Fig. 7. Dorsal lip endoderm generates taste buds only when fused with dorsal lip mesoderm. (A) Dorsal lip endodermal explants remained as rounded balls throughout the culture period. (B) Mesodermal explants underwent extensive morphogenesis, and developed obvious notochords (arrows), and rough regions of muscle (arrowheads). (C) Fused explants again underwent morphogenesis, but the notochord and muscle elements were typically not as apparent, which is probably due to the presence of the endodermal epithelium. (D) No taste buds are evident in this typical section of an En30 explant immunostained for calretinin. (E) In this cryosection of an animal mesoderm dorsal lip explant, while CR-IR taste buds are absent, notochord (not) and parvalbumin-IR muscle (red) are clearly present. In addition, adjacent tissue has been neuralized, as evidenced by the presence of a neural tube (nt) with CR-IR neurons and axons (green), as well as of the otic vesicle (ov) with parvalbumin- and CR-IR hair cells (arrow; yellow). (F) This micrograph shows a higher magnification view of the parvalbumin- and CR-IR hair cells shown in E. (G) A section through a fused mesoderm-endoderm explant reveals 3 CR-IR taste buds (green; arrows), as well as notochord (not) and parvalbumin-IR muscle (red). (H) This micrograph is a high magnification view of the three taste buds shown in G. Although the plane of section is not optimal, these organs clearly comprise multiple CR-IR cells. Scale bars: 200 µm in C,D,E; are 25 µm in F,H.
