摘要:

Electron paramagnetic resonance spectroscopy (EPR) was used to study free radicals and transition metal complexes in liver tissue taken from patients with liver disease. Samples were frozen to 77K directly following biopsy to prevent deterioration. Our major aim was to compare signals from patients suffering from alcohol abuse with those from patients having liver damage not induced by alcohol. Samples were obtained from 19 chronic alcohol abusers and 7 non-alcoholic liver disease patients. Of the 19 alcoholic patients, 18 had an increased fat content, 6 had Mallory's hyaline, 12 had an acute inflammatory response, 9 had increased stainable iron and 4 had evidence of fibrosis. A signal derived from free radicals with a spectroscopic splitting factor of g = 2.0045 was found in all samples. This signal in the alcoholic patients had a mean amplitude of 2.96 cm (±1.42 SD), and in patients with non-alcoholic liver disease 2.12cm (±0.82) (p = 0.10NS), measured under identical instrument settings.The molar proportion of diene conjugated linoleic acid (DCLA), a free radical marker, in the sera of alcoholic patients was 2.68% (±1.93), but did not correlate with the free radical signals obtained by EPR spectroscopy. Also, there was no correlation between the free radical derived EPR signal and fat content, Mallory's hyaline, inflammatory infiltrate, iron or fibrosis in the liver biopsy specimens. Similarly the concentrations of aspartate transaminase, albumin, and gamma-glutamyl transferase in serum samples showed no correlations with free radical concentrations.The absence of any significant increase in the stable free radical signal in the presence of alcohol induced liver disease and the lack of correlation between the signal and either histological or serological evidence of liver damage, suggests that alcohol derived free radicals may not be involved in the pathogenesis of alcoholic liver disease.Unusually large sextet features characteristic of MN(II) complexes were observed for all liver samples. Such signals are very rare in human tissue, showing that there is a strong accumulation of Mn (II) in the liver. However, no systematic trends were observed. In some samples signals characteristic of iron-sulphur cluster units were detected, but again no correlations could be discovered.

ISSN:1071-5762    

DOI:10.3109/10715769509147532

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

Chemical reduction of mitosenes under aerobic conditions in DMSO showed characteristic ESR signals of the mitosene derived semiquinone free radicals. However, these signals diminished strongly upon addition of water to the reaction mixture, indicating a short lifetime of the mitosene semiquinone free radicals under aqueous conditions. In addition, enzymatic one-electron reduction of these mitosenes with either xanthine oxidase or purified NADPH cytochrome P450 reductase under anaerobic conditions showed no signals of the mitosene semiquinone free radicals. Subsequent cyclic voltammetry measurements demonstrated facilitation of the further one-electron reduction of the mitosene semiquinone free radicals in the presence of water in comparison with non-aqueous conditions. The present results strongly suggest that in the presence of water relatively stable hydroquinones are formed upon reduction of mitosenes. Consequently, the steady state concentrations of mitosene semiquinone free radicals will be lowered substantially in aqueous environment. Thus under physiological conditions, two-electron reduction and formation of the mitosene hydroquinone might be important in processes leading to DNA alkylation by these mitosenes.

ISSN:1071-5762    

DOI:10.3109/10715769509147533

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

Scavenging of superoxide radical by angiotensin converting enzyme (ACE) inhibitor captopril (CAP), a thiol compound, was studied by several investigators and the results were contradictory; while some reported a high superoxide scavenging activity of CAP others found that CAP removed superoxide inefficiently. In this work we show that in the presence of copper ions the apparent rate of superoxide removal by CAP (molar ratio CAP:CuSO4= 4:1) was two orders of magnitude higher (≈1.5×105M−1s−1at pH 7.4) than the literature value for superoxide scavenging by CAP alone (<10 M−1s−1at pH 7.4). We presume that in the presence of copper ions a CAP/copper complex with a SOD-mimicking activity is being formed. Similar results were also obtained with another thiol glutathione (GSH). The possible role of the CAP/copper complexes in the anti-inflammatory effect of CAP is discussed.

