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Biomedical subjects

I D Volotovskiĭ

Publications and source records attributed to I D Volotovskiĭ.

At least 19 recordsLinked to original sources
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↗
PubMedDate not supplied

[Light inhibits tyrosine kinase in rod outer segments in vitro].

It was shown that short-term (10 min) light exposure of dark-adapted retinal rod outer segments (ROS) leads to a threefold inhibition of the tyrosine kinase activity. Tyrosine kinase activity in the ROS from bleached retinas is by 30% lower than in the dark-adapted ROS. Prolonged illumination (60 min) of the dark-adapted ROS restores the tyrosine kinase activity to the level of ROS from the bleached retinas.

Animals↗
PubMedDate not supplied

[Influence of UV-light on erythrocyte membrane structure and catalytic behaviour of membrane acetylcholine esterase].

UV-light is shown to induce the structural transitions in the erythrocyte membrane described by S-shape curves in plots of the structural response versus the irradiation dose. In contrast to the free acetylcholine esterase (AChE) UV-light acts on the membrane enzyme as a mixed inhibitor (simultaneous change in Vmax and Km). The modification of the environment structure of residual enzyme is suggested to be the main reason of this phenomenon. The effect is under the control of membrane integrity and disappears after its desintegration. Membrane AChE treated ultrasonically both prior to and after irradiation is inactivated without a Km change. The data obtained show the influence of erythrocyte membrane structure on the catalytic behaviour of membrane-bound AChE.

Acetylcholinesterase↗
PubMedDate not supplied

[The calcium-mobilizing effect of inositol-1,4,5-triphosphate in rod outer segments and disks].

The effect of inositol-1,4,5-trisphosphate (IP3) on the release of calcium ions from retinal rod discs was studied. It was shown that the release of Ca2+ from discs is an electroneutral process. The intradiscal calcium concentration during the release of the ion from the organelle decreases by 1 mM. It was found that the IP3-dependent release of Ca2+ ions from discs is activated by guanosine triphosphate and beta gamma-transducin. The increase in calcium concentration in the medium also activates the IP3-dependent release of Ca2+ ions from discs, which probably is due to the stimulation of phospholipase C. It is suggested that the functional role of the release of ions in related not to phototransduction but to slow regulatory and adaptation processes in the photoreceptor cell.

Calcium↗
PubMedDate not supplied

[Role of secondary phosphoinositide messengers in storage of Ca2+ ions in retinal rod microsomes].

The influence of guanosine-5'-triphosphate and secondary messengers forming in rod outer segment membranes during light-stimulated hydrolysis of phosphoinositides on the ATP-dependent Ca(2+)-uptake in microsomes of the retinal rod inner segment was studied. The water-soluble cytoplasmic components of the retinal rod outer segment were shown to be capable of stimulating the Ca(2+)-pump of endoplasmic reticulum after light illumination. This process is likely to proceed with the participation of 1,2-diacylglycerol localized in microsome membrane.

Adenosine Triphosphate↗
PubMedDate not supplied

[Isolation and identification of tyrosine kinase from the cytosolic fraction of bovine retinal rod outer segments].

It was shown that the cytosol fraction of bovine retinal rod outer segments contains three forms of tyrosine kinase. One of them was purified 171-fold to attain a specific activity of 1.6 nmol/min per mg protein. The isolated protein had a molecular weight of about 54,000 in SDS electrophoresis. It was shown that this protein is a tyrosine-specific protein kinase, capable of autophosphorylation at the tyrosine residues and restoration of kinase activity upon denaturation-renaturation.

Animals↗
PubMedDate not supplied

[The role of intracellular Ca(2+) pools in the regulation of protoplast volume. Effect of red light on the Ca(2+) mobilization in cytoplasm of Arabidopsis cells].

The changes in cytosol Ca2+ concentration associated with the shrinkage of Arabidopsis cells induced by the inhibitor of Ca(2+)-ATPase, cyclopiazonic acid and the Ca2+ ionophore ionomycin were monitored using the fluorescence of Ca(2+)-sensitive probe chlortetracycline hydrochloride. It was found that these compounds elicited a substantial decrease in fluorescence intensity closely associated with Ca(2+)-release from the intracellular stores to the cytoplasm. The release of Ca2+ from the intracellular depots was accompanied by decrease of plant cell volume. Thapsigargin and 2,5'-ditert-butyl-1,4-benzohydroquinone (highly specific inhibitors of Ca(2+)-ATPase of endoplasmic reticulum) resulted in much weaker changes than cyclopiazonic acid did. It was also found with the help of the same technique that red light (lambda = 660 nm) illumination induced a similar Ca2+ release from the intracellular stores. Moreover, the amplitudes of light-induced fluorescence responses registered in mutant plants differing in the content of phytochrome A (phyAOX) and phytochrome B (phyBOX) were much higher than those registered in wild-type of Arabidopsis.

Arabidopsis↗
PubMedDate not supplied

[A model of the dynamics of intracellular calcium based on refined kinetics of inhibiting the inositol-1,4,5-trisphoshate-sensitive calcium channel].

Several new models of intracellular calcium dynamics based on refined inositol-1,4,5-triphosphate-sensitive calcium channel kinetics were studied. The refined kinetic schemes take into account that a cytosolic calcium cannot inhibit inositol-1,4,5-triphosphate receptors when they are bound to inositol-1,4,5-triphosphate. The mathematical analysis of intracellular calcium dynamics based on one of these schemes allowed us to show how different types of Ca response to extracellular stimuli, such as excitability, oscillations, sustained elevation of Ca and frequency encoding can arise with a reasonably good fit to experimental data.

Calcium↗
PubMedDate not supplied

[A role of protein kinase C in signal reactions in outer segments of the bovine retinal rods].

The effect of modulators of protein kinase C activity on Ca2+ translocation in dark-adapted and bleached retinal rod outer segments (ROS) was studied. The activators (1,2-diacyl glycerol and phorbol-12-myristate-13-acetate) and the inhibitor (chelerythrine chloride) of protein kinase C were shown to stimulate and inhibit the ATP-dependent Ca(2+)-uptake in dark-adapted retinal ROS, correspondingly. Apparently, this action is due to the influence of protein kinase C on Ca(2+)-ATPase activity in these vesicular structures. No involvement of modulators of protein kinase C activity on ATP-dependent Ca(2+)-uptake in bleached retinal ROS was found. The influence of protein kinase C on Ca(2+)-release from retinal ROS was observed. It was shown that the activators and inhibitors of protein kinase C increased the efficiency of this process both in dark-adapted and bleached retinal ROS. The mechanisms of action of the protein kinase C activity modulators on the Ca(2+)-uptake and Ca(2+)-release in retinal ROS are discussed.

Adenosine Triphosphate↗
PubMedDate not supplied

[Phytochrome regulation of the plant phospholipase activity].

The interaction of external stimuli with receptors of plant cell surface can activate the enzymes of lipid metabolism such as phospholipases C and D. The products of the catalysis, i.e., posphoinositide metabolites, phosphatidic acid, fatty acids, etc. participate in signal transduction as secondary messengers related to numerous regulatory processes. One of the physiologically important factors of regulatory control in plants is light, which plays the crucial role in triggering the cellular signaling network. This review presents the information on phospholipid signaling in plants, which is connected with light transduction processes occurring with the involvement of the plant regulatory pigment phytochrome.

Enzyme Activation↗