Thesis (M.S.)--Oregon State University, 1991. / Typescript (photocopy). Includes bibliographical references (leaves 100-106). Also available via the World Wide Web.

Thesis (M.S.)--Oregon State University, 1971. / Typescript (photocopy). Includes bibliographical references. Also available via the World Wide Web.

Thesis (M.S.)--Humboldt State University, 2009. / Includes bibliographical references (leaves 49-57). Also available via Humboldt Digital Scholar.

The present study investigated the effects of stress and exercise on seawater (SW) adaptation and cortisol dynamics in juvenile steelhead (Oncorhynchus mykiss). To examine the effects of stress, fish acclimated to freshwater (FW) were subjected for 3 hours to confinement stress in FW, and subsequently SW (25 ppt) was introduced to all tanks. Fish were sampled immediately after the stress treatment, and 1, 7, and 14 days after introduction of SW. Electrolytes, cortisol, glucose and lactate followed the typical pattern that we expected after stress treatment in FW. Fish regained osmotic balance within 24 hours. Glucose concentrations were increasing throughout the experiment and lactate levels stayed elevated during the time spent in SW. IGF-1 did not show an immediate response to stress but after transfer to SW we detected significantly higher concentrations for control fish at days 1 and 14. The differences in IGF-1 levels between stressed and control fish are not reflected in SW adaptability but positive correlations between IGF-1 and electrolyte levels in control fish may indicate its role for osmoregulation. Confinement stress did not impair feed intake subsequently in SW, but our results suggest that feed intake was suppressed by the change of the media from FW to SW. The second study investigated the effects of exercise treatment in FW on SW adaptation and cortisol dynamics in juvenile steelhead. Plasma cortisol and in vitro cortisol secretion by interrenal cells after a 24 hr SW challenge test were neither affected by moderate exercise nor by water temperature (13��C, 21��C), however, plasma osmolality was lower in exercised fish compared to unexercised fish. Half-life (T[subscript 1/2]) of ��H-cortisol was shorter in fish exposed to exercise whereas metabolic clearance rate (MCR) did not respond to exercise treatment. Uptake and retention of corticosteroids in liver and gall bladder were enhanced in exercised fish, and retention of corticosteroids in muscle tissue was longer in unexercised fish. Our findings suggest that exercise likely decreases stress levels in fish and improves the adaptation to seawater (SW) in juvenile steelhead. / Graduation date: 2004

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 168-178).

Crosses were made between a stock of summer steelhead (Salmo gairdneri) known to be resistant to infection by Ceratomyxa shasta and stocks of summer steelhead known to be susceptible. Ceratomyxosis, the disease caused by C. shasta was initiated by exposure to Willamette River water. I found that the crosses were intermediate in susceptibility to ceratomyxosis relative to the parental stocks. There was no difference in susceptibility to ceratomyxosis between reciprocal crosses of the same stocks. Persistence of moderate susceptibility in the F₂ generation of experimental stock crosses and examples from both wild and hatchery stocks of mixed ancestry indicate long term disease problems may result from introductions of less adapted, foreign stocks. / Graduation date: 1987

Numerous natural and anthropogenic chemicals interact with endocrine systems of animals. The most widely studied of these endocrine active chemicals (EACs) are estrogen receptor agonists and antagonists. Because of the many important roles of estrogens in animals, xenoestrogens have the potential to impact environmental health. It has been proposed that xenoestrogen contaminants are responsible for recent increases in estrogen dependent human diseases and sexual and developmental abnormalities in wildlife. Aquatic species are particularly susceptible to persistent EACs that accumulate in sediments and biomagnify along trophic levels. Rainbow trout, Oncorhynchus mykiss, commonly used in biomedical research and as a sentinel species, was chosen as a model for studying mechanisms of xenoestrogen activity. The aims of this research were to assess the estrogenic activity of individual persistent, organic contaminants and simple mixtures in vivo. Emphasis was placed on determining the potential for xenoestrogens to alter sexual development or to induce sexually dimorphic biochemical responses. Gonadal abnormalities in trout exposed as embryos to the xenoestrogen o,p'-DDE showed that xenobiotics can affect trout sexual development. However, the absence of endocrine disruption by low doses of o,p'-DDE, by the xenoestrogens chlordecone and octylphenol, or by the anti-androgen p,p'-DDE, suggested that lethality is likely to precede endocrine disruption in highly exposed, feral salmonid populations. Sexually distinct responses in immature trout were documented with respect to vitellogenin induction (2 to 4 fold higher in females) and cytochrome P450 expression. Sex differences occurred only when doses of estrogens or xenoestrogens were below levels that cause maximal estrogenic responses. Evidence suggests that estrogen regulation may be fundamentally different in immature males and females, which may have implications for natural populations exposed to xenoestrogens. Vitellogenin induction and P450 modulation were responsive to mixtures of estrogens and xenoestrogens in a manner suggestive of additive activation of estrogen receptors. Cytochrome P450 dependent induction of lauric acid hydroxylation was observed for the first time in trout, in response to tamoxifen and mixtures of tamoxifen and 17��-estradiol. The estrogenic activity of tamoxifen and 4-hydroxy-2',4',6'-trichlorobiphenyl were greater in vivo than what was predicted by in vitro studies, which emphasized the need for mechanism based investigations of xenoestrogens in whole organisms. / Graduation date: 1999

Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves 88-98.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves - ). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 101-111). Also available on the World Wide Web.