Mailing address:
Department of Environmental and Molecular Toxicology
Box 7633, NC State University
Raleigh, NC 27695-7633
Shipping address:
Suite 1104, 850 Main Campus Dr.
Raleigh, NC 27606
Phone 919.515.2274
Fax 919.515.7169
Gerald A. LeBlanc, Ph.D.
Department Head and Professor
Department of Environmental and Molecular Toxicology
Phone: 919-515-7404
E-mail: ga_leblanc@ncsu.edu
Dr. LeBlanc's CV
Education
BS, University of Massachusetts
PhD, University of South Florida
Postdoctoral, Harvard Medical School
Research Interests
Environmental Signaling and Sex Determination/Differentiation
Hormones orchestrate a variety of processes related to embryonic and reproductive development including sex differentiation and, in some species, sex determination. 
These hormone signaling cascades often are regulated by environmental cues such as temperature and photoperiod, but can be interfered with by environmental pollutants (pesticides, chemical wastes, personal care products). We seek to understand how environmental signals regulate embryo and reproductive development. This research involves the identification of environmental factors that initiate the signaling, the hormones and hormone receptors that transduce these signals, and the terminal genes that are regulated by these signaling cascades. This research is conducted primarily in two animal models, the crustacean Daphnia magna and the mud snail Ilyanassa obsoleta. Research includes field studies of natural populations, laboratory assessments of the roles of environmental factors, chemicals, and hormones in sex determination and differentiation, as well as, molecular analyses of hormone receptors, response elements, and hormone-responsive genes.
Studies of environmental sex determination in daphnids have shown that the signaling cascade responsible for this phenomenon is:
-initiated by food deprivation and crowding,
-transduced by retinoid-type hormones (i.e., methyl farnesoate),
-perturbed by the ‘insect growth regulating’ class of insecticides.
Studies in the mud snail have focused upon signaling processes that are responsible for sex differentiation. Toxicological interest in this signaling process stems from the fact that the ubiquitous environmental contaminant tributyltin causes a condition called ‘imposex’ in some snails whereby females express male sex characteristics. The goal of this program is to identify the entire signaling cascade responsible for environmental sex differentiation as well as identifying the specific site at which tributyltin interferes with the cascade.
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Toxicity Assessment of Chemical Mixtures
The development of approaches for the hazard characterization of chemical mixtures is among the major research needs in toxicology. We have adopted a computational approach, integrating biological experimentation and mathematical modeling, to develop means of evaluating and predicting the toxicity associated with chemical mixtures. Biological research includes hypothesizing and testing modes of chemical interaction (synergy, antagonism), toxicological characterizations of the consequences of interactions, and generations of toxicological databases that can be used in modeling toxicity. Mathematical research includes the development of algorithms that explain biological observations, integration of various models used in mixtures toxicity characterizations, and development of computer programs that facilitate computational assessments.
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