References of "Thomé, Jean-Pierre"
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See detailEffects of Aroclor 1254 on oxidative stress in developing Xenopus laevis tadpoles.
Gillardin, Virginie; Silvestre, Frederic; Divoy, Celine et al

in Ecotoxicology & Environmental Safety (2009), 72(2), 546-51

Over the last decades, amphibians decline has been reported worldwide. Exposure to polychlorinated biphenyls (PCBs) is one of the possible causes in addition to climate changes, UV-radiation or habitat ... [more ▼]

Over the last decades, amphibians decline has been reported worldwide. Exposure to polychlorinated biphenyls (PCBs) is one of the possible causes in addition to climate changes, UV-radiation or habitat destruction. In the present study, we tested the hypothesis that PCBs could induce oxidative stress in young tadpoles. Developing Xenopus laevis were exposed from 2- to 5-d postfertilization (pf) to 0.1 or 1 mg/l of Aroclor 1254. Lipid peroxidation and antioxidant systems (SOD, CAT, GST, GPx, GR activities and t-GSH level) were investigated in whole organisms. Exposure to both concentrations did not impact on the survival and development whereas the average body weight decreased. Exposure to 1 mg/l of Aroclor 1254 induced a significant (p<0.05) increase of GST activity when compared to controls 0 and DMSO. The other antioxidant enzymes and LPO evaluation remained unchanged. Our results demonstrate that exposure of X. laevis tadpoles to environmental concentrations of Aroclor 1254 interfere with normal growth. They also highlight that very young X. laevis tadpoles express antioxidant systems. [less ▲]

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See detailProtein expression profiling in the African clawed frog Xenopus laevis tadpoles exposed to the polychlorinated biphenyl mixture aroclor 1254.
Gillardin, Virginie; Silvestre, Frederic; Dieu, Marc et al

in Molecular & Cellular Proteomics (2009), 8(4), 596-611

Exposure to environmental pollutants such as polychlorinated biphenyls (PCBs) is now taken into account to partly explain the worldwide decline of amphibians. PCBs induce deleterious effects on developing ... [more ▼]

Exposure to environmental pollutants such as polychlorinated biphenyls (PCBs) is now taken into account to partly explain the worldwide decline of amphibians. PCBs induce deleterious effects on developing amphibians including deformities and delays in metamorphosis. However, the molecular mechanisms by which they express their toxicity during the development of tadpoles are still largely unknown. A proteomics analysis was performed on developing Xenopus laevis tadpoles exposed from 2 to 5 days postfertilization to either 0.1 or 1 ppm Aroclor 1254, a PCB mixture. Two-dimensional DIGE with a minimal labeling method coupled to nanoflow liquid chromatography-tandem mass spectrometry was used to detect and identify proteins differentially expressed under PCBs conditions. Results showed that 59 spots from the 0.1 ppm Aroclor 1254 condition and 57 spots from the 1 ppm Aroclor 1254 condition displayed a significant increase or decrease of abundance compared with the control. In total, 28 proteins were identified. The results suggest that PCBs induce mechanisms against oxidative stress (peroxiredoxins 1 and 2), adaptative changes in the energetic metabolism (enolase 1, glycerol-3-phosphate dehydrogenase, and creatine kinase muscle and brain types), and the implication of the unfolded protein response system (glucose-regulated protein, 58 kDa). They also affect, at least at the highest concentration tested, the synthesis of proteins involved in normal cytogenesis (alpha-tropomyosin, myosin heavy chain, and alpha-actin). For the first time, proteins such as aldehyde dehydrogenase 7A1, CArG binding factor-A, prolyl 4-hydroxylase beta, and nuclear matrix protein 200 were also shown to be up-regulated by PCBs in developing amphibians. These data argue that protein expression reorganization should be taken into account while estimating the toxicological hazard of wild amphibian populations exposed to PCBs. [less ▲]

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See detailDevelopment of a strategy to study toxicodynamic of pollutants in spawning sea turtles
Dyc, Christelle ULg; Bouquegneau, Jean-Marie ULg; Gillet, Marie-Claire ULg et al

in Proceedings of the 29th Annual Symposium on Sea Turtle Biology and Conservation (2009)

