References of "Schnitzler, Joseph"
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See detailEffects of Methylmercury on Harbour Seal Peripheral Blood Leucocytes In Vitro Studied by Electron Microscopy
Dupont, Aurélie; De Pauw-Gillet, Marie-Claire ULg; Schnitzler, Joseph ULg et al

in Archives of Environmental Contamination & Toxicology (in press)

Methylmercury MeHg is highly immunotoxic and can alter the health status of the harbour seal, Phoca vitulina, from the North Sea. To investigate the mechanism of MeHg-induced toxicity in harbour seal ... [more ▼]

Methylmercury MeHg is highly immunotoxic and can alter the health status of the harbour seal, Phoca vitulina, from the North Sea. To investigate the mechanism of MeHg-induced toxicity in harbour seal lymphocytes, ConA-stimulated peripheral blood leucocytes were exposed in vitro to sub-lethal concentrations of MeHgCl (0.2, 1 and 2 µM) for 72h, and then analysed for their viability and ultrastructure. After 72h of incubation, cells were counted with a propidium iodide staining technique, a metabolic MTS assay was performed, and cells exposed to 1 µM MeHgCl were observed by transmission electron microscopy (TEM). Alive cell numbers decreased with increased MeHgCl concentrations. In presence of ConA and 1µM of MeHgCl, TEM images revealed a higher frequency of apoptotic cells. Exposed cells displayed condensation of the chromatin at the nuclear membrane and mitochondrial damages. The results suggest that in vitro MeHgCl induced apoptosis in harbour seal lymphocytes through a mitochondrial pathway. [less ▲]

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See detailDo Triclosan affect hearing development of Cyprinodon variegatus larvae?
Schnitzler, Joseph ULg; Benichou, Farida; Pinte, Nicolas et al

Poster (2015, August)

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS) has been shown to affect the thyroid system of teleost. Larval stages are ... [more ▼]

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS) has been shown to affect the thyroid system of teleost. Larval stages are particularly vulnerable to deleterious effects of endocrine disrupters because of potential impairment of fish development and behaviour. Thyroid hormones are critical to the development of the brain and auditory system. Thus, TCS could affect the development of the brain and hearing. The aims of this study were: to investigate hearing development in sheepshead minnows (Cyprinodon variegatus) using the ABR technique (Auditory Brainstem Response) and to investigate the effects of triclosan on hearing development. Exposure to TCS was conducted from fertilization of eggs on at concentrations likely to be found in the environment: 20, 50 and 100 µgl-1. We characterized previously the ontogenic variation of thyroid hormones in embryos and larvae of sheepshead minnows. We observed an increase of thyroid hormones level around the 12th and the 15th day post hatching (dph), that may be associated with the transition from larval to juvenile stage during the development of this species. We concluded, that this period could be defined as a critical exposure window to pollutants. We determined hearing thresholds for sheepshead minnows of different ages. Our sheepshead minnows show ontogenic variations in the hearing ability during their development. At 30 days post hatching, their hearing ability is quite bad, with a narrow bandwidth of detected frequencies. But their hearing ability considerably enhance during their development to reach the adult hearing ability at around 80 days post hatching when this species reach sexual maturity. So we observe during the developmental phase of this fish species clear ontogenic improvements of the hearing ability and they showed an ontogenetic expansion in the frequency bandwidth they were able to detect. The effects of TCS in this development have yet to be determined but will be fully discussed. This study proposes an interesting new endpoint in thyroid disruption research. [less ▲]

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See detailThe effects of triclosan exposure in shape changes of sheepshead minnow (Cyprinodon variegatus) during early development and metamorphosis
Schnitzler, Joseph ULg; Frederich, Bruno ULg; Dussenne, Mélanie et al

Conference (2015, August)

Thyroid hormones are essential for normal development, and for maintenance of normal physiological functions in vertebrates [1, 2]. In fish, thyroid hormones are involved in the control of osmoregulation ... [more ▼]

Thyroid hormones are essential for normal development, and for maintenance of normal physiological functions in vertebrates [1, 2]. In fish, thyroid hormones are involved in the control of osmoregulation, metabolism, somatic growth and post-hatching metamorphosis [1, 3, 4]. The regulation of thyroid hormone bioavailability in tissues and cells represents a very complex and unique web of feedback systems [2]. In fish and other vertebrates the thyroid cascade involves two components. First, thyroxine (T4) biosynthesis and secretion are largely under central control by the brain–pituitary–thyroid axis [5]. Second, there is the conversion of T4 to its biologically active form 3,5,3-triiodothyronine (T3) and its metabolism and receptor-mediated actions that seems largely to be under peripheral control in extra-thyroidal tissues [6]. The accumulation in the aquatic environment of anthropogenic chemicals, among which are endocrine disrupting chemicals (EDCs) that alter normal hormonal regulation, is having dramatic consequences for humans and wildlife. Numerous chemicals disrupt thyroid homeostasis affecting thyroid hormone (TH) synthesis and transport, and cellular uptake and metabolism [7, 8]. Triclosan (TCS) is a synthetic chlorinated phenolic compound with a generalized use as an antimicrobial and preservative in many personal care and household products [9-11]. As a result of disposal of TCS through sewage systems and insufficient/variable removal by wastewater treatment plants (WWTP) [9], widespread contamination with TCS has been detected in several countries, particularly in aquatic ecosystems, WWTP influents and effluents; sludges and biosolids; surface or ground water; drinking water; and aquatic sediments [9-11]. TCS and its metabolites have been detected in tissues and body fluids of aquatic organisms including fish, revealing they are accumulating in the food chain [9-11] and TCS has also been detected in human blood, breast milk and urine [9-11]. The structural similarity of TCS with THs [9] suggest it may have adverse effects on the thyroid system. However, little is known about the mechanisms by which TCS disrupts the thyroid axis. TCS effects on fish thyroid axis have not been investigated. It is possible, that the TCS toxic effects reported in fish embryos, larvae and adults [9-11] might be caused, at least in part, through its effect on the thyroid system. We determined how TCS affect ontogenic variations of thyroid hormones in developing sheepshead minnow larvae. Knowing that thyroid hormones are involved in somatic growth and post-hatching metamorphosis, we also tested the hypothesis that TCS alter the development of these larvae. To do this, we used landmark-based geometric morphometric methods. These methods allowed us to analyse the pure shape variations of our developing larvae, regardless orientation, position, and size. [less ▲]

