title: Effect of cytochalasin B on the induction of chromosome missegregation by colchicine at low concentrations in human lymphocytes.
abstract: The aim of the present work was to investigate the possible interference of cytochalasin B (cyt B) with low concentration treatment with colchicine in the induction of chromosome/chromatid loss and micronuclei in human lymphocytes mitotically activated in vitro. Thus, cells from a single female donor were treated with colchicine (10 or 25 nM, from 24 h after PHA addition to fixation at 66 h) either in the presence or absence of cyt B. Single lagging chromosomes/chromatids were scored in bipolar ana-telophases and greater damage (disrupted and c-anaphases) was scored in cells at anaphase. Micronuclei were scored in the first 4000 nuclei observed in both cyt B-treated (in mononucleate and binucleate cells) and untreated cultures. With the same criterion, FISH analysis was performed on 2000 nuclei where chromosome 7 and 11 centromeric DNA probes were used in pairs. Our results showed that: (i) the frequency of laggards and of micronuclei increased with colchicine concentration but in the presence of cyt B there was a lower frequency of both (with a mean reduction of approximately 49%); (ii) FISH analysis showed a colchicine concentration-dependent increase in nuclei with three spots for chromosome 7; (iii) a colchicine concentration-dependent increase in tetraploid cells was observed. This increase was particularly remarkable (5-fold) in cells grown in the presence of cyt B compared with cyt B-untreated cells. The observed 'cyt B effects' can be explained if it is assumed that in cytokinesis-blocked cells there is a shorter distance between the poles. As a consequence: (i) laggards would be engulfed in the nearest daughter nucleus with a consequent lower induction of micronuclei; (ii) segregating sister chromatids in heavily impaired anaphases would not travel a sufficient distance to give rise to two daughter nuclei, leading to an increased frequency of polyploid nuclei.
authors.affiliation: Dipartimento di Biologia, Università di Roma Tor Vergata, Italy. minissi@bio.uniroma2.it
authors.forename: S
authors.initials: S
authors.lastname: Minissi
authors.forename: B
authors.initials: B
authors.lastname: Gustavino
authors.forename: F
authors.initials: F
authors.lastname: Degrassi
authors.forename: C
authors.initials: C
authors.lastname: Tanzarella
authors.forename: M
authors.initials: M
authors.lastname: Rizzoni
mesh_terms: D000328:Adult; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D020090:Chromosome Segregation / Q000187:drug effects*; D003078:Colchicine / Q000378:metabolism*; D003571:Cytochalasin B / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008214:Lymphocytes / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D003571:Cytochalasin B; D003078:Colchicine