Comparative histochemical study of alimentary tracts with special reference to the mucous neck cells of the stomach

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Abstract
Combinations of recently developed paradoxical concanavalin‐A staining (PCS) and other routine histochemical procedures have made it possible to classify mucosubstances more precisely. By taking advantage of these sequences, the present study was undertaken both to characterize the mucinous contents of alimentary tracts of several animal species, and to compare the variability of epithelial mucosubstances with special reference to the mucous neck cells of the stomach. The alimentary tracts obtained from 7 species of fish, 5 amphibians, 3 reptiles, 4 birds, and 6 mammals were used. Acidity of epithelial mucosubstances was highly variable even among the corresponding mucous cells. On the contrary, concanavalin‐A reactivity seemed to be consistent with each cell and species. The mucous neck cells, which were observed in amphibians, reptiles, and mammals, consistently exhibited a characteristic mucosubstance with stable class‐III reactivity by PCS. Inversely, stable class‐III reactivity was found only in species possessing mucous neck cells, and was widely distributed in the esophageal glands of the frog, snake, and man; in esophageal mucous cells of the frog and skink; in pyloric glands of amphibia, reptiles, and mammals; and in Brunner's glands of mammals. These mucous cells seem to form an unique group with morphological and histochemical similarities. It is likely that the stable class‐III reactivity by PCS is a hallmark of the mucous neck cells and related glands and that, in addition, concanavalin‐A reactivity of mucosubstances is evolutionarily more fundamental characteristic.