• Molecules and Cells
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• v.26 no.5
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• pp.462-467
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• 2008

TPA is known to cooperate with an activated Ras oncogene in the transformation of rodent fibroblasts, but the biochemical mechanisms responsible for this effect have not been established. In the present study we used c-fos promoter-luciferase constructs as reporters, in transient transfection assays, in NIH3T3 cells to assess the mechanism of this cooperation. We found a marked synergistic interaction between TPA and a transfected v-Ha-ras oncogene in the activation of c-fos promoter and SRE. SRE has binding sites for TCF and SRF. A dominant-negative Ras (ras-N17) inhibited the TPA-Ras synergy by blocking the PKC-MAPK-TCF pathway. Dominant-negative RhoA and Rac1 (but not Cdc42Hs) inhibited the TPA-Ras synergy by blocking the Ras-Rho-SRF signaling pathway. Constitutively active $PKC{\alpha}$ and $PKC{\varepsilon}$ showed synergy with v-Ras. These results suggest that the activation of two distinct pathways such as Ras-Raf-ERK-TCF pathway and Rho-SRF pathway are responsible for the induction of c-fos by TPA and Ras in mitogenic signaling pathways.

• Journal of Life Science
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• v.5 no.3
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• pp.105-116
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• 1995

To investigate genomic changes in c-myc gene by a chemical carcinogen, human lymphoblast NC-37 cells were exposed to benzo(a)pyrene(BP) and dimethylbenzanthracene(DMBA), and the c-myc gene expression was evaluated by Northern and Southern blot hybridization techniques. The results are as follows: When the genomic DNA of NC-37 cells exposed to several concentrations(1.25, 2.5 and 5ug/ml) of BP concentration. However, the c-myc gene was most significantly enhanced with 2.5ug/ml of BP. The expressions of c-myc gene in NC-37 cells was stimulated by BP and DMBA. Addition of TPA reduced the gene expression BP-treated cells, whereas it enhanced the gene expression in DMBA-treated cells. The expression of c-H-ras gene was slightly increased by treatment with BP and DMBA alone and in combination with TPA, however the magnitude of increase was not significantly different between each other. The expressions of c-myc c-H-ras genes in Burkitt's lymphoma cells were greater than those in NC-37 cells. When the DNA extracted from NC-37 cells exposed to various concentrations of BP were amplified by polymerase chain reaction using a primer set containing c-myc exon I, the amplified products were of the same size in all groups. To evaluate the BP toxicity in E.coli to which human c-myc gene-cloned pBR322 vector was inserted, Southern blot hybridization was conducted on c-myc genes digested with EcoRI/HindIII and Smal/Xbal restriction enzymes, and observing that in 2 ug/ml BP-treated cells a 3.5kb fragment was generated in addition to 1.3kb fragment which can be observed in normal cells. Direct nucleotide sequence analysis of polymerase chain reaction products showed a mutation of G$\longrightarrow$A transition at the Smal recognition site.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2001.11a
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• pp.107-107
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• 2001

During the last decade, enormous progress has been made on the biological significance of apoptosis. Since ras is among the most central molecule in signaling, we asked if ras regulates apoptotic pathway. We have previously shown that H-ras, but not N-ras, induces an invasiveness and motility in human breast epithelial cells (MCF10A), while both H-ras and N-ras induce transformed phenotype. In this study, we wished to seek a chemopreventive agent that effectively induces apoptosis in H-ras-activated cells. Here we show that capsaicin, the major pungent phytochemical in red pepper, induces caspase 3-involved apoptosis selectively in H-ras activated MCF10A cells while the parental MCF10A cells are not effected. In order to study the molecular mechanisms for the increased sensitivity of H-ras MCF10A cells to capsaicin-induced apoptosis, activation of ras downstream signaling molecules, mitogen-activated protein kinases (MAPKinases), upon capsaicin treatment was investigated. Phosphorylated forms of JNK1 and p38 MAPKinase were prominently increased whereas activated ERK-1/2 was decreased by capsaicin in ras-activated cells. The parental cells did not respond to capsaicin, suggesting that capsaicin selectively induces apoptosis through modulating activities of ras downstream signaling molecules in H-ras-activated cells. Studies using chemical inhibitors (CPT-cAMP, SB203580 and PD98059) and dominant negative constructs of JNKl, p38 and MEK show that activation of JNK1 and p38 MAPKinase, but not ERK-1/2, is critical for ras-mediated apoptosis by capsaicin.

