Gastrointestinal torsion in a channel catfish (Ictalurus punctatus)

A case of gastrointestinal torsion with dilatation in a farm-raised channel catfish (Ictalurus punctatus) was examined at the Thad Cochran National Warmwater Aquaculture Center (Stoneville, Mississippi, USA). The affected fish was a gravid female broodfish, which displayed pale gills and a markedly distended abdomen. Internal examination revealed that the gastrointestinal tract and ovaries were rotated around each other four times in a counterclockwise direction as viewed in right lateral recumbency. The catfish had a markedly distended gastrointestinal tract, pale liver, hypoplastic spleen, hypoplastic swim bladder, and high volume of ascitic fluid. Blood analysis indicated multiple abnormalities, including severe anemia and metabolic acidosis. The etiology of the torsion was uncertain; however, the presence of a hypoplastic swim bladder most likely allowed for increased movement of the gastrointestinal tract and ovaries. When examining cases of abdominal distention in fish, gastrointestinal torsion can be considered among the differential diagnoses.     

Ultrastructure of the liver in channel catfish Ictalurus punctatus (Rafinesque)

Livers of 38 channel catfish were studied by light and electron microscopy and the morphology of hepatocytes, endothelial cells, Kupffer cells, fat-storing cells, macrophages, exocrine pancreatic cells, and epithelium of bile pre-ductules and ducts was described, Hepatocytes contained large peri-canalicular bodies which showed acid hydrolase activity. A comparison between catfish liver and that of other teleosts was made. The applicability of the findings to pathobiological studies of teleost liver is described.     

Immune hypersensitivity in the channel catfish, Ictalurus punctatus (Rafinesque)

Channel catfish, Ictalurus punctatus , exhibited passive cutaneous anaphylaxis (PCA) when sensitized with Flexibacter columnaris antiserum produced in channel catfish (the first record of PCA in any fish), but not when sensitized with homologous antiserum against channel catfish virus. Channel catfish did not give delayed skin hypersensitivity responses after immunization with either channel catfish virus or F. columnaris .     

Cortisol-induced hematologic and immunologic changes in channel catfish (Ictalurus punctatus)

1. Intravenous injections of physiologic doses of cortisol resulted in both hematologic and immunologic changes in channel catfish peripheral blood leucocytes. These changes mimicked those seen when catfish were acutely stressed by handling and transport. 2. Eighteen hours after the administration of cortisol, decreases in the number of circulating lymphocytes and concomitant increases in the number of circulating neutrophils were observed, i.e. to the same levels seen previously in stressed fish. 3. Functional analysis of peripheral blood leucocytes from cortisol-injected fish indicated that the remaining lymphocytes were no longer capable of responding to mitogenic stimuli. 4. This suppression of mitogenic stimuli was not seen when peripheral blood leucocytes were cultured in vitro with physiologic doses of cortisol. 5. This latter observation suggests that the cortisol alone was probably not directly responsible for the loss of responsiveness but possibly acted in vivo as an initiator of other events that eventually resulted in the observed immunosuppression.     

Comparative study of mannose-binding C-type lectin isolated from channel catfish (Ictalurus punctatus) and blue catfish (Ictalurus furcatus)

