Fig 3.

Tubules have a lumen lined by a differentiated epithelium. (A) Cross-section and (B) longitudinal section of a tubule. Tubules were stained with DAPI (white). (C) The surface of a tubule is imaged by epifluorescence microscopy (the upper right areas are out of focus). ZO-1 (white) is detected by immunofluorescence. The tubular epithelium shows extensive formation of tight junctions, as indicated by the chicken wire-like ZO-1 patterns. (D) γGTP activity is detected histochemically. Higher levels of γGTP activity result in the darker staining of cells. The image shows high levels of γGTP activity in a tubule, whereas the monolayer cells below display lower levels of activity of this brush border enzyme. Scale bars: (A–C) 100 μm and (D) 200 μm.