University of Florida

Laboratory of P. J. Hansen


Peter J. Hansen, Ph.D
Distinguished Professor & L.E. "Red" Larson Professor

Research Interests

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.

Applied studies have used the knowledge gained from studies of embryo physiology to develop new management strategies for increasing dairy cattle fertility. In embryo transfer schemes, embryos are typically transferred to recipients at a stage of development at which they have acquired substantial resistance to heat shock. It has been demonstrated in the laboratory that pregnancy rate during periods of heat stress can be improved through the use of embryo transfer. Increasing fertility during heat stress has been a difficult task and embryo transfer represents the first successful approach to doing so. A second area of research is devoted to improving the practicality of using embryo transfer as a tool for enhancing fertility in dairy cattle exposed to heat stress or with low fertility.   Much of the new focus in the laboratory is on understanding how maternally derived molecules like CSF2 and IGF1 can alter the pattern of preimplantation development to enhance embryonic and fetal survivial.   A third area of research, focusing largely, on CSF2, is to delineate regulation of preimplantation development and its impact for lineage committment and fate of the conceptus during  fetal life.

A fourth area of research focuses on understanding the molecular correlates of the evolutionary development of the epitheliochorial placenta.  Work has focused on phylogenetic changes in the uterine serpin genes.

Finally, efforts are being initiated to understand the genetic control of fertility and thermotolerance. 

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University of Florida
Department of Animal Sciences
PO Box 110910
2250 Shealy Drive
Gainesville, FL 32611-0920 
Phone: (352) 392-5590
Fax: (352) 392-5595

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