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V A Polunovskiĭ

Publications and source records attributed to V A Polunovskiĭ.

9 recordsLinked to original sources
PubMed1984

[Dependence of the entry of NIH 3T3 cells into a period of DNA synthesis on the duration of their preliminary resting state].

Using radioautography and cell fusion technique, we studied cell kinetics and functional properties of NIH 3T3 mouse fibroblasts stimulated to proliferate after being quiescent for 3, 7 and 14 days. The resting state was achieved by cultivating cells in the medium with 0.5% of serum, the stimulation being achieved by replacement of the depleted medium for a fresh one containing 10% of serum. It was found that the longer cells had been kept resting, the longer their prereplicative period lasted after the stimulation, the lesser was the fraction of cells that entered the S-period. Cell-fusion experiments revealed that the ability of the resting nuclei to suppress the onset of DNA synthesis in the nuclei of stimulated cells in heterodikaryons increased as the cells stayed in the resting state before fusion, and that the period of suppression was prolonged. The data are consistent with the idea of cells going into deeper resting states. It may be concluded that the resting cells undergo a gradual development resulting in the changes of their functional properties.

Animals↗
PubMed1984

[DNA synthesis in the nuclei of resting and proliferating cells of the NIH 3T3 line in monokaryons, homo- and heterodikaryons].

Serum-deprived (0.5%) resting NIH 3T3 mouse fibroblasts were fused with stimulated cells taken at 2 hour intervals after changing the medium to the one containing 10% serum, and DNA synthesis was investigated in monokaryons, homodikaryons, and heterodikaryous using radioautography with double-labeling technique. The presence of the resting nucleus in the common cytoplasm has an inhibitory effect on the entry of the stimulated nucleus into the S period in the medium containing either 0.5 or 10% serum, but DNA synthesis continues. After a 24 hour stay in the common cytoplasm with resting nuclei the stimulated nuclei return into the state of rest. When resting cells are stimulated by 10% serum, their inhibitory effect on stimulated nuclei in heterodikaryons still persists for at least 2 hours following stimulation. Preincubation of resting cells with cycloheximide for 4 hours abolishes their ability to suppress DNA synthesis in stimulated nuclei. The data suggest that the resting cells produce an endogenous inhibitor of cell proliferation whose formation depends upon the synthesis of protein(s). When stimulated, cell can proliferate only upon decreasing the level of this inhibitor. The obtained results are consistent with the idea of a negative control of cell proliferation.

Animals↗
PubMed1982

[Active metabolic processes in resting cells].

A number of intracellular metabolic processes are activated when cells proceed from proliferation to rest. These processes may be classified into 3 main categories: processes regulating the transition of cells from proliferation to rest; metabolic reactions necessary for the suppression of cell proliferation; processes required by a resting cell to maintain viability. Among the last category 2 groups of processes seem to be particularly important: a high rate of macromolecular turnover and an inhancement in the activity of catabolic enzymes. The high rate of RNA and protein turnover prevents the unbalanced cell growth and their death while the enhanced activity of catabolic enzymes maintains partial autolysis of resting cell compensating for the insufficient supply of nutrients due to a decreased external membrane permeability for some low molecular compounds. Thereupon, both these processes provide for the resistance of resting cells against unfavourable ambient effects allowing them to preserve proliferative potentials. Consequently the resting cells are in a special physiological state securing their self-maintenance under conditions of long-lasting absence of proliferation. The ability of cells to pass into a resting state may be regarded as a common feature of living systems acquired in the course of evolution. A co-ordinated activation of certain complexes of metabolic processes appears to be a general principle of resting cells existence in the animate nature.

Acetylation↗
PubMed1982

[Genetic control of cell proliferation and the evolution of the cell cycle].

The characteristics of temperature-sensitive cell cycle mutants along with cell fusion studies suggest that gene-dependent synthesis of the inducers of DNA replication is submitted to negative control via an endogenous inhibitor. The dependence of metazoan cell proliferation on extracellular stimulators (hormones, serum factors etc.) appears to be determined by these inhibitors. By contrast, prokaryotic cells and eukaryotic unicellular organisms seem to synthesize the inducers of DNA replication constitutively which enables these cells to proliferate with no specific stimulators. Thus, the following types of the cell cycle may exist in living organisms: A--prokaryotic type of cell cycle where DNA can be synthesized continuously under conditions of nutrient abundance; B--primitive eukaryotic type where DNA replication is interrupted by the condensation of chromosomes prior to mitosis; C--metazoan eukaryotic cell cycle of a higher order where cells after mitosis pass into a resting state, under the influence of endogenous inhibitors and resume the proliferation in a stochastic manner under the effect of exogenous activators. The alternation of active proliferation and resting in the cell life cycle is a necessary prerequisite for cell specialization and population-size control. The essential feature of evolutionary cell cycle reorganization is a substitution of the unlimited primitive cell multiplication with eukaryotic organization of genome and specific cell functions in the multicellular organism.

Animals↗
PubMed1976

[Morphologic and radioautographic study of reactivation of peritoneal exudate cell nuclei in heterokarya].

The heterokaryons of undifferentiated mouse fibroblasts (L and 3T3-4E/TK-) and various cell elements of the rat peritoneal exudate were obtained under the treatment with inactivated Sendai virus. The reactivation of RNA and DNA synthesis in the nuclei of highly differentiated periotoneal exudate cells and the synthesis of thymidine kinase controlled by the nuclei of peritoneal exudate cells were shown to occur in the heterokaryons. During the process of reactivation, the ring-like nuclei of polymorphonuclear leucocytes acquired the form characteristic of the reactivated nuclei of mononuclears. The morphological changes of heparin-containing granules in the cytoplasm of the heterokaryons of mast cells and undifferentiated fibroblasts suggest the degeneration and breakdown of granules.

Animals↗
PubMed1975

[Protective effect of thymidine in relation to the cytostatic action of cyclic adenosine-3', 5'-monophosphate in mammalian cell cultures].

Under the action of lmM of cyclic adenosine-3',5'-monophosphate (cAMP) the survival and the rate of reproduction of the cells of Chinese hamster in the culture decreased in comparison with control to 27 and 42%, respectively. Addition of 0.02 mM thymidine together with cAMP almost completely eliminated the cytostatic action of the latter. Thymidine also prevented the cytostatic effect of noncyclic 5'-AMR, but failed to influence the death of the cells with the action of dibutyril cAMP and theophylline. Thymidine failed to prevent the inhibitory action of cAMP on the mutant strains of mouse cells defective by thymidinekinase. A conclusion was drawn that in the concentrations under study thecytostatic action of the exogenous cAMP on the cells of mammals served as the sequence of splitting to 5'-AMP in the culture medium and was realized by blocking one of the stages of TMP synthesis.

Bucladesine↗