1. Laboratory Animal Centre, University of Helsinki, Finland
2. Department of Experimental Medicine, University and University Hospital of Copenhagen, 3 Blegdamsvej, 2200 Copehagen N, Denmark
3. Department of Mathematics and Statistics
4. National Laboratory Animal Center, University of Kuopio, PO Box 1627, 70211 Kuopio, Finland
5. Department of Basic Veterinary Sciences, PO Box 66, 00014University of Helsinki, Finland