• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.421-424
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• 2006

Nafion/Pt/Polypyrrole composite membranes were fabricated by chemical in-situ polymerization of pyrrole monomers with Pt precursors in Nafion matrix for DMFC. We demonstrated that positively charged pyrrolinum groups of polypyrrole particles were co-interacted with sulfonic groups of Nafion as verified by FT-IR results. Mutual interaction between $Nafion-SO_3^-$ (or negatively charged Pt precursors) and Polypyrrole$-NH_2^+$ influenced the physical properties of pristine Nafion. Thermal property proton conductivity, methanol permeability, and cell performance of pristine and modified Nafion were analyzed for an application of DMFC membrane. Thermal stabilities of sulfonic groups and side chains in Nafion/Pt/polypyrrole composite membranes were higher than those of Nafion due to mutual interaction between sulfonic groups of Nafion and pyrrolinum groups of polypyrrole. Methanol permeabilities of Nafion/Pt/Polypyrrole composite were reduced more proton conductivities with the increase in the content of Pt particles. As a result of that, the enhancement of cell performance by Nafion/Pt/Polypyrole O2 relative to Nafion was more pronounced under the specific experimental condition such as high temperature and more concentrated methanol solution.

• Reproductive and Developmental Biology
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• 제38권1호
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• pp.1-8
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• 2014

Artificial insemination technique has been contributed immensely for production of livestock worldwide as a critical assisted reproductive technique to preserve and propagate excellent genes in domestic animal industry. In the past decade, methods for semen preservation have been improved mostly in liquid preservation method for boar semen and freezing method for bull semen. Among many factors affecting semen quality during preservation, reactive oxygen species, produced by aerobic respiration in sperm for survival and motility, are unfavorable to sperm physiology. In mammalian cell as well as in the sperm, antioxidant system plays a role in degradation of reactive oxygen species. Magnetized water forms smaller stabilizing water clusters, resulting in high absorption and permeability of the cell for water, implicating its application for semen preservation. Therefore, this review focuses on preservation methods of boar and bull semen with respect to improvement of extender and reduction of reactive oxygen species by using magnetized water and supplementation of antioxidants.

• The Korean Journal of Physiology and Pharmacology
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• 제2권1호
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• pp.95-100
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• 1998

The conductance change evoked by step depolarization was studied in primarily cultured rat adrenal chromaffin cells using patch-clamp and capacitance measurement techniques. When we applied a depolarizing pulse to a chromaffin cell, the inward calcium current was followed by an outward current and depolarization-induced exocytosis was accompanied by an increase in conductance trace. The slow inward tail current which has the same time course as the conductance change was observed in current recording. The activation of slow tail current was calcium-dependent. Reversal potentials agreed with Nernst equation assuming relative permeability of $Cs^+\;to\;K^+$ is 0.095. The outward current and tail current were blocked by apamin (200 nM) and d-tubocurarine (2 mM). The conductance change was blocked by apamin and did not affect membrane capacitance recording. We confirmed that conductance change after depolarization comes from the activation of the SK channel and can be blocked by application of the SK channel blockers. Consequently, it is necessary to consider blocking of the SK channel during membrane capacitance recording.

• 한국환경보건학회지
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• 제12권1호
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• pp.25-38
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• 1986

This paper was intented to charily the cause of an increase of serum guanase activity in rats following injection of $CCI_4$. The cause of increasing serum guanase was focused on the change of guanase activities in both serum and liver, and additionally, these results were compared with the previously known alanine aminotransferase (ALT). Concomitantly the microscopic investigation on the histologic changes, and the determination of lipid peroxides of liver were combined in this experiment for a correlation to observe that the activity of guanase would be effected by the various degree of hepatic injury induced by $CCI_4$. The serum levels of guanase were increased about 2 fold in the fatty change stage (3-12 days), 5.2 fold representing the peak value in necrosis stage (21days), 4.5 fold in early cirrhosis stage (48 days), and 2 fold in severe cirrhosis stage (92 days). These changes of serum guanase activity showed similar patterns to those of ALT activity and lipid peroxides in liver cell. The changes of liver guanase activities showed an increase, whereas ALT activities in liver were markedly decreased. It is likely that the increase of serum guanase activity is based on the excess leaking of guanase into blood by the result of accelerated enzyme synthesis in liver cell of $CCI_4$ intoxicated rats. In addition, the possibility could not be ruled out, however, that the increase of serum guanase activity would be caused by the alteration of membrane permeability.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 2006년도 Spring Conference
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• pp.123-135
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• 2006

Alzheimer's disease (AD) is the most common form of dementia in the aging population and is clinically characterized by a progressive loss of cognitive abilities. Pathologically, it is defined by the appearance of senile plaques - extracellular insoluble, congophilic protein aggregates composed of amyloid $\beta$ (A$\beta$) and neurofibrillary tangles (NFTs) - inyracellular lesions consisting of paired helical filaments from hyperphosphorylated cytoskeletal tau protein as described by Alois Alzheimer a century ago. These hallmarks still serve as the major criteria for a definite diagnosis of the disease. Consequently, one of the key strategy for drug development in this disease area focuses on reducing the concentration of cerebral A$\beta$ plaque by using substances that inhibit A$\beta$ fibril formation. We focused on developing inhibitors by synthesizing several kinds of aromatic molecules. The synthetic compounds were initially screened to evaluate the effective compound by tioflavin T fluorescence assay. The selected effective compounds were tested cytotoxicity and protective effect from A$\beta$-induced neuronal toxicity by cell based MTT assay with HT22 hippocampal neurons. The BBB permeability on effectors was also tested in in vitro co-culture model(HUVEC/C6 cell line). The behavior test wea carried out in mutant APP/PS1 transgenic mouse model of Alzheimer's disease. And inhibition of A$\beta$ fibril formation by the effective compound was monitored with transmitted electron microscopic images.

