Muscle Fiber Type Grouping

  Associated with & Caused by: Axon regeneration or Axon sprouting


ATPase pH 9.4 stain

ATPase pH 9.4 stain

ATPase pH 9.4 stain

Normal: "Checkerboard"
pattern of types I (Light)
& II (Dark) fibers.
Denervation + Reinnervation, Chronic
  Type I & Type II muscle fibers: Clustered in groups.
  Type II fibers in this biopsy are mostly type IIB (ATPase pH 4.6 stain, below right).

ATPase pH 4.3 stain

ATPase pH 4.6 stain

Fiber Type Grouping: Staining Patterns

ATPase pH 9.4 stain
Fiber Type Groups: Denervation & Reinnervation
Clusters of Type I & II fibers
No small muscle fibers or ongoing denervation

NADH stain

ATPase pH 4.3 stain

Fiber type grouping: Incomplete fiber type switching (Varied fiber types in a single group)

ATPase pH 4.3 stain

Fiber type grouping with incomplete type switching: 2C fibers in clusters of grouped muscle fibers

ATPase pH 4.3 stain

Axon Loss

Toluidine blue stained plastic section

Nerve: Chronic Inactive Axon Loss (Denervation)

Also see: Ongoing or Active Denervation

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