Mannose-binding C-type lectin (MBL) was isolated from channel catfish (Ictalurus punctatus) NWAC 102 and 103 strains, blue catfish (Ictalurus furcatus) D+B and Rio Grande strains, hybrid catfish (channel catfish female NWAC 103 x blue catfish male D+B) sera, and purified by affinity chromatography from channel catfish Norris strain serum. Reduction of purified channel catfish MBL with 2-ME yielded a single band of 62 kDa by SDS-PAGE and Western blot analysis using guinea pig anti-MBL IgG as primary antibody. Channel catfish NWAC 102 strain, channel catfish NWAC 103 strain and hybrid catfish sera had molecular masses of 63 kDa for MBL. Blue catfish (D+B strain) serum MBL had a molecular mass of 66 kDa. Rio Grande blue catfish serum MBL had a molecular mass of 65 kDa. Amino acid composition analysis (mol%) of the affinity-purified channel catfish MBL found a high content of serine present. Functional binding studies of channel catfish and blue catfish MBLs binding to Edwardsiella ictaluri were done using a dot-immunoblot ELISA method. A dot-immunoblot ELISA binding assay was done to compare nine different strains and species of channel catfish and blue catfish for their levels of serum MBL. Blue catfish had higher levels of MBL than did the various strains of channel catfish tested. MBL could be used as a genetic marker for selection of disease resistance in the different strains of catfish used in aquaculture. This study describes the presence of serum MBL in catfish and evidence for a C-type lectin complement pathway of innate immunity.     

Novel heme-binding component in the serum of the channel catfish (Ictalurus punctatus)

The serum of the channel catfish (Ictalurus punctatus) was examined for heme- and hemoglobin-binding proteins. Electrophoretic mobility retardation assays failed to detect a hemoglobin-binding material similar to mammalian haptoglobin; however, a heme-binding component (not previously described) was identified in catfish seru. The heme-binding component was purified by gel filtration chromatography; electrophoretic analyses suggested it to be composed of two polypeptide subunits of molecular masses about 115 and 98 kDa. This composition is inconsistent with hemopexin, the known heme-binding serum protein of mammals. Although it was not fully saturated with heme, the catfish component contained detectable heme in normal sera. When complexed by the binding material, heme was used as an iron source by isolates of the bacterial Gram-negative genusAeromonas; the capacity of other bacteria to use the complex was not tested. The physiological function of the catfish heme-binding serum protein is presently not clear.     

Definition of the USDA103 strain of channel catfish (Ictalurus punctatus)

Although there are differences in performance between genetic groups of channel catfish, identification and management of these groups is difficult because catfish strains look alike and individuals cannot be tagged efficiently. Thus, US catfish producers have not been able to objectively identify fish from different strains or populations, and it has been difficult for them to maintain the genetic purity of populations on the farm. We have developed a multiplexed microsatellite genotyping system to define catfish populations based on allelic frequency and exclusion. A commercial catfish genotype database was developed using catfish samples collected from 24 processing plants in the four main US catfish-producing states. The utility of the system was tested by the molecular characterization of the USDA103 research strain. Using eight microsatellite loci, the probability of falsely classifying an individual non-USDA103 catfish as a USDA103 was 0.0065. From a sample of 50 fish from a putative USDA103 pond, the probability of falsely including two non-USDA103 fish was 1 x 10(-105), and the conservative probability of falsely excluding two USDA103 fish was 1 x 10(-6). This genotyping system provides channel catfish producers with an objective mechanism for identification and management of genetically selected fish.     

Structure and expression of transferrin gene of channel catfish,Ictalurus punctatus

Transferrin is important in iron metabolism and has been reported to be involved in disease defence responses after bacterial infection. In this study, we identified, sequenced, and characterized the transferrin gene from channel catfish, Ictalurus punctatus. The catfish transferrin gene was similar to those of other vertebrate species with 17 exons and 16 introns. Sequence analysis indicated the presence of the two duplicated lobes, each containing two sub-domains separated by a cleft harboring the iron-binding site, suggesting their structural conservation. The channel catfish transferrin cDNA encodes 679 amino acids with 42–56% similarity to known transferrin genes from various species. Southern blot analysis suggested the presence of two copies of the transferrin gene in the catfish genome, perhaps arranged in a tandem fashion. The catfish transferrin gene was mapped to a catfish BAC-based physical map. The catfish transferrin gene was highly expressed in the liver, but expression was low in most other tested tissues. Transferrin expression was significantly up-regulated after infection with Edwardsiella ictaluri, the causative agent of enteric septicemia of catfish. Such induction was also found with co-injection of iron-dextran and E. ictaluri, while transferrin expression was not significantly induced with the injection of iron-dextran alone.     

