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Biomedical subjects

S V Konev

Publications and source records attributed to S V Konev.

At least 145 records · Page 8Linked to original sources
PubMedDate not supplied

[Comparative study of beta-adrenoreceptors of rat brain synaptic membranes].

Affinity of beta-adrenoreceptors in the rat brain synaptic membranes to agonists isoproterenol and norepinephrine, as well as to antagonist 125I-hydroxybenzylpindolol is lower in young (1 month) and old (24--26 months) than in mature (8--12 months) rats. Desensitization toward isoproterenol is expressed in the young ones only. In the old but not in other groups simultaneous action of isoproterenol and N-ethylmaleimide decreases the following binding of the antagonist while the same agents added separately produced no effect. It is suggested that beta-adrenoreceptors undergo age-related changes in their conformational state due to modification of the membrane environment.

Aging↗
PubMedDate not supplied

[Effect of the state of the lipid phase of the membrane on the effectiveness of photochemical modification of erythrocyte acetylcholinesterase].

Modification of the lipid phase structure of the erythrocyte membrane by phospholipases A2, C and D as well as the partial depletion of cholesterol was shown to be accompanied by the change of the acetylcholinesterase (AChE) UV-sensitivity. The ability of UV-light to change the catalytic properties (Km) of the membrane-bound AChE not observed for free AChE (constant value of Km) and known as the phenomenon of photochemical allotopy, is retained in the cholesterol depleted membranes and disappears after an enzymatic treatment of the membranes by phospholipases. The possible non-photochemical influence of the membrane lipid phase in response to UV-damage of membrane-bound AChE is discussed.

Acetylcholinesterase↗
PubMedDate not supplied

[Study of the equilibrium dynamics of cell protein structure using the tryptophan fluorescence method at room temperature].

Room-temperature tryptophane phosphorescence (RTTP) of liver tissue cells has been studied. It is shown that over a millisecond range RTTP is absent in soluble proteins of the cytoplasm, karyoplasm, mitochondrial matrix, and the phosphorescent signal is controlled only by proteins of the subcellular structures incorporated into the membranes. It is concluded that, unlike the membrane proteins, the cytoplasm and organelle matrix-soluble proteins are characterized by a high level of intramolecular equilibrium mobility, which causes RTTP quenching following a dynamic mechanism. In membrane proteins, which fluoresce in a millisecond range the level of equilibrium conformation motions is limited, probably, due to protein-protein and protein-lipid interactions.

Animals↗
PubMedDate not supplied

[Structural transformation of human erythrocyte membranes initiated by group specific antibodies].

Some changes have been found in the rates of the desintegration by sodium dodecylsulfate of human erythrocite membranes (EM) after incubation with specific group antibodies (GA) from incompatible blood. GA have no effect on the disintegration rates of EM by sodium desoxycholate and Triton X-100. The data are considered as the evidence of the structural transition in EM induced by GA and resulting in modification of integrative coupling forces primarily in the protein components of the membrane. The stopflow technique has been used to investigate the dependence of the desintegration rates in the quick phase (10 to 100 ms) upon the GA concentrations in the incubation medium and upon the incubation time. The obtained curves are distinctly S-shaped that is peculiar of cooperative processes.

Chemical Phenomena↗
PubMedDate not supplied

[Effect of physiologic concentrations of local anesthetics of the procaine series on the structural and functional state of cerebral synaptosome membranes].

Studies are presented of the effect of procaine group anesthetics on rat brain synaptosome stability to dodecyl sulfate and on catalytic properties of the membrane bound alkaline phosphatase. The dose curves of detergent stability are characterized by two maxima, one at 3.10(-4) M for tetracaine, 2.10(-6) M for lidocaine and 5.10(-5) M for procaine; the other being at 10(-3) M for all anesthetics. The curves of Vmax and KM versus procaine concentration to exhibit the minimum at 5.10(-7) M and maximum at 3,2.10(-6) M. Procaine at 5.10(-7) M increases enthalpy and enthropy of membraneous alkaline phosphatase. It is suggested that interactions between anesthetics and centers of high affinity lead to synaptosome structural rearrangements, which affect the properties of membraneous enzymes.

