Enhanced co-tolerance and co-sensitivity from long-term metal exposures of heterotrophic and autotrophic components of fluvial biofilms

Understanding the interactive effects of multiple stressors on ecosystems has started to become a major concern. The aim of our study was therefore to evaluate the consequences of a long-term exposure to environmental concentrations of Cu, Zn and As on the pollution induced community tolerance (PICT) of lotic biofilm communities in artificial indoor channels. Moreover, the specificity of the PICT was assessed by evaluating the positive and negative co-tolerance between these metals. Photosynthetic efficiency and substrate-induced respiration (SIR), targeting the autotrophic and heterotrophic communities respectively were used in short-term inhibition bioassays with Cu, Zn and As to assess sensitivities of preexposed biofilms to the metals tested. Diversity profiles of a phototrophic, eukaryotic and prokaryotic community in biofilms following the different treatments were determined and analyzed with principal component analysis. The results demonstrated that pre-exposure to metals induced structural shifts in the community and led to tolerance enhancements in the phototrophic and heterotrophic communities. On the other hand, whatever the functional parameter used (i.e. photosynthesis and SIR), communities exposed to Cu were more tolerant to Zn and vice versa. Furthermore, only phototrophic communities pre-exposed to As developed tolerance to Cu but not to Zn, whereas no co-tolerance between Cu and As was observed in the heterotrophic communities. Finally, phototrophic and heterotrophic communities exposed to Cu and Zn became more sensitive to As, reflecting a negative co tolerance between these metals. Overall, our findings support the fact that although the mode of action of the different metals is an important driver for the structure and thus the tolerance of the communities, it appears that the detoxification modes are the most important factors for the occurrence of positive or negative co-tolerance

Predicting rotor heat transfer using the viscous blade element momentum theory and unsteady vortex lattice method

Calculating the unsteady convective heat transfer on helicopter blades is the first step in the prediction of ice accretion and the design of ice-protection systems. Simulations using Computational Fluid Dynamics (CFD) successfully model the complex aerodynamics of rotors as well as the heat transfer on blade surfaces, but for a conceptual design, faster calculation methods may be favorable. In the recent literature, classical methods such as the blade element momentum theory (BEMT) and the unsteady vortex lattice method (UVLM) were used to produce higher fidelity aerodynamic results by coupling them to viscous CFD databases. The novelty of this research originates from the introduction of an added layer of the coupling technique to predict rotor blade heat transfer using the BEMT and UVLM. The new approach implements the viscous coupling of the two methods from one hand and introduces a link to a new airfoil CFD-determined heat transfer correlation. This way, the convective heat transfer on ice-clean rotor blades is estimated while benefiting from the viscous extension of the BEMT and UVLM. The CFD heat transfer prediction is verified using existing correlations for a flat plate test case. Thrust predictions by the implemented UVLM and BEMT agree within 2% and 80% compared to experimental data. Tip vortex locations by the UVLM are predicted within 90% but fail in extreme ground effect. The end results present as an estimate of the heat transfer for a typical lightweight helicopter tail rotor for four test cases in hover, ground effect, axial, and forward flight

Prostaglandin profiling reveals a role for haematopoietic prostaglandin D synthase in adipose tissue macrophage polarisation in mice and humans.

