Cathepsin B activities induced by pharyngeal aspiration exposure to 0, 20, 40, or 80 μg/mouse of either poorly-dispersed (PD) or well-dispersed (WD) NiO- and CeO-NP dispersed in differing dispersion medias (Panel A: pluronics, Panel B: PBS, Panel C: Survanta®, and Panel D: DM) at 1 day post-exposure. Values are given as means ± SE (n=8). *Significant difference of treatment group from control at 1 day post-exposure (p < 0.05). +Significant difference between the poorly-dispersed (5 min sonication) and well-dispersed (20 min sonication) NiO- and CeO2-NP solutions at same post-exposure timepoint (p < 0.05). Cathepsin B activities determined as described in Methods.