Comparative ultrastructure of larval hypodermal cell in normal and oily Bombyx mutants.

Abstract

In order to understand how oily mutation alters the formation and distribution of urate globules, we first examined the formation and degeneration processes of these urate globules in the hypodermal cells of normal Bombyx mori larvae using electron microscopy. The ultrastructures of the hypodermal cells of normal and mutant silkworms were then compared, and it was found that the origin of the urate globules might be concerned with pinocytosis. Early in the process of degeneration of the globules many glycogen granules appear, the membrane of the globules fuses and then the material compassing the globules is discharged. A comparison of ultrastructures of normal and oily mutants indicated that the mutations cause urate globules irregular in shape and distribution. Furthermore, there is a close relationship between the volume of these globules and uric acid content in the hypodermis. We concluded from the evidence that the mechanism of incorporation and accumulation of uric acid is controlled independently by each oily mutant gene.