Contaminação de aflatoxinas em castanha-do-brasil com casca em sistemas extrativista e de plantio.

Diante de problemas de contaminação por aflatoxinas enfrentados na cadeia produtiva da castanha-do-brasil, o objetivo deste trabalho foi estudar o teor de aflatoxinas em castanhas com casca em diferentes etapas dos sistemas de produção: extrativista e de plantio. A produção extrativista consiste na coleta de ouriços recém caídos das árvores e permanecidos no solo por vários dias, empilhamento na floresta, abertura e seleção de castanhas com casca, seguida de armazenamento/secagem sob ventilação durante vários meses. Contudo, no sistema de plantio somente os ouriços com menos de 5 dias no solo são coletados, em seguida são desinfectados com hipoclorito de sódio a 1% e armazenados sob ventilação até abertura e seleção das castanhas com casca. Sessenta amostras de castanha-do-brasil com casca foram coletadas diretamente ou após abertura dos ouriços na região amazônica do Brasil, provenientes da produção extrativista no Acre e do sistema de plantio no Amazonas. As aflatoxinas (B1, B2, G1, G2) foram determinadas por Cromatografia Líquida de Alto Desempenho com detector de fluorescência bem como a atividade de água (aw) nas castanhas descascadas. Nas etapas do sistema extrativista na floresta, dos 33 ouriços coletados, castanhas provenientes de um ouriço com menos de 5 dias de contato com o solo e um ouriço empilhado durante 15 dias apresentaram contaminação por AFB1 inferior a 0,1 µg/kg de matéria fresca (MF). Entretanto o nível de AFB1 variou de 0,6 a 4,4 µg/kg de MF em 3 ouriços com mais de 30 dias em contato com o solo, mais susceptíveis a serem danificados e degradados por condições climáticas e predadores da floresta amazônica. No sistema de plantio, dos 5 ouriços coletados, somente uma amostra proveniente de um ouriço com menos de 5 dias de contato com o solo apresentou contaminação por AFB1, inferior a 0,1 µg/kg de MF. Em armazém ventilado do sistema de plantio, AFB1 foi detectada com teor inferior a 0,1 µg/kg de MF em uma amostra dos 10 ouriços coletados. Todavia no sistema extrativista, os teores de aflatoxinas das castanhas com casca aumentaram e foram superiores ao regulamento europeu (10 µg/kg de MF, UE n°165/2010) ao longo do armazenamento (até 90 dias). A secagem sob ventilação durante o armazenamento não é suficientemente eficaz para atingir rapidamente uma aw inferior a 0,7, evitando o desenvolvimento de fungos aflatoxinogênicos e a produção de aflatoxinas. Resultados sugerem o ouriço como uma barreira de proteção contra estes fungos além de confirmar os estudos anteriores do projeto Safenut que indicam a etapa de secagem sob ventilação e armazenamento das castanhas com casca durante meses no sistema extrativista como etapa crítica na contaminação por aflatoxinas. Portanto, no sistema de plantio, a coleta e o armazenamento após desinfecção com hipoclorito de sódio somente dos ouriços recém caídos das árvores, mesmo por um período de dois meses, permitem evitar a contaminação das castanhas por aflatoxinas

Global sourcing of low-inorganic arsenic rice grain

Arsenic in rice grain is dominated by two species: the carcinogen inorganic arsenic (the sum of arsenate and arsenite) and dimethylarsinic acid (DMA). Rice is the dominant source of inorganic arsenic into the human diet. As such, there is a need to identify sources of low-inorganic arsenic rice globally. Here we surveyed polished (white) rice across representative regions of rice production globally for arsenic speciation. In total 1180 samples were analysed from 29 distinct sampling zones, across 6 continents. For inorganic arsenic the global x ~ x~ was 66 μg/kg, and for DMA this figure was 21 μg/kg. DMA was more variable, ranging from < 2 to 690 μg/kg, while inorganic arsenic ranged from < 2 to 399 μg/kg. It was found that inorganic arsenic dominated when grain sum of species was < 100 μg/kg, with DMA dominating at higher concentrations. There was considerable regional variance in grain arsenic speciation, particularly in DMA where temperate production regions had higher concentrations. Inorganic arsenic concentrations were relatively consistent across temperate, subtropical and northern hemisphere tropical regions. It was only in southern hemisphere tropical regions, in the eastern hemisphere that low-grain inorganic arsenic is found, namely East Africa (x ~ x~  < 10 μg/kg) and the Southern Indonesian islands (x ~ x~  < 20 μg/kg). Southern hemisphere South American rice was universally high in inorganic arsenic, the reason for which needs further exploration

