Catfish Muscle Research Articles

Collagen Extraction from Malaysian Cultured Catfish (Hybrid Clarias Sp.): Kinetics and Optimization of Extraction Conditions Using Response Surface Methodology

A central composite design (CCD) was used for the experimental design and results analysis to obtain the optimal processing parameters (acetic acid concentration, liquid to solid ratio, and stirring speed) for the extraction of pepsin soluble collagen (PSC) from muscles of cultured hybrid catfish of Clarias sp. (Clarias gariepinus × C. macrocephalus). Statistical analysis showed that the linear and quadratic terms of these three independent variables had significant effects on the yield of PSC. There was also an interaction between the ratio of liquid to solid and the stirring speed in affecting the extraction efficiency. Optimal conditions for a higher yield of PSC were an acetic acid concentration of 0.67 M, a liquid to solid ratio of 24.65 ml/g, and the stirring speed of 423.64 rpm. The verification of the optimization showed that the percentage error differences between the experimental and predicted values were in the range of 0.22–4.42%. The experimental values agreed with the predicted values, indicating an excellent fit of the model used and the success of the response surface methodology in modeling the extraction of PSC from the muscles of catfish. The experimental results were also fitted to the power law model and it was proven to be appropriate in describing the kinetics of collagen extraction process.

Molecular characterization, tissue distribution and kinetic analysis of carnitine palmitoyltransferase I in juvenile yellow catfish Pelteobagrus fulvidraco

Up to date, only limited information is available on genetically and functionally different isoforms of CPT I enzyme in fish. In the study, molecular characterization and their tissue expression profile of three CPT Iα isoforms (CPT Iα1a, CPT Iα1b and CPT Iα2a) and a CPT Iβ isoform from yellow catfish Pelteobagrus fulvidraco is determined. The activities and kinetic features of CPT I from several tissues have also been analyzed. The four CPT I isoforms in yellow catfish present distinct differences in amino acid sequences and structure. They are widely expressed in liver, heart, white muscle, spleen, intestine and mesenteric adipose tissue of yellow catfish at the mRNA level, but with the varying levels. CPT I activity and kinetics show tissue-specific differences stemming from co-expression of different isoforms, indicating more complex pathways of lipid utilization in fish than in mammals, allowing for precise control of lipid oxidation in individual tissue.

Cloning and expression of two HSC70 genes in walking catfishClarias macrocephalus(Günther, 1864) challenged withAeromonas hydrophila

Two different cDNAs encoding heat shock cognate protein 70 genes were isolated from the liver of walking catfish. The complete cDNA sequences for walking catfish HSC70-1 and HSC70-2 were of identical length (2278 bp), with an open reading frame of 1950 bp and a predicted 649 amino acid protein. Genomic sequences of the walking catfish HSC70-1 and HSC70-2 genes were composed of eight exons and seven introns, but exon and intron sizes were different. Amino acid sequences of both proteins shared 94% similarity with 38 substitutions. The walking catfish HSC70-1 and HSC70-2 proteins shared 82–95% identity of amino acids with those of other teleosts, chicken and human. Phylogenetic analysis revealed that walking catfish HSC70-1 and HSC70-2 clustered with channel catfish HSC71. Under normal conditions, HSC70-1 and HSC70-2 transcripts were expressed at similar levels in liver, gills, brain and skeletal muscle of walking catfish. Bacterial infection by Aeromonas hydrophila differentially induced the expression of HSC70s in these tissues during 48 h. HSC70-1 was constitutively expressed at low levels in most tissues, whereas HSC70-2 was up-regulated at moderate and high levels in liver and skeletal muscle respectively. The significant increase in the expression of HSC70-2 in these tissues may relate to the role of HSC70-2 in the immune response of walking catfish.

