Fig. 5. Chondrocyte abnormalities. All histological sections have been stained with Safranin O. (A) Longitudinal section of a rib of an Ext2^+/– mouse shows nodules of displaced chondrocytes (arrows). The costochondral boundary is indicated by a broken line. (B) Transverse section through rib showing single displaced chondrocyte (arrow) near the perichondrium (P). (C) Higher magnification of longitudinal section through a rib of an Ext2^+/– mouse showing a nodule, forcing the perichondrium to bulge out. In B and C, the broken lines indicate the boundary between perichondrium and cartilage. (D) Low magnification of Alcian Blue (cartilage) and Alizarin Red (bone) staining of a rib of an Ext2^+/– showing a large nodule (arrow). Scale bars: 200 µm in A; 50 µm in B,C; 300 µm in D.