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An experiment was conducted to mitigate mercury and ammonia toxicity (Hg + NH₃) in Oreochromis niloticus (GIFT strain) using selenium nanoparticles (Se-NPs). The Se-NPs were synthesized using green methods, employing fish waste as the substrate. Experimental diets were prepared by supplementing Se-NPs at 0, 0.3, and 0.6 mg kg⁻¹. The oxidative stress enzymes, including catalase (CAT) and glutathione peroxidase (GPx), in the liver and kidney tissues were significantly reduced by Se-NPs at 0.3 and 0.6 mg kg⁻¹ under Hg + NH₃ stress compared to the control and stressor in 20 and 40 day periods. Additionally, superoxide dismutase (SOD) activity in the kidney at 20 days and in the liver at 40 days was significantly reduced by supplementation of Se-NPs under similar conditions. The activity of acetylcholine esterase (AChE), was significantly inhibited by Hg + NH₃ toxicity. Whereas, AChE activity was enhanced by Se-NPs supplementation at 0.3 and 0.6 mg kg⁻¹ during 20 and 40 day intervals. The gene expression of HSP70, iNOS, CYP450, Caspase-3a, and TNFα in liver tissue, and MYST in muscle tissue was upregulated by Hg+NH₃ toxicity. However, this upregulation was significantly downregulated by supplementation of Se-NPs at 0.3 and 0.6 mg kg⁻¹ under Hg + NH₃ stress. Moreover, immunoglobulin (Ig) and growth hormone (GH) levels were noticeably upregulated with Se-NPs compared to the control and Hg+NH₃ stress. The activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and malate dehydrogenase (MDH) in liver and gill tissues, were significantly elevated by Hg+NH₃ toxicity, were reduced by Se-NPs diet. Conversely, digestive enzyme activities, including protease, amylase, and lipase, were significantly enhanced by Se-NPs under stress conditions. Dietary supplementation with Se-NPs at 0.3 and 0.6 mg kg⁻¹ improved growth performance parameters such as final weight gain percentage, feed conversion ratio, protein conversion ratio, specific growth rate, daily growth index, and relative feed intake compared to the control and other groups. DNA damage, assessed in terms of tail DNA percentage, was significantly reduced with Se-NPs supplementation. Additionally, mercury detoxification was significantly enhanced with Se-NPs-supplemented diets. In conclusion, this study demonstrates that dietary Se-NPs effectively alleviate the adverse effects of mercury and ammonia toxicity by modulating antioxidant status, enhancing immunomodulation, and mitigating stress biomarker impacts through changes in gene expression in fish., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier B.V. All rights reserved.)

This study evaluated the effects of Biocide, containing silicon tetrahedrons and organic acids, on growth performance, feed utilization, immune response, and oxidative status in Nile tilapia (Oreochromis niloticus). A total of 300 Nile tilapia fingerlings (initial weight: 3.55 ± 0.01 g) were distributed across 15 tanks and fed diets containing 0.0 (control), 0.25, 0.5, 1, and 2 g kg⁻¹ Biocide for 90 days, with three replicate tanks per treatment. Biocide is enriched with organic acids (fumaric acid and citric acid) and amino acids (glutamine, tyrosine, methionine, serine, and threonine). Fish fed Biocide-supplemented diets demonstrated significantly improved growth performance, with the highest weight gain, feed conversion ratio, and protein efficiency ratio observed in the 1 g kg⁻¹ group. Survival rates did not differ significantly among treatments. Whole-body crude protein content peaked in the 1 g kg⁻¹ group, while moisture, lipid, and ash contents remained unchanged. Hematological parameters, including red blood cell count, hemoglobin concentration, and packed cell volume, improved significantly. Serum lipid profiles showed reduced cholesterol, triglycerides, low-density lipoprotein, and very-low-density lipoprotein levels, alongside increased high-density lipoprotein levels, particularly in the 1 g kg⁻¹ group. Antioxidant enzyme activities (catalase, glutathione peroxidase) and total antioxidant capacity were significantly elevated in the liver and intestine, while malondialdehyde levels decreased. Digestive enzyme activities (amylase, lipase, and protease) were markedly enhanced. Histopathological analysis revealed improved liver, stomach, and intestinal morphology, including increased mucous secretion and enhanced intestinal villi structure, in fish fed 1 g kg⁻¹ Biocide. In conclusion, Biocide supplementation, particularly at 1 g kg⁻¹, significantly improved growth performance, feed utilization, immune function, and antioxidant capacity in Nile tilapia. Notably, the findings highlight Biocide's primary mode of action on gut health, underscoring its potential as a dietary additive for improving aquaculture productivity., Competing Interests: Declarations. Competing interests: The authors declare no competing interests. Ethical approval: The study was approved and performed in accordance with the guidelines and regulations set by Agriculture Research Center, Egypt (Approval No. ARC/CLAR/89/24). The animal experiments adhered to the regulations and guidelines of ARRIVE ( https://arriveguidelines.org/ ). Consent for publication: Not applicable., (© 2025. The Author(s).)

A feeding trial for 8 weeks was performed to explore whether nutritional supplementation of L-carnitine may minimize the adverse effects of high-fat diet (HFD) on tilapia growth performance, antioxidant, immune parameters, inflammatory response, histopathology of liver, kidney, and intestine, as well as hepatic lipid metabolism aiming to reveal the mechanism and providing a shred of molecular evidence in Nile tilapia (Oreochromis niloticous). Six groups of the Nile tilapia (17.13 ± 0.49 g) in triplicate were fed for 60 days. Six experimental diets were formulated, incorporating different concentrations of L-carnitine. The first three groups were administered a diet comprising 6% fat, with L-carnitine concentrations of 0, 0.5, and 1 g/kg diet was designated as F6Car0, F6Car0.5, and F6Car1, respectively. Moreover, the fourth, fifth, and sixth groups were fed on a diet containing 12% fat, with L-carnitine concentrations of 0, 0.5, and 1 g/kg diet, respectively termed F12Car0, F12Car0.5, and F12Car1. The main results were as follows: compared to the control group HFD caused a significant reduction in BWG and PER (P > 0.05), but significantly increased the feed conversion rate (FCR), hepatosomatic index (HSI), intraperitoneal fat (IPF), as well as increased visceral fat deposits and liver fat accumulation with higher activities of serum aminotransferases, glucose, triglycerides, and cholesterol. HFD exacerbates hepatic lipid accumulation by enhancing lipogenic gene expression. HFD-fed fish exhibited the lowest crude protein and highest crude fat levels. This study demonstrates that dietary supplementation with L-carnitine significantly boosts growth, improves hemato-biochemical parameters, decreases lipogenesis, elevates lipolysis pathway genes, and lowers lipid levels, thereby rebalancing lipid metabolism and lessening hepatic steatosis. It also mitigates inflammation by downregulating pro-inflammatory genes, upregulating immune genes, and positively affecting Nile tilapia's histopathology., Competing Interests: Declarations. Consent to participate: Not applicable. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2025. The Author(s), under exclusive licence to Springer Nature B.V.)

The point of our study was to examine the interaction of ammonia-N poisoning and salinity on serum enzymes and oxidative stress factors of blood and liver in Nile tilapia (Oreochromis niloticus). The 50% lethal concentration (LC 50 ) in 96 h was 0.86 mg/L of ammonia-N. A random allocation was used to divide the fish into 12 treatments. These treatments encompassed various combinations of acute ammonia-N levels (0 and 50% of LC 50 -96 h), sub-acute ammonia-N levels (30% of LC 50 -96 h), and salinity levels (0, 4, 8, and 12 ppt). The experimental design employed a factorial arrangement of 3 × 4.The findings revealed that the amounts of aspartate transferase (AST) and alanine transaminase (ALT) in treatments 3 and 4 increased significantly compared to the treatment 2 (4 ppt) and control. Salinity levels did not affect serum glutathione levels (GSH), nevertheless the reduction of serum GSH and levels of total antioxidant capacity (TAC) and superoxide dismutase (SOD) and catalase activities (CAT) in ammonia poisoning treatments, 5 and 9, compared to the control, states ammonia can stimulate oxidative stress in fish. Similar to the serum measurements, increasing salinity in acute ammonia poisoning treatments (5, 6, 7 and 8) caused an increasing effect on the liver TAC value, which was presumably due to the improving effect of salinity in reducing ambient ammonia. The findings indicate that while elevated salinity levels can be beneficial in mitigating the effects of ammonia toxicity in water, the combined presence of salinity, ammonia, and their interaction had detrimental impacts on the physiological well-being of fish over a 96-hour testing period., Competing Interests: Declarations. Competing interests: The authors declare no competing interests. Ethics approval: This research was carried out according to the standards of the animal protection and ethics committee of Shahid Chamran University, Ahvaz, Iran., (© 2024. The Author(s).)

