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Fig. 1. (a) A section of the oral mucous glands of a Xenopus laevis tadpole stained for EGF. Luminal surface above. Note the positive staining in the apices of the secretory cells but the absence of stain in the squamous epithelial cells between the elevated secretory ridges (sc, secretory cells). (b) The oral mucous glands of a X. laevis tadpole stained for EGFR protein. Note the heavy staining in the lateral portion of the glands. (c) Close-up of oral mucous glands shown in (b), stained for EGFR protein. Luminal survace above. Note the presence of immunoreactive EGFR within the cytosol. Compare the distribution of receptor shown here with that of EGF shown in (a) (sc, secretory cells). (d) A transverse section through the body of a X. laevis tadpole stained for EGFR protein. Dorsal musculature and the spinal canal are shown at the top of the field. Immediately below that are the developing kidneys and below that is the foregut. The ventral and lateral body wall has been torn away on the right side. The photograph shows three regions of the alimentary tract in section. Note the heavy staining of the foreguy and its luminal contents. A section of the midgut, to the right, has luminal contents stained, but less staining of the intestinal epithelium than in the foregut. The hindgut, above and to the left, shows no staining of the luminal contents and only slight staining of its epithelium (f, foregut; m, midgut; h, hindgut). |
