Arsenic distribution and speciation in the fronds of the hyperaccumulator Pteris vittata

Pteris vittata is the first plant reported to be a hyperaccumulator of arsenic (As), and little is known about the mechanisms of As hyperaccumulation in this plant. Arsenic distribution at the whole plant (fronds) and cellular level was investigated using chemical analyses and energy dispersive X-ray microanalyses (EDXA). Speciation of As in the fronds was determined using X-ray absorption near edge spectroscopy (XANES) analyses. The majority of As was found in the pinnae (96% of total As). The concentration of As in pinnae decreased from the base to the apex of the fronds. Arsenic concentrations in spores and midribs were much lower than in the pinnae. EDXA analyses revealed that As was compartmentalized mainly in the upper and lower epidermal cells, probably in the vacuoles. The distribution pattern of potassium was similar to As, whereas other elements (Ca, Cl, K, Mg, P and S) were distributed differently. XANES analyses showed that approximately 75% of the As in fronds was present in the As(III) oxidation state and the remaining as As(V)

Adoptive transfer of regulatory T cells.

<p>Naïve mice that were transferred with different cells, were subsequently sensitized with CMP and CT, and finally challenged with CMP_ig (n = 5/group). <b>A</b>, Transfer of <i>in vitro</i>-differentiated Treg. Sorted naïve CD4⁺CD25^- spleen cells were stimulated with a-CD3/a-CD28, IL-2 and TGF-β for 5 days. CD25⁺FoxP3⁺ cells gated on CD4⁺ lymphocytes were quantified (histogram) by flow cytometry and transferred to naïve receptor mice. <b>B,</b> Skin test, symptoms scored following the oral challenge and serum CMP-specific IgE in receptor mice. a) Control mice: naïve mice only received PBS_iv; b) Control mice: naïve mice received PBS_iv and were sensitized; c) naïve mice received differentiated-Treg and were sensitized. <b>C,</b><i>In vivo</i>-induced Treg in mice that were orally given daily dose of CMP and then sensitized (CMP_prev). As control, donor mice received daily dose of PBS_ig and then were sensitized (PBS_prev). MLN cells were isolated from donor mice and FoxP3⁺ cells (gated from CD4⁺CD25⁺ lymphocytes) were evaluated and quantified by flow cytometry. <b>D</b>, CD25 depletion was performed on MLN cells and evaluated by flow cytometry. Depleted and not depleted cells were adoptively transferred to receptor mice, which were then sensitized. <b>E</b>, Skin test, symptoms scored following the oral challenge and serum CMP-specific IgE in receptor animals. a) Control mice: naïve recipient mice received PBS_iv and then were sensitized; b) Control mice: receptor mice that received MLN cells depleted with a-CD25 isolated from donor PBS_prev animals and then were sensitized; c) Receptor mice that received MLN cells depleted with a-CD25 isolated from donor CMP_prev animals and then were sensitized; d) Receptor mice that received MLN cells from PBS_prev animals treated with isotype control antibody and then were sensitized; e) Receptor mice that received MLN cells from CMP_prev animals treated with isotype control antibody and then were sensitized. Results are representative of two independent experiments with similar results. Two-way ANOVA was used because all the data had normal distribution and equal variances <i>***P</i><0.001, <i>**P</i><0.01, <i>*P</i><0.05.</p