Record Display for the EPA National Library Catalog

RECORD NUMBER: 15 OF 24

OLS Field Name OLS Field Data
Main Title Modeling the Ames Test.
Author Stead, Andrew G. ; Hasselblad, Victor ; Creason, John P. ; Claxton, Larry ;
CORP Author Health Effects Research Lab., Research Triangle Park, NC.
Year Published 1980
Report Number EPA-600/J-80-062;
Stock Number PB81-184806
Additional Subjects Models ; Tests ; Data processing ; Toxicity ; Evaluation ; Reprints ; Ames test ; Analytical methods
Holdings
Library Call Number Additional Info Location Last
Modified
Checkout
Status
NTIS  PB81-184806 Most EPA libraries have a fiche copy filed under the call number shown. Check with individual libraries about paper copy. 06/23/1988
Collation 16p
Abstract
Despite the value and widespread use of the Ames test, little attention has been focused on standardizing quantitative methods of analyzing these data. In this paper, a realistic and statistically tractable model is developed for the evaluation of Ames-type data. The model assumes revertant colony formation at any dose follows a Poisson process while the mean number of revertants per plate is a nonlinear function of up to 4 parameters. An exponential decay term can be included in the model to adjust for toxicity. The resultant system of nonlinear equations is solved using a modified Gauss-Newton iterative scheme to obtain maximum likelihood estimates of the model parameters. Significance of the key parameters is tested by fitting reduced models and using likelihood ratio tests. The model's performance is demonstrated on data from organic extracts of various environmental contaminants. Among the advantages of the proposed model are (1) no data is discarded in the parameter estimation process, (2) no arbitrary constants need to be added to zero counts or doses and (3) no mathematical transformation of the data is required.