Hypoxia inducible factor 1 links fast-patterned muscle activity and fast muscle phenotype in rats.

PubMed

Lunde, Ida G; Anton, Siobhan L; Bruusgaard, Jo C; Rana, Zaheer A; Ellefsen, Stian; Gundersen, Kristian

2011-03-15

Exercise influences muscle phenotype by the specific pattern of action potentials delivered to the muscle, triggering intracellular signalling pathways. PO2 can be reduced by an order of magnitude in working muscle. In humans, carriers of a hyperactive polymorphism of the transcription factor hypoxia inducible factor 1α (HIF-1α) have 50% more fast fibres, and this polymorphism is prevalent among strength athletes. We have investigated the putative role of HIF-1α in mediating activity changes in muscle.When rat muscles were stimulated with short high frequency bursts of action potentials known to induce a fast muscle phenotype, HIF-1α increased by about 80%. In contrast, a pattern consisting of long low frequency trains known to make fast muscles slow reduced the HIF-1α level of the fast extensor digitorum longus (EDL) muscle by 44%. Nuclear protein extracts from normal EDL contained 2.3-fold more HIF-1α and 4-fold more HIF-1β than the slow soleus muscle, while von-Hippel-Lindau protein was 4.8-fold higher in slow muscles. mRNA displayed a reciprocal pattern; thus FIH-1 mRNA was almost 2-fold higher in fast muscle, while the HIF-1α level was half, and consequently protein/mRNA ratio for HIF-1α was more than 4-fold higher in the fast muscle, suggesting that HIF-1α is strongly suppressed post-transcriptionally in slow muscles.When HIF-1α was overexpressed for 14 days after somatic gene transfer in adult rats, a slow-to-fast transformation was observed, encompassing an increase in fibre cross sectional area, oxidative enzyme activity and myosin heavy chain. The latter was shown to be regulated at the mRNA level in C2C12 myotubes.

Attractors of relaxation discrete-time systems with chaotic dynamics on a fast time scale.

PubMed

Maslennikov, Oleg V; Nekorkin, Vladimir I

2016-07-01

In this work, a new type of relaxation systems is considered. Their prominent feature is that they comprise two distinct epochs, one is slow regular motion and another is fast chaotic motion. Unlike traditionally studied slow-fast systems that have smooth manifolds of slow motions in the phase space and fast trajectories between them, in this new type one observes, apart the same geometric objects, areas of transient chaos. Alternating periods of slow regular motions and fast chaotic ones as well as transitions between them result in a specific chaotic attractor with chaos on a fast time scale. We formulate basic properties of such attractors in the framework of discrete-time systems and consider several examples. Finally, we provide an important application of such systems, the neuronal electrical activity in the form of chaotic spike-burst oscillations.

Generation of skeletal mechanism by means of projected entropy participation indices

NASA Astrophysics Data System (ADS)

Paolucci, Samuel; Valorani, Mauro; Ciottoli, Pietro Paolo; Galassi, Riccardo Malpica

2017-11-01

When the dynamics of reactive systems develop very-slow and very-fast time scales separated by a range of active time scales, with gaps in the fast/active and slow/active time scales, then it is possible to achieve multi-scale adaptive model reduction along-with the integration of the ODEs using the G-Scheme. The scheme assumes that the dynamics is decomposed into active, slow, fast, and invariant subspaces. We derive expressions that establish a direct link between time scales and entropy production by using estimates provided by the G-Scheme. To calculate the contribution to entropy production, we resort to a standard model of a constant pressure, adiabatic, batch reactor, where the mixture temperature of the reactants is initially set above the auto-ignition temperature. Numerical experiments show that the contribution to entropy production of the fast subspace is of the same magnitude as the error threshold chosen for the identification of the decomposition of the tangent space, and the contribution of the slow subspace is generally much smaller than that of the active subspace. The information on entropy production associated with reactions within each subspace is used to define an entropy participation index that is subsequently utilized for model reduction.

Prediction of general mental ability based on neural oscillation measures of sleep.

PubMed

Bódizs, Róbert; Kis, Tamás; Lázár, Alpár Sándor; Havrán, Linda; Rigó, Péter; Clemens, Zsófia; Halász, Péter

2005-09-01

The usual assessment of general mental ability (or intelligence) is based on performance attained in reasoning and problem-solving tasks. Differences in general mental ability have been associated with event-related neural activity patterns of the wakeful working brain or physical, chemical and electrical brain features measured during wakeful resting conditions. Recent evidences suggest that specific sleep electroencephalogram oscillations are related to wakeful cognitive performances. Our aim is to reveal the relationship between non-rapid eye movement sleep-specific oscillations (the slow oscillation, delta activity, slow and fast sleep spindle density, the grouping of slow and fast sleep spindles) and general mental ability assessed by the Raven Progressive Matrices Test (RPMT). The grouping of fast sleep spindles by the cortical slow oscillation in the left frontopolar derivation (Fp1) as well as the density of fast sleep spindles over the right frontal area (Fp2, F4), correlated positively with general mental ability. Data from those selected electrodes that showed the high correlations with general mental ability explained almost 70% of interindividual variance in RPMT scores. Results suggest that individual differences in general mental ability are reflected in fast sleep spindle-related oscillatory activity measured over the frontal cortex.

The relationship between gamma frequency and running speed differs for slow and fast gamma rhythms in freely behaving rats

PubMed Central

Zheng, Chenguang; Bieri, Kevin Wood; Trettel, Sean Gregory; Colgin, Laura Lee

2015-01-01

In hippocampal area CA1 of rats, the frequency of gamma activity has been shown to increase with running speed (Ahmed and Mehta, 2012). This finding suggests that different gamma frequencies simply allow for different timings of transitions across cell assemblies at varying running speeds, rather than serving unique functions. However, accumulating evidence supports the conclusion that slow (~25–55 Hz) and fast (~60–100 Hz) gamma are distinct network states with different functions. If slow and fast gamma constitute distinct network states, then it is possible that slow and fast gamma frequencies are differentially affected by running speed. In this study, we tested this hypothesis and found that slow and fast gamma frequencies change differently as a function of running speed in hippocampal areas CA1 and CA3, and in the superficial layers of the medial entorhinal cortex (MEC). Fast gamma frequencies increased with increasing running speed in all three areas. Slow gamma frequencies changed significantly less across different speeds. Furthermore, at high running speeds, CA3 firing rates were low, and MEC firing rates were high, suggesting that CA1 transitions from CA3 inputs to MEC inputs as running speed increases. These results support the hypothesis that slow and fast gamma reflect functionally distinct states in the hippocampal network, with fast gamma driven by MEC at high running speeds and slow gamma driven by CA3 at low running speeds. PMID:25601003

Attractors of relaxation discrete-time systems with chaotic dynamics on a fast time scale

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

Maslennikov, Oleg V.; Nekorkin, Vladimir I.

In this work, a new type of relaxation systems is considered. Their prominent feature is that they comprise two distinct epochs, one is slow regular motion and another is fast chaotic motion. Unlike traditionally studied slow-fast systems that have smooth manifolds of slow motions in the phase space and fast trajectories between them, in this new type one observes, apart the same geometric objects, areas of transient chaos. Alternating periods of slow regular motions and fast chaotic ones as well as transitions between them result in a specific chaotic attractor with chaos on a fast time scale. We formulate basicmore » properties of such attractors in the framework of discrete-time systems and consider several examples. Finally, we provide an important application of such systems, the neuronal electrical activity in the form of chaotic spike-burst oscillations.« less

An Active Learning Mammalian Skeletal Muscle Lab Demonstrating Contractile and Kinetic Properties of Fast- and Slow-Twitch Muscle

ERIC Educational Resources Information Center

Head, S. I.; Arber, M. B.

2013-01-01

The fact that humans possess fast and slow-twitch muscle in the ratio of approximately 50% has profound implications for designing exercise training strategies for power and endurance activities. With the growth of exercise and sport science courses, we have seen the need to develop an undergraduate student laboratory that demonstrates the basic…

Coupled expression of troponin T and troponin I isoforms in single skeletal muscle fibers correlates with contractility.

PubMed

Brotto, Marco A; Biesiadecki, Brandon J; Brotto, Leticia S; Nosek, Thomas M; Jin, Jian-Ping

2006-02-01

Striated muscle contraction is powered by actin-activated myosin ATPase. This process is regulated by Ca(2+) via the troponin complex. Slow- and fast-twitch fibers of vertebrate skeletal muscle express type I and type II myosin, respectively, and these myosin isoenzymes confer different ATPase activities, contractile velocities, and force. Skeletal muscle troponin has also diverged into fast and slow isoforms, but their functional significance is not fully understood. To investigate the expression of troponin isoforms in mammalian skeletal muscle and their functional relationship to that of the myosin isoforms, we concomitantly studied myosin, troponin T (TnT), and troponin I (TnI) isoform contents and isometric contractile properties in single fibers of rat skeletal muscle. We characterized a large number of Triton X-100-skinned single fibers from soleus, diaphragm, gastrocnemius, and extensor digitorum longus muscles and selected fibers with combinations of a single myosin isoform and a single class (slow or fast) of the TnT and TnI isoforms to investigate their role in determining contractility. Types IIa, IIx, and IIb myosin fibers produced higher isometric force than that of type I fibers. Despite the polyploidy of adult skeletal muscle fibers, the expression of fast or slow isoforms of TnT and TnI is tightly coupled. Fibers containing slow troponin had higher Ca(2+) sensitivity than that of the fast troponin fibers, whereas fibers containing fast troponin showed a higher cooperativity of Ca(2+) activation than that of the slow troponin fibers. These results demonstrate distinct but coordinated regulation of troponin and myosin isoform expression in skeletal muscle and their contribution to the contractile properties of muscle.

Coupled expression of troponin T and troponin I isoforms in single skeletal muscle fibers correlates with contractility

PubMed Central

BROTTO, MARCO A.; BIESIADECKI, BRANDON J.; BROTTO, LETICIA S.; NOSEK, THOMAS M; JIN, J.-P.

2005-01-01

(Summary) Brotto, Marco A., Brandon J. Biesiadecki, Leticia S. Brotto, Thomas M. Nosek, and J.-P. Jin. Striated muscle contraction is powered by actin-activated myosin ATPase. This process is regulated by Ca2+ via the troponin complex. Slow and fast twitch fibers of vertebrate skeletal muscle express type I and type II myosin, respectively, and these myosin isoenzymes confer different ATPase activities, contractile velocities and force. Skeletal muscle troponin has also diverged into fast and slow isoforms, but their functional significance is not fully understood. To investigate the expression of troponin isoforms in mammalian skeletal muscle and their functional relationship to that of the myosin isoforms, we concomitantly studied myosin and troponin T (TnT) and troponin I (TnI) isoform contents and isometric contractile properties in single fibers of rat skeletal muscle. We characterized a large number of Triton skinned single fibers from soleus, diaphragm, gastrocnemius and extensor digitorum longus muscles and selected fibers with combinations of a single myosin isoform and a single class (slow or fast) of TnT and TnI isoform to investigate their role in determining contractility. Type IIa, IIx and IIb myosin fibers produced higher isometric force than that of type I fibers. Despite the polyploidy of adult skeletal muscle fibers, the expression of fast or slow isoforms of TnT and TnI is tightly coupled. Fibers containing slow troponin had higher Ca2+ sensitivity than that of the fast troponin fibers, while fibers containing fast troponin showed a higher cooperativity of Ca2+ activation than that of the slow troponin fibers. The results demonstrate distinctive, but coordinated, regulation of troponin and myosin isoform expression in skeletal muscle and their contribution to the contractile properties. PMID:16192301

Activity-dependent extracellular K+ accumulation in rat optic nerve: the role of glial and axonal Na+ pumps

PubMed Central

Ransom, Christopher B; Ransom, Bruce R; Sontheimer, Harald

2000-01-01

We measured activity-dependent changes in [K+]o with K+-selective microelectrodes in adult rat optic nerve, a CNS white matter tract, to investigate the factors responsible for post-stimulus recovery of [K+]o.Post-stimulus recovery of [K+]o followed a double-exponential time course with an initial, fast time constant, τfast, of 0.9 ± 0.2 s (mean ±s.d.) and a later, slow time constant, τslow, of 4.2 ± 1 s following a 1 s, 100 Hz stimulus. τfast, but not τslow, decreased with increasing activity-dependent rises in [K+]o. τslow, but not τfast, increased with increasing stimulus duration.Post-stimulus recovery of [K+]o was temperature sensitive. The apparent temperature coefficients (Q10, 27–37°C) for the fast and slow components following a 1 s, 100 Hz stimulus were 1.7 and 2.6, respectively.Post-stimulus recovery of [K+]o was sensitive to Na+ pump inhibition with 50 μM strophanthidin. Following a 1 s, 100 Hz stimulus, 50 μM strophanthidin increased τfast and τslow by 81 and 464%, respectively. Strophanthidin reduced the temperature sensitivity of post-stimulus recovery of [K+]o.Post-stimulus recovery of [K+]o was minimally affected by the K+ channel blocker Ba2+ (0.2 mm). Following a 10 s, 100 Hz stimulus, 0.2 mm Ba2+ increased τfast and τslow by 24 and 18%, respectively.Stimulated increases in [K+]o were followed by undershoots of [K+]o. Post-stimulus undershoot amplitude increased with stimulus duration but was independent of the peak preceding [K+]o increase.These observations imply that two distinct processes contribute to post-stimulus recovery of [K+]o in central white matter. The results are compatible with a model of K+ removal that attributes the fast, initial phase of K+ removal to K+ uptake by glial Na+ pumps and the slower, sustained decline to K+ uptake via axonal Na+ pumps. PMID:10713967

Thalamic reticular nucleus induces fast and local modulation of arousal state

PubMed Central

Lewis, Laura D; Voigts, Jakob; Flores, Francisco J; Schmitt, L Ian; Wilson, Matthew A

2015-01-01

During low arousal states such as drowsiness and sleep, cortical neurons exhibit rhythmic slow wave activity associated with periods of neuronal silence. Slow waves are locally regulated, and local slow wave dynamics are important for memory, cognition, and behaviour. While several brainstem structures for controlling global sleep states have now been well characterized, a mechanism underlying fast and local modulation of cortical slow waves has not been identified. Here, using optogenetics and whole cortex electrophysiology, we show that local tonic activation of thalamic reticular nucleus (TRN) rapidly induces slow wave activity in a spatially restricted region of cortex. These slow waves resemble those seen in sleep, as cortical units undergo periods of silence phase-locked to the slow wave. Furthermore, animals exhibit behavioural changes consistent with a decrease in arousal state during TRN stimulation. We conclude that TRN can induce rapid modulation of local cortical state. DOI: http://dx.doi.org/10.7554/eLife.08760.001 PMID:26460547

From slow to fast rupture during laboratory earthquakes in dolostones

NASA Astrophysics Data System (ADS)

Passelegue, F. X.; Fondriest, M.; Nicolas, A.; Aubry, J.; Schubnel, A.; Di Toro, G.

2016-12-01

Dolostones are the dominant lithology of the shallow portions of many seismically active regions (e.g., Italian Apennines). Displacement in natural fault zones cutting dolostones and exhumed from < 3-4 km depth is frequently localized on highly reflective (mirror-like) slip surfaces, coated with thin films of nano-granular fault rock. Using saw-cut dolostone samples, we conducted stick-slip experiments under upper crustal stress conditions (confining pressures and temperatures of 30, 60 and 90 MPa at 30, 65 and 100 °C, respectively). Samples were equipped with 15 piezoelectric transducers allowing the record of acoustic activity. At 30 and 65 °C, only slow ruptures (Vr < 200 m/s) were observed and the experimental faults exhibited ductile behaviour. At 65 °C, a slip strengthening behaviour was observed after the main slow rupture, leading to a succession of slow ruptures. At T = 100 °C and 30 MPa confining pressure, fault strengthening increased after each rupture, allowing, while the rupture processes remained slow (no acoustic activity), a sequence of slow stick-slip events. Instead, at the same ambient temperature but under larger confining pressures (60 and 90 MPa), we observed the transition from slow to fast rupture events (up to supershear rupture velocities), associated to clusters of acoustic activity and dynamic stress drop occurring in few tens of microseconds. In all experiments, mirror-like surfaces and nanoparticles were observed under the scanning electron microscope as a result of slow and fast ruptures. Clearly, mirror-like surfaces and nano powders are not representative of seismic slip events in cohesive dolostones. Instead, the transition from slow to fast ruptures (and generation of acoustic emissions) was related to a flash weakening processes, enhanced at 100° C, which allowed the experimental fault to weaken with slip faster than the rate at which the elastic strain was released from the surrounding medium.

Slow slip and the transition from fast to slow fronts in the rupture of frictional interfaces

PubMed Central

Trømborg, Jørgen Kjoshagen; Sveinsson, Henrik Andersen; Scheibert, Julien; Thøgersen, Kjetil; Amundsen, David Skålid; Malthe-Sørenssen, Anders

2014-01-01

The failure of the population of microjunctions forming the frictional interface between two solids is central to fields ranging from biomechanics to seismology. This failure is mediated by the propagation along the interface of various types of rupture fronts, covering a wide range of velocities. Among them are the so-called slow fronts, which are recently discovered fronts much slower than the materials’ sound speeds. Despite intense modeling activity, the mechanisms underlying slow fronts remain elusive. Here, we introduce a multiscale model capable of reproducing both the transition from fast to slow fronts in a single rupture event and the short-time slip dynamics observed in recent experiments. We identify slow slip immediately following the arrest of a fast front as a phenomenon sufficient for the front to propagate further at a much slower pace. Whether slow fronts are actually observed is controlled both by the interfacial stresses and by the width of the local distribution of forces among microjunctions. Our results show that slow fronts are qualitatively different from faster fronts. Because the transition from fast to slow fronts is potentially as generic as slow slip, we anticipate that it might occur in the wide range of systems in which slow slip has been reported, including seismic faults. PMID:24889640

Cortical networks dynamically emerge with the interplay of slow and fast oscillations for memory of a natural scene.

PubMed

Mizuhara, Hiroaki; Sato, Naoyuki; Yamaguchi, Yoko

2015-05-01

Neural oscillations are crucial for revealing dynamic cortical networks and for serving as a possible mechanism of inter-cortical communication, especially in association with mnemonic function. The interplay of the slow and fast oscillations might dynamically coordinate the mnemonic cortical circuits to rehearse stored items during working memory retention. We recorded simultaneous EEG-fMRI during a working memory task involving a natural scene to verify whether the cortical networks emerge with the neural oscillations for memory of the natural scene. The slow EEG power was enhanced in association with the better accuracy of working memory retention, and accompanied cortical activities in the mnemonic circuits for the natural scene. Fast oscillation showed a phase-amplitude coupling to the slow oscillation, and its power was tightly coupled with the cortical activities for representing the visual images of natural scenes. The mnemonic cortical circuit with the slow neural oscillations would rehearse the distributed natural scene representations with the fast oscillation for working memory retention. The coincidence of the natural scene representations could be obtained by the slow oscillation phase to create a coherent whole of the natural scene in the working memory. Copyright © 2015 Elsevier Inc. All rights reserved.

Gravitational unloading effects on muscle fiber size, phenotype and myonuclear number

NASA Technical Reports Server (NTRS)

Ohira, Y.; Yoshinaga, T.; Nomura, T.; Kawano, F.; Ishihara, A.; Nonaka, I.; Roy, R. R.; Edgerton, V. R.

2002-01-01

The effects of gravitational unloading with or without intact neural activity and/or tension development on myosin heavy chain (MHC) composition, cross-sectional area (CSA), number of myonuclei, and myonuclear domain (cytoplasmic volume per myonucleus ratio) in single fibers of both slow and fast muscles of rat hindlimbs are reviewed briefly. The atrophic response to unloading is generally graded as follows: slow extensors > fast extensors > fast flexors. Reduction of CSA is usually greater in the most predominant fiber type of that muscle. The percentage of fibers expressing fast MHC isoforms increases in unloaded slow but not fast muscles. Myonuclear number per mm of fiber length and myonuclear domain is decreased in the fibers of the unloaded predominantly slow soleus muscle, but not in the predominantly fast plantaris. Decreases in myonuclear number and domain, however, are observed in plantaris fibers when tenotomy, denervation, or both are combined with hindlimb unloading. All of these results are consistent with the view that a major factor for fiber atrophy is an inhibition or reduction of loading of the hindlimbs. These data also indicate that predominantly slow muscles are more responsive to unloading than predominantly fast muscles. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

Effect of tibial bone resection on the development of fast- and slow-twitch skeletal muscles in foetal sheep.

PubMed

West, J M; Williams, N A; Luff, A R; Walker, D W

2000-04-01

To determine if longitudinal bone growth affects the differentiation of fast- and slow-twitch muscles, the tibial bone was sectioned at 90 days gestation in foetal sheep so that the lower leg was permanently without structural support. At 140 days (term is approximately 147 days) the contractile properties of whole muscles, activation profiles of single fibres and ultrastructure of fast- and slow-twitch muscles from the hindlimbs were studied. The contractile and activation profiles of the slow-twitch soleus muscles were significantly affected by tibial bone resection (TIBX). The soleus muscles from the TIBX hindlimbs showed: (1) a decrease in the time to peak of the twitch responses from 106.2 +/- 10.7 ms (control, n = 4) to 65.1 +/- 2.48 ms (TIBX, n = 5); (2) fatigue profiles more characteristic of those observed in the fast-twitch muscles: and (3) Ca2+ - and Sr2+ -activation profiles of skinned fibres similar to those from intact hindlimbs at earlier stages of gestation. In the FDL, TIBX did not significantly change whole muscle twitch contraction time, the fatigue profile or the Ca2+ - and Sr2+ -activation profiles of skinned fibres. Electron microscopy showed an increased deposition of glycogen in both soleus and FDL muscles. This study shows that the development of the slow-twitch phenotype is impeded in the absence of the physical support normally provided by the tibial bone. We suggest that longitudinal stretch is an important factor in allowing full expression of the slow-twitch phenotype.

Human skeletal muscle: transition between fast and slow fibre types.

PubMed

Neunhäuserer, Daniel; Zebedin, Michaela; Obermoser, Magdalena; Moser, Gerhard; Tauber, Mark; Niebauer, Josef; Resch, Herbert; Galler, Stefan

2011-05-01

Human skeletal muscles consist of different fibre types: slow fibres (slow twitch or type I) containing the myosin heavy chain isoform (MHC)-I and fast fibres (fast twitch or type II) containing MHC-IIa (type IIA) or MHC-IId (type IID). The following order of decreasing kinetics is known: type IID > type IIA > type I. This order is especially based on the kinetics of stretch activation, which is the most discriminative property among fibre types. In this study we tested if hybrid fibres containing both MHC-IIa and MHC-I (type C fibres) provide a transition in kinetics between fast (type IIA) and slow fibres (type I). Our data of stretch activation kinetics suggest that type C fibres, with different ratios of MHC-IIa and MHC-I, do not provide a continuous transition. Instead, a specialized group of slow fibres, which we called "transition fibres", seems to provide a transition. Apart of their kinetics of stretch activation, which is most close to that of type IIA, the transition fibres are characterized by large cross-sectional areas and low maximal tensions. The molecular cause for the mechanical properties of the transition fibres is unknown. It is possible that the transition fibres contain an unknown slow MHC isoform, which cannot be separated by biochemical methods. Alternatively, or in addition, isoforms of myofibrillar proteins, other than MHC, and posttranslational modifications of myofibrillar proteins could play a role regarding the characteristics of the transition fibres.

Gating of human ClC-2 chloride channels and regulation by carboxy-terminal domains

PubMed Central

Garcia-Olivares, Jennie; Alekov, Alexi; Boroumand, Mohammad Reza; Begemann, Birgit; Hidalgo, Patricia; Fahlke, Christoph

2008-01-01

Eukaryotic ClC channels are dimeric proteins with each subunit forming an individual protopore. Single protopores are gated by a fast gate, whereas the slow gate is assumed to control both protopores through a cooperative movement of the two carboxy-terminal domains. We here study the role of the carboxy-terminal domain in modulating fast and slow gating of human ClC-2 channels, a ubiquitously expressed ClC-type chloride channel involved in transepithelial solute transport and in neuronal chloride homeostasis. Partial truncation of the carboxy-terminus abolishes function of ClC-2 by locking the channel in a closed position. However, unlike other isoforms, its complete removal preserves function of ClC-2. ClC-2 channels without the carboxy-terminus exhibit fast and slow gates that activate and deactivate significantly faster than in WT channels. In contrast to the prevalent view, a single carboxy-terminus suffices for normal slow gating, whereas both domains regulate fast gating of individual protopores. Our findings demonstrate that the carboxy-terminus is not strictly required for slow gating and that the cooperative gating resides in other regions of the channel protein. ClC-2 is expressed in neurons and believed to open at negative potentials and increased internal chloride concentrations after intense synaptic activity. We propose that the function of the ClC-2 carboxy-terminus is to slow down the time course of channel activation in order to stabilize neuronal excitability PMID:18801843

Gating of human ClC-2 chloride channels and regulation by carboxy-terminal domains.

PubMed

Garcia-Olivares, Jennie; Alekov, Alexi; Boroumand, Mohammad Reza; Begemann, Birgit; Hidalgo, Patricia; Fahlke, Christoph

2008-11-15

Eukaryotic ClC channels are dimeric proteins with each subunit forming an individual protopore. Single protopores are gated by a fast gate, whereas the slow gate is assumed to control both protopores through a cooperative movement of the two carboxy-terminal domains. We here study the role of the carboxy-terminal domain in modulating fast and slow gating of human ClC-2 channels, a ubiquitously expressed ClC-type chloride channel involved in transepithelial solute transport and in neuronal chloride homeostasis. Partial truncation of the carboxy-terminus abolishes function of ClC-2 by locking the channel in a closed position. However, unlike other isoforms, its complete removal preserves function of ClC-2. ClC-2 channels without the carboxy-terminus exhibit fast and slow gates that activate and deactivate significantly faster than in WT channels. In contrast to the prevalent view, a single carboxy-terminus suffices for normal slow gating, whereas both domains regulate fast gating of individual protopores. Our findings demonstrate that the carboxy-terminus is not strictly required for slow gating and that the cooperative gating resides in other regions of the channel protein. ClC-2 is expressed in neurons and believed to open at negative potentials and increased internal chloride concentrations after intense synaptic activity. We propose that the function of the ClC-2 carboxy-terminus is to slow down the time course of channel activation in order to stabilize neuronal excitability.

High-frequency gamma oscillations coexist with low-frequency gamma oscillations in the rat visual cortex in vitro.

PubMed

Oke, Olaleke O; Magony, Andor; Anver, Himashi; Ward, Peter D; Jiruska, Premysl; Jefferys, John G R; Vreugdenhil, Martin

2010-04-01

Synchronization of neuronal activity in the visual cortex at low (30-70 Hz) and high gamma band frequencies (> 70 Hz) has been associated with distinct visual processes, but mechanisms underlying high-frequency gamma oscillations remain unknown. In rat visual cortex slices, kainate and carbachol induce high-frequency gamma oscillations (fast-gamma; peak frequency approximately 80 Hz at 37 degrees C) that can coexist with low-frequency gamma oscillations (slow-gamma; peak frequency approximately 50 Hz at 37 degrees C) in the same column. Current-source density analysis showed that fast-gamma was associated with rhythmic current sink-source sequences in layer III and slow-gamma with rhythmic current sink-source sequences in layer V. Fast-gamma and slow-gamma were not phase-locked. Slow-gamma power fluctuations were unrelated to fast-gamma power fluctuations, but were modulated by the phase of theta (3-8 Hz) oscillations generated in the deep layers. Fast-gamma was spatially less coherent than slow-gamma. Fast-gamma and slow-gamma were dependent on gamma-aminobutyric acid (GABA)(A) receptors, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and gap-junctions, their frequencies were reduced by thiopental and were weakly dependent on cycle amplitude. Fast-gamma and slow-gamma power were differentially modulated by thiopental and adenosine A(1) receptor blockade, and their frequencies were differentially modulated by N-methyl-D-aspartate (NMDA) receptors, GluK1 subunit-containing receptors and persistent sodium currents. Our data indicate that fast-gamma and slow-gamma both depend on and are paced by recurrent inhibition, but have distinct pharmacological modulation profiles. The independent co-existence of fast-gamma and slow-gamma allows parallel processing of distinct aspects of vision and visual perception. The visual cortex slice provides a novel in vitro model to study cortical high-frequency gamma oscillations.

Influence of fast and slow alkali myosin light chain isoforms on the kinetics of stretch-induced force transients of fast-twitch type IIA fibres of rat.

PubMed

Andruchov, Oleg; Galler, Stefan

2008-03-01

This study contributes to understand the physiological role of slow myosin light chain isoforms in fast-twitch type IIA fibres of skeletal muscle. These isoforms are often attached to the myosin necks of rat type IIA fibres, whereby the slow alkali myosin light chain isoform MLC1s is much more frequent and abundant than the slow regulatory myosin light chain isoform MLC2s. In the present study, single-skinned rat type IIA fibres were maximally Ca(2+) activated and subjected to stepwise stretches for causing a perturbation of myosin head pulling cycles. From the time course of the resulting force transients, myosin head kinetics was deduced. Fibres containing MLC1s exhibited slower kinetics independently of the presence or absence of MLC2s. At the maximal MLC1s concentration of about 75%, the slowing was about 40%. The slowing effect of MLC1s is possibly due to differences in the myosin heavy chain binding sites of the fast and slow alkali MLC isoforms, which changes the rigidity of the myosin neck. Compared with the impact of myosin heavy chain isoforms in various fast-twitch fibre types, the influence of MLC1s on myosin head kinetics of type IIA fibres is much smaller. In conclusion, the physiological role of fast and slow MLC isoforms in type IIA fibres is a fine-tuning of the myosin head kinetics.

Lower Extremity Muscle Activity During a Women’s Overhand Lacrosse Shot

PubMed Central

Millard, Brianna M.; Mercer, John A.

2014-01-01

The purpose of this study was to describe lower extremity muscle activity during the lacrosse shot. Participants (n=5 females, age 22±2 years, body height 162.6±15.2 cm, body mass 63.7±23.6 kg) were free from injury and had at least one year of lacrosse experience. The lead leg was instrumented with electromyography (EMG) leads to measure muscle activity of the rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and medial gastrocnemius (GA). Participants completed five trials of a warm-up speed shot (Slow) and a game speed shot (Fast). Video analysis was used to identify the discrete events defining specific movement phases. Full-wave rectified data were averaged per muscle per phase (Crank Back Minor, Crank Back Major, Stick Acceleration, Stick Deceleration). Average EMG per muscle was analyzed using a 4 (Phase) × 2 (Speed) ANOVA. BF was greater during Fast vs. Slow for all phases (p<0.05), while TA was not influenced by either Phase or Speed (p>0.05). RF and GA were each influenced by the interaction of Phase and Speed (p<0.05) with GA being greater during Fast vs. Slow shots during all phases and RF greater during Crank Back Minor and Major as well as Stick Deceleration (p<0.05) but only tended to be greater during Stick Acceleration (p=0.076) for Fast vs. Slow. The greater muscle activity (BF, RF, GA) during Fast vs. Slow shots may have been related to a faster approach speed and/or need to create a stiff lower extremity to allow for faster upper extremity movements. PMID:25114727

Neuronal ensemble for visual working memory via interplay of slow and fast oscillations.

PubMed

Mizuhara, Hiroaki; Yamaguchi, Yoko

2011-05-01

The current focus of studies on neural entities for memory maintenance is on the interplay between fast neuronal oscillations in the gamma band and slow oscillations in the theta or delta band. The hierarchical coupling of slow and fast oscillations is crucial for the rehearsal of sensory inputs for short-term storage, as well as for binding sensory inputs that are represented in spatially segregated cortical areas. However, no experimental evidence for the binding of spatially segregated information has yet been presented for memory maintenance in humans. In the present study, we actively manipulated memory maintenance performance with an attentional blink procedure during human scalp electroencephalography (EEG) recordings and identified that slow oscillations are enhanced when memory maintenance is successful. These slow oscillations accompanied fast oscillations in the gamma frequency range that appeared at spatially segregated scalp sites. The amplitude of the gamma oscillation at these scalp sites was simultaneously enhanced at an EEG phase of the slow oscillation. Successful memory maintenance appears to be achieved by a rehearsal of sensory inputs together with a coordination of distributed fast oscillations at a preferred timing of the slow oscillations. © 2011 The Authors. European Journal of Neuroscience © 2011 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

Increase in salivary oxytocin and decrease in salivary cortisol after listening to relaxing slow-tempo and exciting fast-tempo music.

PubMed

Ooishi, Yuuki; Mukai, Hideo; Watanabe, Ken; Kawato, Suguru; Kashino, Makio

2017-01-01

Relaxation and excitation are components of the effects of music listening. The tempo of music is often considered a critical factor when determining these effects: listening to slow-tempo and fast-tempo music elicits relaxation and excitation, respectively. However, the chemical bases that underlie these relaxation and excitation effects remain unclear. Since parasympathetic and sympathetic nerve activities are facilitated by oxytocin and glucocorticoid, respectively, we hypothesized that listening to relaxing slow-tempo and exciting fast-tempo music is accompanied by increases in the oxytocin and cortisol levels, respectively. We evaluated the change in the salivary oxytocin and cortisol levels of participants listening to slow-tempo and fast-tempo music sequences. We measured the heart rate (HR) and calculated the heart rate variability (HRV) to evaluate the strength of autonomic nerve activity. After listening to a music sequence, the participants rated their arousal and valence levels. We found that both the salivary oxytocin concentration and the high frequency component of the HRV (HF) increased and the HR decreased when a slow-tempo music sequence was presented. The salivary cortisol level decreased and the low frequency of the HRV (LF) to HF ratio (LF/HF) increased when a fast-tempo music sequence was presented. The ratio of the change in the oxytocin level was correlated with the change in HF, LF/HF and HR, whereas that in the cortisol level did not show any correlation with indices of autonomic nerve activity. There was no correlation between the change in oxytocin level and self-reported emotions, while the change in cortisol level correlated with the arousal level. These findings suggest that listening to slow-tempo and fast-tempo music is accompanied by an increase in the oxytocin level and a decrease in the cortisol level, respectively, and imply that such music listening-related changes in oxytocin and cortisol are involved in physiological relaxation and emotional excitation, respectively.

Increase in salivary oxytocin and decrease in salivary cortisol after listening to relaxing slow-tempo and exciting fast-tempo music

PubMed Central

Watanabe, Ken; Kawato, Suguru; Kashino, Makio

2017-01-01

Relaxation and excitation are components of the effects of music listening. The tempo of music is often considered a critical factor when determining these effects: listening to slow-tempo and fast-tempo music elicits relaxation and excitation, respectively. However, the chemical bases that underlie these relaxation and excitation effects remain unclear. Since parasympathetic and sympathetic nerve activities are facilitated by oxytocin and glucocorticoid, respectively, we hypothesized that listening to relaxing slow-tempo and exciting fast-tempo music is accompanied by increases in the oxytocin and cortisol levels, respectively. We evaluated the change in the salivary oxytocin and cortisol levels of participants listening to slow-tempo and fast-tempo music sequences. We measured the heart rate (HR) and calculated the heart rate variability (HRV) to evaluate the strength of autonomic nerve activity. After listening to a music sequence, the participants rated their arousal and valence levels. We found that both the salivary oxytocin concentration and the high frequency component of the HRV (HF) increased and the HR decreased when a slow-tempo music sequence was presented. The salivary cortisol level decreased and the low frequency of the HRV (LF) to HF ratio (LF/HF) increased when a fast-tempo music sequence was presented. The ratio of the change in the oxytocin level was correlated with the change in HF, LF/HF and HR, whereas that in the cortisol level did not show any correlation with indices of autonomic nerve activity. There was no correlation between the change in oxytocin level and self-reported emotions, while the change in cortisol level correlated with the arousal level. These findings suggest that listening to slow-tempo and fast-tempo music is accompanied by an increase in the oxytocin level and a decrease in the cortisol level, respectively, and imply that such music listening-related changes in oxytocin and cortisol are involved in physiological relaxation and emotional excitation, respectively. PMID:29211795

Triton-polyacrylamide gel electrophoresis and leucine aminopeptidase activity staining detect Triton-slowed bands including high-molecular-mass aminopeptidase N (CD13) isoform in cholestatic patient sera.

PubMed

Kawai, Makoto; Hara, Yukichi

2006-02-01

Western blotting of aminopeptidase N (APN) detects a high-molecular-mass isoform (260 kDa) [M. Kawai, Y. Otake, Y. Hara High-molecular-mass isoform of aminopeptidase N/CD13 in serum from cholestatic patients. Clin Chim Acta 330 (2003) 141-149] in cholestatic patient serum but is time-consuming. Human sera were electrophoresed on polyacrylamide gel containing Triton-X100 (Triton-PAGE) and stained with leucine-B-naphthylamide (LAP-staining). The stained bands were eluted from the gel, treated with N- and O-glycosidase if necessary, and analyzed by Western blotting [M. Kawai, Y. Otake, Y. Hara High-molecular-mass isoform of aminopeptidase N/CD13 in serum from cholestatic patients. Clin Chim Acta 330 (2003) 141-149]. Triton-PAGE and LAP-staining clearly detected fast bands in all the sera examined. Almost parallel with leucine aminopeptidase activity, slow bands were strongly stained in all 11 cholestatic patients but clearly stained in 3 out of 14 patients with hepatobiliary diseases other than cholestasis. PAGE with various concentrations of Triton showed that Triton slows down slow bands but not fast bands. Western blotting showed that Triton-PAGE-slow bands of cholestasis contained 140 and 260-kDa APN and that fast bands were slightly smaller than monomer-size slow bands after glycosidase treatment. Less time-consuming than Western blotting, Triton-PAGE and LAP-staining detect novel APN bands slowed by Triton and partly composed of the high-molecular-mass isoform in cholestasis. The slow bands seem to be homodimers of APN with transmembrane anchors. The polypeptide of the fast band seems to be processed differently from that of the slow band.

Coherent ongoing subthreshold state of a cortical neural network regulated by slow- and fast-spiking interneurons.

PubMed

Hoshino, Osamu

2006-12-01

Although details of cortical interneurons in anatomy and physiology have been well understood, little is known about how they contribute to ongoing spontaneous neuronal activity that could have a great impact on subsequent neuronal information processing. Simulating a cortical neural network model of an early sensory area, we investigated whether and how two distinct types of inhibitory interneurons, or fast-spiking interneurons with narrow axonal arbors and slow-spiking interneurons with wide axonal arbors, have a spatiotemporal influence on the ongoing activity of principal cells and subsequent cognitive information processing. In the model, dynamic cell assemblies, or population activation of principal cells, expressed information about specific sensory features. Within cell assemblies, fast-spiking interneurons give a feedback inhibitory effect on principal cells. Between cell assemblies, slow-spiking interneurons give a lateral inhibitory effect on principal cells. Here, we show that these interneurons keep the network at a subthreshold level for action potential generation under the ongoing state, by which the reaction time of principal cells to sensory stimulation could be accelerated. We suggest that the best timing of inhibition mediated by fast-spiking interneurons and slow-spiking interneurons allows the network to remain near threshold for rapid responses to input.

The temporal structure of behaviour and sleep homeostasis.

PubMed

Vyazovskiy, Vladyslav V; Tobler, Irene

2012-01-01

The amount and architecture of vigilance states are governed by two distinct processes, which occur at different time scales. The first, a slow one, is related to a wake/sleep dependent homeostatic Process S, which occurs on a time scale of hours, and is reflected in the dynamics of NREM sleep EEG slow-wave activity. The second, a fast one, is manifested in a regular alternation of two sleep states--NREM and REM sleep, which occur, in rodents, on a time scale of ~5-10 minutes. Neither the mechanisms underlying the time constants of these two processes--the slow one and the fast one, nor their functional significance are understood. Notably, both processes are primarily apparent during sleep, while their potential manifestation during wakefulness is obscured by ongoing behaviour. Here, we find, in mice provided with running wheels, that the two sleep processes become clearly apparent also during waking at the level of behavior and brain activity. Specifically, the slow process was manifested in the total duration of waking periods starting from dark onset, while the fast process was apparent in a regular occurrence of running bouts during the waking periods. The dynamics of both processes were stable within individual animals, but showed large interindividual variability. Importantly, the two processes were not independent: the periodic structure of waking behaviour (fast process) appeared to be a strong predictor of the capacity to sustain continuous wakefulness (slow process). The data indicate that the temporal organization of vigilance states on both the fast and the slow time scales may arise from a common neurophysiologic mechanism.

Dependence of cross-bridge kinetics on myosin light chain isoforms in rabbit and rat skeletal muscle fibres.

PubMed

Andruchov, Oleg; Andruchova, Olena; Wang, Yishu; Galler, Stefan

2006-02-15

Cross-bridge kinetics underlying stretch-induced force transients was studied in fibres with different myosin light chain (MLC) isoforms from skeletal muscles of rabbit and rat. The force transients were induced by stepwise stretches (< 0.3% of fibre length) applied on maximally Ca2+-activated skinned fibres. Fast fibre types IIB, IID (or IIX) and IIA and the slow fibre type I containing the myosin heavy chain isoforms MHC-IIb, MHC-IId (or MHC-IIx), MHC-IIa and MHC-I, respectively, were investigated. The MLC isoform content varied within fibre types. Fast fibre types contained the fast regulatory MLC isoform MLC2f and different proportions of the fast alkali MLC isoforms MLC1f and MLC3f. Type I fibres contained the slow regulatory MLC isoform MLC2s and the slow alkali MLC isoform MLC1s. Slow MLC isoforms were also present in several type IIA fibres. The kinetics of force transients differed by a factor of about 30 between fibre types (order from fastest to slowest kinetics: IIB > IID > IIA > I). The kinetics of the force transients was not dependent on the relative content of MLC1f and MLC3f. Type IIA fibres containing fast and slow MLC isoforms were about 1.2 times slower than type IIA fibres containing only fast MLC isoforms. We conclude that while the cross-bridge kinetics is mainly determined by the MHC isoforms present, it is affected by fast and slow MLC isoforms but not by the relative content of MLC1f and MLC3f. Thus, the physiological role of fast and slow MLC isoforms in type IIA fibres is a fine-tuning of the cross-bridge kinetics.

Nerve-dependent changes in skeletal muscle myosin heavy chain after experimental denervation and cross-reinnervation and in a demyelinating mouse model of Charcot-Marie-Tooth disease type 1A.

PubMed

Maggs, Alison M; Huxley, Clare; Hughes, Simon M

2008-12-01

Innervation regulates the contractile properties of vertebrate muscle fibers, in part through the effect of electrical activity on expression of distinct myosins. Herein we analyze the role of innervation in regulating the accumulation of the general, maturational, and adult forms of rodent slow myosin heavy chain (MyHC) that are defined by the presence of distinct antigenic epitopes. Denervation increases the number of fibers that express general slow MyHC, but it decreases the adult slow MyHC epitope. Cross-reinnervation of slow muscle by a fast nerve leads to an increase in the number of fibers that express fast MyHC. In both cases, there is an increase in the number of fibers that express slow and fast IIA MyHCs, but without the adult slow MyHC epitope. The data suggest that innervation is required for maturation and maintenance of diversity of both slow and fast fibers. The sequence of slow MyHC epitope transitions is a useful biomarker, and it may play a significant role during nerve-dependent changes in muscle fiber function. We applied this detailed muscle analysis to a transgenic mouse model of human motor and sensory neuropathy IA, also known as Charcot-Marie-Tooth disease type 1A (CMT1A), in which electrical conduction in some motor nerves is poor due to demyelination. The mice display atrophy of some muscle fibers and changes in slow and fast MyHC epitope expression, suggestive of a progressive increase in innervation of muscle fibers by fast motor neurons, even at early stages. The potential role of these early changes in disease pathogenesis is assessed.

Fast and slow active control of combustion instabilities in liquid-fueled combustors

NASA Astrophysics Data System (ADS)

Lee, Jae-Yeon

This thesis describes an experimental investigation of two different novel active control approaches that are employed to suppress combustion instabilities in liquid-fueled combustors. A "fast" active controller requires continuous modulation of the fuel injection rate at the frequency of the instability with proper phase and gain. Use of developed optical tools reveals that the "fast" active control system suppresses the instability by changing the nearly flat distribution of the phase between pressure and heat release oscillations to a gradually varying phase distribution, thus dividing the combustion zone into regions that alternately damp and drive combustor oscillations. The effects of these driving/damping regions tend to counter one another, which result in significant damping of the unstable oscillations. In contrast, a "slow" active controller operates at a rate commensurate with that at which operating conditions change during combustor operation. Consequently, "slow" controllers need infrequent activation in response to changes in engine operating conditions to assure stable operation at all times. Using two types of fuel injectors that can produce large controllable variation of fuel spray properties, it is shown that by changing the spray characteristics it is possible to significantly damp combustion instabilities. Similar to the aforementioned result of the "fast" active control study, "slow" change of the fuel spray properties also modifies the nearly flat phase distribution during unstable operation to a gradually varying phase distribution, resulting in combustor "stabilization". Furthermore, deconvolutions of CH*-chemiluminescence images reveal the presence of vortex-flame interaction during unstable operation. Strong driving of instabilities occurs where the mean axial velocity of the flow is approximately zero, a short distance downstream of the flame holder where a significant fraction of the fuel burns in phase with the pressure oscillations. It is shown that the "fast" and "slow" active control approaches suppress combustion instabilities in a different manner. Nevertheless, the both control approaches successfully suppress combustion instabilities by modifying the temporal and spatial behavior of the combustion process heat release that is responsible for driving the instability.

Afferent control mechanisms involved in the development of soleus fiber alterations in simulated hypogravity

NASA Astrophysics Data System (ADS)

Shenkman, B. S.; Nemirovskaya, T. L.; Shapovalova, K. B.; Podlubnaya, Z. A.; Vikhliantsev, I. M.; Moukhina, A. M.; Kozlovskaya, I. B.

2007-02-01

It was recently established that support withdrawal (withdrawal of support reaction force) in microgravity provokes a sequence of functional shifts in the activity of motor units (inactivation of slow ones) and peripheral muscle apparatus which lead to the decline of postural muscle contractility and alterations in fiber characteristics. However, mechanisms involved in inactivation of the slow motor units and appropriate slow-twitch muscle fiber disuse under the supportless conditions remained unknown. We show here that artificial inactivation of muscles-antagonists (which are known to be hyperactive during unloading) counteracts some of the unloading-induced events in the rat soleus (fiber size reduction, slow-to-fast fiber-type transition and decline of titin and nebulin content). It was also demonstrated that direct activation of the muscarinic receptors of the neostriatum neurons prevented slow-to-fast fiber-type transformation in soleus of hindlimb suspended rats.

The role of fast and slow EEG activity during sleep in males and females with Major Depressive Disorder

PubMed Central

Cheng, Philip; Goldschmied, Jennifer; Deldin, Patricia; Hoffmann, Robert; Armitage, Roseanne

2015-01-01

Sleep difficulties are highly prevalent in depression, and appears to be a contributing factor in the development and maintenance of symptoms. However, despite the generally acknowledged relationship between sleep and depression, the neurophysiological substrates underlying this relationship still remain unclear. Two main hypotheses were tested in this study. The first hypothesis states that sleep in depression is characterized by inadequate generation of restorative sleep, as indexed by reduced amounts of slow-wave activity. Conversely, the second hypothesis states that poor sleep in depression is due to intrusions of fast-frequency activity that may be reflective of a hyperaroused central nervous system. This study aimed to test both hypotheses in a large sample of individuals with clinically validated depression, as well as examine sex as a moderator. Results suggest that depression is better characterized by an overall decrease in slow-wave activity, which is related to elevated anxious and depressed mood the following morning. Results also suggest that females may be more likely to experience fast frequency activity related to depression symptom severity. PMID:26175101

The effect of growth rate on pyrazinamide activity in Mycobacterium tuberculosis - insights for early bactericidal activity?

PubMed

Pullan, Steven T; Allnutt, Jon C; Devine, Rebecca; Hatch, Kim A; Jeeves, Rose E; Hendon-Dunn, Charlotte L; Marsh, Philip D; Bacon, Joanna

2016-05-17

Pyrazinamide (PZA) plays an essential part in the shortened six-month tuberculosis (TB) treatment course due to its activity against slow-growing and non-replicating organisms. We tested whether PZA preferentially targets slow growing cells of Mycobacterium tuberculosis that could be representative of bacteria that remain after the initial kill with isoniazid (INH), by observing the response of either slow growing or fast growing bacilli to differing concentrations of PZA. M. tuberculosis H37Rv was grown in continuous culture at either a constant fast growth rate (Mean Generation Time (MGT) of 23.1 h) or slow growth rate (69.3 h MGT) at a controlled dissolved oxygen tension of 10 % and a controlled acidity at pH 6.3 ± 0.1. Cultures were exposed to step-wise increases in the concentration of PZA (25 to 500 μgml(-1)) every two MGTs, and bacterial survival was measured. PZA-induced global gene expression was explored for each increase in PZA-concentration, using DNA microarray. At a constant pH 6.3, actively dividing mycobacteria were susceptible to PZA, with similar responses to increasing concentrations of PZA at both growth rates. Three distinct phases of drug response could be distingished for both slow growing (69.3 h MGT) and fast growing (23.1 h MGT) bacilli. A bacteriostatic phase at a low concentration of PZA was followed by a recovery period in which the culture adapted to the presence of PZA and bacteria were actively dividing in steady-state. In contrast, there was a rapid loss of viability at bactericidal concentrations. There was a notable delay in the onset of the recovery period in quickly dividing cells compared with those dividing more slowly. Fast growers and slow growers adapted to PZA-exposure via very similar mechanisms; through reduced gene expression of tRNA, 50S, and 30S ribosomal proteins. PZA had an equivalent level of activity against fast growing and slow growing M. tuberculosis. At both growth rates drug-tolerance to sub-lethal concentrations may have been due to reduced expression of tRNA, 50S, and 30S ribosomal proteins. The findings from this study show that PZA has utility against more than one phenotypic sub-population of bacilli and could be re-assessed for its early bactericidal activity, in combination with other drugs, during TB treatment.

[Alkaline phosphatase in Amoeba proteus].

PubMed

Sopina, V A

2005-01-01

In free-living Amoeba proteus (strain B), 3 phosphatase were found after disc-electrophoresis of 10 microg of protein in PAGE and using 1-naphthyl phosphate as a substrate a pH 9.0. These phosphatases differed in their electrophoretic mobilities - "slow" (1-3 bands), "middle" (one band) and "fast" (one band). In addition to 1-naphthyl phosphate, "slow" phosphatases were able to hydrolyse 2-naphthyl phosphate and p-nitrophenyl phosphate. They were slightly activated by Mg2+, completely inhibited by 3 chelators (EDTA, EGTA and 1,10-phenanthroline), L-cysteine, sodium dodecyl sulfate and Fe2+, Zn2+ and Mn2+ (50 mM), considerably inactivated by orthovanadate, molybdate, phosphatase inhibitor cocktail 1, p-nitrophenyl phosphate, Na2HPO4, DL-dithiothreitol and urea and partly inhibited by H2O2, DL-phenylalanine, 2-mercaptoethanol, phosphatase inhibitor cocktail 2 and Ca2+. Imidazole, L-(+)-tartrate, okadaic acid, NaF and sulfhydryl reagents -p-(hydroxy-mercuri)benzoate and N-ethylmaleimide - had no influence on the activity of "slow" phosphatases. "Middle" and "fast" phosphatases, in contrast to "slow" ones, were not inactivated by 3 chelators. The "middle" phosphatase differed from the "fast" one by smaller resistance to urea, Ca2+, Mn2+, phosphates and H2O2 and greater resistance to dithiothreitol and L-(+)-tartrate. In addition, the "fast" phosphatase was inhibited by L-cysteine but the "middle" one was activated by it. Of 5 tested ions (Mg2+, Cu2+, Mn2+, Ca2+ and Zn2+), only Zn2+ reactivated "slow" phosphatases after their inactivation by EDTA treatment. The reactivation of apoenzyme was only partial (about 35 %). Thus, among phosphatases found in amoebae at pH 9.0, only "slow" ones are Zn-metalloenzymes and may be considered as alkaline phosphatases (EC 3.1.3.1). It still remains uncertain, to which particular phosphatase class "middle" and "fast" phosphatases (pH 9.0) may belong.

Calpain activity in fast, slow, transforming, and regenerating skeletal muscles of rat.

PubMed

Sultan, K R; Dittrich, B T; Pette, D

2000-09-01

Fiber-type transitions in adult skeletal muscle induced by chronic low-frequency stimulation (CLFS) encompass coordinated exchanges of myofibrillar protein isoforms. CLFS-induced elevations in cytosolic Ca(2+) could activate proteases, especially calpains, the major Ca(2+)-regulated cytosolic proteases. Calpain activity determined by a fluorogenic substrate in the presence of unaltered endogenous calpastatin activities increased twofold in low-frequency-stimulated extensor digitorum longus (EDL) muscle, reaching a level intermediate between normal fast- and slow-twitch muscles. micro- and m-calpains were delineated by a calpain-specific zymographical assay that assessed total activities independent of calpastatin and distinguished between native and processed calpains. Contrary to normal EDL, structure-bound, namely myofibrillar and microsomal calpains, were abundant in soleus muscle. However, the fast-to-slow conversion of EDL was accompanied by an early translocation of cytosolic micro-calpain, suggesting that myofibrillar and microsomal micro-calpain was responsible for the twofold increase in activity and thus involved in controlled proteolysis during fiber transformation. This is in contrast to muscle regeneration where m-calpain translocation predominated. Taken together, we suggest that translocation is an important step in the control of calpain activity in skeletal muscle in vivo.

Calcium activation of frog slow muscle fibres

PubMed Central

Costantin, L. L.; Podolsky, R. J.; Tice, Lois W.

1967-01-01

1. Skinned muscle fibres were prepared from the tonus bundle of the frog iliofibularis muscle and the contractile response elicited by applied calcium ions was studied. The fibre type was determined by electron microscopy. 2. Fast fibres shortened many times more rapidly than slow fibres, indicating that the slow contraction of slow fibres is an inherent property of the contractile mechanism. 3. The extent of spread of contraction following local calcium application was much greater in slow than in fast fibres, a difference which is consistent with the relative sparsity of the sarcoplasmic reticulum in slow fibres. 4. The ability of the sarcoplasmic reticulum of slow fibres to accumulate calcium was demonstrated by the in situ immobilization of calcium when oxalate solutions were added to the skinned fibre. ImagesPlate 1Plate 2Plate 3Plate 4Plate 5AB PMID:6030519

Depletion of the outer radiation belt during low activity years

NASA Astrophysics Data System (ADS)

Lazutin, Leonid L.

2017-05-01

During the years of high and moderate activity, the energetic flux of electrons at geostationary region increases compensated by the losses and as a result, the overall level of the population persists. The transitions from high to low intensity and back by 3-4 orders of magnitude are fast within hours and caused by the magnetic disturbances, storms and substorms. During the years of the low activity, the balance of increases and losses is violated; the whole flux of electrons is reduced. Particularly noticeable was the devastation of the outer belt during the minimum of 2009-2010 years. The slow type of decreases became most active. The transition from the fast type to the slow type of decreases was created by the prolonged periods of the low substorm activity. The slow type of intensity decreases is mostly probable caused by the losses on the magnetopause.

Crystal plastic earthquakes in dolostones: from slow to fast ruptures.

NASA Astrophysics Data System (ADS)

Passelegue, F. X.; Aubry, J.; Nicolas, A.; Fondriest, M.; Schubnel, A.; Di Toro, G.

2017-12-01

Dolostone is the most dominant lithology of the seismogenic upper crust around the Mediterranean Sea. Understanding the internal mechanisms controlling fault friction is crucial for understanding seismicity along active faults. Displacement in such fault zones is frequently highlighted by highly reflective (mirror-like) slip surfaces, created by thin films of nanogranular fault rock. Using saw-cut dolostone samples coming from natural fault zones, we conducted stick-slip experiments under triaxial loading conditions at 30, 60 and 90 MPa confining pressure and temperature ranging from 30 to 100 degrees C. At 30 and 65 degrees C, only slow rupture was observed and the experimental fault exhibits frictional behaviour, i.e. a dependence of normal stress on peak shear stress. At 65 degrees C, a strengthening behaviour is observed after the main rupture, leading to a succession of slow rupture. At 100 degrees C, the macroscopic behaviour of the fault becomes ductile, and no dependence of pressure on the peak shear stress is observed. In addition, the increase of the confining pressure up to 60 and 90 MPa allow the transition from slow to fast rupture, highlighted by the records of acoustic activity and by dynamic stress drop occurring in a few tens of microseconds. Using strain gages located along the fault surface and acoustic transducers, we were able to measure the rupture velocities during slow and fast rupture. Slow ruptures propagated around 0.1 m/s, in agreement with natural observations. Fast ruptures propagated up to supershear velocities, i.e. faster than the shear wave speed (>3500 m/s). A complete study of the microstructures was realized before and after ruptures. Slow ruptures lead to the production of mirror-like surface driven by the production of nanograins due to dislocation processes. Fast ruptures induce the production of amorphous material along the fault surface, which may come from decarbonation and melting processes. We demonstrate that the transition from slow to fast instabilities is observed due to an increase of the fault stiffness with increasing both temperature and confining pressure. This increase in the stiffness leads to an increase of the slip velocity during the main instability, which allow flash weakening processes and fast propagation of the seismic rupture.

Prdm1a and miR-499 act sequentially to restrict Sox6 activity to the fast-twitch muscle lineage in the zebrafish embryo.

PubMed

Wang, XinGang; Ono, Yosuke; Tan, Swee Chuan; Chai, Ruth JinFen; Parkin, Caroline; Ingham, Philip W

2011-10-01

Sox6 has been proposed to play a conserved role in vertebrate skeletal muscle fibre type specification. In zebrafish, sox6 transcription is repressed in slow-twitch progenitors by the Prdm1a transcription factor. Here we identify sox6 cis-regulatory sequences that drive fast-twitch-specific expression in a Prdm1a-dependent manner. We show that sox6 transcription subsequently becomes derepressed in slow-twitch fibres, whereas Sox6 protein remains restricted to fast-twitch fibres. We find that translational repression of sox6 is mediated by miR-499, the slow-twitch-specific expression of which is in turn controlled by Prdm1a, forming a regulatory loop that initiates and maintains the slow-twitch muscle lineage.

Alterations of rings B and C of colchicine are cumulative in overall binding to tubulin but modify each kinetic step.

PubMed

Dumortier, C; Gorbunoff, M J; Andreu, J M; Engelborghs, Y

1996-12-10

The role of the elimination of ring B and/or the modification of ring C of colchicine in tubulin binding kinetics and thermodynamics has been characterized, using four different molecules. These ligands are colchicine (COL); 2-methoxy-5-(2',3',4'-trimethoxyphenyl)-2,4,6-cycloheptatrien-1-on e (MTC), in which the central ring B has been reduced to one bond; allocolchicine (ALLO), in which ring C has been replaced by a six-membered ring; and 2,3,4-trimethoxy-4'-carbomethoxy-1,1'-biphenyl (TCB), where the same two modifications are made simultaneously. This paper describes the kinetics of association of ALLO with tubulin. The binding is accompanied by a fluorescence increase with slow biphasic kinetics, indicating binding to fast and slow tubulin isotypes. Binding to each of these isotypes occurs in two steps: a fast initial binding followed by a slower isomerization step. The K1 and k2 values for ALLO at 25 degrees C are 14,000 +/- 2,000 and 25,000 +/- 6,000 M-1 (fast and slow isotypes) and 0.055 +/- 0.003 s-1 and 0.013 +/- 0.001 s-1 (fast and slow isotype), respectively. For ALLO the reaction standard enthalpy change of the initial binding is 68 +/- 5 kJ.mol-1 (fast isotype) and 45 +/- 33 kJ.mol-1 (slow isotype) and the activation energy for the second forward step is 58 +/- 14 kJ.mol-1 (fast isotype) and 81 +/- 17 kJ.mol-1 (slow isotype). Displacement kinetics of bound ALLO by podophyllotoxin was monoexponential. The activation energy for the isomerization in the off direction is 107 +/- 7 kJ.mol-1. Comparison of the thermodynamic parameters for all four compounds shows that the modifications of both rings are cumulative with respect to overall binding. For the intermediate state there is a mutual influence of both modifications, suggesting an alteration of the reaction pathway.

Effects of ambient temperature and early open-field response on the behaviour, feed intake and growth of fast- and slow-growing broiler strains.

PubMed

Nielsen, B L

2012-09-01

Increased activity improves broiler leg health, but also increases the heat production of the bird. This experiment investigated the effects of early open-field activity and ambient temperature on the growth and feed intake of two strains of broiler chickens. On the basis of the level of activity in an open-field test on day 3 after hatching, fast-growing Ross 208 and slow-growing i657 chickens were allocated on day 13 to one of the 48 groups. Each group included either six active or six passive birds from each strain and the groups were housed in floor-pens littered with wood chips and fitted with two heat lamps. Each group was fed ad libitum and subjected to one of the three temperature treatments: two (HH; 26°C), one (HC; 16°C to 26°C) or no (CC; 16°C) heat lamps turned on. Production and behavioural data were collected every 2 weeks until day 57. For both strains, early open-field activity had no significant effects on their subsequent behaviour or on any of the production parameters measured, and overall, the slow-growing strain was more active than the fast-growing strain. Ambient temperature had significant effects on production measures for i657 broilers, with CC chickens eating and weighing more, and with a less efficient feed conversion than HH chickens, with HC birds intermediate. A similar effect was found for Ross 208 only for feed intake from 27 to 41 days of age. Ross 208 chickens distributed themselves in the pen with a preference for cooler areas in the hottest ambient temperature treatments. In contrast, the behaviour of the slow-growing strain appeared to be relatively unaffected by the ambient temperature. In conclusion, fast-growing broilers use behavioural changes when trying to adapt to warm environments, whereas slow-growing broilers use metabolic changes to adapt to cooler ambient temperatures.

Physiological changes in fast and slow muscle with simulated weightlessness

NASA Technical Reports Server (NTRS)

Dettbarn, W. D.; Misulis, K. E.

1984-01-01

A rat hindlimb suspension model of simulated weightlessness was used to examine the physiological characteristics of skeletal muscle. The physiological sequelae of hindlimb suspension were compared to those of spinal cord section, denervation by sciatic nerve crush, and control. Muscle examined were the predominantly slow (Type 1) soleus (SOL) and the predominantly fast (Type 2) extensor digitorum longus (EDL). Two procedures which alter motor unit activity, hindlimb suspension and spinal cord section, produce changes in characteristics of skeletal muscles that are dependent upon fiber type. The SOL develops characteristics more representative of a fast muscle, including smaller Type 1 fiber proportion and higher AChE activity. The EDL, which is already predominantly fast, loses most of its few Type 1 fibers, thus also becoming faster. These data are in agreement with the studies in which rats experienced actual weightlessness.

Role of tempo entrainment in psychophysiological differentiation of happy and sad music?

PubMed

Khalfa, Stéphanie; Roy, Mathieu; Rainville, Pierre; Dalla Bella, Simone; Peretz, Isabelle

2008-04-01

Respiration rate allows to differentiate between happy and sad excerpts which may be attributable to entrainment of respiration to the rhythm or the tempo rather than to emotions [Etzel, J.A., Johnsen, E.L., Dickerson, J., Tranel, D., Adolphs, R., 2006. Cardiovascular and respiratory responses during musical mood induction. Int. J. Psychophysiol. 61(1), 57-69]. In order to test for this hypothesis, this study intended to verify whether fast and slow rhythm, and/or tempo alone are sufficient to induce differential physiological effects. Psychophysiological responses (electrodermal responses, facial muscles activity, blood pressure, heart and respiration rate) were then measured in fifty young adults listening to fast/happy and slow/sad music, and to two control versions of these excerpts created by removing pitch variations (rhythmic version) and both pitch and temporal variations (beat-alone). The results indicate that happy and sad music are significantly differentiated (happy>sad) by diastolic blood pressure, electrodermal activity, and zygomatic activity, while the fast and slow rhythmic and tempo control versions did not elicit such differentiations. In contrast, respiration rate was faster with stimuli presented at fast tempi relative to slow stimuli in the beat-alone condition. It was thus demonstrated that the psychophysiological happy/sad distinction requires the tonal variations and cannot be explained solely by entrainment to tempo and rhythm. The tempo entrainment exists in the tempo alone condition but our results suggest this effect may disappear when embedded in music or with rhythm.

Selective Coupling between Theta Phase and Neocortical Fast Gamma Oscillations during REM-Sleep in Mice

PubMed Central

Scheffzük, Claudia; Kukushka, Valeriy I.; Vyssotski, Alexei L.; Draguhn, Andreas

2011-01-01

Background The mammalian brain expresses a wide range of state-dependent network oscillations which vary in frequency and spatial extension. Such rhythms can entrain multiple neurons into coherent patterns of activity, consistent with a role in behaviour, cognition and memory formation. Recent evidence suggests that locally generated fast network oscillations can be systematically aligned to long-range slow oscillations. It is likely that such cross-frequency coupling supports specific tasks including behavioural choice and working memory. Principal Findings We analyzed temporal coupling between high-frequency oscillations and EEG theta activity (4–12 Hz) in recordings from mouse parietal neocortex. Theta was exclusively present during active wakefulness and REM-sleep. Fast oscillations occurred in two separate frequency bands: gamma (40–100 Hz) and fast gamma (120–160 Hz). Theta, gamma and fast gamma were more prominent during active wakefulness as compared to REM-sleep. Coupling between theta and the two types of fast oscillations, however, was more pronounced during REM-sleep. This state-dependent cross-frequency coupling was particularly strong for theta-fast gamma interaction which increased 9-fold during REM as compared to active wakefulness. Theta-gamma coupling increased only by 1.5-fold. Significance State-dependent cross-frequency-coupling provides a new functional characteristic of REM-sleep and establishes a unique property of neocortical fast gamma oscillations. Interactions between defined patterns of slow and fast network oscillations may serve selective functions in sleep-dependent information processing. PMID:22163023

Myosin isoforms and contractile properties of single fibers of human Latissimus Dorsi muscle.

PubMed

Paoli, Antonio; Pacelli, Quirico F; Cancellara, Pasqua; Toniolo, Luana; Moro, Tatiana; Canato, Marta; Miotti, Danilo; Reggiani, Carlo

2013-01-01

The aim of our study was to investigate fiber type distribution and contractile characteristics of Latissimus Dorsi muscle (LDM). Samples were collected from 18 young healthy subjects (9 males and 9 females) through percutaneous fine needle muscle biopsy. The results showed a predominance of fast myosin heavy chain isoforms (MyHC) with 42% of MyHC 2A and 25% of MyHC 2X, while MyHC 1 represented only 33%. The unbalance toward fast isoforms was even greater in males (71%) than in females (64%). Fiber type distribution partially reflected MyHC isoform distribution with 28% type 1/slow fibers and 5% hybrid 1/2A fibers, while fast fibers were divided into 30% type 2A, 31% type A/X, 4% type X, and 2% type 1/2X. Type 1/slow fibers were not only less abundant but also smaller in cross-sectional area than fast fibers. During maximal isometric contraction, type 1/slow fibers developed force and tension significantly lower than the two major groups of fast fibers. In conclusion, the predominance of fast fibers and their greater size and strength compared to slow fibers reveal that LDM is a muscle specialized mainly in phasic and powerful activity. Importantly, such specialization is more pronounced in males than in females.

Eslicarbazepine and the enhancement of slow inactivation of voltage-gated sodium channels: a comparison with carbamazepine, oxcarbazepine and lacosamide.

PubMed

Hebeisen, Simon; Pires, Nuno; Loureiro, Ana I; Bonifácio, Maria João; Palma, Nuno; Whyment, Andrew; Spanswick, David; Soares-da-Silva, Patrício

2015-02-01

This study aimed at evaluating the effects of eslicarbazepine, carbamazepine (CBZ), oxcarbazepine (OXC) and lacosamide (LCM) on the fast and slow inactivated states of voltage-gated sodium channels (VGSC). The anti-epileptiform activity was evaluated in mouse isolated hippocampal slices. The anticonvulsant effects were evaluated in MES and the 6-Hz psychomotor tests. The whole-cell patch-clamp technique was used to investigate the effects of eslicarbazepine, CBZ, OXC and LCM on sodium channels endogenously expressed in N1E-115 mouse neuroblastoma cells. CBZ and eslicarbazepine exhibit similar concentration dependent suppression of epileptiform activity in hippocampal slices. In N1E-115 mouse neuroblastoma cells, at a concentration of 250 μM, the voltage dependence of the fast inactivation was not influenced by eslicarbazepine, whereas LCM, CBZ and OXC shifted the V0.5 value (mV) by -4.8, -12.0 and -16.6, respectively. Eslicarbazepine- and LCM-treated fast-inactivated channels recovered similarly to control conditions, whereas CBZ- and OXC-treated channels required longer pulses to recover. CBZ, eslicarbazepine and LCM shifted the voltage dependence of the slow inactivation (V0.5, mV) by -4.6, -31.2 and -53.3, respectively. For eslicarbazepine, LCM, CBZ and OXC, the affinity to the slow inactivated state was 5.9, 10.4, 1.7 and 1.8 times higher than to the channels in the resting state, respectively. In conclusion, eslicarbazepine did not share with CBZ and OXC the ability to alter fast inactivation of VGSC. Both eslicarbazepine and LCM reduce VGSC availability through enhancement of slow inactivation, but LCM demonstrated higher interaction with VGSC in the resting state and with fast inactivation gating. Copyright © 2014 Elsevier Ltd. All rights reserved.

Modeling of the Modulation by Buffers of Ca2+ Release through Clusters of IP3 Receptors

PubMed Central

Zeller, S.; Rüdiger, S.; Engel, H.; Sneyd, J.; Warnecke, G.; Parker, I.; Falcke, M.

2009-01-01

Abstract Intracellular Ca2+ release is a versatile second messenger system. It is modeled here by reaction-diffusion equations for the free Ca2+ and Ca2+ buffers, with spatially discrete clusters of stochastic IP3 receptor channels (IP3Rs) controlling the release of Ca2+ from the endoplasmic reticulum. IP3Rs are activated by a small rise of the cytosolic Ca2+ concentration and inhibited by large concentrations. Buffering of cytosolic Ca2+ shapes global Ca2+ transients. Here we use a model to investigate the effect of buffers with slow and fast reaction rates on single release spikes. We find that, depending on their diffusion coefficient, fast buffers can either decouple clusters or delay inhibition. Slow buffers have little effect on Ca2+ release, but affect the time course of the signals from the fluorescent Ca2+ indicator mainly by competing for Ca2+. At low [IP3], fast buffers suppress fluorescence signals, slow buffers increase the contrast between bulk signals and signals at open clusters, and large concentrations of buffers, either fast or slow, decouple clusters. PMID:19686646

Amygdala kindling-resistant (SLOW) or -prone (FAST) rat strains show differential fear responses.

PubMed

Mohapel, P; McIntyre, D C

1998-12-01

The authors compared two rat strains, selectively bred for their susceptibility to amygdala kindling, with respect to their performance on various behavioral and learning tasks that are associated with fear and anxiety. The two rat strains differed significantly in measurements of exploration of novel and familiar environments, as well as in reactivity to footshock and fear-based learning. The kindling-resistant (SLOW) strain exhibited a lower ratio of open- to closed-arm entries in the elevated plus-maze, less activity over days in the open field, greater behavioral suppression in the open-field if previously footshocked, greater freezing in the inhibitory avoidance task, and slower acquisition and poorer retention in the one-way avoidance task than did the kindling-prone (FAST) strain. These experiments suggest that the SLOW rats are more expressively fearful than the FAST rats, particularly with respect to environmentally triggered freezing or immobility. Further, these observations imply that the relatively constrained excitability of the amygdala network in the SLOW rats might mediate their relatively greater expression of fear and anxiety compared with the FAST rats.

Muscle mechanics: adaptations with exercise-training.

PubMed

Fitts, R H; Widrick, J J

1996-01-01

Based on the MHC isoform pattern, adult mammalian limb skeletal muscles contain two and, in some species, three types of fast fibers (Type IIa, IIx, and IIb), and one slow fiber (Type I). Slow muscles, such as the soleus, contain primarily the slow Type I fiber, whereas fast-twitch muscles are composed primarily of a mixture of the fast myosin isozymes. Force generation involves cross-bridge interaction and transition from a weakly bound, low-force state (AM-ADP-P(i)) to the strongly bound, high-force state (AM-ADP). This transition is thought to be rate limiting in terms of dP/dt, and the high-force state is the dominant cross-bridge form during a peak isometric contraction. Intact fast and slow skeletal muscles generate approximately the same amount of peak force (Po) of between 200 and 250 kN.m-2. However, the rate of transition from the low- to high-force state shows Ca2+ sensitivity and is 7-fold higher in fast-twitch, as compared to slow-twitch, skeletal muscle fibers. Fiber Vo or the maximal cross-bridge cycle rate is highly correlated with and thought to be dependent on the specific activity of the myosin or myofibrillar ATPase. The hierarchy for Vo is the Type IIb > IIx > IIa > I. This functional difference for the fast fiber types explains the higher Vo observed in the predominantly Type IIb SVL vs. the mixed fast Type IIa and IIb EDL muscle. A plot of Vo vs. species size demonstrates that an inverse relationship exists between Vo and body mass. From the standpoint of work capacity, the important property is power output. An analysis of individual muscles indicates that peak power is obtained at loads considerably below 50% of Po. Individuals with a high percentage of fast-twitch fibers generate a greater torque and higher power at a given velocity than those with predominantly slow-twitch fibers. In humans, mean peak power occurred in a ratio of 10:5:1 for the Type IIb, IIa, and I fibers. The in vivo measurement of the torque-velocity relationship and Vmax in human muscle is difficult because of limitations inherent in the equipment used and the inability to study the large limb muscles independently. Nevertheless, the in vivo torque-velocity relationships are similar to those measured in vitro in animals. This observation suggests that little central nervous system inhibition exists and that healthy subjects are able to achieve maximal activation of their muscles. Although peak isometric tension is not dependent on fiber type distribution, a positive correlation exists between the percentage of fast fibers and peak torque output at moderate-to-high angular isokinetic velocities. Consequently, peak power output is substantially greater in subjects possessing a predominance of fast fibers. The mechanical properties of slow and fast muscles do adapt to programs of regular exercise. Endurance exercise training has been shown to increase the Vo of the slow soleus by 20%. This increase could have been caused by either a small increase in all, or most, of the fibers, or to a conversion of a few fibers from slow to fast. Recently, the increase was shown to be caused by the former, as the individual slow Type I fibers of the soleus showed a 20% increase in Vo, but there was little or no change in the percentage of fast fibers. The increased Vo was correlated with, and likely caused by, an increased fiber ATPase. We hypothesize that the increased ATPase and cross-bridge cycling speed might be attributable to an increased expression of fast MLCs in the slow Type I fibers (Fig. 14.10). This hypothesis is based on the fact that light chains have been shown to be involved in the power stroke, and removal of light chains depresses force and velocity. Regular endurance exercise training had no effect on fiber size, but with prolonged durations of daily training it depressed Po and peak power. When the training is maintained over prolonged periods, it may even induce atrophy of the slow Type I and fast Type IIa fibers. (ABSTRACT TRUNCATED)

Use it or Lose It: Tonic Activity of Slow Motoneurons Promotes Their Survival and Preferentially Increases Slow Fiber-Type Groupings in Muscles of Old Lifelong Recreational Sportsmen

PubMed Central

Mosole, Simone; Carraro, Ugo; Kern, Helmut; Loefler, Stefan; Zampieri, Sandra

2016-01-01

Histochemistry, immuno-histochemistry, gel electrophoresis of single muscle fibers and electromyography of aging muscles and nerves suggest that: i) denervation contributes to muscle atrophy, ii) impaired mobility accelerates the process, and iii) lifelong running protects against loss of motor units. Recent corroborating results on the muscle effects of Functional Electrical Stimulation (FES) of aged muscles will be also mentioned, but we will in particular discuss how and why a lifelong increased physical activity sustains reinnervation of muscle fibers. By analyzing distribution and density of muscle fibers co-expressing fast and slow Myosin Heavy Chains (MHC) we are able to distinguish the transforming muscle fibers due to activity related plasticity, to those that adapt muscle fiber properties to denervation and reinnervation. In muscle biopsies from septuagenarians with a history of lifelong high-level recreational activity we recently observed in comparison to sedentary seniors: 1. decreased proportion of small-size angular myofibers (denervated muscle fibers); 2. considerable increase of fiber-type groupings of the slow type (reinnervated muscle fibers); 3. sparse presence of muscle fibers co-expressing fast and slow MHC. Immuno-histochemical characteristics fluctuate from those with scarce fiber-type modulation and groupings to almost complete transformed muscles, going through a process in which isolated fibers co-expressing fast and slow MHC fill the gaps among fiber groupings. Data suggest that lifelong high-level exercise allows the body to adapt to the consequences of the age-related denervation and that it preserves muscle structure and function by saving otherwise lost muscle fibers through recruitment to different slow motor units. This is an opposite behavior of that described in long term denervated or resting muscles. These effects of lifelong high level activity seems to act primarily on motor neurons, in particular on those always more active, i.e., on the slow motoneurons. The preferential reinnervation that follows along decades of increased activity maintains neuron and myofibers. All together the results open interesting perspectives for applications of FES and electroceuticals for rejuvenation of aged muscles to delay functional decline and loss of independence that are unavoidable burdens of advanced aging. Trial Registration: ClinicalTrials.gov: NCT01679977 PMID:28078066

Use it or Lose It: Tonic Activity of Slow Motoneurons Promotes Their Survival and Preferentially Increases Slow Fiber-Type Groupings in Muscles of Old Lifelong Recreational Sportsmen.

PubMed

Mosole, Simone; Carraro, Ugo; Kern, Helmut; Loefler, Stefan; Zampieri, Sandra

2016-09-15

Histochemistry, immuno-histochemistry, gel electrophoresis of single muscle fibers and electromyography of aging muscles and nerves suggest that: i) denervation contributes to muscle atrophy, ii) impaired mobility accelerates the process, and iii) lifelong running protects against loss of motor units. Recent corroborating results on the muscle effects of Functional Electrical Stimulation (FES) of aged muscles will be also mentioned, but we will in particular discuss how and why a lifelong increased physical activity sustains reinnervation of muscle fibers. By analyzing distribution and density of muscle fibers co-expressing fast and slow Myosin Heavy Chains (MHC) we are able to distinguish the transforming muscle fibers due to activity related plasticity, to those that adapt muscle fiber properties to denervation and reinnervation. In muscle biopsies from septuagenarians with a history of lifelong high-level recreational activity we recently observed in comparison to sedentary seniors: 1. decreased proportion of small-size angular myofibers (denervated muscle fibers); 2. considerable increase of fiber-type groupings of the slow type (reinnervated muscle fibers); 3. sparse presence of muscle fibers co-expressing fast and slow MHC. Immuno-histochemical characteristics fluctuate from those with scarce fiber-type modulation and groupings to almost complete transformed muscles, going through a process in which isolated fibers co-expressing fast and slow MHC fill the gaps among fiber groupings. Data suggest that lifelong high-level exercise allows the body to adapt to the consequences of the age-related denervation and that it preserves muscle structure and function by saving otherwise lost muscle fibers through recruitment to different slow motor units. This is an opposite behavior of that described in long term denervated or resting muscles. These effects of lifelong high level activity seems to act primarily on motor neurons, in particular on those always more active, i.e., on the slow motoneurons. The preferential reinnervation that follows along decades of increased activity maintains neuron and myofibers. All together the results open interesting perspectives for applications of FES and electroceuticals for rejuvenation of aged muscles to delay functional decline and loss of independence that are unavoidable burdens of advanced aging. ClinicalTrials.gov: NCT01679977.

Inflammation-induced increase in nicotinic acetylcholine receptor current in cutaneous nociceptive DRG neurons from the adult rat.

PubMed

Zhang, X-L; Albers, K M; Gold, M S

2015-01-22

The goals of the present study were to determine (1) the properties of the nicotinic acetylcholine receptor (nAChR) currents in rat cutaneous dorsal root ganglion (DRG) neurons; (2) the impact of nAChR activation on the excitability of cutaneous DRG neurons; and (3) the impact of inflammation on the density and distribution of nAChR currents among cutaneous DRG neurons. Whole-cell patch-clamp techniques were used to study retrogradely labeled DRG neurons from naïve and complete Freund's adjuvant inflamed rats. Nicotine-evoked currents were detectable in ∼70% of the cutaneous DRG neurons, where only one of two current types, fast or slow currents based on rates of activation and inactivation, was present in each neuron. The biophysical and pharmacological properties of the fast current were consistent with nAChRs containing an α7 subunit while those of the slow current were consistent with nAChRs containing α3/β4 subunits. The majority of small diameter neurons with fast current were IB4- while the majority of small diameter neurons with slow current were IB4+. Preincubation with nicotine (1 μM) produced a transient (1 min) depolarization and increase in the excitability of neurons with fast current and a decrease in the amplitude of capsaicin-evoked current in neurons with slow current. Inflammation increased the current density of both slow and fast currents in small diameter neurons and increased the percentage of neurons with the fast current. With the relatively selective distribution of nAChR currents in putative nociceptive cutaneous DRG neurons, our results suggest that the role of these receptors in inflammatory hyperalgesia is likely to be complex and dependent on the concentration and timing of acetylcholine release in the periphery. Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights reserved.

Least-rattling feedback from strong time-scale separation

NASA Astrophysics Data System (ADS)

Chvykov, Pavel; England, Jeremy

2018-03-01

In most interacting many-body systems associated with some "emergent phenomena," we can identify subgroups of degrees of freedom that relax on dramatically different time scales. Time-scale separation of this kind is particularly helpful in nonequilibrium systems where only the fast variables are subjected to external driving; in such a case, it may be shown through elimination of fast variables that the slow coordinates effectively experience a thermal bath of spatially varying temperature. In this paper, we investigate how such a temperature landscape arises according to how the slow variables affect the character of the driven quasisteady state reached by the fast variables. Brownian motion in the presence of spatial temperature gradients is known to lead to the accumulation of probability density in low-temperature regions. Here, we focus on the implications of attraction to low effective temperature for the long-term evolution of slow variables. After quantitatively deriving the temperature landscape for a general class of overdamped systems using a path-integral technique, we then illustrate in a simple dynamical system how the attraction to low effective temperature has a fine-tuning effect on the slow variable, selecting configurations that bring about exceptionally low force fluctuation in the fast-variable steady state. We furthermore demonstrate that a particularly strong effect of this kind can take place when the slow variable is tuned to bring about orderly, integrable motion in the fast dynamics that avoids thermalizing energy absorbed from the drive. We thus point to a potentially general feedback mechanism in multi-time-scale active systems, that leads to the exploration of slow variable space, as if in search of fine tuning for a "least-rattling" response in the fast coordinates.

Two fast-type fibers in claw closer and abdominal deep muscles of the Australian freshwater crustacean, Cherax destructor, differ in Ca2+ sensitivity and troponin-I isoforms.

PubMed

Koenders, Annette; Lamey, Tina M; Medler, Scott; West, Jan M; Mykles, Donald L

2004-07-01

One type of fast fiber and two types of slow (slow-twitch, S1 and slow-tonic, S2) fibers are found in decapod crustacean skeletal muscles that differ in contractile properties and myofibrillar protein isoform compositions. In this study the structural characteristics, protein isoform compositions, and Ca2+-activation properties of fast fibers in the claw closer (F1) and abdominal deep flexor (F2) muscles of Cherax destructor were analyzed. For comparison, myofibrillar protein isoform compositions of slow (long-sarcomere) fibers from claw and abdomen were also determined; our results indicate that the slow fibers in the claw closer were the slow-twitch (S1) type and those in the abdominal superficial flexor were primarily slow-tonic (S2) type. F1 fibers had shorter resting sarcomere lengths (2.93 microm in unstretched fibers and 3.06 microm in stretched fibers) and smaller fiber diameter (256 microm) than F2 fibers (sarcomere lengths 3.48 microm in unstretched and 3.46 microm in stretched; 747 microm diameter). Moreover, F1 fibers showed a narrower range in sarcomere lengths than F2 fibers (2.81 to 3.28 microm vs. 2.47 to 4.05 micro m in unstretched fibers). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting showed that the fast fibers from claw and abdomen differed in troponin-I composition; F1 fibers expressed two isoforms of troponin-I (TnI1 and TnI2) in approximately equal amounts, whereas F2 fibers expressed primarily TnI3 and lower levels of TnI1. F1 fibers were more sensitive to Ca2+, as shown by higher pCa values at threshold activation (pCa(10)=6.50+/-0.07) and at 50% maximum force (pCa(50)=6.43+/-0.07) than F2 fibers (pCa(10)=6.12+/-0.04 and pCa(50)=5.88+/-0.03, respectively). F1 fibers also had a greater degree of co-operativity in Ca2+ activation, as shown by a higher maximum slope of the force-pCa curve (n(Ca)=12.98+/-2.27 vs. 4.34+/-0.64). These data indicate that there is a greater fast fiber-type diversity in crustacean muscles than was previously supposed. Moreover, the differences in activation properties suggest that the TnI isoform composition influences the Ca2+ sensitivity of the contractile mechanism. Copyright 2004 Wiley-Liss, Inc.

