Ex vivo oxidative stress detection. Rat right cranial lobes were dissected to expose the main axial airway and airways were treated with either PFP or PBS. Lungs were incubated with CellROX, a fluorescent dye that indicates oxidative stress, and washed with Live Cell Imaging solution after 1 hour of exposure and imaged continuously. Representative pictures from lungs taken directly (A, D), 2 hours (B, and E) and 4 hours (C and F) after a 1 hour treatment of either PBS (A-C) or PFP (D-F). Substantially more CellROX fluorescence could be observed in the airway lumen of the PFP-treated lung compared to PBS controls in a time dependent and proximal (PROX) to distal (DIST) manner. Focal patches of cells with oxidative stress were observed (arrows) increased over time in the PFP-treated lungs.