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排序方式: 共有271条查询结果,搜索用时 15 毫秒
1.
BH Jhun JL Meinkoth JW Leitner B Draznin JM Olefsky 《Canadian Metallurgical Quarterly》1994,269(8):5699-5704
We have investigated the role of cellular p21ras protein in insulin and insulin-like growth factor-I (IGF-I) signaling pathways. Insulin stimulation increased Ras-GTP formation in Rat-1 fibroblasts overexpressing normal human insulin receptors (HIRc-B), far greater than in parental Rat-1 fibroblasts, indicating that competent insulin receptors mediate this response. Cellular microinjection of a dominant-negative mutant p21ras protein (N17 ras) or anti-p21ras monoclonal antibody (Y13-259) into HIRc-B cells reduced insulin- and IGF-I-stimulated DNA synthesis by 75-90%. Insulin-induced c-fos protein expression was also inhibited by 74%. Microinjection of oncogenic p21ras (T-24 ras) into HIRc-B cells activated the mitogenic pathway, and coinjection of N17 ras and T-24 ras showed that oncogenic p21ras rescued the cells from the N17 ras blockade. This later finding indicates that T-24 ras acts downstream of N17 ras. In conclusion, 1) microinjection of a dominant interferring ras mutant into quiescent cells abrogated subsequent insulin and IGF-I mitogenic signaling; 2) oncogenic ras protein rescued cells from the N17 ras blockade, indicating that T24 ras action is downstream of the site of N17 inhibition; and 3) p21ras is an intermediate signaling molecule in the insulin/IGF-I signal transduction pathway and is required for gene expression and DNA synthesis. 相似文献
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The efficiency of the process of refining technical boron nitride was assessed based on calculations of the chemical equilibrium in the B-N-O-C-Cl-H system. Three refining mixtures, CCl4 + H2, CCl4 + NH3 and CHCl3 + NH3, were considered. The analysis indicates that the use of ammonia-containing mixtures is more convenient, a lower residual oxygen content, lower contamination of the product by carbon and a better overall boron balance emerging. The calculations of the equilibrium composition of the solid phase enabled suitable technological conditions of the refining process (temperature and starting composition of the gaseous phase) to be established. The calculated results are compared with experimental data, and some observed differences are discussed. 相似文献
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ML Goalstone JW Leitner K Wall L Dolgonos KI Rother D Accili B Draznin 《Canadian Metallurgical Quarterly》1998,273(37):23892-23896
We have previously demonstrated that insulin activates farnesyltransferase (FTase) and augments the amounts of farnesylated p21 (Goalstone, M. L., and Draznin, B. (1996) J. Biol. Chem. 271, 27585-27589). We postulated that this aspect of insulin action might explain the "priming effect" of insulin on the cellular response to other growth factors. In the present study, we show the specificity of the effect of insulin on FTase. Insulin, but not insulin-like growth factor-1 (IGF-1), epidermal growth factor (EGF), or platelet-derived growth factor (PDGF), stimulated the phosphorylation of the alpha-subunit of FTase and the amounts of farnesylated p21. Even though all four growth factors utilized the Ras pathway to stimulate DNA synthesis, only insulin used this pathway to influence FTase. Insulin failed to stimulate FTase in cells expressing the chimeric insulin/IGF-1 receptor and in cells derived from the insulin receptor knock-out animals. Insulin potentiated the effects of IGF-1, EGF, and PDGF on DNA synthesis in cells expressing the wild type insulin receptor, but this potentiation was inhibited in the presence of the FTase inhibitor, alpha-hydroxyfarnesylphosphonic acid. We conclude that the effect of insulin on FTase is specific, requires the presence of an intact insulin receptor, and serves as a conduit for the "priming" influence of insulin on the nuclear effects of other growth factors. 相似文献
6.
A new method for measuring the thickness of a micrometer-thin water film on ice is presented. The method is based on confocal detection of fluorescence light, emitted by a special coumarin dye dissolved in ice as well as in water. The spectral position of the fluorescence maximum depends strongly on the matrix surrounding the dye molecules. Thus the analysis of the spectra obtained while the focal position perpendicular to the liquid-ice interface is scanned provides the possibility of measuring the thickness of the water film with the vertical resolution of the confocal system. We demonstrate this principle by a model system. 相似文献
7.
Programs That Test Themselves 总被引:1,自引:0,他引:1
The AutoTest framework automates the software testing process by relying on programs that contain the instruments of their own verification, in the form of contract-oriented specifications of classes and their individual routines. 相似文献
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Johnson K. Agbo Ramachandran Gnanasekaran David M. Leitner 《Israel journal of chemistry》2014,54(8-9):1065-1073
Frequency-resolved communication maps provide a coarse-grained, global mapping of energy transport channels in a protein as a function of frequency of modes that carry energy. We illustrate the approach with a study of the homodimeric hemoglobin of Scapharca inaequivalvis, which exhibits cooperativity during ligand binding. We compare energy transport between the two hemes of the unliganded and oxygenated protein, which is mediated by water as well as residues forming a hydrogen-bonding network at the interface between the globules, and lies along the pathway for allosteric transitions observed in time-resolved X-ray studies. Non-equilibrium molecular simulations on energy transport from the heme corroborate the energy transport pathways identified by the communication maps. 相似文献
10.
Manhal Abouzlam Régis Ouvrard Driss Mehdi Florence Pontlevoy Bertrand Gombert Nathalie Karpel Vel Leitner Sahidou Boukari 《Control Engineering Practice》2013,21(1):105-112
This paper deals with the control of a wastewater treatment pilot by catalytic ozonation. In general, catalytic ozonation processes operate with a deliberate ozone overproduction to obtain a treated water which respects discharge standards. But, in this case, the oxygen consumption is not optimal and the operating costs are important. The objective of this study focuses on the optimization of the catalytic ozonation reactor. A continuous-time transfer function model is identified to represent the pilot behavior, and an optimal control is proposed to obtain a significant abatement of the pollutant. In this application, the pollutant abatement is represented by the absorbance. 相似文献