An ultrastructural examination of early ventral root formation in amphibia

Nordlander, Ruth H.; Singer, Jon F.; Beck, Robert L.; Singer, Marcus

doi:10.1002/cne.901990407

Cited by 27 publications

(12 citation statements)

References 32 publications

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“…These CNS-derived cells shared some molecular similarities to neural crest -derived Schwann cells, including immunoreactivity to HNK-1 (a marker of neural crest-derived cells), but were not identical (Lunn et al 1987). Interestingly, these cells were only observed on the ventral motor root, and Lunn and others hypothesized that they may actually aid in motor axon guidance out of the CNS (Nordlander et al 1981;Lunn et al 1987). Taken together, all of these studies provide strong evidence for the existence of CNSderived ventral motor root glial cells.…”

Section: Cns-derived Perineurial Glia Form the Mature Spinal Motor Nementioning

confidence: 99%

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Perineurial Glia

Kucenas

2015

Cold Spring Harb Perspect Biol

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Section: Cns-derived Perineurial Glia Form the Mature Spinal Motor Nementioning

confidence: 99%

“…1) (Gamble and Eames 1964;Cravioto 1965;Shantha and Bourne 1968;Akert et al 1976;Nordlander et al 1981). Central to all sensory and motor nerves are axons.…”

mentioning

confidence: 99%

Perineurial Glia

Kucenas

2015

Cold Spring Harb Perspect Biol

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“…Older axons tend to lie deeper within fiber bundles. Primitive glial processes accompany growth cones exiting the ventral spinal cord during ventral root formation, and Schwann cells enfold dorsal root ganglion cell axons just as they invade the dorsal neural tube (Tennyson 1970;Nordlander et al 1981) (Fig. 3A).…”

Section: Substrata In Vivomentioning

confidence: 99%

Cellular Strategies of Axonal Pathfinding

Raper

Mason

2010

Cold Spring Harbor Perspectives in Biology

157

130

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Axons follow highly stereotyped and reproducible trajectories to their targets. In this review we address the properties of the first pioneer neurons to grow in the developing nervous system and what has been learned over the past several decades about the extracellular and cell surface substrata on which axons grow. We then discuss the types of guidance cues and their receptors that influence axon extension, what determines where cues are expressed, and how axons respond to the cues they encounter in their environment.T his article provides an overview of how growth cones respond to the cellular substrata and molecular cues they encounter as they extend through the developing nervous system. It elaborates on the primer by Kolodkin and TessierLavigne (2010) and touches on many of the topics covered in greater detail in the articles that follow. The first sections describe how axons extend in a directed manner, the substrata on which they grow, interactions between pioneer and follower axons, and growth cone behaviors in emerging tracts and at decision points. The subsequent sections discuss examples of specific cues, their distributions, how their distributions are determined, and how growth cones integrate multiple cues during pathfinding. AXONS EXTEND IN VIVO IN A DIRECTED MANNERThe first person to visualize the growing tips of axons, Ramon y Cajal, recognized that axons for the most part grow very efficiently towards their ultimate targets. He was a strong advocate for axons finding their way in response to chemotactic cues:"If one admits that neuroblasts are endowed with chemotactic properties, then one might also imagine that they are capable of ameboid movements, initiated by factors secreted from epithelial, neural, or mesodermal elements. As a result, their processes may be oriented in the direction of chemical gradients, and thus guided to the secreting cells" (Ramon y Cajal 1892; trans. English, 1995).This surprisingly modern outlook emphasizing directed guidance was temporarily derailed by the views of Weiss during the 1920s and 1930s. He first argued that functional specificity did not arise as a consequence of specific axonal connections (Weiss 1936), and later argued that nonspecific mechanical guidance cues play a predominant role in guiding axons and organizing them into nerves and tracts

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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%

“…1 (54). Subsequent axons appear to fasciculate along preexisting axons, and in the developing tracts new axons continue to be added in successive layers to the preexisting bundles (46)(47)(48)(49)(50)(51)(60)(61)(62)(63). In this way, the longitudinal pattern of the CNS axon tracts is largely determined by the pattern of the early substrate pathways, while the radial pattern within an axon tract is largely determined by the sequence of addition of axons.…”

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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An ultrastructural examination of early ventral root formation in amphibia

Cited by 27 publications

References 32 publications

Perineurial Glia

Perineurial Glia

Cellular Strategies of Axonal Pathfinding

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

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