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.     

Hepatoprotective and antioxidant effects of dietary Angelica sinensis extract against carbon tetrachloride‐induced hepatic injury in Jian Carp (Cyprinus carpio var. Jian)

The present study aimed to evaluate the hepatoprotective effects of Angelica sinensis extract (ASE) against carbon tetrachloride (CCl₄)‐induced hepatotoxicity in Jian carp (Cyprinus carpio var.Jian). Fish were fed diets containing four doses of ASE (0%, 0.1%, 0.5% and 1.0%) for 60 days, and then given an intraperitoneal injection of 30% CCl₄ in olive oil at a volume of 0.05 mL/10 g body weight. At 72 h post injection, blood and liver samples were collected for biochemical analysis, comet assay, histopathological examination and CYP3A mRNA expression. Results showed that the increases of glutamate pyruvate transaminase (GPT) and glutamate oxalate transaminase (GOT) induced by CCl₄ were significantly inhibited by pre‐treating the fish with 0.1%, 0.5% and 1.0% ASE in the diets. The elevation of lactate dehydrogenase (LDH) and the reductions of the total protein (TP) and albumin (Alb) in the serum induced by CCl₄ were also inhibited by pre‐treatments with 0.5 and 1.0% ASE. In the liver tissue, pre‐treatment with 1.0% ASE significantly inhibited the malondialdehyde (MDA) formation and the reductions of the total antioxidant capacity (T‐AOC), superoxide dismutase (SOD), glutathione (GSH) and CYP3A mRNA expression induced by CCl₄. Comet assay showed that tail moment, olive tail moment, tail length and tail DNA% were positively changed in fish pretreated with 0.5 and 1.0% ASE. CCl₄‐induced histological changes were obviously reduced by 0.5% and 1.0% ASE. Overall results prove the hepatoprotective effect of ASE in a dose‐dependent manner and support the use of ASE (1.0%) as a hepatoprotective and antioxidant agent in fish.     

水飞蓟素对四氯化碳致鲫肝(细胞)损伤的保护和抗氧化作用

为了评价水飞蓟素(Silymarin, SM)对鲫(Cyprinus carpio)肝(细胞)的保护和抗氧化作用,分别从体外和体内两个方面探讨其作用效果.在体外,利用8 mmol/L的四氯化碳(CCl4)作用肝细胞4 h构建鲫肝细胞体外损伤模型,用不同质量浓度的水飞蓟素(100、300和600μg/mL)对鲫肝细胞进行前处理(CCl4损伤前加药)、后处理(CCl4损伤后加药)和前后处理(CCl4损伤前后均加药),然后检测细胞活力和细胞上清中谷丙转氨酶(GPT)、谷草转氨酶(GOT)、乳酸脱氢酶(LDH)、超氧化物歧化酶(SOD)和丙二醛(MDA)含量.在体内,用含水飞蓟素的饲料(0.1、0.5和1.0 g/kg)饲喂鲫60 d,再腹腔注射30%四氯化碳-植物油混合液,然后检测血清和肝组织匀浆中谷丙转氨酶(GPT)、谷草转氨酶(GOT)、乳酸脱氢酶(LDH)、超氧化物歧化酶(SOD)、谷胱甘肽(GSH)等生化指标.研究结果表明,水飞蓟素不同程度地抑制 CCl4损伤引起的肝细胞培养上清中 GPT、GOT、LDH活性和 MDA含量的升高,提高 SOD活性及肝细胞的存活率.体内研究发现,0.5和1.0 g/kg水飞蓟素显著降低CCl4损伤导致的血清中GPT、GOT、LDH活性升高,显著提高总蛋白(TP)、白蛋白(Alb)含量,有效提高肝中谷胱甘肽(GSH)含量、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GPx)、总抗氧化能力(T-AOC)和超氧化物歧化酶(SOD)活性,降低丙二醛(MDA)含量(P<0.05或P<0.01);而0.1g/kg的水飞蓟素除了抑制LDH显著升高外,对其他指标均无效果.综合以上结果认为,水飞蓟素对鲫肝有保护作用,可防治鱼类肝(细胞)损伤,该保护作用可能与其抗氧化作用有关.     

