The Mode of Growth of the Tail in Urodele Larvae

Development ◽  
1958 ◽  
Vol 6 (3) ◽  
pp. 466-478
Author(s):  
J. Hubertha Bijtel
Keyword(s):  
Spinal Cord ◽  
Neural Tube ◽  
Cell Mass ◽  
Vital Staining ◽  
Neural Plate ◽  
Tail Bud ◽  
Morphogenetic Movements ◽  
Separate Cell ◽  
A Cell ◽  
Axial Organs

The idea that the hinder part of the trunk together with the tail or the tail alone develops by the outgrowth of a cell mass which is in every respect indifferent has been disproved since 1928 for the Amphibia. The results of experiments with vital staining (Bijtel & Woerdeman, 1928; Bijtel, 1929, 1931) and with microsurgical methods (Bijtel, 1936) have shown that the presumptive rudiments of the tail organs (epidermis, spinal cord, muscle segments, tail-gut) are already present in the neural plate stage as more or less separate cell territories. During and immediately after the transformation of the neural plate into the neural tube, these cell territories are brought together into the tail-bud by morphogenetic movements. Holmdahl (1939 a, b, 1947) and Vogt (1939) have criticized this conception. They adhered to the view that the organs of the hinder part of the runk and of the tail (Holmdahl) or only the axial organs of the tail (Vogt, p. 127) originate from an indifferent blastema.

FGF signalling controls the timing of Pax6 activation in the neural tube

Development ◽  
2000 ◽  
Vol 127 (22) ◽  
pp. 4837-4843 ◽  
Author(s):  
N. Bertrand ◽  
F. Medevielle ◽  
F. Pituello
Keyword(s):  
Spinal Cord ◽  
Neural Tube ◽  
Inhibitory Activity ◽  
Neural Plate ◽  
Presomitic Mesoderm ◽  
Pax6 Expression ◽  
Epithelial Development ◽  
Repressive Effect ◽  
Caudal Regression ◽  
Fgf Signalling

We have recently demonstrated that Pax6 activation occurs in phase with somitogenesis in the spinal cord. Here we show that the presomitic mesoderm exerts an inhibitory activity on Pax6 expression. This repressive effect is mediated by the FGF signalling pathway. The presomitic mesoderm displays a decreasing caudorostral gradient of FGF8, and grafting FGF8-soaked beads at the level of the neural tube abolishes Pax6 activation. Conversely, when FGF signalling is disrupted, Pax6 is prematurely activated in the neural plate. We propose that the progression of Pax6 activation in the neural tube is controlled by the caudal regression of the anterior limit of FGF activity. Hence, as part of its posteriorising activity, FGF8 downregulation acts as a switch from early (posterior) to a later (anterior) state of neural epithelial development.

Neurodevelopment

2020 ◽  
pp. 91-100
Author(s):  
Karl Zilles ◽  
Nicola Palomero-Gallagher
Keyword(s):  
Spinal Cord ◽  
Nervous System ◽  
Neural Tube ◽  
Neural Plate ◽  
Adult Brain ◽  
The Central Nervous System ◽  
Specialized Region ◽  
The Brain ◽  
Rostral Part ◽  
Human Nervous System

The pre- and post-natal development of the human nervous system is briefly described, with special emphasis on the brain, particularly the cerebral and cerebellar cortices. The central nervous system originates from a specialized region of the ectoderm—the neural plate—which develops into the neural tube. The rostral part of the neural tube forms the adult brain, whereas the caudal part (behind the fifth somite) differentiates into the spinal cord. The embryonic brain has three vesicular enlargements: the forebrain, the midbrain, and the hindbrain. The histogenesis of the spinal cord, hindbrain, cerebellum, and cerebral cortex, including myelination, is discussed. The chapter closes with a description of the development of the hemispheric shape and the formation of gyri.

Retained Medullary Cord in Humans: Late Arrest of Secondary Neurulation

Neurosurgery ◽  
2011 ◽  
Vol 68 (6) ◽  
pp. 1500-1519 ◽  
Author(s):  
Dachling Pang ◽  
John Zovickian ◽  
Greg S. Moes
Keyword(s):  
Spinal Cord ◽  
Cell Mass ◽  
Tethered Cord ◽  
Underlying Mechanism ◽  
Neurological Deficits ◽  
Tail Bud ◽  
Neural Structure ◽  
Nerve Roots ◽  
Secondary Neurulation ◽  
Caudal Spinal Cord

