Somatostatin-Expressing Neuron Populations Revealed by Graded Optogenetic Inhibition123

    PubMed Central

    Koizumi, Hidehiko; Mosher, Bryan; Tariq, Mohammad F.; Zhang, Ruli

    2016-01-01

    Abstract The rhythm of breathing in mammals, originating within the brainstem pre-Bötzinger complex (pre-BötC), is presumed to be generated by glutamatergic neurons, but this has not been directly demonstrated. Additionally, developmental expression of the transcription factor Dbx1 or expression of the neuropeptide somatostatin (Sst), has been proposed as a marker for the rhythmogenic pre-BötC glutamatergic neurons, but it is unknown whether these other two phenotypically defined neuronal populations are functionally equivalent to glutamatergic neurons with regard to rhythm generation. To address these problems, we comparatively investigated, by optogenetic approaches, the roles of pre-BötC glutamatergic, Dbx1-derived, and Sst-expressing neurons in respiratory rhythm generation in neonatal transgenic mouse medullary slices in vitro and also more intact adult perfused brainstem-spinal cord preparations in situ. We established three different triple-transgenic mouse lines with Cre-driven Archaerhodopsin-3 (Arch) expression selectively in glutamatergic, Dbx1-derived, or Sst-expressing neurons for targeted photoinhibition. In each line, we identified subpopulations of rhythmically active, Arch-expressing pre-BötC inspiratory neurons by whole-cell recordings in medullary slice preparations in vitro, and established that Arch-mediated hyperpolarization of these inspiratory neurons was laser power dependent with equal efficacy. By site- and population-specific graded photoinhibition, we then demonstrated that inspiratory frequency was reduced by each population with the same neuronal voltage-dependent frequency control mechanism in each state of the respiratory network examined. We infer that enough of the rhythmogenic pre-BötC glutamatergic neurons also have the Dbx1 and Sst expression phenotypes, and thus all three phenotypes share the same voltage-dependent frequency control property. PMID:27275007

  18. The class III anti-arrhythmic agent, amiodarone, inhibits voltage-dependent K(+) channels in rabbit coronary arterial smooth muscle cells.

    PubMed

    Li, Hongliang; Kim, Han Sol; Kim, Hye Won; Shin, Sung Eun; Jung, Won-Kyo; Ha, Kwon-Soo; Han, Eun-Taek; Hong, Seok-Ho; Firth, Amy L; Bae, Young Min; Choi, Il-Whan; Park, Won Sun

    2016-07-01

    We examined the inhibitory effect of amiodarone, a class III anti-arrhythmic agent, on voltage-dependent K(+) (Kv) currents in freshly isolated rabbit coronary arterial smooth muscle cells, using a whole-cell patch clamp technique. Amiodarone inhibited Kv currents in a concentration-dependent manner, with a half-maximal inhibitory concentration (IC50) value of 3.9 ± 1.44 μM and a Hill coefficient of 0.45 ± 0.14. Amiodarone did not have a significant effect on the steady-state activation of Kv channels, but shifted the inactivation current toward a more negative potential. Application of consecutive pulses progressively augmented the amiodarone-induced Kv channel inhibition. Another class III anti-arrhythmic agent, dofetilide, did not inhibit the Kv current or change the inhibitory effect of amiodarone on Kv channels. Therefore, these results strongly suggest that amiodarone inhibits Kv currents in a concentration- and state-dependent manner.

  19. REST levels affect the functional expression of voltage dependent calcium channels and the migratory activity in immortalized GnRH neurons.

    PubMed

    Antoniotti, Susanna; Ruffinatti, Federico Alessandro; Torriano, Simona; Luganini, Anna; D'Alessandro, Rosalba; Lovisolo, Davide

    2016-08-26

    The repressor element-1 silencing transcription factor (REST) has emerged as a key controller of neuronal differentiation and has been shown to play a critical role in the expression of the neuronal phenotype; however, much has still to be learned about its role at specific developmental stages and about the functional targets affected. Among these targets, calcium signaling mechanisms are critically dependent on the developmental stage and their full expression is a hallmark of the mature, functional neuron. We have analyzed the role played by REST in GN11 cells, an immortalized cell line derived from gonadotropin hormone releasing hormone (GnRH) neurons at an early developmental stage, electrically non-excitable and with a strong migratory activity. We show for the first time that functional voltage-dependent calcium channels are expressed in wild type GN11 cells; down-regulation of REST by a silencing approach shifts these cells towards a more differentiated phenotype, increasing the functional expression of P/Q-type channels and reducing their migratory potential. PMID:27349310

  20. Restricted ADP movement in cardiomyocytes: Cytosolic diffusion obstacles are complemented with a small number of open mitochondrial voltage-dependent anion channels.

    PubMed

    Simson, Päivo; Jepihhina, Natalja; Laasmaa, Martin; Peterson, Pearu; Birkedal, Rikke; Vendelin, Marko

    2016-08-01

    Adequate intracellular energy transfer is crucial for proper cardiac function. In energy starved failing hearts, partial restoration of energy transfer can rescue mechanical performance. There are two types of diffusion obstacles that interfere with energy transfer from mitochondria to ATPases: mitochondrial outer membrane (MOM) with voltage-dependent anion channel (VDAC) permeable to small hydrophilic molecules and cytoplasmatic diffusion barriers grouping ATP-producers and -consumers. So far, there is no method developed to clearly distinguish the contributions of cytoplasmatic barriers and MOM to the overall diffusion restriction. Furthermore, the number of open VDACs in vivo remains unknown. The aim of this work was to establish the partitioning of intracellular diffusion obstacles in cardiomyocytes. We studied the response of mitochondrial oxidative phosphorylation of permeabilized rat cardiomyocytes to changes in extracellular ADP by recording 3D image stacks of NADH autofluorescence. Using cell-specific mathematical models, we determined the permeability of MOM and cytoplasmatic barriers. We found that only ~2% of VDACs are accessible to cytosolic ADP and cytoplasmatic diffusion barriers reduce the apparent diffusion coefficient by 6-10×. In cardiomyocytes, diffusion barriers in the cytoplasm and by the MOM restrict ADP/ATP diffusion to similar extents suggesting a major role of both barriers in energy transfer and other intracellular processes. PMID:27261153

  1. Differential rescue of spatial memory deficits in aged rats by L-type voltage-dependent calcium channel and ryanodine receptor antagonism.

    PubMed

    Hopp, S C; D'Angelo, H M; Royer, S E; Kaercher, R M; Adzovic, L; Wenk, G L

    2014-11-01

    Age-associated memory impairments may result as a consequence of neuroinflammatory induction of intracellular calcium (Ca(+2)) dysregulation. Altered L-type voltage-dependent calcium channel (L-VDCC) and ryanodine receptor (RyR) activity may underlie age-associated learning and memory impairments. Various neuroinflammatory markers are associated with increased activity of both L-VDCCs and RyRs, and increased neuroinflammation is associated with normal aging. In vitro, pharmacological blockade of L-VDCCs and RyRs has been shown to be anti-inflammatory. Here, we examined whether pharmacological blockade of L-VDCCs or RyRs with the drugs nimodipine and dantrolene, respectively, could improve spatial memory and reduce age-associated increases in microglia activation. Dantrolene and nimodipine differentially attenuated age-associated spatial memory deficits but were not anti-inflammatory in vivo. Furthermore, RyR gene expression was inversely correlated with spatial memory, highlighting the central role of Ca(+2) dysregulation in age-associated memory deficits.

  2. Receptor for catecholamines responding to catechol which potentiates voltage-dependent calcium current in single cells from guinea-pig taenia caeci.

    PubMed Central

    Muraki, K.; Bolton, T. B.; Imaizumi, Y.; Watanabe, M.

    1994-01-01

    1. Single isolated cells were obtained from the taenia of the guinea-pig's caecum by enzymic digestion and held under voltage clamp. The effects of various catecholamines, sympathomimetics and related compounds were tested for their ability to potentiate the voltage-dependent calcium current (ICa) evoked in these cells by a depolarizing step. 2. ICa was potentiated by up to 60% by isoprenaline, adrenaline, and noradrenaline which were equipotent. The EC50 for isoprenaline was about 40 nM. 3. The racemic mixtures of the optical isomers of isoprenaline, adrenaline, and noradrenaline, and (+)-isoprenaline, were equipotent with the (-)-isomers of these drugs. Dopamine, L-dopa, and catechol were equipotent with these catecholamines. 4. Removal or substitution of one or more of the hydroxy groups of the catechol moiety, as in phenylephrine, salbutamol, procaterol, methoxamine, terbutaline, BRL 37344, ICI 215001 or tyramine substantially reduced efficacy and/or potency. 5. The adrenoceptor blockers propranolol, phentolamine, dihydroergotamine, atenolol, CGP 20712A and ICI 118551, or the dopamine receptor blockers, haloperidol or flupenthixol, did not block the potentiating action of catechol or the catecholamines. 6. The receptor activated by catecholamines to increase ICa we suggest should be called a C-receptor in view of its sensitivity to catechol. It may arise by enzymic modification of a conventional adrenoceptor but its transduction also involves a novel mechanism which might indicate that it is present in the muscle cells before enzyme treatment. PMID:8032602

  3. Oxaliplatin administration increases expression of the voltage-dependent calcium channel α2δ-1 subunit in the rat spinal cord.

    PubMed

    Yamamoto, Ken; Tsuboi, Mayuko; Kambe, Toshie; Abe, Kenji; Nakatani, Yoshihiko; Kawakami, Kazuyoshi; Utsunomiya, Iku; Taguchi, Kyoji

    2016-02-01

    Oxaliplatin is a chemotherapeutic agent that is effective against various types of cancer including colorectal cancer. Acute cold hyperalgesia is a serious side effect of oxaliplatin treatment. Although the therapeutic drug pregabalin is beneficial for preventing peripheral neuropathic pain by targeting the voltage-dependent calcium channel α2δ-1 (Cavα2δ-1) subunit, the effect of oxaliplatin-induced acute cold hypersensitivity is uncertain. To analyze the contribution of the Cavα2δ-1 subunit to the development of oxaliplatin-induced acute cold hypersensitivity, Cavα2δ-1 subunit expression in the rat spinal cord was analyzed after oxaliplatin treatment. Behavioral assessment using the acetone spray test showed that 6 mg/kg oxaliplatin-induced cold hypersensitivity 2 and 4 days later. Oxaliplatin-induced acute cold hypersensitivity 4 days after treatment was significantly inhibited by pregabalin (50 mg/kg, p.o.). Oxaliplatin (6 mg/kg, i.p.) treatment increased the expression level of Cavα2δ-1 subunit mRNA and protein in the spinal cord 2 and 4 days after treatment. Immunohistochemistry showed that oxaliplatin increased Cavα2δ-1 subunit protein expression in superficial layers of the spinal dorsal horn 2 and 4 days after treatment. These results suggest that oxaliplatin treatment increases Cavα2δ-1 subunit expression in the superficial layers of the spinal cord and may contribute to functional peripheral acute cold hypersensitivity.

  4. Stereoselectivity of butylidenephthalide on non-adrenergic prejunctional voltage-dependent Ca(2+) channels in prostatic portion of rat vas deferens.

    PubMed

    Shih, Chung-Hung; Chen, Chi-Ming; Ko, Wun-Chang

    2016-09-01

    The naturally occurring and synthetic butylinenephthalide (Bdph) has two geometric isomers. Z- and E-Bdph were reported to have geometric stereoselectivity for voltage-dependent calcium channels (VDCCs) in guinea-pig ileum. The aim of this study was to investigate whether the binding of Z- and E-Bdph on prejunctional VDCCs of rat vas deferens (RVD) is stereoselective. The twitch responses to electrical field stimulation (EFS, supramaximal voltage, 1 ms, 0.2Hz) were recorded on a polygraph. Z- and E-Bdph concentration-dependently inhibited the twitch responses to EFS in full tissue, prostatic portion and epididymal portion of RVD. The pIC50 value of Z-Bdph was greater than that of E-Bdph in the electrically stimulated prostatic portion of RVD, suggesting that the binding of Bdph on the non-adrenergic prejunctional VDCCs of cell membrane is stereoselective. In the prostatic portion, exogenous Ca(2+) only partially reversed the twitch inhibition by Z-Bdph, but effectively reversed those by Ca(2+) channel blockers, such as verapamil, diltiazem and aspaminol, suggesting that the action mechanisms may be different from those of Ca(2+) channel blockers. K(+) channel blockers, such as tetraethylammonium (TEA) and 4-aminopyridine (4-AP), may prolong duration of action potential to allow greater Ca(2+) entry and induced more release of transmitters. Therefore both blockers via their prejunctional actions reversed the twitch inhibition induced by Z-Bdph in all preparations of RVD by a non-specific antagonism. PMID:27238973

  5. Cisapride, a selective serotonin 5-HT4-receptor agonist, inhibits voltage-dependent K(+) channels in rabbit coronary arterial smooth muscle cells.

    PubMed

    Kim, Hye Won; Li, Hongliang; Kim, Han Sol; Shin, Sung Eun; Jung, Won-Kyo; Ha, Kwon-Soo; Han, Eun-Taek; Hong, Seok-Ho; Choi, Il-Whan; Park, Won Sun

    2016-09-23

    We investigated the effect of cisapride, a selective serotonin 5-HT4-receptor agonist, on voltage-dependent K(+) (Kv) channels using freshly isolated smooth muscle cells from the coronary arteries of rabbits. The amplitude of Kv currents was reduced by cisapride in a concentration-dependent manner, with an IC50 value of 6.77 ± 6.01 μM and a Hill coefficient of 0.51 ± 0.18. The application of cisapride shifted the steady-state inactivation curve toward a more negative potential, but had no significant effect on the steady-state activation curve. This suggested that cisapride inhibited the Kv channel in a closed state by changing the voltage sensitivity of Kv channels. The application of another selective serotonin 5-HT4-receptor agonist, prucalopride, did not affect the basal Kv current and did not alter the inhibitory effect of cisapride on Kv channels. From these results, we concluded that cisapride inhibited vascular Kv current in a concentration-dependent manner by shifting the steady-state inactivation curve, independent of its own function as a selective serotonin 5-HT4-receptor agonist. PMID:27569285

  6. Identification of mud crab reovirus VP12 and its interaction with the voltage-dependent anion-selective channel protein of mud crab Scylla paramamosain.

    PubMed

    Xu, Hai-Dong; Su, Hong-Jun; Zou, Wei-Bin; Liu, Shan-Shan; Yan, Wen-Rui; Wang, Qian-Qian; Yuan, Li-Li; Chan, Siuming Francis; Yu, Xiao-Qiang; He, Jian-Guo; Weng, Shao-Ping

    2015-05-01

    Mud crab reovirus (MCRV) is the causative agent of a severe disease in cultured mud crab (Scylla paramamosain), which has caused huge economic losses in China. MCRV is a double-stranded RNA virus with 12 genomic segments. In this paper, SDS-PAGE, mass spectrometry and Western blot analyses revealed that the VP12 protein encoded by S12 gene is a structural protein of MCRV. Immune electron microscopy assay indicated that MCRV VP12 is a component of MCRV outer shell capsid. Yeast two hybrid cDNA library of mud crab was constructed and mud crab voltage-dependent anion-selective channel (mcVDAC) was obtained by MCRV VP12 screening. The full length of mcVDAC was 1180 bp with an open reading frame (ORF) of 849 bp encoding a 282 amino acid protein. The mcVDAC had a constitutive expression pattern in different tissues of mud crab. The interaction between MCRV VP12 and mcVDAC was determined by co-immunoprecipitation assay. The results of this study have provided an insight on the mechanisms of MCRV infection and the interactions between the virus and mud crab.

  7. Forgetting of long-term memory requires activation of NMDA receptors, L-type voltage-dependent Ca2+ channels, and calcineurin

    PubMed Central

    Sachser, Ricardo Marcelo; Santana, Fabiana; Crestani, Ana Paula; Lunardi, Paula; Pedraza, Lizeth Katherine; Quillfeldt, Jorge Alberto; Hardt, Oliver; de Oliveira Alvares, Lucas

    2016-01-01

    In the past decades, the cellular and molecular mechanisms underlying memory consolidation, reconsolidation, and extinction have been well characterized. However, the neurobiological underpinnings of forgetting processes remain to be elucidated. Here we used behavioral, pharmacological and electrophysiological approaches to explore mechanisms controlling forgetting. We found that post-acquisition chronic inhibition of the N-methyl-D-aspartate receptor (NMDAR), L-type voltage-dependent Ca2+ channel (LVDCC), and protein phosphatase calcineurin (CaN), maintains long-term object location memory that otherwise would have been forgotten. We further show that NMDAR activation is necessary to induce forgetting of object recognition memory. Studying the role of NMDAR activation in the decay of the early phase of long-term potentiation (E-LTP) in the hippocampus, we found that ifenprodil infused 30 min after LTP induction in vivo blocks the decay of CA1-evoked postsynaptic plasticity, suggesting that GluN2B-containing NMDARs activation are critical to promote LTP decay. Taken together, these findings indicate that a well-regulated forgetting process, initiated by Ca2+ influx through LVDCCs and GluN2B-NMDARs followed by CaN activation, controls the maintenance of hippocampal LTP and long-term memories over time. PMID:26947131

  8. Distinct roles of L- and T-type voltage-dependent Ca2+ channels in regulation of lymphatic vessel contractile activity.

    PubMed

    Lee, Stewart; Roizes, Simon; von der Weid, Pierre-Yves

    2014-12-15

    Lymph drainage maintains tissue fluid homeostasis and facilitates immune response. It is promoted by phasic contractions of collecting lymphatic vessels through which lymph is propelled back into the blood circulation. This rhythmic contractile activity (i.e. lymphatic pumping) increases in rate with increase in luminal pressure and relies on activation of nifedipine-sensitive voltage-dependent Ca(2+) channels (VDCCs). Despite their importance, these channels have not been characterized in lymphatic vessels. We used pressure- and wire-myography as well as intracellular microelectrode electrophysiology to characterize the pharmacological and electrophysiological properties of L-type and T-type VDCCs in rat mesenteric lymphatic vessels and evaluated their particular role in the regulation of lymphatic pumping by stretch. We complemented our study with PCR and confocal immunofluorescence imaging to investigate the expression and localization of these channels in lymphatic vessels. Our data suggest a delineating role of VDCCs in stretch-induced lymphatic vessel contractions, as the stretch-induced increase in force of lymphatic vessel contractions was significantly attenuated in the presence of L-type VDCC blockers nifedipine and diltiazem, while the stretch-induced increase in contraction frequency was significantly decreased by the T-type VDCC blockers mibefradil and nickel. The latter effect was correlated with a hyperpolarization. We propose that activation of T-type VDCCs depolarizes membrane potential, regulating the frequency of lymphatic contractions via opening of L-type VDCCs, which drive the strength of contractions.

  9. Modeling and measurement of vesicle pools at the cone ribbon synapse: Changes in release probability are solely responsible for voltage-dependent changes in release.

    PubMed

    Thoreson, Wallace B; Van Hook, Matthew J; Parmelee, Caitlyn; Curto, Carina

    2016-01-01

    Postsynaptic responses are a product of quantal amplitude (Q), size of the releasable vesicle pool (N), and release probability (P). Voltage-dependent changes in presynaptic Ca(2+) entry alter postsynaptic responses primarily by changing P but have also been shown to influence N. With simultaneous whole cell recordings from cone photoreceptors and horizontal cells in tiger salamander retinal slices, we measured N and P at cone ribbon synapses by using a train of depolarizing pulses to stimulate release and deplete the pool. We developed an analytical model that calculates the total pool size contributing to release under different stimulus conditions by taking into account the prior history of release and empirically determined properties of replenishment. The model provided a formula that calculates vesicle pool size from measurements of the initial postsynaptic response and limiting rate of release evoked by a train of pulses, the fraction of release sites available for replenishment, and the time constant for replenishment. Results of the model showed that weak and strong depolarizing stimuli evoked release with differing probabilities but the same size vesicle pool. Enhancing intraterminal Ca(2+) spread by lowering Ca(2+) buffering or applying BayK8644 did not increase PSCs evoked with strong test steps, showing there is a fixed upper limit to pool size. Together, these results suggest that light-evoked changes in cone membrane potential alter synaptic release solely by changing release probability. PMID:26541100

  10. Echinacoside Inhibits Glutamate Release by Suppressing Voltage-Dependent Ca2+ Entry and Protein Kinase C in Rat Cerebrocortical Nerve Terminals

    PubMed Central

    Lu, Cheng Wei; Lin, Tzu Yu; Huang, Shu Kuei; Wang, Su Jane

    2016-01-01

    The glutamatergic system may be involved in the effects of neuroprotectant therapies. Echinacoside, a phenylethanoid glycoside extracted from the medicinal Chinese herb Herba Cistanche, has neuroprotective effects. This study investigated the effects of echinacoside on 4-aminopyridine-evoked glutamate release in rat cerebrocortical nerve terminals (synaptosomes). Echinacoside inhibited Ca2+-dependent, but not Ca2+-independent, 4-aminopyridine-evoked glutamate release in a concentration-dependent manner. Echinacoside also reduced the 4-aminopyridine-evoked increase in cytoplasmic free Ca2+ concentration but did not alter the synaptosomal membrane potential. The inhibitory effect of echinacoside on 4-aminopyridine-evoked glutamate release was prevented by ω-conotoxin MVIIC, a wide-spectrum blocker of Cav2.2 (N-type) and Cav2.1 (P/Q-type) channels, but was insensitive to the intracellular Ca2+ release-inhibitors dantrolene and 7-chloro-5-(2-chloropheny)-1,5-dihydro-4,1-benzothiazepin-2(3H)-one (CGP37157). Furthermore, echinacoside decreased the 4-aminopyridine-induced phosphorylation of protein kinase C, and protein kinase C inhibitors abolished the effect of echinacoside on glutamate release. According to these results, we suggest that the inhibitory effect of echinacoside on evoked glutamate release is associated with reduced voltage-dependent Ca2+ entry and subsequent suppression of protein kinase C activity. PMID:27347934

  11. L-Type Voltage-Dependent Calcium Channel Currents of Cerebral Arterial Smooth Muscle Cells are Increased by 2-Week Hindlimb Unweighting in Rats

    NASA Astrophysics Data System (ADS)

    Tang, Hao; Xue, Jun-Hui; Bai, Yun-Gang; Xie, Man-Jiang; Bao, Jun-Xiang; Ma, Jin

    2008-06-01

    To investigate alterations of L-type voltage-dependent calcium channel (CaL) in cerebral vascular smooth muscle cells isolated from rats subjected to a two-week simulated weightlessness, and influence of Bay K 8644 (an agonist of CaL) to the channel currents. Tail-suspended rat model was used to simulate the effects of microgravity. Whole-cell patch-clamp technique was used to record CaL currents before and after Bay K 8644 treatment, with intracellular Ca2+ concentration maintained physiological level. The corresponding parameters such as steady state activation and inactivation curves were also recorded. Whole-cell CaL current densities increased obviously, and sensitivity of CaL to Bay K 8644 also increased in cerebral vascular smooth muscle cells from suspension group. But membrane capacitance (Cm), access resistance (Ra), and other parameters of CaL such as steady state activation / inactivation curves have no significant changes compared with those of control group. These results suggest that enhanced CaL function of cerebrovascular smooth muscle cells induced by simulated microgravity may be one of the electrophysiological mechanisms that mediate enhanced vasoreactivity of cerebrovascular smooth muscle cells during adaptation to simulated weightlessness in rats.

  12. Structure and orientation of two voltage-dependent anion-selective channel isoforms. An attenuated total reflection fourier-transform infrared spectroscopy study.

    PubMed

    Abrecht, H; Goormaghtigh, E; Ruysschaert, J M; Homble, F

    2000-12-29

    Two VDAC (voltage-dependent anion-selective channel) isoforms were purified from seed cotyledons of Phaseolus vulgaris by chromatofocusing chromatography. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy was used to study the structural properties of the two isoforms reconstituted in a mixture of asolectin and 5% stigmasterol. The IR spectra of the two VDAC isoforms were highly similar indicating 50 to 53% anti-parallel beta-sheet. The orientation of the beta-strands relative to the barrel axis was calculated from the experimentally obtained dichroic ratios of the amide I beta-sheet component and the amide II band. Comparing the IR spectra of the reconstituted VDAC isoforms with the IR spectra of the bacterial porin OmpF, for which a high resolution structure is available, provided evidence for a general structural organization of the VDAC isoforms similar to that of bacterial porins. Hydrogen-deuterium exchange measurements indicated that the exchange of the amide protons occurs to a higher extent in the two VDAC isoforms than in the OmpF porin.

  13. Melatonin affects voltage-dependent calcium and potassium currents in MCF-7 cell line cultured either in growth or differentiation medium.

    PubMed

    Squecco, Roberta; Tani, Alessia; Zecchi-Orlandini, Sandra; Formigli, Lucia; Francini, Fabio

    2015-07-01

    Big efforts have been dedicated up to now to identify novel targets for cancer treatment. The peculiar biophysical profile and the atypical ionic channels activity shown by diverse types of human cancers suggest that ion channels may be possible targets in cancer therapy. Earlier studies have shown that melatonin exerts an oncostatic action on different tumors. In particular, it was shown that melatonin was able to inhibit growth/viability and proliferation, to reduce the invasiveness and metastatic properties of human estrogen-sensitive breast adenocarcinoma MCF-7 cell line cultured in growth medium, with substantial impairments of epidermal growth factor (EGF) and Notch-1-mediated signaling. The purpose of this work was to evaluate on MCF-7 cells the possible effects of melatonin on the biophysical features known to have a role in proliferation and differentiation, by using the patch-clamp technique. Our results show that in cells cultured in growth as well as in differentiation medium melatonin caused a hyperpolarization of resting membrane potential paralleled by significant changes of the inward Ca(2+) currents (T- and L-type), outward delayed rectifier K(+) currents and cell capacitance. All these effects are involved in MCF-7 growth and differentiation. These findings strongly suggest that melatonin, acting as a modulator of different voltage-dependent ion channels, might be considered a new promising tool for specifically disrupting cell viability and differentiation pathways in tumour cells with possible beneficial effects on cancer therapy. PMID:25843408

  14. A Single Talent Immunogenic Membrane Antigen and Novel Prognostic Predictor: voltage-dependent anion channel 1 (VDAC1) in Pancreatic Cancer

    PubMed Central

    Wang, Weibin; Zhang, Taiping; Zhao, Wenjing; Xu, Lai; Yang, Yu; Liao, Quan; Zhao, Yupei

    2016-01-01

    Immunogenic membrane antigens associated with multiple biological functions of human cancer cells, have significant value in molecule diagnosis and targeted therapy. Here we screened immunogenic membrane antigens in pancreatic cancer by immunobloting IgG purified from sera of 66 pancreatic cancer patients with membrane proteins separated from two-dimensional PAGE of human pancreatic cancer cell line SWl990, and identified voltage-dependent anion channel 1 (VDAC1) as one of the potential immunogenic membrane antigens. Further studies focusing on VDAC1 demonstrated that VDAC1 mRNA and protein were significantly expressed in the tested pancreatic cancer cell lines. VDAC1 silencing with RNAi significantly decreased cell growth, invasion and migration in the pancreatic cancer cell line Capan-1. Additionally, VDAC1 expression was upregulated in pancreatic cancer tissue compared with normal pancreas samples and patients with low VDAC1 expression had a significantly greater median survival compared to those with high expression (27.0 months vs. 17.8 months, P = 0.039). In multivariable analysis, VDAC1 staining was an independent prognostic factor for survival [(Hazard-Ratio) HR = 1.544, 95% CI = 0.794–3.0, P = 0.021]. These results demonstrated that VDAC1 may be a candidate immunogenic membrane antigen for pancreatic cancer, a potential independent prognostic marker, and an ideal drug target. PMID:27659305

  15. Flow- and voltage-dependent blocking effect of ethosuximide on the inward rectifier K⁺ (Kir2.1) channel.

    PubMed

    Huang, Chiung-Wei; Kuo, Chung-Chin

    2015-08-01

    Absence seizures are manifestations of abnormal thalamocortical oscillations characterized by spike-and-wave complexes in EEG. Ethosuximide (ETX) is one of the principal medications against absence seizures. We investigate the effect of ETX on the Kir2.1 channel, a prototypical inward rectifier K(+) channel possibly playing an important role in the setting of neuronal membrane potential. We demonstrate that the outward currents of Kir2.1 channels are significantly inhibited by intracellular ETX. We further show that the movement of neutral molecule ETX in the Kir2.1 channel is accompanied by ∼1.2 K(+), giving rise to the vivid voltage dependence of ETX unbinding rate. Moreover, the apparent affinity (K d ) of ETX in the channels are decreased by single-point mutations involving M183, E224, and S165, and especially by double mutations involving T141/S165, which always also disrupt the flux-coupling feature of ETX block. Molecular dynamics simulation demonstrates narrowing of the pore at ∼D172 by binding of ETX to S165 or T141. ETX block of the Kir2.1 channels may cause a modest but critical depolarization of the relevant neurons, decreasing available T-type Ca(2+) channels and consequently lessening pathological thalamocortical burst discharges.

  16. Voltage-Dependent Charge Storage in Cladded Zn0.56Cd0.44Se Quantum Dot MOS Capacitors for Multibit Memory Applications

    NASA Astrophysics Data System (ADS)

    Khan, J.; Lingalugari, M.; Al-Amoody, F.; Jain, F.

    2013-11-01

    As conventional memories approach scaling limitations, new storage methods must be utilized to increase Si yield and produce higher on-chip memory density. Use of II-VI Zn0.56Cd0.44Se quantum dots (QDs) is compatible with epitaxial gate insulators such as ZnS-ZnMgS. Voltage-dependent charging effects in cladded Zn0.56Cd0.44Se QDs are presented in a conventional metal-oxide-semiconductor capacitor structure. Charge storage capabilities in Si and ZnMgS QDs have been reported by various researchers; this work is focused on II-VI material Zn0.56Cd0.44Se QDs nucleated using photoassisted microwave plasma metalorganic chemical vapor deposition. Using capacitance-voltage hysteresis characterization, the multistep charging and discharging capabilities of the QDs at room temperature are presented. Three charging states are presented within a 10 V charging voltage range. These characteristics exemplify discrete charge states in the QD layer, perfect for multibit, QD-functionalized high-density memory applications. Multiple charge states with low operating voltage provide device characteristics that can be used for multibit storage by allowing varying charges to be stored in a QD layer based on the applied "write" voltage.

  17. Forgetting of long-term memory requires activation of NMDA receptors, L-type voltage-dependent Ca2+ channels, and calcineurin.

    PubMed

    Sachser, Ricardo Marcelo; Santana, Fabiana; Crestani, Ana Paula; Lunardi, Paula; Pedraza, Lizeth Katherine; Quillfeldt, Jorge Alberto; Hardt, Oliver; Alvares, Lucas de Oliveira

    2016-01-01

    In the past decades, the cellular and molecular mechanisms underlying memory consolidation, reconsolidation, and extinction have been well characterized. However, the neurobiological underpinnings of forgetting processes remain to be elucidated. Here we used behavioral, pharmacological and electrophysiological approaches to explore mechanisms controlling forgetting. We found that post-acquisition chronic inhibition of the N-methyl-D-aspartate receptor (NMDAR), L-type voltage-dependent Ca(2+) channel (LVDCC), and protein phosphatase calcineurin (CaN), maintains long-term object location memory that otherwise would have been forgotten. We further show that NMDAR activation is necessary to induce forgetting of object recognition memory. Studying the role of NMDAR activation in the decay of the early phase of long-term potentiation (E-LTP) in the hippocampus, we found that ifenprodil infused 30 min after LTP induction in vivo blocks the decay of CA1-evoked postsynaptic plasticity, suggesting that GluN2B-containing NMDARs activation are critical to promote LTP decay. Taken together, these findings indicate that a well-regulated forgetting process, initiated by Ca(2+) influx through LVDCCs and GluN2B-NMDARs followed by CaN activation, controls the maintenance of hippocampal LTP and long-term memories over time.

  18. Memory reconsolidation and its maintenance depend on L-voltage-dependent calcium channels and CaMKII functions regulating protein turnover in the hippocampus.

    PubMed

    Da Silva, Weber Cláudio; Cardoso, Gabriela; Bonini, Juliana Sartori; Benetti, Fernando; Izquierdo, Ivan

    2013-04-16

    Immediate postretrieval bilateral blockade of long-acting voltage-dependent calcium channels (L-VDCCs), but not of glutamatergic NMDA receptors, in the dorsal CA1 region of the hippocampus hinders retention of long-term spatial memory in the Morris water maze. Immediate postretrieval bilateral inhibition of calcium/calmodulin-dependent protein kinase (CaMK) II in dorsal CA1 does not affect retention of this task 24 h later but does hinder it 5 d later. These two distinct amnesic effects are abolished if protein degradation by proteasomes is inhibited concomitantly. These results indicate that spatial memory reconsolidation depends on the functionality of L-VDCC in dorsal CA1, that maintenance of subsequent reconsolidated memory trace depends on CaMKII, and these results also suggest that the role played by both L-VDCC and CaMKII is to promote the retrieval-dependent, synaptically localized enhancement of protein synthesis necessary to counteract a retrieval-dependent, synaptic-localized enhancement of protein degradation, which has been described as underlying the characteristic labilization of the memory trace triggered by retrieval. Thus, conceivably, L-VDCC and CaMKII would enhance activity-dependent localized protein renewal, which may account for the improvement of the long-term efficiency of the synapses responsible for the maintenance of reactivated long-term spatial memory.

  19. Pumiliotoxin B binds to a site on the voltage-dependent sodium channel that is allosterically coupled to other binding sites.

    PubMed Central

    Gusovsky, F; Rossignol, D P; McNeal, E T; Daly, J W

    1988-01-01

    Pumiliotoxin B (PTX-B), an alkaloid that has cardiotonic and myotonic activity, increases sodium influx in guinea pig cerebral cortical synaptoneurosomes. In the presence of scorpion venom (Leiurus) or purified alpha-scorpion toxin, the PTX-B-induced sodium influx is enhanced severalfold. PTX-B alone has no effect on sodium flux in N18 neuroblastoma cells but, in the presence of alpha-scorpion toxin, stimulation of sodium influx by PTX-B reaches levels comparable to that attained with the sodium channel activator veratridine. In neuroblastoma LV9 cells, a variant mutant that lacks sodium channels, neither veratridine nor PTX-B induces sodium fluxes in either the presence or absence of alpha-scorpion toxin. In synaptoneurosomes and in N18 cells, the sodium influx induced by the combination of PTX-B and alpha-scorpion toxin is inhibited by tetrodotoxin and local anesthetics. PTX-B does not interact with two of the known toxin sites on the sodium channel, as evidenced by a lack of effect on binding of [3H]saxitoxin or [3H]batrachotoxinin A benzoate to brain synaptoneurosomes. Synergistic effects on sodium influx with alpha-scorpion toxin, beta-scorpion toxin, and brevetoxin indicate that PTX-B does not interact directly with three other toxin sites on the sodium channel. Thus, PTX-B appears to activate sodium influx by interacting with yet another site on the voltage-dependent sodium channel, a site that is coupled allosterically to sites for alpha-scorpion toxin, beta-scorpion toxin, and brevetoxin. PMID:2448797

  20. Frequency and voltage dependence dielectric properties, ac electrical conductivity and electric modulus profiles in Al/Co3O4-PVA/p-Si structures

    NASA Astrophysics Data System (ADS)

    Bilkan, Çiğdem; Azizian-Kalandaragh, Yashar; Altındal, Şemsettin; Shokrani-Havigh, Roya

    2016-11-01

    In this research a simple microwave-assisted method have been used for preparation of cobalt oxide nanostructures. The as-prepared sample has been investigated by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM). On the other hand, frequency and voltage dependence of both the real and imaginary parts of dielectric constants (ε‧, ε″) and electric modulus (M‧ and M″), loss tangent (tanδ), and ac electrical conductivity (σac) values of Al/Co3O4-PVA/p-Si structures were obtained in the wide range of frequency and voltage using capacitance (C) and conductance (G/ω) data at room temperature. The values of ε‧, ε″ and tanδ were found to decrease with increasing frequency almost for each applied bias voltage, but the changes in these parameters become more effective in the depletion region at low frequencies due to the charges at surface states and their relaxation time and polarization effect. While the value of σ is almost constant at low frequency, increases almost as exponentially at high frequency which are corresponding to σdc and σac, respectively. The M‧ and M″ have low values at low frequencies region and then an increase with frequency due to short-range mobility of charge carriers. While the value of M‧ increase with increasing frequency, the value of M″ shows two peak and the peaks positions shifts to higher frequency with increasing applied voltage due to the decrease of the polarization and Nss effects with increasing frequency.

  1. Mutations associated with Dent's disease affect gating and voltage dependence of the human anion/proton exchanger ClC-5.

    PubMed

    Alekov, Alexi K

    2015-01-01

    Dent's disease is associated with impaired renal endocytosis and endosomal acidification. It is linked to mutations in the membrane chloride/proton exchanger ClC-5; however, a direct link between localization in the protein and functional phenotype of the mutants has not been established until now. Here, two Dent's disease mutations, G212A and E267A, were investigated using heterologous expression in HEK293T cells, patch-clamp measurements and confocal imaging. WT and mutant ClC-5 exhibited mixed cell membrane and vesicular distribution. Reduced ion currents were measured for both mutants and both exhibited reduced capability to support endosomal acidification. Functionally, mutation G212A was capable of mediating anion/proton antiport but dramatically shifted the activation of ClC-5 toward more depolarized potentials. The shift can be explained by impeded movements of the neighboring gating glutamate Gluext, a residue that confers major part of the voltage dependence of ClC-5 and serves as a gate at the extracellular entrance of the anion transport pathway. Cell surface abundance of E267A was reduced by ~50% but also dramatically increased gating currents were detected for this mutant and accordingly reduced probability to undergoing cycles associated with electrogenic ion transport. Structurally, the gating alternations correlate to the proximity of E267A to the proton glutamate Gluin that serves as intracellular gate in the proton transport pathway and regulates the open probability of ClC-5. Remarkably, two other mammalian isoforms, ClC-3 and ClC-4, also differ from ClC-5 in gating characteristics affected by the here investigated disease-causing mutations. This evolutionary specialization, together with the functional defects arising from mutations G212A and E267A, demonstrate that the complex gating behavior exhibited by most of the mammalian CLC transporters is an important determinant of their cellular function.

  2. IgG anti-GalNAc-GD1a antibody inhibits the voltage-dependent calcium channel currents in PC12 pheochromocytoma cells.

    PubMed

    Nakatani, Yoshihiko; Nagaoka, Takumi; Hotta, Sayako; Utsunomiya, Iku; Yoshino, Hiide; Miyatake, Tadashi; Hoshi, Keiko; Taguchi, Kyoji

    2007-03-01

    We investigated the effects of IgG anti-GalNAc-GD1a antibodies, produced by immunizing rabbits with GalNAc-GD1a, on the voltage-dependent calcium channel (VDCCs) currents in nerve growth factor (NGF)-differentiated PC12 pheochromocytoma cells. VDCCs currents in NGF-differentiated PC12 cells were recorded using the whole-cell patch-clamp technique. Immunized rabbit serum that had a high titer of anti-GalNAc-GD1a antibodies inhibited the VDCCs currents in the NGF-differentiated PC12 cells (36.0+/-9.6% reduction). The inhibitory effect of this serum was reversed to some degree within 3-4 min by washing with bath solution. Similarly, application of purified IgG from rabbit serum immunized with GalNAc-GD1a significantly inhibited the VDCCs currents in PC12 cells (30.6+/-2.5% reduction), and this inhibition was recovered by washing with bath solution. Furthermore, the inhibitory effect was also observed in the GalNAc-GD1a affinity column binding fraction (reduction of 31.1+/-9.85%), while the GalNAc-GD1a affinity column pass-through fraction attenuated the inhibitory effect on VDCCs currents. Normal rabbit serum and normal rabbit IgG did not affect the VDCCs currents in the PC12 cells. In an immunocytochemical study using fluorescence staining, the PC12 cells were stained using GalNAc-GD1a binding fraction. These results indicate that anti-GalNAc-GD1a antibodies inhibit the VDCCs currents in NGF-differentiated PC12 cells.

  3. The calmodulin inhibitor CGS 9343B inhibits voltage-dependent K{sup +} channels in rabbit coronary arterial smooth muscle cells

    SciTech Connect

    Li, Hongliang; Hong, Da Hye; Kim, Han Sol; Kim, Hye Won; Jung, Won-Kyo; Na, Sung Hun; Jung, In Duk; Park, Yeong-Min; Choi, Il-Whan; Park, Won Sun

    2015-06-15

    We investigated the effects of the calmodulin inhibitor CGS 9343B on voltage-dependent K{sup +} (Kv) channels using whole-cell patch clamp technique in freshly isolated rabbit coronary arterial smooth muscle cells. CGS 9343B inhibited Kv currents in a concentration-dependent manner, with a half-maximal inhibitory concentration (IC{sub 50}) value of 0.81 μM. The decay rate of Kv channel inactivation was accelerated by CGS 9343B. The rate constants of association and dissociation for CGS 9343B were 2.77 ± 0.04 μM{sup −1} s{sup −1} and 2.55 ± 1.50 s{sup −1}, respectively. CGS 9343B did not affect the steady-state activation curve, but shifted the inactivation curve toward to a more negative potential. Train pulses (1 or 2 Hz) application progressively increased the CGS 9343B-induced Kv channel inhibition. In addition, the inactivation recovery time constant was increased in the presence of CGS 9343B, suggesting that CGS 9343B-induced inhibition of Kv channel was use-dependent. Another calmodulin inhibitor, W-13, did not affect Kv currents, and did not change the inhibitory effect of CGS 9343B on Kv current. Our results demonstrated that CGS 9343B inhibited Kv currents in a state-, time-, and use-dependent manner, independent of calmodulin inhibition. - Highlights: • We investigated the effects of CGS 9394B on Kv channels. • CGS 9394B inhibited Kv current in a state-, time-, and use-dependent manner. • Caution is required when using CGS 9394B in vascular function studies.

  4. Modulation of voltage-dependent and inward rectifier potassium channels by 15-epi-lipoxin-A4 in activated murine macrophages: implications in innate immunity.

    PubMed

    Moreno, Cristina; Prieto, Patricia; Macías, Álvaro; Pimentel-Santillana, María; de la Cruz, Alicia; Través, Paqui G; Boscá, Lisardo; Valenzuela, Carmen

    2013-12-15

    Potassium channels modulate macrophage physiology. Blockade of voltage-dependent potassium channels (Kv) by specific antagonists decreases macrophage cytokine production and inhibits proliferation. In the presence of aspirin, acetylated cyclooxygenase-2 loses the activity required to synthesize PGs but maintains the oxygenase activity to produce 15R-HETE from arachidonate. This intermediate product is transformed via 5-LOX into epimeric lipoxins, termed 15-epi-lipoxins (15-epi-lipoxin A4 [e-LXA4]). Kv have been proposed as anti-inflammatory targets. Therefore, we studied the effects of e-LXA4 on signaling and on Kv and inward rectifier potassium channels (Kir) in mice bone marrow-derived macrophages (BMDM). Electrophysiological recordings were performed in these cells by the whole-cell patch-clamp technique. Treatment of BMDM with e-LXA4 inhibited LPS-dependent activation of NF-κB and IκB kinase β activity, protected against LPS activation-dependent apoptosis, and enhanced the accumulation of the Nrf-2 transcription factor. Moreover, treatment of LPS-stimulated BMDM with e-LXA4 resulted in a rapid decrease of Kv currents, compatible with attenuation of the inflammatory response. Long-term treatment of LPS-stimulated BMDM with e-LXA4 significantly reverted LPS effects on Kv and Kir currents. Under these conditions, e-LXA4 decreased the calcium influx versus that observed in LPS-stimulated BMDM. These effects were partially mediated via the lipoxin receptor (ALX), because they were significantly reverted by a selective ALX receptor antagonist. We provide evidence for a new mechanism by which e-LXA4 contributes to inflammation resolution, consisting of the reversion of LPS effects on Kv and Kir currents in macrophages.

  5. Mitochondria-associated endoplasmic reticulum membrane (MAM) regulates steroidogenic activity via steroidogenic acute regulatory protein (StAR)-voltage-dependent anion channel 2 (VDAC2) interaction.

    PubMed

    Prasad, Manoj; Kaur, Jasmeet; Pawlak, Kevin J; Bose, Mahuya; Whittal, Randy M; Bose, Himangshu S

    2015-01-30

    Steroid hormones are essential for carbohydrate metabolism, stress management, and reproduction and are synthesized from cholesterol in mitochondria of adrenal glands and gonads/ovaries. In acute stress or hormonal stimulation, steroidogenic acute regulatory protein (StAR) transports substrate cholesterol into the mitochondria for steroidogenesis by an unknown mechanism. Here, we report for the first time that StAR interacts with voltage-dependent anion channel 2 (VDAC2) at the mitochondria-associated endoplasmic reticulum membrane (MAM) prior to its translocation to the mitochondrial matrix. In the MAM, StAR interacts with mitochondrial proteins Tom22 and VDAC2. However, Tom22 knockdown by siRNA had no effect on pregnenolone synthesis. In the absence of VDAC2, StAR was expressed but not processed into the mitochondria as a mature 30-kDa protein. VDAC2 interacted with StAR via its C-terminal 20 amino acids and N-terminal amino acids 221-229, regulating the mitochondrial processing of StAR into the mature protein. In the absence of VDAC2, StAR could not enter the mitochondria or interact with MAM-associated proteins, and therefore steroidogenesis was inhibited. Furthermore, the N terminus was not essential for StAR activity, and the N-terminal deletion mutant continued to interact with VDAC2. The endoplasmic reticulum-targeting prolactin signal sequence did not affect StAR association with the MAM and thus its mitochondrial targeting. Therefore, VDAC2 controls StAR processing and activity, and MAM is thus a central location for initiating mitochondrial steroidogenesis.

  6. The slow and the quick anion conductance in whole guard cells: their voltage-dependent alternation, and the modulation of their activities by abscisic acid and CO2.

    PubMed

    Raschke, Klaus; Shabahang, Mahbobeh; Wolf, Rupert

    2003-08-01

    We explored the functioning of the slowly activating anion conductance, S-type or SLAC, and of the quickly activating anion conductance, R-type or QUAC, in whole guard cells of Vicia faba L.; details of QUAC activity had not previously been demonstrated in guard cells possessing their walls. The discontinuous single-electrode voltage-clamp method was used to record current responses to voltage pulses and voltage ramps as well as the free-running membrane voltage. At all voltages tested between -200 and 60 mV, SLAC activated with two components, one had a time constant similar to 7 s, the other similar to 40 s. The current-voltage relationship resembled that obtained by patch-clamp experiments. In pulse experiments and 1-s ramps, QUAC activity appeared with half-maximum activation near -50 mV and full activation above -10 mV; it inactivated with a half-time of approximately 10 s. Inactivation of QUAC at -40 mV led to the appearance of SLAC. After deactivation of SLAC at -200 mV, QUAC could be activated again. We concluded that voltage-dependent interchanges between SLAC and QUAC had occurred. Frequently, SLAC and QUAC were active simultaneously in the same cell. Abscisic acid (ABA, 20 microM) activated SLAC as well as QUAC. External Ca2+ was not required, but enhanced the activation of QUAC. Rises in the partial pressure of CO2, in the range between 0 and 700 microbar, caused rapid and reversible increases in the activity of SLAC (and outward currents of K+). QUAC also responded to CO2, however in an unpredictable manner (either by increased or by decreased activity). Oscillations in the free-running membrane voltage arose either spontaneously or after changes in CO2. They were correlated with periodic activations and inactivations of QUAC and required the simultaneous activity of an electrogenic pump.

  7. The N-Terminal Peptides of the Three Human Isoforms of the Mitochondrial Voltage-Dependent Anion Channel Have Different Helical Propensities.

    PubMed

    Guardiani, Carlo; Scorciapino, Mariano Andrea; Amodeo, Giuseppe Federico; Grdadolnik, Joze; Pappalardo, Giuseppe; De Pinto, Vito; Ceccarelli, Matteo; Casu, Mariano

    2015-09-15

    The voltage-dependent anion channel (VDAC) is the main mitochondrial porin allowing the exchange of ions and metabolites between the cytosol and the mitochondrion. In addition, VDAC was found to actively interact with proteins playing a fundamental role in the regulation of apoptosis and being of central interest in cancer research. VDAC is a large transmembrane β-barrel channel, whose N-terminal helical fragment adheres to the channel interior, partially closing the pore. This fragment is considered to play a key role in protein stability and function as well as in the interaction with apoptosis-related proteins. Three VDAC isoforms are differently expressed in higher eukaryotes, for which distinct and complementary roles are proposed. In this work, the folding propensity of their N-terminal fragments has been compared. By using multiple spectroscopic techniques, and complementing the experimental results with theoretical computer-assisted approaches, we have characterized their conformational equilibrium. Significant differences were found in the intrinsic helical propensity of the three peptides, decreasing in the following order: hVDAC2 > hVDAC3 > hVDAC1. In light of the models proposed in the literature to explain voltage gating, selectivity, and permeability, as well as interactions with functionally related proteins, our results suggest that the different chemicophysical properties of the N-terminal domain are possibly correlated to different functions for the three isoforms. The overall emerging picture is that a similar transmembrane water accessible conduit has been equipped with not identical domains, whose differences can modulate the functional roles of the three VDAC isoforms.

  8. Frequency and voltage dependent profile of dielectric properties, electric modulus and ac electrical conductivity in the PrBaCoO nanofiber capacitors

    NASA Astrophysics Data System (ADS)

    Demirezen, S.; Kaya, A.; Yerişkin, S. A.; Balbaşı, M.; Uslu, İ.

