The influence of a high-bran diet on trace element retention in primates (PIXE application)

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Abstract
Proton-induced X-ray emission (PIXE) has become an established analytical method for the determination of trace elements in biomedical samples. The standard PIXE technique has been modified, resulting in a considerable improvement in detection limits. Refinements include the use of an external proton beam, the incorporation of a triggered beam-pulsing system, and the backward angle location (135 degrees to the incident ions) of the Si(Li) X-ray detector. The technique is now clearly capable of rapid, multielemental investigations, and requires a minimum of target preparation. Samples of liver and oesophagus tissue were obtained from 26 baboons at autopsy. Of these, 13 had been maintained on a semi-synthetic (high-bran) diet, with the remaining 13 forming the control group. Some 15 elements were analysed quantitatively; optimum detection limits were in the range 10-20 PPB (1 billion=10 degrees ). Clear differences were obtained: the high-bran diet is shown to produce imbalances in biologically active elements such as S, K, Ca, Ni, Cu and Zn. These results are discussed on the basis of the phytate hypothesis in terms which trace elements in the diet are rendered physiologically unavailable to the subject.