[Epigenetic cell reactions induced by ionizing radiation]. / Epigeneticheskie reaktsii kletok na deistvie ioniziruiushchei radiatsii.

The importance of radiation modification of epigenetic activity in the general mechanism of radiobiological reactions is proved. The inheritable epigenetic changes induced by irradiation are one of the basic reasons of formation of the remote radiation pathology. It is noted that epigenetic inheritable changes of cells have the determined character distinguishing them from mutation changes, being individual and not directed. It is underlined the ability of ionizing radiation to modify a level of spontaneous genetic instability inherited in a number of cell generations on the epigenetic mechanism.

[DNA-polymerase activity and DNA synthesis in the hepatocyte nuclear matrix]. / DNK-polimeraznaia aktivnost' i sintez DNK v sostave iadernogo matriksa gepatotsitov.

The comparative analysis of DNA-synthetase activity of hepatocytes, isolated nuclei and nuclear matrix from normal and regenerating rat liver was performed. The highest enrichment with newly-synthesized DNA was registered in the DNA fraction associated with the nuclear matrix both in vivo and in vitro. The functioning of DNA polymerases alpha and beta in the matrix was shown. Our results indicate that DNA polymerase beta is more firmly bound with the nuclear matrix in the cells of normal liver but this enzyme is eluted almost completely from the nuclei of regenerating liver cells. At the first moment after gamma-irradiation of rats the preferential initiation of unscheduled DNA synthesis in vivo has been observed on the nuclear skeletal structures. This may serve as an indication on the possibility that DNA repair process occurs on the nuclear matrix.

[Initiation of unscheduled synthesis on DNA sites associated with a nuclear matrix of irradiated hepatoma cells]. / Ob initsiatsii vneplanovogo sinteza na uchastkakh DNK, assotsiirovannykh s iadernym matriksom obluchennykh kletok gepatomy.

A study was made of the distribution of unscheduled DNA synthesis (induced by UV- or gamma-radiation and resistant to hydroxyurea) between the DNA sites in the nuclear matrix and total nuclear DNA of Zajdela ascites hepatoma cells. It was shown that during the first 1.5 to 5 min of the postirradiation incubation the rate of the unscheduled synthesis of DNA was considerably higher in the DNA fraction, firmly associated with the nuclear matrix proteins, than in the total nuclear DNA.