Fig. 3. Effects of FGF2 on interdigital cell death. (A,B) Interdigital cell death (vital stained with Neutral Red) in left control (A) and right treated (B) chick autopods 14 hours after implantation of a FGF-bead into the third interdigit (arrow). Note that at this time period of treatment cell death is fully inhibited by FGFs. (C) Left control and (D) right treated chick autopodes 48 hours after implantation of an FGF-bead (arrow) into the third interdigit. Note the intense increase of cell death at this time period after the application of FGF2. (E) Control and (F) experimental duck interdigital webs showing the increase in apoptosis 50 hours after implantation of a FGF-bead (*; F). (G) TUNEL labeling of interdigital cell death 30 hours after the implantation of an FGF-bead (*). (H) BrdU incorporation into the interdigital mesoderm 30 hours after the implantation of a FGF-bead. Note that cell proliferation is inhibited in the zone of induced apoptosis (compare with G). (I,J) Illustrate the inhibition of FGF-mediated cell death by co-administration of a Noggin-bead. (I) Cell death 30 hours after the implantation of an FGF-bead (arrow) and (J) its inhibition when a Noggin-bead (arrow) is co-implanted with a FGF-bead (arrowhead).