• The Korean Journal of Physiology and Pharmacology
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• 제2권5호
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• pp.611-616
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• 1998

Although the $Ca^{2+}-activated\;K^+\;(I_{K,Ca})$ channel is known to play an important role in the maintenance of resting membrane potential, the regulation of the channel in physiological condition is not completely understood in vascular myocytes. In this study, we investigated the role of cytoplasmic $Mg^{2+}$ on the regulation of $I_{K,Ca}$ channel in pulmonary arterial myocytes of the rabbit using the inside-out patch clamp technique. $Mg^{2+}$ increased open probability (Po), but decreased the magnitude of single channel current. $Mg^{2+}-induced$ block of unitary current showed strong voltage dependence but increase of Po by $Mg^{2+}$ was not dependent on the membrane potential. The apparent effect of $Mg^{2+}$ might, thus, depend on the proportion between opposite effects on the Po and on the conductance of $I_{K,Ca}$ channel. In low concentration of cytoplasmic $Ca^{2+},\;Mg^{2+}$ increased $I_{K,Ca}$ by mainly enhancement of Po. However, at very high concentration of cytoplasmic $Ca^{2+},$ such as pCa 5.5, $Mg^{2+}$ decreased $I_{K,Ca}$ through the inhibition of unitary current. Moreover, $Mg^{2+}$ could activate the channel even in the absence of $Ca^{2+}.\;Mg^{2+}$ might, therefore, partly contribute to the opening of $I_{K,Ca}$ channel in resting membrane potential. This phenomenon might explain why $I_{K,Ca}$ contributes to the resting membrane potential where membrane potential and concentration of free $Ca^{2+}$ are very low.

• Molecules and Cells
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• 제38권7호
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• pp.657-662
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• 2015

Rapid and efficient engulfment of apoptotic cells is an essential property of phagocytes for removal of the large number of apoptotic cells generated in multicellular organisms. To achieve this, phagocytes need to be able to continuously uptake apoptotic cells. It was recently reported that uncoupling protein 2 (Ucp2) promotes engulfment of apoptotic cells by increasing the phagocytic capacity, thereby allowing cells to continuously ingest apoptotic cells. However, the functions of Ucp2, beyond its possible role in dissipating the mitochondrial membrane potential, that contribute to elevation of the phagocytic capacity have not been determined. Here, we report that the anion transfer or nucleotide binding activity of Ucp2, as well as its dissipation of the mitochondrial membrane potential, is necessary for Ucp2-mediated engulfment of apoptotic cells. To study these properties, we generated Ucp2 mutations that affected three different functions of Ucp2, namely, dissipation of the mitochondrial membrane potential, transfer of anions, and binding of purine nucleotides. Mutations of Ucp2 that affected the proton leak did not enhance the engulfment of apoptotic cells. Although anion transfer and nucleotide binding mutations did not affect the mitochondrial membrane potential, they exerted a dominant-negative effect on Ucp2-mediated engulfment. Furthermore, none of our Ucp2 mutations increased the phagocytic capacity. We conclude that dissipation of the proton gradient by Ucp2 is not the only determinant of the phagocytic capacity and that anion transfer or nucleotide binding by Ucp2 is also essential for Ucp2-mediated engulfment of apoptotic cells.

• 멤브레인
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• 제27권2호
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• pp.109-120
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• 2017

양이온($Na^+$) 및 음이온($Cl^-$)이 각각의 CEM과 AEM을 통해 선택적으로 분리되어 담수로 이동할 때 발생되는 전위차와 산화/환원(redox couple)형 전해질을 포함하고 있는 전극에서 발생하는 전류를 이용하여 전기 에너지로 전환시키는 에너지변환장치이다. RED 시스템의 핵심소재 중 하나인 이온교환막은 높은 출력 밀도를 달성하기 위해 1) 낮은 팽윤거동, 2) 적절한 이온교환능, 3) 높은 이온전도도, 4) 높은 이온선택성을 만족시켜야 한다. 본 논문에서는 이를 만족시키는 소재 및 이온교환막의 연구동향 및 전망에 대해 설명하였다.

