A protein called nerve-growth factor is important for the growth of some parts of the mammalian nervous system. If too much of the nerve-growth factor is present, growth of sympathetic nerve fibres is extensive and aberrant. If the nerve-growth factor is eliminated from the body—by injection of an…

, nerve growth factor) that is essential for the survival of the neuron synapsing with it. Physical guidance cues are involved in contact guidance, or the migration of immature neurons along a scaffold of glial fibers.

…the tumour that they named nerve-growth factor (NGF). Levi-Montalcini further showed that the tumour caused similar cell growth in a nerve-tissue culture kept alive in the laboratory, and Stanley Cohen, who by then had joined her at Washington University, was able to isolate the NGF from the tumour. NGF was…