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Call number: LD2668 .T4 1948 H38 / Master of Science

The ability of wheat bran and oat hulls to bind copper and zinc using a new chromatographic technique was investigated and compared to a centrifugation method. Also investigated was the bioavailability of copper which had been exogenously bound to wheat bran then fed to mice and rats. Wheat bran bound 6 mg Cu/g fiber when pH was raised to 7. Less binding occurred at lower pHs. Seven mg of zinc bound to wheat bran at pH 5 while only a trace bound at pH less than 2. Oat hulls bound 3 mg Cu/g fiber at pH 5, and less than 1 mg of zinc bound per g of oat hull at pH 6. Binding for both fibers depended on the level of mineral added to the fiber slurry during incubation. But only wheat bran binding capacity was influenced by pH. The two methods used did not compare favorably, in all cases, to the amount of mineral bound to fiber. Copper when bound to wheat bran, was utilized in both species, with differences occurring between species was noted. Rats fed the copper bound diet compared favorably with rats fed the copper-adequate diet as determined by body weight, weight gain, heart weight, liver copper concentration and heart copper concentration. Mice, on the other hand showed similar liver and heart concentrations of copper for mice fed either the copper-bound diet or the copper-adequate diets. The in vitro results showed that binding of copper or zinc to wheat bran occurred at a pH similar to the intestinal pH and wheat bran binds more copper and zinc than oat hulls. Oat hulls may prove to be a better dietary fiber source for those people who need to increase their dietary fiber, because oat hulls do not appear to bind copper or zinc and would not likely impair their absorption. Although wheat bran had a high binding capacity for copper, this binding did not significantly inhibit copper absorption as determined in animal studies suggesting that fiber-mineral binding (at least for copper bound to wheat bran) does not cause mineral deficiency symptoms as claimed by many researchers.

published_or_final_version / Chemistry / Master / Master of Philosophy

Liver glutathione peroxidase activity is affected by changes in selenium (Se) status. To investigate the effect of Se status on GSH-Px protein we prepared antibodies against rat liver GSH-Px and used them in an ELISA. The immunoreactivity of the anti-GSH-Px antibodies against GSH-Px was both tissue and species specific. When rats were depleted of Se, liver GSH-Px activity decreased exponentially to zero with a half-life of 2.8 d. Liver GSH-Px protein also decreased exponentially, but not to zero, with a longer half-life of 5.2 d. Dietary repletion of Se-deficient rats with 0.5 mg Se/kg diet increased GSH-Px protein and activity after 1 d. After 14 d of repletion the levels of GSH-Px protein and activity had plateaued at the levels present in Se-adequate rats. When Se-deficient rats were injected with 15 or 60 ug Se, only rats injected with 60 ug Se and killed 24 h later showed an increase in GSH-Px protein and activity. These results suggest that when Se is limiting, GSH-Px protein and GSH-Px activity are coordinately regulated by the available Se, but in Se-adequacy homeostatic processes control the level of GSH-Px.

The effects of dietary methionine (Met) on the utilization of selenium (Se) from stored tissue Se and dietary selenomethionine (SeMet) for glutathione peroxidase (GSH-Px) synthesis were studied in male rats. Plasma, liver and muscle Se significantly increased when rats were fed 0.5 mg Se/kg diet as SeMet in a Met-deficient diet for 21 d, whereas tissue GSH-Px activities decreased 43-50% during the SeMet supplementation period, suggesting that Se is deposited as SeMet in general body proteins. By calculation, a significant lower percentage of Se was associated with GSH-Px in Met-deficient as compared to Met-supplemented rats. Dietary Met supplementation increased the incorporation of 75Se from 75SeMet into specific rat selenoproteins in addition to liver GSH-Px. Overall, these results suggest that intact SeMet is preferentially incorporated non-specifically into general body proteins in Met-deficient rats, whereas with supplemental Met, more SeMet is degraded and the released Se used for specific selenoprotein synthesis. (Abstract shortened with permission of author.)

No description available.

