Thesis (M.S.)--University of North Carolina Wilmington, 2007. / Includes bibliographical references (Leaves: 53-55)

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Thesis (M.Sc.) -- Memorial University of Newfoundland. 1974. / Typescript. Bibliography : leaves 130-138. Also available online.

Summer flounder, Paralichthys dentatus, culture is becoming increasingly popular in the United States because of high market prices and consumer demand. In addition, flounder is a marine fish species that can tolerate a wide range of salinities, allowing for inland intensive fish culture. Oxytetracycline (OTC) is one of two available FDA-approved antibiotics for use in foodfish in the United States. Oxytetracycline was chosen for these studies because it is excreted primarily unchanged through the urine and the absorption, distribution and elimination of this drug may be influenced by environmental and physiological conditions. Four experiments were conducted to investigate: 1) pharmacokinetic parameters of oxytetracycline (50 mg/kg) following intravascular (IV), intraperitoneal (IP), intramuscular (IM) and per os (PO) administration in summer flounder maintained at 28 ppt salinity and 20°C; 2) pharmacokinetic parameters of OTC (50 mg/kg) following IM and PO administration in summer flounder maintained at three different salinity levels of 0 ppt, 15 ppt and 32 ppt and the physiological adjustments summer flounder make to acclimate to environmental salinity; 3) OTC retention times in muscle tissue from summer flounder maintained at three different salinity levels (0 ppt, 15 ppt, 32 ppt) and treated with a single 50 mg/kg OTC dose via IM and PO administration; and 4) pharmacokinetic parameters of OTC (50 mg/kg) following IM and PO administration in clinically healthy and clinically diseased summer flounder maintained at 28 ppt and 20°C. Oxytetracycline plasma concentrations were determined using high performance liquid chromatography (HPLC) and analyzed using a non-compartmental pharmacokinetic model for all routes of drug administration. Statistical comparisons were not made between the different routes of OTC exposure, but results from experiment one indicated that IV administration of OTC resulted in the largest area under the curve (AUC) value (8147.9 µg·h/ml) and the highest maximum plasma concentration (Cmax) of 1173.2 µg/ml OTC at 5 min post-injection. Intramuscular injections of OTC resulted in prolonged total body elimination half-life (T ½) of 301.3 h and high fish-to-fish variability (0.6). Per os administration resulted in low Cmax (0.2 µg/ml OTC) and poor systemic bioavailability (0.2 %). Results from experiment two demonstrated that when OTC is administered IM AUC estimates are significantly (p<0.05) lower in summer flounder held at 0 ppt (1684.8 µg·h/ml) than fish maintained at 15 ppt or 32 ppt salinity (2067.8 µg·h/ml and 2241.3 µg·h/ml, respectively). Although not significantly different from other salinity treatments, time to maximum plasma concentration (Tmax) was longer in fish held at 15 ppt and 32 ppt (312 h and 168 h, respectively) compared to cohorts in freshwater (0.5 h) and Cmax values were higher in animals held at 15 ppt and 32 ppt (8.4 µg/ml OTC and 9.2 µg/ml OTC, respectively) than freshwater fish (4.9 µg/ml OTC) when OTC was administered via IM injection. No significant differences were detected in any of the pharmacokinetic parameters following PO dosing of OTC, however, the AUC estimates were lower in the 32 ppt acclimated fish (127.7 µg·h/ml) than in the 0 ppt or 15 ppt acclimated fish (190.2 µg·h/ml and 180.7 µg·h/ml, respectively). In addition, the T ½ was longer in the higher salinity groups (278.1 h and 266.0 h, respectively) than in the freshwater fish group (256.9 h). Physiological adjustments made by summer flounder including plasma and urine osmolality, urine flow rate and urine character, gill chloride cell size and density, and Na+ - K+ ATPase activity demonstrated trends that suggested physiological differences among the salinity groups. Plasma and urine osmolalities were typically significantly (p<0.05) higher in fish maintained at 32 ppt salinity than at the lower salinity treatments. In addition, urine flow rates were generally significantly (p<0.05) greater in freshwater adapted fish (0.13 - 0.21 ml of urine/kg/hour) in comparison to fish in the salinity treatments of 15 ppt and 32 ppt (0.06 - 0.12 ml of urine/kg/hour and 0.09 – 0.11 ml of urine/kg/hour, respectively). Changes in gill chloride cell size and density and enzyme activity of Na+ - K+ ATPase revealed no significant differences between the salinity treatments but summer flounder in saltwater had numerically larger and more chloride cells than summer flounder in freshwater, but enzyme activity was greater in freshwater acclimated summer flounder compared to fish in seawater. Experiment three results revealed similar OTC muscle tissue pharmacokinetic parameters in summer flounder following IM injection. However, there were significant differences (p<0.05) in the AUC parameters of the plasma and muscle OTC concentrations between fish maintained at different salinities following IM OTC treatment. These effects may be the result of a "depot" effect in the muscle tissue or may be related to the reduced solubility of OTC in the muscle tissue of marine fish. A single PO dose administration of OTC at 50 mg/kg did not result in plasma or tissue concentrations higher than the FDA tissue tolerance limit of 2 ppm. Results of the fourth experiment demonstrated that following IM OTC administration healthy fish had significantly (p<0.05) higher AUC (4700.6 µg·h/ml) values than diseased cohorts (2576.2 µg·h/ml). Maximum plasma concentrations were also higher in the healthy fish than in the diseased fish, although values were not significantly different (23.4 µg OTC/ml and 20.2 µg OTC/ml, respectively for healthy and diseased fish). Additionally, in diseased fish, the mean resident time (MRT) (293.7 h) and T ½ (203.5 h) parameters were longer compared to parameters in healthy fish (253.2 h and 175.4 h, respectively), although values were not significantly different. No significant differences were detected in any of the pharmacokinetic parameters following PO OTC administration, however, healthy fish achieved higher maximum plasma OTC concentrations (1.0 µg OTC/ml) than diseased fish (0.7 µg OTC/ml). Fish-to-fish variation was greater in diseased animals than in healthy regardless of route of drug administration. The results of these experiments indicated that OTC pharmacokinetic parameters are influenced by route of drug administration, environmental salinity and fish health status. These factors must be considered by veterinarians and governmental regulators when developing treatment regimens for summer flounder. / Ph. D.

