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 ...
However, the first question before addressing this problems is whether outside binding is relevant at all. Brand[2] stated that for permeabilized cells outside binding may be ignored for high mitochondrial membrane potential. Initially, this seemed to be confirmed by our own initial sensitivity studies. Using outside binding correction factors similar to the inside ones and using protein content as marker, changing the outside binding correction factor by several hundred percent caused comparable small changes in reasonable high membrane potentials and negligible changes in delta delta Psi values for permeabilized cells. However, with growing experience it became evident that unspecific binding may be underestimated by this approach, resulting in obviously too high membrane potentials especially for states of known low potential. Part of the unreasonable high membrane potential could be explained by wrong assumptions for the amount of mitochondrial protein (Pmt). Non the less, modeling of the ...
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 ...
In the voltageclamp configuration, a current is injected into the cell via a negative feedback loop to compensate changes in membrane potential. This technique is the refinement of the voltage clamp. Neuroscience is available from oxford university press. Sep 29, 20 this screencast describes iv and vi relations derived from patch or current clamp data, and how to calculate conductance or resistance from the data. Still more recently, a technique has been invented, patch clamping, that makes it possible to voltage clamp small regions of the nerve cell membrane, and look at the responses of individual ion channels to changes in voltage across the membrane. Oct 28, 20 the voltage clamp is a technique used to control the voltage across the membrane of a small or isopotential area of a nerve cell by an electronic feedback circuit. Alternatively, the current clamp technique can be used. Identification and regulation of wholecell chloride currents. Theory the basis of the voltage clamp may be ...
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. ...
In this lesson I want to talk about membrane potentials and the role they play in nerve transmission.. So first - what is a membrane potential. Anytime you hear potential related to nerves - think electrical charge. So the membrane potential is just the electrical charge across a membrane. In the nerves, we have a resting potential and an action potential. This should be pretty self-explanatory. The resting potential is when nothing is happening - the nerve is just resting. Well look at this more in a minute, but know that the resting membrane potential - or the resting electrical charge is negative 70 mV - meaning its more negative on the inside than the outside. The other type we have is an Action Potential - as you can see - this is when there is an ACTION happening - so an action potential is sending a stimulus to create a response somewhere in the body. The charge in an Action Potential is more positive - well look at specifics in a minute.. So when I say the resting potential is ...
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 - Hypoxia in striatal and cortical neurones. T2 - Membrane potential and Ca2+ measurements. AU - Pisani, Antonio. AU - Calabresi, Paolo. AU - Bernardi, Giorgio. PY - 1997. Y1 - 1997. N2 - Simultaneous measurements of membrane potential and intracellular Ca2+ were used to study the effects of hypoxia on striatal and cortical neurones. Striatal neurones responded to hypoxia with a reversible membrane depolarization coupled with a transient increase in intracellular Ca2+. Thirty minutes of hypoxia caused an irreversible membrane depolarization associated with a massive raise in Ca2+ levels, leading to cell death. Conversely, cortical neurones were more resistant to O2 deprivation. Hypoxia (4-10 min) induced minimal changes in both membrane potential and Ca2+ signals. Longer periods (20-30 min) caused an initial membrane hyperpolarization followed by a large but reversible depolarization coupled with a transient increase in Ca2+ signals. These results support the hypothesis of a ...
TY - JOUR. T1 - Spike-Threshold Adaptation Predicted by Membrane Potential Dynamics In Vivo. AU - Fontaine, Bertrand. AU - Peña, José Luis. AU - Brette, Romain. N1 - Copyright: Copyright 2014 Elsevier B.V., All rights reserved.. PY - 2014/4. Y1 - 2014/4. 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 ...
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 ...
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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 FLIPR® Membrane Potential Assay Kits deliver homogenous fluorescence-based formulations for observation of real-time membrane potential changes associated with ion channel activation and ion transporter proteins. Each homogeneous assay kit utilizes a proprietary indicator dye and quencher combination to maximize ce
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 ...
