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Abstract  

There is currently great interest in iodine as a micro nutrient. Both high and low intakes have been associated with thyroid cancer incidence. Development of dietary iodine monitors is needed to supplement the use of dietary recall methods which have not been well validated for iodine. In this study, 30 pooled urine samples, from ethnic groups on various islands in the South Pacific, were analyzed for iodine using epithermal instrumental neutron activation analysis (EINAA).

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Journal of Radioanalytical and Nuclear Chemistry
Authors: V. Spate, J. Morris, T. Nichols, C. Baskett, M. Mason, T. Horsman, P. Horn-Ross, A. Shiau, and I. McDougall

Abstract  

The literature on the relationship between diet and thyroid cancer (TC) risk and the higher incidence of TC among Asian immigrants to the US compared to second and third generation subgroups has prompted epidemiologists to hypothesize that increased levels of iodine consumption may be associated with TC risk, particularly among persons with a history of clinical or subclinical thyroid dysfunction. At the University of Missouri Research Reactor (MURR), we have applied epiboron neutron activation analysis to investigate human nails as a dietary monitor for iodine. Preliminary studies have indicated a positive correlation between dietary iodine intake and the concentration of iodine in toenails. However, these studies are confounded by high iodine levels (up to 30 ppm) in approximately 5% of the nails studied. We hypothesize that, in the subjects we have studied, the high iodine levels may be due to iodine-containing medications, in particular contrast-agents containing iopamidol. This paper will report on longitudinal studies using contrast agent subjects who were followed-up for almost two years compared to a longitudinal control and a population mean. Based on this study, we suggest that iodine-containing contrast agents contaminate nail samples via non-specific binding in the short term followed by incorporation in the nail as a result of absorption.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: C. Baskett, J. Morris, V. Spate, M. Mason, T. Cheng, T. Nichols, H. Anderson, C. Tharp, T. Horsman, and R. Dowdy

Abstract  

The objective of this study was to determine if a stable enriched tracer of Se-76 could be used to establish the delay time between a dietary intake of selenium and its appearance in various matrices. Selenium, an essential trace element, has been investigated at the Missouri University Research Reactor (MURR) for several years. Several matrices have been studied to determine selenium status in humans; these include fingernails, toenails, blood, hair, and urine. A cohort of five women and seven men was utilized for this study. Each subject ingested selenium supplements which were enriched in Se-76 (96.48%). Fingernails, toenails, whole blood, and blood sera were collected as biochemical indicators. Selenium concentrations and glutathione peroxidase activities were determined in blood sera and whole blood to monitor the effect of the selenium supplement in these matrices. Selenium concentrations were determined in fingernails and toenails prior to supplementation and for several months afterward to determine the delay time for the appearance of selenium. The effects of the selenium supplement on the selenium concentrations of the fingernails, toenails, whole blood, and blood sera and the effect of the supplement on glutathione peroxidase activity will be reported.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Mason, J. Morris, V. Spate, C. Baskett, T. Nichols, T. Horsman, L. Le Marchand, L. Kolonel, and S. Yukimoto

Abstract  

The measurement of dietary selenium intake in a free-living population using dietary recall techniques has been shown to be spurious. Consequently, in our laboratory, we have focused on the development of biologic monitors such as blood, nails, hair and urine. In this paper, we report on the neutron activation analysis of whole blood, plasma and nail specimens collected from 285 Caucasian subjects, all permanent residents of Hawaii, participating in a malignant melanoma trial. Correlations between monitors are presented and discussed in the context of selenium determinants and integration of selenium intake.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: T. Nichols, J. Morris, M. Mason, V. Spate, C. Baskett, T. Cheng, C. Tharp, J. Scott, T. Horsman, J. Colbert, A. Rawson, M. Karagas, and V. Stannard