• Journal of Photoscience
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• 제6권2호
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• pp.77-83
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• 1999

Calcium has a variety of functions in neuron and muscle cells and blood clotting, especially in the visual system where dark adapted rods cotransport with Na$\^$+/ into the cell. An influx of Ca$\^$++/ flows out of the cell through the Na$\^$+/-Ca$\^$++/ exchanger. By using a modified Using chamber in order to bring in vivo environment close, we have known that Ca$\^$++/ blocks the activity of guanylate cyclase, in consequence, having an effect on the amplitude of electroretinogram (ERG). We have measured the Ca$\^$++/, K$\^$+/, and Na$\^$+/ concentration in dark and light adapted bullfrog＇s (Rana catesbeiana) vitreous humor. The calcium concentration of the light adapted bullfrog＇s vitreous humor was higher than that of the dark adapted bullfrog＇s vitreous humor This means that ion activity between the photoreceptor and vitreous humor side is light dependent and we have found that a Ca$\^$++/ channel and Ca$\^$++/K$\^$+/ exchanger exist in the vitreous humor side. Taken together permeability of Ca$\^$++/, K$\^$+/ and K$\^$+/ ion internal limiting membrane faced in the vitreous humor side has light-dependent activity during the illumination.

• Macromolecular Research
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• 제14권4호
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• pp.449-455
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• 2006

Ionic cluster mimic, polymer electrolyte membranes were prepared using polymer composites of crosslinked poly(vinyl alcohol) (PVA) with sulfated-${\beta}$-cyclodextrins (${\beta}-CDSO_3H$) or phosphated-${\beta}$-cyclodextrins (${\beta}-CDPO(OH)_2$). When Nafion, developed for a fuel cell using low temperature, polymer electrolyte membranes, is used in a direct methanol fuel cell, it has a methanol crossover problem. The ionic inverted micellar structure formed by micro-segregation in Nafion, known as ionic cluster, is distorted in methanol aqueous solution, resulting in the significant transport of methanol through the membrane. While the ionic structure formed by the ionic sites in either ${\beta}-CDSO_3H$ or ${\beta}-CDPO(OH)_2$ in this composite membrane is maintained in methanol solution, it is expected to reduce methanol transport. Proton conductivity was found to increase in PVA membranes upon addition of ionized cyclodextrins. Methanol permeability through the PVA composite membrane containing cyclodextrins was lower than that of Nafion. It is thus concluded that the structure and fixation of ionic clusters are significant barriers to methanol crossover in direct methanol fuel cells.

• Biomolecules & Therapeutics
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• 제3권3호
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• pp.242-244
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• 1995

In vitro cell culture system has been proposed as a promising alternative model to in vivo skin irritation test. These studies were performed to screen the cytotoxicity effects of surfactants using normal human skin fibroblasts. Cell membrane integrity assessed by the leakage of lactate dehydrogenase (LDH) and mitochondrial integrity by MTT [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromides reduction test were affected in a dose dependent manner. The irritation potential of surfactants to human skin patch test, and the changes of capillary permeability by rabbit intradermal safety test were assessed as in vivo methods. Our results suggest that LDH leakage assay and MTT reduction test using cultured human fibroblasts could be predictive for the irritancy of various surfactants in human, and LDH assay is superior correlated with in vivo test (r=0.886) to MTT test with in vivotest (r=0.757).

• 한국수소및신에너지학회논문집
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• 제18권2호
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• pp.157-163
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• 2007

During PEMFC operation, low current and low humidity conditions accelerate the degradation of perfluorosulfonic acid membrane. But, there have been no studies that clearly explain why these conditions accelerate the membrane degradation. In this study, the hydrogen permeability through the membrane, I-V polarization of MEA, fluoride emission rate(FER) in effluent water were measured during cell operation under low current densities and low relative humidity(RH). The experimental results were evaluated with oxygen radical mechanism the most commonly known for membrane degradation. It seems that low RH of anode is a good condition for $H{\cdot}$ radical formation on the Pt catalyst and the low current condition accelerates the $H{\cdot}$ to form $HO_2{\cdot}$ radical attacking the polymer membrane.

• KSBB Journal
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• 제18권6호
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• pp.435-439
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• 2003

형질 전환된 담배 seed에서 담배 식물체를 유도하여 White 액체 배지에서 기관 배양하였다. 암조건, sucrose 2%의 조건에서 좋은 growth pattern을 나타내었고, 계대 배양은 외마디법을 이용하여 2주마다 하였다. 기관 배양에서 hGM-CSF production pattern을 보면, intracellular에서는 큰 변화 없이 약 30 ng/g의 일정한 농도를 나타내었다. Extracellular에서 hGM-CSF 농도는 배양 6일 이후부터 급속하게 증가하기 시작하여 배양 12일째에 약 0.2ng/$m\ell$의 농도를 나타낸다. 기관배양은 다른 식물세포 배양 시스템에 비해 생산되어진 단백질의 안정성이 크다는 장점에 비해 세포 내에서 배지 내로의 단백질 분비가 적다는 단점이 있다. 이를 극복하기 위해 다양한 permeabilizing agents를 투여하여 담배 세포의 permeability를 증가시키고자 하였다. 그 결과, Pluronic F-68과 PEG8000을 첨가한 경우 담배 세포에서 배지 내로의 단백질 분비가 원활해졌음을 확인할 수 있었다.