The use of the oxidative stress responses as biomarkers in Nile tilapia (Oreochromis niloticus) exposed to in vivo cadmium contamination

Risk assessment and toxic effects of metal pollution in two cultured and wild fish species from highly degraded aquatic habitats

Lake Qaroun is an inland lake at the lowest part of El-Fayoum depression, Egypt. It receives agricultural and domestic non-treated drainage waters, which are also used for aquaculture in Qaroun area. The results of the present study aimed to provide comparable data between wild (collected from Lake Qaroun) and cultured (collected from Qaroun fish farms and the reference site) Nile tilapia Oreochromis niloticus and mullet Mugil cephalus, as indicators of natural and anthropogenic impacts on aquatic ecosystem as well as to evaluate the human hazard index associated with fish consumption. Metal concentrations in fish tissues showed a species-specific bioaccumulation pattern. Statistically significant differences were observed in the mean metal concentrations with lower bioavailability in M. cephalus compared with O. niloticus in internal vital organs (liver, kidney, and muscle) but much higher in external organs (gill and skin). Histopathological alterations and evident damages were observed in gill, liver, and kidney of both species collected from Lake Qaroun and Qaroun fish farms compared with those from the reference site. The results showed significant increase of plasma aspartate aminotransferase and alanine aminotransferase activity as well as creatinine and uric acid concentration in both fish species from polluted locations. The human health hazard index showed that the cumulative risk greatly increases with increasing fish consumption rate, thus yielding an alarming concern for consumer health.

Effects of Cd, Zn and Cd + Zn combination on ATPase activitiy in the gill and muscle of tilapia (Oreochromis niloticus)

This study investigated the responses of Na(+)/K(+)-ATPase, Mg(2+)-ATPase and Ca(2+)-ATPase in the gill and muscle of a freshwater fish Oreochromis niloticus exposed to 1 μg/mL of Cd and Zn and their mixture for different periods (0, 7, 14, 21 and 28 days). At the end of experimental periods, the activities Na(+)/K(+)-ATPase, Mg(2+)-ATPase and Ca(2+)-ATPase in gill tissues and only Ca(2+)-ATPase activity in muscle tissues were measured. Gill Na(+)/K(+)-ATPase activity generally decreased following single metal exposures, whereas their combinations increased its activity. Gill Ca(2+)-ATPase activity decreased relative to the control at most exposure times for single exposures of Zn and Cd, as well as for the combined exposure. There was no gill Ca(2+)-ATPase activity after 28 days of exposure to Zn and Cd combined. Mg(2+)-ATPase activity was not affected significantly in gill tissue by exposure to Zn and Cd individually or in combination. Muscle Ca(2+)-ATPase activity also decreased significantly following metal exposure, but not as greatly as in the gill tissue. Tissue protein levels were mostly unaffected by metal exposures. This study showed that certain ATPases are highly sensitive to metal exposure whether the metals are essential or non essential, and suggests using gill tissue Na(+)/K(+)-ATPase and Ca(2+)-ATPase as sensitive biomarkers in metal contaminated waters.

Confinement during field studies may jeopardize antioxidant and physiological responses of Nile tilapia to contaminants

This work evaluates the effects of caging, a known confinement stress, in Nile tilapia (Oreochromis niloticus) during an environmental study in Cubatão river, southern Brazil. Caging animals for 7 days, regardless of being at the reference or at a contaminated site, resulted in lower levels of antioxidant-related defenses (glutathione, glutathione S-transferase, glucose-6-phosphate dehydrogenase) in liver and physiological parameters (blood glucose and lactate) as compared with free-swimming animals. Higher hepatic glutathione reductase activity and elevated Hb content could be associated to contaminant exposure. In conclusion, the confinement stress in caged Nile tilapia biochemical and physiological disturbances, acting as a confounding factor in field studies.

Biochemical responses of juvenile European sturgeon, (Huso huso) to a sub-lethal level of copper and cadmium in freshwater and brackish water environments

In Caspian Sea basin, sturgeons spend the larval and juvenile stages in freshwaters of rivers and then, they migrate to brackish waters of the sea where they grow and mature. With regard to the elevation of the metal concentrations in coastal waters and sediments of the Caspian Sea and its adjacent rivers, it is likely that juvenile sturgeon are exposed to sub-lethal levels of metals during seawater entry process. We compared the biochemical responses of juvenile European sturgeon, (Beluga, Huso huso) exposed to a sub-lethal level of copper (Cu, 20 μg/L) and cadmium (Cd, 300 μg/L) in freshwater (FW, 0 ppt) and brackish water (BW, 11 ppt) for seven days. The results showed that the levels of plasma glucose increased significantly in BW and in all metal exposed groups. Also, plasma cortisol concentrations showed significant increases when juveniles were exposed to BW, Cu(FW/BW) and Cd(BW). The activity of liver superoxide dismutase (SOD) decreased significantly in BW compared with FW. Moreover, Cu and Cd exposure enhanced the activity of SOD in BW, while SOD did not show any changes in FW. The levels of tissue and plasma proteins as well as plasma triiodothyronine (T3), thyroxine (T4) and liver Catalase (CAT) activity remained constant when animals were exposed to Cu/Cd in both FW and BW environments. Our data indicate that exposure of juvenile beluga to BW stimulated the general biochemical responses of stress such as cortisol and glucose, while sub-lethal exposure to Cu and Cd caused oxidative stress in BW environment but not in FW.

Effects of cadmium exposure on digestive enzymes, antioxidant enzymes, and lipid peroxidation in the freshwater crab Sinopotamon henanense

In this study, the effects of cadmium (Cd) stress on the activities of disaccharidases (sucrase, lactase, and maltase), amylase, trypsin, pepsase, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and malondialdehyde (MDA) content in the alimentary system of freshwater crabs Sinopotamon henanense were studied. Results showed that the enzyme activities in the stomach, intestine, and hepatopancreas changed with Cd concentration. In terms of digestive enzymes, Cd exposure had an inhibitory effect on the activities of the disaccharidases, amylase, and pepsase (only in the stomach). Significant induction of trypsin activity by Cd at a lower concentration was observed, but as Cd concentration increased, trypsin activity decreased. Maltase activity showed a slight recovery after inhibition by Cd. The activities of SOD and CAT increased initially and decreased subsequently. Cd significantly inhibited the activity of GPx. MDA content increased with increasing concentration of Cd. These results showed that acute Cd exposure led to harmful effects on the alimentary system of crabs, which are likely linked to Cd induced oxidative stress.

Toxic effects of copper ion in zebrafish in the joint presence of CdTe QDs

Quantum dots (QDs) have strong adsorption capacity; therefore, their potential toxicity of the facilitated transport of other trace toxic pollutants when they co-exist to aquatic organisms has become a hot research topic. The lab study was performed to determine the developmental toxicities to the zebrafish after exposed to the combined pollution of Cadmium-telluride (CdTe) QDs and copper ion (Cu(2+)) compared to the single exposure. Our findings for the first time revealed that: 1) CdTe QDs facilitated the accumulation of Cu(2+) in zebrafish, 2) the higher mortality, lower hatch rate, and more malformations can be clearly observed, 3) the diverse vascular hyperplasia, turbulence, and bifurcation of the exposed FLI-1 transgenic zebrafish larvae appeared together, 4) the synergistic effects played more important role during joint exposure. These observations provide a basic understanding of CdTe QDs and Cu(2+) joint toxicity to aquatic organisms.

