Histological features of neural induction in Xenopus laevis

Development ◽  
1971 ◽  
Vol 26 (3) ◽  
pp. 543-570
Author(s):  
D. Tarin
Keyword(s):  
Xenopus Laevis ◽  
Neural Induction ◽  
Neural Plate ◽  
Paraxial Mesoderm ◽  
Intestinal Tube ◽  
Spinal Cord Regions ◽  
The Central Nervous System ◽  
Dorsal Ectoderm ◽  
Two Stages ◽  
The Brain

It was first established by grafting experiments that neural induction occurs in Xenopus laevis and that it is the mesoderm in the dorsal lip of the blastopore which normally exercises this function. The subsequent histological work provided the following information: At stage 10½ mesodermal invagination was already well under way, in advance of the formation of the archenteric cavity. This confirms the earlier observations of Nieuwkoop & Florschutz(1950). The first evidence of neural induction, thickening of the mid-dorsal ectoderm combined with the development of an inner tier of columnar cells, occurred at stage 11½. By stage 12 there was generalized thickening of the dorsal ectoderm and between stage 12½ and 13 the brain and spinal cord regions of the neural plate became distinguishable. The dorsal mesoderm segregated into notochord rudiment and two lateral masses at stage 13 and the latter further subdivided into paraxial mesoderm and lateral plates by stage 14. The margins of the neural plate were clearly distinguished from presumptive epidermis by stage 15 and the median neural groove was also well marked. In the next two stages the folding of the neural plate in the line of this groove proceeded rapidly. The dorsoventral enlargement of the somites and the relative shrinkage of the notochord were considered to contribute to the mechanism of neurulation. Regionalization of the brain into prosencephalon, mesencephalon and rhombencephalon was in progress at stages 18 and 19. These results indicate that induction consists of an initial activation of dorsal ectoderm (generalized thickening) followed by gradual transformation of the neural plate to form the different parts of the central nervous system (regionalization). Intercellular metachromatic material was noted in various parts of the embryo. This was most plentiful between stage 10½ and stage 13 and thereafter gradually decreased. It was the only feature which persisted long enough to represent a possible inductive agent. At all stages the archenteron was lined with a continuous layer of endoderm. This indicates that the mode of formation of the gastro-intestinal tube in Xenopus is different to that in urodeles. It further implies that the mesoderm is not present on the blastular surface prior to gastrulation but lies in deeper layers.

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.

Activation of Pax6 depends on somitogenesis in the chick embryo cervical spinal cord

Development ◽  
1999 ◽  
Vol 126 (3) ◽  
pp. 587-596 ◽  
Author(s):  
F. Pituello ◽  
F. Medevielle ◽  
F. Foulquier ◽  
A.M. Duprat
Keyword(s):  
Spinal Cord ◽  
Cervical Spinal Cord ◽  
Homeobox Gene ◽  
Neural Plate ◽  
Paraxial Mesoderm ◽  
Presomitic Mesoderm ◽  
Pax6 Expression ◽  
The Central Nervous System ◽  
Initial Activation ◽  
Host Embryo

Pax6 is a paired-type homeobox gene expressed in discrete regions of the central nervous system. In the spinal cord of 7- to 10-somite-stage chicken embryos, Pax6 is not detected within the caudal neural plate, but is progressively upregulated in the neuroepithelium neighbouring each newly formed somite. In the present study, we accumulate data suggesting that this initial activation of Pax6 is controlled via the paraxial mesoderm in correlation with somitogenesis. First, we observed that high levels of Pax6 expression occur independently of the presence of SHH-expressing cells when neural plates are maintained in culture in the presence of paraxial mesoderm. Second, grafting a somite caudally under a neural plate that has not yet expressed the gene induces a premature activation of Pax6. Furthermore, after the graft of a somite, a period of incubation corresponding to the individualization of a new somite in the host embryo produces an appreciable activation of Pax6. Conversely, Pax6 expression is delayed under conditions where somitogenesis is retarded, i.e., when the rostral part of the presomitic mesoderm is replaced by the same tissue isolated more caudally. Finally, Pax6 transcripts disappear from the neural tube when a somite is replaced by presomitic mesoderm, suggesting that the somite is also involved in the maintenance of Pax6 expression in the developing spinal cord. All together these observations lead to the proposal that Pax6 activation is triggered by the paraxial mesoderm in phase with somitogenesis in the cervical spinal cord.

