scholarly journals An elevated free cytosolic Ca2+ wave follows fertilization in eggs of the frog, Xenopus laevis.

1985 ◽  
Vol 100 (4) ◽  
pp. 1325-1329 ◽  
Author(s):  
W B Busa ◽  
R Nuccitelli
Keyword(s):  
Protein Synthesis ◽  
Xenopus Laevis ◽  
Transient Increase ◽  
Cortical Granule ◽  
Entry Site ◽  
Cleavage Division ◽  
Present Evidence ◽  
Granule Exocytosis ◽  
Sperm Entry ◽  
Cortical Granule Exocytosis

The eggs of most or all animals are thought to be activated after fertilization by a transient increase in free cytosolic Ca2+ concentration ([Ca2+]i). We have applied Ca2+-selective microelectrodes to detect such an increase in fertilized eggs of the frog, Xenopus laevis. As observed with an electrode in the animal hemisphere, [Ca2+]i increased from 0.4 to 1.2 microM over the course of 2 min after fertilization, and returned to its original value during the next 10 min. No further changes in [Ca2+]i were detected through the first cleavage division. In eggs impaled with two Ca2+ electrodes, the Ca2+ pulse was observed to travel as a wave from the animal to the vegetal hemisphere, propagating at a rate of approximately 10 microns/s across the animal hemisphere. The apparent delay between the start of the fertilization potential and initiation of the Ca2+ wave at the sperm entry site as approximately 1 min. Through these observations describe only the behavior of subcortical [Ca2+]i, we suggest that our data represent the subcortical extension of the cortical Ca2+ wave thought to trigger cortical granule exocytosis, and we present evidence that both the timing and magnitude of the Ca2+ pulse we observed are consistent with this identity. This first quantification of subcortical [Ca2+]i during fertilization indicates that the Ca2+ transient is available to regulate processes (e.g., protein synthesis) in the subcortical cytosol.

A comparison of intracellular changes in porcine eggs after fertilization and electroactivation

Development ◽  
1992 ◽  
Vol 115 (4) ◽  
pp. 947-956 ◽  
Author(s):  
F.Z. Sun ◽  
J. Hoyland ◽  
X. Huang ◽  
W. Mason ◽  
R.M. Moor
Keyword(s):  
Transient Increase ◽  
Cortical Granule ◽  
Free Calcium ◽  
Granule Exocytosis ◽  
Sperm Entry ◽  
Sperm Penetration ◽  
Ionic Changes ◽  
Cortical Granule Exocytosis ◽  
Intracellular Changes ◽  
Electrical Stimuli

The experiments compare intracellular changes in porcine eggs induced by electrical activation with those induced by sperm penetration. Adequate electrostimulation induces changes in both cortical granule exocytosis and protein synthesis similar to those induced by sperm during fertilization. However, ionic changes induced by electrostimulation differ markedly from those initiated at fertilization. Thus, dynamic video imaging using Fura-2 as a Ca2+ probe provides evidence that parthenogenetic activation induced by electrostimulation is initiated by a single sharp rise in the concentration of intracellular free calcium ([Ca2+]i) in the egg. The intracellular Ca2+ transient increase is triggered by an influx of extracellular Ca2+ immediately after electrostimulation. The amplitude of the intracellular Ca2+ transient increase is a function both of the extracellular Ca2+ concentration and of electric field parameters (field strength and pulse duration). Imaging demonstrates further that a single electrical pulse can only induce a single Ca2+ transient which usually lasts three to five minutes; no further Ca2+ transients are observed unless additional electrical stimuli are applied. By contrast, sperm-induced activation is characterised by a series of Ca2+ spikes which continue for at least 3 hours after sperm-egg fusion. The pattern of Ca2+ spiking after fertilization is not consistent during this period but changes both in frequency and amplitude. Overall, the results demonstrate that, although electrostimulation induces both cortical granule exocytosis and protein reprogramming in porcine eggs, it does not reproduce the pattern of [Ca2+]i changes induced by sperm entry at fertilization.

