4,096 results on '"Resting potential"'
Search Results
2. Lee's "Transmembrane Electrostatically-Localized Proton" model does NOT offer a better understanding of neuronal transmembrane potentials.
- Author
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Silverstein, Todd P.
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MEMBRANE potential , *ACTION potentials , *SOLID state proton conductors , *PROTONS , *MYELIN proteins - Abstract
Recently, in a paper entitled "Protonic conductor: Better understanding [sic] neural resting and action potential," Lee applied his Transmembrane Electrostatically-Localized Protons (TELP) hypothesis to neuronal signaling. He stated that Hodgkin's cable theory "could not fully explain the different conductive patterns in unmyelinated and myelinated nerves," whereas his TELP hypothesis "enables much better understanding of neural resting/action potential and [the biological significance of] axon myelination. . ." However, Lee's TELP hypothesis predicts that under resting conditions, the neuron "accumulat[es] excess negative charge (anions) inside," whereas resting chloride gradients actually feature excess Cl- outside of the cell. Experiments on the neuron have shown that raising external [Kþ] and decreasing external [Cl-] cause membrane potential depolarization, which is predicted by the Goldman equation, but opposite to TELP hypothesis predictions. Finally, based on his TELP hypothesis, Lee predicted that the main purpose of myelin is to insulate the axonal plasma membrane specifically against proton permeability. However, he cited literature showing that myelin contains proteins that may "serve as a proton conductor with the localized protons." Thus, we show here that Lee's TELP hypothesis is highly problematic, and does NOT offer a "better understanding" of neuronal transmembrane potentials. [ABSTRACT FROM AUTHOR]
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- 2023
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3. The model of electrified cell clusters in biological tissues basing on the resting potential difference
- Author
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Yufang He, Peiguo Xu, Huijie Wu, Yong Chu, and Guanglei Zhang
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Electrified cell clusters ,Negative electrical equilibrium system ,Resting potential ,Biological tissues ,Medical technology ,R855-855.5 - Abstract
The resting potential is the potential difference that exists between the inner and outer sides of the cell membrane when the cell is not stimulated. The resting membrane potential is a key regulator of phenomena such as cell proliferation, morphogenesis, migration and differentiation. In this paper, we proposed a model of electrified cell clusters that considers the resting potential of cell clusters in the resting state. By measuring the potential difference between the inner and outer sides of biological tissues, it is verified that the cell cluster has a negative potential difference when taking the outer potential as the reference. In the absence of external conductors, the tissue is electrically neutral; while in the presence of external conductors, the positive net charges escape freely under repulsive forces and the biological tissues form a negative electrical equilibrium system. The model proposed in this study explored the potential situation above the cellular level in the resting state, providing a new perspective for the research on resting potential.
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- 2023
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4. A scenario for the origin of life: Volume regulation by bacteriorhodopsin required extremely voltage sensitive Na‐channels and very selective K‐channels.
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BACTERIORHODOPSIN , *ORIGIN of life , *SODIUM channels , *POTASSIUM channels , *MEMBRANE potential , *RHODOPSIN , *OXYGENATION (Chemistry) , *NUCLEIC acids - Abstract
The osmotic activity produced by internal, non‐permeable, anionic nucleic acids and metabolites causes a persistent and life‐threatening cell swelling, or cellular edema, produced by the Gibbs‐Donnan effect. This evolutionary‐critical osmotic challenge must have been resolved by LUCA or its ancestors, but we lack a cell‐physiology look into the biophysical constraints to the solutions. Like mycoplasma, early cells conceivably preserved their volume with Cl−, Na+, and K+‐channels, Na+/H+‐exchangers, and a light‐dependent bacteriorhodopsin‐like H+‐pump. Here, I simulated protocells having these ionic‐permeabilities and inhabiting an oceanic pond before the Great‐Oxygenation‐Event. Protocells showed better volume control and stable resting potentials at lower external pH and higher temperatures, favoring a certain type of extremophile life. Prevention of Na+‐influx at night, with low bacteriorhodopsin activity, required deep shutdown of highly voltage‐sensitive Na+‐channels and extremely selective K+‐channels, two conserved features essential for modern neuronal encoding. The Gibbs‐Donnan effect universality implies that extraterrestrial cells, if they exist, may reveal similar volume‐controlling mechanisms. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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5. Kir Channel Molecular Physiology, Pharmacology, and Therapeutic Implications
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Cui, Meng, Cantwell, Lucas, Zorn, Andrew, Logothetis, Diomedes E., Barrett, James E., Editor-in-Chief, Flockerzi, Veit, Editorial Board Member, Frohman, Michael A., Editorial Board Member, Geppetti, Pierangelo, Editorial Board Member, Hofmann, Franz B., Editorial Board Member, Kuner, Rohini, Editorial Board Member, Michel, Martin C., Editorial Board Member, Page, Clive P., Editorial Board Member, Wang, KeWei, Editorial Board Member, Rosenthal, Walter, Editorial Board Member, and Gamper, Nikita, editor
- Published
- 2021
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6. From leaves to roots: Biophysical models of transport of substances in plants.
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Melkikh, A.V. and Sutormina, M.I.
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STATISTICAL physics , *BIOLOGICAL transport , *MEMBRANE potential , *PLANT vacuoles , *LEAF physiology , *ORGANELLES , *PLANT cell culture - Abstract
The transport processes of substances in various plant tissues are extremely diverse. However, models aimed at elucidating the mechanisms of such processes are almost absent in the literature. A unified view of all these transport processes is necessary, considering the laws of statistical physics and thermodynamics. A model of active ion transport was constructed based on the laws of statistical physics. Using this model, we traced the entire pathway of substances and energy in a plant. The pathway included aspects of the production of energy in the process of photosynthesis, consumption of energy to obtain nutrients from the soil, transport of such substances to the main organelles of all types of plant cells, the rise of water with dissolved substances along the trunk to the leaves, and the evaporation of water, accompanied by a change in the percentage of isotopes caused by different rates of evaporation. Models of ion transport in the chloroplasts and mitochondria of plant cells have been constructed. A generalized model comprising plant cells and their vacuoles was analyzed. A model of the transport of substances in the roots of plants was also developed. Based on this model, the problem of transport of substances in tall trees has been considered. The calculated concentrations of ions in the vacuoles of cells and resting potentials agreed well with the experimental data. [ABSTRACT FROM AUTHOR]
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- 2022
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7. Na+-K+-ATPase plays a major role in mediating cutaneous thermal hyperemia achieved by local skin heating to 39°C.
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Naoto Fujii, Kenny, Glen P., Tatsuro Amano, Yasushi Honda, Narihiko Kondo, and Takeshi Nishiyasu
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HYPEREMIA ,NITRIC-oxide synthases ,NITRIC oxide ,PHYSIOLOGIC salines ,SKIN temperature ,YOUNG adults - Abstract
Naþ-Kþ-ATPase is integrally involved in mediating cutaneous vasodilation during an exercise-heat stress, which includes an interactive role with nitric oxide synthase (NOS). Here, we assessed if Naþ-Kþ-ATPase also contributes to cutaneous thermal hyperemia induced by local skin heating, which is commonly used to assess cutaneous endothelium-dependent vasodilation. Furthermore, we assessed the extent to which NOS contributes to this response. Cutaneous vascular conductance (CVC) was measured continuously at four forearm skin sites in 11 young adults (4 women). After baseline measurement, local skin temperature was increased from 33°C to 39°C to induce cutaneous thermal hyperemia. Once a plateau in CVC was achieved, each skin site was continuously perfused via intradermal microdialysis with either: 1) lactated Ringer solution (control), 2) 6 mM ouabain, a Naþ-Kþ-ATPase inhibitor, 3) 20 mM L-NAME, a NOS inhibitor, or 4) a combination of both. Relative to the control site, CVC during the plateau phase of cutaneous thermal hyperemia (°50% max) was reduced by the lone inhibition of Naþ-Kþ-ATPase (°19 ± 8% max, P = 0.038) and NOS (-32 ± 4% max, P < 0.001), as well as the combined inhibition of both (-37 ± 9% max, P < 0.001). The magnitude of reduction was similar between NOS inhibition alone and combined inhibition (P = 1.000). The administration of both Naþ-Kþ-ATPase and NOS inhibitors fully abolished the plateau of CVC with values returning to preheating baseline values (P = 0.439). We show that Naþ-Kþ-ATPase contributes to cutaneous thermal hyperemia during local skin heating to 39°C, and this response is partially mediated by NOS. NEW & NOTEWORTHY Cutaneous thermal hyperemia during local skin heating to 39°C, which is highly dependent on nitric oxide synthase (NOS), is frequently used to assess endothelium-dependent cutaneous vasodilation. We showed that Naþ-Kþ-ATPase mediates the regulation of cutaneous thermal hyperemia partly via NOS-dependent mechanisms although a component of the Naþ-Kþ-ATPase modulation of cutaneous thermal hyperemia is NOS independent. Thus, as with NOS, Naþ-Kþ-ATPase may be important in the regulation of cutaneous endothelial vascular function. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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8. Introduction: From Neurons to the Mind
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Popescu, Aurel I., Opris, Ioan, Cutsuridis, Vassilis, Series editor, Opris, Ioan, editor, and Casanova, Manuel F., editor
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- 2017
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9. THE CHANGES OF THE ELECTROPHYSIOLOGICAL PROPERTIES OF NEURONS BY THE ACTION OF SEVOFLURANE AND THEIR ROLE IN THE MECHANISMS OF PRECONDITIONING AND CYTOPROTECTION
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A. I. Vislobokov, Yu. S. Polushin, A. Yu. Polushin, and V. V. Alferova
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planorbarius corneus ,севофлуран ,цитопротекция ,потенциал покоя ,потенциал действия ,импульсная активность ,sevoflurane ,cytoprotection ,resting potential ,action potential ,impulse activity ,Medical emergencies. Critical care. Intensive care. First aid ,RC86-88.9 - Abstract
The changes of the intracellular potentials by the action of sevoflurane were studied for the diagnostic intact neurons of the isolated cerebrospinal axis of the Planorbarius corneus using intracellular electrodes. There observed a two-phase reaction of the neurons de- and hyperpolarization. The sevoflurane concentration of 2 mM depolarized the neurons (to 5 mV), the depolarization was interchanged with the mild hyperpolarization (at 2-5 mV). The impulse activity rate (IA) increased under depolarization, while decreased under hyperpolarization, the parameters of the action potentials (AP) changed slightly. The inversive hyperpolarization occurred for 5-10 minutes upon the anesthetic elimination. There occurred the short-term and inversive depolarization of the neurons at the sevoflurane concentration of 5 mM to 9,4 ± 2,2% of the reference, while the IA rate increased, the amplitude of the action potentials decreased with their duration increase, and sometimes the AP generation was completely abrogated. On action of sevoflurane concentration of 5 mM there developed the inversive hyperpolarization of the neurons to 18,1 ± 16,9% of the reference, that lasted 15-20 minutes thereafter. The repeated neuron exposure with the same anesthetic is always reproduced followed by the florid hyperpolarization. The modulation of the electrical activity with sevoflurane (the hyperpolarization of the neurons and the decrease/termination of AP generation that evidenced the "improvement" of their functional status) may be the basis for the preconditioning, neuro- and cardioprotection.