Generally, energy expenditure and compensation according to food deprivation and refeeding often occur along the life cycle of farmed-raised fish. Fasting and refeeding are also hypothesised to modulate carbohydrate metabolism particularly for herbivorous and/or omnivorous. This study aims to investigate the effects of short-term fasting and subsequent refeeding with high or low-carbohydrate diets on the intermediary carbohydrate metabolism of juvenile and adult Nile tilapia (Oreochromis niloticus) which is known to be a good user of carbohydrate as an energy source. Fish were fasted for 4 days and subsequently refed with either a low carbohydrate and high protein (LC/HP) or high carbohydrate and low protein (HC/LP) diet for 4 days. Our results showed that 4 days of refeeding with either one of the diets could compensate for weight loss due to fasting. Thus, we investigated the effects of a 4-day-refeeding strategy and different carbohydrate-refeeding diets on plasma metabolites, nutrient composition, and glucose and its related metabolism in the liver and muscle of adult fish. Refeeding had similar effects in adults and juveniles and induced modulations to the intermediary metabolism: (1) refeeding with the HC/LP diet elevated plasma glucose levels; (2) refeeding with both diets increased triglyceride levels in the plasma, liver, and muscle, but the effect of the HC/LP diet was superior; (3) refeeding elevated plasma cholesterol levels in adults, irrespective of diet; (4) refeeding with both diets increased hepatic lipid levels in juveniles, with stronger effects observed in those fed the HC/LP diet, and refeeding with the HC/LP diet elevated hepatic lipid levels in adults; (5) refeeding with both diets increased the plasma protein content, but the effect of the LC/HP diet was superior; (6) refeeding with the LC/HP diet increased hepatic protein content in adults; and (7) refeeding with both diets increased hepatic glycogen levels, but the effect of the HC/LP diet was superior. Additionally, in juveniles and adults, refeeding with the HC/LP diet upregulated the expression of glycolytic genes in the liver and muscle, lipogenic genes in the liver, and glucose transport genes. Moreover, refeeding with the HC/LP diet downregulated the expression of gluconeogenic and amino acid catabolism genes in the liver and amino acid catabolism genes in the muscle. Collectively, the effect of short-term refeeding with a high carbohydrate diet on intermediary metabolism resembled that of long-term feeding, supporting the hypothesis that Nile tilapia, an omnivorous fish, is highly responsive to dietary carbohydrates., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Background: Hypoxia stress resulted in mortality during the fish aquaculture program, affecting the sustainable development of the aquaculture industry. The Egyptian strain of O. niloticus showed a strong ability to hypoxia. In this study, a Nile tilapia strain that was kept and selected for 45 years by the author's team was used to elucidate the mechanism of the hypoxia response in the liver, including the identification of metabolic pathways and genes, involved in the hypoxia response of this strain., Results: The effects of hypoxia stress were detected at 0-hour, 6-hour, and 72-hour time points (0 h, 6 h, 72 h) on tilapia liver at 1 mg/L dissolved oxygen conditions. The blood triglyceride, blood glucose and cholesterol values exhibited significantly different change trends, but the hemoglobin content showed no significant differences between 0 h, 6 h and 72 h (P > 0.05). The activities of catalase (CAT), glutathione peroxidase (GSH-PX), total antioxidant capacity (T-AOC), lactate dehydrogenase (LDH), and acid phosphatase (ACP) in the liver tissue gradually increased at 0 h, 6 h and 72 h (P < 0.05). Histological analyses revealed structural changes in intracellular lipid droplets, nuclear migration and dissolution, and cell vacuolization in liver tissues. Six pathways were identified as the main enriched metabolic pathways according to the transcriptome profiling analysis, which were protein processing in endoplasmic reticulum, steroid biosynthesis, peroxisome, PPAR signaling pathway, glycolysis/gluconeogenesis and Insulin signaling pathway. The expressions of the important differentially expressed genes were verified by qPCR analysis, including erola, LOC100692144, sqle, cratb, pipox, cpt1a2b, hik and acss2l, ehhadh, prkcz, fasn and plaa, which showed the same expressions trends as those of RNA-Seq., Conclusions: The Nile tilapia strain improves the abilities of hypoxia response through energy metabolism. Antioxidant enzyme measurements in the liver indicate that these five antioxidant enzymes play important roles in protecting the body from hypoxic damage. The histological changes in liver cells indicate that the damage caused by hypoxia stress. The immune-related metabolic pathways and energy metabolism-related pathways were obtained by transcriptome profiling, and these metabolic pathways and the differentially expressed genes selected from these metabolic pathways may be involved in the mechanism of hypoxia tolerance in this strain. These findings provide a better understanding of the hypoxia response mechanism of fish, and represent a useful resource for the genetic breeding of O. niloticus., (© 2024. The Author(s).)

The solute carrier family 25 member 1 (Slc25a1)-dependent mitochondrial citrate shuttle is responsible for exporting citrate from the mitochondria to the cytoplasm for supporting lipid biosynthesis and protein acetylation. Previous studies on Slc25a1 concentrated on pathological models. However, the importance of Slc25a1 in maintaining metabolic homeostasis under normal nutritional conditions remains poorly understood. Here, we investigated the mechanism of mitochondrial citrate shuttle in maintaining lipid metabolism homeostasis in male Nile tilapia (Oreochromis niloticus). To achieve the objective, we blocked the mitochondrial citrate shuttle by inhibiting Slc25a1 under normal nutritional conditions. Slc25a1 inhibition was established by feeding Nile tilapia with 250 mg/kg 1,2,3-benzenetricarboxylic acid hydrate for 6 weeks or intraperitoneal injecting them with dsRNA to knockdown slc25a1b for 7 days. The Nile tilapia with Slc25a1 inhibition exhibited an obesity-like phenotype accompanied by fat deposition, liver damage and hyperglycemia. Moreover, Slc25a1 inhibition decreased hepatic citrate-derived acetyl-CoA, but increased hepatic triglyceride levels. Furthermore, Slc25a1 inhibition replenished cytoplasmic acetyl-CoA through enhanced acetate pathway, which led to hepatic triglycerides accumulation. However, acetate-derived acetyl-CoA caused by hepatic Slc25a1 inhibition did not activate de novo lipogenesis, but rather modified protein acetylation. In addition, hepatic Slc25a1 inhibition enhanced fatty acids esterification through acetate-derived acetyl-CoA, which increased Lipin1 acetylation and its protein stability. Collectively, our results illustrate that inhibiting mitochondrial citrate shuttle triggers lipid anabolic remodeling and results in lipid accumulation, indicating the importance of mitochondrial citrate shuttle in maintaining lipid metabolism homeostasis., Competing Interests: Declaration of competing interest None., (Copyright © 2024 Elsevier Inc. All rights reserved.)

This study aims to evaluate the effects of substituting soybean meal with fermented rapeseed meal (FRM) on growth, antioxidant capacity, and liver and intestinal health of the genetically improved farmed tilapia (GIFT, Oreochromis niloticus). A total of 450 tilapia (7.22 ± 0.15 g) were fed with five experimental diets, including a basal diet containing 40% soybean meal (CP0), which was subsequently replaced by 25% (CP25), 50% (CP50), 75% (CP75), and 100% (CP100) FRM in a recirculated aquiculture system for 9 weeks (30 fish per tank in triplicates). The results showed that the weight gain, specific growth rate, feed intake, feed efficiency, hepatosomatic index, and viscerosomatic index of fish in both CP75 and CP100 groups were significantly lower than those in CP0 group (P < 0.05). The fish in CP100 group had the lower content of muscle crude protein while the higher level of muscle crude lipid (P < 0.05). Activities of serum aspartate aminotransferase, alanine aminotransferase along with total triglyceride in CP100 group were significantly higher than those in CP0 group (P < 0.05). There were no significant differences in the contents of liver protease, amylase, and lipase among five groups (P > 0.05). The activities of liver total antioxidant capacity and superoxide dismutase exhibited the increased tendency with the increase of FRM replacement levels from 25 to 50% (P < 0.05), while then significantly decreased from 75 to 100% (P < 0.05). Histological morphology indicated that the fish in between CP75 and CP100 groups had poor liver and intestine health. Intestinal microbial diversity analysis showed that the relative abundance of Cetobacterium and Alcaligenaceae in both CP75 and CP100 groups were lower than that in other three groups. In conclusion, the maximum replacement level of soybean meal with FRM in the diet was determined to be 50% without compromising the growth performance, antioxidant status, and liver and intestinal health of tilapia under the current experimental conditions. The observed decrease in food intake and subsequent retarded growth performance in the CP75 and CP100 groups can be attributed directly to a reduction in feed palatability caused by FRM., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

