The mechanism of chick blastoderm expansion

Development ◽  
1976 ◽  
Vol 35 (3) ◽  
pp. 559-575
Author(s):  
J. R. Downie
Keyword(s):  
Cell Shape ◽  
Yolk Sac ◽  
Vitelline Membrane ◽  
Yolk Mass ◽  
Chick Blastoderm ◽  
Tension Level ◽  
Area Vasculosa ◽  
Pull Out ◽  
Cell Organization ◽  
High Level

At the time of laying, the domestic fowl blastoderm measures 4 mm across. After 4 days’ incubation, the extra-embryonic yolk-sac tissues have expanded to encompass the whole yolk mass. This expansion involves the migration over the inner surface of the vitelline membrane of a specialized band of ‘edge cells’ at the blastoderm periphery. As they move, they pull out the blastoderm behind them, setting up a considerable tension. Expansion also involves cell proliferation and changes in cell shape. This paper attempts to show how locomotion, tension, proliferation and changes in cell shape all contribute to the orderlyprocess of expansion. As a simplification, only the extra-embryonic epiblast is considered here. The findings are: 1. Expansion does not occur at a constant rate, but starts slowly, rises to a peak (over 500 μm/h) at around 3 days, and then slows as coverage of the yolk mass nears completion. 2. During the first day of incubation, edge-cell migration produces a tension in the blastoderm. This rises to a peak at 20–24 h, then declines. This tension may be due to an imbalance between expansion by migration and expansion by proliferation. 3. Migration of edge cells can be affected by tension in the blastoderm, i.e. very high tension may hold them back. However, the tension level normally found in the blastoderm seems not to do so. The low rate of expansion in the first day is therefore not due to the high level of tension. It may instead be due to changes in edge-cell organization. 4. Proliferation occurs throughout the extra-embryonic epiblast during the expansion period. It is not restricted to the blastoderm periphery. After the yolk has been covered, the epiblast continues to grow, with proliferation restricted largely to a band just distal to the advancing edge of the area vasculosa. 5. Cell shape and arrangement change considerably during expansion. The epiblast of the unincubated embryo is a monolayer of tall cells. During expansion, these become considerably flattened so that each contributes a larger amount to yolk-sac surface area.

The role of microtubules in chick blastoderm expansion—a quantitative study using colchicine

Development ◽  
1975 ◽  
Vol 34 (1) ◽  
pp. 265-277
Author(s):  
J. R. Downie
Keyword(s):  
Cell Division ◽  
Cell Shape ◽  
Shape Change ◽  
Cell Sheet ◽  
Cell Movement ◽  
Vitelline Membrane ◽  
General Context ◽  
Chick Blastoderm ◽  
Cell Shape Change ◽  
Cytoplasmic Microtubules

Since their discovery, cytoplasmic microtubules have been much studied in the context of cell movement and cell shape change. Much of the work has used drugs, particularly colchicine and its relatives, which break down microtubules — the so-called anti-tubulins. Colchicine inhibits the orientated movements of many cell types in vitro, and disrupts cell shape change in several morphogenetic situations. The investigation reported here used chick blastoderm expansion in New culture in an attempt to quantify the colchicine effect on orientated cell movement. However, although colchicine could halt blastoderm expansion entirely, a simple interpretation was not possible. (1) Colchicine at concentrations capable of blocking mitosis, and of disrupting all or most of the cytoplasmic microtubules of the cells studied, inhibited blastoderm expansion, often resulting in an overall retraction of the cell sheet. (2) Though blastoderm expansion does normally involve considerable cell proliferation, the colchicine effect could not be ascribed to a block on cell division since aminopterin, which stops cell division without affecting microtubules, did not inhibit expansion. (3) Blastoderm expansion is effected by the locomotion of a specialized band of edge cells at the blastoderm periphery. These are the only cells normally attached to the vitelline membrane — the substrate for expansion. When most of the blastoderm was excised, leaving the band of edge cells, and the cultures then treated with colchicine, expansion occurred normally. The colchicine effect on blastoderm expansion could not therefore be ascribed to a direct effect on the edge cells. (4) An alternative site of action of the drug is the remaining cells of the blastoderm. These normally become progressively flatter as expansion proceeds. If flattening in these cells is even partially dependent on their cytoplasmic microtubules, disruption of these microtubules might result in the inherent contractility of the cells resisting and eventually halting edge cell migration. That cell shape in these cells is dependent on microtubules was demonstrated by treating flat blastoderm fragments with colchicine. On incubation, the area occupied by these fragments decreased by 25–30 % more than controls. The significance of these results in the general context of orientated cell movements and cell shape determination is discussed, with particular emphasis on the analogous system of Fundulus epiboly.

