The increase in volume during elongation is accompanied by a vacuolation of the cell.
By this stage the host cell shows characteristic vacuolation and other cytopathic effects.
The histologic lesions were characterized by the remarkable atrophy of intestinal villi, basal vacuolation of enterocytes, increment of the crypt and the villus - to - crypt ratio had significantly decrease. compared with that of noninoculated control chicks. besides. intestinal villi become thin and flat. or cubic, also accompanied with necrosis. many villous enterocytes were detached from the lamina propria and the lamina propria contained a diffuse infiltrate of lymphocytes, plasma cells, macrophages. the characteristic ultrastructural changes observed by electronmicroscope were swelled mitochondria and dilated endo - plasticreticulum. ribosome on the surface of endo - plasticreticulum fall off and the number of ribosome within the cell decrease
These cells displayed metabolic disturbance, such as rough cytoplasmic granules, many vacuolation. nearly all cells in the common medium showed cytoretraction and pyknotic nuclei, and were detached from the plate after 5 - 7 days of culture. while most hepatocytes in special medium showed well condition