The speciation of arsenic in fish has been widely investigated, but bioaccumulation and biotransformation of inorganic As in different tissues of Nile tilapia (Oreochromis niloticus) are not fully understood. The present study aimed to investigate the bioaccumulation of As in Nile tilapia, as well as to evaluate the distribution of the main arsenic species (As(III), As(V), MMA, DMA, and AsB) in liver, stomach, gill, and muscle, after controlled exposures to As(III) and As(V) at concentrations of 5.0 and 10.0 mg L -1 during periods of 1 and 7 days. Total As was determined by inductively coupled plasma mass spectroscopy (ICP-MS). For both exposures (As(III) and As(V)), the total As levels after 7-day exposure were highest in the liver and lowest in the muscle. Overall, the Nile tilapia exposed to As(III) showed higher tissue levels of As after the treatments, compared to As(V) exposure. Speciation of arsenic present in the tissues employed liquid chromatography coupled to ICP-MS (LC-ICP-MS), revealing that the biotransformation of As included As(V) reduction to As(III), methylation to monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), and subsequent conversion to nontoxic arsenobetaine (AsB), which was the predominant arsenic form. Finally, the interactions and antagonistic effects of selenium in the bioaccumulation processes were tested by the combined exposure to As(III), the most toxic species of As, together with tetravalent selenium (Se(IV)). The results indicated a 4-6 times reduction of arsenic toxicity in the tilapia., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The aim of this study is to evaluate the toxic effects of different concentrations of cigarette butt leachate (CBL) (0.0, 0.5, 1, 1.5, and 2.0 µL L -1 ) on blood biochemistry, oxidative stress biomarkers, and the biochemical profile of the liver and muscle of Nile tilapia fish (Oreochromis niloticus) after 21 days. Increased activity of lactate dehydrogenase (LDH), gamma-glutamyl transferase (GGT), and aspartate aminotransferase (AST) in plasma, and decreased activity of alkaline phosphatase (ALP) in fish exposed to CBL, indicated cytotoxicity. Elevated cholesterol, triglycerides, and glucose levels, coupled with reduced total protein, albumin, and globulin levels in the plasma, indicated impaired liver function in the fish. An increase in creatinine showed kidney damage. Increased superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) activities, along with the decrease in liver glutathione (GSH) content and total antioxidant capacity in the hepatocytes of fish exposed to CBL, indicated the occurrence of oxidative stress. Malondialdehyde (MDA) elevation indicated heightened lipid peroxidation in CBL-exposed fish hepatocytes. Raman spectroscopy revealed altered biochemical profiles in fish liver and muscle post-CBL exposure. The results demonstrated that exposure to CBL led to a decrease in phospholipid levels, collagen destruction, changes in phenylalanine levels, and a decrease in the levels of lipids, proteins, and nucleic acids in fish liver and muscle tissue. Furthermore, the metabolites and compounds of cigarette butt juice were detectable in the liver and muscle tissue of fishes. In conclusion, this study showed that exposure to CBL can have adverse effects on fish health., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Carnitine acetyltransferase (CAT) and Enoyl-CoA hydratase short-chain 1 (ECHS1) are considered key enzymes that regulate the β-oxidation of fatty acids. However, very few studies have investigated their full length and expression in genetically improved farmed tilapia (GIFT, Oreochromis niloticus ), an important aquaculture species in China. Here, we cloned CAT and ECHS1 full-length cDNA via the rapid amplification of cDNA ends, and the expressions of CAT and ECHS1 in the liver of juvenile GIFT were detected in different fat and carnitine diets, as were the changes in the lipometabolic enzymes and serum biochemical indexes of juvenile GIFT in diets with different fat and carnitine levels. CAT cDNA possesses an open reading frame (ORF) of 2167 bp and encodes 461 amino acids, and the ECHS1 cDNA sequence is 1354 bp in full length, the ORF of which encodes a peptide of 391 amino acids. We found that juvenile GIFT had higher lipometabolic enzyme activity and lower blood CHOL, TG, HDL-C, and LDL-C contents when the dietary fat level was 2% or 6% and when the carnitine level was 500 mg/kg. We also found that the expression of ECHS1 and CAT genes in the liver of juvenile GIFT can be promoted by a 500 mg/kg carnitine level and 6% fat level feeding. These results suggested that CAT and ECHS1 may participate in regulating lipid metabolism, and when 2% or 6% fat and 500 mg/kg carnitine are added to the feed, it is the most beneficial to the liver and lipid metabolism of juvenile GIFT. Our results may provide a theoretical basis for GIFT feeding and treating fatty liver disease.

Hepatic glucuronidation represents an important phase II biotransformation reaction in both mammals and fish. The kinetic characteristics of uridine 5'-diphosphate (UDP) glucuronosyltransferases (UDPGTs) in rainbow trout liver microsomes were examined using p-nitrophenol (p-NP) as an aglycone and UDP-glucuronic acid (UDPGA) as a glucuronyl donor according to an existing protocol. The kinetic data obtained with varying concentrations of p-NP best fit the Hill equation and UDPGT activity was successfully induced following an i.p. injection of β-naphthoflavone (β-NF). The assay was subsequently adapted to a microplate method for determination of UDPGT activity in microsomal samples obtained from rainbow trout as well as Nile tilapia. In contrast to rainbow trout, UDPGT activity of Nile tilapia was best described by Michaelis-Menten kinetics. Based on the linearity of p-NP glucuronide formation, a p-NP concentration of 0.60 mM and a UDPGA concentration of 6.89 mM were determined to be suitable for assaying UDPGT activity in samples from rainbow trout and Nile tilapia. The microplate method offers several advantages over the historical assay; most notably it enables the observation of successive kinetics which ensures that enzyme activity is calculated in the most linear (initial) rate of the reaction. It also provides practical advantages in terms of ease-of-use and efficiency. This may be relevant to researchers investigating exposure of wild or farmed fish to environmental or feed-borne contaminants which are substrates of UDPGTs., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Baicalin, a main bioactive compound of Scutellaria baicalensis, has a variety of pharmacological activities including antioxidation, anti-inflammation and hepatoprotection. However, there are few reports on these biological activities in fish. Therefore, the aim of this study was to assess the effects of baicalin on growth performance, antioxidative status and hepatoprotection in tilapia. The fish were fed on different doses of baicalin (0, 0.4, 0.8 and 1.6 g/kg diet). After feeding 60 days, parts of fishes were netted, and the blood, liver, gills and muscle tissues were collected to analyze the antioxidative effect. The remaining fishes were injected with saline or hydrogen peroxide (H 2 O 2 ) for challenge test. The results showed that the specific growth rate of fish was slightly increased in three baicalin treatments, and the feed efficiency was clearly improved in 0.4 g/kg baicalin treatment. Meanwhile, the antioxidative capacity in blood, liver and/or gill was enhanced in treatments with 0.4, 0.8 and/or 1.6 g/kg baicalin. After challenge test, the pre-treatments with baicalin effectively alleviated H 2 O 2 -induced liver injury. In serum and liver, pre-treatments with 0.8 and/or 1.6 g/kg baicalin suppressed the oxidative damage induced by H 2 O 2 , as evidenced by improvement of the levels of SOD, T-AOC and GSH and the decline of MDA level. More important, pre-treatments with 0.4, 0.8 and/or 1.6 g/kg baicalin blocked the upregulation of mRNA levels of tlr1, myd88, irak4, rela, tnf-α and il-1β in H 2 O 2 -induced liver injury. In summary, dietary baicalin supplementation could improve feed efficiency, enhance antioxidative ability and alleviate oxidative stress-induced hepatotoxicity in tilapia., (Copyright © 2020. Published by Elsevier Inc.)

The toxic effects of copper (Cu) are linked to dysfunction of metabolism and depletion of adenosine triphosphate (ATP). Nevertheless, the effects related to phosphoryl transfer network, a network of enzymes to precise coupling of the ATP-production and ATP-consuming process for maintenance of bioenergetic, remain unknown. Therefore, the aim of this study was to determine whether the phosphoryl transfer network could be one pathway involved in the bioenergetic imbalance of Cichlasoma amazonarum exposed for 96 h to environmentally relevant concentrations of Cu found in Amazonia water around mines. Branchial mitochondrial creatine kinase (CK) activity was significantly lower in fish exposed to 1500 μg/L Cu than in the control group, while branchial cytosolic CK activity was significantly greater. Branchial (exposed to 750 and 1500 μg/L Cu) and hepatic (exposed to 1500 μg/L Cu) pyruvate kinase (PK) activity was significantly lower in fish exposed to Cu than in the control group. Branchial and hepatic ATP levels were significantly lower in fish exposed to 1500 μg/L than in the control group. Branchial reactive oxygen species (ROS) and lipid peroxidation (LPO) levels were significantly higher in fish exposed to 750 and 1500 μg/L Cu compared to control. Hepatic ROS and LPO levels were significantly higher in fish exposed to 1500 μg/L than in the control group. Branchial and hepatic Cu levels were significantly higher in fish exposed to 1500 μg/L compared to other groups. Exposure to 750 and 1500 μg/L Cu impairs bioenergetics homeostasis, which appears to be mediated by ROS overproduction and lipid peroxidation., Competing Interests: Declaration of competing interest None., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Metals can disturb the integrity of physiological and biochemical mechanisms in fish. Thus components of defense as an antioxidant system are significant biomarkers due to their vital role in coping with metal stress. The aim of the current study is to investigate the direct effects of Cd, Cu, and Zn sublethal exposures (in vitro) on the antioxidant system parameters in the liver and kidney of Nile tilapia., Methods: The antioxidant enzyme activities and GSH levels were analyzed after in vitro sublethal metal (200 and 400 μg/L Cd, Cu, and Zn) treatments of Oreochromis niloticus liver and kidney supernatants., Results: Metals even at lower levels caused significant changes in the levels of antioxidant system parameters due to concentration, metal, and tissue type. GSH metabolism parameters were more responsive to the metal effect. TBARS levels and GPX activity were mostly increased while CAT, SOD, rGSH, and GSH/GSSG levels decreased. The kidney was more affected than the liver in vitro conditions. Cu was more effective in the liver whereas it was Zn for the kidney. Cd caused negative correlations among the antioxidant enzymes. Significant correlations were found between enzymes and GSH levels upon Zn and Cu exposures., Conclusions: Direct metal effects may trigger different response trends due to their nature and tissue differences. The current data provide a knowledge about which antioxidant biomarkers can define better the oxidative stress caused by direct metal effect for further studies including in vivo experiments., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

