NUCLEAR MICROSCOPE ANALYSIS IN ALZHEIMERS AND PARKINSONS-DISEASE - A REVIEW

The scanning nuclear microprobe (nuclear microscope) is becoming a pow erful instrument for the accurate measurement of minor and trace eleme nts in biological tissue. Using the simultaneously applied techniques of Scanning Transmission Ion Microscopy (STIM) to image features in th e tissue, Particle induced X-ray emission (PIXE) to measure trace elem ent concentrations, and Rutherford Backscattering Spectrometry (RBS) t o characterize the tissue matrix, accurate elemental analysis at the p arts per million level can be obtained for most elements. This review describes briefly the results obtained using the nuclear microscope fo r the elemental analysis of Alzheimer's and Parkinson's tissue. In Alz heimer's disease (AD) the identification and subsequent analysis of ne uritic plaque cores in unstained tissue, yielded an absence of alumini um at the limit of 15 parts per million. Previous analyses involving s tained sections were prone to misinterpretation due to aluminium conta mination from the staining procedures. Elemental iron, calcium, phosph orus and sulphur were elevated both in the plaques and the AD backgrou nd tissue compared to age matched controls. Preliminary analyses of ne urofibrillary tangles stained with toluidine blue showed increased lev els of calcium, although the staining procedure may have distorted the results due to element redistribution. In Parkinson's disease (PD) nu clear microscope studies have concentrated on measurements of iron in the substantia nigra (SN) region of the brain; iron was observed to be elevated by a factor 2 in MPTP induced Parkinsonism in African Green monkeys, and by a factor of 1.25 in 6-OHDA induced Parkinsonism in Spr ague Dawley rats. These studies are consistent with other studies show ing a general increase in the concentrations of iron associated with P D, and support the theory that iron mediated free radical production m ay enhance or accelerate the degeneration of dopaminergic cells throug h oxidative stress.