purpose. Tetraphenylphosphonium (TPP+) is a permeant lipophilic cation that accumulates in cultured cells and tissues as a function of the electrical membrane potential across the plasma membrane. This study was undertaken to determine whether TPP+ can be used for assessing membrane potential in intact lenses in organ culture.. methods. Rat lenses were cultured in media containing 10 μM TPP+ and a tracer level of 3H-TPP+ for various times. 3H-TPP+ levels in whole lenses or dissected portions of lenses were determined by liquid scintillation counting. Ionophores, transport inhibitors, and neurotransmitters were also added to investigate their effects on TPP+ uptake.. results. Incubation of lenses in low-K+ balanced salt solution and TC-199 medium, containing physiological concentrations of Na+ and K+, led to a biphasic accumulation of TPP+ in the lens that approached equilibrium by 12 to 16 hours of culture. The TPP+ equilibrated within 1 hour in the epithelium but penetrated more slowly into ...
Ceballos, Cesar C., Antonio C. Roque, and Ricardo M. Leão. A negative slope conductance of the persistent sodium current prolongs subthreshold depolarizations. Biophysical journal 113.10 (2017): 2207-2217.
TY - JOUR. T1 - Sex differences in membrane potential in the intact perfused rat liver. AU - Weisiger, R. A.. AU - Fitz, J. G.. PY - 1988. Y1 - 1988. N2 - The electrical potential difference across the plasma membrane was compared in paired livers from male and female rats perfused single-pass with Krebs-bicarbonate buffer. Variability in the membrane potential measured for different cells within the same liver was small (SD = 1.3 mV). The mean membrane potential was 5.1 mV more negative for male livers than for female livers (-30.3 ± 0.6 vs. -25.2 ± 1.0 mV, P , 0.001), and the female liver in all nine pairs studied. No correlation between membrane potential and perfusion rate was seen. Variability among female livers was more than twice as great (range -19.6 to -30.0 mV) as for male livers (range -26.7 to -31.9 mV). These results suggest that hepatic membrane potential may be modulated by sex hormone levels, which are more variable in female animals. Because the hepatic uptake of bile acids ...
can be generated along the axon while the threshold potential is reached. The greater the strength of the stimulus, causing the membrane depolarisation process to occur. Subsequently, some [[Sodium_voltage-gated_ion_channels,voltage-gated Na,sup,+,/sup, channels]] are opened, allowing the [[Sodium,Na,sup,+,/sup,]] ions to move across the membrane into the intracellular environment. The neuronal membrane now becomes slightly positive, relative to the outside of membrane. As the membrane potential shift from -70 mV to more positive value, the threshold potential is reached, causing all of the voltage-gated Na+ channel to open, creating a rapid rise of membrane potential value into the maximum, +60 mV. During depolarisation, the membrane potential value would not exceed the amount of +60mV as it is the equilibrium potential of Na,sup,+,/sup, ,ref,http://people.eku.edu/ritchisong/301notes2.htm,/ref ...
Peak current‐voltage relationships for ICa,L in fetal ventricular cardiomyocytes. WT calmodulin data are repeated in each panel for clarity of presentation. N
Electrical activity of enzymatically isolated, smooth muscle cells from hog carotid arteries was recorded under current clamp and voltage clamp. Under the experimental conditions, membrane potential usually was not stable, and spontaneous hyperpolarizing transients of approximately 100-msec duration were recorded. The amplitude of the transients was markedly voltage dependent and ranged from about 20 mV at a membrane potential of 0 mV to undetectable at membrane potentials negative to -60 mV. Under voltage clamp, transient outward currents displayed a similar voltage dependency. These fluctuations reflect a K+ current; they were abolished by 10 mM tetraethylammonium chloride, a K+ channel blocker, and the current fluctuations reversed direction in high extracellular K+ concentration. Modulators of intracellular Ca2+ concentration also affected electrical activity. Lowering intracellular Ca2+ concentration by addition of 10 mM EGTA to the pipette solution or suppressing sarcoplasmic reticulum ...
Short muscle fibers (less than 1.5 mm) from the m. lumbricalis IV digiti of Rana pipiens were voltage-clamped at -100 mV with a two-microelectrode technique, in normal Ringers solution containing 10(-6) g/ml tetrodotoxin. The activation curve relating peak tension to membrane potential could be shifted toward more negative or less negative potential values by hyperpolarizing or depolarizing the fiber membrane to -130, -120, or -70 mV, respectively, which indicates that contractile threshold depends on the fiber membrane potential. Long (greater than 5 s) depolarizing (90 mV) pulses induce prolonged contractile responses showing a plateau and a rapid relaxation phase similar to K contractures. Conditioning hyperpolarizations prolong the time course of these responses, while conditioning depolarizations shorten it. The shortening of the response time course, which results in a decrease of the area under the response, is dependent on the amplitude and duration of the conditioning depolarization. ...
In rat mesenteric arteries, the ability of ACh to evoke hyperpolarization of smooth muscle cells and consummate dilatation relies on an increase in endothelial cell cytosolic free [Ca2+] and activation of Ca2+-activated K+ channels (KCa). The time course of average and spatially organized rises in endothelial cell [Ca2+]i and concomitant effects on membrane potential were investigated in individual cells of pressurized arteries and isolated sheets of native cells stimulated with ACh. In both cases, ACh stimulated a sustained and oscillating rise in endothelial cell [Ca2+]i. Overall, the oscillations remained asynchronous between cells, yet occasionally localized intercellular coordination became evident. In pressurized arteries, repetitive waves of Ca2+ moved longitudinally across endothelial cells, and depended on Ca2+-store refilling. The rise in endothelial cell Ca2+ was associated with sustained hyperpolarization of endothelial cells in both preparations. This hyperpolarization was also evident when
Coupled interactions among solute diffusions, membrane surface potentials, and opposing enzyme reactions as a mechanism for active transports performed with biomimetic membranes
It plots for me Hodgkin-Huxley activation and inactivation curves. A little explanation: The Hodgkin-Huxley formalism is a way to describe how neurons transmit signals. Neurons transmit signals by electric impulses. There is always a voltage difference between the interior and the exterior of the cell(called membrane potential). If i change this potential somewhere, this temporary change will spread across the cells surface, like a wave. The mechanisms responsible for this process are molecules in the cell membrane(called ion channels), which can open to let ions flow trough, which causes change in the membrane potential. There are tons of different ion channels, but most of them can be described with the Hodgkin-Huxley formalism. These curves describe how much will be these channels open ( 0-closed; 1-fully open) at different membrane potential values. To make things more complicated each ion channel is modeled by 2 curves (activation and inactivation) and the product at a current membrane ...
