• Title/Summary/Keyword: Ionic currents

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Internal Perfusion of ADP in Mouse Oocytes Increases Outward $K^+$ Currents (ADP에 의한 생쥐 난자의 외향전류 증가 효과)

  • 한재희;박홍기;강다원;이상미;이상호;배인하;홍성근
    • Development and Reproduction
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    • v.4 no.2
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    • pp.243-250
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    • 2000
  • To find the mechanism underlying the ADP-induced increase in the outward current in ovulated mouse oocytes, we examined changes in voltage-dependent currents using the whole cell voltage clamp technique and the internal perfusion technique. Eggs were collected from the oviduct of superovulated mice with PMSG and hCG. Membrane potential was held at -60 mV (or -80 mV in the case of recording $Ca^{2+}$ currents) and step depolarizations or hyperpolarizations were applied for 300 ms. By step depolarizations, outward currents comprising steady-state and time-dependent components were elicited. They were generated in response to the positive potential more than 20 mV with severe outward rectification and were blocked by external TEA, a specific $K^{+}$ channel blocker, suggesting that they be carried via $K^{+}$ channels. Internally-perused 5 mM ADP gradually increased outward $K^{+}$ currents (IK) 1 min after perfusion of ADP and reached slowly to maximum (150~170%) 5 min later over the positive potential range, implying that ADP might not be acted directly to the $K^{+}$ channels. IK were decreased by 5 mM ATP without affecting the steady-state component of outward current. In contrast to the effect of ADP and ATP on IK, both effect of ATP and ADP on inward $Ca^{2+}$ currents (ICa) could not be detected due to the continuous decrease in current amplitudes with time-lapse ("run-down" phenomena). To check if there is a G protein-involved regulation in the ionic current of mouse oocytes, 1 mM GTP was applied to the cytoplasmic side, and the outward current and inward currents were recorded. ICa was promptly increased in the presence of GTP whereas IK was not changed. from these results, it is concluded that the ATP-dependent regulation is likely linked in the ADP-induced increase in the outward $K^{+}$ current, and G protein-involved cellular signalling might affect ion channels carrying $Ca^{2+}$ and $K^{+}$ in mouse oocytes.

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Electrophysiological Properties of the Neurons Dissociated from the Nucleus Raphe Magnus in Postnatal Rats (흰쥐의 Nucleus Raphe Magnus로부터 분리된 신경세포의 전기생리학적 성질)

  • Nam Sang-Chae;Lim Won-Il;Cho Sa-Sun;Kim Jun
    • The Korean Journal of Physiology and Pharmacology
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    • v.1 no.3
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    • pp.233-240
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    • 1997
  • Neurons in the nucleus raphe magnus are involved in descending modulation of nociceptive transmission. In this study, we attempted to investigate electrophysiological properties of the NRM neurons dissociated from the postnatal rat medulla. The NRM neurons in the coronal slices of and the dissociated neurons from the postnatal rat medullae were immunohistochemically identified using antibody against serotonin. Relatively small number of neurons were positively stained in both preparations. The positively stained neurons displayed large cell body with double or multiple neurites. Using whole-cell patch clamp configuration ionic currents were recorded from the dissociated NRM-like neurons selected by criteria such as size and shape of cell body and cell population. Two types, high- and low-threshold, of voltage-dependent calcium currents were recorded from the dissociated NRM-like neurons. Some neurons displayed both types of calcium currents, whereas others displayed only high-threshold calcium current. Voltage-dependent potassium currents were also recorded from the dissociated NRM neurons. Some neurons displayed both transient outward and delayed rectifier currents but others showed only delayed rectifier current. These results suggest that there are at least two types of calcium currents and two types of potassium currents in the dissociated NRM neurons.

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Isolation and Electrical Characterization of the Rat Spinal Dorsal Horn Neurons (랫드 척수후각 단일세포 분리 및 특성에 관한 연구)

