• Toxicological Research
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• v.14 no.3
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• pp.341-348
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• 1998

We established an in vitro experimental system using the following procedure. We first introduced tritium-labelled norepinephrine ([3H]-NE)into PC12 cells. The [3H]-NE incorporated into PC12 cells were then stimulated by a high concentration (60 mM) of $K^+$ during 12 minutes. Then, we counted the amount of [3H]-NE release from PC12 cells with the scintillation counter. After screening fungal, Streptomyces or bacterial product using this experimental system, we obtained S9940 from Streptomyces spp. which inhibited [3H]-NE release from PC12 cells. S9940 also inhibits the release of ATP as a neurotransmitter of PC12 cells and rat cortical neurons. The inhibitory effect was seen even when the PC12 cells were treated with low $K^+$ buffer containing ionomycin $(1\muM)$ as an ionopore. This result suggests that the inhibitory action of S9940 on neurotransmitter release appeared after the influx of $Ca^{2+}$.

• Proceedings of the Ginseng society Conference
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• 1993.09a
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• pp.94-101
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• 1993

Lipophilic fraction(LF) from Panax ginseng C.A. Meyer inhibited the aggregation of human platelets induced by th rombin(0.1u/$m{\ell}$). LF and Molsidomine(vasodilator) induced the stimulation of cGMP - elevation and 50KD - Phosphorylation. and then the inhibition of 20KD - Phosphorylation in human platelets activated by thrombin. LF also inhibited the $Ca^{2-}-influx$ into platelets. When rat(SD : male) was fed with LF, the level of cGMP was increased in rat platelets stimulated by collagen and thrombin. On the other hand. verapamil, $Ca^{2-}-antagonist$ increased cAMP level ;n platelet stimulated by thrombin. but LF does not affected. However LF potently inhibited the thromboxane $A_2(TXA_2)$ production. The results suggest that the inhibitory effects of LF are mediated by regulation the phosphorylatior. of 50KD via cGMP-elevation and depend upon the decrease of $TXA_2$ level.

• Korean Journal of Veterinary Research
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• v.46 no.2
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• pp.87-96
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• 2006

We established an in vitro experimental system using the following procedure. We first introduced tritium-labeled norepinephrine ([$^3$H]-NE) into PC12 cells, The [$^3$H]-NE incorporated into PC12 cells were then stimulated by a high concentration (60 mM) of $K^+$ buffer during 12 minutes. Then, we collected $100{\mu}l$ supernatant and counted the amount of [$^3$H]-NE release from PC12 cells with a scintillation counter. After screening fungal, Streptomyces spp. or bacterial product using this experimental sytem, we obtained FS11052 from Streptomyces spp. which inhibited [$^3$H]-NE release from PC12 cells. FS11052 also inhibits the release of ATP as a neurotransmitter of PC12 cells and rat cortical neurons, The inhibitory effect was seen even when the PC12 cells were treated with low $K^-$ buffer containing ionomycin ($1{\mu}M$) as an ionopore. This result suggests that the inhibitory action of FS11052 on neurotransmitter release appeared after the influx of $Ca^{2+}$.

• Corrosion Science and Technology
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• v.18 no.3
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• pp.102-109
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• 2019

The hydrogen diffusion and trapping model with a numerical finite difference method (FDM) was modified and extended to accommodate $H_2S$ corrosion and scale forming processes of high-strength steel under tensile stress condition. The newly proposed diffusion model makes it possible to clearly understand combined effect of tensile stress and $H_2S$ corrosion process on hydrogen diffusion behaviors. The core concept of this theoretical approach is that overall diffusion behavior is separated into diffusion process through two respective layers: an outer sulfide scale and an inner steel matrix. Diffusion coefficient values determined by curve-fitting permeation data reported previously with the newly proposed diffusion model indicate that the application of tensile stress can contribute to continual increase in the diffusivity in the sulfide scale with a high density of defect. This suggests that the scale with a lower stability under the stress condition can be a key parameter to enhance hydrogen influx in the steel matrix. Consequently, resistance to hydrogen assisted cracking of the steel under tensile stress can be decreased significantly.

