scholarly journals Cell rearrangement induced by filopodial tension accounts for the late phase of convergent extension in the sea urchin archenteron

2019 ◽  
Vol 30 (16) ◽  
pp. 1911-1919 ◽  
Author(s):  
Jeff Hardin ◽  
Michael Weliky
Keyword(s):  
Sea Urchin ◽  
Late Phase ◽  
Convergent Extension ◽  
Elastic Recoil ◽  
Poisson Effect ◽  
Cell Rearrangement ◽  
Starting Point ◽  
Mechanical Models ◽  
Key Features ◽  
Mesenchyme Cells

George Oster was a pioneer in using mechanical models to interrogate morphogenesis in animal embryos. Convergent extension is a particularly important morphogenetic process to which George Oster gave significant attention. Late elongation of the sea urchin archenteron is a classic example of convergent extension in a monolayered tube, which has been proposed to be driven by extrinsic axial tension due to the activity of secondary mesenchyme cells. Using a vertex-based mechanical model, we show that key features of archenteron elongation can be accounted for by passive cell rearrangement due to applied tension. The model mimics the cell elongation and the Poisson effect (necking) that occur in actual archenterons. We also show that, as predicted by the model, ablation of secondary mesenchyme cells late in archenteron elongation does not result in extensive elastic recoil. Moreover, blocking the addition of cells to the base of the archenteron late in archenteron elongation leads to excessive cell rearrangement consistent with tension-induced rearrangement of a smaller cohort of cells. Our mechanical simulation suggests that responsive rearrangement can account for key features of archenteron elongation and provides a useful starting point for designing future experiments to examine the mechanical properties of the archenteron.

Immunogold and immunoblot studies on a cell surface protein found in primary mesenchyme cells and in the cortical secretory vesicles of the sea urchin egg

1987 ◽  
Vol 45 ◽  
pp. 832-833
Author(s):  
G.L. Decker ◽  
M.C. Valdizan
Keyword(s):  
Cell Surface ◽  
Sea Urchin ◽  
Surface Protein ◽  
Egg Cell ◽  
Secretory Vesicles ◽  
Cell Surface Protein ◽  
Surface Complexes ◽  
Mesenchyme Cells ◽  
Lowicryl K4m ◽  
Primary Mesenchyme Cells

A monoclonal antibody designated MAb 1223 has been used to show that primary mesenchyme cells of the sea urchin embryo express a 130-kDa cell surface protein that may be directly involved in Ca2+ uptake required for growth of skeletal spicules. Other studies from this laboratory have shown that the 1223 antigen, although in relatively low abundance, is also expressed on the cell surfaces of unfertilized eggs and on the majority of blastomeres formed prior to differentiation of the primary mesenchyme cells.We have studied the distribution of 1223 antigen in S. purpuratus eggs and embryos and in isolated egg cell surface complexes that contain the cortical secretory vesicles. Specimens were fixed in 1.0% paraformaldehyde and 1.0% glutaraldehyde and embedded in Lowicryl K4M as previously reported. Colloidal gold (8nm diameter) was prepared by the method of Mulpfordt.

Localization and expression of msp130, a primary mesenchyme lineage-specific cell surface protein in the sea urchin embryo

Development ◽  
1987 ◽  
Vol 101 (2) ◽  
pp. 255-265 ◽  
Author(s):  
J.A. Anstrom ◽  
J.E. Chin ◽  
D.S. Leaf ◽  
A.L. Parks ◽  
R.A. Raff
Keyword(s):  
Cell Surface ◽  
Sea Urchin ◽  
Sea Water ◽  
Surface Protein ◽  
Specific Cell ◽  
Cell Surface Protein ◽  
Sea Urchin Embryo ◽  
A Cell ◽  
Mesenchyme Cells ◽  
Primary Mesenchyme Cells

