Testicular disruption in the As (aspermia) mutant rat, with special reference to the aggregate of ribosomes.

The morphology of the testis of the mutant As (aspermia) strain rat with severely interrupted spermatogenesis was investigated in the present study. The most advanced development in spermatogenesis was observed at the step 8 at which spermatids had basally-oriented acrosomes. Multinucleate giant cells derived from round spermatids were frequently encountered within the seminiferous tubules. The functionally normal status of the blood-testis barrier between adjacent Sertoli cells was confirmed by morphological and lanthanum tracer studies. By light microscopy, a peculiar structure was found within the pachytene spermatocyte, consisting of numerous particles of approximately 25 nm in diameter. By histochemical and electron microscopic studies, this structure was identified as an aggregate of ribosomes. Neither immature spermatogenic cells up to the pachytene phase, nor Sertoli cells nor interstitial regions showed a recognizable abnormality. It seems that the testicular disruption in the As mutant rat is due to the abnormality in the protein synthetic pathway in pachytene spermatocytes.