| Abstract: | Nerve growth factor has been isolated from submaxillary glands of mnature male mice at specific activities about a million times, and in yields of biological activity ten million times, greater than best previous results. The major improvement in the isolation is related to the separation of a highly active tosylarginine methyl esterase present in cruder preparations. The new nerve growth factor may be an entity different from the older one, although no gross differences in the qualitative aspects of their actions are apparent on superficial examination of chick ganglia influenced by them. The neurites which develop from a ganglion in the presence of nerve growth factor are of nearly equal length. The amount of nerve growth factor determines the number of neurites but not the extent of individual development. The amount of the new nerve growth factor which evokes the appearance of a hundred neurites from a single ganglion appears to be about ten molecules. Since each neurite seems to arise from a different neuron each molecule of nerve growth factor must affect several cells. This result can be rationalized by a catalytic mechanism or by indirect action of nerve growth factor through a hypothetical cell which produces a neurite evocator on contact with the molecule of nerve growth factor. |
