Aeromonas caviae inhibits hepatic enzymes of the phosphotransfer network in experimentally infected silver catfish: Impairment on bioenergetics

Several studies have been demonstrated that phosphotransfer network, through the adenylate kinase (AK) and pyruvate kinase (PK) activities, allows for new perspectives leading to understanding of disease conditions associated with disturbances in energy metabolism, metabolic monitoring and signalling. In this sense, the aim of this study was to evaluate whether experimental infection by Aeromonas caviae alters hepatic AK and PK activities of silver catfish Rhamdia quelen. Hepatic AK and PK activities decreased in infected animals compared to uninfected animals, as well as the hepatic adenosine triphosphate (ATP) levels. Also, a severe hepatic damage was observed in the infected animals due to the presence of dilation and congestion of vessels, degeneration of hepatocytes and loss of liver parenchyma architecture and sinusoidal structure. Therefore, we have demonstrated, for the first time, that experimental infection by A. caviae inhibits key enzymes linked to the communication between sites of ATP generation and ATP utilization. Moreover, the absence of a reciprocal compensatory mechanism between these enzymes contributes directly to hepatic damage and for a severe energetic imbalance, which may contribute to disease pathophysiology.     

Xanthine oxidase activity exerts pro‐oxidative and pro‐inflammatory effects in serum of silver catfish fed with a diet contaminated with aflatoxin B1

Several studies have associated the involvement of xanthine oxidase (XO) activity, a source of uric acid and reactive oxygen species (ROS), to pro‐oxidative and pro‐inflammatory effects during pathological conditions. Considering this, the aim of this study was to evaluate whether upregulation on seric XO activity may be a pathway involved in the oxidative stress in fish exposed to a diet contaminated with aflatoxin B₁ (AFB₁), as well as whether it may be considered a pathway involved in ROS and NOx production. Xanthine oxidase activity, as well as the uric acid, ROS and NOx levels increased in serum of fish fed with a AFB₁‐contaminated diet on days 14 and 21 post‐feeding compared to fish fed with a basal diet. Based on these evidences, upregulation of seric XO activity induces pro‐oxidant and pro‐inflammatory profiles in serum of fish fed with a AFB₁‐contaminated diet due to excessive formation on uric acid. Also, the excessive uric acid induces the release of pro‐oxidant and pro‐inflammatory mediators, as ROS and NOx, also contributing to oxidative and inflammatory profiles. In summary, the upregulation on seric XO activity may be considered a pathway involved in the oxidative stress of fish exposed to a diet contaminated with AFB₁.     

Aflatoxin B<Subscript>1</Subscript> (AFB<Subscript>1</Subscript>) reduces growth performance,physiological response,and disease resistance in Tra catfish (<Emphasis Type="Italic">Pangasius hypophthalmus</Emphasis>)

Triplicate groups of one hundred Tra catfish (8 g?±?0.2) were fed seven test diets containing increasing levels of AFB₁ (0, 50, 100, 250, 500, and 1000 μg AFB₁ kg^?1). Additionally Mycofix® Secure was added at 1.5% to one diet containing 500 μg AFB₁ kg^?1. Results showed that Tra catfish are sensitive to AFB₁. Reduction in weight gain (P?<?0.05) was observed for fish fed 50 μg AFB₁ kg^?1 and declined further with increasing levels of AFB₁ in the diets. Fish fed diets contaminated with 500 and 1000 μg AFB₁ kg^?1 showed increased (P?>?0.05) hepatosomatic index (HIS), while an increase in adipose somatic index (ASI) was observed in fish fed 50 μg AFB₁ kg^?1 and above when compared to the control and Mycofix® diets. After 12 weeks, blood serum analysis revealed higher alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in fish fed the 50, 100, and 250 μg AFB₁ kg^?1 suggesting occurrence of liver damage. Disease resistance of fish exposed to Edwardsiella ictaluri was also compromised by the presence of AFB₁ in the feed and was directly related to the contamination level. Seven days after Edwardsiella ictaluri exposure, survival rates were 50, 41.7, 31.7, and 8.3% for fish fed control, 50, 100, and 250 μg AFB₁ kg^?1, respectively. This trial shows that AFB₁ at a level of 50 μg AFB₁ kg^?1 and above can affect fish performance and disease resistance. Application of an effective mycotoxin management in the feed seems to be useful to prevent the negative effects of AFB₁.     

