[Chromosomal abnormalities in lymphocytes from a patient with Werner's syndrome in intact culture and after treatment with halogenated analogs of thymidine].

Four balanced chromosomal translocation, deletion of chromosome 15, and a break in chromosome 11 were detected in 100 G-banded metaphases of cultured lymphocytes of a patient with Werner's syndrome. We observed aneuploidy that included both trisomies and monosomies for various chromosomes. Halogenated analogs of thymidine in low doses increased significantly the incidence of chromosome aberrations accompanied by fragments.

[An analysis of the chromosomal combinations in dicentrics with induced telomeric fusion].

Chinese hamster heteroploid cell culture was treated by colcemide for 42 h, of which within the first 17 h by 5-bromedeoxyuridine. Dicentric chromosomes, that were formed at the 2nd mitosis after colcemide administration, were analysed using G-banding. Of 211, only 40 were made of heterological dicentrics.

[Telomeric chromosome fusion in cells with micronuclei under the combined action of hyperthermia and hypothermia and halogenated analogs of thymidine].

The reaction of cells with micronuclei in respect of the induction of specific dicentric chromosomes with halogenated analogs of thymidine at various temperatures was studied. The positive correlation between the temperature and frequency of dicentrics was shown for all halogenated analogs of thymidine. The minimum frequency of dicentrics was found in the case when used 5-iododeoxyuridine and hypothermia (34 degrees C).

[The effect of hyper- and hypothermia on induced telomeric chromosome fusion].

After administration of colcemid and 5-BrdU in the cell culture, the cells pass through the first interphase to delay in mitosis. Then the cells overcome the colcemid blockade, and polykaryocytes with micronuclei are formed. The second interphase in followed by the second mitosis, during which dicentric chromosomes are observed.

[The induction of specific dicentric chromosomes in CHO-6 Chinese hamster ovary cells].

Under a long treatment of cells CHO-6 with 5-bromodeoxyuridine and colcemid it was discovered that dicentric chromosomes in metaphases of the first division of polykaryocytes contained micronuclei. When the cells were treated with colcemid only, the number of dicentrics was less. This phenomenon was described earlier in the Chinese hamster cell line B11d-ii FAF28.

[Telomeric fusion of the chromosomes in cells with micronuclei during the subsequent incorporation into the DNA of thymidine halogenated analogs].

As was shown elsewhere among halogenated analogs of thymidine there exist strong (5-chlorodeoxyuridine, 5-ChldU) and weak (5-iododeoxyuridine, 5-IdU) inducers of dicentric chromosomes in cells with micronuclei. Since from colcemid administration to the moment of fixation two cycles of replication are passed, a study was made of the pattern of induction of dicentric chromosomes under subsequent administration of 5-ChldU and 5-IdU, and the other way round. It was shown that the pattern of induction of dicentric chromosomes was strong or weak, and depended on the fact which analog was administered in the first S-period.

[5-Chlorodeoxyuridine, more effectively than 5-bromodeoxyuridine, induces the formation of specific dicentric chromosomes in cells with micronuclei].

5-chlorodeoxyuridine (5-ChldU) and 5-bromodeoxyuridine (5-BrdU) were tested in respect of the formation of specific dicentric chromosomes in cells with micronuclei. It is shown that the frequency of dicentrics is higher when 5-ChldU is used. On the ground of results of this study and of the previous data it is concluded that the activity of halogenated deoxyuridines is falling with molecular weight increasing.

[The nature of 3 cytogenetic phenomena--delayed spiralization of regions of the metaphase chromosomes, delayed disruption of the telomeric links of chromosomes and the premature division of X-chromosome centromeres].

The phenomena mentioned above in the title cannot be explained by the routine scheme: gene-protein-chromatin. These are presumably associated with the existence of a system of mitotic chromosome transformation independent of the cytoplasm.

[Effect of 5-azacytidine on the frequency of polycentric chromosomes in cells with micronuclei during exposure to 5-bromodeoxyuridine].

Telomeric fusion of metaphase chromosomes was studied in conditions of DNA hypomethylation induced with 5-azacytidine. It was shown that the increased number of dicentric chromosomes was statistically significant in experiments when 5-azacytidine was used together with colcemid and 5-bromodeoxyuridine. These data demonstrate that DNA hypomethylation plays an important role in the manifestation of this phenomenon.

[Enhanced intensity of polycentric chromosome formation in cells with micronuclei exposed to 5-bromodeoxyuridine under prolonged hyperthermia at 40 degrees C].

The formation of polycentric chromosomes in metaphases of the first mitotic division of polykaryocytes containing micronuclei, under 5-BrdU treatment in the condition of a prolonged hyperthermia was studied. It was shown that the enhance of the frequency of polycentric chromosomes at 40 degrees C was statistically reliable. These data propose the existence of an enzymatic mechanism of disrupting the chromosomal ends at mitosis at the optimal condition (37 degrees C).

[5-Iododeoxyuridine as well as 5-bromodeoxyuridine induce the formation of specific dicentric chromosomes in cells with micronuclei].