TY - JOUR. T1 - Membrane potential resonance frequency directly influences network frequency through electrical coupling. AU - Chen, Yinbo. AU - Li, Xinping. AU - Rotstein, Horacio G.. AU - Nadim, Farzan. N1 - Funding Information: Support for this work was provided by the National Institute of Mental Health (R01-MH060605; to F. Nadim), National Institute of Neurological Disorders and Stroke (R01-NS083319; to F. Nadim), and National Science Foundation (DMS1313861; to H. G. Rotstein).. PY - 2016/10. Y1 - 2016/10. N2 - Oscillatory networks often include neurons with membrane potential resonance, exhibiting a peak in the voltage amplitude as a function of current input at a nonzero (resonance) frequency (fres). Although fres has been correlated to the network frequency (fnet) in a variety of systems, a causal relationship between the two has not been established. We examine the hypothesis that combinations of biophysical parameters that shift fres, without changing other attributes of the impedance ...
Other articles where Membrane potential is discussed: nervous system: The neuronal membrane: …neurons this potential, called the membrane potential, is between −60 and −75 millivolts (mV; or thousandths of a volt; the minus sign indicates that the inner surface is negative). When the inside of the plasma membrane has a negative charge compared to the outside, the neuron is said to be…
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 ...
Membrane potential plays a crucial role in many important physiological processes in bacteria. It is a component of the proton-motive force and is used to power various membrane-embedded complexes, including ATP synthase, the flagellar motor, and various small-molecule transport systems (1-5). Membrane potential has also been shown to be critical for bacterial cell division, proliferation, and signaling, and recent studies have begun to elucidate the mechanisms by which bacterial membrane potential is regulated (6-10).. Bacterial membrane potential also plays a critical role in antibiotic susceptibility, highlighting the value in identifying membrane potential-altering compounds in the quest to combat multidrug-resistant pathogens (5, 11-13). For example, carbonyl cyanide 3-chlorophenylhydrazone (CCCP), a well-known proton ionophore, increases Enterobacteriaceae susceptibility to polymyxins, while others have shown that hyperpolarizing conditions, such as those with the addition of alanine and ...
TY - THES. T1 - Studies on membrane properties of cholesterol and 3-beta modified sterol analogs. AU - Lönnfors, Max. PY - 2014. Y1 - 2014. N2 - Cholesterol (Chol) is an important lipid in cellular membranes functioning both as a membrane fluidity regulator, permeability regulator and co-factor for some membrane proteins, e.g. G-protein coupled receptors. It also participates in the formation of signaling platforms and gives the membrane more mechanical strenght to prevent osmotic lysis of the cell. The sterol structure is very conserved and already minor structural modifications can completely abolish its membrane functions. The right interaction with adjacent lipids and the preference of certain lipid structures over others are also key factors in determining the membrane properties of cholesterol. Because of the many important properties of cholesterol it is of value to understand the forces and structural properties that govern the membrane behavior of this sterol. In this thesis we have ...
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. ...
Patch clamp method was used to search for, and characterize ion channel activity which may participate in cation influx in human myeloid K562 cells. In cell-attached, outside-out and whole-cell experiments two types of voltage-insensitive Na-permeable channels were identified with different selectivities for monovalent cations, referred to as channels of high (HS) and low (LS) selectivity. The unitary conductance was similar for both channel types being 12 pS (145 mmol/l Na, 23 degrees C). The relative permeability PNa/PK estimated from the extrapolated reversal potential values were 10 and 3 for HS and LS channels, respectively. Both HS and LS channels were found to be impermeable to bivalent cations (Ca2+ or Ba2+). The activity of HS and LS channels displayed a tendency to increase with depolarization. Both channel types were not blocked by tetrodotoxin and were insensitive to amiloride in the concentration range of up to 100 mumol/l. At higher concentrations (0.1-2 mmol/l), amiloride ...
