1Unidad de Investigación Médica en Inmunoquı́mica, 1er piso Hospital de Especialidades, Centro Médico National Siglo XXI, Instituto Mexicano del Seguro Social (IMSS), P.O. Box A-047, C.P. 06703 México D.F., México
2Intensive Care Unit, Specialties Hospital, National Medical Centre S. XXI, Mexican Institute for Social Security (IMSS), Mexico City, Mexico
3Clinical Laboratory, Specialties Hospital, National Medical Centre S. XXI, Mexican Institute for Social Security (IMSS), Mexico City, Mexico
4Medical Research Unit on Pharmacology, Specialties Hospital, National Medical Centre S. XXI, Mexican Institute for Social Security (IMSS), Mexico City, Mexico