• Proceedings of the Korean Society of Veterinary Pathology Conference
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• 2001.09a
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• pp.13-15
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• 2001

발암성시험연구에 사용되고 있는 형질전환 동물들은 랫드와 마우스 등이 있는데, 그 중 c-Ha-ras proto-oncogene 마우스 (ras H2 mice), v-Ha-ras 형질전환 마우스 (Tg.AC mice), pim-1 형질전환 마우스 및 p53 knockout 마우스 등이 발암유발물질에 감수성이 높아 현재 중기발암성시험에 이용되고 있다. (중략)

• Toxicological Research
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• v.17
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• pp.293-297
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• 2001

The international pharmaceutical and regulatory communities had been recognizing the limited utility of conventional rodent carcinogenicity study particularly on the second species, mouse, after intense investigation of carcinogenicity data base worldwide, and a new scheme for carcinogenicity testing for pharmaceuticals was proposed at the Expert Working Group on Safety in the International Conference on Harmonization (ICH) in 1996. CB6F 1-Tg rasH2 mouse carrying human prototype c-Ha-ras gene with its own promoter/enhancer is one oj the new carcinogenicity assay model for human cancer risk assessment. Studies have been conducted since 1992 to validate the transgenic (Tg) mice for rapid carcinogenicity test-ing, short term (26 weeks) studies with genotoxic (by Salmonella), non-genotoxic carcinogens, genotoxic non-carcinogens, non-genotoxic non-carcinogens revealed relatively high concordance oj the response of the Tg mouse with classical bioassay across classes of carcinogenic agents. Mechanistic basis for carcinogensis in the model are being elucidated in terms of the role of overexpression and/or point mutation of the transgene. This report review the initial studies of validation of the model and preliminary results of on-going ILSI HESI ACT project will be presented.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1202-1206
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• 1998

We have explored the impact of altering the Ras-cAMP pathway on cell survival upon oxidative exposures. A hyperactivated Ras mutant of Saccharomyces cerevisiae, intrinsically more sensitive to heat shock than the wild type, was investigated with regard to oxidative stress. In this paper we report that the response of iral, ira2-deleted mutant (IR2.53) to an oxidant, such as hydrogen peroxide (H2O2) or menadione is more sensitive than that of the wild type. IR2.53 showed a dramatic decrease in survival rate when challenged with 0.1 mM H2O2 for 30 min. The greater sensitivity of IR2.53 was also noticed with treatment of 0.01 mM menadione. Prior to oxidative stresses by these oxidants, both the wild type and the mutant were preconditioned with a mild heat shock (37 ℃, 30 min), resulting in improved survivals against oxidative stresses. Rescue of IR2.53 from menadione stress by heat pretreatment was more clearly demonstrated than that from H2O2 treatment. On the other hand, no significant difference was observed between the wild type and the IR2.53 mutant in their survival rates upon paraquat treatments. These findings imply that the mechanism by which H2O2 and menadione put forth their oxidative effects may be closely associated with the cAMP-Ras pathway whereas that of paraquat is independent of the Ras pathway. Finally, the level of glutathione (GSH) was measured enzymatically as an indicator of antioxidation and compared with the survival rate. Taken all these together, this study provides an insight into a mechanism of the Ras pathway regulated by several oxidants and suggests that the Ras pathway plays a crucial role in protection of cell damage following oxidative stress.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.26 no.3
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• pp.254-261
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• 2000

The present study has attempted to look into the mechanism of ras-induced carcinogenesis in a human epithelial cell system. Human epithelial cells immortalized with Ad12-SV40 hybrid virus were used to assess carcinogenic potential of the ras-oncogene. Cells transfected with pSV2-ras showed characteristics of cellular transformation. The transformation parameters such as cell density, soft-agar colony formation, and cell aggregation were significantly increased in the cells expressing ras oncoprotein. In addition, the duration required for the appearance of foci was shortened in the ras-transfected cells. Consistent with other reports, our results demonstrated an evidence that the ras-oncogene induced the cellular transformation of human epithelial cell system. When a high concentration of glucocorticoid was added into the media, transformation process was accelerated. It is speculated that glucocorticoid may provide an advantageous environment for the proliferation of the transformed cells. The induction of the intracellular free calcium concentrations following agonist treatment was significantly lower in the transformed cells than in the control cells. These effects were more manifested in the presence of extracellular cacium, indicating that the transformation process may alter the influx pathway of extracellular calcium. The induction of $IP_3$ following agonist treatment was also lower in the transformed cells than in the control cells. Thus, it is suggested that phospholipase C-coupled pathway was down-regulated in the process of the ras-induced transformation. While the levels of $TGF-{\beta}_1$ and PAI-2 mRNAs were decreased, the level of fibronectin mRNA was increased. The results indicate that mechanism of the ras-induced transformation may be associated with the altered expressions of growth regulatory factors. The present study demonstrates an evidence that the ras-induced cellular transformation may be associated with alteration of signal transduction and growth regulatory factors. The study will contribute to improve the understanding of molecular mechanism of epithelium-derived cancers including oral cancer.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.816-820
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• 2005