Lubricant oils are among oil-based products that are not fully consumed during its use, thereby producing non-biodegradable residues which can cause contamination of natural systems. This study evaluated the toxicity of new and used lubricating oil (0.01 and 0.1 mL L -1 ) in adult Nile tilapia (Oreochromis niloticus), by assessing the effects on oxidative stress, biotransformation enzymes (liver and gills), and histopathological alterations on hepatic and pancreatic tissues after 3 and 7 days of exposure. Results showed that 3-days exposure to 0.1 mL L -1 of used and new lubricating oil increased the activity of superoxide dismutase (SOD) and malondialdehyde (MDA) levels in liver of O. niloticus, respectively. In gills, catalase (CAT) was decreased in fish exposed to 0.1 mL L -1 of non-used oil after 3 days, but pronounced increases in CAT was detected after 7 days-exposure to both new and used oil. Shorter exposure to both concentrations of new and used oil also raised glutathione-S-transferase activity (GST) in gills. Ethoxyresorufin-O-deethylase (EROD) was induced in liver of fish exposed to 0.1 mL L -1 of used oil after 3 and 7 days, however a reduced response of this enzyme was detected in gills of animals from both oil treatments. In vitro analysis showed that hepatic EROD was inhibited by lubricating oil exposures, with more pronounced responses in treatments containing used oil. Hepatic lesions, such as cytoplasmic vacuolization, nuclei abnormally, changes in hepatocytes shape, steatosis, cholestasis, eosinophilic inclusions and necrosis were mainly increased by 7 days exposure to used lubricating oil at higher concentration., Competing Interests: Declaration of competing interest The authors declare no competing financial or other relationship with other people or organizations interests., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Nerolidol is a sesquiterpene found in essential oils of several plant species. It is found commonly in human and animal diets and is approved by the US Food and Drug Administration as a flavoring agent. Nevertheless, recent studies have suggested that nerolidol has potent hepatotoxic effects. Because use of plant-based products in human and animal food has expanded considerably, it is essential to develop approaches such as nanotechnology to avoid or reduce hepatic toxic effects. Therefore, the aim of the study was to determine whether nerolidol dietary supplementation elicited hepatic damage associated with impairment of energy homeostasis, as well as whether supplementation with nerolidol-loaded in nanospheres prevented hepatotoxic effects in Nile tilapia (Oreochromis niloticus). Nile tilapia were divided into five groups (A-E, n = 10 per group) with four replicates each, as follows: group A received basal feed (without supplementation); group B received feed containing 0.5 mL free nerolidol/kg; group C received feed containing 1.0 mL free nerolidol/kg; group D received feed containing 0.5 mL nanospheres nerolidol/kg; and group E received feed containing 1.0 mL nanospheres nerolidol/kg. All groups received experimental feed once a day (10% total biomass) at 2 p.m. for 60 consecutive days. Hepatic liver weight and relative liver weight were significantly lower in fish fed 1.0 mL free nerolidol/kg feed than in fish given basal diet (control group). Hepatic pyruvate kinase (1.0 mL free nerolidol/kg) and adenylate kinase (0.5 and 1.0 mL free nerolidol/kg) activities were significantly lower than in the control group, while hepatic reactive oxygen species and lipid damage levels were significantly higher. Finally, the comet assay revealed significant increases in the frequency of damage and the damage index in fish given 0.5 and 1.0 mL free nerolidol/kg in a dose-dependent manner. Nerolidol-loaded in nanospheres prevented all alterations elicited by free nerolidol. Based on these data, we concluded that dietary supplementation with free nerolidol elicited severe impairment of hepatic bioenergetics homeostasis that appeared to be mediated by excessive ROS production and lipid damage, contributing to a genotoxic effect. Dietary supplementation with nerolidol-loaded in nanospheres did not elicit hepatic damage, and therefore, should be considered as a replacement so as to limit toxicity, permitting its continued use as a dietary supplement.

The present study evaluated the adverse effects of the hexavalent chromium (Cr (VI)) at sub-lethal concentrations and the ameliorative potential of curcumin (CUR) over a sub-chronic exposure period on Oreochromis niloticus. Fish were exposed to Cr (VI) (4.57 mg/L) and CUR (0.02% in diet or 200 mg/kg diet), individually or in combination for 60-days. The growth rate during the period of experiment, condition factor, body composition, hepatosomatic index (HSI), hematological parameters, oxidative stress, apoptotic and DNA damage, branchial, hepato- and nephrotoxicity were estimated in this study. Moreover, the changes in mRNA expression of Cytochromes (CYP450) and glutathione S-transferase (GST) in kidney and liver tissues were assessed by qRT-PCR. Additionally, the concentration of metallothionine in the liver, histological investigation, and lesion scoring to the branchial, hepatic, renal and gill tissues were applied. The results revealed that Cr (VI) exposure caused a significant decline in most hematological variables and growth rate with down-regulation of CYP450 and GST expression. Histologically, Cr (VI) induced diverse forms of cell injury, vascular, and inflammatory alterations with upregulation of caspase-3 and downregulation of Bcl 2 expression in the examined tissues. Additionally, it elevated the levels of serum MDA and 8-hydroxy-2' -deoxyguanosine than control. CUR-supplementation resulted in a significant improvement in most indices, amelioration of histological alterations and up-regulation of CYP450 and GST expression. These results may conclude that dietary supplements with CUR could be useful for modulation of the growth with protective effects to the branchial, hepatic, and renal tissues in response to Cr (VI) exposure, thereby presenting a promising feed additive for Nile tilapia in aquaculture., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objectives: Endosulfan is a broad-spectrum organochlorine insecticide that has been commercially in use for decades to control insect pests and has been found to pollute the aquatic environment. The current study was carried out to investigate the toxic effects of endosulfan, an organochlorine pesticide, on Nile tilapia (Oreochromis niloticus), a freshwater fish, and the alleviating effects of lycopene on the induced toxicity., Methods: Four treatment groups of fish were investigated (3 replicates of 15 fish for each group): (1) a control group, (2) a group exposed to endosulfan, (3) a group that was fed on a basal diet supplemented with lycopene, and (4) a group that was fed on a basal diet supplemented with lycopene and exposed to endosulfan. The experiment was carried out over a 4-week period., Results: Endosulfan negatively affected liver function, including liver enzymes and plasma proteins. Endosulfan affected blood parameters of fish and reduced the counts of red blood cells (RBCs) and white blood cells (WBCs), as well as affected immunological parameters. Endosulfan caused oxidative stress, as it decreased the values of antioxidants catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPX), and glutathione (GSH), and increased the level of lipid peroxide malondialdehyde (MDA). Additionally, endosulfan increased cytochrome P450 (CYP450) levels, while it decreased glutathione S-transferase (GST) mRNA transcript levels and distorted the normal histological structure of the liver, gills, and spleen of affected fish. Conversely, lycopene partially restored the aforementioned parameters when administered concomitantly with endosulfan., Conclusion: The results showed the beneficial effects of supplementing fish diets with lycopene as a natural antioxidant for ameliorating the toxicity caused by endosulfan., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The aim of this study was to assess the leaf aqueous extract composition of Serjania marginata and the effects of its inclusion on the diet of Nile tilapia (Oreochromis niloticus), with respect to the activity of digestive enzymes and enzymes associated with the metabolism of the liver and intestine and liver histopathology. Fish (initial mean weight, 54.36 ± 17.04 g) were divided into groups: fasting (without feeding), control (commercial feed), and treatment (commercial feed with leaf aqueous extract of Serjania marginata), and in each aquarium, there were five individuals and the fish fed ad libitum for 15 days. Treatment fish had ingested on average 224.3 mg of extract/kg of fish/day. In the extract analysis by mass spectrometry, quercitrin, isoquercitrin, A-type proanthocyanidin trimer, and quinic acid were identified. In the enzymatic activity, fish from the treatment group showed higher level of alkaline phosphatase, while the hepatotoxic markers (AST and ALT) and levels of lipase, amylase, and nonspecific protease did not differ (p > 0.05). In liver histopathological analysis, it was observed that fish from the treatment showed normal structure, while abnormalities were associated with control (fibrosis, loss of cordonal architecture, vacuolated hepatocytes with nucleus displaced to the periphery) and fasting (reduction in hepatocyte size and sinusoidal space). The intestine histopathology evidenced that the extract favored the development of goblet cells and intestinal fold height. The results indicated that the leaf aqueous extract of S. marginata assists in the structural maintenance of the liver and intestine and stimulates intestinal alkaline phosphatase production in Nile tilapia, suggesting that the identified compounds act on the liver and intestine, showing hepatoprotective effects and stimulating intestinal digestion.

Dietary oils of varying fatty acid composition have been used in tilapia feeds; nevertheless, investigation of their effects on metabolism and physiological processes has been limited. Therefore, in this study, using proteomic technology, the effects of different dietary lipids (DLs) on hepatic lipid metabolism and physiological processes were investigaed in Nile tilapia (Oreochromis niloticus). Fish were fed with different DL, which included palm oil (PO), linseed oil (LO) and soybean oil (SBO) for 90 days. Growth performance appeared to be similar among the dietary group. Hepatic FA contents were reflected by DL. Dietary PO (source of saturated fatty acids; SFA) led to an increase in the hepatosomatic index as well as lipid and protein contents in liver. Dietary SBO (source of n-6 polyunsaturated fatty acids; n-6 PUFAs) increased hepatic carbohydrate contents, but decreased the hepatic protein. The proteomic analysis showed that these nutritive changes in the liver were mediated by several proteins involved in lipid, carbohydrate, and amino acid metabolism. Dietary SBO showed an increased accumulation in proteins related to oxidative stress, immune and inflammatory processes. Dietary LO (source of n-3 PUFAs) increased abundance of cytoskeleton-related proteins. qRT-PCR was performed to provide supportive information for the result of proteomic study. Similar effects of DLs on mRNA levels were observed for atp5b, krt18, and selenbp1. Combined together, dietary SFA could supply as energy reservoir for regular activites. Dietary n-3 and n-6 PUFAs led to induce vital metabolic and physiologic processes which would contribute to maintaining normal health and/or providing health-related benefits. SIGNIFICANCE: Dietary SBO increased hepatic carbohydrate contents, but decreased the hepatic protein. Different dietary lipid led to alter the abundance of several proteins (i.e., DHRS1, ATP5B, PLA2G12B, APO, AMY2A, GRP78, PRSS1, FAH, and PRSS36) involved in lipid, carbohydrate, and amino acid metabolism. Dietary SBO showed an increased accumulation in proteins (i.e., QDPR, CABC1, and PRDX6) that respond to oxidative stress, suggesting that n-6 PUFAs induce oxidative conditions. Dietary SBO led to increase the accumulation of proteins (i.e., NITR26, NCCRP1, and LCN) involved in immune and inflammatory processes. Dietary LO increased the abundant levels of cytoskeleton-related proteins (i.e., ACTB, AHNAK, ERC2, KRT18, and RILP1). Other proteins (i.e., SELENBP1, FAM46C, and ANC1) involved in other physiological processes were also modulated by DL. qRT-PCR was performed to provide supportive information of proteomic study. Similar effects of DLs on mRNA levels were observed for atp5b, krt18, and selenbp1., (Copyright © 2018. Published by Elsevier B.V.)

