Biomedical subjects
Publications and source records attributed to G E Fedorov.
The prostaglandin F2 alpha (in concentration 1,4 or 14 microM) has been shown to induce the current fluctuations across the bilayers under the action on the planar bilayer membranes from the soya total phospholipids. The current fluctuations depend on the potential, their number expresses indistinctly and corresponds to the conductivity jumps across the bilayer about 5 pSm.
The effect of C35-dolichol on black planar bilayers from mixture of azolectin and cholesterol has been studied. C35-dolichol in concentration of about 10(-6) g/ml has been found to raise the bilayer conductivity, inducing current jumps with unclearly expressed conductivity level of 0.4-0.5 nSm. According to the data of the first and third harmonic during the several minutes after C35-dolichol addition along one side of the bilayer the capacity of the membranes and transversal module Young increase. It is supposed that dolichols induce the nonbilayer structure in membranes that is the basis for their transfer of oligosaccharides blocks across the membranes of Golgi apparatus.
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The changes of Na, K-ATPase activity of the isolated squid, crab, frog, and rat nerves depended on the stimulation frequency: at the frequency specific for each nerve the maximum deviation from initial resting level occurred. During a certain stimulation the maximum deviation of SH-group content and Na/K ratio as well as of Na, K-ATPase activity developed while the level of acetylcholine esterase activity (AEA) remained at its minimum. The data obtained suggest the mechanism of Na, K-ATPase activity in nerve under rhythmic propagation of excitation. In the resting nerve the minimum level of the acetylcholine concentration is kept because of the AEA. Under stimulation the membrane depolarization induces changes of the protein conformation suppressing the AEA. This results in an increase of the acetylcholine concentration in the nerve which leads to an increase of Na+ influx and K+ efflux. The changes of Na/K ratio in the nerve activate the transport ATPase.
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It was shown that understanding the mechanism of rhythmic excitation in cells and tissues requires the combination of physiological and biophysical approaches. Systemic studies of changes in the physicochemical characteristics of the object were carried out by a protocol that takes into account the mode of rhythmic excitation and the functional sate of the object being studied. The validity of the approach was proved in studies of rhythmic excitation in somatic nonmyelinic and myelinic nerves, and in model systems. The approach can be used in studies of many physiological processes.
The dependence of the diffusion current on the depth of immersion of the electrode was studied by polarography using an open platinum electrode. As the electrode was brought from the depth of the liquid phase to its surface, an increase in the current under aerobic conditions was observed, due to diffusion of oxygen through the interface. The formation of lipid monolayers of phosphatidylcholine, stearic acid, hexadecanol, octadecanol, eicosanol, and docosanol on the water surface led to a decrease in diffusion current; the effect being most pronounced at a minimal depth of immersion of the electrode. The maximum value of the relative decrease in diffusion current R was obtained for docosanol monolaers. It was shown that the R value increases with increasing surface pressure in monolayers of phosphatidylcholine and stearic acid. It is assumed that the decrease in diffusion flow of O2 in the presence of monolayers is caused by the formation of an energy barrier that prevents the sorption of O2, which is related to the presence of hydrocarbon chains weakly interacting with oxygen.
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The effect of some local anesthetics on conductance of bilayer lipid membranes made of egg yolk lecithin has been studied. Low concentrations of anesthetics were shown to gradually increase the integral conductance of bilayers. This effect is connected with the protonophore activity of the tested anesthetics and it caused the stabilization of the bilayers. High concentrations of anesthetics caused destabilization of membranes and formed zones of nonselective increased conductance.
Current fluctuations in black bilayers from phosphatidyl ethanolamine obtained from egg lecithin were registered in the temperature region of the main phase transition of this phospholipid and the bilayer--hexagonal phase transition about 35 degrees; they correspond to the conductivity changes of hundreds of pSm. This transition takes place in the same temperature region as shown by 31P-NMR and depolarization of light-scattering method in phosphatidyl ethanolamine multilamellar liposomes. The scheme of bilayer transformation into hexagonal phase in the temperature region of lipid polymorphic transition is discussed.
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