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Denervated Schwann Cells

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Büngner bands

• Bands of interdigitating Schwann cell processes
  • Surrounded by basal lamina (Schwann tube)
  • Size: > 3 μm
  • Schwann cells: Molecular markers
    • P0 protein + NCAM: Co-expressed in same Schwann cell processess
    • Neurofilament protein (Axon): Not present
  • No associated axons
  • Basement membrane: Irregular
• Due to
  • Loss of Myelinated axons
  • Proliferation of associated Schwann cells
• Axon regeneration: Often occurs within Büngner bands
• Course with no axon regeneration
  • Schwann cells
    • Atrophy
    • May develop characteristics of perineurial cells
      • Pinocytotic vesicles
      • Divide endoneurium into microfascicles
    • Denervated: Also present in onion bulbs
    • Difference from non-myelinating Schwann cells: Contain P₀
  • Collagen accumulates
• Collagen fibers
  • May surround Schwann cell tube
  • Thinner (23 to 30 μM than normal endoneurial collagen
• Some nerves with axon loss: Do not develop Büngner bands

Collagen Pockets

• Due to loss of: Unmyelinated axons
• Non-myelinating Schwann cells (Remak cells) surround: Collagen fibrils
• Proliferation of Remak cells: Response to degeneration of myelinated axons

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Büngner Bands

Toluidine blue

Bands of Büngner: Collections of processes from Denervated Schwann Cells (Black Arrow)

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From: R Schmidt

Bands of Büngner: Collections of processes from Denervated Schwann Cells
  Schwann cell processes are contained within a layer of basal lamina (Arrows)

Schwann cell processes: Multiple collections

Schwann cell processes: Within layer of basal lamina

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Denervated Schwann cells: Have normal Basal lamina outside surface membrane

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Büngner Band Cells: Schwann cells with No associated axon

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Small & Large Axon loss: Severe

Neurofilaments (Green); P0 (Red)

Büngner Band cells stain for P0 protein (Red; In absence of myelin) & NCAM
Axon loss, Severe: Little staining for large or small axons (Green)

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Büngner bands
  p0 & NCAM co-localize in Schwann cells with no associated axons (Yellow)
  Small NCAM positive cells (Green) are associuated with remaining small, unmyelinated axons
  Normal: Many p0 positive myelin sheaths with no NCAM
  In nerves with axon loss but no Büngner bands, remaining denervated Schwann cells express NCAM but not P0.

NCAM (Green) & p0 (Red) stains

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Loss of all myelinated axons

VvG stain

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Loss of all axons

Neurofilament + Gomori stain

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Non-Myelinating Schwann cells (NCAM stain): Remain present all through endoneurium

NCAM + Gomori

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Collagen pockets

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4/20/2021