Gas - Gas - Boltzmann equation: The simple mean free path description of gas transport coefficients accounts for the major observed phenomena, but it is quantitatively unsatisfactory with respect to two major points: the values of numerical constants such as a, a′, a″, and a12 and the description of the molecular collisions that define a mean free path. Indeed, collisions remain a somewhat vague concept except when they are considered to take place between molecules modeled as hard spheres. Improvement has required a different, somewhat indirect, and more mathematical approach through a quantity called the velocity distribution function. This function describes how molecular velocities are distributed
Baseline toxicity of a selection of industrial chemicals and pharmaceuticals is determined experimentally with a new in vitro test system (Kinspec) using membrane vesicles isolated from a photosynthetic bacterium, Rhodobacter sphaeroides. This test system is selective and more sensitive than other mechanistic test systems for baseline toxicity. The only concomitantly determined mechanism is uncoupling, which can be distinguished from baseline toxicity by pH-dependent measurements. Because the tests system contains only the target site for baseline toxicants, the biological membrane, effective target site concentrations can be directly related to observed effects by combining the in vitro test with membrane-water partition experiments. No differences were found between the effective membrane concentrations of nonpolar and polar compounds, confirming the earlier hypothesis that differences in lethal body burdens are primarily caused by unequal distribution of the compounds between target and ...
Neurons in the central nervous system, and in the cortex in particular, are subject to a barrage of pulses from their presynaptic populations. These synaptic pulses are mediated by conductance changes and therefore lead to increases or decreases of the neuronal membrane potential with amplitudes that are dependent on the voltage: synaptic noise is multiplicative. The statistics of the membrane potential are of experimental interest because the measurement of a single subthreshold voltage can be used to probe the activity occurring across the presynaptic population. Though the interpulse interval is not always significantly smaller than the characteristic decay time of the pulses, and so the fluctuations have the nature of shot noise, the majority of results available in the literature have been calculated in the diffusion limit, which is valid for high-rate pulses. Here the effects that multiplicative conductance noise and shot noise have on the voltage fluctuations are examined. It is shown that both
Rien, D., Kern, R., & Kurtz, R. (2011). Synaptic transmission of graded membrane potential changes and spikes between identified visual interneurons. European Journal of Neuroscience, 34(5), 705-716. doi:10.1111/j.1460-9568.2011.07801. ...
If we shift our focus over to the cardiac myocyte in particular well remember that potassium and sodium are the major role players. Potassium is concentrated intracellularly and sodium is hanging out extracellularly. The good old Sodium-Potassium pump is keeping the peace, the peace being a negative resting membrane potential. The concentration gradient across this membrane plays an important role in maintaining this action potential. As the extracellular potassium concentration increases, the resting membrane potential gets less negative. This is important because the resting membrane potential (the flat part before the action potential gets going) directly impacts the number of voltage-gated sodium channels available to generate the action potential. Fewer sodium channels means slower impulse conduction and prolonged membrane depolarization. How do we see this? QRS widening, P wave prolongation, PR widening ...
In midbrain dopamine neurons in vitro, N-methyl-D-aspartate (NMDA) evokes oscillation of membrane potential and burst firing which are dependent on a ouabain-sensitive sodium pump. In the present study, we investigated the ionic dependence and pharmacological modulation of NMDA-mediated currents which might be important in burst firing. By use of patch pipettes to record membrane currents in whole-cell voltage clamps, we found that NMDA (10 microM) evoked inward currents that were significantly reduced in a low extracellular concentration of Na+ (25 mM), but not when extracellular Ca+2 was decreased from 2.5 to 0.5 mM. The current-voltage relationship for subtracted NMDA currents showed a prominent region of negative slope conductance which was absent when the slice was perfused with solution containing zero Mg++. 7-Chlorokynurenic acid, an antagonist at the nonstrychnine-sensitive glycine binding site, produced a concentration-dependent reduction in amplitude of excitatory postsynaptic currents ...
