30 April 2004
Vol 304, Issue 5671

About The Cover

Cover image expansion

COVER Electron micrograph of a cross section of a neuronal axon wrapped tightly by myelin. The thickness of myelin, a spiral extension of Schwann cell membrane, strictly depends on the axonal diameter. Transgenic mice that overexpress the growth factor neuregulin-1 on their axons cause the Schwann cell to produce excess myelin. See page 700. [Image: Eva Niksch]