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Biomedical subjects

S V Konev

Publications and source records attributed to S V Konev.

At least 55 records · Page 3Linked to original sources
PubMed1980

[Membrane regulation of brain Na,K-ATPase inhibition by calcium ions].

In contrast to the purified enzyme. Na, K-ATPase from intact synaptic membranes is inhibited by Ca2+ according to a biphase pattern at Ca2+ concentrations of 10(-6) to 10(-3) M. The membrane damage after three washings with bidistilled water results in elimination of low cocentration phase. Recombination of the sediment and the supernatant restores the initial shape of the inhibition curve. Dithiothreitol greatly increases the inhibition by low Ca concentrations. This effect is absent in the purified enzyme preparation and is considerably reduced after the membrane damage. Recombination restores the dithiothreitol effect. It is suggested that the sensitivity of membrane Na,K-ATPase to low concentrations of Ca2+ is controlled by the components (most likely, peripheral proteins), which are loosely bound to the membrane, this process being dependent on the degree of the SH-group reduction.

Animals↗
PubMed1980

[Mechanisms of protease-induced cell aggregation. II. The effect of trypsin on the structural state of the plasma membrane of chick embryo fibroblasts].

Using freeze-etching, registration of kinetics of tryptophane phosphorescence quenching at room temperature, and measuring the cell electrophoretic mobility, a study has been made of the influence of a short-term treatment (5-10 min) with a low concentration of trypsin (2-100 microgram/ml) on the chick embryo fibroblasts removed from the monolayer with EDTA and suspended in the Henks solution. It is shown that trypsin induces a structural rearrangement of the plasma membrane which is manifested in clustering intramembrane globular particles. Trypsin-induced rearrangement of the plasma membrane is accompanied by an increase in the negative charge of the cell surface. The results obtained by the phosphorescence method show that structural rearrangements involve alongside with plasma membranes the majority of intracellular proteins.

Animals↗
PubMed1980

[Study of the mechanisms of protease-induced cell aggregation. I. Effect of trypsin on the aggregating capacity of chick embryo fibroblasts].

The administration of trypsin (1-100 mcg/ml) to the chick embryo fibroblast suspension, removed from the monolayer by means of EDTA, causes a pronounced aggregation of the cells. The aggregation completes within a few minutes and occurs in two steps. On the first step of the trypsin-induced aggregation, the amount of aggregating cells, grows rather slowly and monotonously, whereas on the second step, a sharp and non-linear acceleration of the aggregation process is observed. The data presented favour an assumption that the second stage of the fibroblast aggregation may be due to a structural rearrangement of cytoplasmic membranes that involves a splitting of a small, critical number of peptide bonds of cell surface proteins.

Animals↗
PubMed1979

[Temperature-dependent structural rearrangements in the cytoplasmic membranes of Escherichia coli cells].

By the freeze-etching method, in has been shown that E. coli plasma membranes undergo a structural transition in the range of temperatures within 0 and 20 degrees C which could be observed as redistribution of intramembrane particles with free-zone formation. The onset of temperature interval of this transition (20 degrees) well correlate with the break in the Arrhenius curves characterizing the cell membrane permeability for free nucleotides and for respiration intensity.

Cell Membrane↗
PubMed1978

[Mechanism of brain Na,K-ATPase activation by adrenaline].

Norepinephrine stimulates Na, K-ATPase from rat brain homogenates at concentrations of 10(-4)--10(-5) and 10(-7)--10(-8) M. A low concentration maximum is observed after 48 hrs of incubation at -20 degrees C and is not changed by the addition of alpha-tocopherol, glycerol and MAO inhibitor ipraside. The maximum observed at the mediator concentration equal to 10(-4)--10(-5) M is eliminated after treatment with EGTA. At all concentrations of norepinephrine the enzyme stimulation is removed by the alpha-adrenoblocker phentolamine. The activated enzyme reveals lower sensitivity to Ca2+ induced inhibition. The role of Ca2+ and conformational state of the membranes in the realization of the remote effect on the adrenoreceptor-Na, K-ATPase system is discussed.

