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Genetic control of mutagenesis in Drosophila
133 52 Deknudt, Gh., and A. Leonard, Laboratory of Mammalian Genetics, S.C.K.C.E.N., B-2400 Mol (Belgium) Interactions between ionizing radiations and chemicals in producing chromosomal aberrations in mammals Synergism between chemicals and X-irradiation for the production of heritable chromosomal aberrations in mouse spermatogonia has been studied by examining dividing spermatocytes 3 months after treatment. Two chemicals, Endoxan (100 mg/kg) and mitomycin (3 mg/kg) were administered at different intervals of time (1/2, 1, 2, 6 or 24 h) before or after exposure to 400 R of X-irradiation. Treatment with mitomycin before or after exposure to ionizing radiation decreases sharply the yield of spermatocytes carrying chromosome rearrangements. When given prior X-irradiation Endoxan modified slightly the incidence of abnormal spermatocytes whereas a significant decrease is observed by injection of the compound after X-ray exposure. The modification in the incidence of scorable chromosomal anomalies results probably from a selective elimination of damaged cells.
53 Gatehouse, D., Pathology Department, Allen and Hanburys Research Limited, Ware, Herts. (United Kingdom) Development of Green's fluctuation test on a "microtitre" scale, for the detection of both direct and indirect mutagens The bacterial fluctuation test first introduced by Green et al. (Mutation Res., 38, 1, 42--52) has been developed on a "microtitre" scale for use with either S. typhimurium or E. coli. This has required modifications of both buffer and glucose concentrations. The levels of limiting amino acid (tryptophan or histidine) present in the system had also to be adjusted to allow for "feeding effects" from extraneous free amino acid present in the post-mitochondrial fraction. This will be discussed. Using 6 direct mutagens (NMNNG, Hycanthone, Proflavin, Mitomycin C, Nifuroxime and Azorubin) and 6 indirect mutagens (2-acetamidofluorine, benzo(a)pyrene, cyclophosphamide, Isoniazid, Ethidium bromide and Tris (2,3dibromopropyl phosphate), the system has proven to be as sensitive as the large scale technique and in some cases more so. The obvious practical advantages of such a microtitre scale system, especially its potential for automation, make it a possible alternative to the Ames test for large-scale mutagenicity screening. 54 Graf, U., and F.E. Wfirgler, Institute of Toxicology, Swiss Federal Institute of Technology and University of Zurich, CH-8603 Schwerzenbach (Switzerland}
134
Genetic control of mutagenesis in Drosophila In Drosophila melanogaster the sex-linked recessive lethal test efficiently detects chemically induced point mutations as well as chromosome breakage effects. The mutagenic activity observed with a large number of indirectly acting carcinogens indicates the presence of potent activating enzyme systems. Other aspects of the versatility of this test system are connected with the relative efficiency of the various DNA repair processes: a number of mutants with defects in different repair systems are available. At present we are studying the cross-sensitivity of larvae of such mutants to the toxic effects of different types of chemical mutagens. Their role in the processes of mutation fixation is analysed by the determination of the maternal effects of these mutants on mutagenized sperm. It was found that one of the mutants is unable to repair nitrogen mustard induced lesions. This leads to increased dominant lethality and lack of induced recessive lethals. How this m u t a n t and others behave with respect to different types of potentially mutagenic lesions is currently under study. We think that it will soon be possible to construct special stocks that are suitable to answer specific questions with respect to the types of premutational lesions responsible for the mutagenic activity of a given test compound. S u p p o r t e d by the Swiss N a t i o n a l Science F o u n d a t i o n , p r o j e c t N o . 3 . 1 5 6 - 0 . 7 7 .