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See detailTHE EFFECTS OF TRICLOSAN ON HEARING DEVELOPMENT OF CYPRINODON VARIEGATUS LARVAE
Schnitzler, Joseph ULg; Benichou, Farida; Pinte et al

Conference (2015, May)

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS) has been shown to affect the thyroid system of teleost. Larval stages are ... [more ▼]

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS) has been shown to affect the thyroid system of teleost. Larval stages are particularly vulnerable to deleterious effects of endocrine disrupters because of potential impairment of fish development and behaviour. Thyroid hormones are critical to the development of the brain and auditory system. Thus, TCS could affect the development of the brain and hearing. The aims of this study were: to investigate hearing development in sheepshead minnows (Cyprinodon variegatus) using the ABR technique (Auditory Brainstem Response) and to investigate the effects of triclosan on hearing development. Exposure to TCS was conducted from fertilization of eggs on at concentrations likely to be found in the environment: 20, 50 and 100 μgl-1. We characterized previously the ontogenic variation of thyroid hormones in embryos and larvae of sheepshead minnows. We observed an increase of thyroid hormones level around the 12th and the 15th day post hatching (dph), that may be associated with the transition from larval to juvenile stage during the development of this species. We concluded, that this period could be defined as a critical exposure window to pollutants. We determined hearing thresholds for sheepshead minnows of different ages. Due to the small size of larvae, first measurements were only possible at 30 dph. Audiograms showed that the hearing ability is not yet completely established at 30 dph compared to adults. So we pursued our experiments in older larvae of 40, 60, 70, and 80 dph when sexual maturity is attained. First results indicate that the hearing ability considerably improves between 50 and 60 dph. The effects of TCS in this development have yet to be determined but will be fully discussed. This study proposes an interesting new endpoint in thyroid disruption research. [less ▲]

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See detailEco-toxicological analysis of free-ranging cetaceans from the North-western Mediterranean Sea
Pinzone, Marianna ULg; Ody, Denis; Lepoint, Gilles ULg et al

Conference (2015, March 25)

The numerous anthropogenic activities occurring nowadays in the North-western Mediterranean Sea strongly affect top predators such as marine mammals, especially through the bioaccumulation of lipophilic ... [more ▼]

The numerous anthropogenic activities occurring nowadays in the North-western Mediterranean Sea strongly affect top predators such as marine mammals, especially through the bioaccumulation of lipophilic contaminants. In order to assess the eco-toxicological status of local living cetaceans blubber biopsies were collected between 2006 and 2013. Selected persistent organic pollutants POPs (31PCBs, 15 organochlorine compounds, 9 PBDEs and 17 PCDD/Fs) were analyzed in 49 long-finned pilot whales Globicephala melas, 61 sperm whales Physeter macrocephalus and 70 fin whales Balaenoptera physalus. δ13C, δ15N values and POPs levels were assessed through IR-MS and GC-MS respectively. To assess the toxic potency of the dioxin-like compounds, the TEQ approach was applied. δ15N values were 12.2±1.3‰ for sperm whales, 10.5±0.7‰ for pilot whales and 7.7±0.8‰ in fin whales, positioning sperm whales at higher trophic levels. δ13C instead was similar and amounted to −17.3±0.4‰, −17.8±0.3‰ and −18.7±0.4‰ respectively. Pilot whales presented higher concentrations than sperm whales for ΣPCBs (38666±25731ng.g-1 lw and 22849±15566ng.g-1 lw respectively), ΣPBDEs (712±412ng.g-1 lw and 347±173ng.g-1 lw respectively) and ΣDDTs (46081±37506ng.g-1 lw and 37647±38518ng.g-1 lw respectively). Fin whales presented the lowest values, in accordance with its trophic position (ΣPCBs: 5721±5180ng.g-1 lw, ΣPBDEs: 177±208ng.g-1 lw and ΣDDTs: 6643±5549ng.g-1 lw). The PCA analysis confirmed how p,p’DDT and p,p’DDE were influential in differentiating the species, as a consequence of their migratory behavior and distribution. Pollutant concentrations were significantly higher than both their Southern Hemisphere and North Atlantic counterparts, possibly due to the particular Mediterranean geomorphology, which influences pollutants distribution and recycle. Dioxin-like  PCBs accounted for over 80% of the total TEQ. This study demonstrated (1) an important exposure to pollutants of Mediterranean toothed-whales, often surpassing the estimated threshold toxicity value of 17000ng.g−1 lw for blubber in marine mammals; and (2) how their geographical distribution can influence the pollutants profile and concentrations. [less ▲]

