Figure 2

DNR-induced apoptosis in the spleen is p53 dependent.  Wt and p53-null mice were treated with vehicle (ctrl) or 10 mg/kg DNR for 3 days. 4 and 24 h after the last DNR injection, the spleens were removed, fixed and processed for paraffin sectioning for histological examination as described in the Experimental section. (A) Presence of pyknotic nuclei in the lymph nodules/white pulp in the spleen (bar diagram), or cell death visualised by TUNEL staining (right panels). The data represent the average number of pyknotic nuclei/lymph nodule. The data in the diagrams in (A,C,D)  are mean ± SEM, n = 3-7 mice. (B)  Haematoxylin- and eosin (H&E) stained paraffin sections of the spleen from Trp53-wt and -null mice four days after the last DNR injection. RP = red pulp, WT = white pulp, arrowheads indicate pyknotic nuclei. (C)  Presence of lipofuscin-like pigments in the red pulp of the spleen. The diagram shows the average number of cells with lipofuscin-like pigments per 400 μm²  of red pulp. H&E-stained sections from red pulp are shown in the panel to the right. The arrowheads indicate cells with lipofuscin-like pigments. (D)  Content of mature or maturing granulocytes, identified by nuclear morphology in the spleen. The diagram represents the average number of polymorphonuclear cells per 400 μm²  of red pulp. The right panels show typical appearance of granulocytes (arrowheads) in the red pulp of wt and p53-null mice. Asterisks indicate p < 0.05 (*), p < 0.01(**) or p <0.005 (***), one-way ANOVA.