Effect of enrofloxacin and emodin on heat-shock proteins’ expression in hepatic cells of grass carp (Ctenopharyngodon idellus)

The aim of the present study was to compare the expression pattern of heat-shock protein 60 (HSP60), 70 (HSP70), and 90 (HSP90) mRNA in hepatic cells of grass carp exposed to enrofloxacin and emodin concentrations. The expression pattern of different genes encoding heat-shock proteins in hepatic cells of grass carp was exposed to graded levels of enrofloxacin (12.5, 25, 50, 100, and 200 μg/ml) or emodin (0.04, 0.2, 1, 5, and 25 μg/ml) for 24 h and were investigated by real-time quantitative PCR. When cells were exposed to up 50 μg/ml enrofloxacin, both HSP60 and HSP70 mRNA levels firstly were increased and thereafter significantly dropped at high concentrations (P < 0.05), while HSP90 decreased with increasing enrofloxacin concentration. Besides, HSP60 and HSP70 expressions were significantly inhibited in the high-concentration groups. In addition, the HSP90 mRNA levels in the treatment exposed to 100 and 200 μg/ml enrofloxacin were significantly lower than those of the control group (P < 0.05). Furthermore, when cells were exposed to graded levels of emodin, HSPs (HSP60, 70, and 90) mRNA levels significantly increased in the groups exposed to 5 and 25 μg/ml of emodin. The different expression pattern of HSPs implied that enrofloxacin could inhibit the expression levels of HSPs, while optimal level of emodin could trigger higher expression levels of HSPs in hepatic cell of grass carp to protect against further damage.     

The effect of dietary folic acid on biochemical parameters and gene expression of three heat shock proteins (HSPs) of blunt snout bream (<Emphasis Type="Italic">Megalobrama amblycephala)</Emphasis> fingerling under acute high temperature stress

The effects of dietary folic acid on biochemical parameters and gene expression of three heat shock proteins (HSPs) of blunt snout bream (Megalobrama amblycephala) fingerling under acute high temperature stress. Six dietary folic acid groups (0.0, 0.5, 1.0, 2.0, 5.0, and 10.0) mg/kg diets were designed and assigned into 18 tanks in three replicates each (300 l/tank) and were administered for 10 weeks in a re-circulated water system. The fingerlings with an initial weight of 27.0 ± 0.03 g were fed with their respective diets four times daily. At the end of the experiment, samples were collected before challenge, 0, 24, 72 h, and 7 days. Serum total protein (TP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), cortisol, glucose, complement C3 (C3), complement C4 (C4, immunoglobulin M (IgM) hepatic superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), and the expression of heat shock protein 60 (HSP60), 70 (HSP70), and 90 (HSP90) were studied. The results showed that fish fed with dietary folic acid between 1.0, 2.0, and 5.0 mg/kg significantly (P < 0.05) increased serum TP, C3, C4 hepatic SOD, CAT, and the expression of HSP60, HSP70, and HSP90 before and after temperature challenge of 32 °C. Also, serum ALP, cortisol, glucose, and hepatic MDA were significantly (P < 0.05) reduced by supplementation of dietary folic acid level 1.0, 2.0, and 5.0 mg/kg before and after the same temperature challenge of 32 °C. Before stress, 0, 24, 72 h, and 7 days significantly (P < 0.05) affects serum biochemical parameters, immune and antioxidant capacities, and expression level of three HSPs. Furthermore, there was no statistical evidence to show that dietary folic acid inclusion level and temperature duration have significant interactive effect on serum biochemical parameters, antioxidant parameters, and gene expression level (P > 0.05) of the three HSPs. However, there were statistical significant interactive effect between dietary folic acid inclusion level and temperature duration on serum C3 and C4 (P < 0.05) except IgM (P > 0.05). The present results indicate that supplementation of basal diet from 1.0 mg/kg; 2.0 and 5.0 mg/kg can enhance acute high temperature resistance ability in M. amblycephala fingerling to some degree and improve physiological response, immune and antioxidant capacities, and expression level of three HSPs.     

