Intraalveolar surfactant ultrastructure. Transmission electron micrographs demonstrating intraalveolar surfactant ultrastructure in Healthy-Gas (A), Healthy-PF5080 (B), Lavaged-Gas (C), and Lavaged-PF5080 (D) groups. The presence of tubular myelin with its characteristic lattice-like structure in the healthy animals is exemplarly shown in (A). Multi- and unilamellar surfactant forms are shown in (B). Tubular myelin was only extremely rarely seen in the lavaged animals where multi- and unilamellar forms (C) and numerous lamellar body-like forms (D) were present.