[Decrease in the electrogenic contribution of Na,K-ATPase and resting membrane potential as a possible mechanism of calcium ion accumulation in filaments of the rat musculus soleus subjected to the short-term gravity unloading].

After three days of hind limb unloading, the depolarization of muscle fibers from -71.0 +/- 0.5 mV to -66.

[Effect of nicotine on electrogenic contribution of the Na,K-ATPase isoforms and contractile characteristics of the rat skeletal muscle].

Nicotine in concentration 100 nM which corresponds to concentration of nicotine circulating in tobacco smokes induced hyperpolarization by approximately 4 mV of muscle fibres of the rat isolated diaphragm, as well as an increase in amplitude and acceleration of action potentials. Similar hyperpolarization was induced by nicotine and acetylcholine in the rat soleus muscle. In this muscle, the hyperpolarization developed more slowly than in diaphragm revealing initial slight depolarization.

[Effects of marinobufagenin on electrophysiological and contractile characteristics of the rat diaphragm].

Effects of Na+,K(+)-ATPase inhibitor: marinobufagenin, on contractile and electric characteristics of isolated rat diaphragm were studied for the first time. Marinobufagenin induced dose-dependent (EC50 = 0.3 +/- 0.

[Role of the alpha2-isoform of Na+, K(+)-ATPase in the positive inotropic effect of ouabain and marinobufagenin in the rat diaphragm].

It was shown that the specific inhibitors of Na+, K(+)-ATPase ouabain and marinobufagenin increased the contraction of an isolated rat diaphragm (positive inotropic effect) by up to approximately 15% in a dose-dependent manner with EC50 = 1.2 +/- 0.3 and 0.

[Analysis of the interaction between nicotinic acetylcholine receptor and Na+,K(+)-ATPase in the rat skeletal muscle and the Torpedo electric organ membrane preparation].

The interaction between the nicotinic acetylcholine receptor and Na+,K(+)-ATPase described previously was further studied in isolated rat diaphragm and in a membrane preparation of Torpedo californica electric organ. Three specific agonists of the nicotinic receptor: acetylcholine, nicotine and carbamylcholine (100 nmol/L each), all hyperpolarized the non-synaptic membranes of muscle fibers by up to 4 mV. Competitive antagonists of nicotinic acetylcholine receptor, d-tubocurarine (2 mcmol/L) or alpha-bungarotoxin (5 nmol/L) completely blocked the acetylcholine-induced hyperpolarization indicating that the effect requires binding of the agonists to their specific sites.

On the functional interaction between nicotinic acetylcholine receptor and Na+,K+-ATPase.

Previous studies have shown that nanomolar acetylcholine (ACh) produces a 2 to 4-mV hyperpolarization of skeletal muscle fibers putatively due to Na(+),K(+)-ATPase activation. The present study elucidates the involvement of the nicotinic ACh receptor (nAChR) and of Na(+),K(+)-ATPase isoform(s) in ACh-induced hyperpolarization of rat diaphragm muscle fibers. A variety of ligands of specific binding sites of nAChR and Na(+),K(+)-ATPase were used.

[Ouabain-induced blockade of alpha2 isoform of the Na,K-ATPase on electrophysiological and contractile characteristics of the rat diaphragm].

In experiments with isolated neuromuscular preparation of the rat diaphragm, selective blockade of alpha2 isoform of the Na,K-ATPase with ouabain (1 mcmol/L) induced steady depolarization of muscle fibers that reached a maximum of 4 mV, a decrease in amplitude of muscle fiber action potential, and prolonged raising and decline phases of the action potential. At the same time, the force, time to peak, and half relaxation time of the isometric muscle twitch were increased, as well as the area under the contraction curve. During continuous fatiguing stimulation (2/s), a more pronounced decline of contraction speed was observed in presence of ouabain; dynamics of the half-relaxation time remaining unchanged.

[From diversity of molecular forms to functional specialization of oligomeric proteins, nicotinic acetylcholine receptor, acetylcholinesterase and Na+, K+-ATPase].

The review is devoted to the issue of diversity of molecular forms of oligomeric proteins using as examples members of the three protein classes: nicotinic acetylcholine receptor, acetylcholinesterase, and Na,K-ATPase. The data are presented on the molecular structure of proteins, subunit compositions, and isoforms of subunits, as well as on some features of gene expression. Particular emphasis has been made on the functional specialization of different molecular forms of one and the same oligomeric protein.

[Functional interaction between nicotinic cholinergic receptors and Na, K-ATPase in the skeletal muscles].

