Channel Catfish Muscle Research Articles

Study of enzyme-hydrolyzed soybean replacing fish meal and/or chicken meal on the growth of channel catfish (Ictalurus punctatus)

This study aimed to evaluate the effect of enzyme-hydrolyzed soybean (EHSB) to replace fish meal and chicken meal in channel catfish (Ictalurus punctatus) on the growth performance, serum biochemical indices and gastrointestinal structure of channel catfish. The channel catfish (initial weight: 21.25 ± 0.25 g) was fed four isonitrogenous, isolipidic and isophosphorous diets for 60 days. The control diet (CON group) contained 8% fish meal and 5% chicken meal. EHSB was used to replace fish meal (100%, RF group), chicken meal (100%, RC group), and 100% of fish meal and chicken meal (RFC group), respectively. The specific growth rate (SGR) and protein deposition rate (PR) of channel catfish in RF, RC and RFC groups were significantly increased compared to the control group and reached their peaks in RFC group (SGR: 2.92%, PR: 45.64%) (P < 0.05). The feed coefficient of channel catfish in RFC group (0.94) was significantly decreased compared to the control group (P < 0.05). The survival rate was not affected by the replacement of fish meal and chicken meal by EHSB (P > 0.05). The catalase and alanine aminotransferase activities in serum were significantly decreased in replacement groups compared to the control group (P < 0.05). Besides, the activities of superoxide dismutase and aspartate aminotransferase in serum of channel catfish were remarkably increased in the RFC group (24.22 U/L and 193.00 U/L, respectively) (P < 0.05). The replacement of fish meal and chicken meal by EHSB, either alone or simultaneously, significantly increased the crude protein (51.68% in RC group) and crude lipid (31.27% in RFC group) in whole body of channel catfish (P < 0.05). The crude lipid in muscle of channel catfish was markedly increased in RF (16.31%, dry matter) and RFC groups (16.45%, dry matter) (P < 0.05). Replacement of fish meal and chicken meal by EHSB could significantly increase the intestinal villi length and intestinal wall thickness, thus improving the digestive capacity of channel catfish. The gastric epithelial cells in the RFC group were plumper and more structurally integrated than in the control group. In summary, replacing 100% of fish meal and 100% of chicken meal with EHSB could effectively improve the growth performance, antioxidation and digestive capacities of channel catfish.

Influence of bleeding on myoglobin and meat quality changes of Channel catfish muscle during freeze‐thaw cycles

The present study investigated the effects of bleeding treatment on myoglobin, color, lipid, and myofibrillar oxidation of Channel catfish fillets during seven freeze-thaw cycles. The oxidation degrees of myoglobin, lipid, and myofibrillar in the samples without bleeding treatment were greater than those in the samples with bleeding treatment during seven freeze-thaw cycles. The L* value of bleeding-treated samples was higher than that of untreated samples, whereas the a* and b* values were lower than those of untreated samples during seven freeze-thaw cycles. Overall, the oxidation of myoglobin exacerbates the oxidation of myofibrillar protein. Moreover, the interaction between the oxidations of myoglobin and the lipid caused changes in the color of Channel catfish fillets. This study reveals the mechanism underlying the complementary oxidation interaction and provides a basis for explaining quality deterioration in fish meat. Our results can be applied for developing strategies to maintain optimal sensory qualities of freshwater fish meat. Novelty Impact Statement Preconditioned aquatic products such as catfish fillets sold by cold chain transportation have a longer shelf life, richer nutritional value, and fresh taste than freshly slaughtered aquatic products, so they are popular among modern consumers. However, insufficient slaughter and bleeding in the preconditioning of aquatic products will cause blood to accumulate in the fish fillets, which will affect the taste and appearance of the product and its shelf life. Therefore, we fully bled the catfish after slaughter and found that the oxidation of lipid, protein, and myoglobin of catfish was delayed, and the color was brighter than that of the no bleeding catfish group. The bleeding treatment after slaughter can be used as an important part of the pretreatment of preconditioned aquatic products to extend the freshness of the conditioned aquatic products.

