On the amyloid-Congo red complex in histological sections and the genesis of the amyloid substance

Tetracysteine-tagged prion protein allows discrimination between the native and converted forms

The conformational conversion of prion protein (PrP) from a native conformation to the amyloid form is a hallmark of transmissible spongiform encephalopathies. Conversion is usually monitored by fluorescent dyes, which bind generic amyloids and are less suited for living cell imaging. We report a new method for the synthesis of membrane-permeable and membrane-impermeable biarsenical reagents, which are then used to monitor murine PrP (mPrP) misfolding. We introduced tetracysteine (TC) tags into three different positions of mPrP, which folded into a native-like structure. Whereas mPrPs with a TC tag inserted at the N-terminus or C-terminus supported fibril formation, insertion into the helix 2-helix 3 loop inhibited conversion. We devised a quantitative protease-free method to determine the fraction of converted PrP, based on the ability of the fluorescein arsenical helix binder reagent to differentiate between the monomeric and fibrilized form of TC-tagged PrP, and showed that TC-tagged mPrP could be detected on transfected cells, thereby expanding the potential use of this method for the detection and study of conformational diseases.

Renal hyalin. A study of amyloidosis and diabetic fibrinous vasculosis with new staining methods

This describes the sodium sulphate-Alcian Blue (SAB) method for staining amyloid in paraffin sections. Its value lies in the possibility of subsequent counterstaining and thus of revealing the structural relationships of amyloid. In the kidney the topical disposition of amyloid closely resembles the disposition of fibrin in the kidney of diabetics; this suggests that upset in vascular permeability plays a part in determining the site of the amyloid deposits. Furthermore, an aging process in amyloid can now be envisaged resembling the aging of extraluminal fibrin. Both materials proceed to a hyalin material that, staining like collagen, merits the name pseudo-collagen. This term we apply to a hyalin, staining like collagen, for which, we can postulate a specific precursor.

Immunohistochemical analysis of amyloid by the fluorescence technique

The immunohistochemical composition of amyloid deposits in secondary human amyloidosis and experimental amyloidosis in rabbits was studied by means of the "fluorescent antibody" technique of Coons et al. Quantitative studies of the relative amounts of gamma globulin present in the amyloid deposits by the use of radioiodinated fluorescent antibody are reported. It is concluded that amyloid deposits in several organs from cases of secondary human amyloidosis and experimental amyloidosis in rabbits contain considerable concentrations of gamma globulin. The presence of gamma globulin in amyloid might be interpreted as either a metabolic deposition of circulating globulin present in high concentrations in the plasma or as a result of an immunologic reaction involving antigen and antibody.