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

Development ◽  
1972 ◽  
Vol 28 (1) ◽  
pp. 13-26
Author(s):  
J. Cooke
Keyword(s):  
Marginal Zone ◽  
Organizer Region ◽  
Angular Distance ◽  
Cell Polarization ◽  
Subsequent Paper ◽  
Basic Operation ◽  
Primary Organization ◽  
Organizer Activity ◽  
Set Up ◽  
Cell Immigration

The work presented, in this and the subsequent papers of a series, was begun in order to re-examine the properties of the amphibian primary embryonic field, in the light of current theories concerning the nature of individuation fields in developing animal systems. A detailed description is given of the basic operation whose results are described in this and the subsequent paper. This involves the transplantation, into a late blastula or stage-10 gastrula host, of a supernumerary stage-10 organizer region. The consequences of such operations during the following 4–6 h, up to the late gastrula stage, are also described. Evidence is presented that, from a time some 2·5 h before the organizer site first becomes externally visible, its presumptive region is immune from interference by the proximity of another, implanted organizer, even one which is itself 2·5 h older. That is to say, the final site of development of host organizer activity is not altered by the presence of such an implant. Pairs of early organizers at comparable stages of activity appear to set up competing fields of cellular orientation and immigration, which show a fairly sharp boundary at their interface. This is most obvious for pairs of organizers fairly close together, since the cell polarization and stretching is most pronounced in the region near to the apex of the field, i.e. the initial site of cell immigration. Independent initial fields of immigration due to two organizers can reliably be distinguished in cases where they are as little as 30° of angular distance apart in the marginal zone of the host. These results are to be considered in relation to those of Paper II, for the same series of operations, where the final patterns of cell differentiation are studied, and to those of Paper III, where evidence is given for the development of autonomous polarity in the region of the organizer.

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

Development ◽  
1972 ◽  
Vol 28 (1) ◽  
pp. 27-46
Author(s):  
J. Cooke
Keyword(s):  
Early Stage ◽  
Organizer Region ◽  
Positional Information ◽  
Bilateral Symmetry ◽  
Angular Distance ◽  
Organ Differentiation ◽  
Primary Organization ◽  
Cell Commitment ◽  
Time Of Operation ◽  
Field Formation

The results are reported of a series of experiments, the exact geometry of which has been presented in a previous paper. Late blastulae and early stage-10 gastrulae are supplied with a second head organizer region at varying angular distances, in the marginal zone, from the presumptive site of their own organizer. The configuration of positional information existing in the mesodermal mantle of the late gastrula or earliest neurula, as a final result of such operations, was recorded by observing the pattern of axial organ differentiation obtained by tailbud stages (26–28). The operational differences between various current theories as to the nature of embryonic differentiation fields are briefly discussed, as a framework within which to consider the results of experiments such as those reported here. It is suggested that in the future, and using the present results as a basis, experiments may be possible that are more critical in distinguishing between the various theoretical suppositions involved. Evidence is presented that the final configuration of positional information, achieved as a result of the implantation of a second head organizer at or before the onset of host gastrulation, becomes stable some time before it is irreversibly expressed in terms of a pattern of cell commitment in the mesodermal/endodermal mantle. It is insensitive both to relative ages of host and graft at the time of operation, over the range employed and, probably, to the ambient temperature of development between operation and the time of cell differentiation, being dependent only on the angular distance originally existing between graft and presumptive host organizer sites. In the discussion, a model is given for the visualization of positional information in partially double fields, produced in a two-dimensional sheet of cells where the normal end-point of field formation is a bilateral symmetry of differentiation zones.

Axis-inducing activities and cell fates of the zebrafish organizer

Development ◽  
2000 ◽  
Vol 127 (16) ◽  
pp. 3407-3417 ◽  
Author(s):  
L. Saude ◽  
K. Woolley ◽  
P. Martin ◽  
W. Driever ◽  
D.L. Stemple
Keyword(s):  
Organizer Region ◽  
Complete Removal ◽  
Floor Plate ◽  
Significant Loss ◽  
Cell Fates ◽  
Deep Tissue ◽  
Head Formation ◽  
Prechordal Plate ◽  
Embryonic Shield ◽  
Organizer Activity

