Figure 4.

Lung morphology after exposure to 95% FiO₂. Adult (8–10 weeks of age) Stat-3^Δ/Δ mice and nondeleted littermates were exposed to 95% FiO₂ for 65 hours. Minor histologic changes (perivascular edema) in lung histology were observed in control mice after oxygen exposure (a–c). Severe epithelial cell necrosis (arrows), thickened alveoli, lymphotic edema (open arrow), and extensive inflammation were observed in the Stat-3^Δ/Δ mice (d–f). Airspace enlargement was observed in some Stat-3^Δ/Δ mice (g–i). Photomicrographs are representative of n = 7 in each group. Scale bar: 100 μm.