The relationship between cleavage and blastocoel formation in Xenopus laevis

Development ◽  
1971 ◽  
Vol 26 (1) ◽  
pp. 37-49
Author(s):  
Marvin R. Kalt
Keyword(s):  
Cell Division ◽  
Xenopus Laevis ◽  
Light Microscopy ◽  
Serial Sections ◽  
Distinct Entity ◽  
Animal Pole ◽  
Amphibian Embryos ◽  
Vegetal Pole ◽  
Morula Stage ◽  
The Relationship

Blastocoel formation in Xenopus laevis was investigated by light microscopy using serial sections of epoxy-embedded, staged embryos. The earliest manifestation of the blastocoel in the embryo appeared during the first cleavage as a modification in the animal pole furrow tip. This modification consisted of an expansion of a localized area of the furrow. As the blastocoel became a distinct entity, it remained stationary, while the furrow tip continued to advance inwardly. In contrast, no such furrow cavity was observed in the vegetal pole furrow during its formation. During subsequent cleavages, up to the late morula stage, furrows on opposite sides of any given blastomere had different morphologies. As further divisions occurred, the mode of furrow formation became identical regardless of location in the embryo. It is suggested that the cytokinetic pattern in early amphibian embryos is modified to allow for the formation of the blastocoel. After the blastocoel has formed, the cytokinetic pattern changes to one which is concerned solely with cell division.

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.

scholarly journals Oriented cell divisions and cellular morphogenesis in the zebrafish gastrula and neurula: a time-lapse analysis

Development ◽  
1998 ◽  
Vol 125 (6) ◽  
pp. 983-994 ◽  
Author(s):  
M.L. Concha ◽  
R.J. Adams
Keyword(s):  
Cell Division ◽  
Time Lapse ◽  
Ventral Surface ◽  
Neural Plate ◽  
Common Mechanism ◽  
Gradual Transition ◽  
Animal Pole ◽  
Dorsal Midline ◽  
Vegetal Pole ◽  
The Central Nervous System

We have taken advantage of the optical transparency of zebrafish embryos to investigate the patterns of cell division, movement and shape during early stages of development of the central nervous system. The surface-most epiblast cells of gastrula and neurula stage embryos were imaged and analysed using a computer-based, time-lapse acquisition system attached to a differential interference contrast (DIC) microscope. We find that the onset of gastrulation is accompanied by major changes in cell behaviour. Cells collect into a cohesive sheet, apparently losing independent motility and integrating their behaviour to move coherently over the yolk in a direction that is the result of two influences: towards the vegetal pole in the movements of epiboly and towards the dorsal midline in convergent movements that strengthen throughout gastrulation. Coincidentally, the plane of cell division becomes aligned to the surface plane of the embryo and oriented in the anterior-posterior (AP) direction. These behaviours begin at the blastoderm margin and propagate in a gradient towards the animal pole. Later in gastrulation, cells undergo increasingly mediolateral-directed elongation and autonomous convergence movements towards the dorsal midline leading to an enormous extension of the neural axis. Around the equator and along the dorsal midline of the gastrula, persistent AP orientation of divisions suggests that a common mechanism may be involved but that neither oriented cell movements nor shape can account for this alignment. When the neural plate begins to differentiate, there is a gradual transition in the direction of cell division from AP to the mediolateral circumference (ML). ML divisions occur in both the ventral epidermis and dorsal neural plate. In the neural plate, ML becomes the predominant orientation of division during neural keel and nerve rod stages and, from late neural keel stage, divisions are concentrated at the dorsal midline and generate bilateral progeny (C. Papan and J. A. Campos-Ortega (1994) Roux's Arch. Dev. Biol. 203, 178–186). Coincidentally, cells on the ventral surface also orient their divisions in the ML direction, cleaving perpendicular to the direction in which they are elongated. The ML alignment of epidermal divisions is well correlated with cell shape but ML divisions within the neuroepithelium appear to be better correlated with changes in tissue morphology associated with neurulation.

