Effects of sodium nitrite reduction, removal or replacement on cured and cooked meat for microbiological growth, food safety, colon ecosystem, and colorectal carcinogenesis in Fischer 344 rats

Epidemiological and experimental evidence indicated that processed meat consumption is associated with colorectal cancer risks. Several studies suggest the involvement of nitrite or nitrate additives via N-nitroso-compound formation (NOCs). Compared to the reference level (120 mg/kg of ham), sodium nitrite removal and reduction (90 mg/kg) similarly decreased preneoplastic lesions in F344 rats, but only reduction had an inhibitory effect on Listeria monocytogenes growth comparable to that obtained using the reference nitrite level and an effective lipid peroxidation control. Among the three nitrite salt alternatives tested, none of them led to a significant gain when compared to the reference level: vegetable stock, due to nitrate presence, was very similar to this reference nitrite level, yeast extract induced a strong luminal peroxidation and no decrease in preneoplastic lesions in rats despite the absence of NOCs, and polyphenol rich extract induced the clearest downward trend on preneoplastic lesions in rats but the concomitant presence of nitrosyl iron in feces. Except the vegetable stock, other alternatives were less efficient than sodium nitrite in reducing L. monocytogenes growth

Queen bee pheromone binding protein pH-induced domain swapping favors pheromone release

International audienceIn honeybee (Apis mellifera) societies, the queen controls the development and the caste status of the members of the hive. Queen bees secrete pheromonal blends comprising 10 or more major and minor components, mainly hydrophobic. The major component, 9-keto-2(E)-decenoic acid (9-ODA), acts on the workers and male bees (drones), eliciting social or sexual responses. 9-ODA is captured in the antennal lymph and transported to the pheromone receptor(s) in the sensory neuron membranes by pheromone binding proteins (PBPs). A key issue is to understand how the pheromone, once tightly bound to its PBP, is released to activate the receptor. We report here on the structure at physiological pH of the main antennal PBP, ASP1, identified in workers and male honeybees, in its apo or complexed form, particularly with the main component of the queen mandibular pheromonal mixture (9-ODA). Contrary to the ASP1 structure at low pH, the ASPI structure at pH 7.0 is a domain-swapped dimer with one or two ligands per monomer. This dimerization is disrupted by a unique residue mutation since Asp35 Asn and Asp35 Ala mutants remain monomeric at pH 7.0, as does native ASP1 at pH 4.0. Asp35 is conserved in only similar to 30% of medium-chain PBPs and is replaced by other residues, such as Asn, Ala and Ser, among others, thus excluding that they may perform domain swapping. Therefore, these different medium-chain PBPs, as well as PBPs from moths, very likely exhibit different mechanisms of ligand release or receptor recognition. (C) 2009 Elsevier Ltd. All rights reserved

A new odorant-binding protein XlaeOBP identified in the aerial olfactory system of Xenopus laevis and Xenopus tropicalis

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A new olfactory binding protein : XlaeOBP identified in the aerial olfactory system of Xenopus laevis and Xenopus tropicalis

International audienc

Exposition orale aux microplastiques dans des populations à risque : un continuum in vitro-in vivo

International audienc

Structural basis of the honey bee PBP pheromone and pH-induced conformational change

International audienceThe behavior of insects and their perception of their surroundings are driven, in a large part, by odorants and pheromones. This is especially true for social insects, such as the honey bee, where the queen controls the development and the caste status of the other individuals. Pheromone perception is a complex phenomenon relying on a cascade of recognition events, initiated in antennae by pheromone recognition by a pheromone-binding protein and fishing with signal transduction at the axon membrane level. With to the objective of deciphering this initial step, we have determined the structures of the bee antennal pheromone-binding protein (ASP1) in the apo form and m complex with the main component of the queen mandibular pheromonal mixture, 9-keto-2(E)-decenoic acid (9-ODA) and with nonpheromonal components. In the apo protein, the C terminus obstructs the binding site. In contrast, ASP1 complexes have different open conformations, depending on the ligand shape, leading to different volumes of the binding cavity. The binding site integrity depends on the C terminus (111-119) conformation, which involves the interplay of two factors; i.e. the presence of a ligand and a low pH. Ligand binding to ASP1 is favored by low pH, opposite to what is observed with other pheromone-binding proteins, such as those of Bombyx mori and Anopheles gambiae. (C) 2008 Elsevier Ltd. All rights reserved

Exposition orale aux microplastiques dans des populations à risque : un continuum in vitro-in vivo

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Tas1R1-Tas1R3 taste receptor variants in human fungiform papillae.

International audienceMonosodium glutamate as well as metabotropic and ionotropic glutamate receptor agonists have been reported to be perceived as umami by humans. In spite of the fact that Tas1R1-Tas1R3 has been shown to mediate most of the glutamate taste sensation in mice other candidate receptors have been put forward for which a clear role in detection is still lacking. This work was aimed at investigating the molecular determinants underlying umami taste detection in humans. First, we show evidence supporting expression of Tas1R1 and Tas1R3 but not mGluRs in the fungiform papillae of several individuals. Next, we report a number of naturally occurring l-glutamate taste receptor variants and their frequency in a population of Caucasian subjects. Detailed analysis of 9 non-synonymous single nucleotide polymorphisms from three l-glutamate taste GPCR candidates uncovers receptor specific clusters such that all substitutions in Tas1R1 are located in the extracellular N-terminal ligand-binding domain while in Tas1R3 they mostly affect residues in the seven transmembrane-spanning core domain responsible for the interaction with antagonists and allosteric modulators. In mGluR1, nsSNPs identified are clustered in the intracellular C-terminal tail, which is thought to play a role in signaling. Taken together, these results suggest that Tas1R1-Tas1R3 receptor variants found in human fungiform papillae might contribute to inter-individual differences of sensitivity to l-glutamate

Evidence of an odorant-binding protein in the human olfactory mucus : location, structural characterization , and odorant-binding properties

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