Consulta: creatorFacets:"Medhioub, Walid"
Registros recuperados: 9
Data/hora: 08/06/2024 18:47:11

A Feedback Mechanism to Control Apoptosis Occurs in the Digestive Gland of the Oyster Crassostrea gigas Exposed to the Paralytic Shellfish Toxins Producer Alexandrium catenella
Provedor de dados: 5
Autores: Rolland, Jean-luc; Medhioub, Walid; Vergnes, Agnes; Abi-khalil, Celina; Savar, Veronique; Abadie, Eric; Masseret, Estelle; Amzil, Zouher; Laabir, Mohamed.
To better understand the effect of Paralytic Shellfish Toxins (PSTs) accumulation in the digestive gland of the Pacific oyster, Crassostrea gigas, we experimentally exposed individual oysters for 48 h to a PSTs producer, the dinoflagellate Alexandrium catenella. In comparison to the effect of the non-toxic Alexandrium tamarense, on the eight apoptotic related genes tested, Bax and BI.1 were significantly upregulated in oysters exposed 48 h to A. catenella. Among the five detoxification related genes tested, the expression of cytochrome P450 (CYP1A) was shown to be correlated with toxin concentration in the digestive gland of oysters exposed to the toxic dinoflagellate. Beside this, we observed a significant increase in ROS production, a decrease in...
Tipo: Text
Palavras-chave: Shellfish; Toxin; Biomarker; Expression; Phytoplankton.
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00225/33606/32003.pdf

Effets de l'algue toxique Alexandrium catenella sur le système de défense de l'huître creuse Crassostrea gigas
Provedor de dados: 5
Autores: Medhioub, Walid; Duchiron, Marie; Masseret, Estelle; Savar, Veronique; Amzil, Zouher; Laabir, Mohamed; Rolland, Jean-luc.
Tipo: Text
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00172/28332/26618.pdf

Exposure to the Neurotoxic Dinoflagellate, Alexandrium catenella, Induces Apoptosis of the Hemocytes of the Oyster, Crassostrea gigas
Provedor de dados: 5
Autores: Medhioub, Walid; Ramondenc, Simon; Vanhove, Audrey; Vergnes, Agnes; Masseret, Estelle; Savar, Veronique; Amzil, Zouher; Laabir, Mohamed; Rolland, Jean-luc.
This study assessed the apoptotic process occurring in the hemocytes of the Pacific oyster, Crassostrea gigas, exposed to Alexandrium catenella, a paralytic shellfish toxins (PSTs) producer. Oysters were experimentally exposed during 48 h to the toxic algae. PSTs accumulation, the expression of 12 key apoptotic-related genes, as well as the variation of the number of hemocytes in apoptosis was measured at time intervals during the experiment. Results show a significant increase of the number of hemocytes in apoptosis after 29 h of exposure. Two pro-apoptotic genes (Bax and Bax-like) implicated in the mitochondrial pathway were significantly upregulated at 21 h followed by the overexpression of two caspase executor genes (caspase-3 and caspase-7) at 29 h,...
Tipo: Text
Palavras-chave: Shellfish; Toxins; Apoptosis; Gene expression.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00176/28744/27213.pdf

Physiological responses of Manila clams Venerupis (=Ruditapes) philippinarum with varying parasite Perkinsus olseni burden to toxic algal Alexandrium ostenfeldii exposure
Provedor de dados: 5
Autores: Lassudrie, Malwenn; Soudant, Philippe; Richard, Gaelle; Henry, N.; Medhioub, Walid; Da Silva, P.m.; Donval, Anne; Bunel, M.; Le Goïc, Nelly; Lambert, Christophe; De Montaudoin, X.; Fabioux, Caroline; Hegaret, Helene.
Manila clam stock from Arcachon Bay, France, is declining, as is commercial harvest. To understand the role of environmental biotic interactions in this decrease, effects of a toxic dinoflagellate, Alexandrium ostenfeldii, which blooms regularly in Arcachon bay, and the interaction with perkinsosis on clam physiology were investigated. Manila clams from Arcachon Bay, with variable natural levels of perkinsosis, were exposed for seven days to a mix of the nutritious microalga T-Iso and the toxic dinoflagellate A. ostenfeldii, a producer of spirolides, followed by seven days of depuration fed only T-Iso. Following sacrifice and quantification of protozoan parasite Perkinsus olseni burden, clams were divided into two groups according to intensity of the...
Tipo: Text
Palavras-chave: Bivalve; Harmful algal bloom; Oxidative stress; Venerupis philippinarum; Alexandrium ostenfeldii; Perkinsus olseni.
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00189/30022/28507.pdf

Alexandrium ostenfeldii growth and spirolide production in batch culture and photobioreactor
Provedor de dados: 5
Autores: Medhioub, Walid; Sechet, Veronique; Truquet, Philippe; Bardouil, Michele; Amzil, Zouher; Lassus, Patrick; Soudant, Philippe.
Growth and spirolide production of the toxic dinoflagellate Alexandrium ostenfeldii (Danish strain CCMP1773) were studied in batch culture and a photobioreactor (continuous cultures). First, batch cultures were grown in 450 mL flasks without aeration and under varying conditions of temperature (16 and 22 degrees C) and culture medium (L1, f/2 and L1 with addition of soil extract). Second, cultures were grown at 16 degrees C in 8 L aerated flat-bottomed vessels using L1 with soil extract as culture medium. Finally, continuous cultures in a photobioreactor were conducted at 18 degrees C in L1 with soil extract; pH was maintained at 8.5 and continuous stirring was applied. This study showed that A. ostenfeldii growth was significantly affected by temperature....
Tipo: Text
Palavras-chave: Alexandrium ostenfeldii; Batch; Growth; Photobioreactor; Spirolide production.
Ano: 2011
URL: http://archimer.ifremer.fr/doc/00049/16050/15784.pdf

