| dc.description.abstract | Radiochemical and instrumental neutron activation analysis methods coupled with high-resolution Ge(Li) gamma-ray spectrometry have been developed in this work to study the role of trace elements in some models of neoplasia, namely,
EL4 lymphoma in C57BL/6J mice and H6 hepatoma in A/J mice.
Because of its simplicity, an instrumental neutron activation analysis (INAA) method has been developed for the simultaneous determination of trace concentrations of up to 23 elements. The method consists of irradiation of the mice tissue samples for JOs, 5min and 8h, and counting for 1min, 5min and 1h after 10s, 3min and a maximum of 14d decay, respectively.
Concentrations of a few elements, namely Fe, Mg, Mn, Se and Zn in mice tissues are high enough so that they can be
determined by INAA without much problem. However, the levels of certain elements such as Cu and Mo in tissues are sometimes too low to be determined by INAA in the presence of highly active nuclides· of the irradiated matrix. Alternatively, a specially designed rapid radiochemical neutron activation analysis (RNAA) method has been developed to analyze the tissues after INAA.
A few other elements can also be determined by the RNAA method. Among these elements, noble metals are of interest, because of their potential of being used in chemotherapy, as demonstrated by the application of Pt-complexes.
The elements that may be determined by this RNAA method are Ag, As, Au, Cu, Hg, Mo, Pd, Pt, Sb, Se and Zn. Except Ag, Se and Zn which may be better analyzed by INAA, other elements in mice tissues may not be easily determined by INAA even with
a high resolution Ge(Li) detector. Instead, the irradiated tissues have been digested and separated into 5 fractions with the removal of major interferences by means of two main stages, namely distillation and iodide column chromatography.
Four fractions (containing Mo-Zn; Cu; Cd; Ag-Au-Pd-Pt) have been obtained by the latter method. The chemical yields of all the elements have been observed to be about 100% with the exception of molybdenum which is about 90%. Of particular interest is the determination of copper. Since the separated copper is radiochemically pure, the 511-keV gamma-ray emitted by 64cu can be used for assaying the copper content, which has an advantage factor of about 200 over the 1J46-keV gamma-ray of 64cu which is normally used in RNAA group separation methods.
Another fraction obtained by distillation of the digested tissues has been found to contain As, Br,: Hg, Sb and Se. In the presence of highly active 82Br, the determination of other elements are seriously hindered. In this work, a simple single-precipitation process has been developed to remove 82Br. The photo-peaks of 76As, 197Hg and 122sb can then be used for elemental determination.
The results obtained by both INAA and RNAA are reported here. Differences in elemental contents among tumors, tissues of mice with tumors and tissues of normal mice of both strains have been statistically tested using the student's t-test and Wilcoxon two-sample-test. Correlation among pairs of element and multielement regression have also been studied in some cases. The results indicate that copper and selenium levels are lowest in the tumor tissues of H6, and highest in the control among the group of tumor H6, livers of H6-bearing mice, and livers of normal mice. Interestingly, both of the elements have been reported to have some functions in oxidation-reduction processes in biochemistry of cells. Since system of H6-livers is a good model, the results obtained may be indicative of the role of these two elements in the hepatoma H6. The importance of other elements determined are also reported here. | en_US |
