DMTs and Covid-19 severity in MS: a pooled analysis from Italy and France

We evaluated the effect of DMTs on Covid-19 severity in patients with MS, with a pooled-analysis of two large cohorts from Italy and France. The association of baseline characteristics and DMTs with Covid-19 severity was assessed by multivariate ordinal-logistic models and pooled by a fixed-effect meta-analysis. 1066 patients with MS from Italy and 721 from France were included. In the multivariate model, anti-CD20 therapies were significantly associated (OR = 2.05, 95%CI = 1.39–3.02, p < 0.001) with Covid-19 severity, whereas interferon indicated a decreased risk (OR = 0.42, 95%CI = 0.18–0.99, p = 0.047). This pooled-analysis confirms an increased risk of severe Covid-19 in patients on anti-CD20 therapies and supports the protective role of interferon

Invasion de Spartina alterniflora en rade de Brest (comportement invasif et impact sur le cycle biogéochimique du silicium)

Ce travail se propose d évaluer l impact de la plante invasive Spartina alterniflora sur l écosystème de la Rade de Brest. Cette espèce, originaire de la côte Est nord-américaine où elle est trouvée dans les marais maritime, a récemment colonisé la Rade de Brest. Les résultats obtenus au cours de ce travail reposent à la fois sur l écologie, écophysiologie et biogéochimie, ils sont exposés an trois parties. La première partie est dédiée à l étude de l écologie de la plante invasive. S. alterniflora a envahi la Rade de Brest où elle se développe des marais salés jusqu aux marais tidaux d eau douce. Le manque de compétiteur lui a même permis de se développer jusqu en haut du schorre. Il en résulte une homogénéisation de la composition spécifique de la végétation des marais. Afin de mieux comprendre les distributions de S. alterniflora dans la Rade de Brest, nous avons mesurés les variations des densités, des tailles, et des productions primaires en fonction de l hydrodynamisme, de la salinité et de la durée de l immersion. Les productions primaires les plus importantes ont été mesurées chez les plantes soumises à un faible hydrodynamisme, de faibles salinités et des durées d immersion intermédiaires. La valeur moyenne de la production primaire calculée pour la Rade de Brest est de 1034 g poids sec m-2 an-1. Ce résultat est en accord avec d autres valeurs estimées pour des spartines dans leurs milieux d'origine et ainsi que dans d autres sites envahis. La seconde partie porte sur les effets de l accumulation du silicium chez les plantes sur les mécanismes de résistance aux stress environnementaux. Les phanérogames représentent une composante sous étudiée du cycle du silicium, elles peuvent absorber le silicium sous forme dissoute (dSi) et le stocker sous forme biogénique (bSiO2). Le Si est connu pour sa capacité à réduire l effet de stress environnementaux de type physique, chimique, et biologique comme les tempêtes, les fortes salinités, la toxicité des métaux lourds, le broutage et certaines maladies. Les objectifs de cette partie étaient de déterminer (1) dans quels organes et quand la bSiO2 est accumulée au cours du cycle de vie de la plante, (2) de savoir si cette accumulation varie en fonction de l hydrodynamisme, de la salinité, et de la durée de l'immersion, et (3) de savoir si l accumulation est limitée par la disponibilité en dSi dans les sédiments des marais. Un suivi terrain de 2 ans nous a permis d échantillonner des plantes dont les contenus en silicium ont été mesurés. Des échantillons de sédiment ont été prélevés à l échelle saisonnière, et les concentrations en dSi des eaux interstitielles ont été mesurées de O à 10 cm de profondeur. Les résultats permettre de montrer que la bSiO2 s accumule plus dans les feuilles matures des spartines que dans les autres organes. Nous avons observé une relation linéaire entre les concentrations en bSiO2 et la longueur des plantes. Les concentrations en bSiO2 dans les plantes décroissent avec l augmentation de l exposition aux facteurs abiotiques testés. Nous n avons pas observés de différences entre les disponibilités en dSi de tous les sites étudiés. Les profils de dSi n ont pas montré de fortes pertes ducs à l absorption par les racines. Nos résultats suggèrent que la disponibilité en dSi n est pas un facteur limitant pour l espèce étudiée. Nous avons montré que chez S. alteniflora la concentration en bSiO2 n augmente pas avec l exposition aux stress, mais à l inverse qu elle augmente en corrélation avec la croissance dc la plante. II semble donc que S. alterniflora