It plots for me Hodgkin-Huxley activation and inactivation curves. A little explanation: The Hodgkin-Huxley formalism is a way to describe how neurons transmit signals. Neurons transmit signals by electric impulses. There is always a voltage difference between the interior and the exterior of the cell(called membrane potential). If i change this potential somewhere, this temporary change will spread across the cells surface, like a wave. The mechanisms responsible for this process are molecules in the cell membrane(called ion channels), which can open to let ions flow trough, which causes change in the membrane potential. There are tons of different ion channels, but most of them can be described with the Hodgkin-Huxley formalism. These curves describe how much will be these channels open ( 0-closed; 1-fully open) at different membrane potential values. To make things more complicated each ion channel is modeled by 2 curves (activation and inactivation) and the product at a current membrane ...
The modeling of particle transport involves anomalous diffusion, (x²(t) ) ∝ t{sup α} with α ≠ 1, with subdiffusive transport corresponding to 0 , α , 1 and superdiffusive transport to α , 1. These anomalies give rise to fractional advection-dispersion equations with memory in space and time. The usual Boltzmann equation, with only isolated binary collisions, is Markovian and, in particular, the contributions of the three-particle distribution function are neglected. We show that the inclusion of higher-order distribution functions give rise to an exact, non-Markovian Boltzmann equation with resulting transport equations for mass, momentum, and kinetic energy with memory in both time and space. The two- and the three-particle distribution functions are considered under the assumption that the two- and the three-particle correlation functions are translationally invariant that allows us to obtain advection-dispersion equations for modeling transport in terms of spatial and temporal ...
1. A method is described that enables the calculation of resting membrane potential from the electrolyte and water contents in blood plasma and in a sample of human muscle tissue obtained by the percutaneous needle-biopsy technique. In this calculation, the previously described equations for calculating resting membrane potential via the intra- and extra-cellular distribution of chloride were combined with the equation utilizing potassium distribution over the cell membrane.. 2. The method of calculation was applied to 60 healthy subjects divided into three groups aged 19-40, 41-60 and 61-85 years. The calculated resting membrane potential in the subjects as a whole was −88.4 mV (SD 1.35; n = 60). A lower value was observed in the group aged 61-85 years (−87.7 mV, SD 1.0; n = 12) than in the group aged 19-40 years (−88.6 mV; SD 1.4; n = 32). No difference was observed between female and male subjects.. 3. The RMP calculated with the present method in 60 healthy subjects was also compared ...
Under the voltage clamp condition, the K inactivation was analyzed in cells bathed in the isosmotic KCl Lophius-Ringer solution. After conditioning hyperpolarization, the cells respond to depolarizations with increased K permeability, which in turn is decreased during maintained depolarizations. The steady-state levels of the K inactivation as a function of the membrane potential are related by an S-shaped curve similar to that which describes the steady-state Na inactivation in the squid giant axon. TEA reduced the K conductance by a factor which is independent of the potential, and without a shift of the inactivation curve along the voltage axis. The rapid phase of the K activation is less susceptible to TEA than the slow phase of the K activation. Hyperpolarizing steps remove the K inactivation, the rate of the removal being faster the larger the hyperpolarization from the standard potential of about -60 mv.. ...
But this polarity is not static; it is actually a very tenuous thing. With respect to which, it is of utmost importance to realize that this polarity is not the result of the asymmetry or lopsideness of the arrangement of its atoms (if that was the case then its polarity really would be static--this being the biggest mistake conventional theorists are making). Rather this polarity is the result of the asymmetry or lopsideness of its electrical gradients, what I refer to hereafter as the H2O molecules intrinsic electrical gradients. And this is especially important with repect to the fact that when an H2O molecule makes hydrogen bonds with adjacent H2O molecules additional electrical gradients are brought into play from this adjacent H2O molecule. And these additional electrical gradients, what I will refer to hereafter as incidental (or you could use external rather than incidental) electrical gradients, oppose or neutralize the H2O molecules intrinsic electrical gradients. The net effect ...
Voltage-gated n-type K(V) and Ca(2+)-activated K+ [K(Ca)] channels were studied in cell-attached patches of activated human T lymphocytes. The single-channel conductance of the K(V) channel near the resting membrane potential (Vm) was 10 pS with low K+ solution in the pipette, and 33 pS with high K+ solution in the pipette. With high K+ pipette solution, the channel showed inward rectification at positive potentials. K(V) channels in cell-attached patches of T lymphocytes inactivated more slowly than K(V) channels in the whole-cell configuration. In intact cells, steady state inactivation at the resting membrane potential was incomplete, and the threshold for activation was close to Vm. This indicates that the K(V) channel is active in the physiological Vm range. An accurate, quantitative measure for Vm was obtained from the reversal potential of the K(V) current evoked by ramp stimulation in cell-attached patches, with high K+ solution in the pipette. This method yielded an average resting Vm ...
Gonadotropin Inhibitory Hormone (GnIH) expressing neurons, through projections and interactions with gonadotropin releasing hormone (GnRH)-expressing and POMC-expressing neurons in the arcuate nucleus of the hypothalamus are suggested to serve as a fulcrum for neuroendocrine regulation of reproduction and appetite. Relatively little is known of the intrinsic membrane and extrinsic synaptic mechanisms regulating activity of GnIH neurons. Here, using the whole-cell patch clamp technique, the electrophysiological and pharmacological profile of GFP-labelled GnIH neurons has been investigated in rats in vitro.. Whole-cell recordings were obtained from 35 GnIH-GFP expressing neurons of the rat dorsomedial hypothalamus (DMH). Passive membrane properties included a mean resting membrane potential, firing rate and input resistance of 39.3 ± 0.7 mV, 0.94 ± 0.18 Hz and 1489 ± 98 mΩ, respectively. DMH GnIH neurons expressed: a 4-AP-sensitive transient outward rectification in 91% neurons; a ...
Kretzberg J, Warzecha AK, Egelhaaf M JOURNAL OF COMPUTATIONAL NEUROSCIENCE 11 (2): 153-164 2001 The neural encoding of sensory stimuli is usually investigated for spike responses, although many neurons are known to convey information by graded membrane potential changes. We compare by model simulations how well different dynamical stimuli can be discriminated on the basis of spiking or graded responses. Although a continuously varying membrane potential contains more information than binary spike trains, we find situations where different stimuli can be better discriminated on the basis of spike responses than on the basis of graded responses. Spikes can be superior to graded membrane potential fluctuations if spikes sharpen the temporal structure of neuronal responses by amplifying fast transients of the membrane potential. Such fast membrane potential changes can be induced deterministically by the stimulus or can be due to membrane potential noise that is influenced in its statistical ...
Intracellular recordings were obtained from rat neocortical neurons in vitro. The current-voltage-relationship of the neuronal membrane was investigated using current- and single-electrode-voltage-clamp techniques. Within the potential range up to 25 mV positive to the resting membrane potential (RMP: -75 to -80 mV) the steady state slope resistance increased with depolarization (i.e. steady state inward rectification in depolarizing direction). Replacement of extracellular NaCl with an equimolar amount of choline chloride resulted in the conversion of the steady state inward rectification to an outward rectification, suggesting the presence of a voltage-dependent, persistent sodium current which generated the steady state inward rectification of these neurons. Intracellularly injected outward current pulses with just subthreshold intensities elicited a transient depolarizing potential which invariably triggered the first action potential upon an increase in current strength. ...