Effects of cold acclimation on the survival,feeding rate,and non-specific immune responses of the freshwater red claw crayfish (<Emphasis Type="Italic">Cherax quadricarinatus</Emphasis>)

The effect of cold acclimation on growth performance, non-specific immune responses, and expression level of HSP21 and CSP gene were studied in red claw crayfish (Cherax quadricarinatus) using a 4-week stress trial. We set a four-temperature gradient, with water temperatures of 25, 20, 15, and 9 °C, respectively. With the gradual decrease of temperature, the survival rate, feeding rate, and hepatopancreas index (HIS) of the red claw crayfish showed a decreasing trend. Decreased total hemocyte count (THC) and hemocyanin concentration were observed when water temperature decreased. The activities of superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) in the hepatopancreas and hemolymph all gradually declined with decreasing temperatures and then significantly lowered at 9 °C compared with those at 25 °C. The activity of glutathione peroxidase (GPx) in these two tissues showed in the opposite trend, indicating that they may have different regulation mechanisms. A gradual increase of malondialdehyde (MDA) concentration was detected in the hepatopancreas and hemolymph when the temperature decreased. Low temperature stress also affected the expression of heat shock proteins 21(HSP21) and cold shock domain protein (CSP). These results indicate that cold acclimation may induce oxidative stress on the crayfish and then cause oxidative damage and hemocyte apoptosis, as well as immunosuppression in Cherax quadricarinatus, which may finally affect the growth and survival of Cherax quadricarinatus.     

Effect of high temperature on survival,oxygen consumption,behavior, ammonia-N excretion,and related immune indicators of the Japanese scallop Mizuhopecten yessoensis

In this study, two experiments were conducted to test the effect of high temperature on survival, behavior, oxygen consumption, ammonia-N excretion, and enzyme activities related to oxidative stress of the Japanese scallop Mizuhopecten yessoensis. In the first test, we abruptly transferred scallops from the rearing temperature (15 °C, control temperature) to 20, 22, 24, and 26 °C. Scallops exposed to 26 °C were significantly affected by temperature, with 100 % mortality after 12 h. The 8-, 12-, 24-, 48-, and 96-h lethal temperatures for 50 % mortality (LT₅₀) were 27.5, 24.4, 24.3, 24.2, and 23.8 °C, respectively. The activities of CAT and SOD and the T-AOC in the coelomic fluid of M. yessoensis changed significantly after high-temperature stress (P < 0.05). They reached to the highest levels after 8 h of stress in the 22, 24, and 26 °C treatment groups then returned to the control group level. The content of MDA reached the highest level after 12 h in each temperature treatment. In the second test, scallops were acclimatized to the different temperature levels (20, 22, 24, and 26 °C) and then maintained for 30 days. Survival was significantly lower at 26 °C than at the other temperatures, and the highest survival occurred in the 15 °C treatment. High temperature also significantly influenced the oxygen consumption rates and ammonia-N excretion rates (P < 0.05). As the temperature increased, the CAT and SOD activities and the T-AOC in the coelomic fluid of M. yessoensis declined significantly, whereas the MDA content increased. These results illustrate that high temperature can significantly affect the survival, behavior, oxygen consumption, ammonia-N excretion, and enzyme activities related to oxidative stress of M. yessoensis.     

Effect of nitrite exposure on oxygen-carrying capacity and gene expression of <Emphasis Type="Italic">NF-κB</Emphasis>/<Emphasis Type="Italic">HIF-1α</Emphasis> pathway in gill of bighead carp (<Emphasis Type="Italic">Aristichthys nobilis</Emphasis>)

