1. Department of Medicine, Diabetes, Endocrinology and Metabolism, Dartmouth Medical School and Dartmouth-Hitchcock Medical Center, 1 Medical Center Drive, Lebanon, NH 03756, U.S.A.
2. Phoenix Epidemiology and Clinical Research Branch, NIDDK, 1550 East Indian School Road, Phoenix, AZ 85014-4972, U.S.A.
3. Department of Pediatric Nephrology, University of Minnesota, MMC 491, 420 Delaware St S.E., Minneapolis, MN 55455, U.S.A.