Differential gene expression in the anterior neural plate during gastrulation of Xenopus laevis

Development ◽  
1989 ◽  
Vol 105 (4) ◽  
pp. 779-786 ◽  
Author(s):  
M. Jamrich ◽  
S. Sato
Keyword(s):  
Gene Expression ◽  
Xenopus Laevis ◽  
Neural Induction ◽  
Neural Plate ◽  
Cement Gland ◽  
Cdna Clones ◽  
Differential Gene ◽  
Anteroposterior Polarity ◽  
Xenopus Laevis Embryos ◽  
Anterior Neural Plate

We have isolated three cDNA clones that are preferentially expressed in the cement gland of early Xenopus laevis embryos. These clones were used to study processes involved in the induction of this secretory organ. Results obtained show that the induction of this gland coincides with the process of neural induction. Genes specific for the cement gland are expressed very early in the anterior neural plate of stage-12 embryos. This suggests that the anteroposterior polarity of the neural plate is already established during gastrulation. At later stages of development, two of the three genes have secondary sites of expression. The expression of these genes can be induced in isolated animal caps by incubation in 10 mM-NH4Cl, a treatment that is known to induce cement glands.

scholarly journals XASH genes promote neurogenesis in Xenopus embryos

Development ◽  
1994 ◽  
Vol 120 (12) ◽  
pp. 3649-3655 ◽  
Author(s):  
B. Ferreiro ◽  
C. Kintner ◽  
K. Zimmerman ◽  
D. Anderson ◽  
W.A. Harris
Keyword(s):  
Neural Development ◽  
Neural Induction ◽  
Neural Tissue ◽  
Neural Plate ◽  
Binding Partner ◽  
Helix Loop Helix ◽  
Neural Genes ◽  
Dorsal Ectoderm ◽  
Bhlh Transcription Factors ◽  
Beta Tubulin Gene

Neural development in Drosophila is promoted by a family of basic helix-loop-helix (bHLH) transcription factors encoded within the Achaete Scute-Complex (AS-C). XASH-3, a Xenopus homolog of the Drosophila AS-C genes, is expressed during neural induction within a portion of the dorsal ectoderm that gives rise to the neural plate and tube. Here, we show that XASH-3, when expressed with the promiscuous binding partner XE12, specifically activates the expression of neural genes in naive ectoderm, suggesting that XASH-3 promotes neural development. Moreover, XASH-3/XE12 RNA injections into embryos lead to hypertrophy of the neural tube. Interestingly, XASH-3 misexpression does not lead to the formation of ectopic neural tissue in ventral regions, suggesting that the domain of XASH proneural function is restricted in the embryo. In contrast to the neural inducer noggin, which permanently activates the NCAM gene, the activation of neural genes by XASH-3/XE12 is not stable in naive ectoderm, yet XASH-3/XE12 powerfully and stably activates NCAM, Neurofilament and type III beta-tubulin gene expression in noggin-treated ectoderm. These results show that the XASH-3 promotes neural development, and suggest that its activity depends on additional factors which are induced in ectoderm by factors such as noggin.

scholarly journals The Origin of Competence for Lens Formation in the Amphibia

1936 ◽  
Vol 13 (1) ◽  
pp. 86-91
Author(s):  
C. H. WADDINGTON
Keyword(s):  
Thin Layer ◽  
Neural Differentiation ◽  
Neural Induction ◽  
Neural Plate ◽  
Necessary Condition ◽  
Neural Tubes ◽  
Normal Larva ◽  
Lens Formation ◽  
Previous Occurrence ◽  
The Brain

