Paracrystalline structures in the epithelial principal cells of the epididymis of water buffalo (Bubalus bubalis)

The ultrastructure of many principal cells in the cauda epididymis of water buffaloes with ages varying between 4, 18, 24, 30 and 36 months, revealed, in many cells, the presence of long, curved paracrystalline structures tha t are quite large and frequently encountered in the cytoplasm, usually near the nucleus. Concomitantly or not, smaller rod-like, hexagonal or curled s tructures can be found in the nucleus. Both structures, cytoplasmic and int ranuclear, are made up of a sheath of parallel filaments. These paracrystal s may appear as thin, regularly spaced filaments that are associated with f ine, evenly spaced subunits, Occasionally, the association of paracrystalli ne structures with membranes similar to the endoplasmic reticulum was obser ved, but no membranes were consistently found in close contact with the nuc lear crystalloids. It is postulated that both structures are proteinaceous and may represent stored enzymes or substances present in the intraluminal fluid, which are absorbed and initially stored in numerous intraepithelial vacuoles of the corpus and cauda of the buffalo epididymis.