[Chromosomal abnormalities in lymphocytes from a patient with Werner's syndrome in intact culture and after treatment with halogenated analogs of thymidine]. / Khromosomnye anomalii u bol'nogo sindromom Vernera v intaktnoi kul'ture limfotsitov i posle vozdeistviia galogenovykh analogov timidina.

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. 5-Iododeoxyuridine induced lesions in centromeric regions of B-group chromosomes in 44.4% of all the cases of breaks. A hypothesis is proposed about the existence of a special mechanism for genetic control in changes in the cell nucleus and mitotic chromosome transformation. This mechanism can be manifested after the application of halogenated analogs of thymidine. The mutation involved in Werner's syndrome is presumably related to this mode of genetic control.

[An analysis of the chromosomal combinations in dicentrics with induced telomeric fusion]. / Analiz sochetanii khromosom v ditsentrikakh pri indutsirovannom telomernom sliianii.

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. Other 171 dicentrics were formed by telomeric fusion of autological chromosomes. No correlation was found between the length, centromeric index and frequency of dicentric formation. A probability of telomeric fusion of chromosomes determined by nucleotide sequences specific for each chromosome is proposed.

[Telomeric chromosome fusion in cells with micronuclei under the combined action of hyperthermia and hypothermia and halogenated analogs of thymidine]. / Telomernoe sliianie khromosom v kletkakh s mikroiadrami v usloviiakh sochetannogo vozdeistviia giper- ili gipotermii i galogenovykh analogov timidina.

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 using of 5-bromodeoxyuridine at different temperatures displayed the intermediate results. The maximum level of dicentrics discovered under action of 5-chlorodeoxyuridine and hyperthermia (40 degrees C). In the former case the depression of mitotic chromosome condensation of micronuclei registered, in the latter one the chromosomes with portions of delayed spiralization were not found.

[The effect of hyper- and hypothermia on induced telomeric chromosome fusion]. / Vliianie giper- i gipotermii na indutsirovannoe telomernoe sliianie khromosom.

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. These dicentrics are the result of telomeric chromosome fusion. The action of hyperthermia (40 degrees C) during the whole period of colcemid and 5-BrdU treatment or that of the hyperthermia (40 degrees C) only during the first 17 hours (the first interphase and the first mitosis) lead to the increased frequency of dicentrics. Under condition of hypothermia (34 degrees C) the frequency of dicentric formation decreases. Changes in cultivation temperature during the latest 25 hr of colcemid and 5-BrdU action (the second interphase and the second mitosis) exert no influence on the dicentric formation frequency. Because there are no dicentrics in cells during the metaphase of the first mitosis, it is supposed that the temperature--sensitive period may be the latest steps of colcemid blockade, i.e. the period of formation of micronuclei.

[The induction of specific dicentric chromosomes in CHO-6 Chinese hamster ovary cells]. / Induktsiia spetsificheskikh ditsentricheskikh khromosom v kletkakh iaichnika kitaiskogo khomiachka CHO-6.

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. Under the similar testing of continuous cell lines of human, swine, African green monkey and Syrian hamster origin this result failed be reproduced. From the data of experiments it was testified that the phenomenon in question may be very likely the characteristics of all the Chinese hamster continuous cell lines.

[Telomeric fusion of the chromosomes in cells with micronuclei during the subsequent incorporation into the DNA of thymidine halogenated analogs]. / Telomernoe sliianie khromosom v kletkakh s mikroiadrami pri posledovatel'nom vkliuchenii v DNK galogenovykh analogov timidina.

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-Khlordezoksiuridin bolee éffektivno chem 5-bromdezoksiuridin, indutsiruet obrazovanie spetsificheskikh ditsentricheskikh khromosom v kletkakh s mikroiadrami.

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]. / O prirode trekh tsitogeneticheskikh fenomenov--zaderzhki spiralizatsiiuchastkov metafaznykh khromosom, zaderzhki raspada telomernykh sviazei khromosom i prezhdevremennom raskhozhdenii tsentromer X-khromosomy.

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]. / Vliianie 5-azatsitidina na chastotu politsentricheskikh khromosom v kletkakh s mikroiadrami pri vozdeistvii 5-bromdezoksiuridina.