1. Presumptive ectoderm of Triton alpestris was removed from the young gastrula and cultivated in Holtfreter solution at 25° C. until control embryos had developed open neural plates. 2. Presumptive eye material from neural plate embryos, with some attached archenteron roof, was then implanted into the isolated fragments of ectoderm. 3. The grafted tissue formed single complete eyes, and bilaterally symmetrical portions of the brain, although the implant contained asymmetrical portions of the neural plate. 4. In some of the explants the competence for neural differentiation was retained even to this late stage, and neural tubes were induced. In other specimens the inner layer of ectoderm consists of long, cylindrical, regularly arranged cells, like those of the sensory inner layer of ectoderm in the mouth region of a normal larva. Still other specimens formed thin-walled vesicles with no sensorisation, and others again differentiated into the compact masses of tissue normally formed by isolated gastrula ectoderm. 5. Lenses were induced in all types of explant mentioned above except the last. 6. It is concluded that the formation of lens competence is not dependent on the presence of non-axial mesoderm or on the previous occurrence of a process of neural induction, but is dependent on the differentiation of the ectoderm into a thin layer, which differentiation may be brought about in various ways, and perhaps purely mechanically. The formation of a thin layer of ectoderm is probably a sufficient as well as a necessary condition for the origin of lens competence.

scholarly journals Investigations on the Regional Determination of the Central Nervous System

1947 ◽  
Vol 24 (1-2) ◽  
pp. 145-183 ◽  
Author(s):  
P. D. NIEUWKOOP
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Causal Analysis ◽  
Neural Plate ◽  
The Central Nervous System ◽  
Primary Structures ◽  
Regional Determination ◽  
The Brain ◽  
Early Gastrula

1. With the aseptic operation method of Woerdeman (1930) it is possible to rear duplicitas larvae, formed after grafting of the dorsal blastoporal lip in the place of the ventral one at the early gastrula stage (Spemann, 1918), till an age of about 4 weeks, a time at which they have completely consumed their yolk material. 2. Various forces acting in the normal development and in the development of the duplicitas larvae are discussed in connexion with the external form and the internal organization of the latter. 3. The sources of errors in the method of graphic reconstruction of the brain used in this investigation are checked and their elimination is discussed. 4. The structure of the duplicitas shows that there exists a mediolateral and probably also a cranio-caudal regulation in grafts of the dorsal blastoporal lip of the early gastrula. 5. In the brain one may distinguish between ‘primary’ structures which are always present, and ‘secondary’ structures which are more variable. Therefore, one may probably divide the causal analysis of the development of the central nervous system into the determination of the ‘ground plan’ of the primary structures and the more dependent development of the ‘secondary’ ones (specific formations). 6. The brains of the secondary embryonic rudiments of these duplicitas are formed in all cases up to a certain level; caudally to this level the brain-parts are normally proportioned, but the most anterior part may be reduced in size. This material can be arranged into a complete regression series, beginning with the reduction of the telencephalon and ending with a completely acephalic embryo. From this development one may conclude that the determination of the central nervous system occurs in a large number of successive zones, which are qualitatively ‘equivalent’, and which are determined by (qualitatively or quantitatively) different values of the organizing ‘agent’. 7. There are indications that the infundibulum and hypophysis are determined by a triple contact between presumptive neural plate, prechordal plate and cephalic ectoderm after the appearance of the neural plate. 8. After special staining these incomplete nervous systems may form a very important source of data for the causal analysis of the development of tracts and nuclei in the central nervous system. 9. With the conclusions drawn from these experiments and the data given in the extensive literature on this subject, a new working hypothesis on the determination of the central nervous system is put forward. This theory involves the assumption (among others) of an equilibrium reaction between a strong mesodermal and a weak ectodermal gradient. The character of the determination process probably changes from being at first purely quantitative to become qualitative with increasing age. 10. Finally, the regional determination of the secondary rudiment in duplicitas is probably determined by a triple interaction between the induction field of the graft, the primary regional structure of the ectoderm and the regional influences of the primary rudiment.

