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S V Popova

Publications and source records attributed to S V Popova.

At least 19 recordsLinked to original sources
PubMed2003

Pressure-induced crossover between diffusive and displacive mechanisms of phase transitions in single-crystalline alpha-GeO2.

We present the first example of the phase transition occurring via the different kinetic mechanisms, displacive or diffusive, competing with each other in quartz-like alpha-GeO2 single crystals. Upon room-pressure heating, alpha-GeO2 transforms to the rutile-type phase (the alpha-->r transition) via the diffusive mechanism. With increase of the treatment pressure the diffusive mode of the temperature-induced alpha-->r transition is substituted at approximately 4 GPa by a displacive-like mode, and then at approximately 6 GPa the transition type changes from the alpha-->r sequence to a displacive martensitic-like transition to a distorted rutile-like phase (alpha-->r'. A crossover between diffusive and displacive transition modes suggests a new way to control the meso- and nanometer-scale morphology of high-pressure phases.

Journal Article↗
PubMed1989

Effect of chronic ethanol treatment on lipid peroxidation in rat liver homogenate and subcellular fractions.

1. The effect of chronic ethanol treatment on the level of lipid peroxidation in rat liver homogenate and subcellular fractions was measured using chemiluminescence technique and malondialdehyde formation. 2. It was shown that after chronic ethanol treatment the level of Fe/ADP-ascorbate-induced lipid peroxidation was decreased in the whole and "postnuclear" liver homogenates. Dilution of the homogenates prevented depressive effect of ethanol on lipid peroxidation. 3. Chronic ethanol treatment did not affect the intensity of the Fe/ADP-ascorbate-induced process in rat liver mitochondria and microsomes. 4. Peroxidative alteration of the liver lipids in vivo was evaluated by measurement of conjugated dienes (absorbance at 233 nm). It was shown that ethanol did not increase the level of u.v. absorption of lipids from mitochondria and microsomes. Chronic alcohol treatment did not influence the steady-state concentration of malonic dialdehyde in the whole liver homogenate. 5. The data obtained indicate that cytosol from the ethanol treated rat liver contains a factor(s) which prevents Fe/ADP-ascorbate-dependent lipid peroxidation in biological membranes.

Adenosine Diphosphate↗
PubMed1989

Effect of chronic ethanol, catalase inhibitor 3-amino-1,2,4-triazole and clofibrate treatment on lipid peroxidation in rat myocardium.

1. The effect of chronic alcohol consumption, catalase inhibitor 3-amino-1,2,4-triazole (amino-triazole) and peroxisome proliferator clofibrate on the level of Fe/ADP-ascorbate-induced lipid peroxidation has been studied in the rat myocardium. The intensity of lipid peroxidation was measured using chemiluminescence technique and malondialdehyde formation. 2. Combined us well as separate treatment with ethanol (36% of dietary calories) and aminotriazole caused elevation of the rate of lipid peroxidation in the nuclear-free homogenate or total particulate fraction of the rat heart. The most pronounced effect was noted during combined application of ethanol and aminotriazole. 3. Prolonged clofibrate treatment significantly increased the level of nonenzymatic lipid peroxidation in the rat myocardium. 4. Peroxidative alteration of the myocardial lipids in vivo was evaluated by measurement of conjugated dienes (absorbance at 233 nm). Separate ethanol, aminotriazole or clofibrate treatment did not affect the level of u.v. absorption of lipids from the total particulate fraction. However, when ethanol and aminotriazole were administered simultaneously an increase of conjugated diene formation was observed. 5. The data obtained confirm the hypothesis that ethanol or clofibrate-induced activation of the myocardial lipid peroxidation may be due to the increase of hydrogen peroxide-generating capacity of the heart microperoxisomes.

Amitrole↗
PubMed1988

Effect of clofibrate treatment on lipid peroxidation in rat liver homogenate and subcellular fractions.