Slow Magnetosonic Waves and Fast Flows in Active Region Loops

NASA Technical Reports Server (NTRS)

Ofman, L.; Wang, T. J.; Davila, J. M.

2012-01-01

Recent extreme ultraviolet spectroscopic observations indicate that slow magnetosonic waves are present in active region (AR) loops. Some of the spectral data were also interpreted as evidence of fast (approx 100-300 km/s) quasiperiodic flows. We have performed three-dimensional magnetohydrodynamic (3D MHD) modeling of a bipolar AR that contains impulsively generated waves and flows in coronal loops. The model AR is initiated with a dipole magnetic field and gravitationally stratified density, with an upflow-driven steadily or periodically in localized regions at the footpoints of magnetic loops. The resulting flows along the magnetic field lines of the AR produce higher density loops compared to the surrounding plasma by injection of material into the flux tubes and the establishment of siphon flow.We find that the impulsive onset of flows with subsonic speeds result in the excitation of damped slow magnetosonic waves that propagate along the loops and coupled nonlinearly driven fast-mode waves. The phase speed of the slow magnetosonic waves is close to the coronal sound speed. When the amplitude of the driving pulses is increased we find that slow shock-like wave trains are produced. When the upflows are driven periodically, undamped oscillations are produced with periods determined by the periodicity of the upflows. Based on the results of the 3D MHD model we suggest that the observed slow magnetosonic waves and persistent upflows may be produced by the same impulsive events at the bases of ARs.

Inter- and Intrasubject Similarity of Muscle Synergies During Bench Press With Slow and Fast Velocity.

PubMed

Samani, Afshin; Kristiansen, Mathias

2018-01-01

We investigated the effect of low and high bar velocity on inter- and intrasubject similarity of muscle synergies during bench press. A total of 13 trained male subjects underwent two exercise conditions: a slow- and a fast-velocity bench press. Surface electromyography was recorded from 13 muscles, and muscle synergies were extracted using a nonnegative matrix factorization algorithm. The intrasubject similarity across conditions and intersubject similarity within conditions were computed for muscle synergy vectors and activation coefficients. Two muscle synergies were sufficient to describe the dataset variability. For the second synergy activation coefficient, the intersubject similarity within the fast-velocity condition was greater than the intrasubject similarity of the activation coefficient across the conditions. An opposite pattern was observed for the first muscle synergy vector. We concluded that the activation coefficients are robust within conditions, indicating a robust temporal pattern of muscular activity across individuals, but the muscle synergy vector seemed to be individually assigned.

Comparison of Cryopreservation Protocols (Single and Two-steps) and Thawing (Fast and Slow) for Canine Sperm.

PubMed

Brito, Maíra M; Lúcio, Cristina F; Angrimani, Daniel S R; Losano, João Diego A; Dalmazzo, Andressa; Nichi, Marcílio; Vannucchi, Camila I

2017-01-02

In addition to the existence of several cryopreservation protocols, no systematic research has been carried out in order to confirm the suitable protocol for canine sperm. This study aims to assess the effect of adding 5% glycerol during cryopreservation at 37°C (one-step) and 5°C (two-steps), in addition of testing two thawing protocols (37°C for 30 seconds, and 70°C for 8 seconds). We used 12 sperm samples divided into four experimental groups: Single-Step - Slow Thawing Group; Two-Step - Slow Thawing Group; Single-Step - Fast Thawing Group; and Two-Step - Fast Thawing Group. Frozen-thawed samples were submitted to automated analysis of sperm motility, evaluation of plasmatic membrane integrity, acrosomal integrity, mitochondrial activity, sperm morphology, sperm susceptibility to oxidative stress, and sperm binding assay to perivitellinic membrane of chicken egg yolk. Considering the comparison between freezing protocols, no statistical differences were verified for any of the response variables. When comparison between thawing protocols was performed, slow thawing protocol presented higher sperm count bound to perivitelline membrane of chicken egg yolk, compared to fast thawing protocol. Regardless of the freezing process, the slow thawing protocol can be recommended for the large scale cryopreservation of canine semen, since it shows a consistent better functional result.

[Phosphatase activity in Amoeba proteus at pH 9.0].

PubMed

Sopina, V A

2007-01-01

In the free-living amoeba Amoeba proteus (strain B), after PAAG disk-electrophoresis of the homogenate supernatant, at using 1-naphthyl phosphate as a substrate and pH 9.0, three forms of phosphatase activity were revealed; they were arbitrarily called "fast", "intermediate", and "slow" phosphatases. The fast phosphatase has been established to be a fraction of lysosomal acid phosphatase that preserves some low activity at alkaline pH. The question as to which particular class the intermediate phosphatase belongs to has remained unanswered: it can be both acid phosphatase and protein tyrosine phosphatase (PTP). Based on data of inhibitor analysis, large substrate specificity, results of experiments with reactivation by Zn ions after inactivation with EDTA, other than in the fast and intermediate phosphatases localization in the amoeba cell, it is concluded that only slow phosphatase can be classified as alkaline phosphatase (EC 3.1.3.1).

The effects of ramp stretches on active contractions in intact mammalian fast and slow muscle fibres.

PubMed

Mutungi, G; Ranatunga, K W

2001-01-01

The effects of a ramp stretch (amplitude <6% muscle fibre length (L0), speed < 13L0 s(-1)) on twitch tension and twitch tension re-development were examined in intact mammalian (rat) fast and slow muscle fibre bundles. The experiments were done in vitro at 20 degrees C and at an initial sarcomere length of 2.68 microm. In both fibre types, a stretch applied during the rising phase of the twitch response (including the time of stimulation) increased the re-developed twitch tension (15-35%). A stretch applied before the stimulus had little or no effect on the twitch myogram in fast muscle fibres, but it increased the twitch tension (approximately 5%) in slow muscle fibres. A similar stretch had little or no effect on tetanic tension in either muscle fibre type. In general, the results indicate that the contractile-activation mechanism may be stretch sensitive and this is particularly pronounced in slow muscle fibres. Recorded at a high sampling rate and examined at an appropriate time scale, the transitory tension response to a stretch rose in at least two phases; an initial rapid tension rise to a break (break point tension, P1a) followed by a slower tension rise (apparent P2a) to a peak reached at the end of the stretch. Plotted against stretch velocity, P1a tension increased in direct proportion to stretch velocity (viscous-like) whereas, P2a tension (calculated as peak tension minus P1a tension) increased with stretch velocity to a plateau (visco-elastic). Examined at the peak of a twitch, P1a tension had a slope (viscosity coefficient) of 1.8 kN m(-2) per L0 s(-1) in fast fibres and 4.7 kN m(-2) per L0 s(-1) in slow muscle fibres. In the same preparations, P2a tension had a relaxation time of 8 ms in the fast muscle fibres and 25 ms in the slow muscle fibres. The amplitudes of both tension components scaled with the instantaneous twitch tension in qualitatively the same way as the instantaneous fibre stiffness. These fast/slow fibre type differences probably reflect differences in their cross-bridge kinetics.

Left–right coordination from simple to extreme conditions during split‐belt locomotion in the chronic spinal adult cat

PubMed Central

Desrochers, Étienne; Thibaudier, Yann; Hurteau, Marie‐France; Dambreville, Charline

2016-01-01

Key points Coordination between the left and right sides is essential for dynamic stability during locomotion.The immature or neonatal mammalian spinal cord can adjust to differences in speed between the left and right sides during split‐belt locomotion by taking more steps on the fast side.We show that the adult mammalian spinal cord can also adjust its output so that the fast side can take more steps.During split‐belt locomotion, only certain parts of the cycle are modified to adjust left–right coordination, primarily those associated with swing onset.When the fast limb takes more steps than the slow limb, strong left–right interactions persist.Therefore, the adult mammalian spinal cord has a remarkable adaptive capacity for left–right coordination, from simple to extreme conditions. Abstract Although left–right coordination is essential for locomotion, its control is poorly understood, particularly in adult mammals. To investigate the spinal control of left–right coordination, a spinal transection was performed in six adult cats that were then trained to recover hindlimb locomotion. Spinal cats performed tied‐belt locomotion from 0.1 to 1.0 m s−1 and split‐belt locomotion with low to high (1:1.25–10) slow/fast speed ratios. With the left hindlimb stepping at 0.1 m s−1 and the right hindlimb stepping from 0.2 to 1.0 m s−1, 1:1, 1:2, 1:3, 1:4 and 1:5 left–right step relationships could appear. The appearance of 1:2+ relationships was not linearly dependent on the difference in speed between the slow and fast belts. The last step taken by the fast hindlimb displayed longer cycle, stance and swing durations and increased extensor activity, as the slow limb transitioned to swing. During split‐belt locomotion with 1:1, 1:2 and 1:3 relationships, the timing of stance onset of the fast limb relative to the slow limb and placement of both limbs at contact were invariant with increasing slow/fast speed ratios. In contrast, the timing of stance onset of the slow limb relative to the fast limb and the placement of both limbs at swing onset were modulated with slow/fast speed ratios. Thus, left–right coordination is adjusted by modifying specific parts of the cycle. Results highlight the remarkable adaptive capacity of the adult mammalian spinal cord, providing insight into spinal mechanisms and sensory signals regulating left–right coordination. PMID:27426732

Suppression of chaos at slow variables by rapidly mixing fast dynamics

NASA Astrophysics Data System (ADS)

Abramov, R.

2012-04-01

One of the key questions about chaotic multiscale systems is how the fast dynamics affects chaos at the slow variables, and, therefore, impacts uncertainty and predictability of the slow dynamics. Here we demonstrate that the linear slow-fast coupling with the total energy conservation property promotes the suppression of chaos at the slow variables through the rapid mixing at the fast variables, both theoretically and through numerical simulations. A suitable mathematical framework is developed, connecting the slow dynamics on the tangent subspaces to the infinite-time linear response of the mean state to a constant external forcing at the fast variables. Additionally, it is shown that the uncoupled dynamics for the slow variables may remain chaotic while the complete multiscale system loses chaos and becomes completely predictable at the slow variables through increasing chaos and turbulence at the fast variables. This result contradicts the common sense intuition, where, naturally, one would think that coupling a slow weakly chaotic system with another much faster and much stronger mixing system would result in general increase of chaos at the slow variables.

Intracellular calcium movements during excitation–contraction coupling in mammalian slow-twitch and fast-twitch muscle fibers

PubMed Central

Hollingworth, Stephen

2012-01-01

In skeletal muscle fibers, action potentials elicit contractions by releasing calcium ions (Ca2+) from the sarcoplasmic reticulum. Experiments on individual mouse muscle fibers micro-injected with a rapidly responding fluorescent Ca2+ indicator dye reveal that the amount of Ca2+ released is three- to fourfold larger in fast-twitch fibers than in slow-twitch fibers, and the proportion of the released Ca2+ that binds to troponin to activate contraction is substantially smaller. PMID:22450485

Quantifying Fast and Slow Responses of Terrestrial Carbon Exchange across a Water Availability Gradient in North American Flux Sites

NASA Astrophysics Data System (ADS)

Biederman, J. A.; Scott, R. L.; Goulden, M.

2014-12-01

Climate change is predicted to increase the frequency and severity of water limitation, altering terrestrial ecosystems and their carbon exchange with the atmosphere. Here we compare site-level temporal sensitivity of annual carbon fluxes to interannual variations in water availability against cross-site spatial patterns over a network of 19 eddy covariance flux sites. This network represents one order of magnitude in mean annual productivity and includes western North American desert shrublands and grasslands, savannahs, woodlands, and forests with continuous records of 4 to 12 years. Our analysis reveals site-specific patterns not identifiable in prior syntheses that pooled sites. We interpret temporal variability as an indicator of ecosystem response to annual water availability due to fast-changing factors such as leaf stomatal response and microbial activity, while cross-site spatial patterns are used to infer ecosystem adjustment to climatic water availability through slow-changing factors such as plant community and organic carbon pools. Using variance decomposition, we directly quantify how terrestrial carbon balance depends on slow- and fast-changing components of gross ecosystem production (GEP) and total ecosystem respiration (TER). Slow factors explain the majority of variance in annual net ecosystem production (NEP) across the dataset, and their relative importance is greater at wetter, forest sites than desert ecosystems. Site-specific offsets from spatial patterns of GEP and TER explain one third of NEP variance, likely due to slow-changing factors not directly linked to water, such as disturbance. TER and GEP are correlated across sites as previously shown, but our site-level analysis reveals surprisingly consistent linear relationships between these fluxes in deserts and savannahs, indicating fast coupling of TER and GEP in more arid ecosystems. Based on the uncertainty associated with slow and fast factors, we suggest a framework for improved prediction of terrestrial carbon balance. We will also present results of ongoing work to quantify fast and slow contributions to the relationship between evapotranspiration and precipitation across a precipitation gradient.

Functional properties of slow and fast gastrocnemius muscle fibers after a 17-day spaceflight

NASA Technical Reports Server (NTRS)

Widrick, J. J.; Romatowski, J. G.; Norenberg, K. M.; Knuth, S. T.; Bain, J. L.; Riley, D. A.; Trappe, S. W.; Trappe, T. A.; Costill, D. L.; Fitts, R. H.

2001-01-01

The purpose of this investigation was to study the effects of a 17-day spaceflight on the contractile properties of individual fast- and slow-twitch fibers isolated from biopsies of the fast-twitch gastrocnemius muscle of four male astronauts. Single chemically skinned fibers were studied during maximal Ca2+-activated contractions with fiber myosin heavy chain (MHC) isoform expression subsequently determined by SDS gel electrophoresis. Spaceflight had no significant effect on the mean diameter or specific force of single fibers expressing type I, IIa, or IIa/IIx MHC, although a small reduction in average absolute force (P(o)) was observed for the type I fibers (0.68 +/- 0.02 vs. 0.64 +/- 0.02 mN, P < 0.05). Subject-by-flight interactions indicated significant intersubject variation in response to the flight, as postflight fiber diameter and P(o) where significantly reduced for the type I and IIa fibers obtained from one astronaut and for the type IIa fibers from another astronaut. Average unloaded shortening velocity [V(o), in fiber lengths (FL)/s] was greater after the flight for both type I (0.60 +/- 0.03 vs. 0.76 +/- 0.02 FL/s) and IIa fibers (2.33 +/- 0.25 vs. 3.10 +/- 0.16 FL/s). Postflight peak power of the type I and IIa fibers was significantly reduced only for the astronaut experiencing the greatest fiber atrophy and loss of P(o). These results demonstrate that 1) slow and fast gastrocnemius fibers show little atrophy and loss of P(o) but increased V(o) after a typical 17-day spaceflight, 2) there is, however, considerable intersubject variation in these responses, possibly due to intersubject differences in in-flight physical activity, and 3) in these four astronauts, fiber atrophy and reductions in P(o) were less for slow and fast fibers obtained from the phasic fast-twitch gastrocnemius muscle compared with slow and fast fibers obtained from the slow antigravity soleus [J. J. Widrick, S. K. Knuth, K. M. Norenberg, J. G. Romatowski, J. L. W. Bain, D. A. Riley, M. Karhanek, S. W. Trappe, T. A. Trappe, D. L. Costill, and R. H. Fitts. J Physiol (Lond) 516: 915-930, 1999].

EMG analysis tuned for determining the timing and level of activation in different motor units

PubMed Central

Lee, Sabrina S.M.; de Boef Miara, Maria; Arnold, Allison S.; Biewener, Andrew A.; Wakeling, James M.

2011-01-01

Recruitment patterns and activation dynamics of different motor units greatly influence the temporal pattern and magnitude of muscle force development, yet these features are not often considered in muscle models. The purpose of this study was to characterize the recruitment and activation dynamics of slow and fast motor units from electromyographic (EMG) recordings and twitch force profiles recorded directly from animal muscles. EMG and force data from the gastrocnemius muscles of seven goats were recorded during in vivo tendon-tap reflex and in situ nerve stimulation experiments. These experiments elicited EMG signals with significant differences in frequency content (p<0.001). The frequency content was characterized using wavelet and principal components analysis, and optimized wavelets with centre frequencies, 149.94Hz and 323.13Hz, were obtained. The optimized wavelets were used to calculate the EMG intensities and, with the reconstructed twitch force profiles, to derive transfer functions for slow and fast motor units that estimate the activation state of the muscle from the EMG signal. The resulting activation-deactivation time constants gave r values of 0.98 to 0.99 between the activation state and the force profiles. This work establishes a framework for developing improved muscle models that consider the intrinsic properties of slow and fast fibres within a mixed muscle, and that can more accurately predict muscle force output from EMG. PMID:21570317

EMG analysis tuned for determining the timing and level of activation in different motor units.

PubMed

Lee, Sabrina S M; Miara, Maria de Boef; Arnold, Allison S; Biewener, Andrew A; Wakeling, James M

2011-08-01

Recruitment patterns and activation dynamics of different motor units greatly influence the temporal pattern and magnitude of muscle force development, yet these features are not often considered in muscle models. The purpose of this study was to characterize the recruitment and activation dynamics of slow and fast motor units from electromyographic (EMG) recordings and twitch force profiles recorded directly from animal muscles. EMG and force data from the gastrocnemius muscles of seven goats were recorded during in vivo tendon-tap reflex and in situ nerve stimulation experiments. These experiments elicited EMG signals with significant differences in frequency content (p<0.001). The frequency content was characterized using wavelet and principal components analysis, and optimized wavelets with centre frequencies, 149.94 Hz and 323.13 Hz, were obtained. The optimized wavelets were used to calculate the EMG intensities and, with the reconstructed twitch force profiles, to derive transfer functions for slow and fast motor units that estimate the activation state of the muscle from the EMG signal. The resulting activation-deactivation time constants gave r values of 0.98-0.99 between the activation state and the force profiles. This work establishes a framework for developing improved muscle models that consider the intrinsic properties of slow and fast fibres within a mixed muscle, and that can more accurately predict muscle force output from EMG. Copyright © 2011 Elsevier Ltd. All rights reserved.

Common oscillatory mechanisms across multiple memory systems

NASA Astrophysics Data System (ADS)

Headley, Drew B.; Paré, Denis

2017-01-01

The cortex, hippocampus, and striatum support dissociable forms of memory. While each of these regions contains specialized circuitry supporting their respective functions, all structure their activities across time with delta, theta, and gamma rhythms. We review how these oscillations are generated and how they coordinate distinct memory systems during encoding, consolidation, and retrieval. First, gamma oscillations occur in all regions and coordinate local spiking, compressing it into short population bursts. Second, gamma oscillations are modulated by delta and theta oscillations. Third, oscillatory dynamics in these memory systems can operate in either a "slow" or "fast" mode. The slow mode happens during slow-wave sleep and is characterized by large irregular activity in the hippocampus and delta oscillations in cortical and striatal circuits. The fast mode occurs during active waking and rapid eye movement (REM) sleep and is characterized by theta oscillations in the hippocampus and its targets, along with gamma oscillations in the rest of cortex. In waking, the fast mode is associated with the efficacious encoding and retrieval of declarative and procedural memories. Theta and gamma oscillations have similar relationships with encoding and retrieval across multiple forms of memory and brain regions, despite regional differences in microcircuitry and information content. Differences in the oscillatory coordination of memory systems during sleep might explain why the consolidation of some forms of memory is sensitive to slow-wave sleep, while others depend on REM. In particular, theta oscillations appear to support the consolidation of certain types of procedural memories during REM, while delta oscillations during slow-wave sleep seem to promote declarative and procedural memories.

Improving the antidepressant efficacy of transcranial magnetic stimulation: Maximizing the number of stimulations and treatment location in treatment resistant depression

PubMed Central

McDonald, William M.; Durkalski, Valerie; Ball, Edward R.; Holtzheimer, Paul E.; Pavlicova, Martina; Lisanby, Sarah H.; Avery, David; Anderson, Berry S.; Nahas, Ziad; Zarkowski, Paul; Sackeim, Harold A.; George, Mark S.

2015-01-01

Objective To assess the efficacy of increasing the number of fast left repetitive transcranial magnetic stimulations (rTMS) (10 Hz @ 120% of motor threshold (MT) over the left dorsolateral prefrontal cortex (DLPFC)) needed to achieve remission in treatment resistant depression (TRD). And, to determine if patients who do not remit to fast left will remit using slow right rTMS (1 Hz @ 120% MT over the right DLPFC). Method Patients were part of a multicenter sham controlled trial investigating the efficacy of fast left rTMS 1. Patients who failed to meet minimal response criteria in the sham controlled study could enroll in this open fast left rTMS study for an additional 3- 6 weeks. Patients who failed to remit to fast left could switch to slow right rTMS for up to four additional weeks. The final outcome measure was remission, defined as a HAM-D score of ≤ 3 or two consecutive HAM-D scores less than 10. Results Forty-three of 141 (30.5%) patients who enrolled in the open phase study eventually met criteria for remission. Patients who remitted during fast left treatment received a mean of 26 active treatments (90,000 pulses). 26% of patients who failed fast left remitted during slow right treatment. Conclusion The total number of rTMS stimulations needed to achieve remission in TRD may be higher than is used in most studies. TRD patients who do not respond to fast left rTMS may remit to slow right rTMS or additional rTMS stimulations. PMID:21898711

Is There a Relation between EEG-Slow Waves and Memory Dysfunction in Epilepsy? A Critical Appraisal

PubMed Central

Höller, Yvonne; Trinka, Eugen

2015-01-01

Is there a relationship between peri-ictal slow waves, loss of consciousness, memory, and slow-wave sleep, in patients with different forms of epilepsy? We hypothesize that mechanisms, which result in peri-ictal slow-wave activity as detected by the electroencephalogram, could negatively affect memory processes. Slow waves (≤4 Hz) can be found in seizures with impairment of consciousness and also occur in focal seizures without impairment of consciousness but with inhibited access to memory functions. Peri-ictal slow waves are regarded as dysfunctional and are probably caused by mechanisms, which are essential to disturb the consolidation of memory entries in these patients. This is in strong contrast to physiological slow-wave activity during deep sleep, which is thought to group memory-consolidating fast oscillatory activity. In patients with epilepsy, slow waves may not only correlate with the peri-ictal clouding of consciousness, but could be the epiphenomenon of mechanisms, which interfere with normal brain function in a wider range. These mechanisms may have transient impacts on memory, such as temporary inhibition of memory systems, altered patterns of hippocampal–neocortical interactions during slow-wave sleep, or disturbed cross-frequency coupling of slow and fast oscillations. In addition, repeated tonic–clonic seizures over the years in uncontrolled chronic epilepsy may cause a progressive cognitive decline. This hypothesis can only be assessed in long-term prospective studies. These studies could disentangle the reversible short-term impacts of seizures, and the impacts of chronic uncontrolled seizures. Chronic uncontrolled seizures lead to irreversible memory impairment. By contrast, short-term impacts do not necessarily lead to a progressive cognitive decline but result in significantly impaired peri-ictal memory performance. PMID:26124717

Suppression of chaos at slow variables by rapidly mixing fast dynamics through linear energy-preserving coupling

NASA Astrophysics Data System (ADS)

Abramov, R. V.

2011-12-01

Chaotic multiscale dynamical systems are common in many areas of science, one of the examples being the interaction of the low-frequency dynamics in the atmosphere with the fast turbulent weather dynamics. One of the key questions about chaotic multiscale systems is how the fast dynamics affects chaos at the slow variables, and, therefore, impacts uncertainty and predictability of the slow dynamics. Here we demonstrate that the linear slow-fast coupling with the total energy conservation property promotes the suppression of chaos at the slow variables through the rapid mixing at the fast variables, both theoretically and through numerical simulations. A suitable mathematical framework is developed, connecting the slow dynamics on the tangent subspaces to the infinite-time linear response of the mean state to a constant external forcing at the fast variables. Additionally, it is shown that the uncoupled dynamics for the slow variables may remain chaotic while the complete multiscale system loses chaos and becomes completely predictable at the slow variables through increasing chaos and turbulence at the fast variables. This result contradicts the common sense intuition, where, naturally, one would think that coupling a slow weakly chaotic system with another much faster and much stronger chaotic system would result in general increase of chaos at the slow variables.

Fast and slow brain rhythms in rule/expectation violation tasks: focusing on evaluation processes by excluding motor action.

PubMed

Tzur, Gabriel; Berger, Andrea

2009-03-17

Theta rhythm has been connected to ERP components such as the error-related negativity (ERN) and the feedback-related negativity (FRN). The nature of this theta activity is still unclear, that is, whether it is related to error detection, conflict between responses or reinforcement learning processes. We examined slow (e.g., theta) and fast (e.g., gamma) brain rhythms related to rule violation. A time-frequency decomposition analysis on a wide range of frequencies band (0-95 Hz) indicated that the theta activity relates to evaluation processes, regardless of motor/action processes. Similarities between the theta activities found in rule-violation tasks and in tasks eliciting ERN/FRN suggest that this theta activity reflects the operation of general evaluation mechanisms. Moreover, significant effects were found also in fast brain rhythms. These effects might be related to the synchronization between different types of cognitive processes involving the fulfillment of a task (e.g., working memory, visual perception, mathematical calculation, etc.).

Typical examples of classical novae

NASA Technical Reports Server (NTRS)

Hack, Margherita; Selvelli, Pierluigi; Bianchini, Antonio; Duerbeck, Hilmar W.

1993-01-01

Because of the very complicated individualistic behavior of each nova, we think it necessary to review the observations of a few well-observed individuals. We have selected a few objects of different speed classes, which have been extensively observed. They are: V1500 Cygni 1975, a very fast nova; V603 Aql 1918, fast nova; CP Pup 1942, fast nova; GK Per 1901, fast nova; V 1668 Cyg 1979, moderately fast nova; FH Ser 1970, slow nova; DQ Her 1934, slow nova; T Aur 1891, slow nova; RR Pic 1925, slow nova; and HR Del 1967, very slow nova.

Typical examples of classical novae

NASA Astrophysics Data System (ADS)

Hack, Margherita; Selvelli, Pierluigi; Bianchini, Antonio; Duerbeck, Hilmar W.

1993-09-01

Because of the very complicated individualistic behavior of each nova, we think it necessary to review the observations of a few well-observed individuals. We have selected a few objects of different speed classes, which have been extensively observed. They are: V1500 Cygni 1975, a very fast nova; V603 Aql 1918, fast nova; CP Pup 1942, fast nova; GK Per 1901, fast nova; V 1668 Cyg 1979, moderately fast nova; FH Ser 1970, slow nova; DQ Her 1934, slow nova; T Aur 1891, slow nova; RR Pic 1925, slow nova; and HR Del 1967, very slow nova.

UNC-13L, UNC-13S, and Tomosyn form a protein code for fast and slow neurotransmitter release in Caenorhabditis elegans

PubMed Central

Hu, Zhitao; Tong, Xia-Jing; Kaplan, Joshua M

2013-01-01

Synaptic transmission consists of fast and slow components of neurotransmitter release. Here we show that these components are mediated by distinct exocytic proteins. The Caenorhabditis elegans unc-13 gene is required for SV exocytosis, and encodes long and short isoforms (UNC-13L and S). Fast release was mediated by UNC-13L, whereas slow release required both UNC-13 proteins and was inhibited by Tomosyn. The spatial location of each protein correlated with its effect. Proteins adjacent to the dense projection mediated fast release, while those controlling slow release were more distal or diffuse. Two UNC-13L domains accelerated release. C2A, which binds RIM (a protein associated with calcium channels), anchored UNC-13 at active zones and shortened the latency of release. A calmodulin binding site accelerated release but had little effect on UNC-13’s spatial localization. These results suggest that UNC-13L, UNC-13S, and Tomosyn form a molecular code that dictates the timing of neurotransmitter release. DOI: http://dx.doi.org/10.7554/eLife.00967.001 PMID:23951547

A soil-column gas chromatography (SCGC) approach to explore the thermal desorption behavior of hydrocarbons from soils.

PubMed

Yu, Ying; Liu, Liang; Shao, Ziying; Ju, Tianyu; Sun, Bing; Benadda, Belkacem

2016-01-01

A soil-column gas chromatography approach was developed to simulate the mass transfer process of hydrocarbons between gas and soil during thermally enhanced soil vapor extraction (T-SVE). Four kinds of hydrocarbons-methylbenzene, n-hexane, n-decane, and n-tetradecane-were flowed by nitrogen gas. The retention factor k' and the tailing factor T f were calculated to reflect the desorption velocities of fast and slow desorption fractions, respectively. The results clearly indicated two different mechanisms on the thermal desorption behaviors of fast and slow desorption fractions. The desorption velocity of fast desorption fraction was an exponential function of the reciprocal of soil absolute temperature and inversely correlated with hydrocarbon's boiling point, whereas the desorption velocity of slow desorption fraction was an inverse proportional function of soil absolute temperature, and inversely proportional to the log K OW value of the hydrocarbons. The higher activation energy of adsorption was found on loamy soil with higher organic content. The increase of carrier gas flow rate led to a reduction in the apparent activation energy of adsorption of slow desorption fraction, and thus desorption efficiency was significantly enhanced. The obtained results are of practical interest for the design of high-efficiency T-SVE system and may be used to predict the remediation time.

Mitochondrial oxidative enzyme activity in individual fibre types in hypo- and hyperthyroid rat skeletal muscles.

PubMed

Johnson, M A; Turnbull, D M

1984-04-01

Quantitative cytochemical and biochemical techniques have been used in combination to study the response of mitochondrial oxidative enzymes in individual muscle fibre types to hypo- and hyperthyroidism. Hypothyroidism resulted in decreased activity of succinate dehydrogenase (SDH), L-glycerol-3-phosphate dehydrogenase (L-GPDH), and D-3-hydroxybutyrate dehydrogenase (D-HBDH) in all fibre types of both slow-twitch soleus and fast-twitch extensor digitorum longus (e.d.l.) muscles. In hyperthyroidism, only L-GPDH activity increased in e.d.l. but more marked increases were seen in soleus muscles, which also showed increased SDH activity. In addition to these alterations in the enzyme activity in individual fibre types the metabolic profile of the muscle is further modified by the hormone-induced interconversion of slow- to fast-twitch fibres and vice versa.

Length dependence of force generation exhibit similarities between rat cardiac myocytes and skeletal muscle fibres.

PubMed

Hanft, Laurin M; McDonald, Kerry S

2010-08-01

According to the Frank-Starling relationship, increased ventricular volume increases cardiac output, which helps match cardiac output to peripheral circulatory demand. The cellular basis for this relationship is in large part the myofilament length-tension relationship. Length-tension relationships in maximally calcium activated preparations are relatively shallow and similar between cardiac myocytes and skeletal muscle fibres. During twitch activations length-tension relationships become steeper in both cardiac and skeletal muscle; however, it remains unclear whether length dependence of tension differs between striated muscle cell types during submaximal activations. The purpose of this study was to compare sarcomere length-tension relationships and the sarcomere length dependence of force development between rat skinned left ventricular cardiac myocytes and fast-twitch and slow-twitch skeletal muscle fibres. Muscle cell preparations were calcium activated to yield 50% maximal force, after which isometric force and rate constants (k(tr)) of force development were measured over a range of sarcomere lengths. Myofilament length-tension relationships were considerably steeper in fast-twitch fibres compared to slow-twitch fibres. Interestingly, cardiac myocyte preparations exhibited two populations of length-tension relationships, one steeper than fast-twitch fibres and the other similar to slow-twitch fibres. Moreover, myocytes with shallow length-tension relationships were converted to steeper length-tension relationships by protein kinase A (PKA)-induced myofilament phosphorylation. Sarcomere length-k(tr) relationships were distinct between all three cell types and exhibited patterns markedly different from Ca(2+) activation-dependent k(tr) relationships. Overall, these findings indicate cardiac myocytes exhibit varied length-tension relationships and sarcomere length appears a dominant modulator of force development rates. Importantly, cardiac myocyte length-tension relationships appear able to switch between slow-twitch-like and fast-twitch-like by PKA-mediated myofibrillar phosphorylation, which implicates a novel means for controlling Frank-Starling relationships.

Calcineurin regulates slow myosin, but not fast myosin or metabolic enzymes, during fast-to-slow transformation in rabbit skeletal muscle cell culture

PubMed Central

Meißner, Joachim D; Gros, Gerolf; Scheibe, Renate J; Scholz, Michael; Kubis, Hans-Peter

2001-01-01

The addition of cyclosporin A (500 ng ml−1) - an inhibitor of the Ca2+-calmodulin-regulated serine/threonine phosphatase calcineurin - to primary cultures of rabbit skeletal muscle cells had no influence on the expression of fast myosin heavy chain (MHC) isoforms MHCIIa and MHCIId at the level of protein and mRNA, but reduced the expression of slow MHCI mRNA. In addition, no influence of cyclosporin A on the expression of citrate synthase (CS) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA was found. The level of enzyme activity of CS was also not affected. When the Ca2+ ionophore A23187 (4 × 10−7m) was added to the medium, a partial fast-to-slow transformation occurred. The level of MHCI mRNA increased, and the level of MHCIId mRNA decreased. Cotreatment with cyclosporin A was able to prevent the upregulation of MHCI at the level of mRNA as well as protein, but did not reverse the decrease in MHCIId expression. The expression of MHCIIa was also not influenced by cyclosporin A. Cyclosporin A was not able to prevent the upregulation of CS mRNA under Ca2+ ionophore treatment and failed to reduce the increased enzyme activity of CS. The expression of GAPDH mRNA was reduced under Ca2+ ionophore treatment and was not altered under cotreatment with cyclosporin A. When the myotubes in the primary muscle culture were electrostimulated at 1 Hz for 15 min periods followed by pauses of 30 min, a partial fast-to-slow transformation was induced. Again, cotreatment with cyclosporin A prevented the upregulation of MHCI at the level of mRNA and protein without affecting MHCIId expression. The nuclear translocation of the calcineurin-regulated transcription factor nuclear factor of activated thymocytes (NFATc1) during treatment with Ca2+ ionophore, and the prevention of the translocation in the presence of cyclosporin A, were demonstrated immunocytochemically in the myotubes of the primary culture. The effects of cyclosporin A demonstrate the involvement of calcineurin-dependent signalling pathways in controlling the expression of MHCI, but not of MHCIIa, MHCIId, CS and GAPDH, during Ca2+ ionophore- and electrostimulation-induced fast-to-slow transformations. The data indicate a differential regulation of MHCI, of MHCII and of metabolism. Calcineurin alone is not sufficient to mediate the complete transformation. PMID:11351029

Sleep and satisfaction in 8- and 12-h forward-rotating shift systems: Industrial employees prefer 12-h shifts.

PubMed

Karhula, Kati; Härmä, Mikko; Ropponen, Annina; Hakola, Tarja; Sallinen, Mikael; Puttonen, Sampsa

2016-01-01

Twelve-hour shift systems have become more popular in industry. Survey data of shift length, shift rotation speed, self-rated sleep, satisfaction and perceived health were investigated for the associations among 599 predominantly male Finnish industrial employees. The studied forward-rotating shift systems were 12-h fast (12fast, DDNN------, n = 268), 8-h fast (8fast, MMEENN----, n = 161) and 8-h slow (8slow, MMMM-EEEE-NNNN, n = 170). Satisfaction with shift system differed between the groups (p < 0.01) after controlling for age, gender, shift work experience and self-rated stress. In the 12fast, 98% of employees were satisfied with their shift system (75% 8fast, 54% 8slow). Negative effects on sleep and alertness were rare (8%) in the 12fast group (53% 8fast, 66% 8 slow, p < 0.01) and self-reported sleep difficulties were less frequent than in the 8fast and 8slow groups (8%, 27%, 41%, respectively, p < 0.01). The self-reported average sleep duration (12fast 7:50, 8fast 7:24, 8slow 7:15, p < 0.01), and shift-specific sleep before and between morning shifts and after first night shift were longer in the 12fast group. Perceived negative effects of the current shift system on general health (12fast 4%, 8fast 30%, 8slow 41%, p < 0.001) and work-life balance (12fast 8%, 8fast 52%, 8slow 63%, p < 0.001) differed strongly between the groups. In conclusion, the perceived effects of shift work were dependent on both shift length and shift rotation speed: employees in the 12-h rapidly forward-rotating shift system were most satisfied, perceived better work-life balance and slept better than the employees in the 8fast or especially the employees in the 8-h slowly rotating systems.

Differential changes in myoelectric characteristics of slow and fast fatigable frog muscle fibres during long-lasting activity.

PubMed

Vydevska-Chichova, M; Mileva, K; Radicheva, N

2007-04-01

The electrical activity of different muscle fibre types during fatigue at varying stimulation frequency and fibre stretch was studied. Extracellular action potentials (ECAPs) were recorded from isolated frog muscle fibres at initial length and stretched by 15%, 25% and 35% and stimulated for 180 s by suprathreshold pulses with frequencies of 5, 6.7 and 10Hz. The changes in ECAP negative phase duration (T(0)), propagation velocity of excitation (PV), potential power spectrum and its median frequency (MDF) were analysed for the period of uninterrupted activity (endurance time, ET). Slow (SMF) and fast (FMF) fatigable muscle fibre types were distinguished by the rate of PV decrease during ET. With the increase of stimulation frequency and fibre stretch, the rate of ECAP parameter changes increased and was larger in FMF, but this proportion was reversed with stretching over 25% and 10Hz stimulation. In both fibre types the power spectrum shift to lower frequencies during continuous activity was more pronounced with higher stimulation frequency. In FMFs the rates of MDF changes were positively and more strongly correlated with the rates of PV changes, whilst in SMFs the inverse correlation between the rates of changes of MDF and T(0) was stronger. The results indicate specific adaptation of slow and fast fatigable muscle fibres to stretch and activation frequency due to the differences in their membrane processes.

Time-domain separation of interfering waves in cancellous bone using bandlimited deconvolution: simulation and phantom study.

PubMed

Wear, Keith A

2014-04-01

In through-transmission interrogation of cancellous bone, two longitudinal pulses ("fast" and "slow" waves) may be generated. Fast and slow wave properties convey information about material and micro-architectural characteristics of bone. However, these properties can be difficult to assess when fast and slow wave pulses overlap in time and frequency domains. In this paper, two methods are applied to decompose signals into fast and slow waves: bandlimited deconvolution and modified least-squares Prony's method with curve-fitting (MLSP + CF). The methods were tested in plastic and Zerdine(®) samples that provided fast and slow wave velocities commensurate with velocities for cancellous bone. Phase velocity estimates were accurate to within 6 m/s (0.4%) (slow wave with both methods and fast wave with MLSP + CF) and 26 m/s (1.2%) (fast wave with bandlimited deconvolution). Midband signal loss estimates were accurate to within 0.2 dB (1.7%) (fast wave with both methods), and 1.0 dB (3.7%) (slow wave with both methods). Similar accuracies were found for simulations based on fast and slow wave parameter values published for cancellous bone. These methods provide sufficient accuracy and precision for many applications in cancellous bone such that experimental error is likely to be a greater limiting factor than estimation error.

Changes in contractile activation characteristics of rat fast and slow skeletal muscle fibres during regeneration.

PubMed

Gregorevic, Paul; Plant, David R; Stupka, Nicole; Lynch, Gordon S

2004-07-15

Damaged skeletal muscle fibres are replaced with new contractile units via muscle regeneration. Regenerating muscle fibres synthesize functionally distinct isoforms of contractile and regulatory proteins but little is known of their functional properties during the regeneration process. An advantage of utilizing single muscle fibre preparations is that assessment of their function is based on the overall characteristics of the contractile apparatus and regulatory system and as such, these preparations are sensitive in revealing not only coarse, but also subtle functional differences between muscle fibres. We examined the Ca(2+)- and Sr(2+)-activated contractile characteristics of permeabilized fibres from rat fast-twitch (extensor digitorum longus) and slow-twitch (soleus) muscles at 7, 14 and 21 days following myotoxic injury, to test the hypothesis that fibres from regenerating fast and slow muscles have different functional characteristics to fibres from uninjured muscles. Regenerating muscle fibres had approximately 10% of the maximal force producing capacity (P(o)) of control (uninjured) fibres, and an altered sensitivity to Ca(2+) and Sr(2+) at 7 days post-injury. Increased force production and a shift in Ca(2+) sensitivity consistent with fibre maturation were observed during regeneration such that P(o) was restored to 36-45% of that in control fibres by 21 days, and sensitivity to Ca(2+) and Sr(2+) was similar to that of control (uninjured) fibres. The findings support the hypothesis that regenerating muscle fibres have different contractile activation characteristics compared with mature fibres, and that they adopt properties of mature fast- or slow-twitch muscle fibres in a progressive manner as the regeneration process is completed.

Scene segmentation by spike synchronization in reciprocally connected visual areas. I. Local effects of cortical feedback.

PubMed

Knoblauch, Andreas; Palm, Günther

2002-09-01

To investigate scene segmentation in the visual system we present a model of two reciprocally connected visual areas using spiking neurons. Area P corresponds to the orientation-selective subsystem of the primary visual cortex, while the central visual area C is modeled as associative memory representing stimulus objects according to Hebbian learning. Without feedback from area C, a single stimulus results in relatively slow and irregular activity, synchronized only for neighboring patches (slow state), while in the complete model activity is faster with an enlarged synchronization range (fast state). When presenting a superposition of several stimulus objects, scene segmentation happens on a time scale of hundreds of milliseconds by alternating epochs of the slow and fast states, where neurons representing the same object are simultaneously in the fast state. Correlation analysis reveals synchronization on different time scales as found in experiments (designated as tower, castle, and hill peaks). On the fast time scale (tower peaks, gamma frequency range), recordings from two sites coding either different or the same object lead to correlograms that are either flat or exhibit oscillatory modulations with a central peak. This is in agreement with experimental findings, whereas standard phase-coding models would predict shifted peaks in the case of different objects.

Effect of the speed of a single-channel dynamic range compressor on intelligibility in a competing speech task

NASA Astrophysics Data System (ADS)

Stone, Michael A.; Moore, Brian C. J.

2003-08-01

Using a ``noise-vocoder'' cochlear implant simulator [Shannon et al., Science 270, 303-304 (1995)], the effect of the speed of dynamic range compression on speech intelligibility was assessed, using normal-hearing subjects. The target speech had a level 5 dB above that of the competing speech. Initially, baseline performance was measured with no compression active, using between 4 and 16 processing channels. Then, performance was measured using a fast-acting compressor and a slow-acting compressor, each operating prior to the vocoder simulation. The fast system produced significant gain variation over syllabic timescales. The slow system produced significant gain variation only over the timescale of sentences. With no compression active, about six channels were necessary to achieve 50% correct identification of words in sentences. Sixteen channels produced near-maximum performance. Slow-acting compression produced no significant degradation relative to the baseline. However, fast-acting compression consistently reduced performance relative to that for the baseline, over a wide range of performance levels. It is suggested that fast-acting compression degrades performance for two reasons: (1) because it introduces correlated fluctuations in amplitude in different frequency bands, which tends to produce perceptual fusion of the target and background sounds and (2) because it reduces amplitude modulation depth and intensity contrasts.

Reading strategies of fast and slow readers.

PubMed

Haberlandt, K F; Graesser, A C; Schneider, N J

1989-09-01

In three subject-paced experiments we evaluated reading patterns at the word, line, and sentence level for fast and slow readers. A moving-window method was used to collect word reading times for natural texts. At the word level, reading times of word N were influenced by features of word N-1 for fast readers but not for slow readers. The lag effect exhibited by fast readers indicates that they continue to process a word when it is no longer in view, thus limiting the notion of immediate processing. Contrary to our initial expectation that fast readers would process only a single new argument from a sentence, whereas slow readers would process several new arguments, we found that both reader groups adopted a many-argument strategy. However, fast and slow readers differed in terms of the text units (lines vs. sentences) defining the new-argument effects: Fast readers exhibited greater new-argument effects relative to lines, whereas slow readers exhibited greater new-argument effects relative to sentences. Specifically, slow readers integrated the new arguments primarily at the end of the sentence, whereas fast readers did so at line boundaries. These results are discussed in terms of a buffer-and-integrate model of reading comprehension.

Bilateral experimental neck pain reorganize axioscapular muscle coordination and pain sensitivity.

PubMed

Christensen, S W; Hirata, R P; Graven-Nielsen, T

2017-04-01

Neck pain is a large clinical problem where reorganized trunk and axioscapular muscle activities have been hypothesised contributing to pain persistence and pain hypersensitivity. This study investigated the effects of bilateral experimental neck pain on trunk and axioscapular muscle function and pain sensitivity. In 25 healthy volunteers, bilateral experimental neck pain was induced in the splenius capitis muscles by hypertonic saline injections. Isotonic saline was used as control. In sitting, subjects performed slow, fast and slow-resisted unilateral arm movements before, during and after injections. Electromyography (EMG) was recorded from eight shoulder and trunk muscles bilaterally. Pressure pain thresholds (PPTs) were assessed bilaterally at the neck, head and arm. Data were normalized to the before-measures. Compared with control and post measurements, experimental neck pain caused (1) decreased EMG activity of the ipsilateral upper trapezius muscles during all but slow-resisted down movements (p < 0.001), and (2) increased EMG activity in the ipsilateral erector spinae muscle during slow and fast movements (p < 0.02), and in the contralateral erector spinae muscle during all but fast up and slow-resisted down movements (p < 0.007). The PPTs in the painful condition increased at the head and arm compared with post measurements and the control condition (p < 0.001). In the post-pain condition, the neck PPT was decreased compared with the control condition (p < 0.001). Acute bilateral neck pain reorganized axioscapular and trunk muscle activity together with local hyperalgesia and widespread hypoalgesia indicating that acute neck pain immediately affects trunk and axioscapular function which may affect both assessment and treatment. Bilateral clinical neck pain alters axioscapular muscle coordination but only effects of unilateral experimental neck pain has been investigated. Bilateral experimental neck pain causes task-dependent reorganized axioscapular and trunk muscle activity in addition to widespread decrease in pressure pain sensitivity. © 2016 European Pain Federation - EFIC®.

Pressure-overload-induced angiotensin-mediated early remodeling in mouse heart

PubMed Central

Kim, Jeremy H.; Jiang, Ya-Ping; Cohen, Ira S.; Lin, Richard Z.; Mathias, Richard T.

2017-01-01

Our previous work on angiotensin II-mediated electrical-remodeling in canine left ventricle, in connection with a long history of other studies, suggested the hypothesis: increases in mechanical load induce autocrine secretion of angiotensin II (A2), which coherently regulates a coterie of membrane ion transporters in a manner that increases contractility. However, the relation between load and A2 secretion was correlative. We subsequently showed a similar or identical system was present in murine heart. To investigate whether the relation between mechanical load and A2-mediated electrical remodeling was causal, we employed transverse aortic constriction in mice to subject the left ventricle to pressure overload for short-term (1 to 2 days) or long-term (1 to 2 weeks) periods. Heart-to-body weight ratios and cell capacitance measurements were used to determine hypertrophy. Whole-cell patch clamp recordings of the predominant repolarization currents Ito,fast and IK,slow were used to assess electrical remodeling. Hearts or myocytes subjected to long-term load displayed significant hypertrophy, which was not evident in short-term load. However, short-term load induced significant reductions in Ito,fast and IK,slow. Incubation of these myocytes with the angiotensin II type 1 receptor inhibitor saralasin for 2 hours restored Ito,fast and IK,slow to control levels. The number of Ito.fast or IK,slow channels did not change with A2 or long-term load, however the hypertrophic increase in membrane area reduced the current densities for both channels. For Ito,fast but not IK,slow there was an additional reduction that was reversed by inhibition of angiotensin receptors. These results suggest increased load activates an endogenous renin angiotensin system that initially reduces Ito,fast and IK,slow prior to the onset of hypertrophic growth. However, there are functional interactions between electrical and anatomical remodeling. First, hypertrophy tends to reduce all current densities. Second, the hypertrophic program can modify signaling between the angiotensin receptor and target current. PMID:28464037

Gravity Plays an Important Role in Muscle Development and the Differentiation of Contractile Protein Phenotype

NASA Technical Reports Server (NTRS)

Adams, Gregory A.; Haddad, Fadia; Baldwin, Kenneth M.

2003-01-01

Several muscles in the body exist mainly to work against gravity. Whether gravity is important in the development of these muscles is not known. By examining the basic proteins that compose muscle, questions about the role of gravity in muscle development can be answered. Myosin heavy chains (MHCs) are a family of proteins critically important for muscle contraction. Several types of MHCs exist (e.g., neonatal, slow, fast), and each type is produced by a particular gene. Neonatal MHCs are produced early in life. Slow MHCs are important in antigravity muscles, and fast MHCs are found in fast-twitch power muscles. The gene that is turned on or expressed will determine which MHC is produced. Early in development, antigravity skeletal muscles (muscles that work against gravity) normally produce a combination of the neonatal/embryonic MHCs. The expression of these primitive MHCs is repressed early in development; and the adult slow and fast MHC genes become fully expressed. We tested the hypothesis that weightbearing activity is critical for inducing the normal expression of the slow MHC gene typically expressed in adult antigravity muscles. Also, we hypothesized that thyroid hormone, but not opposition to gravity, is necessary for expressing the adult fast IIb MHC gene essential for high-intensity muscle performance. Groups of normal thyroid and thyroid-deficient neonatal rats were studied after their return from the 16-day Neurolab mission and compared to matched controls. The results suggest: (1) Weightlessness impaired body and limb skeletal muscle growth in both normal and thyroid-deficient animals. Antigravity muscles were impaired more than those used primarily for locomotion andor nonweightbearing activity. (2) Systemic and muscle expression of insulin-like growth factor-I (IGF-I), an important body and tissue growth factor, was depressed in flight animals. (3) Normal slow, type I MHC gene expression was markedly repressed in the normal thyroid flight group. (4) Fast IIb MHC gene expression was enhanced in fast-twitch muscles of normal thyroid animals exposed to spaceflight; however, thyroid deficiency markedly repressed expression of this gene independently of spaceflight. In summary, the absence of gravity, when imposed at critical stages of development, impaired body and skeletal muscle growth, as well as expression of the MHC gene family of motor proteins. This suggests that normal weightbearing activity is essential for establishing body and muscle growth in neonatal animals, and for expressing the motor gene essential for supporting antigravity functions.

Inadequate Antioxidative Responses in Kidneys of Brain-Dead Rats.

PubMed

Hoeksma, Dane; Rebolledo, Rolando A; Hottenrott, Maximilia; Bodar, Yves S; Wiersema-Buist, Janneke J; Van Goor, Harry; Leuvenink, Henri G D

2017-04-01

Brain death (BD)-related lipid peroxidation, measured as serum malondialdehyde (MDA) levels, correlates with delayed graft function in renal transplant recipients. How BD affects lipid peroxidation is not known. The extent of BD-induced organ damage is influenced by the speed at which intracranial pressure increases. To determine possible underlying causes of lipid peroxidation, we investigated the renal redox balance by assessing oxidative and antioxidative processes in kidneys of brain-dead rats after fast and slow BD induction. Brain death was induced in 64 ventilated male Fisher rats by inflating a 4.0F Fogarty catheter in the epidural space. Fast and slow inductions were achieved by an inflation speed of 0.45 and 0.015 mL/min, respectively, until BD confirmation. Healthy non-brain-dead rats served as reference values. Brain-dead rats were monitored for 0.5, 1, 2, or 4 hours, after which organs and blood were collected. Increased MDA levels became evident at 2 hours of slow BD induction at which increased superoxide levels, decreased glutathione peroxidase (GPx) activity, decreased glutathione levels, increased inducible nitric oxide synthase and heme-oxygenase 1 expression, and increased plasma creatinine levels were evident. At 4 hours after slow BD induction, superoxide, MDA, and plasma creatinine levels increased further, whereas GPx activity remained decreased. Increased MDA and plasma creatinine levels also became evident after 4 hours fast BD induction. Brain death leads to increased superoxide production, decreased GPx activity, decreased glutathione levels, increased inducible nitric oxide synthase and heme-oxygenase 1 expression, and increased MDA and plasma creatinine levels. These effects were more pronounced after slow BD induction. Modulation of these processes could lead to decreased incidence of delayed graft function.

Properties of slow- and fast-twitch muscle fibres in a mouse model of amyotrophic lateral sclerosis.

PubMed

Atkin, Julie D; Scott, Rachel L; West, Jan M; Lopes, Elizabeth; Quah, Alvin K J; Cheema, Surindar S

2005-05-01

This investigation was undertaken to determine if there are altered histological, pathological and contractile properties in presymptomatic or endstage diseased muscle fibres from representative slow-twitch and fast-twitch muscles of SOD1 G93A mice in comparison to wildtype mice. In presymptomatic SOD1 G93A mice, there was no detectable peripheral dysfunction, providing evidence that muscle pathology is secondary to motor neuronal dysfunction. At disease endstage however, single muscle fibre contractile analysis demonstrated that fast-twitch muscle fibres and neuromuscular junctions are preferentially affected by amyotrophic lateral sclerosis-induced denervation, being unable to produce the same levels of force when activated by calcium as muscle fibres from their age-matched controls. The levels of transgenic SOD1 expression, aggregation state and activity were also examined in these muscles but there no was no preference for muscle fibre type. Hence, there is no simple correlation between SOD1 protein expression/activity, and muscle fibre type vulnerability in SOD1 G93A mice.

Proline 54 trans-cis isomerization is responsible for the kinetic partitioning at the last-step photocycle of photoactive yellow protein

PubMed Central

Lee, Byoung-Chul; Hoff, Wouter D.

2008-01-01

Photoactive yellow protein (PYP), a blue-light photoreceptor for Ectothiorhodospira halophila, has provided a unique system for studying protein folding that is coupled with a photocycle. Upon receptor activation by blue light, PYP proceeds through a photocycle that includes a partially folded signaling state. The last-step photocycle is a thermal recovery reaction from the signaling state to the native state. Bi-exponential kinetics had been observed for the last-step photocycle; however, the slow phase of the bi-exponential kinetics has not been extensively studied. Here we analyzed both fast and slow phases of the last-step photocycle in PYP. From the analysis of the denaturant dependence of the fast and slow phases, we found that the last-step photocycle proceeds through parallel channels of the folding pathway. The burial of the solvent-accessible area was responsible for the transition state of the fast phase, while structural rearrangement from the compact state to the native state was responsible for the transition state of the slow phase. The photocycle of PYP was linked to the thermodynamic cycle that includes both unfolding and refolding of the fast- and slow-phase intermediates. In order to test the hypothesis of proline-limited folding for the slow phase, we constructed two proline mutants: P54A and P68A. We found that only a single phase of the last-step photocycle was observed in P54A. This suggests that there is a low energy barrier between trans to cis conformation in P54 in the light-induced state of PYP, and the resulting cis conformation of P54 generates a slow-phase kinetic trap during the photocycle-coupled folding pathway of PYP. PMID:18794212

Stimulatory and inhibitory mechanisms of slow muscle-specific myosin heavy chain gene expression in fish: Transient and transgenic analysis of torafugu MYH{sub M86-2} promoter in zebrafish embryos

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

Asaduzzaman, Md.; Kinoshita, Shigeharu, E-mail: akino@mail.ecc.u-tokyo.ac.jp; Bhuiyan, Sharmin Siddique

The myosin heavy chain gene, MYH{sub M86-2}, exhibited restricted expression in slow muscle fibers of torafugu embryos and larvae, suggesting its functional roles for embryonic and larval muscle development. However, the transcriptional mechanisms involved in its expression are still ambiguous. The present study is the first extensive analysis of slow muscle-specific MYH{sub M86-2} promoter in fish for identifying the cis-elements that are crucial for its expression. Combining both transient transfection and transgenic approaches, we demonstrated that the 2614 bp 5′-flanking sequences of MYH{sub M86-2} contain a sufficient promoter activity to drive gene expression specific to superficial slow muscle fibers. Bymore » cyclopamine treatment, we also demonstrated that the differentiation of such superficial slow muscle fibers depends on hedgehog signaling activity. The deletion analyses defined an upstream fragment necessary for repressing ectopic MYH{sub M86-2} expression in the fast muscle fibers. The transcriptional mechanism that prevents MYH{sub M86-2} expression in the fast muscle fibers is mediated through Sox6 binding elements. We also demonstrated that Sox6 may function as a transcriptional repressor of MYH{sub M86-2} expression. We further discovered that nuclear factor of activated T cells (NFAT) binding elements plays a key role and myocyte enhancer factor-2 (MEF2) binding elements participate in the transcriptional regulation of MYH{sub M86-2} expression. - Highlights: ► MYH{sub M86-2} is highly expressed in slow muscle fibers of torafugu embryos and larvae. ► MYH{sub M86-2} promoter activity depends on the hedgehog signaling. ► Sox6 binding elements inhibits MYH{sub M86-2} expression in fast muscle fibers. ► Sox6 elements function as transcriptional repressor of MYH{sub M86-2} promoter activity. ► NFAT and MEF2 binding elements play a key role for directing MYH{sub M86-2} expression.« less

A contemporary view of atrioventricular nodal physiology.

PubMed

Markowitz, Steven M; Lerman, Bruce B

2018-06-16

In delaying transmission of the cardiac impulse from the atria to the ventricles, the atrioventricular (AV) node serves a critical function in augmenting ventricular filling during diastole and limiting the ventricular response during atrial tachyarrhythmias. The complex structure of the nodal region, however, also provides the substrate for reentrant rhythms. Recent discoveries have elucidated the cellular basis and anatomical determinants of slow conduction in the node. Based on analysis of gap junction proteins, distinct structural components of the AV node have been defined, including the compact node, right and left inferior nodal extensions, the lower nodal bundle, and transitional tissue. Emerging evidence supports the role of the inferior nodal extensions in mediating slow pathway conduction. The most common form of reentry involving the node, slow-fast AV nodal reentrant tachycardia (AVNRT), utilizes the inferior nodal extensions for anterograde slow pathway conduction; the structures responsible for retrograde fast pathway activation in the superior septum are less well defined and likely heterogeneous. Atypical forms of AVNRT arise from circuits that activate at least one of the inferior extensions in the retrograde direction.

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

Shamoo, D.A.; Johnson, T.R.; Trim, S.C.

We investigated summer activity patterns in a panel of volunteers drawn from a population segment with potentially high exposure to ambient oxidant pollution. The subjects were 15 men and 5 women aged 19-50, all of whom worked outdoors in the Los Angeles area at least 10 hr per week. The general approach was to (i) calibrate the relationship between ventilation rate (VR) and heart rate (HR) for each subject in controlled exercise; (ii) have subjects monitor their own normal activities with diaries and electronic HR recorders; (iii) estimate VR from HR recordings; and (iv) relate VR with diary descriptions ofmore » activities. Calibration data were fit to the equation log (VR) = (intercept) + (slope x HR), intercept and slope being determined separately for each individual to provide a specific equation to predict her/his VR from measured HR. Individuals' correlation coefficients relating log (VR) with HR ranged from 0.83 to 0.95. Subjects monitored themselves for three 24-hr periods during one week, including their most active work day and their most active non-work day. They wore Heart Watch(R) athletic training instruments which recorded HR once per minute; and recorded each change in their activity, location, or breathing rate in diaries. Breathing rates were classified as sleep, slow, medium, or fast. Diaries showed that sleep occupied about 33% of subject's time, slow activity 59%, medium 7%, and fast 1%. Fast activity was reported only at leisure, never at work. For the group, arithmetic means and standard deviations of predicted VR were 7 +/- 3 L/min for sleep, 12 +/- 7 for slow activity, 14 +/- 8 for medium, and 44 +/- 36 for fast. For the group and for most individuals, distributions of predicted VR within a given activity level (breathing rate) were approximately lognormal, with many values in a narrow range below the arithmetic mean and fewer values in a broader range above it.« less

Crystal plastic earthquakes in dolostones

NASA Astrophysics Data System (ADS)

Passelegue, Francois; Aubry, Jerome; Nicolas, Aurelien; Fondriest, Michele; Schubnel, Alexandre; Di Toro, Giulio

2017-04-01

Dolostone is the most dominant lithology of the seismogenic upper crust around the Mediterranean Sea. Understanding the internal mechanisms controlling fault friction is crucial for understanding seismicity along active faults. Displacement in such fault zones is frequently highlighted by highly reflective (mirror-like) slip surfaces, created by thin films of nanogranular fault rock. Using saw-cut dolostone samples coming from natural fault zones, we conducted friction experiments under triaxial loading conditions. To reproduce the natural conditions, experiments were conducted at 30, 60 and 90 MPa confining pressure at respectively 30, 65 and 100 degrees C. At 30 and 65 degrees C, only slow rupture was observed and the experimental fault exhibits frictional behaviour, i.e. a dependence of normal stress on peak shear stress. At 65 degrees C, a strengthening behaviour is observed after the main rupture, leading to a succession of slow rupture. At 100 degrees C, the macroscopic behaviour of the fault becomes ductile, and no dependence of pressure on the peak shear stress is observed. In addition, the increase of the confining pressure up to 60 and 90 MPa allow the transition from slow to fast rupture, highlighted by the records of acoustic activity and by dynamic stress drop occurring in a few tens of microseconds. Using strain gages located along the fault surface and acoustic transducers, we were able to measure the rupture velocities during slow and fast rupture. Slow ruptures propagated around 0.1 m/s, in agreement with natural observations. Fast ruptures propagated up the supershear velocities, i.e. faster than the shear wave speed (>3500 m/s). A complete study of the microstructures was realized before and after ruptures. Slow ruptures lead to the production of mirror-like surface driven by the production of nanograins due to dislocation processes. Fast ruptures induce the production of amorphous material along the fault surface, which may come from melting processes. We demonstrate that the transition from slow to dynamic instabilities is observed when the entire fault exhibits plastic processes, which increase the stiffness of the fault.

A model and simulation of fast space charge pulses in polymers

NASA Astrophysics Data System (ADS)

Lv, Zepeng; Rowland, Simon M.; Wu, Kai

2017-11-01

The transport of space charge packets across polyethylene and epoxy resin in high electric fields has been characterized as fast or slow depending on packet mobility. Several explanations for the formation and transport of slow space charge packets have been proposed, but the origins of fast space charge pulses, with mobilities above 10-11 m2 V-1 s-1, are unclear. In one suggested model, it is assumed that the formation of fast charge pulses is due to discontinuous electromechanical compression and charge injection at the electrode-insulation interface, and their transport is related to corresponding relaxation processes. In that model, charges travel as a pulse because of group polarization. This paper provides an alternative model based on the reduction of charge carrier activation energy due to charge density triggered polymer chain movement and subsequent chain relaxation times. The generation and transport of fast charge pulses are readily simulated by a bipolar charge transport model with three additional parameters: reduced activation energy, charge density threshold, and chain relaxation time. Such a model is shown to reproduce key features of fast space charge pulses including speed, duration, repetition rate and pulse size. This model provides the basis for a deep understanding of the physical origins of fast space charge pulses in polymers.

Fast vesicle transport is required for the slow axonal transport of synapsin.

PubMed

Tang, Yong; Scott, David; Das, Utpal; Gitler, Daniel; Ganguly, Archan; Roy, Subhojit

2013-09-25

Although it is known that cytosolic/soluble proteins synthesized in cell bodies are transported at much lower overall velocities than vesicles in fast axonal transport, the fundamental basis for this slow movement is unknown. Recently, we found that cytosolic proteins in axons of mouse cultured neurons are conveyed in a manner that superficially resembles diffusion, but with a slow anterograde bias that is energy- and motor-dependent (Scott et al., 2011). Here we show that slow axonal transport of synapsin, a prototypical member of this rate class, is dependent upon fast vesicle transport. Despite the distinct overall dynamics of slow and fast transport, experimentally induced and intrinsic variations in vesicle transport have analogous effects on slow transport of synapsin as well. Dynamic cotransport of vesicles and synapsin particles is also seen in axons, consistent with a model where higher-order assemblies of synapsin are conveyed by transient and probabilistic associations with vesicles moving in fast axonal transport. We posit that such dynamic associations generate the slow overall anterogradely biased flow of the population ("dynamic-recruitment model"). Our studies uncover the underlying kinetic basis for a classic cytosolic/soluble protein moving in slow axonal transport and reveal previously unknown links between slow and fast transport, offering a clearer conceptual picture of this curious phenomenon.

The relationship between two fast/slow analysis techniques for bursting oscillations

PubMed Central

Teka, Wondimu; Tabak, Joël; Bertram, Richard

2012-01-01

Bursting oscillations in excitable systems reflect multi-timescale dynamics. These oscillations have often been studied in mathematical models by splitting the equations into fast and slow subsystems. Typically, one treats the slow variables as parameters of the fast subsystem and studies the bifurcation structure of this subsystem. This has key features such as a z-curve (stationary branch) and a Hopf bifurcation that gives rise to a branch of periodic spiking solutions. In models of bursting in pituitary cells, we have recently used a different approach that focuses on the dynamics of the slow subsystem. Characteristic features of this approach are folded node singularities and a critical manifold. In this article, we investigate the relationships between the key structures of the two analysis techniques. We find that the z-curve and Hopf bifurcation of the two-fast/one-slow decomposition are closely related to the voltage nullcline and folded node singularity of the one-fast/two-slow decomposition, respectively. They become identical in the double singular limit in which voltage is infinitely fast and calcium is infinitely slow. PMID:23278052

In situ hybridisation of a large repertoire of muscle-specific transcripts in fish larvae: the new superficial slow-twitch fibres exhibit characteristics of fast-twitch differentiation.

PubMed

Chauvigné, F; Ralliere, C; Cauty, C; Rescan, P Y

2006-01-01

Much of the present information on muscle differentiation in fish concerns the early embryonic stages. To learn more about the maturation and the diversification of the fish myotomal fibres in later stages of ontogeny, we investigated, by means of in situ hybridisation, the developmental expression of a large repertoire of muscle-specific genes in trout larvae from hatching to yolk resorption. At hatching, transcripts for fast and slow muscle protein isoforms, namely myosins, tropomyosins, troponins and myosin binding protein C were present in the deep fast and the superficial slow areas of the myotome, respectively. During myotome expansion that follows hatching, the expression of fast isoforms became progressively confined to the borders of the fast muscle mass, whereas, in contrast, slow muscle isoform transcripts were uniformly expressed in all the slow fibres. Transcripts for several enzymes involved in oxidative metabolism such as citrate synthase, cytochrome oxidase component IV and succinate dehydrogenase, were present throughout the whole myotome of hatching embryos but in later stages became concentrated in slow fibre as well as in lateral fast fibres. Surprisingly, the slow fibres that are added externally to the single superficial layer of the embryonic (original) slow muscle fibres expressed not only slow twitch muscle isoforms but also, transiently, a subset of fast twitch muscle isoforms including MyLC1, MyLC3, MyHC and myosin binding protein C. Taken together these observations show that the growth of the myotome of the fish larvae is associated with complex patterns of muscular gene expression and demonstrate the unexpected presence of fast muscle isoform-expressing fibres in the most superficial part of the slow muscle.

Timescale Halo: Average-Speed Targets Elicit More Positive and Less Negative Attributions than Slow or Fast Targets

PubMed Central

Hernandez, Ivan; Preston, Jesse Lee; Hepler, Justin

2014-01-01

Research on the timescale bias has found that observers perceive more capacity for mind in targets moving at an average speed, relative to slow or fast moving targets. The present research revisited the timescale bias as a type of halo effect, where normal-speed people elicit positive evaluations and abnormal-speed (slow and fast) people elicit negative evaluations. In two studies, participants viewed videos of people walking at a slow, average, or fast speed. We find evidence for a timescale halo effect: people walking at an average-speed were attributed more positive mental traits, but fewer negative mental traits, relative to slow or fast moving people. These effects held across both cognitive and emotional dimensions of mind and were mediated by overall positive/negative ratings of the person. These results suggest that, rather than eliciting greater perceptions of general mind, the timescale bias may reflect a generalized positivity toward average speed people relative to slow or fast moving people. PMID:24421882

Temperature-dependent changes in the viscoelasticity of intact resting mammalian (rat) fast- and slow-twitch muscle fibres.

PubMed

Mutungi, G; Ranatunga, K W

1998-04-01

1. The tension and sarcomere length responses induced by ramp stretches (at amplitudes of 1-3 % fibre length (Lo) and speeds of 0.01-12 Lo s-1) were examined at different temperatures (range, 10-35 degrees C) in resting intact muscle fibre bundles isolated from the soleus (a slow-twitch muscle) and extensor digitorum longus (a fast-twitch muscle) of the rat. Some observations are also presented on the effects of chemical skinning on passive viscoelasticity at 10 degrees C. 2. As previously reported, the tension response to a ramp stretch, in different preparations and under various conditions, could be resolved into a viscous (P1), a viscoelastic (P2) and an elastic (P3) component and showed characteristic differences between slow and fast muscle fibres. 3. Chemical skinning of the muscle fibres led to a decrease in the amplitude of all three tension components. However, the fast-slow fibre differences remained after skinning. For example, the viscosity coefficient derived from P1 tension data decreased from 0.84 +/- 0.06 before skinning to 0.44 +/- 0.06 kN s m-2 after skinning in fast fibres; the corresponding values in slow fibres were 2.1 +/- 0.08 and 0.87 +/- 0.09 kN s m-2, respectively. 4. Increasing the experimental temperature from 10 to 35 degrees C led to a decrease in all the tension components in both fast and slow muscle fibre bundles. The decrease of P1 (viscous) tension was such that the viscosity coefficient calculated using P1 data was reduced from 0.84 +/- 0.1 to 0.43 +/- 0.05 kN s m-2 in fast fibres and from 2.0 +/- 0.1 to 1.0 +/- 0.1 kN s m-2 in slow fibres (Q10 of approximately 1.3 in both). 5. In both fast and slow muscle fibre preparations, the plateau tension of the viscoelastic component (P2) decreased by 60-80 % as the temperature was increased from 10 to 35 degrees C giving P2 tension a Q10 of approximately 1.4 in slow fibres and approximately 1.7 in the fast fibres. Additionally, the relaxation time of the viscoelasticity decreased from 11.9 +/- 1 ms (fast) and 43.1 +/- 1 ms (slow) at 10 degrees C to 3 +/- 0.5 ms (fast) at 25 C degrees and 8. 7 +/- 0.6 ms (slow) at 35 degrees C (Q10 of approximately 2.0 in slow and approximately 2.5 in fast fibres). 6. The fast-slow fibre differences in passive viscoelasticity remained at the high physiological temperatures. The physiological significance of such fibre-type differences and their possible underlying mechanisms are discussed.

Multimotor Transport in a System of Active and Inactive Kinesin-1 Motors

PubMed Central

Scharrel, Lara; Ma, Rui; Schneider, René; Jülicher, Frank; Diez, Stefan

2014-01-01

Long-range directional transport in cells is facilitated by microtubule-based motor proteins. One example is transport in a nerve cell, where small groups of motor proteins, such as kinesins and cytoplasmic dynein, work together to ensure the supply and clearance of cellular material along the axon. Defects in axonal transport have been linked to Alzheimer’s and other neurodegenerative diseases. However, it is not known in detail how multimotor-based cargo transport is impaired if a fraction of the motors are defective. To mimic impaired multimotor transport in vitro, we performed gliding motility assays with varying fractions of active kinesin-1 motors and inactive kinesin-1 motor mutants. We found that impaired transport manifests in multiple motility regimes: 1), a fast-motility regime characterized by gliding at velocities close to the single-molecule velocity of the active motors; 2), a slow-motility regime characterized by gliding at close-to zero velocity or full stopping; and 3), a regime in which fast and slow motilities coexist. Notably, the transition from the fast to the slow regime occurred sharply at a threshold fraction of active motors. Based on single-motor parameters, we developed a stochastic model and a mean-field theoretical description that explain our experimental findings. Our results demonstrate that impaired multimotor transport mostly occurs in an either/or fashion: depending on the ratio of active to inactive motors, transport is either performed at close to full speed or is out of action. PMID:25028878

Motor cortical representation of the pelvic floor muscles.

PubMed

Schrum, A; Wolff, S; van der Horst, C; Kuhtz-Buschbeck, J P

2011-07-01

Pelvic floor muscle training involves rhythmical voluntary contractions of the external urethral sphincter and ancillary pelvic floor muscles. The representation of these muscles in the motor cortex has not been located precisely and unambiguously. We used functional magnetic resonance imaging to determine brain activity during slow and fast pelvic floor contractions. Cerebral responses were recorded in 17 healthy male volunteers, 21 to 47 years old, with normal bladder control. Functional magnetic resonance imaging was performed during metronome paced slow (0.25 Hertz) and fast (0.7 Hertz) contractions of the pelvic floor that mimicked the interruption of voiding. To study the somatotopy of the cortical representations, flexion-extension movements of the right toes were performed as a control task. Functional magnetic resonance imaging during pelvic floor contractions detected activity of the supplementary motor area in the medial wall and of the midcingulate cortex, insula, posterior parietal cortex, putamen, thalamus, cerebellar vermis and upper ventral pons. There were no significant differences in activation between slow and fast contractions. Toe movements involved significantly stronger activity of the paracentral lobule (ie the medial primary motor cortex) than did the pelvic floor contractions. Otherwise the areas active during pelvic floor and leg muscle contractions overlapped considerably. The motor cortical representation of pelvic floor muscles is located mostly in the supplementary motor area. It extends further ventrally and anteriorly than the representation of distal leg muscles. Copyright © 2011 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Intracochlear Scala Media Pressure Measurement: Implications for Models of Cochlear Mechanics.

PubMed

Kale, Sushrut S; Olson, Elizabeth S

2015-12-15

Models of the active cochlea build upon the underlying passive mechanics. Passive cochlear mechanics is based on physical and geometrical properties of the cochlea and the fluid-tissue interaction between the cochlear partition and the surrounding fluid. Although the fluid-tissue interaction between the basilar membrane and the fluid in scala tympani (ST) has been explored in both active and passive cochleae, there was no experimental data on the fluid-tissue interaction on the scala media (SM) side of the partition. To this aim, we measured sound-evoked intracochlear pressure in SM close to the partition using micropressure sensors. All the SM pressure data are from passive cochleae, likely because the SM cochleostomy led to loss of endocochlear potential. Thus, these experiments are studies of passive cochlear mechanics. SM pressure close to the tissue showed a pattern of peaks and notches, which could be explained as an interaction between fast and slow (i.e., traveling wave) pressure modes. In several animals SM and ST pressure were measured in the same cochlea. Similar to previous studies, ST-pressure was dominated by a slow, traveling wave mode at stimulus frequencies in the vicinity of the best frequency of the measurement location, and by a fast mode above best frequency. Antisymmetric pressure between SM and ST supported the classic single-partition cochlear models, or a dual-partition model with tight coupling between partitions. From the SM and ST pressure we calculated slow and fast modes, and from active ST pressure we extrapolated the passive findings to the active case. The passive slow mode estimated from SM and ST data was low-pass in nature, as predicted by cochlear models. Copyright © 2015 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Intracochlear Scala Media Pressure Measurement: Implications for Models of Cochlear Mechanics

PubMed Central

Kale, Sushrut S.; Olson, Elizabeth S.

2015-01-01

Models of the active cochlea build upon the underlying passive mechanics. Passive cochlear mechanics is based on physical and geometrical properties of the cochlea and the fluid-tissue interaction between the cochlear partition and the surrounding fluid. Although the fluid-tissue interaction between the basilar membrane and the fluid in scala tympani (ST) has been explored in both active and passive cochleae, there was no experimental data on the fluid-tissue interaction on the scala media (SM) side of the partition. To this aim, we measured sound-evoked intracochlear pressure in SM close to the partition using micropressure sensors. All the SM pressure data are from passive cochleae, likely because the SM cochleostomy led to loss of endocochlear potential. Thus, these experiments are studies of passive cochlear mechanics. SM pressure close to the tissue showed a pattern of peaks and notches, which could be explained as an interaction between fast and slow (i.e., traveling wave) pressure modes. In several animals SM and ST pressure were measured in the same cochlea. Similar to previous studies, ST-pressure was dominated by a slow, traveling wave mode at stimulus frequencies in the vicinity of the best frequency of the measurement location, and by a fast mode above best frequency. Antisymmetric pressure between SM and ST supported the classic single-partition cochlear models, or a dual-partition model with tight coupling between partitions. From the SM and ST pressure we calculated slow and fast modes, and from active ST pressure we extrapolated the passive findings to the active case. The passive slow mode estimated from SM and ST data was low-pass in nature, as predicted by cochlear models. PMID:26682824

Interneuron-mediated inhibition synchronizes neuronal activity during slow oscillation.

PubMed

Chen, Jen-Yung; Chauvette, Sylvain; Skorheim, Steven; Timofeev, Igor; Bazhenov, Maxim

2012-08-15

The signature of slow-wave sleep in the electroencephalogram (EEG) is large-amplitude fluctuation of the field potential, which reflects synchronous alternation of activity and silence across cortical neurons. While initiation of the active cortical states during sleep slow oscillation has been intensively studied, the biological mechanisms which drive the network transition from an active state to silence remain poorly understood. In the current study, using a combination of in vivo electrophysiology and thalamocortical network simulation, we explored the impact of intrinsic and synaptic inhibition on state transition during sleep slow oscillation. We found that in normal physiological conditions, synaptic inhibition controls the duration and the synchrony of active state termination. The decline of interneuron-mediated inhibition led to asynchronous downward transition across the cortical network and broke the regular slow oscillation pattern. Furthermore, in both in vivo experiment and computational modelling, we revealed that when the level of synaptic inhibition was reduced significantly, it led to a recovery of synchronized oscillations in the form of seizure-like bursting activity. In this condition, the fast active state termination was mediated by intrinsic hyperpolarizing conductances. Our study highlights the significance of both intrinsic and synaptic inhibition in manipulating sleep slow rhythms.

Interneuron-mediated inhibition synchronizes neuronal activity during slow oscillation

PubMed Central

Chen, Jen-Yung; Chauvette, Sylvain; Skorheim, Steven; Timofeev, Igor; Bazhenov, Maxim

2012-01-01

The signature of slow-wave sleep in the electroencephalogram (EEG) is large-amplitude fluctuation of the field potential, which reflects synchronous alternation of activity and silence across cortical neurons. While initiation of the active cortical states during sleep slow oscillation has been intensively studied, the biological mechanisms which drive the network transition from an active state to silence remain poorly understood. In the current study, using a combination of in vivo electrophysiology and thalamocortical network simulation, we explored the impact of intrinsic and synaptic inhibition on state transition during sleep slow oscillation. We found that in normal physiological conditions, synaptic inhibition controls the duration and the synchrony of active state termination. The decline of interneuron-mediated inhibition led to asynchronous downward transition across the cortical network and broke the regular slow oscillation pattern. Furthermore, in both in vivo experiment and computational modelling, we revealed that when the level of synaptic inhibition was reduced significantly, it led to a recovery of synchronized oscillations in the form of seizure-like bursting activity. In this condition, the fast active state termination was mediated by intrinsic hyperpolarizing conductances. Our study highlights the significance of both intrinsic and synaptic inhibition in manipulating sleep slow rhythms. PMID:22641778

Physiological Mechanisms Only Tell Half Story: Multiple Biological Processes are involved in Regulating Freezing Tolerance of Imbibed Lactuca sativa Seeds

PubMed Central

Jaganathan, Ganesh K.; Han, Yingying; Li, Weijie; Song, Danping; Song, Xiaoyan; Shen, Mengqi; Zhou, Qiang; Zhang, Chenxue; Liu, Baolin

2017-01-01

The physiological mechanisms by which imbibed seeds survive freezing temperatures in their natural environment have been categorized as freezing avoidance by supercooling and freezing tolerance by extracellular freeze-desiccation, but the biochemical and molecular mechanisms conferring seed freezing tolerance is unexplored. In this study, using imbibed Lactuca sativa seeds we show that fast cooled seeds (60 °C h−1) suffered significantly higher membrane damage at temperature between −20 °C and −10 °C than slow cooled (3 °Ch−1) seeds (P < 0.05), presumably explaining viability loss during fast cooling when temperature approaches −20 °C. Total soluble sugars increase in low temperature environment, but did not differ significantly between two cooling rates (P > 0.05). However, both SOD activity and accumulation of free proline were induced significantly after slow cooling to −20 °C compared with fast cooling. RNA-seq demonstrated that multiple pathways were differentially regulated between slow and fast cooling. Real-time verification of some differentially expressed genes (DEGs) revealed that fast cooling caused mRNA level changes of plant hormone and ubiquitionation pathways at higher sub-zero temperature, whilst slow cooling caused mRNA level change of those pathways at lower sub-zero ttemperatures. Thus, we conclude that imbibed seed tolerate low temperature not only by physiological mechanisms but also by biochemical and molecular changes. PMID:28287125

Physiological Mechanisms Only Tell Half Story: Multiple Biological Processes are involved in Regulating Freezing Tolerance of Imbibed Lactuca sativa Seeds.

PubMed

Jaganathan, Ganesh K; Han, Yingying; Li, Weijie; Song, Danping; Song, Xiaoyan; Shen, Mengqi; Zhou, Qiang; Zhang, Chenxue; Liu, Baolin

2017-03-13

The physiological mechanisms by which imbibed seeds survive freezing temperatures in their natural environment have been categorized as freezing avoidance by supercooling and freezing tolerance by extracellular freeze-desiccation, but the biochemical and molecular mechanisms conferring seed freezing tolerance is unexplored. In this study, using imbibed Lactuca sativa seeds we show that fast cooled seeds (60 °C h -1 ) suffered significantly higher membrane damage at temperature between -20 °C and -10 °C than slow cooled (3 °Ch -1 ) seeds (P < 0.05), presumably explaining viability loss during fast cooling when temperature approaches -20 °C. Total soluble sugars increase in low temperature environment, but did not differ significantly between two cooling rates (P > 0.05). However, both SOD activity and accumulation of free proline were induced significantly after slow cooling to -20 °C compared with fast cooling. RNA-seq demonstrated that multiple pathways were differentially regulated between slow and fast cooling. Real-time verification of some differentially expressed genes (DEGs) revealed that fast cooling caused mRNA level changes of plant hormone and ubiquitionation pathways at higher sub-zero temperature, whilst slow cooling caused mRNA level change of those pathways at lower sub-zero ttemperatures. Thus, we conclude that imbibed seed tolerate low temperature not only by physiological mechanisms but also by biochemical and molecular changes.

Skeletal muscle fiber type conversion during the repair of mouse soleus: potential implications for muscle healing after injury.

PubMed

Matsuura, Tetsuya; Li, Yong; Giacobino, Jean-Paul; Fu, Freddie H; Huard, Johnny

2007-11-01

We used a mouse model of cardiotoxin injury to examine fiber type conversion during muscle repair. We evaluated the soleus muscles of 37 wild-type mice at 2, 4, 8, and 12 weeks after injury. We also used antibodies (fMHC and sMHC) against fast and slow myosin heavy chain to classify the myofibers into three categories: fast-, slow-, and mixed (hybrid)-type myofibers (myofibers expressing both fMHC and sMHC). Our results revealed an increase in the percentage of slow-type myofibers and a decrease in the percentage of fast-type myofibers during the repair process. The percentage of hybrid-type myofibers increased 2 weeks after injury, then gradually decreased over the following 6 weeks. Similarly, our analysis of centronucleated myofibers showed an increase in the percentage of slow-type myofibers and decreases in the percentages of fast- and hybrid-type myofibers. We also investigated the relationship between myofiber type conversion and peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1alpha). The expression of both PGC-1alpha protein, which is expressed in both the nucleus and the cytoplasm of regenerating myofibers, and sMHC protein increased with time after cardiotoxin injection, but we observed no significant differential expression of fMHC protein in regenerating muscle fibers during muscle repair. PGC-1alpha-positive myofibers underwent fast to slow myofiber type conversion during the repair process. These results suggest that PGC-1alpha contributes to myofiber type conversion after muscle injury and that this phenomenon could influence the recovery of the injured muscle. (c) 2007 Orthopaedic Research Society.