The relationship between food exposure frequency and expression of AMP‐activated protein kinase (AMPK) mRNA in the brain, liver, and muscle of channel catfish

Obesity poses serious challenges to our healthcare system with serious consequences of associated diseases. Our laboratory has been examining how the expression of genes involved in food intake and tissue nutrient metabolism is associated with the development of obese‐like phenotypes in channel catfish. The objective of the study was to examine changes in expression of AMPK mRNA in response to changes in feeding frequency. Fish were fed every 12 (overfed), 24 (control), or 48 (underfed) hours (n= 4 tanks per treatment, 8 fish per tank) for 28 days. Brain, liver, and muscle tissue were collected at the end of the study. The expression of the AMPK mRNA was examined using quantitative RT‐PCR. The muscle expression of all AMPK subunit mRNA was unaffected by feeding frequency. In contrast, brain expression of alpha 1 and beta 1 subunit mRNA had a linear tendency for increase in response to increased feeding frequency. Hepatic expression of alpha 2 and beta 1 mRNA was lower in the overfeed group compared to those assigned as control or underfeed. Hepatic expression of alpha 1 mRNA decreased linearly in response to increased feeding frequency. Our results demonstrated that the hepatic and the brain expression of AMPK mRNA was influenced by increase in exposure to food in a transcript‐specific manner. Given that the AMPK serves as a regulator of tissue nutrient sensing and metabolism in mammals, it is possible that AMPK may share a similar function in the brain and liver but not in the muscle of channel catfish.Support or Funding InformationKansas IDeA Network of Biomedical Research Excellence Network (NIH/NIGMS grant number P20GM103418)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Expression of muscle mTOR mRNA in relation to changes in food intake in channel catfish

Objectives of this study were to examine the relationship between expression of mechanistic target of rapamycin (mTOR) mRNA and increased food intake in the muscle of channel catfish. mTOR plays a key role in the regulation of protein synthesis, cell growth, cell proliferation, and nutrient metabolism. In our previous study, we characterized tissue distribution of mTOR mRNA and changes in its expression in response to prolonged fasting and showed that fasting increased the expression of mTOR mRNA in muscle of channel catfish. Given that genetic selection towards growth causes the development of obese‐like phenotype in channel catfish, it is possible that increased food intake affects the expression of mTOR mRNA in muscle. Therefore, the relationship between muscle expression of mTOR mRNA and increased feeding frequency was examined in our current study. Juvenile channel catfish were fed at every 12, 24, or 48 hours for 28 days (n=4 tanks per treatment, 8 fish per tank). Muscle expression of mTOR mRNA was measured using quantitative RT‐PCR from the samples collected at the end of the 28‐day feeding period. Muscle expression of mTOR mRNA was significantly greater in fish fed every 48 hours compared to those fed every 24 hours (p&lt;0.05). In contrast, the expression of mTOR mRNA was similar between fish fed every 24 hours and those fed every 12 hours. Our results suggest that the expression of mTOR mRNA in muscle is sensitive to nutritional stress, which is similar to observations made in mammals.Support or Funding InformationThis study is supported by the Kansas IDeA Network of Biomedical Research Excellence.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of nutrient restriction and re-feeding on calpain family genes in skeletal muscle of channel catfish (Ictalurus punctatus).

BackgroundCalpains, a superfamily of intracellular calcium-dependent cysteine proteases, are involved in the cytoskeletal remodeling and wasting of skeletal muscle. Calpains are generated as inactive proenzymes which are activated by N-terminal autolysis induced by calcium-ions.Methodology/Principal FindingsIn this study, we characterized the full-length cDNA sequences of three calpain genes, clpn1, clpn2, and clpn3 in channel catfish, and assessed the effect of nutrient restriction and subsequent re-feeding on the expression of these genes in skeletal muscle. The clpn1 cDNA sequence encodes a protein of 704 amino acids, Clpn2 of 696 amino acids, and Clpn3 of 741 amino acids. Phylogenetic analysis of deduced amino acid sequences indicate that catfish Clpn1 and Clpn2 share a sequence similarity of 61%; catfish Clpn1 and Clpn3 of 48%, and Clpn2 and Clpn3 of only 45%. The domain structure architectures of all three calpain genes in channel catfish are similar to those of other vertebrates, further supported by strong bootstrap values during phylogenetic analyses. Starvation of channel catfish (average weight, 15–20 g) for 35 days influenced the expression of clpn1 (2.3-fold decrease, P<0.05), clpn2 (1.3-fold increase, P<0.05), and clpn3 (13.0-fold decrease, P<0.05), whereas the subsequent refeeding did not change the expression of these genes as measured by quantitative real-time PCR analysis. Calpain catalytic activity in channel catfish skeletal muscle showed significant differences only during the starvation period, with a 1.2- and 1.4- fold increase (P<0.01) after 17 and 35 days of starvation, respectively.Conclusion/SignificanceWe have assessed that fasting and refeeding may provide a suitable experimental model to provide us insight into the role of calpains during fish muscle atrophy and how they respond to changes in nutrient supply.