5-iododeoxyuridine used instead of 5-bromodeoxyuridine for the induction of delayed disruption of telomeric links between chromosomes in polykaryocytes consisting of micronuclei was studied. It has been shown that treatment with 5-iododeoxyuridine (20 micrograms/ml) and colcemide (0.1 microgram/ml) for 42 hours induced the dicentric formation.

[Delayed disruption of the telomeric links between chromosomes in experimentally induced cells with micronuclei exposed to 5-bromodeoxyuridine in the 1st S period after colcemid administration].

Under a long-term administration of colcemid in the Chinese hamster cell culture some cells with micronuclei are seen to form. In the case of co-treatment with colcemid and 5-bromodeoxyuridine (5-BrdU) at metaphases of the first division of cells with micronuclei polycentric chromosomes were observed. These polycentric chromosomes occur due to delayed disruption of telomeric links, previously existing in the interphase.

[Behavior of the nucleolus organizer regions of the chromosomes in polykaryocytes consisting of micronuclei].

The nucleolar organizer regions (NORs) of Chinese hamster chromosomes (clone 237, cell line BIId-ii-FAF28) were studied in mononuclear cells and polykaryocytes induced with colcemid. The chromosomes with NORs were marked as 1, 2, 3, 4. The activity of NORs in mononuclear cells was higher in chromosomes 1, 2, 3.

[Activity of the nucleolus-organizing regions of the chromosomes of normal and transformed spleen cells in the African green monkey].

The activity of nucleolus organizer regions (NOR's) of chromosomes in the African green monkey cells has been studied before and after the transformation. In cells before their transformation, one or two chromosomes entering into association and possessing NORs are involved in the formation of one nucleolus. In transformed cells no correlation between the numbers of nucleoli in interphase and those of chromosomes possessing NORs was revealed in metaphase plates.

[Phenomenon of delayed disruption of telomeric links between chromosomes in polykaryocytes formed from human-Chinese hamster hybrid cells].

The clones MOM-8-1 and MOM-8-3 of human--Chinese hamster cell hybrids were used for induction of the phenomenon of delayed disruption of the telomeric links between chromosomes. Colcemide (0.08 microgram/ml) and 5-bromodeoxyuridine (20 micrograms/ml) were present in cell culture for 30 hours.

[African green monkey cell line RAMP simultaneously resistant to 8-azaguanine, 6-mercaptopurine, and 6-thioguanine].

African green monkey RAMT cell line was isolated from the permanent cell line 4647 in a medium containing 10 micrograms/ml 8-azaguanine, 6-mercaptopurine, and 6-thioguanine. The RAMT cells cannot grow in a medium containing thymidine, hypoxanthine, aminopterine and glycine because of the lack of hypoxanthine utilization due to hypoxanthine phosphoribosyltransferase deficiency. It was shown that 40% of the RAMT cells contain 57-58 chromosomes, and 20% of the cells are tetraploid.

[Spontaneous sister chromatid exchanges in cultured African green monkey cells].

The frequencies of sister chromatid exchanges (SCE) were studied in primary kidney cell culture, diploid cell line 5018, pseudodiploid spontaneously transformed cell line 4647 and hypotetraploid cell line 455 of the African green monkey. Bromodeoxyuridine was used at a concentration of 10 micrograms/ml. The slides were stained with acridine orange and Giemsa for sister chromatid differentiation.

[Chromosome nucleolus organizer regions of the African green monkey].

The silver staining Ag-I for detection of nucleolar organizer regions (NOR) in the African green monkey chromosomes was used. NOR were situated on the secondary constrictions of one pair of homologous marker chromosomes and consisted of two parts. A block of condensed chromatin was seen in the middle of the despiralized portion corresponding to the secondary constriction.

[Segregation of Q-polymorphic variants of human chromosomes].

The inheritance of Q-band polymorphism has been investigated in 15 families from 2 villages of the Uzbek SSR on six pairs of chromosomes (3, 13, 14, 15, 21 and 22th). Q-band polymorphism appears to segregate in a Mendelian manner. No Q-bands arisen de novo were found in this population.

[Telomeric chromosome fusion in cells treated with colcemid and 5-bromdeoxyuridine].

Specific chromosomes with two or more centromeres were found in the tetraploid metaphases of the second mitotic division after combined treatment with coldemid (0.05 mug/ml) and 5-bromodeoxyuridine (50 mug/ml) for 24 hours in the aneuploid Chinese hamster cell line. They were formed by telometric fusion of chromosomes and were absent in the cells treated with colcemid or 5-bromodeoxyuridine separately.

[Late replicating human X-chromosome in the early S-period].

The early S-period in cultured human lymphocytes was studied using the premature chromosome condensation technique. In the lymphocytes, isolated from females but not from males, one uncondensed G1-chromosome was detected among "pulverized" chromosomes which remained unlabeled with H3-thymidine. This chromosome is regarded as an inactivated X-chromosome.