The vicious circle and infection intensity: The case of Trypanosoma microti in field vole populations

Objective: In natural populations, infection and condition may act synergistically to trigger a vicious circle: poor condition predisposes to host infections, which further reduce condition, and so on. If this vicious circle originates from a reduced resistance to infection, it will not only result in greater proneness to becoming infected of those that are in poorer condition, but it may also cause infections of higher intensity. Here, we investigate the temporal relationship between host condition and intensity of infection by a specific pathogen using as a system the dynamics of the protozoan Trypanosoma microti in field vole (Microtus agrestis) populations. Methods and results: With two years of longitudinal data from three monthly-sampled populations, we evaluated if individuals acquiring a high intensity of infection previously had lower haematological indicators of condition (red blood cells [RBCs] and lymphocyte counts) than those that acquired lower infection intensities. Also, the association of these indicators with past and present trypanosome blood levels was investigated. The individuals that developed high levels of parasitaemia were those that previously had low lymphocyte counts. Greater intensity of infection corresponded with lower RBCs only in low to moderate weight females, and no effect of intensity of infection on lymphocyte counts was observed. However, delayed effects of high trypanosome intensity were seen on both RBCs and lymphocytes. Conclusions: The vicious circle may also result in high infection intensity: individuals in poor condition are not only more likely to become infected by one pathogen; they may also be the most important source of infection for that and for other pathogens, and thus key protagonists for parasite dynamics.Fil: Beldomenico, Pablo Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Ciencias Veterinarias del Litoral. Universidad Nacional del Litoral. Facultad de Ciencias Veterinarias. Instituto de Ciencias Veterinarias del Litoral; ArgentinaFil: Telfer, Sandra. University of Liverpool; Reino UnidoFil: Gebert, Stephanie. University of Liverpool; Reino UnidoFil: Lukomski, Lukasz. University of Liverpool; Reino UnidoFil: Bennett, Malcolm. University of Liverpool; Reino UnidoFil: Begon, Michael. University of Liverpool; Reino Unid

Montaigne i Descartes: dues propostes modernes de vida

S'intenta mostrar que tant Montaigne com Descartes són dos filòsofs moderns i que defensen una idea de la filosofia com a discurs orientat a la praxi i que implica viure d'una determinada manera. L'escriptura de l'assaig és l'element de modernitat de la proposta de vida montaniana, resultat de la constatació que tot coneixement és coneixement d'un subjecte i que, per tant, correspon al subjecte posar-se a prova construint un discurs sobre si mateix, que és un discurs transformador. La imatge cartesiana de l'arbre de la filosofia s'orienta a l'acció humana. Tant en Montaigne com en Descartes la filosofia és considerada com a activitat teòrico-pràctica. Els dos escriuen per jutjar millor i jutjarse millor, si bé hi ha una diferència epistemològica entre l?home montanià i l'home cartesià.I will try to show that both Montaigne and Descartes are modern philosophers who conceive philosophy as a praxis-oriented discourse, which implies living in a certain way. Essay writing is the element of modernity in Montaigne?s proposal of a way of life,resulting from the fact that there is no knowledge without a subject having it, so that it is the subject?s task to put himself to a test by producing a self-transforming discourse on himself. In a similar vein, the cartesian image of the tree of philosophy is also supposed to guide human action. Both Montaigne and Descartes consider philosophy to be a theoretico-practical activity. Both write to judge better and to judge themselves better, although it is necessary to acknowledge there is an epistemological difference between montaignian man and cartesian man

