The NT-3 levels of secreted plasmid in conditioned medium from transfected OEG cultures were determined by ELISA, as described by Woodhall et al. The medium was refreshed 3 d post-trans-fection and the cultures were left for 24 h for determination of the production per day.
The Emax immunoassay system (Promega) was used to assess the NT-3 levels in OEG conditioned medium. The amount of NT-3 secreted from 1×105 transfected cells per day was recorded.