43 research outputs found
Caractérisation des risques de contamination des agrosystÚmes périurbains de Dakar par les éléments traces métalliques
Lâapplication de produits rĂ©siduaires organiques (PRO) amĂ©liore la fertilitĂ© des sols, mais induit des effets nĂ©gatifs sur les agrosystĂšmes, en raison de la prĂ©sence de contaminants tels que les Ă©lĂ©ments traces mĂ©talliques (ETM). Cette Ă©tude vise Ă Ă©valuer lâinfluence de deux doses (20 et 60 T.ha-1) dâapport de boue de station dâĂ©puration STEP et de fiente de volaille sur la disponibilitĂ© de quatre ETM (Ni, Cd, Cr et Pb) dans un arenosol et un fluvisol. Une incubation de 88 jours en conditions contrĂŽlĂ©es a Ă©tĂ© conduite sur les deux sols mĂ©langĂ©s aux diffĂ©rentes doses de boue et de fiente. La disponibilitĂ© des ETM dans les sols incubĂ©s a Ă©tĂ© Ă©valuĂ©e par la technique DGT (Diffusive Gradient in Thin films). Les boues ont abaissĂ© le pH des deux sols tandis que les fientes ont alcalinisĂ© lâarenosol durant les 14 premiers jours dâincubation. Ces PRO ont augmentĂ© les concentrations de Ni, Cd, Pb et Cr disponibles dans les sols. Les disponibilitĂ©s du Ni, Cd et Pb sont plus Ă©levĂ©es dans lâarenosol que dans le fluvisol. La boue Ă 60 T.ha-1 a induit les plus fortes disponibilitĂ©s en Cd et Pb tandis que la fiente Ă 60 T.ha-1 a induit les plus fortes disponibilitĂ©s en Ni et Cr dans les deux sols.Mots clĂ©s : ElĂ©ments traces mĂ©talliques, arenosol, fluvisol, boue dâĂ©puration, fiente.  CHARACTERIZATION OF CONTAMINATION RISKS OF THE SUBURBANAGROECOSYSTEMS OF DAKAR BY TRACE ELEMENTSOrganic wastes (OW) spreading improve soil fertility, but can induce negative effects on agroecosystems, due to the presence of contaminants such as trace elements (TE). This study aims to evaluate the impacts of two doses (20 and 60 T.ha-1) of sewage sludge and poultry manure on the availability of four trace elements (Ni, Cd, Cr and Pb) in arenosol and fluvisol. Soils mixed with different doses of sewage sludge and poultry manure were incubated for 88 days under controlled conditions. The availability of trace elements in incubated soils was evaluated by the DGT (Diffusive Gradient in Thin films) technique. Sewage sludge has decreased the pH of both soils while poultry manure induced an alkalinization of arenosol during the first 14 days of incubation. OW increased Ni, Cd, Pb and Cr availability in the soils. Availability of Ni, Cd and Pb were higher in arenosol than in the fluvisol. Sewage sludge at 60 T.ha-1 induced the highest availability of Cd and Pb while the poultry manure at 60 T.ha-1 induced the highest availability of Ni and Cr in both soils.Keywords : Trace elements, arenosol, fluvisol, sewage sludge, poultry manure
The human OPA1delTTAG mutation induces premature age-related systemic neurodegeneration in mouse
Dominant optic atrophy is a rare inherited optic nerve degeneration caused by mutations in the mitochondrial fusion gene OPA1. Recently, the clinical spectrum of dominant optic atrophy has been extended to frequent syndromic forms, exhibiting various degrees of neurological and muscle impairments frequently found in mitochondrial diseases. Although characterized by a specific loss of retinal ganglion cells, the pathophysiology of dominant optic atrophy is still poorly understood. We generated an Opa1 mouse model carrying the recurrent Opa1(delTTAG) mutation, which is found in 30% of all patients with dominant optic atrophy. We show that this mouse displays a multi-systemic poly-degenerative phenotype, with a presentation associating signs of visual failure, deafness, encephalomyopathy, peripheral neuropathy, ataxia and cardiomyopathy. Moreover, we found premature age-related axonal and myelin degenerations, increased autophagy and mitophagy and mitochondrial supercomplex instability preceding degeneration and cell death. Thus, these results support the concept that Opa1 protects against neuronal degeneration and opens new perspectives for the exploration and the treatment of mitochondrial diseases
Variations in the cation exchange capacity of a ferralsol supplied with vinasse, under changing aeration conditions. Comparison between CEC measuring methods
International audienceThe spreading of vinasse may favour soil anoxia and affect cation exchange capacity (CEC). Our aims were to assess the reliability of CEC measurements in reducing conditions, quantify CEC variations in a ferralsol under changing aeration conditions, and understand the mechanisms involved. In a first experiment, soil slurry was incubated for a succession of 7 oxic, 28 anoxic and 28 oxic days, vinasse being supplied when anoxia began. CEC was measured at intervals by exchanging Mg2+, Cu-trien or Co(NH3)63+, the solutions being characterized before and after exchange. In a second experiment, soil CEC was measured after the elution of NH4+ solutions of pH 5 to 7. In a third experiment, we assessed the reduction of Co(NH3)63+ by Fe2+ and checked for induced changes by geochemical simulations. During the first oxic period, CEC varied according to method, in the order: Cu-trien < Mg2+<Co(NH3)63+<NH4+. It increased by 2 cmolc kgâ 1 when pH increased from 5 to 7. After 28 days of anoxia, CEC estimates were 2.75, 1.43 and 5.1 times their initial values for the 0.05 M Mg2+, Cu-trien and Co(NH3)63+ methods respectively; pH after exchange was about the same as initial slurry pH (6.9), except after Co(NH3)63+ exchange when it was 9.4. This complex was partly reduced by Fe2+ leading to NH3 release, pH increase, Fe(OH)3 and Co(OH)2 precipitations, Co(II) adsorption and overestimation of CEC. After the return to oxic conditions, the CEC did not return to its initial value. At all dates, CEC measured by 0.05 M Mg2+ method agreed with the exchangeable cation measurement
Retroviral GAG proteins recruit AGO2 on viral RNAs without affecting RNA accumulation and translation
Cellular micro(mi)RNAs are able to recognize viral RNAs through imperfect micro-homologies. Similar to the miRNA-mediated repression of cellular translation, this recognition is thought to tether the RNAi machinery, in particular Argonaute 2 (AGO2) on viral messengers and eventually to modulate virus replication. Here, we unveil another pathway by which AGO2 can interact with retroviral mRNAs. We show that AGO2 interacts with the retroviral Group Specific Antigen (GAG) core proteins and preferentially binds unspliced RNAs through the RNA packaging sequences without affecting RNA stability or eliciting translation repression. Using RNAi experiments, we provide evidences that these interactions, observed with both the human immunodeficiency virus 1 (HIV-1) and the primate foamy virus 1 (PFV-1), are required for retroviral replication. Taken together, our results place AGO2 at the core of the retroviral life cycle and reveal original AGO2 functions that are not related to miRNAs and translation repression