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See detailAcetylcholinesterase activity as a biomarker of exposure to antibiotics and pesticides in the black tiger shrimp (Penaeus monodon).
Tu, Huynh Thi; Silvestre, Frederic; Scippo, Marie-Louise ULg et al

in Ecotoxicology & Environmental Safety (2009), 72(5), 1463-70

This study aimed to assess the potentiality to use cholinesterase activity (ChE) in black tiger shrimp (Penaeus monodon) as a biomarker of exposure to 2 antibiotics (enrofloxacin, furazolidone) and 2 ... [more ▼]

This study aimed to assess the potentiality to use cholinesterase activity (ChE) in black tiger shrimp (Penaeus monodon) as a biomarker of exposure to 2 antibiotics (enrofloxacin, furazolidone) and 2 pesticides (endosulfan, deltamethrin), commonly used in Vietnamese farms. ChE from muscle and gills was first characterised using three different substrates and specific inhibitors. Results showed that both tissues possess only one ChE which displays the typical properties of an acetylcholinesterase (AChE). In a second part, shrimp (average weight of 8.8-10 g) were fed with medicated-feed containing 4g enrofloxacin (quinolone) or furazolidone (nitrofuran)/kg for 7 days, or exposed to 3 actual concentrations of endosulfan (0, 0.009, 0.09, 0.9 microg/L) or deltamethrin (0, 0.0007, 0.007, 0.07 microg/L) for 4 days. After treatment, animals were decontaminated during 7 days. We observed that AChE activity in muscle was not significantly affected in shrimp fed with enrofloxacin or furazolidone, while it significantly decreased (up to 28%) in gills of shrimp fed with furazolidone. Following endosulfan and deltamethrin exposure, no significant changes in AChE activity were observed in gills. However, a significant decrease occurred in muscle after 4 days exposure (inhibition of 30% and 49% at 0.9 microg/L endosulfan and 0.07 microg/L deltamethrin, respectively). While muscle AChE activity should be assessed to point out endosulfan or deltamethrin exposure, gill AChE activity impairment could indicate an exposure to furazolidone. The present study underlines the benefits to use AChE as a biomarker of chemotherapeutics as part of an integrated aquaculture management to reach industry sustainability. [less ▲]

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See detailDevelopment of a strategy to study toxicodynamic of pollutants in spawning sea turtles from French West Indies (Guadeloupe and Martinique)
Dyc, Christelle ULg; Debier, Cathy; Thomé, Jean-Pierre ULg et al

Conference (2008, November)

Sea turtles including the green turtle Chelonia mydas and the hawksbill turtle Eretmochelys imbricata are critically endangered species, facing different factors as marine pollution. There is a blatant ... [more ▼]

Sea turtles including the green turtle Chelonia mydas and the hawksbill turtle Eretmochelys imbricata are critically endangered species, facing different factors as marine pollution. There is a blatant lack of data dealing with toxicants such as metals and persistent organic pollutants (POPs) in sea turtles. We developed a strategy to apprehend levels, effects and transfer to offspring of several pollutants in sea turtles. Sampling of blood, subcutaneous tissue and eggs of 15 gravid C. mydas and E. imbricata was carried out between July and September 2008 in Martinique (Diamant’s beach) and Guadeloupe (Petite Terre and Marie-Galante). Blood was collected from the dorso-cervical sinus and subcutaneous tissue was sampled in shoulder of the spawning females using a 5 mm biopsy punch (Kai Europe GmbH, Germany). Total blood and serum were successfully taken for metal, POP and biomarker investigations. T-mercury was analyzed by DMA milestones while PCBs, DDT and chlordecone were analyzed by EDC Ni63 high performance gas chromatography HPLC. Samples of serum were analyzed for vitamins (A and E) by HPLC and for thyroid hormones (triiodothyronine and thyroxine) by radioimmunoassay. In parallel to this field study, a cell model using 3T3-L1 cell line was built up to test in vitro effects of PCBs and mercury as well as the relationship between in vitro exposure and fat mobilization. Preliminary results showed a dose-response relationship between increased Aroclor 1234 and 1252 concentrations (0.5 ppb, 1 ppb and 1.5 ppb) and adipocyte mortality (Nucleocounter). The strategy we propose here will bring further insights on levels and potential impact of pollutants on female sea turtles and their offspring. [less ▲]

