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Sample records for action potential initiation

  1. Action potential initiation in neocortical inhibitory interneurons.

    Directory of Open Access Journals (Sweden)

    Tun Li

    2014-09-01

    Full Text Available Action potential (AP generation in inhibitory interneurons is critical for cortical excitation-inhibition balance and information processing. However, it remains unclear what determines AP initiation in different interneurons. We focused on two predominant interneuron types in neocortex: parvalbumin (PV- and somatostatin (SST-expressing neurons. Patch-clamp recording from mouse prefrontal cortical slices showed that axonal but not somatic Na+ channels exhibit different voltage-dependent properties. The minimal activation voltage of axonal channels in SST was substantially higher (∼7 mV than in PV cells, consistent with differences in AP thresholds. A more mixed distribution of high- and low-threshold channel subtypes at the axon initial segment (AIS of SST cells may lead to these differences. Surprisingly, NaV1.2 was found accumulated at AIS of SST but not PV cells; reducing NaV1.2-mediated currents in interneurons promoted recurrent network activity. Together, our results reveal the molecular identity of axonal Na+ channels in interneurons and their contribution to AP generation and regulation of network activity.

  2. Action potential initiation in the hodgkin-huxley model.

    Directory of Open Access Journals (Sweden)

    Lucy J Colwell

    2009-01-01

    Full Text Available A recent paper of B. Naundorf et al. described an intriguing negative correlation between variability of the onset potential at which an action potential occurs (the onset span and the rapidity of action potential initiation (the onset rapidity. This correlation was demonstrated in numerical simulations of the Hodgkin-Huxley model. Due to this antagonism, it is argued that Hodgkin-Huxley-type models are unable to explain action potential initiation observed in cortical neurons in vivo or in vitro. Here we apply a method from theoretical physics to derive an analytical characterization of this problem. We analytically compute the probability distribution of onset potentials and analytically derive the inverse relationship between onset span and onset rapidity. We find that the relationship between onset span and onset rapidity depends on the level of synaptic background activity. Hence we are able to elucidate the regions of parameter space for which the Hodgkin-Huxley model is able to accurately describe the behavior of this system.

  3. 7 CFR 1945.19 - Reporting potential natural disasters and initial actions.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 13 2010-01-01 2009-01-01 true Reporting potential natural disasters and initial... Assistance-General § 1945.19 Reporting potential natural disasters and initial actions. (a) Purpose. The purpose of reporting potential natural disasters is to provide a systematic procedure for rapid...

  4. Dynamics of action potential initiation in the GABAergic thalamic reticular nucleus in vivo.

    Directory of Open Access Journals (Sweden)

    Fabián Muñoz

    Full Text Available Understanding the neural mechanisms of action potential generation is critical to establish the way neural circuits generate and coordinate activity. Accordingly, we investigated the dynamics of action potential initiation in the GABAergic thalamic reticular nucleus (TRN using in vivo intracellular recordings in cats in order to preserve anatomically-intact axo-dendritic distributions and naturally-occurring spatiotemporal patterns of synaptic activity in this structure that regulates the thalamic relay to neocortex. We found a wide operational range of voltage thresholds for action potentials, mostly due to intrinsic voltage-gated conductances and not synaptic activity driven by network oscillations. Varying levels of synchronous synaptic inputs produced fast rates of membrane potential depolarization preceding the action potential onset that were associated with lower thresholds and increased excitability, consistent with TRN neurons performing as coincidence detectors. On the other hand the presence of action potentials preceding any given spike was associated with more depolarized thresholds. The phase-plane trajectory of the action potential showed somato-dendritic propagation, but no obvious axon initial segment component, prominent in other neuronal classes and allegedly responsible for the high onset speed. Overall, our results suggest that TRN neurons could flexibly integrate synaptic inputs to discharge action potentials over wide voltage ranges, and perform as coincidence detectors and temporal integrators, supported by a dynamic action potential threshold.

  5. Perturbation analysis of spontaneous action potential initiation by stochastic ion channels

    KAUST Repository

    Keener, James P.

    2011-07-01

    A stochastic interpretation of spontaneous action potential initiation is developed for the Morris-Lecar equations. Initiation of a spontaneous action potential can be interpreted as the escape from one of the wells of a double well potential, and we develop an asymptotic approximation of the mean exit time using a recently developed quasistationary perturbation method. Using the fact that the activating ionic channel\\'s random openings and closings are fast relative to other processes, we derive an accurate estimate for the mean time to fire an action potential (MFT), which is valid for a below-threshold applied current. Previous studies have found that for above-threshold applied current, where there is only a single stable fixed point, a diffusion approximation can be used. We also explore why different diffusion approximation techniques fail to estimate the MFT. © 2011 American Physical Society.

  6. Axon initial segment Kv1 channels control axonal action potential waveform and synaptic efficacy.

    Science.gov (United States)

    Kole, Maarten H P; Letzkus, Johannes J; Stuart, Greg J

    2007-08-16

    Action potentials are binary signals that transmit information via their rate and temporal pattern. In this context, the axon is thought of as a transmission line, devoid of a role in neuronal computation. Here, we show a highly localized role of axonal Kv1 potassium channels in shaping the action potential waveform in the axon initial segment (AIS) of layer 5 pyramidal neurons independent of the soma. Cell-attached recordings revealed a 10-fold increase in Kv1 channel density over the first 50 microm of the AIS. Inactivation of AIS and proximal axonal Kv1 channels, as occurs during slow subthreshold somatodendritic depolarizations, led to a distance-dependent broadening of axonal action potentials, as well as an increase in synaptic strength at proximal axonal terminals. Thus, Kv1 channels are strategically positioned to integrate slow subthreshold signals, providing control of the presynaptic action potential waveform and synaptic coupling in local cortical circuits.

  7. Initiation and blocking of the action potential in the axon in a weak ultrasonic field

    CERN Document Server

    Shneider, M N

    2013-01-01

    It is shown that the longitudinal standing ultrasonic wave of low intensity leads to the lateral drift and to redistribution of the transmembrane ion channels in the initial segment of the myelinated axon of a neuron. The analysis is based on the Hodgkin - Huxley model of an axon. Redistribution of the density of transmembrane sodium channels, caused by ultrasound, may reduce the threshold of the action potential, up to its spontaneous initiation. At significant redistribution of sodium channels in membrane, the zones of rarefaction of the transmembrane channels density are formed blocking the propagation of the action potential. After switching the ultrasound off, the unperturbed uniform distribution of transmembrane channels in the axon recovers due to lateral diffusion. The blocking effect of the action potential can be used in anesthesia.

  8. Axonal action-potential initiation and Na+ channel densities in the soma and axon initial segment of subicular pyramidal neurons.

    Science.gov (United States)

    Colbert, C M; Johnston, D

    1996-11-01

    A long-standing hypothesis is that action potentials initiate first in the axon hillock/initial segment (AH-IS) region because of a locally high density of Na+ channels. We tested this idea in subicular pyramidal neurons by using patch-clamp recordings in hippocampal slices. Simultaneous recordings from the soma and IS confirmed that orthodromic action potentials initiated in the axon and then invaded the soma. However, blocking Na+ channels in the AH-IS with locally applied tetrodotoxin (TTX) did not raise the somatic threshold membrane potential for orthodromic spikes. TTX applied to the axon beyond the AH-IS (30-60 microm from the soma) raised the apparent somatic threshold by approximately 8 mV. We estimated the Na+ current density in the AH-IS and somatic membranes by using cell-attached patch-clamp recordings and found similar magnitudes (3-4 pA/microm2). Thus, the present results suggest that orthodromic action potentials initiate in the axon beyond the AH-IS and that the minimum threshold for spike initiation of the neuron is not determined by a high density of Na+ channels in the AH-IS region.

  9. Multiple modes of action potential initiation and propagation in mitral cell primary dendrite

    DEFF Research Database (Denmark)

    Chen, Wei R; Shen, Gongyu Y; Shepherd, Gordon M

    2002-01-01

    to support the back-propagation of the evoked somatic action potential to produce the second dendritic spike. In summary, the balance of spatially distributed excitatory and inhibitory inputs can dynamically switch the mitral cell firing among four different modes: axo-somatic initiation with back......-to-moderate olfactory nerve input, an action potential was initiated near the soma and then back-propagated into the primary dendrite. As olfactory nerve input increased, the initiation site suddenly shifted to the distal primary dendrite. Multi-compartmental modeling indicated that this abrupt shift of the spike......-propagation, dendritic initiation either with no forward propagation, forward propagation alone, or forward propagation followed by back-propagation....

  10. Action potentials initiate in the axon initial segment and propagate through axon collaterals reliably in cerebellar Purkinje neurons.

    Science.gov (United States)

    Foust, Amanda; Popovic, Marko; Zecevic, Dejan; McCormick, David A

    2010-05-19

    Purkinje neurons are the output cells of the cerebellar cortex and generate spikes in two distinct modes, known as simple and complex spikes. Revealing the point of origin of these action potentials, and how they conduct into local axon collaterals, is important for understanding local and distal neuronal processing and communication. By using a recent improvement in voltage-sensitive dye imaging technique that provided exceptional spatial and temporal resolution, we were able to resolve the region of spike initiation as well as follow spike propagation into axon collaterals for each action potential initiated on single trials. All fast action potentials, for both simple and complex spikes, whether occurring spontaneously or in response to a somatic current pulse or synaptic input, initiated in the axon initial segment. At discharge frequencies of less than approximately 250 Hz, spikes propagated faithfully through the axon and axon collaterals, in a saltatory manner. Propagation failures were only observed for very high frequencies or for the spikelets associated with complex spikes. These results demonstrate that the axon initial segment is a critical decision point in Purkinje cell processing and that the properties of axon branch points are adjusted to maintain faithful transmission.

  11. Serotonin spillover onto the axon initial segment of motoneurons induces central fatigue by inhibiting action potential initiation

    DEFF Research Database (Denmark)

    Cotel, Florence; Exley, Richard; Cragg, Stephanie

    2013-01-01

    --as during motor exercise--activated 5-HT1A receptors that decreased motoneuronal excitability. Electrophysiological tests combined with pharmacology showed that focal activation of 5-HT1A receptors at the axon initial segment (AIS), but not on other motoneuronal compartments, inhibited the action potential...... adequately independently of the muscle physiology. Indirect evidence indicates that central fatigue is caused by serotonin (5-HT), but the cellular mechanisms are unknown. In a slice preparation from the spinal cord of the adult turtle, we found that prolonged stimulation of the raphe-spinal pathway...

  12. High Threshold, Proximal Initiation, and Slow Conduction Velocity of Action Potentials in Dentate Granule Neuron Mossy Fibers

    OpenAIRE

    Kress, Geraldine J.; Dowling, Margaret J.; Meeks, Julian P.; Mennerick, Steven

    2008-01-01

    Dentate granule neurons give rise to some of the smallest unmyelinated fibers in the mammalian CNS, the hippocampal mossy fibers. These neurons are also key regulators of physiological and pathophysiological information flow through the hippocampus. We took a comparative approach to studying mossy fiber action potential initiation and propagation in hippocampal slices from juvenile rats. Dentate granule neurons exhibited axonal action potential initiation significantly more proximal than CA3 ...

  13. Action potential-simulated weak electric fields can directly initiate myelination

    Institute of Scientific and Technical Information of China (English)

    Lei Liu; Shifu Zhao; Haiming Wang

    2008-01-01

    BACKGROUND: Myelination is a process whereby glial cells identify, adhere, wrap and enclose axons to form a spiral myelin sheath.OBJECTIVE: To investigate the effects of action potential-simulated weak electric fields on myelination in the central nervous system.DESIGN AND SETTING: This single-sample observation study was performed at the 324 Hospital of Chinese PLA.MATERIALS: Two 5 μm carbon fibers were provided by the Institute of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. One Sprague Dawley rat, aged 1 day, was used.METHODS: Cerebral cortex was harvested from the rat to prepare a suspension [(1-2)×105/mL] containing neurons and glial cells. To simulate the axon, carbon fibers were placed at the bottom of the neuron-glial cell coculture dish, and were electrified with a single phase square wave current, 1×10-2, 1×10-3, 1×10-4, and 1×10-5 seconds, 1 Hz, 40 mV, and 10 μA, 30 minutes each, once aday for 10 consecutive days to simulate weak negative electric fields during action potential conduction.MAIN OUTCOME MEASURES: Glial cell growth and wrapping of carbon fibers were observed by phase contrast microscopy and immunohistochemistry.RESULTS: On culture day 7, cell groups were found to adhere to negative carbon fibers in the 1×10-3 seconds square wave group. Cell membrane-like substances grew out of cell groups, wrapped the carbon fibers, and stretched to the ends of carbon fibers. Only some small and round cells close to negative carbon fibers were found on culture day 12. In the 1×10-4 and 1×10-3 seconds square wave groups, the negative carbon fibers were wrapped by oligodendrocytes or their progenitor cells.CONCLUSION: The local negative electric field which is generated by action potentials at 1×(10-4-10-3)seconds, 40 mV can directly initiate and participate in myelination in the central nervous system.

  14. Serotonin spillover onto the axon initial segment of motoneurons induces central fatigue by inhibiting action potential initiation

    Science.gov (United States)

    Cotel, Florence; Exley, Richard; Cragg, Stephanie J.; Perrier, Jean-François

    2013-01-01

    Motor fatigue induced by physical activity is an everyday experience characterized by a decreased capacity to generate motor force. Factors in both muscles and the central nervous system are involved. The central component of fatigue modulates the ability of motoneurons to activate muscle adequately independently of the muscle physiology. Indirect evidence indicates that central fatigue is caused by serotonin (5-HT), but the cellular mechanisms are unknown. In a slice preparation from the spinal cord of the adult turtle, we found that prolonged stimulation of the raphe-spinal pathway—as during motor exercise—activated 5-HT1A receptors that decreased motoneuronal excitability. Electrophysiological tests combined with pharmacology showed that focal activation of 5-HT1A receptors at the axon initial segment (AIS), but not on other motoneuronal compartments, inhibited the action potential initiation by modulating a Na+ current. Immunohistochemical staining against 5-HT revealed a high-density innervation of 5-HT terminals on the somatodendritic membrane and a complete absence on the AIS. This observation raised the hypothesis that a 5-HT spillover activates receptors at this latter compartment. We tested it by measuring the level of extracellular 5-HT with cyclic voltammetry and found that prolonged stimulations of the raphe-spinal pathway increased the level of 5-HT to a concentration sufficient to activate 5-HT1A receptors. Together our results demonstrate that prolonged release of 5-HT during motor activity spills over from its release sites to the AIS of motoneurons. Here, activated 5-HT1A receptors inhibit firing and, thereby, muscle contraction. Hence, this is a cellular mechanism for central fatigue. PMID:23487756

  15. Morphological Characterization of the Action Potential Initiation Segment in GnRH Neuron Dendrites and Axons of Male Mice.

    Science.gov (United States)

    Herde, Michel K; Herbison, Allan E

    2015-11-01

    GnRH neurons are the final output neurons of the hypothalamic network controlling fertility in mammals. In the present study, we used ankyrin G immunohistochemistry and neurobiotin filling of live GnRH neurons in brain slices from GnRH-green fluorescent protein transgenic male mice to examine in detail the location of action potential initiation in GnRH neurons with somata residing at different locations in the basal forebrain. We found that the vast majority of GnRH neurons are bipolar in morphology, elaborating a thick (primary) and thinner (secondary) dendrite from opposite poles of the soma. In addition, an axon-like process arising predominantly from a proximal dendrite was observed in a subpopulation of GnRH neurons. Ankyrin G immunohistochemistry revealed the presence of a single action potential initiation zone ∼27 μm in length primarily in the secondary dendrite of GnRH neurons and located 30 to 140 μm distant from the cell soma, depending on the type of process and location of the cell body. In addition to dendrites, the GnRH neurons with cell bodies located close to hypothalamic circumventricular organs often elaborated ankyrin G-positive axon-like structures. Almost all GnRH neurons (>90%) had their action potential initiation site in a process that initially, or ultimately after a hairpin loop, was coursing in the direction of the median eminence. These studies indicate that action potentials are initiated in different dendritic and axonal compartments of the GnRH neuron in a manner that is dependent partly on the neuroanatomical location of the cell body.

  16. The spatio-temporal characteristics of action potential initiation in layer 5 pyramidal neurons: a voltage imaging study.

    Science.gov (United States)

    Popovic, Marko A; Foust, Amanda J; McCormick, David A; Zecevic, Dejan

    2011-09-01

    The spatial pattern of Na(+) channel clustering in the axon initial segment (AIS) plays a critical role in tuning neuronal computations, and changes in Na(+) channel distribution have been shown to mediate novel forms of neuronal plasticity in the axon. However, immunocytochemical data on channel distribution may not directly predict spatio-temporal characteristics of action potential initiation, and prior electrophysiological measures are either indirect (extracellular) or lack sufficient spatial resolution (intracellular) to directly characterize the spike trigger zone (TZ). We took advantage of a critical methodological improvement in the high sensitivity membrane potential imaging (V(m) imaging) technique to directly determine the location and length of the spike TZ as defined in functional terms. The results show that in mature axons of mouse cortical layer 5 pyramidal cells, action potentials initiate in a region ∼20 μm in length centred between 20 and 40 μm from the soma. From this region, the AP depolarizing wave invades initial nodes of Ranvier within a fraction of a millisecond and propagates in a saltatory fashion into axonal collaterals without failure at all physiologically relevant frequencies. We further demonstrate that, in contrast to the saltatory conduction in mature axons, AP propagation is non-saltatory (monotonic) in immature axons prior to myelination.

  17. Quantum entanglement in the voltage dependent sodium channel can reproduce the salient features of neuronal action potential initiation

    CERN Document Server

    Summhammer, Johann

    2007-01-01

    We investigate the effects of a quantum entanglement regime within an ion conducting molecule (ion channel) of the neuronal plasma membrane on the onset dynamics of propagating nerve pulses (action potentials). In particular, we model the onset parameters of the sodium current in the Hodgkin Huxley equation as three similar but independent probabilistic mechanisms which become quantum entangled. The underlying physics is general and can involve entanglement between various degrees of freedom underlaying ion transition states or 'gating states' during conduction, e.g. Na$^+$ ions in different channel locations, or different 'affinity' states of ions with atoms lining the sub-regions of the channel protein ('filter-states'). We find that the 'quantum corrected' Hodgkin Huxley equation incorporating entangled systems states can reproduce action potential pulses with the critical onset dynamics observed recently in neocortical neurons in vivo by Naundorf et al. [Nature {\\bf 440}, 1060 (20 April 2006)]. Interestin...

  18. Perfect Actions with Chemical Potential

    CERN Document Server

    Bietenholz, W

    1998-01-01

    We show how to include a chemical potential \\mu in perfect lattice actions. It turns out that the standard procedure of multiplying the quark fields \\Psi, an example, the case of free fermions with chemical potential is worked out explicitly. Even after truncation, cut-off effects in the pressure and the baryon density are small. Using a (quasi-)perfect action, numerical QCD simulations for non-zero chemical potential become more powerful, because coarse lattices are sufficient for extracting continuum physics.

  19. Action potential initial dynamical control and analysis of a minimum neuron model%最小神经元模型放电起始动态控制与分析

    Institute of Scientific and Technical Information of China (English)

    金淇涛; 王江; 魏熙乐; 邓斌; 车艳秋

    2011-01-01

    本文采用最小神经元模型,从生理学角度设计wash-out滤波器,实现了不同放电起始动态机理之间的转换,并证明wash-out滤波器控制通过影响阈下电流的竞争结果改变了神经元的放电起始动态机理.%Neuron is a basic unit of information transmission in the nervous system . Neuron encodes the information input from the dendrites by generating action potential sequences of different firing patterns. The different firing patterns result from different action potential initial dynamic mechanisms for neurons to generate spikes. The result of competition between neuron ion currents with different dynamic features in the sub threshold potential determines the action potential initial dynamic mechanism. In this paper, we adopt a minimum neuron model to design the wash-out filter from a physiological view for achieving the transition between different action potential initial dynamic mechanisms and for verifying that the wash-out filter control changes the action potential initial dynamic mechanism of neuron by affecting the result of competition between currents with different dynamic features in the sub-threshold potential.

  20. Initiating Teachers' Action Research: Empowering Teachers' Voices

    Science.gov (United States)

    Bognar, Branko

    2013-01-01

    The role of a teacher as an action researcher in Croatia is still insufficiently appreciated and promoted in initial teachers' training, school students learning and in the employed teachers' professional post-qualification development. In this country, teachers are most frequently perceived as mediators or technicians whose task is to prepare and…

  1. Improved Lattice Actions with Chemical Potential

    CERN Document Server

    Bietenholz, W

    1998-01-01

    We give a prescription how to include a chemical potential \\mu into a general lattice action. This inclusion does not cause any lattice artifacts. Hence its application to an improved - or even perfect - action at \\mu =0 yields an improved resp. perfect action at arbitrary \\mu. For short-ranged improved actions, a good scaling behavior holds over a wide region, and the upper bound for the baryon density - which is known for the standard lattice actions - can be exceeded.

  2. Action-potential modulation during axonal conduction.

    Science.gov (United States)

    Sasaki, Takuya; Matsuki, Norio; Ikegaya, Yuji

    2011-02-04

    Once initiated near the soma, an action potential (AP) is thought to propagate autoregeneratively and distribute uniformly over axonal arbors. We challenge this classic view by showing that APs are subject to waveform modulation while they travel down axons. Using fluorescent patch-clamp pipettes, we recorded APs from axon branches of hippocampal CA3 pyramidal neurons ex vivo. The waveforms of axonal APs increased in width in response to the local application of glutamate and an adenosine A(1) receptor antagonist to the axon shafts, but not to other unrelated axon branches. Uncaging of calcium in periaxonal astrocytes caused AP broadening through ionotropic glutamate receptor activation. The broadened APs triggered larger calcium elevations in presynaptic boutons and facilitated synaptic transmission to postsynaptic neurons. This local AP modification may enable axonal computation through the geometry of axon wiring.

  3. Action initiation in the human dorsal anterior cingulate cortex.

    Directory of Open Access Journals (Sweden)

    Lakshminarayan Srinivasan

    Full Text Available The dorsal anterior cingulate cortex (dACC has previously been implicated in processes that influence action initiation. In humans however, there has been little direct evidence connecting dACC to the temporal onset of actions. We studied reactive behavior in patients undergoing therapeutic bilateral cingulotomy to determine the immediate effects of dACC ablation on action initiation. In a simple reaction task, three patients were instructed to respond to a specific visual cue with the movement of a joystick. Within minutes of dACC ablation, the frequency of false starts increased, where movements occurred prior to presentation of the visual cue. In a decision making task with three separate patients, the ablation effect on action initiation persisted even when action selection was intact. These findings suggest that human dACC influences action initiation, apart from its role in action selection.

  4. 33 CFR 1.07-20 - Initiation of action.

    Science.gov (United States)

    2010-07-01

    ... GENERAL PROVISIONS Enforcement; Civil and Criminal Penalty Proceedings § 1.07-20 Initiation of action. (a... Hearing Officer; (5) The right to examine all materials in the case file and have a copy of all...

  5. Correlation of action potentials in adjacent neurons

    CERN Document Server

    Shneider, M N

    2015-01-01

    A possible mechanism for the synchronization of action potential propagation along a bundle of neurons (ephaptic coupling) is considered. It is shown that this mechanism is similar to the salutatory conduction of the action potential between the nodes of Ranvier in myelinated axons. The proposed model allows us to estimate the scale of the correlation, i.e., the distance between neurons in the nervous tissue, wherein their synchronization becomes possible. The possibility for experimental verification of the proposed model of synchronization is discussed.

  6. Screening action potentials: The power of light

    Directory of Open Access Journals (Sweden)

    Lars eKaestner

    2011-07-01

    Full Text Available Action potentials reflect the concerted activity of all electrogenic constituents in the plasma membrane during the excitation of a cell. Therefore, the action potential is an integrated readout and a promising parameter to detect electrophysiological failures or modifications thereof in diagnosis as well as in drug screens. Cellular action potentials can be recorded by optical approaches. To fulfill the pre-requirements to scale up for e.g. pharmacological screens the following preparatory work has to be provided: (i model cells under investigation need to represent target cells in the best possible manner; (ii optical sensors that can be either small molecule dyes or genetically encoded potential probes need to provide a reliable readout with minimal interaction with the naive behavior of the cells and (iii devices need to be capable to stimulate the cells, read out the signals with the appropriate speed as well as provide the capacity for a sufficient throughput. Here we discuss several scenarios for all three categories in the field of cardiac physiology and pharmacology and provide a perspective to use the power of light in screening cardiac action potentials.

  7. Action potential broadening in a presynaptic channelopathy

    OpenAIRE

    R. Begum; Bakiri, Y.; Volynski, K. E.; Kullmann, D M

    2016-01-01

    Brain development and interictal function are unaffected in many paroxysmal neurological channelopathies, possibly explained by homoeostatic plasticity of synaptic transmission. Episodic ataxia type 1 is caused by missense mutations of the potassium channel Kv1.1, which is abundantly expressed in the terminals of cerebellar basket cells. Presynaptic action potentials of small inhibitory terminals have not been characterized, and it is not known whether developmental plasticity compensates for...

  8. Differential potential noise measurement during crack initiation

    Energy Technology Data Exchange (ETDEWEB)

    Hettiarachchi, S. [GE-Hitachi Nuclear Energy, Vallecitos Nuclear Center, Sunol, California (United States)]. E-mail: samson.hettiarachchi@gene.ge.com

    2007-07-01

    Electrochemical potential and current noise have been used over the past two decades as methods of detecting general corrosion, pitting corrosion, crevice corrosion, stress corrosion, corrosion in concrete and corrosion under coatings. The methods involved the use of self-generated potential noise/current noise or both, of the material of choice in a given environment. In a variety of these studies, data processing involved techniques such as fast fourier transforms (FFT) to generate the power spectrum that provided the unique signature associated with the type of the corrosion process. This paper deals with a more simplistic method of monitoring differential potential noise measured between two identical slow strain rate test (SSRT) specimens placed close to each other, in a high temperature aqueous environment, while one is being subjected to dynamic strain and the other maintained under static conditions. The differential potential noise (DPN) was monitored as the applied load increased on the slow strain rate test specimen. Unlike self-generated noise, differential potential noise is less affected by electrical noise in the surroundings, and is able to signal the point of oxide film cracking or crack initiation more conveniently without extensive data processing. This method also allows the in-situ detection of crack initiation without interruption of the SSRT test. The DPN signal at the crack initiation stage is different from the signals acquired as cracking progressed due to continuing dynamic strain. Furthermore, the nature of the DPN signal response depends on the type of material used in this study, Type 304 stainless steel or Inconel 182. (author)

  9. Action potential broadening in a presynaptic channelopathy

    Science.gov (United States)

    Begum, Rahima; Bakiri, Yamina; Volynski, Kirill E.; Kullmann, Dimitri M.

    2016-07-01

    Brain development and interictal function are unaffected in many paroxysmal neurological channelopathies, possibly explained by homoeostatic plasticity of synaptic transmission. Episodic ataxia type 1 is caused by missense mutations of the potassium channel Kv1.1, which is abundantly expressed in the terminals of cerebellar basket cells. Presynaptic action potentials of small inhibitory terminals have not been characterized, and it is not known whether developmental plasticity compensates for the effects of Kv1.1 dysfunction. Here we use visually targeted patch-clamp recordings from basket cell terminals of mice harbouring an ataxia-associated mutation and their wild-type littermates. Presynaptic spikes are followed by a pronounced afterdepolarization, and are broadened by pharmacological blockade of Kv1.1 or by a dominant ataxia-associated mutation. Somatic recordings fail to detect such changes. Spike broadening leads to increased Ca2+ influx and GABA release, and decreased spontaneous Purkinje cell firing. We find no evidence for developmental compensation for inherited Kv1.1 dysfunction.

  10. Decoupling Action Potential Bias from Cortical Local Field Potentials

    Directory of Open Access Journals (Sweden)

    Stephen V. David

    2010-01-01

    Full Text Available Neurophysiologists have recently become interested in studying neuronal population activity through local field potential (LFP recordings during experiments that also record the activity of single neurons. This experimental approach differs from early LFP studies because it uses high impendence electrodes that can also isolate single neuron activity. A possible complication for such studies is that the synaptic potentials and action potentials of the small subset of isolated neurons may contribute disproportionately to the LFP signal, biasing activity in the larger nearby neuronal population to appear synchronous and cotuned with these neurons. To address this problem, we used linear filtering techniques to remove features correlated with spike events from LFP recordings. This filtering procedure can be applied for well-isolated single units or multiunit activity. We illustrate the effects of this correction in simulation and on spike data recorded from primary auditory cortex. We find that local spiking activity can explain a significant portion of LFP power at most recording sites and demonstrate that removing the spike-correlated component can affect measurements of auditory tuning of the LFP.

  11. Conduction velocity of antigravity muscle action potentials.

    Science.gov (United States)

    Christova, L; Kosarov, D; Christova, P

    1992-01-01

    The conduction velocity of the impulses along the muscle fibers is one of the parameters of the extraterritorial potentials of the motor units allowing for the evaluation of the functional state of the muscles. There are no data about the conduction velocities of antigravity muscleaction potentials. In this paper we offer a method for measuring conduction velocity of potentials of single MUs and the averaged potentials of the interference electromiogram (IEMG) lead-off by surface electrodes from mm. sternocleidomastoideus, trapezius, deltoideus (caput laterale) and vastus medialis. The measured mean values of the conduction velocity of antigravity muscles potentials can be used for testing the functional state of the muscles.

  12. Evaluating Maori community initiatives to promote healthy eating, healthy action.

    Science.gov (United States)

    Hamerton, Heather; Mercer, Christine; Riini, Denise; McPherson, Brighid; Morrison, Laurie

    2014-03-01

    Māori, the indigenous people of Aotearoa New Zealand, experience poorer health than non-Māori across a range of health measures. Interventions focused at an individual level have proved largely ineffective; 'bottom-up' approaches where communities determine their own priorities may be more sustainable than 'top-down' approaches where goals are determined by health authorities. The purpose of this paper is to illustrate an innovative health promotion programme aimed at improving Māori health and to discuss the importance of ownership and control of health initiatives by Māori. Evaluators conducted a comprehensive evaluation of a Healthy Eating Healthy Action programme in six small Māori health agencies, gathering information from programme managers and co-ordinators, participants and wider community members about what changes were occurring at individual, family and community levels. Effective interventions built on cultural values and practices and were delivered by Māori with close connections to the community. Changes in nutrition and physical activity made by participants also benefitted their wider families and community. The changes demonstrated subtle but important shifts in thinking about healthy eating and healthy activity that in the longer term could lead to more measurable change towards improved quality of life for people within communities.

  13. The 3D Elevation Program initiative: a call for action

    Science.gov (United States)

    Sugarbaker, Larry J.; Constance, Eric W.; Heidemann, Hans Karl; Jason, Allyson L.; Lukas, Vicki; Saghy, David L.; Stoker, Jason M.

    2014-01-01

    The 3D Elevation Program (3DEP) initiative is accelerating the rate of three-dimensional (3D) elevation data collection in response to a call for action to address a wide range of urgent needs nationwide. It began in 2012 with the recommendation to collect (1) high-quality light detection and ranging (lidar) data for the conterminous United States (CONUS), Hawaii, and the U.S. territories and (2) interferometric synthetic aperture radar (ifsar) data for Alaska. Specifications were created for collecting 3D elevation data, and the data management and delivery systems are being modernized. The National Elevation Dataset (NED) will be completely refreshed with new elevation data products and services. The call for action requires broad support from a large partnership community committed to the achievement of national 3D elevation data coverage. The initiative is being led by the U.S. Geological Survey (USGS) and includes many partners—Federal agencies and State, Tribal, and local governments—who will work together to build on existing programs to complete the national collection of 3D elevation data in 8 years. Private sector firms, under contract to the Government, will continue to collect the data and provide essential technology solutions for the Government to manage and deliver these data and services. The 3DEP governance structure includes (1) an executive forum established in May 2013 to have oversight functions and (2) a multiagency coordinating committee based upon the committee structure already in place under the National Digital Elevation Program (NDEP). The 3DEP initiative is based on the results of the National Enhanced Elevation Assessment (NEEA) that was funded by NDEP agencies and completed in 2011. The study, led by the USGS, identified more than 600 requirements for enhanced (3D) elevation data to address mission-critical information requirements of 34 Federal agencies, all 50 States, and a sample of private sector companies and Tribal and local

  14. Social Audits for Community Action: A tool to Initiate Community Action for Reducing Child Mortality

    Directory of Open Access Journals (Sweden)

    Nandan D

    2005-01-01

    Full Text Available Research question : (i What is the community′s perception (assessment & analysis of causes underlying neonatal, infant and under five deaths? (ii What action does the community take thereafter? Objectives : To stimulate the community to assess and analyze the causes and underlying social delays responsible for neonatal, infant and under five deaths in their villages and subsequently take collective action to prevent these deaths in future using Social Audits for Community Action (SACA. Design : Retrospective Participatory study. Setting : Rural community development blocks, district Agra, Uttar Pradesh. Material and Methods : SACA were conducted in a total of 152 villages of Fathehpur Sikri and Bichpuri blocks of district Agra, U.P. One SACA was conducted in each of the 211 anganwadi catchment areas, wherein 10-15 women from different socio-clusters of the community participated in a participatory discussion on issues pertaining to number of births and deaths of children less than five years of age in the last one-year. Results : 7656 live births and 749 under-five deaths were reported during the year 2002. The neonatal, infant and under-five mortality rate was 39.4, 73.5 and 85 per 1,000 live births respectively. Hypothermia, pneumonia, birth asphyxia, prematurity and low birth weight emerged as major causes of neonatal deaths. Majority of deaths of infants and children 1-5 years of age were found to have occurred due to severe malnutrition and diarrhoea. The community realized that majority of deaths occurred because of the delay in recognition of the seriousness of problem, delay in taking decision to seek appropriate care and delay in arranging transport/money. Subsequently, behaviour change communication strategies were re-defined to help community assess signs of illness and take preparedness measures to prevent child deaths in future. Conclusion : Strategies like dialoguing with the community using social audits for community action is

  15. Fast and reliable identification of axons, axon initial segments and dendrites with local field potential recording

    DEFF Research Database (Denmark)

    Petersen, Anders V.; Johansen, Emil O.; Perrier, Jean-Francois

    2015-01-01

    The axon initial segment (AIS) is an essential neuronal compartment. It is usually where action potentials are initiated. Recent studies demonstrated that the AIS is a plastic structure that can be regulated by neuronal activity and by the activation of metabotropic receptors. Studying the AIS...... of neurons, we can detect sinks caused by inward currents flowing across the membrane. We determine the location of the AIS by comparing the timing of these events with the action potential. We demonstrate that this method allows the unequivocal identification of the AIS of different types of neurons from...

  16. Role of Sodium Channel on Cardiac Action Potential

    Directory of Open Access Journals (Sweden)

    S. H. Sabzpoushan

    2012-06-01

    Full Text Available Sudden cardiac death is a major cause of death worldwide. In most cases, it's caused by abnormal action potential propagation that leads to cardiac arrhythmia. The aim of this article is to study the abnormal action potential propagation through sodium ion concentration variations. We use a new electrophysiological model that is both detailed and computationally efficient. This efficient model is based on the partial differential equation method. The central finite difference method is used for numerical solving of the two-dimensional (2D wave propagation equation. Simulations are implemented in two stages, as a single cardiac cell and as a two-dimensional grid of cells. In both stages, the normal action potential formation in case of a single cell and it's normal propagation in case of a two-dimensional grid of cells were simulated with nominal sodium ion conductance. Then, the effect of sodium ion concentration on the action potential signal was studied by reducing the sodium ion conductance. It is concluded that reducing the sodium ion conductance, decreases both passing ability and conduction velocity of the action potential wave front.

  17. A fast algorithm for estimating actions in triaxial potentials

    Science.gov (United States)

    Sanders, Jason L.; Binney, James

    2015-03-01

    We present an approach to approximating rapidly the actions in a general triaxial potential. The method is an extension of the axisymmetric approach presented by Binney, and operates by assuming that the true potential is locally sufficiently close to some Stäckel potential. The choice of Stäckel potential and associated ellipsoidal coordinates is tailored to each individual input phase-space point. We investigate the accuracy of the method when computing actions in a triaxial Navarro-Frenk-White potential. The speed of the algorithm comes at the expense of large errors in the actions, particularly for the box orbits. However, we show that the method can be used to recover the observables of triaxial systems from given distribution functions to sufficient accuracy for the Jeans equations to be satisfied. Consequently, such models could be used to build models of external galaxies as well as triaxial components of our own Galaxy. When more accurate actions are required, this procedure can be combined with torus mapping to produce a fast convergent scheme for action estimation.

  18. QCD Effective action at high temperature and small chemical potential

    CERN Document Server

    Villavicencio, C

    2007-01-01

    We present a construction of an effective Yang-Mills action for QCD, from the expansion of the fermionic determinant in terms of powers of the chemical potential at high temperature, for the case of massless quarks. We analyze this expansion in the perturbative region and find that it gives extra spurious information. We propose for the non-perturbative sector a simplified effective action which, in principle, contains only the relevant information.

  19. Numerical investigation of action potential transmission in plants

    Directory of Open Access Journals (Sweden)

    Mariusz Pietruszka

    2014-01-01

    Full Text Available In context of a fairly concise review of recent literature and well established experimental results we reconsider the problem of action potential propagating steadily down the plant cell(s. Having adopted slightly modified Hodgkin-Huxley set of differential equations for the action potential we carried out the numerical investigation of these equations in the course of time. We argue that the Hodgkin-Huxley-Katz model for the nerve impulse can be used to describe the phenomena which take place in plants - this point of view seems to be plausible since the mechanisms involving active ionic transport across membranes from the mathematical point of view are similar. Besides, we compare in a qualitative way our theoretical outcomes with typical experimental results for the action potentials which arise as the reaction of plants to electrical, mechanical and light stimuli. Moreover, we point out the relevance of the sequence of events during the pulse with the appropriate ionic fluxes.

  20. Changes in science classrooms resulting from collaborative action research initiatives

    Science.gov (United States)

    Oh, Phil Seok

    Collaborative action research was undertaken over two years between a Korean science teacher and science education researchers at the University of Iowa. For the purpose of realizing science learning as envisioned by constructivist principles, Group-Investigations were implemented three or five times per project year. In addition, the second year project enacted Peer Assessments among students. Student perceptions of their science classrooms, as measured by the Constructivist Learning Environment Survey (CLES), provided evidence that the collaborative action research was successful in creating constructivist learning environments. Student attitudes toward science lessons, as examined by the Enjoyment of Science Lessons Scale (ESLS), indicated that the action research also contributed to developing more positive attitudes of students about science learning. Discourse analysis was conducted on video-recordings of in-class presentations and discussions. The results indicated that students in science classrooms which were moving toward constructivist learning environments engaged in such discursive practices as: (1) Communicating their inquiries to others, (2) Seeking and providing information through dialogues, and (3) Negotiating conflicts in their knowledge and beliefs. Based on these practices, science learning was viewed as the process of constructing knowledge and understanding of science as well as the process of engaging in scientific inquiry and discourse. The teacher's discursive practices included: (1) Wrapping up student presentations, (2) Addressing misconceptions, (3) Answering student queries, (4) Coaching, (5) Assessing and advising, (6) Guiding students discursively into new knowledge, and (7) Scaffolding. Science teaching was defined as situated acts of the teacher to facilitate the learning process. In particular, when the classrooms became more constructivist, the teacher intervened more frequently and carefully in student activities to fulfill a

  1. Variations in retrieval monitoring during action memory judgments: evidence from event-related potentials (ERPs).

    Science.gov (United States)

    Leynes, P Andrew; Kakadia, Bhavika

    2013-02-01

    The present study investigated the neuroscience of memory for actions using event-related potentials (ERPs). Actions were performed, initiated but not completed (i.e., interrupted), or watched while the experimenter performed the action during encoding. Memory was assessed in a reality monitoring (RM) test (performed vs. watched actions), as well as in an internal source monitoring (ISM) test (performed vs. interrupted) while ERPs were recorded. Behavioral measures provided evidence of robust old/new recognition for all actions, but the analysis of source errors revealed that interrupted actions were often confused with performed actions. The ERP correlate of recollection, the parietal "old/new" effect (700-900ms), was observed for all actions. The right frontal "old/new" effect (1500-1800ms) that correlates with general memory monitoring was observed in RM but not in ISM. Instead, ISM was associated with the late posterior negativity (LPN) that has been connected to more specific memory monitoring. This pattern of ERP findings suggest that, in this context, general monitoring was used to discriminate self- versus other-performed actions, whereas more specific monitoring was required to support the discrimination of completed and interrupted actions. We argue that the mix of general/specific monitoring processes is shaped by the global retrieval context, which includes the number of memory features that overlap and the combination of sources being considered among other factors.

  2. Action prediction based on anticipatory brain potentials during simulated driving

    Science.gov (United States)

    Khaliliardali, Zahra; Chavarriaga, Ricardo; Gheorghe, Lucian Andrei; Millán, José del R.

    2015-12-01

    Objective. The ability of an automobile to infer the driver’s upcoming actions directly from neural signals could enrich the interaction of the car with its driver. Intelligent vehicles fitted with an on-board brain-computer interface able to decode the driver’s intentions can use this information to improve the driving experience. In this study we investigate the neural signatures of anticipation of specific actions, namely braking and accelerating. Approach. We investigated anticipatory slow cortical potentials in electroencephalogram recorded from 18 healthy participants in a driving simulator using a variant of the contingent negative variation (CNV) paradigm with Go and No-go conditions: count-down numbers followed by ‘Start’/‘Stop’ cue. We report decoding performance before the action onset using a quadratic discriminant analysis classifier based on temporal features. Main results. (i) Despite the visual and driving related cognitive distractions, we show the presence of anticipatory event related potentials locked to the stimuli onset similar to the widely reported CNV signal (with an average peak value of -8 μV at electrode Cz). (ii) We demonstrate the discrimination between cases requiring to perform an action upon imperative subsequent stimulus (Go condition, e.g. a ‘Red’ traffic light) versus events that do not require such action (No-go condition; e.g. a ‘Yellow’ light); with an average single trial classification performance of 0.83 ± 0.13 for braking and 0.79 ± 0.12 for accelerating (area under the curve). (iii) We show that the centro-medial anticipatory potentials are observed as early as 320 ± 200 ms before the action with a detection rate of 0.77 ± 0.12 in offline analysis. Significance. We show for the first time the feasibility of predicting the driver’s intention through decoding anticipatory related potentials during simulated car driving with high recognition rates.

  3. Uncertainty propagation in nerve impulses through the action potential mechanism

    NARCIS (Netherlands)

    Torres Valderrama, A.; Witteveen, J.A.S.; Navarro Jimenez, M.I.; Blom, J.G.

    2015-01-01

    We investigate the propagation of probabilistic uncertainty through the action potential mechanism in nerve cells. Using the Hodgkin-Huxley (H-H) model and Stochastic Collocation on Sparse Grids, we obtain an accurate probabilistic interpretation of the deterministic dynamics of the transmembrane po

  4. Sodium and potassium conductance changes during a membrane action potential.

    Science.gov (United States)

    Bezanilla, F; Rojas, E; Taylor, R E

    1970-12-01

    1. A method for turning a membrane potential control system on and off in less than 10 musec is described. This method was used to record membrane currents in perfused giant axons from Dosidicus gigas and Loligo forbesi after turning on the voltage clamp system at various times during the course of a membrane action potential.2. The membrane current measured just after the capacity charging transient was found to have an almost linear relation to the controlled membrane potential.3. The total membrane conductance taken from these current-voltage curves was found to have a time course during the action potential similar to that found by Cole & Curtis (1939).4. The instantaneous current voltage curves were linear enough to make it possible to obtain a good estimate of the individual sodium and potassium channel conductances, either algebraically or by clamping to the sodium, or potassium, reversal potentials. Good general agreement was obtained with the predictions of the Hodgkin-Huxley equations.5. We consider these results to constitute the first direct experimental demonstration of the conductance changes to sodium and potassium during the course of an action potential.

  5. Origin of ulnar compound muscle action potential investigated in patients with ulnar neuropathy at the wrist.

    Science.gov (United States)

    Higashihara, Mana; Sonoo, Masahiro; Imafuku, Ichiro; Ugawa, Yoshikazu; Tsuji, Shoji

    2010-05-01

    The compound muscle action potential from the abductor digiti minimi muscle is bi-lobed, and its second peak is formed by far-field potentials (FFPs). We investigated their origin in two patients with ulnar neuropathy at the wrist that spared the hypothenar muscles. FFPs were lost or distorted, which indicated that the deep motor branch-innervated muscles, such as the interossei, mainly contributed to the FFPs, especially to their initial N1 and steep following P1 components.

  6. Compound sensory action potential in normal and pathological human nerves

    DEFF Research Database (Denmark)

    Krarup, Christian

    2004-01-01

    , with fiber loss or increased conduction velocity variability changes of the SNAP may be smaller than expected from normal nerve. The biophysical characteristics of sensory and motor fibers differ, and this may to some extent determine divergent pathophysiological changes in sensory and motor fibers......The compound sensory nerve action potential (SNAP) is the result of phase summation and cancellation of single fiber potentials (SFAPs) with amplitudes that depend on fiber diameter, and the amplitude and shape of the SNAP is determined by the distribution of fiber diameters. Conduction velocities...... at different conduction distances are determined by summation of SFAPs of varying fiber diameters, and differ in this respect, also, from the compound muscle action potential (CMAP) for which conduction velocities are determined by the very fastest fibers in the nerve. The effect and extent of temporal...

  7. Compound sensory action potential in normal and pathological human nerves

    DEFF Research Database (Denmark)

    Krarup, Christian

    2004-01-01

    The compound sensory nerve action potential (SNAP) is the result of phase summation and cancellation of single fiber potentials (SFAPs) with amplitudes that depend on fiber diameter, and the amplitude and shape of the SNAP is determined by the distribution of fiber diameters. Conduction velocities...... at different conduction distances are determined by summation of SFAPs of varying fiber diameters, and differ in this respect, also, from the compound muscle action potential (CMAP) for which conduction velocities are determined by the very fastest fibers in the nerve. The effect and extent of temporal......, with fiber loss or increased conduction velocity variability changes of the SNAP may be smaller than expected from normal nerve. The biophysical characteristics of sensory and motor fibers differ, and this may to some extent determine divergent pathophysiological changes in sensory and motor fibers...

  8. 76 FR 22404 - Analgesic Clinical Trials Innovation, Opportunities, and Networks (ACTION) Initiative

    Science.gov (United States)

    2011-04-21

    ... HUMAN SERVICES Food and Drug Administration Analgesic Clinical Trials Innovation, Opportunities, and... Analgesic Clinical Trials Innovation, Opportunities, and Networks (ACTION) Initiative. The goal of the... major gaps in scientific information, which can slow down analgesic clinical trials and analgesic...

  9. The National Nanotechnology Initiative: Potential Impact on DoD

    Science.gov (United States)

    2016-07-13

    number. 1. REPORT DATE 19 MAR 2007 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE The National Nanotechnology Initiative...THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 The National Nanotechnology Initiative: Potential Impact on...that may be technologically exploitable. Why is nanotechnology the current rage? First, beginning in 1980, the discovery and development of

  10. 'Catching the waves' - slow cortical potentials as moderator of voluntary action.

    Science.gov (United States)

    Schmidt, Stefan; Jo, Han-Gue; Wittmann, Marc; Hinterberger, Thilo

    2016-09-01

    The readiness potential is an ongoing negativity in the EEG preceding a self-initiated movement by approximately 1.5s. So far it has predominantly been interpreted as a preparatory signal with a causal link to the upcoming movement. Here a different hypothesis is suggested which we call the selective slow cortical potential sampling hypothesis. In this review of recent research results we argue that the initiation of a voluntary action is more likely during negative fluctuations of the slow cortical potential and that the sampling and averaging of many trials leads to the observed negativity. That is, empirical evidence indicates that the early readiness potential is not a neural correlate of preconscious motor preparation and thus a determinant of action. Our hypothesis thereafter challenges the classic interpretation of the Libet experiment which is often taken as proof that there is no free will. We furthermore suggest that slow cortical potentials are related to an urge to act but are not a neural indicator of the decision process of action initiation.

  11. Personality Traits and Training Initiation Process: Intention, Planning, and Action Initiation

    OpenAIRE

    Mariola Laguna; Ewelina Purc

    2016-01-01

    The article aims at investigating the role of personality traits in relation to training initiation. Training initiation is conceptualized as a goal realization process, and explained using goal theories. There are three stages of the process analyzed: intention to undertake training, plan formulation, and actual training undertaking. Two studies tested the relationships between five personality traits, defined according to the five factor model, and the stages of the goal realization process...

  12. Cortical Interneuron Subtypes Vary in Their Axonal Action Potential Properties

    OpenAIRE

    Casale, Amanda E.; Foust, Amanda J.; Bal, Thierry; McCormick, David A.

    2015-01-01

    The role of interneurons in cortical microcircuits is strongly influenced by their passive and active electrical properties. Although different types of interneurons exhibit unique electrophysiological properties recorded at the soma, it is not yet clear whether these differences are also manifested in other neuronal compartments. To address this question, we have used voltage-sensitive dye to image the propagation of action potentials into the fine collaterals of axons and dendrites in two o...

  13. Warm body temperature facilitates energy efficient cortical action potentials.

    Directory of Open Access Journals (Sweden)

    Yuguo Yu

    Full Text Available The energy efficiency of neural signal transmission is important not only as a limiting factor in brain architecture, but it also influences the interpretation of functional brain imaging signals. Action potential generation in mammalian, versus invertebrate, axons is remarkably energy efficient. Here we demonstrate that this increase in energy efficiency is due largely to a warmer body temperature. Increases in temperature result in an exponential increase in energy efficiency for single action potentials by increasing the rate of Na(+ channel inactivation, resulting in a marked reduction in overlap of the inward Na(+, and outward K(+, currents and a shortening of action potential duration. This increase in single spike efficiency is, however, counterbalanced by a temperature-dependent decrease in the amplitude and duration of the spike afterhyperpolarization, resulting in a nonlinear increase in the spike firing rate, particularly at temperatures above approximately 35°C. Interestingly, the total energy cost, as measured by the multiplication of total Na(+ entry per spike and average firing rate in response to a constant input, reaches a global minimum between 37-42°C. Our results indicate that increases in temperature result in an unexpected increase in energy efficiency, especially near normal body temperature, thus allowing the brain to utilize an energy efficient neural code.

  14. 经颅磁刺激感应外电场作用下最小神经元模型放电起始动态机理分析%Action potential initial dynamical mechanism analysis in a minimum neuron model exposure to TMS induced electric field

    Institute of Scientific and Technical Information of China (English)

    金淇涛; 王江; 伊国胜; 李会艳; 邓斌; 魏熙乐; 车艳秋

    2012-01-01

    经颅磁刺激(TMS)是一种采用电磁线圈在大脑指定区域产生磁场的刺激方式.TMS的治疗原理是通过电磁感应产生作用于神经元的外加电场进而影响神经元编码.然而目前TMS感应外电场改变神经元编码的内在机理尚不清楚.研究表明,神经元编码由神经元的放电起始动态机理决定.本文建立了TMS感应外电场作用下的最小神经元模型,采用相平面分析和分岔分析方法,研究了外电场作用下神经元放电起始动态的动力学机理,并从阈下电位的不同动力学特性离子电流竞争角度揭示了TMS感应外电场作用下神经元放电起始动态的生理学机理.%Transcranial magnetic stimulation(TMS) is a kind of brain stimulation method of producing magnetic field at the designated area of brain employing electromagnetic coils.The principle of TMS is to apply an electric field which is generated through the electromagnetic induction to neuron,thereby influencing the excitability of neuron.Though it has been used for decades,its underlying mechanism,i.e.,how TMS induction electric field changes neuronal excitability,is still unknown.To address this problem,we establish a minimum neuron model under action of TMS induced electric field,analyze the mechanism from the viewpoint of action potential initial dynamical mechanism which has been proved to be the decision factor of neural coding in previous studies.Through phase plane and bifurcation analysis,we reveal the dynamical mechanism of different firing patterns of neuron.Finally,we find that the physiological basis of different excitabilities under action of TMS induced electric field,which is the different outcomes of competition between ion currents of neuron with different kinetic behaviors in sub-threshold potential.

  15. Variations in onset of action potential broadening: effects on calcium current studied in chick ciliary ganglion neurones.

    Science.gov (United States)

    Pattillo, J M; Artim, D E; Simples, J E; Meriney, S D

    1999-02-01

    1. The voltage dependence and kinetic properties of stage 40 ciliary ganglion calcium currents were determined using short (10 ms) voltage steps. These properties aided the interpretation of the action potential-evoked calcium current described below, and the comparison of our data with those observed in other preparations. 2. Three different natural action potential waveforms were modelled by a series of ramps to generate voltage clamp commands. Calcium currents evoked by these model action potentials were compared before and after alterations in the repolarization phase of each action potential. 3. Abrupt step repolarizations from various time points were used to estimate the time course of calcium current activation during each action potential. Calcium current evoked by fast action potentials (duration at half-amplitude, 0.5 or 1.0 ms) did not reach maximal activation until the action potential had repolarized by 40-50 %. In contrast, calcium current evoked by a slow action potential (duration at half-amplitude, 2.2 ms) was maximally activated near the peak of the action potential. 4. Slowing the rate of repolarization of the action potential (broadening) from different times was used to examine effects on peak and total calcium influx. With all three waveforms tested, broadening consistently increased total calcium influx (integral). However, peak calcium current was either increased or decreased depending on the duration of the control action potential tested and the specific timing of the initiation of broadening the repolarization phase. 5. The opposite effects on peak calcium current observed with action potential broadening beginning at different time points in repolarization may provide a mechanism for the variable effects of potassium channel blockers on transmitter release magnitude.

  16. Democracy under Fire: Voter Confusion and Influences in Colorado's Anti-Affirmative Action Initiative

    Science.gov (United States)

    Farley, Amy N.; Gaertner, Matthew N.; Moses, Michele S.

    2013-01-01

    In this article, Amy N. Farley, Matthew N. Gaertner, and Michele S. Moses examine the use of ballot initiatives as a particularly attractive form of direct democracy for opponents of affirmative action in higher education. Building on previous scholarship, the authors question whether anti-affirmative ballot initiatives validly reflect voters'…

  17. Noisy unmaskers of multistability of periodic rhythms in a model of the ventricular cardiac action potential

    Science.gov (United States)

    Surovyatkina, Elena; Egorchenkov, Roman; Ivanov, Guennady

    2007-06-01

    The coexistence of different dynamical regimes of cardiac cell-model at a fixed set of stimulation parameters, i.e. multistability, revealed by noise is presented in this paper. Numerical simulations are performed using Luo-Rudy (LR1) action potential model. Numerical experiments with LR1 model conducted via noisy periodical stimulation showed the coexistence of several periodic rhythms. Weak noise in period of stimulation causes a hopping process between all the (meta-) stable rhythms of cell-model. This process is reflected in several parallel branches of the bifurcation diagram: noise unveils new, invisible before, stable rhythms which could appear in this model at different initial conditions. The phenomenon of multistability is directly evidenced by other numerical experiments: we have established the multistability property of a cell consisting in the fact that different initial conditions of stimulation (different extrasystole application times) lead to different stable periodic rhythms. We have obtained the shaping of attraction basins on the action potential curves. Such basins of attraction contain a set of initial conditions which determinate a stable periodic rhythm. We have found a close association between the attraction basins of the complex rhythms on the curves of action potential and the cardiac vulnerable windows on ECG record, during which extra stimuli can induce life threatening arrhythmias. Obtained results allow us to make a conclusion that multistability is very important for the electrical conduction system of the heart from the cell level to the integrated function of the heart.

  18. Vanadium compounds biological actions and potential as pharmacological agents.

    Science.gov (United States)

    Tsiani, E; Fantus, I G

    1997-03-01

    Vanadium is an element found in low concentrations in mammals, for which a function remains to be discovered. Over the past century, vanadium compounds have been suggested anecdotally as therapeutic agents for a variety of diseases. The discovery that vanadate inhibits various enzymes, in particular protein tyrosine phosphatases, and mimics many of the biological actions of insulin suggested a potential role in the therapy of diabetes mellitus. Successful use and an enhancement of insulin sensitivity in rodents and human diabetic subjects, as well as the finding that these agents are capable of stimulating metabolic effects while bypassing the insulin receptor and the early steps in insulin action, target these agents preferentially toward type II diabetes mellitus. Long-term safety remains a major concern, as tissue accumulation and relative nonspecificity of enzyme inhibition may result in adverse effects. Continued research into mechanism of action, consequences of chronic administration, and improvement of specificity is warranted. Regardless of their ultimate success or failure as therapeutic agents, vanadium compounds continue to be useful probes of enzyme structure and function in various biological processes. (Trends Endocrinol Metab 1997;8:51-58). (c) 1997, Elsevier Science Inc.

  19. Flexible graphene transistors for recording cell action potentials

    Science.gov (United States)

    Blaschke, Benno M.; Lottner, Martin; Drieschner, Simon; Bonaccini Calia, Andrea; Stoiber, Karolina; Rousseau, Lionel; Lissourges, Gaëlle; Garrido, Jose A.

    2016-06-01

    Graphene solution-gated field-effect transistors (SGFETs) are a promising platform for the recording of cell action potentials due to the intrinsic high signal amplification of graphene transistors. In addition, graphene technology fulfills important key requirements for in-vivo applications, such as biocompability, mechanical flexibility, as well as ease of high density integration. In this paper we demonstrate the fabrication of flexible arrays of graphene SGFETs on polyimide, a biocompatible polymeric substrate. We investigate the transistor’s transconductance and intrinsic electronic noise which are key parameters for the device sensitivity, confirming that the obtained values are comparable to those of rigid graphene SGFETs. Furthermore, we show that the devices do not degrade during repeated bending and the transconductance, governed by the electronic properties of graphene, is unaffected by bending. After cell culture, we demonstrate the recording of cell action potentials from cardiomyocyte-like cells with a high signal-to-noise ratio that is higher or comparable to competing state of the art technologies. Our results highlight the great capabilities of flexible graphene SGFETs in bioelectronics, providing a solid foundation for in-vivo experiments and, eventually, for graphene-based neuroprosthetics.

  20. Fears, Uncertainties, and Hopes: Patient-Initiated Actions and Doctors' Responses During Oncology Interviews.

    Science.gov (United States)

    Beach, Wayne A; Dozier, David M

    2015-01-01

    New cancer patients frequently raise concerns about fears, uncertainties, and hopes during oncology interviews. This study sought to understand when and how patients raise their concerns, how doctors responded to these patient-initiated actions, and implications for communication satisfaction. A subsampling of video recorded and transcribed encounters was investigated involving 44 new patients and 14 oncologists. Patients completed pre/post self-report measures about fears, uncertainties, and hopes as well as postevaluations of interview satisfaction. Conversation analysis was used to initially identify pairs of patient-initiated and doctor-responsive actions. A coding scheme was subsequently developed, and two independent coding teams, comprised of two coders each, reliably identified patient-initiated and doctor-responsive social actions. Interactional findings reveal that new cancer patients initiate actions much more frequently than previous research had identified, concerns are usually raised indirectly, and with minimal emotion. Doctors tend to respond to these concerns immediately, but with even less affect, and rarely partner with patients. From pre/post results, it was determined that the higher patients' reported fears, the higher their postvisit fears and lower their satisfaction. Patients with high uncertainty were highly proactive (e.g., asked more questions), yet reported even greater uncertainties after encounters. Hopeful patients also exited interviews with high hopes. Overall, new patients were very satisfied: oncology interviews significantly decreased patients' fears and uncertainties, while increasing hopes. Discussion raises key issues for improving communication and managing quality cancer care.

  1. Military Personnel: DOD Needs to Take Further Actions to Prevent Sexual Assault During Initial Military Training

    Science.gov (United States)

    2014-09-01

    supervisory or command position who uses or condones any form of sexual behavior to control, influence , or affect the career, pay, or job of a military...in the armed forces must have signed parental consent prior to age 18. Page 37 GAO-14-806 Sexual Assault during Initial Training...MILITARY PERSONNEL DOD Needs to Take Further Actions to Prevent Sexual Assault during Initial Military Training

  2. 20 CFR 658.702 - Initial action by the Regional Administrator.

    Science.gov (United States)

    2010-04-01

    ..., ETA staff shall review the State agency's efforts as documented by the State agency at the end of the... to State Agencies § 658.702 Initial action by the Regional Administrator. (a) The ETA Regional... are elevated to ETA after the exhaustion of State agency administrative remedies, the...

  3. 44 CFR 350.8 - Initial FEMA action on State plan.

    Science.gov (United States)

    2010-10-01

    ... 44 Emergency Management and Assistance 1 2010-10-01 2010-10-01 false Initial FEMA action on State plan. 350.8 Section 350.8 Emergency Management and Assistance FEDERAL EMERGENCY MANAGEMENT AGENCY... acknowledge in writing within ten days the receipt of the State application. (b) FEMA shall publish a...

  4. Pressure wave model for action potential propagation in excitable cells

    CERN Document Server

    Rvachev, M M

    2003-01-01

    Speed of propagation of small-amplitude pressure waves through the cytoplasmic interior of myelinated and unmyelinated axons of different diameters is theoretically estimated and is found to generally agree with the action potential (AP) conduction velocities. This remarkable coincidence allows to surmise a model in which AP spread along axon is propelled not by straggling ionic currents as in the widely accepted local circuit theory, but by mechanoactivation of the membrane ion channels by a traveling pressure pulse. Hydraulic pulses propagating in the viscous axoplasm are calculated to decay over ~1 mm distances, and it is further hypothesized that it is the role of influxing during the AP calcium ions to activate membrane skeletal protein network attached to the membrane cytoplasmic side for a brief radial contraction amplifying the pressure pulse and preventing its decay. The model correctly predicts that the AP conduction velocity should vary as the one-half power of axon diameter for large unmyelinated ...

  5. Regulation of cough and action potentials by voltage-gated Na channels.

    Science.gov (United States)

    Carr, Michael J

    2013-10-01

    The classical role ascribed to voltage-gated Na channels is the conduction of action potentials. Some excitable tissues such as cardiac muscle and skeletal muscle predominantly express a single voltage-gated Na channels isoform. Of the nine voltage-gated Na channels, seven are expressed in neurons, of these Nav 1.7, 1.8 and 1.9 are expressed in sensory neurons including vagal sensory neurons that innervate the airways and initiate cough. Nav 1.7 and Nav 1.9 are of particular interest as they represent two extremes in the functional diversity of voltage-gated Na channels. Voltage-gated Na channel isoforms expressed in airway sensory neurons produce multiple distinct Na currents that underlie distinct aspects of sensory neuron function. The interaction between voltage-gated Na currents underlies the characteristic ability of airway sensory nerves to encode encounters with irritant stimuli into action potential discharge and evoke the cough reflex.

  6. Aircraft accident investigation: the decision-making in initial action scenario.

    Science.gov (United States)

    Barreto, Marcia M; Ribeiro, Selma L O

    2012-01-01

    In the complex aeronautical environment, the efforts in terms of operational safety involve the adoption of proactive and reactive measures. The process of investigation begins right after the occurrence of the aeronautical accident, through the initial action. Thus, it is in the crisis scenario, that the person responsible for the initial action makes decisions and gathers the necessary information for the subsequent phases of the investigation process. Within this scenario, which is a natural environment, researches have shown the fragility of rational models of decision making. The theoretical perspective of naturalistic decision making constitutes a breakthrough in the understanding of decision problems demanded by real world. The proposal of this study was to verify if the initial action, after the occurrence of an accident, and the decision-making strategies, used by the investigators responsible for this activity, are characteristic of the naturalistic decision making theoretical approach. To attend the proposed objective a descriptive research was undertaken with a sample of professionals that work in this activity. The data collected through individual interviews were analyzed and the results demonstrated that the initial action environment, which includes restricted time, dynamic conditions, the presence of multiple actors, stress and insufficient information is characteristic of the naturalistic decision making. They also demonstrated that, when the investigators make their decisions, they use their experience and the mental simulation, intuition, improvisation, metaphors and analogues cases, as strategies, all of them related to the naturalistic approach of decision making, in order to satisfy the needs of the situation and reach the objectives of the initial action in the accident scenario.

  7. Action potential shape change in an electrically coupled network during propagation: a computer simulation.

    Science.gov (United States)

    Buckingham, Steven D; Spencer, Andrew N

    2008-06-01

    We applied compartmental computer modeling to test a model of spike shape change in the jellyfish, Polyorchis penicillatus, to determine whether adaptive spike shortening can be attributed to the inactivation properties of a potassium channel. We modeled the jellyfish outer nerve-ring as a continuous linear segment, using ion channel and membrane properties derived in earlier studies. The model supported action potentials that shortened as they propagated away from the site of initiation and this was found to be largely independent of potassium channel inactivation. Spike broadening near the site of initiation was found to be due to a depolarization plateau that collapsed as two spikes spread from the point of initiation. The lifetime of this plateau was found to depend critically on the inward current flux and the space constant of the membrane. These data suggest that the spike shape changes may be due not only to potassium channel inactivation, but also to the passive properties of the membrane.

  8. Readiness potential and movement initiation in the rat.

    Science.gov (United States)

    Seki, Tomomi; Gemba, Hisae; Matsuzaki, Ryuichi; Nakao, Kazuko

    2005-02-01

    Cortical field potentials were recorded by electrodes implanted chronically on the surface and at a 2.0 mm depth in various cortical areas in the left hemisphere in the rat during self-paced movements of the right forelimb. A surface-negative (s-N), depth-positive (d-P) cortical field potential appeared about 1.0 s (range: 0.5-1.5 s) before movement onset in the rostral (RFA) and caudal (CFA) forelimb areas of the motor cortex, and the somatosensory cortex, but not in the occipital cortex. Bipolar recording of electromyographic activities induced by the electrical stimulation of various cortical loci was also performed by pairs of steel electrodes inserted in the face, trunk, forelimb and hindlimb muscles on both sides. The stimulation of the forelimb motor cortex activated the face and/or forelimb muscles, while that of the somatosensory cortex generally activated several body part muscles including the forelimb muscle. Stronger stimulus intensity was requested to elicit the activities of most of the ipsilateral muscles to the cortex stimulated than the contralateral ones. The minimum intensity for inducing the forelimb muscle activity was lowest in the CFA among cortical areas producing the activity. The stimulation of cortical loci in which the s-N, d-P potential was recorded could induce muscle activities in the forelimb contralateral to the stimulation. It is suggested that the s-N, d-P potential is the readiness potential for activating muscles to initiate movement in the rat forelimb.

  9. Ultrafast action potentials mediate kilohertz signaling at a central synapse.

    Science.gov (United States)

    Ritzau-Jost, Andreas; Delvendahl, Igor; Rings, Annika; Byczkowicz, Niklas; Harada, Harumi; Shigemoto, Ryuichi; Hirrlinger, Johannes; Eilers, Jens; Hallermann, Stefan

    2014-10-01

    Fast synaptic transmission is important for rapid information processing. To explore the maximal rate of neuronal signaling and to analyze the presynaptic mechanisms, we focused on the input layer of the cerebellar cortex, where exceptionally high action potential (AP) frequencies have been reported in vivo. With paired recordings between presynaptic cerebellar mossy fiber boutons and postsynaptic granule cells, we demonstrate reliable neurotransmission up to ∼1 kHz. Presynaptic APs are ultrafast, with ∼100 μs half-duration. Both Kv1 and Kv3 potassium channels mediate the fast repolarization, rapidly inactivating sodium channels ensure metabolic efficiency, and little AP broadening occurs during bursts of up to 1.5 kHz. Presynaptic Cav2.1 (P/Q-type) calcium channels open efficiently during ultrafast APs. Furthermore, a subset of synaptic vesicles is tightly coupled to Ca(2+) channels, and vesicles are rapidly recruited to the release site. These data reveal mechanisms of presynaptic AP generation and transmitter release underlying neuronal kHz signaling.

  10. Acute nerve stretch and the compound motor action potential

    Directory of Open Access Journals (Sweden)

    Wolfe Jacob

    2011-08-01

    Full Text Available Abstract In this paper, the acute changes in the compound motor action potential (CMAP during mechanical stretch were studied in hamster sciatic nerve and compared to the changes that occur during compression. In response to stretch, the nerve physically broke when a mean force of 331 gm (3.3 N was applied while the CMAP disappeared at an average stretch force of 73 gm (0.73 N. There were 5 primary measures of the CMAP used to describe the changes during the experiment: the normalized peak to peak amplitude, the normalized area under the curve (AUC, the normalized duration, the normalized velocity and the normalized velocity corrected for the additional path length the impulses travel when the nerve is stretched. Each of these measures was shown to contain information not available in the others. During stretch, the earliest change is a reduction in conduction velocity followed at higher stretch forces by declines in the amplitude of the CMAP. This is associated with the appearance of spontaneous EMG activity. With stretch forces Multiple means of predicting when a change in the CMAP suggests a significant stretch are discussed and it is clear that a multifactorial approach using both velocity and amplitude parameters is important. In the case of pure compression, it is only the amplitude of the CMAP that is critical in predicting which changes in the CMAP are associated with significant compression.

  11. Action-specific effects in perception and their potential applications

    OpenAIRE

    Witt, Jessica K.; Linkenauger, Sally; Wickens, Chris

    2016-01-01

    Spatial perception is biased by action. Hills appear steeper and distances appear farther to individuals who would have to exert more effort to transverse the space. Objects appear closer, smaller, and faster when they are easier to obtain. Athletes who are playing better than others see their targets as bigger. These phenomena are collectively known as action-specific effects on perception. In this target article, we review evidence for action-specific effects, including evidence that they r...

  12. Initiating an Action Research Programme for University EFL Teachers: Early Experiences and Responses

    Directory of Open Access Journals (Sweden)

    Anne Burns

    2016-10-01

    Full Text Available Accounts of how teacher educators begin to plan, develop, and support action research programmes for language teachers are rare, as are descriptions of the responses of the teachers who participate. This article documents and analyses the initial processes of introducing and supporting a new programme of action research for language teachers at the Universidad Chileno-Británica de Cultura (UCBC in Santiago, Chile. To evaluate the setting up of the programme and how the teachers have perceived it in its early stages, the authors, who are the programme facilitators, have conducted a meta- study. Data include workshop and meeting recordings, workshop observation notes, a reflective account, and a teacher questionnaire. The findings indicate that the teachers value the input and collaboration provided by an initial workshop, and subsequent meetings and discussions, very highly, but that issues of time, student involvement, and academic literature are areas for further debate and development. The article ends by drawing out the broader implications for UCBC and for others wishing to initiate similar action research programmes.

  13. Initiation of breakout of half-buried submarine pipe from sea bed due to wave action

    Energy Technology Data Exchange (ETDEWEB)

    Law, A.W.K. [Nanyang Technological Univ. (Singapore). School of Civil and Structural Engineering; Foda, M.A. [California Univ., Berkeley, CA (United States). Dept. of Civil Engineering

    1996-12-31

    A formulation is presented for the analysis of the breakout of a half-buried submarine pipe due to wave action. The formulation accounts for the contact between the pipe and the soil due to the oscillating horizontal hydrodynamic force. Results demonstrate the existence of an initial gap in the breakout experiments. With this initial gap the gap flux dominated the influx of water into the gap throughout the breakout process. The linear pipe rise persisted although the second-order expansion of the gap should have grown to the same order of magnitude as the initial gap with the poro-rigid soil assumption. It is postulated that the persistence of the linear rise was due to the localized passive failure around the ends of the soil trench which inhibited the growth of the opening due to the pipe`s rise. (Author)

  14. Differential effects of K(+) channel blockers on frequency-dependent action potential broadening in supraoptic neurons.

    Science.gov (United States)

    Hlubek, M D; Cobbett, P

    2000-09-15

    Recordings were made from magnocellular neuroendocrine cells dissociated from the supraoptic nucleus of the adult guinea pig to determine the role of voltage gated K(+) channels in controlling the duration of action potentials and in mediating frequency-dependent action potential broadening exhibited by these neurons. The K(+) channel blockers charybdotoxin (ChTx), tetraethylammonium (TEA), and 4-aminopyridine (4-AP) increased the duration of individual action potentials indicating that multiple types of K(+) channel are important in controlling action potential duration. The effect of these K(+) channel blockers was almost completely reversed by simultaneous blockade of voltage gated Ca(2+) channels with Cd(2+). Frequency-dependent action potential broadening was exhibited by these neurons during trains of action potentials elicited by membrane depolarizing current pulses presented at 10 Hz but not at 1 Hz. 4-AP but not ChTx or TEA inhibited frequency-dependent action potential broadening indicating that frequency-dependent action potential broadening is dependent on increasing steady-state inactivation of A-type K(+) channels (which are blocked by 4-AP). A model of differential contributions of voltage gated K(+) channels and voltage gated Ca(2+) channels to frequency-dependent action potential broadening, in which an increase of Ca(2+) current during each successive action potential is permitted as a result of the increasing steady-state inactivation of A-type K(+) channels, is presented.

