Mesoderm induction and the control of gastrulation in Xenopus laevis: the roles of fibronectin and integrins

Development ◽  
1990 ◽  
Vol 108 (2) ◽  
pp. 229-238 ◽  
Author(s):  
J.C. Smith ◽  
K. Symes ◽  
R.O. Hynes ◽  
D. DeSimone
Keyword(s):  
Marginal Zone ◽  
Single Cells ◽  
Mesoderm Induction ◽  
Convergent Extension ◽  
Animal Pole ◽  
Post Translational Modifications ◽  
Coated Surface ◽  
Pole Cells ◽  
And Control ◽  
Future Work

Exposure of isolated Xenopus animal pole ectoderm to the XTC mesoderm-inducing factor (XTC-MIF) causes the tissue to undergo gastrulation-like movements. In this paper, we take advantage of this observation to investigate the control of various aspects of gastrulation in Xenopus. Blastomeres derived from induced animal pole regions are able, like marginal zone cells, but unlike control animal pole blastomeres, to spread and migrate on a fibronectin-coated surface. Dispersed animal pole cells are also able to respond to XTC-MIF in this way; this is one of the few mesoderm-specific responses to induction that has been observed in single cells. The ability of induced animal pole cells to spread on fibronectin is abolished by the peptide GRGDSP. However, the elongation of intact explants is unaffected by this peptide. This may indicate that fibronectin-mediated cell migration is not required for convergent extension. We have investigated the molecular basis of XTC-MIF-induced gastrulation-like movements by measuring rates of synthesis of fibronectin and of the integrin beta 1 chain in induced and control explants. No significant differences were observed, and this suggests that gastrulation is not initiated simply by control of synthesis of these molecules. In future work, we intend to investigate synthesis of other integrin subunits and to examine possible post-translational modifications to fibronectin and the integrins.

scholarly journals Gastrulation movements provide an early marker of mesoderm induction in Xenopus laevis

Development ◽  
1987 ◽  
Vol 101 (2) ◽  
pp. 339-349 ◽  
Author(s):  
K. Symes ◽  
J.C. Smith
Keyword(s):  
Cell Division ◽  
Xenopus Laevis ◽  
Early Response ◽  
Model System ◽  
Mesoderm Induction ◽  
Animal Pole ◽  
Inductive Interaction ◽  
Vegetal Pole ◽  
Pole Cells ◽  
General Appearance

The first inductive interaction in amphibian development is mesoderm induction, in which an equatorial mesodermal rudiment is induced from the animal hemisphere under the influence of a signal from vegetal pole blastomeres. We have recently discovered that the Xenopus XTC cell line secretes a factor which has the properties we would expect of a mesoderm-inducing factor. In this paper, we show that an early response to this factor by isolated Xenopus animal pole regions is a change in shape, involving elongation and constriction. We show by several criteria, including general appearance, timing, rate of elongation and the nonrequirement for cell division that these movements resemble the events of gastrulation. We also demonstrate that the movements provide an early, simple and reliable indicator of mesoderm induction and are of use in providing a ‘model system’ for the study of mesoderm induction and gastrulation. For example, we show that the timing of gastrulation movements does not depend upon the time of receipt of a mesoderm-induction signal, but on an intrinsic gastrulation ‘clock’ which is present even in those animal pole cells that would not nomally require it.