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See detailPersistent organic pollutants in wild seabass (Dicentrarchus labrax) from the Northeast atlantic coastal regions and relationship with thyroid hormone levels
Schnitzler, Joseph ULg; Thomé, Jean-Pierre ULg; Das, Krishna ULg

Poster (2008, October 30)

Polychlorinated biphenyls (PCBs) and organochlorine pesticides like Dichloro-Diphenyl-Trichloroethane (DDTs), Hexachlorocyclohexanes (HCHs), Aldrin and Dieldrin were analysed in the muscle of sea bass ... [more ▼]

Polychlorinated biphenyls (PCBs) and organochlorine pesticides like Dichloro-Diphenyl-Trichloroethane (DDTs), Hexachlorocyclohexanes (HCHs), Aldrin and Dieldrin were analysed in the muscle of sea bass (Dicentrarchus labrax) sampled in coastal regions near several important European river mouths (Garonne, Charente, Loire, Seine and Scheldt). These organochlorinated compounds are known to influence the endocrine system of many fish species and mammals and are thus qualified as endocrine disrupters. To highlight a potentially harmful effect of these compounds on the thyroid function of these fishes, we measured the muscular concentrations of thyroid hormones T3 and T4 by Radio-Immuno-Assay. The contamination levels were as follows: the highest concentrations were measured in individuals collected from the coastal region near the Scheldt > Seine > Loire > Charente and the lowest levels were observed in sea bass from coastal regions near the Garonne (from 2422 to 6188 ng.g-1 lw). The measured levels were generally higher than those reported in literature in sea bass from other regions in the Mediterranean Sea. Contamination patterns were different depending on the sampling area and thus the river input of pollutants. The multivariate statistical analysis revealed a significant relationship between the measured persistent organic pollutants and thyroid hormones in muscle. We cannot exclude the assumption that an endocrine disruption of the thyroid related to these pollutants could be the origin of these modifications of the thyroid hormone concentrations. [less ▲]

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See detailEffects of persistent organic pollutants on the thyroid function of the European sea bass (Dicentrarchus labrax) from the Aegean Sea, is it an endocrine disruption?
Schnitzler, Joseph ULg; Koutrarkis, Emmanuil; Siebert, Ursula et al

in Marine Pollution Bulletin (2008), 56(10), 1755-1764

We evaluated the alterations of organochlorinated compounds such as polychlorobiphenyls (PCB), dichloro-diphenyl-dichloroethylene (DDE) and dichloro-diphenyl-trichloroethane (DDT) on the thyroid in wild ... [more ▼]

We evaluated the alterations of organochlorinated compounds such as polychlorobiphenyls (PCB), dichloro-diphenyl-dichloroethylene (DDE) and dichloro-diphenyl-trichloroethane (DDT) on the thyroid in wild and cultured sea bass (Dicentrarchus labrax) at environmental concentrations. These compounds influence the endocrine system of many fish species and are qualified as endocrine disruptors. The thyroid seems to be a target organ. Two alteration endpoints: the thyroid histology and the muscular thyroid hormone concentrations, were used simultaneously. High concentrations in PCBs and DDT were detected in muscles, supporting the idea that the Mediterranean fauna could be more polluted than the Atlantic fauna. The high abundance of DDE indicates a progressive degradation of remnant DDT load and the absence of new inputs in this area. Aquaculture sea bass shows a significant higher amount of pollutants on fresh weight basis (especially PCBs) in their muscles compared to the wild sea bass. Those differences may be related mainly to the contaminations of diet. Thyroid parameters vary between wild and aquaculture sea bass, wild sea bass were characterized by higher follicle diameters, epithelial cell heights and muscular T4 concentrations. A significant relationship between persistent organic pollutants (muscular PCBs and DDT concentration) and the different thyroid parameters (diameters of follicles, epithelial cell heights and muscular T4 levels) could be observed, which support the hypothesis that these compounds have an adverse impact on thyroid morphometry and function. [less ▲]

