Left: Analysis of ubiquitin expression (brown) in FFPE section of human cerebral cortex of an Alzheimer patient by Immunohistochemistry. Signal was generated with DAB. Counterstain: haemotoxylin (blue). A typical flame-shaped tangle is seen in a pyramidal neuron in the center and is surrounded by dystrophic neurites, also strongly ubiquitin-positive. Both are commonly seen in cortical and hippocampal Alzheimer brain sections and are typical for this disease, but are rare or absent in healthy brain. Right: Western blot analysis of HEK293 cell lysates for ubiquitin expression (green, 1:1,000). [1] protein standard, [2] cells maintained in normal medium, [3] cells treated with 10 uM of proteasome inhibitor lactacystin (Lc) for 16 hours. The smear detected above the 200 kDa standard represents accumulation of ubiquitinated proteins in proteasome inhibitor-Lc treated cells. The prominent band at 8 kDa corresponds to monoubiquitin. The same blot was probed with an antibody to HSP60 as loading control.