Production of specific-protein secretion granules by fat body cells of the blowfly, Calliphora erythrocephala. Substitution of an ovarian key factor by beta-ecdysone.

During the first four days of the imaginal stage the fat cells of ovariectomized females of Calliphora develop a protein synthetic apparatus, and produce dense bodies (lysosomes) as do the fat cells of normal females, but apparently they cannot synthesize the protein secretion granules that characterize the productive phase of the fat cells of normal females and that we believe to represent vitellogenin. Injection of ovariectomized females with beta-ecdysone restored the ability of the fat cells to produce the secretion granules. It is suggested that the ovary gives off a factor which induces the production of the protein secretion granules by the fat cells, and that the factor from the ovary can be substituted by beta-ecdysone. This, we believe, is the first ultrastructural evidence for an effect of the ovary and of beta-ecdysone on the synthesis of specific protein.