Electron microscopic observations of the bronchial epithelium of dogs: II. Smoking Dogs

Changes are noted in the bronchial epithelium of dogs subjected to 44 and more than 420 days of experimental cigarette smoke inhalation. At the early time point goblet cells are more numerous and the surface lining cells possess fewer cilia. By 420 days the apparent number of cell layers in the epithelium is double that of the controls. The luminal surface is devoid of ciliated columnar cells and goblet cells, these being replaced by columnar and cuboidal cells whose free surface is covered by stubby projections. Basal cells are frequently columnar-shaped and mitotic figures are common. Most cells contain a profusion of cytoplasmic filaments which often appear to displace cell organelles. A “special type cell” with cell-specific granules, first described in the control, is found in great abundance in the intermediate region between the basal cells and the surface lining cells. In both osmium- and acrolein-fixed tissue the two special migratory cell types, which are so common in the controls, are rarely seen. The basement membrane is frequently interrupted by gaps through which cytoplasmic processes of basal cells protrude; a thickened zone underlying the basement membrane contains an increase in fibrillar components and multiple layers of basement membrane material.