Letteratura scientifica selezionata sul tema "Pecten maximus – Toxicologie"

Prevalence, impact on shellfish resources and interspecific, spatial, and temporal variabilities of domoic acid (DA) in bivalves from Galicia (NW Spain) have been studied based on more than 25 years of monitoring data. The maximum prevalence (samples in which DA was detected) (100%) and incidence (samples with DA levels above the regulatory limit) (97.4%) were recorded in Pecten maximus, and the minimum ones in Mytilus galloprovincialis (12.6 and 1.1%, respectively). The maximum DA concentrations were 663.9 mg kg−1 in P. maximus and 316 mg kg−1 in Venerupis corrugata. After excluding scallop P. maximus data, DA was found (prevalence) in 13.3% of bivalve samples, with 1.3% being over the regulatory limit. In general, the prevalence of this toxin decreased towards the North but not the magnitude of its episodes. The seasonal distribution was characterized by two maxima, in spring and autumn, with the later decreasing in intensity towards the north. DA levels decreased slightly over the studied period, although this decreasing trend was not linear. A cyclic pattern was observed in the interannual variability, with cycles of 4 and 11 years. Intoxication and detoxification rates were slower than those expected from laboratory experiments, suggesting the supply of DA during these phases plays an important role.

The king scallop Pecten maximus retains the amnesic shellfish poisoning toxin, domoic acid (DA), for a long time. Most of the toxin is accumulated in the digestive gland, but this organ contains several cell types whose contribution to the accumulation of the toxin is unknown. Determining the time-course of the depuration by analyzing whole organs is difficult because the inter-individual variability is high. A sampling method, using biopsies of the digestive gland, has been developed. This method allows for repetitive sampling of the same scallop, but the representativeness of the samples obtained in this way needs to be validated. In this work, we found that the distribution of DA in the digestive gland of the scallops is mostly homogeneous. Only the area closest to the gonad, and especially its outer portion, had a lower concentration than the other ones, probably due to a transfer of the toxin to the intestinal loop. Samples obtained by biopsies can therefore be considered to be representative. Most of the toxin was accumulated in large cells (mostly digestive cells), which could be due to differences during the toxin absorption or to the preferential depuration of the toxin from the small cells (mostly secretory).

Some diatom species of the genus Pseudo-nitzschia produce the toxin domoic acid. The depuration rate of domoic acid in Pecten maximus is very low; for this reason, king scallops generally contain high levels of domoic acid in their tissues. A transcriptomic approach was used to identify the genes differentially expressed in the P. maximus digestive gland after the injection of domoic acid. The differential expression analysis found 535 differentially expressed genes (226 up-regulated and 309 down-regulated). Protein–protein interaction networks obtained with the up-regulated genes were enriched in gene ontology terms, such as vesicle-mediated transport, response to stress, signal transduction, immune system process, RNA metabolic process, and autophagy, while networks obtained with the down-regulated genes were enriched in gene ontology terms, such as response to stress, immune system process, ribosome biogenesis, signal transduction, and mRNA processing. Genes that code for cytochrome P450 enzymes, glutathione S-transferase theta-1, glutamine synthase, pyrroline-5-carboxylate reductase 2, and sodium- and chloride-dependent glycine transporter 1 were among the up-regulated genes. Therefore, a stress response at the level of gene expression, that could be caused by the domoic acid injection, was evidenced by the alteration of several biological, cellular, and molecular processes.

Aim: To study the enhancement of solasodine content using elicitors such as NaCl, pectin, salicylic acid and yeast extract in cell suspension cultures of Solanum incanum, Solanum nigrum, Solanum surattense and Solanum villosum. Methodology: In-vitro callus induction from leaf explants was carried out on MS media supplemented with auxin, 2, 4- Dichlorophenoxyacetic acid (2.0 mg l-1). MS liquid medium supplemented with 2, 4-D (2.0 mg l-1) and varied concentrations of different elicitors were used for cell suspension culture. Results: The elicitor NaCl (150 mM) indicated maximum increment in solasodine production in three Solanum species studied. Salicylic acid with 75 μM resulted in considerable elevation in solasodine content in Solanum spp. Response to elicitation by pectin was high at different concentrations for different species of Solanum. Biotic elicitor yeast extract at 3.0 g l-1 concentration considerably increased solasodine production in S. nigrum and S. villosum. Solanum villosum exhibited best results in terms of solasodine concentration enhancement in response to pectin and yeast extract elicitors whereas Solanum incanum responded best to pectin followed by NaCl. Interpretation: The current results indicated that NaCl, pectin, salicylic acid and yeast extract can be effectively applied as influential elicitors for the enhancing the production of solasodine in cell suspension culture of different Solanum species. Key words: Callus, Cell suspension culture, Elicitors, Solanum, Solasodine, Steroidal alkaloids

