scholarly journals STRUCTURAL VARIATIONS DURING MITOSIS IN THE CHICK EMBRYO

1967 ◽  
Vol 33 (1) ◽  
pp. 179-196 ◽  
Author(s):  
Allan L. Allenspach ◽  
L. E. Roth
Keyword(s):  
Free Surface ◽  
Cell Division ◽  
Epithelial Cells ◽  
Chick Embryo ◽  
Mesenchymal Cells ◽  
Cleavage Furrow ◽  
Chick Embryos ◽  
Structural Variations ◽  
Spindle Elongation ◽  
Elongation Process

Selected tissues from chick embryos were fixed in 2% glutaraldehyde and 1% OsO4, both buffered at pH 7.6 with Veronal-acetate, and were embedded in Maraglas or Araldite. Two types of cell division have been noted. Generally, epithelial cells divide predominantly by a shortening of the chromosome-to-pole distance rather than by spindle elongation; mesenchymal cells undergo extensive spindle elongation. The presence of numerous continuous microtubules in cells that undergo extensive spindle elongation functionally implicates these tubules in the elongation process. In most embryonic epithelia, the cleavage furrow converges to a fixed site forming a mid-body near the anchoring desmosomes at the free surface; symmetrical furrow formation is typical of mesenchymal cells which lack desmosomes. The hypothesis of cleavage furrow formation and the fate of the mid-body that is formed during cytokinesis are discussed.

scholarly journals Bayesian inference of agent-based models: a tool for studying kidney branching morphogenesis

2017 ◽  
Author(s):  
Ben Lambert ◽  
Adam L. MacLean ◽  
Alexander G. Fletcher ◽  
Alexander N. Combes ◽  
Melissa H. Little ◽  
...  
Keyword(s):  
Cell Division ◽  
Growth Factor ◽  
Epithelial Cell ◽  
Epithelial Cells ◽  
Ex Vivo ◽  
Collecting Duct ◽  
Mesenchymal Cells ◽  
Ureteric Bud ◽  
Agent Based ◽  
Kidney Morphogenesis

AbstractThe adult mammalian kidney has a complex, highly-branched collecting duct epithelium that arises as a ureteric bud sidebranch from an epithelial tube known as the nephric duct. Subsequent branching of the ureteric bud to form the collecting duct tree is regulated by subcellular interactions between the epithelium and a population of mesenchymal cells that surround the tips of outgrowing branches. The mesenchymal cells produce glial cell-line derived neurotrophic factor (GDNF), that binds with RET receptors on the surface of the epithelial cells to stimulate several subcellular pathways in the epithelium. Such interactions are known to be a prerequisite for normal branching development, although competing theories exist for their role in morphogenesis. Here we introduce the first agent-based model of ex vivo kidney uretic branching. Through comparison with experimental data, we show that growth factor-regulated growth mechanisms can explain early epithelial cell branching, but only if epithelial cell division depends in a switch-like way on the local growth factor concentration; cell division occurring only if the driving growth factor level exceeds a threshold. We also show how a recently-developed method, “Approximate Approximate Bayesian Computation”, can be used to infer key model parameters, and reveal the dependency between the parameters controlling a growth factor-dependent growth switch. These results are consistent with a requirement for signals controlling proliferation and chemotaxis, both of which are previously identified roles for GDNF.Author SummaryA number of important congenital disorders arise due to incomplete development of the mammalian kidney. Elucidating the cause of these conditions requires an understanding of the mechanisms that contribute to kidney morphogenesis. Whilst experimental work has suggested several candidate mechanisms, their importance is still not well understood. Here we develop a computational model of kidney morphogenesis at the individual cell level to compare these different hypotheses. Guided by existing experimental evidence we propose that a generic growth factor, that we term “GDNF”, produced from the mesenchyme surrounding the epithelium, can drive a number of cellular responses. Simulations of our agent-based model reveal that diffusion of GDNF, coupled with GDNF-stimulated epithelial cell division, can generate the branching patterns seen in ex vivo kidney explant experiments. We also find that branching depends on the sensitivity of cell proliferation to changes in GDNF levels. In particular our model only generates realistic branching when there is significant variation in GDNF levels along the boundary of the epithelium, and most cells divide only if the local concentration of GDNF exceeds a threshold value. We conclude that feedback between mesenchymal cells that produce GDNF, and epithelial cells that consume it, is vital for normal kidney organogenesis.

scholarly journals Interference with thyroid histogenesis by inhibitors of collagen synthesis.

1977 ◽  
Vol 75 (2) ◽  
pp. 446-463 ◽  
Author(s):  
S R Hilfer ◽  
G L Pakstis
Keyword(s):  
Carboxylic Acid ◽  
Epithelial Cell ◽  
Epithelial Cells ◽  
Chick Embryo ◽  
Collagen Synthesis ◽  
Mesenchymal Cells ◽  
Cell Product ◽  
Fibrillar Material ◽  
Epithelial Origin ◽  
Material Form

Histogenesis of thyroid follicles in the chick embryo begins with a penetration by cells of the mesenchymal capsule into a solid epithelial primordium. Before penetration occurs, slits containing fibrillar material form between the epithelial cells. The fibrillar material is an epithelial cell product as shown by its formation within channels that form in cultures of isolated epithelial primordia. The drugs L-azetidine-2-carboxylic acid (LACA) and alpha, alpha'-dipyridyl, which interfere with collagen synthesis, prevent the formation of fibrils in cultured epithelial primordia and in cultures of whole thyroids. Furthermore, mesenchymal cells do not invade when whole thyroid primordia are cultured in the presence of either drug. The effects of alpha, alpha'-dipyridyl are reversed by washing out the drug; the effects of LACA are reversed by incubation with equimolar or greater amounts of L-proline added to the medium along with the drug. The results are interpreted to mean that the fibrillar material is collagen of epithelial origin, that the collagen in some way plays a role in mesenchymal penetration of the epithelial primordium, and that the epithelium is responsible for the pattern of lobulation within the developing gland.

scholarly journals OBSERVATIONS ON THE INFECTION OF CHICK EMBRYOS WITH BACTERIUM TULARENSE, BRUCELLA, AND PASTEURELLA PESTIS

1941 ◽  
Vol 74 (3) ◽  
pp. 213-222 ◽  
Author(s):  
G. John Buddingh ◽  
Frank C. Womack
Keyword(s):  
Epithelial Cells ◽  
Chick Embryo ◽  
Vascular Endothelium ◽  
Brucella Abortus ◽  
Brucella Melitensis ◽  
Chick Embryos ◽  
Intracellular Growth ◽  
Early Stages ◽  
Brucella Suis ◽  
Natural Hosts

1. Comparison of the infections of chick embryos by the chorio-allantoic route indicates that Bacterium tularense and Brucella suis, abortus, and melitensis exhibit varying degrees of facultative intracellular parasitism. Pasteurella pestis is adapted to rapid proliferation and spread in the intercellular fluids. 2. In the early stages of infection Bacterium tularense has a marked affinity for growth within ectodermal epithelial cells. Brucella suis and Brucella abortus differ in their selectivity for cells of mesodermal derivation and especially in their effect on vascular endothelium. The strain of Brucella melitensis studied is limited in its intracellular growth to ectodermal epithelium. 3. Many of the features characteristic of these infections in the natural hosts are reproduced in the chick embryo and its membranes. 4. The possible implications regarding the differences in behavior of these microorganisms in relation to the problem of infection and pathogenesis of these diseases are discussed.

Periodic segmental anomalies induced by heat shock in the chick embryo are associated with the cell cycle

Development ◽  
1989 ◽  
Vol 105 (1) ◽  
pp. 119-130 ◽  
Author(s):  
D.R. Primmett ◽  
W.E. Norris ◽  
G.J. Carlson ◽  
R.J. Keynes ◽  
C.D. Stern
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Heat Shock ◽  
Simple Model ◽  
Chick Embryo ◽  
Heat Shock Proteins ◽  
Cell Division Cycle ◽  
The Other ◽  
Chick Embryos ◽  
Shock Proteins

This study provides evidence that cells destined to segment together into somites have a degree of cell division synchrony. We have measured the duration of the cell division cycle in somite and segmental plate cells of the chick embryo as 9.5 h using [3H]thymidine pulse- and-chase. Treatment of embryos with any of a variety of inhibitors known to affect the cell division cycle causes discrete periodic segmental anomalies: these anomalies appear about 6–7 somites after treatment and, in some cases, a second anomaly is observed 6 to 7 somites after the first. Since somites take 1.5 h to form, the 6- to 7- somite interval corresponds to about 9–10 h, which is the duration of the cell cycle as determined in these experiments. The anomalies are similar to those seen after heat shock of 2-day chick embryos. Heat shock and some of the other treatments induce the expression of heat-shock proteins (hsp); however, since neither the expression nor the distribution of these proteins relate to the presence or distribution of anomalies seen, we conclude that hsps are not responsible for the pattern of segmental anomalies observed. The production of periodic segmental anomalies appears to be linked to the cell cycle. A simple model is proposed, in which we suggest that the cell division cycle is involved directly in gating cells that will segment together.

Endogenous stages of a ‘chick embryo-adapted’ strain ofEimeria tenella

Parasitology ◽  
1973 ◽  
Vol 66 (1) ◽  
pp. 55-62 ◽  
Author(s):  
P. L. Long
Keyword(s):  
Epithelial Cells ◽  
Chick Embryo ◽  
Second Generation ◽  
Chick Embryos ◽  
Tunica Propria ◽  
High Degree ◽  
Allantoic Cavity ◽  
Pathogenic Effects ◽  
Endogenous Stages

A strain ofE. tenellawhich had been passaged serially in 42 batches of chick embryos appeared to have lost its ability to produce the characteristically large second-generation schizonts in both the embryonic chorioallantois and in the chicken caeca. Numerous small schizonts (10–16 µm in diameter), which contained 8–30 small merozoites, replaced the large second-generation schizonts characteristic of this species. The small schizonts were numerous 3–5 days after inoculation and were restricted to epithelial cells of the embryo allantois when sporozoites were inoculated via the allantoic cavity. These schizonts also occurred in epithelial cells of the caeca of chickens given oocysts via the crop. Cell reactions in the chicken caeca in response to infection were minimal. Numerous minute lesions were present in the chorioallantois 4–6 days after inoculation; these were associated with the small schizonts and later with gamonts and oocysts. The strain reproduced well in the embryo but failed to induce gross pathogenic effects and no mortality resulted from the infection.Only two passages of this strain in chickens were needed to restore a high degree of pathogenicity. This change was accompanied by the reappearance of the characteristically large second-generation schizonts in the tunica propria of the caecal wall.

