Comparison of the Ames II and traditional Ames test responses with respect to mutagenicity, strain specificities, need for metabolism and correlation with rodent carcinogenicity.

The Ames II Salmonella mutagenicity assay procedure was used to test 71 chemicals, and the results were compared with those from the traditional Ames Salmonella test using the NTP database as the reference. All Ames II tests were performed using a fluctuation procedure in microplate format, using TAMix for the detection of base pair substitutions and TA98 to detect frameshift mutations. There was 84% agreement between the two procedures in identifying mutagens and non-mutagens, which is equivalent to the intra- and interlaboratory reproducibility of 87% for the traditional test.

Benzene and its methyl-derivatives: derivation of maximum exposure levels in automobiles.

Automobile drivers are exposed to several organic hydrocarbons. Concentrations measured in passenger compartments have been reported to range between 13 and 560 microg/m(3) for benzene, 33-258 microg/m(3) for toluene, 20-250 microg/m(3) for xylene (mixed isomers) and 3-23 microg/m(3) for trimethylbenzene (mixed isomers). These aromatic hydrocarbons are emitted from gasoline and from materials inside a car.

Investigations on cell proliferation and enzyme induction in male rat kidney and female mouse liver caused by tetrahydrofuran.

To elucidate possible mechanism(s) of carcinogenic action of tetrahydrofuran (THF) that had been demonstrated in previous inhalation studies, groups of male F344 rats and female B6C3F(1) mice were exposed to dynamic atmospheric concentrations of 0, 600, 1800, or 5400 mg/m(3) for 6 h per day, either for 5 consecutive days or for a period of 4 weeks (5 days per week). The reversibility of treatment-related changes was investigated in rats and mice exposed for 5 days and sacrificed 21 days after the last exposure. Female B6C3F(1) mice exposed to 5400 mg/m(3) showed significantly increased cytochrome P450 content, increased ethoxyresorufin-O-deethylase and pentoxyresorufin-O-depentylase activities, increased cell proliferation (5-bromo-2'-deoxyuridine-method) and an increased mitotic index in liver zones 2 (midzonal region) and 3 (central vein region).

Structure-activity relationships in toxicology and ecotoxicology: An assessment.

A critical assessment of the scope, applicability and limitations of structure-activity relationships (QSARs) in toxicology and ecotoxicology opens with a general explanation of QSARs and a description of the components of a QSAR (chemical descriptors, biological descriptors and the techniques used to seek a relationship between them). The main statistical terms used to assess the validity of certain types of QSAR are briefly explained and attention is drawn to a number of common errors in the statistical assessments. This is followed by a detailed analysis of 18 typical QSAR publications, which were chosen to represent the main types of chemical and biological descriptors that have been studied and a range of techniques for deriving the structure-activity relationships.