Biomedical subjects

N A Poriadkova

Publications and source records attributed to N A Poriadkova.

At least 19 recordsLinked to original sources

PubMed1990

[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. Direct modification of chromosomal radiosensitivity by BrdU is excluded. The results obtained suggest the interference of free BrdU present in culture medium with processes of DNA reparation at the G1 stage.

Bromodeoxyuridine↗

PubMed1988

[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. at different relative frequencies of cells in the first and second mitotic cycle. The frequency of aberrations produced in the G2 stage was analysed. The total yield of aberrations gradually increased with the increase of time lapse between the onset of cultivation and irradiation. If, however, the relative frequencies of the first and second mitoses are taken into account, it could be concluded that radiosensitivity of chromosomes remains constant in each cycle and independent from its duration. Besides, radiosensitivity of chromosomes during the second cycle is one and half times stronger, as compared to the first cycle. In accordance with the data of other authors, 5-bromodeoxyuridine has been found to significantly increase radiosensitivity.

Bromodeoxyuridine↗

PubMed1987

[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. Formation of IL in heterochromatin follows the statistical regularities: IL were only observed in some fraction of cells and, as a rule, involved not all heterochromatic segments. The regularities established witness against the uninemic model of chromosome.

Animals↗

PubMed1985

[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 2.5 h. Non-irradiated cells were subjected to the same treatments. Chromosomal aberrations were analysed in metaphase cells of the first mitosis. When administered alone, all chemicals increased the frequency of chromatid aberrations. The special analysis showed that these chemicals were not mutagens in a strict sense, as the observed increase of aberration frequency was due to inhibition of repair processes, which increased the probability of manifestation of spontaneous changes (so-called "pseudomutagenesis"). The same chemicals increased the frequency of radiation-induced aberrations during two periods of the mitotic cycle, namely, in the end of the G1 stage and in the G2 stage. It has been recently shown that the inhibitor of DNA synthesis, 5-fluorodeoxyuridine, increased the frequency of radiation-induced aberrations during the same periods. It follows that the process of repair proceeding during these periods requires both DNA synthesis and energy supply.

Chromosome Aberrations↗

PubMed1982

[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. Radiation produced 18 fold increase of the frequency of SsCE, whereas the increase of usual SCE was less than two fold. The shape of stage-effect curves for induces SCE and SsCE was the same; the maximal yield was observed in the middle of the S stage, and no exchanges were produced in the G2 stage. It is concluded that SsCE is nothing other than minute intercalary SCE produced by the single-hit mechanism.

Animals↗

PubMed1981

[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. When administered alone, FUdR increased the frequency of chromatid aberrations and gaps over the spontaneous level. This increase took place mainly during two periods of the mitotic cycle, namely, on the borderline between G1 and S stages and at the end of the G2 stage. FudR barely affected the frequency of chromosomal aberrations. THe effect did not depend upon the concentration of FUdR. Irradiation during the G1 stage produced chromatid aberrations and gaps with the same frequency as FUdR, whereas the frequency of chromosome aberrations was much higher. When administered after irradiation, FUdR increased the frequency of all types of aberrations; the periods of mitotic cycle when this increase was statistically significant correspond to those of "mutagenic" action of FUdR mentioned above. This pattern may be easily explained if one postulates that in our experiments FUdR exhibited the features of a "pseudomutagen" i.e. the factor which suppresses repair of primary lesions (spontaneous or radiation-induced) without giving rise to new mutational changes.

Cells, Cultured↗

PubMed1981

[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.e. bifiliary substituted) chromatids was significantly lower, as compared with dark (i.e. unifiliary substituted) ones. The comparison of these data with the previously published suggests that the relative frequency of breaks in uni- and bifiliary substituted chromatids depends on the energy of quanta. A hypothesis is discussed that a resonance absorption of energy by Br atoms and an increased interaction between BrdUrd-substituted structures, which favours the repair of double-strand breaks, can explain the noted regularity.

Animals↗

PubMed1978

[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. Irradiation after a 47 hours incubation (mainly G2 stage of the first cycle) increased the frequency of SCE, whereas the irradiation 2 hours before fixation (G2 stage of the second cycle) decreased it. The change of the frequence of SCE produced by irradiation was not proportional to the chromosome length.

Animals↗

PubMed1977