OCEES GRADUATE RESEARCH FELLOW

2007-2008

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Jeffrey M. Grim

Dr. Elizabeth L. Crockett

Biological Sciences

Doctor of Philosophy

Fellowship Project:

Changes in Susceptibility to Lipid Peroxidation, Antioxidant Responses, and Phospholipid Composition of Biological Membranes from Thermally-acclimated Teleost Fishes

 

Research Summary:

   Organisms face many challenges associated with the formation of reactive oxygen species (ROS) as by-products from the reduction of oxygen by the electron transport chain during routine aerobic metabolism. These ROS have the potential to cause oxidative damage to biological membranes. Cells are protected from ROS-induced damage by two classes of antioxidant defenses (AOX): low molecular weight antioxidants (e.g. glutathione, vitamins E and C) and enzymatic antioxidants (e.g. catalase, glutathione peroxidase, and superoxide dismutase). Under most physiological conditions, ROS production is closely matched by responses of AOX systems. When ROS production is unmatched by AOX, however, organisms may experience bouts of oxidative stress. Oxidative stress to biological membranes can include damaging lipid peroxidation (LPO). LPO is a distinct set of ROS-induced, self-propagating reactions which may result in a loss of structural integrity of biological membranes. Cold-acclimated (or adapted) poikilotherms defend membrane fluidity by increasing the degree of unsaturation through incorporation of polyunsaturated fatty acids (PUFA) and by increasing the ratio of the two common phospholipid classes, phosphatidylethanolamine (PE)/phosphatidylcholine (PC). These changes in membrane composition, however, may leave these animals at an elevated risk of LPO, as both PUFA and PE are more oxidizable than are PC or saturated lipids. Additionally, muscular tissues from cold-acclimated fishes show increased mitochondrial densities and enhanced oxidative capacity, which could increase rates of ROS production. Phospholipid remodeling, coupled with an expansion of oxidative capacity during cold-acclimation, may therefore elevate the LPO susceptibility in tissues of these animals. The central goal of my fellowship work was to determine whether temperature-induced changes in PUFA content and phospholipid class composition alter mitochondrial membrane oxidizability.

 

Research completed during the fellowship:

 

During the fellowship period I made progress on several research-related fronts. I fulfilled my department requirement by presenting dissertation research at Ecolunch. Additionally, I've successfully completed all of the research objectives outlined for my OCEES Fellowship project. I've spent time optimizing our assay for LPO susceptibility to mitochondrial membranes from our study species, killifish, Fundulus heteroclitus. Subsequently, I'll have assayed n=7 for each of two treatment groups in duplicate. Rates of oxidizability from these assays will be compared between treatment groups using unpaired t-tests. Lipids were extracted from the duplicate aliquots of these mitochondria and lipid extracts were sent to the Kansas State Lipidomics Center for fatty acid and phospholipid head group analyses. The results of these analyses are pending. Between LPO susceptibility analyses I was able to make significant progress on two manuscripts based on my dissertation research; one regarding the effects of exercise training on enzymatic antioxidants in fishes will be submitted to Fish Physiology and Biochemistry by June 2008 and the other on the effects of temperature acclimation on membrane composition, LPO susceptibility, and enzymatic antioxidants will be submitted to Physiological and Biochemical Zoology by July 2008.

 

Webpage:

http://oak.cats.ohiou.edu/~grimj/ UNDER CONSTRUCTION

Email:

grimj@ohio.edu