Calcul de probabilités de dépassement d'objectifs environnementaux de rejets de sources ponctuelle et diffuse à l'aide du système de modélisation intégrée GIBSI

Dans un contexte de gestion intégrée de l'eau par bassin versant, on doit, avant d'implanter tout programme d'assainissement, comparer les solutions de rechange, distinguer les contributions des différentes sources de pollution aux problèmes de qualité de l'eau, et définir des objectifs environnementaux de rejet (OER) associés aux activités et aux pressions anthropiques. Dans le cas des sources de pollution d'origine ponctuelle, on détermine un OER et son risque de dépassement en fonction d'un débit d'étiage critique d'une période de retour donnée. Dans le cas de la pollution diffuse d'origine agricole, il n'existe pas de concepts similaires pour définir des OER. L'approche que nous proposons, c'est de simuler, à l'aide de chroniques météorologiques et de divers scénarios de gestion de ces rejets, les concentrations résultantes dans les cours d'eau et de calculer les probabilités de dépassement des critères de qualité de l'eau (CQE). Cette approche permet de caractériser la prise de décision pour la période de contrôle en matière du nombre moyen de jours de dépassement d'un CQE. Ceci représente une quantification plus exacte du risque car ce dernier est interprété en fonction de ce qui est mesuré en rivière, c'est-à-dire les concentrations de polluants. Dans cette étude, on illustre l'application de ce concept à partir d'un cas de figure dans le bassin versant de la rivière Chaudière (Québec, Canada) qui est simulé avec le système de modélisation intégrée GIBSI. Dans le cadre d'une analyse de scénarios de restauration des activités récréatives conduisant à des contacts directs et fréquents avec l'eau, on illustre comment on peut, en réduisant respectivement les pressions agricole et urbaine de 32 et 17%, abaisser globalement les probabilités de dépassement des critères esthétique et bactériologique de 0,32 à 0,19 et de 0,94 à 0, respectivement.In an integrated watershed management context, the implementation of any clean water program requires the evaluation of the contribution of pollutant loads associated with wet (nonpoint or diffuse) and dry weather (point) sources to the studied water quality problem. It is also necessary to set environmental load allocations (ELA) or total maximum daily loads (TMDL) for various anthropogenic activities and to link these loads to water pollutant concentrations. The ELA or TMDL is a numerical quantity determining the maximum load of pollutants from point and nonpoint sources as well as background sources, to receiving water bodies that will meet designated water uses (e.g., swimming or fishing) in terms of water quality standards (WQS). The American Congress included a TMDL program in the Clean Water Act of 1972 (US EPA, 1997; 1999). The outcome of the TMDL program corresponds to the drafting of a watershed management plan (NOVOTNY, 1999).Estimation of ELA from point sources is generally based on simultaneous occurrence of severe low flows and maximum daily loads. The ensuing risk of not meeting WQS is usually linked to the inverse of the return period of the design flow. Meanwhile, estimation of ELA from diffuse sources, and associated environmental risks, is not as well established since diffuse sources of pollution generally occur during important runoff events and strongly depend on land use and management practices. These wet weather loads may be allocated using continuous hydrological modelling. Simulation results can then in return be used to link ELA from point sources and diffuse sources to pollutant concentrations and, for a given time period (e.g., summer), to evaluate the probabilities (namely the risks) of exceeding WQS designating the water use.The objective of this study was to present, using the integrated modelling system GIBSI (VILLENEUVE et al., 1998b; MAILHOT et al.,1997), this new approach to assess the risk associated with the establisment of ELA from point and diffuse sources. A case study on the Chaudière River watershed (Quebec, Canada) was defined and simulations were performed (scenarios A-E). The case study focussed on determining whether WQS defining the designated recreational use of water requiring direct and prolonged contact were attainable. Untreated municipal waste waters from a small town (St. Martin) and nonpoint source pollution were responsible for impairment of the studied river segment. Water contaminants considered were fecal coliforms (FC) and phosphorus (P).Two base case scenarios, A and C, were simulated using four years (1982-1985) of meteorological data to illustrate the degraded bacteriological and aesthetic conditions of the river segment due to dry and wet weather sources, respectively. Dry weather sources were assumed to solely contribute to the bacteriological impairment. Meanwhile, both wet and dry weather sources were assumed to contribute to aesthetic impairment. Scenario B was defined to examine the impact of constructing a waste water treatment plant (WWTP) for the town of St. Martin on the bacteriological conditions. Scenarios D and E were elaborated to quantify the impact of both reducing diffuse and point source loads on aesthetic conditions, respectively. For scenario C, on average 31 kg P/ha were applied on cultivated land according to local fertilization calendars. Similarly, the fertilization rate for scenarios D and E was on average 13 kg P/ha. The design stream flow for ELA from point sources was a30 Q5 (30-day low flow, 5-year return period) and estimated at 6.05 m3 /s for the studied river segment. It is noteworthy to mention that for the 1982-1985 summers (June 21 through September 20), simulated daily stream flows exceeded the design flow 31, 62, 19 and 2 times and that 150, 48, 348, and 270 Mm3 of water flowed through the studied river segment, respectively. This means the 1983 meteorological series was three times as dry as that of 1982 despite the fact it was the latter that produced the30 Q5. The ELA from both point and diffuse sources for the river segment receiving the St. Martin's effluent and the studied river segment were 0.75*1012 UFC and 11.21 kg P and 1.05* 1012 UFC and 15.68 kg P, respectively.For scenario A, simulation results showed that respectively 94% and 14% of the time, the bacteriological (WQSFC < 200 UFC/100 ml) and aesthetic (WQSP < 0,03 P mg/l) WQS were not met over the summer season of the four-year meteorological series. Similarly, for scenario C, the simulation results indicated that 32% of the time, the aesthetic WQS was not achieved. Dry weather sources, namely WWTP and wet weather sources, namely agricultural runoff, accounted for P loads. During the driest summer, dry weather sources accounted for 63% of the P loads. For the other summers, wet weather sources accounted for 71, 88, and 78% of total P loads. For scenario B, simulation results showed that the bacteriological WQS was met 100% of the time. Meanwhile, scenario D was designed to see whether a 27% reduction of the agricultural nonpoint source load could alone restore the aesthetic properties. The simulation results showed an improvement as the probability of exceedence dropped from 0.32 to 0.27. This probability was further lowered to 0.19 when St. Martin's waste waters were treated using aerated lagoons and dephosphotation. This corresponded to an additional 17% abatement of the dry weather sources loads (scenario E).It is noteworthy that this study did not specifically attempt to specify the reasons why WQS were not met, whether it was due to low stream flows or large point or nonpoint sources loads although the integrated modelling system allows for this. Also, this study did not attempt to determine impacts of local management scenarios instead of a systematic reduction though GIBSI also allows for this. However, this study clearly illustrated how the proposed methodology, which is rooted in a risk assessment approach based on evaluation of the probability of exceeding WQS, is well suited to characterise ELA for various anthropogenic activities. Indeed, simulation results clearly demonstrated the benefits of assessing independently the impacts of ELA from point and diffuse sources on the attainability of a designated water use. It is believed that this type of ELA assessment approach will facilitate communication with stakeholders. Ideally, these exceeding probabilities should be evaluated using long meteorological series (e.g., 30 years)