  15. The Initial and Sustaining Leadership Actions Taken by the Transformational Leadership Group in the Development of the "Dallas Achieves!" Transformational Theory of Action Framework

    Science.gov (United States)

    Ponce, James Joseph

    2009-01-01

    Given the prominence of the transformational theory of action in major urban educational reform efforts, this study intends to describe and analyze the initial and sustaining leadership actions taken by the superintendent and his leadership team, the board of trustees and the "Dallas Achieves!" Commission in the development of the…

  16. Circadian- and Light-Dependent Regulation of Resting Membrane Potential and Spontaneous Action Potential Firing of Drosophila Circadian Pacemaker Neurons

    OpenAIRE

    Sheeba, Vasu; Gu, Huaiyu; Sharma, Vijay K.; O'Dowd, Diane K.; Holmes, Todd C

    2007-01-01

    The ventral lateral neurons (LNvs) of adult Drosophila brain express oscillating clock proteins and regulate circadian behavior. Whole cell current-clamp recordings of large LNvs in freshly dissected Drosophila whole brain preparations reveal two spontaneous activity patterns that correlate with two underlying patterns of oscillating membrane potential: tonic and burst firing of sodium-dependent action potentials. Resting membrane potential and spontaneous action potential firing are rapidly ...

  17. Ontogeny of vestibular compound action potentials in the domestic chicken

    Science.gov (United States)

    Jones, S. M.; Jones, T. A.

    2000-01-01

    Compound action potentials of the vestibular nerve were measured from the surface of the scalp in 148 chickens (Gallus domesticus). Ages ranged from incubation day 18 (E18) to 22 days posthatch (P22). Responses were elicited using linear acceleration cranial pulses. Response thresholds decreased at an average rate of -0.45 dB/day. The decrease was best fit by an exponential model with half-maturity time constant of 5.1 days and asymptote of approximately -25.9 dB re:1.0 g/ms. Mean threshold approached within 3 dB of the asymptote by ages P6-P9. Similarly, response latencies decreased exponentially to within 3% of mature values at ages beyond P9. The half-maturity time constant for peripheral response peak latencies P1, N1, and P2 was comparable to thresholds and ranged from approximately 4.6 to 6.2 days, whereas central peaks (N2, P3, and N3) ranged from 2.9 to 3.4 days. Latency-intensity slopes for P1, N1, and P2 tended to decrease with age, reaching mature values within approximately 100 hours of hatching. Amplitudes increased as a function of age with average growth rates for response peaks ranging from 0.04 to 0.09 microV/day. There was no obvious asymptote to the growth of amplitudes over the ages studied. Amplitude-intensity slopes also increased modestly with age. The results show that gravity receptors are responsive to transient cranial stimuli as early as E19 in the chicken embryo. The functional response of gravity receptors continues to develop for many days after all major morphological structures are in place. Distinct maturational processes can be identified in central and peripheral neural relays. Functional improvements during maturation may result from refinements in the receptor epithelia, improvements in central and peripheral synaptic transmission, increased neural myelination, as well as changes in the mechanical coupling between the cranium and receptor organ.

  18. Distribution of Action Potential Duration and T-wave Morphology: a Simulation Study

    CERN Document Server

    Ryzhii, Elena; Wei, Daming

    2009-01-01

    The results of a simulation study of the action potential duration (APD) distribution and T-wave morphology taking into account the midmyocardial cells (M-cells) concept are described. To investigate the effect of M-cells we present a computer model in which ion channel action potential formulations are incorporated into three-dimensional whole heart model. We implemented inhomogeneous continuous action potential duration distribution based on different distributions of maximal slow delayed rectifier current conductance. Using the proposed action potential distribution procedure midmural zeniths with longest action potential length were created as islands of model cells in the depth of thickest areas of ventricular tissue. Different spatial functions on layer indexes were simulated and their influences on electrocardiogram waveforms were analyzed. Changing parameters of ion channel model we varied duration of minimal and maximal action potential and investigated T-wave amplitude, Q-Tpeak and QT intervals vari...

  19. Understanding the Electrical Behavior of the Action Potential in Terms of Elementary Electrical Sources

    Science.gov (United States)

    Rodriguez-Falces, Javier

    2015-01-01

    A concept of major importance in human electrophysiology studies is the process by which activation of an excitable cell results in a rapid rise and fall of the electrical membrane potential, the so-called action potential. Hodgkin and Huxley proposed a model to explain the ionic mechanisms underlying the formation of action potentials. However,…

  20. Action potential broadening and frequency-dependent facilitation of calcium signals in pituitary nerve terminals.

    OpenAIRE

    Jackson, M B; Konnerth, A.; Augustine, G.J.

    1991-01-01

    Hormone release from nerve terminals in the neurohypophysis is a sensitive function of action potential frequency. We have investigated the cellular mechanisms responsible for this frequency-dependent facilitation by combining patch clamp and fluorimetric Ca2+ measurements in single neurosecretory terminals in thin slices of the rat posterior pituitary. In these terminals both action potential-induced changes in the intracellular Ca2+ concentration ([Ca2+]i) and action potential duration were...

  1. Stability of cylindrical shells with initial imperfections under the action of external pressure

    Science.gov (United States)

    Lopanitsyn, E. A.; Matveev, E. A.

    2011-04-01

    We use the equations of nonlinear theory of shallow shells to solve the problem of stability of thin elastic isotropic cylindrical shells, with small initial shape imperfections, that are under the action of external uniform pressure. The problem solution is constructed by the Rayleigh-Ritz method with the approximation of the shell midsurface displacement by double functional sums in trigonometric and beam functions. The system of nonlinear algebraic equations is solved by using the methods of continuation with respect to a close-to-best parameter. For the initial imperfections of the shells, we use their normalized deflections from the limit points of overcritical branches of the loading trajectories. We consider various cases of the shell fixation and support under loading by lateral and hydrostatic uniform pressure. We also construct the range of values of the critical pressure, which, with the maximal deviation of the shell shape from the cylindrical shape up to 30%, covers practically all known experimental data.

  2. Effect of a prenylamine analog (MG8926) on spontaneous action potentials in isolated rabbit sinoatrial node.

    Science.gov (United States)

    Nakanishi, H; Matsuoka, I; Ono, T; Yoshida, H; Uchibori, T; Kogi, K

    1996-12-01

    Effects of verapamil, prenylamine and a prenylamine analog, MG8926 on the intracellular spontaneous action potentials recorded from the isolated rabbit sinoatrial (SA) node were studied. Verapamil (1 microM), a selective inhibitor for slow Ca2+ channels, prolonged the cycle length, decreased the rate of diastolic depolarization, the rate of rise of action potential, the amplitude of action potential and the maximal diastolic potential, and usually arrested showing subthreshold fluctuation of the membrane potential within several ten min. Prenylamine (10 microM), a nonselective inhibitor for slow Ca2+ channels, tended to prolong the cycle length to decrease the diastolic depolarization, the rate of rise of action potential, the amplitude of action potential. However, these changes were statistically insignificant. Prenylamine at the concentration of 10 microM had no effect on the maximal diastolic potential. MG8926 (10 microM) prolonged the cycle length, decreased the rate of diastolic depolarization, the rate of rise of action potential and tended to decrease the amplitude of action potential. MG8926 at the concentration of 10 microM had almost no effect on the maximal diastolic potential. The present findings may indicate that replacement of phenyl residue of prenylamine by cyclohexyl residue increases the inhibitory action on the slow Ca2+ channels in rabbit SA node.

  3. Action potential broadening induced by lithium may cause a presynaptic enhancement of excitatory synaptic transmission in neonatal rat hippocampus.

    Science.gov (United States)

    Colino, A; García-Seoane, J J; Valentín, A

    1998-07-01

    Lithium enhances excitatory synaptic transmission in CA1 pyramidal cells, but the mechanisms remain unclear. The present study demonstrates that lithium enhances the N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-isoxazole propionic acid (AMPA) receptor-mediated components of the excitatory postsynaptic current (EPSC). Lithium decreased the magnitude of paired-pulse facilitation and presented an inverse correlation between the lithium-induced enhancement of synaptic transmission and initial paired-pulse facilitation, which is consistent with a presynaptic mode of action. The enhancement of synaptic strength is likely to act, at least in part, by increasing the amplitude of the presynaptic Ca2+ transient. One mechanism which could account for this change of the presynaptic Ca2+ transient is an increase in the duration of the action potential. We investigated action potential in hippocampal pyramidal neurons and found that lithium (0.5-6 mM) increased the half-amplitude duration and reduced the rate of repolarization, whereas the rate of depolarization remained similar. To find out whether the lithium synaptic effects might be explained by spike broadening, we investigated the field recording of the excitatory postsynaptic potential (EPSP) in hippocampal slices and found three lines of evidence. First, the prolongation of the presynaptic action potential with 4-aminopyridine and tetraethylammonium blocked or reduced the synaptic effects of lithium. Second, the lithium-induced synaptic enhancement was modulated when presynaptic Ca2+ influx was varied by changing the external Ca2+ concentration. Finally, both effects, the synaptic transmission increment and the action potential broadening, were independent of inositol depletion. These results suggest that lithium enhances synaptic transmission in the hippocampus via a presynaptic site of action: the mechanism underlying the potentiating effect may be attributable to an increased Ca2+ influx consequent

  4. Still at the choice-point: action selection and initiation in instrumental conditioning.

    Science.gov (United States)

    Balleine, Bernard W; Ostlund, Sean B

    2007-05-01

    Contrary to classic stimulus-response (S-R) theory, recent evidence suggests that, in instrumental conditioning, rats encode the relationship between their actions and the specific consequences that these actions produce. It has remained unclear, however, how encoding this relationship acts to control instrumental performance. Although S-R theories were able to give a clear account of how learning translates into performance, the argument that instrumental learning constitutes the acquisition of information of the form "response R leads to outcome O" does not directly imply a particular performance rule or policy; this information can be used both to perform R and to avoid performing R. Recognition of this problem has forced the development of accounts that allow the O and stimuli that predict the O (i.e., S-O) to play a role in the initiation of specific Rs. In recent experiments, we have used a variety of behavioral procedures in an attempt to isolate the processes that contribute to instrumental performance, including outcome devaluation, reinstatement, and Pavlovian-instrumental transfer. Our results, particularly from experiments assessing outcome-selective reinstatement, suggest that both "feed-forward" (O-R) and "feed-back" (R-O) associations are critical and that although the former appear to be important to response selection, the latter-together with processes that determine outcome value-mediate response initiation. We discuss a conceptual model that integrates these processes and its neural implementation.

  5. On the excitation of action potentials by protons and its potential implications for cholinergic transmission

    CERN Document Server

    Fillafer, Christian

    2014-01-01

    One of the most conserved mechanisms for transmission of a nerve pulse across a synapse relies on acetylcholine. Ever since the Nobel-prize winning works of Dale and Loewi, it has been assumed that acetylcholine - subsequent to its action on a postsynaptic cell - is split into inactive by-products by acetylcholinesterase. Herein, this widespread assumption is falsified. Excitable cells (Chara australis internodes), which had previously been unresponsive to acetylcholine, became acetylcholine-sensitive in presence of acetylcholinesterase. The latter was evidenced by a striking difference in cell membrane depolarisation upon exposure to 10 mM intact acetylcholine (deltaV=-2plus/minus5 mV) and its hydrolysate respectively (deltaV=81plus/minus19 mV) for 60 sec. This pronounced depolarization, which also triggered action potentials, was clearly attributed to one of the hydrolysis products: acetic acid (deltaV=87plus/minus9 mV at pH 4.0; choline ineffective in range 1-10 mM). In agreement with our findings, numerou...

  6. Carbon Monoxide Effects onHuman Ventricle Action PotentialAssessed by Mathematical Simulations

    Directory of Open Access Journals (Sweden)

    Beatriz eTrenor

    2013-10-01

    Full Text Available Carbon monoxide (CO that is produced in a number of different mammalian tissues is now known to have significant effects on the cardiovascular system. These include: i vasodilation, ii changes in heart rate and strength of contractions and iii modulation of autonomic nervous system input to both the pacemaker and the working myocardium. Excessive CO in the environment is toxic and can initiate or mediate life threatening cardiac rhythm disturbances. Recent reports link these ventricular arrhythmias to an increase in the slowly inactivating, or ‘late’ component of the Na+ current in the mammalian heart.The main goal of this paper is to explore the basis of this pro-arrhythmic capability of CO by incorporating recently reported changes in CO-induced ion channel activity and intracellular signalling pathways in the mammalian heart. To do this, a quite well-documented mathematical model of the action potential and intracellular calcium transient in the human ventricular myocyte has been employed. In silico iterations based on this model provide a useful first step in illustrating the cellular electrophysiological consequences of CO that have been reported from mammalian heart experiments. Specifically, when the Grandi et al. model of the human ventricular action potential is utilized, and after the Na+ and Ca2+ currents in a single myocyte are modified based on the experimental literature, early after-depolarization (EAD rhythm disturbances appear, and important elements of the underlying causes of these EADs are revealed/illustrated. Our modified mathematical model of the human ventricular action potential also provides a convenient digital platform for designing future experimental work and relating these changes in cellular cardiac electrophysiology to emerging clinical and epidemiological data on CO toxicity.

  7. Making Class Actions Work: The Untapped Potential of the Internet

    Directory of Open Access Journals (Sweden)

    Robert H. Klonoff

    2008-04-01

    Full Text Available Over twenty years ago, the Supreme Court recognized that in class action litigation, absent class members “must receive notice plus an opportunity to be heard and participate in the litigation, whether in person or through counsel.” Although the absent class members’ rights to receive notice and an opportunity to opt out are of vital importance, the ability to be heard and participate in the litigation are also important.

  8. The characteristics of action potential and nonselective cation current of cardiomyocytes in rabbit superior vena cava

    Institute of Scientific and Technical Information of China (English)

    WANG Pan; YANG XinChun; LIU XiuLan; BAO RongFeng; LIU TaiFeng

    2008-01-01

    As s special focus in initiating and maintaining atrial fibrillation (AF), cardiomyocytes in superior vena cavs (SVC) have distinctive electrophysiological characters. In this study, we found that comparing with the right atrial (RA) cardiomyoctyes, the SVC cardiomyoctyes had longer APD90 at the different basic cycle lengths; the conduction block could be observed on both RA and SVC cardiomyoctyes. A few of SVC cardiomyoctyes showed slow response action potentials with automatic activity and some others showed early afterdepolarization (EAD) spontaneously. Further more, we found that there are nonselective cation current (INs) in both SVC and RA cardiomyocytes. The peak density of INs in SVC cardiomyocytes was smaller than that in RA cardiomyocytes. Removal of extracellular divalent cation and glucose could increase INs in SVC cardiomyocytes. The agonist or the antagonist of INs may increase or decrease APD. To sum up, some SVC cardiomyocytes possess the ability of spontaneous activity; the difference of transmembrane action potentials between SVC and RA cardiomyocytes is partly because of the different density of INs between them; the agonist or the antagonist of INs can increase or decrease APD leading to the enhancement or reduction of EAD genesis in SVC cardiomyocytes. INs in rabbit myocytes is fairly similar to TRPC3 current in electrophysiological property, which might play an important role in the mechanisms of AF.

  9. Triangulation of the monophasic action potential causes flattening of the electrocardiographic T-wave

    DEFF Research Database (Denmark)

    Bhuiyan, Tanveer Ahmed; Graff, Claus; Thomsen, Morten Bækgaard

    2012-01-01

    of the action potential under the effect of the IKr blocker sertindole and associated these changes to concurrent changes in the morphology of electrocardiographic T-waves in dogs. We show that, under the effect of sertindole, the peak changes in the morphology of action potentials occur at time points similar...

  10. Closing the Civic Engagement Gap: The Potential of Action Civics

    Science.gov (United States)

    Pope, Alexander; Stolte, Laurel; Cohen, Alison K.

    2011-01-01

    When taught in an engaging manner, civic education can help stimulate and motivate students to excel in other academic areas, while simultaneously preparing them to be active citizens in the democracy. As an initial attempt to more systematically analyze civic education practice, this article presents four case studies of projects in one action…

  11. Prolonged modification of action potential shape by synaptic inputs in molluscan neurones.

    Science.gov (United States)

    Winlow, W

    1985-01-01

    1. Somatic action potentials of Lymnaea neurons are modified by excitatory or inhibitory synaptic inputs and have been studied using phase-plane techniques and an action potential duration monitor. 2. Excitatory synaptic inputs increase the rate of neuronal discharge, cause action potential broadening, a decrease in the maximum rate of depolarization (Vd) and a decrease in the maximum rate of repolarization (Vr). 3. Inhibitory synaptic inputs decrease the discharge rate and cause narrowing of action potentials, an increase in Vd and an increase in Vr. 4. The effects reported above outlast the original synaptic inputs by many seconds and, if the somatic action potentials are similar to those in the axon terminals, they may have far-reaching effects on transmitter release.

  12. Consumer-Related Food Waste: Causes and Potential for Action

    Directory of Open Access Journals (Sweden)

    Jessica Aschemann-Witzel

    2015-05-01

    Full Text Available In the past decade, food waste has received increased attention on both academic and societal levels. As a cause of negative economic, environmental and social effects, food waste is considered to be one of the sustainability issues that needs to be addressed. In developed countries, consumers are one of the biggest sources of food waste. To successfully reduce consumer-related food waste, it is necessary to have a clear understanding of the factors influencing food waste-related consumer perceptions and behaviors. The present paper presents the results of a literature review and expert interviews on factors causing consumer-related food waste in households and supply chains. Results show that consumers’ motivation to avoid food waste, their management skills of food provisioning and food handling and their trade-offs between priorities have an extensive influence on their food waste behaviors. We identify actions that governments, societal stakeholders and retailers can undertake to reduce consumer-related food waste, highlighting that synergistic actions between all parties are most promising. Further research should focus on exploring specific food waste contexts and interactions more in-depth. Experiments and interventions in particular can contribute to a shift from analysis to solutions.

  13. The COST 731 Action and the MAP D-PHASE Initiative - Overview on Main Outcomes

    Science.gov (United States)

    Rossa, A. M.

    2010-09-01

    The COST 731 Action, launched in 2005, addresses the problem of forecasting (heavy) precipitation events and the corresponding hydrological processes in connection with the uncertainty inherent in this task. The actual threat to society that potentially occurs from intense (and thus rare) events only becomes effective after the involvement of the hydrosphere. The main focus of the Action is the quantification of forecast uncertainty and its propagation through a meteo-hydrological forecast chain. COST 731 is structured in three working groups, which deal with uncertainty cascading from observation (predominantly from radar) into numerical weather prediction (NWP) models, from observation and NWP into hydrological models, and the use of uncertainty as support in decision making. The groups of scientists involved in the action therefore represent radar meteorology, NWP, hydrological modeling, as well as social scientists who deal with risk communication. MAP D-PHASE (Mesoscale Alpine Programme, Demonstration of Probabilistic Hydrological and Atmospheric Simulation of Flooding Events in the Alps) is the second WMO/WWRP Forecast Demonstration Project and constitutes an important element of COST 731. Its Operations Period (June - November 2007) was centred in the Alpine region and experienced a number of interesting weather cases. Real-time forecast information of 7 limited area ensemble prediction systems, 23 high-resolution limited area numerical weather prediction models, as well as 7 hydrological models coupled to NWP QPF and/or radar QPE input were collected, and synthetically displayed on a visualization platform. In this presentation an overview of the COST 731 main achievements of the action as well as open issues and future opportunities are given. They are put into context with the results and perspectives of D-PHASE, first verification results, end user feedback, lessons learnt. A notable number of operational groups in hydrological modeling are in the

  14. Action potential generation in an anatomically constrained model of medial superior olive axons.

    Science.gov (United States)

    Lehnert, Simon; Ford, Marc C; Alexandrova, Olga; Hellmundt, Franziska; Felmy, Felix; Grothe, Benedikt; Leibold, Christian

    2014-04-09

    Neurons in the medial superior olive (MSO) encode interaural time differences (ITDs) with sustained firing rates of >100 Hz. They are able to generate such high firing rates for several hundred milliseconds despite their extremely low-input resistances of only few megaohms and high synaptic conductances in vivo. The biophysical mechanisms by which these leaky neurons maintain their excitability are not understood. Since action potentials (APs) are usually assumed to be generated in the axon initial segment (AIS), we analyzed anatomical data of proximal MSO axons in Mongolian gerbils and found that the axon diameter is <1 μm and the internode length is ∼100 μm. Using a morphologically constrained computational model of the MSO axon, we show that these thin axons facilitate the excitability of the AIS. However, for ongoing high rates of synaptic inputs the model generates a substantial fraction of APs in its nodes of Ranvier. These distally initiated APs are mediated by a spatial gradient of sodium channel inactivation and a strong somatic current sink. The model also predicts that distal AP initiation increases the dynamic range of the rate code for ITDs.

  15. Loss of Saltation and Presynaptic Action Potential Failure in Demyelinated Axons

    Science.gov (United States)

    Hamada, Mustafa S.; Popovic, Marko A.; Kole, Maarten H. P.

    2017-01-01

    In cortical pyramidal neurons the presynaptic terminals controlling transmitter release are located along unmyelinated axon collaterals, far from the original action potential (AP) initiation site, the axon initial segment (AIS). Once initiated, APs will need to reliably propagate over long distances and regions of geometrical inhomogeneity like branch points (BPs) to rapidly depolarize the presynaptic terminals and confer temporally precise synaptic transmission. While axon pathologies such as demyelinating diseases are well established to impede the fidelity of AP propagation along internodes, to which extent myelin loss affects propagation along BPs and axon collaterals is not well understood. Here, using the cuprizone demyelination model, we performed optical voltage-sensitive dye (VSD) imaging from control and demyelinated layer 5 pyramidal neuron axons. In the main axon, we find that myelin loss switches the modality of AP propagation from rapid saltation towards a slow continuous wave. The duration of single AP waveforms at BPs or nodes was, however, only slightly briefer. In contrast, by using two-photon microscopy-guided loose-seal patch recordings from axon collaterals we revealed a presynaptic AP broadening in combination with a reduced velocity and frequency-dependent failure. Finally, internodal myelin loss was also associated with de novo sprouting of axon collaterals starting from the primary (demyelinated) axon. Thus, the loss of oligodendrocytes and myelin sheaths bears functional consequences beyond the main axon, impeding the temporal fidelity of presynaptic APs and affecting the functional and structural organization of synaptic connectivity within the neocortex.

  16. Membrane-initiated Actions of Estradiol that Regulate Reproduction, Energy Balance and Body Temperature

    Science.gov (United States)

    Kelly, Martin J.; Rønnekleiv, Oline K.

    2012-01-01

    It is well known that many of the actions of estrogens in the central nervous system are mediated via intracellular receptor/transcription factors that interact with steroid response elements on target genes. However, there now exists compelling evidence for membrane estrogen receptors in hypothalamic and other brain neurons. But, it is not well understood how estrogens signal via membrane receptors, and how these signals impact not only membrane excitability but also gene transcription in neurons. Indeed, it has been known for sometime that estrogens can rapidly alter neuronal activity within seconds, indicating that some cellular effects can occur via membrane delimited events. In addition, estrogens can affect second messenger systems including calcium mobilization and a plethora of kinases to alter cell signaling. Therefore, this review will consider our current knowledge of rapid membrane-initiated and intracellular signaling by estrogens in the hypothalamus, the nature of receptors involved and how they contribute to homeostatic functions. PMID:22871514

  17. Neuronal oscillations enhance stimulus discrimination by ensuring action potential precision

    DEFF Research Database (Denmark)

    Schaefer, Andreas T; Angelo, Kamilla; Spors, Hartwig

    2006-01-01

    Although oscillations in membrane potential are a prominent feature of sensory, motor, and cognitive function, their precise role in signal processing remains elusive. Here we show, using a combination of in vivo, in vitro, and theoretical approaches, that both synaptically and intrinsically gene......, membrane potential oscillations dramatically enhance the discriminatory capabilities of individual neurons and networks of cells and provide one attractive explanation for their abundance in neurophysiological systems....

  18. Non-nuclear-initiated actions of the estrogen receptor protect cortical bone mass.

    Science.gov (United States)

    Bartell, Shoshana M; Han, Li; Kim, Ha-neui; Kim, Sung Hoon; Katzenellenbogen, John A; Katzenellenbogen, Benita S; Chambliss, Ken L; Shaul, Philip W; Roberson, Paula K; Weinstein, Robert S; Jilka, Robert L; Almeida, Maria; Manolagas, Stavros C

    2013-04-01

    Extensive evidence has suggested that at least some of the effects of estrogens on bone are mediated via extranuclear estrogen receptor α signaling. However, definitive proof for this contention and the extent to which such effects may contribute to the overall protective effects of estrogens on bone maintenance have remained elusive. Here, we investigated the ability of a 17β-estradiol (E2) dendrimer conjugate (EDC), incapable of stimulating nuclear-initiated actions of estrogen receptor α, to prevent the effects of ovariectomy (OVX) on the murine skeleton. We report that EDC was as potent as an equimolar dose of E2 in preventing bone loss in the cortical compartment that represents 80% of the entire skeleton, but was ineffective on cancellous bone. In contrast, E2 was effective in both compartments. Consistent with its effect on cortical bone mass, EDC partially prevented the loss of both vertebral and femoral strength. In addition, EDC, as did E2, prevented the OVX-induced increase in osteoclastogenesis, osteoblastogenesis, and oxidative stress. Nonetheless, the OVX-induced decrease in uterine weight was unaltered by EDC but was restored by E2. These results demonstrate that the protection of cortical bone mass by estrogens is mediated, at least in part, via a mechanism that is distinct from the classic mechanism of estrogen action on reproductive organs.

  19. Gene networks activated by specific patterns of action potentials in dorsal root ganglia neurons

    Science.gov (United States)

    Lee, Philip R.; Cohen, Jonathan E.; Iacobas, Dumitru A.; Iacobas, Sanda; Fields, R. Douglas

    2017-01-01

    Gene regulatory networks underlie the long-term changes in cell specification, growth of synaptic connections, and adaptation that occur throughout neonatal and postnatal life. Here we show that the transcriptional response in neurons is exquisitely sensitive to the temporal nature of action potential firing patterns. Neurons were electrically stimulated with the same number of action potentials, but with different inter-burst intervals. We found that these subtle alterations in the timing of action potential firing differentially regulates hundreds of genes, across many functional categories, through the activation or repression of distinct transcriptional networks. Our results demonstrate that the transcriptional response in neurons to environmental stimuli, coded in the pattern of action potential firing, can be very sensitive to the temporal nature of action potential delivery rather than the intensity of stimulation or the total number of action potentials delivered. These data identify temporal kinetics of action potential firing as critical components regulating intracellular signalling pathways and gene expression in neurons to extracellular cues during early development and throughout life. PMID:28256583

  20. Potential synergy of phytochemicals in cancer prevention: mechanism of action.

    Science.gov (United States)

    Liu, Rui Hai

    2004-12-01

    Epidemiological studies have consistently shown that regular consumption of fruits and vegetables is strongly associated with reduced risk of developing chronic diseases, such as cancer and cardiovascular disease. It is now widely believed that the actions of the antioxidant nutrients alone do not explain the observed health benefits of diets rich in fruits and vegetables, because taken alone, the individual antioxidants studied in clinical trials do not appear to have consistent preventive effects. Work performed by our group and others has shown that fruits and vegetable phytochemical extracts exhibit strong antioxidant and antiproliferative activities and that the major part of total antioxidant activity is from the combination of phytochemicals. We proposed that the additive and synergistic effects of phytochemicals in fruits and vegetables are responsible for these potent antioxidant and anticancer activities and that the benefit of a diet rich in fruits and vegetables is attributed to the complex mixture of phytochemicals present in whole foods. This explains why no single antioxidant can replace the combination of natural phytochemicals in fruits and vegetables to achieve the health benefits. The evidence suggests that antioxidants or bioactive compounds are best acquired through whole-food consumption, not from expensive dietary supplements. We believe that a recommendation that consumers eat 5 to 10 servings of a wide variety of fruits and vegetables daily is an appropriate strategy for significantly reducing the risk of chronic diseases and to meet their nutrient requirements for optimum health.

  1. Intravenous nitroglycerin for rest angina. Potential pathophysiologic mechanisms of action.

    Science.gov (United States)

    DePace, N L; Herling, I M; Kotler, M N; Hakki, A H; Spielman, S R; Segal, B L

    1982-10-01

    Twenty patients with refractory rest angina pectoris were treated with intravenously (IV) administered nitroglycerin (mean dosage, 72.4 micrograms/min; range, 15 to 226 micrograms/min). There was a considerable reduction or abolition in the number of ischemic episodes in 85% of patients without overall substantial changes in heart rate, mean arterial BP, pulmonary capillary wedge pressure (PCWP), and pulmonary arterial mean pressure. However, those patients with an initial PCWP of more than 12 mm Hg or a systolic pressure of more than 130 mm Hg had a substantial reduction in PCWP and systolic BP following IV nitroglycerin. We conclude that IV nitroglycerin may relieve rest angina by different pathophysiologic mechanisms. In some patients, IV nitroglycerin favorably altered the hemodynamic determinants of myocardial oxygen consumption. In others, however, no change in these determinants occurred, suggesting a direct effect on the coronary circulation.

  2. Alterations in nerve and muscle compound action potentials after acute acrylamide administration.

    OpenAIRE

    Anderson, R. J.

    1982-01-01

    The early deficits of neurotoxicity induced by acrylamide were examined in rats by comparing nerve and muscle action potentials before and 24 hr after exposure to acrylamide (25, 50 or 100 mg/kg). No changes were seen in the nerve action potential amplitude or duration. The 25 mg/kg dose produced a more variable nerve conduction velocity. There was also a significant broadening of the muscle compound action potential. Neither of these effects were seen in the fasted controls. However, the len...

  3. Consequences of converting graded to action potentials upon neural information coding and energy efficiency.

    Science.gov (United States)

    Sengupta, Biswa; Laughlin, Simon Barry; Niven, Jeremy Edward

    2014-01-01

    Information is encoded in neural circuits using both graded and action potentials, converting between them within single neurons and successive processing layers. This conversion is accompanied by information loss and a drop in energy efficiency. We investigate the biophysical causes of this loss of information and efficiency by comparing spiking neuron models, containing stochastic voltage-gated Na(+) and K(+) channels, with generator potential and graded potential models lacking voltage-gated Na(+) channels. We identify three causes of information loss in the generator potential that are the by-product of action potential generation: (1) the voltage-gated Na(+) channels necessary for action potential generation increase intrinsic noise and (2) introduce non-linearities, and (3) the finite duration of the action potential creates a 'footprint' in the generator potential that obscures incoming signals. These three processes reduce information rates by ∼50% in generator potentials, to ∼3 times that of spike trains. Both generator potentials and graded potentials consume almost an order of magnitude less energy per second than spike trains. Because of the lower information rates of generator potentials they are substantially less energy efficient than graded potentials. However, both are an order of magnitude more efficient than spike trains due to the higher energy costs and low information content of spikes, emphasizing that there is a two-fold cost of converting analogue to digital; information loss and cost inflation.

  4. Antioxidant properties of melatonin and its potential action in diseases.

    Science.gov (United States)

    Karaaslan, Cigdem; Suzen, Sibel

    2015-01-01

    In recent years, relationship between free radicals and oxidative stress with aging, cancer, atherosclerosis, neurodegenerative disorders, diabetes, and inflammatory diseases became increasingly clear. Confirming the role of oxidants in numerous pathological conditions such as cancer, the antioxidants developed as therapeutics have been proven ineffective. It is well established that melatonin (MLT) and its metabolites are able to function as endogenous free-radical scavengers and broadspectrum antioxidants. Numerous studies also proved the role of MLT and its derivatives in many physiological processes and therapeutic functions, such as the regulation of circadian rhythm and immune functions. The aim of this review is to arouse attention to MLT as a potentially valuable agent in the prevention and/or treatment of some diseases.

  5. Spatial and frequency domain ring source models for the single muscle fiber action potential

    DEFF Research Database (Denmark)

    Henneberg, Kaj-åge; R., Plonsey

    1994-01-01

    In the paper, single-fibre models for the extracellular action potential are developed that will allow the potential to the evaluated at an arbitrary field point in the extracellular space. Fourier-domain models are restricted in that they evaluate potentials at equidistant points along a line...

  6. Control of Secretion by Encodes of Action Potentials in Neuronal Cells

    Institute of Scientific and Technical Information of China (English)

    Kailai Duan; Zhuan Zhou

    2003-01-01

    @@ Action potentials (APs) are principle physiological stimuli of neurotransmitter secretion or synaptic transmis sion. Most studies on stimulus-secretion-coupling have been performed under voltage clamp using artificial electric stimulations.

  7. Epidermal Laser Stimulation of Action Potentials in the Frog Sciatic Nerve

    Science.gov (United States)

    2008-10-01

    Laser Stimulation of Action Potentials in the Frog Sciatic Nerve Nichole M. Jindra Robert J. Thomas Human Effectiveness Directorate Directed...in the Frog Sciatic Nerve 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62202F 6. AUTHOR(S) .Nichole M. Jindra, Robert J. Thomas, Douglas N...Alan Rice 14. ABSTRACT Measurements of laser stimulated action potentials in the sciatic nerve of leopard frogs (Rana pipiens) were made using

  8. Uniform Action Potential Repolarization within the Sarcolemma of In Situ Ventricular Cardiomyocytes

    OpenAIRE

    Bu, Guixue; Adams, Heather; Berbari, Edward J.; Rubart, Michael

    2009-01-01

    Previous studies have speculated, based on indirect evidence, that the action potential at the transverse (t)-tubules is longer than at the surface membrane in mammalian ventricular cardiomyocytes. To date, no technique has enabled recording of electrical activity selectively at the t-tubules to directly examine this hypothesis. We used confocal line-scan imaging in conjunction with the fast response voltage-sensitive dyes ANNINE-6 and ANNINE-6plus to resolve action potential-related changes ...

  9. Action potential broadening and frequency-dependent facilitation of calcium signals in pituitary nerve terminals.

    Science.gov (United States)

    Jackson, M B; Konnerth, A; Augustine, G J

    1991-01-15

    Hormone release from nerve terminals in the neurohypophysis is a sensitive function of action potential frequency. We have investigated the cellular mechanisms responsible for this frequency-dependent facilitation by combining patch clamp and fluorimetric Ca2+ measurements in single neurosecretory terminals in thin slices of the rat posterior pituitary. In these terminals both action potential-induced changes in the intracellular Ca2+ concentration ([Ca2+]i) and action potential duration were enhanced by high-frequency stimuli, all with a frequency dependence similar to that of hormone release. Furthermore, brief voltage clamp pulses inactivated a K+ current with a very similar frequency dependence. These results support a model for frequency-dependent facilitation in which the inactivation of a K+ current broadens action potentials, leading to an enhancement of [Ca2+]i signals. Further experiments tested for a causal relationship between action potential broadening and facilitation of [Ca2+]i changes. First, increasing the duration of depolarization, either by broadening action potentials with the K(+)-channel blocker tetraethylammonium or by applying longer depolarizing voltage clamp steps, increased [Ca2+]i changes. Second, eliminating frequency-dependent changes in duration, by voltage clamping the terminal with constant duration pulses, substantially reduced the frequency-dependent enhancement of [Ca2+]i changes. These results indicate that action potential broadening contributes to frequency-dependent facilitation of [Ca2+]i changes. However, the small residual frequency dependence of [Ca2+]i changes seen with constant duration stimulation suggests that a second process, distinct from action potential broadening, also contributes to facilitation. These two frequency-dependent mechanisms may also contribute to activity-dependent plasticity in synaptic terminals.

  10. Glutamate induces series of action potentials and a decrease in circumnutation rate in Helianthus annuus.

    Science.gov (United States)

    Stolarz, Maria; Król, Elzbieta; Dziubińska, Halina; Kurenda, Andrzej

    2010-03-01

    Reports concerning the function of glutamate (Glu) in the electrical and movement phenomena in plants are scarce. Using the method of extracellular measurement, we recorded electrical potential changes in the stem of 3-week-old Helianthus annuus L. plants after injection of Glu solution. Simultaneously, circumnutation movements of the stem were measured with the use of time-lapse images. Injection of Glu solution at millimolar (200, 50, 5 mM) concentrations in the basal part of the stem evoked a series of action potentials (APs). The APs appeared in the site of injection and in different parts of the stem and were propagated acropetally and/or basipetally along the stem. Glu injection also resulted in a transient, approximately 5-h-long decrease in the stem circumnutation rate. The APs initiated and propagating in the sunflower stem after Glu injection testify the existence of a Glu perception system in vascular plants and suggest its involvement in electrical, long-distance signaling. Our experiments also demonstrated that Glu is a factor affecting circumnutation movements.

  11. Detection of Variability of the Motor Unit Action Potential Shape by Means of the Firing Patterns

    DEFF Research Database (Denmark)

    Krarup, Christian; Nikolic, Mile; Dahl, Kristian;

    1997-01-01

    The motor unit action potential is a summation of the potentials of the individual muscle fibers from the same motor unit.By using a newly developed automatic EMG decomposition system, variability of the firing patterns of the muscle fibers are analyzed.......The motor unit action potential is a summation of the potentials of the individual muscle fibers from the same motor unit.By using a newly developed automatic EMG decomposition system, variability of the firing patterns of the muscle fibers are analyzed....

  12. Inhibitors of protein kinase C prevent enhancement of calcium current and action potentials in peptidergic neurons of Aplysia.

    Science.gov (United States)

    Conn, P J; Strong, J A; Kaczmarek, L K

    1989-02-01

    Following brief stimulation of an afferent pathway, the bag cell neurons of Aplysia undergo a dramatic change in excitability, resulting in a prolonged discharge of spontaneous action potentials. During the discharge, the action potentials of the bag cell neurons become enhanced in height and width. The afterdischarge triggers release of neuroactive peptides that initiate egg-laying behavior in this animal. Evidence suggests that changes in excitability of the bag cell neurons may be mediated by activation of protein kinase C (PKC) and cAMP-dependent protein kinase (cAMP-PK). PKC activators, such as the phorbol ester TPA (12-O-tetradecanoyl-13-phorbol acetate), enhance the amplitude of action potentials in isolated bag cell neurons in cell culture. These agents act by unmasking a previously covert species of voltage-dependent calcium channel resulting in an increase in calcium current. In the accompanying paper (Conn et al., 1989), we showed that H-7, a protein kinase inhibitor, inhibits the effect of TPA, and is a selective inhibitor of PKC relative to cAMP-PK in these cells. We now report that another PKC inhibitor, sphinganine, also inhibits the effect of TPA on action potential height and calcium current in cultured bag cell neurons, and that N-acetylsphinganine, an inactive sphinganine analog, fails to inhibit the effects of PKC activators. Although both H-7 and sphinganine prevent the effects of TPA when added prior to TPA addition, neither compound reverses the effects of TPA when added after the action potentials have already become enhanced by TPA.(ABSTRACT TRUNCATED AT 250 WORDS)

  13. Pulsed magnetic stimulation modifies amplitude of action potentials in vitro via ionic channels-dependent mechanism.

    Science.gov (United States)

    Ahmed, Zaghloul; Wieraszko, Andrzej

    2015-07-01

    This paper investigates the influence of pulsed magnetic fields (PMFs) on amplitude of evoked, compound action potential (CAP) recorded from the segments of sciatic nerve in vitro. PMFs were applied for 30 min at frequency of 0.16 Hz and intensity of 15 mT. In confirmation of our previous reports, PMF exposure enhanced amplitude of CAPs. The effect persisted beyond PMF activation period. As expected, CAP amplitude was attenuated by antagonists of sodium channel, lidocaine, and tetrodotoxin. Depression of the potential by sodium channels antagonists was reversed by subsequent exposure to PMFs. The effect of elevated potassium concentration and veratridine on the action potential was modified by exposure to PMFs as well. Neither inhibitors of protein kinase C and protein kinase A, nor known free radicals scavengers had any effects on PMF action. Possible mechanisms of PMF action are discussed.

  14. Action-space clustering of tidal streams to infer the Galactic potential

    CERN Document Server

    Sanderson, Robyn E; Hogg, David W

    2014-01-01

    We present a new method for constraining the Milky Way halo gravitational potential by simultaneously fitting multiple tidal streams. This method requires full three-dimensional positions and velocities for all stars in the streams, but does not require identification of any specific stream, nor determination of stream membership for any star. We exploit the principle that the action distribution of stream stars is most clustered---that is, most informative---when the potential used to calculate the actions is closest to the true potential. We measure the amount of clustering with the Kullback-Leibler Divergence (KLD) or relative entropy, a statistical measure of information which also provides uncertainties for our parameter estimates. We show, for toy Gaia-like data in a spherical isochrone potential, that maximizing the KLD of the action distribution relative to a smoother distribution recovers the true values of the potential parameters. The precision depends on the observational errors and the number and...

  15. Effect of an educational game on university students' learning about action potentials.

    Science.gov (United States)

    Luchi, Kelly Cristina Gaviao; Montrezor, Luís Henrique; Marcondes, Fernanda K

    2017-06-01

    The aim of this study was to evaluate the effect of an educational game that is used for teaching the mechanisms of the action potentials in cell membranes. The game was composed of pieces representing the intracellular and extracellular environments, ions, ion channels, and the Na(+)-K(+)-ATPase pump. During the game activity, the students arranged the pieces to demonstrate how the ions move through the membrane in a resting state and during an action potential, linking the ion movement with a graph of the action potential. To test the effect of the game activity on student understanding, first-year dental students were given the game to play at different times in a series of classes teaching resting membrane potential and action potentials. In all experiments, students who played the game performed better in assessments. According to 98% of the students, the game supported the learning process. The data confirm the students' perception, indicating that the educational game improved their understanding about action potentials.

  16. Effects of acetylcholine and noradrenalin on action potentials of isolated rabbit sinoatrial and atrial myocytes

    Directory of Open Access Journals (Sweden)

    Arie O. Verkerk

    2012-05-01

    Full Text Available The autonomic nervous system controls heart rate and contractility through sympathetic and parasympathetic inputs to the cardiac tissue, with acetylcholine (ACh and noradrenalin (NA as the chemical transmitters. In recent years, it has become clear that specific Regulators of G protein Signalling proteins (RGS proteins suppress muscarinic sensitivity and parasympathetic tone, identifying RGS proteins as intriguing potential therapeutic targets. In the present study, we have identified the effects of 1 µM ACh and 1 µM NA on the intrinsic action potentials of sinotrial (SA nodal and atrial myocytes. Single cells were enzymatically isolated from the SA node or from the left atrium of rabbit hearts. Action potentials were recorded using the amphotericin-perforated patch-clamp technique in the absence and presence of ACh, NA or a combination of both. In SA nodal myocytes, ACh increased cycle length and decreased diastolic depolarization rate, whereas NA decreased cycle length and increased diastolic depolarization rate. Both ACh and NA increased maximum upstroke velocity. Furthermore, ACh hyperpolarized the maximum diastolic potential. In atrial myocytes stimulated at 2 Hz, both ACh and NA hyperpolarized the maximum diastolic potential, increased the action potential amplitude, and increased the maximum upstroke velocity. Action potential duration at 50 and 90% repolarization was decreased by ACh, but increased by NA. The effects of both ACh and NA on action potential duration showed a dose dependence in the range of 1–1,000 nM, while a clear-cut frequency dependence in the range of 1–4 Hz was absent. Intermediate results were obtained in the combined presence of ACh and NA in both SA nodal and atrial myocytes. Our data uncover the extent to which SA nodal and atrial action potentials are intrinsically dependent on ACh, NA or a combination of both and may thus guide further experiments with RGS proteins.

  17. Frequency-dependent action potential prolongation in Aplysia pleural sensory neurones.

    Science.gov (United States)

    Edstrom, J P; Lukowiak, K D

    1985-10-01

    The effects of repetitive activity on action-potential shape in Aplysia californica pleural sensory cells are described. Action potentials were evoked by intracellular current injection at frequencies between 7.41 and 0.2 Hz. In contrast to other molluscan neurons having brief action potentials, it was found that at these firing rates the normally brief action potential develops a prominent shoulder or plateau during the repolarization phase. Higher stimulus rates broaden the action potential more rapidly and to a greater extent than lower stimulus rates. Inactivation is slow relative to activation; effects of 3-s 6-Hz trains are detectable after 1 min rest. The amplitude of the plateau voltage reaches a maximum of 50-70 mV at the highest stimulus rates tested. Frequency-dependent increases in action-potential duration measured at half-amplitude normally range between 6 and 15 ms. Cadmium, at concentrations between 0.05 and 0.5 mM, antagonizes frequency-dependent broadening. The increases in duration induced by repetitive activity are more sensitive to cadmium than are the increases in plateau amplitude. Tetraethylammonium, at concentrations between 0.5 and 10 mM, slightly increases the duration and amplitude of single action potentials. During repetitive activity at high stimulus rates the maximum duration and rate of broadening are both increased but the amplitude of the plateau potential is not affected by these tetraethylammonium concentrations. Above 10 mM, tetraethylammonium greatly increases the duration and amplitude of single action potentials as well as the rates of action-potential duration and amplitude increase during repetitive activity. These high tetraethylammonium concentrations also cause the normally smoothly increasing duration and amplitude to reach a maximum value early in a train and then decline slowly during the remainder of the train. The consequences of frequency-dependent spike broadening in these neurons have not yet been investigated

  18. Don't wait till the cows come home: Action Research and Initial Teacher Education in three different countries.

    NARCIS (Netherlands)

    Ponte, P.; Beijaard, D.

    2004-01-01

    This article outlines the experiences of educators in three teacher education institutes in the USA, Australia and the UK as they experiment with carrying out programmes based on ideas of Action Research. The emphasis is on experiences with programmes of initial education for secondary school teache

  19. Sodium and calcium currents shape action potentials in immature mouse inner hair cells.

    Science.gov (United States)

    Marcotti, Walter; Johnson, Stuart L; Rusch, Alfons; Kros, Corne J

    2003-11-01

    Before the onset of hearing at postnatal day 12, mouse inner hair cells (IHCs) produce spontaneous and evoked action potentials. These spikes are likely to induce neurotransmitter release onto auditory nerve fibres. Since immature IHCs express both alpha1D (Cav1.3) Ca2+ and Na+ currents that activate near the resting potential, we examined whether these two conductances are involved in shaping the action potentials. Both had extremely rapid activation kinetics, followed by fast and complete voltage-dependent inactivation for the Na+ current, and slower, partially Ca2+-dependent inactivation for the Ca2+ current. Only the Ca2+ current is necessary for spontaneous and induced action potentials, and 29 % of cells lacked a Na+ current. The Na+ current does, however, shorten the time to reach the action-potential threshold, whereas the Ca2+ current is mainly involved, together with the K+ currents, in determining the speed and size of the spikes. Both currents increased in size up to the end of the first postnatal week. After this, the Ca2+ current reduced to about 30 % of its maximum size and persisted in mature IHCs. The Na+ current was downregulated around the onset of hearing, when the spiking is also known to disappear. Although the Na+ current was observed as early as embryonic day 16.5, its role in action-potential generation was only evident from just after birth, when the resting membrane potential became sufficiently negative to remove a sizeable fraction of the inactivation (half inactivation was at -71 mV). The size of both currents was positively correlated with the developmental change in action-potential frequency.

  20. Action Research as an educational strategy in post-initial teacher training: an example

    NARCIS (Netherlands)

    Ponte, P.; Beers, R.

    2000-01-01

    The purpose of this article is to describe the value of action-research within the context of the professionalization of teachers in further education. Further education based on action research will be elaborated on with reference to the training course for 'School Counselling & Guidance' at the Fa

  1. Unmyelinated visceral afferents exhibit frequency dependent action potential broadening while myelinated visceral afferents do not.

    Science.gov (United States)

    Li, Bai-Yan; Feng, Bin; Tsu, Hwa Y; Schild, John H

    2007-06-21

    Sensory information arising from visceral organ systems is encoded into action potential trains that propagate along afferent fibers to target nuclei in the central nervous system. These information streams range from tight patterns of action potentials that are well synchronized with the sensory transduction event to irregular, patternless discharge with no clear correlation to the sensory input. In general terms these afferent pathways can be divided into unmyelinated and myelinated fiber types. Our laboratory has a long standing interest in the functional differences between these two types of afferents in terms of the preprocessing of sensory information into action potential trains (synchrony, frequency, duration, etc.), the reflexogenic consequences of this sensory input to the central nervous system and the ionic channels that give rise to the electrophysiological properties of these unique cell types. The aim of this study was to determine whether there were any functional differences in the somatic action potential characteristics of unmyelinated and myelinated vagal afferents in response to different rates of sensory nerve stimulation. Our results showed that activity and frequency-dependent widening of the somatic action potential was quite prominent in unmyelinated but not myelinated vagal afferents. Spike broadening often leads to increased influx of Ca(2+) ions that has been associated with a diverse range of modulatory mechanisms both at the cell body and central synaptic terminations (e.g. increased neurotransmitter release.) We conclude that our observations are indicative of fundamentally different mechanisms for neural integration of sensory information arising from unmyelinated and myelinated vagal afferents.

  2. A new three-variable mathematical model of action potential propagation in cardiac tissue.

    Science.gov (United States)

    Fenton, Flavio; Karma, Alain

    1996-03-01

    Modeling the electrical activity of the heart, and the complex signaling patterns which underly dangerous arrhythmias such as tachycardia and fibrillation, requires a quantitative model of action potential (AP) propagation. At present, there exist detailed ionic models of the Hodgkin-Huxley form that accurately reproduce dynamical features of the AP at a single cell level (e.g. Luo-Rudy, 1994). However, such models are not computationally tractable to study propagation in two and three-dimensional tissues of many resistively coupled cells. At the other extreme, there exists generic models of excitable media, such as the well-known FitzHugh-Nagumo model, which are only qualitative and do not reproduce essential dynamical features of cardiac AP. A new three-variable model is introduced which bridges the gap between these two types of models. It reproduces quantitatively important `mesoscopic' dynamical properties which are specific to cardiac AP, namely restitution and dispersion. At the same time, it remains computationally tractable and makes it possible to study the effect of these properties on the initiation, dynamics, and stability of complex reentrant excitations in two and three dimensions. Preliminary numerical results of the effect of restitution and dispersion on two-dimensional reentry (i.e. spiral waves) are presented.

  3. Motor unit action potential conduction velocity estimated from surface electromyographic signals using image processing techniques.

    Science.gov (United States)

    Soares, Fabiano Araujo; Carvalho, João Luiz Azevedo; Miosso, Cristiano Jacques; de Andrade, Marcelino Monteiro; da Rocha, Adson Ferreira

    2015-09-17

    In surface electromyography (surface EMG, or S-EMG), conduction velocity (CV) refers to the velocity at which the motor unit action potentials (MUAPs) propagate along the muscle fibers, during contractions. The CV is related to the type and diameter of the muscle fibers, ion concentration, pH, and firing rate of the motor units (MUs). The CV can be used in the evaluation of contractile properties of MUs, and of muscle fatigue. The most popular methods for CV estimation are those based on maximum likelihood estimation (MLE). This work proposes an algorithm for estimating CV from S-EMG signals, using digital image processing techniques. The proposed approach is demonstrated and evaluated, using both simulated and experimentally-acquired multichannel S-EMG signals. We show that the proposed algorithm is as precise and accurate as the MLE method in typical conditions of noise and CV. The proposed method is not susceptible to errors associated with MUAP propagation direction or inadequate initialization parameters, which are common with the MLE algorithm. Image processing -based approaches may be useful in S-EMG analysis to extract different physiological parameters from multichannel S-EMG signals. Other new methods based on image processing could also be developed to help solving other tasks in EMG analysis, such as estimation of the CV for individual MUs, localization and tracking of innervation zones, and study of MU recruitment strategies.

  4. Action potential energy efficiency varies among neuron types in vertebrates and invertebrates.

    Directory of Open Access Journals (Sweden)

    Biswa Sengupta

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

  5. Emotions predictably modify response times in the initiation of human motor actions: A meta-analytic review.

    Science.gov (United States)

    Beatty, Garrett F; Cranley, Nicole M; Carnaby, Giselle; Janelle, Christopher M

    2016-03-01

    Emotions motivate individuals to attain appetitive goals and avoid aversive consequences. Empirical investigations have detailed how broad approach and avoidance orientations are reflected in fundamental movement attributes such as the speed, accuracy, and variability of motor actions. Several theoretical perspectives propose explanations for how emotional states influence the speed with which goal directed movements are initiated. These perspectives include biological predisposition, muscle activation, distance regulation, cognitive evaluation, and evaluative response coding accounts. A comprehensive review of literature and meta-analysis were undertaken to quantify empirical support for these theoretical perspectives. The systematic review yielded 34 studies that contained 53 independent experiments producing 128 effect sizes used to evaluate the predictions of existing theories. The central tenets of the biological predisposition (Hedges' g = -0.356), distance regulation (g = -0.293; g = 0.243), and cognitive evaluation (g = -0.249; g = -0.405; g = -0.174) accounts were supported. Partial support was also identified for the evaluative response coding (g = -0.255) framework. Our findings provide quantitative evidence that substantiate existing theoretical perspectives, and provide potential direction for conceptual integration of these independent perspectives. Recommendations for future empirical work in this area are discussed.

  6. Docosahexaenoic acid has influence on action potentials and transient outward potassium currents of ventricular myocytes

    Directory of Open Access Journals (Sweden)

    Yang Zhen-Yu

    2010-04-01

    Full Text Available Abstract Background There are many reports about the anti-arrhythmic effects of ω-3 polyunsaturated fatty acids, however, the mechanisms are still not completely delineated. The purpose of this study was to investigate the characteristics of action potentials and transient outward potassium currents (Ito of Sprague-Dawley rat ventricular myocytes and the effects of docosahexaenoic acid (DHA on action potentials and Ito. Methods The calcium-tolerant rat ventricular myocytes were isolated by enzyme digestion. Action potentials and Ito of epicardial, mid-cardial and endocardial ventricular myocytes were recorded by whole-cell patch clamp technique. Results 1. Action potential durations (APDs were prolonged from epicardial to endocardial ventricular myocytes (P 2. Ito current densities were decreased from epicardial to endocardial ventricular myocytes, which were 59.50 ± 15.99 pA/pF, 29.15 ± 5.53 pA/pF, and 12.29 ± 3.62 pA/pF, respectively at +70 mV test potential (P 3. APDs were gradually prolonged with the increase of DHA concentrations from 1 μmol/L to 100 μmol/L, however, APDs changes were not significant as DHA concentrations were in the range of 0 μmol/L to 1 μmol/L. 4. Ito currents were gradually reduced with the increase of DHA concentrations from 1 μmol/L to 100 μmol/L, and its half-inhibited concentration was 5.3 μmol/L. The results showed that there were regional differences in the distribution of action potentials and Ito in rat epicardial, mid-cardial and endocardial ventricular myocytes. APDs were prolonged and Ito current densities were gradually reduced with the increase of DHA concentrations. Conclusion The anti-arrhythmia mechanisms of DHA are complex, however, the effects of DHA on action potentials and Ito may be one of the important causes.

  7. Initiation of ignition by the action of a high-current pulsed discharge on a gas

    NARCIS (Netherlands)

    Starikovskii, AY

    2003-01-01

    The possibility of nonthermal initiation of chemical reactions by a uniform pulsed nanosecond discharge is demonstrated. Dependences of variation of the ignition delay on initial conditions are obtained. It is shown that the main role in combustion initiation under conditions of a pulsed gas dischar

  8. Modeling and simulation of ion channels and action potentials in taste receptor cells

    Institute of Scientific and Technical Information of China (English)

    CHEN PeiHua; LIU Xiaodong; ZHANG Wei; ZHOU Jun; WANG Ping; YANG Wei; LUO JianHong

    2009-01-01

    Based on patch clamp data on the ionic currents of rat taste receptor cells,a mathematical model of mammalian taste receptor cells was constructed to simulate the action potentials of taste receptor cells and their corresponding ionic components,including voltage-gated Na~+ currents and outward delayed rectifier K~+ currents.Our simulations reproduced the action potentials of taste receptor cells in response to electrical stimuli or sour tastants.The kinetics of ion channels and their roles in action potentials of taste receptor cells were also analyzed.Our prototype model of single taste receptor cell and simulation results presented in this paper provide the basis for the further study of taste information processing in the gustatory system.

  9. Modeling and simulation of ion channels and action potentials in taste receptor cells

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Based on patch clamp data on the ionic currents of rat taste receptor cells, a mathematical model of mammalian taste receptor cells was constructed to simulate the action potentials of taste receptor cells and their corresponding ionic components, including voltage-gated Na+ currents and outward delayed rectifier K+ currents. Our simulations reproduced the action potentials of taste receptor cells in response to electrical stimuli or sour tastants. The kinetics of ion channels and their roles in action potentials of taste receptor cells were also analyzed. Our prototype model of single taste receptor cell and simulation results presented in this paper provide the basis for the further study of taste information processing in the gustatory system.

  10. An eikonal-curvature equation for action potential propagation in myocardium.

    Science.gov (United States)

    Keener, J P

    1991-01-01

    We derive an "eikonal-curvature" equation to describe the propagation of action potential wavefronts in myocardium. This equation is used to study the effects of fiber orientation on propagation in the myocardial wall. There are significant computational advantages to the use of an eikonal-curvature equation over a full ionic model of action potential spread. With this model, it is shown that the experimentally observed misalignment of spreading action potential "ellipses" from fiber orientation in level myocardial surfaces is adequately explained by the rotation of fiber orientation through the myocardial wall. Additionally, it is shown that apparently high propagation velocities on the epicardial and endocardial surfaces are the result of propagation into the midwall region and acceleration along midwall fibers before reemergence at an outer surface at a time preceding what could be accomplished with propagation along the surface alone.

  11. Phase lagging model of brain response to external stimuli - modeling of single action potential

    CERN Document Server

    Seetharaman, Karthik; Kulish, Vladimir V

    2012-01-01

    In this paper we detail a phase lagging model of brain response to external stimuli. The model is derived using the basic laws of physics like conservation of energy law. This model eliminates the paradox of instantaneous propagation of the action potential in the brain. The solution of this model is then presented. The model is further applied in the case of a single neuron and is verified by simulating a single action potential. The results of this modeling are useful not only for the fundamental understanding of single action potential generation, but also they can be applied in case of neuronal interactions where the results can be verified against the real EEG signal.

  12. Optical magnetic detection of single-neuron action potentials using NV-diamond

    Science.gov (United States)

    Turner, Matthew; Barry, John; Schloss, Jennifer; Glenn, David; Walsworth, Ron

    2016-05-01

    A key challenge for neuroscience is noninvasive, label-free sensing of action potential dynamics in whole organisms with single-neuron resolution. Here, we report a new approach to this problem: using nitrogen-vacancy (NV) color centers in diamond to measure the time-dependent magnetic fields produced by single-neuron action potentials. We demonstrate our method using excised single neurons from two invertebrate species, marine worm and squid; and then by single-neuron action potential magnetic sensing exterior to whole, live, opaque marine worms for extended periods with no adverse effect. The results lay the groundwork for real-time, noninvasive 3D magnetic mapping of functional mammalian neuronal networks.

  13. Modulation of presynaptic action potential kinetics underlies synaptic facilitation of type B photoreceptors after associative conditioning in Hermissenda.

    Science.gov (United States)

    Gandhi, C C; Matzel, L D

    2000-03-01

    Descriptions of conditioned response generation in Hermissenda stipulate that the synaptic interaction between type B and A photoreceptors should be enhanced after associative pairings of light and rotation. Although evidence from several laboratories has confirmed this assumption, the mechanism underlying this synaptic facilitation has not been elucidated. Here we report that in vitro conditioning (i.e., light paired with stimulation of vestibular hair cells) modifies the kinetics of presynaptic action potentials in the B photoreceptor in a manner sufficient to account for this synaptic facilitation. After paired training, we observed an increase in the duration of evoked action potentials and a decrease in the amplitude of the spike afterhyperpolarization in the B-cell. As previously reported, paired training also enhanced the excitability (i.e., input resistance and evoked spike rate) of the B photoreceptor. In a second experiment, simultaneous recordings were made in type B and A photoreceptors, and paired training was found to produce an increase in the amplitude of the IPSP in the A photoreceptor in response to an evoked spike in the B-cell. Importantly, there was no change in the initial slope of the postsynaptic IPSP in the A photoreceptor, suggesting that spike duration-independent mechanisms of neurotransmitter exocytosis or postsynaptic receptor sensitivity did not contribute to the observed synaptic facilitation. Perfusion of 4-aminopyridine (4-AP) mimicked a known effect of behavioral conditioning in that it specifically reduced the amplitude of the transient voltage-dependent K(+) current (I(A)) in the B-cell, but in addition, produced action potential broadening and synaptic facilitation that was analogous to that observed after in vitro conditioning. Finally, the effect of 4-AP on B-cell action potentials and on the postsynaptic IPSP in the A-cell was occluded by previous paired (but not unpaired) training, suggesting that the prolongation of the B

  14. Incorporated fish oil fatty acids prevent action potential shortening induced by circulating fish oil fatty acids

    Directory of Open Access Journals (Sweden)

    Hester M Den Ruijter

    2010-11-01

    Full Text Available Increased consumption of fatty fish, rich in omega-3 polyunsaturated fatty acids (3-PUFAs reduces the severity and number of arrhythmias. Long term 3-PUFA-intake modulates the activity of several cardiac ion channels leading to cardiac action potential shortening. Circulating 3-PUFAs in the bloodstream and incorporated 3-PUFAs in the cardiac membrane have a different mechanism to shorten the action potential. It is, however, unknown whether circulating 3-PUFAs in the bloodstream enhance or diminish the effects of incorporated 3-PUFAs. In the present study, we address this issue. Rabbits were fed a diet rich in fish oil (3 or sunflower oil (9, as control for 3 weeks. Ventricular myocytes were isolated by enzymatic dissociation and action potentials were measured using the perforated patch clamp technique in the absence and presence of acutely administered 3-PUFAs. Plasma of 3 fed rabbits contained more free eicosapentaenoic acid (EPA and isolated myocytes of 3 fed rabbits contained higher amounts of both EPA and docosahexaenoic acid (DHA in their sarcolemma compared to control. In the absence of acutely administered fatty acids, 3 myocytes had a shorter action potential with a more negative plateau than 9 myocytes. In the 9 myocytes, but not in the 3 myocytes, acute administration of a mixture of EPA+DHA shortened the action potential significantly. From these data we conclude that incorporated 3-PUFAs into the sarcolemma and acutely administered 3 fatty acids do not have a cumulative effect on action potential duration and morphology. As a consequence, patients with a high cardiac 3-PUFA status will probably not benefit from short term 3 supplementation as an antiarrhythmic therapy.

  15. Attenuation by phentolamine of hypoxia and levcromakalim-induced abbreviation of the cardiac action potential.

    OpenAIRE

    Tweedie, D.; Boachie-Anash, G.; Henderson, C. G.; Kane, K. A.

    1993-01-01

    1. The effects of phentolamine (5-30 microM) and glibenclamide (10 microM) on action potential characteristics were examined in guinea-pig papillary muscle exposed to either hypoxia or levcromakalim (20 microM). 2. The hypoxia-induced abbreviation of action potential duration (APD) and effective refractory period (ERP) were attenuated but not abolished by glibenclamide (10 microM). Hypoxia reduced APD by 24 +/- 2 vs 65 +/- 4% in glibenclamide- and vehicle-treated tissue, respectively. 3. Phen...

  16. Differential effects of thioridazine enantiomers on action potential duration in rabbit papillary muscle

    DEFF Research Database (Denmark)

    Jensen, A. S.; Pennisi, C. P.; Sevcencu, C.;

    2015-01-01

    with (+)-thioridazine. In this study we for the first time investigate the cardiotoxicity of the isolated thioridazine enantiomers and show their effects on ventricular repolarization. The effects of (+)-thioridazine, (-)-thioridazine, and racemate on the rabbit ventricular action potential duration (APD) were...... investigated in a randomized controlled blinded experiment. Action potentials were measured in papillary muscles isolated from 21 female rabbits, and the drug effect on 90% APD in comparison with control (DeltaDelta-APD90) was evaluated. Increasing concentrations of (+)-thioridazine and the racemate caused...

  17. Effects of some heavy metals on the action potentials of an identified Helix pomatia photosensitive neuron.

    Science.gov (United States)

    Kartelija, Gordana; Radenović, Lidija; Todorović, Natasa; Nedeljković, Miodrag

    2005-06-01

    In the photosensitive MB neuron in the left parietal ganglion of Helix pomatia, the onset of light prolongs significantly (by about 40%) the duration of the action potential. The broadening of the action potential after the onset of light was found to be due to its calcium component and could not be induced after blocking Ca(2+) channels by Cd(2+) and Pb(2+) and in absence of Ca(2+) in medium. The blocking effect of both compounds was reversible. It was found that CdCl(2) exhibited a more intense blocking effect than PbCl(2).

  18. High-Bandwidth Atomic Force Microscopy Reveals A Mechanical spike Accompanying the Action Potential in mammalian Nerve Terminals

    Science.gov (United States)

    Salzberg, Brian M.

    2008-03-01

    Information transfer from neuron to neuron within nervous systems occurs when the action potential arrives at a nerve terminal and initiates the release of a chemical messenger (neurotransmitter). In the mammalian neurohypophysis (posterior pituitary), large and rapid changes in light scattering accompany secretion of transmitter-like neuropeptides. In the mouse, these intrinsic optical signals are intimately related to the arrival of the action potential (E-wave) and the release of arginine vasopressin and oxytocin (S-wave). We have used a high bandwidth (20 kHz) atomic force microscope (AFM) to demonstrate that these light scattering signals are associated with changes in nerve terminal volume, detected as nanometer-scale movements of a cantilever positioned on top of the neurohypophysis. The most rapid mechanical response, the ``spike'', has duration comparable to that of the action potential (˜2 ms) and probably reflects an increase in terminal volume due to H2O movement associated with Na^+-influx. Elementary calculations suggest that two H2O molecules accompanying each Na^+-ion could account for the ˜0.5-1.0 å increase in the diameter of each terminal during the action potential. Distinguishable from the mechanical ``spike'', a slower mechanical event, the ``dip'', represents a decrease in nerve terminal volume, depends upon Ca^2+-entry, as well as on intra-terminal Ca^2+-transients, and appears to monitor events associated with secretion. A simple hypothesis is that this ``dip'' reflects the extrusion of the dense core granule that comprises the secretory products. These dynamic high bandwidth AFM recordings are the first to monitor mechanical events in nervous systems and may provide novel insights into the mechanism(s) by which excitation is coupled to secretion at nerve terminals.

  19. Noise Enhances Action Potential Generation in Mouse Sensory Neurons via Stochastic Resonance

    Science.gov (United States)

    Onorato, Irene; D'Alessandro, Giuseppina; Di Castro, Maria Amalia; Renzi, Massimiliano; Dobrowolny, Gabriella; Musarò, Antonio; Salvetti, Marco; Limatola, Cristina; Crisanti, Andrea; Grassi, Francesca

    2016-01-01

    Noise can enhance perception of tactile and proprioceptive stimuli by stochastic resonance processes. However, the mechanisms underlying this general phenomenon remain to be characterized. Here we studied how externally applied noise influences action potential firing in mouse primary sensory neurons of dorsal root ganglia, modelling a basic process in sensory perception. Since noisy mechanical stimuli may cause stochastic fluctuations in receptor potential, we examined the effects of sub-threshold depolarizing current steps with superimposed random fluctuations. We performed whole cell patch clamp recordings in cultured neurons of mouse dorsal root ganglia. Noise was added either before and during the step, or during the depolarizing step only, to focus onto the specific effects of external noise on action potential generation. In both cases, step + noise stimuli triggered significantly more action potentials than steps alone. The normalized power norm had a clear peak at intermediate noise levels, demonstrating that the phenomenon is driven by stochastic resonance. Spikes evoked in step + noise trials occur earlier and show faster rise time as compared to the occasional ones elicited by steps alone. These data suggest that external noise enhances, via stochastic resonance, the recruitment of transient voltage-gated Na channels, responsible for action potential firing in response to rapid step-wise depolarizing currents. PMID:27525414

  20. Investigating a Potential Auxin-Related Mode of Hormetic/Inhibitory Action of the Phytotoxin Parthenin.

    Science.gov (United States)

    Belz, Regina G

    2016-01-01

    Parthenin is a metabolite of Parthenium hysterophorus and is believed to contribute to the weed's invasiveness via allelopathy. Despite the potential of parthenin to suppress competitors, low doses stimulate plant growth. This biphasic action was hypothesized to be auxin-like and, therefore, an auxin-related mode of parthenin action was investigated using two approaches: joint action experiments with Lactuca sativa, and dose-response experiments with auxin/antiauxin-resistant Arabidopsis thaliana genotypes. The joint action approach comprised binary mixtures of subinhibitory doses of the auxin 3-indoleacetic acid (IAA) mixed with parthenin or one of three reference compounds [indole-3-butyric acid (IBA), 2,3,5-triiodobenzoic acid (TIBA), 2-(p-chlorophenoxy)-2-methylpropionic acid (PCIB)]. The reference compounds significantly interacted with IAA at all doses, but parthenin interacted only at low doses indicating that parthenin hormesis may be auxin-related, in contrast to its inhibitory action. The genetic approach investigated the response of four auxin/antiauxin-resistant mutants and a wildtype to parthenin or two reference compounds (IAA, PCIB). The responses of mutant plants to the reference compounds confirmed previous reports, but differed from the responses observed for parthenin. Parthenin stimulated and inhibited all mutants independent of resistance. This provided no indication for an auxin-related action of parthenin. Therefore, the hypothesis of an auxin-related inhibitory action of parthenin was rejected in two independent experimental approaches, while the hypothesis of an auxin-related stimulatory effect could not be rejected.

  1. Phenobarbital but not diazepam reduces AMPA/Kainate receptor mediated currents and exerts opposite actions on initial seizures in the neonatal rat hippocampus

    Directory of Open Access Journals (Sweden)

    Romain eNardou

    2011-07-01

    Full Text Available Diazepam (DZP and phenobarbital (PB are extensively used as first and second line drugs to treat acute seizures in neonates and their actions are thought to be mediated by increasing the actions of GABAergic signals. Yet, their efficacy is variable with occasional failure or even aggravation of recurrent seizures questioning whether other mechanisms are not involved in their actions. We have now compared the effects of DZP and PB on ictal-like events (ILEs in an in vitro model of mirror focus (MF. Using the three-compartment chamber with the two immature hippocampi and their commissural fibers placed in 3 different compartments, kainate was applied to one hippocampus and PB or DZP to the contralateral one, either after one ILE or after many recurrent ILEs that produce an epileptogenic MF. We report that in contrast to PB, DZP aggravated propagating ILEs from the start and did not prevent the formation of MF. PB reduced and DZP increased the network driven Giant Depolarising Potentials suggesting that PB may exert additional actions that are not mediated by GABA signalling. In keeping with this, PB but not DZP reduced field potentials recorded in the presence of GABA and NMDA receptor antagonists. These effects are mediated by a direct action on AMPA/Kainate receptors since PB: i reduced AMPA/Kainate receptor mediated currents induced by focal applications of glutamate ; ii reduced the amplitude and the frequency of AMPA but not NMDA receptor mediated miniature EPSCs; iii augmented the number of AMPA receptor mediated EPSCs failures evoked by minimal stimulation. These effects persisted in MF. Therefore, PB exerts its anticonvulsive actions partly by reducing AMPA/Kainate receptors mediated EPSCs in addition to the pro-GABA effects. We suggest that PB may have advantage over DZP in the treatment of initial neonatal seizures since the additional reduction of glutamate receptors mediated signals may reduce the severity of neonatal seizures.

  2. Inhibition by TRPA1 agonists of compound action potentials in the frog sciatic nerve

    Energy Technology Data Exchange (ETDEWEB)

    Matsushita, Akitomo; Ohtsubo, Sena; Fujita, Tsugumi; Kumamoto, Eiichi, E-mail: kumamote@cc.saga-u.ac.jp

    2013-04-26

    Highlights: •TRPA1 agonists inhibited compound action potentials in frog sciatic nerves. •This inhibition was not mediated by TRPA1 channels. •This efficacy was comparable to those of lidocaine and cocaine. •We found for the first time an ability of TRPA1 agonists to inhibit nerve conduction. -- Abstract: Although TRPV1 and TRPM8 agonists (vanilloid capsaicin and menthol, respectively) at high concentrations inhibit action potential conduction, it remains to be unknown whether TRPA1 agonists have a similar action. The present study examined the actions of TRPA1 agonists, cinnamaldehyde (CA) and allyl isothiocyanate (AITC), which differ in chemical structure from each other, on compound action potentials (CAPs) recorded from the frog sciatic nerve by using the air-gap method. CA and AITC concentration-dependently reduced the peak amplitude of the CAP with the IC{sub 50} values of 1.2 and 1.5 mM, respectively; these activities were resistant to a non-selective TRP antagonist ruthenium red or a selective TRPA1 antagonist HC-030031. The CA and AITC actions were distinct in property; the latter but not former action was delayed in onset and partially reversible, and CA but not AITC increased thresholds to elicit CAPs. A CAP inhibition was seen by hydroxy-α-sanshool (by 60% at 0.05 mM), which activates both TRPA1 and TRPV1 channels, a non-vanilloid TRPV1 agonist piperine (by 20% at 0.07 mM) and tetrahydrolavandulol (where the six-membered ring of menthol is opened; IC{sub 50} = 0.38 mM). It is suggested that TRPA1 agonists as well as TRPV1 and TRPM8 agonists have an ability to inhibit nerve conduction without TRP activation, although their agonists are quite different in chemical structure from each other.

  3. Preservation of cardiac function by prolonged action potentials in mice deficient of KChIP2

    DEFF Research Database (Denmark)

    Grubb, Søren Jahn; Aistrup, Gary L; Koivumäki, Jussi T

    2015-01-01

    Inherited ion channelopathies and electrical remodeling in heart disease alter the cardiac action potential with important consequences for excitation-contraction coupling. Potassium channel-interacting protein 2 (KChIP2) is reduced in heart failure and interacts under physiological conditions...

