Ugly, Good and Bad Nerve Regeneration (IMAGE) University of Utah Caption All three photos show severed nerves from nematode worms. Axons -- the wiry part of nerve cells -- had stretched from top to bottom but were cut by a laser beam. In each case, the "stump" of the severed nerve hangs downward from the top. In the left image, the nerve regeneration gene dlk-1 operates normally -- which means not very well -- so the upward-growing axon branches too much and lacks what is known as a "growth cone," so it never reaches the major nerve that runs horizontally near the top of each image. In the center photo, the regeneration gene has been over-activated, so it grows upward with a normal growth cone and not too many branches, allowing it to eventually reach the major nerve. The right image shows the severed nerve in a worm in which the regeneration gene was crippled, so there is no regeneration of the nerve axon, just stumps at top and bottom. Credit Michael Bastiani, University of Utah. Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.