Protective effect of <Emphasis Type="Italic">Ganoderma lucidum</Emphasis> polysaccharide against carbon tetrachloride-induced hepatic damage in precision-cut carp liver slices

The aim of the present study was to investigate the protective effects of Ganoderma lucidum polysaccharide (GLPS) against carbon tetrachloride (CCl₄)-induced hepatotoxicity in vitro in common carp. Precision-cut liver slices (PCLSs), which closely resemble the organ from which they are derived, were employed as an in vitro model system. GLPS (0.1, 0.3, and 0.6 mg/ml) was added to PCLS culture system before the exposure to 12 mM CCl₄. The supernatants and slices were collected to detect molecular and biochemical responses to CCl₄ and PCLS treatments. The levels of CYP1A, CYP3A, and CYP2E1 were measured by ELISA; the mRNA expressions of TNF-α, IL-1β, IL-6, and iNOS were determined by RT-PCR; and the relative protein expressions of c-Rel and p65 were analyzed by western blotting. Results showed that GLPS inhibited the elevations of the marker enzymes (GOT, GPT, LDH) and MDA induced by CCl₄; it also enhanced the suppressed activity of antioxidant enzymes (SOD, CAT, GSH-Px, T-AOC). The treatment with GLPS resulted in significant downregulation of NF-κB and inflammatory cytokine mRNA levels and significant decreases in the hepatic protein levels of CYP1A, CYP3A, and CYP2E1. These results suggest that GLPS can protect CCl₄-induced PCLS injury through inhibiting lipid peroxidation, elevating antioxidant enzyme activity, and suppressing immune inflammatory response.     

饲料中添加姜黄素对尼罗罗非鱼幼鱼生长和四氯化碳诱导肝损伤的影响

本试验旨在研究饲料中姜黄素对尼罗罗非鱼(Oreochromis niloticus)幼鱼生长性能的影响和对四氯化碳(CCl_4)诱导鱼体急性肝损伤的保护作用,为筛选治疗鱼类肝脏综合征的绿色药物提供理论依据。在基础饲料中分别添加不同水平(0、15 mg/kg、30 mg/kg、60 mg/kg、120 mg/kg和240 mg/kg)的姜黄素,连续饲喂鱼体8周后进行采样,探讨姜黄素对尼罗罗非鱼生长的影响,并采用CCl_4诱导鱼体急性肝损伤,72 h后采集血液和肝组织,检测相关抗氧化指标以及肝组织切片的变化。结果显示,饲料中添加60 mg/kg和120 mg/kg姜黄素可显著增加鱼体的增重率和特定生长率(P0.05);当罗非鱼经CCl_4诱导72 h后,60 mg/kg和120 mg/kg姜黄素组的血浆谷草转氨酶(GOT)、谷丙转氨酶(GPT)活力和丙二醛(MDA)含量显著低于对照组(P0.05),而血浆总蛋白(TP)、白蛋白(ALB)、谷胱甘肽(GSH)、血浆总抗氧化能力(T-AOC)、肝超氧化物歧化酶(SOD)活力、谷胱甘肽过氧化物酶(GSH-Px)活力却显著高于对照组(P0.05);姜黄素在一定程度上可保护鱼体肝不受损伤,且以添加120 mg/kg水平时效果最佳。综上,饲料中添加60～120 mg/kg姜黄素可促进尼罗罗非鱼幼鱼生长性能的提高,而当饲料中添加120 mg/kg姜黄素时,对其肝的保护作用最强,可有效地抑制肝组织的脂质过氧化。     

Investigation of the cytotoxicity of apidaecin on intestinal epithelial cells of tilapia (Oreochromis niloticus) in vitro

Antimicrobial peptides (AMPs) are a diverse group of small polypeptides that can inhibit the growth of microbes; the investigation of their cytotoxicity is critical before they can be considered for use. The purpose of the present study was to examine the cytotoxicity of apidaecin at different concentrations (0.0, 10.0, 20.0, and 30.0 μg/ml) on tilapia, Oreochromis niloticus, primary intestinal epithelial cells in vitro through cells morphology observation, methylthiazolyldiphenyl-tetrazolium bromide (MTT) conversion assay, and cellular viability assay. The lactate dehydrogenase (LDH) activity, cytosolic free Ca²⁺ concentration, and phospholipase A₂ (PLA₂) activity of primary cells treated with/without apidaecin were also determined. No significant differences (P > 0.05) in MTT assay and viability were found between the treated and the control cells. LDH activities were slightly increased when treated with apidaecin for 24 h compared with the control (19.97 ± 1.24 U/l), but not significantly (P > 0.05). When treated with 20.0 μg/ml apidaecin for 24 h, the concentrations of cytosolic free Ca²⁺ was the highest among all the treatments (133.65 ± 9.65 nmol/l), but not the difference was not significant when compared with the control (P > 0.05). Similar results were found for the activity of cytosolic PLA₂. The current results indicate that apidaecin did not show significant cytotoxicity to primary epithelial cells within 30.0 μg/ml and that it can be used as a new candidate for infection control in fish culture.     

