Fig. 1. Electron microscopy. ( A and B ) Lung tissue of healthy animals after 240 min of mechanical ventilation. B is a magnification of a section of A ( rectangle ). Mostly the membrane of type I pneumocyte stayed intact ( black arrowhead , B ); sporadically, signs of membrane disruption and partial detachment of endothelium occurred ( black arrow , B ). Animals that were allowed to recover for 2 days (group R) and unventilated healthy control animals (group C) showed no signs of membrane disruption and no detachment of endothelium ( C ). Animals ventilated with tidal volume of 16 ml/kg showed extensive damage with lungs appearing overinflated with loss of septal walls ( black arrowheads , D ) and injury of type I pneumocyte and endothelium ( inset , D ). Magnification: A and C : 5,000×; B : 15,000×; D : 3,000× ( inset 7,000×). E = erythrocyte; L = leukocyte; PI = type I pneumocyte; PII = type II pneumocyte.