Secretory functions of egg cortical granules in fertilization and development: A critical review

Schuel, Herbert

doi:10.1002/mrd.1120010311

Cited by 214 publications

(77 citation statements)

References 283 publications

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“…Thus, the fact it is preserved can only be explained in the two following ways: (1) either the involved Na+ channels are masked within the membrane and are not directly accessible, which may explain why sperm only can activate them and possibly their resistance to irradiation, although this look a more questionable assumption. (2) or the responsible channels are not true Na+ channels, but rather non specific channels, as already reported for the ascidian eggs (21). However these channels may possibly be more selective for Na+ than for the other ions as supported by previous data obtained both on Urechis and sea urchin eggs (3, 11,12,18).…”

Section: Discussionsupporting

confidence: 57%

“…In Echinoderms, a two step mechanism has been mainly assumed to protect the eggs from such a lethal issue. A slow and complete block to polyspermy is mediated via the cortical reaction which is completed within 2 min following the first successfull sperm-egg interaction and leads to the elevation of a mechanical barrier, the fertilization membrane (2,3). This definitive block is preceded by a faster and transient block which appears within 2-3 sec.…”

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confidence: 99%

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U.V. Irradiation Inhibits The Electrical Block to Polyspermy in Echinoderms*

David¹,

Moreau²,

Vilain³

et al. 1985

Dev Growth Differ

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Oocytes o f the sea urchin Sphuerechinus grunuluris and the starfish Marfhusterius glacialis have been submitted to U . V . irradiation beforc fertilization. This treatment significantly increased the incidence and severity of polyspermy in the sea urchin and was also found effective on starfish oocytes. These were found more resistant to damage than sea urchin eggs and U . V . irradiation did not affect either their response to the hormone I-methyladenine or the rate of elevation of the fertilization envelope, which assures the late and definitive block to polyspermy.Electrophysiological measurements performed on M . gluciulis oocytes definitively demonstrate that U.V. irradiation completely inactivates voltage-dependent sodium channels, without altering the other main conductances, C I , K + or Ca". After such a treatment, the relative permeability of the mcmbrane to N a t as compared to K +-shifted from 0.019+0.0(13 to 0 . 0 0 3~0 . 0 0 2 and only the calcium component of the action potentials could be observed. However, a fertilization potential, preceded by small sperm induced steps. is still present in these conditions. although its peak and plateau level are greatly reduced.These new findings are discussed, which confirm the electrical nature of the fast block to polyspermy but qucstion about the specificity of those sperm-gated channels which are supposed to trigger the fertilization potential.Polyspermy, i.e. the fusion of more than one sperm pronucleus with the female pronucleus usually produces an excess of mitotic centers as well as defects in ploidy which result ultimately in death of the embryos (1). In Echinoderms, a two step mechanism has been mainly assumed to protect the eggs from such a lethal issue. A slow and complete block to polyspermy is mediated via the cortical reaction which is completed within 2 min following the first successfull sperm-egg interaction and leads to the elevation of a mechanical barrier, the fertilization membrane (2, 3). This definitive block is preceded by a faster and transient block which appears within 2-3 sec. and lowers the receptivity of the egg plasma membrane to supernumary sperms (4-6). It consists in a rapid depolarization of the plasma membrane, the fertilization potential, which attains positive values for, at least, 60 sec (7).In the starfish (8), as well as in the sea urchin (7, 9, 10-14), a good correlation has been found to exist between the amplitude of the plateau phase of the fertilization potential and the block to polyspermy. Moreover, it is generally agreed (3, 9, 15) that sperm triggers an initial small depolarization that is further amplified by a voltage dependent calcium action potential, relayed by a sodium component responsible for the long-lasting depolarized state. Final repolarization is associated with an increased potassium conductance resulting from alkali-* This paper is dedicated to the memory of the late Dr. H. Kanatani. 333

