Regeneration_01_06 - Plasticity and Regeneration Lecture 1...

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1 Plasticity and Regeneration Lecture 1 Monday, April 10, 2006 James R. Unnerstall, Ph.D. Injuries to axons and axon bundles were once thought to result in neuronal death and irreversible losses of function. We now know that neurons have the capacity to remodel and restructure their projections and synaptic connections. A challenge for modern neuroscience is to take advantage of the innate plasticity of the neuron and its connections to promote recovery and regeneration after injury. Initiation of regenerative responses by injured neurons recapitulate many of the molecular and cellular events observed during development. As in development, successful axonal elongation and targeting is dependent upon the regulated sequential expression of appropriate signaling molecules that initiate neuronal differentiation, axonal elongation and guidance, and the accurate synaptic targeting of the neuron. The retrograde (cellular) response typifies the switching of cellular activity from neurotransmission to the activation of a development-like regenerative program. o Vacuolation. o Enlargement of the nucleus and formation of multiple nucleoli. o Displacement of the nucleus from a central to eccentric cellular location. o Dissolution of Nissle substance characterized by lightened somal staining (chromatolysis). o Retraction of dendrites and stripping of synapses. The anterograde (Wallerian degeneration) response depicts the clearance of proteins normally involved in maintaining cell-cell interactions that would inhibit neurite extension and elongation, developing an environment permissive to axonal regeneration and delivering signals to the neuron that would initiate the regenerative response. o Varicose axonal swelling with ultimate fragmentation of the axolemma. o Breakdown of the myelin sheath. o Proliferation of Schwann cells (PNS) or astrocytes (CNS). o Accumulation of fibroblasts and macrophages (PNS) or astrocytes amd microglia (CNS). o Terminal degeneration. Regeneration is initiated by: o Phagocytosis of axonal and myelin debris that act as physical and chemical inhibitors of neuritic sprouting within the endoneurial tube. o
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This note was uploaded on 05/02/2008 for the course BIOS 286 taught by Professor Murphy during the Spring '06 term at Ill. Chicago.

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Regeneration_01_06 - Plasticity and Regeneration Lecture 1...

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