Nitrite (NO₂^?) contamination of water can severely impact the health of aquatic life and is a major concern for commercial aquaculture. In order to study the effect of nitrite on Aristichthys nobilis, we investigated the oxygen-carrying capacity, NF-κB/HIF-1α pathway, and the gill tissue structure under nitrite stress. In the current study, bighead carp (initial weight 180.05?±?0.092 g) were exposed to nitrite (48.634 mg/L) for 96 h and then for 96 h recovery test. After nitrite exposure for 6 h, hypoxia-inducible factor-1α (HIF-1α) and nuclear factor-κB (NF-κB) mRNA expression increased significantly in the gill of bighead carp (P?<?0.05). After nitrite exposure for 12 h, hemoglobin (Hb) and methemoglobin reductase (MHBR) content in blood decreased significantly (P?<?0.05); TLR4 mRNA expression increased significantly (P?<?0.05). After nitrite exposure for 24 h, methemoglobin (MetHb) content increased significantly (P?<?0.05). After recovery test, all the indicators except TLR4 mRNA expression level recovered to initial level. In conclusion, nitrite exposure can affect hemoglobin dynamics, as oxidization of nitrite by hemoglobin results in the reduction of Hb to MetHb leading to hypoxia and nitrite exposure can also result into gill tissue damage. In the face of nitrite exposure, NF-κB and HIF-1α mRNA expression level increased immediately to protect the body from oxidative damage and eased hypoxic condition caused by nitrite. It was also observed that nitrite damage is recoverable in Aristichthys nobilis, but it may be need more than 96 h.     

Immunogene expression in head kidney and spleen of common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.) following thermal stress and challenge with Gram-negative bacterium, <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

To evaluate the effect of thermal and microbial stress on the immune response of common carp (Cyprinus carpio L.), relative mRNA expression level of pro-inflammatory cytokines [tumor necrosis factor alpha (TNF-α) and interleukin (IL)-1β] and other genes related to immune or stress response [inducible nitric oxide synthase (iNOS), heat shock protein 70 (Hsp70), superoxide dismutase one (SOD1), and glucocorticoid receptor (GR)] was measured by quantitative PCR (qPCR). In addition, total protein and total immunoglobulin level in blood plasma of experimental common carp was also assayed. All the above parameters were estimated 24 h post-challenge with Gram-negative bacterium, Aeromonas hydrophila. Common carp (54.89?±?6.90 g) were initially exposed to 20 °C (control group) and 30 °C (thermal stress group) water temperature for 30 days, followed by experimental challenge with 2.29?×?10⁸ colony forming unit/mL (CFU/mL; LD₅₀ dose) of A. hydrophila. Exposure of fish to thermal stress and subsequently challenge with A. hydrophila significantly (P?<?0.05) increases the IL-1β mRNA expression in head kidney and spleen of common carp by ~?39.94 and ~?4.11-fold, respectively. However, TNF-α mRNA expression in spleen decreased ~?5.63-fold in control fish challenged with A. hydrophila. Thermal stress and challenge with bacterium suppresses the iNOS and GR mRNA expression in spleen of common carp. Moreover, significant (P?<?0.05) increase in total protein content of blood plasma (~?43 mg/g) was evident in fish exposed to thermal stress and challenged with A. hydrophila. In conclusion, our study highlights the importance of elevated temperature stress and microbial infection in differential regulation of expression of several immunogenes in common carp.     

In vitro and in vivo hepatoprotective and antioxidant effects of Astragalus polysaccharides against carbon tetrachloride-induced hepatocyte damage in common carp (Cyprinus carpio)

The present study is aiming at evaluating the hepatoprotective and antioxidant effects of Astragalus polysaccharide (APS) on the carbon tetrachloride (CCl₄)-induced hepatocyte and liver injury in common carp in vitro and in vivo. In vitro, APS (200, 400 and 800 μg/ml) was added to the carp primary hepatocytes before (pre-treatment), after (post-treatment) and both before and after (pre- and post-treatment) the incubation of the hepatocytes with CCl₄ at 8 mM in the culture medium. APS at concentrations of 200, 400 and 800 μg/ml significantly improved cell viability and inhibited the elevation of glutamate pyruvate transaminase (GPT), glutamate oxalate transaminase (GOT), lactate dehydrogenase (LDH) and malondialdehyde (MDA) and significantly increased the reduced level of superoxide dismutase (SOD). In vivo administration of APS at the doses of 1.5 and 3 g/kg in the diet for 60 days prior to CCl₄ intoxication significantly reduced the elevated activities of GPT, GOT and LDH and increased the reduced levels of total protein and albumin in the serum; meanwhile, the reduced levels of SOD, glutathione and total antioxidant capacity (T-AOC) were markedly increased and the MDA formation was significantly inhibited in liver tissue. Overall results proved the hepatoprotective action of APS, which is likely related to its antioxidant activity. The results support the use of APS as a hepatoprotective and antioxidant agent in fish.     

