Structural and cytochemical features of the yolk globules and of the nucleolus in the growing oocytes of the mollusc Murex trunculus L.

A relationship between the second phase of the nucleolar activity and the variations which the yolk globules undergo in their staining affinities and in their chemical constitution has been found in growing oocytes o Murex trunculus. The results obtained enable us to recognize that the different staining affinities among the initial intermediate and definitive yolk granules correlate with the variations in their chemical constitution. The variations are due to the lack of proteins with disulfide groups, tryptophan, indolic and phenolic substances and tyrosine in the initial yolk globules, substances which, on the other hand, are found in both intermediate and final globules. Furthermore, the final globules are lacking in lipids. The presence of both acid and alkaline phosphatase activities is limited mostly to the initial yolk globules. It was possible to deduce from the chemical constitution in the nucleus of the oocytes under examination that the phase in which the nucleous modifies its content of chemical substances and when the transformation in the chemical constitution of the yolk globules occurs, is not coincidental. Both of these phenomena occur when vitellogenesis is advances although the nucleus undergoes vacuolization through out the time in which previtellogenesis passes to vitellogenesis. That the presence of the hydrolytic enzymes is correlated with nucleolar activity and that their probable role is connected with the yolk transformation and subsequent reconstruction is discussed.

A comparative cytochemical study of the yolk platelets in the growing oocytes of Triturus cristatus and Rana esculenta.

Recent cytochemical techniques for the detection of proteins, neutral and acid mucopolysaccharides, lipids and phospholipids in the yolk platelets of the growing oocytes of Rana esculenta and Triturus vulgaris are employed. Cytochemical analysis showed that the yolk in the form of granules or platelets, in the constituting itself the most prominent cytoplasmic inclusion of amphibian eggs, contains a protein moiety consisting of individual typical amino acids lacking tryptophan in Triturus, a carbohydrate fraction consisting of neutral mucopolysaccharides distributed in the superficial layer of each platelet, and phospholipids, phosphoproteins and lipoproteins which are present only in the main body of the same platelets. The different amino acid composition indicated a protein heterogeneity which could be connected with the tissue incompatibility of the transplantations when these last were effected between the orders Urodela and Anura. The different protein composition of the yolk also can be reflected at the species-specific level. The cytochemical data are further reviewed with the mode of utilization of the yolk platelets.