  4. RXP-E: a connexin43-binding peptide that prevents action potential propagation block

    DEFF Research Database (Denmark)

    Lewandowski, Rebecca; Procida, Kristina; Vaidyanathan, Ravi;

    2008-01-01

    of action potential propagation in control monolayers; however, propagation was maintained in CTP-RXP-E-treated cells, although at a slower rate. Patch-clamp experiments revealed that RXP-E did not prevent heptanol-induced block of sodium currents, nor did it alter voltage dependence or amplitude of Kir2...

  5. Ca2+ involvement in the action potential generation of myenteric neurones in the rat oesophagus.

    Science.gov (United States)

    De Laet, A; Cornelissen, W; Adriaensen, D; Van Bogaert, P-P; Scheuermann, D W; Timmermans, J-P

    2002-04-01

    Intracellular recordings were used to study the physiological behaviour of rat oesophageal myenteric neurones, which are embedded in striated muscle. Injection of depolarizing pulses evoked action potentials with a clear 'shoulder' in all neurones. This shoulder disappeared under low Ca2+/high Mg2+ conditions. Tetrodotoxin (TTX; 1 micromol L-1) did not impede spike firing, whereas under combined TTX and low Ca2+/high Mg2+ conditions the action potentials were completely abolished, indicating that TTX- resistant action potentials are mediated by a Ca2+ current. Further experiments with omega-conotoxin GVIA (100 nmol L-1) revealed that these Ca2+ currents enter the cell via N-type voltage-activated Ca2+ channels (see also accompanying paper). Tetraethylammonium (10 mmol L-1) caused broadening of the action potentials, which probably resulted from prolonged Ca2+ influx due to blockade of the delayed rectifier K+ channel. Although Ca2+ appears to be involved in the spike generation of all rat oesophageal myenteric neurones, only a minority (14%) shows a slow afterhyperpolarization. Thus, no strict correlation exists between the presence of a shoulder and a slow afterhyperpolarization. Furthermore, morphological identification of 25 of the impaled neurones revealed that there was no strict correlation between morphology and electrophysiological behaviour. Consequently, rat oesophageal myenteric neurones appear to differ in several aspects from myenteric neurones in smooth muscle regions of the gastrointestinal tract.

  6. Youth Participatory Action Research and Educational Transformation: The Potential of Intertextuality as a Methodological Tool

    Science.gov (United States)

    Bertrand, Melanie

    2016-01-01

    In this article, Melanie Bertrand explores the potential of using the concept of intertextuality--which captures the way snippets of written or spoken text from one source become incorporated into other sources--in the study and practice of youth participatory action research (YPAR). Though this collective and youth-centered form of research…

  7. Zinc-dependent action potentials in giant neurons of the snail, Euhadra quaestia.

    Science.gov (United States)

    Kawa, K

    1979-09-14

    In giant neurons of subesophageal ganglion of the Japanese land snail, Euhadra quaestia Deshayes, permeation of Zn ions through Ca channels were investigated with a conventional current clamp method. All-or-none action potentials of long duration (90 to 120 sec) were evoked in 24 mM Zn containing salines. The overshoots were about +10 mV and the maximum rate of rises (MRRs) was about 2.9 V/sec. The amplitudes and the MRRs of the action potentials depended on external Zn ion concentrations. The action potentials were suppressed by specific Ca-channel inhibitors such as Co2+, La3+ and Verapamil, but they were resistant to Na-channel inhibitor, tetrodotoxin, even at 30 microM. It is concluded that these action potentials are generated by Zn ions permeating Ca channels in snail neuronal membrane. On the basis of Hagiwara and Takahashi's (S. Hagiwara & K. Takahashi, 1967, J. Gen. Physiol. 50:583) model of Ca channels, it is inferred that Zn ions are 5 to 10 times stronger in affinity to Ca channels than Ca ions, but 10 to 20 times less permeable.

  8. A dual potassium channel activator improves repolarization reserve and normalizes ventricular action potentials

    DEFF Research Database (Denmark)

    Calloe, Kirstine; Di Diego, José M; Hansen, Rie Schultz

    2016-01-01

    in cultured canine cardiac myocytes and determined whether a dual K(+) current activator can normalize K(+) currents and restore action potential (AP) configuration. METHODS AND RESULTS: Ventricular myocytes were isolated and cultured for up to 48h. Current and voltage clamp recordings were made using patch...... of EADs. Our results suggest a potential benefit of K(+) current activators under conditions of reduced repolarization reserve including heart failure....

  9. Force Structure: Actions Needed to Improve DOD’s Ability to Manage, Assess, and Report on Global Defense Posture Initiatives

    Science.gov (United States)

    2009-07-02

    Representatives Subject: Force Structure: Actions Needed to Improve DOD’s Ability to Manage, Assess, and Report on Global Defense Posture ...as well as the fidelity of the global basing plan given the rapidly changing global security environment. GAO-09-706R Global Defense Posture ...to Manage, Assess, and Report on Global Defense Posture Initiatives 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S

  10. Time evolution of initial states that extend beyond the potential interaction region in quantum decay

    Science.gov (United States)

    García-Calderón, Gastón; Villavicencio, Jorge; Hernández-Maldonado, Alberto; Romo, Roberto

    2016-08-01

    We investigate the decay of initial states that possess a tail that extends beyond the interaction potential region, for potentials of arbitrary shape that vanish exactly after a distance. This is the case for a relevant class of artificial quantum structures. We obtain that along the internal interaction region, the time evolution of the decaying wave function is formed by two terms. The first one refers to the proper decay of the internal portion of the initial state, whereas the second one, that arises from the external tail, yields a transient contribution that tunnels into the internal region, builds up to a value, and then decays. We obtain that depending on the parameters of the initial state, the nonexponential tail decaying contribution may be larger than the contribution of the proper nonexponential term. These results are illustrated by an exactly solvable model and the Heidelberg potential for decay of ultracold atoms and open the possibility to control initial states in artificial decaying systems.

  11. An Initial Attempt at Operationalizing and Testing the Community Coalition Action Theory

    Science.gov (United States)

    Kegler, Michelle C.; Swan, Deanne W.

    2011-01-01

    The Community Coalition Action Theory (CCAT) blends practice wisdom with empirical data to explain how community coalitions achieve community change and community capacity outcomes. The current study uses data from an evaluation of 20 "California Healthy Cities" and "Communities" coalitions to test relationships between…

  12. Meeting the Information Needs of the American People: Past Actions and Future Initiatives

    Science.gov (United States)

    Davenport, Nancy; Russell, Judith

    2008-01-01

    In the FY2007 and FY2008 Budgets, the President recommended that the National Commission on Libraries and Information Sciences (NCLIS) be consolidated with the Institute of Museum and Library Services (IMLS). In FY2007, while waiting for Congressional action on the proposal in the President's FY2008 Budget, the Commission recognized the need to…

  13. Effects of benactyzine on action potentials and contractile force of guinea pig papillary muscles

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Aim:To explore the effects of benactyzine (BEN) on the action potential and contractile force in guinea pig papillary muscles.Methods:Conventional microelectrode technique was used to record the fast action potentials (FAP) and slow action potentials (SAP) of guinea pig papillary muscles.Results:Benactyzine 5,10,50 μmol·L-1 suppressed the maximal upstroke velocity (vmax) of FAP and contractile force (Fc) concentration-dependently while prolonged the action potential duration at 50%,90% repolarization (APD50,APD90) and effective refractory period (ERP) of FAP.The suppression on the vmax was frequency-dependent.Benactyzine 5,10,50μmol·L-1 lengthened the APD50,APD90 of SAP induced by isoprenaline or histamine when perfused with KCl 22 mmol·L-1 Tyrode's solution.The vmax of the SAP was not decreased by benactyzine 5,10 μmol·L-1 but by 50 μmol·L-1.The effects on the SAP were antagonized by elevation of the extracellular calcium from 2.0 to 5.6 mmol·L-1.The effects of benactyzine on SAP elicited by tetrodotoxin resembled that by isoprenaline or histamine except the more pronounced suppression on vmax and action potential amplitude (APA).The persistent rapid spontaneous activity and triggered tachyarrhythmia induced by ouabain were also abolished immediately by benactyzine 5 μmol·L-1.Conclusion:Benactyzine can inhibit Na+,K+,Ca2+ transmembrane movement and intracellular Ca2+ mobilization in the myocardium,and this may be the electrophysiological basis of its effects against experimental arrhythmias.

  14. Developmental impairment of compound action potential in the optic nerve of myelin mutant taiep rats.

    Science.gov (United States)

    Roncagliolo, Manuel; Schlageter, Carol; León, Claudia; Couve, Eduardo; Bonansco, Christian; Eguibar, José R

    2006-01-05

    The taiep rat is a myelin mutant with an initial hypomyelination, followed by a progressive demyelination of the CNS. The neurological correlates start with tremor, followed by ataxia, immobility episodes, epilepsy and paralysis. The optic nerve, an easily-isolable central tract fully myelinated by oligodendrocytes, is a suitable preparation to evaluate the developmental impairment of central myelin. We examined the ontogenic development of optic nerve compound action potentials (CAP) throughout the first 6 months of life of control and taiep rats. Control optic nerves (ON) develop CAPs characterized by three waves. Along the first month, the CAPs of taiep rats showed a delayed maturation, with lower amplitudes and longer latencies than controls; at P30, the conduction velocity has only a third of the normal value. Later, as demyelination proceeds, the conduction velocity of taiep ONs begins to decrease and CAPs undergo a gradual temporal dispersion. CAPs of control and taiep showed differences in their pharmacological sensitivity to TEA and 4-AP, two voltage dependent K+ channel-blockers. As compared with TEA, 4-AP induced a significant increase of the amplitudes and a remarkable broadening of CAPs. After P20, unlike controls, the greater sensitivity to 4-AP exhibited by taiep ONs correlates with the detachment and retraction of paranodal loops suggesting that potassium conductances could regulate the excitability as demyelination of CNS axons progresses. It is concluded that the taiep rat, a long-lived mutant, provides a useful model to study the consequences of partial demyelination and the mechanisms by which glial cells regulate the molecular organization and excitability of axonal membranes during development and disease.

  15. Encoding of High Frequencies Improves with Maturation of Action Potential Generation in Cultured Neocortical Neurons

    Science.gov (United States)

    Nikitin, Evgeny S.; Bal, Natalia V.; Malyshev, Aleksey; Ierusalimsky, Victor N.; Spivak, Yulia; Balaban, Pavel M.; Volgushev, Maxim

    2017-01-01

    The ability of neocortical neurons to detect and encode rapid changes at their inputs is crucial for basic neuronal computations, such as coincidence detection, precise synchronization of activity and spike-timing dependent plasticity. Indeed, populations of cortical neurons can respond to subtle changes of the input very fast, on a millisecond time scale. Theoretical studies and model simulations linked the encoding abilities of neuronal populations to the fast onset dynamics of action potentials (APs). Experimental results support this idea, however mechanisms of fast onset of APs in cortical neurons remain elusive. Studies in neuronal cultures, that are allowing for accurate control over conditions of growth and microenvironment during the development of neurons and provide better access to the spike initiation zone, may help to shed light on mechanisms of AP generation and encoding. Here we characterize properties of AP encoding in neocortical neurons grown for 11–25 days in culture. We show that encoding of high frequencies improves upon culture maturation, which is accompanied by the development of passive electrophysiological properties and AP generation. The onset of APs becomes faster with culture maturation. Statistical analysis using correlations and linear model approaches identified the onset dynamics of APs as a major predictor of age-dependent changes of encoding. Encoding of high frequencies strongly correlated also with the input resistance of neurons. Finally, we show that maturation of encoding properties of neurons in cultures is similar to the maturation of encoding in neurons studied in slices. These results show that maturation of AP generators and encoding is, to a large extent, determined genetically and takes place even without normal micro-environment and activity of the whole brain in vivo. This establishes neuronal cultures as a valid experimental model for studying mechanisms of AP generation and encoding, and their maturation. PMID

  16. Development of the table of initial isolation distances and protective action distances for the 2004 emergency response guidebook.

    Energy Technology Data Exchange (ETDEWEB)

    Brown, D. F.; Freeman, W. A.; Carhart, R. A.; Krumpolc, M.; Decision and Information Sciences; Univ. of Illinois at Chicago

    2005-09-23

    This report provides technical documentation for values in the Table of Initial Isolation and Protective Action Distances (PADs) in the 2004 Emergency Response Guidebook (ERG2004). The objective for choosing the PADs specified in the ERG2004 is to balance the need to adequately protect the public from exposure to potentially harmful substances against the risks and expenses that could result from overreacting to a spill. To quantify this balance, a statistical approach is adopted, whereby the best available information is used to conduct an accident scenario analysis and develop a set of up to 1,000,000 hypothetical incidents. The set accounts for differences in containers types, incident types, accident severity (i.e., amounts released), locations, times of day, times of year, and meteorological conditions. Each scenario is analyzed using detailed emission rate and atmospheric dispersion models to calculate the downwind chemical concentrations from which a 'safe distance' is determined. The safe distance is defined as the distance downwind from the source at which the chemical concentration falls below health protection criteria. The American Industrial Hygiene Association's Emergency Response Planning Guideline Level 2 (ERPG-2) or equivalent is the health criteria used. The statistical sample of safe distance values for all incidents considered in the analysis are separated into four categories: small spill/daytime release, small spill/nighttime release, large spill/daytime release, and large spill/nighttime release. The 90th-percentile safe distance values for each of these groups became the PADs that appear in the ERG2004.

  17. Phorbol esters broaden the action potential in CA1 hippocampal pyramidal cells.

    Science.gov (United States)

    Storm, J F

    1987-03-20

    Intracellular recordings were made from CA1 pyramidal cells in rat hippocampal slices. Single action potentials were elicited by injection of brief current pulses. Bath application of phorbol esters (4 beta-phorbol-12,13-diacetate, 0.3-5 microM; or 4 beta-phorbol-12,13-dibutyrate, 5-10 microM) broadened the action potential in each of the cells tested (n = 9). The broadening reflected slowing of the repolarization, whereas the upstroke of the spike was unchanged. This effect may enhance transmitter release from synaptic terminals, and contribute to enhancement of synaptic transmission through activation of protein kinase C, a mechanism which has been associated with long term potentiation.

  18. Initial Condition Model from Imaginary Part of Action and the Information Loss

    CERN Document Server

    Nielsen, H B

    2009-01-01

    We review slightly a work by Horowitz and Maldecena solving the information loss problem for black holes by having inside the blackhole - near to the singularity - a boundary condition, as e.g the no boundary proposal by Hartle and Hawking. Here we propose to make this boundary condition come out of our imaginary action model (together with Masao Ninomiya). This model naturally begins effectively to set up boundaries - whether it be in future or past! - especially strongly whenever we reach to high energy physics regimes, such as near the black hole singularity, or in Higgs producing machines as LHC or SSC. In such cases one can say our model predicts miracles. The point is that you may say that the information loss problem, unless you solve it in other ways, call for such a violation of time causality as in our imaginary action model!

  19. An experimental study on a function of the cupula. Effect of cupula removal on the ampullary nerve action potential.

    Science.gov (United States)

    Suzuki, M; Harada, Y; Sugata, Y

    1984-01-01

    We used a posterior semicircular canal that had been isolated from a frog. From the utricular side the ampulla was cut open at a position one third of the way along the long axis. The cupula was removed through this opening using a glass micropipette. The action potential from the posterior ampullary nerve was recorded before and after removal of the cupula. After removal, the action potential disappeared almost completely. When the cupula was put back on the crista, the action potential was restored. When the cupula was put back upside down, the action potential recovered, but to a lesser extent.

  20. The mode of action of quinidine on isolated rabbit atria interpreted from intracellular potential records.

    Science.gov (United States)

    VAUGHAN WILLIAMS, E M

    1958-09-01

    An attempt has been made to show why quinidine, which has long been known not to lengthen the duration of the cardiac action potential, measured with external electrodes, and also not to lengthen, and sometimes to shorten, the absolute refractory period, nevertheless reduces the maximum frequency at which atria can respond to a stimulus. Simultaneous measurements have been made in electrically driven isolated rabbit atria of contractions, conduction velocity and intracellular potentials before and during exposure to a wide range of concentrations of quinidine sulphate. The resting potential remained undiminished, in contrast to the effect of quinidine on Purkinje fibres. In the therapeutic range of doses, up to 10 mg./l., the half-time for repolarization was either shortened or unchanged, thus providing an explanation for the failure of quinidine to prolong the absolute refractory period. In contrast, even at low concentrations of quinidine, conduction velocity and the rate of rise of the action potential were greatly slowed, and the height of the overshoot was reduced. The terminal phase of the action potential was prolonged. It is known that the rate of rise of the action potential is a function of the level of repolarization at which an impulse takes off (the more negative the take-off point, the faster the rate of rise). Normally, a stimulus introduced when repolarization has proceeded to 2/3 of the resting potential evokes a response with a rate of rise fast enough for propagation, so that the duration of the terminal 1/3 of the phase of repolarization has no influence upon the length of the effective refractory period. In the presence of quinidine, however, the rate of rise itself was directly reduced, thus repolarization had to proceed further before the critical take-off point was reached at which the rate of rise was fast enough for propagation, and the duration of the terminal phase of repolarization thus became significant. It has been concluded that

  1. The DBI Action, Higher-derivative Supergravity, and Flattening Inflaton Potentials

    CERN Document Server

    Bielleman, Sjoerd; Pedro, Francisco G; Valenzuela, Irene; Wieck, Clemens

    2016-01-01

    In string theory compactifications it is common to find an effective Lagrangian for the scalar fields with a non-canonical kinetic term. We study the effective action of the scalar position moduli of Type II D$p$-branes. In many instances the kinetic terms are in fact modified by a term proportional to the scalar potential itself. This can be linked to the appearance of higher-dimensional supersymmetric operators correcting the K\\"ahler potential. We identify the supersymmetric dimension-eight operators describing the $\\alpha'$ corrections captured by the D-brane Dirac-Born-Infeld action. Our analysis then allows an embedding of the D-brane moduli effective action into an $\\mathcal N = 1$ supergravity formulation. The effects of the potential-dependent kinetic terms may be very important if one of the scalars is the inflaton, since they lead to a flattening of the scalar potential. We analyze this flattening effect in detail and compute its impact on the CMB observables for single-field inflation with monomia...

  2. Identification of an unconventional process of instrumental learning characteristically initiated with outcome devaluation-insensitivity and generalized action selection.

    Science.gov (United States)

    Iguchi, Yoshio; Lin, Ziqiao; Nishikawa, Hiromi; Minabe, Yoshio; Toda, Shigenobu

    2017-02-27

    The distinction between goal-directed action and habitual response, particularly with respect to moderate or extended appetitive instrumental training, is well documented; however, the propensity toward instrumental behavior in the early training stage has not been elucidated. In this study, we trained Sprague Dawley rats to press a lever to obtain food as an outcome for various time periods and monitored the changes in their sensitivity to outcome devaluation and choice between the levers they had been trained with and unfamiliar levers. After the extensive training with a random interval schedule, the rats were insensitive to outcome devaluation, and exhibited a typical habit-like phenotype, as previously reported, and the untrained leverpresses were relatively rare and sporadic. During the initial stage of training (≤1 week), the rats exhibited a similar insensitivity to the devaluation; however, in contrast to the overtrained condition, they performed distinctive unbiased leverpresses on both the trained and untrained levers. Thus, we propose a possibility that, contrary to the authentic concept that instrumental learning is initiated with an outcome devaluation-sensitive goal-directed stage, under some conditions, this learning can unconventionally begin with the initial stage that is distinct from both goal-directed action and habitual response.

  3. Identification of an unconventional process of instrumental learning characteristically initiated with outcome devaluation-insensitivity and generalized action selection

    Science.gov (United States)

    Iguchi, Yoshio; Lin, Ziqiao; Nishikawa, Hiromi; Minabe, Yoshio; Toda, Shigenobu

    2017-01-01

    The distinction between goal-directed action and habitual response, particularly with respect to moderate or extended appetitive instrumental training, is well documented; however, the propensity toward instrumental behavior in the early training stage has not been elucidated. In this study, we trained Sprague Dawley rats to press a lever to obtain food as an outcome for various time periods and monitored the changes in their sensitivity to outcome devaluation and choice between the levers they had been trained with and unfamiliar levers. After the extensive training with a random interval schedule, the rats were insensitive to outcome devaluation, and exhibited a typical habit-like phenotype, as previously reported, and the untrained leverpresses were relatively rare and sporadic. During the initial stage of training (≤1 week), the rats exhibited a similar insensitivity to the devaluation; however, in contrast to the overtrained condition, they performed distinctive unbiased leverpresses on both the trained and untrained levers. Thus, we propose a possibility that, contrary to the authentic concept that instrumental learning is initiated with an outcome devaluation-sensitive goal-directed stage, under some conditions, this learning can unconventionally begin with the initial stage that is distinct from both goal-directed action and habitual response. PMID:28240299

  4. Dynamic properties of the action potential encoder in an insect mechanosensory neuron.

    Science.gov (United States)

    French, A S

    1984-08-01

    A variety of sensory receptors show adaptation to dynamic stimuli that can be well characterized as fractional differentiation of the input signal. The cause of this behavior is unknown, but because it can be represented by linear systems theory, it has been assumed to arise during early linear processes of transduction or adaptation, rather than during the nonlinear process of action potential encoding. I measured the action potential encoding properties of an insect mechanoreceptor by direct electrical stimulation of the sensory cell axon and found a dynamic response that is identical to the response given by mechanical stimulation. This indicates that the fractional differentiation is a property of the encoder rather than the transducer.

  5. Getting Started: Initiating Critical Ethnography and Community-Based Action Research in a Program of Rural Health Studies

    Directory of Open Access Journals (Sweden)

    Jennifer B. Averill

    2006-06-01

    Full Text Available Rural populations experience higher rates of illness, less access to health care resources, and lower rates of health insurance coverage than do urban populations. A need exists to identify and address the health care needs of rural communities and other isolated populations and to contextualize the findings in the larger rural health environment. Critical ethnography combined with community-based action research is a constructive approach for improving the health status of rural elders as well as other members of isolated communities. Detailed guidelines on how to initiate an ethnographic community-based action study, as shown through a study that explores the definitions of health, health care perceptions, and health care issues for rural elders in the southwestern United States, highlight the value of this type of research for the study of the health care issues of rural populations.

  6. A Study of Surface Motor Unit Action Potentials in First Dorsal Interosseus (FDI) Muscle

    Science.gov (United States)

    2007-11-02

    Lefever and Carlo J. Deluca, "A Procedure for Decomposing the Myoelectric Signal Into It’s Constituent Action Potentials---Part 1, Technique, Theory, and...of surface MUAP’s using wavelet matching technique. II. SURFACE MUAP’S AND WAVELETS EMG signals are composed of different MUAP’s. Each...displays an impulse property, which means that it changes in a rapid fashion. Due to this property, the EMG signal is well suited to wavelet analysis

  7. Activity dependence of action potential duration in rat supraoptic neurosecretory neurones recorded in vitro.

    Science.gov (United States)

    Bourque, C W; Renaud, L P

    1985-06-01

    Action potential durations, measured at one-third peak amplitude, were examined during intracellular recordings in 134 supraoptic nucleus neurones maintained in vitro in perfused hypothalamic explants. Spike durations ranged between 1.2 and 3.9 ms and were dependent on firing frequency. Shortest measurements (1.74 +/- 0.03 ms; mean +/- S.E. of mean) were obtained during relative quiescence, i.e. less than or equal to 0.5 Hz. A gradual increase in firing frequency through continuous injection of depolarizing current prolonged spike duration, with maximum levels (2.68 +/- 0.05 ms) achieved at 20 Hz. When interspike interval variability was eliminated and firing was more precisely regulated by brief 15-20 ms intracellular current pulses given at pre-determined frequencies, a proportional relationship between increasing spike duration and firing frequency was retained but the change in spike duration at frequencies between 2 and 10 Hz was less pronounced. Once action potentials had achieved the long duration configuration, their return to the shorter duration took place gradually during any succeeding silent interval with a time constant of 4.9 s. Action potential broadening occurred progressively and was most pronounced at the onset of spontaneous or current-induced bursts. In thirty-six phasically active neurones, spike broadening at the onset of a burst was concurrent with the presence of 5-10 consecutive short (less than or equal to 100 ms) interspike intervals; thereafter, despite a greater than 50% reduction in firing frequency, action potential durations remained prolonged throughout the burst. In all of nineteen cells tested, frequency-dependent changes in spike duration were reversibly decreased or blocked by Cd2+, Co2+ and Mn2+, or when CaCl2 was exchanged for equimolar amounts of EGTA in the perfusion medium. These observations indicate that a Ca2+ conductance contributes to frequency- and firing-pattern-dependent changes in spike duration in rat supraoptic

  8. SHAPING OF ACTION POTENTIALS BY TYPE I AND TYPE II BK CHANNELS

    OpenAIRE

    Jaffe, David B.; Wang, Bin; Brenner, Robert

    2011-01-01

    The BK channel is a Ca2+ and voltage-gated conductance responsible for shaping action potential waveforms in many types of neurons. Type II BK channels are differentiated from type I channels by their pharmacology and slow gating kinetics. The β4 accessory subunit confers type II properties on BK α subunits. Empirically derived properties of BK channels, with and without the β4 accessory subunit, were obtained using a heterologous expression system under physiological ionic conditions. These ...

  9. FMRP Regulates Neurotransmitter Release and Synaptic Information Transmission by Modulating Action Potential Duration via BK channels

    OpenAIRE

    Deng, Pan-Yue; Rotman, Ziv; Blundon, Jay A.; Cho, Yongcheol; Cui, Jianmin; Cavalli, Valeria; Zakharenko, Stanislav S; Klyachko, Vitaly A.

    2013-01-01

    Loss of FMRP causes Fragile X syndrome (FXS), but the physiological functions of FMRP remain highly debatable. Here we show that FMRP regulates neurotransmitter release in CA3 pyramidal neurons by modulating action potential (AP) duration. Loss of FMRP leads to excessive AP broadening during repetitive activity, enhanced presynaptic calcium influx and elevated neurotransmitter release. The AP broadening defects caused by FMRP loss have a cell-autonomous presynaptic origin and can be acutely r...

  10. Auxin Biosynthesis, Accumulation, Action and Transport are Involved in Stress-Induced Microspore Embryogenesis Initiation and Progression in Brassica napus.

    Science.gov (United States)

    Rodríguez-Sanz, Héctor; Solís, María-Teresa; López, María-Fernanda; Gómez-Cadenas, Aurelio; Risueño, María C; Testillano, Pilar S

    2015-07-01

    Isolated microspores are reprogrammed in vitro by stress, becoming totipotent cells and producing embryos and plants via a process known as microspore embryogenesis. Despite the abundance of data on auxin involvement in plant development and embryogenesis, no data are available regarding the dynamics of auxin concentration, cellular localization and the expression of biosynthesis genes during microspore embryogenesis. This work involved the analysis of auxin concentration and cellular accumulation; expression of TAA1 and NIT2 encoding enzymes of two auxin biosynthetic pathways; expression of the PIN1-like efflux carrier; and the effects of inhibition of auxin transport and action by N-1-naphthylphthalamic acid (NPA) and α-(p-chlorophenoxy) isobutyric acid (PCIB) during Brassica napus microspore embryogenesis. The results indicated de novo auxin synthesis after stress-induced microspore reprogramming and embryogenesis initiation, accompanying the first cell divisions. The progressive increase of auxin concentration during progression of embryogenesis correlated with the expression patterns of TAA1 and NIT2 genes of auxin biosynthetic pathways. Auxin was evenly distributed in early embryos, whereas in heart/torpedo embryos auxin was accumulated in apical and basal embryo regions. Auxin efflux carrier PIN1-like gene expression was induced in early multicellular embryos and increased at the globular/torpedo embryo stages. Inhibition of polar auxin transport (PAT) and action, by NPA and PCIB, impaired embryo development, indicating that PAT and auxin action are required for microspore embryo progression. NPA also modified auxin embryo accumulation patterns. These findings indicate that endogenous auxin biosynthesis, action and polar transport are required in stress-induced microspore reprogramming, embryogenesis initiation and progression.

  11. Serotonin spillover onto the axon initial segment of motoneurons induces central fatigue by inhibiting action potential initiation

    OpenAIRE

    Cotel, Florence; Exley, Richard; Cragg, Stephanie J.; Perrier, Jean-François

    2013-01-01

    Motor fatigue induced by physical activity is an everyday experience characterized by a decreased capacity to generate motor force. Factors in both muscles and the central nervous system are involved. The central component of fatigue modulates the ability of motoneurons to activate muscle adequately independently of the muscle physiology. Indirect evidence indicates that central fatigue is caused by serotonin (5-HT), but the cellular mechanisms are unknown. In a slice preparation from the spi...

  12. Mephenesin, methocarbamol, chlordiazepoxide and diazepam: actions on spinal reflexes and ventral root potentials.

    Science.gov (United States)

    Crankshaw, D P; Raper, C

    1970-01-01

    1. Dose levels of mephenesin, methocarbamol, chlordiazepoxide and diazepam which abolished polysynaptic reflex contractions had no effect on monosynaptic knee-jerk reflexes in chloralose anaesthetized cats.2. Ventral root potentials were recorded following stimulation of the corresponding dorsal root (L7 or S1), and the areas of the mono- and polysynaptic components were measured by planimetry.3. Dose levels of the drugs which abolished polysynaptic reflex contractions reduced the areas of the polysynaptic component of the ventral root potentials by about 50%. Mephenesin and methocarbamol reduced the area of the monosynaptic component to a similar extent. Chlordiazepoxide was less potent in this respect while diazepam was without effect at this dose level.4. Linear regression lines were calculated for the reduction in the mono- and polysynaptic components of ventral root potentials with increasing doses of each of the four drugs. With methocarbamol and mephenesin the lines were parallel and coincident. With chlordiazepoxide and diazepam they were parallel but not coincident. Large doses of diazepam were required to reduce the area of the monosynaptic component, this drug being the only one of the four tested to have a differential action on the two components which was statistically significant.5. The results are discussed in terms of depressant actions of the drugs on alpha-motorneurones, effects of the drugs at higher centres concerned with motor function, and the lack of evidence that spinal interneurones represent a specific site of action for centrally acting skeletal muscle relaxants.

  13. Action potential characteristics of demyelinated rat sciatic nerve following application of 4-aminopyridine.

    Science.gov (United States)

    Targ, E F; Kocsis, J D

    1986-01-15

    The sciatic nerves of rats were demyelinated by microinjection of lysophosphatidylcholine. A variety of abnormalities such as conduction slowing and block were present. Application of the potassium channel blocker 4-aminopyridine (4-AP) to the lesion site, led to an increase in area of the compound action potential recorded across the site of demyelination. Single axon recordings revealed three types of changes that may account for the 4-AP-induced increase in the compound response. One group showed broadening of the action potential. Other axons showed hyperexcitability following 4-AP, as manifest by spontaneous firing and multiple spike discharge following a single stimulus. In some of the axons studied, 4-AP led to overcoming of conduction block. Although many axons showed increased excitability properties in the presence of 4-AP, the frequency-following ability of the axons was reduced, and the absolute refractory period of the axons was increased. These results indicate that pharmacological blockade of potassium channels with 4-AP not only leads to action potential broadening in demyelinated axons, but to a variety of excitability changes. These heterogeneous effects of 4-AP should be considered in the rationale for its clinical use.

  14. Carbon nanotube multi-electrode array chips for noninvasive real-time measurement of dopamine, action potentials, and postsynaptic potentials.

    Science.gov (United States)

    Suzuki, Ikuro; Fukuda, Mao; Shirakawa, Keiichi; Jiko, Hideyasu; Gotoh, Masao

    2013-11-15

    Multi-electrode arrays (MEAs) can be used for noninvasive, real-time, and long-term recording of electrophysiological activity and changes in the extracellular chemical microenvironment. Neural network organization, neuronal excitability, synaptic and phenotypic plasticity, and drug responses may be monitored by MEAs, but it is still difficult to measure presynaptic activity, such as neurotransmitter release, from the presynaptic bouton. In this study, we describe the development of planar carbon nanotube (CNT)-MEA chips that can measure both the release of the neurotransmitter dopamine as well as electrophysiological responses such as field postsynaptic potentials (fPSPs) and action potentials (APs). These CNT-MEA chips were fabricated by electroplating the indium-tin oxide (ITO) microelectrode surfaces. The CNT-plated ITO electrode exhibited electrochemical response, having much higher current density compared with the bare ITO electrode. Chronoamperometric measurements using these CNT-MEA chips detected dopamine at nanomolar concentrations. By placing mouse striatal brain slices on the CNT-MEA chip, we successfully measured synaptic dopamine release from spontaneous firings with a high S/N ratio of 62. Furthermore, APs and fPSPs were measured from cultured hippocampal neurons and slices with high temporal resolution and a 100-fold greater S/N ratio. Our CNT-MEA chips made it possible to measure neurotransmitter dopamine (presynaptic activities), postsynaptic potentials, and action potentials, which have a central role in information processing in the neuronal network. CNT-MEA chips could prove useful for in vitro studies of stem cell differentiation, drug screening and toxicity, synaptic plasticity, and pathogenic processes involved in epilepsy, stroke, and neurodegenerative diseases.

  15. T-type calcium channels consolidate tonic action potential output of thalamic neurons to neocortex.

    Science.gov (United States)

    Deleuze, Charlotte; David, François; Béhuret, Sébastien; Sadoc, Gérard; Shin, Hee-Sup; Uebele, Victor N; Renger, John J; Lambert, Régis C; Leresche, Nathalie; Bal, Thierry

    2012-08-29

    The thalamic output during different behavioral states is strictly controlled by the firing modes of thalamocortical neurons. During sleep, their hyperpolarized membrane potential allows activation of the T-type calcium channels, promoting rhythmic high-frequency burst firing that reduces sensory information transfer. In contrast, in the waking state thalamic neurons mostly exhibit action potentials at low frequency (i.e., tonic firing), enabling the reliable transfer of incoming sensory inputs to cortex. Because of their nearly complete inactivation at the depolarized potentials that are experienced during the wake state, T-channels are not believed to modulate tonic action potential discharges. Here, we demonstrate using mice brain slices that activation of T-channels in thalamocortical neurons maintained in the depolarized/wake-like state is critical for the reliable expression of tonic firing, securing their excitability over changes in membrane potential that occur in the depolarized state. Our results establish a novel mechanism for the integration of sensory information by thalamocortical neurons and point to an unexpected role for T-channels in the early stage of information processing.

  16. The characteristics of action potential and nonselec-tive cation current of cardiomyocytes in rabbit superior vena cava

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    As a special focus in initiating and maintaining atrial fibrillation (AF), cardiomyocytes in superior vena cava (SVC) have distinctive electrophysiological characters. In this study, we found that comparing with the right atrial (RA) cardiomyoctyes, the SVC cardiomyoctyes had longer APD90 at the different basic cycle lengths; the conduction block could be observed on both RA and SVC cardiomyoctyes. A few of SVC cardiomyoctyes showed slow response action potentials with automatic activity and some others showed early afterdepolarization (EAD) spontaneously. Further more, we found that there are nonselective cation current (INs) in both SVC and RA cardiomyocytes. The peak density of INs in SVC cardiomyocytes was smaller than that in RA cardiomyocytes. Removal of extracellular divalent cation and glucose could increase INs in SVC cardiomyocytes. The agonist or the antagonist of INs may in-crease or decrease APD. To sum up, some SVC cardiomyocytes possess the ability of spontaneous activity; the difference of transmembrane action potentials between SVC and RA cardiomyocytes is partly because of the different density of INs between them; the agonist or the antagonist of INs can in-crease or decrease APD leading to the enhancement or reduction of EAD genesis in SVC cardiomyo-cytes. INs in rabbit myocytes is fairly similar to TRPC3 current in electrophysiological property, which might play an important role in the mechanisms of AF.

  17. Relation between size of compound sensory or muscle action potentials, and length of nerve segment.

    Science.gov (United States)

    Kimura, J; Machida, M; Ishida, T; Yamada, T; Rodnitzky, R L; Kudo, Y; Suzuki, S

    1986-05-01

    In 24 median nerves from 12 healthy subjects, antidromic digital sensory potentials progressively diminished in size, averaging 40.4, 37.0, 30.7, and 23.9 microV X msec with stimulation at the palm, wrist, elbow, and axilla, respectively. In contrast, compound muscle action potentials changed minimally, measuring 19.4, 19.8, 19.0, and 18.2 mV X msec, respectively. Similar studies of the ulnar and radial nerves showed identical trends. Physiologic temporal dispersion can mimic conduction block of sensory nerves by summating the peaks of opposite polarity generated by fast- and slow-conducting axons. This type of cancellation affects muscle responses much less because motor unit potentials of longer duration superimpose nearly in phase, given the same latency shift as the sensory potentials.

  18. ACTION-SPACE CLUSTERING OF TIDAL STREAMS TO INFER THE GALACTIC POTENTIAL

    Energy Technology Data Exchange (ETDEWEB)

    Sanderson, Robyn E.; Helmi, Amina [Kapteyn Astronomical Institute, P.O. Box 800, 9700 AV Groningen (Netherlands); Hogg, David W., E-mail: robyn@astro.columbia.edu [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States)

    2015-03-10

    We present a new method for constraining the Milky Way halo gravitational potential by simultaneously fitting multiple tidal streams. This method requires three-dimensional positions and velocities for all stars to be fit, but does not require identification of any specific stream or determination of stream membership for any star. We exploit the principle that the action distribution of stream stars is most clustered when the potential used to calculate the actions is closest to the true potential. Clustering is quantified with the Kullback-Leibler Divergence (KLD), which also provides conditional uncertainties for our parameter estimates. We show, for toy Gaia-like data in a spherical isochrone potential, that maximizing the KLD of the action distribution relative to a smoother distribution recovers the input potential. The precision depends on the observational errors and number of streams; using K III giants as tracers, we measure the enclosed mass at the average radius of the sample stars accurate to 3% and precise to 20%-40%. Recovery of the scale radius is precise to 25%, biased 50% high by the small galactocentric distance range of stars in our mock sample (1-25 kpc, or about three scale radii, with mean 6.5 kpc). 20-25 streams with at least 100 stars each are required for a stable confidence interval. With radial velocities (RVs) to 100 kpc, all parameters are determined with ∼10% accuracy and 20% precision (1.3% accuracy for the enclosed mass), underlining the need to complete the RV catalog for faint halo stars observed by Gaia.

  19. Action Research’s Potential to Foster Institutional Change for Urban Water Management

    Directory of Open Access Journals (Sweden)

    Dimitrios Zikos

    2013-04-01

    Full Text Available The paper discusses the potential of action research to meet the challenges entailed in institutional design for urban water management. Our overall aim is to briefly present action research and discuss its methodological merits with regard to the challenges posed by the different conceptual bases for extrapolating the effects of institutional design on institutional change. Thus, our aim is to explore how Action Research meets the challenge of scoping the field in an open fashion for determining the appropriate mechanisms of institutional change and supporting the emerging of new water institutions. To accomplish this aim, we select the Water Framework Directive (WFD as an illustrative driving force requiring changes in water management practices and implying the need for the emergence of new institutions. We employ a case of urban water management in the Volos Metropolitan Area, part of the Thessaly region in Greece, where a Pilot River Basin Plan was implemented. By applying action research and being involved in a long process of interaction between stakeholders, we examine the emergence of new institutions dealing with urban water management under the general principles of the major driving force for change: the WFD.

  20. Antibacterial free fatty acids: activities, mechanisms of action and biotechnological potential.

    Science.gov (United States)

    Desbois, Andrew P; Smith, Valerie J

    2010-02-01

    Amongst the diverse and potent biological activities of free fatty acids (FFAs) is the ability to kill or inhibit the growth of bacteria. The antibacterial properties of FFAs are used by many organisms to defend against parasitic or pathogenic bacteria. Whilst their antibacterial mode of action is still poorly understood, the prime target of FFA action is the cell membrane, where FFAs disrupt the electron transport chain and oxidative phosphorylation. Besides interfering with cellular energy production, FFA action may also result from the inhibition of enzyme activity, impairment of nutrient uptake, generation of peroxidation and auto-oxidation degradation products or direct lysis of bacterial cells. Their broad spectrum of activity, non-specific mode of action and safety makes them attractive as antibacterial agents for various applications in medicine, agriculture and food preservation, especially where the use of conventional antibiotics is undesirable or prohibited. Moreover, the evolution of inducible FFA-resistant phenotypes is less problematic than with conventional antibiotics. The potential for commercial or biomedical exploitation of antibacterial FFAs, especially for those from natural sources, is discussed.

  1. Initial Study on the Antibacterial Action of Mentha spicata Linn Extract in Vitro

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hong-ying; WANG Xue-bing; HAN Wei-li; CUI Bao-an

    2010-01-01

    [Objective] The research aimed to study the antibacterial action of Mentha spicata Linn extract in vitro.[Method] The cylinder-plate method was used to measure the inhibitory zone size of Mentha spicata Linn extract.The test-tube double dilution method was used to measure the minimal inhibitory concentration(MIC)of Mentha spicata Linn extract on the four kinds of animal pathogenic bacteria,which could determine the antibacterial effect.[Result] The decoction,alcohol extract and volatile oil of Mentha spicata Linn had the different antibacterial effects on the four kinds of animal pathogenic bacteria.Especially the inhibition effect on the pig staphylococcus was comparatively obvious.MIC of Mentha spicata Linn decoction I,alcohol extract III,volatile oil V and volatile oil VI were respectively 31.25,62.5,2.32 and 2.31 mg/ml.[Conclusion] The decoction,alcohol extract and volatile oil of Mentha spicata Linn had the certain antibacterial effect in vitro,and the extracts which were gained by the different extraction methods had the different inhibition effects on the experimental bacteria.

  2. Overexpression of the Large-Conductance, Ca2+-Activated K+ (BK) Channel Shortens Action Potential Duration in HL-1 Cardiomyocytes.

    Science.gov (United States)

    Stimers, Joseph R; Song, Li; Rusch, Nancy J; Rhee, Sung W

    2015-01-01

    Long QT syndrome is characterized by a prolongation of the interval between the Q wave and the T wave on the electrocardiogram. This abnormality reflects a prolongation of the ventricular action potential caused by a number of genetic mutations or a variety of drugs. Since effective treatments are unavailable, we explored the possibility of using cardiac expression of the large-conductance, Ca2+-activated K+ (BK) channel to shorten action potential duration (APD). We hypothesized that expression of the pore-forming α subunit of human BK channels (hBKα) in HL-1 cells would shorten action potential duration in this mouse atrial cell line. Expression of hBKα had minimal effects on expression levels of other ion channels with the exception of a small but significant reduction in Kv11.1. Patch-clamped hBKα expressing HL-1 cells exhibited an outward voltage- and Ca2+-sensitive K+ current, which was inhibited by the BK channel blocker iberiotoxin (100 nM). This BK current phenotype was not detected in untransfected HL-1 cells or in HL-1 null cells sham-transfected with an empty vector. Importantly, APD in hBKα-expressing HL-1 cells averaged 14.3 ± 2.8 ms (n = 10), which represented a 53% reduction in APD compared to HL-1 null cells lacking BKα expression. APD in the latter cells averaged 31.0 ± 5.1 ms (n = 13). The shortened APD in hBKα-expressing cells was restored to normal duration by 100 nM iberiotoxin, suggesting that a repolarizing K+ current attributed to BK channels accounted for action potential shortening. These findings provide initial proof-of-concept that the introduction of hBKα channels into a cardiac cell line can shorten APD, and raise the possibility that gene-based interventions to increase hBKα channels in cardiac cells may hold promise as a therapeutic strategy for long QT syndrome.

  3. Action potential generation in the small intestine of W mutant mice that lack interstitial cells of Cajal

    DEFF Research Database (Denmark)

    Malysz, J; Thuneberg, L; Mikkelsen, Hanne Birte

    1996-01-01

    The small intestine of W/Wv mice lacks both the network of interstitial cells of Cajal (ICC), associated with Auerbach's plexus, and pacemaker activity, i.e., it does not generate slow-wave-type action potentials. The W/Wv muscle preparations showed a wide variety of electrical activities, ranging...... from total quiescence to generation of action potentials at regular or irregular frequency with or without periods of quiescence. The action potentials consisted of a slow component with superimposed spikes, preceded by a slowly developing depolarization and followed by a transient hyperpolarization....... The action potentials were completely abolished by L-type Ca2+ channel blockers. W/Wv mice responded to K+ channel blockade (0.5 mM Ba2+ or 10 mM tetraethylammonium chloride) with effects on amplitude, frequency, rate of rise, and duration of the action potentials. In quiescent tissues from W/Wv mice, K...

  4. The real-time link between person perception and action: brain potential evidence for dynamic continuity.

    Science.gov (United States)

    Freeman, Jonathan B; Ambady, Nalini; Midgley, Katherine J; Holcomb, Phillip J

    2011-01-01

    Using event-related potentials, we investigated how the brain extracts information from another's face and translates it into relevant action in real time. In Study 1, participants made between-hand sex categorizations of sex-typical and sex-atypical faces. Sex-atypical faces evoked negativity between 250 and 550 ms (N300/N400 effects), reflecting the integration of accumulating sex-category knowledge into a coherent sex-category interpretation. Additionally, the lateralized readiness potential revealed that the motor cortex began preparing for a correct hand response while social category knowledge was still gradually evolving in parallel. In Study 2, participants made between-hand eye-color categorizations as part of go/no-go trials that were contingent on a target's sex. On no-go trials, although the hand did not actually move, information about eye color partially prepared the motor cortex to move the hand before perception of sex had finalized. Together, these findings demonstrate the dynamic continuity between person perception and action, such that ongoing results from face processing are immediately and continuously cascaded into the motor system over time. The preparation of action begins based on tentative perceptions of another's face before perceivers have finished interpreting what they just saw.

  5. FMRP regulates neurotransmitter release and synaptic information transmission by modulating action potential duration via BK channels.

    Science.gov (United States)

    Deng, Pan-Yue; Rotman, Ziv; Blundon, Jay A; Cho, Yongcheol; Cui, Jianmin; Cavalli, Valeria; Zakharenko, Stanislav S; Klyachko, Vitaly A

    2013-02-20

    Loss of FMRP causes fragile X syndrome (FXS), but the physiological functions of FMRP remain highly debatable. Here we show that FMRP regulates neurotransmitter release in CA3 pyramidal neurons by modulating action potential (AP) duration. Loss of FMRP leads to excessive AP broadening during repetitive activity, enhanced presynaptic calcium influx, and elevated neurotransmitter release. The AP broadening defects caused by FMRP loss have a cell-autonomous presynaptic origin and can be acutely rescued in postnatal neurons. These presynaptic actions of FMRP are translation independent and are mediated selectively by BK channels via interaction of FMRP with BK channel's regulatory β4 subunits. Information-theoretical analysis demonstrates that loss of these FMRP functions causes marked dysregulation of synaptic information transmission. FMRP-dependent AP broadening is not limited to the hippocampus, but also occurs in cortical pyramidal neurons. Our results thus suggest major translation-independent presynaptic functions of FMRP that may have important implications for understanding FXS neuropathology.

  6. Big data to smart data in Alzheimer's disease: The brain health modeling initiative to foster actionable knowledge.

    Science.gov (United States)

    Geerts, Hugo; Dacks, Penny A; Devanarayan, Viswanath; Haas, Magali; Khachaturian, Zaven S; Gordon, Mark Forrest; Maudsley, Stuart; Romero, Klaus; Stephenson, Diane

    2016-09-01

    Massive investment and technological advances in the collection of extensive and longitudinal information on thousands of Alzheimer patients results in large amounts of data. These "big-data" databases can potentially advance CNS research and drug development. However, although necessary, they are not sufficient, and we posit that they must be matched with analytical methods that go beyond retrospective data-driven associations with various clinical phenotypes. Although these empirically derived associations can generate novel and useful hypotheses, they need to be organically integrated in a quantitative understanding of the pathology that can be actionable for drug discovery and development. We argue that mechanism-based modeling and simulation approaches, where existing domain knowledge is formally integrated using complexity science and quantitative systems pharmacology can be combined with data-driven analytics to generate predictive actionable knowledge for drug discovery programs, target validation, and optimization of clinical development.

  7. Whey protein potentiates the intestinotrophic action of glucagon-like peptide-2 in parenterally fed rats

    DEFF Research Database (Denmark)

    Liu, Xiaowen; Murali, Sangita G; Holst, Jens J

    2009-01-01

    Glucagon-like peptide-2 (GLP-2) is a nutrient-regulated intestinotrophic hormone derived from proglucagon in the distal intestine. Enteral nutrients (EN) potentiate the action of GLP-2 to reverse parenteral nutrition (PN)-induced mucosal hypoplasia. The objective was to determine what enteral...... protein component, casein, soy, or whey protein, potentiates the intestinal growth response to GLP-2 in rats with PN-induced mucosal hypoplasia. Rats received PN and continuous intravenous infusion of GLP-2 (100 microg/kg/day) for 7 days. Six EN groups received PN+GLP-2 for days 1-3 and partial PN+GLP-2...... whey protein, and not casein or soy, potentiated the ability of GLP-2 to reverse PN-induced mucosal hypoplasia and further increase ileal villus height, crypt depth, and mucosa cellularity compared with PN+GLP-2 alone, P

  8. Cues-to-Action in Initiating Lesbian, Gay, Bisexual, and Transgender-Related Policies Among Magnet Hospital Chief Nursing Officers: A Demographic Assessment.

    Science.gov (United States)

    Klotzbaugh, Ralph; Spencer, Gale

    2015-01-01

    This study explored Magnet Chief Nursing Officers' cues-to-action initiating lesbian, gay, bisexual, or transgender (LGBT)-specific policies. Homonegativity has a negative effect on employee recruitment and retention and patient satisfaction. Little has been known about what cues-to-action might initiate LGBT inclusive training. Surveys were mailed to 343 Chief Nursing Officers. Cues-to-action survey was used to assess what inspires initiation of LGBT training. Demographic surveys were used to assess what impact variables might have on cues-to-action. Age, sex, religiosity, location, and region had significant effect on cues-to-action. Developing demographically informed training and policies for LGBT equality in health care is suggestive of greater employee and patient satisfaction.

  9. Cortical field potentials associated with audio-initiated vocalization in monkeys.

    Science.gov (United States)

    Gemba, H; Kyuhou, S; Matsuzaki, R; Amino, Y

    1999-09-03

    Five monkeys vocalizing at self-pace (self-paced vocalization) were well trained to vocalize in response to a monkey call (audio-initiated vocalization). Field potentials associated with audio-initiated vocalizations were recorded by using electrodes which were implanted chronically on the surface and at a 2.0-3.0 mm depth in various cortical areas. A surface-negative (s-N), depth-positive (d-P) potential (at about 70 ms latency after stimulus onset) was recorded in the rostral bank of the inferior limb of the arcuate sulcus in the left hemisphere, in which an insignificant potential was associated with self-paced vocalizations. An s-N, d-P slow potential which occurred in the motor and somatosensory cortices with a latency of about 300 ms after stimulus, started about 700 ms before vocalizations. The duration and amplitude of this potential was substantially the same with those of the potential which occurred with self-paced vocalizations. Reaction times from stimulus onset to vocalization start were variable, but were about 0.9s on the average. The findings were discussed in connection with reaction-time hand movements.

  10. An Excel-based implementation of the spectral method of action potential alternans analysis.

    Science.gov (United States)

    Pearman, Charles M

    2014-12-01

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

  11. The Effects of Action Potential Stimulation on Pain, Swelling and Function of Patients with Knee Osteoarthritis

    Directory of Open Access Journals (Sweden)

    Razieh Sepehri

    2012-06-01

    Full Text Available Background: Knee osteoarthritis (OA is one of the most prevalent joint diseases. Electrical muscle stimulation is effective to improve its symptoms. Today, action potential stimulation (APS with various currents and periods is used to treat OA. This study aims at analyzing the effect of action potential stimulation in improving knee OA symptoms. Materials and Methods: In this clinical trial, patients with mild to moderate knee OA divided randomly in two groups each had 15 people. Along with the conventional exercises of physiotherapy, one group received 16 minutes action potential stimulation with the lowest intensity (sensible; but the other group besides receiving the conventional exercises of physiotherapy was connected into a plugged off machine for 16 minutes. Certain variables were measured and recorded four times. Results: Comparing the variables before and after intervention did not show any meaningful difference between the two groups. But within group, pain with p=0.0001 showed a meaningful decrease. Decreasing of swelling (inflammation in group 1 and 2 was meaningful with p<0.001 and p<0.001, respectively. For group 1, knee flexion range was improved meaningfully between first and fourth times as p<0.031, but it was not meaningful for group 2. Duration of 50 meters walking and step up and down from three steps significantly decreased in both groups. Conclusion: Although there was no significant difference in variables between two groups, but within both groups’ pain and swelling decreased and functional ability increased, thus, it can be concluded that type of APS does not play a key role in treating knee OA.

  12. A Legal Analysis of the Equal Protection Clause of the Fourteenth Amendment and Its Impact on Ballot Initiatives and Affirmative Action Programs in Higher Education

    Science.gov (United States)

    Waters, Harold Davon

    2012-01-01

    This dissertation explores the controversial issues surrounding affirmative action in higher education. Are anti-affirmative action ballot initiatives in violation of the Equal Protection Clause of the Fourteenth Amendment by restructuring the political process of minorities in such a way that places special burden on their ability to secure…

  13. Effects of Potassium Currents upon Action Potential of Cardiac Cells Exposed to External Electric fields

    Institute of Scientific and Technical Information of China (English)

    An-Ying Zhang; Xiao-Feng Pang

    2008-01-01

    Previous studies show that exposure to high-voltage electric fields would influence the electro cardiogram both in experimental animate and human beings. The effects of the external electric fields upon action potential of cardiac cells are studied in this paper based on the dynamical model, LR91. Fourth order Runger-Kuta is used to analyze the change of potassium ion channels exposed to external electric fields in detail. Results indicate that external electric fields could influence the current of potassium ion by adding an induced component voltage on membrane. This phenomenon might be one of the reasons of heart rate anomaly under the high-voltage electric fields.

  14. On modelling of physical effects accompanying the propagation of action potentials in nerve fibres

    CERN Document Server

    Engelbrecht, Jüri; Tamm, Kert; Laasmaa, Martin; Vendelin, Marko

    2016-01-01

    The recent theoretical and experimental studies have revealed many details of signal propagation in nervous systems. In this paper an attempt is made to unify various mathematical models which describe the signal propagation in nerve fibres. The analysis of existing single models permits to select the leading physiological effects. As a result, a more general mathematical model is described based on the coupling of action potentials with mechanical waves in a nerve fibre. The crucial issue is how to model coupling effects which are strongly linked to the ion currents through biomembranes.

  15. The Healthy Bus project in Denmark: need for an action potential assessment.

    Science.gov (United States)

    Poulsen, Kjeld B

    2004-06-01

    Research over the last 50 years has repeatedly documented that bus drivers are exposed to several physical and psychological risk factors, which are associated with health problems in the form of heart, musculo-skeletal and stomach disease, and increased coronary mortality. So why has there been little action to improve the situation when it is so obviously indicated by such assessments? This article describes the long and complex process that has made it possible to launch almost 200 interventions among the 3500 municipal bus drivers in Copenhagen. Using a participative action research design, new evidence was gathered by broadening the traditional work environmental scope to lifestyle, health issues and private matters. Comparing this updated needs assessment with a national reference population, it was found that drivers were often still worse off. Again, simply presenting new evidence did not seem to lead to changes and further work is needed to empower the stakeholders so that they can commit to start making effective interventions. It is concluded that every needs assessment has to be supplemented with an evaluation of the action potential.

  16. Increase in action potential duration and inhibition of the delayed rectifier outward current IK by berberine in cat ventricular myocytes.

    OpenAIRE

    Sánchez-Chapula, J.

    1996-01-01

    1. In the present work, the effects of the antiarrhythmic drug, berberine, on action potential and ionic currents of cat ventricular myocytes were studied. 2. Berberine prolonged action potential duration in cat ventricular myocytes without altering other variables of the action potential. 3. The drug at concentrations of 0.3-30 microM blocked only the delayed rectifier (IK) current with an IC50 = 4.1 microM. Berberine produced a tonic block and a phasic block that was increased with the dura...

  17. Three-dimensional mapping and regulation of action potential propagation in nanoelectronics-innervated tissues

    Science.gov (United States)

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

    2016-09-01

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

  18. Supernormal Conduction and Suppression of Spatially Discordant Alternans of Cardiac Action Potentials.

    Science.gov (United States)

    Jing, Linyuan; Agarwal, Anuj; Patwardhan, Abhijit

    2015-01-01

    Spatially discordant alternans (DA) of action potential durations (APD) is thought to be more pro-arrhythmic than concordant alternans. Super normal conduction (SNC) has been reported to suppress formation of DA. An increase in conduction velocity (CV) as activation rate increases, i.e., a negative CV restitution, is widely considered as hallmark of SNC. Our aim in this study is to show that it is not an increase in CV for faster rates that prevents formation of DA, rather, it is the ratio of the CV for the short relative to the long activation that is critical in DA suppression. To illustrate this subtlety, we simulated this phenomenon using two approaches; (1) by using the standard, i.e., S1S2 protocol to quantify restitution and disabling the slow inactivation gate j of the sodium current (INa), and (2) by using the dynamic, i.e., S1S1 protocol for quantification of restitution and increasing INa at different cycle lengths (CL). Even though both approaches produced similar CV restitution curves, DA was suppressed only during the first approach, where the CV of the short of the long-short action potential (AP) pattern was selectively increased. These results show that negative CV restitution, which is considered characteristic of SNC, per se, is not causal in suppressing DA, rather, the critical factor is a change in the ratio of the velocities of the short and the long APs.

  19. Supernormal Conduction and Suppression of Spatial Discord in Alternans of Cardiac Action Potentials

    Directory of Open Access Journals (Sweden)

    Linyuan eJing

    2016-01-01

    Full Text Available Spatially discordant alternans (DA of action potential durations (APD is thought to be more pro-arrhythmic than concordant alternans. Super normal conduction (SNC has been reported to suppress formation of DA. An increase in conduction velocity (CV as activation rate increases, i.e. a negative CV restitution, is widely considered as hallmark of SNC. Our aim in this study is to show that it is not an increase in CV for faster rates that prevents formation of DA, rather, it is the ratio of the CV for the short relative to the long activation that is critical in DA suppression. To illustrate this subtlety, we simulated this phenomenon using two approaches; (1 by using the standard, i.e. S1S2 protocol to quantify restitution and disabling the slow inactivation gate j of the sodium current (INa, and (2 by using the dynamic, i.e. S1S1 protocol for quantification of restitution and increasing INa at different cycle lengths (CL. Even though both approaches produced similar CV restitution curves, DA was suppressed only during the first approach, where the CV of the short of the long-short action potential (AP pattern was selectively increased. These results show that negative CV restitution, which is considered characteristic of SNC, per se, is not causal in suppressing DA, rather, the critical factor is a change in the ratio of the velocities of the short and the long APs.

  20. Applications of control theory to the dynamics and propagation of cardiac action potentials.

    Science.gov (United States)

    Muñoz, Laura M; Stockton, Jonathan F; Otani, Niels F

    2010-09-01

    Sudden cardiac arrest is a widespread cause of death in the industrialized world. Most cases of sudden cardiac arrest are due to ventricular fibrillation (VF), a lethal cardiac arrhythmia. Electrophysiological abnormalities such as alternans (a beat-to-beat alternation in action potential duration) and conduction block have been suspected to contribute to the onset of VF. This study focuses on the use of control-systems techniques to analyze and design methods for suppressing these precursor factors. Control-systems tools, specifically controllability analysis and Lyapunov stability methods, were applied to a two-variable Karma model of the action-potential (AP) dynamics of a single cell, to analyze the effectiveness of strategies for suppressing AP abnormalities. State-feedback-integral (SFI) control was then applied to a Purkinje fiber simulated with the Karma model, where only one stimulating electrode was used to affect the system. SFI control converted both discordant alternans and 2:1 conduction block back toward more normal patterns, over a wider range of fiber lengths and pacing intervals compared with a Pyragas-type chaos controller. The advantages conferred by using feedback from multiple locations in the fiber, and using integral (i.e., memory) terms in the controller, are discussed.

  1. Effects of acoustic noise on the auditory nerve compound action potentials evoked by electric pulse trains.

    Science.gov (United States)

    Nourski, Kirill V; Abbas, Paul J; Miller, Charles A; Robinson, Barbara K; Jeng, Fuh-Cherng

    2005-04-01

    This study investigated the effects of acoustic noise on the auditory nerve compound action potentials in response to electric pulse trains. Subjects were adult guinea pigs, implanted with a minimally invasive electrode to preserve acoustic sensitivity. Electrically evoked compound action potentials (ECAP) were recorded from the auditory nerve trunk in response to electric pulse trains both during and after the presentation of acoustic white noise. Simultaneously presented acoustic noise produced a decrease in ECAP amplitude. The effect of the acoustic masker on the electric probe was greatest at the onset of the acoustic stimulus and it was followed by a partial recovery of the ECAP amplitude. Following cessation of the acoustic noise, ECAP amplitude recovered over a period of approximately 100-200 ms. The effects of the acoustic noise were more prominent at lower electric pulse rates (interpulse intervals of 3 ms and higher). At higher pulse rates, the ECAP adaptation to the electric pulse train alone was larger and the acoustic noise, when presented, produced little additional effect. The observed effects of noise on ECAP were the greatest at high electric stimulus levels and, for a particular electric stimulus level, at high acoustic noise levels.

  2. The use of sensory action potential to evaluate inferior alveolar nerve damage after orthognathic surgery.

    Science.gov (United States)

    Calabria, Francesca; Sellek, Lucy; Gugole, Fabio; Trevisiol, Lorenzo; Trevisol, Lorenzo; Bertolasi, Laura; D'Agostino, Antonio

    2013-03-01

    To assess and monitor the common event of neurosensory disturbance to the inferior alveolar nerve (IAN) after bilateral sagittal split osteotomy, we used clinical sensory tests and neurophysiologic test sensory action potentials. The diagnostic value of these tests was evaluated by comparing them with the degree of nerve damage reported by patients. Fourteen patients undergoing bilateral sagittal split osteotomy were analyzed preoperatively and 2 years postoperatively. Patients were evaluated bilaterally for positive and negative symptoms: light touch sensation, paraesthesia, hyperesthesia, and dysaesthesia; a "sensation score" was then calculated for each patient. Patients were also asked if they would be willing to repeat the procedure knowing the sensation loss they had now. Next, the right and left IAN were evaluated using sensory action potential and correlated with the other results. Before surgery, the medium latency difference between left and right was lower compared with postsurgery, with all patients having some deficit. The reduction in medium amplitude of 67% after the intervention was statistically significant. The frequency of abnormal findings in the electrophysiologic tests indicating IAN injury correlated with subjective sensory alteration. All patients said that they would repeat the surgery. Electrophysiologic testing is recommended for the evaluation of nerve dysfunction and seems a sensitive method for accurately assessing postsurgical nerve conduction.

  3. Modulation of action potential and calcium signaling by levetiracetam in rat sensory neurons.

    Science.gov (United States)

    Ozcan, Mete; Ayar, Ahmet

    2012-06-01

    Levetiracetam (LEV), a new anticonvulsant agent primarily used to treat epilepsy, has been used in pain treatment but the cellular mechanism of this action remains unclear. This study aimed to investigate effects of LEV on the excitability and membrane depolarization-induced calcium signaling in isolated rat sensory neurons using the whole-cell patch clamp and fura 2-based ratiometric Ca(2+)-imaging techniques. Dorsal root ganglia (DRG) were excised from neonatal rats, and cultured following enzymatic and mechanical dissociation. Under current clamp conditions, acute application of LEV (30 µM, 100 µM and 300 µM) significantly increased input resistance and caused the membrane to hyperpolarize from resting membrane potential in a dose-dependent manner. Reversal potentials of action potential (AP) after hyperpolarising amplitudes were shifted to more negative, toward to potassium equilibrium potentials, after application of LEV. It also caused a decrease in number of APs in neurons fired multiple APs in response to prolonged depolarization. Fura-2 fluorescence Ca(2+) imaging protocols revealed that HiK(+) (30 mM)-induced intracellular free Ca(2+) ([Ca(2+)](i)) was inhibited to 97.8 ± 4.6% (n = 17), 92.6 ± 4.8% (n = 17, p < 0.01) and 89.1 ± 5.1% (n = 18, p < 0.01) after application of 30 µM, 100 µM and 300 µM LEV (respectively), without any significant effect on basal levels of [Ca(2+)](i). This is the first evidence for the effect of LEV on the excitability of rat sensory neurons through an effect which might involve activation of potassium channels and inhibition of entry of Ca(2+), providing new insights for cellular mechanism(s) of LEV in pain treatment modalities.

  4. Whey protein potentiates the intestinotrophic action of glucagon-like peptide-2 in parenterally fed rats.

    Science.gov (United States)

    Liu, Xiaowen; Murali, Sangita G; Holst, Jens J; Ney, Denise M

    2009-11-01

    Glucagon-like peptide-2 (GLP-2) is a nutrient-regulated intestinotrophic hormone derived from proglucagon in the distal intestine. Enteral nutrients (EN) potentiate the action of GLP-2 to reverse parenteral nutrition (PN)-induced mucosal hypoplasia. The objective was to determine what enteral protein component, casein, soy, or whey protein, potentiates the intestinal growth response to GLP-2 in rats with PN-induced mucosal hypoplasia. Rats received PN and continuous intravenous infusion of GLP-2 (100 microg/kg/day) for 7 days. Six EN groups received PN+GLP-2 for days 1-3 and partial PN+GLP-2 plus EN for days 4-7. EN was provided by ad libitum intake of a semielemental liquid diet with different protein sources: casein, hydrolyzed soy, whey protein concentrate (WPC), and hydrolyzed WPC+casein. Controls received PN+GLP-2 alone. EN induced significantly greater jejunal sucrase activity and gain of body weight, and improved feed efficiency compared with PN+GLP-2 alone. EN induced greater ileal proglucagon expression, increased plasma concentration of bioactive GLP-2 by 35%, and reduced plasma dipeptidyl peptidase IV (DPP-IV) activity compared with PN+GLP-2 alone, P whey protein, and not casein or soy, potentiated the ability of GLP-2 to reverse PN-induced mucosal hypoplasia and further increase ileal villus height, crypt depth, and mucosa cellularity compared with PN+GLP-2 alone, P whey protein to induce greater mucosal surface area was associated with decreased DPP-IV activity in ileum and colon compared with casein, soy, or PN+GLP-2 alone, P whey protein potentiates the action of GLP-2 to reverse PN-induced mucosal hypoplasia in association with decreased intestinal DPP-IV activity.

  5. Urocortin2 prolongs action potential duration and modulates potassium currents in guinea pig myocytes and HEK293 cells.

    Science.gov (United States)

    Yang, Li-Zhen; Zhu, Yi-Chun

    2015-07-01

    We previously reported that activation of corticotropin releasing factor receptor type 2 by urocortin2 up-regulates both L-type Ca(2+) channels and intracellular Ca(2+) concentration in ventricular myocytes and plays an important role in cardiac contractility and arrhythmogenesis. This study goal was to further test the hypothesis that urocortin2 may modulate action potentials as well as rapidly and slowly activating delayed rectifier potassium currents. With whole cell patch-clamp techniques, action potentials and slowly activating delayed rectifier potassium currents were recorded in isolated guinea pig ventricular myocytes, respectively. And rapidly activating delayed rectifier potassium currents were tested in hERG-HEK293 cells. Urocortin2 produced a time- and concentration-dependent prolongation of action potential duration. The EC50 values of action potential duration and action potential duration at 90% of repolarization were 14.73 and 24.3nM respectively. The prolongation of action potential duration of urocortin2 was almost completely or partly abolished by H-89 (protein kinase A inhibitor) or KB-R7943 (Na(+)/Ca(2+) exchange inhibitor) pretreatment respectively. And urocortin2 caused reduction of rapidly activating delayed rectifier potassium currents in hERG-HEK293 cells. In addition, urocortin2 slowed the rate of slowly activating delayed rectifier potassium channel activation, and rightward shifted the threshold of slowly activating delayed rectifier potassium currents to more positive potentials. Urocortin2 prolonged action potential duration via activation of protein kinase A and Na(+)/ Ca(2+) exchange in isolated guinea pig ventricular myocytes in a time- and concentration- dependent manner. In hERG-HEK293 cells, urocortin2 reduced rapidly activating delayed rectifier potassium current density which may contribute to action potential duration prolongation.

  6. Non-lethal heat treatment of cells results in reduction of tumor initiation and metastatic potential

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yoo-Shin; Lee, Tae Hoon; O' Neill, Brian E., E-mail: BEOneill@houstonmethodist.org

    2015-08-14

    Non-lethal hyperthermia is used clinically as adjuvant treatment to radiation, with mixed results. Denaturation of protein during hyperthermia treatment is expected to synergize with radiation damage to cause cell cycle arrest and apoptosis. Alternatively, hyperthermia is known to cause tissue level changes in blood flow, increasing the oxygenation and radiosensitivity of often hypoxic tumors. In this study, we elucidate a third possibility, that hyperthermia alters cellular adhesion and mechanotransduction, with particular impact on the cancer stem cell population. We demonstrate that cell heating results in a robust but temporary loss of cancer cell aggressiveness and metastatic potential in mouse models. In vitro, this heating results in a temporary loss in cell mobility, adhesion, and proliferation. Our hypothesis is that the loss of cellular adhesion results in suppression of cancer stem cells and loss of tumor virulence and metastatic potential. Our study suggests that the metastatic potential of cancer is particularly reduced by the effects of heat on cellular adhesion and mechanotransduction. If true, this could help explain both the successes and failures of clinical hyperthermia, and suggest ways to target treatments to those who would most benefit. - Highlights: • Non-lethal hyperthermia treatment of cancer cells is shown to cause a reduction in rates of tumor initiation and metastasis. • Dynamic imaging of cells during heat treatment shows temporary changes in cell shape, cell migration, and cell proliferation. • Loss of adhesion may lead to the observed effect, which may disproportionately impact the tumor initiating cell fraction. • Loss or suppression of the tumor initiating cell fraction results in the observed loss of metastatic potential in vivo. • This result may lead to new approaches to synergizing hyperthermia with surgery, radiation, and chemotherapy.

  7. Regulation of action potential waveforms by axonal GABAA receptors in cortical pyramidal neurons.

    Directory of Open Access Journals (Sweden)

    Yang Xia

    Full Text Available GABAA receptors distributed in somatodendritic compartments play critical roles in regulating neuronal activities, including spike timing and firing pattern; however, the properties and functions of GABAA receptors at the axon are still poorly understood. By recording from the cut end (bleb of the main axon trunk of layer -5 pyramidal neurons in prefrontal cortical slices, we found that currents evoked by GABA iontophoresis could be blocked by picrotoxin, indicating the expression of GABAA receptors in axons. Stationary noise analysis revealed that single-channel properties of axonal GABAA receptors were similar to those of somatic receptors. Perforated patch recording with gramicidin revealed that the reversal potential of the GABA response was more negative than the resting membrane potential at the axon trunk, suggesting that GABA may hyperpolarize the axonal membrane potential. Further experiments demonstrated that the activation of axonal GABAA receptors regulated the amplitude and duration of action potentials (APs and decreased the AP-induced Ca2+ transients at the axon. Together, our results indicate that the waveform of axonal APs and the downstream Ca2+ signals are modulated by axonal GABAA receptors.

  8. Membrane-initiated actions of estradiol (E2 in the regulation of LH secretion in ovariectomized (OVX ewes

    Directory of Open Access Journals (Sweden)

    Oakley Amy E

    2010-05-01

    Full Text Available Abstract Background We demonstrated that E2 conjugated to BSA (E2BSA induces a rapid membrane-initiated inhibition of LH secretion followed hours later by a slight increase in LH secretion. Whether these actions of E2BSA are restricted to the pituitary gland and whether the membrane-initiated pathway of E2BSA contributes to the up-regulation of the number of GnRH receptors during the positive feedback effect of E2 were evaluated here. We have shown that the suppression of LH secretion induced by E2 and E2BSA is the result of a decreased responsiveness of the pituitary gland to GnRH. In this study we further tested the ability of E2BSA to decrease the responsiveness of the pituitary gland to GnRH under the paradigm of the preovulatory surge of LH induced by E2. Methods For the first experiment GnRH and LH secretions were determined in samples of pituitary portal and jugular blood, respectively, in ewes treated with 12 mg E2BSA. In the second experiment, the number of GnRH receptors was quantified in ewes 12 h after administration of 25 micrograms E2 (the expected time for the increase in the number of GnRH receptors and the positive feedback effect of E2 in LH secretion or 12 mg E2BSA. In the third experiment, the preovulatory-like surge of LH was characterized in ewes injected with 25 micrograms E2 alone or followed 8 h later (before the beginning of the LH surge with 60 mg E2BSA. Results a the decrease in LH secretion induced by E2BSA was not accompanied by changes in the pulsatile pattern of GnRH, b E2BSA increased the number of GnRH receptors, and c the presence of E2BSA in E2-treated ewes delayed the onset, reduced the length, and decreased the amount of LH released during the preovulatory surge of LH. Conclusions a the rapid suppression of LH secretion induced by E2BSA is mediated only via a direct action on the pituitary gland, b E2 acting via a membrane-initiated pathway contributes to increase the number of GnRH receptors and, c

  9. Modulation by K+ channels of action potential-evoked intracellular Ca2+ concentration rises in rat cerebellar basket cell axons.

