Morphology of WPBs in nonstimulated cells. (A) Immunofluorescence image of a human umbilical vein endothelial cell (HUVEC) labeled with an antibody against VWF, revealing the numerous elongated WPBs throughout the cell. Note the reticular staining representing the ER (white arrow). Scale bar represents 5 μm. (B) EM image of a HUVEC showing several WPBs (arrows). N, nucleus. Scale bar, 1 μm. (C-E) Digital slices through electron tomograms of WPBs displaying irregular shapes suggesting homotypic fusion between WPBs.3 (C) The delimiting membrane of the WPB is not straight along the long axis of the WPB. Scale bar, 200 nm. (D) Several WPBs are aligned against each other and are connected at some extremities (arrows). Scale bar, 200 nm. (E) Transverse section of an atypical WPB with an oval shape displaying 2 indentations (arrows). Scale bar, 100 nm.
