1. Department of Pediatrics, Hennepin County Medical Center and University of Minnesota, Minneapolis, Minn. 55415, US.
2. Department of Pathology, Minneapolis Veterans Administration Hospital and University of Minnesota, Minneapolis, Minn. 55415, US.
3. Department of Pathology and Medical Examiners Office, Hennepin County Medical Center, 5th St. and Portland Ave., South, Minneapolis, Minn. 55415, US.