Light microscopical and ultrastructural characterization of goat preantralfollicles

Goat ovarian preantral follicles were morphologically and ultrastructurally described in this work. Primordial follicles are oocytes surrounded by one layer of squamous or squamous-cuboidal granulosa cells; primary follicles have a single layer of cuboidal granulosa cells, and secondary follicles ar e oocytes surrounded by two or more layers of cuboidal granulosa cells. At all developmental stages a thick layer of glycoproteins, the basement membr ane, surrounded the preantral follicles. The quiescent oocyte is spherical or oval and it has a large eccentrically located nucleus with a conspicuous nucleolus. The organelles were uniformly distributed in the cytoplasm. A l arge number of vesicles were spread throughout the cytoplasm in all the ooc ytes. The cytoplasm of oocytes also contains numerous rounded mitochondria besides the usual organelles. As the follicle develops, the mitochondria be come elongated. The communication between the oocyte and the granulosa cell s is apparently mediated through endocytosis as indicated by the abundant c oated pits and vesicles noted in the cortical cytoplasm of the oocyte. The oocyte plasma membrane presented projections that penetrated between adjace nt granulosa cells and a few short microvilli lying parallel to the oocyte surface. In secondary follicles, patches of zona pellucida material were ob served. Overall, the results indicate that the morphological and ultrastruc tural organization of caprine preantral follicles resembles that of other m ammals. However, some particularities were observed, and that may indicate species specific differences. (C) 2001 Elsevier Science B.V. All rights res erved.