In this report, we use a monoclonal antibody (B2C2) and antibodies against a fusion protein (Leaf et al. 1987) to characterize msp130, a cell surface protein specific to the primary mesenchyme cells of the sea urchin embryo. This protein first appears on the surface of these cells upon ingression into the blastocoel. Immunoelectronmicroscopy shows that msp130 is present in the trans side of the Golgi apparatus and on the extracellular surface of primary mesenchyme cells. Four precursor proteins to msp130 are identified and we show that B2C2 recognizes only the mature form of msp130. We demonstrate that msp130 contains N-linked carbohydrate groups and that the B2C2 epitope is sensitive to endoglycosidase F digestion. Evidence that msp130 is apparently a sulphated glycoprotein is presented. The recognition of the B2C2 epitope of msp130 is disrupted when embryos are cultured in sulphate-free sea water. In addition, two-dimensional immunoblots show that msp130 is an acidic protein that becomes substantially less acidic in the absence of sulphate. We also show that two other independently derived monoclonal antibodies, IG8 (McClay et al. 1983; McClay, Matranga & Wessel, 1985) and 1223 (Carson et al. 1985), recognize msp130, and suggest this protein to be a major cell surface antigen of primary mesenchyme cells.

Inhibitors of metalloendoproteases block spiculogenesis in sea urchin primary mesenchyme cells

1989 ◽  
Vol 181 (2) ◽  
pp. 542-550 ◽  
Author(s):  
Judith L. Roe ◽  
Helen R. Park ◽  
Warren J. Strittmatter ◽  
William J. Lennarz
Keyword(s):  
Sea Urchin ◽  
Mesenchyme Cells ◽  
Primary Mesenchyme Cells

Using the Delphi Technique to Explore Complex Concepts in Speech-Language Pathology: An Illustrative Example From Children's Social Communication

2017 ◽  
Vol 26 (4) ◽  
pp. 1225-1235 ◽  
Author(s):  
Kristen Izaryk ◽  
Elizabeth Skarakis-Doyle
Keyword(s):  
Social Communication ◽  
Delphi Study ◽  
Delphi Technique ◽  
Complex Problem ◽  
Consensus Building ◽  
Speech Language Pathology ◽  
Speech Language Pathologists ◽  
Starting Point ◽  
Language Pathology ◽  
Key Features

PurposeIn recent years, there has been an increasing interest in expanding the research approaches that speech-language pathologists utilize, particularly for addressing complex questions. Consensus-building techniques can be useful for addressing such questions. The Delphi technique is a consensus-building process involving structured communication among members of an expert panel via independent responses to iterative rounds of questionnaires. The purpose of this research note is to describe and demonstrate the Delphi technique using an application to a complex problem in speech-language pathology, that is, the bases of social communication and pragmatics.MethodThe Delphi technique was described and illustrated via the following study: 10 expert speech-language pathologists participated in a 3-round Delphi study. Participants were asked to list the key features of social communication and pragmatics in Round 1. Questions for Rounds 2 and 3 were developed on the basis of the participants' responses to previous rounds.ResultsThe Delphi technique was useful in bringing participants to consensus on the key features of social communication and pragmatics and offered a starting point for the continued exploration of this complex problem.ConclusionA discussion of the benefits and limitations of the technique is included, highlighting the utility of the technique to the field of speech-language pathology.

Cell interactions and mesodermal cell fates in the sea urchin embryo

Development ◽  
1992 ◽  
Vol 116 (Supplement) ◽  
pp. 43-51 ◽  
Author(s):  
Charles A. Ettensohn
Keyword(s):  
Sea Urchin ◽  
Cell Interactions ◽  
Cell Labeling ◽  
Cell Fates ◽  
Mesodermal Cell ◽  
Sea Urchin Embryo ◽  
Present Information ◽  
Cell Type Specific ◽  
Mesenchyme Cells

Cell interactions during gastrulation play a key role in the determination of mesodermal cell fates in the sea urchin embryo. An interaction between primary and secondary mesenchyme cells (PMCs and SMCs, respectively), the two principal populations of mesodermal cells, regulates the expression of SMC fates. PMCs are committed early in cleavage to express a skeletogenic phenotype. During gastrulation, they transmit a signal that suppresses the skeletogenic potential of a subpopulation of SMCs and directs these cells into an alternative developmental pathway. This review summarizes present information concerning the cellular basis of the PMC-SMC interaction, as analyzed by cell transplantation and ablation experiments, fluorescent cell labeling methods and the use of cell type-specific molecular markers. The nature and stability of SMC fate switching, the timing of the PMC-SMC interaction and its quantitative characteristics, and the lineage, numbers and normal fate of the population of skeletogenic SMCs are discussed. Evidence is presented indicating that PMCs and SMCs come into direct filopodial contact during the late gastrula stage, when the signal is transmitted. Finally, evolutionary questions raised by these studies are briefly addressed.

