Glycogen metabolism and the nuclear envelope-annulate lamella system in the early chick embryo.

The intracellular sites of glycogen degradation in the mid to late uterine chick embryo were determined by cytochemical localization of glucose-6-phosphatase at the ultrastructural level. Enzyme activity was found between the two membranes of the nuclear envelope, in the annulate lamellae and in specialized glycogen-containing membrane scrolls. Annulate lamellae and glycogen scrolls were most frequent during the stages of intensive glycogen degradation. Annulate lamellae appear to be formed from the nuclear envelope. During the early post-laying stages annulate lamellae disappeared and were replaced by endoplasmic reticulum that appeared initially in scroll-like formations.