Fig. 5. Progeny of the serosal mesothelium contribute to blood vessels of the mesentery and gut. (A-D) Whole-mount lacZ staining characterizes Wt1-expressing cells and their descendents during postnatal stages in the gut (A-C) and heart (D). (A,B) After birth, major vessels in the mesentery and on the gut surface (black arrowheads) contain lacZ-positive cells. Veins are very lightly stained in whole mounts (B, white arrowheads). Note the blue staining outside of the vessel (B, white arrows). (C) At high magnification, lacZ-stained samples show the characteristic `corkscrew' deposition of smooth muscle cells around a sample artery (arrowheads). (D) In the newborn (NB0) heart, coronary vessels contain lacZ-positive cells (arrowheads). in, intestine; m, mesentery. Scale bars: 1 mm in A; 500 µm in B,D; 200 µm in C.