Glutathione and its dependent enzymes' modulatory responses to toxic metals and metalloids in fish--a review

Toxic metals and metalloid are being rapidly added from multiple pathways to aquatic ecosystem and causing severe threats to inhabiting fauna including fish. Being common in all the type of aquatic ecosystems such as freshwater, marine and brackish water fish are the first to get prone to toxic metals and metalloids. In addition to a number of physiological/biochemical alterations, toxic metals and metalloids cause enhanced generation of varied reactive oxygen species (ROS) ultimately leading to a situation called oxidative stress. However, as an important component of antioxidant defence system in fish, the tripeptide glutathione (GSH) directly or indirectly regulates the scavenging of ROS and their reaction products. Additionally, several other GSH-associated enzymes such as GSH reductase (GR, EC 1.6.4.2), GSH peroxidase (EC 1.11.1.9), and GSH sulfotransferase (glutathione-S-transferase (GST), EC 2.5.1.18) cumulatively protect fish against ROS and their reaction products accrued anomalies under toxic metals and metalloids stress conditions. The current review highlights recent research findings on the modulation of GSH, its redox couple (reduced glutathione/oxidised glutathione), and other GSH-related enzymes (GR, glutathione peroxidase, GST) involved in the detoxification of harmful ROS and their reaction products in toxic metals and metalloids-exposed fish.

Bioavailability and oxidative stress of cadmium to Corbicula fluminea

This work set out to study the effects of cadmium (Cd) in sediments on the antioxidant enzyme activities in the digestive gland of Asian clam Corbicula fluminea and to explore the potential for applying these responses to evaluate the Cd-contaminated sediment. Additionally, diffusive gradients in thin-films (DGT) technique was used to predict the response of its antioxidant defense system. The sediments, collected from Taihu Lake, were spiked with Cd at different concentrations (0.72, 0.91, 1.62, 2.59, 11.2, 20.4 and 40.6 mg kg(-1), dry weight). Asian clam was cultivated for 28 days. Concentrations of Cd in the body of Asian clam had a good relationship with concentrations of Cd in overlying water and sediments, as measured by DGT. Cd affected these biochemical parameters significantly, especially for superoxide (SOD), peroxidase (POD) and glutathione (GSH), which began to show higher sensitivity and have a significant difference in low dosage (0.91 mg Cd kg(-1)) compared with blank. Contents of MDA and MT, which were induced by Cd, increased with the increasing Cd concentration in sediments and reached peak values at 11.2 and 20.4 mg kg(-1), respectively, after 28 days exposure. All of these results suggested that biochemical responses cooperated in detoxifying and maintaining cellular metabolic homeostasis. The R(2) of regression analysis between the contents of MT and the concentrations of Cd measured by DGT, in sediments and soft body were 0.71, 0.94 and 0.88 after 28 days exposure. This suggested that DGT measurement could predict the response of MT. Cd accumulation, GSH and MT were indispensable biomarkers and the MDA content and DGT appeared to be promising biomarkers. The results clearly indicated that Cd could induce oxidative stress in the digestive gland of Asian clam. The combination of biomonitors with DGT can obtain different information about Cd bioavailability and confirm the significance of applying a suite of biomarkers rather than a selective index to assess the sublethal effect. It also offered theoretical methods for the prediction of sediment Cd pollution.

Exposure of silver carp (Hypophthalmichthys molitrix) to environmentally relevant levels of cadmium: hematology, muscle physiology, and implications for stock enhancement in the Xiangjiang River (Hunan, China)

Cadmium is a non-essential metal with a wide distribution that has severe toxic effects on aquatic animals. Changes in hematology and muscle physiology were examined in silver carp (Hypophthalmichthys molitrix) exposed to environmentally relevant levels of cadmium (0.01 mg L(-1)) for 96 h. Cadmium exposure induced significant increases in the red blood cell count, and in the plasma concentrations of cortisol, glucose, and lactate. This suggests that the dose of cadmium was sufficient to cause stress, possibly associated with impaired gas exchange at the gills. There were no changes in hemoglobin concentration or plasma protein concentration. Significant decreases in muscle energy fuels (ATP and glycogen), and increases in muscle lactate persisted until the end of the exposure period, respectively. The changes in muscle lactate and protein in silver carp differed from those observed in response to exposure of fish to cadmium and heavy metals in other studies. The study highlights the importance of selecting unpolluted release sites with suitable water conditions for the survival of newly released individuals for stock enhancement of the Xiangjiang River.

Effects of mercury on glutathione and glutathione-dependent enzymes in hares (Lepus europaeus Pallas)

The aim of this study was to analyze and evaluate risks of long-term exposure to mercury in hares (Lepus europaeus Pallas), with a chemical-analytical approach evaluating median mass fraction of toxic mercury in the hares organs (liver, kidney, muscle and brain). To obtain better insight into possible effects of mercury, the study included screening of the oxidative status after long term exposure to low concentrations of mercury. Hares organs were analyzed for total mercury concentration by AAS. Glutathione and glutathione-dependent enzymes status was also investigated. The median mercury concentrations (wet weight) in the liver, kidney, muscle and brain of the hares ranged from 0.058-0.189, 0.138-0.406, 0.013-0.046 and 0.022-0.102 μg/g respectively. Concentration of the glutathione (GSH), glutathione-peroxidase (GPx), and glutathione-reductase (GR) activity increased with the mercury concentration. However, glutathione S-transferase (GST) and superoxide-dismutase (SOD) activity decreased with the mercury concentration. The results of this study show the impact of environmentally absorbed mercury on the antioxidant status of the examined hares. Further research on long-term exposure to low concentrations of mercury is needed.

Comparative genomic analysis and benzene, toluene, ethylbenzene, and o-, m-, and p-xylene (BTEX) degradation pathways of Pseudoxanthomonas spadix BD-a59

Pseudoxanthomonas spadix BD-a59, isolated from gasoline-contaminated soil, has the ability to degrade all six BTEX (benzene, toluene, ethylbenzene, and o-, m-, and p-xylene) compounds. The genomic features of strain BD-a59 were analyzed bioinformatically and compared with those of another fully sequenced Pseudoxanthomonas strain, P. suwonensis 11-1, which was isolated from cotton waste compost. The genome of strain BD-a59 differed from that of strain 11-1 in many characteristics, including the number of rRNA operons, dioxygenases, monooxygenases, genomic islands (GIs), and heavy metal resistance genes. A high abundance of phage integrases and GIs and the patterns in several other genetic measures (e.g., GC content, GC skew, Karlin signature, and clustered regularly interspaced short palindromic repeat [CRISPR] gene homology) indicated that strain BD-a59's genomic architecture may have been altered through horizontal gene transfers (HGT), phage attack, and genetic reshuffling during its evolutionary history. The genes for benzene/toluene, ethylbenzene, and xylene degradations were encoded on GI-9, -13, and -21, respectively, which suggests that they may have been acquired by HGT. We used bioinformatics to predict the biodegradation pathways of the six BTEX compounds, and these pathways were proved experimentally through the analysis of the intermediates of each BTEX compound using a gas chromatograph and mass spectrometry (GC-MS). The elevated abundances of dioxygenases, monooxygenases, and rRNA operons in strain BD-a59 (relative to strain 11-1), as well as other genomic characteristics, likely confer traits that enhance ecological fitness by enabling strain BD-a59 to degrade hydrocarbons in the soil environment.

Heavy metal (Cd, Cr, Cu, Hg, Pb, Zn) concentrations in seven fish species in relation to fish size and location along the Yangtze River

PURPOSE

The objective of this paper is to assess the regulation of the accumulation of heavy metals in the aquatic environment and different fish species.

METHODS

Water and fish samples were collected from upper to lower reaches of the Yangtze River. The heavy metal (Cd, Cr, Cu, Hg, Pb, Zn) concentrations in the muscle tissue of seven fishes were measured. Additionally, the relationships between heavy metal concentrations in fish tissue and fish size (length and weight), condition factor, water layer distribution, and trophic level were investigated.

