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8 result(s) for "Bec, Stéphane"
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Present conditions may mediate the legacy effect of past land-use changes on species richness and composition of above- and below-ground assemblages
In forest ecosystems, the influence of landscape history on contemporary biodiversity patterns has been shown to provide a convenient framework to explain shifts in plant assemblages. However, very few studies have controlled for present human‐induced activities when analysing the effect of forest continuity on community structures. By cutting and removing trees, foresters substantially change stand ecological conditions, with consequences on biodiversity patterns. Disentangling the effect of past and present human activities on biodiversity is thus crucial for ecosystem management and conservation. We explored the response of plant and springtail species richness and composition to forest continuity (ancient vs. recent) in montane forests, while controlling for stand maturity (mature vs. overmature). We established 70 sites in landscapes dominated by unfragmented ancient forests where we surveyed plants and assessed springtails by analysing environmental DNA. Neither plant nor springtail species richness was influenced by forest continuity or by stand maturity. Instead, site‐specific characteristics, especially soil properties and canopy openness, were of major importance in shaping above‐ and below‐ground richness. For plant and springtail species composition, the effect of forest continuity was mediated by stand maturity. Thus, both plants and springtails showed a convergence in assemblage patterns with the increasing availability of overmature stand attributes. Moreover, soil and stand‐scale factors were evidently more important than landscape‐scale factors in shaping above‐ and below‐ground species composition. Synthesis. We clearly demonstrated that biodiversity patterns are more strongly influenced by present human‐induced activities than by past human‐induced activities. In the Northern Alps where our study sites were located, the colonization credit of most species has been paid off and the transient biodiversity deficit usually related to forest continuity has moved towards equilibrium. These findings emphasize the necessity to better control for local‐scale factors when analysing the response of biodiversity to forest continuity; we call for more research into the effects of forest continuity in unfragmented mountain forests.
First comparison of commercial systems to prepare nanofat: technical performances and biological quality differ among obtained products
Nanofat is a relatively recent fat grafting technique obtained involving the mechanical emulsification of adipose tissue whose preparation is produced at the patient’s bedside. Although it was initially reported to improve skin quality in intradermal applications, it is now increasingly used in regenerative medicine. However, the absence of standardized protocols and the diversity of commercial devices result in nanofat products of variable quality. This study presents the first comprehensive comparison of nanofat obtained from different commercially available preparation systems, combining both their technical performance and biological characterization. Lipoaspirates from five healthy donors were processed using eight commercially available devices for nanofat production using emulsification or micronization techniques. The technical parameters included preparation time, ease of preparation and injection, volumetric yield, and residual aqueous fraction. Biological analyses included stromal vascular fraction isolation with evaluation of cell viability, viable nucleated cell yield, immunophenotypic cell subtype characterization and clonogenic capacity. These parameters were compared using a scoring model that enabled inter-kit ranking, integrating both a technical performance score and a biological quality score. Additionally, nanofat-conditioned media were collected for extracellular vesicles (EVs) quantification and subtyping by flow cytometry, and confocal microscopy was performed to evaluate the preservation of mature adipocytes, capillary networks, and the extracellular matrix. All devices demonstrated satisfactory technical performance, with Puregraft Boost V2 and Emulsfat achieving the highest overall technical scores. Cell viability was consistently high, with median values above 85% across all devices. Adinizer provided the greatest proportion of adipose-derived stromal/stem cells and achieved the highest overall biological score. In contrast, Hy-Tissue Nanofat produced the lowest cell yields together with the highest leukocyte proportions. All nanofats contained clonogenic progenitors. Extracellular vesicles concentrations were comparable between devices, and were mainly influenced by donor variability, although Emulsfat was enriched in adipocyte-derived EVs. Microscopic analysis revealed preservation of adipocytes, vascular networks, and the extracellular matrix across devices, challenging the assumption that emulsification or micronization completely disrupts tissue architecture. Nanofat properties are strongly device dependent, with possible dissociation between technical ease and biological quality. This first comparative study highlights the need for standardized preparation methods and qualification criteria, and provides guidance for selecting devices aligned with specific clinical objectives to optimize regenerative outcomes.