• Journal of Chest Surgery
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• v.43 no.4
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• pp.345-355
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• 2010

Background: Extracellular and intracellular pH ($pH_o$ and $pH_i$), which can be changed in various pathological conditions such as hypoxia, affects vascular contractility. To elucidate the mechanism to alter vascular contractility by pH, the effects of pH on reactivity to vasocontracting agents, intracellular $Ca^{2+}$ influx, and $Ca^{2+}$ sensitivity in vascular smooth muscle were examined. Material and Method: Isometric contractions in rat superior mesenteric arteries (SMA) were observed. Intracellular $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) was recorded by microfluorometer using Fura-2/acetoxylmethyl ester in muscle cells. $pH_o$ was increased from 7.4 to 7.8 or decreased to 6.9 or 6.4. $pH_i$ was decreased by applying $NH_4^+$ or propionic acid or modulated by changing $pH_o$ after increasing membrane permeability using $\beta$-escin. Result: Decreases in $pH_o$ from 7.4 to 6.9 or 6.4 shifted concentration-response curve by norepinephrine (NE) or serotonin (SE) to the right and significantly increased half maximal effective concentration (EC50) to NE or SE. Increase in $pH_o$ from 7.4 to 7.8 shifted concentration-response curve by norepinephrine (NE) or serotonin (SE) to the left and significantly reduced EC50 to NE or SE. NE increased $[Ca^{2+}]_i$ in cultured smooth muscle cells from SMA and the increased $[Ca^{2+}]_i$ was reduced by decreases in $pH_o$. NE-induced contraction was inhibited by $NH_4^+$, whereas the resting tension was increased by $NH_4^+$ or propionic acid. When the cell membrane of SMA was permeabilized using ${\beta}$-escin, SMA was contracted by increasing extracellular $Ca^{2+}$ concentration from 0 to $10{\mu}M$ and the magnitude of contraction was decreased by a decrease in $pH_o$ and vice versa. Conclusion: From these results, it can be concluded that a decrease in $pH_o$ might inhibit vascular contraction by reducing the reactivity of vascular smooth muscle to vasoactive agents, $Ca^{2+}$ influx and the sensitivity of vascular smooth muscle to $Ca^{2+}$.

• Development and Reproduction
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• v.3 no.1
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• pp.87-93
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• 1999

The possible role of Na$^{+}$/H$^{+}$ antiporter in both the capacitation and the acrosome reaction (AR) was examined in mouse epididymal spermatozoa. Spontaneous acrosome reaction was inhibited by dimethyl amiloride (DMA), a specific inhibitor of Na$^{+}$/H$^{+}$ antiporter, with dose dependent manner. Follicular fluid- or A23l 87-induced acrosome reaction was not inhibited by DMA. It suggests that change in pH$_{i}$ by monovalent cation transport through the Na$^{+}$/H$^{+}$ antiporter is possibly engaged in the capacitation and that agonist- as well as A23l87-induced AR in capacitated sperm might be independent from the Na$^{+}$/H$^{+}$ antiporter. Conclusively, changes in pH$_{i}$ through the Na$^{+}$/H$^{+}$ antiporter might be important for sperm capacitation and it virtually occurs upstream of the $Ca^{2+}$ influx which precedes the acrosome reaction in mouse epididymal spermatozoa.pididymal spermatozoa.

• Journal of Life Science
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• v.27 no.1
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• pp.15-22
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• 2017

Streptococcus mutans (S. mutans), which plays a major role in the etiology of human dental caries, is able to tolerate exposure to acid shock in addition to its acidogenicity. We investigated the effects of pH stress on membrane fluidity, activities and expression levels of F-ATPase, and proton permeability in S. mutans. Using 1,6-diphenyl-1,3,5-hexatriene, we observed membrane ordering at pH 4.8 and pH 8.8. The ordering effects were larger at pH 4.8 in cytoplasmic membranes isolated from S. mutans (CMSM). Increasing pH resulted in a decrease in the activities and expression levels of F-ATPase. The proton permeability was decreased at both acidic and alkaline pHs, and the lowest permeability was observed at pH 4.8. The lower permeability at pH 8.8 than pH 6.8 is likely to be caused by the decreased proton influx due to the decreased CMSM fluidity. In addition, it seems to be evident that extremely low permeability at pH 4.8 was caused by the decreased proton influx due to the decreased CMSM fluidity as well as the increased proton efflux due to the increased activity and expression level of F-ATPase. It is likely that CMSM fluidity and F-ATPase activity are two major key factors that determine proton permeability in S. mutans. We suggest that CMSM fluidity plays an important role in the determination of proton permeability, which sheds light on the possibility of using nonspecific membrane fluidizers, e.g., ethanol, for anti-caries purposes.