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See detailInfluences of blubber composition and profile in the assessment of POPs levels in free-ranging cetaceans
Pinzone, Marianna ULg; Budzinski, Hélène; Tasciotti, Aurelie et al

Poster (2015, February 28)

Investigating the food and feeding ecology of free-ranging cetaceans has always been very challenging. Still now, mass stranding events represent almost the only opportunity to collect valid information ... [more ▼]

Investigating the food and feeding ecology of free-ranging cetaceans has always been very challenging. Still now, mass stranding events represent almost the only opportunity to collect valid information on these large and elusive animals. Biopsy darting is a non-lethal tissue sampling technique which permits the collection of tissues from living and healthy individuals. However, important discussions exist about how efficient this method is in chemical analyses where the percentage lipid content of the tissue is of great importance. Biopsies of skin and blubber were conducted on 49 long-finned pilot whales (Globicephala melas), 61 sperm whales (Physeter macrocephalus) and 70 fin whales (Balaenoptera physalus) in the North Western Mediterranean Sea (NWMS) from 2006 to 2013. Lipid content, δ13C, δ15N values and ΣPCBs were analysed and compared with previous studies conducted on stranded and biopsied individuals. Lipids extraction was operated via ASE; δ13C, δ15N values and POPs levels were assessed through IR-MS and GC-MS respectively. δ15N values were 12.2±1.3‰ for sperm whales, 10.5±0.7‰ for pilot whales and 7.7±0.8‰ in fin whales, positioning sperm whales at higher trophic levels. δ13C instead was similar and amounted to −17.3±0.4‰, −17.8±0.3‰ and −18.7±0.4‰ respectively. Pilot whales presented the highest concentrations of ΣPCBs (38666 ± 25731ng.g-1 lw) followed by sperm whales (22849 ± 15566ng.g-1 lw) and fin whales (5721±5180ng.g-1 lw). Lipids percentage differed significantly between species. Sperm whales showed the lowest lipid content with an average of 12±9%, whereas for long-finned pilot whales it was 22±21% and for fin whales 31±14%. Lipid content of the two odontocetes varied between years of sampling, whilst for fin whales remained similar. The PCBs concentrations, especially in sperm whales, were in discordance with previous studies conducted in the same area and our δ13C, δ15N values. We hypothesized that (1) the extreme low lipid content found in the blubber, (2) the extraction procedure and (3) the biopsies technique, could explain such different pattern. Several papers demonstrated how POPs concentrations in cetaceans blubber are strongly influenced by its thickness, stratification and lipid profile. Therefore, the particular characteristics of blubber composition of deep—diving income breeders such as sperm whales, may not allow an efficient representation of POPs concentrations through the use of biopsies. [less ▲]

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See detailPOPs in free-ranging pilot whales, sperm whales and fin whales from the Mediterranean Sea: Influence of biological and ecological factors
Pinzone, Marianna ULg; Budzinski, Hélène; Tasciotti, Aurélie et al

in Environmental Research (2015), 142

The pilot whale Globicephala melas, the sperm whale Physeter macrocephalus and the fin whale Balaenoptera physalus are large cetaceans permanently inhabiting the Mediterranean Sea. These species are ... [more ▼]

The pilot whale Globicephala melas, the sperm whale Physeter macrocephalus and the fin whale Balaenoptera physalus are large cetaceans permanently inhabiting the Mediterranean Sea. These species are subjected to numerous anthropogenic threats, such as exposure to high levels of contaminants. Therefore, selected persistent organic pollutants, POPs (29 PCBs, 15 organochlorine compounds, nine PBDEs and 17 PCDD/Fs), were analysed in the blubber biopsies of 49 long-finned pilot whales, 61 sperm whales and 70 fin whales collected in the north-western Mediterranean Sea (NWMS) from 2006 to 2013. The contamination profile and species feeding ecology were combined through the use of stable isotopes. δ13C, δ15N values and POPs levels were assessed through IR-MS and GC-MS, respectively. To assess the toxic potency of the dioxin-like compounds, the TEQ approach was applied. δ15N values were 12.2 ± 1.3‰ for sperm whales, 10.5 ± 0.7‰ for pilot whales and 7.7±0.8‰ in fin whales, which positions sperm whales at higher trophic levels. δ13C of the two odontocetes were similar and amounted to −17.3±0.4‰ for sperm whales and −17.8±0.3‰ for pilot whales, whereas the result for fin whales reflected more depleted (−18.7±0.4‰). This outcome indicates a partial overlap in the feeding habits of toothed whales and confirms the differences in feeding behaviour of the mysticete. Pilot whales had higher concentrations than sperm whales for ΣPCBs (38666 ± 25731 ng.g-1 lw and 22849 ± 15566 ng.g-1 lw, respectively), ΣPBDEs (712±412 ng.g-1 lw and 347±173 ng.g-1 lw, respectively) and ΣDDTs (46081±37506 ng.g-1 lw and 37647±38518 ng.g-1 lw, respectively). Fin whales had the lowest values, which reflected its trophic position (ΣPCBs: 5721±5180 ng.g-1 lw, ΣPBDEs: 177±208 ng.g-1 lw and ΣDDTs: 6643±5549 ng.g-1 lw). Each species was characterized by large inter-individual variations that are more related to sex than trophic level. Males presented a higher contaminant burden than females. The discriminant analysis (DA) confirmed how DDTs and highly chlorinated PCBs could differentiate the three species. The pollutant concentrations of our species were significantly higher than both their southern hemisphere and North Atlantic counterparts. This result is possibly due to Mediterranean geomorphology, which influences the distribution and recycling of pollutants. Dioxin-like PCBs accounted for over 80% of the total TEQ. This study demonstrated (1) the pollutants of Mediterranean cetaceans often surpassed the estimated threshold toxicity value of 17000 ng.g−1 lw for blubber in marine mammals and (2) how the final pollutant burden in these animals is strongly influenced not only by trophic position but also by numerous other factors, including sex, age, body size and geographical distribution. [less ▲]

