Novel flame retardants, 1,2-bis(2,4,6-tribromophenoxy)ethane and 2,3,4,5,6-pentabromoethylbenzene, in United States' environmental samples

Two brominated flame retardants, 1,2-bis(2,4,6-tribromophenoxy)ethane (TBE) and 2,3,4,5,6-pentabromoethylbenzene (PEB), were detected and identified in ambient air samples from various sites in the United States. The identifications were confirmed by comparing the gas chromatographic retention times and mass spectra of the compounds found in the environment with those of authentic materials. Generally, the TBE concentrations in air were comparable to those of tetra- through hexabrominated diphenyl ethers (PBDEs) and often higher than those of decabromodiphenyl ether (BDE-209). The atmospheric TBE concentrations at locations in the southern United States were higher than those in the northern United States. TBE was also found in a sediment core from Lake Michigan; the concentrations of TBE increased with time, were lower than those of BDE-209, but were approximately 10 times higher than the sum of BDE-47, -99, and -100. The maximum PEB concentration in Chicago air was 550 pg/ m3, which was 10 times higherthan the concentration of total PBDEs in this sample. In general, the concentrations of PEB in air samples were low but detectable and were less than those of PBDEs. PEB was not found in the sediment core from Lake Michigan. These occurrences of relatively high concentrations of TBE and PEB in environmental samples may reflect the increasing usage of these compounds as flame retardants.     

Examination of isomer specific bioaccumulation parameters and potential in vivo hepatic metabolites of syn- and anti-Dechlorane Plus isomers in juvenile rainbow trout (Oncorhynchus mykiss)

Juvenile rainbow trout (Oncorhynchus mykiss) were exposed in the laboratory to elevated doses of syn- and anti-isomers of Dechlorane Plus (DP) via their diet for 49 days (uptake phase), followed by 112 days of untreated food (depuration phase) to examine bioaccumulation parameters and possible metabolic products. Three groups of 60 fish were used in the study. Two groups were exposed separately to food fortified with known concentrations of syn- (0.79 +/- 0.03 microg/g, lipid weight) and anti-DP (1.17 +/- 0.12 microg/g, lipid weight) while a third control group was fed unfortified food. Neither isomer reached steady-state after 49 days of exposure. Only the syn-isomer accumulated linearly in the fish (whole-body minus liver) during the dosing phase with a calculated uptake rate constant of 0.045 +/- 0.005 (arithmetic mean +/- 1 x standard error) nmoles per day. A similar uptake rate was also observed for this isomer in the liver. The elimination of both isomers from the whole fish (minus liver) obeyed first order depuration kinetics (syn-: r2 = 0.6427, p < 0.001, anti-: r2 = 0.5350, p < 0.005) with calculated half-lives (t1/2) of 53.3 +/- 13.1 (syn-) and 30.4 +/- 5.7 (anti-) days. Elimination of the isomers from the liver was difficult to interpret because of suspected enterohepatic circulation and redistribution of the isomers in the liver during clearance from other tissues. The biomagnification factor (BMF, determined in whole fish minus liver) of the syn-isomer (5.2) was greater than the anti-isomer (1.9) suggesting that the former isomer is more bioavailable. A suite of metabolites were screened for in the liver including dechlorinated, hydroxylated, methoxylated and methyl sulfone degradates. Even with the purposely high dose used in the uptake phase, none of these degradates could be detected in the extracts. This suggests that if metabolites of DP are detected in fish from aquatic food webs their presence is likely not from in vivo biotransformation of the parent compound.     

Dietary bioaccumulation of perfluorophosphonates and perfluorophosphinates in juvenile rainbow trout: evidence of metabolism of perfluorophosphinates

The perfluorophosphonates (PFPAs) and perfluorophosphinates (PFPiAs) are high production volume chemicals that have been observed in Canadian surface waters and wastewater environments. To examine whether their occurrence would result in contamination of organisms in aquatic ecosystems, juvenile rainbow trout (Oncorhynchus mykiss) were separately exposed to a mixture of C6, C8, and C10 monoalkylated PFPAs and a mixture of C6/C6, C6/C8, and C8/C8 dialkylated PFPiAs in the diet for 31 days, followed by 32 days of depuration. Tissue distribution indicated preferential partitioning to blood and liver. Depuration half-lives ranged from 3 to 43 days and increased with the number of perfluorinated carbons present in the chemical. The assimilation efficiencies (α, 7-34%) and biomagnification factors (BMFs, 0.007-0.189) calculated here for PFPAs and PFPiAs were lower than those previously observed for the perfluorocarboxylates (PFCAs) and perfluorosulfonates (PFSAs) in the same test organism. Bioaccumulation was observed to decreased in the order of PFSAs > PFCAs > PFPAs of equal perfluorocarbon chain length and was dependent on the charge of the polar headgroup. Bioaccumulation of the PFPiAs was observed to be low due to their rapid elimination via metabolism to the corresponding PFPAs. Here, we report the first observation of an in vivo cleavage of the carbon-phosphorus bond in fish, as well as, the first in vivo biotransformation of a perfluoroalkyl acid (PFAA). As was previously observed for PFCAs and PFSAs, none of the BMFs determined here for the PFPAs and PFPiAs were greater than one, which suggests PFAAs do not biomagnify from dietary exposure in juvenile rainbow trout.     