Abstract BACKGROUND: Formation of the caudal spinal cord in vertebrates is by secondary neurulation, which begins with mesenchyme-epithelium transformation within a pluripotential blastema called the tail bud or caudal cell mass, from thence initiating an event sequence proceeding from the condensation of mesenchyme into a solid medullary cord, intrachordal lumen formation, to eventual partial degeneration of the cavitatory medullary cord until, in human and tailless mammals, only the conus and filum remain. OBJECTIVE: We describe a secondary neurulation malformation probably representing an undegenerated medullary cord that causes tethered cord symptoms. METHOD: We present 7 patients with a robust elongated neural structure continuous from the conus and extending to the dural cul-de-sac, complete with issuing nerve roots, which, except in 2 infants, produced neurological deficits by tethering. RESULTS: Intraoperative motor root and direct cord stimulation indicated that a large portion of this stout neural structure was “redundant” nonfunctional spinal cord below the true conus. Histopathology of the redundant cord resected at surgery showed a glioneuronal core with ependyma-lined lumen, nerve roots, and dorsal root ganglia, corroborating the picture of a blighted spinal cord. CONCLUSION: We propose that these redundant spinal cords are portions of the medullary cord normally destined to regress but are here retained because of late arrest of secondary neurulation before the degenerative phase. Because programmed cell death almost certainly plays a central role during degeneration, defective apoptosis may be the underlying mechanism.

Development of the central nervous system

2013 ◽  
Author(s):  
Martin E. Atkinson
Keyword(s):  
Spinal Cord ◽  
Nervous System ◽  
Neural Tube ◽  
Large Diameter ◽  
Floor Plate ◽  
Neural Plate ◽  
Ependymal Cells ◽  
High Dose ◽  
Neuronal Processes ◽  
Mantle Layer

The early development of the nervous system, the process of neurulation, has already been outlined in Chapter 8 and illustrated in Figure 8.4. To briefly recap, an area of dorsal ectoderm is induced by the underlying notochord to form the neural plate during the third week of development. The lateral edges of the neural plate rise to form the neural folds which eventually fold over and unite in the midline by the end of the fourth week to produce the neural tube. A distinct cell population on the crest of the neural folds, the neural crest, migrates from the forming neural tube to form various structures, including components of the peripheral nervous system. The closed neural tube consists of a large diameter anterior portion that will become the brain and a longer cylindrical posterior section, the future spinal cord. Initially, the neural plate is a single cell layer, but concentric layers of cells can be recognized by the time the neural tube has closed. An inner layer of ependymal cells surrounds the central spinal canal. Neuroblasts, the precursors of neurons, make up the bulk of the neural tube called the mantle layer; this will become the grey matter of the spinal cord. Neuroblasts do not extend processes until they have completed their differentiation. When the cells in a particular location are fully differentiated, the neuronal processes emerging from the neuroblasts form an outer marginal layer which ultimately becomes the white matter of the spinal cord. Figure 19.1B shows that the neural tube changes shape due to proliferation of cells in the mantle layer. This figure also indicates two midline structures in the roof and floor of the tube, known as the roof plate and floor plate. They are important in the determination of the types of neurons that develop from the mantle layer. The floor plate is induced by the expression of a protein product of a gene called sonic hedgehog (SHH) produced by the underlying notochord; the floor plate then expresses the same gene itself. Neuroblasts nearest to the floor plate receive a high dose of SHH protein and respond by differentiating into motor neurons; as seen in Figure 19.1B, these cells group together to form bilateral ventrolateral basal plates.

scholarly journals On The Existence of Regionally Specific Evocators

1952 ◽  
Vol 29 (3) ◽  
pp. 490-495
Author(s):  
C. H. WADDINGTON
Keyword(s):  
Cross Section ◽  
Neural Tube ◽  
Direct Action ◽  
Specific Effect ◽  
Neural Tissue ◽  
Neural Plate ◽  
Normal Embryo ◽  
Tail Bud ◽  
The Brain ◽  
Brain Parts

1. Pieces of the embryonic axis, taken from the anterior and posterior regions of embryos from the open neural plate to the late tail-bud stages which had been coagulated by a few seconds' immersion in water at 90°C, were inserted into flaps of gastrula ectoderm which were then cultivated in Holtfreter solution. No induction of mesoderm occurred, but neural tissue was evoked in a high percentage of cases. 2. In early stages the neural tissue usually formed a more or less chaotic tangle of tubes and rods. At later stages it assumed a variety of forms, some of which were similar to parts of the brain, and such brain-parts might be accompanied by secondary structures such as eyes, nasal pits, ears, etc. No elongated tubes resembling the trunk neural tube were seen, although certain neural vesicles may have a cross-section very like that of the neural tube. 3. The induction of recognizable brain or eye was not uncommon when anterior implants were used, but was not seen at all with posterior implants. There was no other difference between the two sets of experiments. 4. It is suggested that the appearance of such organs is not due to the direct action of a regionally specific inducing factor, but rather that all such definite forms arise by a process of self-individuation which occurs within the induced mass of neural tissue. The direction this self-individuation takes, and thus the nature of the organ finally formed, is supposed to depend on chance resemblances between the mass and shape of parts of the original chaotic mass and some part of the normal embryo. It is argued that this could account for the apparently specific effect of the anterior implants. 5. In other experiments in which mesodermal tissues are also induced (e.g. with implants of adult tissues) it is likely that these take part in the self-individuation processes and tend to direct these towards the formation of posterior organs such as trunk and tail.

Morphogenetic movements in the neural plate and neural tube: mouse

2013 ◽  
Vol 3 (1) ◽  
pp. 59-68 ◽  
Author(s):  
R'ada Massarwa ◽  
Heather J. Ray ◽  
Lee Niswander
Keyword(s):  
Neural Tube ◽  
Neural Plate ◽  
Morphogenetic Movements

Experiments on ß-mercaptoethanol as an inhibitor of neurulation movements in amphibian larvae

Development ◽  
1970 ◽  
Vol 23 (2) ◽  
pp. 463-471
Author(s):  
Carl-Olof Jacobson
Keyword(s):  
Neural Tube ◽  
Neural Plate ◽  
Neural Tube Closure ◽  
The Other ◽  
Lateral Direction ◽  
Morphogenetic Movements ◽  
Amphibian Larvae ◽  
Other Hand ◽  
Columnar Cells ◽  
Tube Closure

The morphogenetic movements of the ectoderm during neurulation include: (1) the movements taking place within the neural plate, which becomes longer and more concentrated in a medio-lateral direction (Jacobson, 1962); and (2) those found in the lateral epidermis layer which, in an epibolic way, moves in a dorsal direction, thus exerting a pushing effect on the lateral edges of the neural plate (Lewis, 1947). The former is, to a great extent, realized by a change of form of the neuroepithelium cells, from cuboidal in early neurulae to the high columnar cells observed during later phases of neural-tube closure. In the epidermis, on the other hand, the case is the reverse. The dorsal spreading of the layer is made possible by a flattening of the cells. In a series of papers, Brachet and his group have show that β-mercaptoethanol (HSCH2·CH2OH; in this article, called ME) inhibits neurulation (for review, see Brachet, 1964).

scholarly journals Hallmarks of primary neurulation are conserved in the zebrafish forebrain

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jonathan M. Werner ◽  
Maraki Y. Negesse ◽  
Dominique L. Brooks ◽  
Allyson R. Caldwell ◽  
Jafira M. Johnson ◽  
...  
Keyword(s):  
Neural Tube ◽  
Time Lapse ◽  
Neural Plate ◽  
Neural Tube Closure ◽  
Developmental Studies ◽  
Underlying Causes ◽  
The Central Nervous System ◽  
Resolution Imaging ◽  
Fold Formation ◽  
Anterior Neural Plate

AbstractPrimary neurulation is the process by which the neural tube, the central nervous system precursor, is formed from the neural plate. Incomplete neural tube closure occurs frequently, yet underlying causes remain poorly understood. Developmental studies in amniotes and amphibians have identified hingepoint and neural fold formation as key morphogenetic events and hallmarks of primary neurulation, the disruption of which causes neural tube defects. In contrast, the mode of neurulation in teleosts has remained highly debated. Teleosts are thought to have evolved a unique mode of neurulation, whereby the neural plate infolds in absence of hingepoints and neural folds, at least in the hindbrain/trunk where it has been studied. Using high-resolution imaging and time-lapse microscopy, we show here the presence of these morphological landmarks in the zebrafish anterior neural plate. These results reveal similarities between neurulation in teleosts and other vertebrates and hence the suitability of zebrafish to understand human neurulation.

The Effects of β-Mercaptoethanol on the Morphogenetic Movements of Amphibian Embryos

Development ◽  
1963 ◽  
Vol 11 (1) ◽  
pp. 155-166
Author(s):  
P. Malpoix ◽  
J. Quertier ◽  
J. Brachet
Keyword(s):  
Neural Tube ◽  
Tube Formation ◽  
Animal Pole ◽  
Morphogenetic Movements ◽  
Complete Development ◽  
Early Stages ◽  
Amphibian Embryos ◽  
Biological Specificity ◽  
Neural Tube Formation

The inhibition by β-mercaptoethanol of morphogenesis in amphibians, freshwater hydra, planarians and regenerating tadpoles, has already been reported by one of us (Brachet, 1958, 1959a, b, c). The present work provides a closer analysis of the biological specificity of j8-mercaptoethanol with regard to the different movements which produce gastrulation in amphibians: invagination, epiboly, convergent stretching and ingression. The main result, obtained with Pleurodeles, was that gastrulation is completely inhibited by M/100 β-mercaptoethanol. Lower concentrations (M/300) permit more complete development, but the resulting embryos are abnormal. β-Mercaptoethanol interferes with neural tube formation, but has less effect on the development of the notochord and the mesodermal somites. It was further noted that, when embryos are treated at very early stages (1–2 cells, young blastulae), the blastocoele seems to collapse and the ectoblast of the animal pole is deeply puckered.

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