Multi-class, multi-residue analysis of pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers and novel flame retardants in fish using fast, low-pressure gas chromatography–tandem mass spectrometry

A multi-class, multi-residue method for the analysis of 13 novel flame retardants, 18 representative pesticides, 14 polychlorinated biphenyl (PCB) congeners, 16 polycyclic aromatic hydrocarbons (PAHs), and 7 polybrominated diphenyl ether (PBDE) congeners in catfish muscle was developed and evaluated using fast low pressure gas chromatography triple quadrupole tandem mass spectrometry (LP-GC/MS–MS). The method was based on a QuEChERS (quick, easy, cheap, effective, rugged, safe) extraction with acetonitrile and dispersive solid-phase extraction (d-SPE) clean-up with zirconium-based sorbent prior to LP-GC/MS–MS analysis. The developed method was evaluated at 4 spiking levels and further validated by analysis of NIST Standard Reference Materials (SRMs) 1974B and 1947. Sample preparation for a batch of 10 homogenized samples took about 1h/analyst, and LP-GC/MS–MS analysis provided fast separation of multiple analytes within 9min achieving high throughput. With the use of isotopically labeled internal standards, recoveries of all but one analyte were between 70 and 120% with relative standard deviations less than 20% (n=5). The measured values for both SRMs agreed with certified/reference values (72–119% accuracy) for the majority of analytes. The detection limits were 0.1–0.5ngg−1 for PCBs, 0.5–10ngg−1 for PBDEs, 0.5–5ngg−1 for select pesticides and PAHs and 1–10ngg−1 for flame retardants. The developed method was successfully applied for analysis of catfish samples from the market.

Heavy metals distribution in muscle, liver, kidney and gill of European catfish (Silurus glanis) from Italian Rivers

The accumulation of heavy metals in freshwaters has direct consequences to man and ecosystem. Thus, in this study, the concentrations of mercury, cadmium, lead, arsenic and chromium in organs of the predator European catfish (Silurus glanis) were investigated. Samples were collected annually in five sites covering the area of the Po River (North Italy) between 2007 and 2009.Metals were differently distributed in the various organs, the highest concentrations of Hg were found in muscle and liver, Cd in kidney, Pb in gill and liver, as in muscle, and of Cr in gill and liver. Our survey found Hg exceeding the Maximum Levels (MLs) of 0.5ppm in 18% of samples, while Pb and Cd were lower than the MLs set by European regulations in muscle tissues (1881/2006/EC and 629/2008/EC). Hg concentrations were significantly related to sampling stations studied, according to the presence of many industrial activities in the catchment area of Bormida and Tanaro Rivers. The finding that Hg did not fit food fish legislation limits indicated that S. glanis flesh might not be utilised for human consumption. A close monitoring of metals pollution is strongly recommended especially in piscivorous fish, cause their bioaccumulation capacity.

Isolation, purification and characterisation of angiotensin I‐converting enzyme–inhibitory peptides derived from catfish (Clarias batrachus) muscle protein thermolysin hydrolysates

SummaryThe angiotensin I‐converting enzyme (ACE)‐inhibitory activities of catfish (Clarias batrachus) muscle protein hydrolysates were investigated. Thermolytic digests of C. batrachus sarcoplasmic and myofibrillar proteins exhibited inhibitory activity towards ACE and were purified with the aim of ultrafiltration, gel filtration and reversed‐phase high‐performance liquid chromatography (RP‐HPLC). The amino acid sequences of hydrolysates with the highest ACE‐inhibitory activities were determined using electrospray quadrupole time‐of‐flight tandem mass spectrometry (ESI‐TOFQ MS/MS). The sequences of GPPP (IC50 = 0.86 μm) and IEKPP (IC50 = 1.2 μm) corresponding to the fragments 986–989 and 441–445 of myosin‐I heavy chain were identified for the sarcoplasmic and myofibrillar protein hydrolysates, respectively. Peptide GPPP exhibited a mixed‐type inhibition whereas peptide IEKPP could only bind to the active sites of ACE. The results demonstrate that hydrolysates of C. batrachus muscle proteins obtained by thermolysin may contain bioactive peptides.

