[Response to tamoxifen in estrogen receptor-positive cell line MCF-7 is independent of p53 expression].

The study was concerned with identification of predictive value of p53 expression on sensitivity to tamoxifen in breast cancer management. Estrogen receptor-positive cell line MCF-7 was used to establish p53 expression influence on the rate of cell proliferation after tamoxifen. The investigation demonstrated the absence of that effect when p53 was silenced.

[Process of active dissociation of vital stain Hoechst 33342 from DNa in cells of cultured rodent cell lines]. / Protsess aktivnoi dissotsiatsii prizhiznennogo krasitelia Khëkhsta 33342 iz DNK kletok perevivaemykh kletochnykh linii gryzunov.

The process of active dissociation or "DNA clearing" of not covalently binding agents from DNA in living HeLa cells was shown by the flow cytometry technique. The vital fluorescent bisbenzimidazole dye Hoechst 33342, which binds tightly but not covalently to DNA in a minor groove, was used as a basic model to study the interaction of not covalently binding agents with DNA. In this paper, we continue to analyse the "DNA clearing" process in the living fibroblasts of different rodent species (mouse, rat, Chinese hamster). The obtained data suggest that the processes of active dissociation or "DNA clearing" of Hoechst 33342 have some common features in all investigated mammalian cells. Nevertheless, some differences in the process were found in these lines. The role of nucleotide excision repair genes in the process of DNA clearing was not established.

[Adaptation of the body to the effects of stress increases the resistance of cardiac nuclei to damaging effects of single-chain exogenous DNA]. / Adaptatsiia organizma k stressornym vozdeistviiam povyshaet ustoichivost' iader serdechnykh kletok k povrezhdaiushchemu deistviiu odnonitevoi ékzogennoi DNK.

The effect of adaptation to stress exposure on the resistance of nuclear DNA to damaging effect of one-chain exogenous DNA was investigated by flow cytometric fluorescence method. It was shown that after the administration of one-chain DNA in concentration of 50 micrograms/ml into the nuclei suspension almost half of nuclear DNA was damaged in control. In adaptation this phenomenon was 5.5 times less pronounced. When the one-chain DNA concentration was increased, this protective effect of adaptation remained. The possible mechanism of the DNA-protective effect of adaptation is under consideration.

[Chromatin packing in the nuclei of mammalian cells studied by flow cytometry]. / Izuchenie upakovki khromatina v iadrakh kletok mlekopitaiushchikh metodom protochnoi tsitometrii.

A phenomenon of limited accessibility of mammalian cell nuclear DNA to external agents is described, which is revealed by altered binding of DNA-specific fluorescent dyes after fixation of nuclei with glutaraldehyde. This approach is demonstrated to permit visualizing different degrees of DNA shielding by proteins in cells of diverse differentiation and functional state, as well as measuring an alteration of nature chromatin conformation after different treatment. The treatment of nuclei with single-stranded DNA was found to result in a considerable increase in nuclear DNA accessibility to fluorescent dyes, probably by activation of endogenous nuclear DNA-dependent serine proteases. The data obtained allow to suppose the existence of a specific nuclear DNA accessibility regulating system based on protease action and regulated by the appearance of single-stranded DNA stretches which accompanied such genetic processes as DNA repair, transcription, recombination and replication.