Autoradiographic and ultrastructural studies on the origin of yolk protein in the housefly, Musca domestica L.

Abstract

The mechanisms of yolk protein formation during vitellogenesis in the housefly have been investigated by autoradiographic and ultrastructural techniques. Female houseflies were injected with H3-histidine. These flies showed an accumulation of radioactivity at the oocyte border of the follicle cells after 30 min and labeling of yolk particles in the egg cortex after 1 h. Most of the yolk protein was labeled after 6 h. In vitro studies in which isolated ovaries were immersed in insect saline containing H3-histidine gave similar results. Further evidence for the synthesis and assemblage of yolk protein precursors within the follicle cells, their migration, and final incorporation into the oocyte is presented from electron microscope studies.