Analysis of competence: receptors for fibroblast growth factor in early Xenopus embryos

Development ◽  
1989 ◽  
Vol 106 (1) ◽  
pp. 203-208 ◽  
Author(s):  
L.L. Gillespie ◽  
G.D. Paterno ◽  
J.M. Slack
Keyword(s):  
Binding Sites ◽  
Marginal Zone ◽  
Developmental Competence ◽  
Relative Molecular Mass ◽  
Scatchard Analysis ◽  
Animal Pole ◽  
Basic Fgf ◽  
Affinity Labelling ◽  
Pole Cells ◽  
Mesodermal Tissue

Xenopus ectodermal cells have previously been shown to respond to acidic and basic FGF by differentiating into mesodermal tissue. In the present study, ectodermal explants from Xenopus blastulae were shown to have high affinity binding sites for 125I-aFGF (Kd = 1.4 X 10(−10) M). The total number of sites, determined by Scatchard analysis, was 3 X 10(8) per explant (surface area of approximately 1 mm2). Two putative receptors of relative molecular mass 130,000 and 140,000 were identified by chemical crosslinking to 125I-aFGF. Both acidic and basic FGF, but not TGF beta 2, could compete for affinity labelling of these bands. The receptor density at the cell surface parallels the developmental competence of Xenopus animal pole cells to respond to FGF. Receptors are present at highest density in the marginal zone but are not restricted to cells in this region.

Mesoderm induction by fibroblast growth factor in early Xenopus development

1990 ◽  
Vol 327 (1239) ◽  
pp. 75-84 ◽  
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Marginal Zone ◽  
Mesoderm Induction ◽  
Fibroblast Growth ◽  
Heparin Binding ◽  
Cell Stage ◽  
Animal Pole

In early amphibian development the mesoderm is formed around the equator of the blastula in response to inductive signals from the endoderm. At the time of its formation the mesoderm consists of a large ‘ventral type’ zone and a small ‘organizer’ zone. A screen of candidate substances showed that a small group of heparin binding growth factors (HBGFs) were active as mesoderm inducing agents in vitro . The fibroblast growth factors (aFGF and bFGF) and embryonal carcinoma derived growth factor (ECDGF) all show similar potency and can produce ventral inductions at concentrations above about 100 pM. Single blastula ectoderm cells can be induced and will differentiate in a defined medium to form mesodermal tissues and all inner blastula cells are competent to respond to the factors. Inducing activity can be extracted from Xenopus blastulae and can be purified by heparin affinity chromatography. Antibody neutralization and Western blotting experiments identify this activity as bFGF. The amounts present are small but would be sufficient to evoke ventral inductions in vivo. It is not yet known whether the bFGF is localized to the endoderm, although it is known that inducing activity secreted by endodermal cells can be neutralized by heparin. The competence of ectoderm to respond to FGF rises from about the 128-cell-stage and falls again by the onset of gastrulation. This change is paralleled by a rise and fall of binding of 125I-labelled aFGF. Chemical cross-linking reveals that this binding is attributable to a receptor of molecular mass about 130 kilodaltons (kDa). The receptor is present both in the marginal zone, which responds to the signal in vivo, and in the animal pole region, which is not induced in vivo but which will respond to HBGFs in vitro . In intact embryos we believe that the ventral type mesoderm forms the somites, kidney and other intermediate structures as well as the blood islands of the ventral midline. These intermediate structures are induced as a function of distance from the organizer in a process called ‘dorsalization’. Lithium salts have a dorsalizing effect on whole embryos and also on explants from the ventral marginal zone, causing them to form large blocks of muscle. Lithium will also cause large muscle blocks to form when applied to ectoderm explants together with FGF. It is difficult to extend these results directly to mammalian embryos, but we have shown that the products of the murine int-2 gene and of the human k-fgf genes are active as mesoderm inducing factors.

Mesoderm induction in Xenopus laevis: responding cells must be in contact for mesoderm formation but suppression of epidermal differentiation can occur in single cells

Development ◽  
1988 ◽  
Vol 104 (4) ◽  
pp. 609-618 ◽  
Author(s):  
K. Symes ◽  
M. Yaqoob ◽  
J.C. Smith
Keyword(s):  
Growth Factor ◽  
Transforming Growth Factor Beta ◽  
Transforming Growth Factor ◽  
Early Stage ◽  
Divalent Cations ◽  
Single Cells ◽  
Epidermal Differentiation ◽  
Mesoderm Induction ◽  
Animal Pole ◽  
Mesodermal Cell

