Nervous System

Brain - Axonopathy

    Narrative
    Spinal cord axonopathy in a male F344/N rat from a subchronic study. The arrow in this toluidine blue-stained section indicates the subtle pallor of the dorsal funiculus in which axonopathy is present.
    Toluidine blue-stained section in a male F344/N rat from a subchronic study. Note that the axons (arrows) are distended but still surrounded by myelin sheaths.
    Section in a male B6C3F1 mouse from a subchronic study. Note that some axons are swollen (arrows) and that the tissue is vacuolated from loss of axons and their myelin sheaths.
    In this higher magnification image in a female Sprague-Dawley rat from a chronic study, the swollen and degenerate axons devoid of myelin sheath (arrows) are more apparent. Figure
    Section in a female F344/N rat from a subchronic study. The arrow indicates a large swollen axon, and the arrowhead locates the presence of a degenerate macrophage occupying the space of a former axon.
    Axonal spheroids (arrows) in brain parenchyma in a male B6C3F1 mouse from a subchronic study.
    This longitudinal section of nerve in a female B6C3F1 mouse from a subchronic study shows an example of axonal fragmentation referred to as Wallerian-type degeneration (arrow).
    Increased cellularity created by proliferating Schwann cells (arrows) as a response to axonopathy in a male B6C3F1 mouse from a subchronic study. These linear arrays are known as bands of Büngner.

    Authors 

    Peter Little, DVM, MS, PhD, DACVP
    Neuropathology Consultant
    Experimental Pathology Laboratories, Inc.  
    Research Triangle Park, NC

    Deepa B. Rao, BVSc, MS, PhD, DABT, DACVP
    NTP Pathologist (Contractor)
    Integrated Laboratory Systems, Inc.
    Research Triangle Park, NC

    Reviewers

    James P. Morrison, DVM, DACVP
    Scientific Director
    Charles River Laboratories, Pathology Associates
    Research Triangle Park, NC

    Robert C. Sills, DVM, PhD, FIATP
    Chief, Cellular and Molecular Pathology Branch
    National Toxicology Program
    National Institute of Environmental Health Sciences
    Research Triangle Park, NC