RESULTS

Metal concentrations (milligrams per kilogram wet weight) were found to be distributed differently among different fish species. The highest concentrations of Cu (1.22 mg/kg) and Zn (7.55 mg/kg) were measured in Pelteobagrus fulvidraco, the highest concentrations of Cd (0.115 mg/kg) and Hg (0.0304 mg/kg) were measured in Silurus asotus, and the highest concentrations of Pb (0.811 mg/kg) and Cr (0.239 mg/kg) were measured in Carassius auratus and Cyprinus carpio. A positive relationship was found between fish size and metal level in most cases. The variance of the relationships may be the result of differences in habitat, swimming behavior, and metabolic activity. In this study, fishes living in the lower water layer and river bottom had higher metals concentrations than in upper and middle layers. Benthic carnivorous and euryphagous fish had higher metals concentrations than phytoplankton and herbivorous fish. Generally, fish caught from the lower reach had higher metals concentrations than those from the upper reach.

CONCLUSIONS

Cadmium and lead concentrations in several fishes exceeded the permissible food consumption limits, this should be considered to be an important warning signal.

Multiparametric approach for assessing environmental quality variations in West African aquatic ecosystems using the black-chinned tilapia (Sarotherodon melanotheron) as a sentinel species

The study highlights the potential of the black-chinned tilapia to be used as a sentinel to assess environmental contaminants based on the use of a set of biomarkers. The usefulness of fish species as sentinels for assessing aquatic environment contamination was tested using a set of biomarkers in Senegalese environments characterized by multi-pollution sources. The black-chinned tilapia (Sarotherodon melanotheron) was selected as a sentinel because of its abundance, wide distribution in all coastal aquatic ecosystems and physiological properties. The potential influence of confounding factors such as salinity on biomarker in the tilapia has been examined. Individuals were sampled during two seasons (dry and wet) in eight sites characterized by various degrees of anthropogenic contamination and different salinities (from 0 to 102 psu). Biomarkers-including growth rate (GR), condition factor (CF), biotransformation enzymes such as 7-ethoxyresorufin-O-deethylase (EROD) and glutathione-S-transferase (GST), lipid peroxidation (TBARS) and acetylcholinesterase (AChE)-were measured. Chemical contaminant [polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs)] levels showed different sources of contamination with relatively high concentrations of PAHs in the Hann Bay and Foundiougne locations. The most sensitive biomarker present in different sites according to the principal component analysis is EROD. Few variations of the AChE activity and TBARS levels were found. No clear relationship was found between biomarker responses and salinity, but GR and CF were lower in hypersaline conditions. Tilapia is responsive to environmental contaminants such as PAHs, OCPs and PCBs. The S. melanotheron multiparametric approach showed a better discrimination of sites.

Biomarkers responses in muscle of Senegal sole (Solea senegalensis) from a heavy metals and PAHs polluted estuary

The biochemical responses in muscle, such as the enzymatic activities of acetylcholinesterase, lactate dehydrogenase and isocitrate dehydrogenase, were studied in sole (Solea senegalensis) collected in Huelva estuary (SW Spain), in the vicinity of a petrochemical and mining industry. The sampling sites showed different type and degree of pollution. The results demonstrated significant differences in muscle activities of AChE and IDH in Odiel and Tinto Rivers compared to control fish. LDH activity did not show any difference between sampling sites. Significant correlations were established between some biomarkers and heavy metals: AChE was correlated with Pb, Cd and Cu concentrations in water; IDH activity was correlated with Cd and Cu concentrations in water and As, Pb and Cd concentrations in sediments; LDH activity was correlated with As and Zn concentration in water and Cd concentration in sediment. Only one correlation was established between the biomarkers analysed and the concentrations of PAHs: benzo(b)fluoranthene concentration in sediment and IDH.

Biomarker responses as indication of contaminant effects in Oreochromis niloticus

The current study investigated oxidative stress parameters (enzymes activities, metallothionein content and lipid peroxidation) in freshwater fish, Oreochromis niloticus, tilapia exposure to Monjolinho River (in 4 months of year: January, April, July and November). One critical site in Monjolinho River (site B) was assessed in comparison to a reference site (site A). Water pH and oxygen concentration was lower than that recommended by CONAMA (Brazilian National Environmental Committee), resolution 357/2005 for protection of aquatic communities, and ammonium and the metals Cu, Zn, Mn and Fe (on all months) concentrations were higher than the maximum concentration recommended. Glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities were significantly decreased in liver and muscle in tilapia from Monjolinho River, throughout the year, in relation to reference except in gills that SOD activity increased. Glutathione S-transferase (GST) activity was significantly increased in liver of the tilapia from Monjolinho River in all sites, in relation to reference except in gills that GST activity increased in July and decreased in November, suggesting that GST activity could be induced to neutralize the pollutants toxicity. On the other hand, GST activity was significantly decreased in white muscle indicating a toxic effect of pollutants, resulting in a decreased ability of tilapia to perform defense reactions associated to GSTs. The decrease of catalase (CAT) activity in gills of the O. niloticus together with the increase of SOD activity, could explain the increased lipid peroxidation (LPO) level in this organ. Metallothionein levels in liver and gills were significantly high in all sites. Results indicate that the exposure to metals caused severe damage to tissues; despite the consensually assumed antioxidant induction as a sign of exposure to contaminants the effects seem in part to be mediated by suppression of antioxidant system with SOD, CAT and GPx as potential candidates for tissues toxicity biomarkers of pollutants.

Bioaccumulation and toxicodynamics of cadmium to freshwater planarian and the protective effect of N-acetylcysteine

Although toxic responses of freshwater planarians after exposure to environmental toxicants can be observed through external toxicological end points, physiological responses inside the bodies of treated planarians have rarely been investigated. The present study was designed, using cadmium (Cd) as a reference toxicant, to determine its bioaccumulation and toxicodynamics in the freshwater planarian, Dugesia japonica, after acute toxicity was obtained. Accumulated Cd concentrations, metallothionein levels, and the oxidative status in planarians were determined after exposure to Cd. Furthermore, we hypothesized that the acute death of Cd-treated planarians was associated with increased oxidative stress. After Cd-treated planarians were coexposed to antioxidant, N-acetylcysteine (NAC), we found that NAC protected planarians from Cd lethality by maintaining the oxidative status and decreasing the bioaccumulation of Cd. The results of the present study support planarians being used as a practical model for toxicological studies of environmental contaminants in the future.

Assessment of Toxicity of Cdse/Cds/Zns/S,S-Dihydrolipoic Acid/Polyacrylic Acid Quantum Dots at Danio rerio Embryos and Larvae

Quantum dots (QDs) are nanosized semiconductor crystals. They are currently applied in different science fields such as medicine, namely, cancer diagnostics and treatment. QD toxicity is caused by the toxicity of their components. In vivo application of QDs requires their toxicity assessment, so the purpose of this work has been the estimation of acute and chronic toxicity of the QDs at Danio rerio embryos and larvae, QDs being composed of CdSe/CdS/ZnS/S,S-dihydrolipoic acid/polyacrylic acid. We have found no QD acute toxicity during 48 hours of QDs action at the embryo up to the concentration of 185 μM Cd. QDs have been found to be toxic only at 5–7 days of action, it shows that QDs act accumulatively. Beside lethality, we have observed different larval development defects, that is, differently localized edemas, lag of development, tail curvature, and swimming bladder malformation. Our experimental data as well as literature data show that toxicity of the quantum dots at Danio rerio embryos and larvae is primarily caused by toxic action of Cd2+ ion which arises from partial dissociation of CdSe and CdS molecules.

