title: Micronuclei, centromere-positive micronuclei and chromosome nondisjunction in cytokinesis blocked human lymphocytes following mitomycin C or vincristine treatment.
abstract: The influence of sampling time on the frequencies of micronuclei, centromere-positive micronuclei and chromosome nondisjunction was investigated in binucleated lymphocytes following treatment with a known clastogen (mitomycin C) or an aneuploidy-inducing agent (vincristine sulfate). Cytochalasin B (6 micrograms/ml) was added 44 h after mitogen stimulation and cultures were harvested 12, 28, 36 and 48 h thereafter. Micronucleated cells and micronuclei were significantly induced by the two treatments at all sampling times. Furthermore, in situ hybridization with an 'all centromeres' probe showed that vincristine-induced micronuclei were prevalently centromere-positive whereas in mitomycin C-treated cultures only a minor fraction of induced micronuclei contained the hybridization signals. Chromosome nondisjunction rates, as measured by in situ hybridization with chromosome 7- and 11-specific alphoid probes, significantly increased following vincristine treatment. Chromosome nondisjunction and total micronucleus frequencies were found to increase with time both in controls and in mutagen-treated cultures, whereas the percentage of centromere-positive micronuclei in the different treatments was not influenced by the sampling time. Our data suggest that even in the presence of 6 micrograms/ml cytochalasin B, the abnormal segregation of binucleated cells may contribute to the baseline level of micronuclei and influence the results obtained. The introduction of a short cytochalasin B treatment (between 12 and 28 h) in the cytokinesis-blocked micronucleus assay may avoid the cytochalasin B effect on micronucleus frequencies.
authors.affiliation: Dipartimento Genetica e Biologia Molecolare, Università La Sapienza Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Sgura
authors.forename: A
authors.initials: A
authors.lastname: Antoccia
authors.forename: M J
authors.initials: MJ
authors.lastname: Ramirez
authors.forename: R
authors.initials: R
authors.lastname: Marcos
authors.forename: C
authors.initials: C
authors.lastname: Tanzarella
authors.forename: F
authors.initials: F
authors.lastname: Degrassi
mesh_terms: D000782:Aneuploidy; D002455:Cell Division; D002503:Centromere; D002880:Chromosomes, Human, Pair 11 / Q000235:genetics; D002897:Chromosomes, Human, Pair 7 / Q000235:genetics; D003571:Cytochalasin B; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods; D008214:Lymphocytes; D008297:Male; D015162:Micronucleus Tests / Q000379:methods*; D016685:Mitomycin / Q000633:toxicity; D009153:Mutagens / Q000633:toxicity; D009630:Nondisjunction, Genetic; D014750:Vincristine / Q000633:toxicity
chemical_list: D009153:Mutagens; D003571:Cytochalasin B; D016685:Mitomycin; D014750:Vincristine