http://http://dspace.unitus.it:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Sat, 18 May 2013 22:59:43 GMT 2013-05-18T22:59:43Z http://hdl.handle.net/2067/1721 Title: Distribution of camptothecin-induced breakpoints in Chinese hamster cells treated in late S and G2 phases of the cell cycle. Authors: Bassi, Loredana; Palitti, Fabrizio; Mosesso, Pasquale; Natarajan, Adayapalam T. Abstract: The distribution of camptothecin (CPT)-induced break points in late S or G2 phase of the cell cycle observed in Chinese hamster chromosomes was analysed in 400 metaphases. Contrary to expectation, they were not localized in the heterochromatic regions, suggesting that these chromatid-type aberrations arise by a mechanism which does not involve collision of the CPT-trapped 'cleavable complex' with the replication fork. Since many break points mapped more frequently to light bands (DAPI negative) than dark bands (DAPI positive) with a frequency of 73 and 15% respectively, it could be argued that the presence of the CPT-trapped 'cleavable complex' probably interferes with chromatin condensation. In fact, the euchromatic regions, which are expected to be more actively condensed in G2 phase, were more involved in chromosomal damage. These results do not completely confirm the idea that some residual DNA synthesis occurring in G2 is responsible for the G2 clastogenic effects of CPT as the heterochromatic regions should, in this case, be more involved. Description: L'articolo è disponibile sul sito dell'editore: http://www.oxfordjournals.org Wed, 31 Dec 1997 23:00:00 GMT http://hdl.handle.net/2067/1721 1997-12-31T23:00:00Z http://hdl.handle.net/2067/1719 Title: The involvement of chromatin condensation in campthotecin-induced chromosome breaks in G0 human lymphocytes Authors: Mosesso, Pasquale; Fonti, Enrica; Bassi, Loredana; Lorenti Garcia, Claudia; Palitti, Fabrizio Abstract: In the present study we evaluated campthotecin (CPT)-induced chromosomal damage in human lymphocytes in the G0 phase of the cell cycle as revealed by the premature chromosome condensation technique. The results obtained here indicate that CPT was able to induce chromosome fragments in the G0 phase of the cell cycle of human lymphocytes as detected in prematurely condensed chromosomes. This result appears to be rather surprising, since the DNA lesions produced by CPT (e.g. 'protein concealed' DNA single-strand breaks) should not produce any damage in G0. A possible explanation for this result could come from much evidence to suggest that chromatin condensation processes are significantly involved in the conversion of DNA lesions into chromosome breaks in prematurely condensed chromosomes. The unexpected clastogenic behaviour of CPT can be explained taking into account the chromosome condensation induced by mitosis promoting factors when human lymphocytes are fused in G0, thus converting the 'protein concealed' DNA single-strand breaks induced by CPT into chromosome breaks. The same perspective should be taken into consideration for breaks induced by CPT under normal physiological conditions in the G2 phase of the cell cycle. Description: L'articolo é disponibile sul sito dell'editore: http://www.oxfordjournals.org Thu, 31 Dec 1998 23:00:00 GMT http://hdl.handle.net/2067/1719 1998-12-31T23:00:00Z