Membrane-damaging agents cause mitotic non-disjunction in Aspergillus nidulans (original) (raw)
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Analysis of mitotic nondisjunction with Aspergillus nidulans
Environmental Health Perspectives, 1979
Two methods to detect the induction of nondisjunction with a diploid stable strain of A. nidulans are described. The first method gives only qualitative results, while the second method is quantitative and dose-effect curves can be done. Some physiological parameters affecting the induction ofnondisjunction can also be studied, because either quiescent or germinating conidia can be treated with the drug under test. Some agents inducing nondisjunction were also tested for the induction of point mutation and somatic crossing-over with these comparative analysis. Two classes of agents inducing nondisjunction may be detected: the first causes ail possible types of genetic damage either on quiescent or germinating conidia (a representative of this chss is MMS) and acts presumably on the DNA level; the second acts only on germinating conidia and does not produce point mutation or crossing over. A representative of this class is Benomyl which interferes with spindle microtubules. A list of compounds tests is included.
Benznidazole-induced genotoxicity in diploid cells of Aspergillus nidulans
Memórias do Instituto Oswaldo Cruz, 2005
Genotoxic effects of benznidazole were studied by the induction of homozygosis of genes previously present in heterozygous. UT448//A757 diploid strain was used in the benznidazole's recombinagenesis test. Although toxic effects on growth of colonies were not observed, 75 and 100 µM benznidazole induced an increasing of mitotic recombination events in diploid strain. Results were related to the induction of chromosomal breaks by the antiparasitic drug.
Induced gene mutation and mitotic non-disjunction in A. nidulans
Toxicology Letters, 1981
Toxicants of different classes were analysed for capacity to induce gene mutation and mitotic nondisjunction in Aspergillus nidulans, using selective and permissive tests, respectively. Ethanol, Amphotericin B and Micanozole, all affecting membrane integrity, induced only nondisjunction, emphasizing the role of the membrane in mitosis. Benomyl and isopropyl-3-chlorophenyl carbamate (CIPC), two pesticides which interfere with spindle system, induced only non-disjunction. Conversely, Mitomycin C markedly increased mutation rate but not non-disjunction and scarcely affected the viability. The comparative analysis of these two different genetic damages should prove useful in evaluating hazards of drugs.
Mitotic slippage in non-cancer cells induced by a microtubule disruptor, disorazole C1
BMC Chemical Biology, 2010
Background: Disorazoles are polyene macrodiolides isolated from a myxobacterium fermentation broth. Disorazole C 1 was newly synthesized and found to depolymerize microtubules and cause mitotic arrest. Here we examined the cellular responses to disorazole C 1 in both non-cancer and cancer cells and compared our results to vinblastine and taxol. Results: In non-cancer cells, disorazole C 1 induced a prolonged mitotic arrest, followed by mitotic slippage, as confirmed by live cell imaging and cell cycle analysis. This mitotic slippage was associated with cyclin B degradation, but did not require p53. Four assays for apoptosis, including western blotting for poly(ADP-ribose) polymerase cleavage, microscopic analyses for cytochrome C release and annexin V staining, and gel electrophoresis examination for DNA laddering, were conducted and demonstrated little induction of apoptosis in non-cancer cells treated with disorazole C 1 . On the contrary, we observed an activated apoptotic pathway in cancer cells, suggesting that normal and malignant cells respond differently to disorazole C 1 . Conclusion: Our studies demonstrate that non-cancer cells undergo mitotic slippage in a cyclin B-dependent and p53-independent manner after prolonged mitotic arrest caused by disorazole C 1 . In contrast, cancer cells induce the apoptotic pathway after disorazole C 1 treatment, indicating a possibly significant therapeutic window for this compound.