The role of secondary mesenchyme cells during sea urchin gastrulation studied by laser ablation

Development ◽  
1988 ◽  
Vol 103 (2) ◽  
pp. 317-324 ◽  
Author(s):  
J. Hardin
Keyword(s):  
Laser Ablation ◽  
Sea Urchin ◽  
Normal Rate ◽  
Common Mechanism ◽  
Gastrula Stage ◽  
Mechanical Tension ◽  
Lytechinus Pictus ◽  
Final Length ◽  
Mesenchyme Cells

It has long been thought that traction exerted by filopodia of secondary mesenchyme cells (SMCs) is a sufficient mechanism to account for elongation of the archenteron during sea urchin gastrulation. The filopodial traction hypothesis has been directly tested here by laser ablation of SMCs in gastrulae of the sea urchin, Lytechinus pictus. When SMCs are ablated at the onset of secondary invagination, the archenteron doubles in length at the normal rate of elongation, but advance of the tip of the archenteron stops at the 2/3 gastrula stage. In contrast, when all SMCs are ablated at or following the 2/3 gastrula stage, further elongation does not occur. However, if a few SMCs are allowed to remain in 2/3-3/4 gastrulae, elongation continues, although more slowly than in controls. The final length of archenterons in embryos ablated at the 1/3-1/2 gastrula stage is virtually identical to the final length of everted archenterons in LiCl-induced exogastrulae; since filopodial traction is not exerted in either case, an alternate, common mechanism of elongation probably operates in both cases. These results suggest that archenteron elongation involves two processes: (1) active, filopodia-independent elongation, which depends on active cell rearrangement and (2) filopodia-dependent elongation, which depends on mechanical tension exerted by the filopodia.

A Problematic Genre

2019 ◽  
pp. 25-51
Author(s):  
Anna Peterson
Keyword(s):  
Old Comedy ◽  
Starting Point ◽  
Key Features

Plutarch is famous for his disapproval of Old Comedy despite the fact that he invokes the genre as a source in his biographies. This chapter takes as its starting point the negative comparison that Plutarch draws between Aristophanes and Menander, arguing that Plutarch recasts the agonistic language of Old Comedy into an attack on its figurehead. Comic language in this text serves to reinforce social and educational hierarchies. Plutarch employs a similar approach in the Lives, where the negative example of Old Comedy is used to highlight both the positive virtues of Pericles and the character flaws of Nicias. Plutarch thus shows himself to be an astute reader of Old Comedy even when he expresses strong disapproval of key features of the genre.

An analysis of the mechanics of phonation

1965 ◽  
Vol 20 (2) ◽  
pp. 301-307 ◽  
Author(s):  
G. A. Cavagna ◽  
R. Margaria
Keyword(s):  
Sound Production ◽  
Respiratory Muscles ◽  
Sound Intensity ◽  
Sound Level ◽  
Intensity Level ◽  
Elastic Recoil ◽  
Mechanical Models ◽  
Fine Regulation ◽  
Flow Through ◽  
Work Done

The mechanical work done by the chest in phonation has been measured together with the sound intensity level. The regulation of the sound intensity is done by regulating the intrapulmonary pressure. This is achieved at high intensity levels through the activity of the respiratory muscles that, together with the elastic recoil of the chest, sustain the work of phonation. At sound intensities below a critical level an additional mechanism for changing the intensity is given by a fine regulation of the opening of the glottis, thus allowing more air to escape without contributing to sound production. The contribution of the respiratory muscles, of the chest elasticity, and of the opening of the glottis to phonation at different intensity levels depend on the degree of inflation of the chest. The efficiency of phonation, as of sound production in mechanical models, seems to increase with increasing intensity and pitch. voice production; work done by chest during phonation; mechanical models of glottis generator; subglottic pressure as a function of sound level; air flow through glottis during phonation; efficiency changes of sound production; variation of sound intensity by regulating opening of glottis; variations of the area of glottis depending on extent of elastic recoil of chest Submitted on February 10, 1964

Sign in / Sign up

Export Citation Format

Share Document