Maternal exposure to a Western-style diet causes differences in intestinal microbiota composition and gene expression of suckling mouse pups

Scope:The long-lasting consequences of nutritional programming during the early phase of life have become increasingly evident. The effects of maternal nutrition on the developing intestine are still underexplored. Methods and results: In this study we observed 1) altered microbiota composition of the colonic luminal content, and 2) differential gene expression in the intestinal wall in two-week-old mouse pups born from dams exposed to a Western-style (WS) diet during the perinatal period. A sexually dimorphic effect was found for the differentially expressed genes in the offspring of WS diet-exposed dams but no differences between male and female pups were found for the microbiota composition. Integrative analysis of the microbiota and gene expression data revealed that the maternal WS diet independently affected gene expression and microbiota composition. However, the abundance of bacterial families not affected by the WS diet (Bacteroidaceae, Porphyromonadaceae and Lachnospiraceae) correlated with the expression of genes playing a key role in intestinal development and functioning (e.g. Pitx2 and Ace2). Conclusion: Our data reveal that maternal consumption of a WS diet during the perinatal period alters both gene expression and microbiota composition in the intestinal tract of two-week-old offspring

Characterization of Ceftazidime Resistance Mechanisms in Clinical Isolates of Burkholderia pseudomallei from Australia

Burkholderia pseudomallei is a Gram-negative bacterium that causes the serious human disease, melioidosis. There is no vaccine against melioidosis and it can be fatal if not treated with a specific antibiotic regimen, which typically includes the third-generation cephalosporin, ceftazidime (CAZ). There have been several resistance mechanisms described for B. pseudomallei, of which the best described are amino acid changes that alter substrate specificity in the highly conserved class A β-lactamase, PenA. In the current study, we sequenced penA from isolates sequentially derived from two melioidosis patients with wild-type (1.5 µg/mL) and, subsequently, resistant (16 or ≥256 µg/mL) CAZ phenotypes. We identified two single-nucleotide polymorphisms (SNPs) that directly increased CAZ hydrolysis. One SNP caused an amino acid substitution (C69Y) near the active site of PenA, whereas a second novel SNP was found within the penA promoter region. In both instances, the CAZ resistance phenotype corresponded directly with the SNP genotype. Interestingly, these SNPs appeared after infection and under selection from CAZ chemotherapy. Through heterologous cloning and expression, and subsequent allelic exchange in the native bacterium, we confirmed the role of penA in generating both low-level and high-level CAZ resistance in these clinical isolates. Similar to previous studies, the amino acid substitution altered substrate specificity to other β-lactams, suggesting a potential fitness cost associated with this mutation, a finding that could be exploited to improve therapeutic outcomes in patients harboring CAZ resistant B. pseudomallei. Our study is the first to functionally characterize CAZ resistance in clinical isolates of B. pseudomallei and to provide proven and clinically relevant signatures for monitoring the development of antibiotic resistance in this important pathogen

Les externalités polluantes : une source de fluctuations endogènes de l’activité économique

Depuis l'article de Zhang (1999), un nombre croissant de contributions académiques s'attellent à explorer les canaux par lesquels la pollution peut être la source de cycles économiques endogènes. Nous sommes convaincus que cette ligne de recherche est d'une grande importance pour le décideur public car elle réconcilie ses impératifs de court terme avec le long terme qu'impose la préservation de l'environnement. C'est pourquoi, cette thèse se propose d'explorer de nouveaux canaux par lesquels la pollution peut induire l'apparition de cycles économiques endogènes. Les chapitres 1,2 et 3 se basent sur des résultats empiriques récents arguant que la pollution agit négativement sur la productivité du travail et sur l'offre de travail. Au travers de ces chapitres, nous montrons que de tels effets de la pollution peuvent conduire à l'apparition de cycles économiques, tant déterministes que stochastiques, au voisinage de l'état stationnaire.Le chapitre 4 se concentre sur l'étude du système de taxe verte existant dans la plupart des pays de l'OCDE. Nous montrons en particulier que sa régressivité par rapport aux revenus des ménages peut conduire à l'apparition d'équilibres à tâches solaires.Since Zhang (1999), a rising number of contributions explore channels by which pollution can induce endogenous business cycles. We believe that this research line is of great interest because it reconciles the short run imperative of policy leaders and the long run imperative of environmental preservation. Consequently, the present dissertation aims to contribute to this strand of literature by pointing out new channels by which pollution can induce endogenous business cycles.Chapters 1, 2 and 3 depart from some new empirical findings who stress nonmarginal negative effect of pollution on labor productivity and on labor supply. Within those chapters, we show that such pollution effects can lead to deterministic cycles as well as stochastic fluctuations around the steady state.The chapter 4 is devoted to the study of the already existing green fiscal policies in most of OECD countries. We show in particular that their well-known regressivity, with respect to households' incomes, may promote sunspot equilibria

