Peter J. Hansen, Ph.D.
University of Florida
Department of Animal Sciences
Ph.D., University of Wisconsin
Postdoctoral, University of Florida

Dr. P.J. Hansens's Homepage

The overall research goal is to understand determinants of pregnancy success in ruminants. One major area of research is the elucidation of the cellular and molecular processes by which cellular stress disrupts embryonic function and the intercellular defense systems that embryos use to limit these effects. Of special interest is understanding the molecular basis for the thermotolerance that embryos develop as they advance through development. Focus has been on the role of heat shock proteins, antioxidants, and apoptosis in determining resistance of embryos to elevated temperature. Additional studies are being conducted to elucidate the molecular basis for breed differences in thermal resistance (i.e., cells from Brahman more resistant to heat shock than cells from Angus and Holstein). Applied studies that center largely on embryo transfer are also ongoing to develop strategies for overcoming effects of heat stress on fertility.

A second area of research concerns the importance of immunological interactions between the conceptus and mother. Much of this work focuses on progesterone since this hormone plays an important role in suppressing uterine immune function during pregnancy. It is believed progesterone acts, at least in part, by inducing secretion of other molecules that inhibit lymphocyte proliferation. In the sheep, the model species for much of the work, this molecule has been identified as a protein called ovine uterine serpin. Research goals are to document the role of ovine uterine serpin in mediating effects of progesterone and determine the specific steps in lymphocyte activation controlled by the protein. Other research is being conducted to determine the actions of various lymphocyte populations on the function of the preimplantation embryo and placenta.

Representative Publications:

de Castro e Paula LA, Hansen PJ Ceramide inhibits development and cytokinesis and induces apoptosis in preimplantation bovine embryos. Mol Reprod Dev 2007, in press.

Block J, Wrenzycki C, Niemann H, Herrmann D, Hansen PJ. Effects of insulin-like growth factor-1 on cellular and molecular characteristics of bovine blastocysts produced in vitro. Mol Reprod  Dev 2007; in press.

Brad AM, Hansen PJ. The block to apoptosis in bovine two-cell embryos involves inhibition of caspase-9 activation and caspase-mediated DNA damage. Reproduction 2007; 134: 789-797.

Jousan, F.D. and Hansen, P.J. (2007) Insulin-like growth factor-I promotes resistance of bovine preimplantation embryos to heat shock through actions independent of its anti-apoptotic actions requiring PI3K signaling. Mol. Reprod. Dev. 74, 189-196.

Block J, Hansen PJ. Interaction between season and culture with insulin-like growth factor-1 on survival of in-vitro produced embryos following transfer to lactating dairy cows. Theriogenology 2007; 67:1518-1529.

Loureiro B, Brad AM, Hansen PJ. Heat shock and tumor necrosis factor-α induce apoptosis in bovine preimplantation embryos through a caspase-9 dependent mechanism Reproduction 2007; 133:1129-1137.

Rhodes M, Brendemuhl JH, Hansen PJ. Litter characteristics of gilts artificially inseminated with TFG-β. Am J Reprod Immunol 2006; 56:153-156.

Tekin S, Padua MB, Brad AM, Rhodes ML, Hansen PJ. Expression and properties of recombinant ovine uterine serpin, Exp. Biol. Med. 2006; 231:1313-1323.

Padua MB, Tekin S, Spencer TE, Hansen PJ. Actions of progesterone on uterine immunosuppression and endometrial gland development in the uterine gland knockout (UGKO) ewe.  Mol Reprod Dev 2005; 71: 347-357.

Tekin S, Padua MB, Newton GR, Hansen PJ. Identification and cloning of caprine uterine serpin. Mol. Reprod. Dev 2005; 70, 262-270.