Enhanced dark field microscopy examination of mice exposed to DM, NS (30 µg), NB1 (30 µg), or NB2 (30 µg) at 112 days postexposure. NSs and NBs are generally white against the dull colored background of tissue in these images. Arrows in the figure indicate AMs that contain NS, NB1, or NB2 in the respective figures. Filled triangles indicate NBs that are either contained in or penetrating into the alveolar interstitial space. NSs were infrequently observed in the lungs as the total lung burden remaining at 112 days postexposure was less than 4% of initial lung burden. No NPs were observed in lungs from DM-exposed mice.