ISSN:1071-5762    

DOI:10.3109/10715769509147534

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

Attempts to establish the presence of oxidant stress and tissue damage in inflammatory bowel disease (IBD) have relied on determining the capacity of peripheral blood inflammatory cells to produce reactive oxygen species (ROS) and other indirect indices. These approaches have failed to address whether or not there are adequate chemical antioxidant defences to prevent oxidative injury in the inflamed mucosa. In this investigation we have determined the mucosal concentrations of reduced and total ascorbic acid and the redox status in paired non-inflamed and inflamed mucosa using colonic biopsies from IBD patients. In inflamed mucosa from Crohn's disease (CD) patients, reduced and total ascorbic acid content decreased by 35% (p= 0.014 andp = 0.009, respectively). In ulcerative colitis (UC) patients, mucosal total ascorbic acid content decreased by 73% (p= 0.069) and reduced ascorbic acid by 41% (p= 0.014). The proportion of total ascorbic acid present in its reduced form in histologically normal mucosa from CD patients was unusually low at∼30%. In the paired-inflamed mucosa from CD patients, the redox ratio was also∼30% despite the loss of 35% of total ascorbate. In UC patients, the ascorbate redox ratio in the non-inflamed mucosa was 23% which increased to 51% in paired inflamed mucosa. This increase reflected the loss (73%) of total ascorbate. Reduction of dehydroascorbic acid by GSH/NADPH dependent dehydroascorbic acid reductase decreased significantly (p= 0.046) in inflamed mucosa from UC patients, suggesting that the capacity of the inflamed mucosa to maintain the concentration of reduced ascorbic acid is also diminished. HPLC analysis of mucosal preparations for diketogulonic acid, the decomposition product of dehydroascorbic acid, did not account for the loss of total ascorbate in the inflamed mucosa suggesting that ascorbate equivalents underwent further decomposition reactions or were excreted to the colonic lumen.We conclude that the normal luminal environment is strongly oxidising in character and that oxidant stress derived from inflammatory cells contributes to the loss of 35-73% total and reduced ascorbate. In absolute terms, the overall loss of this antioxidant buffering capacity would decrease the capacity of the inflamed mucosa to prevent oxidative tissue damage and hinder recovery of the inflamed mucosa.

ISSN:1071-5762    

DOI:10.3109/10715769509147535

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

During the last decade increasing attention has been given to the role of free radicals in biological oxidations. The subject has been of increasing interest to both the food scientist and the physiologist. Free radical scavengers in the form of both indigenous and added antioxidants are necessary for the successful preservation of food; free radicals are increasingly being implicated in the onset of, among others, ischaemic heart disease and for protection against these diseases it is suggested that the dietary intake of the antioxidant vitamins should be increased especially for diets high in polyunsaturated fats.1,2Convenience and snack foods which absorb substantial amounts of frying oils are being increasingly consumed. Since poly-unsaturated fatty acids are particularly susceptible to oxidation by free radicals during the storage, cooking and frying of foods, the potential risk of exposure to lipid degradation products' is likely to have increased. In foods the non-enzymic and lipoxygenase catalysed oxidation of polyunsaturated fatty acids,β-carotene and vitamin A can result in the loss of essential nutrients and the development of off-flavours.

ISSN:1071-5762    

DOI:10.3109/10715769509147536

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

Male Sprague-Dawley rats were fed diets that varied qualitatively and quantitatively in antioxidants. Kidney, heart, lung, and spleen homogenates were incubated at 37°C with and without hydroperoxide or Fe+2. Protection of antioxidants against oxidative damage to tissue was determined by measurement of oxidized heme proteins. Tissues from rats supplemented with dietary vitamin E and selenium showed protection compared to tissues from rats on the basal diet. Tissues from rats with diets containing larger quantities of antioxidants and both fat soluble antioxidants: vitamin E,β-carotene, coenzyme Q10, ascorbic acid 6-palmitate and water soluble antioxidants: selenium, trolox C, acetylcysteine, coenzyme Q0, (+)-catechin, showed the highest protection.

ISSN:1071-5762    

DOI:10.3109/10715769509147537

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

The rate constants for reaction of several lipid-soluble antioxidants with trichloromethylperoxyl radicals are tabulated.

ISSN:1071-5762    

DOI:10.3109/10715769509147538

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor