Morphology of the regenerated spinal cord in the lizard, <i>Anolis carolinensis</i>

Simpson, Sidney B.

doi:10.1002/cne.901340207

Cited by 105 publications

(67 citation statements)

References 14 publications

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“…In contrast to the lack of spinal cord regeneration evident in mammals, some anamniote animals, such as fish and some amphibians, regenerate damaged nerves and recover locomotor ability in a remarkably short period following SCI (Simpson, 1968;Bernstein and Gelderd, 1970;Zottoli et al, 1994;Becker et al, 1997). This difference in regenerative capacity occurs even though similar cell types are present in the spinal cords of species both capable and incapable of regeneration (Naujoks-Manteuffel and Roth, 1989;Bastmeyer et al, 1993).…”

Section: Introductionmentioning

confidence: 97%

Fgf-Dependent Glial Cell Bridges Facilitate Spinal Cord Regeneration in Zebrafish

et al. 2012

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Adult zebrafish show a remarkable capacity to regenerate their spinal column after injury, an ability that stands in stark contrast to the limited repair that occurs within the mammalian CNS post-injury. The reasons for this interspecies difference in regenerative capacity remain unclear. Here we demonstrate a novel role for Fgf signaling during glial cell morphogenesis in promoting axonal regeneration after spinal cord injury. Zebrafish glia are induced by Fgf signaling, to form an elongated bipolar morphology that forms a bridge between the two sides of the resected spinal cord, over which regenerating axons actively migrate. Loss of Fgf function inhibits formation of this "glial bridge" and prevents axon regeneration. Despite the poor potential for mammalian axonal regeneration, primate astrocytes activated by Fgf signaling adopt a similar morphology to that induced in zebrafish glia. This suggests that differential Fgf regulation, rather than intrinsic cell differences, underlie the distinct responses of mammalian and zebrafish glia to injury.

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Section: Introductionmentioning

confidence: 97%

Fgf-Dependent Glial Cell Bridges Facilitate Spinal Cord Regeneration in Zebrafish

et al. 2012

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“…Our group has focused on the process of central nervous system (CNS) reconstruction within the tail regenerate after tail excision. We have examined this phenomenon in the lizard (Simpson, 1968;Egar et al, 1970) and newt (Egar and Singer, 1972;Nordlander and Singer, 1978;Singer et al, 1979;Egar and Singer, 1981). In particular, we have concentrated on patterns of longitudinal tract development.…”

Section: Introductionmentioning

confidence: 99%

Early stages of spinal ganglion formation during tail regeneration in the newt, Notophthalmus viridescens

et al. 1988

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Stages in the development of sensory ganglia in the regenerating newt tail after amputation are described by taking advantage of the rostrocaudal developmental gradient of the regenerating tail. A series of ganglia, beginning at the tip of the regenerate and progressing rostrally, were examined. Eight-week regenerates were used because they showed the most complete array of stages. The first recognizable ganglia appear as small clusters of cells sitting dorsally on the already established ventral roots. The cluster of ganglionic cells steadily expands with the addition of many new cells. Signs of cell differentiation within the ganglion precede the formation of the dorsal root rudiment, which assumes several different configurations but most commonly enters the cord close to the ventral root. Our material suggests that ganglion precursor cells originate in the ventral region of the developing spinal cord and migrate out of the cord by travelling along the ventral root until, at a suitable distance from the cord, they halt, proliferate, and eventually differentiate. In the regenerate, we saw no evidence of neural crest cells--such as those that give rise to ganglia in the trunk region during development--forming at the dorsal region of the regenerated neural tube. Nor was there any morphological evidence of mesenchymal contribution to the ganglion cell clusters.

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“…Axon guidance pathways appear to be important factors in organizing the overall layout of axon tracts of projection neurons, such as the neurons of the two major cortical commissures-the corpus callosum and the anterior commissure (38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54) …”

Section: Substrate Pathwaysmentioning

confidence: 99%

Ontophyletics of the nervous system: development of the corpus callosum and evolution of axon tracts.

Katz¹,

Lasek²,

Silver³

1983

Proc. Natl. Acad. Sci. U.S.A.

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The evolution of nervous systems has included significant changes in the axon tracts of the central nervous system. These evolutionary changes required changes in axonal growth in embryos. During development, many axons reach their targets by following guidance cues that are organized as pathways in the embryonic substrate, and the overall pattern of the major axon tracts in the adult can be traced back to the fundamental pattern of such substrate pathways. Embryological and comparative anatomical studies suggest that most axon tracts, such as the anterior commissure, have evolved by the modified use of preexisting substrate pathways. On the other hand, recent developmental studies suggest that a few entirely new substrate pathways have arisen during evolution; these apparently provided opportunities for the formation of completely new axon tracts. The corpus callosum, which is found only in placental mammals, may be such a truly new axon tract. We propose that the evolution of the corpus callosum is founded on the emergence of a new preaxonal substrate pathway, the "glial sling," which bridges the two halves of the embryonic forebrain only in placental mammals.Increases in the number of central nervous system (CNS) neurons and in the complexity of the synaptic neuropil characterize the vertebrate phylogeny (1, 2). These increases are usually manifest as enlargements of specific CNS areas such as the cerebellum, the tectum, and the cerebrum. Local enlargements can be attributed to focal increases in the dominant class of vertebrate neurons-local circuit neurons-neurons with axons that extend only short distances in the CNS before synapsing (1).Local areas of the CNS are connected by another important class of neurons-projection neurons-which send their axons along a few long stereotyped routes to target areas far from their cell bodies. The white matter of the vertebrate CNS is composed largely of axon tracts of projection neurons, and many of the same major axon tracts can be identified throughout the vertebrates. Although the overall pattern of these major tracts appears to have been conserved during evolution (2-8), there are some significant variations. Frequently, the compactness of particular tracts varies, as in the spinal lemniscal tracts (2, 9-11). In some cases, the particular stereotyped route taken by homologous axons varies-e.g., the stereotyped routes of the corticospinal tracts differ among most primates, ungulates, rodents, and marsupials (12-14). Moreover, a few major vertebrate axon tracts have appeared with no apparent precursors. The most dramatic example is the (dorsal) corpus callosum, which is found only in placental mammals (15,16).The corpus callosum is a large interhemispheric commissure, and most axons of the corpus callosum interconnect homotopic neocortical areas (17)(18)(19)(20)(21)(22). for exceptions to this general rule.) Monotremes and marsupials have no dorsal corpus callosum (2,16,(26)(27)(28). Among the placental mammals, the corpus callosum generally increases as t...

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Morphology of the regenerated spinal cord in the lizard, Anolis carolinensis

Cited by 105 publications

References 14 publications

Fgf-Dependent Glial Cell Bridges Facilitate Spinal Cord Regeneration in Zebrafish

Fgf-Dependent Glial Cell Bridges Facilitate Spinal Cord Regeneration in Zebrafish

Early stages of spinal ganglion formation during tail regeneration in the newt, Notophthalmus viridescens

Ontophyletics of the nervous system: development of the corpus callosum and evolution of axon tracts.

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