Figure 1.

Oxidant production is focal. (A–C) An adherent human neutrophil was stimulated with PMA for 3 min, forming a broad lamellipodium (arrowheads). H₂O₂ was detected as a cerium perhydroxide reaction product (B) and was pseudocolored and overlaid on the phase-contrast image (C). Oxidants are heavily concentrated in the ruffling lamellipodium. (D and E) Endothelial cells were loaded with the oxidant-sensitive fluorescent dye dichlorofluorescein and imaged live. Cells expressed either an oxidase-inactive mutant p47^phox(W193R) (D) or a constitutively activating mutant p47^phox(S303,304,328D) (E). Activation of the oxidase is associated with focal oxidant production at cell edges (E, arrows). (F–H) Root hairs from the plant A. thaliana stained with nitroblue tetrazolium show oxidant production as the blue formazan reaction product. Oxidants are formed at the initiating bulge (F, arrows) and at the actively growing root tip (G and H, arrows). (I) An endothelial cell expressing a DsRed fusion of p47^phox was imaged with total internal reflection fluorescence microscopy, showing discrete targeting of the oxidase protein to ventral leading edge structures, which were likely integrin complexes (arrows). A–C are reproduced with permission from Heyworth et al., 1997 in Histochem. Cell Biol., Vol. 108. F–H are reproduced with permission from Macmillan Publishers Ltd. from Carol et al., 2005 in Nature, Vol. 438. Bars: (A–C and F–H) 10 μm; (D, E, and I) 20 μm.