• Journal of Preventive Medicine and Public Health
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• v.29 no.3 s.54
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• pp.597-607
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• 1996

Genotoxic agents can induce various DNA lesions. DNA-Protein Crosslinks(DPCs) were known as the important DNA lesions which could impair gene expression because DPCs had a high probability of resisting repair and persisting through cell cycle. This repair resistance of DPCs could have biological significance but had not been evaluated clearly yet. Most of the studies that have evaluated the repair of DPCs only compared the extent of DPCs repair with other DNA lesions. We injected $K_2CrO_4$, a genotoxic agent, into Sprague-Dawley rats intraperitoneally(5mg/kg) and isolated blood lymphocytes 12 hours later. These lymphocytes were cultured in the mitogen added growth media and mitogen free media separately. The degree of the repair of DPCs was monitored for 4 days by the K-SDS assay. 4 days later, the amount of DPCs decreased by 4.6% in the mitogen added media high increased by 10.9% in the mitogen free media. These results showed that DPCs induced by $K_2CrO_4$ were not repaired easily and the DPCs were biologically significant DNA lesions. We thought the decrease of DPCs in the mitogen added media was not due to the repair of DPCs, but from the increase of normal cell proliferation. Therefore, it is very important to consider the proliferation of normal cells when estimating the repair of DPCs.

• Journal of Hydrogen and New Energy
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• v.20 no.6
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• pp.455-463
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• 2009

코발트 보호막 코팅이 적용된 페라이트계 스테인리스 스틸인 STS 430과 STS 444 소재에 대해 고체산화물 연료전지용 금속연결재로서의 고온 산화 특성에 대해 살펴보았다. 코발트 코팅층은 $800^{\circ}C$ 고온 산화 후 코발트 산화물 및 $Co_2CrO_4$, $CoCr_2O_4$, $CoCrFeO_4$ 등과 같은 코발트가 함유된 스피넬 상을 형성하였다. 또한 페라이트계 스테인리스 스틸과 코발트 코팅의 계면에서 크롬과 철이 함유된 치밀한 산화층을 형성하여 금속연결재 표면의 스케일 성장속도를 감소시키고 금속연결재 내에 함유된 크롬의 외부 확산을 효과적으로 억제하였다. 한편 STS 430은 고온 산화 후 표면에 형성된 스케일 하부에 $SiO_2$와 같은 내부 산화물이 형성된 반면 STS 444는 표면 스케일 이외에 다른 내부 산화물은 확인되지 않았으며 고온에서의 면저항 측정 결과, 코발트가 코팅된 STS 444의 전기 전도성이 STS 430 보다 우수한 것으로 나타났다.

• Development and Reproduction
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• v.1 no.2
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• pp.117-124
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• 1997

Guanidinoacetate N-methyltransferase (GAMT) catalyzes the last step of creatine biosynthesis and the resultant creatine plays an important role in cellular energy metabolism. GAMT is mainly found in liver, kidney as well as testis and epididymis. We have localized the site of creatine biosynthesis in mouse epididymis by immunoperoxidase staining of GAMT using anti-GAMT antibody. Gamt is extensively expressed in the microvilli of epididymal epithelial cells and also expressed weakly in the cyto plasm of the cells. The staining of GAMT was most prominent in the microvilli of proximal caput epididymis and the intensity was progressively diminished as the epididymal tubule proceeds toward caudal part. The result suggests that GAMT or Cr might be involved in sperm function and/or maturation process in epididymis.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1430-1432
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• 1997

A solar cell conversion effiency was degraded by grain boundary effect in polycrystalline silicon. To reduce these effects of the grain boundaries, we investigated various influencing factors such as preferential chemical etching of grain boundaries, grid design, transparent conductive thin film, and top metallization along grain boundaries. Pretreatment in $N_2$ atmosphere and gettering by $POCl_3$ and Al were performed to obtain polycrystalline silicon of the reduced defect density. Structural, electrical, and optical properties of solar cells were characterized. Improved conversion efficiencies of solar cell were obtained by a combination of Al diffusion into grain boundaries on rear side, fine grid finger, top Yb metal grid on Cr thin film of $200{\AA}$ and buried contact metallization along grain boundaries.

• Journal of Environmental Science International
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• v.6 no.1
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• pp.61-67
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• 1997

Heavy metal adsorption by microbial cells is an alternative to conventional methods of heavy metal removal and recovery from metal-bearing wastewater The waste Sac-chuomyces cerevisiae is an inexpensive, relatively available source of biomass for heavy metal biosorption. Biosorption was investigated by free and immobilized-S. cerevisiae. The order of biosorption capacity was Pb>Cu>Cd with batch system. The biosorption parameters had been determined for Pb with free , cells according to the Freundlich and Langmuir model. It was found that the data fitted reasonably well to the Freundlich model. The selective uptake of immobilized-S. cerevisiae was observed when all the metal ions were dissolved in a mixed metals solution(Pb, Cu, Cr and Cd). The biosorption of mixed metals solution by immobilized-cell was studied in packed bed reactor. The Pb uptake was Investigated in particular, as it represents one of the most widely distributed heavy metals in water. We also tested the desorption of Pb from immobilized-cell by us- ing HCI, $H_2SO_4$ and EDTA.