    In this study, praseodymium barium cobalt oxide nanofiber interfacial layer was sandwiched between Au and n-Si. Frequency and voltage dependence of ε‧, ε‧, tanδ, electric modulus (M‧ and M″) and σac of PrBaCoO nanofiber capacitor have been investigated by using impedance spectroscopy method. The obtained experimental results show that the values of ε‧, ε‧, tanδ, M‧, M″ and σac of the PrBaCoO nanofiber capacitor are strongly dependent on frequency of applied bias voltage. The values of ε‧, ε″ and tanδ show a steep decrease with increasing frequency for each forward bias voltage, whereas the values of σac and the electric modulus increase with increasing frequency. The high dispersion in ε‧ and ε″ values at low frequencies may be attributed to the Maxwell-Wagner and space charge polarization. The high values of ε‧ may be due to the interfacial effects within the material, PrBaCoO nanofibers interfacial layer and electron effect. The values of M‧ and M″ reach a maximum constant value corresponding to M∞ ≈ 1/ε∞ due to the relaxation process at high frequencies, but both the values of M‧ and M″ approach almost to zero at low frequencies. The changes in the dielectric and electrical properties with frequency can be also attributed to the existence of Nss and Rs of the capacitors. As a result, the change in the ε‧, ε″, tanδ, M‧, M″ and ac electric conductivity (σac) is a result of restructuring and reordering of charges at the PrBaCoO/n-Si interface under an external electric field or voltage and interface polarization.

  9. The biology of some intraerythrocytic parasites of fishes, amphibia and reptiles.

    PubMed

    Davies, A J; Johnston, M R

    2000-01-01

    Fishes, amphibia and reptiles, the ectothermic vertebrates, are hosts for a variety of intraerythrocytic parasites including protists, prokaryotes, viruses and structures of uncertain status. These parasites may experience host temperature fluctuations, host reproductive strategies, population genetics, host habitat and migratory behaviour quite unlike those of endothermic hosts. Few blood infections of fishes, amphibia and reptiles have proven pathogenicity, in contrast to the many intraerythrocytic parasites of mammals and some birds which harm their hosts. Although not given the attention afforded to intraerythrocytic parasites of endotherms, those of ectotherms have been studied for more than a century. This review reports on the diversity, general biology and phylogeny of intraerythrocytic parasites of ectotherms. The existence of taxonomic confusion is emphasized and the main taxonomic features of most of the 23 better characterized genera, particularly the kinetoplastid and apicomplexan protists, are summarized. Transmission of protistan infections of aquatic ectotherms is also discussed. Leeches can transfer sporozoties or merozoites to the vertebrate host during feeding. Dormant sporozoites of Lankesterella may permit transmission of species of this genus between vertebrates by predation. The fish haemogregarine, Haemogregarina bigemina, probably has gnathiid isopods, rather than leeches, as its definitive hosts. Hepatozoon spp. in aquatic hosts, and Progarnia of caiman, may also use invertebrate hosts other than leeches. Protistan infections of terrestrial or semi-terrestrial hosts are transmitted by a variety of arthropods, or, in some cases, leeches, contaminated paratenic hosts, or sporocysts free in water. Transfer of protists between vertebrates by predation and congenitally may also occur. The biology of the host cells of these infections, the red blood cells of ectotherm vertebrates, is summarized and compared with that of mammalian erythrocytes

  10. Splice-variant changes of the CaV3.2 T-type calcium channel mediate voltage-dependent facilitation and associate with cardiac hypertrophy and development

    PubMed Central

    David, Laurence S; Garcia, Esperanza; Cain, Stuart M; Thau, Elana M; Tyson, John R

    2010-01-01

    Low voltage-activated T-type calcium (Ca) channels contribute to the normal development of the heart and are also implicated in pathophysiological states such as cardiac hypertrophy. Functionally distinct T-type Ca channel isoforms can be generated by alternative splicing from each of three different T-type genes (CaV3.1, CaV3.2, CaV3.3), although it remains to be described whether specific splice variants are associated with developmental states and pathological conditions. We aimed to identify and functionally characterize CaV3.2 T-type Ca channel alternatively spliced variants from newborn animals and to compare with adult normotensive and spontaneously hypertensive rats (SHR). DNA sequence analysis of full-length CaV3.2 cDNA generated from newborn heart tissue identified ten major regions of alternative splicing, the more common variants of which were analyzed by quantitative real-time PCR (qRT-PCR) and also subject to functional examination by whole-cell patch clamp. The main findings are that: (1) cardiac CaV3.2 T-type Ca channels are subject to considerable alternative splicing, (2) there is preferential expression of CaV3.2(−25) splice variant channels in newborn rat heart with a developmental shift in adult heart that results in approximately equal levels of expression of both (+25) and (−25) exon variants, (3) in the adult stage of hypertensive rats there is both an increase in overall CaV3.2 expression and a shift towards expression of CaV3.2(+25) containing channels as the predominant form and (4) alternative splicing confers a variant-specific voltage-dependent facilitation of CaV3.2 channels. We conclude that CaV3.2 alternative splicing generates significant T-type Ca channel structural and functional diversity with potential implications relevant to cardiac developmental and pathophysiological states. PMID:20699644

  11. Comparative acid phosphatase distribution in the suprarenal gland of Discoglossus pictus, Xenopus laevis and Bufo bufo (Anurans, Amphibia).

    PubMed

    Manelli, H; Mastrolia, L; Arizzi, M

    1981-01-01

    Acid phosphatase activity was found to have a similar distribution in the suprarenal glands of Discoglossus pictus, Xenopus laevis and Bufo Bufo (Anurans, Amphibia) as determined by light and electron histochemical localization. The enzymatic activity is localized in the lysosomes of both the interrenal cells and the chromaffin cells. It is, moreover, positive on the granule membranes of the adrenaline cells whereas it appears only occasionally on the granule membranes of the noradrenaline cells. Some precipitates can also be seen occasionally at the level of the Golgi membranes.

  12. A new lungless caecilian (Amphibia: Gymnophiona) from Guyana.

    PubMed

    Wake, Marvalee H; Donnelly, Maureen A

    2010-03-22

    We report the discovery of a single specimen of a small, terrestrial, lungless caecilian, the second known taxon of lungless caecilians. It differs from all other caecilians in lacking open external nares, and from the large aquatic lungless species described by Nussbaum & Wilkinson (Nussbaum, R. A. & Wilkinson, M. 1995 Proc. R. Soc. Lond. B 261, 331-335) in having no significant skull modifications. All modifications are of 'soft morphology' (covered external nares and choanae, lung and pulmonary vessel loss, etc.). A new genus and species are described to accommodate this form. Aspects of its skull and visceral morphology are described and considered in terms of the possible life history and evolution of the species, and compared with those of other lungless amphibians.

  13. A new lungless caecilian (Amphibia: Gymnophiona) from Guyana

    PubMed Central

    Wake, Marvalee H.; Donnelly, Maureen A.

    2010-01-01

    We report the discovery of a single specimen of a small, terrestrial, lungless caecilian, the second known taxon of lungless caecilians. It differs from all other caecilians in lacking open external nares, and from the large aquatic lungless species described by Nussbaum & Wilkinson (Nussbaum, R. A. & Wilkinson, M. 1995 Proc. R. Soc. Lond. B 261, 331–335) in having no significant skull modifications. All modifications are of ‘soft morphology’ (covered external nares and choanae, lung and pulmonary vessel loss, etc.). A new genus and species are described to accommodate this form. Aspects of its skull and visceral morphology are described and considered in terms of the possible life history and evolution of the species, and compared with those of other lungless amphibians. PMID:19923127

  14. A new lungless caecilian (Amphibia: Gymnophiona) from Guyana.

    PubMed

    Wake, Marvalee H; Donnelly, Maureen A

    2010-03-22

    We report the discovery of a single specimen of a small, terrestrial, lungless caecilian, the second known taxon of lungless caecilians. It differs from all other caecilians in lacking open external nares, and from the large aquatic lungless species described by Nussbaum & Wilkinson (Nussbaum, R. A. & Wilkinson, M. 1995 Proc. R. Soc. Lond. B 261, 331-335) in having no significant skull modifications. All modifications are of 'soft morphology' (covered external nares and choanae, lung and pulmonary vessel loss, etc.). A new genus and species are described to accommodate this form. Aspects of its skull and visceral morphology are described and considered in terms of the possible life history and evolution of the species, and compared with those of other lungless amphibians. PMID:19923127

  15. [Enzyme histochemical study of the brain of Chthonerpeton indistinctum (Gymnophiona, Amphibia)].

    PubMed

    Welsch, U; Tan, S H

    1979-01-01

    In the brain of the Caecilian species Chthonerpeton indistinctum the following enzymes have been demonstrated by means of histochemical techniques: acid phosphatase, alpha-naphthylacetate esterase, acetylcholin esterase. Acid phosphatase occurs in the cytoplasm of the neurons in 4 different types of localization. Its activity in the ventral parts of the brain is markedly higher than in the dorsal ones. Of particularly high activity are: the motor neurons in the tegmentum, the nucleus mesencephali trigemini, individual large neurons in the marginal zone of the grey matter of the telencephalon, which seems to be a special character of the Caecilians among the Amphibia. The ependyma exhibits local differences in respect of acid phosphatase activity. alpha-Naphthylacetate esterase marks in particular the secretory neurons of the hypothalamus, the large perikarya of the nucleus mesencephali trigemini and the motor neurons of the tegmentum. In the telencephalon the alpha-naphthylacetate esterase activity corresponds to that of acid phosphatase. Acetylcholin esterase marks--with certain restrictions--cholinergic neurons. These predominate in Chthonerpeton in the caudal parts of the brain. In the telencephalon amygdala, septal area striatum and the mitral cells are of comparatively high activity. The neurosecretory neurons of the hypothalamus are particularly rich in this enzyme. As an anurans the cholinergic fasciculus retroflexus as asymmetric. The tectum opticum is of secondary simplicity and does not exhibit a clearly recognizable stratification. PMID:524986

  16. A new species of Odorrana (Amphibia: Anura: Ranidae) from Vietnam.

    PubMed

    Pham, Cuong The; Nguyen, Truong Quang; Le, Minh Duc; Bonkowski, Michael; Ziegler, Thomas

    2016-01-01

    A new species of Odorrana is described from the karst forests in northeastern Vietnam based on morphological differences and molecular divergence. Morphologically, the new species is distinguishable from its congeners on the basis of a combination of the following diagnostic characters: (1) size large (SVL 85.9-91.6 mm in males, 108.7-110.1 mm in females); (2) head longer than wide; (3) vomerine teeth present; (4) external vocal sacs absent; (5) snout short (SL/SVL 0.16-0.17); (6) tympanum large (TD/ED 0.70 in males, 0.68 in females); (7) dorsal surface of head and anterior part of body smooth, posterior part of body and flanks with small tubercles; (8) supratympanic fold present; (9) dorsolateral fold absent; (10) webbing formula I0-0II0-0III0-1/2IV1/2-0V; (11) in life, dorsum green with dark brown spots; (12) flanks greyish brown with dark brown spots; (13) throat and chest grey, underside of limbs with large dark brown spots, edged in white, forming a network. In the phylogenetic analyses, the new species is unambiguously nested within the O. andersonii group, and placed as the sister taxon to O. wuchuanensis. PMID:27394273

  17. A new species of Odorrana (Amphibia: Anura: Ranidae) from Vietnam.

    PubMed

    Pham, Cuong The; Nguyen, Truong Quang; Le, Minh Duc; Bonkowski, Michael; Ziegler, Thomas

    2016-02-26

    A new species of Odorrana is described from the karst forests in northeastern Vietnam based on morphological differences and molecular divergence. Morphologically, the new species is distinguishable from its congeners on the basis of a combination of the following diagnostic characters: (1) size large (SVL 85.9-91.6 mm in males, 108.7-110.1 mm in females); (2) head longer than wide; (3) vomerine teeth present; (4) external vocal sacs absent; (5) snout short (SL/SVL 0.16-0.17); (6) tympanum large (TD/ED 0.70 in males, 0.68 in females); (7) dorsal surface of head and anterior part of body smooth, posterior part of body and flanks with small tubercles; (8) supratympanic fold present; (9) dorsolateral fold absent; (10) webbing formula I0-0II0-0III0-1/2IV1/2-0V; (11) in life, dorsum green with dark brown spots; (12) flanks greyish brown with dark brown spots; (13) throat and chest grey, underside of limbs with large dark brown spots, edged in white, forming a network. In the phylogenetic analyses, the new species is unambiguously nested within the O. andersonii group, and placed as the sister taxon to O. wuchuanensis.

  18. mu and delta opioid agonists at low concentrations decrease voltage-dependent K+ currents in F11 neuroblastoma x DRG neuron hybrid cells via cholera toxin-sensitive receptors.

    PubMed

    Fan, S F; Shen, K F; Crain, S M

    1993-03-12

    In a previous study, we showed that microM concentrations of mu or delta opioid agonists increase voltage-dependent outward K+ currents in neuroblastoma x DRG neuron hybrid F11 cells via pertussis toxin-sensitive receptors. The present study demonstrates that much lower concentrations (fM to nM) of these opioids (DAGO and DPDPE) decreased voltage-dependent outward K+ currents during step depolarization. The opioid antagonist, naloxone (3 nM) prevented these decreases in K+ current as did the cholera toxin subunits A or B (ca. 1 nM). Furthermore, the specific mu opioid receptor antagonist, beta-funaltrexamine (5 nM) blocked the decrease by DAGO and the specific delta antagonist, naltrindole (1 nM) blocked that by DPDPE. Acute GM1 ganglioside (1 microM) treatment markedly enhanced the efficacy of opioid-induced decrease in K+ current. After treating the cells with pertussis toxin (1 microgram/ml) for 2 days or more, these opioids decreased the K+ current even when tested at concentrations as high as 1 microM. These results indicate that the decrease in K+ current elicited in F11 cells by low concentrations of mu and delta opioid agonists resembles the opioid-induced prolongation of the action potential duration and decrease in voltage-dependent K+ conductance that occur in DRG neurons in primary cultures. The F11 cell line provides therefore a valuable model system for correlative pharmacologic, electrophysiologic and biochemical analyses of Gs-coupled, GM1 ganglioside-regulated excitatory opioid receptor functions, in addition to G(i)/G(o)-coupled inhibitory receptor functions, in sensory neurons.

  19. Complete mitochondrial genome of the Seoul frog Rana chosenica (Amphibia, Ranidae): comparison of R. chosenica and R. plancyi.

    PubMed

    Ryu, Shi Hyun; Hwang, Ui Wook

    2011-06-01

    Here, we have sequenced the complete mitochondrial genome of the Seoul frog Rana chosenica (Amphibia, Ranidae), which is known as a Korean endemic species. It is listed as a vulnerable species by IUCN Red List and also an endangered species in South Korea. The complete mitochondrial genome of R. chosenica consists of 18,357 bp. Its gene arrangement pattern was identical with those of other Rana frogs. We compared the mitochondrial genome of R. chosenica with that of the Peking frog Rana plancyi that has been known closely related to R. chosenica. Nucleotide sequence similarity between the two whole mitochondrial genomes was 95.7%, and the relatively low similarity seems to indicate that the two species are distinctly separated on the species level. The information of mitochondrial genome comparison of the two species was discussed in detail.

  20. Morphology, ultrastructure and molecular characterisation of Spiroxys japonica Morishita, 1926 (Spirurida: Gnathostomatidae) from Pelophylax nigromaculatus (Hallowell) (Amphibia: Ranidae).

    PubMed

    Li, Liang; Hasegawa, Hideo; Roca, Vicente; Xu, Zhen; Guo, Yan-Ning; Sato, Akiko; Zhang, Lu-Ping

    2014-03-01

    Gnathostomatid nematodes identified morphologically as Spiroxys japonica Morishita, 1926 were collected from the dark-spotted frog Pelophylax nigromaculatus (Hallowell) (Amphibia: Ranidae) in China. Light and scanning electron microscopy were used to study the morphology of this species in detail. Previously unreported morphological features are revealed and others corrected. In addition, adult nematodes of S. japonica collected from P. nigromaculatus and Spiroxys hanzaki Hasegawa, Miyata & Doi, 1998 collected from Andrias japonicus (Temminck) (Caudata: Cryptobranchidae) in China and Japan, respectively, and the third-stage larva of S. japonica collected from Lithobates catesbeianus (Shaw) (Anura: Ranidae) in Japan, were characterised using molecular methods by sequencing and analysing ribosomal [large ribosomal DNA (18S) and internal transcribed space] and mitochondrial [cytochrome c oxidase subunit 1] target regions, respectively. The new morphological and genetic data contributes to a more accurate diagnosis of this hitherto little known nematode genus.

  1. Morphometrics of the skeleton of Dermophis mexicanus (Amphibia: Gymnophiona). Part I. The vertebrae, with comparisons to other species.

    PubMed

    Wake, M H

    1980-08-01

    Morphometric analysis of vertebral structure in caecilians (Amphibia: Gymnophiona) is presented. Ontogenetic variation in Dermophis mexicanus is analyzed through the 100+ vertebrae composing the column. Vertebral structure in adult D. mexicanus is compared with that in Ichthyophis glutinosus and Typhlonectes compressicauda. Centra of the atlas, second, tenth, 20th, and 50th vertebrae grow at allometrically different rates in D. mexicanus, though the 20th and 50th are not significantly different. Growth appears significantly slower in several dimensions of anterior and posterior vertebrae relative to midtrunk vertebrae in all three species. Mensural patterns throughout the entire column are similar in the terrestrail burrowers D. mexicanus and I. glutinosus; patterns in the aquatic T. compressicauda differ substantially from those of the burrowing species and are strongly influenced by allometry. Of the 112 D. mexicanus examined, 13.4% had vertebral anomalies, usually fusions. PMID:7452726

  2. Effects of a glyphosate-based herbicide on the development of Common toads (Bufo bufo L.; Amphibia) at different temperatures

    NASA Astrophysics Data System (ADS)

    Baier, Fabian; Gruber, Edith; Spangl, Bernhard; Zaller, Johann G.

    2016-04-01

    Herbicides based on the active ingredient glyphosate are frequently applied in agriculture, horticulture and private gardens all over the world. Recently, leaching of glyphosate or its metabolite (AMPA) into water bodies inhabited by amphibians has been reported. However, very little is known about non-target effects of these herbicides on amphibians and even less is known to what extent different temperatures might alter these effects. Using climate chambers, we investigated the effects of the glyphosate-based herbicide Roundup PowerFlex® (480 g L-1 glyphosate, formulated as 588 g L-1 potassium salt) on the larval development of Common toads (Bufo bufo L.; Amphibia: Anura) under different temperature regimes (15°C vs. 20°C). We established five herbicide concentrations: 0, 1.5, 3, 4 mg acid equivalent L-1 and a 4 mg a.e. L-1 pulse treatment (totally three applications of 1.5, 1.5 and another 1 mg a.e. L-1) at each temperature in a full-factorial design. Each treatment combination was replicated five times, the experiment ran for 24 days. Results showed a highly significant effect of temperature on body length and body width but no effect of herbicide concentration on these growth parameters. Moreover, highly significant interactions between herbicide and temperature on body length and body width were observed suggesting that herbicides had different effects on different temperatures. In conclusion, although Roundup PowerFlex® at the tested concentrations appeared to have no acute toxicity to larvae of Common toads, the observed effects on tadpole morphology will potentially affect competitive interactions in spawning ponds of amphibia. Our findings of herbicide x temperature interactions might become more prevalent when human-induced climate change will lead to more extreme temperatures.

  3. Bias voltage dependence of tunneling anisotropic magnetoresistance in magnetic tunnel junctions with MgO and Al2O3 tunnel barriers.

    PubMed

    Gao, Li; Jiang, Xin; Yang, See-Hun; Burton, J D; Tsymbal, Evgeny Y; Parkin, Stuart S P

    2007-11-30

    Tunneling anisotropic magnetoresistance (TAMR) is observed in tunnel junctions with transition metal electrodes as the moments are rotated from in-plane to out-of-plane in sufficiently large magnetic fields that the moments are nearly parallel to one another. A complex angular dependence of the tunneling resistance is found with twofold and fourfold components that vary strongly with bias voltage. Distinctly different TAMR behaviors are obtained for devices formed with highly textured crystalline MgO(001) and amorphous Al2O3 tunnel barriers. A tight-binding model shows that a fourfold angular dependence can be explained by the presence of an interface resonant state that affects the transmission of the contributing tunneling states through a spin-orbit interaction. PMID:18233308

  4. Localization of the gene encoding the [alpha][sub 2]/[delta] subunit (CACNL2A) of the human skeletal muscle voltage-dependent Ca[sup 2+] channel to chromosome 7q21-q22 by somatic cell hybrid analysis

    SciTech Connect

    Powers, P.A.; Hogan, K.; Gregg, R.G. ); Scherer, S.W.; Tsui, L.C. Hospital for Sick Children, Ontario )

    1994-01-01

    Activation of voltage-dependent calcium channels (VDCCs) by membrane depolarization triggers key cellular responses such as contraction, secretion, excitation, and electrical signaling. The skeletal muscle L-type VDCC is a heteromultimer complex containing four subunits, [alpha][sub 1],[alpha][sub 2]/[delta],[beta][sub 1], and [gamma]. The [alpha][sub 2]/[delta] subunit, an integral component of the VDCC, appears to modulate the channel kinetics. The [alpha][sub 2]/[delta] gene is expressed in many tissues, including skeletal muscle, brain, heart, and lung, and cDNAs representing the skeletal muscle and brain isoforms have been isolated. DNA sequence comparisons indicate that these cDNAs are encoding by a single gene. 15 refs., 1 fig.

  5. Protein kinase C modulates the release of [3H]5-hydroxytryptamine in the spinal cord of the rat: the role of L-type voltage-dependent calcium channels.

    PubMed

    Gandhi, V C; Jones, D J

    1992-11-01

    The present studies examined the relationship between protein kinase C (PKC) and L-type voltage-dependent calcium channels in modulating the release of neurotransmitter from K(+)-depolarized rat spinal cord synaptosomes. Activators of PKC, such as phorbol 12-myristate 13-acetate (PMA), mezerein and oleoyl acetylglycerol produced a concentration-dependent potentiation of K(+)-induced release of [3H]5-hydroxytryptamine ([3H]5-HT). Enhanced release was dependent on the concentration of both Ca2+ and K+ in the superfusion medium. Calcium-independent release of [3H]5-HT or release induced by the Ca2+ ionophore were unaffected by PKC activators. Calcium-dependent release of [3H]5-HT, evoked by K+, was enhanced under similar conditions by the L-type Ca2+ channel agonists Bay K 8644 and (+)-SDZ 202-791. Nimodipine, an L-type Ca2+ channel antagonist, while having no independent effect on K(+)-induced release of [3H]5-HT, abolished the potentiative effects of Bay K 8644 and PMA. Similarly, the PKC inhibitors, polymyxin B and staurosporine, blocked effects of both PMA and Bay K 8644 on K(+)-stimulated release of [3H]5-HT. Neither PMA nor Bay K 8644 altered the uptake of [3H]5-HT. These results suggest that PKC-dependent mechanisms utilize calcium influx, via the L-type calcium channel, to modulate release of neurotransmitter and indicate a possible functional link between PKC and L-type voltage-dependent calcium channels in the spinal cord.

  6. Quantification of the Mg2+-induced potency shift of amantadine and memantine voltage-dependent block in human recombinant GluN1/GluN2A NMDARs.

    PubMed

    Otton, H J; Lawson McLean, A; Pannozzo, M A; Davies, C H; Wyllie, D J A

    2011-01-01

    Clinically, amantadine and memantine are drugs whose therapeutic utility is linked to their ability to block N-methyl-D-aspartate receptors (NMDARs) in a voltage-dependent manner. Nevertheless many studies that have characterized the pharmacological actions of amantadine and memantine have done so in the absence of physiological levels of Mg(2+) ions. This study quantifies the extent to which Mg(2+) alters the potency of the block produced by both amantadine and memantine at human recombinant GluN1/GluN2A NMDARs. Human recombinant GluN1/GluN2A NMDARs were expressed in Xenopus laevis oocytes and two-electrode voltage-clamp recordings were made at -80, -60 and -40 mV to quantify amantadine and memantine block in the absence and presence of Mg(2+). Amantadine and memantine blocked human GluN1/GluN2A NMDARs in a voltage-dependent manner with IC(50) values (at -80 mV) of 49 ± 6 μM (n = 7) and 1.0 ± 0.3 μM (n = 7), respectively. In the presence of Mg(2+) (1mM) the equivalent IC(50) values were 165 ± 10 μM (n=6) and 6.6 ± 0.3 μM (n = 5). Similarly in the presence of amantadine or memantine the potency of Mg(2+) in blocking GluN1/GluN2A NMDARs was reduced. The decrease in the potencies of both amantadine and memantine in the presence of physiological concentrations of Mg(2+) indicates that other targets (e.g. α7-nicotinic acetylcholine receptors and 5-HT(3) receptors) in addition to NMDARs may well be sites of the therapeutic action of these channel blockers.

  7. Characterization of the Ca2+-gated and voltage-dependent K+-channel Slo-1 of nematodes and its interaction with emodepside.

    PubMed

    Kulke, Daniel; von Samson-Himmelstjerna, Georg; Miltsch, Sandra M; Wolstenholme, Adrian J; Jex, Aaron R; Gasser, Robin B; Ballesteros, Cristina; Geary, Timothy G; Keiser, Jennifer; Townson, Simon; Harder, Achim; Krücken, Jürgen

    2014-12-01

    The cyclooctadepsipeptide emodepside and its parent compound PF1022A are broad-spectrum nematicidal drugs which are able to eliminate nematodes resistant to other anthelmintics. The mode of action of cyclooctadepsipeptides is only partially understood, but involves the latrophilin Lat-1 receptor and the voltage- and calcium-activated potassium channel Slo-1. Genetic evidence suggests that emodepside exerts its anthelmintic activity predominantly through Slo-1. Indeed, slo-1 deficient Caenorhabditis elegans strains are completely emodepside resistant. However, direct effects of emodepside on Slo-1 have not been reported and these channels have only been characterized for C. elegans and related Strongylida. Molecular and bioinformatic analyses identified full-length Slo-1 cDNAs of Ascaris suum, Parascaris equorum, Toxocara canis, Dirofilaria immitis, Brugia malayi, Onchocerca gutturosa and Strongyloides ratti. Two paralogs were identified in the trichocephalids Trichuris muris, Trichuris suis and Trichinella spiralis. Several splice variants encoding truncated channels were identified in Trichuris spp. Slo-1 channels of trichocephalids form a monophyletic group, showing that duplication occurred after the divergence of Enoplea and Chromadorea. To explore the function of a representative protein, C. elegans Slo-1a was expressed in Xenopus laevis oocytes and studied in electrophysiological (voltage-clamp) experiments. Incubation of oocytes with 1-10 µM emodepside caused significantly increased currents over a wide range of step potentials in the absence of experimentally increased intracellular Ca2+, suggesting that emodepside directly opens C. elegans Slo-1a. Emodepside wash-out did not reverse the effect and the Slo-1 inhibitor verruculogen was only effective when applied before, but not after, emodepside. The identification of several splice variants and paralogs in some parasitic nematodes suggests that there are substantial differences in channel properties among

  8. Characterization of the Ca2+-Gated and Voltage-Dependent K+-Channel Slo-1 of Nematodes and Its Interaction with Emodepside

    PubMed Central

    Kulke, Daniel; von Samson-Himmelstjerna, Georg; Miltsch, Sandra M.; Wolstenholme, Adrian J.; Jex, Aaron R.; Gasser, Robin B.; Ballesteros, Cristina; Geary, Timothy G.; Keiser, Jennifer; Townson, Simon; Harder, Achim; Krücken, Jürgen

    2014-01-01

    The cyclooctadepsipeptide emodepside and its parent compound PF1022A are broad-spectrum nematicidal drugs which are able to eliminate nematodes resistant to other anthelmintics. The mode of action of cyclooctadepsipeptides is only partially understood, but involves the latrophilin Lat-1 receptor and the voltage- and calcium-activated potassium channel Slo-1. Genetic evidence suggests that emodepside exerts its anthelmintic activity predominantly through Slo-1. Indeed, slo-1 deficient Caenorhabditis elegans strains are completely emodepside resistant. However, direct effects of emodepside on Slo-1 have not been reported and these channels have only been characterized for C. elegans and related Strongylida. Molecular and bioinformatic analyses identified full-length Slo-1 cDNAs of Ascaris suum, Parascaris equorum, Toxocara canis, Dirofilaria immitis, Brugia malayi, Onchocerca gutturosa and Strongyloides ratti. Two paralogs were identified in the trichocephalids Trichuris muris, Trichuris suis and Trichinella spiralis. Several splice variants encoding truncated channels were identified in Trichuris spp. Slo-1 channels of trichocephalids form a monophyletic group, showing that duplication occurred after the divergence of Enoplea and Chromadorea. To explore the function of a representative protein, C. elegans Slo-1a was expressed in Xenopus laevis oocytes and studied in electrophysiological (voltage-clamp) experiments. Incubation of oocytes with 1-10 µM emodepside caused significantly increased currents over a wide range of step potentials in the absence of experimentally increased intracellular Ca2+, suggesting that emodepside directly opens C. elegans Slo-1a. Emodepside wash-out did not reverse the effect and the Slo-1 inhibitor verruculogen was only effective when applied before, but not after, emodepside. The identification of several splice variants and paralogs in some parasitic nematodes suggests that there are substantial differences in channel properties among

  9. Slow recovery from inactivation regulates the availability of voltage-dependent Na(+) channels in hippocampal granule cells, hilar neurons and basket cells.

    PubMed

    Ellerkmann, R K; Riazanski, V; Elger, C E; Urban, B W; Beck, H

    2001-04-15

    1. Fundamental to the understanding of CNS function is the question of how individual neurons integrate multiple synaptic inputs into an output consisting of a sequence of action potentials carrying information coded as spike frequency. The availability for activation of neuronal Na(+) channels is critical for this process and is regulated both by fast and slow inactivation processes. Here, we have investigated slow inactivation processes in detail in hippocampal neurons. 2. Slow inactivation was induced by prolonged (10-300 s) step depolarisations to -10 mV at room temperature. In isolated hippocampal dentate granule cells (DGCs), recovery from this inactivation was biexponential, with time constants for the two phases of slow inactivation tau(slow,1) and tau(slow,2) ranging from 1 to 10 s and 20 to 50 s, respectively. Both (slow,1) and tau(slow,2) were related to the duration of prior depolarisation by a power law function of the form tau(t) = a (t/a)b, where t is the duration of the depolarisation, a is a constant kinetic setpoint and b is a scaling power. This analysis yielded values of a = 0.034 s and b = 0.62 for tau(slow,1) and a = 24 s and b = 0.30 for tau(slow,2) in the rat. 3. When a train of action potential-like depolarisations of different frequencies (50, 100, 200 Hz) was used to induce inactivation, a similar relationship was found between the frequency of depolarisation and both tau(slow,1) and tau(slow,2) (a = 0.58 s, b = 0.39 for tau(slow,1) and a = 3.77 s and b = 0.42 for tau(slow,2)). 4. Using nucleated patches from rat hippocampal slices, we have addressed possible cell specific differences in slow inactivation. In fast-spiking basket cells a similar scaling relationship can be found (a = 3.54 s and b = 0.39) as in nucleated patches from DGCs (a = 2.3 s and b = 0.48) and non-fast-spiking hilar neurons (a = 2.57 s and b = 0.49). 5. Likewise, comparison of human and rat granule cells showed that properties of ultra-slow recovery from inactivation

  10. Cloning and expression of the translocator protein (18 kDa), voltage-dependent anion channel, and diazepam binding inhibitor in the gonad of largemouth bass (Micropterus salmoides) across the reproductive cycle.

    PubMed

    Doperalski, Nicholas J; Martyniuk, Christopher J; Prucha, Melinda S; Kroll, Kevin J; Denslow, Nancy D; Barber, David S

    2011-08-01

    Cholesterol transport across the mitochondrial membrane is rate-limiting for steroidogenesis in vertebrates. Previous studies in fish have characterized expression of the steroidogenic acute regulatory protein, however the function and regulation of other genes and proteins involved in piscine cholesterol transport have not been evaluated. In the current study, mRNA sequences of the 18 kDa translocator protein (tspo; formerly peripheral benzodiazepine receptor), voltage-dependent anion channel (vdac), and diazepam binding inhibitor (dbi; also acyl-CoA binding protein) were cloned from largemouth bass. Gonadal expression was examined across reproductive stages to determine if expression is correlated with changes in steroid levels and with indicators of reproductive maturation. In testis, transcript abundance of tspo and dbi increased with reproductive maturation (6- and 23-fold maximal increase, respectively) and expression of tspo and dbi was positively correlated with reproductive stage, gonadosomatic index (GSI), and circulating levels of testosterone. Testis vdac expression was positively correlated with reproductive stage and GSI. In females, gonadal tspo and vdac expression was negatively correlated with GSI and levels of plasma testosterone and 17β-estradiol. Ovarian dbi expression was not correlated with indicators of reproductive maturation. These studies represent the first investigation of the steroidogenic role of tspo, vdac, and dbi in fish. Findings suggest that cholesterol transport in largemouth bass testis, but not in ovary, may be transcriptionally-regulated, however further investigation will be necessary to fully elucidate the role of these genes in largemouth bass steroidogenesis.

  11. Genotypic to expression profiling of bovine calcium channel, voltage-dependent, alpha-2/delta subunit 1 gene, and their association with bovine mastitis among Frieswal (HFX Sahiwal) crossbred cattle of Indian origin.

    PubMed

    Deb, Rajib; Singh, Umesh; Kumar, Sushil; Kumar, Arun; Singh, Rani; Sengar, Gyanendra; Mann, Sandeep; Sharma, Arjava

    2014-04-01

    Calcium channel, voltage-dependent, alpha-2/delta subunit 1 (CACNA2D1) gene is considered to be an important noncytokine candidate gene influencing mastitis. Scanty of reports are available until today regarding the role play of CACNA2D1 gene on the susceptibility of bovine mastitis. We interrogated the CACNA2D1 G519663A [A>G] SNP by PCR-RFLP among two hundreds Frieswal (HF X Sahiwal) crossbred cattle of Indian origin. Genotypic frequency of AA (51.5, n=101) was comparatively higher than AG (35, n=70) and GG (14.5, n=29). Association of Somatic cell score (SCS) with genotypes revealed that, GG genotypes showing lesser count (less susceptible to mastitis) compare to AA and AG. Relative expression of CACNA2D1 transcript (in milk samples) was significantly higher among GG than AG and AA. Further we have also isolated blood sample from the all groups and PBMCs were cultured from each blood sample as per the standard protocol. They were treated with Calcium channel blocker and the expression level of the CACNA2D1 gene was evaluated by Real Time PCR. Results show that expression level decline in each genotypic group after treatment and expression level of GG are again significantly higher than AA and AG. Thus, it may be concluded that GG genotypic animals are favorable for selecting disease resistant breeds.

  12. Airway Surface Dehydration by Transforming Growth Factor β (TGF-β) in Cystic Fibrosis Is Due to Decreased Function of a Voltage-dependent Potassium Channel and Can Be Rescued by the Drug Pirfenidone*

    PubMed Central

    Manzanares, Dahis; Krick, Stefanie; Baumlin, Nathalie; Dennis, John S.; Tyrrell, Jean; Tarran, Robert; Salathe, Matthias

    2015-01-01

    Transforming growth factor β1 (TGF-β1) is not only elevated in airways of cystic fibrosis (CF) patients, whose airways are characterized by abnormal ion transport and mucociliary clearance, but TGF-β1 is also associated with worse clinical outcomes. Effective mucociliary clearance depends on adequate airway hydration, governed by ion transport. Apically expressed, large-conductance, Ca2+- and voltage-dependent K+ (BK) channels play an important role in this process. In this study, TGF-β1 decreased airway surface liquid volume, ciliary beat frequency, and BK activity in fully differentiated CF bronchial epithelial cells by reducing mRNA expression of the BK γ subunit leucine-rich repeat-containing protein 26 (LRRC26) and its function. Although LRRC26 knockdown itself reduced BK activity, LRRC26 overexpression partially reversed TGF-β1-induced BK dysfunction. TGF-β1-induced airway surface liquid volume hyper-absorption was reversed by the BK opener mallotoxin and the clinically useful TGF-β signaling inhibitor pirfenidone. The latter increased BK activity via rescue of LRRC26. Therefore, we propose that TGF-β1-induced mucociliary dysfunction in CF airways is associated with BK inactivation related to a LRRC26 decrease and is amenable to treatment with clinically useful TGF-β1 inhibitors. PMID:26338706

  13. Dissecting the age-related decline on spatial learning and memory tasks in rodent models: N-methyl-D-aspartate receptors and voltage-dependent Ca2+ channels in senescent synaptic plasticity

    PubMed Central

    Foster, Thomas C.

    2012-01-01

    In humans, heterogeneity in the decline of hippocampal-dependent episodic memory is observed during aging. Rodents have been employed as models of age-related cognitive decline and the spatial water maze has been used to show variability in the emergence and extent of impaired hippocampal-dependent memory. Impairment in the consolidation of intermediate-term memory for rapidly acquired and flexible spatial information emerges early, in middle-age. As aging proceeds, deficits may broaden to include impaired incremental learning of a spatial reference memory. The extent and time course of impairment has been be linked to senescence of calcium (Ca2+) regulation and Ca2+-dependent synaptic plasticity mechanisms in region CA1. Specifically, aging is associated with altered function of N-methyl-D-aspartate receptors (NMDARs), voltage-dependent Ca2+ channels (VDCCs), and ryanodine receptors (RyRs) linked to intracellular Ca2+ stores (ICS). In young animals, NMDAR activation induces long-term potentiation of synaptic transmission (NMDAR-LTP), which is thought to mediate the rapid consolidation of intermediate-term memory. Oxidative stress, starting in middle-age, reduces NMDAR function. In addition, VDCCs and ICS can actively inhibit NMDAR-dependent LTP and oxidative stress enhances the role of VDCC and RyR-ICS in regulating synaptic plasticity. Blockade of L-type VDCCs promotes NMDAR-LTP and memory in older animals. Interestingly, pharmacological or genetic manipulations to reduce hippocampal NMDAR function readily impair memory consolidation or rapid learning, generally leaving incremental learning intact. Finally, evidence is mounting to indicate a role for VDCC-dependent synaptic plasticity in associative learning and the consolidation of remote memories. Thus, VDCC-dependent synaptic plasticity and extrahippocampal systems may contribute to incremental learning deficits observed with advanced aging. PMID:22307057

  14. Complex regulation of voltage-dependent activation and inactivation properties of retinal voltage-gated Cav1.4 L-type Ca2+ channels by Ca2+-binding protein 4 (CaBP4).

    PubMed

    Shaltiel, Lior; Paparizos, Christos; Fenske, Stefanie; Hassan, Sami; Gruner, Christian; Rötzer, Katrin; Biel, Martin; Wahl-Schott, Christian A

    2012-10-19

    Cav1.4 L-type Ca(2+) channels are crucial for synaptic transmission in retinal photoreceptors and bipolar neurons. Recent studies suggest that the activity of this channel is regulated by the Ca(2+)-binding protein 4 (CaBP4). In the present study, we explored this issue by examining functional effects of CaBP4 on heterologously expressed Cav1.4. We show that CaBP4 dramatically increases Cav1.4 channel availability. This effect crucially depends on the presence of the C-terminal ICDI (inhibitor of Ca(2+)-dependent inactivation) domain of Cav1.4 and is absent in a Cav1.4 mutant lacking the ICDI. Using FRET experiments, we demonstrate that CaBP4 interacts with the IQ motif of Cav1.4 and that it interferes with the binding of the ICDI domain. Based on these findings, we suggest that CaBP4 increases Cav1.4 channel availability by relieving the inhibitory effects of the ICDI domain on voltage-dependent Cav1.4 channel gating. We also functionally characterized two CaBP4 mutants that are associated with a congenital variant of human night blindness and other closely related nonstationary retinal diseases. Although both mutants interact with Cav1.4 channels, the functional effects of CaBP4 mutants are only partially preserved, leading to a reduction of Cav1.4 channel availability and loss of function. In conclusion, our study sheds new light on the functional interaction between CaBP4 and Cav1.4. Moreover, it provides insights into the mechanism by which CaBP4 mutants lead to loss of Cav1.4 function and to retinal disease. PMID:22936811

  15. The BH4 domain of anti-apoptotic Bcl-XL, but not that of the related Bcl-2, limits the voltage-dependent anion channel 1 (VDAC1)-mediated transfer of pro-apoptotic Ca2+ signals to mitochondria.

    PubMed

    Monaco, Giovanni; Decrock, Elke; Arbel, Nir; van Vliet, Alexander R; La Rovere, Rita M; De Smedt, Humbert; Parys, Jan B; Agostinis, Patrizia; Leybaert, Luc; Shoshan-Barmatz, Varda; Bultynck, Geert

    2015-04-01

    Excessive Ca(2+) fluxes from the endoplasmic reticulum to the mitochondria result in apoptotic cell death. Bcl-2 and Bcl-XL proteins exert part of their anti-apoptotic function by directly targeting Ca(2+)-transport systems, like the endoplasmic reticulum-localized inositol 1,4,5-trisphosphate receptors (IP3Rs) and the voltage-dependent anion channel 1 (VDAC1) at the outer mitochondrial membranes. We previously demonstrated that the Bcl-2 homology 4 (BH4) domain of Bcl-2 protects against Ca(2+)-dependent apoptosis by binding and inhibiting IP3Rs, although the BH4 domain of Bcl-XL was protective independently of binding IP3Rs. Here, we report that in contrast to the BH4 domain of Bcl-2, the BH4 domain of Bcl-XL binds and inhibits VDAC1. In intact cells, delivery of the BH4-Bcl-XL peptide via electroporation limits agonist-induced mitochondrial Ca(2+) uptake and protects against staurosporine-induced apoptosis, in line with the results obtained with VDAC1(-/-) cells. Moreover, the delivery of the N-terminal domain of VDAC1 as a synthetic peptide (VDAC1-NP) abolishes the ability of BH4-Bcl-XL to suppress mitochondrial Ca(2+) uptake and to protect against apoptosis. Importantly, VDAC1-NP did not affect the ability of BH4-Bcl-2 to suppress agonist-induced Ca(2+) release in the cytosol or to prevent apoptosis, as done instead by an IP3R-derived peptide. In conclusion, our data indicate that the BH4 domain of Bcl-XL, but not that of Bcl-2, selectively targets VDAC1 and inhibits apoptosis by decreasing VDAC1-mediated Ca(2+) uptake into the mitochondria.

  16. Ethanol (EtOH) inhibition of NMDA-activated ion current is not voltage-dependent and EtOH does not interact with other binding sites on the NMDA receptor/ionophore complex

    SciTech Connect

    Lovinger, D.M.; White, G.; Weight, F.F. )

    1990-02-26

    Recent studies indicate that intoxicating concentrations of EtOH inhibit neuronal responses to activation of NMDA-type glutamate receptors. The authors have observed that the potency of different alcohols for inhibiting NMDA-activated ion current in hippocampal neurons increases as a function of increasing hydrophobicity, suggesting that EtOH acts at a hydrophobic site. To further characterize the mechanisms of this effect, the authors examined the voltage-dependence of the EtOH inhibition of NMDA-activated ion current as well as potential interactions of EtOH with other effectors of the NMDA receptor/ionophore complex. The amount of inhibition of peak NMDA-activated current by 50 mM EtOH did not differ over a range of membrane potentials from {minus}60 to +60 mV, and EtOH did not alter the reversal potential of NMDA-activated current. The percent inhibition observed in the presence of 10-100 mM EtOH did not differ with NMDA concentrations from 10-100 {mu}M. The percent inhibition by 50 mM EtOH (30-48%) did not differ in the absence or presence of the channel blockers Mg{sup 2+} (50-500 {mu}M), Zn{sup 2+} (5 and 20 {mu}M) or ketamine (2 and 10 {mu}M), or with increasing concentrations of the NMDA receptor cofactor glycine (0.01-1 {mu}M). These data indicate that: (i) EtOH does not change the ion selectivity of the ionophore, and (ii) EtOH does not appear to interact with previously described binding sites on the NMDA receptor/ionophore complex.

  17. Translocation of glycogen synthase kinase-3β (GSK-3β), a trigger of permeability transition, is kinase activity-dependent and mediated by interaction with voltage-dependent anion channel 2 (VDAC2).

    PubMed

    Tanno, Masaya; Kuno, Atsushi; Ishikawa, Satoko; Miki, Takayuki; Kouzu, Hidemichi; Yano, Toshiyuki; Murase, Hiromichi; Tobisawa, Toshiyuki; Ogasawara, Makoto; Horio, Yoshiyuki; Miura, Tetsuji

    2014-10-17

    Glycogen synthase kinase-3β (GSK-3β) is a major positive regulator of the mitochondrial permeability transition pore (mPTP), a principle trigger of cell death, under the condition of oxidative stress. However, the mechanism by which cytosolic GSK-3β translocates to mitochondria, promoting mPTP opening, remains unclear. Here we addressed this issue by analyses of the effect of site-directed mutations in GSK-3β on mitochondrial translocation and protein/protein interactions upon oxidative stress. H9c2 cardiomyoblasts were transfected with GFP-tagged GSK-3β (WT), a mutant GSK-3β insensitive to inhibitory phosphorylation (S9A), or kinase-deficient GSK-3β (K85R). Time lapse observation revealed that WT and S9A translocated from the cytosol to the mitochondria more promptly than did K85R after exposure to oxidative stress. H2O2 increased the density of nine spots on two-dimensional gel electrophoresis of anti-GSK-3β-immunoprecipitates by more than 3-fold. MALDI-TOF/MS analysis revealed that one of the spots contained voltage-dependent anion channel 2 (VDAC2). Knockdown of VDAC2, but not VDAC1 or VDAC3, by siRNA attenuated both the mitochondrial translocation of GSK-3β and mPTP opening under stress conditions. The mitochondrial translocation of GSK-3β was attenuated also when Lys-15, but not Arg-4 or Arg-6, in the N-terminal domain of GSK-3β was replaced with alanine. The oxidative stress-induced mitochondrial translocation of GSK-3β was associated with an increase in cell death, which was suppressed by lithium chloride (LiCl), a GSK-3β inhibitor. These results demonstrate that GSK-3β translocates from the cytosol to mitochondria in a kinase activity- and VDAC2-dependent manner in which an N-terminal domain of GSK-3β may function as a mitochondrial targeting sequence.

  18. Translocation of Glycogen Synthase Kinase-3β (GSK-3β), a Trigger of Permeability Transition, Is Kinase Activity-dependent and Mediated by Interaction with Voltage-dependent Anion Channel 2 (VDAC2)*

    PubMed Central

    Tanno, Masaya; Kuno, Atsushi; Ishikawa, Satoko; Miki, Takayuki; Kouzu, Hidemichi; Yano, Toshiyuki; Murase, Hiromichi; Tobisawa, Toshiyuki; Ogasawara, Makoto; Horio, Yoshiyuki; Miura, Tetsuji

    2014-01-01

    Glycogen synthase kinase-3β (GSK-3β) is a major positive regulator of the mitochondrial permeability transition pore (mPTP), a principle trigger of cell death, under the condition of oxidative stress. However, the mechanism by which cytosolic GSK-3β translocates to mitochondria, promoting mPTP opening, remains unclear. Here we addressed this issue by analyses of the effect of site-directed mutations in GSK-3β on mitochondrial translocation and protein/protein interactions upon oxidative stress. H9c2 cardiomyoblasts were transfected with GFP-tagged GSK-3β (WT), a mutant GSK-3β insensitive to inhibitory phosphorylation (S9A), or kinase-deficient GSK-3β (K85R). Time lapse observation revealed that WT and S9A translocated from the cytosol to the mitochondria more promptly than did K85R after exposure to oxidative stress. H2O2 increased the density of nine spots on two-dimensional gel electrophoresis of anti-GSK-3β-immunoprecipitates by more than 3-fold. MALDI-TOF/MS analysis revealed that one of the spots contained voltage-dependent anion channel 2 (VDAC2). Knockdown of VDAC2, but not VDAC1 or VDAC3, by siRNA attenuated both the mitochondrial translocation of GSK-3β and mPTP opening under stress conditions. The mitochondrial translocation of GSK-3β was attenuated also when Lys-15, but not Arg-4 or Arg-6, in the N-terminal domain of GSK-3β was replaced with alanine. The oxidative stress-induced mitochondrial translocation of GSK-3β was associated with an increase in cell death, which was suppressed by lithium chloride (LiCl), a GSK-3β inhibitor. These results demonstrate that GSK-3β translocates from the cytosol to mitochondria in a kinase activity- and VDAC2-dependent manner in which an N-terminal domain of GSK-3β may function as a mitochondrial targeting sequence. PMID:25187518

  19. A new species of Rhabdias Stiles et Hassall, 1905 (Nematoda: Rhabdiasidae) from Blommersia domerguei (Guibé) (Amphibia: Mantellidae) in Madagascar.

    PubMed

    Kuzmin, Yuriy; Junker, Kerstin; du Preez, Louis; Bain, Odile

    2013-11-01

    Rhabdias blommersiae sp. n. (Nematoda: Rhabdiasidae) is described from the lungs of Domergue's Madagascar frog, Blommersia domerguei (Guibé) (Amphibia: Mantellidae), in Madagascar. The new species differs from congeners parasitizing amphibians in having a smaller body and buccal capsule, six equal lips, large excretory glands of unequal length and a posteriorly inflated body vesicle. A combination of characters distinguishes it from Afromalagasy species of Rhabdias Stiles et Hassall, 1905. Rhabdias blommersiae is the third species of the genus described from amphibians in Madagascar. Close similarities in the number and shape of circumoral structures in two Rhabdias species described from mantellid hosts in Madagascar suggest a close relationship and common origin of the two species, with subsequent adaptation to separate hosts within the Mantellidae.

