A useful approach for the screening of active neural-inducing factors.

The present study suggests that the membrane-binding molecules of mesodermal cells and/or the modulated extracellular matrix (ECM) with them play an important role in induction of the central nervous system. Artificially mesodermalized ectoderm (mE) or chordamesoderm (cM) was placed on a collagen and flbronectin (CF)-coated dish for 24 h. After mechanical removal of the mesoderm sheet, competent ectoderm of early gastrulae was placed on the same spot. Many melanocytes and neuronal cells were observed after 1 week, along with many cells which reacted specifically with a neuralspecific monoclonal antibody. However, when presumptive ectoderm (pE) instead of mE or cM was used as the control, only epidermal cells with cilia were observed in the competent ectoderm, except for a few melanocytes in rare cases. The proteins synthesized and remaining on the CF substrate during placement of the mE and pE were analysed by two-dimensional polyacrylamide gel electrophoresis (PAGE) fluorography. The fluorography indicated that there were significant differences between the polypeptides spots of mE and pE.