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771.
ROBERTO DOCAMPO FERNANDO S. CRUZ WILSON LEON GABRIEL A. SCHMUNIS 《The Journal of eukaryotic microbiology》1979,26(2):301-303
Bloodstream forms of Trypanosoma cruzi had a substantial increase in respiration in the presence of acetate. Oxidation of acetate took place via the tricarboxylic acid cycle and involved an antimycin A-sensitive respiratory pathway. Oxygen uptake in the presence of acetate was as sensitive to antimycin A inhibition as was CO2 production. There was a 6–7% residual O2 uptake which was not inhibited by high antimycin concentrations. Human anti-T. cruzi sera had no effect on oxygen uptake. 相似文献
772.
A carboxylesterase activity (E.C.3.1.1) was found in all four strains of Acinetobacter calcoaceticus tested. The activity was present in both 2 X 10(4) gav h-1 supernatant and bacterial wall-membrane fractions. The activity in the supernatant was in two molecular weight forms, the predominant form with a Mr of about 10(3) K and a minor form Mr approximately 600 K. The activity was inhibited by phenylmethylsulfonyl fluoride. SDS-PAGE showed that in A. calcoaceticus NCIB 8250 the activity was composed of three components of Mr 43, 40 and 38 K. The individual components showed different activities with 1- or 2-naphthyl esters. Of the other strains used, one showed a nearly identical pattern of component activities, while the other two showed only two component activities. 相似文献
773.
Bill X. Wu Youssef H. ZeidanYusuf A. Hannun 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2009,1791(8):730-739
Gemcitabine (GMZ) is a chemotherapeutic agent with well established effects on cell growth arrest and apoptosis. In this study, we investigated the potential roles of bioactive sphingolipids in mediating the growth suppressing effects of GMZ on a polyoma middle T transformed murine endothelial cell line. After 12-hour GMZ (0.6 μM) treatment, cell growth was arrested at the G0/G1 phase as detected by flow cytometric cell cycle analysis and MTT cell viability analysis, and this was accompanied by dephosphorylation of the retinoblastoma protein (Rb). Furthermore, GMZ treatment resulted in increased levels of specifically the very long chain ceramides as determined by mass spectrometry. Mechanistically, GMZ did not appear to affect the activities of many enzymes of ceramide metabolism; however, GMZ caused a selective reduction in the protein levels of neutral ceramidase (NCDase), as indicated by Western blot analysis, with a concomitant decrease in NCDase activity. The significance of NCDase loss on cell cycle regulation was investigated by specific knockdown of the enzyme using small interfering RNA (siRNA). Interestingly, NCDase siRNA transfection was sufficient to induce a cell cycle arrest at G0/G1 and an increase in total ceramide levels, with significant elevation in very long chain ceramides (C24:1 and C24:0). NCDase siRNA also induced Rb dephosphorylation. These data provide evidence for a novel mechanism of action for GMZ and highlight downregulation of NCDase as a critical step in GMZ-mediated ceramide elevation and cell cycle arrest. 相似文献
774.
V. M. Tischenko 《Biochemistry. Biokhimii?a》2001,66(12):1352-1355
Covalently cross-linked rod-like dimers of human myeloma IgG3 are more efficient in the inhibition of the complement system reaction than compact dimers. This correlates with an increase in the stability of CH2 domains of the immunoglobulin in the state with the rod-like hinge region. 相似文献