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.

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.

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

Cyano Metabolite as a Biomarker of Nitrofurazone in Channel Catfish

The use of nitrofuran drugs in food-producing animals continues to attract international concern as a food safety issue. Methods for monitoring nitrofuran residues have been directed to the intact side chain of tissue-bound metabolites. Semicarbazide, the side chain of nitrofurazone (NFZ), can enter food products from non-NFZ sources, suggesting the need for an alternative biomarker for confirmatory purposes. We characterized a cyano derivative as a major metabolite of NFZ in channel catfish (Ictalurus punctatus). The depletion of cyano metabolite was examined in the muscle of channel catfish after oral dosing (10 mg of NFZ/kg of body weight). Parent NFZ was rapidly eliminated in muscle, with a half-life of 6.3 h. The cyano metabolite was detected for up to 2 weeks, with an elimination half-life of 81 h. The cyano metabolite represents an alternative biomarker for confirming the use of NFZ in channel catfish.

Residue Depletion of Nitrofuran Drugs and Their Tissue-Bound Metabolites in Channel Catfish (Ictalurus punctatus) after Oral Dosing

The depletion of the nitrofuran drugs furazolidone, nitrofurazone, furaltadone, and nitrofurantoin and their tissue-bound metabolites [3-amino-2-oxazolidinone (AOZ), semicarbazide (SC), 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ), and 1-aminohydantoin (AH), respectively] were examined in the muscle of channel catfish following oral dosing (1 mg/kg body weight). Parent drugs were measurable in muscle within 2 h. Peak levels were found at 4 h for furazolidone (30.4 ng/g) and at 12 h for nitrofurazone, furaltadone, and nitrofurantoin (104, 35.2, and 9.8 ng/g respectively). Parent drugs were rapidly eliminated from muscle, and tissue concentrations fell below the limit of detection (1 ng/g) at 96 h. Peak levels of tissue-bound AMOZ and AOZ (46.8 and 33.7 ng/g respectively) were measured at 12 h, and of SC and AH (31.1 and 9.1 ng/g, respectively) at 24 h. Tissue-bound metabolites were measurable for up to 56 days postdose. These results support the use of tissue-bound metabolites as target analytes for monitoring nitrofuran drugs in channel catfish.

Most cited papers from 2005

Annually we recognize the papers published 2 years previously that have been cited the most, as reported in Thomson's Citation Index. We are pleased to announce the papers in each section that have achieved this distinction. Congratulations to the authors. We look forward to receiving new contributions from them. Choe E, Min DB. Chemistry and reactions of reactive oxygen species in foods. J Food Sci 70(9):R142-59. Nov/Dec 2005 Times Cited: 14 Kristinsson HG, Theodore AE, Demir N, Ingadottir B. A comparative study between acid- and alkali-aided processing and surimi processing for the recovery of proteins from channel catfish muscle. J Food Sci 70(4):C298-306. May 2005 Times Cited: 11 Thomazine M, Carvalho RA, Sobral PIA. Physical properties of gelatin films plasticized by blends of glycerol and sorbitol. J Food Sci 70(3):E172-6. Apr. 2005 Times Cited: 7 Donkor ON, Henriksson A, Vasiljevic T, Shah NP. Probiotic strains as starter cultures improve angiotensin-converting enzyme inhibitory activity in soy yogurt. J Food Sci 70(8):M375-81. Oct. 2005 Times Cited: 12 Suvarnakuta P, Devahastin S, Mujumdar AS. Drying kinetics and beta-carotene degradation in carrot undergoing different drying processes. J Food Sci 70(8):S520-6. Oct. 2005 Times Cited: 8

