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Potassium current voltage clamp

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https://www.readbyqxmd.com/read/28228734/%C3%AE-subunits-functionally-differentiate-human-kv4-3-potassium-channel-splice-variants
#1
Geoffrey W Abbott
The human ventricular cardiomyocyte transient outward K(+) current (Ito) mediates the initial phase of myocyte repolarization and its disruption is implicated in Brugada Syndrome and heart failure (HF). Human cardiac Ito is generated primarily by two Kv4.3 splice variants (Kv4.3L and Kv4.3S, diverging only by a C-terminal, S6-proximal, 19-residue stretch unique to Kv4.3L), which are differentially remodeled in HF, but considered functionally alike at baseline. Kv4.3 is regulated in human heart by β subunits including KChIP2b and KCNEs, but their effects were previously assumed to be Kv4...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/28197715/vacuolar-ion-channels-in-the-liverwort-marchantia-polymorpha-influence-of-ion-channel-inhibitors
#2
Mateusz Koselski, Kazimierz Trebacz, Halina Dziubinska
Potassium-permeable slow activating vacuolar channels (SV) and chloride-permeable channels in the vacuole of the liverwort Marchantia polymorpha were characterized in respect to calcium dependence, selectivity, and pharmacology. The patch-clamp method was used in the study of ion channel activity in the vacuoles from the liverwort Marchantia polymorpha. The whole-vacuole recordings allowed simultaneous observation of two types of currents-predominant slow activated currents recorded at positive voltages and fast activated currents recorded at negative voltages...
February 14, 2017: Planta
https://www.readbyqxmd.com/read/28119399/an-als-associated-mutant-sod1-rapidly-suppresses-kcnt1-slack-na-activated-k-channels-in-aplysia-neurons
#3
Yalan Zhang, Weiming Ni, Arthur L Horwich, Leonard K Kaczmarek
: Mutations that alter levels of Slack (KCNT1) Na(+)-activated K(+) current produce devastating effects on neuronal development and neuronal function. We now find that Slack currents are rapidly suppressed by oligomers of mutant human Cu/Zn superoxide dismutase 1 (SOD1), which are associated with motor neuron toxicity in an inherited form of amyotrophic lateral sclerosis (ALS). We recorded from bag cell neurons of Aplysia Californica, a model system to study neuronal excitability. We found that injection of fluorescent wild-type SOD1 (wt SOD1YFP) or monomeric mutant G85R SOD1YFP had no effect on net ionic currents measured under voltage clamp...
January 24, 2017: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
https://www.readbyqxmd.com/read/28119170/existence-of-atp-sensitive-potassium-currents-on-human-periodontal-ligament-cells
#4
Phuong Thi Huyen Tran, Young Hee Lee, Janardhan Prasad Bhattarai, Soo Joung Park, Ho-Keun Yi, Seong Kyu Han
OBJECTIVE: Potassium channels of the ATP-sensitive family (KATP channel) are inhibited by increase in intracellular ATP. Electrophysiological studies have demonstrated that the kinetics and pharmacological properties of KATP channels vary among different tissues, suggesting structurally and functionally distinct types. There are studies showing human periodontal ligament (PDL) cells respond to mechanical stress by increasing ATP release, which participates in bone resorption or bone homeostasis...
January 17, 2017: Archives of Oral Biology
https://www.readbyqxmd.com/read/28096388/competition-of-calcified-calmodulin-n-lobe-and-pip2-to-an-lqt-mutation-site-in-kv7-1-channel
#5
William Sam Tobelaim, Meidan Dvir, Guy Lebel, Meng Cui, Tal Buki, Asher Peretz, Milit Marom, Yoni Haitin, Diomedes E Logothetis, Joel Alan Hirsch, Bernard Attali
Voltage-gated potassium 7.1 (Kv7.1) channel and KCNE1 protein coassembly forms the slow potassium current IKS that repolarizes the cardiac action potential. The physiological importance of the IKS channel is underscored by the existence of mutations in human Kv7.1 and KCNE1 genes, which cause cardiac arrhythmias, such as the long-QT syndrome (LQT) and atrial fibrillation. The proximal Kv7.1 C terminus (CT) binds calmodulin (CaM) and phosphatidylinositol-4,5-bisphosphate (PIP2), but the role of CaM in channel function is still unclear, and its possible interaction with PIP2 is unknown...
