摘要:

The aliphatic n-butyr- and n-valeraldehyde as well as the aromatic benz- and anisaldehyde induced DNA strand breaks in PM2 DNA in the presence of CuCl2. Neither aldehydes nor CuCl2alone showed DNA breakage properties. The maximum of single strand breaks (SSBs) induced by the combination of CuCl2and aldehydes was dependent on the CuCl2-concentration. The aliphatic aldehydes induced SSBs and double strand breaks (DSBs) at lower concentrations than aromatic aldehydes when optimal CuCl2concentration were used. Catalaseandneocuproine nearly completely inhibited strand break formation induced by aromatic aldehydes/CuCl2.The prevention of strand breaks induced by aliphatic aldehydes/CuCl2was less effective. While the inhibition by neocuproine was only 25 %, catalase was totally ineffective. In all aldehydes/CuCl2mixtures the formation of Cu(I) was observed. The results point to different DNA damaging species produced during redox reactions of aromatic and aliphatic aldehydes in combination with CuCl2.

ISSN:1071-5762    

DOI:10.3109/10715769609088030

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Human monocyte-macrophage cultures were exposed to native low density lipoprotein (LDL) for up to 24 h in Ham's F10 medium and the extent of cell-mediated LDL oxidation was determined by measurement of electrophoretic mobility on agarose gels and measurement of lipids and oxidised lipids (including 7β-hydroxycholesterol) by GC. After an initial lag phase, which varied from 2–8 h, there was a steady increase in oxidation over 24 h. No-cell control incubations showed minimal increases in oxidation over 24 h. Significant toxicity, measured as release of radioactivity from macrophages pre-loaded with tritiated adenine, was observed in the cells when they oxidised LDL and the extent of radioactivity release correlated closely with the extent of LDL oxidation. Inhibition of oxidation usingα-tocopherol or probucol reduced toxicity within the oxidising culture. This self-inflicted toxicity may help to explain the origin and enlargement of the lipid core of advanced atherosclerotic lesions.

ISSN:1071-5762    

DOI:10.3109/10715769609088031

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Profiles of the local nitric oxide (*NO) diffusion-concentration product across the egg yolk phospha-tidylcholine membrane in the absence and presence of 30 mol% cholesterol were obtained using line-broadening electron paramagnetic resonance (EPR) and lipid-soluble nitroxide spin labels. Membrane *NO permeability coefficients were calculated from these profiles. At 20°C, values of 93 and77cm/s for membranes in the absence and presence of cholesterol were obtained, compared with 73 and 66 cm/s for water layers of the same thickness as the membranes. Fluid-phase membranes are not barriers to *NO transport. Cholesterol significantly increases *NO transport in the center of the lipid bilayer.

ISSN:1071-5762    

DOI:10.3109/10715769609088032

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

The most widely used routine technique for determination of LDL 'oxidizability' is the continuous monitoring of the absorption at 234 nm in the UV spectrum of LDL, following the addition of an oxidation promotor such as copper ions. This absorption is commonly attributed to the conjugated dienes formed upon oxidation as the major intermediate, namely the hydroperoxides of polyunsaturated fatty acids, mostly linoleate hydro-peroxides. These, however, are not the only products of oxidation that absorb light at 234 nm. Other products, particularly 7-ketocholesterol, also absorb light at the same wavelength. Furthermore, enals and dienals also absorb in the wavelength range of 210–300 nm. The aim of the present work was to develop a simple spectro-scopic method for more detailed investigation of the kinetics of lipoprotein oxidation. The method is based on continuous measurement of the UV spectrum in the wavelength range of 210–300 nm and subsequent decomposition of the spectra into four absorption bands due to hydroperoxides, 7-ketocholesterol, dienals and enals. The sixth derivatives of the spectra, recorded during the first seven hours of copper-induced oxidation of LDL were used to monitor the growth and subsequent decay of the hydroperoxides. The resultant time course, in conjunction with difference spectra obtained after the concentration of these intermediates decay to zero, enabled us to determine the spectra of the other oxidation products and, by that, to evaluate their time dependencies. Based on these results, we present a series of four simple equations that can be used to evaluate the concentrations of the individual products of LDL oxidation from UV absorption measurements of the mixtures at merely four different wavelengths. The resultant time dependencies of the accumulation of four major products of lipid oxidation are consistent with published data obtained through separation and chemical analysis. This simple method can be used for more meaningful routine kinetic measurements of lipids oxidation.

