Cinematographic observation of an ?activation wave? (AW) on the locally inseminated egg ofXenopus laevis

Hara, Kimihiko; Tydeman, P.

doi:10.1007/bf00848113

Cited by 48 publications

(14 citation statements)

References 6 publications

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“…In fertilized eggs, a similar rate of propagation is observed (16,29), but here the delay between fertilization and onset of exocytosis is unknown. It may be that pricking bypasses an initial step in sperm-induced egg activation (such as the generation of inositol trisphosphate discussed above), so that fertilization (but not pricking) could involve a delay similar to that which we observe; the important point is the approximate temporal correlation between the subeortical Ca 2÷ wave and exocytosis, as well as the good agreement in their rates of propagation.…”

Section: The Subcortical Ca 2+ Wave May Be An Extension Of a Similar mentioning

confidence: 65%

“…Other cortical events thought to be regulated by this same Ca 2+ wave include a ring-shaped wave of plasma membrane permeability change (Kline, D., and R. Nuccitelli, manuscript in preparation) and the "activation waves," narrow tings of cortical contraction which propagate across the egg at activation (16,29). An important consequence of the broad spatial extent of this wave is thus that future models of the mechanism(s) of Ca2+-induced triggering of the (relatively narrow) "activation" and transcellular current waves must address the means whereby they are terminated at their trailing edges while [Ca2+]i is still elevated, or even near its peak value (at least subcortically), in the same sector of the cell.…”

Section: Rapid Communicationsmentioning

confidence: 99%

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

Busa¹,

Nuccitelli²

1985

The Journal of Cell Biology

315

132

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The eggs of most or all animals are thought to be activated after fertilization by a transient increase in free cytosolic Ca 2+ 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+]~ increased from 0.4 to 1.2 pM over the course of 2 min after fertilization, and returned to its original value during the next 10 min. No further changes in [Ca2+]~ were detected through the first cleavage division. In eggs impaled with two Ca 2+ electrodes, the Ca 2+ pulse was observed to travel as a wave from the animal to the vegetal hemisphere, propagating at a rate of ~10 #m/s across the animal hemisphere. The apparent delay between the start of the fertilization potential and initiation of the Ca 2+ wave at the sperm entry site as ~1 min. Though these observations describe only the behavior of subcortical [Ca2+]i, we suggest that our data represent the subcortical extension of the cortical Ca 2+ wave thought to trigger cortical granule exocytosis, and we present evidence that both the timing and magnitude of the Ca 2+ pulse we observed are consistent with this identity. This first quantification of subcortical [Ca2+]~ during fertilization indicates that the Ca 2+ transient is available to regulate processes (e.g., protein synthesis) in the subcortical cytosol.The calcium theory of egg activation, which holds that an increase in free cytosolic Ca 2÷ concentration ([Ca2÷]i) 1 sets in motion the early events of the "program of fertilization" (e.g., see reference 34), is amply supported by a variety of studies (2, 5-7, 10, 13, 14, 23, 27, 28, 37, 38). Qualitative measurements of [Ca2÷]i changes after fertilization in eggs of the medaka fish (14, 23), sea urchin (7, 28), starfish (7a), and mouse (6) MATERIALS AND METHODS Procurement and Handling of Gametes:Mature Xenopus oocytes were squeezed from females induced to ovulate via subcutaneous injection of 800-1,000 IU of human chorionic gonadotropin (Sigma Chemical Co., St. Louis, MO) on the previous night. Sperm were prepared by mincing dissected testes in FI solution (see below). To prevent prick activation, eggs were impaled in FI that contained 10 mM chlorobutanol, which was replaced with regular FI just before insemination. FI solution was prepared as previously described (17). Experiments were conducted at room temperature, between 20.5 and 24"C. Fabrication of Microelectrodes:Our Ca 2+ electrodes were a modified version of those of Tsien and Rink (31,32). Chromic acid-cleaned borosilicate glass micropipettes without an inner fiber were broken to ~2-~m tip diameter and rendered hydrophobic by baking for 30 min at 200"C in a chamber that contained tri-N-chlorobutylsilane (Pfaltz & Bauer Inc., Stamford, CT) vapor in air. The pipettes were then backfilled with pCa 7 calibration buffer (see below) by applying gentle pressure from a syringe to the back end of the pipettes, then the tips were filled via suction with a 50-...