Duality of trophic supply and hydrodynamic connectivity drives spatial patterns of Pacific oyster recruitment
The recent discovery of Pacific oyster Crassostrea gigas (also known as Magallana gigas) spatfields in a Mediterranean lagoon intensely exploited for shellfish farming (Thau lagoon) revealed significant contrasts in spatial patterns of recruitment. We evaluated the processes that drive spatial patterns in oyster recruitment by comparing observed recruitment, simulated hydrodynamic connectivity and ecological variables. We hypothesized that spatial variability of recruitment depends on (1) hydrodynamic connectivity and (2) the ecology of the larval supply, settlement, metamorphosis, survival and biotic environmental parameters. We assessed recruitment at 6−8 experimental sites by larval sampling and spat collection inside and outside oyster farming areas and on an east−west gradient, from 2012−2014. Hydro dyna - mic connectivity was simulated using a numerical 3D transport model assessed with a Eulerian indicator. The supply of large umbo larvae did not differ significantly inside and outside oyster farming areas, whereas the supply of pediveligers to sites outside shellfish farms was structured by hydrodynamic connectivity. Inside shellfish farming zones, unfavorable conditions due to trophic competition with filter-feeders jeopardized their settlement. In this case, our results suggest loss of settlement competence by oyster larvae. This confirms our hypo thesis of top-down trophic control by the oysters inside farming zones of Thau lagoon in summer that fails to meet the ecological requirements of these areas as oyster nurseries. Knowledge of oyster dispersal, connectivity and recruitment in coastal lagoons will help local development of sustainable natural spat collection. On a global scale, our method could be transposed to other basins or used for other species such as mussels, clams or scallops, to better understand the spatial patterns of bivalve recruitment. Management of the oyster industry based on natural spat collection will help develop a sustainable activity, based on locally adapted oyster strains but also by reducing the risks of transferring pathogens between basins and the global carbon footprint of this industry.
Recruitment of the Pacific oyster Crassostrea gigas in a shellfish-exploited Mediterranean lagoon
In the context of increasing demand for environmental recovery, aquatic systems may face the challenge of evolving under oligotrophication. This is the case in Mediterranean lagoons, in particular the shellfish-farmed Thau lagoon in France, where we studied recruitment of the Pacific oyster Crassostrea gigas. Oyster spat and environmental parameters were monitored at several sampling sites for 3 yr (2012 to 2014) using an original method with a temporal overlap deployment of collectors to study pre- and post-settlement processes and to identify the best conditions for recruitment. Contrary to the ‘no Pacific oyster reproduction’ paradigm in Mediterranean lagoons, our study showed that recruitment of this introduced species is possible in the Thau lagoon at levels comparable to those in other traditional French breeding basins. We identified a favorable environmental window for recruitment characterized by high water temperature (>26.5°C) and high nanophytoplankton and Chaetoceros spp. abundances (>4.3 × 10⁶ and 345 × 10³ cells l−1, respectively). In these favorable conditions, we hypothesize that the ecosystem functions as an autotrophic system, in contrast to the heterotrophic system that characterizes unfavorable conditions. Under heterotrophic conditions, high abundances of mixotrophic and heterotrophic organisms (ciliates and dinoflagellates) limited the metamorphosis of C. gigas larvae, leading to poor recruitment. This study provides new knowledge on the reproduction of the Pacific oyster in a Mediterranean lagoon under warming and oligotrophication. The shellfish industry will profit from the discovery of spatfields to develop new nursery practices that are eco-friendly and limit risks of transfers with other spatfall areas.
