Studies on Regional Specificity Within the Organization Centre of Urodeles

1950 ◽  
Vol 27 (2) ◽  
pp. 126-144
Author(s):  
C. H. WADDINGTON ◽  
T. YAO
Keyword(s):  
Spina Bifida ◽  
Anterior Part ◽  
Organizer Region ◽  
Neural Plate ◽  
Normal Embryo ◽  
Median Part ◽  
Regional Specificity ◽  
Spatio Temporal ◽  
Regional Character ◽  
Organization Centre

1. In young gastrulae of Triton alpestris the median part of the organization centre immediately in front of the blastopore was excised and replaced after reversal of its anterior-posterior axis. Completely normal embryos developed in many cases, but in others there was some degree of microcephaly or spina bifida. 2. Similar normal embryos can develop after exchange of the anterior and posterior regions of the organizer, either with normal or reversed orientation. 3. The spina bifida which frequently appears is a consequence of the impediment offered by the graft to the normal gastrulation movements. 4. Microcephaly may also result if the presence of the graft prevents the proper development of the anterior part of the archenteron roof. 5. It may also be caused when the posterior organizer region is brought into the anterior region, if the host fails to convert it into anterior material. This occurs the more frequently the older the grafted posterior material is. 6. Even at the end of gastrulation (slit yolk-plug stage) the regional character of the archenteron roof is not finally determined. A fairly normal embryo (with over-thick mesoderm) may develop if an extra archenteron roof is added with reversed orientation between the normal archenteron roof and the presumptive neural plate. 7. The determination of the regional structure of the archenteron roof and the neural plate is discussed. Attention is drawn to the spatio-temporal factors involved in the production and diffusion of the evocator with the dynamic system of the gastrulating egg.

scholarly journals Studies on the nature of the amphibian organization centre. I—Chemical properties of the evocator

1935 ◽  
Vol 117 (804) ◽  
pp. 289-310 ◽  
Keyword(s):  
Active Substance ◽  
Chemical Properties ◽  
Egg Laying ◽  
Embryonic Induction ◽  
Soluble Substance ◽  
Animal Kingdom ◽  
Whole Process ◽  
Adult Tissues ◽  
Regional Character ◽  
Organization Centre

During the amphibian egg-laying season of 1933, Needham, Waddington, and Needham (1933, a , b ; 1934) obtained evidence that the activity of the organization centre of the newt gastrula is partly due to the presence of an ether-soluble substance. The active ether extracts were found to be capable of evoking the formation of a neural tube from the competent presumptive epidermis of the gastrula. It seems difficult, however, to suppose that they can determine the regional character of the evoked neural plate, as normal living organizers do, and the active substance is therefore spoken of as the evocator, to emphasize the fact that its functions represent only one part of the whole process of embryonic induction. The presence of the evocator could also be demonstrated in ether extracts of adult newt tissues; and in a research carried out at the same time Holtfreter (1933) showed that the evocator is present in a large number, if not in all, adult tissues from animals belonging to nearly all the groups of the animal kingdom. Holtfreter found that evocation occurred after the implantation of adult tissues which had been killed and treated with various solvents, but he showed that a prolonged extraction with ether tended to lessen, though it did not entirely destroy, the evocating power of the tissue. This result, which so far as it went was confirmatory of Needham, Waddington, and Needham’s work, was, however, denied by Fischer and Wehmeier (1934), who, on repeating the extraction experiments, could confirm the fact that the ether extracts were active, but claimed that the evocating ability of the tissues was not much lessened by the extraction. In a more recent communication (1934, a ) Holtfreter has repeated his extractions, and finds that the activity of the extracted tissue is only slightly lowered. It is very probable, however, that there will be difficulty in extracting the whole of the active ether-soluble substances from a given mass of tissue. There is general agreement that ether extracts contain an active substance.

scholarly journals Building the Border: Development of the Chordate Neural Plate Border Region and Its Derivatives

2020 ◽  
Vol 11 ◽  
Author(s):  
Ankita Thawani ◽  
Andrew K. Groves
Keyword(s):  
Neural Crest ◽  
Signaling Pathways ◽  
Regulatory Networks ◽  
Neural Plate ◽  
Bmp Signaling ◽  
Border Region ◽  
Thin Strip ◽  
Morphogenetic Protein ◽  
Neural Plate Border ◽  
Spatio Temporal

