Fish Reproductive Physiology/Marine Environmental Toxicology
Purification and molecular actions of hormones and their receptors, environmental endocrinology, applications of endocrinology to fish culture; biochemical and environmental toxicology of marine fishes, especially reproductive and endocrine toxicology.
Most of the complex series of morphological, physiological, behavioral and developmental changes that occur during the reproductive cycle are thought to be under endocrine control. However, the hormonal regulation of many reproductive processes remains poorly understood, especially in marine perciform fish, which represent the largest order of extant vertebrates. Extensive research on Atlantic croaker and spotted seatrout in our laboratory has identified many novel features of the endocrine control of reproduction in these marine perciform fish, particularly during final maturation of eggs and sperm. Research is being conducted on the purification, biological functions and physiological regulation of nuclear and membrane steroid hormone receptors, the cloning, sequencing and expression of steroid receptor mRNAs, the biosynthesis and molecular actions of steroid hormones, the endocrine control of egg growth, spermatogenesis and meiotic maturation, the neuroendocrine control of gonadotropin secretion, and applications of endocrinology to fish culture. The goal of this research is to develop a comprehensive model of the endocrine control of reproduction for representatives of this important vertebrate group.
The release of toxic chemicals into marine and estuarine environments has increased dramatically as a result of rapid industrialization in many regions of the world, but the longterm ecological consequences of increased environmental contamination are not known. The development of early-warning biomarkers of pollutant exposure may enable deleterious changes in the environment to be detected early enough so that remedial actions can be taken. Our research emphasis has been on the development of endocrine biomarkers of impaired reproductive function in marine fish because relatively low pollutant concentrations can disrupt fish reproduction with serious consequences for the long-term survival of the entire population. Mechanisms of chemical interference with reproductive endocrine function, the relationship between endocrine dysfunction and impairment of critical reproductive processes, and the long term population effects of reproductive impairment are under investigation. In addition, reproductive biomarkers are being evaluated in fish collected from degraded sites in Texas and California as indicators of ecosystem health.
Hawkins, M.B., J.W. Thornton, D. Crews, J.K. Skipper, A. Dotte and P. Thomas. 2000. Identification of a third distinct estrogen receptor and reclassification of estrogen receptors in teleosts. Proceedings National Academy of Sciences, USA 97:10751-10756.
Thomas, P. 1999. Nontraditional sites of endocrine disruption by chemicals on the hypothalamus-pituitary-gonadal axis: interactions with steroid membrane receptors, monoaminergic pathways and signal transduction systems. pp. 3-38. In: R.K. Naz (ed.). Endocrine Disruptors: Effects on Male and Female Reproductive Systems. CRC Press, Boca Raton, Forida.
Sperry, T. and P. Thomas. 1999. Characterization of two nuclear androgen receptors in Atlantic croaker: comparison of their biochemical properties and binding specificities. Endocrinology 140(4):1602-1611.
Das, S. and P. Thomas. 1999. Pesticides interfere with nongenomic action of a progestogen on meiotic maturation by binding to its plasma membrane receptor on fish oocytes. Endocrinology 140(4):1953-1956.
Created: Tue Jan 2 13:44:00 CST 2001