93484 research outputs found
Sort by
New triterpenoid saponin from the stems of Albizia adianthifolia (Schumach.) W.Wight
No full textAs part of our continuing study of apoptosis-inducing saponins from CameroonianAlbiziagenus, one new triterpenoid saponin, named adianthifolioside J (1), together with the known gummiferaoside E (2), were isolated fromAlbizia adianthifoliastems. The structure of the new saponin (1), was established on the basis of extensive analysis of 1 D and 2 D NMR (H-1-,C-13-NMR, DEPT, COSY, TOCSY, NOESY, HSQC, HSQC-TOCSY and HMBC) and HRESIMS experiments, and by chemical evidence as 3-O-[beta-D-xylopyranosyl-(1 -> 2)-beta-D-fucopyranosyl-(1 -> 6)-beta-D-glucopyranosyl]-21-O-{(2E,6S)-2-(hydroxymethyl)-6-methyl-6-O-{4-O-[(2E,6S)-2,6-dimethyl-6-O-(beta-D-quinovopyranosyl)octa-2,7-dienoyl]-(beta-D-quinovopyranosyl)octa-2,7-dienoyl]}acacic acid-28-O-beta-D-glucopyranosyl-(1 -> 3)-[5-O-acetyl-alpha-L-arabinofuranosyl-(1 -> 4)]-alpha-L-rhamnopyranosyl-(1 -> 2)-beta-D-glucopyranosyl ester (1).The pro-apoptotic activity of the new isolated saponin1was evaluated, using Annexin V-FITC binding assay, on the A431 human epidermoid cancer cell. The result showed that adianthifolioside J (1) displayed weak pro-apoptotic activity
In vitro screening of a FDA approved chemical library reveals potential inhibitors of SARS-CoV-2 replication
No full textA novel coronavirus, named SARS-CoV-2, emerged in 2019 in China and rapidly spread worldwide. As no approved therapeutics exists to treat COVID-19, the disease associated to SARS-Cov-2, there is an urgent need to propose molecules that could quickly enter into clinics. Repurposing of approved drugs is a strategy that can bypass the time-consuming stages of drug development. In this study, we screened the PRESTWICK CHEMICAL LIBRARY composed of 1,520 approved drugs in an infected cell-based assay. The robustness of the screen was assessed by the identification of drugs that already demonstrated in vitro antiviral effect against SARS-CoV-2. Thereby, 90 compounds were identified as positive hits from the screen and were grouped according to their chemical composition and their known therapeutic effect. Then EC50 and CC50 were determined for a subset of 15 compounds from a panel of 23 selected drugs covering the different groups. Eleven compounds such as macrolides antibiotics, proton pump inhibitors, antiarrhythmic agents or CNS drugs emerged showing antiviral potency with 220 mu M. By providing new information on molecules inhibiting SARS-CoV-2 replication in vitro, this study provides information for the selection of drugs to be further validated in vivo. Disclaimer: This study corresponds to the early stages of antiviral development and the results do not support by themselves the use of the selected drugs to treat SARS-CoV-2 infection
Are fission-fusion dynamics consistent among populations ? A large-scale study with Cape buffalo
No full textFission-fusion dynamics allow animals to manage costs and benefits of group living by adjusting group size. The degree of intraspecific variation in fission-fusion dynamics across the geographical range is poorly known. During 2008-2016, 38 adult female Cape buffalo were equipped with GPS collars in three populations located in different protected areas (Gonarezhou National Park and Hwange National Park, Zimbabwe; Kruger National Park, South Africa) to investigate the patterns and environmental drivers of fission-fusion dynamics among populations. We estimated home range overlap and fission and fusion events between Cape buffalo dyads. We investigated the temporal dynamics of both events at daily and seasonal scales and examined the influence of habitat and distance to water on event location. Fission-fusion dynamics were generally consistent across populations: Fission and fusion periods lasted on average between less than one day and three days. However, we found seasonal differences in the underlying patterns of fission and fusion, which point out the likely influence of resource availability and distribution in time on group dynamics: During the wet season, Cape buffalo split and associated more frequently and were in the same or in a different subgroup for shorter periods. Cape buffalo subgroups were more likely to merge than to split in open areas located near water, but overall vegetation and distance to water were very poor predictors of where fission and fusion events occurred. This study is one of the first to quantify fission-fusion dynamics in a single species across several populations with a common methodology, thus robustly questioning the behavioral flexibility of fission-fusion dynamics among environments