January 31, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28075010/stimulatory-actions-of-a-novel-thiourea-derivative-on-large-conductance-calcium-activated-potassium-channels
#6
Sheng-Nan Wu, Jyh-Haur Chern, Santai Shen, Hwei-Hisen Chen, Ying-Ting Hsu, Chih-Chin Lee, Ming-Huan Chan, Ming-Chi Lai, Feng-Shiun Shie
AIM: In this study, we examine whether an anti-inflammatory thiourea derivative, compound #326, actions on ion channels. METHODS: The effects of compound #326 on Ca(2+) -activated K(+) channels were evaluated by patch-clamp recordings obtained in cell-attached, inside-out or whole-cell configuration. RESULTS: In pituitary GH3 cells, compound #326 increased the amplitude of Ca(2+) -activated K(+) currents (IK(Ca) ) with an EC50 value of 11...
January 11, 2017: Journal of Cellular Physiology
https://www.readbyqxmd.com/read/28072464/genistein-and-tyrphostin-ag556-decrease-ultra-rapidly-activating-delayed-rectifier-k-current-of-human-atria-by-inhibiting-egf-receptor-tyrosine-kinase
#7
Guo-Sheng Xiao, Yan-Hui Zhang, Wei Wu, Hai-Ying Sun, Yan Wang, Gui-Rong Li
BACKGROUND AND PURPOSE: The ultra-rapidly activating delayed rectifier K(+) current IKur (encoded by Kv 1.5 or KCNA5) plays an important role in human atrial repolarization. The present study investigates the regulation of this current by protein tyrosine kinases (PTKs). EXPERIMENTAL APPROACH: Whole-cell patch voltage clamp technique and immunoprecipitation and Western blotting analysis were used to investigate whether the PTK inhibitors genistein, tyrphostin AG556 (AG556) and PP2 regulate human atrial IKur and hKv1...
March 2017: British Journal of Pharmacology
https://www.readbyqxmd.com/read/28066143/acepromazine-inhibits-herg-potassium-ion-channels-expressed-in-human-embryonic-kidney-293-cells
#8
Young Shin Joo, Hong Joon Lee, Jin-Sung Choi, Ki-Wug Sung
The effects of acepromazine on human ether-à-go-go-related gene (hERG) potassium channels were investigated using whole-cell voltage-clamp technique in human embryonic kidney (HEK293) cells transfected with hERG. The hERG currents were recorded with or without acepromazine, and the steady-state and peak tail currents were analyzed for the evaluating the drug effects. Acepromazine inhibited the hERG currents in a concentration-dependent manner with an IC50 value of 1.5 µM and Hill coefficient of 1.1. Acepromazine blocked hERG currents in a voltage-dependent manner between -40 and +10 mV...
January 2017: Korean Journal of Physiology & Pharmacology
https://www.readbyqxmd.com/read/28058990/restoration-of-the-response-of-the-middle-cerebral-artery-of-the-rat-to-acidosis-in-hyposmotic-hyponatremia-by-the-opener-of-large-conductance-calcium-sensitive-potassium-channels-bkca
#9
Marta Aleksandrowicz, Beata Dworakowska, Krzysztof Dolowy, Ewa Kozniewska
Hyposmotic hyponatremia (the decrease of extracellular concentration of sodium ions from 145 to 121 mM and the decrease of hyposmolality from 300 to 250 mOsm/kg H2O) impairs response of the middle cerebral artery (MCA) to acetylcholine and NO donor (S-nitroso-N-acetyl-DL-penicillamine). Since acidosis activates a similar intracellular signaling pathway, the present study was designed to verify the hypothesis that the response of the MCA to acidosis is impaired during acute hyposmotic hyponatremia due to abnormal NO-related signal transduction in vascular smooth muscle cells...
January 1, 2017: Journal of Cerebral Blood Flow and Metabolism
https://www.readbyqxmd.com/read/28056022/l-type-calcium-channel-inhibition-contributes-to-the-proarrhythmic-effects-of-aconitine-in-human-cardiomyocytes
#10
Jianjun Wu, Xiangchong Wang, Ying Ying Chung, Cai Hong Koh, Zhenfeng Liu, Huicai Guo, Qiang Yuan, Chuan Wang, Suwen Su, Heming Wei
Aconitine (ACO) is well-known for causing lethal ventricular tachyarrhythmias. While cardiac Na+ channel opening during repolarization has long been documented in animal cardiac myocytes, the cellular effects and mechanism of ACO in human remain unexplored. This study aimed to assess the proarrhythmic effects of ACO in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). ACO concentration-dependently (0.3 ~ 3.0 μM) shortened the action potentials (AP) durations (APD) in ventricular-like hiPSC-CMs by > 40% and induced delayed after-depolarization...
