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Never too Late to Boogie:
Nerve Cells Still Active in "Mature" Brain
Films that offer the mind a chance to watch the brain at work will be shown during a 14 February panel discussion at the AAAS Annual Meeting titled, "How and Why Brain Cells Boogie: Motility in Neural Development."
Recent advances in high-resolution microscopy and image analysis have made it possible for researchers to "look under the hood of the molecular engine," to view nerve cells and the interaction among components of their basic cytoskeletal structures and among nerve cells in general. Study of the images has led to some unexpected findings, particularly regarding the adult brain, according to Shelley Halpain, associate professor in the Department of Cell Biology at The Scripps Research Institute in La Jolla, CA.
"We have found that the synapses themselves are motile and undergo metamorphoses that we consider to be very surprising in a mature person," Halpain said. "The idea that the mature brain is plastic is quite new. If we could find out more about this capacity for restructuring and reorganization, we could probably harness that information to promote recovery from diseases that involve synaptic abnormalities." Halpain added that the brain cells of children and young adults are considerably more active than those of older adults.
Neurons the brain has billions of them first migrate from their place of birth to appropriate locations within the brain. Each neuron then grows a long axon, which transmits messages from the neuron to other nerve cells, using chemical messengers called neurotransmitters. Dendrites, which also extend out from the new neuron, are charged with bringing messages to the neuron from other nerve cells. The tentacle-like axons and dendrites form synapses with other axons and dendrites, eventually "wiring up" the brain.
Halpain and two colleagues will discuss the role of "motility," or movement, in the development of neurons, as well as the way in which the nerve cells' "signaling machinery" attracts or repulses the cells' growth cones, which ultimately decide the direction in which the neuron will grow. This may someday have important applications for addressing conditions such as spinal injury, as scar tissue seems to emit chemical signals that repel neurons as their axons approach damaged tissue.
"We can now watch the underlying molecular machinery at work," said Paul Forscher, an associate professor of molecular, cellular and developmental biology at Yale University. "You can watch the growth cone make a guidance decision make a turn, for example."
14 February 2003