• Title/Summary/Keyword: membrane potentials

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Effects of Prostaglandin $F_{2{\alpha}}$ on Membrane Potentials and $K^+$ Currents in Rabbit Middle Cerebral Arterial Cells

  • Kim, Na-Ri;Han, Jin;Kim, Won-Gue;Kim, Eui-Yong
    • The Korean Journal of Physiology and Pharmacology
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    • v.4 no.4
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    • pp.301-309
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    • 2000
  • The purpose of our investigation was to examine the effects of prostaglandin $F_{2{\alpha}}\;(PGF_{2{\alpha}})$ on membrane potentials, $Ca^{2+}-activated\;K^+\;(K_{Ca})$ channels, and delayed rectifier $K^+(K_V)$ channels using the patch-clamp technique in single rabbit middle cerebral arterial smooth muscle cells. $PGF_{2{\alpha}}$ significantly hyperpolarized membrane potentials and increased outward whole-cell K currents. $PGF_{2{\alpha}}$ increased open-state probability of $K_{Ca}$ channels without the change of the open and closed kinetics. $PGF_{2{\alpha}}$ increased the amplitudes of $K_V$ currents with a leftward shift of activation and inactivation curves and a decrease of activation time constant. Our results suggest that the activation of $K_{Ca}$ and $K_V$ channels, at least in part, may lead to attenuate or counteract vasoconstriction by $PGF_{2{\alpha}}$ in middle cerebral artery.

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THE IMPORTANCE OF BICARBONATE-BUFFER ON CARDIAC FUNCTION: Contractility, Membrane Potentials and ATP Content of Isolated Atria in the Absence of External Buffers (심장기능(心臟機能)에 미치는 Bicarbonate-Buffer의 중요성(重要性) : Buffer 제거(除去)에 의(依)한 유리심방(遊離心房)의 수축성(收縮性), 막전위(膜電位) 및 ATP 함량(含量)의 변동(變動))

  • Ko, Kye-Chang;Han, Dae-Sup;Jung, Jee-Chang
    • The Korean Journal of Pharmacology
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    • v.8 no.2
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    • pp.63-69
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    • 1972
  • The effects of omission of buffers from Krebs-Ringer medium on contractile activity, membrane potentials and ATP content of electrically stimulated isolated rat atria were investigated. 1) Contractile status: A rapid and marked depression of the contractile activity of atria occurred when buffer-free medium was substituted for the normal Krebs-Ringer medium. 2) Electrical status: The omission of buffers from medium did not alter the resting or action potential magnitudes of atria. However, the action potential duration was on initial increase followed by a decrease in the buffer-free medium. 3) ATP concentration: The omission of buffers from medium resulted in a marked decrease in the ATP levels of atria. It has been also found in the present study that bicarbonate buffer plays an important role for the maintenance of the contractility and ATP levels of the heart. The contractile depression by the omission of buffers was not directly associated with electrical alterations in resting or action potentials of the heart. In the absence of bicarbonate-buffer, glucose no longer plays to maintain the contractile activity and the ATP levels of rat atria.

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Effect of Mylabris phalerata on colorectaladenocarcinoma cells (SNU-C5 cell lines) (반모가 대장암세포에 미치는 영향)

  • Kim, Jin-Sung;Yoon, Sang-Hyub;Ryu, Bong-Ha;Ryu, Ki-Won;Kim, Hyeon-Yil
    • The Journal of Internal Korean Medicine
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    • v.25 no.2
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    • pp.214-223
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    • 2004
  • The study examines the anti-cancer effects of the hot water extract of Mylabris phalerata(MP) using SNU-C5 cell lines. Microscopic analysis showed that 12 hours after MP treatment, the number of dead cells increased prominently. Significant cell death was observed 12, 24, and 48 hours after MP treatment through trypan blue exclusion testing. This suggests that MP is time-dependently cytotoxic. Mitotracker Red CMXRos staining and flowcytometry revealed that MP decreased mitochondrial membrane potentials. The absence of peaks on PI staining showed that DNA damage occurred in MP treated cells. Taken together, measurements suggest that MP has a strong anti-cancer effect on SNU-5 cell lines, and that this is likely to be due to the destruction of mitochondria and DNA damage.