The influence of the area opaca on the development of the young chick embryo

Development ◽  
1967 ◽  
Vol 17 (1) ◽  
pp. 195-212
Author(s):  
Ruth Bellairs ◽  
D. R. Bromham ◽  
C. C. Wylie
Keyword(s):  
Chick Embryo ◽  
Chorioallantoic Membrane ◽  
Yolk Sac ◽  
Vitelline Membrane ◽  
Young Chick ◽  
Chick Blastoderm ◽  
Inner Surface ◽  
Peripheral Cells ◽  
Area Pellucida

The area opaca of the chick blastoderm is generally regarded as being merely the primordium of the yolk sac. Thus it might be expected that during the early stages of development its role would be essentially to grow and to differentiate, rather than to exert any influence on the development of the area pellucida. Such a view would be supported by the fact that pieces of the area pellucida can differentiate in the absence of the area opaca if they are isolated on the chorioallantoic membrane (Rawles, 1936) or in vitro (de Haan, 1964). There are, however, reasons for enquiring whether the area opaca does exert some influence on the area pellucida. The first is that New (1959) has demonstrated that the blastoderm is normally under tension, and that this tension is produced by the peripheral cells of the area opaca which adhere to the inner surface of the vitelline membrane.

R452 – Nasopharyngeal Yolk Sac Tumors: A Rare Pediatric Occurrence

2008 ◽  
Vol 139 (2_suppl) ◽  
pp. P196-P196 ◽  
Author(s):  
Lorraine M Smith ◽  
Ryan F Osborne
Keyword(s):  
Head And Neck ◽  
Clinical Presentation ◽  
Yolk Sac ◽  
High Dose ◽  
Presenting Symptoms ◽  
Mild Improvement ◽  
Pathologic Features ◽  
Yolk Sac Tumors ◽  
Infant Girl ◽  
High Level

Problem To report the rare occurrence of a yolk sac tumor of the nose and nasopharynx presenting as acute sinusitis and bilateral complete blindness. Methods The clinical presentation, pathologic features, and management of this 2-year-old infant girl is reviewed. We also performed a medical literature search in English using PUBMED and OVID databases. We then analyzed the literature with respect to clinical presentation, manifestations and therapies for other extra-gonadal yolk sac tumors presenting in the head and neck. Results The patient was treated with 4 courses of high dose cis-platinum, etoposide, bleomycin repeated every 3 weeks along with surgery. She had initial mild improvement in visual perception along with shrinkage of her tumor. The yolk sac malignancies of the head and neck are often, large, aggressive lesions on presentation that once treated have a tendency to recur. Conclusion Yolk sac tumors (endodermal sinus tumors) represent 3–5% of pediatric malignancies. They are rare malignancies in the head and neck, of germ cell origin. Successful treatment usually requires a combination of chemotherapy and surgical extirpation followed by postoperative chemotherapy. Significance Recurrent sinusitis and nasal obstruction in children should be evaluated carefully and with a high level of suspicion for rare nasal and nasopharyngeal malignancies. Early diagnosis and prompt treatment may alleviate many of the presenting symptoms and prolong life.

The Adhesive Properties and Expansion of the Chick Blastoderm

Development ◽  
1959 ◽  
Vol 7 (2) ◽  
pp. 146-164
Author(s):  
D. A. T. New
Keyword(s):  
Tissue Culture ◽  
Vitelline Membrane ◽  
Cell Surfaces ◽  
Adhesive Properties ◽  
Chick Blastoderm ◽  
Inner Surface

During the first 4 days of incubation the chick blastoderm expands to surround the yolk. Its expansion takes place over the inner surface of the vitelline membrane, and the edge of the blastoderm is firmly attached to this membrane. Little attention has been paid hitherto to the mechanism of this expansion, presumably because it lies outside the embryo proper. But many of the problems involved are of considerable interest, not only as they relate to development within cleidoic eggs, but also in connexion with more general questions affecting expansion of epithelia and the nature of cell surfaces. Blastoderm expansion has many points of similarity with the spreading of epithelia across wounds, and some of the factors involved may prove to be similar to those affecting the radiation of loose sheets of cells in tissue culture.

Differentiation of the yolk-sac endoderm under the influence of the digestive-tract mesenchyme

Development ◽  
1981 ◽  
Vol 62 (1) ◽  
pp. 277-289
Author(s):  
Tohru Masui
Keyword(s):  
Digestive Tract ◽  
Goblet Cells ◽  
Yolk Sac ◽  
Intestinal Type ◽  
Area Vasculosa ◽  
Self Differentiation ◽  
Parenchymal Cells ◽  
Endodermal Cells ◽  
Area Pellucida

To reveal differentiation potency of yolk-sac endoderm, this tissue from quail embryos was cultured alone or in association with digestive-tract mesenchymes of chick embryos. When yolk-sac endoderm was cultured alone in vitro, the endoderm of the area vitellina differentiated into the yolk-sac parenchyma, but the endoderm of the extraembryonic area pellucida (EEAP) failed to differentiate into yolk-sac parenchyma, and the endoderm of the area vasculosa became necrotic. When endoderm of the area vitellina was cultured in association with digestive-tract mesenchymes, all the endodermal cells developed into yolk-sac parenchymal cells after two days. Later, basophilic cells appeared among them, and differentiated into both mesenchymespecific epithelia and intestinal-type epithelium with a striated border, and villi were also formed. Goblet cells appeared in all types of recombinations. The endoderm of the EEAP cultured with digestive-tract mesenchymes gave similar results to that of the area vitellina. In contrast, endoderm of the area vasculosa, when cultured with digestive-tract mesenchymes,became necrotic. The present investigation demonstrated that the endoderms of the area vitellina and of the EEAP differ in self-differentiation potency, and that their developmental fates can be modified by the influence of digestive-tract mesenchymes. These endoderms can differentiate into the mesenchyme-specific epithelia, though they often differentiate also into the intestinal-type epithelium.

