1. Departments of Anesthesiology, Pharmacology/Toxicology, and Physiology, Medical College of Wisconsin and Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin 53295
2. Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh 15261;
3. Department of Medicine, Yale University School of Medicine, New Haven, Connecticut 06520; and
4. Pulmonary and Critical Care Division, Department of Medicine, New England Medical Center and Tufts University School of Medicine, Boston, Massachusetts 02111;
5. Institute for Environmental Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104;