55 Gualandi, G., G. Morpurgo, S. Puppo and D. Bellincampi, Otto Botanico and Istituto Superiore di SanitY, Rome (Italy)
Influence of physiological parameters in induction of different types of genetic damage with MMS and UV in A. nidulans We have tested the influence of various physiological parameters in the induction of different types of genetic damage in A. nidulans, i.e. point mutation, somatic crossing-over and non-disjunction. When possible the experiments were done: (a) on quiescent and on germinating conidia; (b) with selective and non-selective methods; (c) on selective media with and without replication after treatment and plating. The results show that the induction of the genetic damage may be strongly or also totally dependent on the physiological condition of the cell, i.e. on its possibility of multiplication on selective media. For instance on selective media, UV induces crossing-over only on germinating conidia while it is totally ineffective on quiescent conidia. These results show that in the identification of environmental mutagens it is necessary to develop experimental protocols which take into account the effects of the physiological parameters. Work partially g r a n t e d b y C.E.E. ( c o n t r a c t No. 177-77-1 E N V 1).
53 Gatehouse, D., Pathology Department, Allen and Hanburys Research Limited, Ware, Herts. (United Kingdom) Development of Green's fluctuation test on a "microtitre" scale, for the detection of both direct and indirect mutagens The bacterial fluctuation test first introduced by Green et al. (Mutation Res., 38, 1, 42--52) has been developed on a "microtitre" scale for use with either S. typhimurium or E. coli. This has required modifications of both buffer and glucose concentrations. The levels of limiting amino acid (tryptophan or histidine) present in the system had also to be adjusted to allow for "feeding effects" from extraneous free amino acid present in the post-mitochondrial fraction. This will be discussed. Using 6 direct mutagens (NMNNG, Hycanthone, Proflavin, Mitomycin C, Nifuroxime and Azorubin) and 6 indirect mutagens (2-acetamidofluorine, benzo(a)pyrene, cyclophosphamide, Isoniazid, Ethidium bromide and Tris (2,3dibromopropyl phosphate), the system has proven to be as sensitive as the large scale technique and in some cases more so. The obvious practical advantages of such a microtitre scale system, especially its potential for automation, make it a possible alternative to the Ames test for large-scale mutagenicity screening. 54 Graf, U., and F.E. Wfirgler, Institute of Toxicology, Swiss Federal Institute of Technology and University of Zurich, CH-8603 Schwerzenbach (Switzerland}
134
Genetic control of mutagenesis in Drosophila In Drosophila melanogaster the sex-linked recessive lethal test efficiently detects chemically induced point mutations as well as chromosome breakage effects. The mutagenic activity observed with a large number of indirectly acting carcinogens indicates the presence of potent activating enzyme systems. Other aspects of the versatility of this test system are connected with the relative efficiency of the various DNA repair processes: a number of mutants with defects in different repair systems are available. At present we are studying the cross-sensitivity of larvae of such mutants to the toxic effects of different types of chemical mutagens. Their role in the processes of mutation fixation is analysed by the determination of the maternal effects of these mutants on mutagenized sperm. It was found that one of the mutants is unable to repair nitrogen mustard induced lesions. This leads to increased dominant lethality and lack of induced recessive lethals. How this m u t a n t and others behave with respect to different types of potentially mutagenic lesions is currently under study. We think that it will soon be possible to construct special stocks that are suitable to answer specific questions with respect to the types of premutational lesions responsible for the mutagenic activity of a given test compound. S u p p o r t e d by the Swiss N a t i o n a l Science F o u n d a t i o n , p r o j e c t N o . 3 . 1 5 6 - 0 . 7 7 .
55 Gualandi, G., G. Morpurgo, S. Puppo and D. Bellincampi, Otto Botanico and Istituto Superiore di SanitY, Rome (Italy)
Influence of physiological parameters in induction of different types of genetic damage with MMS and UV in A. nidulans We have tested the influence of various physiological parameters in the induction of different types of genetic damage in A. nidulans, i.e. point mutation, somatic crossing-over and non-disjunction. When possible the experiments were done: (a) on quiescent and on germinating conidia; (b) with selective and non-selective methods; (c) on selective media with and without replication after treatment and plating. The results show that the induction of the genetic damage may be strongly or also totally dependent on the physiological condition of the cell, i.e. on its possibility of multiplication on selective media. For instance on selective media, UV induces crossing-over only on germinating conidia while it is totally ineffective on quiescent conidia. These results show that in the identification of environmental mutagens it is necessary to develop experimental protocols which take into account the effects of the physiological parameters. Work partially g r a n t e d b y C.E.E. ( c o n t r a c t No. 177-77-1 E N V 1).