1. Biology and Biotechnology Research Program, L-452, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551-9900, Environmental Epidemiology Branch, National Cancer Institute, National Institutes of Health, Executive Plaza North, Room 443, 6130 Executive Boulevard, Rockville, Maryland 20892, and Nutrient Requirements and Functions Laboratory, BHNRC, ARS, U.S. Department of Agriculture, Building 307, Room 117, 10300 Baltimore Avenue, Beltsville, Maryland 20705-2350