Electron microscopical x-ray microanalysis of mineralization nodules and several other tissue compartments in fetal bone.

Several chemical components are involved in bone and cartilage mineralization. Acid glycosaminoglycans (GAG) form one class of these components. In this study, the possible presence of sulfated GAG in areas of beginning bone mineralization was investigated. We analyzed areas containing acid groups, which were made visible with positive colloidal ThO2, by means of x-ray microanalysis. Four tissue compartments were internodular matrix, and noncalcified cartilage matrix. Sulfur proved to be present in a higher concentration in the mineralization nodules than in the osteoid, whereas no significant difference could be demonstrated between the sulfur concentrations in mineralized internodular matrix and osteoid. The ratio of the sulfur content between the mineralization nodules and the cartilage matrix is significantly lower than the corresponding thorium ratio. This difference suggests that acid groups different from sulfate groups occur in a relatively larger amount in mineralization nodules than in cartilage matrix.