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V I Shvets

Publications and source records attributed to V I Shvets.

At least 73 records · Page 4Linked to original sources
PubMed1984

[Effect of phenothiazines on Ca-ATPase in the sarcoplasmic reticulum of rabbit skeletal muscles].

The phenothiazines trifluoroperazine , chlorpromazine and etmozine inhibit Ca-ATPase of the sarcoplasmic reticulum of rabbit skeletal muscles. The inhibitory action decreases in the order of trifluoroperazine greater than chlorpromazine greater than etmozine . The data are provided, indicating that the inhibitory effects of the phenothiazines on Ca-ATPase of the reticulum of the skeletal muscles are not mediated via calmodulin.

Animals↗
PubMed1983

[Interaction of tertiapin, a neurotoxin from bee venom, with calmodulin].

Tertiapin, a neurotoxin from the honey bee venom, interacts specifically with calmodulin in the presence of Ca2+. The nature of this interaction was studied using calmodulin-cAMP phosphodiesterase system. Tertiapin does not affect the unstimulated basal activity of phosphodiesterase. However, it totally inhibits the enzyme-activating capacity of calmodulin. Analysis of the dose-dependent activation of phosphodiesterase by calmodulin in the presence of tertiapin indicated that inhibition is caused by the interaction of two tertiapin molecules with calmodulin (Kd 2 microM). The data obtained suggest that the toxic effect of tertiapin in nervous tissue is mediated by blockade of calmodulin function.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1983

[Effect of lipids on the binding of calmodulin with cyclic nucleotide phosphodiesterase].

The effects of various lipids on calmodulin interaction with Ca-dependent phosphodiesterase were investigated. Palmitic, myristic and stearic acids increased the enzyme activity; the degree of the enzyme activation by calmodulin was decreased thereby. Oleic acid produced a weak activating effect on phosphodiesterase but completely blocked calmodulin action. The effects of the fatty acids under study were reversible, the activation constant was equal to 10(-4)-5 X 10(-4) M. In the presence of Ca2+ phosphoinositides and fatty acids changed the fluorescence intensity of dansyl-labelled calmodulin; in the absence of Ca2+ the lipids did not affect protein fluorescence. The lipids had no influence on the protein affinity for Ca2+. During chromatography of phosphodiesterase on calmodulin-Sepharose the enzyme was eluted from the column both in the presence of EGTA and palmitic acid. It was concluded that fatty acids prevent the formation of the calmodulin - phosphodiesterase complex. This effects may both be due to the lipid binding to the enzyme and to calmodulin.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1983

[Effect of fatty acids on calmodulin regulation of adenylate cyclase from the brain striatal system].

p3eincubation of striatal membranes for 1 hour at 37 degrees C in the presence of calmodulin results in thermal inactivation of the calmodulin-insensitive adenylate cyclase; the activity of the calmodulin-sensitive form of the enzyme remains practically unchanged. Using a membrane preparation of striatal adenylate cyclase possessing a high sensitivity to calmodulin, the effects of fatty acids on regulation of adenylate cyclase by Ca2+ and calmodulin were studied. It was found that linolenic and palmitic acids exert a weak activating effect on adenylate cyclase in the presence of Ca2+, but do not practically affect the enzyme in Ca2+ free media. Linolenic acid almost completely inhibits the activation of adenylate cyclase by calmodulin; palmitic acid has no such effect. It was assumed that unsaturated fatty acids may prevent the interaction of adenylate cyclase with calmodulin.

Adenylyl Cyclases↗
PubMed1983

[The effect of phospholipid metabolites on the structure of model membranes].

The influence of 1,2-diacylglycerols on the structure of model membranes made of phosphatidylcholine or phosphatidylcholine-phosphatidylethanolamine and phosphatidylcholine-phosphatidylinositol mixtures was studied by 31P NMR and freeze-fracture technique. It was shown that 1,2-diacylglycerols (1,2-dipalmitoyl-rac-glycerol, 1-palmitoyl-2-oleoyl-rac-glycerol, 1,2-dioleoyl-rac-glycerol and also naturally occurring 1,2-diacyl-sn-glycerols) induced in the lipid bilayer markedly curved regions with concomitant formation of the folds and intramembrane particles. This process is accompanied by the appearance of isotropic signals in the 31P NMR spectra.

