Microwave treatment enhances the immunostaining of amyloid deposits in both the transmissible and non-transmissible brain amyloidoses.

The immunolocalization of amyloid deposits containing either protease-resistant prion protein (PrP) or amyloid beta protein (A beta) in the brains of patients with transmissible or non-transmissible cerebral amyloidoses has been greatly facilitated by the pretreatment of tissue sections with concentrated formic acid. We have investigated whether microwave processing of formalin-fixed tissue sections would obviate the need for formic acid pretreatment. Exposure of brain sections to microwaves, even for periods as brief as 1 sec, greatly enhanced the immunostaining of PrP and A beta amyloid deposits in both the transmissible and non-transmissible brain amyloidoses. Microwaving for 1 min yielded staining intensities similar to that following pretreatment with concentrated formic acid for 10 min. Moreover, the combination of formic acid pretreatment and microwave processing resulted in an even more intense staining of amyloid deposits. Microwave processing, which is easy to perform and comparatively inexpensive, makes exposure to the potentially toxic fumes of formic acid unnecessary.