• Parasites, Hosts and Diseases
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• v.29 no.3
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• pp.267-278
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• 1991

The natural killer (NK) cell activity of splenocytes and recycling capacity of NK cells were observed by combining the $^{51}Cr-release$ cytotoxicity assay and single cell cytotoxicity assay against YAC-1. The ICR mice were infected intranasally with Naegleria fewleri, that is a pathogenic free-living amoeba. The mice infected with $1{\times}10^5$ trophosoites showed mortality rate of 76.7% and mean survival time of 12. 9 days. The cytotoxic activity of NK cells in infected mice was significantly higher than that of non-infected mice during the period between 12 hours and day 3 after infection, and highest on day 1. The target-binding capacity of NK cells in infected mice was not different from that of non-infected ones. Maximal killing potential and maximal recycling capacity were remarkably increased in infected mice as compared with the control. The results obtained in this observation indicated that elevated NK cell activity in mice infected with N. fowieri was not due to target-binding capacity of NK cells but due to the increased activity of NK cells and increased recycling capacity of individual NK cells.

• Korean Journal of Veterinary Research
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• v.43 no.2
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• pp.171-180
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• 2003

Certain hexavalent chromium compounds when administered via inhalation have the potential to induce lung injury in human and experimental animals. In present study, the inhalation effect of hexavalent chromium on morphological change and weight change of rat organ were investigated. Rats were exposed to hexavalent chromium ($Na_2CrO_4{\cdot}4H_2O$) at concentration of $0.36mg/m^3$ (group 1), $1.8mg/m^3$ (group 2), ascorbic acid and $1.8mg/m^3$ (group 3) and filtered air (group 0, control group) for I week, 2 weeks and 3 weeks. The weight of lung and kidney in group 2 and group 3 significantly higher than in control group at same exposure period. The epithilial cells of bronchiole in group 1, 2, 3 were more flatten than group 0. In the lung, the number of macrophage was significantly increased and morphologically changed macrophages were observed in group 1, 2, 3. The morphological change of the lung did not significant between group 2 and group 3, however, in group 1 was milder than in group 2 and group 3. The severity of morphological change were depend on exposure period in the lung. The morphological changes by hexavalent chromium of the liver and kidney were also observed These results suggest that inhalation of hexavalent chromium effects on not only respiratory organ, but also the liver and the kidney via blood stream.

• Tuberculosis and Respiratory Diseases
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• v.45 no.6
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• pp.1265-1276
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• 1998

Background : Nitric oxide(NO) is an endogenously produced free radical that plays an important role in regulating vascular tone, inhibition of platelet aggregation and white blood cell adhesion to endothelial cells, and host defense against infection. The highly reactive nature of NO with oxygen radicals suggests that it may either promote or reduce oxidant-induced cell injury in several biological pathways. Oxidant injury and interactions between pulmonary vascular endothelium and leukocytes are important in the pathogenesis of acute lung injury, including acute respiratory distress syndrome(ARDS). In ARDS, therapeutic administration of NO is a clinical condition providing exogenous NO in oxidant-induced endothelial injury. The role of exogenous NO from NO donor or the suppression of endogenous NO production was evaluated in oxidant-induced endothelial injury. Method : The oxidant injury in cultured rat lung microvascular endothelial cells(RLMVC) was induced by hydrogen peroxide generated from glucose oxidase(GO). Cell injury was evaluated by $^{51}$chromium($^{51}Cr$) release technique. NO donor, such as S-nitroso-N-acetylpenicillamine(SNAP) or sodium nitroprusside(SNP), was added to the endothelial cells as a source of exogenous NO. Endogenous production of NO was suppressed with N-monomethyl-L-arginine(L-NMMA) which is an NO synthase inhibitor. L-NMMA was also used in increased endogenous NO production induced by combined stimulation with interferon-$\gamma$(INF-$\gamma$), tumor necrosis factor-$\alpha$(TNF-$\alpha$), and lipopolysaccharide(LPS). NO generation from NO donor or from the endothelial cells was evaluated by measuring nitrite concentration. Result : $^{51}Cr$ release was $8.7{\pm}0.5%$ in GO 5 mU/ml, $14.4{\pm}2.9%$ in GO 10 mU/ml, $32.3{\pm}2.9%$ in GO 15 mU/ml, $55.5{\pm}0.3%$ in GO 20 mU/ml and $67.8{\pm}0.9%$ in GO 30 mU/ml ; it was significantly increased in GO 15 mU/ml or higher concentrations when compared with $9.6{\pm}0.7%$ in control(p < 0.05; n=6). L-NMMA(0.5 mM) did not affect the $^{51}Cr$ release by GO. Nitrite concentration was increased to $3.9{\pm}0.3\;{\mu}M$ in culture media of RLMVC treated with INF-$\gamma$ (500 U/ml), TNF-$\alpha$(150 U/ml) and LPS($1\;{\mu}g/ml$) for 24 hours ; it was significantly suppressed by the addition of L-NMMA. The presence of L-NMMA did not affect $^{51}Cr$ release induced by GO in RLMVC pretreated with INF-$\gamma$, TNF-$\alpha$ and LPS. The increase of $^{51}Cr$ release with GO(20 mU/ml) was prevented completely by adding 100 ${\mu}M$ SNAP. But the add of SNP, potassium ferrocyanate or potassium ferricyanate did not protect the oxidant injury. Nitrite accumulation was $23{\pm}1.0\;{\mu}M$ from 100 ${\mu}M$ SNAP at 4 hours in phenol red free Hanks' balanced salt solution. But nitrite was not detectable from SNP upto 1 mM The presence of SNAP did not affect the time dependent generation of hydrogen peroxide by GO in phenol red free Hanks' balanced salt solution. Conclusion : Hydrogen peroxide generated by GO causes oxidant injury in RLMVC. Exogenous NO from NO donor prevents oxidant injury, and the protective effect may be related to the ability to release NO. These results suggest that the exogenous NO may be protective on oxidant injury to the endothelium.

