• The Korean Journal of Physiology and Pharmacology
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• 제2권3호
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• pp.279-286
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• 1998

It has been well documented that transient forebrain global ischemia causes selective neuronal degeneration in hippocampal CA1 pyramidal neurons with a delay of a few days. The mechanism of this delayed hippocampal CA1 pyramidal neuronal death (DND) is still controversial. To delineate the mechanisms of the DND, the effects of treatment with MK-801, an NMDA receptor antagonist, kynurenic acid, a NMDA/non-NMDA receptor antagonist, and/or cycloheximide, a protein synthesis inhibitor, on the DND were investigated in male Wistar rats. To examine the participation of apoptotic neuronal death in the DND, TUNEL staining was performed in ischemic brain section. Global ischemia was induced by 4-vessel occlusion for 20 min. All animals in this study showed the DND 3 and 7 days after the ischemic insult. The DND that occured 3 days and 7 days after the ischemia were not affected by pretreatment with MK-801 (1 mg/kg), but markedly attenuated by the pretreatment with kynurenic acid (500 mg/kg). Treatment with cycloheximide (1 mg/kg) also markedly inhibited the DND. The magnitudes of attenuation by the two drugs were similar. The magnitude of attenuation by co-treatments with kynurenic acid and cycloheximide was not greater than that with any single treatment. TUNEL staining was negative in the sections obtained 1 or 2 days after the ischemic insults, but it was positive at hippocampal CA1 pyramidal cells in sections collected 3 days after the ischemia. These results suggested that the DND should be mediated by the activation of non-NMDA receptor, not by the activation of NMDA receptor and that the activation of AMPA receptor should induce the apoptotic process in the DND.

• 융합신호처리학회논문지
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• 제14권4호
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• pp.222-230
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• 2013

망막 쌍극세포는 광자극에 대하여 완만한 전위응답을 하며, 막전위에 의존하여 전달물질(glutamine 산)을 방출한다. 본 논문에서는 ON형 쌍극세포의 시냅스 앞단에서 전달물질 방출 기구에 관한 여러 가지의 생리학적 정보를 수식적 모델로 통합하였다. 전달물질 방출의 빠른 성분과 느린 성분의 공급원을 병렬로 배치한 본 모델은 전달물질 방출의 막전위 및 세포 내 $Ca^{2+}$ 농도 의존성을 충실하게 재현할 수가 있었다. 또한 전달물질의 빠른 방출 성분은 사다리꼴 모양의 막전위 의존성을 나타내는 데에 반하여, 느린 방출 성분은 종모양의 막전위 의존성을 나타내기 때문에 세포 내의 $Ca^{2+}$ 농도 상승을 $Ca^{2+}$ 완충제로 억제하여 느린 방출 성분이 감소되고, 전달 물질 방출의 막전위 의존성이 사다리꼴 모양의 특성이 되는 것을 확인하였다. 그리고 ON 형 쌍극세포의 광응답에서 일시적 성분과 지속적 성분에 의하여 발생하는 전달물질 방출을 시뮬레이션한 결과 광응답의 시작은 전달물질을 빠르게 방출하게 하였으며, 광응답의 일시적 성분과 초기의 지속적 성분은 전달물질을 느리게 방출하도록 하였다. 또한 광응답의 후기 지속적 성분은 저장 pool로부터 보충된 시냅스 소포에 의하여 지속적인 방출이 발생하기 때문이라는 것을 확인하였다.

• The Korean Journal of Physiology and Pharmacology
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• 제15권4호
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• pp.217-239
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• 2011

We carried out a series of experiment demonstrating the role of mitochondria in the cytosolic and mitochondrial $Ca^{2+}$ transients and compared the results with those from computer simulation. In rat ventricular myocytes, increasing the rate of stimulation (1~3 Hz) made both the diastolic and systolic [$Ca^{2+}]$ bigger in mitochondria as well as in cytosol. As L-type $Ca^{2+}$ channel has key influence on the amplitude of $Ca^{2+}$ -induced $Ca^{2+}$ release, the relation between stimulus frequency and the amplitude of $Ca^{2+}$ transients was examined under the low density (1/10 of control) of L-type $Ca^{2+}$ channel in model simulation, where the relation was reversed. In experiment, block of $Ca^{2+}$ uniporter on mitochondrial inner membrane significantly reduced the amplitude of mitochondrial $Ca^{2+}$ transients, while it failed to affect the cytosolic $Ca^{2+}$ transients. In computer simulation, the amplitude of cytosolic $Ca^{2+}$ transients was not affected by removal of $Ca^{2+}$ uniporter. The application of carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP) known as a protonophore on mitochondrial membrane to rat ventricular myocytes gradually increased the diastolic [$Ca^{2+}$] in cytosol and eventually abolished the $Ca^{2+}$ transients, which was similarly reproduced in computer simulation. The model study suggests that the relative contribution of L-type $Ca^{2+}$ channel to total transsarcolemmal $Ca^{2+}$ flux could determine whether the cytosolic $Ca^{2+}$ transients become bigger or smaller with higher stimulus frequency. The present study also suggests that cytosolic $Ca^{2+}$ affects mitochondrial $Ca^{2+}$ in a beat-to-beat manner, however, removal of $Ca^{2+}$ influx mechanism into mitochondria does not affect the amplitude of cytosolic $Ca^{2+}$ transients.

