FIG. 4.

Histology and ultrastructure of small intestinal crypts in wild-type and CF mice. (A and B) Conventional hematoxylin and eosin staining. In the wild-type mouse tissue shown in panel A, the crypt lumen is small and clear. At the base of the crypts Paneth cells with characteristic eosinophilic secretory granules are observed (arrow), and there are traces of eosinophilic material in the lumen (arrowhead). Goblet cells are compact in appearance. In the CF mouse tissue shown in panel B, the crypt lumen is greatly dilated and filled with eosinophilic material (arrowheads) that appears to emanate from distended Paneth cells (arrow) at the base of the crypt. Goblet cells also appear distended. (C and D) Immunohistochemistry for the Paneth cell protein lysozyme. In the wild-type mouse tissue shown in panel C, ly-sozyme is primarily localized to the Paneth cells at the base of the crypt (arrows). In the CF mouse tissue shown in panel D, lysozyme immunoreactivity is greater and both the Paneth cells (arrows) and the crypt lumen (arrowheads) are strongly labeled. (E to H) Transmission electron microscopy. In the wild-type mouse tissue shown in panels E and G, Paneth cell granules (*) are observed inside Paneth cells, and there is little material in the small lumen (indicated by an arrow in panel E and by L in panel G). (F and H) In the CF mouse tissue Paneth cell granules are observed inside cells (*), and there are almost intact granules in the lumen (+) of the crypt. L, lumen; G, goblet.