  20. Phylogenetic relationships of Oriental torrent frogs in the genus Amolops and its allies (Amphibia, Anura, Ranidae).

    PubMed

    Matsui, Masafumi; Shimada, Tomohiko; Liu, Wan-Zhao; Maryati, Mohamed; Khonsue, Wichase; Orlov, Nikolai

    2006-03-01

    We investigated the phylogenetic relationships among 20 species of Oriental torrent frogs in the genus Amolops and its allies from China and Southeast Asia based on 1346-bp sequences of the mitochondrial 12S and 16S rRNA genes. Oriental species of the tribe Ranini form a monophyletic group containing 11 clades (Rana temporaria + Pseudoamolops, R. chalconota, four clades of Amolops, Meristogenys, three clades of Huia species, and Staurois) for which the phylogenetic relationships are unresolved. The genus Amolops consists of southern Chinese, southwestern Chinese, Thai, and Vietnamese-Malaysian lineages, but their relationships are also unresolved. The separation of southern and southwestern lineages within China conforms to previous morphological and karyological results. Species of Huia do not form a monophyletic group, whereas those of Meristogenys are monophyletic. Because P. sauteri is a sister species of R. temporaria, distinct generic status of Pseudoamolops is unwarranted.

  1. One hundred million years of skin feeding? Extended parental care in a Neotropical caecilian (Amphibia: Gymnophiona).

    PubMed

    Wilkinson, Mark; Kupfer, Alexander; Marques-Porto, Rafael; Jeffkins, Hilary; Antoniazzi, Marta M; Jared, Carlos

    2008-08-23

    Maternal dermatophagy, the eating of maternal skin by offspring, is an unusual form of parental investment involving co-evolved specializations of both maternal skin and offspring dentition, which has been recently discovered in an African caecilian amphibian. Here we report the discovery of this form of parental care in a second, distantly related Neotropical species Siphonops annulatus, where it is characterized by the same syndrome of maternal and offspring specializations. The detailed similarities of skin feeding in different caecilian species provide strong evidence of its homology, implying its presence in the last common ancestor of these species. Biogeographic considerations, the separation of Africa and South American land masses and inferred timescales of amphibian diversification all suggest that skin feeding is an ancient form of parental care in caecilians, which has probably persisted in multiple lineages for more than 100 Myr. These inferences support the hypotheses that (i) maternal dermatophagy is widespread in oviparous direct-developing caecilians, and (ii) that viviparous caecilians that feed on the hypertrophied maternal oviduct evolved from skin-feeding ancestors. In addition to skin-feeding, young S. annulatus were observed to congregate around, and imbibe liquid exuded from, the maternal cloacal opening.

  2. One hundred million years of skin feeding? Extended parental care in a Neotropical caecilian (Amphibia: Gymnophiona).

    PubMed

    Wilkinson, Mark; Kupfer, Alexander; Marques-Porto, Rafael; Jeffkins, Hilary; Antoniazzi, Marta M; Jared, Carlos

    2008-08-23

    Maternal dermatophagy, the eating of maternal skin by offspring, is an unusual form of parental investment involving co-evolved specializations of both maternal skin and offspring dentition, which has been recently discovered in an African caecilian amphibian. Here we report the discovery of this form of parental care in a second, distantly related Neotropical species Siphonops annulatus, where it is characterized by the same syndrome of maternal and offspring specializations. The detailed similarities of skin feeding in different caecilian species provide strong evidence of its homology, implying its presence in the last common ancestor of these species. Biogeographic considerations, the separation of Africa and South American land masses and inferred timescales of amphibian diversification all suggest that skin feeding is an ancient form of parental care in caecilians, which has probably persisted in multiple lineages for more than 100 Myr. These inferences support the hypotheses that (i) maternal dermatophagy is widespread in oviparous direct-developing caecilians, and (ii) that viviparous caecilians that feed on the hypertrophied maternal oviduct evolved from skin-feeding ancestors. In addition to skin-feeding, young S. annulatus were observed to congregate around, and imbibe liquid exuded from, the maternal cloacal opening. PMID:18547909

  3. A new species of Microcaecilia Taylor, 1968 (Amphibia: Gymnophiona: Siphonopidae) from Amazonian Brazil.

    PubMed

    Wilkinson, Mark; Antoniazzi, Marta Maria; Jared, Carlos

    2015-01-13

    A new species of siphonopid caecilian, Microcaecilia butantan sp. nov., is described based on four specimens from Belterra, in the State of Pará, Brazil. The new species differs from all other Microcaecilia in having a combination of more than 135 primary annuli and long premaxillary-maxillary tooth series that extend posteriorly beyond the choanae. Some specimens were dug from soil in a cupuaçu (Theobroma grandiflorum) plantation suggesting that this form of agriculture provides an environment suitable for at least some caecilians.

  4. Three new species of the salamander genus Hynobius (Amphibia, Urodela, Hynobiidae) from Kyushu, Japan.

    PubMed

    Nishikawa, Kanto; Matsui, Masafumi

    2014-08-14

    Three new species of lotic breeding Hynobius, formerly assigned to H. boulengeri, are described from the Kyushu region, southwestern Japan. They differ from all the known congeners by a unique combination of body size, character ratios, coloration, mtDNA, and allozymic characteristics. Together with H. stejnegeri they form a clade, which is not a sister group of H. boulengeri, and their speciation in Kyushu is surmised to have occurred at the end of Miocene, accompanied by differentiations in larval period and metamorphosing size. Measures of conservation of these new species are discussed briefly. 

  5. A new species of Microcaecilia Taylor, 1968 (Amphibia: Gymnophiona: Siphonopidae) from Amazonian Brazil.

    PubMed

    Wilkinson, Mark; Antoniazzi, Marta Maria; Jared, Carlos

    2015-01-01

    A new species of siphonopid caecilian, Microcaecilia butantan sp. nov., is described based on four specimens from Belterra, in the State of Pará, Brazil. The new species differs from all other Microcaecilia in having a combination of more than 135 primary annuli and long premaxillary-maxillary tooth series that extend posteriorly beyond the choanae. Some specimens were dug from soil in a cupuaçu (Theobroma grandiflorum) plantation suggesting that this form of agriculture provides an environment suitable for at least some caecilians. PMID:25661220

  6. Skull mechanics and the evolutionary patterns of the otic notch closure in capitosaurs (Amphibia: Temnospondyli).

    PubMed

    Fortuny, Josep; Marcé-Nogué, Jordi; Gil, Lluis; Galobart, Angel

    2012-07-01

    Capitosaurs were among the largest amphibians that have ever lived. Their members displayed an amphibious lifestyle. We provide new information on functional morphology data, using finite element analysis (FEA) which has palaeoecological implications for the group. Our analyses included 17 taxa using (2D) plate models to test four loading cases (bilateral, unilateral and lateral bitings and skull raising system simulation). Our results demonstrates that, when feeding, capitosaurs concentrated the stress at the circumorbital region of the capitosaur skull and cranial sutures probably played a key role in dissipating and absorbing the stress generated during biting. Basal members (as Wetlugasaurus) were probably less specialized forms, while during Middle- and Late Triassic the group radiated into different ecomorphotypes with closed otic notch forms (as Cyclotosaurus) resulting in the strongest skulls during biting. Previous interpretations discussed a trend from an open to closed otic notch associated with lateral repositioning of the tabular horns, but the analysis of the skull-raising system reveals that taxa exhibiting posteriorly directed tabular horns display similar results during skull raising to those of closed otic notch taxa. Our results suggest that various constraints besides otic notch morphology, such as the elongation of the tabular horns, snout length, skull width and position, and size of the orbits affect the function of the skull. On the light of our results, capitosaur skull showed a trend to reduce the stresses and deformation during biting. Capitosaurs could be considered crocodilian analogues as they were top-level predators in fluvial and brackish Triassic ecosystems.

  7. A New Basal Salamandroid (Amphibia, Urodela) from the Late Jurassic of Qinglong, Hebei Province, China

    PubMed Central

    Jia, Jia; Gao, Ke-Qin

    2016-01-01

    A new salamandroid salamander, Qinglongtriton gangouensis (gen. et sp. nov.), is named and described based on 46 fossil specimens of juveniles and adults collected from the Upper Jurassic (Oxfordian) Tiaojishan Formation cropping out in Hebei Province, China. The new salamander displays several ontogenetically and taxonomically significant features, most prominently the presence of a toothed palatine, toothed coronoid, and a unique pattern of the hyobranchium in adults. Comparative study of the new salamander with previously known fossil and extant salamandroids sheds new light on the early evolution of the Salamandroidea, the most species-diverse clade in the Urodela. Cladistic analysis places the new salamander as the sister taxon to Beiyanerpeton, and the two taxa together form the basalmost clade within the Salamandroidea. Along with recently reported Beiyanerpeton from the same geological formation in the neighboring Liaoning Province, the discovery of Qinglongtriton indicates that morphological disparity had been underway for the salamandroid clade by early Late Jurassic (Oxfordian) time. PMID:27144770

  8. A New Basal Salamandroid (Amphibia, Urodela) from the Late Jurassic of Qinglong, Hebei Province, China.

    PubMed

    Jia, Jia; Gao, Ke-Qin

    2016-01-01

    A new salamandroid salamander, Qinglongtriton gangouensis (gen. et sp. nov.), is named and described based on 46 fossil specimens of juveniles and adults collected from the Upper Jurassic (Oxfordian) Tiaojishan Formation cropping out in Hebei Province, China. The new salamander displays several ontogenetically and taxonomically significant features, most prominently the presence of a toothed palatine, toothed coronoid, and a unique pattern of the hyobranchium in adults. Comparative study of the new salamander with previously known fossil and extant salamandroids sheds new light on the early evolution of the Salamandroidea, the most species-diverse clade in the Urodela. Cladistic analysis places the new salamander as the sister taxon to Beiyanerpeton, and the two taxa together form the basalmost clade within the Salamandroidea. Along with recently reported Beiyanerpeton from the same geological formation in the neighboring Liaoning Province, the discovery of Qinglongtriton indicates that morphological disparity had been underway for the salamandroid clade by early Late Jurassic (Oxfordian) time.

  9. Neoteny and progenesis as two heterochronic processes involved in paedomorphosis in Triturus alpestris (Amphibia: Caudata).

    PubMed Central

    Denoël, M; Joly, P

    2000-01-01

    Current theories on the evolution of paedomorphosis suppose that several ontogenetic pathways have appeared according to different selective pressures. The aim of this study was to find out whether two distinct processes can lead to paedomorphosis in the Alpine newt, Triturus alpestris. In this respect, we compared age structures of paedomorphic and metamorphic individuals in two newt populations where the two forms lived syntopically. Whereas paedomorphosis resulted in a slower rate of somatic development in one population, it resulted in an acceleration of sexual maturation in the other population. These processes correspond to neoteny and progenesis, respectively. These results suggest that phenotypic plasticity can result from contrasted ontogenetic pathways between two populations of the same species. They give support to models that consider gonadic development as the target of selection under different environmental pressures. PMID:10983835

  10. A New Basal Salamandroid (Amphibia, Urodela) from the Late Jurassic of Qinglong, Hebei Province, China.

    PubMed

    Jia, Jia; Gao, Ke-Qin

    2016-01-01

    A new salamandroid salamander, Qinglongtriton gangouensis (gen. et sp. nov.), is named and described based on 46 fossil specimens of juveniles and adults collected from the Upper Jurassic (Oxfordian) Tiaojishan Formation cropping out in Hebei Province, China. The new salamander displays several ontogenetically and taxonomically significant features, most prominently the presence of a toothed palatine, toothed coronoid, and a unique pattern of the hyobranchium in adults. Comparative study of the new salamander with previously known fossil and extant salamandroids sheds new light on the early evolution of the Salamandroidea, the most species-diverse clade in the Urodela. Cladistic analysis places the new salamander as the sister taxon to Beiyanerpeton, and the two taxa together form the basalmost clade within the Salamandroidea. Along with recently reported Beiyanerpeton from the same geological formation in the neighboring Liaoning Province, the discovery of Qinglongtriton indicates that morphological disparity had been underway for the salamandroid clade by early Late Jurassic (Oxfordian) time. PMID:27144770

  11. Molecular systematics of caeciliid caecilians (Amphibia: Gymnophiona) of the Western Ghats, India.

    PubMed

    Gower, David J; San Mauro, Diego; Giri, Varad; Bhatta, Gopalakrishna; Govindappa, Venu; Kotharambath, Ramachandran; Oommen, Oommen V; Fatih, Farrah A; Mackenzie-Dodds, Jacqueline A; Nussbaum, Ronald A; Biju, S D; Shouche, Yogesh S; Wilkinson, Mark

    2011-06-01

    Together, Indian plus Seychelles caeciliid caecilian amphibians (Gymnophiona) constitute approximately 10% of the extant species of this order. A molecular phylogenetic analysis of all but one (or two) nominal species (16, in five genera) is presented based on mitochondrial (12S, 16S, cytb, cox1) and nuclear (RAG1) sequence data. Results strongly support monophyly of both Seychelles and peninsular Indian caeciliids, and their sister-group status. Within the Indian caeciliids, Indotyphlus and Gegeneophis are monophyletic sister genera. The phylogenetic position of Gegeneophis ramaswamii, Gegeneophis seshachari, and Gegeneophis carnosus are not well resolved, but all lie outside a well-supported clade of most northern Western Ghats Gegeneophis (madhavai, mhadeiensis, goaensis, danieli/nadkarnii). Most nominal species of Indian caeciliid are diagnosed by robust haplotype clades, though the systematics of G. carnosus-like forms in northern Kerala and southern Karnataka requires substantial further investigation. For the most part, Indian caeciliid species comprise narrowly distributed, allopatric taxa with low genetic diversity. Much greater geographic genetic diversity exists among populations referred to G. seshachari, such that some populations likely represent undescribed species. This, the first phylogenetic analysis of Indian caeciliids, generally provides additional support for recent increases in described species (eight since 1999), and a framework for ongoing taxonomic revision.

  12. Patterns of peripheral innervation of the tongue and hyobranchial apparatus in caecilians (Amphibia: Gymnophiona).

    PubMed

    Wake, M H

    1992-04-01

    The innervation of the musculature of the tongue and the hyobranchial apparatus of caecilians has long been assumed to be simple and to exhibit little interspecific variation. A study of 14 genera representing all six families of caecilians demonstrates that general patterns of innervation by the trigeminal, facial, glossopharyngeal, and vagus nerves are similar across taxa but that the composition of the "hypoglossal" nerve is highly variable. Probably in all caecilians, spinal nerves 1 and 2 contribute to the hypoglossal. In addition, in certain taxa, an "occipital," the vagus, and/or spinal 3 appear to contribute fibers to the composition of the hypoglossal nerve. These patterns, the lengths of fusion of the contributing elements, and the branching patterns of the hypoglossal are assessed according to the currently accepted hypothesis of phylogenetic relationships of caecilians, and of amphibians. An hypothesis is proposed that limblessness and a simple tongue, with concomitant reduced complexity of innervation of muscles associated with limbs and the tongue, has released a constraint on pattern of innervation. As a consequence, a greater diversity and, in several taxa, greater complexity of neuroanatomical associations of nerve roots to form the hypoglossal are expressed.

  13. Oviduct modifications in foam-nesting frogs, with emphasis on the genus Leptodactylus (Amphibia, Leptodactylidae)

    USGS Publications Warehouse

    Furness, Andrew I.; McDiarmid, Roy W.; Heyer, W. Ronald; Zug, George R.

    2010-01-01

    Various species of frogs produce foam nests that hold their eggs during development. We examined the external morphology and histology of structures associated with foam nest production in frogs of the genus Leptodactylus and a few other taxa. We found that the posterior convolutions of the oviducts in all mature female foam-nesting frogs that we examined were enlarged and compressed into globular structures. This organ-like portion of the oviduct has been called a "foam gland" and these structures almost certainly produce the secretion that is beaten by rhythmic limb movements into foam that forms the nest. However, the label "foam gland" is a misnomer because the structures are simply enlarged and tightly folded regions of the pars convoluta of the oviduct, rather than a separate structure; we suggest the name pars convoluta dilata (PCD) for this feature. Although all the foam-nesters we examined had a pars convoluta dilata, its size and shape showed considerable interspecific variation. Some of this variation likely reflects differences in the breeding behaviors among species and in the size, type, and placement of their foam nests. Other variation, particularly in size, may be associated with the physiological periodicity and reproductive state of the female, her age, and/or the number of times she has laid eggs.

  14. Cytonuclear discordance and historical demography of two brown frogs, Rana tagoi and R. sakuraii (Amphibia: Ranidae).

    PubMed

    Eto, Koshiro; Matsui, Masafumi

    2014-10-01

    Prior studies of mitochondrial genomic variation reveal that the Japanese brown frog Rana tagoi comprises a complex of cryptic species lineages, and that R. sakuraii arose from within this complex. Neither species forms a monophyletic group on the mitochondrial haplotype tree, precluding a simple explanation for the evolutionary origins of R. sakuraii. We present a more complete sampling of mitochondrial haplotypic variation (from the ND1 and 16S genes) plus DNA sequence variation for five nuclear loci (from the genes encoding NCX1, NFIA, POMC, SLC8A3, and TYR) to resolve the evolutionary histories of these species. We test hypotheses of population assignment (STRUCTURE) and isolation-with-migration (IM) using the more slowly evolving nuclear markers. These demographic analyses of nuclear genetic variation confirm species-level distinctness and integrity of R. sakuraii despite its apparent polyphyly on the mitochondrial haplotype tree. Divergence-time estimates from both the mitochondrial haplotypes and nuclear genomic markers suggest that R. sakuraii originated approximately one million years ago, and that incomplete sorting of mitochondrial haplotype lineages best explains non-monophyly of R. sakuraii mitochondrial haplotypes. Cytonuclear discordance elsewhere in R. tagoi reveals a case of mitochondrial introgression between two species lineages on Honshu. The earliest phylogenetic divergence within this species group occurred approximately four million years ago, followed by cladogenetic events in the Pliocene and early Pleistocene yielding 10-13 extant species lineages, including R. sakuraii as one of the youngest.

  15. Reduced genetic variation in the Japanese giant salamander, Andrias japonicus (Amphibia: Caudata).

    PubMed

    Matsui, Masafumi; Tominaga, Atsushi; Liu, Wan-zhao; Tanaka-Ueno, Tomoko

    2008-10-01

    The phylogenetic relationships among 46 samples from 27 populations of the Japanese giant salamander, Andriasjaponicus and its congener, A. davidianus from China was investigated, using 3664 bp sequences of the mitochondrial genes NADH1, NADH3, cyt b and CR, partial NADH6 and intervening genes. In phylogenetic trees constructed by MP, ML, and Bayesian methods, the family Cryptobranchidae and the genus Andrias both form monophyletic groups. Japanese A. japonicus and Chinese A. davidianus are sister taxa and can be regarded as separate species despite a small degree of genetic differentiation. Andriasjaponicus is divided into central and western clades, but the phylogenetic relationships within the latter clade are unresolved. As previously reported from allozyme analyses, A. japonicus exhibits little genetic differentiation, in strong contrast to salamanders of the genus Hynobius with which their distributions overlap. This reduced genetic variability in A. japonicus is attributable to a unique mating system of polygyny, delayed sexual maturity, notable longevity, life in a stable aquatic environment, and gigantism, as well as bottleneck effects following habitat fragmentation and extinction of local populations during Quaternary glaciations. The species is thus susceptible to extinction by potential environmental fluctuations, and requires extensive conservation measures. PMID:18723097

  16. [Episodes of adaptive evolution of mitochondrial genome in Asiatic salamanders (Amphibia, Caudata, Hynobiidae)].

    PubMed

    Maliarchuk, B A; Derenko, M V; Denisova, G A

    2014-02-01

    To elucidate the effect of natural selection on the evolution of mitochondrial DNA (mtDNA) in Asiatic salamanders of the family Hynobiidae, nucleotide sequences of 12 protein-coding genes were analyzed. Using a mixed effects model of evolution, it was found that, in spite of the pronounced effect of negative selection on the mtDNA evolution in Hynobiidae (which is typical for the animals in general), two phylogenetic clusters, the West Asian one, represented by the genera Ranodon and Paradactylodon, and North Eurasian one, represented by the genus Salamandrella, were formed under the influence of episodic positive selection. Analysis of protein sequences encoded by the mitochondrial genome also supported the influence of positive selection on the evolution of Hynobiidae at some stages of their cladogenesis. It is suggested that the signatures of adaptive evolution detected in the mtDNA of Hynobiidae were determined by the complex and long-lasting history of their formation, accompanied by adaptation to the changing environment. PMID:25711027

  17. Light shines through the spindrift--phylogeny of African torrent frogs (Amphibia, Anura, Petropedetidae).

    PubMed

    Barej, Michael F; Rödel, Mark-Oliver; Loader, Simon P; Menegon, Michele; Gonwouo, Nono L; Penner, Johannes; Gvoždík, Václav; Günther, Rainer; Bell, Rayna C; Nagel, Peter; Schmitz, Andreas

    2014-02-01

    Torrent frogs of the genus Petropedetes Reichenow, 1874 as currently understood have a disjunct distribution with species endemic to West, Central or East Africa. We herein present a phylogenetic analysis including all but one of the currently described 12 species of the genus. Maximum Likelihood and Bayesian analyses of combined nuclear (rag1, SIA, BDNF) and mitochondrial (16S, 12S, cytb) genes of more than 3500 base pairs, revealed clades corresponding to the three sub-Saharan regions. Molecular results are confirmed by morphological differences. Surprisingly, the three geographic clades do not form a monophyletic group with respect to closely related families Pyxicephalidae and Conrauidae and therefore require taxonomic changes. We resurrect Arthroleptides Nieden, 1911 for the East African taxa. The Central African taxa remain in the genus Petropedetes. The West African members are placed in the new genus Odontobatrachus gen. nov. The taxonomic position of the new genus remains incertae sedis as it was not assigned to any of the four families included in our analyses. Potential new species have been detected within all three major clades, pointing to a still not fully clarified diversity within African torrent frogs.

  18. Molecular phylogeny and diversification of the genus Odorrana (Amphibia, Anura, Ranidae) inferred from two mitochondrial genes.

    PubMed

    Chen, Xiaohong; Chen, Zhuo; Jiang, Jianping; Qiao, Liang; Lu, Youqiang; Zhou, Kaiya; Zheng, Guangmei; Zhai, Xiaofei; Liu, Jianxin

    2013-12-01

    A diversity of hypotheses have been proposed for phylogenetic relationships and taxonomy within the genus Odorrana, and great progress has been made over the past several decades. However, there is still some controversy concerning relationships among Odorrana species. Here, we used many paratypes and topotypes and utilized 1.81 kb of mitochondrial sequence data to generate a phylogeny for approximately 4/5 of Odorrana species, and Odorrana haplotypes form a strongly supported monophyletic group relative to the other genera sampled. The deepest phylogenetic divergences within Odorrana separate 3 lineages whose interrelationships are not recovered with strong support. These lineages include the ancestral lineage of O. chapaensis, the ancestral lineage of a strongly supported clade comprising many western species, and the ancestral lineage of a strongly supported clade comprising all other Odorrana sampled. Within the latter clade, the first phylogenetic split separates O. ishikawae from a well-supported clade comprising its other species. These divergences likely occurred in the middle Miocene, approximately 12-15 million years ago. Separation of the ancestral lineage of Odorrana from its closest relative, Babina in our study, likely occurred in the early Miocene or possibly late Oligocene. Rates of lineage accumulation remained high from the middle Miocene through the Pleistocene.

  19. Helminth parasites of the leopard frog Lithobates sp. Colima (Amphibia: Ranidae) from Colima, Mexico.

    PubMed

    Cabrera-Guzmán, Elisa; Garrido-Olvera, Lorena; León-Règagnon, Virginia

    2010-08-01

    The helminth fauna inhabiting Lithobates sp. Colima from Ticuizitán, Colima, Mexico, comprises 10 species: 4 digeneans ( Clinostomum sp., Glypthelmins quieta , Haematoloechus sp., and Langeronia macrocirra ), 5 nematodes ( Aplectana itzocanensis , Cosmocerca podicipinus , Foleyellides striatus , Oswaldocruzia subauricularis , and Rhabdias sp.), and 1 cestode (Cyclophyllidea). Glypthelmins quieta , L. macrocirra , and A. itzocanensis represent new host records. These observations, added to previous records from Acapulco, Guerrero, Mexico, indicate that the helminth fauna of Lithobates sp. from Colima comprises 25 taxa. Frogs are being parasitized by 3 infection routes: ingestion of intermediate host, skin penetration by larval forms, and transmission by vectors. Species of Aplectana , Cosmocerca , Foleyellides , and Oswaldocruzia occurred in high prevalence in Colima, similar to a previous study on the same frog species from Guerrero. In Colima, Glypthelmins , Haematoloechus , and Rhabdias also occurred in high prevalence. Haematoloechus species reached the highest mean intensity in both localities. The semiaquatic habits of this species of frog and the availability of particular feeding resources appear to determine the helminth composition and infection levels; however, co-speciation events also play an important role structuring these helminth communities.

  20. Molecular systematics of caeciliid caecilians (Amphibia: Gymnophiona) of the Western Ghats, India.

    PubMed

    Gower, David J; San Mauro, Diego; Giri, Varad; Bhatta, Gopalakrishna; Govindappa, Venu; Kotharambath, Ramachandran; Oommen, Oommen V; Fatih, Farrah A; Mackenzie-Dodds, Jacqueline A; Nussbaum, Ronald A; Biju, S D; Shouche, Yogesh S; Wilkinson, Mark

    2011-06-01

    Together, Indian plus Seychelles caeciliid caecilian amphibians (Gymnophiona) constitute approximately 10% of the extant species of this order. A molecular phylogenetic analysis of all but one (or two) nominal species (16, in five genera) is presented based on mitochondrial (12S, 16S, cytb, cox1) and nuclear (RAG1) sequence data. Results strongly support monophyly of both Seychelles and peninsular Indian caeciliids, and their sister-group status. Within the Indian caeciliids, Indotyphlus and Gegeneophis are monophyletic sister genera. The phylogenetic position of Gegeneophis ramaswamii, Gegeneophis seshachari, and Gegeneophis carnosus are not well resolved, but all lie outside a well-supported clade of most northern Western Ghats Gegeneophis (madhavai, mhadeiensis, goaensis, danieli/nadkarnii). Most nominal species of Indian caeciliid are diagnosed by robust haplotype clades, though the systematics of G. carnosus-like forms in northern Kerala and southern Karnataka requires substantial further investigation. For the most part, Indian caeciliid species comprise narrowly distributed, allopatric taxa with low genetic diversity. Much greater geographic genetic diversity exists among populations referred to G. seshachari, such that some populations likely represent undescribed species. This, the first phylogenetic analysis of Indian caeciliids, generally provides additional support for recent increases in described species (eight since 1999), and a framework for ongoing taxonomic revision. PMID:21406239

  1. Patterns of peripheral innervation of the tongue and hyobranchial apparatus in caecilians (Amphibia: Gymnophiona).

    PubMed

    Wake, M H

    1992-04-01

    The innervation of the musculature of the tongue and the hyobranchial apparatus of caecilians has long been assumed to be simple and to exhibit little interspecific variation. A study of 14 genera representing all six families of caecilians demonstrates that general patterns of innervation by the trigeminal, facial, glossopharyngeal, and vagus nerves are similar across taxa but that the composition of the "hypoglossal" nerve is highly variable. Probably in all caecilians, spinal nerves 1 and 2 contribute to the hypoglossal. In addition, in certain taxa, an "occipital," the vagus, and/or spinal 3 appear to contribute fibers to the composition of the hypoglossal nerve. These patterns, the lengths of fusion of the contributing elements, and the branching patterns of the hypoglossal are assessed according to the currently accepted hypothesis of phylogenetic relationships of caecilians, and of amphibians. An hypothesis is proposed that limblessness and a simple tongue, with concomitant reduced complexity of innervation of muscles associated with limbs and the tongue, has released a constraint on pattern of innervation. As a consequence, a greater diversity and, in several taxa, greater complexity of neuroanatomical associations of nerve roots to form the hypoglossal are expressed. PMID:1588590

  2. Description of a new species of Microhyla from Bali, Indonesia (Amphibia, Anura).

    PubMed

    Matsui, Masafumi; Hamidy, Amir; Eto, Koshiro

    2013-01-01

    We describe a microhylid frog from Bali, Indonesia as a new species, Microhyla orientalis sp. nov. It belongs to the M. achatina group and is close to M. mantheyi, M. malang, and M. borneensis. It is distinguished from its congeners by a combination of the following characters: small size (adult males about 16-17 mm in SVL); a faint vertebral stripe present; a black lateral stripe from behind eye to half length of trunk; snout rounded in profile; eyelid without supraciliary spines; first finger less than one-fifth of third; tips of three outer fingers weakly dilated, forming weak disks, dorsally with median longitudinal groove; outer palmar tubercle single; tibiotarsal articulation reaching up to center of eye; tips of toes distinctly dilated into disks, dorsally with median longitudinal groove; inner and outer metatarsal tubercles present; four or more phalanges on inner and outer sides of fourth toe, and three phalanges on inner side of fifth toe free of web; and tail of larva with a black marking at middle. The male advertisement call of the new species consists of a series of notes each lasts for 0.01-0.08 s and composed of 3-5 pulses with a dominant frequency of 3.2-3.6 kHz. Uncorrected sequence divergences between M. orientalis and all homologous 16S rRNA sequences available were > 6.6%. At present, the new species is known from rice fields between 435-815 m elevation in Wongaya Gede and Batukaru.

  3. A molecular assessment of phylogenetic relationships and lineage accumulation rates within the family Salamandridae (Amphibia, Caudata).

    PubMed

    Weisrock, David W; Papenfuss, Theodore J; Macey, J Robert; Litvinchuk, Spartak N; Polymeni, Rosa; Ugurtas, Ismail H; Zhao, Ermi; Jowkar, Houman; Larson, Allan

    2006-11-01

    We examine phylogenetic relationships among salamanders of the family Salamandridae using approximately 2700 bases of new mtDNA sequence data (the tRNALeu, ND1, tRNAIle, tRNAGln, tRNAMet, ND2, tRNATrp, tRNAAla, tRNAAsn, tRNACys, tRNATyr, and COI genes and the origin for light-strand replication) collected from 96 individuals representing 61 of the 66 recognized salamandrid species and outgroups. Phylogenetic analyses using maximum parsimony and Bayesian analysis are performed on the new data alone and combined with previously reported sequences from other parts of the mitochondrial genome. The basal phylogenetic split is a polytomy of lineages ancestral to (1) the Italian newt Salamandrina terdigitata, (2) a strongly supported clade comprising the "true" salamanders (genera Chioglossa, Mertensiella, Lyciasalamandra, and Salamandra), and (3) a strongly supported clade comprising all newts except S. terdigitata. Strongly supported clades within the true salamanders include monophyly of each genus and grouping Chioglossa and Mertensiella as the sister taxon to a clade comprising Lyciasalamandra and Salamandra. Among newts, genera Echinotriton, Pleurodeles, and Tylototriton form a strongly supported clade whose sister taxon comprises the genera Calotriton, Cynops, Euproctus, Neurergus, Notophthalmus, Pachytriton, Paramesotriton, Taricha, and Triturus. Our results strongly support monophyly of all polytypic newt genera except Paramesotriton and Triturus, which appear paraphyletic, and Calotriton, for which only one of the two species is sampled. Other well-supported clades within newts include (1) Asian genera Cynops, Pachytriton, and Paramesotriton, (2) North American genera Notophthalmus and Taricha, (3) the Triturus vulgaris species group, and (4) the Triturus cristatus species group; some additional groupings appear strong in Bayesian but not parsimony analyses. Rates of lineage accumulation through time are evaluated using this nearly comprehensive sampling of

  4. Morphology of the kidney in the West African caecilian, Geotrypetes seraphini (Amphibia, Gymnophiona, Caeciliidae).

    PubMed

    Møbjerg, N; Jespersen, A; Wilkinson, M

    2004-11-01

    This study deals with the morphology and ultrastructure of the mesonephros in adult caecilians of the species Geotrypetes seraphini. Based on serial sections in paraffin and araldite, nephrons are reconstructed and the cellular characteristics of different nephron segments described. The long and slender mesonephric kidneys of G. seraphini are broadest caudally and taper toward the front, where the organs are divided into smaller segmental divisions. Two nephron types can be distinguished on the basis of their connections to the coelom and their position within the nephric tissue: ventral nephrons connect to the coelom via a ciliated peritoneal funnel, whereas medial nephrons lack this connection. Both nephron types are composed of a filtration unit, the Malpighian corpuscle, and a renal tubule, which can be divided into six morphologically distinct segments: neck segment, proximal tubule, intermediate segment, early distal tubule, late distal tubule, and collecting tubule. Collecting tubules merge and form a branch system that opens into collecting ducts. Collecting ducts empty into the Wolffian duct. Proximal tubules of nephrons in the frontal divisions are morphologically different from the proximal tubules of more caudal kidney regions. Distal tubule subdivision is only clearly recognizable at the electron microscopic level. The length of each nephron segment is calculated from a ventral nephron with a total length of approximately 3.8 mm, and the course of the segments within the nephric tissue is reported. The number of nephrons was estimated at 1,700 units in each kidney. The segmentation and ultrastructure of the mesonephric nephrons in G. seraphini are discussed in relation to nephron descriptions from other caecilians and we further discuss the evolutionary origin of the amphibian nephron.

  5. Morphology of the kidney in the West African caecilian, Geotrypetes seraphini (Amphibia, Gymnophiona, Caeciliidae).

    PubMed

    Møbjerg, N; Jespersen, A; Wilkinson, M

    2004-11-01

    This study deals with the morphology and ultrastructure of the mesonephros in adult caecilians of the species Geotrypetes seraphini. Based on serial sections in paraffin and araldite, nephrons are reconstructed and the cellular characteristics of different nephron segments described. The long and slender mesonephric kidneys of G. seraphini are broadest caudally and taper toward the front, where the organs are divided into smaller segmental divisions. Two nephron types can be distinguished on the basis of their connections to the coelom and their position within the nephric tissue: ventral nephrons connect to the coelom via a ciliated peritoneal funnel, whereas medial nephrons lack this connection. Both nephron types are composed of a filtration unit, the Malpighian corpuscle, and a renal tubule, which can be divided into six morphologically distinct segments: neck segment, proximal tubule, intermediate segment, early distal tubule, late distal tubule, and collecting tubule. Collecting tubules merge and form a branch system that opens into collecting ducts. Collecting ducts empty into the Wolffian duct. Proximal tubules of nephrons in the frontal divisions are morphologically different from the proximal tubules of more caudal kidney regions. Distal tubule subdivision is only clearly recognizable at the electron microscopic level. The length of each nephron segment is calculated from a ventral nephron with a total length of approximately 3.8 mm, and the course of the segments within the nephric tissue is reported. The number of nephrons was estimated at 1,700 units in each kidney. The segmentation and ultrastructure of the mesonephric nephrons in G. seraphini are discussed in relation to nephron descriptions from other caecilians and we further discuss the evolutionary origin of the amphibian nephron. PMID:15376276

  6. Autoradiographic localization of voltage-dependent sodium channels on the mouse neuromuscular junction using /sup 125/I-alpha scorpion toxin. I. Preferential labeling of glial cells on the presynaptic side

    SciTech Connect

    Boudier, J.L.; Jover, E.; Cau, P.

    1988-05-01

    Alpha-scorpion toxins bind specifically to the voltage-sensitive sodium channel in excitable membranes, and binding is potential-dependent. The radioiodinated toxin II from the scorpion Androctonus australis Hector (alpha ScTx) was used to localize voltage-sensitive sodium channels on the presynaptic side of mouse neuromuscular junctions (NMJ) by autoradiography using both light and electron microscopy. Silver grain localization was analyzed by the cross-fire method. At the light-microscopic level, grain density over NMJ appeared 6-8x higher than over nonjunctional muscle membrane. The specificity of labeling was verified by competition/displacement with an excess of native alpha ScTx. Labeling was also inhibited by incubation in depolarizing conditions, showing its potential-dependence. At the electron-microscopic level, analysis showed that voltage-sensitive sodium channels labeled with alpha ScTx were almost exclusively localized on membranes, as expected. Due to washout after incubation, appreciable numbers of binding sites were not found on the postsynaptic membranes. However, on the presynaptic side, alpha ScTx-labeled voltage-sensitive sodium channels were localized on the membrane of non-myelin-forming Schwann cells covering NMJ. The axonal presynaptic membrane was not labeled. These results show that voltage-sensitive sodium channels are present on glial cells in vivo, as already demonstrated in vitro. It is proposed that these glial channels could be indirectly involved in the ionic homeostasis of the axonal environment.

  7. Isochannels and blocking modes of voltage-dependent sodium channels.

    PubMed

    Moczydlowski, E; Uehara, A; Guo, X; Heiny, J

    1986-01-01

    Our results support the existence of three different Na-channel subtypes or isochannels. These isochannels can be readily distinguished as the predominant Na-channel types in mammalian brain, skeletal muscle, and cardiac muscle. The sensitivity to mu-conotoxin GIIIA and tetrodotoxin is sufficient to classify these channels. The skeletal muscle channel is very sensitive to both tetrodotoxin and mu-conotoxin, the brain channel is sensitive to tetrodotoxin but insensitive to mu-conotoxin, and the heart and denervated muscle channels are insensitive to both toxins. In addition to block at the external receptor site for guanidinium toxins, several other blocking modes can be generalized for batrachotoxin-activated Na channels. One mode is peculiar to certain hydrophobic molecules so far represented by our studies of benzocaine and procaine. These molecules induce discrete blocking events with dwell times that apparently increase with anesthetic concentration and a blocking frequency that increases with negative voltage. This mode is quite distinct from the fast internal block by charged organic molecules that increases with positive voltage. These results imply that it is not possible to ascribe the diverse effects of local anesthetics to a single site in the interior channel mouth, as previously proposed by Hille. Our observations thus support the conclusions of other workers who used mixtures of two local anesthetics to show that the dose-response behavior does not fit single-site behavior, but requires at least two distinct sites. Two additional blocking modes can be distinguished for the interactions of cations at the internal and external mouths of the channel. Organic molecules can apparently enter the electric field from the internal but not the external side of the channel. This result suggests a wide internal entry way to the field and an external constriction that prevents the entry of molecules with a single methyl group but permits entry of divalent inorganic cations such as Ca2+ and Co2+.

  8. Voltage-Dependent Intrinsic Bursting in Olfactory Bulb Golgi Cells

    ERIC Educational Resources Information Center

    Pressler, R. Todd; Rozman, Peter A.; Strowbridge, Ben W.

    2013-01-01

    In the mammalian olfactory bulb (OB), local synaptic circuits modulate the evolving pattern of activity in mitral and tufted cells following olfactory sensory stimulation. GABAergic granule cells, the most numerous interneuron subtype in this brain region, have been extensively studied. However, classic studies using Golgi staining methods…

  9. Evolutionarily conserved intracellular gate of voltage-dependent sodium channels

    NASA Astrophysics Data System (ADS)

    Oelstrom, Kevin; Goldschen-Ohm, Marcel P.; Holmgren, Miguel; Chanda, Baron

    2014-03-01

    Members of the voltage-gated ion channel superfamily (VGIC) regulate ion flux and generate electrical signals in excitable cells by opening and closing pore gates. The location of the gate in voltage-gated sodium channels, a founding member of this superfamily, remains unresolved. Here we explore the chemical modification rates of introduced cysteines along the S6 helix of domain IV in an inactivation-removed background. We find that state-dependent accessibility is demarcated by an S6 hydrophobic residue; substituted cysteines above this site are not modified by charged thiol reagents when the channel is closed. These accessibilities are consistent with those inferred from open- and closed-state structures of prokaryotic sodium channels. Our findings suggest that an intracellular gate composed of a ring of hydrophobic residues is not only responsible for regulating access to the pore of sodium channels, but is also a conserved feature within canonical members of the VGIC superfamily.

  10. Further classification of skin alkaloids from neotropical poison frogs (Dendrobatidae), with a general survey of toxic/noxious substances in the amphibia.

    PubMed

    Daly, J W; Myers, C W; Whittaker, N

    1987-01-01

    Cutaneous granular glands are a shared character of adult amphibians, including caecilians, and are thought to be the source of most biologically active compounds in amphibian skin. Data are available from one or more species in over 100 of nearly 400 genera comprising the three living orders of Amphibia. Many species contain unidentified substances judged to be noxious based on predator aversion or human taste. Additionally, there is a great diversity of known compounds, some highly toxic as well as noxious, which can be tabulated under four broad categories: biogenic amines, peptides, bufodienolides (bufogenins) and alkaloids. The last category includes alkaloids derived from biogenic amines, water-soluble alkaloids (tetrodotoxins) and lipophilic alkaloids. Most compounds are known only from skin of adult amphibians, but the toxic and noxious properties of eggs and larvae of certain salamanders and toads can be attributed to tetrodotoxins and bufodienolides, which occur also in adult tissues other than skin. Predator aversion and various antipredator behaviors and aposematic colorations clearly prove the defensive value of these diverse metabolites, whether or not they are elaborated primarily (e.g. alkaloids) or secondarily (e.g. some peptides and biogenic amines) for this function. Lipophilic alkaloids include the samandarine alkaloids, known definitely only from an Old World genus of salamanders, and the more than 200 dendrobatid alkaloids. Nearly all the latter are unique to neotropical poison frogs of the genera Dendrobates and Phyllobates (Dendrobatidae), except for seemingly homoplastic occurrences of a few such alkaloids in small brightly colored anurans of several other families. Owing to recent discoveries and new structural information, the dendrobatid alkaloids are here partitioned among the following major and minor classes: batrachotoxins, histrionicotoxins, indolizidines, pumiliotoxin-A class and its allopumiliotoxin and homopumiliotoxin subclasses

  11. Further classification of skin alkaloids from neotropical poison frogs (Dendrobatidae), with a general survey of toxic/noxious substances in the amphibia.

    PubMed

    Daly, J W; Myers, C W; Whittaker, N

    1987-01-01

    Cutaneous granular glands are a shared character of adult amphibians, including caecilians, and are thought to be the source of most biologically active compounds in amphibian skin. Data are available from one or more species in over 100 of nearly 400 genera comprising the three living orders of Amphibia. Many species contain unidentified substances judged to be noxious based on predator aversion or human taste. Additionally, there is a great diversity of known compounds, some highly toxic as well as noxious, which can be tabulated under four broad categories: biogenic amines, peptides, bufodienolides (bufogenins) and alkaloids. The last category includes alkaloids derived from biogenic amines, water-soluble alkaloids (tetrodotoxins) and lipophilic alkaloids. Most compounds are known only from skin of adult amphibians, but the toxic and noxious properties of eggs and larvae of certain salamanders and toads can be attributed to tetrodotoxins and bufodienolides, which occur also in adult tissues other than skin. Predator aversion and various antipredator behaviors and aposematic colorations clearly prove the defensive value of these diverse metabolites, whether or not they are elaborated primarily (e.g. alkaloids) or secondarily (e.g. some peptides and biogenic amines) for this function. Lipophilic alkaloids include the samandarine alkaloids, known definitely only from an Old World genus of salamanders, and the more than 200 dendrobatid alkaloids. Nearly all the latter are unique to neotropical poison frogs of the genera Dendrobates and Phyllobates (Dendrobatidae), except for seemingly homoplastic occurrences of a few such alkaloids in small brightly colored anurans of several other families. Owing to recent discoveries and new structural information, the dendrobatid alkaloids are here partitioned among the following major and minor classes: batrachotoxins, histrionicotoxins, indolizidines, pumiliotoxin-A class and its allopumiliotoxin and homopumiliotoxin subclasses

  12. Channels Formed by Botulinum, Tetanus, and Diphtheria Toxins in Planar Lipid Bilayers: Relevance to Translocation of Proteins across Membranes

    NASA Astrophysics Data System (ADS)

    Hoch, David H.; Romero-Mira, Miryam; Ehrlich, Barbara E.; Finkelstein, Alan; Dasgupta, Bibhuti R.; Simpson, Lance L.

    1985-03-01

    The heavy chains of both botulinum neurotoxin type B and tetanus toxin form channels in planar bilayer membranes. These channels have pH-dependent and voltage-dependent properties that are remarkably similar to those previously described for diphtheria toxin. Selectivity experiments with anions and cations show that the channels formed by the heavy chains of all three toxins are large; thus, these channels could serve as ``tunnel proteins'' for translocation of active peptide fragments. These findings support the hypothesis that the active fragments of botulinum neurotoxin and tetanus toxin, like that of diphtheria toxin, are translocated across the membranes of acidic vesicles.

  13. Permission Forms

    ERIC Educational Resources Information Center

    Zirkel, Perry A.

    2005-01-01

    The prevailing practice in public schools is to routinely require permission or release forms for field trips and other activities that pose potential for liability. The legal status of such forms varies, but they are generally considered to be neither rock-solid protection nor legally valueless in terms of immunity. The following case and the…

  14. Immunocytochemical localization of gonadotropin-releasing hormones in the brain of a viviparous caecilian amphibian, Typhlonectes natans (Amphibia: Gymnophiona).

    PubMed

    Ebersole, T J; Boyd, S K

    2000-01-01

    The molecular forms and brain distribution of gonadotropin-releasing hormone (GnRH) have been well studied in the amphibian orders Urodela (salamanders and newts) and Anura (frogs and toads). In the order Gymnophiona (caecilians), however, few species have been investigated. Antibodies against different molecular forms of GnRH were used to immunohistochemically localize the GnRH-containing neurons in the brain of the caecilian, Typhlonectes natans which differs from most other amphibians in that it is viviparous. An antibody selective for mammalian GnRH recognized cell bodies predominantly in the septo-preoptic area but only with occasional cell bodies in the lateral hypothalamus and ventral thalamic eminence. Thick, prominent fibers in the septal region and fibers within the terminal nerve were also labeled. An antibody selective for chicken-II GnRH labeled a population of cell bodies in the dorsal hypothalamus, ventral thalamus and midbrain tegmentum. Thin fibers projected laterally from these cells. An antibody specific for salmon GnRH did not label cell bodies but did show intense terminal field immunoreactivity. The brain of this caecilian, therefore, contains three antigenically distinct forms of GnRH. The mammalian and chicken-II GnRH peptides have been shown in other amphibians but the distribution of cells and fibers was unique in this caecilian.

  15. Immunocytochemical localization of gonadotropin-releasing hormones in the brain of a viviparous caecilian amphibian, Typhlonectes natans (Amphibia: Gymnophiona).

    PubMed

    Ebersole, T J; Boyd, S K

    2000-01-01

    The molecular forms and brain distribution of gonadotropin-releasing hormone (GnRH) have been well studied in the amphibian orders Urodela (salamanders and newts) and Anura (frogs and toads). In the order Gymnophiona (caecilians), however, few species have been investigated. Antibodies against different molecular forms of GnRH were used to immunohistochemically localize the GnRH-containing neurons in the brain of the caecilian, Typhlonectes natans which differs from most other amphibians in that it is viviparous. An antibody selective for mammalian GnRH recognized cell bodies predominantly in the septo-preoptic area but only with occasional cell bodies in the lateral hypothalamus and ventral thalamic eminence. Thick, prominent fibers in the septal region and fibers within the terminal nerve were also labeled. An antibody selective for chicken-II GnRH labeled a population of cell bodies in the dorsal hypothalamus, ventral thalamus and midbrain tegmentum. Thin fibers projected laterally from these cells. An antibody specific for salmon GnRH did not label cell bodies but did show intense terminal field immunoreactivity. The brain of this caecilian, therefore, contains three antigenically distinct forms of GnRH. The mammalian and chicken-II GnRH peptides have been shown in other amphibians but the distribution of cells and fibers was unique in this caecilian. PMID:10773622

  16. Good form.

    PubMed

    Sorrel, Amy Lynn

    2015-03-01

    New standardized prior authorization forms for health care services and prescription drugs released by the Texas Department of Insurance promise to alleviate administrative busy work and its related costs.

  17. Highly complex mitochondrial DNA genealogy in an endemic Japanese subterranean breeding brown frog Rana tagoi (Amphibia, Anura, Ranidae).

    PubMed

    Eto, Koshiro; Matsui, Masafumi; Sugahara, Takahiro; Tanaka-Ueno, Tomoko

    2012-10-01

    The endemic Japanese frog Rana tagoi is unique among Holarctic brown frogs in that it breeds in small subterranean streams. Using mitochondrial 16S ribosomal RNA and NADH dehydrogenase subunit 1 genes, we investigated genealogical relationships among geographic samples of this species together with its relative R. sakuraii, which is also a unique stream breeder. These two species together form a monophyletic group, within which both are reciprocally paraphyletic. Rana tagoi is divided into two major clades (Clade A and B) that are composed of 14 genetic groups. Rana sakuraii is included in Clade A and split into two genetic groups, one of which forms a clade (Subclade A-2) with sympatric R. tagoi. This species-level paraphyly appears to be caused by incomplete taxonomy, in addition to introgressive hybridization and/or incomplete lineage sorting. Rana tagoi strongly differs from other Japanese anurans in its geographic pattern of genetic differentiation, most probably in relation to its unique reproductive habits. Taxonomically, R. tagoi surely includes many cryptic species.

  18. A Phenotypic Point of View of the Adaptive Radiation of Crested Newts (Triturus cristatus Superspecies, Caudata, Amphibia).

    PubMed

    Ivanović, Ana; Džukić, Georg; Kalezić, Miloš

    2012-01-01

    The divergence in phenotype and habitat preference within the crested newt Triturus cristatus superspecies, examined across different ontogenetic stages, provides an excellent setting to explore the pattern of adaptive radiation. The crested newts form a well-supported monophyletic clade for which at least the full mitochondrial DNA phylogeny is resolved. Here we summarise studies that explored the variation in morphological (larval and adult body form, limb skeleton, and skull shape) and other phenotypic traits (early life history, developmental sequences, larval growth rate, and sexual dimorphism) to infer the magnitude and direction of evolutionary changes in crested newts. The phenotypic traits show a high level of concordance in the pattern of variation; there is a cline-like variation, from T. dobrogicus, via T. cristatus, T. carnifex, and T. macedonicus to the T. karelinii group. This pattern matches the cline of ecological preferences; T. dobrogicus is relatively aquatic, followed by T. cristatus. T. macedonicus, T. carnifex, and the T. karelinii group are relatively terrestrial. The observed pattern indicates that phenotypic diversification in crested newts emerged due to an evolutionary switch in ecological preferences. Furthermore, the pattern indicates that heterochronic changes, or changes in the timing and rate of development, underlie the observed phenotypic evolutionary diversification.