Arsenic (As) is a carcinogenic agent that is present in varying levels in environmental matrices including water and food. Long term As exposure can lead to skin lesions, peripheral neuropathy, diabetes, renal system effects and cardiovascular diseases. Bio-monitoring of human urine, toenail, serum and cerebrospinal fluid was carried out in this thesis to assess the exposure to arsenic and other trace elements. A multidisciplinary approach based on Inductively Coupled Plasma Mass Spectrometry (ICP-MS), HPLC-ICP-MS and Proton-Nuclear Magnetic Resonance Spectroscopy (1H-NMR) in conjunction with a questionnaire based survey was employed. The impact of rice consumption (a well-known vector of arsenic in the general population) on human urinary As levels was assessed. Results obtained show that the Bangladeshi (UK-B) community in the United Kingdom, who consume ca. 30-fold more rice than the white Caucasians (UK-C), are exposed to a higher level of arsenic. ICP-MS and HPLC-ICP-MS revealed a significant increase in dimethylarsinic acid (DMA) and inorganic arsenic (iAs) species in UK-B compared to UK-C, while cationic compounds were lower in UK-B than in UK-C. DMA and iAs levels in the Bangladeshis were positively correlated to rice consumption. Rice is likely to be responsible for the increase in levels of DMA and iAs in urine of UK-B. The link between this and the disproportional occurrence of diabetes and cardiovascular diseases (CVD) in UK-B needs to be investigated. Another important finding of this study is that the DMA to monomethyl arsenic (MA) ratio, which is often used as an indication of arsenic methylation capacity, should be applied with caution in populations consuming large quantities of rice because variation in the quantity and type of rice eaten may alter the urinary DMA levels and thereby the DMA/MA ratio. Urinary arsenic, selenium, copper and zinc were monitored for a group of Bangladeshis, Pakistanis, Indians and Caucasians living in the UK. The most striking finding was the increase in urinary copper in the UK-B group compared to other ethnicities and to reference values reported for the general UK population. Among the possible reasons for this could include dietary exposure via ethnic food consumption or a change in copper metabolism in the Bangladeshis. High serum copper levels have been correlated to CVD in the US population. In this context, further work is recommended to investigate if there is a relationship between urinary copper and the disproportionately high incidence of CVD in UK Bangladeshis. An approach based on 1H-NMR was used to detect changes in human urinary metabolomic profile as a function of As exposure through different routes. For this, the urine of UK-B, UK-C and a group residing in Bangladesh (BD-B) were monitored. The effects of other factors were explored, including arsenic urinary profile, chewing pan, ethnicity, rice consumption, selenium and diabetes. The three populations show distinctive metabolomic profiles. Urinary arsenic speciation was used in evaluating the effects of arsenic on the metabolomic profile for the UK group. This revealed that the %DMA positively correlates to %N,N-dymethylglycine, %alanine and %betaine. Comparative analysis of the 1H NMR spectra revealed that the BD-B urinary profiles were depleted in the number and quantity of metabolites. Visible signs of lower protein intake and undernourishment emerged from the urinary metabolomic profile of BD-B including a 2.5 decrease in creatinine levels compared to UK-B. Urinary creatinine and the metabolomic profile provide evidence for undernourishment in the BD-B population group that was not evident from previous studies on dietary protein intake in this population performed using food frequency questionnaires. Public health officials might consider also using bio-monitoring studies for nutrient intake rather than solely relying on estimations from food frequency questionnaires. The results reveal the complexity of the subject and pave the way for future studies, highlighting the need for awareness about diet and other specific confounding factors. Multiple Sclerosis (MS) is considered a multifactorial disease and its cause remains unknown. A case-control study on a MS cluster from the volcanic region of Mt. Etna (a natural emitter of geogenic trace elements in the environment) was undertaken. Urine and toenails were monitored for trace elements along with food consumption and life-style habits. Levels of a range of trace elements were reported for the first time for a population living in the Mt. Etna region. No significant differences were found in trace element levels in urine and toenails of MS patients and controls. However, urinary levels of nickel, manganese and selenium were higher than those reported in the literature for the general population from Italy, Germany and the UK. These findings and observations might suggest a role for nickel in the pathology of MS. However, larger studies on the possible role of nickel on MS, and trace elements in general, should be performed. Cerebrospinal fluid (CSF) and some serum from MS patients and controls from the Mt. Etna region were also monitored in this study using ICP-MS. There were significant differences in the trace elemental profile of CSF of MS volunteers and controls, including an increase in arsenic and zinc in the CSF of MS patients. Lead, aluminium, cadmium and molybdenum were significantly increased in the CSF of MS patients as well. In contrast, selenium was lower in MS patients compared to controls. The enrichment of certain trace elements in the CSF of MS patients could be the result of an impairment of the blood brain barrier and tight junction disruption due to MS and its progression, resulting in serum protein leakage and trace elements across the blood–brain barrier. Studies are necessary in the future to identify the chemical species present in the CSF and also determine their role in biological processes including their harmful effects on the brain.