a du développer d autres stratégies pour lutter contre l effet des stress abiotiques, cependant, cela n exclut pas le fait que l accumulation de Si par les plantes peut avoir un effet positif dans la résistance aux stress. Ce travail soulève des questions intéressantes sur les mécanismes d absorption du Si par les plantes, la disponibilité du Si dans les sédiments et sur son rôle dans la croissance des plantes. La dernière partie de cette thèse est consacrée à l étude de l impact de cette plante invasive sur la rétention du silicium dans les marais maritimes. Le silicium (Si) est le second élément le plus important composant la croûte terrestre. Les principaux apports de Si à l océan proviennent du lessivage des sols cn milieu terrestre et sont véhiculés par les rivières. La silice dissoute (dSi) est bioassimilable par de nombreux organismes aquatiques, marins et terrestres aussi divers que les plantes, les microalgues, les champignons et les bactéries. Les plantes accumulent de la silice biogénique (bSiO2) sous forme de phytolithes qui représentent une part importante des apports fluviaux de Si le long du continuum terre-mer. Le rôle des phanérogames et de leurs phytolithes dans le cycle du Si est encore mal connu. Les activités anthropiques peuvent avoir un impact important sur les apports fluviaux de Si. L eutrophisation, la construction de barrage et le développement d espèces invasives peuvent modifier significativement la rétention du Si dans les estuaires. Nous avons étudié les variabilités temporelles et spatiales des profils de dSi et bSiO2 dans les sédiments des marais envahis ou non par la spartine. Nous avons aussi comparé les concentrations annuelles en dSi et bSiO2 des sédiments des marais envahis en fonction de la salinité et de la durée d immersion. De plus, nous avons réalisé des expériences de dissolution de la bSiO2 dans la litière de spartine et dans les sédiments des marais afin de calculer des constantes de dissolution (kdiss). Dans la seconde partie de cc travail, nous avons utilisé les données obtenues dans la seconde partie de ce travail pour établir des bilans de Si pour des marais envahis et non envahis Nous avons pu observer une tendance saisonnière dans les profils de dSi dont les concentrations augmenteraient du printemps jusqu à l automne. Les moyennes annuelles des concentrations en bSiO2 et en dSi dans les sédiments augmentent avec la diminution de la salinité le long du gradient estuarien. A l inverse, les constantes de dissolution de la bSiO2 augmentent avec la salinité, et la bSiO2 dans la litière de spartine se dissout 5 fois plus vite que celle des sédiments. En comparant les bilans des marais envahis et non envahis, nous avons estimé que la rétention de Si est 2 fois plus importante dans le marais envahis (8 %) que dans le marais non envahis (4 %). L enfouissement de bSiO2 augmente de 50% dans les marais envahis. Les différences observées peuvent s expliquer par le fait que S. alterniflora est une espèce bioingénieure qui augmente la sédimentation. L effet de l invasion de S. a1ternlora sur la rétention du Si dans les marais semble plus dû à des processus physiques que biologiques puisque le flux d absorption de la plante ne représente que 0,1 % de l apport total de Si dans les rivières.The aim of this study was to evaluate the impact of the invasive plant Spartina alterniflora on the ecosystem of the Bay of Brest. This species is a tidal marsh plant originating from the East coast of North America, and that have recently colonized the Bay of Brest. This work was performed by coupling studies of ecology, ecophysiology, and biogeochemistry. The first part of this work is dedicated to the ecology of this invasive plant. S. alterniflora has invaded the Bay of Brest and can now be found from salt marshes to freshwater tidal marshes. The lack of apparent competitors on the high marsh allowed S. alterniflora to colonize higher tidal elevations and resulted in a homogenization of plant diversity in tidal marshes. To better understand cordgrasses large distribution in the diverse environments of the Bay of Brest (France), we measured stem densities and lengths, and above-ground living and dead biomass at sites differing in their hydrodynamics, soil and water column salinities, and durations of immersion. Low wave energy, low salinity, and intermediate levels of flooding were associated with relatively high levels of growth and primary production determined from calculations of net aerial primary production (NAPP). The