Herring-gull (Larus argentatus) eggs were collected from five locations on the Great Lakes and from one colony on the Atlantic coast for organochlorine analysis and mutagenesis testing. The Great Lakes colonies were chosen for their different contaminant levels, while the Atlantic coast colony was used as a relatively clean control. The eggs were homogenized and extracted, and the extracts were tested in the Salmonella/mammalian microsome assay for induction of point mutations and in Chinese hamster ovary (CHO) cells for the induction of sister chromatid exchanges (SCEs) and chromosome aberrations. None of the extracts was mutagenic in Salmonella, either in the presence or absence of metabolic activation. However, all of the extracts, including the clean control, caused significant increases in both the SCE rate and in the number of chromosome aberrations in the CHO cells. There was no apparent relationship between contaminant levels and the magnitude of these responses or the doses at which they occurred, although the chemical analysis indicated a wide range in the concentrations of the different organochlorides present.
The concept of combining several histidine-dependent Salmonella strains in a single test, the SIMULTEST, has been applied to the microtitre fluctuation test. The activity of five mutagens was determined in strains TA97, TA98, TA100, and TA102 individually as well as in a SIMULTEST mixture. All five compounds were mutagenic in the SIMULTEST, demonstrating the utility of this time and labour-saving approach of combining strains for testing with this method. The microtitre fluctuation SIMULTEST results were quantitatively comparable to those of the SIMULTEST Salmonella/microsome plate test. The microtitre fluctuation test compared with the plate incorporation assay generally showed more favourable "sensitivity" and "quantity" indices in that four of the five chemicals tested in the fluctuation test were mutagenic at lower doses than in the plate test.
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