Magazine article Science News

Molecules That Guide or Nourish Nerves

Magazine article Science News

Molecules That Guide or Nourish Nerves

Article excerpt

In every developing organism, nerve cells must thread their way through a jumble of other cells to particular targets, be they muscles, sense organs, or other nerve cells. Two reports now shed light on molecules that may guide or promote the survival of these connections.

In one experiment, geneticists determined that a particular docking site for nerve growth factors plays a role in the success of some nerve cell connections. In the other experiment, neurohiologists learned that nerve cells grow toward a chemical messenger called acetylcholine.

As a nerve cell develops, it sprouts axons and dendrites, appendages that eventually link it with other nerve cells. A specialized nerve growth cone makes up each appendage's leading edge.

There, cellular fingers continually extend and retract, explains James Q. Zheng of Columbia University. Like insect antennae, these fingers sense the chemicals around them, some of which may define a pathway for the nerve.

Zheng and his colleagues used a very fine needle to squirt acetychotine into one side of a dish containing a sprouting nerve cell taken from a frog. As the acetylcholine diffused away from the needle's tip, it created a concentration gradient that was strongest near the tip.

Two hours later, the nerve cell's axon had turned and grown about 25 micrometers toward the tip, Zheng and his colleagues report in the March 10 NATURE.

The researchers suspected that calcium was involved somehow. They observed that in a calcium free solution the axons grew but did not turn. …

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