Selective mineral transport barriers at Cuscuta-host infection sites.

The uptake of inorganic nutrients by rootless parasitic plants, which depend on host connections for all nutrient supplies, is largely uncharted. Using X-ray fluorescence spectroscopy (XRF), we analyzed the element composition of macro- and micronutrients at infection sites of the parasitic angiosperm Cuscuta reflexa growing on hosts of the genus Pelargonium. Imaging methods combining XRF with 2-D or 3-D (confocal) microscopy show that most of the measured elements are present at similar concentrations in the parasite compared to the host. However, calcium and strontium levels drop pronouncedly at the host/parasite interface, and manganese appears to accumulate in the host tissue surrounding the interface. Chlorine is present in the haustorium at similar levels as in the host tissue but is decreased in the stem of the parasite. Thus, our observations indicate a restricted uptake of calcium, strontium, manganese and chlorine by the parasite. Xylem-mobile dyes, which can probe for xylem connectivity between host and parasite, provided evidence for an interspecies xylem flow, which in theory would be expected to carry all of the elements indiscriminately. We thus conclude that inorganic nutrient uptake by the parasite Cuscuta is regulated by specific selective barriers whose existence has evaded detection until now.

The choice of biomarkers determines the selenium status in young German vegans and vegetarians.

Daily nutrition varies considerably among individuals. The number of vegetarians is increasing continuously due to ethical, environmental, religious or other reasons. There is growing concern over their nutritional status with respect to micronutrient deficiencies. Among the essential trace elements, Se is of prime importance as it is part of the active site in selenoproteins. European soil and plants are relatively poor sources of Se, while farm animals are generally supplemented with Se in order to improve their health and avoid deficiency syndromes. We therefore wondered whether German vegetarians display a measurable Se deficiency. To this end, we compared young vegetarians (n 54) and omnivores (n 53). We assessed their Se status by measuring extracellular glutathione peroxidase 3 (GPX3) activity, and concentrations of total serum Se and circulating Se-transport protein selenoprotein P (SEPP). GPX3 activities were not different between the groups, whereas both total Se and SEPP concentrations were reduced to 79.5 and 71.2 % in vegetarians compared with omnivores. When splitting the group of vegetarians into vegans (n 26) and vegetarians consuming egg and milk products (n 28), analyses of the Se-dependent biomarkers did not reveal significant differences. We conclude that low serum Se is mirrored by circulating SEPP concentrations, but not by GPX3 activities in marginally supplied individuals. The specific dietary Se sources, divergent metabolic routes of selenomethionine v. selenocysteine and the different saturation kinetics of GPX3 and SEPP probably underlie our contradictory findings. Whether German vegetarians and vegans need to be considered as a Se-deficient group depends on the biomarker chosen.

Publisher Correction: Pattern of Altered Plasma Elemental Phosphorus, Calcium, Zinc, and Iron in Alzheimer's Disease.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Method for measurement of serum copper, zinc and selenium using total reflection X-ray fluorescence spectroscopy on the PICOFOX analyser: Validation and comparison with atomic absorption spectroscopy and inductively coupled plasma mass spectrometry.

BACKGROUND: Total reflection X-ray fluorescence is a comparably new method for the measurement of trace elements in biological samples. METHODS: Results obtained by total reflection X-ray fluorescence were compared to atomic absorption spectroscopy for Cu and Zn and inductively coupled plasma mass spectrometry for Cu, Zn and Se in patient serum. The total reflection X-ray fluorescence assay was characterized for accuracy; recovery; intra- and inter-assay imprecision (using patients' samples, external quality assurance and quality control materials); limit of blank; limit of detection; linearity; interference and stability of prepared samples. RESULTS: Minimal sample preparation is required for total reflection X-ray fluorescence and simultaneous multi-elemental analysis is possible in clinical samples. There was a small positive bias for Cu and Zn measurements using total reflection X-ray fluorescence compared to atomic absorption spectroscopy and inductively coupled plasma mass spectrometry and a significant negative bias for Se measurements by total reflection X-ray fluorescence relative to inductively coupled plasma mass spectrometry. Recovery, imprecision and linearity were acceptable. The limit of detection was shown to be 1.2 µmol/L for serum Cu, 1.8 µmol/L for serum Zn and 0.2 µmol/L for serum Se. CONCLUSIONS: Measurement of Cu and Zn in serum samples using total reflection X-ray fluorescence would be a viable alternative to atomic absorption spectroscopy or inductively coupled plasma mass spectrometry. The volatility of some Se compounds results in lower Se results being reported using total reflection X-ray fluorescence and further work would be necessary to identify whether total reflection X-ray fluorescence has an acceptable clinical sensitivity and specificity for the assessment of Se deficiency. Measurement of copper, zinc and selenium on whole blood samples is possible using total reflection X-ray fluorescence which may provide a more accurate assessment of trace element deficiency for patients with an acute phase response.