메기(Silurus asotus)에 투여한 멜라민의 체내함량 변화

In 2007, pet food contaminated with melamine caused hundreds of dogs and cats to develop renal failure all over the world. In 2008, over 294,000 infants consumed infant formula and developed kidney stones in China. Further investigation revealed that fish feed also contained melamine; this raised concerns about melamine residues in edible fish tissues, which could have caused the urinary tract stone epidemic. In Korea, catfish fed with assorted feed that included cuttlefish organs that contained melamine developed whitening syndrome and fell dead in some populations in 2008. This event raised suspicions about the toxicity of melamine and all feeds containing melamine were immedi-ately recalled. In this study, we investigated the rates of melamine accumulation and depletion in muscle and viscera of catfish to propose proper withdrawal periods. One group of catfish was fed a commercially available diet that con-tained 30, 100 and 300 mg melamine per kg diet for 14 days. To investigate residual melamine contents in muscle and viscera, other experimental groups were fed a melamine free diet after being fed melamine for 7 days. The residual amount of melamine was analyzed by LC-MS/MS. The melamine concentration in muscle was estimated to be 3.7 mg/kg after 6 days of feeding with a diet containing 300 mg melamine/kg. After 2 days of culture with a melamine free diet, the residual melamine was depleted and the concentration had decreased from 1.15 mg/kg to 0.19 mg/kg in the muscle of catfish fed a diet containing 300 mg melamine/kg for 7 days. The residual amount of melamine was reduced to 0.03 mg/kg in muscle after 7 days of culture with a melamine free diet and was undetectable after a pro-longed culture period of 14 days. Catfish tend to excrete melamine rapidly after oral administration and changes in body color were not observed during the short dosing period. Key words: Melamine, Catfish, LC-MS/MS

Heavy Metal Concentrations in Predator Fish

Waters can be polluted by heavy metals which are accumulated and concentrated by fish ; therefore they show the degree of environmental pollution. The aim of this paper was to determine concentrations of heavy metals in water, mud and fish organs, to determine whether these concentrations are allowed and in accordance with normative provisions and, considering the pollution by heavy metals, if the fish meat is hygienically safe food of animal origin. Concentrations of heavy metals (lead, chromium, manganese, iron, copper, and zinc) were determined in water, mud and different organs (liver, kidney, intestine, milt and skin + muscle) of pike (Esox lucius) and European catfish (Silurus glanis) by Energy Dispersive X – Ray Fluorescence Method (EDXRF). Statistically significant difference was determined between the concentrations of heavy metals in mud and water (p< 0.05), as well as in fish organs (p< 0.05). The obtained results show that the highest concentrations of heavy metals were determined in liver, and the lowest ones in skin and muscle, i.e. in edible fish parts. In accordance with normative provisions of the European Union and the Republic of Croatia, the determined values are lower than the maximally allowed concentrations of heavy metals in fish muscle. When the pollution by heavy metals is taken into account, it indicates that the researched fish meat is hygienically safe food of animal origin.

A study on dietary l-lysine requirement of juvenile yellow catfish Pelteobagrus fulvidraco

An 8-week feeding trial was conducted to determine lysine requirement of juvenile yellow catfish (Pelteobagrus fulvidraco) by feeding formulated diets containing crystalline l-lysine. Six isonitrogenous and isoenergetic diets (405 g kg−1 protein, 18 kJ g−1 gloss energy) containing fish meal together with soybean protein concentrate as protein sources and fish oil together with soybean oil as lipid sources were formulated. Crystalline l-lysine was added into the six diets to acquire lysine concentrations of 17.3, 21.8, 26.0, 31.3, 35.5 and 41.9 g kg−1 dry diets, respectively. Mixture of crystalline amino acid was supplemented to simulate the amino acid profile in muscle of yellow catfish. The results indicated that final body weight (FBW), weight gain (WG), specific growth rate (SGR), feed efficiency (FE) and protein efficiency (PE) increased with the increase in dietary lysine level from 17.3 to 31.3 g kg−1 of diet and then decreased as the dietary lysine levels further increased. No significant difference in survival rate was found among all the dietary treatments. One-slope, quadratic broken-line analysis on the basis of SGR showed that the dietary l-lysine requirement of juvenile yellow catfish was 33.1 g kg−1 of dry diet (83.2 g kg−1 of dietary protein).

