Figure 2.

Immunohistochemical staining of the expression of Ki67 in lung tissues. A, B, C, D) From preterm infants with respiratory distress syndrome who were ventilated at elevated oxygen concentrations for 1–3 days, 4–8 days, 9–16 days and >16 days, respectively. E) From premature infants who died without lung disorders; the positive staining of Ki67 was preferentially localized in alveolar and bronchiolar epithelial cells and fibroblasts; Ki67 positive cells are more numerous in preterm infants with respiratory distress syndrome after 4 days duration of mechanical ventilation at elevated oxygen concentrations than in premature infants who died without lung disorders.