Affiliation: | (1) Division of Biological Sciences, The University of Michigan, 48109-1048 Ann Arbor, Michigan, USA;(2) Present address: The Netherlands Cancer Institute, Plesmalan 121, 1066 CX Amsterdam, The Netherlands;(3) Present address: E. I. Dupont de Nemours and Co., New Technology Research, 331 Treble Cove Road, 01862 North Billerica, Massachusetts, USA |