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Biomedical subjects

M B Rekhtman

Publications and source records attributed to M B Rekhtman.

14 recordsLinked to original sources
PubMed1979

[Pathogenetic factors in experimental photogenic epilepsy].

Male albino rats were used in chronic experiments. The photogenic epilepsy syndrome was induced by local tetanus toxin injection into the lateral geniculate blody (LGB) which caused the formation of a pathologically enhanced excitation. The primary symptoms of photogenic epilepsy resulted from the pathologically enhanced specific sensory excitation in the LGB, and correlated with a significant increase of the evoked potential amplitude in the corresponding visual cortex field. The following progress of the neuropathological syndrome was connected with generalized disturbances of the rhythmic electrical activity of the brain, characterizing the state of increased epileptic sensibility. The experimental results demonstrate an important role of specific and nonspecific factors in the pathogenesis of experimental photogenic epilepsy.

Animals↗
PubMed1979

[Effect of diazepam on the Na, K-ATPase state in a penicillin--induced hyperactivity focus in the cerebral cortex].

Intramuscular injection of diazepam to rats at doses of 0.01 and 2 mg/kg 25-30 min after penicillin application to the rat brain cortex leads to alteration of periodic appearance of epileptic seizures (ES), to changes in the seizure pattern, and to emergence of periodic acceleration of epileptiform discharges (ED). Injection of diazepam at a dose of 2 mg/kg 20 min before penicillin application results in the reduction of ED latency in the epileptogenic focus and in a decrease in their frequency before seizures as compared to the control animals without diazepam injection. ES appear irregularly, their quantity is markedly reduced while duration is increased. Diazepam injection leads to disappearance of the rat moving reaction during ER and ES. In vivo experiments diazepam (2 mg/kg) does not influence brain cortex Na, K-ATPase of crude synaptosomes. However, diazepam leads to an increase in Na, K-ATPase activity both in the primary and dependent secondary epileptogenic foci. It is suggested that the anticonvulsant action of diazepam may be underlain by its activating effect on Na, K-ATPase of neuronal membranes in the epileptogenic focus.

Animals↗
PubMed1979

[Neuropathologic effects developing after administration of tetanus toxin to several rat brain structures].

Neuropathological syndromes following local tetanus toxin (TT) injection into different rat brain structures were studied. As demonstrated, there arose specific neuropathological signs dissimilar to those developing with different TT localization, i.e. as a rule the action of TT in the given brain parts was local. Experiments carried out confirmed the theory of the generator mechanisms of the neuropathological syndromes according to which specific manifestations of the corresponding syndrome were due to the localization of a generator of pathologically-enhanced excitation in definite brain structures.

Amygdala↗
PubMed1979

[Effect of diazepam on the epileptic activity of rats with experimental photogenic epilepsy].

Chronic experiments were conducted on rats. A study was made of the effect of diazepam (in a dose of 4 mg/kg of body weight) on the specific and nonspecific mechanisms of experimentally-induced photogenic epilepsy developing as a result of tetanus toxin injection into the lateral geniculate body (LGB) and formation in this nucleus of a pathologically enhanced excitation generator (PEEG). Diazepam in the mentioned dose had a relatively weak effect on the extent of pathological enhancement of the sensory visual signal in the LGB under conditions of PEEG formation aided detection of focal interictal discharges in this nucleus, and completely inhibited generalized epileptic activity in experimental animals in the course of one hour.

Animals↗
PubMed1979

[Problem of focal pathology in "genuine" epilepsy].

Chronic experiments on rats permitted one to obtain an experimental model of photogenic epilepsy. This was accomplished by creating in the external geniculate body (EGB) a generator of pathologically intensified excitation (GPIE) with the aid of tetanus toxin (TT). According to some clinical and electrographic characteristics this form of epilepsy may be alloted to the type of primarily generalized or "genuine" epilepsy. The existance of focal pathology in the respective EGB was detected only by special electrophysiological and pharmacological methods. The studied model demonstrates a necessity of using special methods of detecting brain focal pathology (GPIE) in order to determine the focus of neuron hyperactivity in those cases where the clinical picture is characterized by signs of the so-called genuine epilepsy. Experimental photogenic epilepsy attained by creating GPIE in the EGB with the aid of TT, is proposed as a model for studying the mechanism of epileptogenesis and testing the efficacy of anticonvulsive drugs.

Animals↗
PubMed1978

[Analysis of the neuronal activity of the lateral geniculate body in cats].

Activity of the lateral geniculate body neurons was studied in immobilized cats. Four parameters of impulse activity of every neuron were determined by computer analysis: T1, minimal, T2, average interspike intervals of the spontaneous activity, T3, latent period, and T4, duration of the first cluster of poststimulation activity. Classification of neuronal groups was made according to these parameters. This classification was used as a basis for the construction of a scheme of neuronal interaction in the lateral geniculate body.

Animals↗
PubMed1978

[Alteration of the functional organization of the lateral geniculate body after injection of tetanus toxin into it].