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See detailDevelopment of a strategy to study toxicodynamic of pollutants in spawning sea turtles from the French West Indies
Dyc, Christelle ULg; Bouquegneau, Jean-Marie ULg; Gillet, Marie-Claire ULg et al

Poster (2008, October)

Sea turtles including the green turtle Chelonia mydas and the hawksbill turtle Eretmochelys imbricata are critically endangered species, facing different factors as marine pollution. There is a blatant ... [more ▼]

Sea turtles including the green turtle Chelonia mydas and the hawksbill turtle Eretmochelys imbricata are critically endangered species, facing different factors as marine pollution. There is a blatant lack of data dealing with toxicants such as metals and persistent organic pollutants (POPs) in sea turtles. We developed a strategy to apprehend levels, effects and transfer to offspring of several pollutants in sea turtles. Sampling of blood, subcutaneous tissue and eggs of 15 gravid C. mydas and E. imbricata was carried out between July and September 2008 in Martinique (Diamant’s beach) and Guadeloupe (Petite Terre and Marie-Galante). Blood was collected from the dorso-cervical sinus and subcutaneous tissue was sampled in shoulder of the spawning females using a 5 mm biopsy punch (Kai Europe GmbH, Germany). Total blood and serum were successfully taken for metal, POP and biomarker investigations. T-mercury was analyzed by DMA milestones while PCBs, DDT and chlordecone were analyzed by EDC Ni63 high performance gas chromatography HPLC. Samples of serum were analyzed for vitamins (A and E) by HPLC and for thyroid hormones (triiodothyronine and thyroxine) by radioimmunoassay. In parallel to this field study, a cell model using 3T3-L1 cell line was built up to test in vitro effects of PCBs and mercury as well as the relationship between in vitro exposure and fat mobilization. Preliminary results showed a dose-response relationship between increased Aroclor 1234 and 1252 concentrations (0.5 ppb, 1 ppb and 1.5 ppb) and adipocyte mortality (Nucleocounter). The strategy we propose here will bring further insights on levels and potential impact of pollutants on female sea turtles and their offspring. [less ▲]

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See detailEFFECT OF ANTI-ANDROGENIC SUBSTANCES ON THE SEXUAL REPRODUCTION OF ROTIFERS : IMPACTS ON BRACHIONUS CALYCIFLORUS MALE FERTILITY
Joaquim-Justo, Célia ULg; Maule, P; Luy, N et al

Conference (2007, August 12)

Many substances released in aquatic ecosystems have been reported to disrupt endocrine systems in vertebrates and invertebrates. In the rotifer Brachionus calyciflorus, studies show that chemicals ... [more ▼]

Many substances released in aquatic ecosystems have been reported to disrupt endocrine systems in vertebrates and invertebrates. In the rotifer Brachionus calyciflorus, studies show that chemicals characterized by a high affinity to the vertebrate androgen receptor depress sexual reproduction at concentrations one to two orders of magnitude below those that affect asexual reproduction. We studied the effect of cyproterone acetate, an anti-androgen of steroid like structure, and of the pesticide fenitrothion, a non steroidal molecular which has a high affinity to the vertebrate androgen receptor, on the sexual reproduction of rotifers. In mating experiments we crossed control females with exposed males and vice versa to determine whether anti-androgens affected males, females or both. Fertilization rate and number of resting eggs produced were affected by both substances tested. With fenitrothion, depression of these endpoints was observed exclusively when males were treated. Cyproterone acetate enhanced production of resting eggs whereas fertilization rate was not significantly affected. Increased production of resting eggs was observed both with treated females and males. Parameters of male fertility were compared in control and in exposed males. We report impacts on spermatozoa numbers, morphology and fertilizing potential, and on male morphology, longevity and mating behaviour for the two substances tested. [less ▲]