Biotransformation enzymes and thyroid axis disruption in juvenile rainbow trout (Oncorhynchus mykiss) exposed to hexabromocyclododecane diastereoisomers

Juvenile rainbow trout (Oncorhynchus mykiss) were fed either a reference diet or one of three diets enriched with alpha, beta, or gamma diastereoisomers of hexabromocyclododecane (HBCD, C12H18Br6) for 56 days. This exposure period was followed by 112 days during which all fish were fed the reference diet. Potential effects of HBCD on phase I and II biotransformation enzyme activities and thyroid axis disruption were examined. Disruption of the thyroid axis was most evident in the gamma-HBCD exposed group, as indicated by lower circular FT4 and higher FT3 as well as an increase in thyroid epithelial cell height. However, fish fed the alpha-HBCD enriched diet also exhibited altered glucuronyltransferase activity and thyroid epithelial cell heights and the beta-HBCD group had altered FT4 and FT3 and glucuronyltransferase activity. T4ORD activity was not affected after 14 days, but was significantly lower among all HBCD exposed fish compared to the reference fish after 56 days. Results from these experiments indicate that all isomers have the potential to disrupt thyroid homeostasis.     

Tissue distribution and residue depletion of metronidazole in rainbow trout (Oncorhynchus mykiss)

Tissue distribution and residue depletion of metronidazole (MNZ) was studied in rainbow trout (Oncorhynchus mykiss) following oral administration of MNZ in feed at the average dose of 25 mg kg^?1 body weight day^?1 for 7 days at 11 ± 2°C. The MNZ concentration in feed was 0.25% while daily feed intake was 1% of body weight. The concentrations of MNZ and its main metabolite, hydroxymetronidazole (MNZOH), in fish tissues were determined by LC-MS/MS. The drug was well distributed in tissues with maximum concentrations on day 1 post-administration. At this time, the mean MNZ concentrations in muscle, skin, kidney, liver and gill were 14 999, 20 269, 15 070, 10 102 and 16 467 µg kg^?1 respectively. MNZ was converted into MNZOH with the ratio of MNZOH:MNZ up to 7% in all fish tissues throughout the withdrawal period. This shows that MNZ itself is the main residue in rainbow trout. MNZ was detected at the level close to the decision limit (0.20 µg kg^?1) in muscle, skin and muscle with adhering skin up to 42 days, while in kidney, liver and gill it was up to 28 days post-administration. MNZOH was eliminated more rapidly from fish tissues and it was present in muscle alone up to 21 days. The elimination half-lives of MNZ and MNZOH in rainbow trout tissues were 1.83–2.53 and 1.24–2.12 days, respectively. When muscle without skin was analysed, higher MNZ and MNZOH concentrations were detected, and for a longer period of time, than in muscle with adhering skin. Thus muscle alone could be more appropriate for the effective residue control of MNZ in rainbow trout. For the same reason, it is also essential to ensure direct cooling immediately after sampling, since MNZ and its metabolite degrade in fish muscle and skin stored in non-freezing conditions.     

Kinetics of degradation of adenosine triphosphate in chill-stored rainbow trout (Oncorhynchus mykiss)

Trout that had been held in freshwater or in sea water were stored at 0, 5, or 10 °C, and in the case of sea‐water‐held trout, also at 15 °C. Samples were taken during storage for analysis of ATP‐derived metabolites. The kinetics of degradation of ATP were investigated using two mathematical models, one depending on only endogenous enzymes acting in a sequence of consecutive first order reactions, and one assuming inosine was additionally converted to hypoxanthine by bacterial action. The former model adequately fitted the data from trout held in sea water, but the latter model was a better fit to data from the trout held in freshwater. The activation energy of loss of inosine monophosphate was estimated to be 17.4 kcal mol^?1.     

