Fig. 4. Delay of the secondary ossification center in the Vhlh null growth plate. (A-D) Hematoxylin and Eosin staining of histological sections of control (A,C) and null (B,D) proximal tibia growth plates from 5-day-(A,B), and 1-month-old (C,D) mice. (E-J) In situ hybridization analysis of histological sections of tibia proximal growth plates from control (E,G,I) and Vhlh null (F,H,J) 5-day-old mice, with type X collagen (E,F), PTH/PTHrP receptor (G,H) and Indian Hedgehog (I,J) cRNA; darkfield images are shown. (K,L) Articular cartilage of control and Vhlh null animals, one month after birth, at higher magnification.