Search PubMed⌕ Search

Biomedical subjects

V N Kazakov

Publications and source records attributed to V N Kazakov.

At least 37 records · Page 2Linked to original sources
PubMed1992

[Sources of cortical, hypothalamic and spinal serotoninergic projections: topical organization in the dorsal Raphe nucleus].

Distribution of primuline, fast blue, fluoro-gold and nuclear yellow-labelled monoamine-containing cells in periventricular gray and dorsolateral tegmentum (including locus coeruleus) was studied in the rat after injection of these fluorochromes into the frontal cortex, hypothalamus and spinal cord. Combination of monoamine fluorescence method and retrograde cell-labelling was used. Two big groups of serotonin-positive cells projecting into the upper thoracic spinal segments were found in dorsomedial zone of the dorsal raphe. Part of these units also had divergent axon projections to the frontal cortex. Such cellular arrangement allows a supposition that analgetic effects of dorsal raphe stimulation can be partially based on the direct participation of this structure in the descending control at the spinal level. Neurones, sources of cortical projections are intermingled with the cells projecting to the hypothalamus but some topical differentiation can be distinguished. Neurotransmitter and neuroregulatory roles of separate cortical and hypothalamic projections of serotonin-containing neurons of the dorsal raphe cells is discussed.

Animals↗
PubMed1991

[Hepatocytes from the liver of mice with experimental post-toxic cirrhosis stimulate in heterokaryons DNA synthesis in the nuclei of resting fibroblasts of the NIH 373 line].

Hepatocytes from mouse liver with experimental post-toxic cirrhosis (received by means of 10-12 inhalations with CCl4) were fused with serum-deprived (0.2%) resting NIH 3T3 mouse fibroblasts to elucidate mechanisms of liver stroma cells proliferation at cirrhosis. After fusion, nuclei of fibroblasts in such heterokaryons were found to enter into S-period without any exogenous stimulation of cell proliferation (in the medium with low content of serum). The obtained data allow us to suggest that hepatocytes from mouse liver with experimental post-toxic cirrhosis can produce and secrete into the medium (blood) factor (s) capable of stimulating the mesenchymal origin cell proliferation.

Animals↗
PubMed1991

[Electrophysiological analysis of corticofugal influences on neurons of the preoptic area].

Evoked potentials (EPs) and neuronal responses of the medial (MPO) and lateral (LPO) preoptic region (RPO) and adjacent areas of the hypothalamus to stimulation of the prefrontal (area 8), cingulum (area 24), periamigdaloideus (RPA) cortex and hippocampus (area CA3) have been studied on cats anesthetized with ketamine. Cortical areas were selected according to their evolutionary status. It is determined that the most pronounced EPs are generated in the RPO to stimulation of the periamigdaloideus and cingulum cortex. A close correlation between responses of single units and EPs waveforms is shown. The majority of neurons responsible for cortical stimuli are located mainly in the basal part of the LPO. It is this area of the RPO where the prevalence of initial excitatory reactions is observed. The MPO contains much less neurons responding to cortical stimulation. In this area of the RPO mainly initial inhibitory reactions are registered. For the LPO a ratio between the inhibitory and excitatory reactions is 0.6:1, for the MPO the same ratio is 5.8:1. In the area of the RPO adjoining the bed nucleus stria terminalis (BST) the initial inhibitory reactions prevail over the initial excitatory ones too (ratio 4.9:1). In the area of the RPO immediately adjoining the nucleus supraopticus the initial excitatory reactions are registered and the ratio between the initial inhibitory reactions and initial excitatory ones is 0.7:1. In the RPO a pronounced convergence of the stimuli from the different cortical areas to the definite cells is found as well. In the RPO which is a zone of wide convergence 3/4 of neurons responded to stimulation of two and more cortical inputs. The combinations of inputs from the prefrontal and cingulum cortex as well as from prefrontal and periamigdaloideus cortex are the most frequent types of convergence of different cortical stimuli to the preoptic neurons.

Animals↗
PubMed1991

[Reactions of neurons of the preoptic area in the presence of serial cortical stimuli].

Evoked potentials (EPs) and neuronal responses of the medial (MPO) and lateral (LPO) preoptic region (RPO) and adjacent areas of the anterior hypothalamus to serial (6-300 s) stimulation of the prefrontal (area 8), cingulum (area 24), periamygdaloideus (RPA) cortex and hippocampus (field CA3) were studied on experimental cats anesthetized by ketamine. Cortical areas were selected according to their evolutionary status. Responses of preoptic neurons to serial stimulation were grouped into four main types: excitatory, inhibitory, excitatory on-off-effect and inhibitory on-off-effect. No pronounced changes in the patterns of response reactions were found when frequency of the stimuli increased, only intensity of the reactions changed. Neurons responding to serial cortical stimulation were located mainly in the central part of the MPO and in the basal part of the LPO. These areas of the RPO contained neurons with the most pronounced convergence of different cortical stimuli to the same cell. In serial cortical stimulation inhibitory reactions developed more frequently than excitatory ones (ratio 3.4:1). A gradient of inhibitory reactions to stimulation of different cortical areas was observed while comparing them in terms of evolution from new to old structures. Prevalence of inhibitory responses over excitatory ones was minimal (ratio 1.7:1), when the neocortex (area 8) was stimulated and it was more pronounced (ratio 1.9:1) during stimulation of the evolutionary intermediate cortex (area 24). That prevalence was still more significant (ratio 4.5:1) in case of paleocortical (RPA) stimulation and it was the most pronounced (ratio 10.2:1) during stimulation of the archicortex (hippocampus).