PCNA appears in two populations of slow and fast diffusion with a constant ratio throughout S-phase in replicating mammalian cells.

PubMed

Zessin, Patrick J M; Sporbert, Anje; Heilemann, Mike

2016-01-13

DNA replication is a fundamental cellular process that precedes cell division. Proliferating cell nuclear antigen (PCNA) is a central scaffold protein that orchestrates DNA replication by recruiting many factors essential for the replication machinery. We studied the mobility of PCNA in live mammalian cells using single-particle tracking in combination with photoactivated-localization microscopy (sptPALM) and found two populations. The first population which is only present in cells with active DNA replication, showed slow diffusion and was found to be located in replication foci. The second population showed fast diffusion, and represents the nucleoplasmic pool of unbound PCNA not involved in DNA replication. The ratio of these two populations remained constant throughout different stages of S-phase. A fraction of molecules in both populations showed spatially constrained mobility. We determined an exploration radius of ~100 nm for 13% of the slow-diffusing PCNA molecules, and of ~600 nm for 46% of the fast-diffusing PCNA molecules.

Maternal and genetic effects on broiler bone properties during incubation period.

PubMed

Yair, R; Cahaner, A; Uni, Z; Shahar, R

2017-07-01

In order to examine the differences in bone properties between fast-growing and slow-growing broiler embryos and to understand the effects of genotype and egg size on these differences, fast- and slow-growing hens and males were reciprocally crossed to create 4 egg groups: FST (laid by fast-growing hens, inseminated by fast-growing males), H-FST (fast-growing hens and slow-growing males), H-SLW (slow-growing hens and fast-growing males), and SLW (slow-growing hens and slow-growing males). Embryos (n = 8) from these 4 groups were sacrificed and weighed, and both tibiae were harvested on embryonic d (E) 17, 19, and 21. Left tibiae were tested for their whole-bone mechanical properties using a micromechanical device. Cortical bone structure and bone mineral density (BMD) were examined by micro-computed tomography of the left tibiae. Bone mineralization was evaluated by measuring BMD and ash content, while the rate and location of mineralization were evaluated by fluorochrome labeling. Osteoclastic activity and osteocyte density were evaluated by histological stains [TRAP (Tartrate resistant acid phosphatase) and H&E (Hematoxylin and Eosin), respectively]. Groups with larger eggs (FST and H-FST) had higher BW and tibia weight than groups with smaller eggs (SLW and H-SLW); however, they had a lower ratio of tibia weight to BW. Between groups with similar egg weight, stiffness, maximal load, and yield load of the bones were higher in the SLW than the H-SLW, while no differences were found between the FST and H-FST. Additionally, the tibiae of the SLW were stiffer and their osteocyte density higher than in the FST on E21 and their periosteal mineralization rate was higher between E19 and E21. No differences were found between the groups in cortical bone structure. This study demonstrates that faster growing hatchlings, especially those that hatch from relatively small eggs, have inferior bone mechanical properties in comparison to slower growing hatchlings, and suggests that fast-growing chicks hatching from small eggs are at a higher risk for developing bone pathologies. Accordingly, selection for increased egg size may lead to improved mechanical performance of the skeleton of fast-growing broilers. © 2017 Poultry Science Association Inc.

Type 2 iodothyronine deiodinase levels are higher in slow-twitch than fast-twitch mouse skeletal muscle and are increased in hypothyroidism.

PubMed

Marsili, Alessandro; Ramadan, Waile; Harney, John W; Mulcahey, Michelle; Castroneves, Luciana Audi; Goemann, Iuri Martin; Wajner, Simone Magagnin; Huang, Stephen A; Zavacki, Ann Marie; Maia, Ana Luiza; Dentice, Monica; Salvatore, Domenico; Silva, J Enrique; Larsen, P Reed

2010-12-01

Because of its large mass, relatively high metabolic activity and responsiveness to thyroid hormone, skeletal muscle contributes significantly to energy expenditure. Despite the presence of mRNA encoding the type 2 iodothyronine-deiodinase (D2), an enzyme that activates T(4) to T3, very low or undetectable activity has been reported in muscle homogenates of adult humans and mice. With a modified D2 assay, using microsomal protein, overnight incubation and protein from D2 knockout mouse muscle as a tissue-specific blank, we examined slow- and fast-twitch mouse skeletal muscles for D2 activity and its response to physiological stimuli. D2 activity was detectable in all hind limb muscles of 8- to 12-wk old C57/BL6 mice. Interestingly, it was higher in the slow-twitch soleus than in fast-twitch muscles (0.40 ± 0.06 vs. 0.076 ± 0.01 fmol/min · mg microsomal protein, respectively, P < 0.001). These levels are greater than those previously reported. Hypothyroidism caused a 40% (P < 0.01) and 300% (P < 0.001) increase in D2 activity after 4 and 8 wk treatment with antithyroid drugs, respectively, with no changes in D2 mRNA. Neither D2 mRNA nor activity increased after an overnight 4 C exposure despite a 10-fold increase in D2 activity in brown adipose tissue in the same mice. The magnitude of the activity, the fiber specificity, and the robust posttranslational response to hypothyroidism argue for a more important role for D2-generated T(3) in skeletal muscle physiology than previously assumed.

Type 2 Iodothyronine Deiodinase Levels Are Higher in Slow-Twitch than Fast-Twitch Mouse Skeletal Muscle and Are Increased in Hypothyroidism

PubMed Central

Marsili, Alessandro; Ramadan, Waile; Harney, John W.; Mulcahey, Michelle; Castroneves, Luciana Audi; Goemann, Iuri Martin; Wajner, Simone Magagnin; Huang, Stephen A.; Zavacki, Ann Marie; Maia, Ana Luiza; Dentice, Monica; Salvatore, Domenico; Silva, J. Enrique; Larsen, P. Reed

2010-01-01

Because of its large mass, relatively high metabolic activity and responsiveness to thyroid hormone, skeletal muscle contributes significantly to energy expenditure. Despite the presence of mRNA encoding the type 2 iodothyronine-deiodinase (D2), an enzyme that activates T4 to T3, very low or undetectable activity has been reported in muscle homogenates of adult humans and mice. With a modified D2 assay, using microsomal protein, overnight incubation and protein from D2 knockout mouse muscle as a tissue-specific blank, we examined slow- and fast-twitch mouse skeletal muscles for D2 activity and its response to physiological stimuli. D2 activity was detectable in all hind limb muscles of 8- to 12-wk old C57/BL6 mice. Interestingly, it was higher in the slow-twitch soleus than in fast-twitch muscles (0.40 ± 0.06 vs. 0.076 ± 0.01 fmol/min · mg microsomal protein, respectively, P < 0.001). These levels are greater than those previously reported. Hypothyroidism caused a 40% (P < 0.01) and 300% (P < 0.001) increase in D2 activity after 4 and 8 wk treatment with antithyroid drugs, respectively, with no changes in D2 mRNA. Neither D2 mRNA nor activity increased after an overnight 4 C exposure despite a 10-fold increase in D2 activity in brown adipose tissue in the same mice. The magnitude of the activity, the fiber specificity, and the robust posttranslational response to hypothyroidism argue for a more important role for D2-generated T3 in skeletal muscle physiology than previously assumed. PMID:20881246

Merging Structural Motifs of Functionalized Amino Acids and α-Aminoamides Results in Novel Anticonvulsant Compounds with Significant Effects on Slow and Fast Inactivation of Voltage-Gated Sodium Channels and in the Treatment of Neuropathic Pain

PubMed Central

2011-01-01

We recently reported that merging key structural pharmacophores of the anticonvulsant drugs lacosamide (a functionalized amino acid) with safinamide (an α-aminoamide) resulted in novel compounds with anticonvulsant activities superior to that of either drug alone. Here, we examined the effects of six such chimeric compounds on Na+-channel function in central nervous system catecholaminergic (CAD) cells. Using whole-cell patch clamp electrophysiology, we demonstrated that these compounds affected Na+ channel fast and slow inactivation processes. Detailed electrophysiological characterization of two of these chimeric compounds that contained either an oxymethylene ((R)-7) or a chemical bond ((R)-11) between the two aromatic rings showed comparable effects on slow inactivation, use-dependence of block, development of slow inactivation, and recovery of Na+ channels from inactivation. Both compounds were equally effective at inducing slow inactivation; (R)-7 shifted the fast inactivation curve in the hyperpolarizing direction greater than (R)-11, suggesting that in the presence of (R)-7 a larger fraction of the channels are in an inactivated state. None of the chimeric compounds affected veratridine- or KCl-induced glutamate release in neonatal cortical neurons. There was modest inhibition of KCl-induced calcium influx in cortical neurons. Finally, a single intraperitoneal administration of (R)-7, but not (R)-11, completely reversed mechanical hypersensitivity in a tibial-nerve injury model of neuropathic pain. The strong effects of (R)-7 on slow and fast inactivation of Na+ channels may contribute to its efficacy and provide a promising novel therapy for neuropathic pain, in addition to its antiepileptic potential. PMID:21765969

Abrupt plate acceleration during rifted margin formation: Cause and effect

NASA Astrophysics Data System (ADS)

Brune, Sascha; Williams, Simon; Butterworth, Nathaniel; Müller, Dietmar

2017-04-01

Extension rate is known to control key processes during rifted margin formation such as crust-mantle coupling, decompression melting, magmatism, and serpentinisation. Here we build on recent advances in plate tectonic reconstructions by quantifying the extension velocity history of Earth's major rifted margins during the last 240 million years. We find that many successful rifts start with a slow phase of extension followed by rapid acceleration that introduces a fast phase. The transition from slow to fast rifting takes place long before crustal break-up: approximately half of the present day rifted margin area was created during the slow, and the other half during the fast rift phase. We reproduce the rapid transition from slow to fast extension using analytical and numerical modelling with constant force boundary conditions. In these models, rift velocities are not imposed but instead evolve naturally in response to the changing strength of the rift. Our results demonstrate that abrupt plate acceleration during continental rifting is controlled by a rift-intrinsic strength-velocity feedback. The abruptness of rift acceleration is thereby governed by the nonlinearity of lithospheric localization. Realistic brittle and power-law rheologies lead to a speed-up duration between two and ten million years. For successful rifts that generate a new ocean basin, the duration of rift speed-up is notably almost independent of the applied extensional force. Instead, the force controls the duration of the slow phase: higher forces shorten the slow phase while lower forces prolong it. If the force is too low, however, delocalisation processes prevent the rift from reaching the point of speed-up and produce a failed rift, even if the extensional system was active for many million years.

Distinct slow and fast cortical theta dynamics in episodic memory retrieval.

PubMed

Pastötter, Bernhard; Bäuml, Karl-Heinz T

2014-07-01

Brain oscillations in the theta frequency band (3-8 Hz) have been shown to be critically involved in human episodic memory retrieval. In prior work, both positive and negative relationships between cortical theta power and retrieval success have been reported. This study examined the hypothesis that slow and fast cortical theta oscillations at the edges of the traditional theta frequency band are differentially related to retrieval success. Scalp EEG was recorded in healthy human participants as they performed a cued-recall episodic memory task. Slow (~3 Hz) and fast (~7 Hz) theta oscillations at retrieval were examined as a function of whether an item was recalled or not and as a function of the items' output position at test. Recall success typically declines with output position, due to increases in interference level. The results showed that slow theta power was positively related but fast theta power was negatively related to retrieval success. Concurrent positive and negative episodic memory effects for slow and fast theta oscillations were dissociable in time and space, showing different time courses and different spatial locations on the scalp. Moreover, fast theta power increased from early to late output positions, whereas slow theta power was unaffected by items' output position. Together with prior work, the results suggest that slow and fast theta oscillations have distinct functional roles in episodic memory retrieval, with slow theta oscillations being related to processes of recollection and conscious awareness, and fast theta oscillations being linked to processes of interference and interference resolution. Copyright © 2014 Elsevier Inc. All rights reserved.

Fast- or Slow-inactivated State Preference of Na+ Channel Inhibitors: A Simulation and Experimental Study

PubMed Central

Karoly, Robert; Lenkey, Nora; Juhasz, Andras O.; Vizi, E. Sylvester; Mike, Arpad

2010-01-01

Sodium channels are one of the most intensively studied drug targets. Sodium channel inhibitors (e.g., local anesthetics, anticonvulsants, antiarrhythmics and analgesics) exert their effect by stabilizing an inactivated conformation of the channels. Besides the fast-inactivated conformation, sodium channels have several distinct slow-inactivated conformational states. Stabilization of a slow-inactivated state has been proposed to be advantageous for certain therapeutic applications. Special voltage protocols are used to evoke slow inactivation of sodium channels. It is assumed that efficacy of a drug in these protocols indicates slow-inactivated state preference. We tested this assumption in simulations using four prototypical drug inhibitory mechanisms (fast or slow-inactivated state preference, with either fast or slow binding kinetics) and a kinetic model for sodium channels. Unexpectedly, we found that efficacy in these protocols (e.g., a shift of the “steady-state slow inactivation curve”), was not a reliable indicator of slow-inactivated state preference. Slowly associating fast-inactivated state-preferring drugs were indistinguishable from slow-inactivated state-preferring drugs. On the other hand, fast- and slow-inactivated state-preferring drugs tended to preferentially affect onset and recovery, respectively. The robustness of these observations was verified: i) by performing a Monte Carlo study on the effects of randomly modifying model parameters, ii) by testing the same drugs in a fundamentally different model and iii) by an analysis of the effect of systematically changing drug-specific parameters. In patch clamp electrophysiology experiments we tested five sodium channel inhibitor drugs on native sodium channels of cultured hippocampal neurons. For lidocaine, phenytoin and carbamazepine our data indicate a preference for the fast-inactivated state, while the results for fluoxetine and desipramine are inconclusive. We suggest that conclusions based on voltage protocols that are used to detect slow-inactivated state preference are unreliable and should be re-evaluated. PMID:20585544

The effect of fast and slow motor unit activation on whole-muscle mechanical performance: the size principle may not pose a mechanical paradox

PubMed Central

Holt, N. C.; Wakeling, J. M.; Biewener, A. A.

2014-01-01

The output of skeletal muscle can be varied by selectively recruiting different motor units. However, our knowledge of muscle function is largely derived from muscle in which all motor units are activated. This discrepancy may limit our understanding of in vivo muscle function. Hence, this study aimed to characterize the mechanical properties of muscle with different motor unit activation. We determined the isometric properties and isotonic force–velocity relationship of rat plantaris muscles in situ with all of the muscle active, 30% of the muscle containing predominately slower motor units active or 20% of the muscle containing predominately faster motor units active. There was a significant effect of active motor unit type on isometric force rise time (p < 0.001) and the force–velocity relationship (p < 0.001). Surprisingly, force rise time was longer and maximum shortening velocity higher when all motor units were active than when either fast or slow motor units were selectively activated. We propose this is due to the greater relative effects of factors such as series compliance and muscle resistance to shortening during sub-maximal contractions. The findings presented here suggest that recruitment according to the size principle, where slow motor units are activated first and faster ones recruited as demand increases, may not pose a mechanical paradox, as has been previously suggested. PMID:24695429

The effect of fast and slow motor unit activation on whole-muscle mechanical performance: the size principle may not pose a mechanical paradox.

PubMed

Holt, N C; Wakeling, J M; Biewener, A A

2014-05-22

The output of skeletal muscle can be varied by selectively recruiting different motor units. However, our knowledge of muscle function is largely derived from muscle in which all motor units are activated. This discrepancy may limit our understanding of in vivo muscle function. Hence, this study aimed to characterize the mechanical properties of muscle with different motor unit activation. We determined the isometric properties and isotonic force-velocity relationship of rat plantaris muscles in situ with all of the muscle active, 30% of the muscle containing predominately slower motor units active or 20% of the muscle containing predominately faster motor units active. There was a significant effect of active motor unit type on isometric force rise time (p < 0.001) and the force-velocity relationship (p < 0.001). Surprisingly, force rise time was longer and maximum shortening velocity higher when all motor units were active than when either fast or slow motor units were selectively activated. We propose this is due to the greater relative effects of factors such as series compliance and muscle resistance to shortening during sub-maximal contractions. The findings presented here suggest that recruitment according to the size principle, where slow motor units are activated first and faster ones recruited as demand increases, may not pose a mechanical paradox, as has been previously suggested.

The Effect of Involuntary Motor Activity on Myoelectric Pattern Recognition: A Case Study with Chronic Stroke Patients

PubMed Central

Zhang, Xu; Li, Yun; Chen, Xiang; Li, Guanglin; Rymer, William Zev; Zhou, Ping

2013-01-01

This study investigates the effect of involuntary motor activity of paretic-spastic muscles on classification of surface electromyography (EMG) signals. Two data collection sessions were designed for 8 stroke subjects to voluntarily perform 11 functional movements using their affected forearm and hand at a relatively slow and fast speed. For each stroke subject, the degree of involuntary motor activity present in voluntary surface EMG recordings was qualitatively described from such slow and fast experimental protocols. Myoelectric pattern recognition analysis was performed using different combinations of voluntary surface EMG data recorded from slow and fast sessions. Across all tested stroke subjects, our results revealed that when involuntary surface EMG was absent or present in both training and testing datasets, high accuracies (> 96%, > 98%, respectively, averaged over all the subjects) can be achieved in classification of different movements using surface EMG signals from paretic muscles. When involuntary surface EMG was solely involved in either training or testing datasets, the classification accuracies were dramatically reduced (< 89%, < 85%, respectively). However, if both training and testing datasets contained EMG signals with presence and absence of involuntary EMG interference, high accuracies were still achieved (> 97%). The findings of this study can be used to guide appropriate design and implementation of myoelectric pattern recognition based systems or devices toward promoting robot-aided therapy for stroke rehabilitation. PMID:23860192

Regulation of gene expression mediating indeterminate muscle growth in teleosts.

PubMed

Ahammad, A K Shakur; Asaduzzaman, Md; Asakawa, Shuichi; Watabe, Shugo; Kinoshita, Shigeharu

2015-08-01

Teleosts are unique among vertebrates due to their indeterminate muscle growth, i.e., continued production of neonatal muscle fibers until death. However, the molecular mechanism(s) underlying this property is unknown. Here, we focused on the torafugu (Takifugu rubripes) myosin heavy chain gene, MYHM2528-1, which is specifically expressed in neonatal muscle fibers produced by indeterminate muscle growth. We examined the flanking region of MYHM2528-1 through an in vivo reporter assay using zebrafish (Danio rerio) and identified a 2100 bp 5'-flanking sequence that contained sufficient promoter activity to allow specific gene expression. The effects of enhanced promoter activity were observed at the outer region of the fast muscle and the dorsal edge of slow muscle in zebrafish larvae. At the juvenile stage, the promoter was specifically activated in small diameter muscle fibers scattered throughout fast muscle and in slow muscle near the septum separating slow and fast muscles. This spatio-temporal promoter activity overlapped with known myogenic zones involved in teleost indeterminate muscle growth. A deletion mutant analysis revealed that the -2100 to -600 bp 5'flanking sequence of MYHM2528-1 is essential for promoter activity. This region contains putative binding sites for several representative myogenesis-related transcription factors and nuclear factor of activated T-cell (NFAT), a transcription activator involved in regeneration of mammalian adult skeletal muscle. A significant reduction in the promoter activity of the MYHM2528-1 deletion constructs was observed in accordance with a reduction in the number of these binding sites, suggesting the involvement of specific transcription factors in indeterminate muscle growth. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

ATP Released by Electrical Stimuli Elicits Calcium Transients and Gene Expression in Skeletal Muscle*

PubMed Central

Buvinic, Sonja; Almarza, Gonzalo; Bustamante, Mario; Casas, Mariana; López, Javiera; Riquelme, Manuel; Sáez, Juan Carlos; Huidobro-Toro, Juan Pablo; Jaimovich, Enrique

2009-01-01

ATP released from cells is known to activate plasma membrane P2X (ionotropic) or P2Y (metabotropic) receptors. In skeletal muscle cells, depolarizing stimuli induce both a fast calcium signal associated with contraction and a slow signal that regulates gene expression. Here we show that nucleotides released to the extracellular medium by electrical stimulation are partly involved in the fast component and are largely responsible for the slow signals. In rat skeletal myotubes, a tetanic stimulus (45 Hz, 400 1-ms pulses) rapidly increased extracellular levels of ATP, ADP, and AMP after 15 s to 3 min. Exogenous ATP induced an increase in intracellular free Ca2+ concentration, with an EC50 value of 7.8 ± 3.1 μm. Exogenous ADP, UTP, and UDP also promoted calcium transients. Both fast and slow calcium signals evoked by tetanic stimulation were inhibited by either 100 μm suramin or 2 units/ml apyrase. Apyrase also reduced fast and slow calcium signals evoked by tetanus (45 Hz, 400 0.3-ms pulses) in isolated mouse adult skeletal fibers. A likely candidate for the ATP release pathway is the pannexin-1 hemichannel; its blockers inhibited both calcium transients and ATP release. The dihydropyridine receptor co-precipitated with both the P2Y2 receptor and pannexin-1. As reported previously for electrical stimulation, 500 μm ATP significantly increased mRNA expression for both c-fos and interleukin 6. Our results suggest that nucleotides released during skeletal muscle activity through pannexin-1 hemichannels act through P2X and P2Y receptors to modulate both Ca2+ homeostasis and muscle physiology. PMID:19822518

Coordinate changes of myosin light and heavy chain isoforms during forced fiber type transitions in rabbit muscle.

PubMed

Leeuw, T; Pette, D

1996-01-01

Skeletal muscle fibers are versatile entities, capable of changing their phenotype in response to altered functional demands. In the present study, fast-to-slow fiber type transitions were induced in rabbit tibialis anterior (fA) muscles by chronic low-frequency stimulation (CLFS). The time course of changes in relative protein concentrations of fast and slow myosin light chain (MLC) isoforms and changes in their relative synthesis rates by in vivo labeling with [35S]methionine were followed during stimulation periods of up to 60 days. Generally, relative synthesis rates and protein concentrations changed in parallel; i.e., fast isoforms decreased and slow isoforms increased. MLC3f, however, which turns over at a higher rate than the other light chains, exhibited a conspicuous discrepancy between a markedly reduced relative synthesis but only a moderate decrease in protein amount during the initial 2 weeks of CLFS. Apparently, MLC3f is regulated independent of MLC1f, with protein degradation playing an important role in its regulation. The exchange of fast MLC isoforms with their slow counterparts seemed to correspond to the ultimate fast-to-slow (MHCIIa-->MHCI) transition at the MHC level. However, due to an earlier onset of the fast-to-slow transition of the regulatory light chain and the delayed fast-to-slow exchange of the alkali light chains, a spectrum of hybrid isomyosins composed of fast and slow light and heavy chains must have existed transiently in transforming fibers. Such hybrid isomyosins appeared to be restricted to MHCIIa- and MHCI-based combinations. In conclusion, fiber type specific programs that normally coordinate the expression of myofibrillar protein isoforms seem to be maintained during fiber type transitions. Possible differences in post-transcriptional regulation may result in the transient accumulation of atypical combinations of fast and slow MLC and MHC isoforms, giving rise to the appearance of hybrid fibers under the conditions of forced fiber type conversion.

Degradation kinetics of ptaquiloside in soil and soil solution.

PubMed

Ovesen, Rikke Gleerup; Rasmussen, Lars Holm; Hansen, Hans Christian Bruun

2008-02-01

Ptaquiloside (PTA) is a carcinogenic norsesquiterpene glycoside produced in bracken (Pteridium aquilinum (L.) Kuhn), a widespread, aggressive weed. Transfer of PTA to soil and soil solution eventually may contaminate groundwater and surface water. Degradation rates of PTA were quantified in soil and soil solutions in sandy and clayey soils subjected to high natural PTA loads from bracken stands. Degradation kinetics in moist soil could be fitted with the sum of a fast and a slow first-order reaction; the fast reaction contributed 20 to 50% of the total degradation of PTA. The fast reaction was similar in all horizons, with the rate constant k(1F) ranging between 0.23 and 1.5/h. The slow degradation, with the rate constant k(1S) ranging between 0.00067 and 0.029/ h, was more than twice as fast in topsoils compared to subsoils, which is attributable to higher microbial activity in topsoils. Experiments with sterile controls confirmed that nonmicrobial degradation processes constituted more than 90% of the fast degradation and 50% of the slow degradation. The lower nonmicrobial degradation rate observed in the clayey compared with the sandy soil is attributed to a stabilizing effect of PTA by clay silicates. Ptaquiloside appeared to be stable in all soil solutions, in which no degradation was observed within a period of 28 d, in strong contrast to previous studies of hydrolysis rates in artificial aqueous electrolytes. The present study predicts that the risk of PTA leaching is controlled mainly by the residence time of pore water in soil, soil microbial activity, and content of organic matter and clay silicates.

Unexpectedly increased anorexigenic postprandial responses of PYY and GLP-1 to fast ice cream consumption in adult patients with Prader-Willi syndrome.

PubMed

Rigamonti, A E; Bini, S; Grugni, G; Agosti, F; De Col, A; Mallone, M; Cella, S G; Sartorio, A

2014-10-01

The effect of eating rate on the release of anorexigenic gut peptides in Prader-Willi syndrome (PWS), a neurogenetic disorder clinically characterized by hyperphagia and excessive obesity, has not been investigated so far. Postprandial PYY and GLP-1 levels to fast (5 min) and slow (30 min) ice cream consumption were measured in PWS adult patients and age-matched patients with simple obesity and normal-weighted subjects. Visual analog scales (VASs) were used to evaluate the subjective feelings of hunger and satiety. Fast ice cream consumption stimulated GLP-1 release in normal subjects, a greater increase being observed with slow feeding. Fast or slow feeding did not change circulating levels of GLP-1 in obese patients, while, unexpectedly, fast feeding (but not slow feeding) stimulated GLP-1 release in PWS patients. Plasma PYY concentrations increased in all groups, irrespective of the eating rate. Slow feeding was more effective in stimulating PYY release in normal subjects, while fast feeding was more effective in PWS patients. Slow feeding evoked a lower hunger and higher satiety compared with fast feeding in normal subjects, this finding being not evident in obese patients. Unexpectedly, fast feeding evoked a lower hunger and higher satiety in PWS patients in comparison with slow feeding. Fast feeding leads to higher concentrations of anorexigenic gut peptides and favours satiety in PWS adult patients, this pattern being not evident in age-matched patients with simple obesity, thus suggesting the existence of a different pathophysiological substrate in these two clinical conditions. © 2013 John Wiley & Sons Ltd.

Two-wave propagation in in vitro swine distal ulna

NASA Astrophysics Data System (ADS)

Mano, Isao; Horii, Kaoru; Matsukawa, Mami; Otani, Takahiko

2015-07-01

Ultrasonic transmitted waves were obtained in an in vitro swine distal ulna specimen, which mimics a human distal radius, that consists of interconnected cortical bone and cancellous bone. The transmitted waveforms appeared similar to the fast waves, slow waves, and overlapping fast and slow waves measured in the specimen after removing the surface cortical bone (only cancellous bone). In addition, the circumferential waves in the cortical bone and water did not affect the fast and slow waves. This suggests that the fast-and-slow-wave phenomenon can be observed in an in vivo human distal radius.

The fast milk acidifying phenotype of Streptococcus thermophilus can be acquired by natural transformation of the genomic island encoding the cell-envelope proteinase PrtS.

PubMed

Dandoy, Damien; Fremaux, Christophe; de Frahan, Marie Henry; Horvath, Philippe; Boyaval, Patrick; Hols, Pascal; Fontaine, Laetitia

2011-08-30

In industrial fermentation processes, the rate of milk acidification by Streptococcus thermophilus is of major technological importance. The cell-envelope proteinase PrtS was previously shown to be a key determinant of the milk acidification activity in this species. The PrtS enzyme is tightly anchored to the cell wall via a mechanism involving the typical sortase A (SrtA) and initiates the breakdown of milk casein into small oligopeptides. The presence or absence of PrtS divides the S. thermophilus strains into two phenotypic groups i.e. the slow and the fast acidifying strains. The aim of this study was to improve the milk acidification rate of slow S. thermophilus strains, and hence optimise the fermentation process of dairy products. In the present work, we developed for the first time a strategy based on natural transformation to confer the rapid acidification phenotype to slow acidifying starter strains of S. thermophilus. First, we established by gene disruption that (i) prtS, encoding the cell-envelope proteinase, is a key factor responsible for rapid milk acidification in fast acidifying strains, and that (ii) srtA, encoding sortase A, is not absolutely required to express the PrtS activity. Second, a 15-kb PCR product encompassing the prtS genomic island was transferred by natural transformation using the competence-inducing peptide in three distinct prtS-defective genetic backgrounds having or not a truncated sortase A gene. We showed that in all cases the milk acidification rate of transformants was significantly increased, reaching a level similar to that of wild-type fast acidifying strains. Furthermore, it appeared that the prtS-encoded activity does not depend on the prtS copy number or on its chromosomal integration locus. We have successfully used natural competence to transfer the prtS locus encoding the cell-envelope proteinase in three slow acidifying strains of S. thermophilus, allowing their conversion into fast acidifying derivatives. The efficient protocol developed in this article will provide the dairy industry with novel and optimised S. thermophilus starter strains.

Fiber-type distribution in insect leg muscles parallels similarities and differences in the functional role of insect walking legs.

PubMed

Godlewska-Hammel, Elzbieta; Büschges, Ansgar; Gruhn, Matthias

2017-10-01

Previous studies have demonstrated that myofibrillar ATPase (mATPase) enzyme activity in muscle fibers determines their contraction properties. We analyzed mATPase activities in muscles of the front, middle and hind legs of the orthopteran stick insect (Carausius morosus) to test the hypothesis that differences in muscle fiber types and distributions reflected differences in their behavioral functions. Our data show that all muscles are composed of at least three fiber types, fast, intermediate and slow, and demonstrate that: (1) in the femoral muscles (extensor and flexor tibiae) of all legs, the number of fast fibers decreases from proximal to distal, with a concomitant increase in the number of slow fibers. (2) The swing phase muscles protractor coxae and levator trochanteris, have smaller percentages of slow fibers compared to the antagonist stance muscles retractor coxae and depressor trochanteris. (3) The percentage of slow fibers in the retractor coxae and depressor trochanteris increases significantly from front to hind legs. These results suggest that fiber-type distribution in leg muscles of insects is not identical across leg muscles but tuned towards the specific function of a given muscle in the locomotor system.

Conventional, Bayesian, and Modified Prony's methods for characterizing fast and slow waves in equine cancellous bone

PubMed Central

Groopman, Amber M.; Katz, Jonathan I.; Holland, Mark R.; Fujita, Fuminori; Matsukawa, Mami; Mizuno, Katsunori; Wear, Keith A.; Miller, James G.

2015-01-01

Conventional, Bayesian, and the modified least-squares Prony's plus curve-fitting (MLSP + CF) methods were applied to data acquired using 1 MHz center frequency, broadband transducers on a single equine cancellous bone specimen that was systematically shortened from 11.8 mm down to 0.5 mm for a total of 24 sample thicknesses. Due to overlapping fast and slow waves, conventional analysis methods were restricted to data from sample thicknesses ranging from 11.8 mm to 6.0 mm. In contrast, Bayesian and MLSP + CF methods successfully separated fast and slow waves and provided reliable estimates of the ultrasonic properties of fast and slow waves for sample thicknesses ranging from 11.8 mm down to 3.5 mm. Comparisons of the three methods were carried out for phase velocity at the center frequency and the slope of the attenuation coefficient for the fast and slow waves. Good agreement among the three methods was also observed for average signal loss at the center frequency. The Bayesian and MLSP + CF approaches were able to separate the fast and slow waves and provide good estimates of the fast and slow wave properties even when the two wave modes overlapped in both time and frequency domains making conventional analysis methods unreliable. PMID:26328678

Linking state regulation, brain laterality, and self-reported attention-deficit/hyperactivity disorder (ADHD) symptoms in adults.

PubMed

Mohamed, Saleh M H; Börger, Norbert A; Geuze, Reint H; van der Meere, Jaap J

2016-10-01

Many clinical studies have shown that performance of subjects with attention-deficit/hyperactivity disorder (ADHD) is impaired when stimuli are presented at a slow rate compared to a medium or fast rate. According to the cognitive-energetic model, this finding may reflect difficulty in allocating sufficient effort to regulate the motor activation state. Other studies have shown that the left hemisphere is relatively responsible for keeping humans motivated, allocating sufficient effort to complete their tasks. This leads to a prediction that poor effort allocation might be associated with an affected left-hemisphere functioning in ADHD. So far, this prediction has not been directly tested, which is the aim of the present study. Seventy-seven adults with various scores on the Conners' Adult ADHD Rating Scale performed a lateralized lexical decision task in three conditions with stimuli presented in a fast, a medium, and a slow rate. The left-hemisphere functioning was measured in terms of visual field advantage (better performance for the right than for the left visual field). All subjects showed an increased right visual field advantage for word processing in the slow presentation rate of stimuli compared to the fast and the medium rate. Higher ADHD scores were related to a reduced right visual field advantage in the slow rate only. The present findings suggest that ADHD symptomatology is associated with less involvement of the left hemisphere when extra effort allocation is needed to optimize the low motor activation state.

Time-frequency dynamics during sleep spindles on the EEG in rodents with a genetic predisposition to absence epilepsy (WAG/Rij rats)

NASA Astrophysics Data System (ADS)

Hramov, Alexander E.; Sitnikova, Evgenija Y.; Pavlov, Alexey N.; Grubov, Vadim V.; Koronovskii, Alexey A.; Khramova, Marina V.

2015-03-01

Sleep spindles are known to appear spontaneously in the thalamocortical neuronal network of the brain during slow-wave sleep; pathological processes in the thalamocortical network may be the reason of the absence epilepsy. The aim of the present work is to study developed changes in the time-frequency structure of sleep spindles during the progressive development of the absence epilepsy in WAG/Rij rats. EEG recordings were made at age 7 and 9 months. Automatic recognition and subsequent analysis of sleep spindles on the EEG were performed using the continuous wavelet transform. The duration of epileptic discharges and the total duration of epileptic activity were found to increase with age, while the duration of sleep spindles, conversely, decreased. In terms of the mean frequency, sleep spindles could be divided into three classes: `slow' (mean frequency 9.3Hz), `medium' (11.4Hz), and `fast' (13.5Hz). Slow and medium (transitional) spindles in five-month-old animals showed increased frequency from the beginning to the end of the spindle. The more intense the epilepsy is, the shorter are the durations of spindles of all types. The mean frequencies of `medium' and `fast' spindles were higher in rats with more intense signs of epilepsy. Overall, high epileptic activity in WAG/Rij rats was linked with significant changes in spindles of the transitional type, with less marked changes in the two traditionally identified types of spindle, slow and fast.

Adaptation of rat soleus muscles to 4 wk of intermittent strain

NASA Technical Reports Server (NTRS)

Stauber, W. T.; Miller, G. R.; Grimmett, J. G.; Knack, K. K.

1994-01-01

The effect of repeated strains on rat soleus muscles was investigated by stretching active muscles 3 times/wk for 4 wk with two different methods of stretching. The adaptation of myofibers and noncontractile tissue was followed by histochemical techniques and computer-assisted image analysis. Muscle hypertrophy was seen in the slow-stretched muscles, which increased in mass by 13% and increased in myofiber cross-sectional area by 30%. In the fast-stretched muscle, mass increased by 10% but myofiber cross-sectional area actually decreased. This decrease in mean fiber area was the result of a population of very small fibers (population A) that coexisted with slightly smaller normal-sized fibers (population B). Fibers in population A did not have the distribution expected from atrophy compared with atrophic fibers from unloaded muscles; they were much smaller. In addition, there was a 44% increase in noncontractile tissue in the fast-stretched muscles. Thus, soleus muscles subjected to repeated strains respond differently to slow and fast stretching. Slow stretching results in typical muscle hypertrophy, whereas fast stretching produces somewhat larger muscles but with a mixture of small and normal-sized myofibers accompanied by a marked proliferation of noncontractile tissue.

Can Fast and Slow Intelligence Be Differentiated?

ERIC Educational Resources Information Center

Partchev, Ivailo; De Boeck, Paul

2012-01-01

Responses to items from an intelligence test may be fast or slow. The research issue dealt with in this paper is whether the intelligence involved in fast correct responses differs in nature from the intelligence involved in slow correct responses. There are two questions related to this issue: 1. Are the processes involved different? 2. Are the…

A shared resource between declarative memory and motor memory.

PubMed

Keisler, Aysha; Shadmehr, Reza

2010-11-03

The neural systems that support motor adaptation in humans are thought to be distinct from those that support the declarative system. Yet, during motor adaptation changes in motor commands are supported by a fast adaptive process that has important properties (rapid learning, fast decay) that are usually associated with the declarative system. The fast process can be contrasted to a slow adaptive process that also supports motor memory, but learns gradually and shows resistance to forgetting. Here we show that after people stop performing a motor task, the fast motor memory can be disrupted by a task that engages declarative memory, but the slow motor memory is immune from this interference. Furthermore, we find that the fast/declarative component plays a major role in the consolidation of the slow motor memory. Because of the competitive nature of declarative and nondeclarative memory during consolidation, impairment of the fast/declarative component leads to improvements in the slow/nondeclarative component. Therefore, the fast process that supports formation of motor memory is not only neurally distinct from the slow process, but it shares critical resources with the declarative memory system.

A shared resource between declarative memory and motor memory

PubMed Central

Keisler, Aysha; Shadmehr, Reza

2010-01-01

The neural systems that support motor adaptation in humans are thought to be distinct from those that support the declarative system. Yet, during motor adaptation changes in motor commands are supported by a fast adaptive process that has important properties (rapid learning, fast decay) that are usually associated with the declarative system. The fast process can be contrasted to a slow adaptive process that also supports motor memory, but learns gradually and shows resistance to forgetting. Here we show that after people stop performing a motor task, the fast motor memory can be disrupted by a task that engages declarative memory, but the slow motor memory is immune from this interference. Furthermore, we find that the fast/declarative component plays a major role in the consolidation of the slow motor memory. Because of the competitive nature of declarative and non-declarative memory during consolidation, impairment of the fast/declarative component leads to improvements in the slow/non-declarative component. Therefore, the fast process that supports formation of motor memory is not only neurally distinct from the slow process, but it shares critical resources with the declarative memory system. PMID:21048140

Lacosamide Inhibition of Nav1.7 Voltage-Gated Sodium Channels: Slow Binding to Fast-Inactivated States

PubMed Central

Jo, Sooyeon

2017-01-01

Lacosamide is an antiseizure agent that targets voltage-dependent sodium channels. Previous experiments have suggested that lacosamide is unusual in binding selectively to the slow-inactivated state of sodium channels, in contrast to drugs like carbamazepine and phenytoin, which bind tightly to fast-inactivated states. Using heterologously expressed human Nav1.7 sodium channels, we examined the state-dependent effects of lacosamide. Lacosamide induced a reversible shift in the voltage dependence of fast inactivation studied with 100-millisecond prepulses, suggesting binding to fast-inactivated states. Using steady holding potentials, lacosamide block was very weak at −120 mV (3% inhibition by 100 µM lacosamide) but greatly enhanced at −80 mV (43% inhibition by 100 µM lacosamide), where there is partial fast inactivation but little or no slow inactivation. During long depolarizations, lacosamide slowly (over seconds) put channels into states that recovered availability slowly (hundreds of milliseconds) at −120 mV. This resembles enhancement of slow inactivation, but the effect was much more pronounced at −40 mV, where fast inactivation is complete, but slow inactivation is not, than at 0 mV, where slow inactivation is maximal, more consistent with slow binding to fast-inactivated states than selective binding to slow-inactivated states. Furthermore, inhibition by lacosamide was greatly reduced by pretreatment with 300 µM lidocaine or 300 µM carbamazepine, suggesting that lacosamide, lidocaine, and carbamazepine all bind to the same site. The results suggest that lacosamide binds to fast-inactivated states in a manner similar to other antiseizure agents but with slower kinetics of binding and unbinding. PMID:28119481

Lacosamide Inhibition of Nav1.7 Voltage-Gated Sodium Channels: Slow Binding to Fast-Inactivated States.

PubMed

Jo, Sooyeon; Bean, Bruce P

2017-04-01

Lacosamide is an antiseizure agent that targets voltage-dependent sodium channels. Previous experiments have suggested that lacosamide is unusual in binding selectively to the slow-inactivated state of sodium channels, in contrast to drugs like carbamazepine and phenytoin, which bind tightly to fast-inactivated states. Using heterologously expressed human Nav1.7 sodium channels, we examined the state-dependent effects of lacosamide. Lacosamide induced a reversible shift in the voltage dependence of fast inactivation studied with 100-millisecond prepulses, suggesting binding to fast-inactivated states. Using steady holding potentials, lacosamide block was very weak at -120 mV (3% inhibition by 100 µ M lacosamide) but greatly enhanced at -80 mV (43% inhibition by 100 µ M lacosamide), where there is partial fast inactivation but little or no slow inactivation. During long depolarizations, lacosamide slowly (over seconds) put channels into states that recovered availability slowly (hundreds of milliseconds) at -120 mV. This resembles enhancement of slow inactivation, but the effect was much more pronounced at -40 mV, where fast inactivation is complete, but slow inactivation is not, than at 0 mV, where slow inactivation is maximal, more consistent with slow binding to fast-inactivated states than selective binding to slow-inactivated states. Furthermore, inhibition by lacosamide was greatly reduced by pretreatment with 300 µ M lidocaine or 300 µ M carbamazepine, suggesting that lacosamide, lidocaine, and carbamazepine all bind to the same site. The results suggest that lacosamide binds to fast-inactivated states in a manner similar to other antiseizure agents but with slower kinetics of binding and unbinding. Copyright © 2017 by The American Society for Pharmacology and Experimental Therapeutics.

Slow-onset and fast-onset symptom presentations in acute coronary syndrome (ACS): new perspectives on prehospital delay in patients with ACS.

PubMed

O'Donnell, Sharon; McKee, Gabrielle; Mooney, Mary; O'Brien, Frances; Moser, Debra K

2014-04-01

Patient decision delay is the main reason why many patients fail to receive timely medical intervention for symptoms of acute coronary syndrome (ACS). This study examines the validity of slow-onset and fast-onset ACS presentations and their influence on ACS prehospital delay times. A fast-onset ACS presentation is characterized by sudden, continuous, and severe chest pain, and slow-onset ACS pertains to all other ACS presentations. Baseline data pertaining to medical profiles, prehospital delay times, and ACS symptoms were recorded for all ACS patients who participated in a large multisite randomized control trial (RCT) in Dublin, Ireland. Patients were interviewed 2-4 days after their ACS event, and data were gathered using the ACS Response to Symptom Index. Only baseline data from the RCT, N = 893 patients, were analyzed. A total of 65% (n = 577) of patients experienced slow-onset ACS presentation, whereas 35% (n = 316) experienced fast-onset ACS. Patients who experienced slow-onset ACS were significantly more likely to have longer prehospital delays than patients with fast-onset ACS (3.5 h vs. 2.0 h, respectively, t = -5.63, df 890, p < 0.001). A multivariate analysis of delay revealed that, in the presence of other known delay factors, the only independent predictors of delay were slow-onset and fast-onset ACS (β = -.096, p < 0.002) and other factors associated with patient behavior. Slow-onset ACS and fast-onset ACS presentations are associated with distinct behavioral patterns that significantly influence prehospital time frames. As such, slow-onset ACS and fast-onset ACS are legitimate ACS presentation phenomena that should be seriously considered when examining the factors associated with prehospital delay. Copyright © 2014 Elsevier Inc. All rights reserved.

Cationic cure kinetics of a polyoxometalate loaded epoxy nanocomposite

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

Anderson, Benjamin J.

2012-08-06

The reaction cure kinetics of a novel polyoxometalate (POM) loaded epoxy nanocomposite is described. The POM is dispersed in the epoxy resin up to volume fractions of 0.1. Differential scanning calorimetry measurements show the cure of the epoxy resin to be sensitive to the POM loading. A kinetics study of the cure exotherm confirms that POM acts as a catalyst promoting cationic homopolymerization of the epoxy resin. The cure reaction is shown to propagate through two cure regimes. A fast cure at short time is shown to be propagation by the activated chain end (ACE) mechanism. A slow cure atmore » long time is shown to be propagation by the activated monomer (AM) mechanism. The activation energies for the fast and slow cure regimes agree well with other epoxy based systems that have been confirmed to propagate by the ACE and AM mechanisms.« less

Slow to fast alterations in skeletal muscle fibers caused by clenbuterol, a beta(2)-receptor agonist

NASA Technical Reports Server (NTRS)

Zeman, Richard J.; Ludemann, Robert; Easton, Thomas G.; Etlinger, Joseph D.

1988-01-01

The effects of a beta(2)-receptor agonist, clenbuterol, and a beta(2) antagonist, butoxamine, on the skeletal muscle fibers of rats were investigated. It was found that chronic treatment of rats with clenbuterol caused hypertrophy of histochemically identified fast-twitch, but not slow-twitch, fibers within the soleus, while in the extensor digitorum longus the mean areas of both fiber types were increased; in both muscles, the ratio of the number of fast-twitch to slow-twitch fibers was increased. In contrast, a treatment with butoxamine caused a reduction of the fast-twitch fiber size in both muscles, and the ratio of the fast-twitch to slow-twitch fibers was decreased.

Three Hierarchies in Skeletal Muscle Fibre Classification Allotype, Isotype and Phenotype

NASA Technical Reports Server (NTRS)

Hoh, Joseph F. Y.; Hughes, Suzanne; Hugh, Gregory; Pozgaj, Irene

1991-01-01

Immunocytochemical analyses using specific anti-myosin antibodies of mammalian muscle fibers during regeneration, development, and after denervation have revealed two distinct myogenic components determining fiber phenotype. The jaw-closing muscles of the cat contain superfast fibers which express a unique myosin not found in limb muscles. When superfast muscle is transplanted into a limb muscle bed, regenerating myotubes synthesize superfast myosin independent of innervation. Reinnervation by the nerve to a fast muscle leads to the expression of superfast and not fast myosin, while reinnervation by the nerve to a slow muscle leads to the expression of a slow myosin. When limb muscle is transplanted into the jaw muscle bed, only limb myosins are synthesized. Thus jaw and limb muscles belong to distinct allotypes, each with a unique range of phenotype options, the expressions of which may be modulated by the nerve. Primary and secondary myotubes in developing jaw and limb muscles are observed to belong to different categories characterized by different patterns of myosin gene expression. By taking into consideration the pattern of myosins synthesized and the changes in fiber size after denervation, 3 types of primary (fast, slow, and intermediate) fibers can be distinguished in rat fast limb muscles. All primaries synthesize slow myosin soon after their formation, but this is withdrawn in fast and intermediate primaries at different times. After neonatal denervation, slow and intermediate primaries express slow primaries hypertrophy with other fibers atrophy. In the mature rat, the number of slow fibers in the EDL is less than the number of slow primaries. Upon denervation, hypertrophic slow fibers matching the number and topographic distribution of slow primaries appear, suggesting that a subpopulation of the slow primaries acquire the fast phenotype during adult life, but reveal their original identity as slow primaries in response to denervation by hypertrophying and synthesizing slow myosin. It is proposed that within each muscle allotype, the various isotypes of primary and secondary fibers are myogenically determined, and are derived from different lineage of myoblasts.

The Action of Botulinum Toxin at the Neuromuscular Junction

DTIC Science & Technology

1980-12-22

fast - twitch " (gastrocnemius) and " slow - twitch " (soleus) muscles ... muscle fibers -"_re not significantly affected by the toxin. It is interesting to note that, although fast - twitch and slow - twitch mucles were...Duchen LW: An electron microscopic study of the changes induced by borulinum o::in in the motor end-plates of slow and fast skeletal muscle fibres of

Selective functional interactions between excitatory and inhibitory cortical neurons and differential contribution to persistent activity of the slow oscillation.

PubMed

Tahvildari, Babak; Wölfel, Markus; Duque, Alvaro; McCormick, David A

2012-08-29

The neocortex depends upon a relative balance of recurrent excitation and inhibition for its operation. During spontaneous Up states, cortical pyramidal cells receive proportional barrages of excitatory and inhibitory synaptic potentials. Many of these synaptic potentials arise from the activity of nearby neurons, although the identity of these cells is relatively unknown, especially for those underlying the generation of inhibitory synaptic events. To address these fundamental questions, we developed an in vitro submerged slice preparation of the mouse entorhinal cortex that generates robust and regular spontaneous recurrent network activity in the form of the slow oscillation. By performing whole-cell recordings from multiple cell types identified with green fluorescent protein expression and electrophysiological and/or morphological properties, we show that distinct functional subpopulations of neurons exist in the entorhinal cortex, with large variations in contribution to the generation of balanced excitation and inhibition during the slow oscillation. The most active neurons during the slow oscillation are excitatory pyramidal and inhibitory fast spiking interneurons, receiving robust barrages of both excitatory and inhibitory synaptic potentials. Weak action potential activity was observed in stellate excitatory neurons and somatostatin-containing interneurons. In contrast, interneurons containing neuropeptide Y, vasoactive intestinal peptide, or the 5-hydroxytryptamine (serotonin) 3a receptor, were silent. Our data demonstrate remarkable functional specificity in the interactions between different excitatory and inhibitory cortical neuronal subtypes, and suggest that it is the large recurrent interaction between pyramidal neurons and fast spiking interneurons that is responsible for the generation of persistent activity that characterizes the depolarized states of the cortex.

Gene regulation mediating fiber-type transformation in skeletal muscle cells is partly glucose- and ChREBP-dependent.

PubMed

Hanke, Nina; Scheibe, Renate J; Manukjan, Georgi; Ewers, David; Umeda, Patrick K; Chang, Kin-Chow; Kubis, Hans-Peter; Gros, Gerolf; Meissner, Joachim D

2011-03-01

Adaptations in the oxidative capacity of skeletal muscle cells can occur under several physiological or pathological conditions. We investigated the effect of increasing extracellular glucose concentration on the expression of markers of energy metabolism in primary skeletal muscle cells and the C2C12 muscle cell line. Growth of myotubes in 25mM glucose (high glucose, HG) compared with 5.55mM led to increases in the expression and activity of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a marker of glycolytic energy metabolism, while oxidative markers peroxisome proliferator-activated receptor γ coactivator 1α and citrate synthase decreased. HG induced metabolic adaptations as are seen during a slow-to-fast fiber transformation. Furthermore, HG increased fast myosin heavy chain (MHC) IId/x but did not change slow MHCI/β expression. Protein phosphatase 2A (PP2A) was shown to mediate the effects of HG on GAPDH and MHCIId/x. Carbohydrate response element-binding protein (ChREBP), a glucose-dependent transcription factor downstream of PP2A, partially mediated the effects of glucose on metabolic markers. The glucose-induced increase in PP2A activity was associated with an increase in p38 mitogen-activated protein kinase activity, which presumably mediates the increase in MHCIId/x promoter activity. Liver X receptor, another possible mediator of glucose effects, induced only an incomplete metabolic shift, mainly increasing the expression of the glycolytic marker. Taken together, HG induces a partial slow-to-fast transformation comprising metabolic enzymes together with an increased expression of MHCIId/x. This work demonstrates a functional role for ChREBP in determining the metabolic type of muscle fibers and highlights the importance of glucose as a signaling molecule in muscle. Copyright © 2011 Elsevier B.V. All rights reserved.

Fiber transformation and replacement in low-frequency stimulated rabbit fast-twitch muscles.

PubMed

Schuler, M; Pette, D

1996-08-01

The fast-to-slow conversion of rabbit skeletal muscles by chronic low-frequency (10 Hz, 12 h daily) stimulation involves (1) sequential fast-to-slow fiber-type transitions in the order of type IID-->type IIA-->type I, and (2) the replacement of deteriorating fast-twitch glycolytic fibers by new fibers derived from satellite cells and myotubes. These two processes were analyzed in 30- and 60-day stimulated extensor digitorum longus and tibialis anterior muscles. Fast-to-slow transforming fibers were identified by myofibrillar actomyosin histochemistry as type C fibers and immunohistochemically by their reaction with monoclonal antibodies specific to slow and fast myosin heavy chain isoforms. In situ hybridization of mRNA specific to the myosin heavy chain I isoform identified all fibers expressing slow myosin, i.e., type I and C fibers. The fraction of transforming fibers ranged between 35% and 50% in 30-day stimulated muscles. The percentage of type I fibers (20%) was threefold elevated in extensor digitorum longus muscle, but unaltered (3.5%) in tibialis anterior muscle, suggesting that fast-to-slow fiber conversion was more advanced in the former than in the latter. Fiber replacement was indicated by the finding that the fiber populations of both muscles contained 15% myotubes or small fibers with central nuclei. In situ hybridization revealed that myotubes and small regenerating fibers uniformly expressed myosin heavy chain I mRNA. Similarly, high percentages of slow-myosin-expressing myotubes and small fibers were found in 60-day stimulated muscles.

Responses of neuromuscular systems under gravity or microgravity environment.

PubMed

Ishihara, Akihiko; Kawano, Fuminori; Wang, Xiao Dong; Ohira, Yoshinobu

2004-11-01

Hindlimb suspension of rats induces induces fiber atrophy and type shift of muscle fibers. In contrast, there is no change in the cell size or oxidative enzyme activity of spinal motoneurons innervating muscle fibers. Growth-related increases in the cell size of muscle fibers and their spinal motoneurons are inhibited by hindlimb suspension. Exposure to microgravity induces atrophy of fibers (especially slow-twitch fibers) and shift of fibers from slow- to fast-twitch type in skeletal muscles (especially slow, anti-gravity muscles). In addition, a decrease in the oxidative enzyme activity of spinal motoneurons innervating slow-twitch fibers and of sensory neurons in the dorsal root ganglion is observed following exposure to microgravity. It is concluded that neuromuscular activities are important for maintaining metabolism and function of neuromuscular systems at an early postnatal development and that gravity effects both efferent and afferent neural pathways.

Once upon a (slow) time in the land of recurrent neuronal networks….

PubMed

Huang, Chengcheng; Doiron, Brent

2017-10-01

The brain must both react quickly to new inputs as well as store a memory of past activity. This requires biology that operates over a vast range of time scales. Fast time scales are determined by the kinetics of synaptic conductances and ionic channels; however, the mechanics of slow time scales are more complicated. In this opinion article we review two distinct network-based mechanisms that impart slow time scales in recurrently coupled neuronal networks. The first is in strongly coupled networks where the time scale of the internally generated fluctuations diverges at the transition between stable and chaotic firing rate activity. The second is in networks with finitely many members where noise-induced transitions between metastable states appear as a slow time scale in the ongoing network firing activity. We discuss these mechanisms with an emphasis on their similarities and differences. Copyright © 2017 Elsevier Ltd. All rights reserved.

N-fertilization has different effects on the growth, carbon and nitrogen physiology, and wood properties of slow- and fast-growing Populus species

PubMed Central

Luo, Zhi-Bin

2012-01-01

To investigate how N-fertilization affects the growth, carbon and nitrogen (N) physiology, and wood properties of poplars with contrasting growth characteristics, slow-growing (Populus popularis, Pp) and fast-growing (P. alba×P. glandulosa, Pg) poplar saplings were exposed to different N levels. Above-ground biomass, leaf area, photosynthetic rates (A), instantaneous photosynthetic nitrogen use efficiency (PNUE i), chlorophyll and foliar sugar concentrations were higher in Pg than in Pp. Foliar nitrate reductase (NR) activities and root glutamate synthase (GOGAT) activities were higher in Pg than in Pp as were the N amount and NUE of new shoots. Lignin contents and calorific values of Pg wood were less than that of Pp wood. N-fertilization reduced root biomass of Pg more than of Pp, but increased leaf biomass, leaf area, A, and PNUEi of Pg more than of Pp. Among 13 genes involved in the transport of ammonium or nitrate or in N assimilation, transcripts showed more pronounced changes to N-fertilization in Pg than in Pp. Increases in NR activities and N contents due to N-fertilization were larger in Pg than in Pp. In both species, N-fertilization resulted in lower calorific values as well as shorter and wider vessel elements/fibres. These results suggest that growth, carbon and N physiology, and wood properties are more sensitive to increasing N availability in fast-growing poplars than in slow-growing ones, which is probably due to prioritized resource allocation to the leaves and accelerated N physiological processes in fast-growing poplars under higher N levels. PMID:23028021

N-fertilization has different effects on the growth, carbon and nitrogen physiology, and wood properties of slow- and fast-growing Populus species.

PubMed

Li, Hong; Li, Mengchun; Luo, Jie; Cao, Xu; Qu, Long; Gai, Ying; Jiang, Xiangning; Liu, Tongxian; Bai, Hua; Janz, Dennis; Polle, Andrea; Peng, Changhui; Luo, Zhi-Bin

2012-10-01

To investigate how N-fertilization affects the growth, carbon and nitrogen (N) physiology, and wood properties of poplars with contrasting growth characteristics, slow-growing (Populus popularis, Pp) and fast-growing (P. alba×P. glandulosa, Pg) poplar saplings were exposed to different N levels. Above-ground biomass, leaf area, photosynthetic rates (A), instantaneous photosynthetic nitrogen use efficiency (PNUE (i)), chlorophyll and foliar sugar concentrations were higher in Pg than in Pp. Foliar nitrate reductase (NR) activities and root glutamate synthase (GOGAT) activities were higher in Pg than in Pp as were the N amount and NUE of new shoots. Lignin contents and calorific values of Pg wood were less than that of Pp wood. N-fertilization reduced root biomass of Pg more than of Pp, but increased leaf biomass, leaf area, A, and PNUE(i) of Pg more than of Pp. Among 13 genes involved in the transport of ammonium or nitrate or in N assimilation, transcripts showed more pronounced changes to N-fertilization in Pg than in Pp. Increases in NR activities and N contents due to N-fertilization were larger in Pg than in Pp. In both species, N-fertilization resulted in lower calorific values as well as shorter and wider vessel elements/fibres. These results suggest that growth, carbon and N physiology, and wood properties are more sensitive to increasing N availability in fast-growing poplars than in slow-growing ones, which is probably due to prioritized resource allocation to the leaves and accelerated N physiological processes in fast-growing poplars under higher N levels.

Molecular Population Genetics of the Alcohol Dehydrogenase Gene Region of DROSOPHILA MELANOGASTER

PubMed Central

Aquadro, Charles F.; Desse, Susan F.; Bland, Molly M.; Langley, Charles H.; Laurie-Ahlberg, Cathy C.

1986-01-01

Variation in the DNA restriction map of a 13-kb region of chromosome II including the alcohol dehydrogenase structural gene (Adh) was examined in Drosophila melanogaster from natural populations. Detailed analysis of 48 D. melanogaster lines representing four eastern United States populations revealed extensive DNA sequence variation due to base substitutions, insertions and deletions. Cloning of this region from several lines allowed characterization of length variation as due to unique sequence insertions or deletions [nine sizes; 21–200 base pairs (bp)] or transposable element insertions (several sizes, 340 bp to 10.2 kb, representing four different elements). Despite this extensive variation in sequences flanking the Adh gene, only one length polymorphism is clearly associated with altered Adh expression (a copia element approximately 250 bp 5' to the distal transcript start site). Nonetheless, the frequency spectra of transposable elements within and between Drosophila species suggests they are slightly deleterious. Strong nonrandom associations are observed among Adh region sequence variants, ADH allozyme (Fast vs. Slow), ADH enzyme activity and the chromosome inversion ln(2L) t. Phylogenetic analysis of restriction map haplotypes suggest that the major twofold component of ADH activity variation (high vs. low, typical of Fast and Slow allozymes, respectively) is due to sequence variation tightly linked to and possibly distinct from that underlying the allozyme difference. The patterns of nucleotide and haplotype variation for Fast and Slow allozyme lines are consistent with the recent increase in frequency and spread of the Fast haplotype associated with high ADH activity. These data emphasize the important role of evolutionary history and strong nonrandom associations among tightly linked sequence variation as determinants of the patterns of variation observed in natural populations. PMID:3026893

Muscle Contractile Properties in Severely Burned Rats

DTIC Science & Technology

2010-01-01

slow - twitch muscles such as sloeus (data not shown). In rats, the TA contains predominantly fast ...Hasselgren PO. The molecular regulation of protein breakdown following burn injury is different in fast - and slow - twitch skeletal muscle . Int J Mol Med 1998;1...burn model, it was reported that only fast muscle fibers are affected and slow muscle fibers were mostly preserved [30–32]. We found similar results

Heat-Stress effects on the myosin heavy chain phenotype of rat soleus fibers during the early stages of regeneration.

PubMed

Oishi, Yasuharu; Roy, Roland R; Ogata, Tomonori; Ohira, Yoshinobu

2015-12-01

We investigated heat-stress effects on the adult myosin heavy chain (MyHC) profile of soleus muscle fibers at an early stage of regeneration. Regenerating fibers in adult rats were analyzed 2, 4, or 6 days after bupivacaine injection. Rats were heat stressed by immersion in water (42 ± 1°C) for 30 minutes 24 hours after bupivacaine injection and every other day thereafter. No adult MyHC isoforms were observed after 2 days, whereas some fibers expressed only fast MyHC after 4 days. Heat stress increased fast and slow MyHC in regenerating fibers after 6 days. Regenerating fibers expressing only slow MyHC were observed only in heat-stressed muscles. Bupivacaine injection increased the number of Pax7(+) and MyoD(+) satellite cells in regenerating fibers, more so in heat-stressed rats. The results indicate that heat stress accelerates fast-to-slow MyHC phenotype conversion in regenerating fibers via activation of satellite cells. © 2015 Wiley Periodicals, Inc.

Effects of tripolar TENS on slow and fast motoneurons: a preliminary study using H-reflex recovery curve method.

PubMed

Simorgh, L; Torkaman, G; Firoozabadi, S M

2008-01-01

This study aimed at examining the effect of tripolar TENS of vertebral column on the activity of slow and fast motoneurons on 10 healthy non-athlete women aged 22.7 +/- 2.21 yrs. H-reflex recovery curve of soleus (slow) and gastrocnemius (fast) muscles were recorded before and after applying tripolar TENS. For recording of this curve, rectangular paired stimuli were applied on tibial nerve (with 40-520 ISI, frequency of 0.2 Hz and pulse width of 600 micros). Our findings showed that maximum H-reflex recovery in gastrocnemius muscle appeared in the shorter ISI, while in soleus muscle, it appeared in the longer ISI and its amplitude slightly decreased after applying tripolar TENS. It is suggested that tripolar TENS excites not only the skin but also Ia and Ib afferents in the dorsal column. A Synaptic interaction of these afferents in spinal cord causes the inhibition of type I MNs and facilitation of type II MNs. This effect can be used in muscle tone modulation.

Can fast-twitch muscle fibres be selectively recruited during lengthening contractions? Review and applications to sport movements.

PubMed

Chalmers, Gordon R

2008-01-01

Literature examining the recruitment order of motor units during lengthening (eccentric) contractions was reviewed to determine if fast-twitch motor units can be active while lower threshold slow-twitch motor units are not active. Studies utilizing surface electromyogram (EMG) amplitude, single motor unit activity, spike amplitude-frequency analyses, EMG power spectrum, mechanomyographic, and phosphocreatine-to-creatine ratio (PCr/Cr) techniques were reviewed. Only single motor unit and PCr/Cr data were found to be suitable to address the goals of this review. Nine of ten single motor unit studies, examining joint movement velocities up to 225 degrees/s and forces up to 53% of a maximum voluntary contraction, found that the size principle of motor unit recruitment applied during lengthening contractions. Deviation from the size principle was demonstrated by one study examining movements within a small range of low velocities and modest forces, although other studies examining similar low forces and lengthening velocities reported size-ordered recruitment. The PCr/Cr data demonstrated the activation of all fibre types in lengthening maximal contractions. Most evidence indicates that for lengthening contractions of a wide range of efforts and speeds, fast-twitch muscle fibres cannot be selectively recruited without activity of the slow-twitch fibres of the same muscle.

Expression of multiple slow myosin heavy chain genes reveals a diversity of zebrafish slow twitch muscle fibres with differing requirements for Hedgehog and Prdm1 activity.

PubMed

Elworthy, Stone; Hargrave, Murray; Knight, Robert; Mebus, Katharina; Ingham, Philip W

2008-06-01

The zebrafish embryo develops a series of anatomically distinct slow twitch muscle fibres that characteristically express genes encoding lineage-specific isoforms of sarcomeric proteins such as MyHC and troponin. We show here that different subsets of these slow fibres express distinct members of a tandem array of slow MyHC genes. The first slow twitch muscle fibres to differentiate, which are specified by the activity of the transcription factor Prdm1 (also called Ubo or Blimp1) in response to Hedgehog (Hh) signalling, express the smyhc1 gene. Subsequently, secondary slow twitch fibres differentiate in most cases independently of Hh activity. We find that although some of these later-forming fibres also express smyhc1, others express smyhc2 or smyhc3. We show that the smyhc1-positive fibres express the ubo (prdm1) gene and adopt fast twitch fibre characteristics in the absence of Prdm1 activity, whereas those that do not express smyhc1 can differentiate independently of Prdm1 function. Conversely, some smyhc2-expressing fibres, although independent of Prdm1 function, require Hh activity to form. The adult trunk slow fibres express smyhc2 and smyhc3, but lack smyhc1 expression. The different slow fibres in the craniofacial muscles variously express smyhc1, smyhc2 and smyhc3, and all differentiate independently of Prdm1.

Effects of cannabinoids on caffeine contractures in slow and fast skeletal muscle fibers of the frog.

PubMed

Huerta, Miguel; Ortiz-Mesina, Mónica; Trujillo, Xóchitl; Sánchez-Pastor, Enrique; Vásquez, Clemente; Castro, Elena; Velasco, Raymundo; Montoya-Pérez, Rocío; Onetti, Carlos

2009-05-01

The effect of cannabinoids on caffeine contractures was investigated in slow and fast skeletal muscle fibers using isometric tension recording. In slow muscle fibers, WIN 55,212-2 (10 and 5 microM) caused a decrease in tension. These doses reduced maximum tension to 67.43 +/- 8.07% (P = 0.02, n = 5) and 79.4 +/- 14.11% (P = 0.007, n = 5) compared to control, respectively. Tension-time integral was reduced to 58.37 +/- 7.17% and 75.10 +/- 3.60% (P = 0.002, n = 5), respectively. Using the CB(1) cannabinoid receptor agonist ACPA (1 microM) reduced the maximum tension of caffeine contractures by 68.70 +/- 11.63% (P = 0.01, n = 5); tension-time integral was reduced by 66.82 +/- 6.89% (P = 0.02, n = 5) compared to controls. When the CB(1) receptor antagonist AM281 was coapplied with ACPA, it reversed the effect of ACPA on caffeine-evoked tension. In slow and fast muscle fibers incubated with the pertussis toxin, ACPA had no effect on tension evoked by caffeine. In fast muscle fibers, ACPA (1 microM) also decreased tension; the maximum tension was reduced by 56.48 +/- 3.4% (P = 0.001, n = 4), and tension-time integral was reduced by 57.81 +/- 2.6% (P = 0.006, n = 4). This ACPA effect was not statistically significant with respect to the reduction in tension in slow muscle fibers. Moreover, we detected the presence of mRNA for the cannabinoid CB(1) receptor on fast and slow skeletal muscle fibers, which was significantly higher in fast compared to slow muscle fiber expression. In conclusion, our results suggest that in the slow and fast muscle fibers of the frog cannabinoids diminish caffeine-evoked tension through a receptor-mediated mechanism.

Computer Three-Dimensional Reconstruction of the Atrioventricular Node

PubMed Central

Li, Jue; Greener, Ian D.; Inada, Shin; Nikolski, Vladimir P.; Yamamoto, Mitsuru; Hancox, Jules C.; Zhang, Henggui; Billeter, Rudi; Efimov, Igor R.; Dobrzynski, Halina; Boyett, Mark R.

2009-01-01

Because of its complexity, the atrioventricular node (AVN), remains 1 of the least understood regions of the heart. The aim of the study was to construct a detailed anatomic model of the AVN and relate it to AVN function. The electric activity of a rabbit AVN preparation was imaged using voltage-dependent dye. The preparation was then fixed and sectioned. Sixty-five sections at 60- to 340-μm intervals were stained for histology and immunolabeled for neurofilament (marker of nodal tissue) and connexin43 (gap junction protein). This revealed multiple structures within and around the AVN, including transitional tissue, inferior nodal extension, penetrating bundle, His bundle, atrial and ventricular muscle, central fibrous body, tendon of Todaro, and valves. A 3D anatomically detailed mathematical model (≈13 million element array) of the AVN and surrounding atrium and ventricle, incorporating all cell types, was constructed. Comparison of the model with electric activity recorded in experiments suggests that the inferior nodal extension forms the slow pathway, whereas the transitional tissue forms the fast pathway into the AVN. In addition, it suggests the pacemaker activity of the atrioventricular junction originates in the inferior nodal extension. Computer simulation of the propagation of the action potential through the anatomic model shows how, because of the complex structure of the AVN, reentry (slow-fast and fast-slow) can occur. In summary, a mathematical model of the anatomy of the AVN has been generated that allows AVN conduction to be explored. PMID:18309098

The effect of involuntary motor activity on myoelectric pattern recognition: a case study with chronic stroke patients

NASA Astrophysics Data System (ADS)

Zhang, Xu; Li, Yun; Chen, Xiang; Li, Guanglin; Zev Rymer, William; Zhou, Ping

2013-08-01

Objective. This study investigates the effect of the involuntary motor activity of paretic-spastic muscles on the classification of surface electromyography (EMG) signals. Approach. Two data collection sessions were designed for 8 stroke subjects to voluntarily perform 11 functional movements using their affected forearm and hand at relatively slow and fast speeds. For each stroke subject, the degree of involuntary motor activity present in the voluntary surface EMG recordings was qualitatively described from such slow and fast experimental protocols. Myoelectric pattern recognition analysis was performed using different combinations of voluntary surface EMG data recorded from the slow and fast sessions. Main results. Across all tested stroke subjects, our results revealed that when involuntary surface EMG is absent or present in both the training and testing datasets, high accuracies (>96%, >98%, respectively, averaged over all the subjects) can be achieved in the classification of different movements using surface EMG signals from paretic muscles. When involuntary surface EMG was solely involved in either the training or testing datasets, the classification accuracies were dramatically reduced (<89%, <85%, respectively). However, if both the training and testing datasets contained EMG signals with the presence and absence of involuntary EMG interference, high accuracies were still achieved (>97%). Significance. The findings of this study can be used to guide the appropriate design and implementation of myoelectric pattern recognition based systems or devices toward promoting robot-aided therapy for stroke rehabilitation.

First demonstration of the fast-to-slow corrector current shift in the NSLS-II storage ring

NASA Astrophysics Data System (ADS)

Yang, Xi; Tian, Yuke; Yu, Li Hua; Smaluk, Victor

2018-04-01

To realize the full benefits of the high brightness and ultra-small beam sizes of NSLS-II, it is essential that the photon beams are exceedingly stable. In the circumstances of implementing local bumps, changing ID gaps, and long term drifting, the fast orbit feedback (FOFB) requires shifting the fast corrector strengths to the slow correctors to prevent the fast corrector saturation and to make the beam orbit stable in the sub-micron level. As the result, a reliable and precise technique of fast-to-slow corrector strength shift has been developed and tested at NSLS-II. This technique is based on the fast corrector response to the slow corrector change when the FOFB is on. In this article, the shift technique is described and the result of proof-of-principle experiment carried out at NSLS-II is presented. The maximum fast corrector current was reduced from greater than 0.45 A to less than 0.04 A with the orbit perturbation within ±1 μm.

Spatio-temporal error growth in the multi-scale Lorenz'96 model

NASA Astrophysics Data System (ADS)

Herrera, S.; Fernández, J.; Rodríguez, M. A.; Gutiérrez, J. M.

2010-07-01

The influence of multiple spatio-temporal scales on the error growth and predictability of atmospheric flows is analyzed throughout the paper. To this aim, we consider the two-scale Lorenz'96 model and study the interplay of the slow and fast variables on the error growth dynamics. It is shown that when the coupling between slow and fast variables is weak the slow variables dominate the evolution of fluctuations whereas in the case of strong coupling the fast variables impose a non-trivial complex error growth pattern on the slow variables with two different regimes, before and after saturation of fast variables. This complex behavior is analyzed using the recently introduced Mean-Variance Logarithmic (MVL) diagram.

Fast and slow myosins as markers of muscle injury.

PubMed

Guerrero, M; Guiu-Comadevall, M; Cadefau, J A; Parra, J; Balius, R; Estruch, A; Rodas, G; Bedini, J L; Cussó, R

2008-07-01

The diagnosis of muscular lesions suffered by athletes is usually made by clinical criteria combined with imaging of the lesion (ultrasonography and/or magnetic resonance) and blood tests to detect the presence of non-specific muscle markers. This study was undertaken to evaluate injury to fast and slow-twitch fibres using specific muscle markers for these fibres. Blood samples were obtained from 51 non-sports people and 38 sportsmen with skeletal muscle injury. Western blood analysis was performed to determine fast and slow myosin and creatine kinase (CK) levels. Skeletal muscle damage was diagnosed by physical examination, ultrasonography and magnetic resonance and biochemical markers. The imaging tests were found to be excellent for detecting and confirming grade II and III lesions. However, grade I lesions were often unconfirmed by these techniques. Grade I lesions have higher levels of fast myosin than slow myosin with a very small increase in CK levels. Grade II and III lesions have high values of both fast and slow myosin. The evaluation of fast and slow myosin in the blood 48 h after the lesion occurs is a useful aid for the detection of type I lesions in particular, since fast myosin is an exclusive skeletal muscle marker. The correct diagnosis of grade I lesions can prevent progression of the injury in athletes undergoing continual training sessions and competitions, thus aiding sports physicians in their decision making.

Controlling slow and fast light and dynamic pulse-splitting with tunable optical gain in a whispering-gallery-mode microcavity

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

Asano, M.; Ikuta, R.; Imoto, N.

We report controllable manipulation of slow and fast light in a whispering-gallery-mode microtoroid resonator fabricated from Erbium (Er{sup 3+}) doped silica. We observe continuous transition of the coupling between the fiber-taper waveguide and the microresonator from undercoupling to critical coupling and then to overcoupling regimes by increasing the pump power even though the spatial distance between the resonator and the waveguide was kept fixed. This, in turn, enables switching from fast to slow light and vice versa just by increasing the optical gain. An enhancement of delay of two-fold over the passive silica resonator (no optical gain) was observed inmore » the slow light regime. Moreover, we show dynamic pulse splitting and its control in slow/fast light systems using optical gain.« less

Identifying factors contributing to slow growth in pigs.

PubMed

He, Y; Deen, J; Shurson, G C; Wang, L; Chen, C; Keisler, D H; Li, Y Z

2016-05-01

Pigs that grow slower than their contemporaries can cause complications for animal welfare and profitability. This study was conducted to investigate factors that may contribute to slow growth of pigs. Pigs ( = 440) farrowed by 65 sows were monitored from birth to market. Pigs were categorized as slow, average, and fast growers based on market weight adjusted to 170 d of age (slow growers were <105 kg, average growers were between 105 and 125 kg, and fast growers were >125 kg). Blood samples were collected from 48 focal pigs at 9 and 21 wk of age and analyzed for hormone and free AA concentrations. Data were analyzed using the Mixed and Logistic procedures of SAS. Slow-growing pigs accounted for 10% of pigs marketed, average growers accounted for 49% of pigs marketed, and fast growers accounted for 41% of pigs marketed. Compared with fast growers, slow growers were lighter at birth ( < 0.01), at weaning ( < 0.01), and at nursery exit ( < 0.01) and had less backfat ( < 0.01) and smaller loin muscle area ( < 0.01) at marketing at 21 wk of age. Slow growers had lower plasma concentrations of IGF-1 ( = 0.03) and insulin ( < 0.001) during the nursery period and lower concentrations of leptin ( < 0.001) and insulin ( < 0.001) during the finishing period compared with average and fast growers. Serum concentrations of several essential, nonessential, and total free AA were less for slow growers during both the nursery and finishing periods compared with average and fast growers. Gilts were more likely to become slow growers than barrows (odds ratio = 2.17, 95% confidence interval = 1.19 to 3.96, = 0.01). Litter size and parity of the pigs' dam were not associated with slow growth. These results suggest that low concentrations of IGF-1, insulin, leptin, and AA may contribute to or be associated with slow growth in pigs.

Influence of Fiber-Type Composition on Recovery from Tourniquet-Induced Skeletal Muscle Ischemia-Reperfusion Injury

DTIC Science & Technology

2008-03-11

slow - twitch muscle , would be less vulnerable to tourniquet-induced ischemia–reperfusion than the plantaris (Plant), a predominantly fast - twitch muscle ...predominantly fast - and slow - twitch muscle reported after 2–3 h of ischemia will be erased after longer periods of ischemia (Carvalho et al. 1997a). The...functional loss in predominantly fast - twitch muscle than in predominantly slow - twitch muscle in response

Determining attenuation properties of interfering fast and slow ultrasonic waves in cancellous bone.

PubMed

Nelson, Amber M; Hoffman, Joseph J; Anderson, Christian C; Holland, Mark R; Nagatani, Yoshiki; Mizuno, Katsunori; Matsukawa, Mami; Miller, James G

2011-10-01

Previous studies have shown that interference between fast waves and slow waves can lead to observed negative dispersion in cancellous bone. In this study, the effects of overlapping fast and slow waves on measurements of the apparent attenuation as a function of propagation distance are investigated along with methods of analysis used to determine the attenuation properties. Two methods are applied to simulated data that were generated based on experimentally acquired signals taken from a bovine specimen. The first method uses a time-domain approach that was dictated by constraints imposed by the partial overlap of fast and slow waves. The second method uses a frequency-domain log-spectral subtraction technique on the separated fast and slow waves. Applying the time-domain analysis to the broadband data yields apparent attenuation behavior that is larger in the early stages of propagation and decreases as the wave travels deeper. In contrast, performing frequency-domain analysis on the separated fast waves and slow waves results in attenuation coefficients that are independent of propagation distance. Results suggest that features arising from the analysis of overlapping two-mode data may represent an alternate explanation for the previously reported apparent dependence on propagation distance of the attenuation coefficient of cancellous bone. © 2011 Acoustical Society of America

Determining attenuation properties of interfering fast and slow ultrasonic waves in cancellous bone

PubMed Central

Nelson, Amber M.; Hoffman, Joseph J.; Anderson, Christian C.; Holland, Mark R.; Nagatani, Yoshiki; Mizuno, Katsunori; Matsukawa, Mami; Miller, James G.

2011-01-01

Previous studies have shown that interference between fast waves and slow waves can lead to observed negative dispersion in cancellous bone. In this study, the effects of overlapping fast and slow waves on measurements of the apparent attenuation as a function of propagation distance are investigated along with methods of analysis used to determine the attenuation properties. Two methods are applied to simulated data that were generated based on experimentally acquired signals taken from a bovine specimen. The first method uses a time-domain approach that was dictated by constraints imposed by the partial overlap of fast and slow waves. The second method uses a frequency-domain log-spectral subtraction technique on the separated fast and slow waves. Applying the time-domain analysis to the broadband data yields apparent attenuation behavior that is larger in the early stages of propagation and decreases as the wave travels deeper. In contrast, performing frequency-domain analysis on the separated fast waves and slow waves results in attenuation coefficients that are independent of propagation distance. Results suggest that features arising from the analysis of overlapping two-mode data may represent an alternate explanation for the previously reported apparent dependence on propagation distance of the attenuation coefficient of cancellous bone. PMID:21973378

Double-HE-Layer Detonation-Confinement Sandwich Tests: The Effect of Slow-Layer Density

NASA Astrophysics Data System (ADS)

Hill, Larry

2013-06-01

Over a period of several years, we have explored the phenomenon in which slabs of high explosives (HEs) with differing detonation speeds are joined along one of their faces. Both are initiated (usually by a line-wave generator) at one edge. If there were no coupling between the layers, the detonation in the fast HE would outrun that in the slow HE. In reality, the detonation in the fast HE transmits an oblique shock into the slow HE, the phase speed of which is equal to the speed of the fast HE. This has one of two effects depending on the particulars. First, the oblique shock transmitted to the slow HE can pre-shock and deaden it, extinguishing the detonation in the slow HE. Second, the oblique shock can transversely initiate the slow layer, pulling its detonation along at the fast HE speed. When the second occurs, it does so at the ``penalty'' of a nominally dead layer, which forms in the slow HE adjacent to the material interface. We present the results of tests in which the fast layer was 3-mm-thick PBX 9501 (95 wt% HMX), and the slow layer was 8-mm-thick PBX 9502 (95 wt% TATB). The purpose was to observe the effect of slow layer density on the ``dead'' layer thickness. Very little effect was observed across the nominal PBX 9502 density range, 1.885-1.895 g/cc.

Effects of hypothyroidism on myosin heavy chain composition and fibre types of fast skeletal muscles in a small marsupial, Antechinus flavipes.

PubMed

Zhong, Wendy W H; Withers, Kerry W; Hoh, Joseph F Y

2010-04-01

Effects of drug-induced hypothyroidism on myosin heavy chain (MyHC) content and fibre types of fast skeletal muscles were studied in a small marsupial, Antechinus flavipes. SDS-PAGE of MyHCs from the tibialis anterior and gastrocnemius revealed four isoforms, 2B, 2X, 2A and slow, in that order of decreasing abundance. After 5 weeks treatment with methimazole, the functionally fastest 2B MyHC significantly decreased, while 2X, 2A and slow MyHCs increased. Immunohistochemistry using monospecific antibodies to each of the four MyHCs revealed decreased 2b and 2x fibres, and increased 2a and hybrid fibres co-expressing two or three MyHCs. In the normally homogeneously fast superficial regions of these muscles, evenly distributed slow-staining fibres appeared, resembling the distribution of slow primary myotubes in fast muscles during development. Hybrid fibres containing 2A and slow MyHCs were virtually absent. These results are more detailed but broadly similar to the earlier studies on eutherians. We hypothesize that hypothyroidism essentially reverses the effects of thyroid hormone on MyHC gene expression of muscle fibres during myogenesis, which differ according to the developmental origin of the fibre: it induces slow MyHC expression in 2b fibres derived from fast primary myotubes, and shifts fast MyHC expression in fibres of secondary origin towards 2A, but not slow, MyHC.

The Effects of Tempo and Intensity on Hyperactive Children.

DTIC Science & Technology

1984-08-01

randomly assigned to one of four treatment conditions. Treatment conditions consisted of listening to music that varied according to intensity (high...and low) and tempo (fast and slow). The four combinations of -l music were high and fast, high and slow, low and fast, and low and P slow. The subjects...performed a cognitive task during the assigned treatment condition and also during a no- music condition. Behavioral observations and ratings were also

Differential effect of denervation on free radical scavenging enzymes in slow and fast muscle of rat

NASA Technical Reports Server (NTRS)

Asayama, K.; Dettbarn, W. D.; Burr, I. M.

1985-01-01

To determine the effect of denervation on the free radical scavenging systems in relation to the mitochondrial oxidative metabolism in the slow twitch soleus and fast twitch extensor digitorum longus (EDL) muscles, the sciatic nerve of the rat was crushed in the mid-thigh region and the muscle tissue levels of 5 enzymes were studied 2 and 5 weeks following crush. Radioimmunoassays were utilized for the selective measurement of cuprozinc (cytosolic) and mangano (mitochondrial) superoxide dismutases. These data represent the first systematic report of free radical scavening systems in slow and fast muscles in response to denervation. Selective modification of cuprozinc and manganosuperoxide dismutases and differential regulation of GSH-peroxidase was demonstrated in slow and fast muscle.

