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S V Konev

Publications and source records attributed to S V Konev.

At least 91 records · Page 5Linked to original sources
PubMedDate not supplied

[Comparative study of membrane-bound acetylcholinesterase in guinea pig and rabbit brains].

As a result of kinetic studies on acetylcholinesterase inhibition by allosteric effector d-tubocurarine it was shown that interaction between modifier and catalytic sites of rabbit and guinea pig acetylcholinesterase are different for these two species. Judging by the inhibition curves and sensitivity of d-tubocurarine theses differences involve enzyme microenvironment in the membrane. Addition to 7,15-10-6 M d-tubocurarune to solubilized preparation led to a significant fall in the value of Hill coefficient for enzyme-substrate interaction. This may be indicative of the changes in the conformational state of the enzyme after its dissociation from the membrane, i. e. of the membrane structure role in the formation of the structural and functional enzyme properties.

Acetylcholinesterase↗
PubMedDate not supplied

[Structural rearrangements in synaptosomal membranes of the brain].

Studies were carried out on structural state of synaptosomes and synaptic plasma membranes from brain of rats and guinea pigs at 5--50C. In membranes from guinea pig brain there were two breaks at 8 and at 18--20C in the curves of temperature dependence of light scattering. At the same temperatures adhesive properties of membranes had changed in jump-like manner when evaluating the degree of aggregation at pH4. The degree of aggregation in membranes from rat brain as well as rate of solubilization by 0.2% SDS (stoped-flow measurements) are characterized by single break point at 27C in Arrhenius curves. The breaks were interpreted as phase transitions with membrane surface involvement. Chlorpromazine and tetraciane (10(4)--10(3) M) abolished or modified these transitions. Because the number of negative charges and tryptophanyl and ANS fluorescence parameters were unchanged it was suggested that redistribution of ionogenic and hydrophobic goups took place at membrane surface during phase transitions.

Animals↗
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[Osmotic regulation of the sodium pump in rat brain synaptosomes].

Effect of medium osmolarity on 3H-ouabain binding and the rate of ouabain-sensitive 86Rb+ transport in the rat brain synaptosomes was studied. A decrease in tonicity to 230 mOsm increases both parameters indicating the activation of the sodium pump upon synaptosome swelling. The effect is retained in the absence of inside-oriented Na+ gradient, i. e. a rise in Na(in) is not responsible for hypoosmotic activation. Colchicine (5mM) decreased and cytochalasin B (40 microM) increased the ouabain binding. In the presence of cytochalasin B the inhibition of binding observed under hypotonic conditions was shifted to higher osmolarity values. It is suggested that volume regulation of the sodium pump is controlled by the cytoskeleton elements.

Animals↗
PubMedDate not supplied

Volume-dependent regulation of ion carriers in human and rat erythrocytes: role of cytoskeleton and protein phosphorylation.

This study examines the effect of heat-induced cytoskeleton transitions and phosphoprotein phosphatase inhibitors on the activity of shrinkage-induced Na+, K+, 2Cl- cotransport and Na+/H+ exchange in rat erythrocytes and swelling-induced K+, Cl- cotransport in human and rat blood cells. Preincubation of human and rat erythrocytes at 49 degrees C drastically activated K+, Cl- cotransport and completely (rat) or partly (human) abolished its volume-dependent regulation. The same procedure did not affect basal activity of Na+, K+, 2Cl- cotransport but completely abolished its activation by shrinkage thus suggesting the involvement of a thermosensitive element of cytoskeleton network in the volume-dependent regulation of cotransporters. Both the shrinkage- and electrochemical proton gradient-induced Na+/H+ exchange was inhibited by the heat treatment to the same extent (50-70%), thus indicating the different signaling pathways involved in the activation of Na+, K+, 2Cl- cotransport and Na+/H+ exchange by cell shrinkage. This suggestion is in accordance with data on the different kinetics of volume-dependent activation and inactivation of these carriers as well as on their sensitivity to medium osmolality. Both swelling- and heat-induced increments of K+, Cl- cotransport activity were diminished by inhibitors of phosphoprotein phosphatases (okadaic acid and calyculin). In rat erythrocytes these compounds potentiate shrinkage-induced Na+/H+ exchange. On the contrary, neither basal nor shrinkage-induced Na+, K+, 2Cl- cotransport was affected by these compounds. Our results indicate a key role of cytoskeleton network in volume-dependent activation of K+, Cl- and Na+, K+, 2Cl- cotransport and the involvement of protein phosphorylation-dephosphorylation cycle in regulation of the activity of K+, Cl- cotransport and Na+/H+ exchange.