Animals↗
PubMed1991

[Hepatocytes in heterokaryons do not retard the nuclei of stimulated fibroblasts entering the S period].

Serum-deprived (0.2%) resting and serum-stimulated (10%) proliferating NIH 3T3 mouse fibroblasts were fused with hepatocytes from intact, regenerating and embryonic mouse livers to elucidate mechanisms of liver cell proliferation, DNA synthesis being investigated in nuclei of heterokaryons and non-fused cells using radioautography. Hepatocytes in heterokaryons were found to have no inhibitory effect on the entry of stimulated fibroblast nuclei into the S-period, but on the contrary they were involved in DNA synthesis. In addition, the nuclei in heterokaryons mutually stimulated each other to enter the S-period. In their turn, the resting fibroblasts did not prevent the proliferating hepatocytes from the regenerating and embryonic livers to enter the S-period. Possible reasons of the absence of inhibitory effect of differentiated cells in heterokaryons are discussed. The data obtained enable us to conclude that the mechanism of proliferative process control in resting immortalized cells differs from that in differentiated cells where proliferation seems to be stopped without affecting the endogenous inhibitor postulated for the resting and ageing fibroblasts.

3T3 Cells↗
PubMed1991

[The effect of cycloheximide on the entry into the S period of the nuclei in heterodikaryons].

Serum-deprived (0.2%) resting NIH 3T3 mouse fibroblasts were fused with serum-stimulated (10%) proliferating cells to elucidate mechanisms of entering into S-period operating in the nuclei of the heterokaryons under the effect of cycloheximide--an inhibitor of protein synthesis. Using radioautography DNA synthesis was investigated in mono-, homo- and heterodikaryons. After short (0.5-3.0 h) depressing of protein synthesis, the nuclei of stimulated cells in heterokaryons were found to enter into S-period. Under these conditions no induction of DNA synthesis was found in the nuclei of resting cells in heterodikaryons. In other experiments, resting cells were under the effect of cycloheximide during 2-4 h before the fusion, that led to a great induction of DNA synthesis in the nuclei of these cells in heterodikaryons. The data obtained are consistent with the idea of fibroblast transition to the rest under the action of labile proteins-repressors.

3T3 Cells↗
PubMed1990

[An organizational analysis of the neurons forming the descending cortico-hypothalamic pathways].

Quantitative assessment of spatial organization of cortical neurons forming descending fibre systems and hypothalamic structures has been made using technique of retrograde axonal transport of horseradish peroxidase. Heterogeneity of cortico-hypothalamic bonds is determined: the prefrontal cortex exerts a more pronounced effect on the hypothalamus as compared with other cortical areas of the limbic brain. Cortico-hypothalamic neurons form neuronal groups on different frontal levels of the prefrontal cortex and convolution of the cingulum, a form and orientation of the group being determined by the topography of dominating axonal systems running to the hypothalamus. There are various forms of cell associations in the frames of neuronal populations. Ensemble groupings of neurons may underlie the principle of organization of direct cortico-hypothalamic ways.

Afferent Pathways↗
PubMed1989

[DNA synthesis in the nuclei of stimulated NIH 3T3 cells in heterodikaryons obtained by the fusion of these cells with resting cells treated with cycloheximide].

Serum-deprived (0.2%) resting NIH 3T3 mouse fibroblasts preincubated with cycloheximide (7.5 micrograms/ml) were fused with stimulated cells taken 10 hours after changing the medium to the one containing 10% serum, and DNA synthesis was investigated in nuclei of heterodikaryons, homodikaryons, and monokaryons, using radioautography with double-labeling technique. Preincubation of resting cells with the inhibitor of protein synthesis cycloheximide for 4, 3, 2, but not for 1 or 0.5 hours abolishes their ability to suppress DNA synthesis in stimulated nuclei in heterodikaryons. Three hours after the removal of cycloheximide from the media, the resting cells acquire once again the inhibitory effect towards the entry of stimulated nuclei into the S-period. The data suggest that the resting cells may produce a labile endogenous inhibitor of cell proliferation, and support the idea on the active metabolic processes occurring in the resting cells.

Animals↗