Metabolism and depletion of albendazole in the muscle tissue of channel catfish following oral treatment

The residue depletion of albendazole (ABZ) and its metabolites was studied in channel catfish muscle tissue. Channel catfish were dosed once with 10 mg/kg ABZ via stomach tube with manual restraint. Muscle tissue samples were collected at 8, 16, 24, 48, 72, 96 and 120 h postdose. A high-performance liquid chromatographic method was used to assay ABZ and its major metabolites: ABZ sulfoxide (ABZ-SO), ABZ sulfone (ABZ-SO2) and ABZ aminosulfone (ABZ-2-NH2SO2) in the muscle tissue. The results indicate that ABZ and ABZ-SO were present in low concentrations, i.e. <15 and <10 microg/kg, respectively, at 8 h postdose in catfish muscle with and without skin. ABZ-SO2 was present at 1 microg/kg concentration levels until 48 h in muscle alone and 72 h in muscle with skin. ABZ-2-NH2SO2 was not detected at any withdrawal periods.

A Comparative Study between Acid-and Alkali-aided Processing and Surimi Processing for the Recovery of Proteins from Channel Catfish Muscle

ABSTRACT: Channel catfish muscle was subjected to 2 novel protein extraction and precipitation techniques using acid (pH 2.5) or alkaline (pH 11) pH and compared with surimi processing (3 wash cycles). Solubility of catfish proteins was found to be highest at pH 2.5 and 11, and at these pH levels, viscosity was found to be low enough to cause separation of proteins from insoluble materials via centrifugation. Both the acid-aided and alkali-aided processes led to higher recoveries (P < 0.05) of protein and larger reduction (P < 0.05) in lipids compared with surimi processing. The protein recovery could be increased even more with a modified version of the acid-aided and alkali-aided processes. There was no hydrolytic breakdown detected during low and high pH. The acid-aided process recovered more protein types than the alkali-aided process during isolelectric precipitation (pH 5.5), which indicated that it led to more protein denaturation and thus more aggregation at pH 5.5. The alkali-aided process had more soluble proteins (including heme proteins) at isoelectric precipitation than the acid-aided process, and the soluble proteins were of the same type as the soluble proteins for non-pH-treated catfish muscle at pH 5.5. This suggested the alkali-aided process led to less denaturation than the acid-aided process. Both acid-aided and alkali-aided processes recovered proteins of higher (P < 0.05) whiteness scores than surimi. The alkali-aided process recovered proteins of higher whiteness (P < 0.05) than the acid-aided process. The acid-aided process led to higher yellowness (P < 0.05) than the other 2 processes. All processes led to minimal levels of lipid oxidation as assessed by secondary oxidation products.

Determination of florfenicol amine in channel catfish muscle by liquid chromatography.

A method for quantifying florfenicol amine (FFA) in channel catfish muscle was validated according to U.S. Food and Drug Administration guidelines. FFA is the proposed marker residue for the veterinary antibiotic florfenicol in catfish muscle for regulatory surveillance purposes. The method includes acid hydrolysis followed by sample cleanup with ethyl acetate extraction, basification, solid-phase extraction, and quantitation by liquid chromatography with UV detection. The assay was validated at 5 concentrations in the range of 0.075-35 microg/g muscle. The overall mean recovery of FFA from fish tissues fortified at these concentrations ranged from 85.7 to 92.3%, 4.8-17.2% relative standard deviation (RSD). The assay limit of detection was 0.044 microg/g muscle based on analysis of control muscle. Catfish muscle samples containing incurred florfenicol residues were analyzed in quintuplicate with RSD < 5%. Acid hydrolysis has previously been demonstrated to convert florfenicol and its known metabolites to FFA and to release a significant amount of FFA from nonextractable florfenicol residues in tissues containing incurred residues in other species. By using acid hydrolysis, this method should yield a more accurate estimate of the total florfenicol-related residue level in muscle tissue from florfenicol-treated catfish than could be achieved by solvent extraction alone.

