Fig. 5. Immuno-TEM detection of 3xMyc-Nodal at the node. (A-D) Immunohistochemical staining for 3xMyc-Nodal in transverse frozen sections of E8.0 mouse embryos positive (A-C) or negative (D) for the transgene shown in Fig. 4A. (E-H) Ultrathin sections corresponding to the boxed regions shown in A to D, respectively, were examined by TEM at x1000. (I-M) The boxed regions in E-G are shown at higher magnification (x4000) in I-K, respectively. Black dots, cell boundaries; green dots delineate the nucleus. The boxed regions in J and K are shown at even higher magnification (x6000) in L and M, respectively, revealing apparent secretion of 3xMyc-Nodal at the basolateral membranes. Scale bars: 10 µm in A-H; 2.5 µm in I-K; 1 µm in L,M.