Organisms synthesize stress proteins in response to a variety of stressors. The 68/70-kDa proteins (synonymous to the 72/73-kDa proteins) have shown to be the most promising stress proteins, and have been proposed as a biomarker of general organismal stress. The 68/70-kDa proteins were used in an antigen/antibody based approach to determine the duration of the stress protein response of Pimephales promelas following an acute exposure to copper sulphate.

Selenium (Se), an essential element, can bioaccumulate and become toxic. The main toxicity symptom in fish, teratogenicity, is mediated by oxidative stress; however, little is known about the effect of Se on the physiological stress response (PSR). The effects of Se on the PSR and oxidative stress parameters were investigated in rainbow trout, brook trout, and white suckers. The PSR was activated by acute and sub-chronic laboratory exposures to NaSeO3, but not exposure to environmental levels of Se. Species-specific sensitivity to Se may be explained by biochemical differences. Rainbow trout (exhibit oxidative damage with Se exposure) have greater GSH reserves (cycles with Se causing oxidative stress) than brook trout. Selenium in agricultural drain water did not accumulate to dangerous levels in white suckers, but additional stressors (e.g. pesticides) were present. Differences in sensitivity to Se may alter competitive interactions between species, changing community compositions and putting additional pressure on threatened species. / xiii, 150 leaves ; 29 cm.

Fish are exposed to multiple stressors in their environment. The interactive effects of pesticide exposure and increased temperature on the physiological stress response were investigated in a comparative field study with cold-water (whitefish, Prosopium williamsoni) and cool-water (sucker, Catostomus) fish from the Oldman River, Alberta, Canada, and in a laboratory study with rainbow trout, Oncorhynchus mykiss. Physiogical stress indicators were measured, and exposure to pesticides was estimated using acetylcholinesterase (AChE) inhibition. Species-specific differences in AChE activities and responses of the physiological stress axis were detected in whitefish and suckers, suggesting that whitefish are a more sensitive species to temperature and pesticide stress. In vivo Dimethoate exposure inhibited AChE activity in various tissues and disrupted the physiogical stress response. Commercial Dimethoate, in vitro, caused a decrease in viability and cortisol secretion while pure grade Dimethoate did not. The results from this study can be used in predictions of fish vulnerability to stress. / ix, 137 leaves : ill. ; 29 cm.

Chapter 1: Antarctic fishes are extremely cold adapted. Despite their inability to upregulate heat shock proteins, recent studies have demonstrated a capacity for heat response in these animals. A cDNA microarray study looked at the Notothenioid fish Trematomus bernacchii and revealed heat sensitivities for hundreds of genes, two of which code for members of the CCAAT/Enhancer-binding protein (C/EBP) family of transcription factors. These molecular switches are best known for their roles in apoptosis, inflammation and cell cycle arrest. This dissertation further elucidates the role of C/EBP-delta in the Antarctic fishes T. bernacchii and Pagothenia borchgrevinki. Chapter 2: C/EBP-delta is constitutively expressed in unstressed, field-acclimated (ca. -1.86°C) animals in a highly tissue-specific manner. White muscle tissue contains the highest C/EBP-delta concentration, which is further increased in response to sublethal heat stress at 2.0 or 4.0°C. This response is mostly acute and transitory, but a lesser upregulation was observed in fishes held for one month at 4.0°C. Chapter 3: The heat-induced nuclear translocation of C/EBP-delta--as determined by immunohistochemistry--appears to be time, tissue and species specific with spleen, heart and retinae being particularly responsive in certain situations. Chapter 4: Protein concentrations of proliferating cell nuclear antigen are tissue specific and variably heat responsive. Surprisingly, levels appear to be positively correlated with C/EBP-delta. Chapter 5: Flow cytometry revealed increasingly high temperatures reduce the proportion of G1 cells while increasing the abundance of apoptotic cells. Chapter 6: These findings are discussed in the context of global climate change and the cellular stress response.