  19. Spermiogenesis in caecilians Ichthyophis tricolor and Uraeotyphlus cf. narayani (Amphibia: Gymnophiona): analysis by light and transmission electron microscopy.

    PubMed

    Smita, Mathew; George, Jancy M; Girija, R; Akbarsha, M A; Oommen, Oommen V

    2004-10-01

    Spermiogenesis, known as spermateleosis in lower vertebrates, is the transformation of the round spermatid into a highly specialized spermatozoon with a species-specific structure. Spermateleosis and sperm morphology of two species of caecilians, Ichthyophis tricolor and Uraeotyphlus cf. narayani, from the Western Ghats of Kerala, India, were studied using light and transmission electron microscopy. Spermateleosis is described in early, mid-, and late phases. During the early phase, the spermatid nucleus does not elongate, but the acrosome vesicle is Golgi-derived and its material is produced as a homogeneous substance rather than as discrete granules. In development of the acrosome, the centrioles shift in position to the lower half of the cell. The acrosomal vesicles take the full shape of the acrosome with the establishment of the perforatorium in midphase. An endonuclear canal develops and accommodates the perforatorium. The incipient flagellum is laid down when the proximal centriole attaches to the posterior side of the nucleus and the distal centriole connects to the proximal centriole, which forms the basal granule of the acrosome. The axial fiber also appears during midphase. The mitochondria shift in position to the posterior pole of the cell to commence establishment of the midphase. Late phase is characterized by nuclear condensation and elongation. Consequently, the final organization of the sperm is established with the head containing the nucleus and the acrosome. The undulating membrane separates the axoneme and axial fiber. Most of the cytoplasm is lost as residual bodies.

  20. Long bone histology of the stem salamander Kokartus honorarius (Amphibia: Caudata) from the Middle Jurassic of Kyrgyzstan.

    PubMed

    Skutschas, Pavel; Stein, Koen

    2015-04-01

    Kokartus honorarius from the Middle Jurassic (Bathonian) of Kyrgyzstan is one of the oldest salamanders in the fossil record, characterized by a mixture of plesiomorphic morphological features and characters shared with crown-group salamanders. Here we present a detailed histological analysis of its long bones. The analysis of a growth series demonstrates a significant histological maturation during ontogeny, expressed by the progressive appearance of longitudinally oriented primary vascular canals, primary osteons, growth marks, remodelling features in primary bone tissues, as well as progressive resorption of the calcified cartilage, formation of endochondral bone and development of cartilaginous to bony trabeculae in the epiphyses. Apart from the presence of secondary osteons, the long bone histology of Kokartus is very similar to that of miniaturized temnospondyls, other Jurassic stem salamanders, miniaturized seymouriamorphs and modern crown-group salamanders. We propose that the presence of secondary osteons in Kokartus honorarius is a plesiomorphic feature, and the loss of secondary osteons in the long bones of crown-group salamanders as well as in those of miniaturized temnospondyls is the result of miniaturization processes. Hitherto, all stem salamander long bong histology (Kokartus, Marmorerpeton and 'salamander A') has been generally described as having paedomorphic features (i.e. the presence of Katschenko's Line and a layer of calcified cartilage), these taxa were thus most likely neotenic forms. The absence of clear lines of arrested growth and annuli in long bones of Kokartus honorarius suggests that the animals lived in an environment with stable local conditions.

  1. Spermiogenesis in caecilians Ichthyophis tricolor and Uraeotyphlus cf. narayani (Amphibia: Gymnophiona): analysis by light and transmission electron microscopy.

    PubMed

    Smita, Mathew; George, Jancy M; Girija, R; Akbarsha, M A; Oommen, Oommen V

    2004-10-01

    Spermiogenesis, known as spermateleosis in lower vertebrates, is the transformation of the round spermatid into a highly specialized spermatozoon with a species-specific structure. Spermateleosis and sperm morphology of two species of caecilians, Ichthyophis tricolor and Uraeotyphlus cf. narayani, from the Western Ghats of Kerala, India, were studied using light and transmission electron microscopy. Spermateleosis is described in early, mid-, and late phases. During the early phase, the spermatid nucleus does not elongate, but the acrosome vesicle is Golgi-derived and its material is produced as a homogeneous substance rather than as discrete granules. In development of the acrosome, the centrioles shift in position to the lower half of the cell. The acrosomal vesicles take the full shape of the acrosome with the establishment of the perforatorium in midphase. An endonuclear canal develops and accommodates the perforatorium. The incipient flagellum is laid down when the proximal centriole attaches to the posterior side of the nucleus and the distal centriole connects to the proximal centriole, which forms the basal granule of the acrosome. The axial fiber also appears during midphase. The mitochondria shift in position to the posterior pole of the cell to commence establishment of the midphase. Late phase is characterized by nuclear condensation and elongation. Consequently, the final organization of the sperm is established with the head containing the nucleus and the acrosome. The undulating membrane separates the axoneme and axial fiber. Most of the cytoplasm is lost as residual bodies. PMID:15352204

  2. Early development of chondrocranium in the tailed frog Ascaphus truei (Amphibia: Anura): implications for anuran palatoquadrate homologies.

    PubMed

    Reiss, J O

    1997-01-01

    Chondrocranial development in Ascaphus truei was studied by serial sectioning and graphical reconstruction. Nine stages (21-29; 9-18 mm TL) were examined. Mesodermal cells were distinguished from ectomesenchymal (neural crest derived) cells by retained yolk granules. Ectomesenchymal parts of the chondrocranium include the suprarostrals, pila preoptica, anterior trabecula, and palatoquadrate. Mesodermal parts of the chondrocranium include the orbital cartilage, posterior trabecula, parachordal, basiotic lamina, and otic capsule. Development of the palatoquadrate is as follows. The pterygoid process first connects with the trabecula far rostrally; their fusion progresses caudally. The ascending process connects with a mesodermal bar that extends from the orbital cartilage to the otic capsule, and forms the ventral border of the dorsal trigeminal outlet. This bar is the "ascending process" of Ascaphus adults; it is a neurocranial, not palatoquadrate structure. The basal process chondrifies in an ectomesenchymal strand running from the quadrate keel to the postpalatine commissure. Later, the postpalatine commissure and basal process extend anteromedially to contact the floor of the anterior cupula of the otic capsule, creating separate foramina for the palatine and hyomandibular branches of the facial nerve. Based on these data, and on comparison with other frogs and salamanders, the anuran anterior quadratocranial commissure is homologized with the pterygoid process of salamanders, the anuran basal process (= "pseudobasal" or "hyobasal" process) with the basal process of salamanders, and the anuran otic ledge with the basitrabecular process of salamanders. The extensive similarities in palatoquadrate structure and development between frogs and salamanders, and lacking in caecilians, are not phylogenetically informative. Available information on fossil outgroups suggests that some of these similarities are primitive for Lissamphibia, whereas for others the polarity is

  3. Distribution of somatostatin-like immunoreactivity in the brain of the caecilian Dermophis mexicanus (Amphibia: Gymnophiona): comparative aspects in amphibians.

    PubMed

    López, Jesús M; Moreno, Nerea; Morona, Ruth; Muñoz, Margarita; Domínguez, Laura; González, Agustín

    2007-03-20

    The organization of the somatostatin-like-immunoreactive (SOM-ir) structures in the brain of anuran and urodele amphibians has been well documented, and significant differences were noted between the two amphibian orders. However, comparable data are not available for the third order of amphibians, the gymnophionans (caecilians). In the present study, we analyzed the anatomical distribution of SOM-ir cells and fibers in the brain of the gymnophionan Dermophis mexicanus. In addition, because of its known relationship with catecholamines in other vertebrates, double immunostaining for SOM and tyrosine hydroxylase was used to investigate this situation in the gymnophionan. Abundant SOM-ir cell bodies and fibers were widely distributed throughout the brain. In the telencephalon, pallial and subpallial cells were labeled, being most numerous in the medial pallium and amygdaloid region. Most of the SOM-ir neurons were found in the preoptic area and hypothalamus and showed a clear projection to the median eminence. Less conspicuously, SOM-ir structures were found in the thalamus, tectum, tegmentum, and reticular formation. Both SOM-ir cells and fibers were demonstrated in the spinal cord. The double-immunohistofluorescence technique revealed that catecholaminergic neurons and SOM-ir cells are largely intermingled in many brain regions but form totally separated populations. Many differences were found between the distribution of SOM-ir structures in Dermophis and that in anurans or urodeles. Some features were shared only with anurans, such as the abundant pallial SOM-ir cells, whereas others were common only to urodeles, such as the organization of the hypothalamohypophysial SOM-ir system. In addition, some characteristics were found only in Dermophis, such as the localization of the SOM-ir spinal cells and the lack of colocalization of catecholamines and SOM throughout the brain. Therefore, any conclusions concerning the SOM system in amphibians are incomplete without

  4. Apoptosis, proliferation and presence of estradiol receptors in the testes and Bidder's organ of the toad Rhinella arenarum (Amphibia, Anura).

    PubMed

    Scaia, María Florencia; Czuchlej, Silvia Cristina; Cervino, Nadia; Ceballos, Nora Raquel

    2016-04-01

    The dynamic equilibrium between spermatogonial proliferation and testicular apoptosis determines the progression of spermatogenesis in amphibians. Estrogens and their receptors play a central role in regulating spermatogenesis in vertebrates, and in some species of anurans, estradiol (E2 ) is involved in the regulation of spermatogonial proliferation and apoptosis of germ cells. Bidder's organ (BO) is a structure characteristic of Bufonidae that has historically been compared to an undeveloped ovary. In adult Rhinella arenarum males, BO is one of the main sources of plasma E2 . The aim of this study was 1) to describe the seasonal variations in testicular apoptosis, spermatogonial proliferation, and cellular proliferation in BO; and 2) to analyze the presence and localization of estrogen receptor β (ERβ) in the testes and BO of R. arenarum. Testicular fragments and BOs from animals collected during the year were labeled with 5-bromo-2'-deoxyuridine (BrdU) and BrdU incorporation was determined using immunohistochemistry. Apoptosis in testicular sections was detected using the TUNEL method, and ERβ localization was assessed using immunohistochemistry in testes and BOs. The results indicate that spermatogonial proliferation is highest during the reproductive season and that cysts of spermatocytes and spermatids undergo apoptosis during the postreproductive season. Furthermore, the proliferation of follicular cells is highest during the reproductive and postreproductive seasons. ERβ was primarily detected by immunolocalization in Sertoli cells, follicular cells, and oocytes. Taken together, these results suggest that cysts that do not form spermatozoa are removed from testes by apoptosis and that estrogens regulate both spermatogenesis and oogenesis in adult males of R. arenarum.

  5. Distribution of somatostatin-like immunoreactivity in the brain of the caecilian Dermophis mexicanus (Amphibia: Gymnophiona): comparative aspects in amphibians.

    PubMed

    López, Jesús M; Moreno, Nerea; Morona, Ruth; Muñoz, Margarita; Domínguez, Laura; González, Agustín

    2007-03-20

    The organization of the somatostatin-like-immunoreactive (SOM-ir) structures in the brain of anuran and urodele amphibians has been well documented, and significant differences were noted between the two amphibian orders. However, comparable data are not available for the third order of amphibians, the gymnophionans (caecilians). In the present study, we analyzed the anatomical distribution of SOM-ir cells and fibers in the brain of the gymnophionan Dermophis mexicanus. In addition, because of its known relationship with catecholamines in other vertebrates, double immunostaining for SOM and tyrosine hydroxylase was used to investigate this situation in the gymnophionan. Abundant SOM-ir cell bodies and fibers were widely distributed throughout the brain. In the telencephalon, pallial and subpallial cells were labeled, being most numerous in the medial pallium and amygdaloid region. Most of the SOM-ir neurons were found in the preoptic area and hypothalamus and showed a clear projection to the median eminence. Less conspicuously, SOM-ir structures were found in the thalamus, tectum, tegmentum, and reticular formation. Both SOM-ir cells and fibers were demonstrated in the spinal cord. The double-immunohistofluorescence technique revealed that catecholaminergic neurons and SOM-ir cells are largely intermingled in many brain regions but form totally separated populations. Many differences were found between the distribution of SOM-ir structures in Dermophis and that in anurans or urodeles. Some features were shared only with anurans, such as the abundant pallial SOM-ir cells, whereas others were common only to urodeles, such as the organization of the hypothalamohypophysial SOM-ir system. In addition, some characteristics were found only in Dermophis, such as the localization of the SOM-ir spinal cells and the lack of colocalization of catecholamines and SOM throughout the brain. Therefore, any conclusions concerning the SOM system in amphibians are incomplete without

  6. Early development of chondrocranium in the tailed frog Ascaphus truei (Amphibia: Anura): implications for anuran palatoquadrate homologies.

    PubMed

    Reiss, J O

    1997-01-01

    Chondrocranial development in Ascaphus truei was studied by serial sectioning and graphical reconstruction. Nine stages (21-29; 9-18 mm TL) were examined. Mesodermal cells were distinguished from ectomesenchymal (neural crest derived) cells by retained yolk granules. Ectomesenchymal parts of the chondrocranium include the suprarostrals, pila preoptica, anterior trabecula, and palatoquadrate. Mesodermal parts of the chondrocranium include the orbital cartilage, posterior trabecula, parachordal, basiotic lamina, and otic capsule. Development of the palatoquadrate is as follows. The pterygoid process first connects with the trabecula far rostrally; their fusion progresses caudally. The ascending process connects with a mesodermal bar that extends from the orbital cartilage to the otic capsule, and forms the ventral border of the dorsal trigeminal outlet. This bar is the "ascending process" of Ascaphus adults; it is a neurocranial, not palatoquadrate structure. The basal process chondrifies in an ectomesenchymal strand running from the quadrate keel to the postpalatine commissure. Later, the postpalatine commissure and basal process extend anteromedially to contact the floor of the anterior cupula of the otic capsule, creating separate foramina for the palatine and hyomandibular branches of the facial nerve. Based on these data, and on comparison with other frogs and salamanders, the anuran anterior quadratocranial commissure is homologized with the pterygoid process of salamanders, the anuran basal process (= "pseudobasal" or "hyobasal" process) with the basal process of salamanders, and the anuran otic ledge with the basitrabecular process of salamanders. The extensive similarities in palatoquadrate structure and development between frogs and salamanders, and lacking in caecilians, are not phylogenetically informative. Available information on fossil outgroups suggests that some of these similarities are primitive for Lissamphibia, whereas for others the polarity is

  7. Preparation and ultrastructure of spermatozoa from green poison frogs, Dendrobates auratus, following hormonal induced spermiation (Amphibia, Anura, Dendrobatidae).

    PubMed

    Lipke, Christian; Meinecke-Tillmann, Sabine; Meyer, Wilfried; Meinecke, Burkhard

    2009-07-01

    mitochondrial collar with a proximal and a distal centriole. The latter gives rise to the axoneme which alone forms the flagellum. The sperm ultrastructure of D. auratus differs from that of other Dendrobatidae because of the absence of a nuclear space and the absence of the undulating membrane associated with an axial fibre. This tail conformation is found in the Ranoidea but not in the Bufonoidea. These results show that the spermatozoa of D. auratus are the first within the Dendrobatidae without accessory tail structures. Methods of using sperm samples from hormonal treated frogs for ultrastructural studies is not only reasonable to examine e.g. amphibian phylogeny without killing frogs threatened with extinction but allows investigations in the field of assisted reproduction and male fertility for example in conservation programs for endangered amphibians. PMID:18657373

  8. Dimers of mitochondrial ATP synthase form the permeability transition pore

    PubMed Central

    Giorgio, Valentina; von Stockum, Sophia; Antoniel, Manuela; Fabbro, Astrid; Fogolari, Federico; Forte, Michael; Glick, Gary D.; Petronilli, Valeria; Zoratti, Mario; Szabó, Ildikó; Lippe, Giovanna; Bernardi, Paolo

    2013-01-01

    Here we define the molecular nature of the mitochondrial permeability transition pore (PTP), a key effector of cell death. The PTP is regulated by matrix cyclophilin D (CyPD), which also binds the lateral stalk of the FOF1 ATP synthase. We show that CyPD binds the oligomycin sensitivity-conferring protein subunit of the enzyme at the same site as the ATP synthase inhibitor benzodiazepine 423 (Bz-423), that Bz-423 sensitizes the PTP to Ca2+ like CyPD itself, and that decreasing oligomycin sensitivity-conferring protein expression by RNAi increases the sensitivity of the PTP to Ca2+. Purified dimers of the ATP synthase, which did not contain voltage-dependent anion channel or adenine nucleotide translocator, were reconstituted into lipid bilayers. In the presence of Ca2+, addition of Bz-423 triggered opening of a channel with currents that were typical of the mitochondrial megachannel, which is the PTP electrophysiological equivalent. Channel openings were inhibited by the ATP synthase inhibitor AMP-PNP (γ-imino ATP, a nonhydrolyzable ATP analog) and Mg2+/ADP. These results indicate that the PTP forms from dimers of the ATP synthase. PMID:23530243

  9. Densified waste form and method for forming

    DOEpatents

    Garino, Terry J.; Nenoff, Tina M.; Sava Gallis, Dorina Florentina

    2016-05-17

    Materials and methods of making densified waste forms for temperature sensitive waste material, such as nuclear waste, formed with low temperature processing using metallic powder that forms the matrix that encapsulates the temperature sensitive waste material. The densified waste form includes a temperature sensitive waste material in a physically densified matrix, the matrix is a compacted metallic powder. The method for forming the densified waste form includes mixing a metallic powder and a temperature sensitive waste material to form a waste form precursor. The waste form precursor is compacted with sufficient pressure to densify the waste precursor and encapsulate the temperature sensitive waste material in a physically densified matrix.

  10. Densified waste form and method for forming

    SciTech Connect

    Garino, Terry J.; Nenoff, Tina M.; Sava Gallis, Dorina Florentina

    2015-08-25

    Materials and methods of making densified waste forms for temperature sensitive waste material, such as nuclear waste, formed with low temperature processing using metallic powder that forms the matrix that encapsulates the temperature sensitive waste material. The densified waste form includes a temperature sensitive waste material in a physically densified matrix, the matrix is a compacted metallic powder. The method for forming the densified waste form includes mixing a metallic powder and a temperature sensitive waste material to form a waste form precursor. The waste form precursor is compacted with sufficient pressure to densify the waste precursor and encapsulate the temperature sensitive waste material in a physically densified matrix.

  11. Evolution of alanine:glyoxylate aminotransferase 1 peroxisomal and mitochondrial targeting. A survey of its subcellular distribution in the livers of various representatives of the classes Mammalia, Aves and Amphibia.

    PubMed

    Danpure, C J; Fryer, P; Jennings, P R; Allsop, J; Griffiths, S; Cunningham, A

    1994-08-01

    As part of a wider study on the molecular evolution of alanine:glyoxylate aminotransferase 1 (AGT1) intracellular compartmentalization, we have determined the subcellular distribution of immunoreactive AGT1, using postembedding protein A-gold immunoelectron microscopy, in the livers of various members of the classes Mammalia, Aves, and Amphibia. As far as organellar distribution is concerned, three categories could be distinguished. In members of the first category (type I), all, or nearly all, of the immunoreactive AGT1 was concentrated within the peroxisomes. In the second category (type II), AGT1 was found more evenly distributed in both peroxisomes and mitochondria. In the third category (type III), AGT1 was localized mainly within the mitochondria with much lower, but widely variable, amounts in the peroxisomes. Type I animals include the human, two great apes (gorilla, orangutan), two Old World monkeys (anubis baboon, Japanese macaque), a New World monkey (white-faced Saki monkey), a lago, morph (European rabbit), a bat (Seba's short-tailed fruit bat), two caviomorph rodents (guinea pig, orange-rumped agouti), and two Australian marsupials (koala, Bennett's wallaby). Type II animals include two New World monkeys (common marmoset, cotton-top tamarin), three prosimians (brown lemur, fat-tailed dwarf lemur, pygmy slow loris), five rodents (a hybrid crested porcupine, Colombian ground squirrel, laboratory rat, laboratory mouse, golden hamster), an American marsupial (grey short-tailed opossum), and a bird (raven). Type III animals include the large tree shrew, three insectivores (common Eurasian mole, European hedgehog, house shrew), four carnivores (domestic cat, ocelot, domestic dog, polecat ferret), and an amphibian (common frog). In addition to these categories, some animals (e.g. guinea pig, common frog) possessed significant amounts of cytosolic AGT1. Whereas the subcellular distribution of AGT1 in some orders (e.g. Insectivora and Carnivora) did not appear

  12. Helicobacter pylori vacuolating toxin forms anion-selective channels in planar lipid bilayers: possible implications for the mechanism of cellular vacuolation.

    PubMed Central

    Tombola, F; Carlesso, C; Szabò, I; de Bernard, M; Reyrat, J M; Telford, J L; Rappuoli, R; Montecucco, C; Papini, E; Zoratti, M

    1999-01-01

    The Helicobacter pylori VacA toxin plays a major role in the gastric pathologies associated with this bacterium. When added to cultured cells, VacA induces vacuolation, an effect potentiated by preexposure of the toxin to low pH. Its mechanism of action is unknown. We report here that VacA forms anion-selective, voltage-dependent pores in artificial membranes. Channel formation was greatly potentiated by acidic conditions or by pretreatment of VacA at low pH. No requirement for particular lipid(s) was identified. Selectivity studies showed that anion selectivity was maintained over the pH range 4.8-12, with the following permeability sequence: Cl- approximately HCO3- > pyruvate > gluconate > K+ approximately Li+ approximately Ba2+ > NH4+. Membrane permeabilization was due to the incorporation of channels with a voltage-dependent conductance in the 10-30 pS range (2 M KCl), displaying a voltage-independent high open probability. Deletion of the NH2 terminus domain (p37) or chemical modification of VacA by diethylpyrocarbonate inhibited both channel activity and vacuolation of HeLa cells without affecting toxin internalization by the cells. Collectively, these observations strongly suggest that VacA channel formation is needed to induce cellular vacuolation, possibly by inducing an osmotic imbalance of intracellular acidic compartments. PMID:10049322

  13. Molecular phylogeny and biogeography of caecilians from Southeast Asia (Amphibia, Gymnophiona, Ichthyophiidae), with special reference to high cryptic species diversity in Sundaland.

    PubMed

    Nishikawa, Kanto; Matsui, Masafumi; Yong, Hoi-Sen; Ahmad, Norhayati; Yambun, Paul; Belabut, Daicus M; Sudin, Ahmad; Hamidy, Amir; Orlov, Nikolai L; Ota, Hidetoshi; Yoshikawa, Natsuhiko; Tominaga, Atsushi; Shimada, Tomohiko

    2012-06-01

    We investigated the phylogenetic relationships and estimated the history of species diversification and character evolution in two ichthyophiid genera: Caudacaecilia and Ichthyophis. We estimated the phylogenetic relationships of 67 samples from 33 localities in Southeast Asia from 3840-bp sequences of the mitochondrial 12S rRNA, 16S rRNA, and cyt b genes using Bayesian inference, maximum likelihood, and maximum parsimony methods. The Southeast Asian samples formed a well-supported clade differentiated from a South Asian sample. The Southeast Asian clade was divided into two subclades, one containing samples from South China, Indochina, Malay Peninsula, and Java. The other consisted of samples from Borneo and the Philippines. Neither Caudacaecilia nor Ichthyophis was monophyletic, nor did samples with or without light stripes lateral to the body form clades. We found several distinct sympatric lineages and undescribed species, especially from Sundaland.

  14. Molecular phylogeny and biogeography of caecilians from Southeast Asia (Amphibia, Gymnophiona, Ichthyophiidae), with special reference to high cryptic species diversity in Sundaland.

    PubMed

    Nishikawa, Kanto; Matsui, Masafumi; Yong, Hoi-Sen; Ahmad, Norhayati; Yambun, Paul; Belabut, Daicus M; Sudin, Ahmad; Hamidy, Amir; Orlov, Nikolai L; Ota, Hidetoshi; Yoshikawa, Natsuhiko; Tominaga, Atsushi; Shimada, Tomohiko

    2012-06-01

    We investigated the phylogenetic relationships and estimated the history of species diversification and character evolution in two ichthyophiid genera: Caudacaecilia and Ichthyophis. We estimated the phylogenetic relationships of 67 samples from 33 localities in Southeast Asia from 3840-bp sequences of the mitochondrial 12S rRNA, 16S rRNA, and cyt b genes using Bayesian inference, maximum likelihood, and maximum parsimony methods. The Southeast Asian samples formed a well-supported clade differentiated from a South Asian sample. The Southeast Asian clade was divided into two subclades, one containing samples from South China, Indochina, Malay Peninsula, and Java. The other consisted of samples from Borneo and the Philippines. Neither Caudacaecilia nor Ichthyophis was monophyletic, nor did samples with or without light stripes lateral to the body form clades. We found several distinct sympatric lineages and undescribed species, especially from Sundaland. PMID:22387289

  15. Size and voltage dependence of effective anisotropy in sub-100-nm perpendicular magnetic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Piotrowski, Stephan K.; Bapna, Mukund; Oberdick, Samuel D.; Majetich, Sara A.; Li, Mingen; Chien, C. L.; Ahmed, Rizvi; Victora, R. H.

    2016-07-01

    Magnetic tunnel junctions with perpendicular magnetic anisotropy are investigated using a conductive atomic force microscope. The 1.23 -nm Co40Fe40B20 recording layer coercivity exhibits a size dependence which suggests single-domain behavior for diameters ≤100 nm. Focusing on devices with diameters smaller than 100 nm, we determine the effect of voltage and size on the effective device anisotropy Keff using two different techniques. Keff is extracted both from distributions of the switching fields of the recording and reference layers and from measurement of thermal fluctuations of the recording layer magnetization when a field close to the switching field is applied. The results from both sets of measurements reveal that Keff increases monotonically with decreasing junction diameter, consistent with the size dependence of the demagnetization energy density. We demonstrate that Keff can be controlled with a voltage down to the smallest size measured, 64 nm.

  16. Voltage-dependent magnetic phase transition in magneto-electric epitaxial Cr2O3 nanoclusters

    NASA Astrophysics Data System (ADS)

    Halley, David; Najjari, Nabil; Godel, Florian; Hamieh, Mohamad; Doudin, Bernard; Henry, Yves

    2016-06-01

    We observe, as a function of temperature, a second order magnetic phase transition in nanometric Cr2O3 clusters that are epitaxially embedded in an insulating MgO matrix. They are investigated through their tunnel magneto-resistance signature, the MgO layer being used as a tunnel barrier. We infer the small magnetic dipoles carried by the Cr2O3 clusters and provide evidence of a magnetic phase transition at low temperature in those clusters: they evolve from an anti ferromagnetic state, with zero net moment close to 0 K, to a weak ferromagnetic state that saturates above about 10 K. The influence of magneto-electric effects on the weak ferromagnetic phase is also striking: the second order transition temperature turns out to be linearly dependent on the applied electric field.

  17. Voltage dependence of cluster size in carbon films using plasma immersion ion implantation

    NASA Astrophysics Data System (ADS)

    McKenzie, D. R.; Tarrant, R. N.; Bilek, M. M. M.; Pearce, G.; Marks, N. A.; McCulloch, D. G.; Lim, S. H. N.

    2003-05-01

    Carbon films were prepared using a cathodic arc with plasma immersion ion implantation (PIII). Using Raman spectroscopy to determine cluster size, a comparison is made between cluster sizes at high voltage and a low duty cycle of pulses with the cluster sizes produced at low voltage and a higher duty cycle. We find that for ion implantation in the range 2-20 kV, the cluster size depends more on implantation energy ( E) than implantation frequency ( f), unlike stress relief, which we have previously shown [M.M.M. Bilek, et al., IEEE Trans. in Plasma Sci., Proceedings 20th ISDEIV 1-5 July 2002, Tours, France, Cat. No. 02CH37331, IEEE, Piscataway, NJ, USA, p. 95] to be dependent on the product Ef. These differences are interpreted in terms of a model in which the ion impacts create thermal spikes.

  18. Down-regulation of voltage-dependent sodium channels initiated by sodium influx in developing neurons

    SciTech Connect

    Dargent, B.; Couraud, F. )

    1990-08-01

    To address the issue of whether regulatory feedback exists between the electrical activity of a neuron and ion-channel density, the authors investigated the effect of Na{sup +}-channel activators (scorpion {alpha} toxin, batrachotoxin, and veratridine) on the density of Na{sup +} channels in fetal rat brain neurons in vitro. A partial but rapid (t{sub 1/2}, 15 min) disappearance of surface Na{sup +} channels was observed as measured by a decrease in the specific binding of ({sup 3}H)saxitoxin and {sup 125}I-labeled scorpion {beta} toxin and a decrease in specific {sup 22}Na{sup +} uptake. Moreover, the increase in the number of Na{sup +} channels that normally occurs during neuronal maturation in vitro was inhibited by chronic channel activator treatment. The induced disappearance of Na{sup +} channels was abolished by tetrodotoxin, was found to be dependent on the external Na{sup +} concentration, and was prevented when either choline (a nonpermeant ion) or Li{sup +} (a permeant ion) was substituted for Na{sup +}. Amphotericin B, a Na{sup +} ionophore, and monensin were able to mimick the effect of Na{sup +}-channel activators, while a KCl depolarization failed to do this. This feedback regulation seems to be a neuronal property since Na{sup +}-channel density in cultured astrocytes was not affected by channel activator treatment or by amphotericin B. The present evidence suggests that an increase in intracellular Na{sup +} concentration, whether elicited by Na{sup +}-channel activators or mediated by a Na{sup +} ionophore, can induce a decrease in surface Na{sup +} channels and therefore is involved in down-regulation of Na{sup +}-channel density in fetal rat brain neurons in vitro.

  19. Contribution of voltage-dependent K+ and Ca2+ channels to coronary pressure-flow autoregulation.

    PubMed

    Berwick, Zachary C; Moberly, Steven P; Kohr, Meredith C; Morrical, Ethan B; Kurian, Michelle M; Dick, Gregory M; Tune, Johnathan D

    2012-05-01

    The mechanisms responsible for coronary pressure-flow autoregulation, a critical physiologic phenomenon that maintains coronary blood flow relatively constant in the presence of changes in perfusion pressure, remain poorly understood. This investigation tested the hypothesis that voltage-sensitive K(+) (K(V)) and Ca(2+) (Ca(V)1.2) channels play a critical role in coronary pressure-flow autoregulation in vivo. Experiments were performed in open-chest, anesthetized Ossabaw swine during step changes in coronary perfusion pressure (CPP) from 40 to 140 mmHg before and during inhibition of K(V) channels with 4-aminopyridine (4AP, 0.3 mM, ic) or Ca(V)1.2 channels with diltiazem (10 μg/min, ic). 4AP significantly decreased vasodilatory responses to H(2)O(2) (0.3-10 μM, ic) and coronary flow at CPPs = 60-140 mmHg. This decrease in coronary flow was associated with diminished ventricular contractile function (dP/dT) and myocardial oxygen consumption. However, the overall sensitivity to changes in CPP from 60 to 100 mmHg (i.e. autoregulatory gain; Gc) was unaltered by 4-AP administration (Gc = 0.46 ± 0.11 control vs. 0.46 ± 0.06 4-AP). In contrast, inhibition of Ca(V)1.2 channels progressively increased coronary blood flow at CPPs > 80 mmHg and substantially diminished coronary Gc to -0.20 ± 0.11 (P < 0.01), with no effect on contractile function or oxygen consumption. Taken together, these findings demonstrate that (1) K(V) channels tonically contribute to the control of microvascular resistance over a wide range of CPPs, but do not contribute to coronary responses to changes in pressure; (2) progressive activation of Ca(V)1.2 channels with increases in CPP represents a critical mechanism of coronary pressure-flow autoregulation.

  20. Voltage-dependent K channels in protoplasts of trap-lobe cells of Dionaea muscipula.

    PubMed

    Iijima, T; Hagiwara, S

    1987-01-01

    The outward rectification of the K+ current in mesophyll cell protoplasts from trap-lobes of Dionaea muscipula was studied with the patch-clamp technique. The rectification had instantaneous and time-dependent components. Changes in [K+]i strongly affected the conductance voltage relation of the plasma membrane while changes in [K+]o had little effect on the relation. Thus, the outward rectification depends on the membrane voltage and the concentration of intracellular K+. Corresponding single-channel activities were observed both in the intact membrane (cell-attached recording) and in excised patches. The single-channel conductance was about 3.3 pS with symmetrical solutions containing 30 mM K+.

  1. Down-regulation of voltage-dependent sodium channels initiated by sodium influx in developing neurons.

    PubMed Central

    Dargent, B; Couraud, F

    1990-01-01

    To address the issue of whether regulatory feedback exists between the electrical activity of a neuron and ion-channel density, we investigated the effect of Na(+)-channel activators (scorpion alpha toxin, batrachotoxin, and veratridine) on the density of Na+ channels in fetal rat brain neurons in vitro. A partial but rapid (t1/2, 15 min) disappearance of surface Na+ channels was observed as measured by a decrease in the specific binding of [3H]saxitoxin and 125I-labeled scorpion beta toxin and a decrease in specific 22Na+ uptake. Moreover, the increase in the number of Na+ channels that normally occurs during neuronal maturation in vitro was inhibited by chronic channel activator treatment. The induced disappearance of Na+ channels was abolished by tetrodotoxin, was found to be dependent on the external Na+ concentration, and was prevented when either choline (a nonpermeant ion) or Li+ (a permeant ion) was substituted for Na+. Amphotericin B, a Na+ ionophore, and monensin were able to mimick the effect of Na(+)-channel activators, while a KCl depolarization failed to do this. This feedback regulation seems to be a neuronal property since Na(+)-channel density in cultured astrocytes was not affected by channel activator treatment or by amphotericin B. The present evidence suggests that an increase in intracellular Na+ concentration, whether elicited by Na(+)-channel activators or mediated by a Na+ ionophore, can induce a decrease in surface Na+ channels and therefore is involved in down-regulation of Na(+)-channel density in fetal rat brain neurons in vitro. PMID:2165609

  2. Mitochondrial Ca2+ uptake by the voltage-dependent anion channel 2 regulates cardiac rhythmicity

    PubMed Central

    Shimizu, Hirohito; Schredelseker, Johann; Huang, Jie; Lu, Kui; Naghdi, Shamim; Lu, Fei; Franklin, Sarah; Fiji, Hannah DG; Wang, Kevin; Zhu, Huanqi; Tian, Cheng; Lin, Billy; Nakano, Haruko; Ehrlich, Amy; Nakai, Junichi; Stieg, Adam Z; Gimzewski, James K; Nakano, Atsushi; Goldhaber, Joshua I; Vondriska, Thomas M; Hajnóczky, György; Kwon, Ohyun; Chen, Jau-Nian

    2015-01-01

    Tightly regulated Ca2+ homeostasis is a prerequisite for proper cardiac function. To dissect the regulatory network of cardiac Ca2+ handling, we performed a chemical suppressor screen on zebrafish tremblor embryos, which suffer from Ca2+ extrusion defects. Efsevin was identified based on its potent activity to restore coordinated contractions in tremblor. We show that efsevin binds to VDAC2, potentiates mitochondrial Ca2+ uptake and accelerates the transfer of Ca2+ from intracellular stores into mitochondria. In cardiomyocytes, efsevin restricts the temporal and spatial boundaries of Ca2+ sparks and thereby inhibits Ca2+ overload-induced erratic Ca2+ waves and irregular contractions. We further show that overexpression of VDAC2 recapitulates the suppressive effect of efsevin on tremblor embryos whereas VDAC2 deficiency attenuates efsevin's rescue effect and that VDAC2 functions synergistically with MCU to suppress cardiac fibrillation in tremblor. Together, these findings demonstrate a critical modulatory role for VDAC2-dependent mitochondrial Ca2+ uptake in the regulation of cardiac rhythmicity. DOI: http://dx.doi.org/10.7554/eLife.04801.001 PMID:25588501

  3. Voltage-dependent blockade by bupivacaine of cardiac sodium channels expressed in Xenopus oocytes.

    PubMed

    Zhang, Heng; Ji, Hui; Liu, Zhirui; Ji, Yonghua; You, Xinmin; Ding, Gang; Cheng, Zhijun

    2014-08-01

    Bupivacaine ranks as the most potent and efficient drug among class I local anesthetics, but its high potential for toxic reactions severely limits its clinical use. Although bupivacaine-induced toxicity is mainly caused by substantial blockade of voltage-gated sodium channels (VGSCs), how these hydrophobic molecules interact with the receptor sites to which they bind remains unclear. Nav1.5 is the dominant isoform of VGSCs expressed in cardiac myocytes, and its dysfunction may be the cause of bupivacaine-triggered arrhythmia. Here, we investigated the effect of bupivacaine on Nav1.5 within the clinical concentration range. The electrophysiological measurements on Nav1.5 expressed in Xenopus oocytes showed that bupivacaine induced a voltage- and concentration-dependent blockade on the peak of I Na and the half-maximal inhibitory dose was 4.51 μmol/L. Consistent with other local anesthetics, bupivacaine also induced a use-dependent blockade on Nav1.5 currents. The underlying mechanisms of this blockade may contribute to the fact that bupivacaine not only dose-dependently affected the gating kinetics of Nav1.5 but also accelerated the development of its open-state slow inactivation. These results extend our knowledge of the action of bupivacaine on cardiac sodium channels, and therefore contribute to the safer and more efficient clinical use of bupivacaine.

  4. The voltage dependence of NADPH oxidase reveals why phagocytes need proton channels

    NASA Astrophysics Data System (ADS)

    DeCoursey, Thomas E.; Morgan, Deri; Cherny, Vladimir V.

    2003-04-01

    The enzyme NADPH oxidase in phagocytes is important in the body's defence against microbes: it produces superoxide anions (O2-, precursors to bactericidal reactive oxygen species). Electrons move from intracellular NADPH, across a chain comprising FAD (flavin adenine dinucleotide) and two haems, to reduce extracellular O2 to O2-. NADPH oxidase is electrogenic, generating electron current (Ie) that is measurable under voltage-clamp conditions. Here we report the complete current-voltage relationship of NADPH oxidase, the first such measurement of a plasma membrane electron transporter. We find that Ie is voltage-independent from -100mV to >0mV, but is steeply inhibited by further depolarization, and is abolished at about +190mV. It was proposed that H+ efflux mediated by voltage-gated proton channels compensates Ie, because Zn2+ and Cd2+ inhibit both H+ currents and O2- production. Here we show that COS-7 cells transfected with four NADPH oxidase components, but lacking H+ channels, produce O2- in the presence of Zn2+ concentrations that inhibit O2- production in neutrophils and eosinophils. Zn2+ does not inhibit NADPH oxidase directly, but through effects on H+ channels. H+ channels optimize NADPH oxidase function by preventing membrane depolarization to inhibitory voltages.

  5. Bothriurus bonariensis scorpion venom activates voltage-dependent sodium channels in insect and mammalian nervous systems.

    PubMed

    Dos Santos, Douglas Silva; Carvalho, Evelise Leis; de Lima, Jeferson Camargo; Breda, Ricardo Vaz; Oliveira, Raquel Soares; de Freitas, Thiago Carrazoni; Salamoni, Simone Denise; Domingues, Michelle Flores; Piovesan, Angela Regina; Boldo, Juliano Tomazzoni; de Assis, Dênis Reis; da Costa, Jaderson Costa; Dal Belo, Cháriston André; Pinto, Paulo Marcos

    2016-10-25

    Animal venoms have been widely recognized as a major source of biologically active molecules. Bothriurus bonariensis, popularly known as black scorpion, is the arthropod responsible for the highest number of accidents involving scorpion sting in Southern Brazil. Here we reported the first attempt to investigate the neurobiology of B. bonariensis venom (BBV) in the insect and mammalian nervous system. BBV (32 μg/g) induced a slow neuromuscular blockade in the in vivo cockroach nerve-muscle preparations (70 ± 4%, n = 6, p < 0.001), provoking repetitive twitches and significantly decreasing the frequency of spontaneous leg action potentials (SNCAPs) from 82 ± 3 min(-1) to 36 ± 1.3 min(-1) (n = 6, p < 0.05), without affecting the amplitude. When tested in primary cultures of rat hippocampal cells, BBV induced a massive increase of Ca(2+) influx (250 ± 1% peak increase, n = 3, p < 0.0001). The disturbance of calcium homeostasis induced by BBV on the mammalian central nervous system was not accompanied by cellular death and was prevented by the co-treatment of the hippocampal cells with tetrodotoxin, a selective sodium channel blocker. The results suggest that the biological activity of BBV is mostly related to a modulation of sodium channels function. Our biological activity survey suggests that BBV may have a promising insecticidal and therapeutic potential. PMID:27544632

  6. Controlled ambipolar doping and gate voltage dependent carrier diffusion length in lead sulfide nanowires.

    PubMed

    Yang, Yiming; Li, Jiao; Wu, Hengkui; Oh, Eunsoon; Yu, Dong

    2012-11-14

    We report a simple, controlled doping method for achieving n-type, intrinsic, and p-type lead sulfide (PbS) nanowires (NWs) grown by chemical vapor deposition without introducing any impurities. A wide range of carrier concentrations is realized by adjusting the ratio between the Pb and S precursors. The field effect electron mobility of n-type PbS NWs is up to 660 cm(2)/(V s) at room temperature, in agreement with a long minority carrier diffusion length measured by scanning photocurrent microscopy (SPCM). Interestingly, we have observed a strong dependence of minority carrier diffusion length on gate voltage, which can be understood by considering a carrier concentration dependent recombination lifetime. The demonstrated ambipolar doping of high quality PbS NWs opens up exciting avenues for their applications in photodetectors and photovoltaics.

  7. Structural and dipolar properties of the voltage-dependent pore former alamethicin in octanol/dioxane.

    PubMed Central

    Schwarz, G; Savko, P

    1982-01-01

    Dielectric constant and loss of the membrane-active peptide alamethicin in octanol/dioxane mixtures have been measured at frequencies between 5 kHz and 50 MHz. On the basis of a rotational mechanism of dipolar orientation, the observed dispersion provides information regarding size, shape, and dipole moment of the structural entities which the solute may assume in media of diverse lipophilicity. Particularly detailed results are obtained in a pure octanol solvent where an apparent molecular weight of alamethicin could be determined. It turns out that in this quite lipophilic medium most of the peptide material exists as a monomer particle that has approximate length and diameter of 35 and 13 A, respectively. It carries a dipole moment of approximately 75 Debye units (directed nearly parallel to the long axis). At our concentrations of a few milligrams per milliliters, appreciable formation of dimers by head-to-tail linkage is indicated. When the octanol content is reduced by adding greater amounts of dioxane, larger particles are encountered. This is accompanied by a decrease of the effective polarity. The inherent increase of hydrophilicity in the dioxane-enriched solvent apparently favors another monomer conformation that has a low dipole moment and easily aggregates to some kind of micelle. PMID:7115881

  8. Voltage-Dependent Regulation of Complex II Energized Mitochondrial Oxygen Flux

    PubMed Central

    Bai, Fan; Fink, Brian D.; Yu, Liping; Sivitz, William I.

    2016-01-01

    Oxygen consumption by isolated mitochondria is generally measured during state 4 respiration (no ATP production) or state 3 (maximal ATP production at high ADP availability). However, mitochondria in vivo do not function at either extreme. Here we used ADP recycling methodology to assess muscle mitochondrial function over intermediate clamped ADP concentrations. In so doing, we uncovered a previously unrecognized biphasic respiratory pattern wherein O2 flux on the complex II substrate, succinate, initially increased and peaked over low clamped ADP concentrations then decreased markedly at higher clamped concentrations. Mechanistic studies revealed no evidence that the observed changes in O2 flux were due to altered opening or function of the mitochondrial permeability transition pore or to changes in reactive oxygen. Based on metabolite and functional metabolic data, we propose a multifactorial mechanism that consists of coordinate changes that follow from reduced membrane potential (as the ADP concentration in increased). These changes include altered directional electron flow, altered NADH/NAD+ redox cycling, metabolite exit, and OAA inhibition of succinate dehydrogenase. In summary, we report a previously unrecognized pattern for complex II energized O2 flux. Moreover, our findings suggest that the ADP recycling approach might be more widely adapted for mitochondrial studies. PMID:27153112

  9. The voltage dependence of GABAA receptor gating depends on extracellular pH.

    PubMed

    Pytel, Maria; Mercik, Katarzyna; Mozrzymas, Jerzy W

    2005-11-28

    Recent studies have indicated that changes in extracellular pH and in membrane voltage affect the gamma-amino-n-butyric acid type A receptor gating mainly by altering desensitization and binding. To test whether the effects of membrane potential and pH are additive, their combined actions were investigated. By analyzing the current responses to rapid gamma-amino-n-butyric acid applications, we found that the current to voltage relationship was close to linear at acid pH but the increasing pH induced an inward rectification. Desensitization was enhanced at depolarizing potentials, but this strongly depended on pH, being weak at acidic and strong at basic pH values. A similar trend was observed for the onset rate of responses to saturating gamma-amino-n-butyric acid concentration. These data provide evidence that the voltage sensitivity of GABAA receptors depends on extracellular pH.

  10. The voltage dependence of GABAA receptor gating depends on extracellular pH

    PubMed Central

    Pytel, Maria; Mercik, Katarzyna; Mozrzymas, Jerzy W.

    2007-01-01

    Recent studies have indicated that changes in extracellular pH and in membrane voltage affect the γ-amino-n-butyric acid type A receptor gating mainly by altering desensitization and binding. To test whether the effects of membrane potential and pH are additive, their combined actions were investigated. By analyzing the current responses to rapid γ-amino-n-butyric acid applications, we found that the current to voltage relationship was close to linear at acid pH but the increasing pH induced an inward rectification. Desensitization was enhanced at depolarizing potentials, but this strongly depended on pH, being weak at acidic and strong at basic pH values. A similar trend was observed for the onset rate of responses to saturating γ-amino-n-butyric acid concentration. These data provide evidence that the voltage sensitivity of GABAA receptors depends on extracellular pH. PMID:16272885

  11. Wavelength, temperature, and voltage dependent calibration of a nematic liquid crystal multispectral polarization generating device

    SciTech Connect

    Baba, Justin S; Boudreaux, Philip R

    2007-01-01

    Rapid calibration of liquid crystal variable retarder (LCVR) devices is critical for successful clinical implementation of a LC-based Mueller matrix imaging system being developed for noninvasisve skin cancer detection. For multispectral implementation of such a system, the effect of wavelength (), temperature (T), and voltage (V) on the retardance () required to generate each desired polarization state needs to be clearly understood. Calibration involves quantifying this interdependence such that for a given set of system input variables, T, the appropriate voltage is applied across a LC cell to generate a particular retardance. This paper presents findings that elucidate the dependence of voltage, for a set retardance, on the aforementioned variables for a nematic LC cell: 253 mv100 nm-dependence andd 10 mVC T-dependence. Additionally, an empirically derived model is presented that enables initial voltage calibration of retardance for any desired input wavelength within the calibration range of 460-905 nm. copyright 2007 Optical Society of America

  12. Voltage-dependent magnetic phase transition in magneto-electric epitaxial Cr2O3 nanoclusters.

    PubMed

    Halley, David; Najjari, Nabil; Godel, Florian; Hamieh, Mohamad; Doudin, Bernard; Henry, Yves

    2016-06-17

    We observe, as a function of temperature, a second order magnetic phase transition in nanometric Cr2O3 clusters that are epitaxially embedded in an insulating MgO matrix. They are investigated through their tunnel magneto-resistance signature, the MgO layer being used as a tunnel barrier. We infer the small magnetic dipoles carried by the Cr2O3 clusters and provide evidence of a magnetic phase transition at low temperature in those clusters: they evolve from an anti ferromagnetic state, with zero net moment close to 0 K, to a weak ferromagnetic state that saturates above about 10 K. The influence of magneto-electric effects on the weak ferromagnetic phase is also striking: the second order transition temperature turns out to be linearly dependent on the applied electric field. PMID:27159190

  13. Bilayer reconstitution of voltage-dependent ion channels using a microfabricated silicon chip.

    PubMed Central

    Pantoja, R; Sigg, D; Blunck, R; Bezanilla, F; Heath, J R

    2001-01-01

    Painted bilayers containing reconstituted ion channels serve as a well defined model system for electrophysiological investigations of channel structure and function. Horizontally oriented bilayers with easy solution access to both sides were obtained by painting a phospholipid:decane mixture across a cylindrical pore etched into a 200-microm thick silicon wafer. Silanization of the SiO(2) layer produced a hydrophobic surface that promoted the adhesion of the lipid mixture. Standard lithographic techniques and anisotropic deep-reactive ion etching were used to create pores with diameters from 50 to 200 microm. The cylindrical structure of the pore in the partition and the surface treatment resulted in stable bilayers. These were used to reconstitute Maxi K channels in the 100- and 200-microm diameter pores. The electrophysiological characteristics of bilayers suspended in microchips were comparable with that of other bilayer preparations. The horizontal orientation and good voltage clamping properties make the microchip bilayer method an excellent system to study the electrical properties of reconstituted membrane proteins simultaneously with optical probes. PMID:11566808

  14. Bacteria form tellurium nanocrystals

    USGS Publications Warehouse

    Oremland, R.S.

    2007-01-01

    A team of researchers have found two bacterial species that produce tellurium oxyanions as respiratory electron acceptors for growth, leaving elemental tellurium in the form of nanoparticles. The crystals from the two organisms exhibit distinctively different structures. Bacillus selenitireducens initially forms nanorods that cluster together to form rosettes. Sulfurospirillum barnesii forms irregularly-shaped nanospheres that coalesce into larger composite aggregates.