The effects of dietary thiamin on oxidative damage and antioxidant defence of juvenile fish

The present study explored the effects of thiamin on antioxidant capacity of juvenile Jian carp (Cyprinus carpio var. Jian). In a 60-day feeding trial, a total of 1,050 juvenile Jian carp (8.20 ± 0.02 g) were fed graded levels of thiamin at 0.25, 0.48, 0.79, 1.06, 1.37, 1.63 and 2.65 mg thiamin kg^?1 diets. The results showed that malondialdehyde and protein carbonyl contents in serum, hepatopancreas, intestine and muscle were significantly decreased with increasing dietary thiamin levels (P < 0.05). Conversely, the anti-superoxide anion capacity and anti-hydroxyl radical capacity in serum, hepatopancreas, intestine and muscle were the lowest in fish fed the thiamin-unsupplemented diet. Meanwhile, the activities of catalase (CAT), glutathione peroxidase, glutathione S-transferase and glutathione reductase, and the contents of glutathione in serum, hepatopancreas, intestine and muscle were enhanced with increasing dietary thiamin levels (P < 0.05). Superoxide dismutase (SOD) activity in serum, hepatopancreas and intestine followed a similar trend as CAT (P < 0.05). However, SOD activity in muscle was not affected by dietary thiamin level (P > 0.05). The results indicated that thiamin could improve antioxidant defence and inhibit lipid peroxidation and protein oxidation of juvenile Jian carp.     

Effects of dietary astaxanthins on pigmentation of flesh and tissue antioxidation of rainbow trout (Oncorhynchus mykiss)

The present study was conducted to evaluate the effects of three commercial astaxanthin preparations (100 mg kg^?1 diet) with different solubilities in water, from DSM (Dutch State Mines), BASF (Badische Anilin and Soda Fabrik) and Wisdom Company on pigmentation of flesh and antioxidation of flesh, serum and liver in rainbow trout with an initial weight of 52.07 g. After 60 days of feeding, there were no significant differences in growth or flesh proximate composition of rainbow trout among groups (P > 0.05); the Salmo Fan score, redness and astaxanthin content of flesh in rainbow trout fed diets supplemented with astaxanthins were higher than those of the control group (P < 0.05). At 0, 12, 24, 48 and 72 h after thawing, the flesh malondialdehyde (MDA) content of the three astaxanthin groups was lower than that of the control group (P < 0.05). The total antioxidation capacity (T-AOC) of liver in the three astaxanthin groups was significantly higher, but serum catalase (CAT) activities were lower, than that of the control group (P < 0.05). The results indicate that addition of 100 mg kg^?1 astaxanthin from DSM, BASF or Wisdom to the diet could improve flesh redness and liver T-AOC, reduce serum CAT, SOD and flesh MDA and extend the shelf life of flesh, in spite of the different solubilities of the three sources in water.     

Modulatory role of L-carnitine against microcystin-LR-induced immunotoxicity and oxidative stress in common carp