Channel Catfish (Ictalurus punctatus) Muscle Protein Isolate Performance Processed under Different Acid and Alkali pH Values

Channel catfish (Ictalurus punctatus) muscle was subjected to 6 protein extraction and precipitation techniques using acid solubilization (pH 2.0, 2.5, and 3.0) or alkaline solubilization (pH 10.5, 11.0, 11.5) followed by precipitation at pH 5.5. The catfish protein isolate was compared with ground defatted white muscle. Alkali-processed catfish showed increased gel rigidity, gel strength, and gel flexibility compared to acid-processed catfish, which exhibited inconsistent functional performance, increasing and decreasing gel rigidity, gel strength, and gel flexibility. The gel rigidity (G') at pH 3.0 in the absence of salt had the highest G' of the acid treatments and was not significantly different from the alkaline-treated catfish muscle (P>0.05). However in the presence of added salt pH treatment it had the lowest G' and was different from alkaline treatments (P<0.05) during break force testing. These results show that pH-shift processing of channel catfish muscle provides highly functional isolates with a potentially broad range of applications. This range of applications is possible due to the modification of the textural properties of catfish muscle protein produced using different acidic or alkaline pH solubility treatments.

Functional Properties of Protein Fractions of Channel Catfish (Ictalurus punctatus) and Their Effects in an Emulsion System

This study demonstrated the feasibility of producing soluble protein (CFSP) and insoluble protein (CFISP) fractions from catfish muscle protein. CFSP and CFISP contained 60.6% and 73.8% protein and 8.6% and 20.3% fat, respectively. Both CFSP and CFISP contained essential amino acids. Differences were observed between physicochemical properties of the 2 protein fractions, including nitrogen solubility, emulsion stability, and fat adsorption capacity. The flow and viscoelastic properties of the emulsions prepared with CFSP and CFISP were investigated using a rheometer. The power law model and the Casson model were used to determine the flow behavior index (n), consistency index (K), and yield stress. Emulsion containing CFSP (ECFSP) had a higher K value than emulsion containing CFISP (ECFISP). Both ECFSP and ECFISP emulsions exhibited pseudoplastic behavior and viscoelastic characteristics. The G' (an elastic or storage modulus) and G″ (a viscous or loss modulus) values for ECFSP were higher than ECFISP. Catfish muscle tissue can be easily separated into soluble and insoluble protein powders that have desirable functional properties.

Bioaccumulation of melamine in catfish muscle following continuous, low-dose, oral administration.

In this study, catfish muscle was analyzed for melamine (MEL) and cyanuric acid (CYA) residues following experimental feeding with low doses of MEL and MEL and CYA (MEL+CYA) and with the insoluble melamine-cyanurate complex (MEL=CYA). Catfish were daily fed 0.1 mg/kg BW of MEL for 15, 28, or 42 days, 0.1 mg/kg BW of MEL+CYA for 28 days, 2.5 mg/kg BW of MEL+CYA for 14 days, or 400 mg/kg BW of MEL=CYA for 3 days. Residues in the tissue were determined by LC-MS/MS. MEL was extracted with acidic acetonitrile, followed by defatting with dichloromethane, and isolated with cation exchange solid phase extraction (SPE). For CYA analysis, fish were extracted with dilute acetic acid, defatted with hexane, and cleaned up with a graphitic carbon SPE. Catfish fed 0.1 mg/kg BW of MEL reached a maximum muscle residue concentration of 0.33 ± 0.04 mg/kg (ppm) after 28 days of continuous feeding. The same concentration was found for MEL+CYA feeding at the 0.1 mg/kg BW level for 28 days. Feeding at 2.5 mg/kg BW of MEL+CYA yielded muscle concentrations above the 2.5 mg/kg level of concern for most of the study fish. Finally, catfish fed high levels of the MEL=CYA complex (400 mg/kg BW) accumulated relatively little MEL in the muscle (0.14 ± 0.07 mg/kg) and, unlike treatment with MEL+CYA, did not form renal melamine-cyanurate crystals. Appreciable concentrations of CYA were not detected in any of the muscles tested. These studies provide data to model the bioaccumulation of triazine residues into edible fish tissue as a result of the continuous consumption of adulterated feed.