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REPONSE OF POLYMERIC MEMBRANES AS SENSING ELEMENTS FOR ELECTRONIC TOUGUE

  • Bae, Y.M.;Cho, S.I.
    • Proceedings of the Korean Society for Agricultural Machinery Conference
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    • pp.219-226
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    • 2000
  • The study was executed for development of sensing elements of electronic tongue which could discriminate taste of liquid and semi-liquid foods. Five polymeric membranes which were composed of polymer, plasticizer, electro-active materials were prepared. After each polymeric membranes were mounted in an electrode body, membrane potentials due to electrochemical reaction with taste stimuli were measured. The experimental results were interpreted in view of the membrane's non-selective responses to stimuli.

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Effects of Ginseng Extract on Excitable Cell Membrane Potential (인삼추출물이 흥분성세포의 막전압에 미치는 영향)

  • Chung, Jin-Mo;Paik, Kwang-Se;Nam, Taick-Sang;Kim, In-Kyo;Kang, Doo-Hee
    • The Korean Journal of Physiology
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    • v.15 no.1
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    • pp.3-8
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    • 1981
  • Studies have been conducted to test the effect of Ginseng alcohol extract on the membrane potentials of frog skeletal muscle. The gastrocnemius muscle was isolated and placed in a chamber containing the Clark-frog Ringer solution. Membrane potentials were recorded using microelectrodes filled with 3 M KCI and muscle was electrically stimulated to obtain action potential. Changes in both the action potential and the resting membrane potential were observed after adding an appropriate amount of Ginseng alcohol extract in the perfusing Ringer solution. The results obtained from 346 muscle cells are summarized as follows : 1) The average resting membrane potential of the normal frog gastrocnemius muscle cell was -92.8 mV and the peak of the action potential reached at 29.8 mV. 2) Both the resting membrane potential and the peak of the action potential decreased by Ginseng alcohol extract, the effect being proportional to the dose of Ginseng alcohol extract. 3) The resting membrane potential and the peak of the action potential continuously decreased until about 40 min after Ginseng addition and leveled off thereafter. The potentials recovered to its original value after Ginseng was washed out. 4) The resting membrane potential was more sensitive to the Ginseng alcohol extract than was the action potential. These results strongly suggest that Ginseng alcohol extract increases both the $Na^+$ and $K^+$ permeability in the skeletal muscle cell membrane.

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Diffusive transport through surface functionalized nanoporous alumina membranes by atomic layer deposition of metal oxides

  • Vega, V.;Gelde, L.;Gonzalez, A.S.;Prida, V.M.;Hernando, B.;Benavente, J.
    • Journal of Industrial and Engineering Chemistry
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    • v.52
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    • pp.66-72
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    • 2017
  • Changes associated to surface functionalization of nanoporous alumina membranes by atomic layer deposition (ALD) of metal oxides ($Al_2O_3$, $SiO_2$, $TiO_2$, $Fe_2O_3$, ZnO) are presented. ALD modification of the alumina membranes reveals a reduction up to 25-35% in porosity, and confirms the presence of the metal oxide layer coating the pores. Its effect on the membrane permselectivity and other characteristic transport parameters was determined from membrane potential measurements, being correlated with changes in morphology and physic-chemical characteristics of the alumina membranes. According to our results, ALD provides a straight-forward and efficient method to adjust membrane performance for specific applications.