Microcystin-LR (MCLR), one of the most popular microcystins (MCs) found in many field water bodies around the world, poses great health risks to animals and humans. In the present study, healthy common carp (initial weight 24.8 ± 2.3 g) were randomly assigned to five groups. Group I was fed on normal diet as control. Group II was maintained on normal diet and received MCLR intraperitoneal injection (150 μg kg^?1 BW). Common carp in groups III, IV, and V were daily pretreated with L-carnitine (LC) at doses of 0.5, 1.0, and 2.0 g kg^?1 of the diet for 4 weeks prior to MCLR intraperitoneal injection. The results showed that MCLR alone led to a significant downregulation in immune response, including serum complement C3, lysozyme, and bactericidal activity. However, oxidative stress response: catalase (CAT), superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GPx), and lipid peroxidation (LPO) levels were significantly increased. Similarly, gene expressions of inflammatory IL-1β, TNF-α, IFN I, and heat shock proteins (HSP70 and HSP90) were also upregulated after challenged with MCLR. However, LC pretreated group caused a significant elevation in immune response (C3, lysozyme, and bactericidal activity) and gene expressions of inflammatory IL-1β, TNF-α, IFN I, and heat shock proteins (HSP70 and HSP90) after MCLR stress. Antioxidant activities (CAT, SOD, GSH, GPx, and LPO) were returned to background levels at 96 h after MCLR challenge. Strikingly, LC supplementation at 2.0 g kg^?1 has been considered the optimum for common carp since it exhibited enhancement of immune response and antioxidant activity over the level 0.5 and 1.0 g kg^?1, and even better than that of control level. It was concluded that LC as a functional feed additive significantly inhibited the progression of MCLR-induced immunotoxicity and oxidative stress in common carp.     

Respiratory response of grass carp <Emphasis Type="Italic">Ctenopharyngodon idellus</Emphasis> to dissolved oxygen changes at three acclimation temperatures

Respiratory parameters of grass carp were studied during dissolved oxygen (DO) changes from normal DO to hypoxia, then return to normal DO at 15, 25, and 30 °C acclimation, respectively. The results showed that with increases of acclimation temperature at normoxia the respiratory frequency (f_R), oxygen consumption rate (VO₂), respiratory stroke volume (V_S.R), gill ventilation (V_G), and V_G/VO₂ of grass carp increased significantly, but the oxygen extraction efficiency (EO₂) of fish decreased significantly (P < 0.05). With declines of DO levels, the f_R, V_S.R, V_G, and V_G/VO₂ of fish increased significantly at different acclimation temperatures (P < 0.05). A slight increase was found in VO₂, and the EO₂ of fish remained almost constant above DO levels of 3.09, 2.91, and 2.54 mg l^?1 at 15, 25, and 30 °C, while the VO₂ and EO₂ began to decrease significantly with further reductions in DO levels (P < 0.05). After 0.5 h of recovery to normoxia from hypoxia at three acclimation, the f_R, V_S.R, V_G, and V_G/VO₂ of the fish decreased sharply; meanwhile, the VO₂ and EO₂ increased sharply (P < 0.05). The respiratory parameters of fish gradually approached initial values with prolonged recovery time to normoxia, and reached their initial values in 2.5 h at 25 and 30 °C acclimation. The critical oxygen concentrations (C_c) of fish for VO₂ were 2.42 mg l^?1 at 15 °C, 2.02 mg l^?1 at 25 °C, and 1.84 mg l^?1 at 30 °C, respectively. The results suggest that grass carp are highly adapted to varied DO and short-term hypoxia environments.     

Effects of Bacillus preparations on immunity and antioxidant activities in grass carp (Ctenopharyngodon idellus)

This experiment was conducted to study the effects of Bacillus preparations on immunity and antioxidant activities in grass carp. A total of 315 grass carp, with similar initial weight (average weight of fish 45?g), were randomly divided into three groups with three replicates. The control group was fed the basal diet without Bacillus; treatment group 1 was added Bacillus preparation no. 1 with 1?×?10⁸?cfu/m³ per 7?days in culture water and also fed the basal diet; treatment group 2 was fed the basal diet mixed with 0.5?% Bacillus preparation no. 2, and the culture water was added 1?×?10⁸?cfu/m³ Bacillus preparation no. 1 per 7?days. After 4?weeks of culture, 12 grass carp from each replicate were taken randomly for the determination of immune response and oxidization resistance indices. The results showed that compared with control, the level of globulin and IgM of treatment group 2 was significantly increased (P?<?0.05), which was also significantly higher (P?<?0.05) than that of group 1. For the non-specific immunity index, compared with control, the lysozyme activity and complement (C3) content of treatment group 1 significantly increased (P?<?0.05), and the level of myeloperoxidase and C3 of treatment group 2 was significantly higher (P?<?0.05) than that of control, which was also significantly higher (P?<?0.05) than that of group 1. In the serum, compared with the control, the level of total antioxidant activity (T-AOC), antisuperoxide anion free radical (ASAFR) and glutathione (GSH) of two treatment groups was significantly increased (P?<?0.05); GSH content of treatment group 2 was significantly (P?<?0.05) higher than that of treatment group 1 and control. There was no significant difference between T-AOC and ASAFR among the two treatment groups; no significant effect was found on glutathione peroxidase (GSH-Px) and maleic dialdehyde (MDA) among the three groups. In the liver, T-AOC, SOD, ASAFR, GSH-Px and GSH from two treatment groups were significantly higher (P?<?0.05) than those of control; T-AOC, SOD and catalase from treatment group 2 were significantly higher (P?<?0.05) than those of treatment group 1; and MDA of two treatment groups was significantly decreased (P?<?0.05) as compared with the control. The results indicate that Bacillus preparations added into water can increase serum immunoglobulin levels and most of non-specific immune parameters content and enhance the antioxidant ability of grass carp, while adding Bacillus preparation into the water and feed is much better.     

