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2.9%). The frequency of chromosome aberrations detected in the mouse bone marrow cells and in spermatogonia as well as the number of detected sperm ab- normalities give a clear-cut evidence that ECHH was mutagenic for mice at 5 mg/m 3.

Vachkova-Petrova, R., Institute of Nutrit ion, Sofia, Bulgaria

Mutagenicity study of endodan in rats

Endodan, etem (ethylene thiuram monosulphide), is a new fungicide with good prospects for agriculture. The mutagenic activity of technical endodan was evaluated with the method of cytogenetic analysis of rat bone marrow after acute and short-term oral exposure. In the acute s tudy groups of 6 male and female animals were treated with endodan at a dose of 1/5 LDs0 and then killed 6, 12, 24 and 36 h following administration. In the short-term studies several doses of endodan were administered to groups of 6 animals (a) twice at an interval of 24 h, (b) for 5 successive days. The animals were killed 6 h after the last administration. The cells in metaphase are analysed for aneuploi- dy and aberrations.

Preliminary evaluation of the results failed to reveal mutagenic effects that could be at tr ibuted to the chemical.

Horvat, Dj., R. Rozgaj, A. Bauman and J. Ra~id, Institute for Medical Research and Occupational Health, 41000 Zagreb (Yugoslavia)

Cytogenetic effect of uranyl nitrate and cadmium chloride on V79 Chinese hamster cells

In technological processes where fossil fuels are used for energy product ion chemical and radiochemical contaminations are present. The most frequent pollutants are heavy metals and uranium compounds.

The purpose of this work was to establish an in vitro model system in a mammalian cell culture. Two mutagenic agents, uranyl nitrate (UO~(NO3)2 × 6 H~O, 0.18 mg/ml and. 0.26 mg/ml) and cadmium chloride (CdC12, 10 -6 M and 10 -s M) were added to the nutrient medium. Chromosome aberrations were investigated after the agents were applied separately or simultaneously in different concentrations.

In each experimental group of 300 analysed metaphases a significant increase of chromatid and chromosome damages was found.

Djordjevid, O., and Lj. Kostid, Insti tute of Nuclear Sciences "Boris Kidri~", Radiobiological Laboratory, Beograd (Yugoslavia)

Potentiation of the effect of cytostatics in ~mmRlian cells in vitro

The present s tudy was undertaken to investigate the effect of cytostat ic drugs on the induction of chromosomal aberrations and the possibility of

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potentiation of this effect by physical or chemical agents. Exponentially grow- ing cultures of NCTC clone of L cells were used in these experiments. Cells were exposed to cytostatic drugs (m-[di(2~hloroethyl)amino]-L-phenylala. nine and adriamycin) at 37 or 42°C. We also investigated the effect of hyper- thermia before or after cytostatic treatment. At different post.treatment incubation periods cells were harvested for chromosomal preparations using the conventional air<lrying method.

The results show that the extent of chromosomal aberrations is dose and time dependent. The frequency of the chromosomal aberrations is significantly potentiated after different sequences of heat (42°C) and drug exposure.

This research was part ly supported by IAEA, Vienna, Contract No. 1677/R4/RB.

Kostid, Lj., O. Djordjevid and G. Brkid, Institute of Nuclear Sciences "Boris Kidri~", Radiobiological Laboratory, Beograd (Yugoslavia)

Effect of cytostatics on the survival of mammalian cells growing in vitro

The present investigations were carried out to evaluate the response of mam- malian cells t o t h e treatment with the cytostatic drugs PTC and VM-26 at nor- mal (37°C) or hyperthermic {42°C) condition. These drugs possess a high thera- peutic effectiveness on various types of malignant tumors. The effects of drug exposure and inhibitors of repair processes on the survival of NCTC clone of L cells were studied by the method of colony-forming units. Mammalian cells treated with these cytostatics accumulate sublethal damage which is evidenced by the presence of a shoulder on the survival curves. When the cells were exposed to these drugs at elevated temperature (42°C) the potentiation of kill- ing effect was observed. From the shape of the survival curves it is evident that hyperthermia suppresses repair processes. This is shown by a reduction of the shoulder and a steeper slope resp. The suppression of the repair system is also investigated by exposing cells to the inhibitor of repair processes during post- treatment incubation.

This research was par t ly supported by IAEA, Vienna, Contract No. 1677/R3/RB.

Kubiak, R., Institute of Systematic and Experimental Zoology, Polish Acad- emy of Sciences, Cracow (Poland)

SCE induced by rubratoxin B

Chinese hamster embryonal fibroblasts were exposed to different concentra- tions of rubratoxin B in the presence of serum and without the addition of mixed function oxidases ("$9 mix"). After a 1,h treatment with lower concen- trations (10 and 20 /~g/ml) an increase of SCE was seen. The number of SCEs