Fig. 2.

YO-PRO-1 positivity in adult mouse liver tissue is influenced by the amount of physical damage inflicted during dissection. a A section of liver from an adult mouse was stained with YO-PRO-1 and Hoechst 33342. Exhibiting a general similarity to what was seen with human samples, a majority of the liver cells are YO-PRO-1-positive. b A higher magnification image reveals that nonhepatic cells with elongated nuclei seem to avoid YO-PRO-1 penetration (arrows). c TUNEL staining of mouse liver tissue shows that cells near sites of physical damage are particularly susceptible to apoptosis. We know that this is not an edge effect since TUNEL positivity is not observed near intact edge of the tissue (asterisks). d, e An entire lobe of liver was dissected gently and stained and imaged while intact. The proportion of YO-PRO-1-positive cells was significantly less and these cells formed small clusters (arrows). f TUNEL staining of intact liver lobe shows minimal apoptosis. Scale bars: a = 100 μm, b = 40 μm, c = 500 μm, 50 μm, d = 100 μm, e = 50 μm, f = 1 mm, 100 μm