Resolution of inflammation is modulated by inhibition of the caspase family of apoptotic proteases. Tailfins of transgenic zebrafish were transected at 4 days after fertilization. At 4 hours after injury, either control medium (E3 only) or 100 μM zVD.fmk was added to the culture medium. At 6 and 24 hours after injury, each fish was taken individually and anesthetized with tricaine, and the number of fluorescent cells visible in the tail was assessed by fluorescence microscopy as described for Figure 1. Larvae treated with DMSO vehicle at equivalent concentrations were indistinguishable from controls (data not shown). (A) The region to the right of the black line corresponds to the region included in the analysis shown here. The number of cells to the right of this line was reduced from 6 to 24 hours in control fish but remained the same in zVD.fmk-treated fish. For each image, a series of fluorescence images in Z was projected to a single image using the maximum intensity at each point. These images were normalized and superimposed in the best in-focus image from a bright-field stack or an extended depth-of-field image generated from the best in-focus information from each image in the Z series. (B) Fluorescent cells at the site of injury were counted for the conditions shown. The reduction in neutrophil numbers was not seen for zVD.fmk-treated larvae (n = 16-19; P < .05 [control 24 hours after injury vs all other groups]). (C) The reduction in neutrophil numbers seen in each individual fish in the control group was not seen in the zVD.fmk-treated group (P values shown).