I. Spermatogonial Cell Development, Function, and Regulation -- 1. Cloning and Characterization of Genes Specifically Expressed in Germ Line Cells -- 2. Gonocyte-Sertoli Cell Interactions in Testes of Neonatal Rats -- 3. Spermatogonial Transplantation -- 4. Telomerase Activity Is Lost During Male Germ Cell Differentiation -- II. Meiosis -- 5. Regulation of Sister-Chromatid Cohesion During Drosophila Meiosis -- 6. Role of Cell-Cycle Genes in the Regulation of Mammalian Meiosis -- 7. Acquisition of Competence to Enter Meiotic Metaphase During Mammalian Spermatogenesis -- 8. Regulated Synthesis and Role of DNA Methyltransferase During Meiosis -- III. Molecular Regulation of Spermatogenesis -- 9. CREM: A Master-Switch Governing Transcription in Male Germ Cells -- 10. Expression of Activator and Repressor Isoforms of Transcription Factor CREB During Spermatogenesis -- 11. Repression and Activation of Protamine mRN A Translation During Murine Spermatogenesis -- IV. Regulation of Cell Death/Aging -- 12. Cell Senescence and Aging -- 13. Testicular Aging: Leydig Cells and Spermatogenesis -- 14. Molecular Regulation of Testicular Cell Death -- 15. Hormonal Regulation of Germ Cell Apoptosis -- V. Toxicant Effects on Spermatogenesis -- 16. Estrogen Effects on Development and Function of the Testis -- 17. Developmental Effects and Molecular Mechanisms of Environmental Antiandrogens -- 18. Targets of Chemotherapeutic Drug Action in Testis and Epididymis -- 19. Hormonal Protection of Spermatogenic Stem Cells Against Cytotoxic Agents -- Author Index