Abstract
Summary Spindle or needle-shaped crystalloids are observed in Sertoli cells of the intersex and experimental cryptorchid swine in the light and electron microscopes. Small crystalloids are also observed in Sertoli cells of the normal swine only by electron microscopy. These crystalloids consist of fine filaments. The filaments are about 5 nm in diameter and arranged parallel to the long axis of the crystalloid. In cross sections of the crystalloid, the close packing of the filaments shows hexagonal arrays. The interfilamentous distance is about 5 nm. In all animals examined, bundles of short filaments, which are 5 nm in diameter, are observed in the basal part of the Sertoli cells. Ultrastructural similarities among the crystalloids, the bundles of fine filaments, and the filamentous layer in the junctional specialization of the Sertoli cell are shown. These morphological similarities suggest that the crystalloids are formed by the aggregation of the bundles in the Sertoli cells of azoospermic testes.