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See detailImpact of triclosan on behaviour and neural development of Cyprinodon variegatus
Benichou, Farida; Rahmouni, Chahrazed; Denoël, Mathieu ULg et al

Poster (2014, December)

The study focussed on the effects of triclosan (TCS) exposure on mobility and hearing capacities of Cyprinodon variegatus larvae. TCS is an omnipresent antimicrobial and contaminant of aquatic ecosystems ... [more ▼]

The study focussed on the effects of triclosan (TCS) exposure on mobility and hearing capacities of Cyprinodon variegatus larvae. TCS is an omnipresent antimicrobial and contaminant of aquatic ecosystems, which can act as endocrine disruptor, mainly by modifying thyroid functioning. Larval stages are particularly vulnerable to deleterious effects of endocrine disrupters because of potential impairment of fish development and behaviour. Exposure to TCS was conducted at fertilization of eggs at concentrations likely to be found in the environment: 20, 50 and 100 μg.l-1. The analysis of growth parameters of C. variegatus showed no effect of TCS on the fertility of eggs, survival and larval weight. Subsequently, THs concentrations were measured on 15 days post hatching larvae. THs are initially produced as T4 (thyroxine) cells and then converted in the bioactive form of T3 (triiodothyronine) cells. The observed increase of T4 and T3 cells in larvae exposed to 50 and 100 μg.l-1 suggests an increase in THs synthesis as a consequence of TCS exposure. Auditory thresholds of larvae were determined using ABR (Auditory Brainstem Response) technique, and finally larval mobility was measured. For both parameters no significant differences were observed among the three different treatments. Audiograms showed that the auditory system is not yet completely established at 30 days post hatching. However, these results allowed us to consider C. variegatus as an “hearing generalist” because this species have a hearing sensitivity lower than 2000 Hz. Regarding locomotion, our result summarized short time experiences targeting only swimming speed, distance and degree of mobility. It would be interesting to expand the behavioural aspects on other parameters of locomotion and integrate Cyprinodon reaction to different stress (light or touch). In conclusion, our results require an extensive long-term study on the full life cycle of C. variegatus, in order to evaluate the impact of triclosan on neural function and behaviour through several generations. [less ▲]

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See detailEvaluation of the impact of Triclosan on the functioning of the thyroid system in Cyprinodon variegatus L., 1803.
Rahmouni, Chahrazed; Benichou, Farida; Klaren, PHM et al

Poster (2014, December)

Triclosan (5-chloro-2-[2, 4-dichlorophenoxy] phenol) is an antimicrobial widely used in various industrial products such as textiles, cosmetics and body care products. It is often detected in aquatic ... [more ▼]

Triclosan (5-chloro-2-[2, 4-dichlorophenoxy] phenol) is an antimicrobial widely used in various industrial products such as textiles, cosmetics and body care products. It is often detected in aquatic environments. The presence of the main biotransformation product, methyl TCS, indicates that this compound is not only degraded, but also persistent and accumulates in aquatic organisms. In this study, the effects of TCS on the thyroid system during embryonic and larval stages in Cyprinodon variegatus were evaluated. In particular, whole body thyroid hormone levels and the activity of deiodinases, enzymes involved in the activation of the thyroid prohormone T4, were measured. Couples of three females and two males were placed in breeding chambers designed for this experiment from which 3832 eggs were obtained by reproduction in the laboratory. Eggs were collected and maintained in seawater. Embryos were selected under a dissection microscope, randomly assigned to each of five treatment groups: Control, DMSO control (vehicle), 20 μg/L TCS, 50 μg/L TCS and 100 μg/L TCS and placed in incubation dishes (50 per dish) at 25°C. On day 6, embryos hatched and larvae were transferred to 1L dishes. The larvae were fed on artemia and on flaked fish food till day 15 post hatching when the fish were analyzed. The fertilization and survival rate, as well as the larval dry weight did not vary significantly between individuals exposed to 20, 50 and 100 μg/L TCS. T3 and T4 concentrations increased significantly in larvae exposed to 50 and 100 μg/L TCS. The study of the activity of enzymes involved in the deiodination of thyroid hormones (ORD) represents a new aspect in the study of endocrine disruption in C. variegatus. Unfortunately, we were not able to detect a net enzymatic T4 deiodination activity, most likely due to the very small amounts of protein and low specific enzyme activity in brain homogenates, carcass and liver. [less ▲]

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See detailThe thyroid gland and thyroid hormones in sheepshead minnow (Cyprinodon variegatus) during early development and metamorphosis
Schnitzler, Joseph ULg; Benichou, Farida; Klaren, PHM et al

Poster (2014, December)

