Fig. 6. Increased cell proliferation and Fgf8 upregulation after CNC ablation in chick embryos. (A-C'') A combined in situ hybridization for Myf5 (purple) and BrdU staining (red) in transverse sections of stage 18 embryos in the trunk (A-A'') and BA2 region (B-B'', control) or CNC-ablated embryo (C-C''). Arrowheads point to Myf5 expression and BrdU staining in the muscle anlagen. (D) A quantification analysis of proliferating myoblasts in branchial arches of control and CNC-ablated embryos at 26 and 45 hours of incubation. Similar results were obtained in three independent experiments and in each experiment the bars represent counts from three adjacent sections. ^*P<0.05, ^**P<0.01. (E-G'''') A double immunostaining for Myf5 (red) and BrdU (green). (E-E'''') A transverse section at the trunk level. (F-F'''') A transverse section at the level of BA2 in control embryos. (G-G'''') A transverse section at the level of BA2 in CNC-ablated embryos. Merged BrdU/Myf5 images plus higher magnifications (inset) are shown on the right. In situ hybridization for Fgf8 in control (H,H') or CNC-ablated embryos (I,I'). (J) RT-PCR results of CPM explants from control or 100 ng/ml FGF8b-treated explants incubated for 3 days in culture, n=2/2. (K) RT-PCR results of CPM explants from control or CNC-ablated embryos. Whereas CPM explants underwent myogenesis in control cultures, a reduction in myogenesis was observed following CNC ablation (n=4/4). my, myotome; nt, neural tube; ov, otic vesicle; ph, pharynx. Scale bars: in A and E, 0.15 mm for B,C,F,G and 75 µm for A'-A'',B'-B'',C'-C'',E'-E'',F'-F'',G'-G''; in H, 0.5 mm for H'-I'.