Inertial Range Turbulence of Fast and Slow Solar Wind at 0.72 AU and Solar Minimum

NASA Astrophysics Data System (ADS)

Teodorescu, Eliza; Echim, Marius; Munteanu, Costel; Zhang, Tielong; Bruno, Roberto; Kovacs, Peter

2015-05-01

We investigate Venus Express observations of magnetic field fluctuations performed systematically in the solar wind at 0.72 Astronomical Units (AU), between 2007 and 2009, during the deep minimum of solar cycle 24. The power spectral densities (PSDs) of the magnetic field components have been computed for time intervals that satisfy the data integrity criteria and have been grouped according to the type of wind, fast and slow, defined for speeds larger and smaller, respectively, than 450 km s-1. The PSDs show higher levels of power for the fast wind than for the slow. The spectral slopes estimated for all PSDs in the frequency range 0.005-0.1 Hz exhibit a normal distribution. The average value of the trace of the spectral matrix is -1.60 for fast solar wind and -1.65 for slow wind. Compared to the corresponding average slopes at 1 AU, the PSDs are shallower at 0.72 AU for slow wind conditions suggesting a steepening of the solar wind spectra between Venus and Earth. No significant time variation trend is observed for the spectral behavior of both the slow and fast wind.

Scene segmentation by spike synchronization in reciprocally connected visual areas. II. Global assemblies and synchronization on larger space and time scales.

PubMed

Knoblauch, Andreas; Palm, Günther

2002-09-01

We present further simulation results of the model of two reciprocally connected visual areas proposed in the first paper [Knoblauch and Palm (2002) Biol Cybern 87:151-167]. One area corresponds to the orientation-selective subsystem of the primary visual cortex, the other is modeled as an associative memory representing stimulus objects according to Hebbian learning. We examine the scene-segmentation capability of our model on larger time and space scales, and relate it to experimental findings. Scene segmentation is achieved by attention switching on a time-scale longer than the gamma range. We find that the time-scale can vary depending on habituation parameters in the range of tens to hundreds of milliseconds. The switching process can be related to findings concerning attention and biased competition, and we reproduce experimental poststimulus time histograms (PSTHs) of single neurons under different stimulus and attentional conditions. In a larger variant the model exhibits traveling waves of activity on both slow and fast time-scales, with properties similar to those found in experiments. An apparent weakness of our standard model is the tendency to produce anti-phase correlations for fast activity from the two areas. Increasing the inter-areal delays in our model produces alternations of in-phase and anti-phase oscillations. The experimentally observed in-phase correlations can most naturally be obtained by the involvement of both fast and slow inter-areal connections; e.g., by two axon populations corresponding to fast-conducting myelinated and slow-conducting unmyelinated axons.

Voltage-Sensitive Fluorescence of Indocyanine Green in the Heart

PubMed Central

Martišienė, Irma; Mačianskienė, Regina; Treinys, Rimantas; Navalinskas, Antanas; Almanaitytė, Mantė; Karčiauskas, Dainius; Kučinskas, Audrius; Grigalevičiūtė, Ramunė; Zigmantaitė, Vilma; Benetis, Rimantas; Jurevičius, Jonas

2016-01-01

So far, the optical mapping of cardiac electrical signals using voltage-sensitive fluorescent dyes has only been performed in experimental studies because these dyes are not yet approved for clinical use. It was recently reported that the well-known and widely used fluorescent dye indocyanine green (ICG), which has FDA approval, exhibits voltage sensitivity in various tissues, thus raising hopes that electrical activity could be optically mapped in the clinic. The aim of this study was to explore the possibility of using ICG to monitor cardiac electrical activity. Optical mapping experiments were performed on Langendorff rabbit hearts stained with ICG and perfused with electromechanical uncouplers. The residual contraction force and electrical action potentials were recorded simultaneously. Our research confirms that ICG is a voltage-sensitive dye with a dual-component (fast and slow) response to membrane potential changes. The fast component of the optical signal (OS) can have opposite polarities in different parts of the fluorescence spectrum. In contrast, the polarity of the slow component remains the same throughout the entire spectrum. Separating the OS into these components revealed two different voltage-sensitivity mechanisms for ICG. The fast component of the OS appears to be electrochromic in nature, whereas the slow component may arise from the redistribution of the dye molecules within or around the membrane. Both components quite accurately track the time of electrical signal propagation, but only the fast component is suitable for estimating the shape and duration of action potentials. Because ICG has voltage-sensitive properties in the entire heart, we suggest that it can be used to monitor cardiac electrical behavior in the clinic. PMID:26840736

Changes of contractile responses due to simulated weightlessness in rat soleus muscle

NASA Astrophysics Data System (ADS)

Elkhammari, A.; Noireaud, J.; Léoty, C.

1994-08-01

Some contractile and electrophysiological properties of muscle fibers isolated from the slow-twitch soleus (SOL) and fast-twitch extensor digitorum longus (EDL) muscles of rats were compared with those measured in SOL muscles from suspended rats. In suspendede SOL (21 days of tail-suspension) membrane potential (Em), intracellular sodium activity (aiNa) and the slope of the relationship between Em and log [K]o were typical of fast-twitch muscles. The relation between the maximal amplitude of K-contractures vs Em was steeper for control SOL than for EDL and suspended SOL muscles. After suspension, in SOL muscles the contractile threshold and the inactivation curves for K-contractures were shifted to more positive Em. Repriming of K-contractures was unaffected by suspencion. The exposure of isolated fibers to perchlorate (ClO4-)-containing (6-40 mM) solutions resulted ina similar concentration-dependent shift to more negative Em of activation curves for EDL and suspended SOL muscles. On exposure to a Na-free TEA solution, SOL from control and suspended rats, in contrast to EDL muscles, generated slow contractile responses. Suspended SOL showed a reduced sensitivity to the contracture-producing effect of caffeine compared to control muscles. These results suggested that the modification observed due to suspension could be encounted by changes in the characteristics of muscle fibers from slow to fast-twitch type.

Acute molecular response of mouse hindlimb muscles to chronic stimulation.

PubMed

LaFramboise, W A; Jayaraman, R C; Bombach, K L; Ankrapp, D P; Krill-Burger, J M; Sciulli, C M; Petrosko, P; Wiseman, R W

2009-09-01

Stimulation of the mouse hindlimb via the sciatic nerve was performed for a 4-h period to investigate acute muscle gene activation in a model of muscle phenotype conversion. Initial force production (1.6 +/- 0.1 g/g body wt) declined 45% within 10 min and was maintained for the remainder of the experiment. Force returned to initial levels upon study completion. An immediate-early growth response was present in the extensor digitorum longus (EDL) muscle (FOS, JUN, activating transcription factor 3, and musculoaponeurotic fibrosarcoma oncogene) with a similar but attenuated pattern in the soleus muscle. Transcript profiles showed decreased fast fiber-specific mRNA (myosin heavy chains 2A and 2B, fast troponins T(3) and I, alpha-tropomyosin, muscle creatine kinase, and parvalbumin) and increased slow transcripts (myosin heavy chain-1beta/slow, troponin C slow, and tropomyosin 3y) in the EDL versus soleus muscles. Histological analysis of the EDL revealed glycogen depletion without inflammatory cell infiltration in stimulated versus control muscles, whereas ultrastructural analysis showed no evidence of myofiber damage after stimulation. Multiple fiber type-specific transcription factors (tea domain family member 1, nuclear factor of activated T cells 1, peroxisome proliferator-activated receptor-gamma coactivator-1alpha and -beta, circadian locomotor output cycles kaput, and hypoxia-inducible factor-1alpha) increased in the EDL along with transcription factors characteristic of embryogenesis (Kruppel-like factor 4; SRY box containing 17; transcription factor 15; PBX/knotted 1 homeobox 1; and embryonic lethal, abnormal vision). No established in vivo satellite cell markers or genes activated in our parallel experiments of satellite cell proliferation in vitro (cyclins A(2), B(2), C, and E(1) and MyoD) were differentially increased in the stimulated muscles. These results indicated that the molecular onset of fast to slow phenotype conversion occurred in the EDL within 4 h of stimulation without injury or satellite cell recruitment. This conversion was associated with the expression of phenotype-specific transcription factors from resident fiber myonuclei, including the activation of nascent developmental transcriptional programs.

Fast-slow asymptotics for a Markov chain model of fast sodium current

NASA Astrophysics Data System (ADS)

Starý, Tomáš; Biktashev, Vadim N.

2017-09-01

We explore the feasibility of using fast-slow asymptotics to eliminate the computational stiffness of discrete-state, continuous-time deterministic Markov chain models of ionic channels underlying cardiac excitability. We focus on a Markov chain model of fast sodium current, and investigate its asymptotic behaviour with respect to small parameters identified in different ways.

Anatomy and histochemistry of spread-wing posture in birds. 2. Gliding flight in the California gull, Larus californicus: a paradox of fast fibers and posture.

PubMed

Meyers, R A; Mathias, E

1997-09-01

Gliding flight is a postural activity which requires the wings to be held in a horizontal position to support the weight of the body. Postural behaviors typically utilize isometric contractions in which no change in length takes place. Due to longer actin-myosin interactions, slow contracting muscle fibers represent an economical means for this type of contraction. In specialized soaring birds, such as vultures and pelicans, a deep layer of the pectoralis muscle, composed entirely of slow fibers, is believed to perform this function. Muscles involved in gliding posture were examined in California gulls (Larus californicus) and tested for the presence of slow fibers using myosin ATPase histochemistry and antibodies. Surprisingly small numbers of slow fibers were found in the M. extensor metacarpi radialis, M. coracobrachialis cranialis, and M. coracobrachialis caudalis, which function in wrist extension, wing protraction, and body support, respectively. The low number of slow fibers in these muscles and the absence of slow fibers in muscles associated with wing extension and primary body support suggest that gulls do not require slow fibers for their postural behaviors. Gulls also lack the deep belly to the pectoralis found in other gliding birds. Since bird muscle is highly oxidative, we hypothesize that fast muscle fibers may function to maintain wing position during gliding flight in California gulls.

Partial fast-to-slow conversion of regenerating rat fast-twitch muscle by chronic low-frequency stimulation.

PubMed

Pette, Dirk; Sketelj, Janez; Skorjanc, Dejan; Leisner, Elmi; Traub, Irmtrud; Bajrović, Fajko

2002-01-01

Chronic low-frequency stimulation (CLFS) of rat fast-twitch muscles induces sequential transitions in myosin heavy chain (MHC) expression from MHCIIb --> MHCIId/x --> MHCIIa. However, the 'final' step of the fast-to-slow transition, i.e., the upregulation of MHCI, has been observed only after extremely long stimulation periods. Assuming that fibre degeneration/regeneration might be involved in the upregulation of slow myosin, we investigated the effects of CLFS on extensor digitorum longus (EDL) muscles regenerating after bupivacaine-induced fibre necrosis. Normal, non-regenerating muscles responded to both 30- and 60-day CLFS with fast MHC isoform transitions (MHCIIb --> MHCIId --> MHCIIa) and only slight increases in MHCI. CLFS of regenerating EDL muscles caused similar transitions among the fast isoforms but, in addition, caused significant increases in MHCI (to approximately 30% relative concentration). Stimulation periods of 30 and 60 days induced similar changes in the regenerating bupivacaine-treated muscles, indicating that the upregulation of slow myosin was restricted to regenerating fibres, but only during an early stage of regeneration. These results suggest that satellite cells and/or regenerating fast rat muscle fibres are capable of switching directly to a slow program under the influence of CLFS and, therefore, appear to be more malleable than adult fibres.

P/Q-type calcium channels activate neighboring calcium-dependent potassium channels in mouse motor nerve terminals.

PubMed

Protti, D A; Uchitel, O D

1997-08-01

The identity of the voltage-dependent calcium channels (VDCC), which trigger the Ca2+-gated K+ currents (IK(Ca)) in mammalian motor nerve terminals, was investigated by means of perineurial recordings. The effects of Ca2+ chelators with different binding kinetics on the activation of IK(Ca) were also examined. The calcium channel blockers of the P/Q family, omega-agatoxin IVA (omega-Aga-IVA) and funnel-web spider toxin (FTX), have been shown to exert a strong blocking effect on IK(Ca). In contrast, nitrendipine and omega-conotoxin GVIA (omega-CgTx) did not affect the Ca2+-activated K+ currents. The intracellular action of the fast Ca2+ buffers BAPTA and DM-BAPTA prevented the activation of the IK(Ca), while the slow Ca2+ buffer EGTA was ineffective at blocking it. These data indicate that P/Q-type VDCC mediate the Ca2+ influx which activates IK(Ca). The spatial association between Ca2+ and Ca2+-gated K+ channels is discussed, on the basis of the differential effects of the fast and slow Ca2+ chelators.

Response of the neuromuscular unit to spaceflight: what has been learned from the rat model

NASA Technical Reports Server (NTRS)

Roy, R. R.; Baldwin, K. M.; Edgerton, V. R.

1996-01-01

Despite the inherent limitations placed on spaceflight investigations, much has been learned about the adaptations of the neuromuscular system to weightlessness from studies of rats flown for relatively short periods (approximately 4-22 days). Below is a summary of the major effects of spaceflight observed in muscles of rats that are not in their rapid growth stage: 1. Skeletal muscles atrophy rapidly during spaceflight; significant atrophy is observed as early as after 4 days of flight. 2. The atrophic response appears to be related to the primary function of the muscle. In the hindlimb, the relative amount of atrophy can be characterized as slow extensors > fast extensors > fast flexors. This pattern of relative atrophy does not appear to be occurring in the forelimb; however, not enough data are available to draw any definitive conclusions at this time. 3. Both slow and fast fibers atrophy during spaceflight, with the largest fibers within an individual muscle generally showing the greatest atrophic response. Interestingly, the amount of fiber atrophy appears to reach a plateau after about 14 days of flight. 4. Adaptations have been observed in the concentration and content of all muscle proteins pools, with the protein pools in slow muscles the most affected. 5. Some slow and fast fibers in predominantly slow and fast muscles show shifts in their histochemical and biochemical properties, toward those observed in a "faster" phenotype. 6. Some fibers, presumably expressing slow MHC isoforms before flight, begin to express fast MHC isoforms during flight. 7. The oxidative capacity of the muscles or fibers is relatively unaffected by spaceflight, particularly in the slow muscles. Any change in whole-body fatigability associated with spaceflight most likely reflects the loss in muscle and fiber mass. 8. The glycolytic capacity of the muscles and muscle fibers is enhanced after spaceflight. This metabolic adaptation seems to be related to the shift in the contractile proteins towards "faster" isoforms. 9. The vascularity of muscles appears to be maintained after flight, based, at least, on histological observations of capillarity. 10. The force capabilities of the muscles and fibers appear to decrease in parallel with the decreases in size, i.e., the specific tension is not significantly affected after flight. 11. Changes in the speed-related properties of the slow muscles are consistent with the adaptations in the myosin molecule, i.e., the slow muscles and some fibers in the slow muscles become "faster." 12. Some muscle fiber and neuromuscular junction damage has been observed after flight, particularly in the slow muscles. The extent of damage may be related to the amount of time that the muscles are allowed to reload before removal, i.e., in general, shorter intervals result in less fiber damage. 13. Adaptations in the motor (ventral horn) and sensory (spinal ganglia) neurons have been quite variable, but this may be related to the amount of time that the muscles are allowed to reload before removal. Morphological adaptations after relatively short periods of reloading may reflect a decrease in the activation of the neural elements during flight.

Transcription Factor Networks Directing the Development, Function, and Evolution of Innate Lymphoid Effectors

PubMed Central

Kang, Joonsoo; Malhotra, Nidhi

2015-01-01

Mammalian lymphoid immunity is mediated by fast and slow responders to pathogens. Fast innate lymphocytes are active within hours after infections in mucosal tissues. Slow adaptive lymphocytes are conventional T and B cells with clonal antigen receptors that function days after pathogen exposure. A transcription factor (TF) regulatory network guiding early T cell development is at the core of effector function diversification in all innate lymphocytes, and the kinetics of immune responses is set by developmental programming. Operational units within the innate lymphoid system are not classified by the types of pathogen-sensing machineries but rather by discrete effector functions programmed by regulatory TF networks. Based on the evolutionary history of TFs of the regulatory networks, fast effectors likely arose earlier in the evolution of animals to fortify body barriers, and in mammals they often develop in fetal ontogeny prior to the establishment of fully competent adaptive immunity. PMID:25650177

Fast and slow light generated by surface plasmon wave and gold grating coupling effects

NASA Astrophysics Data System (ADS)

Amiri, Iraj S.; Ariannejad, M. M.; Tajdidzadeh, M.; Sorger, Volker J.; Ling, Xi; Yupapin, P.

2018-06-01

We present here the results of a simulation of the effect of gold and graphene coatings on silicon micro-ring resonators. We studied the effect of different radii of graphene on the time delay, from which one an interesting aspect of light pulse behaviors, such as fast light, was numerically investigated. The obtained results indicate that the time delay can be varied, which is in good agreement with theoretical predictions. Fast and slow light pulse trains can be obtained by modifying the throughput port, which forms the gold grating length. The temporal gaps between the fast and slow light in the used graphene and gold are 140 and 168 fs, respectively, which can be tuned by varying the radius or grating length. The obtained results show that such a device may be useful in applications requiring fast and slow light pulse train pairs, such as optical switching, sensors, communications, and security applications.

Fast and slow light generated by surface plasmon wave and gold grating coupling effects

NASA Astrophysics Data System (ADS)

Amiri, Iraj S.; Ariannejad, M. M.; Tajdidzadeh, M.; Sorger, Volker J.; Ling, Xi; Yupapin, P.

2018-01-01

We present here the results of a simulation of the effect of gold and graphene coatings on silicon micro-ring resonators. We studied the effect of different radii of graphene on the time delay, from which one an interesting aspect of light pulse behaviors, such as fast light, was numerically investigated. The obtained results indicate that the time delay can be varied, which is in good agreement with theoretical predictions. Fast and slow light pulse trains can be obtained by modifying the throughput port, which forms the gold grating length. The temporal gaps between the fast and slow light in the used graphene and gold are 140 and 168 fs, respectively, which can be tuned by varying the radius or grating length. The obtained results show that such a device may be useful in applications requiring fast and slow light pulse train pairs, such as optical switching, sensors, communications, and security applications.

Distinguishing the rates of gene activation from phenotypic variations.

PubMed

Chen, Ye; Lv, Cheng; Li, Fangting; Li, Tiejun

2015-06-18

Stochastic genetic switching driven by intrinsic noise is an important process in gene expression. When the rates of gene activation/inactivation are relatively slow, fast, or medium compared with the synthesis/degradation rates of mRNAs and proteins, the variability of protein and mRNA levels may exhibit very different dynamical patterns. It is desirable to provide a systematic approach to identify their key dynamical features in different regimes, aiming at distinguishing which regime a considered gene regulatory network is in from their phenotypic variations. We studied a gene expression model with positive feedbacks when genetic switching rates vary over a wide range. With the goal of providing a method to distinguish the regime of the switching rates, we first focus on understanding the essential dynamics of gene expression system in different cases. In the regime of slow switching rates, we found that the effective dynamics can be reduced to independent evolutions on two separate layers corresponding to gene activation and inactivation states, and the transitions between two layers are rare events, after which the system goes mainly along deterministic ODE trajectories on a particular layer to reach new steady states. The energy landscape in this regime can be well approximated by using Gaussian mixture model. In the regime of intermediate switching rates, we analyzed the mean switching time to investigate the stability of the system in different parameter ranges. We also discussed the case of fast switching rates from the viewpoint of transition state theory. Based on the obtained results, we made a proposal to distinguish these three regimes in a simulation experiment. We identified the intermediate regime from the fact that the strength of cellular memory is lower than the other two cases, and the fast and slow regimes can be distinguished by their different perturbation-response behavior with respect to the switching rates perturbations. We proposed a simulation experiment to distinguish the slow, intermediate and fast regimes, which is the main point of our paper. In order to achieve this goal, we systematically studied the essential dynamics of gene expression system when the switching rates are in different regimes. Our theoretical understanding provides new insights on the gene expression experiments.

Quantifying variability in fast and slow solar wind: From turbulence to extremes

NASA Astrophysics Data System (ADS)

Tindale, E.; Chapman, S. C.; Moloney, N.; Watkins, N. W.

2017-12-01

Fast and slow solar wind exhibit variability across a wide range of spatiotemporal scales, with evolving turbulence producing fluctuations on sub-hour timescales and the irregular solar cycle modulating the system over many years. Here, we apply the data quantile-quantile (DQQ) method [Tindale and Chapman 2016, 2017] to over 20 years of Wind data, to study the time evolution of the statistical distribution of plasma parameters in fast and slow solar wind. This model-independent method allows us to simultaneously explore the evolution of fluctuations across all scales. We find a two-part functional form for the statistical distributions of the interplanetary magnetic field (IMF) magnitude and its components, with each region of the distribution evolving separately over the solar cycle. Up to a value of 8nT, turbulent fluctuations dominate the distribution of the IMF, generating the approximately lognormal shape found by Burlaga [2001]. The mean of this core-turbulence region tracks solar cycle activity, while its variance remains constant, independent of the fast or slow state of the solar wind. However, when we test the lognormality of this core-turbulence component over time, we find the model provides a poor description of the data at solar maximum, where sharp peaks in the distribution dominate over the lognormal shape. At IMF values higher than 8nT, we find a separate, extremal distribution component, whose moments are sensitive to solar cycle phase, the peak activity of the cycle and the solar wind state. We further investigate these `extremal' values using burst analysis, where a burst is defined as a continuous period of exceedance over a predefined threshold. This form of extreme value statistics allows us to study the stochastic process underlying the time series, potentially supporting a probabilistic forecast of high-energy events. Tindale, E., and S.C. Chapman (2016), Geophys. Res. Lett., 43(11) Tindale, E., and S.C. Chapman (2017), submitted Burlaga, L.F. (2001), J. Geophys. Res., 106(A8)

Heart rate measurement as a tool to quantify sedentary behavior.

PubMed

Åkerberg, Anna; Koshmak, Gregory; Johansson, Anders; Lindén, Maria

2015-01-01

Sedentary work is very common today. The aim of this pilot study was to attempt to differentiate between typical work situations and to investigate the possibility to break sedentary behavior, based on physiological measurement among office workers. Ten test persons used one heart rate based activity monitor (Linkura), one pulse oximeter device (Wrist) and one movement based activity wristband (Fitbit Flex), in different working situations. The results showed that both heart rate devices, Linkura and Wrist, were able to detect differences in heart rate between the different working situations (resting, sitting, standing, slow walk and medium fast walk). The movement based device, Fitbit Flex, was only able to separate differences in steps between slow walk and medium fast walk. It can be concluded that heart rate measurement is a promising tool for quantifying and separating different working situations, such as sitting, standing and walking.

(Biphenyl-4-yl)methylammonium chlorides: potent anticonvulsants that modulate Na+ currents.

PubMed

Lee, Hyosung; Park, Ki Duk; Yang, Xiao-Fang; Dustrude, Erik T; Wilson, Sarah M; Khanna, Rajesh; Kohn, Harold

2013-07-25

We have reported that compounds containing a biaryl linked unit (Ar-X-Ar') modulated Na(+) currents by promoting slow inactivation and fast inactivation processes and by inducing frequency (use)-dependent inhibition of Na(+) currents. These electrophysiological properties have been associated with the mode of action of several antiepileptic drugs. In this study, we demonstrate that the readily accessible (biphenyl-4-yl)methylammonium chlorides (compound class B) exhibited a broad range of anticonvulsant activities in animal models, and in the maximal electroshock seizure test the activity of (3'-trifluoromethoxybiphenyl-4-yl)methylammonium chloride (8) exceeded that of phenobarbital and phenytoin upon oral administration to rats. Electrophysiological studies of 8 using mouse catecholamine A-differentiated cells and rat embryonic cortical neurons confirmed that 8 promoted slow and fast inactivation in both cell types but did not affect the frequency (use)-dependent block of Na(+) currents.

Electroencephalographic activity and mood in cocaine-dependent outpatients: effects of cocaine cue exposure.

PubMed

Bauer, L O; Kranzler, H R

1994-08-01

Electroencephalographic (EEG) and subjective reactions to cocaine cues were evaluated in 18 cocaine-dependent outpatients, after 14 or fewer days of abstinence, and 16 noncocaine-dependent controls. EEG activity and desire for cocaine were recorded while subjects viewed three 5-min films that featured either cocaine-associated, erotic, or neutral stimuli. Other measures of mood state and cocaine craving, derived from the Mood Adjective Checklist and the Cocaine Craving Questionnaire, respectively, were recorded immediately after each film. Analyses of absolute EEG power within six frequency bands (delta, theta, slow and fast alpha, slow and fast beta) revealed no EEG abnormalities in the cocaine-dependent group under any condition. In both subject groups, the cocaine-associated and erotic films produced a similar reduction in total EEG power. The cocaine-associated and erotic films also produced a similar increase in the self-rated desire for cocaine, but this change only occurred in the cocaine-dependent group.

The Impact of Cortical Deafferentation on the Neocortical Slow Oscillation

PubMed Central

Lemieux, Maxime; Chen, Jen-Yung; Lonjers, Peter; Bazhenov, Maxim

2014-01-01

Slow oscillation is the main brain rhythm observed during deep sleep in mammals. Although several studies have demonstrated its neocortical origin, the extent of the thalamic contribution is still a matter of discussion. Using electrophysiological recordings in vivo on cats and computational modeling, we found that the local thalamic inactivation or the complete isolation of the neocortical slabs maintained within the brain dramatically reduced the expression of slow and fast oscillations in affected cortical areas. The slow oscillation began to recover 12 h after thalamic inactivation. The slow oscillation, but not faster activities, nearly recovered after 30 h and persisted for weeks in the isolated slabs. We also observed an increase of the membrane potential fluctuations recorded in vivo several hours after thalamic inactivation. Mimicking this enhancement in a network computational model with an increased postsynaptic activity of long-range intracortical afferents or scaling K+ leak current, but not several other Na+ and K+ intrinsic currents was sufficient for recovering the slow oscillation. We conclude that, in the intact brain, the thalamus contributes to the generation of cortical active states of the slow oscillation and mediates its large-scale synchronization. Our study also suggests that the deafferentation-induced alterations of the sleep slow oscillation can be counteracted by compensatory intracortical mechanisms and that the sleep slow oscillation is a fundamental and intrinsic state of the neocortex. PMID:24741059

Evidence accumulation detected in BOLD signal using slow perceptual decision making.

PubMed

Krueger, Paul M; van Vugt, Marieke K; Simen, Patrick; Nystrom, Leigh; Holmes, Philip; Cohen, Jonathan D

2017-04-01

We assessed whether evidence accumulation could be observed in the BOLD signal during perceptual decision making. This presents a challenge since the hemodynamic response is slow, while perceptual decisions are typically fast. Guided by theoretical predictions of the drift diffusion model, we slowed down decisions by penalizing participants for incorrect responses. Second, we distinguished BOLD activity related to stimulus detection (modeled using a boxcar) from activity related to integration (modeled using a ramp) by minimizing the collinearity of GLM regressors. This was achieved by dissecting a boxcar into its two most orthogonal components: an "up-ramp" and a "down-ramp." Third, we used a control condition in which stimuli and responses were similar to the experimental condition, but that did not engage evidence accumulation of the stimuli. The results revealed an absence of areas in parietal cortex that have been proposed to drive perceptual decision making but have recently come into question; and newly identified regions that are candidates for involvement in evidence accumulation. Previous fMRI studies have either used fast perceptual decision making, which precludes the measurement of evidence accumulation, or slowed down responses by gradually revealing stimuli. The latter approach confounds perceptual detection with evidence accumulation because accumulation is constrained by perceptual input. We slowed down the decision making process itself while leaving perceptual information intact. This provided a more sensitive and selective observation of brain regions associated with the evidence accumulation processes underlying perceptual decision making than previous methods. Copyright © 2017 Elsevier B.V. All rights reserved.

Preliminary fMRI findings on the effects of event rate in adults with ADHD.

PubMed

Kooistra, Libbe; van der Meere, Jaap J; Edwards, Jodi D; Kaplan, Bonnie J; Crawford, Susan; Goodyear, Bradley G

2010-05-01

Inhibition problems in attention deficit hyperactivity disorder (ADHD) are sensitive to stimulus event rate. This pilot study explores the neural basis of this increased susceptibility to event rate in ADHD. Event-related functional magnetic resonance imaging was used in conjunction with the administration of a fast (1.5 s) and a slow (7 s) Go/No-Go task. Brain activity patterns and reaction times of ten young male adults with ADHD (two of whom were in partial remission) and ten healthy male controls were compared. The ADHD group responded slower than controls with greater variability but with similar number of errors. Accurate response inhibition in the ADHD group in the slow condition was associated with widespread fronto-striatal activation, including the thalamus. For correct Go trials only, the ADHD group compared with controls showed substantial under-activation in the slow condition. The observed abnormal brain activation in the slow condition in adults with ADHD supports a fronto-striatal etiology, and underlines a presumed activation regulation deficit. Larger sample sizes to further validate these preliminary findings are needed.

Negative stereotype activation alters interaction between neural correlates of arousal, inhibition and cognitive control

PubMed Central

Cox, Christine L.; Schmader, Toni; Ryan, Lee

2012-01-01

Priming negative stereotypes of African Americans can bias perceptions toward novel Black targets, but less is known about how these perceptions ultimately arise. Examining how neural regions involved in arousal, inhibition and control covary when negative stereotypes are activated can provide insight into whether individuals attempt to downregulate biases. Using fMRI, White egalitarian-motivated participants were shown Black and White faces at fast (32 ms) or slow (525 ms) presentation speeds. To create a racially negative stereotypic context, participants listened to violent and misogynistic rap (VMR) in the background. No music (NM) and death metal (DM) were used as control conditions in separate blocks. Fast exposure of Black faces elicited amygdala activation in the NM and VMR conditions (but not DM), that also negatively covaried with activation in prefrontal regions. Only in VMR, however, did amygdala activation for Black faces persist during slow exposure and positively covary with activation in dorsolateral prefrontal cortex while negatively covarying with activation in orbitofrontal cortex. Findings suggest that contexts that prime negative racial stereotypes seem to hinder the downregulation of amygdala activation that typically occurs when egalitarian perceivers are exposed to Black faces. PMID:21954239

Negative stereotype activation alters interaction between neural correlates of arousal, inhibition and cognitive control.

PubMed

Forbes, Chad E; Cox, Christine L; Schmader, Toni; Ryan, Lee

2012-10-01

Priming negative stereotypes of African Americans can bias perceptions toward novel Black targets, but less is known about how these perceptions ultimately arise. Examining how neural regions involved in arousal, inhibition and control covary when negative stereotypes are activated can provide insight into whether individuals attempt to downregulate biases. Using fMRI, White egalitarian-motivated participants were shown Black and White faces at fast (32 ms) or slow (525 ms) presentation speeds. To create a racially negative stereotypic context, participants listened to violent and misogynistic rap (VMR) in the background. No music (NM) and death metal (DM) were used as control conditions in separate blocks. Fast exposure of Black faces elicited amygdala activation in the NM and VMR conditions (but not DM), that also negatively covaried with activation in prefrontal regions. Only in VMR, however, did amygdala activation for Black faces persist during slow exposure and positively covary with activation in dorsolateral prefrontal cortex while negatively covarying with activation in orbitofrontal cortex. Findings suggest that contexts that prime negative racial stereotypes seem to hinder the downregulation of amygdala activation that typically occurs when egalitarian perceivers are exposed to Black faces.

The effects of short-term exercise training on peak-torque are time- and fiber-type dependent.

PubMed

Ureczky, Dóra; Vácz, Gabriella; Costa, Andreas; Kopper, Bence; Lacza, Zsombor; Hortobágyi, Tibor; Tihanyi, József

2014-08-01

We examined the susceptibility of fast and slow twitch muscle fibers in the quadriceps muscle to eccentric exercise-induced muscle damage. Nine healthy men (age: 22.5 ± 1.6 years) performed maximal eccentric quadriceps contractions at 120°·s-1 over a 120° of knee joint range of motion for 6 consecutive days. Biopsies were taken from the vastus lateralis muscle before repeated bouts of eccentric exercise on the third and seventh day. Immunohistochemical procedures were used to determine fiber composition and fibronectin activity. Creatine kinase (CK) and lactate dehydrogenase (LDH) were determined in serum. Average torque was calculated in each day for each subject. Relative to baseline, average torque decreased 37.4% till day 3 and increased 43.0% from the day 3 to day 6 (p < 0.001). Creatine kinase and LDH were 70.6 and 1.5 times higher on day 3 and 75.5 and 1.4 times higher on day 6. Fibronectin was found in fast fibers in subjects with high CK level on day 3 and 7 after exercise, but on day 7, fibronectin seemed in both slow and fast fibers except in muscles of 2 subjects with high fast fiber percentage. Peak torque and muscle fiber-type composition measured at baseline showed a strong positive association on day 3 (r = 0.76, p < 0.02) and strong negative association during recovery between day 3 and day 6 (r = -0.76, p < 0.02), and day 1 and day 6 (r = 0.84, p < 0.001). We conclude that the damage of fast fibers preceded the damage of slow fibers, and muscles with slow fiber dominance were more susceptible to repeated bouts of eccentric exercise than fast fiber dominance muscles. The data suggest that the responses to repeated bouts of eccentric exercise are fiber-type-dependent in the quadriceps muscle, which can be the basis for the design of individualized strength training protocols.

Engineering Design of ITER Prototype Fast Plant System Controller

NASA Astrophysics Data System (ADS)

Goncalves, B.; Sousa, J.; Carvalho, B.; Rodrigues, A. P.; Correia, M.; Batista, A.; Vega, J.; Ruiz, M.; Lopez, J. M.; Rojo, R. Castro; Wallander, A.; Utzel, N.; Neto, A.; Alves, D.; Valcarcel, D.

2011-08-01

The ITER control, data access and communication (CODAC) design team identified the need for two types of plant systems. A slow control plant system is based on industrial automation technology with maximum sampling rates below 100 Hz, and a fast control plant system is based on embedded technology with higher sampling rates and more stringent real-time requirements than that required for slow controllers. The latter is applicable to diagnostics and plant systems in closed-control loops whose cycle times are below 1 ms. Fast controllers will be dedicated industrial controllers with the ability to supervise other fast and/or slow controllers, interface to actuators and sensors and, if necessary, high performance networks. Two prototypes of a fast plant system controller specialized for data acquisition and constrained by ITER technological choices are being built using two different form factors. This prototyping activity contributes to the Plant Control Design Handbook effort of standardization, specifically regarding fast controller characteristics. Envisaging a general purpose fast controller design, diagnostic use cases with specific requirements were analyzed and will be presented along with the interface with CODAC and sensors. The requirements and constraints that real-time plasma control imposes on the design were also taken into consideration. Functional specifications and technology neutral architecture, together with its implications on the engineering design, were considered. The detailed engineering design compliant with ITER standards was performed and will be discussed in detail. Emphasis will be given to the integration of the controller in the standard CODAC environment. Requirements for the EPICS IOC providing the interface to the outside world, the prototype decisions on form factor, real-time operating system, and high-performance networks will also be discussed, as well as the requirements for data streaming to CODAC for visualization and archiving.

Design of collimating and rearrangement systems of laser diode array beam

NASA Astrophysics Data System (ADS)

Gao, Runmei; Fang, Tao; Fu, Rulian; Yao, Jianquan

2015-10-01

To improve the laser diode output beam quality, micro-cylindrical lens and the step-type lens combination are designed. The former is used to collimate beam in fast-axis direction, while the latter plays a role in the slow-axis of splitting and the rearrangement. The micro-column semi-elliptical lens is made with the drops of spherical zoom lensin electric field and with the help of the material properties of light-cured production, which can reduce the reflection of the front surface and total reflection loss of the after. The divergence angle in the fast axis is compressed to roughly the same as that in the slow-axis direction; Stepped lens splits compressed long strip beam in the slow axis, with parallelogram style of level equidistant and rearrange in the fast axis direction. The spot in the slow axis gets smaller and the spot becomes larger in the fast axis. At last divergence angle and the beam spot achieve balanced in the fast axis and slow axis, optical parameters BPP integrates approximate the same, and beam quality can be improved.

Examining the validity of the ActivPAL monitor in measuring posture and ambulatory movement in children.

PubMed

Aminian, Saeideh; Hinckson, Erica A

2012-10-02

Decreasing sedentary activities that involve prolonged sitting may be an important strategy to reduce obesity and other physical and psychosocial health problems in children. The first step to understanding the effect of sedentary activities on children's health is to objectively assess these activities with a valid measurement tool. To examine the validity of the ActivPAL monitor in measuring sitting/lying, standing, and walking time, transition counts and step counts in children in a laboratory setting. Twenty five healthy elementary school children (age 9.9 ± 0.3 years; BMI 18.2 ± 1.9; mean ± SD) were randomly recruited across the Auckland region, New Zealand. Children were fitted with ActivPAL monitors and observed during simulated free-living activities involving sitting/lying, standing and walking, followed by treadmill and over-ground activities at various speeds (slow, normal, fast) against video observation (criterion measure). The ActivPAL sit-to-stand and stand-to-sit transition counts and steps were also compared with video data. The accuracy of step counts measured by the ActivPAL was also compared against the New Lifestyles NL-2000 and the Yamax Digi-Walker SW-200 pedometers. We observed a perfect correlation between the ActivPAL monitor in time spent sitting/lying, standing, and walking in simulated free-living activities with direct observation. Correlations between the ActivPAL and video observation in total numbers of sit-to-stand and stand-to-sit transitions were high (r = 0.99 ± 0.01). Unlike pedometers, the ActivPAL did not misclassify fidgeting as steps taken. Strong correlations (r = 0.88-1.00) between ActivPAL step counts and video observation in both treadmill and over-ground slow and normal walking were also observed. During treadmill and over-ground fast walking and running, the correlations were low (r = 0.21-0.46). The ActivPAL monitor is a valid measurement tool for assessing time spent sitting/lying, standing, and walking, sit-to-stand and stand-to-sit transition counts and step counts in slow and normal walking. The device did not measure accurately steps taken during treadmill and over-ground fast walking and running in children.

Fast-to-slow transformation and nuclear import/export kinetics of the transcription factor NFATc1 during electrostimulation of rabbit muscle cells in culture

PubMed Central

Kubis, Hans-Peter; Scheibe, Renate J; Meißner, Joachim D; Hornung, Gunther; Gros, Gerolf

2002-01-01

Contractile activity imposed by chronic electrical stimulation of a primary skeletal muscle cell culture grown on microcarriers over several days led to an increase of slow myosin heavy chain I (MHCI) and a decrease of fast MHCII expression at mRNA and protein levels, indicating an ongoing fast-to-slow transformation. Only patterns with periods of continuous stimulation of > 5 min in a 45 min cycle were capable of inducing a fibre type transformation, and this was independent of the applied stimulation frequency over the range 1-10 Hz. We have shown before that the calcineurin-NFATc1 signalling pathway is indispensable in mediating MHCI upregulation during fibre type transformation. Therefore, subcellular localization of NFATc1 was studied immunocytochemically. This revealed that only one stimulation train lasting for > 5 min was sufficient to induce nuclear import of this factor, which was about complete after 20 min of continuous stimulation. For both induction of NFATc1 import and MHCI mRNA upregulation, the minimum stimulation interval of > 5 min was sufficient and stimulation frequency was not crucial between 1 and 10 Hz. Repetition of stimulation cycles, with pauses (< 40 min) shorter than the time required for complete export of NFATc1, led to an accumulation of NFATc1 in the nuclei with each cycle and thus to an amplification of the transformation signal during extended periods of electrostimulation. The temporal behaviour of NFATc import/export appears to determine the effectiveness of various electrostimulation protocols in inducing fast-to-slow fibre transformation. PMID:12068044

Fiber-specific regulation of Ca(2+)-ATPase isoform expression by thyroid hormone in rat skeletal muscle.

PubMed

van der Linden, C G; Simonides, W S; Muller, A; van der Laarse, W J; Vermeulen, J L; Zuidwijk, M J; Moorman, A F; van Hardeveld, C

1996-12-01

We studied the effect of thyroid hormone (3,5,3'-triiodo-L-thyronine, T3) on the expression of sarcoplasmic reticulum (SR) fast- and slow-type Ca(2+)-ATPase isoforms, SERCA1 and SERCA2a, respectively, and total SR Ca(2+)-ATPase activity in rat skeletal muscle. Cross sections and homogenates of soleus and extensor digitorum longus muscles from hypo-, eu-, and hyperthyroid rats were examined, and expression of Ca(2+)-ATPase isoforms in individual fibers was compared with expression of fast (MHC II) and slow (MHC I) myosin heavy chain isoforms. In both muscles, T3 induced a coordinated and full conversion to a fast-twitch phenotype in one-half of the fibers that were slow twitch in the absence of T3. The conversion was partial in the other one-half of the fibers, giving rise to a mixed phenotype. The stimulation by T3 of total SERCA expression in all fibers was reflected by increased SR Ca(2+)-ATPase activity. The time course of the T3-induced changes of SERCA isoform expression was examined 1-14 days after the start of daily T3 treatment of euthyroid rats. SERCA1 expression was stimulated by T3 at a pretranslational level in all fibers. SERCA2a mRNA expression was transiently stimulated and disappeared in a subset of fibers. In these fibers SR Ca(2+)-ATPase activity was high because of high SERCA1 protein levels. These data suggest that the ultimate downregulation of SERCA2a expression, which is always associated with high SR Ca(2+)-ATPase activities, occurs at a pretranslational level.

Depolarized inactivation overcomes impaired activation to produce DRG neuron hyperexcitability in a Nav1.7 mutation in a patient with distal limb pain.

PubMed

Huang, Jianying; Yang, Yang; Dib-Hajj, Sulayman D; van Es, Michael; Zhao, Peng; Salomon, Jody; Drenth, Joost P H; Waxman, Stephen G

2014-09-10

Sodium channel Nav1.7, encoded by SCN9A, is expressed in DRG neurons and regulates their excitability. Genetic and functional studies have established a critical contribution of Nav1.7 to human pain disorders. We have now characterized a novel Nav1.7 mutation (R1279P) from a female human subject with distal limb pain, in which depolarized fast inactivation overrides impaired activation to produce hyperexcitability and spontaneous firing in DRG neurons. Whole-cell voltage-clamp recordings in human embryonic kidney (HEK) 293 cells demonstrated that R1279P significantly depolarizes steady-state fast-, slow-, and closed-state inactivation. It accelerates deactivation, decelerates inactivation, and facilitates repriming. The mutation increases ramp currents in response to slow depolarizations. Our voltage-clamp analysis showed that R1279P depolarizes channel activation, a change that was supported by our multistate structural modeling. Because this mutation confers both gain-of-function and loss-of-function attributes on the Nav1.7 channel, we tested the impact of R1279P expression on DRG neuron excitability. Current-clamp studies reveal that R1279P depolarizes resting membrane potential, decreases current threshold, and increases firing frequency of evoked action potentials within small DRG neurons. The populations of spontaneously firing and repetitively firing neurons were increased by expressing R1279P. These observations indicate that the dominant proexcitatory gating changes associated with this mutation, including depolarized steady-state fast-, slow-, and closed-state inactivation, faster repriming, and larger ramp currents, override the depolarizing shift of activation, to produce hyperexcitability and spontaneous firing of nociceptive neurons that underlie pain. Copyright © 2014 the authors 0270-6474/14/3412328-13$15.00/0.

Generic torus canards

NASA Astrophysics Data System (ADS)

Vo, Theodore

2017-10-01

Torus canards are special solutions of fast/slow systems that alternate between attracting and repelling manifolds of limit cycles of the fast subsystem. A relatively new dynamic phenomenon, torus canards have been found in neural applications to mediate the transition from tonic spiking to bursting via amplitude-modulated spiking. In R3, torus canards are degenerate: they require one-parameter families of 2-fast/1-slow systems in order to be observed and even then, they only occur on exponentially thin parameter intervals. The addition of a second slow variable unfolds the torus canard phenomenon, making it generic and robust. That is, torus canards in fast/slow systems with (at least) two slow variables occur on open parameter sets. So far, generic torus canards have only been studied numerically, and their behaviour has been inferred based on averaging and canard theory. This approach, however, has not been rigorously justified since the averaging method breaks down near a fold of periodics, which is exactly where torus canards originate. In this work, we combine techniques from Floquet theory, averaging theory, and geometric singular perturbation theory to show that the average of a torus canard is a folded singularity canard. In so doing, we devise an analytic scheme for the identification and topological classification of torus canards in fast/slow systems with two fast variables and k slow variables, for any positive integer k. We demonstrate the predictive power of our results in a model for intracellular calcium dynamics, where we explain the mechanisms underlying a novel class of elliptic bursting rhythms, called amplitude-modulated bursting, by constructing the torus canard analogues of mixed-mode oscillations. We also make explicit the connection between our results here with prior studies of torus canards and torus canard explosion in R3, and discuss how our methods can be extended to fast/slow systems of arbitrary (finite) dimension.

Different event-related patterns of gamma-band power in brain waves of fast- and slow-reacting subjects.

PubMed Central

Jokeit, H; Makeig, S

1994-01-01

Fast- and slow-reacting subjects exhibit different patterns of gamma-band electroencephalogram (EEG) activity when responding as quickly as possible to auditory stimuli. This result appears to confirm long-standing speculations of Wundt that fast- and slow-reacting subjects produce speeded reactions in different ways and demonstrates that analysis of event-related changes in the amplitude of EEG activity recorded from the human scalp can reveal information about event-related brain processes unavailable using event-related potential measures. Time-varying spectral power in a selected (35- to 43-Hz) gamma frequency band was averaged across trials in two experimental conditions: passive listening and speeded reacting to binaural clicks, forming 40-Hz event-related spectral responses. Factor analysis of between-subject event-related spectral response differences split subjects into two near-equal groups composed of faster- and slower-reacting subjects. In faster-reacting subjects, 40-Hz power peaked near 200 ms and 400 ms poststimulus in the react condition, whereas in slower-reacting subjects, 40-Hz power just before stimulus delivery was larger in the react condition. These group differences were preserved in separate averages of relatively long and short reaction-time epochs for each group. gamma-band (20-60 Hz)-filtered event-related potential response averages did not differ between the two groups or conditions. Because of this and because gamma-band power in the auditory event-related potential is small compared with the EEG, the observed event-related spectral response features must represent gamma-band EEG activity reliably induced by, but not phase-locked to, experimental stimuli or events. PMID:8022783

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

Twu, Nancy; Metzger, Michael; Balasubramanian, Mahalingam

Here, the lithium-excess Li xNi 2-4x/3Sb x/3O 2 (LNSO) materials were previously shown to demonstrate higher capacities and improved cyclability with increasing lithium content. While the performance trend is promising, observed capacities are much lower than theoretical capacities, pointing to a need for further understanding of active redox processes in these materials. In this work, we study the electrochemical behavior of the LNSO materials as a function of lithium content and at slow and fast rates. Surprisingly, Li 1.15Ni 0.47Sb 0.38O 2 (LNSO-15) exhibits higher discharge capacities at faster rates and traverses distinct voltage curves at slow and fast rates.more » To understand these two peculiarities, we characterize the redox activity of nickel, antimony, and oxygen at different rates. While experiments confirm some nickel redox activity and oxygen loss, these two mechanisms cannot account for all observed capacity. We propose that the balance of the observed capacity may be due reversible oxygen redox and that the rate-dependent voltage curve features may derive from irreversible nickel migration occurring on slow charge. As future high energy density cathodes are likely to contain both lithium excess and high nickel content, both of these findings have important implications for the development of novel high capacity cathode materials.« less

Fast and Loud Background Music Disrupts Reading Comprehension

ERIC Educational Resources Information Center

Thompson, William Forde; Schellenberg, E. Glenn; Letnic, Adriana Katharine

2012-01-01

We examined the effect of background music on reading comprehension. Because the emotional consequences of music listening are affected by changes in tempo and intensity, we manipulated these variables to create four repeated-measures conditions: slow/low, slow/high, fast/low, fast/high. Tempo and intensity manipulations were selected to be…

Fiber type conversion alters inactivation of voltage-dependent sodium currents in murine C2C12 skeletal muscle cells.

PubMed

Zebedin, Eva; Sandtner, Walter; Galler, Stefan; Szendroedi, Julia; Just, Herwig; Todt, Hannes; Hilber, Karlheinz

2004-08-01

Each skeletal muscle of the body contains a unique composition of "fast" and "slow" muscle fibers, each of which is specialized for certain challenges. This composition is not static, and the muscle fibers are capable of adapting their molecular composition by altered gene expression (i.e., fiber type conversion). Whereas changes in the expression of contractile proteins and metabolic enzymes in the course of fiber type conversion are well described, little is known about possible adaptations in the electrophysiological properties of skeletal muscle cells. Such adaptations may involve changes in the expression and/or function of ion channels. In this study, we investigated the effects of fast-to-slow fiber type conversion on currents via voltage-gated Na+ channels in the C(2)C(12) murine skeletal muscle cell line. Prolonged treatment of cells with 25 nM of the Ca2+ ionophore A-23187 caused a significant shift in myosin heavy chain isoform expression from the fast toward the slow isoform, indicating fast-to-slow fiber type conversion. Moreover, Na+ current inactivation was significantly altered. Slow inactivation less strongly inhibited the Na+ currents of fast-to-slow fiber type-converted cells. Compared with control cells, the Na+ currents of converted cells were more resistant to block by tetrodotoxin, suggesting enhanced relative expression of the cardiac Na+ channel isoform Na(v)1.5 compared with the skeletal muscle isoform Na(v)1.4. These results imply that fast-to-slow fiber type conversion of skeletal muscle cells involves functional adaptation of their electrophysiological properties.

Mechanical properties of frog skeletal muscles in iodoacetic acid rigor.

PubMed Central

Mulvany, M J

1975-01-01

1. Methods have been developed for describing the length: tension characteristics of frog skeletal muscles which go into rigor at 4 degrees C following iodoacetic acid poisoning either in the presence of Ca2+ (Ca-rigor) or its absence (Ca-free-rigor). 2. Such rigor muscles showed less resistance to slow stretch (slow rigor resistance) that to fast stretch (fast rigor resistance). The slow and fast rigor resistances of Ca-free-rigor muscles were much lower than those of Ca-rigor muscles. 3. The slow rigor resistance of Ca-rigor muscles was proportional to the amount of overlap between the contractile filaments present when the muscles were put into rigor. 4. Withdrawing Ca2+ from Ca-rigor muscles (induced-Ca-free rigor) reduced their slow and fast rigor resistances. Readdition of Ca2+ (but not Mg2+, Mn2+ or Sr2+) reversed the effect. 5. The slow and fast rigor resistances of Ca-rigor muscles (but not of Ca-free-rigor muscles) decreased with time. 6.The sarcomere structure of Ca-rigor and induced-Ca-free rigor muscles stretched by 0.2lo was destroyed in proportion to the amount of stretch, but the lengths of the remaining intact sarcomeres were essentially unchanged. This suggests that there had been a successive yielding of the weakeast sarcomeres. 7. The difference between the slow and fast rigor resistance and the effect of calcium on these resistances are discussed in relation to possible variations in the strength of crossbridges between the thick and thin filaments. Images Plate 1 Plate 2 PMID:1082023

SDSS-IV MaNGA: the different quenching histories of fast and slow rotators

NASA Astrophysics Data System (ADS)

Smethurst, R. J.; Masters, K. L.; Lintott, C. J.; Weijmans, A.; Merrifield, M.; Penny, S. J.; Aragón-Salamanca, A.; Brownstein, J.; Bundy, K.; Drory, N.; Law, D. R.; Nichol, R. C.

2018-01-01

Do the theorized different formation mechanisms of fast and slow rotators produce an observable difference in their star formation histories? To study this, we identify quenching slow rotators in the MaNGA sample by selecting those that lie below the star-forming sequence and identify a sample of quenching fast rotators that were matched in stellar mass. This results in a total sample of 194 kinematically classified galaxies, which is agnostic to visual morphology. We use u - r and NUV - u colours from the Sloan Digital Sky Survey and GALEX and an existing inference package, STARPY, to conduct a first look at the onset time and exponentially declining rate of quenching of these galaxies. An Anderson-Darling test on the distribution of the inferred quenching rates across the two kinematic populations reveals they are statistically distinguishable (3.2σ). We find that fast rotators quench at a much wider range of rates than slow rotators, consistent with a wide variety of physical processes such as secular evolution, minor mergers, gas accretion and environmentally driven mechanisms. Quenching is more likely to occur at rapid rates (τ ≲ 1 Gyr) for slow rotators, in agreement with theories suggesting slow rotators are formed in dynamically fast processes, such as major mergers. Interestingly, we also find that a subset of the fast rotators quench at these same rapid rates as the bulk of the slow rotator sample. We therefore discuss how the total gas mass of a merger, rather than the merger mass ratio, may decide a galaxy's ultimate kinematic fate.

Revisiting the relationship between exercise heart rate and music tempo preference.

PubMed

Karageorghis, Costas I; Jones, Leighton; Priest, David-Lee; Akers, Rose I; Clarke, Adam; Perry, Jennifer M; Reddick, Benjamin T; Bishop, Daniel T; Lim, Harry B T

2011-06-01

In the present study, we investigated a hypothesized quartic relationship (meaning three inflection points) between exercise heart rate (HR) and preferred music tempo. Initial theoretical predictions suggested a positive linear relationship (Iwanaga, 1995a, 1995b); however, recent experimental work has shown that as exercise HR increases, step changes and plateaus that punctuate the profile of music tempo preference may occur (Karageorghis, Jones, & Stuart, 2008). Tempi bands consisted of slow (95-100 bpm), medium (115-120 bpm), fast (135-140 bpm), and very fast (155-160 bpm) music. Twenty-eight active undergraduate students cycled at exercise intensities representing 40, 50, 60, 70, 80, and 90% of their maximal HR reserve while their music preference was assessed using a 10-point scale. The Exercise Intensity x Music Tempo interaction was significant, F(6.16, 160.05) = 7.08, p < .001, 7,2 = .21, as was the test for both cubic and quartic trajectories in the exercise HR-preferred-music-tempo relationship (p < .001). Whereas slow tempo music was not preferred at any exercise intensity, preference for fast tempo increased, relative to medium and very fast tempo music, as exercise intensity increased. The implications for the prescription of music in exercise and physical activity contexts are discussed.

Self-selected speeds and metabolic cost of longboard skateboarding.

PubMed

Board, Wayne J; Browning, Raymond C

2014-11-01

The purpose of this study was to determine self-selected speeds, metabolic rate, and gross metabolic cost during longboard skateboarding. We measured overground speed and metabolic rate while 15 experienced longboarders traveled at their self-selected slow, typical and fast speeds. Mean longboarding speeds were 3.7, 4.5 and 5.1 m s(-1), during slow, typical and fast trials, respectively. Mean rates of oxygen consumption were 24.1, 29.1 and 37.2 ml kg(-1) min(-1) and mean rates of energy expenditure were 33.5, 41.8 and 52.7 kJ min(-1) at the slow, typical and fast speeds, respectively. At typical speeds, average intensity was ~8.5 METs. There was a significant positive relationship between oxygen consumption and energy expenditure versus speed (R(2) = 0.69 (P < 0.001), and R(2) = 0.78 (P < 0.001), respectively). The gross metabolic cost was ~2.2 J kg(-1) m(-1) at the typical speed, greater than that reported for cycling and ~50% smaller than that of walking. These results suggest that longboarding is a novel form of physical activity that elicits vigorous intensity, yet is economical compared to walking.

Rescue of dystrophic skeletal muscle by PGC-1α involves a fast to slow fiber type shift in the mdx mouse.

PubMed

Selsby, Joshua T; Morine, Kevin J; Pendrak, Klara; Barton, Elisabeth R; Sweeney, H Lee

2012-01-01

Increased utrophin expression is known to reduce pathology in dystrophin-deficient skeletal muscles. Transgenic over-expression of PGC-1α has been shown to increase levels of utrophin mRNA and improve the histology of mdx muscles. Other reports have shown that PGC-1α signaling can lead to increased oxidative capacity and a fast to slow fiber type shift. Given that it has been shown that slow fibers produce and maintain more utrophin than fast skeletal muscle fibers, we hypothesized that over-expression of PGC-1α in post-natal mdx mice would increase utrophin levels via a fiber type shift, resulting in more slow, oxidative fibers that are also more resistant to contraction-induced damage. To test this hypothesis, neonatal mdx mice were injected with recombinant adeno-associated virus (AAV) driving expression of PGC-1α. PGC-1α over-expression resulted in increased utrophin and type I myosin heavy chain expression as well as elevated mitochondrial protein expression. Muscles were shown to be more resistant to contraction-induced damage and more fatigue resistant. Sirt-1 was increased while p38 activation and NRF-1 were reduced in PGC-1α over-expressing muscle when compared to control. We also evaluated if the use a pharmacological PGC-1α pathway activator, resveratrol, could drive the same physiological changes. Resveratrol administration (100 mg/kg/day) resulted in improved fatigue resistance, but did not achieve significant increases in utrophin expression. These data suggest that the PGC-1α pathway is a potential target for therapeutic intervention in dystrophic skeletal muscle.

Use and disuse and the control of acetylcholinesterase activity in fast and slow twitch muscle of rat

NASA Technical Reports Server (NTRS)

Dettbarn, W. D.; Groswald, D.; Gupta, R. C.; Misulis, K. E.

1985-01-01

The role of acetylcholinesterase (AChE) in neuromuscular transmission is relatively well established, little is known, however, of the mechanisms that regulate its synthesis and control its specific distribution in fast and slow muscle. Innervation plays an important role in the regulation of AChE and elimination of the influence of the nerve by surgical denervation results in a loss of AChE. The influences of the nerve and how they are mediated was investigated. It is suggested that muscle usage and other factors such as materials carried by axonal transport may participate in the regulation of this enzyme. The mechanisms that regulate AChE and its molecular forms in two functionally different forms are studied.

Neural-Thyroid Interaction on Skeletal Isomyosin in Zero Gravity

NASA Technical Reports Server (NTRS)

Baldwin, Kenneth M.

2000-01-01

The primary goal of the project was to develop a ground based model to first study the role of the nerve and of thyroid hormone (T3) in the regulation of body growth and skeletal muscle growth and differentiation in rodents. A primary objective was to test the hypothesis that normal weight bearing activity is essential for the development of antigravity, slow twitch skeletal muscle and the corresponding slow myosin heavy chain (MHC) gene; whereas, T3 was obligatory for general body and muscle growth and the establishment of fast MHC phenotype in typically fast locomoter muscles. These ground based experiments would provide both the efficacy and background for a spaceflight experiment (referred to as the Neurolab Mission) jointly sponsored by the NIH and NASA.

Generation kinetics of boron-oxygen complexes in p-type compensated c-Si

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

Wu, Yichao; Yu, Xuegong, E-mail: yuxuegong@zju.edu.cn; Chen, Peng

2014-03-10

Kinetics characteristics of boron-oxygen complexes responsible for light-induced degradation in p-type compensated c-Si have been investigated. The generation of B-O complexes is well fitted by a fast-forming process and a slow-forming one. Activation energies of complexes generation during the fast-forming process are determined to be 0.29 and 0.24 eV in compensated and non-compensated c-Si, respectively, and those during the slow-forming process are the same, about 0.44 eV. Moreover, it is found that the pre-exponential factors of complexes generation in compensated c-Si is proportional to the square of the net doping concentration, which suggests that the latent centers should exist.

Slow-Mode MHD Wave Penetration into a Coronal Null Point due to the Mode Transmission

NASA Astrophysics Data System (ADS)

Afanasyev, Andrey N.; Uralov, Arkadiy M.

2016-11-01

Recent observations of magnetohydrodynamic oscillations and waves in solar active regions revealed their close link to quasi-periodic pulsations in flaring light curves. The nature of that link has not yet been understood in detail. In our analytical modelling we investigate propagation of slow magnetoacoustic waves in a solar active region, taking into account wave refraction and transmission of the slow magnetoacoustic mode into the fast one. The wave propagation is analysed in the geometrical acoustics approximation. Special attention is paid to the penetration of waves in the vicinity of a magnetic null point. The modelling has shown that the interaction of slow magnetoacoustic waves with the magnetic reconnection site is possible due to the mode transmission at the equipartition level where the sound speed is equal to the Alfvén speed. The efficiency of the transmission is also calculated.

Analysis of myofibrillar proteins and transcripts in adult skeletal muscles of the American lobster Homarus americanus: variable expression of myosins, actin and troponins in fast, slow-twitch and slow-tonic fibres.

PubMed

Medler, Scott; Mykles, Donald L

2003-10-01

Skeletal muscles are diverse in their contractile properties, with many of these differences being directly related to the assemblages of myofibrillar isoforms characteristic of different fibers. Crustacean muscles are similar to other muscles in this respect, although the majority of information about differences in muscle organization comes from vertebrate species. In the present study, we examined the correlation between myofibrillar protein isoforms and the patterns of myofibrillar gene expression in fast, slow-phasic (S(1)) and slow-tonic (S(2)) fibers of the American lobster Homarus americanus. SDS-PAGE and western blotting were used to identify isoform assemblages of myosin heavy chain (MHC), P75, troponin T (TnT) and troponin I (TnI). RT-PCR was used to monitor expression of fast and slow (S(1)) MHC, P75 and actin in different fiber types, and the MHC and actin levels were quantified by real-time PCR. Fast and slow fibers from the claw closers predominantly expressed fast and S(1) MHC, respectively, but also lower levels of the alternate MHC. By contrast, fast fibers from the deep abdominal muscle expressed fast MHC exclusively. In addition, slow muscles expressed significantly higher levels of actin than fast fibers. A distal bundle of fibers in the cutter claw closer muscle was found to be composed of a mixture of S(1) and S(2) fibers, many of which possessed a mixture of S(1) and S(2) MHC isoforms. This pattern supports the idea that S(1) and S(2) fibers represent extremes in a continuum of slow muscle phenotype. Overall, these patterns demonstrate that crustacean skeletal muscles cannot be strictly categorized into discrete fiber types, but a muscle's properties probably represent a point on a continuum of fiber types. This trend may result from differences in innervation pattern, as each muscle is controlled by a unique combination of phasic, tonic or both phasic and tonic motor nerves. In this respect, future studies examining how muscle phenotype correlates with innervation pattern may help account for variation in crustacean fiber types.

Modulation of synaptic transmission in the rabbit coeliac ganglia by gastric and duodenal mechanoreceptors.

PubMed

Mazet, B; Miolan, J P; Niel, J P; Julé, Y; Roman, C

1989-01-01

The involvement of duodenal and gastric mechanoreceptors in the modulation of synaptic transmission was investigated in a rabbit sympathetic prevertebral ganglion. The present study was performed in vitro on the coeliac plexus connected to the stomach and the duodenum. The electrical activity of ganglionic neurons was recorded using intracellular recording techniques. The patterns of synaptic activation of these ganglionic neurons in response to the activation of mechanoreceptors by gastric or duodenal distension were investigated. Although gastric or duodenal distension was unable to elicit any fast synaptic activity in ganglionic neurons, it produced either an inhibition or a facilitation of the fast nicotinic excitatory postsynaptic potentials elicited by stimulation of the thoracic splanchnic nerves. In addition, this distension triggered long-lasting (3-11 min) modifications in the electrical properties of the ganglionic neurons, i.e. slow depolarizations (6-18 mV) or slow hyperpolarizations (3-6 mV), which were sometimes associated with a decrease in the input membrane resistance. After cooling of the nerves connecting the coeliac ganglia to the stomach, the activation of gastric or duodenal mechanoreceptors was no longer able to modify the fast synaptic activation or the electrical properties of the ganglionic neurons. The results demonstrate that gastric and duodenal mechanoreceptors project onto neurons of the coeliac ganglia and change their excitability as well as the central inputs they receive. The long duration of these modifications suggests that gastric and duodenal mechanoreceptors can modulate the activity of the neurons of the coeliac ganglia.

Alterations in speed of squat movement and the use of accommodated resistance among college athletes training for power.

PubMed

Rhea, Matthew R; Kenn, Joseph G; Dermody, Bryan M

2009-12-01

The purpose of this study was to assess the effect of heavy/slow movements and variable resistance training on peak power and strength development. Forty-eight National Collegiate Athletic Association (NCAA) Division I athletes (age: 21.4 +/- 2.1 years, all men) were recruited for this 12-week training intervention study. Maximum strength and jumping power were assessed before and after the training program. Athletes were randomly assigned to 1 of 3 training groups: heavy resistance/slow movement (Slow), lighter resistance and fast movement (Fast), or fast movements with accommodated resistance (FACC). All training groups performed similar training programs comprising free weight resistance training with lower-body compound exercises. The only difference among the training interventions was the speed at which subjects performed the squat exercise and the use of bands (Slow group: 0.2-0.4 meters/second; Fast group: 0.6-0.8 meters/second; FACC group trained 0.6-0.8 meters/second with the addition of accommodated resistance in the form of large elastic bands). Post-test data revealed a significant difference between power improvements between the Slow and FACC groups (p = 0.02). Percent increases and effect sizes (ES) demonstrated a much greater treatment effect in the FACC group (17.8%, ES = 1.06) with the Fast group (11.0%, ES = 0.80) adapting more than the Slow group (4.8%, ES = 0.28). The FACC and Slow groups improved strength comparatively (FACC: 9.44%, ES = 1.10; Slow: 9.59%, ES = 1.08). The Fast group improved strength considerably less, 3.20% with an effect size of only 0.38. Variable resistance training with elastic bands appears to provide greater performance benefits with regard to peak force and peak power than heavy, slow resistance exercise. Sports conditioning professionals can utilize bands, and high-speed contractions, to increase power development.

Can exposure variation be promoted in the shoulder girdle muscles by modifying work pace and inserting pauses during simulated assembly work?

PubMed

Januario, Leticia Bergamin; Madeleine, Pascal; Cid, Marina Machado; Samani, Afshin; Oliveira, Ana Beatriz

2018-01-01

This study investigated the acute effects of changing the work pace and implementing two pause types during an assembly task. Eighteen healthy women performed a simulated task in four different conditions: 1) slow or 2) fast work pace with 3) passive or 4) active pauses every two minutes. The root mean square (RMS) and exposure variation analysis (EVA) from the trapezius and serratus anterior muscles, as well as the rate of perceived exertion (RPE) from the neck-shoulder region, were observed. Decreased RMS and RPE as well as more variable muscle activity (EVA) were observed in the slow work pace compared with the fast one. The pause types had a limited effect, but active pauses resulted in increased RMS of the clavicular trapezius. The findings revealed the importance of work pace in the reduction of perceived exertion and promotion of variation in muscle activation during assembly tasks. However, the pause types had no important effect on the evaluated outcomes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Drastic increase of myosin light chain MLC-2 in senescent skeletal muscle indicates fast-to-slow fibre transition in sarcopenia of old age.

PubMed

Gannon, Joan; Doran, Philip; Kirwan, Anne; Ohlendieck, Kay

2009-11-01

The age-dependent decline in skeletal muscle mass and function is believed to be due to a multi-factorial pathology and represents a major factor that blocks healthy aging by increasing physical disability, frailty and loss of independence in the elderly. This study has focused on the comparative proteomic analysis of contractile elements and revealed that the most striking age-related changes seem to occur in the protein family representing myosin light chains (MLCs). Comparative screening of total muscle extracts suggests a fast-to-slow transition in the aged MLC population. The mass spectrometric analysis of the myofibril-enriched fraction identified the MLC2 isoform of the slow-type MLC as the contractile protein with the most drastically changed expression during aging. Immunoblotting confirmed an increased abundance of slow MLC2, concomitant with a switch in fast versus slow myosin heavy chains. Staining of two-dimensional gels of crude extracts with the phospho-specific fluorescent dye ProQ-Diamond identified the increased MLC2 spot as a muscle protein with a drastically enhanced phosphorylation level in aged fibres. Comparative immunofluorescence microscopy, using antibodies to fast and slow myosin isoforms, confirmed a fast-to-slow transformation process during muscle aging. Interestingly, the dramatic increase in slow MLC2 expression was restricted to individual senescent fibres. These findings agree with the idea that aged skeletal muscles undergo a shift to more aerobic-oxidative metabolism in a slower-twitching fibre population and suggest the slow MLC2 isoform as a potential biomarker for fibre type shifting in sarcopenia of old age.

Disuse Induced Changes in the Cholinergic System of Sciatic Nerve and Slow and Fast Twitch Muscle of Rats

NASA Technical Reports Server (NTRS)

Dettbarn, W. D.; Gupta, R. C.; Misulis, K. E.

1985-01-01

Hindlimb suspension was used as a model of disuse in experiments studing the effects of reduced muscle activity on AChE and its molecular forms, choline acetyltransferase and nicotinic receptor binding in innervated slow and fast muscle. The weight of SOL was reduced to 64% within one week and continued to decrease progressively up to the third week when the weight was reduced to 40% as compared to controls. EDL showed a significant decrease in its weight only at the end of three weeks hypokinesia when it was reduced to 71% of control. Biochemical and histochemical findings are summarized. From these data and from morphological findings it is evident that some properties of skeletal muscles are strongly dependent on patterns and level of loadbearing and on motor unit activiy. With suspension-induced disuse, the usually slow SOL appeared to change its characteristics such as fiber type distribution and AChE activity to one that more resembled a faster muscle. It is important to note that hypokinesia induced changes either physiological, biochemical or morphological, are totally reversible as the induced changes returned to control levels within a week after cessation of disuse.

Characterization of the transcriptome of fast and slow muscle myotomal fibres in the pacu (Piaractus mesopotamicus).

PubMed

Mareco, Edson A; Garcia de la Serrana, Daniel; Johnston, Ian A; Dal-Pai-Silva, Maeli

2015-03-14

The Pacu (Piaractus mesopotamicus) is a member of the Characiform family native to the Prata Basin (South America) and a target for the aquaculture industry. A limitation for the development of a selective breeding program for this species is a lack of available genetic information. The primary objectives of the present study were 1) to increase the genetic resources available for the species, 2) to exploit the anatomical separation of myotomal fibres types to compare the transcriptomes of slow and fast muscle phenotypes and 3) to systematically investigate the expression of Ubiquitin Specific Protease (USP) family members in fast and slow muscle in response to fasting and refeeding. We generated 0.6 Tb of pair-end reads from slow and fast skeletal muscle libraries. Over 665 million reads were assembled into 504,065 contigs with an average length of 1,334 bp and N50 = 2,772 bp. We successfully annotated nearly 47% of the transcriptome and identified around 15,000 unique genes and over 8000 complete coding sequences. 319 KEGG metabolic pathways were also annotated and 380 putative microsatellites were identified. 956 and 604 genes were differentially expressed between slow and fast skeletal muscle, respectively. 442 paralogues pairs arising from the teleost-specific whole genome duplication were identified, with the majority showing different expression patterns between fibres types (301 in slow and 245 in fast skeletal muscle). 45 members of the USP family were identified in the transcriptome. Transcript levels were quantified by qPCR in a separate fasting and refeeding experiment. USP genes in fast muscle showed a similar transient increase in expression with fasting as the better characterized E3 ubiquitin ligases. We have generated a 53-fold coverage transcriptome for fast and slow myotomal muscle in the pacu (Piaractus mesopotamicus) significantly increasing the genetic resources available for this important aquaculture species. We describe significant differences in gene expression between muscle fibre types for fundamental components of general metabolism, the Pi3k/Akt/mTor network and myogenesis, including detailed analysis of paralogue expression. We also provide a comprehensive description of USP family member expression between muscle fibre types and with changing nutritional status.

MusTRD can regulate postnatal fiber-specific expression.

PubMed

Issa, Laura L; Palmer, Stephen J; Guven, Kim L; Santucci, Nicole; Hodgson, Vanessa R M; Popovic, Kata; Joya, Josephine E; Hardeman, Edna C

2006-05-01

Human MusTRD1alpha1 was isolated as a result of its ability to bind a critical element within the Troponin I slow upstream enhancer (TnIslow USE) and was predicted to be a regulator of slow fiber-specific genes. To test this hypothesis in vivo, we generated transgenic mice expressing hMusTRD1alpha1 in skeletal muscle. Adult transgenic mice show a complete loss of slow fibers and a concomitant replacement by fast IIA fibers, resulting in postural muscle weakness. However, developmental analysis demonstrates that transgene expression has no impact on embryonic patterning of slow fibers but causes a gradual postnatal slow to fast fiber conversion. This conversion was underpinned by a demonstrable repression of many slow fiber-specific genes, whereas fast fiber-specific gene expression was either unchanged or enhanced. These data are consistent with our initial predictions for hMusTRD1alpha1 and suggest that slow fiber genes contain a specific common regulatory element that can be targeted by MusTRD proteins.

Cancer Strikes Out!/Definitions/ Glossary/ Common Types

MedlinePlus

... have an indolent (slow-growing) course or an aggressive (fast-growing) course. These subtypes behave and respond ... non-Hodgkin's lymphoma, which can be divided into aggressive (fast-growing) and indolent (slow-growing) types and ...

Does fast or slow evaluation foster greater certainty?

PubMed

Tormala, Zakary L; Clarkson, Joshua J; Henderson, Marlone D

2011-03-01

This research investigates the effect of perceived evaluation duration--that is, the perceived time or speed with which one generates an evaluation--on attitude certainty. Integrating diverse findings from past research, the authors propose that perceiving either fast or slow evaluation can augment attitude certainty depending on specifiable factors. Across three studies, it is shown that when people express opinions, evaluate familiar objects, or typically trust their gut reactions, perceiving fast rather than slow evaluation generally promotes greater certainty. In contrast, when people form opinions, evaluate unfamiliar objects, or typically trust more thoughtful responses, perceiving slow rather than fast evaluation generally promotes greater certainty. Mediation analyses reveal that these effects stem from trade-offs between perceived rational thought and the perceived ease of retrieving an attitude. Implications for research on deliberative versus intuitive decision making are discussed.

Fast but fleeting: adaptive motor learning processes associated with aging and cognitive decline.

PubMed

Trewartha, Kevin M; Garcia, Angeles; Wolpert, Daniel M; Flanagan, J Randall

2014-10-01

Motor learning has been shown to depend on multiple interacting learning processes. For example, learning to adapt when moving grasped objects with novel dynamics involves a fast process that adapts and decays quickly-and that has been linked to explicit memory-and a slower process that adapts and decays more gradually. Each process is characterized by a learning rate that controls how strongly motor memory is updated based on experienced errors and a retention factor determining the movement-to-movement decay in motor memory. Here we examined whether fast and slow motor learning processes involved in learning novel dynamics differ between younger and older adults. In addition, we investigated how age-related decline in explicit memory performance influences learning and retention parameters. Although the groups adapted equally well, they did so with markedly different underlying processes. Whereas the groups had similar fast processes, they had different slow processes. Specifically, the older adults exhibited decreased retention in their slow process compared with younger adults. Within the older group, who exhibited considerable variation in explicit memory performance, we found that poor explicit memory was associated with reduced retention in the fast process, as well as the slow process. These findings suggest that explicit memory resources are a determining factor in impairments in the both the fast and slow processes for motor learning but that aging effects on the slow process are independent of explicit memory declines. Copyright © 2014 the authors 0270-6474/14/3413411-11$15.00/0.

Particle-in-cell studies of fast-ion slowing-down rates in cool tenuous magnetized plasma

NASA Astrophysics Data System (ADS)

Evans, Eugene S.; Cohen, Samuel A.; Welch, Dale R.

2018-04-01

We report on 3D-3V particle-in-cell simulations of fast-ion energy-loss rates in a cold, weakly-magnetized, weakly-coupled plasma where the electron gyroradius, ρe, is comparable to or less than the Debye length, λDe, and the fast-ion velocity exceeds the electron thermal velocity, a regime in which the electron response may be impeded. These simulations use explicit algorithms, spatially resolve ρe and λDe, and temporally resolve the electron cyclotron and plasma frequencies. For mono-energetic dilute fast ions with isotropic velocity distributions, these scaling studies of the slowing-down time, τs, versus fast-ion charge are in agreement with unmagnetized slowing-down theory; with an applied magnetic field, no consistent anisotropy between τs in the cross-field and field-parallel directions could be resolved. Scaling the fast-ion charge is confirmed as a viable way to reduce the required computational time for each simulation. The implications of these slowing down processes are described for one magnetic-confinement fusion concept, the small, advanced-fuel, field-reversed configuration device.

First demonstration of the fast-to-slow corrector current shift in the NSLS-II storage ring

DOE PAGES

Yang, Xi; Tian, Yuke; Yu, Li Hua; ...

2018-04-01

In order to realize the full benefits of the high brightness and ultra-small beam sizes of NSLS-II, it is essential that the photon beams are exceedingly stable. In the circumstances of implementing local bumps, changing ID gaps, and long term drifting, the fast orbit feedback (FOFB) requires shifting the fast corrector strengths to the slow correctors to prevent the fast corrector saturation and to make the beam orbit stable in the sub-micron level. As the result, a reliable and precise technique of fast-to-slow corrector strength shift has been developed and tested at NSLS-II. This technique is based on the fastmore » corrector response to the slow corrector change when the FOFB is on. In this article, the shift technique is described and the result of proof-of-principle experiment carried out at NSLS-II is presented. The maximum fast corrector current was reduced from greater than 0.45 A to less than 0.04 A with the orbit perturbation within ±1 μm.« less

First demonstration of the fast-to-slow corrector current shift in the NSLS-II storage ring

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

Yang, Xi; Tian, Yuke; Yu, Li Hua

In order to realize the full benefits of the high brightness and ultra-small beam sizes of NSLS-II, it is essential that the photon beams are exceedingly stable. In the circumstances of implementing local bumps, changing ID gaps, and long term drifting, the fast orbit feedback (FOFB) requires shifting the fast corrector strengths to the slow correctors to prevent the fast corrector saturation and to make the beam orbit stable in the sub-micron level. As the result, a reliable and precise technique of fast-to-slow corrector strength shift has been developed and tested at NSLS-II. This technique is based on the fastmore » corrector response to the slow corrector change when the FOFB is on. In this article, the shift technique is described and the result of proof-of-principle experiment carried out at NSLS-II is presented. The maximum fast corrector current was reduced from greater than 0.45 A to less than 0.04 A with the orbit perturbation within ±1 μm.« less

KW-4679-induced inhibition of tachykininergic contraction in the guinea-pig bronchi by prejunctional inhibition of peripheral sensory nerves.

PubMed

Ikemura, T; Okarmura, K; Sasaki, Y; Ishi, H; Ohmori, K

1996-03-01

1. Sensory mechanisms play an important role in the vagal regulation of tracheobronchial smooth muscle tone. We examined the effect of KW-4679, an anti-allergic drug, on guinea-pig tachykinin-mediated contractile responses induced by electrical field stimulation (EFS) in guinea-pig bronchial muscles. 2. EFS (8 Hz, 0.5 ms, 15 V, for 15 s) evoked biphasic contractile responses in the guinea-pig isolated main bronchus in the presence of 5 microM indomethacin. The contractions consisted of a fast phase of an atropine-sensitive transient contraction and a slow phase of a sustained contraction which was inhibited by a combination of the tachykinin NK1 receptor antagonist, (+/-)-CP-96,345 (1 microM) and the NK2 receptor antagonist, SR 48969 (0.1 microM). 3. KW-4679 preferentially inhibited the slow phase in a concentration-dependent manner by 43.2 +/- 7.7% at 10 microM, whereas the drug had no effect on the fast phase at concentrations up to 10 microM. KW-4679, at a concentration of 100 microM, inhibited not only the slow phase by 49.2 +/- 11.4%, but also the fast phase by 36.8 +/- 9.3% [corrected]. 4. KW-4679 (10 microM and 100 microM) did not affect the substance P-induced or neurokinin A-induced contraction. Against the acetylcholine-induced contractile responses, 100 microM KW-4679 had a marked effect producing a 10.2 fold shift to the right in the curve. 5. The inhibitory effect of KW-4679 (10 microM) on the slow phase contraction was not influenced by treatment with naloxone (100 nM), propranolol (1 microM), thioperamide (1 microM), saclofen (50 microM), yohimbine (1 microM), methiothepin (1 microM) or methysergide (1 microM). 6. The inhibitory effect of KW-4679 (10 microM) on the slow phase contraction was not influenced by treatment with intermediate or large conductance Ca(2+)-activated K+ channel blockers (charybdotoxin (10 nM) or iberiotoxin (10 nM)), but suppressed by treatment with small conductance Ca(2+)-activated K+ channel blockers, apamin (500 nM) or scyllatoxin (300 nM). Apamin or scyllatoxin per se did not influence the slow phase contractions. 7. The results suggest that KW-4679 preferentially inhibits the release of tachykinins from the bronchial sensory nerves through activation of small conductance Ca(2+)-activated K+ channels.

Brain state-dependent recruitment of high-frequency oscillations in the human hippocampus.

PubMed

Billeke, Pablo; Ossandon, Tomas; Stockle, Marcelo; Perrone-Bertolotti, Marcela; Kahane, Philippe; Lachaux, Jean-Philippe; Fuentealba, Pablo

2017-09-01

Ripples are high-frequency bouts of coordinated hippocampal activity believed to be crucial for information transfer and memory formation. We used intracortical macroelectrodes to record neural activity in the human hippocampus of awake subjects undergoing surgical treatment for refractory epilepsy and distinguished two populations of ripple episodes based on their frequency spectrum. The phase-coupling of one population, slow ripples (90-110 Hz), to cortical delta oscillations was differentially modulated by cognitive task; whereas the second population, fast ripples (130-170 Hz), was not seemingly correlated to local neural activity. Furthermore, as cognitive tasks changed, the ongoing coordination of neural activity associated to slow ripples progressively augmented along the parahippocampal axis. Thus, during resting states, slow ripples were coordinated in restricted hippocampal territories; whereas during active states, such as attentionally-demanding tasks, high frequency activity emerged across the hippocampus and parahippocampal cortex, that was synchronized with slow ripples, consistent with ripples supporting information transfer and coupling anatomically distant regions. Hence, our results provide further evidence of neural diversity in hippocampal high-frequency oscillations and their association to cognitive processing in humans. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nanomedicines for Inflammatory Arthritis: Head-To-Head Comparison of Glucocorticoid-Containing Polymers, Micelles and Liposomes

PubMed Central

Crielaard, Bart J.; Dusad, Anand; Lele, Subodh M.; Rijcken, Cristianne J. F.; Metselaar, Josbert M; Kostková, Hana; Etrych, Tomáš; Ulbrich, Karel; Kiessling, Fabian; Mikuls, Ted R.; Hennink, Wim E.; Storm, Gert; Lammers, Twan; Wang, Dong

2014-01-01

As an emerging research direction, nanomedicine has been increasingly utilized to treat inflammatory diseases. In this head-to-head comparison study, four established nanomedicine formulations of dexamethasone, including liposomes (L-Dex), core-crosslinked micelles (M-Dex), slow releasing polymeric prodrugs (P-Dex-slow) and fast releasing polymeric prodrugs (P-Dex-fast), were evaluated in an adjuvant-induced arthritis rat model with an equivalent dose treatment design. It was found that after a single i.v. injection, the formulations with the slower drug release kinetics (i.e. M-Dex and P-Dex-slow) maintained longer duration of therapeutic activity than those with relatively faster drug release kinetics, resulting in better joint protection. This finding will be instructional in the future development and optimization of nanomedicines for the clinical management of rheumatoid arthritis. The outcome of this study also illustrates the value of such head-to-head comparison studies in translational nanomedicine research. PMID:24341611

Experiment K-308: Automatic analysis of muscle fibers from rats subjected to spaceflight

NASA Technical Reports Server (NTRS)

Castleman, K. R.; Chui, L. A.; Vandermeullen, J. P.

1981-01-01

The morphology of histochemically prepared muscle sections from the gastrocnemius and plantaris muscles of flight and vivarium control rats was studied quantitatively. Both fast-twitch and slow-twitch fibers were significantly smaller in flight groups than in control groups. Fibers in group 4F were somewhat larger than in 1F, presumably due to growth after recovery. Fibers in 4V were slightly larger than in 1V, presumably due to age. The slow fibers showed more spaceflight induced size loss than fast fibers, suggesting they suffered more from hypogravity. The proportion of slow fibers was also lower in the flight groups, suggesting spaceflight induced fiber type conversion from slow to fast.

Assessing the Role of Place and Timing Cues in Coding Frequency and Amplitude Modulation as a Function of Age.