Roles of Cortical and Subcortical Components in Cleavage Furrow Formation in Amphibia

1972 ◽  
Vol 11 (2) ◽  
pp. 543-556
Author(s):  
TSUYOSHI SAWAI
Keyword(s):  
Surface Layer ◽  
Xenopus Laevis ◽  
Species Specificity ◽  
Cleavage Furrow ◽  
Entire Surface ◽  
Animal Pole ◽  
The Future ◽  
Vegetal Pole ◽  
Triturus Pyrrhogaster

In the eggs of the newt, Triturus pyrrhogaster, 2 separate factors are recognized which take part in cleavage furrow formation. (1) The inductive capacity for the furrow formation by the cytoplasm lying under the cortex along the cleavage furrow (FIC); and (2) the reactivity of the overlying cortex to form a furrow in response to FIC. (1) FIC. The inductive capacity is shown by the fact that FIC induces a furrow on whichever part of the surface under which FIC is transplanted. FIC is distributed along the cleavage furrow and even extends along the future furrow plane ahead of the furrow tip. The distance FIC precedes the furrow tip is about 1.0 mm in the animal hemisphere and is less in the vegetal hemisphere. In the direction at right angles to the furrow plane, FIC does not spread more than 0.1 mm. FIC is also present in the eggs of Xenopus laevis. Species specificity of FIC for induction is not found between Triturus and Xenopus. (2) Surface layer. At the onset of the first cleavage, the reactivity of the cortex to form the furrow in answer to FIC induction is localized on the animal pole region. The reactivity of the cortex propagates medially as a belt along the surface towards the vegetal pole with the advancing tip of the cleavage furrow. After the furrow is completed, the reactivity begins to be lost from the animal pole region, and eventually over the entire surface. The reactivity, however, reappears on the animal pole region simultaneously with the second cleavage.

The Effects of β-Mercaptoethanol on the Morphogenetic Movements of Amphibian Embryos

Development ◽  
1963 ◽  
Vol 11 (1) ◽  
pp. 155-166
Author(s):  
P. Malpoix ◽  
J. Quertier ◽  
J. Brachet
Keyword(s):  
Neural Tube ◽  
Tube Formation ◽  
Animal Pole ◽  
Morphogenetic Movements ◽  
Complete Development ◽  
Early Stages ◽  
Amphibian Embryos ◽  
Biological Specificity ◽  
Neural Tube Formation

The inhibition by β-mercaptoethanol of morphogenesis in amphibians, freshwater hydra, planarians and regenerating tadpoles, has already been reported by one of us (Brachet, 1958, 1959a, b, c). The present work provides a closer analysis of the biological specificity of j8-mercaptoethanol with regard to the different movements which produce gastrulation in amphibians: invagination, epiboly, convergent stretching and ingression. The main result, obtained with Pleurodeles, was that gastrulation is completely inhibited by M/100 β-mercaptoethanol. Lower concentrations (M/300) permit more complete development, but the resulting embryos are abnormal. β-Mercaptoethanol interferes with neural tube formation, but has less effect on the development of the notochord and the mesodermal somites. It was further noted that, when embryos are treated at very early stages (1–2 cells, young blastulae), the blastocoele seems to collapse and the ectoblast of the animal pole is deeply puckered.

