Sodium transport and the control of epiblast polarity in the early chick embryo

Development ◽  
1983 ◽  
Vol 77 (1) ◽  
pp. 73-98
Author(s):  
Claudio D. Stern ◽  
Debora O. MacKenzie
Keyword(s):  
Chick Embryo ◽  
Transport Properties ◽  
Sodium Transport ◽  
Primitive Streak ◽  
Reverse Polarity ◽  
Ouabain Binding ◽  
Physiological Functions ◽  
Rapid Reversal ◽  
Electrophysiological Studies ◽  
Morphological Polarity

The sodium transport properties of chick epiblast during gastrulation were studied by various techniques. It was found that the epiblast is capable of unidirectional apical tobasal sodium transport, in towards the underlying intraembryonic space. The Na-K-ATPasewas localized by [3H]ouabain binding and autoradiography near the basal surfaces of the cells, and the number of pump sites was quantified. The transport rate of sodium was determined with 22Na. Electrophysiological studies on embryos at primitive streak stages showed a transepithelial potential of about + 16 ± 5mV (basal side positive) which was sensitive to strophanthidin. Applying similar voltages but of reverse polarity to isolated sheets of epiblast caused a rapid reversal of some oftheir morphological polarity markers as well as some of their physiological functions. The relevance of these results to development is discussed.

Fluid transport across the epiblast of the early chick embryo

Development ◽  
1985 ◽  
Vol 88 (1) ◽  
pp. 365-384
Author(s):  
Claudio D. Stern ◽  
Simon Manning ◽  
James I. Gillespie
Keyword(s):  
Chick Embryo ◽  
Large Volume ◽  
Sodium Transport ◽  
Fluid Transport ◽  
Osmotic Gradient ◽  
Simple Method ◽  
Volume Increase ◽  
Early Chick Embryo ◽  
Fluid Uptake ◽  
Electrophysiological Studies

A simple method is described which allows quantitation of the rate of fluid transport across the isolated epiblast of the early chick embryo. This method consists of allowing the tissue to form spheres, which then spontaneously undergo a large volume increase. The rate of fluid uptake into the spheres can be estimated by measuring the dimensions of the spheres. Pharmacological and electrophysiological studies were performed on the spheres to determine the mechanisms of fluid transport. It was found that fluid is driven into the interior of the spheres by the osmotic gradient generated by unidirectional sodium transport and to a lesser extent by another mechanism, as yet unknown. We discuss possible candidates for this mechanism, and consider the significance of these findings to early development.

Cell proliferation in the gastrulating chick embryo: a study using BrdU incorporation and PCNA localization

Development ◽  
1993 ◽  
Vol 118 (2) ◽  
pp. 389-399 ◽  
Author(s):  
E.J. Sanders ◽  
M. Varedi ◽  
A.S. French
Keyword(s):  
Cell Proliferation ◽  
Chick Embryo ◽  
Cell Density ◽  
Generation Time ◽  
Primitive Streak ◽  
S Phase ◽  
Nuclear Antigen ◽  
Brdu Incorporation ◽  
Similar Proportion ◽  
Differential Growth

Cell proliferation in the gastrulating chick embryo was assessed using two independent techniques which mark cells in S phase of the mitotic cycle: nuclear incorporation of bromodeoxyuridine (BrdU) detected immunocytochemically and immunolocalization of proliferating cell nuclear antigen (PCNA). Computer-reconstructed maps were produced showing the distribution of labelled nuclei in the primitive streak and the cell layers. These distributions were also normalized to take into account regional differences in cell density across the embryo. Results from a 2 hour pulse of BrdU indicated that although cells at caudal levels of the primitive streak showed the highest incorporation, this region showed a similar proportion of labelled cells to the surrounding caudal regions of the epiblast and mesoderm when normalized for cell density. The entire caudal third of the embryo showed the highest proportion of cells in S phase. Cells of Hensen's node showed a relatively low rate of incorporation and, although the chordamesoderm cells showed many labelled nuclei, this appeared to be a reflection of a high cell density in this region. Combining this result with results from a 4 hour pulse of BrdU permitted mapping of cell generation time across the entire embryo. Generation times ranged from a low value of approximately 2 hours at caudal levels of both the epiblast and mesoderm, to an upper value of approximately 10 hours in the rostral regions of the primitive streak, in the mid-lateral levels of the epiblast and in the chordamesoderm rostral to Hensen's node. Cells at caudal regions of the primitive streak showed a generation time of approximately 5 hours. Taking into account that cells are generally considered to be continuously moving through the primitive streak, we conclude that cell division, as judged by generation time, is greatly reduced during transit through this region, despite the presence there of cells in S phase and M phase. Immunocytochemical localization of PCNA-positive nuclei gave generally similar distributions to those obtained with BrdU incorporation, confirming that this endogenous molecule is a useful S-phase marker during early embryogenesis. Mid-levels and caudal levels of the primitive streak showed the highest numbers of positive nuclei, and the highest proportion of labelling after cell density was accounted for. As with BrdU incorporation, the highest proportions of PCNA-positive nuclei were found towards the caudal regions of the epiblast and mesoderm. These results suggest that the differential growth of the caudal region of the embryo at this time is a direct consequence of elevated levels of cell proliferation in this region.(ABSTRACT TRUNCATED AT 400 WORDS)