Iron corrosion induced by the hyperthermophilic sulfate-reducing archaeon Archaeoglobus fulgidus at 70 degrees C
No full textThis work assessed the role of the hyperthermophilic sulfate-reducing archaeon, Archaeoglobus fulgidus in anaerobic iron corrosion, at 70 degrees C, in the presence and the absence of lactate as energy source. Experiments performed with A. fulgidus planktonic cells, displayed their capacity to form a biofilm on an iron coupon and exhibited their biocorrosive activity. A. fulgidus was shown to cause indirect corrosion by producing sulfide while oxidizing lactate. Furthermore, the archaeon could grow lithotrophically by using elemental iron as a mineral energy source. Under these latter conditions, A. fulgidus formed chimneys enhancing the direct corrosion process. Moreover, physiological modifications occurred under these conditions notably highlighting the probable use of CO2 instead of sulfate as a terminal electron acceptor to produce acetate similarly to homoacetogens. All together, these results illustrate the metabolic versatility and hence the importance of this hyperthermophilic archaeon in microbial induced corrosion (MIC)
Effect of a transducer horizontality default on lake fish stock assessment
No full textFreshwater hydroacoustic surveys are frequently performed with small research boats. Thus, the transducer, usually fixed on a pole on the side of the boat, could be misaligned with the horizontal axis (i.e., the lake surface). Given that fish acoustic responses are strongly directional, the transducer angle could induce attenuation of their backscattering strengths. To test the influence of a small shift of the transducer orientation, we compared hydroacoustics estimates from two sampling nights on the Lake Annecy: the first one being a transducer angle of 1.5 degrees with the horizontal and the second one being strictly horizontal. We showed that the effect of such an angle is negligible over the sampling variability on the TS distribution of the fish population and the biomass assessment. We conclude that a small shift in the transducer horizontality (<= 1.5 degrees) will not degrade the quality of the acoustic data
Integrating thermal stress indexes within Shuttleworth-Wallace model for evapotranspiration mapping over a complex surface
No full textThe main goal of this work was to evaluate the potential of the Shuttleworth-Wallace (SW) model for mapping actual crop evapotranspiration (ET) over complex surface located in the foothill of the Atlas Mountain (Morocco). This model needs many input variables to compute soil (r(s)(s)) and vegetation (r(s)(v)) resistances, which are often difficult to estimate at large scale particularly soil moisture. In this study, a new approach to spatialize r(s)(s) and r(s)(v) based on two thermal-based proxy variables was proposed. Land Surface Temperature (LST) and Normalized Difference Vegetation Index (NDVI) derived from Landsat data were combined with the endmember temperatures for soil (Ts-min and Ts-max) and vegetation (Tv(min) and Tv(max)), which were simulated by a surface energy balance model, to compute the soil (Ts) and the vegetation (Tv) temperatures. Based on these temperatures, two thermal proxies (SIss for soil and SIsv for vegetation) were calculated and related to r(s)(s) and r(s)(v), with an empirical exponential relationship [with a correlation coefficient (R) of about 0.6 and 0.5 for soil and vegetation, respectively]. The proposed approach was initially evaluated at a local scale, by comparing the results to observations by an eddy covariance system installed over an area planted with olive trees intercropped with wheat. In a second step, the new approach was applied over a large area which contains a mixed vegetation (tall and short) crossed by a river to derive r(s)(s) and r(s) (v), and thereafter to estimate ET. A Large aperture scintillometer (LAS) installed over a line transect of 1.4 km and spanning the total area was used to validate the obtained ET. The comparison confirmed the ability of the proposed approach to provide satisfactory ET maps with an RMSE, bias and R-2 equal to 0.08 mm/h, 0.06 mm/h and 0.80, respectively
