Fig. 5. The effect of Rac1Leu61 on the intracellular epithelial distribution of ß-actin and p-Jnk in adult mice. (A) Section containing neighboring 129/Sv and B6-ROSA26 jejunal villi from a 9-month-old Rac1Leu61 chimeric mouse, stained with FITC-labeled mouse anti-ß-actin and bis-benzimide. The apical cytoplasmic staining in the 129/Sv-Rac1Leu61villus epithelium (arrow) is diminished relative to the adjacent B6-ROSA26 epithelium (arrowhead). (B) Polyclonal villus from a normal chimera stained with the same reagents as in A. Actin staining is equivalent in 129/Sv and B6-ROSA26 epithelium. (C) Polyclonal villus from an adult chimeric-transgenic mouse stained with mouse anti-p-Jnk, Cy3-labeled sheep anti-mouse Ig and bis-benzimide. The p-Jnk staining is increased in the apical cytoplasm of 129/Sv-Rac1Leu61 villus epithelial cells (arrow) compared to B6-ROSA26 cells (arrowhead). (D) Section from a normal chimeric jejunal villus stained with the same reagents as in C. Increased exposure of D (compare the intensity of staining of lamina propria lymphocytes in C) shows faint but equivalent p-Jnk staining in the cytoplasm of 129/Sv and B6-ROSA26 epithelial cells. (E,F) Pak1 (E) and Rac1 (F) distribution in adult villus epithelium. In E, villi have been sectioned perpendicular to the crypt-villus axis. Pak1 (red) is prominent in the apical cytoplasm of epithelial cells (arrow), irrespective of genotype (B6-ROSA26 cells are shown in this example). Rac1 (red in panel F) is evident throughout the cytoplasm. Scale bars: 25 µm.