Phloem transport of arsenic species from flag leaf to grain during grain filling

Strategies to reduce arsenic (As) in rice grain, below concentrations that represent a serious human health concern, require that the mechanisms of As accumulation within grain be established. Therefore, retranslocation of As species from flag leaves into filling rice grain was investigated.

Arsenic species were delivered through cut flag leaves during grain fill. Spatial unloading within grains was investigated using synchrotron X-ray fluorescence (SXRF) microtomography. Additionally, the effect of germanic acid (a silicic acid analog) on grain As accumulation in arsenite-treated panicles was examined.

Dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) were extremely efficiently retranslocated from flag leaves to rice grain; arsenate was poorly retranslocated, and was rapidly reduced to arsenite within flag leaves; arsenite displayed no retranslocation. Within grains, DMA rapidly dispersed while MMA and inorganic As remained close to the entry point. Germanic acid addition did not affect grain As in arsenite-treated panicles. Three-dimensional SXRF microtomography gave further information on arsenite localization in the ovular vascular trace (OVT) of rice grains.

These results demonstrate that inorganic As is poorly remobilized, while organic species are readily remobilized, from leaves to grain. Stem translocation of inorganic As may not rely solely on silicic acid transporters.

Selenium Characterization in the Global Rice Supply Chain

For up to 1 billion people worldwide, insufficient dietary intake of selenium (Se) is a serious health constraint Cereals are the dominant Se source for those on low protein diets, as typified by the global malnourished population. With crop Se content constrained largely by underlying geology, regional soil Se variations are often mirrored by their locally grown staples. Despite this, the Se concentrations of much of the world's rice, the mainstay of so many, is poorly characterized, for both total Se content and Se speciation. In this study, 1092 samples of market sourced polished rice were obtained. The sampled rice encompassed dominant rice producing and exporting countries. Rice from the U.S. and India were found to be the most enriched, while mean average levels were lowest in Egyptian rice: similar to 32-fold less than their North American equivalents. By weighting country averages by contribution to either global production or export, modeled baseline values for both were produced. Based on a daily rice consumption of 300 g day(-1), around 75% of the grains from the production and export pools would fail to provide 70% of daily recommended Se intakes. Furthermore, Se localization and speciation characterization using X-ray fluorescence (mu-XRF) and X-ray absorption near edge structure (mu-XANES) techniques were investigated in a Se-rich sample. The results revealed that the large majority of Se in the endosperm was present in organic forms.

Inorganic arsenic in rice bran and its products are an order of magnitude higher than in bulk grain

Rice is more elevated in arsenic than all other grain crops tested to date, with whole grain (brown) rice having higher arsenic levels than polished (white). It is reported here that rice bran, both commercially purchased and specifically milled for this study, have levels of inorganic arsenic, a nonthreshold, class 1 carcinogen, reaching concentrations of approximately 1 mg/kg dry weight, around 10-20 fold higher than concentrations found in bulk grain. Although pure rice bran is used as a health food supplement, perhaps of more concern is rice bran solubles, which are marketed as a superfood and as a supplement to malnourished children in international aid programs. Five rice bran solubles products were tested, sourced from the United States and Japan, and were found to have 0.61-1.9 mg/kg inorganic arsenic. Manufactures recommend approximately 20 g servings of the rice bran solubles per day, which equates to a 0.012-0.038 mg intake of inorganic arsenic. There are no maximum concentration levels (MCLs) set for arsenic or its species in food stuffs. EU and U.S. water regulations, set at 0.01 mg/L total or inorganic arsenic, respectively, are based on the assumption that 1 L of water per day is consumed, i.e., 0.01 mg of arsenic/ day. At the manufacturers recommended rice bran solubles consumption rate, inorganic arsenic intake exceeds 0.01 mg/ day, remembering that rice bran solubles are targeted at malnourished children and that actual risk is based on mg kg(-1) day(-1) intake.

Survey of arsenic and its speciation in rice products such as breakfast cereals, rice crackers and Japanese rice condiments

Rice has been demonstrated to be one of the major contributors to arsenic (As) in human diets in addition to drinking water, but little is known about rice products as an additional source of As exposure. Rice products were analyzed for total As and a subset of samples were measured for arsenic speciation using high performance liquid chromatography interfaced with inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). A wide range of rice products had total and inorganic arsenic levels that typified those found in rice grain including, crisped rice, puffed rice, rice crackers, rice noodles and a range of Japanese rice condiments as well as rice products targeted at the macrobiotic, vegan, lactose intolerant and gluten intolerance food market. Most As in rice products are inorganic As (75.2-90.1%). This study provides a wider appreciation of how inorganic arsenic derived from rice products enters the human diet. (C) 2008 Elsevier Ltd. All rights reserved.

