The ultrastrcture of wallerian degeneration in the severed optic nerve of the newt (Triturus viridescens)

Authors

  • James E. Turner,

    1. Department of Anatomy, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
    Current affiliation:
    1. Department of Anatomy, Bowman Gray School of Medicine of Wake Forest University, Winston-Salem, North Carolina 27103
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  • Marcus Singer

    1. Department of Anatomy, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
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  • Supported by grants from the American Cancer Society, the National Institutes of Health and the Multiple Sclerosis Society awarded to MS, and by an NIH Postdoctoral Fellowship (GM54013-02) awarded to JET.

Abstract

Wallerian degeneration in the severed newt's (Triturus viridescens) optic nerve is complete between the 10–14th post operative day (p.o.d.). Consequently, the newt optic nerve displays one of the most rapid degenerative responses yet reported for the central nervous system of vertebrates. In most cases it also exhibits the speed of degenerative phenomena in the vertebrate peripheral nervous system.

The degeneration of unmyelinated axons is most rapid and is completed by 2–3 p.o.d., compared to myelinated axons, most of which degenerate between 2–10 p.o.d. Myelin ring formation (vesicular transformation) is the principal form of lamellar breakdown and occurs in a highly organized manner which can be clearly staged.

The glial cell response to Wallerian degeneration is two-fold: cytoplasmic hypertrophy and myelin-lytic. Glial hypertrophy subsides by the 10–14 p.o.d. with the ingrowth of numerous regenerating nerve fibers. The myelin-lytic response accounts for most of the myelin destruction. Leukocyte-like and microglialike cells also participate in myelin breakdown but to a lesser degree.

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