Fig. 5. Evidence for a decreased cell proliferation rate within the Vhlh null growth plate. (A,B) Detection of BrdU-labeled chondrocytes in histological sections of E16.5 control (A) and Vhlh null (B) proximal tibia growth plates. (C,D) In situ hybridization analysis with p57^kip2 cRNA on histological sections of newborn control (C) and Vhlh null (D) growth plates; darkfield images are shown. (E) Percentage of BrdU-labeled cells; bars represent mean percentages (±s.d.) of BrdU-labeled chondrocytes in Vhlh null and wild-type (WT) growth plates at E14.5, E15.5 and E16.5, separated into proliferating zone (PZ) and resting zone (RZ). Statistical differences in each zone were identified using the unpaired t-test. ^**P<0.01.