Catalase in salivary gland striated and excretory duct cells. II. phi body: an ellipsoidal peroxisomal organelle with crystalloid axial projections.

A new distinctive and unique peroxisomal organelle with a spindle shape has been observed in luminal epithelial cells of striated and excretory ducts of mouse salivary glands. Light microscopic studies indicate it has an ellipsoidal centre from which catalase-positive filamentous or rod-like processes protrude along its major axis; hence, it is called a phi body. A role for this specialized peroxisome in the formation of nearby free filaments and rods is suggested by the frequent observation of segmentation of its axial processes. Complementary ultrastructural studies of osmium-fixed preparations show that the deformation to an oval shape results from the pressure of the extruding crystalloid coincident with the major axis of the ellipsoidal body. The size range and conformation of phi body axial processes are comparable to those of free catalase-positive rods and filaments observed in the same cells. The periodic substructure of the crystalloid in the phi body core is identical with that of nearby cytoplasmic rods. These observations are consistent with the view that the rods and filaments observed free in the cytoplasm are formed by extrusion from the crystalloid core of the phi body. phi Bodies could also be responsible for the Aver rods of leukemic leukocytes.