[Conformational changes in DNA during development of spontaneous leukosis in AKR mice]. / Konformatsionnye izmeneniia DNK v protsesse razvitiia spontannogo leikoza u myshei linii AKR.

The dynamics of conformational changes in thymus and spleen DNA of 3-9-month old mice line AKR during the development of spontaneous lymphoid leukosis was studied by the retention on nitrocellulose filters. It was shown that the degree of DNA condensation for healthy and deceased animals differs, which is probably due to different intensity of endogenous oxidation. Seasonal conformational changes in spleen DNA from healthy mice of line F1 were revealed.

[The characteristics of the biological action of low doses of irradiation]. / Osobennosti biologicheskogo deistviia malykh doz oblucheniia.

Biochemical, biophysical and functional properties of the genetic and membrane apparatus of the cell were considered activity and regulatory properties of the membrane and cytosolic enzymes of organs and tissues of mice exposed to radiation in the wide range of doses of 6 to 1800 mGy with the radiation intensity of 4.1 x 10(-3) and 41 x 10(-3) mGy/min. It was shown that the dose-dependence of changes in the investigated properties is of non-linear polymodal (bimodal) nature. The value of the maximum and the dose at which the latter was observed depend on the object's nature, radiation intensity and time passed after irradiation. An essential factor is that sensitivity of molecules, cells, organs and animals exposed to low-dose radiation to other damaging effects changes. The explanation is given in terms of the changes in the relation between the quantity of damages and the activity of reparation systems induced by low-dose irradiation.

[The possible role of the molecular products from DNA radiolysis in mutagenesis]. / Vozmozhnaia rol' molekuliarnykh produktov radioliza DNK v mutageneze.

Analysis of literature data on molecular products of DNA radiolysis and their possible role in mutagenesis enabled us to define a number of potentially mutagenic products of modified DNA nitrogen base and to correlate primary mechanisms of free radical products formation and their transformation with the formation of final potentially mutagenic products of DNA nitrogen base and consequently with the formation of cell mutations induced by radiation. In the review general schemes of radiation mutagenesis are proposed for potentially mutagenic products of all DNA nitrogen base. Analysis of radiation-chemical yield of these products is also given. Possible role of apurinic (apyrimidinic) sites and the modified sugar fragment of DNA in mutagenesis has been discussed as well.

[The effect of low doses of ionizing radiation on the DNA in the spleen in the irradiation of mice]. / Vliianie malykh doz ioniziruiushchei radiatsii na DNK selezenki pri obluchenii myshei.

The research of low dose gamma-irradiation 137Cs effect on mice line F1 has been carried out under two different intensities: 0.6 cGy per day (dose range 0.6-9.6 cGy) and 6.0 cGy per day (dose range 6.0-60 cGy). High molecular DNA was isolated from spleen of irradiated and intact mice and analyzed by DNA retention method to nitrocellulose filters under physiological ionic strength. Increase in percentage of DNA retention after mice irradiation by doses of 0.6-5.4 cGy with maximum of 1.2 has been found. In dose range 6.0-24 cGy maximum of DNA retention has been observed at dose of 6.0 cGy. DNA preparation did not contain single-strand breaks. It is supposed that the phenomena of increase in percentage of DNA retention is the result of its compactization during the process of adaptive cell response to low dose ionizing radiation exposure.

[The Z-form of bacteriophage lambda DNA, modified in situ]. / Z-forma modifitsirovannoi in situ DNK bakteriofaga lambda.

Using the methods of chemical modification, restriction analysis and immune-electron microscopy it has been shown that the definite regions of the bacteriophage lambda DNA contain unpaired bases in situ. The distribution map of such sites along the genome has been constructed. The correlation of the in situ modification and the reaction with anti-Z-DNA antibodies is shown for the 44972 bp site of bacteriophage DNA. The possibility of the existence of Z-form DNA in situ is discussed.

[Analysis of radiation injuries of DNA from liver and transplanted tumors in vitro]. / Analiz radiatsionnogo povrezhdeniia in vitro DNK pecheni i perevivaemykh opukholei.

A comparative study of some radiation effects on DNAs from mouse liver, Ehrlich ascites tumor and hepatoma 22A was made after X-irradiation of the 0.02% aerated solutions in 0.1 M NaCl. The electrophoretic and spectrophotometric methods were used to measure the radiation-chemical yields of single- and double-strand breaks, DNA secondary structure defects, a malonaldehyde analogue and pyrimidine hydroperoxides. DNA from tumors was found to be more affected by radiation than DNA from normal liver: this may be due to a higher degree of base damage (the yield of hydroperoxides) and to transformation of original secondary structure defects into single-strand breaks at low irradiation doses.