Ultrastructural findings on lipoproteins in vitro and in xanthomatous tissue

The application of OSO4 plus K3 [Fe(CN)6] as a secondary fixative following aldehyde fixation, permitted demonstration of the presence of 30-300 nm 'membrane-bound' particles in xanthomatous tissue. With the same fixation method, isolated low density lipoprotein particles in a fibrin matrix could be observed in the transmission electron microscope in a way permitting comparison with similarly fixed tissue. However, isolated particles of very low density lipoproteins treated in the same way as low density particles had an irregular appearance and a diameter varying between 30 and 80 nm.