Fig. 4. Both Keller sandwiches and endomesodermal isolates thereof give rise to CR-IR taste buds. (A) Live Keller sandwiches 24 hours after construction have undergone normal convergence and extension of the mesoderm (arrows) and neurectoderm (asterisks). (B) This transverse section through an intact Keller sandwich explant at stage 41 or hatching was immunostained for calretinin (green) to show the presence of taste buds, and parvalbumin (red), which reveals the location of muscle. Notochord (noto) is also easily recognize via its distinct morphology. (C) Numerous multicellular CR-IR taste buds (arrow) are evident in most Keller sandwiches. (D) Immunostained sections of hatchling stage Keller sandwich endomesoderm isolated at stage 13 also revealed CR-IR (green) taste buds with apical processes (arrow), and parvalbumin-IR muscle (red). (E) At higher magnification, each taste bud is clearly multicellular, comprising fusiform, CR-IR cells. Scale bars: 100 µm in B; 50 µm in C,D,E.
