[1] Univ Southampton, Brooke Labs, Southampton SO9 5NH, Hants, England
[2] Univ Palermo, Human Anat Div, Dept Expt Med, I-90133 Palermo, Italy
[3] Univ London Imperial Coll Sci Technol & Med, Natl Heart & Lung Inst, Dept Resp Med, London SW7 2AZ, England