We have investigated axis-inducing activities and cellular fates of the zebrafish organizer using a new method of transplantation that allows the transfer of both deep and superficial organizer tissues. Previous studies have demonstrated that the zebrafish embryonic shield possesses classically defined dorsal organizer activity. When we remove the morphologically defined embryonic shield, embryos recover and are completely normal by 24 hours post-fertilization. We find that removal of the morphological shield does not remove all goosecoid- and floating head-expressing cells, suggesting that the morphological shield does not comprise the entire organizer region. Complete removal of the embryonic shield and adjacent marginal tissue, however, leads to a loss of both prechordal plate and notochord. In addition, these embryos are cyclopean, show a significant loss of floor plate and primary motorneurons and display disrupted somite patterning. Motivated by apparent discrepancies in the literature we sought to test the axis-inducing activity of the embryonic shield. A previous study suggested that the shield is capable of only partial axis induction, specifically being unable to induce the most anterior neural tissues. Contrary to this study, we find shields can induce complete secondary axes when transplanted into host ventral germ-ring. In induced secondary axes donor tissue contributes to notochord, prechordal plate and floor plate. When explanted shields are divided into deep and superficial fragments and separately transplanted we find that deep tissue is able to induce the formation of ectopic axes with heads but lacking posterior tissues. We conclude that the deep tissue included in our transplants is important for proper head formation.

Behavior-Form Double Directions Creative Conceptual Design Model and Its Quotient Space Implementation

2008 ◽  
Author(s):  
Yu-Xin Wang ◽  
Yu-Tong Li ◽  
Jian-Wei Wang
Keyword(s):  
Conceptual Design ◽  
Design Process ◽  
Quotient Space ◽  
Basic Structure ◽  
Basic Operation ◽  
Decomposition Tree ◽  
Function Decomposition ◽  
Design Variables ◽  
Set Up

This paper presents a novel indirect matching approach between the function layer and the form layer to enhance the capability for the FBS method to obtain the creative conceptual design results. Firstly, the basic operation actions set, which is composed of the basic operation actions obtained by decomposing each function in the lowest level of the function decomposition tree in the FBS model into the sub-functions, in the function layer is regrouped dynamically. This behavior regroup process has introduced the new design variables into the conceptual design process and leads the behavior creativity to produce. On the other hand, considering the multi-functions for each basic structure to have and representing these functions with the basic operation actions, then the basic operation actions set in the form layer is set up. Dynamic regrouping this set in the form layer, the new design variables has been introduced into the conceptual design process, and leads the form creativity to produce. Through the above behavior-form double directions creative process, the solution scope of the conceptual design is enlarged obviously. Therefore, the method present in this paper has enough capability to obtain the creative conceptual results. Furthermore, the model presented in this paper is represented with the quotient space mathematically. The case study has shown that in the function layer, through adjusting the attribute function, which determines the partition grain of the basic operation actions set in the function layer or in the form layer, the new behaviors can be generated.

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.

The anterior extent of dorsal development of the Xenopus embryonic axis depends on the quantity of organizer in the late blastula

Development ◽  
1990 ◽  
Vol 109 (2) ◽  
pp. 363-372 ◽  
Author(s):  
R.M. Stewart ◽  
J.C. Gerhart
Keyword(s):  
Xenopus Laevis ◽  
Cell Population ◽  
Marginal Zone ◽  
Organizer Region ◽  
Blastula Stage ◽  
Dorsal Midline ◽  
Anterior Dorsal ◽  
Lateral Width ◽  
Anterior Extent ◽  
Anterior Posterior

In amphibian gastrulae, the cell population of the organizer region of the marginal zone (MZ) establishes morphogenesis and patterning within itself and within surrounding regions of the MZ, presumptive neurectoderm, and archenteron roof. We have tested the effects on pattern of reducing the amount of organizer region by recombining halves of Xenopus laevis late blastulae cut at different angles from the bilateral plane. When regions within 30 degrees of the dorsal midline are excluded from recombinants, ventralized embryos develop lacking the entire anterior-posterior sequence of dorsal structures, suggesting that the organizer is only 60 degrees wide (centered on the dorsal midline) at the late blastula stage. As more and more dorsal MZ (organizer) is included in the recombinant, progressively more anterior dorsal structures are formed. In all cases, when any dorsal structures are missing they are deleted serially from the anterior end. Thus, we suggest that the amount (lateral width) of the organizer in the MZ determines the anterior extent of dorsal development.

