PARP1 and Alzheimer disease: Consistent with the light microscopy data, we found that 66.1% and 62.2% of CA1 and CA4 hippocampal pyramidal cell nucleoli stained positive for PARP-1 in controls, whereas, in AD, nucleolar PARP-1 staining was present in only 29.3% and 32.0% of CA1 and CA4 pyramidal cells, respectively (Figure 2).