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Section: The Subcortical Ca 2+ Wave May Be An Extension Of a Similar mentioning

confidence: 65%

Section: Rapid Communicationsmentioning

confidence: 99%

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

Busa¹,

Nuccitelli²

1985

The Journal of Cell Biology

315

132

View full text Add to dashboard Cite

show abstract

“…Actin accumulation propagated very quickly all over the cortex of H. pulcherrimus eggs: This may be the reason we saw neither the shape change of the egg nor the cytoplasmic flow with this species. Surface contraction phenomena during fertilization were observed in other kinds of eggs [Hara and Tydeman, 1979;Jeffery and Meier, 1983;Sawada and Osanai, 19851. The correlated accumulation of aactinin in the cortex [Mabuchi et al, 1985;Hamaguchi and Mabuchi, 19861 also suggests that a-actinin contributes to force generation because a-actinin is able to enhance the actin-myosin interaction [Ebashi and Ebashi, 1965;Condeelis et al, 19841.…”

Section: Contractility Of the Egg Cortex After Fertilizationmentioning

confidence: 93%

Accumulation of fluorescently labeled actin in the cortical layer in sea urchin eggs after fertilization

Hamaguchi

Mabuchi

1988

Cell Motil. Cytoskeleton

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Actin from sea urchin eggs was fluorescently labeled with fluorescein isothiocyanate (FITC), N-(7-dimethylamino-4-methylcoumarinyl)-maleimide (DACM), or 5-iodoacetamidofluorescein (IAF) and microinjected into sea urchin eggs and oocytes. It distributed evenly in the cytoplasm of unfertilized eggs. Upon fertilization, actin accumulated first around the sperm binding site and, soon afterwards, in the fertilization cone. The accumulation propagated all over the cortex after a latent period of 10-20 sec. In the case of Clypeuster juponicus eggs, propagation of the accumulation coincided with a shape change in the egg, suggesting that the accumulated actin in the cortex generates forces. FITC-actin was incorporated into microvilli and retained in the cortex after cleavage. On the other hand, DACM-or IAF-actin was not incorporated into microvilli and was dispersed from the cortex by cleavage. These differences may be attributable to differences in the properties of the actins labeled at different sites. After photobleaching by laser light irradiation, FITC-or IAF-actin redistributed in the cortex of fertilized egg as quickly as it did before fertilization. When an unfertilized egg was injected with both actin and a calcium buffer (intracellular free Ca2+ concentration 9 pM), the actin accumulation was similar to that during fertilization but without the latent period. This suggests that the accumulation depended on the increase in the intracelluiar free Ca2' concentration. When the unfertilized egg was injected with 0.2 M EGTA after injection of labeled actin and then inseminated, it accumulated only in the protrusion of cytoplasm where the sperm had entered, and fertilization was not completed. In immature oocytes, the accumulation was observed in the cortical region, including the huge protrusion of the cytoplasm where the sperm had entered. These results suggest that actin accumulation in the sperm binding site plays an important role in the sperm reception mechanism of the egg.

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“…About 1 minute after sperm binding, there is an increase in intracellular calcium from 0.4 to 1.2 pM, which travels around the egg as a wave, propagating at a rate of about 10 kdsecond (Busa and Nuccitelli, 1985). Cortical granule exocytosis follows the calcium wave, also at a rate of 10 pm per second, until virtually all granules have fused with the plasma membrane and secreted their contents into the PS (Grey et al, 1974;Hara andTydeman, 1979, Picheral andCharbonneau, 1982;Elinson, 1980). The cortical granules lie just beneath the plasma membrane.…”

Section: Formation Of Fe In Amphibian Eggsmentioning

confidence: 99%

Fertilization‐Induced changes in the vitelline envelope of echinoderm and amphibian eggs: Self‐assembly of an extracellular matrix

Larabell

Chandler

1991

J. Elec. Microsc. Tech.

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The surface of the unfertilized sea urchin egg is covered by the vitelline layer (VL), a fibrous extracellular matrix that contains receptors for sperm. At fertilization, cortical granule exocytosis releases enzymes and structural proteins that cause the VL to elevate and become remodelled into the mechanically and chemically tough fertilization envelope. This envelope prevents further penetration of sperm and protects the embryo during early development. A thicker, more complex vitelline envelope surrounds the Xenopus laevis egg. This fibrous coat is also restructured at fertilization to produce an impenetrable barrier to sperm. The biochemical steps that occur during self-assembly of these fertilization envelopes are reviewed, and the ultrastructural changes that occur, as seen in platinum replicas of quick-frozen, deep-etched, and rotary-shadowed eggs, are illustrated.

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Cinematographic observation of an ?activation wave? (AW) on the locally inseminated egg ofXenopus laevis

Abstract: Shortly after local artificial insemination, but well before egg rotation,Xenopus eggs show a wave-like propagation of dark-light-dark zones from the site of sperm entrance. This presumably reflects the movement of the front of cortical granule breakdown.

Cited by 48 publications

References 6 publications

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

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

Accumulation of fluorescently labeled actin in the cortical layer in sea urchin eggs after fertilization

Fertilization‐Induced changes in the vitelline envelope of echinoderm and amphibian eggs: Self‐assembly of an extracellular matrix

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