The Performance Evaluation Mechanism Based on Information Construction for Large Stand-Alone Medical Equipment and Its Support for Decision-Making of Purchasing

2020 ◽  
Author(s):  
Qing LU
Keyword(s):  
Decision Making ◽  
Performance Evaluation ◽  
Medical Equipment ◽  
Public Hospitals ◽  
Maximum Effect ◽  
Basic Operation ◽  
Post Evaluation ◽  
Information Construction ◽  
Evaluation Mechanism ◽  
Set Up

Background: Continuously deeper reform of public hospitals has put forward the need to innovate the philosophy and system of large medical equipment operation and management, and the phenomenon featuring “more attention to purchasing and less attention to management” need to be turned around. Methods: This research took use of information management to set up ID fields (unique number) for target stand-alone equipment; integrated statistics functions of HIS, PACS, LIS, RIS and equipment management system to get the basic operation data; informationized the work flow and reform technology to set up a post evaluation indictor system for the performance of stand-alone equipment; compared the service condition of newly purchased equipment with the feasibility application of relative department from various dimensions; designed objective post-evaluation indicators from various angles to scientifically manage existing medical equipment and support decision-making of new application for purchasing medical equipment. Results: Application performance of stand-alone equipment and clinical departments were ranked in a standardized manner. Decision-making mode based on data case of stand-alone equipment was set up. Net present value was evaluated. However, re-purchasing the instrument did not continuously increase the contribution of each instrument. The laboratory can purchase new instruments again, while the imaging department is not recommended to purchase. Conclusion: The performance evaluation mechanism based on information construction for large stand-alone medical equipment and its support for decision-making of purchasing is of great significance to improve the service life of equipment, exert the maximum effect and reduce economic waste.

scholarly journals The Rsr1/Bud1 GTPase Interacts with Itself and the Cdc42 GTPase during Bud-Site Selection and Polarity Establishment in Budding Yeast

2010 ◽  
Vol 21 (17) ◽  
pp. 3007-3016 ◽  
Author(s):  
Pil Jung Kang ◽  
Laure Béven ◽  
Seethalakshmi Hariharan ◽  
Hay-Oak Park
Keyword(s):  
Budding Yeast ◽  
Cell Polarization ◽  
Spatial Cues ◽  
Division Site ◽  
Heterotypic Interactions ◽  
Polarity Establishment ◽  
Set Up ◽  
Bud Site

Cell polarization occurs along a single axis that is generally determined in response to spatial cues. In budding yeast, the Rsr1 GTPase and its regulators direct the establishment of cell polarity at the proper cortical location in response to cell type–specific cues. Here we use a combination of in vivo and in vitro approaches to understand how Rsr1 polarization is established. We find that Rsr1 associates with itself in a spatially and temporally controlled manner. The homotypic interaction and localization of Rsr1 to the mother-bud neck and to the subsequent division site are dependent on its GDP-GTP exchange factor Bud5. Analyses of rsr1 mutants suggest that Bud5 recruits Rsr1 to these sites and promotes the homodimer formation. Rsr1 also exhibits heterotypic interaction with the Cdc42 GTPase in vivo. We show that the polybasic region of Rsr1 is necessary for the efficient homotypic and heterotypic interactions, selection of a proper growth site, and polarity establishment. Our findings thus suggest that dimerization of GTPases may be an efficient mechanism to set up cellular asymmetry.

Goosecoid promotes head organizer activity by direct repression of Xwnt8 in Spemann’s organizer

Development ◽  
2001 ◽  
Vol 128 (15) ◽  
pp. 2975-2987 ◽  
Author(s):  
Jie Yao ◽  
Daniel S. Kessler
Keyword(s):  
Marginal Zone ◽  
The Body ◽  
Treated Animal ◽  
Homeodomain Protein ◽  
Regulatory Domains ◽  
Spemann's Organizer ◽  
Transcriptional Regulatory ◽  
Head Formation ◽  
Wnt Inhibitor ◽  
Organizer Activity