Immunité innée : Expression cutanée et fonction des récepteurs Toll-like

Les récepteurs Toll-like (TLR) sont des récepteurs membranaires de découverte récente, impliqués dans l’immunité immédiate. Découverts chez la drosophile, ils se sont révélés être des structures phylogénétiquement très conservées. Ubiquitaires dans l’organisme, ils sont particulièrement présents dans les cellules de l’immunité et les tissus barrières. Les TLR, au nombre de 11 chez l’homme, reconnaissent un petit nombre de structures moléculaires propres aux micro-organismes, communes à de nombreux pathogènes. Les TLR peuvent également être activés par des ligands endogènes physiologiques. L’activation d’un TLR est à l’origine d’une cascade signalétique aboutissant à la translocation nucléaire de NF-κB et à la sécrétion de cytokines pro-inflammatoires. La peau, qui constitue une barrière contre les aggressions, exprime de nombreux TLR à la surface des kératinocytes.Toll receptors were first identified as an essential molecule for embryonic patterning in Drosophila and were subsequently shown to be a key in antibacterial and antifungal immunity in adult flies. Toll receptors have been conserved throughout evolution. In mammals, TLRs have been implicated in both inflammatory responses and innate host defense to pathogens. The 11 different TLRs recognize conserved molecular patterns of microbial pathogens termed pathogen-specific molecular patterns (PAMPs), that permit to confer responsiveness to a wide variety of pathogens. Endogenous ligands are also able to activate TLRs. All adult tissue is capable to express at least one of member of TLR family, but a largest repertoire of TLRs is found in tissues exposed to the external environment. The TLR activation induce the NF-κB translocation to the nucleus and cytokine secretion. Since the primary function of skin is to provide an effective barrier against outside agression, it is likely that keratinocytes may play a role in a rapid and efficient host defence system, and the fact that keratinocytes are capable of expressing a wide variety of TLRs is subsequently not surprising

Transcriptome-wide analysis reveals different categories of response to a standardised immune challenge in a wild rodent

Individuals vary in their immune response and, as a result, some are more susceptible to infectious disease than others. Little is known about the nature of this individual variation in natural populations, or which components of immune pathways are most responsible, but defining this underlying landscape of variation is an essential first step to understanding the drivers of this variation and, ultimately, predicting the outcome of infection. We describe transcriptome-wide variation in response to a standardised immune challenge in wild field voles. We find that markers can be categorised into a limited number of types. For the majority of markers, the response of an individual is dependent on its baseline expression level, with significant enrichment in this category for conventional immune pathways. Another, moderately sized, category contains markers for which the responses of different individuals are also variable but independent of their baseline expression levels. This category lacks any enrichment for conventional immune pathways. We further identify markers which display particularly high individual variability in response, and could be used as markers of immune response in larger studies. Our work shows how a standardised challenge performed on a natural population can reveal the patterns of natural variation in immune response

Three cases of identity (re)construction through art interventions: the dialogical and the 'sensible'

Identity construction (IC) cannot be reduced to discourses, nor to individual responsibility. Alvesson & Wilmott (2002) suggest two main processes of identity construction : identity regulation (IR, the discursive practices of identity definition) and identity work (IW, the interpretive activities involved in reproduction of self-identity). Based on this dialogic conception of IC, we wonder whether artistic interventions could play a significant role in the IC process, especially through its ability to address the relational, sensible, emotional, and affective dimensions. In other words, our paper intends to better understand the role of experience and the embodiment of sensemaking in the dialogic process of identity construction. In this perspective, we will focus on cases where art interventions take place in working situations at some crucial moments of IC. Exploring the dimension of the sensible encapsulated in artworks and art interventions allows in particular to better grasp how collective understanding of organizations and their transformations hinge on subjectivity (Abrir 2012). This knowledge is generally recognized as disruptive, because of the heterogeneity of the two words of art and organization, the ability of art for ―not-knowing or more generally the ability of art and aesthetics for promoting contradictory emotions. The dimension of the sensible brought by art is characterized by its subjectification power and by its value sharing (the role of emotions and affects, the construction of subjectivity) and value-adding. Our argument is that art, by organizing the co-creation of work-related sensible forms, triggers and performs - in ways we strive at investigating - a collective and dialogic process between IR and IW