摘要:

Homocystinuria is an inborn error of methionine metabolism that is characterized by the premature development of arteriosclerosis. As one of the major factors in the pathogenesis of arteriosclerosis, modification of low-density lipoprotein (LDL) has received widespread attention by many investigators. In this study, to elucidate the relationship between elevated homocysteine levels and premature arteriosclerosis, we investigated the role of homocysteine in the iron-catalyzed oxidative modification of LDL. When LDL isolated from a healthy subject was incubated with homocysteine and ferric ion, a gradual decrease of polyunsaturated fatty acids (PUFA), formation of thiobarbituric acid-reactive substances (TBARS) and fluorescent substances, and the fragmentation of apoprotein B (apoB) were observed. The extent of oxidative modification was dependent on the concentration of homocysteine. Modification of LDL was suppressed until the remainingα-tocopherol concentration reached a critical level. When theα-tocopherol content of LDL was increased by 2.6-fold, both the formation of TBARS and the fragmentation of apoB were suppressed. These results suggest that homocysteine might promote iron-catalyzed oxidation of LDL and imply its role for the development of premature arteriosclerosis.

ISSN:1071-5762    

DOI:10.3109/10715769409056579

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The electrochemical properties of the benzotriazine di-N-oxide, tirapazamine (SR4233), and the mono-and zero-N-oxides, SR4317 and SR4330 respectively, have been investigated in dimethylformamide and acetonitrile. The voltammetry of tirapazamine is complicated, with up to 6 reduction steps being identified, depending on the solvent. Both SR4317 and SR4330 show two reduction steps. The first reduction of all three compounds is a reversible or quasi-reversible step, which is assigned to a 1-electron addition. Cyclic voltammetric studies show that the anion radical product is stable, although the tirapazamine 1-electron addition product shows a tendency to participate in a chemical following reaction. Subsequent reduction steps are all highly irreversible in nature. The 2nd electron transfer of SR4317 results in the formation of the free base, SR4330, which is identified voltammetrically. Comparison is made with the voltammetric behaviour of quinoline and quinoline-oxide.

ISSN:1071-5762    

DOI:10.3109/10715769409056580

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The activities of superoxide dismutase, catalase, glutathione reductase, glutathione peroxidase, glutathione transferase and glyoxalase I have been studied during the embryologic development of rainbow trout (Salmo iridaeus) and in several other trout tissues to investigate the protective development metabolism.A gradual increase of superoxide dismutase, catalase, glutathione reductase, glyoxalase I and glutathione transferase activities was noted throughout embryo development.In all trout tissues investigated glutathione peroxidase was found to be extremely low compared to catalase activity. The highest activity of superoxide dismutase, glyoxalase I and glutathione reductase was found in liver followed by kidney.No change in the number of GST subunits was noted with the transition from the embryonic to the adult stages of life according to the SDS/PAGE and HPLC analyses performed on the GSH-affinity purified fractions.

ISSN:1071-5762    

DOI:10.3109/10715769409056581

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The oxidative modification of low-density lipoprotein by macrophages may be an important mechanism in the pathogenesis of atherosclerosis. The human monocytic leukaemia cell line THP-1, when stimulated with phorbol ester, shares many properties with human monocyte-derived macrophages. Oxidation of LDL by these cells was characterised by depletion ofα-tocopherol, increases in thiobarbituric acid reactive substances and increases in electrophoretic mobility. The LDL particles were also converted to a form which increased accumulation of cholesteryl esters within macrophages. The oxidative mechanism appeared to be dependent upon the presence of thiols in the cellular medium. Oxidation of LDL by THP-1 macrophages, and production of thiols by these cells, were dependent upon the presence of L-cystine in the medium. Furthermore, cellular oxidation of LDL could be partially mimicked by the addition of cysteine to Hams F10 medium. Macrophage-independent oxidation of LDL, mediated by the addition of copper ions, was inhibited by cystine and cysteine in phosphate buffered saline, but not in Hams F10 medium. The glutathione content of THP-1 macrophages was also dependent upon the presence of cysteine or cystine in the medium, but inhibition of glutathione synthesis by buthionine sulfoximine did not prevent the production of thiols or the oxidation of LDL by THP-1 macrophages.

