A histochemical study of epithelial mucin in the chick chorioallantois

Histochemical methods demonstrate the accumulation of two types of mucous inclusion in the allantoic epithelial cells of the chick embryo. One type of inclusion contains a sialomucin that is PAS‐reactive, unstained by Alcian blue and other anionophilic dyes and is susceptible to digestion by Vibrio cholerae neuraminidase. The second inclusion contains an apparent sulfomucin which is Alcianophilic at pH 1.0, unstained by anionophilic dyes after a methylation‐demethylation sequence and resistant to testicular hyaluronidase. This sulfomucin exhibits PAS reactivity after desulfation procedures. Both types of mucus occur in individual cells and are normal components of the chorioallantois. Accumulation of the inclusions is enhanced by lowering the pH of the allantoic fluid or as a result of organ transplantation.