Light- and electron-microscopic observations on the relationship between prelampbrush oocytes and surrounding granulosa cells in the laying Japanese quail (Coturnix coturnix japonica).

Transmission electronmicroscopic (TEM) observations demonstrated that the most superficial region of quail oocytes during the prelampbrush stage differs locally from the deeper ooplasm and is an active zone which forms exooplasmic cones, ridges or knob-like protrusions in the direction of/or in the granulosa cells. This exooplasm, in which no mitochondria were seen, is separated from the endooplasm, by a narrow interrupted filamentous layer. Using a lipid-preserving method of fixation, morphological evidence was found for the transport of lipid material from the granulosa cells into the exooplasm of the oocyte. Open intercellular bridges between exooplasm and granulosa cell cytoplasm were also seen. Differences between the electronmicroscopic aspect of clear and dark granulosa cells have been described.