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This study reports the quantitative,and qualitative changesin the small airways after exposure to volcanic ash and quartz,and fol-lowed by an additional nine months of clean air.Three matched groupsof 75 rats were exposed to volcanic ash,quartz,and clean air in a Ro-chester exposure chamber 6 hours daily for 14 days.Animals were sac-rificed and studied,at pariodic intervals.Morphologic and morphometricevaluations were made using light microscope,transmissional electron mi-croscope and scanning electron microscope.The results showed:a.volcanicash produced the same damage in the small ailway as quartz did but lesssevere,b.Clara cells were the most severely damaged cell type occuringmost often at the end of exposure,and c.the damaged epithelial cellsmight be repaired by means of proliferation and differentiation of re-maining Clara cells,and perhaps type Ⅱ cells and Clara cells couldtransform mutually,and d.peribronchiolar fibrosis was greater after3 month exposure which may be persistent.These evidences indicate the exposure to either quartz or volcanic ashhas a persistent fibrogenic effect on the small airways in rats,butbronchiolar epithelium can be repaired as the stimulus is terminated.
This study reports the quantitative, and qualitative changes in the small airways after exposure to volcanic ash and quartz, and fol-lowed by an additional nine months of clean air. Thh matched matched groups of 75 rats were exposed to volcanic ash, quartz, and clean air in a Ro-chester exposure chamber for 6 hours daily for 14 days. Animals were sac-rificed and studied, at pariodic intervals. Morphologic and morphometricevaluations were made using a light microscope, transmissional electron mi-croscope and scanning electron microscope. The results showed: a. volcanicash produced the same damage in the small ailway as quartz did but lesssevere, b. Clara cells were the most severely damaged cell type occuringmost often at the end of exposure, and c. the damaged epithelial cells can be repaired by means of proliferation and differentiation of re-maining Clara cells, and perhaps type II cells and Clara cells could transiently couple, and d.peribronchiolar fibrosis was greater after3 month exposure which may be persiste nt. these evidences indicate the exposure to either quartz or volcanic ashhas a persistent fibrogenic effect on the small airways in rats, butbronchiolar epithelium can be repaired as the stimulus is terminated.