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- 2017
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10. CHANGES IN INTRACELLULAR POTENTIALS AND ION FLUXES OF NEURONS OF MOLLUSKS BY EXTRACELLULAR AND INTRACELLULAR ACTION OF SEVOFLURANE AND DESFLURANE
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A. I. Vislobokov, E. E. Zvartau, Yu. S. Polushin, V. V. Alferova, and I. G. Bukhankov
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planorbarius corneus ,lymnaea stagnalis ,десфлуран ,севофлуран ,потенциал покоя ,потенциал действия ,импульсная активность ,ионные токи ,desflurane ,sevoflurane ,resting potential ,potential-action ,impulse activity ,ion currents ,Medical emergencies. Critical care. Intensive care. First aid ,RC86-88.9 - Abstract
Intercellular potentials changes of identifiable intact neurons ini solated CNS of great ramshorn (Planorbarius corneus) have been investigated with the help of intercellular microelectrodes and ion currents of isolated neurons of great ramshorns and pond snails (Lymnaea stagnalis) with the fixation of potential influenced by desflurane in concentrations of 1 and 10 mM (1.2 и 12 MAC) and sevoflurane in concentrations of 1 and 5 mM (2.27 and 11.36 MAC). In 3-5 minutes after the start of anesthetics' action some neurons developed insignificant hyperpolarization (for 2-5 mV), and some other developed depolarization (up to 10 mV). When anesthetics were being washed out for 5-10 minutes the reversible depolarization appeared. Changes in ion currents under the influence of anesthetics were more homogeneous compared to changes in biopotentials. Desflurane and sevoflurane in 1 mM concentrations suppressed amplitudes of sodium, calcium and potassium currents by 40%, and inactivation of potassium low currents was speed up. Anesthetics in the concentration of 5-10 mM suppressed currents by 70-80%. It developed fast (for 20-30 seconds) and after this action the amplitudes restored slowly (for 5-15 minutes) and it failed to reach the initial values in all the times. Intercellular activity of sevoflurane did not suppress ion currents, i.e. it was ineffective.
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- 2017
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11. Non-synaptic Plasticity in Leech Touch Cells.
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Meiser, Sonja, Ashida, Go, and Kretzberg, Jutta
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MEMBRANE potential ,T cells ,HYPERPOLARIZATION (Cytology) ,LEECHES ,POTASSIUM channels ,SENSORY neurons - Abstract
The role of Na
+ /K+ -pumps in activity-dependent synaptic plasticity has been described in both vertebrates and invertebrates. Here, we provide evidence that the Na+ /K+ -pump is also involved in activity-dependent non-synaptic cellular plasticity in leech sensory neurons. We show that the resting membrane potential (RMP) of T cells hyperpolarizes in response to repeated somatic current injection, while at the same time their spike count (SC) and the input resistance (IR) increase. Our Hodgkin–Huxley-type neuron model, adjusted to physiological T cell properties, suggests that repetitive action potential discharges lead to increased Na+ /K+ -pump activity, which then hyperpolarizes the RMP. In consequence, a slow, non-inactivating current decreases, which is presumably mediated by voltage-dependent, low-threshold potassium channels. Closing of these putative M-type channels due to hyperpolarization of the resting potential increases the IR of the cell, leading to a larger number of spikes. By this mechanism, the response behavior switches from rapidly to slowly adapting spiking. These changes in spiking behavior also effect other T cells on the same side of the ganglion, which are connected via a combination of electrical and chemical synapses. An increased SC in the presynaptic T cell results in larger postsynaptic responses (PRs) in the other T cells. However, when the number of elicited presynaptic spikes is kept constant, the PR does not change. These results suggest that T cells change their responses in an activity-dependent manner through non-synaptic rather than synaptic plasticity. These changes might act as a gain-control mechanism. Depending on the previous activity, this gain could scale the relative impacts of synaptic inputs from other mechanoreceptors, versus the spike responses to tactile skin stimulation. This multi-tasking ability, and its flexible adaptation to previous activity, might make the T cell a key player in a preparatory network, enabling the leech to perform fast behavioral reactions to skin stimulation. [ABSTRACT FROM AUTHOR]- Published
- 2019
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12. Reduction of spike generation frequency by cooling in brain slices from rats and from patients with epilepsy.
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Nomura, Sadahiro, Kida, Hiroyuki, Hirayama, Yuya, Imoto, Hirochika, Inoue, Takao, Moriyama, Hiroshi, Mitsushima, Dai, and Suzuki, Michiyasu
- Abstract
This study aimed to understand the mechanism by which brain cooling terminates epileptic discharge. Cortical slices were prepared from rat brains (n = 19) and samples from patients with intractable epilepsy that had undergone temporal lobectomy (n = 7). We performed whole cell current clamp recordings at approximately physiological brain temperature (35℃) and at cooler temperatures (25℃ and 15℃). The firing threshold in human neurons was lower at 25℃ (−32.6 mV) than at 35℃ (−27.0 mV). The resting potential and spike frequency were similar at 25℃ and 35℃. Cooling from 25℃ to 15℃ did not change the firing threshold, but the resting potential increased from −65.5 to −54.0 mV and the waveform broadened from 1.85 to 6.55 ms, due to delayed repolarization. These changes enhanced the initial spike appearance and reduced spike frequency; moreover, spike frequency was insensitive to increased levels of current injections. Similar results were obtained in rat brain studies. We concluded that the reduction in spike frequency at 15℃, due to delayed repolarization, might be a key mechanism by which brain cooling terminates epileptic discharge. On the other hand, spike frequency was not influenced by the reduced firing threshold or the elevated resting potential caused by cooling. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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13. Forward Transport of K2P3.1: Mediation by 14‐3‐3 and COPI, Modulation by p11
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O’Kelly, Ita and Goldstein, Steve AN
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Biochemistry and Cell Biology ,Biological Sciences ,Biotechnology ,14-3-3 Proteins ,Animals ,Annexin A2 ,Binding Sites ,Coat Protein Complex I ,Electrophysiology ,Endoplasmic Reticulum ,G Protein-Coupled Inwardly-Rectifying Potassium Channels ,Immunoprecipitation ,Organ Specificity ,Peptide Fragments ,Phosphorylation ,Potassium Channels ,Tandem Pore Domain ,Protein Interaction Mapping ,Protein Transport ,Rats ,Rats ,Wistar ,Recombinant Fusion Proteins ,S100 Proteins ,Xenopus laevis ,14-3-3 ,annexin ,background ,COPI retention ,leak ,p11 ,potassium channel ,resting potential ,TASK-1 ,Medical Microbiology ,Developmental Biology ,Biochemistry and cell biology - Abstract
Surface expression of the K(2P)3.1 two-pore domain potassium channel is regulated by phosphorylation-dependent binding of 14-3-3, leading to suppression of coatomer coat protein I (COPI)-mediated retention in endoplasmic reticulum (ER). Here, we investigate the nature of the macromolecular regulatory complexes that mediate forward and retrograde transport. We demonstrate that (i) the channel employs two separate but interacting COPI binding sites on the N- and C-termini; (ii) disrupting COPI binding to either site interferes with the ER retention; (iii) p11 and 14-3-3 do not interact on their own; (iv) p11 binding to the C-terminal retention motif is dependent on 14-3-3; and (v) p11 is coexpressed in only a subset of tissues with K(2P)3.1, while 14-3-3 expression is ubiquitous. We conclude that K(2P)3.1 forward transport requires 14-3-3 suppression of COPI binding, whereas p11 serves a modulatory role.
- Published
- 2008
14. Forward Transport of K2p3.1: mediation by 14-3-3 and COPI, modulation by p11.
- Author
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O'Kelly, Ita and Goldstein, Steve AN
- Subjects
Endoplasmic Reticulum ,Animals ,Xenopus laevis ,Rats ,Rats ,Wistar ,14-3-3 Proteins ,Peptide Fragments ,Annexin A2 ,S100 Proteins ,Potassium Channels ,Tandem Pore Domain ,Coat Protein Complex I ,Recombinant Fusion Proteins ,Immunoprecipitation ,Protein Interaction Mapping ,Electrophysiology ,Organ Specificity ,Binding Sites ,Protein Transport ,Phosphorylation ,G Protein-Coupled Inwardly-Rectifying Potassium Channels ,14-3-3 ,annexin ,background ,COPI retention ,leak ,p11 ,potassium channel ,resting potential ,TASK-1 ,Biotechnology ,Wistar ,Potassium Channels ,Tandem Pore Domain ,Biochemistry and Cell Biology ,Developmental Biology - Abstract
Surface expression of the K(2P)3.1 two-pore domain potassium channel is regulated by phosphorylation-dependent binding of 14-3-3, leading to suppression of coatomer coat protein I (COPI)-mediated retention in endoplasmic reticulum (ER). Here, we investigate the nature of the macromolecular regulatory complexes that mediate forward and retrograde transport. We demonstrate that (i) the channel employs two separate but interacting COPI binding sites on the N- and C-termini; (ii) disrupting COPI binding to either site interferes with the ER retention; (iii) p11 and 14-3-3 do not interact on their own; (iv) p11 binding to the C-terminal retention motif is dependent on 14-3-3; and (v) p11 is coexpressed in only a subset of tissues with K(2P)3.1, while 14-3-3 expression is ubiquitous. We conclude that K(2P)3.1 forward transport requires 14-3-3 suppression of COPI binding, whereas p11 serves a modulatory role.