Preliminary Observations on the Effects of Water Hardness on Free Taurine and Other Amino Acids in Plasma and Muscle of Channel Catfish

An interesting metabolic adjustment that fish make in their adaptation to a particular environment concerns the maintenance of the proper osmotic balance in their tissues. Free amino acids can be important isosmotic regulators; they contribute to intra- and extracellular fluid osmolality and are important in cell volume regulation. For this reason, a laboratory experiment was conducted to evaluate the effects of water ionic composition on the level of free amino acids in the plasma and muscles of juvenile channel catfish Ictalurus punctatus. Duplicate groups of fish were fed a commercial diet (40% crude protein) twice daily to apparent satiation. Fish were held under two different regimes of water hardness, 17.9 and 407 mg/L as CaCO3, which were considered soft and hard water, respectively. Blood and muscle samples were obtained from fish at the start and termination of the 4-week experiment. Mean plasma osmolarity was 294 and 273 mmol/kg for fish reared in hard and soft water, respectively. Analysis of the free amino acid concentrations of plasma and muscle with high-performance liquid chromatography revealed that the ionic environment had significant (P < 0.05) effects on the concentration of taurine and other amino acids. Circulating plasma amino acid concentrations indicated an increased release of taurine, glycine, serine, glutamine, and histidine in fish acclimated to soft water. In contrast, fish acclimated to hard water accumulated taurine, alanine, and tyrosine in the muscle free amino acid pool. Although the magnitude of the changes in amino acid level that occurred in the plasma and skeletal muscle indicates that taurine is the principal organic osmolyte in channel catfish, these changes are of less significance than the total osmotic concentration of plasma. However, the responsiveness of taurine to water hardness suggests an important role for this amino acid in regulating cell membrane permeability; it may also have physiological significance, as taurine mediates many other biological functions in fish. To our knowledge, the present study is the first to report the effects of water hardness on free amino acid profiles in the tissues of channel catfish.

Effect of Waterborne Potassium Permanganate Exposure on Manganese Content in Liver and Axial Muscle of Channel Catfish

Abstract Adult channel catfish Ictalurus punctatus were exposed to waterborne potassium permanganate for 12 weeks to determine if such exposure would alter the manganese content of axial muscle or liver tissue. Continuous exposure to 0.5 mg KMnO4/L or exposure to 1 or 2 mg KMnO4/L on alternate days did not cause a significant increase in manganese in axial muscle or liver tissue. The mean (±SE) concentration of manganese in axial muscle of unexposed controls was 0.262 ± 0.018 mg/kg (wet weight). Means of manganese concentrations in axial muscle of the three exposure groups during the 12 weeks of exposure were 0.289 ± 0.021 mg/kg, 0.269 ± 0.018 mg/kg, and 0.239 ± 0.013 mg/kg for 0.5 (continuous), 1, or 2 mg/L (alternate days), respectively. At specific sampling times there were differences between controls and exposure groups; however, no trend toward higher or lower manganese concentrations in muscle could be detected within groups. The mean (±SE) concentration of manganese in liver tissue of controls was...

Ultrastructure of Leukocytes in Acutely Inflamed Dermis and Muscle of Channel Catfish at Different Temperatures

Channel catfish Ictalurus punctatus were acclimated for 35 d at 21°C, 15°C, and 9°C. Fish were injected 3 mm beneath the skin surface with 15 μL of turpentine, and inflamed skin and muscle samples were excised after 48 and 72 h for ultrastructural examination. Neutrophils, lymphocytes, and macrophages were present in the inflamed tissues at all times and temperatures; eosinophils and basophils were not found. Neutrophils were identified by their oval-to-elongate granules with a striated or crystalline core, heavy deposits of glycogen, longitudinal cristae of the mitochondria, and eccentrically located nuclei. Macrophages were distinguished by their numerous pseudopodia, vacuoles, lysosomes, and rough endoplasmic reticulum. Lymphocytes were distinguished by their chromatin-dense nucleus, numerous free ribosomes, and small volume of cytoplasm. Neutrophils were the most common inflammatory cell present, and there were no apparent differences in relative abundance within the inflammatory foci of fish acclimated to the three temperatures. Compared with neutrophils in peripheral blood, neutrophils in inflamed tissues had comparatively rare, swollen mitochondria, and cytoplasmic tubules were not observed. A few neutrophils had vacuoles, phagosomes, or pseudopodia. Lymphocytes in inflamed foci did not contain a Golgi apparatus, granules, vacuoles, or vesicles and had less cytoplasm than did lymphocytes in peripheral blood. Macrophages were the rarest type of inflammatory cell within inflamed areas and differed from peripheral blood monocytes in that macrophages contained numerous lysosomes and vacuoles. No structural differences were associated with particular temperatures for any type of leukocyte.