Determination of xenobiotic intrinsic clearance in freshly isolated hepatocytes from rainbow trout (Oncorhynchus mykiss) and rat and its application in bioaccumulation assessment

Bioaccumulation in fish depends on the dynamics of various processes that involve fish uptake, storage, and elimination of xenobiotics. Elimination via fish biotransformation is a primary process that can be evaluated in an in vitro system to improve the performance of the prediction of xenobiotic bioaccumulation potentials. In this study, values of intrinsic clearance (CLint) of seven reference compounds (atrazine, molinate, 4,4-bis(dimethylamino)-benzophenone, 4-nonylphenol, 2,4-di-tert-butylphenol, trifluralin, benzo(a)pyrene) in hepatocytes freshly isolated from rainbow trout and rat were determined using a substrate depletion approach. Atrazine was metabolized in rat hepatocytes with a CLint value of 3.81 +/- 1.96 mL/h/ 10(6) cells, whereas in trout hepatocytes, the clearance was not significant until very high cell concentration was used and the rate was estimated to be approximately 0.002 mL/h/10(6) cells. Intrinsic clearance values for all other compounds were 5.5-78.5-fold lower in trout hepatocytes than those in rat hepatocytes. Trout hepatic clearance (CL(H)) values were extrapolated from the CLint values using a "well-stirred" liver model. Biotransformation rate constants (kMET) of the compounds in trout were subsequently estimated and used as inputs to a kinetic model for the prediction of bioconcentration factors (BCF) in fish. Compared to the BCF values predicted without consideration of fish biotransformation, the inclusion of estimated kMET values significantly improved fish BCF predictions for the reference compounds. This study demonstrates a framework for future bioaccumulation assessment of xenobiotics using combined information of the physical-chemical properties of the compounds and the biotransformation potentials of the compounds in fish.     

Enzyme leakage in muscle tissue of rainbow trout (Oncorhynchus mykiss) related to various thawing treatments

Frozen rainbow trout (Oncorhynchus mykiss) was thawed so that different tempering times, followed by different duration times in the temperature intervall called the latent zone (LZ), were obtained. The different thawing treatments resulted in different effects on the muscle membrane system. To estimate the resulting tissue damage, the leakage of the lysosomal enzymesα-glucosidase (E.C. 3.2.1.20) andβ-N-glucosaminidase (E.C. 3.2.1.30) was measured as the relationship between the enzyme activity in centrifuged tissue fluid (CTF) and in total homogenate. The volume and protein content of the CTF were also measured. The tempering rate seemed to influence the enzyme leakage more than different duration times in the LZ. Slow tempering increased the enzyme leakage more than fast tempering. Samples taken 1 h in the LZ showed an increased activity compared with samples taken directly after completed tempering. No significant further increase was found in samples taken after 10 or 24 h in the LZ, either for the rapidly or the slowly tempered group.     

Determination of the exposure parameters that maximise the concentrations of the anaesthetic/sedative eugenol in rainbow trout (Oncorhynchus mykiss) skin-on fillet tissue

Studies were conducted to determine the anaesthetic/sedative concentrations and durations that would maximise anaesthetic/sedative residue concentrations in rainbow trout (Oncorhynchus mykiss) skin-on fillet tissue. Rainbow trout (167–404 g) were exposed to 50 mg l^?1 AQUI-S^® 20E (10% active ingredient, eugenol) in 17°C freshwater for durations up to 1440 min, 100 and 250 mg l^?1 AQUI-S^® 20E for durations up to 240 min, and 500 and 1000 mg l^?1 AQUI-S^® 20E for durations up to 90 min. Fish exposed to 100 mg l^?1 AQUI-S^® 20E for durations of 30, 60, 120 and 240 min had the greatest eugenol concentrations in the fillet tissue, 50, 58, 54 and 62 µg g^?1, respectively. All other exposure concentrations and durations resulted in significantly lower eugenol concentrations, i.e. all < 39 µg g^?1.     

