Electron microscopy (EM) of cultured human glomerular microvascular endothelial cells (HGMEC). A) HGMEC were cultured on nitrocellulose membranes and processed for EM. Transmission EM showing general cell structures such as lysosome (L), mitochondria (M), and endoplasmic reticulum (ER). Also the endothelial characteristic Weibel Palade bodies can be seen (circle). B) Magnification of a Weibel Palade body from panel A), showing rod shaped microtubules. C) Scanning EM of a HGMEC cell showing numerous fenestrae.