Profiles of plasma estradiol and testosterone concentrations, cathepsin D, L, and B activities, and quantitative and qualitative protein content were developed and evaluated in four commercial strains of channel catfish, Gold Kist (2), Thompson and NWAC-103 for one year (age 2 to age 3). Great variation between individuals of the same strain precluded the identification of any significant, strain-specific differences for the variables under investigation. When variables from fish of all strains were collectively evaluated over time, both estradiol and testosterone concentrations significantly increased in July and then later from February to April. The increase in hormone concentration was accompanied by oocyte growth and increases in proteolytic activity of cathepsins D, L, and B, supporting the role of estradiol in regulating vitellogenesis. Vitellogenin was enzymatically broken down into smaller protein units by cathepsins L, D, and B that were separately predominant at different stages of oocyte development. During oocyte development, there were sequential relationships among hormone concentration, cathepsin activity, protein content, and predominant oocyte proteins. This observation was associated with high levels of activity of cathepsin L in February, suggesting an important role in protein degradation during that time, while high activity of cathepsin B occurred, stimulating during November to January. Cathepsin B is more important in oogenesis or early vitellogenesis, and cathepsin L assumes a principal role during middle vitellogenesis. Twenty hours subsequent to the injection of fish with either carp pituitary hormone or luteinizing hormone releasing hormone, increases in the concentration of plasma estradiol and testosterone, activities of cathepsins L, D, and B, egg size, and egg protein content occurred, stimulating the process of oocyte maturation. The percentages of spawning obtained were 18.8% of LHRH injected fish, 12.4% of CPE injected fish, 9.4% of fish not injected, and 0% of saline injected fish. Injection of females with LHRH can potentially serve as a tool to increase spawning success in appropriate commercial settings, particularly for improving three year old catfish spawning success early in the spawning season. Low estradiol levels in all three-year-old fish suggest that insufficient stimulation of vitellogenin production by estradiol may underlie the lack of vitellogenin incorporation into developing oocytes. In the present study, the measurement of the activities of the cathepsins and their relationships to other parameters were evaluated for the first time. This is also the first study to report plasma estradiol and testosterone concentrations, protein content, and egg size in 2 to 3-year old channel catfish. All of the parameters collectively evaluated may serve to assist in the selection of the best 2- year old channel catfish female broodstock, and to determine the optimal timing of treatments of hormone injection to increase reproductive performance.

Proliferative gill disease (PGD) caused by the myxozoan parasite Henneguya ictaluri is one of the most devastating parasitic infections in channel catfish aquaculture. Currently, there is no effective treatment for H. ictaluri and the unpredictable outbreaks can result in 100% mortality. Management strategies have been developed to prevent losses in newly stocked fingerlings by evaluating the PGD status of a pond prior to stocking, which is difficult since resident fish may not show clinical signs even when actinospore levels are lethal to naive fish. Current diagnostic methods are limited to the identification of an active infection and methods of predicting potential outbreaks have several limitations. The PGD status of a pond to be stocked can be determined using sentinel fish exposures which are labor intensive and require a source of parasite free fish. These limitations necessitated the development of more rapid and efficient means of determining actinospore concentrations to determine the risk of losing fish prior to stocking. The development of a quantitative real-time polymerase chain reaction (QPCR) assay provided a more rapid, sensitive and quantitative method of diagnosing active infections and also provides a means to predict potential PD outbreaks and determine the PGD status of a pond prior to stocking. Another approach in the control of this parasite is the identification of a less susceptible culturable species or to identify traits that could be targeted in a selective breeding program. Challenge studies have shown that the closely related blue catfish (Ictalurus furcatus) does not exhibit as severe an inflammatory response to H. ictaluri and mortalities are significantly lower than in channel catfish. Comparisons of PGD severity and H. ictaluri infection in channel catfish, blue catfish and channel x blue catfish backcross hybrids by gross examination, histopathology and the newly developed H. ictaluri real-time PCR (QPCR) assay supported previous research suggesting the life cycle of the parasite can not be completed as efficiently through the blue catfish host. This dissertation describes the development and validation of a QPCR assay to detect H. ictaluri in both fish tissues and environmental samples and the application of this assay in both research and production settings.

