• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.494-497
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• 2006

For commercialization of polymer electrolytemembrane fuel cell (PEMFC), durability of membrane electrode assemblies (MEAs) has to be improved. Especially, long-term stability of MEA is one of the most important issues for frequent shut-down and start-up processes of PEMFC. The degradation of MEA could be attributed to chemical attack of hydrogen peroxide radicals that are formed at high cell voltages without any special treatment to remove residual hydrogen from anode gas channel after shut-down of the fuel cell. In this study, we investigated the long-term stability of MEA under different on/off operation conditions. Residential hydrogen gas was removed from the anode flow channel by purging air or nitrogen. Also, a dummy resistance was applied to the fuel cell to exhaust residential hydrogen at the anode. In these cases, MEA showed much more stable durability. Electrochemical characteristics of the fuel cell were measured byrepeating the on/off cycles with the hydrogen removal processes. Also, degradation of MEA components was examined by SEM, TEM and XRD analyses.

• BMB Reports
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• v.46 no.12
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• pp.611-616
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• 2013

Luteolin-7-O-glucoside (LUT7G), a flavone subclass of flavonoids, has been found to increase anti-oxidant and anti-inflammatory activity, as well as cytotoxic effects. However, the mechanism of how LUT7G induces apoptosis and regulates cell cycles remains poorly understood. In this study, we examined the effects of LUT7G on the growth inhibition of tumors, cell cycle arrest, induction of ROS generation, and the involved signaling pathway in human hepatocarcinoma HepG2 cells. The proliferation of HepG2 cells was decreased by LUT7G in a dose-dependent manner. The growth inhibition was due primarily to the G2/M phase arrest and ROS generation. Moreover, the phosphorylation of JNK was increased by LUT7G. These results suggest that the anti-proliferative effect of LUT7G on HepG2 is associated with G2/M phase cell cycle arrest by JNK activation.

• Development and Reproduction
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• v.18 no.1
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• pp.65-71
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• 2014

Cell cycle process is regulated by a number of protein kinases and among them, serine/threonine kinases carry phosphate group from ATP to substrates. The most important three kinase families are Cyclin-dependent kinase (Cdk), Polo-like kinase (Plk), and Aurora kinase. Polo-like kinase family consists of 5 members (Plk1-Plk5) and they are involved in multiple functions in eukaryotic cell division. It regulates a variety of aspects such as, centrosome maturation, checkpoint recovery, spindle assembly, cytokinesis, apoptosis and many other features. Recently, it has been reported that Plks are related to tumor development and over-expressed in many kinds of tumor cells. When injected the anti-Plk antibody into human cells, the cells show aneuploidy, and if inhibit Plks, most of the mitotic cell division does not proceed properly. For that reasons, many inhibitors of Plk have been recently emerged as new target for remedy of the cancer therapeutic research. In this paper, we reviewed briefly the characteristics of Plk families and how Plks work in regulating cell cycles and cancer formation, and the possibilities of Plks as target for cancer therapy.

• Korean Journal of Veterinary Research
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• v.39 no.3
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• pp.455-462
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• 1999

