The eyes of fish grow larger throughout their lives because stem cells produce new tissue in the retina, the light-sensitive lining at the back of the eye. Humans and other mammals lack these stem cells, so the retina can neither grow nor be repaired naturally. Studies of zebrafish show that the development of stem cells in the retina is controlled by chemicals from nerve cells nearby. This research may lead to a better understanding of degenerative diseases of the eyes and nervous system in humans and the causes of cancer, which can occur when stem cells go out of control. Pictured is a cross-section of a zebrafish eye. The ring stained green with the dark centre is the lens, with the retina appearing as a semi-circle around it. Stem cells are concentrated in the regions at either end of the red-stained arcs of nerve connecting tissue.
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.
BPoD is also available in Catalan at www.bpod.cat with translations by the University of Valencia.