Changes in neuronal activity of the lateral geniculate body were studied in cat under conditions of the formation of a generator of pathologically enhanced excitation after local injection of tetanus toxin into this nucleus. To evaluate the changes, an analysis of interdischarge intervals histograms of spontaneous activity and poststimulation histograms were performed. A conclusion was made that as a result of the tetanus toxin injection the inhibitory mechanisms of many relay neurons became destructed, producing substantial changes in their discharge patterns.

Animals↗
PubMed1978

[Change in the evoked potentials in the visual centers of the rat brain following administration of tetanus toxin to the lateral geniculate body].

Changes in visual evoked potentials were studied under conditions of tetanus-toxin injection into the lateral geniculate body in rats. The main abnormality of the evoked potentials in the geniculate body was the function of a new phase of the primary response. At the same time a strong increase in the amplitude of the first negative component of the evoked response in the ipsilateral cortical visual field was observed. The results show the formation of disturbances in the relay function of the lateral geniculate body during the formation of a generator of pathologically enhanced excitation in this nucleus.

Animals↗
PubMed1978

[Neuronal activity in an epileptic focus formed as a result of the effect of tetanus toxin on the motor area of the cat cerebral cortex].

Activity of single neurons was recorded intracellularly in the cortical epileptic focus produced by tetanus toxin. The activity of all studied neurons correlated positively with ECoG during the interictal period. A group of neurons was found with continuous background activity. The membrane potential of these neurons gradually decreased and the frequency of discharges increased during the interictal intervals. The neurons with continuous background activity during the interictal intervals revealed paroxismal depolarization without the following hyperpolarization. In some neurons with random background spikes hyperpolarizing shifts after paroxismal depolarization were observed. The mechanisms of the organization of the neuronal "epileptic aggregates" as well as of inhibition of these functional structures are considered.

Animals↗
PubMed1976

[Photogenic epilepsy with localization of the generator of excitation in the lateral geniculate body (the phenomenon of a determining dispatch station)].

The photogenic seizure syndrome was produced in experiments on rats and cats by injection of purified tetanus toxin into the lateral geniculate body (LGB). The seizures followed light stimulus or arose spontaneously. At the intervals between the attacks every light stimulus provoked a specific photojerk. Disturbance of the inhibitory mechanisms by tetanus toxin proved to result in a rise in the LGB of a generator of pathologically enhanced excitation underlying the hyperactive determinative dispatch station causing the described photogenic epilepsy.

Animals↗
PubMed1976

[Experimental vestibulopathy produced as a result of formation of a generator of pathologically enhanced excitation in the vestibular nuclei (phenomenon of a determinative dispatch station)].

A possibility of formation of a generator of pathologically enhanced excitation in the system of the vestibular nuclei of the medulla oblongata by disturbance of their inhibitory processes (resulting in development of contralateral rotatory motions in animals) was shown. Experiments with electrical stimulation of the lateral vestibular nucleus and its coagulation showed the system of the vestibular neurons organizing the synchronous message by the vestibulo-spinal pathways to underlie the generator of the pathologically enhanced excitation. It was concluded that the generator of the pathologically enhanced excitation formed in the lateral vestibular nucleus as a result of disturbed inhibition underlied the hyperactive determinative dispatch station causing the syndrome of vestibulopathy

Animals↗
PubMed1976

[A study of the interaction between the peripheral motor neurons of muscle antagonists by the H-reflex method under normal conditions and in spastic hemiparesis].

With the aid of the reflex method the authors studied the functional condition and interconnection of peripheral motoneurons of the muscles-antogonists in normal conditions and in spastic hemiparesis. In patients with spastic hemiparesis there was an increase in the inhibition latent period of the H-reflex following a conditioning stimula of the fibular nerve and a nonmonotonous restitution in the amplitude of the H-reflex during the periods of "late inhibition". These data permit to assume that in patients with pyramidal insufficiency the changes in the system of reciprocal inhibitive interaction of muscles-antagonists are fixed and are not subjected to a supraspinal control. This may determine the spastic character of the muscle tone in such patients.

Adolescent↗
PubMed1975

[Formation of a generator of excitation in the gigantocellular nucleus of the medulla oblongata during disruption of inhibitory processes].

Neuronal activity in the gigantocellular nucleus after injection of tetanus toxin was studied on decerebrated cats. The toxin was used as a substance producing a deep and continuous suppression of inhibitory processes. The increase in the amplitude and rate of neuronal discharges, in the integral background and evoked activity as well as in the number of active neurons and that of neurons with burst activity was recorded in the "poisoned" nucleus. The enhanced activity in the investigated regions of the poisoned nucleus might be temporarily suppressed by a strong direct electrical shock and by glycin administrations to those regions. The obtained data indicate that a pool of neurons with disturbed inhibitory processes forms a generator of enhanced excitation. The mechanisms and characteristic features of the activity of such generators are discussed. The possibility of modelling neurological syndromes by production of similar generators in various parts of the central nervous system and their relation to the earlier described phenomenon of "dispatch station" are considered.

Animals↗