1. The Gade Institute, Department of Pathology, University of Bergen, Haukeland Hospital, Bergen, Norway
2. The Laboratory of Biochemical Endocrinology, University of Bergen, Haukeland Hospital, Bergen, Norway
3. The Wallenberg Laboratory, University of Lund, Lund, Sweden
4. Division of Cell Kinetics, Central Institute of Molecular Biology, Academy of Sciences of the GDR, Berlin‐Buch, German Democratic Republic
5. Institute of Pharmacy, Free University of Berlin, Berlin, Federal Republic of Germany