Activation of dorsal development by contact between the cortical dorsal determinant and the equatorial core cytoplasm in eggs of Xenopus laevis

Development ◽  
1997 ◽  
Vol 124 (8) ◽  
pp. 1543-1551 ◽  
Author(s):  
H. Kageura
Keyword(s):  
Xenopus Laevis ◽  
Dorsal Side ◽  
Equatorial Region ◽  
Normal Embryo ◽  
Dorsal Region ◽  
The Core ◽  
Dorsal Axis ◽  
The Future ◽  
Vegetal Pole ◽  
Cell Embryo

In eggs of Xenopus laevis, dorsal development is activated on the future dorsal side by cortical rotation, after fertilization. The immediate effect of cortical rotation is probably the transport of a dorsal determinant from the vegetal pole to the equatorial region on the future dorsal side. However, the identity and action of the dorsal determinant remain problematic. In the present experiments, individual isolated cortices from various regions of the unfertilized eggs and embryos were implanted into one of several positions of a recipient 8-cell embryo. The incidence of secondary axes was used not only to locate the cortical dorsal determinant at different times but also to locate the region of the core competent to respond to the dorsal determinant. The dorsal axis-inducing activity of the cortex occurred around the vegetal pole of the unfertilized egg. During cortical rotation, it shifted from there to a wide dorsal region. This is apparently the first evidence for the presence of a dorsal determinant in the egg cortex. The competence of the core of the 8-cell embryo was distributed in the form of gradient with the highest responsiveness at the equator. These results suggest that, in the normal embryo, dorsal development is activated by contact between the cortical dorsal determinant and the equatorial core cytoplasm, brought together through cortical rotation.

Ultrastructural changes in the avian vitelline membrane during embryonic development

Development ◽  
1969 ◽  
Vol 21 (3) ◽  
pp. 467-484
Author(s):  
Cynthia Jensen
Keyword(s):  
Embryonic Development ◽  
Mechanical Strength ◽  
Dual Role ◽  
Early Embryonic Development ◽  
Ultrastructural Changes ◽  
Vitelline Membrane ◽  
Entire Surface ◽  
Animal Pole ◽  
The Third ◽  
Vegetal Pole

The vitelline (yolk) membrane of the avian egg plays a dual role during early embryonic development; it encloses the yolk and provides a substratum for expansion of the embryo (Fig. 1). Expansion appears to be dependent upon the movement of cells at the edge of the blastoderm which is intimately associated with the inner layer of the vitelline membrane (New, 1959; Bellairs, 1963). The blastoderm (embryonic plus extraembryonic cells) has almost covered the entire surface of the yolk by the third and fourth days of incubation, and when this stage has been reached the vitelline membrane ruptures over the embryo and slips toward the vegetal pole. Rupture of the membrane during development appears to be the consequence of a decrease in its mechanical strength (Moran, 1936), which changes most rapidly at the animal pole (over the embryo).

An ultrastructural study of the effects of wheat germ agglutinin (WGA) on cell cortex organization during the first cleavage of Xenopus laevis eggs. II. Cortical wound healing

1979 ◽  
Vol 37 (1) ◽  
pp. 59-67
Author(s):  
M. Geuskens ◽  
R. Tencer
Keyword(s):  
Wound Healing ◽  
Plasma Membrane ◽  
Electron Microscope ◽  
Xenopus Laevis ◽  
Ultrastructural Study ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Cell Cortex ◽  
Animal Pole ◽  
Annular Zone

Uncleaved fertilized eggs of Xenopus laevis treated with wheat germ agglutinin (WGA) have been pricked at the animal pole both inside and outside the regressed furrow region. The wounded cortex of both regions has been studied with the electron microscope and compared with the same region of wounded, untreated eggs. In all 3 cases, filaments are organized in an annular zone in the damaged cortex. When the surface is pricked outside the regressed furrow of WGA-treated embryos, bundles of microfilaments radiate from the ring and extend in deep folds which form a ‘star’ around the wound at the surface of the embryo. However, when the surface is pricked in the new membrane of the regressed furrow, filaments are intermingled with internalized portions of the plasma membrane. It is suggested that, when the surface is pricked outside the furrow region, more filaments are mobilized to counteract the tangential retraction of the membrane which has acquired more rigidity after WGA binding.

