Ames test functionality

Studies on the reproductive function (three generations) and intrauterine development of rat showed no impairment of the rate of fertility and no sign of any teratogenic effect. The Ames test on mutagenicity was negative [101]. 

Primary assay Microsomal Rule-of-Five Functional Ames test... 

Polychlorinated biphenyls (PCBs) are routinely used to induce rodent hepatic mixed-function oxidases in tissues used in the Ames test. 

In the Ames test (with or without metabolism by extracts of rat livers induced for microsomal mixed-function oxygenases with methylcholanthrene, or Arochlor) 2-4 were inactive at low-medium... 

The presence of chemically reactive structural features in potential drug candidates, especially when caused by metabolism, has been linked to idiosyncratic toxicity [56,57] although in most cases this is hard to prove unambiguously, and there is no evidence that idiosyncratic toxicity is correlated with specific physical properties per se. The best strategy for the medicinal chemist is avoidance of the liabilities associated with inherently chemically reactive or metabolically activated functional groups [58]. For reactive metabolites, protein covalent-binding screens [59] and genetic toxicity tests (Ames) of putative metabolites, for example, embedded anilines, can be employed in risky chemical series. 

Histological examination of reproductive organs did not reveal any effects in rats or mice treated by gavage with isophorone for 13 or 103 weeks (NTP 1986), in rats treated with isophorone in the diet for 13 weeks (AME Inc 1972a), or in dogs treated with isophorone in gelatine capsules for 13 weeks (AME Inc 1972b). In none of these studies, however, were specific tests of reproductive function performed, which would be necessary to rule out an effect. Therefore, the doses used in these studies cannot be considered NOAELs for effects on reproduction. 

Ames developed strains of bacteria that had carefully selected lethal mutations. In a test system the bacteria could survive only when its mutation had been corrected by experiencing another mutation caused by the tested material. This correction could be accomplished by causing a point mutation or frameshift mutations . Point mutations are base-pair substitutions, that is, a base change in DNA of at least one DNA base pair. In a reverse mutation test, this change in base pairs may occur at the site of the original mutation, or at a secondary site in the bacterial genome. Frameshift mutations are the addition or deletion of one or more base pairs in the DNA. Since amino acids are encoded by triplets of base pairs in sequence, any addition or deletion of 1 or 2 base pairs will dramatically alter the expressed protein from that point on. The Ames system employs strains of Salmonella typhimurium and Escherichia coli that require amino acids (histidine or tryptophan, respectively) to detect such reverse point and frameshift mutations. The reverse mutation allows the S. typhimurium or E. coli strains to restore the functional capability of the bacteria to be able to synthesize the specific amino acid on their own, independent of amino acid content in the medium. 

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