Recent advances in molecular biology have provided new dimensions in the study of the reproductive system. There has been major progress in our understanding of the molecular mechanisms of hormone action in the past few' years. The symposium on "Molecular Basis of Reproductive Endocrinology" was organized to highlight new research findings on the regulation of the hypothalamic-pituitary-gonadal axis. The emphasis of the symposium was on physiological questions answered by the molecular biology approach. Studies on the functional relevance of gonadotropin releasing hormone and LH and FSH gene expression were presented, together with research on the molecular biology of ovarian and testicular steroidogenic enzymes and protein hormones. Also, several novel aspects of hormone gene expression in placental tissues were reviewed. The symposium was held July 25 to 26, 1991, immediately prior to the 24th Annual Meeting of the Society for the Study of Reproduction, on the campus of the University of British Columbia in Vancouver. Serono Symposia, USA generously financed and coordinated the meeting. We are indebted to Dr. Bruce K. Burnett and Dr. L. Lisa Kern for their professional assistance in the organization of the symposium. We would also like to thank Drs. Victor Gomel, Basil Ho Yuen, and John Challis, who served as session moderators. Most of all, we truly appreciate the efforts of all the invited speakers, poster presenters, and discussants in making this a memorable event as the largest one-day meeting of the Serono Symposia USA, series.

Inhalt
I. Hypothalamus and Pituitary.- 1. Social Control of Reproduction: Molecular Studies of GnRH in the African Cichlid Haplochromis burtoni.- 2. GnRH and Its Mechanism of Action.- 3. Molecular Mechanisms Underlying Placenta- and Pituitary-Specific Expression of the Glycoprotein Hormone ?-Subunit Gene.- 4. Role of Inhibins and Activins in Reproduction.- II. Ovary and Testis.- 5. Hormonal Regulation and Tissue-Specific Expression of Steroidogenic Enzymes.- 6. Regulation of LH and FSH Receptor Gene Expression in the Ovary and Testis.- 7. Hormonal Control of Gene Expression during Ovarian Cell Differentiation.- 8. Structure and Control of Expression of the 3?HSD and 17?HSD Genes in Classical Steroidogenic and Peripheral Intracrine Tissues.- 9. Structure and Regulation of Gonadal Cell Phosphodiesterases.- III. Placenta and Fetus.- 10. Differentiation of Human Trophoblasts: Structure-Function Relationships.- 11. Placental Lactogen/Growth Hormone Gene Family.- 12. Human Relaxin Genes in the Decidua and Placenta.- 13. Molecular Mechanisms Regulating Oxytocin Gene Expression.- IV. Poster Presentation Manusscripts.- 14. Structure-Function Relationships of Multiple Rat Members of the 3?-Hydroxysteroid Dehydrogenase Family.- 15. Preovulatory Collagenase Activity in the Follicle of the Chicken.- 16. Transforming Growth Factor ?1 Stimulation of Progesterone Production in Cultured Granulosa Cells from Gonadotropin-Primed Adult Rats.- 17. Induction of Steroidogenesis in a Retrovirus-Transformed Rat Granulosa Cell Line.- 18. Arachidonic Acid as a Second Messenger for Regulation of Aromatase Activity in Porcine Granulosa Cells.- 19. Inhibition of Progesterone Production in Cultured Porcine Granulosa Cells by Transforming Growth Factor ?1.- 20. Biological Relevance and Analysis ofc-myc Gene Expression in Normal Human Ovary.- 21. Signal Transduction of PGF2? in Rat Corpora Lutea.- 22. Protein Changes in the Rat Corpus Luteum during Luteolysis.- 23. Detection of Relaxin Secretion and Gene Expression in Individual Porcine Luteal Cells.- 24. Oxytocin Receptors in Myometrium: Preliminary Evidence for a Receptor Switch Mechanism.- 25. GnRH- and cAMP-Stimulated Human Chorionic Gonadotropin Secretion from Perifused Placental Cells.- 26. 3?-Hydroxysteroid Dehydrogenase Activity of Human Placental Cytotrophoblast Following Differentiation in Vitro.- Author Index.