Trajectories of self-rated health in people with diabetes: Associations with functioning in a prospective community sample

© 2013 Schmitz et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Background: Self-rated health (SRH) is a single-item measure that is one of the most widely used measures of general health in population health research. Relatively little is known about changes and the trajectories of SRH in people with chronic medical conditions. The aims of the present study were to identify and describe longitudinal trajectories of self-rated health (SRH) status in people with diabetes. Methods: A prospective community study was carried out between 2008 and 2011. SRH was assessed at baseline and yearly at follow-ups (n=1288). Analysis was carried out through trajectory modeling. The trajectory groups were subsequently compared at 4 years follow-up with respect to functioning. Results: Four distinct trajectories of SRH were identified: 1) 72.2% of the participants were assigned to a persistently good SRH trajectory; 2) 10.1% were assigned to a persistently poor SRH trajectory; 3) mean SRH scores changed from good to poor for one group (7.3%); while 4) mean SRH scores changed from poor to medium/good for another group (10.4%). Those with a persistently poor perception of health status were at higher risk for poor functioning at 4 years follow-up than those whose SRH scores decreased from good to poor. Conclusions: SRH is an important predictor for poor functioning in diabetes, but the trajectory of SRH seems to be even more important. Health professionals should pay attention to not only SRH per se, but also changes in SRH over time.This work was supported by Operating Grant MOP-84574 from the Canadian Institutes of Health Research (CIHR). GG was supported by a doctoral fellowship from the CIHR. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Phototoxic aptamers selectively enter and kill epithelial cancer cells

The majority of cancers arise from malignant epithelial cells. We report the design of synthetic oligonucleotides (aptamers) that are only internalized by epithelial cancer cells and can be precisely activated by light to kill such cells. Specifically, phototoxic DNA aptamers were selected to bind to unique short O-glycan-peptide signatures on the surface of breast, colon, lung, ovarian and pancreatic cancer cells. These surface antigens are not present on normal epithelial cells but are internalized and routed through endosomal and Golgi compartments by cancer cells, thus providing a focused mechanism for their intracellular delivery. When modified at their 5′ end with the photodynamic therapy agent chlorin e6 and delivered to epithelial cancer cells, these aptamers exhibited a remarkable enhancement (>500-fold increase) in toxicity upon light activation, compared to the drug alone and were not cytotoxic towards cell types lacking such O-glycan-peptide markers. Our findings suggest that these synthetic oligonucleotide aptamers can serve as delivery vehicles in precisely routing cytotoxic cargoes to and into epithelial cancer cells

Effects of an Early Handling-Like Procedure and Individual Housing on Anxiety-Like Behavior in Adult C57BL/6J and DBA/2J Mice