Call number: LD2668 .T4 1957 R46 / Master of Science

Trace elements are highly fractionated during large-scale melting associated with planetary differentiation events. The resulting partition coefficients are used to constrain a range of geological processes and are known to be influenced by pressure, temperature, and compositional changes in crystalline structures. Although recent studies have shown that melt compositional changes affect the partitioning of trace elements, the degree to which these ratios are influenced by alterations in the melt structure, especially with increasing pressure, is poorly constrained due to the difficulty of collecting structural information on bonding environments in situ. A basic understanding of how these elements are incorporated in silicate melts is critical to interpreting early planetary differentiation and crust forming events. This thesis presents results from both x-ray diffraction and absorption techniques on trace element (Y, Zr, Lu and Nd) incorporation in silicate melt structures. The structure of two rare Earth element doped model end member silicate liquids, a highly polymerised haplogranite (Si- Al-Na-K-O) and a less polymerised anorthite-diopside (Si-Al-Mg-Ca-O), have been studied. The results are the first to identify trace rare Earth element (REE) incorporation in silicate melts at high pressure using x-ray diffraction techniques. The local melt structure around Y and Zr in a highly polymerised haplogranite has been studied using x-ray absorption spectroscopy up to 8GPa and 1650 K. Both elements appear to adopt 8-fold coordination within the melt structure with no variation over the pressure range studied. This was also found for the Lu bonding environment in the same composition where the coordination number of Lu-O was found to be 8, with a bond distance rLu-O = 2:36A in the haplogranite melt. At low pressures, < 5GPa, the bonding environment of Lu-O was found to be dependent on composition with coordination decreasing to CNLu-O = 6 and rLu-O = 2:29A in the anorthite-diopside melt. This compositional variance in coordination number at low pressure is consistent with observations made for Y-O in glasses at ambient conditions and is coincident with a dramatic increase in the partition coefficients previously observed for rare Earth elements (REE) with increasing melt polymerisation. However, an abrupt change in both Lu-O coordination and bond distance is observed at 5GPa in the anorthite-diopside melt, with CNLu-O increasing from 6 to 8-fold and rLu-O from 2.29 to 2.39A. This occurs over a similar pressure range where a reduction in the reported heavy REE partition coefficients is observed. X-ray diffraction experiments up to 60GPa and 2000K have also been performed on the incorporation of the larger light REE, Nd, in basaltic-like melts. The results presented show that incorporation within the anorthite-diopside composition is dependent on the size of the REE. Nd-O initially shows the same 6-fold coordination as Lu-O at ambient conditions, although the change to 8-fold coordination appears to occur at considerably lower pressure between 1-2GPa. Coordination change in both cases can be attributed to collapse of the silicate network and an increase in the average number of available 'crystal like' sites in the liquid, with ionic radius of the REE controlling at which pressure the preference for these sites in the melt occurs. Published mineral-melt partition coefficients for Nd, with major mineral phases such as garnet, show very little variation with pressure, in contrast to Lu. The difference in structural incorporation of Lu and Nd in the melts presented in this thesis could explain this partitioning behaviour. Overall this thesis highlights that important structural changes of the trace element bonding environment in silicate melts occur with both compositional variation and pressure. Melt structural changes with pressure cannot be neglected in predictive models of trace element behaviour, and using a single melt term to normalise the effects of melt on trace element partitioning will not accurately predict partitioning behaviour at depth during magma formation or differentiation.