mean NAPP value for S. alterniflora in the Bay of Brest was 1034 g DW m-2 y-1, agreeing with similar estimates from the east coast of the USA and other invaded sites. The second part of this work focused on the effect of the accumulation of silicium and the alleviation of environmental stresses in S. alterniflora. Vascular plants are an understudied component of the global silicon cycle; they can absorb silicic acid (dSi) and store it as biogenic silica (bSiO2). S. alterniflora is a Si-accumulating plant in such species Si is believed to alleviate physical, chemical, and biological stresses such as storms, high salinity, heavy metal toxicity, grazing, and disease. Our objectives were to determine (1) in which organ and when bSiO2 accumulates in the plant during its life cycle, (2) whether this accumulation varies with abiotic factors: wave action, estuarine salinity, and duration of immersion, and (3) if the accumulation was limited by dSi availability in marsh porewater. A 2 years field survey allowed to sample plants which were analyzed for there bSiO2 concentrations. Sediment cores were sampled seasonally and the dSi concentrations in the porewater were measured from 0 to 10 cm. bSiO2 accumulated more in mature leaves than in other organs. There was a strong linear relationship between bSiO2 concentration and plant length. bSiO2 concentration did not increase, but rather decreased as a function of exposure to the three abiotic factors tested. dSi availability was not significantly different for each of the tested sites and dSi profiles did not exhibit huge losses in the root zone Our evidence suggests that dSi availability did not seem to be a limiting factor in this case. We showed that bSiO2 did not increase with increasing abiotic stresses but was strongly correlated with growth Hence, S. alterniflora is likely to have other adaptive strategies for dealing with environmental stressors but it did not exclude the possible role of Si m alleviating these stresses If this is the case, further work is needed to better understand Si uptake, its availability, and its role in silicification and growth in this species. The last part of this work is deals with the impact of the invasive plant on the retention of Si in tidal marshes. Silicon (Si) is the second most import element composition the terrestrial crust. Through weathering, the main inputs of Si to oceans come from lands and are delivered by rivers. Dissolved silica (dSi), is bioavailable for number of aquatic, marine and terrestrial organisms as diverse as terrestrial plants, micro algae, fungi and bacteria. Plants accumulate biogenic silica (bSiO2) as phytoliths, which represents an important component of the riverine Si input along the land-ocean continuum. The role of vascular plants and their phytoliths in the Si cycle remains unclear. Anthropogenic activities have an important impact on riverine nutrient inputs. Eutrophication, dam constructions, and invasive species can significantly modify the retention of Si in estuaries. In this part of the study we investigated temporal and spatial variability and studied the effect of salinity and duration of immersion on the concentration of bSiO2 and dSi measured in sediments of an invaded and non-invaded marsh. In addition, we realized a dissolution experiment of Spartina litter and of marsh sediment in order to estimate the dissolution constant (kdiss). We finally calculated Si budgets m an invaded marsh and in a non-evaded marsh from previously obtained results. This work showed a possible seasonal trend in dSi concentrations increasing from spring to fall. The bSiO2 and the dSi annual mean concentrations m sediment increase with decreasing salinities along the estuarine gradient. We also showed that bSiO2 dissolution rate increase with salinity and that the bSiO2 in S. alteniflora litter dissolve 5 times faster than in marsh sediments. Comparing the budgets of the invaded and the non-invaded marsh, we observed that the j retention of Si is two times higher in the invaded marsh (8 %) than in the non-invaded marsh (4%). Burial increases by 50 % in the invaded marsh. These differences are explained by the fact that S. alteniflora is a bioengineer species that increases sediment deposition. The impact of the invasive S. alterniflora on the retention of bSiO2 seems to be more due to physical than biological processes as uptake of the invasive plant itself represent only 0.1% of the total Si input.BREST-SCD-Bib. electronique (290199901) / SudocSudocFranceF

