Hierarchical clustering of Alzheimer and "normal" brains using elemental concentrations and glucose metabolism determined by PIXE, INAA and PET

Brain tissue samples, obtained from the Alzheimer Disease Brain Bank, Insti tute of Psychiatry, London, were taken from both left and right hemispheres of three regions of the cerebrum, namely the frontal, parietal and occipit al lobes for both Alzheimer and 'normal' subjects. Trace element concentrat ions in the frontal lobe were determined for twenty six Alzheimer (15 male, I I female) and twenty six 'normal' (8 male, 18 female) brain tissue sampl es. In the parietal lobe ten Alzheimer (2 male, 8 female) and ten 'normal' (8 male, 22 female) samples were taken along with ten Alzheimer (4 male, 6 female) and ten 'normal' (6 male, 4 female) from the occipital lobe. For th e frontal lobe trace element concentrations were determined using proton in duced X-ray emission (PIXE) analysis while in parietal and occipital region s instrumental neutron activation analysis (INAA) was used. Additionally ei ghteen Alzheimer (9 male, 9 female) and eighteen age matched 'normal' (8 ma le, 10 female) living subjects were examined using positron emission tomogr aphy (PET) in order to determine regional cerebral metabolic rates of gluco se (rCMRGlu). The rCMRGlu of 36 regions of the brain was investigated inclu ding frontal, occipital and parietal lobes as in the trace element study. H ierarchical cluster analysis was applied to the trace element and glucose m etabolism data to discover which variables in the resulting dendrograms dis played the most significant separation between Alzheimer and 'normal' subje cts.