The protective role of vitamin E on the fatty acid composition of phospholipid structure in gill and liver tissues of Oreochromis niloticus exposed to deltamethrin

Deltamethrin is a commonly used pyrethroid pesticide. Vitamin E is a antioxidant that plays an important role in protecting cells against toxicity by inactivating free radicals generated following pesticides exposure. Therefore, in the present study, it was evaluated whether deltamethrin induced changes on the fatty acid composition of phospholipid in gill and liver tissues in Oreochromis niloticus and, the possible protective effect of vitamin E against deltamethrin was determined. Fish was fed with no pesticide+control diet, no pesticide+vitamin E-supplemented diet, 1.45 μg/l deltamethrin+control diet, 1.45 μg/l deltamethrin+vitamin E-supplemented diet for twenty days. Pesticide and diet quality made an impact on the fatty acid composition of phospholipid. In treatments of deltamethrin, group fed with control diet showed much greater damage in comparison with group fed with vitamin E supplemented diet. The results indicated that the deltamethrin led to an increase in the percentages of total SFAs (saturated fatty acids) and total MUFAs (monounsaturated fatty acids) and a decrease in total PUFAs (polyunsaturated fatty acids) in the gill tissues. However, coadministration of deltamethrin and vitamin E showed decrease in the percentages of saturated fatty acids and increase in the percentages of polyunsaturated fatty acids in the gill tissues. In group fed with control diet, deltamethrin led to a decrease in the percentage of SFAs and a increase in total MUFAs in the liver. Coadministration of deltamethrin and vitamin E showed increase in the percentages of polyunsaturated fatty acids in the liver tissues. These results have demonstrated that administration of vitamin E along with deltamethrin decreases the peroxidation of unsaturated fatty acids and thus protects the cell membranes.

The effects of heart and skeletal muscle inflammation and cardiomyopathy syndrome on creatine kinase and lactate dehydrogenase levels in Atlantic salmon (Salmo salar L.)

Heart and skeletal muscle inflammation (HSMI) and cardiomyopathy syndrome (CMS) are putative viral cardiac diseases of Atlantic salmon. This study examined the levels and correlated the serum enzymes creatine kinase (CK) and lactate dehydrogenase (LDH) to the histopathology of clinical outbreaks of HSMI and chronic CMS in farmed Atlantic salmon. A total of 75 fish from 3 different HSMI outbreaks, 30 chronic CMS fish, and 68 fish from 3 nondiseased fish groups were used as the study population (N = 173). Serum CK and LDH levels correlated significantly with the total inflammation and total necrosis scores for HSMI fish (P = 0.001). However, no correlation was identified for enzyme levels and histopathology scores for chronic CMS fish. The significantly increased CK and LDH levels and their positive correlations to histopathology differentiate HSMI from CMS clinically suggesting the potential use of enzymes for screening for HSMI is promising.

Gonad differential proteins revealed with proteomics in oyster (Saccostrea cucullata) using alga as food contaminated with cadmium

As mercury and lead, cadmium (Cd) is one of the highly toxic metals in both the ocean and land environments, but its toxicological mechanism in organisms including human is still unclear because of the complex toxicological pathways in vivo. Here, the alga Chlorella vulgaris were cultivated at room temperature under the stress of cadmium (1 mg L(-1)) to obtain a toxic food, and then the contaminated food were directly supplied to oyster (Saccostrea cucullata) in seawater. After feeding with C. vulgaris contaminated with Cd (C. vulgaris-Cd), the differential proteins in the oyster gonad (OG) were effectively separated and identified with proteomic approaches. Eleven protein spots were observed to be significantly changed in the OG feeding with C. vulgaris-Cd, which seven spots of these differential proteins were down-regulated while four spots were up-regulated. These altered spots were further excised in gels and identified by a combined technique of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/TOF MS) and database searching. A portion of these differential proteins were further proofed by real-time PCR and Western blotting. The results indicate that the major functions of these differential proteins were described as follows: binding, protein translocation, catalysis, regulation of energy metabolism, reproductive function and skeleton structure. These differential proteins in part may effectively provide a few novel biomarkers for the evaluation of Cd pollution level via a food pathway for harming halobios, mammal and human health, and for understanding the complex mechanisms of Cd toxicity in vivo.

Benzo(a)pyrene induces hepatic AKR1A1 mRNA expression in tilapia fish (Oreochromis niloticus)

AKR1A1 or aldehyde reductase is a member of the aldo-keto reductases superfamily that is evolutionarily conserved among species. AKR1A1 is one of the five AKRs (AKR1A1 and 1C1-1C4) implicated in the metabolic benzo(a)pyrene (BaP) activation to reactive BaP 7,8-dione. BaP is a polycyclic aromatic hydrocarbon (PAH) widely distributed in aquatic ecosystems and its metabolic activation is necessary to produce its toxic effects. Although the presence of AKR1A1 in fish has been reported, its tissue distribution in tilapia (Oreochromis niloticus) and AKR1A1 inducibility by BaP are not known yet. Moreover, cytochrome P4501A (CYP1A) mRNA expression in fish has been used as a PAH biomarker of effect. Therefore, BaP effects on AKR1A1 and CYP1A gene expressions in tilapia, a species of commercial interest, were investigated by real-time RT-PCR. A partial AKR1A1 cDNA was identified, sequenced and compared with AKR1A1 reported sequences in the GenBank DNA database. Constitutive AKR1A1 mRNA expression was detected mainly in liver, similarly to that of CYP1A. BaP exposure resulted in statistically significant AKR1A1 and CYP1A mRNA induction in liver (20- and 120-fold, respectively) at 24 h. On the other hand, ethoxyquin (EQ) was used as control inducer for AKR1A1 mRNA. Interestingly, EQ also induced CYP1A mRNA levels in tilapia liver. Our results suggest that teleost AKR1A1, in addition to CYP1A, are inducible by BaP. The mechanism of AKR1A1 induction by BaP and its role in fish susceptibility to BaP toxic effects remains to be elucidated.

Proteasome and antioxidant responses in Cottus gobio during a combined exposure to heat stress and cadmium

Temperature and trace metals are common environmental stressors, and their importance is increasing due to global climate change and anthropogenic pollution. Oxidative damage and antioxidant properties have been studied in liver and gills of the European bullhead (Cottus gobio) subjected to cadmium (CdCl(2) at nominal concentrations of 0.01 and 1mg/L) for 4 days at either 15°C or 21°C. First, exposure to 1mg Cd/L induced a high mortality rate (67%) in fish held at 21°C. Regarding the antioxidant enzymes, exposure to 0.01 mg Cd/L significantly increased the activity of superoxide dismutase (SOD) and decreased the activity of glutathione reductase (GR) in liver, independently of heat stress. In gills, exposure to 21°C resulted in a significantly increased activity of glutathione peroxidase (GPx), whereas the activity of glutathione S-transferase (GST) was significantly reduced as compared to fish exposed to 15°C. Furthermore, regardless of Cd stress, exposure to elevated temperature resulted in a significant decrease of lipid peroxidation (LPO) level in liver and in a significant increase in the activity of chymotrypsin-like 20S proteasome in both studied tissues of C. gobio. Overall, the present results indicated that elevated temperature and cadmium exposure independently influenced the antioxidant defense system in bullhead with clear tissue-specific and stress-specific antioxidant responses. Further, elevated temperature affected the hepatic lipid peroxidation and the activity of 20S proteasome in both tissues.

Construction and characterization of a normalized cDNA library from the river snail Bellamya aeruginosa after exposure to copper

The construction of a normalized cDNA library is a popular tool for identifying novel biomarkers for monitoring environmental pollution. In the present study, a normalized cDNA library was constructed from the river snail Bellamya aeruginosa after exposure to Cu(2+) by using the SMART technique. The titer of the cDNA library was 1.78 × 10(6) pfu/ml, with a recombinant efficiency of 95.8%. In addition, from 6,000 randomly selected and sequenced clones, 5,473 high-quality ESTs were identified. After processing the sequences, 3,961 unigenes representing 897 contigs and 3,064 singlets were obtained with 27.6% redundancy. Analysis of expressed sequenced tags using COG and GO annotation and KEGG pathway data showed that a large group of genes related to growth and development, signal transduction, and defense mechanisms were present in the cDNA library. Based on our findings, this normalized cDNA library will provide a valuable resource for further research on functional genes and ecotoxicology in B. aeruginosa.

