The responses of guinea pigs and rats to inhaled sulfuric acid aerosols were compared to define species differences and to determine the small-animal model most relevant to human exposures. Rats were exposed for 6 h to 1, 10, and 100 mg H2SO4/m3. Guinea pigs were exposed for 6 h to 1, 10, and 27 mg H2SO4/m3. Tracheal mucous clearance of guinea pigs was slowed 1 d after exposures to 1 mg H2SO4/m3. A tendency toward faster clearance was observed at high concentrations of H2SO4 for both guinea pigs and rats (statistically significant only for the rats). The speeding of mucous clearance was correlated with increases in airway sialic acid and also with the appearance of excess tracheal secretions, detected using scanning electron microscopy in both rats and guinea pigs. The responses of guinea pigs to sulfuric acid exposures were more similar to those reported for humans than were those of rats.

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Phagocytosis and exocytosis are two cellular processes involving membrane dynamics. While it is easy to understand the purpose of these processes, it can be extremely difficult for students to comprehend the actual mechanisms. As membrane dynamics play a significant role in many cellular processes ranging from cell signaling to cell division to organelle renewal and maintenance, we felt that we needed to do a better job of teaching these types of processes. Thus, we developed a classroom-based protocol to simultaneously study phagocytosis and exocytosis in Tetrahymena pyriformis. In this paper, we present our results demonstrating that our undergraduate classroom experiment delivers results comparable with those acquired in a professional research laboratory. In addition, students performing the experiment do learn the mechanisms of phagocytosis and exocytosis. Finally, we demonstrate a mathematical exercise to help the students apply their data to the cell. Ultimately, this assay sets the stage for future inquiry-based experiments, in which the students develop their own experimental questions and delve deeper into the mechanisms of phagocytosis and exocytosis.