Dynamique de population en habitat fragmenté chez deux espèces d'amphibiens Urodèles ((Triturus alpestris et T. cristatus))

La dispersion est un processus clé en écologie en raison de ses implications multiples tant au niveau de la dynamique des populations fragmentées, des variations des stratégies d'occupations de l'espace que de la viabilité des populations. Nous avons cherché dans ce travail à mettre en évidence les modalités de dispersion chez deux espèces d'amphibiens urogèles : les tritons alpestres et les tritons crêtés (espèce patrimoniale). Ces deux espèces, par leur mode de reproduction qui généère une agrégation des adultes dans des mares, représentent typiquement le schéma structurel d'espèces se reproduisant dans des patches d'habitats framgentés (les mares). L'habitat est caractérisé par une hétérogénéité spatio-temporelle de la capacité d'accueil qui est à l'origine de processus de dispersion. Les méthodes utilisées pour appréhender les processus dispersifs seront tour à tour l'analyse démographique par capture-marquage-recapture (CMR) dans différentes populations framgentées, la modélisation mathématique et l'expérimentation. Nous avons tout d'abord caractérisé l'impact des méthodes de marquage (tatouage et transpondeur) sur la survie des tritons alpestres. [...] Les mécanismes comportementaux qui influencent la sélection de l'habitat lors de la dispersion sont étudiés. [...] L'ensemble de ces résultats sont ensuite discutés en regard avec les théories actuelles concernant l'évolution de la dispersion, la variabilité spatio-temporelle de la distribution des individus dans les populations fragmentées liées à la dispersion, et enfin, en rapport avec la sélection de l'habitat par le comportement d'attraction par les congénères comme vecteur d'agrégation lors de la reproduction de ces amphibiensLYON1-BU.Sciences (692662101) / SudocSudocFranceF

Transience, dispersal and survival rates in newt patchy populations

International audience1. This work aims to illustrating how it is possible to measure different modalities of adult dispersal in two subdivided populations of the alpine newt (Triturus alpestris). Recent developments in capture-mark-recapture methods make it possible to estimate transience rates from individuals captured only once. In the context of subdivided newt populations, transience is assumed to express nomadic behaviour that contribute to breeding dispersal. Skeletochronology and recaptures within each pond system also made it possible to estimate emigration rates and local dispersal. 2. Two subdivided populations of alpine newts were monitored over 4 and 5 years, respectively. Whereas population A is suspected to have been established for more than 100 years, population B was monitored when colonizing a newly created archipelago of ponds. 3. Transience was detected in each population at similar rates (37% in population A and 35% in the population B). Annual apparent survival rates were estimated as 82% in population A vs. 33% in population B. Similarity of age structures between populations leads us to consider such low survival rates in population B as resulting from emigration. Emigration was thus negligible in population A and was estimated to reach 57·3% in population B. Conversely, high local dispersal (movements within a pond system) was detected in population A, but not in population B. 4. Even though the causation of dispersal in newts (genetic polymorphism vs. pheno-typic plasticity) remains unexplored, our study succeeded in identifying several dispersal components that could result from different selective pressures (habitat heterogeneity at different temporal scales). Experimental approaches are needed to investigate the causative bases of these traits

Transience, dispersal and survival rates in newt patchy populations

International audience1. This work aims to illustrating how it is possible to measure different modalities of adult dispersal in two subdivided populations of the alpine newt (Triturus alpestris). Recent developments in capture-mark-recapture methods make it possible to estimate transience rates from individuals captured only once. In the context of subdivided newt populations, transience is assumed to express nomadic behaviour that contribute to breeding dispersal. Skeletochronology and recaptures within each pond system also made it possible to estimate emigration rates and local dispersal. 2. Two subdivided populations of alpine newts were monitored over 4 and 5 years, respectively. Whereas population A is suspected to have been established for more than 100 years, population B was monitored when colonizing a newly created archipelago of ponds. 3. Transience was detected in each population at similar rates (37% in population A and 35% in the population B). Annual apparent survival rates were estimated as 82% in population A vs. 33% in population B. Similarity of age structures between populations leads us to consider such low survival rates in population B as resulting from emigration. Emigration was thus negligible in population A and was estimated to reach 57·3% in population B. Conversely, high local dispersal (movements within a pond system) was detected in population A, but not in population B. 4. Even though the causation of dispersal in newts (genetic polymorphism vs. pheno-typic plasticity) remains unexplored, our study succeeded in identifying several dispersal components that could result from different selective pressures (habitat heterogeneity at different temporal scales). Experimental approaches are needed to investigate the causative bases of these traits

Cross-talk between Staphylococcus aureus leukocidins-intoxicated macrophages and lung epithelial cells triggers chemokine secretion in an inflammasome-dependent manner.

