Axon Regeneration: Peripheral Nerve
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Axons Regeneration Post-regeneration Regenerating Clusters Thin myelination Pseudo-onion bulb Muscle pathology Fiber type groups Regenerated motor axon Also see Collateral Sprouting |
Regenerated Axon Clusters
 Toluidine blue stain |
Clusters of 2 to 12 axons
Myelin thickness
Thin for axon size
Similar for all axons in cluster
There is also axon loss
Reduced numbers of large & small myelinated axons
Büngner bands
Clusters of regenerating axons often occur with chronic changes in muscle
Partial denervation
Fiber type grouping
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Regenerating Clusters
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Pairs of axons within Schwann cell bands (Above & Below)
Also see: Pseudo-onion bulbs
Empty Schwann cell (Büngner) bands (Below)
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Regenerating Cluster: Late
All axons in cluster (Arrow) have nearly normal myelin sheath thickness
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Thinly myelinated large axons have similar degrees of myelination
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Regenerated axons
Usually thinly myelinated with short internodal length
May be distributed individually (Above), or in clusters (Below)
Thinly myelinated large axons may comprise: Most myelinated axons in a nerve
A few myelin ovoids (Arrow head) or thickly myelined axons (Arrow) remain (Below)
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Regenerated axons
Usually thinly myelinated with short internodal length
May be distributed individually (Above), or in clusters (Below)
Thinly myelinated large axons may comprise: Most myelinated axons in a nerve
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Regenerated axons
Size: Small
Distribution: Present in clusters
POST-REGENERATION
Myelin around Regenerated axons
Myelin sheaths (Below): Contain both P0 & MBP (Yellow)
Differs from myelin around normal smaller myelinated axons which contains mainly P0
 P0 green; Myelin Basic Protein (MBP) (Red); Both Yellow |
 P0 (Red); Neurofilament stained axons (Green); Both Yellow |
MBP-containing Myelin around Regenerated axons
Most MBP-containing myelin sheaths
Surround small, rather than large, axons
Are smaller than in control nerves
See: MBP myelin in control nerve, mostly associated with larger axons
 P0 (Red); Neurofilament stained axons (Green); Both Yellow |
POST-REGENERATION
Regenerated axons: Scattered (Below; Arrows) among larger axons
Myelinated axons: Reduced numbers
 Toluidine blue stain: From Chunyu Cai |
 Toluidine blue stains of plastic nerve sections |
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Post-Regeneration: Few thickly myelinated large axons
 VvG stain |
POST-REGENERATION: Reduced numbers of large axons
 Neurofilament stain |
POST-REGENERATION: Proliferation of non-myelinating Schwann cells
 NCAM stain |
Onion Bulb-like structures (Dark Arrow) & Redundant Schwann cell processes (White arrow) around thinly myelinated axons
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Pseudo Onion bulb
Thinly myelinated large axon: Surrounded by a pseudo onion bulb (Multiple Schwann cell processes)
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2/14/2024