Can proventricular mesenchyme promote differentiation of endocrine cells in gizzard endoderm?

Previous findings prompted the suggestion that avian proventricular mesenchyme might induce differentiation of endocrine cells with gastrin-releasing peptide (GRP)-like immunoreactivity in endoderm from an organ which, at hatching, is deficient in such cells. Therefore gizzard endoderm and proventricular mesenchyme from chick embryos of 5 days' incubation were combined and grown as chorio-allantoic grafts. Controls comprised re-associated endoderm and mesenchyme of the gizzard and of the proventriculus. In the experimental grafts, as in proventricular controls, immunocytochemistry revealed not only GRP cells, but also the other endocrine cell types characteristic of proventriculus. All these cell types were either absent or very rare in gizzard controls.