Freeze Fracturing↗
PubMed1982

[Regulation of the superprecipitation of an actomyosin-like protein from the brain by glycolipids].

The optimal conditions (ionic strength, pH, Mg2+ and ATP concentrations) for nephelometric determination of the superprecipitation reaction of the actomyosin-like protein (AMLP) from ox brain cortex are described. At low ionic strength (0.1 M KCl, 200 micrograms of protein, pH 6.8, 37 degrees) MgATP (1 mM) first causes a fast (1--2 min) dissociation of AMLP with a decrease in the optical density (A620) at 620 nm and then a slow (15--20 min) true superprecipitation associated with a substantial rise of A620. EGTA (0.1 mM) moderately, i. e. by 20%, inhibits the reaction. The effects of glycolipids (total gangliosides and cerebrosides from ox brain) and phosphatidyl choline from chicken egg yolk on aggregation (without Mg-ATP), dissociation and superprecipitation of AMLP were examined. It was found that gangliosides (40 micrograms) and cerebrosides (2--80 micrograms) cause aggregation of AMLP; phosphatidylcholine (4--160 micrograms) has no effect on protein aggregation. Gangliosides within the concentration range of 0.8--4.0 micrograms do not cause AMLP aggregation but strongly inhibit superprecipitation of the protein, whereas phosphatidylcholine (40--80 micrograms) has practically no effect on the reaction intensity. A hypothesis on regulation by glycolipids on contractile proteins from brain presynaptic membranes under varying rest--excitation conditions is postulated.

Actomyosin↗
PubMed1978

[Effects of anticonvulsive substances on Na,K-ATPase from the synaptic membranes of animal brain].

The distribution pattern of marker enzymes (Na, K-ATPase, acetylcholinesterase) in three fractions of synaptic membranes (SM) of rat brain were studied. The effects of three anticonvulsive agents on Na, K-ATPase from the total fraction of rat brain SM and purified membrane preparation from ox brain were estimated by different methods. Under optimal conditions (Na/K = 5) diphenylhydantoin (DPH) at a concentration of 0,1 mM activates Na, K-ATPase from the total SM fraction only in the absence of ouabain, whereas carbamazepine and pyrroxane taken at the same concentrations have no effect on Na, K-ATPase, irrespective of the type of the enzyme assay. DPH seems to compete with ouabain. Under non-optimal ionic conditions (Na/K = 250) all the anticonvulsive substances studied inhibit Na, K-ATPase of the total SM fraction. The mixture of hydrophobic agents (propylene glycol and ethanol) used to dissolve carbamazepine inhibits Na, K-ATPase from the total SM fraction only under non-optimal conditions. The inhibiting effect of the anticonvulsive substances under study on Na, K-ATPase from the purified membrane preparations is maximal at the concentration of 10(-6) M; at higher concentrations the effect is less pronounced.

Adenosine Triphosphatases↗
PubMed1977

[Regulation of Na, K-ATPase activity by monovalent cations].

A deviation from optimal conditions of the Na, K-ATPase reaction results in a drastic change in the plot: enzyme activity versus Na/K ratio. Acidification of the medium and a decrease in Mg2+ concentration and temperature results in two peaks on the curve at Na/K ratio of about 1 and at Na/K ratio greater than 4. The enhancement of pH of the medium and increase in Mg2+ concentration decreases the first peak and increases the second one. A comparison of these curves for hydrolysis of ATP, UTP and p-nitrophenylphosphate and temperature dependence of the hydrolysis of the substrates suggest that the anomalies observed may be accounted for the Na+ effect on the K-sites or K+ effect on the Na-sites under conditions when cation-binding sites are heterogeneous.

Adenosine Triphosphatases↗