[Effect of free 5-bromodeoxyuridine on induction of SCE in human lymphocytes gamma-irradiated at the presynthetic stage of primary and secondary mitotic cycles].

Formation of SCE was studied in lymphocytes irradiated by 60Co gamma-rays at the G1 stage of the first or second mitotic cycles. The yield of SCEs induced by irradiation in the presence of 5-bromodeoxyuridine (BrdU) proved to be significantly higher than that obtained in the absence of BrdU. The enhancing influence of BrdU on SCE induction depends on neither replication cycle nor the molecular constitution of chromosomes under irradiation.

[Chromosome radiosensitivity in 2 successive mitotic cycles of human lymphocytes].

A culture of human lymphocytes was irradiated with gamma-quanta (0.5 Gy) after incubation during different time intervals, i.e.

[Duration of the mitotic cycle and radiosensitivity of chromosomes in human lymphocytes].

The frequency of chromosome aberrations was studied in human lymphocytes, with different duration of the mitotic cycle (from 48 to 73 h), exposed to gamma-quanta 2 h before fixation (i. e. at the G2 stage).

[Effect of radiation on the formation of isolabels in the late replicating regions of the Chinese hamster genome].

The cells synchronized in the G1 stage were incubated in a medium containing 5-bromodeoxyuridine, and chromosomes were analysed after two rounds of replication Iso-labels (IL) were observed in the late-replicating (heterochromatic) segments. The frequency of IL increased after irradiation during the G2 stage of the second cycle. Moreover, IL were observed in euchromatic segments (not recorded in control cells), whereas the frequency of sister chromatid exchanges decreased.

[Effect of cell respiration inhibitors on the formation of structural mutations in human lymphocytes irradiated at different stages of the mitotic cycle].

Human lymphocytes were irradiated by 60Co gamma-rays after 0, 10, 20, 35, 45, 48 and 49.5 h of incubation. Immediately after irradiation sodium cyanide, sodium fluoride or monoiodoacetic acid was given for 2.

[Unscheduled DNA synthesis during gamma-irradiation of human lymphocytes in the G1 stage].

A study was made of the unscheduled synthesis of DNA in gamma-irradiated nuclei of human lymphocytes 10, 15 and 20 hr following PHA-stimulation. It was shown that the unscheduled DNA synthesis is a function of radiation dose and time after PHA-stimulation.

[Dependence of the frequency of radiation-induced iso-labels on the colchicine concentration].

In experiments on human lymphocytes it was demonstrated that the frequency of iso-labels induced by irradiation of cells at the G2 phase decreases with increasing concentration of colchicine used for accumulation of metaphases. This might be explained by the possible influence of colchicine on the pattern of chromosome replication.

[Effect of irradiation at different stages of the mitotic cycle on the formation of sister chromatid exchanges in a Chinese hamster cell culture].

Cultured Chinese hamster cells (line 237) grown in a medium containing 5-bromo-deoxyuridine were irradiated with 1 Gy of 60Co gamma-rays and fixed at different times there after 1-18 hours. Sister chromatid exchanges (SCE) were analysed in harlequine-stained cells. It was established that SCE may occur involving only part hitherto only recorded in plant cells.

[Frequency of aberrations in uni- and biliary 5-bromodeoxyuridine-substituted chromatids].

Chinese hamster cells and human lymphocytes were incubated with BrdUrd during two cycles of replication and stained using the "harlequine" technique. The G2 cells were irradiated with 1 Gy of gamma-rays from the 60 Co source. The frequency of breaks in light (i.

[Formation of chromosome aberrations in human lymphocytes to the action of 5-fluorodeoxyuridine used separately and in combination with gamma irradiation: changes in the effect in the course of the mitotic cycle].

Human lymphocytes were treated after different times of incubation, either by 60Co gamma-rays (1 Gy) followed by 5-fluorodeoxyuridine (FUdR, 2.10-7 M during 2,5 h) or by radiation and FUdR, separately. Chromosomal aberrations were studied after 51 h of incubation.

[Method of differential staining of sister chromatids for the study of the effects of gamma rays on the frequency of sister chromatid exchange in human lymphocytes].

Human lymphocytes were incubated during two cycles of replication in the presence of 5-bromodeoxyuridine, fixed after a 96 hours cultivation, stained with fluorescenct compound "Hoechst 33258", illuminated with sunlight and repeatedly stained with azureosine. After such a treatment, the two chromatids of metaphase chromosomes are stained with different intensity revealing numerous sister chromatid exchanges (SCE) which could be exactly recorded. In spite of the use if tge standard technique, the frequency of SCE was different in two donors.