In situ biogenic silica variations in the invasive salt marsh plant, Spartina alterniflora : A possible link with environmental stress

International audienceAims Higher plants are an understudied component of the global silicon cycle; they absorb silicic acid (dSi) which is stored as biogenic silica (bSiO2). Si is believed to alleviate physical, chemical, and biological stresses such as storms, high salinity, heavy metal toxicity, grazing, and disease. We investigated a Si-accumulating invasive species growing in the tidal marshes of the Bay of Brest (France), viz., Spartina alterniflora. Our objectives were to determine (1) where and when bSiO2 accumulates in the plant during its life cycle, (2) whether this accumulation varies with abiotic factors: wave action, estuarine salinity, and duration of immersion, and (3) if the accumulation was limited by dSi availability in marsh porewater. Methods A 2 years field survey permitted to sample plants which were analyzed for there bSiO2 concentrations. Sediment cores were sampled seasonally and the dSi concentrations in the porewater were measured from 0 to 10 cm. Results bSiO2 accumulated more in mature leaves than in other organs. There was a strong linear relationship between bSiO2 concentration and plant length. bSiO2 concentrations did not increase, but rather decreased as a function of exposure to the three abiotic factors tested. dSi availability was not significantly different for each of the tested sites and dSi profiles did not exhibit huge losses in the root zone. Conclusions Our evidence suggests that dSi availability did not seem to be a limiting factor. bSiO2 did not increase with increasing abiotic stresses but was strongly correlated with growth. Hence, S. alterniflora is likely to have other adaptive strategies for dealing with environmental stressors but it did not exclude the possible role of Si in alleviating these stresses. If this is the case, there remain intriguing questions about Si uptake, its availability, and its role in silicification and growth

Radiations UV et composés photoprotecteurs (étude comparée chez deux végétaux marins, l'algue brune Pelvetia canaliculata et l'angiosperme Salicornia ramosissima)

Les fortes intensités lumineuses, et notamment l augmentation actuelle de l intensité des radiations UV-B due à l amincissement de la couche d ozone, peuvent être des facteurs stressants majeurs pour la plupart des organismes phototrophes peuplant les écosystèmes terrestres et aquatiques. L algue brune Pelvetia canaliculata et l angiosperme des marais salés littoraux Salicornia ramosissima sont deux végétaux marins peuplant les hauts niveaux de l estran, zone où ils sont soumis à de longues périodes d exondation, exposés de manière directe au rayonnement solaire et susceptibles de posséder des mécanismes de photoprotection convergents efficaces. Dans cette étude, grâce à la mise au point d un système de co-culture, leurs réponses métaboliques contre l exposition â différentes niveaux de radiations UV-B ont été comparées en conditions contrôlées, notamment la synthèse de composés photoprotecteurs impliqués dans le maintien de la photosynthèse par la filtration des radiations UV et la défense contre le stress oxydatif. Les résultats montrent que les composés phénoliques semblent être la classe majoritaire de composés photoprotecteurs impliquée chez les deux espèces, avec un rôle écran préférentiel des flavonoïdes chez Salicornia ramosissima et une forte activité antioxydante des phlorotannins chez Pelvetia canaliculata. Cependant, les deux espèces pourraient moduler la composition de leur pool de composés phénoliques en jouant sur une de ces activités protectrices ou sur les deux, en fonction des conditions lumineuses. La fonction spécifique de filtration des radiations UV des composés photoprotecteurs a été mise en évidence après le développement d une nouvelle méthode de mesure in vitro de l activité écran d extraits végétaux.High light irradiances, especially enhanced UV-B radiations due to present stratospheric ozone depletion, may be major stress factors for many phototrophic organisms in both aquatic and terrestrial ecosystems. The brown seaweed Pelvetia canaliculata and the coastal salt marsh angiosperm Salicornia ramosissima are two marine plants growing in the upper intertidal zone, where they are subjected to long emersion periods, to direct solar exposure and are likely to have convergent efficient photoprotective mechanisms. In this study, thanks to the development of a coculture system, their metabolic responses against various UV-B radiation levels have been compared in controlled conditions, especially the synthesis of photoprotective compounds implied in the photosynthesis maintaining by either a UV-absorbing function or a defence capacity against oxidative stress. Results show that phenols seem to be the main class of photoprotective compounds in both species, with a preferential sunscreen function of flavonoids in Salicornia ramosissima and a strong antioxidant activity of phlorotannins in Pelvetia canaliculata. However, both species could modulate the composition of their phenol pool through either 011e protective function or both depending on light conditions. The specific UV-absorbing function of these compounds has been evidenced thanks to the development of a new in vitro method for evaluating the sunscreen activity of plant extracts.BREST-BU Droit-Sciences-Sports (290192103) / SudocPLOUZANE-Bibl.La Pérouse (290195209) / SudocSudocFranceF