Detoxification and antioxidant effects of garlic and curcumin in <Emphasis Type="Italic">Oreochromis niloticus</Emphasis> injected with aflatoxin B<Subscript>1</Subscript> with reference to gene expression of glutathione peroxidase (GPx) by RT-PCR

The present study aims to investigate the effects of both garlic and curcumin through evaluating their therapeutic properties as antioxidants on liver and kidney functions, hepatic antioxidants and GPx gene expression against aflatoxicosis of O. niloticus. In total, 180 of tilapia were divided into ten groups; T₁ represented the negative control fed on a basal diet, and T₂ was injected with a single intraperitoneal (i.p.) dose of AFB₁ (6 mg/kg b.w.). Fish in T₃–T₆ were fed on a basal diet supplemented with both garlic (T₃ and T₄) and curcumin (T₅ and T₆) at the two concentrations of 10 and 20 g/kg diet, respectively. Fish in T₇–T₁₀ groups were injected with AFB₁ and fed on the garlic (T₇ and T₈) and curcumin (T₉ and T₁₀) dietaries. The results showed that AFB₁ has significant potency for increasing the activity of plasma AST, ALT, creatinine and uric acid values, and hepatic MDA as well as for reducing the concentrations of plasma TP, AL, GL and hepatic activity of TAC, while AFB₁ led to up-regulated GPx gene expression when compared to the control (T₁). These harmful effects of AFB₁ were alleviated due to the garlic and curcumin dietaries in some studied parameters. Garlic reflected the highest induction of gene expression (T₇); however, curcumin showed significant down-regulated (T₉). These results concluded that the effects of garlic were better than curcumin at the two concentrations and the low concentration of them is more beneficial than the high concentration when it used against AFB₁ in O. niloticus.     

Low levels of Aflatoxin B1 could cause mortalities in juvenile hybrid sturgeon,Acipenser ruthenus ♂×A. baeri♀

Toxicity of aflatoxin B₁ (AFB₁) was investigated in juvenile hybrid sturgeon Acipenser ruthenus ♂ × A. baeri♀, an important coldwater finfish farmed in China and other countries. Seven experimental diets (Diet A–G) containing different levels of AFB₁ (0, 1, 5, 10, 20, 40 and 80 μg kg^?1 diet) were fed to juvenile sturgeon weighing 10.53 ± 0.17 g kg^?1 to determine its effect on survival, growth, feed consumption, hematocrit, liver histology as well as muscular and hepatic toxin accumulation. The experiment lasted for 35 days and was conducted in two periods of 25 and 10 days each. No external changes or unusual behaviour was observed in the fish fed diets with AFB₁. Mortality was observed in fish fed with highest levels of AFB₁ (80 μg kg^?1– Diet G) from day 12 onwards. After 25 days, fish fed the diet of 80 μg AFB₁ kg^?1 showed significant lower survival (50 ± 5.77%) followed by those fed 40 μg AFB₁ kg^?1 diet (80 ± 5.77%) and 20 μg AFB₁ kg^?1 diet (86.66 ± 3.33%). No significant difference was observed in specific growth rate (SGR) or hepatosomatic index (HSI) between groups. Hematocrit was significantly higher in the fish fed the diet of highest AFB₁. The fish were weighed at day 25 in some treatments (Diets F and G) because of high mortality. However, feeding was continued for another 10 days to observe mortality or behavioural changes if any in the other groups. After 35 days, survival in the fish fed Diet F (40 μg AFB₁ kg^?1) was 40% and those fed Diet E (20 μg AFB₁ kg^?1) was 36.2%. Significant histopathological changes including nuclear hypertrophy, hyperchromasia, extensive biliary hyperplasia, focal hepatocyte necrosis and presence of inflammatory cells were observed in the liver of fish fed high levels of aflatoxin (40 and 80 μg kg^?1). AFB₁ accumulation in fish muscle and liver increased with increased dietary AFB₁ levels. It could be confirmed that 10 μg AFB₁ kg^?1 diet was the maximum allowable level in hybrid sturgeon diet.     