Essential metal (Cu, Zn) exposures alter the activity of ATPases in gill, kidney and muscle of tilapia Oreochromis niloticus

An acute (96 h--0.1, 0.5, 1.0, 1.5 μg/ml) and chronic (up to 30 days--0.05 μg/ml) protocols of Cu and Zn were applied to freshwater fish Oreochromis niloticus to investigate these essential metal effects on the activities of gill, kidney and muscle Na(+)/K(+)-ATPase, Mg(2+)-ATPase and Ca(2+)-ATPase. In vitro effects of both metals (20 min--0.1, 0.5, 1.0, 1.5 μg/ml) were also measured to be able to compare both exposure routes. Data showed that ATPase activities, in general, decreased following all the exposure conditions, though there were some increases especially in Mg(2+)-ATPase activity. Among the enzymes, Na(+)/K(+)-ATPase and Ca(2+)-ATPase appeared to be more sensitive than Mg(2+)-ATPase to the metals. The data also indicated that effects of Cu on ATPase activity in the tissues of O. niloticus were stronger than the effects of Zn, possibly due to higher toxic effects of Cu. In vivo and in vitro exposures of metals showed similar trends with a few exceptions, especially in the gill. Variability of ATPase activity is determined by tissue type, metal species, concentration and duration. This work showed that even essential metals can alter significantly activities of ATPases in fish and thus suggests using them as a sensitive biomarker in metal contaminated waters.

Acute effects of pure cylindrospermopsin on the activity and transcription of antioxidant enzymes in tilapia (Oreochromis niloticus) exposed by gavage

The cyanobacterial toxin cylindrospermopsin (CYN) is a widely distributed contaminant of freshwater systems with the consequent risk for human and wildlife, particularly fish. However, CYN toxicity data on fish are still scarce. It is known that CYN inhibits glutathione synthesis and this could contribute to oxidative damage. In the present work tilapia (Oreochromis niloticus) were exposed by gavage to 200 and 400 μg/kg bw of pure CYN and sacrificed after 24 h. The activity and relative mRNA expression by real-time PCR of antioxidant enzymes glutathione peroxidase (GPx) and soluble glutathione-S-transferases (sGST) and the sGST protein abundance by Western blot analysis were evaluated in liver and kidney. Also the induction of lipid peroxidation (LPO) was assayed. Results show an increase of LPO products in both organs. Moreover, CYN altered the activity, gene expression and protein abundance of the enzymes, indicating the importance of GPx and sGST in CYN pathogenicity. This is the first time that CYN is reported to affect these enzymes in fish and they have shown to be responsive biomarkers of CYN toxicity.

Ecological risk assessment of heavy metals in sediment and human health risk assessment of heavy metals in fishes in the middle and lower reaches of the Yangtze River basin

The concentrations of heavy metals (Cr, Cd, Hg, Cu, Zn, Pb and As) in the water, sediment, and fish were investigated in the middle and lower reaches of the Yangtze River, China. Potential ecological risk analysis of sediment heavy metal concentrations indicated that six sites in the middle reach, half of the sites in the lower reach, and two sites in lakes, posed moderate or considerable ecological risk. Health risk analysis of individual heavy metals in fish tissue indicated safe levels for the general population and for fisherman but, in combination, there was a possible risk in terms of total target hazard quotients. Correlation analysis and PCA found that heavy metals (Hg, Cd, Pb, Cr, Cu, and Zn) may be mainly derived from metal processing, electroplating industries, industrial wastewater, and domestic sewage. Hg may also originate from coal combustion. Significant positive correlations between TN and As were observed.

Responses of antioxidant enzymes, lipid peroxidation, and Na+/K+-ATPase in liver of the fish Goodea atripinnis exposed to Lake Yuriria water

Lake Yuriria, located in the heavily populated and polluted Mexican Central Plateau, receives domestic sewage, industrial effluents, and municipal wastewaters that are still directly discharged without treatment into the tributaries and the lake. Pollutants in water and sediments include heavy metals, aromatic hydrocarbons, and organochlorine pesticides. Activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), as well as Na⁺/K⁺-adenosine triphosphatase (Na⁺/K⁺-ATPase) activity, and lipid peroxidation (LPO) were evaluated in the livers of the fish Goodea atripinnis after 96 h of exposure to water collected in March and June 2005 from three sites: Y (limnetic zone), L (Lerma tributary), and C (la Cinta tributary). Physical and chemical parameters of the lake water were also analyzed. Increases in CAT activity and LPO levels at all three sites were detected compared with control fish (P < 0.05), while GPx and SOD activities decreased significantly (P < 0.05). Na⁺/K⁺-ATPase activities were similar to the control in fish exposed to limnetic water from both March and June but were higher than control at the two tributary sites in March (P < 0.05); fish exposed to water from the Lerma tributary in June exhibited lower Na⁺/K⁺-ATPase than the control (P < 0.05). During March, CAT and Na⁺/K⁺-ATPase activities were increasing more than in June in Y and L, respectively, while in June, SOD and GPx were depleted more than March in L and Y and L, respectively. Despite the antioxidant defenses of the fish liver, exposure to all water samples from Lake Yuriria exerted alterations in hepatic LPO levels, antioxidant enzymes, and Na⁺/K⁺-ATPase activities that could substantially impair the mechanisms of fish defenses against oxidative stress.

Physiological effects of nanoparticles on fish: a comparison of nanometals versus metal ions

The use of nanoscale materials is growing exponentially, but there are also concerns about the environmental hazard to aquatic biota. Metal-containing engineered nanoparticles (NPs) are an important group of these new materials, and are often made of one metal (e.g., Cu-NPs and Ag-NPs), metal oxides (e.g., ZnO and TiO(2) NPs), or composite of several metals. The physiological effects and toxicity of trace metals in the traditional dissolved form are relatively well known and the overall aim of this review was to use our existing conceptual framework of metal toxicity in fish to compare and contrast the effects of nanometals. Conceptually, there are some fundamental differences that relate to bioavailability and uptake. The chemistry and behaviour of nanometals involves dynamic aspects of aggregation theory, rather than the equilibrium models traditionally used for free metal ions. Some NPs, such as Cu-NPs, may also release free metal ions from the surface of the particle. Biological uptake of NPs is not likely via ion transporters, but endocytosis is a possible uptake mechanism. The body distribution, metabolism, and excretion of nanometals is poorly understood and hampered by a lack of methods for measuring NPs in tissues. Although data sets are still limited, emerging studies on the acute toxicity of nanometals have so far shown that these materials can be lethal to fish in the mg-μgl(-1) range, depending on the type of material. Evidence suggests that some nanometals can be more acutely toxic to some fish than dissolved forms. For example, juvenile zebrafish have a 48-h LC(50) of about 0.71 and 1.78mgl(-1) for nano- and dissolved forms of Cu respectively. The acute toxicity of metal NPs is not always explained, or only partly explained, by the presence of free metal ions; suggesting that other novel mechanisms may be involved in bioavailability. Evidence suggests that nanometals can cause a range of sublethal effects in fish including respiratory toxicity, disturbances to trace elements in tissues, inhibition of Na(+)K(+)-ATPase, and oxidative stress. Organ pathologies from nanometals can be found in a range of organs including the gill, liver, intestine, and brain. These sublethal effects suggest some common features in the sublethal responses to nanometals compared to metal salts. Effects on early life stages of fish are also emerging, with reports of nanometals crossing the chorion (e.g., Ag-NPs), and suggestions that the nano-forms of some metals (Cu-NPs and ZnO NPs) may be more toxic to embryos or juveniles, than the equivalent metal salt. It remains possible that nanometals could interfere with, and/or stimulate stress responses in fish; but data has yet to be collected on this aspect. We conclude that nanometals do have adverse physiological effects on fish, and the hazard for some metal NPs will be different to the traditional dissolved forms of metals.

