edcentral.com/1471-2474/7/92/prepub Go to: chttp://www.ncbi.nlm.nih.gov/pmc/articles/PMC1693558/#> Acknowledgements This research was supported =y the Health Department of the Government of Extremadura (Socio =anitary Research SCSS0466) in Spain and the Portuguese Fundation =uganio d'Almeida. Go to: <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC16935