Effects of diesel on survival, growth, and gene expression in rainbow trout (Oncorhynchus mykiss) fry

Diesel spills are all too frequent disturbances of freshwater ecosystems, largely as a result of the quantities transported and consumed. Assessing the risk that such events may pose to aquatic life remains a difficult process, because of the complexity of this hydrocarbon mixture and our limited knowledge of its toxicity. A diesel spike experiment with rainbow trout (Oncorhynchus mykiss) fry was carried out to fill this knowledge gap. Survival, growth, and gene expression changes were assessed and toxicity thresholds were determined. Whereas the biological end points were consistent in the determination of (sub)lethal doses, microarrays supplied additional information on the mechanism of toxicity (oxygen deprivation) and potential long-term effects (feminization, immune system alterations) of diesel exposure on salmonids. Hemoglobins, prostaglandins, cytochromes, and gluthathion-S-transferases were among the molecular biomarkers proposed for use in future risk assessments based on microarray results. By bridging traditional toxicity testing with recent microarray technologies, this study shows the potential of genomics tools in ecotoxicity studies as well as industrial applications, including risk assessment, in the near future.     

Activities of antioxidant enzymes in rats fed with hot-smoked rainbow trout (Oncorhynchus mykiss)

The activities of antioxidant enzymes in rats fed with hot‐smoked rainbow trout (Oncorhynchus mykiss) was investigated. Four diets containing fresh and hot‐smoked rainbow trout flesh and vitamin were prepared and commercial pellet food purchased. Four groups of rats were fed with the diets for 28 days. Body weight was checked weekly. No significant (P > 0.05) differences were found in weight between groups. Malondialdehyde (MDA) values of group B and group D were found to be significantly increased (P < 0.05). Differences in glutathione peroxidase (GPX) and glutathione reductase (GR) values were not significant (P > 0.05) between groups. The difference in superoxide dismutase (SOD) and catalase (CAT) values was found to be significant (P < 0.05). The hot smoked process led to significant changes as decreased in the antioxidant enzymes activities. Our results indicate that determination of MDA, GPX, GR, SOD and CAT parameters in blood may help to point out cancer risk in humans.     

Bioavailability and chronic toxicity of zinc to juvenile rainbow trout (Oncorhynchus mykiss): comparison with other fish species and development of a biotic ligand model

In this study, the effects of modifying Ca (0.2-4 mM), Mg (0.05-3 mM), Na (0.75-5 mM), and pH (5.5-7.5) on the chronic toxicity of zinc to juvenile rainbow trout (Oncorhynchus mykiss) were investigated using standard 30-d assays in which survival and growth were monitored. Survival was observed to be a more sensitive end point than growth, and mortality mainly occurred during the initial stages of the exposure. This suggested that the mode of action of zinc toxicity was mainly of an acute nature. A review and analysis of existing literature demonstrated similar results for most other fish species investigated. Overall, up to a 30-fold variation of zinc toxicity was observed, as indicated by no observed effect concentrations varying between 32.7 and 974 microg of Zn L(-1). Increased concentrations of Ca2+, Mg2+, Na+, and H+ (within the tested ranges) resulted in a reduction of chronic zinc toxicity by a factor of 12, 3, >2, and 2, respectively. This suggests the major importance of Ca competing with zinc and protecting against zinc toxicity, which seems to be a ubiquitous concept in fish species (and probably also invertebrate). On the basis of the toxicity data obtained, a chronic biotic ligand model (BLM) was developed that takes into account both chemical speciation of zinc and competition between zinc and the above-mentioned cations. The developed model was able to predict chronic effect concentrations with an error of less than a factor of 2 in most cases. Hence, it was concluded that the chronic Zn BLM can reduce toxicity variability due to bioavailability to a considerable extent and that the BLM can become an important tool in criteria setting and risk assessment practice of zinc and zinc substances.     

Cryoprotection of frozen-stored actomyosin of farmed rainbow trout (Oncorhynchus mykiss) by some sugars and polyols

A study on the effectiveness of several cryoprotectants (polydextrose, lactitol, glucose syrup and a mixture of sucrose and sorbitol [1:1]) in preventing freeze-induced perturbations of fish proteins was carried out in in vitro systems of natural actomyosin of rainbow trout (Oncorhyncus mykiss) muscle. Adding these cryoprotectants prevented drastic decreases of ATPase activity, as well as a rapid exposure of hydrophobic and sulphydryl groups on the protein surface. Cryoprotectants therefore slowed down the kinetics of aggregation via intermolecular secondary forces and disulphide bonds, thus greatly reducing losses in solubility.     

