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John E. Parks   -   Professor

PhD from Virginia Polytechnic Institute  
Graduate fields:      Animal Science
 
Area(s) of interest:      gamete physiology, biochemistry, cryobiology

Teaching: 

  • Raptor Biolorgy and Captive Management (summer) ANSC2140
  • Animal reproduction and development - ANSC2400
  • Animal reproduction and development lab -ANSC2410
  • Gamete physiology and fertilization - ANSC4250

Professional Organizations: 

     
     
     
     

Email: jep5@cornell.edu
Website(s): Raptor Program

Current Research:

The focus of research in this laboratory is on gamete physiology, with emphasis on understanding (1) the relationship of sperm plasma membrane characteristics to sperm function and preservation; and (2) the influence of in vitro maturation and cryopreservation procedures on cytological features of mammalian oocytes. Research in these areas is intended to provide a better understanding of gamete function and interaction, and can be used to develop more effective procedures for enhancing sperm survival in vivo and in vitro, in vitro maturation and fertilization of oocytes, in vitro embryo development, and cryopreservation of gametes and embryos. These procedures, in turn, are critical to the development and application of emerging reproductive technologies such as in vitro fertilization, cloning and genetic engineering, A brief overview of projects in each of these areas and their long-term objectives are presented below.

Effects of in vitro maturation and cryopreservation procedures on cytological features of the mammalian oocyte.

Mature mammalian oocytes require a highly specialized arrangement of their organelles for normal activation, fertilization and development. We are interested in how in vitro maturation procedures influence this organization and how the organization is perturbed by requisite steps for cryopreservation. Currently, we are using specific fluorescent probes with epifluorescence and laser scanning confocal microscopy to evaluate effects of cooling and cryoprotective agents on the spindle apparatus and cortical cytoskeleton of oocytes. In addition, we have recently completed a series of experiments using a diffusion chamber and cryomicroscope to measure biophysical properties of bovine oocytes which can be used to predict optimal cooling rates in a cryopreservation protocol. The long range objectives of these studies are to improve the developmental competence of in vitro matured oocytes and to develop effective procedures for their cryopreservation which do not exist currently.

Relationship of sperm membrane composition to fertility and cryopreservation.

The bilayer of the mammalian sperm plasma membrane is directly involved in recognition and fusion events required for fertilization, but is also labile to cryopreservation procedures. In our laboratory, we have developed a number of preparative and analytical procedures to isolate and purify the sperm plasma membrane, to modify and analyze its composition, and to evaluate the effects of these modifications on sperm function and fertility. We have used these procedures to test the hypothesis that sperm cholesterol transfer to high density lipoproteins in oviductal fluid is a prefertilization change correlated to the acquisition of fertilizing ability. We have also established that species differences in sperm membrane protein, sterol, and polar lipid composition and phase behavior are correlated to the sensitivity of sperm to cooling. In addition to a better understanding of normal membrane structure and function, these studies will help to establish how membrane lipid composition may be modified to provide more effective in vitro fertilization and cryopreservation procedures.