1. UNC Kidney Center, 7024 Burnett-Womack CB # 7155, Chapel Hill, NC 27599-7155, USA
2. Centro de Investigaciones e Intervenciones en Salud, León, Nicaragua
3. Centro de Salud Torre Ramona, Unidad Docente de Medicina Familiar y Comunitaria, Sector II, Zaragoza, España
4. Duke University, Durham, NC
5. Department of Physiological Sciences, UNAN-León, Nicaragua
6. Department of Medicine, Vanderbilt University, Nashville, TN, USA
7. Department of Medicine, UNC Chapel Hill, NC, USA