- Published
- 2008
15. SHORT-TERM EXPOSURE OF FRESHWATER ALGAE TO LEAD ORGANIC COMPOUNDS STUDIED WITH NON-INVASIVE ELECTRICAL AND LUMINESCENT METHODS
- Author
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Robert Borc, Anna Jaśkowska, and Andrzej Dudziak
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ultraweak luminescence ,chemiluminescence ,Nitellopsis obtusa ,organic lead ,membrane resistance ,resting potential ,Environmental sciences ,GE1-350 - Abstract
In this paper the non-invasive biophysical methods were applied to assess the organic lead compounds absorption by freshwater algae Nitellopsis obtusa. Two biophysical techniques were used: the electrical method AC bridge with four external electrodes and the luminescent with the registration of ultraweak photon radiation emitted by plants. They allow to study the electrical and luminescent cell membrane properties. Research was performed with the lead acetate and trimethyl-lead chloride to verify whether algae cells were able to absorb Pb ions from water medium contaminated by these compounds. When the concentration of lead acetate solution increased up to 25 -100 µM the membrane resting potential changed from -140 mV to -175 mV. On the other hand, the electrical resistance of cell membrane (for 12-50 µM) increased with exposure time exceeding its starting value up to 1.5 times. In contrast to these electrical changes, the intensity of ultraweak luminescence was constant at concentrations below 1 µM lead acetate. These results with comparison of literature data can suggest that there was no lipid peroxidation in cell membranes for such organic lead compound concentrations. Chemiluminescent responses of algae were observed in the first 5 hours of experiments for lead concentration higher than 1 µM. The luminescence intensity increased immediately for both reagents, but no more than 4 times for concentrations of 1-10 µM lead acetate. For tetramethyl-lead chloride, the luminescence intensity started to increase slowly about 40 minutes after injection. These results with comparison of literature data may suggest lipid peroxidation in cell membrane for higher, toxic lead concentrations. It means that higher concentrations of lead can trigger lethal processes in the living cells. We conclude that the return of the electrical and chemiluminescent plant parameters to the starting values (before the action of lead ions) can indicate whether living cells are able to cope with detoxifying from heavy metals and whether they can survive when exposed to certain concentration of lead compounds. Algae of Nitellopsis obtusa in the first stage of exposure (5 hours) are able to accumulate organic compounds of lead without essential perturbations only up to specified concentrations (for example 1 µM of lead acetate). For higher lead content, an increase of ultraweak luminescence occurred which was probably associated with free radical productions and lipid peroxidation, as many researchers suggested.
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- 2016
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16. A 0.034% Charge-Imbalanced Neural Stimulation Front-End (SFE) IC With on-Chip Voltage Compliance Monitoring Circuit and Analysis on Resting Potential by Utilizing the SFE IC.
- Author
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Jeon, Yong-Joon, Yao, Lei, Gao, Yuan, and Arasu, Muthukumaraswamy Annamalai
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MEMBRANE potential , *NEURAL stimulation , *ELECTRIC potential , *VOLTAGE control , *METAL oxide semiconductor field-effect transistors - Abstract
The proposed SFE IC adopts an eight-channel H-bridge structure with an integrated voltage compliance monitoring circuit. It has stimulation current ranged from 0.78mA to 6.2mA selected by 3b control and the stimulation current level can be controlled with 7b resolution within a selected current range. The current range can be expanded by using a high current option ranged from 2.71mA to 21.7mA under 3b control. The worst DNL and INL of the stimulation current source are 0.32 LSB and 0.3 LSB, respectively, from all the current ranges. The average mismatch between the cathodic and anodic current pulses in a biphasic stimulus is measured as 0.034% without using charge balancing techniques. The voltage compliance monitoring circuit is based on triode detection of a sensing MOSFET and it shows the detection accuracy of 45mV from its measurement results. The maximum steady-state voltage across the electrodes/ solution interface (resting potential) is also rigorously analyzed and verified through bench-top and saline experiments by utilizing the proposed stimulator. The SFE IC was fabricated in $0.18~\mu \text{m}$ 24 V CMOS process. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
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17. Classification of needle-EMG resting potentials by machine learning.
- Author
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Nodera, Hiroyuki, Osaki, Yusuke, Yamazaki, Hiroki, Mori, Atsuko, Izumi, Yuishin, and Kaji, Ryuji
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DIAGNOSIS of muscle diseases , *SKELETAL muscle physiology , *COMPARATIVE studies , *ELECTROMYOGRAPHY , *EVOKED potentials (Electrophysiology) , *HYPODERMIC needles , *MATHEMATICS , *RESEARCH methodology , *MEDICAL cooperation , *MUSCLE diseases , *REGRESSION analysis , *RELAXATION for health , *RESEARCH , *RESEARCH funding , *SIGNAL processing , *EVALUATION research - Abstract
Introduction: The diagnostic importance of audio signal characteristics in needle electromyography (EMG) is well established. Given the recent advent of audio-sound identification by artificial intelligence, we hypothesized that the extraction of characteristic resting EMG signals and application of machine learning algorithms could help classify various EMG discharges.Methods: Data files of 6 classes of resting EMG signals were divided into 2-s segments. Extraction of characteristic features (384 and 4,367 features each) was used to classify the 6 types of discharges using machine learning algorithms.Results: Across 841 audio files, the best overall accuracy of 90.4% was observed for the smaller feature set. Among the feature classes, mel-frequency cepstral coefficients (MFCC)-related features were useful in correct classification.Conclusions: We showed that needle EMG resting signals were satisfactorily classifiable by the combination of feature extraction and machine learning, and this can be applied to clinical settings. Muscle Nerve 59:224-228, 2019. [ABSTRACT FROM AUTHOR]- Published
- 2019
- Full Text
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18. After-effect induced by microwave radiation in human electroencephalographic signal: a feasibility study.
- Author
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Bachmann, Maie, Päeske, Laura, Ioannides, Andreas A., Lass, Jaanus, and Hinrikus, Hiie
- Subjects
- *
MICROWAVES , *ELECTROENCEPHALOGRAPHY , *SIGNAL-to-noise ratio , *BIOMEDICAL signal processing , *DIAGNOSIS of brain diseases - Abstract
Purpose: This feasibility study is aimed to clarify the possibility of detection of microwave radiation (MWR)-induced event related potential (ERP) in electroencephalographic (EEG) signal. Methods: To trigger onset and offset effects in EEG, repetitive MWR stimuli were used. Four 30-channel EEG recordings on a single subject were performed, each about one month apart. The subject was exposed to 450 MHz MWR modulated at 40 Hz at the 1 g peak spatial average specific absorption rate of 0.3 W/kg. During a recording, 40 cycles of 30 s on-off MWR exposure were used. The artifact-free responses to 126 MWR-ON stimuli and 134 MWR-OFF stimuli were averaged over stimuli and channels. Results: Regarding EEG signals locked to MWR-OFF stimulus, the enhanced signal level at alpha frequency band and about twice higher signal to noise ratio at 200 to 440 ms after the stimulus have been detected. No remarkable response in EEG signals locked to MWR-ON stimulus. Conclusions: The detection of offset effect confirms that there should be an imprint generated by MWR in brain. The results of this preliminary study provide evidence for the detection of MWR-induced ERP in EEG signal and encourage further research in this direction. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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19. Na+-K+-ATPase plays a major role in mediating cutaneous thermal hyperemia achieved by local skin heating to 39°C
- Author
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Narihiko Kondo, Glen P. Kenny, Naoto Fujii, Tatsuro Amano, Takeshi Nishiyasu, and Yasushi Honda
- Subjects
medicine.medical_specialty ,biology ,Physiology ,Chemistry ,Hyperpolarization (biology) ,Thermoregulation ,Resting potential ,Microcirculation ,Nitric oxide synthase ,Endocrinology ,Physiology (medical) ,Internal medicine ,Cutaneous vasodilation ,medicine ,biology.protein ,Na+/K+-ATPase ,Endothelium dependent vasodilation - Abstract
Cutaneous thermal hyperemia during local skin heating to 39°C, which is highly dependent on nitric oxide synthase (NOS), is frequently used to assess endothelium-dependent cutaneous vasodilation. We showed that Na+-K+-ATPase mediates the regulation of cutaneous thermal hyperemia partly via NOS-dependent mechanisms although a component of the Na+-K+-ATPase modulation of cutaneous thermal hyperemia is NOS independent. Thus, as with NOS, Na+-K+-ATPase may be important in the regulation of cutaneous endothelial vascular function.
- Published
- 2021
20. Function of K2P channels in the mammalian node of Ranvier
- Author
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Jürgen R. Schwarz
- Subjects
Node of Ranvier ,Physiology ,Chemistry ,Action Potentials ,Conductance ,Depolarization ,Stimulus (physiology) ,Nerve Fibers, Myelinated ,Resting potential ,Axons ,Axolemma ,Membrane Potentials ,medicine.anatomical_structure ,medicine ,Biophysics ,Animals ,Node (circuits) ,NODAL ,Myelin Sheath - Abstract
In myelinated nerve fibers, action potentials are generated at nodes of Ranvier. These structures are located at interruptions of the myelin sheath, forming narrow gaps with small rings of axolemma freely exposed to the extracellular space. The mammalian node contains a high density of Na channels and K-selective leakage channels. Voltage-dependent Kv1 channels are only present in the juxta-paranode. Recently, the leakage channels have been identified as K2P channels (TRAAK, TREK-1). K2P channels are K-selective "background" channels, characterized by outward rectification and their ability to be activated, e.g. by temperature, mechanical stretch, or arachidonic acid. We are only beginning to elucidate the peculiar functions of nodal K2P channels. I will discuss two functions of the nodal K2P-mediated conductance. First, at body temperature K2P channels have a high open probability, thereby inducing a resting potential of about -85 mV. This negative resting potential reduces steady-state Na channel inactivation and ensures a large Na inward current upon a depolarizing stimulus. Second, the involvement of the K2P conductance in nodal action potential repolarization. The identification of nodal K2P channels is exciting since it shows that the nodal K conductance is not a fixed value but can be changed, it can be increased or decreased by a broad range of K2P modulators, thereby modulating e.g. the resting potential. I will exemplify the functional importance of nodal K2P channels by describing in more detail the function of the K2P conductance increase by increasing the temperature to 37°C. This article is protected by copyright. All rights reserved.
