Clearance study and specificity controls. Mice were induced for arthritis, and they developed footpad swelling at the level of a 45% to 50% increase in thickness. They were put on an AIN-76A diet for 4 to 6 days and then given 30 μl of 1 mM freshly prepared PSVue 794 (n = 24) or control dye (n = 3) retro-orbitally, as described in the text. The images shown were obtained using the LI-COR Odyssey Infrared Imaging System at the times indicated. The arrows point to the presence or absence of signals in mouse feet using the near-infrared dye and the control dye. The fur at the abdomen of the mice injected with the control dye had not been removed and was contaminated with unbound dye excreted in urine.