Development of a new in vitro method to evaluate the photoprotective sunscreen activity of plant extracts against high UV-B radiation

International audienceSunscreen efficiency of biomolecules against UV-B radiation was generally determined in vitro by cosmetic methods which are not well-adapted for routine ecophysiological and bio-guidance studies in plant research laboratories. In this article, we propose a new in vitro method to evaluate the sunscreen photoprotective activity of plant extracts against high UV-B radiation. Because photosynthetic pigments are one of the first targets of UV-B radiation in plants, the experimental design is based on the ability of the tested substances to limit the degradation of sodium magnesium chlorophyllin (SMC), a derivative compound of natural chlorophyll. SMC photodegradation comparatively to natural chlorophyll and related to temperature, concentration and sample solvent were analyzed in order to optimize the experimental parameters. Then, the method was validated by testing nine standard UV filters used in the European cosmetic industry and by comparing results of their activity with those of a reference in vitro procedure. Finally, the method was applied to coastal and marine crude plant extracts. Results have shown that our procedure can be a good alternative to cosmetic methods with a rapid, sensitive and reproducible evaluation of the sunscreen activity of either pure standards or crude plant extracts in small amounts (30 mg)

Evidence for bioaccumulation of PAHs within internal shoot tissues by a halophytic plant artificially exposed to petroleum-polluted sediments

International audiencePolycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants of natural and anthropic origins. Despite their poor water solubility, they can be taken up and bioaccumulated by plants. This study was aimed at determining whether the PAHs present in sediments artificially polluted by heavy fuel oil are transferred to shoots of a coastal and edible plant, Salicornia fragilis Ball et Tutin. Bioaccumulation was quantified after a one-week exposure to sediments polluted with 0.2%, 2% and 20% fuel oil (w/w) and over a six-week monitoring at 0.2%. Quantification by GC-MS of PAH amounts in plants and sediments evidenced a bioaccumulation in the shoots by a soil-to-plant transfer through the root system. This bioaccumulation depended on the duration of exposure and on the substratum contamination. PAHs distributions in plants and sediments looked alike with a predominance of low- and medium-weight hydrocarbons. Moreover, high-weight PAHs were also detected in the upper part of plant

Relationship between heavy fuel oil phytotoxicity and polycyclic aromatic hydrocarbon contamination in Salicornia fragilis

International audienceGreenhouse experiments were carried out to study the effects of heavy fuel oil contamination on the growth and the development of Salicornia fragilis Ball and Tutin, a salt-marsh edible species. Plants were sampled in spring at the "Aber du Conquet" (Finistère, France), and artificially exposed by coating shoot sections with N°6 fuel oil or by mixing it in their substratum. The impact of petroleum on plant development was followed by phytotoxicity assessments and PAH shoots assays. The plants exhibited visual symptoms of stress, i.e. chlorosis, yellowing, growth reduction and perturbations in developmental parameters. The contamination of plants by shoot coating appeared to be less than through soil. Moreover, the increase of the degree of pollution induced more marked effects on plants, likely because of the physical effects of fuel. However, bioaccumulation of PAHs in shoot tissues was also found to be significant, even at very low levels of contamination, and highly related to the conditions of exposure to oil. The strong relationships between the PAH contents of Salicornia plants and growth reduction suggest a chemical toxicity of fuel oil, compounds like PAHs being known to inhibit physiological processes in plants