  • Han, Seong-Kyu;Ryu, Pan-Dong
    • The Korean Journal of Pharmacology
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    • v.32 no.2
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    • pp.283-292
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    • 1996
  • The spinal dorsal horn is the area where primary afferent fibers terminate and cutaneous sensory information is processed. A number of putative neurotransmitter substances, including excitatory and inhibitory amino acids and peptides, are present in this region. In this study, single neurons of the spinal dorsal horn were acutely isolated and the properties of whole cell current and responses to excitatory and inhibitory neurotransmitters were studied by patch clamp technique. Transverse slice ($(300{\mu}m$) of lumbar spinal cords from young rats$(7{\sim}14\;days)$ were sequentially treated with two pretenses(pronase 0.75 mg/ml and thermolysin 0.75 mg/ml), then single neurons were mechanically dissociated. These neurons showed near-intact morphology such as multipolar, ellipsoidal and bipolar, and pyramidal cells and we recorded the typical whole cell currents of $K^+$, $Ca^{2+}$ and ligand-operated channels from these neurons. Glutamate $(30{\mu}M)$ and N-methyl-D-aspartate(NMDA, $30{\mu}M)$ induced inward currents of $117{\pm}12.4$ pA(n=5) and $49{\pm}6.9$ pA(n=3), respectively. Glycine $(1{\mu}M)$ potentiated glutamate-induced currents $4{\sim}5$ times and NMDA-induced currents $8{\sim}10$ times. In addition, glycine $(30{\mu}M)$ induced Inward current ($31{\pm}6.1$ nA, n=2), which was rapidly desensitized after the peak to a new steady-state level. However, the inward currents induced by ${\gamma}-amino$ butyric acid(GABA, $1{\mu}M$) decreased continuously after the peak($226{\pm}41.6$ pA, n=3) under the similar experimental condition. The ionic currents and pharmacological responses of isolated neurons in this work were similar to those observed in vivo or in vitro spinal cord slice, indicating that acutely isolated neurons could be effectively used for further pharmacological studies.

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Lithspermic acid-A slows down the inactivation kinetics of cardiac $Na^+$ current by intracellular $Ca^{2+}$-dependent mechanisms

  • Yoon, Jin-Young;Hyuncheol Oh;Ho, Won-Kyung;Lee, Suk-Ho
    • Proceedings of the Korean Biophysical Society Conference
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    • 2003.06a
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    • pp.46-46
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    • 2003
  • Salviae Miltiorrhizae Radix has been used for treatment of cardiovascular diseases in oriental medicine. To investigate the possible involvement of cardiac ion channel in this effect, we examined electrophysiological effects of the extract of Salviae Miltiorrhizae Radix on action potentials and ionic currents in rat ventricular myocytes. The extracts of Salviae Miltiorrhizae Radix were fractionated into nine fractions, and the effect of each fraction on action potential was tested. The fraction containing monomethyl lithospermic acid-A (LSA-A) induced a significant prolongation of action potential duration (APD). LSA-B which is a major component of Salviae Miltiorrhizae Radix, however, did not cause a significant effect. In voltage clamp experiments, the effects of LSA-A on K currents, Ca currents and Na currents were tested. Neither K currents nor L-type Ca currents were affected by LSA-A. On the contrary, LSA-A significantly slowed down the inactivation kinetics of the Na current with no effect on the fast component of the inactivation process. The amplitude of the peak current and the voltage-dependence of activation were not changed by LSA-A. The effect of LSA-A on Na current was abolished when high concentration of $Ca^{2+}$ buffer (10 mM BAPTA) was included in the pipette solution or when Ca2+ current was blocked by nicardipine (1 $\mu$M) in the bath solution.n.

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Thermally Stimulated Currents of PE/Ionomer Blends (PE/Ionomer블렌드의 열자격 전류)

  • ;John Tanaka;Dwight H. Damon
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.40 no.8
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    • pp.808-815
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    • 1991
  • The behavior of space charge in PE/ionomer blends has been investigated using the thermally stimulated current (TSC) technique. In the blends, at least two TSC peaks over the temperature range from -50 to 100\ulcorner are observed, one at -5 ~ 10\ulcorner (a peak) and the others at above 60\ulcorner (a peak). The a peak is assigned as the orientation of dipoles from the ionomer component. Two a peaks seem to be related to the charge trapping at sites related to the crystalline phases. One a peak is associated with the ionic interfaces and the other with the ethylene chains without the ionic interfaces. The amount of charges stored in PE/Surlyn 1652 blends increases as the poling field increases over the field range of +8 ~ +30 kV/mm, whereas that in PE/Surlyn 1601 blends increases slightly at low poling fields and then decreases at high poling fields above +10 kV/mm. Exact reasons for such a dirrerence are not known at this point.

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A Study on Advanced Lithium-Ion Battery with Polyurethane-Based Gel Polymer Electrolyte (Polyurethane기 겔폴리머전해질을 이용한 Advanced Lithium-Ion Battery에 관한 연구)

  • 김현수;문성인;윤문수;김상필
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.07a
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    • pp.252-254
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    • 2002
  • In this study, polyurethane acrylate macromer was synthesized and it was used in a gel polymer electrolyte, and then its electrochemical performances were evaluated. LiCoO$_2$/GPE/MCF cells were also prepared and their performances depending on discharge currents and temperatures were evaluated. ionic conductivity of the gel polymer electrolyte with PUA at room temperature and -20$^{\circ}C$ was ca. 4.5 x 10$\^$-3/ S/cm and 1.7${\times}$10$\^$-3/ S/cm, respectively. GPE was stable electrochemically up to 4.5 V vs. Li/Li$\^$+/. LiCoO$_2$/GPE/MCF cell showed a good high-rate and a low-temperature performance.