This study was designed to investigate the number of the growing and mature follicles in each stage of estrus cycle in mature rats. Eighteen mature rats(Sprague-Dawley, initially 190~230gm) were randomly alloted into 4 groups(proestrus, estrus, metestrus, and diestrus) according to estrus cycles. The uteri and ovaries of rats were collected and then alternative sections of paraffin embedding ovaries were stained with H-E. Numbers of large, middle and small follicles or only large and middle follicles from secondary and tertiary follicles were investigated by LM photography of preparations. Small follicles were defined as secondary follicles with 2~5 cell layers of granulosa cells surrounding the oocyte, and middle follicles were defined as secondary follicles with more than 5 cell layers or with early signs of antral cavity or with more than one small cleft on either side of the oocytes and large follicles were defined as tertiary follicles with a single medium or large antral cavity. The number of follicles in a pair ovary per rat was appeared to be ranged from 207 to 370 and the mean number of these follicles was $270.4{\pm}52.6$ and the mean number of follicles per ovary was $134.9{\pm}32.0$. The mean number of large, middle and small follicles per ovary was appeared to be $16.4{\pm}4.4$($12.2{\pm}3.3%$), $36.2{\pm}8.6$($26.8{\pm}6.4%$), and $82.7{\pm}24.0$($61.3{\pm}17.8%$), respectively. The mean number of large and middle follicles in each stage group of estrus cycle was appeared to be $17.8{\pm}2.1$ and $38.3{\pm}7.4$ at proestrus stage group, $15.7{\pm}5.2$ and $38.0{\pm}10.0$ at estrus stage group, $16.5{\pm}3.5$ and $33.8{\pm}7.0$ at metestrus stage group, $16.7{\pm}5.8$ and $29.7{\pm}5.5$ at diestrus group, respectively. In histological findings of large follicles during each estrus cycle, the large follicles in proestrus group contain single small antrum, thick granulosa cell layers, and were $300{\sim}500{\mu}m$ in diameter and were growing follicles with PCNA-positive cells in the granulosa cell layers, and other luteinizing follicles of proestrus cycle stage were decreased in size and were thicker in wall thickness and more luteinized than those in metestrus and diestrus stage groups. The large follicles in estrus stage group contain thick granulosa cell layers and nonprominent cumulus-oocyte complexes in antrum, and were $400{\sim}700{\mu}m$ in diameter and were growing follicles with PCNA-positive cells in the granulosa cell layers. The large follicles in metestrus and diestrus stage groups contain enlarged antrums, thinner layers of walls and prominent cumulus-oocyte complexes, and were $700-950{\mu}m$ in diameter, and were nongrowing follicles without PCNA-positive cells or another large follicles contain cells with dark stainability and distinct boundary.

• YAKHAK HOEJI
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• v.41 no.1
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• pp.86-93
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• 1997

Even though both N-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine have been widely used to establish the experimental model for dopaminergic neuronal ce ll death. mechanisms underlying this phenomenon have not been firmly explored. To investigate how these dopaminergic neurotoxins induce neuronal cell death, murine dopaminergic neuronal cell line, MN9D cells were treated with various concentration of either 6-hydroxydopamine or active form of MPTP, N methyl-4-phenylpyridinium (MPP$^+$). Treatment of cells with 5-100 uM 6-hydroxydopamine resulted in apoptotic cell death whereas cell death induced by 5~50 uM MPP$^+$ was not demonstrated typical apoptotic characteristics such as cell shrinkage, apoptotic body and nuclear condensation. Cell death induced by 6-hydroxydopamine was partially blocked in the presence of antioxidants including soluble form of vitamin E or desferrioxamine suggesting that generation of oxidative stress may be associated with 6-hydroxydopamine-induced cell death in MN9D cells. In contrast, MPP$^+$-induced cell death was not blocked by treatment with any of antioxidants tested. As previously demonstrated that MPP$^+$ caused metabolic alterations such as glucose metabolism, removal of glucose from the medium partially inhibited MPP$^+$-induced cell death suggesting excessive cycles of glycolysis may be associated with MPP$^+$-induced cell death. Taken together, these studies demonstrate that two types of dopaminergic neurotoxins recruit distinct neuronal cell death pathways.

