Fig. 7. Direct detection of caspase activity in situ using the viable reagent CaspACE^TM FITC-VAD-FMK. (A-C) Double-detection of activated caspase and apoptosis in the tail of Ciona at metamorphosis stage (28 hpf). TUNEL labeling was performed after in vivo incorporation of caspACE/FITC-VAD-FMK. Digitized images were merged to superimpose the caspACE-labeled cells (green pseudo-color field) over the respective TUNEL-labeled field (TUNEL-positive nuclei appear in red pseudo-color). Note the presence of caspACE-positive/TUNEL-positive cells (yellow nuclei/green cytoplasm) that co-exist with caspACE-positive/TUNEL-negative cells (green nuclei/green cytoplasm) and CaspACE-negative/TUNEL-positive cells (red nuclei). (D) In vivo incorporation of caspACE in striated muscle cells of Ciona tail at 28 hpf. (E) Pan-caspase inhibitor treatment blocks the metamorphosis of Ciona intestinalis. Data represent the mean of four independent experiments expressed as a percentage. Vertical bars correspond to the interval of confidence for percentage at 5%. The results were assessed by variance analysis and were found to be significant (P<0.05). Scale bars: 80 µm.