Growth performance,haematological and serum biochemical profiles in rainbow trout (Oncorhynchus mykiss) fed diets with varying levels of lupin (Lupinus albus) meal

A feeding experiment was conducted to study the response of rainbow trout juveniles fed different levels of lupin meal in diets for rainbow trout juveniles. Very limited information is available on the relationship between dietary lupin meal in rainbow trout health status. Therefore, this study aimed to determine the effects of lupin meal inclusion levels (0%, 15%, 30%, 45%, and 60%) on growth performance and health status of rainbow trout juveniles. The experimental diets (LM₀, LM₁₅, LM₃₀, LM₄₅, and LM₆₀) were formulated iso‐nitrogenous (41% crude protein) and iso‐calorific (18% crude lipid). The fish were fed twice a day. As a result, the best growth performance was observed in fish fed with LM₁₅ and LM₃₀ diets. No significant differences were detected among experimental groups in terms of body compositions. The haematological values showed significantly (p < 0.05) lower heamatocrit and mean cellular volume (MCV) in the group of LM₆₀ compared with the other groups. For the other haematological parameters such as haemoglobin, red blood cell and mean cellular haemoglobin studied in the present study no significant differences were observed (p < 0.05). The lupin meal included groups showed significant reduction in total protein (TPROT), triglyceride (TROG), cholesterol (CHOL), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) compared with the control group (p < 0.05). The inclusion of lupin meal did not cause any changes in glucose (GLU), glutamic oxaloacetic transaminase (GOT), and glutamic pyruvic transaminase (GPT) between the treatment groups (p < 0.05). In conclusion, lupin meal might be used in rainbow trout diets up to 30% without any malnutrition effect on growth performance, haemotological and serum biochemical parameters.     

Antifouling steroids isolated from red alga epiphyte filamentous bacterium Leucothrix mucor

Active antifouling steroids were isolated from the filamentous bacterium Leucothrix mucor. Bioactivity-guided isolation by silica gel column chromatography and high-performance liquid chromatography generated two compounds. The chemical constituents having the antifouling activities were identified as 17-(1,2-dihydroxyl-5-methyl-hexane)-2,3-dihydroxyl-cholest-4-en-6-one [compound (a)] and 13-acetate-17-(1,5-dimethylhexane)-cholest-7-en-3,5,6,15-tetraol [compound (b)] by interpreting one- and two-dimensional nuclear magnetic resonance and mass spectroscopy data. The two compounds were isolated from 780 mg of crude extract, yielding 12 and 14 mg, respectively. Antifouling activities were determined against a representative soft fouling macroalgae (Ulva pertusa), a biofouling diatom (Navicula annexa), and the bacteria Pseudomonas aeruginosa KNP-3 and Alteromonas sp. KNS-8. The two compounds were able to inhibit the spore settlement of Ulva pertusa zoospores with a low half maximal effective concentration (EC50) (1.2–2.1 μg/ml) and inhibit diatom growth with an EC50 of 5.2–7.5 μg/ml. Compound (a) showed activity with minimum inhibitory concentration values of 32–56 μg/ml and compound (b) showed an activity of 66–90 μg/ml. Among the two compounds, compound (a) is a new compound, whereas compound (b) was previously reported to have been isolated from a marine invertebrate.     