Di-(2-ethylhexyl) phthalate (DEHP) is currently the most frequently detected phthalic acid esters (PAEs) compounds and can induce diverse toxicities on aquatic organisms. To understand the molecular responses of fish to DEHP, we performed transcriptomic profiles in liver of tilapia (Oreochromis niloticus) which were exposed to environmental concentration of DEHP. A total of 30.10 Mb and 30.16 Mb clean reads were retrieved from the control and DEHP treated libraries, respectively. De-novo assembly of all the clean reads obtained 58,585 unigenes. After comparing the two libraries, 2814 and 1790 genes were identified as significantly increased and depressed, respectively. Gene ontology (GO) classification system and Kyoto Encyclopedia of Genes and Genomes (KEGG) database analysis demonstrated that DEHP significantly disturbed the expression level of genes associated with immunity, endocrine and reproductive system, lipid metabolism and so on. Quantitative real-time PCR was performed to validate the results of RNA-sequencing (RNA-seq) analysis. The resulting data provide new insights for exploring the molecular basis of tilapia response to DEHP exposure., (Copyright © 2018. Published by Elsevier Inc.)

One of the metal detoxifying mechanisms that occurs in fish is metallothionein (MT) induction and metal binding. Hepatic MT induction has been well described, but biliary MT metal detoxification has only recently been described in fish. In this scenario, metal-metal interactions have been increasingly evaluated to further understand the behavior of these contaminants regarding homeostasis and biological functions, as well as their toxic effects. Studies, however, have been mainly conducted concerning the elemental pair Se-Hg, and scarce reports are available concerning other metal pairs. Therefore, this study aimed to evaluate biliary and hepatic MT metal detoxification mechanisms in a territorial neotropical cichlid, Geophagus brasiliensis. Fish were sampled from the anthropogenically impacted estuarine Rodrigo de Freitas Lagoon, located in Southern Rio de Janeiro, and trace elements and MT were determined by inductively coupled plasma mass spectrometry (ICP-MS) and UV-Vis spectrophotometry, respectively, in fish liver and bile. MT in bile were significantly lower than in liver. Significant differences between bile and liver were observed for many trace elements, and, although most were higher in liver, Cd and Ni were significantly higher in bile, indicating efficient excretion from the body via the biliary route. A significant correlation was observed between MT and Fe in bile, and between MT in liver and Cu and Zn in bile. Molar ratio calculations demonstrated protective elements effects against Al, As, Cd, Hg, Pb and V in both bile and liver, as well as some novel interrelationships, indicating the importance of these investigations regarding the elucidation of element detoxifying mechanisms. Furthermore, investigation of other elemental associations may aid in decision-making processes regarding environmental contamination scenarios linked to public health., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

MicroRNAs (miRNAs) are non-coding RNAs that function as post-transcriptional gene regulators and that play vital roles controlling lipid metabolism. miR-205 is an important miRNA related to adipogenesis and lipid metabolism. However, little is known about the potential role of miR-205-5p in genetically improved farmed tilapia (GIFT, Oreochromis niloticus). In this study, we used miRanda software to search for potential miR-205-5p target genes and found a lipid-metabolism-related gene called acetyl-CoA carboxylase β (ACACβ). Quantitative real-time polymerase chain reaction data indicated that there may be a negative regulation relationship between miR-205-5p and ACACβ gene expression under HFD rearing. Using luciferase reporter assays, we verified the binding site of miR-205-5p in the 3'-untranslated region of the ACACβ mRNA. Furthermore, an in vivo functional analysis of miR-205-5p was performed by injecting GIFT juveniles with a miR-205-5p antagomir. Reduced levels of miR-205-5p in GIFT liver increased ACACβ mRNA expression 12 h post-injection. miR-205-5p suppression also increased fatty acid synthase and peroxisome proliferator-activated receptor-α mRNA levels 48 h and 120 h post-injection, respectively. Taken together, our results indicate that miR-205-5p negative regulates hepatic ACACβ mRNA expression, and may serve as an important regulator in controlling hepatic lipid metabolism in GIFT., (Copyright © 2018. Published by Elsevier B.V.)

Growth hormone (GH) release is a process that is well regulated by several factors, including GH secretagogues. GH can mediate the regulation of the fatty acid level and composition. The aim of this study was to determine the effect of a synthetic GH secretagogue peptide (A233) on the growth and fatty acid composition in tilapia (Oreochromis niloticus). To address this objective, we administrated a diet supplemented with A233 to juvenile tilapia for 60 days. The group fed with a diet supplemented with 600 μg of A233 per kg of feed increased in weight (4.81 ± 0.09 g) and specific growth rate (2.49 ± 0.03%/day) compared to the control diet group (3.63 ± 0.08 g, 2.07 ± 0.04%/day; respectively) (p < 0.001). In the muscle, the total lipids for the control diet group were higher than that in the group fed with 600 μg of A233 per kg feed; however, no differences were detected in the liver. In both tissues, the patterns of fatty acid composition and content were generally similar, with some exceptions. Tilapia fed with 600 μg of A233 per kg of feed showed, in liver and muscle, a significantly higher composition and content of n-3 polyunsaturated fatty acids (such as 20:5n-3, 22:5n-3, 22:6n-3) and n-3/n-6 PUFA than animals fed with the control diet. To our knowledge, this is the first report on the the effects of natural or synthetic GH secretagogues (GHS) on fatty acid composition, implying an increase in the nutritional quality of the tilapia., (© 2018 AOCS.)

The purpose of this investigation was to evaluate the effects of lead (Pb) and lead + zinc (Zn) combination on the oxidative stress, total ATPase and Pb accumulation in the tissues of Oreochromis niloticus (Linnaeus, 1758). The fish were exposed to 0.1 mg/L Pb (T1), 1.0 mg/L Pb (T2) and mixtures of 0.1 mg/L Pb and 0.5 mg/L Zn (M1); 1.0 mg/L Pb and 5.0 mg/L Zn (M2) for 7 and 21 days. Pb accumulation, total ATPase activity, several antioxidant enzyme activities such as catalase, glutathione peroxidase (GPX), glutathione S-transferase, glutathione reductase, and thiobarbituric acid reactive substances concentrations were measured in the liver and kidney tissues. Metal accumulation in the tissues was higher in Pb exposure compare with mixtures of Pb and Zn exposures. Beside the inhibition of liver GPX activity, general increases of antioxidant enzyme activities in the tissues were recorded after metal exposures. This investigation emphasizes the oxidative stress in O. niloticus caused by Pb, and adaptation of the organisms to the changes in enzyme activities.

The GIFT (Genetically Improved Farmed Tilapia) tilapia, Oreochromis niloticus, is cultured widely for the production of freshwater fish in China. Streptococcosis, which is related to pathogenic infections, occurs frequently in juvenile and adult female GIFT individuals. Resveratrol (RES) has been used in feed to control these infections in freshwater tilapia. To address the effects of RES on tilapia, we used high-throughput RNA sequencing technology (RNA-Seq, HiSeq. 2500) to explore the global transcriptomic response and specific involvement of hepatic mRNA of juvenile O. niloticus fed with diets containing different concentrations of (0, 0.025, 0.05, and 0.1g/kg) RES. A total of > 24,513,018 clean reads were generated and then assembled into 23,244 unigenes. The unigenes were annotated by comparing them against non-redundant protein sequence (Nr), non-redundant nucleotide (Nt), Swiss-Prot, Pfam, Gene Ontology database (GO), Clusters of Orthologous Groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases, and 12,578 unigenes were annotated to the GO database. A total of 1444 (0.025g/kg RES), 1526 (0.05g/kg RES), and 3135 (0.1g/kg RES) genes were detected as significant differentially expressed genes (DEGs), when compared with the controls. A total of 6 (0.025 vs 0.05g/kg RES), 19 (0.025 vs 0.1g/kg RES), and 124 (0.05 vs 0.1g/kg RES) genes were detected as significant DEGs. Six genes, including dnah7x1, sox4, fam46a, hsp90a, ddit4, and nmrk2, were associated with an immune response. These findings provide information on the innate immunity of GIFT and might contribute to the development of strategies for the effective management of diseases and long-term sustainability of O. niloticus culture., (Copyright © 2017 Elsevier Inc. All rights reserved.)

MicroRNAs (miRNAs) play vital roles in modulating diverse metabolic processes in the liver, including lipid metabolism. Genetically improved farmed tilapia (GIFT, Oreochromis niloticus), an important aquaculture species in China, is susceptible to hepatic steatosis when reared in intensive culture systems. To investigate the miRNAs involved in GIFT lipid metabolism, two hepatic small RNA libraries from high-fat diet-fed and normal-fat diet-fed GIFT were constructed and sequenced using high-throughput sequencing technology. A total of 204 known and 56 novel miRNAs were identified by aligning the sequencing data with known Danio rerio miRNAs listed in miRBase 21.0. Six known miRNAs (miR-30a-5p, miR-34a, miR-145-5p, miR-29a, miR-205-5p, and miR-23a-3p) that were differentially expressed between the high-fat diet and normal-fat diet groups were validated by quantitative real-time PCR. Bioinformatics tools were used to predict the potential target genes of these differentially expressed miRNAs, and Gene Ontology enrichment analysis indicated that these miRNAs may play important roles in diet-induced hepatic steatosis in GIFT. Our results provide a foundation for further studies of the role of miRNAs in tilapia lipid homeostasis regulation, and may help to identify novel targets for therapeutic interventions to reduce the occurrence of fatty liver disease in farmed tilapia., (Copyright © 2017. Published by Elsevier Ltd.)