• 대한생식의학회:학술대회논문집
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• 2007.11a
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• pp.98.1-98.1
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• 2007

• Proceedings of the Ginseng society Conference
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• 2002.10a
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• pp.376-384
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• 2002

Object To find out which of the 27 ginsenosides isolated from Panax ginseng C.A. Mey that may inhibit the proliferation of human osteosaocoma cell line $U_2OS$. Methods Effects of each individual ginsenoside on the proliferation of $U_2OS$ cell were studied by determining the viability of cancer cells during culture with or without the presence of the test compound. DNA assay was determined by flow cytometry. Results Ginsonosides -Ro, $-Rh_l,\;-Rh_2,\;-F_1\;and\;-L_8$ at concentrations of 5 ,umol/L could obviously suppress the proliferation of $U_2OS$ cells while ginsenosides $-Rg_1,\;-F_3,$ -Rf, PPT and PT significantly inhibited the cancer cells. Flow cytometry revealed that ginsenosides $-Ro,-Rg_1-Rf,-F_1-Rh_2,PPT$ and PT induced cell cycle arrest at $G_0/G_1$ phase with obvious decrease of cell count at Sand $G_2+M$ phase, Moreover, ginsenosides $-Rf_1,-Rg_1,\;-F_1$ and PPT induced significantly high rates of cell death as compared with the control. Conclusion These data suggested that ginsenosides inhibited $U_2OS$ proliferation Via cell cycle arrest or induction of cell death.

• Korean Journal of Animal Reproduction
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• v.20 no.2
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• pp.155-161
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• 1996

For a large sclase production of genetically identical or cloned animals, the effect of cryopreservation by vitrification on the post-thaw viability of nuclear transplant rabbit embryos were investigated. The embryos of 16-cell stage were collected from the mated does at 48 hours post-hCG injection, and they were synchronized to G1 phase of 32-cell stage were injected into enucleated recipient cytoplasms by micromanipulation. After culture until 20h post-hCG injection, the nuclear transplant oocytes were electrofused and activated by electrical stimulation. After in vitro culture for 48h, the nuclear transplant embryos developed to morula stage were cryoperserved with EFS solution by vitrification method. The forzen nuclear transplant embryos were thawed and cultured for 72h and the nuclear transplant of blastomeres under a fluorescence microscopy. The in vitro development to blastocyst of intact-fresh and intact-frozen 16-cell embryos was found to be 96.9 and 63.9%, respectively. The in vitro development to blastocyst of nuclear transplant and frozen-thawed nuclear transplant embryos was found to be 74.5 and 42.9%, respectively. Also, their mean blastomere numbers and mean cell cycles/day was 153 and 105, 145 and 1.34, respectively. From the above results it was concluded that the present cryopreservation by vitrification of nuclear transplant rabbit embryos might be useful though was decreased significantly.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.7
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• pp.789-793
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• 2010

Recently, flash memory-based non-volatile cache (NVC) is emerging as an effective solution to enhance both I/O performance and energy consumption of storage systems. To get significant performance and energy gains by NVC, it would be better to use multi-level-cell (MLC) flash memories since it can provide a large capacity of NVC with low cost. However, the number of available program/erase cycles of MLC flash memory is smaller than that of single-level-cell (SLC) flash memory limiting the lifespan of NVC. To overcome such a limitation, SLC/MLC combined flash memory is a promising solution for NVC. In this paper, we propose an effective management scheme for heterogeneous SLC and MLC regions of the combined flash memory.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.968-970
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• 1999

The trend of increasing of portable electric devices and demand for global environmental conservation have demands the development of high energy density rechargeable batteries. Lithium polymer battery has excellent theoretical energy density and energy conversion efficiency. Lithium polymer battery, included solid polymer electrolyte(SPE), can be viewed as a system suitable for wide applications from thin film batteries for microelectronics to electric vehicle batteries. The purpose of this paper is to research and development of flyash anode for lithium polymer battery. We investigated AC impedance response and charge/discharge characteristics of flyash/SPE/Li cells. The radius of semicircle associated with the interfacial resistance of flyash/SPE/Li cell increased very slowly during discharge process from 3.11V to 0.478V. And then the cell resistance was decreased at discharge process from 10% SOC to 0% SOC. Also, The radius of semicircle associated with the interfacial resistance of flyash/SPE/Li cell decreasing very slowly during charge process. And then the cell resistance was increased after 20th discharge precess. The discharge capacity based on flyash of 1st and 20th cycles was 276mAh/g and 143mAh/g.