    Science.gov (United States)

    Tan, Y P; Llano, I

    1999-10-01

    1. Action potential-evoked [Ca2+]i rises in basket cell axons of rat cerebellar slices were studied using two-photon laser scanning microscopy and whole-cell recording, to identify the K+ channels controlling the shape of the axonal action potential. 2. Whole-cell recordings of Purkinje cell IPSCs were used to screen K+ channel subtypes which could contribute to axonal repolarization. alpha-Dendrotoxin, 4-aminopyridine, charybdotoxin and tetraethylammonium chloride increased IPSC rate and/or amplitude, whereas iberiotoxin and apamin failed to affect the IPSCs. 3. The effects of those K+ channel blockers that enhanced transmitter release on the [Ca2+]i rises elicited in basket cell axons by action potentials fell into three groups: 4-aminopyridine strongly increased action potential-evoked [Ca2+]i; tetraethylammonium and charybdotoxin were ineffective alone but augmented the effects of 4-aminopyridine; alpha-dendrotoxin had no effect. 4. We conclude that cerebellar basket cells contain at least three pharmacologically distinct K+ channels, which regulate transmitter release through different mechanisms. 4-Aminopyridine-sensitive, alpha-dendrotoxin-insensitive K+ channels are mainly responsible for repolarization in basket cell presynaptic terminals. K+ channels blocked by charybdotoxin and tetraethylammonium have a minor role in repolarization. alpha-Dendrotoxin-sensitive channels are not involved in shaping the axonal action potential waveform. The two last types of channels must therefore exert control of synaptic activity through a pathway unrelated to axonal action potential broadening.

  10. Intracellular recordings of action potentials by an extracellular nanoscale field-effect transistor

    Science.gov (United States)

    Duan, Xiaojie; Gao, Ruixuan; Xie, Ping; Cohen-Karni, Tzahi; Qing, Quan; Choe, Hwan Sung; Tian, Bozhi; Jiang, Xiaocheng; Lieber, Charles M.

    2012-03-01

    The ability to make electrical measurements inside cells has led to many important advances in electrophysiology. The patch clamp technique, in which a glass micropipette filled with electrolyte is inserted into a cell, offers both high signal-to-noise ratio and temporal resolution. Ideally, the micropipette should be as small as possible to increase the spatial resolution and reduce the invasiveness of the measurement, but the overall performance of the technique depends on the impedance of the interface between the micropipette and the cell interior, which limits how small the micropipette can be. Techniques that involve inserting metal or carbon microelectrodes into cells are subject to similar constraints. Field-effect transistors (FETs) can also record electric potentials inside cells, and because their performance does not depend on impedance, they can be made much smaller than micropipettes and microelectrodes. Moreover, FET arrays are better suited for multiplexed measurements. Previously, we have demonstrated FET-based intracellular recording with kinked nanowire structures, but the kink configuration and device design places limits on the probe size and the potential for multiplexing. Here, we report a new approach in which a SiO2 nanotube is synthetically integrated on top of a nanoscale FET. This nanotube penetrates the cell membrane, bringing the cell cytosol into contact with the FET, which is then able to record the intracellular transmembrane potential. Simulations show that the bandwidth of this branched intracellular nanotube FET (BIT-FET) is high enough for it to record fast action potentials even when the nanotube diameter is decreased to 3 nm, a length scale well below that accessible with other methods. Studies of cardiomyocyte cells demonstrate that when phospholipid-modified BIT-FETs are brought close to cells, the nanotubes can spontaneously penetrate the cell membrane to allow the full-amplitude intracellular action potential to be

  11. FMRP Regulates Neurotransmitter Release and Synaptic Information Transmission by Modulating Action Potential Duration via BK channels

    Science.gov (United States)

    Deng, Pan-Yue; Rotman, Ziv; Blundon, Jay A.; Cho, Yongcheol; Cui, Jianmin; Cavalli, Valeria; Zakharenko, Stanislav S.; Klyachko, Vitaly A.

    2013-01-01

    SUMMARY Loss of FMRP causes Fragile X syndrome (FXS), but the physiological functions of FMRP remain highly debatable. Here we show that FMRP regulates neurotransmitter release in CA3 pyramidal neurons by modulating action potential (AP) duration. Loss of FMRP leads to excessive AP broadening during repetitive activity, enhanced presynaptic calcium influx and elevated neurotransmitter release. The AP broadening defects caused by FMRP loss have a cell-autonomous presynaptic origin and can be acutely rescued in postnatal neurons. These presynaptic actions of FMRP are translation-independent and are mediated selectively by BK channels via interaction of FMRP with BK channel’s regulatory β4 subunits. Information-theoretical analysis demonstrates that loss of these FMRP functions causes marked dysregulation of synaptic information transmission. FMRP-dependent AP broadening is not limited to the hippocampus, but also occurs in cortical pyramidal neurons. Our results thus suggest major translation-independent presynaptic functions of FMRP that may have important implications for understanding FXS neuropathology. PMID:23439122

  12. QCD Dirac Spectrum at Finite Chemical Potential: Anomalous Effective Action, Berry Phase and Composite Fermions

    CERN Document Server

    Liu, Yizhuang

    2015-01-01

    We show that the QCD Dirac spectrum at finite chemical potential using a 2-matrix model in the spontaneously broken phase, is amenable to a generic 2-dimensional effective action on a curved eigenvalue manifold. The eigenvalues form a droplet with strong screening and non-linear plasmons. The droplet is threaded by a magnetic vortex which is at the origin of a Berry phase. The adiabatic transport in the droplet maps onto the one in the fractional quantum Hall effect, suggesting that composite fermions at half filling are Dirac particles. We use this observation to argue for two novel anomalous effects in the edge transport of composite fermions, and conversely on a novel contribution to the QCD quark condensate in a rotating frame.

  13. Effect of sampling frequency on the measurement of phase-locked action potentials.

    Directory of Open Access Journals (Sweden)

    Go eAshida

    2010-09-01

    Full Text Available Phase-locked spikes in various types of neurons encode temporal information. To quantify the degree of phase-locking, the metric called vector strength (VS has been most widely used. Since VS is derived from spike timing information, error in measurement of spike occurrence should result in errors in VS calculation. In electrophysiological experiments, the timing of an action potential is detected with finite temporal precision, which is determined by the sampling frequency. In order to evaluate the effects of the sampling frequency on the measurement of VS, we derive theoretical upper and lower bounds of VS from spikes collected with finite sampling rates. We next estimate errors in VS assuming random sampling effects, and show that our theoretical calculation agrees with data from electrophysiological recordings in vivo. Our results provide a practical guide for choosing the appropriate sampling frequency in measuring VS.

  14. Optical magnetic detection of single-neuron action potentials using quantum defects in diamond

    CERN Document Server

    Barry, J F; Schloss, J M; Glenn, D R; Song, Y; Lukin, M D; Park, H; Walsworth, R L

    2016-01-01

    A key challenge for neuroscience is noninvasive, label-free sensing of action potential (AP) dynamics in whole organisms with single-neuron resolution. Here, we present a new approach to this problem: using nitrogen-vacancy (NV) quantum defects in diamond to measure the time-dependent magnetic fields produced by single-neuron APs. Our technique has a unique combination of features: (i) it is noninvasive, as the light that probes the NV sensors stays within the biocompatible diamond chip and does not enter the organism, enabling activity monitoring over extended periods; (ii) it is label-free and should be widely applicable to most organisms; (iii) it provides high spatial and temporal resolution, allowing precise measurement of the AP waveforms and conduction velocities of individual neurons; (iv) it directly determines AP propagation direction through the inherent sensitivity of NVs to the associated AP magnetic field vector; (v) it is applicable to neurons located within optically opaque tissue or whole org...

  15. Inhomogeneity of action potential waveshape assists frequency entrainment of cardiac pacemaker cells.

    Science.gov (United States)

    Cloherty, S L; Lovell, N H; Celler, B G; Dokos, S

    2001-10-01

    In this paper, we have employed ionic models of sinoatrial node cells to investigate the synchronization of a pair of coupled cardiac pacemaker cells from central and peripheral regions of the sinoatrial node. The free-running cycle length of the cell models was perturbed using two independent techniques and the minimum coupling conductance required to achieve frequency entrainment was used to assess the relative ease with which various cell pairs achieve entrainment. The factors effecting entrainment were further investigated using single-cell models paced with an artificial biphasic coupling current. Our simulation results suggest that dissimilar cell types, those with largely different upstroke velocities entrain more easily, that is, they require less coupling conductance to achieve 1:1 frequency entrainment. We, therefore, propose that regional variation in action-potential waveshape within the sinoatrial node assists frequency synchronization in vivo.

  16. Distributed computing for membrane-based modeling of action potential propagation.

    Science.gov (United States)

    Porras, D; Rogers, J M; Smith, W M; Pollard, A E

    2000-08-01

    Action potential propagation simulations with physiologic membrane currents and macroscopic tissue dimensions are computationally expensive. We, therefore, analyzed distributed computing schemes to reduce execution time in workstation clusters by parallelizing solutions with message passing. Four schemes were considered in two-dimensional monodomain simulations with the Beeler-Reuter membrane equations. Parallel speedups measured with each scheme were compared to theoretical speedups, recognizing the relationship between speedup and code portions that executed serially. A data decomposition scheme based on total ionic current provided the best performance. Analysis of communication latencies in that scheme led to a load-balancing algorithm in which measured speedups at 89 +/- 2% and 75 +/- 8% of theoretical speedups were achieved in homogeneous and heterogeneous clusters of workstations. Speedups in this scheme with the Luo-Rudy dynamic membrane equations exceeded 3.0 with eight distributed workstations. Cluster speedups were comparable to those measured during parallel execution on a shared memory machine.

  17. A Shab potassium channel contributes to action potential broadening in peptidergic neurons.

    Science.gov (United States)

    Quattrocki, E A; Marshall, J; Kaczmarek, L K

    1994-01-01

    We have cloned the gene for a potassium channel, Aplysia Shab, that is expressed in the bag cell neurons of Aplysia. The voltage dependence and kinetics of the Aplysia Shab current in oocytes match those of IK2, one of the two delayed rectifiers in these neurons. Like IK2, but in contrast with other members of the Shab subfamily, the Aplysia Shab current inactivates within several hundred milliseconds. This inactivation occurs by a process whose properties do not match those previously described for C-type and N-type mechanisms. Neither truncation of the N-terminus nor block by tetraethylammonium alters the time course of inactivation. By incorporating the characteristics of Aplysia Shab into a computational model, we have shown how this current contributes to the normal enhancement of action potentials that occurs in the bag cell neurons at the onset of neuropeptide secretion.

  18. Sequential dissection of multiple ionic currents in single cardiac myocytes under action potential-clamp.

    Science.gov (United States)

    Banyasz, Tamas; Horvath, Balazs; Jian, Zhong; Izu, Leighton T; Chen-Izu, Ye

    2011-03-01

    The cardiac action potential (AP) is shaped by myriad ionic currents. In this study, we develop an innovative AP-clamp Sequential Dissection technique to enable the recording of multiple ionic currents in the single cell under AP-clamp. This new technique presents a significant step beyond the traditional way of recording only one current in any one cell. The ability to measure many currents in a single cell has revealed two hitherto unknown characteristics of the ionic currents in cardiac cells: coordination of currents within a cell and large variation of currents between cells. Hence, the AP-clamp Sequential Dissection method provides a unique and powerful tool for studying individual cell electrophysiology.

  19. Mechanism of Action and Clinical Potential of Fingolimod for the Treatment of Stroke

    Directory of Open Access Journals (Sweden)

    Wentao Li

    2016-08-01

    Full Text Available Fingolimod (FTY720 is an orally bio-available immunomodulatory drug currently approved by the FDA for the treatment of multiple sclerosis. Currently, there is a significant interest in the potential benefits of FTY720 on stroke outcomes. FTY720 and the sphingolipid signaling pathway it modulates has a ubiquitous presence in the central nervous system and both rodent models and pilot clinical trials seem to indicate that the drug may improve overall functional recovery in different stroke subtypes. Although the precise mechanisms behind these beneficial effects are yet unclear, there is evidence that FTY720 has a role in regulating cerebrovascular responses, blood brain barrier permeability, and cell survival in the event of cerebrovascular insult. In this article, we critically review the data obtained from the latest laboratory findings and clinical trials involving both ischemic and hemorrhagic stroke, and attempt to form a cohesive picture of FTY720’s mechanisms of action in stroke

  20. BK channels regulate spontaneous action potential rhythmicity in the suprachiasmatic nucleus.

    Directory of Open Access Journals (Sweden)

    Jack Kent

    Full Text Available BACKGROUND: Circadian ( approximately 24 hr rhythms are generated by the central pacemaker localized to the suprachiasmatic nucleus (SCN of the hypothalamus. Although the basis for intrinsic rhythmicity is generally understood to rely on transcription factors encoded by "clock genes", less is known about the daily regulation of SCN neuronal activity patterns that communicate a circadian time signal to downstream behaviors and physiological systems. Action potentials in the SCN are necessary for the circadian timing of behavior, and individual SCN neurons modulate their spontaneous firing rate (SFR over the daily cycle, suggesting that the circadian patterning of neuronal activity is necessary for normal behavioral rhythm expression. The BK K(+ channel plays an important role in suppressing spontaneous firing at night in SCN neurons. Deletion of the Kcnma1 gene, encoding the BK channel, causes degradation of circadian behavioral and physiological rhythms. METHODOLOGY/PRINCIPAL FINDINGS: To test the hypothesis that loss of robust behavioral rhythmicity in Kcnma1(-/- mice is due to the disruption of SFR rhythms in the SCN, we used multi-electrode arrays to record extracellular action potentials from acute wild-type (WT and Kcnma1(-/- slices. Patterns of activity in the SCN were tracked simultaneously for up to 3 days, and the phase, period, and synchronization of SFR rhythms were examined. Loss of BK channels increased arrhythmicity but also altered the amplitude and period of rhythmic activity. Unexpectedly, Kcnma1(-/- SCNs showed increased variability in the timing of the daily SFR peak. CONCLUSIONS/SIGNIFICANCE: These results suggest that BK channels regulate multiple aspects of the circadian patterning of neuronal activity in the SCN. In addition, these data illustrate the characteristics of a disrupted SCN rhythm downstream of clock gene-mediated timekeeping and its relationship to behavioral rhythms.

  1. Sensitivity of Cyclone Tracks to the Initial Moisture Distribution: A Moist Potential Vorticity Perspective

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    In this study, the characteristics of moist potential vorticity (MPV) in the vicinity of a surface cyclone center and their physical processes are investigated. A prognostic equation of surface absolute vorticity is then used to examine the relationship between the cyclone tracks and negative MPV (NMPV) using numerical simulations of the life cycle of an extratropical cyclone. It is shown that the MPV approach developed herein, i.e., by tracing the peak NMPV, can be used to help trace surface cyclones during their development and mature stages. Sensitivity experiments are conducted to investigate the impact of different initial moisture fields on the effectiveness of the MPV approach. It is found that the lifetime of NMPV depends mainly on the initial moisture field, the magnitude of condensational heating, and the advection of NMPV. When NMPV moves into a saturated environment at or near a cyclone center, it can trace better the evolution of the surface cyclone due to the conservative property of MPV. It is also shown that the NMPV generation is closely associated with the coupling of large potential temperature and moisture gradients as a result of frontogenesis processes. Analyses indicate that condensation, confluence and tilting play important but different roles in determining the NMPV generation. NMPV is generated mainly through the changes in the strength of baroclinicity and in the direction of the moisture gradient due to moist and/or dry air mass intrusion into the baroclinic zone.

  2. Potential Beneficiaries of the Obama Administration’s Executive Action Programs Deeply Embedded in US Society

    Directory of Open Access Journals (Sweden)

    Donald Kerwin

    2016-03-01

    Full Text Available The Obama administration has developed two broad programs to defer immigration enforcement actions against undocumented persons living in the United States: (1 Deferred Action for Parents of Americans and Lawful Permanent Residents (DAPA; and (2 Deferred Action for Childhood Arrivals (DACA. The DACA program, which began in August 2012, was expanded on November 20, 2014. DAPA and the DACA expansion (hereinafter referred to as “DACA-plus” are currently under review by the US Supreme Court and subject to an active injunction.This paper offers a statistical portrait of the intended direct beneficiaries of DAPA, DACA, and DACA-plus. It finds that potential DAPA, DACA, and DACA-plus recipients are deeply embedded in US society, with high employment rates, extensive US family ties, long tenure, and substantial rates of English-language proficiency. The paper also notes various groups that would benefit indirectly from the full implementation of DAPA and DACA or, conversely, would suffer from the removal of potential beneficiaries of these programs. For example, all those who would rely on the retirement programs of the US government will benefit from the high employment rates and relative youth of the DACA population, while many US citizens who rely on the income of a DAPA-eligible parent would fall into poverty or extreme poverty should that parent be removed from the United States.This paper offers an analysis of potential DAPA and DACA beneficiaries. In an earlier study, the authors made the case for immigration reform based on long-term trends related to the US undocumented population, including potential DAPA and DACA beneficiaries (Warren and Kerwin 2015. By contrast, this paper details the degree to which these populations have become embedded in US society. It also compares persons eligible for the original DACA program with those eligible for DACA-plus.As stated, the great majority of potential DAPA and DACA recipients enjoy strong family

  3. Modulation of hERG potassium channel gating normalizes action potential duration prolonged by dysfunctional KCNQ1 potassium channel

    Science.gov (United States)

    Zhang, Hongkang; Zou, Beiyan; Yu, Haibo; Moretti, Alessandra; Wang, Xiaoying; Yan, Wei; Babcock, Joseph J.; Bellin, Milena; McManus, Owen B.; Tomaselli, Gordon; Nan, Fajun; Laugwitz, Karl-Ludwig; Li, Min

    2012-01-01

    Long QT syndrome (LQTS) is a genetic disease characterized by a prolonged QT interval in an electrocardiogram (ECG), leading to higher risk of sudden cardiac death. Among the 12 identified genes causal to heritable LQTS, ∼90% of affected individuals harbor mutations in either KCNQ1 or human ether-a-go-go related genes (hERG), which encode two repolarizing potassium currents known as IKs and IKr. The ability to quantitatively assess contributions of different current components is therefore important for investigating disease phenotypes and testing effectiveness of pharmacological modulation. Here we report a quantitative analysis by simulating cardiac action potentials of cultured human cardiomyocytes to match the experimental waveforms of both healthy control and LQT syndrome type 1 (LQT1) action potentials. The quantitative evaluation suggests that elevation of IKr by reducing voltage sensitivity of inactivation, not via slowing of deactivation, could more effectively restore normal QT duration if IKs is reduced. Using a unique specific chemical activator for IKr that has a primary effect of causing a right shift of V1/2 for inactivation, we then examined the duration changes of autonomous action potentials from differentiated human cardiomyocytes. Indeed, this activator causes dose-dependent shortening of the action potential durations and is able to normalize action potentials of cells of patients with LQT1. In contrast, an IKr chemical activator of primary effects in slowing channel deactivation was not effective in modulating action potential durations. Our studies provide both the theoretical basis and experimental support for compensatory normalization of action potential duration by a pharmacological agent. PMID:22745159

  4. Optophysiological approach to resolve neuronal action potentials with high spatial and temporal resolution in cultured neurons

    Directory of Open Access Journals (Sweden)

    Stephane ePages

    2011-10-01

    Full Text Available Cell to cell communication in the central nervous system is encoded into transient and local membrane potential changes (ΔVm. Deciphering the rules that govern synaptic transmission and plasticity entails to be able to perform Vm recordings throughout the entire neuronal arborization. Classical electrophysiology is, in most cases, not able to do so within small and fragile neuronal subcompartments. Thus, optical techniques based on the use of fluorescent voltage-sensitive dyes (VSDs have been developed. However, reporting spontaneous or small ΔVm from neuronal ramifications has been challenging, in part due to the limited sensitivity and phototoxicity of VSD-based optical measurements. Here we demonstrate the use of water soluble VSD, ANNINE-6plus, with laser scanning microscopy to optically record ΔVm in cultured neurons. We show that the sensitivity (> 10 % of fluorescence change for 100 mV depolarization and time response (submillisecond of the dye allows the robust detection of action potentials (APs even without averaging, allowing the measurement of spontaneous neuronal firing patterns. In addition, we show that back-propagating APs can be recorded, along distinct dendritic sites and within dendritic spines. Importantly, our approach does not induce any detectable phototoxic effect on cultured neurons. This optophysiological approach provides a simple, minimally invasive and versatile optical method to measure electrical activity in cultured neurons with high temporal (ms resolution and high spatial (µm resolution.

  5. Phase relationship between alternans of early and late phases of ventricular action potentials.

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    Linyuan eJing

    2012-06-01

    Full Text Available Background: Alternans of early phase and of duration of action potential (AP critically affect dispersion of refractoriness through their influence on conduction and repolarization. We investigated the phase relationship between the two alternans and its effect on conduction. Methods and Results: Transmembrane potentials recorded from ventricles of 8 swine and 3 canines during paced activation intervals of ≤ 300 ms were used to quantify alternans of maximum rate of depolarization (|dv/dt|max and of APD. Incidence of APD alternans was 62% and 76% in swine and canines. Alternans of APD was frequently accompanied with alternans of |dv/dt|max. Of these, 4 and 26 % were out of phase in swine and canines, i.e. low |dv/dt|max preceded long APD. Computer simulations show that out of phase alternans attenuate variation of wavelength and thus minimize formation of spatially discordant alternans. Conclusions: The spontaneous switching of phase relationship between alternans of depolarization and repolarization suggests that mechanisms underlying these alternans may operate independent of each other. The phase between these alternans can critically impact spatial dispersion of refractoriness and thus stability of conduction, with the in phase relation promoting transition from concord to discord while out of phase preventing formation of discord.

  6. Zinc-related actions of sublethal levels of benzalkonium chloride: Potentiation of benzalkonium cytotoxicity by zinc.

    Science.gov (United States)

    Mitani, Tsuyoshi; Elmarhomy, Ahmed Ibrahim Elhossany; Dulamjav, Luvsandorj; Anu, Enkhtumur; Saitoh, Shohei; Ishida, Shiro; Oyama, Yasuo

    2017-04-25

    Benzalkonium chloride (BZK) is a common preservative used in pharmaceutical and personal care products. ZnCl2 was recently reported to significantly potentiate the cytotoxicity of some biocidal compounds. In the present study, therefore, we compared the cytotoxic potency of BZK and then further studied the Zn(2+)-related actions of the most cytotoxic agent among BZK, using flow cytometric techniques with appropriate fluorescent probes in rat thymocytes. Cytotoxicity of benzylcetyldimethylammonium (BZK-C16) was more potent that those of benzyldodecyldimethylammonium and benzyldimethyltetradecylammonium. ZnCl2 (1-10 μM) significantly potentiated the cytotoxicity of BZK-C16 at a sublethal concentration (1 μM). The co-treatment of cells with 3 μM ZnCl2 and 1 μM BZK-C16 increased the population of both living cells with phosphatidylserine exposed on membrane surfaces and dead cells. BZK-C16 at 0.3-1.0 μM elevated intracellular Zn(2+) levels by increasing Zn(2+) influx, and augmented the cytotoxicity of 100 μM H2O2. Zn(2+) is concluded to facilitate the toxicity of BZK. We suggest that the toxicity of BZK is determined after taking extracellular (plasma) and/or environmental Zn(2+) levels into account.

  7. Optimisation of Ionic Models to Fit Tissue Action Potentials: Application to 3D Atrial Modelling

    Directory of Open Access Journals (Sweden)

    Amr Al Abed

    2013-01-01

    Full Text Available A 3D model of atrial electrical activity has been developed with spatially heterogeneous electrophysiological properties. The atrial geometry, reconstructed from the male Visible Human dataset, included gross anatomical features such as the central and peripheral sinoatrial node (SAN, intra-atrial connections, pulmonary veins, inferior and superior vena cava, and the coronary sinus. Membrane potentials of myocytes from spontaneously active or electrically paced in vitro rabbit cardiac tissue preparations were recorded using intracellular glass microelectrodes. Action potentials of central and peripheral SAN, right and left atrial, and pulmonary vein myocytes were each fitted using a generic ionic model having three phenomenological ionic current components: one time-dependent inward, one time-dependent outward, and one leakage current. To bridge the gap between the single-cell ionic models and the gross electrical behaviour of the 3D whole-atrial model, a simplified 2D tissue disc with heterogeneous regions was optimised to arrive at parameters for each cell type under electrotonic load. Parameters were then incorporated into the 3D atrial model, which as a result exhibited a spontaneously active SAN able to rhythmically excite the atria. The tissue-based optimisation of ionic models and the modelling process outlined are generic and applicable to image-based computer reconstruction and simulation of excitable tissue.

  8. Calcium Transients Closely Reflect Prolonged Action Potentials in iPSC Models of Inherited Cardiac Arrhythmia

    Directory of Open Access Journals (Sweden)

    C. Ian Spencer

    2014-08-01

    Full Text Available Long-QT syndrome mutations can cause syncope and sudden death by prolonging the cardiac action potential (AP. Ion channels affected by mutations are various, and the influences of cellular calcium cycling on LQTS cardiac events are unknown. To better understand LQTS arrhythmias, we performed current-clamp and intracellular calcium ([Ca2+]i measurements on cardiomyocytes differentiated from patient-derived induced pluripotent stem cells (iPS-CM. In myocytes carrying an LQT2 mutation (HERG-A422T, APs and [Ca2+]i transients were prolonged in parallel. APs were abbreviated by nifedipine exposure and further lengthened upon releasing intracellularly stored Ca2+. Validating this model, control iPS-CM treated with HERG-blocking drugs recapitulated the LQT2 phenotype. In LQT3 iPS-CM, expressing NaV1.5-N406K, APs and [Ca2+]i transients were markedly prolonged. AP prolongation was sensitive to tetrodotoxin and to inhibiting Na+-Ca2+ exchange. These results suggest that LQTS mutations act partly on cytosolic Ca2+ cycling, potentially providing a basis for functionally targeted interventions regardless of the specific mutation site.

  9. Different mechanisms underlying the repolarization of narrow and wide action potentials in pyramidal cells and interneurons of cat motor cortex.

    Science.gov (United States)

    Chen, W; Zhang, J J; Hu, G Y; Wu, C P

    1996-07-01

    Two different types of action potentials were observed among the pyramidal cells and interneurons in cat motor cortex: the narrow action potentials and the wide action potentials. These two types of action potentials had similar rising phases (528.8 +/- 77.0 vs 553.1 +/- 71.8 mV/ms for the maximal rising rate), but differed in spike duration (0.44 +/- 0.09 vs 1.40 +/- 0.39 ms) and amplitude (57.31 +/- 8.22 vs 72.52 +/- 8.31 mV), implying that the ionic currents contributing to repolarization of these action potentials are different. Here we address this issue by pharmacological manipulation and using voltage-clamp technique in slices of cat motor cortex. Raising extracellular K+ concentration (from 3 mM to 10 mM), applying a low dose of 4-aminopyridine (2-200 microM) or administering a low concentration of tetraethylammonium (0.2-1.0 mM) each not only broadened the narrow action potentials, but also increased their amplitudes. In contrast, high K+ medium or low dose of tetraethylammonium only broadened the wide action potentials, leaving their amplitudes unaffected, and 4-aminopyridine had only a slight broadening effect on the wide spikes. These results implied that K+ currents were involved in the repolarization of both types of action potentials, and that the K+ currents in the narrow action potentials seemed to activate much earlier than those in the wide spikes. This early activated K+ current may counteract the rapid sodium current, yielding the extremely brief duration and small amplitude of the narrow spikes. The sensitivity of the narrow spikes to 4-aminopyridine may not be mainly attributed to blockade of the classical A current (IA), because depolarizing the membrane potential to inactivate IA did not reproduce the effects of 4-aminopyridine. Blockade of Ca2+ influx slowed the last two-thirds repolarization of the wide action potentials. On the contrary, the narrow action potentials were not affected by Ca(2+)-current blockers, but if they were first

  10. Potential involvement of serotonergic signaling in ketamine's antidepressant actions: A critical review.

    Science.gov (United States)

    du Jardin, Kristian Gaarn; Müller, Heidi Kaastrup; Elfving, Betina; Dale, Elena; Wegener, Gregers; Sanchez, Connie

    2016-11-03

    A single i.v. infusion of ketamine, classified as an N-methyl-d-aspartate (NMDA) receptor antagonist, may alleviate depressive symptoms within hours of administration in treatment resistant depressed patients, and the antidepressant effect may last for several weeks. These unique therapeutic properties have prompted researchers to explore the mechanisms mediating the antidepressant effects of ketamine, but despite many efforts, no consensus on its antidepressant mechanism of action has been reached. Recent preclinical reports have associated the neurotransmitter serotonin (5-hydroxytryptamine; 5-HT) with the antidepressant-like action of ketamine. Here, we review the current evidence for a serotonergic role in ketamine's antidepressant effects. The pharmacological profile of ketamine may include equipotent activity on several non-NMDA targets, and the current hypotheses for the mechanisms responsible for ketamine's antidepressant activity do not appear to preclude the possibility that non-glutamate neurotransmitters are involved in the antidepressant effects. At multiple levels, the serotonergic and glutamatergic systems interact, and such crosstalk could support the notion that changes in serotonergic neurotransmission may impact ketamine's antidepressant potential. In line with these prospects, ketamine may increase 5-HT levels in the prefrontal cortex of rats, plausibly via hippocampal NMDA receptor inhibition and activation of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors. In addition, a number of preclinical studies suggest that the antidepressant-like effects of ketamine may depend on endogenous activation of 5-HT receptors. Recent imaging and behavioral data predominantly support a role for 5-HT1A or 5-HT1B receptors, but the full range of 5-HT receptors has currently not been systematically investigated in this context. Furthermore, the nature of any 5-HT dependent mechanism in ketamine's antidepressant effect is currently not

  11. Averaging methods for extracting representative waveforms from motor unit action potential trains.

    Science.gov (United States)

    Malanda, Armando; Navallas, Javier; Rodriguez-Falces, Javier; Rodriguez-Carreño, Ignacio; Gila, Luis

    2015-08-01

    In the context of quantitative electromyography (EMG), it is of major interest to obtain a waveform that faithfully represents the set of potentials that constitute a motor unit action potential (MUAP) train. From this waveform, various parameters can be determined in order to characterize the MUAP for diagnostic analysis. The aim of this work was to conduct a thorough, in-depth review, evaluation and comparison of state-of-the-art methods for composing waveforms representative of MUAP trains. We evaluated nine averaging methods: Ensemble (EA), Median (MA), Weighted (WA), Five-closest (FCA), MultiMUP (MMA), Split-sweep median (SSMA), Sorted (SA), Trimmed (TA) and Robust (RA) in terms of three general-purpose signal processing figures of merit (SPMF) and seven clinically-used MUAP waveform parameters (MWP). The convergence rate of the methods was assessed as the number of potentials per MUAP train (NPM) required to reach a level of performance that was not significantly improved by increasing this number. Test material comprised 78 MUAP trains obtained from the tibialis anterioris of seven healthy subjects. Error measurements related to all SPMF and MWP parameters except MUAP amplitude descended asymptotically with increasing NPM for all methods. MUAP amplitude showed a consistent bias (around 4% for EA and SA and 1-2% for the rest). MA, TA and SSMA had the lowest SPMF and MWP error figures. Therefore, these methods most accurately preserve and represent MUAP physiological information of utility in clinical medical practice. The other methods, particularly WA, performed noticeably worse. Convergence rate was similar for all methods, with NPM values averaged among the nine methods, which ranged from 10 to 40, depending on the waveform parameter evaluated.

  12. Surface electrocardiogram and action potential in mice lacking urea transporter UT-B

    Institute of Scientific and Technical Information of China (English)

    MENG Yan; ZHAO ChunYan; ZHANG XueXin; ZHAO HuaShan; GUO LiRong; Lü Bin; ZHAO XueJian; YANG BaoXue

    2009-01-01

    UT-B is a urea transporter protein expressed in the kidney and in many non-renal tissues including erythrocytes, brain, heart, bladder and the testis. The objective of this study was to determine the phenotype of UT-B deletion in the heart. UT-B expression in the heart was studied in wild-type mice vs UT-B null mice by utilizing RT-PCR and Western blot. A surface electrocardiogram (ECG) recording (lead Ⅱ) was measured in wild-type mice and UT-B null mice at the ages of 6, 16 and 52 weeks. For the action potential recording, the ventricular myocytes of 16 w mice were isolated and recorded by float-ing microelectrode method. The sodium current was recorded by the patch clamp technique. RT-PCR and Western blot showed the UT-B expression in the heart of wild-type mice. No UT-B transcript and protein was found in UT-B null mice. The ECG recording showed that the P-R interval was significantly prolonged in UT-B null mice ((43.5±4.2), (45.5±6.9) and (43.8±7.6) ms at ages of 6, 16 and 52 weeks) vs wild-type mice ((38.6±2.9), (38.7±5.6) and (38.2±7.3) ms, P<0.05). The atrial ventricular heart block type Ⅱ and Ⅲ only appeared in the aging UT-B null mice (52 w old). The amplitude of action potential and Vmax decreased significantly in UT-B null mice ((92.17±10.56) and (101.89±9.54) mV/s) vs those in wild-type mice (vs (110.51±10.38) and (109.53±10.64) mV/s, P<0.05). The action potential duration at 50% and 90% (APD50 and APD90) was significantly prolonged in UT-B null mice ((123.83±11.17) and (195.43±16.41) ms) vs that in wild-type mice ((108.27±10.85) and (171.00±15.53) ms, P<0.05). The maximal sodium current decreased significantly in UT-B null mice (-8.80±0.92) nA vs that in wild-type mice ((-5.98±1.07) nA, P<0.05). These results provide the first evidence that UT-B deletion causes progressive heart block in mice.

  13. Surface electrocardiogram and action potential in mice lacking urea transporter UT-B

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    UT-B is a urea transporter protein expressed in the kidney and in many non-renal tissues including erythrocytes, brain, heart, bladder and the testis. The objective of this study was to determine the phenotype of UT-B deletion in the heart. UT-B expression in the heart was studied in wild-type mice vs UT-B null mice by utilizing RT-PCR and Western blot. A surface electrocardiogram (ECG) recording (lead II) was measured in wild-type mice and UT-B null mice at the ages of 6, 16 and 52 weeks. For the action potential recording, the ventricular myocytes of 16 w mice were isolated and recorded by floating microelectrode method. The sodium current was recorded by the patch clamp technique. RT-PCR and Western blot showed the UT-B expression in the heart of wild-type mice. No UT-B transcript and protein was found in UT-B null mice. The ECG recording showed that the P-R interval was significantly prolonged in UT-B null mice ((43.5 ± 4.2), (45.5 ± 6.9) and (43.8 ± 7.6) ms at ages of 6, 16 and 52 weeks) vs wild-type mice ((38.6 ± 2.9), (38.7 ± 5.6) and (38.2 ± 7.3) ms, P<0.05). The atrial ventricular heart block type II and III only appeared in the aging UT-B null mice (52 w old). The amplitude of action potential and Vmax decreased significantly in UT-B null mice ((92.17 ± 10.56) and (101.89 ± 9.54) mV/s) vs those in wild-type mice (vs (110.51 ± 10.38) and (109.53 ± 10.64) mV/s, P<0.05). The action potential duration at 50% and 90% (APD50 and APD90) was significantly prolonged in UT-B null mice ((123.83 ± 11.17) and (195.43 ± 16.41) ms) vs that in wild-type mice ((108.27 ± 10.85) and (171.00 ± 15.53) ms, P<0.05). The maximal sodium current decreased significantly in UT-B null mice (-8.80 ± 0.92) nA vs that in wild-type mice ((-5.98 ± 1.07) nA, P<0.05). These results provide the first evidence that UT-B deletion causes progressive heart block in mice.

  14. CLINICAL AND EXPERIMENTAL STUDIES OF LARGE AMPLITUDE ACTION POTENTIAL OF THE SUFFERED FACIAL MUSCLES IN INTRATEMPORAL FACIAL NERVE PARALYSIS

    Institute of Scientific and Technical Information of China (English)

    任重; 惠莲

    1999-01-01

    Objctive. To testify the phenomenon that large amplitude action potential appears at the early stage oil facial paralysis, and to search for the mechanism through clinical and experimental studies. Patients(aninmls) and methods. The action potentials of the orbicular ocular and oral museles were recorded in 34 normal persons by electromyogram instrtiments. The normal range of amplitude percentage was found out according to the normal distribution, One hundred patients with facial paralysis were also studied. The action potentials of facial muscles were recorded ia 17 guinea pigs before and after the facial nerve was comp~ and the facial nerve was examined under electromicroscope before and after the compression.Results. The amplitude percentage of the suffered side to the healthy side was more than 153 percent in 6 of the 100 patients. Large amplitude action potential occured in 35 per cent guinea pigs which were performed the experiment of facial nerve compression. Electromicroscopic examination revealed separation of the lammae of the facial nerve's myelin sheath in the guinea pigs which exhibited large amplitude action potential Conclusion. The facial nerve exhibited a temporary over-excitability at the early stage of facial nerve injury in scane patients and guinea pigs. If the injury was limited in the myelin sheath, the prognods was relatively good.

  15. CLINICAL AND EXPERIMENTAL STUDIES OF LARGE AMPLITUDE ACTION POTENTIAL OF THE SUFFERED FACIAL MUSCLES IN INTRATEMPORAL FACIAL NERVE PARALYSIS

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Ojective. To testify the phenomenon that large amplitude action potential appears at the early stage of facial paralysis, and to search for the mechanism through clinical and experimental studies. Patients(animals) and methods. The action potentials of the orbicular ocular and oral muscles were recorded in 34 normal persons by electromyogram instruments. The normal range of amplitude percentage was found out according to he normal distribution. One hundred patients with facial paralysis were also studied. The action potentials of facial muscles were recorded in 17 guinea pigs before and after the facial nerve was compressed and the facial nerve was examined under electromicroscope before and after the compression.Results. The amplitude percentage of the suffered ide to the healthy side was more than 153 percent in 6 of the 100 patients. Lare amplitude action potential ocured in 35 per cent guinea pigs which were performed the experiment of facial nrve compression. Electromicroscopic examination revealed separation of the lammae of the facial nerve's myelin sheath in the guinea pigs which exhibited large amplitude action potential.Conclusion. The facial nerve exhibited a temporary over-exciability at the early stage of facial nerve injury in some patients and guinea pigs. If the injury waslimited in the myelin sheath, te prognosis was relatively good.

  16. An experimental study on the physical properties of the cupula. Effect of cupular sectioning on the ampullary nerve action potential.

    Science.gov (United States)

    Suzuki, M; Harada, Y; Kishimoto, A

    1985-01-01

    The frog posterior semicircular canal (PSC) was isolated and a part of the ampullary wall was cut to allow removal of the cupula from the crista. The cupula was replaced on the crista and the PSC ampullary action potential was recorded. The cupula was again removed and was sectioned in half, either in the plane vertical to the crista (vertical sectioning), or in the plane parallel to the crista (horizontal sectioning). The sectioned half of the cupula was then replaced on the crista. The action potentials after replacement of the vertical or horizontal segments of the cupula were compared to those achieved when the entire cupula was replaced. After vertical sectioning, the action potentials were significantly reduced; they were 50.3% of the completely replaced cupula when a small stimulus was used and 79.1% when a large stimulus was used. A reduced attachment surface between the cupular base and the crista is possibly responsible for the decreased action potential in the vertically sectioned specimen. After horizontal sectioning, the action potentials were 64.5% for the small stimulus and 108.2% for the large stimulus. These results indicate that elicited responses are related to the height of the cupula and the deflection angle. This further suggests that the movement of the cupula is represented by that of the elastic system.

  17. Action potential duration heterogeneity of cardiac tissue can be evaluated from cell properties using Gaussian Green's function approach.

    Directory of Open Access Journals (Sweden)

    Arne Defauw

    Full Text Available Action potential duration (APD heterogeneity of cardiac tissue is one of the most important factors underlying initiation of deadly cardiac arrhythmias. In many cases such heterogeneity can be measured at tissue level only, while it originates from differences between the individual cardiac cells. The extent of heterogeneity at tissue and single cell level can differ substantially and in many cases it is important to know the relation between them. Here we study effects from cell coupling on APD heterogeneity in cardiac tissue in numerical simulations using the ionic TP06 model for human cardiac tissue. We show that the effect of cell coupling on APD heterogeneity can be described mathematically using a Gaussian Green's function approach. This relates the problem of electrotonic interactions to a wide range of classical problems in physics, chemistry and biology, for which robust methods exist. We show that, both for determining effects of tissue heterogeneity from cell heterogeneity (forward problem as well as for determining cell properties from tissue level measurements (inverse problem, this approach is promising. We illustrate the solution of the forward and inverse problem on several examples of 1D and 2D systems.

  18. Surface electrocardiogram and action potential in mice lacking urea transporter UT-B.

    Science.gov (United States)

    Meng, Yan; Zhao, Chunyan; Zhang, Xuexin; Zhao, Huashan; Guo, Lirong; Lü, Bin; Zhao, Xuejian; Yang, Baoxue

    2009-05-01

    UT-B is a urea transporter protein expressed in the kidney and in many non-renal tissues including erythrocytes, brain, heart, bladder and the testis. The objective of this study was to determine the phenotype of UT-B deletion in the heart. UT-B expression in the heart was studied in wild-type mice vs UT-B null mice by utilizing RT-PCR and Western blot. A surface electrocardiogram (ECG) recording (lead II) was measured in wild-type mice and UT-B null mice at the ages of 6, 16 and 52 weeks. For the action potential recording, the ventricular myocytes of 16 w mice were isolated and recorded by floating microelectrode method. The sodium current was recorded by the patch clamp technique. RT-PCR and Western blot showed the UT-B expression in the heart of wild-type mice. No UT-B transcript and protein was found in UT-B null mice. The ECG recording showed that the P-R interval was significantly prolonged in UT-B null mice ((43.5 +/- 4.2), (45.5 +/- 6.9) and (43.8 +/- 7.6) ms at ages of 6, 16 and 52 weeks) vs wild-type mice ((38.6 +/- 2.9), (38.7 +/- 5.6) and (38.2 +/- 7.3) ms, PUT-B null mice (52 w old). The amplitude of action potential and V (max) decreased significantly in UT-B null mice ((92.17 +/- 10.56) and (101.89 +/- 9.54) mV/s) vs those in wild-type mice (vs (110.51 +/- 10.38) and (109.53 +/- 10.64) mV/s, PUT-B null mice ((123.83 +/- 11.17) and (195.43 +/- 16.41) ms) vs that in wild-type mice ((108.27 +/- 10.85) and (171.00 +/- 15.53) ms, PUT-B null mice (-8.80 +/- 0.92) nA vs that in wild-type mice ((-5.98 +/- 1.07) nA, PUT-B deletion causes progressive heart block in mice.

  19. Potential application of LIBS to NNSA next generation safeguards initiative (NGSI)

    Energy Technology Data Exchange (ETDEWEB)

    Barefield Ii, James E [Los Alamos National Laboratory; Clegg, Samuel M [Los Alamos National Laboratory; Veirs, Douglas K [Los Alamos National Laboratory; Browne, Mike [Los Alamos National Laboratory; Lopez, Leon [Los Alamos National Laboratory; Martinez, Ron [Los Alamos National Laboratory; Le, Loan [Los Alamos National Laboratory; Lamontagne, Stephen A [DOE/NNSA/NA241; Veal, Kevin [NN/ADTR

    2009-01-01

    In a climate in which states and nations have been and perhaps currently are involved in the prol iferation of nuclear materials and technologies, advanced methodologies and improvements in current measurement techniques are needed to combat new threats and increased levels of sophistication. The Department of Energy through the National Nuclear Security Administration (NNSA) has undertaken a broad review of International Safeguards. The conclusion from that review was that a comprehensive initiative to revitalize international safeguards technology and the human resource base was urgently needed to keep pace with demands and increasingly sophisticated emerging safeguards challenges. To address these challenges, NNSA launched the Next Generation Safeguards Initiative (NGSI) to develop policies, concepts, technologies, expertise, and infrastructure necessary to sustain the international safeguards system as its mission evolves for the next 25 years. NGSI is designed to revitalize and strengthen the U.S. safeguards technical base, recognizing that without a robust program the United States of America will not be in a position to exercise leadership or provide the necessary support to the IAEA (International Atomic Energy Agency). International safeguards as administrated by the IAEA are the primary vehicle for verifying compliance with the peaceful use and nonproliferation of nuclear materials and technologies. Laser Induced Breakdown Spectroscopy or LIBS has the potential to support the goals of NGSI as follows: by providing (1) automated analysis in complex nuclear processing or reprocessing facilities in real-time or near real-time without sample preparation or removal, (2) isotopic and important elemental ratio (Cm/Pu, Cm/U, ... etc) analysis, and (3) centralized remote control, process monitoring, and analysis of nuclear materials in nuclear facilities at multiple locations within the facility. Potential application of LIBS to international safeguards as

  20. SLAM family predicting the initiation potential of human acute lymphoblastic leukemia in NOD/SCID mice

    Institute of Scientific and Technical Information of China (English)

    WANG Na; ZHOU Jian-feng; HUANG Liang; XIAO Fei; LIU Jin-ping; WANG Di; GENG Zhe; WANG Jin; MA Shu-yan; SHU Li-li; CHEN Tai-ping

    2011-01-01

    Background The SLAM family recently has been reported to show an important biological role in lymphocyte development and immunological function, and it is efficient to highly purify hematopoietic stem cells using a simple combination of SLAM family members. To elucidate the presence of this family on acute lymphoblastic leukemia (ALL),as well as its relationship with the leukemia-initiating potential, we analyzed the expression pattern of this family members on human ALL progenitor cells, combined with serial xenotransplantation assay.Methods Expression analysis was carried out by flow cytometry. We combined the expression pattern of human CD150,CD244 and CD48 with serial xenotransplantation of B-ALL progenitor cells to indicate their relationship.Results CD48 and CD244 were expressed on most B-ALL progenitor cells, the percentage being (93.08±6.46)% and (63.37±29.31)%, respectively. Interestingly, the proportion of CD150+ cells declined obviously in engrafted cases ((24.94±7.32)%) compared with non-engrafted cases ((77.54±5.93)%, P <0.01), which indicated that only blast cells with low percentage of CD150+ population were able to reconstitute leukemia into primary, secondary and tertiary NOD/SCID mice.Conclusions SLAM family members are present on B-ALL progenitor cells and the leukemia-initiating potential of leukemic blasts is correlated negatively with the proportion of CD150+ cells, the percentage of which can serve as a useful predictor for engraftment success of B-ALL to immune deficient mice.

  1. Modification of surface layers of copper under the action of the volumetric discharge initiated by an avalanche electron beam in nitrogen and CO2 at atmospheric pressure

    Science.gov (United States)

    Shulepov, M. A.; Akhmadeev, Yu. Kh.; Tarasenko, V. F.; Kolubaeva, Yu. A.; Krysina, O. V.; Kostyrya, I. D.

    2011-05-01

    The results of experimental investigations of the action of the volumetric discharge initiated by an avalanche electron beam on the surface of copper specimens are presented. The volumetric (diffuse) discharge in nitrogen and CO2 at atmospheric pressure was initiated by applying high voltage pulses of nanosecond duration to a tubular foil cathode. It has been found that the treatment of a copper surface by this type of discharge increases the hardness of the surface layer due to oxidation.

  2. Role of calcium stores and membrane voltage in the generation of slow wave action potentials in guinea-pig gastric pylorus.

    Science.gov (United States)

    van Helden, D F; Imtiaz, M S; Nurgaliyeva, K; von der Weid, P; Dosen, P J

    2000-04-01

    1. Intracellular recordings made in single bundle strips of a visceral smooth muscle revealed rhythmic spontaneous membrane depolarizations termed slow waves (SWs). These exhibited 'pacemaker' and 'regenerative' components composed of summations of more elementary events termed spontaneous transient depolarizations (STDs). 2. STDs and SWs persisted in the presence of tetrodotoxin, nifedipine and ryanodine, and upon brief exposure to Ca2+-free Cd2+-containing solutions; they were enhanced by ACh and blocked by BAPTA AM, cyclopiazonic acid and caffeine. 3. SWs were also inhibited in heparin-loaded strips. SWs were observed over a wide range of membrane potentials (e.g. -80 to -45 mV) with increased frequencies at more depolarized potentials. 4. Regular spontaneous SW activity in this preparation began after 1-3 h superfusion of the tissue with physiological saline following the dissection procedure. Membrane depolarization applied before the onset of this activity induced bursts of STD-like events (termed the 'initial' response) which, when larger than threshold levels initiated regenerative responses. The combined initial-regenerative waveform was termed the SW-like action potential. 5. Voltage-induced responses exhibited large variable latencies (typical range 0.3-4 s), refractory periods of approximately 11 s and a pharmacology that was indistinguishable from those of STDs and spontaneous SWs. 6. The data indicate that SWs arise through more elementary inositol 1,4,5-trisphosphate (IP3) receptor-induced Ca2+ release events which rhythmically synchronize to trigger regenerative Ca2+ release and induce inward current across the plasmalemma. The finding that action potentials, which were indistinguishable from SWs, could be evoked by depolarization suggests that membrane potential modulates IP3 production. Voltage feedback on intracellular IP3-sensitive Ca2+ release is likely to have a major influence on the generation and propagation of SWs.

  3. Action potential repolarization and a fast after-hyperpolarization in rat hippocampal pyramidal cells.

    Science.gov (United States)

    Storm, J F

    1987-04-01

    1. The repolarization of the action potential, and a fast after-hyperpolarization (a.h.p.) were studied in CA1 pyramidal cells (n = 76) in rat hippocampal slices (28-37 degrees C). Single spikes were elicited by brief (1-3 ms) current pulses, at membrane potentials close to rest (-60 to -70 mV). 2. Each action potential was followed by four after-potentials: (a) the fast a.h.p., lasting 2-5 ms; (b) an after-depolarization; (c) a medium a.h.p., (50-100 ms); and (d) a slow a.h.p. (1-2 s). Both the fast a.h.p. and the slow a.h.p. (but not the medium a.h.p.) were inhibited by Ca2+-free medium or Ca2+-channel blockers (Co2+, Mn2+ or Cd2+); but tetraethylammonium (TEA; 0.5-2 nM) blocked only the fast a.h.p., and noradrenaline (2-5 microM) only the slow a.h.p. This suggests that two Ca2+-activated K+ currents were involved: a fast, TEA-sensitive one (IC) underlying the fast a.h.p., and a slow noradrenaline-sensitive one (IAHP) underlying the slow a.h.p. 3. Like the fast a.h.p., spike repolarization seems to depend on a Ca2+-dependent K+ current of the fast, TEA-sensitive kind (IC). The repolarization was slowed by Ca2+-free medium, Co2+, Mn2+, Cd2+, or TEA, but not by noradrenaline. Charybdotoxin (CTX; 30 nM), a scorpion toxin which blocks the large-conductance Ca2+-activated K+ channel in muscle, had a similar effect to TEA. The effects of TEA and Cd2+ (or Mn2+) showed mutual occlusion. Raising the external K+ concentration reduced the fast a.h.p. and slowed the spike repolarization, whereas Cl- loading of the cell was ineffective. 4. The transient K+ current, IA, seems also to contribute to spike repolarization, because: (a) 4-aminopyridine (4-AP; 0.1 mM), which blocks IA, slowed the spike repolarization; (b) depolarizing pre-pulses, which inactivate IA, had a similar effect; (c) hyperpolarizing pre-pulses speeded up the spike repolarization; (d) the effects of 4-AP and pre-pulses persisted during Ca2+ blockade (like IA); and (e) depolarizing pre-pulses reduced the

  4. Sensitivity analysis of potential events affecting the double-shell tank system and fallback actions

    Energy Technology Data Exchange (ETDEWEB)

    Knutson, B.J.

    1996-09-27

    Sensitivity analyses were performed for fall-back positions (i.e., management actions) to accommodate potential off-normal and programmatic change events overlaid on the waste volume projections and their uncertainties. These sensitivity analyses allowed determining and ranking tank system high-risk parameters and fall- back positions that will accommodate the respective impacts. This quantification of tank system impacts shows periods where tank capacity is sensitive to certain variables that must be carefully managed and/or evaluated. Identifying these sensitive variables and quantifying their impact will allow decision makers to prepare fall-back positions and focus available resources on the highest impact parameters where technical data are needed to reduce waste projection uncertainties. For noncomplexed waste, the period of capacity vulnerability occurs during the years of single-shell tank (SST) retrieval (after approximately 2009) due to the sensitivity to several variables. Ranked by importance these variables include the pretreatment rate and 200-East SST solids transfer volume. For complexed waste, the period of capacity vulnerability occurs during the period after approximately 2005 due to the sensitivity to several variables. Ranked by importance these variables include the pretreatment rate. 200-East SST solids transfer volume. complexed waste reduction factor using evaporation, and 200-west saltwell liquid porosity.

  5. Direction-selective circuitry in rat retina develops independently of GABAergic, cholinergic and action potential activity.

    Directory of Open Access Journals (Sweden)

    Le Sun

    Full Text Available The ON-OFF direction selective ganglion cells (DSGCs in the mammalian retina code image motion by responding much more strongly to movement in one direction. They do so by receiving inhibitory inputs selectively from a particular sector of processes of the overlapping starburst amacrine cells, a type of retinal interneuron. The mechanisms of establishment and regulation of this selective connection are unknown. Here, we report that in the rat retina, the morphology, physiology of the ON-OFF DSGCs and the circuitry for coding motion directions develop normally with pharmacological blockade of GABAergic, cholinergic activity and/or action potentials for over two weeks from birth. With recent results demonstrating light independent formation of the retinal DS circuitry, our results strongly suggest the formation of the circuitry, i.e., the connections between the second and third order neurons in the visual system, can be genetically programmed, although emergence of direction selectivity in the visual cortex appears to require visual experience.

  6. A regenerative microchannel device for recording multiple single-unit action potentials in awake, ambulatory animals.

    Science.gov (United States)

    Srinivasan, Akhil; Tipton, John; Tahilramani, Mayank; Kharbouch, Adel; Gaupp, Eric; Song, Chao; Venkataraman, Poornima; Falcone, Jessica; Lacour, Stéphanie P; Stanley, Garrett B; English, Arthur W; Bellamkonda, Ravi V

    2016-02-01

    Despite significant advances in robotics, commercially advanced prosthetics provide only a small fraction of the functionality of the amputated limb that they are meant to replace. Peripheral nerve interfacing could provide a rich controlling link between the body and these advanced prosthetics in order to increase their overall utility. Here, we report on the development of a fully integrated regenerative microchannel interface with 30 microelectrodes and signal extraction capabilities enabling evaluation in an awake and ambulatory rat animal model. In vitro functional testing validated the capability of the microelectrodes to record neural signals similar in size and nature to those that occur in vivo. In vitro dorsal root ganglia cultures revealed striking cytocompatibility of the microchannel interface. Finally, in vivo, the microchannel interface was successfully used to record a multitude of single-unit action potentials through 63% of the integrated microelectrodes at the early time point of 3 weeks. This marks a significant advance in microchannel interfacing, demonstrating the capability of microchannels to be used for peripheral nerve interfacing.

  7. Computer Simulations Support a Morphological Contribution to BDNF Enhancement of Action Potential Generation

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    Domenico F Galati

    2016-09-01

    Full Text Available Abstract Brain-derived neurotrophic factor (BDNF regulates both action potential (AP generation and neuron morphology. However, whether BDNF-induced changes in neuron morphology directly impact AP generation is unclear. We quantified BDNF’s effect on cultured cortical neuron morphological parameters and found that BDNF stimulates dendrite growth and addition of dendrites while increasing both excitatory and inhibitory presynaptic inputs in a spatially restricted manner. To gain insight into how these combined changes in neuron structure and synaptic input impact AP generation, we used the morphological parameters we gathered to generate computational models. Simulations suggest that BDNF-induced neuron morphologies generate more APs under a wide variety of conditions. Synapse and dendrite addition have the greatest impact on AP generation. However, subtle alterations in excitatory/inhibitory synapse ratio and strength have a significant impact on AP generation when synaptic activity is low. Consistent with these simulations, BDNF rapidly enhances spontaneous activity in cortical cultures. We propose that BDNF promotes neuron morphologies that are intrinsically more efficient at translating barrages of synaptic activity into APs, which is a previously unexplored aspect of BDNF’s function.

  8. Potential action of androstenedione on the proliferation and apoptosis of stromal endometrial cells

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    Anido Mabel

    2004-12-01

    Full Text Available Abstract Background Hyperandrogenic conditions have been associated with a high prevalence of endometrial pathologies related to cell survival. However, the action of androgens on proliferation and apoptosis in endometrial cells is poorly understood. Therefore, the aim of the present study was to evaluate the effect of androstenedione on cell proliferation, cell death and expression of estrogen receptor (ER isoforms and proteins related to apoptosis in endometrial cells using two in vitro experimental approaches. Methods The endometrial tissue was obtained from 20 eumenorrheic women [28.7 (25 – 35 years] during the early secretory phase. We analyzed cell proliferation (immunohistochemistry of Ki-67 and spectrophotometric assay; apoptosis (DNA fragmentation (TUNEL and Annexin V-FITC binding; ER-alpha, ER-beta bcl-2 and bax mRNA abundance (RT-PCR in explants and isolated endometrial epithelial (EEC and stromal cells (ESC incubated with androstenedione 1 micro mol/l (A4 or A4 plus hydroxyflutamide 10 micro mol/l (F for 24 h. Results In explants, A4 induced an increase of cell proliferation and a decrease on apoptosis in the stromal compartment (p Conclusions These results indicate that androstenedione may modulate cell survival, expression of ER-beta and proteins related to apoptosis, suggesting a potential mechanism that associates the effect of hyperandrogenemia on the endometrial tissue.

  9. Adhesion to carbon nanotube conductive scaffolds forces action-potential appearance in immature rat spinal neurons.

    Science.gov (United States)

    Fabbro, Alessandra; Sucapane, Antonietta; Toma, Francesca Maria; Calura, Enrica; Rizzetto, Lisa; Carrieri, Claudia; Roncaglia, Paola; Martinelli, Valentina; Scaini, Denis; Masten, Lara; Turco, Antonio; Gustincich, Stefano; Prato, Maurizio; Ballerini, Laura

    2013-01-01

    In the last decade, carbon nanotube growth substrates have been used to investigate neurons and neuronal networks formation in vitro when guided by artificial nano-scaled cues. Besides, nanotube-based interfaces are being developed, such as prosthesis for monitoring brain activity. We recently described how carbon nanotube substrates alter the electrophysiological and synaptic responses of hippocampal neurons in culture. This observation highlighted the exceptional ability of this material in interfering with nerve tissue growth. Here we test the hypothesis that carbon nanotube scaffolds promote the development of immature neurons isolated from the neonatal rat spinal cord, and maintained in vitro. To address this issue we performed electrophysiological studies associated to gene expression analysis. Our results indicate that spinal neurons plated on electro-conductive carbon nanotubes show a facilitated development. Spinal neurons anticipate the expression of functional markers of maturation, such as the generation of voltage dependent currents or action potentials. These changes are accompanied by a selective modulation of gene expression, involving neuronal and non-neuronal components. Our microarray experiments suggest that carbon nanotube platforms trigger reparative activities involving microglia, in the absence of reactive gliosis. Hence, future tissue scaffolds blended with conductive nanotubes may be exploited to promote cell differentiation and reparative pathways in neural regeneration strategies.

  10. Effects of stochastic channel gating and distribution on the cardiac action potential.

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    Lemay, Mathieu; de Lange, Enno; Kucera, Jan P

    2011-07-21

    Ion channels exhibit stochastic conformational changes determining their gating behavior. In addition, the process of protein turnover leads to a natural variability of the number of membrane and gap junctional channels. Nevertheless, in computational models, these two aspects are scarcely considered and their impacts are largely unknown. We investigated the effects of stochastic current fluctuations and channel distributions on action potential duration (APD), intercellular conduction delays (ICDs) and conduction blocks using a modified ventricular cell model (Rudy et al.) with Markovian formulations of the principal ion currents (to simulate their stochastic open-close gating behavior) and with channel counts drawn from Poisson distributions (to simulate their natural variability). In single cells, APD variability (coefficient of variation: 1.6% at BCL=1000ms) was essentially caused by stochastic channel gating of I(Ks), persistent I(Na) and I(Ca,L). In cell strands, ICD variability induced by stochastic channel gating and Poissonian channel distributions was low under normal conditions. Nonetheless, at low intercellular coupling levels, Poissonian gap junctional channel distribution resulted in a large ICD variability (coefficient of variation >20%), highly heterogeneous conduction patterns and conduction blocks. Therefore, the stochastic behavior of current fluctuations and channel distributions can contribute to the heterogeneity of conduction patterns and to conduction block, as observed previously in experiments in cardiac tissue with altered intercellular coupling.

  11. Low Somatic Sodium Conductance Enhances Action Potential Precision in Time-Coding Auditory Neurons.

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    Yang, Yang; Ramamurthy, Bina; Neef, Andreas; Xu-Friedman, Matthew A

    2016-11-23

    Auditory nerve fibers encode sounds in the precise timing of action potentials (APs), which is used for such computations as sound localization. Timing information is relayed through several cell types in the auditory brainstem that share an unusual property: their APs are not overshooting, suggesting that the cells have very low somatic sodium conductance (gNa). However, it is not clear how gNa influences temporal precision. We addressed this by comparing bushy cells (BCs) in the mouse cochlear nucleus with T-stellate cells (SCs), which do have normal overshooting APs. BCs play a central role in both relaying and refining precise timing information from the auditory nerve, whereas SCs discard precise timing information and encode the envelope of sound amplitude. Nucleated-patch recording at near-physiological temperature indicated that the Na current density was 62% lower in BCs, and the voltage dependence of gNa inactivation was 13 mV hyperpolarized compared with SCs. We endowed BCs with SC-like gNa using two-electrode dynamic clamp and found that synaptic activity at physiologically relevant rates elicited APs with significantly lower probability, through increased activation of delayed rectifier channels. In addition, for two near-simultaneous synaptic inputs, the window of coincidence detection widened significantly with increasing gNa, indicating that refinement of temporal information by BCs is degraded by gNa Thus, reduced somatic gNa appears to be an adaption for enhancing fidelity and precision in time-coding neurons.

  12. 'Action potential-like' ST elevation following pseudo-Wellens' electrocardiogram.

    Science.gov (United States)

    Oksuz, Fatih; Sensoy, Baris; Sen, Fatih; Celik, Ethem; Ozeke, Ozcan; Maden, Orhan

    2015-01-01

    Coronary artery vasospasm is an important cause of chest pain syndromes that can lead to myocardial infarction, ventricular arrhythmias, and sudden death. In 1959, Prinzmetal et al described a syndrome of nonexertional chest pain with ST-segment elevation on electrocardiography. Persistent angina is challenging, and repeated coronary angioplasty may be required in this syndrome. Calcium antagonists are extremely effective in treating and preventing coronary spasm, and may provide long-lasting relief for the patient. Whereas the Wellens' syndrome is characterized by symmetrically inverted T-waves with preserved R waves in the precordial leads suggestive of impending myocardial infarction due to a critical proximal left anterior descending stenosis, the pseudo-Wellens' syndrome caused by coronary artery spasm has also rarely been reported in literature. We present a pseudo-Wellens syndrome as a cause of vasospastic angina, and a diffuse ST segment elavation on electrocardiogram resembling the Greek letter lambda, called also 'action potential-like' ECG in a patient with vasospastic-type Printzmetal angina.

  13. Modulation of action potential trains in rabbit saphenous nerve unmyelinated fibers.

    Science.gov (United States)

    Zhu, Zhi-Ru; Liu, Yi-Hui; Ji, Wei-Gang; Duan, Jian-Hong; Hu, San-Jue

    2013-01-01

    Usually, the main axon is assumed to faithfully conduct action potentials (APs). Recent data have indicated that neural processing can occur along the axonal path. However, the patterns and mechanisms of temporal coding are not clear. In the present study, single fiber recording was used to analyze activity-dependent modulation of AP trains in the main axons of C fibers in the rabbit saphenous nerve. Trains of 5 superthreshold electrical pulses at interstimulus intervals of 20 or 50 ms were applied to the nerve trunk for 200 s. The interspike intervals (ISIs) for these trains were compared to the input interstimulus intervals. Three basic types of C fibers were observed in response to repeated stimuli: first, the ISI between the first and second AP (ISI1-2) of type 1 was longer than the interstimulus interval; second, the ISI1-2 of type 2 showed wavelike fluctuations around the interstimulus interval, and third, the ISI1-2 of type 3 exhibited shorter intervals for a long period. Furthermore, both 4-aminopyridine-sensitive potassium and hyperpolarization-activated cation currents were involved in the modulation of ISI1-2 of train pulses. These data provide new evidence that multiple modes of neural conduction can occur along the main axons of C fibers.

  14. Kv3.1 uses a timely resurgent K(+) current to secure action potential repolarization.

    Science.gov (United States)

    Labro, Alain J; Priest, Michael F; Lacroix, Jérôme J; Snyders, Dirk J; Bezanilla, Francisco

    2015-12-17

    High-frequency action potential (AP) transmission is essential for rapid information processing in the central nervous system. Voltage-dependent Kv3 channels play an important role in this process thanks to their high activation threshold and fast closure kinetics, which reduce the neuron's refractory period. However, premature Kv3 channel closure leads to incomplete membrane repolarization, preventing sustainable AP propagation. Here, we demonstrate that Kv3.1b channels solve this problem by producing resurgent K(+) currents during repolarization, thus ensuring enough repolarizing power to terminate each AP. Unlike previously described resurgent Na(+) and K(+) currents, Kv3.1b's resurgent current does not originate from recovery of channel block or inactivation but results from a unique combination of steep voltage-dependent gating kinetics and ultra-fast voltage-sensor relaxation. These distinct properties are readily transferrable onto an orthologue Kv channel by transplanting the voltage-sensor's S3-S4 loop, providing molecular insights into the mechanism by which Kv3 channels contribute to high-frequency AP transmission.

  15. Effects of terpineol on the compound action potential of the rat sciatic nerve

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    M.R. Moreira

    2001-10-01

    Full Text Available Terpineol, a volatile terpenoid alcohol of low toxicity, is widely used in the perfumery industry. It is an important chemical constituent of the essential oil of many plants with widespread applications in folk medicine and in aromatherapy. The effects of terpineol on the compound action potential (CAP of rat sciatic nerve were studied. Terpineol induced a dose-dependent blockade of the CAP. At 100 µM, terpineol had no demonstrable effect. At 300 µM terpineol, peak-to-peak amplitude and conduction velocity of CAP were significantly reduced at the end of 180-min exposure of the nerve to the drug, from 3.28 ± 0.22 mV and 33.5 ± 7.05 m/s, respectively, to 1.91 ± 0.51 mV and 26.2 ± 4.55 m/s. At 600 µM, terpineol significantly reduced peak-to-peak amplitude and conduction velocity from 2.97 ± 0.55 mV and 32.8 ± 3.91 m/s to 0.24 ± 0.23 mV and 2.72 ± 2.72 m/s, respectively (N = 5. All these effects developed slowly and were reversible upon 180-min washout.

  16. The transformative potential of action research and ICT in the Second Language (L2 classroom

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    Farren Margaret

    2015-12-01

    Full Text Available This study shows the transformative potential of action research and information and communications technology (ICT in the second language (L2 classroom. Two enquiries from teacher-researchers are detailed in the article. Their engagement in a collaborative professional development Masters programme was pivotal in designing and implementing ICT creatively in their classroom. Gee (2008 advocates the use of the preferred media of our classroom students in order to address their learning. Prensky (2001 urges us to feel the fear and do it anyway with our digital native classes. A post-primary teacher and a primary teacher show us how they felt the fear, did it and transformed aspects of their own teaching in the process. The Masters programme required the teachers to engage with innovative practices, informed by their own values, and integrate technologies that were new to them into their repertoire of classroom strategies. Peer validation meetings with colleagues enabled meaningful insights to emerge from the research. The teachers improve and transform their second language (L2 practice in collaboration and validation with others.

  17. Wavelet transform for real-time detection of action potentials in neural signals.

    Science.gov (United States)

    Quotb, Adam; Bornat, Yannick; Renaud, Sylvie

    2011-01-01

    We present a study on wavelet detection methods of neuronal action potentials (APs). Our final goal is to implement the selected algorithms on custom integrated electronics for on-line processing of neural signals; therefore we take real-time computing as a hard specification and silicon area as a price to pay. Using simulated neural signals including APs, we characterize an efficient wavelet method for AP extraction by evaluating its detection rate and its implementation cost. We compare software implementation for three methods: adaptive threshold, discrete wavelet transform (DWT), and stationary wavelet transform (SWT). We evaluate detection rate and implementation cost for detection functions dynamically comparing a signal with an adaptive threshold proportional to its SD, where the signal is the raw neural signal, respectively: (i) non-processed; (ii) processed by a DWT; (iii) processed by a SWT. We also use different mother wavelets and test different data formats to set an optimal compromise between accuracy and silicon cost. Detection accuracy is evaluated together with false negative and false positive detections. Simulation results show that for on-line AP detection implemented on a configurable digital integrated circuit, APs underneath the noise level can be detected using SWT with a well-selected mother wavelet, combined to an adaptive threshold.

  18. Latencies in action potential stimulation in a two-dimensional bidomain: A numerical simulation

    Science.gov (United States)

    Barach, John Paul

    1991-05-01

    A numerical simulation is performed in which a uniform planar slab of idealized cardiac tissue is stimulated at the center. The cardiac slab is modeled as an anisotropic bidomain; within each domain current flow is determined by a forced diffusion equation in which the transmembrane current connecting the domains provides the forcing term. An action potential (AP) propagates outward after a time latency dependent upon the stimulus size and the physiological variables. Its isochrones are elliptical with an asymmetry that is a small fraction of the imposed asymmetry in resistivity. External voltages resemble the first derivative of those in the internal domain and tests with continuing stimuli exhibit a relaxation time of about 3 ms and space constants that agree with other work. The AP latency increases very strongly near threshold stimulus and decreases as the log (stimulus) for large stimuli in the ``virtual cathode'' range. Latencies in the longitudinal, transverse, and diagonal directions are found to be the same over a wide range of stimulus size and type.

  19. Dispersion of compound muscle action potential in hereditary neuropathies and chronic inflammatory demyelinating polyneuropathy.

    Science.gov (United States)

    Stanton, Michael; Pannoni, Valerie; Lewis, Richard A; Logigian, Eric L; Naguib, Demian; Shy, Michael E; Cleland, James; Herrmann, David N

    2006-10-01

    Distal compound muscle action potential (DCMAP) dispersion, defined as a DCMAP duration > or = 9 ms, and proximal-distal (P-D) CMAP dispersion are considered useful in the electrodiagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP). Distal and P-D CMAP dispersion have not been fully studied in hereditary neuropathies, and it is not known whether these measures distinguish hereditary from acquired demyelination. We compared DCMAP duration and P-D CMAP dispersion in 91 genetically characterized hereditary neuropathies and 33 subjects with CIDP. DCMAP dispersion was more frequent in nerves affected by CIDP (41.5%) than in Charcot-Marie-Tooth disease (CMT)1A (24.4%), CMT1B (7.4%), hereditary neuropathy with liability to pressure palsies (HNPP) (10.5%), or CMTX (9.8%). P-D CMAP dispersion was more frequent in CIDP (27.7% of nerves) than in hereditary neuropathies (16.3%) when applying American Academy of Neurology (AAN) criteria; however, its frequency was similar in CIDP and the hereditary neuropathies using the more restrictive criteria of the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM). Although dispersion is more common in CIDP than in the hereditary neuropathies, DCMAP and P-D dispersion occur in at least one motor nerve in a significant proportion of hereditary neuropathies, and cannot be used in isolation to distinguish acquired from hereditary demyelination.

  20. An overview of skin penetration enhancers: penetration enhancing activity, skin irritation potential and mechanism of action

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    Sarunyoo Songkro

    2009-08-01

    Full Text Available Transdermal drug delivery has attracted considerable attention over the past 2-3 decades in regard of its many potentialadvantages. However, the role of the skin as a protective barrier renders skin absorption of most drugs problematic. Therefore,skin penetration enhancers are frequently used in the field of transdermal drug delivery in order to reversibly reduce thebarrier function of the stratum corneum, the outermost layer of the skin. To date, a wide range of chemical compounds havebeen shown to enhance the skin penetration of therapeutic drugs. This review presents a critical account of the most commonlyused chemical penetration enhancers (fatty acids and surfactants, and some newer classes of chemical enhancers (terpenes,polymers, monoolein, oxazolidinones, with emphasis on their efficacy, mechanism of action, and skin irritation potential. Thisreview also discusses the traditional and more recently developed methods for the screening and evaluation of chemical penetration enhancers, and addresses the continuing problems in the rational selection of a chemical penetration enhancer for a specific drug to be delivered via the transdermal route.

