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Biomedical subjects

A K Tikhaze

Publications and source records attributed to A K Tikhaze.

At least 55 records · Page 3Linked to original sources
PubMed1985

On the nature of the stimulation of the lipoxygenase from rabbit reticulocytes by biological membranes.

The oxygenation of concentrated emulsions (about 260 microM) of arachidonic acid or linoleic acid catalyzed by the purified lipoxygenase from rabbit reticulocytes is strongly stimulated in the presence of low concentrations of beef heart submitochondrial particles or other membrane preparations. Maximal stimulation was observed at a proportion of about 5 mumoles polyenoic acid per mg of membrane protein. Whereas at a constant ratio of arachidonic acid and membranes the reaction rate obeyed the Michaelis-Menten kinetics with an apparent Km value of 75 microM for arachidonic acid, sigmoid kinetics was observed under conditions of constant concentration of membranes and, consequently, varying proportions of arachidonate and membranes. Under conditions of maximal stimulation binding of reticulocyte lipoxygenase to the membranes was insignificant. Moreover, one-third of the arachidonic acid sedimented during ultracentrifugation of the membranes as judged from experiments with [14C] arachidonic acid. From other sedimentation experiments and from the comparison with soybean lipoxygenase which is not stimulated by membranes it is concluded that the emulsion droplets interacting with the membranes are the substrate of the stimulated reaction. The stimulation may be brought about by facilitating the susceptibility of the fatty acids to reticulocyte lipoxygenase. The membrane-stimulated reaction of reticulocyte lipoxygenase was not inhibited by the antioxidant 2,6-di-t-butyl-4-hydroxytoluene (BHT) excluding the participation of free radicals. The stimulatory effect of membranes seems not to be related to their susceptibility towards lipoxygenase attack which varied strongly in order mitochondrialmembranes greater than endoplasmic membranes greater than erythrocyte ghosts. The stimulation by membranes resembles that produced by the detergent sodium cholate at concentrations near to the critical micellar concentration. Moreover, the stimulations by membranes and by cholate do not behave synergistically or abolish each other. The stimulatory effect of membranes did not occur at a proportion of 200 nmoles per mg of membrane protein.

Animals↗
PubMed1985

[Animal lipoxygenases. The nature of substrates and changes in conformation of reticulocyte lipoxygenase in its interaction with membranes].

In the presence of natural (liver mitochondria and microsomes) and artificial (liposomes from saturated phosphatidyl cholines) membranes, the rate of oxidation of an emulgated polyunsaturated fatty acid by reticulocyte lipoxygenase sharply increases and correlates with the amount of polyunsaturated fatty acid incorporated into the membrane. Hydrolysis of egg lecithine polyunsaturated acyls by phospholipase A2 drastically increases the rate of their enzymatic oxidation. It was shown that 15-hydroperoxyarachidonate is incorporated into lecithine liposomes at a much slower rate that the non-oxidized arachidonic acid. Solubilization of membranes with a detergent leads to the disappearance of the activating effect. Addition of saturated lecithine liposomes results in quenching of protein fluorescence of reticulocyte lipoxygenase, thus suggesting conformational changes in the enzyme structure upon its interaction with the membrane. The experimental results suggest that free polyunsaturated membraneous fatty acids are physiological substrates for animal lipoxygenases. One possible reason for the elevated rate of the lipoxygenase reaction in membranes is the alteration of enzyme conformation upon its interaction with the membrane matrix.

Animals↗
PubMed1984

Enzymatic detoxication of superoxide anion-radicals and lipoperoxides in intima and media of atherosclerotic aorta.

Unusually high activities of the "antioxidative" enzymes (superoxide dismutase, glutathione peroxidase) have been found in the cells isolated from the intima and media of normal human aorta. The activities of "antioxidative" enzymes of the intima and media of the human aorta in different types of atherosclerotic lesions (lipid spots, fibrous plaques) have been demonstrated to be greatly lowered.

Adult↗
PubMed1983

[Animal lipoxygenase: activation of reticulocyte lipoxygenase during interaction with natural and artificial membranes].

