Electron microscopic and cytochemical study on paraboloid glycogen of the accessory cone of the chick retina.

Glycogen synthetase and phosphorylase activities in the paraboloid glycogen of the accessory cone of the chick retina were studied electron histochemically, while the paraboloid glycogen was observed by electron microscopy. Some of the paraboloid of the accessory cone of the chick retina contained abundant glycogen granules, but some showed no glycogen granules. Some inner segments of the accessory cones were occupied by deposition of glycogen granules. Polyglucose particles synthesized by glycogen synthetase activity in the chick paraboloid were demonstrated in fine granular form with diameter from 70 to 130 A. These particles were less stainable with lead citrate than native glycogen granules. Synthesized polyglucose particles were located in the cytoplasmic matrices and expanded them. Lamellar and membrane structures were not related to synthesized polyglucose. Polyglucose particles synthesized by phosphorylase activity in the chick paraboloid were located in the cytoplasmic matrices and expanded them widely. Tubular structure appeared to be flattened by deposition of synthesized polyglucose particles. These features showed the resemblance to the inner segment of the accessory cone filled with a great amount of glycogen granules. Synthesized polyglucose was demonstrated in macromolecular form with diameter from 200 to 500 A. There were no relationships between lamellar or membrane structures and polyglucose. The present study suggests that the chick paraboloid not only is a field for active glycogen metabolism, but also becomes a storage of glycogen.