- Published
- 2021
21. The role of voltage-gated ion channels in visual function and disease in mammalian photoreceptors
- Author
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David M. Hunt, Rabab Rashwan, and Livia S. Carvalho
- Subjects
Membrane potential ,genetic structures ,Voltage-dependent calcium channel ,Voltage-gated ion channel ,Physiology ,Chemistry ,Cone dystrophy with supernormal rod response ,Clinical Biochemistry ,Voltage-gated potassium channel ,Resting potential ,Light intensity ,Physiology (medical) ,sense organs ,Neuroscience ,Ion channel - Abstract
Light activation of the classical light-sensing retinal neurons, the photoreceptors, results in a graded change in membrane potential that ultimately leads to a reduction in neurotransmitter release to the post-synaptic retinal neurons. Photoreceptors show striking powers of adaptation, and for visual processing to function optimally, they must adjust their gain to remain responsive to different levels of ambient light intensity. The presence of a tightly controlled balance of inward and outward currents modulated by several different types of ion channels is what gives photoreceptors their remarkably dynamic operating range. Part of the resetting and modulation of this operating range is controlled by potassium and calcium voltage-gated channels, which are involved in setting the dark resting potential and synapse signal processing, respectively. Their essential contribution to visual processing is further confirmed in patients suffering from cone dystrophy with supernormal rod response (CDSRR) and congenital stationary night blindness type 2 (CSNB2), both conditions that lead to irreversible vision loss. This review will discuss these two types of voltage-gated ion channels present in photoreceptors, focussing on their structure and physiology, and their role in visual processing. It will also discuss the use and benefits of knockout mouse models to further study the function of these channels and what routes to potential treatments could be applied for CDSRR and CSNB2.
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- 2021
22. A Model of Activity Generation in the Epileptic Focus
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E. L. Masherov
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Physics ,Focus (geometry) ,Intraoperative Electrocorticography ,Extinction (neurology) ,Biophysics ,medicine ,medicine.disease ,Resting potential ,Neuroscience ,Synchronization - Abstract
A model of activity generation in the epileptic focus was proposed based on the ideas that synchronization occurs between the oscillations that arise to regulate the resting potential level and that neuronal discharges are synchronized with slow oscillations. Four phases were identified in seizure development: an increase in slow-wave activity, high-frequency spike activity, synchronization in the presence of sharp peaks, and extinction of the seizure. The model was compared with an intraoperative electrocorticography record.
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- 2021
23. Electricity in Medicine: Philosophy Meets Physiology
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Fishman, Loren M., Wilkins, Allen N., Fishman, Loren M., and Wilkins, Allen N
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- 2011
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24. 成年大鼠心室和窦房结细胞急性 分离方法和动作电位比较.
- Author
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范 茁
- Abstract
Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2019
- Full Text
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25. The Role of Mechanosensitive Fibroblasts in the Heart: Evidence from Acutely Isolated Single Cells, Cultured Cells and from Intracellular Microelectrode Recordings on Multicellular Preparations from Healthy and Diseased Cardiac Tissue
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Kamkin, Andre, Kiseleva, Irina, Lozinsky, Ilya, Kamkin, Andre, editor, and Kiseleva, Irina, editor
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- 2010
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26. Mechanosensitive Alterations of Action Potentials and Membrane Currents in Healthy and Diseased Cardiomyocytes: Cardiac Tissue and Isolated Cell
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Lozinsky, Ilya, Kamkin, Andre, Kamkin, Andre, editor, and Kiseleva, Irina, editor
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- 2010
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27. Bioelectric signaling in regeneration: Mechanisms of ionic controls of growth and form.
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McLaughlin, Kelly A. and Levin, Michael
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- *
REGENERATION (Biology) , *CELL communication , *EMBRYOLOGY , *GENE regulatory networks , *ION flow dynamics - Abstract
The ability to control pattern formation is critical for the both the embryonic development of complex structures as well as for the regeneration/repair of damaged or missing tissues and organs. In addition to chemical gradients and gene regulatory networks, endogenous ion flows are key regulators of cell behavior. Not only do bioelectric cues provide information needed for the initial development of structures, they also enable the robust restoration of normal pattern after injury. In order to expand our basic understanding of morphogenetic processes responsible for the repair of complex anatomy, we need to identify the roles of endogenous voltage gradients, ion flows, and electric fields. In complement to the current focus on molecular genetics, decoding the information transduced by bioelectric cues enhances our knowledge of the dynamic control of growth and pattern formation. Recent advances in science and technology place us in an exciting time to elucidate the interplay between molecular-genetic inputs and important biophysical cues that direct the creation of tissues and organs. Moving forward, these new insights enable additional approaches to direct cell behavior and may result in profound advances in augmentation of regenerative capacity. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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28. Cannabidiol Inhibition of Murine Primary Nociceptors: Tight Binding to Slow Inactivated States of Nav1.8 Channels
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Han-Xiong Bear Zhang and Bruce P. Bean
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Chemistry ,General Neuroscience ,Sodium channel ,Depolarization ,Afterhyperpolarization ,Resting potential ,digestive system diseases ,surgical procedures, operative ,nervous system ,Mechanism of action ,medicine ,Biophysics ,Nociceptor ,Repolarization ,medicine.symptom ,Cannabidiol ,medicine.drug - Abstract
The nonpsychoactive phytocannabinoid cannabidiol (CBD) has been shown to have analgesic effects in animal studies but little is known about its mechanism of action. We examined the effects of CBD on intrinsic excitability of primary pain-sensing neurons. Studying acutely dissociated capsaicin-sensitive mouse DRG neurons at 37°C, we found that CBD effectively inhibited repetitive action potential firing, from 15–20 action potentials evoked by 1 s current injections in control to 1–3 action potentials with 2 μm CBD. Reduction of repetitive firing was accompanied by a reduction of action potential height, widening of action potentials, reduction of the afterhyperpolarization, and increased propensity to enter depolarization block. Voltage-clamp experiments showed that CBD inhibited both TTX-sensitive and TTX-resistant (TTX-R) sodium currents in a use-dependent manner. CBD showed strong state-dependent inhibition of TTX-R channels, with fast binding to inactivated channels during depolarizations and slow unbinding on repolarization. CBD alteration of channel availability at various voltages suggested that CBD binds especially tightly [Kd (dissociation constant), ∼150 nm] to the slow inactivated state of TTX-R channels, which can be substantially occupied at voltages as negative as −40 mV. Remarkably, CBD was more potent in inhibiting TTX-R channels and inhibiting action potential firing than the local anesthetic bupivacaine. We conclude that CBD might produce some of its analgesic effects by direct effects on neuronal excitability, with tight binding to the slow inactivated state of Nav1.8 channels contributing to effective inhibition of repetitive firing by modest depolarizations. SIGNIFICANCE STATEMENT Cannabidiol (CBD) has been shown to inhibit pain in various rodent models, but the mechanism of this effect is unknown. We describe the ability of CBD to inhibit repetitive action potential firing in primary nociceptive neurons from mouse dorsal root ganglia and analyze the effects on voltage-dependent sodium channels. We find that CBD interacts with TTX-resistant sodium channels in a state-dependent manner suggesting particularly tight binding to slow inactivated states of Nav1.8 channels, which dominate the overall inactivation of Nav1.8 channels for small maintained depolarizations from the resting potential. The results suggest that CBD can exert analgesic effects in part by directly inhibiting repetitive firing of primary nociceptors and suggest a strategy of identifying compounds that bind selectively to slow inactivated states of Nav1.8 channels for developing effective analgesics.
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- 2021
29. Dynamic Clamp in Electrophysiological Studies on Stem Cell-Derived Cardiomyocytes-Why and How?
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Ronald Wilders and Arie O. Verkerk
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0301 basic medicine ,Pharmacology ,Membrane potential ,Computer science ,Cardiac electrophysiology ,Inward-rectifier potassium ion channel ,030204 cardiovascular system & hematology ,Resting potential ,03 medical and health sciences ,Electrophysiology ,030104 developmental biology ,0302 clinical medicine ,Clamp ,Patch clamp ,Cardiology and Cardiovascular Medicine ,Neuroscience ,Ion channel - Abstract
Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) are supposed to be a good human-based model, with virtually unlimited cell source, for studies on mechanisms underlying cardiac development and cardiac diseases, and for identification of drug targets. However, a major drawback of hPSC-CMs as a model system, especially for electrophysiological studies, is their depolarized state and associated spontaneous electrical activity. Various approaches are used to overcome this drawback, including the injection of "synthetic" inward rectifier potassium current (IK1), which is computed in real time, based on the recorded membrane potential ("dynamic clamp"). Such injection of an IK1-like current results in quiescent hPSC-CMs with a nondepolarized resting potential that show "adult-like" action potentials on stimulation, with functional availability of the most important ion channels involved in cardiac electrophysiology. These days, dynamic clamp has become a widely appreciated electrophysiological tool. However, setting up a dynamic clamp system can still be laborious and difficult, both because of the required hardware and the implementation of the dedicated software. In the present review, we first summarize the potential mechanisms underlying the depolarized state of hPSC-CMs and the functional consequences of this depolarized state. Next, we explain how an existing manual patch clamp setup can be extended with dynamic clamp. Finally, we shortly validate the extended setup with atrial-like and ventricular-like hPSC-CMs. We feel that dynamic clamp is a highly valuable tool in the field of cellular electrophysiological studies on hPSC-CMs and hope that our directions for setting up such dynamic clamp system may prove helpful.
