Intestinalization of the area-vitellina endoderm cultured in association with digestive-tract mesenchymes.

Small-intestine-type differentiation of the area-vitellina endoderm of quail embryos, cultured in association with digestive-tract mesenchymes of chick embryos, was analysed chronologically with special attention to the appearance of a striated border and its enzymes (alkaline phosphatase and a-glucosidase). Undifferentiated endoderm of the area vitellina differentiated first into yolk-sac parenchyma expressing cysteine lyase, then gradually lost the cysteine lyase activity, and eventually manifested small intestine-type differentiation with the expression of the striated border and its enzymes.