The efficacy of three mycotoxin adsorbents to alleviate aflatoxin B1-induced toxicity in Oreochromis niloticus

Aflatoxicosis, toxicity of aflatoxin, is of great concern in aquaculture. This study was conducted to assess the efficacies of three adsorbents, a hydrated sodium calcium aluminosilicates (HSCAS), Saccharomyces cerevisiae (S.C.) and an esterified glucomannan (EGM), against feed contaminated with contained 200 μg/kg (ppb) aflatoxin B₁ (AFB₁). A total of 240 Nile tilapia fingerlings, Oreochromis niloticus (15 ± 2 g), were randomly divided into eight experimental groups (30 fish per group) with three replicates. Group T₁ represented the negative control fed on a basal diet, and T₂ was the positive control group fed on a basal diet supplemented with 200 ppb AFB₁. Groups T₃, T₄ and T₅ were fed the AFB₁-contaminated diet (200 ppb) supplemented with 0.5 % HSCAS, 0.25 % S.C or 0.25 % EGM, respectively. Groups T₆, T₇ and T₈ were fed a basal diet supplemented with 0.5 % HSCAS, 0.25 % S.C or 0.25 % EGM, respectively. The reduction in AFB₁-bioavailability was judged by toxin residues in fish musculature throughout the study beginning at the second week of exposure. AFB₁ reduced the survivability, total weight gain, average daily gain and specific growth rate, evident as early as the second week of exposure. The total erythrocyte count, hemoglobin content and total leukocyte count were significantly decreased after AFB₁ exposure for 6, 8 and 10 weeks, respectively. Prolonged administration of AFB₁ led to significant increases in serum alanine transaminase, aspartate transaminase and creatinine activity, and produced significant decreases in plasma proteins, including serum globulin. The specific immune response was assessed by an agglutinating antibody titer after immunization of the fish with an Aeromonas hydrophila vaccine. The antibody titer and relative level of protection of fish challenged with Aeromonas hydrophila were reduced throughout the period of examination in AFB₁-exposed fish. Supplementation with HSCAS, S.C. or EGM significantly improved growth performance, blood parameters and immune status; in addition, these groups showed decreased AFB₁ residues in fish musculature when compared with AFB₁-treated fish. HSCAS effectively reduced AFB₁ toxicity, whereas S.C. and EGM were less efficacious.     

Aflatoxin B1 induced alterations in the stability of the lysosomal membrane in Oreochromis mossambicus (Peters, 1852)

This article elucidates the effect of crude dietary aflatoxin B₁ (AFB₁) on the stability of the lysosomal membrane in tilapia (Oreochromis mossambicus), and the analysis was made at the biochemical and cellular level. The liver lysosomal acid phosphatase activity was used to evaluate the functional integrity of the lysosome. Three experimental groups were fed on diets containing 0.375, 2.5 and 6 mg kg^?1 of AFB₁ for a time period of 6 weeks, whereas a fourth group fed on the semi‐purified diet formed the control. Significant changes were observed in the stability of the lysosomal membrane in aflatoxin exposed groups. This is the first report, so far, of changes induced by AFB₁ on the stability of lysosomal membrane in tilapia (O. mossambicus).     

Effects of dietary aflatoxin B1 on growth performance,body composition,haematological parameters and histopathology of juvenile Pacific white shrimp (Litopenaeus vannamei)

An 8‐week feeding trial was conducted to evaluate the effects of dietary aflatoxin B₁ (AFB₁) on growth performance, haematological parameters and histological changes in juvenile Pacific white shrimp, Litopenaeus vannamei. Six practical diets (455 g kg^‐1 protein, 78 g kg^‐1 lipid) with different levels of AFB₁ (0, 25, 50, 100, 500, 1000 μg kg^?1) were formulated. Each diet was fed to triplicate groups of shrimps (initial weight: 0.52 g). The results showed that shrimp fed with control diet (0 μg kg^?1 AFB₁) had significant higher weight gain (WG) and specific growth rate (SGR) than other groups. However, there were no significant differences in feed efficiency (FE) or hepatosomatic index (HSI) among all groups. Compared to the control diet, AFB₁ supplementation significantly changed the activities of shrimp serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), total antioxidant capacity (T‐AOC) and glutathione S‐transferase (GST) and the content of cholesterol (CHO). Histological damages were identified in the hepatopancreas of shrimp when dietary AFB₁ level was over 107.6 μg kg^?1. Based on this study, it was concluded that the AFB₁ level in Pacific white shrimp diet should be <38.1 μg kg^?1.     

