b isoforms induce vascularization in vivo. A: Angiogenesis analysis in Matrigel plugs with Alexa-647-labelled isolectin. No signal is found in controls, whereas Matrigel plugs carrying any of the VEGFxxxb isoforms show a strong signal, thus demonstrating angiogenesis in vivo. B: Analysis of Matrigels using FITC-labelled dextran. Control Matrigels do not show fluorescent signal; a large amount of FITC-labelled dextran is observed in VEGF121b- and bFGF-containing plugs, whereas VEGF165b- and VEGF165-containing plugs display a weaker signal.