Antiviral activities of Clinacanthus nutans (Burm.f.) Lindau extract against Cyprinid herpesvirus 3 in koi (Cyprinus carpio koi)

Cyprinid herpesvirus 3 (CyHV‐3) or koi herpesvirus (KHV) is a virulent viral infection in common carp and koi. The disease has caused global epizootic and economic loss in fish aquaculture and in the wild. Clinacanthus nutans (Burm. f.) Lindau is a well‐known medicinal plant used in Thai traditional medicine. Virucidal effects of the plant extract against human herpes simplex virus have been reported. In this study, C. nutans crude extract was tested for antiviral activities against CyHV‐3 in koi carp. Results showed effective antiviral activity against CyHV‐3 pre‐ and post‐infection. The 50% lethal concentration (LC₅₀) of extract was higher than 5 mg/ml. The 50% effective dose (ED₅₀) was 0.99 mg/ml, 0.78 mg/ml, 0.75 mg/ml and 0.71 mg/ml at 1, 2, 3 and 4 hr pre‐infection, respectively. The ED₅₀ from post‐infection tests was 2.05 mg/ml and 2.34 mg/ml at 0 and 24 hr, respectively. These results demonstrated that crude extract expressed antiviral activity against CyHV‐3 and can be applied as a therapeutic agent in common carp and koi aquaculture.     

Relative potencies of natural estrogens on vitellogenin and choriogenin levels in the Indian freshwater spotted snakehead, <Emphasis Type="Italic">Channa punctata</Emphasis>: in vivo and in vitro studies

The relative efficacies of three natural estrogens viz., estrone (E₁), estradiol-17β (E₂) and estriol (E₃) to induce synthesis of vitellogenin (Vg) and choriogenin (Chg) were assessed in primary hepatocyte cultures of the Indian freshwater spotted snakehead, Channa punctata. Hepatocytes were isolated from the spotted snakehead liver by a non-enzymatic protocol. Optimum culture conditions were standardized for ensuring their viability and functioning. Isolated hepatocytes were cultured for 48 h for monolayer formation and then exposed to various concentrations (0.001–10 μM) of the three estrogens. Competitive homologous ELISAs, developed and validated for spotted snakehead Vg and Chg were employed to determine the amounts of these two proteins secreted into the culture medium after 48 h of incubation. The results reveal that although all the three estrogens were effective in inducing the production of Vg and Chg in a dose-dependent manner, there were differences in their relative potencies. Of three estrogens, E₁ was the least potent and could induce synthesis of Vg and Chg only at a minimum concentration of 0.5 μM; whereas significant levels of both the proteins were quantified in culture medium by exposing the hepatocytes to E₂ or E₃ even at a concentration of 0.001 μM. All three estrogens were effective in inducing synthesis of Vg and Chg in vivo also. These results suggest the possibility of employing the above in vitro experimental design to monitor the presence of estrogens/estrogen-like chemicals in natural waters, which could interfere with the estrogen receptor system of fish. This study further points to the possibility of using Chg, in addition to Vg, as a parameter for screening various chemicals for their estrogenic activity.     

Induction of larval metamorphosis in the sea cucumber Apostichopus japonicus by neurotransmitters

Larval metamorphosis inducers of the sea cucumber Apostichopus japonicus were screened from physiologically active compounds. Doliolaria larvae completed their metamorphosis to juveniles in 120 h when treated with 5–10 μM of dopamine and l-DOPA, and 50 μM of l-adrenaline and l-noradrenaline. Doliolaria larvae had to be exposed to dopamine or l-DOPA for at least 24 h. D1-like dopamine receptor antagonists SKF87566 and LE300 (10 μM) inhibited metamorphosis by dopamine. However, the D2-like dopamine receptor antagonists sulpiride and nemonapride (10 μM) did not inhibit the effect of dopamine. The results suggest that D1-like dopamine receptors are involved in larval metamorphosis of the sea cucumber A. japonicus.     

Henneguya pseudorhinogobii n. sp. (Myxozoa: Myxosporea) parasitizing the gills of the freshwater goby Rhinogobius sp. OR from the Nagara River and redescription of Henneguyarhinogobii

Two types of infection with myxosporean parasites, which were different in cyst size, were found from the gill of Rhinogobius sp. OR collected from the Nagara River, Gifu Prefecture, Japan. A myxosporean forming large-type cysts in the gill filament was morphologically identified as Henneguya rhinogobii. Another myxosporean forming small-type cysts was found to be parasitic in the gill lamella. Average spore sizes of the latter myxosporean were 15.8 (range 14.2–17.8) μm in length, 5.3 (4.7–5.8) μm in width, 6.5 (5.9–7.6) μm in polar capsule length and 34.9 (25.3–42.9) μm in caudal appendage length, which were almost identical to those of H. rhinogobii. However, the two were distinguishable by the location in the gill (intrafilamental or intralamellar) and by the difference in the sequence of SSU rDNA (about 96% similarity). We propose the myxosporean forming intralamellar small-type cysts as Henneguya pseudorhinogobii n. sp. and redescribe H. rhinogobii by morphological and molecular studies.     

