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Synthesis and Characterization of Poly(ethynyldimethylsilane-co-dimethylsiloxanes). Ⅱ.
( Choi Hae-kyun ),( Baek Jong-bum ),( Seo Kwan-ho ),( P. R. Jones ),( W. Brostow ) 한국공업화학회 1992 한국공업화학회 연구논문 초록집 Vol.1992 No.0
Silicone polymers have been known for their exceptional ability to exhibit and retain superior chemical properties over a broad temperature range. The main interests in these materials stems from the fact that they can be possessd unique properties such as good low-temperature flexibility, chemical inertness and water repellency etc. Poly(ethynyldialkylsilanes) can be considered as siloxane analogs having lone pair electrons on oxygen have been replaced by the C≡C linkage having two π electron pairs. We were able to prepare as the alkynyl analogs of -[Si(CH<sub>3</sub>)<sub>2</sub>O]<sub>n</sub>-, n=1, 2, 3, …, and -[Si(CH<sub>3</sub>)<sub>2</sub>C≡C]<sub>m</sub>-, m=2, 3, 4, …, which they are stable, separable compounds. As a result that poly(ethynyldialkylsilanes) were very rigid and high crystalline materials and siloxane were known as a very flexible substances. Therefore, the polymer having various thermal properties can be got from these synthesized monomers by combination of m and n. In this study, we synthesized the ethynyldimethylsilanes winch have various unit lengths from the digrignard ethyne and diohlorodimethylsilane in THF as a solvent. Then we prepared the poly(ethynyldimethylsilane-co-dimethylsiloxanes), -[{Si(CH<sub>3</sub>)<sub>2</sub>C≡C}<sub>m+1</sub>-{Si(CH<sub>3</sub>)<sub>2</sub>O}<sub>1</sub>]<sub>n</sub>-, from various ethynyldimethylsiloxanes and dichlorotetramethylsiloxane by using the grignard reaction or Cul catalyst. These polymers were identified by IR and NMR. Their molecular weights and molecular weight distributions were measured by GPC. Their thermal properties were investigated by DSC and TGA.
Yong, Hae-Young,Hwang, Jin-Sun,Son, Hwajin,Park, Hae-In,Oh, Eok-Soo,Kim, Hyun-Hwi,Kim, Do Kyun,Choi, Wahn Soo,Lee, Bong-Jin,Kim, Hyeong-Reh Choi,Moon, Aree Stockton Press 2011 Neoplasia Vol.13 No.2
<P>Increased expression and/or activation of H-Ras are often associated with tumor aggressiveness in breast cancer. Previously, we showed that H-Ras, but not N-Ras, induces MCF10A human breast epithelial cell invasion and migration, whereas both H-Ras and N-Ras induce cell proliferation and phenotypic transformation. In an attempt to determine the sequence requirement directing the divergent phenotype induced by H-Ras and N-Ras with a focus on the induction of human breast cell invasion, we investigated the structural and functional relationships between H-Ras and N-Ras using domain-swap and site-directed mutagenesis approaches. Here, we report that the hypervariable region (HVR), consisting of amino acids 166 to 189 in H-Ras, determines the invasive/migratory signaling program as shown by the exchange of invasive phenotype by swapping HVR sequences between H-Ras and N-Ras. We also demonstrate that the H-Ras-specific additional palmitoylation site at Cys184 is not responsible for the signaling events that distinguish between H-Ras and N-Ras. Importantly, this work identifies the C-terminal HVR, especially the flexible linker domain with two consecutive proline residues Pro173 and Pro174, as a critical domain that contributes to activation of H-Ras and its invasive potential in human breast epithelial cells. The present study sheds light on the structural basis for the Ras isoform-specific invasive program of breast epithelial cells, providing information for the development of agents that specifically target invasion-related H-Ras pathways in human cancer.</P>
Association Between Plasma Homocysteine Level and Mortality: A Mendelian Randomization Study
Chang Kyun Choi,Sun-Seog Kweon,Young-Hoon Lee,Hae-Sung Nam,Seong-Woo Choi,Hye-Yeon Kim,Min-Ho Shin 대한심장학회 2023 Korean Circulation Journal Vol.53 No.10
Background and Objectives: In previous studies, high homocysteine levels were associated with high cardiovascular mortality. However, these results were inconsistent with those of randomized controlled trials. We aimed to evaluate the causal role of homocysteine on all-cause and cardiovascular mortality using Mendelian randomization (MR) analysis. Methods: This study included the 10,005 participants in the Namwon Study. In conventional observational analysis, age, sex, survey years, lifestyles, body mass index, comorbidities, and serum folate level were adjusted using multivariate Cox proportional regression. MR using 2-stage least squares regression was used to evaluate the association between genetically predicted plasma homocysteine levels and mortality. Age, sex, and survey years were adjusted for each stage. The methylenetetrahydrofolate reductase (MTHFR) polymorphism was used as an instrumental variable for predicting plasma homocysteine levels. Results: Observed homocysteine levels were positively associated with all-cause (hazard ratio [HR], 1.40; 95% confidence interval [CI], 1.26–1.54) and cardiovascular (HR, 1.62; 95% CI, 1.28–2.06) mortality when plasma homocysteine levels doubled. However, these associations were not significant in MR analysis. The HRs of doubling genetically predicted plasma homocysteine levels for all-cause and cardiovascular mortality were 0.99 (95% CI, 0.62–1.57) and 1.76 (95% CI, 0.54–5.77), respectively. Conclusions: This MR analysis did not support a causal role for elevated plasma homocysteine concentrations in premature deaths.