• The Korean Journal of Physiology
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• 제23권1호
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• pp.35-42
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• 1989

The present study was performed to observe the effects of cations on resting membrane potential and pump activity in the unfertilized eggs of ICR strain mice. After an induction of superovulation, the fresh eggs with zona pellucida were collected and the membrane potentials were recorded. Recordings of membrane potential in this study was obtained from the physiological conditions ($37^{\circ}C$ and 4mM Ca in standard solution), differently from the another reports with unphysiological conditions (room temprature and high Ca in standard solution) for a stable and long-lasting observations. Presented data was obtained within 6 hours after collection from the oviduct. The results observed are as follows, 1) Resting potential of the unfertilized eggs was $-25.8{\pm}3.8mV$ $(Mean{\pm}Se,\;n=31)$. 2) As the K ion concentration was increased, resting membrane potential was depolarized but showed hyperpolarization with $K^{+}$ below 25mM. 3) Alteration of the resting membrane potential for the changes of $Na^{+}$ concentration were hardly observed, while resting potential was hyperpolarized as $Ca^{2+}$ concentration was increased. 4) Pump activity as transient or prolonged hyperpolarization was $-2.29{\pm}0.75mV$ $(Mean{\pm}Se,\;n=16)$, the hyperpolarization was increased in both amplitude and duration under the 10mM $Ca^{2+}$ solution. 5) Hyperpolarization due to pump activity was decreased or disappeared by $5{\times}10^{-5}\;M$ ouabain treatment and could not be observed under the both Na-free and Ca-free solutions. 6) Above results are likely to suggest that the resting potential of the mouse unfertilized eggs is affected to mainly by Ca-dependent K conductance and Na-Ca exchange mechanism and that there is pump activity coupling between $K{+}$, $Na^{+}$ and $Ca^{2+}$.

• Animal cells and systems
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• 제16권5호
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• pp.376-384
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• 2012

Although ginsenosides have a variety of physiologic or pharmacologic functions in various regions, there are only a few reports on the effects of transient receptor potential melastatin 7 (TRPM7) channels. Here, we showed evidence suggesting that TRPM7 channels play an important role in ginseng total saponin (GTS)-mediated cellular injury. The combination techniques of electrophysiology, pharmacological analysis, small interfering RNA (siRNA) method and cell death assays were used. GTS depolarized the resting membrane potentials and decreased the amplitude of pacemaker potentials in cultured interstitial cells of Cajal (ICCs) in gastrointestinal (GI) tract. The TRPM7-like currents in single ICCs and the overexpressing TRPM7 in HEK293 cells were inhibited by GTS. However, GTS had no effect on $Ca^{2+}$-activated $Cl^-$ conductance. GTS inhibited the survival of human gastric (AGS) and brea (MCF-7) adenocarcinoma cells. Also, GTS inhibited the TRPM7-like currents in AGS and MCF-7 cells. The GTS-mediated cytotoxicity was inhibited by TRPM7-specific siRNA. In addition, we showed that overexpression of TRPM7 channels in HEK293 cells was inhibited by GTS. Thus, TRPM7 channels are involved in GTS-mediated cell death in AGS and MCF-7 cells, and these channels may represent a novel target for physiological disorders where GTS plays an important role.

• Bulletin of the Korean Chemical Society
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• 제24권11호
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• pp.1675-1679
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• 2003

The photodynamics of excited-state intramolecular proton transfer reaction of 1-hydroxyanthraquinone (1-HAQ) and 1-deuterioanthraquinone was investigated in toluene with time-resolved emission and femtosecond transient transmittance techniques at room temperature. The temporal profiles of transient transmittance of 1-HAQ could be well described with multi-decaying time constants. The ultrafast time constant within ca. 260 fs reflects the dynamics of proton transfer. The decay component of 2 ps is assigned to an additional proton translocation process induced by the intramolecular vibrational relaxation, whereas the decay component of 18 ps is assigned to the vibrational cooling process, while the long component (200 ps) can be explained in terms of the relaxation from excited-state keto-tautomer to its ground state. Time-resolved anisotropy decay dynamics and isotope effects on the photodynamics reveals that the ESIPT from enol-tautomer to keto-one of 1-HAQ is barrierless reaction and coupled to a vibrational relaxation process.

• Animal cells and systems
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• 제15권2호
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• pp.123-130
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• 2011

Transient receptor potential melastatin 7 (TRPM7) channels are novel $Ca^{2+}$-permeable non-selective cation channels that are ubiquitously expressed. Activation of TRPM7 channels has been shown to be involved in the survival of gastric cancer cells. Here we show evidence suggesting that TRPM7 channels play an important role in $Zn^{2+}$- mediated cellular injury. Using a combination of electrophysiology, pharmacological analysis, small interfering RNA (siRNA) methods and cell death assays, we showed that activation of TRPM7 channels augmented $Zn^{2+}$-induced apoptosis of AGS cells, the most common human gastric adenocarcinoma cell line. The $Zn^{2+}$-mediated cytotoxicity was inhibited by the non-specific TRPM7 blockers $Gd^{3+}$ or 2 aminoethoxydiphenyl borate (2-APB) and TRPM7 specific siRNA. In addition, we showed that overexpression of TRPM7 channels in HEK293 cells increased $Zn^{2+}$- induced cell injury. Thus, TRPM7 channels may represent a novel target for physiological disorders where $Zn^{2+}$ toxicity plays an important role.

• Interdisciplinary Bio Central
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• 제5권3호
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• pp.6.1-6.7
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• 2013

Many insects such as mosquitoes cause life-threatening diseases such as malaria, yellow fever and West Nile virus. Malaria alone infects 500 million people annually and causes 1-3 million death per year. Volatile insect repellents, which are detected through the sense of smell, have long been used to protect humans against insect pests. Antifeed-ants are non-volatile aversive compounds that are detected through the sense of taste and prevent insects from feeding on plants. The molecular targets and signaling path-ways required for sensing insect repellents and antifeedants are poorly understood. Transient Receptor Potential (TRP) Ca2+-permeable cation channels exist in organisms ranging from C. elegans to D. melanogaster and Homo sapiens. Drosophila has 13 family members, which mainly function in sensory physiology such as vision, thermotaxis and chemotaxis. G protein-coupled receptors (GPCRs) initiate olfactory signaling cascades in mammals and in nematodes C.elegans. However, the mechanisms of G protein signaling cascades in insect chemosensation are controversial. In this review, I will discuss the putative roles of G protein-coupled receptors (GPCRs) and Transient Receptor Potential (TRP) channels as targets for insect repellents.

• The Korean Journal of Physiology and Pharmacology
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• 제18권1호
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• pp.15-23
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• 2014

Transient receptor potential melastatin 7 (TRPM7) is a member of the melastatin-related subfamily and contains a channel and a kinase domain. TRPM7 is known to be associated with cell proliferation, survival, and development. It is ubiquitously expressed, highly permeable to $Mg^{2+}$ and $Ca^{2+}$, and its channel activity is negatively regulated by free $Mg^{2+}$ and Mg-complexed nucleotides. Recent studies have investigated the relationships between TRPM7 and a number of diseases. TRPM7 regulates cell proliferation in several cancers, and is associated with ischemic cell death and vascular smooth muscle cell (VSMC) function. This review discusses the physiologic and pathophysiologic functions and significance of TRPM7 in several diseases.

• 한국초전도ㆍ저온공학회논문지
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• 제5권2호
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• pp.66-70
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• 2003

Transient magnetic diffusion process in a melt-cast Bi2Sr2CaCu20X(Bi-2212) tube was studied by experimental and numerical analyses. The transient diffusion partial differential equation is transformed into an ordinary differential equation by integral method. The penetration depth of magnetic field into a superconducting tube is obtained by solving the differential equation numerically. The results show that the penetration depth as a function of time which is somewhat different from the results by Bean's critical state model. The reason of the difference between the present results and that of Bean's model is discussed and compared in this paper. This experiment measure the magnetic flux density in the supercondutor after supply direct-current of Bi-2212 rounded by copper coil. This study was discussed of valid of a previous numerical solution which is compared by the penetrate time and the magnetic flux density difference of between the present results and the numerical solution.