Influence of acute cadmium exposure on the liver proteome of a teleost fish, ayu (Plecoglossus altivelis)

Cadmium (Cd) is a toxic heavy metal that causes the disruption of a variety of physiological processes. In this study, the effect of Cd on liver proteome of ayu, Plecoglossus altivelis, was investigated by two-dimensional gel electrophoresis (2-DE) and matrix assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF-MS/MS). Twenty-three altered protein spots were successfully identified. They were involved in oxidative stress response, metal metabolism, methylation, and so on. The mRNA expression of 60S acidic ribosomal protein P0, heat shock protein 70, apolipoprotein A-I, betaine-homocysteine S-methyltransferase, parahox cluster neighbor, and transferrin was subsequently determined by real-time PCR. The mRNA expression of these genes was consistent with proteomic results. These findings enrich our knowledge on the influence of Cd toxicity to teleost fish, and may be worthy of further investigation to develop biomarkers.

Expression of superoxide dismutase (SOD) genes from the copper-exposed polychaete, Neanthes succinea

To evaluate the superoxide dismutase (SOD) genes as a potential indicator of environmental stress, we cloned and sequenced the full-length cDNA of a Cu/Zn-SOD and Mn-SOD genes from the marine polychaete, Neanthes succinea. Ns-Cu/Zn- and Mn-SOD expression was measured using quantitative real-time RT-PCR in response to the oxidative stress induced by copper in the form of CuCl2. Ns-Cu/Zn-SOD expression increased in a dose dependent manner but the increase of Mn-SOD expression was evident only at a high concentration of copper. Particularly, Ns-Mn-SOD dramatically increased in the 72 μg/L CuCl2-exposed groups, indicating that both Ns-SOD genes were induced by copper exposure. These results suggest that Ns-Cu/Zn- and Ns-Mn-SOD would play important roles in the detoxification of cellular oxidative stresses in the polychaete, N. succinea. Furthermore, as part of field work, the marine polychaete, N. succineaCu/Zn-SOD mRNA collected from the polluted area was accordingly upregulated in expression but not for NS-Mn-SOD.

Toxins and stress in fish: proteomic analyses and response network

Fish models are increasingly used in toxicological studies in the laboratory as well as in the field. In addition to contributing to the analysis of toxicity mechanisms, one major aim is to select biomarkers from among the metabolic responses to toxic agents observed that could be useful for surveying the aquatic environment. Since proteomics is a developing field in toxicological research, it seems opportune to explore the data obtained using this approach. This article proposes an overview of proteomic studies of fish exposed to environmental stressors comprising a cyanotoxin and the response networks observed. We tend to take a broad view of how proteins communicate and function within the cell, often encompassing large numbers of proteins that operate in pathways. We start by presenting and discussing the data from four experiments in which the medaka fish was treated under the same conditions with the cyanotoxin, microcystin-LR (MC-LR). Liver proteins were analyzed using two techniques: 2D electrophoresis and LCMSMS. In the second and main part of our paper, the proteomic data obtained from fish contaminated with chemicals, including those reported above concerning the medaka fish intoxicated with MC-LR, are considered in the round in order to identify fish responses to chemical stress. A tentative general overview of how groups of proteins work together depending on exposure and/or subcellular location is proposed, with the inclusion of MC-LR data obtained in mice for comparison.

Pathogenicity and oxidative stress in Nile tilapia caused by Aphanomyces laevis and Phoma herbarum isolated from farmed fish

Identified (n = 17) and unidentified (n = 1) fish-pathogenic fungal species from 10 genera of Oomycetes and soil fungi were isolated from 40 infected freshwater fish samples of the species Oreochromis niloticus niloticus (Nile tilapia) and Clarias gariepinus (African catfish). Samples were collected from various fish farms in the Nile Delta, Egypt. Nile tilapia were tested in aquaria for their susceptibility to the commonest Oomycetes species, Aphanomyces laevis and Achlya klebsiana, and also against the 2 most prevalent pathogenic soil fungi, Paecilomyces lilacinus and Phoma herbarum. Two techniques were used: water bath exposure and intramuscular (subcutaneous) injection. Water bath exposure to the 2 species of Oomycetes caused greater mortalities of O. niloticus niloticus than intramuscular injection, but the reverse was true of the soil fungal species. Regardless of the infection method, the 2 Oomycetes species were more potent pathogens than the soil fungal species. In both gills and mytomal muscles of fish infected by A. laevis and P. herbarum, we measured and compared with controls the oxidative stress parameters total peroxide (TP), lipid peroxidation (LPO) and nitric oxide (NO), as well as levels of the antioxidants vitamin E and glutathione (GSH), and superoxide dismutase (SOD) and catalase (CAT) activities. Infection by these 2 fungal species through either spore suspension or spore injection significantly increased oxidative damage in gills and induced marked decrease in most studied antioxidants. In addition, both routes showed similar effects and A. laevis depressed the antioxidants CAT, vitamin E and GSH more than P. herbarum.

Effects of cadmium on some haematological and biochemical characteristics of Oreochromis niloticus (Linnaeus, 1758) dietary supplemented with tomato paste and vitamin E

The present study investigates the potential protective effects of tomato paste (9 mg/kg-lycopene) in comparison with vitamin E (50 mg/kg) against the impacts of cadmium (Cd) toxicity (4.64 mg/l: ¼ of 96 h LC50) on fishes Cd exposed for 15 and 30 days. Cd impacts were evaluated in terms of biological, haematological and biochemical characteristics. Cd significantly induced free radicals in serum and liver. The activities of aspartate aminotransferase and alanine aminotransferase in serum were significantly increased due to Cd. Treatment with Cd caused a significant increase in Lipid peroxidation and DNA fragmentation in liver tissue and serum glucose and total lipid. On the other hand, Cd significantly led to decline in serum total protein, blood haemoglobin, red blood cell count, haematocrit value, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration. Dietary supplementation with vitamin E and/or tomato paste to Cd-exposed fish declined significantly the increased lipid peroxidation and DNA fragmentation in liver tissue and the increased aspartate aminotransferase, alanine aminotransferase, glucose and total lipid in serum to the normal condition. This supplementation also significantly increased the declined serum total protein, blood haemoglobin, red blood cell count, haematocrit value, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration to the normal state. Cd impacts and tomato paste/or vitamin E supplementations did not reflected on the condition factor of the fish. These findings demonstrated the beneficial diet supplementation of tomato paste phytonutrients and vitamin E in counteracting the harmful effects of Cd on the characters investigated.

Molecular cloning and differential expression patterns of copper/zinc superoxide dismutase and manganese superoxide dismutase in Hypophthalmichthys molitrix

Copper/zinc superoxide dismutase (Cu,Zn-SOD) cDNA and manganese superoxide dismutase (Mn-SOD) cDNA were first cloned from silver carp Hypophthalmichthys molitrix using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) method. The open reading frame (ORF) of Cu,Zn-SOD is 465 bp and encodes a 154 amino acids (aa) protein, whereas the ORF of Mn-SOD is 675 bp and encodes a 224 aa protein. Multiple polypeptide sequence alignment showed high identity both of Cu,Zn-SOD (70-87%) and Mn-SOD (80-96%) with the species compared. Both Cu,Zn-SOD and Mn-SOD were detected in heart, brain, liver, kidney, spleen, muscle, gill and blood. Cu,Zn-SOD and Mn-SOD were expressed throughout the embryogenesis, indicating their important roles during embryonic development specially at the cleavage stage. Acute hypoxia suppressed expression of Cu,Zn-SOD and Mn-SOD in liver significantly, up-regulated them in gill relatively, indicating that tissue-specific expression of Cu,Zn-SOD and Mn-SOD is an important stress response adapted to hypoxia.