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- 2021
30. The mechanism of non‐blocking inhibition of sodium channels revealed by conformation‐selective photolabeling
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Tamás Hegedűs, Katalin Zboray, Peter Lukacs, Arpad Mike, Krisztina Pesti, András Málnási-Csizmadia, Ádám Tóth, and Mátyás C. Földi
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0301 basic medicine ,Drug ,media_common.quotation_subject ,Sodium Channels ,Membrane Potentials ,03 medical and health sciences ,0302 clinical medicine ,medicine ,Humans ,Binding site ,media_common ,Pharmacology ,Binding Sites ,Riluzole ,Mechanism (biology) ,Chemistry ,Sodium channel ,Resting potential ,Small molecule ,Electrophysiology ,HEK293 Cells ,030104 developmental biology ,Biophysics ,030217 neurology & neurosurgery ,Sodium Channel Blockers ,medicine.drug - Abstract
Background and purpose Sodium channel inhibitors can be used to treat hyperexcitability-related diseases, including epilepsies, pain syndromes, neuromuscular disorders and cardiac arrhythmias. The applicability of these drugs is limited by their nonspecific effect on physiological function. They act mainly by sodium channel block and in addition by modulation of channel kinetics. While channel block inhibits healthy and pathological tissue equally, modulation can preferentially inhibit pathological activity. An ideal drug designed to target the sodium channels of pathological tissue would act predominantly by modulation. Thus far, no such drug has been described. Experimental approach Patch-clamp experiments with ultra-fast solution exchange and photolabeling-coupled electrophysiology were applied to describe the unique mechanism of riluzole on Nav1.4 sodium channels. In silico docking experiments were used to study the molecular details of binding. Key results We present evidence that riluzole acts predominantly by non-blocking modulation. We propose that, being a relatively small molecule, riluzole is able to stay bound to the binding site, but nonetheless stay off the conduction pathway, by residing in one of the fenestrations. We demonstrate how this mechanism can be recognized. Conclusions and implications Our results identify riluzole as the prototype of this new class of sodium channel inhibitors. Drugs of this class are expected to selectively prevent hyperexcitability, while having minimal effect on cells firing at a normal rate from a normal resting potential.
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- 2021
31. ATP‐sensitive K + channels control the spontaneous firing of a glycinergic interneuron in the auditory brainstem
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Ricardo M. Leão, Paulo Sergio Strazza, and Daniela Vanessa de Siqueira
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0301 basic medicine ,Dorsal cochlear nucleus ,Membrane potential ,Interneuron ,Physiology ,Chemistry ,Neurotransmission ,Inhibitory postsynaptic potential ,NERVO COCLEAR ,Resting potential ,Potassium channel ,03 medical and health sciences ,030104 developmental biology ,0302 clinical medicine ,medicine.anatomical_structure ,nervous system ,otorhinolaryngologic diseases ,medicine ,Neuron ,Neuroscience ,030217 neurology & neurosurgery - Abstract
Key points Cartwheel neurons provide potent inhibition to fusiform neurons in the dorsal cochlear nucleus (DCN). Most cartwheel neurons fire action potentials spontaneously, but the ion channels responsible for this intrinsic activity are unknown. We investigated the ion channels responsible for the intrinsic firing of cartwheel neurons and the stable resting membrane potential found in a fraction of these neurons (quiet neurons). Among the ion channels controlling membrane potential of cartwheel neurons, the presence of open ATP-sensitive potassium channels (KATP ) is responsible for the existence of quiet neurons. Our results pinpoint KATP channel modulation as a critical factor controlling the firing of cartwheel neurons. Hence, it is a crucial channel influencing the balance of excitation and inhibition in the DCN. Abstract Cartwheel neurons from the dorsal cochlear nucleus (DCN) are glycinergic interneurons and the primary source of inhibition on the fusiform neurons, the DCN's principal excitatory neuron. Most cartwheel neurons present spontaneous firing (active neurons), producing a steady inhibitory tone on fusiform neurons. In contrast, a small fraction of these neurons do not fire spontaneously (quiet neurons). Hyperactivity of fusiform neurons is seen in animals with behavioural evidence of tinnitus. Because of its relevance in controlling the excitability of fusiform neurons, we investigated the ion channels responsible for the spontaneous firing of cartwheel neurons in DCN slices from rats. We found that quiet neurons presented an outward conductance not seen in active neurons, which generates a stable resting potential. This current was sensitive to tolbutamide, an ATP-sensitive potassium channel (KATP ) antagonist. After inhibition with tolbutamide, quiet neurons start to fire spontaneously, while the active neurons were not affected. On the other hand, in active neurons, KATP agonist diazoxide activated a conductance similar to quiet neurons' KATP conductance and stopped spontaneous firing. According to the effect of KATP channels on cartwheel neuron firing, glycinergic neurotransmission in DCN was increased by tolbutamide and decreased by diazoxide. Our results reveal a role of KATP channels in controlling the spontaneous firing of neurons not involved in fuel homeostasis.
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- 2021
32. KCNQ5 Potassium Channel Activation Underlies Vasodilation by Tea
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Thomas A. Jepps, Kaitlyn E Redford, Geoffrey W. Abbott, and Salomé Rognant
- Subjects
0301 basic medicine ,Male ,Protein Conformation, alpha-Helical ,Vascular smooth muscle ,Patch-Clamp Techniques ,Physiology ,Protein Conformation ,Wistar ,Kv7 ,Vasodilation ,Green tea extract ,Pharmacology ,lcsh:Physiology ,Catechin ,Membrane Potentials ,Tissue Culture Techniques ,chemistry.chemical_compound ,KCNQ ,Xenopus laevis ,0302 clinical medicine ,Protein Isoforms ,lcsh:QD415-436 ,Mesenteric arteries ,Electrical impedance myography ,lcsh:QP1-981 ,KCNQ Potassium Channels ,Chemistry ,food and beverages ,Resting potential ,Potassium channel ,Mesenteric Arteries ,Molecular Docking Simulation ,medicine.anatomical_structure ,Milk ,030220 oncology & carcinogenesis ,KCNQ1 Potassium Channel ,Protein Binding ,Polyphenol ,Hypotensive ,complex mixtures ,Article ,lcsh:Biochemistry ,03 medical and health sciences ,medicine ,Animals ,Rats, Wistar ,Binding Sites ,Tea ,Plant Extracts ,alpha-Helical ,Myography ,Green tea ,IKS ,Rats ,030104 developmental biology ,Epicatechin gallate ,Oocytes ,beta-Strand ,Protein Conformation, beta-Strand - Abstract
BACKGROUND/AIMS: Tea, produced from the evergreen Camellia sinensis, has reported therapeutic properties against multiple pathologies, including hypertension. Although some studies validate the health benefits of tea, few have investigated the molecular mechanisms of action. The KCNQ5 voltage-gated potassium channel contributes to vascular smooth muscle tone and neuronal M-current regulation.METHODS: We applied electrophysiology, myography, mass spectrometry and in silico docking to determine effects and their underlying molecular mechanisms of tea and its components on KCNQ channels and arterial tone.RESULTS: A 1% green tea extract (GTE) hyperpolarized cells by augmenting KCNQ5 activity >20-fold at resting potential; similar effects of black tea were inhibited by milk. In contrast, GTE had lesser effects on KCNQ2/Q3 and inhibited KCNQ1/E1. Tea polyphenols epicatechin gallate (ECG) and epigallocatechin-3-gallate (EGCG), but not epicatechin or epigallocatechin, isoform-selectively hyperpolarized KCNQ5 activation voltage dependence. In silico docking and mutagenesis revealed that activation by ECG requires KCNQ5-R212, at the voltage sensor foot. Strikingly, ECG and EGCG but not epicatechin KCNQ-dependently relaxed rat mesenteric arteries.CONCLUSION: KCNQ5 activation contributes to vasodilation by tea; ECG and EGCG are candidates for future anti-hypertensive drug development.
- Published
- 2021
33. The Crawdad Project: Crustaceans as Model Systems for Teaching Principles of Neuroscience
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Johnson, Bruce R., Wyttenbach, Robert A., Hoy, Ronald R., and Wiese, Konrad, editor
- Published
- 2002
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34. Review on Muscle Movement Recording System Using EMG
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Satheesh
- Subjects
medicine.medical_specialty ,medicine.diagnostic_test ,End-plate potential ,business.industry ,Electromyography ,Recording system ,Neurophysiology ,Resting potential ,Physical medicine and rehabilitation ,Surgical Manipulation ,Medicine ,Brainstem ,business ,Muscle movement - Abstract
Electromyography is a neurophysiological technique for examining the electrical activity of skeletal muscles. It occurred from the muscle membrane potential. In a healthy muscle at rest, the spontaneous physiological activity can be a record by End plate potential, insertion activity. EMG recording of the activity of selective cranial nerve muscles is currently included in the intraoperative set during surgical manipulation of the brainstem. When during the process, weak muscles can be detected and treat those muscles to regain their function. EMG is also used to diagnose neuromuscular performance. Its gain is less and frequency response may be broader. Using the EMG technique to record the potential of muscle is an easy way to generate the resting potential of muscle.
- Published
- 2020
35. Silica Nanoparticles Disturb Ion Channels and Transmembrane Potentials of Cardiomyocytes and Induce Lethal Arrhythmias in Mice
- Author
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De-Ping Wang, Ya-Qin Liu, Lin-Na Xu, Ji-Min Cao, Peng Zhang, Guang Li, and Si-Meng Xue
- Subjects
Membrane potential ,Chemistry ,Organic Chemistry ,Biophysics ,Pharmaceutical Science ,Bioengineering ,02 engineering and technology ,General Medicine ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Resting potential ,In vitro ,0104 chemical sciences ,Biomaterials ,In vivo ,Nanotoxicology ,Drug Discovery ,Toxicity ,0210 nano-technology ,Homeostasis ,Ion channel - Abstract
Background The toxicity of silica nanoparticles (SiNPs) on cardiac electrophysiology has seldom been evaluated. Methods Patch-clamp was used to investigate the acute effects of SiNP-100 (100 nm) and SiNP-20 (20 nm) on the transmembrane potentials (TMPs) and ion channels in cultured neonatal mouse ventricular myocytes. Calcium mobilization in vitro, cardiomyocyte ROS generation, and LDH leakage after exposure to SiNPs in vitro and in vivo were measured using a microplate reader. Surface electrocardiograms were recorded in adult mice to evaluate the arrhythmogenic effects of SiNPs in vivo. SiNP endocytosis was observed using transmission electron microscopy. Results Within 30 min, both SiNPs (10-8-10-6 g/mL) did not affect the resting potential and IK1 channels. SiNP-100 increased the action potential amplitude (APA) and the INa current density, but SiNP-20 decreased APA and INa density. SiNP-100 prolonged the action potential duration (APD) and decreased the Ito current density, while SiNP-20 prolonged or shortened the APD, depending on exposure concentrations and increased Ito density. Both SiNPs (10-6 g/mL) induced calcium mobilization but did not increase ROS and LDH levels and were not endocytosed within 10 min in cardiomyocytes in vitro. In vivo, SiNP-100 (4-10 mg/kg) and SiNP-20 (4-30 mg/kg) did not elevate myocardial ROS but increased LDH levels depending on dose and exposure time. The same higher dose of SiNPs (intravenously injected) induced tachyarrhythmias and lethal bradyarrhythmias within 90 min in adult mice. Conclusion SiNPs (i) exert rapid toxic effects on the TMPs of cardiomyocytes in vitro largely owing to their direct interfering effects on the INa and Ito channels and Ca2+ homeostasis but not IK1 channels and ROS levels, and (ii) induce tachyarrhythmias and lethal bradyarrhythmias in vivo. SiNP-100 is more toxic than SiNP-20 on cardiac electrophysiology, and the toxicity mechanism is likely more complicated in vivo.