International audienceStaphylococcus aureus is a major pathogen responsible for both nosocomial and community-acquired infections. Central to its virulence is its ability to secrete haemolysins, pore-forming toxins and cytolytic peptides. The large number of membrane-damaging toxins and peptides produced during S. aureus infections has hindered a precise understanding of their specific roles in diseases. Here, we used comprehensive libraries of recombinant toxins and synthetic cytolytic peptides, of S. aureus mutants and clinical strains to investigate the role of these virulence factors in targeting human macrophages and triggering IL-1β release. We found that the Panton Valentine leukocidin (PVL) is the major trigger of IL-1β release and inflammasome activation in primary human macrophages. The cytolytic peptides, δ-haemolysin and PSMα3; the pore-forming toxins, γ-haemolysin and LukDE; and β-haemolysin synergize with PVL to amplify IL-1β release, indicating that these factors cooperate with PVL to trigger inflammation. PVL(+) S. aureus causes necrotizing pneumonia in children and young adults. The severity of this disease is due to the massive recruitment of neutrophils that cause lung damage. Importantly, we demonstrate that PVL triggers IL-1β release in human alveolar macrophages. Furthermore, IL-1β released by PVL-intoxicated macrophages stimulates the secretion of the neutrophil attracting chemokines, IL-8 and monocyte chemotactic protein-1, by lung epithelial cells. Finally, we show that PVL-induced IL-8/monocyte chemotactic protein-1 release is abolished by the inclusion of IL-1 receptor antagonist (IL-1Ra) in a mixed culture of lung epithelial cells and macrophages. Together, our results identify PVL as the predominant S. aureus secreted factor for triggering inflammasome activation in human macrophages and demonstrate how PVL-intoxicated macrophages orchestrate inflammation in the lung. Finally, our work suggests that anakinra, a synthetic IL-1Ra, may be an effective therapeutic agent to reduce the massive neutrophils infiltration observed during necrotizing pneumonia and decrease the resulting host-mediated lung injury

Associations Between Physical Activity, Blood-Based Biomarkers of Neurodegeneration, and Cognition in Healthy Older Adults: The MAPT Study

International audiencePhysical activity (PA) demonstrated benefits on brain health, but its relationship with blood biomarkers of neurodegeneration remains poorly investigated. We explored the cross-sectional associations of PA with blood concentrations of neurofilament light chain (NFL) and beta amyloid (Aβ)42/40. We further examined whether the interaction between PA and these biomarkers was longitudinally related to cognition. Four-hundred and sixty-five nondemented older adults engaged in an interventional study and who had a concomitant assessment of PA levels and blood measurements of NFL (pg/mL) and Aβ 42/40 were analyzed. A composite Z-score combining 4 cognitive tests was used for cognitive assessment up to a 4-year follow-up. Multiple linear regressions demonstrated that people achieving 500–999 and 2000+ MET-min/week of PA had lower (ln)NFL concentrations than their inactive peers. Logistic regressions revealed that achieving at least 90 MET-min/week of PA was associated with a lower probability of having high NFL concentrations (ie, ≥91.961 pg/mL [third quartile]). PA was not associated with (Aβ)42/40. Mixed-model linear regressions demonstrated that the reverse relationship between PA and cognitive decline tended to be more pronounced as Aβ 42/40 increased, while it was dampened with increasing levels of (ln)NFL concentrations. This study demonstrates that PA is associated with blood NFL but not with Aβ 42/40. Furthermore, it suggests that PA may attenuate the negative association between amyloid load and cognition, while having high NFL levels mitigates the favorable relationship between PA and cognition. More investigations on non demented older adults are required for further validation of the present findings

Plasma neurofilament light chain is associated with cognitive decline in non-dementia older adults

