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381.
382.
Regulation of cyclooxygenase enzymes by nitric oxide 总被引:12,自引:0,他引:12
D. Salvemini 《Cellular and molecular life sciences : CMLS》1997,53(7):576-582
383.
J. W. M. Lagerberg J. VanSteveninck T. M. A. R. Dubbelman 《Cellular and molecular life sciences : CMLS》1997,53(3):257-262
The fluorescent dye Merocyanine 540 (MC540) is often used as a probe to monitor the molecular packing of phospholipids in
the outer leaflet of biomembranes. In a previous study we showed that the increased staining of erythrocytes with a perturbed
membrane structure was mainly due to an increase in the fluorescence yield of cell-bound MC540, rather than to an increase
of the number of bound molecules. Erythrocytes and ghosts exposed to continuous fluxes of H2O2 exhibited pronounced lipid peroxidation. Further, red blood cells subjected to this form of oxidative stress also showed
increased staining with MC540. It appeared that this was caused by a strong increase in binding of MC540, together with a
slight red shift of the fluorescence emission maximum and a small increase in the fluorescence yield of bound MC540. The changed
MC540 binding characteristics were not observed when lipid peroxidation was suppressed by the presence of the antioxidant
BHT in the incubation medium. However, open ghosts exposed to H2O2 showed no increase of MC540 binding, excluding a direct involvement of lipid peroxidation. Measurement of fluorescence emission
spectra and gel filtration studies showed that MC540 can bind to H2O2-exposed hemoglobin. Experiments with erythrocytes lysed in hypotonic medium after exposure to H2O2 revealed that peroxidation of lipids with H2O2 induced a non-specific permeabilization of the plasma membrane to MC540, thereby allowing MC540 to bind to the oxidatively
denatured, more hydrophobic hemoglobin. These results indicate that conclusions about packing of phospholipids in the outer
leaflet of the membrane based on increased MC540-staining should be drawn with care.
Received 27 September 1996; received after revision 5 November 1996; accepted 27 November 1996 相似文献
384.
385.
Conclusion The optimum wavelength of Nd3+-doped double-clad fiber laser or amplifier made in China is near 830 nm. The efficiency of Nd3+-doped double-clad fiber devices pumped by 820-nm laser is low due to ESA. In order to increase the photochemical stability
of the outer cladding, the material of the outer cladding must be advanced. 相似文献
386.
用AM1MO方法计算了质子化卟吩的构型,并通过结构分析、电荷布局分析和前线轨道分析,讨论了其质子化过程的构型变化及Raman光谱变化的原因。 相似文献
387.
388.
Two classes of metabolites fromTheonella swinhoei are localized in distinct populations of bacterial symbionts 总被引:7,自引:0,他引:7
C. A. Bewley N. D. Holland D. J. Faulkner 《Cellular and molecular life sciences : CMLS》1996,52(7):716-722
The marine spongeTheonella swinhoei (lithistid Family Theonellidae, Order Astrophorida) has yielded many important, bioactive natural products, most of which share structural features with bacterial natural products. The presence of microbial symbionts inT. swinhoei has been reported, and it was originally suggested that the cytotoxic macrolide swinholide A and many of the bioactive cyclic peptides fromT. swinhoei were all produced by symbiotic cyanobacteria. By transmission electron microscopy, we found four distinct cell populations to be consistently present inT. swinhoei: eukaryotic sponge cells, unicellular heterotrophic bacteria, unicellular cyanobacteria and filamentous heterotrophic bacteria. Purification and chemical analyses of each cell type showed the macrolide swinholide A to be limited to the mixed population of unicellular heterotrophic bacteria, and an anti-fungal cyclic peptide occurred only in the filamentous heterotrophic bacteria. Contrary to prior speculation, no major metabolites were located in the cyanobacteria or sponge cells. 相似文献
389.
A. A. Shaheen A. A. Abd El-Fattah M. Z. Gad 《Cellular and molecular life sciences : CMLS》1996,52(4):336-339
The level of malondialdehyde (MDA), an index of lipid peroxidation, and the antioxidants superoxide dismutase (SOD) and glutathione (GSH), as well as the activity of Na+, K+-ATPase, were assessed in whole rat brain after immobilization, anemic hypoxia (NaNO2) and 72 h starvation. The effect of these stressors on plasma glucose and corticosterone levels was also observed. Hypoxia and starvation stimulated the lipidj peroxide formation in braini as indicated by an increase in the level of MDA, being higher after starvation than hypoxia. Brain SOD activity was also increased in response to hypoxia and starvation while GSH content was only diminished ini hypoxia. However, neither MDA nor antioxidants were affected by immobilization. On the other hand, the activity of brain Na+, K+-ATPase was significantly increased by immobilization and hypoxia but decreased in starvation. A similar pattern of change was also observed in plasma glucose and corticosterone levels in response to these stressors. These results elucidate differences in the biochemical response of animals towards various types of stress, with increased lipid peroxide formation in hypoxia and starvation. 相似文献
390.
Antioxidant survey to assess antagonism to redox stress using a prokaryotic and an eukaryotic system
H. Baker B. DeAngelis O. Frank M. Khalil S. H. Hutner E. R. Baker 《Cellular and molecular life sciences : CMLS》1996,52(6):597-599
Using a prokaryote (Escherichia coli) and a metazoa-resembling eukaryote (Ochromonas danica), we surveyed antioxidants which might overcome redox stress imposed by menadione sodium bisulphite (MD) and buthionine sulphoximine (BSO). BSO oxidant stress was evident only inO. danica; MD oxidant stress was evident in both organisms. Glutathione, its precursors, e.g. cysteine, homocysteine, and 2-oxo-4-thiazolidine carboxylic acid, and red blood cells, emerged as prime antioxidants for relieving BSO and MD oxidant stress. BSO and MD oxidant activity and antioxidant-annulling effect inO. danica were judged comparable to those found in animal cells whereas the resultsE. coli were not entirely equivalent. TheO. danica system emerged as a practical, rapid, and useful system for pinpointing oxidant stressors and antioxidants, and shows promise for studies with mammalian systems. 相似文献