[A biophysical approach to the investigation of physiological processes]. / Biofizicheskii podkhod k issledovaniiu fiziologicheskikh protsessov.

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 role of membrane protein SH-groups in regulating ouabain and bungarotoxin binding in the crab nerve]. / Rol' SH-grupp membrannykh belkov v reguliatsii sviazyvaniia ouabaina i bungarotoksina v nerve kraba.

Structural alterations in plasma membrane proteins promoting transition from inactive forms of Na-pump and acetylcholine receptor to active ones during propagation of rhythmic excitation were examined. The role of SH-groups of the nerve (fibre and glial cell) plasma membrane proteins in providing regulation of the pump and receptor state by generalized alterations in the membrane structure is discussed.

[Levels of free fatty acids and calcium absorption in giant squid axons at rest and upon stimulation]. / Soderzhanie svobodnykh zhirnykh kislot i pogloshchenie Ca v gigantskom aksone kal'mara v pokoe i pri vozbuzhdenii.

Nine free fatty acids (FFA) were discovered in the squid axons at rest: 12:0, 14:0, 15:0, 16:0, 16:1, 18:0, 18:1, 20:3, 20:4. The relative amount of FFA equaled 14.1 micrograms per mg of lipids. Stimulation of nervous conductors decreased the amount of acids--14:0, 15:0, 16:1, 20:3. Simultaneously a considerable increase of the content of 20:4 was observed and three new fatty acids 20:0, 20:1, 22:2 appeared. The content of FFA increased to 27.2 micrograms/mg of lipids. Calcium absorption in the squid axons was equal to 23 nmol/g, but under stimulation this parameter increased to 37 nmol/g. Exogenous fatty acids brought about also an increase of calcium absorption. The accumulation of FFA under excitation was suggested to be the result of the increase of phosphoinositides content and related to the regulation of Ca transport.

[Distribution of calcium in unmyelinated and myelinated nerve trunks]. / Raspredelenie kal'tsii v nemielinovykh i mielinovykh nervnykh stvolakh.

Exchange of Ca2+ between non-myelinated and myelinated nerves at the surface of axoglial complex of the nerve seems to be one of the extracellular systems controlling the Ca2+ level.

[Effect of changes in temperature on the cholesterol and phospholipid ratio in nerve fibers of the frog and squid]. / Vliianie izmenenii temperatury na sootnoshenie kholesterina i fosfolipidov v nervnykh provodnikakh liagushki i kal'mara.

The character of changes in molar correlation of cholesterol and phospholipids has been studied at different functional states in frog myelinic nerve and squid nonmyelinic nerve trunk. The correlation cholesterol/phospholipid (C/P) found for both nerves in rest increases at temperature 38 degrees C. The electrical stimulation on the background of higher temperature action leads to unequal shift of C/P: the increase compared with the rest in frog and decrease in squid.

[Binding of 3H-bungarotoxin by nerve trunks of the frog during excitatory conduction]. / Sviazyvanie 3H-bungarotoksina nervnymi stvolami liagushki pri provedenii vozbuzhdeniia.

In the frog nerve, 3H-bungarotoxin and 3H-acetylcholine binding increased whereas the acetylcholinesterase activity decreased in rhythmic stimulation. The enhancement of 3H-bungarotoxin binding to nerve during the rhythmic stimulation seems to stem from transformation of "inactive" forms of acetylcholine receptor of glial membrane to "active" ones.

[Changes in the permeability of nerve fiber membranes during the initiation of lipid peroxidation]. / Izmenenie pronitsaemosti membran nervnykh volokon v usloviiakh initsiatsii perekisnogo okisleniia lipidov.

The role of lipid oxidation in the mechanism of ion transport was investigated. During initiation of lipid oxidation by actin "Fe2+--ascorbic acid" in the crab nerve 45Ca and 22Na accumulation and level of lipid oxidation were increased, but electric stimulation of the nerve greatly changed ion accumulation. Increased Na+Ca2+ accumulation during the initiation of lipid oxidation is explained not only by changes in the lipid phase of excitable membranes but by the effects of rhythmic excitation on potential-dependent channels.

[Calcium ion binding in somatic nerves during conduction of rhythmic excitation]. / Sviazyvanie ionov kal'tsiia v somaticheskikh nervakh pri provedenii ritmicheskogo vozbuzhdeniia.

Increase of Ca entry upon excitation depended on stimulation frequency and the types of nerves in crab, frog and squid. The amount of absorbed Ca was high in myelinated nerves whereas the velocity of absorption was higher in nonmyelinated nerves. The maximal level of Ca entry during rhythmic excitation was observed in the frog nerve. The data obtained suggest a mechanism of Ca entry in somatic nerves during rhythmic excitation.

[Proton transport during nerve stimulation]. / Transport protona v nerve pri vozbuzhdenii.

A decrease of external pH during rhythmic excitation of the nerve of frog and squid was investigated. The level of pH was dependent on frequency excitation, concentration of sodium potassium and hydrogen ions was changed after ouabain, 2,4-dinitrophenol, tetraethylammonium and tetrodotoxin effect. The mechanism of proton transport was discussed in relation to Na-channel function.

[Dependence of calcium influx in squid axons on rhythmic excitation frequency]. / Pogloshchenie kal'tsiia nervnymi stvolami kal'mara v zavisimosti ot chastoty ritmicheskogo vozbuzhdeniia.

Calcium-45 influx was measured in squid axons during excitation. Different stimulation frequencies changed this influx and general concentration of calcium ions in squid axons. The maximum influx was recorded at the frequency 10 imp/s and 30 imp/s. Calcium influx and general content of calcium ions in axoplasma during excitation was independent of the number of excitation impulses. The role of sodium and calcium channels during excitation is discussed.

[Mechanism of activation of Na,K-ATPase in nerve fibers during rhythmic excitation]. / O mekhanizme aktivatsii Na,K-ATFazy v nervnykh voloknakh pri provedenii ritmicheskogo vozbuzhdeniia.

The activation mechanism of Na,K-ATPase in nerve fibres after rhythmic excitation was studied. 3H-ouabain binding to a nerve was found to depend on the frequency of rhythmic excitation. The maximum of 3H-ouabain binding to a nerve crab was at 10 imp/sec. Rhythmic excitation was found not to change Na,K-ATPase affinity to ouabain, but appeared to increase the concentration of ouabain-sensitive sites in the nerve membrane. Transformation of inactive forms of the enzyme into active ones was supposed to be a possible cause of greater 3H-ouabain binding to the nerve during rhythmic exitation.

[Regulation of Na, K-ATPase activity in nerves during propagation of rhythmic excitation]. / Reguliatsii aktivnosti Na, K-ATFazy v nerve pri provedenii ritmicheskogo vozbuzhdeniia.

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.