The paired cranial sensory organs and peripheral nervous system of vertebrates arise from a thin strip of cells immediately adjacent to the developing neural plate. The neural plate border region comprises progenitors for four key populations of cells: neural plate cells, neural crest cells, the cranial placodes, and epidermis. Putative homologues of these neural plate border derivatives can be found in protochordates such as amphioxus and tunicates. In this review, we summarize key signaling pathways and transcription factors that regulate the inductive and patterning events at the neural plate border region that give rise to the neural crest and placodal lineages. Gene regulatory networks driven by signals from WNT, fibroblast growth factor (FGF), and bone morphogenetic protein (BMP) signaling primarily dictate the formation of the crest and placodal lineages. We review these studies and discuss the potential of recent advances in spatio-temporal transcriptomic and epigenomic analyses that would allow a mechanistic understanding of how these signaling pathways and their downstream transcriptional cascades regulate the formation of the neural plate border region.

Properties of the primary organization field in the embryo of Xenopus laevis

Development ◽  
1973 ◽  
Vol 30 (2) ◽  
pp. 283-300
Author(s):  
J. Cooke
Keyword(s):  
Organizer Region ◽  
Positional Information ◽  
Host Cells ◽  
Normal Embryo ◽  
Tail Bud ◽  
Essentially Normal ◽  
Head Formation ◽  
Source Data ◽  
Primary Organization ◽  
Host Embryo

Patterns of individuation occurring in the primary embryonic axis of Xenopus following excision of the organizer region of the early gastrula are described. In some 70% of cases the information for induction of the complete head is qualitatively restored by the time of cell determination, giving rise to an essentially normal embryo. In some 40% of cases a second posterior axis of bilaterality is formed, causing development of a secondary anus, tail-fin and spinal cord, and often somites. The probabilities of twinning in the tailfield and of failure to complete apical regulation (= head formation) are largely independent. After such excision of the head organizer region, a delay of some 3 h in the schedule of visible differentiation in the neurula/tail-bud embryo is commonly incurred, whether or not apical regulation is successful. When the apex is excised from a host embryo which has already contained for some hours a second apex (= head organizer) as described in an earlier paper, that grafted apex then captures a considerably increased territory in the host material, as seen from the size of the individuation field finally caused by it. Such a shift across host cells, of the boundary between fields of positional information due to two organizers, is not seen under any conditions where these are left intact, or where host excision is carried out soon after implanting the donor organizer. In discussing the results and reconciling them with earlier observations, it is shown that they strongly suggest the presence of local polar (i.e. vectorial) properties in the presumptive mesoderm, due to signals from restricted regions which have achieved a special apical state. Repolarization of cells by a new organizer is not very rapid, and may spread decrementally from the source. Data on further delays in development, caused by the presence of the second organizer during regulation in the host apex, suggest that one organizer may act directly on cells elsewhere to delay or prevent the restoration of the apical state there.

In vitro experiments on axonal guidance and growth-cone collapse

1990 ◽  
Vol 153 (1) ◽  
pp. 29-46
Author(s):  
B. Muller ◽  
B. Stahl ◽  
F. Bonhoeffer
Keyword(s):  
Anterior Part ◽  
Lipid Vesicles ◽  
Axonal Guidance ◽  
In Vitro Experiments ◽  
Growth Cone Collapse ◽  
Retinal Axons ◽  
Regional Specificity ◽  
Membrane Components ◽  
Guidance Molecule

In the retinotectal projection, nasal retinal axons project to posterior tectum, while temporal axons project to the anterior part of the tectum. In in vitro experiments, a similar specificity can be observed: the nasal and temporal retinal axons can be guided by tectal membrane components so that, for example, temporal retinal axons, when growing on a striped substratum consisting of anterior and posterior tectal membranes, express a very strong preference for the anterior stripes. This preference is not due to attractivity of anterior membranes but rather to avoidance of posterior material, although the pure posterior membranes are a very good substratum for growth of temporal axons. The repellent guidance molecule has been identified. Interestingly, besides guidance this molecule causes another reaction: when growing temporal axons are exposed to medium containing either posterior membranes or artificial lipid vesicles containing the repellent guidance molecule, the axonal growth cones collapse. As in guidance, there is a clear regional specificity: e.g. the repellent guidance molecule derived from posterior tectum induces collapse of temporal but not of nasal axons. Since the guiding and the collapse-inducing activity are expressed by one and the same glycoprotein molecule (Mr 33 × 10(3), linked to the membrane by phosphatidylinositol) and since another molecule has been identified by Keynes' group which also expresses both guiding and collapse-inducing activity, one might speculate that axonal guidance and axonal collapse have something in common. Models of axonal guidance will be discussed.