Cylindrospermopsin (CYN) is a cytotoxin highly water-soluble, which is easily taken up by several aquatic organisms. CYN acts as a potent protein and glutathione synthesis inhibitor, as well as inducing genotoxicity, oxidative stress, and histopathological alterations. This is the first study reporting the protective effect of a l-carnitine (LC) pretreatment (400 or 880 mg LC/kg bw fish/day, for 21 days) on the histopathological alterations induced by pure CYN or Aphanizomenon ovalisporum lyophilized cells (400 µg CYN/kg bw fish) in liver, kidney, heart, intestines, and gills of tilapia (Oreochromis niloticus) acutely exposed to the toxin by oral route. The main histopathological changes induced by CYN were disorganized parenchyma with presence of glycogen and lipids in the cytoplasm (liver), glomerulonephritis, glomerular atrophy, and dilatation of Bowman's capsule (kidney), myofibrolysis, loss of myofibrils, with edema and hemorrhage (heart), intestinal villi with necrotic enterocytes and partial loss of microvilli (gastrointestinal tract), and hyperemia and hemorrhage (gills). LC pretreatment was able to totally prevent those CYN-induced alterations from 400 mg LC/kg bw fish/day in almost all organs, except in the heart, where 880 mg LC/kg bw fish/day were needed. In addition, the morphometric study indicated that LC managed to recover totally the affectation in the cross sections of the proximal and distal convoluted tubules in CYN-exposed fish. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 241-254, 2017., (© 2015 Wiley Periodicals, Inc.)

Cylindrospermopsin (CYN) is a cyanotoxin frequently involved in blooms with a predominantly extracellular availability, which makes it easily taken up by a variety of aquatic organisms. CYN is a potent protein and glutathione synthesis inhibitor, and also induces genotoxicity, oxidative stress and several histopathological lesions. The present study investigates the protective role of a vitamin E pretreatment (700 mg vit E/kg fish bw/day, for 7 days) on the histopathological alterations induced in different organs of tilapia (Oreochromis niloticus) acutely exposed to a single oral dose of 400 µg pure CYN/kg bw fish. The major histological changes observed were degenerative glucogenic process and loss of the hepatic structure in the liver, glomerulopathy and tubular tumefaction in the kidney, myofibrolysis and edema in the heart, catarrhal enteritis and necrosis in the gastrointestinal tract, hyperemic processes in the gill lamellae, and high basophilia, degeneration and tumefaction of granular neurons in the brain. Vitamin E pretreatment was effective in preventing or ameliorating the abovementioned alterations induced by CYN. In addition, a morphometric study indicated that the average nuclear diameter of hepatocytes, and cross-sections of proximal and distal convoluted tubules, together with the cardiac fiber and capillaries diameters represent a useful tool to evaluate the damage induced by CYN. This is the first study reporting vitamin E prevention of histopathological damage in tissues (liver, kidney, heart, gastrointestinal tract, gills and brain) of fish intoxicated with CYN. Therefore, vitamin E can be considered a useful chemoprotectant in the treatment of histopathological changes induced in CYN-intoxicated fish. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1469-1485, 2016., (© 2015 Wiley Periodicals, Inc.)

Agricultural activity demands the use of pesticides for plague control and extermination. In that matter, diazinon is one of the most widely used organophosphorus pesticides (OPs). Despite its benefits, the use of OPs in agricultural activities can also have negative effects since the excessive use of these substances can represent a major contamination problem for water bodies and organisms that inhabit them. The aim of this paper was to evaluate oxidative damage in lipids and proteins of Nile tilapia (Oreochromis niloticus) exposed acutely to diazinon (0.97, 1.95 and 3.95ppm) for 12 or 24h. The evaluation of oxidative damage was determined by quantifying lipid hydroperoxides (Fox method) and oxidized proteins (DNPH method). The data from this study suggest that diazinon induces a concentration-dependent oxidative damage in proteins, but not lipids, of the liver and gills of Nile tilapia. Furthermore, the treatment leads to a decrease in the concentration of total proteins, which can have serious consequences in cell physiology and fish development., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Sulfamethazine (SMZ) is one of the most commonly used sulfonamide compounds in fish farming, and its physiological effects on fish are unknown. SMZ was administered to juvenile Nile tilapia (Oreochromis niloticus) at a dose level of 422 mg kg(-1) body weight, for a period of 11 days, via medicated feed. Fish were divided into two groups, the control group (CG) and the group fed with SMZ in feed. The administration of SMZ did not alter the erythrograms and leukograms of the Nile tilapia. The SMZ-fed group showed the same hepatic lipid peroxidation (LPO) concentration as the CG. Nonetheless, the oral administration of SMZ raised the hepatic catalase (CAT) and glutathione S-transferase (GST) activities, the increase probably being sufficient to prevent hepatic LPO production. The oral administration of SMZ affects the hepatic GST and CAT activities of Nile tilapia.

Cadmium (Cd) is one of the naturally occurring heavy metals having adverse effects, while vitamin C (L-ascorbic acid) is an essential micronutrient for fish, which can attenuate tissue damage owing to its chain-breaking antioxidant and free radical scavenger properties. The adult Nile tilapia fish were exposed to Cd at 5 mg/l with and without vitamin C (500 mg/kg diet) for 45 days in addition to negative and positive controls fed with the basal diet and basal diet supplemented with vitamin C, respectively. Hepatic relative mRNA expression of genes involved in antioxidant function, metallothionein (MT), glutathione S-transferase (GST-α1), and glutathione peroxidase (GPx1), was assessed using real-time reverse transcription polymerase chain reaction (RT-PCR). Hepatic architecture was also histopathologically examined. Tilapia exposed to Cd exhibited upregulated antioxidants' gene transcript levels, GST-⍺1, GPx1, and MT by 6.10-, 4.60-, and 4.29-fold, respectively. Histopathologically, Cd caused severe hepatic changes of multifocal hepatocellular and pancreatic acinar necrosis, and lytic hepatocytes infiltrated with eosinophilic granular cells. Co-treatment of Cd-exposed fish with vitamin C overexpressed antioxidant enzyme-related genes, GST-⍺1 (16.26-fold) and GPx1 (18.68-fold), and maintained the expression of MT gene close to control (1.07-fold), averting the toxicopathic lesions induced by Cd. These results suggested that vitamin C has the potential to protect Nile tilapia from Cd hepatotoxicity via sustaining hepatic antioxidants' genes transcripts and normal histoarchitecture.

In the aquatic environment, biotransformation enzymes are established biomarkers for assessing PAH exposure in fish, but little is known about the effect of 17β-estradiol (E2) on these enzymes during exposure to benzo(a)pyrene (BaP). In this study, Nile tilapia (Oreochromis niloticus) were exposed for 3, 5, and 10 days to BaP (300 μg L(-1)) and E2 (5 μg L(-1)). These substances were applied isolated or mixed. In the mixture experiment, fish were analyzed pre- and postexposure in order to better understand whether preexposure to the hormone masks the responses activated by PAH or vice versa. Phase I enzymes ethoxyresorufin-O-deethylase (EROD), pentoxyresorufin-O-depenthylase (PROD), and benzyloxyresorufin-O-debenzylase (BROD) activities as well as the phase II enzyme glutathione S-transferase (GST) were analyzed. Isolated E2 treatment decreased EROD activity after 3 days, but this enzyme activity returned to control values after 5 and 10 days of exposure. Isolated BaP treatment significantly induced EROD activity after 3 and 5 days, and the activity returned to control levels after ten exposure days. Combined treatment (E2 + Bap) significantly increased EROD activity, both in the pre- and postexposure. This increase was even higher than in the isolated BaP treatment, suggesting a synergism between these two compounds. When E2 and BaP were used singly, they did not change BROD and PROD activities. However, combined treatment (E2 + Bap) significantly increased PROD activity. Isolated BaP treatment increased GST activity after 10 days. However, this response was not observed in the mixture treatment, suggesting that E2 suppressed the GST induction modulated by BaP. The results put together indicated that E2 altered the biotransformation pathway regarding enzymes activated by BaP in Nile tilapia.

This study estimated end compared the potential toxic effects of the water-soluble fractions (WSF) of biodiesel (B100), diesel and the commercial biodiesel (B5) on Oreochromis niloticus. After a 24 h-exposition to WSF-0% (control) and WSF-serial concentrations of 4.6%, 10%, 22%, 46% and 100%, samples of gill and liver of the exposed fishes were fixed in Bouin's solution, processed, stained using hematoxylin/eosin and analyzed by light-microscopy. WSF-hydrocarbons and methanol contents, analyzed by gas chromatography, were checked against the occurrence of abnormal histopathological alterations. These were not found in the control and WSF-4.6% exposed fishes, while exposures to or above 10%-WSF resulted in histopathological alterations whose severity increased in a dose-dependent manner, being higher in fishes exposed to WSF-diesel, or WSF-B5 when compared to biodiesel. These results, which were corroborated by the chemical analyses, highlighted the histological technique as an appropriate diagnostic tool that can be used for the preservation of water bodies' quality.

The glutathione metabolism contains crucial antioxidant molecules to defend the organisms against oxidants. Thus, the aim of this study was to investigate the response of the glutathione metabolism in the liver of freshwater fish Oreochromis niloticus exposed to metals (Cu, Cd, Cr, Pb, Zn) in different periods. Fish were exposed to metals (as 1 μg/mL) individually for 1, 7, and 14 days and subsequently antioxidant enzymes (glutathione peroxidase, GPX; glutathione reductase, GR and glutathione S-transferase, GST) and glutathione levels (total glutathione, tGSH; reduced glutathione, rGSH; oxidized glutathione, GSSG and GSH/GSSG ratios) in the liver were measured. There was no fish mortality during the experiments, except Cu exposure. The antioxidant enzymes responded differently to metal exposures depending on metal types and exposure durations. GPX activity increased only after Cd exposure, while GST activity increased following 7 days of all metal exposures. However, GR activity did not alter in most cases. Total GSH and GSH/GSSG levels generally decreased, especially after 7 days. Data showed that metal exposures significantly altered the response of antioxidant system parameters, particularly at day 7 and some recovery occurred after 14 days. This study suggests that the response of antioxidant system could help to predict metal toxicity in the aquatic environments and be useful as an "early warning tool" in natural monitoring studies.

