Histochemical Studies of Lipids in Oocytes

Abstract

Judging from their sizes and histochemical reactions, three types of lipid bodies in the form of granules and spheres have been observed in the early stages of oogenesis. The minute granules (L1), belonging to the first type appear to consist of phospholipids, triglycerides, and fatty acids, but the presence of proteins cannot be ruled out. They correspond to the so-called granular mitochondria of other authors of papers on the oogenesis of birds. The second type of lipids (L2) are of medium size and they contain phospholipids and a certain amount of triglycerides. They resemble the socalled ‘Golgi bodies’ of earlier authors in appearance and react like them with osmium tetroxide and silver nitrate. They seem to originate from the granules of the first category (L1). The third type of lipids (L3) are the AH-negative spheres consisting of triglycerides and cholesterol and its esters. They correspond to the ‘fatty yolk’ of earlier authors. Their origin appears to be from the second type of lipid bodies (L2), as intermediate bodies (int) of varying chemical composition between the L2 and L3 have been observed. The ‘peripheral lipid bodies’ (pl) found in association with vacuoles are larger than the second type of AH-positive bodies (L2), but they seem to contain different types of phospholipids, triglycerides, and some other substances also. Besides these lipid bodies, a mass of lipoprotein bodies has also been observed. At the time of their origin, the yolk globules of the advanced oocytes do not contain lipids but later on they develop triglycerides and phospholipids. The lipid bodies of the follicular cells correspond very closely to the first two categories of sudanophil AH-positive bodies (L1 and L2) of the oocyte proper.