Education: Ph.D., 1983, University of Idaho
M.S., 1979, University of Rhode Island
B.S., 1977, Saint John’s University
Heat shock proteins
The heat shock proteins (hsps) are a highly conserved family of proteins essential for several critical cell functions including protein folding and transport. During or following perturbation of the intracellular environment (e.g. thermal shock, heavy metal exposure), hsps restore structure and function to denatured proteins, where such denaturation is reversible, or target proteins for removal from the cell, where denaturation is irreversible. We have cloned the cDNAs coding for the major hsps of fish and are investigating the roles that these proteins play in enabling fish to adapt to environmental stressors including temperature and osmotic stress and exposure to a variety of xenobiotic compounds. Interestingly, we have demonstrated that exposure of salmon to a mild thermal shock capable of inducing hsp 70, significantly enhances survival of fish subjected to osmotic stress (Dubeau et al. 1998).
Anadromous salmonids must contend with osmotic shock twice in their life cycle, first when juveniles migrate from freshwater to the marine environment and later when adults return to natal streams to spawn. Although most species of salmonids undergo a physiological transformation that prepares them for the transition from freshwater to life in the dehydrating marine environment (smoltification or parr-smolt transformation), a transient rise in plasma ion concentration suggests they experience an osmotic shock over several days. Homeostasis is ultimately attained through a variety of mechanisms, including de novo synthesis of branchial Na+/K+ ATPase, proliferation of chloride cells and associated accessory cells, and improved hydration through increased drinking. The degree of osmotic shock is more severe in commercial aquaculture, wherein juvenile salmon are transferred from freshwater to seawater directly, without the moderating influence of gradual transition to full salinity seawater afforded in nature. Further, osmotic shock can be exacerbated by transferring salmon outside the narrow time-frame of parr-smolt transformation (4-6 weeks) when osmoregulatory abilities are compromised. The resultant increases in plasma and tissue osmolality can disrupt biochemical processes (e.g. enzyme catalytic rates and Km) perturb cellular homeostasis and lead to stunted growth or death. Conversely, stenohaline marine fish exposed to waters of low salinity must contend with over hydration which also can disrupt cell physiology. Recently, we have cloned multiple genes that are upregulated in fish exposed to osmotic stress and are in the process of characterizing and identifying the proteins. The ultimate goal is to determine the role of these genes in adaptation of fish to osmotic stress.
Marine Finfish Aquaculture
The decline in traditional capture fisheries and increased consumer demand for fish has highlighted the importance of aquaculture in meeting this demand. Although the culture conditions and techniques for many species of freshwater species in North America are well defined, limited efforts have been undertaken for marine species. As such, we are developing methods for culture of several species of finfish of commercial importance to the New England region. Current efforts are focused on black sea bass (Centropristis striata), cod (Gadus morhua) and haddock (Melanogrammus aeglefinus).
- Howell, R.A., Berlinsky, D.L. and Bradley, T.M. 2003. The effects of photoperiod manipulation on the reproduction of black sea bass, Centropristis striata. Aquaculture 218: 651-669.
- Zarate, J. and Bradley, T.M. 2003. Heat shock proteins are not sensitive indicators of hatchery stress. Aquaculture (In Press).
- Simpson, J.M., Kocherginshaya, S.A., Aminov, R.I., Skerlos, L.T.,Bradley, T.M., Mackie, R.I. and White, B.A. 2002. Comparative microbial diversity in the gastrointestinal tracts of food animal species. Integ. Comp. Biol. 42: 327-331.
- Pan, F., Zarate, J., and Bradley, T.M. 2002. A homolog of the E3 ubiquitin ligase RBX1 is induced during hyperosmotic stress of salmon. Amer. J. Physiol. 282 : R1643-R1653.
- Berlinsky, D., Watson, M., Nardi, G. and Bradley, T.M. 2000. Aquaculture of black sea bass (Centropristis striata): Investigation of selected parameters for larval and juvenile growth. J. World Aquaculture Soc.31(3):426-435.
- Buckley, L.J., Bradley, T.M., and Allen-Guilmette, J. 2000. Production, quality, and low temperature incubation of eggs of Atlantic cod Gadus morhua and haddock Melanogrammus aeglefinus in captivity. J. World Aquaculture Soc. 31: 22-29.
- Berlinsky, D., Watson, M., Nardi, G., and Bradley, T.M. 2000. Investigations of selected parameters for growth of larval and juvenile black sea bass Centropristis striata L. J World Aquaculture Soc. 31: 426-435.
- Smith, T.R., Tremblay, G.C. and Bradley, T.M. 1999. Characterization of the heat shock protein response of Atlantic salmon (Salmo salar). Fish Physiol. Biochem. 20:279-292.
- Smith, T.R., Tremblay, G.C. and Bradley, T.M. 1999. Hsp70 and osp54 are induced in salmon (Salmo salar) in response to osmotic shock. J. Exp. Zool. 284(3):286-298.
- Dubeau, S.F., Pan, F., Tremblay, G.C and Bradley, T.M. 1998. Thermal shock of salmon in vivo induces the heat shock protein hsp70 and confers protection against osmotic shock. Aquaculture 168:311-323.
- Bradley, T.M., E. Hidalgo, V. Leautaud, H. Ding and B. Demple. 1997. Cysteine-to-alanine in the Escherichia coli SoxR protein and the role of the [2Fe-2S] centers in transcriptional activation. Nucl. Acids Res.
- Ji, H, Bradley, T.M. and Tremblay, G.C. 1996. Atlantic salmon (Salmo salar) fed L-carnitine exhibit altered intermediary metabolism and reduced tissue lipid, but no change in growth rate. J. Nutrition 126:1937-1950.
- Lo,Y.H., Bellis, S., Cheng, L.-J., Pang, J., Bradley, T.M. and Rhoads, D.E. 1994. Signal transduction for taurocholic acid in the olfactory system of Atlantic salmon. Chem. Senses, 19(5):371-380.
- Carranza, M.L, Allen, J.A. and Bradley, T.M. 1994. The effects of smoltification and seawater adaptation on pancreatic B-cells of Atlantic salmon. Aquaculture 121:157-170.
- Robertson, J.C. and Bradley, T.M. 1991. Hepatic ultrastructure changes associated with parr-smolt transformation of Atlantic salmon (Salmo salar). J. Exp. Zool. 260:135-148.