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정효균,이인규,강효경,서재미,김호,박기철,김동욱,김영근,오흥규,성민호 생화학분자생물학회 2002 Experimental and molecular medicine Vol.34 No.6
Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, known as statins, are widely used for primary and secondary prevention atherosclerosis is multistep processes where trans-endothelial migration of various leukocytes includ-ing monocytes is a crucial step. Interferon-γ (IFN-γ) contributes in this process by activating macro-phages and T-lymphocytes, and by inducing adhe-sion molecules in vascular endothelial and smooth muscle cells. In this study we investigated the expresion of intercellular cell adhesion mole-cule-1 (ICAM-1) in transformed endothelial cell line ECV304 cells as influenced by lovastatin, tumor necrosis factor-α (TNF-α) and IFN-γ. Results show that lovastatin suppresses expression of ICAM-1 by inhibiting the IFN-γ-induced extracellular signal- regulated kinase (ERK) p44/p42-STAT1 signaling pathway. In cells treated with lovastatin and IFN-γ, ICAM-1 was expressed at a lower level than in cells treated with IFN-γ alone. However, lovastatin does not reduce TNF-α induced expression of ICAM-1. A similar result was observed in cells N-γ. Cis-acting DNA sequence elements were identified in the 5'-flanking region of the ICAM-1 promoter that mediate inhibition by lovastatin; these se-quences map to the IFN-γ activated site which also binds the STAT1 homodimer. However, lovastatin did not inhibit IFN-γ-mediated induction of the Y701 phosphorylated form of STAT1. But lovasta-tin does inhibit the IFN-γ-mediated phosphoryla-tion of ERK1/ERK2 (T202/Y204) and S727 phos-phorylation of STAT1. TNF-αphosphorylation of ERK1/ERK2 and S727 in ECV304 and smooth muscle cels. The results provide the evidences that statins may have beneficial effects by inhibiting IFN-γ action in atherosclerotic pro-cess
고무 소재 메타물질을 활용한 샌드위치 복합재료 진동/소음 평가
정효균(H. G. Jeong),김민겸(M. K. Kim),윤재원(J. W. Yun),이주은(J. E. Lee),오병주(B. J. Oh),김윤철(Y. C. Kim),서종환(J. Suhr) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월
샌드위치 복합구조는 항공기에 활용되고 있는 구조로 경량, 고강도(High Strength) 및 고강성(High Stiffness) 특성이 탁월하다는 이점이 있다. 하지만 기존의 샌드위치 복합재료는 Face Sheet 을 탄소강화복합재료(Carbon Fiber Reinforced Polymer, CFRP)를 활용하고 코어를 Honeycomb 구조를 활용하여 진동 소음에 취약한 단점이 있다. 따라서 본 연구에서는 기존의 경량 고강도/ 고강성 기계적 특성을 유지한 채 진동/소음 저감 특성을 개선한 새로운 개념의 샌드위치 복합재료를 개발하고 이를 평가하고자 한다. 기존 샌드위치 복합재료의 단점을 개선하기 위해, Face Sheet 은 CFRP 를 활용하고 코어 구조는 고무(Rubber-like) 소재의 자연 모방(Bio-inspired Material) 혹은 메타물질(Metamaterial)을 활용하여 샌드위치 복합재료를 제작하였다. 진동으로 인한 소음 특성을 분석하기 위해 Wave Numbers, Frequency Response Function (FRF) 및 모드 형상을 분석하였고, 기존의 샌드위치 복합소재 특성과 비교하였다. 분석 결과, 자연 모방 혹은 메타 물질의 진동/소음 저감 특성이 기존의 샌드위치 복합소재 보다 탁월한 것을 확인하였다. 형상에 따라 크게 격자형(Lattice/Truss), 판형(Plate), 발포형(Foam), 외피형(Shellular) 메타 물질로 설계하였으며, 형상별 응답함수 특성이 상이한 것을 관측하였다. 본 연구에서 개발한 샌드위치 복합재료는 향후 샌드위치 복합소재가 활용될 수 있는 항공, 드론, 도심형 플라잉카 등의 다양한 산업군에 적용 가능할 것으로 사료된다.