Pattern of Altered Plasma Elemental Phosphorus, Calcium, Zinc, and Iron in Alzheimer's Disease.

Metal/mineral dyshomeostasis has been implicated in the development of Alzheimer's disease (AD). The aim of the study was to investigate the difference in absolute and percentage levels of plasma phosphorus, calcium, iron, zinc, copper, selenium in cognitively normal (CN) and AD subjects. Total reflection X-ray fluorescence (TXRF) spectroscopy was used to detect plasma metals/minerals in CN and AD subjects (n = 44 per group). TXRF detected significantly increased plasma levels of phosphorus (p = 1.33 × 10-12) and calcium (p = 0.025) in AD compared to CN subjects, with higher phosphorus/calcium (p = 2.55 × 10-14) ratio in the former. Percentage concentrations calculated for phosphorus, calcium, iron, zinc, copper, selenium by dividing the concentration of each element by the total concentration of these elements and multiplying by 100%, demonstrated phosphorus was higher in AD compared to CN subjects, while calcium, iron, zinc, copper and selenium were lower in AD subjects, with area under the curves as high as 0.937 (p = 6 × 10-5) computed from receiver operating curves. With exclusion of high levels of phosphorus and calcium from percentage calculations, iron levels remained low in AD whereas zinc was higher in AD, and copper and selenium levels were similar. We demonstrate altered distribution of elements in the plasma of AD subjects with high interdependencies between elemental levels and propose the potential of TXRF measurements for disease monitoring.

Level of minerals and trace elements in the urine of the participants of mountain ultra-marathon race.

The aim of the present study was to explore impact of endurance exercise on urinary level of minerals and trace elements as well as on some oxidative stress and biochemical parameters. Urine samples were collected from participants (n=21) of mountain ultra-marathon race (53km; Medvednica, Zagreb, Croatia), before (baseline value), immediately after, 12h and 24h after the race. In urine samples level of minerals (Ca, P, K and Na) and trace elements (Se, Zn, Mn, Cu, Fe and Co) were assessed using the bench top Total reflection X-ray Fluorescence (TXRF) spectrometer. Oxidative stress was determined as level of malondialdehyde (MDA). Immediately after the race level of minerals, trace elements, MDA, creatinine, ketones, erythrocytes and specific gravity increased compared to their baseline value. In 24h follow-up trace elements involved in antioxidant defence, MDA and biochemical parameters returned to their baseline values, Cu and Co remained increased as after the race, Fe and K tended to return to baseline values while Ca, P and Na continued to increase. Mountain ultra-marathon resulted in alteration of physiologically important minerals and trace elements that for some minerals and trace elements persist, indicating their involvement in recovery processes. However, due to their loss in urine, level of minerals and trace elements in athletes participating in endurance exercise should be monitored.

Environmental trace-element analysis using a benchtop total reflection X-ray fluorescence spectrometer.

Total reflection X-ray fluorescence (TXRF) analysis is an established technique for trace-element analysis in various types of samples. Though expensive large-scale systems restricted the applications in the past, in this study the capability of a benchtop system for trace elemental analysis is reported. The suitability of this system for the mobile on-site analysis of heavy metal contaminated soils and sediments is reported as well as the possibilities and restrictions of TXRF for additional applications, including trace-element analysis of water, glass and biological samples.