Selenium speciation in different organs of African catfish (Clarias gariepinus) enriched through a selenium-enriched garlic based diet

Speciation of Se in fish is needed to elucidate the metabolism of this element in living organisms in the marine environment. In this paper, selenium concentration and its species distribution in several organs and tissues (liver, gills, kidney, muscle and gastrointestinal tract) of African catfish fed with a selenium-enriched garlic based diet was studied. The intention of this paper is focused on both the investigation of selenium distribution in the soluble protein fraction and the detection of selenoaminoacids. Thus, two different procedures have been developed. In the first procedure, screening of selenium in proteins in the Tris-buffer soluble fraction of different tissues was carried out by size exclusion chromatography-inductively coupled plasma-mass spectrometry (SEC-ICP-MS) and by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) after sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) separation and electroblotting onto membranes. For the amino acid analysis, several sample treatments for Se-species extraction, based on enzymatic hydrolysis, were compared. The best results were obtained for incubation at controlled temperature. Application of several sample treatments in conjunction with different chromatographic techniques (reverse phase, anion exchange and ion exchange/size exclusion) was crucial to unambiguous Se-species identification. In Se-enriched African catfish a noticeable increase in the content of selenium in different organs was observed, except for the liver, where the Se level remained unaltered. The kidney was the Se-target organ in animals fed with enriched Se food. Selenomethionine (SeMet) was the main Se species identified in fillet extracts, whereas the presence of selenocysteine (SeCys) was detected in the liver and both SeMet and SeCys were present in the kidney.

The role of sarcoplasmic reticulum and sarcolemma in the regulation of cardiac contractility at different times and higher extracellur potassium in the cardiac muscle of catfish and toad.

The relative contribution of sarcoplasmic reticulum (SR) and sarcolemma in the regulation of cardiac contractility (twitch force, the rate of contraction and the rate of relaxation) at different time periods (10, 20 and 30 minuted) and at elevated extracellular potassium (5.omM) was assessed in the ventricular tissues of catfish and toad using adrenaline as an activator of SRCa2+ uptake, caffeine as an inhibitor of SRCa2+ uptake and verapamil as an inhibitor of sarcolemmal Ca2+ exchange. Cardiac contractility (twitch force, rate of contraction and the rate of relaxation – df/dt) tended to decrease with increasing of the time periods from 10 to 20 and 30 minutes in the catfish and toad ventricular tissues at 2.5 and 5.omMK+, Elevated extracellular K+ had a positive inotropic effect on the twitch force developed at 20 and 30 minutes in the catfish cardiac muscle, but it had non significant negative effect in the toad cardiac muscle at the same periods. The df/dt developed after 30 minutes was significantly lower in the presence of 5.omMK+ than that developed at 2.5mMK+ in the catfish cardiac muscle, whereas the effect of elevated K+ on df/dt was similar to that of 2.5mMKO at all the time periods applied in the toad cardiac muscle. Elevated K+ had a negative inotropic effect on the-df/dt developed at all time periods applied in the catfish cardiac muscle, but it had no effect on the-df/dt developed in the toad cardiac muscle at the same time periods. Adrenaline, like caffeine had a positive inotropic effect on the twitch force, df/dt and – df/dt developed after all the time periods applied at 2.5 and 5.omMK+ in the ventricular tissues of both animals, relative to that of control. But, the positive inotropic effect of caffeine on the cardiac contractility was significantly lower than that of adrenaline at 2.5 and 5.omMK+ O and at the different time periods applied (specially after 30 minutes) for both animals. Verapamil had a significantly negative inotropic effect on the cardiac contractility developed after all time periods applied at 2.5 and 5.omMK+ in both animals, relative to that of control. However the negative inotropic effect of verapamil on the cardiac contractility was significantly higher at elevated K+ than at 2.5mMK+. The twitch force developed after all time periods applied in the toad cardiac muscle was significantly lower than that in the catfish cardiac muscle after the same periods in either 2.5 or 5.omMK+. In the presence of adrenaline, the twitch force developed in the toad cardiac muscle after each period applied was non-significantly higher than that developed in the catfish cardiac muscle at 2.5 and 5.omMK,+ whereas it was significantly higher than that of catfish cardiac muscle in the presence of caffeine at 2.5 and 5.omMK+ after the same time periods. In the presence of verapamil, the twitch force developed after each time periods in the toad cardiac muscle was significantly and non- significantly higher than that of catfish cardiac muscle at 2.5 and 5.omMK+ respectively. The df/dt developed after each period applied in the catfish cardiac muscle was to somewhat similar to that developed in the toad cardiac muscle at 2.5 and 5.omMK+, but in the presence of adrenaline, it was significantly lower than that of toad cardiac muscle at 2.5 and 5.omMK+, whereas in the presence of caffeine, it was non-signifantly higher than that of toad cardiac muscle. In the presence of verapamil, the df/dt developed in the catfish cardiac muscle after the time period applied was significantly lower than that of toad cardiac muscle at 2.5 and 5.omMK+, also. The - df/dt developed in the catfish cardiac muscle after the time periods applied was similar to that of toad cardiac muscle at 2.5mMK+, but it was non-significantly lower than that of toad cardiac muscle at 5.omMK+. In the presence of adrenaline, the - df/dt developed after the time periods applied in the catfish cardiac muscle was significantly lower than that of the toad cardiac muscle at 2.5 and 5.omMK+, whereas the opposite situation was recorded in the presence of caffeine. In the presence of verapamil at 2.5mMK+, the-df/dt developed after the time periods applied in the catfish cardiac muscle was signifantly lower than that of the toad cardiac muscle, whereas it was similar in the cardiac muscle of both animals at 5.omMK+. So, it can be concluded that the cardiac contractility in the catfish and toad ventricular tissues is time dependent. Also, it seems that the sarcolemmal Ca2+ exchanges partake in the regulation of cardiac contractility in the ventricular tissue of both animal But, the contribution of sarcoplasmic reticulum in the regulation of cardiac force was higher in the toad cardiac muscle than that of catfish cardiac muscle. Elevated extracellular K+ had a positive inotropic effect on the cardiac contractility in both animals.