HMG-CoA 환원효소 억제제에 의한 ICAM-1 유전자의 발현조절
김현진,정효균,홍우정,김군순,조영석,김도희,채수흥,구본정,송민호,노흥규,김영건 충남대학교 의과대학 지역사회의학연구소 2001 충남의대잡지 Vol.28 No.1
Background : ICAM-1 act as one of major adhesion molecules in the atherosclerotic lesion. ICAM-1 expression is mainly regulated at the level of transcription and depend on IFN-γ signal transduction pathway in which the STAT1 transcrption factor is a critical intermediate. IFN-γreceptor not only initiates tyrosine 701 phosphorylation of STAT1 by Jak1 and Jak2, but also phosphorylates serine 727 through the activation of Raf-1/MAP kinases. HMG-CoA reductase inhibitors have anti-atherosclertic effects, beyond normalization of hypercholesterolemia, by directly acting on endothelial cells, macrophages and vascular smooth muscle cells. HMG-CoA reductase inhibitors suppress the synthesis of isoprenoid intermediates such as geranylgeranyl-pyrophosphate or farnesylpyrophosphate. These effects results inhibitors suppress the synthesis of isoprenoid intermediates such as geranylgeranyl-pyrophosphate or farnesylpyrophosphate. These effects results inhibition posttranslational farnesylation and geranyl-geranylation processing of small GTP-binding preoteins and inhibition of normal signaling activities. Method : We made several 5'-deletion constructs of rat ICAM-1 promoter and analyzed the promoter activities by measuring the luciferase activity after transfection into ECV304 cells and smooth muscle cells. We checked the level of total and phosphorylated STAT1 protein by immunoblot analysis using specific antibodies. Results : Lovastatin inhibits IFN-γ-induced ICAM-1 gene expression in the ECV304cell. The cells pretreated with PD98059, MEKK inhibitor showed significantly low ICAM-1 RNA induction with IFN-γ stimulatio. IFN-γ induced phosphorylation of tyrosine 701 was not significantly changed by the pretreatment of lovastatin. But lovastatin suppresses IFN-γ-induced phosphorylation of ERK1/ERK2 which are responsible for the seine 727 phosphorylation in STAT1. Conclusion : We showed that HMG-CoA reductase inhibitors, lovastatin, suppresses IFN-γ mediated ICAM-1 gene expression through the inhibition of transcription. HMG-CoA reductase inhibitor suppresses IFN-γ-induced phosphorylation of serine 727 in STAT1 through the modulation of MAP kinases.
GDF15 Is a Novel Biomarker for Impaired Fasting Glucose
홍준화,정효균,박혜윤,정경혜,이주희,정진규,김군순,김현진,구본정,송민호 대한당뇨병학회 2014 Diabetes and Metabolism Journal Vol.38 No.6
Background: Growth differentiation factor-15 (GDF15) is a protein that belongs to the transforming growth factor β superfamily. An elevated serum level of GDF15 was found to be associated with type 2 diabetes mellitus (T2DM). T2DM is an inflammatory disease that progresses from normal glucose tolerance (NGT) to impaired fasting glucose (IFG). Hence, we aimed to validate the relationship between GDF15 and IFG. Methods: The participants were divided into the following three groups: NGT (n=137), IFG (n=29), and T2DM (n=75). The controls and T2DM outpatients visited the hospital for routine health check-ups. We used fasting blood glucose to detect IFG in nondiabetic patients. We checked the body mass index (BMI), C-reactive protein level, metabolic parameters, and fasting serum GDF15 level. Results: Age, BMI, triglyceride, insulin, glucose, homeostatic model assessment-insulin resistance (HOMA-IR), and GDF15 levels were elevated in the IFG and T2DM groups compared to the NGT group. In the correlation analysis between metabolic parameters and GDF15, age and HOMA-IR had a significant positive correlation with GDF15 levels. GDF15 significantly discriminated between IFG and NGT, independent of age, BMI, and HOMA-IR. The serum levels of GDF15 were more elevated in men than in women. As a biomarker for IFG based on the receiver operating characteristic curve analysis, the cutoff value of GDF15 was 510 pg/mL in males and 400 pg/mL in females. Conclusion: GDF15 had a positive correlation with IR independent of age and BMI, and the serum level of GDF15 was increased in the IFG and T2DM groups. GDF15 may be a novel biomarker for detecting IFG in nondiabetic patients.