Cytoplasmic protein extracts for the analysis of caspase activity were prepared as described [24] . Briefly, tissue fragments were dounced on ice in a buffer containing 25 mM KPO 4 pH 7.8, 8 mM MgCl 2 , 1 mM EDTA, 1% Triton X-100 and 15% glycerol. The extracts were incubated on ice for 5 min. and then centrifuged at 4uC for 1 min. at 10000 g. The supernatants were then aliquoted and stored at 280uC.