1. Department of Physiology, Baylor College of Medicine, Houston, USA
2. Department of Medicine (Division of Pulmonary Diseases/Critical Care Medicine), the University of Texas Health Science Center at San Antonio, the South Texas Veterans Health Care System, Audie L. Murphy Memorial Veterans Hospital Division, San Antonio, USA
3. Department of Physiology, the University of Texas Health Science Center at San Antonio, the South Texas Veterans Hospial Division, San Antonio, Texas, USA