Fig. 2. ir expression in the principal cells of the tubule main segment and the ureter. (A) Low-power views, showing little expression in the spermatheca (SP) and rectum (R). (B) Low-power view of the tubule, showing strongest staining in the ureter (U), with further staining along the length of the main segment (MS) and lower segment (LS) but not in the initial segment (IS). (C) High-power view, showing staining in the ureter. (D) High-power view, showing staining in the main segment but no expression in the IS. (E) High-power view of tubule main segment, showing that expression is confined to principal cells but is not in the very narrow stellate cells (SC). Sense controls did not produce any staining (data not shown). Tubule diameter can be taken as 35 µm throughout.