Zinc Homeostasis and isotopic fractionation in plants: a review

Aims Recent advances in mass spectrometry have dem- onstrated that higher plants discriminate stable Zn iso- topes during uptake and translocation depending on environmental conditions and physiological status of the plant. Stable Zn isotopes have emerged as a prom- ising tool to characterize the plants response to inade- quate Zn supply. The aim of this review is to build a comprehensive model linking Zn homeostasis and Zn isotopic fractionation in plants and advance our current view of Zn homeostasis and interaction with other micronutrients. Methods The distribution of stable Zn isotopes in plants and the most likely causes of fractionation are reviewed, and the interactions with micronutrients Fe, Cu, and Ni are discussed. Results The main sources of Zn fractionation in plants are i) adsorption, ii) low- and high-affinity transport phenomena, iii) speciation, iv) compartmentalization, and v) diffusion. We propose a model for Zn fraction- ation during uptake and radial transport in the roots, root-to-shoot transport, and remobilization. Conclusions Future work should concentrate on better understanding the molecular mechanisms underlying the fractionations as this will be the key to future devel- opment of this novel isotope system. A combination of stable isotopes and speciation analyses might prove a powerful tool for plant nutrition and homeostasis studies

Zinc isotopic fractionation in Phragmites australis in response to toxic levels of zinc

Stable isotope signature of Zn have shown great promise in elucidating changes in uptake and translocation mechanisms of this metal in plants during environmental changes. Here we tested this potential by investigating the effect of high Zn concentrations on the isotopic fractionation patterns of Phragmites australis (Cav.) Trin. ex Steud. Plants were grown for 40 d in a nutritive solution containing 3.2 µM (sufficient) or 2 mM (toxic) Zn. The Zn isotopic composition of roots, rhizomes, shoots and leaves was analysed. Stems and leaves were sampled at different heights to evaluate the effect of long-distance transport on Zn fractionation. During Zn sufficiency, roots, rhizomes and shoots were isotopically heavy (δ66ZnJMC Lyon = 0.2¿) while the youngest leaves were isotopically light (-0.5 ¿). During Zn excess, roots were still isotopically heavier (δ66Zn = 0.5 ¿) and the rest of the plant was isotopically light (up to -0.5 ¿). The enrichment of heavy isotopes at the roots was attributed to Zn uptake mediated by transporter proteins under Zn sufficient conditions and to chelation and compartmentation in Zn excess. The isotopically lighter Zn in shoots and leaves is consistent with long distance root to shoot transport. The tolerance response of P. australis increased the range of Zn fractionation within the plant and with respect to the environment

Zinc Homeostasis and isotopic fractionation in plants: a review

Aims Recent advances in mass spectrometry have dem- onstrated that higher plants discriminate stable Zn iso- topes during uptake and translocation depending on environmental conditions and physiological status of the plant. Stable Zn isotopes have emerged as a prom- ising tool to characterize the plants response to inade- quate Zn supply. The aim of this review is to build a comprehensive model linking Zn homeostasis and Zn isotopic fractionation in plants and advance our current view of Zn homeostasis and interaction with other micronutrients. Methods The distribution of stable Zn isotopes in plants and the most likely causes of fractionation are reviewed, and the interactions with micronutrients Fe, Cu, and Ni are discussed. Results The main sources of Zn fractionation in plants are i) adsorption, ii) low- and high-affinity transport phenomena, iii) speciation, iv) compartmentalization, and v) diffusion. We propose a model for Zn fraction- ation during uptake and radial transport in the roots, root-to-shoot transport, and remobilization. Conclusions Future work should concentrate on better understanding the molecular mechanisms underlying the fractionations as this will be the key to future devel- opment of this novel isotope system. A combination of stable isotopes and speciation analyses might prove a powerful tool for plant nutrition and homeostasis studies

Effect of reduced z-axis scan coverage on diagnostic performance and radiation dose of neck computed tomography in patients with suspected cervical abscess