  1. MCH and apomorphine in combination enhance action potential firing of nucleus accumbens shell neurons in vitro

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    F Woodward Hopf

    2013-04-01

    Full Text Available The MCH and dopamine receptor systems have been shown to modulate a number of behaviors related to reward processing, addiction, and neuropsychiatric conditions such as schizophrenia and depression. In addition, MCH and dopamine receptors can interact in a positive manner, for example in the expression of cocaine self-administration. A recent report (Chung et al., 2011a showed that the DA1/DA2 dopamine receptor activator apomorphine suppresses pre-pulse inhibition, a preclinical model for some aspects of schizophrenia. Importantly, MCH can enhance the effects of lower doses of apomorphine, suggesting that co-modulation of dopamine and MCH receptors might alleviate some symptoms of schizophrenia with a lower dose of dopamine receptor modulator and thus fewer potential side effects. Here, we investigated whether MCH and apomorphine could enhance action potential firing in vitro in the nucleus accumbens shell (NAshell, a region which has previously been shown to mediate some behavioral effects of MCH. Using whole-cell patch-clamp electrophysiology, we found that MCH, which has no effect on firing on its own, was able to increase NAshell firing when combined with a subthreshold dose of apomorphine. Further, this MCH/apomorphine increase in firing was prevented by an antagonist of either a DA1 or a DA2 receptor, suggesting that apomorphine acts through both receptor types to enhance NAshell firing. The MCH/apomorphine-mediated firing increase was also prevented by an MCH receptor antagonist or a PKA inhibitor. Taken together, our results suggest that MCH can interact with lower doses of apomorphine to enhance NAshell firing, and thus that MCH and apomorphine might interact in vivo within the NAshell to suppress pre-pulse inhibition.

  2. Ionic mechanisms maintaining action potential conduction velocity at high firing frequencies in an unmyelinated axon.

    Science.gov (United States)

    Cross, Kevin P; Robertson, R Meldrum

    2016-05-01

    The descending contralateral movement detector (DCMD) is a high-performance interneuron in locusts with an axon capable of transmitting action potentials (AP) at more than 500 Hz. We investigated biophysical mechanisms for fidelity of high-frequency transmission in this axon. We measured conduction velocities (CVs) at room temperature during exposure to 10 mmol/L cadmium, a calcium current antagonist, and found significant reduction in CV with reduction at frequencies >200 Hz of ~10%. Higher temperatures induced greater CV reductions during exposure to cadmium across all frequencies of ~20-30%. Intracellular recordings during 15 min of exposure to cadmium or nickel, also a calcium current antagonist, revealed an increase in the magnitude of the afterhyperpolarization potential (AHP) and the time to recover to baseline after the AHP (Medians for Control: -19.8%; Nickel: 167.2%; Cadmium: 387.2%), that could be due to a T-type calcium current. However, the removal of extracellular calcium did not mimic divalent cation exposure suggesting calcium currents are not the cause of the AHP increase. Computational modeling showed that the effects of the divalent cations could be modeled with a persistent sodium current which could be blocked by high concentrations of divalent cations. Persistent sodium current shortened the AHP duration in our models and increased CV for high-frequency APs. We suggest that faithful, high-frequency axonal conduction in the DCMD is enabled by a mechanism that shortens the AHP duration like a persistent or resurgent sodium current.

  3. Burst analysis tool for developing neuronal networks exhibiting highly varying action potential dynamics

    Directory of Open Access Journals (Sweden)

    Fikret Emre eKapucu

    2012-06-01

    Full Text Available In this paper we propose a firing statistics based neuronal network burst detection algorithm for neuronal networks exhibiting highly variable action potential dynamics. Electrical activity of neuronal networks is generally analyzed by the occurrences of spikes and bursts both in time and space. Commonly accepted analysis tools employ burst detection algorithms based on predefined criteria. However, maturing neuronal networks, such as those originating from human embryonic stem cells (hESC, exhibit highly variable network structure and time-varying dynamics. To explore the developing burst/spike activities of such networks, we propose a burst detection algorithm which utilizes the firing statistics based on interspike interval (ISI histograms. Moreover, the algorithm calculates interspike interval thresholds for burst spikes as well as for pre-burst spikes and burst tails by evaluating the cumulative moving average and skewness of the ISI histogram. Because of the adaptive nature of the proposed algorithm, its analysis power is not limited by the type of neuronal cell network at hand. We demonstrate the functionality of our algorithm with two different types of microelectrode array (MEA data recorded from spontaneously active hESC-derived neuronal cell networks. The same data was also analyzed by two commonly employed burst detection algorithms and the differences in burst detection results are illustrated. The results demonstrate that our method is both adaptive to the firing statistics of the network and yields successful burst detection from the data. In conclusion, the proposed method is a potential tool for analyzing of hESC-derived neuronal cell networks and thus can be utilized in studies aiming to understand the development and functioning of human neuronal networks and as an analysis tool for in vitro drug screening and neurotoxicity assays.

  4. Effect of thermal acclimation on action potentials and sarcolemmal K+ channels from Pacific bluefin tuna cardiomyocytes.

    Science.gov (United States)

    Galli, G L J; Lipnick, M S; Block, B A

    2009-08-01

    To sustain cardiac muscle contractility relatively independent of temperature, some fish species are capable of temporarily altering excitation-contraction coupling processes to meet the demands of their environment. The Pacific bluefin tuna, Thunnus orientalis, is a partially endothermic fish that inhabits a wide range of thermal niches. The present study examined the effects of temperature and thermal acclimation on sarcolemmal K(+) currents and their role in action potential (AP) generation in bluefin tuna cardiomyocytes. Atrial and ventricular myocytes were enzymatically isolated from cold (14 degrees C)- and warm (24 degrees C)-acclimated bluefin tuna. APs and current-voltage relations of K(+) channels were measured using the whole cell current and voltage clamp techniques, respectively. Data were collected either at the cardiomyocytes' respective acclimation temperature of 14 or 24 degrees C or at a common test temperature of 19 degrees C (to reveal the effects of acclimation). AP duration (APD) was prolonged in cold-acclimated (CA) cardiomyocytes tested at 14 degrees C compared with 19 degrees C and in warm-acclimated (WA) cardiomyocytes tested at 19 degrees C compared with 24 degrees C. This effect was mirrored by a decrease in the density of the delayed-rectifier current (I(Kr)), whereas the density of the background inward-rectifier current (I(K1)) was unchanged. When CA and WA cardiomyocytes were tested at a common temperature of 19 degrees C, no significant effects of temperature acclimation on AP shape or duration were observed, whereas I(Kr) density was markedly increased in CA cardiomyocytes. I(K1) density was unaffected in CA ventricular myocytes but was significantly reduced in CA atrial myocytes, resulting in a depolarization of atrial resting membrane potential. Our results indicate the bluefin AP is relatively short compared with other teleosts, which may allow the bluefin heart to function at cold temperatures without the necessity for thermal

  5. The Venus Flytrap Dionaea muscipula Counts Prey-Induced Action Potentials to Induce Sodium Uptake.

    Science.gov (United States)

    Böhm, Jennifer; Scherzer, Sönke; Krol, Elzbieta; Kreuzer, Ines; von Meyer, Katharina; Lorey, Christian; Mueller, Thomas D; Shabala, Lana; Monte, Isabel; Solano, Roberto; Al-Rasheid, Khaled A S; Rennenberg, Heinz; Shabala, Sergey; Neher, Erwin; Hedrich, Rainer

    2016-02-01

    Carnivorous plants, such as the Venus flytrap (Dionaea muscipula), depend on an animal diet when grown in nutrient-poor soils. When an insect visits the trap and tilts the mechanosensors on the inner surface, action potentials (APs) are fired. After a moving object elicits two APs, the trap snaps shut, encaging the victim. Panicking preys repeatedly touch the trigger hairs over the subsequent hours, leading to a hermetically closed trap, which via the gland-based endocrine system is flooded by a prey-decomposing acidic enzyme cocktail. Here, we asked the question as to how many times trigger hairs have to be stimulated (e.g., now many APs are required) for the flytrap to recognize an encaged object as potential food, thus making it worthwhile activating the glands. By applying a series of trigger-hair stimulations, we found that the touch hormone jasmonic acid (JA) signaling pathway is activated after the second stimulus, while more than three APs are required to trigger an expression of genes encoding prey-degrading hydrolases, and that this expression is proportional to the number of mechanical stimulations. A decomposing animal contains a sodium load, and we have found that these sodium ions enter the capture organ via glands. We identified a flytrap sodium channel DmHKT1 as responsible for this sodium acquisition, with the number of transcripts expressed being dependent on the number of mechano-electric stimulations. Hence, the number of APs a victim triggers while trying to break out of the trap identifies the moving prey as a struggling Na(+)-rich animal and nutrition for the plant.

  6. Burst analysis tool for developing neuronal networks exhibiting highly varying action potential dynamics.

    Science.gov (United States)

    Kapucu, Fikret E; Tanskanen, Jarno M A; Mikkonen, Jarno E; Ylä-Outinen, Laura; Narkilahti, Susanna; Hyttinen, Jari A K

    2012-01-01

    In this paper we propose a firing statistics based neuronal network burst detection algorithm for neuronal networks exhibiting highly variable action potential dynamics. Electrical activity of neuronal networks is generally analyzed by the occurrences of spikes and bursts both in time and space. Commonly accepted analysis tools employ burst detection algorithms based on predefined criteria. However, maturing neuronal networks, such as those originating from human embryonic stem cells (hESCs), exhibit highly variable network structure and time-varying dynamics. To explore the developing burst/spike activities of such networks, we propose a burst detection algorithm which utilizes the firing statistics based on interspike interval (ISI) histograms. Moreover, the algorithm calculates ISI thresholds for burst spikes as well as for pre-burst spikes and burst tails by evaluating the cumulative moving average (CMA) and skewness of the ISI histogram. Because of the adaptive nature of the proposed algorithm, its analysis power is not limited by the type of neuronal cell network at hand. We demonstrate the functionality of our algorithm with two different types of microelectrode array (MEA) data recorded from spontaneously active hESC-derived neuronal cell networks. The same data was also analyzed by two commonly employed burst detection algorithms and the differences in burst detection results are illustrated. The results demonstrate that our method is both adaptive to the firing statistics of the network and yields successful burst detection from the data. In conclusion, the proposed method is a potential tool for analyzing of hESC-derived neuronal cell networks and thus can be utilized in studies aiming to understand the development and functioning of human neuronal networks and as an analysis tool for in vitro drug screening and neurotoxicity assays.

  7. Atria selective prolongation by NIP-142, an antiarrhythmic agent, of refractory period and action potential duration in guinea pig myocardium.

    Science.gov (United States)

    Matsuda, Tomoyuki; Takeda, Kentaro; Ito, Mie; Yamagishi, Reiko; Tamura, Miku; Nakamura, Hideki; Tsuruoka, Noriko; Saito, Tomoaki; Masumiya, Haruko; Suzuki, Takeshi; Iida-Tanaka, Naoko; Itokawa-Matsuda, Maho; Yamashita, Toru; Tsuruzoe, Nobutomo; Tanaka, Hikaru; Shigenobu, Koki

    2005-05-01

    NIP-142 is a novel benzopyran compound that was shown to prolong the atrial effective refractory period and terminate experimental atrial fibrillation in the dog. In the present study, we examined the effects of NIP-142 on isolated guinea pig myocardium and on the G-protein-coupled inwardly rectifying potassium channel current (acetylcholine-activated potassium current; I(KACh)) expressed in Xenopus oocytes. NIP-142 (10 and 100 microM) concentration-dependently prolonged the refractory period and action potential duration in the atrium but not in the ventricle. E-4031 and 4-aminopyridine prolonged action potential duration in both left atrium and right ventricle. Prolongation by NIP-142 of the atrial action potential duration was observed at stimulation frequencies between 0.5 and 5 Hz. In contrast, the prolongation by E-4031 was not observed at higher frequencies. Tertiapin, a blocker of I(KACh), prolonged action potential duration in the atrium but not in the ventricle. NIP-142 completely reversed the carbachol-induced shortening of atrial action potential duration. NIP-142 (1 to 100 microM), as well as tertiapin (0.1 to 100 nM), concentration-dependently blocked I(KACh) expressed in Xenopus oocytes; the blockade by NIP-142 was not affected by membrane voltage. In conclusion, NIP-142 was shown to prolong atrial refractory period and action potential duration through blockade of I(KACh) which may possibly explain its previously described antiarrhythmic activity. NIP-142 has pharmacological properties that are different from classical class III antiarrhythmic agents such as atria specificity and lack of reverse frequency dependence, and thus appears promising for the treatment of supraventricular arrhythmia.

  8. Resilient RTN fast spiking in Kv3.1 null mice suggests redundancy in the action potential repolarization mechanism.

    Science.gov (United States)

    Porcello, Darrell M; Ho, Chi Shun; Joho, Rolf H; Huguenard, John R

    2002-03-01

    Fast spiking (FS), GABAergic neurons of the reticular thalamic nucleus (RTN) are capable of firing high-frequency trains of brief action potentials, with little adaptation. Studies in recombinant systems have shown that high-voltage-activated K(+) channels containing the Kv3.1 and/or Kv3.2 subunits display biophysical properties that may contribute to the FS phenotype. Given that RTN expresses high levels of Kv3.1, with little or no Kv3.2, we tested whether this subunit was required for the fast action potential repolarization mechanism essential to the FS phenotype. Single- and multiple-action potentials were recorded using whole-cell current clamp in RTN neurons from brain slices of wild-type and Kv3.1-deficient mice. At 23 degrees C, action potentials recorded from homozygous Kv3.1 deficient mice (Kv3.1(-/-)) compared with their wild-type (Kv3.1(+/+)) counterparts had reduced amplitudes (-6%) and fast after-hyperpolarizations (-16%). At 34 degrees C, action potentials in Kv3.1(-/-) mice had increased duration (21%) due to a reduced rate of repolarization (-30%) when compared with wild-type controls. Action potential trains in Kv3.1(-/-) were associated with a significantly greater spike decrement and broadening and a diminished firing frequency versus injected current relationship (F/I) at 34 degrees C. There was no change in either spike count or maximum instantaneous frequency during low-threshold Ca(2+) bursts in Kv3.1(-/-) RTN neurons at either temperature tested. Our findings show that Kv3.1 is not solely responsible for fast spikes or high-frequency firing in RTN neurons. This suggests genetic redundancy in the system, possibly in the form of other Kv3 members, which may suffice to maintain the FS phenotype in RTN neurons in the absence of Kv3.1.

  9. Stimulation rate modulates effects of the dihydropyridine CGP 28 392 on cardiac calcium-dependent action potentials.

    OpenAIRE

    Kamp, T. J.; Miller, R. J.; Sanguinetti, M C

    1985-01-01

    Calcium (Ca2+)-dependent action potentials were recorded from 22 mM potassium (K+)-depolarized guinea-pig papillary muscle at several different pacing frequencies in the absence and presence of CGP 28 392 (10 microM), a Ca2+ channel agonist. The maximum upstroke velocity (Vmax) of the slow response action potential was measured to determine relative changes in Ca2+ current as a function of pacing frequency. CGP 28 392 increased Vmax more than two fold at low rates of stimulation (1 or 12 puls...

  10. Toxicity, sublethal effects, and potential modes of action of select fungicides on freshwater fish and invertebrates

    Science.gov (United States)

    Elskus, Adria A.

    2012-01-01

    Despite decades of agricultural and urban use of fungicides and widespread detection of these pesticides in surface waters, relatively few data are available on the effects of fungicides on fish and invertebrates in the aquatic environment. Nine fungicides are reviewed in this report: azoxystrobin, boscalid, chlorothalonil, fludioxonil, myclobutanil, fenarimol, pyraclostrobin, pyrimethanil, and zoxamide. These fungicides were identified as emerging chemicals of concern because of their high or increasing global use rates, detection frequency in surface waters, or likely persistence in the environment. A review of the literature revealed significant sublethal effects of fungicides on fish, aquatic invertebrates, and ecosystems, including zooplankton and fish reproduction, fish immune function, zooplankton community composition, metabolic enzymes, and ecosystem processes, such as leaf decomposition in streams, among other biological effects. Some of these effects can occur at fungicide concentrations well below single-species acute lethality values (48- or 96-hour concentration that effects a response in 50 percent of the organisms, that is, effective concentration killing 50 percent of the organisms in 48 or 96 hours) and chronic sublethal values (for example, 21-day no observed adverse effects concentration), indicating that single-species toxicity values may dramatically underestimate the toxic potency of some fungicides. Fungicide modes of toxic action in fungi can sometimes reflect the biochemical and (or) physiological effects of fungicides observed in vertebrates and invertebrates; however, far more studies are needed to explore the potential to predict effects in nontarget organisms based on specific fungicide modes of toxic action. Fungicides can also have additive and (or) synergistic effects when used with other fungicides and insecticides, highlighting the need to study pesticide mixtures that occur in surface waters. For fungicides that partition to

  11. The mitochondrial monoamine oxidase-aldehyde dehydrogenase pathway: a potential site of action of daidzin.

    Science.gov (United States)

    Rooke, N; Li, D J; Li, J; Keung, W M

    2000-11-02

    Recent studies showed that daidzin suppresses ethanol intake in ethanol-preferring laboratory animals. In vitro, it potently and selectively inhibits the mitochondrial aldehyde dehydrogenase (ALDH-2). Further, it inhibits the conversion of monoamines such as serotonin (5-HT) and dopamine (DA) into their respective acid metabolites, 5-hydroxyindole-3-acetic acid (5-HIAA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in isolated hamster or rat liver mitochondria. Studies on the suppression of ethanol intake and inhibition of 5-HIAA (or DOPAC) formation by six structural analogues of daidzin suggested a potential link between these two activities. This, together with the finding that daidzin does not affect the rates of mitochondria-catalyzed oxidative deamination of these monoamines, raised the possibility that the ethanol intake-suppressive (antidipsotropic) action of daidzin is not mediated by the monoamines but rather by their reactive biogenic aldehyde intermediates such as 5-hydroxyindole-3-acetaldehyde (5-HIAL) and/or 3,4-dihydroxyphenylacetaldehyde (DOPAL) which accumulate in the presence of daidzin. To further evaluate this possibility, we synthesized more structural analogues of daidzin and tested and compared their antidipsotropic activities in Syrian golden hamsters with their effects on monoamine metabolism in isolated hamster liver mitochondria using 5-HT as the substrate. Effects of daidzin and its structural analogues on the activities of monoamine oxidase (MAO) and ALDH-2, the key enzymes involved in 5-HT metabolism in the mitochondria, were also examined. Results from these studies reveal a positive correlation between the antidipsotropic activities of these analogues and their abilities to increase 5-HIAL accumulation during 5-HT metabolism in isolated hamster liver mitochondria. Daidzin analogues that potently inhibit ALDH-2 but have no or little effect on MAO are most antidipsotropic, whereas those that also potently inhibit MAO exhibit little, if

  12. Kv2 channel regulation of action potential repolarization and firing patterns in superior cervical ganglion neurons and hippocampal CA1 pyramidal neurons.

    Science.gov (United States)

    Liu, Pin W; Bean, Bruce P

    2014-04-02

    Kv2 family "delayed-rectifier" potassium channels are widely expressed in mammalian neurons. Kv2 channels activate relatively slowly and their contribution to action potential repolarization under physiological conditions has been unclear. We explored the function of Kv2 channels using a Kv2-selective blocker, Guangxitoxin-1E (GxTX-1E). Using acutely isolated neurons, mixed voltage-clamp and current-clamp experiments were done at 37°C to study the physiological kinetics of channel gating and action potentials. In both rat superior cervical ganglion (SCG) neurons and mouse hippocampal CA1 pyramidal neurons, 100 nm GxTX-1E produced near-saturating block of a component of current typically constituting ∼60-80% of the total delayed-rectifier current. GxTX-1E also reduced A-type potassium current (IA), but much more weakly. In SCG neurons, 100 nm GxTX-1E broadened spikes and voltage clamp experiments using action potential waveforms showed that Kv2 channels carry ∼55% of the total outward current during action potential repolarization despite activating relatively late in the spike. In CA1 neurons, 100 nm GxTX-1E broadened spikes evoked from -70 mV, but not -80 mV, likely reflecting a greater role of Kv2 when other potassium channels were partially inactivated at -70 mV. In both CA1 and SCG neurons, inhibition of Kv2 channels produced dramatic depolarization of interspike voltages during repetitive firing. In CA1 neurons and some SCG neurons, this was associated with increased initial firing frequency. In all neurons, inhibition of Kv2 channels depressed maintained firing because neurons entered depolarization block more readily. Therefore, Kv2 channels can either decrease or increase neuronal excitability depending on the time scale of excitation.

  13. Interest Groups Vie for Public Support: The Battle Over Anti-Affirmative Action Initiatives in California and Michigan

    Science.gov (United States)

    Hinz, Serena E.

    2016-01-01

    Although affirmative action in college admissions has not been declared unconstitutional by the Supreme Court, the consideration of race in admissions has been banned in nine states--in six of them by public vote. This article analyzes the campaigns to ban affirmative action in California and Michigan as a battle between interest groups. The…

  14. Ionic basis of the different action potential configurations of single guinea-pig atrial and ventricular myocytes.

    Science.gov (United States)

    Hume, J R; Uehara, A

    1985-11-01

    Single myocardial cells were enzymatically dispersed from guinea-pig atria and ventricles. At 25 degrees C, atrial cell action potentials differed significantly from ventricular cell action potentials in duration (atrial = 141 ms, ventricular = 497 ms) and over-shoot (atrial = +36 mV, ventricular = +42 mV). Action potentials of atrial and ventricular cells responded differently to changes in external K+ concentration ([K+]o). Elevation of [K+]o from 6 to 11 mM depolarized atrial cells but produced no significant change in action potential duration; similar changes in [K+]o depolarized ventricular cells and produced a significant shortening of the action potential duration. Voltage-clamp experiments were performed to investigate the ionic basis underlying the different action potential configurations of single atrial and ventricular myocytes. A single-micropipette voltage-clamp technique was used, employing either extremely small-tip diameter pipettes, without internal cell dialysis (Hume & Giles, 1983), or larger tip diameter pipettes, with internal dialysis (Hamill, Marty, Neher, Sakmann & Sigworth, 1981). Two significant differences in background K+ conductance in single atrial and ventricular myocytes were observed: (i) the isochronal (5 s) current-voltage relationship of single ventricular myocytes exhibited a region of prominent negative slope conductance and elevation of [K+]o produced cross-over; a negative slope conductance region was absent in atrial cells and elevation of [K+]o produced very little cross-over of isochronal current-voltage relationships, and (ii) hyperpolarizing voltage pulses applied from holding potentials of -50 mV elicited inward current in ventricular cells which decayed with time; similar voltage-clamp pulses in atrial cells elicited inward currents which fail to decay. Single K+ channel current measurements confirmed the existence of different resting K+ channel properties in single atrial and ventricular myocytes. Resting K

  15. Conopressin affects excitability, firing, and action potential shape through stimulation of transient and persistent inward currents in mulluscan neurons.

    Science.gov (United States)

    van Soest, P F; Kits, K S

    1998-04-01

    The molluscan vasopressin/oxytocin-related neuropeptide conopressin activates two persistent inward currents in neurons from the anterior lobe of the right cerebral ganglion of Lymnaea stagnalis that are involved in the control of male copulatory behavior. The low-voltage-activated (LVA) current is activated at a wide range of membrane potentials, its amplitude being only weakly voltage dependent. The high-voltage-activated (HVA) current is activated at potentials positive to -40 mV only and shows a steep voltage dependence. Occurrence of both currents varies from cell to cell, some expressing both and others only the HVA current. In most neurons that have the LVA current, a conopressin-independent persistent inward current (INSR) is found that resembles the HVA current in its voltage dependence. The functional importance of the LVA and HVA currents was studied under current-clamp conditions in isolated anterior lobe neurons. In cells exhibiting both current types, the effect of activation of the LVA current alone was investigated as follows: previously recorded LVA current profiles were injected into the neurons, and the effects were compared with responses induced by conopressin. Both treatments resulted in a strong depolarization and firing activity. No differences in firing frequency and burst duration were observed, indicating that activation of the LVA current is sufficient to evoke bursts. In cells exhibiting only the HVA current, the effect of conopressin on the response to a depolarizing stimulus was tested. Conopressin reversibly increased the number of action potentials generated by the stimulus, suggesting that the HVA current enhances excitability and counteracts accommodation. Conopressin enhanced action potential broadening during depolarizing stimuli in many neurons. Voltage-clamp experiments performed under ion-selective conditions revealed the presence of transient sodium and calcium currents. Using the action potential clamp technique, it was

  16. Effect of knockout of α2δ-1 on action potentials in mouse sensory neurons

    Science.gov (United States)

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

    2016-01-01

    Gene deletion of the voltage-gated calcium channel auxiliary subunit α2δ-1 has been shown previously to have a cardiovascular phenotype, and a reduction in mechano- and cold sensitivity, coupled with delayed development of neuropathic allodynia. We have also previously shown that dorsal root ganglion (DRG) neuron calcium channel currents were significantly reduced in α2δ-1 knockout mice. To extend our findings in these sensory neurons, we have examined here the properties of action potentials (APs) in DRG neurons from α2δ-1 knockout mice in comparison to their wild-type (WT) littermates, in order to dissect how the calcium channels that are affected by α2δ-1 knockout are involved in setting the duration of individual APs and their firing frequency. Our main findings are that there is reduced Ca2+ entry on single AP stimulation, particularly in the axon proximal segment, reduced AP duration and reduced firing frequency to a 400 ms stimulation in α2δ-1 knockout neurons, consistent with the expected role of voltage-gated calcium channels in these events. Furthermore, lower intracellular Ca2+ buffering also resulted in reduced AP duration, and a lower frequency of AP firing in WT neurons, mimicking the effect of α2δ-1 knockout. By contrast, we did not obtain any consistent evidence for the involvement of Ca2+-activation of large conductance calcium-activated potassium (BK) and small conductance calcium-activated potassium (SK) channels in these events. In conclusion, the reduced Ca2+ elevation as a result of single AP stimulation is likely to result from the reduced duration of the AP in α2δ-1 knockout sensory neurons. This article is part of the themed issue ‘Evolution brings Ca2+ and ATP together to control life and death’. PMID:27377724

  17. Dynamics of the late Na(+) current during cardiac action potential and its contribution to afterdepolarizations.

    Science.gov (United States)

    Horvath, Balazs; Banyasz, Tamas; Jian, Zhong; Hegyi, Bence; Kistamas, Kornel; Nanasi, Peter P; Izu, Leighton T; Chen-Izu, Ye

    2013-11-01

    The objective of this work is to examine the contribution of late Na(+) current (INa,L) to the cardiac action potential (AP) and arrhythmogenic activities. In spite of the rapidly growing interest toward this current, there is no publication available on experimental recording of the dynamic INa,L current as it flows during AP with Ca(2+) cycling. Also unknown is how the current profile changes when the Ca(2+)-calmodulin dependent protein kinase II (CaMKII) signaling is altered, and how the current contributes to the development of arrhythmias. In this study we use an innovative AP-clamp Sequential Dissection technique to directly record the INa,L current during the AP with Ca(2+) cycling in the guinea pig ventricular myocytes. First, we found that the magnitude of INa,L measured under AP-clamp is substantially larger than earlier studies indicated. CaMKII inhibition using KN-93 significantly reduced the current. Second, we recorded INa,L together with IKs, IKr, and IK1 in the same cell to understand how these currents counterbalance to shape the AP morphology. We found that the amplitude and the total charge carried by INa,L exceed that of IKs. Third, facilitation of INa,L by Anemone toxin II prolonged APD and induced Ca(2+) oscillations that led to early and delayed afterdepolarizations and triggered APs; these arrhythmogenic activities were eliminated by buffering Ca(2+) with BAPTA. In conclusion, INa,L contributes a significantly large inward current that prolongs APD and unbalances the Ca(2+) homeostasis to cause arrhythmogenic APs.

  18. Dynamics of the Late Na+ current during cardiac action potential and its contribution to afterdepolarizations

    Science.gov (United States)

    Horvath, Balazs; Banyasz, Tamas; Jian, Zhong; Hegyi, Bence; Kistamas, Kornel; Nanasi, Peter P.; Izu, Leighton T.; Chen-Izu, Ye

    2013-01-01

    The objective of this work is to examine the contribution of late Na+ current (INa,L) to the cardiac action potential (AP) and arrhythmogenic activities. In spite of the rapidly growing interest toward this current, there is no publication available on experimental recording of the dynamic INa,L current as it flows during AP with Ca2+ cycling. Also unknown is how the current profile changes when the Ca2+-calmodulin dependent protein kinase II (CaMKII) signaling is altered, and how the current contributes to the development of arrhythmias. In this study we use an innovative AP-clamp Sequential Dissection technique to directly record the INa,L current during the AP with Ca2+ cycling in the guinea pig ventricular myocytes. First, we found that the magnitude of INa,L measured under AP-clamp is substantially larger than earlier studies indicated. CaMKII inhibition using KN-93 significantly reduced the current. Second, we recorded INa,L together with IKs, IKr, and IK1 in the same cell to understand how these currents counterbalance to shape the AP morphology. We found that the amplitude and the total charge carried by INa,L exceed that of IKs. Third, facilitation of INa,L by Anemone toxin II prolonged APD and induced Ca2+ oscillations that led to early and delayed afterdepolarizations and triggered APs; these arrhythmogenic activities were eliminated by buffering Ca2+ with BAPTA. In conclusion, INa,L contributes a significantly large inward current that prolongs APD and unbalances the Ca2+ homeostasis to cause arrhythmogenic APs. PMID:24012538

  19. Beta-adrenergic stimulation reverses the IKr–IKs dominant pattern during cardiac action potential

    Science.gov (United States)

    Banyasz, Tamas; Jian, Zhong; Horvath, Balazs; Khabbaz, Shaden; Izu, Leighton T.; Chen-Izu, Ye

    2014-01-01

    β-adrenergic stimulation differentially modulates different K+ channels and thus fine-tunes cardiac action potential (AP) repolarization. However, it remains unclear how the proportion of IKs, IKr, and IK1 current in the same cell would be altered by β-adrenergic stimulation, which would change the relative contribution of individual K+ current to the total repolarization reserve. In this study we used an innovative AP-clamp Sequential Dissection technique to directly record the dynamic –IKs, IKr, IK1– currents during the AP in guinea pig ventricular myocytes under physiologically relevant conditions. Our data provide quantitative measures of the magnitude and time course of IKs, IKr, IK1 currents in the same cell under its own steady-state AP, in a physiological milieu, and with preserved Ca2+ homeostasis. We found that isoproterenol treatment significantly enhanced IKs, moderately increased IK1, but slightly decreased IKr in a dose-dependent manner. The dominance pattern of the K+ currents was IKr>IK1>IKs at the control condition, but reversed to IKr

  20. Effects of estragole on the compound action potential of the rat sciatic nerve

    Directory of Open Access Journals (Sweden)

    J.H. Leal-Cardoso

    2004-08-01

    Full Text Available Estragole, a relatively nontoxic terpenoid ether, is an important constituent of many essential oils with widespread applications in folk medicine and aromatherapy and known to have potent local anesthetic activity. We investigated the effects of estragole on the compound action potential (CAP of the rat sciatic nerve. The experiments were carried out on sciatic nerves dissected from Wistar rats. Nerves, mounted in a moist chamber, were stimulated at a frequency of 0.2 Hz, with electric pulses of 50-100-µs duration at 10-20 V, and evoked CAP were monitored on an oscilloscope and recorded on a computer. CAP control parameters were: peak-to-peak amplitude (PPA, 9.9 ± 0.55 mV (N = 15, conduction velocity, 92.2 ± 4.36 m/s (N = 15, chronaxy, 45.6 ± 3.74 µs (N = 5, and rheobase, 3.9 ± 0.78 V (N = 5. Estragole induced a dose-dependent blockade of the CAP. At 0.6 mM, estragole had no demonstrable effect. At 2.0 and 6.0 mM estragole, PPA was significantly reduced at the end of 180-min exposure of the nerve to the drug to 85.6 ± 3.96 and 13.04 ± 1.80% of control, respectively. At 4.0 mM, estragole significantly altered PPA, conduction velocity, chronaxy, and rheobase (P <= 0.05, ANOVA; N = 5 to 49.3 ± 6.21 and 77.7 ± 3.84, 125.9 ± 10.43 and 116.7 ± 4.59%, of control, respectively. All of these effects developed slowly and were reversible upon a 300-min wash-out. The data show that estragole dose-dependently blocks nerve excitability.

  1. Inter-subject variability in human atrial action potential in sinus rhythm versus chronic atrial fibrillation.

    Directory of Open Access Journals (Sweden)

    Carlos Sánchez

    Full Text Available Human atrial electrophysiology exhibits high inter-subject variability in both sinus rhythm (SR and chronic atrial fibrillation (cAF patients. Variability is however rarely investigated in experimental and theoretical electrophysiological studies, thus hampering the understanding of its underlying causes but also its implications in explaining differences in the response to disease and treatment. In our study, we aim at investigating the ability of populations of human atrial cell models to capture the inter-subject variability in action potential (AP recorded in 363 patients both under SR and cAF conditions.Human AP recordings in atrial trabeculae (n = 469 from SR and cAF patients were used to calibrate populations of computational SR and cAF atrial AP models. Three populations of over 2000 sampled models were generated, based on three different human atrial AP models. Experimental calibration selected populations of AP models yielding AP with morphology and duration in range with experimental recordings. Populations using the three original models can mimic variability in experimental AP in both SR and cAF, with median conductance values in SR for most ionic currents deviating less than 30% from their original peak values. All cAF populations show similar variations in G(K1, G(Kur and G(to, consistent with AF-related remodeling as reported in experiments. In all SR and cAF model populations, inter-subject variability in I(K1 and I(NaK underlies variability in APD90, variability in I(Kur, I(CaL and I(NaK modulates variability in APD50 and combined variability in Ito and I(Kur determines variability in APD20. The large variability in human atrial AP triangulation is mostly determined by I(K1 and either I(NaK or I(NaCa depending on the model.Experimentally-calibrated human atrial AP models populations mimic AP variability in SR and cAF patient recordings, and identify potential ionic determinants of inter-subject variability in human atrial AP

  2. Synthesis of a dendritic estrogen cluster: A potential tool for studies of nuclear versus extranuclear pathways of estrogen actions

    Institute of Scientific and Technical Information of China (English)

    Jian Chen; Hu Zheng; Yan Song; Yu Feng Liang; Qing Rong Qi

    2012-01-01

    A novel estrogen dendrimer has been synthesized through a combination of divergent and convergent approaches in 9 practical steps and in good yields.It was characterized and confirmed by elemental analysis,FT-IR,MS,1H NMR,13C NMR.The dendrimer contains 16 estrone units and is potentially a useful tool for the studies of estrogen actions.

  3. Flattening of the electrocardiographic T-wave is a sign of proarrhythmic risk and a reflection of action potential triangulation

    DEFF Research Database (Denmark)

    Bhuiyan, Tanveer Ahmed; Graff, Claus; Kanters, J.K.;

    2013-01-01

    Drug-induced triangulation of the cardiac action potential is associated with increased risk of arrhythmic events. It has been suggested that triangulation causes a flattening of the electrocardiographic T-wave but the relationship between triangulation, T-wave flattening and onset of arrhythmia...

  4. Therapeutic concentrations of varenicline in the presence of nicotine increase action potential firing in human adrenal chromaffin cells.

    Science.gov (United States)

    Hone, Arik J; Michael McIntosh, J; Rueda-Ruzafa, Lola; Passas, Juan; de Castro-Guerín, Cristina; Blázquez, Jesús; González-Enguita, Carmen; Albillos, Almudena

    2017-01-01

    Varenicline is a nicotinic acetylcholine receptor (nAChR) agonist used to treat nicotine addiction, but a live debate persists concerning its mechanism of action in reducing nicotine consumption. Although initially reported as α4β2 selective, varenicline was subsequently shown to activate other nAChR subtypes implicated in nicotine addiction including α3β4. However, it remains unclear whether activation of α3β4 nAChRs by therapeutically relevant concentrations of varenicline is sufficient to affect the behavior of cells that express this subtype. We used patch-clamp electrophysiology to assess the effects of varenicline on native α3β4* nAChRs (asterisk denotes the possible presence of other subunits) expressed in human adrenal chromaffin cells and compared its effects to those of nicotine. Varenicline and nicotine activated α3β4* nAChRs with EC50 values of 1.8 (1.2-2.7) μM and 19.4 (11.1-33.9) μM, respectively. Stimulation of adrenal chromaffin cells with 10 ms pulses of 300 μM acetylcholine (ACh) in current-clamp mode evoked sodium channel-dependent action potentials (APs). Under these conditions, perfusion of 50 or 100 nM varenicline showed very little effect on AP firing compared to control conditions (ACh stimulation alone), but at higher concentrations (250 nM) varenicline increased the number of APs fired up to 436 ± 150%. These results demonstrate that therapeutic concentrations of varenicline are unlikely to alter AP firing in chromaffin cells. In contrast, nicotine showed no effect on AP firing at any of the concentrations tested (50, 100, 250, and 500 nM). However, perfusion of 50 nM nicotine simultaneously with 100 nM varenicline increased AP firing by 290 ± 104% indicating that exposure to varenicline and nicotine concurrently may alter cellular behavior such as excitability and neurotransmitter release.

  5. Non-chemical stressors and cumulative risk assessment: an overview of current initiatives and potential air pollutant interactions.

    Science.gov (United States)

    Lewis, Ari S; Sax, Sonja N; Wason, Susan C; Campleman, Sharan L

    2011-06-01

    Regulatory agencies are under increased pressure to consider broader public health concerns that extend to multiple pollutant exposures, multiple exposure pathways, and vulnerable populations. Specifically, cumulative risk assessment initiatives have stressed the importance of considering both chemical and non-chemical stressors, such as socioeconomic status (SES) and related psychosocial stress, in evaluating health risks. The integration of non-chemical stressors into a cumulative risk assessment framework has been largely driven by evidence of health disparities across different segments of society that may also bear a disproportionate risk from chemical exposures. This review will discuss current efforts to advance the field of cumulative risk assessment, highlighting some of the major challenges, discussed within the construct of the traditional risk assessment paradigm. Additionally, we present a summary of studies of potential interactions between social stressors and air pollutants on health as an example of current research that supports the incorporation of non-chemical stressors into risk assessment. The results from these studies, while suggestive of possible interactions, are mixed and hindered by inconsistent application of social stress indicators. Overall, while there have been significant advances, further developments across all of the risk assessment stages (i.e., hazard identification, exposure assessment, dose-response, and risk characterization) are necessary to provide a scientific basis for regulatory actions and effective community interventions, particularly when considering non-chemical stressors. A better understanding of the biological underpinnings of social stress on disease and implications for chemical-based dose-response relationships is needed. Furthermore, when considering non-chemical stressors, an appropriate metric, or series of metrics, for risk characterization is also needed. Cumulative risk assessment research will benefit

  6. The afterhyperpolarizing potential following a train of action potentials is suppressed in an acute epilepsy model in the rat Cornu Ammonis 1 area.

    Science.gov (United States)

    Kernig, K; Kirschstein, T; Würdemann, T; Rohde, M; Köhling, R

    2012-01-10

    In hippocampal Cornu Ammonis 1 (CA1) neurons, a prolonged depolarization evokes a train of action potentials followed by a prominent afterhyperpolarizing potential (AHP), which critically dampens neuronal excitability. Because it is not known whether epileptiform activity alters the AHP and whether any alteration of the AHP is independent of inhibition, we acutely induced epileptiform activity by bath application of the GABA(A) receptor blocker gabazine (5 μM) in the rat hippocampal slice preparation and studied its impact on the AHP using intracellular recordings. Following 10 min of gabazine wash-in, slices started to develop spontaneous epileptiform discharges. This disinhibition was accompanied by a significant shift of the resting membrane potential of CA1 neurons to more depolarized values. Prolonged depolarizations (600 ms) elicited a train of action potentials, the number of which was not different between baseline and gabazine treatment. However, the AHP following the train of action potentials was significantly reduced after 20 min of gabazine treatment. When the induction of epileptiform activity was prevented by co-application of 6-cyano-7-nitroquinoxaline-2,3-dione disodium (CNQX, 10 μM) and D-(-)-2-amino-5-phosphonopentanoic acid (D-AP5, 50 μM) to block α-amino-3-hydroxy-5-methylisoxazolepropionate (AMPA) and N-methyl-d-aspartate (NMDA) receptors, respectively, the AHP was preserved despite of GABA(A) receptor inhibition suggesting that the epileptiform activity was required to suppress the AHP. Moreover, the AHP was also preserved when the slices were treated with the protein kinase blockers H-9 (100 μM) and H-89 (1 μM). These results demonstrate that the AHP following a train of action potentials is rapidly suppressed by acutely induced epileptiform activity due to a phosphorylation process-presumably involving protein kinase A.

  7. Problems, Prescriptions and Potential in Actionable Climate Change Science - A Case Study from California Coastal Marsh Research

    Science.gov (United States)

    MacDonald, G. M.; Ambrose, R. F.; Thorne, K.; Takekawa, J.; Brown, L. N.; Fejtek, S.; Gold, M.; Rosencranz, J.

    2015-12-01

    Frustrations regarding the provision of actionable science extend to both producers and consumers. Scientists decry the lack of application of their research in shaping policy and practices while decision makers bemoan the lack of applicability of scientific research to the specific problems at hand or its narrow focus relative to the plethora of engineering, economic and social considerations that they must also consider. Incorporating climate change adds additional complexity due to uncertainties in estimating many facets of future climate, the inherent variability of climate and the decadal scales over which significant changes will develop. Recently a set of guidelines for successful science-policy interaction was derived from the analysis of transboundary water management. These are; 1 recognizing that science is a crucial but bounded input into the decision-making processes, 2 early establishment of conditions for collaboration and shared commitment among participants, 3 understanding that science-policy interactions are enhanced through greater collaboration and social or group-learning processes, 4 accepting that the collaborative production of knowledge is essential to build legitimate decision-making processes, and 5 engaging boundary organizations and informal networks as well as formal stakeholders. Here we present as a case study research on California coastal marshes, climate change and sea-level that is being conducted by university and USGS scientists under the auspices of the Southwest Climate Science Center. We also present research needs identified by a seperate analysis of best practices for coastal marsh restoration in the face of climate change that was conducted in extensive consultation with planners and managers. The initial communication, scientific research and outreach-dissemination of the marsh scientfic study are outlined and compared to best practices needs identified by planners and the science-policy guidelines outlined above

  8. Construction of initial vortex-surface fields and Clebsch potentials for flows with high-symmetry using first integrals

    Science.gov (United States)

    He, Pengyu; Yang, Yue

    2016-03-01

    We report a systematic study on the construction of the explicit, general form of vortex-surface fields (VSFs) and Clebsch potentials in the initial fields with the zero helicity density and high symmetry. The construction methodology is based on finding independent first integrals of the characteristic equation of a given three-dimensional velocity-vorticity field. In particular, we derive the analytical VSFs and Clebsch potentials for the initial field with the Kida-Pelz symmetry. These analytical results can be useful for the evolution of VSFs to study vortical structures in transitional flows. Moreover, the generality of the construction method is discussed with the synthetic initial fields and the initial Taylor-Green field with multiple wavenumbers.

  9. The initial value problem, scattering and inverse scattering, for Schroedinger equations with a potential and a non-local nonlinearity

    Energy Technology Data Exchange (ETDEWEB)

    Romero, MarIa de los Angeles Sandoval; Weder, Ricardo [Instituto de Investigaciones en Matematicas Aplicadas y en Sistemas, Universidad Nacional Autonoma de Mexico, Apartado Postal 20-726, Mexico DF 01000 (Mexico)

    2006-09-15

    We consider nonlinear Schroedinger equations with a potential, and non-local nonlinearities, that are models in mesoscopic physics, for example of a quantum capacitor, and that are also models of molecular structure. We study in detail the initial value problem for these equations, in particular, existence and uniqueness of local and global solutions, continuous dependence on the initial data and regularity. We allow for a large class of unbounded potentials. We have no restriction on the growth at infinity of the positive part of the potential. We also construct the scattering operator in the case of potentials that go to zero at infinity. Furthermore, we give a method for the unique reconstruction of the potential from the small amplitude limit of the scattering operator. In the case of the quantum capacitor, our method allows us to uniquely reconstruct all the physical parameters from the small amplitude limit of the scattering operator.

  10. Layer I neurons of rat neocortex. I. Action potential and repetitive firing properties.

    Science.gov (United States)

    Zhou, F M; Hablitz, J J

    1996-08-01

    1. Whole cell patch-clamp techniques, combined with direct visualization of neurons, were used to study action potential (AP) and repetitive firing properties of layer I neurons in slices of rat neocortex. 2. Layer I neurons had resting membrane potentials (RMP) of -59.8 +/- 4.7 mV (mean +/- SD) and input resistances (RN) of 592 +/- 284 M Omega. Layer II/III pyramidal neurons had RMPs and RNs of -61.5 +/- 5.6 mV and 320 +/- 113 M omega, respectively. A double exponential function was needed to describe the charging curves of both neuron types. In layer I neurons, tau(0) was 45 +/- 22 ms and tau(1) was 5 +/- 3.3 ms whereas in layer II/III pyramidal neurons, tau(0) was 41 +/- 11 ms and tau(1) was 3 +/- 2.6 ms. Estimates of specific membrane resistance (Rm) for layer I and layer II/III cells were 45 +/- 22 and 41 +/- 11 k omega cm2, respectively (Cm was assumed to be 1 microF/cm2). 3. AP threshold was -41 +/- 2 mV in layer I neurons. Spike amplitudes, measured from threshold to peak, were 90.6 +/- 7.7 mV. AP durations, measured both at the base and half maximal amplitude, were 2.5 +/- 0.4 and 1.1 +/- 0.2 ms, respectively. AP 10-90% rise and repolarization times were 0.6 +/- 0.1 and 1.1 +/- 0.2 ms, respectively. In layer II/III pyramidal neurons, AP threshold was -41 +/- 2.5 mV and spike amplitude was 97 +/- 9.7 mV. AP duration at base and half maximal amplitude was 5.4 +/- 1.1 ms and 1.8 +/- 0.2 ms, respectively. AP 10-90% rise and decay times were 0.6 +/- 0.1 ms and 2.8 +/- 0.6 ms, respectively. 4. Layer I neurons were fast spiking cells that showed little frequency adaptation, a large fast afterhyperpolarization (fAHP), and no slow afterhyperpolarization (sAHP). Some cells had a medium afterhyperpolarization (mAHP) and a slow afterdepolarization (sADP). All pyramidal cells in layer II/III and "atypical" pyramidal neurons in upper layer II showed regular spiking behavior, prominent frequency adaptation, and marked sAHPs. 5. In both layer I neurons and layer II

  11. Reactive species modify NaV1.8 channels and affect action potentials in murine dorsal root ganglion neurons.

    Science.gov (United States)

    Schink, Martin; Leipold, Enrico; Schirmeyer, Jana; Schönherr, Roland; Hoshi, Toshinori; Heinemann, Stefan H

    2016-01-01

    Dorsal root ganglion (DRG) neurons are important relay stations between the periphery and the central nervous system and are essential for somatosensory signaling. Reactive species are produced in a variety of physiological and pathophysiological conditions and are known to alter electric signaling. Here we studied the influence of reactive species on the electrical properties of DRG neurons from mice with the whole-cell patch-clamp method. Even mild stress induced by either low concentrations of chloramine-T (10 μM) or low-intensity blue light irradiation profoundly diminished action potential frequency but prolonged single action potentials in wild-type neurons. The impact on evoked action potentials was much smaller in neurons deficient of the tetrodotoxin (TTX)-resistant voltage-gated sodium channel NaV1.8 (NaV1.8(-/-)), the channel most important for the action potential upstroke in DRG neurons. Low concentrations of chloramine-T caused a significant reduction of NaV1.8 peak current and, at higher concentrations, progressively slowed down inactivation. Blue light had a smaller effect on amplitude but slowed down NaV1.8 channel inactivation. The observed effects were less apparent for TTX-sensitive NaV channels. NaV1.8 is an important reactive-species-sensitive component in the electrical signaling of DRG neurons, potentially giving rise to loss-of-function and gain-of-function phenomena depending on the type of reactive species and their effective concentration and time of exposure.

  12. Mode of action of Bacillus thuringiensis Cry and Cyt toxins and their potential for insect control.

    Science.gov (United States)

    Bravo, Alejandra; Gill, Sarjeet S; Soberón, Mario

    2007-03-15

    Bacillus thuringiensis Crystal (Cry) and Cytolitic (Cyt) protein families are a diverse group of proteins with activity against insects of different orders--Lepidoptera, Coleoptera, Diptera and also against other invertebrates such as nematodes. Their primary action is to lyse midgut epithelial cells by inserting into the target membrane and forming pores. Among this group of proteins, members of the 3-Domain Cry family are used worldwide for insect control, and their mode of action has been characterized in some detail. Phylogenetic analyses established that the diversity of the 3-Domain Cry family evolved by the independent evolution of the three domains and by swapping of domain III among toxins. Like other pore-forming toxins (PFT) that affect mammals, Cry toxins interact with specific receptors located on the host cell surface and are activated by host proteases following receptor binding resulting in the formation of a pre-pore oligomeric structure that is insertion competent. In contrast, Cyt toxins directly interact with membrane lipids and insert into the membrane. Recent evidence suggests that Cyt synergize or overcome resistance to mosquitocidal-Cry proteins by functioning as a Cry-membrane bound receptor. In this review we summarize recent findings on the mode of action of Cry and Cyt toxins, and compare them to the mode of action of other bacterial PFT. Also, we discuss their use in the control of agricultural insect pests and insect vectors of human diseases.

  13. Doubts about actions and flanker incongruity-related potentials and performance

    NARCIS (Netherlands)

    Tops, Mattie; Wijers, Albertus A.

    2012-01-01

    The brain networks that are involved in flanker incongruity and error processing are also consistently implicated in mental disorders such as obsessive compulsive disorder (OCD) that feature increased "Doubts about Actions" (DaA) scores. In the present study we investigated whether DaA scores, simil

  14. How a Small Family Run Business Adopted Critical Reflection Action Learning Using Hand Drawn Images to Initiate Organisational Change

    Science.gov (United States)

    Shepherd, Gary

    2016-01-01

    In this account of practice I would like to share my experiences of facilitating a Critical Reflection Action Learning (CRAL) set with a small family run business, struggling to make change and expand their services due to the problems they encountered in separating their business lives from their family lives. The account I present here is based…

  15. The europa initiative for esa's cosmic vision: a potential european contribution to nasa's Europa mission

    Science.gov (United States)

    Blanc, Michel; Jones, Geraint H.; Prieto-Ballesteros, Olga; Sterken, Veerle J.

    2016-04-01

    The assessment of the habitability of Jupiter's icy moons is considered of high priority in the roadmaps of the main space agencies, including the decadal survey and esa's cosmic vision plan. the voyager and galileo missions indicated that europa and ganymede may meet the requirements of habitability, including deep liquid aqueous reservoirs in their interiors. indeed, they constitute different end-terms of ocean worlds, which deserve further characterization in the next decade. esa and nasa are now both planning to explore these ice moons through exciting and ambitious missions. esa selected in 2012 the juice mission mainly focused on ganymede and the jupiter system, while nasa is currently studying and implementing the europa mission. in 2015, nasa invited esa to provide a junior spacecraft to be carried on board its europa mission, opening a collaboration scheme similar to the very successful cassini-huygens approach. in order to define the best contribution that can be made to nasa's europa mission, a europa initiative has emerged in europe. its objective is to elaborate a community-based strategy for the proposition of the best possible esa contribution(s) to nasa's europa mission, as a candidate for the upcoming selection of esa's 5th medium-class mission . the science returns of the different potential contributions are analysed by six international working groups covering complementary science themes: a) magnetospheric interactions; b) exosphere, including neutrals, dust and plumes; c) geochemistry; d) geology, including expressions of exchanges between layers; e) geophysics, including characterization of liquid water distribution; f) astrobiology. each group is considering different spacecraft options in the contexts of their main scientific merits and limitations, their technical feasibility, and of their interest for the development of esa-nasa collaborations. there are five options under consideration: (1) an augmented payload to the europa mission main

  16. Estimating Renewable Energy Economic Potential in the United States: Methodology and Initial Results

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Austin [National Renewable Energy Lab. (NREL), Golden, CO (United States); Beiter, Philipp [National Renewable Energy Lab. (NREL), Golden, CO (United States); Heimiller, Donna [National Renewable Energy Lab. (NREL), Golden, CO (United States); Davidson, Carolyn [National Renewable Energy Lab. (NREL), Golden, CO (United States); Denholm, Paul [National Renewable Energy Lab. (NREL), Golden, CO (United States); Melius, Jennifer [National Renewable Energy Lab. (NREL), Golden, CO (United States); Lopez, Anthony [National Renewable Energy Lab. (NREL), Golden, CO (United States); Hettinger, Dylan [National Renewable Energy Lab. (NREL), Golden, CO (United States); Mulcahy, David [National Renewable Energy Lab. (NREL), Golden, CO (United States); Porro, Gian [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2016-08-01

    The report describes a geospatial analysis method to estimate the economic potential of several renewable resources available for electricity generation in the United States. Economic potential, one measure of renewable generation potential, is defined in this report as the subset of the available resource technical potential where the cost required to generate the electricity (which determines the minimum revenue requirements for development of the resource) is below the revenue available in terms of displaced energy and displaced capacity.

  17. On the use of upper extremity proximal nerve action potentials in the localization of focal nerve lesions producing axonotmesis.

    Science.gov (United States)

    White, J C

    1997-09-01

    Ulnar, median, and radial proximal nerve action potentials (PNAPs) were recorded from the axilla and supraclavicularly, with stimulation of the nerves at the elbow or the radial groove, in 30 control subjects for each nerve. In addition to routine nerve conduction studies, wrist to elbow median nerve action potentials were recorded proximal to the lesion in 76 patients with carpal tunnel syndrome of varying degrees of severity to determine the effect that the distal lesion might have on more proximal nerve conduction. Utilizing this information, PNAPs, standard nerve conduction studies, and needle electrode examinations were carried out in patients with focal elbow area nerve or brachial plexus lesions producing axonotmesis. PNAPs confirmed the site of the lesions producing axonotmesis when localization was possible with standard nerve conduction and/or needle electrode studies and were the sole means by which localization of the lesions producing only sensory axonotmesis was accomplished.

  18. Regenerating mammalian nerve fibres: changes in action potential waveform and firing characteristics following blockage of potassium conductance.

    Science.gov (United States)

    Kocsis, J D; Waxman, S G; Hildebrand, C; Ruiz, J A

    1982-12-22

    Extracellular application of potassium channel blocking agents is known to increase the amplitude and duration of the compound action potential in non-myelinated and demyelinated axons, but not in mature mammalian myelinated fibres. In the present study we used intra-axonal and whole nerve recording techniques to study the effects of the potassium channel blocking agent 4-aminopyridine (4-AP) on regenerating rat nerve fibres. Our results indicate that early regenerating (premyelinated) axons show considerable broadening of the action potential after 4-AP application and late regenerating (myelinated) axons give rise to burst activity following a single stimulus after 4-AP application. 4-AP did not affect spike waveform or firing properties of normal mature sciatic nerve fibres. These results demonstrate the importance of potassium conductance in stabilizing firing properties of myelinated regenerating axons.

  19. Asphalt fume dermal carcinogenicity potential: II. Initiation-promotion assay of Type III built-up roofing asphalt.

    Science.gov (United States)

    Freeman, James J; Schreiner, Ceinwen A; Beazley, S; Burnett, Donald M; Clark, Charles R; Mahagaokar, Suneeta; Parker, Craig M; Stewart, Christopher W; Swanson, Mark S; Arp, Earl W

    2011-10-01

    Clark et al. (accepted for publication) reported that a sample of field-matched fume condensate from a Type III built-up roofing asphalt (BURA) resulted in a carcinogenic response in a mouse skin bioassay, with relatively few tumor-bearing animals, long tumor latency and chronic skin irritation. This mouse skin initiation/promotion study was conducted to assess possible mechanisms, i.e., genotoxic initiation vs. tumor promotion subsequent to repeated skin injury and repair. The same Type III BURA fume condensate sample was evaluated in groups of 30 male Crl:CD1® mice by skin application twice per week (total dose of 50 mg/week) for 2 weeks during the initiation phase and for 26 weeks during the promotion phase. Positive control substances were 7,12-dimethylbenz(a)anthracene (DMBA, 50 μg applied once) as an initiator and 12-O-tetradecanoyl-13-acetate (TPA, 5 μg, applied twice weekly) during the promotion phase. During the 6 months of study with the asphalt fume condensate, eight skin masses were observed when tested for initiation, five of which were confirmed microscopically to be benign squamous cell papillomas. Only two papillomas were observed when tested for promotion. There was no apparent relationship between skin irritation and tumor development in this study. These results are more indicative of genotoxicity rather than a non-genotoxic mode of action.

  20. Effects of nerve growth factor on the action potential duration and repolarizing currents in a rabbit model of myocardial infarction

    OpenAIRE

    Lan, Yun-Feng; Zhang, Jian-Cheng; Gao, Jin-Lao; Wang, Xue-Ping; Fang, Zhou; Fu, Yi-Cheng; Chen, Mei-Yan; Lin, Min; Xue, Qiao; Li, Yang

    2013-01-01

    Objectives To investigate the effect of nerve growth factor (NGF) on the action potential and potassium currents of non-infarcted myocardium in the myocardial infarcted rabbit model. Methods Rabbits with occlusion of the left anterior descending coronary artery were prepared and allowed to recover for eight weeks (healed myocardial infarction, HMI). During ligation surgery of the left coronary artery, a polyethylene tube was placed near the left stellate ganglion in the subcutis of the neck f...

  1. Sodium entry during action potentials of mammalian central neurons: incomplete inactivation and reduced metabolic efficiency in fast-spiking neurons

    OpenAIRE

    Carter, Brett C.; Bean, Bruce P.

    2009-01-01

    We measured the time course of sodium entry during action potentials of mouse central neurons at 37 °C to examine how efficiently sodium entry is coupled to depolarization. In cortical pyramidal neurons, sodium entry was nearly completely confined to the rising phase of the spike: only ~25% more sodium enters than the theoretical minimum necessary for spike depolarization. However, in fast-spiking GABAergic neurons (cerebellar Purkinje cells and cortical interneurons), twice as much sodium en...

  2. Microparticles generated by decompression stress cause central nervous system injury manifested as neurohypophysial terminal action potential broadening

    OpenAIRE

    Yang, Ming; Kosterin, Paul; Salzberg, Brian M.; Milovanova, Tatyana N.; Bhopale, Veena M.; Thom, Stephen R.

    2013-01-01

    The study goal was to use membrane voltage changes during neurohypophysial action potential (AP) propagation as an index of nerve function to evaluate the role that circulating microparticles (MPs) play in causing central nervous system injury in response to decompression stress in a murine model. Mice studied 1 h following decompression from 790 kPa air pressure for 2 h exhibit a 45% broadening of the neurohypophysial AP. Broadening did not occur if mice were injected with the MP lytic agent...

  3. Shaping of action potentials by type I and type II large-conductance Ca²+-activated K+ channels.

    Science.gov (United States)

    Jaffe, D B; Wang, B; Brenner, R

    2011-09-29

    The BK channel is a Ca(2+) and voltage-gated conductance responsible for shaping action potential waveforms in many types of neurons. Type II BK channels are differentiated from type I channels by their pharmacology and slow gating kinetics. The β4 accessory subunit confers type II properties on BK α subunits. Empirically derived properties of BK channels, with and without the β4 accessory subunit, were obtained using a heterologous expression system under physiological ionic conditions. These data were then used to study how BK channels alone (type I) and with the accessory β4 subunit (type II) modulate action potential properties in biophysical neuron models. Overall, the models support the hypothesis that it is the slower kinetics provided by the β4 subunit that endows the BK channel with type II properties, which leads to broadening of action potentials and, secondarily, to greater recruitment of SK channels reducing neuronal excitability. Two regions of parameter space distinguished type II and type I effects; one where the range of BK-activating Ca(2+) was high (>20 μM) and the other where BK-activating Ca(2+) was low (∼0.4-1.2 μM). The latter required an elevated BK channel density, possibly beyond a likely physiological range. BK-mediated sharpening of the spike waveform associated with the lack of the β4 subunit was sensitive to the properties of voltage-gated Ca(2+) channels due to electrogenic effects on spike duration. We also found that depending on Ca(2+) dynamics, type II BK channels may have the ability to contribute to the medium AHP, a property not generally ascribed to BK channels, influencing the frequency-current relationship. Finally, we show how the broadening of action potentials conferred by type II BK channels can also indirectly increase the recruitment of SK-type channels decreasing the excitability of the neuron.

  4. Action Potential Modulation in CA1 Pyramidal Neuron Axons Facilitates OLM Interneuron Activation in Recurrent Inhibitory Microcircuits of Rat Hippocampus

    OpenAIRE

    Sooyun Kim

    2014-01-01

    Oriens-lacunosum moleculare (O-LM) interneurons in the CA1 region of the hippocampus play a key role in feedback inhibition and in the control of network activity. However, how these cells are efficiently activated in the network remains unclear. To address this question, I performed recordings from CA1 pyramidal neuron axons, the presynaptic fibers that provide feedback innervation of these interneurons. Two forms of axonal action potential (AP) modulation were identified. First, repetitive ...

  5. Corticospinal neurons in macaque ventral premotor cortex with mirror properties: a potential mechanism for action suppression?

    Science.gov (United States)

    Kraskov, Alexander; Dancause, Numa; Quallo, Marsha M; Shepherd, Samantha; Lemon, Roger N

    2009-12-24

    The discovery of "mirror neurons" in area F5 of the ventral premotor cortex has prompted many theories as to their possible function. However, the identity of mirror neurons remains unknown. Here, we investigated whether identified pyramidal tract neurons (PTNs) in area F5 of two adult macaques exhibited "mirror-like" activity. About half of the 64 PTNs tested showed significant modulation of their activity while monkeys observed precision grip of an object carried out by an experimenter, with somewhat fewer showing modulation during precision grip without an object or grasping concealed from the monkey. Therefore, mirror-like activity can be transmitted directly to the spinal cord via PTNs. A novel finding is that many PTNs (17/64) showed complete suppression of discharge during action observation, while firing actively when the monkey grasped food rewards. We speculate that this suppression of PTN discharge might be involved in the inhibition of self-movement during action observation.

  6. Potential pathways of pesticide action on erectile function-a contributory factor in male infertility

    Institute of Scientific and Technical Information of China (English)

    RP Kaur; V Gupta; AF Christopher; P Bansal

    2015-01-01

    One of the important objectives of this manuscript is to focus on the place of erectile dysfunction as an important factor for infertility. The review is about correlating the indiscriminate use of pesticides and to find out and highlight the evidences for mechanism of action of these pesticides for erectile dysfunction and find out the most used and most dangerous pesticide from erectile dysfunction point of view. The review suggests that erectile dysfunction is having a significant place as a causal factor for infertility. Study infers that pesticides are having multiple mechanisms of action through which these cause erectile dysfunction. It also reflects that acetamiprid is having most devastating effect causing erectile dysfunction as it acts through multiple inhibitory pathways. The review successfully highlights the indiscriminate regional use of pesticides.

  7. An antioxidant-like action for non-peroxidisable phospholipids using ferrous iron as a peroxidation initiator.

    Science.gov (United States)

    Cortie, Colin H; Else, Paul L

    2015-06-01

    The degradation of phospholipids containing polyunsaturated fatty acids, termed peroxidation, poses a constant challenge to membranes lipid composition and function. Phospholipids with saturated (e.g. PC 16:0/16:0) and monounsaturated fatty acids (e.g. PC 16:0/18:1) are some of the most common phospholipids found in membranes and are generally not peroxidisable. The present experiments show that these non-peroxidisable phospholipids, when present in liposomes with peroxidisable phospholipids (i.e. those containing polyunsaturated fatty acids) such as PC 16:0/18:2 and Soy PC, produce an inhibitory effect on rates of peroxidation induced by ferrous-iron. This inhibitory effect acts to extend the duration of the lag phase by several-fold. If present in natural systems, this action could enhance the capacity of conventional antioxidant mechanisms in membranes. The results of this preliminary work suggest that non-peroxidisable phospholipids may exert an antioxidant-like action in membranes.

  8. Amplitude of sensory nerve action potential in early stage diabetic peripheral neuropathy:an analysis of 500 cases

    Institute of Scientific and Technical Information of China (English)

    Yunqian Zhang; Jintao Li; Tingjuan Wang; Jianlin Wang

    2014-01-01

    Early diagnosis of diabetic peripheral neuropathy is important for the successful treatment of diabetes mellitus. In the present study, we recruited 500 diabetic patients from the Fourth Afifl-iated Hospital of Kunming Medical University in China from June 2008 to September 2013: 221 cases showed symptoms of peripheral neuropathy (symptomatic group) and 279 cases had no symptoms of peripheral impairment (asymptomatic group). One hundred healthy control sub-jects were also recruited. Nerve conduction studies revealed that distal motor latency was longer, sensory nerve conduction velocity was slower, and sensory nerve action potential and amplitude of compound muscle action potential were signiifcantly lower in the median, ulnar, posterior tibial and common peroneal nerve in the diabetic groups compared with control subjects. More-over, the alterations were more obvious in patients with symptoms of peripheral neuropathy. Of the 500 diabetic patients, neural conduction abnormalities were detected in 358 cases (71.6%), among which impairment of the common peroneal nerve was most prominent. Sensory nerve abnormality was more obvious than motor nerve abnormality in the diabetic groups. The ampli-tude of sensory nerve action potential was the most sensitive measure of peripheral neuropathy. Our results reveal that varying degrees of nerve conduction changes are present in the early, as-ymptomatic stage of diabetic peripheral neuropathy.

  9. Amplitude of sensory nerve action potential in early stage diabetic peripheral neuropathy: an analysis of 500 cases.

    Science.gov (United States)

    Zhang, Yunqian; Li, Jintao; Wang, Tingjuan; Wang, Jianlin

    2014-07-15

    Early diagnosis of diabetic peripheral neuropathy is important for the successful treatment of diabetes mellitus. In the present study, we recruited 500 diabetic patients from the Fourth Affiliated Hospital of Kunming Medical University in China from June 2008 to September 2013: 221 cases showed symptoms of peripheral neuropathy (symptomatic group) and 279 cases had no symptoms of peripheral impairment (asymptomatic group). One hundred healthy control subjects were also recruited. Nerve conduction studies revealed that distal motor latency was longer, sensory nerve conduction velocity was slower, and sensory nerve action potential and amplitude of compound muscle action potential were significantly lower in the median, ulnar, posterior tibial and common peroneal nerve in the diabetic groups compared with control subjects. Moreover, the alterations were more obvious in patients with symptoms of peripheral neuropathy. Of the 500 diabetic patients, neural conduction abnormalities were detected in 358 cases (71.6%), among which impairment of the common peroneal nerve was most prominent. Sensory nerve abnormality was more obvious than motor nerve abnormality in the diabetic groups. The amplitude of sensory nerve action potential was the most sensitive measure of peripheral neuropathy. Our results reveal that varying degrees of nerve conduction changes are present in the early, asymptomatic stage of diabetic peripheral neuropathy.

  10. Ventricular filling slows epicardial conduction and increases action potential duration in an optical mapping study of the isolated rabbit heart

    Science.gov (United States)

    Sung, Derrick; Mills, Robert W.; Schettler, Jan; Narayan, Sanjiv M.; Omens, Jeffrey H.; McCulloch, Andrew D.; McCullough, A. D. (Principal Investigator)

    2003-01-01

    INTRODUCTION: Mechanical stimulation can induce electrophysiologic changes in cardiac myocytes, but how mechanoelectric feedback in the intact heart affects action potential propagation remains unclear. METHODS AND RESULTS: Changes in action potential propagation and repolarization with increased left ventricular end-diastolic pressure from 0 to 30 mmHg were investigated using optical mapping in isolated perfused rabbit hearts. With respect to 0 mmHg, epicardial strain at 30 mmHg in the anterior left ventricle averaged 0.040 +/- 0.004 in the muscle fiber direction and 0.032 +/- 0.006 in the cross-fiber direction. An increase in ventricular loading increased average epicardial activation time by 25%+/- 3% (P myocardial perfusion or the presence of an electromechanical decoupling agent (butanedione monoxime) during optical mapping. CONCLUSION: Acute loading of the left ventricle of the isolated rabbit heart decreased apparent epicardial conduction velocity and increased action potential duration by a load-dependent mechanism that may not involve stretch-activated channels.

  11. Role of gap junction channel in the development of beat-to-beat action potential repolarization variability and arrhythmias.

    Science.gov (United States)

    Magyar, Janos; Banyasz, Tamas; Szentandrassy, Norbert; Kistamas, Kornel; Nanasi, Peter P; Satin, Jonathan

    2015-01-01

    The short-term beat-to-beat variability of cardiac action potential duration (SBVR) occurs as a random alteration of the ventricular repolarization duration. SBVR has been suggested to be more predictive of the development of lethal arrhythmias than the action potential prolongation or QT prolongation of ECG alone. The mechanism underlying SBVR is not completely understood but it is known that SBVR depends on stochastic ion channel gating, intracellular calcium handling and intercellular coupling. Coupling of single cardiomyocytes significantly decreases the beat-to-beat changes in action potential duration (APD) due to the electrotonic current flow between neighboring cells. The magnitude of this electrotonic current depends on the intercellular gap junction resistance. Reduced gap junction resistance causes greater electrotonic current flow between cells, and reduces SBVR. Myocardial ischaemia (MI) is known to affect gap junction channel protein expression and function. MI increases gap junction resistance that leads to slow conduction, APD and refractory period dispersion, and an increase in SBVR. Ultimately, development of reentry arrhythmias and fibrillation are associated post-MI. Antiarrhythmic drugs have proarrhythmic side effects requiring alternative approaches. A novel idea is to target gap junction channels. Specifically, the use of gap junction channel enhancers and inhibitors may help to reveal the precise role of gap junctions in the development of arrhythmias. Since cell-to-cell coupling is represented in SBVR, this parameter can be used to monitor the degree of coupling of myocardium.

  12. Complex Dynamic Thresholds and Generation of the Action Potentials in the Neural-Activity Model

    Science.gov (United States)

    Kirillov, S. Yu.; Nekorkin, V. I.

    2016-05-01

    This work is devoted to studying the processes of activation of the neurons whose excitation thresholds are not constant and vary in time (the so-called dynamic thresholds). The neuron dynamics is described by the FitzHugh-Nagumo model with nonlinear behavior of the recovery variable. The neuron response to the external pulsed activating action in the presence of a slowly varying synaptic current is studied within the framework of this model. The structure of the dynamic threshold is studied and its properties depending on the external-action parameters are established. It is found that the formation of the "folds" in the separatrix threshold manifold in the model phase space is a typical feature of the complex dynamic threshold. High neuron sensitivity to the action of the comparatively weak slow control signals is established. This explains the capability of the neurons to perform flexible tuning of their selective properties for detecting various external signals in sufficiently short times (of the order of duration of several spikes).

  13. Initial phases of design-based research into the educational potentials of NAO-robots

    DEFF Research Database (Denmark)

    Majgaard, Gunver; Bertel, Lykke Brogaard

    2014-01-01

    In this paper, we describe our initial research, using the humanoid robot NAO in primary and secondary schools. How does a programmable humanoid enrich teaching and how do we prepare the teachers? Ten school classes are using the robot for creative programming. So far we have experienced that the......In this paper, we describe our initial research, using the humanoid robot NAO in primary and secondary schools. How does a programmable humanoid enrich teaching and how do we prepare the teachers? Ten school classes are using the robot for creative programming. So far we have experienced...

  14. Potential impact on HIV incidence of higher HIV testing rates and earlier antiretroviral therapy initiation in MSM

    DEFF Research Database (Denmark)

    Phillips, Andrew N; Cambiano, Valentina; Miners, Alec

    2015-01-01

    BACKGROUND: Increased rates of testing, with early antiretroviral therapy (ART) initiation, represent a key potential HIV-prevention approach. Currently, in MSM in the United Kingdom, it is estimated that 36% are diagnosed by 1 year from infection, and the ART initiation threshold is at CD4 cell...... on HIV in MSM in the United Kingdom. Outcomes were projected according to future alternative HIV testing and ART initiation scenarios to 2030, considering also potential changes in levels of condomless sex. RESULTS: For ART use to result in an incidence of close to 1/1000 person-years requires...... the proportion of all HIV-positive MSM with viral suppression to increase from below 60% currently to 90%, assuming no rise in levels of condomless sex. Substantial increases in HIV testing, such that over 90% of men are diagnosed within a year of infection, would increase the proportion of HIV-positive men...

