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James G. Burkhart,¹ Judy C. Helgen,² Douglas J. Fort,³ Kathryn Gallagher,¹ Dorothy Bowers,⁴ Timothy L. Propst,³ Mark Gernes,² Joe Magner,² Michael D. Shelby,¹ and George Lucier¹

¹National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709 USA
²Minnesota Pollution Control Agency, St. Paul, MN 75155 USA
³Stover Group, Stillwater, OK 74075 USA
⁴Department of Fisheries and Wildlife, University of Minnesota, St. Paul, MN 55108 USA

Abstract

Water samples from several ponds in Minnesota were evaluated for their capacity to induce malformations in embryos of Xenopus laevis. The FETAX assay was used to assess the occurrence of malformations following a 96-hr period of exposure to water samples. These studies were conducted following reports of high incidences of malformation in natural populations of frogs in Minnesota wetlands. The purpose of these studies was to determine if a biologically active agent(s) was present in the waters and could be detected using the FETAX assay. Water samples from ponds with high incidences of frog malformations (affected sites) , along with water samples from ponds with unaffected frog populations (reference sites) , were studied. Initial experiments clearly showed that water from affected sites induced mortality and malformation in Xenopus embryos, while water from reference sites had little or no effect. Induction of malformation was dose dependent and highly reproducible, both with stored samples and with samples taken at different times throughout the summer. The biological activity of the samples was reduced or eliminated when samples were passed through activated carbon. Limited evidence from these samples indicates that the causal factor(s) is not an infectious organism nor are ion concentrations or metals responsible for the effects observed. Results do indicate that the water matrix has a significant effect on the severity of toxicity. Based on the FETAX results and the occurrence of frog malformations observed in the field, these studies suggest that water in the affected sites contains one or more unknown agents that induce developmental abnormalities in Xenopus. These same factors may contribute to the increased incidence of malformation in native species. Key words: amphibian malformations, environmental sentinels, FETAX, teratogenesis. Environ Health Perspect 106:841-848 (1998) . [Online 18 November 1998]

http://ehpnet1.niehs.nih.gov/docs/1998/106p841-848burkhart/ abstract.html

Address correspondence to J.G. Burkhart, National Institute of Environmental Health Sciences, MD C4-07, PO Box 12233, Research Triangle Park, NC 27709 USA.

This work was supported in a partnership between the National Institute of Environmental Health Sciences and the Minnesota Pollution Control Agency. We thank Carol Meteyer, David Gardiner, Rick Levy, and Cary Weinberger for helpful discussion, and we especially appreciate the the assistance of David Hoppe and Eric Mottl in collecting field data.

Received 20 May 1998 ; accepted 27 July 1998.