Transfert racinaire de l'uranium (VI) en solution chez une plante supérieure (spéciation en solution hydroponique, prise en charge par la plante, microlocalistion et effets biologiques induits)

L'uranium est un élément naturel trace dans l'environnement. Dans la solution du sol et en condition oxique, il est présent à l'état d'oxydation + VI et peut former un grand nombre de complexes inorganiques ou organiques. En première approche, un ensemble d'expériences ont été mises en place de manière à appréhender les espèces d'uranium biodisponibles pour les racines des plantes. Le milieu d'exposition choisi, la solution nutritive a été établie de manière à contrôler la spéciation de l'uranium en solution. Dans ce sens, le modèle de spéciation géochimique JCHESS a été utilisé pour déterminer les formes d'uranium en solution en fonction du pH et a permis de définir 3 domaines de pH pour lesquels une espèce dominait : le pH 4,9 avec l'ion uranyle, le pH 5,8 avec les hydroxocomplexes et le pH 7 avec les hydroxocomplexes carbonatés. Pour ces 3 pH, des expériences d'exposition ont été menées à court terme (5 heures) sur notre modèle biologique Phaseolus vulgaris. Les résultats ont montré que le transfert d'uranium n'était pas affecté par les cations compétiteurs tels que ca2+, ou des ligands comme les phosphates ou le citrate (sauf une diminution de 60 % à pH 5,8 avec 10 [mu]M de citrate) dans nos conditions expérimentales. Par ailleurs, les observations, microscopiques (MET-EDAX) ont révélé l'association de l'uranium avec des granules riches en phosphore dans les cellules et la présence d'anomalies des chloroplastes. Enfin, la présence d'uranium affecte la CEC racinaire en la réduisant et provoque une stimulation de l'élongation racinaire à faible concentration (100 nM, 400 nM et 2 [mu]M aux pH 4,9, 5,8 et 7 respectivement) et une inhibition à plus forte concentration.AIX-MARSEILLE1-BU Sci.St Charles (130552104) / SudocSudocFranceF

Rapid diagnostic tests failing to detect infections by Plasmodium falciparum encoding pfhrp2 and pfhrp3 genes in a non-endemic setting

International audienceBackground Rapid diagnostic tests (RDTs) detecting the histidine-rich protein 2 (PfHRP2) have a central position for the management of Plasmodium falciparum infections. Yet, variable detection of certain targeted motifs, low parasitaemia, but also deletion of pfhrp2 gene or its homologue pfhrp3, may result in false-negative RDT leading to misdiagnosis and delayed treatment. This study aimed at investigating the prevalence, and understanding the possible causes, of P. falciparum RDT-negative infections at Montpellier Academic Hospital, France. Methods The prevalence of falsely-negative RDT results reported before and after the introduction of a loop-mediated isothermal amplification (LAMP) assay, as part as the malaria screening strategy in January 2017, was analysed. Negative P. falciparum RDT infections were screened for pfhrp2 or pfhrp3 deletion; and exons 2 were sequenced to show a putative genetic diversity impairing PfHRP2 detection. Results The overall prevalence of P. falciparum negative RDTs from January 2006 to December 2018 was low (3/446). Whereas no cases were reported from 2006 to 2016 (0/373), period during which the malaria diagnostic screen was based on microscopy and RDT, prevalence increased up to 4.1% (3/73) between 2017 and 2018, when molecular detection was implemented for primary screening. Neither pfhrp2/3 deletion nor major variation in the frequency of repetitive epitopes could explain these false-negative RDT results. Conclusion This paper demonstrates the presence of pfhrp2 and pfhrp3 genes in three P. falciparum RDT-negative infections and reviews the possible reasons for non-detection of HRP2/3 antigens in a non-endemic setting. It highlights the emergence of falsely negative rapid diagnostic tests in a non-endemic setting and draws attention on the risk of missing malaria cases with low parasitaemia infections using the RDT plus microscopy-based strategy currently recommended by French authorities. The relevance of a novel diagnostic scheme based upon a LAMP assay is discussed

Evaluation of a new point-of-care testing for creatinine and urea measurement

International audiencePoint of care testing makes it possible to obtain results in an extremely short time. Recently, radiometer has expanded the panel of tests available on its ABL90 FLEX PLUS blood gas analyzer (ABL90) by adding urea and creatinine. The aim of this study was to verify the performance of these new parameters. This included assessment of imprecision, linearity, accuracy by comparison with central laboratory standard assays and interferences. In addition, clinical utility in a dialysis center was evaluated. Within-lab coefficients of variation were close to 2%. The mean and limits of agreement (mean ± 1.96 SD) of the difference between ABL90 and Roche enzymatic assays on cobas 8000 were 0.5 (from -1.4 to 2.3) mmol/L and -0.9 (from -19.5 to 17.8) µmol/L for urea and creatinine, respectively. The ABL90 enzymatic urea and creatinine assays met the acceptance criteria based on biological variation for imprecision and showed good agreement with central laboratory. The two assays were unaffected by hematocrit variation between 20 and 70%, hemolysis and icterus interferences. It should be noted that the relationship between lab methods and ABL90 was conserved even for high pre-dialysis values allowing easy access to dialysis adequacy parameters (Kt/V) and muscle mass evaluation (creatinine index). Rapid measurement of creatinine and urea using whole blood specimens on ABL90 appears as a fast and convenient method. Analytical performances were in accordance with our expectations without any significant interferences by hemolysis or icterus