Uptake, translocation and transformation of arsenate and arsenite in sunflower (Helianthus annuus):formation of arsenic-phytochelatin complexes during exposure to high arsenic concentrations

The aim of the study was to determine the time-dependent formation of arsenic-phytochelatin (As-PC) complexes in the roots, stems and leaves of an arsenic-nontolerant plant (Helianthus annuus) during exposure to 66 mol l(-1) arsenite (As(III)) or arsenate (As(V)). We used our previously developed method of simultaneous element-specific (inductively coupled plasma mass spectrometry, ICP-MS) and molecular-specific (electrospray-ionization mass spectrometry, ES-MS) detection systems interfaced with a suitable chromatographic column and eluent conditions, which enabled us to identify and quantify As-PC complexes directly. Roots of As-exposed H. annuus contained up to 14 different arsenic species, including the complex of arsenite with two (gamma-Glu-Cys)(2)-Gly molecules [As((III))-(PC(2))(2)], the newly identified monomethylarsonic phytochelatin-2 or (gamma-Glu-Cys)(2)-Gly CH(3)As (MA((III))-PC(2)) and at least eight not yet identified species. The complex of arsenite with (gamma-Glu-Cys)(3)-Gly (As((III))-PC(3)) and the complex of arsenite with glutathione (GSH) and (gamma-Glu-Cys)(2)-Gly (GS-As((III))-PC(2)) were present in all samples (roots, stems and leaves) taken from plants exposed to As. The GS-As((III))-PC(2) complex was the dominant complex after 1 h of exposure. As((III))-PC(3) became the predominant As-PC complex after 3 h, binding up to 40% of the As present in the exposed plants. No As-PC complexes were found in sap (mainly xylem sap from the root system), in contrast to roots, stems and leaves, which is unequivocal evidence that As-PC complexes are not involved in the translocation of As from root to leaves of H. annuus.

Genetic optimism:Framing genes and mental illness in the news

Over the past two decades the pace and specificity of discoveries associating genetics with mental illness has accelerated, which is reflected in an increase in news coverage about the genetics of mental disorder. The news media is a major source of public understanding of genetics and a strong influence on public discourse. This paper examines the news coverage of genetics and mental illness (i.e., bipolar illness and schizophrenia) over a 25 year period, emphasizing the peak period of 1987-1994. Using a sample of 110 news stories from 5 major American newspapers and 3 news magazines, we identify the frame of "genetic optimism" which dominated the reporting of genetics and mental illness beginning in the mid-1980s. The structure of the frame is comprised of 3 elements: a gene for the disorder exists; it will be found; and it will be good. New discoveries of genes were announced with great fanfare, but the most promising claims could not be replicated or were retracted in short order. Despite these disconfirmations, genetic optimism persisted in subsequent news stories. While the scientific accuracy of the gene stories is high, the genetic optimism frame distorts some of the findings, misrepresents and reifies the impact of genes on mental disorder, and leaves no space for critics or an examination of potential negative impacts. The stances of reporters, scientists and editors may all in different ways contribute to the perpetuation of genetic optimism. Genetic optimism presents an overly sanguine picture of the state of genetics; as we enter the genetic age it is important to balance the extraneous "hype and hope" contained in news stories of genetics and mental illness.

Mutagenesis of RpoE-like sigma factor genes in Bdellovibrio reveals differential control of groEL and two groES genes

BACKGROUND: Bdellovibrio bacteriovorus HD100 must regulate genes in response to a variety of environmental conditions as it enters, preys upon and leaves other bacteria, or grows axenically without prey. In addition to "housekeeping" sigma factors, its genome encodes several alternate sigma factors, including 2 Group IV-RpoE-like proteins, which may be involved in the complex regulation of its predatory lifestyle.

RESULTS: We find that one sigma factor gene, bd3314, cannot be deleted from Bdellovibrio in either predatory or prey-independent growth states, and is therefore possibly essential, likely being an alternate sigma 70. Deletion of one of two Group IV-like sigma factor genes, bd0881, affects flagellar gene regulation and results in less efficient predation, although not due to motility changes; deletion of the second, bd0743, showed that it normally represses chaperone gene expression and intriguingly we find an alternative groES gene is expressed at timepoints in the predatory cycle where intensive protein synthesis at Bdellovibrio septation, prior to prey lysis, will be occurring.

