• Title, Summary, Keyword: $Ba^{2+}-sensitive$ currents

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Inwardly Rectifying $K^+$ Currents in Gastric Myocytes of Guinea-pig

  • Jun, Jae-Yeoul;Yeum, Cheol-Ho;Yoon, Pyung-Jin;Jang, In-Youb;Cho, Nam-Soo;Cho, Soo-Hyeong;Kong, In-Deok;Kim, Tae-Wan;So, In-Suk;Kim, Ki-Whan
    • The Korean Journal of Physiology and Pharmacology
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    • v.6 no.1
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    • pp.47-55
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    • 2002
  • To identify the presence of inwardly rectifying $K^+$ channels and its characteristics, membrane currents were measured using a whole-cell patch clamp from isolated gastric myocytes of guinea-pig. Change of external $K^+$ concentration from 5 to 90 mM induced an inward current at a holding potential of -80 mV. The high $K^+-induced$ inward current was blocked by $Ba^{2+}$ and $Cs^+,$ but not by glibenclamide. With 90 mM $K^+$ in bath, the $Ba^{2+}-$ and $Cs^+-sensitive$ currents showed strong inward rectification. Ten mM TEA weakly blocked the inward current only at potentials more negative than -50 mV. With 90 mM $K^+$ in bath, hyperpolarizing step pulses from -10 mV induced inward currents, which were inactivated at potentials more negative than -70 mV. Reduction of external $K^+$ to 60 mM decreased the amplitudes of the currents and shifted the reversal potential to more negative potential. The inactivation of inward $K^+$ current at negative clamp voltage was not affected by removing external $Na^+.$ These results suggest that the inwardly rectifying $K^+$ channels may exist in gastric smooth muscle.

Characterization of Ionic Currents in Human Neural Stem Cells

  • Lim, Chae-Gil;Kim, Sung-Soo;SuhKim, Hae-Young;Lee, Young-Don;Ahn, Seung-Cheol
    • The Korean Journal of Physiology and Pharmacology
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    • v.12 no.4
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    • pp.131-135
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    • 2008
  • The profile of membrane currents was investigated in differentiated neuronal cells derived from human neural stem cells (hNSCs) that were obtained from aborted fetal cortex. Whole-cell voltage clamp recording revealed at least 4 different currents: a tetrodotoxin (TTX)-sensitive $Na^+$ current, a hyperpolarization-activated inward current, and A-type and delayed rectifier-type $K^+$ outward currents. Both types of $K^+$ outward currents were blocked by either 5 mM tetraethylammonium (TEA) or 5 mM 4-aminopyridine (4-AP). The hyperpolarization-activated current resembled the classical $K^+$ inward current in that it exhibited a voltage-dependent block in the presence of external $Ba^{2+}$ (30 ${\mu}$M) or $Cs^+$ (3${\mu}$M). However, the reversal potentials did not match well with the predicted $K^+$ equilibrium potentials, suggesting that it was not a classical $K^+$ inward rectifier current. The other $Na^+$ inward current resembled the classical $Na^+$ current observed in pharmacological studies. The expression of these channels may contribute to generation and repolarization of action potential and might be regarded as functional markers for hNSCs-derived neurons.

Preparation and Properties of Ba($Zr_{0.2}Ti_{0.8}$)$O_3$ Thin Films Grown by RF Magnetron Sputtering Method (RF Magnetron 스퍼터링법으로 성장시킨 Ba($Zr_{0.2}Ti_{0.8}$)$O_3$ 박막의 특성)

  • 최원석;장범식;김진철;박태석;이준신;홍병유
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.14 no.7
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    • pp.567-571
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    • 2001
  • We investigated the structural and electrical properties of Ba(Zr$_{x}$Ti$_{1-x}$ )O$_3$(BZT) thin films with a mole fraction of x=0.2 and a thickness of 150 nm. BZT films were prepared on Pt/SiO$_2$/Si substrate with the various substrate temperature by a RF magnetron sputtering system. When the substrate temperature was above 50$0^{\circ}C$, we obtained multi-crystalline BZT films oriented to (110), (111), and (200) directions. As the substrate temperature increases, the films are crystallized and their dielectric constants become high. C-V characteristic curve of the film deposited at high temperature is more sensitive than that of the film deposited at low temperature. The parameters of the BZT film are as follows; the dielectric constants(dissipation factors) at 1 MHz are 95(0.021), 140(0.024), and 240(0.033) deposited at 400, 500, $600^{\circ}C$, respectively; the leakage currents at 666.7 kV/cm are 5.73, 23.5, and 72.8x10$^{-8}$ A/$\textrm{cm}^2$ fo the films deposited at 400, 500, and 600 $^{\circ}C$, respectively; the leakage currents at 666.7kV/cm are 5.73, 23.5, and 72.8x10$^{-8}$ A/$\textrm{cm}^2$ for the films deposited at 400, 500, $600^{\circ}C$, respectively. The BZT film deposited at 40$0^{\circ}C$ shows stable electrical properties, but dielectric constant for application is a little small.ll.

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Expression and Characterization of G Protein-activated Inward Rectifier $K^+$ Channels in Xenopus Oocytes

  • Kim, Han-Seop;Lee, Chang-Ho;Min, Churl K.
    • Animal cells and systems
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    • v.2 no.4
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    • pp.471-476
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    • 1998
  • The G protein-activated inwardly rectifying $K^+$ channel (GIRK1) was coex-pressed in Xenopus oocytes along with the $5-HT_{1A}$ receptor, a 7-helix receptor known to be coupled to $K^+$ channels in many neural tissues. Thus, the activation of the $5-HT_{1A}$ receptor by its agonist leads to the opening of GIRK1. The GIRK1 current was measured using the two electrode voltage clamp technique with bath application of 5-HT in the presence of various external potassium concentrations $[K^+]_0$. GIRK1 showed a strong inward rectification since only hyperpolarizing voltages evoked inward currents. $K^{+}$ was the major ion carrier as evidenced by about 44㎷ voltage shift corresponding to a 10-fold external 〔$K^+$〕 change. 5-HT induced a concentration-dependent inward $K^+$ current ($EC_{50}{\equation omitted}10.7nM$) which was blocked by $Ba^{2+}$. Pertussis toxin (PTX) pre-treatment reduced the $K^+$ current by as much as about 70%, suggesting that PTX-sensitive G protein ($G_i or G_o$ type) are involved in the $5-HT_{1A}$ receptor-GIRK1 coupling in Xenopus oocytes.

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