Pollution, carrying capacity and the Allee effect

Pollution, carrying capacity and the Allee effec

Pollution effects on disease transmission and economic stability

International audienceIn this article, we embed a model of disease spread into a Ramsey model. A stock of pollution, viewed as a productive externality, affects both the disease transmission and the consumption demand. An eco-friendly government levies a proportional Pigouvian tax on production to depollute. We show the coexistence of two steady states in the long run: a disease-free and an endemic steady state. At the endemic steady state, a higher green-tax rate always reduces the pollution level. In the short run, we show the existence of limit cycles (through a Hopf bifurcation) as well as more complex dynamics of codimension two (a Gavrilov-Guckenheimer bifurcation). We complete the study with a numerical illustration of these bifurcations and a new facet of the Green Paradox: a higher tax rate can allow more scope for cycles by lowering the critical aversion to pollution and, thus, contribute to destabilization of the economy and promotion of the intergenerational inequalities

Demography and pollution

Forthcomin

Local bifurcations of three and four-dimensional systems: A tractable characterization with economic applications

We provide necessary and sufficient conditions to detect local bifurcations of three and four-dimensional dynamical systems in continuous time. We characterize not only the bifurcations of codimension one but also those of codimension two. For the sake of completeness, we give also the non-degeneracy conditions for each bifurcation. The added value of our methodology rests on its generality. To illustrate the tractability of our approach, we provide two analytical applications of dimension three and four to environmental economics, complemented with numerical simulations. (C) 2018 Elsevier B.V. All rights reserved

Pollution effects on disease transmission and economic stability

International audienceIn this article, we embed a model of disease spread into a Ramsey model. A stock of pollution, viewed as a productive externality, affects both the disease transmission and the consumption demand. An eco-friendly government levies a proportional Pigouvian tax on production to depollute. We show the coexistence of two steady states in the long run: a disease-free and an endemic steady state. At the endemic steady state, a higher green-tax rate always reduces the pollution level. In the short run, we show the existence of limit cycles (through a Hopf bifurcation) as well as more complex dynamics of codimension two (a Gavrilov-Guckenheimer bifurcation). We complete the study with a numerical illustration of these bifurcations and a new facet of the Green Paradox: a higher tax rate can allow more scope for cycles by lowering the critical aversion to pollution and, thus, contribute to destabilization of the economy and promotion of the intergenerational inequalities

Natural cycles and pollution

In this paper, we study a competitive economy where a pollution externality, coming from production, impairs the renewable resource affecting the consumption demand in turn. A proportional tax, levied on the production level, is introduced to finance public depollution expenditures.In the long run, two steady states can coexist, the one with a lower resource level, the other with a higher level. Interestingly, a higher green tax rate reduces the natural resource in the low steady state, giving rise to a Green Paradox (Sinn, 2008). Moreover, the green tax can be welfare-improving in the higher steady state but never in the lower one. Therefore, in the second one, it is better to reduce the green tax rate as much as possible. Conversely, the optimal tax rate is positive and unique in the steady state with more natural resource.In the short run, the two steady states can collide and disappear through a saddle-node bifurcation. Since consumption and natural resource are substitutable goods, a limit cycle can arise around the higher stationary state. To the contrary, this kind of cycles never occurs around the lower steady state, no matter the resource effect on consumption. Finally, focusing on the variety of bifurcations of codimension two, we find a Bogdanov-Takens loop. (C) 2018 Elsevier B.V. All rights reserved

Biodiversity, Infectious Diseases, and the Dilution Effect

International audienceBiologists point out that biodiversity loss contributes to promote the transmission of diseases. In epidemiology, this phenomenon is known as dilution effect. Our paper aims to introduce this effect in an economic model where the spread of an infectious disease is considered. More precisely, we embed a SIS model into a Ramsey model (1928) where a pollution externality coming from production affects the evolution of biodiversity. Biodiversity is assimilated to a renewable resource and affects the infectivity of the disease (dilution effect). A green tax is levied on production at the firm level to finance depollution according to a balanced budget rule. In the long run, a disease-free and an endemic regime are possible. We focus only on the second case and we find that the magnitude of the dilution effect determines the number of steady states. When the dilution effect remains low, there are two cases depending on the environmental impact of production: (1) a low impact implies two steady states with high and low biodiversity respectively; (2) a large impact rules out any steady state. Conversely, when the dilution effect becomes high, a (unique) steady state always exists: a strong dilution effect works as a buffer and prevents the human pressure from being lethal for biodiversity in the long run. Moreover, under a low dilution effect, a higher green tax rate always impairs biodiversity at the low steady state, while this green paradox is over under a high dilution effect. In the short run, we show that a limit cycle can arise around the high biodiversity steady state when the dilution effect is low. Surprisingly, the limit cycle is preserved under a high dilution effect. In other words, even if a strong dilution effect preserves the biodiversity in the long run and prevents the economy from the green paradox, it does not shelter the economy from the occurrence of biodiversity fluctuations