[1] UNIV NIJMEGEN,INST PATHOL,6525 PB NIJMEGEN,NETHERLANDS
[2] STATE UNIV LEIDEN,DEPT CYTOCHEM & CYTOMETRY,SYLVIUS LABS,2333 AL LEIDEN,NETHERLANDS
[3] UNIV HEIDELBERG,INST APPL PHYS 1,D-6900 HEIDELBERG,FED REP GER
[4] QUEENS UNIV,DEPT BIOL,KINGSTON K7L 3N6,ONTARIO,CANADA