[1] Univ Calif Davis, Dept Internal Med, Ctr Comparat Resp Biol & Med, Livermore, CA 95616 USA
[2] Univ London Kings Coll, Neurodegenerat Dis Res Ctr, London SW3 6LX, England
[3] Univ Alabama, Dept Anesthesiol, Birmingham, AL 35233 USA
[4] Univ London Kings Coll, Neurodegenerat Dis Res Ctr, London SW3 6LX, England