TY - JOUR. T1 - Effect of the non-linear membrane potential on the migration of ionic species in concrete. AU - Marriaga, J.L.. AU - Claisse, Peter A.. PY - 2008/11. Y1 - 2008/11. KW - Concrete. KW - Electromigration. KW - Chloride modelling. KW - Membrane potential. KW - Ion transport. U2 - 10.1016/j.electacta.2008.11.031. DO - 10.1016/j.electacta.2008.11.031. M3 - Article. VL - 54. SP - 2761. EP - 2769. JO - Electrochimica Acta. JF - Electrochimica Acta. SN - 0013-4686. IS - 10. ER - ...
TY - JOUR. T1 - Spike-Threshold Adaptation Predicted by Membrane Potential Dynamics In Vivo. AU - Fontaine, Bertrand. AU - Pena, Jose L.. AU - Brette, Romain. PY - 2014. Y1 - 2014. N2 - Neurons encode information in sequences of spikes, which are triggered when their membrane potential crosses a threshold. In vivo, the spiking threshold displays large variability suggesting that threshold dynamics have a profound influence on how the combined input of a neuron is encoded in the spiking. Threshold variability could be explained by adaptation to the membrane potential. However, it could also be the case that most threshold variability reflects noise and processes other than threshold adaptation. Here, we investigated threshold variation in auditory neurons responses recorded in vivo in barn owls. We found that spike threshold is quantitatively predicted by a model in which the threshold adapts, tracking the membrane potential at a short timescale. As a result, in these neurons, slow voltage ...
The voltage across a cell membrane is known as the cell membrane potential. Cells that generally have cell membrane potentials are nerve cells that are electrically active....
View Notes - 7 Membrane Potential from KINESIOLOG 1Y03 at McMaster University. Membrane Potential Membrane Potential -1 Two Types of Ion Channels Leakage (nongated) channels always open Gated
Ang II elicited a relatively small inward current (9.7 pA on average in response to 1 μmol/L peptide). However, because of the high input resistance of the cells (0.8 to 0.9 GΩ), this current is sufficient to produce the 7- to 8-mV depolarization consistently observed in current-clamp experiments. Because the cells are slowly active at rest, a depolarization of this magnitude leads to a substantial increase in discharge rate (250% of control). The depolarization (current clamp) or inward current (voltage clamp at −40 to −55 mV) was associated with a decrease in membrane conductance. This reduction of conductance is likely due to closure of K+ channels for the following reasons: First, in the presence of 3.8 mmol/L [K+]o, the current elicited by Ang II reversed polarity very close to EK (Erev, −89 mV; Fig 8A⇑), suggesting that it was carried selectively by K+. Second, raising [K+]o to 10 mmol/L shifted the Erev of the Ang II-induced current to between −60 and −68 mV, a shift that is ...
Manual patch clamp assays: Ionic current measurements. Request a Study Outline from IPST. Whole-cell current amplitude and kinetics measurements verify the results of the interaction of a test article with a selected ionic current. (The popular hERG assay is an example of ionic current assay, saimed specifically at the well-known hERG channel.) The assay is generally used to elucidate the mechanism behind various ion-channel-related arrhythmic events, and uncover ion current inhibition, either as a primary or secondary pharmacology manifestation.. A typical patch clamp study involves a pulse protocol whereby a patched cell is held at an interpulse low enough to prevent the channels from activating/opening. Generally, activation requires a depolarization to a threshold potential. Increasing voltage pulses are applied to the cell and when the voltage applied approaches, and eventually reaches that threshold potential, the current measures across the cell increases as more and more of the ...
In short, since the 1940s a dedicated slew of people have been trying different approaches to solve that equation with a precision that is unheard of in other areas of physics and engineering. All this in the name of shielding us from harmful radiation. This is all good, but why are we having this discussion in the context of synthesis and analysis based reconstructions ? It turns out that the freaks have looked at the Linear Boltzmann Equation through **many** angles. One of these angles is to decompose the flux in some eigenfunctions of the Linear Transport Operator (they are in fact distributions). There are some completude results for 1-D but 2D or 3-D are still really unexplored and not really well understood. Anyway, what was noticed empirically is that solution fluxes always end up following a diffusion equation a few mean free path away from the boundaries or sources. Close to the boundaries or sources, the full transport solution needs those eigendistributions expansions. While you may ...
The reverse use-dependence observed with GLG-V-13 and KMC-IV-84 in the present experiments has been previously reported for methanesulfonalide class III drugs such as dofetilide (Gwilt et al., 1991;Jurkiewicz and Sanguinetti, 1993), E-4031 (Wettwer et al., 1991), d,l-sotalol (Strauss et al., 1970; Hafneret al., 1988), MK-499 (Baskin and Lynch, 1994; Krafte and Volberg, 1994) and sematilide (Krafte and Volberg, 1994). The actual mechanism(s) for reverse use-dependence is/are controversial. The earliest mechanism for reverse use-dependence of action potential duration was advanced by Hondeghem and Snyders (1990). Experimental data from their laboratory demonstrated a time- and voltage-dependent modulation of Ik with quinidine. Quinidine primarily reduced time-dependent outward potassium currents at negative membrane potentials, with blockade of outward potassium currents becoming less pronounced with depolarization (Roden et al., 1988). Later data, however, have failed to demonstrate a similar ...
The results demonstrate that dendritic NMDA spike/plateau potentials can be evoked in TC neurons by local glutamate stimulation on a single dendritic arbor. The potentials had similar electrophysiological and pharmacological properties as NMDA spike/plateau potentials in cortical pyramidal neurons (Schiller et al., 2000; Nevian et al., 2007; Major et al., 2008; Larkum et al., 2009). Weak stimulation elicited a small-amplitude, EPSP-like potential at soma that gradually grew in amplitude with increasing stimulus intensity to a threshold where a marked increase of amplitude was elicited indicating a spike-like potential. Further increase caused an elongation of the potential into a plateau that could last up to several hundred milliseconds. The spike/plateau potentials were selectively blocked by the NMDA-R antagonist CPP. The Ca2+ channel blockers Cd2+, Ni2+ and nimodipine, and the Na+ channel blocker TTX had only minor effects. Even at hyperpolarized membrane potentials (−70 mV or −65 mV), ...
