1. Departments of Ophthalmology, Anatomy and Neurobiology, University of Tennessee Health Science Center , Memphis, TN 38163 , USA
2. Research, Memphis VA Medical Center , Memphis, TN 38104 , USA
3. Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Tennessee Health Science Center , Memphis, TN 38163 , USA
4. Department of Preventive Medicine, University of Tennessee Health Science Center , Memphis, TN 38163 , USA
5. General Clinical Research Center, University of Tennessee Health Science Center , Memphis, TN 38163 , USA