When Xenopus embryos are cultured in calcium- and magnesium-free medium (CMFM), the blastomeres lose adhesion but continue dividing to form a loose heap of cells. If divalent cations are restored at the early gastrula stage the cells re-adhere and eventually form muscle (a mesodermal cell type) as well as epidermis. If, however, the cells are dispersed during culture in CMFM, muscle does not form following reaggregation although epidermis does. This suggests that culturing blastomeres in a heap allows the transmission of mesoderm-induction signals from cell to cell while dispersion effectively dilutes the signal. In this paper, we have attempted to substitute for cell proximity by culturing dispersed blastomeres in XTC mesoderm-inducing factor (MIF). We find that dispersed cells do not respond to XTC-MIF by forming mesodermal cell types after reaggregation, but the factor does inhibit epidermal differentiation. One interpretation of this observation is that an early stage in mesoderm induction is the suppression of epidermal differentiation and that formation of mesoderm may require contact-mediated signals that are produced in response to XTC-MIF. We have gone on to study the suppression of epidermal differentiation in more detail. We find that this is a dose-dependent phenomenon that can occur in single cells in the absence of cell division. Animal pole blastomeres become more difficult to divert from epidermal differentiation at later stages of development and by stage 12 they are ‘determined’ to this fate. Fibroblast growth factor (FGF) also suppresses epidermal differentiation in isolated animal pole blastomeres and transforming growth factor-beta 1 acts synergistically with FGF in doing so.

Effects of carbamylcholine on chick embryo aggregate retina cell cultures

1988 ◽  
Vol 46 ◽  
pp. 350-351
Author(s):  
Glenn M. Cohen ◽  
Radharaman Ray
Keyword(s):  
Cell Cultures ◽  
Single Cells ◽  
Retinal Cell ◽  
Cell Aggregates ◽  
High Concentration ◽  
In Ovo ◽  
Sterile Culture ◽  
Retinal Tissue ◽  
Synaptic Junctions ◽  
And Control

Retinal,cell aggregates develop in culture in a pattern similar to the in ovo retina, forming neurites first and then synapses. In the present study, we continuously exposed chick retinal cell aggregates to a high concentration (1 mM) of carbamylcholine (carbachol), an acetylcholine (ACh) analog that resists hydrolysis by acetylcholinesterase (AChE). This situation is similar to organophosphorus anticholinesterase poisoning in which the ACh level is elevated at synaptic junctions due to inhibition of AChE, Our objective was to determine whether continuous carbachol exposure either damaged cholino- ceptive neurites, cell bodies, and synaptic elements of the aggregates or influenced (hastened or retarded) their development.The retinal tissue was isolated aseptically from 11 day embryonic White Leghorn chicks and then enzymatically (trypsin) and mechanically (trituration) dissociated into single cells. After washing the cells by repeated suspension and low (about 200 x G) centrifugation twice, aggregate cell cultures (about l0 cells/culture) were initiated in 1.5 ml medium (BME, GIBCO) in 35 mm sterile culture dishes and maintained as experimental (containing 10-3 M carbachol) and control specimens.

Reading the phosphorylation code: binding of the 14-3-3 protein to multivalent client phosphoproteins

2020 ◽  
Vol 477 (7) ◽  
pp. 1219-1225 ◽  
Author(s):  
Nikolai N. Sluchanko
Keyword(s):  
Protein Function ◽  
Intrinsically Disordered Protein ◽  
Structural Basis ◽  
Major Protein ◽  
Post Translational Modifications ◽  
Protein Protein Interaction ◽  
Intrinsically Disordered ◽  
Biochemical Journal ◽  
Multiple Binding ◽  
And Control

