EXAMINATION OF THE REGIONAL DISTRIBUTION OF MINOR AND TRACE-ELEMENTS IN NORMAL HUMAN BRAIN BY PIXE AND CHEMOMETRIC TECHNIQUES

Particle-induced X-ray emission (PIXE) was used to measure two minor and six trace elements, i.e. K, Ca, Mn, Fe, Cu, Zn, Se, and Rb, in up to 50 different structures (regions) of brains from Belgian individuals without neurological disorders. The data matrix with the mean dry-weight elemental concentrations and mean wet-to-dry weight ratio (means over 18 brains) for the various structures was subjected to two chemometric techniques, i.e., VARIMAX rotated absolute principal component analysis (APCA) and hierarchical cluster analysis. Three components were identified by APCA: components 1 and 3 represented aqueous fractions of the brain (respectively the intracellular and extracellular fluid), whereas component 2 apparently represented the solid brain fraction. The elements K, Cu, Zn, Se, and Rb were predominantly attributed to component 1, Ca to component 3, and Fe to component 2. In the hierarchical cluster analysis seven different agglomerative cluster strategies were compared. The dendrograms obtained from the furthest neighbor and Ward's error sum strategy were virtually identical, and they consisted of two large clusters with 30 and 16 structures, respectively. The first cluster included all gray matter structures, while the second comprised all while matter. Furthermore, structures involved in the same physiological function or morphologically similar regions often conglomerated in one subcluster. This strongly suggests that there is some relationship between the trace element profile of a brain structure and its function.