Biocompatible polymer-assisted dispersion of multi walled carbon nanotubes in water, application to the investigation of their ecotoxicity using Xenopus laevis amphibian larvae

Carbon nanotubes (CNTs) tend to readily agglomerate and settle down in water, while the adsorption of compounds present in natural aquatic media could enhance their dispersion and stabilization in the water column. We designed a new exposure protocol to compare the biological responses of Xenopus laevis larvae exposed in semi-static conditions to size-reduced agglomerates of multi-walled carbon nanotubes (MWCNTs) in suspension in the water column and/or to larger agglomerates. Suspensions were prepared using a combination of a non-covalent functionalization with a non-toxic polymer (either carboxymethylcellulose, CMC, or gum arabic, GA) and mechanical dispersion methods (mainly ultrasonication). The ingestion of agglomerates which have settled down was incriminated in the disruption of the intestinal transit and the assimilation of nutrients, leading to acute and chronic toxicities at the highest tested concentrations. Rise in mortality, decrease in the growth rate and induction of genotoxicity from low concentrations (1 mg/L in the presence of CMC) were evidenced in presence of suspended MWCNTs in the water column. The biological responses seemed to be modulated when GA, a potential antioxidant, was used. We hypothesized that MWCNTs should interfere mainly at the surface of the gills, acting as a potential respiratory toxicant and generally inducing indirect effects

International standardized procedures forin vivoevaluation of multi-walled carbon nanotube toxicity in water

The classical approach in ecotoxicological evaluation of chemical substances consists of conducting standardized bioassays on organism models. In this work, the potential impact of industrial multiwalled carbon nanotubes was investigated by ecotoxicological standardized procedures using aquatic organisms of different trophic levels, namely bacteria, green algae, invertebrates, fish, and amphibians. The results indicated (1) inhibition of growth in amphibians at 50 mg L¡1 and higher, and (2) no effects on daphnia and fish up to 100 mg L¡1. With the exception of algae (for which Fe deficiency is measured), it seems that the observed toxicity may be due to physiological effects in relation to the ingestion of carbon nanotubes not necessarily related to their intrinsic effects

Multi-walled carbon nanotubes, natural organic matter, and the benthic diatom Nitzschia palea: “A sticky story”

Different effects of multi-walled carbon nanotubes (MWCNTs) on the freshwater diatom Nitzschia palea were examined. MWCNTs used in this study (MWCNT) were dispersed either by sonication without (MWCNTsonicated) or with a realistic concentration (10mgL-1) of Natural Organic Matter (MWCNT+NOM). A pocket-size device was designed to distinguish shading effect (using MWCNT suspensions as external filters) from total exposure effect of MWCNTsonicated and MWCNT+NOM on benthic algae. This study demonstrates that cell division was strongly inhibited after a 48 h exposure to MWCNT+NOM compared to MWCNTsonicated. This device did not yield a quantifiable contribution of shading to growth inhibition of MWCNTsonicated and below 10mgL-1 of MWCNT+NOM. In all cases, neither lethal effects nor drops in photosynthetic quantum yield were observed. After a 6-d exposure, a complete growth recovery was observed for all conditions except at the highest concentration of MWCNT+NOM. Different microscopic approaches using carbohydrates markers revealed the strong affinity between MWCNT and extracellular polymeric substances (EPS) produced by N. palea. These seem to constitute a defensive mechanism against MWCNT

Etude des effets des nanotubes de carbone multi-parois sur l'homme et l'environnement (exemple du graphistrength C 100®)

PARIS-BIUP (751062107) / SudocSudocFranceF

La dynamique ovine dans les Alpes-de-Haute-Provence: Entre rémunération des qualités de viande et des services environnementaux, l’équilibre incertain.

Whereas the crisis of ovine farming concerns the whole of the French production areas, it manifests itself in a specific way in the territories of the South of France, owing to the pastoral nature of the farms and to the diversity of meat products and of the associated industries. Starting from a study carried out in the Alpes-de-Haute-Provence, well-known today for its Sisteron lamb, this article retraces the evolution of sheep farming in the pre-Alpine agrarian systems during the twentieth century and summarizes the present situation through the analysis of the workings of the different farming systems. It discusses the relationships, often ambiguous, established between the quality of the products and the maintenance of the area and considers the the prospects which, in this context, to the sheep-farming sector of the area is facing.Si elle concerne l’ensemble des zones de production françaises, la crise de l’élevage ovin allaitant se manifeste de manière spécifique dans les territoires du sud de la France, du fait du caractère pastoral des élevages et de la diversité des produits « viande » et des filières associées. À partir d’une étude conduite dans les Alpes-de-Haute-Provence, aujourd’hui connues pour leur agneau de Sisteron, cet article retrace les évolutions de l’élevage ovin dans les systèmes agraires préalpins au cours du xx e siècle et rend compte de la situation actuelle à travers l’analyse du fonctionnement des différents systèmes d’élevage. Il discute des relations, souvent ambiguës, qui s’établissent entre qualité des produits et entretien de l’espace et réfléchit aux perspectives qui, dans ce contexte, s’offrent au secteur ovin du département

Valorisation des produits ovins : quelles stratégies d'élevage ?