Kv2.1 protein is expressed in female and male arterial myocytes, where its assumed functional role has been as a voltage-gated ion channel that, upon opening, hyperpolarizes the membrane potential of these cells to impact myocyte [Ca2+]i and myogenic tone (16). Here, we propose a model in which Kv2.1 channels have a more complex function to exert opposing actions on vascular smooth muscle. In its canonical role, the opening of conducting Kv2.1 hyperpolarizes arterial myocytes, which decreases the Po of CaV1.2 channels. This lowers [Ca2+]i, inducing relaxation. Our data indicate that Kv2.1 protein has an additional nonconducting structural role in arterial myocytes: to enhance CaV1.2 clustering and activity, thereby increasing [Ca2+]i and inducing contraction. It is paradoxical that Kv2.1 could control both relaxation and contraction in arterial smooth muscle. Notably, we find that the relative contribution of the electrical and structural roles of Kv2.1 to the control of membrane potential and ...
1. 1. ACh dose-response curves for the radular retractor muscle of Buccinum showed maximum force and membrane depolarisation of 3.3 mV at 50 μmol 1−1 ACh. 2. 2. PCh was found to be almost a full agonist for force and induced higher membrane depolarisations than ACh while BCh was only a partial agonist of very low potency. This suggests an AChR neither muscarinic nor nicotinic in mammalian terminology. 3. 3. Neither muscarine nor nicotine had any direct agonistic effects on the muscle but pre-exposure to nicotine inhibited both force and membrane depolarisation induced by a subsequent dose of ACh. 4. 4. The specific muscarinic and nicotinic antagonists atropine, d-tubocurarine and gallamine all inhibited ACh responses in a dose-dependent manner. 5. 5. Single sucrose-gap recording showed that ACh induced a depolarisation resulting in a contracture. Double sucrose-gap voltage clamp recording showed that 10 μmol 1−1 ACh induced an inward transmembrane current of ca 2 μA. Both ACh-induced ...
All living cells display a difference in electrical potential between their cytoplasm and the extracellular space. This difference in potential across the plasma membrane, commonly referred to as membrane potential, not only constitutes a signal of life, but it also constitutes a source of energy for the translocation of many kinds of molecules in and out of the intracellular space. Changes in the membrane potential are related to a number of cellular events ranging from development to rapid electrical signaling in excitable tissues. For decades, the realm of cellular electrical activity has been limited to the action of ion channels and ionotropic ATPases and transporters. Indeed, the main molecular entities responsible for rapid signaling, such as action potentials and synaptic activity, have been identified. Yet, identification of the link between electrical activity at the plasma membrane and cell proliferation, differentiation and migration remains elusive. The quest to identify this link reached a
For a nerve cell at its resting potential, the forces acting on potassium ions (K+) are: an electrical gradient, pulling K+ inward and a chemical gradient, pushing K+ outward. Suppose a cells membrane potential shifts from -move -numb. What changes in the cells permeability to K+ or An+ could cause a shift? An+ depopulating here. So we bring An+ ions into the cell. So to do this, you change membrane permeability by adding more An+ ion channels. To fill in and label the diagram.. Tell what the flow of potassium and sodium. Label Membrane potential (NV), Resting potential, Action potential, time mess. Explain deportation. Rising potential-more An going into the cell. Falling- Undershoot= potassium ion channels are still inactivated. So they would fall below the resting potential. Graded response vs. action potential-action potential is independent of the stimulus. Graded response potential is everything below the threshold. Things to know: what the threshold is. Intervention-more in the ...
Instantaneous current-voltage relations for α1G channels. (A) Sample current records, with 5 kHz Gaussian filtering, from cell e8612. The initial step to +60
Protocols for antitachycardial pacing including biphasic stimulation administered at, or just above, the diastolic depolarization threshold potential; biphasic or conventional stimulation initiated at, or just above, the diastolic depolarization threshold potential, reduced, upon capture, to below threshold; and biphasic or conventional stimulation administered at a level set just below the diastolic depolarization threshold potential. These protocols result in reliable cardiac capture with a lower stimulation level, thereby causing less damage to the heart, extending battery life, causing less pain to the patient and having greater therapeutic effectiveness. In those protocols using biphasic cardiac pacing, a first and second stimulation phase is administered. The first stimulation phase has a predefined polarity, amplitude and duration. The second stimulation phase also has a predefined polarity, amplitude and duration. The two phases are applied sequentially. Contrary to current thought, anodal
It is present in the plasma membrane. It is powered by ATP. It keeps the concentrations of Na and K ions constant on the two side of the membrane. The pump actively move Na+ ions outside of the cell. It pumps K ions inside of the cell. It moves three Na+ out for each two K+moves inside. Thus this pump establishes resting potential across the membrane. Both ions also leak back across the membrane. But K+ move more easily back to the outside. It adds to the positive charge there. Thus membrane potential of -70mV is established ...
The first step in the generation of an action potential is to depolarize the cell by injecting current into the axon. This will partially depolarize the cell membrane, causing it to become less negative and this change in membrane potential triggers voltage gated Na+ to open. Na+ ions are now free to pass through this channel, resulting in a relatively massive influx of Na+ inside the axon. Since the membrane is now overwhelmingly permeable to Na+ the membrane potential at the top of the spike will be driven close to the Na+ Nernst potential of 55+mV. Voltage gated K+ channels also open as a response to depolarization but they only do so after the opening of the Na+ channels allowing a relatively large amount of K+ to leave the axon. As the voltage gated K+ channels open, the voltage gated Na+ channels now close preventing additional Na+ from entering the axon. So much positive charged K+ leaves the axon under these conditions that the membrane potential temporarily becomes hyperpolarized at a ...
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Cells are surrounded by a plasma membrane, which defines their extent and acts as a barrier between the cells and their external environment, for example interstitial fluid or blood plasma. The membrane, as a result of its lipid bilayer structure and specific membrane proteins, is selectively permeable (the hydrophobic interior prevents the passage of both large polar molecules and ions) and therefore will only allow certain species through. This selective permeability allows asymmetric concentrations of ions to exist between the intra- and extracellular fluids. These differences can be chemical or electrical (i.e. the difference in charge between the inside and outside). Most cells maintain a membrane potential of around 80mV relative to the surrounding fluid. The membrane potential is negative because usually cells have a net negative charge due to leakiness of potassium channels and the large size of negatively charged macromolecules such as proteins and RNA. In animal cells, passive ion ...
The body wall muscles in Drosophila larvae are suitable for voltage clamp analysis of changes in membrane excitability caused by mutations. Both inward and outward ionic currents are present in these muscle fibers. The inward current is mediated by voltage-dependent Ca2+ channels. In Ca2+-free saline, the inward current is eliminated. The remaining outward K+ currents consist of two distinct components, an early transient IA and a delayed steady IK, which are separable by differences in the rate and voltage dependence of activation and inactivation. The steady-state and kinetic properties of the activation and inactivation processes of these two currents are analyzed. The results provide a basis for quantitative analysis of altered membrane currents in behavioral mutants of Drosophila. Previous studies indicate that mutations in the Shaker (Sh) locus alter excitability in both nerve and muscle in Drosophila. Our results support the idea that the channels mediating IA are molecularly distinct ...
