Ugly, Good and Bad Nerve Regeneration (IMAGE)
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.
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