Role of cooperative cell movements and mechano-geometric constrains in patterning of axial rudiments in Xenopus laevis embryos

Through the injection of f-aequorin (a calcium-sensitive bioluminescent reporter) into the dorsal micromeres of 8-cell stage Xenopus laevis embryos, and the use of a Photon Imaging Microscope, distinct patterns of calcium signalling were visualised during the gastrulation period. We present results to show that localised domains of elevated calcium were observed exclusively in the anterior dorsal part of the ectoderm, and that these transients increased in number and amplitude between stages 9 to 11, just prior to the onset of neural induction. During this time, however, no increase in cytosolic free calcium was observed in the ventral ectoderm, mesoderm or endoderm. The origin and role of these dorsal calcium-signalling patterns were also investigated. Calcium transients require the presence of functional L-type voltage-sensitive calcium channels. Inhibition of channel activation from stages 8 to 14 with the specific antagonist R(+)BayK 8644 led to a complete inhibition of the calcium transients during gastrulation and resulted in severe defects in the subsequent formation of the anterior nervous system. BayK treatment also led to a reduction in the expression of Zic3 and geminin in whole embryos, and of NCAM in noggin-treated animal caps. The possible role of calcium transients in regulating developmental gene expression is discussed.

Download Full-text

Tension-dependent collective cell movements in the early gastrula ectoderm of Xenopus laevis embryos

Development Genes and Evolution ◽

10.1007/s004270050015 ◽

2000 ◽

Vol 210 (2) ◽

pp. 92-104 ◽

Cited By ~ 67

Author(s):

L. V. Beloussov ◽

N. N. Louchinskaia ◽

A. A. Stein

Keyword(s):

Xenopus Laevis ◽

Cell Movements ◽

Early Gastrula ◽

Xenopus Laevis Embryos

Download Full-text

Reinvestigation of the role of the optic vesicle in embryonic lens induction

Development ◽

10.1242/dev.102.3.517 ◽

1988 ◽

Vol 102 (3) ◽

pp. 517-526 ◽

Cited By ~ 3

Author(s):

R.M. Grainger ◽

J.J. Herry ◽

R.A. Henderson

Keyword(s):

Xenopus Laevis ◽

Optic Vesicle ◽

Multistep Process ◽

Optic Vesicles ◽

Original Report ◽

Lens Formation ◽

Embryonic Ectoderm ◽

Transplantation Experiments ◽

Xenopus Laevis Embryos

The induction of the lens by the optic vesicle in amphibians is often cited as support for the view that a single inductive event can lead to determination in a multipotent tissue. This conclusion is based on transplantation experiments whose results indicate that many regions of embryonic ectoderm which would normally form epidermis can form a lens if brought into contact with the optic vesicle. Although additional evidence argues that during normal development other tissues, acting before the optic vesicle, also contribute to lens induction, it is still widely held, on the basis of these transplantation experiments, that the optic vesicle alone can elicit lens formation in ectoderm. While testing this conclusion by transplanting optic vesicles beneath ventral ectoderm in Xenopus laevis embryos, it became apparent that contamination of optic vesicles by presumptive lens ectoderm cells can generate lenses in these experiments, illustrating the need for adequate host and donor marking procedures. Since previous studies rarely used host and donor marking, it was not clear whether they actually demonstrated that the optic vesicle can induce lenses. Using careful host and donor marking procedures with horseradish peroxidase as a lineage tracer, we show that the optic vesicle cannot stimulate lens formation in neurula- or gastrula-stage ectoderm of Xenopus laevis. Since the general conclusion that the optic vesicle is sufficient for lens induction rests on studies in many organisms, we felt it was important to begin to test this conclusion in other amphibians as well. Similar experiments were therefore performed with Rana Palustris embryos, since it was in this organism that optic vesicle transplant studies had originally argued that this tissue alone can cause lens induction. Under conditions similar to those used in the original report, but with careful controls to assess the origin of lenses in transplants, we found that the optic vesicle alone cannot elicit lens formation. Our data lead us to propose that the optic vesicle in amphibians is not generally sufficient for lens induction. Instead, we argue that lens induction occurs by a multistep process in which an essential phase in lens determination occurs as a result of inductive interactions preceding contact of ectoderm with the optic vesicle.

Download Full-text

The role of premotor interneurons in phase-dependent modulation of a cutaneous reflex during swimming in Xenopus laevis embryos

Journal of Neuroscience ◽

10.1523/jneurosci.12-05-01647.1992 ◽

1992 ◽

Vol 12 (5) ◽

pp. 1647-1657 ◽

Cited By ~ 11

Author(s):

KT Sillar ◽

A Roberts

Keyword(s):

Xenopus Laevis ◽

Cutaneous Reflex ◽

Xenopus Laevis Embryos

Download Full-text

The role of neurohumors in early embryogenesis

Development ◽

10.1242/dev.20.1.119 ◽

1968 ◽

Vol 20 (1) ◽

pp. 119-128

Author(s):

G. A. Buznikov ◽

I. V. Chudakova ◽

L. V. Berdysheva ◽

N. M. Vyazmina

Keyword(s):

Molecular Weight ◽

Xenopus Laevis ◽

Sea Urchin ◽

Early Embryogenesis ◽

Low Molecular Weight ◽

Insect Eggs ◽

Insect Embryos ◽

Related Compounds ◽

Xenopus Laevis Embryos

In a previous paper (Buznikov, Chudakova & Zvezdina, 1964) it has been reported that serotonin (5-hydroxytryptamine, 5-HT) may be involved in early embryogenesis in various groups of animals. This conclusion was confirmed by Baker's recent publication (Baker, 1965) concerning 5-HT synthesis in Xenopus laevis embryos. Some other low molecular weight substances, neurohumors or related compounds, are known to be synthesized in fertilized eggs as well. Acetylcholine (ACh) synthesis in sea-urchin eggs and embryos was demonstrated by Numanoi (1953, 1955, 1959, 1961). It seems possible that ACh can be synthesized in fertilized insect eggs as well (Morley & Schachter, 1963; Schachter, 1964). The synthesis of another neurohumor, dopamine (DA), in early insect embryos seems to be indisputable (Furneaux & McFarlane, 1965). However, in most cases changes in the level of neurohumors with age have not been studied. In the present paper data concerning the change of concentration with age of ACh and catecholamines (adrenaline (A) and noradrenaline (NA)) in early sea-urchin embryos will be presented.

Download Full-text