Ultrastructural alterations observed in mouse lung after prolonged He/O2 exposure

Three generations of mice were exposed to an atmosphere of 80% helium and 20% oxygen. The parent generation, born and raised in air until the experiment began, was sacrificed in two groups--one after 160 d and the other after 350 d of exposure. The F1 generation, conceived in air, born and raised in an He/O2 environment, was sacrificed after 160 d. The F2 generation, conceived, born, and raised in the He/O2 atmosphere, was sacrificed also in two groups--one after 85 d and the other after 280 d. Lung tissue from these animals was prepared by conventional methods for ultrastructural study. The most obvious alteration observed was the extensive blebbing, possibly indicative of cellular edema, seen in both the capillary endothlium and the alveolar epithelium. In addition, a highly convoluted basement membrane was observed in many areas. There was debris in some of the alveoli and an increase in platelets in the capillaries.