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Electrochemical Properties of Lithium-Ion Polymer Battery with PMMA IPN-Based Gel Polymer Electrolyte (PMMA IPN계 겔폴리머전해질을 채용한 리튬이온폴리머전지의 전기화학적 특성)

  • 김현수;신정한;나성환;엄승욱;문성인;김상필
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.16 no.11
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    • pp.994-1000
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    • 2003
  • In this study, gel polymer electrolytes (GPE) with semi-interpenerating network of poly (methyl methacrylate) and hexanediol dimethacrylate were synthesized and their electrochemical performances were evaluated. LiCoO$_2$/GPE/graphite cells were prepared and their performances depending on discharge currents and temperatures were evaluated. The precursor containing 5 vol% curable mixture had a low viscosity relatively. GPE showed good electrochemical stability up to potential of 4.8 V vs. Li/Li$\^$+/. Ionic conductivity of the gel polymer electrolyte at room temperature and -20$^{\circ}C$ was ca. 5.9 and 1.4${\times}$10$\^$-3/ Scm$\^$-1/, respectively. LiCoO$_2$/GPE/graphite cells showed good rate capability, low-temperature performance and cycleability.

Electrochemical Properties of Cross-linked Polyurethane Acrylate-Based Gel Polymer Electrolyte

  • Kim, Hyun-Soo;Kim, Sung-Il;Choi, Gwan-Young;Moon, Seong-In;Kim, Sang-Pil
    • Journal of the Korean Electrochemical Society
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    • v.5 no.4
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    • pp.197-201
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    • 2002
  • In this study, a gel polymer electrolyte was prepared from urethane acrylate and its electrochemical performances were evaluated. And, $LiCoO_2/GPE/graphite$ cells were prepared and their performances depending on discharge currents and temperatures were evaluated. The precursor containing $5 vol\%$ curable mixture had a low viscosity relatively. Ionic conductivity of the gel polymer electrolyte at room temperature and $-20^{\circ}C$ was ca. $5.9\times10^{-3}S{\cdot}cm^{-1}\;and\;1.7\times10^{-3}S{\cdot}cm^{-1}$, respectively. GPE showed electrochemical stability up to potential of 4.5V vs. $Li/Li^+.LiCoO_2/GPE/graphite$ cell showed a good high-rate and a low-temperature performance.

Simultaneous Determination of Cd2+, Pb2+, Cu2+ and Hg2+ at a Carbon Paste Electrode Modified with Ionic Liquid-functionalized Ordered Mesoporous Silica

  • Zhang, Penghui;Dong, Sheying;Gu, Guangzhe;Huang, Tinglin
    • Bulletin of the Korean Chemical Society
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    • v.31 no.10
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    • pp.2949-2954
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    • 2010
  • Ionic liquid-functionalized ordered mesoporous silica SBA-15 modified carbon paste electrode (CISPE) was fabricated and its electrochemical performance was investigated by cyclic voltammetry, electrochemical impedance spectra. The electrochemical behavior of $Cd^{2+}$, $Pb^{2+}$, $Cu^{2+}$ and $Hg^{2+}$ at CISPE was studied by differential pulse anodic stripping voltammetry (DPASV). Compared with carbon paste electrode, the stripping peak currents had a significant increase at CISPE. Under the optimized conditions, the detection limits were $8.0{\times}10^{-8}\;M$ ($Cd^{2+}$), $4.0{\times}10^{-8}\;M$ ($Pb^{2+}$), $6.0{\times}10^{-8}\;M$ ($Cu^{2+}$), $1.0{\times}10^{-8}\;M$ ($Hg^{2+}$), respectively. Furthermore, the present method was applied to the determination of $Cd^{2+}$, $Pb^{2+}$, $Cu^{2+}$ and $Hg^{2+}$ in water samples and people hair sample.

Correlation between leakage current and temperature Rise for artificially aged insulators (인위적 열화 애자에 대한 누설전류와 온도와의 관계)

  • Kim, J.T.;Kim, J.H.;Koo, J.Y.;Yoon, J.H.;Ham, G.H.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.05c
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    • pp.186-188
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    • 2001
  • In this study, the correlation between leakage currents and temperature rise was investigated for the more accurate diagnosis of bad insulator by use of the infrared camera. For the purpose, leakage currents and thermal images were measured for the artificially aged insulators using salt fog. From the results, it is concluded as follows ; in case of artificially aged insulators, the leakage. current was decreased with the duration of voltage application and was largely affected by humidity, which seems due to ionic conduction. Also, the correlation between temperature rise and leakage current was appeared to be quite linear, although it showed below linearity at large leakage current.

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