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.