[DNA-tropic inhibitors of nuclease action on DNA in liver nuclei]. / DNK-tropnye ingibitory deistviia nukleaz na DNK v iadrakh pecheni.

Distamycin is a potent, wide-spectrum inhibitor of the breaking of both free and intranuclear DNA with DNAse I and with own nuclear nucleases. It compares very favourably with actinomycin D, proflavin and ethidium bromide, especially in the inhibition of DNAse I action in the nuclei. This seems likely to be due to partial overlapping of the binding sites of the nuclei with chromatin proteins in contrast to distamycin that interacts with a minor furrow of DNA being blocked to a less extent by proteins. The DNA-tropic agents under test exert no qualitative effect on the kinetics of intranuclear DNA splitting by DNAse I. Carminomycin and bleomycin are the least effective inhibitors in all the systems depicted.

[Kinetics of deoxyribonuclease I action on the DNA of different white rat tissues]. / Kinetika deistviia dezoksiribonukleazy I na DNK iader razlichnykh tkanei beloi krysy.

Studies have been made on the kinetics of the effect of DNAse I on nuclear DNA from the brain cortex, liver, spleen and kidney of albino rats. In all the nuclei studied, two DNA sites revealed which especially differ in the rate of their splitting. The share of rapidly splitted DNA amounts in the nuclei of the kidney and brain cortex up to 30%, in those of the liver and spleen -- about 25%. These findings are discussed in relation to the data available on the share of transcribed chromatin in the same tissues obtained by hybridization with nuclear RNA. For the brain and liver this method yields the same values, whereas for the spleen and kidney this test yields significantly lower values, i. e. about 10%.

[Effect of DNA-tropic antineoplastic and antiparasitic agents on DNAase I activity]. / Deistvie nekotorykh DNK-tropnykh protivorakovykh i protivoparazitnykh agentov na aktivnost' DNK-azy I.

Kinetics of DNAase I activity was studied in reaction mixtures containing tightly bound to DNA drugs used for study and treatment of cancer and some other diseases. Distamycin proved to be the strongest inhibitor. The inhibitory activity of the substances studied decreased as follows: distamycin greater than or equal to actinomycin D greater than or equal to ethidium bromide > proflavine > carminomycin > bleomycin. The latter substance did not possess any inhibitory action. The data obtained are discussed in relation to mechanisms of interaction of the substances studied and DNA. High efficiency was typical for substances, which were bound with the DNA molecules on their small curvature.

[Kinetic study of acid-soluble DNA formation under the effect of DNase I]. / Izuchenie kinetiki protsessa obrazovaniia kislotorastvorimykh produktov DNK pod deistviem DNK-azy I.

A mathematical model of acid-soluble DNA formation under the effect of DNase I was developed. The data from the kinetic analysis suggest that at the stage of 10-60% solubilization the number of breaks in DNA single strands seem to be linearly dependent on the increment of acid-soluble DNA. This stage of acid-soluble DNA formation may be interpreted in terms of the monomolecular (pseudomonomolecular) reaction.