Many major protein–protein interaction networks are maintained by ‘hub’ proteins with multiple binding partners, where interactions are often facilitated by intrinsically disordered protein regions that undergo post-translational modifications, such as phosphorylation. Phosphorylation can directly affect protein function and control recognition by proteins that ‘read’ the phosphorylation code, re-wiring the interactome. The eukaryotic 14-3-3 proteins recognizing multiple phosphoproteins nicely exemplify these concepts. Although recent studies established the biochemical and structural basis for the interaction of the 14-3-3 dimers with several phosphorylated clients, understanding their assembly with partners phosphorylated at multiple sites represents a challenge. Suboptimal sequence context around the phosphorylated residue may reduce binding affinity, resulting in quantitative differences for distinct phosphorylation sites, making hierarchy and priority in their binding rather uncertain. Recently, Stevers et al. [Biochemical Journal (2017) 474: 1273–1287] undertook a remarkable attempt to untangle the mechanism of 14-3-3 dimer binding to leucine-rich repeat kinase 2 (LRRK2) that contains multiple candidate 14-3-3-binding sites and is mutated in Parkinson's disease. By using the protein-peptide binding approach, the authors systematically analyzed affinities for a set of LRRK2 phosphopeptides, alone or in combination, to a 14-3-3 protein and determined crystal structures for 14-3-3 complexes with selected phosphopeptides. This study addresses a long-standing question in the 14-3-3 biology, unearthing a range of important details that are relevant for understanding binding mechanisms of other polyvalent proteins.

Asymptotic Behavior in Slumping From a Cylindrical Tank

1984 ◽  
Vol 106 (3) ◽  
pp. 279-284 ◽  
Author(s):  
Y. Bai ◽  
W. Johnson ◽  
R. G. M. Low ◽  
S. K. Ghosh
Keyword(s):  
Transition Period ◽  
Health And Safety ◽  
Local Environment ◽  
Theoretical Background ◽  
Hazardous Substance ◽  
Substance Flows ◽  
Linear Relationships ◽  
Characteristic Features ◽  
And Control ◽  
Future Work

When an oil tank collapses or ruptures any contained hazardous substance flows outwards and can damage nearby plant or people as well as lead to pollution of the local environment. In recent years, this and similar subjects have given rise to a new kind of engineering—spill prevention and control. However, theoretical background, backed by experiment, is lacking to work out reliable regulations. An intermediate-asymptotic analysis for late-stage spreading is carried out in this paper. This analysis reveals several characteristic features of the spill wave such as transition period and linear relationships between spreading area and time, and wave front velocity and the inverse of zone radius. Most of the latter results have been verified by model experiment. This paper also discusses the discrepancies between observations and the theory suggested in a recent UK Health and Safety Executive report. Finally, the present paper puts forward proper modeling rules for future work.

Pre-service music teachers' satisfaction: person–environment fit approach

2012 ◽  
Vol 29 (3) ◽  
pp. 371-385 ◽  
Author(s):  
Serkan Perkmen ◽  
Beste Cevik ◽  
Mahir Alkan
Keyword(s):  
Music Education ◽  
Music Teachers ◽  
Music Teacher ◽  
Theoretical Frameworks ◽  
Vocational Satisfaction ◽  
Highly Correlated ◽  
Service Music ◽  
And Control ◽  
Future Work

Guided by three theoretical frameworks in vocational psychology, (i) theory of work adjustment, (ii) two factor theory, and (iii) value discrepancy theory, the purpose of this study was to investigate Turkish pre-service music teachers' values and the role of fit between person and environment in understanding vocational satisfaction. Participants were 85 students enrolled in the department of music education in a Turkish university. The Minnesota Importance Questionnaire (MIQ) was used to examine the participants’ values in six dimensions: achievement, comfort, status, altruism, safety and autonomy. Results revealed that the pre-service teachers value achievement most followed by autonomy, which suggests that they would like to have a sense of accomplishment and control in their future job. The degree to which their values fit their predictions about future work environment was found to be highly correlated with vocational satisfaction. These results provided evidence that the vocational theories used in the current study offers a helpful and different perspective to understand the pre-service teachers' satisfaction with becoming a music teacher in the future. We believe that researchers in the field of music education may use these theories and MIQ to examine the role of values in pre-service and in-service music teachers' job satisfaction.

