[Effect of extreme factors, differing in nature, on distribution of repetitive sequences in extracellular DNA]. / Vliianie razlichaiushchikhsia po svoei prirode ékstremal'nykh faktorov na raspredelenie povtoriaiushchikhsia posledovatel'nostei vo vnekletochnoi DNK.

Extreme exposures induce changes of content and fractional composition of extracellular DNA. The degree of these changes is dependent on the nature of stressor and conditioned by genome destabilization. The character of distribution in the separate fractions instable in genome of repeating sequences determines the function of extracellular DNA as an adaptogenic factor.

Postradiation DNA polymorphism.

The presence of DNA molecules with tumor-specific genetic alterations has been demonstrated in the plasma of cancer patients. Such plasma DNA fragments may be immunogenic and provide immunologic support to the malignant cells. Further, the tumor-specific plasma DNA may participate in the adaptive processes of the tumor cells in the cancer host. The mechanisms of the latter are unclear. However, from the standpoint of the resistance problem, understanding of DNA transformation after exposure of extreme factors is of great interest.

[Changes in the content and fractional composition of blood plasma nucleic acids in radiation lesions. The effect of radioprotectors]. / Izmenenie soderzhaniia i fraktsionnogo sostava nukleinovykh kislot plazmy krovi pri radiatsionnykh porazheniiakh. Effekt radioprotektorov.

The content of DNA in blood plasma increased in early stages after irradiation (2 and 5 h), the low-molecular DNA (160-180 bp) being revealed as opposed to intact animals. Protection of gamma-irradiated rats by cystamine or gammaphos enhanced this phenomenon. The injections of cystamine and gammaphos to nonirradiated animals stimulated DNA ejection into blood stream in 2 h only with normalization by 5 h. Cystamine was the most effective, and in experiment with non-irradiated animals the low-molecular DNA was detected for cystamine only.

[Structure of low-molecular DNA in the blood plasma of irradiated rats]. / O strukture nizkomolekuliarnoi DNK plazmy krovi obluchënnykh krys.

Low-molecular DNA in blood plasma of rats appeared after gamma-irradiation in a dose 8-100 Gy. This DNA has been cloned and the 26 clones have been sequenced. The search for sequence similarity between the designated sequences and sequences in EMBL allowed the three homology to LINE 3 sequences to be found. The differences in the structure of low-molecular DNAs extracted from rat blood plasma after irradiation of rats in doses 8 and 100 Gy were not found.

Extracellular DNA level in the blood of irradiated rats.

There is high-molecular DNA in the blood of unirradiated rats which moves as a single fraction during electrophoresis in 0.5% agarose. At short times (2-5 h) after gamma-irradiation at doses from 1 to 100 Gy a low-molecular species of DNA appears (about 180 nucleotide pairs), the amount of which is directly proportional to exposure dose at 5 h after exposure. It has been established by Southern hybridization that the low-molecular DNA has few nucleotide sequences common with those of the high-molecular DNA, but it shows homologously to genomic sequences.

[Contents of extracellular DNA in blood of irradiated rats]. / Soderzhanie vnekletochnoi DNK v krovi obluchennykh krys.

Intact rat plasma contains high-molecular DNA which moves as a single fraction in 0.5% agarose electrophoresis. As early as 2-5 hours after gamma-irradiation in a dose of 1-100 Gy there appears low-molecular DNA (about 180 nucleotide pairs), the amount of which directly correlates with the irradiation dose 5 hours after the exposure. Blot-hybridization showed that low-molecular DNA has no common nucleotide sequences with high-molecular DNA, though has sites similar to genome repeat sequences.

[Changes in the serum fraction composition of nucleic acids in radiation injuries. Alterations in an early period after gamma-irradiation of rats]. / Izmeneniia fraktsionnogo sostava nukleinovykh kislot syvorotki krovi pri radiatsionnykh porazheniiakh. Narusheniia v rannie sroki posle gamma-oblucheniia krys.

The content and fractional composition of nucleic acids of blood serum change after lethal (8 Gy) particularly superlethal (100 Gy) gamma-irradiation of rats. This concerns DNA the content of which increases by 7 times 5 h following 100 Gy irradiation. It has been shown by electrophoresis in 0.85% agarose that a heterogeneous DNA fraction with the molecular weight of (1-15) X 10(6) dalton increases. The analysis of the preparation in the polyacrylamide gel has revealed a DNA fraction that is not found in norm: the fraction possesses the electrophoretic mobility corresponding to that of nucleosome DNA.