Demonstration of mitochondrial mineral deposits in osteoblasts after anhydrous fixation and processing.

The fine structure of early developing bone was examined using a modification of a new non-aqueous processing method in which anhydrous glutaraldehyde dissolved in dimethylsulphoxide (GLUT-DMSO) is used as a fixative. Preliminary results show that the basic morphological features of the cellular and extracellular compartments of developing bone were preserved. The cytoplasm of osteoblasts revealed numerous well-preserved mitochondria and other membranous organelles. Inside the mitochondria there were large and conspicuous electron-opaque granules of mineral which were more prominent and numerous than in specimens prepared by conventional aqueous procedures. The collagenous matrix also revealed electron-opaque deposits of mineral. These results support the evidence for the existence of mitochondrial calcium phosphate in osteoblasts in the form of granules.