BACKGROUND/OBJECTIVES: Obesity has been associated with both changes in adipose tissue lipid metabolism and inflammation. A key class of lipid-derived signalling molecules involved in inflammation are the prostaglandins. In this study, we aimed to determine how obesity affects the levels of prostaglandins within white adipose tissue (WAT) and determine which cells within adipose tissue produce them. To avoid the effects of cellular stress on prostaglandin levels, we developed a multivariate statistical approach in which metabolite concentrations and transcriptomic data were integrated, allowing the assignment of metabolites to cell types. SUBJECTS/METHODS: Eicosanoids were measured by liquid chromatography-tandem mass spectrometry and mRNA levels using real-time PCR. Eicosanoid levels and transcriptomic data were combined using principal component analysis and hierarchical clustering in order to associate metabolites with cell types. Samples were obtained from C57Bl/6 mice aged 16 weeks. We studied the ob/ob genetically obese mouse model and diet-induced obesity model. We extended our results in mice to a cohort of morbidly obese humans undergoing bariatric surgery. RESULTS: Using our modelling approach, we determined that prostglandin D₂ (PGD₂) in adipose tissue was predominantly produced in macrophages by the haematopoietic isoform of prostaglandin D synthase (H-Pgds). Analysis of sub-fractionated WAT confirmed that H-Pgds was expressed in adipose tissue macrophages (ATMs). Furthermore, H-Pgds expression in ATMs isolated from lean and obese mice was consistent with it affecting macrophage polarisation. Functionally, we demonstrated that H-PGDS-produced PGD₂ polarised macrophages toward an M2, anti-inflammatory state. In line with a potential anti-inflammatory role, we found that H-PGDS expression in ATMs was positively correlated with both peripheral insulin and adipose tissue insulin sensitivity in humans. CONCLUSIONS: In this study, we have developed a method to determine the cellular source of metabolites within an organ and used it to identify a new role for PGD₂ in the control of ATM polarisation.HQL-79 was a kind gift of Professor Yoshihiro Urade. Professor Vidal-Puig was funded by the BHF, MRC and BBSRC. Dr Virtue was funded by the BBSRC and the BHF. Dr Eiden, Dr Masoodi and Dr Griffin were funded by the MRC. Dr Mok was funded by the Wellcome Trust.This is the final published version. It first appeared at http://www.nature.com/ijo/journal/vaop/ncurrent/full/ijo201534a.htm

Aldo Keto Reductase 1B7 and Prostaglandin F2α Are Regulators of Adrenal Endocrine Functions

Prostaglandin F2α (PGF2α), represses ovarian steroidogenesis and initiates parturition in mammals but its impact on adrenal gland is unknown. Prostaglandins biosynthesis depends on the sequential action of upstream cyclooxygenases (COX) and terminal synthases but no PGF2α synthases (PGFS) were functionally identified in mammalian cells. In vitro, the most efficient mammalian PGFS belong to aldo-keto reductase 1B (AKR1B) family. The adrenal gland is a major site of AKR1B expression in both human (AKR1B1) and mouse (AKR1B3, AKR1B7). Thus, we examined the PGF2α biosynthetic pathway and its functional impact on both cortical and medullary zones. Both compartments produced PGF2α but expressed different biosynthetic isozymes. In chromaffin cells, PGF2α secretion appeared constitutive and correlated to continuous expression of COX1 and AKR1B3. In steroidogenic cells, PGF2α secretion was stimulated by adrenocorticotropic hormone (ACTH) and correlated to ACTH-responsiveness of both COX2 and AKR1B7/B1. The pivotal role of AKR1B7 in ACTH-induced PGF2α release and functional coupling with COX2 was demonstrated using over- and down-expression in cell lines. PGF2α receptor was only detected in chromaffin cells, making medulla the primary target of PGF2α action. By comparing PGF2α-responsiveness of isolated cells and whole adrenal cultures, we demonstrated that PGF2α repressed glucocorticoid secretion by an indirect mechanism involving a decrease in catecholamine release which in turn decreased adrenal steroidogenesis. PGF2α may be regarded as a negative autocrine/paracrine regulator within a novel intra-adrenal feedback loop. The coordinated cell-specific regulation of COX2 and AKR1B7 ensures the generation of this stress-induced corticostatic signal