International audienceOur study aims at understanding the strategies of the Cevennes gardoises' sheep breeders. This region is localized between the pool of consumption of the Mediterranean coast and the pool of production of Roquefort's milk. Six strategies-type were described, according to the animal's products and the circuits of marketing: 1) everything in light lamb (L), 2) based on the date of Aïd (A), 3) combining various types of lambs (C), 4) integrating a part of the process chain (I) 5) cheeses and meat-based products (FPC) and 6) finished lambs (S). The technico-economic evaluation shows the interests and the limits of these various strategies. We conclude that these strategies are enhanced or not with the degree of economy in forage distribution and forage autonomy. This study also permits us to identify three type of "range of animal products" for those livestock systems. This types are defined according to the principal product's add value and if there is or not complementary products. Finally, we emitted hypotheses on the capacity of these sheep systems to maintain and adapt themselves, especially to the evolutions of outlets.Notre étude vise à comprendre les stratégies des éleveurs ovins des Cévennes gardoises, région située entre le bassin de consommation du littoral méditerranéen et le bassin de production ovin lait de Roquefort. Six stratégies-type ont été mises en évidence, en fonction des produits de l'élevage et des circuits de commercialisation : 1) tout en agneau léger, 2) basé sur la date de l'Aïd, 3) combinant différents types d'agneaux, 4) intégrant une part de la chaîne de transformation, 5) fromages et produits carnés et 6) agneaux lourd finis. L'évaluation économique montre les intérêts et les limites de ces différentes stratégies, variant selon le degré d'autonomie des systèmes et les quantités de fourrage distribué. Nous avons également identifier trois types de " gammes de produits animaux " issus de ces systèmes d'élevage, en fonction de la valeur ajoutée du produit principal et de la présence ou non de produits complémentaires. Enfin, nous avons émis des hypothèses sur la capacité de ces systèmes ovins à se maintenir et s'adapter aux évolutions du milieu, et spécialement des débouchés

Entre hétérogénéité et diversité des agneaux : comment les éleveurs et les opérateurs de la filière construisent une offre variée pour le marché de la viande d’agneaux ?

During the XXth century, meat became the main objective of sheep farming systems of South-East France, as wool and manure have lost the importance they had in the XIXth century. (Aubron and al., 2012). Dairy sheep are very profitable thanks to high value cheese production, but remain limited and localized near Roquefort. Sheep meat production continuously decreased during the last 30 years, in connection with the diminution of the number sheep farms. Languedoc Roussillon does not escape this movement, but remains a high consumer of sheep, so offering real marketing opportunities. In the first time, our works show how the lamb meat remains a specific product, due to its important symbolic value (production and consumption marked by the celebrations of Easter and Aïd-el-Adha), and how the few level of processing of animals, mostly marketed in life, in whole carcass or in parts, ready for cooking, but rarely in the form of transformed products or of delicatessen, leads the consumer to have access to the biological heterogeneity, linked to the conditions of production (genetic type, practices of food and reproduction). The ovine production in French Mediterranean regions (which include Languedoc Roussillon) is characterized by a diversity of products which must be, for Tchackérian and al., 2008, a way to answering a diversity of the demand. Secondly, from discussions with livestock farmers (n=26) and with operators of sheep meat supply chain (n=22), we thus investigate the diversity of the categories of lambs, by studying the variety of the commercial names used by the operators of the sheep meat supply chain (traders, wholesale butchers) and the types of qualifications of animals used in the transactions during the first marketing by the breeders. Finally, we show, on one hand, how the breeders compose with the heterogeneity of animals, according to the structure of their system of production and their practices of breeding, by trying to reduce it, to aim at a unique product, or on the contrary to increase it to produce a diversity of lambs, and, on the other hand, how the operators of the sheep meat supply chain use this diversity to supply the market with lambs.La production de viande est devenue au cours du XXème siècle l’objectif principal de l’élevage ovin du Sud Est de la France, avec un abandon progressif de la fonction de production de laine et de fumure (Aubron et al. 2012), la production de lait pour la production de fromages de qualité restant dynamique mais minoritaire et localisée à proximité de Roquefort. La production de viande ovine française n’a cessé de diminuer depuis les années 1980, en lien avec une diminution du nombre d’élevages. Le Languedoc Roussillon n’échappe pas à ce mouvement, mais reste fortement consommatrice de viande ovine, offrant ainsi de réelles opportunités de débouchés. Dans un premier temps, nous montrons comment l’agneau demeure un produit spécifique, de par sa valeur symbolique importante (production et consommation marquées par les fêtes de Pâques et de l’Aïd-el-Adha), et comment le peu de transformation des animaux, le plus souvent commercialisés en vif, en carcasse entière ou en pièces prêtes à cuire, mais rarement sous forme de plats transformés ou de charcuterie, conduit à ce que le consommateur ait accès à l’hétérogénéité biologique, liée aux conditions de la production (type génétique, pratiques d’alimentation et de reproduction). L’élevage ovin allaitant des régions méditerranéennes françaises (dont le Languedoc Roussillon) est ainsi caractérisé par une diversité d’agneaux produits qui serait, pour Tchackérian et al., 2008, un mode de réponse à une diversité de la demande. Dans un deuxième temps, à partir d’entretiens auprès d’éleveurs (n=26) et d’opérateurs de la filière (n=22), nous explorons donc la diversité des catégories d’agneaux, en étudiant la variété des dénominations commerciales utilisés par les opérateurs de la filière (négociants, groupements de producteurs, chevillards) et les modes de qualifications des animaux utilisées dans les transactions lors de la première mise en marché par les éleveurs. Enfin, nous montrons, d’une part, comment les éleveurs composent avec l’hétérogénéité des animaux, selon la structure de leur système de production et leurs pratiques d’élevage, en cherchant à la réduire, pour viser un produit unique, ou au contraire à l’augmenter pour produire une diversité d’agneaux, et, d’autre part, comment les opérateurs de la filière utilisent cette diversité pour fournir le marché en viandes d’agneau