Cloning and characterisation of a channel catfish (Ictalurus punctatus) Mx gene

A 2.5 kb full-length cDNA clone of a channel catfish (Ictalurus punctatus) Mx gene was obtained using RACE (rapid amplification of cDNA ends) polymerase chain reaction (PCR) from RNA extracted from the liver of poly I:C stimulated channel catfish. The gene consists of an open reading frame of 1905 nucleotides encoding a 635 amino acid protein. The predicted protein is 72.5 kDa and contains the dynamin family signature, a tripartite GTP binding motif and a leucine zipper, characteristic of all known Mx proteins. The catfish Mx protein exhibited 79% identity with perch Mx and between 71% and 74% identity with the three Atlantic salmon and the three rainbow trout Mx proteins. Mx mRNA was constitutively expressed in channel catfish ovary (CCO) cells, but in higher quantities in response to poly I:C treatment. Mx was induced in channel catfish following injection with channel catfish virus (CCV) and poly I:C.     

Genetic and virulence characterization of Flavobacterium columnare from channel catfish (Ictalurus punctatus)

Aim: To develop a method for conducting pulsed-field gel electrophoresis (PFGE) on Flavobacterium columnare, to use PFGE to characterize F. columnare channel catfish isolates, and to determine whether variation in pathogenic potential exists in F. columnare isolates from channel catfish. Methods and Results: On the basis of PFGE-derived profiles, similarity dendrograms constructed for more than 30 F. columnare isolates showed two major genetic groups with more than 60% similarity. Channel catfish fingerlings challenged with PFGE group A isolates by bath immersion had significantly higher average mortalities (>60%) than fish challenged with PFGE group B isolates (<9%). However, abrasion and skin mucus removal made channel catfish fingerlings susceptible to disease caused by group B isolates following immersion exposure. Conclusion: Our results suggest that two genetic divisions of F. columnare channel catfish isolates exist, and that isolates in PFGE group A isolates tend to be more pathogenic to immunocompetent channel catfish fingerlings than PFGE group B isolates. Significance and Impact of the Study: PFGE is a potentially useful tool for determining whether F. columnare isolates are more likely to be primary or secondary pathogens. Pathogenesis research for columnaris disease in catfish should focus on pathogenic isolates from PFGE group A.     

Organization of the telencephalon in the channel catfish,Ictalurus punctatus

The cytoarchitectonics of the telencephalon of the channel catfish, Ictalurus punctatus, are described as a basis for experimental analysis of telencephalic afferents and efferents. The olfactory bulb comprises: (1) an outer layer of olfactory nerve fibers, (2) a glomerular layer, (3) an external cell layer, (4) an inner fiber layer, and (5) an internal cell layer. The telencephalic hemispheres comprise the areas ventralis and dorsalis telencephali. The area ventralis consists of: (1) a precommissural, periventricular zone including nucleus 'nother (Vn), the ventral nucleus (Vv), and the dorsal nucleus (Vd); (2) a precommissural, migrated zone of central (Vc) and lateral (VI) nuclei; (3) a supracommissural nucleus (Vs); (4) a caudal commissural zone of postcommissural (Vp) and intermediate (Vi) nuclei; and (5) a preoptic area (PP). The area dorsalis comprises: (1) medial (DM), (2) dorsal (Dd), (3) lateral [DL, containing dorsal (DLd), ventral (DLv), and posterior (DLp) regions], (4) posterior (DP), and (5) central (DC-1, -2, -3) areas. Nucleus taeniae (NT) is transitional between areas dorsalis and ventralis.     