Reparation of chlorpyrifos-induced impairment by thyroxine and vitamin C in fish

The organophosphate pesticide chlorpyrifos significantly decreased the specific activities of catalase (CAT) and lactate dehydrogenase (LDH) in brain, liver, gill and skeletal muscle of the freshwater catfish, Heteropneustes fossilis. It may be due to binding of the pesticide or its metabolite(s) with the enzyme molecules or affecting the synthesis and/or degradation of the enzymes. RNA and protein content also declined significantly in different tissues of the fish in response to chlorpyrifos, which may be due to alterations in turnover of macromolecules involved in protein synthesis. Administration of thyroxine (T4) and ascorbic acid (vitamin C) separately or conjointly to chlorpyrifos-exposed fish brought CAT, LDH, RNA and protein up to their control levels. The protective effect may be attributed to hormone, vitamin and pesticide interaction. Therefore, chlorpyrifos-induced impairment in antioxidative, anaerobic and protein synthesizing capacity can be repaired by ascorbic acid and T4 in fish.

HPLC Determination and MS Confirmation of Malachite Green, Gentian Violet, and Their Leuco Metabolite Residues in Channel Catfish Muscle

Residues of malachite green (MG), gentian violet (GV), and their leuco metabolites in channel catfish muscle were individually determined by HPLC using diode array and fluorescence detectors and confirmed by tandem mass spectrometry. This detection scheme obviates a PbO(2) reactor that converts leuco forms to chromatic forms for absorbance detection, therefore eliminating uncertainties in oxidant depletion and data integrity. Extraction was performed once in pH 3 McIlvaine buffer and acetonitrile, followed by cleanup using a polymeric strong cation-exchange column. Liquid-liquid extraction was excluded to provide an environmentally responsible and relatively rapid protocol. Spectrometric limits of detection (LOD; S/N = 3) for MG (lambda = 620 nm) and GV (lambda = 588 nm) were 0.38 and 0.26 ng/g with 44.5-49.2% and 92.2-101.4% recoveries (1-10 ng/g, n = 6), respectively. Fluorometric LOD (S/N = 3) for LMG and LGV (lambda(ex) = 266 nm, lambda(em) = 360 nm) were 0.10 and 0.09 ng/g with 74.3-84.5% and 80.6-86.5% recoveries (1-10 ng/g, n = 6), respectively. This simplified protocol saves costs and meets the sensitivity requirements set by the Food and Drug Administration and the European Union.