• Korean Journal of Animal Reproduction
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• v.19 no.3
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• pp.227-234
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• 1995

This study was carried out to investigate the effects according to the time course of glucose exposure on the development of one-cell embryos beyond morula in CR$_laa$ medium. One-cell zygotes from B6CBA F$_1$ mice were recovered at 24 ~ 25h after hCG and cumulus cells were removed with 0.1% hyaluronidase. The embryos were pooled and subsequently divided into each groups and cultured in CR$_laa$ at 37$^{\circ}C$ in 5% CO$_2$ in aIr. The embryos were either, placed in CR$_laa$ containing various concentration (5.5, 16.5, 27.5 and 38.5 mM) of glucose for 1 min. and subsequently returned to the fresh culture medium (without glucose), or were transferred to the same media containing glucose at 72 h post hCG. The results obtained in these experiments were summarized as follows: 1. The development rates of zygotes, recovered from the oviducts in M2 and cultured in CR$_laa$ with 3mg/Im FAF-BSA, to expanded blastocysts (25.7%) and hatching bIastocysts (17.6%) were significantly higher than those of zygotes recovered in TL Hepes (0% and 0%, respectively). 2. The development rates of one-cell embryos exposed to 27.5 mM glucose at 72 h post hCG for 1 min, were 68.8% (CR$_1$+BSA) a and 77.1% (CR$_1$+FBS) of expanded blastocyst stage, but there were no significant differences between the embryos exposed for 1 min. or transferred at 72 h. 3. Regardless of glucose concentration (5.5, 16.5, 27.5 & 38.5mM), 45.7~61.5% of embryos developed to the blastocyst stage. There were no significant differences between any of the treatments on the devel-opment of one-cell embryos. Therefore, the detrimental effect of highly concentration was not appeared.

• Korean Journal of Pharmacognosy
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• v.18 no.2
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• pp.118-126
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• 1987

Natural Killer cells are considerd to play an important role in antitumor immune surveilance mechanism. In this study, 21 putative anticancer drugs selected from reference were assessed by evaluating the effect on rat Natural Killer cell activity (NKCA). All 21 herb drugs were extracted in boiling water, lyophilized, autoclaved, and then used for experiment. Culture supernatant of concanavalin-A (Con-A)-stimulated rat spleen cells as a source of lymphokine was also used as a control of comparison. Rat spleen cells were used as effector and NKCA was measured in 4hr $^{51}Cr-release$ assay against Yac-1 mouse lymphoma cell line. In order to determine the optimal conditions for NKCA augmentation, effector cells were treated with 3 different concentrations of each drug for 24, or 48 hrs before testing of NKCA, In optimal conditions determined from previous results, the effect of herb drugs on NKCA were assessed in 3 to 5experiments. NKCA was significantly enhanced by treatment with 4 herb drugs(Ponciri Fructus, Houttuyniae Herba, Aurantii Pericarpium, Nepetae Herba). Culture supernatant of Con-A-stimulated spleen cells also augmented the rat NKCA more significantly. The results show that 4 of the herb medicines supposed to display anticancer effect may have activity as a biological response modifier through augmentation of NKCA.