Characterization of Chick Gizzard Extract That Promotes Neurite Outgrowth in Cultured Ciliary Neurons

Abstract

Chicken gizzard extract contains a macromolecule(s) that promotes the neurite outgrowth of dissociated neurons from the ciliary ganglia (CG) of chick embryos. The factor in gizzard extract was partially purified and estimated to be .apprx. 12S (MW 200,000-300,000) on sucrose density gradient centrifugation. The neurite outgrowth of CG neurons by the factor strictly depends on the embryonal age. The maximal neurite outgrowth was observed when CG neurons were dissociated from the embryos younger than 10 days. After that time the response of CG neurons to the factor rapidly declined and was almost lost at day 14. The amount of factor in the gizzard began to increase rapidly from 12-day-old embryo and reached the maximal level at day 16, and, thereafter, a fairly steady level was maintained. When CG neurons were cocultured with rat myotubes, the ratio of muscle cells with synaptic responses (miniature end-plate potentials) was significantly higher in the presence of the gizzard factor than in its absence. This factor may act as an external signal on CG neurons to form synaptic connnections in vivo.