Gas chromatographic-mass spectrometric method for polycyclic aromatic hydrocarbon analysis in plant biota

International audienceUsing gas chromatography-mass spectrometry, a new method was developed for the identification and the quantification of polycyclic aromatic hydrocarbons (PAHs) in plants. This method was particularly optimised for PAH analyses in marine plants such as the halophytic species, Salicornia fragilis Ball et Tutin. The saponification of samples and their clean up by Florisil solid-phase extraction succeeded in eliminating pigments and natural compounds, which may interfere with GC-MS analysis. Moreover, a good recovery of the PAHs studied was obtained with percentages ranging from 88 to 116%. Application to the determination of PAH in a wide range of coastal halophytic plants is presented and validated the efficiency, the accuracy and the reproducibility of this method

Phylogenetic relationships and genetic diversity of the Salicornieae (Chenopodiaceae) native to the Atlantic coasts of France.

International audiencePhylogenetic relationships of members of the tribe Salicornieae, native to the Atlantic coasts of France, were assessed by three molecular markers: the nuclear ribosomal internal transcribed spacer (ITS), the chloroplast trnL-F and the chloroplast matK sequences. In parallel to the phylogenetic studies, a population genetic study was carried out based on randomly amplified polymorphic DNAs (RAPD). Neither the MP/ML analyses of the sequences, nor the AMOVA and NJ analyses of RAPD fingerprints confirmed the morphologybased classification at the specific level within Salicornia. Instead, our investigations are in favour of the species aggregate concept. Two sister groups were revealed in the genus: one is composed of the diploid taxa, while the other clusters the tetraploid taxa. Conflicting nuclear versus plastid phylogenetic positions of some tetraploid samples, referred to as S. fragilis, indicate that they most likely derive from a reticulate evolution

Comparison of photoprotective responses to UV radiation in the brown seaweed Pelvetia canaliculata and the marine angiosperm Salicornia ramosissima

International audienceThe brown seaweed Pelvetia canaliculata and the marine angiosperm Salicornia ramosissima (purple glasswort) are two marine macrophytes growing in the upper intertidal zone. This location implies long emersion periods that lead to a direct exposure to UV solar radiation and to a potential photooxidative stress involving photoprotective compounds, such as phenols and pigments. To investigate the photoprotective responses in both species, which live under the same natural conditions but grow on different substrates, an experimental co-culture system was developed. Then, two three-week independent experiments were carried out with the artificial exposure of both macrophytes to a PAR alone treatment and either a PAR + dominant UV-A treatment (PA) simulating natural sunlight or a PAR + dominant UV-B treatment (PB) corresponding to high doses of UV-B radiations to enhance metabolic responses. Chlorophyll, carotenoid and phenol contents, as well as antioxidant activity, were determined for both species as a function of each light condition and exposure time (0, 7, 14 and 21 d). The accuracy and reproducibility of the first co-culture system created for both seaweeds and halophytes was confirmed by almost similar evolutions of pigments, phenols and antioxidant status after seven days of both PAR experiments. However, it seemed that young, annual and fast-growing plants of Salicornia ramosissima obtained from seed cultures acclimated slowly related to aging, perennial and apparently slow reacting thalli of P. canaliculata harvested in the field. Results showed that both UV treatments have almost no effect on chlorophyll contents. Carotenoid and phenol levels, as well as antioxidant activity, seemed to be less affected under PA treatment for both species. High doses of UV-B radiations induced few changes in carotenoid contents for both species, suggesting efficient constitutive contents for photoprotection. In contrast, phenol contents and antioxidant activity were not affected in P. canaliculata, whereas they decreased gradually in S. ramosissima. This could be explained by a fast acclimation of P. canaliculata to high UV-B radiations based on efficient contents of both phenols and carotenoids related to a strong antioxidant protection, versus a slow acclimation of S. ramosissima with a putative down regulation of phenols and the preferential involvement of carotenoids and/or other photoprotective systems