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  • Author or Editor: V. L. Spate x
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Summary  

The evaluation of human nails as a measure of selenium intake and to assess selenium status in critical tissues is now being used routinely to investigate hypotheses relating selenium status to chronic disease, especially cancer. In this study we report on our observations of the major determinants of toenail selenium concentrations. Toenail specimens (3575) were, under a protocol we provided, self-collected by adult females (1940, 54.3%) and males (1635, 45.7%) living in 111 of Missouri's 114 counties. The health-conscious participants ranged in age from 18 to 94 years with means of 53.7±14.1 and 56.4±14.2 years for females and males, respectively. Selenium supplement use was over represented, 39.1% and 42.7%, and smoking was under represented, 7.5% and 7.8%, for females and males, respectively. The major determinants of toenail selenium concentration were supplement use, sex and cigarette smoking. We found no overall correlations with age, body mass index or diet selection.

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Abstract  

A chemical and radiochemical neutron activation analysis (CNAA/RNAA) method has been developed for the determination of three calcium isotopes (48Ca,46Ca, and44Ca) in a single sample derived from urine. This method was developed in support of clinical research using a dual enriched stable isotope methodology to study bone mineralization in premature infants, juvenile rheumatoid arthritics, and cystic fibrosis. In these studies, one enriched isotope of calcium is administered orally, and one is administered intravenously. By making determinations of three isotopes (two enriched, one unenriched) within the same sample, the perturbation from natural isotopic ratios can be determined and used to calculate true absorption of calcium. In our method,48Ca is determined via the48Ca(n,γ)49Ca reaction and 3084 keV gamma-ray,46Ca via the46Ca(n,γ)47Ca reaction and 1296 keV gamma-ray, and44Ca via the44Ca(n,γ)45Ca reaction and 256 keV (max) beta-particle. A pair of chemical separation steps are employed to separate calcium from urine as calcium oxalate with a yield in the range of 80–90%, and a radiochemical step is employed prior to the measurement of45Ca to remove interfering radionuclides.

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Summary  

Selenium is a required trace-element that has been found to be protective against serious chronic diseases such as cancer and cardiovascular disease in some, but not all, epidemiological studies using both case-control and intervention designs. As a result, the fraction of the adult U.S. population now taking a daily selenium supplement is steadily increasing. In this study, we analyzed 10 or more replicate Se supplement tablets, from each of 15 different products representing 12 different brand names with most being sampled at two different times separated by approximately 30 months. Two chemical forms, seleno-yeast and selenate were tested in 50, 100 and 200 µg/tablet dosages (seleno-yeast) and 25 and 200 µg/tablet dosages (selenate). Variations in contemporary lots were evaluated at both sampling periods. The Se content provided on the product label is generally understated. One tablet contained 2.5 times more selenium than the stated dose. Selenate supplements are less accurately labeled and more highly variable compared to yeast supplements. One popular multivitamin, labeled at 200 µg/tablet, contained tablets in excess of 300 µg. Many subjects using this supplement will exceed the 400 µg/day tolerable upper limit of intake, recently established, for Se by the Institute of Medicine’s Food and Nutrition Board.

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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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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: 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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