Portland State University. Department of Biology
Date of Award
Doctor of Philosophy (Ph.D.) in Biology
1 online resource (xv, 173 pages)
Fishes -- Effect of stress on -- Antarctic Ocean, Climatic changes -- Antarctica, DNA-protein interactions -- Research, Marine animals -- Adaptation -- Polar regions
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.
Sleadd, Isaac Martin, "CCAAT/Enhancer-Binding Protein Delta (C/EBP-delta) Expression in Antarctic Fishes: Implications for Cell Cycle and Apoptosis" (2013). Dissertations and Theses. Paper 994.