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See detailEffects of persistent organic pollutants on the thyroid function of the sea bass (Dicentrarchus labrax), an endocrine disruption?
Schnitzler, Joseph ULg; Koutrakis, Emmanuil; Thomé, Jean-Pierre ULg et al

Conference (2007, May 23)

Organochlorinated compounds such as polychlorobiphenyls (PCB), dichloro-diphenyl-dichloroethylene (DDE) and dichloro-diphenyl-trichloroethane (DDT) have the characteristic to influence the endocrine ... [more ▼]

Organochlorinated compounds such as polychlorobiphenyls (PCB), dichloro-diphenyl-dichloroethylene (DDE) and dichloro-diphenyl-trichloroethane (DDT) have the characteristic to influence the endocrine system of many fish species and mammals and are thus qualified as endocrine disruptors. The objective of this project aims a better understanding of the effects of these compounds on the thyroid function of European seabass (Dicentrarchus labrax). Thyroid tissue and muscle of 46 seabass from the Aegean Sea in Greece (fished and aquaculture, n=15 and n=31, respectively) were sampled. The levels in PCBs, DDT and DDE were evaluated in the muscles of 30 individuals. The diameter of follicles and the epithelial cell heights were measured in each individual by optical microscopy. The concentration of the thyroid hormone T4 (thyroxin) was measured by Radio-Immuno-Assay (RIA). Finally, the potential relationships between these thyroid parameters and these organic compounds were investigated using factor analysis and multiple regressions. A significant relationship between persistent organic pollutants (muscular PCBs and DDT concentration) and the different thyroid parameters (diameters of follicles, epithelial cell heights and muscular T4 levels) could be observed. We cannot exclude the assumption that an endocrine disruption of thyroid gland related to these pollutants could be the origin of the modifications of these thyroid parameters. [less ▲]

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See detailOrganochlorines and lactation : mobilization and transfer to offspring in northern elephant seals
Debier, Cathy; Crocker, D.; Xhonneux, V. et al

in Organohalogen Compounds (2007), 69

The transfer of PCBs and DDTs from mother to pup was studied in 20 Northern elephant seal Mirounga angustirostris mother-pup pairs. Organochlorine concentrations in milk increased from 127.3 ± 25.0 ng/g ... [more ▼]

The transfer of PCBs and DDTs from mother to pup was studied in 20 Northern elephant seal Mirounga angustirostris mother-pup pairs. Organochlorine concentrations in milk increased from 127.3 ± 25.0 ng/g to 200.9 ± 39.6 ng/g for PCBs and from 278.2 ± 92.4 ng/g to 494.9 ± 163.4 ng/g for DDTs between day 4 and day 21 of lactation. A similar longitudinal rise was observed in the serum of mothers (5.4 ± 0.8 to 7.7 ± 1.4 ng/ml for PCBs and 7.8 ± 2.4 to 11.9 ± 4.1 ng/ml for DDTs) and, to a lesser extend, in the serum of their pups (5.8 ± 1.4 to 6.1 ± 2.5 ng/ml for PCBs and 8.3 ± 2.5 to 9.9 ± 4.3 ng/ml for DDTs) between early and late lactation. The rise of contaminants in serum and milk might originate from the changes observed in maternal inner blubber in which PCB and DDT levels increased significantly throughout lactation (604.2 ± 142.8 to 1292.5 ± 421.6 ng/g lipids for PCBs and 1223.9 ± 460.0 to 2395.9 ± 737.3 ng/g lipids for DDTs). By contrast, contaminant levels remained constant in outer blubber (933.2 ± 271.8 to 999.7 ± 223.5 ng/g lipids for PCBs and 2010.7 ± 698.3 to 2061.9 ± 603.5 ng/g lipids for DDTs). [less ▲]

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See detailEnfer et Paradis : la toxicité de l'oxygène chez les organismes abyssaux
Rees, J. F.; Zal, F.; Thomé, Jean-Pierre ULg

in Océanis (2007), 30.3

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See detailWater quality assessment of a recently refilled reservoir: The case of Bütgenbach Reservoir, Belgium
Lourantou, Anna; Thomé, Jean-Pierre ULg; Goffart, Anne ULg

in Lakes & Reservoirs : Research & Management (2007), 12

Bütgenbach Reservoir is situated in the High Ardennes plateau in eastern Belgium (50°25′N; 6°13′E). It is used principally for flood control and for production of hydroelectric energy. It has been ... [more ▼]