PubMed

Whiteford, Kelly L; Kreft, Heather A; Oxenham, Andrew J

2017-08-01

Natural sounds can be characterized by their fluctuations in amplitude and frequency. Ageing may affect sensitivity to some forms of fluctuations more than others. The present study used individual differences across a wide age range (20-79 years) to test the hypothesis that slow-rate, low-carrier frequency modulation (FM) is coded by phase-locked auditory-nerve responses to temporal fine structure (TFS), whereas fast-rate FM is coded via rate-place (tonotopic) cues, based on amplitude modulation (AM) of the temporal envelope after cochlear filtering. Using a low (500 Hz) carrier frequency, diotic FM and AM detection thresholds were measured at slow (1 Hz) and fast (20 Hz) rates in 85 listeners. Frequency selectivity and TFS coding were assessed using forward masking patterns and interaural phase disparity tasks (slow dichotic FM), respectively. Comparable interaural level disparity tasks (slow and fast dichotic AM and fast dichotic FM) were measured to control for effects of binaural processing not specifically related to TFS coding. Thresholds in FM and AM tasks were correlated, even across tasks thought to use separate peripheral codes. Age was correlated with slow and fast FM thresholds in both diotic and dichotic conditions. The relationship between age and AM thresholds was generally not significant. Once accounting for AM sensitivity, only diotic slow-rate FM thresholds remained significantly correlated with age. Overall, results indicate stronger effects of age on FM than AM. However, because of similar effects for both slow and fast FM when not accounting for AM sensitivity, the effects cannot be unambiguously ascribed to TFS coding.

48 CFR 52.241-6 - Service Provisions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... such errors. However, any meter which registers not more than __ percent slow or fast shall be deemed... the Government if the percentage of errors is found to be not more than __ percent slow or fast. (3...

48 CFR 52.241-6 - Service Provisions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... such errors. However, any meter which registers not more than __ percent slow or fast shall be deemed... the Government if the percentage of errors is found to be not more than __ percent slow or fast. (3...

48 CFR 52.241-6 - Service Provisions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... such errors. However, any meter which registers not more than __ percent slow or fast shall be deemed... the Government if the percentage of errors is found to be not more than __ percent slow or fast. (3...

48 CFR 52.241-6 - Service Provisions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... such errors. However, any meter which registers not more than __ percent slow or fast shall be deemed... the Government if the percentage of errors is found to be not more than __ percent slow or fast. (3...

48 CFR 52.241-6 - Service Provisions.

Code of Federal Regulations, 2013 CFR

2013-10-01

... such errors. However, any meter which registers not more than __ percent slow or fast shall be deemed... the Government if the percentage of errors is found to be not more than __ percent slow or fast. (3...

Moderate Cortical Cooling Eliminates Thalamocortical Silent States during Slow Oscillation.

PubMed

Sheroziya, Maxim; Timofeev, Igor

2015-09-23

Reduction in temperature depolarizes neurons by a partial closure of potassium channels but decreases the vesicle release probability within synapses. Compared with cooling, neuromodulators produce qualitatively similar effects on intrinsic neuronal properties and synapses in the cortex. We used this similarity of neuronal action in ketamine-xylazine-anesthetized mice and non-anesthetized mice to manipulate the thalamocortical activity. We recorded cortical electroencephalogram/local field potential (LFP) activity and intracellular activities from the somatosensory thalamus in control conditions, during cortical cooling and on rewarming. In the deeply anesthetized mice, moderate cortical cooling was characterized by reversible disruption of the thalamocortical slow-wave pattern rhythmicity and the appearance of fast LFP spikes, with frequencies ranging from 6 to 9 Hz. These LFP spikes were correlated with the rhythmic IPSP activities recorded within the thalamic ventral posterior medial neurons and with depolarizing events in the posterior nucleus neurons. Similar cooling of the cortex during light anesthesia rapidly and reversibly eliminated thalamocortical silent states and evoked thalamocortical persistent activity; conversely, mild heating increased thalamocortical slow-wave rhythmicity. In the non-anesthetized head-restrained mice, cooling also prevented the generation of thalamocortical silent states. We conclude that moderate cortical cooling might be used to manipulate slow-wave network activity and induce neuromodulator-independent transition to activated states. Significance statement: In this study, we demonstrate that moderate local cortical cooling of lightly anesthetized or naturally sleeping mice disrupts thalamocortical slow oscillation and induces the activated local field potential pattern. Mild heating has the opposite effect; it increases the rhythmicity of thalamocortical slow oscillation. Our results demonstrate that slow oscillation can be influenced by manipulations to the properties of cortical neurons without changes in neuromodulation. Copyright © 2015 the authors 0270-6474/15/3513006-14$15.00/0.

Decoding the Formation of New Semantics: MVPA Investigation of Rapid Neocortical Plasticity during Associative Encoding through Fast Mapping.

PubMed

Atir-Sharon, Tali; Gilboa, Asaf; Hazan, Hananel; Koilis, Ester; Manevitz, Larry M

2015-01-01

Neocortical structures typically only support slow acquisition of declarative memory; however, learning through fast mapping may facilitate rapid learning-induced cortical plasticity and hippocampal-independent integration of novel associations into existing semantic networks. During fast mapping the meaning of new words and concepts is inferred, and durable novel associations are incidentally formed, a process thought to support early childhood's exuberant learning. The anterior temporal lobe, a cortical semantic memory hub, may critically support such learning. We investigated encoding of semantic associations through fast mapping using fMRI and multivoxel pattern analysis. Subsequent memory performance following fast mapping was more efficiently predicted using anterior temporal lobe than hippocampal voxels, while standard explicit encoding was best predicted by hippocampal activity. Searchlight algorithms revealed additional activity patterns that predicted successful fast mapping semantic learning located in lateral occipitotemporal and parietotemporal neocortex and ventrolateral prefrontal cortex. By contrast, successful explicit encoding could be classified by activity in medial and dorsolateral prefrontal and parahippocampal cortices. We propose that fast mapping promotes incidental rapid integration of new associations into existing neocortical semantic networks by activating related, nonoverlapping conceptual knowledge. In healthy adults, this is better captured by unique anterior and lateral temporal lobe activity patterns, while hippocampal involvement is less predictive of this kind of learning.

Exercise-Induced Hypertrophic and Oxidative Signaling Pathways and Myokine Expression in Fast Muscle of Adult Zebrafish

PubMed Central

Rovira, Mireia; Arrey, Gerard; Planas, Josep V.

2017-01-01

Skeletal muscle is a plastic tissue that undergoes cellular and metabolic adaptations under conditions of increased contractile activity such as exercise. Using adult zebrafish as an exercise model, we previously demonstrated that swimming training stimulates hypertrophy and vascularization of fast muscle fibers, consistent with the known muscle growth-promoting effects of exercise and with the resulting increased aerobic capacity of this tissue. Here we investigated the potential involvement of factors and signaling mechanisms that could be responsible for exercise-induced fast muscle remodeling in adult zebrafish. By subjecting zebrafish to swimming-induced exercise, we observed an increase in the activity of mammalian target of rapamycin (mTOR) and Mef2 protein levels in fast muscle. We also observed an increase in the protein levels of the mitotic marker phosphorylated histone H3 that correlated with an increase in the protein expression levels of Pax7, a satellite-like cell marker. Furthermore, the activity of AMP-activated protein kinase (AMPK) was also increased by exercise, in parallel with an increase in the mRNA expression levels of pgc1α and also of pparda, a β-oxidation marker. Changes in the mRNA expression levels of slow and fast myosin markers further supported the notion of an exercise-induced aerobic phenotype in zebrafish fast muscle. The mRNA expression levels of il6, il6r, apln, aplnra and aplnrb, sparc, decorin and igf1, myokines known in mammals to be produced in response to exercise and to signal through mTOR/AMPK pathways, among others, were increased in fast muscle of exercised zebrafish. These results support the notion that exercise increases skeletal muscle growth and myogenesis in adult zebrafish through the coordinated activation of the mTOR-MEF2 and AMPK-PGC1α signaling pathways. These results, coupled with altered expression of markers for oxidative metabolism and fast-to-slow fiber-type switch, also suggest improved aerobic capacity as a result of swimming-induced exercise. Finally, the induction of myokine expression by swimming-induced exercise support the hypothesis that these myokines may have been produced and secreted by the exercised zebrafish muscle and acted on fast muscle cells to promote metabolic remodeling. These results support the use of zebrafish as a suitable model for studies on muscle remodeling in vertebrates, including humans. PMID:29326600

Co-existence and switching between fast and Ω-slow wind solutions in rapidly rotating massive stars

NASA Astrophysics Data System (ADS)

Araya, I.; Curé, M.; ud-Doula, A.; Santillán, A.; Cidale, L.

2018-06-01

Most radiation-driven winds of massive stars can be modelled with m-CAK theory, resulting in the so-called fast solution. However, the most rapidly rotating stars among them, especially when the rotational speed is higher than {˜ } 75 per cent of the critical rotational speed, can adopt a different solution, the so-called Ω-slow solution, characterized by a dense and slow wind. Here, we study the transition region of the solutions where the fast solution changes to the Ω-slow solution. Using both time-steady and time-dependent numerical codes, we study this transition region for various equatorial models of B-type stars. In all cases, in a certain range of rotational speeds we find a region where the fast and the Ω-slow solution can co-exist. We find that the type of solution obtained in this co-existence region depends stongly on the initial conditions of our models. We also test the stability of the solutions within the co-existence region by performing base-density perturbations in the wind. We find that under certain conditions, the fast solution can switch to the Ω-slow solution, or vice versa. Such solution-switching may be a possible contributor of material injected into the circumstellar environment of Be stars, without requiring rotational speeds near critical values.

Injury and mortality of juvenile salmon entrained in a submerged jet entering still water

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

Deng, Zhiqun; Mueller, Robert P.; Richmond, Marshall C.

Juvenile salmon can be injured and killed when they pass through hydroelectric turbines and other downstream passage alternatives. The hydraulic conditions in these complex environments that pose a risk to the health of fish include turbulent shear flows, collisions with hydraulic structures, cavitation, and rapid change of pressure. Improvements in the understating of the biological responses of juvenile salmon in turbulent shear flows can reduce salmon injury and mortality. In a series of studies, juvenile fall Chinook salmon (Oncorhynchus tshawythscha) were exposed to turbulent shear flows in two mechanisms: 1) the slow-fish-to-fast-water mechanism, where test fish were introduced into amore » turbulent jet from slow-moving water through an introduction tube placed just outside the edge of the jet; 2) the fast-fish-to-slow-water mechanism, where test fish were carried by the fast-moving water of a submerged turbulent jet into the slow-moving water of a flume. All fish exposures to the water jet were recorded by two high-speed, high-resolution cameras. Motion-tracking analysis was then performed on the digital videos to quantify associated kinematic and dynamic parameters. The main results for the slow-fish-to-fast-water mechanism were described in Deng et al (2005). This chapter will discuss the test results of the fast-fish-to-slow-water mechanism and compare the results of the two mechanisms.« less

Effect of phenytoin on sodium conductances in rat hippocampal CA1 pyramidal neurons

PubMed Central

Zeng, Zhen; Hill-Yardin, Elisa L.; Williams, David; O'Brien, Terence; Serelis, Andris

2016-01-01

The antiepileptic drug phenytoin (PHT) is thought to reduce the excitability of neural tissue by stabilizing sodium channels (NaV) in inactivated states. It has been suggested the fast-inactivated state (IF) is the main target, although slow inactivation (IS) has also been implicated. Other studies on local anesthetics with similar effects on sodium channels have implicated the NaV voltage sensor interactions. In this study, we reexamined the effect of PHT in both equilibrium and dynamic transitions between fast and slower forms of inactivation in rat hippocampal CA1 pyramidal neurons. The effects of PHT were observed on fast and slow inactivation processes, as well as on another identified “intermediate” inactivation process. The effect of enzymatic removal of IF was also studied, as well as effects on the residual persistent sodium current (INaP). A computational model based on a gating charge interaction was derived that reproduced a range of PHT effects on NaV equilibrium and state transitions. No effect of PHT on IF was observed; rather, PHT appeared to facilitate the occupancy of other closed states, either through enhancement of slow inactivation or through formation of analogous drug-bound states. The overall significance of these observations is that our data are inconsistent with the commonly held view that the archetypal NaV channel inhibitor PHT stabilizes fast inactivation states, and we demonstrate that conventional slow activation “IS” and the more recently identified intermediate-duration inactivation process “II” are the primary functional targets of PHT. In addition, we show that the traditional explanatory frameworks based on the “modulated receptor hypothesis” can be substituted by simple, physiologically plausible interactions with voltage sensors. Additionally, INaP was not preferentially inhibited compared with peak INa at short latencies (50 ms) by PHT. PMID:27489371

Fiber-type-specific sensitivities and phenotypic adaptations to dietary fat overload differentially impact fast- versus slow-twitch muscle contractile function in C57BL/6J mice.

PubMed

Ciapaite, Jolita; van den Berg, Sjoerd A; Houten, Sander M; Nicolay, Klaas; van Dijk, Ko Willems; Jeneson, Jeroen A

2015-02-01

High-fat diets (HFDs) have been shown to interfere with skeletal muscle energy metabolism and cause peripheral insulin resistance. However, understanding of HFD impact on skeletal muscle primary function, i.e., contractile performance, is limited. Male C57BL/6J mice were fed HFD containing lard (HFL) or palm oil (HFP), or low-fat diet (LFD) for 5weeks. Fast-twitch (FT) extensor digitorum longus (EDL) and slow-twitch (ST) soleus muscles were characterized with respect to contractile function and selected biochemical features. In FT EDL muscle, a 30%-50% increase in fatty acid (FA) content and doubling of long-chain acylcarnitine (C14-C18) content in response to HFL and HFP feeding were accompanied by increase in protein levels of peroxisome proliferator-activated receptor-γ coactivator-1α, mitochondrial oxidative phosphorylation complexes and acyl-CoA dehydrogenases involved in mitochondrial FA β-oxidation. Peak force of FT EDL twitch and tetanic contractions was unaltered, but the relaxation time (RT) of twitch contractions was 30% slower compared to LFD controls. The latter was caused by accumulation of lipid intermediates rather than changes in the expression levels of proteins involved in calcium handling. In ST soleus muscle, no evidence for lipid overload was found in any HFD group. However, particularly in HFP group, the peak force of twitch and tetanic contractions was reduced, but RT was faster than LFD controls. The latter was associated with a fast-to-slow shift in troponin T isoform expression. Taken together, these data highlight fiber-type-specific sensitivities and phenotypic adaptations to dietary lipid overload that differentially impact fast- versus slow-twitch skeletal muscle contractile function. Copyright © 2015 Elsevier Inc. All rights reserved.

[EFFECTS OF ELECTRICAL STIMULATION OF NUCLEUS RETICULARIS PONTIS ORALIS ON THE SLEEP-WAKING STATES IN KRUSHINSKII-MOLODKINA STRAIN RATS].

PubMed

Vataev, S I; Malgina, N A; Oganesyan, G A

2015-07-01

The effects of electrical stimulation of nucleus reticularis pontis oralis on the behavior and brain electrical activity during all phases of the sleep-waking cycle was studied in Krushinskii-Molodkina strain rats, which have an inherited predisposition to audiogenic seizures. Electrical stimulation with 7 Hz frequency in the deep stage of slow-wave sleep cause appearance the fast-wave sleep. Similar stimulation during fast-wave sleep periods did not effects on the electrographic patterns and EEG spectral characteristics of hippocampus, visual, auditory and somatocnen nrnrenc nf the cnrtey ThPe sfimul1stinns did nnt break a fast-wave sleenhut increased almost twice due the duration of these sleep episodes. After electrical stimulation by same frequency during the wakeftlness and superficial slow-wave sleep states, the patterns and spectral characteristics of brain electrical activity in rats showed no significant changes as compared with controls. The results of this study indicate that the state of the animals sleep-waking cycle at the time of stimulation is a critical variable that influences the responses which are induced by electrical stimulation of the nucleus reticularis pontis oralis.

The slow and fast pyrolysis of cherry seed.

PubMed

Duman, Gozde; Okutucu, Cagdas; Ucar, Suat; Stahl, Ralph; Yanik, Jale

2011-01-01

The slow and fast pyrolysis of cherry seeds (CWS) and cherry seeds shells (CSS) was studied in fixed-bed and fluidized bed reactors at different pyrolysis temperatures. The effects of reactor type and temperature on the yields and composition of products were investigated. In the case of fast pyrolysis, the maximum bio-oil yield was found to be about 44 wt% at pyrolysis temperature of 500 °C for both CWS and CSS, whereas the bio yields were of 21 and 15 wt% obtained at 500 °C from slow pyrolysis of CWS and CSS, respectively. Both temperature and reactor type affected the composition of bio-oils. The results showed that bio-oils obtained from slow pyrolysis of CWS and CSS can be used as a fuel for combustion systems in industry and the bio-oil produced from fast pyrolysis can be evaluated as a chemical feedstock. Copyright © 2010 Elsevier Ltd. All rights reserved.

Sleep Spindles in the Right Hemisphere Support Awareness of Regularities and Reflect Pre-Sleep Activations.

PubMed

Yordanova, Juliana; Kolev, Vasil; Bruns, Eike; Kirov, Roumen; Verleger, Rolf

2017-11-01

The present study explored the sleep mechanisms which may support awareness of hidden regularities. Before sleep, 53 participants learned implicitly a lateralized variant of the serial response-time task in order to localize sensorimotor encoding either in the left or right hemisphere and induce implicit regularity representations. Electroencephalographic (EEG) activity was recorded at multiple electrodes during both task performance and sleep, searching for lateralized traces of the preceding activity during learning. Sleep EEG analysis focused on region-specific slow (9-12 Hz) and fast (13-16 Hz) sleep spindles during nonrapid eye movement sleep. Fast spindle activity at those motor regions that were activated during learning increased with the amount of postsleep awareness. Independently of side of learning, spindle activity at right frontal and fronto-central regions was involved: there, fast spindles increased with the transformation of sequence knowledge from implicit before sleep to explicit after sleep, and slow spindles correlated with individual abilities of gaining awareness. These local modulations of sleep spindles corresponded to regions with greater presleep activation in participants with postsleep explicit knowledge. Sleep spindle mechanisms are related to explicit awareness (1) by tracing the activation of motor cortical and right-hemisphere regions which had stronger involvement already during learning and (2) by recruitment of individually consolidated processing modules in the right hemisphere. The integration of different sleep spindle mechanisms with functional states during wake collectively supports the gain of awareness of previously experienced regularities, with a special role for the right hemisphere. © Sleep Research Society 2017. Published by Oxford University Press [on behalf of the Sleep Research Society].

Changes in the cholinergic system of rat sciatic nerve and skeletal muscle following suspension induced disuse

NASA Technical Reports Server (NTRS)

Gupta, R. C.; Misulis, K. E.; Dettbarn, W. D.

1984-01-01

Muscle disused induced changes in the cholinergic system of sciatic nerve, slow twitch soleus (SOL) and fast twitch extensor digitorum longus (EDL) muscle were studied in rats. Rats with hindlimbs suspended for 2 to 3 weeks showed marked elevation in the activity of choline acetyltransferase (ChAT) in sciatic nerve (38%), in SOL (108%) and in EDL (67%). Acetylcholinesterase (AChE) activity in SOL increased by 163% without changing the molecular forms pattern of 4S, 10S, 12S, and 16S. No significant changes in activity and molecular forms pattern of AChE were seen in EDL or in AChE activity of sciatic nerve. Nicotinic receptor binding of 3H-acetylcholine was increased in both muscles. When measured after 3 weeks of hindlimb suspension the normal distribution of type 1 fibers in SOL was reduced and a corresponding increase in type IIa and IIb fibers is seen. In EDL no significant change in fiber proportion is observed. Muscle activity, such as loadbearing, appears to have a greater controlling influence on the characteristics of the slow twitch SOL muscle than upon the fast twitch EDL muscle.

A wrist tendon travel assessment of hand movements associated with industrial repetitive activities.

PubMed

Ugbolue, U Chris; Nicol, Alexander C

2012-01-01

To investigate slow and fast paced industrial activity hand repetitive movements associated with carpal tunnel syndrome where movements are evaluated based on finger and wrist tendon travel measurements. Nine healthy subjects were recruited for the study aged between 23 and 33 years. Participants mimicked an industrial repetitive task by performing the following activities: wrist flexion and extension task, palm open and close task; and pinch task. Each task was performed for a period of 5 minutes at a slow (0.33 Hz) and fast (1 Hz) pace for a duration of 3 minutes and 2 minutes respectively. Tendon displacement produced higher flexor digitorum superficialis (FDS) tendon travel when compared to the flexor digitorum profundus (FDP) tendons. The left hand mean (SD) tendon travel for the FDS tendon and FDP tendon were 11108 (5188) mm and 9244 (4328) mm while the right hand mean tendon travel (SD) for the FDS tendon and FDP tendon were 9225 (3441) mm and 7670 (2856) mm respectively. Of the three tasks mimicking an industrial repetitive activity, the wrist flexion and extension task produced the most tendon travel. The findings may be useful to researchers in classifying the level of strenuous activity in relation to tendon travel.

Equatorial Magnetohydrodynamic Shallow Water Waves in the Solar Tachocline

NASA Astrophysics Data System (ADS)

Zaqarashvili, Teimuraz

2018-03-01

The influence of a toroidal magnetic field on the dynamics of shallow water waves in the solar tachocline is studied. A sub-adiabatic temperature gradient in the upper overshoot layer of the tachocline causes significant reduction of surface gravity speed, which leads to trapping of the waves near the equator and to an increase of the Rossby wave period up to the timescale of solar cycles. Dispersion relations of all equatorial magnetohydrodynamic (MHD) shallow water waves are obtained in the upper tachocline conditions and solved analytically and numerically. It is found that the toroidal magnetic field splits equatorial Rossby and Rossby-gravity waves into fast and slow modes. For a reasonable value of reduced gravity, global equatorial fast magneto-Rossby waves (with the spatial scale of equatorial extent) have a periodicity of 11 years, matching the timescale of activity cycles. The solutions are confined around the equator between latitudes ±20°–40°, coinciding with sunspot activity belts. Equatorial slow magneto-Rossby waves have a periodicity of 90–100 yr, resembling the observed long-term modulation of cycle strength, i.e., the Gleissberg cycle. Equatorial magneto-Kelvin and slow magneto-Rossby-gravity waves have the periodicity of 1–2 years and may correspond to observed annual and quasi-biennial oscillations. Equatorial fast magneto-Rossby-gravity and magneto-inertia-gravity waves have periods of hundreds of days and might be responsible for observed Rieger-type periodicity. Consequently, the equatorial MHD shallow water waves in the upper overshoot tachocline may capture all timescales of observed variations in solar activity, but detailed analytical and numerical studies are necessary to make a firm conclusion toward the connection of the waves to the solar dynamo.

Sources of the solar wind - the heliospheric point of view

NASA Astrophysics Data System (ADS)

Von Steiger, Rudolf; Shearer, Paul; Zurbuchen, Thomas

The solar wind as observed in the heliosphere has several properties that can be interpreted as signatures of conditions and processes at its source in the solar atmosphere. Traditionally it has been customary to distinguish between solar wind types solely based on its speed, "fast" and "slow" wind. Over the last couple of decades new instruments resolving not only the main constituents (protons and alpha particles) but also heavy ions from C to Fe have added new observables, in particular the charge state and elemental composition of these ions. The charge states are indicators of the coronal temperature at the source region; they have confirmed that the "fast" wind emanates from the relatively cool coronal hole regions, while the "slow" wind originates from hotter sources such as the streamer belt and active regions. Thus they are more reliable indicators of solar wind source than the speed alone could be because they readily discriminate between "fast" wind from coronal holes and fast coronal mass ejections (CMEs). The elemental composition in the solar wind compared to the abundances in the photosphere shows a typical fractionation that depends on the first ionization potential (FIP) of the elements. Since that fractionation occurs beneath the corona, in the chromosphere, its strength is indicative of the conditions in that layer. While the "fast" wind is very similar to photospheric composition, the fractionation of the "slow" wind and of CMEs is higher and strongly variable. We will review the observations of the SWICS composition instruments on both the ACE and the Ulysses missions, which have made composition observations between 1 and 5 AU and at all latitudes in the heliosphere over the last two decades. Specifically, analysis of the "slow" wind observations at all time scales, from hours to complete solar cycles, will be used to better characterize its source regions.

Extratropical response to Fast and Slow episodes of Madden-Julian Oscillation in observation and using intervention experiments with CFSv2

NASA Astrophysics Data System (ADS)

Yadav, P.; Straus, D. M.

2017-12-01

The Madden-Julian Oscillation (MJO) is a potential source of predictability in the extratropics in extended range weather forecasting. The nature of MJO is sporadic and therefore, the mid-latitude response may depend on the nature of the MJO event, in particular the phase speed. We discuss the results of our observational and modeling study of mid-latitude circulation response to Fast and Slow MJO episodes using wintertime ERA-Interim reanalysis data and the CFSv2 coupled model of NOAA. The observational study shows that the mid-latitude response to different propagating speeds is not the same. The propagation speed is defined by the time the OLR takes to propagate from phase 3 to phase 6. The mid-latitude response is assessed in terms of composite maps and frequency of occurrence of robust circulation regimes. Fast episode composite anomalies of 500hPa height show a developing Rossby wave in the mid-Pacific with downstream propagation through MJO phases 2- 4. Development of NAO+ teleconnection pattern is stronger in Slow that in Fast MJO episodes, and occurs with a greater time lag after MJO heating is in the Indian Ocean (phase 3). Previous results find an increase in occurrence of NAO- regime following phase 6. We have found that much of this behavior is due to the slow episodes. Based on these observational results, intervention experiments using CFSv2 are designed to better understand the impact of heating/cooling and to estimate mid-latitude response to Fast and Slow MJO episodes. The added heating experiments consist of 31 year reforecasts for December 1 initial conditions from CFS reanalysis (1980-2011) in which the identical MJO evolution of three-dimensional diabatic heating has been added, thus producing fast and slow MJO episodes with well-defined phase speeds. We will discuss the results of these experiments with a focus on understanding the role of phase speed and interference in setting up the response, and to understand the mechanisms that distinguish fast and slow types of response We will also discuss the diagnostics using Predictable Component Analysis to distinguish the signal forced by common diabatic heating signal from noise, and weather regime response to fast and slow MJO using cluster analysis.

Novel murine clonal cell lines either express slow or mixed (fast and slow) muscle markers following differentiation in vitro.

PubMed

Peltzer, J; Colman, L; Cebrian, J; Musa, H; Peckham, M; Keller, A

2008-05-01

We have investigated whether the phenotype of myogenic clones derived from satellite cells of different muscles from the transgenic immortomouse depended on muscle type origin. Clones derived from neonatal, or 6- to 12-week-old fast and slow muscles, were analyzed for myosin and enolase isoforms as phenotypic markers. All clones derived from slow-oxidative muscles differentiated into myotubes with a preferentially slow contractile phenotype, whereas some clones derived from rapid-glycolytic or neonatal muscles expressed both fast and slow myosin isoforms. Thus, muscle origin appears to bias myosin isoform expression in myotubes. The neonatal clone (WTt) was cultivated in various medium and substrate conditions, allowing us to determine optimized conditions for their differentiation. Matrigel allowed expressions of adult myosin isoforms, and an isozymic switch from embryonic alpha- toward muscle-specific beta-enolase, never previously observed in vitro. These cells will be a useful model for in vitro studies of muscle fiber maturation and plasticity.

Particle-in-cell studies of fast-ion slowing-down rates in cool tenuous magnetized plasma

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

Evans, Eugene S.; Cohen, Samuel A.; Welch, Dale R.

We report on 3D-3V particle-in-cell simulations of fast-ion energy-loss rates in a cold, weakly-magnetized, weakly-coupled plasma where the electron gyroradius, ρe, is comparable to or less than the Debye length, λ De, and the fast-ion velocity exceeds the electron thermal velocity, a regime in which the electron response may be impeded. These simulations use explicit algorithms, spatially resolve ρ e and λ De, and temporally resolve the electron cyclotron and plasma frequencies. For mono-energetic dilute fast ions with isotropic velocity distributions, these scaling studies of the slowing-down time, τ s, versus fast-ion charge are in agreement with unmagnetized slowing-down theory;more » with an applied magnetic field, no consistent anisotropy between τs in the cross-field and field-parallel directions could be resolved. Scaling the fast-ion charge is confirmed as a viable way to reduce the required computational time for each simulation. In conclusion, the implications of these slowing down processes are described for one magnetic-confinement fusion concept, the small, advanced-fuel, field-reversed configuration device.« less

Particle-in-cell studies of fast-ion slowing-down rates in cool tenuous magnetized plasma

DOE PAGES

Evans, Eugene S.; Cohen, Samuel A.; Welch, Dale R.

2018-04-05

We report on 3D-3V particle-in-cell simulations of fast-ion energy-loss rates in a cold, weakly-magnetized, weakly-coupled plasma where the electron gyroradius, ρe, is comparable to or less than the Debye length, λ De, and the fast-ion velocity exceeds the electron thermal velocity, a regime in which the electron response may be impeded. These simulations use explicit algorithms, spatially resolve ρ e and λ De, and temporally resolve the electron cyclotron and plasma frequencies. For mono-energetic dilute fast ions with isotropic velocity distributions, these scaling studies of the slowing-down time, τ s, versus fast-ion charge are in agreement with unmagnetized slowing-down theory;more » with an applied magnetic field, no consistent anisotropy between τs in the cross-field and field-parallel directions could be resolved. Scaling the fast-ion charge is confirmed as a viable way to reduce the required computational time for each simulation. In conclusion, the implications of these slowing down processes are described for one magnetic-confinement fusion concept, the small, advanced-fuel, field-reversed configuration device.« less

The role of Sox6 in zebrafish muscle fiber type specification.

PubMed

Jackson, Harriet E; Ono, Yosuke; Wang, Xingang; Elworthy, Stone; Cunliffe, Vincent T; Ingham, Philip W

2015-01-01

The transcription factor Sox6 has been implicated in regulating muscle fiber type-specific gene expression in mammals. In zebrafish, loss of function of the transcription factor Prdm1a results in a slow to fast-twitch fiber type transformation presaged by ectopic expression of sox6 in slow-twitch progenitors. Morpholino-mediated Sox6 knockdown can suppress this transformation but causes ectopic expression of only one of three slow-twitch specific genes assayed. Here, we use gain and loss of function analysis to analyse further the role of Sox6 in zebrafish muscle fiber type specification. The GAL4 binary misexpression system was used to express Sox6 ectopically in zebrafish embryos. Cis-regulatory elements were characterized using transgenic fish. Zinc finger nuclease mediated targeted mutagenesis was used to analyse the effects of loss of Sox6 function in embryonic, larval and adult zebrafish. Zebrafish transgenic for the GCaMP3 Calcium reporter were used to assay Ca2+ transients in wild-type and mutant muscle fibres. Ectopic Sox6 expression is sufficient to downregulate slow-twitch specific gene expression in zebrafish embryos. Cis-regulatory elements upstream of the slow myosin heavy chain 1 (smyhc1) and slow troponin c (tnnc1b) genes contain putative Sox6 binding sites required for repression of the former but not the latter. Embryos homozygous for sox6 null alleles expressed tnnc1b throughout the fast-twitch muscle whereas other slow-specific muscle genes, including smyhc1, were expressed ectopically in only a subset of fast-twitch fibers. Ca2+ transients in sox6 mutant fast-twitch fibers were intermediate in their speed and amplitude between those of wild-type slow- and fast-twitch fibers. sox6 homozygotes survived to adulthood and exhibited continued misexpression of tnnc1b as well as smaller slow-twitch fibers. They also exhibited a striking curvature of the spine. The Sox6 transcription factor is a key regulator of fast-twitch muscle fiber differentiation in the zebrafish, a role similar to that ascribed to its murine ortholog.

Hydrogen peroxide increases depolarization-induced contraction of mechanically skinned slow twitch fibres from rat skeletal muscles.

PubMed

Plant, David R; Lynch, Gordon S; Williams, David A

2002-03-15

The effect of exogenous hydrogen peroxide (H(2)O(2)) on excitation-contraction (E-C) coupling and sarcoplasmic reticulum (SR) function was compared in mechanically skinned slow twitch fibres (prepared from the soleus muscles) and fast twitch fibres (prepared from the extensor digitorum longus; EDL muscles) of adult rats. Equilibration (5 min) with 1 mM H(2)O(2) diminished the ability of the Ca(2+)-depleted SR to reload Ca(2+) in both slow (P < 0.01) and fast twitch fibres (P < 0.05) compared to control. Under conditions when all Ca(2+) uptake was prevented, 1 mM H(2)O(2) increased SR Ca(2+) "leak" in fast twitch fibres by 24 +/- 5 % (P < 0.05), but leak was not altered in slow twitch fibres. Treatment with 1 mM H(2)O(2) also increased the peak force of low [caffeine] contracture by approximately 45% in both fibre types compared to control (P < 0.01), which could be partly reversed following treatment with 10 mM dithiothreitol (DTT). The changes in SR function caused by 1 mM H(2)O(2) were associated with an approximately 65% increase in the peak height of depolarization-induced contractile response (DICR) in slow twitch fibres, compared to control (no H(2)O(2); P < 0.05). In contrast, peak contractile force of fast twitch fibres was not altered by 1 mM H(2)O(2) treatment. Equilibration with 5 mM H(2)O(2) induced a spontaneous force response in both slow and fast twitch fibres, which could be partly reversed by 2 min treatment with 10 mM DTT. Peak DICR was also increased approximately 40% by 5 mM H(2)O(2) in slow twitch fibres compared to control (no H(2)O(2); P < 0.05). Our results indicate that exogenous H(2)O(2) increases depolarization-induced contraction of mechanically skinned slow but not fast twitch fibres. The increase in depolarization-induced contraction in slow twitch fibres might be mediated by an increased SR Ca(2+) release during contraction and/or an increase in Ca(2+) sensitivity.

Hydrogen peroxide increases depolarization-induced contraction of mechanically skinned slow twitch fibres from rat skeletal muscles

PubMed Central

Plant, David R; Lynch, Gordon S; Williams, David A

2002-01-01

The effect of exogenous hydrogen peroxide (H2O2) on excitation-contraction (E-C) coupling and sarcoplasmic reticulum (SR) function was compared in mechanically skinned slow twitch fibres (prepared from the soleus muscles) and fast twitch fibres (prepared from the extensor digitorum longus; EDL muscles) of adult rats. Equilibration (5 min) with 1 mm H2O2 diminished the ability of the Ca2+-depleted SR to reload Ca2+ in both slow (P < 0.01) and fast twitch fibres (P < 0.05) compared to control. Under conditions when all Ca2+ uptake was prevented, 1 mm H2O2 increased SR Ca2+ ‘leak’ in fast twitch fibres by 24 ± 5 % (P < 0.05), but leak was not altered in slow twitch fibres. Treatment with 1 mm H2O2 also increased the peak force of low [caffeine] contracture by ∼45 % in both fibre types compared to control (P < 0.01), which could be partly reversed following treatment with 10 mm dithiothreitol (DTT). The changes in SR function caused by 1 mm H2O2 were associated with an ∼65 % increase in the peak height of depolarization-induced contractile response (DICR) in slow twitch fibres, compared to control (no H2O2; P < 0.05). In contrast, peak contractile force of fast twitch fibres was not altered by 1 mm H2O2 treatment. Equilibration with 5 mm H2O2 induced a spontaneous force response in both slow and fast twitch fibres, which could be partly reversed by 2 min treatment with 10 mm DTT. Peak DICR was also increased ∼40 % by 5 mm H2O2 in slow twitch fibres compared to control (no H2O2; P < 0.05). Our results indicate that exogenous H2O2 increases depolarization-induced contraction of mechanically skinned slow but not fast twitch fibres. The increase in depolarization-induced contraction in slow twitch fibres might be mediated by an increased SR Ca2+ release during contraction and/or an increase in Ca2+ sensitivity. PMID:11897857

Factors in Maximal Power Production and in Exercise Endurance Relative to Maximal Power

DTIC Science & Technology

1988-10-13

Mechanical efficiency of fast -and slow - twitch muscle fibers in mnan during cycling. J. ADLi Physiol.:Reespirat. Environ. Exercise Physiol. 47: 263- 267...R.S. Hikida, and F.C. Hagerman. Myofibrillar ATPase activity in hu-man muscle fast - twitch subtypes. Histochem. 78: 405-408, 1983. 31. Suzuki, Y...capacity and muscle fibre composition in mnan. J. Physiol (London) 354: 73P, 1984. 21. Margaria, R., P. Aghemo, and E. Rovelli. Measurement of muscular

Third Congress on Information System Science and Technology

DTIC Science & Technology

1968-04-01

versions of the same compiler. The " fast compile-slow execute" and the "slow compile- fast execute" gimmick is the greatest hoax ever per- petrated on the... fast such natural language analysis and translation can be accomplished. If the fairly superficial syntactic anal- ysis of a sentence which is...two kinds of computer: a fast computer with large immediate access and bulk memory for rear echelon and large installation em- ployment, and a

The Investigation of Pointing Behaviors in Web Browsing

DTIC Science & Technology

2016-09-26

fast movements have a different error model from slow movements and study the impact induced by the open-loop nature of fast 1. REPORT DATE (DD-MM-YYYY...whether or not fast movements have a different error model from slow movements and study the impact induced by the open-loop nature of fast movements. (3...PI will comparison of Fitts’ law results for natural browsing using two different pointing devices: physical mouse and laptop touchpad in order to

Characterization and modelling of the boron-oxygen defect activation in compensated n-type silicon

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

Schön, J.; Niewelt, T.; Broisch, J.

2015-12-28

A study of the activation of the light-induced degradation in compensated n-type Czochralski grown silicon is presented. A kinetic model is established that verifies the existence of both the fast and the slow components known from p-type and proves the quadratic dependence of the defect generation rates of both defects on the hole concentration. The model allows for the description of lifetime degradation kinetics in compensated n-type silicon under various intensities and is in accordance with the findings for p-type silicon. We found that the final concentrations of the slow defect component in compensated n-type silicon only depend on themore » interstitial oxygen concentration and on neither the boron concentration nor the equilibrium electron concentration n{sub 0}. The final concentrations of the fast defect component slightly increase with increasing boron concentration. The results on n-type silicon give new insight to the origin of the BO defect and question the existing models for the defect composition.« less

Altered fast- and slow-twitch muscle fibre characteristics in female mice with a (S248F) knock-in mutation of the brain neuronal nicotinic acetylcholine receptor.

PubMed

Cannata, David J; Finkelstein, David I; Gantois, Ilse; Teper, Yaroslav; Drago, John; West, Jan M

2009-01-01

We generated a mouse line with a missense mutation (S248F) in the gene (CHRNA4) encoding the alpha4 subunit of neuronal nicotinic acetylcholine receptor (nAChR). Mutant mice demonstrate brief nicotine induced dystonia that resembles the clinical events seen in patients with the same mutation. Drug-induced dystonia is more pronounced in female mice, thus our aim was to determine if the S248F mutation changed the properties of fast- and slow-twitch muscle fibres from female mutant mice. Reverse transcriptase-PCR confirmed CHRNA4 gene expression in the brain but not skeletal muscles in normal and mutant mice. Ca(2+) and Sr(2+) force activation curves were obtained using skinned muscle fibres prepared from slow-twitch (soleus) and fast-twitch (EDL) muscles. Two significant results were found: (1) the (pCa(50) - pSr(50)) value from EDL fibres was smaller in mutant mice than in wild type (1.01 vs. 1.30), (2) the percentage force produced at pSr 5.5 was larger in mutants than in wild type (5.76 vs. 0.24%). Both results indicate a shift to slow-twitch characteristics in the mutant. This conclusion is supported by the identification of the myosin heavy chain (MHC) isoforms. Mutant EDL fibres expressed MHC I (usually only found in slow-twitch fibres) as well as MHC IIa. Despite the lack of spontaneous dystonic events, our findings suggest that mutant mice may be having subclinical events or the mutation results in a chronic alteration to muscle neural input.

Twitch analysis as an approach to motor unit activation during electrical stimulation.

PubMed

Heyters, M; Carpentier, A; Duchateau, J; Hainaut, K

1994-12-01

The mechanical twitch in response to increasing electrical stimulus intensity, delivered both over the motor point and motor nerve, was recorded in the first dorsal interosseous (FDI) and the adductor pollicis (AP), and only over the motor point in the soleus (Sol), lateral (LG), and medial (MG) gastrocnemius muscles of human subjects. The relationship between intensity of electrical stimulation (ES) and twitch torque showed a positive linear regression in all muscles. In the FDI and AP the relationship was not significantly different when ES was applied at the motor point or over the motor nerve. At small intensities of activation, ES induced larger twitch torques in the MG and LG, which contain a roughly equal proportion of slow and fast motor units (MUs) compared to the Sol, which is composed mainly of slow type fibres. Moreover, the relationship between ES intensity and twitch time-to-peak is best fitted in all muscles by a power curve that shows a greater twitch time-to-peak range in its initial part for muscles containing a larger proportion of fast MUs (LG, MG) than for muscles mainly composed of slow MUs (Sol). In conclusion, these results induced by ES at the motor point and/or over the motor nerve confirm the concept of a reversed sequence of MU activation, as compared to voluntary contractions, and document this viewpoint in muscles of different function and composition. The reversed sequence of MU activation is more clearly evident during motor point ES.

Lacosamide

PubMed Central

Curia, Giulia; Biagini, Giuseppe; Perucca, Emilio; Avoli, Massimo

2016-01-01

The mechanism of action of several antiepileptic drugs (AEDs) rests on their ability to modulate the activity of voltage-gated sodium currents that are responsible for fast action potential generation. Recent data indicate that lacosamide (a compound with analgesic and anticonvulsant effects in animal models) shares a similar mechanism. When compared with other AEDs, lacosamide has the unique ability to interact with sodium channel slow inactivation without affecting fast inactivation. This article reviews these findings and discusses their relevance within the context of neuronal activity seen during epileptiform discharges generated by limbic neuronal networks in the presence of chemical convulsants. These seizure-like events are characterized by sustained discharges of sodium-dependent action potentials supported by robust depolarizations, thus providing synchronization within neuronal networks. Generally, AEDs such as phenytoin, carbamazepine and lamotrigine block sodium channels when activated. In contrast, lacosamide facilitates slow inactivation of sodium channels both in terms of kinetics and voltage dependency. This effect may be relatively selective for repeatedly depolarized neurons, such as those participating in seizure activity in which the persistence of sodium currents is more pronounced and promotes neuronal excitation. The clinical effectiveness of lacosamide has been demonstrated in randomized, double-blind, parallel-group, placebo-controlled, adjunctive-therapy trials in patients with refractory partial seizures. Further studies should determine whether the effects of lacosamide in animal models and in clinical settings are fully explained by its selective action on sodium current slow inactivation or whether other effects (e.g. interactions with the collapsin-response mediator protein-2) play a contributory role. PMID:19552484

Associative desorption of hydrogen isotopologues from copper surfaces: Characterization of two reaction mechanisms

NASA Astrophysics Data System (ADS)

Kaufmann, Sven; Shuai, Quan; Auerbach, Daniel J.; Schwarzer, Dirk; Wodtke, Alec M.

2018-05-01

We report quantum-state resolved measurements of angular and velocity distributions of the associative desorption of H2, HD, and D2 from Cu(111) and Cu(211) surfaces. The desorbing molecules have bimodal velocity distributions comprising a "fast" channel and a "slow" channel on both facets. The "fast channel" is promoted by both hydrogen incidence translational and vibrational energy, while the "slow channel" is promoted by vibrational energy but inhibited by translational energy. Using detailed balance, we determine state-specific reaction probabilities for dissociative adsorption and compare these to theoretical calculations. The results for the activation barrier for the "fast channel" on Cu(111) are in agreement with theory within "chemical accuracy" (1 kcal/mole). Results on the Cu(211) facet provide direct information on the effect of increasing step density, which is commonly believed to increase reactivity. Differences in reactivity on the (111) and (211) facets are subtle - quantum state specific reactivity on the (211) surface is characterized by a broader distribution of barrier heights whose average values are higher than for reaction on (111). We fully characterize the "slow channel," which has not been found in theoretical calculations although it makes up a large fraction of the reactivity in these experiments.

Effects of motion speed in action representations

PubMed Central

van Dam, Wessel O.; Speed, Laura J.; Lai, Vicky T.; Vigliocco, Gabriella; Desai, Rutvik H.

2017-01-01

Grounded cognition accounts of semantic representation posit that brain regions traditionally linked to perception and action play a role in grounding the semantic content of words and sentences. Sensory-motor systems are thought to support partially abstract simulations through which conceptual content is grounded. However, which details of sensory-motor experience are included in, or excluded from these simulations, is not well understood. We investigated whether sensory-motor brain regions are differentially involved depending on the speed of actions described in a sentence. We addressed this issue by examining the neural signature of relatively fast (The old lady scurried across the road) and slow (The old lady strolled across the road) action sentences. The results showed that sentences that implied fast motion modulated activity within the right posterior superior temporal sulcus and the angular and middle occipital gyri, areas associated with biological motion and action perception. Sentences that implied slow motion resulted in greater signal within the right primary motor cortex and anterior inferior parietal lobule, areas associated with action execution and planning. These results suggest that the speed of described motion influences representational content and modulates the nature of conceptual grounding. Fast motion events are represented more visually whereas motor regions play a greater role in representing conceptual content associated with slow motion. PMID:28160739

Recovery time course in contractile function of fast and slow skeletal muscle after hindlimb immobilization

NASA Technical Reports Server (NTRS)

Witzmann, F. A.; Kim, D. H.; Fitts, R. H.

1982-01-01

The present study was undertaken to characterize the time course and extent of recovery in the isometric and isotonic contractile properties of fast and slow skeletal muscle following 6 wk of hindlimb immobilization. Female Sprague-Dawley rats were randomly assigned to an immobilized group or a control group. The results of the study show that fast and slow skeletal muscles possess the ability to completely recover normal contractile function following 6 wk of hindlimb immobilization. The rate of recovery is dependent on the fiber type composition of the affected muscle.

Two-stage dilute acid prehydrolysis of biomass

DOEpatents

Grohmann, Karel; Torget, Robert W.

1992-01-01

A two-stage dilute acid prehydrolysis process on xylan containing hemicellulose in biomass is effected by: treating feedstock of hemicellulosic material comprising xylan that is slow hydrolyzable and xylan that is fast hydrolyzable under predetermined low temperature conditions with a dilute acid for a residence time sufficient to hydrolyze the fast hydrolyzable xylan to xylose; removing said xylose from said fast hydrolyzable xylan and leaving a residue; and treating said residue having a slow hydrolyzable xylan with a dilute acid under predetermined high temperature conditions for a residence time required to hydrolyze said slow hydrolyzable xylan to xylose.

A study of adaptation mechanisms based on ABR recorded at high stimulation rate.

PubMed

Valderrama, Joaquin T; de la Torre, Angel; Alvarez, Isaac; Segura, Jose Carlos; Thornton, A Roger D; Sainz, Manuel; Vargas, Jose Luis

2014-04-01

This paper analyzes the fast and slow mechanisms of adaptation through a study of latencies and amplitudes on ABR recorded at high stimulation rates using the randomized stimulation and averaging (RSA) technique. The RSA technique allows a separate processing of auditory responses, and is used, in this study, to categorize responses according to the interstimulus interval (ISI) of their preceding stimulus. The fast and slow mechanisms of adaptation are analyzed by the separated responses methodology, whose underlying principles and mathematical basis are described in detail. The morphology of the ABR is influenced by both fast and slow mechanisms of adaptation. These results are consistent with previous animal studies based on spike rate. Both fast and slow mechanisms of adaptation are present in all subjects. In addition, the distribution of the jitter and the sequencing of the stimuli may be critical parameters when obtaining reliable ABRs. The separated responses methodology enables for the first time the analysis of the fast and slow mechanisms of adaptation in ABR obtained at stimulation rates greater than 100 Hz. The non-invasive nature of this methodology is appropriate for its use in humans. Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Siderosomal ferritin. The missing link between ferritin and haemosiderin?

PubMed Central

Andrews, S C; Treffry, A; Harrison, P M

1987-01-01

A minor electrophoretically fast component was found in ferritin from iron-loaded rat liver in addition to a major electrophoretically slow ferritin similar to that observed in control rats. The electrophoretically fast ferritin showed immunological identity with the slow component, but on electrophoresis in SDS it gave a peptide of 17.3 kDa, in contrast with the electrophoretically slow ferritin, which gave a major band corresponding to the L-subunit (20.7 kDa). Thus the electrophoretically fast ferritin resembles that reported by Massover [(1985) Biochim. Biophys. Acta 829, 377-386] in livers of mice with short-term parenteral iron overload. The electrophoretically fast ferritin had a lower iron content (2000 Fe atoms/molecule) than the electrophoretically slow ferritin (3000 Fe atoms/molecule). Removal and re-incorporation of iron was possible without effect on the electrophoretic mobility of either ferritin species. On subcellular fractionation the electrophoretically fast ferritin was enriched in pellet fractions and was the sole soluble ferritin isolated from iron-laden secondary lysosomes (siderosomes). The amount and relative proportion of the electrophoretically fast species increased with iron loading. Haemosiderin isolated from siderosomes was found to contain a peptide reactive to anti-ferritin serum and corresponding to the 17.3 kDa peptide of the electrophoretically fast ferritin species. Unlike the electrophoretically slow ferritin, the electrophoretically fast ferritin did not become significantly radioactive in a 1 h biosynthetic labelling experiment. We conclude that the minor ferritin is not, as has been suggested for mouse liver ferritin, 'a completely new species of smaller holoferritin that represents a shift in the ferritin phenotype' in response to siderosis, but a precursor of haemosiderin, in agreement with the proposal by Richter [(1984) Lab. Invest. 50, 26-35] concerning siderosomal ferritin. Images Fig. 1. Fig. 2. Fig. 4. Fig. 5. PMID:3663170

Reversible Ca2+-induced fast-to-slow transition in primary skeletal muscle culture cells at the mRNA level

PubMed Central

Meißner, Joachim D; Kubis, Hans-Peter; Scheibe, Renate J; Gros, Gerolf

2000-01-01

The adult fast character and a Ca2+-inducible reversible transition from a fast to a slow type of rabbit myotube in a primary culture were demonstrated at the mRNA level by Northern blot analysis with probes specific for different myosin heavy chain (MyHC) isoforms and enzymes of energy metabolism. No non-adult MyHC isoform mRNA was detected after 22 days of culture. After 4 weeks of culture the fast MyHCIId mRNA was strongly expressed while MyHCI mRNA was virtually absent, indicating the fast adult character of the myotubes in the primary skeletal muscle culture. The data show that a fast-to-slow transition occurred in the myotubes at the level of MyHC isoform gene expression after treatment with the Ca2+ ionophore A23187. The effects of ionophore treatment were decreased levels of fast MyHCII mRNA and an augmented expression of the slow MyHCI gene. Changes in gene expression started very rapidly 1 day after the onset of ionophore treatment. Levels of citrate synthase mRNA increased and levels of glyceraldehyde 3-phosphate dehydrogenase mRNA decreased during ionophore treatment. This points to a shift from anaerobic to oxidative energy metabolism in the primary skeletal muscle culture cells at the level of gene expression. Withdrawal of the Ca2+ ionophore led to a return to increased levels of MyHCII mRNA and decreased levels of MyHCI mRNA, indicating a slow-to-fast transition in the myotubes and the reversibility of the effect of ionophore on MyHC isoform gene expression. PMID:10673542

Examining the validity of the ActivPAL monitor in measuring posture and ambulatory movement in children

PubMed Central

2012-01-01

Background Decreasing sedentary activities that involve prolonged sitting may be an important strategy to reduce obesity and other physical and psychosocial health problems in children. The first step to understanding the effect of sedentary activities on children’s health is to objectively assess these activities with a valid measurement tool. Purpose To examine the validity of the ActivPAL monitor in measuring sitting/lying, standing, and walking time, transition counts and step counts in children in a laboratory setting. Methods Twenty five healthy elementary school children (age 9.9 ± 0.3 years; BMI 18.2 ± 1.9; mean ± SD) were randomly recruited across the Auckland region, New Zealand. Children were fitted with ActivPAL monitors and observed during simulated free-living activities involving sitting/lying, standing and walking, followed by treadmill and over-ground activities at various speeds (slow, normal, fast) against video observation (criterion measure). The ActivPAL sit-to-stand and stand-to-sit transition counts and steps were also compared with video data. The accuracy of step counts measured by the ActivPAL was also compared against the New Lifestyles NL-2000 and the Yamax Digi-Walker SW-200 pedometers. Results We observed a perfect correlation between the ActivPAL monitor in time spent sitting/lying, standing, and walking in simulated free-living activities with direct observation. Correlations between the ActivPAL and video observation in total numbers of sit-to-stand and stand-to-sit transitions were high (r = 0.99 ± 0.01). Unlike pedometers, the ActivPAL did not misclassify fidgeting as steps taken. Strong correlations (r = 0.88-1.00) between ActivPAL step counts and video observation in both treadmill and over-ground slow and normal walking were also observed. During treadmill and over-ground fast walking and running, the correlations were low (r = 0.21-0.46). Conclusion The ActivPAL monitor is a valid measurement tool for assessing time spent sitting/lying, standing, and walking, sit-to-stand and stand-to-sit transition counts and step counts in slow and normal walking. The device did not measure accurately steps taken during treadmill and over-ground fast walking and running in children. PMID:23031188

Differential Sensitivities of Fast- and Slow-Cycling Cancer Cells to Inosine Monophosphate Dehydrogenase 2 Inhibition by Mycophenolic Acid

PubMed Central

Chen, Kan; Cao, Wanlu; Li, Juan; Sprengers, Dave; Hernanda, Pratika Y; Kong, Xiangdong; van der Laan, Luc JW; Man, Kwan; Kwekkeboom, Jaap; Metselaar, Herold J; Peppelenbosch, Maikel P; Pan, Qiuwei

2015-01-01

As uncontrolled cell proliferation requires nucleotide biosynthesis, inhibiting enzymes that mediate nucleotide biosynthesis constitutes a rational approach to the management of oncological diseases. In practice, however, results of this strategy are mixed and thus elucidation of the mechanisms by which cancer cells evade the effect of nucleotide biosynthesis restriction is urgently needed. Here we explored the notion that intrinsic differences in cancer cell cycle velocity are important in the resistance toward inhibition of inosine monophosphate dehydrogenase (IMPDH) by mycophenolic acid (MPA). In short-term experiments, MPA treatment of fast-growing cancer cells effectively elicited G0/G1 arrest and provoked apoptosis, thus inhibiting cell proliferation and colony formation. Forced expression of a mutated IMPDH2, lacking a binding site for MPA but retaining enzymatic activity, resulted in complete resistance of cancer cells to MPA. In nude mice subcutaneously engrafted with HeLa cells, MPA moderately delayed tumor formation by inhibiting cell proliferation and inducing apoptosis. Importantly, we developed a lentiviral vector–based Tet-on label-retaining system that enables to identify, isolate and functionally characterize slow-cycling or so-called label-retaining cells (LRCs) in vitro and in vivo. We surprisingly found the presence of LRCs in fast-growing tumors. LRCs were superior in colony formation, tumor initiation and resistance to MPA as compared with fast-cycling cells. Thus, the slow-cycling compartment of cancer seems predominantly responsible for resistance to MPA. PMID:26467706

Dynamic functional connectivity shapes individual differences in associative learning.

PubMed

Fatima, Zainab; Kovacevic, Natasha; Misic, Bratislav; McIntosh, Anthony Randal

2016-11-01

Current neuroscientific research has shown that the brain reconfigures its functional interactions at multiple timescales. Here, we sought to link transient changes in functional brain networks to individual differences in behavioral and cognitive performance by using an active learning paradigm. Participants learned associations between pairs of unrelated visual stimuli by using feedback. Interindividual behavioral variability was quantified with a learning rate measure. By using a multivariate statistical framework (partial least squares), we identified patterns of network organization across multiple temporal scales (within a trial, millisecond; across a learning session, minute) and linked these to the rate of change in behavioral performance (fast and slow). Results indicated that posterior network connectivity was present early in the trial for fast, and later in the trial for slow performers. In contrast, connectivity in an associative memory network (frontal, striatal, and medial temporal regions) occurred later in the trial for fast, and earlier for slow performers. Time-dependent changes in the posterior network were correlated with visual/spatial scores obtained from independent neuropsychological assessments, with fast learners performing better on visual/spatial subtests. No relationship was found between functional connectivity dynamics in the memory network and visual/spatial test scores indicative of cognitive skill. By using a comprehensive set of measures (behavioral, cognitive, and neurophysiological), we report that individual variations in learning-related performance change are supported by differences in cognitive ability and time-sensitive connectivity in functional neural networks. Hum Brain Mapp 37:3911-3928, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Distinguishing splanchnic nerve and chromaffin cell stimulation in mouse adrenal slices with fast-scan cyclic voltammetry

PubMed Central

Walsh, Paul L.; Petrovic, Jelena

2011-01-01

Electrical stimulation is an indispensible tool in studying electrically excitable tissues in neurobiology and neuroendocrinology. In this work, the consequences of high-intensity electrical stimulation on the release of catecholamines from adrenal gland slices were examined with fast-scan cyclic voltammetry at carbon fiber microelectrodes. A biphasic signal, consisting of a fast and slow phase, was observed when electrical stimulations typically used in tissue slices (10 Hz, 350 μA biphasic, 2.0 ms/phase pulse width) were applied to bipolar tungsten-stimulating electrodes. This signal was found to be stimulation dependent, and the slow phase of the signal was abolished when smaller (≤250 μA) and shorter (1 ms/phase) stimulations were used. The slow phase of the biphasic signal was found to be tetrodotoxin and hexamethonium independent, while the fast phase was greatly reduced using these pharmacological agents. Two different types of calcium responses were observed, where the fast phase was abolished by perfusion with a low-calcium buffer while both the fast and slow phases could be modulated when Ca2+ was completely excluded from the solution using EGTA. Perfusion with nifedipine resulted in the reduction of the slow catecholamine release to 29% of the original signal, while the fast phase was only decreased to 74% of predrug values. From these results, it was determined that high-intensity stimulations of the adrenal medulla result in depolarizing not only the splanchnic nerves, but also the chromaffin cells themselves resulting in a biphasic catecholamine release. PMID:21048165

Slow recovery of the impaired fatigue resistance in postunloading mouse soleus muscle corresponding to decreased mitochondrial function and a compensatory increase in type I slow fibers

PubMed Central

Feng, Han-Zhong; Chen, Xuequn; Malek, Moh H.

2015-01-01

Unloading or disuse rapidly results in skeletal muscle atrophy, switching to fast-type fibers, and decreased resistance to fatigue. The recovery process is of major importance in rehabilitation for various clinical conditions. Here we studied mouse soleus muscle during 60 days of reloading after 4 wk of hindlimb suspension. Unloading produced significant atrophy of soleus muscle with decreased contractile force and fatigue resistance, accompanied by switches of myosin isoforms from IIa to IIx and IIb and fast troponin T to more low-molecular-weight splice forms. The total mass, fiber size, and contractile force of soleus muscle recovered to control levels after 15 days of reloading. However, the fatigue resistance showed a trend of worsening during this period with significant infiltration of inflammatory cells at days 3 and 7, indicating reloading injuries that were accompanied by active regeneration with upregulations of filamin-C, αB-crystallin, and desmin. The fatigue resistance partially recovered after 30–60 days of reloading. The expression of peroxisome proliferator-activated receptor γ coactivator 1α and mitofusin-2 showed changes parallel to that of fatigue resistance after unloading and during reloading, suggesting a causal role of decreased mitochondrial function. Slow fiber contents in the soleus muscle were increased after 30–60 days of reloading to become significantly higher than the normal level, indicating a secondary adaption to compensate for the slow recovery of fatigue resistance. PMID:26447205

An ATM-independent S-phase checkpoint response involves CHK1 pathway

NASA Technical Reports Server (NTRS)

Zhou, Xiang-Yang; Wang, Xiang; Hu, Baocheng; Guan, Jun; Iliakis, George; Wang, Ya

2002-01-01

After exposure to genotoxic stress, proliferating cells actively slow down the DNA replication through a S-phase checkpoint to provide time for repair. We report that in addition to the ataxia-telangiectasia mutated (ATM)-dependent pathway that controls the fast response, there is an ATM-independent pathway that controls the slow response to regulate the S-phase checkpoint after ionizing radiation in mammalian cells. The slow response of S-phase checkpoint, which is resistant to wortmannin, sensitive to caffeine and UCN-01, and related to cyclin-dependent kinase phosphorylation, is much stronger in CHK1 overexpressed cells, and it could be abolished by Chk1 antisense oligonucleotides. These results provide evidence that the ATM-independent slow response of S-phase checkpoint involves CHK1 pathway.

Modulation of electroencephalograph activity by manual acupuncture stimulation in healthy subjects: An autoregressive spectral analysis

NASA Astrophysics Data System (ADS)

Yi, Guo-Sheng; Wang, Jiang; Deng, Bin; Wei, Xi-Le; Han, Chun-Xiao

2013-02-01

To investigate whether and how manual acupuncture (MA) modulates brain activities, we design an experiment where acupuncture at acupoint ST36 of the right leg is used to obtain electroencephalograph (EEG) signals in healthy subjects. We adopt the autoregressive (AR) Burg method to estimate the power spectrum of EEG signals and analyze the relative powers in delta (0 Hz-4 Hz), theta (4 Hz-8 Hz), alpha (8 Hz-13 Hz), and beta (13 Hz-30 Hz) bands. Our results show that MA at ST36 can significantly increase the EEG slow wave relative power (delta band) and reduce the fast wave relative powers (alpha and beta bands), while there are no statistical differences in theta band relative power between different acupuncture states. In order to quantify the ratio of slow to fast wave EEG activity, we compute the power ratio index. It is found that the MA can significantly increase the power ratio index, especially in frontal and central lobes. All the results highlight the modulation of brain activities with MA and may provide potential help for the clinical use of acupuncture. The proposed quantitative method of acupuncture signals may be further used to make MA more standardized.

Hexamethonium sensitivity of the swim musculature of the pteropod mollusc, Clione limacina.

PubMed

Satterlie, Richard A; Courtney, Christopher

2008-12-01

Swimming in reduced electrophysiological preparations of the pteropod mollusc, Clione limacina, was blocked by bath application of hexamethonium even though pattern generator activity continued with this treatment. Neuromuscular recordings indicated that hexamethonium blocked synaptic input from Pd-3 and Pd-4 motoneurons to slow-twitch muscle cells, while connections from Pd-1A and Pd-2A motoneurons to fast-twitch muscle cells were variable in their response to hexamethonium-synaptic inputs were suppressed in most cases and occasionally blocked, but the latter only with high concentrations and long incubations. Acutely dissociated wing muscle cells showed a concentration-dependency in the percentage of contracted cells with bath application of acetylcholine, and this contractile activity was blocked in preparations that were first bathed in hexamethonium. Intracellular recordings from dissociated slow-twitch muscle cells showed conductance-increase depolarizations of approximately 20 mV following 1 s pressure ejections of 10(-4) M acetylcholine from micropipettes placed immediately adjacent to the muscle cells. These responses were blocked when hexamethonium was bath applied prior to the pressure-applied acetylcholine. The results suggest the Pd-3/Pd-4 motoneuron to slow-twitch muscle cell junctions are cholinergic with nicotinic-like receptors, while the Pd-1A/Pd-2A to fast-twitch muscle cell connections are likely cholinergic, but with a different receptor type.

Influence of chewing rate on salivary stress hormone levels.

PubMed

Tasaka, Akinori; Tahara, Yasuaki; Sugiyama, Tetsuya; Sakurai, Kaoru

2008-10-01

The purpose of this study was to clarify the effect of different chewing rates on salivary cortisol levels as a stress indicator. The subject group consisted of 16 healthy males. They were required to rest for 30 min, and then given arithmetic calculations to perform for 30 min as stress loading. Immediately after, the first set of saliva specimens (S1) was collected over a period of 1 min to measure cortisol levels. Next, they were asked to chew a tasteless gum base for 10 min, and the second set of saliva specimens (S2) was collected in the same manner. They were then required to rest for 10 min, after which the third set of saliva specimens (S3) was collected. Chewing rates were set to slow, habitual, and fast in time with a metronome. Salivary cortisol levels were analyzed by radioimmunoassay. Changes in salivary cortisol levels comparing S1 with S2, and S1 with S3 were determined. Changes in salivary cortisol levels between S1 and S2 showed a reduction of 4.7%, 14.6%, and 16.2% with slow, habitual, and fast chewing, respectively. A significant difference was observed between slow and fast chewing. Changes in salivary cortisol levels between S1 and S3 showed a reduction of 14.4%, 22.2%, and 25.8% with slow, habitual, and fast chewing, respectively. A significant difference was observed between slow and fast chewing. This study showed that differences in chewing rate affected salivary cortisol levels as a stress indicator, and suggested that the effect on stress release with fast chewing is greater than that with slow chewing.

Charge immobilization of the voltage sensor in domain IV is independent of sodium current inactivation.

PubMed

Sheets, Michael F; Hanck, Dorothy A

2005-02-15

Recovery from fast inactivation in voltage-dependent Na+ channels is associated with a slow component in the time course of gating charge during repolarization (i.e. charge immobilization), which results from the slow movement of the S4 segments in domains III and IV (S4-DIII and S4-DIV). Previous studies have shown that the non-specific removal of fast inactivation by the proteolytic enzyme pronase eliminated charge immobilization, while the specific removal of fast inactivation (by intracellular MTSET modification of a cysteine substituted for the phenylalanine in the IFM motif, ICMMTSET, in the inactivation particle formed by the linker between domains III and IV) only reduced the amount of charge immobilization by nearly one-half. To investigate the molecular origin of the remaining slow component of charge immobilization we studied the human cardiac Na+ channel (hH1a) in which the outermost arginine in the S4-DIV, which contributes approximately 20% to total gating charge (Qmax), was mutated to a cysteine (R1C-DIV). Gating charge could be fully restored in R1C-DIV by exposure to extracellular MTSEA, a positively charged methanethiosulphonate reagent. The RIC-DIV mutation was combined with ICMMTSET to remove fast inactivation, and the gating currents of R1C-DIV-ICM(MTSET) were recorded before and after modification with MTSEAo. Prior to MTSEAo, the time course of the gating charge during repolarization (off-charge) was best described by a single fast time constant. After MTSEA, the off-charge had both fast and slow components, with the slow component accounting for nearly 35% of Qmax. These results demonstrate that the slow movement of the S4-DIV during repolarization is not dependent upon the normal binding of the inactivation particle.

Differences in sodium voltage-gated channel properties according to myosin heavy chain isoform expression in single muscle fibres.

PubMed

Rannou, F; Droguet, M; Giroux-Metges, M A; Pennec, Y; Gioux, M; Pennec, J P

2009-11-01

The myosin heavy chain (MHC) isoform determines the characteristics and shortening velocity of muscle fibres. The functional properties of the muscle fibre are also conditioned by its membrane excitability through the electrophysiological properties of sodium voltage-gated channels. Macropatch-clamp is used to study sodium channels in fibres from peroneus longus (PL) and soleus (Sol) muscles (Wistar rats, n = 8). After patch-clamp recordings, single fibres are identified by SDS-PAGE electrophoresis according to their myosin heavy chain isoform (slow type I and the three fast types IIa, IIx, IIb). Characteristics of sodium currents are compared (Student's t test) between fibres exhibiting only one MHC isoform. Four MHC isoforms are identified in PL and only type I in Sol single fibres. In PL, maximal sodium current (I(max)), maximal sodium conductance (g(Na,max)) and time constants of activation and inactivation ((m) and (h)) increase according to the scheme I-->IIa-->IIx-->IIb (P < 0.05). (m) values related to sodium channel type and/or function, are similar in Sol I and PL IIb fibres (P = 0.97) despite different contractile properties. The voltage dependence of activation (V(a,1/2)) shows a shift towards positive potentials from Sol type I to IIa, IIx and finally IIb fibres from PL (P < 0.05). These data are consistent with the earlier recruitment of slow fibres in a fast-mixed muscle like PL, while slow fibres of postural muscle such as soleus could be recruited in the same ways as IIb fibres in a fast muscle.

Validity of the iPhone M7 motion co-processor as a pedometer for able-bodied ambulation.

PubMed

Major, Matthew J; Alford, Micah

2016-12-01

Physical activity benefits for disease prevention are well-established. Smartphones offer a convenient platform for community-based step count estimation to monitor and encourage physical activity. Accuracy is dependent on hardware-software platforms, creating a recurring challenge for validation, but the Apple iPhone® M7 motion co-processor provides a standardised method that helps address this issue. Validity of the M7 to record step count for level-ground, able-bodied walking at three self-selected speeds, and agreement with the StepWatch TM was assessed. Steps were measured concurrently with the iPhone® (custom application to extract step count), StepWatch TM and manual count. Agreement between iPhone® and manual/StepWatch TM count was estimated through Pearson correlation and Bland-Altman analyses. Data from 20 participants suggested that iPhone® step count correlations with manual and StepWatch TM were strong for customary (1.3 ± 0.1 m/s) and fast (1.8 ± 0.2 m/s) speeds, but weak for the slow (1.0 ± 0.1 m/s) speed. Mean absolute error (manual-iPhone®) was 21%, 8% and 4% for the slow, customary and fast speeds, respectively. The M7 accurately records step count during customary and fast walking speeds, but is prone to considerable inaccuracies at slow speeds which has important implications for certain patient groups. The iPhone® may be a suitable alternative to the StepWatch TM for only faster walking speeds.

Adult fast myosin pattern and Ca2+-induced slow myosin pattern in primary skeletal muscle culture

PubMed Central

Kubis, Hans-Peter; Haller, Ernst-August; Wetzel, Petra; Gros, Gerolf

1997-01-01

A primary muscle cell culture derived from newborn rabbit muscle and growing on microcarriers in suspension was established. When cultured for several weeks, the myotubes in this model develop the completely adult pattern of fast myosin light and heavy chains. When Ca2+ ionophore is added to the culture medium on day 11, raising intracellular [Ca2+] about 10-fold, the myotubes develop to exhibit properties of an adult slow muscle by day 30, expressing slow myosin light as well as heavy chains, elevated citrate synthase, and reduced lactate dehydrogenase. The remarkable plasticity of these myotubes becomes apparent, when 8 days after withdrawal of the ionophore a marked slow-to-fast transition, as judged from the expression of isomyosins and metabolic enzymes, occurs. PMID:9108130

Estimation of fast and slow wave properties in cancellous bone using Prony's method and curve fitting.

PubMed

Wear, Keith A

2013-04-01

The presence of two longitudinal waves in poroelastic media is predicted by Biot's theory and has been confirmed experimentally in through-transmission measurements in cancellous bone. Estimation of attenuation coefficients and velocities of the two waves is challenging when the two waves overlap in time. The modified least squares Prony's (MLSP) method in conjuction with curve-fitting (MLSP + CF) is tested using simulations based on published values for fast and slow wave attenuation coefficients and velocities in cancellous bone from several studies in bovine femur, human femur, and human calcaneus. The search algorithm is accelerated by exploiting correlations among search parameters. The performance of the algorithm is evaluated as a function of signal-to-noise ratio (SNR). For a typical experimental SNR (40 dB), the root-mean-square errors (RMSEs) for one example (human femur) with fast and slow waves separated by approximately half of a pulse duration were 1 m/s (slow wave velocity), 4 m/s (fast wave velocity), 0.4 dB/cm MHz (slow wave attenuation slope), and 1.7 dB/cm MHz (fast wave attenuation slope). The MLSP + CF method is fast (requiring less than 2 s at SNR = 40 dB on a consumer-grade notebook computer) and is flexible with respect to the functional form of the parametric model for the transmission coefficient. The MLSP + CF method provides sufficient accuracy and precision for many applications such that experimental error is a greater limiting factor than estimation error.

Nonselective Currents and Channels in Plasma Membranes of Protoplasts from Coats of Developing Seeds of Bean1

PubMed Central

Zhang, Wen-Hao; Skerrett, Martha; Walker, N. Alan; Patrick, John W.; Tyerman, Stephen D.

2002-01-01

In developing bean (Phaseolus vulgaris) seeds, phloem-imported nutrients move in the symplast from sieve elements to the ground parenchyma cells where they are transported across the plasma membrane into the seed apoplast. To study the mechanisms underlying this transport, channel currents in ground parenchyma protoplasts were characterized using patch clamp. A fast-activating outward current was found in all protoplasts, whereas a slowly activating outward current was observed in approximately 25% of protoplasts. The two currents had low selectivity for univalent cations, but the slow current was more selective for K+ over Cl− (PK:PCl = 3.6–4.2) than the fast current (PK:PCl = 1.8–2.5) and also displayed Ca2+ selectivity. The slow current was blocked by Ba2+, whereas both currents were blocked by Gd3+ and La3+. Efflux of K+ from seed coat halves was inhibited 25% by Gd3+ and La3+ but was stimulated by Ba2+ and Cs+, suggesting that only the fast current may be a component in the pathway for K+ release. An “instantaneous” inward current observed in all protoplasts exhibited similar pharmacology and permeability for univalent cations to the fast outward current. In outside-out patches, two classes of depolarization-activated cation-selective channels were observed: one slowly activating of low conductance (determined from nonstationary noise to be 2.4 pS) and another with conductances 10-fold higher. Both channels occurred at high density. The higher conductance channel in 10 mm KCl had PK:PCl = 2.8. Such nonselective channels in the seed coat ground parenchyma cell could function to allow some of the efflux of phloem-imported univalent ions into the seed apoplast. PMID:11842143

Monoamines and glycogen levels in cerebral cortices of fast and slow methionine sulfoximine-inbred mice.

PubMed

Boissonnet, Arnaud; Hévor, Tobias; Landemarre, Ludovic; Cloix, Jean-François

2013-05-01

The experimental model of seizures which depends upon methionine sulfoximine (MSO) simulates the most striking form of human epilepsy. MSO generates epileptiform seizures in a large variety of animals, increases brain glycogen content and induces brain monoamines modifications. We selected two inbred lines of mice based upon their latency toward MSO-dependent seizures, named as MSO-Fast (sensitive), having short latency toward MSO, and MSO-Slow (resistant) with a long latency. We determined 13 monoamines and glycogen contents in brain cortices of the MSO-Fast and slow lines in order to determine the relationships with MSO-dependent seizures. The present data show that using these MSO-Fast and MSO-Slow inbred lines it could be demonstrated that: (1) in basal conditions the neurotransmitter 5-HT is significantly higher in MSO-Fast mice than in MSO-Slow ones; (2) MSO in both lines induced a significant increase in brain content of DOPAC (3,4-dihydroxyphenylacetic acid), HVA (homovanillic acid), MHPG (3-methoxy-4-hydroxyphenylglycol), and 5-HT (serotonin); a significant decrease in MSO-Slow mice in brain content of NME (normetepinephrine), and 5-HIAA (5-hydroxyindoleacetic acid) and the variation of other monoamines were not significant; (3) the brain glycogen content is significantly higher in MSO-Fast mice than in MSO-Slow ones, both in basal conditions and after MSO administration. From our data, we propose that brain glycogen content may constitute a defense against epileptic attack, as glycogen may be degraded down to glucose-6-phosphate that can be used to either postpone the epileptic attack or to provide neurons with energy when they needed it. Brain glycogen might therefore be considered as a molecule that can contribute to struggle seizures, at least in MSO-dependent seizure. The 5-HT content may constitute a defense against MSO-dependent epilepsy. Copyright © 2013 Elsevier B.V. All rights reserved.

Reinnervation of the lateral gastrocnemius and soleus muscles in the rat by their common nerve.

PubMed Central

Gillespie, M J; Gordon, T; Murphy, P R

1986-01-01

To determine whether there is any specificity of regenerating nerves for their original muscles, the common lateral gastrocnemius soleus nerve (l.g.s.) innervating the fast-twitch lateral gastrocnemius (l.g.) and slow-twitch soleus muscles was sectioned in the hind limb of twenty adult rats. The proximal nerve stump was sutured to the dorsal surface of the l.g. muscle and 4-14 months later, the contractile properties of the reinnervated l.g. and soleus muscles and their single motor units were studied by dissection and stimulation of the ventral root filaments. Contractile properties of normal contralateral muscles were examined for comparison and motor units were isolated in l.g. and soleus muscles for study in a group of untreated animals. Measurement of time and rate parameters of maximal twitch and tetanic contractions showed that the rate of development of force increased significantly in reinnervated soleus muscles and approached the speed of l.g. muscles but rate of relaxation did not change appreciably. In reinnervated l.g. muscles, contraction speed was similar to normal l.g. muscles but relaxation rate declined toward the rates of relaxation in control soleus muscles. After reinnervation by the common l.g.s. nerve, the proportion of slow motor units in l.g. increased from 10 to 31% and decreased in soleus from 80 to 31%. The relative proportions of fast and slow motor units in each muscle were the same as the proportions of fast and slow units in the normal l.g. and soleus muscles combined. It was concluded that fast and slow muscles do not show any preference for their former nerves and that the change in the force profile of the reinnervated muscles is indicative of the relative proportions of fast and slow motor units: fast units dominate the contraction phase and slow units the relaxation phase of twitch and tetanic contractions of the muscle. PMID:3723414

Inactivation gating of Kv7.1 channels does not involve concerted cooperative subunit interactions.

PubMed

Meisel, Eshcar; Tobelaim, William; Dvir, Meidan; Haitin, Yoni; Peretz, Asher; Attali, Bernard

2018-01-01

Inactivation is an intrinsic property of numerous voltage-gated K + (Kv) channels and can occur by N-type or/and C-type mechanisms. N-type inactivation is a fast, voltage independent process, coupled to activation, with each inactivation particle of a tetrameric channel acting independently. In N-type inactivation, a single inactivation particle is necessary and sufficient to occlude the pore. C-type inactivation is a slower process, involving the outermost region of the pore and is mediated by a concerted, highly cooperative interaction between all four subunits. Inactivation of Kv7.1 channels does not exhibit the hallmarks of N- and C-type inactivation. Inactivation of WT Kv7.1 channels can be revealed by hooked tail currents that reflects the recovery from a fast and voltage-independent inactivation process. However, several Kv7.1 mutants such as the pore mutant L273F generate an additional voltage-dependent slow inactivation. The subunit interactions during this slow inactivation gating remain unexplored. The goal of the present study was to study the nature of subunit interactions along Kv7.1 inactivation gating, using concatenated tetrameric Kv7.1 channel and introducing sequentially into each of the four subunits the slow inactivating pore mutation L273F. Incorporating an incremental number of inactivating mutant subunits did not affect the inactivation kinetics but slowed down the recovery kinetics from inactivation. Results indicate that Kv7.1 inactivation gating is not compatible with a concerted cooperative process. Instead, adding an inactivating subunit L273F into the Kv7.1 tetramer incrementally stabilizes the inactivated state, which suggests that like for activation gating, Kv7.1 slow inactivation gating is not a concerted process.

Existence domains of slow and fast ion-acoustic solitons in two-ion space plasmas

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

Maharaj, S. K., E-mail: smaharaj@sansa.org.za; Bharuthram, R., E-mail: rbharuthram@uwc.ac.za; Singh, S. V., E-mail: satyavir@iigs.iigm.res.in

2015-03-15

A study of large amplitude ion-acoustic solitons is conducted for a model composed of cool and hot ions and cool and hot electrons. Using the Sagdeev pseudo-potential formalism, the scope of earlier studies is extended to consider why upper Mach number limitations arise for slow and fast ion-acoustic solitons. Treating all plasma constituents as adiabatic fluids, slow ion-acoustic solitons are limited in the order of increasing cool ion concentrations by the number densities of the cool, and then the hot ions becoming complex valued, followed by positive and then negative potential double layer regions. Only positive potentials are found formore » fast ion-acoustic solitons which are limited only by the hot ion number density having to remain real valued. The effect of neglecting as opposed to including inertial effects of the hot electrons is found to induce only minor quantitative changes in the existence regions of slow and fast ion-acoustic solitons.« less

Reconsidering earthquake scaling

USGS Publications Warehouse

Gomberg, Joan S.; Wech, Aaron G.; Creager, Kenneth; Obara, K.; Agnew, Duncan

2016-01-01

The relationship (scaling) between scalar moment, M0, and duration, T, potentially provides key constraints on the physics governing fault slip. The prevailing interpretation of M0-T observations proposes different scaling for fast (earthquakes) and slow (mostly aseismic) slip populations and thus fundamentally different driving mechanisms. We show that a single model of slip events within bounded slip zones may explain nearly all fast and slow slip M0-T observations, and both slip populations have a change in scaling, where the slip area growth changes from 2-D when too small to sense the boundaries to 1-D when large enough to be bounded. We present new fast and slow slip M0-T observations that sample the change in scaling in each population, which are consistent with our interpretation. We suggest that a continuous but bimodal distribution of slip modes exists and M0-T observations alone may not imply a fundamental difference between fast and slow slip.

Fast and ultrafast endocytosis.

PubMed

Watanabe, Shigeki; Boucrot, Emmanuel

2017-08-01

Clathrin-mediated endocytosis (CME) is the main endocytic pathway supporting housekeeping functions in cells. However, CME may be too slow to internalize proteins from the cell surface during certain physiological processes such as reaction to stress hormones ('fight-or-flight' reaction), chemotaxis or compensatory endocytosis following exocytosis of synaptic vesicles or hormone-containing vesicles. These processes take place on a millisecond to second timescale and thus require very rapid cellular reaction to prevent overstimulation or exhaustion of the response. There are several fast endocytic processes identified so far: macropinocytosis, activity-dependent bulk endocytosis (ABDE), fast-endophilin-mediated endocytosis (FEME), kiss-and-run and ultrafast endocytosis. All are clathrin-independent and are not constitutively active but may use different molecular mechanisms to rapidly remove receptors and proteins from the cell surface. Here, we review our current understanding of fast and ultrafast endocytosis, their functions, and molecular mechanisms. Copyright © 2017 Elsevier Ltd. All rights reserved.

Alterations in intrinsic mitochondrial function with aging are fiber type-specific and do not explain differential atrophy between muscles.

PubMed

Picard, Martin; Ritchie, Darmyn; Thomas, Melissa M; Wright, Kathryn J; Hepple, Russell T

2011-12-01

To determine whether mitochondrial dysfunction is causally related to muscle atrophy with aging, we examined respiratory capacity, H(2) O(2) emission, and function of the mitochondrial permeability transition pore (mPTP) in permeabilized myofibers prepared from four rat muscles that span a range of fiber type and degree of age-related atrophy. Muscle atrophy with aging was greatest in fast-twitch gastrocnemius (Gas) muscle (-38%), intermediate in both the fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (Sol) muscles (-21%), and non-existent in adductor longus (AL) muscle (+47%). In contrast, indices of mitochondrial dysfunction did not correspond to this differential degree of atrophy. Specifically, despite higher protein expression for oxidative phosphorylation (oxphos) system in fast Gas and EDL, state III respiratory capacity per myofiber wet weight was unchanged with aging, whereas the slow Sol showed proportional decreases in oxphos protein, citrate synthase activity, and state III respiration. Free radical leak (H(2) O(2) emission per O(2) flux) under state III respiration was higher with aging in the fast Gas, whereas state II free radical leak was higher in the slow AL. Only the fast muscles had impaired mPTP function with aging, with lower mitochondrial calcium retention capacity in EDL and shorter time to mPTP opening in Gas and EDL. Collectively, our results underscore that the age-related changes in muscle mitochondrial function depend largely upon fiber type and are unrelated to the severity of muscle atrophy, suggesting that intrinsic changes in mitochondrial function are unlikely to be causally involved in aging muscle atrophy. © 2011 The Authors. Aging Cell © 2011 Blackwell Publishing Ltd/Anatomical Society of Great Britain and Ireland.

Heat exposure enhances radiosensitivity by depressing DNA-PK kinase activity during double strand break repair.