ISSN:1071-5762    

DOI:10.3109/10715769409056582

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

A study of peroxyl radical-mediated bovine serum albumin oxidation in the presence of the quinolinic aminoxyl 1,2-dihydro-2,2-diphenyl-4-ethoxy-quinoline-1-oxyl (QAO) was carried out in order to test its efficiency as a protein antioxidant. Albumin oxidation was induced by thetert-butylhydroperoxide/PbO2system. The extent of protein oxidation, measured by monitoring the formation of carbonyl groups, was considerably reduced in the presence of QAO. ESR measurements were carried out to confirm the consumption of the nitroxide during oxidation and its incorporation in the protein. The data obtained indicate that the quinolinic aminoxyl function can be used as an effective antioxidant in biological systems.

ISSN:1071-5762    

DOI:10.3109/10715769409056583

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

Birds are unique since they can combine a high rate of oxygen consumption at rest with a high maximum life span (MLSP). The reasons for this capacity are unknown. A similar situation is present in primates including humans which show MLSPs higher than predicted from their rates of O2consumption. In this work rates of oxygen radical production and O2consumption by mitochondria were compared between adult male rats (MLSP = 4 years) and adult pigeons (MLSP = 35 years), animals of similar body size. Both the O2consumption of the whole animal at rest and the O2consumption of brain, lung and liver mitochondria were higher in the pigeon than in the rat. Nevertheless, mitochondrial free radical production was 2–4 times lower in pigeon than in rat tissues. This is possible because pigeon mitochondria show a rate of free radical production per unit O2consumed one order of magnitude lower than rat mitochondria: bird mitochondria show a lower free radical leak at the respiratory chain. This result, described here for the first time, can possibly explain the capacity of birds to simultaneously increase maximum longevity and basal metabolic rate. It also suggests that the main factor relating oxidative stress to aging and longevity is not the rate of oxygen consumption but the rate of oxygen radical production. Previous inconsistencies of the rate of living theory of aging can be explained by a free radical theory of aging which focuses on the rate of oxygen radical production and on local damage to targets relevant for aging situated near the places where free radicals are continuously generated.

ISSN:1071-5762    

DOI:10.3109/10715769409056584

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The aim of this work was to characterize large unilamellar vesicles (LUVETs) prepared by a hand-driven extrusion device in order to use them for studies of lipid peroxidation and antioxidant activity. Vesicle structure and size were examined by electron microscopy. Lipid and antioxidant content was determined before and after the extrusion procedure. Then LUVETs were subjected to autoxidation initiated by both the lipid-soluble 2,2′-azobis(2,4-dimethylvaleronitrile) and the water-soluble 2,2′-azobis(2-amidinopropane hydrochloride) azocompounds. The results demonstrated that: i) LUVETs prepared with lipid concentrations ranging between 25 and 150 mM were essentially unilamellar and reasonably homogeneous, with an average diameter of 90 nm; ii) the phospholipid, cholesterol and antioxidant amounts retained by filters were about 10–15%; iii) LUVETs were suitable for autoxidation studies initiated by the water-soluble azocompound both in the absence and presence of antioxidants. The lipid-soluble azocompound could be used only at low concentrations and its vesicle content had to be determined since part of the initiator was not incorporated into the lipid bilayer. These data suggest that LUVETs seem to be recommended for studies of lipid peroxidation and antioxidant activity.

ISSN:1071-5762    

DOI:10.3109/10715769409056585

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

The reaction of 3,5-dibromo-4-nitrosobenzenesulfonate (DBNBS) with non-radical biological components produced spin adducts with ESR signals. The reactions of DBNBS with Trp, Gly-Trp, Trp-Gly, Pro, Cys and glutathione at pH 7.5 and room temperature for more than 1 hour gave the nitroxyl free radicals with ESR signals, whereas the reactions with other amino acids and bovine serum albumin did not. Among the amino acids and the peptides, Trp and Trp-containing peptides gave the most intense signals. The reactions of DBNBS with unsaturated fatty acids,i.e., linoleic acid and oleic acid, gave weak ESR signals, whereas the reaction with stearic acid did not. While DBNBS gave no ESR signals by the reactions with DNA, nucleosides and nucleobases, it caused strand breaking in supercoiled DNA. DBNBS also gave ESR signals by the reaction with human plasma similar to those from the reaction with Trp. It was suggested that the nitroxyl free radicals were produced by the addition of DBNBS to the amino acids and unsaturated fatty acids followed by oxidation in the presence of DBNBS. Hence, the use of DBNBS spin trap to detect free radicals in systems containing these biological components after long incubation may give misleading results.

ISSN:1071-5762    

DOI:10.3109/10715769409056586

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

ISSN:1071-5762    

DOI:10.3109/10715769409056587

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor