Alzheimers disease brain cell. Coloured transmission electron micrograph (TEM) of a neurofibrillary tangle in a nerve cell from the brain of a patient with Alzheimers disease. The tangle (yellow) lies in the cytoplasm (green) of the cell, and consists of abnormal aggregates of the protein tau. In the healthy cell, tau stabilises microtubules in the cytoplasm. It is not known precisely how the tangles are formed, nor their impact on the neurons function, but they are seen in a range of neural disorders including Alzheimers disease, CreutzfeldJakob disease (CJD), some forms of Parkinsons disease, and Supranuclear Palsy.