Motility of spermatozoa ofAlburnus alburnus (Cyprinidae) and its relationship to seminal plasma composition and sperm metabolism

The composition of seminal plasma and metabolism of sperm of the cyprinid fishAlburnus alburnus were investigated. Statistically significant correlations were found between motility parameters and seminal fluid osmolality, pH, Na⁺, K⁺ and protein levels (negative correlations: % immotile spermatozoa-Na⁺, K⁺; positive correlations: % motile spermatozoa-osmolality, pH, Na⁺, K⁺, protein; % linear motile spermatozoa-pH protein; swimming velocity of spermatozoa-pH, Na⁺, protein). Spermatozoan motility and ATP metabolism and glycolysis were correlated as indicated by measurement of ATPase, pyruvate kinase, adenylate kinase and lactate dehydrogenase activity. The physiological meanings of these correlations and their possible significance for quality control of semen are discussed.Abbreviations used ACP acid phosphatase - ADP adenosine diphosphate - AK adenylate kinase - ALP alkaline phosphatase - ASPAT aspartate aminotransferase - ATP adenosine triphosphate - ATPase magnesium dependent adenosine triphosphatase - CRPO creatine phosphate - -GLU \-D-glucuronidase - ICDH isocitrate dehydrogenase - LDH lactate dehydrogenase - PK pyruvate kinase     

Growth and hepatopancreas performances of gibel carp fed diets containing low levels of aflatoxin B1

The effects of aflatoxin B₁ (AFB₁) on growth, physiological responses and histological changes were investigated in juvenile gibel carp (Carassius auratus gibelio). Triplicate groups of gibel carp (3.53 ± 0.02 g) were fed seven semipurified diets (Diet 1 to 7) containing 3.20, 5.37, 7.08, 9.55, 12.70, 17.90 and 28.60 μg AFB₁ kg^?1 diet for 3 months. The results showed fish weight gain fed Diet 6 was 112.6% of that of control group (Diet 1) after 3 months, but there was no significant difference of weight gain between fish fed Diet 7 and the control group. Alanine aminotransferase (ALT) of fish hepatopancreas fed Diet 7 was significantly higher than the control group (P < 0.05), but no significant difference was observed in ALT activities of the fish fed with more than 10 μg AFB₁ kg^?1 (Diet 4, 5, 6 and 7). No significant histological lesions were identified between the control and increasing AFB₁ treatments. AFB₁ accumulated in hepatopancreas was logarithmically related to the dietary AFB₁ levels, and AFB₁ also accumulated in muscles and ovaries of gibel carp fed Diet 3 to Diet 7. The present results indicated that fish fed with more than 10 μg AFB₁ kg^?1 diet showed impaired physiological responses and more AFB₁ residue of muscles and ovaries above the safety limitation of European Union.     

Growth,enzymatic glutathione peroxidase activity and biochemical status of juvenile barramundi (<Emphasis Type="Italic">Lates calcarifer</Emphasis>) fed dietary fermented soybean meal and organic selenium

Solvent-extracted soybean meal (SBM) was fermented using baker’s yeast Saccharomyces cerevisae at 30 °C for 5 days. Four isonitrogenous and isocaloric diets containing 75% SBM protein, either fermented or non-fermented (SBM and FSBM), and supplemented or not with organic Se (OS) (SBM_OS and FSBM_OS), were fed to triplicate groups of juvenile barramundi (Lates calcarifer) (initial weight of 5 g) for 75 days. A fishmeal (FM)-based diet formulated for juvenile barramundi was used as a reference diet. The growth of fish was significantly affected by either the interaction of SBM type or by the OS level. In fish fed diets supplemented with OS (SBM_OS and FSBM_OS), final weight (FW), specific growth rate (SGR) and weight gain (WG) were higher in fish fed the fermented SBM (FSBM_OS) than in those fed the non-fermented SBM (SBM_OS). The apparent digestibility coefficient (ADC) of protein was higher in the fish fed the fermented SBM, either supplemented or unsupplemented with OS. However, there were no significant differences in the ADC of dry matter (DM) and lipids among the tested diets and in comparison to the reference diet. The haematocrit and leucocrit of fish fed the FSBM_OS diet were lower than those of fish fed the FM diet. Furthermore, glutathione peroxidase (GPx) activity was significantly influenced by OS supplementation in the experimental diets; GPx activity was greater in the fish fed diets supplemented with OS. Creatinine kinase (CK) of all groups of fish was higher than the CK of those fed the reference diet. These results suggest that with a proper nutritional level, OS supplementation may act as an important factor in enzymatic GPx activity and in the haematology and blood biochemistry status of juvenile barramundi fed fermented SBM-based diets, encouraging improvement of the overall growth performance.     

