[Effects of low temperatures on glycogen storage in oocytes ofMusca domestica]

The effect of cold (4° C) on protein synthesis and glycogen content of intermediate egg follicles was studied. Under normal conditions (21°) these developmental stages were still free of carbohydrates. 1. As shown by autoradiography, in the cold the incorporation of amino acids was reduced to 1/4. No cold adaptation was observed within 2 weeks. The growth of the follicles was stopped. 2. A decrease in temperature brings above a storage of glycogen with the same frequency in the early and middle stages of oogenesis. 3. In permanent cold about 75% of the intermediate oocytes were storing glycogen. 4. After a short period of 2 cold days glycogen which had accumulated in young follicles was catabolized again. The oocyte development then continued normally. 5. After a long period of 10 cold days disarrangements occurred. Follicle development was retarded and became asynchronous or even atretic. 6. If eggs affected by a period of cold became ripe, they had normal developmental abilities. Several results indicate that the enzymes necessary for glycogen synthesis are already present but inactivated during intermediate stages of oogenesis. They can be activated by low temperature. Some possibilities of a hormonal or an intracellular regulation of precocious glycogen storage are discussed. The regulatory system normally releases glycogen synthesis only towards the end of oogenesis.