2017: PloS One
https://www.readbyqxmd.com/read/27997898/mechanisms-of-iherg-ikr-modulation-by-%C3%AE-1-adrenoceptors-in-hek293-cells-and-cardiac-myocytes
#11
Janire Urrutia, Aintzane Alday, Mónica Gallego, L Layse Malagueta-Vieira, Ivan Arael Aréchiga-Figueroa, Oscar Casis, José Antonio Sánchez-Chapula
BACKGROUND: The rapid delayed rectifier K+ current (IKr), carried by the hERG protein, is one of the main repolarising currents in the human heart and a reduction of this current increases the risk of ventricular fibrillation. α1-adrenoceptors (α1-AR) activation reduces IKr but, despite the clear relationship between an increase in the sympathetic tone and arrhythmias, the mechanisms underlying the α1-AR regulation of the hERG channel are controversial. Thus, we aimed to investigate the mechanisms by which α1-AR stimulation regulates IKr...
2016: Cellular Physiology and Biochemistry
https://www.readbyqxmd.com/read/27924669/effects-of-15%C3%A2-hz-square-wave-magnetic-fields-on-the-voltage-gated-sodium-and-potassium-channels-in-prefrontal-cortex-pyramidal-neurons
#12
Yu Zheng, Jun-Rong Dou, Yang Gao, Lei Dong, Gang Li
PURPOSE: Although magnetic fields have significant effects on neurons, little is known about the mechanisms behind their effects. The present study aimed to measure the effects of magnetic fields on ion channels in cortical pyramidal neurons. MATERIALS AND METHODS: Cortical pyramidal neurons of Kunming mice were isolated and then subjected to 15 Hz, 1 mT square wave (duty ratio 50%) magnetic fields stimulation. Sodium currents (INa), transient potassium currents (IA) and delayed rectifier potassium currents (IK) were recorded by whole-cell patch clamp method...
December 7, 2016: International Journal of Radiation Biology
https://www.readbyqxmd.com/read/27861889/margatoxin-bound-quantum-dots-as-a-novel-inhibitor-of-the-voltage-gated-ion-channel-kv1-3
#13
Austin B Schwartz, Anshika Kapur, Wentao Wang, Zhenbo Huang, Erminia Fardone, Goutam Palui, Hedi Mattoussi, Debra Ann Fadool
Venom-derived ion channel inhibitors have strong channel selectivity, potency, and stability; however, tracking delivery to their target can be challenging. Herein, we utilized luminescent quantum dots (QDs) conjugated to margatoxin (MgTx) as a traceable vehicle to target a voltage-dependent potassium channel, Kv1.3, which has a select distribution and well-characterized role in immunity, glucose metabolism, and sensory ability. We screened both unconjugated (MgTx) and conjugated MgTx (QD-MgTx) for their ability to inhibit Shaker channels Kv1...
February 2017: Journal of Neurochemistry
https://www.readbyqxmd.com/read/27832077/high-frequency-resonance-in-the-gerbil-medial-superior-olive
#14
Jason Mikiel-Hunter, Vibhakar Kotak, John Rinzel
A high-frequency, subthreshold resonance in the guinea pig medial superior olive (MSO) was recently linked to the efficient extraction of spatial cues from the fine structure of acoustic stimuli. We report here that MSO neurons in gerbil also have resonant properties and, based on our whole-cell recordings and computational modeling, that a low-voltage-gated potassium current, IKLT, underlies the resonance. We show that resonance was lost following dynamic clamp replacement of IKLT with a leak conductance and in the model when voltage-gating of IKLT was suppressed...
November 2016: PLoS Computational Biology
https://www.readbyqxmd.com/read/27796577/regulation-of-human-cardiac-kv1-5-channels-by-extracellular-acidification
#15
Shuang Wang, Wei-Guang Ding, Jia-Yu Bai, Futoshi Toyoda, Min-Jie Wei, Hiroshi Matsuura
Human Kv1.5 channels (hKv1.5) conduct the ultra-rapid delayed rectifier potassium current (I Kur), which plays an important role in action potential repolarization of atrial myocytes. The present study was undertaken to examine the effects of acidic pH on hKv1.5 wild-type (WT) and its pore mutant channels heterologously expressed in Chinese hamster ovary (CHO) cells using site-directed mutagenesis combined with whole-cell patch-clamp technique. Both extracellular and intracellular acidifications equally and reversely reduced the amplitude of hKv1...