PubMed

Ihara, Makoto; Takeshita, Satoshi; Okaichi, Kumio; Okumura, Yutaka; Ohnishi, Takeo

2014-03-01

From the role of double strand DNA dependent protein kinase (DNA-PKcs) activity of non-homologous end joining (NHEJ) repair for DNA double strand breaks (DSBs), we aim to define possible associations between thermo-sensitisation and the enzyme activities in X-ray irradiated cells. DNA-PKcs deficient mouse, Chinese hamster and human cultured cells were compared to the parental wild-type cells. The radiosensitivities, the number of DSBs and DNA-PKcs activities after heat-treatment were measured. Both DNA-PKcs deficient cells and the wild-type cells showed increased radiosensitivities after heat-treatment. The wild-type cells have two repair processes; fast repair and slow repair. In contrast, DNA-PKcs deficient cells have only the slow repair process. The fast repair component apparently disappeared by heat-treatment in the wild-type cells. In both cell types, additional heat exposure enhanced radiosensitivities. Although DNA-PKcs activity was depressed by heat, the inactivated DNA-PKcs activity recovered during an incubation at 37 °C. DSB repair efficiency was dependent on the reactivation of DNA-PKcs activity. It was suggested that NHEJ is the major process used to repair X-ray-induced DSBs and utilises DNA-PKcs activity, but homologous recombination repair provides additional secondary levels of DSB repair. The thermo-sensitisation in X-ray-irradiated cells depends on the inhibition of NHEJ repair through the depression of DNA-PKcs activities.

Exercise Performance and Corticospinal Excitability during Action Observation

PubMed Central

Wrightson, James G.; Twomey, Rosie; Smeeton, Nicholas J.

2016-01-01

Purpose: Observation of a model performing fast exercise improves simultaneous exercise performance; however, the precise mechanism underpinning this effect is unknown. The aim of the present study was to investigate whether the speed of the observed exercise influenced both upper body exercise performance and the activation of a cortical action observation network (AON). Method: In Experiment 1, 10 participants completed a 5 km time trial on an arm-crank ergometer whilst observing a blank screen (no-video) and a model performing exercise at both a typical (i.e., individual mean cadence during baseline time trial) and 15% faster than typical speed. In Experiment 2, 11 participants performed arm crank exercise whilst observing exercise at typical speed, 15% slower and 15% faster than typical speed. In Experiment 3, 11 participants observed the typical, slow and fast exercise, and a no-video, whilst corticospinal excitability was assessed using transcranial magnetic stimulation. Results: In Experiment 1, performance time decreased and mean power increased, during observation of the fast exercise compared to the no-video condition. In Experiment 2, cadence and power increased during observation of the fast exercise compared to the typical speed exercise but there was no effect of observation of slow exercise on exercise behavior. In Experiment 3, observation of exercise increased corticospinal excitability; however, there was no difference between the exercise speeds. Conclusion: Observation of fast exercise improves simultaneous upper-body exercise performance. However, because there was no effect of exercise speed on corticospinal excitability, these results suggest that these improvements are not solely due to changes in the activity of the AON. PMID:27014037

Simultaneous realization of slow and fast acoustic waves using a fractal structure of Koch curve.

PubMed

Ding, Jin; Fan, Li; Zhang, Shu-Yi; Zhang, Hui; Yu, Wei-Wei

2018-01-24

An acoustic metamaterial based on a fractal structure, the Koch curve, is designed to simultaneously realize slow and fast acoustic waves. Owing to the multiple transmitting paths in the structure resembling the Koch curve, the acoustic waves travelling along different paths interfere with each other. Therefore, slow waves are created on the basis of the resonance of a Koch-curve-shaped loop, and meanwhile, fast waves even with negative group velocities are obtained due to the destructive interference of two acoustic waves with opposite phases. Thus, the transmission of acoustic wave can be freely manipulated with the Koch-curve shaped structure.

Subjective and Objective Effects of Fast and Slow Compression on the Perception of Reverberant Speech in Listeners with Hearing Loss

ERIC Educational Resources Information Center

Shi, Lu-Feng; Doherty, Karen A.

2008-01-01

Purpose: The purpose of the current study was to assess the effect of fast and slow attack/release times (ATs/RTs) on aided perception of reverberant speech in quiet. Method: Thirty listeners with mild-to-moderate sensorineural hearing loss were tested monaurally with a commercial hearing aid programmed in 3 AT/RT settings: linear, fast (AT = 9…

Numerical simulations of fast-axis instability of vector solitons in mode-locked fiber lasers.

PubMed

Du, Yueqing; Shu, Xuewen; Cheng, Peiyun

2017-01-23

We demonstrate the fast-axis instability in mode-locked fiber lasers numerically for the first time. We find that the energy of the fast mode will be transferred to the slow mode when the strong pump strength makes the soliton period short. A nearly linearly polarized vector soliton along the slow-axis could be generated under certain cavity parameters. The final polarization of the vector soliton is related to the initial polarization of the seed pulse. Two regimes of energy exchanging between the slow mode and the fast mode are explored and the direction of the energy flow between two modes depends on the phase difference. The dip-type sidebands are found to be intrinsic characteristics of the mode-locked fiber lasers under high pulse energy.

Analysis of slow- and fast-α band asymmetry during performance of a saccadic eye movement task: dissociation between memory- and attention-driven systems.

PubMed

Sanfim, Antonio; Velasques, Bruna; Machado, Sergio; Arias-Carrión, Oscar; Paes, Flávia; Teixeira, Silmar; Santos, Joana Luz; Bittencourt, Juliana; Basile, Luis F; Cagy, Mauricio; Piedade, Roberto; Sack, Alexander T; Nardi, Antonio Egídio; Ribeiro, Pedro

2012-01-15

This study aimed at analyzing the relationship between slow- and fast-alpha asymmetry within frontal cortex and the planning, execution and voluntary control of saccadic eye movements (SEM), and quantitative electroencephalography (qEEG) was recorded using a 20-channel EEG system in 12 healthy participants performing a fixed (i.e., memory-driven) and a random SEM (i.e., stimulus-driven) condition. We find main effects for SEM condition in slow- and fast-alpha asymmetry at electrodes F3-F4, which are located over premotor cortex, specifically a negative asymmetry between conditions. When analyzing electrodes F7-F8, which are located over prefrontal cortex, we found a main effect for condition in slow-alpha asymmetry, particularly a positive asymmetry between conditions. In conclusion, the present approach supports the association of slow- and fast-alpha bands with the planning and preparation of SEM, and the specific role of these sub-bands for both, the attention network and the coordination and integration of sensory information with a (oculo)-motor response. Copyright © 2011 Elsevier B.V. All rights reserved.

Annual brome control using a native fungal seed pathogen

Treesearch

Susan E. Meyer; Suzette Clement; Julie Beckstead

2013-01-01

Formulations having a selective, mycoherbicide activity for killing ungerminated seeds of invasive grass species are provided. An agricultural, mycoherbicide formulation is taught for killing ungerminated seeds of invasive grass species. The formulations can comprise, for example, a slow-growing strain of Pyrenophora semeniperda, a fast-growing strain of Pyrenophora...

Lennox-Gastaut Syndrome: Potential Mechanisms of Cognitive Regression

ERIC Educational Resources Information Center

Blume, Warren T.

2004-01-01

Lennox-Gastaut (L-G) syndrome is an intractable generalized epilepsy of childhood onset, associated with spike waves at a slow rate and paroxysmal fast activity. These epileptiform discharge patterns are thought to reflect excessive neocortical excitability and arise from neuronal and synaptic features peculiar to the immature central nervous…

Dynamical Model for Spindown of Solar-type Stars

NASA Astrophysics Data System (ADS)

Sood, Aditi; Kim, Eun-jin; Hollerbach, Rainer

2016-12-01

After their formation, stars slow down their rotation rates by the removal of angular momentum from their surfaces, e.g., via stellar winds. Explaining how this rotation of solar-type stars evolves in time is currently an interesting but difficult problem in astrophysics. Despite the complexity of the processes involved, a traditional model, where the removal of angular momentum by magnetic fields is prescribed, has provided a useful framework to understand observational relations between stellar rotation, age, and magnetic field strength. Here, for the first time, a spindown model is proposed where loss of angular momentum by magnetic fields evolves dynamically, instead of being prescibed kinematically. To this end, we evolve the stellar rotation and magnetic field simultaneously over stellar evolution time by extending our previous work on a dynamo model which incorporates nonlinear feedback mechanisms on rotation and magnetic fields. We show that our extended model reproduces key observations and is capable of explaining the presence of the two branches of (fast and slow rotating) stars which have different relations between rotation rate Ω versus time (age), magnetic field strength | B| versus rotation rate, and frequency of magnetic field {ω }{cyc} versus rotation rate. For fast rotating stars we find that: (I) there is an exponential spindown {{Ω }}\\propto {e}-1.35t, with t measured in Gyr; (II) magnetic activity saturates for higher rotation rate; (III) {ω }{cyc}\\propto {{{Ω }}}0.83. For slow rotating stars we find: (I) a power-law spindown {{Ω }}\\propto {t}-0.52; (II) that magnetic activity scales roughly linearly with rotation rate; (III) {ω }{cyc}\\propto {{{Ω }}}1.16. The results obtained from our investigations are in good agreement with observations. The Vaughan-Preston gap is consistently explained in our model by the shortest spindown timescale in this transition from fast to slow rotators. Our results highlight the importance of self-regulation of magnetic fields and rotation by direct and indirect interactions involving nonlinear feedback in stellar evolution.

Effect of Time-Dependent Pinning Pressure on Abnormal Grain Growth: Phase Field Simulation

NASA Astrophysics Data System (ADS)

Kim, Jeong Min; Min, Guensik; Shim, Jae-Hyeok; Lee, Kyung Jong

2018-05-01

The effect of the time-dependent pinning pressure of precipitates on abnormal grain growth has been investigated by multiphase field simulation with a simple precipitation model. The application of constant pinning pressure is problematic because it always induces abnormal grain growth or no grain growth, which is not reasonable considering the real situation. To produce time-dependent pinning pressure, both precipitation kinetics and precipitate coarsening kinetics have been considered with two rates: slow and fast. The results show that abnormal grain growth is suppressed at the slow precipitation rate. At the slow precipitation rate, the overall grain growth caused by the low pinning pressure in the early stage indeed plays a role in preventing abnormal grain growth by reducing the mobility advantage of abnormal grains. In addition, the fast precipitate coarsening rate tends to more quickly transform abnormal grain growth into normal grain growth by inducing the active growth of grains adjacent to the abnormal grains in the early stage. Therefore, the present study demonstrates that the time dependence of the pinning pressure of precipitates is a critical factor that determines the grain growth mode.

Effect of Time-Dependent Pinning Pressure on Abnormal Grain Growth: Phase Field Simulation

NASA Astrophysics Data System (ADS)

Kim, Jeong Min; Min, Guensik; Shim, Jae-Hyeok; Lee, Kyung Jong

2018-03-01

The effect of the time-dependent pinning pressure of precipitates on abnormal grain growth has been investigated by multiphase field simulation with a simple precipitation model. The application of constant pinning pressure is problematic because it always induces abnormal grain growth or no grain growth, which is not reasonable considering the real situation. To produce time-dependent pinning pressure, both precipitation kinetics and precipitate coarsening kinetics have been considered with two rates: slow and fast. The results show that abnormal grain growth is suppressed at the slow precipitation rate. At the slow precipitation rate, the overall grain growth caused by the low pinning pressure in the early stage indeed plays a role in preventing abnormal grain growth by reducing the mobility advantage of abnormal grains. In addition, the fast precipitate coarsening rate tends to more quickly transform abnormal grain growth into normal grain growth by inducing the active growth of grains adjacent to the abnormal grains in the early stage. Therefore, the present study demonstrates that the time dependence of the pinning pressure of precipitates is a critical factor that determines the grain growth mode.

Precursory changes in seismic velocity for the spectrum of earthquake failure modes

PubMed Central

Scuderi, M.M.; Marone, C.; Tinti, E.; Di Stefano, G.; Collettini, C.

2016-01-01

Temporal changes in seismic velocity during the earthquake cycle have the potential to illuminate physical processes associated with fault weakening and connections between the range of fault slip behaviors including slow earthquakes, tremor and low frequency earthquakes1. Laboratory and theoretical studies predict changes in seismic velocity prior to earthquake failure2, however tectonic faults fail in a spectrum of modes and little is known about precursors for those modes3. Here we show that precursory changes of wave speed occur in laboratory faults for the complete spectrum of failure modes observed for tectonic faults. We systematically altered the stiffness of the loading system to reproduce the transition from slow to fast stick-slip and monitored ultrasonic wave speed during frictional sliding. We find systematic variations of elastic properties during the seismic cycle for both slow and fast earthquakes indicating similar physical mechanisms during rupture nucleation. Our data show that accelerated fault creep causes reduction of seismic velocity and elastic moduli during the preparatory phase preceding failure, which suggests that real time monitoring of active faults may be a means to detect earthquake precursors. PMID:27597879

Fast calcium and voltage-sensitive dye imaging in enteric neurones reveal calcium peaks associated with single action potential discharge.

PubMed

Michel, K; Michaelis, M; Mazzuoli, G; Mueller, K; Vanden Berghe, P; Schemann, M

2011-12-15

Slow changes in [Ca(2+)](i) reflect increased neuronal activity. Our study demonstrates that single-trial fast [Ca(2+)](i) imaging (≥200 Hz sampling rate) revealed peaks each of which are associated with single spike discharge recorded by consecutive voltage-sensitive dye (VSD) imaging in enteric neurones and nerve fibres. Fast [Ca(2+)](i) imaging also revealed subthreshold fast excitatory postsynaptic potentials. Nicotine-evoked [Ca(2+)](i) peaks were reduced by -conotoxin and blocked by ruthenium red or tetrodotoxin. Fast [Ca(2+)](i) imaging can be used to directly record single action potentials in enteric neurones. [Ca(2+)](i) peaks required opening of voltage-gated sodium and calcium channels as well as Ca(2+) release from intracellular stores.

Corticosterone and pace of life in two life-history ecotypes of the garter snake Thamnophis elegans.

PubMed

Palacios, Maria G; Sparkman, Amanda M; Bronikowski, Anne M

2012-02-01

Glucocorticoids are main candidates for mediating life-history trade-offs by regulating the balance between current reproduction and survival. It has been proposed that slow-living organisms should show higher stress-induced glucocorticoid levels that favor self-maintenance rather than current reproduction when compared to fast-living organisms. We tested this hypothesis in replicate populations of two ecotypes of the garter snake (Thamnophis elegans) that exhibit slow and fast pace of life strategies. We subjected free-ranging snakes to a capture-restraint protocol and compared the stress-induced corticosterone levels between slow- and fast-living snakes. We also used a five-year dataset to assess whether baseline corticosterone levels followed the same pattern as stress-induced levels in relation to pace of life. In accordance with the hypothesis, slow-living snakes showed higher stress-induced corticosterone levels than fast-living snakes. Baseline corticosterone levels showed a similar pattern with ecotype, although differences depended on the year of study. Overall, however, levels of glucocorticoids are higher in slow-living than fast-living snakes, which should favor self-maintenance and survival at the expense of current reproduction. The results of the present study are the first to relate glucocorticoid levels and pace of life in a reptilian system and contribute to our understanding of the physiological mechanisms involved in life-history evolution. Copyright © 2011 Elsevier Inc. All rights reserved.

Lidocaine reduces the transition to slow inactivation in Nav1.7 voltage-gated sodium channels

PubMed Central

Sheets, Patrick L; Jarecki, Brian W; Cummins, Theodore R

2011-01-01

BACKGROUND AND PURPOSE The primary use of local anaesthetics is to prevent or relieve pain by reversibly preventing action potential propagation through the inhibition of voltage-gated sodium channels. The tetrodotoxin-sensitive voltage-gated sodium channel subtype Nav1.7, abundantly expressed in pain-sensing neurons, plays a crucial role in perception and transmission of painful stimuli and in inherited chronic pain syndromes. Understanding the interaction of lidocaine with Nav1.7 channels could provide valuable insight into the drug's action in alleviating pain in distinct patient populations. The aim of this study was to determine how lidocaine interacts with multiple inactivated conformations of Nav1.7 channels. EXPERIMENTAL APPROACH We investigated the interactions of lidocaine with wild-type Nav1.7 channels and a paroxysmal extreme pain disorder mutation (I1461T) that destabilizes fast inactivation. Whole cell patch clamp recordings were used to examine the activity of channels expressed in human embryonic kidney 293 cells. KEY RESULTS Depolarizing pulses that increased slow inactivation of Nav1.7 channels also reduced lidocaine inhibition. Lidocaine enhanced recovery of Nav1.7 channels from prolonged depolarizing pulses by decreasing slow inactivation. A paroxysmal extreme pain disorder mutation that destabilizes fast inactivation of Nav1.7 channels decreased lidocaine inhibition. CONCLUSIONS AND IMPLICATIONS Lidocaine decreased the transition of Nav1.7 channels to the slow inactivated state. The fast inactivation gate (domain III–IV linker) is important for potentiating the interaction of lidocaine with the Nav1.7 channel. PMID:21232038

Neuromuscular plasticity in the locust after permanent removal of an excitatory motoneuron of the extensor tibiae muscle.

PubMed

Büschges, A; Djokaj, S; Bässler, D; Bässler, U; Rathmayer, W

2000-01-01

The capacity of the larval insect nervous system to compensate for the permanent loss of one of the two excitatory motoneurons innervating a leg muscle was investigated in the locust (Locusta migratoria). In the fourth instar, the fast extensor tibiae (FETi) motoneuron in the mesothoracic ganglion was permanently removed by photoinactivation with a helium-cadmium laser. Subsequently, the animals were allowed to develop into adulthood. When experimental animals were tested as adults after final ecdysis, fast-contracting fibers in the most proximal region of the corresponding extensor muscle, which are normally predominantly innervated by FETi only, uniformly responded to activity of the slow extensor tibiae (SETi) neuron. In adult operated animals, single pulses to SETi elicited large junctional responses in the fibers which resulted in twitch contractions of these fibers similar to the responses to FETi activity in control animals. The total number of muscle fibers, their properties as histochemically determined contractional types (fast and slow), and their distribution were not affected by photoinactivation of FETi. Possible mechanisms enabling the larval neuromuscular system to compensate for the loss of FETi through functionally similar innervation by a different motoneuron, i.e. SETi, are discussed. Copyright 2000 John Wiley & Sons, Inc.

Histone deacetylase degradation andMEF2 activation promote the formation of slow-twitch myofibers

PubMed Central

Potthoff, Matthew J.; Wu, Hai; Arnold, Michael A.; Shelton, John M.; Backs, Johannes; McAnally, John; Richardson, James A.; Bassel-Duby, Rhonda; Olson, Eric N.

2007-01-01

Skeletal muscle is composed of heterogeneous myofibers with distinctive rates of contraction, metabolic properties, and susceptibility to fatigue. We show that class II histone deacetylase (HDAC) proteins, which function as transcriptional repressors of the myocyte enhancer factor 2 (MEF2) transcription factor, fail to accumulate in the soleus, a slow muscle, compared with fast muscles (e.g., white vastus lateralis). Accordingly, pharmacological blockade of proteasome function specifically increases expression of class II HDAC proteins in the soleus in vivo. Using gain- and loss-of-function approaches in mice, we discovered that class II HDAC proteins suppress the formation of slow twitch, oxidative myofibers through the repression of MEF2 activity. Conversely, expression of a hyperactive form of MEF2 in skeletal muscle of transgenic mice promotes the formation of slow fibers and enhances running endurance, enabling mice to run almost twice the distance of WT littermates. Thus, the selective degradation of class II HDACs in slow skeletal muscle provides a mechanism for enhancing physical performance and resistance to fatigue by augmenting the transcriptional activity of MEF2. These findings provide what we believe are new insights into the molecular basis of skeletal muscle function and have important implications for possible therapeutic interventions into muscular diseases. PMID:17786239

Fast and slow shifts of the zonal-mean intertropical convergence zone in response to an idealized anthropogenic aerosol

DOE PAGES

Voigt, Aiko; Pincus, Robert; Stevens, Bjorn; ...

2017-04-03

Previous modeling work showed that aerosol can affect the position of the tropical rain belt, i.e., the intertropical convergence zone (ITCZ). Yet it remains unclear which aspects of the aerosol impact are robust across models, and which are not. Here we present simulations with seven comprehensive atmosphere models that study the fast and slow impacts of an idealized anthropogenic aerosol on the zonal-mean ITCZ position. The fast impact, which results from aerosol atmospheric heating and land cooling before sea-surface temperature (SST) has time to respond, causes a northward ITCZ shift. Yet the fast impact is compensated locally by decreased evaporationmore » over the ocean, and a clear northward shift is only found for an unrealistically large aerosol forcing. The local compensation implies that while models differ in atmospheric aerosol heating, this does not contribute to model differences in the ITCZ shift. The slow impact includes the aerosol impact on the ocean surface energy balance and is mediated by SST changes. The slow impact is an order of magnitude more effective than the fast impact and causes a clear southward ITCZ shift for realistic aerosol forcing. Models agree well on the slow ITCZ shift when perturbed with the same SST pattern. However, an energetic analysis suggests that the slow ITCZ shifts would be substantially more model-dependent in interactive-SST setups due to model differences in clear-sky radiative transfer and clouds. In conclusion, we also discuss implications for the representation of aerosol in climate models and attributions of recent observed ITCZ shifts to aerosol.« less

Mechanisms of High-Temperature Fatigue Failure in Alloy 800H

NASA Technical Reports Server (NTRS)

BhanuSankaraRao, K.; Schuster, H.; Halford, G. R.

1996-01-01

The damage mechanisms influencing the axial strain-controlled Low-Cycle Fatigue (LCF) behavior of alloy 800H at 850 C have been evaluated under conditions of equal tension/compression ramp rates (Fast-Fast (F-F): 4 X 10(sup -3)/s and Slow-Slow (S-S): 4 X 10(sup -5)/s) and asymmetrical ramp rates (Fast-Slow (F-S): 4 x 10(sup -3)/s / 4 X 10(sup -5/s and Slow-Fast (S-F): 4 X 10(sup -5) / 4 X 10(sup -3)/s) in tension and compression. The fatigue life, cyclic stress response, and fracture modes were significantly influenced by the waveform shape. The fatigue lives displayed by different loading conditions were in the following order: F-F greater than S-S greater than F-S greater than S-F. The fracture mode was dictated by the ramp rate adopted in the tensile direction. The fast ramp rate in the tensile direction led to the occurrence of transgranular crack initiation and propagation, whereas the slow ramp rate caused intergranular initiation and propagation. The time-dependent processes and their synergistic interactions, which were at the basis of observed changes in cyclic stress response and fatigue life, were identified. Oxidation, creep damage, dynamic strain aging, massive carbide precipitation, time-dependent creep deformation, and deformation ratcheting were among the several factors influencing cyclic life. Irrespective of the loading condition, the largest effect on life was exerted by oxidation processes. Deformation ratcheting had its greatest influence on life under asymmetrical loading conditions. Creep damage accumulated the greatest amount during the slow tensile ramp under S-F conditions.

Slow versus fast subcutaneous heparin injections for prevention of bruising and site-pain intensity.

PubMed

Akbari Sari, Ali; Janani, Leila; Mohammady, Mina; Nedjat, Saharnaz

2014-07-18

Heparin is an anticoagulant medication that is normally injected subcutaneously. Subcutaneous administration of heparin may result in complications such as bruising, haematoma and pain at the injection site. One of the factors that may affect pain, haematoma and bruising is injection speed. To assess the effects of the duration (speed) of subcutaneous heparin injection on pain, haematoma and bruising at the injection site in people admitted to hospitals or clinics who require treatment with unfractionated heparin or low molecular weight heparin. The Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched August 2013) and CENTRAL (2013, Issue 7). We searched MEDLINE, EMBASE, CINAHL and two Persian databases Iranmedex and SID (August 2013). We sought randomised controlled trials (RCTs) comparing the effects of different durations of subcutaneous injections of heparin on pain, bruising and haematoma at the injection site. Two review authors, working independently, extracted data onto a structured form and assessed study quality. We used the criteria recommended by the Cochrane Handbook to assess the quality of included studies. The study outcomes were summarised using quantitative and qualitative methods. One RCT was identified which met the inclusion criteria, involving 50 participants with a mean age of 55.25 (± 12.37) years. In this trial it was not possible to blind the participants and care givers. The method of sequence generation and allocation concealment was not described. The overall quality of the evidence was moderate due to the single small included study. Each participant had two injections, one in the left side and one in right side of the abdomen. One of these was injected slowly (intervention) and the other was injected fast (control). The second injection was 12 hours after the first injection. The duration of fast injection was 10 seconds and the duration of slow injection was 30 seconds. The study reported a significantly lower pain intensity for slow versus fast injection. The mean pain intensity was 13.9 ± 17.1 mm with the slow injection and 20.6 ± 22.3 mm with the fast injection (P < 0.001). In addition the bruising sizes were smaller with slow injections compared to fast injections at 48 hours follow-up (mean bruising size 18.76 ± 9.32 mm(2) with the slow injection and 109.2 ± 468.66 mm(2) with the fast injection, P = 0.033) and 72 hours follow-up (mean bruising size 21.72 ± 76.16 mm(2) with the slow injection and 110.12 ± 472.86 mm(2) with the fast injection, P = 0.025). The incidence of haematoma was not measured as an outcome. There is only limited evidence of any difference in pain intensity and bruising sizes following slow versus fast injections due to the inclusion of only one small unblinded trial. The single included study suggests that slow injection might have slightly lower pain intensity and bruising size at the heparin injection site, but the results should be considered with caution. Until more reliable evidence emerges, slow injection might be the preferred approach.

SDSS-IV MaNGA: a distinct mass distribution explored in slow-rotating early-type galaxies

NASA Astrophysics Data System (ADS)

Rong, Yu; Li, Hongyu; Wang, Jie; Gao, Liang; Li, Ran; Ge, Junqiang; Jing, Yingjie; Pan, Jun; Fernández-Trincado, J. G.; Valenzuela, Octavio; Ortíz, Erik Aquino

2018-06-01

We study the radial acceleration relation (RAR) for early-type galaxies (ETGs) in the SDSS MaNGA MPL5 data set. The complete ETG sample show a slightly offset RAR from the relation reported by McGaugh et al. (2016) at the low-acceleration end; we find that the deviation is due to the fact that the slow rotators show a systematically higher acceleration relation than the McGaugh's RAR, while the fast rotators show a consistent acceleration relation to McGaugh's RAR. There is a 1σ significant difference between the acceleration relations of the fast and slow rotators, suggesting that the acceleration relation correlates with the galactic spins, and that the slow rotators may have a different mass distribution compared with fast rotators and late-type galaxies. We suspect that the acceleration relation deviation of slow rotators may be attributed to more galaxy merger events, which would disrupt the original spins and correlated distributions of baryons and dark matter orbits in galaxies.

Proprioceptive reaction times and long-latency reflexes in humans.

PubMed

Manning, C D; Tolhurst, S A; Bawa, P

2012-08-01

The stretch of upper limb muscles results in two electromyographic (EMG) peaks, M1 and M2. The amplitude of M2 peak can generally be modified by giving prior instruction to the subject on how to react to the applied perturbation. The unresolved question is whether the amplitude modulation results from change in the gain of the reflex pathway contributing to M2, or by superposition of reaction time (RT) activity. The following study attempted to resolve this question by examining the overlap between proprioceptive RT and M2 activities. Subject's right wrist flexors were stretched, and he/she was instructed either (1) not to intervene (passive task) or (2) to react as fast as possible by simultaneously flexing both wrists (active or compensate task). Under passive and active conditions, M1 and M2 were observed from EMG of right wrist flexors, and during the active condition, RT activities were additionally observed from both sides. The onset and offset of M2 (M1(onset), M2(offset)) were measured from the passive averages, while the RT was measured from the averaged EMG response of the left wrist flexors. For between-subject correlations, the data were divided into two sets: (1) subjects with RT shorter than M2(offset) (fast group) and (2) subjects with RT more than 10 ms longer than their M2(offset) (slow group). Modulation during M2 period was large for the fast group, and it was almost zero for the slow group. These results indicate that the superimposition of RT activity mainly contributes to the instruction-dependent modulation of M2 peak.

Finite Element Analysis of a Highly Flexible Flapping Wing

DTIC Science & Technology

2013-03-01

normal operating conditions the duck was powered by a rechargeable lithium- ion battery. Placing this battery in a vacuum could be potentially hazardous ...Figure 26. Wingtip trace for (a) albatross fast gait, (b) pigeon slow gait, (c) horseshoe bat fast gait, (d) horseshoe bat slow gait, (e) blowfly, (f

CONTROL SYSTEM FOR NEUTRONIC REACTORS

DOEpatents

Crever, F.E.

1962-05-01

BS>A slow-acting shim rod for control of major variations in reactor neutron flux and a fast-acting control rod to correct minor flux variations are employed to provide a sensitive, accurate control system. The fast-acting rod is responsive to an error signal which is produced by changes in the neutron flux from a predetermined optimum level. When the fast rod is thus actuated in a given direction, means is provided to actuate the slow-moving rod in that direction to return the fast rod to a position near the midpoint of its control range. (AEC)

Evaluation of Visual Alerts in the Maritime Domain. Study 2. Program Modifications

DTIC Science & Technology

2009-02-01

feedback that they were wrong, and without consulting the Status screen again enter the alternate answer (“ qwe ”). That is, the need to consult the...Neutral Large Slow No QWE Hostile Small Fast Yes ASD DRDC Atlantic CR 2008-268 5 Table 3. First proposed target types and...classification scheme. Target Size Speed Weapons Flag Response Type Neutral Large Slow No Other QWE Hostile Small Fast Yes Other ASD Friendly Large/Small Slow

Complex interplay of body condition, life history, and prevailing environment shapes immune defenses of garter snakes in the wild.

PubMed

Palacios, Maria G; Cunnick, Joan E; Bronikowski, Anne M

2013-01-01

The immunocompetence "pace-of-life" hypothesis proposes that fast-living organisms should invest more in innate immune defenses and less in adaptive defenses compared to slow-living ones. We found some support for this hypothesis in two life-history ecotypes of the snake Thamnophis elegans; fast-living individuals show higher levels of innate immunity compared to slow-living ones. Here, we optimized a lymphocyte proliferation assay to assess the complementary prediction that slow-living snakes should in turn show stronger adaptive defenses. We also assessed the "environmental" hypothesis that predicts that slow-living snakes should show lower levels of immune defenses (both innate and adaptive) given the harsher environment they live in. Proliferation of B- and T-lymphocytes of free-living individuals was on average higher in fast-living than slow-living snakes, opposing the pace-of-life hypothesis and supporting the environmental hypothesis. Bactericidal capacity of plasma, an index of innate immunity, did not differ between fast-living and slow-living snakes in this study, contrasting the previously documented pattern and highlighting the importance of annual environmental conditions as determinants of immune profiles of free-living animals. Our results do not negate a link between life history and immunity, as indicated by ecotype-specific relationships between lymphocyte proliferation and body condition, but suggest more subtle nuances than those currently proposed.

A comparative study of charge movement in rat and frog skeletal muscle fibres.

PubMed

Hollingworth, S; Marshall, M W

1981-12-01

1. The middle of the fibre voltage--clamp technique (Adrian & Marshall, 1977), modified where necessary for electrically short muscle fibres, has been used to measure non-linear charge movements in mammalian fast twitch (rat extensor digitorum longus), mammalian slow twitch (rat soleus) and frog (sartorius) muscles. 2. The maximum amount of charge moved in mammalian fast twitch muscle at 2 degrees C in hypertonic solution, was 3--5 times greater than in slow twitch muscle. The voltage distribution of fast twitch charge was 10--15 mV more positive when compared to slow twitch. 3. In both mammalian muscle types hypertonic Ringer solution negatively shifted the voltage distribution of charge some 6 mV. The steepness of charge moved around mechanical threshold was unaffected by hypertonicity. 4. The amount of charge in frog sartorius fibres at 2 degrees C in hypertonic solution was about half of that in rat fast twitch muscle; the voltage distribution of the frog charge was similar to rat soleus muscle. 5. Warming between 2 and 15 degrees C had no effect on either the amount of steady-state distribution of charge in mammalian or frog muscles. 6. At 2 degrees C, the kinetics of charge movement in fast and slow twitch mammalian muscles were similar and 2--3 times faster than frog muscle at the same temperature. In fast and slow mammalian fibres at 2 degrees C similar times were taken to shift the same fractions of the total amount of charge. The Q10 of charge movement kinetics was between 1.2 and 2.0 in the three muscles studied.

From single muscle fiber to whole muscle mechanics: a finite element model of a muscle bundle with fast and slow fibers.

PubMed

Marcucci, Lorenzo; Reggiani, Carlo; Natali, Arturo N; Pavan, Piero G

2017-12-01

Muscles exhibit highly complex, multi-scale architecture with thousands of muscle fibers, each with different properties, interacting with each other and surrounding connective structures. Consequently, the results of single-fiber experiments are scarcely linked to the macroscopic or whole muscle behavior. This is especially true for human muscles where it would be important to understand of how skeletal muscles disorders affect patients' life. In this work, we developed a mathematical model to study how fast and slow muscle fibers, well characterized in single-fiber experiments, work and generate together force and displacement in muscle bundles. We characterized the parameters of a Hill-type model, using experimental data on fast and slow single human muscle fibers, and comparing experimental data with numerical simulations obtained from finite element (FE) models of single fibers. Then, we developed a FE model of a bundle of 19 fibers, based on an immunohistochemically stained cross section of human diaphragm and including the corresponding properties of each slow or fast fiber. Simulations of isotonic contractions of the bundle model allowed the generation of its apparent force-velocity relationship. Although close to the average of the force-velocity curves of fast and slow fibers, the bundle curve deviates substantially toward the fast fibers at low loads. We believe that the present model and the characterization of the force-velocity curve of a fiber bundle represents the starting point to link the single-fiber properties to those of whole muscle with FE application in phenomenological models of human muscles.

Understanding the Origins of Higher Capacities at Faster Rates in Lithium-Excess Li xNi 2–4x/3Sb x/3O 2

DOE PAGES

Twu, Nancy; Metzger, Michael; Balasubramanian, Mahalingam; ...

2017-02-08

Here, the lithium-excess Li xNi 2-4x/3Sb x/3O 2 (LNSO) materials were previously shown to demonstrate higher capacities and improved cyclability with increasing lithium content. While the performance trend is promising, observed capacities are much lower than theoretical capacities, pointing to a need for further understanding of active redox processes in these materials. In this work, we study the electrochemical behavior of the LNSO materials as a function of lithium content and at slow and fast rates. Surprisingly, Li 1.15Ni 0.47Sb 0.38O 2 (LNSO-15) exhibits higher discharge capacities at faster rates and traverses distinct voltage curves at slow and fast rates.more » To understand these two peculiarities, we characterize the redox activity of nickel, antimony, and oxygen at different rates. While experiments confirm some nickel redox activity and oxygen loss, these two mechanisms cannot account for all observed capacity. We propose that the balance of the observed capacity may be due reversible oxygen redox and that the rate-dependent voltage curve features may derive from irreversible nickel migration occurring on slow charge. As future high energy density cathodes are likely to contain both lithium excess and high nickel content, both of these findings have important implications for the development of novel high capacity cathode materials.« less

Chronic clenbuterol treatment compromises force production without directly altering skeletal muscle contractile machinery

PubMed Central

Py, G; Ramonatxo, C; Sirvent, P; Sanchez, A M J; Philippe, A G; Douillard, A; Galbès, O; Lionne, C; Bonnieu, A; Chopard, A; Cazorla, O; Lacampagne, A; Candau, R B

2015-01-01

Clenbuterol is a β2-adrenergic receptor agonist known to induce skeletal muscle hypertrophy and a slow-to-fast phenotypic shift. The aim of the present study was to test the effects of chronic clenbuterol treatment on contractile efficiency and explore the underlying mechanisms, i.e. the muscle contractile machinery and calcium-handling ability. Forty-three 6-week-old male Wistar rats were randomly allocated to one of six groups that were treated with either subcutaneous equimolar doses of clenbuterol (4 mg kg−1 day−1) or saline solution for 9, 14 or 21 days. In addition to the muscle hypertrophy, although an 89% increase in absolute maximal tetanic force (Po) was noted, specific maximal tetanic force (sPo) was unchanged or even depressed in the slow twitch muscle of the clenbuterol-treated rats (P < 0.05). The fit of muscle contraction and relaxation force kinetics indicated that clenbuterol treatment significantly reduced the rate constant of force development and the slow and fast rate constants of relaxation in extensor digitorum longus muscle (P < 0.05), and only the fast rate constant of relaxation in soleus muscle (P < 0.05). Myofibrillar ATPase activity increased in both relaxed and activated conditions in soleus (P < 0.001), suggesting that the depressed specific tension was not due to the myosin head alteration itself. Moreover, action potential-elicited Ca2+ transients in flexor digitorum brevis fibres (fast twitch fibres) from clenbuterol-treated animals demonstrated decreased amplitude after 14 days (−19%, P < 0.01) and 21 days (−25%, P < 0.01). In conclusion, we showed that chronic clenbuterol treatment reduces contractile efficiency, with altered contraction and relaxation kinetics, but without directly altering the contractile machinery. Lower Ca2+ release during contraction could partially explain these deleterious effects. PMID:25656230

Two coffins and a funeral: early or late caspase activation determines two types of apoptosis induced by DNA damaging agents.

PubMed

Oropesa-Ávila, Manuel; de la Cruz-Ojeda, Patricia; Porcuna, Jesús; Villanueva-Paz, Marina; Fernández-Vega, Alejandro; de la Mata, Mario; de Lavera, Isabel; Rivero, Juan Miguel Suarez; Luzón-Hidalgo, Raquel; Álvarez-Córdoba, Mónica; Cotán, David; Zaderenko, Ana Paula; Cordero, Mario D; Sánchez-Alcázar, José A

2017-03-01

Cell cytoskeleton makes profound changes during apoptosis including the organization of an Apoptotic Microtubule Network (AMN). AMN forms a cortical structure which plays an important role in preserving plasma membrane integrity during apoptosis. Here, we examined the cytoskeleton rearrangements during apoptosis induced by camptothecin (CPT), a topoisomerase I inhibitor, in human H460 and porcine LLCPK-1α cells. Using fixed and living cell imaging, we showed that CPT induced two dose- and cell cycle-dependent types of apoptosis characterized by different cytoskeleton reorganizations, time-dependent caspase activation and final apoptotic cell morphology. In the one referred as "slow" (~h) or round-shaped, apoptosis was characterized by a slow contraction of the actinomyosin ring and late caspase activation. In "slow" apoptosis the γ-tubulin complexes were not disorganized and microtubules were not depolymerized at early stages. In contrast, "fast" (~min) or irregular-shaped apoptosis was characterized by early caspase activation followed by full contraction of the actinomyosin ring. In fast apoptosis γ-tubulin complexes were disorganized and microtubules were initially depolymerized. However, after actinomyosin contraction, microtubules were reformed adopting a cortical but irregular disposition near plasma membrane. In addition to distinctive cytoskeleton reorganization kinetics, round and irregular-shaped apoptosis showed different biological properties with respect to AMN maintenance, plasma membrane integrity and phagocytes response. Our results suggest that the knowledge and modulation of the type of apoptosis promoted by genotoxic agents may be important for deciding a better therapeutic option and predicting the immune response in cancer treatment.

Deficiency of slow skeletal muscle troponin T causes atrophy of type I slow fibres and decreases tolerance to fatigue.

PubMed

Wei, Bin; Lu, Yingru; Jin, J-P

2014-03-15

The total loss of slow skeletal muscle troponin T (ssTnT encoded by TNNT1 gene) due to a nonsense mutation in codon Glu(180) causes a lethal form of recessively inherited nemaline myopathy (Amish nemaline myopathy, ANM). To investigate the pathogenesis and muscle pathophysiology of ANM, we studied the phenotypes of partial and total loss of ssTnT in Tnnt1 gene targeted mice. An insertion of neomycin resistance cassette in intron 10 of Tnnt1 gene caused an approximately 60% decrease in ssTnT protein expression whereas cre-loxP-mediated deletion of exons 11-13 resulted in total loss of ssTnT, as seen in ANM muscles. In diaphragm and soleus muscles of the knockdown and knockout mouse models, we demonstrated that ssTnT deficiency resulted in significantly decreased levels of other slow fibre-specific myofilament proteins whereas fast fibre-specific myofilament proteins were increased correspondingly. Immunohistochemical studies revealed that ssTnT deficiency produced significantly smaller type I slow fibres and compensatory growth of type II fast fibres. Along with the slow fibre atrophy and the changes in myofilament protein isoform contents, ssTnT deficiency significantly reduced the tolerance to fatigue in soleus muscle. ssTnT-deficient soleus muscle also contains significant numbers of small-sized central nuclei type I fibres, indicating active regeneration. The data provide strong support for the essential role of ssTnT in skeletal muscle function and the causal effect of its loss in the pathology of ANM. This observation further supports the hypothesis that the function of slow fibres can be restored in ANM patients if a therapeutic supplement of ssTnT is achieved.

Deficiency of slow skeletal muscle troponin T causes atrophy of type I slow fibres and decreases tolerance to fatigue

PubMed Central

Wei, Bin; Lu, Yingru; Jin, J-P

2014-01-01

The total loss of slow skeletal muscle troponin T (ssTnT encoded by TNNT1 gene) due to a nonsense mutation in codon Glu180 causes a lethal form of recessively inherited nemaline myopathy (Amish nemaline myopathy, ANM). To investigate the pathogenesis and muscle pathophysiology of ANM, we studied the phenotypes of partial and total loss of ssTnT in Tnnt1 gene targeted mice. An insertion of neomycin resistance cassette in intron 10 of Tnnt1 gene caused an approximately 60% decrease in ssTnT protein expression whereas cre-loxP-mediated deletion of exons 11–13 resulted in total loss of ssTnT, as seen in ANM muscles. In diaphragm and soleus muscles of the knockdown and knockout mouse models, we demonstrated that ssTnT deficiency resulted in significantly decreased levels of other slow fibre-specific myofilament proteins whereas fast fibre-specific myofilament proteins were increased correspondingly. Immunohistochemical studies revealed that ssTnT deficiency produced significantly smaller type I slow fibres and compensatory growth of type II fast fibres. Along with the slow fibre atrophy and the changes in myofilament protein isoform contents, ssTnT deficiency significantly reduced the tolerance to fatigue in soleus muscle. ssTnT-deficient soleus muscle also contains significant numbers of small-sized central nuclei type I fibres, indicating active regeneration. The data provide strong support for the essential role of ssTnT in skeletal muscle function and the causal effect of its loss in the pathology of ANM. This observation further supports the hypothesis that the function of slow fibres can be restored in ANM patients if a therapeutic supplement of ssTnT is achieved. PMID:24445317

Slow Wave Sleep Induced by GABA Agonist Tiagabine Fails to Benefit Memory Consolidation

PubMed Central

Feld, Gordon B.; Wilhelm, Ines; Ma, Ying; Groch, Sabine; Binkofski, Ferdinand; Mölle, Matthias; Born, Jan

2013-01-01

Study Objectives: Slow wave sleep (SWS) plays a pivotal role in consolidating memories. Tiagabine has been shown to increase SWS in favor of REM sleep without impacting subjective sleep. However, it is unknown whether this effect is paralleled by an improved sleep-dependent consolidation of memory. Design: This double-blind within-subject crossover study tested sensitivity of overnight retention of declarative neutral and emotional materials (word pairs, pictures) as well as a procedural memory task (sequence finger tapping) to oral administration of placebo or 10 mg tiagabine (at 22:30). Participants: Fourteen healthy young men aged 21.9 years (range 18-28 years). Measurements and Results: Tiagabine significantly increased the time spent in SWS and decreased REM sleep compared to placebo. Tiagabine also enhanced slow wave activity (0.5-4.0 Hz) and density of < 1 Hz slow oscillations during NREM sleep. Fast (12-15 Hz) and slow (9-12 Hz) spindle activity, in particular that occurring phase-locked to the slow oscillation cycle, was decreased following tiagabine. Despite signs of deeper and more SWS, overnight retention of memory tested after sleep the next evening (19:30) was generally not improved after tiagabine, but on average even lower than after placebo, with this impairing effect reaching significance for procedural sequence finger tapping. Conclusions: Our data show that increasing slow wave sleep with tiagabine does not improve memory consolidation. Possibly this is due to functional differences from normal slow wave sleep, i.e., the concurrent suppressive influence of tiagabine on phase-locked spindle activity. Citation: Feld GB; Wilhelm I; Ma Y; Groch S; Binkofski F; Mölle M; Born J. Slow wave sleep induced by GABA agonist tiagabine fails to benefit memory consolidation. SLEEP 2013;36(9):1317-1326. PMID:23997364

Slow and fast fatigable frog muscle fibres: electrophysiological and histochemical characteristics.

PubMed

Vydevska-Chichova, M; Mileva, K; Todorova, R; Dimitrova, M; Radicheva, N

2005-12-01

Continuous activity of isolated frog gastrocnemius muscle fibres provoked by repetitive stimulation of 5 Hz was used as an experimental model for fatigue development in different fibre types. Parameter changes of the elicited intracellular action potentials and mechanical twitches during the period of uninterrupted activity were used as criteria for fatigue evaluation. Slow fatigable muscle fibre (SMF) and fast fatigable muscle fibre (FMF) types were distinguished depending on the duration of their uninterrupted activity, which was significantly longer in SMFs than in FMFs. The normalized changes of action potential amplitude and duration were significantly smaller in FMFs than in SMFs. The average twitch force and velocity of contraction and relaxation were significantly higher in FMFs than in SMFs. Myosin ATPase (mATPase) and succinate dehydrogenase activity were studied by histochemical assessment in order to validate the fibre type classification based on their electrophysiological characteristics. Based on the relative mATPase reactivity, the fibres of the studied muscle were classified as one of five different types (1-2, 2, 2-3, 3 and tonic). Smaller sized fibres (tonic and type 3) expressed higher succinate dehydrogenase activity than larger sized fibres (type 1-2, 2), which is related to the fatigue resistance. The differences between fatigue development in SMFs and FMFs during continuous activity were associated with fibre-type specific mATPase and succinate dehydrogenase activity.

Effects of chronic Akt/mTOR inhibition by rapamycin on mechanical overload-induced hypertrophy and myosin heavy chain transition in masseter muscle.

PubMed

Umeki, Daisuke; Ohnuki, Yoshiki; Mototani, Yasumasa; Shiozawa, Kouichi; Fujita, Takayuki; Nakamura, Yoshiki; Saeki, Yasutake; Okumura, Satoshi

2013-01-01

To examine the effects of the Akt/mammalian target of rapamycin (mTOR) pathway on masseter muscle hypertrophy and myosin heavy chain (MHC) transition in response to mechanical overload, we analyzed the effects of bite-opening (BO) on the hypertrophy and MHC composition of masseter muscle of BO-rats treated or not treated with rapamycin (RAPA), a selective mTOR inhibitor. The masseter muscle weight in BO-rats was significantly greater than that in controls, and this increase was attenuated by RAPA treatment. Expression of slow-twitch MHC isoforms was significantly increased in BO-rats with/without RAPA treatment, compared with controls, but the magnitude of the increase was much smaller in RAPA-treated BO-rats. Phosphorylation of p44/42 MAPK (ERK1/2), which preserves fast-twitch MHC isoforms in skeletal muscle, was significantly decreased in BO-rats, but the decrease was abrogated by RAPA treatment. Calcineurin signaling is known to be important for masseter muscle hypertrophy and fast-to-slow MHC isoform transition, but expression of known calcineurin activity modulators was unaffected by RAPA treatment. Taken together, these results indicate that the Akt/mTOR pathway is involved in both development of masseter muscle hypertrophy and fast-to-slow MHC isoform transition in response to mechanical overload with inhibition of the ERK1/2 pathway and operates independently of the calcineurin pathway.

Removal of sodium inactivation and block of sodium channels by chloramine-T in crayfish and squid giant axons.

PubMed Central

Huang, J. M.; Tanguy, J.; Yeh, J. Z.

1987-01-01

Modification of sodium channels by chloramine-T was examined in voltage clamped internally perfused crayfish and squid giant axons using the double sucrose gap and axial wire technique, respectively. Freshly prepared chloramine-T solution exerted two major actions on sodium channels: (a) an irreversible removal of the fast Na inactivation, and (b) a reversible block of the Na current. Both effects were observed when chloramine-T was applied internally or externally (5-10 mM) to axons. The first effect was studied in crayfish axons. We found that the removal of the fast Na inactivation did not depend on the states of the channel since the channel could be modified by chloramine-T at holding potential (from -80 to -100 mV) or at depolarized potential of -30 mV. After removal of fast Na inactivation, the slow inactivation mechanism was still present, and more channels could undergo slow inactivation. This result indicates that in crayfish axons the transition through the fast inactivated state is not a prerequisite for the slow inactivation to occur. During chloramine-T treatment, a distinct blocking phase occurred, which recovered upon washing out the drug. This second effect of chloramine-T was studied in detail in squid axons. After 24 h, chloramine-T solution lost its ability to remove fast inactivation but retained its blocking action. After removal of the fast Na inactivation, both fresh and aged chloramine-T solutions blocked the Na currents with a similar potency and in a voltage-dependent manner, being more pronounced at lower depolarizing potentials. A similar voltage-dependent block was observed with aged chloramine-T solution in an axon with intact inactivation. In contrast to the action of the fresh solution, the aged chloramine-T solution was found to accelerate the decay of Na currents.These results suggest that chloramine-T solution contains at least two active molecular forms that act at different sites in the Na channel. PMID:2444276

Slow sleep spindle and procedural memory consolidation in patients with major depressive disorder.

PubMed

Nishida, Masaki; Nakashima, Yusaku; Nishikawa, Toru

2016-01-01

Evidence has accumulated, which indicates that, in healthy individuals, sleep enhances procedural memory consolidation, and that sleep spindle activity modulates this process. However, whether sleep-dependent procedural memory consolidation occurs in patients medicated for major depressive disorder remains unclear, as are the pharmacological and physiological mechanisms that underlie this process. Healthy control participants (n=17) and patients medicated for major depressive disorder (n=11) were recruited and subjected to a finger-tapping motor sequence test (MST; nondominant hand) paradigm to compare the averaged scores of different learning phases (presleep, postsleep, and overnight improvement). Participants' brain activity was recorded during sleep with 16 electroencephalography channels (between MSTs). Sleep scoring and frequency analyses were performed on the electroencephalography data. Additionally, we evaluated sleep spindle activity, which divided the spindles into fast-frequency spindle activity (12.5-16 Hz) and slow-frequency spindle activity (10.5-12.5 Hz). Sleep-dependent motor memory consolidation in patients with depression was impaired in comparison with that in control participants. In patients with depression, age correlated negatively with overnight improvement. The duration of slow-wave sleep correlated with the magnitude of motor memory consolidation in patients with depression, but not in healthy controls. Slow-frequency spindle activity was associated with reduction in the magnitude of motor memory consolidation in both groups. Because the changes in slow-frequency spindle activity affected the thalamocortical network dysfunction in patients medicated for depression, dysregulated spindle generation may impair sleep-dependent memory consolidation. Our findings may help to elucidate the cognitive deficits that occur in patients with major depression both in the waking state and during sleep.

Slow Sleep Spindle Activity, Declarative Memory, and General Cognitive Abilities in Children

PubMed Central

Hoedlmoser, Kerstin; Heib, Dominik P.J.; Roell, Judith; Peigneux, Philippe; Sadeh, Avi; Gruber, Georg; Schabus, Manuel

2014-01-01

Study Objectives: Functional interactions between sleep spindle activity, declarative memory consolidation, and general cognitive abilities in school-aged children. Design: Healthy, prepubertal children (n = 63; mean age 9.56 ± 0.76 y); ambulatory all-night polysomnography (2 nights); investigating the effect of prior learning (word pair association task; experimental night) versus nonlearning (baseline night) on sleep spindle activity; general cognitive abilities assessed using the Wechsler Intelligence Scale for Children-IV (WISC-IV). Measurements and Results: Analysis of spindle activity during nonrapid eye movement sleep (N2 and N3) evidenced predominant peaks in the slow (11-13 Hz) but not in the fast (13-15 Hz) sleep spindle frequency range (baseline and experimental night). Analyses were restricted to slow sleep spindles. Changes in spindle activity from the baseline to the experimental night were not associated with the overnight change in the number of recalled words reflecting declarative memory consolidation. Children with higher sleep spindle activity as measured at frontal, central, parietal, and occipital sites during both baseline and experimental nights exhibited higher general cognitive abilities (WISC-IV) and declarative learning efficiency (i.e., number of recalled words before and after sleep). Conclusions: Slow sleep spindles (11-13 Hz) in children age 8–11 y are associated with inter-individual differences in general cognitive abilities and learning efficiency. Citation: Hoedlmoser K, Heib DPJ, Roell J, Peigneux P, Sadeh A, Gruber G, Schabus M. Slow sleep spindle activity, declarative memory, and general cognitive abilities in children. SLEEP 2014;37(9):1501-1512. PMID:25142558

Interaction of solitons for obliquely propagating magnetoacoustic waves in stellar atmosphere

NASA Astrophysics Data System (ADS)

Jahangir, R.; Masood, W.; Siddiq, M.; Batool, Nazia

2016-12-01

We study here the nonlinear oblique propagation of magnetoacoustic waves in dense plasmas with degenerate electrons by deriving Kadomtsev-Petviashvili (KP) equation for small but finite amplitude perturbations. The two soliton interaction has been studied by finding the solution of the KP equation using the Hirota bilinear formalism. For illustrative purposes, we have used the plasma parameters typically found in white dwarf stars for both the fast and slow modes of magnetoacoustic waves. It has been observed that the soliton interaction in the fast and slow modes is strongly influenced by the predominant and weak dispersive coefficients of the KP equation. The single soliton behavior has also been explained for the fast and slow magnetoacoustic modes.

Metabolic adaptation of skeletal muscles to gravitational unloading

NASA Astrophysics Data System (ADS)

Ohira, Y.; Yasui, W.; Kariya, F.; Wakatsuki, T.; Nakamura, K.; Asakura, T.; Edgerton, V. R.

Responses of high-energy phosphates and metabolic properties to hindlimb suspension were studied in adult rats. The relative content of phosphocreatine (PCr) in the calf muscles was significantly higher in rats suspended for 10 days than in age-matched cage controls. The Pi/PCr ratio, where Pi is inorganic phosphate, in suspended muscles was less than controls. The absolute weights of soleus and medial gastrocnemius (MG) were approximately 40% less than controls. Although the % fiber distribution in MG was unchanged, the % slow fibers decreased and the % fibers which were classified as both slow and fast was increased in soleus. The activities (per unit weight or protein) of succinate dehydrogenase and lactate dehydrogenase in soleus were unchanged but those of cytochrome oxidase, β-hydroxyacyl CoA dehydrogenase, and citrate synthase were decreased following unloading. None of these enzyme activities in MG changed. However, the total levels of all enzymes in whole muscles decreased by suspension. It is suggested that shift of slow muscle toward fast type by unloading is associated with a decrease in mitochondrial biogenesis. Further, gravitational unloading affected the levels of muscle proteins differently even in the same mitochondrial enzymes. Unloading-related atrophy is prominent in red muscle or slow-twitch fiber 1, 2. Such atrophy is accompanied by a shift of contractile properties toward fast-twitch type 2-9. Further, inhibition of mitochondrial metabolism in these muscles is also reported by some studies 10-14 suggesting a lowered mitochondrial biogenesis, although results from some studies do not necessarily agree 1, 7, 15. However, the precise mechanism responsible for such alterations of muscle properties in response to gravitational unloading is unclear. On the contrary, mitochondrial biogenesis, suggested by mitochondrial enzyme activities and/or mass, is stimulated in muscles with depleted high-energy phosphates by cold exposure 16 and/or by feeding creatine analogue β-guanidinopropionic acid 17-19. Tension production may be inhibited in unloaded antigravity muscles 20, although the muscular activity detected by electromyography is not necessarily decreased 21. Thus, the contents of high-energy phosphates or turnover rate of adenosine triphosphate (ATP), which then affect the mitochondrial energy metabolism, may be altered. Therefore, the responses of high-energy phosphates and metabolic properties of rat hindlimb muscles to gravitational unloading were investigated.

Fast to forgive, slow to retaliate: intuitive responses in the ultimatum game depend on the degree of unfairness.

PubMed

Ferguson, Eamonn; Maltby, John; Bibby, Peter A; Lawrence, Claire

2014-01-01

Evolutionary accounts have difficulty explaining why people cooperate with anonymous strangers they will never meet. Recently models, focusing on emotional processing, have been proposed as a potential explanation, with attention focusing on a dual systems approach based on system 1 (fast, intuitive, automatic, effortless, and emotional) and system 2 (slow, reflective, effortful, proactive and unemotional). Evidence shows that when cooperation is salient, people are fast (system 1) to cooperate, but with longer delays (system 2) they show greed. This is interpreted within the framework of the social heuristic hypothesis (SHH), whereby people overgeneralize potentially advantageous intuitively learnt and internalization social norms to 'atypical' situations. We extend this to explore intuitive reactions to unfairness by integrating the SHH with the 'fast to forgive, slow to anger' (FFSA) heuristic. This suggests that it is advantageous to be prosocial when facing uncertainty. We propose that whether or not someone intuitively shows prosociality (cooperation) or retaliation is moderated by the degree (certainty) of unfairness. People should intuitively cooperate when facing mild levels of unfairness (fast to forgive) but when given longer to decide about another's mild level of unfairness should retaliate (slow to anger). However, when facing severe levels of unfairness, the intuitive response is always retaliation. We test this using a series of one-shot ultimatum games and manipulate level of offer unfairness (50:50 60:40, 70:30, 80:20, 90:10) and enforced time delays prior to responding (1s, 2s, 8s, 15s). We also measure decision times to make responses after the time delays. The results show that when facing mildly unfair offers (60:40) people are fast (intuitive) to cooperate but with longer delays reject these mildly unfair offers: 'fast to forgive, and slow to retaliate'. However, for severely unfair offers (90:10) the intuitive and fast response is to always reject.

Fast to Forgive, Slow to Retaliate: Intuitive Responses in the Ultimatum Game Depend on the Degree of Unfairness

PubMed Central

Ferguson, Eamonn; Maltby, John; Bibby, Peter A.; Lawrence, Claire

2014-01-01

Evolutionary accounts have difficulty explaining why people cooperate with anonymous strangers they will never meet. Recently models, focusing on emotional processing, have been proposed as a potential explanation, with attention focusing on a dual systems approach based on system 1 (fast, intuitive, automatic, effortless, and emotional) and system 2 (slow, reflective, effortful, proactive and unemotional). Evidence shows that when cooperation is salient, people are fast (system 1) to cooperate, but with longer delays (system 2) they show greed. This is interpreted within the framework of the social heuristic hypothesis (SHH), whereby people overgeneralize potentially advantageous intuitively learnt and internalization social norms to ‘atypical’ situations. We extend this to explore intuitive reactions to unfairness by integrating the SHH with the ‘fast to forgive, slow to anger’ (FFSA) heuristic. This suggests that it is advantageous to be prosocial when facing uncertainty. We propose that whether or not someone intuitively shows prosociality (cooperation) or retaliation is moderated by the degree (certainty) of unfairness. People should intuitively cooperate when facing mild levels of unfairness (fast to forgive) but when given longer to decide about another's mild level of unfairness should retaliate (slow to anger). However, when facing severe levels of unfairness, the intuitive response is always retaliation. We test this using a series of one-shot ultimatum games and manipulate level of offer unfairness (50:50 60:40, 70:30, 80:20, 90:10) and enforced time delays prior to responding (1s, 2s, 8s, 15s). We also measure decision times to make responses after the time delays. The results show that when facing mildly unfair offers (60:40) people are fast (intuitive) to cooperate but with longer delays reject these mildly unfair offers: ‘fast to forgive, and slow to retaliate’. However, for severely unfair offers (90:10) the intuitive and fast response is to always reject. PMID:24820479

Fermentation of Ammonia Fiber Expansion Treated and Untreated Barley Straw in a Rumen Simulation Technique Using Rumen Inoculum from Cattle with Slow versus Fast Rate of Fiber Disappearance.

PubMed

Griffith, Candace L; Ribeiro, Gabriel O; Oba, Masahito; McAllister, Tim A; Beauchemin, Karen A

2016-01-01

The purpose of this study was to determine the effect of rumen inoculum from heifers with fast vs. slow rate of in situ fiber digestion on the fermentation of complex versus easily digested fiber sources in the forms of untreated and Ammonia Fiber Expansion (AFEX) treated barley straw, respectively, using an artificial rumen simulation technique (Rusitec). In situ fiber digestion was measured in a previous study by incubating untreated barley straw in the rumen of 16 heifers fed a diet consisting of 700 g/kg barley straw and 300 g/kg concentrate. The two heifers with fastest rate of digestion (Fast ≥ 4.18% h -1 ) and the two heifers with the slowest rate of digestion (Slow ≤ 3.17% h -1 ) were chosen as inoculum donors for this study. Two Rusitec apparatuses each equipped with eight fermenters were used in a completely randomized block design with two blocks (apparatus) and four treatments in a 2 × 2 factorial arrangement of treatments (Fast or Slow rumen inoculum and untreated or AFEX treated straw). Fast rumen inoculum and AFEX straw both increased ( P < 0.05) disappearance of dry matter (DMD), organic matter, true DMD, neutral detergent fiber, acid detergent fiber, and nitrogen (N) with an interactive effect between the two ( P < 0.05). Fast rumen inoculum increased ( P > 0.05) methane production per gram of digested material for both untreated and AFEX straw, and reduced (interaction, P < 0.05) acetate: propionate ratio for untreated straw. Greater relative populations of Ruminococcus albus ( P < 0.05) and increased microbial N production ( P = 0.045) were observed in Fast rumen inoculum. AFEX straw in Fast inoculum had greater total bacterial populations than Slow, but for untreated straw this result was reversed (interaction, P = 0.013). These findings indicate that differences in microbial populations in rumen fluid contribute to differences in the capacity of rumen inoculum to digest fiber.

The current and ideal state of anatomic pathology patient safety.

PubMed

Raab, Stephen Spencer

2014-01-01

An anatomic pathology diagnostic error may be secondary to a number of active and latent technical and/or cognitive components, which may occur anywhere along the total testing process in clinical and/or laboratory domains. For the pathologist interpretive steps of diagnosis, we examine Kahneman's framework of slow and fast thinking to explain different causes of error in precision (agreement) and in accuracy (truth). The pathologist cognitive diagnostic process involves image pattern recognition and a slow thinking error may be caused by the application of different rationally-constructed mental maps of image criteria/patterns by different pathologists. This type of error is partly related to a system failure in standardizing the application of these maps. A fast thinking error involves the flawed leap from image pattern to incorrect diagnosis. In the ideal state, anatomic pathology systems would target these cognitive error causes as well as the technical latent factors that lead to error.

[Morphohistochemical study of skeletal muscles in rats after experimental flight on "Kosmos-1887"].

PubMed

Il'ina-Kakueva, E I

1990-01-01

Morphometric and histochemical methods were used to examine the soleus, gastrocnemius (medial portion), quadriceps femoris (central portion) and biceps brachii muscles of Wistar SPF rats two days after the 13-day flight on Cosmos-1887. It was found that significant atrophy developed only in the soleus muscle. The space flight did not change the percentage content of slow (type I) and fast (type II) fibers in fast twitch muscles. During two days at 1 g the slow soleus muscle developed substantial circulation disorders, which led to interstitial edema and necrotic changes. The gastrocnemius muscle showed small foci containing necrotic myofibers. Two days after recovery no glycogen aggregates were seen in myofibers, which were previously observed in other rats examined 4--8 hours after flight. An initial stage of muscle readaptation to 1 g occurred, when NAD.H2-dehydrogenase activity was decreased.

Calorie restriction enhances insulin-stimulated glucose uptake and Akt phosphorylation in both fast-twitch and slow-twitch skeletal muscle of 24-month-old rats.

PubMed

Sequea, Donel A; Sharma, Naveen; Arias, Edward B; Cartee, Gregory D

2012-12-01

Calorie restriction (CR) induces enhanced insulin-stimulated glucose uptake in fast-twitch (type II) muscle from old rats, but the effect of CR on slow-twitch (type I) muscle from old rats is unknown. The purpose of this study was to assess insulin-stimulated glucose uptake and phosphorylation of key insulin signaling proteins in isolated epitrochlearis (fast-twitch) and soleus (slow-twitch) muscles from 24-month-old ad libitum fed and CR (consuming 65% of ad libitum, intake) rats. Muscles were incubated with and without 1.2 nM insulin. CR versus ad libitum rats had greater insulin-stimulated glucose uptake and Akt phosphorylation (pAkt) on T308 and S473 for both muscles incubated with insulin. GLUT4 protein abundance and phosphorylation of the insulin receptor (Y1162/1163) and AS160 (T642) were unaltered by CR in both muscles. These results implicate enhanced pAkt as a potential mechanism for the CR-induced increase in insulin-stimulated glucose uptake by the fast-twitch epitrochlearis and slow-twitch soleus of old rats.

Fast and Slow Responses of the South Asian Monsoon System to Anthropogenic Aerosols

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

Ganguly, Dilip; Rasch, Philip J.; Wang, Hailong

2012-09-25

Using a global climate model with fully predictive aerosol life cycle, we investigate the fast and slow responses of the South Asian monsoon system to anthropogenic aerosol forcing. Our results show that the feedbacks associated with sea surface temperature (SST) change caused by aerosols play a more important role than the aerosol's direct impact on radiation, clouds and land surface (rapid adjustments) in shaping the total equilibrium climate response of the monsoon system to aerosol forcing. Inhomogeneous SST cooling caused by anthropogenic aerosols eventually reduces the meridional tropospheric temperature gradient and the easterly shear of zonal winds over the region,more » slowing down the local Hadley cell circulation, decreasing the northward moisture transport, and causing a reduction in precipitation over South Asia. Although total responses in precipitation are closer to the slow responses in general, the fast component dominates over land areas north of 25°N. Our results also show an east-west asymmetry in the fast responses to anthropogenic aerosols causing increases in precipitation west of 80°E but decreases east of it.« less

Fast decomposition of two ultrasound longitudinal waves in cancellous bone using a phase rotation parameter for bone quality assessment: Simulation study.

PubMed

Taki, Hirofumi; Nagatani, Yoshiki; Matsukawa, Mami; Kanai, Hiroshi; Izumi, Shin-Ichi

2017-10-01

Ultrasound signals that pass through cancellous bone may be considered to consist of two longitudinal waves, which are called fast and slow waves. Accurate decomposition of these fast and slow waves is considered to be highly beneficial in determination of the characteristics of cancellous bone. In the present study, a fast decomposition method using a wave transfer function with a phase rotation parameter was applied to received signals that have passed through bovine bone specimens with various bone volume to total volume (BV/TV) ratios in a simulation study, where the elastic finite-difference time-domain method is used and the ultrasound wave propagated parallel to the bone axes. The proposed method succeeded to decompose both fast and slow waves accurately; the normalized residual intensity was less than -19.5 dB when the specimen thickness ranged from 4 to 7 mm and the BV/TV value ranged from 0.144 to 0.226. There was a strong relationship between the phase rotation value and the BV/TV value. The ratio of the peak envelope amplitude of the decomposed fast wave to that of the slow wave increased monotonically with increasing BV/TV ratio, indicating the high performance of the proposed method in estimation of the BV/TV value in cancellous bone.

Modeling fast and slow earthquakes at various scales

PubMed Central

IDE, Satoshi

2014-01-01

Earthquake sources represent dynamic rupture within rocky materials at depth and often can be modeled as propagating shear slip controlled by friction laws. These laws provide boundary conditions on fault planes embedded in elastic media. Recent developments in observation networks, laboratory experiments, and methods of data analysis have expanded our knowledge of the physics of earthquakes. Newly discovered slow earthquakes are qualitatively different phenomena from ordinary fast earthquakes and provide independent information on slow deformation at depth. Many numerical simulations have been carried out to model both fast and slow earthquakes, but problems remain, especially with scaling laws. Some mechanisms are required to explain the power-law nature of earthquake rupture and the lack of characteristic length. Conceptual models that include a hierarchical structure over a wide range of scales would be helpful for characterizing diverse behavior in different seismic regions and for improving probabilistic forecasts of earthquakes. PMID:25311138

Modeling fast and slow earthquakes at various scales.

PubMed

Ide, Satoshi

2014-01-01

Earthquake sources represent dynamic rupture within rocky materials at depth and often can be modeled as propagating shear slip controlled by friction laws. These laws provide boundary conditions on fault planes embedded in elastic media. Recent developments in observation networks, laboratory experiments, and methods of data analysis have expanded our knowledge of the physics of earthquakes. Newly discovered slow earthquakes are qualitatively different phenomena from ordinary fast earthquakes and provide independent information on slow deformation at depth. Many numerical simulations have been carried out to model both fast and slow earthquakes, but problems remain, especially with scaling laws. Some mechanisms are required to explain the power-law nature of earthquake rupture and the lack of characteristic length. Conceptual models that include a hierarchical structure over a wide range of scales would be helpful for characterizing diverse behavior in different seismic regions and for improving probabilistic forecasts of earthquakes.

Fiber type conversion by PGC-1α activates lysosomal and autophagosomal biogenesis in both unaffected and Pompe skeletal muscle.

PubMed

Takikita, Shoichi; Schreiner, Cynthia; Baum, Rebecca; Xie, Tao; Ralston, Evelyn; Plotz, Paul H; Raben, Nina

2010-12-13

PGC-1α is a transcriptional co-activator that plays a central role in the regulation of energy metabolism. Our interest in this protein was driven by its ability to promote muscle remodeling. Conversion from fast glycolytic to slow oxidative fibers seemed a promising therapeutic approach in Pompe disease, a severe myopathy caused by deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA) which is responsible for the degradation of glycogen. The recently approved enzyme replacement therapy (ERT) has only a partial effect in skeletal muscle. In our Pompe mouse model (KO), the poor muscle response is seen in fast but not in slow muscle and is associated with massive accumulation of autophagic debris and ineffective autophagy. In an attempt to turn the therapy-resistant fibers into fibers amenable to therapy, we made transgenic KO mice expressing PGC-1α in muscle (tgKO). The successful switch from fast to slow fibers prevented the formation of autophagic buildup in the converted fibers, but PGC-1α failed to improve the clearance of glycogen by ERT. This outcome is likely explained by an unexpected dramatic increase in muscle glycogen load to levels much closer to those observed in patients, in particular infants, with the disease. We have also found a remarkable rise in the number of lysosomes and autophagosomes in the tgKO compared to the KO. These data point to the role of PGC-1α in muscle glucose metabolism and its possible role as a master regulator for organelle biogenesis - not only for mitochondria but also for lysosomes and autophagosomes. These findings may have implications for therapy of lysosomal diseases and other disorders with altered autophagy.

Adaptive Changes in the Perception of Fast and Slow Movement at Different Head Positions.

PubMed

Panichi, Roberto; Occhigrossi, Chiara; Ferraresi, Aldo; Faralli, Mario; Lucertini, Marco; Pettorossi, Vito E

2017-05-01

This paper examines the subjective sense of orientation during asymmetric body rotations in normal subjects. Self-motion perception was investigated in 10 healthy individuals during asymmetric whole-body rotation with different head orientations. Both on-vertical axis and off-vertical axis rotations were employed. Subjects tracked a remembered earth-fixed visual target while rotating in the dark for four cycles of asymmetric rotation (two half-sinusoidal cycles of the same amplitude, but of different duration). The rotations induced a bias in the perception of velocity (more pronounced with fast than with slow motion). At the end of rotation, a marked target position error (TPE) was present. For the on-vertical axis rotations, the TPE was no different if the rotations were performed with a 30° nose-down, a 60° nose-up, or a 90° side-down head tilt. With off-vertical axis rotations, the simultaneous activation of the semicircular canals and otolithic receptors produced a significant increase of TPE for all head positions. This difference between on-vertical and off-vertical axis rotation was probably partly due to the vestibular transfer function and partly due to different adaptation to the speed of rotation. Such a phenomenon might be generated in different components of the vestibular system. The adaptive process enhancing the perception of dynamic movement around the vertical axis is not related to the specific semicircular canals that are activated; the addition of an otolithic component results in a significant increase of the TPE.Panichi R, Occhigrossi C, Ferraresi A, Faralli M, Lucertini M, Pettorossi VE. Adaptive changes in the perception of fast and slow movement at different head positions. Aerosp Med Hum Perform. 2017; 88(5):463-468.

Modulation of the binding of basic fibroblast growth factor and heparanase activity by purified λ-carrageenan oligosaccharides.

PubMed

Niu, Ting-Ting; Zhang, Dong-Sheng; Chen, Hai-Min; Yan, Xiao-Jun

2015-07-10

Inhibitors of angiogenesis and tumor metastasis are increasingly emerging as promising agents for cancer therapy. Here, we report λ-carrageenan oligosaccharides (λ-COs), highly-sulfated oligosaccharides acting as a basic fibroblast growth factor (bFGF) antagonist and heparanase inhibitor. λ-COs with degree of polymerization (DP) from 2 to 8 degraded by λ-carrageenase were separated and purified. The structures were identified by mass spectrometry. The activities of λ-COs are closely related with DP. λ-COs showed no cytotoxicity, but inactivated bFGF-induced cell proliferation; among them, λ-carraheptaose showed highest capability. Only λ-carraheptaose can effectively bind to bFGF. Binding kinetics showed that λ-carraheptaose and suramin had different binding modes, i.e., suramin displayed a fast association and fast dissociation, but λ-carraheptaose exhibited a slow association and slow dissociation. In addition, λ-COs showed the highest heparanase inhibitory ability and abolished the endothelial cell invasion. Thus, λ-COs may provide a tool to develop of new carbohydrate-based therapeutics against cancer and angiogenesis. Copyright © 2015 Elsevier Ltd. All rights reserved.

Distributions of Thermal-Annealing Activation Energies for Light-Induced Spins in Fast and Slow Processes in a-Si1-xNx:H Alloys

NASA Astrophysics Data System (ADS)

Zhang, Jinyan; Kumeda, Minoru; Shimizu, Tatsuo

1995-10-01

We report on the thermal annealing of light-induced neutral dangling bonds (DB's) created by strong band-gap illumination at 77 K and room temperature (RT) in amorphous silicon-nitrogen alloys ( a-Si1- xN x:H). We find that the light-induced DB's are annealed out with distinct distributions of annealing activation energies (E A's). The distribution for the light-induced DB's created in the fast process (FDB's) and the one for those created in the slow process (SDB's) are separated unambiguously: E A for FDB's is in the range from 0 to 0.7 eV, in which two separated peaks (centered at about 0.09 and 0.4 eV) are embodied, and E A for SDB's is in the range from 0.6 to 1.4 eV, centered at about 1 eV, in a-Si0.5N0.5:H. Moreover, the results demonstrate that the distributions of E A for FDB's and SDB's depend on illumination temperature and illumination time.

An electrophysiological validation of stochastic DCM for fMRI

PubMed Central

Daunizeau, J.; Lemieux, L.; Vaudano, A. E.; Friston, K. J.; Stephan, K. E.

2013-01-01

In this note, we assess the predictive validity of stochastic dynamic causal modeling (sDCM) of functional magnetic resonance imaging (fMRI) data, in terms of its ability to explain changes in the frequency spectrum of concurrently acquired electroencephalography (EEG) signal. We first revisit the heuristic model proposed in Kilner et al. (2005), which suggests that fMRI activation is associated with a frequency modulation of the EEG signal (rather than an amplitude modulation within frequency bands). We propose a quantitative derivation of the underlying idea, based upon a neural field formulation of cortical activity. In brief, dense lateral connections induce a separation of time scales, whereby fast (and high spatial frequency) modes are enslaved by slow (low spatial frequency) modes. This slaving effect is such that the frequency spectrum of fast modes (which dominate EEG signals) is controlled by the amplitude of slow modes (which dominate fMRI signals). We then use conjoint empirical EEG-fMRI data—acquired in epilepsy patients—to demonstrate the electrophysiological underpinning of neural fluctuations inferred from sDCM for fMRI. PMID:23346055

Identification on commercialized products of AFLP markers able to discriminate slow- from fast-growing chicken strains.

PubMed

Fumière, Olivier; Dubois, Marc; Grégoire, Dimitrie; Théwis, André; Berben, Gilbert

2003-02-26

The European chicken meat market is characterized by numerous quality marks: "Label de Qualité Wallon" in Belgium, "Label Rouge" in France, denominations of geographical origin, organic agriculture, etc. Most of those certified productions have specifications requiring the use of slow-growing chicken strains. The amplified fragment length polymorphism (AFLP) technique has been used to search molecular markers able to discriminate slow-growing chicken strains from fast-growing ones and to authenticate certified products. Two pairs of restriction enzymes (EcoRI/MseI and EcoRI/TaqI) and 121 selective primer combinations were tested on individual DNA samples from chicken products essentially in carcass form that were ascribed as belonging to either slow- or fast-growing strains. Within the resulting fingerprints, two fragments were identified as type-strains specific markers. One primer combination gives a band (333 bp) that is specific for slow-growing chickens, and another primer pair generates a band (372 bp) that was found to be characteristic of fast-growing chickens. The two markers were isolated, cloned, and sequenced. The effectiveness and the specificity of the two interesting determinants were assessed on individuals of two well-known strains (ISA 657 and Cobb 500) and on commercialized products coming from various origins.

S1-S3 counter charges in the voltage sensor module of a mammalian sodium channel regulate fast inactivation.

PubMed

Groome, James R; Winston, Vern

2013-05-01

The movement of positively charged S4 segments through the electric field drives the voltage-dependent gating of ion channels. Studies of prokaryotic sodium channels provide a mechanistic view of activation facilitated by electrostatic interactions of negatively charged residues in S1 and S2 segments, with positive counterparts in the S4 segment. In mammalian sodium channels, S4 segments promote domain-specific functions that include activation and several forms of inactivation. We tested the idea that S1-S3 countercharges regulate eukaryotic sodium channel functions, including fast inactivation. Using structural data provided by bacterial channels, we constructed homology models of the S1-S4 voltage sensor module (VSM) for each domain of the mammalian skeletal muscle sodium channel hNaV1.4. These show that side chains of putative countercharges in hNaV1.4 are oriented toward the positive charge complement of S4. We used mutagenesis to define the roles of conserved residues in the extracellular negative charge cluster (ENC), hydrophobic charge region (HCR), and intracellular negative charge cluster (INC). Activation was inhibited with charge-reversing VSM mutations in domains I-III. Charge reversal of ENC residues in domains III (E1051R, D1069K) and IV (E1373K, N1389K) destabilized fast inactivation by decreasing its probability, slowing entry, and accelerating recovery. Several INC mutations increased inactivation from closed states and slowed recovery. Our results extend the functional characterization of VSM countercharges to fast inactivation, and support the premise that these residues play a critical role in domain-specific gating transitions for a mammalian sodium channel.

Automated nystagmus analysis. [on-line computer technique for eye data processing

NASA Technical Reports Server (NTRS)

Oman, C. M.; Allum, J. H. J.; Tole, J. R.; Young, L. R.

1973-01-01

Several methods have recently been used for on-line analysis of nystagmus: A digital computer program has been developed to accept sampled records of eye position, detect fast phase components, and output cumulative slow phase position, continuous slow phase velocity, instantaneous fast phase frequency, and other parameters. The slow phase velocity is obtained by differentiation of the calculated cumulative position rather than the original eye movement record. Also, a prototype analog device has been devised which calculates the velocity of the slow phase component during caloric testing. Examples of clinical and research eye movement records analyzed with these devices are shown.

Dependence of intravoxel incoherent motion diffusion MR threshold b-value selection for separating perfusion and diffusion compartments and liver fibrosis diagnostic performance.

PubMed

Wáng, Yì Xiáng J; Li, Yáo T; Chevallier, Olivier; Huang, Hua; Leung, Jason Chi Shun; Chen, Weitian; Lu, Pu-Xuan

2018-01-01

Background Intravoxel incoherent motion (IVIM) tissue parameters depend on the threshold b-value. Purpose To explore how threshold b-value impacts PF ( f), D slow ( D), and D fast ( D*) values and their performance for liver fibrosis detection. Material and Methods Fifteen healthy volunteers and 33 hepatitis B patients were included. With a 1.5-T magnetic resonance (MR) scanner and respiration gating, IVIM data were acquired with ten b-values of 10, 20, 40, 60, 80, 100, 150, 200, 400, and 800 s/mm 2 . Signal measurement was performed on the right liver. Segmented-unconstrained analysis was used to compute IVIM parameters and six threshold b-values in the range of 40-200 s/mm 2 were compared. PF, D slow , and D fast values were placed along the x-axis, y-axis, and z-axis, and a plane was defined to separate volunteers from patients. Results Higher threshold b-values were associated with higher PF measurement; while lower threshold b-values led to higher D slow and D fast measurements. The dependence of PF, D slow , and D fast on threshold b-value differed between healthy livers and fibrotic livers; with the healthy livers showing a higher dependence. Threshold b-value = 60 s/mm 2 showed the largest mean distance between healthy liver datapoints vs. fibrotic liver datapoints, and a classification and regression tree showed that a combination of PF (PF < 9.5%), D slow (D slow  < 1.239 × 10 -3 mm 2 /s), and D fast (D fast  < 20.85 × 10 -3 mm 2 /s) differentiated healthy individuals and all individual fibrotic livers with an area under the curve of logistic regression (AUC) of 1. Conclusion For segmented-unconstrained analysis, the selection of threshold b-value = 60 s/mm 2 improves IVIM differentiation between healthy livers and fibrotic livers.

Afferent control of central pattern generators: experimental analysis of locomotion in the decerebrate cat.

PubMed

Baev, K V; Esipenko, V B; Shimansky YuP

1991-01-01

Changes in the motor activity of the spinal locomotor generator evoked by tonic and phasic peripheral afferent signals during fictitious locomotion of both slow and fast rhythms were analysed in the cat. The tonic afferent inflow was conditioned by the position of the hindlimb. The phasic afferent signals were imitated by electrical stimulation of hindlimb nerves. The correlation between the kinematics of hindlimb locomotor movement and sensory inflow was investigated during actual locomotion. Reliable correlations between motor activity parameters during fictitious locomotion were revealed in cases of both slow and fast "locomotor" rhythms. The main difference between these cases was that correlations "duration-intensity" were positive in the first and negative in the second case. The functional role of "locomotor" pattern dependence on tonic sensory inflow consisted of providing stability for planting the hindlimb on the ground. For any investigated afferent input the phase moments in the "locomotor" cycle were found, in which an afferent signal caused no rearrangement in locomotor generator activity. These moments corresponded to the transitions between "flexion" and "extension" phases and to the bursts of integral afferent activity observed during real locomotion. The data obtained are compared with the results previously described for the scratching generator. The character of changes in "locomotor" activity in response to tonic and phasic sensory signals was similar to that of such changes in "scratching" rhythm in the case of fast "locomotion". Intensification of the "flexion" phase caused by phasic high-intensity stimulation of cutaneous afferents during low "locomotor" rhythm was changed to inhibition (such as observed during "scratching") when this rhythm was fast. It is concluded that the main regularities of peripheral afferent control for both the locomotor and scratching generators are the same. Moreover, these central pattern generators are just working regimes of a general spinal motor optimal control system containing the intrinsic model of limb movement dynamics. The consequences of this concept and ways of further research are discussed.

Residual number processing in dyscalculia☆

PubMed Central

Cappelletti, Marinella; Price, Cathy J.

2013-01-01

Developmental dyscalculia – a congenital learning disability in understanding numerical concepts – is typically associated with parietal lobe abnormality. However, people with dyscalculia often retain some residual numerical abilities, reported in studies that otherwise focused on abnormalities in the dyscalculic brain. Here we took a different perspective by focusing on brain regions that support residual number processing in dyscalculia. All participants accurately performed semantic and categorical colour-decision tasks with numerical and non-numerical stimuli, with adults with dyscalculia performing slower than controls in the number semantic tasks only. Structural imaging showed less grey-matter volume in the right parietal cortex in people with dyscalculia relative to controls. Functional MRI showed that accurate number semantic judgements were maintained by parietal and inferior frontal activations that were common to adults with dyscalculia and controls, with higher activation for participants with dyscalculia than controls in the right superior frontal cortex and the left inferior frontal sulcus. Enhanced activation in these frontal areas was driven by people with dyscalculia who made faster rather than slower numerical decisions; however, activation could not be accounted for by response times per se, because it was greater for fast relative to slow dyscalculics but not greater for fast controls relative to slow dyscalculics. In conclusion, our results reveal two frontal brain regions that support efficient number processing in dyscalculia. PMID:24266008

Interaction of various mechanical activity models in regulation of myosin heavy chain isoform expression

NASA Technical Reports Server (NTRS)

Diffee, Gary M.; Mccue, Samuel; Larosa, Angela; Herrick, Robert E.; Baldwin, Kenneth M.

