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Further Development and Validation of the Frog Embryo Teratogenesis Assay- Xenopus (FETAX).

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Midterm rept. 8 Mar 91-30 Nov 94,

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The Frog Embryo Teratogenesis Assay- Xenopus FETAX is a 96-h whole embryo developmental toxicity screening assay that can be used in ecotoxicology and in detecting mammalian developmental toxic ants when an in vitro metabolic activation system is employed. A standardized American Society for Testing and Materials ASTM guide for the conduct of FETAX has been published along with a companion atlas that helps in embryo staging and identifying malformations. As part of the ASTM process, a three phase interlaboratory validation study was undertaken to evaluate the repeatability and reliability of FETAX. Seven different laboratories participated in the study. In Phase I, FETAX proved to be more repeatable and reliable than many other bioassays. However, some excessive variation was observed in a few laboratories. Some of this variation may have been due to an initial lack of experience with the assay by some technicians. Phase II showed far less intra- and interlaboratory variability than Phase I. Nonteratogens showed the most consistent results while more variability was observed for the two teratogens tested. Interlaboratory coefficient of variation values for all FETAX endpoints ranged from 7.3 to 54.7. Phase III, using coded samples and test concentration ranges selected by each laboratory showed results similar to Phase I. Analysis of the causes of variation suggested that some technicians judged malformations more severely than others and that the ranges of concentrations tested by some of the laboratories varied greatly. A new protocol for selecting concentrations for initial testing were written to reduce variation from this source. Testing to date suggests that FETAX is as repeatable and reliable as other standard bioassays.

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  • Anatomy and Physiology
  • Pharmacology

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