The rate of oxidation of exogenous arachidonate by homogenous samples of lipoxygenase from rabbit reticulocyte cytosol is significantly increased in the presence of various biological membranes (mitochondria, microsomes, erythrocyte ghosts, etc.). Unlike reticulocyte lipoxygenase, the rate of arachidonate oxidation by soybean lipoxygenase I in the presence of biomembranes is considerably reduced. The rate of arachidonate oxidation by reticulocyte lipoxygenase is also strongly increased in the presence of artificial membranes, e. g. liposomes from various phospholipids.

Animals↗
PubMed1983

[Effect of alpha-tocopherol on superoxide dismutase and glutathione lipoperoxidase activities of mouse liver cytosol and mitochondria].

The maximal radioactivity of mouse liver cytosol was observed 18 hours after intraperitoneal injection of 5-CH3-[3H] alpha-tocopherol emulsion with Tween 80. Intraperitoneal injections of Tween 80 (500 mg/kg) without alpha-tocopherol significantly decreased the glutathione lipoperoxidase and superoxide dismutase activities of liver cytosol. Vitamin E effect on the glutathione lipoperoxidase activity was weakly pronounced, while the superoxide dismutase activities of cytosol and liver mitochondria were markedly increased thereby. It was assumed that natural free radical scavengers can induce enzymatic utilization of superoxide radical anions, while synthetic free radical scavengers can trigger on enzymatic systems of lipoperoxide utilization.

Animals↗
PubMed1981

[Possibility of studying lipoperoxidation processes in surviving tissues].

A study was made of postmortem changes in the activity of "antioxidative" enzymes and in the content of primary and secondary products of lipid peroxidation in rabbit tissues (aorta, liver). It was found that the content of primary and secondary products of lipid peroxidation in the liver sharply rises already 1.5 h after the animals were sacrificed whereas no significant changes developed in the aorta over 9 hours. The activity of the "antioxidative" enzymes in the aorta or liver remains unchanged during these hours. Possibilities are discussed of studying the activity of superoxide dismutase and glutathion peroxidase, and the products of lipid peroxidation in cadaveric material obtained on rapid autopsy of suddenly deceased people.

Animals↗
PubMed1981

[Changes in superoxide dismutase and glutathione peroxidase activities during the process of intensification of lipid peroxidation in hepatic ischemia].

A study was made of changes in the activity of superoxide dismutase and glutathione peroxidase, in the level of the antioxidant activity and lipid peroxides during development of liver ischemia. It was shown that the intensification of peroxidation in ischemia is determined by the impairment of the systems maintaining the constant low level of peroxide reactions in an intact cells. The level of antioxidants, glutathione peroxidase and superoxide dismutase drastically falls in liver ischemia.

Animals↗
PubMed1980

[Glutathione peroxidase II activity in the blood of hypercholesteremic mammals].

The activity of the lipoperoxide-detoxicating enzyme glutathion--peroxidase II (GP II) in the blood of intact mammals predisposed to atherogenesis (rabbits, mini-pigs, men) is considerably less as compared to the species resistant to atherosclerosis development (rats). Hypercholesterolemia produces an abrupt decrease in GP II activity in the whole blood, plasma and formed elements (red cells, platelets) of the blood of mammals susceptible to atherosclerosis, while in the atherogenesis-resistant species (rats) the activity of the enzyme remains unchanged in spite of a considerable rise in the cholesterol blood content. In the course of the development of mini-pigs, the decreased cholesterol blood content is associated with a respective increase in the activity of GP II and lowered content of the primary and secondary products of lipid peroxidation in the blood of adult animals. The role of decreased activity of the enzymatic systems involved in lipoperoxide detoxication in the pathogenesis of atherosclerosis is discussed.

Adult↗
PubMed1980

[Lipid peroxides and atherosclerosis. Free radical peroxidation of polyene lipids in the blood in ischemic heart disease].

Examination of blood in 114 males (35--60 years of age) with stage III of lipid hydroperoxides, acylhydroperoxides, intermol ecular cross-links in the aminophosphatides and secondary products of lipoperoxidation was increased considerably as compared to that in practically healthy males (30) of the same age. The activity of blood glutathione lipoperoxidase in the examined group of patients was sharply reduced.

Adult↗