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V N Kazakov

Publications and source records attributed to V N Kazakov.

At least 19 recordsLinked to original sources
PubMed1992

Influences from different areas of the cerebral cortex on preoptic neurons: morphological and electrophysiological data.

Spatial organization of neurons in the prefrontal and cingulate cortex, cortex of the piriform lobe and the hippocampus which project axons to the preoptic region, has been studied in cats using horseradish peroxidase tracing. Cortical areas were selected taking into consideration their phylogenetical distinctions. The prefrontal cortex was found to send a major portion of fibres to the preoptic region, while the density of units forming such connections was maximal in the cingulate cortex. Field potentials and neuronal reactions of the medial and lateral divisions of the preoptic region and the adjacent hypothalamic zones were studied in ketamine-anaesthetized cats. The most pronounced field potentials were recorded in the preoptic region upon stimulation of the cortex of the piriform lobe and cingulate cortex. There was a close correlation between the responses of single neurons and components of the field potentials. The majority of neurons responding to cortical stimuli were located mainly in the lateral preoptic region, where the larger amount of primary excitatory reactions were recorded. The medial preoptic region contained a smaller number of responsive neurons prevailingly generating the primary inhibitory reactions. For the lateral preoptic region the inhibition/excitation ratio was 0.6:1 at all cortical stimulations, but for the medial region it was 5.8:1. In the preoptic division adjoining the bed nucleus of the stria terminalis, the primary inhibitory reactions considerably prevailed over the primary excitatory; on the other hand, in the supraoptic nucleus the primary excitatory reactions prevailed weakly (ratios of 4.9:1 and 0.7:1, respectively). The preoptic region was found to be a zone of wide convergence of cortical inputs to single cells, where three-quarters of neurons responded to the stimulation of two, three or even four cortical areas.

Animals↗
PubMed1992

Protein synthesis inhibitors, like growth factors, may render resting 3T3 cells competent for DNA synthesis: a radioautographic and cell fusion study.

Serum-deprived (0.1-0.2%) resting NIH 3T3 mouse fibroblasts pre-incubated with cycloheximide (7.5 micrograms/ml), or puromycin (10 micrograms/ml), were fused with stimulated cells taken 10 h after changing the medium to one containing 10% serum, and DNA synthesis was investigated in the nuclei of monokaryons, homodikaryons and heterodikaryons using radioautography with the double-labelling technique. Pre-incubation of resting cells with inhibitors of protein synthesis for 1-4 h abolished their ability to suppress DNA synthesis in stimulated nuclei in heterokaryons. Three hours after the removal of cycloheximide from the medium, the resting cells acquired once again the inhibitory capacity for entry of stimulated nuclei into the S period. This inhibitory influence disappeared also in the case of post-fusion cycloheximide application as well as following an 8-12 h pre-treatment of resting cells with actinomycin D (1 microgram/ml) prior to fusion. Pre-incubation of resting cells for 12 h with PDGF (1 u/ml-1) followed by an 8-48 h incubation in serum-free medium stimulated the onset of DNA synthesis. A brief exposure (45 min) of resting cells to cycloheximide (7.5 micrograms/ml), or puromycin (7.5 micrograms/ml), exerted a similar effect, inducing by itself the entry of cells into the S period. The results support the assumption that acquirement, by resting cells, of competence for DNA replication includes as a necessary step the down-regulation of intracellular growth inhibitors whose formation depends on protein synthesis.

3T3 Cells↗
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↗
PubMed1978

[Interaction of heterosensory afferent impulses in the neurons of the thalamic associative nuclei].

The interaction of visual, auditory and cutaneous afferent signals on neurons of pulvinar (Pulv), posterior lateral (LP) and mediodorsal (MD) thalamic nuclei was studied in acute experiments on cats anaesthetized with a mixture of nembutal and chloralorse. The first (more frequent) type of the interaction was characterized by inhibition or inhibition followed by facilitation of the response; the second--by facilitation or facilitation followed by inhibition of neuronal activity. The capacity for interaction in MD neurons was less expressed than in cells of the Pulv-LP complex (P less than 0.05). The interaction could be better seen in three-sensory elements. Certain peculiarities were found in the interaction of afferent signals coming from different peripheral receptive areas in neurons of both structures.

Animals↗
PubMed1978

[Responses of neurons of hypothalamic nuclei to stimulation of the frontobasal regions of the neocortex].

Neuronal responses of different hypothalamic nuclei to frontobasal cerebral cortex (proreal, posterior orbital, basal and temporal regions) were studied in acute experiments on cats narcotized by membutal mixed with chloraloze. Neurons which could be activated antidromically during stimulation of another region were recorded. On the basis of their response a number of neuronal chains (circles) functioning in forebrain was distinguished. The first chain is orbital gyrus--preoptical zone--proreal gyrus. The second chain has the same cortical components as the first one, but switching over in the hypothalamus takes place in the region of mamillary bodies. The third chain is basal temporal cortex--lateral hypothalamus--prefrontal cortex.

Animals↗
PubMed1978

[Reactions of neurons in the associative thalamic nuclei to peripheral stimulation of different modality].

Reactions of 252 neurons of the mediodorsal nucleus (MD) and 329 cells of the pulvinar-posterior-lateral complex (Pulv-LP) of the thalamus to separate the complex peripheral stimulations (visual, auditory and somatosensory) were studied in acute experiments on cats anaesthetized with a mixture of chloralose and nembutal. According to the character of the neuronal responses to peripheral stimuli three types of reactions were found: acceleration of the background activity (32.0% neurons in Pulv-LP and 20.6% in MD), inhibition (21.0% neurons in Pulv-LP and 24.2% in MD) and mixed (8.8% neurons in Pulv-LP and 4.0% in MD). No responses were observed in 37.4% neurons of Pulv-LP and in 51.2% of MD. Along with certain similarity, some specific features in the organization of Pulv-LP and MD were found. According to the response latency, the neuronal reactions to stimulation were divided into three groups: with short (less than 20 ms), medium (21--40 ms) and long (over 41 ms) latent period. The second group was the most numerous.

