HAL-Université de Bretagne Occidentale
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Modèle précurseur et compréhension du phénomène de formation des ombres en maternelle
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Cerebral diffusion of posaconazole in an experimental model of disseminated scedosporiosis
No full textInternational audienceBackground: Posaconazole, a broad spectrum antifungal, may be used in salvage therapy for cerebral infections caused by Scedosporium species. In this study, its pharmacokinetics was investigated in a rat model of scedosporiosis to evaluate the effect of the infection on cerebral diffusion.Methods: Posaconazole was administered to two groups of rats randomized according to the infection status. Drug levels in plasma, cerebrospinal fluid, and brain tissue were measured up to 168 h after administration, and data were analyzed using a non-compartmental approach. In addition, interleukins (IL) (IL-1β and IL-10) were quantified by ELISA, and cerebral expression of genes encoding some efflux pumps was assessed by reverse transcription-quantitative PCR.Results: Cerebral diffusion of posaconazole and, to a lesser extent, cerebrospinal fluid exposure were significantly affected by infection. A ten-fold increase in the area under the curve and a delayed time (Tmax) to reach the maximum concentration (Cmax) were observed in the brain, along with a time lag to reach Cmax and Tmax between plasma and the brain. Infection was associated with changes in plasma pharmacokinetics, particularly at late sampling times.Conclusions: These findings suggest increased permeability of the blood-brain-barrier, possibly related to changes in IL or gene expression levels in the brain. Infection and the resulting inflammation should therefore be considered for therapeutic drug monitoring, especially in cases of cerebral infection
Spatial Distribution of European Grayling Reflects Longitudinal Temperature Patterns in a Swiss River
No full textInternational audienceMost salmonid populations are declining across their entire habitat range, partly because of large‐scale loss of crucial physical habitats. Alterations in river flow and temperature resulting from climate change are likely to further degrade habitat quality, particularly summer thermal conditions experienced by temperature‐sensitive fish species. Understanding how summer thermal conditions control the spatial distribution of ectotherms is thus central to helping project the consequences of climate change and develop management solutions. This study uses snorkelling fish surveys collected over 10 years and airborne thermal infrared (TIR) mapping of surface temperature acquired in 2022 to assess the relationship between European grayling distribution and thermal habitats along a 9‐km long reach of the Allondon River, Switzerland. Results show that all 3 grayling life stages (adults, sub‐adults and juveniles) respond negatively to elevated summer temperature, with distribution patterns highlighting thermal structuring effects on fish populations. The presence of two cooler reaches appears critical to the survival of the Allondon's declining grayling population, while the warmest reach that separates these habitats potentially acts as a thermal barrier during critical summer conditions. These results were used to guide local stakeholders towards short‐term and longer‐term actions to be taken on the river, which include: concerted trans‐national management to protect key upstream tributaries, tree planting to limit summer peak temperature and strategic protection of cold‐water patches that may act as thermal refuges during critical periods
Decoupling surface stiffness from surface chemistry: Impact on bacterial adhesion and retention under shear conditions
No full textInternational audienceUnderstanding how substrate mechanics influence bacterial adhesion and retention is essential for controlling biofilm formation on synthetic materials. Studies on soft polymers such as PDMS are often confounded by uncontrolled variations in surface chemistry and topography. In this work, a PS-PIB bilayer system was designed to decouple surface chemistry from mechanics, enabling independent control of stiffness while maintaining constant surface properties. Static adhesion assays with Pseudomonas aeruginosa PAO1 showed that initial attachment was insensitive to substrate modulus when surface chemistry and roughness were held constant. In contrast, retention under shear flow decreased with increasing stiffness and correlated more closely with the work of separation obtained from nanoindentation experiments. This parameter, which integrates both adhesive and dissipative contributions, is introduced as an empirical descriptor of interfacial mechanical resistance. Retention data were described by a power-law model consistent with stochastic frameworks of multivalent adhesion, reflecting population heterogeneity in the number and strength of adhesive contacts. Altogether, these findings suggest that viscoelastic dissipation is a key factor influencing P. aeruginosa PAO1 detachment under flow and highlight the need for future studies using bacterial mutants and diverse species to assess the generality of this correlation across different adhesion strategies
Une messe publique en l'honneur de Pétain n'est pas contraire à l'ordre public…
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Social acceptability of leisure activities regulations in French marine protected areas
No full textInternational audienceThe increase in nautical leisure activities within French marine protected areas (MPAs) presents complex challenges for managers. While these activities bring economic benefits and cultural value, they also intensify pressures on marine ecosystems. In response, managers and public authorities are seeking legal solutions to regulate both individual activities and overall visitation. This article examines the legal constraints and opportunities for regulating recreational uses in MPAs through an interdisciplinary design combining (i) legal analysis of the relevant regulatory framework and competent authorities and (ii) empirical fieldwork in two case studies-Port-Cros National Park and the Iroise Marine Park-based on semi-structured interviews with key stakeholders and visitor questionnaires (n = 228). The results show that social acceptability of rules varies by activity, stakeholder profile, and distance from decision-making centres. They also highlight persistent misunderstandings regarding regulatory competence, with many users attributing greater authority and legitimacy to MPA managers than to maritime prefects, despite the latter holding key administrative police powers at sea. The article concludes that improving communication and strengthening participatory procedures are necessary conditions to enhance the perceived legitimacy and effectiveness of leisure-activity regulation in French MPAs.</div
Resource partitioning among small pelagic fish remains stable regardless of food availability in a seasonally pulsed upwelling system
No full textInternational audienceSmall pelagic fishes (SPF) in eastern boundary upwelling systems share space and must adapt to strong seasonal and inter-annual variations in their environment. This raises questions about how these species share food resources in a changing environment and whether they compete with each other when their food resources are reduced. We approach these questions on three SPF species (sardine Sardinops sagax, anchovy Engraulis encrasicolus and round herring Etrumeus whiteheadi) living on the west and south coasts of South Africa. We combined fish muscle fatty acid profiles as a proxy for prey taxa diversity, stable isotope compositions as a proxy for habitat and trophic position, and satellite-derived chlorophyll-a and zooplankton concentrations as proxies for food availability. We found that the total fatty acid content (energy reserve) of the three species increased with chlorophyll-a concentration, suggesting that chlorophyll-a is a good proxy for food quantity. For the three SPF species, the niche width increased with the amount of chlorophyll-a. However, the niche overlap (i.e. the potential for competition) remained relatively unchanged as chlorophyll-a concentrations increased, though it varied considerably depending on local conditions (from 0 to 100 %), higher on the west coast (influenced by the Benguela upwelling) than in the south coast. The relative trophic level of the species (round herring > anchovy > sardine) was confirmed in both regions and the round herring remained on average 25 % fattier than the other two species. These results suggest that on a relatively short time scale (month) SPF species are more selective when food levels decrease but that competition for resources may or may not operate depending on local conditions. However, integrated over a larger time scale, the three species do feed on different resources (resulting in different trophic levels) and cannot be considered an ecological substitute. The recent changes in their respective biomasses could impact the amount of fat (energy) available to higher trophic levels