  15. Efficient Procedure to Compute the Microcanonical Volume of Initial Conditions that Lead to Escape Trajectories from a Multidimensional Potential Well

    NARCIS (Netherlands)

    Waalkens, Holger; Burbanks, Andrew; Wiggins, Stephen

    2005-01-01

    A procedure is presented for computing the phase space volume of initial conditions for trajectories that escape or ‘‘react’’ from a multidimensional potential well. The procedure combines a phase space transition state theory, which allows one to construct dividing surfaces that are free of local r

  16. Comparison of regulated passive membrane conductance in action potential-firing fast- and slow-twitch muscle.

    Science.gov (United States)

    Pedersen, Thomas Holm; Macdonald, William Alexander; de Paoli, Frank Vincenzo; de Paoli, Frank Vinzenco; Gurung, Iman Singh; Nielsen, Ole Baekgaard

    2009-10-01

    In several pathological and experimental conditions, the passive membrane conductance of muscle fibers (G(m)) and their excitability are inversely related. Despite this capacity of G(m) to determine muscle excitability, its regulation in active muscle fibers is largely unexplored. In this issue, our previous study (Pedersen et al. 2009. J. Gen. Physiol. doi:10.1085/jgp.200910291) established a technique with which biphasic regulation of G(m) in action potential (AP)-firing fast-twitch fibers of rat extensor digitorum longus muscles was identified and characterized with temporal resolution of seconds. This showed that AP firing initially reduced G(m) via ClC-1 channel inhibition but after approximately 1,800 APs, G(m) rose substantially, causing AP excitation failure. This late increase of G(m) reflected activation of ClC-1 and K(ATP) channels. The present study has explored regulation of G(m) in AP-firing slow-twitch fibers of soleus muscle and compared it to G(m) dynamics in fast-twitch fibers. It further explored aspects of the cellular signaling that conveyed regulation of G(m) in AP-firing fibers. Thus, in both fiber types, AP firing first triggered protein kinase C (PKC)-dependent ClC-1 channel inhibition that reduced G(m) by approximately 50%. Experiments with dantrolene showed that AP-triggered SR Ca(2+) release activated this PKC-mediated ClC-1 channel inhibition that was associated with reduced rheobase current and improved function of depolarized muscles, indicating that the reduced G(m) enhanced muscle fiber excitability. In fast-twitch fibers, the late rise in G(m) was accelerated by glucose-free conditions, whereas it was postponed when intermittent resting periods were introduced during AP firing. Remarkably, elevation of G(m) was never encountered in AP-firing slow-twitch fibers, even after 15,000 APs. These observations implicate metabolic depression in the elevation of G(m) in AP-firing fast-twitch fibers. It is concluded that regulation of G(m) is

  17. Estimating Renewable Energy Economic Potential in the United States. Methodology and Initial Results

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Austin; Beiter, Philipp; Heimiller, Donna; Davidson, Carolyn; Denholm, Paul; Melius, Jennifer; Lopez, Anthony; Hettinger, Dylan; Mulcahy, David; Porro, Gian

    2016-08-01

    This report describes a geospatial analysis method to estimate the economic potential of several renewable resources available for electricity generation in the United States. Economic potential, one measure of renewable generation potential, may be defined in several ways. For example, one definition might be expected revenues (based on local market prices) minus generation costs, considered over the expected lifetime of the generation asset. Another definition might be generation costs relative to a benchmark (e.g., a natural gas combined cycle plant) using assumptions of fuel prices, capital cost, and plant efficiency. Economic potential in this report is defined as the subset of the available resource technical potential where the cost required to generate the electricity (which determines the minimum revenue requirements for development of the resource) is below the revenue available in terms of displaced energy and displaced capacity. The assessment is conducted at a high geospatial resolution (more than 150,000 technology-specific sites in the continental United States) to capture the significant variation in local resource, costs, and revenue potential. This metric can be a useful screening factor for understanding the economic viability of renewable generation technologies at a specific location. In contrast to many common estimates of renewable energy potential, economic potential does not consider market dynamics, customer demand, or most policy drivers that may incent renewable energy generation.

  18. Matrix metalloproteinase-10 is required for lung cancer stem cell maintenance, tumor initiation and metastatic potential.

    Directory of Open Access Journals (Sweden)

    Verline Justilien

    Full Text Available Matrix metalloproteinases (Mmps stimulate tumor invasion and metastasis by degrading the extracellular matrix. Here we reveal an unexpected role for Mmp10 (stromelysin 2 in the maintenance and tumorigenicity of mouse lung cancer stem-like cells (CSC. Mmp10 is highly expressed in oncosphere cultures enriched in CSCs and RNAi-mediated knockdown of Mmp10 leads to a loss of stem cell marker gene expression and inhibition of oncosphere growth, clonal expansion, and transformed growth in vitro. Interestingly, clonal expansion of Mmp10 deficient oncospheres can be restored by addition of exogenous Mmp10 protein to the culture medium, demonstrating a direct role for Mmp10 in the proliferation of these cells. Oncospheres exhibit enhanced tumor-initiating and metastatic activity when injected orthotopically into syngeneic mice, whereas Mmp10-deficient cultures show a severe defect in tumor initiation. Conversely, oncospheres implanted into syngeneic non-transgenic or Mmp10(-/- mice show no significant difference in tumor initiation, growth or metastasis, demonstrating the importance of Mmp10 produced by cancer cells rather than the tumor microenvironment in lung tumor initiation and maintenance. Analysis of gene expression data from human cancers reveals a strong positive correlation between tumor Mmp10 expression and metastatic behavior in many human tumor types. Thus, Mmp10 is required for maintenance of a highly tumorigenic, cancer-initiating, metastatic stem-like cell population in lung cancer. Our data demonstrate for the first time that Mmp10 is a critical lung cancer stem cell gene and novel therapeutic target for lung cancer stem cells.

  19. Adaptation decision-making in the Nordic Countries: assessing the potential for joint action

    DEFF Research Database (Denmark)

    Juhola, Sirkku; Goodsite, Michael Evan; Davis, Marion

    2014-01-01

    on the issue. This paper explores the potential for Nordic cooperation on adaptation; specifically, for the development of a regional adaptation strategy. In particular, it addresses two questions (1) What is the current state of adaptation in the Nordic countries? and (2) What are the potential benefits...

  20. Antidiabetic Drugs: Mechanisms of Action and Potential Outcomes on Cellular Metabolism.

    Science.gov (United States)

    Meneses, Maria J; Silva, Branca M; Sousa, Mário; Sá, Rosália; Oliveira, Pedro F; Alves, Marco G

    2015-01-01

    Diabetes mellitus (DM) is one of the most prevalent chronic diseases and has been a leading cause of death in the last decades. Thus, methods to detect, prevent or delay this disease and its co-morbidities have long been a matter of discussion. Nowadays, DM patients, particularly those suffering with type 2 DM, are advised to alter their diet and physical exercise regimens and then proceed progressively from monotherapy, dual therapy, and multi-agent therapy to insulin administration, as the disease becomes more severe. Although progresses have been made, the pursuit for the "perfect" antidiabetic drug still continues. The complexity of DM and its impact on whole body homeodynamics are two of the main reasons why there is not yet such a drug. Moreover, the molecular mechanisms by which DM can be controlled are still under an intense debate. As the associated risks, disadvantages, side effects and mechanisms of action vary from drug to drug, the choice of the most suitable therapy needs to be thoroughly investigated. Herein we propose to discuss the different classes of antidiabetic drugs available, their applications and mechanisms of action, particularly those of the newer and/or most widely prescribed classes. A special emphasis will be made on their effects on cellular metabolism, since these drugs affect those pathways in several cellular systems and organs, promoting metabolic alterations responsible for either deleterious or beneficial effects. This is a crucial property that needs to be carefully investigated when prescribing an antidiabetic.

  1. [Potentials of cooperative quality management initiatives: BQS Institute projects, January 2010 - July 2013].

    Science.gov (United States)

    Veit, Christof; Bungard, Sven; Hertle, Dagmar; Grothaus, Franz-Josef; Kötting, Joachim; Arnold, Nicolai

    2013-01-01

    Alongside the projects of internal quality management and mandatory quality assurance there is a variety of quality driven projects across institutions initiated and run by various partners to continuously improve the quality of care. The multiplicity and characteristics of these projects are discussed on the basis of projects run by the BQS Institute between 2010 and 2013. In addition, useful interactions and linking with mandatory quality benchmarking and with internal quality management are discussed. (As supplied by publisher).

  2. Potential savings of harmonising hospital and community formularies for chronic disease medications initiated in hospital.

    Directory of Open Access Journals (Sweden)

    Lauren Lapointe-Shaw

    Full Text Available BACKGROUND: Hospitals in Canada manage their formularies independently, yet many inpatients are discharged on medications which will be purchased through publicly-funded programs. We sought to determine how much public money could be saved on chronic medications if hospitals promoted the initiation of agents with the lowest outpatient formulary prices. METHODS: We used administrative databases for the province of Ontario to identify patients initiated on a proton pump inhibitor (PPI, angiotensin-converting enzyme (ACE inhibitor or angiotensin receptor blocker (ARB following hospital admission from April 1(st 2008-March 31(st 2009. We assessed the cost to the Ontario Drug Benefit Program (ODB over the year following initiation and determined the cost savings if prescriptions were substituted with the least expensive agent in each class. RESULTS: The cost for filling all PPI, ACE inhibitor and ARB prescriptions was $ 2.48 million, $968 thousand and $325 thousand respectively. Substituting the least expensive agent could have saved $1.16 million (47% for PPIs, $162 thousand (17% for ACE inhibitors and $14 thousand (4% for ARBs over the year following discharge. INTERPRETATION: In a setting where outpatient prescriptions are publicly funded, harmonising outpatient formularies with inpatient therapeutic substitution resulted in modest cost savings and may be one way to control rising pharmaceutical costs.

  3. Modulatory action of acetylcholine on the Na+-dependent action potentials in Kenyon cells isolated from the mushroom body of the cricket brain.

    Science.gov (United States)

    Terazima, E; Yoshino, M

    2010-12-01

    Kenyon cells, intrinsic neurons of the insect mushroom body, have been assumed to be a site of conditioning stimulus (CS) and unconditioned stimulus (US) association in olfactory learning and memory. Acetylcholine (ACh) has been implicated to be a neurotransmitter mediating CS reception in Kenyon cells, causing rapid membrane depolarization via nicotinic ACh receptors. However, the long-term effects of ACh on the membrane excitability of Kenyon cells are not fully understood. In this study, we examined the effects of ACh on Na(+) dependent action potentials (Na(+) spikes) elicited by depolarizing current injection and on net membrane currents under the voltage clamp condition in Kenyon cells isolated from the mushroom body of the cricket Gryllus bimaculatus. Current-clamp studies using amphotericin B perforated-patch recordings showed that freshly dispersed cricket Kenyon cells could produce repetitive Na(+) spikes in response to prolonged depolarizing current injection. Bath application of ACh increased both the instantaneous frequency and the amplitudes of Na(+) spikes. This excitatory action of ACh on Kenyon cells is attenuated by the pre-treatment of the cells with the muscarinic receptor antagonists, atropine and scopolamine, but not by the nicotinic receptor antagonist mecamylamine. Voltage-clamp studies further showed that bath application of ACh caused an increase in net inward currents that are sensitive to TTX, whereas outward currents were decreased by this treatment. These results indicate that in order to mediate CS, ACh may modulate the firing properties of Na(+) spikes of Kenyon cells through muscarinic receptor activation, thus increasing Na conductance and decreasing K conductance.

  4. Waveform Similarity Analysis: A Simple Template Comparing Approach for Detecting and Quantifying Noisy Evoked Compound Action Potentials.

    Science.gov (United States)

    Potas, Jason Robert; de Castro, Newton Gonçalves; Maddess, Ted; de Souza, Marcio Nogueira

    2015-01-01

    Experimental electrophysiological assessment of evoked responses from regenerating nerves is challenging due to the typical complex response of events dispersed over various latencies and poor signal-to-noise ratio. Our objective was to automate the detection of compound action potential events and derive their latencies and magnitudes using a simple cross-correlation template comparison approach. For this, we developed an algorithm called Waveform Similarity Analysis. To test the algorithm, challenging signals were generated in vivo by stimulating sural and sciatic nerves, whilst recording evoked potentials at the sciatic nerve and tibialis anterior muscle, respectively, in animals recovering from sciatic nerve transection. Our template for the algorithm was generated based on responses evoked from the intact side. We also simulated noisy signals and examined the output of the Waveform Similarity Analysis algorithm with imperfect templates. Signals were detected and quantified using Waveform Similarity Analysis, which was compared to event detection, latency and magnitude measurements of the same signals performed by a trained observer, a process we called Trained Eye Analysis. The Waveform Similarity Analysis algorithm could successfully detect and quantify simple or complex responses from nerve and muscle compound action potentials of intact or regenerated nerves. Incorrectly specifying the template outperformed Trained Eye Analysis for predicting signal amplitude, but produced consistent latency errors for the simulated signals examined. Compared to the trained eye, Waveform Similarity Analysis is automatic, objective, does not rely on the observer to identify and/or measure peaks, and can detect small clustered events even when signal-to-noise ratio is poor. Waveform Similarity Analysis provides a simple, reliable and convenient approach to quantify latencies and magnitudes of complex waveforms and therefore serves as a useful tool for studying evoked compound

  5. Methanol extract of Tephrosia vogelii leaves potentiates the contractile action of acetylcholine on isolated rabbit jejunum

    Directory of Open Access Journals (Sweden)

    Tavershima Dzenda

    2015-09-01

    Conclusions: The findings demonstrate that methanol extract of Tephrosia vogelii leaves potentiates the contractile effect of ACh on intestinal smooth muscle, supporting the traditional claim that the plant is purgative.

  6. Carbon Monoxide Effects onHuman Ventricle Action PotentialAssessed by Mathematical Simulations

    OpenAIRE

    Beatriz eTrenor; Karen eCardona; Javier eSaiz; Sridharan eRajamani; Luiz eBelardinelli; Wayne Rodney Giles

    2013-01-01

    Carbon monoxide (CO) that is produced in a number of different mammalian tissues is now known to have significant effects on the cardiovascular system. These include: i) vasodilation, ii) changes in heart rate and strength of contractions and iii) modulation of autonomic nervous system input to both the pacemaker and the working myocardium. Excessive CO in the environment is toxic and can initiate or mediate life threatening cardiac rhythm disturbances. Recent reports link these ventricular...

  7. Local, organic food initiatives and their potentials for transforming the conventional food system

    Directory of Open Access Journals (Sweden)

    Geir Lieblein

    2005-05-01

    Full Text Available L’objectif de cet article est de discuter l’importance des initiatives locales dans la distribution de produits biologiques. Le sujet est abordé d’une part en fonction de la relation entre ce type d’initiatives et le système agroalimentaire conventionnel et d’autre part en fonction de la possibilité du développement d’un système agroalimentaire plus durable. Basé sur trois études scandinaves, concernant des produits biologiques en Norvège et au Danemark, cet article souligne le fait que les différents acteurs intreviewés jouent à la fois sur le tableau du local et du biologique et sur le tableau du conventionnel. En dépit de différences structurelles distinctes, les deux systèmes, et les conventions qui leur sont rattachées, s’influencent mutuellement. Afin de mettre au point une agriculture plus durable, il semble donc important de mettre en valeur le fondement global de l’agriculture écologique, qui repose non seulement sur des valeurs biologiques et locales, mais encore sur des aspects économiques, sociaux et culturels qui doivent être pris en considération.The aim of this article is to discuss the importance of local initiatives for distribution of organic food. This subject is discussed both in relation to how such initiatives may affect the overall conventional food system and the possible implications for development of a more sustainable food system. The article is based on findings from three different cases of local, organic food in Norway and Denmark. We found that actors within the cases are both involved with local, organic food initiatives and at the same time part of the overall conventional food system. Even though there are distinctive structural differences between these distribution systems, they mutually affect each other. This means that conventions normally associated with local, organic food systems may ‘rub off’ to the conventional food system and vice versa. In order to develop

  8. Cardiovascular pleiotropic actions of DPP-4 inhibitors: a step at the cutting edge in understanding their additional therapeutic potentials.

    Science.gov (United States)

    Balakumar, Pitchai; Dhanaraj, Sokkalingam A

    2013-09-01

    Dipeptidyl peptidase 4 (DPP-4) is a serine protease enzyme expressed widely in many tissues, including the cardiovascular system. The incretin hormones such as glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are released from the small intestine into the vasculature during a meal, and these incretins have a potential to release insulin from pancreatic beta cells of islets of Langerhans, affording a glucose-lowering action. However, both incretins are hurriedly degraded by the DPP-4. Inhibitors of DPP-4, therefore, enhance the bioavailability of GLP-1 and GIP, and thus have been approved for better glycemic management in patients afflicted with type 2 diabetes mellitus (T2DM). Five different DPP-4 inhibitors, often called as 'gliptins', namely sitagliptin, vildagliptin, saxagliptin, linagliptin and alogliptin have been approved hitherto for clinical use. These drugs are used along with diet and exercise to lower blood sugar in diabetic subjects. T2DM is intricately related with an increased risk of cardiovascular disease. Growing body of evidence suggests that gliptins, in addition to their persuasive anti-diabetic action, have a beneficial pleiotropic action on the heart and vessels. In view of the fact of cardiovascular disease susceptibility of patients afflicted with T2DM, gliptins might offer additional therapeutic benefits in treating diabetic cardiovascular complications. Exploring further the cardiovascular pleiotropic potentials of gliptins might open a panorama in impeccably employing these agents for the dual management of T2DM and T2DM-associated perilous cardiovascular complications. This review will shed lights on the newly identified beneficial pleiotropic actions of gliptins on the cardiovascular system.

  9. Computational modeling of voltage-gated Ca channels inhibition: identification of different effects on uterine and cardiac action potentials

    Directory of Open Access Journals (Sweden)

    Wing Chiu eTong

    2014-10-01

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

  10. Ionic mechanisms in the generation of subthreshold oscillations and action potential clustering in entorhinal layer II stellate neurons.

    Science.gov (United States)

    Fransén, Erik; Alonso, Angel A; Dickson, Clayton T; Magistretti, Jacopo; Hasselmo, Michael E

    2004-01-01

    A multicompartmental biophysical model of entorhinal cortex layer II stellate cells was developed to analyze the ionic basis of physiological properties, such as subthreshold membrane potential oscillations, action potential clustering, and the medium afterhyperpolarization. In particular, the simulation illustrates the interaction of the persistent sodium current (I(Nap)) and the hyperpolarization activated inward current (Ih) in the generation of subthreshold membrane potential oscillations. The potential role of Ih in contributing to the medium hyperpolarization (mAHP) and rebound spiking was studied. The role of Ih and the slow calcium-activated potassium current Ikappa(AHP) in action potential clustering was also studied. Representations of Ih and I(Nap) were developed with parameters based on voltage-clamp data from whole-cell patch and single channel recordings of stellate cells (Dickson et al., J Neurophysiol 83:2562-2579, 2000; Magistretti and Alonso, J Gen Physiol 114:491-509, 1999; Magistretti et al., J Physiol 521:629-636, 1999a; J Neurosci 19:7334-7341, 1999b). These currents interacted to generate robust subthreshold membrane potentials with amplitude and frequency corresponding to data observed in the whole cell patch recordings. The model was also able to account for effects of pharmacological manipulations, including blockade of Ih with ZD7288, partial blockade with cesium, and the influence of barium on oscillations. In a model with a wider range of currents, the transition from oscillations to single spiking, to spike clustering, and finally tonic firing could be replicated. In agreement with experiment, blockade of calcium channels in the model strongly reduced clustering. In the voltage interval during which no data are available, the model predicts that the slow component of Ih does not follow the fast component down to very short time constants. The model also predicts that the fast component of Ih is responsible for the involvement in the

  11. CK2 phosphorylation of eukaryotic translation initiation factor 5 potentiates cell cycle progression

    Science.gov (United States)

    Homma, Miwako Kato; Wada, Ikuo; Suzuki, Toshiyuki; Yamaki, Junko; Krebs, Edwin G.; Homma, Yoshimi

    2005-01-01

    Casein kinase 2 (CK2) is a ubiquitous eukaryotic Ser/Thr protein kinase that plays an important role in cell cycle progression. Although its function in this process remains unclear, it is known to be required for the G1 and G2/M phase transitions in yeast. Here, we show that CK2 activity changes notably during cell cycle progression and is increased within 3 h of serum stimulation of quiescent cells. During the time period in which it exhibits high enzymatic activity, CK2 associates with and phosphorylates a key molecule for translation initiation, eukaryotic translation initiation factor (eIF) 5. Using MS, we show that Ser-389 and -390 of eIF5 are major sites of phosphorylation by CK2. This is confirmed using eIF5 mutants that lack CK2 sites; the phosphorylation levels of mutant eIF5 proteins are significantly reduced, relative to WT eIF5, both in vitro and in vivo. Expression of these mutants reveals that they have a dominant-negative effect on phosphorylation of endogenous eIF5, and that they perturb synchronous progression of cells through S to M phase, resulting in a significant reduction in growth rate. Furthermore, the formation of mature eIF5/eIF2/eIF3 complex is reduced in these cells, and, in fact, restricted diffusional motion of WT eIF5 was almost abolished in a GFP-tagged eIF5 mutant lacking CK2 phosphorylation sites, as measured by fluorescence correlation spectroscopy. These results suggest that CK2 may be involved in the regulation of cell cycle progression by associating with and phosphorylating a key molecule for translation initiation. PMID:16227438

  12. Bursting regimes in a reaction-diffusion system with action potential-dependent equilibrium.

    Directory of Open Access Journals (Sweden)

    Stephen R Meier

    Full Text Available The equilibrium Nernst potential plays a critical role in neural cell dynamics. A common approximation used in studying electrical dynamics of excitable cells is that the ionic concentrations inside and outside the cell membranes act as charge reservoirs and remain effectively constant during excitation events. Research into brain electrical activity suggests that relaxing this assumption may provide a better understanding of normal and pathophysiological functioning of the brain. In this paper we explore time-dependent ionic concentrations by allowing the ion-specific Nernst potentials to vary with developing transmembrane potential. As a specific implementation, we incorporate the potential-dependent Nernst shift into a one-dimensional Morris-Lecar reaction-diffusion model. Our main findings result from a region in parameter space where self-sustaining oscillations occur without external forcing. Studying the system close to the bifurcation boundary, we explore the vulnerability of the system with respect to external stimulations which disrupt these oscillations and send the system to a stable equilibrium. We also present results for an extended, one-dimensional cable of excitable tissue tuned to this parameter regime and stimulated, giving rise to complex spatiotemporal pattern formation. Potential applications to the emergence of neuronal bursting in similar two-variable systems and to pathophysiological seizure-like activity are discussed.

  13. Exercise-induced expression of cardiac ATP-sensitive potassium channels promotes action potential shortening and energy conservation

    Science.gov (United States)

    Zingman, Leonid V.; Zhu, Zhiyong; Sierra, Ana; Stepniak, Elizabeth; Burnett, Colin M-L.; Maksymov, Gennadiy; Anderson, Mark E.; Coetzee, William A.; Hodgson-Zingman, Denice M.

    2011-01-01

    Physical activity is one of the most important determinants of cardiac function. The ability of the heart to increase delivery of oxygen and metabolic fuels relies on an array of adaptive responses necessary to match bodily demand while avoiding exhaustion of cardiac resources. The ATP-sensitive potassium (KATP) channel has the unique ability to adjust cardiac membrane excitability in accordance with ATP and ADP levels, and up-regulation of its expression that occurs in response to exercise could represent a critical element of this adaption. However, the mechanism by which KATP channel expression changes result in a beneficial effect on cardiac excitability and function remains to be established. Here, we demonstrate that an exercise-induced rise in KATP channel expression enhanced the rate and magnitude of action potential shortening in response to heart rate acceleration. This adaptation in membrane excitability promoted significant reduction in cardiac energy consumption under escalating workloads. Genetic disruption of normal KATP channel pore function abolished the exercise-related changes in action potential duration adjustment and caused increased cardiac energy consumption. Thus, an expression-driven enhancement in the KATP channel-dependent membrane response to alterations in cardiac workload represents a previously unrecognized mechanism for adaptation to physical activity and a potential target for cardioprotection. PMID:21439969

  14. NUMERICAL SIMULATION FOR DYNAMIC INITIAL SHOCK PARAMETERS OF COUPLING CHARGE ON BOREHOLE WALL UNDER THE ACTION OF HIGH EXPLOSIVES

    Institute of Scientific and Technical Information of China (English)

    倪芝芳; 李玉民

    1996-01-01

    According to detonation theory and hydrodynamic principle, a physical model has been set up in this paper. Based on the model a methodology for calculating dynamic initial shock parameters such as shock pressure p,,, shock wave velosity Dm etc. of coupling charge on borehole wall has ben developed. The shock parameters have been calculated when high explosives works on granite, limestone and marble respectively. The magnitude of every parameter on borehole wall has been obtained from ignited dot to the end of borehole along axial direction. Some important conclusions are also gained.

  15. Frequency-dependent effects of phenytoin on the maximum upstroke velocity of action potentials in guinea-pig papillary muscles.

    Science.gov (United States)

    Kojima, M; Ichiyama, M; Ban, T

    1986-07-01

    Phenytoin, at 50 to 200 micrograms reduced the maximum upstroke velocity of action potentials (Vmax) with increases in frequency from 0.25 to 5 Hz and in the external potassium concentration [( K+]0) from 2.7 to 8.1 mM. The drug-induced shortening of action potential duration was evident at 0.25 to 2 Hz but little at 3 to 5 Hz. Time courses of recovery of Vmax was studied by applying premature responses between the conditioning responses at 1 Hz both in control and in drug-treated preparations. Concerning the time courses of the difference between the Vmax values before and after drug treatments at the same diastolic interval, with increases in drug concentrations the intercepts at APD90 were increased but the time constants were not changed or slightly decreased in 8.1 to 5.4 mM [K+]0, whereas they were increased in 2.7 mM [K+]0. To understand the kinetic behavior of this drug on sodium channels, rate constants for the interaction of phenytoin with three states of channels in terms of Hondeghem-Katzung model were estimated from the above experiments of Vmax. The model most consistent with the present experiments was that with an affinity for inactivated channels 20 times greater than that for resting channels and with a minor affinity for open channels. Phenytoin produced a delay in the time course of recovery of overshoot and action potential duration at 0 mV (APD0), suggesting an additional inhibition of the slow channel by this drug.

  16. EFFECTS OF DESENSITIZATION AND REBOUND TO ADENOSINE ON ACTION POTENTIAL AND CONTRACTILITY IN ATRIAL CELLS IN GUINEA-PIGS

    Institute of Scientific and Technical Information of China (English)

    张凤杰; 臧伟进; 于晓江; 胡浩; 张春虹; 孙强; 吕军

    2002-01-01

    Objective To investigate the effects of desensitization and rebound to adenosine(Ado) on action potential duration(APD) and contractility in guinea-pig atrial cells. Methods Electrical activity was recorded using standard intracellular microelectrode technique and contractility was recorded using. We studied the effects of adenosine on the action potential and desensitization of contractility and rebound of contractility. Results The results showed that action potential duration were shortened by 1,10,100μmol*L-1Ado, the ratio of shortened APD was (9.58±1.40)%,(13.80±2.26)%,(24.80±3.19)%, respectively. 1μmol*L-1Ado had no desensitization (P>0.05), but the time of desensitization of 10μmol*L-1 Ado and 100μmol*L-1 Ado was 1 minute(P<0.05) and 5 minutes(P<0.05), respectively. The desensitization of contractility of 10*!μmol*L-1 Ado was obvious in atrial cells, the decrease of contractility of 10*!μmol*L-1 Ado was obvious in atrial cells, the decrease of contractility was changed from (31.4±16.04)%(2 minutes) to (50.60±15.87)% (4 minutes), compared with control. After washing out Ado, contractility was shown to rebound, the ratio of increase of contractility by 1,10,100μmol*L-1 Ado was (12.38±7.50)%,(19.00±8.14)% and (27.60±13.44)%, respectively. Conclusion Ado can abbreviate APD in atrial cells. The desensitization of Ado on APD is characterized by concentration-dependent and time-dependent in atrial cells, and the desensitization of contractility of Ado is obvious and contractility was shown to rebound after washing out Ado.

  17. Recovery time of motor evoked potentials following lengthening and shortening muscle action in the tibialis anterior

    NARCIS (Netherlands)

    Tallent, J.; Goodall, S.; Hortobagyi, T.; Gibson, A. St Clair; French, D. N.; Howatson, G.

    2012-01-01

    Motor evoked potentials (MEP) at rest remain facilitated following an isometric muscle contraction. Because the pre-synaptic and post-synaptic control of shortening (SHO) and lengthening (LEN) contractions differs, the possibility exists that the recovery of the MEP is also task specific. The time c

  18. Effect of initialization time on application potentiality of a ZnO thin film based LPG sensor

    Directory of Open Access Journals (Sweden)

    Parta Mitra

    2009-09-01

    Full Text Available A prototype electronic LPG (Liquid Petroleum Gas sensor based on zinc oxide (ZnO film has been fabricated. The objective of the present work was to investigate the importance of initialization time (also called warm-up time on the application potentiality of the ZnO based alarm. The role of sensor geometry on initialization time is presented. The electronic circuitry of the prototype LPG device alarm is discussed. It is shown that that the initialization time depends on the switch off time (or the time for which the sensor was kept idle. The resistive mode sensors can be fixed at 40% LEL (Lower Explosive Limit of LPG for safe operation.

  19. A major role for calcium-dependent potassium current in action potential repolarization in adrenal chromaffin cells.

    Science.gov (United States)

    Pancrazio, J J; Johnson, P A; Lynch, C

    1994-12-30

    To determine the extent which Ca dependent K current (IKCa) contributes during an action potential (AP), bovine chromaffin cells were voltage-clamped using a pre-recorded AP as the command voltage waveform. Based on (1) differential sensitivity of IKCa and Ca-independent K current (IK) to tetraethylammonium; (2) measurements of AP currents under conditions where Ca activation of IKCa had been abolished; and (3) blockade by charybdotoxin, IKCa comprised 70-90% of the outward K current during AP repolarization. In addition, observations are made concerning the form of AP-evoked Ca current.

  20. Potential Mechanism of Action of meso-Dihydroguaiaretic Acid on Mycobacterium tuberculosis H37Rv

    Directory of Open Access Journals (Sweden)

    Aldo F. Clemente-Soto

    2014-12-01

    Full Text Available The isolation and characterization of the lignan meso-dihydroguaiaretic acid (MDGA from Larrea tridentata and its activity against Mycobacterial tuberculosis has been demonstrated, but no information regarding its mechanism of action has been documented. Therefore, in this study we carry out the gene expression from total RNA obtained from M. tuberculosis H37Rv treated with MDGA using microarray technology, which was validated by quantitative real time polymerase chain reaction. Results showed that the alpha subunit of coenzyme A transferase of M. tuberculosis H37Rv is present in both geraniol and 1-and 2-methylnaphthalene degradation pathways, which are targeted by MDGA. This assumption was supported by molecular docking which showed stable interaction between MDGA with the active site of the enzyme. We propose that inhibition of coenzyme A transferase of M. tuberculosis H37Rv results in the accumulation of geraniol and 1-and 2-methylnaphtalene inside bacteria, causing membrane destabilization and death of the pathogen. The natural product MDGA is thus an attractive template to develop new anti-tuberculosis drugs, because its target is different from those of known anti-tubercular agents.

  1. Immunomodulatory effects of fluoxetine: A new potential pharmacological action for a classic antidepressant drug?

    Science.gov (United States)

    Di Rosso, María Emilia; Palumbo, María Laura; Genaro, Ana María

    2016-07-01

    Selective serotonin reuptake inhibitors are frequently used antidepressants. In particular, fluoxetine is usually chosen for the treatment of the symptoms of depression, obsessive-compulsive, panic attack and bulimia nervosa. Antidepressant therapy has been associated with immune dysfunction. However, there is contradictory evidence about the effect of fluoxetine on the immune system. Experimental findings indicate that lymphocytes express the serotonin transporter. Moreover it has been shown that fluoxetine is able to modulate the immune function through a serotonin-dependent pathway and through a novel independent mechanism. In addition, several studies have shown that fluoxetine can alter tumor cell viability. Thus, it was recently demonstrated in vivo that chronic fluoxetine treatment inhibits tumor growth by increasing antitumor T-cell activity. Here we briefly review some of the literature referring to how fluoxetine is able to modify, for better or worse, the functionality of the immune system. These results of our analysis point to the relevance of the novel pharmacological action of this drug as an immunomodulator helping to treat several pathologies in which immune deficiency and/or deregulation is present.

  2. Potential mechanism of action of meso-dihydroguaiaretic acid on Mycobacterium tuberculosis H37Rv.

    Science.gov (United States)

    Clemente-Soto, Aldo F; Balderas-Rentería, Isaías; Rivera, Gildardo; Segura-Cabrera, Aldo; Garza-González, Elvira; del Rayo Camacho-Corona, María

    2014-12-02

    The isolation and characterization of the lignan meso-dihydroguaiaretic acid (MDGA) from Larrea tridentata and its activity against Mycobacterial tuberculosis has been demonstrated, but no information regarding its mechanism of action has been documented. Therefore, in this study we carry out the gene expression from total RNA obtained from M. tuberculosis H37Rv treated with MDGA using microarray technology, which was validated by quantitative real time polymerase chain reaction. Results showed that the alpha subunit of coenzyme A transferase of M. tuberculosis H37Rv is present in both geraniol and 1-and 2-methylnaphthalene degradation pathways, which are targeted by MDGA. This assumption was supported by molecular docking which showed stable interaction between MDGA with the active site of the enzyme. We propose that inhibition of coenzyme A transferase of M. tuberculosis H37Rv results in the accumulation of geraniol and 1-and 2-methylnaphtalene inside bacteria, causing membrane destabilization and death of the pathogen. The natural product MDGA is thus an attractive template to develop new anti-tuberculosis drugs, because its target is different from those of known anti-tubercular agents.

  3. H+CH4 → H2 + CH3 initial state-selected reaction probabilities on different potential energy surfaces

    Science.gov (United States)

    Ellerbrock, Roman; Manthe, Uwe

    2017-01-01

    Initial state-selected reaction probabilities for the H +CH4 →H2 +CH3 reaction on a recently developed potential energy surface which employs neutral network fitting based on permutational invariant polynomials are reported. The quantum dynamics calculations use the quantum transition state concept and the multi-layer multi-configurational time-dependent Hartree approach and study the reaction process in full-dimensionality for vanishing total angular momentum. A detailed comparison with previous results obtained on other high-level potential energy surfaces is given. The connection between the level of quantum state resolution and the sensitivity of the results on differences in the potential energy surfaces is highlighted. Employing a decomposition of the total reactivity into contributions of the different vibrational states of the activated complex, it is found that differences between the potential energy surfaces are mainly related to the umbrella motion of the methyl group.

  4. Chemopreventive potential of chlorophyllin: a review of the mechanisms of action and molecular targets.

    Science.gov (United States)

    Nagini, Siddavaram; Palitti, Fabrizio; Natarajan, Adayapalam T

    2015-01-01

    Chlorophyllin (CHL), a water soluble semisynthetic derivative of the ubiquitous plant pigment chlorophyll used as a food additive, is recognized to confer a wide range of health benefits. CHL has been shown to exhibit potent antigenotoxic, anti-oxidant, and anticancer effects. Numerous experimental and epidemiological studies have demonstrated that dietary supple-mentation of CHL lowers the risk of cancer. CHL inhibits cancer initiation and progression by targeting multiple molecules and pathways involved in the metabolism of carcinogens, cell cycle progression, apoptosis evasion, invasion, and angiogenesis. The modulatory effects of CHL on the hallmark capabilities of cancer appear to be mediated via abrogation of key oncogenic signal transduction pathways such as nuclear factor kappa B, Wnt/β-catenin, and phosphatidylinositol-3-kinase/Akt signaling. This review provides insights into the molecular mechanisms of the anticancer effects of dietary CHL.

  5. Genotoxic and cytotoxic action potential of Terminalia citrina, a medicinal plant of ethnopharmacological significance

    Science.gov (United States)

    Akhtar, Muhammad Furqan; Saleem, Ammara; Sharif, Ali; Akhtar, Bushra; Nasim, Maaz Bin; Peerzada, Sohaib; Raza, Moosa; Ijaz, Hira; Ahmed, Shoaib; Shabbir, Maryam; Ali, Sajid; Akbar, Zeeshan; Ul Hassan, Syed Saeed

    2016-01-01

    Most herbal medicines utilized in complementary and alternative medicine lack safety evaluation setting our lives under unwarranted risks. Present study comprised of genotoxic and cytotoxic appraisal of Terminalia citrina fruits which are used as a folklore medicine for treatment of various ailments. Aqueous and ethanolic extracts of T. citrina fruit extracts were evaluated for the presence of different phytochemicals. Genotoxic potential of both the extract of T. citrina was assessed through Ames reverse mutagenicity assay in Salmonella TA 100 and 102 strains. Cytotoxic potential of T. citrina was determined in baby hamster kidney cell line (BHK-21). Statistical analysis was carried out by ANOVA following post hoc test. Phytochemical analysis showed the presence of alkaloids, carbohydrates, phenolic compounds, tannins, catechins and saponins. It was revealed that both the extracts of T. citrina exhibited significant mutagenicity in tester strains. Ethanolic extract showed higher mutagenicity in TA 100 strain, whereas aqueous extract of T. citrina exhibited higher mutagenicity in TA 102 strain than TA 100. Both the extracts of T. citrina showed dose-dependent mutagenicity. Fifty percent cell viability was exhibited by 260 and 545 µg/mL of ethanolic and aqueous extracts respectively. This study concludes that the ethanolic and aqueous fruit extracts of T. citrina may not be safe owing to their mutagenic and cytotoxic potential and it necessitates further investigation regarding its safety evaluation. PMID:28096789

  6. The mechanism of action of two bradykinin-potentiating peptides on isolated smooth muscle.

    Science.gov (United States)

    Ufkes, J G; Aarsen, P N; van der Meer, C

    1977-07-15

    Bradykinin-induced contractions in the guinea-pig ileum were potentiated by the peptides A-VI-5 (Val-Glu-Ser-Ser-Lys) and BPP5a (Pyr-Lys-Trp-Ala-Pro), while the contractions induced by other agonists were not affected. Neither peptide added alone caused any response. Previous addition of the peptides shortened the latent period following the addition of bradykinin to a value corresponding to the contraction height with an equivalent dose of bradykinin added alone. Bradykinin in contact with a piece of ileum was inactivated at a relatively slow rate. This inactivation was not inhibited by either A-VI-5 or BPP5a in doses causing potentiation. Suppression of the cholinergic activity by cooling, atropine, morphine or tetrodotoxin did not influence the potentiating activity. Addition of the peptides at the moment a submaximal contraction due to bradykinin had been fully established, increased the contraction height within seconds. The two peptides caused a parallel shift to the left of the dose-effect curve of bradykinin, whereas the maximum bradykinin effect remained unchanged. It is concluded that sensitization of bradykinin receptors due to an increased affinity of the receptor for bradykinin is the hypothesis which best fits the experimental findings.

  7. Heteromeric Kv7.2/7.3 channels differentially regulate action potential initiation and conduction in neocortical myelinated axons

    NARCIS (Netherlands)

    Battefeld, A.; Tran, Baouyen T; Gavrilis, Jason; Cooper, Edward C; Kole, Maarten H P

    2014-01-01

    Rapid energy-efficient signaling along vertebrate axons is achieved through intricate subcellular arrangements of voltage-gated ion channels and myelination. One recently appreciated example is the tight colocalization of K(v)7 potassium channels and voltage-gated sodium (Na(v)) channels in the axon

  8. Heteromeric Kv7.2/7.3 channels differentially regulate action potential initiation and conduction in neocortical myelinated axons

    NARCIS (Netherlands)

    Battefeld, A.; Tran, B.T.; Gavrilis, J.; Cooper, E.C.; Kole, Maarten

    2014-01-01

    Rapid energy-efficient signaling along vertebrate axons is achieved through intricate subcellular arrangements of voltage-gated ion channels and myelination. One recently appreciated example is the tight colocalization of Kv7 potassium channels and voltage-gated sodium (Nav ) channels in the axonal

  9. Decreased use of glucocorticoids in biological-experienced patients with rheumatoid arthritis who initiated intravenous abatacept: results from the 2-year ACTION study

    Science.gov (United States)

    Alten, Rieke; Nüßlein, Hubert; Galeazzi, Mauro; Lorenz, Hanns-Martin; Nurmohamed, Michael T; Bensen, William G; Burmester, Gerd R; Peter, Hans-Hartmut; Pavelka, Karel; Chartier, Mélanie; Poncet, Coralie; Rauch, Christiane; Elbez, Yedid; Le Bars, Manuela

    2016-01-01

    Introduction Prolonged glucocorticoid use may increase the risk of adverse safety outcomes, including cardiovascular events. The European League Against Rheumatism and the Canadian Rheumatology Association advise tapering glucocorticoid dose as rapidly as clinically feasible. There is a paucity of published data on RA that adequately describe concomitant treatment patterns. Methods ACTION (AbataCepT In rOutiNe clinical practice) is a non-interventional cohort study of patients from Europe and Canada that investigated the long-term retention of intravenous abatacept in clinical practice. We assessed concomitant glucocorticoids in patients with established RA who had participated in ACTION and received ≥1 biological agent prior to abatacept initiation. Results The analysis included 1009 patients. Glucocorticoids were prescribed at abatacept initiation in 734 (72.7%) patients at a median 7.5 mg/day dose (n=692). Of the patients who remained on abatacept at 24 months, 40.7% were able to decrease their dose of glucocorticoids, including 26.9% who decreased their dose from >5 mg/day to ≤5 mg/day. Conclusion Reduction and/or cessation of glucocorticoid therapy is possible with intravenous abatacept in clinical practice. PMID:26925253

  10. Effect of cardiac glycosides on action potential characteristics and contractility in cat ventricular myocytes: role of calcium overload.

    Science.gov (United States)

    Ruch, Stuart R; Nishio, Manabu; Wasserstrom, J Andrew

    2003-10-01

    There is increasing evidence that cardiac glycosides act through mechanisms distinct from inhibition of the sodium pump but which may contribute to their cardiac actions. To more fully define differences between agents indicative of multiple sites of action, we studied changes in contractility and action potential (AP) configuration in cat ventricular myocytes produced by six cardiac glycosides (ouabain, ouabagenin, dihydroouabain, actodigin, digoxin, and resibufogenin). AP shortening was observed only with ouabain and actodigin. There was extensive inotropic variability between agents, with some giving full inotropic effects before automaticity occurred whereas others produced minimal inotropy before toxicity. AP shortening was not a result of alterations in calcium current or the inward rectifier potassium current, but correlated with an increase in steady-state outward current (Iss), which was sensitive to KB-R7943, a Na+-Ca2+ exchange (NCX) inhibitor. Interestingly, Iss was observed following exposure to ouabain and dihydroouabain, suggesting that an additional mechanism is operative with dihydroouabain that prevents AP shortening. Further investigation into differences in inotropy between ouabagenin, dihydroouabain and ouabain revealed almost identical responses under AP voltage clamp. Thus all agents appear to act on the sodium pump and thereby secondarily increase the outward reverse mode NCX current, but the extent of AP duration shortening and positive inotropy elicited by each agent is limited by development of their toxic actions. The quantitative differences between cardiac glycosides suggest that mechanisms independent of sodium pump inhibition may result from an altered threshold for calcium overload possibly involving direct or indirect effects on calcium release from the sarcoplasmic reticulum.

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

    Science.gov (United States)

    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.

  12. Recessive Resistance to Plant Viruses: Potential Resistance Genes Beyond Translation Initiation Factors

    Directory of Open Access Journals (Sweden)

    Masayoshi Hashimoto

    2016-10-01

    Full Text Available The ability of plant viruses to propagate their genomes in host cells depends on many host factors. In the absence of an agrochemical that specifically targets plant viral infection cycles, one of the most effective methods for controlling viral diseases in plants is taking advantage of the host plant’s resistance machinery. Recessive resistance is conferred by a recessive gene mutation that encodes a host factor critical for viral infection. It is a branch of the resistance machinery and, as an inherited characteristic, is very durable. Moreover, recessive resistance may be acquired by a deficiency in a negative regulator of plant defense responses, possibly due to the autoactivation of defense signaling. Eukaryotic translation initiation factor (eIF 4E and eIF4G and their isoforms are the most widely exploited recessive resistance genes in several crop species, and they are effective against a subset of viral species. However, the establishment of efficient, recessive resistance-type antiviral control strategies against a wider range of plant viral diseases requires genetic resources other than eIF4Es. In this review, we focus on recent advances related to antiviral recessive resistance genes evaluated in model plants and several crop species. We also address the roles of next-generation sequencing and genome editing technologies in improving plant genetic resources for recessive resistance-based antiviral breeding in various crop species.

  13. Recessive Resistance to Plant Viruses: Potential Resistance Genes Beyond Translation Initiation Factors

    Science.gov (United States)

    Hashimoto, Masayoshi; Neriya, Yutaro; Yamaji, Yasuyuki; Namba, Shigetou

    2016-01-01

    The ability of plant viruses to propagate their genomes in host cells depends on many host factors. In the absence of an agrochemical that specifically targets plant viral infection cycles, one of the most effective methods for controlling viral diseases in plants is taking advantage of the host plant’s resistance machinery. Recessive resistance is conferred by a recessive gene mutation that encodes a host factor critical for viral infection. It is a branch of the resistance machinery and, as an inherited characteristic, is very durable. Moreover, recessive resistance may be acquired by a deficiency in a negative regulator of plant defense responses, possibly due to the autoactivation of defense signaling. Eukaryotic translation initiation factor (eIF) 4E and eIF4G and their isoforms are the most widely exploited recessive resistance genes in several crop species, and they are effective against a subset of viral species. However, the establishment of efficient, recessive resistance-type antiviral control strategies against a wider range of plant viral diseases requires genetic resources other than eIF4Es. In this review, we focus on recent advances related to antiviral recessive resistance genes evaluated in model plants and several crop species. We also address the roles of next-generation sequencing and genome editing technologies in improving plant genetic resources for recessive resistance-based antiviral breeding in various crop species. PMID:27833593

  14. The growth cones of Aplysia sensory neurons: Modulation by serotonin of action potential duration and single potassium channel currents.

    Science.gov (United States)

    Belardetti, F; Schacher, S; Kandel, E R; Siegelbaum, S A

    1986-09-01

    Serotonin (5-HT) closes a specific K channel ("S") in the cell body of Aplysia sensory neurons, resulting in a slow excitatory postsynaptic potential and spike broadening. To determine whether the S channel is present and can be modulated in processes of the neuron other than the cell body, we studied the effects of 5-HT on growth cones of sensory neurons in culture by using the patch-clamp technique. Simultaneous application of 5-HT to the cell body and to the growth cones of sensory neurons produced, in both, a slow depolarization of approximately 5 mV. Also, 5-HT produced a lengthening of the duration of action potential in the growth cone and cell body by 20-30%. Similar effects were observed in isolated growth cones that had been severed from the rest of the neuron, implying that the growth cones contain all the molecular components (i.e., receptors, channels, cAMP cascade) necessary for 5-HT action. Cell-attached patch-clamp recordings demonstrated the presence of S channels in sensory neuron growth cones. Application of serotonin to the bath produced long-lasting all-or-none closures of these channels in a manner identical to the previously characterized action of 5-HT in the cell body. Thus, channel modulation is not restricted to the cell body and probably occurs throughout the sensory neuron. This strengthens the view that S-channel modulation may also occur at the sensory neuron presynaptic terminal, where it could play a role in the presynaptic facilitation produced by 5-HT.

  15. The impact of age on oncogenic potential: tumor-initiating cells and the brain microenvironment.

    Science.gov (United States)

    Stoll, Elizabeth A; Horner, Philip J; Rostomily, Robert C

    2013-10-01

    Paradoxically, aging leads to both decreased regenerative capacity in the brain and an increased risk of tumorigenesis, particularly the most common adult-onset brain tumor, glioma. A shared factor contributing to both phenomena is thought to be age-related alterations in neural progenitor cells (NPCs), which function normally to produce new neurons and glia, but are also considered likely cells of origin for malignant glioma. Upon oncogenic transformation, cells acquire characteristics known as the hallmarks of cancer, including unlimited replication, altered responses to growth and anti-growth factors, increased capacity for angiogenesis, potential for invasion, genetic instability, apoptotic evasion, escape from immune surveillance, and an adaptive metabolic phenotype. The precise molecular pathogenesis and temporal acquisition of these malignant characteristics is largely a mystery. Recent studies characterizing NPCs during normal aging, however, have begun to elucidate mechanisms underlying the age-associated increase in their malignant potential. Aging cells are dependent upon multiple compensatory pathways to maintain cell cycle control, normal niche interactions, genetic stability, programmed cell death, and oxidative metabolism. A few multi-functional proteins act as 'critical nodes' in the coordination of these various cellular activities, although both intracellular signaling and elements within the brain environment are critical to maintaining a balance between senescence and tumorigenesis. Here, we provide an overview of recent progress in our understanding of how mechanisms underlying cellular aging inform on glioma pathogenesis and malignancy.

  16. Markov models of use-dependence and reverse use-dependence during the mouse cardiac action potential.

    Directory of Open Access Journals (Sweden)

    Qinlian Zhou

    Full Text Available The fast component of the cardiac transient outward current, I(Ktof, is blocked by a number of drugs. The major molecular bases of I(Ktof are Kv4.2/Kv4.3 voltage-gated potassium channels. Drugs with similar potencies but different blocking mechanisms have differing effects on action potential duration (APD. We used in silico analysis to determine the effect of I(Ktof-blocking drugs with different blocking mechanisms on mouse ventricular myocytes. We used our existing mouse model of the action potential, and developed 4 new Markov formulations for I(Ktof, I(Ktos, I(Kur, I(Ks. We compared effects of theoretical I(Ktof-specific channel blockers: (1 a closed state, and (2 an open channel blocker. At concentrations lower or close to IC(50, the drug which bound to the open state always had a much greater effect on APD than the drug which bound to the closed state. At concentrations much higher than IC(50, both mechanisms had similar effects at very low pacing rates. However, an open state binding drug had a greater effect on APD at faster pacing rates, particularly around 10 Hz. In summary, our data indicate that drug effects on APD are strongly dependent not only on IC(50, but also on the drug binding state.

  17. Sensitivity of Rabbit Ventricular Action Potential and Ca2+ Dynamics to Small Variations in Membrane Currents and Ion Diffusion Coefficients

    Directory of Open Access Journals (Sweden)

    Yuan Hung Lo

    2013-01-01

    Full Text Available Little is known about how small variations in ionic currents and Ca2+ and Na+ diffusion coefficients impact action potential and Ca2+ dynamics in rabbit ventricular myocytes. We applied sensitivity analysis to quantify the sensitivity of Shannon et al. model (Biophys. J., 2004 to 5%–10% changes in currents conductance, channels distribution, and ion diffusion in rabbit ventricular cells. We found that action potential duration and Ca2+ peaks are highly sensitive to 10% increase in L-type Ca2+ current; moderately influenced by 10% increase in Na+-Ca2+ exchanger, Na+-K+ pump, rapid delayed and slow transient outward K+ currents, and Cl− background current; insensitive to 10% increases in all other ionic currents and sarcoplasmic reticulum Ca2+ fluxes. Cell electrical activity is strongly affected by 5% shift of L-type Ca2+ channels and Na+-Ca2+ exchanger in between junctional and submembrane spaces while Ca2+-activated Cl−-channel redistribution has the modest effect. Small changes in submembrane and cytosolic diffusion coefficients for Ca2+, but not in Na+ transfer, may alter notably myocyte contraction. Our studies highlight the need for more precise measurements and further extending and testing of the Shannon et al. model. Our results demonstrate usefulness of sensitivity analysis to identify specific knowledge gaps and controversies related to ventricular cell electrophysiology and Ca2+ signaling.

  18. Effects of changes in frequency on guinea pig ventricular action potential duration and on QT interval under different experimental conditions.

    Science.gov (United States)

    von Savigny, L; Hohnloser, S; Antoni, H

    1981-01-01

    Isolated perfused guinea pig hearts (Langendorff preparation) were arrested by carbachol (0.1-0.2 mg/l) and electrically stimulated in the region of the av-conducting system. The QT interval was determined by means of extracellular electrodes at different driving frequencies. Separate experiments were performed on papillary muscles from the right ventricle to measure the duration of the transmembrane action potential under comparable conditions. At 35 degrees C (Ke+ 5.4 mmol/l) increasing the frequency of stimulation (range 12-120/min) caused the action potential duration (APD) to decrease to a greater extent than the QT interval. Stepwise rising of the external K+ concentration up to 16.2 mmol/l produced a nearly parallel shift to the APD-frequency relation to lower values. Again, the QT interval was less affected by increasing the external K+ concentration than the APD. Stepwise reduction of the temperature down to 20 degrees C prolonged the APD as well as the QT interval, the effects being more pronounced at lower than at higher stimulation frequencies. Under all examined experimental conditions, the APD proved to be markedly shorter than the QT interval even when the latter is diminished by the duration of QRS. The results suggest that no close relation exists between the APD and the QT interval. The observed divergencies may be due to functional differences among various parts of the ventricles.

  19. Changes in intracellular calcium concentration influence beat-to-beat variability of action potential duration in canine ventricular myocytes.

    Science.gov (United States)

    Kistamas, K; Szentandrassy, N; Hegyi, B; Vaczi, K; Ruzsnavszky, F; Horvath, B; Banyasz, T; Nanasi, P P; Magyar, J

    2015-02-01

    The aim of the present work was to study the influence of changes in intracellular calcium concentration ([Ca(2+)]i) on beat-to-beat variability (short term variability, SV) of action potential duration (APD) in isolated canine ventricular cardiomyocytes. Series of action potentials were recorded from enzymatically isolated canine ventricular cells using conventional microelectrode technique. Drug effects on SV were evaluated as relative SV changes determined by plotting the drug-induced changes in SV against corresponding changes in APD and comparing these data to the exponential SV-APD function obtained with inward and outward current injections. Exposure of myocytes to the Ca(2+) chelator BAPTA-AM (5 μM) decreased, while Ca(2+) ionophore A23187 (1 μM) increased the magnitude of relative SV. Both effects were primarily due to the concomitant changes in APD. Relative SV was reduced by BAPTA-AM under various experimental conditions including pretreatment with veratridine, BAY K8644, dofetilide or E-4031. Contribution of transient changes of [Ca(2+)]i due to Ca(2+) released from the sarcoplasmic reticulum (SR) was studied using 10 μM ryanodine and 1 μM cyclopiazonic acid: relative SV was reduced by both agents. Inhibition of the Na(+)-Ca(2+) exchanger by 1 μM SEA0400 increased relative SV. It is concluded that elevation of [Ca(2+)]i increases relative SV significantly. More importantly, Ca(2+) released from the SR is an important component of this effect.

  20. Ruby laser-assisted depilation: The mode of action and potential ways of improved outcome

    Science.gov (United States)

    Topping, Adam Partington

    Aim - To improve efficacy and lessen side effects resulting from normal mode ruby laser (NMRL)-assisted depilation via a greater understanding of its mode of action and the development of novel methods of reducing associated epidermal damage. Employing a thermal imaging camera and ex vivo hair-bearing skin, the targets for the NMRL (pulse duration 900 musec and spot size 7 mm) were defined, the temperatures reached and the heat dissipation rates determined. Production of heat was confined to the hair follicles, with the peak temperatures reached varying considerably between hairs within the same treatment area and also between individuals. Histological assessment for a known indicator of cellular damage (p53 expression) identified the sites and extent of damage, which correlated with the peak temperatures measured. An energy meter was used to detect the penetration of NMRL light through ex vivo skin, which was found to be deeper than previously theorised. The black-haired mouse (C57B1/10) was assessed both macroscopically and histologically and found to be an acceptable animal model of NMRL depilation and associated epidermal damage. Attempts to reduce the epidermal damage by simply stopping the light reaching the epidermis using a chromophore block were assessed. Chromophore did indeed reduce the amount of epidermal damage detected in laser-irradiated ex vivo human skin, whereas in contrast it increased the wounding seen in the much thinner skin of the mouse. Nevertheless the mouse model showed that this technique did not affect the depilation efficacy. An alternative method of reducing epidermal damage using induction of the cells' intrinsic protective mechanisms (heat shock proteins, HSP) was assessed using cultured keratinocytes and the mouse model. Primarily, the sub-lethal temperature optimum for HSP expression in human keratinocytes was determined, then an in vitro model of NMRL-associated epidermal damage was established and the heat pre-treatment assessed

  1. Initial Investigation into the Potential of CSP Industrial Process Heat for the Southwest United States

    Energy Technology Data Exchange (ETDEWEB)

    Kurup, Parthiv [National Renewable Energy Lab. (NREL), Golden, CO (United States); Turchi, Craig [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2015-11-01

    After significant interest in the 1970s, but relatively few deployments, the use of solar technologies for thermal applications, including enhanced oil recovery (EOR), desalination, and industrial process heat (IPH), is again receiving global interest. In particular, the European Union (EU) has been a leader in the use, development, deployment, and tracking of Solar Industrial Process Heat (SIPH) plants. The objective of this study is to ascertain U.S. market potential of IPH for concentrating collector technologies that have been developed and promoted through the U.S. Department of Energy's Concentrating Solar Power (CSP) Program. For this study, the solar-thermal collector technologies of interest are parabolic trough collectors (PTCs) and linear Fresnel (LF) systems.

  2. MIF-1 potentiates the action of tricyclic antidepressants in an animal model of depression.

    Science.gov (United States)

    Kostowski, W; Danysz, W; Dyr, W; Jankowska, E; Krzaścik, P; Pałejko, W; Stefański, R; Płaźnik, A

    1991-01-01

    In the present paper, the effect of simultaneous treatment of rats with low doses of MIF-1 and tricyclic antidepressants on rat behavior in the forced swim test was studied. It was found that MIF-1 stimulated in a dose-dependent manner "active" behavior of animals in this paradigm. The effect of MIF-1 appeared to be independent of changes in rats' locomotion in the open field test. The combined treatment of rats with MIF-1 (0.01 mg/kg IP) and amitriptyline (5 mg/kg IP) or desipramine (1.25 mg/kg) IP) significantly stimulated active behavior in the forced swim test above the level obtained with each of the drugs given separately. The present data suggest the potential clinical efficacy of a combined therapy of depressive patients with MIF-1 and small doses of tricyclic antidepressants.

  3. Potential food applications of biobased materials. An EU- concerted action project

    DEFF Research Database (Denmark)

    Haugaard, V.K.; Udsen, A.M.; Mortensen, G.

    2001-01-01

    and coatings to food but novel commercial applications of these are scarce. Based on information currently available on the properties of biobased packaging materials the study identified products in the fresh meat, dairy, ready meal, beverage, fruit and vegetable, snack, frozen food and dry food categories......The objective of the study was to ascertain the state of the art with regard to the applicability of biobased packaging materials to foods and to identify potential food applications for biobased materials. The study revealed relatively few examples of biobased materials used as primary, secondary...... or tertiary packaging materials for foods. This is due to the fact that published investigations on the use of biobased materials are still scarce, and results obtained remain unpublished because of commercial pressures. The scientific literature contains numerous reports on applications of edible films...

  4. Dopamine receptor modulation of repetitive grooming actions in the rat: potential relevance for Tourette syndrome.

    Science.gov (United States)

    Taylor, Jennifer L; Rajbhandari, Abha K; Berridge, Kent C; Aldridge, J Wayne

    2010-03-31

    Studies of rodent grooming can provide valuable insight for dopamine contributions to the initiation, organization, and repetition of motor patterns. This information is useful for understanding how brain dysfunctions contribute to movement disorders such as Tourette syndrome and obsessive compulsive disorder, in which patients are driven to reiterate particular movement patterns. In rodents, dopamine D1 receptor stimulation causes a complex behavioral super-stereotypy in the form of excessive production and rigid execution of whole sequences of movements known as syntactic grooming chains. Sequential super-stereotypy of grooming chains may be particularly advantageous for modeling movement sequences and treatments in Tourette syndrome and related disorders. Here, we report that co-administration of haloperidol, one available treatment for Tourette syndrome and primarily a D2 receptor antagonist, prevented D1 stimulation with SKF38393 from inducing sequential super-stereotypy, which manifests as an exaggeration of the tendency to complete all four phases of a syntactic chain in rigid serial order once the first phase has begun. In a separate experiment, we showed that in contrast to acute D1 agonist administration, 39h withdrawal from chronic (3weeks) administration of the D1 antagonist SCH23390 (which has been suggested to increase D1 receptor expression in the basal ganglia) did not elicit sequential super-stereotypy after drug cessation. Instead, rats suddenly removed from repeated SCH23390 spent more time performing simple stereotypies that included intense scratching and biting behaviors. Together, these results have implications for understanding how dopamine receptors facilitate particular stereotypies manifest in animal models of Tourette syndrome and obsessive compulsive disorder.

  5. 'Working' cardiomyocytes exhibiting plateau action potentials from human placenta-derived extraembryonic mesodermal cells.

    Science.gov (United States)

    Okamoto, Kazuma; Miyoshi, Shunichiro; Toyoda, Masashi; Hida, Naoko; Ikegami, Yukinori; Makino, Hatsune; Nishiyama, Nobuhiro; Tsuji, Hiroko; Cui, Chang-Hao; Segawa, Kaoru; Uyama, Taro; Kami, Daisuke; Miyado, Kenji; Asada, Hironori; Matsumoto, Kenji; Saito, Hirohisa; Yoshimura, Yasunori; Ogawa, Satoshi; Aeba, Ryo; Yozu, Ryohei; Umezawa, Akihiro

    2007-07-15

    The clinical application of cell transplantation for severe heart failure is a promising strategy to improve impaired cardiac function. Recently, an array of cell types, including bone marrow cells, endothelial progenitors, mesenchymal stem cells, resident cardiac stem cells, and embryonic stem cells, have become important candidates for cell sources for cardiac repair. In the present study, we focused on the placenta as a cell source. Cells from the chorionic plate in the fetal portion of the human placenta were obtained after delivery by the primary culture method, and the cells generated in this study had the Y sex chromosome, indicating that the cells were derived from the fetus. The cells potentially expressed 'working' cardiomyocyte-specific genes such as cardiac myosin heavy chain 7beta, atrial myosin light chain, cardiac alpha-actin by gene chip analysis, and Csx/Nkx2.5, GATA4 by RT-PCR, cardiac troponin-I and connexin 43 by immunohistochemistry. These cells were able to differentiate into cardiomyocytes. Cardiac troponin-I and connexin 43 displayed a discontinuous pattern of localization at intercellular contact sites after cardiomyogenic differentiation, suggesting that the chorionic mesoderm contained a large number of cells with cardiomyogenic potential. The cells began spontaneously beating 3 days after co-cultivation with murine fetal cardiomyocytes and the frequency of beating cells reached a maximum on day 10. The contraction of the cardiomyocytes was rhythmical and synchronous, suggesting the presence of electrical communication between the cells. Placenta-derived human fetal cells may be useful for patients who cannot supply bone marrow cells but want to receive stem cell-based cardiac therapy.

  6. Menthol-induced action potentials in Conocephalum conicum as a result of unspecific interactions between menthol and the lipid phase of the plasma membrane.

    Science.gov (United States)

    Kupisz, Kamila; Trebacz, Kazimierz; Gruszecki, Wiesław I

    2015-07-01

    Our previous study has shown that the liverwort Conocephalum conicum generates action potentials (APs) in response to both temperature drop and menthol, which are also activators of the TRPM8 (transient receptor potential melastatin 8) receptor in animals. Not only similarities but also differences between electrical reactions to menthol and cooling observed in the liverwort aroused our interest in the action of menthol at the molecular level. Patch-clamp investigations have shown that menthol causes a reduction of current flowing through slow vacuolar (SV) channels to 29 ± 10% of the initial value (n = 9); simultaneously, it does not influence magnitudes of currents passing through a single SV channel. This may point to an unspecific interaction between menthol and the lipid phase of the membrane. An influence of menthol on lipid organization in membranes was investigated in two-component monomolecular layers formed with menthol and dipalmitoylphosphatidylcholine (DPPC) at the argon-water interface. Analyses of the mean molecular area parameters vs the molar fraction of the menthol component have shown over-additivity (approximately 20 Å(2) ) in the region of high molar fractions of menthol. Infrared absorption spectroscopy studies have shown that menthol, most probably, induces breaking of a hydrogen bond network formed by ester carbonyl groups and water bridges in the lipid membrane and binds to the polar head group region of DPPC. We conclude that the disruption in the lipid phase of the membrane influences ion channels and/or pumps and subsequently causes generation of APs in excitable plants such as C. conicum.

  7. Simulations of the cardiac action potential based on the Hodgkin-Huxley kinetics with the use of Microsoft Excel spreadsheets.

    Science.gov (United States)

    Wu, Sheng-Nan

    2004-03-31

    The purpose of this study was to develop a method to simulate the cardiac action potential using a Microsoft Excel spreadsheet. The mathematical model contained voltage-gated ionic currents that were modeled using either Beeler-Reuter (B-R) or Luo-Rudy (L-R) phase 1 kinetics. The simulation protocol involves the use of in-cell formulas directly typed into a spreadsheet. The capability of spreadsheet iteration was used in these simulations. It does not require any prior knowledge of computer programming, although the use of the macro language can speed up the calculation. The normal configuration of the cardiac ventricular action potential can be well simulated in the B-R model that is defined by four individual ionic currents, each representing the diffusion of ions through channels in the membrane. The contribution of Na+ inward current to the rate of depolarization is reproduced in this model. After removal of Na+ current from the model, a constant current stimulus elicits an oscillatory change in membrane potential. In the L-R phase 1 model where six types of ionic currents were defined, the effect of extracellular K+ concentration on changes both in the time course of repolarization and in the time-independent K+ current can be demonstrated, when the solutions are implemented in Excel. Using the simulation protocols described here, the users can readily study and graphically display the underlying properties of ionic currents to see how changes in these properties determine the behavior of the heart cell. The method employed in these simulation protocols may also be extended or modified to other biological simulation programs.

  8. Methanol extract of Tephrosia vogelii leaves potentiates the contractile action of acetylcholine on isolated rabbit jejunum

    Institute of Scientific and Technical Information of China (English)

    Tavershima Dzenda; Joseph Olusegun Ayo; Alexander Babatunde Adelaiye; Ambrose Osemattah Adaudi

    2015-01-01

    To investigate the modulating role of methanol extract of Tephrosia vogelii leaves on acetylcholine (ACh)-induced contraction of isolated rabbit jejunum. Methods: Rabbit jejunum segment was removed and placed in an organ bath containing Tyrode’s solution, and its contractions were recorded isometrically. Results: ACh (2.0 × 10-10 g/mL) and the extract (2.0 × 10-4 g/mL) individually increased the frequency of contraction (mean ± SEM) of the isolated smooth muscle tissue by 47.6% ± 9.5%and 77.8% ± 66.5%, respectively. When ACh and the extract were combined, the frequency of contraction of the tissue was increased by 222.2% ± 25.9%, representing a 366.7% increase (P < 0.001) over the effect of ACh alone. Similarly, ACh (2.0 × 10-9 g/mL) and the extract individually increased significantly (P < 0.001) the amplitude of contraction of the tissue by 685.7% ± 61.1% and 455.2% ± 38.1%, respectively. When ACh and the extract were combined, the amplitude of contraction of the tissue rose by 1263.8% ± 69.0%, representing 84.3% increase over the effect of ACh alone. Conclusions: The findings demonstrate that methanol extract of Tephrosia vogelii leaves potentiates the contractile effect of ACh on intestinal smooth muscle, supporting the traditional claim that the plant is purgative.

  9. Control of Postharvest Bacterial Soft Rot by Gamma Irradiation and its Potential Modes of Action

    Directory of Open Access Journals (Sweden)

    Rae-Dong Jeong

    2016-04-01

    Full Text Available Gamma irradiation was evaluated for its in vitro and in vivo antibacterial activity against a postharvest bacterial pathogen, Erwinia carotovora subsp. carotovora (Ecc. Gamma irradiation in a bacteria cell suspension resulted in a dramatic reduction of the viable counts as well as an increase in the amounts of DNA and protein released from the cells. Gamma irradiation showed complete inactivation of Ecc, especially at a dose of 0.6 kGy. In addition, scanning electron microscopy of irradiated cells revealed severe damage on the surface of most bacterial cells. Along with the morphological changes of cells by gamma irradiation, it also affected the membrane integrity in a dose-dependent manner. The mechanisms by which the gamma irradiation decreased the bacterial soft rot can be directly associated with the disruption of the cell membrane of the bacterial pathogen, along with DNA fragmentation, results in dose-dependent cell inactivation. These findings suggest that gamma irradiation has potential as an antibacterial approach to reduce the severity of the soft rot of paprika.

  10. Short communication: Initial evidence supporting existence of potential rumen epidermal stem and progenitor cells.

    Science.gov (United States)

    Yohe, T T; Tucker, H L M; Parsons, C L M; Geiger, A J; Akers, R M; Daniels, K M

    2016-09-01

    The bovine rumen epidermis is a keratinized multilayered tissue that experiences persistent cell turnover. Because of this constant cell turnover, epidermal stem cells and their slightly more differentiated daughter cells, epidermal progenitor cells, must exist in the stratum basale of rumen epidermis. To date, these 2 epidermal cell populations and any unique cellular markers they may possess remain completely uncharacterized in the bovine rumen. An important first step in this new research area is the demonstration of the relative abundance and existence of markers for these cells in rumen tissue. A related second step is to document rumen epidermal proliferative responses to an extrinsic signal such as nutrient concentration within the rumen. The objectives of this experiment were to evaluate the extrinsic effect of diet on (1) gene expression of 6 potential rumen epidermal stem or progenitor cell markers and (2) rumen epidermal cell proliferation within the stratum basale. Twelve preweaned Holstein heifers were fed either a restricted diet (R) or an enhanced diet (EH). Animals on R received a milk replacer (MR) diet fed at 0.44kg of powder dry matter (DM)/d (20.9% crude protein, 29.8% fat, DM basis) and EH received MR at 1.08kg of powder dry matter/d (28.9% crude protein, 26.2% fat, DM basis). All calves had access to a 20% crude protein starter and were weaned during wk 7 of the experiment. Lifetime DM intake was 0.73kg of DM/calf per day for R (5.88 Mcal of net energy/calf per day) and 1.26kg of DM/calf per day for EH (10.68 Mcal of net energy/calf per day). Twenty-four hours before slaughter heifers received an intravenous dose of 5-bromo-2'-deoxyuridine to label proliferating cells. Heifers were slaughtered at 8 wk of age, and rumen samples from the ventral sac region were obtained and stored in RNA preservative and processed for routine histology. Quantitative real-time reverse transcriptase PCR was used to analyze relative abundance of genes. Candidate

  11. Potassium conductances mediate bidirectional state-dependent modulation of action potential evoked dendritic calcium signals in dentate gyrus granule cells

    Directory of Open Access Journals (Sweden)

    János Brunner

    2014-03-01

    Full Text Available Backpropagating action potentials (bAPs and local calcium signals that they trigger are fundamental for dendritic functions. Here we addressed the question what extent the changes of local dendritic membrane properties can contribute to the shaping of the coupling between dendritic action potentials and the local calcium responses. Using a combination of in vitro electrophysiological and confocal imaging techniques we found that activation of dendritic GIRK channels via mGlu2 or GABAB receptors enhanced the bAP¬-triggered calcium signals in the dendrites of dentate gyrus granule cells (GCs. The enhancement of calcium signals was significant only in those dendritic regions, where these receptors are predominantly expressed. Similarly to GIRK channel activation, somatic hyperpolarization by DC current injection (from -64 mV to -77 mV, significantly increased bAP-associated calcium signals in the proximal dendrites. The hyperpolarization was associated with a decrease in the input resistance due to the rectification of the membrane potential of GCs. The effect of hyperpolarization on the calcium signals was maintained when T-type calcium currents were blocked but it decreased when GIRK channels were inhibited. Simultaneous dual somato-dendritic recordings from GCs showed that somatic hyperpolarization accelerated the repolarization phase of dendritic bAP in the proximal region whereas the rising phase and peak amplitude was not affected. We hypothesize that the larger driving force for calcium ions during the faster repolarization can contribute to the increasing in calcium signals. Employment of previously recorded dendritic bAP waveforms from hyperpolarized membrane potential as voltage command evoked larger calcium currents in nucleated patches compared to bAP waveform from the same recording at depolarized membrane potential. Furthermore, addition of native, high-voltage activated, inactivating potassium conductance by somatic dynamic clamp

  12. AN INITIAL ASSESSMENT OF POTENTIAL PRODUCTION TECHNOLOGIES FOR EPSILON-METAL WASTE FORMS

    Energy Technology Data Exchange (ETDEWEB)

    Rohatgi, Aashish; Strachan, Denis M.

    2011-03-01

    This report examines and ranks a total of seven materials processing techniques that may be potentially utilized to consolidate the undissolved solids from nuclear fuel reprocessing into a low-surface area form. Commercial vendors of processing equipment were contacted and literature researched to gather information for this report. Typical equipment and their operation, corresponding to each of the seven techniques, are described in the report based upon the discussions and information provided by the vendors. Although the report does not purport to describe all the capabilities and issues of various consolidation techniques, it is anticipated that this report will serve as a guide by highlighting the key advantages and disadvantages of these techniques. The processing techniques described in this report were broadly classified into those that employed melting and solidification, and those in which the consolidation takes place in the solid-state. Four additional techniques were examined that were deemed impractical, but were included for completeness. The techniques were ranked based on criteria such as flexibility in accepting wide-variety of feed-stock (chemistry, form, and quantity), ease of long-term maintenance, hot cell space requirements, generation of additional waste streams, cost, and any special considerations. Based on the assumption of ~2.5 L of waste to be consolidated per day, sintering based techniques, namely, microwave sintering, spark plasma sintering and hot isostatic pressing, were ranked as the top-3 choices, respectively. Melting and solidification based techniques were ranked lower on account of generation of volatile phases and difficulties associated with reactivity and containment of the molten metal.

