Osmium zinc iodide staining of Golgi elements in oocytes of Triturus cristatus.

Developing oocytes of the newt Triturus cristatus were studied in order to clarify the role played by the Golgi apparatus in the formation of yolk. The cytochemical method used for this purpose was that of Maillet (1968) which employs an Osmium Zinc Iodide (OZI) complex. Previtellogenic oocytes reveal a pattern of OZI staining only after hormonal (HCG) stimulation, following which both the Golgi apparatus and the multivesicular bodies are stained. Vitellogenic oocytes taken from non-hormonally stimulated females reveal OZI deposits in a number of vesicles peripheral to the Golgi apparatus as well as within the superficial layer of the forming yolk platelets. Following hormone stimulation, many of the Golgi apparatus located in the central ooplasm of vitellogenic oocytes have all their cisternae blackened by the OZI deposits; other apparatuses,more peripherally located, remain essentially unchanged in their staining pattern. Further, a large number of OZI stained vesicles becomes visible in the vicinity of the Golgi apparatus and within the superficial layer of the forming yolk platelets. The present findings are interpreted as indicating the occurrence of fusion between Golgi derived vesicles and forming yolk platelets. It is also suggested that the vesicles in question function as carriers of Golgi produced enzymes which are presumably required to accomplish the final elaboration of the yolk material.