[Cytochemical properties of prematurely condensed chromosomes]. / Tsitokhimicheskie svoistva prezhdevremenno kondensirovannykh khromosom.

Prematurely condensed chromosomes (PCC) have been obtained by polyethylene glycol (PEG) induced fusion in suspension of the Chinese hamster metaphase cultured cells with those in interphase. As alternative approach the PEG-fusion of the Chinese hamster asynchronous culture cells in monolayer with subsequent incubation in free medium was used. A comparative cytofluorimetric investigation of PCC and chromatin of the interphase nuclei of corresponding ploidy has shown some increase (up to 10%) of acridine orange and olivomycin binding with PCC chromatin. A similar slight increase in low molecular weight ligands binding with chromatin was also found in mitotic chromosomes. The data obtained confirm the opinion about the similarity of events taking place in chromatin during physiological mitosis and premature chromosome condensation. The cytochemical study of chromatin availability to low molecular weight ligands can be used as a criterion for judging on the properties of the artificially condensed chromatin.

[Fluorescence microscopic study of cells and polykaryons in the early periods following polyethylene glycol treatment]. / Fluorestsentno-mikroskopicheskoe issledovanie kletok i polikarionov v rannie sroki posle obrabotki poliétilenglikolem.

A fluorescence-microscopical study is made of cultured murine fibroblasts (L-cells) in early periods after the treatment with polyethylene glycol (PEG). Optimal conditions of fusion procedure were found under which the effectiveness of fusion was the highest and the toxical effect of PEG the lowest. The number of dead cells after the treatment with PEG did not exceed 10%. No significant changes in chromatin cytochemical properties (Acridine Orange and Olivomycin binding) were observed in the early periods of PEG treatment, that allows to use PEG for studying chromatin properties in hybrid cells obtained by PEG fusion. By means of PEG fusion, the hybrid cells with prematurely condensed chromosomes and also hybrids between animal and yeast cells have been obtained.

[Effect of the antitumor antibiotic actinoxanthine on cells cultured in vitro]. / Vliianie protivoopukholevogo antibiotika aktinoksantina na kletki, kul'tiviruemye in vitrol

Significant changes in the nucleus structure, complete suppression of the mitotic activity, markedly decreased synthesis of RNA (by 70--80 per cent according to incorporation of 3H-uridine) and decreased levels of DNA (by 40 per cent according to olivomycin binding) were observed in the fibroblasts cultivated in vitro due to exposure to actinoxanthine in an amount of 50 microgram/ml. The data indicate direct damaging effect of the drug on the cell chromatin. The above nuclear changes were also observed after a short-term exposure of the cells to the drug (up to 5 minutes). Still, they became evident only after the subsequent incubation of the cells in a pure culture medium for at least 15 minutes. No such changes in the nucleus structure were detected when after the 5-minute exposure to actinoxanthine the cells were exposed to trypsin for 3 minutes. When the time of exposure to actinoxanthine was longer (15 minutes and higher), trypsin suppressed the manifestation of the above nuclear changes. The two-stage mechanism of the damaging effect of actinoxanthine on the chromatin of the cells cultivated in vitro is discussed. The damaging effect of actinoxanthine on the cells begins from binding of the drug with the cell membrane. After that a short incubation period follows and then the characteristic changes in the nucleus structure appear.

[Influence of histone kinase phosphorylating lysine-rich histones, on the physico-chemical properties of normal hepatocyte chromatin and after partial hepatectomy]. / Vliianie gistonkinazy, fosforiliruiushchei bogatye lizinom fraktsii gistonov, na fiziko-khimicheskie svoistva khromatina gepatotsitov v norme i posle chastichnoi gepatéktomii.

The influence of a specific histone kinase, phosphorylating lysin-rich histone H1, H2a, H2b on the physico-chemical properties of chromatin from hepatocytes of normal and hepatectomized guinea pigs has been investigated. A cytochemical method has been used which permits to obtain information about the physico-chemical properties of the chromatin in situ, i.e. without its isolation. This approach allows us to evaluate changes in chromatin properties in cell cultures as well as in the intact organism. It is found that the specific histone kinase changes the properties of chromatin in non-dividing cells bringing about an increase of acridine orange binding to the level characteristic for hepatocytes after partial hepatectomy. At the same time the chromatin properties in activated hepatocytes are not changed under the action of the histone kinase. It is concluded that the specific histone kinase, phosphorylating lysine-rich histones can play an important role in the course of chromatin activation in cells stimulated to proliferation.

[Changes in the cytochemical properties of chromatin after stimulating proliferation in a stationary culture of Chinese hamster cells]. / Izmenenie tsitokhimicheskikh svoistv khromatina pri stimulirovanii proliferatsii v statsionarnoi kul'ture kletok kitaiskogo khomiachka

The first part of the prereplicative period in stimulated for cell proliferation steady-state culture of Chinese hamster cells was studied cytochemically. Investigation of the binding pattern of basic dye Acridine orange and Actinomycin D with cell nuclei and the melting profile of chromatin in situ suggests that one of the early events occurring in the course of stimulation of cell proliferation in steady-state culture is chromatin activation, i.e. changes in its physicochemical properties resulting in augmentation of transcription.