  15. Handbook of Poetic Forms.

    ERIC Educational Resources Information Center

    Padgett, Ron, Ed.

    Intended for secondary teachers and student writers but useful for anyone interested in poetic forms, this book defines 74 basic poetic forms, summarizes their histories, quotes examples from noted poets, and offers professional tricks of the trade on how to use each form. The book covers the following poetic forms: abstract poem, acrostic,…

  16. Secretory and basal cells of the epithelium of the tubular glands in the male Mullerian gland of the caecilian Uraeotyphlus narayani (Amphibia: Gymnophiona).

    PubMed

    George, Jancy M; Smita, Matthew; Kadalmani, Balamuthu; Girija, Ramankutty; Oommen, Oommen V; Akbarsha, Mohammad A

    2004-12-01

    Caecilians are exceptional among the vertebrates in that males retain the Mullerian duct as a functional glandular structure. The Mullerian gland on each side is formed from a large number of tubular glands connecting to a central duct, which either connects to the urogenital duct or opens directly into the cloaca. The Mullerian gland is believed to secrete a substance to be added to the sperm during ejaculation. Thus, the Mullerian gland could function as a male accessory reproductive gland. Recently, we described the male Mullerian gland of Uraeotyphlus narayani using light and transmission electron microscopy (TEM) and histochemistry. The present TEM study reports that the secretory cells of both the tubular and basal portions of the tubular glands of the male Mullerian gland of this caecilian produce secretion granules in the same manner as do other glandular epithelial cells. The secretion granules are released in the form of structured granules into the lumen of the tubular glands, and such granules are traceable to the lumen of the central duct of the Mullerian gland. This is comparable to the situation prevailing in the epididymal epithelium of several reptiles. In the secretory cells of the basal portion of the tubular glands, mitochondria are intimately associated with fabrication of the secretion granules. The structural and functional organization of the epithelium of the basal portion of the tubular glands is complicated by the presence of basal cells. This study suggests the origin of the basal cells from peritubular tissue leukocytes. The study also indicates a role for the basal cells in acquiring secretion granules from the neighboring secretory cells and processing them into lipofuscin material in the context of regression of the Mullerian gland during the period of reproductive quiescence. In these respects the basal cells match those in the epithelial lining of the epididymis of amniotes.

  17. Secretory and basal cells of the epithelium of the tubular glands in the male Mullerian gland of the caecilian Uraeotyphlus narayani (Amphibia: Gymnophiona).

    PubMed

    George, Jancy M; Smita, Matthew; Kadalmani, Balamuthu; Girija, Ramankutty; Oommen, Oommen V; Akbarsha, Mohammad A

    2004-12-01

    Caecilians are exceptional among the vertebrates in that males retain the Mullerian duct as a functional glandular structure. The Mullerian gland on each side is formed from a large number of tubular glands connecting to a central duct, which either connects to the urogenital duct or opens directly into the cloaca. The Mullerian gland is believed to secrete a substance to be added to the sperm during ejaculation. Thus, the Mullerian gland could function as a male accessory reproductive gland. Recently, we described the male Mullerian gland of Uraeotyphlus narayani using light and transmission electron microscopy (TEM) and histochemistry. The present TEM study reports that the secretory cells of both the tubular and basal portions of the tubular glands of the male Mullerian gland of this caecilian produce secretion granules in the same manner as do other glandular epithelial cells. The secretion granules are released in the form of structured granules into the lumen of the tubular glands, and such granules are traceable to the lumen of the central duct of the Mullerian gland. This is comparable to the situation prevailing in the epididymal epithelium of several reptiles. In the secretory cells of the basal portion of the tubular glands, mitochondria are intimately associated with fabrication of the secretion granules. The structural and functional organization of the epithelium of the basal portion of the tubular glands is complicated by the presence of basal cells. This study suggests the origin of the basal cells from peritubular tissue leukocytes. The study also indicates a role for the basal cells in acquiring secretion granules from the neighboring secretory cells and processing them into lipofuscin material in the context of regression of the Mullerian gland during the period of reproductive quiescence. In these respects the basal cells match those in the epithelial lining of the epididymis of amniotes. PMID:15487004

  18. Maass Forms and Quantum Modular Forms

    NASA Astrophysics Data System (ADS)

    Rolen, Larry

    This thesis describes several new results in the theory of harmonic Maass forms and related objects. Maass forms have recently led to a flood of applications throughout number theory and combinatorics in recent years, especially following their development by the work of Bruinier and Funke the modern understanding Ramanujan's mock theta functions due to Zwegers. The first of three main theorems discussed in this thesis concerns the integrality properties of singular moduli. These are well-known to be algebraic integers, and they play a beautiful role in complex multiplication and explicit class field theory for imaginary quadratic fields. One can also study "singular moduli" for special non-holomorphic functions, which are algebraic but are not necessarily algebraic integers. Here we will explain the phenomenon of integrality properties and provide a sharp bound on denominators of symmetric functions in singular moduli. The second main theme of the thesis concerns Zagier's recent definition of a quantum modular form. Since their definition in 2010 by Zagier, quantum modular forms have been connected to numerous different topics such as strongly unimodal sequences, ranks, cranks, and asymptotics for mock theta functions. Motivated by Zagier's example of the quantum modularity of Kontsevich's "strange" function F(q), we revisit work of Andrews, Jimenez-Urroz, and Ono to construct a natural vector-valued quantum modular form whose components. The final chapter of this thesis is devoted to a study of asymptotics of mock theta functions near roots of unity. In his famous deathbed letter, Ramanujan introduced the notion of a mock theta function, and he offered some alleged examples. The theory of mock theta functions has been brought to fruition using the framework of harmonic Maass forms, thanks to Zwegers. Despite this understanding, little attention has been given to Ramanujan's original definition. Here we prove that Ramanujan's examples do indeed satisfy his

  19. Revision of the characters of Centrolenidae (Amphibia : Anura : Athesphatanura), with comments on its taxonomy and the description of new taxa of glassfrogs

    USGS Publications Warehouse

    Cisneros-Heredia, D.F.; McDiarmid, Roy W.

    2007-01-01

    Anurans of the family Centrolenidae are a diverse clade of arboreal frogs distributed across tropical America. Knowledge of their taxonomy, systematics, ecology, behavior, morphology, and other evolutionary aspects of their biology is deficient. Relationships among centrolenid species remain largely unresolved, with no satisfactory phylogenetic hypothesis, and none of the current genera has compelling evidence of monophyly. Further, understanding the phylogeny of glassfrogs is constrained by species-level taxonomic problems, including incorrect description of characters, incomplete analyses of intraspecific variation, and lack of appreciation of species diversity. Herein, we define and analyze the 23 characters that are useful, in combination, in diagnosing centrolenid species, and thereby provide a reference for the use of future workers. We propose revised classifications for the parietal and visceral peritoneal pigmentation, liver form and coloration of its associated hepatic peritoneum, nuptial excrescences, and hand ornamentation. We comment on the generic and species-level taxonomy of Centrolenidae, proposing the recognition of a new genus and describing a new species from Ecuador. We treat Hyla ocellifera Boulenger as a synonym of Centrolene prosoblepon (Boettger), Hyalinobatrachium cardiacalyptum McCranie & Wilson as a synonym of Hyalinobatrachium chirripoi (Taylor), and Hyalinobatrachium crybetes McCranie and Wilson as a synonym of Hyalinobatrachium colymbiphyllum (Taylor). We also present an annotated list of the species of glassfrogs from the Republic of Ecuador with some distributional remarks.

  20. Nucleolar cycle and chromatoid body formation: is there a relationship between these two processes during spermatogenesis of Dendropsophus minutus (Amphibia, Anura)?

    PubMed

    Peruquetti, Rita Luiza; Taboga, Sebastião Roberto; Santos, Lia Raquel de Souza; Oliveira, Classius de; Azeredo-Oliveira, Maria Tercília Vilela de

    2011-01-01

    The goals of this study were to monitor the nucleolar material distribution during Dendropsophus minutus spermatogenesis using cytological and cytochemical techniques and ultrastructural analysis, as well as to compare the nucleolar material distribution to the formation of the chromatoid body (CB) in the germ epithelium of this amphibian species. Nucleolar fragmentation occurred during the pachytene of prophase I and nucleolus reorganization occurred in the early spermatid nucleus. The area of the spermatogonia nucleolus was significantly larger than that of the earlier spermatid nucleolus. Ultrastructural analysis showed an accumulation of nuages in the spermatogonia cytoplasm, which form the CB before nucleolar fragmentation. The CB was observed in association with mitochondrial clusters in the cytoplasm of primary spermatocytes, as well as in those of earlier spermatids. In conclusion, the nucleolus seems to be related to CB formation during spermatogenesis of D. minutus, because, at the moment of nucleolus fragmentation in the primary spermatocytes, the CB area reaches a considerable size and is able to execute its important functions during spermatogenesis. The reorganized nucleolus of the earlier spermatids has a smaller area due to several factors, among them the probable migration of nucleolar fragments from the nucleus to the cytoplasm, and plays a part in the CB chemical composition. PMID:20829051

  1. Spermiogenesis and spermatozoon ultrastructure of Diplodiscus subclavatus (Pallas, 1760) (Paramphistomoidea, Diplodiscidae), an intestinal fluke of the pool frog Rana lessonae (Amphibia, Anura).

    PubMed

    Bakhoum, A J S; Torres, J; Shimalov, V V; Bâ, C T; Miquel, J

    2011-01-01

    Spermiogenesis in Diplodiscus subclavatus begins with the formation of the zone of differentiation presenting two centrioles associated with striated roots and an intercentriolar body. The latter presents seven electron-dense layers with a fine central plate and three plates on both sides. The external pair of these electron-dense layers is formed by a granular row. Each centriole develops into a free flagellum, both of them growing orthogonally in relation to the median cytoplasmic process. After the flagellar rotation and before the proximodistal fusion of both flagella with the median cytoplasmic process four attachment zones were already observed in several cross-sections indicating the area of fusion. Spinelike bodies are also observed in the differentiation zone before the fusion of flagella. Finally, the constriction of the ring of arched membranes gives rise to the young spermatozoon that detaches from the residual cytoplasm. The mature spermatozoon of D. subclavatus shows all the classical characters observed in Digenea spermatozoa such as two axonemes of different length of the 9+"1" trepaxonematan pattern, nucleus, mitochondrion, two bundles of parallel cortical microtubules and granules of glycogen. However, some peculiarities such as a well-developed lateral expansion associated with external ornamentation of the plasma membrane and spinelike bodies combined with their area of appearance distinguish the ultrastructural organization of the sperm cells of D. subclavatus from those of other digeneans.

  2. Phylogeny and Differentiation of Wide-Ranging Ryukyu Kajika Frog Buergeria japonica (Amphibia: Rhacophoridae): Geographic Genetic Pattern Not Simply Explained by Vicariance Through Strait Formation.

    PubMed

    Tominaga, Atsushi; Matsui, Masafumi; Eto, Koshiro; Ota, Hidetoshi

    2015-06-01

    To investigate geographic genetic structures and taxonomic relationships among isolated populations of Buergeria japonica, occurring very widely in various habitats of the Ryukyu Archipelago and Taiwan, we conducted phylogenetic and demographic analyses among individuals from various localities, representing their entire distributional ranges. Buergeria japonica is genetically greatly differentiated and comprises three major clades (the Southern Taiwan [ST] clade, the Northern Taiwan + Southern Ryukyu [NT/SR] clade, and the Central + Northern Ryukyu [CR/NR] clade), each of which seems to represent independent species. The first divergence in the species is estimated to have occurred in the middle to late Miocene in areas of current Taiwan, then eastern periphery of the Asian continent. Split of the ST and the remaining clades, and subsequent divergence between the NT/SR and the CR/NR clades in the latter, indicate consecutive south to north vicariant diversifications. However, these vicariances are not always associated with formation of significant barriers such as deep straits. Less but still prominently diverged subclades (the Amami + Tokara [AM/TK] and the Okinawa [ON] subclades) in the CR/NR clade were recognized in spite of the absence of an intervening deep strait. Contrariwise, individuals from Amami and Tokara Groups formed the AM/TK subclade in spite of the presence of the intervening Tokara Gap (a long-standing deep tectonic strait). Furthermore, in the AM/TK subclade, low but definite genetic divergence was found between the Northern Amami + Tokara (NAM/TK) lineage and the Southern Amami (SAM) lineage. Estimated divergence time and gene flow rate within the NAM/TK lineage indicate that this species reached northern Tokara from the south by overseas dispersal over the Tokara Gap long after its formation, but not by more recent artificial transportation. This overseas dispersal would have been facilitated by its more frequent occurrence around coastal

  3. Method for forming ammonia

    DOEpatents

    Kong, Peter C.; Pink, Robert J.; Zuck, Larry D.

    2008-08-19

    A method for forming ammonia is disclosed and which includes the steps of forming a plasma; providing a source of metal particles, and supplying the metal particles to the plasma to form metal nitride particles; and providing a substance, and reacting the metal nitride particles with the substance to produce ammonia, and an oxide byproduct.

  4. Methods of forming steel

    DOEpatents

    Branagan, Daniel J.; Burch, Joseph V.

    2001-01-01

    In one aspect, the invention encompasses a method of forming a steel. A metallic glass is formed and at least a portion of the glass is converted to a crystalline steel material having a nanocrystalline scale grain size. In another aspect, the invention encompasses another method of forming a steel. A molten alloy is formed and cooled the alloy at a rate which forms a metallic glass. The metallic glass is devitrified to convert the glass to a crystalline steel material having a nanocrystalline scale grain size. In yet another aspect, the invention encompasses another method of forming a steel. A first metallic glass steel substrate is provided, and a molten alloy is formed over the first metallic glass steel substrate to heat and devitrify at least some of the underlying metallic glass of the substrate.

  5. Forming of superplastic ceramics

    SciTech Connect

    Lesuer, D.R.; Wadsworth, J.; Nieh, T.G.

    1994-05-01

    Superplasticity in ceramics has now advanced to the stage that technologically viable superplastic deformation processing can be performed. In this paper, examples of superplastic forming and diffusion bonding of ceramic components are given. Recent work in biaxial gas-pressure forming of several ceramics is provided. These include yttria-stabilized, tetragonal zirconia (YTZP), a 20% alumina/YTZP composite, and silicon. In addition, the concurrent superplastic forming and diffusion bonding of a hybrid ceramic-metal structure are presented. These forming processes offer technological advantages of greater dimensional control and increased variety and complexity of shapes than is possible with conventional ceramic shaping technology.

  6. [Benign bone forming tumors].

    PubMed

    Caufourier, C; Leprovost, N; Guillou-Jamard, M-R; Compère, J-F; Bénateau, H

    2009-09-01

    Benign bone forming tumors typically produce dense bone (osteoma, enostosis) or osteoid tissue (osteoid osteoma, osteoblastoma). Even though these four lesions have distinct characteristics, it is sometimes difficult to tell them apart and to rule out malignant bone forming lesions such as osteosarcoma. The first line treatment is surgical exeresis.

  7. Method of forming nanodielectrics

    DOEpatents

    Tuncer, Enis [Knoxville, TN; Polyzos, Georgios [Oak Ridge, TN

    2014-01-07

    A method of making a nanoparticle filled dielectric material. The method includes mixing nanoparticle precursors with a polymer material and reacting the nanoparticle mixed with the polymer material to form nanoparticles dispersed within the polymer material to form a dielectric composite.

  8. Method for forming materials

    DOEpatents

    Tolle, Charles R.; Clark, Denis E.; Smartt, Herschel B.; Miller, Karen S.

    2009-10-06

    A material-forming tool and a method for forming a material are described including a shank portion; a shoulder portion that releasably engages the shank portion; a pin that releasably engages the shoulder portion, wherein the pin defines a passageway; and a source of a material coupled in material flowing relation relative to the pin and wherein the material-forming tool is utilized in methodology that includes providing a first material; providing a second material, and placing the second material into contact with the first material; and locally plastically deforming the first material with the material-forming tool so as mix the first material and second material together to form a resulting material having characteristics different from the respective first and second materials.

  9. Chromosome evolution in dendropsophini (Amphibia, Anura, Hylinae).

    PubMed

    Suárez, P; Cardozo, D; Baldo, D; Pereyra, M O; Faivovich, J; Orrico, V G D; Catroli, G F; Grabiele, M; Bernarde, P S; Nagamachi, C Y; Haddad, C F B; Pieczarka, J C

    2013-01-01

    Dendropsophini is the most species-rich tribe within Hylidae with 234 described species. Although cytogenetic information is sparse, chromosome numbers and morphology have been considered as an important character system for systematic inferences in this group. Using a diversity of standard and molecular techniques, we describe the previously unknown karyotypes of the genera Xenohyla, Scarthyla and Sphaenorhynchus and provide new information on Dendropsophus and Lysapsus. Our results reveal significant karyotype diversity among Dendropsophini, with diploid chromosome numbers ranging from 2n = 22 in S. goinorum, 2n = 24 in Lysapsus, Scinax, Xenohyla, and almost all species of Sphaenorhynchus and Pseudis, 2n = 26 in S. carneus, 2n = 28 in P. cardosoi, to 2n = 30 in all known Dendropsophus species. Although nucleolar organizer regions (NORs) and C-banding patterns show a high degree of variability, NOR positions in 2n = 22, 24 and 28 karyotypes and C-banding patterns in Lysapsus and Pseudis are informative cytological markers. Interstitial telomeric sequences reveal a diploid number reduction from 24 to 22 in Scarthyla by a chromosome fusion event. The diploid number of X. truncata corroborates the character state of 2n = 30 as a synapomorphy of Dendropsophus. PMID:24107475

  10. The phylogenetic problem of Huia (Amphibia: Ranidae).

    PubMed

    Stuart, Bryan L

    2008-01-01

    A taxonomic consensus for the diverse and pan-global frog family Ranidae is lacking. A recently proposed classification of living amphibians [Frost, D.R., Grant, T., Faivovich, J., Bain, R. H., Haas, A., Haddad, C.F.B., de Sá, R.O., Channing, A., Wilkinson, M., Donnellan, S.C., Raxworthy, C.J., Campbell, J.A., Blotto, B.L., Moler, P., Drewes, R.C., Nussbaum, R.A., Lynch, J.D., Green, D.M., Wheeler, W.C., 2006. The amphibian tree of life. B. Am. Mus. Nat. Hist. 297, 1-370] included expansion of the Southeast Asian ranid frog genus Huia from seven to 47 species, but without having studied the type species of Huia. This study tested the monophyly of this concept of Huia by sampling the type species and putative members of Huia. Molecular phylogenetic analyses consistently recovered the type species H. cavitympanum as the sister taxon to other Bornean-endemic species in the genus Meristogenys, rendering all previously published concepts of Huia as polyphyletic. Members of Huia sensu [Frost, D.R., Grant, T., Faivovich, J., Bain, R. H., Haas, A., Haddad, C.F.B., de Sá, R.O., Channing, A., Wilkinson, M., Donnellan, S.C., Raxworthy, C.J., Campbell, J.A., Blotto, B.L., Moler, P., Drewes, R.C., Nussbaum, R.A., Lynch, J.D., Green, D.M., Wheeler, W.C., 2006. The amphibian tree of life. B. Am. Mus. Nat. Hist. 297, 1-370.] appear in four places within the family Ranidae. A clade containing the type species of Odorrana is phylogenetically unrelated to the type species of Huia, and Odorrana is removed from synonymy with Huia. These findings underscore the need to include relevant type species in phylogenetic studies before proposing sweeping taxonomic changes. The molecular phylogenetic analyses revealed a high degree of homoplasy in larval and adult morphology of Asian ranid frogs. Detailed studies are needed to identify morphological synapomorphies that unite members in these major clades of ranid frogs.

  11. Cranial kinesis in the amphibia: a review.

    PubMed

    Iordanskiĭ, N N

    2000-01-01

    All extant orders of amphibians are characterized by kinetic skulls. Main type of intracranial movability in amphibians is pleurokinetism, that is supplemented in different amphibian groups by various types of rhyncho- and prokinetism. The most primitive pattern of cranial kinesis is revealed in the stegocrotaphic gymnophions. More paedomorphic species retain general cranial flexibility that is characteristic of larval skull. That is unfavourable for evolution of well-regulated (adult) cranial kinesis and related feeding adaptations. Kinetism is also reduced in the species with heavily ossified skulls. Adaptive role and evolution of cranial kinesis in amphibians are discussed.

  12. Handprinted Forms and Characters

    National Institute of Standards and Technology Data Gateway

    NIST Handprinted Forms and Characters (PC database for purchase)   NIST Special Database 19 contains NIST's entire corpus of training materials for handprinted document and character recognition. It supersedes NIST Special Databases 3 and 7.

  13. Image forming apparatus

    DOEpatents

    Satoh, Hisao; Haneda, Satoshi; Ikeda, Tadayoshi; Morita, Shizuo; Fukuchi, Masakazu

    1996-01-01

    In an image forming apparatus having a detachable process cartridge in which an image carrier on which an electrostatic latent image is formed, and a developing unit which develops the electrostatic latent image so that a toner image can be formed, both integrally formed into one unit. There is provided a developer container including a discharge section which can be inserted into a supply opening of the developing unit, and a container in which a predetermined amount of developer is contained, wherein the developer container is provided to the toner supply opening of the developing unit and the developer is supplied into the developing unit housing when a toner stirring screw of the developing unit is rotated.

  14. Forms of Arthritis

    MedlinePlus

    ... It typically begins during the early-adult years. Juvenile arthritis — arthritis that is diagnosed before age 16. The most common form of juvenile arthritis, juvenile rheumatoid arthritis, affects between 30,000 and ...

  15. Electromagnetic nucleon form factors

    SciTech Connect

    Bender, A.; Roberts, C.D.; Frank, M.R.

    1995-08-01

    The Dyson-Schwinger equation framework is employed to obtain expressions for the electromagnetic nucleon form factor. In generalized impulse approximation the form factor depends on the dressed quark propagator, the dressed quark-photon vertex, which is crucial to ensuring current conservation, and the nucleon Faddeev amplitude. The approach manifestly incorporates the large space-like-q{sup 2} renormalization group properties of QCD and allows a realistic extrapolation to small space-like-q{sup 2}. This extrapolation allows one to relate experimental data to the form of the quark-quark interaction at small space-like-q{sup 2}, which is presently unknown. The approach provides a means of unifying, within a single framework, the treatment of the perturbative and nonperturbative regimes of QCD. The wealth of experimental nucleon form factor data, over a large range of q{sup 2}, ensures that this application will provide an excellent environment to test, improve and extend our approach.

  16. Comparative waste forms study

    SciTech Connect

    Wald, J.W.; Lokken, R.O.; Shade, J.W.; Rusin, J.M.

    1980-12-01

    A number of alternative process and waste form options exist for the immobilization of nuclear wastes. Although data exists on the characterization of these alternative waste forms, a straightforward comparison of product properties is difficult, due to the lack of standardized testing procedures. The characterization study described in this report involved the application of the same volatility, mechanical strength and leach tests to ten alternative waste forms, to assess product durability. Bulk property, phase analysis and microstructural examination of the simulated products, whose waste loading varied from 5% to 100% was also conducted. The specific waste forms investigated were as follows: Cold Pressed and Sintered PW-9 Calcine; Hot Pressed PW-9 Calcine; Hot Isostatic Pressed PW-9 Calcine; Cold Pressed and Sintered SPC-5B Supercalcine; Hot Isostatic pressed SPC-5B Supercalcine; Sintered PW-9 and 50% Glass Frit; Glass 76-68; Celsian Glass Ceramic; Type II Portland Cement and 10% PW-9 Calcine; and Type II Portland Cement and 10% SPC-5B Supercalcine. Bulk property data were used to calculate and compare the relative quantities of waste form volume produced at a spent fuel processing rate of 5 metric ton uranium/day. This quantity ranged from 3173 L/day (5280 Kg/day) for 10% SPC-5B supercalcine in cement to 83 L/day (294 Kg/day) for 100% calcine. Mechanical strength, volatility, and leach resistance tests provide data related to waste form durability. Glass, glass-ceramic and supercalcine ranked high in waste form durability where as the 100% PW-9 calcine ranked low. All other materials ranked between these two groupings.

  17. Methods for forming particles

    DOEpatents

    Fox, Robert V.; Zhang, Fengyan; Rodriguez, Rene G.; Pak, Joshua J.; Sun, Chivin

    2016-06-21

    Single source precursors or pre-copolymers of single source precursors are subjected to microwave radiation to form particles of a I-III-VI.sub.2 material. Such particles may be formed in a wurtzite phase and may be converted to a chalcopyrite phase by, for example, exposure to heat. The particles in the wurtzite phase may have a substantially hexagonal shape that enables stacking into ordered layers. The particles in the wurtzite phase may be mixed with particles in the chalcopyrite phase (i.e., chalcopyrite nanoparticles) that may fill voids within the ordered layers of the particles in the wurtzite phase thus produce films with good coverage. In some embodiments, the methods are used to form layers of semiconductor materials comprising a I-III-VI.sub.2 material. Devices such as, for example, thin-film solar cells may be fabricated using such methods.

  18. Method for forming targets

    DOEpatents

    Woerner, Robert L.

    1979-01-01

    Method for cryoinduced uniform deposition of cryogenic materials, such as deuterium-tritium (DT) mixtures, on the inner surface of hollow spherical members, such as inertially imploded targets. By vaporizing and quickly refreezing cryogenic materials contained within a hollow spherical member, a uniform layer of the materials is formed on the inner surface of the spherical member. Heating of the cryogenic material, located within a non-isothermal compact freezing cell, is accomplished by an electrical heat pulse, whereafter the material is quickly frozen forming a uniform layer on the inner surface of the spherical member. The method is not restricted to producing a frozen layer on only the inner surface of the innermost hollow member, but where multiple concentric hollow spheres are involved, such as in multiple shell targets for lasers, electron beams, etc., layers of cryogenic material may also be formed on the inner surface of intermediate or outer spherical members, thus providing the capability of forming targets having multiple concentric layers or shells of frozen DT.

  19. Apparatus for forming targets

    DOEpatents

    Woerner, Robert L.

    1980-01-01

    Apparatus and method for cryoinduced uniform deposition of cryogenic materials, such as deuterium-tritium (DT) mixtures, on the inner surface of hollow spherical members, such as inertially imploded targets. By vaporizing and quickly refreezing cryogenic materials contained within a hollow spherical member, a uniform layer of the materials is formed on the inner surface of the spherical member. Heating of the cryogenic material, located within a non-isothermal compact freezing cell, is accomplished by an electrical heat pulse, whereafter the material is quickly frozen forming a uniform layer on the inner surface of the spherical member. The method is not restricted to producing a frozen layer on only the inner surface of the innermost hollow member, but where multiple concentric hollow spheres are involved, such as in multiple shell targets for lasers, electron beams, etc., layers of cryogenic material may also be formed on the inner surface of intermediate or outer spherical members, thus providing the capability of forming targets having multiple concentric layers or shells of frozen DT.

  20. Many Forms of Culture

    ERIC Educational Resources Information Center

    Cohen, Adam B.

    2009-01-01

    Psychologists interested in culture have focused primarily on East-West differences in individualism-collectivism, or independent-interdependent self-construal. As important as this dimension is, there are many other forms of culture with many dimensions of cultural variability. Selecting from among the many understudied cultures in psychology,…

  1. Geodiversity and land form

    NASA Astrophysics Data System (ADS)

    Gray, Murray

    2014-05-01

    The Earth's surface has a dynamic and topographically varied natural landscape. In some cases the resulting landforms are given generic names reflecting their form and/or origin, (e.g. sand dunes, eskers, ox-bow lakes) but in many cases the land surface has a more amorphous form and is less easily categorized other than at a landscape scale (e.g. dissected plateau, Chalk downland). Across much of Europe, while the natural vegetation has been removed or radically modified, the natural land form/topography remains in tact. In this context and in terms of geoconservation we ought to be: • allowing the dynamic natural processes that create, carve and modify landscapes to continue to operate; and • retaining natural topographic character and geomorphological authenticity in the face of human actions seeking to remodel the land surface. In this presentation examples of this approach to geoconservation of land form will be given from the UK and other parts of the world. This will include examples of both appropriate and inappropriate topographic modifications.

  2. Literature: External Forms.

    ERIC Educational Resources Information Center

    Regional Curriculum Project, Atlanta, GA.

    This curriculum guide, developed as part of a total English curriculum for pre-kindergarten through grade 10, suggests that students can best understand literature by understanding its recurring external forms or genres, and includes (1) an overview describing the four literary genres of drama, narrative poetry, narrative fiction, and lyric poetry…

  3. Formed photovoltaic module busbars

    DOEpatents

    Rose, Douglas; Daroczi, Shan; Phu, Thomas

    2015-11-10

    A cell connection piece for a photovoltaic module is disclosed herein. The cell connection piece includes an interconnect bus, a plurality of bus tabs unitarily formed with the interconnect bus, and a terminal bus coupled with the interconnect bus. The plurality of bus tabs extend from the interconnect bus. The terminal bus includes a non-linear portion.

  4. Forms of Soft Sculpture

    ERIC Educational Resources Information Center

    Tucker, Dorothy

    1978-01-01

    For the past several years, students at Madison Senior High School in San Diego have responded to the tactile texture and draping quality of soft materials. They experimented enthusiastically with three-dimensional forms made out of foam rubber. Here is the result of their efforts and experimentation. (Author/RK)

  5. Inelastic Scattering Form Factors

    1992-01-01

    ATHENA-IV computes form factors for inelastic scattering calculations, using single-particle wave functions that are eigenstates of motion in either a Woods-Saxon potential well or a harmonic oscillator well. Two-body forces of Gauss, Coulomb, Yukawa, and a sum of cut-off Yukawa radial dependences are available.

  6. High energy forming facility

    NASA Technical Reports Server (NTRS)

    Ciurlionis, B.

    1967-01-01

    Watertight, high-explosive forming facility, 25 feet in diameter and 15 feet deep, withstands repeated explosions of 10 pounds of TNT equivalent. The shell is fabricated of high strength steel and allows various structural elements to deform or move elastically and independently while retaining structural integrity.

  7. Low Temperature Sheet Forming

    NASA Astrophysics Data System (ADS)

    Voges-Schwieger, Kathrin; Hübner, Sven; Behrens, Bernd-Arno

    2011-05-01

    Metastable austenitic stainless steels change their lattice during forming operations by strain-induced alpha'-martensite formation. Temperatures below T = 20° C can accelerate the phase transformation while temperatures above T = 60° C may suppress the formation of martensite during the forming operation. In past investigations, the effect of high-strength martensitic regions in an austenitic ductile lattice was used in crash relevant parts for transportation vehicles. The local martensitic regions act as reinforcements leading to an increase in crash energy absorption. Moreover, they control the folding behavior as well as the force-distance-characteristic and increase the buckling resistance. This paper deals with a concerted thermomechanical drawing process to increase the local formation of alpha'-martensite caused by low temperatures.

  8. Analytic pion form factor

    NASA Astrophysics Data System (ADS)

    Lomon, Earle L.; Pacetti, Simone

    2016-09-01

    The pion electromagnetic form factor and two-pion production in electron-positron collisions are simultaneously fitted by a vector dominance model evolving to perturbative QCD at large momentum transfer. This model was previously successful in simultaneously fitting the nucleon electromagnetic form factors (spacelike region) and the electromagnetic production of nucleon-antinucleon pairs (timelike region). For this pion case dispersion relations are used to produce the analytic connection of the spacelike and timelike regions. The fit to all the data is good, especially for the newer sets of timelike data. The description of high-q2 data, in the timelike region, requires one more meson with ρ quantum numbers than listed in the 2014 Particle Data Group review.

  9. Waste-form development

    SciTech Connect

    Neilson, R.M. Jr.; Colombo, P.

    1982-01-01

    Contemporary solidification agents are being investigated relative to their applications to major fuel cycle and non-fuel cycle low-level waste (LLW) streams. Work is being conducted to determine the range of conditions under which these solidification agents can be applied to specific LLW streams. These studies are directed primarily towards defining operating parameters for both improved solidification of problem wastes and solidification of new LLW streams generated from advanced volume reduction technologies. Work is being conducted to measure relevant waste form properties. These data will be compiled and evaluated to demonstrate compliance with waste form performance and shallow land burial acceptance criteria and transportation requirements (both as they exist and as they are modified with time).

  10. Formed HIP Can Processing

    SciTech Connect

    Clarke, Kester Diederik

    2015-07-27

    The intent of this report is to document a procedure used at LANL for HIP bonding aluminum cladding to U-10Mo fuel foils using a formed HIP can for the Domestic Reactor Conversion program in the NNSA Office of Material, Management and Minimization, and provide some details that may not have been published elsewhere. The HIP process is based on the procedures that have been used to develop the formed HIP can process, including the baseline process developed at Idaho National Laboratory (INL). The HIP bonding cladding process development is summarized in the listed references. Further iterations with Babcock & Wilcox (B&W) to refine the process to meet production and facility requirements is expected.

  11. Conjunctive visual forms.

    PubMed

    Weaver, Chris

    2009-01-01

    Visual exploration of multidimensional data is a process of isolating and extracting relationships within and between dimensions. Coordinated multiple view approaches are particularly effective for visual exploration because they support precise expression of heterogeneous multidimensional queries using simple interactions. Recent visual analytics research has made significant progress in identifying and understanding patterns of composed views and coordinations that support fast, flexible, and open-ended data exploration. What is missing is formalization of the space of expressible queries in terms of visual representation and interaction. This paper introduces the Conjunctive Visual Form model in which visual exploration consists of interactively-driven sequences of transitions between visual states that correspond to conjunctive normal forms in boolean logic. The model predicts several new and useful ways to extend the space of rapidly expressible queries through addition of simple interactive capabilities to existing compositional patterns. Two recent related visual tools offer a subset of these capabilities, providing a basis for conjecturing about such extensions.

  12. Tube-Forming Assays.

    PubMed

    Brown, Ryan M; Meah, Christopher J; Heath, Victoria L; Styles, Iain B; Bicknell, Roy

    2016-01-01

    Angiogenesis involves the generation of new blood vessels from the existing vasculature and is dependent on many growth factors and signaling events. In vivo angiogenesis is dynamic and complex, meaning assays are commonly utilized to explore specific targets for research into this area. Tube-forming assays offer an excellent overview of the molecular processes in angiogenesis. The Matrigel tube forming assay is a simple-to-implement but powerful tool for identifying biomolecules involved in angiogenesis. A detailed experimental protocol on the implementation of the assay is described in conjunction with an in-depth review of methods that can be applied to the analysis of the tube formation. In addition, an ImageJ plug-in is presented which allows automatic quantification of tube images reducing analysis times while removing user bias and subjectivity.

  13. Certification reporting forms

    SciTech Connect

    Not Available

    1981-02-18

    The required information and formats for the certification report including the cover sheet, compliance statement, and body of the report are given in this document. The body of the reports is different for each product. There are no product-to-product differences in the forms of the other parts of the reports. The products covered in this document include: furnaces, water heaters, refrigerator-freezers, central air conditioners, room air conditioners, and freezers.

  14. Nucleon Electromagnetic Form Factors

    SciTech Connect

    Kees de Jager

    2004-08-01

    Although nucleons account for nearly all the visible mass in the universe, they have a complicated structure that is still incompletely understood. The first indication that nucleons have an internal structure, was the measurement of the proton magnetic moment by Frisch and Stern (1933) which revealed a large deviation from the value expected for a point-like Dirac particle. The investigation of the spatial structure of the nucleon, resulting in the first quantitative measurement of the proton charge radius, was initiated by the HEPL (Stanford) experiments in the 1950s, for which Hofstadter was awarded the 1961 Nobel prize. The first indication of a non-zero neutron charge distribution was obtained by scattering thermal neutrons off atomic electrons. The recent revival of its experimental study through the operational implementation of novel instrumentation has instigated a strong theoretical interest. Nucleon electro-magnetic form factors (EMFFs) are optimally studied through the exchange of a virtual photon, in elastic electron-nucleon scattering. The momentum transferred to the nucleon by the virtual photon can be selected to probe different scales of the nucleon, from integral properties such as the charge radius to scaling properties of its internal constituents. Polarization instrumentation, polarized beams and targets, and the measurement of the polarization of the recoiling nucleon have been essential in the accurate separation of the charge and magnetic form factors and in studies of the elusive neutron charge form factor.

  15. Electromagnetic pion form factor

    SciTech Connect

    Roberts, C.D.

    1995-08-01

    A phenomenological Dyson-Schwinger/Bethe-Salpeter equation approach to QCD, formalized in terms of a QCD-based model field theory, the Global Color-symmetry Model (GCM), was used to calculate the generalized impulse approximation contribution to the electromagnetic pion form factor at space-like q{sup 2} on the domain [0,10] GeV{sup 2}. In effective field theories this form factor is sometimes understood as simply being due to Vector Meson Dominance (VMD) but this does not allow for a simple connection with QCD where the VMD contribution is of higher order than that of the quark core. In the GCM the pion is treated as a composite bound state of a confined quark and antiquark interacting via the exchange of colored vector-bosons. A direct study of the quark core contribution is made, using a quark propagator that manifests the large space-like-q{sup 2} properties of QCD, parameterizes the infrared behavior and incorporates confinement. It is shown that the few parameters which characterize the infrared form of the quark propagator may be chosen so as to yield excellent agreement with the available data. In doing this one directly relates experimental observables to properties of QCD at small space-like-q{sup 2}. The incorporation of confinement eliminates endpoint and pinch singularities in the calculation of F{sub {pi}}(q{sup 2}). With asymptotic freedom manifest in the dressed quark propagator the calculation yields q{sup 4}F{sub {pi}}(q{sup 2}) = constant, up to [q{sup 2}]- corrections, for space-like-q{sup 2} {approx_gt} 35 GeV{sup 2}, which indicates that soft, nonperturbative contributions dominate the form factor at presently accessible q{sup 2}. This means that the often-used factorization Ansatz fails in this exclusive process. A paper describing this work was submitted for publication. In addition, these results formed the basis for an invited presentation at a workshop on chiral dynamics and will be published in the proceedings.

  16. 78 FR 58605 - Proposed Collection; Comment Request for Form 8453-EMP, Form 8453-F, Form 8453-FE, Form 8879-F...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-24

    ... Internal Revenue Service Proposed Collection; Comment Request for Form 8453-EMP, Form 8453-F, Form 8453-FE, Form 8879-F, and 8879-EMP. AGENCY: Internal Revenue Service (IRS), Treasury. ACTION: Notice and request...- file Return; Form 8453-EMP, Employment Tax Declaration for an IRS e- file Return; Form 8879-EMP, IRS...

  17. [Adhesive cutaneous pharmaceutical forms].

    PubMed

    Gafiţanu, E; Matei, I; Mungiu, O C; Pavelescu, M; Mîndreci, I; Apostol, I; Ionescu, G

    1989-01-01

    The adhesive cutaneous pharmaceutical forms aimed to local action release the drug substance in view of a dermatological, traumatological, antirheumatic, cosmetic action. Two such preparations were obtained and their stability, consistency and pH were determined. The "in vitro" tests of their bioavailability revealed the dynamics of calcium ions release according to the associations of each preparation. The bioavailability determined by evaluating the pharmacological response demonstrated the antiinflammatory action obtained by the association of calcium ions with the components extracted from poplar muds. The therapeutical efficiency of the studied preparations has proved in the treatment of some sport injuries.

  18. Nucleon elastic form factors

    SciTech Connect

    D. Day

    2007-03-01

    The nucleon form factors are still the subject of active investigation even after an experimental effort spanning 50 years. This is because they are of critical importance to our understanding of the electromagnetic properties of nuclei and provide a unique testing ground for QCD motivated models of nucleon structure. Progress in polarized beams, polarized targets and recoil polarimetry have allowed an important and precise set of data to be collected over the last decade. I will review the experimental status of elastic electron scattering from the nucleon along with an outlook for future progress.

  19. GlassForm

    2011-09-16

    GlassForm is a software tool for generating preliminary waste glass formulas for a given waste stream. The software is useful because it reduces the number of verification melts required to develop a suitable additive composition. The software includes property models that calculate glass properties of interest from the chemical composition of the waste glass. The software includes property models for glass viscosity, electrical conductivity, glass transition temperature, and leach resistance as measured by the 7-daymore » product consistency test (PCT).« less

  20. Bipolar pulse forming line

    DOEpatents

    Rhodes, Mark A.

    2008-10-21

    A bipolar pulse forming transmission line module for linear induction accelerators having first, second, third, fourth, and fifth planar conductors which form an interleaved stack with dielectric layers between the conductors. Each conductor has a first end, and a second end adjacent an acceleration axis. The first and second planar conductors are connected to each other at the second ends, the fourth and fifth planar conductors are connected to each other at the second ends, and the first and fifth planar conductors are connected to each other at the first ends via a shorting plate adjacent the first ends. The third planar conductor is electrically connectable to a high voltage source, and an internal switch functions to short a high voltage from the first end of the third planar conductor to the first end of the fourth planar conductor to produce a bipolar pulse at the acceleration axis with a zero net time integral. Improved access to the switch is enabled by an aperture through the shorting plate and the proximity of the aperture to the switch.

  1. Cartilage-forming tumors.

    PubMed

    Qasem, Shadi A; DeYoung, Barry R

    2014-01-01

    Cartilage-forming tumors as a group are the most common primary bone tumors; this is largely due to the common occurrence of asymptomatic benign lesions such as osteochondroma and enchondroma. The common feature of these tumors is the presence of chondrocytic cells and the formation of cartilaginous tumor matrix. Some of these tumors are true neoplasms while others are hamartomas or developmental abnormalities. The morphologic heterogeneity of these tumors may be explained by a common multipotent mesenchymal cell differentiating along the lines of fetal-adult cartilage maturation. Recently mutations in IDH1 and IDH2 have been detected in a variety of benign and malignant cartilaginous tumors.(1-4.) PMID:24680178

  2. Nucleon Electromagnetic Form Factors

    SciTech Connect

    Marc Vanderhaeghen; Charles Perdrisat; Vina Punjabi

    2007-10-01

    There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has greatly improved by performing double polarization experiments, in comparison with previous unpolarized data. Here we review the experimental data base in view of the new results for the proton, and neutron, obtained at JLab, MAMI, and MIT-Bates. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed, including the recent progress in the determination of the valence quark generalized parton distributions of the nucleon, as well as the steady rate of improvements made in the lattice QCD calculations.

  3. Pion form factor

    SciTech Connect

    Ryong Ji, C.; Pang, A.; Szczepaniak, A.

    1994-04-01

    It is pointed out that the correct criterion to define the legal PQCD contribution to the exclusive processes in the lightcone perturbative expansion should be based on the large off-shellness of the lightcone energy in the intermediate states. In the lightcone perturbative QCD calculation of the pion form factor, the authors find that the legal PQCD contribution defined by the lightcone energy cut saturates in the smaller Q{sup 2} region compared to that defined by the gluon four-momentum square cut. This is due to the contribution by the highly off-energy-shell gluons in the end point regions of the phase space, indicating that the gluon four-momentum-square cut may have cut too much to define the legal PQCD.

  4. Weird past tense forms.

    PubMed

    Xu, F; Pinker, S

    1995-10-01

    It is often assumed that children go through a stage in which they systematically overapply irregular past tense patterns to inappropriate verbs, as in wipe-wope, bring-brang, trick-truck, walk-has walken. Such errors have been interpreted both as reflecting over-use of minor grammatical rules (e.g. 'change i to a'), and as reflecting the operation of a connectionist pattern associator network that superimposes and blends patterns of various degrees of generality. But the actual rate, time course, and nature of these errors have never been documented. We analysed 20,000 past tense and participle usages from nine children in the CHILDES database, looking for overapplications of irregular vowel-change patterns, as in brang, blends, as in branged, productive suffixations of -en, as in walken, gross distortions, as in mail-membled, and double-suffixation, as in walkeded. These errors were collectively quite rare; children made them in about two tenths of one per cent of the opportunities, and with few stable patterns: the errors were not predominantly word-substitutions, did not occur predominantly with irregular stems, showed no consistency across verbs or ages, and showed no clear age trend. Most (though not all) of the errors were based closely on existing irregular verbs; gross distortions never occurred. We suggest that both rule-theories and connectionist theories have tended to overestimate the predominance of such errors. Children master irregular forms quite accurately, presumably because irregular forms are just a special case of the arbitrary sound-meaning pairings that define words, and because children are good at learning words.

  5. Forming Spirals From Shadows

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-07-01

    What causes the large-scale spiral structures found in some protoplanetary disks? Most models assume theyre created by newly-forming planets, but a new study suggests that planets might have nothing to do with it.Perturbations from Planets?In some transition disks protoplanetary disks with gaps in their inner regions weve directly imaged large-scale spiral arms. Many theories currently attribute the formation of these structures to young planets: either the direct perturbations of a planet embedded in the disk cause the spirals, or theyre indirectly caused by the orbit of a planetary body outside of the arms.Another example of spiral arms detected in a protoplanetary disk, MWC 758. [NASA/ESA/ESO/M. Benisty et al.]But what if you could get spirals without any planets? A team of scientists led by Matas Montesinos (University of Chile) have recently published a study in which they examine what happens to a shadowed protoplanetary disk.Casting Shadows with WarpsIn the teams setup, they envision a protoplanetary disk that is warped: the inner region is slightly tilted relative to the outer region. As the central star casts light out over its protoplanetary disk, this disk warping would cause some regions of the disk to be shaded in a way that isnt axially symmetric with potentially interesting implications.Montesinos and collaborators ran 2D hydrodynamics simulations to determine what happens to the motion of particles within the disk when they pass in and out of the shadowed regions. Since the shadowed regions are significantly colder than the illuminated disk, the pressure in these regions is much lower. Particles are therefore accelerated and decelerated as they pass through these regions, and the lack of axial symmetry causes spiral density waves to form in the disk as a result.Initial profile for the stellar heating rate per unit area for one of the authors simulations. The regions shadowed as a result of the disk warp subtend 0.5 radians each (shown on the left

  6. Moon (Form-Origin)

    NASA Astrophysics Data System (ADS)

    Tsiapas, Elias

    2016-04-01

    When the Earth was formed, it was in a state of burning heat. As time went by, temperature on the planet's surface was falling due to radiation and heat transfer, and various components (crusts) began taking solid form at the Earth's poles. The formation of crusts took place at the Earth's poles, because the stirring of burning and fluid masses on the surface of the Earth was significantly slighter there than it was on the equator. Due to centrifugal force and Coriolis Effect, these solid masses headed towards the equator; those originating from the North Pole followed a south-western course, while those originating from the South Pole followed a north-western course and there they rotated from west to east at a lower speed than the underlying burning and liquid earth, because of their lower initial linear velocity, their solid state and inertia. Because inertia is proportional to mass, the initially larger solid body swept all new solid ones, incorporating them to its western side. The density of the new solid masses was higher, because the components on the surface would freeze and solidify first, before the underlying thicker components. As a result, the western side of the initial islet of solid rocks submerged, while the east side elevated. . As a result of the above, this initial islet began to spin in reverse, and after taking on the shape of a sphere, it formed the "heart" of the Moon. The Moon-sphere, rolling on the equator, would sink the solid rocks that continued to descend from the Earth's poles. The sinking rocks partially melted because of higher temperatures in the greater depths that the Moon descended to, while part of the rocks' mass bonded with the Moon and also served as a heat-insulating material, preventing the descended side of the sphere from melting. Combined with the Earth's liquid mass that covered its emerging eastern surface, new sphere-shaped shells were created, with increased density and very powerful structural cohesion. During the

  7. Moon (Form-Origin)

    NASA Astrophysics Data System (ADS)

    Tsiapas, Elias

    2014-05-01

    When the Earth was formed, it was in a state of burning heat. As time went by, temperature on the planet's surface was falling due to radiation and heat transfer, and various components (crusts) began taking solid form at the Earth's poles. The formation of crusts took place at the Earth's poles, because the stirring of burning and fluid masses on the surface of the Earth was significantly slighter there than it was on the equator. Due to centrifugal force and Coriolis Effect, these solid masses headed towards the equator; those originating from the North Pole followed a south-western course, while those originating from the South Pole followed a north-western course and there they rotated from west to east at a lower speed than the underlying burning and liquid earth, because of their lower initial linear velocity, their solid state and inertia. Because inertia is proportional to mass, the initially larger solid body swept all new solid ones, incorporating them to its western side. The density of the new solid masses was higher, because the components on the surface would freeze and solidify first, before the underlying thicker components. As a result, the western side of the initial islet of solid rocks submerged, while the east side elevated. . As a result of the above, this initial islet began to spin in reverse, and after taking on the shape of a sphere, it formed the "heart" of the Moon. The Moon-sphere, rolling on the equator, would sink the solid rocks that continued to descend from the Earth's poles. The sinking rocks partially melted because of higher temperatures in the greater depths that the Moon descended to, while part of the rocks' mass bonded with the Moon and also served as a heat-insulating material, preventing the descended side of the sphere from melting. Combined with the Earth's liquid mass that covered its emerging eastern surface, new sphere-shaped shells were created, with increased density and very powerful structural cohesion. During the

  8. Moon (Form-Origin)

    NASA Astrophysics Data System (ADS)

    Tsiapas, Elias

    2013-04-01

    When the Earth was formed, it was in a state of burning heat. As time went by, temperature on the planet's surface was falling due to radiation and heat transfer, and various components (crusts) began taking solid form at the Earth's poles. The formation of crusts took place at the Earth's poles, because the stirring of burning and fluid masses on the surface of the Earth was significantly slighter there than it was on the equator. Due to centrifugal force and Coriolis Effect, these solid masses headed towards the equator; those originating from the North Pole followed a south-western course, while those originating from the South Pole followed a north-western course and there they rotated from west to east at a lower speed than the underlying burning and liquid earth, because of their lower initial linear velocity, their solid state and inertia. Because inertia is proportional to mass, the initially larger solid body swept all new solid ones, incorporating them to its western side. The density of the new solid masses was higher, because the components on the surface would freeze and solidify first, before the underlying thicker components. As a result, the western side of the initial islet of solid rocks submerged, while the east side elevated. As a result of the above, this initial islet began to spin in reverse, and after taking on the shape of a sphere, it formed the "heart" of the Moon. The Moon-sphere, rolling on the equator, would sink the solid rocks that continued to descend from the Earth's poles. The sinking rocks partially melted because of higher temperatures in the greater depths that the Moon descended to, while part of the rocks' mass bonded with the Moon and also served as a heat-insulating material, preventing the descended side of the sphere from melting. Combined with the Earth's liquid mass that covered its emerging eastern surface, new sphere-shaped shells were created, with increased density and very powerful structural cohesion. During the

  9. Moon (Form-Origin)

    NASA Astrophysics Data System (ADS)

    Tsiapas, Elias

    2015-04-01

    When the Earth was formed, it was in a state of burning heat. As time went by, temperature on the planet's surface was falling due to radiation and heat transfer, and various components (crusts) began taking solid form at the Earth's poles. The formation of crusts took place at the Earth's poles, because the stirring of burning and fluid masses on the surface of the Earth was significantly slighter there than it was on the equator. Due to centrifugal force and Coriolis Effect, these solid masses headed towards the equator; those originating from the North Pole followed a south-western course, while those originating from the South Pole followed a north-western course and there they rotated from west to east at a lower speed than the underlying burning and liquid earth, because of their lower initial linear velocity, their solid state and inertia. Because inertia is proportional to mass, the initially larger solid body swept all new solid ones, incorporating them to its western side. The density of the new solid masses was higher, because the components on the surface would freeze and solidify first, before the underlying thicker components. As a result, the western side of the initial islet of solid rocks submerged, while the east side elevated. . As a result of the above, this initial islet began to spin in reverse, and after taking on the shape of a sphere, it formed the "heart" of the Moon. The Moon-sphere, rolling on the equator, would sink the solid rocks that continued to descend from the Earth's poles. The sinking rocks partially melted because of higher temperatures in the greater depths that the Moon descended to, while part of the rocks' mass bonded with the Moon and also served as a heat-insulating material, preventing the descended side of the sphere from melting. Combined with the Earth's liquid mass that covered its emerging eastern surface, new sphere-shaped shells were created, with increased density and very powerful structural cohesion. During the

  10. Integration of Shaker-type K+ channel, KAT1, into the endoplasmic reticulum membrane: synergistic insertion of voltage-sensing segments, S3-S4, and independent insertion of pore-forming segments, S5-P-S6.