DNA damage and effects on antioxidative enzymes in zebra fish (Danio rerio) induced by atrazine

The effect of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1, 3, 5-triazine) on the activity of some antioxidative enzymes (superoxide dismutase, SOD; catalase, CAT; and guaiacol peroxidase, POD) and DNA damage induced by atrazine were investigated in zebra fish (Danio rerio). Zebra fish were exposed to four different concentrations of atrazine (0, 2.5, 5, and 10 mg/L) for 7, 14, and 21 days, with three replicates of 10 fishes per treatment. Compared to the controls, the SOD activity in the 2.5 mg/L treatment was markedly stimulated in 21 days, while the SOD activities in the 5 mg/L treatment was stimulated at first and then inhibited. The change of CAT activity at 2.5 mg/L was similar to the SOD activity at 2.5 mg/L. The POD activities in the 2.5, 5, and 10 mg/L treatment were markedly higher on days 14 and 21 compared with the controls. The olive tail moments of single-cell gel electrophoresis (SCGE) of zebra fish enhanced after treatment of different doses on days 7, 14, and 21, and significant differences were found compared to the controls. In conclusion, these findings showed the effect regularity of atrazine to zebra fish, and also provide the basis for the future research of adverse effects induced by atrazine in aquatic ecosystems.

Response of antioxidant system of freshwater fish Oreochromis niloticus to acute and chronic metal (Cd, Cu, Cr, Zn, Fe) exposures

Antioxidant systems are known to be sensitive to metal exposures and are suggested to use in predicting sublethal metal toxicity. In this study, several antioxidant enzymes, such as catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), glutathione peroxidase (GPX) and glutathione reductase (GR) were measured in the liver and kidney of Oreochromis niloticus exposed to sublethal concentrations of metals (Cd, Cu, Cr, Zn and Fe), using an acute (20 μM, 48 h) or subchronic (10 μM, 20 d) protocol. Beside the several increases of antioxidant enzyme activities, general inhibition was recorded after acute and chronic metal exposures. Results indicated that there were variations in responses of the enzymes to metal exposures, depending upon tissues, metals and exposure types. This study emphasized that the antioxidant enzymes are very sensitive to metals as their activities altered significantly, suggesting they could be helpful in predicting sublethal metal toxicity and useful as an early warning tool in natural monitoring studies.

Antioxidative role of cerium against the toxicity of lead in the liver of silver crucian carp

The antioxidative role of cerium was investigated in the liver of silver crucian carp injected with lead. The fish were intraperitoneally injected with 10, 20, or 30 mg/kg wet weight PbCl(2). After a 14-day period of incubation, 35 animals were injected with a solution of 1.5 mg/kg wet weight CeCl(3). After 42 days, the wet weight and the liver weight of the fish were weighed, and the oxidative stress of the fish liver was estimated by assaying lipid peroxide, superoxide dismutase, catalase, ascorbate peroxidase, glutathione peroxidase, glutathione, ascorbic acid, and reactive oxygen species (ROS). The results show that Ce(3+) could decrease ROS accumulation, relieve the inhibition of the activities of the antioxidant enzyme and the reduction of antioxidants in fish liver caused by Pb(2+), and decrease the enhancement of hepatosomatic index of fish under various Pb(2+) dosages.

Effects of crude oil and oil fractions on the liver P450-dependent monooxygenase activities and antioxidant defence system of different freshwater fish species

The effects of crude oil (Szeged-Algyo, Hungary) and oil fractions (F1: rich in aromatics; F2 fraction: free from aromatics) were investigated on liver CYP1A isoenzymes and antioxidant defence system following their i.p. injection into different freshwater fish species: carp (Cyprinus carpio L.), silver carp (Hyphothalmichtys molitrix V.), and European eel (Anquilla anquilla). A dose of 2 mL kg -1 crude oil enhanced EROD activity 8-fold in carp and only 5-fold in eel after 3 days. Oil fraction F1 caused only a 2-fold induction in EROD activity only in carp, while F2 fraction caused significant inhibition in all three investigated fish species. The antioxidant parameters [lipid peroxidation (LP), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione (GSH)] were measured following the treatment. A decrease of 50% in CAT activity was observed after oil treatment. The GSH level enhanced, resulting the protective effects against LP. The same dose of crude oil but a longer duration time resulted in lower CYP1A induction in carp and antioxidant parameters had returned close to control. In all treatments the EROD isoenzymes proved to be more sensitive and the effects of oil treatment showed species to be different. Carp proved to be more sensitive than eel or silver carp.

Oxidative stress and antioxidant enzymes in liver and white muscle of Nile tilapia juveniles in chronic ammonia exposure

Oxidative stress and antioxidant enzyme activities in liver and white muscle of Nile tilapia (Oreochromis niloticus) juveniles (10+/-1.2g) in chronic exposure to sublethal total ammonia nitrogen (TAN) were studied. The fish were exposed to the TAN concentrations, 5 mg L(-1) (low) or 10 mg L(-1) (high) for consecutive 70 days at 26+/-0.5 degrees C temperature. At the end of experimental period, lipid peroxidation and protein carbonylation levels and the activities of xanthine oxidase (XO), aldehyde oxidase (AO), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), glutathione reductase (GR), gamma-glutamyl cysteinyl synthetase (gamma-GCS), and gamma-glutamyl transpeptidase (gamma-GT) in liver and white muscle were assayed. The levels of oxidative stress biomarkers and the activities of the enzymes assayed were significantly increased in liver and white muscle of fish exposed to both low and high TAN levels. The changes in these parameters were intensified at high TAN level. The significance of these alterations in enzyme activities is discussed.

An EST resource for tilapia based on 17 normalized libraries and assembly of 116,899 sequence tags

BACKGROUND

Large collections of expressed sequence tags (ESTs) are a fundamental resource for analysis of gene expression and annotation of genome sequences. We generated 116,899 ESTs from 17 normalized and two non-normalized cDNA libraries representing 16 tissues from tilapia, a cichlid fish widely used in aquaculture and biological research.

RESULTS

The ESTs were assembled into 20,190 contigs and 36,028 singletons for a total of 56,218 unique sequences and a total assembled length of 35,168,415 bp. Over the whole project, a unique sequence was discovered for every 2.079 sequence reads. 17,722 (31.5%) of these unique sequences had significant BLAST hits (e-value < 10(-10)) to the UniProt database.

CONCLUSION

Normalization of the cDNA pools with double-stranded nuclease allowed us to efficiently sequence a large collection of ESTs. These sequences are an important resource for studies of gene expression, comparative mapping and annotation of the forthcoming tilapia genome sequence.

Individual and combined effects of heavy metals on serum biochemistry of Nile tilapia Oreochromis niloticus

Changes in serum biochemistry in response to single- and combined-metal exposure were studied in a freshwater fish Oreochromis niloticus. Fish were exposed to 5.0 mg/L Zn, 1.0 mg/L Cd, and 5.0 mg/L Zn+1.0 mg/L Cd mixtures for 7 and 14 days to determine levels of biochemical parameters and metals in blood serum. The individual and combined effects of metals caused an increase in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities and in levels of albumin, transferrin, ceruloplasmin, cortisol, glucose, and total protein, whereas they caused a decrease in cholesterol levels. At both exposure periods, increased ALT activity of fish exposed to Cd was higher compared with the Zn and Zn+Cd groups, respectively. The decreased cholesterol level was higher in the Cd alone, and for Cd in combination with Zn, than in Zn alone at 14 days. Zn or Cd levels increased in the blood serum of fish exposed to metals individually or in combination. When fish were exposed to the mixtures of Zn+Cd, concentrations of these metals in their serum were lower than in fish exposed to individual metals. One metal blocks or even antagonizes the gill epithelium absorption of the other and thereby limits the distribution of the metal in blood. The results indicate that biochemical parameters in fish blood can be used as an indicator of heavy-metal toxicity.