- Published
- 2020
36. Effect of Plasma Membrane Ion Currents on Chlorophyll Fluorescence and Excitation Quenching in Chara Chloroplasts
- Author
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Alexander A. Bulychev, Natalia A. Krupenina, and A. A. Cherkashin
- Subjects
0301 basic medicine ,Membrane potential ,Chemistry ,Voltage clamp ,Perforation (oil well) ,Biophysics ,Depolarization ,Cell Biology ,Hyperpolarization (biology) ,Biochemistry ,Resting potential ,Chloroplast ,03 medical and health sciences ,030104 developmental biology ,0302 clinical medicine ,Chlorophyll fluorescence ,030217 neurology & neurosurgery - Abstract
Illuminated giant cells of characean algae exhibit membrane excitability as well as the spatial patterns of photosynthesis and transmembrane H+ fluxes. The excitation of plasmalemma under these conditions results in the transient degradation of external alkaline and acid zones and inhibits photosynthesis in the alkaline zones. The generation of action potential in the patterned internodes is followed by cell hyperpolarization that peaks in 1 min and lasts up to 15 min. In order to exclude the influence of drifting resting potential on the chloroplast response to plasma membrane excitation, the voltage clamp mode was applied in this work, and chlorophyll fluorescence changes caused by a short depolarizing pulse were monitored. The depolarizing shift of membrane potential under voltage clamp conditions was found to induce a large depression of $$F_{{\text{m}}}^{{{'}}}$$ chlorophyll fluorescence and photosynthetic activity, provided that inward Ca2+ and Cl– currents were triggered and that a steady-state inward H+ flux (or OH– efflux) persisted before the application of an electric stimulus. The depolarization-induced ion currents measured in the alkaline and acidic cell regions under light and in darkness were found to differ significantly. The results are consistent with the notion that the massive inward H+ flow occurring in the alkaline cell regions under illumination is associated with the acidic shift of cytoplasmic pH. Divergent amplitudes of ionic currents in different cell parts can be partially determined by the presence of numerous plasmalemmal invaginations, charasomes specifically localized in the acid zones, as well as by sharp local changes in external pH in acid zones during the perforation of cell wall with a measuring microelectrode.
- Published
- 2020
37. Diuretic-sensitive electroneutral Na+ movement and temperature effects on central axons.
- Author
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Kanagaratnam, Meneka, Pendleton, Christopher, Souza, Danilo Almeida, Pettit, Joseph, Howells, James, and Baker, Mark D.
- Subjects
- *
DIURETICS , *SODIUM , *OPTIC nerve , *OUABAIN , *BUMETANIDE , *AMILORIDE , *HYPERPOLARIZATION (Cytology) - Abstract
Key points Optic nerve axons get less excitable with warming., F-fibre latency does not shorten at temperatures above 30°C., Action potential amplitude falls when the Na+-pump is blocked, an effect speeded by warming., Diuretics reduce the rate of action potential fall in the presence of ouabain., Our data are consistent with electroneutral entry of Na+ occurring in axons and contributing to setting the resting potential., Abstract Raising the temperature of optic nerve from room temperature to near physiological has effects on the threshold, refractoriness and superexcitability of the shortest latency (fast, F) nerve fibres, consistent with hyperpolarization. The temperature dependence of peak impulse latency was weakened at temperatures above 30°C suggesting a temperature-sensitive process that slows impulse propagation. The amplitude of the supramaximal compound action potential gets larger on warming, whereas in the presence of bumetanide and amiloride (blockers of electroneutral Na+ movement), the action potential amplitude consistently falls. This suggests a warming-induced hyperpolarization that is reduced by blocking electroneutral Na+ movement. In the presence of ouabain, the action potential collapses. This collapse is speeded by warming, and exposure to bumetanide and amiloride slows the temperature-dependent amplitude decline, consistent with a warming-induced increase in electroneutral Na+ entry. Blocking electroneutral Na+ movement is predicted to be useful in the treatment of temperature-dependent symptoms under conditions with reduced safety factor (Uhthoff's phenomenon) and provide a route to neuroprotection. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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38. Cellular electrophysiological principles that modulate secretion from synovial fibroblasts.
- Author
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Clark, R. B., Schmidt, T. A., Sachse, F. B., Boyle, D., Firestein, G. S., and Giles, W. R.
- Subjects
- *
ELECTROPHYSIOLOGY , *RHEUMATOID arthritis , *FIBROBLASTS , *SYNOVIAL fluid , *CYTOKINES - Abstract
Rheumatoid arthritis (RA) is a progressive disease that affects both pediatric and adult populations. The cellular basis for RA has been investigated extensively using animal models, human tissues and isolated cells in culture. However, many aspects of its aetiology and molecular mechanisms remain unknown. Some of the electrophysiological principles that regulate secretion of essential lubricants (hyaluronan and lubricin) and cytokines from synovial fibroblasts have been identified. Data sets describing the main types of ion channels that are expressed in human synovial fibroblast preparations have begun to provide important new insights into the interplay among: (i) ion fluxes, (ii) Ca2+ release from the endoplasmic reticulum, (iii) intercellular coupling, and (iv) both transient and longer duration changes in synovial fibroblast membrane potential. A combination of this information, knowledge of similar patterns of responses in cells that regulate the immune system, and the availability of adult human synovial fibroblasts are likely to provide new pathophysiological insights. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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39. The Dawn and Foundation of Slow Synaptic Potentials and Modulation
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Koketsu, K., Kuba, Kenji, editor, Higashida, Haruhiro, editor, Brown, David A., editor, and Yoshioka, Tohru, editor
- Published
- 2000
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40. KRÓTKOCZASOWA EKSPOZYCJA GLONÓW SŁODKOWODNYCH NA ORGANICZNE ZWIĄZKI OŁOWIU -NIEINWAZYJNE BADANIA ELEKTRYCZNE I LUMINESCENCYJNE.
- Author
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Borc, Robert, Jaśkowska, Anna, and Dudziak, Andrzej
- Abstract
Copyright of Ecological Engineering / Inżynieria Ekologiczna is the property of Polish Society of Ecological Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2016
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41. Physiological Effects of the Electrogenic Current Generated by the Na+/K+Pump in Mammalian Articular Chondrocytes
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Wayne R. Giles, Mary M. Maleckar, Pablo Martín-Vasallo, and Ali Mobasheri
- Subjects
Membrane potential ,Transplantation ,Chemistry ,Biomedical Engineering ,Medicine (miscellaneous) ,Transporter ,Resting potential ,Chondrocyte ,Cell biology ,Electrophysiology ,medicine.anatomical_structure ,medicine ,Extracellular ,Electrical and Electronic Engineering ,Na+/K+-ATPase ,Ion channel - Abstract
Background: Although the chondrocyte is a nonexcitable cell, there is strong interest in gaining detailed knowledge of its ion pumps, channels, exchangers, and transporters. In combination, these transport mechanisms set the resting potential, regulate cell volume, and strongly modulate responses of the chondrocyte to endocrine agents and physicochemical alterations in the surrounding extracellular microenvironment. Materials and Methods: Mathematical modeling was used to assess the functional roles of energy-requiring active transport, the Na+/K+ pump, in chondrocytes. Results: Our findings illustrate plausible physiological roles for the Na+/K+ pump in regulating the resting membrane potential and suggest ways in which specific molecular components of pump can respond to the unique electrochemical environment of the chondrocyte. Conclusion: This analysis provides a basis for linking chondrocyte electrophysiology to metabolism and yields insights into novel ways of manipulating or regulating responsiveness to external stimuli both under baseline conditions and in chronic diseases such as osteoarthritis.
