1. Departments of Pharmacology (T.L., S.R.H., S.K., D.R.S., S.A.K., D.J.M.),University of Texas Southwestern Medical Center, Dallas, Texas 75390
2. Pediatrics (M.U.),University of Texas Southwestern Medical Center, Dallas, Texas 75390
3. Molecular Biology (S.A.K.)University of Texas Southwestern Medical Center, Dallas, Texas 75390
4. Howard Hughes Medical Institute (D.J.M.), University of Texas Southwestern Medical Center, Dallas, Texas 75390