Fig. 5. Presomitic mesoderm explants form VEGF-dependent vascular networks. 8.5 dpc Flt1^+/–, eGFP^+/– mouse presomitic mesoderm explants were embedded in collagen gels and cultured for 72 hours. Explants were stained for ß-gal activity (A,C,E), and the same explants were visualized for eGFP expression (B,D,F). Explants were incubated with basal medium alone (A,B), or with added 30 ng/ml VEGFA (C,D) or 25 ng/ml bFGF (E,F). n7 for all three conditions. The arrows in C indicate the vascular plexus, and the arrowheads in A and E indicate ß-gal positive (blue) presumptive vascular cells. Scale bar: 200 µm for all panels.