Germ cell degeneration during postprophase of meiosis and serum concentrations of gonadotropins in young adult and older adult men.
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abstract
Loss of potential sperm production during postprophase of meiosis was evaluated to determine if reduced daily sperm production in older men could be explained by an enhanced percentage of germ cell degeneration during this period of spermatogenesis. Evaluations were based on enumerating germ cells in homogenates of fixed testes using phase-contrast cytometry from 37 young adult (20-48 yr) and 34 older adult (50-85 yr) men. The time period in which germ cells degenerate was assessed in 10 men by comparing potential daily sperm production based on secondary spermatocytes with that based on primary spermatocytes or with daily sperm production based on spermatids. There was a significant (P less than 0.01) decline in sperm production potential based on primary spermatocytes and on spermatids in the older adult men such that the percentage of loss of potential production during postprophase was similar between the two age groups. Sperm production estimates based on primary spermatocytes and secondary spermatocytes were similar (P greater than 0.05); however, estimates based on secondary spermatocytes were significantly higher than those based on spermatids. Degeneration during postprophase of meiosis in humans appears to occur during or near the second meiotic division. Age-related reduced sperm production was significantly correlated with elevated levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Age-related decline in sperm production could not be explained by enhanced germ cell degeneration during postprophase but may result from reduced germ cell numbers prior to pachytene primary spermatocytes.