    PubMed

    Sato, Yoko; Sakaguchi, Masao; Goshima, Shinobu; Nakamura, Tatsunosuke; Uozumi, Nobuyuki

    2002-01-01

    KAT1 is a member of the Shaker family of voltage-dependent K(+) channels, which has six transmembrane segments (called S1-S6), including an amphipathic S4 with several positively charged residues and a hydrophobic pore-forming region (called P) between S5 and S6. In this study, we systematically evaluated the function of individual and combined transmembrane segments of KAT1 to direct the final topology in the endoplasmic reticulum membrane by in vitro translation and translocation experiments. The assay with single-transmembrane constructs showed that S1 possesses the type II signal-anchor function, whereas S2 has the stop-transfer function. The properties fit well with the results derived from combined insertion of S1 and S2. S3 and S4 failed to integrate into the membrane by themselves. The inserted glycosylation sequence at the S3-S4 loop neither prevented the translocation of S3 and S4 nor impaired the function of voltage-dependent K(+) transport regardless of the changed length of the S3-S4 loop. S3 and S4 are likely to be posttranslationally integrated into the membrane only when somewhat specific interaction occurs between them. S5 had the ability of translocation reinitiation, and S6 had a strong preference for N(exo)/C(cyt) orientation. The pore region resided outside because of its lack of its transmembrane-spanning property. According to their own topogenic function, combined constructs of S5-P-S6 conferred the membrane-pore-membrane topology. This finding supports the notion that a set of S5-P-S6 can be independently integrated into the membrane. The results in this study provide the fundamental topogenesis mechanism of transmembrane segments involving voltage sensor and pore region in KAT1.

  11. Gas Giants Form Quickly

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This is an artist's concept of a hypothetical 10-million-year-old star system. The bright blur at the center is a star much like our sun. The other orb in the image is a gas-giant planet like Jupiter. Wisps of white throughout the image represent traces of gas.

    Astronomers using NASA's Spitzer Space Telescope have found evidence showing that gas-giant planets either form within the first 10 million years of a sun-like star's life, or not at all. The lifespan for sun-like stars is about 10 billion years.

    The scientists came to this conclusion after searching for traces of gas around 15 different sun-like stars, most with ages ranging from 3 million to 30 million years. With the help of Spitzer's Infrared Spectrometer instrument, they were able to search for relatively warm gas in the inner regions of these star systems, an area comparable to the zone between Earth and Jupiter in our own solar system. They also used ground-based radio telescopes to search for cooler gas in the outer regions of these systems, an area comparable to the zone around Saturn and beyond.

  12. How delusion is formed?

    PubMed

    Park, Jong Suk; Kang, Ung Gu

    2016-02-01

    Traditionally, delusions have been considered to be the products of misinterpretation and irrationality. However, some theorists have argued that delusions are normal or rational cognitive responses to abnormal experiences. That is, when a recently experienced peculiar event is more plausibly explained by an extraordinary hypothesis, confidence in the veracity of this extraordinary explanation is reinforced. As the number of such experiences, driven by the primary disease process in the perceptual domain, increases, this confidence builds and solidifies, forming a delusion. We tried to understand the formation of delusions using a simulation based on Bayesian inference. We found that (1) even if a delusional explanation is only marginally more plausible than a non-delusional one, the repetition of the same experience results in a firm belief in the delusion. (2) The same process explains the systematization of delusions. (3) If the perceived plausibility of the explanation is not consistent but varies over time, the development of a delusion is delayed. Additionally, this model may explain why delusions are not corrected by persuasion or rational explanation. This Bayesian inference perspective can be considered a way to understand delusions in terms of rational human heuristics. However, such experiences of "rationality" can lead to irrational conclusions, depending on the characteristics of the subject. PMID:26826642

  13. Can polymersomes form colloidosomes?

    PubMed

    Thompson, Kate L; Chambon, Pierre; Verber, Robert; Armes, Steven P

    2012-08-01

    Hydroxy-functionalized polymersomes (or block copolymer vesicles) were prepared via a facile one-pot RAFT aqueous dispersion polymerization protocol and evaluated as Pickering emulsifiers for the stabilization of emulsions of n-dodecane emulsion droplets in water. Linear polymersomes produced polydisperse oil droplets with diameters of ~50 μm regardless of the polymersome concentration in the aqueous phase. Introducing an oil-soluble polymeric diisocyanate cross-linker into the oil phase prior to homogenization led to block copolymer microcapsules, as expected. However, TEM inspection of these microcapsules after an alcohol challenge revealed no evidence for polymersomes, suggesting these delicate nanostructures do not survive the high-shear emulsification process. Thus the emulsion droplets are stabilized by individual diblock copolymer chains, rather than polymersomes. Cross-linked polymersomes (prepared by the addition of ethylene glycol dimethacrylate as a third comonomer) also formed stable n-dodecane-in-water Pickering emulsions, as judged by optical and fluorescence microscopy. However, in this case the droplet diameter varied from 50 to 250 μm depending on the aqueous polymersome concentration. Moreover, diisocyanate cross-linking at the oil/water interface led to the formation of well-defined colloidosomes, as judged by TEM studies. Thus polymersomes can indeed stabilize colloidosomes, provided that they are sufficiently cross-linked to survive emulsification.

  14. Tautomeric Forms of Metarhodopsin

    PubMed Central

    Matthews, Rowena G.; Hubbard, Ruth; Brown, Paul K.; Wald, George

    1963-01-01

    Light isomerizes the chromophore of rhodopsin, 11-cis retinal (formerly retinene), to the all-trans configuration. This introduces a succession of unstable intermediates—pre-lumirhodopsin, lumirhodopsin, metarhodopsin —in which all-trans retinal is still attached to the chromophoric site on opsin. Finally, retinal is hydrolyzed from opsin. The present experiments show that metarhodopsin exists in two tautomeric forms, metarhodopsins I and II, with λmax 478 and 380 mµ. Metarhodopsin I appears first, then enters into equilibrium with metarhodopsin II. In this equilibrium, the proportion of metarhodopsin II is favored by higher temperature or pH, neutral salts, and glycerol. The change from metarhodopsin I to II involves the binding of a proton by a group with pK 6.4 (imidazole?), and a large increase of entropy. Metarhodopsin II has been confused earlier with the final mixture of all-trans retinal and opsin (λmax 387 mµ), which it resembles in spectrum. These two products are, however, readily distinguished experimentally. PMID:14080814

  15. New education coalition formed

    NASA Astrophysics Data System (ADS)

    Watt Ireto, M. Frank

    The Coalition for Earth Science Education (CESE) was recently formed to promote Earth science education at all levels. Earth science is a diverse group of sciences and as a result, professional and academic organizations from the various areas, though united in their goal to stimulate student enthusiasm for the Earth sciences, have not had an effective way of reaching students or their precollege teachers. Over the past year, meetings sponsored by the National Academy of Science's Board on Earth Sciences and Resources and the National Science Foundation have paved the way for this coalition. Victor Mayer, Director of the Program for Leadership in Earth Systems Science (PLESE) project at the University of Ohio, has been the leader in initiating and promoting this effort for the last several years.The purpose of CESE is to promote communication among the member organizations and to coordinate projects in Earth science education. Individual organizations will continue to develop and run projects, but will be able to find out what types of projects others are working on or have completed through a coalition clearinghouse. The clearinghouse should aid organizations as they design projects and should afford opportunities for collaborative efforts. This will directly benefit teachers, who will be able to contact one source for information on the multitude of projects in the Earth and space sciences. The new coalition's steering committee is working on goals and guidelines, and will give a report at the next coalition meeting at the National Science Teachers Association annual convention in Boston.

  16. How desert varnish forms?

    NASA Astrophysics Data System (ADS)

    Perry, Randall S.; Kolb, Vera M.; Lynne, Bridget Y.; Sephton, Mark A.; Mcloughlin, Nicola; Engel, Michael H.; Olendzenski, Lorraine; Brasier, Martin; Staley, James T., Jr.

    2005-09-01

    Desert varnish is a black, manganese-rich rock coating that is widespread on Earth. The mechanism underlying its formation, however, has remained unresolved. We present here new data and an associated model for how desert varnish forms, which substantively challenges previously accepted models. We tested both inorganic processes (e.g. clays and oxides cementing coatings) and microbial methods of formation. Techniques used in this preliminary study include SEM-EDAX with backscatter, HRTEM of focused ion beam prepared (FIB) wafers and several other methods including XRPD, Raman spectroscopy, XPS and Tof-SIMS. The only hypothesis capable of explaining a high water content, the presence of organic compounds, an amorphous silica phase (opal-A) and lesser quantities of clays than previously reported, is a mechanism involving the mobilization and redistribution of silica. The discovery of silica in desert varnish suggests labile organics are preserved by interaction with condensing silicic acid. Organisms are not needed for desert varnish formation but Bacteria, Archaea, Eukarya, and other organic compounds are passively incorporated and preserved as organominerals. The rock coatings thus provide useful records of past environments on Earth and possibly other planets. Additionally this model also helps to explain the origin of key varnish and rock glaze features, including their hardness, the nature of the "glue" that binds heterogeneous components together, its layered botryoidal morphology, and its slow rate of formation.

  17. Symmetries of Helmholtz forms and globally variational dynamical forms

    NASA Astrophysics Data System (ADS)

    Palese, Marcella; Winterroth, Ekkehart

    2012-02-01

    Invariance properties of classes in the variational sequence suggested to Krupka et al. the idea that there should exist a close correspondence between the notions of variationality of a differential form and invariance of its exterior derivative. It was shown by them that the invariance of a closed Helmholtz form of a dynamical form is equivalent with local variationality of the Lie derivative of the dynamical form, so that the latter is locally the Euler-Lagrange form of a Lagrangian. We show that the corresponding local system of Euler-Lagrange forms is variationally equivalent to a global Euler-Lagrange form.

  18. Anion permeation in calcium-activated chloride channels formed by TMEM16A from Xenopus tropicalis.

    PubMed

    Reyes, J P; López-Rodríguez, A; Espino-Saldaña, A E; Huanosta-Gutiérrez, A; Miledi, R; Martínez-Torres, A

    2014-09-01

    Calcium-activated chloride channels (CaCC) formed by anoctamin1/TMEM16A subunits are ubiquitously expressed, and these channels are known to prevent polyspermy in amphibian oocytes. Here, we describe a TMEM16A clone isolated from Xenopus tropicalis oocytes (xtTMEM16A) and how the anion permeation properties are modified in single-site mutants of the ion pore. The anion permeability sequence was SCN(-) > I(-) > Br(-) > Cl(-) > gluconate (relative permeabilities 5.6:3.0:2.1:1:0.2, respectively). Dose-response curves indicated that the voltage-dependent half-maximal concentration for Ca(2+) activation (K d of the Hill equation at +100 mV) was 120 nM in normal external Cl(-), whereas it was displaced leftward to 75 nM Ca(2+), when I(-) replaced Cl(-). The I(-):Cl(-) mole fraction (MF) of the external solution was varied in order to gain insight into the permeation mechanism of the pore. No anomaly in MF behavior was observed for conductance, but it was observed for current reversal potential, which deviated from the prediction of the Goldman-Hodgkin-Katz equation. Mutations of positively charged amino acids in the pore, R646 and R761, to glutamate resulted in reduction of the relative permeability to I(-). Data from the wild type and mutants could be well fitted by a three-barrier, two-site permeation model. This suggests a multi-ion pore with at least two binding sites for anions, with R646 mole fraction closer to the extracellular membrane surface--being important for the stability of both sites--and R761--located deeper within the membrane--mainly affecting the innermost binding site. Considerations of xtTMEM16A putative pore region topology are discussed in the light of two alternative topological models of the protein. PMID:24352628

  19. Peroxisomal Pex11 is a pore-forming protein homologous to TRPM channels.

    PubMed

    Mindthoff, Sabrina; Grunau, Silke; Steinfort, Laura L; Girzalsky, Wolfgang; Hiltunen, J Kalervo; Erdmann, Ralf; Antonenkov, Vasily D

    2016-02-01

    More than 30 proteins (Pex proteins) are known to participate in the biogenesis of peroxisomes-ubiquitous oxidative organelles involved in lipid and ROS metabolism. The Pex11 family of homologous proteins is responsible for division and proliferation of peroxisomes. We show that yeast Pex11 is a pore-forming protein sharing sequence similarity with TRPM cation-selective channels. The Pex11 channel with a conductance of Λ=4.1 nS in 1.0M KCl is moderately cation-selective (PK(+)/PCl(-)=1.85) and resistant to voltage-dependent closing. The estimated size of the channel's pore (r~0.6 nm) supports the notion that Pex11 conducts solutes with molecular mass below 300-400 Da. We localized the channel's selectivity determining sequence. Overexpression of Pex11 resulted in acceleration of fatty acids β-oxidation in intact cells but not in the corresponding lysates. The β-oxidation was affected in cells by expression of the Pex11 protein carrying point mutations in the selectivity determining sequence. These data suggest that the Pex11-dependent transmembrane traffic of metabolites may be a rate-limiting step in the β-oxidation of fatty acids. This conclusion was corroborated by analysis of the rate of β-oxidation in yeast strains expressing Pex11 with mutations mimicking constitutively phosphorylated (S165D, S167D) or unphosphorylated (S165A, S167A) protein. The results suggest that phosphorylation of Pex11 is a mechanism that can control the peroxisomal β-oxidation rate. Our results disclose an unexpected function of Pex11 as a non-selective channel responsible for transfer of metabolites across peroxisomal membrane. The data indicate that peroxins may be involved in peroxisomal metabolic processes in addition to their role in peroxisome biogenesis. PMID:26597702

  20. Watching How Planets Form

    NASA Astrophysics Data System (ADS)

    2006-09-01

    Anatomy of a Planet-Forming Disc around a Star More Massive than the Sun With the VISIR instrument on ESO's Very Large Telescope, astronomers have mapped the disc around a star more massive than the Sun. The very extended and flared disc most likely contains enough gas and dust to spawn planets. It appears as a precursor of debris discs such as the one around Vega-like stars and thus provides the rare opportunity to witness the conditions prevailing prior to or during planet formation. "Planets form in massive, gaseous and dusty proto-planetary discs that surround nascent stars. This process must be rather ubiquitous as more than 200 planets have now been found around stars other than the Sun," said Pierre-Olivier Lagage, from CEA Saclay (France) and leader of the team that carried out the observations. "However, very little is known about these discs, especially those around stars more massive than the Sun. Such stars are much more luminous and could have a large influence on their disc, possibly quickly destroying the inner part." The astronomers used the VISIR instrument [1] on ESO's Very Large Telescope to map in the infrared the disc surrounding the young star HD 97048. With an age of a few million years [2], HD 97048 belongs to the Chameleon I dark cloud, a stellar nursery 600 light-years away. The star is 40 times more luminous than our Sun and is 2.5 times as massive. The astronomers could only have achieved such a detailed view due to the high angular resolution offered by an 8-metre size telescope in the infrared, reaching a resolution of 0.33 arcsecond. They discovered a very large disc, at least 12 times more extended than the orbit of the farthest planet in the Solar System, Neptune. The observations suggest the disc to be flared. "This is the first time such a structure, predicted by some theoretical models, is imaged around a massive star," said Lagage. ESO PR Photo 36/06 ESO PR Photo 36/06 A Flared Proto-Planetary Disc Such a geometry can only be

  1. Waste form product characteristics

    SciTech Connect

    Taylor, L.L.; Shikashio, R.

    1995-01-01

    The Department of Energy has operated nuclear facilities at the Idaho National Engineering Laboratory (INEL) to support national interests for several decades. Since 1953, it has supported the development of technologies for the storage and reprocessing of spent nuclear fuels (SNF) and the resultant wastes. However, the 1992 decision to discontinue reprocessing of SNF has left nearly 768 MT of SNF in storage at the INEL with unspecified plans for future dispositioning. Past reprocessing of these fuels for uranium and other resource recovery has resulted in the production of 3800 M{sup 3} calcine and a total inventory of 7600 M{sup 3} of radioactive liquids (1900 M{sup 3} destined for immediate calcination and the remaining sodium-bearing waste requiring further treatment before calcination). These issues, along with increased environmental compliance within DOE and its contractors, mandate operation of current and future facilities in an environmentally responsible manner. This will require satisfactory resolution of spent fuel and waste disposal issues resulting from the past activities. A national policy which identifies requirements for the disposal of SNF and high level wastes (HLW) has been established by the Nuclear Waste Policy Act (NWPA) Sec.8,(b) para(3)) [1982]. The materials have to be conditioned or treated, then packaged for disposal while meeting US Environmental Protection Agency (EPA) and Nuclear Regulatory Commission (NRC) regulations. The spent fuel and HLW located at the INEL will have to be put into a form and package that meets these regulatory criteria. The emphasis of Idaho Chemical Processing Plant (ICPP) future operations has shifted toward investigating, testing, and selecting technologies to prepare current and future spent fuels and waste for final disposal. This preparation for disposal may include mechanical, physical and/or chemical processes, and may differ for each of the various fuels and wastes.

  2. Science Grade 7, Long Form.

    ERIC Educational Resources Information Center

    New York City Board of Education, Brooklyn, NY. Bureau of Curriculum Development.

    The Grade 7 Science course of study was prepared in two parallel forms. A short form designed for students who had achieved a high measure of success in previous science courses; the long form for those who have not been able to maintain the pace. Both forms contain similar content. The Grade 7 guide is the first in a three-year sequence for…

  3. 10. VIEW SHOWING THE ARCH FORMS. THE INTRADOS FORM IS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. VIEW SHOWING THE ARCH FORMS. THE INTRADOS FORM IS COMMONLY LIFTED 3 TO 4 DAYS AFTER POURING. REINFORCING STEEL IS THEN PLACED AND THE EXTRADOS FORM RAISED TO POSITION. THE OPERATING OF MOVING FORMS, PLACING STEEL AND CONCRETE FOR EACH ARCH LIFT REQUIRES, ON AVERAGE, EIGHT DAYS. NOTE THE TWO LINES OF WATER PIPE ON THE EXTRADOS FORM. THESE PIPES ARE FILLED WITH SPRAY NOZZLES WHICH ARE IN PRACTICALLY CONTINUOUS OPERATION EXCEPT WHEN WORK IS BEING DONE ON THE FORMS. August 9, 1938 - Bartlett Dam, Verde River, Phoenix, Maricopa County, AZ

  4. Form-definition language for an intelligent form

    SciTech Connect

    Honeyman, J.C.

    1987-01-01

    The formal specification of a form-definition language is described. A new form-based model for office automation is defined informally. The model is called the Intelligent Form System (IFS) and is composed of a knowledge base, a Synchronous Form Manager (SFM), and an Intelligent Form (IF). The IFS is designed to be a distributed system capable of being implemented using existing technology. The syntax for the form definition language (FDL) used to specify the contents and processing for an Intelligent Form is developed. The automatic processing and routing of the form based upon form content and system configuration is formally defined. A control graph describing the necessary routing to complete the form is constructed and a control process directs processing of the form using the control graph and a state table containing a history of form processing. Examples are used to illustrate the syntax of the FDL and the algorithms for construction of the control graph and control process. The end result is the informal definition of a new model and the formal definition of the form-definition language and control process.

  5. Heated die facilitates tungsten forming

    NASA Technical Reports Server (NTRS)

    Chattin, J. H.; Haystrick, J. E.; Laughlin, J. C.; Leidy, R. A.

    1966-01-01

    Tungsten forming in a press brake employs a bottom die assembly with a heating manifold between two water-cooled die sections. The manifold has hydrogen-oxygen burners spaced along its length for even heat during forming.

  6. Resolving voltage-dependent structural changes of a membrane photoreceptor by surface-enhanced IR difference spectroscopy.

    PubMed

    Jiang, X; Zaitseva, E; Schmidt, M; Siebert, F; Engelhard, M; Schlesinger, R; Ataka, K; Vogel, R; Heberle, J

    2008-08-26

    Membrane proteins are molecular machines that transport ions, solutes, or information across the cell membrane. Electrophysiological techniques have unraveled many functional aspects of ion channels but suffer from the lack of structural sensitivity. Here, we present spectroelectrochemical data on vibrational changes of membrane proteins derived from a single monolayer. For the seven-helical transmembrane protein sensory rhodopsin II, structural changes of the protein backbone and the retinal cofactor as well as single ion transfer events are resolved by surface-enhanced IR difference absorption spectroscopy (SEIDAS). Angular changes of bonds versus the membrane normal have been determined because SEIDAS monitors only those vibrations whose dipole moment are oriented perpendicular to the solid surface. The application of negative membrane potentials (DeltaV = -0.3 V) leads to the selective halt of the light-induced proton transfer at the stage of D75, the counter ion of the retinal Schiff base. It is inferred that the voltage raises the energy barrier of this particular proton-transfer reaction, rendering the energy deposited in the retinal by light excitation insufficient for charge transfer to occur. The other structural rearrangements that accompany light-induced activity of the membrane protein, are essentially unaffected by the transmembrane electric field. Our results demonstrate that SEIDAS is a generic approach to study processes that depend on the membrane potential, like those in voltage-gated ion channels and transporters, to elucidate the mechanism of ion transfer with unprecedented spatial sensitivity and temporal resolution.

  7. Modeling the Voltage Dependence of Electrochemical Reactions at Solid-Solid and Solid-Liquid Interfaces in Batteries

    NASA Astrophysics Data System (ADS)

    Leung, Kevin

    2015-03-01

    Electrochemical reactions at electrode/electrolyte interfaces are critically dependent on the total electrochemical potential or voltage. In this presentation, we briefly review ab initio molecular dynamics (AIMD)-based estimate of voltages on graphite basal and edge planes, and then apply similar concepts to solid-solid interfaces relevant to lithium ion and Li-air batteries. Thin solid films on electrode surfaces, whether naturally occuring during power cycling (e.g., undesirable lithium carbonate on Li-air cathodes) or are artificially introduced, can undergo electrochemical reactions as the applied voltage varies. Here the onset of oxidation of lithium carbonate and other oxide thin films on model gold electrode surfaces is correlated with the electronic structure in the presence/absence of solvent molecules. Our predictions help determine whether oxidation first occurs at the electrode-thin film or electrolyte-thin film interface. Finally, we will critically compare the voltage estimate methodology used in the fuel cell community with the lithium cohesive energy calibration method broadly applied in the battery community, and discuss why they may yield different predictions. This work was supported by Nanostructures for Electrical Energy Storage (NEES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DESC0001160. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Deparment of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  8. The apparent voltage dependence of GABAA receptor activation and modulation is inversely related to channel open probability.

    PubMed

    O'Toole, Kate K; Jenkins, Andrew

    2012-02-01

    The GABA type A receptor (GABA(A)R) is expressed ubiquitously throughout the brain and is a target for many therapeutic agents, including general anesthetics and benzodiazepines, which enhance receptor function by increasing the open probability (P(o)) of the ion channel. It is commonplace for in vitro studies of receptor pharmacological characteristics to use negative membrane holding potentials to mimic the resting potential of neurons and symmetrical chloride to eliminate Goldman rectification, which results in chloride flow in the opposite direction, compared with in vivo conditions. This critical difference is usually overlooked because the GABA(A)R has been reported to behave as an ohmic pore, but our results show that the current-voltage relationship is nonlinear with respect to P(o). Specifically, we found that currents were outwardly rectifying at low P(o) and linear at high P(o). We confirmed the correlation between P(o) and rectification with a partial agonist, piperidine-4-sulfonic acid, and a gating-impaired mutation, α1(L277A); both exhibited enhanced outward rectification. Furthermore, this correlation was independent of Goldman rectification and persisted under altered chloride gradient conditions, which suggests that rectification is linked to the direction of chloride flux. Finally, our results showed that the degree of potentiation by general anesthetics (etomidate, propofol, and isoflurane) was greater at negative membrane potentials. Traditional in vitro experiments thus overestimate the action of positive allosteric modulators of the GABA(A)R. Our results show that the direction of the driving force on the permeant ion, as well as P(o), must be considered together for a complete understanding of drug actions on ligand-gated ion channels.

  9. Voltage-dependent decrease in the availability of single calcium channels by nitrendipine in guinea-pig ventricular cells.

    PubMed Central

    Kawashima, Y; Ochi, R

    1988-01-01

    1. The mechanism of Ca2+ channel block by nitrendipine was studied by recording single-channel activity from cell-attached patches on guinea-pig ventricular cells using patch pipettes containing 50 mM-Ba2+. Test depolarization pulses to around 10 mV with a duration of 100 ms were applied repetitively at 2 Hz. 2. The percentage of non-blank sweeps was maximal (about 40%) at a holding potential between -65 and -130 mV and decreased sigmoidally with its depolarization. Nitrendipine shifted the availability-voltage relationship in a hyperpolarizing direction. 3. From the number of consecutive non-blank sweeps and that of blank sweeps, the duration of the available state and that of the unavailable state were estimated. 4. The histogram of the duration of the available state showed a single-exponential distribution. Its mean duration was about 1.5 s and was shortened by nitrendipine. Correspondingly, the decay of the mean current during the depolarization step was accelerated by nitrendipine. 5. In the presence of 100 nM-nitrendipine the histogram of the duration of the unavailable state at large negative holding potentials was simulated as the sum of two exponential components, one with a time constant similar to that in the control and the other with a time constant of 6-7 s. 6. The histogram of the duration of the unavailable state at depolarized holding potentials was simulated by a double-exponential curve also in the control. The duration of the slow component was prolonged by nitrendipine. 7. The prolongation of the unavailable states initiated by drug binding during depolarization steps and maintained during depolarized holding potentials is the mechanism of the blockade. The rate constants of the state transitions between an available state and two unavailable states were estimated. PMID:2853222

  10. Phenotypical manifestations of mutations in the genes encoding subunits of the cardiac voltage-dependent L-type calcium channel

    PubMed Central

    Napolitano, Carlo; Antzelevitch, Charles

    2011-01-01

    The L-type Cardiac Calcium Channel (LTCC) plays a prominent role in the electrical and mechanical function of the heart. Mutations in the LTCC have been associated with a number of inherited cardiac arrhythmia syndromes, including Timothy, Brugada and Early Repolarization syndromes. Elucidation of the genetic defects associated with these syndromes has led to a better understanding of molecular and cellular mechanisms and the development of novel therapeutic approaches to dealing with the arrhythmic manifestations. This review provides an overview of the molecular structure and function of the LTCC, the genetic defects in these channels known to contribute to inherited disorders and the underlying molecular and cellular mechanisms contributing to the development of life-threatening arrhythmias. PMID:21372292

  11. Cardiovascular Action of Insulin in Health and Disease: Endothelial L-Arginine Transport and Cardiac Voltage-Dependent Potassium Channels.

    PubMed

    Dubó, Sebastián; Gallegos, David; Cabrera, Lissette; Sobrevia, Luis; Zúñiga, Leandro; González, Marcelo

    2016-01-01

    Impairment of insulin signaling on diabetes mellitus has been related to cardiovascular dysfunction, heart failure, and sudden death. In human endothelium, cationic amino acid transporter 1 (hCAT-1) is related to the synthesis of nitric oxide (NO) and insulin has a vascular effect in endothelial cells through a signaling pathway that involves increases in hCAT-1 expression and L-arginine transport. This mechanism is disrupted in diabetes, a phenomenon potentiated by excessive accumulation of reactive oxygen species (ROS), which contribute to lower availability of NO and endothelial dysfunction. On the other hand, electrical remodeling in cardiomyocytes is considered a key factor in heart failure progression associated to diabetes mellitus. This generates a challenge to understand the specific role of insulin and the pathways involved in cardiac function. Studies on isolated mammalian cardiomyocytes have shown prolongated action potential in ventricular repolarization phase that produces a long QT interval, which is well explained by attenuation in the repolarizing potassium currents in cardiac ventricles. Impaired insulin signaling causes specific changes in these currents, such a decrease amplitude of the transient outward K(+) (Ito) and the ultra-rapid delayed rectifier (IKur) currents where, together, a reduction of mRNA and protein expression levels of α-subunits (Ito, fast; Kv 4.2 and IKs; Kv 1.5) or β-subunits (KChIP2 and MiRP) of K(+) channels involved in these currents in a MAPK mediated pathway process have been described. These results support the hypothesis that lack of insulin signaling can produce an abnormal repolarization in cardiomyocytes. Furthermore, the arrhythmogenic potential due to reduced Ito current can contribute to an increase in the incidence of sudden death in heart failure. This review aims to show, based on pathophysiological models, the regulatory function that would have insulin in vascular system and in cardiac electrophysiology.

  12. Temperature and voltage dependent current-voltage behavior of single-walled carbon nanotube transparent conducting films

    NASA Astrophysics Data System (ADS)

    Zhang, Ze-Chen; Geng, Hong-Zhang; Wang, Yan; Yang, Hai-Jie; Da, Shi-Xun; Ding, Er-Xiong; Liu, Juncheng; Yu, Ping; Fu, Yun-Qiao; Li, Xu; Pan, Hui

    2015-11-01

    High purified single-walled carbon nanotubes (SWCNTs) were dispersed in water and transparent conducting films (TCFs) were fabricated by a spray coating. The produced uniform SWCNT-TCFs treated by nitric acid have a relatively low sheet resistance and high transmittance. The current-voltage (I-V) behaviors of the TCFs were measured at room to higher temperature during the heating or cooling process. It was found that the I-V behavior of TCFs strongly dependent on the temperature and applied voltage. The sheet resistance showed semiconductor behavior at low temperature and low voltage, while it showed metallic behavior at high temperature and high voltage.

  13. Bias voltage dependence of two-step photocurrent in GaAs/AlGaAs quantum well solar cells

    NASA Astrophysics Data System (ADS)

    Noda, T.; Elborg, M.; Mano, T.; Kawazu, T.; Han, L.; Sakaki, H.

    2016-02-01

    We investigated photoresponses of AlGaAs solar cells in which coupled GaAs quantum wells were embedded in the i-region of p-i-n diodes; we studied how the bias voltage Vb affects the normal photocurrent I generated by the visible light and a "two-step" photocurrent ΔI generated by the absorption of visible and infrared photons. We found that as Vb exceeds -0.2 V, ΔI rises and peaks at 0.6 V, while the normal photocurrent I falls to about half of its saturated level. These findings are discussed in terms of a rate equation model to show that ΔI is mainly determined by the balance of escape and recombination of photogenerated carriers.

  14. Local magnetoresistance through Si and its bias voltage dependence in ferromagnet/MgO/silicon-on-insulator lateral spin valves

    SciTech Connect

    Saito, Y. Tanamoto, T.; Ishikawa, M.; Sugiyama, H.; Inokuchi, T.; Hamaya, K.; Tezuka, N.

    2014-05-07

    Local magnetoresistance (MR) through silicon (Si) and its bias voltage (V{sub bias}) (bias current (I{sub bias})) dependence in ferromagnet (FM)/MgO/silicon-on-insulator lateral spin valves are investigated. From the experimental measurements, we find that the local-MR through Si increases with increasing V{sub bias}. This anomalous increase of local-MR as a function of V{sub bias} can be understood by considering the standard drift-diffusion theory improved by taking into account the difference in the interface resistances and first order quantum effect between FM/MgO/Si (source) and Si/MgO/FM (drain) interfaces. The interface resistance dependence on experimentally obtained local-MR ratios also agrees with the improved standard spin diffusion theory. These results indicate that experimentally observed local-MR is certainly related to the spin signal through the Si bulk band.

  15. The cation selectivity and voltage dependence of the light-activated potassium conductance in scallop distal photoreceptor.

    PubMed Central

    Cornwall, M C; Gorman, A L

    1983-01-01

    Light-dependent voltage and current responses were measured from the distal hyperpolarizing photoreceptors of the scallop (Pecten irradians) retina. In normal external solution, the hyperpolarizing receptor potential was caused by a light-dependent K+ outward current. The magnitude of the hyperpolarizing receptor potential and the light-dependent outward current, measured at the resting potential, was graded with light intensity. In normal external solution, during prolonged illumination the light-dependent K+ outward current was characterized by an early peak and a subsequent plateau. Current responses to brief light flashes were reduced progressively during background illumination. In the absence of external Na+ ions, the reversal potential for the receptor potential changed 58 mV per 10-fold change in the extracellular K+ concentration. The estimated internal K+ concentration was 385 mM. The hyperpolarizing receptor potential produced by prolonged bright illumination consists of an early peak which decays to a plateau. This decay was determined by a decrease in the light-dependent K+ conductance during maintained illumination. The light-dependent conductance pathway passed outward currents better than inward K+ currents. The light-dependent K+ conductance was estimated to increase e-fold per 23-34 mV depolarization at the peak and during the plateau of the light response. The light-dependent conductance pathway was highly selective for K+ ions. The selectivity sequence for monovalent cations was T1+, K+ greater than Rb+ greater than NH4 greater than Cs+, Li+, Na+. External caesium and tetraethylammonium blocked inward but not outward K+ currents through the light-dependent K+ conductance pathway. The data suggest that K+ ions move through an aqueous pore which is controlled by light. PMID:6887051

  16. Voltage-dependent gating of KCNH potassium channels lacking a covalent link between voltage-sensing and pore domains

    PubMed Central

    Lörinczi, Éva; Gómez-Posada, Juan Camilo; de la Peña, Pilar; Tomczak, Adam P.; Fernández-Trillo, Jorge; Leipscher, Ulrike; Stühmer, Walter; Barros, Francisco; Pardo, Luis A.

    2015-01-01

    Voltage-gated channels open paths for ion permeation upon changes in membrane potential, but how voltage changes are coupled to gating is not entirely understood. Two modules can be recognized in voltage-gated potassium channels, one responsible for voltage sensing (transmembrane segments S1 to S4), the other for permeation (S5 and S6). It is generally assumed that the conversion of a conformational change in the voltage sensor into channel gating occurs through the intracellular S4–S5 linker that provides physical continuity between the two regions. Using the pathophysiologically relevant KCNH family, we show that truncated proteins interrupted at, or lacking the S4–S5 linker produce voltage-gated channels in a heterologous model that recapitulate both the voltage-sensing and permeation properties of the complete protein. These observations indicate that voltage sensing by the S4 segment is transduced to the channel gate in the absence of physical continuity between the modules. PMID:25818916

  17. Dopamine Induces LTP Differentially in Apical and Basal Dendrites through BDNF and Voltage-Dependent Calcium Channels

    ERIC Educational Resources Information Center

    Navakkode, Sheeja; Sajikumar, Sreedharan; Korte, Martin; Soong, Tuck Wah

    2012-01-01

    The dopaminergic modulation of long-term potentiation (LTP) has been studied well, but the mechanism by which dopamine induces LTP (DA-LTP) in CA1 pyramidal neurons is unknown. Here, we report that DA-LTP in basal dendrites is dependent while in apical dendrites it is independent of activation of L-type voltage-gated calcium channels (VDCC).…

  18. Temperature- and voltage-dependent trap generation model in high-k metal gate MOS device with percolation simulation

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Yang, Hong; Wang, Yan-Rong; Wang, Wen-Wu; Luo, Wei-Chun; Qi, Lu-Wei; Li, Jun-Feng; Zhao, Chao; Chen, Da-Peng; Ye, Tian-Chun

    2016-08-01

    High-k metal gate stacks are being used to suppress the gate leakage due to tunneling for sub-45 nm technology nodes. The reliability of thin dielectric films becomes a limitation to device manufacturing, especially to the breakdown characteristic. In this work, a breakdown simulator based on a percolation model and the kinetic Monte Carlo method is set up, and the intrinsic relation between time to breakdown and trap generation rate R is studied by TDDB simulation. It is found that all degradation factors, such as trap generation rate time exponent m, Weibull slope β and percolation factor s, each could be expressed as a function of trap density time exponent α. Based on the percolation relation and power law lifetime projection, a temperature related trap generation model is proposed. The validity of this model is confirmed by comparing with experiment results. For other device and material conditions, the percolation relation provides a new way to study the relationship between trap generation and lifetime projection. Project supported by the National High Technology Research and Development Program of China (Grant No. SS2015AA010601), the National Natural Science Foundation of China (Grant Nos. 61176091 and 61306129), and the Opening Project of Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of MicroElectronics of Chinese Academy of Sciences.

  19. The identification and characterization of a noncontinuous calmodulin-binding site in noninactivating voltage-dependent KCNQ potassium channels.

    PubMed

    Yus-Najera, Eva; Santana-Castro, Irene; Villarroel, Alvaro

    2002-08-01

    We show here that in a yeast two-hybrid assay calmodulin (CaM) interacts with the intracellular C-terminal region of several members of the KCNQ family of potassium channels. CaM co-immunoprecipitates with KCNQ2, KCNQ3, or KCNQ5 subunits better in the absence than in the presence of Ca2+. Moreover, in two-hybrid assays where it is possible to detect interactions with apo-CaM but not with Ca2+-bound calmodulin, we localized the CaM-binding site to a region that is predicted to contain two alpha-helices (A and B). These two helices encompass approximately 85 amino acids, and in KCNQ2 they are separated by a dispensable stretch of approximately 130 amino acids. Within this CaM-binding domain, we found an IQ-like CaM-binding motif in helix A and two overlapping consensus 1-5-10 CaM-binding motifs in helix B. Point mutations in helix A or B were capable of abolishing CaM binding in the two-hybrid assay. Moreover, glutathione S-transferase fusion proteins containing helices A and B were capable of binding to CaM, indicating that the interaction with KCNQ channels is direct. Full-length CaM (both N and C lobes) and a functional EF-1 hand were required for these interactions to occur. These observations suggest that apo-CaM is bound to neuronal KCNQ channels at low resting Ca2+ levels and that this interaction is disturbed when the [Ca2+] is raised. Thus, we propose that CaM acts as a mediator in the Ca2+-dependent modulation of KCNQ channels. PMID:12032157

  20. Temperature- and voltage-dependent trap generation model in high-k metal gate MOS device with percolation simulation

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Yang, Hong; Wang, Yan-Rong; Wang, Wen-Wu; Luo, Wei-Chun; Qi, Lu-Wei; Li, Jun-Feng; Zhao, Chao; Chen, Da-Peng; Ye, Tian-Chun

    2016-08-01

    High-k metal gate stacks are being used to suppress the gate leakage due to tunneling for sub-45 nm technology nodes. The reliability of thin dielectric films becomes a limitation to device manufacturing, especially to the breakdown characteristic. In this work, a breakdown simulator based on a percolation model and the kinetic Monte Carlo method is set up, and the intrinsic relation between time to breakdown and trap generation rate R is studied by TDDB simulation. It is found that all degradation factors, such as trap generation rate time exponent m, Weibull slope β and percolation factor s, each could be expressed as a function of trap density time exponent α. Based on the percolation relation and power law lifetime projection, a temperature related trap generation model is proposed. The validity of this model is confirmed by comparing with experiment results. For other device and material conditions, the percolation relation provides a new way to study the relationship between trap generation and lifetime projection. Project supported by the National High Technology Research and Development Program of China (Grant No. SS2015AA010601), the National Natural Science Foundation of China (Grant Nos. 61176091 and 61306129), and the Opening Project of Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of MicroElectronics of Chinese Academy of Sciences.

  1. Selective inhibition of a slow-inactivating voltage-dependent K+ channel in rat PC12 cells by hypoxia.

    PubMed Central

    Conforti, L; Millhorn, D E

    1997-01-01

    1. Electrophysiological (single-channel patch clamp) and molecular biological experiments (reverse transcriptase-polymerase chain reaction) were performed to attempt to identify the O2-sensitive K+ channel in rat phaeochromocytoma (PC12) cells. 2. Four types of K+ channels were recorded in PC12 cells: a small-conductance K+ channel (14 pS), a calcium-activated K+ channel (KCa; 102 pS) and two K+ channels with similar conductance (20 pS). These last two channels differed in their time-dependent inactivation: one was a slow-inactivating channel, while the other belonged to the family of fast transient K+ channels. 3. The slow-inactivating 20 pS K+ channel was inhibited by hypoxia. Exposure to hypoxia produced a 50% reduction in channel activity (number of active channels in the patch x open probability). Hypoxia had no effect on the 20 pS transient K+ channels, whereas reduced O2 stimulated the KCa channels. 4. The genes encoding the alpha-subunits of slow-inactivating K+ channels for two members of the Shaker subfamily of K+ channels (Kv1.2 and Kv1.3) together with the Kv2.1, Kv3.1 and Kv3.2 channel genes were identified in PC12 cells. 5. The expression of the Shaker Kv1.2, but none of the other K+ channel genes, increased in cells exposed to prolonged hypoxia (18 h). The same cells were more responsive to a subsequent exposure to hypoxia (35% inhibition of K+ current measured in whole-cell voltage clamp) compared with the cells maintained in normoxia (19% inhibition). 6. These results indicate that the O2-sensitive K+ channel in PC12 cells is a 20 pS slow-inactivating K+ channel that is upregulated by hypoxia. This channel appears to belong to the Shaker subfamily of voltage-gated K+ channels. Images Figure 4 Figure 7 PMID:9263911

  2. Selective inhibition of a slow-inactivating voltage-dependent K+ channel in rat PC12 cells by hypoxia.

    PubMed

    Conforti, L; Millhorn, D E

    1997-07-15

    1. Electrophysiological (single-channel patch clamp) and molecular biological experiments (reverse transcriptase-polymerase chain reaction) were performed to attempt to identify the O2-sensitive K+ channel in rat phaeochromocytoma (PC12) cells. 2. Four types of K+ channels were recorded in PC12 cells: a small-conductance K+ channel (14 pS), a calcium-activated K+ channel (KCa; 102 pS) and two K+ channels with similar conductance (20 pS). These last two channels differed in their time-dependent inactivation: one was a slow-inactivating channel, while the other belonged to the family of fast transient K+ channels. 3. The slow-inactivating 20 pS K+ channel was inhibited by hypoxia. Exposure to hypoxia produced a 50% reduction in channel activity (number of active channels in the patch x open probability). Hypoxia had no effect on the 20 pS transient K+ channels, whereas reduced O2 stimulated the KCa channels. 4. The genes encoding the alpha-subunits of slow-inactivating K+ channels for two members of the Shaker subfamily of K+ channels (Kv1.2 and Kv1.3) together with the Kv2.1, Kv3.1 and Kv3.2 channel genes were identified in PC12 cells. 5. The expression of the Shaker Kv1.2, but none of the other K+ channel genes, increased in cells exposed to prolonged hypoxia (18 h). The same cells were more responsive to a subsequent exposure to hypoxia (35% inhibition of K+ current measured in whole-cell voltage clamp) compared with the cells maintained in normoxia (19% inhibition). 6. These results indicate that the O2-sensitive K+ channel in PC12 cells is a 20 pS slow-inactivating K+ channel that is upregulated by hypoxia. This channel appears to belong to the Shaker subfamily of voltage-gated K+ channels. PMID:9263911

  3. Responses of pyriform cortex neurons to excitatory amino acids: voltage dependence, conductance changes, and effects of divalent cations.

    PubMed

    Hori, N; Galeno, T; Carpenter, D O

    1987-03-01

    The actions of ionophoretically applied N-methyl aspartate (NMA), quisqualate, and kainate, thought to activate three different types of excitatory amino acid receptors, were studied on pyramidal neurons of the rat pyriform cortex, maintained in an isolated, submerged, and perfused brain slice. Intracellular recordings were made with either K acetate or CsCl electrodes. In most neurons all three agonists elicited monophasic responses which could be evoked at 20-sec intervals. Some neurons showed biphasic responses, most commonly to kainate but, on occasion, also for quisqualate. The slower component appeared to be correlated with excitotoxicity and, consequently, was difficult to study. As a result the kainate responses studied were from neurons selected for having a single component. In neurons selected for having a linear current-voltage relationship or neurons loaded with Cs to suppress K conductance and linearize the current-voltage relationship, the average changes in resistance recorded during ionophoretic responses at resting potential were as follows: NMA, 131.2 +/- 6.7% of control; kainate, 104.7 +/- 5.8% of control; and quisqualate, 92.8 +/- 2.8% of control. The magnitude and direction of the conductance change were very reproducible in any one neuron, but especially for kainate some cells showed clear conductance increases, while others showed clear conductance decreases. Using CsCl electrodes it was possible to reduce K+ conductance and depolarize the neurons over a wider range. By passing depolarizing current it was possible to reverse the responses. The response to all three agonists reversed at the same depolarized potential. This observation indicates that while there are differences in the ionic channels associated with the three agonists at resting potential, the channels have similar properties at more depolarized potentials. Responses to all three agonists were influenced by the concentrations of divalent cations in the perfusion medium. The NMA responses were most sensitive to Mg, increasing in amplitude in the absence of Mg and being depressed by Mg elevation. All responses were sensitive to Ca, with discharges being greatly increased by low Ca and depressed by high Ca. The kainate response was most sensitive to Ca concentration changes. Unlike reports from other preparations the apparent conductance decreases to NMA were not altered by the perfusion of solutions with either no added Mg or no added Ca. The NMA response was very much reduced in either Co (1-2 mM) or Zn (100-200 microM).(ABSTRACT TRUNCATED AT 400 WORDS)

  4. Temperature and bias-voltage dependence of atomic-layer-deposited HfO{sub 2}-based magnetic tunnel junctions

    SciTech Connect

    Fabretti, Savio; Zierold, Robert; Nielsch, Kornelius; Voigt, Carmen; Ronning, Carsten; Peretzki, Patrick; Seibt, Michael; Thomas, Andy

    2014-09-29

    Magnetic tunnel junctions with HfO{sub 2} tunnel barriers were prepared through a combination of magnetron sputtering and atomic layer deposition. We investigated the tunneling transport behavior, including the tunnel magnetoresistance ratio and the current-voltage characteristics between room temperature and 2 K. Here, we achieved a tunneling magneto resistance ratio of 10.3% at room temperature and 19.3% at 2 K. Furthermore, we studied the bias-voltage and temperature dependencies and compared the results with those of commonly used alumina- and magnesia-based magnetic tunnel junctions. We observed a polycrystalline/amorphous electrode-barrier system via high-resolution transmission electron microscopy.

  5. Neurotransmitter receptors and voltage-dependent Ca2+ channels encoded by mRNA from the adult corpus callosum.

    PubMed

    Matute, C; Miledi, R

    1993-04-15

    The presence of mRNAs encoding neurotransmitter receptors and voltage-gated channels in the adult human and bovine corpus callosum was investigated using Xenopus oocytes. Oocytes injected with mRNA extracted from the corpus callosum expressed functional receptors to glutamate, acetylcholine, and serotonin, and also voltage-operated Ca2+ channels, all with similar properties in the two species studied. Acetylcholine and serotonin elicited oscillatory Cl- currents due to activation of the inositol phosphate-Ca2+ receptor-channel coupling system. Glutamate and its analogs N-methyl-D-aspartate (NMDA), kainate, quisqualate, and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) induced smooth currents. The non-NMDA responses showed a strong inward rectification at positive potentials and were potently blocked by 6,7-dinitroquinoxaline-2,3-dione, as observed for the AMPA/kainate glutamate receptors GLUR1 and GLUR3. Furthermore, in situ hybridization experiments showed that GLUR1 and GLUR3 mRNAs are present in corpus callosum cells that were labeled with antiserum to glial fibrillary acid protein and that, in primary cell cultures, had the morphology of type 2 astrocytes. These results indicate that glial cells in the adult corpus callosum possess mRNA encoding functional neurotransmitter receptors and Ca2+ channels. These molecules may provide a mechanism for glial-neuronal interactions. PMID:7682696

  6. Voltage dependence of cardiac excitation-contraction coupling: unitary Ca2+ current amplitude and open channel probability.