1993-01-01

The purpose of this study was to determine the effects of a novel combination of mechanical activity paradigms on the isomyosin distribution in rat hindlimb muscles. Thirty female Sprague-Dawley rats were divided into five experimental groups as follows: normal control, functional overload (OV) of the plantaris, OV in conjunction with hindlimb suspension (OV-S), and a combination of OV-S and either static standing weight-bearing activity (OV-SS) or high-incline treadmill exercise (OV-SE). OV of the plantaris resulted in significant hypertrophy and significant fast-to-slow isomyosin shifts. These changes were completely inhibited by the addition of hindlimb suspension (OV-S). Also, neither of the two weight-bearing regimes (OV-SS and OV-SE) was able to attenuate the suspension-induced atrophy. In the vastus intermedius and vastus lateralis, however, OV-SS was able to partially retard the atrophy associated with suspension. In both the plantaris and vastus intermedius, only OV-SS was able to partially reverse the slow-to-fast isomyosin transitions associated with suspension. These results suggest that the type of mechanical activity is important in determining adaptation to altered loading conditions, with OV-SS appearing more effective than OV-SE in reversing the effects of unweighting.

Residual number processing in dyscalculia.

PubMed

Cappelletti, Marinella; Price, Cathy J

2014-01-01

Developmental dyscalculia - a congenital learning disability in understanding numerical concepts - is typically associated with parietal lobe abnormality. However, people with dyscalculia often retain some residual numerical abilities, reported in studies that otherwise focused on abnormalities in the dyscalculic brain. Here we took a different perspective by focusing on brain regions that support residual number processing in dyscalculia. All participants accurately performed semantic and categorical colour-decision tasks with numerical and non-numerical stimuli, with adults with dyscalculia performing slower than controls in the number semantic tasks only. Structural imaging showed less grey-matter volume in the right parietal cortex in people with dyscalculia relative to controls. Functional MRI showed that accurate number semantic judgements were maintained by parietal and inferior frontal activations that were common to adults with dyscalculia and controls, with higher activation for participants with dyscalculia than controls in the right superior frontal cortex and the left inferior frontal sulcus. Enhanced activation in these frontal areas was driven by people with dyscalculia who made faster rather than slower numerical decisions; however, activation could not be accounted for by response times per se, because it was greater for fast relative to slow dyscalculics but not greater for fast controls relative to slow dyscalculics. In conclusion, our results reveal two frontal brain regions that support efficient number processing in dyscalculia.

Sarcoplasmic reticulum calcium release compared in slow-twitch and fast-twitch fibres of mouse muscle.

PubMed

Baylor, S M; Hollingworth, S

2003-08-15

Experiments were carried out to compare the amplitude and time course of Ca2+ release from the sarcoplasmic reticulum (SR) in intact slow-twitch and fast-twitch mouse fibres. Individual fibres within small bundles were injected with furaptra, a low-affinity, rapidly responding Ca2+ indicator. In response to a single action potential at 16 degrees C, the peak amplitude and half-duration of the change in myoplasmic free [Ca2+] (Delta[Ca2+]) differed significantly between fibre types (slow-twitch: peak amplitude, 9.4 +/- 1.0 microM (mean +/- S.E.M.); half-duration, 7.7 +/- 0.6 ms; fast-twitch: peak amplitude 18.5 +/- 0.5 microM; half-duration, 4.9 +/- 0.3 ms). SR Ca2+ release was estimated from Delta[Ca2+] with a computational model that calculated Ca2+ binding to the major myoplasmic Ca2+ buffers (troponin, ATP and parvalbumin); buffer concentrations and reaction rate constants were adjusted to reflect fibre-type differences. In response to an action potential, the total concentration of released Ca2+ (Delta[CaT]) and the peak rate of Ca2+ release ((d/dt)Delta[CaT]) differed about 3-fold between the fibre types (slow-twitch: Delta[CaT], 127 +/- 7 microM; (d/dt)Delta[CaT], 70 +/- 6 microM ms-1; fast-twitch: Delta[CaT], 346 +/- 6 microM; (d/dt)Delta[CaT], 212 +/- 4 microM ms-1). In contrast, the half-duration of (d/dt)Delta[CaT] was very similar in the two fibre types (slow-twitch, 1.8 +/- 0.1 ms; fast-twitch, 1.6 +/- 0.0 ms). When fibres were stimulated with a 5-shock train at 67 Hz, the peaks of (d/dt)Delta[CaT] in response to the second and subsequent shocks were much smaller than that due to the first shock; the later peaks, expressed as a fraction of the amplitude of the first peak, were similar in the two fibre types (slow-twitch, 0.2-0.3; fast-twitch, 0.1-0.3). The results support the conclusion that individual SR Ca2+ release units function similarly in slow-twitch and fast-twitch mammalian fibres.

The syndromic deafness mutation G12R impairs fast and slow gating in Cx26 hemichannels.

PubMed

García, Isaac E; Villanelo, Felipe; Contreras, Gustavo F; Pupo, Amaury; Pinto, Bernardo I; Contreras, Jorge E; Pérez-Acle, Tomás; Alvarez, Osvaldo; Latorre, Ramon; Martínez, Agustín D; González, Carlos

2018-05-07

Mutations in connexin 26 (Cx26) hemichannels can lead to syndromic deafness that affects the cochlea and skin. These mutations lead to gain-of-function hemichannel phenotypes by unknown molecular mechanisms. In this study, we investigate the biophysical properties of the syndromic mutant Cx26G12R (G12R). Unlike wild-type Cx26, G12R macroscopic hemichannel currents do not saturate upon depolarization, and deactivation is faster during hyperpolarization, suggesting that these channels have impaired fast and slow gating. Single G12R hemichannels show a large increase in open probability, and transitions to the subconductance state are rare and short-lived, demonstrating an inoperative fast gating mechanism. Molecular dynamics simulations indicate that G12R causes a displacement of the N terminus toward the cytoplasm, favoring an interaction between R12 in the N terminus and R99 in the intracellular loop. Disruption of this interaction recovers the fast and slow voltage-dependent gating mechanisms. These results suggest that the mechanisms of fast and slow gating in connexin hemichannels are coupled and provide a molecular mechanism for the gain-of-function phenotype displayed by the syndromic G12R mutation. © 2018 García et al.

Required coefficient of friction during turning at self-selected slow, normal, and fast walking speeds.

PubMed

Fino, Peter; Lockhart, Thurmon E

2014-04-11

This study investigated the relationship of required coefficient of friction to gait speed, obstacle height, and turning strategy as participants walked around obstacles of various heights. Ten healthy, young adults performed 90° turns around corner pylons of four different heights at their self selected normal, slow, and fast walking speeds using both step and spin turning strategies. Kinetic data was captured using force plates. Results showed peak required coefficient of friction (RCOF) at push off increased with increased speed (slow μ=0.38, normal μ=0.45, and fast μ=0.54). Obstacle height had no effect on RCOF values. The average peak RCOF for fast turning exceeded the OSHA safety guideline for static COF of μ>0.50, suggesting further research is needed into the minimum static COF to prevent slips and falls, especially around corners. Copyright © 2014 Elsevier Ltd. All rights reserved.

On forward inferences of fast and slow readers. An eye movement study

PubMed Central

Hawelka, Stefan; Schuster, Sarah; Gagl, Benjamin; Hutzler, Florian

2015-01-01

Unimpaired readers process words incredibly fast and hence it was assumed that top-down processing, such as predicting upcoming words, would be too slow to play an appreciable role in reading. This runs counter the major postulate of the predictive coding framework that our brain continually predicts probable upcoming sensory events. This means, it may generate predictions about the probable upcoming word during reading (dubbed forward inferences). Trying to asses these contradictory assumptions, we evaluated the effect of the predictability of words in sentences on eye movement control during silent reading. Participants were a group of fluent (i.e., fast) and a group of speed-impaired (i.e., slow) readers. The findings indicate that fast readers generate forward inferences, whereas speed-impaired readers do so to a reduced extent - indicating a significant role of predictive coding for fluent reading. PMID:25678030

Myosin content of individual human muscle fibers isolated by laser capture microdissection.

PubMed

Stuart, Charles A; Stone, William L; Howell, Mary E A; Brannon, Marianne F; Hall, H Kenton; Gibson, Andrew L; Stone, Michael H

2016-03-01

Muscle fiber composition correlates with insulin resistance, and exercise training can increase slow-twitch (type I) fibers and, thereby, mitigate diabetes risk. Human skeletal muscle is made up of three distinct fiber types, but muscle contains many more isoforms of myosin heavy and light chains, which are coded by 15 and 11 different genes, respectively. Laser capture microdissection techniques allow assessment of mRNA and protein content in individual fibers. We found that specific human fiber types contain different mixtures of myosin heavy and light chains. Fast-twitch (type IIx) fibers consistently contained myosin heavy chains 1, 2, and 4 and myosin light chain 1. Type I fibers always contained myosin heavy chains 6 and 7 (MYH6 and MYH7) and myosin light chain 3 (MYL3), whereas MYH6, MYH7, and MYL3 were nearly absent from type IIx fibers. In contrast to cardiomyocytes, where MYH6 (also known as α-myosin heavy chain) is seen solely in fast-twitch cells, only slow-twitch fibers of skeletal muscle contained MYH6. Classical fast myosin heavy chains (MHC1, MHC2, and MHC4) were present in variable proportions in all fiber types, but significant MYH6 and MYH7 expression indicated slow-twitch phenotype, and the absence of these two isoforms determined a fast-twitch phenotype. The mixed myosin heavy and light chain content of type IIa fibers was consistent with its role as a transition between fast and slow phenotypes. These new observations suggest that the presence or absence of MYH6 and MYH7 proteins dictates the slow- or fast-twitch phenotype in skeletal muscle. Copyright © 2016 the American Physiological Society.

Myosin content of individual human muscle fibers isolated by laser capture microdissection

PubMed Central

Stone, William L.; Howell, Mary E. A.; Brannon, Marianne F.; Hall, H. Kenton; Gibson, Andrew L.; Stone, Michael H.

2015-01-01

Muscle fiber composition correlates with insulin resistance, and exercise training can increase slow-twitch (type I) fibers and, thereby, mitigate diabetes risk. Human skeletal muscle is made up of three distinct fiber types, but muscle contains many more isoforms of myosin heavy and light chains, which are coded by 15 and 11 different genes, respectively. Laser capture microdissection techniques allow assessment of mRNA and protein content in individual fibers. We found that specific human fiber types contain different mixtures of myosin heavy and light chains. Fast-twitch (type IIx) fibers consistently contained myosin heavy chains 1, 2, and 4 and myosin light chain 1. Type I fibers always contained myosin heavy chains 6 and 7 (MYH6 and MYH7) and myosin light chain 3 (MYL3), whereas MYH6, MYH7, and MYL3 were nearly absent from type IIx fibers. In contrast to cardiomyocytes, where MYH6 (also known as α-myosin heavy chain) is seen solely in fast-twitch cells, only slow-twitch fibers of skeletal muscle contained MYH6. Classical fast myosin heavy chains (MHC1, MHC2, and MHC4) were present in variable proportions in all fiber types, but significant MYH6 and MYH7 expression indicated slow-twitch phenotype, and the absence of these two isoforms determined a fast-twitch phenotype. The mixed myosin heavy and light chain content of type IIa fibers was consistent with its role as a transition between fast and slow phenotypes. These new observations suggest that the presence or absence of MYH6 and MYH7 proteins dictates the slow- or fast-twitch phenotype in skeletal muscle. PMID:26676053

COUPLED FAST-THERMAL POWER BREEDER REACTOR

DOEpatents

Avery, R.

1961-07-18

A nuclear reactor having a region operating predominantly on fast neutrons and another region operating predominantly on slow neutrons is described. The fast region is a plutonium core and the slow region is a natural uranium blanket around the core. Both of these regions are free of moderator. A moderating reflector surrounds the uranium blanket. The moderating material and thickness of the reflector are selected so that fissions in the uranium blanket make a substantial contribution to the reactivity of the reactor.

Differing Event-Related Patterns of Gamma-Band Power in Brain Waves of Fast- and Slow-Reacting Subjects

DTIC Science & Technology

1994-05-01

Wilhelm Wundt proposed that there are two types of subjects in sim- ple RT experiments: fast-reacting subjects, who respond before they fully...quickly as possible to auditory stimuli. This result appears to confirm long-standing speculations of Wundt that fast- and slow-reacting subjects...accord with the hypothesis of Wundt and others that slower ("sensorial") responders wait to fully perceive a stimulus and then react to their perception

A neuro-mechanical model of a single leg joint highlighting the basic physiological role of fast and slow muscle fibres of an insect muscle system.

PubMed

Toth, Tibor Istvan; Schmidt, Joachim; Büschges, Ansgar; Daun-Gruhn, Silvia

2013-01-01

In legged animals, the muscle system has a dual function: to produce forces and torques necessary to move the limbs in a systematic way, and to maintain the body in a static position. These two functions are performed by the contribution of specialized motor units, i.e. motoneurons driving sets of specialized muscle fibres. With reference to their overall contraction and metabolic properties they are called fast and slow muscle fibres and can be found ubiquitously in skeletal muscles. Both fibre types are active during stepping, but only the slow ones maintain the posture of the body. From these findings, the general hypothesis on a functional segregation between both fibre types and their neuronal control has arisen. Earlier muscle models did not fully take this aspect into account. They either focused on certain aspects of muscular function or were developed to describe specific behaviours only. By contrast, our neuro-mechanical model is more general as it allows functionally to differentiate between static and dynamic aspects of movement control. It does so by including both muscle fibre types and separate motoneuron drives. Our model helps to gain a deeper insight into how the nervous system might combine neuronal control of locomotion and posture. It predicts that (1) positioning the leg at a specific retraction angle in steady state is most likely due to the extent of recruitment of slow muscle fibres and not to the force developed in the individual fibres of the antagonistic muscles; (2) the fast muscle fibres of antagonistic muscles contract alternately during stepping, while co-contraction of the slow muscle fibres takes place during steady state; (3) there are several possible ways of transition between movement and steady state of the leg achieved by varying the time course of recruitment of the fibres in the participating muscles.

Experiment K-6-10. Effects of zero gravity on myofibril protein content and isomyosin distribution in rodent skeletal muscle

NASA Technical Reports Server (NTRS)

Baldwin, K.; Herrick, R.; Oganov, V.

1990-01-01

The purpose of this experiment was to investigate the effects of 12 days of zero gravity (0G) exposure (Cosmos 1887 Biosputnik) on the enzymatic properties, protein content, and isomyosin distribution of the myofibril fraction of the slow-twitch vastus intermedius (VI) and the fast-twitch vastus lateralis (VL) muscles of adult male rats. Measurements were obtained on three experimental groups (n=5 each group) designated as flight-group (FG), vivarium-control (VC), and synchronous-control (SC). Body weight of the FG was significantly lower than the two control groups (p less than 0.05). Compared to the two control groups, VI weight was lower by 23 percent (p less than 0.10); whereas no such reduction was observed for the VL muscle. Myofibril yields (mg protein/g of muscle) in the VI were 35 percent lower in the FG compared to the controls (p less than 0.05); whereas, no such pattern was apparent for the VL muscle. When myofibril yields were expressed on a muscle basis (mg/g x muscle weight), the loss of myofibril protein was more exaggerated and suggests that myofibril protein degradation is an early event in the muscle atrophy response to 0G. Analysis of myosin isoforms indicated that slow-myosin was the primary isoform lost in the calculated degradation of total myosin. No evidence of loss of the fast isomyosins was apparent for either muscle following space flight. Myofibril ATPase activity of the VI was increased in the FG compared to controls, which is consistent with the observation of preferential slow-myosin degradation. These data suggest that muscles containing a high percent of slow-twitch fibers undergo greater degrees of myofibril protein degradation than do muscles containing predominantly fast-twitch fibers in response to a relatively short period of 0G exposure, and the primary target appears to be the slow-myosin molecule.

Spike Timing and Reliability in Cortical Pyramidal Neurons: Effects of EPSC Kinetics, Input Synchronization and Background Noise on Spike Timing

PubMed Central

Rodriguez-Molina, Victor M.; Aertsen, Ad; Heck, Detlef H.

2007-01-01

In vivo studies have shown that neurons in the neocortex can generate action potentials at high temporal precision. The mechanisms controlling timing and reliability of action potential generation in neocortical neurons, however, are still poorly understood. Here we investigated the temporal precision and reliability of spike firing in cortical layer V pyramidal cells at near-threshold membrane potentials. Timing and reliability of spike responses were a function of EPSC kinetics, temporal jitter of population excitatory inputs, and of background synaptic noise. We used somatic current injection to mimic population synaptic input events and measured spike probability and spike time precision (STP), the latter defined as the time window (Δt) holding 80% of response spikes. EPSC rise and decay times were varied over the known physiological spectrum. At spike threshold level, EPSC decay time had a stronger influence on STP than rise time. Generally, STP was highest (≤2.45 ms) in response to synchronous compounds of EPSCs with fast rise and decay kinetics. Compounds with slow EPSC kinetics (decay time constants>6 ms) triggered spikes at lower temporal precision (≥6.58 ms). We found an overall linear relationship between STP and spike delay. The difference in STP between fast and slow compound EPSCs could be reduced by incrementing the amplitude of slow compound EPSCs. The introduction of a temporal jitter to compound EPSCs had a comparatively small effect on STP, with a tenfold increase in jitter resulting in only a five fold decrease in STP. In the presence of simulated synaptic background activity, precisely timed spikes could still be induced by fast EPSCs, but not by slow EPSCs. PMID:17389910

Enzymatic Basis for Differentiation of Rhizobium into Fast- and Slow-Growing Groups

PubMed Central

Drets, G. Martinez-De; Arias, A.

1972-01-01

Glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and other enzymes related to carbohydrate metabolism were studied in rhizobia. A nicotinamide adenine dinucleotide phosphate-6-phosphogluconate dehydrogenase was detected in strains of the fast-growing group of Rhizobium but not in strains of the slow-growing group. An enzymatic differentiation of rhizobia was established. PMID:4400417

Novel Fast Adapting Interneurons Mediate Cholinergic-Induced Fast GABAA IPSCs In Striatal Spiny Neurons

PubMed Central

Faust, Thomas W.; Assous, Maxime; Shah, Fulva; Tepper, James M.; Koós, Tibor

2015-01-01

Previous work suggests that neostriatal cholinergic interneurons control the activity of several classes of GABAergic interneurons through fast nicotinic receptor mediated synaptic inputs. Although indirect evidence has suggested the existence of several classes of interneurons controlled by this mechanism only one such cell type, the neuropeptide-Y expressing neurogliaform neuron, has been identified to date. Here we tested the hypothesis that in addition to the neurogliaform neurons that elicit slow GABAergic inhibitory responses, another interneuron type exists in the striatum that receives strong nicotinic cholinergic input and elicits conventional fast GABAergic synaptic responses in projection neurons. We obtained in vitro slice recordings from double transgenic mice in which Channelrhodopsin-2 was natively expressed in cholinergic neurons and a population of serotonin receptor-3a-Cre expressing GABAergic interneurons were visualized with tdTomato. We show that among the targeted GABAergic interneurons a novel type of interneuron, termed the fast-adapting interneuron, can be identified that is distinct from previously known interneurons based on immunocytochemical and electrophysiological criteria. We show using optogenetic activation of cholinergic inputs that fast-adapting interneurons receive a powerful supra-threshold nicotinic cholinergic input in vitro. Moreover, fast adapting neurons are densely connected to projection neurons and elicit fast, GABAA receptor mediated inhibitory postsynaptic responses. The nicotinic receptor mediated activation of fast-adapting interneurons may constitute an important mechanism through which cholinergic interneurons control the activity of projection neurons and perhaps the plasticity of their synaptic inputs when animals encounter reinforcing or otherwise salient stimuli. PMID:25865337

Redox-Active Star Molecules Incorporating the 4-Benzolypyridinium Cation: Implications for the Charge Transfer Efficiency Along Branches versus Across the Perimeter in Dendrimers

NASA Technical Reports Server (NTRS)

Yang, Jin-Hua; Rawashdeh, Abdel Monem M.; Oh, Woon Su; Sotiriou-Leventis, Chariklia; Leventis, Nicholas

2003-01-01

We report the redox properties of four star systems incorporating the 4-benzoyl-N-alkylpyridinium cation; the redox potential varies along the branches, but remains constant at fixed radii. Voltammetric analysis (cyclic voltammetry and differential pulse voltammetry) shows that only two of the three redox-active centers in the perimeter are electrochemically accessible during potential sweeps as slow as 20 mV/s and as fast as 10 V/s. On the contrary, both redox centers of a branch are accessible electrochemically within the same time frame. These results are discussed in terms of slow through-space charge transfer and the globular 3-D folding of the molecules.

Teleseismic surface wave study of S-wave velocity structure in Southern California

NASA Astrophysics Data System (ADS)

Prindle-Sheldrake, K. L.; Tanimoto, T.

2002-12-01

We report on a 3D S-wave velocity structure derived from teleseismic Rayleigh and Love waves using TriNet broadband seismic data. Phase velocity maps, constructed between 20 and 55 mHz for Rayleigh waves and between 25 and 45 mHz for Love waves, were inverted for S-wave velocity structure at depth. Our starting model is SCEC 2.2, which has detailed crustal structure, but laterally homogeneous upper mantle structure. Depth resolution from the data set is good from the surface to approximately 100 km, but deteriorates rapidly beyond this depth. Our analysis indicates that, while Rayleigh wave data are mostly sensitive to mantle structure, Love wave data require some modifications of crustal structure from SCEC 2.2 model. Various regions in Southern California have different seismic-velocity signatures in terms of fast and slow S-wave velocities: In the Southern Sierra, both the crust and mantle are slow. In the Mojave desert, mid-crustal depths tend to show slow velocities, which are already built into SCEC 2.2. In the Transverse Ranges, the lower crust and mantle are both fast. Our Love wave results require much faster crustal velocity than those in SCEC 2.2 in this region. In the Peninsular ranges, both the crust and mantle are fast with mantle fast velocity extending to about 70 km. This is slightly more shallow than the depth extent under the Transverse Ranges, yet it is surprisingly deep. Under the Salton Sea, the upper crust is very slow and the upper mantle is also slow. However, these two slow velocity layers are separated by faster velocity lower crust which creates a distinct contrast with respect to the adjacent slow velocity regions. Existence of such a relatively fast layer, sandwiched by slow velocities, are related to features in phase velocity maps, especially in the low frequency Love wave phase velocity map (25 mHz) and the high frequency Rayleigh wave phase velocity maps (above 40 mHz). Such a feature may be related to partial melting processes under the Salton Sea.

"Paradox of slow frequencies" - Are slow frequencies in upper cortical layers a neural predisposition of the level/state of consciousness (NPC)?

PubMed

Northoff, Georg

2017-09-01

Consciousness research has much focused on faster frequencies like alpha or gamma while neglecting the slower ones in the infraslow (0.001-0.1Hz) and slow (0.1-1Hz) frequency range. These slower frequency ranges have a "bad reputation" though; their increase in power can observed during the loss of consciousness as in sleep, anesthesia, and vegetative state. However, at the same time, slower frequencies have been conceived instrumental for consciousness. The present paper aims to resolve this paradox which I describe as "paradox of slow frequencies". I first show various data that suggest a central role of slower frequencies in integrating faster ones, i.e., "temporo-spatial integration and nestedness". Such "temporo-spatial integration and nestedness" is disrupted during the loss of consciousness as in anesthesia and sleep leading to "temporo-spatial fragmentation and isolation" between slow and fast frequencies. Slow frequencies are supposedly mediated by neural activity in upper cortical layers in higher-order associative regions as distinguished from lower cortical layers that are related to faster frequencies. Taken together, slower and faster frequencies take on different roles for the level/state of consciousness. Faster frequencies by themselves are sufficient and thus a neural correlate of consciousness (NCC) while slower frequencies are a necessary non-sufficient condition of possible consciousness, e.g., a neural predisposition of the level/state of consciousness (NPC). This resolves the "paradox of slow frequencies" in that it assigns different roles to slower and faster frequencies in consciousness, i.e., NCC and NPC. Taken as NCC and NPC, fast and slow frequencies including their relation as in "temporo-spatial integration and nestedness" can be considered a first "building bloc" of a future "temporo-spatial theory of consciousness" (TTC) (Northoff, 2013; Northoff, 2014b; Northoff & Huang, 2017). Copyright © 2017 Elsevier Inc. All rights reserved.

Genetic background and embryonic temperature affect DNA methylation and expression of myogenin and muscle development in Atlantic salmon (Salmo salar)

PubMed Central

Burgerhout, Erik; Mommens, Maren; Johnsen, Hanne; Aunsmo, Arnfinn; Santi, Nina

2017-01-01

The development of ectothermic embryos is strongly affected by incubation temperature, and thermal imprinting of body growth and muscle phenotype has been reported in various teleost fishes. The complex epigenetic regulation of muscle development in vertebrates involves DNA methylation of the myogenin promoter. Body growth is a heritable and highly variable trait among fish populations that allows for local adaptations, but also for selective breeding. Here we studied the epigenetic effects of embryonic temperature and genetic background on body growth, muscle cellularity and myogenin expression in farmed Atlantic salmon (Salmo salar). Eggs from salmon families with either high or low estimated breeding values for body growth, referred to as Fast and Slow genotypes, were incubated at 8°C or 4°C until the embryonic ‘eyed-stage’ followed by rearing at the production temperature of 8°C. Rearing temperature strongly affected the growth rates, and the 8°C fish were about twice as heavy as the 4°C fish in the order Fast8>Slow8>Fast4>Slow4 prior to seawater transfer. Fast8 was the largest fish also at harvest despite strong growth compensation in the low temperature groups. Larval myogenin expression was approximately 4–6 fold higher in the Fast8 group than in the other groups and was associated with relative low DNA methylation levels, but was positively correlated with the expression levels of the DNA methyltransferase genes dnmt1, dnmt3a and dnmt3b. Juvenile Fast8 fish displayed thicker white muscle fibres than Fast4 fish, while Slow 8 and Slow 4 showed no difference in muscle cellularity. The impact of genetic background on the thermal imprinting of body growth and muscle development in Atlantic salmon suggests that epigenetic variation might play a significant role in the local adaptation to fluctuating temperatures over short evolutionary time. PMID:28662198

Genetic background and embryonic temperature affect DNA methylation and expression of myogenin and muscle development in Atlantic salmon (Salmo salar).

PubMed

Burgerhout, Erik; Mommens, Maren; Johnsen, Hanne; Aunsmo, Arnfinn; Santi, Nina; Andersen, Øivind

2017-01-01

The development of ectothermic embryos is strongly affected by incubation temperature, and thermal imprinting of body growth and muscle phenotype has been reported in various teleost fishes. The complex epigenetic regulation of muscle development in vertebrates involves DNA methylation of the myogenin promoter. Body growth is a heritable and highly variable trait among fish populations that allows for local adaptations, but also for selective breeding. Here we studied the epigenetic effects of embryonic temperature and genetic background on body growth, muscle cellularity and myogenin expression in farmed Atlantic salmon (Salmo salar). Eggs from salmon families with either high or low estimated breeding values for body growth, referred to as Fast and Slow genotypes, were incubated at 8°C or 4°C until the embryonic 'eyed-stage' followed by rearing at the production temperature of 8°C. Rearing temperature strongly affected the growth rates, and the 8°C fish were about twice as heavy as the 4°C fish in the order Fast8>Slow8>Fast4>Slow4 prior to seawater transfer. Fast8 was the largest fish also at harvest despite strong growth compensation in the low temperature groups. Larval myogenin expression was approximately 4-6 fold higher in the Fast8 group than in the other groups and was associated with relative low DNA methylation levels, but was positively correlated with the expression levels of the DNA methyltransferase genes dnmt1, dnmt3a and dnmt3b. Juvenile Fast8 fish displayed thicker white muscle fibres than Fast4 fish, while Slow 8 and Slow 4 showed no difference in muscle cellularity. The impact of genetic background on the thermal imprinting of body growth and muscle development in Atlantic salmon suggests that epigenetic variation might play a significant role in the local adaptation to fluctuating temperatures over short evolutionary time.

Transcriptional co-activator PGC-1 alpha drives the formation of slow-twitch muscle fibres.

PubMed

Lin, Jiandie; Wu, Hai; Tarr, Paul T; Zhang, Chen-Yu; Wu, Zhidan; Boss, Olivier; Michael, Laura F; Puigserver, Pere; Isotani, Eiji; Olson, Eric N; Lowell, Bradford B; Bassel-Duby, Rhonda; Spiegelman, Bruce M

2002-08-15

The biochemical basis for the regulation of fibre-type determination in skeletal muscle is not well understood. In addition to the expression of particular myofibrillar proteins, type I (slow-twitch) fibres are much higher in mitochondrial content and are more dependent on oxidative metabolism than type II (fast-twitch) fibres. We have previously identified a transcriptional co-activator, peroxisome-proliferator-activated receptor-gamma co-activator-1 (PGC-1 alpha), which is expressed in several tissues including brown fat and skeletal muscle, and that activates mitochondrial biogenesis and oxidative metabolism. We show here that PGC-1 alpha is expressed preferentially in muscle enriched in type I fibres. When PGC-1 alpha is expressed at physiological levels in transgenic mice driven by a muscle creatine kinase (MCK) promoter, a fibre type conversion is observed: muscles normally rich in type II fibres are redder and activate genes of mitochondrial oxidative metabolism. Notably, putative type II muscles from PGC-1 alpha transgenic mice also express proteins characteristic of type I fibres, such as troponin I (slow) and myoglobin, and show a much greater resistance to electrically stimulated fatigue. Using fibre-type-specific promoters, we show in cultured muscle cells that PGC-1 alpha activates transcription in cooperation with Mef2 proteins and serves as a target for calcineurin signalling, which has been implicated in slow fibre gene expression. These data indicate that PGC-1 alpha is a principal factor regulating muscle fibre type determination.

Thyroid hormone regulates muscle fiber type conversion via miR-133a1.

PubMed

Zhang, Duo; Wang, Xiaoyun; Li, Yuying; Zhao, Lei; Lu, Minghua; Yao, Xuan; Xia, Hongfeng; Wang, Yu-Cheng; Liu, Mo-Fang; Jiang, Jingjing; Li, Xihua; Ying, Hao

2014-12-22

It is known that thyroid hormone (TH) is a major determinant of muscle fiber composition, but the molecular mechanism by which it does so remains unclear. Here, we demonstrated that miR-133a1 is a direct target gene of TH in muscle. Intriguingly, miR-133a, which is enriched in fast-twitch muscle, regulates slow-to-fast muscle fiber type conversion by targeting TEA domain family member 1 (TEAD1), a key regulator of slow muscle gene expression. Inhibition of miR-133a in vivo abrogated TH action on muscle fiber type conversion. Moreover, TEAD1 overexpression antagonized the effect of miR-133a as well as TH on muscle fiber type switch. Additionally, we demonstrate that TH negatively regulates the transcription of myosin heavy chain I indirectly via miR-133a/TEAD1. Collectively, we propose that TH inhibits the slow muscle phenotype through a novel epigenetic mechanism involving repression of TEAD1 expression via targeting by miR-133a1. This identification of a TH-regulated microRNA therefore sheds new light on how TH achieves its diverse biological activities. © 2014 Zhang et al.

Thyroid hormone regulates muscle fiber type conversion via miR-133a1

PubMed Central

Zhang, Duo; Wang, Xiaoyun; Li, Yuying; Zhao, Lei; Lu, Minghua; Yao, Xuan; Xia, Hongfeng; Wang, Yu-cheng; Liu, Mo-Fang; Jiang, Jingjing; Li, Xihua

2014-01-01

It is known that thyroid hormone (TH) is a major determinant of muscle fiber composition, but the molecular mechanism by which it does so remains unclear. Here, we demonstrated that miR-133a1 is a direct target gene of TH in muscle. Intriguingly, miR-133a, which is enriched in fast-twitch muscle, regulates slow-to-fast muscle fiber type conversion by targeting TEA domain family member 1 (TEAD1), a key regulator of slow muscle gene expression. Inhibition of miR-133a in vivo abrogated TH action on muscle fiber type conversion. Moreover, TEAD1 overexpression antagonized the effect of miR-133a as well as TH on muscle fiber type switch. Additionally, we demonstrate that TH negatively regulates the transcription of myosin heavy chain I indirectly via miR-133a/TEAD1. Collectively, we propose that TH inhibits the slow muscle phenotype through a novel epigenetic mechanism involving repression of TEAD1 expression via targeting by miR-133a1. This identification of a TH-regulated microRNA therefore sheds new light on how TH achieves its diverse biological activities. PMID:25512392

Universal GFR determination based on two time points during plasma iohexol disappearance.

PubMed

Ng, Derek K S; Schwartz, George J; Jacobson, Lisa P; Palella, Frank J; Margolick, Joseph B; Warady, Bradley A; Furth, Susan L; Muñoz, Alvaro

2011-08-01

An optimal measurement of glomerular filtration rate (GFR) should minimize the number of blood draws, and reduce procedural invasiveness and the burden to study personnel and cost, without sacrificing accuracy. Equations have been proposed to calculate GFR from the slow compartment separately for adults and children. To develop a universal equation, we used 1347 GFR measurements from two diverse groups consisting of 527 men in the Multicenter AIDS Cohort Study and 514 children in the Chronic Kidney Disease in Children cohort. Both studies used nearly identical two-compartment (fast and slow) protocols to measure GFR. To estimate the fast component from markers of body size and of the slow component, we used standard linear regression methods with the log-transformed fast area as the dependent variable. The fast area could be accurately estimated from body surface area by a simple parameter (6.4/body surface area) with no residual dependence on the slow area or other markers of body size. Our equation measures only the slow iohexol plasma disappearance curve with as few as two time points and was normalized to 1.73 m2 body surface area. It is of the form: GFR=slowGFR/[1+0.12(slowGFR/100)]. In a random sample utilizing a third of the patients for validation, there was excellent agreement between the calculated and measured GFR with low root mean square errors being 4.6 and 1.5 ml/min per 1.73 m2 for adults and children, respectively. Thus, our proposed simple equation, developed in a combined patient group with a broad range of GFRs, may be applied universally and is independent of the injected amount of iohexol.

Effects of walking speed on asymmetry and bilateral coordination of gait

PubMed Central

Plotnik, Meir; Bartsch, Ronny P.; Zeev, Aviva; Giladi, Nir; Hausdorff, Jeffery M.

2013-01-01

The mechanisms regulating the bilateral coordination of gait in humans are largely unknown. Our objective was to study how bilateral coordination changes as a result of gait speed modifications during over ground walking. 15 young adults wore force sensitive insoles that measured vertical forces used to determine the timing of the gait cycle events under three walking conditions (i.e., usual-walking, fast and slow). Ground reaction force impact (GRFI) associated with heel-strikes was also quantified, representing the potential contribution of sensory feedback to the regulation of gait. Gait asymmetry (GA) was quantified based on the differences between right and left swing times and the bilateral coordination of gait was assessed using the phase coordination index (PCI), a metric that quantifies the consistency and accuracy of the anti-phase stepping pattern. GA was preserved in the three different gait speeds. PCI was higher (reduced coordination) in the slow gait condition, compared to usual-walking (3.51% vs. 2.47%, respectively, p=0.002), but was not significantly affected in the fast condition. GRFI values were lower in the slow walking as compared to usual-walking and higher in the fast walking condition (p<0.001). Stepwise regression revealed that slowed gait related changes in PCI were not associated with the slowed gait related changes in GRFI. The present findings suggest that left-right anti-phase stepping is similar in normal and fast walking, but altered during slowed walking. This behavior might reflect a relative increase in attention resources required to regulate a slow gait speed, consistent with the possibility that cortical function and supraspinal input influences the bilateral coordination of gait. PMID:23680424

Recovery from Short Term Intense Exercise: Its Relation to Capillary Supply and Lactate Release,

DTIC Science & Technology

1982-01-01

accumulate at a higher rate in fast twitch (FT or Type II) than in slow twitch (ST or Type I) fibers of exercised muscles . Lactate form- ed and accumulated...is made up by a high percentage of FT fibers than can be expected in a " slow twitch " muscle . Moreover, the over-all metabolic profile of the ST fiber...local muscular fatigue. Eur. J. Appl. Physiol. 38, 9-15 (1978b) Baldwin, K.M., Tipton, C.M.: Work and metabolic patterns of fast and slow twitch

Slow sleep spindle and procedural memory consolidation in patients with major depressive disorder

PubMed Central

Nishida, Masaki; Nakashima, Yusaku; Nishikawa, Toru

2016-01-01

Introduction Evidence has accumulated, which indicates that, in healthy individuals, sleep enhances procedural memory consolidation, and that sleep spindle activity modulates this process. However, whether sleep-dependent procedural memory consolidation occurs in patients medicated for major depressive disorder remains unclear, as are the pharmacological and physiological mechanisms that underlie this process. Methods Healthy control participants (n=17) and patients medicated for major depressive disorder (n=11) were recruited and subjected to a finger-tapping motor sequence test (MST; nondominant hand) paradigm to compare the averaged scores of different learning phases (presleep, postsleep, and overnight improvement). Participants’ brain activity was recorded during sleep with 16 electroencephalography channels (between MSTs). Sleep scoring and frequency analyses were performed on the electroencephalography data. Additionally, we evaluated sleep spindle activity, which divided the spindles into fast-frequency spindle activity (12.5–16 Hz) and slow-frequency spindle activity (10.5–12.5 Hz). Result Sleep-dependent motor memory consolidation in patients with depression was impaired in comparison with that in control participants. In patients with depression, age correlated negatively with overnight improvement. The duration of slow-wave sleep correlated with the magnitude of motor memory consolidation in patients with depression, but not in healthy controls. Slow-frequency spindle activity was associated with reduction in the magnitude of motor memory consolidation in both groups. Conclusion Because the changes in slow-frequency spindle activity affected the thalamocortical network dysfunction in patients medicated for depression, dysregulated spindle generation may impair sleep-dependent memory consolidation. Our findings may help to elucidate the cognitive deficits that occur in patients with major depression both in the waking state and during sleep. PMID:26869818

[Effect of gravitation loading and retabolil on development of atrophy in muscles and bones of rats due to suspension].

PubMed

KaplanskiI, A S; Il'ina-Kakueva, E I; Durnova, G N; Alekseev, E A; Loginov, V I

1999-01-01

In a 3-wk experiment with tail-suspended rats histological and histomorphometric methods were used to determine the effects of graded gravitational loading (GGL) and anabolic steroid retabolil (nortestosterone decanoate) on the course of atrophy in soleus m. (SM), gastrocnemius m. (GM), tibia and humerus, and functioning of somatotrophic hormones (STH) of the pituitary and thyrocytes of the thyroid. Suspension was found to produce atrophy in SM and, to a less degree, in GM, partial transformation of SM slow fibers into the fast ones, suppression of the tibial longitudinal growth, demineralization of the tibial and humeral spongious metaphyses; besides, functional activities of STH-cells and thyrocytes were inhibited. Graded gravitational loading of rats by intermittence of suspension for 2 hrs slowed down atrophy in both muscles and osteopenia in tibia, stimulated the synthetic and secretory functions of STH-cells without any marked effect on thyrocytes or humeral osteopenia. GGL failed to influence the slow-to-fast transformation of SM fibers. Two injections of retabolil at the total dose of 3 mg/kg of the body mass somewhat interfered with the SM atrophy and humoral osteopenia, and were favorable to the synthetic but not secretory activity of STH-cells. Neither SM and tibial atrophies nor thyroid activity of the gland were improved. The prophylactic action of GGL upon the SM and humeral atrophies was significantly higher when combined with retabolil, whereas GM and tibia were not noticeably cured by retabolil. Inhibition of the SM atrophy and humeral osteopenia in rats treated with GGL and retabolil concurred with elevated activities of STH-cells and thyrocytes indirectly suggesting their more intensive production of the growth hormone and thyroid hormones, respectively.

Cheap Labor: Myosin fiber type expression and enzyme activity in the forelimb musculature of sloths (Pilosa: Xenarthra).

PubMed

Spainhower, Kyle B; Cliffe, Rebecca N; Metz, Allan K; Barkett, Ernest M; Kiraly, Paije M; Thomas, Dylan R; Kennedy, Sarah J; Avey-Arroyo, Judy; Butcher, Michael T

2018-05-03

Sloths are canopy-dwelling inhabitants of American neotropical rainforests that exhibit suspensory behaviors. These abilities require both strength and muscular endurance to hang for extended periods of time; however, the skeletal muscle mass of sloths is reduced, thus requiring modifications to muscle architecture and leverage for large joint torque. We hypothesize that intrinsic muscle properties also are modified for fatigue resistance and predict a heterogeneous expression of slow/fast myosin heavy chain (MHC) fibers that utilize oxidative metabolic pathways for economic force production. MHC fiber type distribution and energy metabolism in the forelimb muscles of three-toed ( Bradypus variegatus, N=5) and two-toed ( Choloepus hoffmanni, N=4) sloths were evaluated using SDS-PAGE, immunohistochemistry, and enzyme activity assays. The results partially support our hypothesis by a primary expression of the slow MHC-1 isoform as well as moderate expression of fast MHC-2A fibers, while few hybrid MHC-1/2A fibers were found in both species. MHC-1 fibers were larger in cross-sectional area (CSA) than MHC-2A fibers and comprised the greatest %CSA in each muscle sampled. Enzyme assays showed elevated activity for the anaerobic enzymes creatine kinase (CK) and lactate dehydrogenase (LDH) compared to low activity for aerobic markers citrate synthase (CS) and 3- hydroxyacetyl CoA dehydrogenase (3-HAD). These findings suggest that sloth forelimb muscles may rely heavily on rapid ATP resynthesis pathways, and lactate accumulation may be beneficial. The intrinsic properties observed match well with suspensory requirements, and these modifications may have further evolved in unison with low metabolism and slow movement patterns as means to systemically conserve energy.

Adaptive and Maladaptive Strategy Use in Computer-Assisted Language Learning Activities for Listening Comprehension

ERIC Educational Resources Information Center

McBride, Cara

2008-01-01

College students of English as a foreign language (EFL) in Chile participated in an online mini course designed to improve their listening comprehension. There were four experimental conditions: A) one in which participants listened to fast dialogues; B) one in which participants listened to slow dialogues; C) one in which participants were given…

Slow Versus Fast Robot-Assisted Locomotor Training After Severe Stroke: A Randomized Controlled Trial.

PubMed

Rodrigues, Thais Amanda; Goroso, Daniel Gustavo; Westgate, Philip M; Carrico, Cheryl; Batistella, Linamara R; Sawaki, Lumy

2017-10-01

Robot-assisted locomotor training on a bodyweight-supported treadmill is a rehabilitation intervention that compels repetitive practice of gait movements. Standard treadmill speed may elicit rhythmic movements generated primarily by spinal circuits. Slower-than-standard treadmill speed may elicit discrete movements, which are more complex than rhythmic movements and involve cortical areas. Compare effects of fast (i.e., rhythmic) versus slow (i.e., discrete) robot-assisted locomotor training on a bodyweight-supported treadmill in subjects with chronic, severe gait deficit after stroke. Subjects (N = 18) were randomized to receive 30 sessions (5 d/wk) of either fast or slow robot-assisted locomotor training on a bodyweight-supported treadmill in an inpatient setting. Functional ambulation category, time up and go, 6-min walk test, 10-m walk test, Berg Balance Scale, and Fugl-Meyer Assessment were administered at baseline and postintervention. The slow group had statistically significant improvement on functional ambulation category (first quartile-third quartile, P = 0.004), 6-min walk test (95% confidence interval [CI] = 1.8 to 49.0, P = 0.040), Berg Balance Scale (95% CI = 7.4 to 14.8, P < 0.0001), time up and go (95% CI = -79.1 to 5.0, P < 0.0030), and Fugl-Meyer Assessment (95% CI = 24.1 to 45.1, P < 0.0001). The fast group had statistically significant improvement on Berg Balance Scale (95% CI = 1.5 to 10.5, P = 0.02). In initial stages of robot-assisted locomotor training on a bodyweight-supported treadmill after severe stroke, slow training targeting discrete movement may yield greater benefit than fast training.

"Fast" and "slow" skeleto-fusimotor innervation in cat tenuissimus spindles; a study with the glycogen-depletion method.

PubMed

Jami, L; Lan-Couton, D; Malmgren, K; Petit, J

1978-07-01

The glycogen-depletion method was used to investigate the motor supply to tenuissimus with respect to the presence of fast beta axons and to assess the total proportion of both fast and slow beta-innervated spindles in this muscle. In a first series of 5 expts., groups of motor axons with conduction velocities higher than 85 m/s were repetitively stimulated so as to produce glycogen depletion in the muscle fibres they innervated. The whole muscle was then quick-frozen, serially cut, stained to demonstrate glycogen and examined for intrafusal glycogen depletion. Zones of glycogen depletion were found in 16 of the 46 examined spindles; they were most frequently located in the longest of the chain intrafusal muscle fibres. Since it is known that there are no purely fusimotor axons to tenuissimus with conduction velocities above 50 m/s, it was concluded that beta axons are present among the fastest axons to this muscle. In a second series of 5 expts. as many motor axons as possible with conduction velocities above 60 m/s were stimulated. Zones of glycogen depletion were found in 19 of the 47 examined spindles. They affected chain fibres in about half of the instances and bag1 fibers in the others. As this latter location is characteristic of slow dynamic beta axons, it was concluded that both slow and fast beta axons occur regularly in the motor supply to tenuissimus. beta-innervation is present in at least 40% of tenuissimus spindles with almost no convergence of fast and slow beta axons onto the same spindle.

The interrelationship between disease severity, dynamic stability, and falls in cerebellar ataxia.

PubMed

Schniepp, Roman; Schlick, Cornelia; Pradhan, Cauchy; Dieterich, Marianne; Brandt, Thomas; Jahn, Klaus; Wuehr, Max

2016-07-01

Cerebellar ataxia (CA) results in discoordination of body movements (ataxia), a gait disorder, and falls. All three aspects appear to be obviously interrelated; however, experimental evidence is sparse. This study systematically correlated the clinical rating of the severity of ataxia with dynamic stability measures and the fall frequency in patients with CA. Clinical severity of CA in patients with sporadic (n = 34) and hereditary (n = 24) forms was assessed with the Scale for the Assessment and Rating of Ataxia (SARA). Gait performance was examined during slow, preferred, and maximally fast walking speeds. Spatiotemporal variability parameters in the fore-aft and medio-lateral directions were analyzed. The fall frequency was assessed using a standardized interview about fall events within the last 6 months. Fore-aft gait variability showed significant speed-dependent characteristics with highest magnitudes during slow and fast walking. The SARA score correlated positively with fore-aft gait variability, most prominently during fast walking. The fall frequency was significantly associated to fore-aft gait variability during slow walking. Severity of ataxia, dynamic stability, and the occurrence of falls were interrelated in a speed-dependent manner: (a) Severity of ataxia symptoms was closely related to instability during fast walking. (b) Fall frequency was associated with instability during slow walking. These findings suggest the presence of a speed-dependent, twofold cerebellar locomotor control. Assessment of gait performance during non-preferred, slow and fast walking speeds provides novel insights into the pathophysiology of cerebellar locomotor control and may become a useful approach in the clinical evaluation of patients with CA.

Myosin heavy chain composition in the rat diaphragm - Effect of age and exercise training

NASA Technical Reports Server (NTRS)

Gosselin, Luc E.; Betlach, Michael; Vailas, Arthur C.; Greaser, Marion L.; Thomas, D. P.

1992-01-01

The effects of aging and exercise training on the myosin heavy chain (MHC) composition were determined in both the costal and crural diaphragm regions of female Fischer 344 rats. Treadmill running at 75 percent maximal oxygen consumption resulted in similar increases in plantaris muscle citrate synthase activity in both young (5 mo) and old (23mo) trained animals (P less than 0.05). It was found that the ratio of fast to slow MHC was significantly higher (P less than 0.005) in the crural compared with costal diaphragm region in both age groups. A significant age-related increase in persentage of slow MHC was observed in both diaphragm regions. The relative proportion of slow MHC in either costal or crural region was not changed by exercise training.

A Descriptive Study of High School and University Students' Focus of Attention in Fast and Slow Orchestral Excerpts

ERIC Educational Resources Information Center

MacLeod, Rebecca B.; Geringer, John M.; Scott, Laurie

2009-01-01

The purpose of this study was to investigate listener discrimination of orchestral performances and to ascertain focus of listener attention to technical and expressive music elements of those performances. High School (n = 84) and University (n = 84) music students listened to four orchestral excerpts: two slow/soft excerpts and two fast/loud…

Loss of Prox1 in striated muscle causes slow to fast skeletal muscle fiber conversion and dilated cardiomyopathy.

PubMed

Petchey, Louisa K; Risebro, Catherine A; Vieira, Joaquim M; Roberts, Tom; Bryson, John B; Greensmith, Linda; Lythgoe, Mark F; Riley, Paul R

2014-07-01

Correct regulation of troponin and myosin contractile protein gene isoforms is a critical determinant of cardiac and skeletal striated muscle development and function, with misexpression frequently associated with impaired contractility or disease. Here we reveal a novel requirement for Prospero-related homeobox factor 1 (Prox1) during mouse heart development in the direct transcriptional repression of the fast-twitch skeletal muscle genes troponin T3, troponin I2, and myosin light chain 1. A proportion of cardiac-specific Prox1 knockout mice survive beyond birth with hearts characterized by marked overexpression of fast-twitch genes and postnatal development of a fatal dilated cardiomyopathy. Through conditional knockout of Prox1 from skeletal muscle, we demonstrate a conserved requirement for Prox1 in the repression of troponin T3, troponin I2, and myosin light chain 1 between cardiac and slow-twitch skeletal muscle and establish Prox1 ablation as sufficient to cause a switch from a slow- to fast-twitch muscle phenotype. Our study identifies conserved roles for Prox1 between cardiac and skeletal muscle, specifically implicated in slow-twitch fiber-type specification, function, and cardiomyopathic disease.

Loss of Prox1 in striated muscle causes slow to fast skeletal muscle fiber conversion and dilated cardiomyopathy

PubMed Central

Petchey, Louisa K.; Risebro, Catherine A.; Vieira, Joaquim M.; Roberts, Tom; Bryson, John B.; Greensmith, Linda; Lythgoe, Mark F.; Riley, Paul R.

2014-01-01

Correct regulation of troponin and myosin contractile protein gene isoforms is a critical determinant of cardiac and skeletal striated muscle development and function, with misexpression frequently associated with impaired contractility or disease. Here we reveal a novel requirement for Prospero-related homeobox factor 1 (Prox1) during mouse heart development in the direct transcriptional repression of the fast-twitch skeletal muscle genes troponin T3, troponin I2, and myosin light chain 1. A proportion of cardiac-specific Prox1 knockout mice survive beyond birth with hearts characterized by marked overexpression of fast-twitch genes and postnatal development of a fatal dilated cardiomyopathy. Through conditional knockout of Prox1 from skeletal muscle, we demonstrate a conserved requirement for Prox1 in the repression of troponin T3, troponin I2, and myosin light chain 1 between cardiac and slow-twitch skeletal muscle and establish Prox1 ablation as sufficient to cause a switch from a slow- to fast-twitch muscle phenotype. Our study identifies conserved roles for Prox1 between cardiac and skeletal muscle, specifically implicated in slow-twitch fiber-type specification, function, and cardiomyopathic disease. PMID:24938781

Evaluating the contribution of a neural component of ankle joint resistive torque in patients with stroke using a manual device.

PubMed

Kobayashi, Toshiki; Leung, Aaron K L; Akazawa, Yasushi; Hutchins, Stephen W

2011-01-01

To investigate the methodology using a manual ankle joint resistive torque measurement device to evaluate the contribution of the neural component of ankle joint resistive torque in patients with stroke. Within-subject comparison to compare the ankle joint resistive torque between fast and slow stretching conditions. Ten patients with stroke participated in this study. The incremental ratio of ankle joint resistive torque at the ankle angular position of 5degrees dorsiflexion under the fast stretching condition in comparison to the slow one was calculated in each patient. A significant increase (p<0.01) in the ankle joint resistive torque was demonstrated under the fast stretching condition in comparison to the slow one in all patients and the mean ankle joint resistive torque was 4.6 (SD=1.7) Nm under the slow stretching condition, while it was 8.4 (SD=4.1) Nm under the fast stretching condition at the ankle angular position of 5 degrees dorsiflexion. The incremental ratio ranged from 9.4-139.3% among the patients. The results of this study demonstrated the potential advantage of the device to evaluate the contribution of the neural component of ankle joint resistive torque.

Proline Can Have Opposite Effects on Fast and Slow Protein Folding Phases

PubMed Central

Osváth, Szabolcs; Gruebele, Martin

2003-01-01

Proline isomerization is well known to cause additional slow phases during protein refolding. We address a new question: does the presence of prolines significantly affect the very fast kinetics that lead to the formation of folding intermediates? We examined both the very slow (10–100 min) and very fast (4 μs–2.5 ms) folding kinetics of the two-domain enzyme yeast phosphoglycerate kinase by temperature-jump relaxation. Phosphoglycerate kinase contains a conserved cis-proline in position 204, in addition to several trans-prolines. Native cis-prolines have the largest effect on folding kinetics because the unfolded state favors trans isomerization, so we compared the kinetics of a P204H mutant with the wild-type as a proof of principle. The presence of Pro-204 causes an additional slow phase upon refolding from the cold denatured state, as reported in the literature. Contrary to this, the fast folding events are sped up in the presence of the cis-proline, probably by restriction of the conformational space accessible to the molecule. The wild-type and Pro204His mutant would be excellent models for off-lattice simulations probing the effects of conformational restriction on short timescales. PMID:12885665

Topographical distribution of fast and slow sleep spindles in medicated depressive patients.

PubMed

Nishida, Masaki; Nakashima, Yusaku; Nishikawa, Toru

2014-10-01

To compare the properties of sleep spindles between healthy subjects and medicated patients with major depressive episode, including frequency range, spectra power, and spatial distribution of spindle power. Continuous 16-channel EEG was used to record nocturnal sleep in healthy control subjects and medicated depressive patients. Recordings were analyzed for changes in EEG power spectra and power topography. Additionally, we graphically demonstrated the pattern of spatial distribution of each type of sleep spindle, divided into fast (12.5-14 Hz) and slow spindles (11-12.5 Hz). Sleep EEG records of depressive subjects exhibited a significantly higher amplitude of slow spindles in the prefrontal region, compared with the healthy controls (P < 0.01). Fast spindles were dominant in the centroparietal region in both depressive patients and the control group. Enhanced slow spindles in the prefrontal region were observed in the medicated depressive patients and not in the healthy controls. The frequency of fast spindles in depressive patients was globally higher than that in healthy participants. The alteration in sleep spindles seen in medicated depressive subjects may reflect a pharmacological modulation of synaptic function involving the thalamic-reticular and thalamocortical mechanisms.

A hydrodynamic study of a slow nova outburst. [computerized simulation of thermonuclear runaway in white dwarf envelope

NASA Technical Reports Server (NTRS)

Sparks, W. M.; Starrfield, S.; Truran, J. W.

1978-01-01

The paper reports use of a Lagrangian implicit hydrodynamics computer code incorporating a full nuclear-reaction network to follow a thermonuclear runaway in the hydrogen-rich envelope of a 1.25 solar-mass white dwarf. In this evolutionary sequence the envelope was assumed to be of normal (solar) composition and the resulting outburst closely resembles that of the slow nova HR Del. In contrast, previous CNO-enhanced models resemble fast nova outbursts. The slow-nova model ejects material by radiation pressure when the high luminosity of the rekindled hydrogen shell source exceeds the local Eddington luminosity of the outer layers. This is in contrast to the fast nova outburst where ejection is caused by the decay of the beta(+)-unstable nuclei. Nevertheless, radiation pressure probably plays a major role in ejecting material from the fast nova remnants. Therefore, the sequence from slow to fast novae can be interpreted as a sequence of white dwarfs with increasing amounts of enhanced CNO nuclei in their hydrogen envelopes, although other parameters such as the white-dwarf mass and accretion rate probably contribute to the observed variation between novae.

Inherent length-scales of periodic solar wind number density structures

NASA Astrophysics Data System (ADS)

Viall, N. M.; Kepko, L.; Spence, H. E.

2008-07-01

We present an analysis of the radial length-scales of periodic solar wind number density structures. We converted 11 years (1995-2005) of solar wind number density data into radial length series segments and Fourier analyzed them to identify all spectral peaks with radial wavelengths between 72 (116) and 900 (900) Mm for slow (fast) wind intervals. Our window length for the spectral analysis was 9072 Mm, approximately equivalent to 7 (4) h of data for the slow (fast) solar wind. We required that spectral peaks pass both an amplitude test and a harmonic F-test at the 95% confidence level simultaneously. From the occurrence distributions of these spectral peaks for slow and fast wind, we find that periodic number density structures occur more often at certain radial length-scales than at others, and are consistently observed within each speed range over most of the 11-year interval. For the slow wind, those length-scales are L ˜ 73, 120, 136, and 180 Mm. For the fast wind, those length-scales are L ˜ 187, 270 and 400 Mm. The results argue for the existence of inherent radial length-scales in the solar wind number density.

Two Ca current components of the receptor current in the electroreceptors of the marine catfish Plotosus.

PubMed

Sugawara, Y

1989-02-01

In the isolated sensory epithelium of the Plotosus electroreceptor, the receptor current has been dissected into inward Ca current, ICa, and superimposed outward transient of Ca-gated K current, IK(Ca). In control saline (170 mM/liter Na), with IK(Ca) abolished by K blockers, ICa declined in two successive exponential phases with voltage-dependent time constants. Double-pulse experiments revealed that the test ICa was partially depressed by prepulses, maximally near voltage levels for the control ICa maximum, which suggests current-dependent inactivation. In low Na saline (80 mM/liter), ICa declined in a single phase with time constants similar to those of the slower phase in control saline. The test ICa was then unaffected by prepulses. The implied presence of two Ca current components, the fast and slow ICa's, were further examined. In control saline, the PSP externally recorded from the afferent nerve showed a fast peak and a slow tonic phase. The double-pulse experiments revealed that IK(Ca) and the peak PSP were similarly depressed, i.e., secondarily to inactivation of the peak current. The steady inward current, however, was unaffected by prolonged prepulses that were stepped to 0 mV, the in situ DC level. Therefore, the fast ICa seems to initiate IK(Ca) and phasic release of transmitter, which serves for phasic receptor responses. The slow ICa may provide persistent active current, which has been shown to maintain tonic receptor operation.

Relative arrival-time upper-mantle tomography and the elusive background mean

NASA Astrophysics Data System (ADS)

Bastow, Ian D.

2012-08-01

The interpretation of seismic tomographic images of upper-mantle seismic wave speed structure is often a matter of considerable debate because the observations can usually be explained by a range of hypotheses, including variable temperature, composition, anisotropy, and the presence of partial melt. An additional problem, often overlooked in tomographic studies using relative as opposed to absolute arrival-times, is the issue of the resulting velocity model's zero mean. In shield areas, for example, relative arrival-time analysis strips off a background mean velocity structure that is markedly fast compared to the global average. Conversely, in active areas, the background mean is often markedly slow compared to the global average. Appreciation of this issue is vital when interpreting seismic tomographic images: 'high' and 'low' velocity anomalies should not necessarily be interpreted, respectively, as 'fast' and 'slow' compared to 'normal mantle'. This issue has been discussed in the seismological literature in detail over the years, yet subsequent tomography studies have still fallen into the trap of mis-interpreting their velocity models. I highlight here some recent examples of this and provide a simple strategy to address the problem using constraints from a recent global tomographic model, and insights from catalogues of absolute traveltime anomalies. Consultation of such absolute measures of seismic wave speed should be routine during regional tomographic studies, if only for the benefit of the broader Earth Science community, who readily follow the red = hot and slow, blue = cold and fast rule of thumb when interpreting the images for themselves.

Photodissociation pathways and lifetimes of protonated peptides and their dimers

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

Aravind, G.; Klaerke, B.; Rajput, J.

2012-01-07

Photodissociation lifetimes and fragment channels of gas-phase, protonated YA{sub n} (n = 1,2) peptides and their dimers were measured with 266 nm photons. The protonated monomers were found to have a fast dissociation channel with an exponential lifetime of {approx}200 ns while the protonated dimers show an additional slow dissociation component with a lifetime of {approx}2 {mu}s. Laser power dependence measurements enabled us to ascribe the fast channel in the monomer and the slow channel in the dimer to a one-photon process, whereas the fast dimer channel is from a two-photon process. The slow (1 photon) dissociation channel in themore » dimer was found to result in cleavage of the H-bonds after energy transfer through these H-bonds. In general, the dissociation of these protonated peptides is non-prompt and the decay time was found to increase with the size of the peptides. Quantum RRKM calculations of the microcanonical rate constants also confirmed a statistical nature of the photodissociation processes in the dipeptide monomers and dimers. The classical RRKM expression gives a rate constant as an analytical function of the number of active vibrational modes in the system, estimated separately on the basis of the equipartition theorem. It demonstrates encouraging results in predicting fragmentation lifetimes of protonated peptides. Finally, we present the first experimental evidence for a photo-induced conversion of tyrosine-containing peptides into monocyclic aromatic hydrocarbon along with a formamide molecule both found in space.« less

A Neuro-Mechanical Model Explaining the Physiological Role of Fast and Slow Muscle Fibres at Stop and Start of Stepping of an Insect Leg

PubMed Central

Toth, Tibor Istvan; Grabowska, Martyna; Schmidt, Joachim; Büschges, Ansgar; Daun-Gruhn, Silvia

2013-01-01

Stop and start of stepping are two basic actions of the musculo-skeletal system of a leg. Although they are basic phenomena, they require the coordinated activities of the leg muscles. However, little is known of the details of how these activities are generated by the interactions between the local neuronal networks controlling the fast and slow muscle fibres at the individual leg joints. In the present work, we aim at uncovering some of those details using a suitable neuro-mechanical model. It is an extension of the model in the accompanying paper and now includes all three antagonistic muscle pairs of the main joints of an insect leg, together with their dedicated neuronal control, as well as common inhibitory motoneurons and the residual stiffness of the slow muscles. This model enabled us to study putative processes of intra-leg coordination during stop and start of stepping. We also made use of the effects of sensory signals encoding the position and velocity of the leg joints. Where experimental observations are available, the corresponding simulation results are in good agreement with them. Our model makes detailed predictions as to the coordination processes of the individual muscle systems both at stop and start of stepping. In particular, it reveals a possible role of the slow muscle fibres at stop in accelerating the convergence of the leg to its steady-state position. These findings lend our model physiological relevance and can therefore be used to elucidate details of the stop and start of stepping in insects, and perhaps in other animals, too. PMID:24278108

Determinants of relaxation rate in rabbit skinned skeletal muscle fibres

PubMed Central

Luo, Ye; Davis, Jonathan P; Smillie, Lawrence B; Rall, Jack A

2002-01-01

The influence of Ca2+-activated force, the rate of dissociation of Ca2+ from troponin C (TnC) and decreased crossbridge detachment rate on the time course of relaxation induced by flash photolysis of diazo-2 in rabbit skinned psoas fibres was investigated at 15 °C. The rate of relaxation increased as the diazo-2 chelating capacity (i.e. free [diazo-2]/free [Ca2+]) increased. At a constant diazo-2 chelating capacity, the rate of relaxation was independent of the pre-photolysis Ca2+-activated force in the range 0.3-0.8 of maximum isometric force. A TnC mutant that exhibited increased Ca2+ sensitivity caused by a decreased Ca2+ dissociation rate in solution (M82Q TnC) also increased the Ca2+ sensitivity of steady-state force and decreased the rate of relaxation in fibres by approximately twofold. In contrast, a TnC mutant with decreased Ca2+ sensitivity caused by an increased Ca2+ dissociation rate in solution (NHdel TnC) decreased the Ca2+ sensitivity of steady-state force but did not accelerate relaxation. Decreasing the rate of crossbridge kinetics by reducing intracellular inorganic phosphate concentration ([Pi]) slowed relaxation by approximately twofold and led to two phases of relaxation, a slow linear phase followed by a fast exponential phase. In fibres, M82Q TnC further slowed relaxation in low [Pi] conditions by approximately twofold, whereas NHdel TnC had no significant effect on relaxation. These results are consistent with the interpretation that the Ca2+-dissociation rate and crossbridge detachment rate are similar in fast-twitch skeletal muscle, such that decreasing either rate slows relaxation, but accelerating Ca2+ dissociation has little effect on relaxation. PMID:12482894

Fast activation of dihydropyridine-sensitive calcium channels of skeletal muscle. Multiple pathways of channel gating

PubMed Central

1996-01-01

Dihydropyridine (DHP) receptors of the transverse tubule membrane play two roles in excitation-contraction coupling in skeletal muscle: (a) they function as the voltage sensor which undergoes fast transition to control release of calcium from sarcoplasmic reticulum, and (b) they provide the conducting unit of a slowly activating L-type calcium channel. To understand this dual function of the DHP receptor, we studied the effect of depolarizing conditioning pulse on the activation kinetics of the skeletal muscle DHP-sensitive calcium channels reconstituted into lipid bilayer membranes. Activation of the incorporated calcium channel was imposed by depolarizing test pulses from a holding potential of -80 mV. The gating kinetics of the channel was studied with ensemble averages of repeated episodes. Based on a first latency analysis, two distinct classes of channel openings occurred after depolarization: most had delayed latencies, distributed with a mode of 70 ms (slow gating); a small number of openings had short first latencies, < 12 ms (fast gating). A depolarizing conditioning pulse to +20 mV placed 200 ms before the test pulse (-10 mV), led to a significant increase in the activation rate of the ensemble averaged-current; the time constant of activation went from tau m = 110 ms (reference) to tau m = 45 ms after conditioning. This enhanced activation by the conditioning pulse was due to the increase in frequency of fast open events, which was a steep function of the intermediate voltage and the interval between the conditioning pulse and the test pulse. Additional analysis demonstrated that fast gating is the property of the same individual channels that normally gate slowly and that the channels adopt this property after a sojourn in the open state. The rapid secondary activation seen after depolarizing prepulses is not compatible with a linear activation model for the calcium channel, but is highly consistent with a cyclical model. A six- state cyclical model is proposed for the DHP-sensitive Ca channel, which pictures the normal pathway of activation of the calcium channel as two voltage-dependent steps in sequence, plus a voltage-independent step which is rate limiting. The model reproduced well the fast and slow gating models of the calcium channel, and the effects of conditioning pulses. It is possible that the voltage-sensitive gating transitions of the DHP receptor, which occur early in the calcium channel activation sequence, could underlie the role of the voltage sensor and yield the rapid excitation-contraction coupling in skeletal muscle, through either electrostatic or allosteric linkage to the ryanodine receptors/calcium release channels. PMID:8882865

Velocity, force, power, and Ca2+ sensitivity of fast and slow monkey skeletal muscle fibers

NASA Technical Reports Server (NTRS)

Fitts, R. H.; Bodine, S. C.; Romatowski, J. G.; Widrick, J. J.

1998-01-01

In this study, we determined the contractile properties of single chemically skinned fibers prepared from the medial gastrocnemius (MG) and soleus (Sol) muscles of adult male rhesus monkeys and assessed the effects of the spaceflight living facility known as the experiment support primate facility (ESOP). Muscle biopsies were obtained 4 wk before and immediately after an 18-day ESOP sit, and fiber type was determined by immunohistochemical techniques. The MG slow type I fiber was significantly smaller than the MG type II, Sol type I, and Sol type II fibers. The ESOP sit caused a significant reduction in the diameter of type I and type I/II (hybrid) fibers of Sol and MG type II and hybrid fibers but no shift in fiber type distribution. Single-fiber peak force (mN and kN/m2) was similar between fiber types and was not significantly different from values previously reported for other species. The ESOP sit significantly reduced the force (mN) of Sol type I and MG type II fibers. This decline was entirely explained by the atrophy of these fiber types because the force per cross-sectional area (kN/m2) was not altered. Peak power of Sol and MG fast type II fiber was 5 and 8.5 times that of slow type I fiber, respectively. The ESOP sit reduced peak power by 25 and 18% in Sol type I and MG type II fibers, respectively, and, for the former fiber type, shifted the force-pCa relationship to the right, increasing the Ca2+ activation threshold and the free Ca2+ concentration, eliciting half-maximal activation. The ESOP sit had no effect on the maximal shortening velocity (Vo) of any fiber type. Vo of the hybrid fibers was only slightly higher than that of slow type I fibers. This result supports the hypothesis that in hybrid fibers the slow myosin heavy chain would be expected to have a disproportionately greater influence on Vo.

Fermentation of Ammonia Fiber Expansion Treated and Untreated Barley Straw in a Rumen Simulation Technique Using Rumen Inoculum from Cattle with Slow versus Fast Rate of Fiber Disappearance

PubMed Central

Griffith, Candace L.; Ribeiro, Gabriel O.; Oba, Masahito; McAllister, Tim A.; Beauchemin, Karen A.

2016-01-01

The purpose of this study was to determine the effect of rumen inoculum from heifers with fast vs. slow rate of in situ fiber digestion on the fermentation of complex versus easily digested fiber sources in the forms of untreated and Ammonia Fiber Expansion (AFEX) treated barley straw, respectively, using an artificial rumen simulation technique (Rusitec). In situ fiber digestion was measured in a previous study by incubating untreated barley straw in the rumen of 16 heifers fed a diet consisting of 700 g/kg barley straw and 300 g/kg concentrate. The two heifers with fastest rate of digestion (Fast ≥ 4.18% h-1) and the two heifers with the slowest rate of digestion (Slow ≤ 3.17% h-1) were chosen as inoculum donors for this study. Two Rusitec apparatuses each equipped with eight fermenters were used in a completely randomized block design with two blocks (apparatus) and four treatments in a 2 × 2 factorial arrangement of treatments (Fast or Slow rumen inoculum and untreated or AFEX treated straw). Fast rumen inoculum and AFEX straw both increased (P < 0.05) disappearance of dry matter (DMD), organic matter, true DMD, neutral detergent fiber, acid detergent fiber, and nitrogen (N) with an interactive effect between the two (P < 0.05). Fast rumen inoculum increased (P > 0.05) methane production per gram of digested material for both untreated and AFEX straw, and reduced (interaction, P < 0.05) acetate: propionate ratio for untreated straw. Greater relative populations of Ruminococcus albus (P < 0.05) and increased microbial N production (P = 0.045) were observed in Fast rumen inoculum. AFEX straw in Fast inoculum had greater total bacterial populations than Slow, but for untreated straw this result was reversed (interaction, P = 0.013). These findings indicate that differences in microbial populations in rumen fluid contribute to differences in the capacity of rumen inoculum to digest fiber. PMID:27899919

Observation of fast and slow interatomic Coulombic decay in argon dimers induced by electron-impact ionization

NASA Astrophysics Data System (ADS)

Ren, Xueguang; Miteva, Tsveta; Kolorenč, Přemysl; Gokhberg, Kirill; Kuleff, Alexander I.; Cederbaum, Lorenz S.; Dorn, Alexander

2017-09-01

We investigate the interatomic Coulombic decay (ICD) in argon dimers induced by electron-impact ionization (E0=90 eV ) using a multiparticle coincidence experiment in which the momentum vectors and, consequently, the kinetic energies for electrons and fragment ions are determined. The signature of the ICD process is obtained from a correlation map between ejected electron energy and kinetic energy release (KER) for Ar++Ar+ fragment ions where low-energy ICD electrons can be identified. Furthermore, two types of ICD processes, termed fast and slow interatomic decay, are separated by the ICD initial-state energies and projectile energy losses. The dependence of the energies of emitted low-energy ICD electrons on the initial-state energy is studied. ICD electron energy spectra and KER spectra are obtained separately for fast and slow decay processes where the KER spectra for the slow decay channel are strongly influenced by nuclear motion. The KER and ICD electron energy spectra are well reproduced by ab initio calculations.

Bioavailability of Metsulfuron and Sulfentrazone Herbicides in Soil as Affected by Amendment with Two Contrasting Willow Biochars.

PubMed

Szmigielski, Anna M; Hangs, Ryan D; Schoenau, Jeff J

2018-02-01

This study investigated the effect of two willow (Salix spp.) biochars, produced using either fast- or slow-pyrolysis, on the bioavailability of metsulfuron and sulfentrazone herbicides in soil. Five rates (0%, 1%, 2%, 3%, and 4%; w/w) of each biochar were used, along with varying rates of metsulfuron (0-3.2 µg ai kg -1 ) and sulfentrazone (0-200 µg ai kg -1 ), followed by a sugar beet bioassay. The fast-pyrolysis biochar had minimal effect, while the slow-pyrolysis biochar decreased the bioavailability of both herbicides. Despite using the same feedstock, the two biochars had different physical and chemical properties, of which specific surface area was most contrasting (3.0 and 175 m 2  g -1 for fast- and slow-pyrolysis biochar, respectively). Increased anionic herbicide adsorption associated with greater surface area of the slow-pyrolysis biochar is considered to be the primary mechanism responsible for reducing herbicide bioavailability with this biochar.

Weak rotating flow disturbances in a centrifugal compressor with a vaneless diffuser

NASA Technical Reports Server (NTRS)

Moore, F. K.

1988-01-01

A theory is presented to predict the occurrence of weak rotating waves in a centrifugal compression system with a vaneless diffuser. As in a previous study of axial systems, an undisturbed performance characteristic is assumed known. Following an inviscid analysis of the diffuser flow, conditions for a neutral rotating disturbance are found. The solution is shown to have two branches; one with fast rotation, the other with very slow rotation. The slow branch includes a dense set of resonant solutions. The resonance is a feature of the diffuser flow, and therefore such disturbances must be expected at the various resonant flow coefficients regardless of the compressor characteristic. Slow solutions seem limited to flow coefficients less than about 0.3, where third and fourth harmonics appear. Fast waves seem limited to a first harmonic. These fast and slow waves are described, and effects of diffuser-wall convergence, backward blade angles, and partial recovery of exit velocity head are assessed.

General purpose algorithms for characterization of slow and fast phase nystagmus

NASA Technical Reports Server (NTRS)

Lessard, Charles S.

1987-01-01

In the overall aim for a better understanding of the vestibular and optokinetic systems and their roles in space motion sickness, the eye movement responses to various dynamic stimuli are measured. The vestibulo-ocular reflex (VOR) and the optokinetic response, as the eye movement responses are known, consist of slow phase and fast phase nystagmus. The specific objective is to develop software programs necessary to characterize the vestibulo-ocular and optokinetic responses by distinguishing between the two phases of nystagmus. The overall program is to handle large volumes of highly variable data with minimum operator interaction. The programs include digital filters, differentiation, identification of fast phases, and reconstruction of the slow phase with a least squares fit such that sinusoidal or psuedorandom data may be processed with accurate results. The resultant waveform, slow phase velocity eye movements, serves as input data to the spectral analysis programs previously developed for NASA to analyze nystagmus responses to pseudorandom angular velocity inputs.

A study of video frame rate on the perception of moving imagery detail

NASA Technical Reports Server (NTRS)

Haines, Richard F.; Chuang, Sherry L.

1993-01-01

The rate at which each frame of color moving video imagery is displayed was varied in small steps to determine what is the minimal acceptable frame rate for life scientists viewing white rats within a small enclosure. Two, twenty five second-long scenes (slow and fast animal motions) were evaluated by nine NASA principal investigators and animal care technicians. The mean minimum acceptable frame rate across these subjects was 3.9 fps both for the slow and fast moving animal scenes. The highest single trial frame rate averaged across all subjects for the slow and the fast scene was 6.2 and 4.8, respectively. Further research is called for in which frame rate, image size, and color/gray scale depth are covaried during the same observation period.

Reaction time performance in adolescents with attention deficit/hyperactivity disorder: evidence of inconsistency in the fast and slow portions of the RT distribution.

PubMed

Williams, Benjamin R; Strauss, Esther H; Hultsch, David F; Hunter, Michael A; Tannock, Rosemary

2007-04-01

Inconsistency across trials of 2-choice reaction time (RT) data was analyzed in 72 adolescents (age 12-17 years) within 4 groups differentiated by the presence or absence of attention deficit/hyperactivity disorder (ADHD) and reading difficulties (RD). ADHD participants were more inconsistent (across all trials, and in the slow portion of the RT distribution) than controls, but only when RD was present. Within the fast portion of the RT distribution, ADHD participants were more inconsistent than controls regardless of RD. The results highlight the importance of fluctuations in cognitive performance in ADHD and suggest that there may be independent sources of variation in inconsistency affecting the fast and slow portions of the RT distribution.

Slow oscillations orchestrating fast oscillations and memory consolidation.

PubMed

Mölle, Matthias; Born, Jan

2011-01-01

Slow-wave sleep (SWS) facilitates the consolidation of hippocampus-dependent declarative memory. Based on the standard two-stage memory model, we propose that memory consolidation during SWS represents a process of system consolidation which is orchestrated by the neocortical <1Hz electroencephalogram (EEG) slow oscillation and involves the reactivation of newly encoded representations and their subsequent redistribution from temporary hippocampal to neocortical long-term storage sites. Indeed, experimental induction of slow oscillations during non-rapid eye movement (non-REM) sleep by slowly alternating transcranial current stimulation distinctly improves consolidation of declarative memory. The slow oscillations temporally group neuronal activity into up-states of strongly enhanced neuronal activity and down-states of neuronal silence. In a feed-forward efferent action, this grouping is induced not only in the neocortex but also in other structures relevant to consolidation, namely the thalamus generating 10-15Hz spindles, and the hippocampus generating sharp wave-ripples, with the latter well known to accompany a replay of newly encoded memories taking place in hippocampal circuitries. The feed-forward synchronizing effect of the slow oscillation enables the formation of spindle-ripple events where ripples and accompanying reactivated hippocampal memory information become nested into the single troughs of spindles. Spindle-ripple events thus enable reactivated memory-related hippocampal information to be fed back to neocortical networks in the excitable slow oscillation up-state where they can induce enduring plastic synaptic changes underlying the effective formation of long-term memories. Copyright © 2011 Elsevier B.V. All rights reserved.

Limited fiber type grouping in self-reinnervation cat tibialis anterior muscles.

PubMed

Unguez, G A; Roy, R R; Bodine-Fowler, S; Edgerton, V R

1996-10-01

The percent and distribution patterns of three immunohistochemically identified fiber types within the anterior compartment of the cat tibialis anterior were determined 6 months after denervation and self-reinnervation. After self-reinnervation, mean frequencies of slow (9%) and fast (91%) fibers were similar to those in control (12% and 88%, respectively) muscles. However, a lower proportion of fast-1 (26%) and a higher proportion of fast-2 (65%) fibers were observed in self-reinnervated than control (32% and 56%) muscles. Quantitation of adjacencies between fibers of similar myosin heavy chain (MHC) phenotype, a measure of type grouping, revealed that the frequencies of two slow or two fast-1 fibers being adjacent in self-reinnervated muscles were similar to control. In contrast, the frequency of fast-2/fast-2 fiber adjacencies found in self-reinnervated muscles (45%) was significantly higher than in control muscles (37%). In both groups, the frequency of adjacencies between slow, fast-1, or fast-2 fibers was largely attributable to the number of each fiber type present. These data show that the incidence of grouping within each fiber type present was not altered after 6 months of self-reinnervation. Minimal changes in the spatial distribution of fiber types following self-reinnervation in adults suggests a limited degree of conversion of muscle fibers to a MHC phenotype matching the motoneuron characteristics.

Numerical studies of fast ion slowing down rates in cool magnetized plasma using LSP

NASA Astrophysics Data System (ADS)

Evans, Eugene S.; Kolmes, Elijah; Cohen, Samuel A.; Rognlien, Tom; Cohen, Bruce; Meier, Eric; Welch, Dale R.

2016-10-01

In MFE devices, rapid transport of fusion products from the core into the scrape-off layer (SOL) could perform the dual roles of energy and ash removal. The first-orbit trajectories of most fusion products from small field-reversed configuration (FRC) devices will traverse the SOL, allowing those particles to deposit their energy in the SOL and be exhausted along the open field lines. Thus, the fast ion slowing-down time should affect the energy balance of an FRC reactor and its neutron emissions. However, the dynamics of fast ion energy loss processes under the conditions expected in the FRC SOL (with ρe <λDe) are analytically complex, and not yet fully understood. We use LSP, a 3D electromagnetic PIC code, to examine the effects of SOL density and background B-field on the slowing-down time of fast ions in a cool plasma. As we use explicit algorithms, these simulations must spatially resolve both ρe and λDe, as well as temporally resolve both Ωe and ωpe, increasing computation time. Scaling studies of the fast ion charge (Z) and background plasma density are in good agreement with unmagnetized slowing down theory. Notably, Z-scaling represents a viable way to dramatically reduce the required CPU time for each simulation. This work was supported, in part, by DOE Contract Number DE-AC02-09CH11466.

Differential Responses of Soleus and Plantaris Muscle Fibers to Overloading

NASA Astrophysics Data System (ADS)

Kawano, Fuminori; Shibaguchi, Tsubasa; Ohira, Takashi; Nakai, Naoya; Ohira, Yoshinobu

2013-02-01

Responses of slow and fast fibers in soleus and plantaris muscles of adult rats to overloading by the tendon transection of synergists were studied. Overloading-related hypertrophy was noted in the slow fibers of plantaris and soleus, although the magnitude was greater in plantaris. Five genes with minor expression in slow soleus muscle were identified by microarray analysis. Base-line expressions of these genes in slow fibers of plantaris were also low. Further, repressive effects of overloading on these genes were seen in some fast fibers of plantaris, not in whole plantaris and soleus. The data suggested that the repression of particular genes might be related to the pronounced morphological response of fibers expressing type II, including I+II, myosin heavy chain (MyHC), although these genes with lower base-line expression in slow fibers did not respond to overloading.

Block of Brain Sodium Channels by Peptide Mimetics of the Isoleucine, Phenylalanine, and Methionine (IFM) Motif from the Inactivation Gate

PubMed Central

Eaholtz, Galen; Colvin, Anita; Leonard, Daniele; Taylor, Charles; Catterall, William A.

1999-01-01

Inactivation of sodium channels is thought to be mediated by an inactivation gate formed by the intracellular loop connecting domains III and IV. A hydrophobic motif containing the amino acid sequence isoleucine, phenylalanine, and methionine (IFM) is required for the inactivation process. Peptides containing the IFM motif, when applied to the cytoplasmic side of these channels, produce two types of block: fast block, which resembles the inactivation process, and slow, use-dependent block stimulated by strong depolarizing pulses. Fast block by the peptide ac-KIFMK-NH2, measured on sodium channels whose inactivation was slowed by the α-scorpion toxin from Leiurus quinquestriatus (LqTx), was reversed with a time constant of 0.9 ms upon repolarization. In contrast, control and LqTx-modified sodium channels were slower to recover from use-dependent block. For fast block, linear peptides of three to six amino acid residues containing the IFM motif and two positive charges were more effective than peptides with one positive charge, whereas uncharged IFM peptides were ineffective. Substitution of the IFM residues in the peptide ac-KIFMK-NH2 with smaller, less hydrophobic residues prevented fast block. The positively charged tripeptide IFM-NH2 did not cause appreciable fast block, but the divalent cation IFM-NH(CH2)2NH2 was as effective as the pentapeptide ac-KIFMK-NH2. The constrained peptide cyclic KIFMK containing two positive charges did not cause fast block. These results indicate that the position of the positive charges is unimportant, but flexibility or conformation of the IFM-containing peptide is important to allow fast block. Slow, use-dependent block was observed with IFM-containing peptides of three to six residues having one or two positive charges, but not with dipeptides or phenylalanine-amide. In contrast to its lack of fast block, cyclic KIFMK was an effective use-dependent blocker. Substitutions of amino acid residues in the tripeptide IFM-NH2 showed that large hydrophobic residues are preferred in all three positions for slow, use-dependent block. However, substitution of the large hydrophobic residue diphenylalanine or the constrained residues phenylglycine or tetrahydroisoquinoline for phe decreased potency, suggesting that this phe residue must be able to enter a restricted hydrophobic pocket during the binding of IFM peptides. Together, the results on fast block and slow, use-dependent block indicate that IFM peptides form two distinct complexes of different stability and structural specificity with receptor site(s) on the sodium channel. It is proposed that fast block represents binding of these peptides to the inactivation gate receptor, while slow, use-dependent block represents deeper binding of the IFM peptides in the pore. PMID:9925825

Dynamic formation of microenvironments at the myotendinous junction correlates with muscle fiber morphogenesis in zebrafish

PubMed Central

Snow, Chelsi J.; Henry, Clarissa A.

