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Biomedical subjects

A M Gutman

Publications and source records attributed to A M Gutman.

At least 19 recordsLinked to original sources
PubMed1989

[The effect of cadmium ions on synaptic transmission in the tectum of the frog].

The effect of cadmium ions on the synaptic transmission in the frog tectum was analyzed in acute experiments by the method of recording of the quantum of EEG (the extracellular monosynaptic potential of synapses of a single axon) [1]. It was shown that perfusion of the tectum with CdCl2 in the concentration of 10-200 mumol/l reversibly inhibited the quanta of EEG, decreased their duration and increased the synaptic delay. Consequently, cadmium in industrial waste may be dangerous regarding the harm to the CNS, too. The results of the presented work correspond to the supposition based on experiments in vitro that presynaptic potential-dependent calcium channels prove to be one of the areas of synaptic action of Cd++ ions.

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PubMed1983

[Theoretical analysis of the spike activity of a neuron with an N-shape stationary volt-ampere characteristic of the dendritic membrane].

Neuronal discharge frequency as a function of depolarizing current strength was analyzed using a mathematical model. The dendritic membrane of the model neuron was characterized by an N-shaped stationary current-voltage characteristic which is now confirmed experimentally. The potential of distal dendrites with N-shaped current voltage characteristic changes from rest to stable depolarization as current rises. This change causes discharge frequency augmentation. Two smooth ranges of frequency-current characteristics are explained as follows: in the first low frequency-low current range all dendrites are at rest, and in the second high frequency-strong current range there appears stable depolarization. If stable depolarization of dendrites is a synchronous event, then there is a frequency jump between the ranges and if dendrites depolarize steadily one-by-one, then there is only a nonsmooth point. The steady depolarization causes hysteresis of the frequency-current characteristic, including spontaneous discharge after cessation of strong depolarization.

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PubMedDate not supplied

[Model of a passive 3-dimensional anisotropic syncytium as a continuous medium].

A model is being proposed for analysis passive electrical properties of the syncitium with anisotropy. In terms of the model the potential is expected to decay as approximately e-r/r with an increase of the distance, r, from a polarising electrode. Input resistance of the three-dimensional syncitium loosely depends upon the resistance of electrogenic membrane, and thus should be mainly accounted for by the resistances of the myoplasm and intercellular contacts.

Cell Fusion↗
PubMedDate not supplied

[Properties of extracellular monosynaptic potential of a single afferent in the light of the theory of dendrites with N-shaped volt-ampere characteristics].

In the frog tectum mass extracellular monosynaptic PSP of the set of synapses of one individual afferent--the quantum of EEG--was registered. Using the electrical threshold stimulation of the retina we noticed a large pair facilitation. The radial decline of the facilitated quantum of EEG was measured in order to check the conclusions of the dendritic theory which postulates the N-shaped current-voltage characteristic of the membrane. Therefore, we synchronously derived conditional and test quanta of EEG in the centre and 40-60 microns peripherally of terminal axonal arborization. In a half of the experiments the test quantum of EEG twice as large as the conditional one radially declined 25% less. The half-width and rise-time of the test quantum of EEG were longer as compared with the conditional one, especially in the peripheric derivation, the difference being about 1 ms. The totality of our results agrees with the concept of electrically excitable inward current in non-synaptic membrane of the apical dendrites in the tectum. The current is predicted by the theory of the N-shaped current-voltage characteristic of dendrites.

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PubMedDate not supplied

[Intercellular coupling in the sinus node of the rabbit heart].

Passive electrical properties of SA node region of rabbit's heart were studied. Electrotonic anisotropism was characteristic of the entire SA node; anisotropism decreased moving from crista terminalis to interatrial septum. The input resistance, RBX, was the largest in the region of true pacemakers and decreased moving to the perinodal region. Analysis of the results yielded specific resistance values for contacts and electrogenic membrane of 3 Ohms-cm3 and 10(4) Ohms-cm2 respectively.

Animals↗