Systematic Classification of Spina Bifida

2021 ◽  
Author(s):  
Kim Hannah Schindelmann ◽  
Fabienne Paschereit ◽  
Alexandra Steege ◽  
Gisela Stoltenburg-Didinger ◽  
Angela M Kaindl
Keyword(s):  
Spina Bifida ◽  
Neural Plate ◽  
Review Of Literature ◽  
Precise Description ◽  
Systematic Classification ◽  
Multiple Conditions

Abstract Spina bifida (SB) is an umbrella term for multiple conditions characterized by misclosure of vertebral arches. Neuropathologic findings in SB cases are often reported with imprecise and overlapping terminology. In view of the increasing identification of SB-associated genes and pathomechanisms, the precise description of SB subtypes is highly important. In particular, the term “myelomeningocele” is applied to various and divergent SB subtypes. We reevaluated 90 cases with SB (58 prenatal; 32 postnatal). The most frequent SB phenotype in our cohort was myeloschisis, which is characterized by an open neural plate with exposed ependyma (n = 28; 31.1%). An open neural plate was initially described in only in two-thirds of the myeloschisis cases. An additional 21 cases (23.3%) had myelomeningocele; 2 cases (2.2%) had a meningocele; and 21 cases (23.3%) had an unspecified SB aperta (SBA) subtype. Overall, the SB phenotype was corrected in about one-third of the cases. Our findings highlight that “myelomeningocele” and “SB aperta” cannot be used as synonymous terms and that myeloschisis is an underreported SB phenotype. Based on our findings and a review of literature we propose a classification of SB subtypes in SB occulta and the 3 SBA subtypes, meningocele, myelomeningocele, and myeloschisis.

scholarly journals Segregating expression domains of two goosecoid genes during the transition from gastrulation to neurulation in chick embryos

Development ◽  
1997 ◽  
Vol 124 (8) ◽  
pp. 1443-1452 ◽  
Author(s):  
L. Lemaire ◽  
T. Roeser ◽  
J.C. Izpisua-Belmonte ◽  
M. Kessel
Keyword(s):  
Posterior Margin ◽  
Anterior Part ◽  
Primitive Streak ◽  
Neural Plate ◽  
Chick Embryos ◽  
Positive Part ◽  
Full Extension ◽  
Isolation And Characterization ◽  
Chick Embryogenesis

We report the isolation and characterization of a chicken gene, GSX, containing a homeobox similar to that of the goosecoid gene. The structure of the GSX gene and the deduced GSX protein are highly related to the previously described goosecoid gene. The two homeodomains are 74% identical. In the first few hours of chick embryogenesis, the expression pattern of GSX is similar to GSC, in the posterior margin of the embryo and the young primitive streak. Later during gastrulation, expression of the two genes segregate. GSC is expressed in the anterior part of the primitive streak, then in the node, and finally in the pre-chordal plate. GSX is expressed in the primitive streak excluding the node, and then demarcating the early neural plate around the anterior streak and overlying the pre-chordal plate. We demonstrate that the GSX-positive part of the primitive streak induces gastrulation, while the GSC-expressing part induces neurulation. After full extension of the streak, the fate of cells now characterized by GSX is to undergo neurulation, while those expressing GSC undergo gastrulation. We discuss the effect of a duplicated basic goosecoid identity for the generation of a chordate nervous system in ontogeny and phylogeny.

scholarly journals Studies on the nature of the amphibian organization centre III—The activation of the evocator

1936 ◽  
Vol 120 (817) ◽  
pp. 173-198 ◽  
Keyword(s):  
Normal Development ◽  
Chemical Substance ◽  
Body Cavity ◽  
Neural Plate ◽  
The Body ◽  
Gradient System ◽  
The Third ◽  
Axial Gradient ◽  
Organization Centre ◽  
Made In

