Jeffrey E. Gray
4300 MBRB, CB 7264
Chapel Hill, NC 27599
Tel: (919) 966-2674
Fax: (919) 368-4682
Education
Doctorate of Philosophy
Curriculum in Toxicology
Research Advisor: Dr. Terry Magnuson
Date of Matriculation: 2008
Bachelor of Science in Biology
University of North Carolina at Chapel Hill, 2002
Publications and Recent Abstracts
Gray JE, Magnuson T. Reactive Oxygen Species Present During Cryopreservation Accelerates Capacitation of Mouse Sperm. Abstract: Society for the Study of Reproduction, and Triangle Consortium for Reproductive Biology (to be presented 2008).
Dissertation
“Mechanisms of reactive oxygen species toxicity in the reduction of semen quality.”
The mechanistic link between reactive oxygen species (ROS) generated during cryopreservation of sperm and the capacitation accelerating effect of cryopreservation on sperm is a popular hypothesis. The goal of this research is to investigate this hypothesis, and determine the role of ROS in the cryopreservation-induced acceleration of capacitation of mouse sperm. ROS production by sperm is an obligatory part of sperm capacitation and subsequently fertilization. ROS present in cryopreserved sperm samples after thawing has been shown to increase dramatically when compared to non-cryopreserved samples. Cryopreservation of sperm also results in acceleration of capacitation in a number of species including the mouse. Mouse sperm were cryopreserved by the Nakagata method with the addition of different concentrations of antioxidant enzymes or ROS generating enzymes to the cryoprotectant medium to decrease or increase ROS present respectively. Mouse sperm cryopreserved with high levels of antioxidant enzymes had increased numbers of uncapacitated cells, and decreased numbers of capacitated cells when compared to control as assessed by CTC fluorescent staining pattern. All concentrations of ROS generating enzymes increased acrosome reacted sperm after cryopreservation when compared to control by CTC fluorescent staining pattern. Capacitation as assessed by lysophosphatidylcholine-induced acrosome reaction was decreased in all sperm cryopreserved with antioxidant enzymes, and increased in sperm cryopreserved with higher concentrations of ROS generating enzymes. None of the enzymatic treatments used significantly affected sperm post-thaw motility. In vitro fertilization ability of frozen-thawed sperm negatively correlated with acrosome reacted cells assessed by CTC fluorescent staining pattern (-0.62075, p= 0.0012), and capacitation as assessed by lysophosphatidylcholine-induced acrosome reaction. (-0.41369, p= 0.0445). ROS present in each frozen/thawed sample was measured by luminol-mediated chemiluminescence. This research shows ROS present during the freezing and thawing processes of cryopreservation accelerates capacitation of mouse sperm, and that acrosome reacted cells resultant from this process are detrimental to the sperm fertilization ability in vitro. Understanding the mechanism by which cryopreservation induces acceleration of capacitation may explain the efficacy of empirical sperm cryopreservation techniques utilizing antioxidants, and provide insight on how to improve and evaluate these techniques.