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A unique installation and an original investigation method are described for studying mechanoluminescence of lymphocytes. The spectral content of mechanoluminescence of lymphocytes of human peripheral blood showed maxima of optical emission at 262, 291, 335 and 412 nm. Intraperitoneal administration of hydrocortisone in mice enhances thymocyte mechanoluminescence intensity after 2 and 3 days by 33 and 62%, resp. It is shown that Acridine orange, reacting with murine thymocytes and their nucleoids, affects intensity of their mechanoluminescence, depending on the value of concentration of the injected intercalator.

Comparative analysis of biochemical indices that reflect the proteolysis rate in rat peripheral blood lymphocytes in normal conditions and during the first 4-6 h after whole-body single uniform gamma-irradiation with lethal (7.5 Gy) and nonlethal (3 Gy) doses has revealed that the pronounced activation of proteolysis in lymphocytes and the disturbances in the inhibitor/protease balance are characteristic of the severe form of radiation damage with fatal outcome. Simultaneously changes occur in biochemical indices of plasma that reflect a catabolic pathway of metabolism in the whole-body. The absence of similar changes in the blood of the survived animals permits to recommend the biochemical indices under study to be used for early prognosis of the radiation affection outcome.

Comparative studies of acridine orange (AO) and ethidium bromide interactions with supercoiled DNA (scDNA) of thymocytes were performed in which various conformational changes were induced. AO may be efficiently used for evaluation of conformational alterations of scDNA. Moreover, employing the maximum values of AO fluorescence allows to determine the maximum levels of scDNA relaxation.

Fluorescent analysis of structural changes of nucleotide in the blood associated with AT fragments has been studied in rats, gamma-irradiated with doses of 2 and 4 Gy. It was demonstrated that the haematological, gerontological and cancerogenic late consequences were preceded by the structural genomic disturbances determined by 30 day after irradiation.

The share of lymphocytes with abnormal nuclei in the peripheral rat blood was found to increase during the first 24 h following irradiation with doses LD0, LD50, and LD100. With LD50 the index under study significantly varied in survived, died and control animals. It is suggested that the occurrence of abnormal nuclei in the peripheral rat blood is the result of the two processes, namely, the mitotic division and apoptotic death of cells.

A study was made of the action of novobiocin on degradation and repair events in supercoiled nuclear DNA from three thymocyte fractions obtained by ficoll-paque gradient sedimentation. When added before gamma-irradiation novobiocin (1.9 mg/ml) exerted a radioprotective effect during the "second wave" of supercoiled DNA degradation. It is suggested that this effect may be due to the inhibition of DNA topoisomerase II.

A study was made of the radioprotective and therapeutic effect of potassium orotate on rats subjected to whole-body gamma-irradiated with doses of 11, 9 and 4 Gy. The preparation exerted a radioprotective action when administered intraperitoneally 60 min before irradiation as was estimated with a reference to the survival rate and leukocyte level in the peripheral blood. Fron the analysis of the peripheral blood consumption it was inferred that potassium orotate weakened the radiation damage and enhanced the recovery processes during the postirradiation period.

A simple approach is proposed to determine locally denatured sites and stability characteristics of secondary DNA structure. The method is based on the analysis of the initial part of melting curve and the determination of changes in the optical density of DNA after heating up to a fixed temperature. The potentiality of the approach is illustrated by the experiments with DNA containing defects in the secondary structure caused by gamma-irradiation in vitro. The sensitivity of the method is less than 0.2 Gy.

Some stages of the apoptotic death of lymphoid cells (thymocytes and peripheral blood lymphocytes) have been followed up using light and electron microscopes. Differences have been revealed in the formation of death stages under natural physiological conditions and after gamma-irradiation. High radiation doses are shown to interfere with the process of nuclear chromatin condensation characteristic of the natural physiological death of cells.

A study was made of the dynamics of changes in the amino acid composition of erythrocytes, plasma, whole blood and spleen of albino rats during 3 days after total-body uniform gamma-irradiation with doses of 3, 6 and 12 Gy. The change in the amino acid pool of blood and spleen and the ratio between the amino acid concentration in erythrocytes and plasma were shown to depend upon the degree of radiation injury.

Using the method of electrophoresis in agar gel of superhelical plasmid DNA, which served as a substrate for determining endonuclease activity, the authors showed that the same radiation dose influenced in a different way the activity of acid and alkaline DNAases in rat blood serum. At early times (3-6 h) following irradiation, the activity of acid nucleases increased whereas that of alkaline DNAases decreased.

A direct fluorimetric method is elaborated for studying conformational distortions in the scDNA of "nucleoids" of macrophages and thymocytes. The method is more advantageous compared to methods of viscosimetry and sedimentation.

During the first hours following nonuniform gamma-irradiation (the nonuniformity coefficient was 3:1 and 5:1 with a dose change along the axis directed cranio-caudally and caudo-cranially), endonuclease activity (pH 5.75) in the blood serum increased with the dose which was estimated with a reference to total utilization of the substrate. Supercoiled plasmid DNA served as the substrate. The transformation of a supercoiled form of plasmid DNA into an open circular form was the criterion of estimation of nuclease activity. It was shown that the increase in the nuclease activity correlated with the increase in the nonuniformity coefficient.