La coquille Saint-Jacques {Pecten maximus) fait figure d’exception parmi les organismes contaminés par l’acide domoïque du fait de sa longue rétention au sein de sa glande digestive. Bien que les interdictions de pêche en cas de contamination aient un impact économique important, le mécanisme sous-jacent à cette lente dépuration reste méconnu. Les objectifs de cette thèse ont donc été de i) examiner in situ la contamination de P. maximus en corrélation avec la présence de Pseudo-nitzschia spp. et d’acide domoïque dans l'eau afin d'identifier les diverses sources de contamination possibles, ii) étudier le lien entre la dépuration de l'acide domoïque et la taille de P. maximus, iii) explorer la piste des microorganismes pour accélérer la dépuration de l'acide domoïque dans la glande digestive de P. maximus. Une surveillance menée depuis 2011 dans la rade de Brest a mis en évidence l'importance des eaux de surface et de fond ainsi que la présence de Pseudo-nitzschia spp. et d'acide domoïque dans la contamination de P. maximus, identifiant ainsi trois scénarios de contamination. Une expérience de décontamination sur deux mois a révélé que les petites coquilles semblaint dépurer l'acide domoïque plus rapidement que les grandes. Des isolements bactériens effectués sur des individus contaminés ont révélés des différences avec d'autres espèces de bivalves considérés comme dépurateurs rapides. Bien que des souches bactériennes candidates aient été identifiées, aucune réduction de l'acide domoïque n'a été observée après exposition à toxine. Un transfert de microbiote de M. edulis a été réalisé vers P. maximus, montrant un transfert de souches bactériennes dans la glande digestive de P. maximus. En conclusion, ces travaux enrichissent la compréhension des diverses sources de contamination de P. maximus par l'acide domoïque, ainsi que des réponses de ce bivalve en fonction de sa taille face à cette toxine. Cette thèse offre des pistes qui pourraient permettre d'accélérer la dépuration de l'acide domoïque chez P. maximus
The King scallop {Pecten maximus) is an exception among domoic acid contaminated organisms, due to its long retention within the digestive gland. Although fishing bans in the event of contamination have a significant economie impact, the mechanism behind this slow depuration remains poorly understood. The aims of this thesis were therefore to i) examine in situ the contamination of P. maximus in correlation with the presence of Pseudo-nitzschia spp. and domoic acid in the water, to identify the various sources of contamination, ii) study the link between domoic acid depuration and P. maximus size, iii) explore the possibility of microorganisms accelerating the depuration of domoic acid in the digestive gland of P. maximus. Monitoring carried out since 2011 in the Bay of Brest has shown the importance of surface and bottom waters, as well as the presence of Pseudo-nitzschia spp. and domoic acid in P. maximus contamination, thus identifying three contamination scenarios. A two-month decontamination experiment revealed that smaller scallops seemed to depurate domoic acid faster than larger ones. Bacterial isolations from contaminated individuals revealed differences with other bivalve species considered to be rapid depurators. Although candidate bacterial strains were identified, no toxin reduction was observed after exposure to domoic acid. A transfer of microbiota from M. edulis to P. maximus was performed, showing a transfer of bacterial strains into the digestive gland of P. maximus. In conclusion, this work enriches our understanding of the various sources of domoic acid contamination of scallops, as well as the response of this bivalve to domoic acid according to its size. This thesis offers new insight for accelerating domoic acid depuration in Pecten maximus

Des cultures primaires de cellules atriales de coquilles St Jacques Pecten Maximus ont été établies au cours de ce travail. Ces cultures peuvent être obtenues à partir de cellules inoculées dès l'isolement ou après cryopréservation. Une monocouche cellulaire est observée après une semaine de culture. L'utilisation de facteurs matriciels d'origine marine permet de réduire ce temps en facilitant l'adhésion. Différentes méthodes analytiques appliquées aux cultures asynchrones ou à des cellules synchronisés en transition G1/S selon une méthodologie adaptée de la littérature, montrent qu'environ 15 % de cellules inoculées sont aptes à se diviser. La croissance peut être stimulée par addition de certains compléments au milieu sans toutefois permettre l'obtention d'un lignée. Parmi les cellules adhérentes, les cardiomyocytes, que nous avons caractérisés immunocytochimiquement et electrophysiologiquement (récepteurs de type B-adrénergique et cholinergiques de type muscarinique), sont spontanément contractiles in vitro dès huit jours et le restent durant un mois. Ces cellules s'avèrent intéressantes pour étudier la toxicité de xénobiotiques en utilisant en particulier le Patch-clamp comme méthode analytique. Un deuxième type de cellules adhérentes, qui présentent des analogies structurales avec les cellules des glandes péricardiques dont la littérature signale le rôle dans la détoxication, semble intervenir dans les processus de biotransformation de phase de type I et II. Une stimulation de certaines activités enzymatiques par des inducteurs de référence et par certains contaminants du milieu marin a en effet été notée. L'ensemble de ces résultats ouvre des perspectives d'utilisation du bioessai mis en place tant au plan fondamental qu'appliqué
In this study, atrial cells primary cuture of the scallop, Pecten maximus was established. A monolayer culture can already be observed one week following the initial plating of either fresh or cryopreserved cells. Cell attachment was improved and was obtained faster when the cells were plated on marine substrate. Combined analytical techniques, tested in asynchronous cells and synchronised cells in transition G1/S, showed that about 15 % of plated cells are able to proliferate. The growth can be stimulated by supplementation of the medium with various factors but no permanent cell line have been obtained. Among adherent cells, the cardiomyocytes, characterized by both immunocytochemical and electrophysiological features (beta-adrenergic and muscarinic receptors), were able to spontaneously contract in vitro by using especially patch-clamp technique. One another kind of adherent cells, having structural similitaries with pericardial gland cells described to be important in the dexintoxication function, seems to be involved in biotransformation activities of phase I and II. Indeed, we have actually been able to stimulate these enzymatic activities by reference inductors and by some marine contaminants. Taken together, our cellular model demonstrate its potential for fundamental and applied bioessay research studies