[Effect of low temperatures on molecular parameters of DNA]. / Izuchenie vliiania nizkikh temperatur na molekuliarnye parametry DNK.

Cryoconservation effects on macromolecular parameters of DNA from reproductive cells of fishes are studied as well as cryodamages of DNA in solutions under various freezing conditions, by the viscometry method. A dependence of the low temperature action on DNA concentration in solution and on the action duration is determined. It is stated as well that the nitrogen temperature action on the biopolymer solution results in the formation of both double- and single-stranded breaks. The cryoprotector (ethylenglycol 12%) added into the solution frozen prevents from the formation of double-stranded breaks and decreases the number of single-stranded ones. The long-term (0.5 year) keeping of the biopolymer solution at -196 degrees C both under the cryoprotector (20% 1.2-propanediol) protection and without the cryoprotector induces the significant number of single-stranded breaks. Mechanisms of cryodamages of DNA macromolecules in cells and under the nitrogen temperature action are discussed.

[Structural and physicochemical characteristics of DNA from animal tissue subjected to chronic irradiation in the Chernobyl area]. / Strukturnye i fiziko-khimicheskie kharakteristiki DNK iz tkanei zhivotnykh, podvergavshikhsia dlitel'nomu khronicheskomu oblucheniiu v zone chernobylia.

The properties of animal DNAs exposed to prolonged irradiation in the Chernobyl zone, have been studied by the methods of viscometry, thermal denaturation, IR-spectroscopy, and electrophoresis. High content of low-molecular fractions have been observed in the preparations of DNA from liver and spleen, their quantities increasing with age and generation of animals. This effect is especially strong in DNA from liver. Low-molecular fraction of DNA is shown to be enriched with G-C pairs and to consist of the following four fractions: 1) approximately 500 base pairs (B.p.), 2) approximately 1.5 divided by 2 thousand B.p., 3) approximately 4 divided by 5 thousand B.p. and 4) a mixture of approximately 20 thousand B.p. fragments. Further, it has been observed that the DNA preparations from the tissues of experimental animals contain about ten times higher contents of Fe, Zn, Se and other elements as compared to the control preparations.

[Structural transformations and aggregation stability of lecithin liposomes in cryoprotective media]. / Strukturnye prevrashcheniia i agregatsionnaia ustoichivost' letsitinovykh liposom v sredakh s krioprotektorami.

To study the structural transformations and aggregation stability in liposomes, a new approach is proposed whose efficiency is demonstrated during the analysis of light scattering by lecithin liposome sols doped with low-molecular cryoprotectors . This approach is used to determine absolute dimensions, relative values of weight concentration, masses of vesicules and their surface densities as well as their polydispersity characteristics. The anisotropic scattering data suggest that cryoprotectors eliminate small scale defects which are partially restored at low temperatures. Low-molecular cryoprotectors are found to produce some favourable changes in dimensions and distribution of liposomes and to increase their aggregation and structural stability.

[Isolation and low-temperature preservation of liposomes containing rifampicin]. / Poluchenie i nizkotemperaturnoe konservirovanie liposom, soderzhashchikh rifampitsin.

The optimal conditions for preparations of rifampicin-containing liposomes were determined with the methods of mechanical shaking, gas dispersion and and reversible phases. It was found that the percentage of rifampicin incorporation into liposomes depended on the molar ratio of the antibiotic to the lipid (the optimal ratio was 1 : 10), the size and structure of liposomes, the amount of cholesterol added and the lipid membrane charge. Incorporation of rifampicin amounted to 16.1 +/- 2.4, 39.2 +/- 3.2 and 60.5 +/- 2.9 per cent with respect to neutral lecithin multilamellar liposes, liposomes prepared with the gas dispersion method and liposomes prepared with the method of reversible phases, respectively. Cholesterol in a molar ratio to lecithin equal to 2 : 5 or higher and dicetyl phosphate imparting the negative charge to the membrane had an inhibitory effect on the drug uptake by liposomes, while stearyl amine having the positive charge had a stimulating effect. The effect of the cryoprotectors glucose, polyvinylpyrrolidone, poly-ethylene glycole-400 and glycerol on low-temperature preservation and storage of rifampicin-containing liposomes was studied. It was shown that 10--15 per cent solutions of sucrose and glucose had the highest cryoprotective effect, when the two-stage method of freezing was used. It provided almost 84 per cent preservation of liposomal rifampicin. Electron microscopy showed that after defrosting liposomes no significant changes in the size and structure of lipid membranes were observed.

[Effect of thymosterin A on the immunological reaction of mice]. / Vplyv tymosterynu A na imunolochichnu reaktisiiu myshei

Proliferaiton of thymus-dependent lymphocytes and immunological reaction of the line CBA mice immunized with sheep erythrocytes was studied as affected by thymosterol A. The data obtained confirmed the authors' assumptions on a stimulation effect of thymosterol A on division of thymocytes. Introduction of the mentioned preparation against a background of the antigenic aciton of sheep erythrocytes causes an increase in the amount of cells synthesizing hemolysins more than by 60% as compared to the control. The preparation effect depends on the dose. The data are presented, which makes it possible to assume that the mentioned effects may be due to the action of thymosterol A on the content and activity of the intracellular cyclic AMP.