凡纳滨对虾精氨酸激酶的多克隆抗体制备及组织特异性表达分析

精氨酸激酶（arginine kinase,AK）在调节无脊椎动物磷酸精氨酸与ATP之间能量平衡的过程中具有重要作用。在前期工作基础上,设计特异引物,以凡纳滨对虾肌肉组织cDNA为模版,克隆得到了1 071 bp的凡纳滨对虾精氨酸激酶的完整开放阅读框;将它克隆到原核表达载体pGEX-4T-2上,转化BL21 (DE3) 菌株,经诱导后表达出GST-AK融合蛋白。以纯化的融合蛋白作为抗原免疫小鼠,制备多克隆抗血清,经检测该抗原与抗体识别良好。利用得到的抗体对凡纳滨对虾AK在蛋白质水平上的特异性表达进行分析发现,精氨酸激酶在对虾的肌肉、心脏、神经、血细胞和胃组织中具有高的表达量,而在眼柄、肝胰腺、鳃和皮肤组织中表达量较低。为进一步研究精氨酸激酶在对虾体内的功能奠定了基础。     

Response to T3 treatment and changing environmental salinity of liver lipid composition, mitochondrial respiration and (Na++ ++ K++)-ATPase activity in rainbow trout Oncorhynchus mykiss Walbaum

Rainbow trout Oncorhynchus mykiss Walbaum were fed a pelleted diet (14.3% wet weight lipid) containing 9 p.p.m. 3, 5, 3′‐triiodo‐l ‐thyronine (T₃) for 1 month and then transferred from fresh water to brackish water (average 22 p.p.t. salinity), where they were maintained untreated for 22 days. Trout fed a control diet were subjected to the same protocol. For both treated and control trout, liver lipid and fatty acid composition, mitochondrial respiratory activity and oxidative phosphorylation and (Na⁺ + K⁺)‐ATPase activity were monitored in fish sampled periodically throughout the trial. No differences between treated and control trout occurred in liver total lipid, phospholipid and cholesterol content or fatty acid composition. Conversely, irrespective of T₃ administration, the trout from the two habitats showed adaptive changes to salinity, differing in phospholipids and in the fatty acid composition of total and neutral lipids and selected phospholipids. Liver membrane permeability and mitochondrial respiratory activity were affected by both T₃ treatment and salinity transfer. The latter was apparently greater than the former in affecting mitochondrial respiratory activity. The higher (Na⁺ + K⁺)‐ATPase activity in T₃‐treated trout after 22 days in brackish water may reflect long‐term effects of the hormone linked to salinity adaptation.     

Early insulin and glucagon response associated with food intake in a teleost, the striped bass (Morone saxatilis)

To determine the existence of preabsorptive reflex responses in fish, plasma glucose, insulin and glucagon were measured in striped bass (Morone saxatilis) pre-feeding (baseline: 0 min) and at five times post-feeding (5, 10, 20 and 40 min) following a 15 h fast. Two diets were fed, a basal agar-gel diet, and the agar-gel diet supplemented with a previously identified feeding stimulant mixture comprised of L-alanine, L-serine, betaine and inosine-5-monophosphate at equimolar concentrations (0.1 mol l). After 11 days, blood samples were obtained from the caudal vein. In fish fed the stimulant diet, plasma insulin increased at 5 and 10 min post-feeding but fish fed the basal diet had lower levels than baseline after 5, 10 and 20 min. Glucagon levels were increased in fish fed the stimulant diet at 0–10 min post-feeding, then decreased to levels similar to fish fed the basal diet. Glucose levels were elevated in both treatments post-feeding and were similar in both treatments. These results indicate that there is an early phase of reflex insulin and glucagon secretion in fish, shortly after the beginning of a meal, as has been described in mammals and birds. Furthermore, feed palatability may play an important role in insulin and glucagon secretion.     

