Abstract

Biochemical and ultrastructural methods have been employed to determine the relationship of the lysosomal system to reopening and remodeling of the developing chick esophagus. Biochemical data indicate an increase in both acid phosphatase and β-glucuronidase activity during esophageal organogenesis. The appearance of these hydrolase enzyme activities appears to be independently regulated. The increase in acid hydrolase activities parallels the increase in total protein at a time when the esophagus is greatly enlarging. The greatest activity of acid phosphatase was localized in the anterior occluded segment of the esophagus. With reformation of the lumen, the distribution of acid phosphatase becomes uniform along the organ. Increases in hydrolase activities correlate closely with cell degeneration and the differentiation of the epithelium. Acid phosphatase is identified cytochemically in the Golgi complex and lysosomes of embryonic epithelial cells. Surrounding mesenchyme contains only modest cytochemical activity. Diffuse Golgi complexes and primary lysosomes predominate during early stages studied. Secondary lysosomes and condensed Golgi complexes are characteristic of differentiating epithelium at later stages. Acid phosphatase activity appears selectively localized in vital epithelial cells, while degenerating and moribund cells, whose appearances are obligatory to the reopening process, fail to demonstrate enzymatic activity. The temporal association of increased hydrolase activity and cytochemical maturation of a lyosomal system suggests an active involvement of the system in esophageal organogenesis.

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