Fig. 5. Cranial paraxial mesoderm cells contribute to the myocardium and endocardium of the cardiac outflow tract in vivo. (A-P) Tracking of CPM cells by Dil labelling. DiI injections into the left (A) or right (E,I,M) CPM of stage 10 (or stage 8, I) chick embryos. Lateral (B,F,J) or transverse (C,G,K) views of embryos at stage 17-18 are shown as an overlay of bright field and fluorescence images. (D,H,L) Higher magnification of dissected hearts. Cells labeled on the left side of the CPM contribute to the inner curvature of the cardiac OFT (D), whereas cells from the right side contribute to the outer curvature (H,L). (O,P) The CPM cells contribute to both the myocardium and endocardium: cross section (O) and transverse section (P) of the OFT. (M,N) Embryo dissected shortly after the DiI injection (M) to verify the location of the dye in the paraxial mesoderm (N). ba1, first branchial arch; ba2, second branchial arch; cc, conus cordis; da, dorsal aorta; end, endocardium; ic, inner curvature; myo, myocardium; nc, notochord; nt, neural tube; oc, outer curvature; oft, outflow tract; ov, otic vesicle; ph, pharynx; rv, right ventricle; ta, truncus arteriosus.