Difference Between Tetrodotoxin and Saxitoxins in Accumulation in Puffer Fish Takifugu rubripes Liver Tissue Slices

In vitro accumulation of tetrodotoxin (TTX) and paralytic shellfish toxin (PST) in tiger puffer fish Takifugu rubripes was investigated using liver tissue slices. When T. rubripes liver slices were incubated with Leibovitz’s L-15 medium containing 0.13 mM TTX at 20 °C in air with saturated humidity, they accumulated 21.5 ± 7.3 μg TTX g⁻¹ liver after the incubation for 12 h and increased to 55.3 ± 8.2 μg TTX g⁻¹ liver at 48 h. In the incubation of T. rubripes liver slices with 0.13 mM PST-containing medium, PST was detected 6.3 ± 0.9 μg g⁻¹ liver at 12 h and reached a plateau thereafter. These results reveal the difference between TTX and PST in accumulation in T. rubripes liver tissue slices. To examine the variation in PST accumulation among fish species, the liver tissue slices from tiger puffer fish T. rubripes, parrot-bass Oplegnathus fasciatus and green ling Hexagrammos otakii were incubated at a concentration of 0.027 mM PST. The toxin contents of 3.0 μg g⁻¹ liver were observed at 8 h regardless of fish species but were not increased subsequently, showing no variety among these three species as to accumulation patterns of PST. It is noted that the tiger puffer fish T. rubripes liver specifically accumulate TTX in preference to PST.     

斜带石斑鱼肝细胞分离及原代培养方法的建立

本研究以斜带石斑鱼肝细胞为实验对象,在不同培养条件下进行原代培养,旨在探讨稳定可靠的斜带石斑鱼肝细胞分离及原代培养方法。采用组织块分离法和胰蛋白酶(含EDTA)消化法分离肝细胞,并通过密度梯度离心法分离纯化肝细胞,细胞悬液于DMEM/F-12、M199和L-15培养液中培养;细胞活力及数量采用血球计数板计数,并通过MTT法测定细胞增殖率;同时,测定不同时间培养上清液中乳酸脱氢酶(LDH)活性、白蛋白(ALB)和尿素氮(BUN)的含量,以分析肝细胞生长状态。结果表明,组织块方法不适于斜带石斑鱼肝细胞的培养,未见细胞从组织块中迁出,而胰蛋白酶消化法获得良好稳定的培养效果,细胞产量达到1.6×108个/g肝重,活细胞数达到95%;L-15培养基细胞生长明显优于DMEM/F-12和M199培养基;启动原代培养的48~72 h阶段肝细胞生长代谢旺盛,培养上清液中LDH活性显著降低,ALB和BUN含量显著升高。结果显示,0.25%的胰蛋白酶常温消化法适合斜带石斑鱼肝细胞的分离,斜带石斑鱼肝细胞原代培养的最适培养基为L-15培养基,肝细胞在启动原代培养的48~72 h生长代谢旺盛。     

Are cell redox or lactate dehydrogenase kinetics responsible for the absence of gluconeogenesis from lactate in sea raven,hepatocytes?

