Biomedical subjects
Publications and source records attributed to N S Kositsyn.
A simple original method of simultaneous staining of the cell elements on cerebral cortex and its vascular bed is developed. It is based on perfusion of polyvinyl acetate emulsion prepared on 2% paraformaldehyde solution with phosphate buffer at pH 7.4.
Electrical stimulation of the ventromedial hypothalamus in cats leads to the appearance of an additional component in the structure of evoked potentials of the amygdala lateral nucleus; this component disappears after discontinuation of food reinforcement (suppression of the conditioned reflex). It was concluded that the lateral nucleus of the amygdala and ventrolateral hypothalamus, the structures belonging to the system of defense behavior, can change their congenital characteristics depending on the situation, when involved in the feeding behavior system.
Cross-correlation functions were used to study the time delay (a measure of synchronization) in the appearance of epileptic discharges in distant areas of the cortex in the intact cortex and in neuronally isolated cortical strips in Wistar rats. Experiments were performed at different stages of axon sprouting 30 and 90 days after isolation of cortical areas and in intact cortex. Significant increases in the number of synapses in layer V of isolated cortical strips at 30 days correlated with significant decreases in the time delay, while decreases in the number of synapses at 90 days correlated with a significant increase in the time delay. This is evidence that newly formed synapses increase the extent of synchronization and thus affect epileptogenesis. The data obtained here suggest that large pyramidal cells in layer V of the rat neocortex form a neural network in pathological conditions, this supporting intracortical synchronization of epileptic discharges.
Quantitative analysis of synapses in layer I of the sensorimotor cortex in rats with low resistance to hypoxia revealed pronounced changes in the number of synaptic vesicles docked at the presynaptic membrane in active synaptic zones under conditions of acute hypobaric hypoxia. In high-resistant animals the number of docked synaptic vesicles under these conditions remained unchanged. In was hypothesized that high sensitivity to hypoxia in low-resistant rats is determined by high reactivity of the synaptic transmission system.
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Endoplasmic reticulum structure was studied on Mauthner neurons of adult fish and fry. Two-fold decrease of extension of rough endoplasmic reticulum components and similar increase of extension of smooth endoplasmic reticulum components were found to occur following long-term stimulation of Mauthner neurons. The significance of transformation of rough endoplasmic reticulum into smooth one as a result of neuronal compensatory response was discussed.
Structural and functional properties of the animals olfactory analyzer were studied on different stages of their life. Attention was drawn to defining the correlations between the ultrastructure of primary sensory cells, their sensitivity and realization of adaptive behavior in fish in diverse reproductive period stages. Structural organization in fish olfactory cells appearing during spawning aim both to activate these cells to provide specific receptor function during intercourse and to urgently abolish it when transitioning to paternal behaviour. Not only central mechanisms of nervous system but also reorganizations of peripheral chemoreceptive apparatus are of great importance, which is demonstrated for the first time.
The effect of strychnine and atropine on the amplitude of the evoked potentials (EP) of the cerebral cortex was studied. It was shown, that both drugs increased amplitude of the EP. When we used strychnine, increased amplitude of the EP determined modification of the electrical resistance and current sources of the electrical field of the EP. Atropine did not change electrical resistance and in this case only electrical current sources determined modification of the EP.
The connection between EEG spectrum and structural changes of plexiform layer apical dendrites was revealed during the period of recovery from the deep anesthesia. On the initial phase of recovery when the multiply varicose dendritic enlargements are present, an additional peak in EEG spectrum emerged in a delta-band under weak DC action (10 microA); on the late phase of recovery when the structure of the plexiform layer apical dendrites became normal the peak in EEG spectrum under weak DC action emerged in a tetha-band. Thus, by the absence or appearance of the tetha-rhythm in the cerebral cortex in the response to it direct stimulation we can evaluate the morphological condition of the Plexiform layer apical dendrites.
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Using light and electron microscopic studies it was shown that the most sensitive to different extreme factors influence (deep pentobarbital anesthesia, strong DC brain cortex polarization) were the distal parts of apical dendrites of the plexiform layer. That was a selective, non-specific, reversible varicose-like dendritic swelling. The structure of myelin axons, synaptic boutons and astrocytes was unchanged.
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Cytological aspects of metabolic processes between capillaries and nerve cells, as well as between different elements of neurons were studied electron microscopically. The sensomotor cortex, hippocampus, anterior tubercles of corpora quadrigemina, geniculate body were studied in rats, adult cats and 4-day-old kittens. Metabolic ultrastructure was demonstrated by means of vesicles formed by micropinocytosis, in the endothelial wall of the capillary, in the synaptic plaques, in the growth cones. Coincidence of pinocytic processes with active synaptic zones, especially in the developing nervous system, was revealed. The phenomena of intraneuronal metabolism by means of cytoplasmic fragments (clasmatosis) in the area of synapses were described. Endogenic (formed in the zone of the lamellar apparatus) and exogenic (pinocytic) trophic vesicles were compared. In young animals the exchange of the trophic vesicles was demonstrated to precede the synaptic transmission, while in adult animals it seemed to supplement a short-lasting synaptic interconnection.
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