Conditioning of a culture substratum by the ectodermal layer promotes attachment and oriented locomotion by amphibian gastrula mesodermal cells

1983 ◽  
Vol 59 (1) ◽  
pp. 43-60 ◽  
Author(s):  
N. Nakatsuji ◽  
K.E. Johnson
Keyword(s):  
Cell Migration ◽  
Time Lapse ◽  
Ambystoma Maculatum ◽  
Specific Cell ◽  
Animal Pole ◽  
Micron Diameter ◽  
The Relationship ◽  
Extracellular Fibrils ◽  
Scanning Electron

We have found that ectodermal fragments of Ambystoma maculatum gastrulae deposit immense numbers of 0.1 micron diameter extracellular fibrils on plastic coverslips. When migrating mesodermal cells from A. maculatum gastrulae are seeded on such conditioned plastic substrata, they attach and begin migrating after 15–30 min in vitro. We did a detailed analysis of the relationship between fibril orientation and cell migration using time-lapse cinemicrography, scanning electron microscopy, and a microcomputer with a graphics tablet and morphometric program. We found that cells move in directions closely related to the orientation of fibrils. Usually fibrils are oriented in dense arrays with a predominance of fibrils running parallel to the blastopore-animal pole axis of the explant, and cells move preferentially along lines parallel to the blastopore-animal pole axis. When fibrils are unaligned, cells move at random. We have also shown that cells move with a slightly stronger tendency towards the animal pole direction. These results are discussed concerning the mechanism of specific cell migration during amphibian gastrulation.

GSK3beta/shaggy mediates patterning along the animal-vegetal axis of the sea urchin embryo

Development ◽  
1998 ◽  
Vol 125 (13) ◽  
pp. 2489-2498 ◽  
Author(s):  
F. Emily-Fenouil ◽  
C. Ghiglione ◽  
G. Lhomond ◽  
T. Lepage ◽  
C. Gache
Keyword(s):  
Sea Urchin ◽  
Wnt Pathway ◽  
Dominant Negative ◽  
Early Gene ◽  
Expression Domain ◽  
Animal Pole ◽  
Axial Patterning ◽  
Sea Urchin Embryo ◽  
Vegetal Pole ◽  
Dominant Negative Activity

In the sea urchin embryo, the animal-vegetal axis is defined before fertilization and different embryonic territories are established along this axis by mechanisms which are largely unknown. Significantly, the boundaries of these territories can be shifted by treatment with various reagents including zinc and lithium. We have isolated and characterized a sea urchin homolog of GSK3beta/shaggy, a lithium-sensitive kinase which is a component of the Wnt pathway and known to be involved in axial patterning in other embryos including Xenopus. The effects of overexpressing the normal and mutant forms of GSK3beta derived either from sea urchin or Xenopus were analyzed by observation of the morphology of 48 hour embryos (pluteus stage) and by monitoring spatial expression of the hatching enzyme (HE) gene, a very early gene whose expression is restricted to an animal domain with a sharp border roughly coinciding with the future ectoderm / endoderm boundary. Inactive forms of GSK3beta predicted to have a dominant-negative activity, vegetalized the embryo and decreased the size of the HE expression domain, apparently by shifting the boundary towards the animal pole. These effects are similar to, but even stronger than, those of lithium. Conversely, overexpression of wild-type GSK3beta animalized the embryo and caused the HE domain to enlarge towards the vegetal pole. Unlike zinc treatment, GSK3beta overexpression thus appeared to provoke a true animalization, through extension of the presumptive ectoderm territory. These results indicate that in sea urchin embryos the level of GSKbeta activity controls the position of the boundary between the presumptive ectoderm and endoderm territories and thus, the relative extent of these tissue layers in late embryos. GSK3beta and probably other downstream components of the Wnt pathway thus mediate patterning both along the primary AV axis of the sea urchin embryo and along the dorsal-ventral axis in Xenopus, suggesting a conserved basis for axial patterning between invertebrate and vertebrate in deuterostomes.

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