• The Korean Journal of Physiology
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• 제29권2호
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• pp.203-216
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• 1995

The effects of ${\alpha}_1-adrenergic$ receptor stimulation on membrane potential, intracellular $Na^+$ activity, and twitch force were investigated in ventricular muscles from guinea-pig hearts. Action potentials, intracellular $Na^+$ activity, and twitch force of ventricular papillary muscles were measured simultaneously under various experimental conditions. Stimulation of the ${\alpha}_1-adrenergic$ receptor by phenylephrine produced variable changes in action potential duration, a slight hyperpolarization of the diastolic membrane potential, a decrease in intracellular $Na^+$ activity, and a biphasic inotropic response in which a transient negative inotropic response was followed by a sustained positive inotropic response. These changes were blocked by prazosin, an antagonist of the ${\alpha}_1-adrenergic$ receptor, but not by atenolol, an antagonist of the ${\beta}-adrenergic$ receptor. This indicates that the changes in membrane potential, intracellular $Na^+$ activity, and twitch force are mediated by stimulation of the ${\alpha}_1-adrenergic$ receptor, but not by stimulation of ${\beta}-adrenergic$ receptor. The decrease in intracellular $Na^+$ activity was not observed in quiescent muscles, depending on the rate of the action pontentials in beating muscles. The intracellular $Na^+$ activity decrease was substantially inhibited by tetrodotoxin. However, the decrease in intracellular $Na^+$ activity was not affected by an inhibition of the $Na^+-K^+$ pump. Therefore, the decrease in intracellular $Na^+$ activity mediated by the ${\alpha}_1-adrenergic$ receptor appears to be due to a reduction of $Na^+$ influx during the action potential, perhaps through tetrodotoxin sensitive $Na^+$ channels. Our study also revealed that the decrease in intracellular $Na^+$ activity might be related to the transient negative inotropic response. The intracellular $Na^+$ activity decrease could lower intracellular $Ca^{2+}$ through the $Na^+-Ca^{2+}$ exchanger and thereby produce a decline in twitch force.

• The Korean Journal of Physiology and Pharmacology
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• 제7권1호
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• pp.47-52
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• 2003

The prostate gland contains numerous neuroendocrine cells that are believed to influence the function of the prostate gland. Our recent study demonstrated the expression of both ${\alpha}1$- and ${\alpha}2$-ARs, signaling the release of stored $Ca^{2+}$ and the inhibition of N-type $Ca^{2+}$ channels, respectively, in rat prostate neuroendocrine cells (RPNECs). In this study, the effects of NA on the resting membrane potential (RMP) of RPNECs were investigated using a whole-cell patch clamp method. Fresh RPNECs were dissociated from the ventral lobe of rat prostate and identified from its characteristic shape; round or oval shape with dark cytoplasm. Under zero-current clamp conditions with KCl pipette solution, the resting membrane potential (RMP) of RPNECs was between -35 mV and -85 mV. In those RPNECs with relatively hyperpolarized RMP (＜-60 mV), the application of noradrenaline (NA, $1{\mu}M$) depolarized the membrane to around -40 mV. In contrast, the RPNECs with relatively depolarized RMP (＞-45 mV) showed a transient hyperpolarization and subsequent fluctuation at around -40 mV on application of NA. Under voltage clamp conditions (holding voltage, -40 mV) with CsCl pipette solution, NA evoked a slight inward current (＜-20 pA). NA induced a sharp increase of cytosolic $Ca^{2+}$ concentration ($[Ca^{2+}]_c$), measured by the fura-2 fluorescence, and the voltage clamp study showed the presence of charybdotoxin-sensitive $Ca^{2+}$-activated $K^+$ currents. In summary, adrenergic stimulation induced either depolarization or hyperpolarization of RPNECs, depending on the initial level of RMP. The inward current evoked by NA and the $Ca^{2+}$-activated $K^+$ current might partly explain the depolarization and hyperpolarization, respectively.

• Structural Engineering and Mechanics
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• 제37권4호
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• pp.401-413
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• 2011

The aerodynamic stability of orthotropic tensioned membrane structures with rectangular plane is theoretically studied under the uniform ideal potential flow. The aerodynamic force acting on the membrane surface is determined by the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics. Then, based on the large amplitude theory and the D'Alembert's principle, the interaction governing equation of wind-structure is established. Under the circumstances of single mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction equation into a system of second order nonlinear differential equation with constant coefficients. Through judging the stability of the system characteristic equation, the critical divergence instability wind velocity is determined. Finally, from different parametric analysis, we can conclude that it has positive significance to consider the characteristics of orthotropic and large amplitude for preventing the instability destruction of structures.

