Structure of the glomerular filtration barrier. Transmission electron microscopy of a perfusion fixed rat glomerulus with addition of LaDy GAGa stain (section 80 nm thick). A: A montage of low magnification images depicting two glomeruli. B: A montage of higher magnification images depicting a glomerular filtration capillary (boxed in A). C: A high resolution (24,500 times magnification, boxed in B) of the five layers of the glomerular filtration barrier. There are two layers of staining (dense and sparse) present in this example of endothelial glycocalyx. A thin layer of contrast outside of the podocyte membrane is also commonly present. P = podocyte, C = capillary lumen, PUS = periphery urinary space, F = fenestration, SPS = sub-podocyte space.