Current research is to empirically characterize the physiologic bases underlying how bears are capable of producing litters of mixed paternity (multiple sires of the same litter). My hypothesis is that bears and other carnivores with delayed implantation (blastocysts do not implant until 3-5 months after conception), utilize superfetation (embryos conceived at different sequential estruses within the same mating season) as a physiologic mechanism to control paternity assignment in litters. Emperical tests utilize controlled mating introductions of known genetic identity captive black bears in sequential estruses within the mating season, carefully documented by behavioral observation, and later conduct paternity analyses on unimplanted embryos obtained from the mated females. The field component of this project began in summer 2009, during which time my Masters and undergraduate students assisted me in collection of behavioral data and collection of DNA from adult study subjects.
An additional aspect of this project is to provide a unique multidisciplinary summer research experience for Native American undergraduate students. Because the black bear has strong cultural value to many tribes, this particular project has strong potential to act as a bridge between scientific and indigenous cultural wildlife conservation values and to serve as a platform for science career capacity building among a minority that is extremely underrepresented in science. We seek to improve recruitment and retention of Native Americans in science, as well as to reduce the tensions between the values of science and traditional spiritual beliefs.
Ph.D., Biochemistry and Molecular Biology, University of Nebraska Medical Center, 1999
Dissertation: "Estrogen induced pituitary tumor development in Rattus norvegicus: modulation by environmental and genetic factors."
Research Summary: Study of the physiological, genetic and hormonal changes of the rat pituitary gland in response to prolonged estrogen exposure as a model for estrogen-dependent cancers. The efficacy of caloric restriction to protect against estrogen-induced tumor development was characterized in five rat strains. Following this, rat strains were selectively inbred to maximize tumor growth traits (congenic strains) and the specific regions of chromosomes (quantitative trait loci) containing genes that cumulatively confer estrogen-dependent pituitary and breast growth were identified.
B.S., Biology, University of Nebraska, 1994
Peer-Reviewed Scientific Publications
1. Spady, T.J., H.J. Harlow, G.M. Butterstein and B.S. Durrant. 2009. Leptin as a surrogate indicator of body fat in the American black bear (Ursus americanus). Ursus 20:120-130.
2. Spady, T.J., D.G. Lindburg and B.S. Durrant. 2007. Evolution of reproductive seasonality in bears. Mammal Review 37:21-53.
3. Durrant, B.S., N. Ravida, T.J. Spady and A. Cheng. 2006. New technologies for the study of carnivore reproduction. Theriogenology 66:1729-1736.
4. Shull, J.D., C.M. Lachel, T.E. Strecker, T.J. Spady, M. Tochacek, K.L. Pennington, C.R. Murrin, J.L. Meza, B.S. Schaffer, L.A. Flood and K.A. Gould. 2006. Genetic bases of renal agenesis in the ACI rat: mapping of Renag-1 to chromosome 14. Mammalian Genome 17:751-759.
5. Strecker, T.E., T.J. Spady, B.S. Schaffer, K.A. Gould, A.E. Kaufman, F. Shen, M.T. McLaughlin, K.L. Pennington, J.L. Meza and J.D. Shull. 2005. Genetic bases of estrogen-induced pituitary tumorigenesis: identification of genetic loci determining estrogen-induced pituitary growth in reciprocal crosses between the ACI and Copenhagen rat strains. Genetics 169:2189-2197.
6. Spady, T.J., R. Shayya, V.G. Thackray, L. Ehrensberger, J.M. Bailey and P.L. Mellon. 2004. Androgen regulates FSHb gene expression in an activin-dependent manner in immortalized gonadotropes. Molecular Endocrinology 18:925-940.
7. Pernasetti, F., T.J. Spady, S.B. Hall, S.B. Rosenberg, M.L. Givens, S. Anderson, M. Paulus, W.L. Miller and P.L. Mellon. 2003. Pituitary tumorigenesis targeted by the ovine FSHb subunit gene regulatory region in transgenic mice. Molecular and Cellular Endocrinology 203:169-183.
