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Neurofibrillary tangles are formed by hyperphosphorylation of a microtubule-associated protein known as tau, causing it to aggregate, or group, in an insoluble form. (These aggregations of hyperphosphorylated tau protein are also referred to as PHF, or "paired helical filaments"). The precise mechanism of tangle formation is not completely ...
Some plaques occur in the brain as a result of aging, but large numbers of plaques and neurofibrillary tangles are characteristic features of Alzheimer's disease. [5] The plaques are highly variable in shape and size; in tissue sections immunostained for Aβ, they comprise a log-normal size distribution curve, with an average plaque area of 400 ...
Hyperphosphorylation of tau proteins causes them to dissociate from microtubules and form insoluble aggregates called neurofibrillary tangles. [2] Various neuropathologic phenotypes have been described based on the anatomical regions and cell types involved as well as the unique tau isoforms making up these deposits. The designation 'primary ...
Primary age-related tauopathy (PART) is a neuropathological designation introduced in 2014 to describe the neurofibrillary tangles (NFT) that are commonly observed in the brains of normally aged and cognitively impaired individuals that can occur independently of the amyloid plaques of Alzheimer's disease (AD).
Alzheimer's disease is believed to occur when abnormal amounts of amyloid beta (Aβ), accumulating extracellularly as amyloid plaques and tau proteins, or intracellularly as neurofibrillary tangles, form in the brain, affecting neuronal functioning and connectivity, resulting in a progressive loss of brain function.
The pathological phenotype associated with mutations elsewhere in tau is less predictable, with both typical neurofibrillary tangles (consisting of both 3-repeat and 4-repeat tau) and Pick bodies (consisting of 3-repeat tau) having been described.
Neurofibrillary tangles are insoluble aggregates of tau proteins, and amyloid-beta plaques are extracellular deposits of the amyloid-beta protein. Current thinking in AD pathology goes beyond these two typical hallmarks to suggest that a significant portion of neurodegeneration in Alzheimer's is due to neuroinflammation.
Abnormal accumulation of tau protein, which constitutes neurofibrillary tangles, in neuronal cell bodies (arrow) and neuronal extensions (arrowhead) in the neocortex of a patient who had died with Alzheimer's disease at Braak stage VI. The bar = 25 microns (0.025 millimeters).