Document Type

Theses, Ph.D


Available under a Creative Commons Attribution Non-Commercial Share Alike 4.0 International Licence


Environmental sciences

Publication Details

Successfully submitted for the award of Doctor of Philosophy (Ph.D) to the Technological University Dublin, July, 2010


O’Dowd, C., Mothersill, C.E., Cairns, M.T., Austin, B., Lyng, F.M., McClean, B. and Murphy, J.E.J. Assessing the mitochondrion as a biomarker of fish tissue damage using g radiation as a stress model in vitro.

There is an ever-increasing need for biomarkers to identify toxic stress in the aquatic environment. Such techniques need to be accurate, expeditious, ethical and economical. Typically, in vitro based platforms fit these criteria however many of these systems often undergo ‘assay drift’ and consequently do not fully represent the real-life situation.

In recent years, there has been growing interest in the mitochondrion and its (dys)function or altered function and dynamics as a marker of toxic assault. The mitochondrion is an essential organelle in the cell and is associated with energy production and metabolism in the organism as it is the site of oxidative phosphorylation (OXPHOS). It has its own genetic material which is more susceptible to damage than nuclear DNA (nDNA) due to its proximity to the site of OXPHOS, the absence of introns, the lack of a protective histone coat and effective repair mechanisms which are present in nDNA. Stress responses including increases in mitochondrial mass and alteration in the activity of proteins associated with OXPHOS have been reported and offer potential as putative biomarkers of toxicity.

In this study, we used real-time PCR to identify alterations in mitochondrial genome copy number in cultured fish tissues exposed to g radiation. These values were compared to the activity of the citrate synthase enzyme, an established marker of mitochondrial mass in cells. Results show that while this approach is appropriate and the technique is robust, expeditious and straightforward, further development is required to yield greater enhancement and sensitivity.