Primordial germ cells in normal and transected duck blastoderms

Development ◽  
1968 ◽  
Vol 20 (3) ◽  
pp. 247-260
Author(s):  
Teresa Rogulska
Keyword(s):  
Chick Embryo ◽  
Blood Vessels ◽  
Germ Cells ◽  
Anterior Part ◽  
Primordial Germ Cells ◽  
Primitive Streak ◽  
Experimental Investigations ◽  
Suggestive Evidence ◽  
Area Pellucida

Suggestive evidence for the extragonadal origin of germ cells in birds was first presented by Swift (1914), who described primordial germ cells in the chick embryo at as early a stage as the primitive streak. According to Swift, primordial germ cells are originally located extra-embryonically in the anterior part of the blastoderm and occupy a crescent-shaped region (‘germinal crescent’) on the boundary between area opaca and area pellucida. Swift also found that primordial germ cells later enter into the blood vessels, circulate together with the blood throughout the whole blastoderm and finally penetrate into the genital ridges, where they become definitive germ cells. Swift's views have been confirmed in numerous descriptive and experimental investigations. Among the latter, the publications of Willier (1937), Simon (1960) and Dubois (1964a, b, 1965a, b, 1966) merit special attention. Dubois finally proved that the genital ridges exert a strong chemotactic influence on the primordial germ cells.

Changes in the transferrin requirement of cultured chick embryo mesoderm cells during early differentiation

Development ◽  
1986 ◽  
Vol 95 (1) ◽  
pp. 81-93
Author(s):  
E. J. Sanders
Keyword(s):  
Chick Embryo ◽  
Type I Collagen ◽  
Specific Effect ◽  
Primitive Streak ◽  
Cellular Adhesion ◽  
Type I ◽  
Surface Binding ◽  
Surface Receptors ◽  
Early Differentiation ◽  
Species Specific

Mesodermal tissue from the chick embryo at various stages of early differentiation was cultured in hydrated gels of type I collagen in the presence and absence of transferrin. Primary mesoderm explants from primitive-streak-stage embryos responded to the presence of avian transferrin by significantly improved outgrowth which appeared to be related to the ability of the cells to attach to, and migrate in, the collagen. No evidence was obtained which suggested that this observation was dependent on increased cell proliferation. This outgrowth enhancement was not duplicated by transferrin of human origin. The avian transferrin did not produce this effect on cells cultured on plastic substrata, suggesting that the species-specific effect involves modulation by the extracellular matrix. Mesoderm explants from somite stages of development showed no increase in outgrowth in the presence of either avian or human transferrin as judged by counting the number of outwandering cells. Ultrastructural immunocytochemistry indicated surface binding of transferrin by cells in the gels, and the presence of endogenous transferrin on the surfaces of mesoderm cells in situ and in their extracellular environment. It is suggested that by binding to cell surface receptors, transferrin may be able to influence the strength of cellular adhesion to collagen and hence the capacity for cell locomotion.

Studies on self-differentiating and induction capacities of Hensen's node using intracoelomic grafting technique

Development ◽  
1972 ◽  
Vol 28 (3) ◽  
pp. 547-558
Author(s):  
J. R. Viswanath ◽  
Leela Mulherkar
Keyword(s):  
Chick Embryo ◽  
Neural Tissue ◽  
Primitive Streak ◽  
Germ Layer ◽  
Grafting Technique ◽  
Definite Combination

Living Hensen's node of the definitive primitive streak of chick embryo was prepared into ‘sandwiches’ with the competent ectoderm and the sandwich grafts were transplated into the 2·5 day chick embryo using the intracoelomic grafting technique of Hamburger. One hundred and twenty-four grafts were prepared and transplanted intracoelomically, 28 grafts were lost due to the death of the host embryos, 63 grafts did not differentiate at all, but 33 well-defined grafts were recovered, after cultivating the transplanted hosts for 12–14 days. All kinds of tissues from feather germs to neural tissue were found to have differentiated in the grafts. The more frequently occurring tissues were feather germs, epidermal vesicle, neural tissue, kidney and muscle. Other differentiations were the cartilage notochord and gut. No definite combination pattern has emerged from the tissues. But when the tissues were traced to their germ-layer derivation, 22 of them belonged to the mesodermal complex, 11 to the ectodermal complex and 8 to the endodermal complex. In the light of the above results, the probable existence of a mesodermal factor and an ectodermal factor independently responsible for the respective differentiations, as also the competence of the ectoderm, is discussed.

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