Figure 4: Different integral proteins have specific distributions in the β-cell membrane. (a): electron microscopy after en bloc staining of a pancreatic islet with rhutenium red, shows that the extracellular space between adjacent β-cells contains abundant glycosylated cell adhesion molecule (black), and is markedly narrowed at the site of a gap junction domain (arrow heads) which concentrated connexons. (b): dual immunofluorescence of a pancreas section reveals the distribution of E-cadherin (green in midlle and right images) along the membrane of β-cells in contact, and of exocrine acini. This wide distribution contrasts with the spotted, discrete distribution of Cx36, which is detected only in the small gap junctional domains of β-cell membranes (red in left image). The right image is the merge of the left and middle images. Bar: 250 nm in (a), and 50 μm in (b).