• Title/Summary/Keyword: $Ca^{2+}$current

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Contribution of Different Types of $Ca^{2+}$ channels to Catecholamine Secretion in Rat Adrenal Chromaffin Cells (부신수질 Chromaffin 세포의 $Ca^{2+}$ 통로유형이 카테콜아민 분비에 미치는 영향에 관한 정량적 연구)

  • Goo, Yang-Soak;Roh, Jin-A;Lee, Jung-Hwa;Chao, Eun-Jong
    • Progress in Medical Physics
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    • v.8 no.1
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    • pp.3-15
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    • 1997
  • Adrenal chromaffin cells secrete catecholamine in response to acetylcholine. The secretory response has absolute requirement for extracellular calcium, indication that $Ca^{2+}$ influx through voltage dependent $Ca^{2+}$ channel (VDCC) is the primary trigger of the secretion cascade. Although the existence of various types of $Ca^{2+}$ channels has been explored using patch clamp technique in adrenal chromaffin cells, the contribution of different types of $Ca^{2+}$ channels to catecholamine secretion remains to be established. To investigate the quantative contribution of different types of $Ca^{2+}$ channels to cate-cholamine secretion, $Ca^{2+}$ current($I_{Ca}$) and the resultant membrane capacitance increment($\Delta{C}_{m}$) were simultaneoulsy measured. Software based phasor detector technique was used to monitor $\Delta{C}_{m}$. After blockade of L type VDCC with nicardipine (1$\mu$M), $I_{ca}$ was blocked to 43.85$\pm$6.72%(mean$\pm$SEM) of control and the resultant ㅿC$_{m}$ was reduced ot 30.10$\pm$16.44% of control. In the presence of nicardipine and $\omega$-conotoxin in GVIA(l$\mu$M), an N type VDCC antagonist, $I_{ca}$ was blocked to 11.62$\pm$2.96% of control and the resultant $\Delta{C}_{m}$ was reduced to 26.13$\pm$8.25% of control. Finally, in the presence of L, N, and P type $Ca^{2\pm}$ channel antagonists(nicardipine, $\omega$-Conotoxin GVIA, and $\omega$-agatoxin IVA, respectively), $I_{ca}$ and resultant $\Delta{C}_{m}$ were almost completely blocked. From the observation of parallel effects of $Ca^{2+}$ channel antagonists on $I_{ca}$ and $\Delta{C}_{m}$, it was concluded that L, N, and also P type $Ca^{2+}$ channels served and $Ca^{2+}$ source for exocytosis and no difference was observed in their efficiency to evoke exocytosis amost L, N, and P type $Ca^{2+}$ channels.

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Properties Analysis of Environment Friendly Electrodeposit Films Formed at Various Current Density Conditions in Natural Seawater (천연해수 중 전류밀도 변화에 따라 형성된 환경친화적인 전착 코팅막의 특성 분석)

  • Lee Chan-Sik;Bae Il-Yong;Kim Ki-Joon;Moon Kyung-Man;Lee Myeong-Hoon
    • Journal of the Korean institute of surface engineering
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    • v.37 no.5
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    • pp.253-262
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    • 2004
  • Calcareous deposits are the consequence of pH increase of the electrolyte adjacent to metal surface affected by cathodic current in seawater. It obviously has several advantages over conventional coatings, since the calcareous deposit coating is formed from coating (Mg$^{2+}$, $Ca^{2+}$) naturally existing in seawater. In consideration of this respect, environment friendly calcareous deposit films were formed by an electro deposition technique on steel substrates submerged in 48$^{\circ}C$ natural seawater. And the influence of current density, coating time and attachment of steel mesh on composition ratio, structure and morphology of the electrodeposited films were investigated by Scanning Electron Microscopy(SEM), Energy Dispersive Spectroscopy(EDS) and X-Ray Diffractor(XRD), respectively. Accordingly, this study provides a better understanding of the composition between the growth of $Mg(OH)_2$ and $CaCO_3$ during the formation of electro deposit films on steel substrate under cathodically electrodeposition in $48^{\circ}C$ natural seawater. The Mg compositions, in general, are getting decreased regardless of current density but Ca compositions are getting increased as electrodeposition time runs. That is, $Mg(OH)_2$ compounds of brucite structure shaped as flat type is formed at the initial stage of electrodeposition, but CaCO$_3$ compounds of aragonite structure shaped as flower type is formed in large scale. Besides, $Mg(OH)_2$ compounds were much formed at 5 A/$\m^2$ environment condition compared to the 3 A/$\m^2$ and 4 A/$\m^2$ environment conditions. This is because that OH- which was comparatively largely generated at the metal surface is preferably combined with $Mg^{2+}$TEX>.

