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Physiological & Cellular Mechanisms Of Ammonia Tolerance In The Goldfish (Carassius Auratus), Sanya Sidhu

Theses and Dissertations (Comprehensive)

Ammonia may increase in the blood and tissues of fishes following feeding or exposure to high concentrations of environmental ammonia arising from the degradation of organic matter in aquatic environments, sewage effluent, and run-off from landfills. Ammonia may be detoxified using the enzyme glutamine synthetase (GS), which catalyzes the conversion of ammonia to glutamine. It has been suggested, however that build-ups of glutamine within the astrocytes of the brain can cause brain swelling by increasing intracellular osmolarity and water uptake by the cells. Using in vivo and in vitro approaches, the goal of this thesis was to determine if: (i) …

In Vitro Study Of The Microsporidian Parasite Loma Morhua, Using Cod-Derived Cells And Novel Culture Techniques, Michael J. Macleod

Theses and Dissertations (Comprehensive)

The cod populations of the Canadian Atlantic were once highly productive, generating enormous annual harvests and attracting fishing fleets from many nations. However, through the late 1980s improved fishing technology, unprecedented capture rates, and poor fishery management brought wild stocks beyond the point of collapse. Dwindling harvests in the early 1990s resulted in cod fishing moratoriums, and an end to the productivity for which the fishery was once renowned. Atlantic cod remains a popular food worldwide and the collapse of cod fisheries has done little to abate market demands. Consequently, the cod is considered a prime candidate for aquaculture production, …

Lipid Raft Formation And Peptide-Lipid Interactions In Myelin Model Membranes, Ashtina R. Appadu

Theses and Dissertations (Comprehensive)

Multiple sclerosis (MS), a demyelinating disease affecting 75,000 Canadians and almost 400,000 Americans, is one of the most prevalent diseases in young adults. Unfortunately, there exist no known cures to date and the pathways involved in the progression of the disease remain relatively obscure. The demyelination process triggered by the onset of MS, affects the lipid composition of the myelin membrane and causes a loss in viable myelin which can in turn greatly impact the proper functioning of the central nervous system (CNS). The cholesterol content of myelin fluctuates during MS and consequently this could affect the fluidity as well …

The Effects Of 17Α-Ethynylestradiol (Ee2) On Gonadal Development And Differentiation In The Estuarine Killifish, Fundulus Heteroclitus, Ibrahim Chehade

Theses and Dissertations (Comprehensive)

Endocrine disrupting substances (EDSs) comprise a wide variety of chemicals that perturb normal endocrine function including developmental and reproductive processes in vertebrates. The synthetic estrogen 17α-ethynylestradiol (EE₂) is a commonly-used model EDS because of its environmental relevance and its effects on the reproductive endocrine system. Early life-stage exposure of fish to estrogenic EDSs causes effects such as intersex (ovotestes in males) and feminization. This study aims to confirm the period of gonadal differentiation in the estuarine killifish or mummichog (Fundulus heteroclitus) and to determine the sensitivity of gonadal development to EE₂. Artificially-regressed mummichog were spawned, and …

Effects Of 17Α-Ethinylestradiol (Ee2) On Reproductive Endocrine Status In Mummichog (Fundulus Heteroclitus) Under Differing Salinity And Temperature Conditions, Esteban Gillio Meina

Theses and Dissertations (Comprehensive)

Waterborne exposure to 17α-ethinylestradiol (EE₂), a synthetic estrogen, has previously been shown to decrease reproductive endocrine status in the estuarine killifish or mummichog (Fundulus heteroclitus macrolepidotus; northern subspecies). To evaluate if variations in salinity or temperature holding conditions modify the effects of EE₂ on gonad size, plasma reproductive steroid levels, and gonadal steroidogenesis, mummichog were exposed in vivo for 14 days to 0, 50 and 250 ng/L EE₂ in 0, 16 and 32 ppt salinity at 18°C and to 0 and 250 ng/L EE₂ at 10, 18 and 26°C at 16 ppt salinity. …