International audienceNeurofilament light chain (NfL) has been associated with cognitive status in multiple neurodegenerative conditions. Studies about plasma NfL and cognitive decline in older adults are still limited. 504 older adults (median age 75 years) who expressed memory complaints were selected from the Multidomain Alzheimer’s Preventive Trial (MAPT) and were classified as normal cognition (NC) or mild cognitive impairment (MCI). Cognitive functions were measured as mini mental state examination (MMSE) and composite cognitive score (CCS) over a 4-year period. Plasma NfL was measured at the first or the second year of the MAPT. Mixed-effects linear models were performed to evaluate cross-sectional and longitudinal associations. In the whole population, higher plasma NfL was cross-sectionally associated with lower cognitive functions (MMSE: β = − 0.007, 95% CI [− 0.013, − 0.001]; CCS: β = − 0.003, 95% CI [− 0.006, − 0.001]). In adults with MCI, but not NC, higher plasma NfL was associated with lower CCS at the cross-sectional level (β = − 0.003, 95% CI [− 0.005, − 0.0002]). The upper quartile NfL group further demonstrated more over time decline in CCS (β = − 0.07, 95% CI [− 0.12, − 0.01]) under the MCI status. Plasma NfL can be a promising biomarker of progressive cognition decline in older adults with MCI

Association between urate-lowering therapies and cognitive decline in community-dwelling older adults

International audienceAbstract Long-term use of urate-lowering therapies (ULT) may reduce inflammaging and thus prevent cognitive decline during aging. This article examined the association between long-term use of ULT and cognitive decline among community-dwelling older adults with spontaneous memory complaints. We performed a secondary observational analysis using data of 1673 participants ≥ 70 years old from the Multidomain Alzheimer Preventive Trial (MAPT Study), a randomized controlled trial assessing the effect of a multidomain intervention, the administration of polyunsaturated fatty acids (PUFA), both, or placebo on cognitive decline. We compared cognitive decline during the 5-year follow-up between three groups according to ULT (i.e. allopurinol and febuxostat) use: participants treated with ULT during at least 75% of the study period (PT ≥ 75; n = 51), less than 75% (PT < 75; n = 31), and non-treated participants (PNT; n = 1591). Cognitive function (measured by a composite score) was assessed at baseline, 6 months and every year for 5 years. Linear mixed models were performed and results were adjusted for age, sex, body mass index (BMI), diagnosis of arterial hypertension or diabetes, baseline composite cognitive score, and MAPT intervention groups. After the 5-year follow-up, only non-treated participants presented a significant decline in the cognitive composite score (mean change − 0.173, 95%CI − 0.212 to − 0.135; p < 0.0001). However, there were no differences in change of the composite cognitive score between groups (adjusted between-group difference for PT ≥ 75 vs. PNT: 0.144, 95%CI − 0.075 to 0.363, p = 0.196; PT < 75 vs. PNT: 0.103, 95%CI − 0.148 to 0.353, p = 0.421). Use of ULT was not associated with reduced cognitive decline over a 5-year follow-up among community-dwelling older adults at risk of dementia

Biological and Neuroimaging Markers as Predictors of 5-Year Incident Frailty in Older Adults: A Secondary Analysis of the MAPT Study

International audienceBackground This study aims to investigate the predictive value of biological and neuroimaging markers to determine incident frailty among older people for a period of 5 years. Methods We included 1394 adults aged 70 years and older from the Multidomain Alzheimer Preventive Trial, who were not frail at baseline (according to Fried’s criteria) and who had at least 1 post-baseline measurement of frailty. Participants who progressed to frailty during the 5-year follow-up were categorized as “incident frailty” and those who remained non-frail were categorized as “without frailty.” The differences of baseline biochemical factors (25-hydroxyvitamin D, homocysteine, omega-3 index, C-reactive protein), other biological markers (Apolipoprotein E genotypes, amyloid-β deposits), and neuroimaging data (gray matter volume, hippocampal volume, white matter hyperintensities) were compared between groups. Cox proportional hazard model was used to evaluate the associations between biomarkers and incident frailty. Results A total of 195 participants (14.0%) became frail over 5 years. Although 25-hydroxyvitamin D deficiency, homocysteine levels, low-grade inflammation (persistently increased C-reactive protein 3–10 mg/L), gray matter, and hippocampal volume were significantly associated with incident frailty in unadjusted models, these associations disappeared after adjustment for age, sex, and other confounders. Omega-3 index was the sole marker that presented a trend of association with incident frailty (hazard ratio: 0.92; 95% confidence interval: 0.83–1.01; p = .082). Conclusions This study failed to identify biomarkers able to predict frailty incidence in community-dwelling older adults for a period of 5 years. Further longitudinal research with multiple measurements of biomarkers and frailty is needed to evaluate the long-term relationships between changes in biomarkers levels and frailty evolution

Redox Systems, Antioxidants and Sarcopenia

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