November 2016: Pflügers Archiv: European Journal of Physiology
https://www.readbyqxmd.com/read/27789942/comparison-of-cellular-effects-of-starch-coated-spions-and-poly-lactic-co-glycolic-acid-matrix-nanoparticles-on-human-monocytes
#16
COMPARATIVE STUDY
Dominik Gonnissen, Ying Qu, Klaus Langer, Cengiz Öztürk, Yuliang Zhao, Chunying Chen, Guiscard Seebohm, Martina Düfer, Harald Fuchs, Hans-Joachim Galla, Kristina Riehemann
Within the last years, progress has been made in the knowledge of the properties of medically used nanoparticles and their toxic effects, but still, little is known about their influence on cellular processes of immune cells. The aim of our comparative study was to present the influence of two different nanoparticle types on subcellular processes of primary monocytes and the leukemic monocyte cell line MM6. We used core-shell starch-coated superparamagnetic iron oxide nanoparticles (SPIONs) and matrix poly(lactic-co-glycolic acid) (PLGA) nanoparticles for our experiments...
2016: International Journal of Nanomedicine
https://www.readbyqxmd.com/read/27774053/calretinin-periglomerular-interneurons-in-mice-olfactory-bulb-cells-of-few-words
#17
Alex Fogli Iseppe, Angela Pignatelli, Ottorino Belluzzi
Within the olfactory bulb (OB), periglomerular (PG) cells consist of various types of interneurons, generally classified by their chemical properties such as neurotransmitter and calcium binding proteins. Calretinin (CR) characterizes morphologically and functionally the more numerous and one of the less known subpopulation of PG cells in the OB. Using of transgenic mice expressing eGFP under the CR promoter, we have tried to obtain the first functional characterization of these cells. Electrophysiological recordings were made in these cells using the patch-clamp technique in thin slices...
2016: Frontiers in Cellular Neuroscience
https://www.readbyqxmd.com/read/27749895/a-parsimonious-model-of-the-rabbit-action-potential-elucidates-the-minimal-physiological-requirements-for-alternans-and-spiral-wave-breakup
#18
Richard A Gray, Pras Pathmanathan
Elucidating the underlying mechanisms of fatal cardiac arrhythmias requires a tight integration of electrophysiological experiments, models, and theory. Existing models of transmembrane action potential (AP) are complex (resulting in over parameterization) and varied (leading to dissimilar predictions). Thus, simpler models are needed to elucidate the "minimal physiological requirements" to reproduce significant observable phenomena using as few parameters as possible. Moreover, models have been derived from experimental studies from a variety of species under a range of environmental conditions (for example, all existing rabbit AP models incorporate a formulation of the rapid sodium current, INa, based on 30 year old data from chick embryo cell aggregates)...
October 2016: PLoS Computational Biology
https://www.readbyqxmd.com/read/27747371/estradiol-modified-prolactin-secretion-independently-of-action-potentials-and-ca-2-and-blockade-of-outward-potassium-currents-in-gh3-cells
#19
Manuel Sánchez, Lorena Suárez, Begoña Cantabrana, Javier Bordallo
Estrogens facilitate prolactin (PRL) secretion acting on pituitary cells. In GH3 cells, estradiol induces acute action potentials and oscillations of intracellular Ca(2+) associated with the secretagogue function. Estradiol modulates several ion channels which may affect the action potential rate and the release of PRL in lactotroph cells, which might depend on its concentration. The aims were to characterize the acute effect of supraphysiological concentrations of estradiol on Ca(2+) and noninactivating K(+) currents and measure the effect on the spontaneous action potentials and PRL release in the somatolactotroph cell line, GH3...
January 2017: Naunyn-Schmiedeberg's Archives of Pharmacology
https://www.readbyqxmd.com/read/27746193/the-plc-pkc-ras-mek-kv-channel-pathway-is-involved-in-uncarboxylated-osteocalcin-regulated-insulin-secretion-in-rats
#20
Jingying Gao, Tao Bai, Lele Ren, Yaqin Ding, Xiangqin Zhong, Hui Wang, Yangyan Guo, Jie Li, Yunfeng Liu, Yi Zhang
Uncarboxylated osteocalcin, a bone matrix protein, has been proposed to regulate glucose metabolism by increasing insulin secretion, improving insulin sensitivity and stimulating β cell proliferation. Our previous study also indicated that uncarboxylated osteocalcin stimulates insulin secretion by inhibiting voltage-gated potassium (KV) channels. The goal of this study is to further investigate the underlying mechanisms for the regulation of Kv channels and insulin secretion by uncarboxylated osteocalcin. Insulin secretion and Kv channel currents were examined by radioimmunoassay and patch-clamp technique, respectively...
December 2016: Peptides
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