Modulation of antioxidant defense and immune response in zebra fish (<Emphasis Type="Italic">Danio rerio</Emphasis>) using dietary sodium propionate

The present study explores the effect of dietary sodium propionate on mucosal immune response and expression of antioxidant enzyme genes in zebra fish (Danio rerio). Six hundred healthy zebra fish (0.42 ± 0.06 g) supplied, randomly stocked in 12 aquariums and fed on basal diets supplemented with different levels of sodium propionate [0 (control), 5, 10 and 20 g kg^?1] for 8 weeks. At the end of the feeding trial, mucosal immune parameters (TNF-α, IL-1β, Lyz), antioxidant enzyme (SOD, CAT) as well as heat shock protein 70 (HSP70) gene expression were measured. The results revealed feeding on sodium propionate significantly up-regulated inflammatory response genes (TNF-α, IL-1β, Lyz) in a dose-dependent manner (P < 0.05). However, antioxidant enzyme genes significantly down-regulated in the treated group compared with control (P < 0.05). Also, HSP70 gene expression was higher in the liver of fish fed the basal diet and deceased with elevation of sodium propionate levels in the diet. These results showed beneficial effects of dietary sodium propionate on mucosal immune response as well as the antioxidant defense of zebra fish.     

Molecular cloning and expression of the heat shock protein 70 gene in the Kumamoto oyster <Emphasis Type="Italic">Crassostrea sikamea</Emphasis>

Episodes of summer mortality of the Kumamoto oyster Crassostrea sikamea are a major problem for its cultivation. Expression of the heat shock protein 70 (HSP70) is induced by various environmental stresses, including heat. We cloned and sequenced hsp70 complementary DNA from C. sikamea to investigate the relationship between hsp70 expression and heat tolerance in this oyster. Quantitative real-time polymerase chain reaction was performed using gill tissue dissected from oysters before and after heat shock for 1 h. The results showed hsp70 expression was faster and greater in oysters cultured at 20–22 °C than at 10–12 °C, and survival was lower among oysters cultured at 20–22 °C than at 10–12 °C. Moreover, heat tolerance was investigated by a 1-h pre-heat treatment, followed by exposure to heat shock conditions 5 days later. Survival was higher and hsp70 expression was notably lower in oysters that received the pre-heat treatment compared with those that did not. We conclude that a pre-heat treatment of only 1 h may be useful for inducing heat tolerance in C. sikamea, and that a low level of hsp70 expression after heat shock is an important index in selecting for high heat tolerance in these oysters.     