- Published
- 2020
42. Action Potentials: Generation and Propagation
- Author
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Mohamed A. Fouda and Peter C. Ruben
- Subjects
Membrane potential ,Voltage-gated ion channel ,Chemistry ,Sodium channel ,Biophysics ,Analytical chemistry ,Voltage-gated potassium channel ,Hyperpolarization (biology) ,Resting potential ,Ion channel ,Ventricular action potential - Abstract
All cells maintain a voltage across their plasma membranes. Only excitable cells, however, can generate action potentials, the rapid, transient changes in membrane potential that spread along the surface of these unique cells. Action potential generation and propagation occurs through, and is regulated by, the function of voltage-gated ion channels – proteins with ion-selective pores that span the cell membrane. Ion channels undergo changes in their structural conformation in response to changes in the electrical field across the membrane. These structural changes cause the opening of pores – channels – through which ions can flow down their electrochemical gradient. The charge carried by ions creates an electrical current and rapidly alters the membrane potential with time- and voltage-dependent properties. This rapid, transient membrane potential change is called the action potential. Action potentials transmit information within neurons, trigger contractions within muscle cells, and lead to exocytosis in secretory cells. Key Concepts: All cells maintain a voltage difference across their plasma membranes. Action potentials are all-or-nothing, transient changes in membrane potentials of electrically excitable cells that carry important cellular information. Influx of sodium ions through voltage-gated sodium channels is responsible for the upstroke of the action potential, whereas efflux of potassium ions through voltage-gated potassium channels is responsible for the falling phase. Propagation of action potentials depends on gating kinetics of ion channels and intracellular and membrane resistances. Keywords: membrane potential; ionic current; threshold; refractoriness; length constant
- Published
- 2020
43. A Noninvasive Electrophysiological Investigation of Tactile Sensitivity in Cyprinid Fish (Cyprinidae)
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D. N. Lapshin and G. V. Devitsina
- Subjects
0301 basic medicine ,Sensory stimulation therapy ,Physiology ,Sensory system ,Anatomy ,Biology ,Stimulus (physiology) ,biology.organism_classification ,Biochemistry ,Resting potential ,Tonic (physiology) ,03 medical and health sciences ,Common carp ,030104 developmental biology ,0302 clinical medicine ,Crucian carp ,Cyprinidae ,030217 neurology & neurosurgery ,Ecology, Evolution, Behavior and Systematics - Abstract
Tactile reception in cyprinid fish (silver crucian carp Carassius auratus gibelio and common carp Cyprinus carpio) was investigated by noninvasive recording of action potentials from the head skin in response to rhythmic tactile stimulation. Responses shaped as electric potentials following synchronously with changes in the pressure force on the skin were recorded using chloro-silver electrodes. It was shown that fish, like all terrestrial vertebrates, have phasic and tonic tactile receptors. Three main types of tactile responses were distinguished: (1) tonic responses as potential fluctuations repeating the dynamics of the tactile stimulus, (2) phasic responses as on-, off-, and on-off potentials, and (3) slow deflections from the resting potential. Compound responses comprising simultaneously different types of responses were also recorded. The response latency averaging 6.1 ms for tonic and 4.4 ms for phasic responses was clearly independent of the stimulus direction (switch-on, switch-off). The threshold level of tactile sensitivity in the perioral and gular head areas was 0.05–0.2 g/mm2. Tactile receptors on the silver crucian carp and common carp heads exhibited zonal distribution patterns, with sensory areas differing in their tactile sensitivity. Most sensitive areas were on the upper and lower lips, in the perilabial skin and the gular area on the ventral side of the head. Less sensitive areas were situated rostrally and ventrally to the eyeball. The areas situated dorsally and caudally to the eyeball proved to be insensitive to the applied tactile stimulation. In all sensory areas on the fish head, most intense responses were evoked by sliding tactile stimuli. The distribution specificity of tactile sensory areas meets their functional significance for fish feeding behavior.
- Published
- 2020
44. PRMT7 deficiency causes dysregulation of the HCN channels in the CA1 pyramidal cells and impairment of social behaviors
- Author
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Seul-Yi Lee, Yoo Bin Kim, Ilmin Kwon, Hyun-Kyung So, Tuan Anh Vuong, Hana Cho, Jong-Sun Kang, and Hyun-Ji Kim
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Scaffold protein ,Protein-Arginine N-Methyltransferases ,Patch-Clamp Techniques ,Clinical Biochemistry ,Cell ,Neurophysiology ,Action Potentials ,lcsh:Medicine ,Hippocampal formation ,Biochemistry ,Article ,Cell Line ,lcsh:Biochemistry ,Mice ,Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels ,medicine ,HCN channel ,Animals ,Humans ,lcsh:QD415-436 ,Social Behavior ,CA1 Region, Hippocampal ,Molecular Biology ,Ion channel ,Mice, Knockout ,Messenger RNA ,Excitability ,Behavior, Animal ,biology ,Chemistry ,Pyramidal Cells ,lcsh:R ,Resting potential ,Phenotype ,Cell biology ,medicine.anatomical_structure ,nervous system ,Gene Expression Regulation ,biology.protein ,Molecular Medicine ,Biomarkers - Abstract
HCN channels regulate excitability and rhythmicity in the hippocampal CA1 pyramidal cells. Perturbation in the HCN channel current (Ih) is associated with neuropsychiatric disorders, such as autism spectrum disorders. Recently, protein arginine methyltransferase 7 (PRMT7) was shown to be highly expressed in the hippocampus, including the CA1 region. However, the physiological function of PRMT7 in the CA1 neurons and the relationship to psychiatric disorders are unclear. Here we showed that PRMT7 knockout (KO) mice exhibit hyperactivity and deficits in social interaction. The firing frequency of the CA1 neurons in the PRMT7 KO mice was significantly higher than that in the wild-type (WT) mice. Compared with the WT CA1 neurons, the PRMT7 KO CA1 neurons showed a more hyperpolarized resting potential and a higher input resistance, which were occluded by the Ih-current inhibitor ZD7288; these findings were consistent with the decreased Ih and suggested the contribution of Ih-channel dysfunction to the PRMT7 KO phenotypes. The HCN1 protein level was decreased in the CA1 region of the PRMT7 KO mice in conjunction with a decrease in the expression of Shank3, which encodes a core scaffolding protein for HCN channel proteins. A brief application of the PRMT7 inhibitor DS437 did not reproduce the phenotype of the PRMT7 KO neurons, further indicating that PRMT7 regulates Ih by controlling the channel number rather than the open probability. Moreover, shRNA-mediated PRMT7 suppression reduced both the mRNA and protein levels of SHANK3, implying that PRMT7 deficiency might be responsible for the decrease in the HCN protein levels by altering Shank3 expression. These findings reveal a key role for PRMT7 in the regulation of HCN channel density in the CA1 pyramidal cells that may be amenable to pharmacological intervention for neuropsychiatric disorders., Neuroscience: Finding the brakes in the autistic brain Disrupted expression of an ion channel that helps stabilize brain cell activity contributes to behavioral symptoms in mice resembling those seen in autism spectrum disorders (ASDs). Nerve cell firing depends on the right balance of ions inside and outside cells, and a channel protein called HCN helps establish ionic conditions that prevent excessive activity. Researchers led by Hana Cho and Ilmin Kwon of the Sungkyunkwan University School of Medicine, Suwon, South Korea have demonstrated that mice lacking another protein called PRMT7 exhibit reduced numbers of HCN channels in brain structures known to be affected in animal models of ASDs. These mice exhibit hyperactivity and social anxiety, presumably as a consequence of poor regulation of nerve cell firing. The authors propose that this PRMT7-HCN pathway may offer a fruitful target for the development of neuropsychiatric therapies.
- Published
- 2020
45. Neuronal microRNAs modulate TREK two-pore domain K+ channel expression and current density
- Author
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Panagiota Papazafiri, Tudor Selescu, Skarlatos G. Dedos, Epaminondas Doxakis, Maria Paschou, Larisa Maier, and Alexandru Babes
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Untranslated region ,0303 health sciences ,Voltage clamp ,Cell Biology ,Biology ,Neuroprotection ,Resting potential ,Potassium channel ,Cell biology ,03 medical and health sciences ,0302 clinical medicine ,medicine.anatomical_structure ,Dorsal root ganglion ,030220 oncology & carcinogenesis ,microRNA ,Gene expression ,medicine ,Molecular Biology ,030304 developmental biology - Abstract
The TREK family of leak potassium channels has been found to play critical roles in nociception, sensitivity to general anaesthetics, neuroprotection, and memory. The three members of the family, TREK1, TREK2 and TRAAK establish the resting potential and modify the duration, frequency and amplitude of action potentials. Despite their apparent importance, the repertoire of regulatory interactions utilized by cells to control their expression is poorly understood. Herein, the contribution of miRNAs in the regulation of their post-transcriptional gene expression has been examined. Using different assays, miR-124 and to a lesser extent miR-128 and miR-183 were found to reduce TREK1 and TREK2 levels through specific binding to their 3'UTRs. In contrast, miR-9 which was predicted to bind to TRAAK 3'UTR, did not alter its expression. Expression of miR-124, miR-128 and miR-183 was found to mirror that of Trek1 and Trek2 mRNAs during brain development. Moreover, application of proinflammatory mediators in dorsal root ganglion (DRG) neurons revealed an inverse correlation between miR-124 and Trek1 and Trek2 mRNA expression. Voltage clamp recordings of TREK2-mediated currents showed that miR-124 reduced the sensitivity of TREK2-expressing cells to non-aversive warmth stimulation. Overall, these findings reveal a significant regulatory mechanism by which TREK1 and TREK2 expression and hence activity are controlled in neurons and uncover new druggable targets for analgesia and neuroprotection.Abbreviations: microRNA: miRNA; UTR: untranslated region; K2p channels: two-pore domain K+channels; DRG: dorsal root ganglion; CNS: central nervous system; FBS: fetal bovine serum; TuD: Tough Decoy; TREK: tandem P-domain weak inward rectifying K+ (TWIK)-related K+ channel 1; TRAAK: TWIK-related arachidonic acid K+.
- Published
- 2020
46. Bioelectrical domain walls in homogeneous tissues
- Author
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Gloria Ortiz, Rajath Salegame, Adam E. Cohen, Haitan Xu, Ziad Al Tanoury, Shahinoor Begum, Olivier Pourquié, and Harold M. McNamara
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Physics ,Membrane potential ,General Physics and Astronomy ,Conductance ,01 natural sciences ,Resting potential ,Article ,010305 fluids & plasmas ,Electrophysiology ,Domain wall (string theory) ,0103 physical sciences ,Biophysics ,Myocyte ,Symmetry breaking ,010306 general physics ,Induced pluripotent stem cell - Abstract
Electrical signaling in biology is typically associated with action potentials, transient spikes in membrane voltage that return to baseline. Hodgkin-Huxley and related conductance-based models of electrophysiology belong to a more general class of reaction-diffusion equations which could, in principle, support spontaneous emergence of patterns of membrane voltage which are stable in time but structured in space. Here we show theoretically and experimentally that homogeneous or nearly homogeneous tissues can undergo spontaneous spatial symmetry breaking through a purely electrophysiological mechanism, leading to formation of domains with different resting potentials separated by stable bioelectrical domain walls. Transitions from one resting potential to another can occur through long-range migration of these domain walls. We map bioelectrical domain wall motion using all-optical electrophysiology in an engineered cell line and in human induced pluripotent stem cell (iPSC)-derived myoblasts. Bioelectrical domain wall migration may occur during embryonic development and during physiological signaling processes in polarized tissues. These results demonstrate that nominally homogeneous tissues can undergo spontaneous bioelectrical symmetry breaking.