Effects of the supplementation of vitamin D<Subscript>3</Subscript> on the growth and vitamin D metabolites in juvenile Siberian sturgeon (<Emphasis Type="Italic">Acipenser baerii</Emphasis>)

The objective of this study was to evaluate the effects of the supplementation of vitamin D₃ on the growth, vitamin D metabolites, and osteocalcin secretion in juvenile Siberian sturgeon (Acipenser baerii). A 90-day growth trial was conducted with juvenile Siberian sturgeon (initial body weight 3.47 ± 0.14 g) fed seven isonitrogenous and isoenergetic practical diets (45% CP and 13% lipid) containing 60 (basal diet), 240, 450, 880, 1670, 3300, or 1.0 × 10⁵ IU/kg feed (D60~D 1.0 × 10⁵) vitamin D₃. The results showed that weight gain and specific growth rate increased as the dietary vitamin D₃ levels increased from 450 to 3300 IU/kg (P < 0.05). The fish fed with D1670 and D3300 diets had higher crude lipid and ash levels than the fish fed the D60 diet (P < 0.05). The fish fed D880, D1670, or D3300 diets had higher 25-OH-D₃ and 1,25-(OH)₂-D₃ levels than the fish fed the D60 diet (P < 0.05). The fish fed D880, D1670, D3300, or D1.0 × 10⁵ diets had higher osteocalcin levels than the fish fed the D60 diet (P < 0.05). Based on the broken line method analysis of weight gain and osteocalcin, the dietary vitamin D₃ requirement of juvenile Siberian sturgeon was estimated to be 1683.30 and 1403.27 IU/kg per diet, respectively.     

Effects of lead nitrate on the activity of metabolic enzymes during early developmental stages of the African catfish, <Emphasis Type="Italic">Clarias gariepinus</Emphasis> (Burchell, 1822)

Glucose-6-phosphate dehydrogenase (G6PDH), lactate dehydrogenase (LDH) and pyruvate kinase (PK) are key metabolic enzymes. G6PDH has been used as a biomarker of pollution-induced carcinogenesis in fish. LDH has been used as marker of lesions in toxicology and clinical chemistry, and PK catalyses the conversion of phosphoenol pyruvate to pyruvate, with regeneration of ATP. The effect of different concentrations of lead nitrate on the activity of these enzymes in two different early ontogenetic stages (embryonic and free embryonic stage) of the African catfish Clarias gariepinus was investigated. Embryo homogenates were used for measurements of G6PDH, LDH and PK activity spectrophotometrically at 340 nm and 25°C. The ontogenetic variations of the three enzymes during early ontogeny, from the 30 h to the 168 h post-fertilisation stage (PFS) (beginning of exogenous feeding), were studied. There was a significant decrease in activities of all three enzymes from 30 h-PFS to 96 h-PFS, followed by a significant increase in G6PDH and LDH. PK showed insignificant fluctuations in activity. Different patterns of enzyme activities were recorded due to exposure to different lead nitrate concentrations (100 μg/l, 300 μg/l and 500 μg/l). In the pre-hatching stage (30 h-PFS) the activity of the three enzymes increased at exposure to 100 μg/l lead nitrate and then decreased with increasing dose. In the post-hatching stages (48 h-PFS–168 h-PFS) G6PDH activity increased and LDH activity decreased with increasing lead concentrations. Unlike G6PDH and LDH, the PK enzyme fluctuated during the post-hatching stages and did not reveal a specific trend of response (increase or decrease) with increasing lead concentrations. Therefore, the measurement of G6PDH and LDH activities, but not PK activity, could be useful biomarkers of intoxication to reveal the embryotoxic potential of lead nitrate in fish embryos. The post-hatching stages of the African catfish are more sensitive than the pre-hatching stage (30 h-PFS) is, probably due to the protective capacity provided by the hardened chorion. The interaction and the main effects of age and lead doses were found to be highly significant, referring to the great impact of lead on these enzyme systems with increasing early development.     

Mitochondrial NAD(P)-malic enzyme from herring skeletal muscle

Mitochondrial NAD(P)-dependent malic enzyme [EC 1.1.1.39, L-malate: NAD⁺ oxidoreductase (decarboxylating)] was purified from herring skeletal muscle to a specific activity of 8.2 mol/min/mg. The purification procedure involved chromatography on DEAE-cellulose, Red Agarose and a Sephacryl S-300 with a final recovery of 38% of enzyme activity. This enzyme catalyzes the oxidative decarboxylation of malate in the presence of either NAD or NADP in the presence of Mn²⁺. Some kinetic characteristics of this enzyme were determined. The pH optimum of activity is 7.0. ATP was shown to be a competitive inhibitor with malate. The inhibition by ATP displayed hyperbolic competitive kinetics with a K_i (ATP) of 0.28 mM in the presence of NAD and 0.75 mM in the presence of NADP. Fumarate reversed ATP inhibition.In vivo, regulation of NAD(P)-dependent malic enzyme might respond to changing levels of mitochondrial ATP and fumarate with the enzyme undergoing kinetic activation by an increase in the concentration of mitochondrial fumarate which could reverse enzyme inhibition by ATP.     

Effect of supplemental dietary zinc sources on the growth and carbohydrate utilization of tilapia Smith 1840, Oreochromis niloticus × Oreochromis aureus

An 8‐week feeding trial was conducted to investigate the effect of supplemental dietary zinc sources on the growth performance and carbohydrate utilization of juvenile tilapia Smith 1840, Oreochromis niloticus × O. aureus. The goal was to compare the bioavailability of two zinc sources, zinc sulphate (ZnSO₄) or zinc methionine (ZnMet), by using two practical basal diets with 350 g kg^?1 (C350) or 400 g kg^?1 (C400) carbohydrates based on wheat as the carbohydrate source. The results showed that fish fed with a diet supplemented with 60 mg kg^?1 Zn from either ZnSO₄ or ZnMet had a significantly (P < 0.05) greater specific growth rate and protein efficiency ratio than those fed with the diets of ≤30 mg kg^?1 Zn. The composition of tilapia carcass was also found to be influenced by various levels of dietary zinc from the two zinc sources. The G6P‐DH in fish fed with the 20 mg kg^?1 ZnMet diet and the PK levels in fish fed with 20 mg kg^?1 ZnSO₄ and 30 mg kg^?1 ZnMet diet were significantly (P < 0.05) higher than those in fish fed with the C400 diet. The data suggest that supplemental dietary zinc from either ZnMet or ZnSO₄ significantly affects the growth performance and carbohydrate utilization of tilapia.     

Growth,enzymatic glutathione peroxidase activity and biochemical status of juvenile barramundi (Lates calcarifer) fed dietary fermented lupin meal supplemented with organic selenium

To investigate the effects of high level of lupin meal (LM) supplemented with organic selenium (OS) on the growth and blood biochemistry of barramundi (Lates calcarifer), four isocaloric and isonitrogenous diets were prepared, containing either non‐fermented or fermented LM, and either supplemented with 2 mg OS/kg (LM, LM_OS, FLM and FLM_OS), or not. A fishmeal (FM)‐based diet formulated for juvenile barramundi was used as a control diet. Fish (initial mean weight of 5.88 g) were triplicated and fed the test diets for 75 days. The findings demonstrated that growth performance of fish fed with the FLM and FLM_OS diets were similar to fish fed with the FM diet (p > .05). The antioxidant glutathione peroxidase (GPx) activity, and haemoglobin (Hb) of fish fed with the FLM_OS diet were significantly higher than that of FM‐fed fish (p < .05). Plasma alanine aminotransferase (ALT) activity was significantly increased in fish fed with non‐fermented diets (LM and LM_OS) than in those fed with fermented LM diets (FLM and FLM_OS) (p < .05). However, there were no significant differences in ALT activity among LM_OS, FLM, FLM_OS and FM diets. There was an interaction between the LM and OS on plasma CK activity; the CK of fish fed with diets supplemented with OS was higher in non‐fermented LM diets but lower in fermented LM diets (p < .05). This study suggests that fermented LM have an obvious potential to substantially replace 75% FM protein in the diets of barramundi.