Formation of the vertebrate body plan is controlled by discrete head and trunk organizers that establish the anteroposterior pattern of the body axis. The Goosecoid (Gsc) homeodomain protein is expressed in all vertebrate organizers and has been implicated in the activity of Spemann’s organizer in Xenopus. The role of Gsc in organizer function was examined by fusing defined transcriptional regulatory domains to the Gsc homeodomain. Like native Gsc, ventral injection of an Engrailed repressor fusion (Eng-Gsc) induced a partial axis, while a VP16 activator fusion (VP16-Gsc) did not, indicating that Gsc functions as a transcriptional repressor in axis induction. Dorsal injection of VP16-Gsc resulted in loss of head structures anterior to the hindbrain, while axial structures were unaffected, suggesting a requirement for Gsc function in head formation. The anterior truncation caused by VP16-Gsc was fully rescued by Frzb, a secreted Wnt inhibitor, indicating that activation of ectopic Wnt signaling was responsible, at least in part, for the anterior defects. Supporting this idea, Xwnt8 expression was activated by VP16-Gsc in animal explants and the dorsal marginal zone, and repressed by Gsc in Activin-treated animal explants and the ventral marginal zone. Furthermore, expression of Gsc throughout the marginal zone inhibited trunk formation, identical to the effects of Frzb and other Xwnt8 inhibitors. A region of the Xwnt8 promoter containing four consensus homeodomain-binding sites was identified and this region mediated repression by Gsc and activation by VP16-Gsc, consistent with direct transcriptional regulation of Xwnt8 by Gsc. Therefore, Gsc promotes head organizer activity by direct repression of Xwnt8 in Spemann’s organizer and this activity is essential for anterior development.

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

Development ◽  
1972 ◽  
Vol 28 (1) ◽  
pp. 47-56
Author(s):  
J. Cooke
Keyword(s):  
Xenopus Laevis ◽  
Host Tissue ◽  
Animal Pole ◽  
Axial Structure ◽  
Dorsal Mesoderm ◽  
Primary Organization ◽  
Set Up

An experiment is described whose results strengthen the classical conclusion, due to Spemann and co-workers, that amphibian gastrulation movements are co-ordinated and controlled by properties intrinsic to the invaginating mesodermal zone, rather than by interaction between this and any field of cell-guiding information, symmetrically disposed about the presumptive head ectodermal region in the animal hemisphere of the blastula/gastrula. The possibility remains, however, that the field of information coming to reside in the marginal mesodermal zone, is itself originally set up utilizing the animal pole as an origin, as well as the presumptive organizer site. Experiments are then described where whole organizer apices, and also subapical squares of dorsal mesoderm from stage-10 donors, are implanted with presumptive polarity reversed 180° relative to that of the host. It is found that reasonably extensive migration, on the part of the graft and the influenced host tissue, is required for the individuation of recognizable axial structure, and that such migration is often prevented in reversed implants due to a retention of autonomous polarity in host and graft. Reasons are suggested for the apparently greater autonomy, in this respect, of apical organizer plugs, but evidence is given that autonomy is nevertheless expressed even by squares of dorsal presumptive mesoderm of side ca. 0·1 mm. The significance of this observation, for theory concerning the nature of the cellular properties involved in the maintenance of embryonic fields, is discussed.

scholarly journals Goosecoid is not an essential component of the mouse gastrula organizer but is required for craniofacial and rib development

Development ◽  
1995 ◽  
Vol 121 (9) ◽  
pp. 3005-3012 ◽  
Author(s):  
J.A. Rivera-Perez ◽  
M. Mallo ◽  
M. Gendron-Maguire ◽  
T. Gridley ◽  
R.R. Behringer
Keyword(s):  
Organizer Region ◽  
Embryonic Stem ◽  
Homeobox Gene ◽  
Primary Body ◽  
Evolutionarily Conserved ◽  
Vertebrate Embryos ◽  
Organizer Activity ◽  
Craniofacial Defects ◽  
Transplantation Experiments

Goosecoid (gsc) is an evolutionarily conserved homeobox gene expressed in the gastrula organizer region of a variety of vertebrate embryos, including zebrafish, Xenopus, chicken and mouse. To understand the role of gsc during mouse embryogenesis, we generated gsc-null mice by gene targeting in embryonic stem cells. Surprisingly, gsc-null embryos gastrulated and formed the primary body axes; gsc-null mice were born alive but died soon after birth with numerous craniofacial defects. In addition, rib fusions and sternum abnormalities were detected that varied depending upon the genetic background. Transplantation experiments suggest that the ovary does not provide gsc function to rescue gastrulation defects. These results demonstrate that gsc is not essential for organizer activity in the mouse but is required later during embryogenesis for craniofacial and rib cage development.

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