Histophathology and electron microscopy of channel catfish virus in infected channel catfish,Ictalurus punctatus (Rafinesque)*

A histologic and electron microscopic study was made on selected organs from channel catfish Ictalurus punctatus (Rafinesque) fingerlings that were experimentally infected with channel catfish virus (CCV). Histopathology was characterized by necrosis and haemorrhage in kidney and liver, and haemorrhage in the spleen and gastrointestinal tract. Virus replication occurred in nuclei of cells in the kidney, liver and spleen. Intranuclear inclusion bodies consisting of geometric crystalline arrays and lamellar structures were associated with virus replication.     

Afferent connections of the optic tectum in channel catfish Ictalurus punctatus

Summary Horseradish peroxidase was injected unilaterally into the optic tectum of the channel catfish, Ictalurus punctatus. The sources of tectal afferents were thereby revealed by retrogradely labeled neurons in various brain centers. Retrogradely labeled cells were seen in both the ipsilateral and contralateral telencephalon. The superficial pretectal area was labeled on both sides of the brain. Ipsilateral projections were also observed coming from the entopeduncular nucleus. Both the anterior thalamic nucleus and the ventro-medial thalamic nucleus projected to the ipsilateral optic tectum. Cells in the ipsilateral nucleus of the posterior commissure were seen to project to the tectum. Labeled fibers were visualized in the lateral geniculate nucleus ipsilateral to the injected tectum, however, no labeled cell bodies were observed. Therefore, tectal cells project to the lateral geniculate nucleus, but this projection is not reciprocal. No labeled cells were found in the cerebellum. Labeled cells occurred in both the ipsilateral and contralateral medial reticular formation; they were also observed in the ipsilateral nucleus isthmi. A projection was seen coming from the dorsal funicular nucleus. Furthermore, labeled cells were shown in the inferior raphe nucleus.Abbreviations AP Area pretectalis - C Cerebellum - DPTN Dorsal posterior tegmental nucleus - H Habenula - IRF Inferior reticular formation - LI Inferior lobe - LGN Lateral geniculate nucleus - LR Lateral recess - MB Mammillary body - MRF Medial reticular formation - MZ Medial zone of the telencephalon - NC Nucleus corticalis - NDL-M Nucleus opticus dorsolateralis/pars medialis - NI Nucleus isthmi - NPC Nucleus of the posterior commissure - OPT Optic tectum - OT Optic tract - PC Posterior commissure - PN Pineal organ - PrOP Preoptic nucleus - PT Pretectum - TBt Tectobulbar tract - TEL Telencephalon - TL Torus longitudinalis - TS Torus semicircularis - VC Valvula cerebelli - VLTN Ventrolateral thalamic nucleus - VMTN Ventromedial thalamic nucleus     

A high-affinity zinc-binding plasma protein in channel catfish (Ictalurus punctatus).

1. Channel catfish (Ictalurus punctatus) have a remarkably high concentration of zinc (Zn) in their blood serum, about 20 micrograms/ml. However, compared to mammals, the concentrations of Zn in their tissues are not remarkable. The serum Zn is dialyzable against a solution containing 1 mM EDTA. 2. Following separation of serum proteins by gel-filtration most of the Zn was recovered in a fraction with the same peak volume of elution for the Zn and protein concentrations and having a molecular weight similar to bovine serum albumin. 3. Binding of Zn to such sites was not changed by Cu2+, Cd2+, Ca2+, or La3+. N-ethylemaleimide (NEM) appeared to decrease binding slightly. 4. Equilibrium dialysis with a Scatchard plot analysis of these data suggested that a single set of binding sites was present on the protein(s) with KD of 2 x 10(-5) M. There were binding sites for 35 x 10(-8) M Zn/mg protein. 5. Parallel equilibrium dialysis measurements using human, rabbit and chicken albumins indicated that the catfish serum protein(s) had a much higher affinity and binding capacity for Zn than the albumins in these species. 6. The catfish Zn serum-binding protein may be an albumin. The possible physiological significance of such a serum protein in freshwater fish is discussed.