Cytoplasmic Inclusions in Oogenesis

Abstract

Publisher Summary This chapter focuses on the cytoplasmic inclusions in oogenesis, and discusses the structure and functions of the Golgi apparatus and mitochondria in eggs and their role in vitellogenesis. Investigation of Golgi apparatus in eggs is beset with special difficulty because of the presence of yolk, which becomes enormous in quantity as the egg matures and often chokes the entire cytoplasm leaving only the cortex somewhat free of it. In nearly all cases, the Golgi bodies undergo regular changes in position as the egg enlarges and embarks on yolk formation. The oogonia and early oocytes show the Golgi elements generally aggregated together in a loose or compact juxtanuclear mass. In somewhat advanced eggs this mass is disorganized and the Golgi elements are scattered through the cytoplasm either as single elements, or, more frequently, as small aggregates. Eventually, these elements occupy a cortical position. As is the case of the Golgi elements, mitochondria change position as the egg grows to maturity. In the early oocytes, they occupy a juxtanuclear position. Occasionally, the earliest eggs are reported to contain a perinuclear accumulation of mitochondria. A mitochondrial element is composed of a double limiting membrane and a system of double membranes traversing the interior completely or incompletely. The mitochondria undergo a certain degree of modification in different tissue cells, but these modifications never conceal the fundamental structural plan. Another significance is the association with mitochondria, probably forming an integral part of it, of the respiratory enzymes-several key enzymes of the Krebs tricarboxylic acid cycle and of the cytochrome system.