Attachment of PC-12 cells and neuronal explants to culture dishes. PC-12 cells attached better to plastic surfaces that were pretreated with anchoring-promoting factors, such as PEI (panel A), collagen (panel B), or PDL (panel C), as compared to the untreated plastic surface control (panel D), which contained cells in clusters and very loosely attached to the substratum (pictures were taken midway between center and edge of the plate). PEI coating resulted in a homogeneous distribution of cells firmly attached to the dish substratum (panel A). PEI promotes attachment to culture dishes of retinal explants from zebrafish (panel E). This attachment factor was supportive of neurite extension in retinal explants primed for axonal growth by a pre-conditioning lesion to the optic nerve (panel F). The bar in the photomicrographs corresponds to 25 μm in panels A-D, 50 μm in panel E, and 100 μm in panel F.