1. University of Zurich, Institute of Animal Nutrition (A.T., J.-L.R.), CH-1211 Geneva 14, Switzerland
2. Winterthurerstrasse 260, CH-8057 Zurich; and the Department of Internal Medicine, Division of Clinical Physiopathology, University Hospital of Geneva (P.A.), CH-1211 Geneva 14, Switzerland
3. Institute of Anatomy, Department of Cell Biology, University of Aarhus (L.M., J.S.T.), DK-8000 Aarhus C, Denmark