Animals↗
PubMedDate not supplied

[Effect of osmolar concentration of culture media on exocytosis in isolated presynaptic nerve endings of rat brain ].

The effect of hypotonic and hypertonic shock on exocytosis in rat brain synaptosomes was studied using the fluorescent dye acridine orange. It was shown that an increase in medium osmolarity leads to calcium-independent exocytosis. The response of the probe was directly proportional to the amount of osmolithes added. A decrease in medium osmolarity to 230 mOsm led to an increase of acridine orange fluorescence, which is comparable with exocytosis occurring by the action of 15 mM KCl. This effect was independent of calcium concentration. It is assumed that, under hypotonic shock, part of neurotransmitters are released from the vesicular pool.

Acridine Orange↗
PubMedDate not supplied

[Influence of calcium ionophore A23187 on neurotransmitter release in rat brain synaptosomes].

The effect of calcium ionophore A23187 on the release of nonmetabolizable glutamate analogues [3H]D-aspartate and the exocytosis registered by fluorescent dyes in synaptosomes was investigated. It was shown that A23187 is able to induce neurotransmitter release both in calcium-containing and calcium-free medium, the effect in the latter case being more pronounced. Calcium ionophore is able to induce exocytosis registered by acridine orange and FM 2-10. The influence of A23187 on the fluorescence of acridine orange was mainly calcium-independent, whereas the change in the fluorescence of FM 2-10 was calcium-dependent. It was suggested that the calcium-independent increase in acridine orange fluorescence is related to the dissipation of pH gradient in synaptic vesicles. Probably, the calcium-independent release of D-aspartate is also associated with the dissipation of pH gradient and subsequent leakage of neurotransmitters.

Animals↗
PubMedDate not supplied

[The dynamics of the domains of the IP3-binding site of the inositol-1,4,5-triphosphate-sensitive calcium channel, induced by inositol-1,4,5-triphosphate and calcium].

The dynamics of the inositol-1,4,5-triphosphate-sensitive calcium channel after binding of inositol-1,4,5-triphosphate and Ca2+ was analyzed by the Monte Carlo minimization technique. It was shown that the binding of Ca2+ with the unliganded receptor (channel) leads to a turning of the beta-sheet domain relative to the alpha-helical domain with the formation of the receptor conformation that is open for the entry of ions into the cytoplasmic channel vestibule, sterically closed for their passage through the vestibule in the part adjacent to the alpha-helical domains, and unfavourable for subsequent binding of inositol-1,4,5-triphosphate with the receptor. When both co-agonists bind to the receptor, the structure rearrangements induced eliminate both these steric obstacles for the passage of ions through the IP3-binding domain: one at the entrance of the channel cytoplasmic vestibule and the other that is placed deeper in the vestibule near the alpha-domains. The role of the dynamics of the receptor binding core in the IP3-sensitive channel gating is discussed.

Animals↗
PubMedDate not supplied

[Lanthanides induce neurotransmitter release from the vesicular pool in rat brain synaptosomes].