본 연구에서는 해안 도시 하천의 범람으로 인한 홍수 재해 발생시 예상될 수 있는 피해에 대해 적절한 홍수예경보 및 피난대책을 수립하고자 대표적인 해안 도시 하천의 특성을 가지는 부산시 온천천 유역을 대상으로 수치지도에서 각종 지형자료를 추출하였고 수문 GIS 자료를 구축하였다. 그리고, 하천 수리 분석을 위한 한계유출량 산정을 위해 HEC-RAS 모형을 이용 조위의 영향을 고려하여 홍수위 및 한계유출량을 산정하였고 수문 분석을 위한 도시 돌발 홍수 기준 우량 산정을 위해 PCSWMM 2002를 이용하여 기준 우량을 산정하였다. 전형적인 해안 도시 지역 유역 특성을 나타내는 부산시 온천천 유역에 대한 경보발령 기준을 설정하기 위하여 선정지점 세 곳의 한계수심 $H_{c1},\;H_{c2},\;H_{c3},\;H_{c4}$가 발생할 수 있는 강우량(위험 홍수량을 유발하는 위험 강우량(Trigger Rainfall))을 산정하였고 PCSWMM을 이용한 모형화 기법으로 해안 도시 돌발 홍수 기준 우량을 산정하였다. 산정 결과 온천천 유역의 홍수예경보 시스템과 이에 따른 홍수예경보 발령흐름도, 운영체계가 결정되어 해안 도시 돌발 홍수예경보 방안이 구축되었다. 해안 도시의 홍수 관리는 도시 우수 시스템, 하천, 해안 특성이 복합된 문제이다. 현재 해안 도시 지역의 홍수예경보 시스템 구축 실적이 전무한 실정임을 볼 때 현실적으로 실용화 할 수 있는 시스템 개발을 해내는 것이 무엇보다도 시급하고 중요한 문제이다. 앞으로 더욱 심도있게 연구하여 주요 하천에 대한 홍수예경보 시스템 구축이 절실히 요구된다.

• Animal cells and systems
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• v.13 no.4
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• pp.399-403
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• 2009

$p19^{ras}$ is an alternative splicing variant of the proto-oncogene c-H-ras pre-mRNA of $p21^{ras}$. In contrast to $p21^{ras}$, $p19^{ras}$ does not have a C-terminal CAAX motif that targets the plasma membrane and is localized to both the cytoplasm and nucleus. We found that $p19^{ras}$ activated the transcriptional activity of $p73{\beta}$ through protein-protein interactions in the nucleus. p73 is known to play an important role in cellular damage responses such as apoptosis. Although p73 is a structural and functional homologue of p53, p73-mediated apoptosis has not yet been clearly elucidated. In this study, we demonstrate that the interaction between $p19^{ras}$ and $p73{\beta}$ accelerated $p73{\beta}$-induced apoptosis through a caspase-3 dependent pathway. Treatment with DEVD-CHO, a caspase inhibitor, also strengthened $p73{\beta}$-mediated apoptosis through a caspase-3 dependent pathway. Furthermore, the enhanced transcriptional activity of endogenous $p73{\beta}$ by treatment with Taxol was amplified by $p19^{ras}$ overexpression, which markedly increased caspase-3 dependent apoptosis in the p53-null SAOS2 cancer cell line. Our findings indicate a functional linkage between $p19^{ras}$ and p73 in caspase-3 mediated apoptosis of cancer cells.

• Journal of Powder Materials
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• v.18 no.3
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• pp.297-302
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• 2011

Colloidal stability is one of crucial factors for many applications of nanodiamond. Despite recent development, nanodiamonds available on the market often exhibit a high impurity content, wide size distribution of aggregates and low resistance to sedimentation. In the current study, four commercial nanodiamond powders synthesized by detonation synthesis were surface modified and then separated with respect to the size into six fractions by centrifugation. The fractions were evaluated by zeta potential, particle size distribution and elemental composition. The results showed that the modified nanodiamonds form stable colloidal suspensions without sedimentation for a long time.