Rice grain cadmium concentrations in the global supply-chain

One of cadmium’s major exposure routes to humans is through rice consumption. The concentrations of cadmium in the global polished (white), market rice supply-chain were assessed in 2270 samples, purchased from retailers across 32 countries, encompassing 6 continents. It was found on a global basis that East Africa had the lowest cadmium with a median for both Malawi and Tanzania at 4.9 μg/kg, an order of magnitude lower than the highest country, China with a median at 69.3 μg/kg. The Americas were typically low in cadmium, but the Indian sub-continent was universally elevated. In particular certain regions of Bangladesh had high cadmium, that when combined with the high daily consumption rate of rice of that country, leads to high cadmium exposures. Concentrations of cadmium were compared to the European Standard for polished rice of 200 μg/kg and 5% of the global supply-chain exceeded this threshold. For the stricter standard of 40 μg/kg for processed infant foods, for which rice can comprise up to 100% by composition (such as rice porridges, puffed rice cereal and cakes), 25% of rice would not be suitable for making pure rice baby foods. Given that rice is also elevated in inorganic arsenic, the only region of the world where both inorganic arsenic and cadmium were low in grain was East Africa

G protein-coupled receptor-mediated calcium signaling in astrocytes

Astrocytes express a large variety of G~protein-coupled receptors (GPCRs) which mediate the transduction of extracellular signals into intracellular calcium responses. This transduction is provided by a complex network of biochemical reactions which mobilizes a wealth of possible calcium-mobilizing second messenger molecules. Inositol 1,4,5-trisphosphate is probably the best known of these molecules whose enzymes for its production and degradation are nonetheless calcium-dependent. We present a biophysical modeling approach based on the assumption of Michaelis-Menten enzyme kinetics, to effectively describe GPCR-mediated astrocytic calcium signals. Our model is then used to study different mechanisms at play in stimulus encoding by shape and frequency of calcium oscillations in astrocytes.Comment: 35 pages, 6 figures, 1 table, 3 appendices (book chapter

Gi/o-protein coupled receptors in the aging brain

Cells translate extracellular signals to regulate processes such as differentiation, metabolism and proliferation, via transmembranar receptors. G protein-coupled receptors (GPCRs) belong to the largest family of transmembrane receptors, with over 800 members in the human species. Given the variety of key physiological functions regulated by GPCRs, these are main targets of existing drugs. During normal aging, alterations in the expression and activity of GPCRs have been observed. The central nervous system (CNS) is particularly affected by these alterations, which results in decreased brain functions, impaired neuroregeneration, and increased vulnerability to neuropathologies, such as Alzheimer's and Parkinson diseases. GPCRs signal via heterotrimeric G proteins, such as Go, the most abundant heterotrimeric G protein in CNS. We here review age-induced effects of GPCR signaling via the Gi/o subfamily at the CNS. During the aging process, a reduction in protein density is observed for almost half of the Gi/o-coupled GPCRs, particularly in age-vulnerable regions such as the frontal cortex, hippocampus, substantia nigra and striatum. Gi/o levels also tend to decrease with aging, particularly in regions such as the frontal cortex. Alterations in the expression and activity of GPCRs and coupled G proteins result from altered proteostasis, peroxidation of membranar lipids and age-associated neuronal degeneration and death, and have impact on aging hallmarks and age-related neuropathologies. Further, due to oligomerization of GPCRs at the membrane and their cooperative signaling, down-regulation of a specific Gi/o-coupled GPCR may affect signaling and drug targeting of other types/subtypes of GPCRs with which it dimerizes. Gi/o-coupled GPCRs receptorsomes are thus the focus of more effective therapeutic drugs aiming to prevent or revert the decline in brain functions and increased risk of neuropathologies at advanced ages.This work was supported by Fundação para a Ciência e Tecnologia, Centro 2020 and Portugal 2020, the COMPETE program, QREN, and the European Union (FEDER program) via the GoBack project (PTDC/CVT-CVT/32261/2017), the pAGE program (Centro-01-0145-FEDER-000003), and Institute for Biomedicine iBiMED (UID/BIM/04501/2013; UID/BIM/04501/2019).publishe

Enzymatic degradation of beta-carotene

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Aminobicyclo (2.2.1.)heptane dicarboxylic acids (ABHD), rigid analogs of ACPD and glutamic acid: synthesis and pharmacological activity on metabotropic receptors mGluR1 and mGluR2

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Synthesis of conformationally-constrained stereospecific analogs of glutamic acid as antagonists of metabotropic receptors

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Synthèse d'analogues à conformation figée de l'acide glutamique comme sondes structurales des récepteurs glutamatergiques

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