• 한국의학물리학회지:의학물리
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• 제8권1호
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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.

• 한국표면공학회지
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• 제37권5호
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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>.

• 한국의학물리학회지:의학물리
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• 제11권1호
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• pp.29-38
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• 2000

지금까지 각종 신경전달물질의 칼슘통로 억제 효과는 일반적으로 protein kinase 의 관여없이 G-protein mediated, membrane-delimited mechanism$^{1)}$ 으로 설명되어왔다. 그러나 최근들어 protein kinase C (PKC)의 활성화가 몇몇 신경전달물질에 의한 칼슘통로 억제효과를 야기하는 중요한 세포내 기전으로 보고되고 있다 그러므로 본 연구에서는 흰쥐 교감신경뉴론을 대상으로 하여 whole cell patch clamp technique을 사용하여 칼슘전류를 기록하고, 세포밖에 norepinephrine (NE)과 함께 PKC agonist 인 phorbol-12, 13-dibutyrate (PDBu)을 투여하면서 PDBu 전 처치로 인하여 NE 에 의한 칼슘전류 억제에 어떤 변화가 초래되는 지를 분석함으로써, 신경전달물질의 칼슘전류 억제효과시 PKC의 역할을 밝히고자 하였다. PDBu (500 nM) 처치는 칼슘전류의 크기를 증가시켰으며 이는 막전압 의존성을 보여 -10 mV ~ +10 mV 의 저분극 자극시 가장 크게 전류크기가 증가하였다. 또한 PDBu 처치는 tail current 의 deactivation을 느리게 하였다. PDBu 는 NE 에 의하여 활성화되는 pertussis toxin 예민성 G protein pathway를 통한 칼슘전류 억제를 감소시켰다. 비특이적인 protein kinase 길항제인 staurosporine (1 $\mu$M) 을 전처치 하고 PDBu를 투여하면 PDBu의 칼슘전류 크기 증가 효과가 소실되었으며 또한 NE에 의한 칼슘전류 억제를 해제하는 PDBu 의 조절효과도 소실되었다. 이상의 결과로부터 Protein Kinase C 가 활성되면 G protein을 경유하여 나타나는 칼슘전류 억제 효과가 소실된다고 결론지을 수 있다. Protein Kinase C 에 의하여 인산화되는 부위가 G-protein 인지 혹은 칼슘통로인 지에 관한 해답을 얻기 위하여는 추후 연구가 진행되어야 한다.

• The Korean Journal of Physiology
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• 제26권2호
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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 $Cd^{2+}$.

• The Korean Journal of Physiology and Pharmacology
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• 제11권5호
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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.

• 한국의학물리학회지:의학물리
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• 제14권1호
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• pp.54-67
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• 2003

N형 칼슘전류의 비활성화 vs 전압곡선은 U형을 보인다 - 즉 칼슘 내향전류의 크기와 비활성화 정도가 어느 정도 일치한다. 이러한 U형 비활성화는 순수한 전압의존성 기전으로 설명되어져 왔으나 칼슘의존성 비활성화 기전 또한 보고되었다. 이 연구에서는 흰쥐 상행 경동맥 결절뉴론을 단일 세포로 얻은 후, whole cell patch clamp technique를 사용하여 N형 칼슘전류를 기록하고, 세포외액의 charge carrier 로서 바륨과 칼슘을 사용하면서, 칼슘이 N형 칼슘통로의 비활성화에 미치는 역할을 알아보았다. charge carrier 로 칼슘을 사용하였을 경우에 바륨을 사용하였을 때에 비하여 비활성화 정도가 증가하였으며 이러한 증가는 세포속 $Ca^{2＋}$ Chelator가 11 mM EGTA 로부터 20 mM BAPTA 로 치환되어도 계속 관찰되었다. 비활성화 vs 전압 곡선은 바륨과 칼슘 모두에서 U형이었다. charge carrier 를 칼슘으로 치환시 추가로 유도되는 비활성화 정도는 바륨사용시의 비활성화 정도와 역비례관계를 보여 두 이온에서 같은 기전으로 비활성화가 일어날 가능성을 시사하였다. 이러한 가능성을 지원해 주는 결과로 5초의 긴 저분극 자극시 바륨과 칼슘을 써서 얻은 전류기록은 2중 지수함수로 잘 그려낼 수 있었고, 그 결과 빠른 성분(시정수: -150 ms) 과 느린 성분(시정수 -2500 ms) 를 얻었다. 칼슘이 각각의 성분에 미치는 효과는 각기 달라서 빠른 성분의 amplitude는 증가하였고 느린 성분의 시정수는 빨라졌다. 칼슘에 의해 빠른 성분의 amplitude는 증가하였으므로 이는 더 많은 채널이 빠른 경로로 비활성화되었음을 시사한다. 빠른 성분의 시정수는 변화하지 않았으므로, 이는 비촬성화의 빠른 경로는 칼슘과 바륨에서 같음을 시사하며 즉 비활성화 기전이 칼슘의존성이 아님을 보여주는 증거이다. 그러나 비활성화의 느린 성분은 칼슘에 의해 그 시정수가 빨라졌으므로 칼슘의존성일 가능성이 있다.

• 대한화학회지
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• 제10권1호
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• pp.32-42
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• 1966

$CaCl_2$, CaO 및 $WO_3$로 構成되는 熔融鹽을 黑鉛 陽極과 鐵 陰極으로 電解하여 순수한 金屬텅스텐을 얻는 方法에 관하여 실험하였다. 電氣分解에 적합한 熔融浴을 選定하기 위하여 $CaCl_2$-CaO系와 $CaCl_2-CaWO_4$系에 관한 二相 狀態圖를 작성하였으며 同時에 $CaCl_2$와 $WO_3$와의 高溫下에서의 化學反應을 검토하여 安定한 電解浴을 얻기 위해서는 一定量의 CaO가 添加되어야 할 것임을 알 수 있었다. 炭素陽極을 사용하여 $WO_3$를 W와 CO로 분해시킬 때의 分解電壓은 -0.1 volt이었으며 熱力學的 計算에 의한 것은 -0.3 volt이었다. 熔融鹽을 電氣分解한 結果 金屬텅스텐이 100%에 가까운 電流效率로 電極에 析出되나 이는 陽極에서 二次的으로 발생하는 CO가스에 의하여 쉽게 WC등으로 변화하므로 순수한 텅스텐을 얻기 위해서는 電解浴의 溫度를 $1100^{\circ}C$이상으로 유지하여야 된다는 것을 알게 되었다. 電解浴의 組成은 可及的 低融點과 $WO_3$의 分解, $CaCl_2$의 蒸發 등을 억제하기 위해서는 $CaCl_2$ 100分에 대하여 CaO와 $WO_3$가 각 10 乃至 20分이 適切하였으며 CaO와 $WO_3$의 몰比率은 1이상이 요구되었다. 陰極 電流密度를 1~5 $amp/cm^2$의 範圍에서 變化시켜도 電流效率에 큰 影響이 없었다.

• Transactions on Electrical and Electronic Materials
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• 제15권1호
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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.

• Progress in Superconductivity
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• 제2권2호
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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..

• Animal cells and systems
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• 제7권1호
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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.