1. Department of Biology (R.B., D.T., A.D., T.Z.), University of Massachusetts Amherst, Amherst, Massachusetts 01003
2. Bureau of Chemical Safety, Food Directorate, Health Products, and Food Branch (D.F.K.R., D.W.G., D.L.A.), Health Canada, Ottawa, Ontario, Canada K1A 0K9
3. Toxicity Assessment Division (M.E.G.), US Environmental Protection Agency, Research Triangle Park, North Carolina 27711
4. Molecular and Cellular Biology Program (T.Z.), University of Massachusetts Amherst, Amherst, Massachusetts 01003