granular, and eosinophilic cytoplasm. These macrophages
occasionally formed multinucleated syncytia. Villi were considered
atrophied/blunted when they appeared shortened and/or
thickened relative to those of the control animals. Enterocyte
vacuolation presented as single or multiple, sharply defined,
clear, or slightly flocculent spaces within the cytoplasm of terminal
villus enterocytes. Single-cell necrosis in the villous tips
appeared either as cells with condensed cytoplasm and
smudged nuclei with a peripheral halo (apoptotic appearance)
or more often as cells with karyorrhectic nuclei that were
located either within the villus epithelium or within the lamina
propria. It could not always be readily determined whether such
cells were originally enterocytes or inflammatory cells. Crypt
epithelial hyperplasia was characterized by elongated crypts
that were lined by increased numbers of crowded tall enterocytes
with hyperchromatic basophilic cytoplasm and nuclear
chromatin clumping. In more extensively affected cases (mice
especially), the hyperplastic enterocytes of villi additionally
displayed increased cell height and tinctorial changes compared
to those of controls.