Animals↗
PubMed1977

[Responses of neurons of the medial group of thalamic nuclei to stimulation of the fronto-basal portions of the neocortex].

Neuronal and focal responses of medial thalamic nuclei (mediodorsal, central lateral, parecentral, centrum medianum, parafascicular) to stimulation of frontobasal cerebral cortex (proreal, posterior orbital, basal temporal regions) were studied in acute experiments on cats narcotized by nembutal mixed with chloralose. Proceeding from the data on the number of neurons responding to cortical stimulation and on the duration of the response latent period, three functionally heterogeneous sections of medial nuclei were distinguished: the microcellular and magnocellular regions of the mediodorsal nucleus, and the intralaminar nuclei with the parafascicular complex. Neurons were recorded which could be activated antidromically during stimulation of another region. On this basis a suggestion is made on the integrating function of medial nuclei providing unification of the frontobasal regions of the neocortex.

Animals↗
PubMed1977

[Electrophysiologic analysis of cortico-pontine relationships].

Projections of different regions of orbitofrontal and basotemporal cortex as well as of the hippocampus in the pons varolii area were studied by means of focal recording in acute experiments on cats anesthetized with nembutal and chloralose. It is shown that different formations of the frontobasal regions of the neocortex have local projections into the rostral zones of pons varolii and relatively diffuse projections into its caudal regions. The representation of the hippocampus is weaker as compared with the representation of the frontobasal region, and the focal responses are more diffuse. All the studied structures are represented in the nuclei of the pons varolii. The region of the orbitofrontal cortex is not represented in the caudal part of the reticular formation, the basotemporal cortex has no projections into brachium pontis.

Animals↗
PubMed1976

[The interaction of impulses evoked by stimuli of different modality in neurons of the parietal association cortex].

Interaction of visual, auditory and electro-dermal signals in neurons of the parietal associative cortex was investigated in acute experiments on cats anesthetized by chloralose and nembutal. Two types of the interaction were found, one of which was characterized by inhibition or inhibition followed by facilitation of the response to testing stimuli, and the other by facilitation or facilitation followed by inhibition of background impulses. The interaction between signals of different modality is shown to depend on the properties of the neuron. Interaction ability in polysensory neurons was evidently higher than in bi- and monosensory ones.

Animals↗
PubMed1976

[Electrophysiologic study of cortico-hypothalamic interrelationships in cats].

In acute experiments on cats anesthetized with nembutal and chloralose the projections of different parts of orbito-frontal cortex, basal temporal cortex and hippocampus to hypothalamic nuclei were studied by focal potential recording. It was found that the proreal gyrus has local projections into the latero-dorsal parts of the preoptical region, rostral parts of the forebrain medial bundle, lateral and posterior hypothalamus with mammilary bodies. The orbital gyrus is projected mainly into latero-dorsal parts of the forebrain medial bundle, latero-ventral part of the preoptical region, and the region of lateral and latero-dorsal hypothalamic nuclei. Projections from the orbital gyrus are of a relatively diffuse character. The basal temporal cortex has diffuse projections into the central part of the preoptical region, latero-ventral part of the forebrain medial bundle and lateral mammilary body. No pronounced foci were observed in the hypothalamic structures during stimulation of the hyppocampus, but diffuse projections were found into ventral parts of the preoptical region and ventral regions of the forebrain medial bundle as well as into lateral hypothalamus and lateral mammilary nucleus.

Animals↗
PubMedDate not supplied

Interaction between impulses evoked by stimuli of different modalities in neurons of the parietal associative cortex.

In acute experiments on cats anesthetized with chloralose and nembutal interaction between visual, auditory, and electrodermal stimuli in neurons of the parietal association cortex was studied. Two types of interaction were found; the first characterized by inhibition or by inhibition followed by facilitation of the response to the test stimulus, the second by facilitation or by facilitation followed by inhibition of spontaneous impulses. Interaction between stimuli of different modalities was shown to depend on the properties of the neuron. In polysensory neurons ability to interact was much higher than in bimodal or monomodal neurons.

Acoustic Stimulation↗
PubMedDate not supplied

Electrophysiological investigation of cortico-hypothalamic relations in cats.

Projections of different parts of the orbito-frontal cortex, the basal temporal cortex, and the hippocampus on hypothalamic nuclei were studied by recording focal responses in acute experiments on cats anesthetized with pentobarbital and chloralose. The proreal gyrus was shown to have local projections in the latero-dorsal zones of the preoptic region, in the postral parts of the medial forebrain bundle, and also in the region of the lateral and posterior hypothalamus with the mammillary bodies. The orbital gyrus projects mainly to the latero-dorsal portions of the forebrain bundle, the latero-ventral part of the preoptic region, and the region of the lateral and latero-dorsal hypothalamic nuclei; projections from the orbital gyrus are relatively diffuse in character. The basal temporal cortex has diffuse projections in the central part of the preoptic region, in the latero-ventral parts of the medial forebrain bundle, and in the lateral mammillary body. No marked foci of activity were found in the hypothalamic structures during hippocampal stimulation. Diffuse projections of the hippocampus were traced in the ventral part of the preoptic region and the ventral regions of the medial forebrain bundle, and also in the lateral hypothalamus and in the lateral mammillary nucleus.

Animals↗