J. D. Robertson

Copper, iron and zinc in Alzheimer's disease senile plaques

Concentrations of copper (Cu), iron (Fe) and zinc (Zn) were measured in the rims and cores of senile plaques (SP) and in the neuropil of the amygdala of nine Alzheimers disease (AD) patients and in the neuropil of the amygdala of five neurologically normal control subjects using micro particle-induced X-ray emission (micro-PIXE). Comparison of SP rim and core values revealed no significant differences between levels of Cu, Fe or Zn. Zinc and Fe in SP rims and cores were significantly elevated in AD compared with AD neuropil (P<0.05). Copper was significantly elevated (P<0.05) in the rim of SP compared with AD neuropil. Comparison of AD and control neuropil revealed a significant (P<0.05) elevation of Zn in AD subjects. The elevation of these elements in SP in AD is of interest in light of the observation that Cu, Fe and particularly Zn, can accelerate aggregation of amyloid beta peptide.

Serum Zinc Levels and Alzheimer's Disease

Concentrations of zinc in postmortem serum and four brain regions were measured by flame atomic absorption spectrometry and instrumental neutron activation analysis, respectively, in nine Alzheimer’s disease (AD) and eight control subjects. A statistically significant elevation of zinc serum was observed in AD subjects (136.4±66.8 µg/dL) compared with age-matched control subjects (71.1±35.0 µg/dL). No significant differences were observed between AD and control zinc concentrations in the amygdala, hippocampus, cerebellum, and superior and middle temporal gryi.

Determination of major and trace elements in bones by simultaneous PIXE/PIGE analysis

Simultaneous PIXE/PIGE was used to determine the concentration of 20 elements including N, O, F, Na, Mg, P, Ca (PIGE) and Cr, Mn, Cu, Zn, Cd, Ba, Pb (PIXE) in a number of animal and human rib samples, marrow, and the IAEA CRM Animal Bone (H-5). Samples and standards were bombarded with 2.5 and 4.0 MeV external proton beams. The minimum detection limits for most of the minor and trace elements ranged from 0.5 to 1.5 ppm. The sample preparation procedure for the nondestructive instrumental analysis of bone is discussed in detail. The analysis method is fast, nondestructive and offers selective analysis of the cortical and cancellous surface of the same bone sample.

PIXE analysis of the hydrothermal leaching of trace elements in coal

The minor and trace element content in coal is of great interest due to the potential impact on the environment from the release of these elements during combustion. Reducing the concentrations of potentially hazardous elements in coal prior to combustion is one way of dealing with this issue. In this research particle induced X-ray emission (PIXE) was used to investigate a hydrothermal leaching process for the removal of trace elements from a bituminous coal. The leaching agents HNO3 and NaOH were evaluated along with the effects of process parameters (temperature, pressure, and time) on the methods effectiveness. The variable with the greatest influence was the leaching agent itself. HNO3 was determined to be more effective than NaOH in reducing elemental concentrations for nearly all the elements determined. Increasing the temperature did result in greater reductions for some elements (Cl, Br, Zn) whereas increasing the pressure and duration of the leaching process had minimal impact on reductions, in elemental concentrations.

Lead determinations in human bone by particle induced X-ray emission (PIXE) and graphite furnace atomic absorption spectrometry (GFAAS)

Chronic lead (Pb) intoxication has been linked to Alzheimers disease (AD). Lead, like many heavy elements, tends to accumulate in bone. PIXE is a powerful analytical tool which permits the determination of Pb at the μg/g level without requiring sample digestion. GFAAS is one of the most sensitive methods for the determination of Pb and is capable of determining ng/g levels in solution. For bone analyses by GFAAS, sample dissolution and a matrix modifier are required. Rib bone samples were analyzed for Pb by PIXE and GFAAS. IAEA Animal Bone (H-5) was used as a secondary standard for Pb with both methods to ensure accuracy. The range of Pb concentrations in human rib bone was 1.4–11.5 μg/g for the trabecular surface by PIXE, 1.3–45 μg/g for the cortical surface by PIXE, and 1.54–11.75 μg/g for whole bone by GFAAS. No significant difference (p>0.05) was found for AD versus control for either surface or for whole bone.

PIXE analysis of prehistoric and protohistoric Caborn-Welborn phase copper artifacts from the lower Ohio River Valley

Particle-induced X-ray emission (PIXE) spectrometry is being used to nondestructively determine the elemental composition of copper-based artifacts excavated from prehistoric/protohistoric sites in the Ohio River Valley. Copper objects from Caborn-Welborn (C-W) and contemporary Fort Ancient sites are being studied so as to differentiate between native American and European copper. The trace element analysis of metal artifacts enables archaeologists to more accurately assess the material culture and chronological development of C-W society (A.D. 1400–1700) with particular reference to geological sources of copper and brass.

Comparison of laser microprobe mass spectrometry (LMMS) and micro particle induced X-ray emission (micro-PIXE) for the analysis of senile plaques in Alzheimer's disease: A preliminary study

Results of micro-PIXE analysis of senile plaques (SP) in Alzheimers disease (AD) brain have been utilized to independently confirm levels of iron (Fe) as measured by LMMS in adjacent brain sections. LMMS concentrations were calculated based on the preparation and analysis of an iron calibration curve prepared in our laboratory. The LMMS standards consist of ironcis-dicyclohexano-18-crown-6 ether coordination complexes dissolved in Spurrs low viscosity embedding medium. To our knowledge, this is the first report of the use of micro-PIXE, with its spatial resolution and detection limits comparable to that of LMMS, in the validation of LMMS results. The agreement observed between results obtained for Fe by micro-PIXE and LMMS indicates that the use of our LMMS standards, at least in the case of Fe, yields accurate results.

A radiochemical neutron activation analysis method for the determination of total mercury in coal

A radiochemical neutron activation analysis method has been developed based on pyrolysis followed by double gold amalgamation for the determination of mercury in solid samples. Accurate results were obtained for mercury in six standard reference materials of varying matrices, including coal. Linearity was demonstrated up to mercury concentrations of 10,000 ng/g. The method is capable of yielding precise, reproducible values with a detection limit of 5 ng/g for mercury in coal.

Out of the textbook and into the world: Student projects in the radiochemistry laboratory

A major objective of any laboratory course should be to stimulate students to extend their knowledge of the subject to specific problems. In the radiochemistry laboratory course at the University of Kentucky, we encourage students to make the transition from the textbook or laboratory manual to the “real” world through the use of a special project. This project, which typically replaces two normal laboratory exercises, is a short research problem that the student independently develops and executes. An overview of the incorporation of special projects into our radiochemistry laboratory course is presented.

Nuclear methods of analysis applied to quantitation in laser microprobe mass spectrometry

Laser microprobe mass spectrometry (LMMS) detection limits for mercury have been determined using mercury-doped Spurrs tissue embedding medium. Actual mercury concentrations were confirmed via INAA. Procedures have also been developed to measure lithium and indium concentrations in thin films of polymerized Spurrs samples via PIGE and PIXE. These elements are currently being investigated as laser power density internal standards in the analysis of human tissue for studies of trace element involvement in neurological diseases.