Improved visualization of ultrastructural components in the avian ovarian granulosa basement membrane

By modifying and improving a fixation procedure originally designed for better conservation of tissue lipids, we were able to visualize some ultrastructural, hitherto unobserved components in the theca interna and in the neighbouring granulosa basement membrane of the wall of the largest avian ovarian follicles. The basement membrane was seen to contain a network of stacks of densely staining plasma membrane fragments, probably formed by progressive piling up of thecal membranes during the rapid expansion of the follicle wall. At the same time, uptake at the surface of the basement membrane of intercellular yolk precursor material including lipid spheres was described.