High-Resolution Stereo Electron Microscopy of Neurofilaments and Alzheimer Type Paired Helical Filaments

Abstract

To learn about the ultrastructural similarities and dissimilarities between the Alzheimer's paired helical filaments (PHF) and normal neurofilaments, we developed a new method to cut the plastic embedded block. We call the sections cut by this new method supra-ultrathin sections. To obtain supra-ultrathin EM sections, a selected area of the tissue block was first trimmed to a size about 0.25 mm2 to reduce the sectioning pressure between the knife and the tissue block. The tissue was sectioned as thin as possible. The interference color of the sections was almost as transparent as the water surface. The thicker sections with different interference colors were removed by picking up with hair tip so that all of the sections floating on the water were of same or similar thickness. A saturated solution of uranyl acetate in 50% ethanol was used to maximize the contrast of these supra-ultrathin EM sections on uncoated grids.