- Email: [email protected]
mammalian microsome mutagenicity test
Mutation Research, 85 ( 1981) 437-456 Elsevier/North-Holland Biomedical Press
437
Gesellschaft for Umwelt-Mutationsforschung e.V. (GUM) The German-speaking Section of the European Environmental Mutagen Society Abstracts of Papers presented at the 6th Meeting, Darmstadt, 1981
1 Arni, P., CIBA-GEIGY Limited, CH-4002 Basle (Switzerland) Studies on the influence of microbiological factors and of activation on the results of the Salmonella/mammalian microsome mutagenicity test
There are often considerable discrepancies in the results of Ames tests performed in different laboratories, and even in one and the same laboratory relatively large variations can occur. The present investigation was undertaken to assess the extent of such variations upon the routine application of this test in a large laboratory and to define possible causes. The experiments were carried out with strains TA98, TA100; TA1535 and TA1537 of Salmonella typhimurium. The test substances were 2-aminoanthracene, benzo[a]pyrene, cycloph0sphamide, daunorubicin-HC1, 2,4-diamino-azobenzene and 4-nitroquinoline-N-oxide. $9 fractions from rats treated with Aroclor 1254 were used. Examples of some 150 experiments with TA 100 and 4-nitroquinoline-N-oxide and about 200 experiments with TA1535 and cyclophosphamide are presented, which show that the variations were much greater with the former than with the latter strain. In the experiments with TA1535, it was found that different $9 fractions prepared under identical conditions had an, albeit slight, influence on the results. Cultures that were at the end of the logarithmic growth phase showed slightly greater sensitivity than normal overnight cultures in experiments with 2-aminoanthracene only. The number of back-mutants already present in the cultures did not affect the results. By contrast, variations in the media and solvents produced great differences in the results in individual cases. The following conclusions were drawn. The duration of incubation, bacterial count and number of back-mutants already present in a culture are of subordinate importance with regard to the results. The use of $9 fractions from different 0165- I 161/81/0000-0000/$02.75 © Elsevier/North-Holland Biomedical Press
438 laboratories could, on the other hand, exert an influence on the results, and in individual cases technical factors are undoubtedly important.
2 Daniel, M.R., Huntingdon Research Centre, Huntingdon Cambs, PE18 6ES (England)
Theory and practice in current cell transformation tests for carcinogenicity The ideal cell transformation test would detect, with high sensitivity and specificity, substances of any chemical class which are carcinogenic for man. It would be rapid and reproducible, with an unequivocal indicator of transformation, and economical of space, equipment and money. How far these requirements are met by the 3 most widely used tests will be discussed. These tests all have 3 stages: exposure of cells to the agent, their cultivation to permit transformation, and assessment of transformation from the characteristics of colonial growth; the properties of the cells used influence the procedures for these 3 stages. All 3 tests use rodent rather than human cells as the targets, and an external source of enzymes for activation of some precarcinogens. All require careful selection of the cells used and rigid control of materials and methods. The effect of variations in these Will be illustrated from studies on the Styles test.
