Bioavailability in soils

The consumption of locally-produced vegetables by humans may be an important exposure pathway for soil contaminants in many urban settings and for agricultural land use. Hence, prediction of metal and metalloid uptake by vegetables from contaminated soils is an important part of the Human Health Risk Assessment procedure. The behaviour of metals (cadmium, chromium, cobalt, copper, mercury, molybdenum, nickel, lead and zinc) and metalloids (arsenic, boron and selenium) in contaminated soils depends to a large extent on the intrinsic charge, valence and speciation of the contaminant ion, and soil properties such as pH, redox status and contents of clay and/or organic matter. However, chemistry and behaviour of the contaminant in soil alone cannot predict soil-to-plant transfer. Root uptake, root selectivity, ion interactions, rhizosphere processes, leaf uptake from the atmosphere, and plant partitioning are important processes that ultimately govern the accumulation ofmetals and metalloids in edible vegetable tissues. Mechanistic models to accurately describe all these processes have not yet been developed, let alone validated under field conditions. Hence, to estimate risks by vegetable consumption, empirical models have been used to correlate concentrations of metals and metalloids in contaminated soils, soil physico-chemical characteristics, and concentrations of elements in vegetable tissues. These models should only be used within the bounds of their calibration, and often need to be re-calibrated or validated using local soil and environmental conditions on a regional or site-specific basis.Mike J. McLaughlin, Erik Smolders, Fien Degryse, and Rene Rietr

A Novel Acyl-CoA Beta-Transaminase Characterized from a Metagenome

BACKGROUND: Bacteria are key components in all ecosystems. However, our knowledge of bacterial metabolism is based solely on the study of cultivated organisms which represent just a tiny fraction of microbial diversity. To access new enzymatic reactions and new or alternative pathways, we investigated bacterial metabolism through analyses of uncultivated bacterial consortia. METHODOLOGY/PRINCIPAL FINDINGS: We applied the gene context approach to assembled sequences of the metagenome of the anaerobic digester of a municipal wastewater treatment plant, and identified a new gene which may participate in an alternative pathway of lysine fermentation. CONCLUSIONS: We characterized a novel, unique aminotransferase that acts exclusively on Coenzyme A (CoA) esters, and proposed a variant route for lysine fermentation. Results suggest that most of the lysine fermenting organisms use this new pathway in the digester. Its presence in organisms representative of two distinct bacterial divisions indicate that it may also be present in other organisms

Inhibition of cancer cell invasion and metastasis by genistein

Genistein is a small, biologically active flavonoid that is found in high amounts in soy. This important compound possesses a wide variety of biological activities, but it is best known for its ability to inhibit cancer progression. In particular, genistein has emerged as an important inhibitor of cancer metastasis. Consumption of genistein in the diet has been linked to decreased rates of metastatic cancer in a number of population-based studies. Extensive investigations have been performed to determine the molecular mechanisms underlying genistein’s antimetastatic activity, with results indicating that this small molecule has significant inhibitory activity at nearly every step of the metastatic cascade. Reports have demonstrated that, at high concentrations, genistein can inhibit several proteins involved with primary tumor growth and apoptosis, including the cyclin class of cell cycle regulators and the Akt family of proteins. At lower concentrations that are similar to those achieved through dietary consumption, genistein can inhibit the prometastatic processes of cancer cell detachment, migration, and invasion through a variety of mechanisms, including the transforming growth factor (TGF)-β signaling pathway. Several in vitro findings have been corroborated in both in vivo animal studies and in early-phase human clinical trials, demonstrating that genistein can both inhibit human cancer metastasis and also modulate markers of metastatic potential in humans, respectively. Herein, we discuss the variety of mechanisms by which genistein regulates individual steps of the metastatic cascade and highlight the potential of this natural product as a promising therapeutic inhibitor of metastasis

Temporal variation of biomass and nutrient status of azolla filiculoides lam: (sal viniaceae) in a small shallow dystrophic lake

