BMPC-rich elutriation fraction cultured in DMEM-20% FCS supplemented with dexamethasone, ascorbic acid, and β-glycerophosphate (as described in Fig. 1). After 20 days, about one-third of the cells are very large. Their cytoplasm stains with an anti-calcitonin antibody. Immunoperoxidase staining is also observed in the matrix formed around some of the largest cells. In the same supplemented cultures are large cells containing neutral lipid (Sudan IV; red stain). (a) Shows both anti-calcitonin-stained cells (arrows) and sudanophilic cells (arrowheads) in the same supplemented cultures (×250) and (b) is at higher magnification (×400) showing a cell and its surrounding matrix stained with an anticalcitonin antibody (arrow).