[1] UCL, Dept Biol, London WC1E 6BT, England
[2] Univ Zurich Irchel, Inst Zool, CH-8057 Zurich, Switzerland
[3] UCL, Rayne Inst, Ctr Diabet & Endocrinol, London WC1E 6J, England
[4] London Res Inst, Canc Res UK, Growth Regulat Lab, London WC2A 3PX, England