TY - JOUR. T1 - Kv2.1 channels play opposing roles in regulating membrane potential, Ca2+ channel function, and myogenic tone in arterial smooth muscle. AU - ODwyer, Samantha C.. AU - Palacio, Stephanie. AU - Matsumoto, Collin. AU - Guarina, Laura. AU - Klug, Nicholas R.. AU - Tajada, Sendoa. AU - Rosati, Barbara. AU - McKinnon, David. AU - Trimmer, James S.. AU - Santana, L. Fernando. PY - 2020/2/18. Y1 - 2020/2/18. N2 - The accepted role of the protein Kv2.1 in arterial smooth muscle cells is to form K+ channels in the sarcolemma. Opening of Kv2.1 channels causes membrane hyperpolarization, which decreases the activity of L-type CaV1.2 channels, lowering intracellular Ca2+ ([Ca2+]i) and causing smooth muscle relaxation. A limitation of this model is that it is based exclusively on data from male arterial myocytes. Here, we used a combination of electrophysiology as well as imaging approaches to investigate the role of Kv2.1 channels in male and female arterial myocytes. We confirmed that ...
This experiment deals about understanding the nature of ionic current using a voltage-current plot usually called V-I plot. It also investigates the role of linearity in ionic current behavior.
1. Action potentials recorded in the soma of R15 neurones in the abdominal ganglia of Aplysia juliana were not suppressed by selective inhibition of either Na or Ca conductance alone. It was necessary to block both conductances to suppress action potentials. 2. Membrane currents generated by step depolarizations of the soma consisted of early transient and delayed steady-state currents. The early transient current could have one or two components depending on the activating depolarization. 3. The early more rapid component had a reversal potential at +54 mV and the reversal potential changed with extracellular Na concentration in accord with the Nernst equation. It was blocked by substitution of impermeant cations for Na, by TTX and by internal injections of Zn. It was concluded that this component was normally a Na current. 4. The later slower component of the transient current had a reversal potential at about +65 mV and the reversal potential changed with extracellular Ca concentration is accord with
Purified JC-1 Mitochondrial Membrane Potential Assay Kit from Creative Biomart. JC-1 Mitochondrial Membrane Potential Assay Kit can be used for research.
Thank you, Dr. Ferber- but let me clarify my question- Were making current clamp recordings, and injecting square current pulses whilst in current clamp. Our amplifier seems to turn off capacitance/series resistance compensation in current clamp mode, though Im not so sure. In our preparation, a strong inward rectifying current is expected to be seen in medium spiny neurons by applying hyperpolarizing pulses. Weve been applying 20 pA steps from 0 to -1nA (the maximum current injection possible for our amplifier), yet we do not see any inward rectification. Inward rectification is a defining characteristic of medium spiny neurons. These cells have been labelled iontophoretically with neurobiotin, and we see that they are indeed medium spiny neurons. Weve checked our intracellular and ACSF ionic concentrations against what others are using, and find no great difference. The cell fires what appear to be normal action potentials with depolarizing pulses in current clamp. Im thinking that ...
TY - JOUR. T1 - Self-Sustained Oscillations of Membrane Potential in DOPH-Millipore Membranes. AU - Toko, Kiyoshi. AU - Ryu, Kouichi. AU - Ezaki, Shu. AU - Yamafuji, Kaoru. PY - 1982. Y1 - 1982. N2 - Self-sustained oscillations of membrane potential in an artificial model membrane, where dioleyl phosphate (DOPH) is infiltrated into pores of a Millipore filter, are investigated both experimentally and theoretically. Spike-like selfoscillations with an extremely long period of about one hour were observed for membranes with large adsorbed amounts of DOPH in the absence of external forces such as electric current and pressure gradient. On the basis of a previously-presented model that DOPH molecules make transitions among three phases composed of oil droplets, spherical micelles and multi- or bilayer leaflets, the occurrence of self-oscillations is explained well by taking account of an accumulation and a release of salt in a pore of the filter.. AB - Self-sustained oscillations of membrane ...
