Evaluating the suitability of the human toenail as a biomonitor for manganese status: the one source cohort

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on October 25, 2007)Vita.Includes bibliographical references.Thesis (M.S.) University of Missouri-Columbia 2007.Dissertations, Academic -- University of Missouri--Columbia -- Chemistry.Numerous studies have demonstrated that the human toenail is a reliable biomonitor for the intake of Se and other elements. The objective of this study was to evaluate the hypothesis that Mn intake is reflected in toenail Mn levels. Interest in the status of Mn, a necessary trace nutrient which may also have toxic effects upon overexposure, stems from two recent developments: first, a greater awareness of the role of Mn-based enzymes in human health, and second, a renewed controversy over the use of a Mn-containing gasoline additive in Canada. In order to evaluate the hypothesis, toenail specimens from One Source multivitamin users and matched controls were selected. Using the NAA technique, Se was measured using established methods, and then Mn was measured via a new procedure. The Se results confirmed the accurate classification of the cohort. However, the nail did not demonstrate significant, positive response to Mn supplementation. Several explanations for this lack of response may be offered, including the confounding effect of other, unknown dietary variables; Mn blood level regulation by homeostatic mechanisms; and the masking of endogenous Mn in the toenail by persistent Seleniumexogenous material

Analyzing the effects of lactose on calcium absorption in premature infants using HR-ICP-Mass Spectrometry

Abstract only availableWith advances in neonatal care, premature infants are surviving at increasing rates. During the third trimester of pregnancy, the bone mineral content of infants rapidly increases. It is therefore becoming essential to accurately mimic the womb environment to maintain growth and sustain the health of premature infants as if they were in utero. Regulating calcium absorption in premature infants is crucial primarily for bone formation, as 99% of the calcium in the human body is found in the bones and the teeth. The effect of lactose containing formulas on calcium absorption in premature infants has not been well established. Concerns have been noted in the scientific community regarding lactose intolerance especially in premature infants, as lactase, the enzyme responsible for lactose digestion, is most readily detectible during the third trimester of pregnancy. In this study, in conjunction with Dr. Laura Hillman of the University of Missouri Hospital, each infant was fed lactose and maltose formulas during different weeks using a dual tracer method in which two calcium isotopes were administered, 44Ca orally and 46Ca intravenously. Urine samples were collected after 24 hours. Analysis related natural abundances of calcium isotopes to the measured values in the urine. Polyatomic ion interferences were differentiated from the calcium peaks by analyzing the samples at a resolution of 4000. Mathematical corrections for interferences caused by titanium and doubly charged strontium were determined by measuring the specific isotopes 47Ti and 87Sr++ and using known natural abundances of the interfering isotopes to correct each calcium count rate. Mathematical calculations relate the enriched isotope ratio measurements of 44Ca and 46Ca to calcium absorption. Analysis regarding the effect of lactose on calcium absorption is ongoing. Our data precision on the ICP-MS was acceptable with percent relative standard deviations (%RSD) for external precision over the course of a week at 1.4, 2.2, 0.71, and 1.4 for isotope ratios 42Ca: 43Ca, 42Ca: 44Ca, 42Ca: 46Ca, and 42Ca: 48Ca respectively. Daily internal precision (%RSD) values were .37, 1.3, .69, and 1.5. The precision shows the viability of utilizing HR-ICP-MS analysis for calcium isotope ratios.NSF-REU/NIH Program in Radiochemistr