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- 검색키워드
- 저자 : Seunghoon Oh (검색결과 67 건)
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Disturbance in Testosterone Production in Leydig Cells by Polycyclic Aromatic Hydrocarbons
Oh, Seunghoon The Korean Society of Developmental Biology 2014 발생과 생식 Vol.18 No.4
Polycyclic aromatic hydrocarbons (PAHs), which are ubiquitous in the air, are present as volatile and particulate pollutants that result from incomplete combustion. Most PAHs have toxic, mutagenic, and/or carcinogenic properties. Among PAHs, benzo[a]pyrene (B[a]P) and dimethylbenz[a]anthracene (DMBA) are suspected endocrine disruptors. The testis is an important target for PAHs, yet effects on steroidogenesis in Leydig cells are yet to be ascertained. Particularly, disruption of testosterone production by these chemicals can result in serious defects in male reproduction. Exposure to B[a]P reduced serum and intratesticular fluid testosterone levels in rats. Of note, the testosterone level reductions were accompanied by decreased steroidogenic acute regulatory protein (StAR) and $3{\beta}$-hydroxysteroid dehydrogenase isomerase ($3{\beta}$-HSD) expression in Leydig cells. B[a]P exposure can decrease epididymal sperm quality, possibly by disturbing the testosterone level. StAR may be a key steroidogenic protein that is targeted by B[a]P or other PAHs.
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Formation of Chimeric Gap Junction Channels in Mammalian Ovarian Follicle
Oh Seunghoon 한국동물생명공학회(구 한국동물번식학회) 2004 Reproductive & developmental biology Vol.28 No.3
The oocyte and its surrounding granulosa cells co-exist in a closed compartment called a follicle, although they receive many signals from other parts of the body. It is well established that the intercellular communications between the oocyte and granulosa cells are required for normal oocyte development and ovulation during folliculogenesis. Gap junctions are intercellular channels allowing the direct transmission of ions and small molecules between coupled cells. Several lines of studies have shown that multiple connexins (Cx, subunits of gap junction) are expressed in mammalian ovarian follicles. Among them, two major connexins Cx37 and Cx43 are expressed in different manner. While the gap junction channels formed by Cx37 are localized between the oocyte and encompassing granulosa cells, the intercellular channels by Cx43 are located between granulosa cells. In this review, I will summarize the general properties of gap junction channels and discuss their possible formation (or compatibility) of intercellular channels formed by the oocyte and granulosa cells.
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Bisphenol A and 4-tert-Octylphenol Inhibit Cx46 Hemichannel Currents
Oh, Seunghoon The Korean Society of Pharmacology 2015 The Korean Journal of Physiology & Pharmacology Vol.19 No.1
Connexins (Cx) are membrane proteins and monomers for forming gap junction (GJ) channels. Cx46 and Cx50 are also known to function as conductive hemichannels. As part of an ongoing effort to find GJ-specific blocker(s), endocrine disruptors were used to examine their effect on Cx46 hemichannels expressed in Xenopus oocytes. Voltage-dependent gating of Cx46 hemichannels was characterized by slowly activating outward currents and relatively fast inward tail currents. Bisphenol A (BPA, 10 nM) reduced outward currents of Cx46 hemichannels up to ~18% of control, and its effect was reversible (n=5). 4-tert-Octylphenol (OP, $1{\mu}M$) reversibly reduced outward hemichannel currents up to ~28% (n=4). However, overall shapes of Cx46 hemichannel current traces (outward and inward currents) were not changed by these drugs. These results suggest that BPA and OP are likely to occupy the pore of Cx46 hemichannels and thus obstruct the ionic fluxes. This finding provides that BPA and OP are potential candidates for GJ channel blockers.
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Bisphenol A and 4-tert-Octylphenol Inhibit Cx46 Hemichannel Currents
Seunghoon Oh 대한생리학회-대한약리학회 2015 The Korean Journal of Physiology & Pharmacology Vol.19 No.1
Connexins (Cx) are membrane proteins and monomers for forming gap junction (GJ) channels. Cx46 and Cx50 are also known to function as conductive hemichannels. As part of an ongoing effort to find GJ-specific blocker(s), endocrine disruptors were used to examine their effect on Cx46 hemichannels expressed in Xenopus oocytes. Voltage-dependent gating of Cx46 hemichannels was characterized by slowly activating outward currents and relatively fast inward tail currents. Bisphenol A (BPA, 10 nM) reduced outward currents of Cx46 hemichannels up to ∼18% of control, and its effect was reversible (n=5). 4-tert-Octylphenol (OP, 1 μM) reversibly reduced outward hemichannel currents up to ∼28% (n=4). However, overall shapes of Cx46 hemichannel current traces (outward and inward currents) were not changed by these drugs. These results suggest that BPA and OP are likely to occupy the pore of Cx46 hemichannels and thus obstruct the ionic fluxes. This finding provides that BPA and OP are potential candidates for GJ channel blockers.
