A Study of the Cytoplasmic Inclusions and Nucleolar Phenomena during the Oogenesis of the Mouse

Abstract

1. The Golgi apparatus of the germinal epithelium consists of a dark mass of material situated at one pole of the nucleus. The mitochondria occur scattered throughout the cytoplasm. 2. The Golgi material of the very early oocyte consists of rods and granules clumped together to form a large body at one pole of the nucleus; smaller masses of Golgi material may also be present. 3. In the young oocyte, surrounded by a follicle wall, a single juxta-nuclear body is present; at a later stage the individual Golgi elements break away from the juxta-nuclear body and become distributed throughout the ooplasm. 4. In the late oocytes the Golgi elements occur in close association with the mitochondrial clumps and also scattered through the ooplasm. In tubal eggs the Golgi bodies are smaller in size and more numerous than in the ovarian ova. 5. It is concluded that the large mitochondria of Lams and Doorme correspond to the oocyte Golgi elements of the present contribution. The behaviour of the Golgi material during the growth of the ovum resembles that of the eggs of other mammals. The present findings on the structure of the juxta-nuclear Golgi material agrees with Nihoul's account for the rabbit. 6. The mitochondria of the young oocytes occur scattered through the ooplasm, but are more numerous in the vicinity of the nucleus and Golgi material. Later, the majority of the mitochondria become collected into clumps; in the tubal eggs the mitochondrial clumps are more numerous. 7. The Golgi apparatus of young follicles is situated between the follicle-cell nucleus and the pole of the cell directed towards the oocyte; in follicles consisting of several layers the position of the Golgi apparatus varies, while in fully-formed follicles the Golgi material of many of the cells surrounding the follicular cavity are directed towards the cavity. This agrees with Henneguy's findings for the Golgi apparatus of the follicle-cells of the guinea-pig. The mitochondria of the follicle-cells occur scattered through the cytoplasm but are more numerous towards the pole of the cell adjoining the oocyte. 8. The number of nucleoli present in the early oocyte varies from one to five; the majority of the older oocytes contain a single nucleolus but two may be present. Extrusion into the ooplasm of nucleolar material takes place; the nucleoli and the nucleolar extrusions are basophil (Mann's methyl-blue eosin). 9. Fatty yolk is not present in the mouse ovum. It is suggested that the Golgi elements and mitochondria play some part in yolk-formation, and that some of the granules formed by the fragmentation of the nucleolar extrusions are added to the yolkglobules already present. The yolk-globules of unsegmented tubal eggs are situated towards one pole of the cell; at the twocell stage they appear to be evenly distributed between the two cells. 10. In degenerating eggs the mitochondria are clumped; the Golgi bodies occur in small groups or are closely applied to the mitochondrial clumps. In eggs which have undergone fragmentation the Golgi bodies occur in groups, while the majority of the mitochondria are clumped. The fat-globules, previously recorded by Kingery in degenerating eggs, were identified. In material treated by Ciaccio's method for the identification of fats, appearances suggest that the Golgi elements, and possibly the mitochondria, give rise to fat. Yolk-globules could not be distinguished in the late stages of these eggs.