Journal ArticleDOI
Transient pioneer neurons are essential for formation of an embryonic peripheral nerve.
Monika Klose,David R. Bentley +1 more
TLDR
By crossing a segment boundary early in embryogenesis, the pioneers circumvent an incompatibility between differentiated segment boundary cells and growth cone migration and may resolve similar problems in many systems.Abstract:
In developing nervous systems, many peripheral and central pathways are established by early arising populations of pioneer neurons. The growth cones of these pioneer neurons can migrate while embryonic distances are short and while intervening tissue is relatively uncomplicated. Are these pioneers necessary? In grasshopper embryos, a pair of pioneer neurons arise at the tips of limb buds and extend axons through the limb to the central nervous system. Growth cones of later arising sensory neurons migrate along the pioneer axons. After ingrowth of sensory axons, the pioneer neurons die. If the pioneer neurons are prevented from differentiating by heat shock, then the sensory growth cones that would have migrated along them are blocked and fail to reach the central nervous system. Thus, the pioneer axons are necessary for successful migration of these sensory growth cones. By crossing a segment boundary early in embryogenesis, the pioneers circumvent an incompatibility between differentiated segment boundary cells and growth cone migration. Pioneer neurons may resolve similar problems in many systems.read more
Citations
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sources and effects of ionizing radiation
TL;DR: This annex is aimed at providing a sound basis for conclusions regarding the number of significant radiation accidents that have occurred, the corresponding levels of radiation exposures and numbers of deaths and injuries, and the general trends for various practices, in the context of the Committee's overall evaluations of the levels and effects of exposure to ionizing radiation.
Journal ArticleDOI
The Molecular Biology of Axon Guidance
TL;DR: Evidence is accumulating that these mechanisms act simultaneously and in a coordinated manner to direct pathfinding and that they are mediated by mechanistically and evolutionarily conserved ligand-receptor systems.
Journal ArticleDOI
Developmental mechanisms that generate precise patterns of neuronal connectivity
Corey S. Goodman,Carla J. Shatz +1 more
TL;DR: The range of activityindependent and activity-dependent mechanisms that generate precision of neuronal connections is considered-the connections between motoneurons and muscles and between the retina and higher visual centers--to highlight the extent to which different parts of the nervous system use the same mechanisms but in different proportions to achieve the final specificity.
Journal ArticleDOI
The subplate, a transient neocortical structure: its role in the development of connections between thalamus and cortex
TL;DR: A growing body of evidence suggests that the formation of connections between thalamus and cortex requires the presence of a specific and transient cell type, subplate neurons, which are present early in development, but by adulthood the majority have disappeared.
References
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Journal ArticleDOI
Antibodies to horseradish peroxidase as specific neuronal markers in Drosophila and in grasshopper embryos
Lily Yeh Jan,Yuh Nung Jan +1 more
TL;DR: It is shown that mutations affecting segmentation in Drosophila affect the organization of the embryonic nervous system and the anti-HRPeroxase antibodies are used to show this.
Journal ArticleDOI
Subplate neurons pioneer the first axon pathway from the cerebral cortex
TL;DR: The existence of a similar kind of neuron in the developing mammalian telencephalon is described, raising the possibility that the early axonal scaffold formed by subplate cells may prove essential for the establishment of permanent subcortical projections.
Journal ArticleDOI
Cell recognition during neuronal development.
Corey S. Goodman,Michael J. Bastiani,Chris Q. Doe,Sascha du Lac,Stephen L. Helfand,John Y. Kuwada,John B. Thomas +6 more
TL;DR: It is suggested that early in development cell lineage and cell interactions lead to the differential expression of cell recognition molecules on the surfaces of small subsets of embryonic neurons whose axons selectively fasciculate with one another.
Journal ArticleDOI
Pioneer neurones in an insect embryo.
TL;DR: Observations on the embryonic nervous system of Locusta migratoria are reported which show that the first pathways between the epidermis and the central ganglia are formed by axons which grow inwards from peripheral neurones which differentiate early in embryonic life.
Journal ArticleDOI
Cell recognition by neuronal growth cones in a simple vertebrate embryo
TL;DR: Laser ablation experiments support the hypothesis that early growth cones that pioneer specific spinal tracts appear to recognize cues on subsets of longitudinally arrayed neuroepithelial cells and demonstrate that later growth cone that selectively fasciculate in these spinal tracts seem to recognizing cues on specific subset of axons.