Neural Degeneration

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Science  22 Apr 2005:
Vol. 308, Issue 5721, pp. 469
DOI: 10.1126/science.308.5721.469a

When the spinal cord is injured, degeneration of the nerve fibers, or axons, is not instantaneous but rather is believed to occur in several stages over a period of hours. In principle, this delay creates a window of opportunity for the administration of therapies to reduce the extent of irreversible damage. The development of such therapies, however, requires a better understanding of how mammalian axons respond to injury.

Using time-lapse microscopic imaging of living mice expressing green fluorescent protein (GFP) in individual axons, Kerschensteiner et al.visualized the axonal response to traumatic injury. Beginning about 20 min after trauma, axons were found to die back at both proximal and distal ends by a rapid and previously uncharacterized fragmentation process termed “acute axonal degeneration.” This was followed by slow axonal retraction and ultimately by fragmentation of the axon's distal ends via the well-known Wallerian degeneration. Although many axons mounted a regenerative response within 24 hours of injury, this response was futile because the axons did not grow back to their original targets. This mouse model will likely prove useful for the testing of new therapies for spinal cord injury. — PAK

Nat. Med. 10.1038/nm1229 (2005).

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