Purpose: To evaluate the effect of reduced z-axis scan coverage on diagnostic performance and radiation dose of neck CT in patients with suspected cervical abscess. Methods: Fifty-one patients with suspected cervical abscess were included and underwent contrast-enhanced neck CT on a 2nd or 3rd generation dual-source CT system. Image acquisition ranged from the aortic arch to the upper roof of the frontal sinuses (CTstd). Subsequently, series with reduced z-axis coverage (CTred) were reconstructed starting at the aortic arch up to the orbital floor. CTstd and CTred were independently assessed by two radiologists for the presence/absence of cervical abscesses and for incidental and alternative findings. In addition, diagnostic accuracy for the depiction of the cervical abscesses was calculated for both readers. Furthermore, DLP (dose-length-product), effective dose (ED) and organ doses were calculated and compared for CTred and CTstd, using a commercially available dose management platform. Results: A total of 41 abscesses and 3 incidental/alternative findings were identified in CTstd. All abscesses and incidental/alternative findings could also be detected on CTred resulting in a sensitivity and specificity of 1.0 for both readers. DLP, ED and organ doses of the brain, the eye lenses, the red bone marrow and the salivary glands of CTred were significantly lower than for CTstd (p<0.001). Conclusions: Reducing z-axis coverage of neck CT allows for a significant reduction of effective dose and organ doses at similar diagnostic performance as compared to CTstd

Didactic Strategy for the Teaching of Isotope Mixing Models for Stable Isotopes Relevant to Biogeochemistry Based on the Analogy with Color Composition

The continuous advances in mass spectrometry techniques have pushed forward the frontiers of all branches of the isotope biogeochemistry field. In environmental studies, different isotope ratios as determined in different reservoirs offer the opportunity, for example, to identify pollution sources and to trace metal fluxes within the trophic web and in dietary studies. Despite its relevance, trace metal isotope biogeochemistry is infrequently taught in undergraduate courses because it demands a rather high level of complexity of teaching strategies and abstraction capacity from students. Additionally, available didactic material for introducing mixing source modeling with stable isotopes relevant to biogeochemistry is scarce. In this context, the present study applies a visually appealing didactic strategy based on the analogy between colors (analog domain) and isotopic compositions (target domain), in order to encourage and assist the teaching–learning processes of this new subject in environmental science and chemistry classes. We demonstrate how familiar and simple concepts can be applied for introducing challenging subjects. In a setting that restricts in-person academic activities such as during a pandemic, the development of appealing visual approaches is imperative to engage students during online classes. The didactic strategy proposed herein was put to the test during remotely taught classes on the topic of “Environmental Impact Assessment Methodology” (winter 2021, 18 students) and “Environmental Contamination” (summer 2020, 18 students, and winter 2021, 20 students) of the Postgraduate Program in Geochemistry at the Fluminense Federal University (Rio de Janeiro, Brazil). Students’ feedback was very positive; they found our approach stimulating, and it helped them to better visualize, understand, and interpret the targeted learning outcomes

Application of Zn Isotope Compositions in Oysters to Monitor and Quantify Anthropogenic Zn Bioaccumulation in Marine Environments over Four Decades: A “Mussel Watch Program” Upgrade

The application of zinc (Zn) isotope compositions in bivalve organisms to quantify anthropogenic Zn bioaccumulation in marine biota is of great interest to environmental marine management programs such as the “Mussel Watch Program”. Field studies, however, are urgently needed to test its practical value. To this end, we investigated Zn isotope variations in the oyster Crassostrea gigas collected over four decades near the Loire estuary (France), where previous geochemical studies provided evidence for a regionally uniform but temporally variable metal contamination. We show that the Zn temporal isotope profile of oysters matches that of the sedimentary records with an isotope offset of approximately +0.5–0.7‰, tentatively attributed to compromised estuarine processes and trophic transfer. A Zn isotope model for quantifying anthropogenic Zn bioaccumulation suggests an overall decrease in anthropogenic estuarine Zn levels over the past 40 years. This first successful application of Zn isotope ratios in a bivalve species to quantify anthropogenic Zn bioaccumulation confirms their utility for supporting environmental management strategies in marine biomonitoring programs

Dose values.

<p>Dose values.</p

Scout image and the most cranial as well as most caudal slices of CT_red and CT_std of a 33 year-old patient with a parapharyngeal abscess.

<p>The white lines in the scout image indicate the cranial (CT_std—solid line; CT_red—dashed line) and caudal (solid line for both, CT_std and CT_red) margin of the scan range. Effective dose could be reduced by approximately 10% (2.2 mSv for CT_std and 2.0 mSv for CT_red).</p