The function and transposition of lining bodies in developing avian oocytes

Oocytes, ranging from 0.2 mm to 35 mm in diameter, from White Leghorn hens have been examined. Large numbers of pinocytotic vesicles can be observed in all stages of development. Three categories of specialized organelles can be seen. Examples are: cytoplasmic and macrobodies, oocyte bodies, and lining bodies. In early development the lining body lies in the follicle cell subjacent to the plasma membrane. It consists of a densely staining basal layer, 150 Å thick, to which 200–250 Å knobs are attached. The dense layer can be resolved into five sublayers. The knobs exhibit RNase sensitivity comparable to that of cytoplasmic ribosomes. During development of the oocyte, the lining bodies are transposed to the region between the oocyte and follicle cell and begin to penetrate the oocyte. The lining body becomes the advancing tip of a follicular projection and is encased by follicle cell and oocyte plasma membrane. During later stages of development, yolk sphere material is deposited outside the tip of the projection between the oocyte and follicle cell plasma membranes. With further development the lining body is pinched off and the intercellular space is markedly enlarged to form the mature yolk sphere. It is suggested that the early stages of yolk sphere protein synthesis are mediated and regulated by lining bodies.