Additional file 1.

Chicken embryos can be cultured ex ovo to make them easily accessible for manipulations throughout embryonic development. (a) After two days of incubation at 38.5°C the whole egg content was carefully transferred into a domed dish. After 6 days of ex ovo culturing the embryos reached HH34/E8 (b), the time point when injections and electroporations were performed in this study. The chicken embryo can be kept alive throughout embryonic development. Due to an increasing number of blood vessels in the extraembryonic membranes at later developmental stages (as seen at E18 in (c)), injections and electroporations become more difficult, however. Depending on the time of transfer the survival rate varied slightly but not significantly. (d) When embryos were transferred after two days (black dots), the survival rate of the embryos decreased more slowly during the first eight days compared to embryos that were transferred after 3 days (white dots). In both cases the survival rates stabilized for the following days (after E8). Routinely, we did not take ex ovo cultures out of the incubator before E8, the time point of injection. This resulted in a markedly higher survival rate of 62% at E8 (red dot). The age of the embryos is indicated in days and corresponding developmental stages according to Hamburger and Hamilton [36]. Bar: 1 cm.

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Baeriswyl et al. Neural Development 2008 3:7   doi:10.1186/1749-8104-3-7