1. Laboratory of Pharmacognosy and Phytochemistry, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, B-9000 Ghent, Belgium, Laboratory of Eukaryotic Gene Expression and Signal Transduction, Faculty of Sciences, Department of Molecular Biology, Ghent University, Ledeganckstraat 35, B-9000 Ghent, Belgium, and Endocrinology and Reproduction Research Group, School of Biomedical Sciences, King's College, London SE1 1UL, U.K.