Weak bases partially activate Xenopus eggs and permit changes in membrane conductance whilst inhibiting cortical granule exocytosis

1987 ◽  
Vol 87 (2) ◽  
pp. 205-220
Author(s):  
M. Charbonneau ◽  
D.J. Webb
Keyword(s):  
Polar Body ◽  
Membrane Conductance ◽  
Transient Increase ◽  
Cortical Granule ◽  
Cortical Granules ◽  
Weak Base ◽  
Granule Exocytosis ◽  
Weak Bases ◽  
Prolonged Contact ◽  
Cortical Granule Exocytosis

At extracellular pH values close to their pKa values the weak bases, ammonia and procaine, elicited a series of events in non-activated Xenopus eggs, some of which resembled those normally occurring at fertilization. These included: (1) a transient increase in membrane conductance; (2) modification of the microvilli; (3) thickening of the cortical cytoplasm and displacement of the cortical granules; (4) pigment accumulation; (5) contractions and shape changes. However, these eggs did not undergo the cortical reaction nor emit the second polar body. Cortical granule exocytosis of inseminated or artificially stimulated eggs was inhibited if the eggs had been previously treated for 15 min with the weak base and subsequently rinsed. Multiple sperm-entry sites were exhibited by the inseminated eggs, suggesting polyspermy. However, such eggs did not cleave and although sperm had fused with the egg membrane, they were not incorporated. Nevertheless, a transient increase in membrane conductance was evoked, which was longer in duration and had a slightly different form from that normally accompanying fertilization. In these eggs cortical granules were intact but displaced away from the plasma membrane. Prolonged contact with the weak base rendered eggs totally unresponsive to sperm or artificial stimuli but eggs recovered when rinsed sufficiently. These effects of weak bases on unfertilized Xenopus eggs or during fertilization were completely absent at pH 7.4. Although changes in intracellular pH or Ca2+ may be involved in these phenomena, direct action by the weak base itself cannot be ruled out.

Cortical granule exocytosis in Bufo arenarum oocytes matured in vitro

Zygote ◽  
2001 ◽  
Vol 9 (3) ◽  
pp. 251-259 ◽  
Author(s):  
J. Oterino ◽  
G. Sánchez Toranzo ◽  
L. Zelarayán ◽  
J.N. Valz-Gianinet ◽  
M.I. Bühler
Keyword(s):  
Cortical Granule ◽  
Granule Exocytosis ◽  
Cortical Reaction ◽  
Progesterone Treatment ◽  
Sperm Entry ◽  
Bufo Arenarum ◽  
Chronological Sequence ◽  
Cortical Granule Exocytosis

Denuded Bufo arenarum oocytes matured in vitro by progesterone treatment exhibited abnormal segmentation due to the penetration of more than one sperm. These oocytes were able to respond to activation stimuli and exhibited the external signs characteristic of activation. However, the prevention of polyspermy was not effective in these oocytes, which exhibited numerous sperm in their cytoplasm. The aim of this work was to analyse the cortical reaction in polyspermic Bufo arenarum oocytes matured in vitro. The result indicate that the cortical reaction of these oocytes seems to occur with a chronological sequence similar to that described for ovoposited oocytes of this species. In addition, when, 1 min after pricking, cortical granule exocytosis occurred, the oocytes became refractory to sperm entry, suggesting that they are able to establish a slow block to polyspermy.

Sperm incorporation in Xenopus laevis: characterisation of morphological events and the role of microfilaments

Zygote ◽  
2001 ◽  
Vol 9 (2) ◽  
pp. 167-181 ◽  
Author(s):  
Judith A. Boyle ◽  
Hui Chen ◽  
James R. Bamburg
Keyword(s):  
Plasma Membrane ◽  
Xenopus Laevis ◽  
Morphological Changes ◽  
Actin Dynamics ◽  
Cortical Granule ◽  
Granule Exocytosis ◽  
Sperm Binding ◽  
Transmission Electron ◽  
Latrunculin A ◽  
Cortical Granule Exocytosis