I agree that this is correct in the classical limit. However in http://disciplinas.stoa.usp.br/pluginfile.php/48089/course/section/16461/qsp_chapter10-plank.pdf the complete planck law is derived by assuming that the probability that a single mode is in a state of energy E=nhν (a state of n photons) is given by a Boltzmann distribution. Hence, the derivation does not consider any limit ...
View Notes - lecture_09_26 from NPB 100 at UC Davis. Resting Membrane Potential Lectures What you will learn in these lectures 1. You will learn that all cells, including neurons, have a resting
Passive properties refer to the capacitative and resistive aspects inherent in neuronal membranes, along with the resistivity inherent in the cytoplasm and the extracellular milieu. Together, these properties provide an electrical resemblance between neuronal processes (axons and dendrites) and conduction in electrical cables and hence are termed cable properties. Across this capacitive/resistive membrane an electric field and a voltage difference is maintained by the action of selective ion pumps. While the basic assumption of most electrophysiologists is that the membrane potential may be initially considered as having a resting value (the resting potential) that is uniformly distributed along neuronal compartments, this is an oversimplification, as the ionic conductances (and pumps) which are responsible for setting the resting potential need not have a fixed density throughout the neuronal membrane. Even so, isopotentiality is inherent in most initial cable property assumptions. The value of ...
Passive properties refer to the capacitative and resistive aspects inherent in neuronal membranes, along with the resistivity inherent in the cytoplasm and the extracellular milieu. Together, these properties provide an electrical resemblance between neuronal processes (axons and dendrites) and conduction in electrical cables and hence are termed cable properties. Across this capacitive/resistive membrane an electric field and a voltage difference is maintained by the action of selective ion pumps. While the basic assumption of most electrophysiologists is that the membrane potential may be initially considered as having a resting value (the resting potential) that is uniformly distributed along neuronal compartments, this is an oversimplification, as the ionic conductances (and pumps) which are responsible for setting the resting potential need not have a fixed density throughout the neuronal membrane. Even so, isopotentiality is inherent in most initial cable property assumptions. The value of ...
Inhibitory synapses release an inhibitory neurotransmitter that produces a transient hyperpolarisation called an Inhibitory Post-Synaptic Potential (IPSP). The mechanism is not dissimilar to that described above, except that the neurotransmitter acts on a different ligand-gated channel that opens the channel to potassium and/or chloride ions. The equilibrium potential of the IPSP is between -70 and -90 mV. As a result, when the membrane is already depolarised, the ion movements hyperpolarise the post-synaptic membrane. ...
Inside the cell membrane there is a well-defined environment, in which many complex biochemical processes take place. The interior of the cell differs in important respects from its outside. For example the contents of positive sodium and potassium ions and negatively charged chloride ions are quite different. This leads to a difference in electrical potential over the cell membrane, amounting to 0.03 to 0.1 volts. This is usually referred to as the membrane potential.. The cell uses the membrane potential in several ways. By rapidly opening channels for sodium ions the membrane potential is altered radically within a thousandth of a second. Cells in the nervous system communicate with each other by means of such electrical signals of around a tenth of a volt that rapidly travel along the nerve processes. When they reach the point of contact between two cells - the synapse - they induce the release of a transmitter substance. This substance affects receptors on the target cell, often by opening ...
TY - JOUR. T1 - Voltage-Dependent Inactivation of MscS Occurs Independently of the Positively Charged Residues in the Transmembrane Domain. AU - Nomura, Takeshi. AU - Sokabe, Masahiro. AU - Yoshimura, Kenjiro. PY - 2016. Y1 - 2016. N2 - MscS (mechanosensitive channel of small conductance) is ubiquitously found among bacteria and plays a major role in avoiding cell lysis upon rapid osmotic downshock. The gating of MscS is modulated by voltage, but little is known about how MscS senses membrane potential. Three arginine residues (Arg-46, Arg-54, and Arg-74) in the transmembrane (TM) domain are possible to respond to voltage judging from the MscS structure. To examine whether these residues are involved in the voltage dependence of MscS, we neutralized the charge of each residue by substituting with asparagine (R46N, R54N, and R74N). Mechanical threshold for the opening of the expressed wild-type MscS and asparagine mutants did not change with voltage in the range from -40 to +100 mV. By contrast, ...
Image Analyst MKII back-calculates mitochondrial and plasma membrane potentials in millivolts that drive changes in the fluorescence intensities.
Autor: Adams, P. R. et al.; Genre: Zeitschriftenartikel; Im Druck veröffentlicht: 1978; Titel: A comparison of current voltage relations of full and partial agonists
Smith, J.R., 1985: The electrical properties of plant cell membranes iii. the effects of insulated regions upon the cable properties and measured membrane conductance of charophytes
Video created by 杜克大学 for the course 医学神经科学. We now turn our attention from the tangible (human neuroanatomy) to the physiological as we explore the means by which neurons generate, propagate and communicate electrical signals. After exploring ...
download Noten zur Literatur of the Boltzmann Equation to Townsend Discharge. IEEJ mechanisms on Fundamentals and Materials, 95(9), 357-364. download Noten zur Literatur of the Boltzmann Equation to Townsend Discharge.
Video created by Universidade Duke for the course Neurociência Médica. We now turn our attention from the tangible (human neuroanatomy) to the physiological as we explore the means by which neurons generate, propagate and communicate electrical ...
Video created by Université Duke for the course Neurosciences médicales. We now turn our attention from the tangible (human neuroanatomy) to the physiological as we explore the means by which neurons generate, propagate and communicate ...
Video created by Duke University for the course Medical Neuroscience. We now turn our attention from the tangible (human neuroanatomy) to the physiological as we explore the means by which neurons generate, propagate and communicate electrical ...
The Nernst equation describes the equilibrium potential for a single ion, and assumes that the membrane is completely permeable to that ion.. However, calculation of membrane potential requires examining the effects of many different ions with different permeability. This can be performed with the Goldman-Hodgkin-Katz equation:. , where:. ...