2009-01-01

Muscle development involves the specification and morphogenesis of muscle fibers that attach to tendons. After attachment, muscles and tendons then function as an integrated unit to transduce force to the skeletal system and stabilize joints. The attachment site is the myotendinous junction, or MTJ, and is the primary site of force transmission. We find that attachment of fast-twitch myofibers to the MTJ correlates with the formation of novel microenvironments within the MTJ. The expression or activation of two proteins involved in anchoring the intracellular cytoskeleton to the extracellular matrix, Focal adhesion kinase (Fak) and β-dystroglycan is up-regulated. Conversely, the extracellular matrix protein Fibronectin (Fn) is down-regulated. This degradation of Fn as fast-twitch fibers attach to the MTJ results in Fn protein defining a novel microenvironment within the MTJ adjacent to slow-twitch, but not fast-twitch, muscle. Interestingly, however, Fak, laminin, Fn and β-dystroglycan concentrate at the MTJ in mutants that do not have slow-twitch fibers. Taken together, these data elucidate novel and dynamic microenvironments within the MTJ and indicate that MTJ morphogenesis is spatially and temporally complex. PMID:18783736

Chronic low-frequency stimulation transforms cat masticatory muscle fibers into jaw-slow fibers.

PubMed

Kang, Lucia H D; Hoh, Joseph F Y

2011-09-01

Cat masticatory muscle during regeneration expresses masticatory-specific myofibrillar proteins upon innervation by a fast muscle nerve but acquires the jaw-slow phenotype when innervated by a slow muscle nerve. Here, we test the hypothesis that chronic low-frequency stimulation simulating impulses from the slow nerve can result in masticatory-to-slow fiber-type transformation. In six cats, the temporalis muscle was continuously stimulated directly at 10 Hz for up to 12 weeks using a stimulator affixed to the skull. Stimulated muscles were analyzed by immunohistochemistry using, among others, monoclonal antibodies against masticatory-specific myosin heavy chain (MyHC), myosin binding protein-C, and tropomyosins. Under the electrodes, stimulation induced muscle regeneration, which generated slow fibers. Deep to the electrodes, at two to three weeks, two distinct populations of masticatory fibers began to express slow MyHC: 1) evenly distributed fibers that completely suppressed masticatory-specific proteins but transiently co-expressed fetal MyHCs, and 2) incompletely transformed fibers that express slow and masticatory but not fetal MyHCs. SDS-PAGE confirmed de novo expression of slow MyHC and β-tropomyosin in the stimulated muscles. We conclude that chronic low-frequency stimulation induces masticatory-to-slow fiber-type conversion. The two populations of transforming masticatory fibers may differ in their mode of activation or lineage of their myogenic cells.

Reconstruction of gastric slow wave from finger photoplethysmographic signal using radial basis function neural network.

PubMed

Mohamed Yacin, S; Srinivasa Chakravarthy, V; Manivannan, M

2011-11-01

Extraction of extra-cardiac information from photoplethysmography (PPG) signal is a challenging research problem with significant clinical applications. In this study, radial basis function neural network (RBFNN) is used to reconstruct the gastric myoelectric activity (GMA) slow wave from finger PPG signal. Finger PPG and GMA (measured using Electrogastrogram, EGG) signals were acquired simultaneously at the sampling rate of 100 Hz from ten healthy subjects. Discrete wavelet transform (DWT) was used to extract slow wave (0-0.1953 Hz) component from the finger PPG signal; this slow wave PPG was used to reconstruct EGG. A RBFNN is trained on signals obtained from six subjects in both fasting and postprandial conditions. The trained network is tested on data obtained from the remaining four subjects. In the earlier study, we have shown the presence of GMA information in finger PPG signal using DWT and cross-correlation method. In this study, we explicitly reconstruct gastric slow wave from finger PPG signal by the proposed RBFNN-based method. It was found that the network-reconstructed slow wave provided significantly higher (P < 0.0001) correlation (≥ 0.9) with the subject's EGG slow wave than the correlation obtained (≈0.7) between the PPG slow wave from DWT and the EEG slow wave. Our results showed that a simple finger PPG signal can be used to reconstruct gastric slow wave using RBFNN method.

Effect of rate of administration of propofol or alfaxalone on induction dose requirements and occurrence of apnea in dogs.

PubMed

Bigby, Sarah E; Beths, Thierry; Bauquier, Sébastien; Carter, Jennifer E

2017-11-01

To evaluate the effect of rate of administration of propofol or alfaxalone on induction dose requirements and incidence of postinduction apnea (PIA) in dogs following premedication with methadone and dexmedetomidine. Prospective, randomized clinical trial. Thirty-two healthy American Society of Anesthesiologists class I client-owned dogs (seven females, 25 males), aged between 5 and 54 months, weighing between 2.0 and 48.2 kg. Dogs were premedicated intramuscularly with 0.5 mg kg -1 methadone and 5 μg kg -1 dexmedetomidine. Thirty minutes after premedication, dogs were preoxygenated for 5 minutes before the induction agent was administered intravenously via a syringe driver until orotracheal intubation was achieved. Dogs were randomized to receive alfaxalone 0.5 mg kg -1  minute -1 (A-Slow), alfaxalone 2 mg kg -1  minute -1 (A-Fast), propofol 1 mg kg -1  minute -1 (P-Slow), or propofol 4 mg kg -1 minute -1 (P-Fast). Oxygen saturation of hemoglobin (SpO 2 ), end-tidal carbon dioxide and respiratory rate were monitored. If PIA (≥30 seconds without a breath) occurred, the time to the first spontaneous breath was measured. If SpO 2 decreased below 90%, the experiment was stopped and manual ventilation initiated. The mean±standard deviation induction doses of alfaxalone and propofol were lower in the A-Slow [A-Slow 0.9±0.3 mg kg -1 , A-Fast 2.2±0.5 mg kg -1 (p≤0.001)] and P-Slow [P-Slow 1.8±0.6 mg kg -1 , P-Fast 4.1±0.7 mg kg -1 (p≤0.001)] groups, respectively. The incidence of PIA was 25% for the A-Slow and P-Slow groups and 100% for the A-Fast and P-Fast groups (p = 0.007). Both propofol and alfaxalone following methadone and dexmedetomidine premedication caused PIA. Induction dose requirement and incidence of PIA were affected by the rate of administration of both drugs. When possible, propofol and alfaxalone doses should be reduced and administered slowly to reduce PIA. Copyright © 2017 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.

Selective Attention in Fast and Slow Learners During Discrimination Learning in the Haptic Modality. Information and Research Report.

ERIC Educational Resources Information Center

Hunt, Dennis; And Others

Sixty-four 8-year-old children were divided into fast and slow learner groups and trained on a tactile simultaneous discrimination task. Selective attention was measured in terms of percentage contact time per trial to the relevant dimension. Inter- and intracouplings per trial were also recorded. A multivariate analysis was carried out to examine…

Slow Manifold and Hannay Angle in the Spinning Top

ERIC Educational Resources Information Center

Berry, M. V.; Shukla, P.

2011-01-01

The spin of a top can be regarded as a fast variable, coupled to the motion of the axis which is slow. In pure precession, the rotation of the axis round a cone (without nutation), can be considered as the result of a reaction from the fast spin. The resulting restriction of the total state space of the top is an illustrative example, at…

Disentangling fast and slow attentional influences of negative and taboo spoken words in the emotional Stroop paradigm.

PubMed

Bertels, Julie; Kolinsky, Régine

2016-09-01

Although the influence of the emotional content of stimuli on attention has been considered as occurring within trial, recent studies revealed that the presentation of such stimuli would also involve a slow component. The aim of the present study was to investigate fast and slow effects of negative (Exp. 1) and taboo (Exp. 2) spoken words. For this purpose, we used an auditory variant of the emotional Stroop paradigm in which each emotional word was followed by a sequence of neutral words. Replicating results from our previous study, we observed slow but no fast effects of negative and taboo words, which we interpreted as reflecting difficulties to disengage attention from their emotional dimension. Interestingly, while the presentation of a negative word only delayed the processing of the immediately subsequent neutral word, slow effects of taboo words were long-lasting. Nevertheless, such attentional effects were only observed when the emotional words were presented in the first block of trials, suggesting that once participants develop strategies to perform the task, attention-grabbing effects of emotional words disappear. Hence, far from being automatic, the occurrence of these effects would depend on participants' attentional set.

Heart Rate Effects of Intraosseous Injections Using Slow and Fast Rates of Anesthetic Solution Deposition

PubMed Central

Susi, Louis; Reader, Al; Nusstein, John; Beck, Mike; Weaver, Joel; Drum, Melissa

2008-01-01

The authors, using a crossover design, randomly administered, in a single-blind manner, 3 primary intraosseous injections to 61 subjects using: the Wand local anesthetic system at a deposition rate of 45 seconds (fast injection); the Wand local anesthetic system at a deposition rate of 4 minutes and 45 seconds (slow injection); a conventional syringe injection at a deposition rate of 4 minutes and 45 seconds (slow injection), in 3 separate appointments spaced at least 3 weeks apart. A pulse oximeter measured heart rate (pulse). The results demonstrated the mean maximum heart rate was statistically higher with the fast intraosseous injection (average 21 to 28 beats/min increase) than either of the 2 slow intraosseous injections (average 10 to 12 beats/min increase). There was no statistically significant difference between the 2 slow injections. We concluded that an intraosseous injection of 1.4 mL of 2% lidocaine with 1 : 100,000 epinephrine with the Wand at a 45-second rate of anesthetic deposition resulted in a significantly higher heart rate when compared with a 4-minute and 45-second anesthetic solution deposition using either the Wand or traditional syringe. PMID:18327970

Heart rate effects of intraosseous injections using slow and fast rates of anesthetic solution deposition.

PubMed

Susi, Louis; Reader, Al; Nusstein, John; Beck, Mike; Weaver, Joel; Drum, Melissa

2008-01-01

The authors, using a crossover design, randomly administered, in a single-blind manner, 3 primary intraosseous injections to 61 subjects using: the Wand local anesthetic system at a deposition rate of 45 seconds (fast injection); the Wand local anesthetic system at a deposition rate of 4 minutes and 45 seconds (slow injection); a conventional syringe injection at a deposition rate of 4 minutes and 45 seconds (slow injection), in 3 separate appointments spaced at least 3 weeks apart. A pulse oximeter measured heart rate (pulse). The results demonstrated the mean maximum heart rate was statistically higher with the fast intraosseous injection (average 21 to 28 beats/min increase) than either of the 2 slow intraosseous injections (average 10 to 12 beats/min increase). There was no statistically significant difference between the 2 slow injections. We concluded that an intraosseous injection of 1.4 mL of 2% lidocaine with 1 : 100,000 epinephrine with the Wand at a 45-second rate of anesthetic deposition resulted in a significantly higher heart rate when compared with a 4-minute and 45-second anesthetic solution deposition using either the Wand or traditional syringe.

CAP, epilepsy and motor events during sleep: the unifying role of arousal.

PubMed

Parrino, Liborio; Halasz, Peter; Tassinari, Carlo Alberto; Terzano, Mario Giovanni

2006-08-01

Arousal systems play a topical neurophysiologic role in protecting and tailoring sleep duration and depth. When they appear in NREM sleep, arousal responses are not limited to a single EEG pattern but are part of a continuous spectrum of EEG modifications ranging from high-voltage slow rhythms to low amplitude fast activities. The hierarchic features of arousal responses are reflected in the phase A subtypes of CAP (cyclic alternating pattern) including both slow arousals (dominated by the <1Hz oscillation) and fast arousals (ASDA arousals). CAP is an infraslow oscillation with a periodicity of 20-40s that participates in the dynamic organization of sleep and in the activation of motor events. Physiologic, paraphysiologic and pathologic motor activities during NREM sleep are always associated with a stereotyped arousal pattern characterized by an initial increase in EEG delta power and heart rate, followed by a progressive activation of faster EEG frequencies. These findings suggest that motor patterns are already written in the brain codes (central pattern generators) embraced with an automatic sequence of EEG-vegetative events, but require a certain degree of activation (arousal) to become visibly apparent. Arousal can appear either spontaneously or be elicited by internal (epileptic burst) or external (noise, respiratory disturbance) stimuli. Whether the outcome is a physiologic movement, a muscle jerk or a major epileptic attack will depend on a number of ongoing factors (sleep stage, delta power, neuro-motor network) but all events share the common trait of arousal-activated phenomena.

Pharmacology of the Nav1.1 domain IV voltage sensor reveals coupling between inactivation gating processes.

PubMed

Osteen, Jeremiah D; Sampson, Kevin; Iyer, Vivek; Julius, David; Bosmans, Frank

2017-06-27

The Na v 1.1 voltage-gated sodium channel is a critical contributor to excitability in the brain, where pathological loss of function leads to such disorders as epilepsy, Alzheimer's disease, and autism. This voltage-gated sodium (Na v ) channel subtype also plays an important role in mechanical pain signaling by primary afferent somatosensory neurons. Therefore, pharmacologic modulation of Na v 1.1 represents a potential strategy for treating excitability disorders of the brain and periphery. Inactivation is a complex aspect of Na v channel gating and consists of fast and slow components, each of which may involve a contribution from one or more voltage-sensing domains. Here, we exploit the Hm1a spider toxin, a Na v 1.1-selective modulator, to better understand the relationship between these temporally distinct modes of inactivation and ask whether they can be distinguished pharmacologically. We show that Hm1a inhibits the gating movement of the domain IV voltage sensor (VSDIV), hindering both fast and slow inactivation and leading to an increase in Na v 1.1 availability during high-frequency stimulation. In contrast, ICA-121431, a small-molecule Na v 1.1 inhibitor, accelerates a subsequent VSDIV gating transition to accelerate entry into the slow inactivated state, resulting in use-dependent block. Further evidence for functional coupling between fast and slow inactivation is provided by a Na v 1.1 mutant in which fast inactivation removal has complex effects on slow inactivation. Taken together, our data substantiate the key role of VSDIV in Na v channel fast and slow inactivation and demonstrate that these gating processes are sequential and coupled through VSDIV. These findings provide insight into a pharmacophore on VSDIV through which modulation of inactivation gating can inhibit or facilitate Na v 1.1 function.

Slow-onset myocardial infarction and its influence on help-seeking behaviors.

PubMed

O'Donnell, Sharon; Moser, Debra K

2012-01-01

Patient decision delay continues to be a major factor of delay along the pathway of care for patients with myocardial infarction (MI). Although potentially modifiable, efforts to reduce these delays through educational and media interventions have been relatively unsuccessful. This failure has been due, in part, to the lack of understanding about the complex sociopsychological and clinical dimensions associated with the phenomenon of help-seeking behavior. The aims of this study were to (1) perform an in-depth analysis of patients' MI symptom experiences and (2) describe their help-seeking behavior in response to these symptom experiences. In-depth interviews were used to examine the symptom experiences and help-seeking behavior of men and women with MI. Participants (n = 42) were interviewed 2 to 4 days after their admission to 1 of 2 hospitals in Dublin, Ireland. Two new discrete MI categories emerged from the findings-slow-onset MI and fast-onset MI. Slow-onset MI is characterized by the gradual onset of mild symptoms, whereas fast-onset MI describes the sudden onset of severe chest pain. Most participants (n = 27) experienced slow-onset MI but expected the symptom presentation associated with fast-onset MI. The mismatch of expected and experienced symptoms for participants with slow-onset MI led to the mislabeling of symptoms to a noncardiac cause and protracted help-seeking delays. Participants with fast-onset MI (n = 15) quickly attributed their symptoms to a cardiac cause, which expedited appropriate help-seeking behaviors. Definitions of MI and the educational information provided to the public need to be reviewed. Slow-onset MI and fast-onset MI provide plausible definition alternatives and, possibly, a more authentic version of real MI events than what is currently used. They also provide a unique "delay" perspective, which may inform future educational initiatives targeted at decision delay reduction.

The perforant path projection to hippocampal area CA1 in the rat hippocampal-entorhinal cortex combined slice.

PubMed

Empson, R M; Heinemann, U

1995-05-01

1. The perforant path projection from layer III of the entorhinal cortex to CA1 of the hippocampus was studied within a hippocampal-entorhinal combined slice preparation. We prevented contamination from the other main hippocampal pathways by removal of CA3 and the dentate gyrus. 2. Initially the projection was mapped using field potential recordings that suggested an excitatory sink in stratum lacunosum moleculare with an associated source in stratum pyramidale. 3. However, recording intracellularly from CA1 cells, stimulation of the perforant path produced prominent fast GABAA and slow GABAB IPSPs often preceded by small EPSPs. In a small number of cells we observed EPSPs only. 4. CNQX blocked excitatory and inhibitory responses. This indicated the presence of an intervening excitatory synapse between the inhibitory interneurone and the pyramidal cell. 5. Focal bicuculline applications revealed that the major site of GABAA inhibitory input was to stratum radiatum of CA1. 6. The inhibition activated by the perforant path was very effective at reducing simultaneously activated Schaffer collateral mediated EPSPs and suprathreshold-stimulated action potentials. 7. Blockade of fast inhibition increased excitability and enhanced slow inhibition. Both increases relied upon the activation of NMDA receptors. 8. Perforant path inputs activated prominent and effective disynaptic inhibition of CA1 cells. This has significance for the output of hippocampal processing during normal behaviour and also under pathological conditions.

Hyperpolarization-Activated Current Induces Period-Doubling Cascades and Chaos in a Cold Thermoreceptor Model

PubMed Central

Xu, Kesheng; Maidana, Jean P.; Caviedes, Mauricio; Quero, Daniel; Aguirre, Pablo; Orio, Patricio

2017-01-01

In this article, we describe and analyze the chaotic behavior of a conductance-based neuronal bursting model. This is a model with a reduced number of variables, yet it retains biophysical plausibility. Inspired by the activity of cold thermoreceptors, the model contains a persistent Sodium current, a Calcium-activated Potassium current and a hyperpolarization-activated current (Ih) that drive a slow subthreshold oscillation. Driven by this oscillation, a fast subsystem (fast Sodium and Potassium currents) fires action potentials in a periodic fashion. Depending on the parameters, this model can generate a variety of firing patterns that includes bursting, regular tonic and polymodal firing. Here we show that the transitions between different firing patterns are often accompanied by a range of chaotic firing, as suggested by an irregular, non-periodic firing pattern. To confirm this, we measure the maximum Lyapunov exponent of the voltage trajectories, and the Lyapunov exponent and Lempel-Ziv's complexity of the ISI time series. The four-variable slow system (without spiking) also generates chaotic behavior, and bifurcation analysis shows that this is often originated by period doubling cascades. Either with or without spikes, chaos is no longer generated when the Ih is removed from the system. As the model is biologically plausible with biophysically meaningful parameters, we propose it as a useful tool to understand chaotic dynamics in neurons. PMID:28344550

Walking energetics, fatigability, and fatigue in older adults: the study of energy and aging pilot.

PubMed

Richardson, Catherine A; Glynn, Nancy W; Ferrucci, Luigi G; Mackey, Dawn C

2015-04-01

Slow gait speed increases morbidity and mortality in older adults. We examined how preferred gait speed is associated with energetic requirements of walking, fatigability, and fatigue. Older adults (n = 36, 70-89 years) were categorized as slow or fast walkers based on median 400-m gait speed. We measured VO2peak by graded treadmill exercise test and VO2 during 5-minute treadmill walking tests at standard (0.72 m/s) and preferred gait speeds. Fatigability was assessed with the Situational Fatigue Scale and the Borg rating of perceived exertion at the end of walking tests. Fatigue was assessed by questionnaire. Preferred gait speed over 400 m (range: 0.75-1.58 m/s) averaged 1.34 m/s for fast walkers versus 1.05 m/s for slow walkers (p < .001). VO2peak was 26% lower (18.5 vs 25.1ml/kg/min, p = .001) in slow walkers than fast walkers. To walk at 0.72 m/s, slow walkers used a larger percentage of VO2peak (59% vs 42%, p < .001). To walk at preferred gait speed, slow walkers used more energy per unit distance (0.211 vs 0.186ml/kg/m, p = .047). Slow walkers reported higher rating of perceived exertion during walking and greater overall fatigability on the Situational Fatigue Scale, but no differences in fatigue. Slow walking was associated with reduced aerobic capacity, greater energetic cost of walking, and greater fatigability. Interventions to improve aerobic capacity or decrease energetic cost of walking may prevent slowing of gait speed and promote mobility in older adults. © The Author 2014. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Walking Energetics, Fatigability, and Fatigue in Older Adults: The Study of Energy and Aging Pilot

PubMed Central

Richardson, Catherine A.; Glynn, Nancy W.; Ferrucci, Luigi G.

2015-01-01

Background. Slow gait speed increases morbidity and mortality in older adults. We examined how preferred gait speed is associated with energetic requirements of walking, fatigability, and fatigue. Methods. Older adults (n = 36, 70–89 years) were categorized as slow or fast walkers based on median 400-m gait speed. We measured VO2peak by graded treadmill exercise test and VO2 during 5-minute treadmill walking tests at standard (0.72 m/s) and preferred gait speeds. Fatigability was assessed with the Situational Fatigue Scale and the Borg rating of perceived exertion at the end of walking tests. Fatigue was assessed by questionnaire. Results. Preferred gait speed over 400 m (range: 0.75–1.58 m/s) averaged 1.34 m/s for fast walkers versus 1.05 m/s for slow walkers (p < .001). VO2peak was 26% lower (18.5 vs 25.1ml/kg/min, p = .001) in slow walkers than fast walkers. To walk at 0.72 m/s, slow walkers used a larger percentage of VO2peak (59% vs 42%, p < .001). To walk at preferred gait speed, slow walkers used more energy per unit distance (0.211 vs 0.186ml/kg/m, p = .047). Slow walkers reported higher rating of perceived exertion during walking and greater overall fatigability on the Situational Fatigue Scale, but no differences in fatigue. Conclusions. Slow walking was associated with reduced aerobic capacity, greater energetic cost of walking, and greater fatigability. Interventions to improve aerobic capacity or decrease energetic cost of walking may prevent slowing of gait speed and promote mobility in older adults. PMID:25190069

The Speed Reading Is in Disrepute: Advantages of Slow Reading for the Information Equilibrium

ERIC Educational Resources Information Center

Tsvetkova, Milena I.

2017-01-01

The study is dedicated to the impact of the speed and the acceleration on the preservation of the information equilibrium and the ability for critical thinking in the active person. The methods about the fast reading training are subjected to a critical analysis. On the grounds of the theory for the information equilibrium and the philosophy of…

Event rate and reaction time performance in ADHD: Testing predictions from the state regulation deficit hypothesis using an ex-Gaussian model.

PubMed

Metin, Baris; Wiersema, Jan R; Verguts, Tom; Gasthuys, Roos; van Der Meere, Jacob J; Roeyers, Herbert; Sonuga-Barke, Edmund

2016-01-01

According to the state regulation deficit (SRD) account, ADHD is associated with a problem using effort to maintain an optimal activation state under demanding task settings such as very fast or very slow event rates. This leads to a prediction of disrupted performance at event rate extremes reflected in higher Gaussian response variability that is a putative marker of activation during motor preparation. In the current study, we tested this hypothesis using ex-Gaussian modeling, which distinguishes Gaussian from non-Gaussian variability. Twenty-five children with ADHD and 29 typically developing controls performed a simple Go/No-Go task under four different event-rate conditions. There was an accentuated quadratic relationship between event rate and Gaussian variability in the ADHD group compared to the controls. The children with ADHD had greater Gaussian variability at very fast and very slow event rates but not at moderate event rates. The results provide evidence for the SRD account of ADHD. However, given that this effect did not explain all group differences (some of which were independent of event rate) other cognitive and/or motivational processes are also likely implicated in ADHD performance deficits.

Observation of the molecular organization of calcium release sites in fast- and slow-twitch skeletal muscle with nanoscale imaging.

PubMed

Jayasinghe, Isuru D; Munro, Michelle; Baddeley, David; Launikonis, Bradley S; Soeller, Christian

2014-10-06

Localization microscopy is a fairly recently introduced super-resolution fluorescence imaging modality capable of achieving nanometre-scale resolution. We have applied the dSTORM variation of this method to image intracellular molecular assemblies in skeletal muscle fibres which are large cells that critically rely on nanoscale signalling domains, the triads. Immunofluorescence staining in fixed adult rat skeletal muscle sections revealed clear differences between fast- and slow-twitch fibres in the molecular organization of ryanodine receptors (RyRs; the primary calcium release channels) within triads. With the improved resolution offered by dSTORM, abutting arrays of RyRs in transverse view of fast fibres were observed in contrast to the fragmented distribution on slow-twitch muscle that were approximately 1.8 times shorter and consisted of approximately 1.6 times fewer receptors. To the best of our knowledge, for the first time, we have quantified the nanometre-scale spatial association between triadic proteins using multi-colour super-resolution, an analysis difficult to conduct with electron microscopy. Our findings confirm that junctophilin-1 (JPH1), which tethers the sarcoplasmic reticulum ((SR) intracellular calcium store) to the tubular (t-) system at triads, was present throughout the RyR array, whereas JPH2 was contained within much smaller nanodomains. Similar imaging of the primary SR calcium buffer, calsequestrin (CSQ), detected less overlap of the triad with CSQ in slow-twitch muscle supporting greater spatial heterogeneity in the luminal Ca2+ buffering when compared with fast twitch muscle. Taken together, these nanoscale differences can explain the fundamentally different physiologies of fast- and slow-twitch muscle. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Observation of the molecular organization of calcium release sites in fast- and slow-twitch skeletal muscle with nanoscale imaging

PubMed Central

Jayasinghe, Isuru D.; Munro, Michelle; Baddeley, David; Launikonis, Bradley S.; Soeller, Christian

2014-01-01

Localization microscopy is a fairly recently introduced super-resolution fluorescence imaging modality capable of achieving nanometre-scale resolution. We have applied the dSTORM variation of this method to image intracellular molecular assemblies in skeletal muscle fibres which are large cells that critically rely on nanoscale signalling domains, the triads. Immunofluorescence staining in fixed adult rat skeletal muscle sections revealed clear differences between fast- and slow-twitch fibres in the molecular organization of ryanodine receptors (RyRs; the primary calcium release channels) within triads. With the improved resolution offered by dSTORM, abutting arrays of RyRs in transverse view of fast fibres were observed in contrast to the fragmented distribution on slow-twitch muscle that were approximately 1.8 times shorter and consisted of approximately 1.6 times fewer receptors. To the best of our knowledge, for the first time, we have quantified the nanometre-scale spatial association between triadic proteins using multi-colour super-resolution, an analysis difficult to conduct with electron microscopy. Our findings confirm that junctophilin-1 (JPH1), which tethers the sarcoplasmic reticulum ((SR) intracellular calcium store) to the tubular (t-) system at triads, was present throughout the RyR array, whereas JPH2 was contained within much smaller nanodomains. Similar imaging of the primary SR calcium buffer, calsequestrin (CSQ), detected less overlap of the triad with CSQ in slow-twitch muscle supporting greater spatial heterogeneity in the luminal Ca2+ buffering when compared with fast twitch muscle. Taken together, these nanoscale differences can explain the fundamentally different physiologies of fast- and slow-twitch muscle. PMID:25100314

Fast Versus Slow Strategy of Switching Patients With Schizophrenia to Aripiprazole From Other Antipsychotics.

PubMed

Hwang, Tzung-Jeng; Lo, Wei-Ming; Chan, Hung-Yu; Lin, Ching-Feng; Hsieh, Ming H; Liu, Chen-Chun; Liu, Chih-Min; Hwu, Hai-Gwo; Kuo, Ching-Hua; Chen, Wei J

2015-12-01

This study aimed to compare strategies differing in the speed of switching schizophrenic patients to aripiprazole from other antipsychotic agents, with dual administration for 2 weeks and then tapering off the current antipsychotic in fast (within 1 week) versus slow (within 4 weeks) strategies. This 8-week, open-label, randomized, parallel study assigned patients with a primary Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, diagnosis of schizophrenia or schizoaffective disorder to either the fast-switching (n = 38) or slow-switching (n = 41) group. Efficacy assessments at 5 time points included Positive and Negative Syndrome Scale and Clinical Global Impression scale. Safety assessments included extrapyramidal symptoms, metabolic profile, serum prolactin level, QTc interval, and adverse events. Drug concentrations and cytochrome P450 CYP2D6 and CYP3A4 genotypes were also measured. The fast- and slow-switching groups were comparable in demographical and clinical features at baseline and dropout rate. In the intention-to-treat analysis using mixed-effects models, there were significant within-group decreases over time in the Positive and Negative Syndrome Scale total scores (P = 0.03) and its subscores except for positive subscores, whereas no between-group differences were found. A reduction in body weight (P = 0.01) and lower levels of total cholesterol (P = 0.03), triglycerides (P = 0.03), and prolactin (P = 0.01) were noted in both groups but no increase in extrapyramidal symptoms or prolongation of QTc. The blood concentrations of aripiprazole in all patients were in a therapeutic range at day 56, with CYP2D6*10 polymorphisms being associated with aripiprazole concentrations. In conclusion, there is no significant difference between the fast- and slow-switching strategy in terms of improvements in clinical symptoms and metabolic profile in this 8-week study.

The effects of maternal corticosterone levels on offspring behavior in fast- and slow-growth garter snakes (Thamnophis elegans).

PubMed

Robert, Kylie A; Vleck, Carol; Bronikowski, Anne M

2009-01-01

During embryonic development, viviparous offspring are exposed to maternally circulating hormones. Maternal stress increases offspring exposure to corticosterone and this hormonal exposure has the potential to influence developmental, morphological and behavioral traits of the resulting offspring. We treated pregnant female garter snakes (Thamnophis elegans) with low levels of corticosterone after determining both natural corticosterone levels in the field and pre-treatment levels upon arrival in the lab. Additional measurements of plasma corticosterone were taken at days 1, 5, and 10 during the 10-day exposure, which occurred during the last third of gestation (of 4-month gestation). These pregnant snakes were from replicate populations of fast- and slow-growth ecotypes occurring in Northern California, with concomitant short and long lifespans. Field corticosterone levels of pregnant females of the slow-growth ecotype were an order of magnitude higher than fast-growth dams. In the laboratory, corticosterone levels increased over the 10 days of corticosterone manipulation for animals of both ecotypes, and reached similar plateaus for both control and treated dams. Despite similar plasma corticosterone levels in treated and control mothers, corticosterone-treated dams produced more stillborn offspring and exhibited higher total reproductive failure than control dams. At one month of age, offspring from fast-growth females had higher plasma corticosterone levels than offspring from slow-growth females, which is opposite the maternal pattern. Offspring from corticosterone-treated mothers, although unaffected in their slither speed, exhibited changes in escape behaviors and morphology that were dependent upon maternal ecotype. Offspring from corticosterone-treated fast-growth females exhibited less anti-predator reversal behavior; offspring from corticosterone-treated slow-growth females exhibited less anti-predator tail lashing behavior.

Correlations between the Signal Complexity of Cerebral and Cardiac Electrical Activity: A Multiscale Entropy Analysis

PubMed Central

Lin, Pei-Feng; Lo, Men-Tzung; Tsao, Jenho; Chang, Yi-Chung; Lin, Chen; Ho, Yi-Lwun

2014-01-01

The heart begins to beat before the brain is formed. Whether conventional hierarchical central commands sent by the brain to the heart alone explain all the interplay between these two organs should be reconsidered. Here, we demonstrate correlations between the signal complexity of brain and cardiac activity. Eighty-seven geriatric outpatients with healthy hearts and varied cognitive abilities each provided a 24-hour electrocardiography (ECG) and a 19-channel eye-closed routine electroencephalography (EEG). Multiscale entropy (MSE) analysis was applied to three epochs (resting-awake state, photic stimulation of fast frequencies (fast-PS), and photic stimulation of slow frequencies (slow-PS)) of EEG in the 1–58 Hz frequency range, and three RR interval (RRI) time series (awake-state, sleep and that concomitant with the EEG) for each subject. The low-to-high frequency power (LF/HF) ratio of RRI was calculated to represent sympatho-vagal balance. With statistics after Bonferroni corrections, we found that: (a) the summed MSE value on coarse scales of the awake RRI (scales 11–20, RRI-MSE-coarse) were inversely correlated with the summed MSE value on coarse scales of the resting-awake EEG (scales 6–20, EEG-MSE-coarse) at Fp2, C4, T6 and T4; (b) the awake RRI-MSE-coarse was inversely correlated with the fast-PS EEG-MSE-coarse at O1, O2 and C4; (c) the sleep RRI-MSE-coarse was inversely correlated with the slow-PS EEG-MSE-coarse at Fp2; (d) the RRI-MSE-coarse and LF/HF ratio of the awake RRI were correlated positively to each other; (e) the EEG-MSE-coarse at F8 was proportional to the cognitive test score; (f) the results conform to the cholinergic hypothesis which states that cognitive impairment causes reduction in vagal cardiac modulation; (g) fast-PS significantly lowered the EEG-MSE-coarse globally. Whether these heart-brain correlations could be fully explained by the central autonomic network is unknown and needs further exploration. PMID:24498375

Bounded tracking for nonminimum phase nonlinear systems with fast zero dynamics

DOT National Transportation Integrated Search

1996-12-01

A PostScript file. In this paper, tracking control laws for nonminimum phase nonlinear systems with both fast and slow, possibly unstable, zero dynamics are derived. The fast zero dynamics arise from a perturbation of a nominal system. These fast zer...

Multifunctional High Drug Loading Nanocarriers for Cancer Drug Delivery

NASA Astrophysics Data System (ADS)

Jin, Erlei

2011-12-01

Most anticancer drugs have poor water-solubility, rapid blood clearance, low tumor-selectivity and severe systemic toxicity to healthy tissues. Thus, polymeric nanocarriers have been widely explored for anticancer drugs to solve these problems. However, polymer nanocarriers developed to date still suffer drawbacks including low drug loading contents, premature drug release, slow cellular internalization, slow intracellular drug release and thereby low therapeutic efficiency in cancer thermotherapy. Accordingly, in this dissertation, functional nanocapsules and nanoparticles including high drug loading liposome-like nanocapsules, high drug loading phospholipid-mimic nanocapsules with fast intracellular drug release, high drug loading charge-reversal nanocapsules, TAT based long blood circulation nanoparticles and charge-reversal nuclear targeted nanoparticles are designed and synthesized. These functional carriers have advantages such as high drug loading contents without premature drug release, fast cellular internalization and intracellular drug release, nuclear targeted delivery and long blood circulation. As a result, all these drug carriers show much higher in vitro and in vivo anti-cancer activities.

A method for multiprotein assembly in cells reveals independent action of kinesins in complex

PubMed Central

Norris, Stephen R.; Soppina, Virupakshi; Dizaji, Aslan S.; Schimert, Kristin I.; Sept, David; Cai, Dawen; Sivaramakrishnan, Sivaraj

2014-01-01

Teams of processive molecular motors are critical for intracellular transport and organization, yet coordination between motors remains poorly understood. Here, we develop a system using protein components to generate assemblies of defined spacing and composition inside cells. This system is applicable to studying macromolecular complexes in the context of cell signaling, motility, and intracellular trafficking. We use the system to study the emergent behavior of kinesin motors in teams. We find that two kinesin motors in complex act independently (do not help or hinder each other) and can alternate their activities. For complexes containing a slow kinesin-1 and fast kinesin-3 motor, the slow motor dominates motility in vitro but the fast motor can dominate on certain subpopulations of microtubules in cells. Both motors showed dynamic interactions with the complex, suggesting that motor–cargo linkages are sensitive to forces applied by the motors. We conclude that kinesin motors in complex act independently in a manner regulated by the microtubule track. PMID:25365993

Down-regulation of adipose tissue lipoprotein lipase during fasting requires that a gene, separate from the lipase gene, is switched on.

PubMed

Bergö, Martin; Wu, Gengshu; Ruge, Toralph; Olivecrona, Thomas

2002-04-05

During short term fasting, lipoprotein lipase (LPL) activity in rat adipose tissue is rapidly down-regulated. This down-regulation occurs on a posttranslational level; it is not accompanied by changes in LPL mRNA or protein levels. The LPL activity can be restored within 4 h by refeeding. Previously, we showed that during fasting there is a shift in the distribution of lipase protein toward an inactive form with low heparin affinity. To study the nature of the regulatory mechanism, we determined the in vivo turnover of LPL activity, protein mass, and mRNA in rat adipose tissue. When protein synthesis was inhibited with cycloheximide, LPL activity and protein mass decreased rapidly and in parallel with half-lives of around 2 h, and the effect of refeeding was blocked. This indicates that maintaining high levels of LPL activity requires continuous synthesis of new enzyme protein. When transcription was inhibited by actinomycin, LPL mRNA decreased with half-lives of 13.3 and 16.8 h in the fed and fasted states, respectively, demonstrating slow turnover of the LPL transcript. Surprisingly, when actinomycin was given to fed rats, LPL activity was not down-regulated during fasting, indicating that actinomycin interferes with the transcription of a gene that blocks the activation of newly synthesized LPL protein. When actinomycin was given to fasted rats, LPL activity increased 4-fold within 6 h, even in the absence of refeeding. The same effect was seen with alpha-amanitin, another inhibitor of transcription. The response to actinomycin was much less pronounced in aging rats, which are obese and insulin-resistant. These data suggest a default state where LPL protein is synthesized on a relatively stable mRNA and is processed into its active form. During fasting, a gene is switched on whose product prevents the enzyme from becoming active even though synthesis of LPL protein continues unabated.

The Ca2+ sensitizer CK‐2066260 increases myofibrillar Ca2+ sensitivity and submaximal force selectively in fast skeletal muscle

PubMed Central

Cheng, Arthur J.; Hartman, James J.; Hinken, Aaron C.; Lee, Ken; Durham, Nickie; Russell, Alan J.; Malik, Fady I.; Westerblad, Håkan; Jasper, Jeffrey R.

2017-01-01

Key points We report that the small molecule CK‐2066260 selectively slows the off‐rate of Ca2 + from fast skeletal muscle troponin, leading to increased myofibrillar Ca2 + sensitivity in fast skeletal muscle.Rodents dosed with CK‐2066260 show increased hindlimb muscle force and power in response to submaximal rates of nerve stimulation in situ.CK‐2066260 has no effect on free cytosolic [Ca2 +] during contractions of isolated muscle fibres.We conclude that fast skeletal muscle troponin sensitizers constitute a potential therapy to address an unmet need of improving muscle function in conditions of weakness and premature muscle fatigue. Abstract Skeletal muscle dysfunction occurs in many diseases and can lead to muscle weakness and premature muscle fatigue. Here we show that the fast skeletal troponin activator, CK‐2066260, counteracts muscle weakness by increasing troponin Ca2+ affinity, thereby increasing myofibrillar Ca2+ sensitivity. Exposure to CK‐2066260 resulted in a concentration‐dependent increase in the Ca2+ sensitivity of ATPase activity in isolated myofibrils and reconstituted hybrid sarcomeres containing fast skeletal muscle troponin C. Stopped‐flow experiments revealed a ∼2.7‐fold decrease in the Ca2+ off‐rate of isolated troponin complexes in the presence of CK‐2066260 (6 vs. 17 s−1 under control conditions). Isolated mouse flexor digitorum brevis fibres showed a rapidly developing, reversible and concentration‐dependent force increase at submaximal stimulation frequencies. This force increase was not accompanied by any changes in the free cytosolic [Ca2+] or its kinetics. CK‐2066260 induced a slowing of relaxation, which was markedly larger at 26°C than at 31°C and could be linked to the decreased Ca2+ off‐rate of troponin C. Rats dosed with CK‐2066260 showed increased hindlimb isometric and isokinetic force in response to submaximal rates of nerve stimulation in situ producing significantly higher absolute forces at low isokinetic velocities, whereas there was no difference in force at the highest velocities. Overall muscle power was increased and the findings are consistent with a lack of effect on crossbridge kinetics. In conclusion, CK‐2066260 acts as a fast skeletal troponin activator that may be used to increase muscle force and power in conditions of muscle weakness. PMID:27869319

Peptide-gated ion channels and the simple nervous system of Hydra.

PubMed

Gründer, Stefan; Assmann, Marc

2015-02-15

Neurons either use electrical or chemical synapses to communicate with each other. Transmitters at chemical synapses are either small molecules or neuropeptides. After binding to their receptors, transmitters elicit postsynaptic potentials, which can either be fast and transient or slow and longer lasting, depending on the type of receptor. Fast transient potentials are mediated by ionotropic receptors and slow long-lasting potentials by metabotropic receptors. Transmitters and receptors are well studied for animals with a complex nervous system such as vertebrates and insects, but much less is known for animals with a simple nervous system like Cnidaria. As cnidarians arose early in animal evolution, nervous systems might have first evolved within this group and the study of neurotransmission in cnidarians might reveal an ancient mechanism of neuronal communication. The simple nervous system of the cnidarian Hydra extensively uses neuropeptides and, recently, we cloned and functionally characterized an ion channel that is directly activated by neuropeptides of the Hydra nervous system. These results demonstrate the existence of peptide-gated ion channels in Hydra, suggesting they mediate fast transmission in its nervous system. As related channels are also present in the genomes of the cnidarian Nematostella, of placozoans and of ctenophores, it should be considered that the early nervous systems of cnidarians and ctenophores have co-opted neuropeptides for fast transmission at chemical synapses. © 2015. Published by The Company of Biologists Ltd.

Design of extraction system in BRing at HIAF

NASA Astrophysics Data System (ADS)

Ruan, Shuang; Yang, Jiancheng; Zhang, Jinquan; Shen, Guodong; Ren, Hang; Liu, Jie; Shangguan, Jingbing; Zhang, Xiaoying; Zhang, Jingjing; Mao, Lijun; Sheng, Lina; Yin, Dayu; Wang, Geng; Wu, Bo; Yao, Liping; Tang, Meitang; Cai, Fucheng; Chen, Xiaoqiang

2018-06-01

The Booster Ring (BRing), which is the key part of HIAF (High Intensity heavy ion Accelerator Facility) complex at IMP (Institute of Modern Physics, Chinese Academy of Sciences), can provide uranium (A / q = 7) beam with a wide extraction energy range of 200-800 MeV/u. To fulfill a flexible beam extraction for multi-purpose experiments, both fast and slow extraction systems will be accommodated in the BRing. The fast extraction system is used for extracting short bunched beam horizontally in single-turn. The slow extraction system is used to provide quasi-continuous beam by the third order resonance and RF-knockout scheme. To achieve a compact structure, the two extraction systems are designed to share the same extraction channel. The general design of the fast and slow extraction systems and simulation results are discussed in this paper.

Slow rupture of frictional interfaces

NASA Astrophysics Data System (ADS)

Bar Sinai, Yohai; Brener, Efim A.; Bouchbinder, Eran

2012-02-01

The failure of frictional interfaces and the spatiotemporal structures that accompany it are central to a wide range of geophysical, physical and engineering systems. Recent geophysical and laboratory observations indicated that interfacial failure can be mediated by slow slip rupture phenomena which are distinct from ordinary, earthquake-like, fast rupture. These discoveries have influenced the way we think about frictional motion, yet the nature and properties of slow rupture are not completely understood. We show that slow rupture is an intrinsic and robust property of simple non-monotonic rate-and-state friction laws. It is associated with a new velocity scale cmin, determined by the friction law, below which steady state rupture cannot propagate. We further show that rupture can occur in a continuum of states, spanning a wide range of velocities from cmin to elastic wave-speeds, and predict different properties for slow rupture and ordinary fast rupture. Our results are qualitatively consistent with recent high-resolution laboratory experiments and may provide a theoretical framework for understanding slow rupture phenomena along frictional interfaces.

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

Voigt, Aiko; Pincus, Robert; Stevens, Bjorn

Previous modeling work showed that aerosol can affect the position of the tropical rain belt, i.e., the intertropical convergence zone (ITCZ). Yet it remains unclear which aspects of the aerosol impact are robust across models, and which are not. Here we present simulations with seven comprehensive atmosphere models that study the fast and slow impacts of an idealized anthropogenic aerosol on the zonal-mean ITCZ position. The fast impact, which results from aerosol atmospheric heating and land cooling before sea-surface temperature (SST) has time to respond, causes a northward ITCZ shift. Yet the fast impact is compensated locally by decreased evaporationmore » over the ocean, and a clear northward shift is only found for an unrealistically large aerosol forcing. The local compensation implies that while models differ in atmospheric aerosol heating, this does not contribute to model differences in the ITCZ shift. The slow impact includes the aerosol impact on the ocean surface energy balance and is mediated by SST changes. The slow impact is an order of magnitude more effective than the fast impact and causes a clear southward ITCZ shift for realistic aerosol forcing. Models agree well on the slow ITCZ shift when perturbed with the same SST pattern. However, an energetic analysis suggests that the slow ITCZ shifts would be substantially more model-dependent in interactive-SST setups due to model differences in clear-sky radiative transfer and clouds. In conclusion, we also discuss implications for the representation of aerosol in climate models and attributions of recent observed ITCZ shifts to aerosol.« less

Sensitivity of wave propagation in the LHRF to initial poloidal position in finite-aspect-ratio toroidal plasmas

NASA Astrophysics Data System (ADS)

Larson, J. J.; Pinsker, R. I.; Bonoli, P. T.; Porkolab, M.

2017-10-01

The important effect of varying the initial poloidal wave-launching location to the core accessibility of lower hybrid slow waves in a torus of finite aspect ratio has been understood for many years. Since the qualitative properties of the wave propagation of the other branch in this regime, known as the `whistler', `helicon' or simply the `fast wave', are similar in some ways to those of the slow wave, we expect a dependence on launch position for this wave also. We study this problem for both slow and fast waves, first with simplified analytic models and then using the ray-tracing code GENRAY for realistic plasma equilibria. We assess the prospects of inside, top, bottom or conventional outside launch of waves on each of the two branches. Although the slow wave has been the focus of research for LHRF heating and current drive in the past, the fast wave will play a major role in burning plasmas beyond ITER where Te(0) = 10-20 keV. The stronger electron Landau damping of the slow wave will restrict the power deposition to the outer third of the plasma, while the fast wave's weaker damping allows the wave to penetrate to the hot plasma core before depositing its power. Work supported in part by US DoE under the Science Undergraduate Laboratory Internship (SULI) program and under DE-FC02-04ER54698 and DE-FG02-91-ER54109.

tRNA modification profiles of the fast-proliferating cancer cells

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

Dong, Chao; Niu, Leilei; Song, Wei

Despite the recent progress in RNA modification study, a comprehensive modification profile is still lacking for mammalian cells. Using a quantitative HPLC/MS/MS assay, we present here a study where RNA modifications are examined in term of the major RNA species. With paired slow- and fast-proliferating cell lines, distinct RNA modification profiles are first revealed for diverse RNA species. Compared to mRNAs, increased ribose and nucleobase modifications are shown for the highly-structured tRNAs and rRNAs, lending support to their contribution to the formation of high-order structures. This study also reveals a dynamic tRNA modification profile in the fast-proliferating cells. In additionmore » to cultured cells, this unique tRNA profile has been further confirmed with endometrial cancers and their adjacent normal tissues. Taken together, the results indicate that tRNA is a actively regulated RNA species in the fast-proliferating cancer cells, and suggest that they may play a more active role in biological process than expected. -- Highlights: •RNA modifications were first examined in term of the major RNA species. •A dynamic tRNA modifications was characterized for the fast-proliferating cells. •The unique tRNA profile was confirmed with endometrial cancers and their adjacent normal tissues. •tRNA was predicted as an actively regulated RNA species in the fast-proliferating cancer cells.« less

Buffers and Oscillations in Intracellular Ca2+ Dynamics

PubMed Central

Falcke, Martin

2003-01-01

I model the behavior of intracellular Ca2+ release with high buffer concentrations. The model uses a spatially discrete array of channel clusters. The channel subunit dynamics is a stochastic representation of the DeYoung-Keizer model. The calculations show that the concentration profile of fast buffer around an open channel is more localized than that of slow buffers. Slow buffers allow for release of larger amounts of Ca2+ from the endoplasmic reticulum and hence bind more Ca2+ than fast buffers with the same dissociation constant and concentration. I find oscillation-like behavior for high slow buffer concentration and low Ca2+ content of the endoplasmic reticulum. High concentration of slow buffer leads to oscillation-like behavior by repetitive wave nucleation for high Ca2+ content of the endoplasmic reticulum. Localization of Ca2+ release by slow buffer, as used in experiments, can be reproduced by the modeling approach. PMID:12524263

Initiation of Solar Eruptions

NASA Technical Reports Server (NTRS)

Sterling, Alphonse C.; Moore, Ronald L.

2007-01-01

We consider processes occurring just prior to and at the start of the onset of flare- and CME-producing solar eruptions. Our recent work uses observations of filament motions around the time of eruption onset as a proxy for the evolution of the fields involved in the eruption. Frequently the filaments show a slow rise prior to fast eruption, indicative of a slow expansion of the field that is about co explode. Work by us and others suggests that reconnection involving emerging or canceling flux results in a lengthening of fields restraining the filament-carrying field, and the consequent upward expansion of the field in and around the filament produces the filament's slow rise: that is, the reconnection weakens the magnetic "tethers" ("tether-weakening" reconnection), and results in the slow rise of the filament. It is still inconclusive, however, what mechanism is responsible for the switch from the slow rise to the fast eruption.

A Cost Framework for the Economic Feasibility of Wide-Scale Biochar Production

NASA Astrophysics Data System (ADS)

Pourhashem, G.; Masiello, C. A.; Medlock, K. B., III

2017-12-01

Biochar is a product of biomass pyrolysis, one of the main thermal pathways of producing biofuels. In addition to sequestering carbon, biochar's soil application helps sustainable agriculture by enhancing soil's structure and ecological functions, as well as lowering NO release from fertilized soils. However, wide-scale biochar land amendment has been limited in part due to its high cost. To examine biochar's cost dynamics, we develop a comprehensive framework for a representative biochar production facility and identify system inputs that are the key drivers of cost and profitability. We assess the production cost of fast and slow pyrolysis-biochar considering a range of parameters e.g. biomass type, process design and scale. We analyzed techno-economic cost data for producing biochar using simulated data from academic literature, and active producer data collected under confidentiality agreement. The combined approach was used to enhance the depth of the dataset and allowed for a reasonable check on published simulated data. Fast and slow pyrolysis have different biofuel and biochar yields and profit. A slow pyrolysis facility recovers its expenses mainly through biochar sale while a fast pyrolysis facility generates its primary revenue through biofuel sale, largely considering biochar a byproduct. Unlike fast pyrolysis that has received most attention in techno-economic studies, publicly available techno-economic data of slow pyrolysis is sparse. This limits the ability to run a thorough cost-benefit analysis to inform the feasibility of wider adoption of biochar for capturing its carbon sequestration and broader environmental benefits. Our model allows for consideration of various market-based policy instruments and can be used as an analytical decision making tool for investors and policy makers to estimate the cost and optimum facility size. This dynamic framework can also be adapted to account for the availability of new data as technology improves and industry evolves. Our study helps identify pyrolysis pathways that are most economically suitable for scaling up biochar production for ecosystem carbon storage and environmental improvement. Finally, we discuss the market development or policy strategies that can make biochar an attractive environmental mitigation tool for decision makers.

Polarization/Spatial Combining of Laser-Diode Pump Beams

NASA Technical Reports Server (NTRS)

Gelsinger, Paul; Liu, Duncan

2008-01-01

A breadboard version of an optical beam combiner is depicted which make it possible to use the outputs of any or all of four multimode laser diodes to pump a non-planar ring oscillator (NPRO) laser. The output of each laser diode has a single-mode profile in the meridional plane containing an axis denoted the 'fast' axis and a narrower multimode profile in the orthogonal meridional plane, which contains an axis denoted the 'slow' axis and a narrower multimode profile in the orthogonal meridional plane, which contains an axis denoted the 'slow' axis. One of the purposes served by the beam-combining optics is to reduce the fast-axis numerical aperture (NA) of the laser-diode output to match the NA of the optical fiber. Along the slow axis, the unmodified laser-diode NA is already well matched to the fiber optic NA, so no further slow-axis beam shaping is needed. In this beam combiner, the laser-diode outputs are collimated by aspherical lenses, then half-wave plates and polarizing beam splitters are used to combine the four collimated beams into two beams. Spatial combination of the two beams and coupling into the optical fiber is effected by use of anamorphic prisms, mirrors, and a focusing lens. The anamorphic prisms are critical elements in the NA-matching scheme, in that they reduce the fast-axis beam width to 1/6 of its original values. Inasmuch as no slow-axis beam shaping is needed, the collimating and focusing lenses are matched for 1:1 iumaging. Because these lenses are well corrected for infinite conjugates the combiner offers diffraction-limited performance along both the fast and slow axes.

Effects of muscle fiber type on glycolytic potential and meat quality traits in different Tibetan pig muscles and their association with glycolysis-related gene expression.

PubMed

Shen, L Y; Luo, J; Lei, H G; Jiang, Y Z; Bai, L; Li, M Z; Tang, G Q; Li, X W; Zhang, S H; Zhu, L

2015-11-13

The myosin heavy chain (MyHC) composition, glycolytic potential, mitochondrial content, and gene expression related to energy metabolism were analyzed in eight muscles from Tibetan pigs, to study how meat quality develops in different muscle tissues. The muscles were classified into three clusters, based on MyHC composition: masseter, trapezius, and latissimus dorsi as 'slow-oxidative-type'; psoas major and semimembranosus as 'intermediate-type'; and longissimus dorsi, obliquus externus abdominis, and semitendinosus as 'fast-glycolytic-type'. The 'slow-oxidative-type' muscles had the highest MyHC I and MyHC IIA content (P < 0.01); 'intermediate-type' muscles, the highest MyHC IIx content (P < 0.01); and 'fast-glycolytic-type' muscles, the highest MyHC IIb content (P < 0.01). The pH values measured in 'slow-oxidative-type' muscles were higher than those in the other clusters were; however, the color of 'fast-glycolytic-type' muscles was palest (P < 0.01). Mitochondrial content increased in the order: fast-glycolytic-type < intermediate-type < slow-oxidative-type. In the 'slow-oxidative-type' muscles, the expression levels of genes related to ATP synthesis were higher, but were lower for those related to glycogen synthesis and glycolysis. Mitochondrial content was significantly positively correlated with MyHC I content, but negatively correlated with MyHC IIb content. MyHC I and mitochondrial content were both negatively correlated with glycolytic potential. Overall, muscles used frequently in exercise had a higher proportion of type I fibers. 'Slow-oxidative-type' muscles, rich in type I fibers with higher mitochondrial and lower glycogen and glucose contents, had a higher ATP synthesis efficiency and lower glycolytic capacity, which contributed to their superior meat quality.

Cancellous bone analysis with modified least squares Prony's method and chirp filter: phantom experiments and simulation.

PubMed

Wear, Keith A

2010-10-01

The presence of two longitudinal waves in porous media is predicted by Biot's theory and has been confirmed experimentally in cancellous bone. When cancellous bone samples are interrogated in through-transmission, these two waves can overlap in time. Previously, the Modified Least-Squares Prony's (MLSP) method was validated for estimation of amplitudes, attenuation coefficients, and phase velocities of fast and slow waves, but tended to overestimate phase velocities by up to about 5%. In the present paper, a pre-processing chirp filter to mitigate the phase velocity bias is derived. The MLSP/chirp filter (MLSPCF) method was tested for decomposition of a 500 kHz-center-frequency signal containing two overlapping components: one passing through a low-density-polyethylene plate (fast wave) and another passing through a cancellous-bone-mimicking phantom material (slow wave). The chirp filter reduced phase velocity bias from 100 m/s (5.1%) to 69 m/s (3.5%) (fast wave) and from 29 m/s (1.9%) to 10 m/s (0.7%) (slow wave). Similar improvements were found for 1) measurements in polycarbonate (fast wave) and a cancellous-bone-mimicking phantom (slow wave), and 2) a simulation based on parameters mimicking bovine cancellous bone. The MLSPCF method did not offer consistent improvement in estimates of attenuation coefficient or amplitude.

Hybrid mechanosensing system to generate the polarity needed for migration in fish keratocytes

PubMed Central

Okimura, Chika; Iwadate, Yoshiaki

2016-01-01

ABSTRACT Crawling cells can generate polarity for migration in response to forces applied from the substratum. Such reaction varies according to cell type: there are both fast- and slow-crawling cells. In response to periodic stretching of the elastic substratum, the intracellular stress fibers in slow-crawling cells, such as fibroblasts, rearrange themselves perpendicular to the direction of stretching, with the result that the shape of the cells extends in that direction; whereas fast-crawling cells, such as neutrophil-like differentiated HL-60 cells and Dictyostelium cells, which have no stress fibers, migrate perpendicular to the stretching direction. Fish epidermal keratocytes are another type of fast-crawling cell. However, they have stress fibers in the cell body, which gives them a typical slow-crawling cell structure. In response to periodic stretching of the elastic substratum, intact keratocytes rearrange their stress fibers perpendicular to the direction of stretching in the same way as fibroblasts and migrate parallel to the stretching direction, while blebbistatin-treated stress fiber-less keratocytes migrate perpendicular to the stretching direction, in the same way as seen in HL-60 cells and Dictyostelium cells. Our results indicate that keratocytes have a hybrid mechanosensing system that comprises elements of both fast- and slow-crawling cells, to generate the polarity needed for migration. PMID:27124267

Magnetization transfer studies of the fast and slow tissue water diffusion components in the human brain.

PubMed

Mulkern, Robert V; Vajapeyam, Sridhar; Haker, Steven J; Maier, Stephan E

2005-05-01

Magnetization transfer (MT) properties of the fast and slow diffusion components recently observed in the human brain were assessed experimentally. One set of experiments, performed at 1.5 T in healthy volunteers, was designed to determine whether the amplitudes of fast and slow diffusion components, differentiated on the basis of biexponential fits to signal decays over a wide range of b-factors, demonstrated a different or similar magnetization transfer ratio (MTR). Another set of experiments, performed at 3 T in healthy volunteers, was designed to determine whether MTRs differed when measured from high signal-to-noise images acquired with b-factor weightings of 350 vs 3500 s/mm2. The 3 T studies included measurements of MTR as a function of off-resonance frequency for the MT pulse at both low and high b-factors. The primary conclusion drawn from all the studies is that there appears to be no significant difference between the magnetization transfer properties of the fast and slow tissue water diffusion components. The conclusions do not lend support to a direct interpretation of the 'components' of the biexponential diffusion decay in terms of the 'compartments' associated with intra- and extracellular water. Copyright 2004 John Wiley & Sons, Ltd.

Mixed-mode oscillations in a three-store calcium dynamics model

NASA Astrophysics Data System (ADS)

Liu, Peng; Liu, Xijun; Yu, Pei

2017-11-01

Calcium ions are important in cell process, which control cell functions. Many models on calcium oscillation have been proposed. Most of existing literature analyzed calcium oscillations using numerical methods, and found rich dynamical behaviours. In this paper, we explore a further study on an established three-store model, which contains endoplasmic reticulum (ER), mitochondria and calcium binding proteins. We conduct bifurcation analysis to identify two Hopf bifurcations, and apply normal form theory to study their stability and show that one of them is supercritical while the other is subcritical. Further, we transform the model into a slow-fast system, and then apply the geometrical singular perturbation theory to investigate the mechanism of generating slow-fast motions. The study reveals that the mechanism of generating the slow-fast oscillating behaviour in the three-store calcium model for certain parameter values is due to the relative fast change in the free calcium in cytosol, and relative slow changes in the free calcium in mitochondria and in the bounded Ca2+ binding sites on the cytosolic proteins. A further parametric study may provide some useful information for controlling harmful effect, by adjusting the amount of calcium in a human body. Numerical simulations are present to demonstrate the correct analytical predictions.

Slow and fast visual motion channels have independent binocular-rivalry stages.

PubMed Central

van de Grind, W. A.; van Hof, P.; van der Smagt, M. J.; Verstraten, F. A.

2001-01-01

We have previously reported a transparent motion after-effect indicating that the human visual system comprises separate slow and fast motion channels. Here, we report that the presentation of a fast motion in one eye and a slow motion in the other eye does not result in binocular rivalry but in a clear percept of transparent motion. We call this new visual phenomenon 'dichoptic motion transparency' (DMT). So far only the DMT phenomenon and the two motion after-effects (the 'classical' motion after-effect, seen after motion adaptation on a static test pattern, and the dynamic motion after-effect, seen on a dynamic-noise test pattern) appear to isolate the channels completely. The speed ranges of the slow and fast channels overlap strongly and are observer dependent. A model is presented that links after-effect durations of an observer to the probability of rivalry or DMT as a function of dichoptic velocity combinations. Model results support the assumption of two highly independent channels showing only within-channel rivalry, and no rivalry or after-effect interactions between the channels. The finding of two independent motion vision channels, each with a separate rivalry stage and a private line to conscious perception, might be helpful in visualizing or analysing pathways to consciousness. PMID:11270442

From perception to action: phase-locked gamma oscillations correlate with reaction times in a speeded response task

PubMed Central

Fründ, Ingo; Busch, Niko A; Schadow, Jeanette; Körner, Ursula; Herrmann, Christoph S

2007-01-01

Background Phase-locked gamma oscillations have so far mainly been described in relation to perceptual processes such as sensation, attention or memory matching. Due to its very short latency (≈90 ms) such oscillations are a plausible candidate for very rapid integration of sensory and motor processes. Results We measured EEG in 13 healthy participants in a speeded reaction task. Participants had to press a button as fast as possible whenever a visual stimulus was presented. The stimulus was always identical and did not have to be discriminated from other possible stimuli. In trials in which the participants showed a fast response, a slow negative potential over central electrodes starting approximately 800 ms before the response and highly phase-locked gamma oscillations over central and posterior electrodes between 90 and 140 ms after the stimulus were observed. In trials in which the participants showed a slow response, no slow negative potential was observed and phase-locked gamma oscillations were significantly reduced. Furthermore, for slow response trials the phase-locked gamma oscillations were significantly delayed with respect to fast response trials. Conclusion These results indicate the relevance of phase-locked gamma oscillations for very fast (not necessarily detailed) integration processes. PMID:17439642

Slow and fast dynamics model of a Malaria with Sickle-Cell genetic disease with multi-stage infections of the mosquitoes population

NASA Astrophysics Data System (ADS)

Dewi Siawanta, Shanti; Adi-Kusumo, Fajar; Irwan Endrayanto, Aluicius

2018-03-01

Malaria, which is caused by Plasmodium, is a common disease in tropical areas. There are three types of Plasmodium i.e. Plasmodium Vivax, Plasmodium Malariae, and Plasmodium Falciparum. The most dangerous cases of the Malaria are mainly caused by the Plasmodium Falciparum. One of the important characteristics for the Plasmodium infection is due to the immunity of erythrocyte that contains HbS (Haemoglobin Sickle-cell) genes. The individuals who has the HbS gene has better immunity against the disease. In this paper, we consider a model that shows the spread of malaria involving the interaction between the mosquitos population, the human who has HbS genes population and the human with normal gene population. We do some analytical and numerical simulation to study the basic reproduction ratio and the slow-fast dynamics of the phase-portrait. The slow dynamics in our model represents the response of the human population with HbS gene to the Malaria disease while the fast dynamics show the response of the human population with the normal gene to the disease. The slow and fast dynamics phenomena are due to the fact that the population of the individuals who have HbS gene is much smaller than the individuals who has normal genes.

Distinct mechanisms explain the control of reach speed planning: evidence from a race model framework.

PubMed

Venkataratamani, Prasanna Venkhatesh; Murthy, Aditya

2018-05-16

Previous studies have investigated the computational architecture underlying the voluntary control of reach movements that demands a change in position or direction of movement planning. Here we used a novel task, where subjects either had to increase or decrease the movement speed according to a change in target color that occurred randomly during a trial. The applicability of different race models to such a speed redirect task was assessed. We found that the predictions of an independent race model that instantiated an abort and re-plan strategy was consistent with all aspects of performance in the fast to slow speed condition. The results from modeling indicated a peculiar asymmetry, in that while the fast to slow speed change required inhibition, none of the standard race models were able to explain how movements changed from slow to fast speeds. Interestingly, a weighted averaging model that simulated the gradual merge of two kinematic plans explained behavior in the slow to fast speed task. In summary, our work shows how a race model framework can provide an understanding of how the brain controls of different aspects of reach movement planning and help distinguish between an abort and re-plan strategy from merging of plans.

LSP simulations of fast ions slowing down in cool magnetized plasma

NASA Astrophysics Data System (ADS)

Evans, Eugene S.; Cohen, Samuel A.

2015-11-01

In MFE devices, rapid transport of fusion products, e.g., tritons and alpha particles, from the plasma core into the scrape-off layer (SOL) could perform the dual roles of energy and ash removal. Through these two processes in the SOL, the fast particle slowing-down time will have a major effect on the energy balance of a fusion reactor and its neutron emissions, topics of great importance. In small field-reversed configuration (FRC) devices, the first-orbit trajectories of most fusion products will traverse the SOL, potentially allowing those particles to deposit their energy in the SOL and eventually be exhausted along the open field lines. However, the dynamics of the fast-ion energy loss processes under conditions expected in the FRC SOL, where the Debye length is greater than the electron gyroradius, are not fully understood. What modifications to the classical slowing down rate are necessary? Will instabilities accelerate the energy loss? We use LSP, a 3D PIC code, to examine the effects of SOL plasma parameters (density, temperature and background magnetic field strength) on the slowing down time of fast ions in a cool plasma with parameters similar to those expected in the SOL of small FRC reactors. This work supported by DOE contract DE-AC02-09CH11466.

A point implicit time integration technique for slow transient flow problems

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

Kadioglu, Samet Y.; Berry, Ray A.; Martineau, Richard C.

2015-05-01

We introduce a point implicit time integration technique for slow transient flow problems. The method treats the solution variables of interest (that can be located at cell centers, cell edges, or cell nodes) implicitly and the rest of the information related to same or other variables are handled explicitly. The method does not require implicit iteration; instead it time advances the solutions in a similar spirit to explicit methods, except it involves a few additional function(s) evaluation steps. Moreover, the method is unconditionally stable, as a fully implicit method would be. This new approach exhibits the simplicity of implementation ofmore » explicit methods and the stability of implicit methods. It is specifically designed for slow transient flow problems of long duration wherein one would like to perform time integrations with very large time steps. Because the method can be time inaccurate for fast transient problems, particularly with larger time steps, an appropriate solution strategy for a problem that evolves from a fast to a slow transient would be to integrate the fast transient with an explicit or semi-implicit technique and then switch to this point implicit method as soon as the time variation slows sufficiently. We have solved several test problems that result from scalar or systems of flow equations. Our findings indicate the new method can integrate slow transient problems very efficiently; and its implementation is very robust.« less

Effect of bowel decontamination with metronidazole and vancomycin on gastroduodenal myoelectric activity.

PubMed

Królczyk, Grzegorz; Czupryna, Antoni; Sobocki, Jacek; Nowak, Lukasz; Zurowski, Daniel; Szatyłowiczi, Jadwiga; Strus, Magdalena; Thor, Piotr J

2004-01-01

It is well recognized that prolonged antibiotic therapy leading to gut decontamination often results in side effects and may lead to colonization of gut with pathologic bacteria. Changes of a gut microflora could play a role in dysmotility of gastrointestinal tract. The aim of the study was to evaluate influence of intraluminal colon anaerobic and aerobic bacterial flora on myoelectric activity of duodenum and stomach. A myoelectric activity recordings using electrodes implanted on small bowel of the conscious rats were performed. Group I was scheduled for control recording, group II for recordings in 4th day after metronidazole (M) administration (30 mg/kg) and group III for recordings after vancomycin (V) administration (15 mg/kg) respectively. Rat's stools were cultured for confirmation of changes in colon flora composition. Recordings were previously filtered digitally with bandwidth filter 0.01-0.1 Hz and 0.1-1.0 Hz to extract gastric and duodenal slow wave respectively and than analyzed with Fast Fourier Transformation. Baseline duodenal slow wave frequency in control group revealed 0.60 +/- 0.05 Hz. M increased slow waves frequency to 0.64 +/- 0.13 Hz and V did not 0.58 +/- 0.09 Hz (p > 0.05). Slow wave dominant frequency of the stomach showed decrease of frequency from control 0.035 +/- 0.04 to 0.025 +/- 0.06 Hz after M (p < 0.05). Pretreatment with V also did not influence slow wave dominant frequency in comparison to control group (0.036 +/- 0.07 Hz, p > 0.05). Only pretreatment with M significantly decreased gastric slow wave frequency. One can speculate that M effects are related not only to gut decontamination but also directly affects ENS. We propose hypothesis that M influence on slow wave frequency may be related not only to its antimicrobial activity but to its potential neurotoxic action on intramural ENS neurons.

Data management software concept for WEST plasma measurement system

NASA Astrophysics Data System (ADS)

Zienkiewicz, P.; Kasprowicz, G.; Byszuk, A.; Wojeński, A.; Kolasinski, P.; Cieszewski, R.; Czarski, T.; Chernyshova, M.; Pozniak, K.; Zabolotny, W.; Juszczyk, B.; Mazon, D.; Malard, P.

2014-11-01

This paper describes the concept of data management software for the multichannel readout system for the GEM detector used in WEST Plasma experiment. The proposed system consists of three separate communication channels: fast data channel, diagnostics channel, slow data channel. Fast data channel is provided by the FPGA with integrated ARM cores providing direct readout data from Analog Front Ends through 10GbE with short, guaranteed intervals. Slow data channel is provided by multiple, fast CPUs after data processing with detailed readout data with use of GNU/Linux OS and appropriate software. Diagnostic channel provides detailed feedback for control purposes.

Cold exposure increases slow-type myosin heavy chain 1 (MyHC1) composition of soleus muscle in rats.

PubMed

Mizunoya, Wataru; Iwamoto, Yohei; Sato, Yusuke; Tatsumi, Ryuichi; Ikeuchi, Yoshihide

2014-03-01

The aim of this study was to examine the effects of cold exposure on rat skeletal muscle fiber type, according to myosin heavy chain (MyHC) isoform and metabolism-related factors. Male Wistar rats (7 weeks old) were housed individually at 4 ± 2°C as a cold-exposed group or at room temperature (22 ± 2°C) as a control group for 4 weeks. We found that cold exposure significantly increased the slow-type MyHC1 content in the soleus muscle (a typical slow-type fiber), while the intermediate-type MyHC2A content was significantly decreased. In contrast to soleus, MyHC composition of extensor digitorum longus (EDL, a typical fast-type fiber) and gastrocnemius (a mix of slow-type and fast-type fibers) muscle did not change from cold exposure. Cold exposure increased mRNA expression of mitochondrial uncoupling protein 3 (UCP3) in both the soleus and EDL. Cold exposure also increased mRNA expression of myoglobin, peroxisome proliferator-activated receptor gamma coactivator 1α (PGC1α) and forkhead box O1 (FOXO1) in the soleus. Upregulation of UCP3 and PGC1α proteins were observed with Western blotting in the gastrocnemius. Thus, cold exposure increased metabolism-related factors in all muscle types that were tested, but MyHC isoforms changed only in the soleus. © 2013 Japanese Society of Animal Science.

Long-term high-level exercise promotes muscle reinnervation with age.

PubMed

Mosole, Simone; Carraro, Ugo; Kern, Helmut; Loefler, Stefan; Fruhmann, Hannah; Vogelauer, Michael; Burggraf, Samantha; Mayr, Winfried; Krenn, Matthias; Paternostro-Sluga, Tatjana; Hamar, Dusan; Cvecka, Jan; Sedliak, Milan; Tirpakova, Veronika; Sarabon, Nejc; Musarò, Antonio; Sandri, Marco; Protasi, Feliciano; Nori, Alessandra; Pond, Amber; Zampieri, Sandra

2014-04-01

The histologic features of aging muscle suggest that denervation contributes to atrophy, that immobility accelerates the process, and that routine exercise may protect against loss of motor units and muscle tissue. Here, we compared muscle biopsies from sedentary and physically active seniors and found that seniors with a long history of high-level recreational activity up to the time of muscle biopsy had 1) lower loss of muscle strength versus young men (32% loss in physically active vs 51% loss in sedentary seniors); 2) fewer small angulated (denervated) myofibers; 3) a higher percentage of fiber-type groups (reinnervated muscle fibers) that were almost exclusive of the slow type; and 4) sparse normal-size muscle fibers coexpressing fast and slow myosin heavy chains, which is not compatible with exercise-driven muscle-type transformation. The biopsies from the old physically active seniors varied from sparse fiber-type groupings to almost fully transformed muscle, suggesting that coexpressing fibers appear to fill gaps. Altogether, the data show that long-term physical activity promotes reinnervation of muscle fibers and suggest that decades of high-level exercise allow the body to adapt to age-related denervation by saving otherwise lost muscle fibers through selective recruitment to slow motor units. These effects on size and structure of myofibers may delay functional decline in late aging.

In vivo fascicle behavior of the flexor hallucis longus muscle at different walking speeds.

PubMed

Péter, A; Hegyi, A; Finni, T; Cronin, N J

2017-12-01

Ankle plantar flexor muscles support and propel the body in the stance phase of locomotion. Besides the triceps surae, flexor hallucis longus muscle (FHL) may also contribute to this role, but very few in vivo studies have examined FHL function during walking. Here, we investigated FHL fascicle behavior at different walking speeds. Ten healthy males walked overground at three different speeds while FHL fascicle length changes were recorded with ultrasound and muscle activity was recorded with surface electromyography (EMG). Fascicle length at heel strike at toe off and at peak EMG activity did not change with speed. Range of FHL fascicle length change (3.5-4.5 and 1.9-2.9 mm on average in stance and push-off phase, respectively), as well as minimum (53.5-54.9 and 53.8-55.7 mm) and maximum (58-58.4 and 56.8-57.7 mm) fascicle length did not change with speed in the stance or push-off phase. Mean fascicle velocity did not change in the stance phase, but increased significantly in the push-off phase between slow and fast walking speeds (P=.021). EMG activity increased significantly in both phases from slow to preferred and preferred to fast speed (P<.02 in all cases). FHL muscle fascicles worked near-isometrically during the whole stance phase (at least during slow walking) and operated at approximately the same length at different walking speeds. FHL and medial gastrocnemius (MG) have similar fiber length to muscle belly length ratios and, according to our results, also exhibit similar fascicle behavior at different walking speeds. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Pyrethroids Differentially Alter Voltage-Gated Sodium Channels from the Honeybee Central Olfactory Neurons

PubMed Central

Kadala, Aklesso; Charreton, Mercedes; Jakob, Ingrid; Cens, Thierry; Rousset, Matthieu; Chahine, Mohamed; Le Conte, Yves; Charnet, Pierre; Collet, Claude

2014-01-01

The sensitivity of neurons from the honey bee olfactory system to pyrethroid insecticides was studied using the patch-clamp technique on central ‘antennal lobe neurons’ (ALNs) in cell culture. In these neurons, the voltage-dependent sodium currents are characterized by negative potential for activation, fast kinetics of activation and inactivation, and the presence of cumulative inactivation during train of depolarizations. Perfusion of pyrethroids on these ALN neurons submitted to repetitive stimulations induced (1) an acceleration of cumulative inactivation, and (2) a marked slowing of the tail current recorded upon repolarization. Cypermethrin and permethrin accelerated cumulative inactivation of the sodium current peak in a similar manner and tetramethrin was even more effective. The slow-down of channel deactivation was markedly dependent on the type of pyrethroid. With cypermethrin, a progressive increase of the tail current amplitude along with successive stimulations reveals a traditionally described use-dependent recruitment of modified sodium channels. However, an unexpected decrease in this tail current was revealed with tetramethrin. If one considers the calculated percentage of modified channels as an index of pyrethroids effects, ALNs are significantly more susceptible to tetramethrin than to permethrin or cypermethrin for a single depolarization, but this difference attenuates with repetitive activity. Further comparison with peripheral neurons from antennae suggest that these modifications are neuron type specific. Modeling the sodium channel as a multi-state channel with fast and slow inactivation allows to underline the effects of pyrethroids on a set of rate constants connecting open and inactivated conformations, and give some insights to their specificity. Altogether, our results revealed a differential sensitivity of central olfactory neurons to pyrethroids that emphasize the ability for these compounds to impair detection and processing of information at several levels of the bees olfactory pathway. PMID:25390654

In Vivo Voltage-Sensitive Dye Study of Lateral Spreading of Cortical Activity in Mouse Primary Visual Cortex Induced by a Current Impulse

PubMed Central

Fehérvári, Tamás Dávid; Sawai, Hajime; Yagi, Tetsuya

2015-01-01

In the mammalian primary visual cortex (V1), lateral spreading of excitatory potentials is believed to be involved in spatial integrative functions, but the underlying cortical mechanism is not well understood. Visually-evoked population-level responses have been shown to propagate beyond the V1 initial activation site in mouse, similar to higher mammals. Visually-evoked responses are, however, affected by neuronal circuits prior to V1 (retina, LGN), making the separate analysis of V1 difficult. Intracortical stimulation eliminates these initial processing steps. We used in vivo RH1691 voltage-sensitive dye (VSD) imaging and intracortical microstimulation in adult C57BL/6 mice to elucidate the spatiotemporal properties of population-level signal spreading in V1 cortical circuits. The evoked response was qualitatively similar to that measured in single-cell electrophysiological experiments in rodents: a fast transient fluorescence peak followed by a fast and a slow decrease or hyperpolarization, similar to EPSP and fast and slow IPSPs in single cells. The early cortical response expanded at speeds commensurate with long horizontal projections (at 5% of the peak maximum, 0.08–0.15 m/s) however, the bulk of the VSD signal propagated slowly (at half-peak maximum, 0.05–0.08 m/s) suggesting an important role of regenerative multisynaptic transmission through short horizontal connections in V1 spatial integrative functions. We also found a tendency for a widespread and fast cortical response suppression in V1, which was eliminated by GABAA-antagonists gabazine and bicuculline methiodide. Our results help understand the neuronal circuitry involved in lateral spreading in V1. PMID:26230520

Propagating Neural Source Revealed by Doppler Shift of Population Spiking Frequency

PubMed Central

Zhang, Mingming; Shivacharan, Rajat S.; Chiang, Chia-Chu; Gonzalez-Reyes, Luis E.

2016-01-01

Electrical activity in the brain during normal and abnormal function is associated with propagating waves of various speeds and directions. It is unclear how both fast and slow traveling waves with sometime opposite directions can coexist in the same neural tissue. By recording population spikes simultaneously throughout the unfolded rodent hippocampus with a penetrating microelectrode array, we have shown that fast and slow waves are causally related, so a slowly moving neural source generates fast-propagating waves at ∼0.12 m/s. The source of the fast population spikes is limited in space and moving at ∼0.016 m/s based on both direct and Doppler measurements among 36 different spiking trains among eight different hippocampi. The fact that the source is itself moving can account for the surprising direction reversal of the wave. Therefore, these results indicate that a small neural focus can move and that this phenomenon could explain the apparent wave reflection at tissue edges or multiple foci observed at different locations in neural tissue. SIGNIFICANCE STATEMENT The use of novel techniques with an unfolded hippocampus and penetrating microelectrode array to record and analyze neural activity has revealed the existence of a source of neural signals that propagates throughout the hippocampus. The source itself is electrically silent, but its location can be inferred by building isochrone maps of population spikes that the source generates. The movement of the source can also be tracked by observing the Doppler frequency shift of these spikes. These results have general implications for how neural signals are generated and propagated in the hippocampus; moreover, they have important implications for the understanding of seizure generation and foci localization. PMID:27013678

Genetic variation in aryl N-acetyltransferase results in significant differences in the pharmacokinetic and safety profiles of amifampridine (3,4-diaminopyridine) phosphate.

PubMed

Haroldsen, Peter E; Garovoy, Marvin R; Musson, Donald G; Zhou, Huiyu; Tsuruda, Laurie; Hanson, Boyd; O'Neill, Charles A

2015-02-01

The clinical use of amifampridine phosphate for neuromuscular junction disorders is increasing. The metabolism of amifampridine occurs via polymorphic aryl N-acetyltransferase (NAT), yet its pharmacokinetic (PK) and safety profiles, as influenced by this enzyme system, have not been investigated. The objective of this study was to assess the effect of NAT phenotype and genotype on the PK and safety profiles of amifampridine in healthy volunteers (N = 26). A caffeine challenge test and NAT2 genotyping were used to delineate subjects into slow and fast acetylators for PK and tolerability assessment of single, escalating doses of amifampridine (up to 30 mg) and in multiple daily doses (20 mg QID) of amifampridine. The results showed that fast acetylator phenotypes displayed significantly lower C max, AUC, and shorter t 1/2 for amifampridine than slow acetylators. Plasma concentrations of the N-acetyl metabolite were approximately twofold higher in fast acetylators. Gender differences were not observed. Single doses of amifampridine demonstrated dose linear PKs. Amifampridine achieved steady state plasma levels within 1 day of dosing four times daily. No accumulation or time-dependent changes in amifampridine PK parameters occurred. Overall, slow acetylators reported 73 drug-related treatment-emergent adverse events versus 6 in fast acetylators. Variations in polymorphic NAT corresponding with fast and slow acetylator phenotypes significantly affects the PK and safety profiles of amifampridine.

Sensing of substratum rigidity and directional migration by fast-crawling cells

NASA Astrophysics Data System (ADS)

Okimura, Chika; Sakumura, Yuichi; Shimabukuro, Katsuya; Iwadate, Yoshiaki

2018-05-01

Living cells sense the mechanical properties of their surrounding environment and respond accordingly. Crawling cells detect the rigidity of their substratum and migrate in certain directions. They can be classified into two categories: slow-moving and fast-moving cell types. Slow-moving cell types, such as fibroblasts, smooth muscle cells, mesenchymal stem cells, etc., move toward rigid areas on the substratum in response to a rigidity gradient. However, there is not much information on rigidity sensing in fast-moving cell types whose size is ˜10 μ m and migration velocity is ˜10 μ m /min . In this study, we used both isotropic substrata with different rigidities and an anisotropic substratum that is rigid on the x axis but soft on the y axis to demonstrate rigidity sensing by fast-moving Dictyostelium cells and neutrophil-like differentiated HL-60 cells. Dictyostelium cells exerted larger traction forces on a more rigid isotropic substratum. Dictyostelium cells and HL-60 cells migrated in the "soft" direction on the anisotropic substratum, although myosin II-null Dictyostelium cells migrated in random directions, indicating that rigidity sensing of fast-moving cell types differs from that of slow types and is induced by a myosin II-related process.

Sensing of substratum rigidity and directional migration by fast-crawling cells.

PubMed

Okimura, Chika; Sakumura, Yuichi; Shimabukuro, Katsuya; Iwadate, Yoshiaki

2018-05-01

Living cells sense the mechanical properties of their surrounding environment and respond accordingly. Crawling cells detect the rigidity of their substratum and migrate in certain directions. They can be classified into two categories: slow-moving and fast-moving cell types. Slow-moving cell types, such as fibroblasts, smooth muscle cells, mesenchymal stem cells, etc., move toward rigid areas on the substratum in response to a rigidity gradient. However, there is not much information on rigidity sensing in fast-moving cell types whose size is ∼10 μm and migration velocity is ∼10 μm/min. In this study, we used both isotropic substrata with different rigidities and an anisotropic substratum that is rigid on the x axis but soft on the y axis to demonstrate rigidity sensing by fast-moving Dictyostelium cells and neutrophil-like differentiated HL-60 cells. Dictyostelium cells exerted larger traction forces on a more rigid isotropic substratum. Dictyostelium cells and HL-60 cells migrated in the "soft" direction on the anisotropic substratum, although myosin II-null Dictyostelium cells migrated in random directions, indicating that rigidity sensing of fast-moving cell types differs from that of slow types and is induced by a myosin II-related process.