ISSN:1071-5762    

DOI:10.3109/10715769609088033

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

MCI-186 (3-methyl-1-phenyl-2-pyrazolin-5-one) is a newly developed antioxidant which has been shown to reduce brain edema in cerebral ischemia through inhibition of the lipoxygenase pathway of arachidonic acid. However, its effect on myocardial reperfusion injury after prolonged ischemia has not yet been demonstrated. We compared the mode of the effect of MCI-186 and recombinant human CuZn superoxide dismutase (rh-SOD) in isolated perfused rat hearts subjected to 60-min ischemia followed by 60-min reperfusion. Left ventricular developed pressure (LVDP), necrotic area and the release of creatine phosphokinase (CPK) and endogenous CuZn superoxide dismutase (endoge-SOD) were measured to evaluate myocardial damage. The decrease in left coronary flow (CBF) was measured as an index of the damage of left coronary circulation. MCI-186 (17.5 mg/L) was perfused for 10 min in the MCI group and rh-SOD (70 mg/L) was perfused during the reperfusion period in the SOD group starting 5 min prior to reperfusion. The release patterns of CPK and endoge-SOD were analyzed to elucidate the difference in the mode of protection of MCI-186 and rh-SOD. The LVDP remained higher in both MCI and SOD groups than that of control (76±1,77±2 and 69±1% of preischemic value, respectively). The necrotic area was significantly attenuated in both MCI and SOD groups compared with that in the control group (16±1,14±1 and 32±170, respectively, p<0.05). Total CPK release was lower in both MCI and SOD groups thfn in the control (78±7, 100±2 and 116±4×103units/g myocardium respectively). The decrease in CPK release was more marked in the MCI group than that in the SOD group (p<0.05). The reduction in CBF was significantly attenuated by the treatment with rh-SOD or MCI-186, but the effect was much higher in the SOD group than in the MCI group (69±5, 58±2, and 48±2% in SOD, MCI and control groups, respectively). The release pattern of endoge-SOD was identical to that of CPK and thus this did not distinguish the mode of effect of MCI-186 from that of rh-SOD. These results indicate that MCI-186 reduces reperfusion injury in isolated perfused hearts with prolonged ischemia and the effect is more closely related to the reduction of myocyte damage than the preservation of the coronary circulation.

ISSN:1071-5762    

DOI:10.3109/10715769609088034

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Reaction of nitric oxide with superoxide anion produces the highly reactive species peroxynitrite (ONOO−). This compound has been shown to be a strong oxidant of lipids and proteins. However, no data are available on its effect on DNA, with the exception of the induction of strand breaks. We report the result of studies on the reactions of peroxynitrite with the adenine and guanine moieties of nucleosides and isolated DNA. The samples were analyzed for 8-oxo-7,8-dihydro-2′-deoxyguano-sine (8-oxo-dGuo), 2,2-diamino-4–[(2-deoxy-β-D-erythro-pentofuranosyl)amino]-5–(2H)-oxazolone (oxazolone) and 8-oxo-7,8-dihydro-2′-deoxyadenosine (8-oxo-dAdo). The effects of peroxynitrite treatment were compared with those of ionizing radiation in aerated aqueous solution, chosen as a source of hydroxyl radicals. At the nucleoside level, both oxidizing conditions led to the formation of oxazolone and 8-oxo-dAdo. In addition, evidence was provided for the formation of the 4R* and 4S* diastereoisomers of 4-hydroxy-8-oxo-4,8-dihydro-2′-deoxyguanosine. The latter dGuo oxidation products were chosen as markers of the release of singlet oxygen (1O2) upon reaction of peroxynitrous acid with hydrogen peroxide. Oxidation of purine bases was then studied within isolated DNA. A significant increase in the level of 8-oxp-dGuo, oxazolone and 8-oxo-dAdo was observed within double stranded DNA upon exposure toγ-radiation. Oxazolone and 8-oxo-dAdo were formed upon peroxynitrite treatment but no significant increase in the amount of 8-oxo-dGuo was detected. These results showed that peroxynitrite exhibits oxidizing properties toward purine moieties both in nucleosides and isolated DNA. However, the significant differences in the oxidative damage distribution within DNA observed after exposure toγradiation by comparison with peroxynitrite treatment questions the involvement of hydroxyl radicals as the main oxidizing species released by decomposition of peroxynitrous acid.

