Evidence for neuron-survival and neurite-promoting factors from skeletal muscle: their effects on embryonic spinal cord.

Explants of 8- and 9-day embryonic chick spinal cord were cultured for 4 days in medium which had been conditioned by skeletal muscle cells. When the conditioned medium was preincubated over polylysine substrata, it lost the ability to induce extensive neuritic outgrowth from the spinal cord. This ability was restored when the spinal cord was exposed to preincubated conditioned medium on preincubated polylysine substrata. Skeletal muscle thus appears to contain two separable components; one is a soluble factor which supports neuronal survival, and the other is an adsorbable factor which binds to appropriate substrata and promotes neuritic outgrowth.