摘要:

Antioxidant reactions of mixtures of vitamin E, vitamin C and phospholipids in autoxidizing lipids at 90°C have been studied by ESR spectroscopy. When the phospholipid contained a tertiary amine (e.g. phosphatidylcholine), the vitamin C and the vitamin E radicals were successively observed as these two vitamins were sequentially oxidised during lipid oxidation. In the presence of the primary amine contained in phosphatidylserine, the vitamin E oxidation was delayed for a few hours. In this case neither the vitamin C, nor the vitamin E radicals but a nitroxide radical derived from the phospholipid was observed. Similar results to those obtained with PS were obtained in the presence of either phospha-tidylethanolamine or soybean lecithin. The participation in the radical reactions of phospholipids possessing a primary amine can therefore explain the synergistic effect of these phospholipids in a mixture of vitamins E and C.

ISSN:1071-5762    

DOI:10.3109/10715769409145621

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The hydrogen peroxide dose-response curves forEscherichia colikilling and DNA nickingin vitrodisplay remarkably similar bimodal patterns. The concentrations of the oxidant resulting in maximum mode one killing, however, exceeds by two orders of magnitude those resulting in the mode one DNA nicking response. Addition of histidine differentially affects the experimental curves describing the dose-dependency for bacterial killing and DNA damagein vitro. Indeed, the lethal effect elicited by the oxidant in the presence of the amino acid is strictly concentration-dependent and thus the inactivation curve loses its bimodal character. In marked contrast, histidine abolishes DNA damage generated by low concentrations of hydrogen peroxide (<100μM) in thein vitrosystem (the mode one DNA nicking response) but greatly increases DNA damage produced by concentrations of the oxidant higher than 1 mM (the mode two DNA nicking response).Experimental results also suggest that treatment of covalently closed circular double-stranded super-coiled DNA with hydrogen peroxide, in the presence of both histidine and iron, may result in the formation of DNA double strand breakage, a type of lesion which is not efficiently produced by the oxidant in the absence of the amino acid.Taken together, the above results indicate that histidine differentially affects thein vitroDNA cleavage andE. colilethality induced by hydrogen peroxide and suggest that different molecular events mediate mode one DNA nickingin vitroand mode one killing of bacterial cells.

ISSN:1071-5762    

DOI:10.3109/10715769409145622

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Six patiems undergoing vascular reconstructive surgery were examined for evidence of oxygen-derived free radical (OFR) damage to the protein, immunoglobulin G (IgG). OFR damage was determined as an increase in the fluorescence (ex 360 nm em 454 nm) to ultraviolet absorption (280 nm) ratio of IgG, representing N-Formyl kynurenine and other as yet unidentified fluorophores. The IgG ratio was found to increase slightly during ischaemia and to undergo marked elevation upon reperfusion (275±405% baseline value at 40 min post-clamp; mean±sd). A high ratio was maintained post-reperfusion, even after 60 min reperfusion. Determination of thromboxane B2, (TXB2), leukotriene B4, (LTB4) and 6-keto prostaglandin Flalpha, (PGFla), revealed a decrease in their concentrations during ischaemia and a transient, marked increase on reperfusion. Only TXB2 concentrations were found to correlate with the IgG ratio (negative correlation, p<0.05). No correlation was observed between von Willebrand antigen factor, a marker of endothelial cell damage and fluorescent IgG ratio. However, levels of the factor increased slightly during ischaemia and more sharply upon reperfusion. These preliminary results therefore suggest that a more likely source of the OFRs responsible for IgG damage is endothelial cell xanthine oxidase, rather than cyclo-oxygenase or lipoxygenase.

ISSN:1071-5762    

DOI:10.3109/10715769409145623

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The oxidized intermediates generated upon exposure ofAspergillus nigercatalase to hydrogen peroxide and superoxide radical fluxes were examined with UV-visible spectrophotometry. Hydrogen peroxide and superoxide radical were generated by means of glucose/glucose oxidase and xanthine/xanthine oxidase systems. Serial overlay of absorption spectra in the Soret (350–450 nm) and visible regions (450–700 nm) showed that the decomposition of hydrogen peroxide by the catalase ofAspergillus nigercan proceed through one of two distinct pathways: (i), the normal“catalatic”cycle consisting of ferric catalase→Compound I→ferric catalase; (ii), a longer cycle where superoxide radical transforms Compound I to Compound II which is then converted to the resting ferric enzyme via Compound III. The latter sequence of reactions ensures that the catalase ofAspergillus nigerrestores entirely its activity upon exposure to low levels of superoxide radicals due to the actions of oxidases.

ISSN:1071-5762    

DOI:10.3109/10715769409145624

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The generation of hydroxyl radicals by rat liver microsomes was monitored by spin trapping with 5, 5-dimethylpyrroline N-oxide (DMPO). The results confirm and extend previous data which demonstrated that hydroxyl radicals are produced by microsomes in the presence of NADPH and O2, and without the exogenous addition of iron. No EPR signals could be detected unless catalase activity which was associated with the microsomes could be substantially diminished. Addition of azide was the most effective means of eliminating catalase activity, but azide also reacted rapidly with hydroxyl radicals, forming azidyl radicals which were in turn trapped by DMPO. Extensive washing and preincubation of microsomes with 3-amino-1, 2,4-triazole in the presence of H2O2were evaluated as alternative methods of decreasing the catalase contamination of microsomes. Although neither method completely eliminated microsomal catalase activity, addition of azide was no longer necessary for hydroxyl radical detection with DMPO. When highly washed microsomal preparations were tested, weak signals of the superoxide radical adduct of DMPO could also be detected. These data indicate that the sensitivity of spin trapping in microsomal systems can be improved substantially when care is taken to eliminate cytosolic contaminants such as catalase.

ISSN:1071-5762    

DOI:10.3109/10715769409145625

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

By using Electron Spin Resonance (ESR) spectroscopy, we have detected free radicals in red wine, whether fermented on oak or not, and in white wine only when it has been fermented on oak. These radicals would appear to be associated with the phenolics, because the ESR signal from the residue of red wine treated with polyvinyl polypyrrolidone is reduced by -80%. Any inhibition of lipid oxidation by red wine phenolicsin vitrowill take place in the presence of these radicals, which have a linewidth of 2.0±0.1 gauss and a g-value of 2.0038±0.0001.

ISSN:1071-5762    

DOI:10.3109/10715769409145626

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor