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Evaluation of the human testis and its age-related dysfunction.
Links Evaluation of the human testis and its age-related dysfunction. Johnson LProg Clin Biol Res. 1989;302:35-60; discussion 61-7. Links Evaluation of the human testis and its age-related dysfunction. Johnson L. Department of Veterinary Anatomy, College of Veterinary Medicine, Texas A&M University, College Station 77843-4458. The human testis has been evaluated by its endocrine function, daily sperm output in ejaculates, general appearance of seminiferous tubules, differential cell counts in the testis, and daily sperm production. Within-subject variation for total sperm count in ejaculates is extremely high at 42% to 75% coefficient variation. This variation can be reduced to 12% by averaging the counts obtained for the last three of five daily ejaculates. Plasma FSH concentrations are particularly useful in assessing the status of seminiferous epithelium and/or its Sertoli cell function in infertile men. In aged men, plasma LH, FSH, and estradiol concentrations are higher while plasma testosterone, free testosterone, and the ability of the testis to secrete testosterone following stimulation are reduced. Other age-related changes in human testes include a high incidence of azoospermia, reduced sexual activity, reduced testicular size, impaired spermatogenesis, reduced tubular length, increased thickness of tubular boundary tissue, sclerosis, focal mononuclear orchitis, and dilation of the rete testis. Due to the long duration of the spermatogenic cycle and low numbers of germ cells in human testis, daily sperm production per g parenchyma (efficiency of spermatogenesis) is much lower in humans than in other species. Testicular parenchymal weight, proportion of testis occupied by seminiferous epithelium, volume of seminiferous epithelium, and daily sperm production are significantly reduced in aged men. In various species, including man, germ cell degeneration occurs during spermatocytogenesis, meiosis, and/or spermiogenesis. Germ cell degeneration plays a pivotal role in spermatogenesis, but the mechanisms of degeneration, its etiology, and approaches for its prevention remain unclear. PMID: 2666991 [PubMed - indexed for MEDLINE] Related Links Ethnic differences in testicular structure and spermatogenic potential may predispose testes of Asian men to a heightened sensitivity to steroidal contraceptives. [J Androl. 1998] PMID: 9639052 Heterotopic transplantation as a model to study the regulation of spermatogenesis; some histomorphological considerations about sperm decline in man. [Contracept Fertil Sex. 1997] PMID: 9343904 Testis morphometry, seminiferous epithelium cycle length, and daily sperm production in domestic cats (Felis catus). [Biol Reprod. 2003] PMID: 12606460 Leydig cell numbers, daily sperm production, and serum gonadotropin levels in aging men. [J Clin Endocrinol Metab. 1984] PMID: 6434579 Efficiency of spermatogenesis. [Microsc Res Tech. 1995] PMID: 8563040 See all Related Articles... Display Summary Brief Abstract AbstractPlus Citation MEDLINE XML UI List LinkOut ASN.1 Related Articles Cited Articles Cited in Books CancerChrom Links Domain Links 3D Domain Links GEO DataSet Links Gene Links Gene (GeneRIF) Links Genome Links Project Links GENSAT Links GEO Profile Links HomoloGene Links Nucleotide Links Nucleotide (RefSeq) Links OMIA Links OMIM (calculated) Links OMIM (cited) Links BioAssay Links Compound Links Compound via MeSH Substance Links Substance via MeSH PMC Links Cited in PMC PopSet Links Probe Links Protein Links Protein (RefSeq) Links SNP Links Structure Links Taxonomy via GenBank UniGene Links UniSTS Links Show 5 10 20 50 100 200 500 Sort by Pub Date First Author Last Author Journal Send to Text File Printer Clipboard E-mail Order .
Department of Veterinary Anatomy, College of Veterinary Medicine, Texas A&M University, College Station 77843-4458.
The human testis has been evaluated by its endocrine function, daily sperm output in ejaculates, general appearance of seminiferous tubules, differential cell counts in the testis, and daily sperm production. Within-subject variation for total sperm count in ejaculates is extremely high at 42% to 75% coefficient variation. This variation can be reduced to 12% by averaging the counts obtained for the last three of five daily ejaculates. Plasma FSH concentrations are particularly useful in assessing the status of seminiferous epithelium and/or its Sertoli cell function in infertile men. In aged men, plasma LH, FSH, and estradiol concentrations are higher while plasma testosterone, free testosterone, and the ability of the testis to secrete testosterone following stimulation are reduced. Other age-related changes in human testes include a high incidence of azoospermia, reduced sexual activity, reduced testicular size, impaired spermatogenesis, reduced tubular length, increased thickness of tubular boundary tissue, sclerosis, focal mononuclear orchitis, and dilation of the rete testis. Due to the long duration of the spermatogenic cycle and low numbers of germ cells in human testis, daily sperm production per g parenchyma (efficiency of spermatogenesis) is much lower in humans than in other species. Testicular parenchymal weight, proportion of testis occupied by seminiferous epithelium, volume of seminiferous epithelium, and daily sperm production are significantly reduced in aged men. In various species, including man, germ cell degeneration occurs during spermatocytogenesis, meiosis, and/or spermiogenesis. Germ cell degeneration plays a pivotal role in spermatogenesis, but the mechanisms of degeneration, its etiology, and approaches for its prevention remain unclear.
This abstract is being posted for educational purposes, as well as for comment and criticism, by the visitors to the Epididymitis Foundation website (EpididymitisFoundation.org). This abstract is representative of a larger article that is indexed on Medline.
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