Inhibition of Apoptosis by Nitric Oxide in MCF-7 Cells
Kyun Ha Kim(김균하),Sang Geun Roh(노상근),Hae-Ryun Park(박혜원),Won Chul Choi(최원철) 한국생명과학회 2009 생명과학회지 Vol.19 No.2
Nitric oxide (NO)는 세포 안의 다양한 생리학적, 병리학적 조건에서 확산, 세포 간 messenger와 같은 다양한 기능이 있으며, NO는 암세포나 macrophage 등과 같은 세포에서는 apoptosis를 유도하고, 정상세포나 내피 세포에서는 apoptosis를 억제한다고 보고되어져 있다. NO가 유방암 세포주인 MCF-7 세포에서는 apoptosis를 유도하는지 확인하기 위해 NO donor인 SIN-1을 처리하였다. SIN-1은 48시간 처리 시에도 세포 생존율에 영향을 주지 않았고, 세포주기나 성장 패턴에도 아무런 변화를 주지 않았다. 그러나 p53의 발현은 SIN-1 처리 시간에 따라 증가하였고, bcl-2, MDM2, p21의 발현도 함께 증가하였다. Bax의 발현은 SIN-1 처리 시에 변화가 없었다. MCF-7 세포에서 NO에 의한 apoptosis 억제를 보기 위하여, SIN-1을 선처리한 세포에 CoCl₂를 처리하였다. 세포에 CoCl₂ 만을 처리한 군에서는 확연한 apoptosis를 나타내었지만, SIN-1을 24 시간 선처리한 세포에서는 apoptosis를 관찰할 수 없었다. Cobalt Chloride에 의해 감소되었던 p53, MDM2, bcl-2 발현 역시 SIN-1을 24시간 선처리한 세포에서 증가하였다. 이런 결과들은 SIN-1에 의해 발현된 MDM2가 p53의 기능을 막으며, 또한 p21과 bcl-2의 발현이 유도되어 apoptosis를 억제함을 제시한다. Nitric oxide (NO) is a diffusible, multifunctional and transcellular messenger that has been implicated in numerous physiological and pathological conditions. It has been reported that NO induced apoptosis in tumor cells, macrophage cells and inhibited apoptosis in normal cells, endothelial cells. To examine whether NO could induce apoptosis in MCF-7 cells, cells were treated with SIN-1 (3-morpholinosydnonimine), NO donor. Cell viability did not change in SIN-1 treated cells for 48 h and there was no significantly changes in cell cycle progression or growth pattern by FACS analysis. But p53 protein, an apoptosis-related factor, increased SIN-1 treatment time dependently. Bcl-2, MDM2 and p21 were also accumulated. Bax level did not change. A major role of inhibiting apoptosis by NO in MCF-7 cells, cobalt chloride (CoCl₂) was added to cells preincubated with SIN-1. Whereas CoCl₂ treated cells underwent apoptosis, for 24 h SIN-1 preincubated cells were not induced apoptosis. Inactivated proteins, MDM2 and bcl-2, by CoCl₂ levels also increased in SIN-1 pre-treated cells. These results suggested that SIN-1 blocked p53 by MDM2 activation and inhibited apoptosis by inducing p21 and bcl-2 expression.
Choi, In Su,Kim, Han Kyul,Han, Dong Kyun,Baek, Hee Jo,Jang, Hae In,Kim, Chan Jong,Kook, Hoon The Korean Pediatric Society 2015 Clinical and Experimental Pediatrics (CEP) Vol.58 No.7
Antithymocyte globulin (ATG) is used as an immunosuppressive treatment (IST) to deplete clonal suppressor T cells in patients with severe aplastic anemia (SAA). The depletion of suppressor T cells by ATG may affect the activation of B cells, which results in an increased risk for autoimmune conditions. A 12-year-old boy was diagnosed with idiopathic SAA. As he did not have an human leukocyte antigen-matched sibling, he was treated with rabbit ATG (3.5 mg/kg/day for 5 days) and cyclosporine. Five months later, he became transfusion independent. However, 23 months after IST, he complained of mild hand tremors, sweating, weight loss, palpitations, and goiter. Results of thyroid function tests revealed hyperthyroidism (free thyroxine, 3.42 ng/dL; thyroid stimulating hormone [TSH], <0.01 nIU/mL; triiodothyronine, 3.99 ng/mL). Results of tests for autoantibodies were positive for the antimicrosome antibody and TSH-binding inhibitory immunoglobulin, but negative for the antithyroglobulin antibody and antinuclear antibody. He was treated with methimazole, and his symptoms improved. The patient has been disease free for 39 months after IST and 9 months after methimazole treatment. This case report suggests that although rare, rabbit ATG may have implications in the pathogenesis of autoimmune hyperthyroidism. Our findings suggest that thyroid function tests should be incorporated in the routine follow-up of SAA patients treated with ATG.