8. Shull, J.D., K.L. Pennington, T.M. Reindl, M.C. Snyder, T.E. Strecker, T.J. Spady, M. Tochacek and R.D. McComb. 2001. Susceptibility to estrogen-induced mammary cancer segregates as an incompletely dominant phenotype in reciprocal crosses between the ACI and Copenhagen rat strains. Endocrinology 142:5124-5130.
9. Spady, T.J., R.D. McComb and J.D. Shull. 1999. Estrogen action in the regulation of cell proliferation, cell survival, and tumorigenesis in the rat anterior pituitary gland. Endocrine 11:217-233.
10. Spady, T.J., K.L. Pennington, R.D. McComb, D.F. Birt and J.D. Shull. 1999. Estrogen induced pituitary tumor development in the ACI rat is not inhibited by dietary energy restriction. Molecular Carcinogenesis 26:239-253.
11. Spady, T.J., K.L. Pennington, R.D. McComb and J.D. Shull. 1999. Genetic bases of estrogen-induced pituitary growth in an intercross between the ACI and Copenhagen rat strains: dominant Mendelian inheritance of the ACI phenotype. Endocrinology 140:2828-2835.
12. Spady, T.J., D.M.E. Harvell, A.M. Lemus-Wilson, T.E. Strecker, K.L. Pennington, E.A. VanderWoude, D.F. Birt, R.D. McComb and J.D. Shull. 1999. Modulation of estrogen action in pituitary and mammary glands by dietary energy consumption. Journal of Nutrition 129:587S-590S.
13. Shull, J.D., D.F. Birt, R.D. McComb, T.J. Spady, K.L. Pennington and C.M. Shaw-Bruha. 1998. Estrogen induction of prolactin producing pituitary tumors in the Fischer 344 rat: modulation by dietary energy, but not protein, consumption. Molecular Carcinogenesis 23:96-105.
14. Spady, T.J., A.M. Lemus-Wilson, K.L. Pennington, D.J. Blackwood, T.M. Paschall, D.F. Birt, R.D. McComb and J.D. Shull. 1998. Dietary energy restriction abolishes development of prolactin producing pituitary tumors in Fischer 344 rats treated with 17b-estradiol. Molecular Carcinogenesis 23:86-95.
15. Spady, T.J., D.M.E. Harvell, M.C. Snyder, K.L. Pennington, R.D. McComb and J.D. Shull. 1998. Estrogen-induced tumorigenesis in the Copenhagen rat: disparate susceptibilities to development of prolactin-producing pituitary tumors and mammary carcinomas. Cancer Letters 124:95-103.
16. Shull, J.D., T.J. Spady, M.C. Snyder, S.L. Johansson and K.L. Pennington. 1997. Ovary intact, but not ovariectomized, female ACI rats treated with 17b-estradiol rapidly develop mammary carcinoma. Carcinogenesis 18:1595-1601.
1. Harvell, D.M.E., T.J. Spady, T.E. Strecker, A. Lemus-Wilson, K.L. Pennington, F. Shen, R.D. McComb and J.D. Shull. Dietary energy restriction inhibits estrogen induced pituitary tumorigenesis in a rat strain specific manner. In: Hormonal Carcinogenesis, vol.3, Springer-Verlag, 1999.
2. Tochacek, M., E.A. VanderWoude, T.J. Spady, D.M.E. Harvell, M.C. Snyder, K.L. Pennington, T.M. Reindl and J.D. Shull. The ACI rat as a genetically defined animal model for the study of estrogen induced mammary cancers. In: Hormonal Carcinogenesis, vol.3, Springer-Verlag, 1999.
Courses currently being taught at CSUSM:
- BIOL 212 - Evolution
- BIOL 327 - Biology of Human Reproduction
- BIOL 375 - Endocrinology
- BIOL 380/380L - Comparative Animal Behavior and Lab
- BIOL 411/411L - Animal Reproductive Physiology and Lab
- BIOL 563 - Seminar in Physiology
- Conservation Biology 339: CSUSM, Spring 2008.
- Behavioral Biology 430: Point Loma Nazarene College, Fall 2007
- Biology 197/Ornithology: Palomar College, Spring 2006
- General Biology 100: Palomar College, Spring & Fall 2005
- AP Biology: Steele Canyon High School, Spring 2003-2008