Polyunsaturated fatty acids (PUFA) comprise a significant portion of mammalian brain tissue, and are involved in neural signalling and cellular homeostasis. One brain PUFA, arachidonic acid, represents an attractive target for manipulation, with evidence suggesting it plays a role in the pathology of several neurological diseases. In this study, we fed rats a 15-week diet of an n-3 PUFA adequate or deprived diet, and then injected 3H arachidonic acid into the right lateral ventricle and measured its rate of loss over time. The half-life was 44 and 46 days for the n-3 PUFA adequate and deprived dietary groups, respectively. We compared the rate of loss with a predicted rate of loss (~45 days). We concluded that plasma unesterified AA is quantitatively a major source of brain phospholipid AA. Furthermore, we demonstrated selective regulation of brain PUFA by showing AA, unlike DHA, is not conserved in n-3 PUFA deprivation.

Polyunsaturated fatty acids (PUFA) comprise a significant portion of mammalian brain tissue, and are involved in neural signalling and cellular homeostasis. One brain PUFA, arachidonic acid, represents an attractive target for manipulation, with evidence suggesting it plays a role in the pathology of several neurological diseases. In this study, we fed rats a 15-week diet of an n-3 PUFA adequate or deprived diet, and then injected 3H arachidonic acid into the right lateral ventricle and measured its rate of loss over time. The half-life was 44 and 46 days for the n-3 PUFA adequate and deprived dietary groups, respectively. We compared the rate of loss with a predicted rate of loss (~45 days). We concluded that plasma unesterified AA is quantitatively a major source of brain phospholipid AA. Furthermore, we demonstrated selective regulation of brain PUFA by showing AA, unlike DHA, is not conserved in n-3 PUFA deprivation.

Title page, summary and table of contents only. The complete thesis in print form is available from the University of Adelaide Library. / Tumor necrosis factor (TNF) is a pro-inflammatory cytokine with multiple biological effects. The receptors for this cytokine on neutrophils have been shown to be rapidly down-regulated following activation, leading to the release of soluble forms of these receptors. Thus neutrophils become less responsive to TNF and the soluble TNF receptors (TNFR) serve to control TNF activity. During inflammation, leukocytes become activated as a result of the action of a variety of mediators. These mediators include not only cytokines but also lipids, such as the pro-inflammatory 00-6 fatty acid, arachidonic acid (AA) and its metabolites. Cellular activation leads to the release of AA from membrane phospholipids. AA regulates the function of many cell types including neutrophils. In view of the known pro-inflammatory properties of AA and the anti-inflammatory properties of 00-3 fatty acids, a study was undertaken to examine whether or not these fatty acids regulate the expression and release of TNFR in neutrophils. While much emphasis has been placed on agonist-induced down-regulation of TNFR, our data show that AA causes a rapid (10-20 min) and dose-dependent (0.5 to 30 uM) increase (8-fold) in the surface expression of both classes of TNFR (TNFRl and TNFRlI) on human neutrophils, at concentrations found in inflammatory fluids. This correlates with an increase in superoxide production to a TNF challenge. In contrast, both fMLP and LPS significantly reduce the expression of both TNF receptors. Interestingly, in neutrophils pretreated with AA, fMLP causes an increase in TNF receptor expression, consistent with AA preventing the fMLP-induced receptor release in neutrophil culture. In addition, while AA causes an increase in TNF receptor expression on matured HL-60 cells (neutrophil-like cells), a decrease occurs on HUVEC and non-matured HL-60 cells. These data demonstrate a unique effect of AA on neutrophils. The relationship between AA and the anti-inflammatory (0-3 fatty acids, DHA and eicosapentaenoic acid (EPA), in the modulation of TNF receptor expression has also been examined. These (0-3 polyunsaturated fatty acids, including linolenic acid (LNA), cause a decrease in TNFR expression on neutrophils. The (0-6 linoleic acid (LA) and (0-9 oleic acid (OA) both cause an increase in TNFR expression. Furthermore, pre-exposure of neutrophils to nanomolar amounts of EPA or DHA prevents the AA-induced up-regulation of TNFR. These results thus identify another mechanism of regulating the inflammatory reaction by the (0-3 fatty acids. The mechanisms by which AA induces an increase in TNFR expression have been studied. Masking of the carboxyl group results in loss of activity. It is unlikely that a product of AA is responsible since neither the hydroperoxyeicosatetraenoic acid, nor hydroxyeicosatetraenoic acid derivatives show activity. Also, the effects of AA are not sensitive to the action of inhibitors of the cyclooxygenases and lipoxygenases. Using chemical inhibitors of intracellular signaling pathways, we demonstrate that the effect of AA on TNFRI is very sensitive to GFI09203X, PD098059, AACOCF3 and wortmannin, showing a role for protein kinase C, the extracellular signal regulated protein kinases and cytoplasmic phospholipase A2, and PI-3 kinase respectively, in the enhancement of TNF receptor expression by AA. Although the effects of AA on TNFRII are also decreased by the chemical inhibitors, the results show that these signalling molecules only contribute in part to the mechanisms of increased TNFRII receptor expression. The data presented in this thesis suggest a novel role for AA in the inflammatory reaction, through its action on neutrophil TNFR expression. The work has identified a unique effect of 00-3 polyunsaturated fatty acids for regulating this AA-induced increase in the expression of TNF receptors. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1141955 / Thesis (Ph.D.) -- University of Adelaide, Dept. of Paediatrics, 2004

Thesis (Ph. D.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 260-285).

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Thesis (Ph. D.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains viii, 156 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

Thesis (M.S.Ed.)--Baylor University, 2006. / Includes bibliographical references (p. 87-98).

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Cod hatcheries rely greatly on wild-caught broodstock as egg quality from farm-reared broodstock tends to be poor. Broodstock diet and levels of essential fatty acids have been linked to fecundity and egg quality in cod. Arachidonic acid (ARA) and astaxanthin (Ax) are important nutrients linked to fish egg quality and differences in levels have ben found between eggs from wild and farmed cod. The aim of this thesis was to investigate the impact of dietary supplementation with ARA and Ax on fecundity and egg quality in cod. The first experiment investigated the effect of feeding a diet supplemented with ARA, for 1, 2 or 3 months prior to peak spawning. Results showed that supplementation increased ARA in eggs and that Groups fed the supplement had improved fecundity and egg quality (though with no correlation between the duration of supplementation and number/quality of eggs). The second experiment investigated the effect of supplementation of Ax in broodstock diets on egg quality in farmed cod and showed that Ax was taken up into eggs and that fish fed supplemented diet had improved fecundity and egg quality. The third experiment compared the effect of diet supplementation with ARA and Ax on egg quality in wild and farmed cod and showed that despite the dietary supplementation, wild origin fish performed better on a number of egg quality and fecundity indices. However, it was not possible to take the greater ages and spawning experience of the wild broodstock into account, which may have influenced the results. The fourth experiment measured lipid and fatty acid profiles of eggs from two UK cod hatcheries. Variation was found between farms and across seasons. Results showed that supplementation of cod broodstock diet with ARA and Ax had a positive impact on egg quality and fecundity, although effects were not consistent across all egg quality parameters.