MitoPedia ,abbr=mtMP, Δψ [V] ,description=The mitochondrial membrane potential, mtMP, is the electric part of the protonmotive [[force]], Δp,sub>H+,/sub>. Δψ = Δp,sub>H+,/sub> - Δµ,sub>H+,/sub> / F mtMP or Δψ is the potential difference across the inner mitochondrial (mt) membrane, expressed in the electric unit of volt [V]. Electric force of the mitochondrial membrane potential is the electric energy change per motive electron or per electron moved across the transmembrane potential difference, with the number of motive electrons expressed in the unit coulomb [C]. ,info=[[Mitchell 1961 Nature]], [[Gnaiger 2014 Preface MiP2014]] }} Communicated by [[Gnaiger E]] 2012-10-05, edited 2016-02-06, 2017-09-05. :::: The chemical part of the protonmotive force, µ,sub>H+,/sub> / F stems from the difference of pH across the mt-membrane. It contains a factor that bridges the gap between the electric force [J/C] and the chemical force [J/mol]. This ...
We have discussed simple concentration gradients-differential concentrations of a substance across a space or a membrane-but in living systems, gradients are more complex. Because ions move into and out of cells and because cells contain proteins that do not move across the membrane and are mostly negatively charged, there is also an electrical gradient, a difference of charge, across the plasma membrane. The interior of living cells is electrically negative with respect to the extracellular fluid in which they are bathed, and at the same time, cells have higher concentrations of potassium (K+) and lower concentrations of sodium (Na+) than does the extracellular fluid. So in a living cell, the concentration gradient of Na+ tends to drive it into the cell, and the electrical gradient of Na+ (a positive ion) also tends to drive it inward to the negatively charged interior. The situation is more complex, however, for other elements such as potassium. The electrical gradient of K+, a positive ion, ...
Dear Sir / Madam,. I cant patch on cardiomyocytes to record action potentials at 37 degree C using a perforated patch technique. I tried many things, but failed.. Following the suggestions from this forum, I patched the cell at room temperature. After cell got gigaohm sealed, I turned on the temperature controller. At this moment, I found that it was very easy to loss the cell, because of an electric shock?. So late on, I made a little bit changes and did as followings: (1) I turned on the temperature controller but set temperature at 22oC; (2) patched the cell to get gigaohm seal; (3) waited for about 40 minutes to allow Gramicidin to perforate the cell membrane; (4) switched voltage clmap mode to current clamp mode to see if action potential could be induced or not and (5) if the action potential could be seen, then turned the wheel of temperature controller to increase the bath temperature to 37oC at once. But I found that the cell still losed ...
View Notes - 4 Influence of Passive Membrane Properties on Neural Signals - lecture slides from IPHY 4720 at Colorado. Signaling Within & Between Nerve Cells Influence of Passive Membrane
The fundamental cellular parameters of cell volume (Vc) and resting membrane potential (Em) profoundly influence cellular, tissue, organ and whole-body physiology. Earlier work has identified a wide range of mechanisms that maintain, regulate, or otherwise influence the values of each parameter individually. However, both Vc and Em change during normal activity in skeletal muscle, and their resting values are interdependent. New quantitative theoretical and experimental techniques were developed to permit an investigation of the interrelationships between Vc and Em, in order to study the determination, maintenance and short-term regulation of each parameter in skeletal muscle. Thus a cellular model was developed that permitted accurate theoretical analysis of the influences upon both Vc and Em of the diverse mechanisms known to maintain and regulate Vc, and a laser-confocal microscope technique was developed for the dynamic measurement of Vc in viable whole-muscle preparations. These new ...
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BioAssay record AID 767820 submitted by ChEMBL: Inhibition of human ERG expressed in HEK293 cells assessed as membrane depolarization at 3 uM by patch-clamp method.
