1. Hormone and Metabolic Research Unit (C.E.P., G.G.R., F.P.L.) Louvain University Medical School Christian de Duve Institute of Cellular Pathology (ICP) B-1200 Brussels, Belgium
2. Department of Molecular Signaling (B.U., P.D.M.) Hagedorn Research Institute DK-2820 Gentofte, Denmark