The first attempts to produce a capacity for induction in tissue which is normally incapable of performing such an action were made by Spemann and Geinitz in 1927. They grafted a fragment of presumptive ectoderm into the organization centre of another embryo, and, removing it a few hours later, found that it had been “infected” with the inducing capacity of the tissues by which it had been surrounded. The experiment inevitably suggested that the inducing capacity is the property of a chemical substance which had diffused out of the organizer tissue into the grafted ectoderm fragment. A similar hypothesis could be used to explain the observation of Mangold and Spemann (1927) that in normal development the presumptive neural plate acquires inducing capacity at the same time and in proportion as it is underlain and determined by the mesodermal organizer. The first suggestion that the non-inducing parts of a Urodele gastrula themselves possess an organizing capacity, which is masked but only awaits activation or release, emerged in the work of Dürken (1926), Bautzmann (1929, a , b ), Kusche (1929), and Holtfreter (1931), and attention was first drawn to it by Huxley (1930). The German authors showed that if fragments of the gastrula are “interplanted” into the body cavity or optic vesicle of older larvae, they may develop into something other than their presumptive fate, and in particular, presumptive epidermis or neural plate may develop into various mesodermal derivatives such as notochord or muscle. Huxley pointed out the similarity between this phenomenon, which was called bedeutungsfremde Selbstdifferenzierung , and the results of isolating parts of the axial gradient system of lower organisms, which have been particularly described by Child (summaries 1928, 1929). An isolated part of an axial gradient system reconstructs a “dominant region”; and Huxley suggested that we could account for bedeutungsfremde Selbstdifferenzierung by supposing that an isolated part of a gastrula reconstructs the dominant region, i.e ., the organization centre. In the spring of 1932 one of us (C. H. W.), while on a visit to the laboratory of Dr. O. Mangold in Berlin for the purpose of learning the technique of amphibian operations, attempted to carry the matter a step further. If Huxley’s explanation were correct, one would have to suppose that a capacity for behaving like a “dominant region”, that is, for inducing, is latent in the presumptive ectoderm, and this capacity should become manifest when the ectoderm changes into a dominant region after isolation. The following experiment was therefore made to test this point. Fragments of presumptive ectoderm from a young gastrula were interplanted into the eye-cavity of Anuran tadpoles, from which the eye-ball had previously been removed. After two days the interplanted tissue was removed and grafted by the Einsteck method into the blastocoele of young newt gastrulae, to discover whether they were capable of inducing the formation of neural plate. Three sets of controls were made. In one set organizing tissues were interplanted for two days and then tested to see whether their inducing capacity had been impaired, in the second set organizing tissue was isolated for two days in Holtfreter solution, and then tested, and in the third set presumptive ectoderm was isolated for two days in Holtfreter solution and tested for inducing capacity.

scholarly journals Induction by the Primitive Streak and its Derivatives in the Chick

1933 ◽  
Vol 10 (1) ◽  
pp. 38-46 ◽  
Author(s):  
C. H. WADDINGTON
Keyword(s):  
Anterior Part ◽  
Primitive Streak ◽  
Neural Plate ◽  
Embryonic Axis ◽  
Host Embryo

1. Specimens are described which demonstrate the induction of neural plateby (a) the mesodermal part of the primitive streak, (b) the head process and sinus rhomboidalis, and (c) neural plate. 2. The neural plate which was induced by the mesodermal part of the primitive streak was in reversed orientation as regards the host embryo. Thus the orientation of the embryo must be already fixed in the mesodermal part of the streak, and must in this case have overcome any influence which the host may be able to exert. 3. The same embryo was more complete than indicated by the presumptive fate of the tissue which induced it, whence it is concluded that the chick organiser,like the amphibian, shows a tendency to complete itself, and to this extent behaves like part of a harmonious equipotential system. 4. Grafts of the anterior part of the embryonic axis (head process and neuralplate) into the anterior part of the host blastoderm, have induced structures which in nearly all cases give indications of being heads. Inductions by posterior parts of the axis (sinus rhomboidalis) have never given such indications. 5. Grafts of the notochord have not, as yet, given satisfactory inductions.

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.

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