Due to commercial and government interest in devices capable of functioning in high-power, high-frequency space applications, radiation tolerant AlGaNGaN devices have been under study in recent years. Passivation of the AlGaN surface by Si3N4 prevents electron trapping and enhances the 2DEG, but it also increases gate leakage currents, which can lead to device failure. This study sought information about current leakage mechanisms by introducing displacement damage close to the Si3N4AlGaN interface. The effects of irradiation damage around the Si3N4AlGaN interface on irradiation-induced leakage current were investigated for three thicknesses of a Si3N4 passivation layer in addition to an unpassivated sample. AlGaNGaN samples were irradiated at room temperature with 15-50keV nitrogen ions. Hall measurements determined mobility and 2DEG carrier density. C-V measurements provided insight into charge location and effects of the band structure. Pre-irradiation measurements were compared to the irradiation
Na Channel Has a quick onset and quickly turns off: inactivating channel. K is the opposite with slow onset and slow turn off: noninactivating channel. This difference is caused by differences in the two proteins. The Na channel has two gates: the activation gate and the inactivation gate. The activation gate is sensitive to the potential. When the activation gate is closed the inactivation gate is closed. When the inside of the cell is depolarized, the activation gate quickly opens. The inactivation gate, composed of negative proteins, slowly is repelled by the positive change in the intracellular environment, so it closes the channel by find its way into the pore of the channel.. K Channel. Has a single gate activated by the membrane potential, so it will stay open all the time the membrane has a certain potential. Na and K Conductances Nas conductance is characterized by a rapid onset and a rapid offset. Ks conductance is characterized by a slow onset and a slow offset. Membrane potential ...
Ion channel conductance can be influenced by electrostatic effects originating from fixed surface charges that are remote from the selectivity filter. To explore whether surface charges contribute to the conductance properties of Kir2.1 channels, unitary conductance was measured in cell-attached recordings of Chinese hamster ovary (CHO) cells transfected with Kir2.1 channels over a range of K + activities (4.6-293.5 mM) using single-channel measurements as well as nonstationary fluctuation analysis for low K + activities. K + ion concentrations were shown to equilibrate across the cell membrane in our studies using the voltage-sensitive dye DiBAC 4 (5). The dependence of γ on the K + activity (a K ) was fit well by a modified Langmuir binding isotherm, with a nonzero intercept as a K approaches 0 mM, suggesting electrostatic surface charge effects. Following the addition of 100 mM N-methyl-D-glucamine (NMG + ), a nonpermeant, nonblocking cation or following pretreatment with 50 mM ...
Action potentials are used in neurons to conduct signals along the axon and occur in electrically excitable cells like neurons and cardiac muscle cells. The action potentials travel in a wave along the membrane causing the voltage sensitive channels to open to allow influx of Na+ thereby causing the conduction of the signal along the axon. The resting membrane potential of cells including neurons is -70mv. An action potential is generated by a change in the membrane potential from -70mv to +40mv when voltage gated ion channels open altering membrane permeability to Na+ and K+. ...
Complex mixtures, commonly encountered in metabolomics and food analytics, are now routinely measured by nuclear magnetic resonance (NMR) spectroscopy. Since many samples must be measured, one-dimensional proton (1D 1H) spectroscopy is the experiment of choice. A common challenge in complex mixture 1H NMR sp Lab on a Chip Recent Open Access Articles
Laboratory of Engineering Thermodynamics - University of Kaiserslautern . Laboratory of Engineering Thermodynamics (LTD) University of Kaiserslautern
We introduce and validate new computational tools that enable efficient generation and simulation of models containing stochastic ion channels distributed across dendritic and axonal membranes. Comparison of five morphologically distinct neuronal cell types reveals that when all simulated neurons contain identical densities of stochastic ion channels, the amplitude of stochastic membrane potential fluctuations differs between cell types and depends on sub-cellular location. ... The code is downloadable and more information is available at ,a href=http://www.psics.org/,http://www.psics.org/,/a ...