The relationship between oöcyte and follicle in the hen’s ovary as shown by electron microscopy

Abstract

ABSTRACT In the early stages of oogenesis, the follicle cells contain a ‘complex mass’ of organelles which from its size and position apparently corresponds with the region identified as Golgi body by authors using light microscopy. It contains paired centrioles, radiating tubules, patches of Golgi apparatus and an orderly series of stacks of rough-surfaced endoplasmic reticulum which contain a granular material. It is concluded that these cells are probably secretory. The ‘complex mass’ disappears in the final stages of oogenesis. Using the methyl-green-pyronin test, the follicle cells have been shown to be rich in ribonucleoproteins. Specialized structures termed ‘lining bodies’ are found at irregular intervals at the surfaces of the follicle cells where they abut on to each other or on to the oöcyte. Long processes from the follicle cells indent the surface of the oöcyte, bearing lining bodies with them. Although there is no direct evidence that these lining bodies become engulfed by the oöcyte, nevertheless structures that are found several microns deep within the oöcyte so closely resemble the lining bodies that it seems probable they are derived from them. The available evidence does not support the ideas of Schjeide and his coworkers that the lining bodies give rise to mitochondria. No evidence was found of intercellular bridges between follicle and oöcyte. At first, the follicle and oöcyte membranes lie close together. Gradually, villous-like elevations arise on the oöcyte cell membrane which increase in number and in height. These constitute the zona radiata. Vesicles, containing a granular material, are common in the cortical region of the oöcyte. It is possible that these are formed by pinocytosis, for pinocytoticlike invaginations of the oöcyte cell membrane are visible. These are especially apparent in the zona radiata. The inner layer of the vitelline membrane forms between the follicle and zona radiata, and at first appears to be moulded around projections of the follicle cells. Just before ovulation the cell membrane of the ovum appears to become fragmented into a series of large vacuoles at the cell surface.