Stimulatory effect of dietary taurine on growth performance,digestive enzymes activity,antioxidant capacity,and tolerance of common carp, <Emphasis Type="Italic">Cyprinus carpio</Emphasis> L., fry to salinity stress

The present study was carried out to evaluate the effect of dietary taurine (Tau) on performance, digestive enzymes, antioxidant activity, and resistance of common carp, Cyprinus carpio L., fry to salinity stress. Fish (0.97?±?0.033 g) were fed on different taurine levels of 0.0 (control), 5, 10, 15, or 20 g/kg diet up to satiation twice daily for 8 weeks. At the end of the feeding trial, fish were stressed by exposure to 10 ppt salinity for 3 days during which fish mortality was observed. Fish performance was significantly (P?<?0.05) improved by dietary taurine up to 15 g Tau/kg diet after which fish growth and feed intake were almost the same. Also, taurine supplementation significantly (P?<?0.05) elevated activities of intestinal amylase, lipase, and protease resulting in an improving in feed intake giving better performance. Furthermore, Tau-stimulated antioxidant activity of common carp was observed in a dose-related manner, where activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were significantly (P?<?0.05) higher, but malondialdehyde (MDA) value was significantly (P?<?0.05) lower in Tau-fed fish groups than those fed the control diet. In salinity stress experiment, highest survival rate was observed at fish fed Tau-supplemented diets without significant (P?>?0.05) differences over fish fed the control diet. It appears that taurine could be used as a feed supplement to confer better growth and health of common carp fry with optimal level of 15 g/kg diet.     

Protective Effect of Emodin against Hyperthermia‐induced Stress in Hepatic Cells of Grass Carp,Ctenopharyngodon idellus

Emodin is an anthraquinone exhibiting several positive benefits of anti‐inflammatory, free radical scavenging, and resistance to stress. The goal of this study is to investigate the effects of emodin on the hepatic cell line of grass carp exposed to hyperthermic stress. Cultured cells were treated with various emodin concentrations (0, 0.04, 0.2, and 1.0 µg/mL) at 27 C for 24 h. Then all cultured cells were exposed to thermal stress by increasing the culture temperature (32 ± 0.5 C) for 0.5 h. Increased temperatures significantly reduced cell viability and increased lactate dehydrogenase (LDH) release in three of the four experimental groups (0, 0.2, and 1 µg/mL emodin) compared with the control. Additionally, reactive oxygen species (ROS) were significantly higher in cells exposed to elevated temperatures and treated with 0.2 or 1 µg/mL emodin and mitochondrial membrane potential was significantly lower in cells treated with 0, 0.2, or 1 µg/mL emodin. Expressions of heat shock proteins (HSP60, HSP70, and HSP90) were significantly higher in all but one of the experimental groups. Our results suggest that 0.04 µg/mL emodin can increase cell viability and HSP90 mRNA level, reduce LDH release and concentration of ROS, and contribute to enhance the resistance to high temperature stress in the hepatic cells of grass carp.     

Dietary docosahexaenoic acid decreased lipid accumulation via inducing adipocytes apoptosis of grass carp, <Emphasis Type="Italic">Ctenopharygodon idella</Emphasis>

The purpose of this study was to explore the mechanism of by which docosahexaenoic acid (DHA) inhibit the accumulation of adipose tissue lipid in grass carp (Ctenopharyngodon idella). We therefore designed two semi-purified diets, namely DHA-free (control) and DHA-supplemented, and fed them to grass carp (22.19 ± 1.76 g) for 3 and 6 weeks. DHA supplementation led to a significantly lower intraperitoneal fat index (IPFI) than that in the control group by reducing the number of adipocytes but significantly higher adipocyte size (P < 0.05). In the intraperitoneal adipose tissue, the DHA-fed group showed significantly higher peroxisome proliferator-activated receptor (PPAR)γ, CCAAT enhancer-binding protein (C/EBP)α, and sterol regulatory element-binding protein (SREBP)1c mRNA expression levels at both 3 and 6 weeks (P < 0.05). However, the ratio of the expression levels of B cell leukemia 2 (Bcl-2) and Bcl-2-associated X protein (Bax) was significantly lower in the DHA-fed group than in the control group (P < 0.05), and the protein expression levels of the apoptosis-related proteins caspase 3, caspase 8, and caspase 9 were also significantly higher (P < 0.05). Overall, although DHA promotes lipid synthesis, it is more likely that DHA could suppress the lipid accumulation in adipocytes of grass carp by inducing adipocyte apoptosis.