title: Scanning electron microscopy of terminal airways of guinea pigs chronically inhaling diesel exhaust.
abstract: The structural physiology of airways from 80 guinea pigs was examined for changes induced by diesel exhaust (DE) exposure. Acute, subacute and chronic studies contrasted inhalation effects of 250, 750, 1500 and 6000 micrograms DE/m3 with "clean air" breathing of age-matched controls. Nonciliated epithelial (Clara) cells, epithelial type 2 cells and alveolar macrophages were increased in a DE dose dependent fashion. Also, eosinophils, were recruited. Epithelial type 1 cells of the distal airways internalized DEP. The relative dustiness (particulate density) of airways was assessed from coded specimens. Some 86% of DE exposed animals were correctly identified. Scanning Electron Microscopy (SEM) resolved surface located DE particulates (DEP). Single particles, loose clusters, low density agglomerates occurred. While SEM visual clues are insufficient for absolute identification of DE particles, there was supporting evidence from transmission electron microscopy (TEM) and from SEM studies comparing vascular with intratracheally fixed specimens. Presumptive DEP were notable on bifurcation bridges in respiratory bronchioles and alveolar ducts while alveolar outpockets had heavy dust burdens. Clumps of macrophages in such alveoli almost occluded the airspace. We conclude that normal guinea pigs appear to adapt to a chronic DE stress environment. But, the ultrastructural basis (cellular protrusions, DEP agglomerates and secretional debris) exists in peripheral airways for airflow instability and increased airflow resistance.
mesh_terms: D000818:Animals; D001980:Bronchi / Q000187:drug effects / Q000648:ultrastructure; D006168:Guinea Pigs; D008168:Lung / Q000187:drug effects / Q000473:pathology*; D008264:Macrophages / Q000187:drug effects / Q000648:ultrastructure; D008297:Male; D008855:Microscopy, Electron, Scanning / Q000379:methods; D011650:Pulmonary Alveoli / Q000648:ultrastructure; D001335:Vehicle Emissions / Q000633:toxicity*
chemical_list: D001335:Vehicle Emissions