Inorganic mercury exposure: toxicological effects, oxidative stress biomarkers and bioaccumulation in the tropical freshwater fish matrinxã, Brycon amazonicus (Spix and Agassiz, 1829)

Alterations in the antioxidant cellular system have often been proposed as biomarkers of pollutant-mediated toxicity. This study evaluated the effects of mercury on oxidative stress biomarkers and bioaccumulation in the liver, gills, white muscle and heart of the freshwater fish matrinxã, Brycon amazonicus, exposed to a nominal and sub-lethal concentration (~20% of 96 h-LC(50)) of 0.15 mg L(-1) of mercury chloride (HgCl(2)) for 96 h in a static system. Increases in superoxide dismutase, catalase, glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione reductase (GR) were observed in all tissues after HgCl(2) exposure, except for white muscle GR activity and hepatic GPx. In the liver and gills, the exposure to HgCl(2) also induced significant increases in reduced glutathione (GSH). Conversely, exposure to HgCl(2) caused a significant decrease in the GSH levels and an increase in the oxidized glutathione (GSSG) content in the white muscle, while both GSH and GSSG levels increased significantly in the heart muscle. Metallothionein concentrations were significantly high after HgCl(2) exposure in the liver, gills and heart, but remained at control values in the white muscle. HgCl(2) exposure induced oxidative damage, increasing the lipid peroxidation and protein carbonyl content in all tissues. Mercury accumulated significantly in all the fish tissue. The pattern of accumulation follows the order gills > liver >> heart > white muscle. In conclusion, these data suggest that oxidative stress in response to inorganic mercury exposure could be the main pathway of toxicity induced by this metal in fish.

A study on biochemical changes in the penaeid shrimp, Metapenaeus monoceros (Fabricius) following exposure to sublethal doses of organochlorine pesticide (endosulfan)

Endosulfan, a broad-spectrum non-systemic organochlorine (OC) pesticide is extensively used to control a wide variety of pests in agriculture, horticulture and public health programmes. Biochemical changes occurring in the metabolically active tissues of gills (GL), hepatopancreas (HP) and muscle (MU) of the penaeid shrimp, Metapenaeus monoceros (Fabricius) on exposure to two sublethal doses (40 and 60 ng L(-1)) of endosulfan were studied for 23 days of exposure (DoE). Sublethal doses of endosulfan significantly (P<0.05) altered the levels of the total protein (TP), the total carbohydrates (TC), the glycogen (GLY), the total free sugars (TFS) and the total lipids (TL) in test shrimps. Concentrations of biochemical components significantly varied with the DoE but were dose-independent (P<0.05). Percent decrease in all biochemical components increased with the progress of the DoE irrespective of the exposure concentrations. The order of percent decrease in the concentrations of the TP, TC, GLY, TL and TFS in different tissues at the end of 23 DoE was found to be MU>GL>HP, HP>GL>MU, MU>HP>GL, HP>MU>GL and MU>GL>HP, respectively. The results of the study revealed that sublethal doses of endosulfan significantly alters the proximate composition of major tissues, particularly the TP levels in the MU tissues thereby reducing the nutritive value of this economically important penaeid shrimp. Since M. monoceros exhibits significant biochemical changes on exposure to endosulfan, this species could possibly be used as biosensor of coastal marine and estuarine pollution by OCs.

Time-dependent protective efficacy of Trolox (vitamin E analog) against microcystin-induced toxicity in tilapia (Oreochromis niloticus)

Microcystins (MCs), hepatotoxins from cyanobacteria, induce oxidative stress and pathological changes in fish that can be ameliorated with chemoprotectants such as vitamin E (vit E). This study investigated the time period after MCs exposure in which Trolox, a vitamin E analog, is effective against oxidative and histological damage in different organs of tilapia (Oreochromis niloticus). Fish were fed Trolox supplement (700 mg/kg diet) for 7 days, or received only commercial fish food, and then were exposed to a single oral dose of 120 microg/fish microcystin-LR, and sacrificed in 24, 48, or 72 h. The Trolox protective efficacy was evaluated based on lipid peroxidation (LPO), protein oxidation, enzymatic and non-enzymatic antioxidants, and a morphologic study. Regarding the oxidative stress biomarkers altered by MCs, the higher protective action of Trolox was observed 24 h post toxin exposure, although it extends also until 48 h in gills (superoxide dismutase (SOD), catalase (CAT)), and liver, where glutathione reductase (GR) backed to control values 48 and 72 h after the toxin application. Glutathione-S- transferase (GST) activity in the liver was ameliorated by the chemoprotectant after 24 and 48 h, although control values were not recovered. Trolox modulation of these biomarkers and its ability to quench free radicals explain the recovery of LPO values in all organs at 24 h and also in gills at 48 h. Histopathologically, Trolox efficacy was more evident after 72 h.

Biochemical response of the copepod Tigriopus japonicus Mori experimentally exposed to cadmium

The response of the copepod (Tigriopus japonicus Mori) to cadmium (Cd) additions was investigated under laboratory-controlled conditions in a 12-day exposure. Superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione-S-transferase (GST), acetylcholinesterase (AchE), reduced glutathione (GSH), the ratio of reduced to oxidized glutathione (GSH/GSSG), and metallothionein (MT) were analyzed for Cd treatments (0, 10, 20, 40, and 100 microg/L) after exposure for 1, 4, 7, and 12 days. Additionally, thiobarbituric reactive species assay was used to evaluate lipid peroxidation (LPO) of the copepod after the 12-day exposure. The results indicated that Cd treatments significantly influenced the biochemical indexes (SOD, GPx, GST, AchE, GSH, and GSH/GSSG) after certain exposure times. Exposure to Cd induced LPO in the treated copepods, hinting that the copepods had suffered from oxidative damage. During exposure, the Cd initiated an induced MT synthesis in the copepods by day 7, which peaked at day 12 and which was probably responsible for Cd detoxification. Thus, Cd exposure significantly affected the detoxification process and antioxidant system of this copepod, and T. japonicus could be used as a suitable bioindicator of exposure to Cd using SOD, GPx, GST, LPO, and GSH/GSSG as biomarkers.

Joint stress of copper and petroleum hydrocarbons on the polychaete Perinereis aibuhitensis at biochemical levels

Responses of the polychaete Perinereis aibuhitensis Grube to single and joint stress of copper (Cu) and petroleum hydrocarbons (PHCs) at biochemical levels (including superoxide dismutases, SOD; peroxidases, POD; and the content of total soluble protein, TSP) were investigated under controlled laboratorial conditions. Significant decreases in SOD activity in the first 3 days of single exposure to Cu or PHCs were observed. Although SOD activity increased and returned to the level of the control on day 6 after having decreased on day 3 under single stress of Cu or PHCs, Cu and PHCs had complicated interactive influences on SOD activity in P. aibuhitensis. Their joint effects on SOD activity depended on concentration combinations and exposure time, called double-dose dependent effects. The POD activity and the content of TSP remained generally constant under both single and joint stress of Cu and/or PHCs, compared with the control. The beef-witted responses of investigated biochemical parameters in this study might suggest that toxic effects of pollutants with emphasis on the action of abiotic parameters and the time factor on the antioxidant enzymes in the polychaete should be addressed in the future work.