Fig. 5. Proton-activated currents associated with AtMHX expression in vacuolar giant patches. (A) Patch from a vacuole of a transformed cell. Currents are activated by switching from a pH 7.7 solution to a pH 5.7 solution and back to pH 7.7. N-methyl-glucamine (NMG) is the only monovalent cation in solution. The pipette solution (pH 7.0; cytoplasmic membrane side) contains 2 mM Mg2 and 2 mM Ca2 ; the bath solution contains 0.5 mM Mg2 . (B) Typical current records for the same protocol in a vacuolar patch from a non-transformed cell. (C) Current-voltage relations for the proton-activated current in Figure 5A (2-1), whereby records were subtracted just before (1) and after (2) application of the pH 5.7 solution. In addition, the current- voltage relation is given for the reverse current observed on removing protons, whereby the subtracted records were obtained just after returning to pH 7.7 (3) and 30 s later when the current had decayed (4). (D) Current-voltage relation of the 10 times smaller current
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Figure 6. Voltage dependence of intracellular PhTx block under low Na+ conditions. (A) Macroscopic current traces recorded in an inside-out patch containing CNGA1 channels in the absence or presence of 5 µM of intracellular PhTx in symmetrical 30 mM Na+. Currents were activated with 2 mM of intracellular cGMP and elicited with the voltage protocol shown. Dotted line indicates 0 current level. (B) Fraction of current not blocked (mean ± SEM; n = 4-8) by the indicated concentrations of intracellular PhTx is plotted against membrane voltage. Curves are fits of Eq. 3 to the three datasets simultaneously with Z1 fixed at 0. The best-fit parameters were: K1 = 1.04 ± 0.03 × 10−5 M, K2 = 2.03 ± 0.14 × 10−3, and Z2 = 2.08 ± 0.04. (C) Fraction of current not blocked (mean ± SEM; n = 8) by 1 µM of intracellular PhTx in the presence of 0.02 mM (filled circles) or 2 mM (open circles; taken from B) cGMP is plotted against membrane voltage. Curves are fits of Eq. 3 to both datasets simultaneously, ...
We explain Membrane Potential with video tutorials and quizzes, using our Many Ways(TM) approach from multiple teachers.|p|This lesson will describe how the differences in concentrations of ions across a plasma membrane set the stage for a nerve impulse.|/p|
This figure shows how the membrane potential can be measured by using a special voltmeter that is electrically connected to the interior of the cell via a glass microelectrode.
S. Kuyucak and S. H. Chung. Temperature dependence of conductivity in electrolyte solutions and ionic channels of biological membrane. Biophysical Chemistry 52, 15-24, 1994.. P. W. Gage and S. H. Chung. Influence of membrane potential on conductance sublevels of chloride channels activated by GABA. Proceedings of the Royal Society, London B225, 167-172, 1994.. D. A. Saint, M. K. Pugsley and S. H. Chung. An analysis of cardiac sodium channel properties using digital signal processing techniques. Biochimica et Biophysica Acta 1196, 131-138, 1994.. L. J. Reece, S. S. Dhanjal and S. H. Chung. Zinc induces hyper-excitability in the hippocampus. Neuroreport 5, 2669-2672, 1994.. G. W. Pulford, R. A. Kennedy and S. H. Chung. Identification of individual kinetics from recordings containing many identical channels. Signal Processing 43 (No. 2), 207-221, 1995 ...
When this happens, the ion (lets suppose, potassium or K+) with a higher permeability will flow more rapidly to the other side, following its chemical gradient. The other ion (lets suppose, chloride or Cl-) will do the same, but it will flow slowlier. In this manner, after some time, there will be a higher concentration of K+ than Cl- in the right side of membrane, and a higher concentration of Cl- than of K+ in the left side. Because of this, an electrical charge appears across the membrane. Since there are more K+ inside than outside and more Cl- ions outside than inside, there will appear a negative potential outside in relation to inside. This is essentially how the resting potential is generated. Now, since there is a polarized charge of one side of the membrane in relation to the other side, ions tend to obey also their electrical gradient. Since K+ is a positive ion and is repelled by positive charges, it eventually will stop following its chemical gradient because the positive charge ...
For each ion, the equilibrium (or reversal) potential is the membrane potential where the net flow through any open channels is 0. In other words, at Erev, the chemical and electrical forces are in balance. Erev can be calculated using the Nernst equation. In mammalian neurons, the equilibrium potential for Na+ is ~+60 mV and for K+ is ~-88 mV. ...
1. Several ions are responsible for the resting membrane potential. Describe the forces that determine resting membrane potential. 2. How are graded potentials created, and how are they different from action potentials? 3.
The first EPG system - called feeding monitor - was introduced by McLean and Kinsey (1964) supplying an alternating current (AC) voltage source (Vs). This source was in fact the carrier wave of which the amplitude was modulated by resistance fluctuations of the insect. This fluctuating amplitude was processed in the same way as AM radio signals. The demodulated signal reflected exactly the resistance fluctuations of the insect. This first monitor has been called an AC system but as this AM signal was only sensitive to resistance fluctuations it can also be frerred to as an R-EPG system. Later, using a different system design with a DC voltage supply it appeared that the EPG signal also contains electromotive force (emf) originated components, i.e. fluctuating voltages at the mesuring point that are generated by the insect activities and active electrical components in the plant, mainly cell membrane potentials (Tjallingii, 1978, 1988). Similar to the carrier wave amplitude modulation in the ...
To examine this further, we subtracted the membrane potential in the soma from the membrane potential simultaneously recorded in the axon. Shown here is a plot of membrane potential difference between the axon initial segment and the soma in a layer 5 pyramidal cell during injection of noise into the soma. Note that
Using a specially designed computational tool as a lure, scientists have netted the genomic sequences of almost 12,500 previously uncharacterized viruses from public databases.
The action potenial can only occur if the threshild value has been exceeded. It hasd to be rather strong to trigger the openming of the NA channels.. If the threshod is not exceed the "ALL OR NOTHIUNG LAW" will occur. The action potenial is always the same strength. The intensity of a particular stimulus is distinguished by the frequency of teh action poptenial it initiates, & not the strength of them.. Greater no of receptors that pick up the stimulus, greater the strength of the stimulus.. Hyperpolarisation: overshoot which occurs because teh outward flow of K reaches equilibrium before the restring potenial.. Refactory period: for a millisecond repolarisation teh restijng potenial has not been restored. therefore impossible for another action potenial to occur. absolute refactory period. Important role: ensures that each wave of action potenials travels as a discrete impulse and travels in one direction only.. Relative refactory period: an action potenial can be initiated but only if the ...
Potassium, Spinal Cord, Horn, Neurons, Mouse, Muscle, Skin, Viscera, Cell, Injection, Membrane, Membrane Potential, Resting Membrane Potential, Glycine, Joints, Pain, Mice, Action Potential, Animals, Birth
There are two negative pins and one positive on the Leica M8 & M9 charger. I put a meter on them and got readings I cannot understand - yet. They vacillate wildly within different voltage ranges. Ive yet to apply the meter to a charged battery because the contacts are buried in plastic, but I will soon. Before I make an utter fool of myself, does anyone have an idea regarding the roles of the negative pins? Does one read the internal chip? Why do voltages change every second? One objective is to eventually read the internal chip to detect fake or defective batteries ...