To evaluate the ameliorative effect of curcumin on dietary aflatoxin-induced changes in the expression of genes in Nile tilapia Oreochromis niloticus liver, the fish were fed with a diet contaminated by 200 ppb of atlatoxin B1 (AFB1) with and without curcumin (5 mg/kg diet) for 16 weeks in addition to a negative and positive controls fed with the basal diet and basal diet supplemented with curcumin, respectively. Further, two recovery groups with and without curcumin were tested after 2 more weeks. Relative mRNA expression of genes involved in antioxidant function (superoxide dismutase, SOD), biotransformation (cytochrome P4501A, CYPA) and immune response (interleukin-1β, IL-1β and transforming growth factor β, TGF-β) were assessed using RT-PCR. Also, fish weight gain and survival rate were determined. Results revealed that AFB1 significantly-reduced the survivability and weight gain, while curcumin inclusion improved them. Fish fed with AFB1-contaminated diet showed the up-regulation of CYP1A and down-regulation of SOD, IL-1β and TGF-β. This expression pattern was still evident in the recovery group without curcumin, but to a lesser extent. Supplementation of curcumin ameliorated the overall gene expression close to the control levels. It appears that curcumin exhibited protective effects on AFB1-induced liver toxicity in O. niloticus by moderating oxidative stress, toxin biotransformation, immune response, and hence growth performance.

The size of a fish is an important factor in its physiology, and metal uptake is affected by animal physiology. In this study, small and large tilapias (Oreochromis niloticus) differing approximately twofold in length and fivefold in weight were compared for their antioxidant response. Both groups were exposed to Cu or Cr (1.0 μg/mL) in a freshwater (-80 mg CaCO3/L, conductivity 1.77 mS/cm) using 2 exposure protocols (20 μM for 48 h and 10 μM for 6 days). Following the exposures, the antioxidant enzyme activities (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPX; glutathione reductase, GR and glutathione S-transferase, GST) and glutathione (GSH) levels were measured in the liver of fish. Results showed that small fish was affected from exposure conditions much more than large ones as their antioxidant parameters significantly decreased even in controls. Metal exposures of small fish caused significant increases in SOD and CAT activity in acute Cu or Cr exposures. Subchronic Cr exposure of small fish also caused significant increases in CAT, GPx and GST activities, while there was no significant change in Cu-exposed ones. Large fish, however, showed different antioxidant responses as their levels mostly decreased. This study demonstrated that the response of antioxidant system in the liver of tilapia varied in relation to fish sizes and emphasized using different size groups in environmental monitoring and also in evaluation of fish biomarkers.

Background: The homeopathic complex HomeoAqua Mega 3(®) was designed to stimulate fish liver function resulting in enhanced lipid metabolism and improved overall performance. The effect of the complex in fatty acid compounds in the muscle tissues and the performance of Nile tilapia (O. niloticus) were evaluated., Methods: A control diet with 40 mL of alcohol solution (30° Gay Lussac (GL) alcohol) per kg of feed and another diet with 40 mL/kg of the homeopathic complex were analysed in sex-reversed juvenile male Nile tilapia with mean initial weights of 89.54 g (±7.97) and 89.74 g (±8.83) and initial total mean lengths of 16.93 cm (±0.56) and 16.85 cm (±0.56) for the control and homeopathy-treated fish, respectively. Overall, 200 fish were distributed into 10 water tanks, with 20 specimens in each 600 L tank, they were kept for 63 days. Monitoring of the water's physical and chemical parameters was performed. Additionally, the percentage chemical composition and the composition of the muscle tissue fatty acids were determined, and fish performance was evaluated., Results: No significant differences (p > 0.05) were found between treatments with regard to the water's physical and chemical parameters, moisture, ashes, proteins of the Nile tilapia muscular tissue and mean rates of total weight and length of the animals in the final period of the assay. The total lipid (TL) rates of the tilapia muscle tissue were 1.133 ± 0.2% at the start (control and homeopathy) and 0.908 ± 0.14% (control) and 0.688 ± 0.14% (homeopathy) at the end of the experiment (p < 0.06). The sum total of the SFAs (saturated fatty acids) was 338.50 ± 0.15 at the start (control and homeopathy) and 271.49 ± 0.34 mg/g of the TLs for the control and 226.12 ± 0.77 mg/g of TL for the homeopathy at the end of the experiment (p < 0.05). The n-6/n-3 ratio was also lower for the homeopathy-treated fish (8.45 ± 0.40) compared with the control fish (9.60 ± 0.14), (p < 0.05) at the end of the 63-day period., Conclusion: Nile tilapia juveniles that received the HomeoAqua Mega-3(®) in their diets had a decrease in the TL rates, mainly for the SFAs, and the n-6/n-3 ratio, compared with the control group, without any changes in the animal performance during the experimental period., (Copyright © 2014 The Faculty of Homeopathy. Published by Elsevier Ltd. All rights reserved.)

Fish bile metallothioneins (MT) have been recently reported as biomarkers for environmental metal contamination; however, no studies regarding standardizations for their purification are available. Therefore, different procedures (varying centrifugation times and heat-treatment temperatures) and reducing agents (DTT, β-mercaptoethanol and TCEP) were applied to purify MT isolated from fish (Oreochromis niloticus) bile and liver. Liver was also analyzed, since these two organs are intrinsically connected and show the same trend regarding MT expression. Spectrophotometrical analyses were used to quantify the resulting MT samples, and SDS-PAGE gels were used to qualitatively assess the different procedure results. Each procedure was then statistically evaluated and a multivariate statistical analysis was then applied. A response surface methodology was also applied for bile samples, in order to further evaluate the responses for this matrix. Heat treatment effectively removes most undesired proteins from the samples, however results indicate that temperatures above 70 °C are not efficient since they also remove MTs from both bile and liver samples. Our results also indicate that the centrifugation times described in the literature can be decreased in order to analyze more samples in the same timeframe, of importance in environmental monitoring contexts where samples are usually numerous. In an environmental context, biliary MT was lower than liver MT, as expected, since liver accumulates MT with slower detoxification rates than bile, which is released from the gallbladder during feeding, and then diluted by water. Therefore, bile MT seems to be more adequate in environmental monitoring scopes regarding recent exposure to xenobiotics that may affect the proteomic and metalloproteomic expression of this biological matrix., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Background: This study evaluated the performance, prevalence of ectoparasites and morpho-functional response of the liver and the branchiae of Nile tilapia (Oreochromis niloticus) raised on fish meal with added of the homeopathic complex Homeopatila 100(®) at different concentrations., Methods: Post-reversed juvenile Nile tilapia (O. niloticus) of the GIFT (Genetic Improvement of Farmed Tilapia) strain were used in this study. The performance, ectoparasite prevalence and parasite load in the branchiae and skin as well as the liver and branchial histology. Fish were randomly assigned to receive one of four treatments: control, 20 mL hydroalcoholic solution (alcohol 30° GL); 20 mL Homeopatila 100(®) per kg of meal; 40 mL Homeopatila 100(®) per kg of meal; or 60 mL of Homeopatila 100(®) per kg of meal, compared to control with out the addition of the complex. There were four replications per treatment type (16 experimental units total) at a density of 40 fish per m(3) over a period of 57 days. The Kruskal-Wallis H test (p < 0.05) was employed to analyse the physical and chemical parameters of water as well as for parasite prevalence; whereas analysis of variance was used for liver performance. If the values were significant (p < 0.05), they were compared by Tukey's test. Multiple comparisons of averages were performed using Student's t test (p < 0.05)., Results: There were no significant between the physical and chemical parameters of the water between the different groups at the end of the experiment. Significant differences (p < 0.05) in the mixed parasite conditions were found within the different Homeopatila 100(®) treatments. The hepatosomatic ratio of fish treated with Homeopatila 100(®) was significantly lower than that of fish from the control group. The best results in the liver and branchiae occurred in fish receiving Homeopatila 100(®) at 40 mL/kg in terms of the number of hepatocytes/mm(2), the intercellular glycogenic behaviour, the rates of histological changes (hyperplasia, lamella fusion and telangiectasia) and the percentage of neutral and acidic mucin-producing cells., Conclusion: The addition of Homeopatila 100(®) at a concentration 40 mL per kg/meal to the diet of juvenile Nile tilapias resulted in improved hepatocytes and intracellular glycogen levels as well as the lowest mean rate of branchial histological changes with an increase in acidic mucin-producing cells compared to neutral mucin-producing cells, compared to control., (Copyright © 2013 The Faculty of Homeopathy. Published by Elsevier Ltd. All rights reserved.)

The cyanobacterial toxin, MC-LR, is predominantly presented during toxic cyanobacterial blooms and is consumed by phytoplanktivorous fish and zooplanktivorous fish directly. Detoxification of MC-LR in liver was believed to begin with conjugate formation with GSH, catalyzed by GSTs. MC-LR GSH conjugates display increased solubility and are subjected to accelerated biliary excretion. In this study, we showed that the mRNA transcriptions of GSTA, GPX and UCP2 were increased within 8h following MC-LR exposure in isolated hepatocytes of Nile tilapia, confirming the roles of phase II enzymes, especially GSTs, in MC-LR detoxification in tilapia. The widely used food-additive, synthetic antioxidant, tert-butylhydroquinone (tBHQ) has been shown to induce phase II enzymes including GSTs, via the antioxidant responsive elements (ARE) locate in the regulatory regions of these genes. Our results also showed that the transcription of various GSTs, including GSTA, GSTR2 and GSTT were significantly induced by tBHQ in Nile tilapia. In consistence, fish fed on tBHQ-containing diet (0.01 percent tBHQ) showed significantly reduced MC-LR accumulation in liver tissues 48 h after an oral administration of a single dose of 250 μg MC-LR/kg body weight (bwt). The findings in this research suggested that tBHQ could reduce MC-LR accumulations in liver, likely through the induction of phase II metabolizing enzymes such as GSTs. Subacute effects of tBHQ and its potential applications in fishery need to be further investigated., (Crown Copyright © 2012. Published by Elsevier Inc. All rights reserved.)