    PubMed

    Altamirano, Julio; Bers, Donald M

    2007-09-14

    Excitation-contraction coupling in cardiac myocytes occurs by Ca2+-induced Ca2+ release, where L-type Ca2+ current evokes a larger sarcoplasmic reticulum (SR) Ca2+ release. The Ca2+-induced Ca2+ release amplification factor or gain (SR Ca2+ release/I(Ca)) is usually assessed by the V(m) dependence of current and Ca2+ transients. Gain rises at negative V(m), as does single channel I(Ca) (i(Ca)), which has led to the suggestion that the increases of i(Ca) amplitude enhances gain at more negative V(m). However, I(Ca) = NP(o) x i(Ca) (where NP(o) is the number of open channels), and NP(o) and i(Ca) both depend on V(m). To assess how i(Ca) and NP(o) separately influence Ca2+-induced Ca2+ release, we measured I(Ca) and junctional SR Ca2+ release in voltage-clamped rat ventricular myocytes using "Ca2+ spikes" (confocal microscopy). To vary i(Ca) alone, we changed [Ca2+](o) rapidly at constant test V(m) (0 mV) or abruptly repolarized from +120 mV to different V(m) (at constant [Ca2+](o)). To vary NP(o) alone, we altered Ca2+ channel availability by varying holding V(m) (at constant test V(m)). Reducing either i(Ca) or NP(o) alone increased excitation-contraction coupling gain. Thus, increasing i(Ca) does not increase gain at progressively negative test V(m). Such enhanced gain depends on lower NP(o) and reduced redundant Ca2+ channel openings (per junction) and a consequently smaller denominator in the gain equation. Furthermore, modest i(Ca) (at V(m) = 0 mV) may still effectively trigger SR Ca2+ release, whereas at positive V(m) (and smaller i(Ca)), high and well-synchronized channel openings are required for efficient excitation-contraction coupling. At very positive V(m), reduced i(Ca) must explain reduced SR Ca2+ release.

  7. Involvement of voltage-dependent potassium channels in the EDHF-mediated relaxation of rat hepatic artery

    PubMed Central

    Zygmunt, Peter M; Edwards, Gillian; Weston, Arthur H; Larsson, Bengt; Högestätt, Edward D

    1997-01-01

    In the rat hepatic artery, the acetylcholine-induced relaxation mediated by endothelium-derived hyperpolarizing factor (EDHF) is abolished by a combination of apamin and charybdotoxin, inhibitors of small (SKCa) and large (BKCa) conductance calcium-sensitive potassium (K)-channels, respectively, but not by each toxin alone. The selective BKCa inhibitor iberiotoxin cannot replace charybdotoxin in this combination. Since delayed rectifier K-channels (KV) represent another target for charybdotoxin, we explored the possible involvement of KV in EDHF-mediated relaxation in this artery. The KV inhibitors, agitoxin-2 (0.3 μM), kaliotoxin (0.3 μM), β-dendrotoxin (0.3 μM), dofetilide (1 μM) and terikalant (10 μM), each in combination with apamin (0.3 μM) had no effect on the EDHF-mediated relaxation induced by acetylcholine in the presence of Nω-nitro-L-arginine (0.3 mM) and indomethacin (10 μM), inhibitors of nitric oxide (NO) synthase and cyclo-oxygenase, respectively (n=2–3). Although the KV inhibitor margatoxin (0.3 μM) was also without effect (n=5), the combination of margatoxin and apamin produced a small inhibition of the response (pEC50 and Emax values were 7.5±0.0 and 95±1% in the absence and 7.0±0.1 and 81±6% in the presence of margatoxin plus apamin, respectively; n=6; P<0.05). Ciclazindol (10 μM) partially inhibited the EDHF-mediated relaxation by shifting the acetylcholine-concentration-response curve 12 fold to the right (n=6; P<0.05) and abolished the response when combined with apamin (0.3 μM; n=6). This combination did not inhibit acetylcholine-induced relaxations mediated by endothelium-derived NO (n=5). A 4-aminopyridine-sensitive delayed rectifier current (IK(V)) was identified in freshly-isolated single smooth muscle cells from rat hepatic artery. None of the cells displayed a rapidly-activating and -inactivating A-type current. Neither charybdotoxin (0.3 μM; n=3) nor ciclazindol (10 μM; n=5), alone or in combination with apamin (0.3 μM; n=4–5), had an effect on IK(V). A tenfold higher concentration of ciclazindol (0.1 mM, n=4) markedly inhibited IK(V), but this effect was not increased in the additional presence of apamin (0.3 μM; n=2). By use of membranes prepared from rat brain cortex, [125I]-charybdotoxin binding was consistent with an interaction at a single site with a KD of approximately 25 pM. [125I]-charybdotoxin binding was unaffected by iberiotoxin (0.1 μM, n=6), but was increased by apamin in a concentration-dependent manner (Emax 43±10%, P<0.05 and pEC50 7.1±0.2; n=7–8). Agitoxin-2 (10 nM) displaced [125I]-charybdotoxin binding by 91±3% (n=6) and prevented the effect of apamin (1 μM; n=6). It is concluded that the EDHF-mediated relaxation in the rat hepatic artery is not mediated by the opening of either KV or BKCa. Instead, the target K-channels for EDHF seem to be structurally related to both KV and BKCa. The possibility that a subtype of SKCa may be the target for EDHF is discussed. PMID:9146898

  8. Cardiovascular Action of Insulin in Health and Disease: Endothelial L-Arginine Transport and Cardiac Voltage-Dependent Potassium Channels

    PubMed Central

    Dubó, Sebastián; Gallegos, David; Cabrera, Lissette; Sobrevia, Luis; Zúñiga, Leandro; González, Marcelo

    2016-01-01

    Impairment of insulin signaling on diabetes mellitus has been related to cardiovascular dysfunction, heart failure, and sudden death. In human endothelium, cationic amino acid transporter 1 (hCAT-1) is related to the synthesis of nitric oxide (NO) and insulin has a vascular effect in endothelial cells through a signaling pathway that involves increases in hCAT-1 expression and L-arginine transport. This mechanism is disrupted in diabetes, a phenomenon potentiated by excessive accumulation of reactive oxygen species (ROS), which contribute to lower availability of NO and endothelial dysfunction. On the other hand, electrical remodeling in cardiomyocytes is considered a key factor in heart failure progression associated to diabetes mellitus. This generates a challenge to understand the specific role of insulin and the pathways involved in cardiac function. Studies on isolated mammalian cardiomyocytes have shown prolongated action potential in ventricular repolarization phase that produces a long QT interval, which is well explained by attenuation in the repolarizing potassium currents in cardiac ventricles. Impaired insulin signaling causes specific changes in these currents, such a decrease amplitude of the transient outward K+ (Ito) and the ultra-rapid delayed rectifier (IKur) currents where, together, a reduction of mRNA and protein expression levels of α-subunits (Ito, fast; Kv 4.2 and IKs; Kv 1.5) or β-subunits (KChIP2 and MiRP) of K+ channels involved in these currents in a MAPK mediated pathway process have been described. These results support the hypothesis that lack of insulin signaling can produce an abnormal repolarization in cardiomyocytes. Furthermore, the arrhythmogenic potential due to reduced Ito current can contribute to an increase in the incidence of sudden death in heart failure. This review aims to show, based on pathophysiological models, the regulatory function that would have insulin in vascular system and in cardiac electrophysiology. PMID:27014078

  9. Warm Forming of Mg Sheets: From Incremental to Electromagnetic Forming

    NASA Astrophysics Data System (ADS)

    Ulacia, Ibai; Galdos, Lander; Esnaola, Jon Ander; Larrañaga, Jon; Arruebarrena, Gurutze; de Argandoña, Eneko Saenz; Hurtado, Iñaki

    2014-07-01

    Magnesium alloys are generating interest in the automotive and aeronautic industries due to their low density and potential to reduce gross vehicular weight. However, the formability of these alloys is poor and they are very difficult to be formed at room temperature due to their strong basal texture in rolled form. In this paper, the potential of magnesium alloy sheets to be processed at warm conditions is studied for four different forming technologies: incremental forming (IF), deep drawing (DD), hydroforming (HF), and electromagnetic forming (EMF). Forming mechanisms and process window are experimentally characterized by monitoring different process parameters. Special focus is made on the influence of the forming temperature and the strain rate. Thus, experiments at temperatures from room to 523 K (250 °C) and a wide range of strain rates, between 10-3 up to 103 s-1 according to each process nature and scope, are conducted. It is observed that, even the inherent forming rate range of each process vary considerably, increasing forming temperature increases formability for all of these forming processes. In the other hand, an opposing effect of the strain rate is observed between the quasi-static processes (IF, DD, and HF) and the high speed process (EMF). Thus, a detrimental effect on formability is observed when increasing strain rate for quasi-static processes, while a mild increase is observed for EMF.

  10. Index of NASA prefixed forms

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This Handbook sets forth information for the guidance of all users of the NASA Forms Management Program System. It is issued in accordance with the Federal Information Resources Management Regulation (FIRMR), Subpart 201-9.1. This Handbook sets forth an alpha-functional index of NASA-prefixed forms by title, identifying number, and unit of issue. The automated processing two-letter code (NF) has been substituted for the spelling out of the NASA form-prefix preceding the form number. To indicate a description in lieu of a distinct title, the entire reference under the Form Title/Description column has been enclosed in parentheses. A list of current forms, shown by number and page, is included for cross-reference and to preclude the ordering of those forms which have been deleted from the system. This Handbook will be updated, as appropriate. NHB 1420.2H dated July 1986, is cancelled.

  11. Undercuts by Laser Shock Forming

    NASA Astrophysics Data System (ADS)

    Wielage, Hanna; Vollertsen, Frank

    2011-05-01

    In laser shock forming TEA-CO2-laser induced shock waves are used to form metal foils, such as aluminum or copper. The process utilizes an initiated plasma shock wave on the target surface, which leads to a forming of the foil. A challenge in forming technologies is the manufacturing of undercuts. By conventional forming methods these special forms are not feasible. In this article, it is presented that undercuts in the micro range can be produced by laser shock deep drawing. Different drawing die diameters, drawing die depths and the material aluminum in the thicknesses 20 and 50 μm were investigated. It will be presented that smaller die diameters facilitate undercuts compared to bigger die diameters. The phenomena can be explained by Barlow's formula. Furthermore, it is shown which maximum undercut depth at different die diameters can be reached. To this end, cross-sections of the different parameter combinations are displayed.

  12. The semantics of biological forms.

    PubMed

    Albertazzi, Liliana; Canal, Luisa; Dadam, James; Micciolo, Rocco

    2014-01-01

    This study analyses how certain qualitative perceptual appearances of biological forms are correlated with expressions of natural language. Making use of the Osgood semantic differential, we presented the subjects with 32 drawings of biological forms and a list of 10 pairs of connotative adjectives to be put in correlations with them merely by subjective judgments. The principal components analysis made it possible to group the semantics of forms according to two distinct axes of variability: harmony and dynamicity. Specifically, the nonspiculed, nonholed, and flat forms were perceived as harmonic and static; the rounded ones were harmonic and dynamic. The elongated forms were somewhat disharmonious and somewhat static. The results suggest the existence in the general population of a correspondence between perceptual and semantic processes, and of a nonsymbolic relation between visual forms and their adjectival expressions in natural language.

  13. Undercuts by Laser Shock Forming

    SciTech Connect

    Wielage, Hanna; Vollertsen, Frank

    2011-05-04

    In laser shock forming TEA-CO{sub 2}-laser induced shock waves are used to form metal foils, such as aluminum or copper. The process utilizes an initiated plasma shock wave on the target surface, which leads to a forming of the foil. A challenge in forming technologies is the manufacturing of undercuts. By conventional forming methods these special forms are not feasible. In this article, it is presented that undercuts in the micro range can be produced by laser shock deep drawing. Different drawing die diameters, drawing die depths and the material aluminum in the thicknesses 20 and 50 {mu}m were investigated. It will be presented that smaller die diameters facilitate undercuts compared to bigger die diameters. The phenomena can be explained by Barlow's formula. Furthermore, it is shown which maximum undercut depth at different die diameters can be reached. To this end, cross-sections of the different parameter combinations are displayed.

  14. Seal for fluid forming tools

    DOEpatents

    Golovashchenko, Sergey Fedorovich; Bonnen, John Joseph Francis

    2012-03-20

    An electro-hydraulic forming tool for forming a sheet metal blank in a one-sided die has first and second rigid rings that engage opposite sides of a sheet metal blank. The rigid rings are contained within slots on a die portion and a hydraulic force applicator portion of the forming tool. The seals are either resiliently biased by an elastomeric member or inherently resiliently biased into contact with the blank.

  15. Improving the forming capability of laser dynamic forming by using rubber as a forming medium

    NASA Astrophysics Data System (ADS)

    Shen, Zongbao; Liu, Huixia; Wang, Xiao; Wang, Cuntang

    2016-04-01

    Laser dynamic forming (LDF) is a novel high velocity forming technique, which employs laser-generated shock wave to load the sample. The forming velocity induced by the high energy laser pulse may exceed the critical forming velocity, resulting in the occurrence of premature fracture. To avoid the above premature fracture, rubber is introduced in LDF as a forming medium to prolong the loading duration in this paper. Laser induced shock wave energy is transferred to the sample in different forming stages, so the forming velocity can be kept below the critical forming velocity when the initial laser energy is high for fracture. Bulge forming experiments with and without rubber were performed to study the effect of rubber on loading duration. The experimental results show that, the shock wave energy attenuates during the propagation through the rubber layer, the rubber can avoid the premature fracture. So the plastic deformation can continue, the forming capability of LDF is improved. Due to the severe plastic deformation under rubber compression, adiabatic shear bands (ASB) occur in LDF with rubber. The material softening in ASB leads to the irregular fracture, which is different from the premature fracture pattern (regular fracture) in LDF without rubber. To better understand this deformation behavior, Johnson-Cook model is used to simulate the dynamic response and the evolution of ASB of copper sample. The simulation results also indicate the rubber can prolong the loading duration.

  16. Legal forms and reproductive norms.

    PubMed

    Fletcher, Ruth

    2003-06-01

    This article draws on Pashukanis's concept of legal form and on O'Brien's concept of synthetic value to argue that legal form plays a role in reproductive relations by constructing legal subjects as the bearers of reproductive responsibilities. Pashukanis conceived of legal form as playing a particular role in capitalist exchange relations by interpellating subjects as the bearers of property rights. O'Brien argued that reproduction's specific value is synthetic value, which represents the value of integrating nature and reason in species continuity. Synthetic value is distinct from exchange value or emotional value which may also attach to reproductive process. By working through Pashukanis's method of extracting legal form from specific social relations and by adapting it to reproductive relations, an example is provided of how legal form analysis can be extended beyond the particular context of capitalist exchange relations. Just as legal form constitutes owners and non-owners as legal subjects, so it constitutes reproducers and non-reproducers. By tracing the way in which law attributes reproductive responsibility, legal form analysis shows us how law draws a line between wanting to attribute responsibility and not to attribute it, and this contradiction is a hook which social forces such as sexuality, gender, race, class and disability can latch on to in pushing legal form to shape reproductive responsibilities in a particular way. Each legal form is also externally contradicted by other legal forms. When law negotiates a balance between the reproductive norms of responsibilities and rights, it demonstrates how particular legal forms manage the interaction of different sets of social relations, such as reproduction and exchange. PMID:15871155

  17. Transient Potential Gradients and Impedance Measures of Tethered Bilayer Lipid Membranes: Pore-Forming Peptide Insertion and the Effect of Electroporation

    PubMed Central

    Cranfield, Charles G.; Cornell, Bruce A.; Grage, Stephan L.; Duckworth, Paul; Carne, Sonia; Ulrich, Anne S.; Martinac, Boris

    2014-01-01

    In this work, we present experimental data, supported by a quantitative model, on the generation and effect of potential gradients across a tethered bilayer lipid membrane (tBLM) with, to the best of our knowledge, novel architecture. A challenge to generating potential gradients across tBLMs arises from the tethering coordination chemistry requiring an inert metal such as gold, resulting in any externally applied voltage source being capacitively coupled to the tBLM. This in turn causes any potential across the tBLM assembly to decay to zero in milliseconds to seconds, depending on the level of membrane conductance. Transient voltages applied to tBLMs by pulsed or ramped direct-current amperometry can, however, provide current-voltage (I/V) data that may be used to measure the voltage dependency of the membrane conductance. We show that potential gradients >∼150 mV induce membrane defects that permit the insertion of pore-forming peptides. Further, we report here the novel (to our knowledge) use of real-time modeling of conventional low-voltage alternating-current impedance spectroscopy to identify whether the conduction arising from the insertion of a polypeptide is uniform or heterogeneous on scales of nanometers to micrometers across the membrane. The utility of this tBLM architecture and these techniques is demonstrated by characterizing the resulting conduction properties of the antimicrobial peptide PGLa. PMID:24411250

  18. Automated Test-Form Generation

    ERIC Educational Resources Information Center

    van der Linden, Wim J.; Diao, Qi

    2011-01-01

    In automated test assembly (ATA), the methodology of mixed-integer programming is used to select test items from an item bank to meet the specifications for a desired test form and optimize its measurement accuracy. The same methodology can be used to automate the formatting of the set of selected items into the actual test form. Three different…

  19. When Permission Forms Work Best

    ERIC Educational Resources Information Center

    Zirkel, Perry A.

    2005-01-01

    Public schools routinely require permission or release forms for field trips and other activities of potential liability. The legal status of such forms varies, but they are generally considered neither rock-solid protection nor legally valueless in terms of immunity. This article presents a case involving a student who sustained bicycle injuries…

  20. Method of forming ceramic bricks

    DOEpatents

    Poeppel, R.B.; Claar, T.D.; Silkowski, P.

    1987-04-22

    A method for forming free standing ceramic bricks for use as tritium breeder material is disclosed. Aqueous solutions of sodium carbonate and potassium carbonate are mixed with an organic hydrocolloid dispersion and powdered lithium carbonate, spray dried, and ceramic bricks formed by molding in a die and firing.

  1. Method of forming ceramic bricks

    DOEpatents

    Poeppel, Roger B.; Claar, Terry D.; Silkowski, Peter

    1988-09-06

    A method for forming free standing ceramic bricks for use as tritium breeder material is disclosed. Aqueous solutions of sodium carbonate and potassium carbonate are mixed with an organic hydrocolloid dispersion and powdered lithium carbonate, spray dried, and ceramic bricks formed by molding in a die and firing.

  2. Method of forming ceramic bricks

    DOEpatents

    Poeppel, Roger B.; Claar, Terry D.; Silkowski, Peter

    1988-01-01

    A method for forming free standing ceramic bricks for use as tritium breeder material is disclosed. Aqueous solutions of sodium carbonate and potassium carbonate are mixed with an organic hydrocolloid dispersion and powdered lithium carbonate, spray dried, and ceramic bricks formed by molding in a die and firing.

  3. Quantum modular forms, mock modular forms, and partial theta functions

    NASA Astrophysics Data System (ADS)

    Kimport, Susanna

    Defined by Zagier in 2010, quantum modular forms have been the subject of an explosion of recent research. Many of these results are aimed at discovering examples of these functions, which are defined on the rational numbers and have "nice" modularity properties. Though the subject is in its early stages, numerous results (including Zagier's original examples) show these objects naturally arising from many areas of mathematics as limits of other modular-like functions. One such family of examples is due to Folsom, Ono, and Rhoades, who connected these new objects to partial theta functions (introduced by Rogers in 1917) and mock modular forms (about which there is a rich theory, whose origins date back to Ramanujan in 1920). In this thesis, we build off of the work of Folsom, Ono, and Rhoades by providing an infinite family of quantum modular forms of arbitrary positive half-integral weight. Further, this family of quantum modular forms "glues" mock modular forms to partial theta functions and is constructed from a so-called "universal" mock theta function by extending a method of Eichler and Zagier (originally defined for holomorphic Jacobi forms) into a non-holomorphic setting. In addition to the infinite family, we explore the weight 1/2 and 3/2 functions in more depth. For both of these weights, we are able to explicitly write down the quantum modular form, as well as the corresponding "errors to modularity," which can be shown to be Mordell integrals of specific theta functions and, as a consequence, are real-analytic functions. Finally, we turn our attention to the partial theta functions associated with these low weight examples. Berndt and Kim provide asymptotic expansions for a certain class of partial theta functions as q approaches 1 radially within the unit disk. Here, we extend this work to not only obtain asymptotic expansions for this class of functions as q approaches any root of unity, but also for a certain class of derivatives of these functions

  4. Process to form mesostructured films

    DOEpatents

    Brinker, C.J.; Anderson, M.T.; Ganguli, R.; Lu, Y.F.

    1999-01-12

    This invention comprises a method to form a family of supported films with pore size in the approximate range 0.8-20 nm exhibiting highly ordered microstructures and porosity derived from an ordered micellar or liquid-crystalline organic-inorganic precursor structure that forms during film deposition. Optically transparent, 100-500-nm thick films exhibiting a unique range of microstructures and uni-modal pore sizes are formed in seconds in a continuous coating operation. Applications of these films include sensors, membranes, low dielectric constant interlayers, anti-reflective coatings, and optical hosts. 12 figs.

  5. Process to form mesostructured films

    DOEpatents

    Brinker, C. Jeffrey; Anderson, Mark T.; Ganguli, Rahul; Lu, Yunfeng

    1999-01-01

    This invention comprises a method to form a family of supported films film with pore size in the approximate range 0.8-20 nm exhibiting highly ordered microstructures and porosity derived from an ordered micellar or liquid-crystalline organic-inorganic precursor structure that forms during film deposition. Optically transparent, 100-500-nm thick films exhibiting a unique range of microstructures and uni-modal pore sizes are formed in seconds in a continuous coating operation. Applications of these films include sensors, membranes, low dielectric constant interlayers, anti-reflective coatings, and optical hosts.

  6. Triggered pore-forming agents

    DOEpatents

    Bayley, Hagan; Walker, Barbara J.; Chang, Chung-yu; Niblack, Brett; Panchal, Rekha

    1998-01-01

    An inactive pore-forming agent which is activated to lytic function by a condition such as pH, light, heat, reducing potential, or metal ion concentration, or substance such as a protease, at the surface of a cell.

  7. Arbitrary p-form Galileons

    SciTech Connect

    Deffayet, C.; Deser, S.; Esposito-Farese, G.

    2010-09-15

    We show that scalar, 0-form, Galileon actions--models whose field equations contain only second derivatives--can be generalized to arbitrary even p-forms. More generally, they need not even depend on a single form, but may involve mixed p combinations, including equal p multiplets, where odd p fields are also permitted: We construct, for given dimension D, general actions depending on scalars, vectors, and higher p-form field strengths, whose field equations are of exactly second derivative order. We also discuss and illustrate their curved-space generalizations, especially the delicate nonminimal couplings required to maintain this order. Concrete examples of pure and mixed actions, field equations, and their curved-space extensions are presented.

  8. Differential form analysis using MACSYMA

    NASA Technical Reports Server (NTRS)

    Wahlquist, H. D.

    1977-01-01

    The MACSYMA file was written to perform these operations and discusses the improvements and additions which are needed to accomplish a complete and efficient implementation. Examples of differential form calculations are displayed.

  9. Process for forming planarized films

    DOEpatents

    Pang, Stella W.; Horn, Mark W.

    1991-01-01

    A planarization process and apparatus which employs plasma-enhanced chemical vapor deposition (PECVD) to form plarnarization films of dielectric or conductive carbonaceous material on step-like substrates.

  10. [Aspergillosis. Clinical forms and treatment].

    PubMed

    Fortún, Jesús; Meije, Yolanda; Fresco, Gema; Moreno, Santiago

    2012-04-01

    Invasive aspergillosis, chronic pulmonary aspergillosis and allergic bronchopulmonary aspergillosis are the clinical forms of aspergillosis. Although there is a great number of Aspergillus species, Aspergillus fumigatus-complex is the more frequent aetiological agent, regardless of clinical form or baseline condition. The increase in immunosuppressive agents and the higher use of corticosteroids in chronic obstructive pulmonary disease have led to aspergillosis becoming more prominent in recent years. Galactomannan detection and radiological diagnostic images complement the limitations of microbiology cultures in these patients. Voriconazole and liposomal amphotericin B are the gold standard in patients requiring therapy, and posaconazole, itraconazole, caspofungin and other echinocandins are effective alternatives. The prognosis depends of clinical forms and characteristics of the host, but it is particularly poor in the disseminated invasive forms.

  11. Confectionery-based dose forms.

    PubMed

    Tangso, Kristian J; Ho, Quy Phuong; Boyd, Ben J

    2015-01-01

    Conventional dosage forms such as tablets, capsules and syrups are prescribed in the normal course of practice. However, concerns about patient preferences and market demands have given rise to the exploration of novel unconventional dosage forms. Among these, confectionery-based dose forms have strong potential to overcome compliance problems. This report will review the availability of these unconventional dose forms used in treating the oral cavity and for systemic drug delivery, with a focus on medicated chewing gums, medicated lollipops, and oral bioadhesive devices. The aim is to stimulate increased interest in the opportunities for innovative new products that are available to formulators in this field, particularly for atypical patient populations. PMID:25146440

  12. Methods of forming hardened surfaces

    DOEpatents

    Branagan, Daniel J.

    2004-07-27

    The invention encompasses a method of forming a metallic coating. A metallic glass coating is formed over a metallic substrate. After formation of the coating, at least a portion of the metallic glass can be converted into a crystalline material having a nanocrystalline grain size. The invention also encompasses metallic coatings comprising metallic glass. Additionally, the invention encompasses metallic coatings comprising crystalline metallic material, with at least some of the crystalline metallic material having a nanocrystalline grain size.

  13. Method of forming pointed structures

    NASA Technical Reports Server (NTRS)

    Pugel, Diane E. (Inventor)

    2011-01-01

    A method of forming an array of pointed structures comprises depositing a ferrofluid on a substrate, applying a magnetic field to the ferrofluid to generate an array of surface protrusions, and solidifying the surface protrusions to form the array of pointed structures. The pointed structures may have a tip radius ranging from approximately 10 nm to approximately 25 micron. Solidifying the surface protrusions may be carried out at a temperature ranging from approximately 10 degrees C. to approximately 30 degrees C.

  14. Method for forming metal contacts

    DOEpatents

    Reddington, Erik; Sutter, Thomas C; Bu, Lujia; Cannon, Alexandra; Habas, Susan E; Curtis, Calvin J; Miedaner, Alexander; Ginley, David S; Van Hest, Marinus Franciscus Antonius Maria

    2013-09-17

    Methods of forming metal contacts with metal inks in the manufacture of photovoltaic devices are disclosed. The metal inks are selectively deposited on semiconductor coatings by inkjet and aerosol apparatus. The composite is heated to selective temperatures where the metal inks burn through the coating to form an electrical contact with the semiconductor. Metal layers are then deposited on the electrical contacts by light induced or light assisted plating.

  15. Superplastic forming of alloy 718

    SciTech Connect

    Smith, G.D.; Flower, H.L. )

    1994-04-01

    Inconel Alloy 718 (UNS N07718) is now available in a fine-grained, controlled composition modification that can be super-plastically formed. The new superplastic forming (SPF) capability allows the manufacture of large, complex, and detailed parts, which improves integrity by reducing the need for joining. Furthermore, it allows designers to fabricate components having higher strength, fatigue resistance, and temperature capability than parts made of aluminum or titanium alloys.

  16. INEL Spray-forming Research

    NASA Technical Reports Server (NTRS)

    Mchugh, Kevin M.; Key, James F.

    1993-01-01

    Spray forming is a near-net-shape fabrication technology in which a spray of finely atomized liquid droplets is deposited onto a suitably shaped substrate or mold to produce a coherent solid. The technology offers unique opportunities for simplifying materials processing without sacrificing, and oftentimes substantially improving, product quality. Spray forming can be performed with a wide range of metals and nonmetals, and offers property improvements resulting from rapid solidification (e.g., refined microstructures, extended solid solubilities and reduced segregation). Economic benefits result from process simplification and the elimination of unit operations. Researchers at the Idaho National Engineering Laboratory (INEL) are developing spray-forming technology for producing near-net-shape solids and coatings of a variety of metals, polymers, and composite materials. Results from several spray forming programs are presented to illustrate the range of capabilities of the technique as well as the accompanying technical and economic benefits. Low-carbon steel strip greater than 0.75 mm thick and polymer membranes for gas/gas and liquid/liquid separations that were spray formed are discussed; recent advances in spray forming molds, dies, and other tooling using low-melting-point metals are described.

  17. INEL spray-forming research

    SciTech Connect

    McHugh, K.M.; Key, J.F.

    1992-01-01

    Spray forming is a near-net-shape fabrication technology in which a spray of finely atomized liquid droplets is deposited onto a suitably shaped substrate or mold to produce a coherent solid. The technology offers unique opportunities for simplifying materials processing without sacrificing, and oftentimes substantially improving, product quality. Spray forming can be performed with a wide range of metals and nonmetals, and offers property improvements resulting from rapid solidification (e.g. refined microstructures, extended solid solubilities and reduced segregation). Economic benefits result from process simplification and the elimination of unit operations. Researchers at the Idaho National Engineering Laboratory (INEL) are developing spray-forming technology for producing near-net-shape solids and coatings of a variety of metals, polymers, and composite materials. Results from several spray-forming programs are presented to illustrate the range of capabilities of the technique as well as the accompanying technical and economic benefits. Low-carbon steel strip >0.75 mm thick and polymer membranes for gas/gas and liquid/liquid separations that were spray formed are discussed; recent advances in spray forming molds, dies, and other tooling using low-melting-point metals are described.

  18. INEL spray-forming research

    SciTech Connect

    McHugh, K.M.; Key, J.F.

    1992-12-31

    Spray forming is a near-net-shape fabrication technology in which a spray of finely atomized liquid droplets is deposited onto a suitably shaped substrate or mold to produce a coherent solid. The technology offers unique opportunities for simplifying materials processing without sacrificing, and oftentimes substantially improving, product quality. Spray forming can be performed with a wide range of metals and nonmetals, and offers property improvements resulting from rapid solidification (e.g. refined microstructures, extended solid solubilities and reduced segregation). Economic benefits result from process simplification and the elimination of unit operations. Researchers at the Idaho National Engineering Laboratory (INEL) are developing spray-forming technology for producing near-net-shape solids and coatings of a variety of metals, polymers, and composite materials. Results from several spray-forming programs are presented to illustrate the range of capabilities of the technique as well as the accompanying technical and economic benefits. Low-carbon steel strip >0.75 mm thick and polymer membranes for gas/gas and liquid/liquid separations that were spray formed are discussed; recent advances in spray forming molds, dies, and other tooling using low-melting-point metals are described.

  19. Superplastic forming of ceramic insulation

    NASA Technical Reports Server (NTRS)

    Nieh, T. G.; Wittenauer, J. P.; Wadsworth, J.

    1992-01-01

    Superplasticity has been demonstrated in many fine-grained structural ceramics and ceramic composites, including yttria-stabilized tetragonal zirconia polycrystal (YTZP), alumina, and Al2O3-reinforced zirconia (Al2O3/YTZ) duplex composites and SiC-reinforced Si3N4. These superplastic ceramics obviously offer the potential benefit of forming net shape or near net shape parts. This could be particularly useful for forming complicated shapes that are difficult to achieve using conventional forming techniques, or require elaborate, subsequent machining. In the present study, we successfully demonstrated the following: (1) superplastic 3Y-TXP and 20 percent Al2O3/YTZ composite have for the first time been successfully deformed into hemispherical caps via a biaxial gas-pressure forming technique; (2) no experimental difficulty was encountered in applying the required gas pressures and temperatures to achieve the results, thus, it is certain that higher rates of deformation than those presented in this study will be possible by using the current test apparatus at higher temperatures and pressures; and (3) an analytical model incorporating material parameters, such as variations during forming in the strain rate sensitivity exponent and grain growth-induced strain hardening, is needed to model accurately and therefore precisely control the biaxial gas-pressure forming of superplastic ceramics. Based on the results of this study, we propose to fabricate zirconia insulation tubes by superplastic extrusion of zirconia polycrystal. This would not only reduce the cost, but also improve the reliability of the tube products.

  20. Characterization of polymorphic ampicillin forms.

    PubMed

    Baraldi, C; Tinti, A; Ottani, S; Gamberini, M C

    2014-11-01

    In this work polymorphs of α-aminobenzylpenicillin (ampicillin), a β-lactamic antibiotic, were prepared and investigated by several experimental and theoretical methods. Amorphous monohydrate and three crystalline forms, the trihydrate, the crystal form I and the crystal form II, were investigated by FT-IR and micro-Raman. Also data obtained by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray powder diffraction (XRPD) and hot-stage Raman spectroscopy are reported. Finally, quantum mechanical calculations were performed by density functional theory (DFT) to assist the assignment of spectroscopic experimental bands. For the first time, the ampicillin molecule in its zwitterionic form was studied at the B3LYP/aug-cc-pVDZ level and the corresponding theoretical vibrational spectra were computed. In fact, ampicillin in the crystal is in zwitterionic form and concentrations of this same form are quite relevant in solutions at physiological pH. Experimental and theoretical results allowed identification of specific features for polymorph characterization. Bands typical of the different polymorphs are identified both in IR and Raman spectra: in particular in the NH stretching region (IR), in the amide I+δNH region (both techniques), in the 1520-1490cm(-1) region (IR), in the 1320-1300cm(-1) and 1280-1220cm(-1) (IR), in the 1200-1170cm(-1) (Raman), in the amide V region (IR), and, finally, in the 715-640cm(-1) and 220-200cm(-1) (Raman). Interconversion among different polymorphs was investigated by hot-stage Raman spectroscopy and thermal analysis, clarifying the complex pattern of transformations undergone as a function of temperature and heating rate. In particular, DSC scans show how the trihydrate crystals transform into anhydrous forms on heating. Finally, stability tests demonstrated, after a two years period, that no transformation or degradation of the polymorphs occurred.

  1. The discovery of structural form

    PubMed Central

    Kemp, Charles; Tenenbaum, Joshua B.

    2008-01-01

    Algorithms for finding structure in data have become increasingly important both as tools for scientific data analysis and as models of human learning, yet they suffer from a critical limitation. Scientists discover qualitatively new forms of structure in observed data: For instance, Linnaeus recognized the hierarchical organization of biological species, and Mendeleev recognized the periodic structure of the chemical elements. Analogous insights play a pivotal role in cognitive development: Children discover that object category labels can be organized into hierarchies, friendship networks are organized into cliques, and comparative relations (e.g., “bigger than” or “better than”) respect a transitive order. Standard algorithms, however, can only learn structures of a single form that must be specified in advance: For instance, algorithms for hierarchical clustering create tree structures, whereas algorithms for dimensionality-reduction create low-dimensional spaces. Here, we present a computational model that learns structures of many different forms and that discovers which form is best for a given dataset. The model makes probabilistic inferences over a space of graph grammars representing trees, linear orders, multidimensional spaces, rings, dominance hierarchies, cliques, and other forms and successfully discovers the underlying structure of a variety of physical, biological, and social domains. Our approach brings structure learning methods closer to human abilities and may lead to a deeper computational understanding of cognitive development. PMID:18669663

  2. The discovery of structural form.

    PubMed

    Kemp, Charles; Tenenbaum, Joshua B

    2008-08-01

    Algorithms for finding structure in data have become increasingly important both as tools for scientific data analysis and as models of human learning, yet they suffer from a critical limitation. Scientists discover qualitatively new forms of structure in observed data: For instance, Linnaeus recognized the hierarchical organization of biological species, and Mendeleev recognized the periodic structure of the chemical elements. Analogous insights play a pivotal role in cognitive development: Children discover that object category labels can be organized into hierarchies, friendship networks are organized into cliques, and comparative relations (e.g., "bigger than" or "better than") respect a transitive order. Standard algorithms, however, can only learn structures of a single form that must be specified in advance: For instance, algorithms for hierarchical clustering create tree structures, whereas algorithms for dimensionality-reduction create low-dimensional spaces. Here, we present a computational model that learns structures of many different forms and that discovers which form is best for a given dataset. The model makes probabilistic inferences over a space of graph grammars representing trees, linear orders, multidimensional spaces, rings, dominance hierarchies, cliques, and other forms and successfully discovers the underlying structure of a variety of physical, biological, and social domains. Our approach brings structure learning methods closer to human abilities and may lead to a deeper computational understanding of cognitive development.

  3. Form und Sinn: Sprachwissenschaftliche Betrachtungen (Form and Meaning: Linguistic Observations).

    ERIC Educational Resources Information Center

    Jakobson, Roman

    This collection of 14 papers and articles by Roman Jakobson contains works written and published between 1931 and 1970 which deal either with global aspects of language or with specific grammatical issues. The collection emphasizes Jakobson's concern for finding the links between form and meaning in language. The text is entirely in German with…

  4. Acceptance of Ideas of Others [Number Form and Star Form].

    ERIC Educational Resources Information Center

    Masters, James R.; Laverty, Grace E.

    As part of the instrumentation to assess the effectiveness of the Schools Without Failure (SWF) program in 10 elementary schools in the New Castle, Pa. School District, the Acceptance of Ideas of Others (Number and Star Forms) were developed to determine pupils' attitudes toward classmates. Given a list of all class members, pupils are asked to…

  5. Sixth-Form Colleges: An Endangered Organisational Form?

    ERIC Educational Resources Information Center

    Stoten, David William

    2014-01-01

    The sixth-form college sector is often marginalised in policy and academic discourse, where the much larger school and further education sectors dominate. This paper sets out to describe the sector's key features, assess its position within the wider education system and consider its future in an increasingly competitive education market. The…

  6. Substrate system for spray forming

    DOEpatents

    Chu, Men G.; Chernicoff, William P.

    2002-01-01

    A substrate system for receiving a deposit of sprayed metal droplets including a movable outer substrate on which the sprayed metal droplets are deposited. The substrate system also includes an inner substrate disposed adjacent the outer substrate where the sprayed metal droplets are deposited on the outer substrate. The inner substrate includes zones of differing thermal conductivity to resist substrate layer porosity and to resist formation of large grains and coarse constituent particles in a bulk layer of the metal droplets which have accumulated on the outer substrate. A spray forming apparatus and associated method of spray forming a molten metal to form a metal product using the substrate system of the invention is also provided.

  7. Substrate system for spray forming

    DOEpatents

    Chu, Men G.; Chernicoff, William P.

    2000-01-01

    A substrate system for receiving a deposit of sprayed metal droplets including a movable outer substrate on which the sprayed metal droplets are deposited. The substrate system also includes an inner substrate disposed adjacent the outer substrate where the sprayed metal droplets are deposited on the outer substrate. The inner substrate includes zones of differing thermal conductivity to resist substrate layer porosity and to resist formation of large grains and coarse constituent particles in a bulk layer of the metal droplets which have accumulated on the outer substrate. A spray forming apparatus and associated method of spray forming a molten metal to form a metal product using the substrate system of the invention is also provided.

  8. PROCESS OF FORMING POWDERED MATERIAL

    DOEpatents

    Glatter, J.; Schaner, B.E.

    1961-07-14

    A process of forming high-density compacts of a powdered ceramic material is described by agglomerating the powdered ceramic material with a heat- decompossble binder, adding a heat-decompossble lubricant to the agglomerated material, placing a quantity of the material into a die cavity, pressing the material to form a compact, pretreating the compacts in a nonoxidizing atmosphere to remove the binder and lubricant, and sintering the compacts. When this process is used for making nuclear reactor fuel elements, the ceramic material is an oxide powder of a fissionsble material and after forming, the compacts are placed in a cladding tube which is closed at its ends by vapor tight end caps, so that the sintered compacts are held in close contact with each other and with the interior wall of the cladding tube.

  9. Methods of forming boron nitride

    DOEpatents

    Trowbridge, Tammy L; Wertsching, Alan K; Pinhero, Patrick J; Crandall, David L

    2015-03-03

    A method of forming a boron nitride. The method comprises contacting a metal article with a monomeric boron-nitrogen compound and converting the monomeric boron-nitrogen compound to a boron nitride. The boron nitride is formed on the same or a different metal article. The monomeric boron-nitrogen compound is borazine, cycloborazane, trimethylcycloborazane, polyborazylene, B-vinylborazine, poly(B-vinylborazine), or combinations thereof. The monomeric boron-nitrogen compound is polymerized to form the boron nitride by exposure to a temperature greater than approximately 100.degree. C. The boron nitride is amorphous boron nitride, hexagonal boron nitride, rhombohedral boron nitride, turbostratic boron nitride, wurzite boron nitride, combinations thereof, or boron nitride and carbon. A method of conditioning a ballistic weapon and a metal article coated with the monomeric boron-nitrogen compound are also disclosed.

  10. Method of forming structural heliostat

    DOEpatents

    Anderson, Alfred J.

    1984-06-26

    In forming a heliostat having a main support structure and pivoting and tilting motors and gears and a mirror module for reflecting solar energy onto a collector, the improvement characterized by a method of forming the mirror module in which the mirror is laid upon a solid rigid supporting bed in one or more sections, with or without focusing; a mirror backing sheet is applied by first applying respective thin layers of silicone grease and, thereafter, progressively rolling application to eliminate air bubbles; followed by affixing of a substrate assembly to the mirror backing sheet to form a mirror module that does not curve because of thermally induced stresses and differential thermal expansion or contraction effects. The silicone grease also serves to dampen fluttering of the mirror and protect the mirror backside against adverse effects of the weather. Also disclosed are specific details of preferred embodiments.

  11. Auxin biosynthesis and storage forms

    PubMed Central

    Strader, Lucia C.

    2013-01-01

    The plant hormone auxin drives plant growth and morphogenesis. The levels and distribution of the active auxin indole-3-acetic acid (IAA) are tightly controlled through synthesis, inactivation, and transport. Many auxin precursors and modified auxin forms, used to regulate auxin homeostasis, have been identified; however, very little is known about the integration of multiple auxin biosynthesis and inactivation pathways. This review discusses the many ways auxin levels are regulated through biosynthesis, storage forms, and inactivation, and the potential roles modified auxins play in regulating the bioactive pool of auxin to affect plant growth and development. PMID:23580748

  12. FORM version 4.0

    NASA Astrophysics Data System (ADS)

    Kuipers, J.; Ueda, T.; Vermaseren, J. A. M.; Vollinga, J.

    2013-05-01

    We present version 4.0 of the symbolic manipulation system FORM. The most important new features are manipulation of rational polynomials and the factorization of expressions. Many other new functions and commands are also added; some of them are very general, while others are designed for building specific high level packages, such as one for Gröbner bases. New is also the checkpoint facility, that allows for periodic backups during long calculations. Finally, FORM 4.0 has become available as open source under the GNU General Public License version 3. Program summaryProgram title: FORM. Catalogue identifier: AEOT_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEOT_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License, version 3 No. of lines in distributed program, including test data, etc.: 151599 No. of bytes in distributed program, including test data, etc.: 1 078 748 Distribution format: tar.gz Programming language: The FORM language. FORM itself is programmed in a mixture of C and C++. Computer: All. Operating system: UNIX, LINUX, Mac OS, Windows. Classification: 5. Nature of problem: FORM defines a symbolic manipulation language in which the emphasis lies on fast processing of very large formulas. It has been used successfully for many calculations in Quantum Field Theory and mathematics. In speed and size of formulas that can be handled it outperforms other systems typically by an order of magnitude. Special in this version: The version 4.0 contains many new features. Most important are factorization and rational arithmetic. The program has also become open source under the GPL. The code in CPC is for reference. You are encouraged to upload the most recent sources from www.nikhef.nl/form/formcvs.php because of frequent bug fixes. Solution method: See "Nature of Problem", above. Additional comments: NOTE: The code in CPC is for reference. You are encouraged

  13. Auxin biosynthesis and storage forms.

    PubMed

    Korasick, David A; Enders, Tara A; Strader, Lucia C

    2013-06-01

    The plant hormone auxin drives plant growth and morphogenesis. The levels and distribution of the active auxin indole-3-acetic acid (IAA) are tightly controlled through synthesis, inactivation, and transport. Many auxin precursors and modified auxin forms, used to regulate auxin homeostasis, have been identified; however, very little is known about the integration of multiple auxin biosynthesis and inactivation pathways. This review discusses the many ways auxin levels are regulated through biosynthesis, storage forms, and inactivation, and the potential roles modified auxins play in regulating the bioactive pool of auxin to affect plant growth and development.

  14. 48 CFR Appendix - List of IAAR Forms

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 6 2012-10-01 2012-10-01 false List of IAAR Forms Federal Acquisition Regulations System BROADCASTING BOARD OF GOVERNORS CLAUSES AND FORMS FORMS Illustrations of Forms The Broadcasting Board of Governors forms. List of IAAR Forms 1953.370-21The Broadcasting Board of Governors Form IA-21, Abstract...

  15. 48 CFR Appendix - List of IAAR Forms

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Acquisition Regulations System BROADCASTING BOARD OF GOVERNORS CLAUSES AND FORMS FORMS Illustrations of Forms The Broadcasting Board of Governors forms. List of IAAR Forms 1953.370-21The Broadcasting Board of Governors Form IA-21, Abstract of Quotations. 1953.370-44The Broadcasting Board of Governors Form...

  16. 48 CFR 53.301 - Standard forms.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 2 2010-10-01 2010-10-01 false Standard forms. 53.301... AND FORMS FORMS Illustrations of Forms 53.301 Standard forms. This section illustrates the standard... order. The subsection numbers correspond with the standard form numbers (e.g., Standard Form 18...

  17. 48 CFR Appendix - List of IAAR Forms

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 6 2010-10-01 2010-10-01 true List of IAAR Forms Federal Acquisition Regulations System BROADCASTING BOARD OF GOVERNORS CLAUSES AND FORMS FORMS Illustrations of Forms The Broadcasting Board of Governors forms. List of IAAR Forms 1953.370-21The Broadcasting Board of Governors Form IA-21, Abstract...

  18. 48 CFR Appendix - List of IAAR Forms

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 6 2011-10-01 2011-10-01 false List of IAAR Forms Federal Acquisition Regulations System BROADCASTING BOARD OF GOVERNORS CLAUSES AND FORMS FORMS Illustrations of Forms The Broadcasting Board of Governors forms. List of IAAR Forms 1953.370-21The Broadcasting Board of Governors Form IA-21, Abstract...

  19. Triggered pore-forming agents

    DOEpatents

    Bayley, H.; Walker, B.J.; Chang, C.Y.; Niblack, B.; Panchal, R.

    1998-07-07

    An inactive pore-forming agent is revealed which is activated to lytic function by a condition such as pH, light, heat, reducing potential, or metal ion concentration, or substance such as a protease, at the surface of a cell. 30 figs.

  20. Technetium Immobilization Forms Literature Survey

    SciTech Connect

    Westsik, Joseph H.; Cantrell, Kirk J.; Serne, R. Jeffrey; Qafoku, Nikolla

    2014-05-01

    Of the many radionuclides and contaminants in the tank wastes stored at the Hanford site, technetium-99 (99Tc) is one of the most challenging to effectively immobilize in a waste form for ultimate disposal. Within the Hanford Tank Waste Treatment and Immobilization Plant (WTP), the Tc will partition between both the high-level waste (HLW) and low-activity waste (LAW) fractions of the tank waste. The HLW fraction will be converted to a glass waste form in the HLW vitrification facility and the LAW fraction will be converted to another glass waste form in the LAW vitrification facility. In both vitrification facilities, the Tc is incorporated into the glass waste form but a significant fraction of the Tc volatilizes at the high glass-melting temperatures and is captured in the off-gas treatment systems at both facilities. The aqueous off-gas condensate solution containing the volatilized Tc is recycled and is added to the LAW glass melter feed. This recycle process is effective in increasing the loading of Tc in the LAW glass but it also disproportionally increases the sulfur and halides in the LAW melter feed which increases both the amount of LAW glass and either the duration of the LAW vitrification mission or the required supplemental LAW treatment capacity.

  1. How Public Opinion is Formed

    ERIC Educational Resources Information Center

    Block, Edward M.

    1977-01-01

    Investigates the evolution of the definition of public relations by examining cultural and personal determinants of public opinion. Outlines functions of communicators and opinionmakers in forming and influencing public opinion. Available from: Public Relations Review, Ray Hiebert, Dean, College of Journalism, University of Maryland, College Park,…

  2. Acceptance of Others (Number Form).

    ERIC Educational Resources Information Center

    Masters, James R.; Laverty, Grace E.

    As part of the instrumentation to assess the effectiveness of the Schools Without Failure (SWF) program in 10 elementary schools in the New Castle, Pa. School District, the Acceptance of Others (Number Form) was prepared to determine pupil's attitudes toward classmates. Given a list of all class members, pupils are asked to circle a number from 1…

  3. Collaborating with Forms in Nature

    ERIC Educational Resources Information Center

    Castro, Aileen Pugliese

    2011-01-01

    Taking students outside is a great opportunity to make art. In this article, the author describes how her students collaborated with forms in nature to create their own visual structures to communicate ideas. This lesson can be done on the beach, in a sand box on the school playground, in grassy areas, or nature can even be brought into the…

  4. Process for forming sulfuric acid

    DOEpatents

    Lu, Wen-Tong P.

    1981-01-01

    An improved electrode is disclosed for the anode in a sulfur cycle hydrogen generation process where sulfur dioxie is oxidized to form sulfuric acid at the anode. The active compound in the electrode is palladium, palladium oxide, an alloy of palladium, or a mixture thereof. The active compound may be deposited on a porous, stable, conductive substrate.

  5. English Pidgins: Form and Function.

    ERIC Educational Resources Information Center

    Mufwene, Salikoko S.

    1988-01-01

    Highlights similarities and variation in both form and function of English pidgins the world over. It is argued that English pidgins are related more by socio-historical conditions and directions of development than by details of their formal structure. Reference list includes 68 citations. (Author/DJD)

  6. PIC Reading Readiness Test Form.

    ERIC Educational Resources Information Center

    Short, N. J.

