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Biomedical subjects

I M Vinogradova

Publications and source records attributed to I M Vinogradova.

At least 19 recordsLinked to original sources
PubMed2002

Effect of glycine on synaptic transmission at the third order giant synapse of the squids Alloteuthis subulata and Loligo vulgaris.

Intracellular microelectrode recordings were made from presynaptic and postsynaptic regions of the third order giant synapses of the squids Alloteuthis subulata and Loligo vulgaris. Synaptically generated postsynaptic action potential trains, and excitatory postsynaptic potentials (EPSPs) were reversibly decreased by glycine, beta - alanine or taurine while presynaptic action potentials (APs) were unaltered. Glycine was effective in the presence of strychnine (30-50 microM), NMDA (500 microM), AP-5 (50 microM), CPP (100 microM), or MK 801 (which also had no effect on normal synaptic transmission). The glycine effect was reduced reversibly by D-tubocurarine (100 microM) and blocked by reducing extracellular chloride by 50% with propionate. Excitatory postsynaptic currents (EPSCs) were decreased by glycine addition without altering resting membrane conductance. We postulate that glycine or a glycine like substance provides an excitatory postsynaptic input during synaptic stimulation. Bath addition of glycine desensitises these receptors and decreases the amplitude of the EPSPs and EPSCs. Modulation of this synaptic input may provide an effective mechanism to suppress or potentiate synaptic transmission in the squid giant synapse.

Action Potentials↗
PubMed1992

[Atypical endplate miniature potentials in the frog neuromuscular junction after modification of the intercellular matrix and osmotic exposures].

In frog cutaneous-pectoris muscles the frequency of slowly rising atypical miniature endplate potentials (MEPPs) was significantly enhanced after collagenase (0.1%) treatment. Treatment with trypsin, hyaluronidase, hyper- and hypoosmotic solutions caused no changes in slowly rising MEPP (frequency in muscle fibers with intact acetylcholinesterase (AChE). Inhibition of AChE caused appearance of giant MEPPs. Acceleration of acetylcholine diffusion from synaptic cleft after treatment with hyaluronidase decreased giant MEPP frequency demonstrating their dependence upon nonhydrolyzed acetylcholine in synaptic cleft. The relation between slowly rising MEPPs and activity of synaptic Schwann cells in discussed.

Acetylcholine↗
PubMed1992

[Psychosine-induced changes in neuromuscular transmission and in the structure of the neuromuscular junction in the frog].

A decrease in the amplitude of miniature and evoked end-plate potentials (MEPPs and EPPs) as well as changes in EPP facilitation and depression during frequency stimulation were observed in psychosine-treated m. cutaneous-pectoris of the frog. Electron-microscopic investigation demonstrated severe changes in synaptic Schwann cells embracing motor terminals and disturbances in the inner mesaxon structure of the myelinated parts of motor terminals.

Animals↗
PubMed1992

[The possible function of Schwann cells in neuromuscular transmission in the frog].

Anti-galactoside rabbit antisera increased the frequency of slow (atypical) MEPPs. No lysis of the Schwann cells was found in synaptic regions. The data obtained suggest that fixation of antibodies to galactocerebroside on the Schwann cell surface membrane alters the cell's activity thus affecting some characteristics of neuromuscular transmission.

Animals↗
PubMed1990

[Seasonal changes in neuromuscular transmission in experiments on dissected or curarized frog muscles].

The end-plate currents and potentials (EPCs and EPPs) in cut or curarized muscles were investigated in frogs maintained at different temperatures (5 and 20-25 degrees C) before experiments in summer and in winter. EPCs and EPPs were elicited by nerve stimulation with different frequencies (1 and 100/s). Seasonal changes in amplitude, facilitation and depression of the EPPs and EPCs observed in curarized and cut (not curarized) muscles differed quantitatively and qualitatively. These differences may be explained assuming that sensitivity of the neuromuscular junction to the curare action (probably, a presynaptic one) is season-variable.

Animals↗
PubMed1990

[The formation of nerve endings in the phasic muscles of the frog].

Synapses with the complex nerve endings consisting of several terminal branchings of a single axon divided by myelin segments were studied at the cutaneous-pectoris muscles of a frog by histological and electrophysiological methods. It has been revealed that the number of the synapses with complex nerve endings rises during the postnatal development. The relation between the nerve ending complexity, total terminal length and size of the muscle fibres is described. Some of branches in complex nerve endings arise from the Ranvier nodes. They are characterized by a low level of quantal secretion and a peculiar fall of the sodium current along nerve terminals. Mechanisms that induce growth of nerve endings, branching and peculiarities of the transmitter release are discussed. It is supposed that the processes of growth and myelinization of nerve endings take place simultaneously.