Inorganic arsenic levels in rice milk exceed EU and US drinking water standards

Under EU legislation, total arsenic levels in drinking water should not exceed 10 microg l(-1), while in the US this figure is set at 10 microg l(-1) inorganic arsenic. All rice milk samples analysed in a supermarket survey (n = 19) would fail the EU limit with up to 3 times this concentration recorded, while out of the subset that had arsenic species determined (n = 15), 80% had inorganic arsenic levels above 10 microg l(-1), with the remaining 3 samples approaching this value. It is a point for discussion whether rice milk is seen as a water substitute or as a food, there are no EU or US food standards highlighting the disparity between water and food regulations in this respect.

The contribution of N₂O₃ to the cytotoxicity of the nitric oxide donor DETA/NO: an emerging role for S-nitrosylation

The relationship between the biological activity of NO and its chemistry is complex. The objectives of this study were to investigate the influence of oxygen tension on the cytotoxicity of the NO• donor DETA/NO and to determine the effects of oxygen tension on the key RNS (reactive nitrogen species) responsible for any subsequent toxicity. The findings presented in this study indicate that the DETA/NO-mediated cytotoxic effects were enhanced under hypoxic conditions. Further investigations revealed that neither ONOO⁻ (peroxynitrite) nor nitroxyl was generated. Fluorimetric analysis in the presence of scavengers suggest for the first time that another RNS, dinitrogen trioxide may be responsible for the cytotoxicity with DETA/NO. Results showed destabilization of HIF (hypoxia inducible factor)-1α and depletion of GSH levels following the treatment with DETA/NO under hypoxia, which renders cells more susceptible to DETA/NO cytotoxicity, and could account for another mechanism of DETA/NO cytotoxicity under hypoxia. In addition, there was significant accumulation of nuclear p53, which showed that p53 itself might be a target for S-nitrosylation following the treatment with DETA/NO. Both the intrinsic apoptotic pathway and the Fas extrinsic apoptotic pathway were also activated. Finally, GAPDH (glyceraldehyde-3-phosphate dehydrogenase) is another important S-nitrosylated protein that may possibly play a key role in DETA/NO-mediated apoptosis and cytotoxicity. Therefore this study elucidates further mechanisms of DETA/NO mediated cytotoxicity with respect to S-nitrosylation that is emerging as a key player in the signalling and detection of DETA/NO-modified proteins in the tumour microenvironment.

Guideline for the diagnosis and management of myelofibrosis

The guideline group regarding the diagnosis and management of myelofibrosis was selected to be representative of UK-based medical experts, together with a contribution from a single expert from the USA. MEDLINE and EMBASE were searched systematically for publications in English from 1966 until August 2011 using a variety of key words. The writing group produced the draft guideline, which was subsequently revised by consensus of the members of the General Haematology and Haemato-oncology Task Forces of the British Committee for Standards in Haematology (BCSH). The guideline was then reviewed by a sounding board of UK haematologists, the BCSH and the British Society for Haematology Committee and comments incorporated where appropriate. The criteria used to state levels and grades of evidence are as outlined in the Procedure for Guidelines commissioned by the BCSH; the 'GRADE' system was used to score strength and quality of evidence. The objective of this guideline is to provide healthcare professionals with clear guidance on the investigation and management of primary myelofibrosis, as well as post-polycythaemic myelofibrosis (post-PV MF) and post-thrombocythemic myelofibrosis (post-ET MF) in both adult and paediatric patients.

Effect of organic matter amendment, arsenic amendment and water management regime on rice grain arsenic species

Arsenic accumulation in rice grain has been identified as a major problem in some regions of Asia. A study was conducted to investigate the effect of increased organic matter in the soil on the release of arsenic into soil pore water and accumulation of arsenic species within rice grain. It was observed that high concentrations of soil arsenic and organic matter caused a reduction in plant growth and delayed flowering time. Total grain arsenic accumulation was higher in the plants grown in high soil arsenic in combination with high organic matter, with an increase in the percentage of organic arsenic species observed. The results indicate that the application of organic matter should be done with caution in paddy soils which have high soil arsenic, as this may lead to an increase in accumulation of arsenic within rice grains. Results also confirm that flooding conditions substantially increase grain arsenic. (c) 2013 Elsevier Ltd. All rights reserved.