Electron microscopical microprobe analysis of freeze dried and unstained mineralized epiphyseal cartilage.

Electron micrographs have been taken of unfixed, freeze dried, unstained epiphyseal cartilage. In the mineralized long septa round to elliptic clusters (up to 0.6 micron in diameter) consisting mainly of dots and needles could be observed. The clusters were surrounded by microareas with a low contrast consisting mainly of ribbon plate-like crystallites. With the aid of scanning mode (STEM) of a transmission electron microscope, equipped with a Si(Li)-detector system, both regions were analyzed for calcium and phosphorus by electronprobe X-ray microanalysis. In ten series of 106 measurements in each region, it could be determined by registration of the CaKalpha and PKalpha X-ray counts that the mineral content in the clusters was in the range of 30-100% higher than in the light regions. The question of the sequence of the epiphyseal plate mineralization is discussed and whether the dense clusters represent the mineralized matrix vesicles.