Cannabinoid (CB) receptors have been found in most vertebrates that have been studied. The location of various CB receptors in the body and brain are known, but their physiological functions are not fully understood. The effects CBs have on the cardiovascular system have been of growing interest in recent years. Increasing reports from emergency departments and law enforcement agencies detail acute cardiovascular and psychological effects from synthetic CB intoxication, such as JWH-018. This major health concern is substantiated by governmental agencies like the CDC and NIDA. This pilot study investigates the acute toxic effects of the synthetic CB, JWH-018, on the cardiovascular and neuroendocrine systems in Ictalurus punctatus (channel catfish). Research in organisms besides the traditional mammal models can provide new insights into CB function and physiology. Ictalurus punctatus lend multiple benefits as a model organism that permits researchers to investigate in vivo effects of both cardiovascular and neuroendocrine systems without much influence from traditional sampling methods, and further more provide ample size and tissue to perform specific cardiovascular experiments. Multiple methods were used to assess cardiovascular function and sympathetic nervous system activation. Two different doses, low (500 µg/kg) and high 1,500 µg/kg, of JWH-018 were evaluated in the study. Delivery of JWH-018, via dorsal aorta cannulation, was administered to channel catfish in order to measure cardiovascular functions and sample blood. Plasma levels of the hypothalamus-pituitary-adrenal/interrenal (HPA/I) biomarkers; ACTH, cortisol, epinephrine, and norepinephrine, were measured using ELISAs. Myocardial and neural tissue was collected after the exposures for rt-PCR analysis on β2 adrenergic and glucocorticoid receptor density change. Acute exposure of JWH-018 in undisturbed channel catfish yielded several findings: (1) High dose of JWH-018 was responsible for cardio depressor effects in catfish with a tendency to produce tachycardia, (2) rt-PCR results showed a 2.7 fold increase of glucocorticoid receptor mRNA density in catfish cardiomyocytes when exposed to each dose of JWH-018, (3) Catfish plasma ACTH levels were increased with high doses of JWH-018, while plasma cortisol was increased by low doses. Channel catfish is an excellent animal model to examine the effects of synthetic cannabinoids and cardiovascular function. Acute exposures to high levels of JWH-018 appear to produce cardiovascular dysfunction providing evidence that substantiates emergency department reports, in addition yields novel information about the interaction of CBs exposure and the increase of glucocorticoid receptors levels on cardiomyocytes. The channel catfish is a new animal model that can aid in further investigations of CB exposure and multiple physiological functions for health and toxicology studies. With relatively easy adjustments from this pilot study, the effects on CBs can be monitored on Ictalurus punctatus with confident results concerning human health.

Call number: LD2668 .T4 1986 N445 / Master of Science / Grain Science and Industry

Thesis (Ph.D.) -- Mississippi State University. Department of Wildlife and Fisheries. / Title from title screen. Includes bibliographical references.

Channel Catfish (Ictalurus punctatus, Rafinesque, 1818) leukocyte immune-type receptors (IpLITRs) are a family of proteins sharing structural and phylogenetic relationships with mammalian immune receptors. Based on their predicted signalling potential and ligand-binding properties, IpLITRs may be important in the control of immune cell effector responses in fish. The main objectives of this thesis were to determine how stimulatory IpLITRs activate cells and to develop assays for the screening of IpLITR ligands. Using cellular transfections, coimmunoprecipitation, and flow cytometry, I determined that stimulatory IpLITRs associate with specific adaptor molecules, which is required for their surface expression and signalling ability. These adaptors assemble with IpLITRs via their charged transmembrane regions and contain cytoplasmic tails encoding tyrosines that may initiate kinase pathways leading to immune cell activation. This study represents the first step towards elucidating how IpLITRs turn on immune cells. Combined with the development of assays to identify IpLITR ligands, my work sets the stage for further investigations into the functional characterization of these receptors. / Physiology, Cell and Developmental Biology

Thesis (Ph.D.)--Mississippi State University. in Veterinary Medical Sciences in the Department of Basic Sciences. / Title from title screen. Includes bibliographical references.

No description available.

No description available.

This study describes the population characteristics of channel catfish (Ictalurus punctatus) and flathead catfish (Pylodictis olivaris) in the lower 200 miles of the Wabash River in 1998. Densities of channel and flathead catfish did not differ over the study reach for either species. Electrofishing captured twice as many channel as flathead catfish, and hoop nets captured twice as many flatheads as channel catfish. Growth rates of channel catfish were fast as compared to documented growth in other rivers in the United States, with ages ranging from 1-8. Flathead catfish growth was average when compared to that reported in other United States rivers with ages ranging from 0-7. Length-frequency analysis for both species revealed the populations were comprised of small individuals with mortality higher than expected in older fish. This study will aid in the management of the Wabash River, as historic data are limited. / Department of Biology