Fig. 1.

Calcospherulites along the mineralization front of bone. a Transmission mode confocal microscopy images of a toluidine blue-stained undecalcified section of tibial diaphysis tissue from a juvenile rat. Periosteum, osteoblasts, osteoid and bone locations are noted. The box identifies a region of interest at the mineralization front that is shown at higher magnification in b. b Location of the mineralization front (MF) is indicated. The black arrows point to the calcospherulites referred to in the text. c Epifluorescence confocal microscopy image of the periosteal mineralization front labeled in vivo with calcein. Locations are indicated for calcein-labeled spherulites at (white arrows) or within (black arrowhead) the mineralization front.