Bütgenbach Reservoir is situated in the High Ardennes plateau in eastern Belgium (50°25′N; 6°13′E). It is used principally for flood control and for production of hydroelectric energy. It has been subjected to a previous series of studies because of its eutrophication problems and their impacts on the local economy. Bütgenbach Reservoir was emptied during spring 2004 for dam restoration, being refilled in mid-September of the same year. Selected physicochemical and biological parameters (temperature, dissolved oxygen, pH, inorganic and organic nutrients, chlorophyll-a) were measured fortnightly during the lake’s productive season (mid-April to mid-October 2005) at three sampling sites throughout the water column. The water quality conditions after refilling of the lake were compared to previous studies accomplished at the same sampling sites (prior to emptying the lake). The actual trophic status was mesotrophic to eutrophic, based on the combination of total phosphorous and chlorophyll-a concentrations, as well as water transparency. Butgenbach Reservoir generally exhibits good water quality, based on the French water quality system SEQ-eau. A longitudinal decrease in water quality was observed from upstream to downstream, because mainly of the differences in lake bottom morphology and water residence time, and their impacts on nutrient distribution in the lake. [less ▲]

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See detailMobilization of PCBs from blubber to blood in northern elephant seals (Mirounga angustirostris) during the post-weaning fast
Debier, C.; Chalon, Carole ULg; Le Boeuf, B. J. et al

in Aquatic Toxicology (2006), 80(2), 149-157

Northern elephant seals (Mirounga angustirostris) are characterized by extended fasting during which they rely entirely on their own body reserves. During fasts, lipids are mobilized from blubber to match ... [more ▼]

Northern elephant seals (Mirounga angustirostris) are characterized by extended fasting during which they rely entirely on their own body reserves. During fasts, lipids are mobilized from blubber to match the energy requirements of the animal. This transfer frees toxic fat-soluble pollutants into the blood circulation, which may exert adverse health effects, especially in young and developing animals. We investigated the dynamics of mobilization of polychlorinated biphenyls (PCBs) from the blubber of northern elephant seal pups during the post-weaning fast. Longitudinal samples of blubber and serum were collected from free-ranging animals throughout the fast at Ano Nuevo, California. Blubber biopsies were separated into inner and outer layers. The PCB profiles of blubber and serum consisted mainly of penta- (PCB-101, -110, -118), hexa- (PCB-138, -153) and hepta- (PCB-180, -183, -187) chlorobiphenyls, which accounted for almost 90% of the total PCB burden. Total PCB concentrations in inner blubber increased significantly between early and late fasting (563.6 +/- 162.0 mu g/kg lipids at early versus 911.6 +/- 513.1 mu g/kg lipids at late fasting) whereas they remained fairly constant in outer blubber (572.6 +/- 134.8 mu g/kg lipids at early versus 659.2 +/- 158.8 mu g/kg lipids at late fasting). A corresponding rise of PCB concentrations was observed in serum during the second half of the fast (3.8 +/- 1.1 mu g/l serum at early versus 7.2 +/- 0.9 mu g/l at late fasting). The longitudinal changes in circulating total PCBs could not be explained by the changes in serum lipid fractions (cholesterol, phospholipids, triacyl glycerols and free fatty acids). The increases in total PCB concentrations in inner blubber and serum were more pronounced in leaner animals, which suggests that they might be more at risk to potential toxic effects. (c) 2006 Elsevier B.V. All rights reserved. [less ▲]

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See detailExposure to chlordecone and male fertility in Guadeloupe (French West Indies)
Multigner, L.; Kadhel, P.; Huc-Terki, F. et al

in Epidemiology (2006, November), 17(6, Suppl. S), 372

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See detailStudy of endocrine disruption in seabass (Dicentrarchus labrax)
Schnitzler, Joseph ULg; Koutrakis, Emmanuil; Thomé, Jean-Pierre ULg et al

