Some Methods of Electron Microscopic Visualization of Lipoproteins in Plasma and Chyle

Using isolated rat chylomicrons and human hyperlipemic plasma as experimental systems, we have described various methods of preparing lipoproteins for electron microscopic observation. Of these methods three have been found to be particularly useful and are described in detail. They are: (1) long osmium fixation followed by ultracentrifugation of the fixed particles to form a pellet for subsequent embedding and thin sectioning, (2) brief osmium fixation followed by shadow casting of the particles and (3) osmium vapor fixation and direct electron microscopic visualization of the lipoproteins. Shadow casting appears to be the most rapid and reliable means of evaluating the particle size distribution of human plasma lipoprotein. Because of its rapidity, this procedure may be of diagnostic value in clinical research laboratories.