Metal ion effects in microbial screening systems

90 A powerful tool in the assessment of the toxic potential of a chemical is the ability to identify the properties and structural parameters which influence its toxic action in a given test system. Such information is useful both in predicting the activity of untested substances and in elucidation of mechanisms of action. In this paper, the application o f a technique using regression analysis to the identification of parameters affecting the mutagenic activity of chemicals in the Ames' Salmonella typhimurium strains is discussed. Preliminary studies on a series of aromatic nitrogen-containing c o m p o u n d s and a series of aromatic hydrocarbons are described. Relationships which have been derived between various chemical features and the induction of base,substitution mutations (i.e., in S. typhimurium TA1535 and TA100) and frameshift mutations (i.e., in S. typhimurium TA1538 and TA98) are presented. The chemical parameters considered in the analysis cover such factors as the t y p e of substitution on the aromatic ring, lipophilicity, size of the molecule, and degree of aromaticity.

43 E.M. Jensen, R.J. LaPolla, P.E. Kirby and S.R. Haworth, EG and G/Mason Research Institute, Rockville, Md. 20852 (U.S.A.) In vitro studies o f chemical mutagens and carcinogens: stability properties in cell culture medium Cell culture procedures are being used increasingly in the study of chemical mutagens and carcinogens. Little information is available, however, regarding the stability of such c o m p o u n d s in a cell culture environment. Such information is of considerable importance in designing test protocols, preparing stock solutions and in interpreting results. We have determined the biological half-lives of 10 carcinogens and 6 procarcinogens in cell culture medium containing 15% fetal bovine serum at 37 ° . Biological activity was measured by the Salmonella typhimurium mutagenesis assay procedure of Ames using strains TA98 and TA100. All 10 direct acting carcinogens, which included a variety of chemical classes, were inactivated at varying rates. Biological half-lives ranged from 8 minutes for N-methyl-N.nitrosourea to 67 hours for N-nitroquinoline-1oxide. All 6 procarcinogens were stable for up to three weeks.

44 K.R. Tindall, G.R. Warren and P.D. Skaar, Montana State University, Bozeman, Mt. 59715 (U.S.A.)

Metal ion effects in microbial screening systems Selected metal ions were assayed for differential lethality on repair-deficient strains of Escherichia coli. Those ions causing presumptive DNA damage were then further tested for reversion in E. coli WP2 trp and the Ames' Salmonella