Figure 1.

(A, B) Comparison of the gross morphology of the gastrointestinal tracts from wild-type and W/W^V mutant animals, respectively. Note the distended appearance of the stomach and intestines of W/W^V mutants (B). Kit-like immunoreactivity revealed the presence of interstitial cells of Cajal (ICC) at the level of the myenteric plexus (IC-MY) (C; arrows) and ICC at the level of the deep muscular plexus (IC-DMP) (arrowheads) in wild-type animals. In W/W^V mutants, only IC-DMP were observed (D; arrowheads). The absence of IC-MY in W/W^V mutants was also confirmed by electron microscopy (E, F). IC-MY (arrow) and IC-DMP (arrowheads) were readily observed within the circular muscle layer (cm) of jejunums from wild-type animals (E) but only IC-DMP were observed within the cm of W/W^V muscles. IC-MY were never observed at the level of the myenteric plexus (*) of W/W^V mutant animals. Scale bars are as indicated on each panel.