Insensitivity to cytochalasin B of surface contractions keyed to cleavage in the Xenopus egg

Development ◽  
1982 ◽  
Vol 72 (1) ◽  
pp. 143-151
Author(s):  
Kathy Christensen ◽  
R. W. Merriam
Keyword(s):  
Xenopus Laevis ◽  
Internal Pressure ◽  
Cytochalasin B ◽  
Cleavage Furrow ◽  
Initial Appearance ◽  
Xenopus Egg

In fertilized eggs of Xenopus laevis a marked flattening of the pigmented animal hemisphere has been observed. The flattening begins 15–20 minutes before the appearance of the cleavage furrow. As the furrow develops, the pigmented surface relaxes and rounds up. The initial appearance of the furrow is thus shown to be a combination of furrow deepening and rounding up of adjacent pigmented surfaces. It is demonstrated that the flattening is not caused by gravity or osmotic mechanisms and that internal pressure is increased during the flattening. The flattening is interpreted to be an isodiametric contraction of the pigmented surface. The contraction is not inhibited by injected cytochalasin B in sufficient concentrations to completely inhibit cleavage furrow formation. These results are discussed with respect to the presence of two surface contractile systems, distinguishable on the basis of their differing sensitivity to cytochalasin B.

The permeability to cytochalasin B of the new unpigmented surface in the first cleavage furrow of the newt's egg

Development ◽  
1976 ◽  
Vol 36 (2) ◽  
pp. 321-341
Author(s):  
G. G. Selman ◽  
J. Jacob ◽  
M. M. Perry
Keyword(s):  
Osmium Tetroxide ◽  
Cytochalasin B ◽  
Specific Activity ◽  
High Specific Activity ◽  
Scintillation Counting ◽  
Cleavage Furrow ◽  
Limited Extent ◽  
Normal Medium ◽  
Cleavage Initiation ◽  
Whole Egg

Two to 10 µg/ml cytochalasin B (CB) caused retraction of the first cleavage furrow in Triturus eggs, a spreading of the unpigmented surface from the furrow region and a flattening of the whole egg. CB appears to act against the contractility of the microfilamentous band at mid-cleavage so as to relax the furrow and also to weaken unpigmented surface to allow the egg to flatten. Uncleaved eggs and the initial formation of the cleavage groove were unaffected by CB. A fully-retracted first cleavage furrow reformed itself on transfer of the egg to normal medium but only at the time of second cleavage. Initiation of second cleavage depended upon there being sufficient of the original pigmented surface on the animal hemisphere. Tritium-labelled CB of high specific activity was prepared and used to study its ability to penetrate the surface of newt eggs during cleavage. Scintillation counting of whole eggs showed that CB was not taken into the newt egg until mid-cleavage (about 17 min after the double stripe stage) when new surface began to spread in the cleavage furrow. Fixation in glutaraldehyde and osmium tetroxide retained radioactivity in the egg, but more CB was retained after fixation in osmium tetroxide alone than after double fixation. Most of the retained radioactivity was in yolk platelets. Autoradiographs were prepared of sectioned eggs whichad been fixed at late cleavage after [3H]CB had flattened the furrow. These showed that CBentered the egg through the unpigmented surface which formed in the furrow but it could not enter through the pigmented surface. The impermeability of the pigmented surface explains the observations that CB does not prevent initial furrowing at cleavage. Once inside the egg CB is transported slowly. CB penetrates to a limited extent beneath the pigmented surface from its border with the unpigmented surface in the first cleavage furrow and this seems insufficient in some circumstances to suppress the contractile phase of second cleavage.

scholarly journals Protein kinase C acts downstream of calcium at entry into the first mitotic interphase of Xenopus laevis.

1990 ◽  
Vol 1 (3) ◽  
pp. 315-326 ◽  
Author(s):  
W M Bement ◽  
D G Capco
Keyword(s):  
Cell Cycle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Xenopus Laevis ◽  
Mitotic Cell ◽  
Cortical Granule ◽  
Mitotic Cell Cycle ◽  
Cleavage Furrow ◽  
Kinase C ◽  
Cortical Granule Exocytosis

Transit into interphase of the first mitotic cell cycle in amphibian eggs is a process referred to as activation and is accompanied by an increase in intracellular free calcium [( Ca2+]i), which may be transduced into cytoplasmic events characteristic of interphase by protein kinase C (PKC). To investigate the respective roles of [Ca2+]i and PKC in Xenopus laevis egg activation, the calcium signal was blocked by microinjection of the calcium chelator BAPTA, or the activity of PKC was blocked by PKC inhibitors sphingosine or H7. Eggs were then challenged for activation by treatment with either calcium ionophore A23187 or the PKC activator PMA. BAPTA prevented cortical contraction, cortical granule exocytosis, and cleavage furrow formation in eggs challenged with A23187 but not with PMA. In contrast, sphingosine and H7 inhibited cortical granule exocytosis, cortical contraction, and cleavage furrow formation in eggs challenged with either A23187 or PMA. Measurement of egg [Ca2+]i with calcium-sensitive electrodes demonstrated that PMA treatment does not increase egg [Ca2+]i in BAPTA-injected eggs. Further, PMA does not increase [Ca2+]i in eggs that have not been injected with BAPTA. These results show that PKC acts downstream of the [Ca2+]i increase to induce cytoplasmic events of the first Xenopus mitotic cell cycle.

Rotation in Xenopus laevis embryos after the appearance of the first cleavage furrow

2008 ◽  
Vol 421 (1) ◽  
pp. 251-253 ◽  
Author(s):  
S. M. Starodubov ◽  
Yu. K. Doronin ◽  
V. A. Golichenkov
Keyword(s):  
Xenopus Laevis ◽  
Cleavage Furrow ◽  
Xenopus Laevis Embryos

The action of cytochalasin B during egg cleavage in Xenopus laevis: Dependence on cell membrane permeability

1973 ◽  
Vol 31 (1) ◽  
pp. 163-177 ◽  
Author(s):  
Siegfried W. de Laat ◽  
Daniel Luchtel ◽  
John G. Bluemink
Keyword(s):  
Cell Membrane ◽  
Xenopus Laevis ◽  
Membrane Permeability ◽  
Cytochalasin B ◽  
Cell Membrane Permeability

scholarly journals Localized Calcium Signals along the Cleavage Furrow of theXenopus Egg Are Not Involved in Cytokinesis

2002 ◽  
Vol 13 (4) ◽  
pp. 1263-1273 ◽  
Author(s):  
Tatsuhiko Noguchi ◽  
Issei Mabuchi
Keyword(s):  
Xenopus Laevis ◽  
The Other ◽  
Cleavage Furrow ◽  
Calcium Signals ◽  
Other Hand ◽  
Second Wave ◽  
Late Stages

It has been proposed that a localized calcium (Ca) signal at the growing end of the cleavage furrow triggers cleavage furrow formation in large eggs. We have examined the possible role of a Ca signal in cleavage furrow formation in the Xenopus laevis egg during the first cleavage. We were able to detect two kinds of Ca waves along the cleavage furrow. However, the Ca waves appeared after cleavage furrow formation in late stages of the first cleavage. In addition, cleavage was not affected by injection of dibromoBAPTA or EGTA into the eggs at a concentration sufficient to suppress the Ca waves. Furthermore, even smaller classes of Ca release such as Ca puffs and Ca blips do not occur at the growing end of the cleavage furrow. These observations demonstrate that localized Ca signals in the cleavage furrow are not involved in cytokinesis. The two Ca waves have unique characteristics. The first wave propagates only in the region of newly inserted membrane along the cleavage furrow. On the other hand, the second wave propagates along the border of new and old membranes, suggesting that this wave might be involved in adhesion between two blastomeres.

scholarly journals Activation of frog (Xenopus laevis) eggs by inositol trisphosphate. I. Characterization of Ca2+ release from intracellular stores.

1985 ◽  
Vol 101 (2) ◽  
pp. 677-682 ◽  
Author(s):  
W B Busa ◽  
J E Ferguson ◽  
S K Joseph ◽  
J R Williamson ◽  
R Nuccitelli
Keyword(s):  
Xenopus Laevis ◽  
Cortical Granule ◽  
Inositol 1 ◽  
Response Characteristics ◽  
Xenopus Egg ◽  
Cortical Granule Exocytosis ◽  
And Behavior ◽  
Timing Sensitivity ◽  
Early Developmental

Iontophoresis of inositol 1, 4, 5-triphosphate into frog (Xenopus laevis) eggs activated early developmental events such as membrane depolarization, cortical contraction, cortical granule exocytosis, and abortive cleavage furrow formation (pseudocleavage). Inositol 1, 4-bisphosphate also triggered these events, but only at doses approximately 100-fold higher, whereas no level of fructose-1, 6-bisphosphate tested activated eggs. Using Ca2+-selective microelectrodes, we observed that activating doses of inositol 1, 4, 5-trisphosphate triggered a Ca2+ release from intracellular stores that was indistinguishable from that previously observed at fertilization (Busa, W. B., and R. Nuccitelli, 1985, J. Cell Biol., 100:1325-1329), whereas subthreshold doses triggered only a localized Ca2+ release at the site of injection. The subthreshold IP3 response could be distinguished from the major Ca2+ release at activation with respect to their dose-response characteristics, relative timing, sensitivity to external Ca2+ levels, additivity, and behavior in the activated egg, suggesting that the Xenopus egg may possess two functionally distinct Ca2+ pools mobilized by different effectors. In light of these differences, we suggest a model for intracellular Ca2+ mobilization by sperm-egg interaction.

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.

An ultrastructural study of the effects of wheat germ agglutinin (WGA) on cell cortex organization during the first cleavage of Xenopus laevis eggs. I. Inhibition of furrow formation

1979 ◽  
Vol 37 (1) ◽  
pp. 47-58
Author(s):  
M. Geuskens ◽  
R. Tencer
Keyword(s):  
Plasma Membrane ◽  
Xenopus Laevis ◽  
Wheat Germ Agglutinin ◽  
Wheat Germ ◽  
Cytochalasin B ◽  
Outer Side ◽  
Cell Cortex ◽  
Animal Pole ◽  
Continuous Layer ◽  
Close Proximity

Xenopus laevis fertilized eggs have been treated with wheat germ agglutinin (WGA) before the onset of the first cleavage, at the stripe stage and during groove deepening. The ultrastructure of the animal cortex of the arrested embryos has been compared with that of the same region of control embryos at different stages of first furrow formation and of cytochalasin B-treated embryos. The outer side of the plasma membrane of WGA-treated embryos is covered with a coat which is different from the diffuse material observed in either control or cytochalasin B-treated embryos and which is distributed in patches in the groove region. Narrow indentations of the plasma membrane in the cortex of WGA-treated eggs have been observed, particularly in the blocked or regressed groove. In WGA-treated eggs, a few bundles of microfilaments are located under the plasma membrane at the animal pole, but they are never arrayed in a continuous layer as in the control eggs. In the latter, many microtubules are located in close proximity to the microfilament layer at the beginning of cleavage, but they are only occasionally observed in the same region of WGA-treated eggs. It is concluded that the binding of WGA molecules to their receptors on the surface of the Xenopus zygote interferes with the alignment of microfilaments in the furrow region and provokes the disorganization of the aligned microfilaments once the cleavage has begun. Internalization of portions of the nascent membrane in the groove could play an important part in the arrest of cleavage.

scholarly journals Rainbow trout glucose transporter (OnmyGLUT1): functional assessment in Xenopus laevis oocytes and expression in fish embryos

2001 ◽  
Vol 204 (15) ◽  
pp. 2667-2673 ◽  
Author(s):  
Heli Teerijoki ◽  
Aleksei Krasnov ◽  
Yuri Gorodilov ◽  
Sanjeev Krishna ◽  
Hannu Mölsä
Keyword(s):  
Rainbow Trout ◽  
Xenopus Laevis ◽  
Neural Crest ◽  
Glucose Transporter ◽  
Cytochalasin B ◽  
Developmental Stages ◽  
Xenopus Laevis Oocytes ◽  
Embryonic Cells ◽  
Olfactory Organs

SUMMARY Recently, we reported the cloning of a putative glucose transporter (OnmyGLUT1) from rainbow trout embryos. In this paper, we describe the functional characteristics of OnmyGLUT1 and its expression during embryonic development of rainbow trout. Transport of d-glucose was analysed in Xenopus laevis oocytes following microinjection of mRNA transcribed in vitro. These experiments confirmed that OnmyGLUT1 is a facilitative Na+-independent transporter. Assessment of substrate selectivity, sensitivity to cytochalasin B and phloretin and kinetic parameters showed that the rainbow trout glucose transporter was similar to a carp transporter and to mammalian GLUT1. Embryonic expression of OnmyGLUT1 was studied using whole-mount in situ hybridization. Ubiquitous distribution of transcripts was observed until the early phase of somitogenesis. During the course of organogenesis, somitic expression decreased along the rostro-caudal axis, finally ceasing in the mature somites. The OnmyGLUT1 transcripts were detected in the neural crest during the whole study period. Transcripts were also found in structures that are likely to originate from the neural crest cells (gill arches, pectoral fins, upper jaw, olfactory organs and primordia of mouth lips). Hexose transport activity was detected at all developmental stages after blastulation. Cytochalasin B blocked the accumulation of phosphorylated 2-deoxy-d-glucose by dissociated embryonic cells, suggesting an important role for transport in glucose metabolism.

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