Alkaline Phosphatase↗
PubMedDate not supplied

[Insulin-induced structural transformations in the plasma membranes of liver and fat cells].

Two classes of SH-groups have been revealed with Ellman's reagent in isolated plasma membranes of epididimal fat cells from rats. Preincubation with 2 x 10(-9) M insulin (25 degrees C, 30 min) results in a 15% decrease of content of the fast reacting groups. The effect was absent in preparations solubilized with 0,06% Triton X-100 or 0,1% SDS. In the presence of insulin the rates of solubilization of liver plasma membranes by these two detergents have been found to increase. It is suggested that binding of insulin to receptor initiates the generalized structural rearrangement in both types of membranes.

Adipose Tissue↗
PubMedDate not supplied

[The structural membrane control of the reduction of exogenous quinones catalysed by mitochondrial 2-methyl-1,4-naphthoquinone reductase].

The catalytic parameters of mitochondrial 2-methyl-1, 4-naphthoquinone-reductase were studied. Maximal velocity and Michaelis constant of quinone-reducing reaction were shown to depend strongly on the functional state of mitochondria (I, II and IV Chance's states). The changes in catalytic parameters were found for four quinone substrates essentially varying in their structures. For the same conditions the Michaelis constant of isolated enzyme remains unchanged. The data obtained indicate the possibility to control the activity and substrate specificity by structural rearrangements within the biological membrane.

Animals↗
PubMedDate not supplied

[Action of ozone on the membrane-dependent functions of Candida utilis yeast cells].

The action of ozone on the structural-functional state of plasmic membranes was studied with Candida utilis cells. The damage of the membranes resulting in disorders of permeability barriers for nucleotides was not identical to damages which made the cells stained with methylene blue. The curve for the damage of membrane integrity (staining with methylene blue) coincided with the curve for the survival of C. utilis cells; therefore, the bacterial action of ozone consists mainly in damaging the surface cell structures.

Candida↗
PubMedDate not supplied

[Do anesthetics cause conformational changes in the majority of proteins in synaptic membranes?].

Cationic and neutral anesthetics at concentrations 1--10 mM increase SH-group accessibility to DTNB in the rat brain synaptic membranes, these effects for NEM-reactive groups being 5--10 times lower. High ionic strength depresses partially the influence of cationic but not neutral anesthetics in experiments with DTNB. Pronase treatment causing cleavage of all membrane proteins effects the anesthetic action in a small extent only. It is suggested that changes in the number of exposed SH-groups in the presence of anesthetics are related to modification of lipid phase rather than to conformational transitions in a majority of membrane proteins.

Anesthetics↗
PubMedDate not supplied

[Effect of temperature on polarity of an annular and bilayer synaptic membrane lipid].

Using fluorescent probe pyrene a study was carried out of temperature dependence of the annular and lipid bilayer polarity in synaptic membranes. Polarity of microenvironment was evaluated by a ratio of intensities of vibronic bands in pyrene fluorescence spectra at direct excitation of probe or through energy transfer from protein molecules. At the temperature range 10-50 degrees C the polarity of bilayer was shown to increase while that of annular lipid underwent biphasic changes. Above 20 degrees C polarity of the bilayer was higher than of the annular zone. From experiments on pyrene fluorescence quenching with potassium iodide the conclusion has been made that changes in polarity correlate with pyrene accessibility to water.

Animals↗
PubMedDate not supplied

[Response of the rat erythrocyte glycolytic system to hyperosmotic shrinkage].

