[Dynamics of a 3H-lysine pulse label in the culturing of L cells]. / Dinamika impul'snoi 3H-lizinovoi metki pri kul'tivirovanii L-kletok.

Using autoradiography, 3H-lysine, 3H-thymidine, and 3H-tryptophane puls labeled L-cells were examined as long as through four passages. Our studies demonstrate that no renewal of 3H-lysine labels takes place in chromosomes and nuclei. Unlike, the cytoplasmic labels of 3H-lysine and chromosomal, nuclear and cytoplasmic labels of 3H-tryptophane showed an intensive renewal. A question of renewal of lysine-rich histones is discussed.

[Reassociation kinetics of the DNA from rat liver nuclei of varying ploidy]. / Kinetika reassotsiatsii DNK iz iader razlichnoi ploidnosti pecheni krys.

Using sucrose gradient centrifugation, isolated liver cell nuclei were fractionated according to different ploidy classes. DNA was isolated from the di- and polyploid as well as from the total nuclear fractions, and the kinetics of their reassociation was investigated. A similar mode of reassociation was revealed for DNAs isolated from the nuclei of different ploidy classes, testifying in favour of the true polyploidy of liver cell nuclei.

[Autoradiography of lysed L cells with labelled 3H-lysine]. / Avtoradiografiia lizirovannykh L-kletok, mechennykh 3H-lizinom.

Using the method of fibr-DNA autoradiography, 3H-lysine labeled L cells were examined. Fibr-labeled structures as long as 400 mkm were revealed. The pattern of labeling along fibres was same as when cells were labeled with 3H-thymidine. In cross experiments when 3H-lysine and 3H-thymidine were used simultaneously, the pattern of labeling remained the same. The data obtained may evidence that the complexation of new synthesized histones with DNA takes place synchronously with the replication, and in the points of chromosome replication.

[Effect of cycloheximide on DNA replication. III. Results of autoradiography of the DNA of lysed cells]. / Deistvie tsiklogeksimida na replikatsiiu DNK. III. Dannye avtoradiografii DNK lizirovannykh kletok.

With the help of DNA-fiber autoradiography on L cells, the question of mechanism of a rapid block of DNA replication by cycloheximide, an inhibitor of protein synthesis, was examined. The presented data show that the elongation of labeled regions in replicating units is blocked. In non-treated cells the replication rate was 0.4 mcm/min; the mean size of replicon was 21 mcm. The difficulties encountered in the explanation of the data obtained are discussed.

[Penetration of polyene antibiotics into human embryonic kidney tissue cell cultures]. / O proniknovenii polienovykh antibiotikov v kletki kul'tury tkani pochek émbriona cheloveka.

Penetration of 14C-amphotericin AM-2 into the cells of the tissue culture of the human embryon kidneys was studied by means of light autoradiography after incubation with the antibiotic. Microscopic examination of the autographs of the cell slices revealed the presence of the radioactive label in the cytoplasm and nucleoplasm of the cells. The revealed intracellular localization of the label was evident of the antibiotic penetration into the cells.

[The effect of cycloheximide on DNA replication. II. Antibiotic resistance following L cell treatment with hydroxyurea]. / Deistvie tsikogeksimida na replikatsiiu DNK. II. Ustoichivost' k antibiotiku posle obrabotki L-kletok oksimochevinoi

DNA replication in eukaryotic cells is closely associated with protein synthesis. When protein synthesis is specifically inhibited, DNA synthesis stops quickly too. No precise knowledge has been so far available concerning the reasons of this coupling. The data presented confirm an earlier established for Chlorella fact that the inhibition of DNA synthesis in L-cells, due to a several hours treatment with hidroxyurea, results in a consequent stability of DNA synthesis in these cells to a protein synthesis inhibitor--cyclohexamide.

[The prereplicative period in hepatic regeneration]. / K voprosu o prereplikativnom periode pri regeneratsii pecheni

Using H3-thymidine autoradiography and biochemical methods, it was revealed that the inhibition of thymidine incorporation in the nuclei of hepatocytes and duodenal crypt epithelial cells occurs in the middle of the preperlicative period (between the liver resection and the increase of DNA synthesis) in the rat regenerating liver. The transition of cells from G1 to phase S was also blocked. No decrease in the uptake of H3-thymidine by liver cells was seen after hepatectomy.

[Effect of protein synthesis inhibitors on DNA replication. I. Effect of the short-term action of cycloheximide on cell permeability for thymidine in vitro]. / Deistvie ingibitorov belkovogo sinteza na replikatsiia DNK. I. Vliianie kratkovremennogo vozdeistviia tsiklogeksimida na pronitsaemost' kletok dlia timidina in vitro

The effect of protein synthesis inhibitors on DNA replication was studied on L cells. After a 10 minutes' action of the inhibitors, protein synthesis was seen to be completely blocked, and DNA synthesis decreased by 85%. Four hours after a 20-minutes' cycloheximide treatment, the cells completely restored their ability to protein synthesis and DNA replication and even surpass the control level, due, probably, to a partial cell synchronization in S period. The short action of cycloheximide did not interfere with thymidine uptake by the cells. The rate of the exogenous precursor uptake was even higher than that in the control, apparently, because of its much reduced utilization in the inhibited DNA synthesis.