Fig. 8. At stage 11, the inflow tract shows continuity with the primary heart fields. (A) HNK-1 expression in the myocardium and dorsal mesocardium at the cardiac inflow tract. (B) Nkx-2.5 expression overlaps that of HNK-1 but extends slightly farther into the splanchnic mesoderm of the primary heart field. (C) Myocardial differentiation as indicated by MF-20-positive staining (red) in a stage 11 quail embryo double stained for QH-1 to show the endothelium/endocardium (green). (D) Gata-4 expression appears to replicate that of Nkx-2.5. (E) BMP-4 is not expressed in or near the cardiac inflow myocardium. (F) FGF-8 is expressed at very low levels by the ectoderm lateral to the pharynx, but is not seen in or near the cardiac inflow myocardium. All scale bars are 100 µm. Magnification in C is similar to that in B.