The sheepshead minnow is widely used in ecotoxicological studies that recently, begin to focus on potential disruption of the thyroid axis by xenobiotics and endocrine disrupting compounds. However ... [more ▼]

The sheepshead minnow is widely used in ecotoxicological studies that recently, begin to focus on potential disruption of the thyroid axis by xenobiotics and endocrine disrupting compounds. However, reference levels of thyroxin (T4) and 3,5,3’-triiodothyronine (T3) and their developmental patterns are unknown. This study set out to describe the ontogeny and morphology of the thyroid gland in sheepshead minnow, and correlate these with whole body concentrations of thyroid hormones during early development and metamorphosis. Couples of three females and two males were placed in breeding chambers designed for this experiment. More than 1000 eggs were collected and maintained in seawater. Embryos were selected under a dissection microscope and placed in incubation dishes (50 per dish) at 25°C. On day 6, embryos hatched and larvae were transferred to 1L beakers. For one week after hatching, larvae were fed on artemia, and from 8 to 30 days post-hatch they were fed on flaked fish food. Embryos were sampled on day 0, 3, 6 post-fertilization and larvae and juveniles were sampled every three days from day 0 to 28 days post-hatch. The pooled samples were taken from several incubation dishes and divided in three replicate batches of 10-30 individuals. T4 and T3 were extracted from whole fish bodies and an enzyme-linked immunoassay was used to measure whole-body hormone levels. At each sampling point 5 individuals were placed in formalin fixative for histology. Length and body mass were measured. Hatching success, gross morphology, thyroid hormone levels and histology data were recorded. The onset of metamorphosis at 12 days post-hatching coincided with surges in whole body T4 and T3 concentrations. Thyroid follicles were first observed in pre-metamorphic larvae at hatching, and were detected exclusively in the subpharyngeal region, surrounding the ventral aorta. Follicle size and epithelial cell heights varied during the developmental phase, indicating fluctuations in thyroid hormone synthesis activity. The increase in the whole body T3/T4 ratio was indicative of an increase in outer ring deiodination. This study establishes a baseline for thyroid hormones in sheepshead minnows, which will be vital for the understanding of thyroid hormone functions and in future studies of thyroid toxicants in this species. [less ▲]

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See detailThe effects of Triclosan on the metabolism of developing Sheepshead minnow (Cyprinodon variegatus) larvae
Lallemand, Lise; Voisin, Anne-Sophie; Darchambeau, François ULg et al

Poster (2014, December)

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS) has been shown to affect the thyroid system of teleost. Thyroid hormones are ... [more ▼]

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS) has been shown to affect the thyroid system of teleost. Thyroid hormones are involved in the control of metabolism, so changes in hormone levels induced by triclosan may affect respiratory rates and antioxidant stress in exposed fish. Couples of three females and two males were placed in breeding chambers designed for this experiment. Eggs were collected and maintained in seawater. Embryos were selected under a dissection microscope, randomly assigned to each of five treatment groups: Control, DMSO control, 20 μg/L TCS, 50 μg/L TCS and 100 μg/L TCS and placed in incubation dishes (50 per dish) at 25°C. On day 6, embryos hatched and larvae were transferred to 1L dishes. The larvae were fed on artemias and on flaked fish food till day 15 and 30 post hatching when the fish were analyzed. Respiratory rate measurements were carried out by respirometry and assays of antioxidant enzymes, Glutathionreductase (GR), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) were conducted to determine the presence of oxidative stress. Respirometry showed that TCS exposed fish exhibited decreased the metabolism at 15 dph, whereas no differences in respiration rate could be observed between control and exposed larvae at 30 dph. At 15 dph no difference was observed for any of the antioxidant enzymes, whereas at 30 dph a sharp increase in the activity of GR was observed between the control and TCS exposed fish. The activity of GST and Gpx remained stable. Thyroid hormones are major factors controlling the metabolic rate related to respiration and oxidative stress. TCS reduced the metabolism at 15 dph that corresponds to the moment where larvae to juvenile transition of Sheepshead minnows occur. Previous experiments showed that TCS induces an increase in thyroid hormone concentrations and hyperthyroidism induces oxidative stress. So our observed increase of antioxidant protection mechanisms could be a way to compensate oxidative stress. On the other hand, the changes in GR activity observed at 30 dph, may also be related to the reduced metabolism at 15 dph. [less ▲]

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See detailDiscrimination of two geographically distinct populations of sea bass Dicentrarchus labrax, using stable isotopic signatures of mercury (δ202Hg, Δ199Hg)
Cransveld, Alice ULg; Amouroux, David; Koutrakis, Emmanuil et al

Poster (2014, May 15)

Despite the reduction of mercury (Hg) emissions in Europe in the last decades, Hg emissions are increasing worldwide and concentrations found in some marine predators remain high. This raises questions on ... [more ▼]

