Micropapillae: a local modification of the cell surface observed in rabbit oocytes and adjacent follicular cells

Ultrastructure of the oocytes of the Egyptian sping mouse (Acomys cahirinus)

The oocytes of types 2, 3, 4 and 5 follicles from the normal spiny mouse were examined withe the electron microsome. Multiple juxtanuclear Golgi bodies, mitochondria associated with flattened granular endoplasmic reticulum, and large nucleus are the main features of the type 2 follicle oocyte. The numbers of mitochondria and Golgi apparati increase significantly at later stages. Small mitochondrial aggregates lacking "intermitochondrial cement" are seen in the ooplasm of types 3, 4 and 5 follicles. "Lamellar complexes" comprising two to six elongate flattened rough ER cisternae and intercisternal filaments begin to appear in the occyte of the type 3 follicle. The intercisternal filaments may be observed as punctate-, dashed-, and solid-lines in cross sections. In tangential sections the filaments display a paracrystalline structure. In the type 4 follicle oocytes, the "lamellar complex" becomes more extensive; polysomes and ribosomal fibrils are juxtaposed to the "lamellar complexes." Bundles of ribosomal fibrils are abundant in the ooplasm of the type 5 follicle. The origin of ribosomal filaments and the functional significance of "lamellar complexes" are discussed.

A scanning electron microscopic study of the luteo-follicular complex. II. Events leading to ovulation

Morphological changes on the ovarian surface of different mammals both before and during ovulation have been examined by scanning electron microscopy. Preovulatory follicles were blisterlike structures that protruded markedly from the ovarian surface. Basal areas of preovulatory follicles were covered with polyhedral cells containing numerous microvilli, whereas on the lateral surfaces, superficial cells were elongated and possessed few microvilli. At the apex of the follicle, cells were very flattened and possessed few microvilli, which were present only in regions of intercellular contact. In some apical areas, cells appeared to be degenerating, whereas in other regions, groups of cells had "sloughed off." In addition, a fluidlike material was observed to exude from intercellular spaces of the superficial epithelium and to cover some apical cells. By transmission electron microscopy, the same fluidlike material was observed to (1) infiltrate the connective tissue of the tunica albuginea, (2) accumulate under the basal lamina, and (3) distend intercellular spaces of the superficial epithelium. Just prior to ovulation, large, irregular areas of the apex were ruptured and the oocyte, covered with a large amount of fluid, appeared to emerge from the follicle. At ovulation, the oocyte was not completely covered with follicle cells and the zona pellucida was clearly evident. The surface of the zona was quite irregular and contained numerous infoldings, channels and crypts. Follicle cells had polyhedral or star shapes and possessed large cytoplasmic evaginations that obliquely penetrated the zona. Both the zona pellucida and corona cells were covered with a fine layer of granular material. The SEM results and parallel TEM observations suggest that a local increase of fluids (edema) may be an important factor in the final decomposition of the distended and weakened apex of the preovulatory follicle. In addition, the participation of follicle cells, smooth muscle cells and the oviduct in the escape of the oocyte from the ruptured follicle is discussed.