Previous studies have reported very low rates of gluconeogenesis from lactate in sea raven (Hemitripterus americanus) hepatocytes compared to other teleosts studied. This study examines whether hepatic cell redox or lactate dehydrogenase (LDH) characteristics may explain this observation. Sea raven hepatic optimal LDH activities (pyruvate reductase direction) were more than 40 times less compared with rainbow trout liver values (40 vs 1914 μmol·min⁻¹·g⁻¹ protein). The Km(lactate) was 9.24 and 0.86 mM for sea raven and trout hepatic LDH, but the Km(pyruvate) was similar between the two species (0.11 and 0.21 mM, respectively). These results suggested that sea raven liver LDH did not favour lactate use and was more indicative of the mammalian M-isozyme. Gel electrophoresis showed a predominant intermediate isozyme, with a small amount of the M-type LDH. Phosphoenolpyruvate carboxykinase (PEPCK) was localized to the mitochondrial compartment, while there was no apparent mitochondrial glutamate-oxaloacetate transaminase (GOT) activity. No in vitro lactate flux to glucose was found in untreated, 10 mM ethanol-treated, or 3 mM NH₄Cl-treated sea raven hepatocytes, although CO₂ production from lactate was decreased by ethanol and increased by NH₄Cl. These results provide evidence that cell redox does not limit gluconeogenesis from lactate, while low activities and the kinetic characteristics of LDH may partially explain the low lactate gluconeogenesis reported in sea raven hepatocytes. To whom correspondence should be addressed at University of Ottawa.     

Effect of juglone on the survival time of two Brachionus species (Rotifera): species-specific tolerance against oxidative stress

To investigate the effect of oxidative stress on the survival of two Brachionus species of rotifer, we examined the effective dose of juglone, which generates reactive oxygen species, and compared survival times between the two species. First, we observed that juglone affected survival in the rotifers in a dose-dependent manner between 0.02 to 20 μM, and that treatment at above 2 μM showed acute toxicity causing the animals to die within a few hours. Next, we found the difference in survival time between the two species exposed to 20 μM juglone: B. rotundiformis was significantly more tolerant against the substance than the allied species B. plicatilis. The findings suggest that exploring the basis of species-specific abilities to persist under oxidative stress will be of great interest to uncover the underlying mechanisms governing the stress resistance of the rotifer, as well as contributing to their stable mass production for aquaculture.     

Effect of oral administration of l -thyroxine (T4) on growth performance, digestibility, and nutrient retention in Channa punctatus (Bloch) and Heteropneustes fossilis (Bloch)

Effects of oral administration of l-thyroxine (T₄) on growth performance, body composition, and some aspects of nutritional physiology were investigated in two slow-growing air-breathing fish (Channa punctatus and Heteropneustes fossilis) under laboratory conditions (LD 12:12 at 25°C). The results indicate that irrespective of the species, fish fed diets containing lower doses of T₄ (up to 50 mg kg⁻¹ of diet in C. punctatus and up to 100 mg kg⁻¹ of diet in H. fossilis) showed significantly (P < 0.05) higher growth (in terms of live weight and length gain, specific growth rate, percentage gain in body weight and condition factor), low feed conversion ratio, high nutrient retention, high apparent protein digestibility, and high digestive enzyme activity. Viscero-somatic (VSI) and hepato-somatic (HSI) values were also high in fish fed on low dietary T₄ levels. Liver glycogen levels decreased with the increase in the dietary T₄ levels, indicating its utilization during growth. Muscle glycogen levels in H. fossilis coincided with high growth at 100 mg of T₄. Observation of the postprandial excretion of metabolites (N–NH₄ ⁺ and o-PO₄ ⁻) indicated significantly (P < 0.05) low levels in aquaria water where the fish were fed diets with low T₄ levels. These studies further revealed that feeding fishes on higher T₄ levels (above 50 mg in C. punctatus and above 100 mg in H. fossilis) not only repressed growth performance and nutrient retention, but also affected carcass composition by lowering protein accumulation (muscle and carcass protein) and energy assimilation. These studies revealed a biphasic action of thyroxine, i.e., the hormone at lower doses is anabolic, while at higher doses it acts as a catabolic agent, indicating that feeding fishes on higher doses can be detrimental to their growth and metabolism. In summary, the results of the present study show that feeding H. fossilis and C. punctatus on low doses of T₄ enhances growth, decreases excretion of metabolites, and increases nitrogen retention. These observations suggest that T₄ supplementation of the diet may have practical utility in the culture of slow-growing fish species.     