Estimating health state utility from activities of daily living in the French National Hospital Discharge Database: a feasibility study with head and neck cancer
Background Health state utility (HSU) is a core component of QALYs and cost-effectiveness analysis, although HSU is rarely estimated among a representative sample of patients. We explored the feasibility of assessing HSU in head and neck cancer from the French National Hospital Discharge database. Methods An exhaustive sample of 53,258 incident adult patients with a first diagnosis of head and neck cancer was identified in 2010–2012. We used a cross-sectional approach to define five health states over two periods: three \"cancer stages at initial treatment\" (early, locally advanced or metastatic stage); a \"relapse state\" and otherwise a \"relapse-free state\" in the follow-up of patients initially treated at early or locally advanced stage. In patients admitted in post-acute care, a two-parameter graded response model (Item Response Theory) was estimated from all 144,012 records of six Activities of Daily Living (ADLs) and the latent health state scale underlying ADLs was calibrated with the French EQ-5D-3 L social value set. Following linear interpolation between all assessments of the patient, daily estimates of utility in post-acute care were averaged by health state, patient and month of follow-up. Finally, HSU was estimated by health state and month of follow-up for the whole patient population after controlling for survivorship and selection in post-acute care. Results Head and neck cancer was generally associated with poor HSU estimates in a real-life setting. As compared to “distant metastasis at initial treatment”, mean HSU was higher in other health states, although numerical differences were small (0.45 versus around 0.54). It was primarily explained by the negative effects on HSU of an older age (38.4% aged ≥70 years in “early stage at initial treatment”) and comorbidities (> 50% in other health states). HSU estimates significantly improved over time in the “relapse-free state” (from 8 to 12 months of follow-up). Conclusions HSU estimates in head and neck cancer were primarily driven by age at diagnosis, comorbidities, and time to assessment of cancer survivors. This feasibility study highlights the potential of estimating HSU within and across severe conditions in a systematic way at the national level.
Trophic environments influence size at metamorphosis and recruitment performance of Pacific oysters
Reproduction and recruitment of benthic invertebrates are influenced by the climate and by the ecological structure of marine ecosystems, along with local anthropogenic pressures such as eutrophication or oligotrophication. Using the Pacific oyster Crassostrea gigas as a biological model, we tested the hypothesis that the variability in prodissoconch II (PII) size (i.e. size at metamorphosis) depends on ecological functioning. Settlement and recruitment were assessed at 5 sampling sites on the French Mediterranean shellfish farmed Thau lagoon during the main summer recruitment events in 3 consecutive years (2012−2014). Hydrobiological and planktonic analyses were conducted at 3 sampling sites. Our results showed that recruitment was extremely heterogeneous, ranging from 0 to 260 ± 27 SE ind. dm−2 throughout the ecosystem and was linked with variability in PII size, which ranged from 180 to 296 μm. The annual temporal pattern of PII sizes appeared to be controlled by temperature during the settlement period, whereas the spatial pattern depended on phytoplankton biomass and on the trophic functioning of the ecosystem. Smaller PII sizes were significantly correlated with the highest phytoplankton biomass, while larger PII sizes were positively correlated with mixotrophic cryptophyte abundance. We found an inverse relationship between PII size and survival after metamorphosis, showing that recruitment success was associated with smaller PII sizes. Regional climate conditions and local trophic functioning appear to be key factors in metamorphosis and consequently contribute to recruitment heterogeneity. Further studies should be performed in other ecosystems following an oligotrophication trajectory to generalize this result.
Clinical and economic burden of head and neck cancer: a nationwide retrospective cohort study from France
To evaluate the clinical and economic burden of head and neck squamous cell carcinoma (HNSCC) in France. All 53,255 incident adult patients discharged with a first diagnosis of HNSCC in 2010-2012 were identified from the 2008-2013 French National Hospital Discharge (PMSI) database. We conducted a retrospective longitudinal analysis of prognosis and direct costs attributable to HNSCC. Direct medical costs attributable to HNSCC care amounted to 665 million euros in 2012 in France. The majority (62%) of incident patients were 64 years old or less at HNSCC diagnosis and incurred 1.3-fold higher mean direct costs as compared to elderly patients (41,909 vs 32,221 euros over 3 years, respectively; p<0.001). HNSCC stage at initial treatment was the major driver of mean (SD) direct costs over 3 years (p<0.001): 19,819 (23,150) euros in 31% patients diagnosed at early stage; 46,791 (34,841) euros in 60% patients diagnosed at locally advanced stage; and 43,377 (33,953) euros in 9% patients diagnosed with distant metastasis. About half patients died over 3 years at a median (IQR) age of 63 (56-75) years resulting in 10.9 years-of-life lost on average per incident patient. The present study suggests that the clinical and economic burden of HNSCC is substantial in France.