Comparative assessment of proximate composition,physicochemical parameters,fatty acid profile and mineral content in farmed and wild rainbow trout (Oncorhynchus mykiss)

This study was conducted to determine differences between farmed and wild rainbow trout in terms of proximate and fatty acid composition, physicochemical parameters and mineral content. Fat content of farmed fish fillets was higher, while moisture content was lower than wild fish. However, wild fish had higher pH value and water‐holding capacity comparing to farmed fish. The muscle lipids of farmed fish contained higher proportions of 20:0, 18:1n‐9 and 20:1n‐9; and lower proportions of 18:2n‐6, 20:2cis, 18:3n‐3, 20:3n‐6, 20:4n‐6, 20:5n‐3 and 22:6n‐3 fatty acids than wild fish. The percentage of total saturated fatty acids (SFAs) was similar in both fish. Total polyunsaturated fatty acids (PUFAs), n‐3 PUFAs and n‐3/n‐6 PUFAs ratio were higher in the wild fish comparing to farmed fish, whereas its total monounsaturated fatty acids (MUFAs) and n‐6 PUFAs contents were lower. Among the seventeen minerals analysed in fish flesh, differences existed between farmed and wild rainbow trout in Ca and Fe contents. Moreover, toxic trace minerals (As, Cd, Pb and Hg) were all present in amounts below their toxic levels. The differences observed between farmed and wild fish may be attributed to the diet constituents and environmental conditions of the fish.     

Possibilities to raise vitamin D content of rainbow trout (Oncorhynchus mykiss) by elevated feed cholecalciferol contents

Farmed rainbow trout (Oncorhynchus mykiss) is a widely consumed fish species. The cholecalciferol content in the muscle of rainbow trout is, however, quite low compared with that in several wild fish species. The present study was designed to determine whether it is possible to increase the cholecalciferol content of rainbow trout (initial weight about 500 g) with the use of cholecalciferol‐dosed feeds. Three different cholecalciferol concentrations (8.9, 17.4 and 53.9 μg 100 g ⁻¹ feed) were tested. After 4 months of feeding, the cholecalciferol determinations from samples of muscle and liver were performed using an HPLC method. Here, we suggest that the cholecalciferol content of rainbow trout muscle cannot be increased by feeding them with elevated doses of the vitamin. © 1999 Society of Chemical Industry     

Microstructure and instrumentally measured textural changes of rainbow trout (Oncorhynchus mykiss) gravads during production and storage

BACKGROUND: Gravad fish belong to a group of low‐processed products obtained from fresh fish by rubbing fillets with a mixture of sugar and salt and then placing them in cold storage. Little is known about changes in the tissue during the production and storage of gravads. The aim of the present study was to investigate the microstructural and textural changes in rainbow trout (Oncorhynchus mykiss) gravad during processing and vacuum storage at 3 °C and ?30 °C. RESULTS: Microscopic observations of gravad showed greater compactness of structure when compared with raw trout muscle, characterised by the disappearance of the divisions between adjoining myofibrils in gravad. Freezing, on the other hand, caused the myofibrils to again become more clearly distinguishable despite being partly agglomerated into lamellae. The above changes in structure were accompanied by changes in the textural and rheological properties of the product. It was observed that the texture profile (TPA) changed, resulting in an increase in the cohesiveness and chewiness of the gravads when compared to the raw fillets. There was also a lowering of stress decay during the relaxation test and a decrease in the value of the storage modulus (G′) as analysed by oscillatory rheometry. Further changes observed during storage were mainly concerned with an increase in the hardness and chewiness of gravads. CONCLUSION: Gravading significantly changes the rainbow trout fillets by making the microstructure more compact. This process is accompanied by changes in texture and rheological properties, which next are running during the storage of a chilled or frozen product. These changes are significant enough for potential consumers to be made aware of the fact that the texture of the product changes considerably during its shelf life. Copyright © 2009 Society of Chemical Industry     

Variation in sensory profile of individual rainbow trout (Oncorhynchus mykiss) from the same production batch

The variation in sensory profile of rainbow trout (Oncorhynchus mykiss), belonging to the same aquaculture production batch and handled the same way, was explored by using objective sensory profiling on heat-treated minced fillets. In addition, quality index, mechanical texture, pH, fat, and water content were measured. Different groups of fish were sampled 3 different times during a production day. The results showed significant differences in the sensory profiles of individual fish within all 3 groups as well as significant differences between the groups. Differences in mechanical texture were found between individuals in 2 of the 3 groups and between the groups. No differences were found in quality index neither between individuals nor groups. A significant negative correlation between lipid content and firm texture was observed, but in general, the chemical and physical measurements could not explain the differences in the sensory profiling or in the mechanical texture measurements. The results showed that significant differences in the sensory profiles of individual fish from the same aquaculture production batch may occur. Furthermore, the results also showed sensory differences between groups of samples taken at different times during a production day.