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.

Assignment of immune-related genes to the channel catfish, Ictalurus punctatus, genetic map.

Eighteen new genes, adenosine A1 receptor (ADORA1), complement component 4-beta (C4b), complement component 8-beta (C8b), chemokine ligand 19 (CCL19), chemokine ligand 21 (CCL21), chemokine ligand 25 (CCL25), chemokine receptor 2 (CCR2), chemokine receptor 5 (CCR5), chemokine receptor 4 (CCR4), chemokine receptor 7 (CCR7), chemokine receptor 9 (CCR9), interleukin 1-beta (IL1B), integrin II-beta (ITGB2), novel immune type receptor 2 (NITR2), novel immune type receptor 4 (NITR4), natural killer cell lysin (NKLYSIN), nucleotide excision repair (RAD23B) and tumour necrosis factor-alpha (TNF), were assigned to the channel catfish (Ictalurus punctatus) genetic linkage map. Polymorphic microsatellite markers were developed for NITR2, NITR4 and RAD23B from short-tandem repeats in the available sequence. Polymorphic microsatellite markers were developed for the remaining 15 genes by short-tandem repeat-anchored primer sequencing of catfish bacterial artificial chromosomes. Two gene clusters (MYOG-NRAMP-ADORA1) and (CCR4-CCR2-CCR5) displayed conservation of synteny between catfish and mammals. Assignment of 18 new genes to the catfish linkage map will further advance integration of genetic and physical maps and comparative mapping between channel catfish and map rich species.

Use of porcine renal capsule matrix as a full-thickness dermal wound-healing material in rats.

OBJECTIVE: To compare the utility of porcine renal capsule matrix (RCM) with porcine small intestinal mucosa (SIS) in a rat full-thickness skin wound model. METHOD: Groups of rats had surgically-created wounds filled with either SIS or RCM. On each rat a contralateral wound was left unfilled (RCM-U or SIS-U). Wound diameter was measured 3, 7, 12, 17, 26 and 30 days after creation. Wound sites sampled 3, 7, 14, 28, 42 and 56 days after wound creation were numerically graded for degree of histologic change and for collagen content, based on intensity of trichrome staining. RESULTS: Wounds in all groups rapidly contracted to less than 50% of the original diameter within 12 days. There were no differences in wound diameter between RCM- and SIS-treated wounds at any time point, but these wounds had significantly greater (p < 0.001) diameters than their unfilled counterparts on days 7, 12 and 17. There were no differences in histologic scores or trichrome-staining scores between RCM- and SIS-treated wounds and their unfilled counterparts at any time point, except for a greater (p < 0.05) histologic score in SIS-treated wounds compared with unfilled controls on day 14. In both treatment groups an acute inflammatory response at the wound site was soon replaced by an influx of macrophages and fibroblasts. CONCLUSION: The results show that RCM is equivalent to SIS for the treatment of full-thickness wounds and that these materials may enhance wound healing in terms of wound-tissue collagenisation and maturation. These materials therefore merit further study in other wound-care models.

A microsatellite-based genetic linkage map for channel catfish, Ictalurus punctatus.

Microsatellite loci were identified in channel catfish gene sequences or random clones from a small insert genomic DNA library. Outbred populations of channel catfish contained an average of eight alleles per locus and an average heterozygosity of 0.70. A genetic linkage map of the channel catfish genome (N = 29) was constructed from two reference families. A total of 293 microsatellite loci were polymorphic in one or both families, with an average of 171 informative meioses per locus. Nineteen type I loci, 243 type II loci, and one EST were placed in 32 multipoint linkage groups covering 1958 cM. Nine more type II loci were contained in three two-point linkage groups covering 24.5 cM. Twenty-two type II loci remained unlinked. Multipoint linkage groups ranged in size from 11.9 to 110.5 cM with an average intermarker distance of 8.7 cM. Seven microsatellite loci were closely linked with the sex-determining locus. The microsatellite loci and genetic linkage map will increase the efficiency of selective breeding programs for channel catfish.

Survivability and immune responses after challenge with Edwardsiella ictaluri in susceptible and resistant families of channel catfish, Ictalurus punctatus.

Diseases in catfish farming are prevalent and costly, particularly the bacterial disease Enteric Septicemia of Catfish. Considerable research has focused on different aspects of this disease, including the biology of the causative agent, Edwardsiella ictaluri. However, no satisfactory treatment or preventive has resulted from these efforts. One solution is to increase the natural disease resistance of the fish through genetic selection. Recent research has demonstrated that genetic factors influence resistance to infection in mammals as well as fish. Selective breeding for disease resistance in channel catfish is ongoing, however differences in defence mechanisms among E. ictaluri challenged strains and families are only now being investigated. Antigen-specific as well as non-specific immune responses of full-sib families of channel catfish to laboratory challenge with E. ictaluri have been investigated. Both resistant and sensitive families produce a humoral response as specific antibody, but there were no differences found in the level of specific antibody produced. The sensitive family produced a slightly higher percentage of B lymphocytes in mononuclear cell preparations from peripheral blood, while the resistant family had a higher percentage of T lymphocytes in those preparations. The most significant observation was that the resistant family produced more macrophage aggregations in the spleen and posterior kidney throughout the infection than the sensitive family. Neither family produced stress-associated amounts of cortisol.

Isolation, culture and characterization of a primary fibroblast cell line from channel catfish.

A primary cell line (designated as CCf) derived from caudal fin tissue of channel catfish, Ictalurus punctatus, was developed using explant techniques. The cell line grew fastest in media supplied with FBS and channel catfish serum. The duplication time of the cell line under optimal conditions was ∼56 h at a plating density of 1.1 × 10(5) cells/ml. The cell line has been propagated continuously for 25 passages (1:4 dilution per passage), cryopreserved, and recovered successfully at different passages. The cultured cells had fibroblastic morphology, and synthesized fibronectin and Type I and III collagens in the cytoplasm. The cell line maintained the normal diploid chromosome number (58) of channel catfish throughout the experiment. Nucleolus organizer regions were located on the short arms of a pair of medium-sized submetacentrics, which is typical for channel catfish. This study provides a method for acquiring a cell line from juvenile catfish without sacrifice, and is especially useful for early screening of valuable fishes.