J. Gilot-Delhalle

Mutagenicity of some organophosphorus compounds at the ade6 locus of Schizosaccharomyces pombe

12 organophosphorus insecticides were tested for toxicity and mutagenicity in the forward mutation test system ade6 of the yeast Schizosaccharomyces pombe. EMS and MMS were selected as positive controls. 3 compounds, dichlorvos, trichlorfon and paraoxon, showed a linear dose-response relationship. Among the other compounds investigated, methyl derivatives, though in general more toxic than ethyl derivatives, did not significantly increase the mutation frequency. Trichlorfon, tested in combination with malathion, methylparathion or methylazinphos (guthion), produced clearly synergistic effects for both toxicity and mutagenicity. The addition of S9 microsomal liver fraction decreased the efficiency of both single and combined treatments only where a dose-response relationship or a synergistic effect was obtained.

Fast rejoining processes in Nigella damascena chromosomes revealed by fractionated 60Co γ-ray exposures

Dry seeds of Nigella damascena were irradiated by 60Co γ-rays with fractionated exposures (2 × 4 krads), separated by time-intervals ranging from 2 to 3 min with increments of 10 sec. At time-intervals longer than 2 min 10 sec, the frequency of chromosome aberrations was found to be considerably decreased. These fast rejoining processes were oxygen dependent, being suppressed under anoxic conditions. Similarly, respiratory inhibitors: potassium cyanide (1 × 104M), sodium azide (1 × 104M) and dinitrophenol (1 × 105M) suppress the decrease. To test the hypothesis that ionic bonds can be involved in fast rejoining processes, seeds were treated respectively with three chelating agents (at 1 × 104M) before irradiation. Dipyridyl (DP) was found to suppress the decrease whereas diethyldithiocarbamate (DIECA) or cupferron (CUPF) produced a reversion at exactly the same tune-interval. The action of chelating agents was proved to be oxygen dependent. It was also demonstrated that all kinds of aberrations of the chromosome class i.e. breaks, minutes, dicentrics or rings were involved in the processes.

Mutagenicity of atrazine in Schizosaccharomyces pombe lindner with and without metabolic activation by maize

Abstract The mutagenic activity of two preparations of the herbicide atrazine (pure and a commercial formulation) was tested on yeast Schizosaccharomyces pombe (ade 7-C8) with and without in vivo activation by maize. The mutagenicity was much higher after activation (S1 fraction). The commercial formulation showed far higher activity than the pure compound. The genotoxic efficiency of a maize chloroplastic fraction after activation was also much higher than that of the supernatant, suggesting a transformation of the promutagen into an active mutagen in the organelle.

Chromosome-breaking activity of extracts of the mushroom Paxillus involutus Fries ex Batsch.

Dry and presoaked seeds ofNigella damascena were treated with aqueous extracts of the mushroomPaxillus involutus. At the first mitosis after the onset of germination, metaphase chromosomes showed damage independent of the origin of the mushrooms. The damaging substance(s) is (are) thermostable. Except a few achromatic gaps, all the lesions observed are of the chromosome type, i.e. are induced at the pre-synthetic G1 stage.

Clastogenic effects of benzodiazepines in a Nigella damascena seed test

Abstract Nigella damascena seeds were treated (5 hr) with solutions of different benzodiazepines. Chromosome damage was observed at the first mitosis after the onset of germination. At doses ranging from 12.5 to 50 μg/ml, no effects could be detected with the following substances: bromazepam, oxazepam, medazepam, prazepam, clonazepam and camazepam. Nitrazepam was ineffective at doses of up to 250 μg/ml. At doses ranging from 12.5 to 50 μg/ml, the following substances showed a linear dose-effect relationship: lorazepam, flunitrazepam and chlordiazepoxide as well as diazepam to 250 μg/ml. A proportion of damage was localized to constrictions. After diazepam, some aneuploid cells were found which are presumed to have arisen from chromosome non-disjunction.

Clastogenic effects of methoxy-7-nitro-2-naphtho (2,1-b) furan (R7000) on Nigella damascena L.

Abstract Clastogenic effects of a nitronaphthorufan (R7000) were investigated after treatment of seeds (“dry” and 30–50 hr presoake) or root tip cells. Nitronaphthofuran concentrations ranged from 0.12 to 32 × 10 −5 M for seeds and 0.12 to 2 × 10 −5 for root tips. All stages of the mitotic cycle were found to be sensitive, with a maximum of clastogenicity in G 2 . Chromosome lesions were predominantly of the following types: chromosome deletions, double minutes and gaps (isoachromatic or achromatic). R7000 accumulated metaphases, but counteracted the coiling sbfect of colchicine. In contrast, R7000 had a drastic uncoiling effect preferentially at the centromeric regions. This uncoiling leads to centrometric impairment and, eventually, chromosome breaks. Some mechanism(s) of action of the compound are suggested.

Induction of translocations in mouse spermatogonia after fractionated exposure to 60Co γ-rays

Abstract Male mice of the Q strain were exposed to 60 Co γ-rays at 2 Gy and 2 × 2 Gy separated by increasing time intervals (from 0 min to 4 min). The chromosome translocations induced in spermatogonia were scored at diakinesis-metaphase I. A significant decrease of the translocation frequency at time intervals higher than 2 min was observed, confirming results obtained with plant materials.