Fasciola hepatica: A light and electron autoradiographic study of shell-protein and glycogen synthesis by vitelline follicles in tissue slices

Abstract

The incorporation of tritiated amino acids and monosaccharides by the vitelline cells of F. hepatica slices maintained in vitro was studied by light and electron microscope autoradiography. A “pulse-chase” labeling technique was used with tritiated tyrosine, phenylalanine, leucine, and methionine, of which H 3-tyrosine was the most readily incorporated into shell-protein globules of immature vitelline cells. The mechanism of protein synthesis appeared to resemble the GER-Golgi mediated mechanism of vertebrates. Young vitelline cells were the most active in protein synthesis, and they matured considerably during the 60 min chase period. Maturing cells, which were carrying out glycogenesis, incorporated no amino acids. An “accumulation” labeling technique was used with H 3-galactose and H 3-glucose. Both monosaccharides were readily incorporated into glycogen by vitelline cells which had reached the stage of glycogenesis, but mature cells, which were already packed with glycogen, incorporated little monosaccharide. Labeling appeared in the nurse cells of follicles containing many mature vitelline cells. No evidence was found for the involvement of any cell organelle in glycogenesis, but preformed glycogen may have acted as a “template” for further synthesis.