The cycle of the seminiferous epithelium and spermatogenesis in the bovine testis

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Abstract
Morphological changes in the acrosomic system and nuclei of developing spermatids were evaluated as a basis for classifying the stages of the cycle of the seminiferous epithelium in the bovine testis. Light microscopic examination of periodic acid‐Schiff‐stained testicular tissue permitted identification of 14 steps of spermatid development (spermiogenesis). The first 12 steps in this sequence were utilized as the major criterion to divide the cycle of the seminiferous epithelium into 12 distinct stages. Following this, the pattern of germ cell differentiation was investigated by counting the number of germ cells at each stage of the cycle. Based on cell counts, type A spermatogonia divided primarily during stages VII–VIII and IX–X of the cycle. Some type A cells divided again at the end of stage XII to produce intermediate spermatogonia, while others apparently remained “dormant” until the following cycle. At the end of stage IV, intermediate spermatogonia divided to produce type B1 spermatogonia which in turn divided at the end of stage V to produce type B2 spermatogonia. Primary spermatocytes appeared during stage VIII and divided late in stage XI of the following cycle to form secondary spermatocytes. These divided to form young spermatids at the end of stage XII. It was concluded that changes in the acrosomic system and nuclear morphology of developing spermatids provide useful criteria for dividing the cycle of the seminiferous epithelium into stages as well as investigating the pattern of germ cell development during spermatogenesis in the bovine testis.