CONCLUSIONS: We have taken the first step in understanding how alternate sigma factors regulate different processes in the predatory lifecycle of Bdellovibrio and discovered that alternate chaperones regulated by one of them are expressed at different stages of the lifecycle.

Assessing the image quality of pelvic MR images acquired with a flat couch for radiotherapy treatment planning

Objectives: To improve the integration of MRI with radiotherapy treatment planning, our department fabricated a flat couch top for our MR scanner. Setting up using this couch top meant that the patients were physically higher up in the scanner and, posteriorly, a gap was introduced between the patient and radiofrequency coil.

3D deflagration simulations leaving bound remnants:A model for 2002cx-like Type Ia supernovae

2002cx-like supernovae are a sub-class of sub-luminous Type Ia supernovae (SNe). Their light curves and spectra are characterized by distinct features that indicate strong mixing of the explosion ejecta. Pure turbulent deflagrations have been shown to produce such mixed ejecta. Here, we present hydrodynamics, nucleosynthesis and radiative-transfer calculations for a 3D full-star deflagration of a Chandrasekhar-mass white dwarf. Our model is able to reproduce the characteristic observational features of SN 2005hk (a prototypical 2002cx-like supernova), not only in the optical, but also in the near-infrared. For that purpose we present, for the first time, five near-infrared spectra of SN 2005hk from -0.2 to 26.6 d with respect to B-band maximum. Since our model burns only small parts of the initial white dwarf, it fails to completely unbind the white dwarf and leaves behind a bound remnant of ~1.03Mconsisting mainly of unburned carbon and oxygen, but also enriched by some amount of intermediate-mass and iron-group elements from the explosion products that fall back on the remnant.We discuss possibilities for detecting this bound remnant and how it might influence the late-time observables of 2002cx-like SNe. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

The Deubiquitinating Enzyme USP17 Blocks N-Ras Membrane Trafficking and Activation but Leaves K-Ras Unaffected

The proto-oncogenic Ras isoforms (H, N, and K) have a C-terminal CAAX motif and undergo the same post-translational processing steps, although they traffic to the plasma membrane through different routes. Previously, we have shown that overexpression of the deubiquitinating enzyme USP17 inhibits H-Ras localization to the plasma membrane. Now we report that whereas H-Ras and N-Ras were unable to localize to the plasma membrane in the presence of USP17, K-Ras4b localization was unaffected. EGF stimulation was unable to induce N-Ras membrane localization in USP17-expressing cells. In addition, N-Ras activity and downstream signaling through the MAPK MEK/ERK and PI3K/JNK pathways were blunted. However, we still detected abundant N-Ras localization at the ER and Golgi in USP17-expressing cells. Collectively, our data showed that the deubiquitinating enzyme USP17 blocks EGF-induced N-Ras membrane trafficking and activation, but left K-Ras unaffected.

Genetic mapping of the rice ionome in leaves and grain:Identification of QTLs for 17 elements including arsenic, cadmium, iron and selenium

Research into the composition of cereal grains is motivated by increased interest in food quality. Here multi-element analysis is conducted on leaves and grain of the Bala x Azucena rice mapping population grown in the field. Quantitative trait loci (QTLs) for the concentration of 17 elements were detected, revealing 36 QTLs for leaves and 41 for grains. Epistasis was detected for most elements. There was very little correlation between leaf and grain element concentrations. For selenium, lead, phosphorus and magnesium QTLs were detected in the same location for both tissues. In general, there were no major QTL clusters, suggesting separate regulation of each element. QTLs for grain iron, zinc, molybdenum and selenium are potential targets for marker assisted selection to improve seed nutritional quality. An epistatic interaction for grain arsenic also looks promising to decrease the concentration of this carcinogenic element. © Springer Science+Business Media B.V. 2009.