Mitochondrial Uncoupling Attenuates Age-Dependent Neurodegeneration in C. elegans

  • Cho, Injeong;Song, Hyun-Ok;Cho, Jeong Hoon
    • Molecules and Cells
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    • v.40 no.11
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    • pp.864-870
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    • 2017
  • The uncoupling protein 4 (ucp-4) gene is involved in age-dependent neurodegeneration in C. elegans. Therefore, we aimed to investigate the mechanism underlying the association between mitochondrial uncoupling and neurodegeneration by examining the effects of uncoupling agents and ucp-4 overexpression in C. elegans. Treatment with either DNP or CCCP improved neuronal defects in wild type during aging. Uncoupling agents also restored neuronal phenotypes of ucp-4 mutants to those exhibited by wild type, while ucp-4 overexpression attenuated the severity of age-dependent neurodegeneration. Neuronal improvements were further associated with reductions in mitochondrial membrane potentials. However, these age-dependent neuroprotective effects were limited in mitophagy-deficient mutant, pink-1, background. These results suggest that membrane uncoupling can attenuate age-dependent neurodegeneration by stimulating mitophagy.

Novel Purification Method of Kv 4.2 Potassium Channel from Rat Brain Membrane

  • Park, Sung-Soo
    • Biomedical Science Letters
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    • v.18 no.2
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    • pp.96-103
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    • 2012
  • Kv 4.2 ion channel protein has an ability to open at subthreshold membrane potentials and to recover quickly from inactivation. That is very important for neuronal signal transmission in vertebrate brain. In order to purify Kv 4.2 protein, the novel purification methods were experimented. The purification procedure utilized chromatography on DE-52 ion exchange column and affinity chromatography on a WGA-Sepharose 4B, and Kv 4.2 affinity column chromatography. It was found that 0.5% (wt./vol.) Triton X-100 detergent in lysis buffer worked well for Kv 4.2 protein solubilization from rat brain membrane. Protein quantitative determination was conducted by BCA method at 562 nm for each purification step to avoid determination interference of protein at 280 nm by detergent. The confirmation of Kv 4.2 existence and amount is performed using by SDS-PAGE/immunoblotting or 96-well dot blotting. The Kv 4.2 without interacting protein that contains carbohydrate, was purified from novel biochemical 3-steps purification method for further research.

Action of Dopamine as Inhibitory Neuromodulator in Jellyfish Synapse

  • Chung, Jun-mo;Spencert, Andrew N.
    • BMB Reports
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    • v.31 no.3
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    • pp.264-268
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    • 1998
  • Dopamine (DA) acts on swimming motor neurons (SMNs) of Polyorchis penicillatus as an inhibitory neurotransmitter by hyperpolarizing their membrane potentials, which results from the activation of voltagesensitive potassium channels mediated through a $D_2-type$ receptor. In addition, DA, and not the hyperpolarized membrane potential, directly decreased the input resistance of SMNs by ca. 50% from 1.42 to 0.68 $G{\Omega}$. It strongly indicates that DA can shunt other excitatory synaptic signals onto SMNs where DA usually elicited much greater responses in their neurites than soma. All these evidences suggest that DA may operate in this primitive nervous system in dual modes as an inhibitory neurotransmitter and neuromodulator as well.

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Electrophysiological Functions of Intracellular Amyloid β in Specific for Cultured Human Neurones and its Impairment Properties

  • Merlin, Jayalal L.P.
    • Journal of the Chosun Natural Science
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    • v.6 no.3
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    • pp.143-150
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    • 2013
  • Prevailing role of intracellular amyloid ${\beta}$ ($iA{\beta}$) in Alzheimer's disease (AD) initiation and progression attracts more and more attention in recent years. To address whether $iA{\beta}$ induces early alterations of electrophysiological properties in cultured human primary neurons, we delivered $iA{\beta}$ with adenovirus and measured the electrophysiological properties of infected neurons with whole-cell recordings. Our results show that $iA{\beta}$ induces an increase in neuronal resting membrane potentials, a decrease in $K^+$ currents and a hyperpolarizing shift in voltage-dependent activation of $K^+$ currents. These results suggest the electrophysiological impairments induced by $iA{\beta}$ may be responsible for its neuronal toxicity.