Detoxification enhancement in the gymnodimine-contaminated grooved carpet shell, Ruditapes decussatus (Linne)
Provedor de dados: 5
Autores: Medhioub, Walid; Gueguen, Marielle; Lassus, Patrick; Bardouil, Michele; Truquet, Philippe; Sibat, Manoella; Nejib, Medhioub; Philippe, Soudant; Mejdeddine, Kraiem; Amzil, Zouher.
In the Gulf of Gabes (Tunisia, Eastern Mediterranean sea), the grooved carpet shell Ruditapes decussatus has been seen to contain persistent levels of gymnodimine (GYM) for several years. The present experimental work represents the first attempt to assess detoxification kinetics of fast-acting toxins (FAT) in marine molluscs fed specific diets of non-toxic algae (Isochrysis galbana). To find an optimal detoxification method, two experiments were performed in which clams were first fed the toxic dinoflagellate Karenia selliformis to artificially contaminate them with GYM, thus simulating the effect of natural toxic episodes. As a second step, the same clams were fed a non-toxic algae, I. galbana. to speed up the detoxification process. Changes in toxin...
Tipo: Text
Palavras-chave: Ruditapes decussates; Grooved carpet shell; Karenia selliformis; Gymnodimine; Toxicity; Detoxification.
Ano: 2010
URL: http://archimer.ifremer.fr/doc/2010/publication-7488.pdf

Influence of environmental parameters on Karenia selliformis toxin content in culture
Provedor de dados: 5
Autores: Medhioub, Amel; Medhioub, Walid; Amzil, Zouher; Sibat, Manoella; Bardouil, Michele; Ben Neila, Idriss; Mezghani, Salah; Hamza, Asma; Lassus, Patrick.
Karenia selliformis strain GM94GAB was isolated in 1994 from the north of Sfax, Gabes gulf, Tunisia. This species, which produces gymnodimine (GYM) a cyclic imine, has since been responsible for chronic contamination of Tunisian clams. A study was made by culturing the microalgae oil enriched Gaillard f/2 medium. The influence of growing conditions oil toxin content was studied, examining the effects of (i) different culture Volumes (0.25 to 40 litre flasks), (ii) two temperature ranges (17-15 degrees C et 20-21 degrees C) and (iii) two salinities (36 and 44). Chemical analyses were made by mass spectrometry coupled with liquid chromatography (LC-MS/MS). Results showed that (i) the highest growth rate (0.34 +/- 0.14 div d(-1)) was obtained at 20 degrees C...
Tipo: Text
Palavras-chave: Mouse bioassay; Gymnodimine; Toxicity; Growth; Karenia selliformis.
Ano: 2009
URL: http://archimer.ifremer.fr/doc/2009/publication-7383.pdf

Spirolide uptake and detoxification by Crassostrea gigas exposed to the toxic dinoflagellate Alexandrium ostenfeldii
Provedor de dados: 5
Autores: Medhioub, Walid; Lassus, Patrick; Truquet, Philippe; Bardouil, Michele; Amzil, Zouher; Sechet, Veronique; Sibat, Manoella; Soudant, Philippe.
Oysters (Crassostrea gigas) were exposed 4 days to cultures of the toxic dinoflagellate Alexandrium ostenfeldii (strain CCMP1773) that produces spirolides belonging to fast acting toxins (FAT) and let depurate for 7 days. During depuration, oysters were either fed the non-toxic algae Isochrysis galbana Tahitian clone (T. Iso) or starved. The objectives of this experiment were to evaluate (i) spirolide uptake and depuration by oysters (ii) spirolide effects on oysters and (iii) oyster recovery according to food supply during depuration. A. ostenfeldii cells were filtered and ingested by oysters while faeces contained numerous intact cells of the toxic diet. This suggested that ingested cells were not totally digested by oysters. Contents of spirolides (SPX)...
Tipo: Text
Palavras-chave: Spirolides; Alexandrium ostenfeldii; Contamination; Depuration; Crassostrea gigas; Inflammatory responses.
Ano: 2012
URL: http://archimer.ifremer.fr/doc/00098/20953/18740.pdf

Etude des mécanismes de contamination des mollusques bivalves par des neurotoxines à action rapide (FAT) et développement de procédés de détoxification
Provedor de dados: 20
Autores: Medhioub, Walid.
Cette étude à pour objectif de maîtriser les conditions de culture et de production toxinique chez Karenia selliformis et Alexandrium ostenfeldii dans le but de réaliser des contaminations expérimentales indépendamment du caractère aléatoire des proliférations toxiques en zones côtières. Ce travail vise également à étudier l‘impact de l‘alimentation sur la détoxification artificielle de la pa lourde Ruditapes decussatus contaminée par des gymnodimines et de l‘huître Crassostrea gigas contaminées par des spirolides et enfin d‘étudier l‘impact physiologique de ces micro-algues toxiques au niveau des organes accumulateurs des coquillages. Dans un premier temps, il a été mis en évidence que les performances de croissance de K. selliformis (taux de croissance...
Tipo: Theses and Dissertations
Palavras-chave: DETOXICATION; Gymnodimine; Spirolide; Culture; Karenia selliformis; Alexandrium ostenfeldii; Ruditapes decussatus; Histology; Crassostrea gigas.
Ano: 2011
URL: http://hdl.handle.net/1834/4773