Date of Award


Degree Name

Master of Science


Biological Sciences

First Advisor

Dr. Leonard J. Beuving

Second Advisor

Dr. Dale Johnson

Third Advisor

Dr. William Jackson

Access Setting

Masters Thesis-Open Access


This study describes morphological changes in the lung at several time intervals following a single injection of 1-Nitronaphthalene (100 mg/kg intraperitoneal) in male Sprague-Dawley rats using transmission and scanning electron microscopy. Dilation of the smooth endoplasmic reticulum and mitochondrial distension in the nonciliated bronchiolar (Clara) cells was apparent as early as 1 hour after injection, while adjacent ciliated cell showed minimal changes. At 6 hours, when respiratory distress was apparent in the animals, Clara and ciliated cells exhibited chromatin clumping, loss of mitochondrial cristae and cytoplasmic vacuolization. Also at 6 hours, the interstitial area around the terminal bronchioles was infiltrated with mast cells and neutrophils. By 24 hours, terminal bronchioles were denuded of epithelial cells and both Clara and ciliated cells in larger bronchioles exhibited mitochondrial distension and cytoplasmic vacuolization. These findings support the theory that initial toxicity occurs in Clara cells through the in situ formation of reactive intermediates and extrabronchiolar injury results from inflammatory responses.