This study investigated the effects of salinity on biomarkers of oxidative stress, energy metabolism, and neurotransmission of
Carcinus maenas
from an estuary low impacted by pollution and from an ...estuary under chemical stress in the NW Iberian Peninsula. Crabs were collected in the field and, following an acclimation period, they were exposed for 7 days to five salinity levels ranging from 4 to 45 psu. At the end of the exposure period, stress biomarkers were determined in samples of muscle and digestive gland. The biomarkers assessed in the muscle were the activities of the enzymes cholinesterases (ChE), of which acetylcholinesterase is involved in neurotransmission, and lactate dehydrogenase (LDH) and isocitrate dehydrogenase (IDH) that are involved in energy metabolism. The biomarkers assessed in the digestive gland were (1) the activities of the enzymes glutathione
S
-transferases (GST), glutathione reductase (GR), and glutathione peroxidase (GPx), involved in phase II biotransformation and the anti-oxidant defence system; (2) the levels of total glutathiones (TG), also belonging to the anti-oxidant system; and (3) the levels of lipid peroxidation as a measure of oxidative damage. The results showed a significant influence of salinity on neurotransmission, energy metabolism, anti-oxidant status, and oxidative damage of
C. maenas
. For some biomarkers, this influence was dependent on whether the crabs were collected at the low-polluted estuary or at the contaminated estuary. In particular, crabs collected at the low-polluted estuary showed altered neurotransmission and anti-oxidant defences (GR). Crabs collected at the impacted estuary showed alterations in neurotransmission, energy metabolism (IDH and LDH), biotransformation, and anti-oxidant defences (GST, GR, GPx, and TG), as well as in oxidative damage, indicating that salinity change superimposes higher stress on these organisms. For ChE, IDH, and TG, altered responses were induced by both hypo- and hypersalinity.
An integrated chemical–biological effects monitoring was performed in 2010 and 2012 in two NW Iberian estuaries under different anthropogenic pressure. One is low impacted and the other is ...contaminated by metals. The aim was to verify the usefulness of a multibiomarker approach, using Carcinus maenas as bioindicator species, to reflect diminishing environmental contamination and improved health status under abiotic variation. Sampling sites were assessed for metal levels in sediments and C. maenas, water abiotic factors and biomarkers (neurotoxicity, energy metabolism, biotransformation, anti-oxidant defences, oxidative damage). High inter-annual and seasonal abiotic variation was observed. Metal levels in sediments and crab tissues were markedly higher in 2010 than in 2012 in the contaminated estuary. Biomarkers indicated differences between the study sites and seasons and an improvement of effects measured in C. maenas from the polluted estuary in 2012. Integrated Biomarker Response (IBR) index depicted sites with higher stress levels whereas Principal Component Analysis (PCA) showed associations between biomarker responses and environmental variables. The multibiomarker approach and integrated assessments proved to be useful to the early diagnosis of remediation measures in impacted sites.
•Two-year chemical–biological monitoring in estuaries with varying levels of metals.•Biochemical biomarkers reflected differences in environmental stress between sites.•An improvement on biochemical responses was observed from 2010 to 2012.•PCA indicated significant relationships between biomarkers and abiotic variables.•Multibiomarker approach potentially useful to diagnose remediation in impacted sites.
•Effects of Cd on NAGase activity of crabs from low impacted and polluted sites.•Inhibition of epidermal NAGase by Cd in crabs from both sites.•Inhibition of NAGase in digestive gland only in crabs ...from low impacted site.•Glutathione role in enhanced tolerance to Cd of crabs from polluted site.