The influence of lanthanoids on exocytosis was investigated. It was shown that gadolinium increases the spontaneous release of the glutamate nonmetabolizing analogue [3H]D-aspartate. It was established using the fluorescent dye acridine orange that gadolinium and lanthanum induce exocytosis. The effect was dose-dependent and was maximum at 300 microM Gd3+. The exocytosis induced by gadolinium was calcium-independent. It is suggested that lanthanides induce a vesicular release of neurotransmitters by the mechanisms common for all polyvalent cations.

Animals↗
PubMedDate not supplied

[Structural-membrane regulation of intercellular contacts of low-molecular weight peptides].

It has been shown by microelectrode techniques and microcytofluorometry that fragments of the substance P and L-vasopressin--low molecular physiologically active peptides of wide regulatory action--bind to the receptors on the surface of plasma membranes outside the region of high permeable gap contact in unimolar concentrations and cause an increase in the rate of intracellular diffusion exchange of inorganic ions and fluorescein molecules in the salivary gland cells of Drosophila larva. The growth of intracellular contact permeability induced by low peptide concentrations is blocked by carbodiimide--a reagent cross-linking the membrane proteins. On the basis of the previous data it is suggested that the functions of intracellular contacts are regulated by the distant action mechanism involving the generalized structural rearrangements of plasma membranes.

Animals↗
PubMedDate not supplied

[Structural reorganization of the brain synaptic membranes and aging].

Results of the authors' studies and data from literature underlie the development of a notion on structural rearrangement of the brain synaptic membranes in aging. Reorganization results in conformational changes of the key membrane-bound enzymes and receptors underlying the age alterations of neuronal functions.

Aging↗
PubMedDate not supplied

[Interaction of bromophenol blue with serum albumin: criteria for using dyes for assessing the state and quantity of protein].

The optical properties of the complexes of the pH-dependent dye bromophenol blue (BPB) with human serum albumin were investigated by the spectrophotometric method. The solvatochromic longwave displacement of bound BPB-2 absorption and BPB-1/BPB-2 redistribution were shown to form the optical signal of complexes. Because of the distortion of the bound BPB-2 signal its quantity was determined as delta A630 = A630 - A660 and the use of lambda max as structural parameter was limited to low pH less than or equal to 3. The conclusion was made that BPB is inapplicable as a structural probe on account of low structural dependence of delta A630 and pH-limitation of lambda max used. The maximal absorption delta Amax = Amax - A660 and its structural independence were obtained in the region of 70-100% occupation of the dye-binding centers of the protein. It is the optimal conditions for the quantitative determination of protein. After maximal dye binding (15-16 molecules of BPB per 1 molecule of albumin) the aggregation and precipitation of the complexes occurred.

Bromphenol Blue↗
PubMedDate not supplied

[Structural changes in cell nuclei in the physiologic pH range].

Fluorescence of the suspension of cell nuclei from rat liver was investigated under neutral pH range. The pH decrease from 7 to 5 causes the quenching of protein fluorescence of nuclei and leads to an increase of the polarization degree of the fluorescence. Buffering properties of the nuclei in this range were detected. The use of 1-anilino-8-naphthalenesulfonate as the fluorescent probe permits to find the changes of nuclei surface properties with increasing the proton concentration in the solution. Circular dichroism spectra of nuclei were shown to depend on the pH solution too. It was suggested that structure state of the nuclei depends on the pH solution. The structural changes are reversible in the physiological pH range and were concluded to be in the envelope and chromatin of the nuclei. The role of histidine residues of nuclear proteins in the initiation of the structure changes was discussed. It was supposed that structure changes of the nuclei in the physiological pH range have an essential functional role.

Animals↗
PubMedDate not supplied

[Effect of cross-linking agents on electron transport and proton transfer in the mitochondrial respiratory chain].

The effect of protein cross-linkage on proton translocation and electron transport in mitochondria respiratory chain was studied. Dimethylsuberimidate (1 mM) or dicyclohexyl carbodiimide (50 g/ml) inhibit proton translocation with concomitant stimulation of respiration. It is concluded that the definite level of dynamic mobility of proteins is needed for proton translocation.

Animals↗