Role of Protein Kinase C on Norepinephrine Induced Inhibition of Calcium Current in Rat Sympathetic Neurons (흰쥐 교감신경세포에서 Norepinephrine 에 의한 칼슘전류 억제에 미치는 Protein Kinase C 의 역할)

  • ;Keith S. Elmslie
    • Progress in Medical Physics
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    • v.11 no.1
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    • pp.29-38
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    • 2000
  • The signal transduction pathway for most neurotransmitter induced inhibition of $Ca^{2+}$ channels in sympathetic neurons involves a G-protein mediated, membrane-delimited mechanism without the participation of any known protein kinase. However, activation of protein kinase C (PKC) has been proposed as one of the intracellular mechanisms mediating some neurotransmitter induced $Ca^{2+}$ channel inhibition. In the present study, we investigated the effects of phorbol-12, 13-dibutyrate (PDBu) on $Ca^{2+}$ channel currents of acutely dispersed neurons from adult rat superior cervical ganglion (SCG) neurons using whole cell variant of the patch clamp technique. PDBu (500 nM), the activator of PKC, increased $Ca^{2+}$ channel currents and retarded the deactivation of tail currents. The effects of PDBu were voltage dependent and the maximal increase in the current amplitudes was observed between -10 to 10 mV (n=4). PDBu attenuated $Ca^{2+}$ current inhibition induced by norepinephrine (NE), which modulates $Ca^{2+}$ channels via a pertussis toxin (PTX)-sensitive pathway. Inhibition of PDBu by staurosporine (1 $\mu$M) blocked the effects of PDBu on current amplitudes and NE-induced G-protein mediated inhibition of $Ca^{2+}$ currents. Further experiment should be done to know if G-protein or $Ca^{2+}$ channel itself is the target of PKC phosphorvlation.phosphorvlation.

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Effect of Various Divalent Ions on the Calcium Current of Adrenal Medullary Chromaffin Cells in the Rat

  • Kim, Jun;Leem, Chae-Hun;Kim, Sang-Jeong
    • The Korean Journal of Physiology
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    • v.26 no.2
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    • pp.113-122
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    • 1992
  • It is well known that chromaffin cells of adrenal medulla secrete catecholamine in response to sympathetic nerve activation and the influx of $Ca^{2+}$ through the voltage dependent $Ca^{2+}$ channels (VDCC) in the cell membrane do a major role in this secretory process. In this study, we explored the effect of divalent cations on VDCC of rat chromaffin cells. Rat (Sprague-Dawley rat, 150-250 gm) chromaffin cells were isolated and cultured. Standard giga seal, whole cell recording techniques were employed to study $Ca^{2+}$ current with external and internal solutions that could effectively isolate VDCC currents $(NMG\;in\;external\;and\;TEA\;and\;Cs^{2+}\;in\;internal\;solution)$. The voltage dependence and the inactivation time course of VDCC in our cells were identical to those of bovine chromaffin cells. A persistent inward current was first activated by depolarizing step pulse from the holding potential (H.P.) of -80 mV to -40 mV, increased to maximum amplitude at around +10 mV, and became smaller with progressively higher depolarizing pulses to reverse at around +60 mV. The inactivation time constant $(\tau)$, fitted from the long duration test potential (2 sec) was $1295.2{\pm}126.8$ msec $(n=20,\;1\;day\;of\;culture,\;mean\;{\pm}S.E.M.)$ and the kinetic parameters were not altered along the culture duration. Nicardipine $(10\;{\mu}M)$ blocked the current almost completely. Among treated divalent cations such as $Cd^{2+},\;Co^{2+},\;Ni^{2+},\;Zn^{2+}\;and\;,Mn^{2+},\;Cd^{2+}$ was the most potent blocker on VDCC. When the depolarizing step pulse from -80 mV to 10 mV was applied, the equilibrium dissociation constant $(K_d)$ of $Cd^{2+}\;was\;39\;{\mu}M,\;K_d\;of\;Co^{2+}\;was\;100\;{\mu}M\;and\;K_d\;of\;Ni^{2+}];was];780{\mu}M.$ The principal findings of this study are as follows. First, the majority of $Ca^{2+}$ channels in rat chromaffin cells are well classified to L-type $Ca^{2+}$ channel in the view of kinetics and pharmacology. Second, all divalent cations tested could block the $Ca^{2+}$ current and the most potent blocker among the tested was $Cd^{2+}$.

