1. M. B. Kelz, G. W. Dent, T. K. McIntosh, and J. H. Eberwine are in the Department of Pharmacology; M. B. Kelz is in the Department of Anesthesiology; and P. G. Marciano and T. K. McIntosh are in the Department of Neurosurgery at the University of Pennsylvania Medical School, Philadelphia, PA 19104, USA. S. Therianos and P. D. Coleman are at the Center on Aging and Developmental Biology at the University of Rochester Medical Center, Rochester, NY 14642, USA.(J.H.E.)