    This rating form concerns the measurement of basic skills in connection with assessing reading readiness. Motor skills, ability to adjust to learning situations, familiarity with the alphabet, and general knowledge are assessed. See TM 001 111 for details of the Regional PIC program in which it is used. (DLG)

  7. Spin-forming Project Report

    SciTech Connect

    Switzner, Nathan; Henry, Dick

    2009-03-20

    In a second development order, spin-forming equipment was again evaluated using the test shape, a hemispherical shell. In this second development order, pure vanadium and alloy titanium (Ti-6Al-4V) were spin-formed, as well as additional copper and 21-6-9 stainless. In the first development order the following materials had been spin-formed: copper (alloy C11000 ETP), 6061 aluminum, 304L stainless steel, 21-6-9 stainless steel, and tantalum-2.5% tungsten. Significant challenges included properly adjusting the rotations-per-minute (RPM), cracking at un-beveled edges and laser marks, redressing of notches, surface cracking, non-uniform temperature evolution in the titanium, and cracking of the tailstock. Lessons learned were that 300 RPM worked better than 600 RPM for most materials (at the feed rate of 800 mm/min); beveling the edges to lower the stress reduces edge cracking; notches, laser marks, or edge defects in the preform doom the process to cracking and failure; coolant is required for vanadium spin-forming; increasing the number of passes to nine or more eliminates surface cracking for vanadium; titanium develops a hot zone in front of the rollers; and the tailstock should be redesigned to eliminate the cylindrical stress concentrator in the center.

  8. Assessing "Combining Forms" in Science.

    ERIC Educational Resources Information Center

    Floriani, Bernard P.; Cairns, Jack C.

    1982-01-01

    Since there appears to be a direct relationship between reading comprehension and vocabulary, an inventory is offered which assesses students' knowledge of the meaning of "combining forms" (automobile, aero-dynamics, etc.) and not words themselves. The inventory can serve as a model to develop additional inventories for Latin/Greek roots.…

  9. Thermolysin: a peptide forming enzyme.

    PubMed

    Reddy, A V

    1991-02-01

    Thermolysin, a thermostable endopeptidase, is recognised as a potential peptide bond forming enzyme. The importance of structural properties and its stereospecific nature towards peptide bond formation is described. Thermolysin's use in the keystep of the preparation of an artificial sweetener 'aspartame' is highlighted.

  10. Polynomial Algebra in Form 4

    NASA Astrophysics Data System (ADS)

    Kuipers, J.

    2012-06-01

    New features of the symbolic algebra package Form 4 are discussed. Most importantly, these features include polynomial factorization and polynomial gcd computation. Examples of their use are shown. One of them is an exact version of Mincer which gives answers in terms of rational polynomials and 5 master integrals.

  11. Anatomical form defines color: function, form, and aesthetics.

    PubMed

    Terry, Douglas A; Geller, Willi; Tric, Olivier; Anderson, Mark J; Tourville, Monte; Kobashigawa, Alvin

    2002-01-01

    Contemporary composite materials enable the reproduction of polychromatic effects within a tooth. A broader definition of color that incorporates the anatomy and optical properties of a tooth must be developed so the dental professional can better understand the infinite possibilities of color that exist within the tooth and restoration. This article describes a direct protocol for the development of natural restorations in the posterior dentition through the integration of function, form, and color.

  12. Electro-Hydraulic Forming of Sheet Metals: Free-forming vs. Conical-die Forming

    SciTech Connect

    Rohatgi, Aashish; Stephens, Elizabeth V.; Davies, Richard W.; Smith, Mark T.; Soulami, Ayoub; Ahzi, Said

    2012-05-01

    This work builds upon our recent advances in quantifying high-rate deformation behavior of sheet metals, during electro-hydraulic forming (EHF), using high-speed imaging and digital image correlation techniques. Following recent publication of an earlier manuscript, resulting from this project, in the Journal of Materials Processing Technology, this manuscript further details our results and compares forming behavior when the process is carried out inside an open-die or a conical die. It is anticipated that quantitative information of the sheet deformation history, made possible by the experimental technique developed in this work, will improve our understanding on the roles of strain-rate and sheet-die interactions in enhancing the sheet metal formability during high-rate forming. This knowledge will be beneficial to the automotive industry and enable them to fabricate light-weight sheet parts out of Al and advanced high strength steels.

  13. Following passage through the oviduct, the coelomic envelope of Discoglossus pictus (amphibia) acquires fertilizability upon reorganization, conversion of gp 42 to gp 40, extensive glycosylation, and formation of a specific layer.

    PubMed

    Caputo, M; Infante, V; Talevi, R; Vaccaro, M C; Carotenuto, R; Campanella, C

    2001-03-01

    This paper describes the morphological and biochemical changes in Discoglossus pictus coelomic oocyte envelope (CE) following passage through the oviduct. As in other anurans, in this species, the transformation of the envelope into vitelline envelope (VE) leads to the acquisition of fertilizability and involves the cleavage of a glycoprotein. In addition, several features, typical of Discoglossus pictus, were observed. A new layer, VE-D, forms underneath the VE region facing the site of sperm entrance, the dimple. In the VE, arrowhead-like bundles of fibrils are perpendicularly oriented toward the dimple. Ultrastructural observations and staining with UEA-I suggested that VE-D might have a role in supporting sperm penetration into the dimple by orienting VE bundles and exposing sugar residues such as fucose. In 'in vitro' tests, VE binding of sperm occurs only if sperm are exposed to A23187, in agreement with previous data (Campanella et al., 1997: Mol Reprod Dev 47:323-333). Sperm binding occurs all over the VE. Accordingly, extracts of the VE covering the animal or the vegetal hemisphere have the same affinity to lectins (DBA, DSA, GNA, MAA, SBA, SNA, UEA-I, WGA). The CE contains six main glycoproteins. Peptide mapping indicated that during CE transformation into VE, gp 42 shifts to an apparent M(r) of 40 and gp 61 is converted to an apparent M(r) of 63 kDa. Lectin blot analyses showed extensive changes in cross-reactivity of most glycoproteins during the CE-->VE transition. The fact that DBA and UEA-I stain gp 63 rather than gp 61 and that this change is related only to gp 63, suggested that O-glycosylation and terminal fucose might be acquired by gp 63 in preparation of fertilization. Gp 63 has recently been cloned (Vaccaro et al., submitted) and shown to exhibit high homology to Xenopus gp 69/64, a VE sperm ligand (Tian et al., 1997a: J. Cell Biol. 136: 1099-1108; Tian et al., 1997b: Dev Biol 187:143-153), and to ZP2 of mammals.

  14. 76 FR 61725 - Agency Information Collection Activities: Case Submission Form, Case Assistance Form; (Form DHS...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-05

    ... Federal Register on July 18, 2011 at 76 FR 42129, for a 60-day public comment period. No comments were... other forms of information technology, e.g., permitting electronic submissions of responses. FOR FURTHER... to bring to the attention of the CIS Ombudsman (``trend''). For case problems, the CIS Ombudsman...

  15. Method of forming a joint

    DOEpatents

    Butt, Darryl Paul; Cutler, Raymond Ashton; Rynders, Steven Walton; Carolan, Michael Francis

    2006-08-22

    A method of joining at least two sintered bodies to form a composite structure, including providing a first multicomponent metallic oxide having a perovskitic or fluorite crystal structure; providing a second sintered body including a second multicomponent metallic oxide having a crystal structure of the same type as the first; and providing at an interface a joint material containing at least one metal oxide containing at least one metal identically contained in at least one of the first and second multicomponent metallic oxides. The joint material is free of cations of Si, Ge, Sn, Pb, P and Te and has a melting point below the sintering temperatures of both sintered bodies. The joint material is heated to a temperature above the melting point of the metal oxide(s) and below the sintering temperatures of the sintered bodies to form the joint. Structures containing such joints are also disclosed.

  16. Free-form illumination optics

    NASA Astrophysics Data System (ADS)

    Mohedano, Rubén; Chaves, Julio; Hernández, Maikel

    2016-04-01

    In many illumination problems, the beam pattern needed and/or some geometrical constraints lead to very asymmetric design conditions. These asymmetries have been solved in the past by means of arrangements of rotationally symmetric or linear lamps aimed in different directions whose patterns overlap to provide the asymmetric prescriptions or by splitting one single lamp into several sections, each one providing a part of the pattern. The development of new design methods yielding smooth continuous free-form optical surfaces to solve these challenging design problems, combined with the proper CAD modeling tools plus the development of multiple axes diamond turn machines, give birth to a new generation of optics. These are able to offer the performance and other advanced features, such as efficiency, compactness, or aesthetical advantages, and can be manufactured at low cost by injection molding. This paper presents two examples of devices with free-form optical surfaces, a camera flash, and a car headlamp.

  17. Cyclodextrin Inclusion Polymers Forming Hydrogels

    NASA Astrophysics Data System (ADS)

    Li, Jun

    This chapter reviews the advances in the developments of supramolecular hydrogels based on the polypseudorotaxanes and polyrotaxanes formed by inclusion complexes of cyclodextrins threading onto polymer chains. Both physical and chemical supramolecular hydrogels of many different types are discussed with respect to their preparation, structure, property, and gelation mechanism. A large number of physical supramolecular hydrogels were formed induced by self-assembly of densely packed cyclodextrin rings threaded on polymer or copolymer chains acting as physical crosslinking points. The thermo-reversible and thixotropic properties of these physical supramolecular hydrogels have inspired their applications as injectable drug delivery systems. Chemical supramolecular hydrogels synthesized from polypseudorotaxanes and polyrotaxanes were based on the chemical crosslinking of either the cyclodextrin molecules or the included polymer chains. The chemical supramolecular hydrogels were often made biodegradable through incorporation of hydrolyzable threading polymers, end caps, or crosslinkers, for their potential applications as biomaterials.

  18. Sphere forming method and apparatus

    NASA Technical Reports Server (NTRS)

    Youngberg, C. L.; Miller, C. G.; Stephens, J. B.; Finnerty, A. A. (Inventor)

    1983-01-01

    A system is provided for forming small accurately spherical objects. Preformed largely spherical objects are supported at the opening of a conduit on the update of hot gas emitted from the opening, so the object is in a molten state. The conduit is suddenly jerked away at a downward incline, to allow the molten object to drop in free fall, so that surface tension forms a precise sphere. The conduit portion that has the opening, lies in a moderate vacuum chamber, and the falling sphere passes through the chamber and through a briefly opened valve into a tall drop tower that contains a lower pressure, to allow the sphere to cool without deformation caused by falling through air.

  19. Unsplit bipolar pulse forming line

    DOEpatents

    Rhodes, Mark A.

    2011-05-24

    A bipolar pulse forming transmission line module and system for linear induction accelerators having first, second, third, and fourth planar conductors which form a sequentially arranged interleaved stack having opposing first and second ends, with dielectric layers between the conductors. The first and second planar conductors are connected to each other at the first end, and the first and fourth planar conductors are connected to each other at the second end via a shorting plate. The third planar conductor is electrically connectable to a high voltage source, and an internal switch functions to short at the first end a high voltage from the third planar conductor to the fourth planar conductor to produce a bipolar pulse at the acceleration axis with a zero net time integral. Improved access to the switch is enabled by an aperture through the shorting plate and the proximity of the aperture to the switch.

  20. Method for forming hermetic seals

    NASA Technical Reports Server (NTRS)

    Gallagher, Brian D.

    1987-01-01

    The firmly adherent film of bondable metal, such as silver, is applied to the surface of glass or other substrate by decomposing a layer of solution of a thermally decomposable metallo-organic deposition (MOD) compound such as silver neodecanoate in xylene. The MOD compound thermally decomposes into metal and gaseous by-products. Sealing is accomplished by depositing a layer of bonding metal, such as solder or a brazing alloy, on the metal film and then forming an assembly with another high melting point metal surface such as a layer of Kovar. When the assembly is heated above the temperature of the solder, the solder flows, wets the adjacent surfaces and forms a hermetic seal between the metal film and metal surface when the assembly cools.

  1. Method of forming calthrate ice

    DOEpatents

    Hino, T.; Gorski, A.J.

    1985-09-30

    A method of forming clathrate ice in a supercooled water-based liquid contained in a vessel is disclosed. Initially, an oscillator device is located in the liquid in the vessel. The oscillator device is then oscillated ultransonically so that small crystals are formed in the liquid. Thes small crystals serve as seed crystals for ice formation in the liquid and thereby prevent supercooling of the liquid. Preferably, the oscillating device is controlled by a thermostat which initiates operation of the oscillator device when the temperature of the liquid is lowered to the freezing point. Thereafter, the operation of the oscillator device is terminated when ice is sensed in the liquid by an ice sensor.

  2. Method of forming clathrate ice

    DOEpatents

    Hino, Toshiyuki; Gorski, Anthony J.

    1987-01-01

    A method of forming clathrate ice in a supercooled water-based liquid contained in a vessel is disclosed. Initially, an oscillator device is located in the liquid in the vessel. The oscillator device is then oscillated ultrasonically so that small crystals are formed in the liquid. These small crystals serve as seed crystals for ice formation in the liquid and thereby prevent supercooling of the liquid. Preferably, the oscillating device is controlled by a thermostat which initiates operation of the oscillator device when the temperature of the liquid is lowered to the freezing point. Thereafter, the operation of the oscillator device is terminated when ice is sensed in the liquid by an ice sensor.

  3. Rheology of hydrate forming emulsions.

    PubMed

    Peixinho, Jorge; Karanjkar, Prasad U; Lee, Jae W; Morris, Jeffrey F

    2010-07-20

    Results are reported on an experimental study of the rheology of hydrate-forming water-in-oil emulsions. Density-matched concentrated emulsions were quenched by reducing the temperature and an irreversible transition was observed where the viscosity increased dramatically. The hydrate-forming emulsions have characteristic times for abrupt viscosity change dependent only on the temperature, reflecting the importance of the effect of subcooling. Mechanical transition of hydrate-free water-in-oil emulsions may require longer times and depends on the shear rate, occurring more rapidly at higher rates but with significant scatter which is characterized through a probabilistic analysis. This rate dependence together with dependence on subcooling reflects the importance of hydrodynamic forces to bring drops or particles together.

  4. Studying how protein crystals form

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Watching molecules of the iron-storing protein apoferritin come together to form a nucleus reveals some interesting behavior. In this series of images, researchers observed clusters of four molecules at the corners of a diamond shape (top). As more molecules attach to the cluster, they arrange themselves into rods (second from top), and a raft-like configuration of molecules forms the critical nucleus (third from top), suggesting that crystal growth is much slower than it could be were the molecules arranged in a more compact formation. In the final image, a crystallite consisting of three layers containing approximately 60 to 70 molecules each is formed. Atomic force microscopy made visualizing the process of nucleation possible for the first time. The principal investigator is Peter Vekilov, of the University of Alabama in Huntsville. Vekilov's team at UAH studies protein solutions as they change phases from liquids to crystalline solids. They want to know if the molecules in the solution interact with one another, and if so, how, from the perspectives of thermodynamics and kinetics. They want to understand which forces -- electrical, electrostatic, hydrodynamic, or other kinds of forces -- are responsible for the interactions. They also study nucleation, the begirning stage of crystallization. This process is important to understand because it sets the stage for crystal growth in all kinds of solutions and liquid melts that are important in such diverse fields as agriculture, medicine, and the fabrication of metal components. Nucleation can determine the rate of crystal growth, the number of crystals that will be formed, and the quality and size of the crystals.

  5. How do atmospheric rivers form?

    NASA Astrophysics Data System (ADS)

    Dacre, Helen

    2015-04-01

    The term atmospheric river is used to describe corridors of strong water vapor transport in the troposphere. Filaments of enhanced water vapor, commonly observed in satellite imagery extending from the subtropics to the extratropics, are routinely used as a proxy for identifying these regions of strong water vapor transport. The precipitation associated with these filaments of enhanced water vapor can lead to high impact flooding events. However, there remains some debate as to how these filaments form. In this study we analyse the transport of water vapor within a climatology of wintertime North Atlantic extratropical cyclones. Results show that atmospheric rivers are formed by the cold front which sweeps up water vapor in the warm sector as it catches up with the warm front. This causes a narrow band of high water vapor content to form ahead of the cold front at the base of the warm conveyor belt airflow. Thus, water vapor in the cyclone's warm sector, and not long-distance transport of water vapor from the subtropics, is responsible for the generation of filaments of high water vapor content. A continuous cycle of evaporation and moisture convergence within the cyclone replenishes water vapor lost via precipitation. Thus, rather than representing a direct and continuous feed of moist air from the subtropics into the centre of a cyclone (as suggested by the term atmospheric river), these filaments are, in-fact, the result of water vapor exported from the cyclone and thus they represent the footprints left behind as cyclones travel polewards from subtropics.

  6. Coated particle waste form development

    SciTech Connect

    Oma, K.H.; Buckwalter, C.Q.; Chick, L.A.

    1981-12-01

    Coated particle waste forms have been developed as part of the multibarrier concept at Pacific Northwest Laboratory under the Alternative Waste Forms Program for the Department of Energy. Primary efforts were to coat simulated nuclear waste glass marbles and ceramic pellets with low-temperature pyrolytic carbon (LT-PyC) coatings via the process of chemical vapor deposition (CVD). Fluidized bed (FB) coaters, screw agitated coaters (SAC), and rotating tube coaters were used. Coating temperatures were reduced by using catalysts and plasma activation. In general, the LT-PyC coatings did not provide the expected high leach resistance as previously measured for carbon alone. The coatings were friable and often spalled off the substrate. A totally different concept, thermal spray coating, was investigated at PNL as an alternative to CVD coating. Flame spray, wire gun, and plasma gun systems were evaluated using glass, ceramic, and metallic coating materials. Metal plasma spray coatings (Al, Sn, Zn, Pb) provided a two to three orders-of-magnitude increase in chemical durability. Because the aluminum coatings were porous, the superior leach resistance must be due to either a chemical interaction or to a pH buffer effect. Because they are complex, coated waste form processes rank low in process feasibility. Of all the possible coated particle processes, plasma sprayed marbles have the best rating. Carbon coating of pellets by CVD ranked ninth when compared with ten other processes. The plasma-spray-coated marble process ranked sixth out of eleven processes.

  7. Rib forming tool for tubing

    DOEpatents

    Rowley, James P.; Lewandowski, Edward F.; Groh, Edward F.

    1976-01-01

    Three cylindrical rollers are rotatably mounted equidistant from the center of a hollow tool head on radii spaced 120.degree. apart. Each roller has a thin flange; the three flanges lie in a single plane to form an internal circumferential rib in a rotating tubular workpiece. The tool head has two complementary parts with two rollers in one part of the head and one roller in the other part; the two parts are joined by a hinge. A second hinge, located so the rollers are between the two hinges, connects one of the parts to a tool bar mounted in a lathe tool holder. The axes of rotation of both hinges and all three rollers are parallel. A hole exposing equal portions of the three roller flanges is located in the center of the tool head. The two hinges permit the tool head to be opened and rotated slightly downward, taking the roller flanges out of the path of the workpiece which is supported on both ends and rotated by the lathe. The parts of the tool head are then closed on the workpiece so that the flanges are applied to the workpiece and form the rib. The tool is then relocated for forming of the next rib.

  8. Dynamic Forms. Part 1: Functions

    NASA Technical Reports Server (NTRS)

    Meyer, George; Smith, G. Allan

    1993-01-01

    The formalism of dynamic forms is developed as a means for organizing and systematizing the design control systems. The formalism allows the designer to easily compute derivatives to various orders of large composite functions that occur in flight-control design. Such functions involve many function-of-a-function calls that may be nested to many levels. The component functions may be multiaxis, nonlinear, and they may include rotation transformations. A dynamic form is defined as a variable together with its time derivatives up to some fixed but arbitrary order. The variable may be a scalar, a vector, a matrix, a direction cosine matrix, Euler angles, or Euler parameters. Algorithms for standard elementary functions and operations of scalar dynamic forms are developed first. Then vector and matrix operations and transformations between parameterization of rotations are developed in the next level in the hierarchy. Commonly occurring algorithms in control-system design, including inversion of pure feedback systems, are developed in the third level. A large-angle, three-axis attitude servo and other examples are included to illustrate the effectiveness of the developed formalism. All algorithms were implemented in FORTRAN code. Practical experience shows that the proposed formalism may significantly improve the productivity of the design and coding process.

  9. 48 CFR 253.303 - Agency forms.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 48 Federal Acquisition Regulations System 3 2013-10-01 2013-10-01 false Agency forms. 253.303 Section 253.303 Federal Acquisition Regulations System DEFENSE ACQUISITION REGULATIONS SYSTEM, DEPARTMENT OF DEFENSE CLAUSES AND FORMS FORMS Illustration of Forms 253.303 Agency forms. DoD forms...

  10. 48 CFR 253.303 - Agency forms.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 3 2014-10-01 2014-10-01 false Agency forms. 253.303 Section 253.303 Federal Acquisition Regulations System DEFENSE ACQUISITION REGULATIONS SYSTEM, DEPARTMENT OF DEFENSE CLAUSES AND FORMS FORMS Illustration of Forms 253.303 Agency forms. DoD forms...

  11. 48 CFR 253.303 - Agency forms.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 3 2012-10-01 2012-10-01 false Agency forms. 253.303 Section 253.303 Federal Acquisition Regulations System DEFENSE ACQUISITION REGULATIONS SYSTEM, DEPARTMENT OF DEFENSE CLAUSES AND FORMS FORMS Illustration of Forms 253.303 Agency forms. DoD forms...

  12. 48 CFR 253.303 - Agency forms.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 3 2011-10-01 2011-10-01 false Agency forms. 253.303 Section 253.303 Federal Acquisition Regulations System DEFENSE ACQUISITION REGULATIONS SYSTEM, DEPARTMENT OF DEFENSE CLAUSES AND FORMS FORMS Illustration of Forms 253.303 Agency forms. DoD forms...

  13. Effect of Diaminopropionic acid (Dap) on the Biophysical Properties of a Modified Synthetic Channel-Forming Peptide

    PubMed Central

    Bukovnik, Urska; Sala-Rabanal, Monica; Francis, Simonne; Frazier, Shawnalea J.; Schultz, Bruce D.; Nichols, Colin G.; Tomich, John M.

    2013-01-01

    Channel replacement therapy, based on synthetic channel-forming peptides (CFPs) with the ability to supersede defective endogenous ion channels, is a novel treatment modality that may augment existing interventions against multiple diseases. Previously, we derived CFPs from the second transmembrane segment of the α-subunit of the glycine receptor, M2GlyR, which forms chloride-selective channels in its native form. The best candidate, NK4-M2GlyR T19R, S22W (p22-T19R, S22W), was water-soluble, incorporated into cell membranes and was non-immunogenic, but lacked the structural properties for high conductance and anion selectivity when assembled into a pore. Further studies suggested that the threonine residues at positions 13, 17 and 20 line the pore of assembled p22-T19R, S22W, and here we used 2, 3-diaminopropionic acid (Dap) substitutions to introduce positive charges to the pore-lining interface of the predicted p22-T19R, S22W channel. Dap-substituted p22-T19R, S22W peptides retained the α-helical secondary structure characteristic of their parent peptide, and induced short-circuit transepithelial currents when exposed to the apical membrane of Madin-Darby canine kidney (MDCK) cells; the sequences containing multiple Dap-substituted residues induced larger currents than the peptides with single or no Dap-substitutions. To gain further insights into the effects of Dap residues on the properties of the putative pore, we performed two-electrode voltage clamp electrophysiology on Xenopus oocytes exposed to p22-T19R, S22W or its Dap-modified analogs. We observed that Dap-substituted peptides also induced significantly larger voltage-dependent currents than the parent compound, but there was no apparent change in reversal potential upon replacement of external Na+, Cl− or K+, indicating that these currents remained non-selective. These results suggest that the introduction of positively charged side chains in predicted pore-lining residues does not improve anion

  14. [Adult form of Pompe disease].

    PubMed

    Ziółkowska-Graca, Bozena; Kania, Aleksander; Zwolińska, Grazyna; Nizankowska-Mogilnicka, Ewa

    2008-01-01

    Pompe disease (glycogen-storage disease type II) is an autosomal recessive disorder caused by a deficiency of lysosomal acid alpha-glucosidase (GAA), leading to the accumulation of glycogen in the lysosomes primarily in muscle cells. In the adult form of the disease, proximal muscle weakness is noted and muscle volume is decreased. The infantile form is usually fatal. In the adult form of the disease the prognosis is relatively good. Muscle weakness may, however, interfere with normal daily activities, and respiratory insufficiency may be associated with obstructive sleep apnea. Death usually results from respiratory failure. Effective specific treatment is not available. Enzyme replacement therapy with recombinant human GAA (rh-GAA) still remains a research area. We report the case of a 24-year-old student admitted to the Department of Pulmonary Diseases because of severe respiratory insufficiency. Clinical symptoms such as dyspnea, muscular weakness and increased daytime sleepiness had been progressing for 2 years. Clinical examination and increased blood levels of CK suggested muscle pathology. Histopathological analysis of muscle biopsy, performed under electron microscope, confirmed the presence of vacuoles containing glycogen. Specific enzymatic activity of alpha-glucosidase was analyzed confirming Pompe disease. The only effective method to treat respiratory insufficiency was bi-level positive pressure ventilation. Respiratory rehabilitation was instituted and is still continued by the patient at home. A high-protein, low-sugar diet was proposed for the patient. Because of poliglobulia low molecular weight heparin was prescribed. The patient is eligible for experimental replacement therapy with rh-GAA. PMID:19003770

  15. Weak Energy: Form and Function

    NASA Astrophysics Data System (ADS)

    Parks, Allen D.

    The equation of motion for a time-dependent weak value of a quantum mechanical observable contains a complex valued energy factor—the weak energy of evolution. This quantity is defined by the dynamics of the pre-selected and post-selected states which specify the observable's weak value. It is shown that this energy: (i) is manifested as dynamical and geometric phases that govern the evolution of the weak value during the measurement process; (ii) satisfies the Euler-Lagrange equations when expressed in terms of Pancharatnam (P) phase and Fubini-Study (FS) metric distance; (iii) provides for a PFS stationary action principle for quantum state evolution; (iv) time translates correlation amplitudes; (v) generalizes the temporal persistence of state normalization; and (vi) obeys a time-energy uncertainty relation. A similar complex valued quantity—the pointed weak energy of an evolving quantum state—is also defined and several of its properties in PFS coordinates are discussed. It is shown that the imaginary part of the pointed weak energy governs the state's survival probability and its real part is—to within a sign—the Mukunda-Simon geometric phase for arbitrary evolutions or the Aharonov-Anandan (AA) geometric phase for cyclic evolutions. Pointed weak energy gauge transformations and the PFS 1-form are defined and discussed and the relationship between the PFS 1-form and the AA connection 1-form is established. [Editors note: for a video of the talk given by Prof. Parks at the Aharonov-80 conference in 2012 at Chapman University, see http://quantum.chapman.edu/talk-25.

  16. CERAMIC WASTE FORM DATA PACKAGE

    SciTech Connect

    Amoroso, J.; Marra, J.

    2014-06-13

    The purpose of this data package is to provide information about simulated crystalline waste forms that can be used to select an appropriate composition for a Cold Crucible Induction Melter (CCIM) proof of principle demonstration. Melt processing, viscosity, electrical conductivity, and thermal analysis information was collected to assess the ability of two potential candidate ceramic compositions to be processed in the Idaho National Laboratory (INL) CCIM and to guide processing parameters for the CCIM operation. Given uncertainties in the CCIM capabilities to reach certain temperatures throughout the system, one waste form designated 'Fe-MP' was designed towards enabling processing and another, designated 'CAF-5%TM-MP' was designed towards optimized microstructure. Melt processing studies confirmed both compositions could be poured from a crucible at 1600{degrees}C although the CAF-5%TM-MP composition froze before pouring was complete due to rapid crystallization (upon cooling). X-ray diffraction measurements confirmed the crystalline nature and phase assemblages of the compositions. The kinetics of melting and crystallization appeared to vary significantly between the compositions. Impedance spectroscopy results indicated the electrical conductivity is acceptable with respect to processing in the CCIM. The success of processing either ceramic composition will depend on the thermal profiles throughout the CCIM. In particular, the working temperature of the pour spout relative to the bulk melter which can approach 1700{degrees}C. The Fe-MP composition is recommended to demonstrate proof of principle for crystalline simulated waste forms considering the current configuration of INL's CCIM. If proposed modifications to the CCIM can maintain a nominal temperature of 1600{degrees}C throughout the melter, drain, and pour spout, then the CAF-5%TM-MP composition should be considered for a proof of principle demonstration.

  17. FORMING PROTECTIVE FILMS ON METAL

    DOEpatents

    Gurinsky, D.H.; Kammerer, O.F.; Sadofsky, J.; Weeks, J.R.

    1958-12-16

    Methods are described of inhibiting the corrosion of ferrous metal by contact with heavy liquid metals such as bismuth and gallium at temperatures above 500 icient laborato C generally by bringing nltrogen and either the metal zirconium, hafnium, or titanium into reactlve contact with the ferrous metal to form a thin adherent layer of the nitride of the metal and thereafter maintaining a fractional percentage of the metal absorbed in the heavy liquid metal in contact with the ferrous metal container. The general purpose for uslng such high boiling liquid metals in ferrous contalners would be as heat transfer agents in liquid-metal-fueled nuclear reactors.

  18. Export of newly formed LSW

    NASA Astrophysics Data System (ADS)

    Müller, Katharina; Klein, Birgit; Karstensen, Johannes; Fischer, Jürgen; Baumann, Till; Kanzow, Torsten

    2015-04-01

    The Atlantic meridional overturning circulation represents the strongest mechanism for oceanic northward heat transport. This is accomplished by moving warm water northward in the upper ocean compensated by a deep return flow of cold and dense North Atlantic Deep Water (NADW). Labrador Sea Water (LSW) constitutes the shallowest component of NADW. Since LSW is also supposed to be the most sensitive NADW component to climate change it is of particular interest. LSW is formed by deep convection not only in the centre of the Labrador Sea but also near its western boundary. Recent studies have suggested that LSW formed in the boundary region enters its export route from the Labrador Sea, the Deep Western Boundary Current, faster than LSW originating from the central Labrador Sea. In this study the spatial and temporal evolution of the export of newly formed LSW is investigated. For this purpose hydrographic mooring data from an array located at the western bounndary at 53°N starting in the late 1990s until 2014 and data from the Argo float network is used. The averaged seasonal salinity cycle at the array, particularly at the moorings further onshore, shows a pronounced freshwater signal in May indicating the arrival of newly formed LSW in the boundary current. In order to learn more about its preceding pathway and the corresponding export timescale the mooring data is complemented by data from Argo floats. Besides the annual cycles of LSW formation and export, their interannual variations are important aspects affecting the large-scale circulation. For instance, in years of relatively strong convection, as in 2008 and 2012, LSW is observed to pass the boundary current array at 53°N earlier, i.e. in February and March, respectively, than in years with weak convection, as in 2007 or 2010. Besides seasonal variations in the boundary current, a possible explanation for the earlier freshwater signal in years of enhanced convection might be a shift in convection sites

  19. 76 FR 21946 - Proposed Collection; Comment Request for Form 990-BL; Schedule A (Form 990-BL), Form 6069

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-04-19

    ... Internal Revenue Service Proposed Collection; Comment Request for Form 990-BL; Schedule A (Form 990-BL), Form 6069 AGENCY: Internal Revenue Service (IRS), Treasury. ACTION: Notice and request for comments... Form 990-BL, Schedule A (Form 990-BL), Information and Initial Excise Tax Return for Black Lung...

  20. Gravity, light and plant form.

    PubMed

    Hangarter, R P

    1997-06-01

    Plants have evolved highly sensitive and selective mechanisms that detect and respond to various aspects of their environment. As a plant develops, it integrates the environmental information perceived by all of its sensory systems and adapts its growth to the prevailing environmental conditions. Light is of critical importance because plants depend on it for energy and, thus, survival. The quantity, quality and direction of light are perceived by several different photosensory systems that together regulate nearly all stages of plant development, presumably in order to maintain photosynthetic efficiency. Gravity provides an almost constant stimulus that is the source of critical spatial information about its surroundings and provides important cues for orientating plant growth. Gravity plays a particularly important role during the early stages of seedling growth by stimulating a negative gravitropic response in the primary shoot that orientates it towards the source of light, and a positive gravitropic response in the primary root that causes it to grow down into the soil, providing support and nutrient acquisition. Gravity also influences plant form during later stages of development through its effect on lateral organs and supporting structures. Thus, the final form of a plant depends on the cumulative effects of light, gravity and other environmental sensory inputs on endogenous developmental programs. This article is focused on developmental interactions modulated by light and gravity.

  1. [Kinin forming system and ovulation].

    PubMed

    Seki, M

    1984-06-01

    The aim of the study is to clarify the role of the kinin forming system on ovulation. The results were as follows, Plasma prekallikrein of superovulated prepubertal rats was decreased to 50-60% of the normal level after PMS injection and 80-90% of the normal level after hCG injection. The lowest level was 33.8% 39 hours after PMS injection. Aprotinin suppressed the superovulation of prepubertal rats at doses of 16.7 X 10(4) KIE and 37.8 X 10(4) KIE (p less than 0.01). These results showed that the kinin production system has an effect on ovulation. As the sex steroid hormone, estradil benzoate, progesterone and testosterone propinate were used in oophorectomized mice. They had no effect on the plasma prekallikrein level. The plasma prekallikrein level during the estrus cycle of mature female mice was 85.5% of the control level in preestrus, 80.3% in estrus, 83.7% in metestrus and 89.8% in diestrus. The mean was 83.9%, which was significantly lower than that for oophorectomized mice (94.1%). It is proved that plasma prekallikrein was consumed and the kinin forming system was accelerated in the ovary with ovulation. PMID:6205107

  2. Gravity, light and plant form.

    PubMed

    Hangarter, R P

    1997-06-01

    Plants have evolved highly sensitive and selective mechanisms that detect and respond to various aspects of their environment. As a plant develops, it integrates the environmental information perceived by all of its sensory systems and adapts its growth to the prevailing environmental conditions. Light is of critical importance because plants depend on it for energy and, thus, survival. The quantity, quality and direction of light are perceived by several different photosensory systems that together regulate nearly all stages of plant development, presumably in order to maintain photosynthetic efficiency. Gravity provides an almost constant stimulus that is the source of critical spatial information about its surroundings and provides important cues for orientating plant growth. Gravity plays a particularly important role during the early stages of seedling growth by stimulating a negative gravitropic response in the primary shoot that orientates it towards the source of light, and a positive gravitropic response in the primary root that causes it to grow down into the soil, providing support and nutrient acquisition. Gravity also influences plant form during later stages of development through its effect on lateral organs and supporting structures. Thus, the final form of a plant depends on the cumulative effects of light, gravity and other environmental sensory inputs on endogenous developmental programs. This article is focused on developmental interactions modulated by light and gravity. PMID:11541207

  3. Gravity, light and plant form

    NASA Technical Reports Server (NTRS)

    Hangarter, R. P.

    1997-01-01

    Plants have evolved highly sensitive and selective mechanisms that detect and respond to various aspects of their environment. As a plant develops, it integrates the environmental information perceived by all of its sensory systems and adapts its growth to the prevailing environmental conditions. Light is of critical importance because plants depend on it for energy and, thus, survival. The quantity, quality and direction of light are perceived by several different photosensory systems that together regulate nearly all stages of plant development, presumably in order to maintain photosynthetic efficiency. Gravity provides an almost constant stimulus that is the source of critical spatial information about its surroundings and provides important cues for orientating plant growth. Gravity plays a particularly important role during the early stages of seedling growth by stimulating a negative gravitropic response in the primary shoot that orientates it towards the source of light, and a positive gravitropic response in the primary root that causes it to grow down into the soil, providing support and nutrient acquisition. Gravity also influences plant form during later stages of development through its effect on lateral organs and supporting structures. Thus, the final form of a plant depends on the cumulative effects of light, gravity and other environmental sensory inputs on endogenous developmental programs. This article is focused on developmental interactions modulated by light and gravity.

  4. Integrally formed radio frequency quadrupole

    DOEpatents

    Abbott, Steven R.

    1989-01-01

    An improved radio frequency quadrupole (10) is provided having an elongate housing (11) with an elongate central axis (12) and top, bottom and two side walls (13a-d) symmetrically disposed about the axis, and vanes (14a-d) formed integrally with the walls (13a-d), the vanes (14a-d) each having a cross-section at right angles to the central axis (12) which tapers inwardly toward the axis to form electrode tips (15a-d) spaced from each other by predetermined distances. Each of the four walls (13a-d), and the vanes (14a-d) integral therewith, is a separate structural element having a central lengthwise plane (16) passing through the tip of the vane, the walls (13a-d) having flat mounting surfaces (17, 18) at right angles to and parallel to the control plane (16), respectively, which are butted together to position the walls and vane tips relative to each other.

  5. Preventing Ice Before it Forms

    NASA Technical Reports Server (NTRS)

    2006-01-01

    In the late 1990s, a team of engineers at Ames Research Center invented an anti-icing fluid to keep ice from building up on airplane wings. Ice on wings can be a serious safety hazard, especially during takeoff, when a sheet of ice the thickness of a compact disc can reduce lift by 25 percent or more. The typical approach to clearing off the ice is to use a deicing solution once the ice has built up. The fluid created by the Ames team, though, when applied to a dry surface, prevents the ice from even forming a surface bond, which saves deicing time and money, while also preventing excessive use of chemical solvents. If, however, the solution is not applied before ice forms, it also serves as a traditional deicing formula. The formula contains propylene glycol, which has a very low freezing point, and a thickener, which helps the fluid adhere to the surface. Ice gathers on top of the formula, and then it can be wiped off with little effort. This thickening agent, a pseudo-plastic, sprays on as a liquid, like lemonade, gels like a lemon sherbet, turns back to a liquid when wiped, and then gels again into its sherbet consistency when left to solidify. The sherbet-gel stage is especially important when the formula is sprayed onto a vertical or steeped surface, as it clings better than a liquid would.

  6. Coated particle waste form development

    NASA Astrophysics Data System (ADS)

    Oma, K. H.; Buckwalter, C. Q.; Chick, L. A.

    1981-12-01

    Coated particle waste forms were developed as part of the multibarrier concept. Primary efforts were to coat simulated nuclear waste glass marbles and ceramic pellets with low temperature pyrolytic carbon (LT-PyC) coatings via the process of chemical vapor deposition (CVD). Fluidized bed coaters, screw agitated coaters, and rotating tube coaters were used. Coating temperatures were reduced by using catalysts and plasma activation. In general, the LT-PyC coatings did not provide the expected high leach resistance as previously measured for carbon alone. The coatings were friable and often spalled off the substrate. A totally different concept, thermal spray coating, was investigated as an alternative to CVD coating. Flame spray, wire gun, and plasma gun systems were evaluated using glass, ceramic, and metallic coating materials. Metal plasma spray coatings (Al, Sn, Zn, Pb) provided a two to three orders of magnitude increase in chemical durability.

  7. Frozen Film and FOSDIC Forms

    PubMed Central

    RUGGLES, STEVEN; SCHROEDER, MATTHEW; RIVERS, NATASHA; ALEXANDER, J. TRENT; GARDNER, TODD K.

    2012-01-01

    In this article, the authors describe a collaboration of the Minnesota Population Center (MPC), the U.S. Census Bureau, and the National Archives and Records Administration to restore the lost data from the 1960 Census. The data survived on refrigerated microfilm in a cave in Lenexa, Kansas. The MPC is now converting the data to usable form. Once the restored data are processed, the authors intend to develop three new data sources based on the 1960 census. These data will replace the most inadequate sample in the series of public-use census microdata spanning the years from 1850 to 2000, extend the chronological scope of the public census summary files, and provide a powerful new resource for the Census Bureau and its Research Data Centers. PMID:22544986

  8. Forming impressions from incongruent traits.

    PubMed

    Casselden, P A; Hampson, S E

    1990-08-01

    The factors that affect the ease with which impressions are formed from incongruent trait pairs are investigated. In Experiments 1 and 2, trait pairs that were both descriptively and evaluatively congruent, as well as ones that were only evaluatively congruent, were found to be more imaginable and to be perceived as more frequently co-occurring than incongruent trait pairs. In Experiment 3, response latency provided a converging measure of ease of imaginability. Experiment 4 examined written descriptions of targets described by these trait pairs, and found more attempts to integrate the congruent than the incongruent pairs. These findings are discussed in terms of the relation between laypersons' impressions of personality and formal personality assessment.

  9. Forming parts over small radii

    NASA Astrophysics Data System (ADS)

    Hazra, S. K.; Hughes, D. J.; Pereira, M. P.; Rolfe, B. F.

    2016-08-01

    Stamping simulations usually make the plane stress simplifying assumption. However, this becomes less valid when material draws around features with radius to sheet thickness ratios less than 20. Pereira, Yan & Rolfe (Wear, Vol.265, p.1687 (2008)) predicted that out-of-plane stress equivalent to material yield can occur because a line contact forms briefly at the start of the draw process. The high transient stress can cause high rates of tool wear and may cause the ‘die impact line’ cosmetic defect. In this work, we present residual strain results of a channel section that was drawn over a small radius. Using the neutron source at the Institut Laue-Langevin, in-plane and out-of-plane strains were measured in the channel part to show some support for the conclusions of Pereira et. al.

  10. Method for forming energetic nanopowders

    DOEpatents

    Lee, Kien-Yin; Asay, Blaine W.; Kennedy, James E.

    2013-10-15

    A method for the preparation of neat energetic powders, having nanometer dimensions, is described herein. For these neat powder, a solution of a chosen energetic material is prepared in an aprotic solvent and later combined with liquid hexane that is miscible with such solvent. The energetic material chosen is less soluble in the liquid hexane than in the aprotic solvent and the liquid hexane is cooled to a temperature that is below that of the solvent solution. In order to form a precipitate of said neat powders, the solvent solution is rapidly combined with the liquid hexane. When the resulting precipitate is collected, it may be dried and filtered to yield an energetic nanopowder material.

  11. [Familial form of rheumatoid nodulosis].

    PubMed

    Bosser, H; Schubert, B; Grosshans, E

    1993-01-01

    We report a familial form of rheumatoid nodulosis where the early lesions appeared in the first years of life in a young man and his son. The numerous papular and nodular skin lesions disclosed an ulcerative evolution leaving atrophic scars mainly near the limbs' joints. In both patients the evolution was characterized by the late onset of polyarthralgias and of a non-destructive seronegative polyarthritis; intra-osseous lesions were present in the metatarsal bones in the father. Rheumatoid nodulosis is a rare disease, sometimes considered as a benign variant of rheumatoid arthritis without destructive joint involvement. A serum rheumatoid factor is inconstantly present and the intra-osseous geodes have been shown to be rheumatoid nodules exhibiting the same histological structures of palisading granulomas as the subcutaneous nodules. The main symptom of the disease is the occurrence of multiple nodules followed by the delayed onset of a polyarthritis with a benign course without systemic involvement.

  12. Localization and real Jacobi forms

    NASA Astrophysics Data System (ADS)

    Ashok, Sujay K.; Doroud, Nima; Troost, Jan

    2014-04-01

    We calculate the elliptic genus of two dimensional abelian gauged linear sigma models with (2, 2) supersymmetry using supersymmetric localization. The matter sector contains charged chiral multiplets as well as Stückelberg fields coupled to the vector multiplets. These models include theories that flow in the infrared to non-linear sigma models with target spaces that are non-compact Kähler manifolds with U( N) isometry and with an asymptotically linear dilaton direction. The elliptic genera are the modular completions of mock Jacobi forms that have been proposed recently using complementary arguments. We also compute the elliptic genera of models that contain multiple Stückelberg fields from first principles.

  13. Form factors from lattice QCD

    SciTech Connect

    Dru Renner

    2012-04-01

    Precision computation of hadronic physics with lattice QCD is becoming feasible. The last decade has seen precent-level calculations of many simple properties of mesons, and the last few years have seen calculations of baryon masses, including the nucleon mass, accurate to a few percent. As computational power increases and algorithms advance, the precise calculation of a variety of more demanding hadronic properties will become realistic. With this in mind, I discuss the current lattice QCD calculations of generalized parton distributions with an emphasis on the prospects for well-controlled calculations for these observables as well. I will do this by way of several examples: the pion and nucleon form factors and moments of the nucleon parton and generalized-parton distributions.

  14. Miscellaneous Waste-Form FEPs

    SciTech Connect

    A. Schenker

    2000-12-08

    The US DOE must provide a reasonable assurance that the performance objectives for the Yucca Mountain Project (YMP) potential radioactive-waste repository can be achieved for a 10,000-year post-closure period. The guidance that mandates this direction is under the provisions of 10 CFR Part 63 and the US Department of Energy's ''Revised Interim Guidance Pending Issuance of New US Nuclear Regulatory Commission (NRC) Regulations (Revision 01, July 22, 1999), for Yucca Mountain, Nevada'' (Dyer 1999 and herein referred to as DOE's Interim Guidance). This assurance must be demonstrated in the form of a performance assessment that: (1) identifies the features, events, and processes (FEPs) that might affect the performance of the potential geologic repository; (2) examines the effects of such FEPs on the performance of the potential geologic repository; (3) estimates the expected annual dose to a specified receptor group; and (4) provides the technical basis for inclusion or exclusion of specific FEPs.

  15. Forming impressions from incongruent traits.

    PubMed

    Casselden, P A; Hampson, S E

    1990-08-01

    The factors that affect the ease with which impressions are formed from incongruent trait pairs are investigated. In Experiments 1 and 2, trait pairs that were both descriptively and evaluatively congruent, as well as ones that were only evaluatively congruent, were found to be more imaginable and to be perceived as more frequently co-occurring than incongruent trait pairs. In Experiment 3, response latency provided a converging measure of ease of imaginability. Experiment 4 examined written descriptions of targets described by these trait pairs, and found more attempts to integrate the congruent than the incongruent pairs. These findings are discussed in terms of the relation between laypersons' impressions of personality and formal personality assessment. PMID:2213498

  16. Alumina forming iron base superalloy

    DOEpatents

    Yamamoto, Yukinori; Muralidharan, Govindarajan; Brady, Michael P.

    2014-08-26

    An austenitic stainless steel alloy, consists essentially of, in weight percent 2.5 to 4 Al; 25 to 35 Ni; 12 to 19 Cr; at least 1, up to 4 total of at least one element selected from the group consisting of Nb and Ta; 0.5 to 3 Ti; less than 0.5 V; 0.1 to 1 of at least on element selected from the group consisting of Zr and Hf; 0.03 to 0.2 C; 0.005 to 0.1 B; and base Fe. The weight percent Fe is greater than the weight percent Ni. The alloy forms an external continuous scale including alumina, and contains coherent precipitates of .gamma.'-Ni.sub.3Al, and a stable essentially single phase FCC austenitic matrix microstructure. The austenitic matrix is essentially delta-ferrite-free and essentially BCC-phase-free.

  17. Nuclear waste forms for actinides

    PubMed Central

    Ewing, Rodney C.

    1999-01-01

    The disposition of actinides, most recently 239Pu from dismantled nuclear weapons, requires effective containment of waste generated by the nuclear fuel cycle. Because actinides (e.g., 239Pu and 237Np) are long-lived, they have a major impact on risk assessments of geologic repositories. Thus, demonstrable, long-term chemical and mechanical durability are essential properties of waste forms for the immobilization of actinides. Mineralogic and geologic studies provide excellent candidate phases for immobilization and a unique database that cannot be duplicated by a purely materials science approach. The “mineralogic approach” is illustrated by a discussion of zircon as a phase for the immobilization of excess weapons plutonium. PMID:10097054

  18. 48 CFR 813.307 - Forms.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... following forms provide a purchase or delivery order, vendor's invoice, and receiving report: (1) VA Form 90... Form 10-7078, Authorization and Invoice for Medical and Hospital Services. (2) VA Form 10-7079, Request for Outpatient Medical Services. (3) VA Form 10-2570d, Dental Record Authorization and Invoice...

  19. 48 CFR 813.307 - Forms.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... following forms provide a purchase or delivery order, vendor's invoice, and receiving report: (1) VA Form 90... Form 10-7078, Authorization and Invoice for Medical and Hospital Services. (2) VA Form 10-7079, Request for Outpatient Medical Services. (3) VA Form 10-2570d, Dental Record Authorization and Invoice...

  20. Ynamides in Ring Forming Transformations

    PubMed Central

    WANG, XIAO-NA; YEOM, HYUN-SUK; FANG, LI-CHAO; HE, SHUZHONG; MA, ZHI-XIONG; KEDROWSKI, BRANT L.; HSUNG, RICHARD P.

    2013-01-01

    Conspectus The ynamide functional group activates carbon-carbon triple bonds through an attached nitrogen atom that bears an electron-withdrawing group. As a result, the alkyne has both electrophilic and nucleophilic properties. Through the selection of the electron-withdrawing group attached to nitrogen chemists can modulate the electronic properties and reactivity of ynamides, making these groups versatile synthetic building blocks. The reactions of ynamides also lead directly to nitrogen-containing products, which provides access to important structural motifs found in natural products and molecules of medicinal interest. Therefore, researchers have invested increasing time and research in the chemistry of ynamides in recent years. This Account surveys and assesses new organic transformations involving ynamides developed in our laboratory and in others around the world. We showcase the synthetic power of ynamides for rapid assembly of complex molecular structures. Among the recent reports of ynamide transformations, ring-forming reactions provide a powerful tool for generating molecular complexity quickly. In addition to their synthetic utility, such reactions are mechanistically interesting. Therefore, we focus primarily on the cyclization chemistry of ynamides. This Account highlights ynamide reactions that are useful in the rapid synthesis of cyclic and polycyclic structural manifolds. We discuss the mechanisms active in the ring formations and describe representative examples that demonstrate the scope of these reactions and provide mechanistic insights. In this discussion we feature examples of ynamide reactions involving radical cyclizations, ring-closing metathesis, transition metal and non-transition metal mediated cyclizations, cycloaddition reactions, and rearrangements. The transformations presented rapidly introduce structural complexity and include nitrogen within, or in close proximity to, a newly formed ring (or rings). Thus, ynamides have emerged