Laine, transferts de fertilite, lait et viande: evolution des produits de l'elevage ovin dans les systèmes agraires

This paper focuses on the role of sheep in the agricultural systems from the analysis of situations and Andean Mediterranean, characterized by a strong association between sheep farming and agriculture in the Mediterranean since antiquity, and the introduction of sheep following the Spanish colonization in the Andes. Compared to other domestic animal species in these regions as cattle or Andean camelids, sheep have several advantages (docile, small frame and able to graze difficult areas) that facilitate their livestock. However, their fragility, particularly from predators, forces farmers to collect them at night and invest a lot of work to monitor grazing and lambing. This investment was justified in work until the 19th century by the fact that sheep produced wool, which was often the only monetary income of the family, sometimes milk for family consumption, and realized fertility transfers between space travel (saltus) and cultivated areas (ager, hortus), essential for the production of cereals and tubers, staples of these human populations. The sheep was then a byproduct of this breeding. Only older animals were slaughtered (culls) or very young (animals not kept for herd rebuilding). The opening of the world wool market in the late 19th century signaled the end of this outlet in Western Europe, the development of artificial textiles after World War II led to the decline of the wool industry worldwide and the end of the specific function of sheep as a source of wool. The transfer function of fertility is compromised north of the Mediterranean from 1950 through the use of fertility treatments but continues to play a key role for farmers who can not afford them. Therefore, the question is: under what conditions are sheep, reduced to its function as meat production, viable

Integrating food chain and local development objectives in french mediterranean livestock farming systems

International audienc

Short term exposure to multi-walled carbon nanotubes induce oxidative stress and DNA damage in Xenopus laevis tadpoles

International audienceThe potential impact of Multiwalled Carbon NanoTubes (MWCNTs) was investigated on Xenopus laevis tadpoles exposed to 0.1, 1 and 10mg/L. Oxidative stress was measured in entire larvae exposed and DNA damage (Comet assay) was carried out in erythrocytes of circulating blood from 2h to 24h according to standardized recommendations. Results showed significant H2O2 production when larvae were exposed to 1mg/L and 10mg/L of MWCNTs after 4h and 2h of exposure, respectively. Antioxidant enzyme activities showed significant induction of catalase (CAT), glutathione reductase (GR) and superoxide dismutase (SOD) from only 2h of exposure to 10mg/L of MWCNTs. In presence of 1mg/L of MWCNTs, only GR and CAT activities were significantly induced at 4h. Enzyme activities do not follow a simple dose-effect relation, but the time of induction is shortened in relation with the tested concentration. The Comet assay results showed significant DNA damages with a dose dependent response. The profiles of DNA damages show fluctuations, in course of time, which are characteristics of oxidative stress response in relation with the continuous balance between damage and compensation process