Evaluating family physicians' willingness to prescribe PrEP
No full textIntroduction. - We assessed family physicians' (FP) willingness to integrate PrEP into their clinical practice in Montpellier and its surroundings. Method. - We aimed to randomly assess 92 FPs. Results. - Ninety-six FPs were interviewed from May to December 2018: 78% (95% CI [69; 86]) were willing to integrate PrEP, 65% to be trained, and 52% to be the first providers. Of the 65 (6%) with some knowledge of PrEP, 21 were not aware of targeted populations and 39 never talked about PrEP with their patients. Nearly all FPs declared HIV prevention as part of their job and felt at ease talking about sexuality. Considering HIV prevention as part of their job was associated with increased likelihood to integrate PrEP into their practice (P = 0.015). Conclusions. - Most FPs were willing to integrate and be trained on PrEP. Lack of PrEP prescription seemed related to a lack of knowledge
Vector biology and control : an update for malaria elimination : initiative in India
No full textMalarial threat is receding in India and for achieving malaria-free status, vector biology is regaining its due importance for targeting species-specific interventions in place and time. Anopheles minimus, the major vector of malaria in north-east India, is disappearing fast evidenced by reduced levels of malaria transmission and morbidity. An. minimus is a species complex comprising three sibling species of which An. minimus s.s., formally named as An. minimus, is recorded to occur in east and north-east India. It is highly anthropophilic and responsible for fulminating outbreaks of malaria evidenced by incrimination records in range of its distribution. For its control, DDT continues to be the insecticide of choice for indoor residual spraying; however, populations are highly resilient in response to residual insecticides for paradigm shift in vector behaviour from indoor resting to outdoors resulting in continued transmission. Extra-domiciliary transmission of malaria is a challenge for which newer interventions, viz., attractive toxic sugar bait, eave-tube technology, nano-synthesized pesticides, new adult repellents, oviposition deterrents need to be field-evaluated under local geo-epidemiological conditions. To keep vector populations at bay, it is advocated to upscale interventions for 'universal coverage' of human populations at risk to check malaria transmission and spread of drug-resistant malaria
Bridging the spatiotemporal gap in diazotroph activity and diversity with high-resolution measurements
No full textThe biological fixation of dinitrogen (N-2) by marine microbes called "diazotrophs" sustains similar to 50% new production in the ocean, boosting CO2 absorption by photoautotrophs and thus contributing to the mitigation of climate change. New environmental conditions sustaining N-2 fixation have been revealed in recent years, enabling more accurate forecasting of future nitrogen inputs and localized hot spots. However, at present the paucity and biased geographical coverage of N-2 fixation and diazotroph diversity measurements impede attempts to reconcile global nitrogen budgets with observed rates. Most studies have been conducted at disparate spatiotemporal scales, including: (i) discrete and short duration measurements in small seawater volumes isolated from the environment, and (ii) spatial extrapolations and global models of diazotrophy projected over decades to centuries. We argue that this knowledge gap lies at the fine scales: dynamic seawater structures < 200 km wide and < 2 months lifetime. However, the spatiotemporal resolution of conventional oceanographic cruises, with stations separated by tens to hundreds of kilometers, is too poor to resolve fine scale processes. Bridging this gap requires leveraging high spatiotemporal resolution measurements. Here we present and discuss the advantages and disadvantages of contemporary methods and equipment able to provide high-resolution measurements at sea. We also provide insights into high-resolution sampling approaches to be developed in the near future. Increasing the spatiotemporal resolution of diazotroph activity and diversity will provide more realistic quantifications of nitrogen fluxes in the dynamic ocean