Despite the reduction of mercury (Hg) emissions in Europe in the last decades, Hg emissions are increasing worldwide and concentrations found in some marine predators remain high. This raises questions on mercury's biogeochemical cycle at both local and global scale. In the present work, we investigate the possibility to use mercury isotopic signature in fish as a tool to discriminate different polluted areas and potential pollution sources. Indeed, Hg can exhibit both mass-dependent (MDF) and mass-independent fractionation (MIF). While MDF may occur during biological cycling inter alia and could be used to understand bioaccumulation processes, MIF provides a unique fingerprint of specific chemical pathways, such as photochemical transformations. In this context, information provided by Hg isotopes would help to improve environmental management strategies. A preliminary set of four and ten juvenile common sea bass, Dicentrarchus labrax were collected from the North Sea and the Aegean Sea respectively. T-Hg was analysed by direct mercury analyser (DMA), speciation by gas chromatography inductively coupled plasma mass spectrometer (GC-ICP-MS) and Hg isotope analysis were performed using cold vapour generation with multicollector ICP-MS. Total Hg concentrations in all tissues were higher in individuals from the North Sea ( Hgtot muscle=1,14 ± 0,48 mg.kg-1 dw) than from Greece (0,60 ± 0,06 mg.kg-1 dw). Speciation analysis shows that MeHg is the predominant form of Hg in muscle (89% MeHg on average) but not in liver (51% MeHg on average). Isotopic mass dependent values (δ202Hg) values were always higher in muscle than in liver and related to Hg species distribution. For mass independent isotopic signature, sea bass from the Aegean Sea had a systematically higher Δ199Hg value than individuals from the North sea (e.g.: 0,56 ± 0,05‰ and 0,32 ± 0,06‰ respectively in muscle). While mass dependent isotopic signature probably reflects some internal Hg metabolism, mass independent isotopic signature seems definitely site dependent. Such isotopic discrimination might be in agreement with difference in both mercury sources and cycling in the North and Aegean Seas. These preliminary results indicate that Hg isotopes may thus help to discriminate fish from different areas. This promising outcome must be further confirmed by extending the number of individuals and locations to be investigated. [less ▲]

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See detailUsing features of mercury and methylmercury to discriminate contamination profiles between sea bass, Dicentrarchus labrax, populations
Cransveld, Alice ULg; Amouroux, David; Koutrakis, Emmanuil et al

Poster (2014, March 07)

Despite many efforts consented in the last decades, Mercury (Hg) emissions have kept rising worldwide. Currently, anthropogenic inputs dominate Hg emissions to the atmosphere by far, natural releases ... [more ▼]

Despite many efforts consented in the last decades, Mercury (Hg) emissions have kept rising worldwide. Currently, anthropogenic inputs dominate Hg emissions to the atmosphere by far, natural releases accounting only for a 4th of the total. Because Hg has a stable gaseous form (Hg0) with a long residence time in the atmosphere (~1year), both natural and industrially produced Hg can be transported far from point sources. Therefore, many uncertainties remain in our knowledge about Hg biogeochemistry. Our study aims at identifying the different Hg forms found in marine predators in order to discriminate different polluted areas and potential pollution sources. More specifically, we seek to discriminate contaminations of local origins versus contamination of global origins. To achieve this, we are currently studying different sea bass, Dicentrarchus labrax, populations from the Atlantic Ocean and Mediterranean. In muscle, liver, kidney and brain tissues, we analyze total Mercury (THg) and methylmercury (MeHg). We are also testing the discrimination power of Hg's stable isotopes (199Hg, 201Hg and 202Hg). Indeed, recent findings show that Hg isotopes can exhibit both mass-dependent (MDF) and mass-independent fractionation (MIF). This means that Hg isotopes provide two different types of information at once, both on biological cycling of Hg, including bioaccumulation (MDF), and on chemical pathways such as photochemical transformations (MIF). Eventually, we are planning to extend our results with compound specific isotope analysis (CSIA) on the carbon of methylmercury. Preliminary analysis performed on 14 juvenile specimens from the North Sea and the Aegean Sea indicate that THg concentrations are higher in individuals from the North Sea than from Greece. The lack of correlation with size and weight indicate that it is likely linked to a difference in contamination levels between the two areas. MeHg is the predominant form of Hg in muscle, while the same cannot be asserted for liver. Mass dependent isotopic values (δ202Hg), were always higher in muscle than in liver and, for each tissue, values were similar between the two areas. This is probably related to the species distribution and to some internal Hg metabolism. For mass independent isotopic signature (MIF), sea bass from the Aegean Sea had a systematically higher Δ201Hg value than individuals from the North Sea. Thus, mass independent values seem definitely site dependent and might be in agreement with differences in both mercury sources and cycling in the North and Aegean Seas. These preliminary results consequently indicate that Hg isotopes may help to discriminate fish from different areas. This promising outcome must be further confirmed by extending our sampling and will be coupled to other results obtained through CSIA. [less ▲]

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See detailAbstract Book of ZOOLOGY 2014, 21st Benelux Congress of Zoology
Lepoint, Gilles ULg; Michel, Loïc ULg; Schnitzler, Joseph ULg et al

Book published by Royal Belgian Zoological Society (2014)

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See detailDevelopmental changes of thyroid hormones in sheepshead minnow, Cyprinodon variegatus
Schnitzler, Joseph ULg; Mariavelle, Emeline ULg; Silvestre, Frédéric et al

Poster (2013)

The sheepshead minnow is widely used in ecotoxicological studies and such investigations have begun to focus on potential disruption of the thyroid axis. However, normal levels of thyroxin (T4) and 3,5,3’ ... [more ▼]

