Alkaline Phosphatase/genetics; Calcification, Physiologic/genetics; Cartilage/cytology; Cartilage/metabolism; Gene Expression/genetics; Minerals/metabolism; Osteonectin/genetics; Sialoglycoproteins/genetics; Tretinoin/pharmacology; Alkaline Phosphatase/physiology; Animals; Apatites/metabolism; Ascorbic Acid/pharmacology; Calcium/metabolism; Cells, Cultured; Chick Embryo; Collagen/genetics; Collagen/physiology; Dose-Response Relationship, Drug; Extracellular Matrix/metabolism; Fluorescent Antibody Technique; Hypertrophy/metabolism; Hypertrophy/pathology; Osteonectin/physiology; Osteopontin; Parathyroid Hormone/pharmacology; Sialoglycoproteins/physiology; Time Factors