Manipulations of rearing conditions have been used to examine the effects of early experience on adult behavior with varying results. Evidence suggests that postnatal days (PND) 15–21 are a time of particular susceptibility to environmental influences on anxiety-like behavior in mice. To examine this, we subjected C57BL/6J and DBA/2J mice to an early handling-like procedure. Pups were separated from dams from PND 12–20 for 30 minutes daily or received standard care. On PND 21, pups were weaned and either individually- or group- housed. On PND 60, anxiety-like behavior was examined on the elevated zero-maze. Although individually- housed animals took longer to enter an open quadrant of the maze, they spent more time in the open than group-housed animals. Additionally, we observed a trend of reduced anxiety-like behavior in C57BL/6J, but not DBA/2J mice that underwent the handling-like procedure

Simulation Modifies Prehension: Evidence for a Conjoined Representation of the Graspable Features of an Object and the Action of Grasping It

Movement formulas, engrams, kinesthetic images and internal models of the body in action are notions derived mostly from clinical observations of brain-damaged subjects. They also suggest that the prehensile geometry of an object is integrated in the neural circuits and includes the object's graspable characteristics as well as its semantic properties. In order to determine whether there is a conjoined representation of the graspable characteristics of an object in relation to the actual grasping, it is necessary to separate the graspable (low-level) from the semantic (high-level) properties of the object. Right-handed subjects were asked to grasp and lift a smooth 300-g cylinder with one hand, before and after judging the level of difficulty of a “grasping for pouring” action, involving a smaller cylinder and using the opposite hand. The results showed that simulated grasps with the right hand exert a direct influence on actual motor acts with the left hand. These observations add to the evidence that there is a conjoined representation of the graspable characteristics of the object and the biomechanical constraints of the arm

Charged and Hydrophobic Surfaces on the A Chain of Shiga-Like Toxin 1 Recognize the C-Terminal Domain of Ribosomal Stalk Proteins

Shiga-like toxins are ribosome-inactivating proteins (RIP) produced by pathogenic E. coli strains that are responsible for hemorrhagic colitis and hemolytic uremic syndrome. The catalytic A1 chain of Shiga-like toxin 1 (SLT-1), a representative RIP, first docks onto a conserved peptide SD[D/E]DMGFGLFD located at the C-terminus of all three eukaryotic ribosomal stalk proteins and halts protein synthesis through the depurination of an adenine base in the sarcin-ricin loop of 28S rRNA. Here, we report that the A1 chain of SLT-1 rapidly binds to and dissociates from the C-terminal peptide with a monomeric dissociation constant of 13 µM. An alanine scan performed on the conserved peptide revealed that the SLT-1 A1 chain interacts with the anionic tripeptide DDD and the hydrophobic tetrapeptide motif FGLF within its sequence. Based on these 2 peptide motifs, SLT-1 A1 variants were generated that displayed decreased affinities for the stalk protein C-terminus and also correlated with reduced ribosome-inactivating activities in relation to the wild-type A1 chain. The toxin-peptide interaction and subsequent toxicity were shown to be mediated by cationic and hydrophobic docking surfaces on the SLT-1 catalytic domain. These docking surfaces are located on the opposite face of the catalytic cleft and suggest that the docking of the A1 chain to SDDDMGFGLFD may reorient its catalytic domain to face its RNA substrate. More importantly, both the delineated A1 chain ribosomal docking surfaces and the ribosomal peptide itself represent a target and a scaffold, respectively, for the design of generic inhibitors to block the action of RIPs

Pluronic F-127 hydrogel as a promising scaffold for encapsulation of dental-derived mesenchymal stem cells

Dental-derived mesenchymal stem cells (MSCs) provide an advantageous therapeutic option for tissue engineering due to their high accessibility and bioavailability. However, delivering MSCs to defect sites while maintaining a high MSC survival rate is still a critical challenge in MSC-mediated tissue regeneration. Here, we tested the osteogenic and adipogenic differentiation capacity of dental pulp stem cells (DPSCs) in a thermoreversible Pluronic F127 hydrogel scaffold encapsulation system in vitro. DPSCs were encapsulated in Pluronic(®) F-127 hydrogel and stem cell viability, proliferation and differentiation into adipogenic and osteogenic tissues were evaluated. The degradation profile and swelling kinetics of the hydrogel were also analyzed. Our results confirmed that Pluronic F-127 is a promising and non-toxic scaffold for encapsulation of DPSCs as well as control human bone marrow MSCs (hBMMSCs), yielding high stem cell viability and proliferation. Moreover, after 2 weeks of differentiation in vitro, DPSCs as well as hBMMSCs exhibited high levels of mRNA expression for osteogenic and adipogenic gene markers via PCR analysis. Our histochemical staining further confirmed the ability of Pluronic F-127 to direct the differentiation of these stem cells into osteogenic and adipogenic tissues. Furthermore, our results revealed that Pluronic F-127 has a dense tubular and reticular network morphology, which contributes to its high permeability and solubility, consistent with its high degradability in the tested conditions. Altogether, our findings demonstrate that Pluronic F-127 is a promising scaffold for encapsulation of DPSCs and can be considered for cell delivery purposes in tissue engineering