The sheepshead minnow is widely used in ecotoxicological studies and such investigations have begun to focus on potential disruption of the thyroid axis. However, normal levels of thyroxin (T4) and 3,5,3’-triiodothyronine (T3) and their developmental patterns are unknown. This study set out to determine the profiles of whole-body thyroxin (T4) and 3,5,3'-triiodothyronine (T3) levels during the development of sheepshead minnow from embryo to juvenile and adults. Couples of three females and two males were placed in breeding chambers designed for this experiment. More than 1000 eggs were collected and maintained in seawater. Embryos were selected under a dissection microscope and placed in incubation dishes (50 per dish) at 25°C. On day 8, embryos hatched and larvae were transferred to 1L beakers. For one week after hatching, larvae were fed on artemias and from 8 to 30 days post-hatch they were fed on flaked fish food. Embryos were sampled on day 0, 2, 4, 6 post-fertilization and larvae and juveniles were sampled every three days from day 0 to 28 days post-hatch. The pooled samples were taken from several incubation dishes and divided in three replicate batches of 30 individuals. Enzyme-linked immunoassay were used and validated for analysis of T4 and T3 after extraction from whole fish. At each sampling point 5 individuals were placed in formalin fixative for histology. Length and body mass were measured. Hatching success, gross in vivo observations, thyroid hormone levels and histology data will be determined and discussed in the framework to characterize the profiles of thyroid hormone levels during the development of sheepshead minnow from embryo to adult. This study establishes a baseline for thyroid hormones in sheepshead minnows, which will be vital for the understanding of thyroid hormone functions and in future studies of thyroid toxicants in this species. [less ▲]

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See detailThe sheepshead minnow Cyprinodon variegatus as a marine vertebrate model for investigating endocrine disrupting effects of triclosan
Schnitzler, Joseph ULg; Gauthray, Ghislain ULg; Silvestre, Frédéric et al

Poster (2012)

Zebrafish (Danio rerio) has been a prominent model in toxicology. This freshwater species present many advantages both in identifying endpoints of toxicity and in elucidating mechanisms of toxicity ... [more ▼]

Zebrafish (Danio rerio) has been a prominent model in toxicology. This freshwater species present many advantages both in identifying endpoints of toxicity and in elucidating mechanisms of toxicity. However, marine toxicologists lack such omnipotent model displaying similar advantages to zebrafish: small size, rapid breeding, and easy maintenance. We propose here the use of the sheepshead minnow Cyprinodon variegatus to define thyroid-disrupting effects of triclosan during pre-hatching development. Three females and two males were placed in each of the three breeding chambers designed for this experiment. More than 300 eggs were collected over three days and maintained in seawater with triclosan concentrations at 0, 100 ng.L-1, and 100 µg.L-1. Exposure of larvae to triclosan lasted until hatching. After hatching (six days post-spawning), 5 larvae per condition were placed in Bouin’s fixative for brain and thyroid histology. Length and body mass were measured. The body was frozen at -80oC to determine muscle thyroid hormone levels (T3 and T4), using radio-immunoassay techniques. Hatching success, in vivo observations, gross observation, thyroid hormone levels, histology will be determined and discussed in the framework of whether or not triclosan may alter thyroid metabolism during pre-hatching period of the sheepshead minnow. [less ▲]

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See detailEnvironmental factors affecting thyroid function of wild sea bass (Dicentrarchus labrax) from European coasts
Schnitzler, Joseph ULg; Klaren, Peter; Bouquegneau, Jean-Marie ULg et al

in Chemosphere (2012)

Thyroid functional status of wild fish in relation with the contamination of their environment deserves further investigation. We here applied a multi-level approach of thyroid function assessment in 87 ... [more ▼]

Thyroid functional status of wild fish in relation with the contamination of their environment deserves further investigation. We here applied a multi-level approach of thyroid function assessment in 87 wild sea bass collected near several estuaries: namely the Scheldt, the Seine, the Loire, the Charente and the Gironde. Thyroxine (T4) and triiodothyronine (T3) concentrations in muscle were analyzed by radioimmunoassay. The activity of hepatic enzymes involved in extrathyroidal pathways of thyroid hormone metabolism, viz. deiodination, glucuronidation and sulfatation were analyzed. Last, follicle diameter and epithelial cell heights were measured. We observed changes that are predicted to lead to an increased conversion of T4–T3 and lowered thyroid hormone excretion. The changes in the metabolic pathways of thyroid hormones can be interpreted as a pathway to maintain thyroid hormone homeostasis. From all compounds tested, the higher chlorinated PCBs seemed to be the most implicated in this perturbation. [less ▲]

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See detailThyroid endocrine disruption in situ and in vivo experiments reveals compensatory mechanisms
Schnitzler, Joseph ULg; Celis, Niko; Klaren, Peter et al

Conference (2011, May)

We compared effects of in situ and in vivo exposure of EDC on teleost thyroid system in order to get a complete picture of the putative interactions. A 120-day experimental exposure was designed in ... [more ▼]

We compared effects of in situ and in vivo exposure of EDC on teleost thyroid system in order to get a complete picture of the putative interactions. A 120-day experimental exposure was designed in combination to in situ measurements of persistent organic pollutants in 87 wild sea bass (Dicentrarchus labrax) form European estuaries. Seventy-five individuals were exposed to doses of PCB (0.3 to 1.0 µg Σ7PCBs per g food pellets) that reflects the persistent organic pollution to which the European sea bass population could conceivably be exposed. We applied a series of recommended measurement endpoints in these studies. The centrally controlled thyroidal secretion of T4 was monitored adequately from the muscular T4 levels and from thyroid histological appearance. Muscular T3 levels and enzymatic deiodinase and sulfatase activities in liver were measured. Observations made in experimental exposure to environmental relevant doses of PCB were consistent with those made in our field study. In both studies the muscular T4 levels were unaffected and no multivariate relationship with contaminant exposure could be revealed. Measurements of follicular diameter and epithelial cell heights showed no significant differences. Our findings revealed an increase of the hepatic T4ORD activity by higher chlorinated PCB congeners and DDTs. In both studies, we observed a general decrease the thyroid hormone conjugation by sulfatases that increases their solubility and facilitates their excretion. The muscular T3 levels were well preserved. These changes likely represent compensatory responses to disrupting effects that might otherwise have depressed T3 levels. This approach permitted us to interpret the causes and implications of alterations of the teleost thyroid system. [less ▲]