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[ $Ca^{2+}$ ]-dependent Long-term Inactivation of Cardiac $Na^+/Ca^{2+}$ Exchanger

  • Lee, Jee-Eun;Kang, Tong-Mook
    • The Korean Journal of Physiology and Pharmacology
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    • v.11 no.5
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    • pp.183-188
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    • 2007
  • Using BHK cells with stable expression of cardiac $Na^+/Ca^{2+}$ exchanger(BHK-NCX1), reverse mode(i.e. $Ca^{2+}$ influx mode) of NCX1 current was recorded by whole-cell patch clamp. Repeated stimulation of reverse NCX1 produced a cytosolic $Ca^{2+}$-dependent long-term inactivation of the exchanger activity. The degrees of inactivation correlated with NCX1 densities of the cells and were attenuated by reduced $Ca^{2+}$ influx via the reverse exchanger. The inactivation of NCX1 was attenuated by(i) inhibition of $Ca^{2+}$ influx with reduced extracellular $Ca^{2+}$, (ii) treatment with NCX1 blocker($Na^{2+}$), and (iii) increase of cytoplasmic $Ca^{2+}$ buffer(EGTA). In BHK-NCX1 cells transiently expressing TRPV1 channels, $Ca^{2+}$ influx elicited by capsaicin produced a marked inactivation of NCX1. We suggest that cytoplasmic $Ca^{2+}$ has a dual effect on NCX1 activities, and that allosteric $Ca^{2+}$ activation of NCX1 can be opposed by the $Ca^{2+}$-dependent long-term inactivation in intact cells.

Role of $Ca^{2+}$ for Inactivation of N-type Calcium Current in Rat Sympathetic Neurons (흰쥐 교감신경 뉴론 N형 칼슘전류의 비활성화에 미치는 칼슘효과)

  • Goo, Yong-Sook;Keith S. Elmslie
    • Progress in Medical Physics
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    • v.14 no.1
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    • pp.54-67
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    • 2003
  • The voltage-dependence of N-type calcium current inactivation is U-shaped with the degree of inactivation roughly mirroring inward current. This voltage-dependence has been reported to result from a purely voltage-dependent mechanism. However, $Ca^{2+}$-dependent inactivation of N-channels has also been reported. We have investigated the role of $Ca^{2+}$ in N-channel inactivation by comparing the effects of $Ba^{2+}$and $Ca^{2+}$ on whole-cell N-current in rat superior cervical ganglion neurons. For individual cells in-activation was always larger in $Ca^{2+}$ than in $Ba^{2+}$ even when internal EGTA (11 mM) was replaced with BAPTA (20 mM). The inactivation vs. voltage relationship was U-shaped in both divalent cations. The enhancement of inactivation by $Ca^{2+}$ was inversely related with the magnitude of inactivation in $Ba^{2+}$ as if the mechanisms of inactivation were the same in both $Ba^{2+}$ and $Ca^{2+}$. In support of this idea we could separate fast ( ${\gamma}$ ~150 ms) and slow ( ${\gamma}$ ~ 2500 ms) components of inactivation in both $Ba^{2+}$and $Ca^{2+}$ using 5 sec voltage steps. Differential effects were observed on each component with $Ca^{2+}$ enhancing the magnitude of the fast component and the speed of the slow component. The larger amplitude of fast component indicates that the more channels inactivate via this pathway with $Ca^{2+}$ than with $Ba^{2+}$, but the stable time constants support the idea the fast inactivation mechanism is identical in $Ba^{2+}$and $Ca^{2+}$. The results do not support a $Ca^{2+}$-dependent mechanism for fast inactivation. However, the $Ca^{2+}$-induced acceleration of the slowly inactivating component could result from a $Ca^{2+}$-dependent process.

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Electrowinning of Tungsten From Fused Bath Composed of Calcium Chloride, Calcium Oxide and Tungstic Oxide (텅그스텐의 熔融鹽電解)

  • Kim, Jae-Won;Lee, Dong-Nyung
    • Journal of the Korean Chemical Society
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    • v.10 no.1
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    • pp.32-42
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    • 1966
  • The electrolysis of tungstic oxide dissolved in the bath of calcium chloride and calcium oxide was studied to produce metallic tungsten using carbon as anode and iron as cathode in the temperature range of 900^{\circ}$ to $1200^{\circ}C$. The binary phase diagrams $CaCl_2$-CaO and $CaCl_2-CaWO_4$ systems were constructed to determine the suitability of bath composition and the range of temperatures for the electrolysis. As $WO_3$ reacted with $CaCl_2$ to form oxychloride in the fused salt, the addition of the proper amount of CaO was necessary to avoid the loss of $WO_3$. The optimum compositions of fused bath were $CaCl_2$ 100 parts, CaO and $WO_3$ each 10 to 20 parts, with the CaO, $WO_3$ ratio greater than unity, to keep freezing point low and to prevent the vaporization of $CaCl_2$. The observed decomposition voltage at which $WO_3$ decomposes to W and CO was-0.1 volt, whereas the calculated was -0.3 volt. Metallic tungsten deposited at the cathode reacted easily with CO formed secondarily at the anode surface, to form WC below $1050^{\circ}C$, so that the cell temperature should be above $1050^{\circ}C$. The effects of cathode current densities on current efficiency were minor in the range of 1 to 5 $amp/cm^2$.