1. A study was made of the effect of hypolipidemic drug clofibrate on the level of lipid peroxidation in homogenates and subcellular fractions of rat liver. The intensity of lipid peroxidation was measured using chemiluminescence technique and malondialdehyde formation. 2. It was shown that under the action of clofibrate the levels of Fe/ADP-ascorbate-, as well as t-butyl hydroperoxide (Bu'OOH)-induced lipid peroxidation were decreased in the whole and "post-nuclear" liver homogenates. Dilution of the homogenates prevented depressing effect of clofibrate on lipid peroxidation. 3. Clofibrate significantly decreased the level of the Bu'OOH-dependent lipid peroxidation, but did not affect the activity of the Fe/ADP-ascorbate-induced reaction in rat liver mitochondria and microsomes. 4. Peroxidative alteration of membrane lipids in vivo was evaluated by determining the extent of conjugated dienes formation (absorption at 233 nm). It was shown that clofibrate did not increase the level of ultraviolet absorption of lipids from rat liver subcellular fractions. 5. The data obtained indicate that cytosol from the clofibrate treated rat liver contains a factor(s) which prevents lipid peroxidation in the mitochondria and microsomes.

Animals↗
PubMed1987

[Effect of ethanol and the catalase inhibitor aminotriazole on lipid peroxidation in the rat myocardium].

The influence of chronic alcohol consumption and catalase inhibitor aminotriazole administration on the level of nonenzymatic lipid peroxidation has been studied in the rat myocardium. It was demonstrated that combined as well as separate treatment with ethanol or aminotriazole elevated the levels of chemiluminescence and enhanced the rate of accumulation of thiobarbituric acid-reactive products in the nuclei-free and total particulate fraction of the rat heart homogenate. The most pronounced effect was noted during combined application of ethanol and aminotriazole. The induction of chemiluminescence by ethanol was prevented by addition of natural (vitamin E, reduced glutathione) or artificial (dibunol) antioxidants into the incubation media. A putative role of the myocardial catalase-containing micro-peroxisomes in stimulation of the intracellular lipid peroxidation is discussed.

Amitrole↗
PubMed1983

Theoretical analysis of the glutamate dehydrogenase kinetics under physiological conditions.

A kinetic model of the glutamate dehydrogenase reaction has been formulated for the reversible reaction including all seven reactants (substrates and cofactors NAD(H) and NADP(H)). The model parameters have been evaluated from published initial-rate data. Analysis of the model at cofactor concentration near to that in the intact mitochondrion has shown that the competition for active sites between cofactors and substrates simultaneously present in mitochondria diminishes the steady-state rate of the reaction by a factor of 10 to 100 as compared to the maximal reaction rate. The model predicts near-equilibrium of the reaction substrates with NAD+/NADH cofactor pair and off-equilibrium with NADP+/NADPH. Substrate cycling with futile transfer of hydrogen from NADP+-system to NAD+-system has been found to account under in vivo conditions for no more than 2% of the maximal glutamate dehydrogenase activity in the mitochondria.

Ammonia↗
PubMed1983

[Effect of clofibrate on intracellular enzyme distribution in the rat liver].

The effect of chronic administration of a hypolipaemic agent--clofibrate--on the subcellular distribution of liver enzymes in male rats was studied. Clofibrate produced an increase in the number of peroxisomes and also enhanced the activity of aconitase and histidine: glyoxylate aminotransferase (HGA) in liver homogenate. Differential centrifugation of homogenate revealed an elevation of the relative amounts of catalase, HGA and isocitrate dehydrogenase in the soluble cell fraction in clofibrate pretreated animals. Clofibrate induced peroxisomal HGA but failed to alter the amounts of catalase, urate oxidase and isocitrate dehydrogenase in the particles. In both the experimental and control groups the activity of aconitase, malate dehydrogenase (NAD+), creatine phosphokinase and glutathione reductase was observed in mitochondrial fractions and was not detected in purified peroxisomes.

Animals↗
PubMed1983

[Regulation of ox liver glutamate dehydrogenase activity by coenzymes].