Hyperosmotic shrinkage (adding 300 microM sucrose to isotonic medium) stimulates lactate and ATP accumulation in rat but not human erythrocytes in which ATP pool was preliminary depleted. Inhibitors of Na(+)-K(+)-2Cl(-)-cotransport, Na+/H(+)- exchange and Na(+)- pump known to be activated by hypertonic medium had no influence on volume-induced effect. EGTA (1 microM), Ca(2+)-ATPase inhibitor vanadate (200 microM) and antagonist of calmodulin R24571 (10 microM) suppressed the stimulation of glycolysis by 80 and 30%, respectively. Addition of 1 microM Ca2+ and 1 mM Ca(2+)-ionophore A23187 in Ca2+ free medium stimulated glycolysis by 20% at isotonic conditions while additional hyperosmotic shrinkage resulted in a two-fold activation. It is suggested that shrinkage regulates activity of glycolytic enzymes through the mechanism of intracellular signaling involving Ca2+.

Adenosine Triphosphate↗
PubMedDate not supplied

[Several structural aspects of the interaction of yeast hexokinase with insulin].

It has been noted that due to formation of the complex with insuline light and hear resistance of hexokinase from baker's yeast rises. Variation of luminescence parameters shows structural modification of enzyme upon complex formation. On the basis of comparison the photoinactivation data and hexokinase photolysis conclusion has been drawn that the tryptophanyl residues are not directly involved in the enzyme active site, although play an important role in supporting the specific structure.

Catalysis↗
PubMedDate not supplied

[Influence of heavy water (D20) on the conformation and UV-sensitivity of proteins].

The heavy water (D2O) has been shown to induce the conformational transitions in trypsin, chymotrypsin and pepsin. The transfer of proteins from H2O into D2O results a change in their sensitivity to UV-light. An increase in sensitivity to the irradiation at 248 nm and a decrease in sensitivity to the irradiation at 280 nm were observed. The quantum yield of chromophore photolysis (for cystyne and tryptophan) is correspondingly changed. However, although the quantum yield of sensitized reduction of cystine by solvated electrons photochemically ejected from the aromatic acid residues during irradiation at 280 nm increases instead of a rise a drop in the quantum yield of protein inactivation is registered. The data obtained are discussed in terms of importance of solvated shell for conformational stability of proteins. The solvated electrons are suggested to be transfered mainly to nonessential disulfide bridges within trypsin molecule. Rupture of these bonds does not result in trypsin inactivation.

Chymotrypsin↗
PubMedDate not supplied

[Membrane control of the photodeblocking reaction of cytochrome oxidase in the mitochondrial electron transport chain].

Hyperosmotic shrinkage and hypoosmotic swelling of the internal mitochondrial membrane decrease considerably the efficiency of the reaction of the cyanide photodissociation from the cytochrome oxidase. The osmotic effect increases after the reduction of the membrane potential by a protonophore uncoupler. This suggests that the local photochemical reaction is subject to membrane control.

Animals↗
PubMedDate not supplied

[Prevention of binding of Nile red with hydrophobic proteins and surface cuvettes using detergents].

The nile red fluorescence in solutions containing Triton X-100, human serum albumin and hexadecane in different combinations was investigated. The dye fluorescence in phosphate buffer after 2-4 min incubation strongly decreased because of the dye aggregation and was stable in a detergent solution. The intensity of nile red fluorescence in the detergent solution was not changed after the addition of equal weight concentration of albumin and increased more than 2 times after the addition of the same concentration of hexadecane. The detergent eliminated the nile red sorption by cuvette surface. It is concluded that the detergent addition increases nile red selectivity as a lipid probe in the lipid-protein systems.

Alkanes↗
PubMedDate not supplied

[Effect of a galvanic current on ischemic damage to the myocardium].

Galvanization of precardial region in rats with experimental infarction elicits considerable cardioprotective effect manifested in a decrease of the mass of necrotic tissue and in partial normalization of ion content both in the necrotic focus and outside it.

Animals↗