Conference (2006, October 28)

Organochlorinated compounds such as polychlorobiphenyls (PCB), dichloro-diphenyl-dichloroethylene (DDE) and dichloro-diphenyl-trichloroethane (DDT) have the characteristic to influence the endocrine ... [more ▼]

Organochlorinated compounds such as polychlorobiphenyls (PCB), dichloro-diphenyl-dichloroethylene (DDE) and dichloro-diphenyl-trichloroethane (DDT) have the characteristic to influence the endocrine system of many fish species and mammals and are thus qualified as endocrine disruptors. The objective of this project aims a better understanding of the effects of these compounds on the thyroid function of European seabass (Dicentrarchus labrax). Thyroid tissue and muscle of 46 seabass from the Aegean Sea in Greece (fished and aquaculture, n=15 and n=31, respectively) were sampled. The levels in PCBs, DDT and DDE were evaluated in the muscles of 30 individuals. The diameter of follicles and the epithelial cell heights were measured in each individual by optical microscopy. The concentration of the thyroid hormone T4 (thyroxin) was measured by Radio-Immuno-Assay (RIA). Finally, the potential relationships between these thyroid parameters and these organic compounds were investigated using factor analysis and multiple regressions. A significant relationship between persistent organic pollutants (muscular PCBs and DDT concentration) and the different thyroid parameters (diameters of follicles, epithelial cell heights and muscular T4 levels) could be observed. We cannot exclude the assumption that an endocrine disruption of thyroid gland related to these pollutants could be the origin of the modifications of these thyroid parameters. [less ▲]

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See detailTrophic links in the lowland River Meuse (Belgium): assessing the role of bacteria and protozoans in planktonic food webs
Joaquim-Justo, Célia ULg; Pirlot, S.; Viroux, L. et al

in Journal of Plankton Research (2006), 28(9), 857-870

Trophic interactions within the plankton of the lowland River Meuse (Belgium) were measured in spring and summer 2001. Consumption of bacteria by protozoa was measured by monitoring the disappearance of H ... [more ▼]

Trophic interactions within the plankton of the lowland River Meuse (Belgium) were measured in spring and summer 2001. Consumption of bacteria by protozoa was measured by monitoring the disappearance of H-3-thymidine-labelled bacteria. Metazooplankton bacterivory was assessed using 0.5-mu m fluorescent microparticles (FMPs), and predation of metazooplankton on ciliates was measured using natural ciliate assemblages labelled with FMPs as tracer food. Grazing of metazooplanklon on flagellates was determined through in situ incubations with manipulated metazooplankton densities. Protozooplankton bacterivory varied between 6.08 and 53.90 mg C m(-3) day(-1) (i.e. from 0.12 to 0.86 g C-1 bacteria g C-1 protozoa day(-1)). Metazooplankton, essentially rotfiers, grazing on bacteria was negligible compared with grazing by protozoa (similar to 1000 times lower). Predation of rotfiers on heterotrophic flagellates (HFs) was generally low (on average 1.77 mg C m(-3) day(-1), i.e. 0.084 g C-1 flagellates g C-1 rotfiers day(-1)), the higher contribution of HF in the diet of rotfiers being observed when Keratella cochlearis was the dominant metazooplankter. Predation of rotfiers on ciliates was low in spring samples (0.56 mg C m(-3) day(-1), i.e. 0.014 g C-1 ciliates g C-1 rotfiers day(-1)) in contrast to measurements performed in July (8.72 mg C m(-3) day(-1), i.e. 0.242 g C-1 ciliates g C-1 rotfiers day(-1)). The proportion of protozoa in the diet of rotfiers was low compared with that of phytoplankton (< 30% of total carbon ingestion) except when phytoplankton biomass decreased below the incipient limiting level (ILL) of the main metazooplantonic species. In such conditions, protozoa (mainly ciliates) constituted similar to 50% of total rotfier diet These results give evidence that microbial organisms play a significant role within the planktonic food web of a eutrophic lowland river, ciliates providing an alternative food for metazooplankton when phytoplankton becomes scarce. [less ▲]

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