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]. / Povyshenie intensivnosti obrazovaniia politsentricheskikh khromosom v kletkakh s mikroiadrami pri vozdeistvii 5-bromdezoksiuridina v usloviiakh dlitel'noi gipertermii pri 40 gradusov 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). In cells with micronuclei, under 5-BrdU treatment at 40 degrees C, this mechanism undergoes, presumably, a partial inhibition leading to the enhanced frequency of chromosomes with fused telomeres.

[5-Iododeoxyuridine as well as 5-bromodeoxyuridine induce the formation of specific dicentric chromosomes in cells with micronuclei]. / 5-Ioddezoksiuridin, tak zhe kak i 5-bromdezoksiuridin, indutsiruet obrazovanie spetsificheskikh ditsentricheskikh khromosom v kletkakh s mikroiadrami.

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. Dicentrics were tested in 27% of all metaphases. This index was lower in comparison with 5-bromodeoxyuridine used for the same purpose.

[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]. / Zaderzhka raspada telomernykh sviazei khromosom v éksperimental'no indutsirovannykh kletkakh s mikroiadrami pri vozdeistvii 5-bromdezoksiuridinom v pervom S-periode posle vvedeniia koltsemida.

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. During colcemid treatment the cells pass through two S-periods: one in mononuclear cells, the other in cells with micronuclei. This phenomenon was tested according to the frequency of metaphases with dicentrics after 5-BrdU-treatment of cells at the first or second S-period or during the two cycles of chromosome replication. The 5-BrdU treatment during the first cycle or two cycles of replication resulted in the same frequency of cells with dicentrics--about 50%. The treatment with colcemid alone during two cycles of replication and administration 5-BrdU at the second S-period results in a considerably lower amount (%) of cells with dicentrics--about 10%. Thus, the delayed disruption of telomeric links between chromosomes may occur under the treatment with 5-BrdU at the first S-period after colcemid administration. It is also concluded that this phenomenon can be reproduced in cell with micronuclei when 5-BrdU is incorporated differentially in the sister chromatids.

[Behavior of the nucleolus organizer regions of the chromosomes in polykaryocytes consisting of micronuclei]. / Povedenie iadryshkoobrazuiushchikh raionov khromosom v polikariotsitakh, sostoiashchikh iz mikroiader.

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. The associations of NORs were observed between chromosomes I and 2 (3% of all metaphases). In polykaryocytes the chromosomal pairs 1, 2, 3 showed different NOR activity in different metaphases. The associations of NORs in pairs of chromosome I were found in 51.3% of cases. The associations of NORs in pairs of chromosome 2 were observed in 7.5% of cases. This method may be used for the estimation of association potency of NORs in chromosomes.

[Activity of the nucleolus-organizing regions of the chromosomes of normal and transformed spleen cells in the African green monkey]. / Aktivnost' iadryshkoobrazuiushchikh raionov khromosom normal'nykh i transformirovannykh kletok selezenki afrikanskoi zelenoi martyshki.

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. It is supposed that in chromosomes of the transformed cells with faintly stained NORs the gene activity is preserved only in part.

[Phenomenon of delayed disruption of telomeric links between chromosomes in polykaryocytes formed from human-Chinese hamster hybrid cells]. / Fenomen zaderzhki raspada telomernykh sviazei khromosom v polikariotsitakh, obrazovannykh iz gibridnykh kletok chelovek-kitaiskii khomiachok.

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. The dicentrics were observed in tetraploid, hypotetraploid and hypodiploid metaphases. No differences between the clones were found. The hybrid cells were the second object in which the phenomenon under discussion was reproduced.

[African green monkey cell line RAMP simultaneously resistant to 8-azaguanine, 6-mercaptopurine, and 6-thioguanine]. / Liniia kletok afrikanskoi zelenoi martyshki RAMT, rezistentnaia odnovremenno k 8-azaguaninu, 6-merkaptopurinu i 6 tioguaninu.

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. Like normal karyotype of the animal, the RAMT cells have two chromosomes with nucleolar organizer regions (NOR). One of them has an additional segment on the short arm and a large NOR revealed by silver staining. The cytoplasm of the RAMT cells was not found to have mycoplasma-like particles detected by the Hoechst 33258 fluorescent method. These characteristics enable the use of the RAMT cells for somatic cell hybridization.