  13. Methanol extract of Tephrosia vogelii leaves potentiates the contractile action of acetylcholine on isolated rabbit jejunum

    Institute of Scientific and Technical Information of China (English)

    Tavershima; Dzenda; Joseph; Olusegun; Ayo; Alexander; Babatunde; Adelaiye; Ambrose; Osemattah; Adaudi

    2015-01-01

    Objective:To investigate the modulating role of methanol extract of Tephrosia vogelii leaves on acetylcholine(ACh)-induced contraction of isolated rabbit jejunum.Methods: Rabbit jejunum segment was removed and placed in an organ bath containing Tyrode’s solution, and its contractions were recorded isometrically.Results: ACh(2.0 × 10-10 g/m L) and the extract(2.0 × 10-4 g/m L) individually increased the frequency of contraction(mean ± SEM) of the isolated smooth muscle tissue by 47.6% ± 9.5% and 77.8% ± 66.5%, respectively. When ACh and the extract were combined, the frequency of contraction of the tissue was increased by 222.2% ± 25.9%, representing a 366.7% increase(P < 0.001) over the effect of ACh alone. Similarly, ACh(2.0 × 10-9 g/m L) and the extract individually increased significantly(P < 0.001) the amplitude of contraction of the tissue by 685.7% ± 61.1% and 455.2% ± 38.1%, respectively. When ACh and the extract were combined, the amplitude of contraction of the tissue rose by 1263.8% ± 69.0%, representing 84.3% increase over the ef ect of ACh alone. Conclusions: The findings demonstrate that methanol extract of Tephrosia vogelii leaves potentiates the contractile ef ect of ACh on intestinal smooth muscle, supporting the traditional claim that the plant is purgative.

  14. Exploring potential mechanisms of action of natalizumab in secondary progressive multiple sclerosis.

    Science.gov (United States)

    Sellebjerg, Finn; Cadavid, Diego; Steiner, Deborah; Villar, Luisa Maria; Reynolds, Richard; Mikol, Daniel

    2016-01-01

    Multiple sclerosis (MS) is a common and chronic central nervous system (CNS) demyelinating disease and a leading cause of permanent disability. Patients most often present with a relapsing-remitting disease course, typically progressing over time to a phase of relentless advancement in secondary progressive MS (SPMS), for which approved disease-modifying therapies are limited. In this review, we summarize the pathophysiological mechanisms involved in the development of SPMS and the rationale and clinical potential for natalizumab, which is currently approved for the treatment of relapsing forms of MS, to exert beneficial effects in reducing disease progression unrelated to relapses in SPMS. In both forms of MS, active brain-tissue injury is associated with inflammation; but in SPMS, the inflammatory response occurs at least partly behind the blood-brain barrier and is followed by a cascade of events, including persistent microglial activation that may lead to chronic demyelination and neurodegeneration associated with irreversible disability. In patients with relapsing forms of MS, natalizumab therapy is known to significantly reduce intrathecal inflammatory responses which results in reductions in brain lesions and brain atrophy as well as beneficial effects on clinical measures, such as reduced frequency and severity of relapse and reduced accumulation of disability. Natalizumab treatment also reduces levels of cerebrospinal fluid chemokines and other biomarkers of intrathecal inflammation, axonal damage and demyelination, and has demonstrated the ability to reduce innate immune activation and intrathecal immunoglobulin synthesis in patients with MS. The efficacy of natalizumab therapy in SPMS is currently being investigated in a randomized, double-blind, placebo-controlled trial.

  15. Slow recovery from inactivation of Na+ channels underlies the activity-dependent attenuation of dendritic action potentials in hippocampal CA1 pyramidal neurons.

    Science.gov (United States)

    Colbert, C M; Magee, J C; Hoffman, D A; Johnston, D

    1997-09-01

    Na+ action potentials propagate into the dendrites of pyramidal neurons driving an influx of Ca2+ that seems to be important for associative synaptic plasticity. During repetitive (10-50 Hz) firing, dendritic action potentials display a marked and prolonged voltage-dependent decrease in amplitude. Such a decrease is not apparent in somatic action potentials. We investigated the mechanisms of the different activity dependence of somatic and dendritic action potentials in CA1 pyramidal neurons of adult rats using whole-cell and cell-attached patch-clamp methods. There were three main findings. First, dendritic Na+ currents decreased in amplitude when repeatedly activated by brief (2 msec) depolarizations. Recovery was slow and voltage-dependent. Second, Na+ currents decreased much less in somatic than in dendritic patches. Third, although K+ currents remained constant during trains, K+ currents were necessary for dendritic action potential amplitude to decrease in whole-cell experiments. These results suggest that regional differences in Na+ and K+ channels determine the differences in the activity dependence of somatic and dendritic action potential amplitudes.

  16. Cordycepin Decreases Compound Action Potential Conduction of Frog Sciatic Nerve In Vitro Involving Ca2+-Dependent Mechanisms

    Directory of Open Access Journals (Sweden)

    Li-Hua Yao

    2015-01-01

    Full Text Available Cordycepin has been widely used in oriental countries to maintain health and improve physical performance. Compound nerve action potential (CNAP, which is critical in signal conduction in the peripheral nervous system, is necessary to regulate physical performance, including motor system physiological and pathological processes. Therefore, regulatory effects of cordycepin on CNAP conduction should be elucidated. In this study, the conduction ability of CNAP in isolated frog sciatic nerves was investigated. Results revealed that cordycepin significantly decreased CNAP amplitude and conductive velocity in a reversible and concentration-dependent manner. At 50 mg/L cordycepin, CNAP amplitude and conductive velocity decreased by 62.18 ± 8.06% and 57.34% ± 6.14% compared with the control amplitude and conductive velocity, respectively. However, the depressive action of cordycepin on amplitude and conductive velocity was not observed in Ca2+-free medium or in the presence of Ca2+ channel blockers (CdCl2/LaCl3. Pretreatment with L-type Ca2+ channel antagonist (nifedipine/deltiazem also blocked cordycepin-induced responses; by contrast, T-type and P-type Ca2+ channel antagonists (Ni2+ failed to block such responses. Therefore, cordycepin decreased the conduction ability of CNAP in isolated frog sciatic nerves via L-type Ca2+ channel-dependent mechanism.

  17. Role of AMPA and NMDA receptors and back-propagating action potentials in spike timing-dependent plasticity.

    Science.gov (United States)

    Fuenzalida, Marco; Fernández de Sevilla, David; Couve, Alejandro; Buño, Washington

    2010-01-01

    The cellular mechanisms that mediate spike timing-dependent plasticity (STDP) are largely unknown. We studied in vitro in CA1 pyramidal neurons the contribution of AMPA and N-methyl-d-aspartate (NMDA) components of Schaffer collateral (SC) excitatory postsynaptic potentials (EPSPs; EPSP(AMPA) and EPSP(NMDA)) and of the back-propagating action potential (BAP) to the long-term potentiation (LTP) induced by a STDP protocol that consisted in pairing an EPSP and a BAP. Transient blockade of EPSP(AMPA) with 7-nitro-2,3-dioxo-1,4-dihydroquinoxaline-6-carbonitrile (CNQX) during the STDP protocol prevented LTP. Contrastingly LTP was induced under transient inhibition of EPSP(AMPA) by combining SC stimulation, an imposed EPSP(AMPA)-like depolarization, and BAP or by coupling the EPSP(NMDA) evoked under sustained depolarization (approximately -40 mV) and BAP. In Mg(2+)-free solution EPSP(NMDA) and BAP also produced LTP. Suppression of EPSP(NMDA) or BAP always prevented LTP. Thus activation of NMDA receptors and BAPs are needed but not sufficient because AMPA receptor activation is also obligatory for STDP. However, a transient depolarization of another origin that unblocks NMDA receptors and a BAP may also trigger LTP.

  18. Promoting HIV Vaccine Research in African American Communities: Does the Theory of Reasoned Action Explain Potential Outcomes of Involvement?

    Science.gov (United States)

    Frew, Paula M; Archibald, Matthew; Martinez, Nina; del Rio, Carlos; Mulligan, Mark J

    2007-01-01

    The HIV/AIDS pandemic continues to challenge the African American community with disproportionate rates of infection, particularly among young women ages 25 to 34 years. Development of a preventive HIV vaccine may bring a substantial turning point in this health crisis. Engagement of the African American community is necessary to improve awareness of the effort and favorably influence attitudes and referent norms. The Theory of Reasoned Action (TRA) may be a useful framework for exploration of community engagement outcomes including future attendance, community mobilization, and study participation. Within the context of HIV vaccine outreach, we conducted a cross-sectional survey in early 2007 with 175 African-American adults (>/= 18 years). Confirmatory factor analysis and structural equation modeling were performed and the findings support the potential of the model in understanding behavioral intentions toward HIV vaccine research.

  19. Dendritic Na(+) spikes enable cortical input to drive action potential output from hippocampal CA2 pyramidal neurons.

    Science.gov (United States)

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

    2014-01-01

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

  20. Resveratrol exhibits a strong cytotoxic activity in cultured cells and has an antiviral action against polyomavirus: potential clinical use

    Directory of Open Access Journals (Sweden)

    Galati Gaspare

    2009-07-01

    Full Text Available Abstract Background Resveratrol is a non flavonoid polyphenol compound present in many plants and fruits and, at especially high concentrations, in the grape berries of Vitis vinifera. This compound has a strong bioactivity and its cytoprotective action has been demonstrated, however at high concentrations the drug exhibits also an effective anti-proliferative action. We recently showed its ability to abolish the effects of oxidative stress in cultured cells. In this work we assayed the bioactivity of resveratrol as antiproliferative and antiviral drug in cultured fibroblasts. Studies by other Authors showed that this natural compound inhibits the proliferation of different viruses such as herpes simplex, varicella-zoster and influenza A. The results presented here show an evident toxic activity of the drug at high concentrations, on the other hand at sub-cytotoxic concentrations, resveratrol can effectively inhibit the synthesis of polyomavirus DNA. A possible interpretation is that, due to the damage caused by resveratrol to the plasma membrane, the transfer of the virus from the endoplasmic reticulum to the nucleus, may be hindered thus inhibiting the production of viral DNA. Methods The mouse fibroblast line 3T6 and the human tumor line HL60 were used throughout the work. Cell viability and vital cell count were assessed respectively, by the MTT assay and Trypan Blue staining. Cytotoxic properties and evaluation of viral DNA production by agarose gel electrophoresis were performed according to standard protocols. Results Our results show a clear dose dependent both cytotoxic and antiviral effect of resveratrol respectively at high and low concentrations. The cytotoxic action is exerted towards a stabilized cell-line (3T6 as well as a tumor-line (HL60. Furthermore the antiviral action is evident after the phase of virion entry, therefore data suggest that the drug acts during the synthesis of the viral progeny DNA. Conclusion Resveratrol is

  1. Effects of the histamine H1 receptor antagonist hydroxyzine on hERG K+ channels and cardiac action potential duration

    Institute of Scientific and Technical Information of China (English)

    Byung Hoon LEE; Seung Ho LEE; Daehyun CHU; Jin Won HYUN; Han CHOE; Bok Hee CHOI; Su-Hyun JO

    2011-01-01

    To investigate the effects of hydroxyzine on human ether-a-go-go-related gene (hERG) channels to determine the electrolphysiological basis for its proarrhythmic effects.Methods:hERG channels were expressed in Xenopus oocytes and HEK293 cells,and the effects of hydroxyzine on the channels were examined using two-microelectrode voltage-clamp and patch-clamp techniques,respectively.The effects of hydroxyzine on action potential duration were examined in guinea pig ventricular myocytes using current clamp.Results:Hydroxyzine (0.2 and 2 μmol/L) significantly increased the action potential duration at 90% repolarization (APD90) in both concentration- and time-dependent manners.Hydroxyzine (0.03-3 μmol/L) blocked both the steady-state and tail hERG currents.The block was voltage-dependent,and the values of IC50 for blocking the steady-state and tail currents at +20 mV was 0.18±0.02 μmol/L and 0.16±0.01 μmol/L,respectively,in HEK293 cells.Hydroxyzine (5 μmol/L) affected both the activated and the inactivated states of the channels,but not the closed state.The S6 domain mutation Y652A attenuated the blocking of hERG current by ~6-fold.Conclusion:The results suggest that hydroxyzine could block hERG channels and prolong APD.The tyrosine at position 652 in the channel may be responsible for the proarrhythmic effects of hydroxyzine.

  2. Spine calcium transients induced by synaptically-evoked action potentials can predict synapse location and establish synaptic democracy.

    Directory of Open Access Journals (Sweden)

    David C Sterratt

    Full Text Available CA1 pyramidal neurons receive hundreds of synaptic inputs at different distances from the soma. Distance-dependent synaptic scaling enables distal and proximal synapses to influence the somatic membrane equally, a phenomenon called "synaptic democracy". How this is established is unclear. The backpropagating action potential (BAP is hypothesised to provide distance-dependent information to synapses, allowing synaptic strengths to scale accordingly. Experimental measurements show that a BAP evoked by current injection at the soma causes calcium currents in the apical shaft whose amplitudes decay with distance from the soma. However, in vivo action potentials are not induced by somatic current injection but by synaptic inputs along the dendrites, which creates a different excitable state of the dendrites. Due to technical limitations, it is not possible to study experimentally whether distance information can also be provided by synaptically-evoked BAPs. Therefore we adapted a realistic morphological and electrophysiological model to measure BAP-induced voltage and calcium signals in spines after Schaffer collateral synapse stimulation. We show that peak calcium concentration is highly correlated with soma-synapse distance under a number of physiologically-realistic suprathreshold stimulation regimes and for a range of dendritic morphologies. Peak calcium levels also predicted the attenuation of the EPSP across the dendritic tree. Furthermore, we show that peak calcium can be used to set up a synaptic democracy in a homeostatic manner, whereby synapses regulate their synaptic strength on the basis of the difference between peak calcium and a uniform target value. We conclude that information derived from synaptically-generated BAPs can indicate synapse location and can subsequently be utilised to implement a synaptic democracy.

  3. Responses of action potential and K+ currents to temperature acclimation in fish hearts: phylogeny or thermal preferences?

    Science.gov (United States)

    Haverinen, Jaakko; Vornanen, Matti

    2009-01-01

    Electrical activity of the heart is assumed to be one of the key factors that set thermal tolerance limits for ectothermic vertebrates. Therefore, we hypothesized that in thermal acclimation--the duration of cardiac action potential and the repolarizing K+ currents that regulate action potential duration (APD)--the rapid component of the delayed rectifier K+ current (I(Kr)) and the inward rectifier K+ current (I(K1)) are more plastic in eurythermal than in stenothermal fish species. The hypothesis was tested in six freshwater teleosts representing four different fish orders (Cadiformes, Cypriniformes, Perciformes, Salmoniformes) acclimated at +4 degrees C (cold acclimation) or +18 degrees C (warm acclimation). In cold acclimation, a compensatory shortening of APD occurred in all species regardless of thermal tolerances, life styles, or phylogenies of the fish, suggesting that this response is a common characteristic of the teleost heart. The strength of the response did not, however, obey simple eurythermy-stenothermy gradation but differed among the phylogenetic groups. Salmoniformes fish showed the greatest acclimation capacity of cardiac electrical activity, whereas the weakest response appeared in the perch (Perciformes) heart. The underlying ionic mechanisms were also partly phylogeny dependent. Modification of the I(Kr) current was al- most ubiquitously involved in acclimation response of fish cardiac myocytes to temperature, while the ability to change the I(K1) current under chronic thermal stress was absent or showed inverse compensation in Salmoniformes species. Thus, in Salmoniformes fish, the thermal plasticity of APD is strongly based on I(Kr), while other fish groups rely on both I(Kr) and I(K1).

  4. Corrosion of Steel in Concrete – Potential Monitoring and Electrochemical Impedance Spectroscopy during Corrosion Initiation and Propagation

    DEFF Research Database (Denmark)

    Küter, Andre; Mason, Thomas O.; Geiker, Mette Rica;

    2005-01-01

    A reinforced mortar specimen that allows potential measurements and electrochemical impedance spectroscopy (EIS) immediately after preparation was designed and tested. The specimen consists of a mortar cylinder with a central rebar and a concentric arrangement of embedded Ru/Ir activated titanium...... and titanium wires can be monitored immediately after preparation. The wire arrangement also allows investigation of local changes in the bulk mortar by EIS or by measuring the potential development of the titanium wires versus an external standard electrode. The specimen design was evaluated...... in an investigation on the effect of the steel quality and the steel surface properties on initiation and propagation of chloride-induced reinforcement corrosion. Besides untreated (as received) carbon rebars and stainless rebars, selected surface treatments and galvanization were investigated. The surface treatments...

  5. The effects of propofol on local field potential spectra, action potential firing rate, and their temporal relationship in humans and felines

    Directory of Open Access Journals (Sweden)

    Sara eHanrahan

    2013-04-01

    Full Text Available Propofol is an intravenous sedative hypnotic, which, acting as a GABAA agonist, results in neocortical inhibition. While propofol has been well studied at the molecular and clinical level, less is known about the effects of propofol at the level of individual neurons and local neocortical networks. We used Utah Electrode Arrays (UEAs to investigate the effects of propofol anesthesia on action potentials (APs and local field potentials (LFPs. UEAs were implanted into the neocortex of two humans and three felines. The two human patients and one feline received propofol by bolus injection, while the other two felines received target-controlled infusions. We examined the changes in LFP power spectra and AP firing at different levels of anesthesia. Increased propofol concentration correlated with decreased high-frequency power in LFP spectra and decreased AP firing rates, and the generation of large amplitude spike-like LFP activity; however, the temporal relationship between APs and LFPs remained relatively consistent at all levels of propofol. The probability that an AP would fire at this local minimum of the LFP increased with propofol administration. The propofol-induced suppression of neocortical network activity allowed LFPs to be dominated by low-frequency spike-like activity, and correlated with sedation and unconsciousness. As the low-frequency spike-like activity increased and the AP-LFP relationship became more predictable firing rate encoding capacity is impaired. This suggests a mechanism for decreased information processing in the neocortex that accounts for propofol-induced unconsciousness.

  6. The potential role of COX-2 in cancer stem cell-mediated canine mammary tumor initiation: an immunohistochemical study.

    Science.gov (United States)

    Huang, Jian; Zhang, Di; Xie, Fuqiang; Lin, Degui

    2015-01-01

    Increasing evidence suggests that cancer stem cells (CSCs) are responsible for tumor initiation and maintenance. Additionally, it is becoming apparent that cyclooxygenase (COX) signaling is associated with canine mammary tumor development. The goals of the present study were to investigate COX-2 expression patterns and their effect on CSC-mediated tumor initiation in primary canine mammary tissues and tumorsphere models using immunohistochemistry. Patterns of COX-2, CD44, octamer-binding transcription factor (Oct)-3/4, and epidermal growth factor receptor (EGFR) expression were examined in malignant mammary tumor (MMT) samples and analyzed in terms of clinicopathological characteristics. COX-2 and Oct-3/4 expression was higher in MMTs compared to other histological samples with heterogeneous patterns. In MMTs, COX-2 expression correlated with tumor malignancy features. Significant associations between COX-2, CD44, and EGFR were observed in low-differentiated MMTs. Comparative analysis showed that the levels of COX-2, CD44, and Oct-3/4 expression varied significantly among TSs of three histological grades. Enhanced COX-2 staining was consistently observed in TSs. Similar levels of staining intensity were found for CD44 and Oct-3/4, but EGFR expression was weak. Our findings indicate the potential role of COX-2 in CSC-mediated tumor initiation, and suggest that COX-2 inhibition may help treat canine mammary tumors by targeting CSCs.

  7. Electrode fusion for the prediction of self-initiated fine movements from single-trial readiness potentials.

    Science.gov (United States)

    Abou Zeid, Elias; Chau, Tom

    2015-06-01

    Current human-machine interfaces (HMIs) for users with severe disabilities often have difficulty distinguishing between intentional and inadvertent activations. Pre-movement neuro-cortical activity may aid in this elusive discrimination task but has not been exploited in HMIs. This work investigates the utility of the readiness potential (RP), a slow negative cortical potential preceding voluntary movement, for detecting the intention of self-initiated fine movements prior to their motoric realization. We recorded electroencephalography from the frontal, central, parietal and occipital lobes of 10 participants using a self-initiated switch activation protocol. Eye movement artifacts were removed by regression and the RP was detected on a single-trial basis, in a narrow frequency range (0.1-1 Hz). Common average reference was applied prior to windowed-averaging for feature extraction. Electrodes were selected according to a separability measure based on Fisher projection. Our findings demonstrate that feature fusion from an optimal number of electrodes achieves a statistically significant lower classification error than the best single classifier. Finally, voluntary fine movement intention was detected on a single-trial basis at above-chance levels approximately 396 ms before physical switch activation. These findings encourage the development of rapid-response, intention-aware HMIs for individuals with severe disabilities who struggle with executing voluntary fine motor movements.

  8. Nanoelectronics-biology frontier: From nanoscopic probes for action potential recording in live cells to three-dimensional cyborg tissues

    Science.gov (United States)

    Duan, Xiaojie; Fu, Tian-Ming; Liu, Jia; Lieber, Charles M.

    2013-01-01

    Summary Semiconductor nanowires configured as the active channels of field-effect transistors (FETs) have been used as detectors for high-resolution electrical recording from single live cells, cell networks, tissues and organs. Extracellular measurements with substrate supported silicon nanowire (SiNW) FETs, which have projected active areas orders of magnitude smaller than conventional microfabricated multielectrode arrays (MEAs) and planar FETs, recorded action potential and field potential signals with high signal-to-noise ratio and temporal resolution from cultured neurons, cultured cardiomyocytes, acute brain slices and whole animal hearts. Measurements made with modulation-doped nanoscale active channel SiNW FETs demonstrate that signals recorded from cardiomyocytes are highly localized and have improved time resolution compared to larger planar detectors. In addition, several novel three-dimensional (3D) transistor probes, which were realized using advanced nanowire synthesis methods, have been implemented for intracellular recording. These novel probes include (i) flexible 3D kinked nanowire FETs, (ii) branched intracellular nanotube SiNW FETs, and (iii) active silicon nanotube FETs. Following phospholipid modification of the probes to mimic the cell membrane, the kinked nanowire, branched intracellular nanotube and active silicon nanotube FET probes recorded full-amplitude intracellular action potentials from spontaneously firing cardiomyocytes. Moreover, these probes demonstrated the capability of reversible, stable, and long-term intracellular recording, thus indicating the minimal invasiveness of the new nanoscale structures and suggesting biomimetic internalization via the phospholipid modification. Simultaneous, multi-site intracellular recording from both single cells and cell networks were also readily achieved by interfacing independently addressable nanoprobe devices with cells. Finally, electronic and biological systems have been seamlessly

  9. Study of amplitude frequency spectra of the compound action potentials recorded from normal and M. leprae infected mice using Fourier series analysis.

    Science.gov (United States)

    Vidyasagar, P B; Lokhandwalla, M N; Damle, P S

    1986-01-01

    Compound action potentials recorded from normal and M. leprae infected mice sciatic nerves were analysed in frequency domain using Fourier Series Analysis. Changes in myelinated fibre potentials were detected as early as 2nd post-inoculation month. This technique could be further developed to aid in early diagnosis of leprosy.

  10. Action Learning: Avoiding Conflict or Enabling Action

    Science.gov (United States)

    Corley, Aileen; Thorne, Ann

    2006-01-01

    Action learning is based on the premise that action and learning are inextricably entwined and it is this potential, to enable action, which has contributed to the growth of action learning within education and management development programmes. However has this growth in action learning lead to an evolution or a dilution of Revan's classical…

  11. Effect of phentolamine, alprenolol and prenylamine on maximum rate of rise of action potential in guinea-pig papillary muscles.

    Science.gov (United States)

    Sada, H

    1978-10-01

    Effects of phentolamine (13.3, 26.5 and 53.0 micron), alprenolol (3.5, 7.0 and 17.5 micron) and prenylamine (2.4, 4.8 and 11.9 micron) on the transmembrane potential were studied in isolated guinea-pig papillary muscles, superfused with Tyrode's solution. 1. Phentolamine, alprenolol and prenylamine reduced the maximum rate of rise of action potential (.Vmax) dose-dependently. Higher concentrations of phentolamine and prenylamine caused a loss of plateau in a majority of the preparations. Resting potential was not altered by any of the drugs. Readmittance of drug-free Tyrode's solution reversed these changes induced by 13.3 micron of phentolamine and all conconcentrations of alprenolol almost completely but those induced by higher concentrations of phentolamine and all concentrations of prenylamine only slightly. 2. .Vmax at steady state was increased with decreasing driving frequencies (0.5 and 0.25 Hz) and was decreased with increasing ones (2--5 Hz) in comparison with that at 1 Hz. Such changes were all exaggerated by the above drugs, particularly by prenylamine. 3. Prenylamine and, to a lesser degree, phentolamine and alprenolol delayed dose-dependently the recovery process of .Vmax in premature responses. 4. .Vmax in the first response after interruption of stimulation recovered toward the predrug value in the presence of the above three drugs. The time constants of recovery process ranged between 10.5 and 15.0s for phentolamine, between 4.5 and 15.5s for alprenolol. The time constant of the main component was estimated to be approximately 2s for the recovery process with prenylamine. 5. On the basis of the model recently proposed by Hondeghem and Katzung (1977), it is suggested that the drug molecules associate with the open sodium channels and dissociated slowly from the closed channels and that the inactivation parameter in the drug-associated channels is shifted in the hyperpolarizing direction.

  12. Effectiveness of elite female basketball players’ technical-tactic actions and ways for their improvement at stage of maximal realization of individual potentials

    Directory of Open Access Journals (Sweden)

    Sushko R.A.

    2015-08-01

    Full Text Available Purpose: study effectiveness of elite female basketball players’ technical-tactic actions and determine the ways for their improvement at stage of maximal realization of individual potentials. Material: the authors analyzed competition functioning’s indicators of female basketball players of national combined team of Ukraine and their age characteristics. Results: effectiveness of technical-tactic actions in structure of national female basketball players’ combined team of Ukraine competition functioning at European championship. The authors present: indicators of team composition; roles in team; won and lost games; quantity of scored and skipped points; technical-tactic actions; age of sportswomen. Age indicators of elite female basketball players at stage of maximal realization have been given. Conclusions: we have composed a list of the most important technical-tactic actions in competition functioning. We also outlined ways for their perfection at stage of maximal realization of individual potentials of elite female basketball players of different game roles.

  13. The role of dendritic action potentials and Ca2+ influx in the induction of homosynaptic long-term depression in hippocampal CA1 pyramidal neurons.

    Science.gov (United States)

    Christie, B R; Magee, J C; Johnston, D

    1996-01-01

    Long-term depression (LTD) of synaptic efficacy at CA1 synapses is believed to be a Ca(2+)-dependent process. We used high-speed fluorescence imaging and patch-clamp techniques to quantify the spatial distribution of changes in intracellular Ca2+ accompanying the induction of LTD at Schaffer collateral synapses in CA1 pyramidal neurons. Low-frequency stimulation (3 Hz), which was subthreshold for action potentials, produced small changes in [Ca2+]i and failed to elicit LTD. Increasing the stimulus strength so that action potentials were generated produced both robust LTD and increases in [Ca2+]i. Back-propagating action potentials at 3 Hz in the absence of synaptic stimulation also produced increases in [Ca2+]i, but failed to induce LTD. When subthreshold synaptic stimulation was paired with back-propagating action potentials, however, large increases in [Ca2+]i were observed and robust LTD was induced. The LTD was blocked by the N-methyl-D-aspartate receptor (NMDAr) antagonist APV, and stimulus-induced increases in [Ca2+]i were reduced throughout the neuron under these conditions. The LTD was also dependent on Ca2+ influx via voltage-gated Ca2+ channels (VGCCs), because LTD was severely attenuated or blocked by both nimodipine and Ni2+. These findings suggest that back-propagating action potentials can exert a powerful control over the induction of LTD and that both VGCCs and NMDArs are involved in the induction of this form of plasticity.

  14. Enteral nutrients potentiate the intestinotrophic action of glucagon-like peptide-2 in association with increased insulin-like growth factor-I responses in rats

    DEFF Research Database (Denmark)

    Liu, Xiaowen; Murali, Sangita G; Holst, Jens Juul

    2008-01-01

    compared to GLP-2. This indicates that EN potentiates the intestinotrophic action of GLP-2. Proliferation of enterocytes due to GLP-2 infusion was associated with greater expression of ileal proglucagon, GLP-2 receptor, IGF-I, IGF binding protein-3 mRNAs, and greater IGF-I peptide concentration in ileum (p......action in a physiological model of intestinal growth. Key words...

  15. Action-potential duration and the modulation of transmitter release from the sensory neurons of Aplysia in presynaptic facilitation and behavioral sensitization.

    Science.gov (United States)

    Hochner, B; Klein, M; Schacher, S; Kandel, E R

    1986-11-01

    Presynaptic facilitation of transmitter release from Aplysia sensory neurons is an important contributor to behavioral sensitization of the gill and siphon withdrawal reflex. The enhanced release is accompanied by reduction of the serotonin-sensitive S current in the sensory neurons and a consequent increase in duration of the presynaptic action potential (ranging from 10% to 30%). We find that changes of similar magnitude in the duration of depolarizing voltage-clamp steps in sensory neurons in intact abdominal ganglia yield increases in synaptic potentials of 45-120%. In dissociated cell culture, these changes lead to increases of 25-60% in the synaptic potential. Prolongation of presynaptic depolarization using voltage clamp or prolongation of the duration of the action potential by K(+)-channel blockers leads to prolongation of the time-to-peak of the synaptic potentials; similar changes in time-to-peak occur during presynaptic facilitation. The time-to-peak is not changed by homosynaptic depression or by changing the Ca(2+) concentration, procedures that alter release without changing the duration of the action potential. Preventing the spike from broadening by voltage clamping the presynaptic neuron substantially reduces or blocks the facilitation. These results suggest that broadening of the action potential during facilitation is a causal factor in the enhancement of transmitter release.

  16. The initiator methionine tRNA drives cell migration and invasion leading to increased metastatic potential in melanoma

    Directory of Open Access Journals (Sweden)

    Joanna Birch

    2016-10-01

    Full Text Available The cell's repertoire of transfer RNAs (tRNAs has been linked to cancer. Recently, the level of the initiator methionine tRNA (tRNAiMet in stromal fibroblasts has been shown to influence extracellular matrix (ECM secretion to drive tumour growth and angiogenesis. Here we show that increased tRNAiMet within cancer cells does not influence tumour growth, but drives cell migration and invasion via a mechanism that is independent from ECM synthesis and dependent on α5β1 integrin and levels of the translation initiation ternary complex. In vivo and ex vivo migration (but not proliferation of melanoblasts is significantly enhanced in transgenic mice which express additional copies of the tRNAiMet gene. We show that increased tRNAiMet in melanoma drives migratory, invasive behaviour and metastatic potential without affecting cell proliferation and primary tumour growth, and that expression of RNA polymerase III-associated genes (which drive tRNA expression are elevated in metastases by comparison with primary tumours. Thus, specific alterations to the cancer cell tRNA repertoire drive a migration/invasion programme that may lead to metastasis.

  17. The initiator methionine tRNA drives cell migration and invasion leading to increased metastatic potential in melanoma

    Science.gov (United States)

    Birch, Joanna; Clarke, Cassie J.; Campbell, Andrew D.; Campbell, Kirsteen; Mitchell, Louise; Liko, Dritan; Kalna, Gabriela; Strathdee, Douglas; Sansom, Owen J.; Neilson, Matthew; Blyth, Karen

    2016-01-01

    ABSTRACT The cell's repertoire of transfer RNAs (tRNAs) has been linked to cancer. Recently, the level of the initiator methionine tRNA (tRNAiMet) in stromal fibroblasts has been shown to influence extracellular matrix (ECM) secretion to drive tumour growth and angiogenesis. Here we show that increased tRNAiMet within cancer cells does not influence tumour growth, but drives cell migration and invasion via a mechanism that is independent from ECM synthesis and dependent on α5β1 integrin and levels of the translation initiation ternary complex. In vivo and ex vivo migration (but not proliferation) of melanoblasts is significantly enhanced in transgenic mice which express additional copies of the tRNAiMet gene. We show that increased tRNAiMet in melanoma drives migratory, invasive behaviour and metastatic potential without affecting cell proliferation and primary tumour growth, and that expression of RNA polymerase III-associated genes (which drive tRNA expression) are elevated in metastases by comparison with primary tumours. Thus, specific alterations to the cancer cell tRNA repertoire drive a migration/invasion programme that may lead to metastasis. PMID:27543055

  18. The potential spread of severe footrot in Norway if no elimination programme had been initiated: a simulation model.

    Science.gov (United States)

    Grøneng, Gry M; Vatn, Synnøve; Kristoffersen, Anja Bråthen; Nafstad, Ola; Hopp, Petter

    2015-02-20

    When severe footrot was detected in Norway in 2008, a surveillance programme was initiated and followed by an elimination programme. By 2013 the disease had spread to two of 19 counties and a total of 119 (1%) sheep flocks had been diagnosed with severe footrot. A simulation model was developed to estimate the potential spread of severe footrot in Norway and to estimate the relative importance of the different spreading routes. The model parameters were based on the rate of spread of the first 38 diagnosed cases and the management and climatic factors particular for Norway. The model showed that by 2013, severe footrot would have spread to six counties and infected 16% of the sheep flocks if no elimination programme had been initiated. If this is compared with the 1% of flocks that were diagnosed in Norway by 2013, there seems to be a large effect of the implemented footrot elimination programme. By 2035, it was estimated that severe footrot would have spread to 16 counties and 64% of the sheep flocks. Such an extensive spread would probably impose a large negative impact on the sheep industry and welfare of the sheep. The most effective way to curb the spread of severe footrot was by decreasing the within county infection rate. This could be achieved by decreasing the contact between flocks or by decreasing the environmental load of D. nodosus, for example by footbathing sheep, culling diseased sheep or eliminating severe footrot in the flock.

  19. Phasic excitation of ventral tegmental dopamine neurons potentiates the initiation of conditioned approach behavior: Parametric and reinforcement-schedule analyses

    Directory of Open Access Journals (Sweden)

    Anton eIlango

    2014-05-01

    Full Text Available Midbrain dopamine neurons are implicated in motivation and learning. However, it is unclear how phasic excitation of dopamine neurons, which is implicated in learning, is involved in motivation. Here we used a self-stimulation procedure to examine how mice seek for optogenetically-induced phasic excitation of dopamine neurons, with an emphasis on the temporal dimension. TH-Cre transgenic mice received adeno-associated viral vectors encoding channelrhodopsin-2 into the ventral tegmental area, resulting in selective expression of the opsin in dopamine neurons. These mice were trained to press on a lever for photo-pulse trains that phasically excited dopamine neurons. They learned to self-stimulate in a fast, constant manner, and rapidly reduced pressing during extinction. We first determined effective parameters of photo-pulse trains in self-stimulation. Lever-press rates changed as a function of the manipulation of pulse number, duration, intensity and frequency. We then examined effects of interval and ratio schedules of reinforcement on photo-pulse train reinforcement, which was contrasted with food reinforcement. Reinforcement with food inhibited lever pressing for a few seconds, after which pressing was robustly regulated in a goal-directed manner. In contrast, phasic excitation of dopamine neurons robustly potentiated the initiation of lever pressing; however, this effect did not last more than 1 s and quickly diminished. Indeed, response rates markedly decreased when lever pressing was reinforced with inter-reinforcement interval schedules of 3 or 10 s or ratio schedules requiring multiple responses per reinforcement. Thus, phasic excitation of dopamine neurons briefly potentiates the initiation of approach behavior with apparent lack of long-term motivational regulation.

  20. Phasic excitation of ventral tegmental dopamine neurons potentiates the initiation of conditioned approach behavior: parametric and reinforcement-schedule analyses.

    Science.gov (United States)

    Ilango, Anton; Kesner, Andrew J; Broker, Carl J; Wang, Dong V; Ikemoto, Satoshi

    2014-01-01

    Midbrain dopamine neurons are implicated in motivation and learning. However, it is unclear how phasic excitation of dopamine neurons, which is implicated in learning, is involved in motivation. Here we used a self-stimulation procedure to examine how mice seek for optogenetically-induced phasic excitation of dopamine neurons, with an emphasis on the temporal dimension. TH-Cre transgenic mice received adeno-associated viral vectors encoding channelrhodopsin-2 into the ventral tegmental area, resulting in selective expression of the opsin in dopamine neurons. These mice were trained to press on a lever for photo-pulse trains that phasically excited dopamine neurons. They learned to self-stimulate in a fast, constant manner, and rapidly reduced pressing during extinction. We first determined effective parameters of photo-pulse trains in self-stimulation. Lever-press rates changed as a function of the manipulation of pulse number, duration, intensity, and frequency. We then examined effects of interval and ratio schedules of reinforcement on photo-pulse train reinforcement, which was contrasted with food reinforcement. Reinforcement with food inhibited lever pressing for a few seconds, after which pressing was robustly regulated in a goal-directed manner. In contrast, phasic excitation of dopamine neurons robustly potentiated the initiation of lever pressing; however, this effect did not last more than 1 s and quickly diminished. Indeed, response rates markedly decreased when lever pressing was reinforced with inter-reinforcement interval schedules of 3 or 10 s or ratio schedules requiring multiple responses per reinforcement. Thus, phasic excitation of dopamine neurons briefly potentiates the initiation of approach behavior with apparent lack of long-term motivational regulation.

  1. Effect of procainamide on transmembrane action potentials in guinea-pig papillary muscles as affected by external potassium concentration.

    Science.gov (United States)

    Sada, H; Kojima, M; Ban, T

    1979-11-01

    Effects of procainamide (PA), 0.18, 0.37 and 0.74 mmol/l, on the transmembrane potential were studied in isolated guinea-pig papillary muscles, superfused with modified Tyrode's solution (external K concentration, [K]0 = 5.4 mmol/l) at the basic driving rate of 1 Hz. PA, at 0.37 mmol/l, significantly reduced the maximum rate of rise of action potential (Vmax) with no change in the resting potential. When 2.7 mmol/l [K]0 of the superfusate was exchanged for 15 mmol/l [K]0 solution a decrease in Vmax induced by 0.37 mmol/l PA became more prominent with decrease in resting potential. The reduction of Vmax at steady state was less at lower driving rates (0.25 and 0.5 Hz) and more at higher driving rates (2-5 Hz) than at 1 Hz in 2.7, 5.4 and 10.0 mmol/l [K]0 solution. Such changes were enhanced concentration-dependently by PA at 5.4 mmol/l [K]0. Also, the changes became more significant with an increase in [K]0 from 2.7 mmol/l to 5.4 mmol/l and then to 10.0 mmol/l. The recovery process of Vmax proceeded with two components. The time course of the slow component seen in the Vmax of the first response after interruption of basic driving stimulation at 1 Hz, followed an approximate monoexponential function. The time constants were 6.3, 4.4 and 5.8 s in the presence of 0.18, 0.37 and 0.74 mmol/l PA at 5.4 mmol/l [K]0 and 3.4 and 3.7 s both in the presence of 0.37 mmol/l PA at 2.7 and 10.0 mmol/l [K]0. Vmax values after 30 or 60 s interruption of stimulation were 80-92% of the predrug Vmax value at 1 Hz. The time constants of the first component, estimated by the peeling-off methods at the driving rate of 0.1 Hz, were 11, 31 and 5-22 ms in the presence of 0.37 mmol/l at 5.4, 10.0 and 2.7 mmol/l [K]0 and did not differ significantly from the time constants in control preparations. The results were found to be consistent, to a certain extent, with the model proposed by Hondeghem and Katzung (1977).

  2. Neural recording front-end IC using action potential detection and analog buffer with digital delay for data compression.

    Science.gov (United States)

    Liu, Lei; Yao, Lei; Zou, Xiaodan; Goh, Wang Ling; Je, Minkyu

    2013-01-01

    This paper presents a neural recording analog front-end IC intended for simultaneous neural recording with action potential (AP) detection for data compression in wireless multichannel neural implants. The proposed neural recording front-end IC detects the neural spikes and sends only the preserved AP information for wireless transmission in order to reduce the overall power consumption of the neural implant. The IC consists of a low-noise neural amplifier, an AP detection circuit and an analog buffer with digital delay. The neural amplifier makes use of a current-reuse technique to maximize the transconductance efficiency for attaining a good noise efficiency factor. The AP detection circuit uses an adaptive threshold voltage to generate an enable signal for the subsequent functional blocks. The analog buffer with digital delay is employed using a finite impulse response (FIR) filter which preserves the AP waveform before the enable signal as well as provides low-pass filtering. The neural recording front-end IC has been designed using standard CMOS 0.18-µm technology occupying a core area of 220 µm by 820 µm.

  3. Single mechanically-gated cation channel currents can trigger action potentials in neocortical and hippocampal pyramidal neurons.

    Science.gov (United States)

    Nikolaev, Yury A; Dosen, Peter J; Laver, Derek R; van Helden, Dirk F; Hamill, Owen P

    2015-05-22

    The mammalian brain is a mechanosensitive organ that responds to different mechanical forces ranging from intrinsic forces implicated in brain morphogenesis to extrinsic forces that can cause concussion and traumatic brain injury. However, little is known of the mechanosensors that transduce these forces. In this study we use cell-attached patch recording to measure single mechanically-gated (MG) channel currents and their affects on spike activity in identified neurons in neonatal mouse brain slices. We demonstrate that both neocortical and hippocampal pyramidal neurons express stretch-activated MG cation channels that are activated by suctions of ~25mm Hg, have a single channel conductance for inward current of 50-70pS and show weak selectivity for alkali metal cations (i.e., Na(+)action potentials in both neocortical and hippocampal pyramidal neurons. Not all neuron types studied here expressed MG channel currents. In particular, locus coeruleus and cerebellar Purkinje neurons showed no detectable MG channel activity. Moreover their robust rhythmic spike activity was resistant to mechanical modulation. Our observation that a single MG channel current can trigger spiking predicates the need for reassessment of the long held view that the impulse output of central neurons depends only upon their intrinsic voltage-gated channels and/or their integrated synaptic input.

  4. Anticancer potential and mechanism of action of mango ginger (Curcuma amada Roxb.) supercritical CO₂ extract in human glioblastoma cells.

    Science.gov (United States)

    Ramachandran, Cheppail; Lollett, Ivonne V; Escalon, Enrique; Quirin, Karl-Werner; Melnick, Steven J

    2015-04-01

    Mango ginger (Curcuma amada Roxb.) is among the less-investigated species of Curcuma for anticancer properties. We have investigated the anticancer potential and the mechanism of action of a supercritical CO2 extract of mango ginger (CA) in the U-87MG human glioblastoma cell line. CA demonstrated higher cytotoxicity than temozolomide, etoposide, curcumin, and turmeric force with IC50, IC75, and IC90 values of 4.92 μg/mL, 12.87 μg/mL, and 21.30 μg/mL, respectively. Inhibitory concentration values of CA for normal embryonic mouse hypothalamus cell line (mHypoE-N1) is significantly higher than glioblastoma cell line, indicating the specificity of CA against brain tumor cells. CompuSyn analysis indicates that CA acts synergistically with temozolomide and etoposide for the cytotoxicity with combination index values of <1. CA treatment also induces apoptosis in glioblastoma cells in a dose-dependent manner and downregulates genes associated with apoptosis, cell proliferation, telomerase activity, oncogenesis, and drug resistance in glioblastoma cells.

  5. Liénard-type models for the simulation of the action potential of cardiac nodal cells

    Science.gov (United States)

    Podziemski, P.; Żebrowski, J. J.

    2013-10-01

    Existing models of cardiac cells which include multi-variable cardiac transmembrane current are too complex to simulate the long time dynamical properties of the heart rhythm. The large number of parameters that need to be defined and set for such models make them not only cumbersome to use but also require a large computing power. Consequently, the application of such models for the bedside analysis of heart rate of a specific patient may be difficult. Other ways of modelling need to be investigated. We consider the general problem of developing a model of cardiac pacemaker tissue that allows to combine the investigation of phenomena at a time scale of thousands of heart beats with the ability to reproduce realistic tissue-level characteristics of cell dynamics. We propose a modified van der Pol-Duffing equation-a Liénard-type oscillator-as a phenomenological model for cardiac nodal tissue, with certain important physiological similarities to ion-channel models of cardiac pacemaker cells. The model presented here is specifically designed to qualitatively reproduce mesoscopic characteristics of cell dynamics, including action potential duration (APD) restitution properties, phase response characteristics, and phase space structure. We show that these characteristics agree qualitatively with the extensive ionic models and experimental results in the literature [Anumonwo et al., 1991, [33], Cao et al., 1999, [49], Coster and Celler, 2003, [31], Qu, 2004, [45], Tsalikakis et al., 2007, [32], Inada et al., 2009, [14], Qu et al., 2010, [50

  6. [Correlation of changes in compound action potential (CAP) tuning curves and cochlear lesion in guinea pigs after explosion].

    Science.gov (United States)

    Han, D

    1989-01-01

    The purpose of the present study was to investigate the sensitivity of compound action potential (CAP) tuning curves to changes of the cochlear status in guinea pigs after explosion and their ability to reflect specific histological variations. The results were as follows: 1. The CAP tuning curves were abnormally broad and the Q 10 dB values were reduced by a factor of 1 after explosion, indicating wider tuning. 2. The degree of broadening of the CAP tuning curves seemed to increase as the hair cell loss increased. 3. After explosion, the tip of the tuning curve shifted to frequencies significantly higher or lower than that of the signal, it might be related to the location of hair cell loss in the cochlea. 4. In animals for which damage was restricted to only three rows of outer hair cells, changes of the CAP tuning curves were observed. It provides further evidence that the tuning properties of cochlear nerve fibers are dependent upon the integrity of the outer hair cells even though the great majority of fibers innervate inner hair cells only.

  7. Microparticles generated by decompression stress cause central nervous system injury manifested as neurohypophysial terminal action potential broadening.

    Science.gov (United States)

    Yang, Ming; Kosterin, Paul; Salzberg, Brian M; Milovanova, Tatyana N; Bhopale, Veena M; Thom, Stephen R

    2013-11-01

    The study goal was to use membrane voltage changes during neurohypophysial action potential (AP) propagation as an index of nerve function to evaluate the role that circulating microparticles (MPs) play in causing central nervous system injury in response to decompression stress in a murine model. Mice studied 1 h following decompression from 790 kPa air pressure for 2 h exhibit a 45% broadening of the neurohypophysial AP. Broadening did not occur if mice were injected with the MP lytic agent polyethylene glycol telomere B immediately after decompression, were rendered thrombocytopenic, or were treated with an inhibitor of nitric oxide synthase-2 (iNOS) prior to decompression, or in knockout (KO) mice lacking myeloperoxidase or iNOS. If MPs were harvested from control (no decompression) mice and injected into naive mice, no AP broadening occurred, but AP broadening was observed with injections of equal numbers of MPs from either wild-type or iNOS KO mice subjected to decompression stress. Although not required for AP broadening, MPs from decompressed mice, but not control mice, exhibit NADPH oxidase activation. We conclude that inherent differences in MPs from decompressed mice, rather than elevated MPs numbers, mediate neurological injury and that a component of the perivascular response to MPs involves iNOS. Additional study is needed to determine the mechanism of AP broadening and also mechanisms for MP generation associated with exposure to elevated gas pressure.

  8. Gastrointestinal hormone actions in the central regulation of energy metabolism: potential sensory roles for the circumventricular organs.

    Science.gov (United States)

    Hoyda, T D; Smith, P M; Ferguson, A V

    2009-04-01

    A variety of circulating signals provide essential information to the central nervous system (CNS) regarding nutritional status. The gastrointestinal system produces many such molecules that are now known to have profound effects on feeding behavior and the control of metabolism as a consequence of their ability to regulate the neural circuitry involved in metabolic homeostasis. Although many of these substances have been suggested to directly access such brain centers, their lipophobic characteristics suggest that alternative mechanisms should be considered. In this paper, we consider one such alternative, namely, that a specialized group of CNS structures collectively known as the sensory circumventricular organs (CVOs), which are not protected by the normal blood-brain barrier, may play important roles in such blood to brain communications. Specifically, we review a developing literature that shows receptors for, and functional actions of, gastrointestinal hormones such as amylin, cholecystokinin, ghrelin and peptide YY in the area postrema and subfornical organ. Collectively, these observations suggest potentially significant roles for the sensory CVOs in the regulation of energy balance.

  9. DCT domain feature extraction scheme based on motor unit action potential of EMG signal for neuromuscular disease classification.

    Science.gov (United States)

    Doulah, Abul Barkat Mollah Sayeed Ud; Fattah, Shaikh Anowarul; Zhu, Wei-Ping; Ahmad, M Omair

    2014-01-01

    A feature extraction scheme based on discrete cosine transform (DCT) of electromyography (EMG) signals is proposed for the classification of normal event and a neuromuscular disease, namely the amyotrophic lateral sclerosis. Instead of employing DCT directly on EMG data, it is employed on the motor unit action potentials (MUAPs) extracted from the EMG signal via a template matching-based decomposition technique. Unlike conventional MUAP-based methods, only one MUAP with maximum dynamic range is selected for DCT-based feature extraction. Magnitude and frequency values of a few high-energy DCT coefficients corresponding to the selected MUAP are used as the desired feature which not only reduces computational burden, but also offers better feature quality with high within-class compactness and between-class separation. For the purpose of classification, the K-nearest neighbourhood classifier is employed. Extensive analysis is performed on clinical EMG database and it is found that the proposed method provides a very satisfactory performance in terms of specificity, sensitivity and overall classification accuracy.

  10. Ca2+ imaging of mouse neocortical interneurone dendrites: Ia-type K+ channels control action potential backpropagation

    Science.gov (United States)

    Goldberg, Jesse H; Tamas, Gabor; Yuste, Rafael

    2003-01-01

    GABAergic interneurones are essential in cortical processing, yet the functional properties of their dendrites are still poorly understood. In this first study, we combined two-photon calcium imaging with whole-cell recording and anatomical reconstructions to examine the calcium dynamics during action potential (AP) backpropagation in three types of V1 supragranular interneurones: parvalbumin-positive fast spikers (FS), calretinin-positive irregular spikers (IS), and adapting cells (AD). Somatically generated APs actively backpropagated into the dendritic tree and evoked instantaneous calcium accumulations. Although voltage-gated calcium channels were expressed throughout the dendritic arbor, calcium signals during backpropagation of both single APs and AP trains were restricted to proximal dendrites. This spatial control of AP backpropagation was mediated by Ia-type potassium currents and could be mitigated by by previous synaptic activity. Further, we observed supralinear summation of calcium signals in synaptically activated dendritic compartments. Together, these findings indicate that in interneurons, dendritic AP propagation is synaptically regulated. We propose that interneurones have a perisomatic and a distal dendritic functional compartment, with different integrative functions. PMID:12844506

  11. An experimental study of postoperative monitoring for innervated free muscle graft by the compound muscle action potential in rabbits.

    Science.gov (United States)

    Tan, Soo-Heong; Shigetomi, Mitsunori; Doi, Kazuteru

    2012-07-01

    This experiment establishes the principles of using the compound muscle action potential (CMAP) as a possible postoperative monitor for free muscle grafts. Twenty rabbits were divided into two groups of ten each to investigate the effects of ischemia on CMAP of the muscles. Rectus femoris model was used and contralateral muscle was used as control. In all muscles total normothermic ischemia of 1.5 hours to mimic the time needed for transfer and inset of the flap was followed by occlusion of the artery in one group and vein in another group after 3 hours. During this ischemia of 1 hour, the CMAP amplitudes decreased and the latencies were prolonged. Latency prolongation was detected within 10 minutes of total, arterial, or venous ischemia. During the revascularization, both amplitude and latency improved, but not to the original values at the start. The results show that CMAP monitoring can provide easily detectable, objective indication of vascular compromise to a muscle graft within as early as 10 minutes of total, arterial, and venous ischemia. Changes in latency are more constant and predictable compared with amplitude changes. This method can provide continuous monitoring and can be used in buried muscle grafts.

  12. Establishment of alternative potency test for botulinum toxin type A using compound muscle action potential (CMAP) in rats.

    Science.gov (United States)

    Torii, Yasushi; Goto, Yoshitaka; Nakahira, Shinji; Ginnaga, Akihiro

    2014-11-01

    The biological activity of botulinum toxin type A has been evaluated using the mouse intraperitoneal (ip) LD50 test. This method requires a large number of mice to precisely determine toxin activity, and, as such, poses problems with regard to animal welfare. We previously developed a compound muscle action potential (CMAP) assay using rats as an alternative method to the mouse ip LD50 test. In this study, to evaluate this quantitative method of measuring toxin activity using CMAP, we assessed the parameters necessary for quantitative tests according to ICH Q2 (R1). This assay could be used to evaluate the activity of the toxin, even when inactive toxin was mixed with the sample. To reduce the number of animals needed, this assay was set to measure two samples per animal. Linearity was detected over a range of 0.1-12.8 U/mL, and the measurement range was set at 0.4-6.4 U/mL. The results for accuracy and precision showed low variability. The body weight was selected as a variable factor, but it showed no effect on the CMAP amplitude. In this study, potency tests using the rat CMAP assay of botulinum toxin type A demonstrated that it met the criteria for a quantitative analysis method.

  13. Effects of Ginkgolide B on action potential and calcium,potassium current in guinea pig ventricular myocytes

    Institute of Scientific and Technical Information of China (English)

    Xiao-yan QI; Zhi-xiong ZHANG; You-qiu XU

    2004-01-01

    AIM: To investigate the effect of Ginkgolide B (GB) on action potential (AP), delayed rectifier potassium current (IK), and L-type calcium current (ICa-L) in guinea pig ventricular myocytes. METHODS: Single ventricular myocytes were isolated by an enzymatic dissociation method. AP, IK, ICa-L were recorded by whole-cell patch-clamp technique in either current or voltage clamp mode. RESULTS: GB shortened APD in a concentration-dependent manner. GB 0.1, 1, and 10 μmol/L shortened APD50 by 7.9 % (n=5, P>0.05), 18.4 % (n=5, P<0.01), and 28.9 % (n=6, P<0.01), respectively; APD90 by 12.4 % (n=5, P>0.05), 17.6 % (n=5, P<0.01), 26.4 % (n=5, P<0.01),respectively. GB increased IK in a concentration-dependent manner. GB 0.1, 1, and l0 μmol/L increased IK by 20.1% (n=6, P<0.05), 43.1% (n=6, P<0.01), 55.6 % (n=6, P<0.05); increased IKtail by 10.7 % (n=6, P<0.05),25.1% (n=6, P<0.05), and 37.7 % (n=6, P<0.05), respectively at testing potential of +50 mV and shift the I-V curve of Ik upward. But GB had no significant effect on ICa-L at above concentrations. CONCLUSION: GB significantly shortened APD in a concentration-dependent manner which mainly due to increase of IK.

  14. Blockade of sensory neuron action potentials by a static magnetic field in the 10 mT range

    Energy Technology Data Exchange (ETDEWEB)

    McLean, M.J.; Holcomb, R.R.; Wamil, A.W.; Pickett, J.D. [Vanderbilt Univ. Medical Center, Nashville, TN (United States); Cavopol, A.V. [Northeast Missouri State Univ., Kirksville, MO (United States). Science Div.

    1995-05-01

    To characterize the inhibitory effect of a static magnetic field, action potentials (AP) were elicited by intracellular application of 1 ms depolarizing current pulses of constant amplitude to the somata of adult mouse dorsal root ganglion neurons in monolayer dissociated cell culture. During the control period, < 5% of stimuli failed to elicit AP. During exposure to an {approximately}11 mT static magnetic field at the cell position produced by an array of four permanent center-charged neodymium magnets of alternating polarity (MAG-4A), 66% of stimuli failed to elicit AP. The number of failures was maximal after about 200--250 s in the field and returned gradually to baseline over 400--600 s. A direct or indirect effect on the conformation of AP generating sodium channels could account for these results because (1) failure was preceded often by reduction of maximal rate of rise, an indirect measure of sodium current; (2) recovery was significantly prolonged in more than one-half of neurons that were not stimulated during exposure to the MAG-4A field; and (3) resting membrane potential, input resistance, and chronaxie were unaffected by the field. The effect was diminished or prevented by moving the MAG-4A array along the X or Z axis away from the neuron under study and by increasing the distance between magnets in the XY plane. Reduction of AP firing during exposure to the {approximately}0.1 mT field produced by a MAG-4A array of micromagnets was about the same as that produced by a MAG-4A array of the large magnets above. The {approximately}28 mT field produced at cell position by two magnets of alternating polarity and the {approximately}88 mT field produced by a single magnet had no significant effect on AP firing. These findings suggest that field strength alone cannot account for AP blockade.

  15. Inhibition of the compound action potentials of frog sciatic nerves by aroma oil compounds having various chemical structures.

    Science.gov (United States)

    Ohtsubo, Sena; Fujita, Tsugumi; Matsushita, Akitomo; Kumamoto, Eiichi

    2015-03-01

    Plant-derived chemicals including aroma oil compounds have an ability to inhibit nerve conduction and modulate transient receptor potential (TRP) channels. Although applying aroma oils to the skin produces a local anesthetic effect, this has not been yet examined throughly. The aim of the present study was to know how nerve conduction inhibitions by aroma oil compounds are related to their chemical structures and whether these activities are mediated by TRP activation. Compound action potentials (CAPs) were recorded from the frog sciatic nerve by using the air-gap method. Citral (aldehyde), which activates various types of TRP channels, attenuated the peak amplitude of CAP with the half-maximal inhibitory concentration (IC50) value of 0.46 mmol/L. Another aldehyde (citronellal), alcohol (citronellol, geraniol, (±)-linalool, (-)-linalool, (+)-borneol, (-)-borneol, α-terpineol), ester (geranyl acetate, linalyl acetate, bornyl acetate), and oxide (rose oxide) compounds also reduced CAP peak amplitudes (IC50: 0.50, 0.35, 0.53, 1.7, 2.0, 1.5, 2.3, 2.7, 0.51, 0.71, 0.44, and 2.6 mmol/L, respectively). On the other hand, the amplitudes were reduced by a small extent by hydrocarbons (myrcene and p-cymene) and ketone (camphor) at high concentrations (2-5 mmol/L). The activities of citral and other TRP agonists ((+)-borneol and camphor) were resistant to TRP antagonist ruthenium red. An efficacy sequence for the CAP inhibitions was generally aldehydes ≥ esters ≥ alcohols > oxides > hydrocarbons. The CAP inhibition by the aroma oil compound was not related to its octanol-water partition coefficient. It is suggested that aroma oil compounds inhibit nerve conduction in a manner specific to their chemical structures without TRP activation.

  16. An exploratory investigation of various modes of action and potential adverse outcomes of fluoxetine in marine mussels

    Energy Technology Data Exchange (ETDEWEB)

    Franzellitti, Silvia, E-mail: silvia.franzellitti@unibo.it [University of Bologna, Interdepartment Centre for Environmental Science Research, via S. Alberto 163, 48123 Ravenna (Italy); University of Bologna, Department of Biological, Geological, and Environmental Sciences, via Selmi 3, 40100 Bologna (Italy); Buratti, Sara; Capolupo, Marco [University of Bologna, Interdepartment Centre for Environmental Science Research, via S. Alberto 163, 48123 Ravenna (Italy); Du, Bowen; Haddad, Samuel P. [Department of Environmental Science, Baylor University, Waco, TX 76798 (United States); Chambliss, C. Kevin [Department of Chemistry and Biochemistry, Baylor University, Waco, TX 76798 (United States); Brooks, Bryan W. [Department of Environmental Science, Baylor University, Waco, TX 76798 (United States); Fabbri, Elena [University of Bologna, Interdepartment Centre for Environmental Science Research, via S. Alberto 163, 48123 Ravenna (Italy); University of Bologna, Department of Biological, Geological, and Environmental Sciences, via Selmi 3, 40100 Bologna (Italy)

    2014-06-01

    Highlights: • Mode of action (MOA) related endpoints and biomarkers of toxicity were assessed in mussels exposed to fluoxetine (FX). • Significant FX bioaccumulation was observed in tissues of mussels exposed to 30 and 300 ng/L FX. • Alterations of cAMP-related cell signaling were observed in exposed mussels as part of the MOA of FX. • FX reduced the health status of mussels inducing lysosomal effects in digestive gland and antioxidant responses in gills. • The importance of considering additional MOAs and adverse outcome pathways for FX impacts on mussels is highlighted. - Abstract: The present study investigated possible adverse outcome pathways (AOPs) of the antidepressant fluoxetine (FX) in the marine mussel Mytilus galloprovincialis. An evaluation of molecular endpoints involved in modes of action (MOAs) of FX and biomarkers for sub-lethal toxicity were explored in mussels after a 7-day administration of nominal FX concentrations encompassing a range of environmentally relevant values (0.03–300 ng/L). FX bioaccumulated in mussel tissues after treatment with 30 and 300 ng/L FX, resulting in bioconcentration factor (BCF) values ranging from 200 to 800, which were higher than expected based solely on hydrophobic partitioning models. Because FX acts as a selective serotonin (5-HT) re-uptake inhibitor increasing serotonergic neurotransmission at mammalian synapses, cell signaling alterations triggered by 5-HT receptor occupations were assessed. cAMP levels and PKA activities were decreased in digestive gland and mantle/gonads of FX-treated mussels, consistent with an increased occupation of 5-HT1 receptors negatively coupled to the cAMP/PKA pathway. mRNA levels of a ABCB gene encoding the P-glycoprotein were also significantly down-regulated. This membrane transporter acts in detoxification towards xenobiotics and in altering pharmacokinetics of antidepressants; moreover, it is under a cAMP/PKA transcriptional regulation in mussels. Potential stress

  17. pH Dependent Antimicrobial Peptides and Proteins, Their Mechanisms of Action and Potential as Therapeutic Agents

    Directory of Open Access Journals (Sweden)

    Erum Malik

    2016-11-01

    Full Text Available Antimicrobial peptides (AMPs are potent antibiotics of the innate immune system that have been extensively investigated as a potential solution to the global problem of infectious diseases caused by pathogenic microbes. A group of AMPs that are increasingly being reported are those that utilise pH dependent antimicrobial mechanisms, and here we review research into this area. This review shows that these antimicrobial molecules are produced by a diverse spectrum of creatures, including vertebrates and invertebrates, and are primarily cationic, although a number of anionic examples are known. Some of these molecules exhibit high pH optima for their antimicrobial activity but in most cases, these AMPs show activity against microbes that present low pH optima, which reflects the acidic pH generally found at their sites of action, particularly the skin. The modes of action used by these molecules are based on a number of major structure/function relationships, which include metal ion binding, changes to net charge and conformational plasticity, and primarily involve the protonation of histidine, aspartic acid and glutamic acid residues at low pH. The pH dependent activity of pore forming antimicrobial proteins involves mechanisms that generally differ fundamentally to those used by pH dependent AMPs, which can be described by the carpet, toroidal pore and barrel-stave pore models of membrane interaction. A number of pH dependent AMPs and antimicrobial proteins have been developed for medical purposes and have successfully completed clinical trials, including kappacins, LL-37, histatins and lactoferrin, along with a number of their derivatives. Major examples of the therapeutic application of these antimicrobial molecules include wound healing as well as the treatment of multiple cancers and infections due to viruses, bacteria and fungi. In general, these applications involve topical administration, such as the use of mouth washes, cream formulations

  18. pH Dependent Antimicrobial Peptides and Proteins, Their Mechanisms of Action and Potential as Therapeutic Agents

    Science.gov (United States)

    Malik, Erum; Dennison, Sarah R.; Harris, Frederick; Phoenix, David A.

    2016-01-01

    Antimicrobial peptides (AMPs) are potent antibiotics of the innate immune system that have been extensively investigated as a potential solution to the global problem of infectious diseases caused by pathogenic microbes. A group of AMPs that are increasingly being reported are those that utilise pH dependent antimicrobial mechanisms, and here we review research into this area. This review shows that these antimicrobial molecules are produced by a diverse spectrum of creatures, including vertebrates and invertebrates, and are primarily cationic, although a number of anionic examples are known. Some of these molecules exhibit high pH optima for their antimicrobial activity but in most cases, these AMPs show activity against microbes that present low pH optima, which reflects the acidic pH generally found at their sites of action, particularly the skin. The modes of action used by these molecules are based on a number of major structure/function relationships, which include metal ion binding, changes to net charge and conformational plasticity, and primarily involve the protonation of histidine, aspartic acid and glutamic acid residues at low pH. The pH dependent activity of pore forming antimicrobial proteins involves mechanisms that generally differ fundamentally to those used by pH dependent AMPs, which can be described by the carpet, toroidal pore and barrel-stave pore models of membrane interaction. A number of pH dependent AMPs and antimicrobial proteins have been developed for medical purposes and have successfully completed clinical trials, including kappacins, LL-37, histatins and lactoferrin, along with a number of their derivatives. Major examples of the therapeutic application of these antimicrobial molecules include wound healing as well as the treatment of multiple cancers and infections due to viruses, bacteria and fungi. In general, these applications involve topical administration, such as the use of mouth washes, cream formulations and hydrogel

  19. Heeding a Call to Action for U.S. Coral Reefs: the Untapped Potential of the Clean Water Act

    Science.gov (United States)

    A recently published call to action by Dodge et al. (2008) identifies nine actions needed to protect coral reefs. The authors identify several management goals that cannot be accomplished with MPAs alone, the traditional approach to coral reef protection. For U.S. waters, the Cle...

  20. Germany Initiates the Action Plan for Individualized Medicine%德国实施个体化医学研究行动计划

    Institute of Scientific and Technical Information of China (English)

    赵清华

    2014-01-01

    2013 年 4 月,德国联邦教研部(BMBF)启动了“个体化医学行动计划”。依据该计划,2013—2016年,BMBF 将投入3.6亿欧元,支持从个体化医学基础研究、临床前研究、临床研究到健康经济整个创新链的研发活动,促进企业和高校、科研机构建立新的伙伴关系。BMBF个体化医学行动计划重点研究方向是:系统医学研究,验证生物标志物,优化试验设计,加深产学研联盟,参与国际大协作,研究伦理、法律和社会问题。德国支持个体化医学研究,前瞻性地研讨潜在的社会伦理问题,不断完善相关的法律规章等做法,值得我们深入研究、关注和借鉴。%The German Federal Ministry of Education and Research (BMBF) has initiated the Action Plan for Individualized Medicine in April, 2013. According to this plan, BMBF invests about €360 million during 2013-2016 to support personalized medicine across the whole research and innovation chain ranging from basic research, preclinical research, and clinical research up to health economy through promoting partnership and networking among enterprises, universities and research institutions. The plan emphases on systematic medicine research, biological makers verification, experimental design and optimization, enhancing industry-university-research alliance, participating international cooperation and study on the ethical, legal and social issues. The paper reviews the promotion activities of BMBF in the research ifeld of personalized medicine, and outlines the objectives, focal points and possible international cooperation of the new action plan for individualized medicine.

  1. Neonatal tactile stimulation decreases depression-like and anxiety-like behaviors and potentiates sertraline action in young rats.

    Science.gov (United States)

    Freitas, Daniele; Antoniazzi, Caren T D; Segat, Hecson J; Metz, Vinícia Garzella; Vey, Luciana Taschetto; Barcelos, Raquel C S; Duarte, Thiago; Duarte, Marta M M F; Burger, Marilise Escobar

    2015-12-01

    It is well known that events which occur in early life exert a significant influence on brain development, what can be reflected throughout adulthood. This study was carried out in order to assess the influence of neonatal tactile stimulation (TS) on behavioral and morphological responses related to depression-like and anxiety-like behaviors, assessed following the administration of sertraline (SERT), a selective serotonin re-uptake inhibitor (SSRI). Male pups were submitted to daily TS, from postnatal day 8 (PND8) to postnatal day 14 (PND14), for 10 min every day. On PND50, adult animals were submitted to forced swimming training (15 min). On PND51, half of each experimental group (UH and TS) received a single sub-therapeutic dose of sertraline (SER, 0.3mg/kg body weight, i.p.) or its vehicle (C, control group). Thirty minutes after injection, depression-like behaviors were quantified in forced swimming test (FST, for 5 min). On the following day, anxiety-like behaviors were assessed in elevated plus maze (EPM), followed by biochemical assessments. TS per se increased swimming time, decreasing immobility time in FST. Besides, TS per se was able to increase frequency of head dipping and time spent in the open arms of EPM, resulting in decreased anxiety index. In addition, groups exposed to TS showed decreased plasma levels of corticosterone per se. Interestingly, while TS exposure significantly potentiated the antidepressant activity of a subtherapeutic dose of SERT, this drug was able to exacerbate TS-induced anxiolytic activity, as observed in FST and EPM, respectively. Decreased plasma levels of both corticosterone and cortisol in animals exposed to TS and treated with SERT are able to confirm the interesting interaction between this neonatal handling and the antidepressant drug. From our results, we conclude that neonatal TS is able to exert beneficial influence on the ability to cope with stressful situations in adulthood, preventing depression and favorably

  2. Elevated heart rate triggers action potential alternans and sudden death. translational study of a homozygous KCNH2 mutation.

    Directory of Open Access Journals (Sweden)

    Ulrich Schweigmann

    Full Text Available BACKGROUND: Long QT syndrome (LQTS leads to arrhythmic events and increased risk for sudden cardiac death (SCD. Homozygous KCNH2 mutations underlying LQTS-2 have previously been termed "human HERG knockout" and typically express severe phenotypes. We studied genotype-phenotype correlations of an LQTS type 2 mutation identified in the homozygous index patient from a consanguineous Turkish family after his brother died suddenly during febrile illness. METHODS AND RESULTS: Clinical work-up, DNA sequencing, mutagenesis, cell culture, patch-clamp, in silico mathematical modelling, protein biochemistry, confocal microscopy were performed. Genetic analysis revealed a homozygous C-terminal KCNH2 mutation (p.R835Q in the index patient (QTc ∼506 ms with notched T waves. Parents were I° cousins - both heterozygous for the mutation and clinically unremarkable (QTc ∼447 ms, father and ∼396 ms, mother. Heterologous expression of KCNH2-R835Q showed mildly reduced current amplitudes. Biophysical properties of ionic currents were also only nominally changed with slight acceleration of deactivation and more negative V50 in R835Q-currents. Protein biochemistry and confocal microscopy revealed similar expression patterns and trafficking of WT and R835Q, even at elevated temperature. In silico analysis demonstrated mildly prolonged ventricular action potential duration (APD compared to WT at a cycle length of 1000 ms. At a cycle length of 350 ms M-cell APD remained stable in WT, but displayed APD alternans in R835Q. CONCLUSION: Kv11.1 channels affected by the C-terminal R835Q mutation display mildly modified biophysical properties, but leads to M-cell APD alternans with elevated heart rate and could precipitate SCD under specific clinical circumstances associated with high heart rates.

  3. State-of-the-art automated patch clamp devices: Heat activation, action potentials and high throughput in ion channel screening

    Directory of Open Access Journals (Sweden)

    Sonja eStoelzle

    2011-11-01

    Full Text Available Ion channels are essential in a wide range of cellular functions and their malfunction underlies many disease states making them important targets in drug discovery. Diverse automated patch clamp systems with high-throughput capabilities are available for drug screening, but there are limitations in the application range. For example, solution exchange time, temperature control and the availability of the current clamp mode can be limiting factors. However, further development of existing devices and introduction of new systems widen the range of possible experiments and increase throughput. Here we introduce new features and platforms that meet the needs of drug discovery researchers and basic researchers alike.The Patchliner is an automated patch clamp system capable of recording up to 8 cells simultaneously with high success rates. Novel features such as temperature control and recordings in the current clamp mode are described here. Standard cell lines and excitable cells such as stem cell-derived cardiomyocytes have been used in the voltage clamp and current clamp modes with the view to finding new drug candidates and safety testing methods in a more physiologically relevant environment. The SyncroPatch 96, is a screening platform capable of recording from 96 cells in parallel and offers a throughput of 5000 data points per day. Full dose response curves can be acquired from individual cells reducing the cost per data point. The system is an ideal tool for secondary screening efforts and for safety testing on ligand- and voltage-gated ion channels.The Patchliner and SyncroPatch 96 are ideal platforms for drug discovery, ion channel research and safety testing, combining long awaited features such as parallel action potential recordings and temperature control with extensively increased throughput.

  4. Kv3 potassium conductance is necessary and kinetically optimized for high-frequency action potential generation in hippocampal interneurons.

    Science.gov (United States)

    Lien, Cheng-Chang; Jonas, Peter

    2003-03-15

    Kv3 channels are thought to be essential for the fast-spiking (FS) phenotype in GABAergic interneurons, but how these channels confer the ability to generate action potentials (APs) at high frequency is unknown. To address this question, we developed a fast dynamic-clamp system (approximately 50 kHz) that allowed us to add a Kv3 model conductance to CA1 oriens alveus (OA) interneurons in hippocampal slices. Selective pharmacological block of Kv3 channels by 0.3 mm 4-aminopyridine or 1 mm tetraethylammonium ions led to a marked broadening of APs during trains of short stimuli and a reduction in AP frequency during 1 sec stimuli. The addition of artificial Kv3 conductance restored the original AP pattern. Subtraction of Kv3 conductance by dynamic clamp mimicked the effects of the blockers. Application of artificial Kv3 conductance also led to FS in OA interneurons after complete K+ channel block and even induced FS in hippocampal pyramidal neurons in the absence of blockers. Adding artificial Kv3 conductance with altered deactivation kinetics revealed a nonmonotonic relationship between mean AP frequency and deactivation rate, with a maximum slightly above the original value. Insertion of artificial Kv3 conductance with either lowered activation threshold or inactivation also led to a reduction in the mean AP frequency. However, the mechanisms were distinct. Shifting the activation threshold induced adaptation, whereas adding inactivation caused frequency-dependent AP broadening. In conclusion, Kv3 channels are necessary for the FS phenotype of OA interneurons, and several of their gating properties appear to be optimized for high-frequency repetitive activity.