Scanning and transmission electron microscopy were used to determine the morphological changes in the egg plasma membrane associated with sperm binding, fusion and incorporation in Xenopus laevis. Sperm incorporation in Xenopus is rapid, occurring within 3-5 min following addition of sperm. Images have been obtained of both early sperm-egg interactions and fertilisation bodies. Additionally, two drugs that specifically alter F-actin dynamics, latrunculin and jasplakinolide, were used to determine whether sperm incorporation is a microfilament-dependent process. Jasplakinolide did not prevent sperm incorporation, cortical granule exocytosis or cortical contraction, suggesting these events can occur without depolymerisation of existing, stabilised filaments. Latrunculin A, which competes with thymosin β4 in ooplasm for binding actin monomer, did not inhibit cortical granule exocytosis, but blocked cortical contraction in 100% of eggs at a concentration of 5 μM. Although a single penetrating sperm was found on an egg pretreated in latrunculin, fertilisation bodies were never observed. At <5 μM latrunculin, many eggs did undergo cortical contraction with some exhibiting severe distortions of the plasma membrane and abnormal accumulations of pigment granules. Preincubation of eggs in jasplakinolide before latrunculin mitigated both these effects to some degree. However, eggs incubated in latrunculin either prior to or after insemination never progressed through first cleavage.

Behaviour of the vitelline envelope in Bufo arenarum oocytes matured in vitro in blockade to polyspermy

Zygote ◽  
2006 ◽  
Vol 14 (2) ◽  
pp. 97-106 ◽  
Author(s):  
J. Oterino ◽  
G. Sánchez Toranzo ◽  
L. Zelarayán ◽  
M.T. Ajmat ◽  
F. Bonilla ◽  
...  
Keyword(s):  
Ultrastructural Changes ◽  
Cortical Granule ◽  
Trypsin Activity ◽  
Trypsin Treatment ◽  
Granule Exocytosis ◽  
Sperm Entry ◽  
Bufo Arenarum ◽  
Vitelline Envelope ◽  
Cortical Granule Exocytosis

SummaryDuring activation of amphibian eggs, cortical granule exocytosis causes elaborate ultrastructural changes in the vitelline envelope. These changes involve modifications in the structure of the vitelline envelope and formation of a fertilization envelope (FE) that can no longer be penetrated by sperm. In Bufo arenarum, as the egg traverses the oviduct, the vitelline envelope is altered by a trypsin-like protease secreted by the oviduct, which induces an increased susceptibility of the vitelline envelope to sperm lysins. Full-grown oocytes of B. arenarum, matured in vitro by progesterone, are polyspermic, although cortical granule exocytosis seems to occur within a normal chronological sequence. These oocytes can be fertilized with or without trypsin treatment, suggesting that the vitelline envelope is totally sperm-permeable. Vitelline envelopes without trypsin treatment cannot retain either gp90 or gp96. This suggests that these glycoproteins are involved in the block to polyspermy and that trypsin treatment of matured in vitro oocytes before insemination is necessary to enable vitelline envelopes to block polyspermy. The loss of the binding capacity in vitelline envelopes isolated from B. arenarum oocytes matured in vitro with trypsin treatment and activated by electric shock suggests that previous trypsin treatment is a necessary step for sperm block to occur. When in vitro matured oocytes were incubated with the product of cortical granules obtained from in vitro matured oocytes (vCGP), vitelline envelopes with trypsin treatment were able to block sperm entry. These oocytes exhibited the characteristic signs of activation. These results support the idea that B. arenarum oocytes can be activated by external stimuli and suggest the presence of unknown oocyte surface receptors linked to the activation machinery in response to fertilization. Electrophoretic profiles obtained by SDS-PAGE of solubilized vitelline envelopes from oocytes matured in vitro revealed the conversion of gp40 (in vitro matured oocytes, without trypsin treatment) to gp38 (ascribable to trypsin activity or cortical granule product activity, CGP) and the conversion of gp70 to gp68 (ascribable to trypsin activity plus CGP activity). Taking into account that only the vitelline envelopes of in vitro matured oocytes with trypsin treatment and activated can block sperm entry, we may suggest that the conversion of gp70 to gp68 is related to the changes associated with sperm binding.

scholarly journals Activators of protein kinase C trigger cortical granule exocytosis, cortical contraction, and cleavage furrow formation in Xenopus laevis oocytes and eggs.