Abstract  

Arsenic is toxic to humans with the lethal dose being approximately 1 mg/kg/day. At much lower long-term exposures, arsenic is hypothesized to increase the risk of certain cancers. We have developed an irradiation position for the neutron activation analysis (NAA) of nail specimens for arsenic, in support of a case-control study involving New Hampshire residents consuming well water above the EPA Safe Drinking Water Standard of 0.050 ppm. Arsenic is bound to nail keratin through sulfhydryl groups proportional to intake providing a convenient means of integrating arsenic intake in population-based studies. Our objective was to develop the necessary facilities and procedures by which relatively small samples (i.e. 20 to 100 mg) could be accurately analyzed for arsenic, so that affordable nutritional epidemiology investigations, requiring large numbers of samples (>1000 in this case), could be undertaken. A high-flux reflector position, with minimal axial variation throughout the fuel cycle, suitable for pneumatic-tube irradiations, was characterized by measurement of the neutron flux distribution (thermal and epithermal) within the irradiation capsule over time. Results from application of the method to a case-control study of basal and squamous cell skin cancer will be presented.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: R. Herrera, J. Denison, V. Spate, A. Gudiño, C. Baskett, I. Dubman, M. Mason, E. Bohl, A. Williams, T. Nichols, M. Glascock, and J. Morris

Abstract  

The University of Missouri Research Reactor Center (MURR) has been one of the premier providers of neutron activation analysis (NAA) to the high purity materials industry for the past 20 years. Over the last two decades, significant advances in contamination control in the manufacturing process and the development of alternate analytical techniques have challenged the NAA community to keep pace. This paper presents an overview of the High Purity Materials Analysis Program at MURR. Specifically we present trends in the trace element concentrations that we have observed in our laboratory over the past 10 years and compare our experience with the relevant literature. The prospects for the future success of NAA and the methodological changes required for satisfying the industry's need will be discussed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Mason, J. Morris, B. Derenzy, V. Spate, L. Clarke, L. Hillman, L. Gawenis, T. Horsman, C. Baskett, T. Nichols, and J. Colbert

Abstract  

A genetically engineered “knockout gene” mouse model for human cystic fibrosis (CF) has been utilized to study bone mineralization. In CF, the so-called cystic fibrosis transmembrane conductance regulator (CFTR) protein, a chloride ion channel, is either absent or defective. To produce the animal model the murine CFTR gene has been inactivated producing CF symptoms in the homozygotic progeny. CF results in abnormal intestinal absorption of minerals and nutrients which presumably results in substandard bone mineralization. The objective of this study was to determine the feasibility of using whole-body thermal and fast neutron activation analysis to determine mineral and trace-element differences between homozygote controls (+/+) and CF (−/−), murine siblings. Gender-matched juvenile +/+ and −/− litter mates were lyophilized and placed in a BN capsule to reduce thermal-neutron activation and irradiated for 10 seconds at φfast ≈ 1·1013 n·cm−2·s−1 using the MURR pneumatic-tube facility. Phosphorus was measured via the31P15(n,α)28Al13 reaction. After several days decay, the whole-body specimens were re-irradiated in the same facility, but without thermal-neutron shielding, for 5 seconds and the gamma-ray spectrum was recorded at two different decay periods allowing measurement of77mSe,24Na,27Mg,38Cl,42K,49Ca,56Mn,66Cu and80Br from the corresponding radiative-capture reactions.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: V. Spate, J. Morris, S. Chickos, C. Baskett, M. Mason, T. Cheng, C. Reams, C. West, C. Furnee, W. Willett, and P. Horn-Ross

Abstract  

An epithermal instrumental neutron activation analysis (EINAA) method, using a boron nitride irradiation capsule compatible with use in the University of Missouri Research Reactor pneumatic-tube irradiation facility, has been developed for the analysis of iodine in human nails. The principal objective was to determine if the nail could be used as a means of monitoring dietary intake of iodine. The EINAA method was used to analyze nails from subjects having iodine intakes that could be qualitatively differentiated. Iodine concentrations in nails from these subjects were positively correlated with apparent iodine intake.

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