Mechanisms of temperature acclimation in the channel catfish Ictalurus punctatus: Isozymes and quantitative changes

Enzymes from liver and muscle of channel catfish acclimated to 7, 15 or 25°C were analyzed by starch gel electrophoresis and Western blot analysis to examine the roles of isozymes and quantitative changes in enzyme expression during temperature acclimation. No temperature-induced changes in isozyme expression were found for glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase, lactate dehydrogenase (LDH) or malate dehydrogenase in either muscle or liver. Relative concentration (Western blot scan intensity normalized to protein or DNA content of tissue homogenate) of liver G6PDH was higher for cold-acclimated fish than for warm-acclimated fish. This trend was consistently seen when 7°C-acclimated fish were compared to 15- and 25°C-acclimated fish and in three of four experiments comparing 15- and 25°C-acclimated fish. Differences in G6PDH concentration paralleled differences in G6PDH activity between the temperature groups. Concentration and activity of LDH showed no consistent trend with respect to acclimation temperature. It is concluded that changes in G6PDH activity associated with temperature acclimation are not the result of qualitative isozyme changes but are due to quantitative changes in the enzyme. LDH, which displays little change in activity during temperature acclimation, does not change significantly in concentration during temperature acclimation.

Effect of Waterborne Copper Sulfate Exposure on Copper Content in Liver and Axial Muscle of Channel Catfish

Adult channel catfish Ictalurus punctatus were continuously exposed to waterborne copper sulfate added at concentrations of 1.7, 2.7, or 3.6 mg/L for 10 weeks. Overall, there were no significant differences in the copper content of channel catfish axial muscle during the exposure period, and no significant copper accumulation resulted from exposure. Significantly higher concentrations of copper were present in liver tissue of catfish in all exposed groups 2 weeks after exposure to waterborne copper sulfate began. Extent of copper accumulation in the liver was gender and dose related, with higher concentrations in males at the highest dosage level. Exposures to waterborne copper sulfate were discontinued after 10 weeks, and copper concentrations in liver tissue subsequently returned to levels indistinguishable from controls in 4–8 more weeks. Results indicate that copper sulfate used as a waterborne disease therapeutant for channel catfish does not alter copper content of edible muscle of channel catfish and should not present any hazard to human consumers.

Liquid Chromatographic Determination of Acriflavine and Proflavine Residues in Channel Catfish Muscle

A liquid chromatographic (LC) method was developed for determination of acriflavine (ACR) and proflavine (PRO) residues in channel catfish muscle. Residues were extracted with acidified methanol solution, and extracts were cleaned up with C18 solid-phase extraction columns. Residue concentrations were determined on an LC cyano column, with spectrophotometric detection at 454 nm. Catfish muscle was individually fortified with ACR (purified from commercial product) and PRO at concentrations of 5, 10, 20, 40, and 80 ppb (5 replicates per level). Mean recoveries from fortified muscle at each level ranged from 86 to 95%, with relative standard deviations (RSDs) of 2.5 to 5.7%. The method was applied to incurred residues of ACR and PRO in muscle after waterborne exposure of channel catfish to commercial acriflavine (10 ppm total dye for 4 h). RSDs for incurred residues of ACR and PRO were in the same range as those for fortified muscle. Low residue concentrations (< 1% of exposure water concentration) suggested poor absorption of ACR and PRO in catfish.