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Relationship between chromatin bridges in anaphase and chromosomal aberrations induced by TMP+UVA (365 nm) in CHO cells
Full text linkIn a recent paper, the hypothesis of 'conservative pairing' between complementary DNA strands belonging to both sister chromatids has been proposed as a phenomenon that could account for, at least in part, sister chromatid pairing in late G(2)/mitosis. The hypothesis was verified through a cytogenetic approach, studying the so-called 'sister chromatid chromatin bridges' (SCCBs), induced in the previous G(2)/mitosis by a crosslinking (TMP + UVA 365 nm) treatment in CHO cells (Rizzoni, M., E. Cundari, P. Perticone and B. Gustavino (1993) Chromatin bridges between sister chromatids induced in late G(2) mitosis in CHO cells by trimethylpsoralen + UVA, Experimental Cell Res., 209, 149-155; [1]). The purpose of the present paper is the study of the relationship between chromatin bridges without fragments in ana-telophase, which were demonstrated to be SCCBs, and chromosomal aberrations, in order to investigate their mechanism of induction. The evolution along the time of the two classes of mitotic anomalies was studied and a comparison was carried out to verify whether the bridges rise as a direct and immediate effect of the treatment or represent the misrepair-mediated effect of it. The present data show that single bridges without fragments come from a direct effect of photoinduced crosslinks in late G(2)/mitosis. Moreover TMP + 365 nm UVA treatment shows an S-dependent clastogenic effect. The proposed hypothesis of 'conservative pairing' between DNA strands of sister chromatids is further supported
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No full textRestriction endonuclease Bam H I induces chromosomal aberrations in Chinese hamster ovary (CHO) cells.
No full textTreatment of Chinese hamster ovary (CHO) cells with the restriction endonuclease Bam H I (recognition site: G/GATCC) leads to high frequencies of chromosomal aberrations. Experiments with bromodeoxyuridine-labelled chromosomes show that the aberrations occur nearly exclusively in first post-treatment metaphases. The results are interpreted to mean that only some of the cells take up the enzyme and that these cells are the ones showing the aberrations. Cells which do not take up the enzyme show up as differentially stained metaphases and have no aberrations. Why some cells take up the restriction enzyme and others not is not known, possibly this is dependent on the physiological condition of the cells
SISTER CHROMATID EXCHANGES INDUCED BY DNA DEMETHYLATING AGENTS PERSIST THROUGH SEVERAL CELL-CYCLES IN MAMMALIAN-CELLS
No full textEukaryotic DNA methylation has been extensively studied in recent years. The ability of many carcinogens to interfere with DNA methylation has not yet been directly related to their tumorigenic activity. Recent data obtained using L-ethionine and 5-azacytidine--both demethylating agents--showed a small but significant increase in the sister chromatid exchange (SCE) rate induced in mammalian cells (human lymphocytes and CHO cells). In this paper we show that the SCE increase induced by both these agents in Chinese hamster ovary (CHO) cells persists for as long as 10 cell cycles. On the other hand mitomycin-C and u.v. light-induced SCEs show a rapid decrease to the control value, as reported for all known SCE inducers. We suggest that DNA demethylation and SCEs are connected through a perturbation of the cell machinery at the level of the replication fork, producing an increase of the error-prone ligation. Since the methylation level is maintained (inherited), the SCE increase produced by these recombinational events will not be corrected through several cell cycles
Stima del tasso di non-disgiunzione durante la prima divisione meiotica nel Mus musculus domesticus in topi eterozigoti per diversi cromosomi metacentrici robertsoniani.
No full textNondisjunction rates of mouse specific chromosomes involved in heterozygouus Rb rerarrangements measured by chromosome painting of spermatocytes II. I. The effects of the number of trivalents
No full textMediante dual-colour FISH painting, è riisultato possibile distinguere i diversi cromosomi negli spermatociti II di eterozigoti per traslocazioni Robertsoniane in Mus musculus. E' stata così dimostrata l'assenza di effetti epistatici per quanto riguarda la non disgiunzione dei diversi trivalenti
Segregazione non casuale di cromosomi metacentrici robertsoniani in Mus musculus domesticus in maschi eterozigoti multipli messa in evidenza con analisi FISH degli spermatociti II; implicazioni evolutive.
No full textCosegregation of Robertsonian metacentric chromosomes in the first meiotic division of multiple heterozygous male mice as revealed by FISH analysis of spermatocyte II metaphase
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