• Journal of Microbiology and Biotechnology
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• 제13권6호
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• pp.833-840
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• 2003

Sperm motility of salmonid fishes is suppressed by external $K^{+}$ and initiated by decrease of $K^{+}$ concentration surrounding the sperm. It was shown that the decrease in external $K^{+}$ concentration induced not only the initiation of sperm motility, but also hyperpolarization of the plasma membrane and synthesis of cAMP in the sperm of rainbow trout, steelhead trout, and masu salmon. Inhibitors of $K^{+}$ channels, especially voltage-dependent $K^{+}$ channels, inhibited these three reactions, and the inhibitions were abolished by subsequent addition of a $K^{+}$ ionophore, valinomycin, suggesting that $K^{+}$ efflux through the $K^{+}$ channel contributes to rapid changes in the membrane potential of sperm and cAMP synthesis, thereby resulting in the initiation of sperm motility of salmonid fishes.

• 상하수도학회지
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• 제19권6호
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• pp.775-780
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• 2005

This study was performed to investigate the effect of foulant characteristics on Membrane fouling index such as Silt Density Index (SDI) and Modified Fouling Index (MFI). A linear relationship was found relating the fouling index (both SDI and MFI) on particle concentration, but fouling index values were nonlinearly (exponentially) with increasing organic concentration. When organic matter was the primary cause of fouling, the MFI was not accurately predicted due to internal fouling such as pore adsorption. The fouling index was determined mainly by particle characteristics when both particle and organic coexisted in the feed water. This observation was attributed to lessening of organic pore adsorption by particle cake layer formed on the membrane surface. Bench-scale actual fouling experiments demonstrated that permeate flux declines much faster with feed water containing particles than organic matters although fouling potential predicted by SDI values were identical, indicating that the accurate prediction of fouling potential requires the development of fouling index reflecting different foulant characteristics.

• Journal of Plant Biology
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• 제36권4호
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• pp.383-389
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• 1993

Intact leaf과 detached epidermis에 있는 공변세포의 전기 생리학적 특성에 대한 빛과 이산화탄소의 효과를 조사하였다. 빛을 intact leaf의 abaxial side에 처리하면 공변세포막이 과분극 (hyperpolarization)되었다. 닭의장풀의 intact leaf에 있는 공변세포들은 빛에 의해 최대 13 mV 그리고 이산화탄소에 의해 42 mV까지 membrane potential difference(MPD)가 negative하게 변했다. 자주달개비에서도 비슷한 결과를 얻었다. 그러나, 빛과 이산화탄소를 detached epidermis에 있는 공변세포에 처리할 경우에는 공변세포의 MPD가 변하지 않았다. 위의 결과로부터, 엽육세포가 공변세포의 MPD 변화에 영향을 주는 것으로 사료되어, 엽육세포들을 광합성 억제제들을 침윤시켜 엽육세포 광합성의 어느 기작이 공변세포 MPD 변화에 영향을 주는지 조사하였다. CCCP로 침윤한 잎의 공변세포막은 적색광에 의해 약간 탈분극(depolarization)되었고, 이산화탄소에 의해 과분극되었다. 반면에, DCCD와 DCMU로 침윤한 경우에는 대조구 잎과 마찬자기로 적색광과 이산화탄소에 의해 과분극되었다. Azide로 침윤한 잎에 적색광을 처리하면 공변세포의MPD는 변하지 않았고, 이산화탄소를 처리하면 다른 처리구들에 비해 훨씬 감소한 막의 과분극을 보였다. 이는 azide가 잎에 손상을 유도하며 세포내 대사활성을 감소시킨 결과 이산화탄소에 의한 MPD 변화가 작았고, 적색광은 아무 효과도 보이지 않은 것으로 사료된다. 따라서, 엽육세포가 적색광을 감지하며 빛에 의해 유도된 공변세포막 과분극은 순환적 광인산화 반응에 의해 생성된 에너지에 의존하나 이산화타소에 의해 유도된 공변세포막 과분극은 광합성가 무관하다고 볼 수 있다. 또한 이산화탄소를 intact leaf에 처리하면 공변세포 액포가 알칼리화되는 것을 관찰하였는데, 이는 막의 과분극이 양성자 이온의 방출에 의해 일어난다는 것을 의미한다.

• 상하수도학회지
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• 제20권1호
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• pp.27-34
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• 2006

This study was conducted to evaluate the performance of a membrane bioreactor filled with high concentration of powdered activated carbon (HCPAC-MBR) to reduce DBPs at the drinking water treatment. The pilot system was installed after the rapid sand filtration process whose plant was the conventional treatment process. The removal efficiencies of DBPs were measured during pilot operation period of 2 years. HAA and THM removal rates could be maintained around 80~90% without any troubles and then tremendous reduction of HAA and THM reactivity were observed more than 52%. The average removal rate of HAA formation potential (FP) and THM formation potential (FP) were 70.5% and 67.6% respectively. It is clear that the PAC membrane bioreactor is highly applicable for advanced water treatment to control DBPs.