3 DiPaolo, J.A., National Cancer Institute, Bethesda, MD 20205 (U.S.A.)
The regulation of mammalian cell transformation by chemical substances A well-documented rationale exists for the study of the induction of cancer at the cellular level. Transformation can be quantitated; its frequency follows a linear relationship with dose and is consistent with a "one-hit" phenomenon. Transformed colonies do produce transformed lines with attributes of neoplastic cells including the production of tumors; in vitro activity parallels in vivo activity to provide evidence that chemically induced carcinogenesis can be studied in vitro. In vitro techniques utilizing mammalian cells in culture have made possible the rapid evaluation of carcinogenicity of agents in man's environment. Neoplastic transformation is inductive and not the result of the selection of pre-existing tumor cells. The addition of a host-mediated step in the bioassay makes it possible to decrease the number of false negatives, which may result from the requirement for metabolic activation of the chemical. Thus the in vitro studies described have a high probability of providing practical methods for determining which chemicals in use have a potential of producing cancer. Furthermore, the nature of the cell-target insult interaction can be determined, as well as the chemical nature of the ultimate carcinogen, the degree to which any agent acts alone, be it a chemical, a virus, or
437
Gesellschaft for Umwelt-Mutationsforschung e.V. (GUM) The German-speaking Section of the European Environmental Mutagen Society Abstracts of Papers presented at the 6th Meeting, Darmstadt, 1981
1 Arni, P., CIBA-GEIGY Limited, CH-4002 Basle (Switzerland) Studies on the influence of microbiological factors and of activation on the results of the Salmonella/mammalian microsome mutagenicity test
There are often considerable discrepancies in the results of Ames tests performed in different laboratories, and even in one and the same laboratory relatively large variations can occur. The present investigation was undertaken to assess the extent of such variations upon the routine application of this test in a large laboratory and to define possible causes. The experiments were carried out with strains TA98, TA100; TA1535 and TA1537 of Salmonella typhimurium. The test substances were 2-aminoanthracene, benzo[a]pyrene, cycloph0sphamide, daunorubicin-HC1, 2,4-diamino-azobenzene and 4-nitroquinoline-N-oxide. $9 fractions from rats treated with Aroclor 1254 were used. Examples of some 150 experiments with TA 100 and 4-nitroquinoline-N-oxide and about 200 experiments with TA1535 and cyclophosphamide are presented, which show that the variations were much greater with the former than with the latter strain. In the experiments with TA1535, it was found that different $9 fractions prepared under identical conditions had an, albeit slight, influence on the results. Cultures that were at the end of the logarithmic growth phase showed slightly greater sensitivity than normal overnight cultures in experiments with 2-aminoanthracene only. The number of back-mutants already present in the cultures did not affect the results. By contrast, variations in the media and solvents produced great differences in the results in individual cases. The following conclusions were drawn. The duration of incubation, bacterial count and number of back-mutants already present in a culture are of subordinate importance with regard to the results. The use of $9 fractions from different 0165- I 161/81/0000-0000/$02.75 © Elsevier/North-Holland Biomedical Press
438 laboratories could, on the other hand, exert an influence on the results, and in individual cases technical factors are undoubtedly important.
2 Daniel, M.R., Huntingdon Research Centre, Huntingdon Cambs, PE18 6ES (England)
Theory and practice in current cell transformation tests for carcinogenicity The ideal cell transformation test would detect, with high sensitivity and specificity, substances of any chemical class which are carcinogenic for man. It would be rapid and reproducible, with an unequivocal indicator of transformation, and economical of space, equipment and money. How far these requirements are met by the 3 most widely used tests will be discussed. These tests all have 3 stages: exposure of cells to the agent, their cultivation to permit transformation, and assessment of transformation from the characteristics of colonial growth; the properties of the cells used influence the procedures for these 3 stages. All 3 tests use rodent rather than human cells as the targets, and an external source of enzymes for activation of some precarcinogens. All require careful selection of the cells used and rigid control of materials and methods. The effect of variations in these Will be illustrated from studies on the Styles test.
3 DiPaolo, J.A., National Cancer Institute, Bethesda, MD 20205 (U.S.A.)
The regulation of mammalian cell transformation by chemical substances A well-documented rationale exists for the study of the induction of cancer at the cellular level. Transformation can be quantitated; its frequency follows a linear relationship with dose and is consistent with a "one-hit" phenomenon. Transformed colonies do produce transformed lines with attributes of neoplastic cells including the production of tumors; in vitro activity parallels in vivo activity to provide evidence that chemically induced carcinogenesis can be studied in vitro. In vitro techniques utilizing mammalian cells in culture have made possible the rapid evaluation of carcinogenicity of agents in man's environment. Neoplastic transformation is inductive and not the result of the selection of pre-existing tumor cells. The addition of a host-mediated step in the bioassay makes it possible to decrease the number of false negatives, which may result from the requirement for metabolic activation of the chemical. Thus the in vitro studies described have a high probability of providing practical methods for determining which chemicals in use have a potential of producing cancer. Furthermore, the nature of the cell-target insult interaction can be determined, as well as the chemical nature of the ultimate carcinogen, the degree to which any agent acts alone, be it a chemical, a virus, or