Misexpression of chick Vg1 in the marginal zone induces primitive streak formation

Development ◽  
1997 ◽  
Vol 124 (24) ◽  
pp. 5127-5138 ◽  
Author(s):  
S.B. Shah ◽  
I. Skromne ◽  
C.R. Hume ◽  
D.S. Kessler ◽  
K.J. Lee ◽  
...  
Keyword(s):  
Marginal Zone ◽  
Ectopic Expression ◽  
Primitive Streak ◽  
Axis Formation ◽  
Mesoderm Induction ◽  
Cell Fates ◽  
Signalling Molecules ◽  
Posterior Area ◽  
Area Pellucida

In the chick embryo, the primitive streak is the first axial structure to develop. The initiation of primitive streak formation in the posterior area pellucida is influenced by the adjacent posterior marginal zone (PMZ). We show here that chick Vg1 (cVg1), a member of the TGFbeta family of signalling molecules whose homolog in Xenopus is implicated in mesoderm induction, is expressed in the PMZ of prestreak embryos. Ectopic expression of cVg1 protein in the marginal zone chick blastoderms directs the formation of a secondary primitive streak, which subsequently develops into an ectopic embryo. We have used cell marking techniques to show that cells that contribute to the ectopic primitive streak change fate, acquiring two distinct properties of primitive streak cells, defined by gene expression and cell movements. Furthermore, naive epiblast explants exposed to cVg1 protein in vitro acquire axial mesodermal properties. Together, these results show that cVg1 can mediate ectopic axis formation in the chick by inducing new cell fates and they permit the analysis of distinct events that occur during primitive streak formation.

scholarly journals Expectations and desires of palliative health care personnel concerning their future work culture

2013 ◽  
Vol 2 (3) ◽  
pp. 46 ◽  
Author(s):  
Beate Andre ◽  
Endre Sjøvold ◽  
Marte Holmemo ◽  
Toril Rannestad ◽  
Gerd I. Ringdal
Keyword(s):  
Health Care ◽  
Reference Group ◽  
Health Care Personnel ◽  
Future Perspective ◽  
Work Culture ◽  
Care Workers ◽  
Positive Work Culture ◽  
And Control ◽  
Future Work ◽  
Positive Work

Introduction: Exploring the work culture of health care personnel is important in order to understand the challenges they face and the issues they experience. Believing in and shaping their futures indicates a working culture influenced by promoting factors. The aims of this study were to explore how health care workers at a Palliative Medicine Unit perceive their future work culture would be and whether they perceive that their expectations and desires will be fulfilled. Design: A correlational study. Methods: Health care personnel, physicians, nurses, physiotherapists, and others (N = 26) at a PMU in Norway completed a questionnaire according to the two perspectives, expectations (future) and desire (wish). The findings in these two perspectives were compared. The method seeks to explore what aspects dominate the particular work culture and identifying challenges, limitations, and opportunities. The findings were also compared with a reference group of 347 ratings of well-functioning Norwegian organizations, named the “Norwegian Norm”. Results: The findings for the wish perspective showed significant (p<0.05; p<0.01) higher rates for nurturing and synergy dimensions and significant lower rates (p>0.05; p>0.05) for opposition and control dimensions than the findings for the future perspective. Conclusions: It appears that the health care personnel wish for changes that they don’t believe they will achieve. The changes the respondents wish for are fewer negative work culture qualities, such as assertiveness and resignation, and more positive work culture qualities, such as engagement and empathy. Changes must be made to give the health care personnel improved working conditions and empowerment in order to change their situations to reflect what they wish for. The present findings can give an indication as to the direction that research ought to follow in subsequent studies.

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