Fig. 1. The neural tube directs PNVP formation in vivo. (A) Transverse section through the trunk of a HH stage 24 quail embryo labeled with the QH1 antibody (brown). The arrow indicates a ring of vessels around the neural tube termed the perineural vascular plexus (PNVP). (B) In ovo manipulations placing a mouse neural tube (blue) between the lateral plate and intermediate mesoderm in a quail host. (C) Section of a HH 24 stage quail embryo with an implanted acrylic bead (asterisk) stained with QH1 antibody (purple). Note that a large vessel is positioned near the bead (arrow), but no vascular plexus surrounds the bead. (D) Low magnification of a transverse section through a HH stage 24 quail host with a grafted ROSA^+/– mouse neural tube (asterisk), 3 days post-surgery. Chimeric embryos were whole-mount stained for ß-gal (blue), then sectioned and reacted with QH1 antibody (brown). (E) Higher magnification of D. The arrow indicates a host-derived vascular plexus surrounding the grafted neural tube. n5 for all in ovo manipulations. NC, notochord; NT, neural tube. Scale bar: 100 µm in A; 50 µm in C,E; 200 µm in D.