Studies on mitochondrial structure and function in Physarium polycephalum : I. Fine structure, cytochemistry, and H-uridine autoradiography of a central body in mitochondria

The fine structure, cytochemistry and autoradiography of the rod-shaped central body in the mitochondria of the slime mold, Physarum polycephalum, has been investigated. The central bodies are stained with Feulgen stain and, like the nucleoli, are stained metachromatically with azure B. At the ultrastructural level, they are composed of a semi-electron-dense axial region which is sensitive to treatment with DNase and an electron-dense peripheral region which surrounds the axial region and is sensitive to treatment with RNase. With electronmicroscopic autoradiography it has been shown that the central body and its peripheral region, after short exposure to ³H-uridine, incorporate ³H-uridine into a form, possibly RNA, which is insoluble in trichloroacetic acid and can be extracted with RNase though not with DNase. It is suggested that the central body is composed of an axial component which contains primarily DNA and a peripheral component which contains primarily RNA and that the RNA is synthesized in the central body.