Cholestasis: lamellar structure of the abnormal human serum lipoprotein.

An abnormal lipoprotein was visualized directly in serum by electron microscopy of preparations negatively stained with potassium phosphotungstate. It appears as a unique disk-shaped particle with major axis measuring 400 to 600 angstroms and minor axis measuring about 100 angstroms. Chemical analysis, viscosity measurements, and x-ray diffraction analysis of purified preparations indicate that the particle, consisting of a one-to-one molar mixture of cholesterol and choline phosphatides associated with a small amount of protein, is a flattened vesicle, the wall of which is a continuous lipid bilayer.