Aging↗
PubMed1990

[Atypical miniature end plate currents in neuromuscular synapses of the rat under normal conditions, after acetylcholinesterase inhibition and cooling].

In the end-plates of rat diaphragm among atypical miniature end-plate currents (MEPCs) 2.9% were giant and 5.1% were slowly rising. The frequency of the giant MEPCs was decreased when temperature was lowered and increased when acetylcholinesterase (AChE) was inhibited; the latter effect was reversed if d-tubocurarine was added. Frequency of the slowly rising MEPCs changed insignificantly by all conditions. It is suggested that a highly temperature-dependent presynaptic mechanism of giant MEPC generation does exist which is activated by acetylcholine (ACh). Data about changes in the time course of the slowly rising MEPCs by AChE inhibition and lowering of temperature make it possible to suggest that the slowly rising MEPCs may be accounted for either slow release of ACh quanta or release of quanta on large distances from synaptic cleft and postsynaptic cholinoreceptors. The latter is possible if ACh quanta are released from synaptic Schwann cell to periaxonial space.

Acetylcholine↗
PubMed1989

[Effect of antibodies to glial glycolipid antigens on miniature end-plate potentials].

Less than 4% of miniature end-plate potentials (MEPPs) in frog cutaneous-pectoral muscles, normal or exposed to nonimmune rabbit serum were atypical. These MEPPs were of normal amplitude, but their time course was nearly twice as slow as that of normal MEPPs. The exposure of muscles to rabbit anti-galactocerebroside serum induced more than three-fold increase in the fraction of atypically slow MEPPs. Inhibition of acetylcholinesterase caused an appearance of giant MEPPs, the fraction of slow MEPPs being unchanged. Possible mechanisms of increase in fraction of atypical slow MEPPs based on modification of the synaptic Schwann cell functioning are discussed.

Acetylcholinesterase↗
PubMed1988

[Effect of hyaluronidase on the quantum content and binomial p and n parameters of neuromuscular transmission in frogs].

In the frog dermo-sternal muscle hyaluronidase (0.01--0.1%) caused e.p.p. amplitude and quantum content of transmission to fall when acting in a solution containing 1 mM Ca2+ and 4 mM Mg2+. The change in the quantum content was related to a decrease in binomial parameter n, the probability of mediator p release increased in the first moments of the enzyme action. With the prolongation of hyaluronidase action, negative values of p appeared. Hyaluronidase caused an increase in e.p.p. amplitude and in quantum content of transmission when acting in a solution containing 8 mM Ca2+ and d-tubocurarine. It was suggested that hyaluronidase modifies the normal calcium exchange between the bulk solution and the unstirred layer near nerve terminal membrane thus affecting the transmission.

Animals↗
PubMed1988

[Effect of hyaluronidase on the end-plate miniature currents and potentials in the frog].

The effect of 0.1% hyaluronidase on miniature end-plate potentials and currents (MEPP and MEPC) was studied in the frog cutaneous-pectoris muscle. The action of hyaluronidase on armin-pretreated muscles caused a decrease in the amplitude, duration of half-decay time and rising phase of MEPPs and MEPCs. The positive correlation between the amplitude and half-decay time of MEPPs and MEPCs was diminished. Hyaluronidase treatment of preparations with active acetylcholinesterase caused the half-life time of MEPCs to increase without any changes in the amplitude and rising phase of MEPCs. It is suggested that enzymatic destruction of a part of the glycocalix of cells forming the neuromuscular junction and of a part of the extracellular matrix results in a weakening of the nonspecific acetylcholine binding, thus facilitating the acetylcholine diffusion into the synaptic cleft.

Animals↗
PubMed1986

[Effect of dimedrol on the function of the neuromuscular synapse and the generation of action potentials by motor nerve fibers].

Microelectrode registration of synaptic potentials in the frog cutaneous-pectoris muscle has shown dimedrol (7.9 X 10(-5) M) to act on synaptic transmission decreasing the quantal content, estimated by mean EPP amplitude to mean miniature EPP amplitude ratio, the quantal content calculated by variation coefficient of EPP amplitude being unaffected. The data suggest possible transmitter release and depletion of mediator stock. The experiments on isolated motor nerve fibers have demonstrated dimedrol to cause the increase in transmitter release probability by widening the action potentials in the terminals and thus enhancing Ca2+ influx.

Action Potentials↗
PubMed1983

[Effect of armin on frog myelinated nerve fibers].

Study of the action of armin on the nodes of Ranvier in isolated nerve fibers of the frog has demonstrated that armin at concentrations over 4 X 10(-7) M produces the growth of the input resistance of the nodes of Ranvier at the expense of the decreased leakage conduction. At concentrations of 4 X 10(-6) and 4 X 10(-5) armin leads to a shift of the firing level of action potentials towards more positive values.

Action Potentials↗