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

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 phenomenon 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 degneration 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 microglia-like cells also participate in myelin breakdown but to a lesser degree.

Structural assessment of rat sciatic nerve following tourniquet compression and vascular manipulation

“…Since it has been established that tourniquet application, as used in this study, results in nerve degeneration, the morphology of which conforms to that described in the literature (Nathaniel and Pease, 1963a,b;Thomas, 1964;Friede and Martinez, 1970;Turner and Singer, 1974;Friedrich and Mugnaini, 19811, it is possible to evaluate the structural differences in nerve injury produced by tourniquet compres-sion and vascular manipulation that might provide insight into the etiology of the tourniquet-induced nerve lesion. One difference resultant from the various treatments was related to the volume fraction of fibroblasts.…”

Astrocytes and regenerating axons at the proximal stump of the severed frog optic nerve

“…However, antibodies to other antigens specific to microglia were not tested. Although it has been shown that astrocytes actively participate in cleaning up the debris of retrograde and anterograde degeneration in the amphibian optic nerve (e.g., Turner and Singer 1975;Blanco et al 1993), little attention has been paid to their significance, in contrast to those studies that show that mononuclear macrophages/microglia secrete factors that directly or indirectly favor regeneration (Giulian et al 1988;David et al 1990). …”

Transitory disappearance of microglia during the regeneration of the lizard medial cortex

“…This was a long-lasting process that, in some circumstances, persisted for up to 9 months (unpublished observations). In amphibians, ectodennal cells such as ependymoglial-astrocytic cells have been found to be responsible for eliminating degenerated axons, while mesodermic cells play a minor role (Stensaas, 1983;Turner and Glaze, 1973;Turner and Singer, 1975;Zammit et al, 1993).…”