- Published
- 2020
47. pH-Чувствительный калиевый канал TASK-1 ‒ хемосенсор центральной регуляции дыхания у крыс
- Author
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Y. Y. Zhang, M. S. Xu, Z. M. Pan, Fuxiu Mao, Chengtan Wang, L. M. Wang, Kexing Wan, J. L. Zhu, Qiongqiong Li, and Rui Gao
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medicine.medical_specialty ,Central chemoreceptors ,Chemistry ,Respiratory center ,Depolarization ,General Medicine ,Resting potential ,Potassium channel ,Endocrinology ,Internal medicine ,Extracellular ,medicine ,Brainstem ,Respiratory system - Abstract
TWIK-related acid-sensitive potassium channel-1 (TASK-1) is a "leak" potassium channel sensitive to extracellular protons. It contributes to setting the resting potential in mammalian neurons. TASK-1 channels are widely expressed in respiratory-related neurons in the central nervous system. Inhibition of TASK-1 by extracellular acidosis can depolarize and increase the excitability of these cells. Here we describe the distribution of TASK-1 in the rat brainstem and show that TASK-1 mRNAs are present in respiratory-related nuclei in the ventrolateral medulla, which have been proposed as neural substrates for central chemo-reception in rats. After inhalation of 8% CO2 for 30 and 60 min, TASK-1 mRNA levels in positive-expression neurons were remarkably upregulated. Injection of the TASK-1 blocker anandamide (AEA) into the rat lateral cerebral ventricle, showed a significant excitement of respiratory at 10 min posttreatment, with a marked decrease in inspiratory and expiratory durations and an increased frequency of respiration. We suggest that TASK-1 channel may serve as a chemosensor for in central respiration and may contribute to pH-sensitive respiratory effects. TASK-1 channel might be an attractive candidate for sensing H^(+)/CO2 in several respiratory-related nuclei in the brainstem. It is likely that TASK-1 participates in pH-sensitive chemical regulation in the respiratory center under physiological and pathological conditions.
- Published
- 2020
48. A characterization of the electrophysiological properties of the cardiomyocytes from ventricle, atrium and sinus venosus of the snake heart
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Vladimir V. Matchkov, Tobias Wang, and Denis V. Abramochkin
- Subjects
030110 physiology ,0106 biological sciences ,0301 basic medicine ,medicine.medical_specialty ,Patch-Clamp Techniques ,Physiology ,Heart Ventricles ,Action Potentials ,Reptile ,010603 evolutionary biology ,01 natural sciences ,Biochemistry ,Ion Channels ,03 medical and health sciences ,Endocrinology ,Internal medicine ,medicine ,Animals ,Repolarization ,Myocyte ,Myocytes, Cardiac ,Heart Atria ,cardiovascular diseases ,Patch clamp ,Python molurus ,Ecology, Evolution, Behavior and Systematics ,Sinus venosus ,Atrium (architecture) ,Chemistry ,Action potential ,Heart ,Snakes ,Resting potential ,Acetylcholine ,Electrophysiological Phenomena ,Pacemaker ,Electrophysiology ,medicine.anatomical_structure ,Ventricle ,cardiovascular system ,Cardiology ,Animal Science and Zoology ,Ionic current - Abstract
A detailed description of the electrophysiological features of cardiomyocytes in the various contractile chambers of the vertebrate heart is essential to understand the evolution of cardiac electrical activity, yet very little is known about reptiles. The present study characterizes major ionic currents (I Na, I CaL, I Kr, I K1 and I KACh) and action potential (AP) configuration in cardiomyocytes from the ventricle, the right atrium and the sinus venosus (SV) of Burmese pythons (Python molurus) using sharp microelectrode and patch clamp recordings. Special attention was given to SV, since it consists of myocardial cells and appears to contribute to right atrial filling in snakes. We demonstrate that most of the SV in pythons has a stable resting potential of − 82.3 ± 2.6 mV (n = 9) and lacks pacemaker activity. AP duration at 50% repolarization was similar in cells from SV and atria (350.2 ± 8.7 and 330.4 ± 17.2 ms, respectively; n = 7), but shorter than ventricular APs (557.6 ± 19.2 ms, n = 5) at 30 °C. The densities of ionic currents, however, differed substantially between atrial and SV cells, where the latter had much lower densities of I Na, I CaL and I Kr than atrial and ventricular myocytes. I K1 in ventricle was ninefold greater than in atrial cells and 23-fold greater than in myocytes from SV. However, I KACh was absent in ventricular cells, while it was equally large in atrial and SV myocytes. Consistent with this observation, APs of atrium and SV, but not ventricle, were greatly shortened upon addition of acetylcholine (10 −6 M). Thus, snake SV, right atrium and ventricle have distinct patterns of ionic currents, but the resulting electrical activity is similar in atrium and SV.
- Published
- 2019
49. Outer hair cell electromotility is low-pass filtered relative to the molecular conformational changes that produce nonlinear capacitance
- Author
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Winston Tan, Kuni H. Iwasa, and Joseph Santos-Sacchi
- Subjects
0301 basic medicine ,Frequency response ,Patch-Clamp Techniques ,Physiology ,Voltage clamp ,Guinea Pigs ,Molecular Conformation ,Gating ,Electric Capacitance ,Mechanotransduction, Cellular ,Membrane Potentials ,Mice ,03 medical and health sciences ,0302 clinical medicine ,otorhinolaryngologic diseases ,medicine ,Animals ,Prestin ,Research Articles ,Physics ,biology ,Cell Membrane ,Time constant ,Proteins ,Resting potential ,Cochlea ,Electrophysiology ,Hair Cells, Auditory, Outer ,030104 developmental biology ,medicine.anatomical_structure ,Organ of Corti ,biology.protein ,Biophysics ,sense organs ,Hair cell ,030217 neurology & neurosurgery ,Research Article - Abstract
Cochlear amplification is mediated by the outer hair cell of the organ of Corti. Santos-Sacchi et al. reveal that the cell possesses a voltage-dependent motile frequency response that differs from that of its voltage sensor/effector, the electromotile protein prestin, implying variable coupling between the two., The outer hair cell (OHC) of the organ of Corti underlies a process that enhances hearing, termed cochlear amplification. The cell possesses a unique voltage-sensing protein, prestin, that changes conformation to cause cell length changes, a process termed electromotility (eM). The prestin voltage sensor generates a capacitance that is both voltage- and frequency-dependent, peaking at a characteristic membrane voltage (Vh), which can be greater than the linear capacitance of the OHC. Accordingly, the OHC membrane time constant depends upon resting potential and the frequency of AC stimulation. The confounding influence of this multifarious time constant on eM frequency response has never been addressed. After correcting for this influence on the whole-cell voltage clamp time constant, we find that both guinea pig and mouse OHC eM is low pass, substantially attenuating in magnitude within the frequency bandwidth of human speech. The frequency response is slowest at Vh, with a cut-off, approximated by single Lorentzian fits within that bandwidth, near 1.5 kHz for the guinea pig OHC and near 4.3 kHz for the mouse OHC, each increasing in a U-shaped manner as holding voltage deviates from Vh. Nonlinear capacitance (NLC) measurements follow this pattern, with cut-offs about double that for eM. Macro-patch experiments on OHC lateral membranes, where voltage delivery has high fidelity, confirms low pass roll-off for NLC. The U-shaped voltage dependence of the eM roll-off frequency is consistent with prestin’s voltage-dependent transition rates. Modeling indicates that the disparity in frequency cut-offs between eM and NLC may be attributed to viscoelastic coupling between prestin’s molecular conformations and nanoscale movements of the cell, possibly via the cytoskeleton, indicating that eM is limited by the OHC’s internal environment, as well as the external environment. Our data suggest that the influence of OHC eM on cochlear amplification at higher frequencies needs reassessment.
- Published
- 2019
50. Physiological changes throughout the ear due to age and noise - a longitudinal study
- Author
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Ben Warren, Daisy Ogle, Charlie Woodrow, Alix Blockley, and Fernando Montealegre-Zapata
- Subjects
medicine.medical_specialty ,Longitudinal study ,biology ,Hearing loss ,Audiology ,biology.organism_classification ,Resting potential ,Electrophysiology ,Noise ,medicine.anatomical_structure ,medicine ,Auditory system ,Schistocerca ,medicine.symptom ,Transduction (physiology) - Abstract
Biological and mechanical systems, whether by their overuse or their aging, will inevitably fail. Hearing provides a poignant example of this with noise-induced and age-related hearing loss. Hearing loss is not unique to humans, however, and is experienced by all animals in the face of wild and eclectic differences in ear morphology and operation. Here we exploited the high throughput and accessible tympanal ear of the desert locust, Schistocerca gregaria (mixed sex) to rigorously quantify changes in the auditory system due to noise exposure (3 kHz pure tone at 126 dB SPL) and age. We analysed tympanal dispalcements, morphology of the auditory Müller’s organ and measured activity of the auditory nerve, the transduction current and electrophysiological properties of individual auditory receptors. We found that noise mildly and transiently changes tympanal displacements, decreases both the width of the auditory nerve and the transduction current recorded from individual auditory neurons. Whereas age – but not noise - decreases the number of auditory neurons and increases their resting potential. Multiple other properties of Müller’s organ were unaffected by either age or noise including: the number of supporting cells in Müller’s organ or the nerve, membrane resistance and capacitance of the auditory neurons. The sound-evoked activity of the auditory nerve decreased as a function of age and this decrease was exacerbated by noise, with the largest difference during the middle of their life span. This ‘middle-aged deafness’ pattern of hearing loss mirrors that found for humans exposed to noise early in their life.Key point summaryAge and noise lead to hearing loss.Tympanal displacements have a transient and delayed reduction after noise.The number of auditory neurons decreases with age. The width of the auditory nerve is reduced with noise exposure.Locusts repeatedly exposed to noise lost their hearing compared to silent controls, but their hearing became similar to old silent control locusts due to age-related hearing loss dominating.The electrophysiological properties of the auditory neurons and the transduction current remained unchanged for aged locusts but repeated noise exposure led to a cumulative decrease in the transduction current.
- Published
- 2021
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