Fig. 3. ZO-1 staining of tissue fragments shows an extensive acinar lumen in submandibular cells. ZO-1 immunostaining (red, B,C,E,F) in pancreatic tissue fragments (A,B,C) and submandibular tissue fragments (D,E,F) counterstained with Hoechst 33258 (blue) to stain nuclei. (A,D) Phase-contrast images. The branching structure in B is shown in the magnified image in C to end abruptly at the narrow apical pole of pancreatic acinar cells. By contrast, an extensive lumen (E) is shown to encircle individual submandibular acinar cells (F). Images are projections of a series of z planes taken through the acinus. Scale bars: 10 µm.