A key challenge for establishing a phenotypic screen for neuronal excitability is measurement of membrane potential changes with high throughput and accuracy
A key challenge for establishing a phenotypic screen for neuronal excitability is measurement of membrane potential changes with high throughput and accuracy
Biology Assignment Help, Explain the donnan membrane equilibrium, Explain the Donnan Membrane Equilibrium? If one of the solutions in a two-phase membrane equilibrium contains certain charged solute species that are unable to pass through the membrane, whereas other ions can pass through, the situation is more
Simple Relay Code to control the interface described in Electrically induced bacterial membrane-potential dynamics correspond to cellular proliferation capacity. - Stratford et al. (2019). - ConorEd/ElectrodeStimulation
A plane with a point selected as an origin, some length selected as a unit of distance, and two perpendicular lines that intersect at the origin, with positive and negative direction selected on each line. Traditionally, the lines are called x (drawn from left to right, with positive direction to the right of the origin) and y (drawn from bottom to top, with positive direction upward of the origin). Coordinates of a point are determined by the distance of this point from the lines, and the signs of the coordinates are determined by whether the point is in the positive or in the negative direction from the ...
thanks for your help. so far it work great. But now I was trying to speed up the simulations by using variable time step with cvode. But i_cap is fluctuating pretty much when using this and also dvdt is behaving strange because it is not any longer a linearly scaled version of i_cap. So I tried to set the tolerance with the atolscale method but this didnt work ...
Video created by 杜克大学 for the course 人体生理学导论. We hope you are enjoying the course! Last weeks lectures can be challenging because we introduce many concepts that may be new to you. This module will allow you to apply some of the concepts that ...
Video created by Университет Дьюка for the course Введение в физиологию человека. We hope you are enjoying the course! Last weeks lectures can be challenging because we introduce many concepts that may be new to you. This module will allow you ...
Video created by Universidade Duke for the course Introdução à fisiologia humana. We hope you are enjoying the course! Last weeks lectures can be challenging because we introduce many concepts that may be new to you. This module will allow you ...
An image of a nerve impulse moving (conduction) along an axon. The membrane potential is the result of the distribution of ions across the cell membrane and the permeability of the membrane to these ions. - Stock Image F002/3215
i have a dell inspiron 1150 and i recently had to replace the power supply. i ordered it from impactcomputers.com and it has the same specs as the old one. same voltage, amps and everything. except...
Current Recording Work Instruction - Download as Word Doc (.doc), PDF File (.pdf), Text File (.txt) or read online. surveying how to current meter
At first sight, with superficial reasoning, the rectification, or correction, of a given birth time seems appropriate and necessary: We certainly do need an exact and reliable basis for any astrological interpretation. However, none of the diverse methods of rectification provides the desired safety or assurance.
At first sight, with superficial reasoning, the rectification, or correction, of a given birth time seems appropriate and necessary: We certainly do need an exact and reliable basis for any astrological interpretation. However, none of the diverse methods of rectification provides the desired safety or assurance.
Rainin Pipettes & Pipette Tips. Precision manufactured manual and electronic pipettes. Single-channel, multichannel and adjustable width models.
Specialization or cellular differenciation (please correct me if these are two different concepts) is the process by which a less specialized cell becomes a more specialized cell type, changing dramatically a cells size, shape, membrane potential, metabolic activity, and responsiveness to signals. Now, do you know how this happens? Please be as specific as possible ...
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Also, would you continue to call it maximum C-rate if the cell sagged below 1/2 resting voltage at that C-rate (normally these little feces cells just saturate the current collector and fall on their face before this happens), so that as current output increases, the amount of power youre getting from the cell is decreasing ...
TY - JOUR. T1 - Low doses of ethanol have Ca2+ ionophore-like effects on apical membrane potential of in vitro Necturus antrum. AU - Rutten, Michael. AU - Moore, C. D.. PY - 1991. Y1 - 1991. N2 - The effects of low doses of luminal ethanol on the amiloride-sensitive apical membrane potential of Necturus antral mucosa were studied using conventional microelectrode techniques. Luminal ethanol (0.250-4.0% vol/vol) caused a dose-dependent hyperpolarization of the apical membrane potential (V(mc)), an increase in transepithelial resistance (R(t)) and resistance ratio (R(a)/R(b)), and a decrease in transepithelial potential (V(ms)). Luminal amiloride (100 μM) to 4% ethanol-treated antra did not cause any additional hyperpolarization of V(mc). Compared with luminal 2% ethanol-Ringer, an equivalent osmotic mannitol solution depolarized V(mc) and basolateral potential (V(cs)), decreased R(t) and R(a)/R(b), and increased V(ms). A single dose of 0.50% ethanol attenuated the effects of a second 2% ethanol ...
Several physiological mechanisms allow sensory information to be propagated in neuronal networks. According to the conventional view of signal processing, graded changes of membrane potential at the dendrite are converted into a sequence of spikes. However, in many sensory receptors and several types of mostly invertebrate neurons, graded potential changes have a direct impact on the cells output signals. The visual system of the blowfly Calliphora vicina is a good model system to study synaptic transmission in vivo during sensory stimulation. We recorded extracellularly from an identified motion-sensitive neuron while simultaneously measuring and controlling the membrane potential of individual elements of its presynaptic input ensemble. The membrane potential in the terminals of the presynaptic neuron is composed of two components, graded membrane potential changes and action potentials. To dissociate the roles of action potentials and graded potential changes in synaptic transmission we used ...
TY - JOUR. T1 - Label-free imaging of membrane potential using membrane electromotility. AU - Oh, Seungeun. AU - Fang-Yen, Christopher. AU - Choi, Wonshik. AU - Yaqoob, Zahid. AU - Fu, Dan. AU - Park, Yongkeun. AU - Dassari, Ramachandra R.. AU - Feld, Michael S.. PY - 2012/7/3. Y1 - 2012/7/3. N2 - Electrical activity may cause observable changes in a cells structure in the absence of exogenous reporter molecules. In this work, we report a low-coherence interferometric microscopy technique that can detect an optical signal correlated with the membrane potential changes in individual mammalian cells without exogenous labels. By measuring milliradian-scale phase shifts in the transmitted light, we can detect changes in the cells membrane potential. We find that the observed optical signals are due to membrane electromotility, which causes the cells to deform in response to the membrane potential changes. We demonstrate wide-field imaging of the propagation of electrical stimuli in ...
A Ba(2+)-sensitive K(+) current was studied in neurons of the suprachiasmatic nucleus (SCN) using the whole cell patch-clamp technique in acutely prepared brain slices. This Ba(2+)-sensitive K(+) current was found in approximately 90% of the SCN neurons and was uniformly distributed across the SCN. Current-clamp studies revealed that Ba(2+) (500 microM) reversibly depolarized the membrane potential by 6.7 +/- 1.3 mV (n = 22) and concomitantly Ba(2+) induced an increase in the spontaneous firing rate of 0.8 +/- 0.2 Hz (n = 12). The Ba(2+)-evoked depolarizations did not depend on firing activity or spike dependent synaptic transmission. No significant day/night difference in the hyperpolarizing contribution to the resting membrane potential of the present Ba(2+)-sensitive current was observed. Voltage-clamp experiments showed that Ba(2+) (500 microM) reduced a fast-activating, voltage-dependent K(+) current. This current was activated at levels below firing threshold and exhibited outward ...
