Certain arsenic and selenium compounds show a remarkable mutual cancelation of toxicities, where a lethal dose of one can be voided by an equimolar and otherwise lethal dose of the other. It is now well established that the molecular basis of this antagonism is the formation and biliary excretion of seleno bis-(S-glutathionyl) arsinium anion [(GS)2AsSe](-). Previous work has definitively demonstrated the presence of [(GS)2AsSe](-) in rabbit bile, but only in the presence of other arsenic and selenium species. Rabbits have a gall bladder, which concentrates bile and lowers its pH; it seems likely that this may be responsible for the breakdown of biliary [(GS)2AsSe](-). Since rats have no gall bladder, the bile proceeds directly through the bile duct from the hepatobiliary tree. In the present work we have shown that the primary product of biliary co-excretion of arsenic and selenium in rats is [(GS)2AsSe](-), with essentially 100% of the arsenic and selenium present as this species. The chemical plausibility of the X-ray absorption spectroscopy-derived structural conclusions of this novel arsenic and selenium co-excretion product is supported by density functional theory calculations. These results establish the biomolecular basis to further explore the use of selenium dietary supplements as a possible palliative for chronic low-level arsenic poisoning of human populations.
Arsenicosis, a syndrome caused by ingestion of arsenic contaminated drinking water, currently affects millions of people in South-East Asia and elsewhere. Previous animal studies revealed that the toxicity of arsenite essentially can be abolished if selenium is co-administered as selenite. Although subsequent studies have provided some insight into the biomolecular basis of this striking antagonism, many details of the biochemical pathways that ultimately result in the detoxification and excretion of arsenic using selenium supplements have yet to be thoroughly studied. To this end and in conjunction with the recent Phase III clinical trial "Selenium in the Treatment of Arsenic Toxicity and Cancers", we have applied synchrotron X-ray techniques to elucidate the mechanisms of this arsenic-selenium antagonism at the tissue and organ levels using an animal model. X-ray fluorescence imaging (XFI) of cryo-dried whole-body sections of laboratory hamsters that had been injected with arsenite, selenite, or both chemical species, provided insight into the distribution of both metalloids 30 minutes after treatment. Co-treated animals showed strong co-localization of arsenic and selenium in the liver, gall bladder and small intestine. X-ray absorption spectroscopy (XAS) of freshly frozen organs of co-treated animals revealed the presence in liver tissues of the seleno bis-(S-glutathionyl) arsinium ion, which was rapidly excreted via bile into the intestinal tract. These results firmly support the previously postulated hepatobiliary excretion of the seleno bis-(S-glutathionyl) arsinium ion by providing the first data pertaining to organs of whole animals.
Bambara groundnut (Vigna subterranea (L.) Verdc.) is an underutilised legume crop, which has long been recognised as a protein-rich and drought-tolerant crop, used extensively in Sub-Saharan Africa. The aim of the study was to identify quantitative trait loci (QTL) involved in agronomic and drought-related traits using an expression marker-based genetic map based on major crop resources developed in soybean. The gene expression markers (GEMs) were generated at the (unmasked) probe-pair level after cross-hybridisation of bambara groundnut leaf RNA to the Affymetrix Soybean Genome GeneChip. A total of 753 markers grouped at an LOD (Logarithm of odds) of three, with 527 markers mapped into linkage groups. From this initial map, a spaced expression marker-based genetic map consisting of 13 linkage groups containing 218 GEMs, spanning 982.7 cM (centimorgan) of the bambara groundnut genome, was developed. Of the QTL detected, 46% were detected in both control and drought treatment populations, suggesting that they are the result of intrinsic trait differences between the parental lines used to construct the cross, with 31% detected in only one of the conditions. The present GEM map in bambara groundnut provides one technically feasible route for the translation of information and resources from major and model plant species to underutilised and resource-poor crops.
Fish are an important source of bioavailable micronutrients and essential fatty acids, and capture fisheries have potential to substantially reduce dietary deficiencies. Vigorous debate has focused on trade and fishing in foreign waters as drivers of inequitable distribution of volume and value of fish, but their impact on nutrient supplies from fish is unknown. We analyze global catch, trade, and nutrient composition data for marine fisheries to quantify distribution patterns among countries with differing prevalence of inadequate nutrient intake. We find foreign fishing relocates 1.5 times more nutrients than international trade in fish. Analysis of nutrient flows among countries of different levels of nutrient intake shows fishing in foreign waters predominantly (but not exclusively) benefits nutrient-secure nations, an outcome amplified by trade. Next, we developed a nutritional vulnerability framework that shows those small island developing states and/or African nations currently benefiting from trade and foreign fishing, and countries with low adaptive capacity, are most vulnerable to future changes in nutrient supplies. Climate change exacerbates vulnerabilities for many nations. Harnessing the potential of global fisheries to address dietary deficiencies will require greater attention to nutrition objectives in fisheries’ licensing deals and trade negotiations.