Bacterial activity and its trophic role in a eutrophic pond

The trophic role of bacteria in the microbial loop was examined fish pond receiving organic fertilizer. Two types of experiments were carried out : the first in situ aimed at studying the trophic pathways after the addition of a nitrogen-rich organic fertilizer ; the second in vitro aimed at defining the role of bateria in this particular aquatic environment. In situ experiments showed that addition of a nitrogen-rich fertilizer decreased the C/N ratio of the water and then enhanced mineralization of organic matter by bacteria. A strong phytoplankton outbreak occurred as a result, which then caused the development of a larger-sized filter-feeding zooplankton population with a phytoplankton grazing tendency. On the other hand, according to the literature, a fertilizer having a high C/N should favour bacterial organotrophic activity and growth, which ought to cause the growth of a small-sized bactrerioplankton grazer. This present study discusses the variations of mineralization rates and of biosynthesis rates, two tightly connected processes that occured in fish ponds : these two processes of the trophic pathway govern prey quality for fishes. Small-sized bacteria (under GFF filters) were not uch influenced by the fertilizer ; conversely, large-sized bacteria (over GFF filters) exhibited an increase in activity due to primarily fetilizer input and later due to the lysis of algal cells. / Le rôle trophique des bactéries dans la boucle microbienne a été étudié dans un étang eutrophe fertilisé organiquement. Deux séries d'expériences ont été réalisées : la première avait pour objectif d'étudier les voies trophiques après l'ajout d'un fertilisant riche en azote organique ; la seconde visait à définir le rôle des bactéries dans cet environnement particulier. Des expériences in situ ont montré que l'apport de fertilisant azoté baissait le rapport C/N de l'eau et de ce fait renforçait la minéralisation de la matière organique par les bactéries. Une forte croissance du phytoplancton est apparue, provoquant un augmentation de la population de zooplancton filtreur de grande taille. Par ailleurs, selon la littérature, un fertilisant de fort C/N devrait favoriser l'activité organotrophe et la croissance bactérienne, ce qui devrait entraîner un développement des bactériophages. La présente étude discute des variations des taux de minéralisation et des taux de biosynthèse, qui sont deux processus étroitement connectés en étang de pisciculture: ces deux processus gouvernent la qualité des proies pour les poissons. Les petites bactéries (sous la filtration GFF)ne sont pas très influencées par le fertilisant; à l'opposé, les bactéries de grande taille (au dessus des filtres GFF) montrent une forte augmentation de leur activité due d'abord à l'apport de fertilisant, puis à la lyse des cellules algales

Impact des eaux d'égouttage de sédiments contaminés sur des microorganismes aquatiques : évaluation contradictoire de la toxicité des sédiments

Les sédiments de cours d'eau ou de canaux font l'objet d'opérations de dragage lorsqu'ils augmentent le risque d'inondation ou limitent la navigation. Fréquemment contaminés dans les zones urbanisées, les matériaux collectés peuvent alors être mis en dépôts : décharge contrôlée, comblement de gravières et mise en dépôt sur sol. Dans ce dernier cas, les eaux d'infiltration ou de ruissellement issues des dépôts peuvent entraîner des effets sur les écosystèmes aquatiques adjacents suite à la remobilisation et à la dispersion des polluants sédimentaires. L'objectif de ce travail était d'évaluer les effets de ces eaux d'égouttage sur des microorganismes aquatiques, soit par des bioessais standardisés et normalisés (MetPlateÒ, croissance en 72h de Pseudo-kirchneriella subcapitata) soit par des approches fonctionnelles utilisant des communautés microbiennes naturelles d'un sédiment de référence, dans le cadre d'essais et d'exposition de courte durée aux eaux d'égouttage (mesures d'activités enzymatiques extracellulaires, respiration, nitrification et dénitrification, phosphatase et croissance algale. L'ensemble de ces paramètres décrit le potentiel métabolique (aussi bien sur le plan hydrolytique et dégradatif que sur celui de labiosynthèse) des microorganismes et donc leur capacité à contribuer aux grand cycles biochimiques (C, N, P). 5 sédiments et 5 eaux d'égouttage (EE) ont été analysé (nutriments et MO, micropolluants métalliques et organiques) et testé. Les résultats ont montré une grande diversité de réponse selon les bioessais: inhibition, stimulation ou indifférence. La glucosidase et le test MetplateÒ sont les plus sensibles aux eaux testées, leur inhibition reste faible. A l'inverse, la croissance de l'algue P. subcapitata est stimulée dans des proportions variables selon les concentrations d'EE testées alors que son activité phosphatasique reste peu modifiée. La complexité chimique de ces eaux riches en éléments nutritifs explique probablement la variablité des réponses malgré une forte charge en micropolluants (antagonismes d'action, toxicité masquée par une stimulation de croissance ou d'activité)