Amyloid plaques

[10] Redlich used the term 'miliary sclerosis' to describe plaques because he thought they resembled millet seeds, and he was the first to refer to the lesions as 'plaques'.

[4] In the early 20th century, Oskar Fischer noted their similarity to actinomyces 'Drusen' (geode-like lesions), leading him to call the degenerative process 'drusige Nekrose'.

[20] This discovery led to the generation of new tools to study plaques, particularly antibodies to Aβ, and presented a molecular target for the development of potential therapies for Alzheimer's disease.

[3][4] Under the light microscope, they range from small, wispy accumulations that are a few microns in diameter to much larger dense or diffuse masses.

[4] The normal function of Aβ is not certain, but plaques arise when the protein misfolds and begins to accumulate in the brain by a process of molecular templating ('seeding').

[7][38] Abundant Aβ plaques, along with neurofibrillary tangles consisting of aggregated tau protein, are the two lesions that are required for the neuropathological diagnosis of Alzheimer's disease.

[21] The diagnosis of Alzheimer's disease typically requires a microscopic analysis of plaques and tangles in brain tissue, usually at autopsy.

[41] The ligands cross the blood–brain barrier and attach to aggregated Aβ, and their retention in the brain is assessed by positron emission tomography.

In addition, the presence of plaques and tangles can be estimated by measuring the amounts of the Aβ and tau proteins in the cerebrospinal fluid.

[46] Amyloid plaques naturally occur in the aging brains of nonhuman species ranging from birds to great apes.

[48] Both human samples and experimental models of Alzheimer's disease have been used to study the biochemical, cytological, and inflammatory characteristics of amyloid plaques.

[4] Experimental studies have focused not only on delineating mechanisms by which plaques arise and proliferate, but also on discovering methods by which they can be detected (and potentially prevented/removed) in the living brain.

Amyloid beta immunostaining showing amyloid plaques (brown)
Two amyloid plaques from the brain of a patient with Alzheimer's disease. In this photomicrograph , neurites are darkly stained with the Naoumenko-Feigin silver method, and the pink elements (including the plaque cores) are stained with the periodic acid-Schiff (PAS) counterstain. The bar is 20 microns (0.02 mm) in length.