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- 저자 : H. Vetter (검색결과 3 건)
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Ahn, Hee-Yul,K.R. Hadizadeh Kharrazi,Yun, Y-P,Park, J-B,Choi, W,H. Vetter,A. Sachinidis 이화여자대학교 세포신호전달연구센터 2000 고사리 세포신호전달 심포지움 Vol. No.2
Vascular smooth muscle cells(VSMCs) proliferation may participate in the pathophysiology of cardiovascular diseases. Platelet-derived growth factor-BB(PDGF-BB) is a potent mitogenic factor for VSMCs. Epigallocatechin gallate(EGCG) is the main compound of green tea and is believed to be the active component in tea for the prevention against several diseases. We investigated the effect of EGCG on the PDGF-BB-induced proliferation of VSMCs. VSMCs were preincubated in serum-free medium for 24 h(quiescent VSMCs) before EGCG was added to the medium. Following 24 h incubation with EGCG per se, VSMCs were trypsinized and cell counts were determined using CASY-1 system based on the coulter counter principle(Scharfe). Treatment of the cells with 0μM, 20μM, 50μM and 100μM EGCG resulted in a decrease of cell counts from 1.49×10^(6) ± 1.2×10^(5)(0μM) to 9.7×10^(5) ± 1.1×10⁴, 5.3×10^(5) ± 6.3×10⁴, 3.8×10^(5) ± 2.5×10⁴ counts/ml(mean±SD, n=3), respectively. Stimulation of quiescent cells with 50 ng/ml PDGF-BB for 24 h resulted in a 35% increase in cell counts. In the presence of 50μM EGCG, the effect of PDGF-BB on cell counts was abrogated. Activation of the 42 and 44 kDa mitogen-activated protein kinase(MAP) kinases(p44^(mapk)/p42^(mapk)) was deteced by chemiluminescence western blotting method using primary antibodies which recognizes the Tyr204-phosphorylated active isoforms. Stimulation of quiescent VSMCs with 50 ng/ml PDGF-BB caused at 5 min an 8-fold increase of the the p44^(mapk)/p42^(mapk) phosphorylation above control levels. Pretreatment of cells for 24 h with 50㎍/ml EGCG resulted in 70% inhibition of the p44^(mapk)/p42^(mapk) phosphorylation. Stimulation of the cells with PDGF-BB caused a maximal increase in [Ca^(2+)]_(i) from 40±10(basal value) to 145±15nM(mean±SD, n=4) at 25 sec(determined by the fura-2 method). Preincubation of VSMCs for 24 h with EGCG resulted in a complete inhibition of the PDGF-BB-induced increase in [Ca^(2+)]_(i). These results demonstrate that EGCG may exert its anti-proliferative effects via inhibition of the PDGF-BB-induced intracellular signaling events like stimulation of the p44^(mapk)/p42^(mapk) and elevation of [Ca^(2+)]_(i).
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S.N. Chattopadhyay,C. B. Overton,S. Vetter,M. Azadeh,B. H. Olson,N. El Naga 대한전자공학회 2010 Journal of semiconductor technology and science Vol.10 No.3
An optically controlled silicon MESFET (OPFET) was fabricated by diffusion process to enhance the quantum efficiency, which is the most important optoelectronic device performance usually affected by ion implantation process due to large number of process induced defects. The desired impurity distribution profile and the junction depth were obtained solely with diffusion, and etching processes monitored by atomic force microscope, spreading resistance profiling and C-V measurements. With this approach fabrication induced defects are reduced, leading to significantly improved performance. The fabricated OPFET devices showed proper I-V characteristics with desired pinch-off voltage and threshold voltage for normally-on devices. The peak photoresponsivity was obtained at 620 ㎚ wavelength and the extracted external quantum efficiency from the photoresponse plot was found to be approximately 87.9%. This result is evidence of enhancement of device quantum efficiency fabricated by the diffusion process. It also supports the fact that the diffusion process is an extremely suitable process for fabrication of high performance optoelectronic devices. The maximum gain of OPFET at optical modulated signal was obtained at the frequency of 1 MHz with rise time and fall time approximately of 480 nS. The extracted transconductance shows the possible potential of device speed performance improvements for shorter gate length. The results support the use of a diffusion process for fabrication of high performance optoelectronic devices.
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Chattopadhyay, S.N.,Overton, C.B.,Vetter, S.,Azadeh, M.,Olson, B.H.,Naga, N. El The Institute of Electronics and Information Engin 2010 Journal of semiconductor technology and science Vol.10 No.3
An optically controlled silicon MESFET (OPFET) was fabricated by diffusion process to enhance the quantum efficiency, which is the most important optoelectronic device performance usually affected by ion implantation process due to large number of process induced defects. The desired impurity distribution profile and the junction depth were obtained solely with diffusion, and etching processes monitored by atomic force microscope, spreading resistance profiling and C-V measurements. With this approach fabrication induced defects are reduced, leading to significantly improved performance. The fabricated OPFET devices showed proper I-V characteristics with desired pinch-off voltage and threshold voltage for normally-on devices. The peak photoresponsivity was obtained at 620 nm wavelength and the extracted external quantum efficiency from the photoresponse plot was found to be approximately 87.9%. This result is evidence of enhancement of device quantum efficiency fabricated by the diffusion process. It also supports the fact that the diffusion process is an extremely suitable process for fabrication of high performance optoelectronic devices. The maximum gain of OPFET at optical modulated signal was obtained at the frequency of 1 MHz with rise time and fall time approximately of 480 nS. The extracted transconductance shows the possible potential of device speed performance improvements for shorter gate length. The results support the use of a diffusion process for fabrication of high performance optoelectronic devices.
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