Effect of ethanolic extract of propolis on growth performance and plasma biochemical parameters of rainbow trout (Oncorhynchus mykiss)

This study was conducted to evaluate the effect of ethanolic extract of propolis (EEP) on growth performance and plasma biochemical parameters of rainbow trout (Oncorhynchus mykiss). Graded levels of EEP [0 (control), 1, 2, and 4 g kg⁻¹ diet] were fed to trout juveniles (mean weight 7.73 ± 0.17 g) for 10 weeks. Dietary EEP supplementation regardless of inclusion level significantly improved the specific growth rate of fish. Similarly, supplemental EEP generally improved the feed efficiency ratio and protein efficiency ratio, but no significant differences were observed between the 1 g kg⁻¹ EEP group and the control group. In addition, dietary EEP supplementation generally increased the plasma superoxide dismutase, lysozyme, total antioxidant capacity, glutathione peroxidase, and catalase activities, but decreased the plasma malondialdehyde level. The plasma triglycerides level was significantly lower in the 1 or 4 g kg⁻¹ EEP group as compared with the control group. Dietary EEP supplementation generally decreased the plasma aspartate aminotransferase and alanine aminotransferase activities, but increased the hepatic aspartate aminotransferase and alanine aminotransferase activities. These results indicate the potential to use the EEP as a growth promoter, hepatoprotective agent, and immunostimulant for rainbow trout.     

Dietary protein requirement of the high altitude's representative teleost juveniles Schizopygopsis younghusbandi (Cypriniformes: Cyprinidae)

A 60‐day trial was conducted to investigate the effect of dietary protein on growth, whole‐body composition, hepatopancreas enzymes, digestion and absorption in the juveniles of Schizopygopsis younghusbandi. Six graded levels of dietary protein (200.0, 248.7, 303.5, 351.2, 395.8 and 449.3 g/kg diet) were formulated and assigned to triplicate groups of 60 fish (8.16 ± 0.02) for each aquarium. Results showed a significantly increased specific growth rate (SGR) in fish fed protein containing 351.2 g/kg diet (p < .05). Besides, intestinal ratio (IR), intestinal somatic index (ISI) and hepatosomatic index (HSI) were decreased and the condition factor (CF) was increased with dietary protein up to 351.2 g/kg diet, then altered reversely. Fish fed the optimal dietary protein showed the highest crude protein calcium, phosphorous and lowest crude lipid contents of the whole body in fish. Additionally, plasma ammonia content (PAC), and activities of GOT and GPT were enhanced by dietary protein levels (p < .05). The digestive enzymes of hepatopancreas were generally increased with the quadratic response to dietary protein levels. Optimal dietary protein level increased the intestinal enzyme activities of Na⁺, K⁺‐ATPase (NKA), alkaline phosphatase (AKP), gamma‐glutamyl transpeptidase (γ‐GT) and creatine kinase (CK). Based on the 2‐slope broken‐line model analysis of PWG, dietary protein requirement was determined to be 349.6 g/kg diet.     

Protein-sparing effect of dietary lipid in practical diets for blunt snout bream (Megalobrama amblycephala) fingerlings: effects on digestive and metabolic responses

This study aimed to evaluate the protein-sparing effect of dietary lipid on digestive and metabolic responses of fingerling Megalobrama amblycephala. Fish were fed nine practical diets with three protein levels (270, 310 and 350 g kg⁻¹) and three lipid levels (40, 70 and 100 g kg⁻¹) for 8 weeks. Weight gain was significantly affected only by dietary lipid levels with the highest found in fish fed 70 g kg⁻¹ lipid. Relative feed intake and whole-body protein content showed little difference among all the treatments. Activities of intestine lipase and amylase increased significantly as dietary lipid levels increased, whereas little difference was observed in protease activities. Liver lipid content was significantly affected only by protein levels with the lowest found in fish fed 310 g kg⁻¹ protein. Liver aspartate aminotransferase (GOT) activities increased significantly with decreasing lipid levels, whereas the highest GOT activity was obtained in fish fed 310 g kg⁻¹ protein in terms of dietary protein levels. Activities of liver lipoprotein lipase, total lipase and plasma cholesterol concentration of fish fed 350 g kg⁻¹ protein were significantly lower than that of the other groups, whereas the same was true for plasma 3, 5, 3′-triiodothyronine level of fish fed 270 g kg⁻¹ protein. The results indicated that an increase of dietary lipid content from 40 to 70 g kg⁻¹ can enhance the growth and digestive enzyme activities of this species and reduce the proportion of dietary protein catabolized for energy without inducing hepatic steatosis; meanwhile, decreasing protein level from 350 to 310 g kg⁻¹ leads to the increase of lipase activities both in intestine and liver coupled with the reduced liver lipid content.