The interaction of superoxide radicals with active dicarbonyl compounds

The interaction of superoxide radical anion (O₂ ^??) with active dicarbonyls (methylglyoxal, glyoxal, and malonic dialdehyde) was studied. It was demonstrated that glyoxal and methylglyoxal inhibited superoxide-dependent accumulation of formazan; however, malonic dialdehyde stimulated this process. The formation of O₂ ^?? in these experiments occurred during the decomposition of the SOTS-1 azo initiator. On the other hand, all of the studied dicarbonyls in this system of O₂ ^?? generation competed for superoxide with the TIR ON spin trap. These compounds also inhibited luminal-dependent chemiluminescence during the AIBN azo initiator-induced peroxidation of liposomes from the egg phosphatidylcholine. A mechanism for the antiradical and antioxidant effects of the studied dicarbonyls, assuming the production of free radical intermediates in their reactions with O₂ ^?? or its protonated form, is proposed.     

不同耕作措施对冬小麦-夏玉米复种连作系统土壤有机碳和水分利用效率的影响

在连续8年田间定位试验的基础上,分析了关中平原冬小麦 夏玉米复种连作系统2008—2009年连续两个生长季期间不同耕作措施(结合秸秆还田和不还田)对土壤有机碳和水分利用率的影响.结果表明: 相对于传统耕作,保护性耕作有利于土壤有机碳、水分利用效率和作物产量的提高,其中在“深松+秸秆还田”耕作模式下的增幅最高,土壤有机碳含量在0～30 cm土层增幅达到19.5%,水分利用效率和作物产量提高了16.9%和20.5%,而免耕模式则有效提高了0～10 cm土层有机碳含量.在该地区土壤和气候条件下,深松结合秸秆粉碎还田是最理想的耕作模式,最有利于土壤有机碳累积,并提高水分利用效率和作物产量.     

Protection of Rat Myocardium by Coenzyme Q during Oxidative Stress Induced by Hydrogen Peroxide

Ubiquinone Q(10) (coenzyme Q) is an important component of the mitochondrial electron transport chain and an antioxidant. The purpose of this work was to find out whether an increase in the level of coenzyme Q in the heart changes its maximal working capacity and resistance to oxidative stress. Male Wistar rats were treated with coenzyme Q (10 mg/kg body weight per day) for six weeks, and this increased its content in the myocardium by 63%. The myocardial content of malonic dialdehyde and activities of key antioxidant enzymes were unchanged, except nearly 2.5-fold decrease in the activity of superoxide dismutase. The maximal working capacity of the isolated isovolumic heart did not change, but under conditions of oxidative stress induced by 45-min infusion of hydrogen peroxide (70 micro M) into coronary vessels the contractile function of these hearts decreased significantly more slowly. This was associated with less pronounced lesions in the ultrastructure of cardiomyocytes and lesser disorders in the oxidative metabolism of mitochondria that suggested increased antioxidant protection of the myocardium.     

Decrease in the degree of lipoid infiltration of rabbit tissues during feeding with cholesterol freed from autoxidation products

Lipid accumulation in the rabbit liver and myocardium has been investigated by histochemical and biochemical methods. The rabbits received cholesterol that contained 5% of autooxidation products or purified cholesterol. Lipid accumulation took place in the liver and intramural myocardial vessels during feeding of rabbits with autooxidated cholesterol. Feeding with pure cholesterol free from autooxidation products caused but slight changes or no changes at all.     

Mechanisms of oxidative modification of low density lipoproteins under conditions of oxidative and carbonyl stress

Low-molecular-weight aldehydes (glyoxal, methylglyoxal, 3-deoxyglucosone) generated on autooxidation of glucose under conditions of carbonyl stress react much more actively with amino groups of L-lysine and epsilon-amino groups of lysine residues of apoprotein B-100 in human blood plasma low density lipoproteins (LDL) than their structural analogs (malonic dialdehyde (MDA), 4-hydroxynonenal) resulting on free radical oxidation of lipids under conditions of oxidative stress. Glyoxal-modified LDL aggregate in the incubation medium with a significantly higher rate than LDL modified by MDA, and MDA-modified LDL are markedly more poorly absorbed by cultured human macrophages and significantly more slowly eliminated from the rat bloodstream upon intravenous injection. Studies on kinetics of free radical oxidation of rat liver membrane phospholipids have shown that ubiquinol Q(10) is the most active lipid-soluble natural antioxidant, and suppression of ubiquinol Q(10) biosynthesis by beta-hydroxy-beta-methylglutaryl coenzyme A reductase inhibitors (statins) is accompanied by intensification of lipid peroxidation in rat liver biomembranes and in LDL of human blood plasma. Injection of ubiquinone Q(10) protects the human blood plasma LDL against oxidation and prevents oxidative stress-induced damages to rat myocardium. A unified molecular mechanism of atherogenic action of carbonyl-modified LDL in disorders of lipid and carbohydrate metabolism is discussed.     

Influence of dicarbonyls on kinetic characteristics of glutathione peroxidase

Se-containing glutathione peroxidase (GSH-Px) is one of the key enzymes of the body’s antioxidant system. The kinetic characteristics of GSH-Px (substrate is tert-butyl hydroperoxide) after modification of the enzyme by various concentrations of natural dicarbonyls (glyoxal, methylglyoxal, malonic dialdehyde) were studied. It was shown that dicarbonyls affected both K _m and V _max for GSH-Px. It is suggested that the effect of various dicarbonyls on GSH-Px depends on the molecular mechanisms of their interaction with the amino acid residues of the enzyme.