• The Korean Journal of Physiology and Pharmacology
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• v.11 no.1
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• pp.15-20
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• 2007

To investigate whether hydrogen peroxide($H_2O_2$) affects intestinal motility, pacemaker currents and membrane potential were recorded in cultured interstitial cells of Cajal(ICC) from murine small intestine by using a whole-cell patch clamp. In whole cell patch technique at $30^{\circ}C$, ICC generated spontaneous pacemaker potential under current clamp mode(I=0) and inward currents(pacemaker currents) under voltage clamp mode at a holding potential of -70 mV. When ICC were treated with $H_2O_2$ in ICC, $H_2O_2$ hyperpolarized the membrane potential under currents clamp mode and decreased both the frequency and amplitude of pacemaker currents and increased the resting currents in outward direction under voltage clamp mode. Also, $H_2O_2$ inhibited the pacemaker currents in a dose-dependent manner. Because the properties of $H_2O_2$ action on pacemaker currents were same as the effects of pinacidil(ATP-sensitive $K^+$ channels opener), we tested the effects of glibenclamide(ATP-sensitive $K^+$ channels blocker) on $H_2O_2$ action in ICC, and found that the effects of $H_2O_2$ on pacemaker currents were blocked by co- or pre- treatment of glibenclamide. These results suggest that $H_2O_2$ inhibits pacemaker currents of ICC by activating ATP-sensitive $K^+$ channels.

• Physical Therapy Rehabilitation Science
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• v.11 no.4
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• pp.526-534
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• 2022

Objective: The purpose of this study was to compare muscle activities of stroke patients and healthy participants during bimanual tasks. Design: A cross sectional study. Methods: A total of 25 participants (13 hemiparetic stroke patients and 12 healthy participants) were recruited. The muscle activities using electromyogram (EMG) during bimanual tasks were collected from the following muscles: extensor carpi radialis longus (ECRL), biceps brachii (BB), and triceps brachii (TB). The bimanual tasks included eight tasks consisted of (1) raising the wrists up and down, (2) supinating and pronating the palms, (3) touching the shoulder with fingertips, (4) drawing vertical dot, (5) reaching for a cup and bring it in to drink, (6) drawing a circle outward and (7) inward, and (8) grasping the fingers. The EMG data collected from the muscles of paretic and non-paretic sides of stroke patients and the average from both sides of healthy subjects were normalized and compared after calculating the percentage of maximal isometric voluntary contraction. Results: The ECRL, BB and TB of the paretic side of the stroke patients showed relatively greater muscle activity compared to the non-paretic side as well asaverage of the healthy subject duringall tasks (p<0.05). In addition, the ECRL showed the highest muscle activity during most of the tasks. All of the non-paretic side musclesfrom stroke patients showed higher muscle activity compared to those of healthy subjects. Conclusions: The current study showed that muscle activities of upper extremity varied between paretic and non-paretic sides of stroke patients during bimanual tasks. Interestingly, the non-paretic side muscle activities were also different from those of normal participants.

• Korea Trade Review
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• v.41 no.4
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• pp.245-267
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• 2016

The purpose of this study is to investigate the current situation of foreign direct investment of Korea based on GVC (Global Value Chain) perspective and to presentthe policy direction. From GVC perspective which comprehensively describes the world's increasing FDI and imports/exports phenomenon since the 2000s, the level of internationalization of Korea is excessively concentrated in trade. Therefore, the expansion of foreign investment (OFDI, IFDI) is urgently needed. The results of regression analysis using data from 50 countries and the international comparison of major countries including Germany, Switzerland, Singapore, etc, showed that the level of foreign direct investment of Korea is 20 to 30 years behind compared to those major countries. Therefore, exploiting the benefits of trade and foreign direct investment at the same time is needed to increase the level of GDP per capita.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.2
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• pp.218-231
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• 1999

Pyramidal cells in the hippocampal CA area were recorded from and filled with neurobiotin in anesthetized rats. The extent of their dendrites and the electropharmacological properties of membrane as well as the effect before and after neurobiotin injection were examined. Pyramidal cells had a high resting membrane potential, a low input resistance, and a large amplitude action potential. A afterhyperpolarization was followed a single action potential. Most pyramidal cells did not display a spontaneous firing. Pyramidal cell displayed weak inward rectification and anodal break excitation in response to negative current injection into the cell. Membrane properties of recorded neurons before and after neurobiotin injection with consecutive current injection were compared. Some properties were significantly increased after labelling(P>0.05); the duration and amplitude of sustained AHP, input resistance, and the number of action potentials for simultaneous intra- and extracellular stimulations. Neurobiotin-filled neurons showed pyramidal morphology. Cells were generally bipolar dendrite processes ramifying in stratum lacunosum-moleculare, radiatum, and oriens.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.54-54
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• 2003

Prostate gland contains neuroendocrine cells (PNECs) are playing important roles in physiological and pathophysiological processes of the prostate gland. Here, we investigated the role of purinoceptors in PNECs freshly isolated from rat ventral prostate (RPNECs) that show immunoreactivity to chromogranin A. Fura-2 ratiometry revealed that ATP evokes both fast Ca$\^$2+/ influx and store Ca$\^$2+/ release in RPNECs. A whole-cell patch clamp study demonstrated fast inactivating cationic current activated by ATP or by ${\alpha}$,${\beta}$-MeATP, which was blocked by ATP-TNP. The activation of P2X inward current was tightly associated with a sharp increase in [Ca$\^$2+/]$\sub$c/. The presence of P2X1/3 subtypes were proved by RT-PCR analysis. For the stored Ca$\^$2+/ release, ATP and UTP showed similar effects, suggesting the dominant role or P2Y2 subtypes, also confirmed by RT-PCR. Both P2X (${\alpha}$,${\beta}$-MeATP) and P2Y (UTP) stimulation induced changes in the cell morphology (initial shrinkage and blob formation on the surface) reversibly. Exocytotic membrane trafficking events were monitored with the membrane-bound fluorescent dye, FM1-43 using confocal microscopy. In spite of the similar Ca$\^$2+/ responses, UTP was far less effective in triggering exocytosis than ${\alpha}$,${\beta}$ -MeATP. Since serotonin is reportedly stored in the secretory granule of PNECs, we directly examined whether the aforementioned agonists elicit release of serotonin using carbon fiber electrode-amperometry. In accordance with the results of FM1 -43 experiments, ${\alpha}$,${\beta}$-MeATP efficiently evoke serotonin secretion while not with UTP. In summary, the P2X-mediated Ca$\^$2+/ influx plays crucial roles in the exocytosis of RPNECs. Although a global increase in [Ca$\^$2+]$\sub$c/ might be related with the morphological changes, a sharp rise of [Ca$\^$2+/]$\sub$c/ in the putative sub-plasmalemmal ‘microdomains’ might be a decisive factor for the exocytosis.

• Progress in Medical Physics
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• v.15 no.4
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• pp.220-227
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• 2004

In N-type $Ca^{2＋}$ channels, the mechanism of inactivation - decline of inward current during a depolarizing voltage step- is still controversial between voltage-dependent inactivation and $Ca^{2＋}$ -dependent inactivation. In the previous paper we demonstrated that fast component of inactivation of N-type calcium channels does not involve classic $Ca^{2＋}$ -dependent mechanism and the slowly inactivating component could result from a $Ca^{2＋}$ -dependent process. However, there should be signal transduction pathway which enhances inactivation no matter what the inactivation mechanism is. We have investigated the effect of phosphorylation on calcium channels of rat sympathetic neurons. Intracellular dialysis with the phosphatase inhibitors okadaic acid markedly enhanced the inactivation. The rapidly inactivating component is N-type calcium current, which is blocked by $\omega$-conotoxin GVIA. Staurosporine, a nonselective protein kinase inhibitor, prevented the action of okadaic acid, suggesting that protein phosphorylation is involved. More specifically lavendustin C, inhibitor of CaM kinase II, prevented the action of okadaic acid, suggesting that calmodulin dependent pathway is involved in inactivation process. It is not certain to this point whether phosphorylation process is inactivation itself. Molecular biological research regarding binding site should be followed to address the question of how the divalent cation binding site is related to phoshorylation process.

• Journal of the Korean Vacuum Society
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• v.20 no.2
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• pp.100-105
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• 2011

Simulations were performed using Crystal TRIM software under the same conditions used by previous researchers in order to clarify the mechanism that determines sheet resistance various doses, energies and beam currents. The results showed that the peak of the depth profile (Rp) in the same sample gradually shifts inward and damage increases near the surface as the energy increases for $As^+$ equal dose of $1{\times}10^{15}/cm^2$ implanted into Si(100) energies of 5, 10, and 15 keV. From a theoretical calculation of B+ ion implantation processes at energy of 20 keV using parameters that correspond to 1 mA and 7 mA beam currents with the same dose of $5{\times}10^{15}/cm^2$, it was found that the higher beam currents resulted in more damage near the surface (<100 nm). Likewise, In the simulations employing sets of doses ($1{\times}10^{15}$, $3{\times}10^{15}/cm^2$) and beam currents (0.8 mA, 8 mA), more damage was produced at larger doses and higher current. Thus, sheet resistance at the surface was reduced by the intensified damage from increases in beam energy, dose and beam currents.

