Fig. 7. Local oxidase activation and Ca²⁺ signal reported by fura2-dextran conjugate. The data shows a typical experiment in which neutrophils were micro-injected with fura2-dextran conjugate. In the example shown, a single neutrophil has been micro-injected and hence only that cell appears in the Ca²⁺ image (other neutrophils in the field having no fluorescent signal). The micro-injected cell was challenged with an opsonised particle (at 220 seconds) as before and the phagocytic cup (270 seconds), phagosome closure (340 seconds) and completion of the Ca²⁺ signal (380 seconds) is shown in the upper set of phase contrast images. The lower set of images show the corresponding fura2-dextran signal and the graph on the right shows the complete Ca²⁺ data, with the point of phagosome closure marked by the downward arrow.