ISSN:1071-5762    

DOI:10.3109/10715769609088035

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

Non enzymatic glycation could be involved in the early impairment of Na+/K+ATPase that occurs in sciatic nerve of diabetic rats. In fact, decrease of Na+/K+ATPase activity is one of the first alterations showed in experimental diabetic neuropathy. In this respect, it is known that in the presence of transition metals under physiological conditions, glucose can autoxidize yielding hydrogen peroxide (H2O2) and free radical intermediates, which, in turn, inhibit the cation pump. Our experiments were designed to determine if glucose autoxidation has any relevance in the early steps of Na+/K+ATPase experimental glycation. Compared experiments with and without the sodium borohydride (NaBH4) reduction step demonstrated that incubation of brain Na+/K+ATPase with glucose 6-phosphate (G 6-P) and trace metals induced a significant decrease in enzyme activity dramatically enhanced by addition of copper (Cu2+). A concomitant production of H2O2was noticed. The presence of diethylenetriaminepentaacetic acid (DTPA), a strong metal chelator, completely prevented Na+/K+ATPase impairment and hydrogen-peroxide formation. No gross structural and confor-mational alterations of the enzyme can be demonstrated by intrinsic and extrinsic fluorescence measurements.Our results suggest that during the exposure of brain Na+/K+ATPase to glucose 6-phosphate in vitro (experimental glycation), the decrease in activity can be correlated, at least in the early phases, to metal-catalyzed production of oxidative species, such as H2O2, through the glucose autoxidation process, and not to glucose attachment to the enzyme. Since plasma hydro-peroxides and copper appear to be elevated in diabetic patients with complications, our data suggest a critical role for oxidative reactions in the pathophysiology of the chronic complications of diabetes like neuropathy.

ISSN:1071-5762    

DOI:10.3109/10715769609088036

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

The effect of captopril and of its copper complex on several superoxide-dependent reactions used to detect and assay superoxide dismutase activity was studied, including pyrogallol and hematoxylin autoxidation and Nitro Blue Tetrazolium reduction. ln none of these systems were superoxide dismutase-like properties of captopril/Cu apparent. Captopril/Cu decreased the yield of DMPO-OH adducts generated by KO2but this effect may be due to the acceleration of the decay of the adduct by captopril/Cu.

ISSN:1071-5762    

DOI:10.3109/10715769609088037

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

It has been suggested in the literature that elevated oxidative protein damage, measured as protein carbonyls, is present in the nervous system of patients with sporadic motor neurone disease (MND). However, the actual reported levels of brain protein carbonyls vary over a wide range. We show here that this is probably due to the use of different protocols for the carbonyl assay; results differ depending on when the dinitrophenylhydrazine reagent is added and at what stage in the procedure protein is assayed for the calculation of carbonyls on a unit protein basis. Using a range of different procedures, we were unable to confirm reports of elevated protein carbonyls in motor cortex from brains of patients with MND. We also measured thiobarbituric acid-reactive material in the brain samples using an HPLC-based TBA test in the presence of butylated hydroxytoluene. In general, there was no significant elevation of TBARS in MND motor cortex. However, four patients showed values higher than any of the control patients (both 'normal' control and 'disease control'). There was no correlation of TBARS with protein carbonyl values. We suggest that oxidative damage in motor cortex in sporadic MND, if it occurs, may be confined to a small group of patients and may affect different molecular targets in each patient.

ISSN:1071-5762    

DOI:10.3109/10715769609088038

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

ISSN:1071-5762    

DOI:10.3109/10715769609088039

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor