scholarly journals Imaging patterns of calcium transients during neural induction in Xenopus laevis embryos

2000 ◽  
Vol 113 (19) ◽  
pp. 3519-3529 ◽  
Author(s):  
C. Leclerc ◽  
S.E. Webb ◽  
C. Daguzan ◽  
M. Moreau ◽  
A.L. Miller
Keyword(s):  
Xenopus Laevis ◽  
Calcium Signalling ◽  
Neural Induction ◽  
Calcium Transients ◽  
Free Calcium ◽  
Treated Animal ◽  
Cell Stage ◽  
Subsequent Formation ◽  
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.

Intracellular free calcium oscillations in normal and cleavage-blocked embryos and artificially activated eggs of Xenopus laevis

1994 ◽  
Vol 107 (8) ◽  
pp. 2229-2237 ◽  
Author(s):  
T.J. Keating ◽  
R.J. Cork ◽  
K.R. Robinson
Keyword(s):  
Xenopus Laevis ◽  
Photon Counting ◽  
Calcium Oscillations ◽  
Intracellular Free Calcium ◽  
Free Calcium ◽  
Counting System ◽  
Normal Medium ◽  
Sinusoidal Oscillations ◽  
Cyclic Changes ◽  
Xenopus Laevis Embryos

We have measured levels of intracellular free calcium ([Ca2+]i) in albino Xenopus laevis embryos using recombinant aequorin and a photon-counting system. We observed sinusoidal oscillations in [Ca2+]i that had the same frequency as cleavage, with cleavage occurring when [Ca2+]i was lowest. An increase in calcium was seen to precede first cleavage. The cyclic changes in calcium were superimposed on a secondary pattern that increased, peaked between third and fifth cleavages and then slowly declined to a level similar to that measured before first cleavage. The amplitude of the oscillations was small during the first few cleavages but became larger with each cycle, with the largest oscillations occurring when the secondary pattern peaked (between third and fifth cleavage). As the secondary pattern declined, the amplitude of the oscillations also became smaller. The oscillations are due to release of calcium from intracellular stores, since the signal was the same in calcium-free solution as in normal medium. When cleavage was blocked with the microtubule-disrupting drugs colchicine or nocodazole, the [Ca2+]i oscillations persisted. Calcium oscillations of a similar magnitude and frequency were also present in artificially activated eggs. The secondary pattern was different in cleavage-blocked embryos and artificially activated eggs, the baseline increasing until about the third cycle and then remaining elevated for the rest of the recording (> 8 hours). By fixing embryos at various points in the calcium cycle, we determined that mitosis began shortly after calcium levels reached their peak and was complete before the calcium level dropped to its lowest point.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Role of Fyn kinase in oocyte developmental potential

2010 ◽  
Vol 22 (6) ◽  
pp. 966 ◽  
Author(s):  
Jinping Luo ◽  
Lynda K. McGinnis ◽  
William H. Kinsey
Keyword(s):  
Calcium Signalling ◽  
Dominant Negative ◽  
Rapid Decline ◽  
Protein Tyrosine Phosphorylation ◽  
Cell Stage ◽  
Developmental Potential ◽  
Developmental Arrest ◽  
Fyn Kinase ◽  
The One

Fyn kinase is highly expressed in oocytes, with inhibitor and dominant-negative studies suggesting a role in the signal transduction events during egg activation. The purpose of the present investigation was to test the hypothesis that Fyn is required for calcium signalling, meiosis resumption and pronuclear congression using the Fyn-knockout mouse as a model. Accelerated breeding studies revealed that Fyn-null females produced smaller litter sizes at longer intervals and exhibited a rapid decline in pup production with increasing age. Fyn-null females produced a similar number of oocytes, but the frequency of immature oocytes and mature oocytes with spindle chromosome abnormalities was significantly higher than in controls. Fertilised Fyn-null oocytes frequently (24%) failed to undergo pronuclear congression and remained at the one-cell stage. Stimulation with gonadotropins increased the number of oocytes ovulated, but did not overcome the above defects. Fyn-null oocytes overexpressed Yes kinase in an apparent effort to compensate for the loss of Fyn, yet still exhibited an altered pattern of protein tyrosine phosphorylation. In summary, Fyn-null female mice exhibit reduced fertility that appears to result from actin cytoskeletal defects rather than calcium signalling. These defects cause developmental arrest during oocyte maturation and pronuclear congression.

scholarly journals 5-Hydroxytryptamine-induced calcium-channel gating in rainbow trout (Oncorhynchus mykiss) peripheral blood lymphocytes

1997 ◽  
Vol 323 (1) ◽  
pp. 251-258 ◽  
Author(s):  
François FERRIERE ◽  
Naïm A. KHAN ◽  
Jean P. MEYNIEL ◽  
Pierre DESCHAUX
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Peripheral Blood ◽  
Calcium Signalling ◽  
Peripheral Blood Lymphocytes ◽  
Free Calcium ◽  
Receptor Subtype ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Peripheral Blood Lympho

The present study was conducted on peripheral blood lympho-cytes of rainbow trout (Oncorhynchus mykiss) to assess the role of 5-hydroxytryptamine (5-HT; ‘serotonin’) in calcium signalling. 5-HT-induced increases in intracellular free calcium concentrations, [Ca2+]i, and its action was mediated by 5-HT receptor subtype 3 (5-HT3), but not by 5-HT receptor subtype 1A (5-HT1A) or subtype 2 (5-HT2) in these cells. In Ca2+-containing medium (1 mM CaCl2), 5-HT and 2-methyl-5-HT (5-HT3 receptor agonist) induced increases in [Ca2+]i, whereas in Ca2+-free medium (0 Ca2+, 1 mM EGTA), these two agents failed to evoke increases in [Ca2+]i in these cells, demonstrating that 5-HT mobilizes Ca2+ from the extracellular environment. Furthermore, 5-HT-induced increases in [Ca2+]i are not contributed to by the intracellular endoplasmic reticulum (ER) pool, as thapsigargin, an agent that recruits Ca2+ from ER stores, had additive effects on 5-HT-induced [Ca2+]i responses in fish peripheral lymphocytes. 5-HT-induced increases in [Ca2+]i were mediated by 5-HT3 receptors via gating the calcium through L-type, but not N-type, calcium channels in trout lymphocytes.

Differential gene expression in the anterior neural plate during gastrulation of Xenopus laevis

Development ◽  
1989 ◽  
Vol 105 (4) ◽  
pp. 779-786 ◽  
Author(s):  
M. Jamrich ◽  
S. Sato
Keyword(s):  
Gene Expression ◽  
Xenopus Laevis ◽  
Neural Induction ◽  
Neural Plate ◽  
Cement Gland ◽  
Cdna Clones ◽  
Differential Gene ◽  
Anteroposterior Polarity ◽  
Xenopus Laevis Embryos ◽  
Anterior Neural Plate

We have isolated three cDNA clones that are preferentially expressed in the cement gland of early Xenopus laevis embryos. These clones were used to study processes involved in the induction of this secretory organ. Results obtained show that the induction of this gland coincides with the process of neural induction. Genes specific for the cement gland are expressed very early in the anterior neural plate of stage-12 embryos. This suggests that the anteroposterior polarity of the neural plate is already established during gastrulation. At later stages of development, two of the three genes have secondary sites of expression. The expression of these genes can be induced in isolated animal caps by incubation in 10 mM-NH4Cl, a treatment that is known to induce cement glands.

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

2007 ◽  
Vol 38 (3) ◽  
pp. 152-163
Author(s):  
L. V. Beloussov ◽  
E. G. Korvin-Pavlovskaya ◽  
N. N. Luchinskaya ◽  
E. S. Kornikova
Keyword(s):  
Xenopus Laevis ◽  
Cell Movements ◽  
Axial Rudiments ◽  
Xenopus Laevis Embryos

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

Development ◽  
1988 ◽  
Vol 102 (3) ◽  
pp. 517-526 ◽  
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.

scholarly journals Calcium transients and calcium signalling during early neurogenesis in the amphibian embryo Xenopus laevis

2006 ◽  
Vol 1763 (11) ◽  
pp. 1184-1191 ◽  
Author(s):  
Catherine Leclerc ◽  
Isabelle Néant ◽  
Sarah E. Webb ◽  
Andrew L. Miller ◽  
Marc Moreau
Keyword(s):  
Xenopus Laevis ◽  
Calcium Signalling ◽  
Calcium Transients ◽  
Amphibian Embryo ◽  
Early Neurogenesis
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