scholarly journals Transmembrane H+ fluxes and the regulation of neural induction in Xenopus laevis

Zygote ◽  
2021 ◽  
pp. 1-12
Author(s):  
Ho Chi Leung ◽  
Catherine Leclerc ◽  
Marc Moreau ◽  
Alan M. Shipley ◽  
Andrew L. Miller ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Ex Vivo ◽  
Neural Induction ◽  
Dorsal Side ◽  
The Other ◽  
Bafilomycin A1 ◽  
Selective Electrode ◽  
Solvent Control ◽  
Dorsal Ectoderm

Summary It has previously been reported that in ex vivo planar explants prepared from Xenopus laevis embryos, the intracellular pH (pHi) increases in cells of the dorsal ectoderm from stage 10.5 to 11.5 (i.e. 11–12.5 hpf). It was proposed that such increases (potentially due to H+ being extruded, sequestered, or buffered in some manner), play a role in regulating neural induction. Here, we used an extracellular ion-selective electrode to non-invasively measure H+ fluxes at eight locations around the equatorial circumference of intact X. laevis embryos between stages 9–12 (˜7–13.25 hpf). We showed that at stages 9–11, there was a small H+ efflux recorded from all the measuring positions. At stage 12 there was a small, but significant, increase in the efflux of H+ from most locations, but the efflux from the dorsal side of the embryo was significantly greater than from the other positions. Embryos were also treated from stages 9–12 with bafilomycin A1, to block the activity of the ATP-driven H+ pump. By stage 22 (24 hpf), these embryos displayed retarded development, arresting before the end of gastrulation and therefore did not display the usual anterior and neural structures, which were observed in the solvent-control embryos. In addition, expression of the early neural gene, Zic3, was absent in treated embryos compared with the solvent controls. Together, our new in vivo data corroborated and extended the earlier explant-derived report describing changes in pHi that were suggested to play a role during neural induction in X. laevis embryos.

Presence of antibody in virus-infected brain cells of SSPE ferrets

1983 ◽  
Vol 41 ◽  
pp. 804-805
Author(s):  
Hannah R. Brown ◽  
Tammy L. Donato ◽  
Halldor Thormar
Keyword(s):  
Measles Virus ◽  
Plasma Cells ◽  
Subacute Sclerosing Panencephalitis ◽  
Protein A ◽  
Neutralizing Antibody ◽  
Brain Cells ◽  
Antibody Titers ◽  
A Cell ◽  
The Central Nervous System ◽  
The Brain

Measles virus specific immunoglobulin G (IgG) has been found in the brains of patients with subacute sclerosing panencephalitis (SSPE), a slowly progressing disease of the central nervous system (CNS) in children. IgG/albumin ratios indicate that the antibodies are synthesized within the CNS. Using the ferret as an animal model to study the disease, we have been attempting to localize the Ig's in the brains of animals inoculated with a cell associated strain of SSPE. In an earlier report, preliminary results using Protein A conjugated to horseradish peroxidase (PrAPx) (Dynatech Diagnostics Inc., South Windham, ME.) to detect antibodies revealed the presence of immunoglobulin mainly in antibody-producing plasma cells in inflammatory lesions and not in infected brain cells.In the present experiment we studied the brain of an SSPE ferret with neutralizing antibody titers of 1:1024 in serum and 1:512 in CSF at time of sacrifice 7 months after i.c. inoculation with SSPE measles virus-infected cells. The animal was perfused with saline and portions of the brain and spinal cord were immersed in periodate-lysine-paraformaldehyde (P-L-P) fixative. The ferret was not perfused with fixative because parts of the brain were used for virus isolation.

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