• 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.

• The Korean Journal of Physiology
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• v.23 no.2
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• pp.329-337
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• 1989

Cardiac muscles show stimulation frequency-dependent tension changes i.e. Bowditch phenomenon and Woodworth phenomenon, the former is an increase of tension with the increase of stimulation frequency, whereas the latter is an increase of tension with a decrease of stimulation frequency. Bowditch phenomenon is seen in the range of frequency 1.0 cps and above, and Woodworth phenomenon below the frequency 1.0 cps in the most of mammalian cardiac atrium. To throw some light on the possible mechanism of both phenomena in rat atrium, influences of drugs affecting $Ca^{2+}$ influx through the plasma membrane $(verapamil,\;La^{3+},\;norepinephrine)$ and $Ca^{2+}$ release from sarcoplasmic reticulum (SR) on frequency-tension curve were studied. The results obtained are summarized as follows: 1) At low temperature $(27.5^{\circ}C)$, both Bowditch and Woodworth phenomenon were demonstrated. But Bowditch phenomenon disappeared at the temperature above $(32.5^{\circ}C)$. 2) At $(27.5^{\circ}C)$, in the presence of verapamil, a $Ca^{2+}$ channel blocker, a time course of change in the frequency-tension was studied. It was found that Bowditch phenomenon was affected before the Woodworth phenomenon, then the former was completely disappeared. At $(32.5^{\circ}C)$, where no Bow-ditch is seen in normal atrial muscle, Bowditch phenomenon was reappeared by an administration of norepinephrine suggesting again that slow inward current of such as $Ca^{2+}$ channel is closely related to Bowditch phenomenon. 3) At $27.5^{\circ}C$, in the presence of $La^{3+}$, although tensions were decreased at all stimulation frequencies, Bowditch and Woodworth phenomenon were still demonstrated. However in the presence of both $La^{3+}$ and verapamil, Bowditch phenomena was disappeared suggesting that $La^{3+}$ is less effective in blocking $Ca^{2+}$ channel than verapamil. 4) At $27.5^{\circ}C$, in the presence of ryanodine, an inhibitor of calcium release from SR, Woodworth phenomenon was disappeared, which was consistent with previous reports of others, suggesting that $Ca^{2+}$ release from SR is closely related to Woodworth phenomenon. From the above findings, it may be concluded that Bowditch phenomenon is dependent on the magnitude of $Ca^{2+}$ influx through slow channel and Woodworth phenomenon is dependent on the amount of $Ca^{2+}$ stored in SR.

• Biomolecules & Therapeutics
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• v.24 no.4
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• pp.410-417
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• 2016

Quercetin is a flavonoid usually found in fruits and vegetables. Aside from its antioxidative effects, quercetin, like other flavonoids, has a various neuropharmacological actions. Quercetin-3-O-rhamnoside (Rham1), quercetin-3-O-rutinoside (Rutin), and quercetin-3-(2(G)-rhamnosylrutinoside (Rham2) are mono-, di-, and tri-glycosylated forms of quercetin, respectively. In a previous study, we showed that quercetin can enhance ${\alpha}7$ nicotinic acetylcholine receptor (${\alpha}7$ nAChR)-mediated ion currents. However, the role of the carbohydrates attached to quercetin in the regulation of ${\alpha}7$ nAChR channel activity has not been determined. In the present study, we investigated the effects of quercetin glycosides on the acetylcholine induced peak inward current ($I_{ACh}$) in Xenopus oocytes expressing the ${\alpha}7$ nAChR. $I_{ACh}$ was measured with a two-electrode voltage clamp technique. In oocytes injected with ${\alpha}7$ nAChR copy RNA, quercetin enhanced $I_{ACh}$, whereas quercetin glycosides inhibited $I_{ACh}$. Quercetin glycosides mediated an inhibition of $I_{ACh}$, which increased when they were pre-applied and the inhibitory effects were concentration dependent. The order of $I_{ACh}$ inhibition by quercetin glycosides was Rutin${\geq}$Rham1>Rham2. Quercetin glycosides-mediated $I_{ACh}$ enhancement was not affected by ACh concentration and appeared voltage-independent. Furthermore, quercetin-mediated $I_{ACh}$ inhibition can be attenuated when quercetin is co-applied with Rham1 and Rutin, indicating that quercetin glycosides could interfere with quercetin-mediated ${\alpha}7$ nAChR regulation and that the number of carbohydrates in the quercetin glycoside plays a key role in the interruption of quercetin action. These results show that quercetin and quercetin glycosides regulate the ${\alpha}7$ nAChR in a differential manner.