Assessment of protein changes in farmed giant catfish (Pangasianodon gigas) muscles during refrigerated storage

SummaryFarmed giant catfish (Pangasianodon gigas) muscles (dorsal and ventral sites) were stored in a refrigerator (at 4 °C) for 14 days to determine the effect of refrigerated storage on biochemical and physical changes. The analyses were carried out at 0, 2, 4, 7, 10 and 14 days of storage. At day 14, Ca2+ ‐ATPase activity markedly decreased when compared to its value at day 1 (&gt;90%), while a small decrease was observed for surface hydrophobicity and reactive sulfhydryls content. Total volatile basic nitrogen and trichloroacetic‐soluble peptide content gradually increased when the storage period was extended. The myosin heavy chain decreased slightly on SDS‐PAGE for both meat cuts with increased storage time. Expressible drip and cooking loss were highest during the first day of storage and slightly decreased with storage time. Instrumental hardness was significantly higher in the ventral compared to the dorsal muscle, while the toughness was the highest at the second day of storage. The muscle bundles with scanning electron microscopy were less attached, resulting in the observed big gaps over increasing storage time. Results indicated that changes of proteins have detrimental effects on the quality attributes of farmed giant catfish muscles during refrigerated storage, particularly physical and biochemical properties.

Extraction of Channel Catfish Muscle Oil by Supercritical Carbon Dioxide and Determination of Fatty Acids by Gas Chromatography-Electron Ionization-Mass Spectrometry

Extraction of Channel Catfish Muscle Oil by Supercritical Carbon Dioxide and Determination of Fatty Acids by Gas Chromatography-Electron Ionization-Mass Spectrometry

Enzymatic and histopathologic biomarkers as indicators of aquatic pollution in fishes

In the present study we investigated the alteration in the activity of two metabolic enzymes [Glucose-6-Phosphate Dehydrogenase (G6PDH) and Lactate Dehydrogenase (LDH)] and the histological changes on liver and gills of the African catfish Clarias gariepinus collected from 6 sites along the river Nile, from its spring at Aswan to its estuary at Rosetta and Damietta branches. The results showed that the physical and chemical parameters of the water collected from Damietta and Rosetta branches were higher than those of the water collected from other sites. Remarkable alterations in the activity of the selected enzymes in the liver and muscles of the African catfish were detected. These alterations go in parallel with the elevation in the levels of chemical parameters detected in the water of Damietta and Rosetta branches as a result of pollution stress in these areas. The activity of G6PDH was significantly (p < 0.05) decreased from Aswan to Rosetta and Damietta recording the highest value at Rosetta followed by Damietta water. The activity of LDH showed a significant elevation (p < 0.05) in activity in the liver and muscles of fishes collected from Rosetta and Damietta branches comparing to other sites. These alterations in enzymatic activities were followed, in the present study, by the occurrence of histological lesions and clear damage in liver and gill tissues of the African catfish collected from the same sites. Thus we may conclude that, the altered activities of G6PDH and LDH could be useful biomarkers of water pollution. At the same time, histopathology provides a reliable, easily quantifiable index of low-level toxic stress to a broad range of environmental pollutants.

Fluoride induced alterations in the arginase activity of freshwater catfish, Clarias batrachus (Linn)

Fluoride induced alterations in arginase activity in liver, muscle, kidney, gill and brain of freshwater cat fish, Clarias batrachus (Linn.) were carried out. The effect of fluoride was observed in different concentrations like 1, 10, 20 and 30 ppm in 1, 30 and 60 days of exposure. The arginase activity was found increased in all the tissues, throughout the exposure span. Maximum activity was observed on 60th day of exposure in 30 ppm of fluoride concentration. In most of the cases the elevation of arginase activity significantly differed from the controls. Gill showed maximum activity followed by liver, brain, kidney, and muscle. The increase in arginase activity indicates production of urea or ornithine.