Biochemical effects of miconazole on fungi—I
Biochemical Pharmacology, 1974
The antifungal and antibacterial drug miconazole has been shown to inhibit, at concentrations lower than those affecting growth, the transport of adenine, guanine and hypoxanthine by Candidu albicans in suspension culture. The decrease in the incorporation of purines into nucleic acids seems to be the consequence of an inhibitory effect on their uptake into the cells. When the purines were replaced by adenosine, deoxyadenosine and guanosine, miconazole increased the uptake and incorporation of the radioactivity derived from the nucleosides into macromolecules. The data suggest that the drug-induced increase of nucleoside incorporation into nucleic acids is secondary to enhanced nucleoside transport. Miconazole also slightly affected the uptake of erotic acid. The transport of glucose, glycine and leucine was not affected by miconazole whereas in some way the drug affected glutamine uptake. Studies on the distribution of miconazole and/or its metabolites in the Candida cell indicate that in log-phase cells most of the radioactivity was found in the fraction containing cell walls and plasmalemma. In stationary-phase cells the highest radioactivity was found in the fraction which contained the microsomes. Although more information will be needed, the data presented indicate that at low concentrations, miconazole acts primarily on the yeast cell membranes (cell wall and plasmalemma) resulting in a selective inhibition of the uptake of precursors of RNA and DNA (purines) and mucopolysaccharide (glutamine). Higher doses and longer incubation periods also alter the activities of microsomal membranes. MICONAZOLE (R 14889) is the generic name for 1[2,Cdichloro-/3-(2,4dichlorobenzyloxy)phenethyl] imidazole nitrate. It is a white, microcrystalline or amorphous powder, very slightly soluble in water and moderately soluble in most organic solvents. This fi-substituted 1-phenethylimidazole has broad-spectrum activity against most pathogenic fungi, such as dermatophytes and Candida albicans, against numerous saprophytic fungi as well as against Gram-positive bacteria.lb5 The present paper describes effects of miconazole on the uptake and/or utilization of purines, pyrimidines, purine nucleosides, amino acids and glucose by Candidu albicans. The distribution of miconazole in the Cundidu cell was also determined. The purpose of this study was to formulate a hypothesis on the mode of action of this antifungal agent.
Genotoxic and aneugenic properties of an imidazole derivative
Journal of Applied Toxicology, 2006
To contribute to a more accurate characterization of the mutagenic and aneugenic effects of thiabendazole (TBZ), a widely used antiparasitic and food preservative drug, the induction of sister chromatid exchanges (SCEs) and mitotic spindle anomalies as cytogenetic end-points were investigated. Studies were carried out in Chinese hamster ovary (CHO) cells and human peripheral blood lymphocytes. A significant dose-dependent increase in SCE frequency was observed in CHO cells with S9-Mix (P < < < < < 0.01) in the 50-100 µ µ µ µ µg ml − − − − −1 dose-range, while in the absence of S9-Mix, an enhancement of the SCE frequency was exhibited at the highest dose (P < < < < < 0.01). In CHO-K1 cells a significant increase in mitotic spindle anomalies (P < < < < < 0.01) was observed with the highest concentration assayed reflecting the specific effect of TBZ formulation at the microtubule level. Cell proliferation kinetics (CPK) were not modified by the addition of this pharmaceutical product. In human lymphocyte cultures, exposure to 100 µ µ µ µ µg ml − − − − −1 TBZ formulation resulted in a significant decrease of the mitotic index (MI) (P < < < < < 0.003) and changes in the replication index (RI) (P < < < < < 0.05).
Mutagenesis, 1999
The proportions of aneuploid/polyploid versus euploid cells formed after treatment with spindle poisons like nocodazole are of course dependent on the relative survival of cells with numerical chromosome aberrations. This work aimed at studying the survival of polyploid cells formed after treatment with a nocodazole concentration sufficient to significantly decrease tubulin polymerization (0.1 µg/ml). First, normal primary lymphocytes were analysed and the following complementary chromosomal parameters were quantified: mitotic index, frequency of abnormal mitoses, polyploid metaphases and apoptotic cells. The results clearly indicate a positive correlation between abnormal mitotic figures, apoptosis and the induction of polyploidy. They therefore led to a single cell approach in which both apoptosis and polyploidy induction could be scored in the same cell. For this purpose, actively proliferating cells are required and two human leukaemic cell lines were used, KS (p53-positive) and K562 (p53-negative), which have a near-triploid karyotype. Cells were separated into an apoptotic and a viable fraction by means of annexin-V staining and flow cytometry. In KS, treatment with nocodazole induced a similar fraction of hexaploid cells in both the viable and apoptotic fraction, but no dodecaploid cells were ever observed. In contrast, a population of dodecaploid cells (essentially viable) was clearly observed in the K562 cell line. The results in KS, as compared with K562, confirm that wild-type p53 can prevent further cycling of polyploid cells by blocking rereplication. The most probable explanation for these data is that not only the mitotic spindle but also interphase microtubules are sensitive to nocodazole treatment. Our data thus strongly suggest that besides the G 1 /S checkpoint under the control of p53, the G 2 /M transition may be sensitive to depolymerization of microtubules, possibly under the control of Cdc2, Bcl-2, Raf-1 and/or Rho.