Diagnostic Features of Alzheimers
When analyzing the brain of a diagnosed Alzheimers Disease patient, two biological
hallmarks are evident at the microscopic level: neurofibrillary tangles and senile plaques.
Neurofibrillary tangles, or NFTs, disrupt the neurons resulting in the inhibition of nervous
impulses. Basically, the neurons are unable to transmit messages, and the affected individual
is unable to respond to environmental stimuli, therefore, losing control of the myriad
functions characteristic of senile dementia. NFTs are made up of filament masses
characterized by a paired helical structure within the neuronal cytoplasm1
. The paired helical structures are made up of abnormally phosphorylated tau protein.
Tau protein regulates the dynamic instability of the microtubules in the cell, and is possibly
associated with the polarity and bundling of microtubules. This phosphorylation causes the
tau protein to associate with itself instead of binding with the microtubules, thus, resulting in paired helical structures. Although NFTs are best known as indicators of Alzheimers
Disease, they are also found in the brains of persons afflicted with other neurological
disorders, such as encephalopathic Parkinson's disease.
1 Edwardson et al.
2 "Untangling Alzheimers Disease." Internet. (1996). Netscape Online. (http://cait.cpmc.columbia.edu/news/frontiers/boif.html).
3 Kuroda, Y. et al. "Application of Long-Term Cultured Neurons in Aging and Neurological Research: Aluminum Neurotoxicity, Synaptic Degeneration and Alzheimers Disease." Gerontology. 41 (1994): 2-6.
4 Anderson et al.