The effects of coenzymes NAD(P) and NAD(P)H on the kinetics of the ox liver glutamate dehydrogenase reaction have been studied. The oxidized coenzymes were shown to activate alpha-ketoglutarate amination at inhibiting concentrations of NADH and NADPH. The reduced coenzymes, NADH and NADPH, inhibit glutamate deamination with both NAD and NADP as coenzymes. The data obtained are discussed in terms of literature data on the mechanisms of the coenzyme effects on the glutamate dehydrogenase activity and are inconsistent with the theory of direct ligand--ligand interactions. It was shown that the peculiarities of the glutamate dehydrogenase kinetics can easily be interpreted in the light of the two state models.

Animals↗
PubMedDate not supplied

[Generalization of the Monod-Wyman-Changeux model for the case of multisubstrate reactions].

A general equation is derived for the rate of multisubstrate reaction catalyzed by oligomeric enzyme E(R, T) liable to concerted transitions Ro in equilibrium To or Ro in equilibrium 2To. It is shown that with some assumptions about the enzymes the rate equations can be constructed from the rates of corresponding reactions catalyzed by a single active site. These single active site rate equations are known for the majority of catalysis mechanisms, otherwise they can be easily deduced. As an example the rate equation is derived for the reaction S1 + S2 + S3 in equilibrium S4 + S5 catalyzed by an oligomeric enzyme according to the ordered ter-bi mechanism.

Binding Sites↗
PubMedDate not supplied

[Description of the kinetics of the two substrate reactions S1+S2 goes to and comes from S3+S4 by a generalized Monod, Wyman, Changeux model].

A number of mathematical models, generalizations of the Monod, Wyman, Changeux model, have been derived describing the kinetics of two substrate reactions S1+S2 (formula: see text) S3+S4. Protomers of the olygomeric enzyme E(R, T) undergo concerted conformational transitions of the type R in equilibrium T. Cases of ordered and random substrate and product binding to the active sites of the enzyme have been considered. The models have been shown to account for the isosteric substrate activation (sigmoidal curves upsilon (S1) and upsilon(S2) and substrate inhibition of the enzyme as well as activation by one substrate and inhibition by the other. Products can exert both activating and inhibiting isosteric effects on the enzyme. Relative advantages of the two main methods of parameter estimation, experimental-kinetic and mathematical, have been discussed. The second method has been illustrated by fitting one of the models to experimental data for substrate saturation of human platelet phosphofructokinase.

Adenosine Triphosphate↗
PubMedDate not supplied

[The effect of ethanol and the catalase inhibitor 3-amino-1,2,4-triazole on lipid peroxidation in rat liver homogenate and subcellular fractions].

Effects of repeated administration of ethanol and the catalase inhibitor 3-amino-1,2,4-triazole on the rate of Fe2+/ADP-ascorbate induced (nonenzymatic) lipid peroxidation were studied in rat liver tissue homogenate and subcellular fractions using estimation of low-level chemiluminescence and malonic dialdehyde content. The rate of lipid peroxidation was decreased in whole and nuclear-free homogenates as a result of combined or individual ethanol and aminotriazole treatment. However, this pattern was unaltered in mitochondrial and microsomal fractions. Both these agents did not affect the content of conjugated dienes in lipid containing extracts of subcellular fractions as well as the total malonic dialdehyde concentration in whole liver tissue homogenate. The data obtained suggest that antioxidative protein factor, inhibiting nonenzymatic lipid peroxidation in biological membranes, was induced in liver cytosol of rats repeatedly administered with ethanol and/or amino-triazole.

Amitrole↗
PubMedDate not supplied

[Characteristics of an experimental model of alcoholic cardiomyopathy by diagnostic enzyme tests].

Experimental alcoholic cardiomyopathy was simulated by aminotriazole administration (1 g/kg) into chronically ethanol intoxicated rats. Activity and isozyme spectra of organospecific enzymes and bilirubin concentration were determined in blood plasma. Activity of catalase was assayed in liver and heart homogenates. The data obtained suggest that not only myocardium but also skeletal muscles were impaired in the experimental group of animals. This phenomenon appears to elucidate the similar pathological effect of ethyl alcohol on myocardium and skeletal muscles.

Amitrole↗