Anthropogenic activities can increase the salinity of freshwaters and this may cause stress for fish and affect metal bioavailability. Oxidative stress biomarkers are of great interest due to their responses to environmental stressors which provide valuable data for biological monitoring of aquatic pollution. Thus, the individual and combined effects of salinity and metals (Cr, Pb) were investigated in the liver of freshwater fish Oreochromis niloticus in the present study. Fish were exposed to salinity (2 and 8 ppt) alone and salinity+metal (1 μg/mL Pb and Cr) combination exposures for 0, 1, 7 and 14 days and subsequently antioxidant enzymes (superoxide dismutase, SOD; glutathione peroxidase, GPX; glutathione reductase, GR and glutathione S-transferase, GST) activities and glutathione (GSH) levels in the liver were measured. Data showed that all the parameters varied in relation to metal species, exposure durations and salinity levels. Profound alterations on the measured parameters were detected at the lower salinity compared to the higher one. Salinity increase effectively stimulated the antioxidant parameters. The effects of salinity and metals on the measured parameters increased as the exposure duration prolonged. SOD was the most affected antioxidant parameter from both salinity and metals. Because metal and salinity stresses affect fish antioxidant system, this work suggests that the chemistry of freshwaters should be taken into account in natural monitoring for metal contamination in the field., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Fish live in direct contact with their immediate external environment and, therefore, are highly vulnerable to aquatic pollutants. In this study, Oreochromis niloticus were caught at three different sites in Al-Hassa irrigation channels, namely Al-Jawhariya, Um-Sabah and Al-Khadoud. The histological changes in gills and liver were detected microscopically and evaluated with semi-quantitative analyses. Also, heavy metals have been determined in the water samples in these sites. Results showed that all sites were polluted by different kinds of heavy metals. Cd and Pb were mostly detected at concentrations above the WHO reference values. Meanwhile, various histopathological abnormalities were observed in gills and liver of fish specimens. In the gill filaments, cell proliferation, lamellar cell hyperplasia, lamellar fusion, lifting of the respiratory epithelium, and the presence of aneurysmal areas were observed. In the liver, there was vacuolization of the hepatocytes, sinusoidal congestion, necrosis of the parenchyma tissue, nuclear pyknosis, eosinophilic hepatocellular degeneration, pigment accumulation, an increase in the number and size of melanomacrophage centers. Liver tumors with severe chronic inflammation were occasionally found in fish at Al-Khadoud area (first-time report). The histological lesions were comparatively most severe in the liver. Despite heavy metals assessment did not show marked differences among sites, histopathological biomarkers indicated that the surveyed fish are living under stressful environmental conditions. So, we suggest use those biomarkers in future monitoring of aquatic systems., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The influence of 17α-methyltestosterone (MT) on growth responses, biological parameters and the expression of genes involved in the GH-IGF pathway of the hypothalamic-pituitary-liver-gonadal axis were investigated in female, male, and sex-reversed Nile tilapia to evaluate the relationship between sex and MT-induced changes in these parameters. Female fish had a lower growth rate than male and sex-reversed fish, and MT increased growth performance and duodenal villi in females. Most but not all biological parameters of sex-reversed fish were similar to those of male fish. Male fish had higher red blood cell counts and hemoglobin levels than female and sex-reversed fish, suggesting that these hematological indices reflect a higher metabolic rate in male fish. Greater blood triglyceride levels indicated the vitellogenin process in female fish. MT increased the alternative complement activity in female fish (P<0.05). Sex and MT had no significant effects on the hypothalamic mRNAs of GHRH and PACAP. Although not statistically significant, females tended to have higher GH mRNA levels than male and sex-reversed fish. Additionally, MT tended to decrease and increase GH mRNA levels in female and male fish, respectively. There were significant differences among sexes in the expression of GHR, and IGF mRNAs at the peripheral level in the liver and gonads. Females had lower hepatic GHRs and higher ovarian GHRs than male and sex-reversed fish. While the mRNA levels of IGF-1 were lower in the ovary, the levels of IGF-2 were higher compared with those in testes. A significant correlation between GHRs and IGFs was demonstrated in the liver and gonad (except for IGF-1). Multiple regression analysis showed a significant relationship between GH mRNA and both GHRs and IGFs in the liver and gonad. MT exerted androgenic and, to some extent, estrogenic effects on several physiological parameters and GH-IGF action., (Copyright © 2012 Elsevier Inc. All rights reserved.)

By adopting two-factor central composite design (CCD) and response surface methodology (RSM), this paper studied the synergistic effects of water temperature (16-37 degrees C) and salinity (0-18) on the specific growth rate (SGR) and liver superoxide dismutase (SOD) and catalase (CAT) activities of juvenile GIFT Oreochromis niloticus. Water temperature and salinity had significant linear and quadratic effects on the SGR (P < 0.05), respectively. With increasing water temperature or salinity, the SGR decreased after an initial increase. There existed significant synergistic effects between water temperature and salinity (P < 0.05). The SGR was higher at 16-20 degrees C and salinity 9-10, at 27-32 degrees C and salinity 3-5, and at 35-37 degrees C and in freshwater. The SOD and CAT activities were higher at 28-30 degrees C and salinity 6-8. The linear of temperature and quadratic of salinity had significant effects on the two enzymes (P < 0.05), and there was a significant synergistic effect on CAT activity. High temperature and high salinity were not favorable to the expression of SOD and CAT activities. The coefficients of determination of quadratic regression equations for SGR, SOD and CAT activities reached to 0. 954, 0. 831, and 0. 942 (P < 0. 05), respectively, and could be used for prediction. The growth and antioxidant enzyme activities were more affected by water temperature than by water salinity. In the culture practice of 0. niloticus, it would be necessary to optimize culture environment and reduce oxidative stress to promote the growth and disease-resistance of the tilapia.

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.

Although accumulation of the liver toxin microcystin in phytoplanktivorous fish has been demonstrated in captive fish and in natural ecosystems, the relation between microcystin in ingested algae and the pattern of buildup of microcystin in fish is poorly known. In this month-long study performed at a Brazilian fish farm, 45 mature Oreochromis niloticus were fed daily with fresh seston periodically dominated by toxic Microcystis sp. Microcystin was measured daily in the food and every 5 days in liver and muscle samples. Control fish received a diet of seston that was low in toxic cyanobacteria. Initially, in treatment ponds, microcystin available for fish increased from 6.5 to 66.9 ng microcystin fish(-1)day(-1), which was accompanied by an increase from 5.5 to 35.4 ng microcysting liver(-1). Microcystin in muscle was below our detection limit of 4 ng g tissue(-1) for the entire study. In the bloom phase, available microcystin reached its highest concentration (4450 ng MC fish(-1)day(-1)) then decreased to 910 ng microcystin fish(-1)day(-1) on day 31. During this period, microcystin reached its highest concentration of 81.6 ng MC g liver(-1) and stayed high until the end of the experiment. A model based on rapid uptake, saturation, and exponential loss was built with these experimental results, and verified with data from the literature. Our model showed that accumulation was up to 50% of ingestion at low doses, but at intermediate doses, the onset of elimination led to a decline of liver burden. Although the accumulation rate confirms the high contamination potential of microcystin, it was balanced by a high depuration rate and this efficient systemic elimination may explain the tolerance of these fish to toxic blooms in the wild., (Copyright © 2011 Elsevier B.V. All rights reserved.)

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., (Copyright © 2010 Elsevier Inc. All rights reserved.)

The current study was conducted to evaluate the ability of Egyptian bentonite (EB) and montmorillonite (EM) for the prevention of genotoxicity, histochemical and biochemical changes induced by aflatoxin B(1) (AFB(1)) using the micronucleus (MN) assay, chromosomal aberrations and DNA fragmentation analysis in Tilapia fish. Six groups of fish were treated for 3 weeks and included the control group, AFB(1)-treated group and the groups treated with EB or EM alone or in combination with AFB(1). At the end of experiment period, blood samples were collected for MN, testosterone and biochemical assays. Chromosomal aberrations were determined in kidney tissues, DNA fragmentation test was determined in liver and testis, whereas histochemical study was carried out on liver, testis and gills. The results indicated that a significant decrease in total protein, albumin, globulin, testosterone and DNA content in liver, gills and testis accompanied with a significant increase in number of micronucleated erythrocytes (MnRBCs), total chromosomal aberrations in kidney and DNA fragmentation in testis and liver of fish received AFB(1) alone. Fish treated with EB or EM alone were comparable to the control regarding the biochemical parameters except testosterone in EB-treated group which was significantly decreased. Both clays did not induce any significant differences in number of MnRBCs, chromosomal aberrations in the kidney, DNA fragmentation in testis, but not in liver of EB-treated group. The combined treatment with AFB(1) and EB or EM succeeded to improve all the tested parameters towards the control values although it did not normalize them. Moreover, the improvement was pronounced in the group received EM plus AFB(1). It could be concluded that EB and EM have the ability to tightly bind AFB(1) in the gastrointestinal tract of fish resulting in decreasing its bioavailability. Moreover, the two tested clays were safe and can be used as potential aflatoxin binders in animal feed., (Copyright © 2010 Elsevier Inc. All rights reserved.)