32] In situ electron microscopy of amyloid deposits in tissues

Abstract

Publisher Summary Amyloidosis is a widespread multiform disorder, and amyloids are proteinaceous usually extracellular tissue deposits characterized by positive Congo red staining, red–green birefringence of Congo red-stained tissues under polarized light, and the presence of cross β molecular conformation as detected by X-ray diffraction. Ultrastructurally they are composed mainly of assemblies of fibrils approximately 10 nm in diameter. Fibrils of various types of amyloid have been observed in the electron microscope both in situ in the tissue as well as after isolation. Although all amyloids have the same structural and tinctorial properties, they are quite diverse chemically, with each form of protein being associated with a specific disease or pathological process. More detailed examinations of the ultrastructure and composition of the fibrils in situ have been done in laboratories by means of high-resolution electron microscopy and ultrastructural immunohistochemical labeling. Because amyloid deposits are composed mainly of “amyloid fibrils,” high-resolution ultrastructural characterization of these fibrils in situ is the main subject of this chapter.