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Effect of Ag Capping Layer on the Emission Characteristics of Transparent Organic Light-emitting Devices with Ca/Ag Double-layer Cathodes

  • Lee, Chan-Jae;Moon, Dae-Gyu
    • Transactions on Electrical and Electronic Materials
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    • v.15 no.1
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    • pp.45-48
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    • 2014
  • We have investigated the effects of an Ag capping layer on the emission characteristics of transparent organic light-emitting devices with Ca/Ag double-layer cathodes. The thickness of the Ag layer was varied from 10 to 30 nm, whereas the Ca was fixed to be a 10 nm in the Ca/Ag structure. The luminance and current efficiency on the cathode and anode sides are significantly dependent on the Ag thickness. For example, the current efficiency on the anode side increases from 8.4 to 11.7 cd/A, whereas, on the cathode side, it decreases from 3.2 to 0.2 cd/A as the Ag thickness increases from 10 to 30 nm. These changes in emission characteristics were investigated by measuring electroluminescence, transmission, and reflection spectra.

Tunneling Characteristics in $Pb/Bi_2Sr_2CaCu_2O_{8+\delta}$ Junctions as an Evidence for a d-wave Order Parameter Symmetry in $Bi_2Sr_2CaCu_2O_{8+\delta}$ Superconductors ($Bi_2Sr_2CaCu_2O_{8+\delta}$ 고온초전도체의 d-파 대칭성 증거로서의 $Pb/Bi_2Sr_2CaCu_2O_{8+\delta}$접합 투과전도특성)

  • Chang, Hyun-Sik;Lee, Hu-Jong
    • Progress in Superconductivity
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    • v.2 no.2
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    • pp.65-70
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    • 2001
  • $Pb/Bi_2Sr_2CaCu_2O_{8+\delta}$-single-crystal junctions with the tunneling direction along the c axis of the crystal were fabricated to obtain an s-wave-superconductor/d-wave-superconductor Josephson junctions. The tunneling R (T) curves and current-voltage characteristics show distinct features which can be explained only under the assumption that the order parameter of high-$T_c/Bi_2Sr_2CaCu_2O_{8+{\delta}}$ superconductors has a pure d-wave symmetry, which is in contrast to the case of $YBa_2Cu_3O_{7+{\delta$}}$erconductors where a minor s-wave component is also present..

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Biochemical Characterization of a Putative Calcium Influx Factor as a Diffusible Messenger in Jurkat Cells, Xenopis Oocytes, and Yeast

  • Kim, Hak-Yong
    • Animal cells and systems
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    • v.7 no.1
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    • pp.75-79
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    • 2003
  • Highly purified high performance thin layer chromatography (HPTLC) fractions containing a putative calcium influx factor (CIF) were prepared from the Jurkat cells and Xenopus oocytes in which $Ca^{2+}$ stores were depleted by thapsigargin treatment and from the yeast in which intracellular $Ca^{2+}$ stores were also depleted by genetic means. Microinjection of the fractions has been shown to elicit $Ca^{2+}$ dependent currents in Xenopus oocytes. The nature of the membrane currents evoked by the putative CIF appeared to be carried by chloride ions since the current was blocked by the selective chloride channel blocker 1 mM niflumic acid and its reversal potential was about -24 mV. Injection of the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N, N, N',N'-tetraacetic acid (BAPTA) eradicated the current activities, suggesting the current responses are entirely $Ca^2$-dependent. Moreover, the currents were sensitive to the removal of extracellular calcium, indicating the dependence on calcium entry through the plasma membrane calcium entry channels. CIF activities were insensitive to protease, heat, and acid treatments and to Dische-reaction whereas the activities were sensitive to nucleotide pyrophosphatase and hydrazynolysis. The fraction might have a sugar because it was sensitive to Molisch test and Seliwaniff's resorcinol reaction. From the above results, CIF as a small and stable molecule seems to have pyrimidine, pyrophosphate, and a sugar moiety.oiety.