Figure 2: Culture model using embryonic chick chondrocytes. Chondrocytes were removed from the cephalic and caudal region of 14 day chick embryos, cultured in monolayer and treated with retinoic acid (RA, 10, 35, and 100 nM) to induce maturation. Photomicrographs of cells stained for alkaline phosphatase, show a dose dependent increase in this maturation marker (see increase in red color), only on cephalic chondrocytes.