Configuration and distribution of bovine spermatogonia.

The configuration and distribution of bovine spermatogonia, preleptotene primary spermatocytes and Sertoli cells in the basal seminiferous tubular compartment have been studied by means of whole-mount preparations, immunohistochemistry and quantitative morphology. Three types of spermatogonia (Sg) can be identified. Large A-spermatogonia are irregularly distributed in the tubular periphery. Following the period of propagation of the A-spermatogonia, an interconnected meshwork of medium-sized spermatogonia with different cytogenetic potency is observed. Although the majority of the medium-sized spermatogonia are kinetically of the I type and divide to produce small B-spermatogonia, some members of the medium-sized population are seen in a growth phase and differentiate into large A-spermatogonia. These mark the beginning of a new round of spermatocytogenesis. Only one generation of B-spermatogonia divides into preleptotene primary spermatocytes. The architectural arrangement of multiplying spermatogonia in circles or rows is primarily the result of the distribution of the Sertoli cells. Spermatogonial multiplication is not strictly coordinated with the stages of the seminiferous epithelial cycle. Spermatogonial degeneration amounts on average to 3.6% and has therefore no decisive impact on the yield of primary spermatocytes.