Acetylcholine (ACh) hyperpolarized the rat diaphragm muscle fibers by 4.5 +/- 0.8 mV (K0.

The modulating effects of various muscle factors on the function of motor nerve terminals.

Studies reported here showed that the incubation medium used for frog muscle contains factors able to modulate the secretion of mediator from motor nerve terminals, with increases in release from low-efficiency synapses and decreases in release from high-efficiency synapses. Both the stimulatory and the inhibitory effects of the incubation medium are mediated by the corresponding changes in the number of available mediator quanta stored. Factors with stimulatory presynaptic actions were present mainly in the low-molecular-weight (<10 kDal) fraction of the incubation medium.

[Modulatory effects of various factors of muscular origin on the function of the motor nerve endings].

Muscle incubate was shown to contain factors capable to increase the transmitter release in low-effective synapses and decrease it in high-effective those, dueto activation and inhibition, respectively, of the processes governing formation of available store of the transmitter. Activatiory effect of the low-molecular fraction on the low-effective synapses was correlated with the concentration of histidine-containing substances in this fraction.

Synaptic feed-backs mediated by potassium ions.

Repetitive activity of the neuromuscular system and of neuronal centers leads to K+ efflux from excited cells and to its accumulation within extracellular spaces and synaptic clefts, especially during the generation of postsynaptic responses such as end-plate potentials or excitatory postsynaptic potentials. K+ ions accumulated within the synaptic cleft during activity modulate the transmitter secretion from motor nerve terminals. Depending on the concentration, K+ can either increase the transmitter release due to a specific presynaptic action or decrease it due to depolarization of the presynaptic membrane.

The influence of skeletal muscle incubation medium on fatigue of neuromuscular preparation and on transmitter release at neuromuscular junctions in the frog.

The effect of frog skeletal muscle incubate on fatigue was studied in frog sciatic nerve, sartorius muscle preparation. Fatigue was produced by prolonged repetitive (1 s-1) stimulation of motor nerve or of curarized muscle. The incubate partially restored isometric contraction amplitudes of muscle fatigued by nerve stimulation.

[The effect of carnosine on synaptic transmission in the frog neuromuscular junction].

The influence of carnosine on quantal content of the e.p.p.

[Biochemical characteristics of a muscle perfusate and its effects on mediator release in the neuromuscular synapse].

Histidine-containing compounds (HCC) were found, using diazoreaction and reaction with diethylpyrocarbonate, a specific histidine reagent, in the perfusate of the frog hindlimb vasculature. After gel filtration on sephadex G-25 about 80% of HCC were eluted with a fraction with molecular mass less than 5000 kD. The studies of the perfusate influence on the characteristics of quantum secretion of transmitter in the preparation of frog cutaneopectoral muscle have shown that the perfusate increased the quantum content of end-plate potentials (EPP) due to increasing binominal parameter and decreasing frequency of miniature EPP.

[Genetic mathematical analysis of dermatoglyphic indices in epilepsy].

Dermatoglyphic investigations were performed in 73 male epileptic patients divided into groups according to the age of the disease onset. Besides, epileptic alcohol addicts, normal male subjects having epileptic or normal children were entered into separate groups. A total of 149 subjects underwent this study.

[Effect of a brain extract containing the postural asymmetry factor on the frog neuromuscular synapse].

The influence of the rat brain extract containing a postural asymmetry factor on the synaptic transmission in the right and left preparations of the frog cutaneus-pectoralis muscle was studied. The extract (2.10(-4) mg/ml) increased the quantal content of end-plate potentials (e.

[Characteristics of the time course of miniature endplate currents in different parts of the neuromuscular junction in the frog].

Extracellular glass microelectrodes were used for recording miniature endplate currents (MEPC) from proximal and distal parts of frog sartorius synapse. The amplitude and half-time of decay (t1/2) of MEPC in proximal parts exceeded those in distal parts. These differences were eliminated by tubocurarine and increased under the influence of armin.

[Release of beta-alanine from the frog skeletal muscle determined by thin-layer chromatography].

The release of beta-alanine from the resting and contracting frog sartorius muscles was demonstrated by the two-dimensional thin-layer chromatography. The release of beta-alanine from indirectly stimulated muscles of frogs in winter was about 230% higher than at rest. When synaptic transmission was blocked by d-tubocurarine the release of beta-alanine from directly stimulated muscles did not exceed the release at rest.

[Effect of etimizol on the neuromuscular synapse of the frog].

The effect of aethimizol, a substance activating the memory processes, was studied by intracellular recording at the frog cutaneous pectoris neuro-muscular preparation. Presynaptic action of aethimizol (0.5-2 mM) was found.