1. Endangered Species Spermatozoa: Diversity, Research, and Conservation -- I. Functional Significance of Morphological Relationships -- 2. Stage-Related Functions of Sertoli Cells: Lessons from Lower Vertebrates -- 3. Structure-Function Relationships in Somatic Cells of the Testis and Accessory Reproductive Glands -- 4. Local Growth Factor Effects During Spermatogenesis -- 5. Stage-Specific Expression of the Cathepsin L Gene by Rat Sertoli Cells -- II. Functions of Somatic Cells in the Testis -- 6. Characterization, Regulation, and Tissue-Specific Expression of Steroidogenic Enzymes -- 7. Molecular Genetics, Structure-Function Relationships, and Tissue-Specific Expression and Regulation of the 3?HSD Gene Family -- 8. Regulation of DNA Synthesis in Leydig Cells -- 9. Use of Two-Compartment Cultures of Sertoli Cells for Investigating Blood-Testis Barrier Physiology -- 10. Mediation of the Hormonal Stimulation of Steroidogenesis by the Polypeptide Diazepam Binding Inhibitor -- 11. Inhibition of Spermatogenesis by Tetanus Toxin Expression in Sertoli Cells of Transgenic Mice -- III. Signaling Molecules and Their Receptors -- 12. Pituitary Control of Fetal and Adult Leydig Cells and Physiological Regulation of Gonadotropin Gene Expression and Secretion in the Male -- 13. Expression of the FSH Receptor in the Sertoli Cells -- 14. Regulation of Germ Cell Proliferation In Vitro by Activins, Follistatin, and Other Growth Factors -- 15. Androgen Action in Sertoli and Peritubular Cells -- 16. Hormonal Control of Apoptotic Cell Death in the Testis -- 17. Involvement of Liver-Regulating Protein-Like Molecule in Sertoli-Germ Cell Cross Talk -- 18. 5?-Reductase Activity Increased by Oxytocin in the Rat Testis -- 19. Induction by LH/hCG of an Increase in the Rate of Pig Leydig Cell Receptor mRNA Degradation -- 20. Genetics and Luteinizing Hormone Receptors -- IV. Regulation of Germ Cells, Differentiation, and Gene Expression -- 21. Development of Postnatal Gonocytes In Vivo and In Vitro -- 22. Role of Retinoids in Spermatogonial Proliferation and Differentiation and the Meiotic Prophase -- 23. Role and Regulation of Spermatogenic Cell-Specific Gene Expression: Enzymes of Glycolysis -- 24. Regulation of the Cyclic Nucleotide-Dependent Pathway in Seminiferous Tubule Cells -- 25. Testis-Specific Proprotein Convertase 4: Gene Structure, Optional Exons, and mRNA Isoforms -- 26. Neonatal Propylthiouracil Treatment as a Model System for Studying Factors Controlling Testis Growth and Sperm Production -- V. Recent Developments in the Studies of Male Reproductive Functions -- 27. Molecular Biology of Human Androgen Insensitivity Syndrome -- 28. Congenital Absence of the Vas Deferens and the Cystic Fibrosis Transmembrane Conductance Regulator Gene: Evidence for a Common Genetic Background -- 29. GnRH Neurons in an Interpretation of Kallmannโ{128}{153}s Syndrome -- Author Index