Cadmium is a priority hazardous substance, persistent in the aquatic environment, with the capacity to interfere with crustacean moulting. Moulting is a vital process dictating crustacean growth, reproduction and metamorphosis. However, for many organisms, moult disruption is difficult to evaluate in the short term, what limits its inclusion in monitoring programmes. N-acetyl-β-d-glucosaminidase (NAGase) is an enzyme acting in the final steps of the endocrine-regulated moulting cascade, allowing for the cast off of the old exoskeleton, with potential interest as a biomarker of moult disruption. This study investigated responses to waterborne cadmium of NAGase activity of Carcinus maenas originating from estuaries with different histories of anthropogenic contamination: a low impacted and a moderately polluted one. Crabs from both sites were individually exposed for seven days to cadmium concentrations ranging from 1.3 to 2000μg/L. At the end of the assays, NAGase activity was assessed in the epidermis and digestive gland. Detoxification, antioxidant, energy production, and oxidative stress biomarkers implicated in cadmium metabolism and tolerance were also assessed to better understand differential NAGase responses: activity of glutathione S-transferases (GST), glutathione peroxidase (GPx) glutathione reductase (GR), levels of total glutathiones (TG), lipid peroxidation (LPO), lactate dehydrogenase (LDH), and NADP+-dependent isocitrate dehydrogenase (IDH). Animals from the moderately polluted estuary had lower NAGase activity both in the epidermis and digestive gland than in the low impacted site. NAGase activity in the epidermis and digestive gland of C. maenas from both estuaries was sensitive to cadmium exposure suggesting its usefulness for inclusion in monitoring programmes. However, in the digestive gland NAGase inhibition was found in crabs from the less impacted site but not in those from the moderately contaminated one. Altered glutathione levels were observed in cadmium-treated crabs from the contaminated site possibly conferring enhanced tolerance to these animals through its chelator action. Investigation of enhanced tolerance should thus be accounted for in monitoring programmes employing NAGase as biomarker to avoid data misinterpretation.
Résumé À travers l'observation de l'activité du programmateur d'une salle de cinéma parisienne, cet article propose de rendre compte de la construction de l'indépendance sur le marché de la diffusion ...cinématographique. Cette observation, qui révèle les critères pratiques de la programmation, permet de sortir de visions soit indigènes (choisir selon ses goûts), soit institutionnelles (la grille du label Art et essai), sans pour autant verser dans une interprétation cynique qui attribuerait aux seules visées commerciales la rationalité propre du programmateur indépendant. Le programmateur apparaît par excellence comme celui en qui se condensent les tensions et rapports de force propres aux indépendants sur un marché de biens culturels.
RésuméÀ travers l'observation de l'activité du programmateur d'une salle de cinéma parisienne, cet article propose de rendre compte de la construction de l'indépendance sur le marché de la diffusion ...cinématographique. Cette observation, qui révèle les critères pratiques de la programmation, permet de sortir de visions soit indigènes (choisir selon ses goûts), soit institutionnelles (la grille du label Art et essai), sans pour autant verser dans une interprétation cynique qui attribuerait aux seules visées commerciales la rationalité propre du programmateur indépendant. Le programmateur apparaît par excellence comme celui en qui se condensent les tensions et rapports de force propres aux indépendants sur un marché de biens culturels.
L'« indépendance » est une notion de plus en plus souvent utilisée au sein des industries culturelles et médiatiques, que ce soit dans l'univers de l'édition, de la musique enregistrée, du cinéma ou ...de la presse. Au-delà des structures qui s'en réclament, l'indépendance est notamment mobilisée pour caractériser des genres (rock indé sur les sites de musique à la demande, indie movies sur les plate-forme VOD), des lieux de diffusion ou de consécration (le Sundance Film Festival, le Salon international des éditeurs indépendants, le Pitchfork Music Festival), des publications spécialisées (IndieWire), des collectifs (le mouvement IndieBound, l'Alliance des éditeurs indépendants) et, plus généralement, un rapport au travail ou des styles de vie. La grande variété des usages, des échelles et des significations attachées à l'indépendance montre qu'elle est devenue une catégorie de perception centrale au sein des univers culturels, voire un label. Dès lors, comment expliquer une telle contagion du terme « indépendant » et de ses différentes variantes (indie, indé) au sein des espaces de production symbolique ? En quoi cet engouement est-il révélateur des transformations que connaissent les espaces confrontés à une rationalisation économique de plus en plus pressante ? Autant de questions auxquelles ce dossier se propose d'apporter des réponses, en prenant au sérieux l'usage de ce terme indigène brandi comme emblème, souvent avec fierté, parfois avec cynisme, à partir de trois études de terrain dans les secteurs de la presse en ligne, de la librairie et de l'exploitation cinématographique…
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