Continuum model of epithelial morphogenesis during Caenorhabditis elegans embryonic elongation

2009 ◽  
Vol 367 (1902) ◽  
pp. 3379-3400 ◽  
Author(s):  
P. Ciarletta ◽  
M. Ben Amar ◽  
M. Labouesse
Keyword(s):  
Caenorhabditis Elegans ◽  
Epithelial Cells ◽  
Molecular Motor ◽  
Biomechanical Model ◽  
Epithelial Morphogenesis ◽  
Embryonic Cells ◽  
Microtubule Network ◽  
Theoretical Predictions ◽  
Elongation Process ◽  
Muscle Myosin

The purpose of this work is to provide a biomechanical model to investigate the interplay between cellular structures and the mechanical force distribution during the elongation process of Caenorhabditis elegans embryos. Epithelial morphogenesis drives the elongation process of an ovoid embryo to become a worm-shaped embryo about four times longer and three times thinner. The overall anatomy of the embryo is modelled in the continuum mechanics framework from the structural organization of the subcellular filaments within epithelial cells. The constitutive relationships consider embryonic cells as homogeneous materials with an active behaviour, determined by the non-muscle myosin II molecular motor, and a passive viscoelastic response, related to the directional properties of the filament network inside cells. The axisymmetric elastic solution at equilibrium is derived by means of the incompressibility conditions, the continuity conditions for the overall embryo deformation and the balance principles for the embryonic cells. A particular analytical solution is proposed from a simplified geometry, demonstrating the mechanical role of the microtubule network within epithelial cells in redistributing the stress from a differential contraction of circumferentially oriented actin filaments. The theoretical predictions of the biomechanical model are discussed within the biological scenario proposed through genetic analysis and pharmacological experiments.

Contact behaviour during the reassociation of dissociated epithelial cells in primary culture

1987 ◽  
Vol 88 (4) ◽  
pp. 521-526
Author(s):  
R.M. Brown ◽  
C.A. Middleton
Keyword(s):  
Epithelial Cells ◽  
Chick Embryo ◽  
Primary Culture ◽  
Cell Cultures ◽  
Corneal Epithelium ◽  
Time Lapse ◽  
Cell Types ◽  
Epidermal Cells ◽  
Isolated Cells ◽  
Contact Behaviour

The behaviour in culture of dissociated epithelial cells from chick embryo pigmented retina epithelium (PRE), corneal epithelium (CE) and epidermis has been studied using time-lapse cinematography. The analysis concentrated on the contact behaviour of 60 previously isolated cells of each type during a 24 h period starting 3.5 h after the cells were plated out. During the period analysed the number of isolated cells in cultures of all three types gradually decreased as they became incorporated into islands and sheets of cells. However, there were significant differences in behaviour between the cell types during the establishment of these sheets and islands. In PRE cell cultures, islands of cells developed because, throughout the period of analysis, collisions involving previously isolated cells almost invariably resulted in the development of a stable contact. Once having established contact with another cell these cells rarely broke away again to become reisolated. In contrast the contacts formed between colliding CE and epidermal cells were, at least initially, much less stable and cells of both these types were frequently seen to break away and become reisolated after colliding with other cells. Sheets and islands of cells eventually developed in these cultures because the frequency with which isolated cells become reisolated decreased with increasing time in culture. The possible reasons underlying the different behaviour of PRE cells, when compared with that of CE and epidermal cells, are discussed. It is suggested that the decreasing tendency of isolated CE and epidermal cells to become reisolated may be related to the formation of desmosomes.

Nocodazole and cytochalasin D induce tetraploidy in mammalian cells

1984 ◽  
Vol 246 (1) ◽  
pp. C154-C156 ◽  
Author(s):  
G. W. Zieve
Keyword(s):  
Cell Division ◽  
Mammalian Cells ◽  
Cytochalasin D ◽  
Microtubule Assembly ◽  
Reversible Inhibitor ◽  
Cleavage Furrow ◽  
Synchronized Cells ◽  
Cells In Culture ◽  
Wide Range

Nocodazole, a rapidly reversible inhibitor of microtubule assembly is useful for preparing mammalian cells synchronized at all stages of mitosis. When synchronized cells are allowed to progress through mitosis in the presence of cytochalasin D, the cleavage furrow is inhibited and dikaryon cells are formed. These cells become homogeneous populations of stable mononuclear tetraploid cells after the following cell division. This procedure is applicable to a wide range of mammalian cells in culture.

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