This study determined the temporal variation of the biomass and the concentrations of carbon, nitrogen and phosphorus in Azolla filiculoides Lam. in a small (0.5 ha) shallow dystrophic lake located in the city of Rio Grande (Rio Grande do Sul State, Brazil). Method: Sampling was conducted monthly between November 2000 and October 2001. The macrophytes were collected randomly in three replicates with a circular collector 0.3 m in diameter and subsequently washed with tap water and oven-dried at 60 °C for determination of the dry weight and the nutrient status (i.e., carbon, nitrogen and phosphorus). Primary productivity was estimated by the variation in biomass among successive samples. Results: A. filiculoides was present in the lake throughout the year and occupied between 50 and 80% of the surface area. The biomass values ranged from 34.2 g DW.m–2, recorded in May (autumn), to 170.9 g DW.m–2 in January (summer). The highest rate of primary productivity was 3.3 g DW.m–2.d–1, observed in June. The concentrations of carbon, nitrogen and phosphorus in the plant ranged between 403 and 551 g.kg–1, 13.4 and 25.7 g.kg–1 and 0.5 and 1.9 g.kg–1, respectively. The water N:P ratio ranged between 19:1 and 368:1. Conclusion: The coverage of the surface of the lake by A. filiculoides throughout the study period and the nutritional status of the plant demonstrate the importance of the cycling of nutrients by macrophytes in this aquatic environment. The higher N:P ratio in the water column, compared with other neighboring environments without macrophytes, shows that the enrichment of the lake may result from the biological N-fixation activity produced by A. filiculoides.Este estudo determinou a variação temporal da biomassa e as concentrações de carbono, nitrogênio e fósforo de Azolla filiculoides Lam., em um pequeno lago raso distrófico situado no município do Rio Grande (Rio Grande do Sul, Brasil). Método: As amostragens foram realizadas mensalmente no período entre novembro de 2000 e outubro de 2001. As macrófitas foram coletadas aleatoriamente em três repetições, utilizando-se coletor circular de 0,3 m de diâmetro e posteriormente lavadas com água corrente e secas em estufa 60 °C para determinação do peso seco e dos nutrientes: carbono, nitrogênio e fósforo. A produção primária foi estimada pela variação de biomassa entre coletas sucessivas. Resultados: A. filiculoides esteve presente no lago durante todo o ano, ocupando sempre entre 50 e 80% da superfície do lago. Os valores de biomassa variaram entre 34,2 g PS.m–2, registrado em maio (outono) e 170,9 g PS.m–2 em janeiro (verão). A maior taxa de produtividade primária foi 3,3 g PS.m–2.d–1 foi registrada em Junho. As concentrações de carbono, nitrogênio e fósforo na planta variaram entre: 403 e 551 g. kg–1, 13,4 e 25,7 g.kg–1 e 0,5 e 1,9 g.kg–1, respectivamente. Os valores da relação N:P na coluna de água variou entre 19:1 e 368:1. Conclusão: A cobertura da superfície do lago por A. filiculoides durante todo o período do estudo e o seu estado nutricional demonstram sua importância na ciclagem dos nutrientes neste ambiente aquático. A maior relação N:P na coluna de água quando comparada a outro ambiente próximo sem a presença desta macrófita, apoia a ideia de que A. filiculoides pode ser a responsável pelo enriquecimento do lago por meio da atividade de fixação biológica de nitrogênio

The role of stimulus type in list length effects in recognition memory

While many studies have investigated the list length effect in recognition memory, few have done so with stimuli other than words. This article presents the results of four list length experiments that involved word pairs, faces, fractals, and photographs of scenes as the stimuli. A significant list length effect was identified when faces and fractals were the stimuli, but the effect was nonsignificant when the stimuli were word pairs or photographs of scenes. These findings suggest that the intrastimulus similarity is what dictates whether list length has a significant effect on recognition performance. As is the case with words, word pairs and photographs of scenes are not sufficiently similar to generate detectable item interference.Angela Kinnell, Simon Denni