1989 ◽  
Vol 108 (3) ◽  
pp. 885-892 ◽  
Author(s):  
W M Bement ◽  
D G Capco
Keyword(s):  
Protein Kinase C ◽  
Retinoic Acid ◽  
Protein Kinase ◽  
Xenopus Laevis ◽  
Follicle Cells ◽  
Cortical Granule ◽  
Cleavage Furrow ◽  
Granule Exocytosis ◽  
Kinase C ◽  
Cortical Granule Exocytosis

Prophase I oocytes, free of follicle cells, and metaphase II eggs of the amphibian Xenopus laevis were subjected to transient treatments with the protein kinase C activators, phorbol 12-myristate 13-acetate (PMA), phorbol 12,13-didecanoate, and 1-olyeoyl-2-acetyl-sn-glycerol. In both oocytes and eggs, these treatments triggered early events of amphibian development: cortical granule exocytosis, cortical contraction, and cleavage furrow formation. Surprisingly, activation of oocytes occurred in the absence of meiotic resumption, resulting in cells with an oocytelike nucleus and interior cytoplasm, but with a zygotelike cortex. PMA-induced activation of oocytes and eggs did not require external calcium, a prerequisite for normal activation of eggs. PMA-induced activation of eggs was inhibited by retinoic acid, a known inhibitor of protein kinase C. In addition, pretreatment of eggs with retinoic acid prevented activation by mechanical stimulation and inhibited activation by calcium ionophore A23187. The results suggest that protein kinase C activation is an integral component of the Xenopus fertilization pathway.

scholarly journals Compensatory endocytosis occurs after cortical granule exocytosis in mouse eggs

2019 ◽  
Vol 235 (5) ◽  
pp. 4351-4360
Author(s):  
Matías D. Gómez‐Elías ◽  
Rafael A. Fissore ◽  
Patricia S. Cuasnicú ◽  
Débora J. Cohen
Keyword(s):  
Cortical Granule ◽  
Granule Exocytosis ◽  
Cortical Granule Exocytosis ◽  
Mouse Eggs

scholarly journals Cortical Granule Exocytosis Is Mediated by Alpha-SNAP and N-Ethilmaleimide Sensitive Factor in Mouse Oocytes

PLoS ONE ◽  
2015 ◽  
Vol 10 (8) ◽  
pp. e0135679 ◽  
Author(s):  
Matilde de Paola ◽  
Oscar Daniel Bello ◽  
Marcela Alejandra Michaut
Keyword(s):  
Cortical Granule ◽  
Granule Exocytosis ◽  
Mouse Oocytes ◽  
Sensitive Factor ◽  
Cortical Granule Exocytosis

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.

scholarly journals Poisson-distributed active fusion complexes underlie the control of the rate and extent of exocytosis by calcium.

1996 ◽  
Vol 134 (2) ◽  
pp. 329-338 ◽  
Author(s):  
S S Vogel ◽  
P S Blank ◽  
J Zimmerberg
Keyword(s):  
Poisson Process ◽  
Sea Urchin ◽  
Physiological Responses ◽  
Cortical Granule ◽  
Cortical Granules ◽  
Granule Exocytosis ◽  
Calcium Dependence ◽  
Sea Urchin Egg ◽  
High Calcium ◽  
Cortical Granule Exocytosis

We have investigated the consequences of having multiple fusion complexes on exocytotic granules, and have identified a new principle for interpreting the calcium dependence of calcium-triggered exocytosis. Strikingly different physiological responses to calcium are expected when active fusion complexes are distributed between granules in a deterministic or probabilistic manner. We have modeled these differences, and compared them with the calcium dependence of sea urchin egg cortical granule exocytosis. From the calcium dependence of cortical granule exocytosis, and from the exposure time and concentration dependence of N-ethylmaleimide inhibition, we determined that cortical granules do have spare active fusion complexes that are randomly distributed as a Poisson process among the population of granules. At high calcium concentrations, docking sites have on average nine active fusion complexes.

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