  5. Action potential modulation in CA1 pyramidal neuron axons facilitates OLM interneuron activation in recurrent inhibitory microcircuits of rat hippocampus.

    Directory of Open Access Journals (Sweden)

    Sooyun Kim

    Full Text Available Oriens-lacunosum moleculare (O-LM interneurons in the CA1 region of the hippocampus play a key role in feedback inhibition and in the control of network activity. However, how these cells are efficiently activated in the network remains unclear. To address this question, I performed recordings from CA1 pyramidal neuron axons, the presynaptic fibers that provide feedback innervation of these interneurons. Two forms of axonal action potential (AP modulation were identified. First, repetitive stimulation resulted in activity-dependent AP broadening. Broadening showed fast onset, with marked changes in AP shape following a single AP. Second, tonic depolarization in CA1 pyramidal neuron somata induced AP broadening in the axon, and depolarization-induced broadening summated with activity-dependent broadening. Outside-out patch recordings from CA1 pyramidal neuron axons revealed a high density of α-dendrotoxin (α-DTX-sensitive, inactivating K+ channels, suggesting that K+ channel inactivation mechanistically contributes to AP broadening. To examine the functional consequences of axonal AP modulation for synaptic transmission, I performed paired recordings between synaptically connected CA1 pyramidal neurons and O-LM interneurons. CA1 pyramidal neuron-O-LM interneuron excitatory postsynaptic currents (EPSCs showed facilitation during both repetitive stimulation and tonic depolarization of the presynaptic neuron. Both effects were mimicked and occluded by α-DTX, suggesting that they were mediated by K+ channel inactivation. Therefore, axonal AP modulation can greatly facilitate the activation of O-LM interneurons. In conclusion, modulation of AP shape in CA1 pyramidal neuron axons substantially enhances the efficacy of principal neuron-interneuron synapses, promoting the activation of O-LM interneurons in recurrent inhibitory microcircuits.

  6. Action potential modulation in CA1 pyramidal neuron axons facilitates OLM interneuron activation in recurrent inhibitory microcircuits of rat hippocampus.

    Science.gov (United States)

    Kim, Sooyun

    2014-01-01

    Oriens-lacunosum moleculare (O-LM) interneurons in the CA1 region of the hippocampus play a key role in feedback inhibition and in the control of network activity. However, how these cells are efficiently activated in the network remains unclear. To address this question, I performed recordings from CA1 pyramidal neuron axons, the presynaptic fibers that provide feedback innervation of these interneurons. Two forms of axonal action potential (AP) modulation were identified. First, repetitive stimulation resulted in activity-dependent AP broadening. Broadening showed fast onset, with marked changes in AP shape following a single AP. Second, tonic depolarization in CA1 pyramidal neuron somata induced AP broadening in the axon, and depolarization-induced broadening summated with activity-dependent broadening. Outside-out patch recordings from CA1 pyramidal neuron axons revealed a high density of α-dendrotoxin (α-DTX)-sensitive, inactivating K+ channels, suggesting that K+ channel inactivation mechanistically contributes to AP broadening. To examine the functional consequences of axonal AP modulation for synaptic transmission, I performed paired recordings between synaptically connected CA1 pyramidal neurons and O-LM interneurons. CA1 pyramidal neuron-O-LM interneuron excitatory postsynaptic currents (EPSCs) showed facilitation during both repetitive stimulation and tonic depolarization of the presynaptic neuron. Both effects were mimicked and occluded by α-DTX, suggesting that they were mediated by K+ channel inactivation. Therefore, axonal AP modulation can greatly facilitate the activation of O-LM interneurons. In conclusion, modulation of AP shape in CA1 pyramidal neuron axons substantially enhances the efficacy of principal neuron-interneuron synapses, promoting the activation of O-LM interneurons in recurrent inhibitory microcircuits.

  7. Archaerhodopsin voltage imaging: synaptic calcium and BK channels stabilize action potential repolarization at the Drosophila neuromuscular junction.

    Science.gov (United States)

    Ford, Kevin J; Davis, Graeme W

    2014-10-29

    The strength and dynamics of synaptic transmission are determined, in part, by the presynaptic action potential (AP) waveform at the nerve terminal. The ion channels that shape the synaptic AP waveform remain essentially unknown for all but a few large synapses amenable to electrophysiological interrogation. The Drosophila neuromuscular junction (NMJ) is a powerful system for studying synaptic biology, but it is not amenable to presynaptic electrophysiology. Here, we demonstrate that Archaerhodopsin can be used to quantitatively image AP waveforms at the Drosophila NMJ without disrupting baseline synaptic transmission or neuromuscular development. It is established that Shaker mutations cause a dramatic increase in neurotransmitter release, suggesting that Shaker is predominantly responsible for AP repolarization. Here we demonstrate that this effect is caused by a concomitant loss of both Shaker and slowpoke (slo) channel activity because of the low extracellular calcium concentrations (0.2-0.5 mM) used typically to assess synaptic transmission in Shaker. In contrast, at physiological extracellular calcium (1.5 mM), the role of Shaker during AP repolarization is limited. We then provide evidence that calcium influx through synaptic CaV2.1 channels and subsequent recruitment of Slo channel activity is important, in concert with Shaker, to ensure proper AP repolarization. Finally, we show that Slo assumes a dominant repolarizing role during repetitive nerve stimulation. During repetitive stimulation, Slo effectively compensates for Shaker channel inactivation, stabilizing AP repolarization and limiting neurotransmitter release. Thus, we have defined an essential role for Slo channels during synaptic AP repolarization and have revised our understanding of Shaker channels at this model synapse.

  8. Beta-adrenergic stimulation reverses the I Kr-I Ks dominant pattern during cardiac action potential.

    Science.gov (United States)

    Banyasz, Tamas; Jian, Zhong; Horvath, Balazs; Khabbaz, Shaden; Izu, Leighton T; Chen-Izu, Ye

    2014-11-01

    β-Adrenergic stimulation differentially modulates different K(+) channels and thus fine-tunes cardiac action potential (AP) repolarization. However, it remains unclear how the proportion of I Ks, I Kr, and I K1 currents in the same cell would be altered by β-adrenergic stimulation, which would change the relative contribution of individual K(+) current to the total repolarization reserve. In this study, we used an innovative AP-clamp sequential dissection technique to directly record the dynamic I Ks, I Kr, and I K1 currents during the AP in guinea pig ventricular myocytes under physiologically relevant conditions. Our data provide quantitative measures of the magnitude and time course of I Ks, I Kr, and I K1 currents in the same cell under its own steady-state AP, in a physiological milieu, and with preserved Ca(2+) homeostasis. We found that isoproterenol treatment significantly enhanced I Ks, moderately increased I K1, but slightly decreased I Kr in a dose-dependent manner. The dominance pattern of the K(+) currents was I Kr > I K1 > I Ks at the control condition, but reversed to I Kr < I K1 < I Ks following β-adrenergic stimulation. We systematically determined the changes in the relative contribution of I Ks, I Kr, and I K1 to cardiac repolarization during AP at different adrenergic states. In conclusion, the β-adrenergic stimulation fine-tunes the cardiac AP morphology by shifting the power of different K(+) currents in a dose-dependent manner. This knowledge is important for designing antiarrhythmic drug strategies to treat hearts exposed to various sympathetic tones.

  9. Evaluation of nystatin containing chitosan hydrogels as potential dual action bio-active restorative materials: in vitro approach.

    Science.gov (United States)

    Perchyonok, V Tamara; Reher, Vanessa; Zhang, Shengmiao; Basson, Nicki; Grobler, Sias

    2014-11-28

    Healing is a specific biological process related to the general phenomenon of growth and tissue regeneration and is a process generally affected by several systemic conditions or as detrimental side-effects of chemotherapy- and radiotherapy-induced inflammation of the oral mucosa. The objectives of this study is to evaluate the novel chitosan based functional drug delivery systems, which can be successfully incorporated into "dual action bioactive restorative materials", capable of inducing in vitro improved wound healing prototype and containing an antibiotic, such as nystatin, krill oil as an antioxidant and hydroxyapatite as a molecular bone scaffold, which is naturally present in bone and is reported to be successfully used in promoting bone integration when implanted as well as promoting healing. The hydrogels were prepared using a protocol as previously reported by us. The physico-chemical features, including surface morphology (SEM), release behaviors, stability of the therapeutic agent-antioxidant-chitosan, were measured and compared to the earlier reported chitosan-antioxidant containing hydrogels. Structural investigations of the reactive surface of the hydrogel are reported. Release of nystatin was investigated for all newly prepared hydrogels. Bio-adhesive studies were performed in order to assess the suitability of these designer materials. Free radical defense capacity of the biomaterials was evaluated using established in vitro model. The bio-adhesive capacity of the materials in the in vitro system was tested and quantified. It was found that the favorable synergistic effect of free radical built-in defense mechanism of the new functional materials increased sustainable bio-adhesion and therefore acted as a functional multi-dimensional restorative material with potential application in wound healing in vitro.

  10. Evaluation of Nystatin Containing Chitosan Hydrogels as Potential Dual Action Bio-Active Restorative Materials: in Vitro Approach

    Directory of Open Access Journals (Sweden)

    V. Tamara Perchyonok

    2014-11-01

    Full Text Available Healing is a specific biological process related to the general phenomenon of growth and tissue regeneration and is a process generally affected by several systemic conditions or as detrimental side-effects of chemotherapy- and radiotherapy-induced inflammation of the oral mucosa. The objectives of this study is to evaluate the novel chitosan based functional drug delivery systems, which can be successfully incorporated into “dual action bioactive restorative materials”, capable of inducing in vitro improved wound healing prototype and containing an antibiotic, such as nystatin, krill oil as an antioxidant and hydroxyapatite as a molecular bone scaffold, which is naturally present in bone and is reported to be successfully used in promoting bone integration when implanted as well as promoting healing. The hydrogels were prepared using a protocol as previously reported by us. The physico-chemical features, including surface morphology (SEM, release behaviors, stability of the therapeutic agent-antioxidant-chitosan, were measured and compared to the earlier reported chitosan-antioxidant containing hydrogels. Structural investigations of the reactive surface of the hydrogel are reported. Release of nystatin was investigated for all newly prepared hydrogels. Bio-adhesive studies were performed in order to assess the suitability of these designer materials. Free radical defense capacity of the biomaterials was evaluated using established in vitro model. The bio-adhesive capacity of the materials in the in vitro system was tested and quantified. It was found that the favorable synergistic effect of free radical built-in defense mechanism of the new functional materials increased sustainable bio-adhesion and therefore acted as a functional multi-dimensional restorative material with potential application in wound healing in vitro.

  11. Action potential-evoked calcium release is impaired in single skeletal muscle fibers from heart failure patients.

    Directory of Open Access Journals (Sweden)

    Marino DiFranco

    Full Text Available BACKGROUND: Exercise intolerance in chronic heart failure (HF has been attributed to abnormalities of the skeletal muscles. Muscle function depends on intact excitation-contraction coupling (ECC, but ECC studies in HF models have been inconclusive, due to deficiencies in the animal models and tools used to measure calcium (Ca2+ release, mandating investigations in skeletal muscle from HF patients. The purpose of this study was to test the hypothesis that Ca2+ release is significantly impaired in the skeletal muscle of HF patients in whom exercise capacity is severely diminished compared to age-matched healthy volunteers. METHODS AND FINDINGS: Using state-of-the-art electrophysiological and optical techniques in single muscle fibers from biopsies of the locomotive vastus lateralis muscle, we measured the action potential (AP-evoked Ca2+ release in 4 HF patients and 4 age-matched healthy controls. The mean peak Ca2+ release flux in fibers obtained from HF patients (10±1.2 µM/ms was markedly (2.6-fold and significantly (p<0.05 smaller than in fibers from healthy volunteers (28±3.3 µM/ms. This impairment in AP-evoked Ca2+ release was ubiquitous and was not explained by differences in the excitability mechanisms since single APs were indistinguishable between HF patients and healthy volunteers. CONCLUSIONS: These findings prove the feasibility of performing electrophysiological experiments in single fibers from human skeletal muscle, and offer a new approach for investigations of myopathies due to HF and other diseases. Importantly, we have demonstrated that one step in the ECC process, AP-evoked Ca2+ release, is impaired in single muscle fibers in HF patients.

  12. Topical capsaicin for pain management: therapeutic potential and mechanisms of action of the new high-concentration capsaicin 8% patch

    Science.gov (United States)

    Anand, P.; Bley, K.

    2011-01-01

    Summary Topical capsaicin formulations are used for pain management. Safety and modest efficacy of low-concentration capsaicin formulations, which require repeated daily self-administration, are supported by meta-analyses of numerous studies. A high-concentration capsaicin 8% patch (Qutenza™) was recently approved in the EU and USA. A single 60-min application in patients with neuropathic pain produced effective pain relief for up to 12 weeks. Advantages of the high-concentration capsaicin patch include longer duration of effect, patient compliance, and low risk for systemic effects or drug–drug interactions. The mechanism of action of topical capsaicin has been ascribed to depletion of substance P. However, experimental and clinical studies show that depletion of substance P from nociceptors is only a correlate of capsaicin treatment and has little, if any, causative role in pain relief. Rather, topical capsaicin acts in the skin to attenuate cutaneous hypersensitivity and reduce pain by a process best described as ‘defunctionalization’ of nociceptor fibres. Defunctionalization is due to a number of effects that include temporary loss of membrane potential, inability to transport neurotrophic factors leading to altered phenotype, and reversible retraction of epidermal and dermal nerve fibre terminals. Peripheral neuropathic hypersensitivity is mediated by diverse mechanisms, including altered expression of the capsaicin receptor TRPV1 or other key ion channels in affected or intact adjacent peripheral nociceptive nerve fibres, aberrant re-innervation, and collateral sprouting, all of which are defunctionalized by topical capsaicin. Evidence suggests that the utility of topical capsaicin may extend beyond painful peripheral neuropathies. PMID:21852280

  13. Oscillatory behaviour of ventricular action potential duration in heart failure patients at respiratory rate and low frequency

    Directory of Open Access Journals (Sweden)

    Ben eHanson

    2014-10-01

    Full Text Available Oscillations of arterial pressure occur spontaneously at a frequency of approx. 0.1Hz coupled with synchronous oscillations of sympathetic nerve activity (Mayer waves. This study investigated the extent to which corresponding oscillations may occur in ventricular action potential duration (APD.14 ambulatory (outpatient heart failure patients with biventricular pacing devices were studied while seated upright watching movie clips to maintain arousal. Activation recovery intervals (ARI as a measure of ventricular APD were obtained from unipolar electrograms recorded from the LV epicardial pacing lead during steady state RV pacing from the device. Arterial blood pressure was measured non-invasively (Finapress and respiration monitored. Oscillations were quantified using time frequency and coherence analysis.Oscillatory behaviour of ARI at the respiratory frequency was observed in all subjects. The magnitude of the ARI variation ranged from 2.2 ms to 6.9 ms (mean 5.0 ms. Coherence analysis showed a correlation with respiratory oscillation for an average of 43% of the recording time at a significance level of p < 0.05. Oscillations in systolic blood pressure in the Mayer wave frequency range were observed in all subjects for whom blood pressure was recorded (n=13. ARI oscillation in the Mayer wave frequency range was observed in 6/13 subjects (46% over a range of 2.9ms to 9.2ms. Coherence with Mayer waves at the p < 0.05 significance level was present for an average of 29 % of the recording time. In ambulatory patients with heart failure during enhanced mental arousal, left ventricular epicardial APD (ARI oscillated at the respiratory frequency (approx. 0.25Hz. In 6 patients (46% APD oscillated at the slower Mayer wave frequency (approx. 0.1 Hz. These findings may be important in understanding sympathetic activity-related arrhythmogenesis.

  14. Regulation of ClC-1 and KATP channels in action potential-firing fast-twitch muscle fibers.

    Science.gov (United States)

    Pedersen, Thomas Holm; de Paoli, Frank Vincenzo; de Paoli, Frank Vinzenco; Flatman, John A; Nielsen, Ole Baekgaard

    2009-10-01

    Action potential (AP) excitation requires a transient dominance of depolarizing membrane currents over the repolarizing membrane currents that stabilize the resting membrane potential. Such stabilizing currents, in turn, depend on passive membrane conductance (G(m)), which in skeletal muscle fibers covers membrane conductances for K(+) (G(K)) and Cl(-) (G(Cl)). Myotonic disorders and studies with metabolically poisoned muscle have revealed capacities of G(K) and G(Cl) to inversely interfere with muscle excitability. However, whether regulation of G(K) and G(Cl) occur in AP-firing muscle under normal physiological conditions is unknown. This study establishes a technique that allows the determination of G(Cl) and G(K) with a temporal resolution of seconds in AP-firing muscle fibers. With this approach, we have identified and quantified a biphasic regulation of G(m) in active fast-twitch extensor digitorum longus fibers of the rat. Thus, at the onset of AP firing, a reduction in G(Cl) of approximately 70% caused G(m) to decline by approximately 55% in a manner that is well described by a single exponential function characterized by a time constant of approximately 200 APs (phase 1). When stimulation was continued beyond approximately 1,800 APs, synchronized elevations in G(K) ( approximately 14-fold) and G(Cl) ( approximately 3-fold) caused G(m) to rise sigmoidally to approximately 400% of its level before AP firing (phase 2). Phase 2 was often associated with a failure to excite APs. When AP firing was ceased during phase 2, G(m) recovered to its level before AP firing in approximately 1 min. Experiments with glibenclamide (K(ATP) channel inhibitor) and 9-anthracene carboxylic acid (ClC-1 Cl(-) channel inhibitor) revealed that the decreased G(m) during phase 1 reflected ClC-1 channel inhibition, whereas the massively elevated G(m) during phase 2 reflected synchronized openings of ClC-1 and K(ATP) channels. In conclusion, G(Cl) and G(K) are acutely regulated in AP

  15. Potential effect of matrix stiffness on the enrichment of tumor initiating cells under three-dimensional culture conditions.

    Science.gov (United States)

    Liu, Chang; Liu, Yang; Xu, Xiao-xi; Wu, Hao; Xie, Hong-guo; Chen, Li; Lu, Ting; Yang, Li; Guo, Xin; Sun, Guang-wei; Wang, Wei; Ma, Xiao-jun; He, Xin

    2015-01-01

    Cancer stem cell (CSC) or tumor initiating cell (TIC) plays an important role in tumor progression and metastasis. Biophysical forces in tumor microenvironment have an important effect on tumor formation and development. In this study, the potential effect of matrix stiffness on the biological characteristics of human head and neck squamous cell carcinoma (HNSCC) TICs, especially the enrichment of HNSCC TICs, was investigated under three-dimensional (3D) culture conditions by means of alginate gel (ALG) beads with different matrix stiffnesses. ALG beads with soft (21 kPa), moderate (70 kPa) and hard (105 kPa) stiffness were generated by changing alginate concentration. It was found that significant HNSCC TIC enrichment was achieved in the ALG beads with moderate matrix stiffness (70 kPa). The gene expression of stemness markers Oct3/4 and Nanog, TIC markers CD44 and ABCG2 was enhanced in cells under this moderate (70 kPa) stiffness. HNSCC TIC proportion was also highly enriched under moderate matrix stiffness, accompanying with higher tumorigenicity, metastatic ability and drug resistance. And it was also found that the possible molecular mechanism underlying the regulated TIC properties by matrix stiffness under 3D culture conditions was significantly different from 2D culture condition. Therefore, the results achieved in this study indicated that 3D biophysical microenvironment had an important effect on TIC characteristics and alginate-based biomimetic scaffolds could be utilized as a proper platform to investigate the interaction between tumor cells and 3D microenvironment.

  16. Enteral nutrients potentiate glucagon-like peptide-2 action and reduce dependence on parenteral nutrition in a rat model of human intestinal failure

    DEFF Research Database (Denmark)

    Brinkman, Adam S; Murali, Sangita G; Hitt, Stacy

    2012-01-01

    after 7 days with continued EN sustained the majority of intestinal adaption and significantly increased expression of colonic proglucagon compared with PN + EN + GLP-2 for 18 days, and increased plasma GLP-2 concentrations compared with TPN alone. In summary, EN potentiate the intestinotrophic actions...

  17. Normative findings of electrically evoked compound action potential measurements using the neural response telemetry of the Nucleus CI24M cochlear implant system.

    NARCIS (Netherlands)

    Cafarelli-Dees, D.; Dillier, N.; Lai, W.K.; Wallenberg, E. von; Dijk, B. van; Akdas, F.; Aksit, M.; Batman, C.; Beynon, A.J.; Burdo, S.; Chanal, J.M.; Collet, L.; Conway, M.; Coudert, C.; Craddock, L.; Cullington, H.; Deggouj, N.; Fraysse, B.; Grabel, S.; Kiefer, J.; Kiss, J.G.; Lenarz, T.; Mair, A.; Maune, S.; Muller-Deile, J.; Piron, J.P.; Razza, S.; Tasche, C.; Thai-Van, H.; Toth, F.; Truy, E.; Uziel, A.; Smoorenburg, G.F.

    2005-01-01

    One hundred and forty-seven adult recipients of the Nucleus 24 cochlear implant system, from 13 different European countries, were tested using neural response telemetry to measure the electrically evoked compound action potential (ECAP), according to a standardised postoperative measurement procedu

  18. Effects of PAD on conduction of action potentials within segmental and ascending branches of single muscle afferents in the cat spinal cord.

    Science.gov (United States)

    Lomelí, J; Castillo, L; Linares, P; Rudomin, P

    2000-11-01

    In anesthetized and paralyzed cats under artificial respiration, we examined the extent to which primary afferent depolarization (PAD) might affect invasion of action potentials in intraspinal axonal and/or terminal branches of single muscle afferents. To this end, one stimulating micropipette was placed at the L6 spinal level within the intermediate or motor nucleus, and another one at the L3 level, in or close to Clarke's column. Antidromically conducted responses produced in single muscle afferents by stimulation at these two spinal levels were recorded from fine lateral gastrocnemius nerve filaments. In all fibers examined, stimulation of one branch, with strengths producing action potentials, increased the intraspinal threshold of the other branch when applied at short conditioning testing stimulus intervals (<1.5-2.0 ms), because of the refractoriness produced by the action potentials invading the tested branch. Similar increases in the intraspinal threshold were found in branches showing tonic PAD and also during the PAD evoked by stimulation of group I afferent fibers in muscle nerves. It is concluded that during tonic or evoked PAD, axonal branches in the dorsal columns and myelinated terminals of muscle afferents ending deep in the L6 and L3 segmental levels continue to be invaded by action potentials. These findings strengthen the view that presynaptic inhibition of muscle afferents produced by activation of GABAergic mechanisms is more likely to result from changes in the synaptic effectiveness of the afferent terminals than from conduction failure because of PAD.

  19. Intracellular actions of steroid hormones and their therapeutic value, including the potential of radiohalosteroids against ovarian cancer

    Energy Technology Data Exchange (ETDEWEB)

    Holt, J.A. (Chicago Univ. (United States). Dept. of Obstetrics and Gynecology); Scharl, A. (Koeln Univ., Cologne (Germany). Frauen-Klinik); Kullander, S. (Lund Univ. (Sweden). Womens Hospital Malmoe); Beckmann, M.W. (Johann Wolfgang von Goethe Univ., Frankfurt am Main (Germany). Zentrum fuer Frauenheilkunde und Geburtshilfe)

    1992-01-01

    With recombinant cDNA technology, yeast and cultured animal cells can be made to express mammalian cDNA steroid receptors from cDNA clones that contain deletions and substitutions. Among the leading problems addressed in these models is the characterization of sequences that promote association or interaction with other transcription regulating molecules, including oncogene products. Recently it has been found that heat shock proteins may serve not only to stabilize the receptor proteins but also to precondition the activation imparted by ligand binding. Aberrant receptor proteins can be found in ovarian cancer. Whether aberrant receptor proteins are associated with transformation in general or with a variable clinical response to steroidal or anti-steroidal therapy is not known. Even after chemotherapy, steroid receptors are expressed in the metastases of ovarian cancers seen clinically, and they may have potential use for localization and treatment of receptor-rich cancers. Radioligand pharmaceuticals appropriate for imaging or for site-directed radiocytotoxicity can be sequestered to the nuclei of receptor-rich cancers. Initial clinical imaging and therapy trials with such pharmaceuticals have been approved and begun. In the use of halogenated estrogen radiopharmaceuticals, liver metabolism and enterohepatic recirculation are important considerations. Ascites prolongs retention of radiohalogenated estrogen in the abdominal cavity. Distant metastases have been localized with [[sup 123]I]-estrogen in breast cancer patients in pre-operative procedures. Receptor-mediated cytotoxicity occurs when estrogen receptor radioligand pharmaceuticals that are Auger electron emitters are used in vitro. (au) (119 refs., 3 figs.).

  20. Green tea catechins potentiate the neuritogenic action of brain-derived neurotrophic factor: role of 67-kDa laminin receptor and hydrogen peroxide.

    Science.gov (United States)

    Gundimeda, Usha; McNeill, Thomas H; Fan, Tiffany K; Deng, Ronald; Rayudu, David; Chen, Zachary; Cadenas, Enrique; Gopalakrishna, Rayudu

    2014-02-28

    Delivery of optimal amounts of brain-derived neurotrophic factor (BDNF) to regions of the brain affected by neurodegenerative diseases is a daunting task. Using natural products with neuroprotective properties, such as green tea polyphenols, would be a highly useful complementary approach for inexpensive long-term treatment of these diseases. In this study, we used PC12(TrkB) cells which ectopically express TrkB, a high affinity receptor for BDNF. They differentiate and induce neurite outgrowth in response to BDNF. Using this model, we show for the first time that treatment with extremely low concentrations (BDNF. A synergistic interaction was observed between GTPP constituents, where epigallocatechin and epicatechin, both individually lacking this activity, promoted the action of EGCG. GTPP-induced potentiation of BDNF action required the cell-surface associated 67 kDa laminin receptor (67LR) to which EGCG binds with high affinity. A cell-permeable catalase abolished GTPP/EGCG-induced potentiation of BDNF action, suggesting the possible involvement of H2O2 in the potentiation. Consistently, exogenous sublethal concentrations of H2O2, added as a bolus dose (5 μM) or more effectively through a steady-state generation (1 μM), potentiated BDNF action. Collectively, these results suggest that EGCG, dependent on 67 LR and H2O2, potentiates the neuritogenic action of BDNF. Intriguingly, this effect requires only submicromolar concentrations of EGCG. This is significant as extremely low concentrations of polyphenols are believed to reach the brain after drinking green tea.

  1. Design, synthesis, and initial evaluation of D-glyceraldehyde crosslinked gelatin-hydroxyapatite as a potential bone graft substitute material

    Science.gov (United States)

    Florschutz, Anthony Vatroslav

    Utilization of bone grafts for the treatment of skeletal pathology is a common practice in orthopaedic, craniomaxillofacial, dental, and plastic surgery. Autogenous bone graft is the established archetype but has disadvantages including donor site morbidity, limited supply, and prolonging operative time. In order to avoid these and other issues, bone graft substitute materials are becoming increasingly prevalent among surgeons for reconstructing skeletal defects and arthrodesis applications. Bone graft substitutes are biomaterials, biologics, and guided tissue/bone regenerative devices that can be used alone or in combinations as supplements or alternatives to autogenous bone graft. There is a growing interest and trend to specialize graft substitutes for specific indications and although there is good rationale for this indication-specific approach, the development and utility of a more universal bone graft substitute may provide a better answer for patients and surgeons. The aim of the present research focuses on the design, synthesis, and initial evaluation of D-glyceraldehyde crosslinked gelatin-hydroxyapatite composites for potential use as a bone graft substitutes. After initial establishment of rational material design, gelatinhydroxyapatite scaffolds were fabricated with different gelatin:hydroxyapatite ratios and crosslinking concentrations. The synthesized scaffolds were subsequently evaluated on the basis of their swelling behavior, porosity, density, percent composition, mechanical properties, and morphology and further assessed with respect to cell-biomaterial interaction and biomineralization in vitro. Although none of the materials achieved mechanical properties suitable for structural graft applications, a reproducible material design and synthesis was achieved with properties recognized to facilitate bone formation. Select scaffold formulations as well as a subset of scaffolds loaded with recombinant human bone morphogenetic protein-2 were

  2. Potential hazards to embryo implantation: A human endometrial in vitro model to identify unwanted antigestagenic actions of chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, L.; Deppert, W.R. [Department of Obstetrics and Gynecology, University Hospital Freiburg (Germany); Pfeifer, D. [Department of Hematology and Oncology, University Hospital Freiburg (Germany); Stanzel, S.; Weimer, M. [Department of Biostatistics, German Cancer Research Center, Heidelberg (Germany); Hanjalic-Beck, A.; Stein, A.; Straßer, M.; Zahradnik, H.P. [Department of Obstetrics and Gynecology, University Hospital Freiburg (Germany); Schaefer, W.R., E-mail: wolfgang.schaefer@uniklinik-freiburg.de [Department of Obstetrics and Gynecology, University Hospital Freiburg (Germany)

    2012-05-01

    Embryo implantation is a crucial step in human reproduction and depends on the timely development of a receptive endometrium. The human endometrium is unique among adult tissues due to its dynamic alterations during each menstrual cycle. It hosts the implantation process which is governed by progesterone, whereas 17β-estradiol regulates the preceding proliferation of the endometrium. The receptors for both steroids are targets for drugs and endocrine disrupting chemicals. Chemicals with unwanted antigestagenic actions are potentially hazardous to embryo implantation since many pharmaceutical antiprogestins adversely affect endometrial receptivity. This risk can be addressed by human tissue-specific in vitro assays. As working basis we compiled data on chemicals interacting with the PR. In our experimental work, we developed a flexible in vitro model based on human endometrial Ishikawa cells. Effects of antiprogestin compounds on pre-selected target genes were characterized by sigmoidal concentration–response curves obtained by RT-qPCR. The estrogen sulfotransferase (SULT1E1) was identified as the most responsive target gene by microarray analysis. The agonistic effect of progesterone on SULT1E1 mRNA was concentration-dependently antagonized by RU486 (mifepristone) and ZK137316 and, with lower potency, by 4-nonylphenol, bisphenol A and apigenin. The negative control methyl acetoacetate showed no effect. The effects of progesterone and RU486 were confirmed on the protein level by Western blotting. We demonstrated proof of principle that our Ishikawa model is suitable to study quantitatively effects of antiprogestin-like chemicals on endometrial target genes in comparison to pharmaceutical reference compounds. This test is useful for hazard identification and may contribute to reduce animal studies. -- Highlights: ► We compare progesterone receptor-mediated endometrial effects of chemicals and drugs. ► 4-Nonylphenol, bisphenol A and apigenin exert weak

  3. A Comparative Study On The Action Potential Simulation (APS Therapy And The Routine Physiotherapy Protocol In Knee Osteoarthritisin Elderly People

    Directory of Open Access Journals (Sweden)

    Abbas Rahimi

    2012-04-01

    Full Text Available Background and Aim: Knee osteoarthritis is the most common cause for which the elderly people refere to physiotherapy outpatient clinics. This study aimed to investigate the effects of the Action Potential Stimulation (APS Therapy and the routine physiotherapy (PT protocol on relieving pain and swelling as well as the duration of the relief period in patients with knee osteoarthritis. Materials and Methods: 69 patients (62 females & 7 males with knee osteoarthritis were recruited in this study. The subjects were divided into two groups including APS Therapy (n=37, mean age: 55±13 years old and the routine PT protocol (n=32, mean age: 61±14 years old groups. A 10-session treatment period was carried out for each group; and their pain and swelling were measured at the first, fifth and tenth sessions and also one-month after the last session (follow up. The swelling was measured using measuring the circumference of the knee on the patella, 5 Cm above and 5 Cm below the patella. The routine PT protocol consisted of hot pack, ultrasound, TENS and exercise; and the APS therapy protocol included hot pack, APS Therapy and the same exercise. During the follow up, 50 out of 61 subjects were called on the phone and any pain changes were recorded.Results: In terms of swelling, the results showed significant reduction just on the patella only in the APS Therapy group (P<0.05. Visual Analogue Pain Scale (VAPS indicated a significant pain reduction in both groups. However, the APS Therapy group showed significantly pain reduction at the end of sessions five, ten and the follow up session (P<0.05. It was also revealed that while routine PT subjects showed no significant pain changes between the tenth and the follow up session, a gradual pain reduction was seen in the APS therapy group during this period (P<0.05. A gradual dosage reduction was recorded only in the APS therapy group, indicating a slight correlation with pain reduction (r=0.4.Conclusion: The

  4. A computational model of the ionic currents, Ca2+ dynamics and action potentials underlying contraction of isolated uterine smooth muscle.

    Directory of Open Access Journals (Sweden)

    Wing-Chiu Tong

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

  5. Repeat associated non-ATG translation initiation: one DNA, two transcripts, seven reading frames, potentially nine toxic entities!

    Directory of Open Access Journals (Sweden)

    Christopher E Pearson

    2011-03-01

    Full Text Available Diseases associated with unstable repetitive elements in the DNA, RNA, and amino acids have consistently revealed scientific surprises. Most diseases are caused by expansions of trinucleotide repeats, which ultimately lead to diseases like Huntington's disease, myotonic dystrophy, fragile X syndrome, and a series of spinocerebellar ataxias. These repeat mutations are dynamic, changing through generations and within an individual, and the repeats can be bi-directionally transcribed. Unsuspected modes of pathogenesis involve aberrant loss of protein expression; aberrant over-expression of non-mutant proteins; toxic-gain-of-protein function through expanded polyglutamine tracts that are encoded by expanded CAG tracts; and RNA-toxic-gain-of-function caused by transcripts harboring expanded CUG, CAG, or CGG tracts. A recent advance reveals that RNA transcripts with expanded CAG repeats can be translated in the complete absence of a starting ATG, and this Repeat Associated Non-ATG translation (RAN-translation occurs across expanded CAG repeats in all reading frames (CAG, AGC, and GCA to produce homopolymeric proteins of long polyglutamine, polyserine, and polyalanine tracts. Expanded CTG tracts expressing CUG transcripts also show RAN-translation occurring in all three frames (CUG, UGC, and GCU, to produce polyleucine, polycysteine, and polyalanine. These RAN-translation products can be toxic. Thus, one unstable (CAG•(CTG DNA can produce two expanded repeat transcripts and homopolymeric proteins with reading frames (the AUG-directed polyGln and six RAN-translation proteins, yielding a total of potentially nine toxic entities. The occurrence of RAN-translation in patient tissues expands our horizons of modes of disease pathogenesis. Moreover, since RAN-translation counters the canonical requirements of translation initiation, many new questions are now posed that must be addressed. This review covers RAN-translation and some of the pertinent

  6. Association of somatic action potential shape with sensory receptive properties in guinea-pig dorsal root ganglion neurones.

    Science.gov (United States)

    Djouhri, L; Bleazard, L; Lawson, S N

    1998-12-15

    1. Intracellular voltage recordings were made from the somata of L6 and S1 dorsal root ganglion (DRG) neurones at 28.5-31 C in young guinea-pigs (150-300 g) anaesthetized with sodium pentobarbitone. Action potentials (APs) evoked by dorsal root stimulation were used to classify conduction velocities (CVs) as C, Adelta or Aalpha/beta. Units with overshooting APs and membrane potentials (Vm) more negative than -40 mV were analysed: 40 C-, 45 Adelta- and 94 Aalpha/beta-fibre units. 2. Sensory receptive properties were characterized as: (a) low-threshold mechanoreceptive (LTM) units (5 C-, 10 Adelta- and 57 Aalpha/beta-fibre units); (b) nociceptive units, responding to noxious mechanical stimuli, some also to noxious heat (40 C-, 27 Adelta- and 27 Aalpha/beta-fibre units); (c) unresponsive units that failed to respond to a variety of tests; and (d) C-fibre cooling-sensitive units (n = 4). LTM units made up about 8 % of identified C-fibre units, 36 % of identified Adelta-fibre units and > 73 % of identified Aalpha/beta-fibre units. Compared with LTM units, the nociceptive units had APs that were longer on average by 3 times (C-fibre units), 1.7 times (Adelta-fibre units) and 1.4 times (Aalpha/beta-fibre units). They also had significantly longer rise times (RTs) and fall times (FTs) in all CV ranges. Between Aalpha/beta-nociceptors and Aalpha/beta-LTMs there was a proportionately greater difference in RT than in FT. The duration of the afterhyperpolarization measured to 80 % recovery (AHP80) was also significantly longer in nociceptive than LTM neurones in all CV ranges: by 3 times (C-fibre units), 6.3 times (Adelta-fibre units) and 3.6 times (Aalpha/beta-fibre units). The mean values of these variables in unresponsive units were similar to those of nociceptive units in each CV range; in C- and Adelta-fibre groups their mean AHP duration was even longer than in nociceptive units. 3. A-fibre LTM neurones were divided into Adelta- (D hair units, n = 8), and Aalpha

  7. Loss of ATP-Sensitive Potassium Channel Surface Expression in Heart Failure Underlies Dysregulation of Action Potential Duration and Myocardial Vulnerability to Injury.

    Directory of Open Access Journals (Sweden)

    Zhan Gao

    Full Text Available The search for new approaches to treatment and prevention of heart failure is a major challenge in medicine. The adenosine triphosphate-sensitive potassium (KATP channel has been long associated with the ability to preserve myocardial function and viability under stress. High surface expression of membrane KATP channels ensures a rapid energy-sparing reduction in action potential duration (APD in response to metabolic challenges, while cellular signaling that reduces surface KATP channel expression blunts APD shortening, thus sacrificing energetic efficiency in exchange for greater cellular calcium entry and increased contractile force. In healthy hearts, calcium/calmodulin-dependent protein kinase II (CaMKII phosphorylates the Kir6.2 KATP channel subunit initiating a cascade responsible for KATP channel endocytosis. Here, activation of CaMKII in a transaortic banding (TAB model of heart failure is coupled with a 35-40% reduction in surface expression of KATP channels compared to hearts from sham-operated mice. Linkage between KATP channel expression and CaMKII is verified in isolated cardiomyocytes in which activation of CaMKII results in downregulation of KATP channel current. Accordingly, shortening of monophasic APD is slowed in response to hypoxia or heart rate acceleration in failing compared to non-failing hearts, a phenomenon previously shown to result in significant increases in oxygen consumption. Even in the absence of coronary artery disease, failing myocardium can be further injured by ischemia due to a mismatch between metabolic supply and demand. Ischemia-reperfusion injury, following ischemic preconditioning, is diminished in hearts with CaMKII inhibition compared to wild-type hearts and this advantage is largely eliminated when myocardial KATP channel expression is absent, supporting that the myocardial protective benefit of CaMKII inhibition in heart failure may be substantially mediated by KATP channels. Recognition of Ca

  8. Potential role of TBC1D4 in enhanced post-exercise insulin action in human skeletal muscle

    DEFF Research Database (Denmark)

    Treebak, Jonas Thue; Frøsig, Christian; Pehmøller, Christian

    2009-01-01

    insulin stimulation. CONCLUSION/INTERPRETATION: We provide evidence for site-specific phosphorylation of TBC1D4 in human skeletal muscle in response to physiological hyperinsulinaemia. The data support the idea that TBC1D4 is a nexus for insulin- and exercise-responsive signals that may mediate increased...... insulin action after exercise....

  9. The potential role of COX-2 in cancer stem cell-mediated canine mammary tumor initiation: an immunohistochemical study

    OpenAIRE

    Huang, Jian; Zhang, Di; Xie, Fuqiang; LIN, Degui

    2015-01-01

    Increasing evidence suggests that cancer stem cells (CSCs) are responsible for tumor initiation and maintenance. Additionally, it is becoming apparent that cyclooxygenase (COX) signaling is associated with canine mammary tumor development. The goals of the present study were to investigate COX-2 expression patterns and their effect on CSC-mediated tumor initiation in primary canine mammary tissues and tumorsphere models using immunohistochemistry. Patterns of COX-2, CD44, octamer-binding tran...

  10. Biophysical characterization of inwardly rectifying potassium currents (I(K1) I(K,ACh), I(K,Ca)) using sinus rhythm or atrial fibrillation action potential waveforms

    DEFF Research Database (Denmark)

    Tang, Chuyi; Skibsbye, Lasse; Yuan, Lei

    2015-01-01

    to voltage protocols adapted from atrial action potentials recorded in human tissue at 1 and 3 Hz. The current recordings were performed in the HEK-293 heterologous cell system expressing either I(K1), I(K,ACh) or I(K,Ca) to establish the individual contribution of each of these currents during the voltage...... changes of atrial action potential waveforms. I(K1) primarily contributes to the atrial electrophysiology at the latter part of repolarization and during the diastolic phase, while both I(K,Ca) under high [Ca2+]i and I(K,ACh) contribute relatively most during repolarization.......Although several physiological, pathophysiological and regulatory properties of classical inward rectifier K+ current I(K1), G-protein coupled inwardly-rectifying K+ current I(K,ACh) and the small-conductance Ca2+ activated K+ current I(K,Ca) have been identified, quantitative biophysical details...

  11. Action-potential duration and the modulation of transmitter release from the sensory neurons of Aplysia in presynaptic facilitation and behavioral sensitization

    OpenAIRE

    Hochner, Binyamin; Klein, Marc; Schacher, Samuel; Kandel, Eric R.

    1986-01-01

    Presynaptic facilitation of transmitter release from Aplysia sensory neurons is an important contributor to behavioral sensitization of the gill and siphon withdrawal reflex. The enhanced release is accompanied by reduction of the serotonin-sensitive S current in the sensory neurons and a consequent increase in duration of the presynaptic action potential (ranging from 10% to 30%). We find that changes of similar magnitude in the duration of depolarizing voltage-clamp steps in sensory neurons...

  12. Treatment of acne with tea tree oil (melaleuca) products: a review of efficacy, tolerability and potential modes of action.

    Science.gov (United States)

    Hammer, K A

    2015-02-01

    Over-the-counter acne treatments containing tea tree oil from the plant Melaleuca alternifolia are widely available, and evidence indicates that they are a common choice amongst those self-treating their acne. The aims of this review were to collate and evaluate the clinical evidence on the use of tea tree oil products for treating acne, to review safety and tolerability and to discuss the underlying modes of therapeutic action.

  13. NS5806 partially restores action potential duration but fails to ameliorate calcium transient dysfunction in a computational model of canine heart failure

    DEFF Research Database (Denmark)

    Maleckar, Mary M; Lines, Glenn T; Koivumäki, Jussi T

    2014-01-01

    AIMS: The study investigates how increased Ito, as mediated by the activator NS5806, affects excitation-contraction coupling in chronic heart failure (HF). We hypothesized that restoring spike-and-dome morphology of the action potential (AP) to a healthy phenotype would be insufficient to restore...... potential. Decreased APD50 and APD90 are both due to altered IK1. Analysis revealed that drug effects depend on transmurality. Ca(2+) transient morphology changes-increased amplitude and shorter time to peak-are due to direct increase in ICa,L and indirect larger SR Ca(2+) release subsequent to Ito...

  14. The White House BRAIN Initiative has the potential to further strengthen multidisciplinary research and training in psychology.

    Science.gov (United States)

    Flattau, Pamela

    2014-12-01

    Comments on the original article by Robiner et al. (see record 2014-07939-001) regarding psychologists in medical schools and academic medical center settings. The current authors also discuss how to advance training in psychology using the Brain Research Through Advancing Innovative Neurotechnologies (BRAIN) Initiative. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

  15. Opposing Actions of Chronic[Deta][superscript 9] Tetrahydrocannabinol and Cannabinoid Antagonists on Hippocampal Long-Term Potentiation

    Science.gov (United States)

    Hoffman, Alexander F.; Oz, Murat; Yang, Ruiqin; Lichtman, Aron H.; Lupica, Carl R.

    2007-01-01

    Memory deficits produced by marijuana arise partly via interaction of the psychoactive component, [Deta][superscript 9]-tetrahydrocannabinol ([Deta][superscript 9]-THC), with cannabinoid receptors in the hippocampus. Although cannabinoids acutely reduce glutamate release and block hippocampal long-term potentiation (LTP), a potential substrate for…

  16. A Career Development Plan for Community Action Agencies.

    Science.gov (United States)

    Gartner, Alan; Jones, Nina

    A system for career advancement in the community action agency must be based on the fundamental principle that it is the responsibility of the community action agency to develop the full potential of the nonprofessional staff. The agency must take the initiative on several aspects of its policy and program. Nonprofessional employees must be able…

  17. Blockade by NIP-142, an antiarrhythmic agent, of carbachol-induced atrial action potential shortening and GIRK1/4 channel.

    Science.gov (United States)

    Matsuda, Tomoyuki; Ito, Mie; Ishimaru, Sayoko; Tsuruoka, Noriko; Saito, Tomoaki; Iida-Tanaka, Naoko; Hashimoto, Norio; Yamashita, Toru; Tsuruzoe, Nobutomo; Tanaka, Hikaru; Shigenobu, Koki

    2006-08-01

    Mechanisms for the atria-specific action potential-prolonging action of NIP-142 ((3R*,4S*)-4-cyclopropylamino-3,4-dihydro-2,2-dimethyl-6-(4-methoxyphenylacetylamino)-7-nitro-2H-1-benzopyran-3-ol), a benzopyran compound that terminates experimental atrial arrhythmia, was examined. In isolated guinea-pig atrial tissue, NIP-142 reversed the shortening of action potential duration induced by either carbachol or adenosine. These effects were mimicked by tertiapin, but not by E-4031. NIP-142 concentration-dependently blocked the human G protein-coupled inwardly rectifying potassium channel current (GIRK1/4 channel current) expressed in HEK-293 cells with an EC50 value of 0.64 microM. At higher concentrations, NIP-142 blocked the human ether a go-go related gene (HERG) channel current with an EC50 value of 44 microM. In isolated guinea-pig papillary muscles, NIP-142 had no effect on the negative inotropic effect of carbachol under beta-adrenergic stimulation, indicating lack of effect on the muscarinic receptor and Gi protein. These results suggest that NIP-142 directly inhibits the acetylcholine-activated potassium current.

  18. Circadian rhythm of heart rate in the rabbit: prolongation of action potential duration by sustained beta adrenoceptor blockade is not due to associated bradycardia.

    Science.gov (United States)

    Vaughan Williams, E M; Dennis, P D; Garnham, C

    1986-07-01

    Six litters of six young rabbits were injected intraperitoneally, two per litter, with saline, alinidine, or nadolol once or twice daily for two weeks. In four litters successful radiotransmissions of electrocardiograms were recorded once hourly for four days before and during treatment. Alinidine and nadolol produced an overall mean bradycardia in comparison with saline treated animals, the effect of alinidine exceeding that of nadolol. At 48-70 hours after the end of treatment the hearts were used for in vitro electrophysiological study. Nadolol, but not alinidine, induced a prolongation of action potential duration compared with that of saline treated littermates in both atrial and ventricular muscle. An incidental observation was that heart rate in the rabbit followed a circadian rhythm, heart rates being slower in the morning and faster in late afternoon and evening. The circadian rhythm was attenuated but not abolished by alinidine and nadolol. These results suggest that if prolongation of action potential duration by sustained beta blockade in patients after myocardial infarction contributes to protection against sudden death (by a class III antiarrhythmic action) then alinidine would not be expected to provide a comparable prophylaxis.

  19. [Stimulation of gastric mucosa afferents by phenylephrine potentiates anticonvulsive and eliminates sedative action of sodium valproate in the pentylenetetrazol kindling model in rats].

    Science.gov (United States)

    Serdiuk, S E; Gmiro, V E; Veselkina, O S

    2014-01-01

    Sodium valproate after chronic intragastric administration in the high dose of 100-200 mg/kg eliminates generalized clonic-tonic pentylenetetrazol seizures in 100 % of rats, but only in 33-57 % of rats it prevents local clonic kindling seizures. Strong sedation is induced by the specified doses of sodium valproate. The combined oral chronic administration of phenylephrine in threshold, noneffective alone dose of 0.2 mg/kg and sodium valproate in high doses of 100 mg/kg and 200 mg/kg potentiates anticonvulsive action of sodium valproate, because prevents both clonic-tonic kindling. seizures in 100 % of rats and clonic kindling seizures in 86-100 % of rats, and also it increases in 1.7-1.9 times anticonvulsive activity of valproate. The specified combinations of sodium valproate with phenylephrine do not produce the sedative side effect. The basis of the mechanism of potentiation of anticonvulsive action and elimination of sedative action of sodium valproate in high doses is the stimulation of gastric mucosa afferents by phenylephrine.

  20. Overview of Antagonists Used for Determining the Mechanisms of Action Employed by Potential Vasodilators with Their Suggested Signaling Pathways

    Directory of Open Access Journals (Sweden)

    Yean Chun Loh

    2016-04-01

    Full Text Available This paper is a review on the types of antagonists and the signaling mechanism pathways that have been used to determine the mechanisms of action employed for vasodilation by test compounds. Thus, we exhaustively reviewed and analyzed reports related to this topic published in PubMed between the years of 2010 till 2015. The aim of this paperis to suggest the most appropriate type of antagonists that correspond to receptors that would be involved during the mechanistic studies, as well as the latest signaling pathways trends that are being studied in order to determine the route(s that atest compound employs for inducing vasodilation. The methods to perform the mechanism studies were included. Fundamentally, the affinity, specificity and selectivity of the antagonists to their receptors or enzymes were clearly elaborated as well as the solubility and reversibility. All the signaling pathways on the mechanisms of action involved in the vascular tone regulation have been well described in previous review articles. However, the most appropriate antagonists that should be utilized have never been suggested and elaborated before, hence the reason for this review.

  1. Potential of plant essential oils and their components in animal agriculture – in vitro studies on antibacterial mode of action

    Directory of Open Access Journals (Sweden)

    Corliss A. O'bryan

    2015-09-01

    Full Text Available The broad field of agriculture is currently undergoing major changes in practices, with new catch phrases including organic and sustainable. Consumers are more aware than ever before of the food that they eat and they want food free of toxic chemicals, antibiotics and the like. The antimicrobial activity of essential oils and their components has been recognized for several years. Recent research has demonstrated that many of these essential oils have beneficial effects for livestock, including reduction of foodborne pathogens in these animals. Essential oils as natural antimicrobials offer the opportunity to help maintain the safety of our food supply and minimize consumers’ concerns about consumption of synthetic chemicals. Numerous studies have been made into the mode of action of essential oils and the resulting elucidation of bacterial cell targets have contributed to new perspectives on countering antimicrobial resistance and pathogenicity of these bacteria. In this review, after a brief discussion of the uses essential oils in agriculture as antimicrobials, we give an overview of the current knowledge about the antibacterial mode of action of essential oils and their constituents as determined in vitro.

  2. Acute alterations of somatodendritic action potential dynamics in hippocampal CA1 pyramidal cells after kainate-induced status epilepticus in mice.

    Directory of Open Access Journals (Sweden)

    Daniel Minge

    Full Text Available Pathophysiological remodeling processes at an early stage of an acquired epilepsy are critical but not well understood. Therefore, we examined acute changes in action potential (AP dynamics immediately following status epilepticus (SE in mice. SE was induced by intraperitoneal (i.p. injection of kainate, and behavioral manifestation of SE was monitored for 3-4 h. After this time interval CA1 pyramidal cells were studied ex vivo with whole-cell current-clamp and Ca(2+ imaging techniques in a hippocampal slice preparation. Following acute SE both resting potential and firing threshold were modestly depolarized (2-5 mV. No changes were seen in input resistance or membrane time constant, but AP latency was prolonged and AP upstroke velocity reduced following acute SE. All cells showed an increase in AP halfwidth and regular (rather than burst firing, and in a fraction of cells the notch, typically preceding spike afterdepolarization (ADP, was absent following acute SE. Notably, the typical attenuation of backpropagating action potential (b-AP-induced Ca(2+ signals along the apical dendrite was strengthened following acute SE. The effects of acute SE on the retrograde spread of excitation were mimicked by applying the Kv4 current potentiating drug NS5806. Our data unveil a reduced somatodendritic excitability in hippocampal CA1 pyramidal cells immediately after acute SE with a possible involvement of both Na(+ and K(+ current components.

  3. The Potential Impacts of Warmer-Continent-Related Lower-Layer Equatorial Westerly Wind on Tropical Cyclone Initiation

    Institute of Scientific and Technical Information of China (English)

    YUAN Zhuojian; QIAN Yu-Kun; QI Jindian; WU Junjie

    2012-01-01

    Global climate models predict that the increasing Amazonian-deforestation rates cause rising temperatures (increases of 1.8℃ to 8℃ under different conditions) and Amazonian drying over the 21st century.Observations in the 20th century also show that over the warmer continent and the nearby western South Atlantic Ocean,the lower-layer equatorial westerly wind (LLEWW) strengthens with the initiation of tropical cyclones (TCs).The warmer-continent-related LLEWW can result from the Coriolis-force-induced deflection of the cross-equatorial flow (similar to the well-known heat-island effect on sea breeze) driven by the enhanced land-sea contrast between the warmer urbanized continents and relatively cold oceans.This study focuses on the processes relating the warmer-continent-related LLEWW to the TC initiation and demonstrates that the LLEWW embedded in trade easterlies can directly initiate TCs by creating cyclonic wind shears and forming the intertropical convergence zone.In addition to this direct effect,the LLEWW combined with the rotating Earth can boost additional updraft vapor over the high sea-surface temperature region (factor 1),facilitating a surface-to-midtroposphere moist layer (factor 2) and convective instability (factor 3) followed by diabatic processes.According to previous studies,the diabatic heating in a finite equatorial region also activates TCs (factor 4) on each side of the Equator with weak vertical shear (factor 5).Factors 1 5 are favorable conditions for the initiation of severe TCs.Statistical analyses show that the earliest signal of sustained LLEWW not only leads the earliest signal of sustained tropical depression by >3 days but also explains a higher percentage of total variance.

  4. Increased peritoneal permeability at peritoneal dialysis initiation is a potential cardiovascular risk in patients using biocompatible peritoneal dialysis solution

    OpenAIRE

    Hamasaki, Yoshifumi; Doi, Kent; Tanaka, Mototsugu; Kume, Haruki; Ishibashi, Yoshitaka; Enomoto, Yutaka; Fujita, Toshiro; Homma, Yukio; Nangaku, Masaomi; Noiri, Eisei

    2014-01-01

    Background Cardiovascular disease is a frequent cause of death in peritoneal dialysis patients. Biocompatible peritoneal dialysis solutions with neutral pH have been anticipated to reduce cardiovascular disease more than conventional peritoneal dialysis solutions with low pH, but it remains unclear which factors at peritoneal dialysis initiation increase cardiovascular risk in patients using biocompatible peritoneal dialysis solutions. This study was undertaken to investigate which clinical f...

  5. Solar heating action plan; Solvarme handlingsplan

    Energy Technology Data Exchange (ETDEWEB)

    Nielsen, Jan Erik

    2011-10-15

    This solar action plan should be seen as a follow-up to the Danish Energy Agency's solar heating strategy from 2007, which showed great potential and opportunities for exploitation and use of solar heat in Denmark. In relation to the strategy from 2007, this action plan adjusted the distribution of solar heat from district heating plants and individual plants, but it is still the objective of this action plan to achieve the strategy's overall goal for 2030. With the implementation of the Action Plan in early 2012, it is estimated that in 2030 there will be about. 10 million m2 of solar collectors in operation, 8 million m2 for district heating and 2 million m2 for individual heating, equivalent to an installed capacity totaling 7 GW. The budget for actions in the Action Plan is about 80 million DKK annually over the next 5 years to initiate and ensure this development. (LN)

  6. Inhibition of a cAMP-dependent Ca-activated K conductance by forskolin prolongs Ca action potential duration in lamprey sensory neurons.

    Science.gov (United States)

    Womble, M D; Wickelgren, W O

    1990-06-04

    Intracellular recordings from primary mechanosensory neurons (dorsal cells) of the lamprey spinal cord were made to test the membrane effects of forskolin, an activator of adenylate cyclase in these cells. At a concentration of 50 microM, forskolin was found to have a pronounced broadening effect on calcium action potentials (Ca APs) produced in the presence of voltage-activated K channel blockers (TEA, 3,4-DAP). Forskolin had no effect on passive membrane properties of the cells, such as resting potential or input resistance. Nor did it affect delayed rectification or Na APs and thus appeared not to block voltage-activated K channels. Forskolin's effect was evident only when a significant Ca component to the AP was present. It appeared not to increase the conductance of the Ca channel since its action was accompanied by a decrease in membrane conductance during the Ca AP, indicating instead an inhibition of a repolarizing Ca-activated conductance, other than a Ca-activated Cl conductance. The prolongation of Ca APs by forskolin, barium or the neurotransmitter GABA were all correlated in voltage-clamp with a decrease in outward current. Under the conductions used here, the major outward conductance in dorsal cells is a Ca-activated K conductance (gK(Ca]28, and it is concluded that the most probable mode of action for forskolin is via a cyclic AMP-mediated inhibition of this conductance. GABA has also been shown to prolong Ca APs in lamprey dorsal cells by inhibiting a repolarizing gK(Ca)28. Thus, the action of this transmitter may be mediated by an increase in intracellular cyclic AMP.

  7. Observer-Based Vaccination Strategy for a True Mass Action SEIR Epidemic Model with Potential Estimation of All the Populations

    Directory of Open Access Journals (Sweden)

    M. De la Sen

    2011-01-01

    Full Text Available This paper presents a simple continuous-time linear vaccination-based control strategy for a SEIR (susceptible plus infected plus infectious plus removed populations propagation disease model. The model takes into account the total population amounts as a refrain for the illness transmission since its increase makes more difficult contacts among the susceptible and infected. The control objective is the asymptotically tracking of the removed-by-immunity population to the total population while achieving simultaneously the remaining population (i.e., susceptible plus infected plus infectious to asymptotically converge to zero. A state observer is used to estimate the true various partial populations of the susceptible, infected, infectious, and immune which are assumed to be unknown. The model parameters are also assumed to be, in general, unknown. In this case, the parameters are replaced by available estimates to implement the vaccination action.

  8. Clean Energy Policy Analysis: Impact Analysis of Potential Clean Energy Policy Options for the Hawaii Clean Energy Initiative (HCEI)

    Energy Technology Data Exchange (ETDEWEB)

    Busche, S.; Doris, E.; Braccio, R.; Lippert, D.; Finch, P.; O' Toole, D.; Fetter, J.

    2010-04-01

    This report provides detailed analyses of 21 clean energy policy options considered by the Hawaii Clean Energy Initiative working groups for recommendation to the 2010 Hawaii State Legislature. The report considers the impact each policy may have on ratepayers, businesses, and the state in terms of energy saved, clean energy generated, and the financial costs and benefits. The analyses provide insight into the possible impacts, both qualitative and quantitative, that these policies may have in Hawaii based on the experience with these policies elsewhere. As much as possible, the analyses incorporate Hawaii-specific context to reflect the many unique aspects of energy use in the State of Hawaii.

  9. Investigating potential exogenous tumor initiating and promoting factors for Cutaneous T-Cell Lymphomas (CTCL), a rare skin malignancy

    DEFF Research Database (Denmark)

    Litvinov, Ivan V.; Shtreis, Anna; Kobayashi, Kenneth

    2016-01-01

    -Cell lymphotropic virus type 1 (HTLV1), Epstein-Barr virus (EBV), and herpes simplex virus (HSV). In this report, we review recent evidence evaluating the involvement of these agents in cancer initiation/progression. Most importantly, recent molecular experimental evidence documented for the first time that S...... are then able to activate STAT3 and STAT5 oncogenic signaling and promote cancer progression and IL-17 secretion. In light of these findings, it might be important for patients with exacerbation of their CTCL symptoms to maintain high index of suspicion and treat these individuals for S. aureus colonization and...

  10. Organic food in Denmark – from grass root initiative to market niche: potentials and barriers for further sustainable transition

    DEFF Research Database (Denmark)

    Jørgensen, Michael Søgaard

    2007-01-01

    the recent years’ reduction in the land converted to organic farming. The analyses are based on experiences from projects, analyses and literature and draw on innovation theory and theory about social construction of technology. The analyses show an ongoing interaction between production, consumption....../use, knowledge and governmental regulation, where these systems constantly are co-shaping each other. The role of the initial conditions in the shaping of the area is shown. The big Danish pork export and the specialised farms have implied a limited focus on organic pig production and more focus on the milk...

  11. Combinatorial mutagenesis of the voltage-sensing domain enables the optical resolution of action potentials firing at 60 Hz by a genetically encoded fluorescent sensor of membrane potential.

    Science.gov (United States)

    Piao, Hong Hua; Rajakumar, Dhanarajan; Kang, Bok Eum; Kim, Eun Ha; Baker, Bradley J

    2015-01-07

    ArcLight is a genetically encoded fluorescent voltage sensor using the voltage-sensing domain of the voltage-sensing phosphatase from Ciona intestinalis that gives a large but slow-responding optical signal in response to changes in membrane potential (Jin et al., 2012). Fluorescent voltage sensors using the voltage-sensing domain from other species give faster yet weaker optical signals (Baker et al., 2012; Han et al., 2013). Sequence alignment of voltage-sensing phosphatases from different species revealed conserved polar and charged residues at 7 aa intervals in the S1-S3 transmembrane segments of the voltage-sensing domain, suggesting potential coil-coil interactions. The contribution of these residues to the voltage-induced optical signal was tested using a cassette mutagenesis screen by flanking each transmembrane segment with unique restriction sites to allow for the testing of individual mutations in each transmembrane segment, as well as combinations in all four transmembrane segments. Addition of a counter charge in S2 improved the kinetics of the optical response. A double mutation in the S4 domain dramatically reduced the slow component of the optical signal seen in ArcLight. Combining that double S4 mutant with the mutation in the S2 domain yielded a probe with kinetics voltage-sensing domain could potentially lead to fluorescent sensors capable of optically resolving neuronal inhibition and subthreshold synaptic activity.

  12. Green Tea Polyphenols Potentiate the Action of Nerve Growth Factor to Induce Neuritogenesis: Possible Role of Reactive Oxygen Species

    OpenAIRE

    Gundimeda, Usha; McNeill, Thomas H.; Schiffman, Jason E.; Hinton, David R.; Gopalakrishna, Rayudu

    2010-01-01

    Exogenously administered nerve growth factor (NGF) repairs injured axons, but it does not cross the blood-brain barrier. Thus, agents that could potentiate the neuritogenic ability of endogenous NGF would be of great utility in treating neurological injuries. Using the PC12 cell model, here we show that unfractionated green tea polyphenols (GTPP) at low concentrations (0.1 μg/ml) potentiate the ability of low concentrations of NGF (2 ng/ml) to induce neuritogenesis at a level comparable to th...

  13. Initial stages of anodic oxidation of silver in sodium hydroxide solution studied by potential sweep voltammetry and ellipsometry

    NARCIS (Netherlands)

    Droog, J.M.M.; Alderliesten, P.T.; Bootsma, G.A.

    1979-01-01

    The first stages of the oxidation of polycrystalline silver electrodes in NaOH solutions were studied by potential sweep voltammetry and ellipsometry. Formation of bulk Ag2O was found to be preceded by dissolution of silver species and deposition of a surface oxide. The equilibrium oxide coverage de

  14. Kinetics of rate-dependent shortening of action potential duration in guinea-pig ventricle; effects of IK1 and IKr blockade.

    Science.gov (United States)

    Williams, B A; Dickenson, D R; Beatch, G N

    1999-03-01

    1. The kinetics of shortening of action potential duration (APD) following an increase in pacing rate, from 2 to 3.3 Hz, was characterized in guinea-pig ventricular preparations. Terikalant (RP62719), an inhibitor of the inwardly rectifying K+ current (IK1), and dofetilide, a specific inhibitor of the rapidly activating delayed-rectifier current (IKr), were applied to determine the effect of inhibition of these ion currents on slow APD shortening. 2. Action potentials were recorded from isolated guinea-pig ventricular myocytes using the perforated-patch patch-clamp technique, and monophasic action potentials were recorded from Langendorff-perfused guinea-pig ventricles using a contact epicardial probe. 3. Under control conditions, after an increase in pacing rate, APD immediately decreased, and then shortened slowly with an exponential time course. In ventricular myocytes, the time constant of this exponential shortening was 28+/-4 s and the amount of slow shortening was 21.9+/-0.9 ms (n=8) for an increase in rate from 2 to 3.3 Hz. Similar values were observed in Langendorff-perfused ventricles. 4. Terikalant dose-dependently increased APD and the increase was enhanced by rapid pacing ('positive' rate-dependence). The drug dose-dependently decreased the time constant of shortening and amount of slow APD shortening. In contrast, dofetilide, an inhibitor of IKr, which shows 'reverse' rate-dependent APD widening, had no significant effect on the time constant or amount of slow shortening. 5. These observations suggest that IK1 plays a role in rate-dependent shortening of APD. The results appear to support the hypothesis that 'reverse' rate-dependent effects of IKr blockers are due to these drugs not affecting the ion current(s) mediating intrinsic rate-dependent slow shortening of APD.

  15. Kv4 potassium channel subunits control action potential repolarization and frequency-dependent broadening in rat hippocampal CA1 pyramidal neurones.

    Science.gov (United States)

    Kim, Jinhyun; Wei, Dong-Sheng; Hoffman, Dax A

    2005-11-15

    A-type potassium channels regulate neuronal firing frequency and the back-propagation of action potentials (APs) into dendrites of hippocampal CA1 pyramidal neurones. Recent molecular cloning studies have found several families of voltage-gated K(+) channel genes expressed in the mammalian brain. At present, information regarding the relationship between the protein products of these genes and the various neuronal functions performed by voltage-gated K(+) channels is lacking. Here we used a combination of molecular, electrophysiological and imaging techniques to show that one such gene, Kv4.2, controls AP half-width, frequency-dependent AP broadening and dendritic action potential propagation. Using a modified Sindbis virus, we expressed either the enhanced green fluorescence protein (EGFP)-tagged Kv4.2 or an EGFP-tagged dominant negative mutant of Kv4.2 (Kv4.2g(W362F)) in CA1 pyramidal neurones of organotypic slice cultures. Neurones expressing Kv4.2g(W362F) displayed broader action potentials with an increase in frequency-dependent AP broadening during a train compared with control neurones. In addition, Ca(2)(+) imaging of Kv4.2g(W362F) expressing dendrites revealed enhanced AP back-propagation compared to control neurones. Conversely, neurones expressing an increased A-type current through overexpression of Kv4.2 displayed narrower APs with less frequency dependent broadening and decreased dendritic propagation. These results point to Kv4.2 as the major contributor to the A-current in hippocampal CA1 neurones and suggest a prominent role for Kv4.2 in regulating AP shape and dendritic signalling. As Ca(2)(+) influx occurs primarily during AP repolarization, Kv4.2 activity can regulate cellular processes involving Ca(2)(+)-dependent second messenger cascades such as gene expression and synaptic plasticity.

  16. Determination of thermodynamic potentials and the aggregation number for micelles with the mass-action model by isothermal titration calorimetry

    DEFF Research Database (Denmark)

    Olesen, Niels Erik; Westh, Peter; Holm, René

    2015-01-01

    The aggregation number (n), thermodynamic potentials (ΔG, ΔH, ΔS) and critical micelle concentration (CMC) for 6 natural bile salts were determined on the basis of both original and previously published isothermal titration calorimetry (ITC) data. Different procedures to estimate parameters...

  17. Simple way of determining the dependence of the Hamiltonian on the action variable for certain one-dimensional potentials

    Science.gov (United States)

    Susskind, S. M.

    1986-07-01

    By further developing an idea found in Goldstein's book Classical Mechanics together with a trivial generalization of the virial theorem, an alternative and simple perturbative procedure for obtaining H=H(J) for certain one-dimensional potentials is presented. The anharmonic oscillator and the Stark effect for hydrogen, both in one dimension, are given as examples of the method.

  18. Kv2 Channel Regulation of Action Potential Repolarization and Firing Patterns in Superior Cervical Ganglion Neurons and Hippocampal CA1 Pyramidal Neurons

    OpenAIRE

    Liu, Pin W.; Bean, Bruce P.

    2014-01-01

    Kv2 family “delayed-rectifier” potassium channels are widely expressed in mammalian neurons. Kv2 channels activate relatively slowly and their contribution to action potential repolarization under physiological conditions has been unclear. We explored the function of Kv2 channels using a Kv2-selective blocker, Guangxitoxin-1E (GxTX-1E). Using acutely isolated neurons, mixed voltage-clamp and current-clamp experiments were done at 37°C to study the physiological kinetics of channel gating and ...

  19. Design and application of measuring system of evoked compound action potential%诱发动作电位测量系统的设计与应用

    Institute of Scientific and Technical Information of China (English)

    孟丽; 李平; 訾蕊; 费兴波

    2015-01-01

    目的:为获得电信号刺激神经纤维时的动作电位,本文设计了一种电诱发复合动作电位测量系统,解决了诱发动作电位的精确采集问题,有效去除了本底噪声的影响。方法分析了范围在十几微伏的电诱发复合动作电位到几十毫伏电极电位测量时存在的难点,以及一个测量系统正常工作时需要满足的测量放大器共模容限和差模容限及电流源电压容限问题。基于此,本文提出采用3级运算放大器级联的方式实现诱发动作电位的采集。系统主要由3级级联放大器、自动零点调整环节和基准电压部分组成,实现对弱信号的放大、消除本底噪声和提供过压保护。结果采用本文设计的系统,测量得到11 mV 的蛙类坐骨神经干复合动作电位和17μV 的豚鼠耳蜗电诱发复合动作电位,验证了本系统可有效测量各种诱发电位。结论采用3级放大器级联的方式和自动零点跟踪方式解决了微弱信号的有效放大和精确采集技术,为进一步研究通过电信号直接刺激神经纤维所产生的动作电位的特性提供可靠的测量手段。%Objective When the nerve fiber is stimulated by the electrical pulse,there is an evoked compound action potential which indicates the synchronism property of the nerve fiber. In order to obtain the precise action potential,a measuring system of evoked compound action potential is presented in this paper. The system can collect the compound action potential precisely and eliminate the effect of ground noise. Methods Firstly,we analyzed the difficulty in the measurement of the compound action potential which ranged from μV level to the mV level. Secondly,we discussed the common-mode tolerance,differential mode tolerance and the voltage margin of the electric current which guaranteed the proper functioning of the measuring system. Based on the issues,we proposed a measuring system of compound action

  20. A Carbohydrate Fraction, AIP1, from Artemisia Iwayomogi Reduces the Action Potential Duration by Activation of Rapidly Activating Delayed Rectifier K+ Channels in Rabbit Ventricular Myocytes

    OpenAIRE

    Park, Won Sun; Son, Youn Kyoung; Ko, Eun A.; Choi, Seong Woo; Kim, Nari; Choi, Tae-Hoon; Youn, Hyun Joo; Jo, Su-Hyun; Hong, Da Hye; Han, Jin

    2010-01-01

    We investigated the effects of a hot-water extract of Artemisia iwayomogi, a plant belonging to family Compositae, on cardiac ventricular delayed rectifier K+ current (IK) using the patch clamp technique. The carbohydrate fraction AIP1 dose-dependently increased the heart rate with an apparent EC50 value of 56.1±5.5 µg/ml. Application of AIP1 reduced the action potential duration (APD) in concentration-dependent fashion by activating IK without significantly altering the resting membrane pote...

  1. Anion-selective channelrhodopsin expressed in neuronal cell culture and in vivo in murine brain: Light-induced inhibition of generation of action potentials.

    Science.gov (United States)

    Dolgikh, D A; Malyshev, A Yu; Salozhin, S V; Nekrasova, O V; Petrovskaya, L E; Roshchin, M V; Borodinova, A A; Feldman, T B; Balaban, P M; Kirpichnikov, M P; Ostrovsky, M A

    2015-01-01

    Anionic channelrhodopsin slow ChloC was expressed in the culture of nerve cells and in vivo in mouse brain. We demonstrated ability of slow ChloC to suppress effectively the activity of the neuron in response to the illumination with the visible light. It has been shown for a first time that slow ChloC works equally efficiently in both neuronal culture and in the whole brain being expressed in vivo. Thus, slow ChloC could be considered as an effective optogenetic tool capable in response to light stimulation to inhibit the generation of action potentials in the neuron.

  2. Effect of initiation-inhibition and handedness on the patterns of the P50 event-related potential component: a low resolution electromagnetic tomography study

    Directory of Open Access Journals (Sweden)

    Capsalis Christos N

    2009-12-01

    Full Text Available Abstract Background Recent research recognizes the association between handedness, linguistic processes and cerebral networks subserving executive functioning, but the nature of this association remains unclear. Since the P50 event related potential (ERP is considered to reflect thalamocortical processes in association with working memory (WM operation the present study focuses on P50 patterns elicited during the performance of a linguistic related executive functioning test in right- and left-handers. Methods In 64 young adults with a high educational level (33 left-handed the P50 event-related potential was recorded while performing the initiation and inhibition condition of a modified version of the Hayling Sentence Completion test adjusted to induce WM. The manual preference of the participants was evaluated with the use of the Edinburgh Handedness Inventory (EHI. Results P50 showed greater amplitudes in left- than in right-handers, mainly in frontal leads, in the initiation condition. Reduced amplitudes in inhibition compared to initiation condition were observed in left-handers. Low Resolution Electromagnetic Tomography (LORETA analysis showed lower frontal lobe activation in the inhibition than in the initiation condition in both right- and left-handers. Also, LORETA yielded