Figure 1.

Morphological changes in rat tracheal epithelium after injury induced by 5‐FU observed by HE stain. (N) Normal rat tracheal epithelium is pseudostratified epithelium. (0 h) Only a few cells with less cytoplasm than normal tracheal epithelial cells remained in the basal membrane immediately after 5‐FU treatment. (3 h) The cytoplasm of these cells extended along the basal membrane and cells became flat. (6 h) The number of flat cells increased and the cytoplasm became short. (12 h) Cells appeared cuboidal. (24 h) The number of cells increased sharply. (48 h) Cilia appeared on the luminal side of trachea and the tracheal epithelium became pseudostratified and appeared almost completely recovered (original magnification ×400).