Membrane potential oscillations can be induced in molluscan neurones under a variety of artificial conditions. In the so-called burster neurones oscillations are generated even in isolated cells. A likely mechanism for bursting involves the following ionic currents: 1. A transient inward current carried by Na+ and Ca2+. This current is responsible for the upstroke of the action potentials. 2. A delayed outward current carried by K+. This current is voltage-sensitive and is responsible for the downstroke of the action potential during the early part of the burst. It becomes progressively inactivated during the burst. Its amplitude depends on the intracellular pH. 3. A rapidly developing outward current carried by K+ which is inactivated at potentials close to action potential threshold. This current tends to hold the membrane in the hyperpolarized state and is involved in spacing the action potentials. 4. A prolonged inward current which may not inactivate. It is probably carried by both Na+ ...
The effect has been studied of various media, hormones and of amino acids on the membrane potential of rat hepatoma cells in culture measured by microelectrode impalement. Cells in Eagles minimal essential medium plus 5% serum had a value which varied daily from about 5-8 mV, inside negative. The membrane potential of rat hepatocytes was measured to be 8.7 ± 0.2mV, inside negative. The membrane potential of the hepatoma cells was decreased by insulin and increased by glucagon. Membrane potential was unaffected by change of medium to Hanks or Earles balanced salt solutions or deprivation of serum. It was, however, reduced in cells in phosphate-buffered saline and by reduction of pH. The former effect was shown to be due to the higher [Na+] of phosphat-buffered saline as opposed to the other media. Addition of alanine, glycine, serine, proline and methylaminoisobutyrate all reduced membrane potential by 2-3 mV. Smaller decreases were seen with methionine, leucine and phenylalanine, but none ...
Using sorting protocol based on a simple staining method for mitochondrial membrane potential we were able to isolate subclones from an established monoclonal antibody production cell line with significantly altered physiological properties. The subclone sorted for lower mitochondrial membrane potential had a faster growth rate, attained higher final cell concentrations in batch cultures, had lower glucose and glutamine uptake and lactate production rates as well as a higher specific production rate. The subclone sorted for high mitochondrial membrane potential on the other hand had a lower growth rate and final cell count, increased glucose and glutamine consumption and lactate production rates. These subclones can now be used for genomic or proteomic analysis of properties that characterise a cell line with efficient or inefficient metabolism. In addition, the method described is a valuable tool for cell line development and optimisation, offering the possibility to isolate subclones with both ...
Inwardly rectifying K+ currents were studied in cut muscle fibres from frogs using the Vaseline-gap voltage-clamp method. Both faces of the membrane were exposed to 120 mM-K+ methylsulphate solution. At small negative potentials, -10 and -21 mV, the current noise spectrum, after subtraction of a control spectrum at the zero current potential, could be fitted by a Lorentzian spectral component, usually with an additional 1/f component, where f is the frequency. At more negative potentials the 1/f component predominated. The zero frequency amplitude of the Lorentzian averaged 2.6 X 10(-24) A2 Hz-1 at -10 mV and 4.6 X 10(-24) A2 Hz-1 at -21 mV, with a mean half-power frequency, fc, of 34 Hz and 45 Hz, respectively. The time constant of the K+ current activation upon hyperpolarization agrees with that calculated from fc, and the Lorentzian disappears upon replacement of external K+ by tetraethylammonium (TEA+) or Rb+. Thus, the Lorentzian component appears to be ascribable to fluctuations ...
Similar to the NMDAR, AMPARs are excitatory ionotropic glutamatergic receptors and consist of four subunits. AMPARs mediate the majority of fast excitatory synaptic transmission in the CNS and are mostly composed of two GluA1 and two GluA2 subunits. In contrast to NMDARs, there is no obligatory subunit and there is a larger variability in receptor composition (108). Importantly, the presence of GluA2 determines crucial properties of the receptor: RNA editing of the Q/R site of the GluA2 subunit modifies the pore region of the receptor so that AMPARs containing GluA2 are impermeable to Ca2+ and show a linear current-voltage relationship (109). In contrast, AMPARs without GluA2 are Ca2+ permeable, have a larger single-channel conductance, and are inwardly rectifying, as intracellular polyamines can block the channel pore at positive membrane potentials (109, 110). Patients with anti-AMPAR encephalitis harbor antibodies against either GluA1 or GluA2 subunits, resulting in a reduction of surface ...
TY - JOUR. T1 - Calcium sparklets regulate local and global calcium in murine arterial smooth muscle. AU - Amberg, Gregory C.. AU - Navedo, Manuel F.. AU - Nieves-cintrón, Madeline. AU - Molkentin, Jeffery D.. AU - Santana, Luis F.. PY - 2007/2/15. Y1 - 2007/2/15. N2 - In arterial smooth muscle, protein kinase Cα (PKCα) coerces discrete clusters of L-type Ca2+ channels to operate in a high open probability mode, resulting in subcellular domains of nearly continual Ca2+ influx called persistent Ca2+ sparklets. Our previous work suggested that steady-state Ca2+ entry into arterial myocytes, and thus global [Ca2+]i, is regulated by Ca2+ influx through clusters of L-type Ca2+ channels operating in this persistently active mode in addition to openings of solitary channels functioning in a low-activity mode. Here, we provide the first direct evidence supporting this Ca2+ sparklet model of Ca2+ influx at a physiological membrane potential and external Ca2+ concentration. In support of this ...
Excitotoxicity due to glutamate occurs as part of the ischemic cascade and is associated with stroke[1] and diseases like amyotrophic lateral sclerosis, lathyrism, autism, some forms of mental retardation, and Alzheimers disease.[8][1] Glutamic acid has been implicated in epileptic seizures. Microinjection of glutamic acid into neurons produces spontaneous depolarisations around one second apart, and this firing pattern is similar to what is known as paroxysmal depolarizing shift in epileptic attacks. This change in the resting membrane potential at seizure foci could cause spontaneous opening of voltage-activated calcium channels, leading to glutamic acid release and further depolarization. Experimental techniques to detect glutamate in intact cells include using a genetically-engineered nanosensor.[9] The sensor is a fusion of a glutamate-binding protein and two fluorescent proteins. When glutamate binds, the fluorescence of the sensor under ultraviolet light changes by resonance between the ...
Biological cells express intracellular biomolecular information to the extracellular environment as various physical responses. We show a novel computational approach to estimate intracellular biomolecular pathways from growth cone electrophysiological responses. Previously, it was shown that cGMP signaling regulates membrane potential (MP) shifts that control the growth cone turning direction during neuronal development. We present here an integrated deterministic mathematical model and Bayesian reversed-engineering framework that enables estimation of the molecular signaling pathway from electrical recordings and considers both the system uncertainty and cell-to-cell variability. Our computational method selects the most plausible molecular pathway from multiple candidates while satisfying model simplicity and considering all possible parameter ranges. The model quantitatively reproduces MP shifts depending on cGMP levels and MP variability potential in different experimental conditions. ...