Analysis of the developing avian glycogen body. I. Ultrastructural morphology

An electron microscopic study of several stages in the development of the glycogen body of the chick is reported. During early developmental stages (7.5–11 days) glycogen granules were scattered throughout the cytoplasm of glycogen‐body cells. Lysosomes were observed for the first time on the eleventh day of incubation. In the course of subsequent development three well demarcated cytoplasmic areas became recognizable; a juxtanuclear region that contained most of the organelles and was devoid of glycogen, a peripheral area (ectoplasm) free of glycogen, and a region densely packed with glycogen. Cells that were heavily laden with glycogen contained unusual rounded or “C”‐shaped multivesicular bodies which were associated with the Golgi complex and with Golgi‐like vesicles. Their functional significance did not become evident in this descriptive study. The paucity of smooth endoplasmic reticulum indicated its lack of importance in glycogen metabolism in the glycogen body. Ribosomes, which were the only organelles consistently observed in close proximity to glycogen granules, were thus implicated in glycogen synthesis.