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See detailApproaches for assessing the presence and impact of thyroid hormone disrupting chemicals in sea bass (Dicentrarchus labrax) from European coasts
Schnitzler, Joseph ULg

Doctoral thesis (2011)

Thyroid functional status of wild fish in relation with the contamination of their environment deserves further investigation. Polychlorinated biphenyls (PCBs) and organochlorine pesticides like Dichloro ... [more ▼]

Thyroid functional status of wild fish in relation with the contamination of their environment deserves further investigation. Polychlorinated biphenyls (PCBs) and organochlorine pesticides like Dichloro-Diphenyl-Trichloroethane (DDTs), Hexachlorocyclohexanes (HCHs), aldrin, dieldrin and trace elements (Cd, Cu, Se, Pb, Zn and Hg) were analysed in the muscle of sea bass (Dicentrarchus labrax) sampled in coastal regions near several important European river mouths (Gironde, Charente, Loire, Seine and Scheldt). We applied a multi-level approach of thyroid function assessment. Thyroxine (T4) and triiodothyronine (T3) concentrations in muscle were analyzed by radioimmunoassay. The activity of hepatic enzymes involved in extrathyroidal pathways of thyroid hormone metabolism, viz. deiodination, glucuronidation and sulfation were analyzed. Last, follicle diameter and epithelial cell heights were measured. We observed changes that lead to an increased conversion of T4 to T3 and lowered thyroid hormone excretion. The changes in the metabolic pathways of thyroid hormones can be interpreted as a pathway to maintain thyroid hormone homeostasis. The higher chlorinated PCBs seemed to be the most implicated in this perturbation. To gain a more integrated insight, we examined the effect of subchronic exposure to a mixture of Aroclor standards on thyroid hormone physiology and metabolism in juvenile sea bass. After 120 days of exposure, histomorphometry of thyroid tissue, muscular thyroid hormone concentration and activity of enzymes involved in metabolism of thyroid hormones were assessed. The results show that the effects of PCB exposures on the thyroid system are dose-dependent. Exposure to environmentally relevant doses of PCB (0.3 to 1.0 μg Σ7PCBs per g food pellets) increases thyroid hormone synthesis and stimulates hepatic T4 outer ring deiodinase and T4 sulfation. Thyroid hormone tissue levels were preserved thanks to the PCB induced changes in T4 dynamics. At 10 times higher concentrations (10 μg Σ7PCBs per g food pellets) an important depression of T3 and T4 levels could be observed which are apparently caused by degenerative histological changes in the thyroid tissue. We propose accurate interpretations, by reviewing the different stages of teleost thyroid function and regulation. [less ▲]

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See detailThyroid hormone disrupting chemicals in sea bass (Dicentrarchus labrax) from European coasts
Schnitzler, Joseph ULg; Michel, Loïc ULg; Klaren, Peter et al

Conference (2011, February 25)

Polychlorinated biphenyls (PCBs) and organochlorine pesticides like Dichloro-Diphenyl-Trichloroethane (DDTs), Hexachlorocyclohexanes (HCHs), aldrin, dieldrin and trace elements (Cd, Cu, Se, Pb, Zn and Hg ... [more ▼]

Polychlorinated biphenyls (PCBs) and organochlorine pesticides like Dichloro-Diphenyl-Trichloroethane (DDTs), Hexachlorocyclohexanes (HCHs), aldrin, dieldrin and trace elements (Cd, Cu, Se, Pb, Zn and Hg) were analysed in the muscle of sea bass (Dicentrarchus labrax) sampled in coastal regions near several important European river mouths (Gironde, Charente, Loire, Seine and Scheldt). These potential endocrine disrupting chemicals were present in European coastal waters. Even if their concentrations were well below the Maximum Residue Limits set by the governments, they induced alterations of the endocrine system. We established correlations between contaminant concentrations and effects on the thyroid system in sea bass. The contaminants induced modifications of the metabolic pathways of thyroid hormones and enhanced thyroid hormone synthesis. The activity of T4 Outer Ring Deiodinase was increased, that leads to an intensified conversion of thyroxine (T4) to its more biologically active form triiodothyronine (T3). Meanwhile, the activity of T4 sulfatation was reduced, that leads to a lowered biliary excretion of thyroid hormones. The modified metabolic pathways of the thyroid hormones can be interpreted as a tool to homeostatically maintain the thyroid hormone status. Of all tested compounds, the higher chlorinated PCBs seemed to be the most implicated in this perturbation. The nature of thyroid hormone synthesis, signalling and regulation is highly conserved among vertebrates. Although we cannot extrapolate thyroid toxicity data directly from one species to another, these environmental factors may well affect thyroid function in other species, including humans. [less ▲]

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