• Biomolecules & Therapeutics
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• v.18 no.1
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• pp.65-70
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• 2010

The blood-brain barrier (BBB) transport of acetylcholinesterase (AChE) inhibitors, donepezil and tacrine suggested to be mediated by choline transport system in our previous study. Therefore, in the present study, we investigated the interaction of other AChE inhibitors, rivastigmine and galantamine with choline transporter at the BBB. The effects of rivastigmine and galantamine on the transport of choline by conditionally immortalized rat brain capillary endothelial cell lines (TR-BBB cells) were characterized by cellular uptake study using radiolabeled choline. The uptake of [$^3H$]choline was inhibited by rivastigmine and galantamine, with $IC_{50}$ values (i.e. concentration necessary for 50% inhibition) for 1.13 and 1.15 mM, respectively. Rivastigmine inhibited the uptake of [$^3H$]choline competitively with $K_i$ of 1.01 mM, but galantamine inhibited noncompetitively. In addition, the efflux of [$^3H$]choline was significantly inhibited by rivastigmine and galantamine. Our results indicated that the BBB choline transporter may be involved in a part of the influx and efflux transport of rivastigmine across the BBB. These findings should be therapeutically relevant to the treatment of Alzheimer's disease (AD) with AChE inhibitors, and, more generally, to the BBB transport of CNS-acting cationic drugs via choline transporter.

• Natural Product Sciences
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• v.25 no.2
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• pp.165-171
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• 2019

Although the functions of a standardized extract of Gingko biloba leaves (EGb $761^{(R)}$) has been reported with regard to neurobiological properties, no attention has been paid to the impact of EGb $761^{(R)}$ on the neuronal regulation of energy homeostasis. To evaluate the hypothesis that EGb $761^{(R)}$ affect the secretion of peptide tyrosine tyrosine (PYY) and the activation of free fatty acid receptor 4 (FFA4), which are involved in the neuronal circuitries that control energy homeostasis by inducing the transfer of information about the influx of energy to the brain, we examined whether EGb $761^{(R)}$ can stimulate PYY secretion in the enteroendocrine NCI-H716 cells and if EGb $761^{(R)}$ can activate FFA4 in FFA4-expressing cells. In NCI-H716 cells, EGb $761^{(R)}$ stimulated PYY secretion and the EGb $761^{(R)}$-induced PYY secretion was involved in the increase in intracellular $Ca^{2+}$ concentration and the activation of FFA4. Furthermore, in FFA4-expressing cells, EGb $761^{(R)}$ activated FFA4. These results suggest that EGb $761^{(R)}$ may affect the control of energy homeostasis via the regulation of PYY secretion and FFA4 activation.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 1996.12a
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• pp.70-70
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• 1996

The cytotoxicological effect of Bt 1-endotoxin, well-known as a bioinsecticide, was investigated on ion channel of insect cell lines. This study attempted to evaluted the specificity by simple experiment to measure the cell swelling using lepidopteran cell lines in isotonic solution containing only one cation. Cell swelling was stimulated in KCI-sucrose isotonic solution as well as TC-100 media containg in solubilized crystal 5-endotoxin. It suggested that the cell swelling by Bt toxin have a relation to K+ channel. The cell swelling may be due to the stimulation K+ influx and simultaneously the penetration of H2O induced by Bt toxin, because the stimulation of swelling was observed with the solubilized toxin in KCI-sucrose isotonic solution, but not in sucrose isotonic solution. Moreover the specific K+ channel blocker, such as 4-arnjnopyrimidine(4-AP) and ouabain, showed the significant effect on the cell swelling induced by Bt toxin. The increasement of the cell swelling induced by 4-AP suggested to be caused by the block of K+ efflux through K+ leak channels. The inhibition of cell swelling by ouabain, which is the well-known inhibitor of Na+, K+-ATPase, suggested to be due to decreasement of K+ influx following diminishment of Na+, K+-ATPase activities.