Research Summary

Dr. Thomas's research focuses on metabolic and generalized stress in vertebrates. Her previous work focused on the Na-K-2Cl cotransporter (NKCC) in Ehrlich mouse ascites tumor cells. She found that cells in vivo exhibited limited cotransporter activity under anaerobic conditions (with relatively high lactic acid). In a lactic acid-free environment, the NKCC becomes active and the cells accumulate chloride to such an extent that chloride is not in electrochemical equilibrium. Future research will use murine C2C12 cells, stem cells that can be induced to form myotubes, which are spontaneously contracting skeletal muscle-like cells. The activity of the NKCC during cell differentiation will be studied to determine NKCC's role in cell differentiation and to determine the effect of lactic acid on the NKCC in C2C12 cells. Although muscle fatigue is often correlated with lactic acid build up, neither lactic acid itself, nor the lowered pH that accompanies it, can explain the inability of muscle to continue to generate tension. Other possibilities, such as compromised ion transport, have been speculated to be involved. Chloride and NKCC in myotubules will be examined after exposure to elevated lactic acid concentration. A recent study indicated a connection between lactic acid production and chloride conductance in working skeletal muscles, suggesting that elevated lactic acid levels may compromise chloride transport mechanisms such as the NKCC in C2C12 cells and this may serve as a model for skeletal muscle cells under anaerobic conditions. Most of the research done on these cells has been on the genetics of cell differentiation; little research is available concerning their physiology. One project is an investigation of C2C12 cells that involves transport systems, volume regulation, membrane potential, and ionic composition.
A second investigation examines the expression of stress proteins, also known as heat shock proteins (HSPs), in oysters. Inter-tidal oysters are less susceptible to the adverse effects of Perkinsus marinus infection compared to sub-tidal oysters. P. marinus is a potentially lethal protist parasite that causes the disease Dermo in oysters. The concern is that this resistant group of inter-tidal oysters presents a viable breeding ground for P. marinus resulting in continued infections in both inter- and sub-tidal oyster populations. One potential cause of this resistance to Dermo is the presence of HSPs in inter-tidal oysters due to the increase in temperatures during times when the animals are above water, especially during warmer months. If HSPs allow for tolerance of Dermo, there is a possibility that increased expression of HSPs also allows the oysters to incubate Vibrio vulnificus, an opportunistic bacterium known to cause deaths in humans. The amount of Vibrio carried by oysters is variable and generally increases in warmer months. This project will explore the potential connection between Dermo tolerance and Vibrio infection in oysters