Toward A Functional Characterization Of The Acidic-Domain Of The Chloroplast Protein Import Receptor Toc159, Joseph K. Weston

Theses and Dissertations (Comprehensive)

Chloroplasts are members of a diverse class of organelles called plastids that differentiate plants from other eukaryotes, and are the site of a number of essential biochemical pathways including photosynthesis. Nuclear-encoded pre-proteins, which account for ~95% of chloroplast proteins, are post-translationally imported into plastids across the double envelope membrane. In the model plant Arabidopsis thaliana, the majority of pre-proteins are imported via the Toc (translocon at outer envelope membrane of chloroplasts) and Tic (translocon at inner envelope membrane of chloroplasts) complexes, the key components of which have been identified. The Toc159 …

The Effect Of Cadmium Exposure On Repeat Swimming Performance And Recovery In Rainbow Trout (Oncorhynchus Mykiss), Brown Trout (Salmo Trutta) And Lake Whitefish (Coregonus Clupeaformis), Jessie L. Cunningham

Theses and Dissertations (Comprehensive)

Swim performance provides a measure of the integrated metabolic costs of sub-lethal exposure to stressors, including Cd. While the impacts to sustained swimming performance in Cd exposed fish have already been characterised, effects to repeat swimming ability have not. This thesis identifies the effects of sub-lethal waterborne Cd exposure on ionoregulatory function, repeat swimming ability, anaerobic metabolism and stress response in rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta) and lake whitefish (Coregonus clupeaformis).

Repeat swim trials included an initial swim to 85% of the U_crit of control fish and a recovery period …

Studies On Waterborne Cadmium Exposure To Lymnaea Stagnalis In Varying Water Qualities And The Development Of A Novel Tissue Residue Approach, Nish M. Pais

Theses and Dissertations (Comprehensive)

Recent studies have shown that the use of bioaccumulation (tissue residues) as a predictor for toxic effects for metals is a flawed concept.Adams et al. (2010) suggested a novel tissue residue approach (TRA) in which bioaccumulation in resistant organismsis related to toxic effects in sensitive organisms. The goal of this thesis was to test these assumptions in relation to Cd exposure using the great pond snail, Lymnaea stagnalis by developing and improving the understanding of Cd accumulationin aquatic invertebrates.

The relationship between Cd bioaccumulation and its toxicity was studied in L. stagnalisusing acute (96h) and chronic (one month) …

The Chronic Toxicity Of Titanium Dioxide Nanoparticles To The Freshwater Amphipod Hyalella Azteca, Gurkirpal S. Malhi

Theses and Dissertations (Comprehensive)

There has been an increased use of metal-oxide nanoparticles in both commercial and consumer products. The use of these products and waste generated during manufacture may ultimately be released into the aquatic environment and the potential for these contaminants to cause impacts must be assessed. This study examines the effect of titanium dioxide (TiO₂) nanoparticles (NPs) on Hyalella azteca. Chronic toxicity exposures were conducted in 400mL of spiked test solution and contained 20 neonates. Samples collected for characterization of Ti in TiO₂ NP exposure solutions were digested using ammonium persulfate as an oxidizing agent and dissolved …

Proteomic Analysis Of The Highly Detergent Resistant Radial Component Of Myelin, Vatsal M. Patel

Theses and Dissertations (Comprehensive)

The wrapping of multiple layers of myelin membrane sheets around an axon plays an important role in normal neuronal function. In the central nervous system (CNS), oligodendrocytes are responsible for forming multiple myelin internodes which consist of lipids and proteins. Within these regions, there are various membrane microdomains including the radial component/tight junctions. The radial component is a junctional complex believed to stabilize the myelin membranes in the CNS myelin. In this study, the radial component from bovine and mouse myelin was isolated using differential detergent extraction. A highly detergent resistant fraction, containing previously identified proteins of the radial component …