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Timothy E. Targett, College of Marine and Earth Studies. Includes bibliographical references.

Southern flounder (Paralichthys lethostigma) populations have declined over the last 25-30 years throughout its range. With this rapid decline, the sustainability of the southern flounder fishery and population viability of this commercially and recreationally important fish has come into question. Previous research conducted in the Northern Gulf of Mexico and North Carolina, has shown that southern flounder often reside in freshwater for significant periods of time during the juvenile life history stage. Juvenile southern flounder have been collected at salinities below 10 in Aransas Bay (TX), suggesting that Texas southern flounder might also have critical periods of freshwater residency. However, the presence of a low salinity residency period in southern flounder in Texas has not previously been tested. Patterns of low salinity residence were determined using otolith microchemistry, using Ba/Ca ratios to determine movements across salinity boundaries. Water samples were collected from the major tributaries to the area in order to establish the Ba/Ca freshwater signature. Otolith Ba/Ca values revealed a high degree of variability in habitat use patterns among individuals. The mean percent time that an individual spent in low salinity habitat was skewed toward the lower end (15%) but a significant proportion of the individuals sampled (59%) used low salinity habitat at some point during their life. The remaining individuals (49%) never entered low salinity habitat. This work indicates that there are two distinctly different groups of habitat use patterns in the population. This work demonstrates that southern flounder in Texas exhibit different habitat use patterns from their congeners in North Carolina and the Northern Gulf of Mexico and can help contribute to the spatial management of the southern flounder population on the Gulf Coast of Texas. / text

The goal of this research was to examine the role of the novel membrane progestin receptor alpha (mPR[alpha]) in the stimulation of sperm hypermotility by the progestin 17,20[beta],21-trihydroxy-4-pregnen-3-one (20[beta]-S) in two teleosts; the Atlantic croaker (Micropogonias undulatus) and the southern flounder (Platylicthys lethigstomata). In croaker, the expression, localization and hormonal regulation of mPR[alpha] in testis and sperm were investigated, as were the intracellular signaling pathways activated by 20[beta]-S and mPR[alpha] to induce croaker sperm hypermotility. In flounder, stimulation of sperm hypermotility by 20[beta]-S and binding of this steroid to flounder sperm membranes were examined. Finally, expression of mPR[alpha] was investigated in flounder testes and the expression and localization of this receptor in flounder testis and sperm was examined. In croaker sperm, mPR[alpha] was expressed on the plasma membrane and localized to the midpiece. Expression of mPR[alpha] was also shown to be associated with high sperm motility and regulated by gonadotropin. The signaling pathways activated by 20[beta]-S in croaker sperm were shown to involve activation of olfactory G-proteins (Golf). Subsequent activation of membrane adenylyl cyclases was also demonstrated and shown to be necessary for 20[beta]-S-stimulated cAMP production and 20[beta]-S-induction of sperm hypermotility. Furthermore, co-immunoprecipitation studies show mPR[alpha] and Golf physically associate with one another, establishing mPR[alpha] as the mediator of 20[beta]-S actions in croaker sperm. Finally, evidence was obtained for progestin-stimulation of sperm hypermotility and the presence of mPR[alpha] on sperm membranes in another marine teleost species belonging to a different family, the southern flounder. In addition, mPR[alpha] was shown to be expressed on flounder sperm membranes and also localized to the sperm midpiece. Results from the following studies support the hypothesis that mPR[alpha] is the mediator of 20[beta]S-stimulated sperm hypermotility in croaker and is a likely intermediary in southern flounder. Furthermore, these data provide a plausible mechanism by which 20[beta]-S and mPR[alpha] stimulate croaker sperm hypermotility. In addition, these results provide the first evidence of hormonal activation of Golf proteins for any species. Finally, mPR[alpha]-mediated mechanisms to increase sperm motility are suggested to be evolutionarily conserved in teleosts since they also likely exist in a non-sciaenid species, the southern flounder.

Thesis (M.Sc. )--Memorial University of Newfoundland, 1997. / Bibliography: leaves 77-80.

Thesis (M.Sc.)--College of William and Mary. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.