Animals↗
PubMed1978

[Effect of cAMP on the structural and functional properties of the erythrocytes].

Cyclic AMP inhibits the anion transport and decreases the osmotic resistance and deformability of erythrocytes with the normal level of ATP. With ATP-depleted erythrocytes cAMP exerted the opposite effects on the corresponding characteristics. In addition, it was observed that the pattern of cAMP effect on the cell form depends on the basal level of ATP. These effects may be associated with the two types of structural rearrangements of erythrocyte membranes established earlier: a cooperative transition not connected with protein kinase system, and a non-cooperative one caused by protein phosphorilation.

Biological Transport, Active↗
PubMed1978

[Effect of the critical fragmentation of erythrocyte membranes].

After sonification of erythrocyte membranes, some changes were registered in these including a loss of their ability to structural rearrangements caused by cAMP (ESR-spectroscopy and luminescence data), an increase in cAMP binding and aggregation of intramembrane particles (freeze-fracture data). These findings suggest a non-identity of the structural organization in membranes and in their fragments. The cooperative nature of membrane structural modification at ultrasonic fragmentation is shown.

Cell Fractionation↗
PubMed1978

[Effect of microorganism population density on protein metabolism].

The influence of population density of yeasts Candida utilis on the protein synthesis was investigated using 14C-L-leucine. After 15--30 minutes of exposure in 14C-L-leucine, the isotope incorporation into the protein was negligible at subcritical density of cell suspension (10(4)--5X10(5) cells/mm3), but then beginning from the 10(6) cells/mm3 density, a sharp activation of incorporation was observed. With increased incubation time up to 60--120 minutes for high density suspension (more than 10(6) cells/mm3), the degradation of newly-synthesized protein is the more the higher the cell concentrations and incubation time. The changes of protein synthesis intensity seem to be not associated with the influence of such traditional factors as nutrient medium exhaustion, toxicosis, change of hydrogen ion concentration and oxygen deficiency. It is suggested that structurally functional shifts in cells initiated by intercellular interactions may underlie the dependence of protein synthesis on the suspension culture density.

Aerobiosis↗
PubMed1977

The structural transitions of erythrocyte membranes induced by cyclic AMP.

The generalized structural transitions of erythrocyte membranes induced by cyclic AMP were registered by ESR, fluorescence, freeze-fracture and circular dichroism methods. Two transitions different in nature were revealed. One, which arises at 10-(11)--10-(10) M cyclic AMP, is cooperative and may be considered as a consequence of interaction of cyclic AMP with a receptor. It was calculated that a structural rearrangement in one erythrocyte ghost is induced by three cyclic AMP molecules. As a result of it the membranes are "loosened". The other transition arises at 10-(10)--10-(8) M cyclic AMP and depends on the activity of the protein kinase system. This transition was shown to be non-cooperative and due to phosphorylation of membranous proteins. During this rearrangement the membranes are "stiffened". Both transitions were demonstrated to relate to the membrane integrity.

Circular Dichroism↗
PubMed1977

[Structural lability of membranes].

The present-day state of the problem of membrane structural lability is reviewed. The ways of initiation and the nature of structural rearrangements, the mechanisms of generalization of local structural perturbations in membranes and the effects of rearrangements on the functional activity of organoids and cells are discussed.

Cell Physiological Phenomena↗
PubMed1976

[Age changes in the allosteric properties of brain acetylcholinesterase].

d-tubocurarine and procaine have been shown to inhibit the acetylcholinesterase of rat brain homogenate by coupled and non-competitive mechanism respectively, which suggests binding to enzyme peripheral sites. Judging by values of Hill coefficient negative cooperativity in interactions between procaine sites is characteristic of all ages (n=0,8 and 0,53 for young and old rats) while such cooperativity for d-tubocurarine sites appears only at old age (n=1 and 0,6 for young and old animals). Values of Ki changed in opposite directions for each of the substances with aging. Modification of the enzyme membrane microenvironment with aging was suggested as a reason for differences in enzyme allosteric behaviour.

Aging↗