Figure 4

gpt MFs in the lungs of mice singly and multiply intratracheally instilled with particles. Male mice were treated with single (0.2 mg per animal) or multiple (0.2 mg per animal × 4) doses of particles, and mice were sacrificed 12 (single) and 8 (multiple) weeks after particle administrations. Mean values ± SD are shown. An asterisk (*, **) denotes p < 0.05 (*) and p < 0.01 (**) in a Student's t-test of MF of particle-treated vs. the corresponding vehicle-control mice.