The relationship between the edge of the chick blastoderm and the vitelline membrane

1969 ◽  
Vol 163 (2) ◽  
pp. 113-121 ◽  
Author(s):  
Ruth Bellairs ◽  
A. Boyde ◽  
Joan E. M. Heaysman
Keyword(s):  
Vitelline Membrane ◽  
Chick Blastoderm ◽  
The Relationship

scholarly journals An Empirical Research on Impact of HRD Climate on Infosys Pune

1970 ◽  
Vol 9 (1) ◽  
pp. 7-21
Author(s):  
Geetanjali Bhambhani ◽  
Monica Sainy ◽  
Rajiv Gupta
Keyword(s):  
Human Resource Development ◽  
Service Industry ◽  
Pull Out ◽  
Current Scenario ◽  
Team Spirit ◽  
Highly Correlated ◽  
High Level ◽  
Relationship Of ◽  
General Climate ◽  
One Way Anova

In current scenario of ever changing surroundings IT sector is an emergent and mounting solitary. IT sector being a part Service industry is extreme lyreliant on the proficiencies and enthusiasm of recruits. Thus it’s momentous to investigate Human Resource Development which is comprised of two elements i.e., climate and culture of such organizations. The current research is an attempt to identify the HRD-climate practices in Infosys Pune. The investigator has used standardized planned opinionaire together information from the 50 employees of Infosys opinionaire.The information collected was analyzed by applying Factor analysis, Friedmen-test, one-way anova, Correlations and mean score. The main aim of present research was to examine the temperament of HRD-climate in Infosys and identify the factors conducive towards HRD-climate. Here researcher makes an effort to pull out notable HRD-Climate components derived from the inter-relationship of variables of HRD-Climate. Based on belief of Infosys employee’s influence of HRD components is measured. The result of the study involves 50 respondents from Infosys. The correlation analysis it has been observed that all three components HRD Mechanisms, General climate and OCTAPACE Culture are highly correlated to each other the value of r is lies 0.687 to 0.834, which highlights that deviation in single component will have strong influence on other two components. HRD-mechanisms is the top influencing element with mean score of 2.14. On account of overall result research determines that employees are motivated in their organisation, there is high level of team spirit and employees are encouraged to bring creative ideas and are supported by top management of organisation.

Microfluidic Device for Spatial Control of Cell Seeding in Engineered Tissues

2013 ◽  
Author(s):  
Zaw Win ◽  
Geoffrey D. Vrla ◽  
Emily N. Sevcik ◽  
Patrick W. Alford
Keyword(s):  
Cell Shape ◽  
Microcontact Printing ◽  
Contractile Function ◽  
Cell Coupling ◽  
Engineered Tissues ◽  
Cell Organization ◽  
Microfabrication Techniques ◽  
Cell Cell

In vivo tissues have finely controlled hierarchical structure that is often difficult to mimic in vitro. Microfabrication techniques, such as microcontact printing, can be used to reproduce tissue structure in vitro by controlling cell shape and orientation [1]. Several recent results suggest that cellular organization and structure can influence tissue function in engineered tissues [2–4]. For example, using microcontact printing and muscular thin film technology, we recently demonstrated that engineered vascular tissues whose smooth muscle cells possessed more elongated spindle-like geometries, similar to in vivo structure, exhibited more physiological contractile function [5]. In these studies, cells were seeded using traditional imprecise seeding methods. But recent results have shown that cell-cell coupling plays a significant role in functional contractility [6], suggesting that not only cellular geometry, but cell-cell organization, within a tissue is important to reproduce in engineered tissues to mimic in vivo function.

scholarly journals Image-derived models of cell organization changes during differentiation and drug treatments

2020 ◽  
Vol 31 (7) ◽  
pp. 655-666 ◽  
Author(s):  
Xiongtao Ruan ◽  
Gregory R. Johnson ◽  
Iris Bierschenk ◽  
Roland Nitschke ◽  
Melanie Boerries ◽  
...  
Keyword(s):  
Single Cell ◽  
Pc12 Cells ◽  
Cell Shape ◽  
Nuclear Shape ◽  
Extensive Cell ◽  
Cell Organization ◽  
Drug Treatments ◽  
Mitochondrial Distribution ◽  
Cell Variation ◽  
Time Point

Images of differentiating PC12 cells were used to construct models of cell shape, nuclear shape, and mitochondrial distribution. Likely trajectories that a single cell would have followed if it had been observed at each time point were found, and synthetic movies made that show the extensive cell–cell variation in rate and extent of differentiation.

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