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Disturbance in Testosterone Production in Leydig Cells by Polycyclic Aromatic Hydrocarbons
Seunghoon Oh 한국발생생물학회 2014 발생과 생식 Vol.18 No.4
Polycyclic aromatic hydrocarbons (PAHs), which are ubiquitous in the air, are present as volatile and particulate pollutants that result from incomplete combustion. Most PAHs have toxic, mutagenic, and/or carcinogenic properties. Among PAHs, benzo[a]pyrene (B[a]P) and dimethylbenz[a]anthracene (DMBA) are suspected endocrine disruptors. The testis is an important target for PAHs, yet effects on steroidogenesis in Leydig cells are yet to be ascertained. Particularly, disruption of testosterone production by these chemicals can result in serious defects in male reproduction. Exposure to B[a]P reduced serum and intratesticular fluid testosterone levels in rats. Of note, the testosterone level reductions were accompanied by decreased steroidogenic acute regulatory protein (StAR) and 3β-hydroxysteroid dehydrogenase isomerase (3b-HSD) expression in Leydig cells. B[a]P exposure can decrease epididymal sperm quality, possibly by disturbing the testosterone level. StAR may be a key steroidogenic protein that is targeted by B[a]P or other PAHs. Key words : Polycyclic aromatic hydrocarbons, Endocrine disruptor, Steroidogenesis, Leydig cells
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Current Medical Therapies for Osteoporosis and Its Alternative Treatments Using Natural Products
Seunghoon Oh(오승훈),Soon-Cheol Ahn(안순철) 한국생명과학회 2015 생명과학회지 Vol.25 No.1
골다공증은 골밀도(bone mineral density, BMD)가 평균 성인 정점에서 2.5 이상의 표준편차가 감소되는 뼈의 질환으로서 나이가 들어가면서 점차 증가하고 있다. 골다공증은 뼈를 흡수하는 파골세포와 뼈를 형성하는 조골세포로 이루어진 bone remodeling system의 불균형 때문에 발생한다. 이 불균형의 가장 큰 원인은 여성 폐경기 후에 따르는 에스트로겐 결핍 때문이다. 현재 골다공증의 치료에 사용되는 약들로는 호르몬 대체요법(hormone replacement therapy, HRT), biphosphonate, teriparatide 등이 있지만, 여러 가지 부작용 때문에 그들의 안정성과 실용성엔 의문의 여지가 있다. 더 안전한 대안을 찾기 위해 현재 천연물을 사용한 여러 가지 치료법이 연구되고 있다. Lactoferrin, isoflavone 등과 한약재를 이용한 많은 전통 치료법들이 있으며, 이는 뼈 흡수를 막거나, 뼈 동화를 일으킴으로써 골다공증 치료제로서의 가능성을 보여주고 있다. 그러나 대부분의 천연물 치료법은 지난 10여 년간 괄목할만한 발전에도 불구하고 그 효능을 증명하기 위한 임상 예비단계에 머물고 있다. 따라서 천연물의 전임상 연구와 후속 임상 연구를 통해 새로운 골다공증 치료법으로 소개될 것이다. Osteoporosis is a major bone disorder defined as having bone mineral density (BMD) of 2.5 standard deviations or more below the peak bone mass. Osteoporosis will increasingly be a major disorder that faces the aging mankind. It is the result of an imbalance in the bone remodeling system, where bone constantly undergoes a cycle of resorption by osteoclasts and formation by osteoblasts. Estrogen deficiency in women following menopause is identified as the predominant reason that causes disparity in this system. Current medical treatments for osteoporosis include hormone replacement therapy (HRT), biphosphonates, and teriparatide, but have various side effects that raise questions concerning their medical safety and practicality. Alternative treatments involving natural product sources are under study to find a safer therapy. Many natural sources including lactoferrin and isoflavones and numerous traditional herbal medicines exhibit anti-resorptive or anabolic effects on bone and thus show promises to provide therapeutic agents in treating osteoporosis. Unfortunately, the majority of natural product treatments are still in its preliminary stages to prove their efficacy even though the development pace of treatment for osteoporosis is astounding in the past few decades. Further progress in pre-clinical studies and the subsequent clinical studies will someday lead to a breakthrough that takes us another step forward in science.
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Higher-order Spectral Method for Regular and Irregular Wave Simulations
Seunghoon Oh,Jae-Hwan Jung,Seok-Kyu Cho 한국해양공학회 2020 韓國海洋工學會誌 Vol.34 No.6
In this study, a nonlinear wave simulation code is developed using a higher-order spectral (HOS) method. The HOS method is very efficient because it can determine the solution of the boundary value problem using fast Fourier transform (FFT) without matrix operation. Based on the HOS order, the vertical velocity of the free surface boundary was estimated and applied to the nonlinear free surface boundary condition. Time integration was carried out using the fourth order Runge–Kutta method, which is known to be stable for nonlinear free-surface problems. Numerical stability against the aliasing effect was guaranteed by using the zero-padding method. In addition to simulating the initial wave field distribution, a nonlinear adjusted region for wave generation and a damping region for wave absorption were introduced for wave generation simulation. To validate the developed simulation code, the adjusted simulation was carried out and its results were compared to the eighth order Stokes theory. Long-time simulations were carried out on the irregular wave field distribution, and nonlinear wave propagation characteristics were observed from the results of the simulations. Nonlinear adjusted and damping regions were introduced to implement a numerical wave tank that successfully generated nonlinear regular waves. According to the variation in the mean wave steepness, irregular wave simulations were carried out in the numerical wave tank. The simulation results indicated an increase in the nonlinear interaction between the wave components, which was numerically verified as the mean wave steepness. The results of this study demonstrate that the HOS method is an accurate and efficient method for predicting the nonlinear interaction between waves, which increases with wave steepness.
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