Fig. 2. Morphology of Sftpc-NmycEGFP transgenic and normal lungs at E18.5. (A) External appearance of wild-type and transgenic lungs. (B) The NmycEGFP fusion protein is expressed throughout the distal transgenic epithelium (lower panel). Fluorescence in wild type is background (upper panel). (C) RT-PCR analysis confirming Nmyc overexpression in E18.5 transgenic lungs. (D-I) Low and high power images of sections stained with Haematoxylin and Eosin from normal (D,G) and transgenic lungs (E,F,H,I) with least severe (E,H) and most severe (F,I) phenotypes. Note the cuboidal undifferentiated epithelium, extensive mesenchyme, and lack of apposition of blood vessels to the epithelium in the transgenic lungs. (J-L) Electron micrographs of wild-type (J) and transgenic (K,L) lungs. In J, note the blood vessels (asterisk) close to the lumen of the alveolar sac, and the thin walled type I alveolar cells and two type II cells that have lost their glycogen (arrows). In K, the epithelial cells resemble immature type II cells, as they contain both glycogen and lamellar bodies (inset, arrowheads). Lamellar bodies are also in the lumen (asterisk). (L) Densely packed undifferentiated epithelial cells with glycogen but no lamellar bodies. Scale bars: 50 µm.