Serum hormone levels were estimated by radioimmunoassay using the method described by Verjans et al. for testosterone, the coat-a-count method purchased from Diagnostic Products Corporation (Los Angeles, CA) for estradiol as described earlier, and the method described by Welschen et al. for FSH. Levels of inhibin B were estimated using the immune-enzymometric assay from Serotec (Oxford, U.K.). The use of this assay in rhesus monkeys was described earlier by Ramaswamy et al..
Histological Examination of the Testis
In both the right and the left testis of each monkey, at least 1000 tubular cross-sections were examined for the presence of germ cells, and the repopulation index (RI) was calculated as the percentage of tubular cross-sections containing germ cells.
Furthermore, in each testis, the tubular diameter was measured in 30 tubular cross-sections using an ocular grid. In many monkeys, some of the tubules were grossly enlarged; these tubules were not taken into account when measuring tubular diameters. Also, in those testes in which the majority of the tubules was enlarged, this aspect was not studied.
To evaluate the significance of the correlation between sets of data, regression statistics were calculated and ANOVA analysis carried out using the Analysis ToolPak of the Microsoft Excel 97 program (Microsoft, Redmond, WA). Data are presented as mean ± SEM.