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Section: Discussionsupporting

confidence: 57%

mentioning

confidence: 99%

U.V. Irradiation Inhibits The Electrical Block to Polyspermy in Echinoderms*

David¹,

Moreau²,

Vilain³

et al. 1985

Dev Growth Differ

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“…comparable in scale and in its timing with the discharge of cortical vesicles in sea urchin eggs. Cortical granule release, which results in the formation of the fertilisation (vitelline) membrane and blocks further sperm penetration (Schuel, 1978;Longo et al, I986), is regarded as one of the largest single exocytotic bursts known (Fisher & Rebhun, 1983). Secretion of phenolic bodies by D. potatorum zygotes also occurs in response to plasmogamy, indicating that exocytosis may be regulated and possibly mediated by an in~racellular messenger system.…”

Section: Discussionmentioning

confidence: 99%

Secretion of phenolic bodies following fertilisation inDurvillaea potatorum(Durvillaeales, Phaeophyta)

Clayton

Ashburner

1994

European Journal of Phycology

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Cytological events immediately following plasmogamy in Durvillaea potatorum are described. Eggs contain several types of cytoplasmic vesicle differing in size and appearance. Histochemical tests and measurements are used to characterise and distinguish different types of vesicle containing phenolic compounds, lipids and polysaccharides. Within 2 min of plasmogamy, small phenolic vesicles located just below the egg membrane undergo mass synchronised exocytosis. The contents of these vesicles are discharged as phenolic bodies on the outside of the membrane. Secretion of phenolic bodies precedes secretion of the primary zygote wall by several minutes. Limited secretion of phenolics also occurs in unfertilised eggs. Peripheral phenolic vesicles are distinguishable from physodes, which also 'contain phenolic compounds but which are significantly larger and tend to be localised around the egg nucleus. The possible functional significance of the phenolic bodies is discussed. Coated pits and vesicles are common in zygotes, and their presence is evidence for endocytosis.Key words: Fertilisation, Phaeophyceae, Phenolics, Secretion, Zygote. IntroductionEggs and zygotes of various species of brown algae, mostly fucoids, have been used as model systems in studies of spermatozoid attraction (Maier & M/iller, 1986), fertilisation potential (Brawley, 1987(Brawley, , 1991, polyspermy (Brawley, 1992), cell wall secretion (Evans et al., 1982; Brawley & Bell, 1987;Quatrano, 1992), the development of polarity (Quatrano, 1978;Quatrano et al., 1985;Kropf, 1992) and rhizoid growth (Kropf & Quatrano, 1987, Kropf, 1989. However, despite being the focus of so many investigations, there have been surprisingly few detailed ultrastmctural investigations of the eggs and zygotes of brown algae, possibly due to the notorious problems encountered in the fixation of brown algal tissues. The present study was instigated to examine structural aspects associated with fertilisation in the southern bull kelp, Durvillaea potatorum (Labillardi6re) Areschoug. The study revealed a previously undescribed phenomenon, the mass secretion of phenolic bodies, which occurs immediately following plasmogamy. The possible functional significance of this phenomenon is discussed. Materials and methodsFertile thallus pieces from male and female plants of Durvillaea potatorum were collected at Sorrento, Victoria, and were stored for 24 h without water in polythene bags kept on ice. Release of eggs and spermatozoids was stimulated by washing thallus fragments with chilled seawater. Dense suspensions of eggs and spermatozoids were prepared separately, checked microscopically to ensure they were in good condition, and then used immediately as outlined below. Electron microscopyFor transmission electron microscopy, egg and sperm suspensions were mixed and samples were taken after 2, 15, 30 and 60 min, and 25 h. For comparison, a series of unfertilised eggs (not mixed with spermatozoids) was fixed at the same times. Specimens were preserved in a fixative similar to that us...

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“…There are many ways in which this alteration might be brought about. A hydrolytic enzyme, for example, the protease or glucanhydrolase which are present within the granule (Schuel, 1978) may increase the osmolality of the granule contents or unmask charged groups on the macromolecular constituents. Another possible mechanism would entail the loss of stabilizing constituents by efflux or degradation.…”

Section: Discussionmentioning

confidence: 99%

Inhibition of secretory granule discharge during exocytosis in sea urchin eggs by polymer solutions.

Whitaker

Zimmerberg

1987

The Journal of Physiology

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SUMMARY1. We have investigated the effects of the osmotic pressure exerted by polymer solutions on exocytosis in sea urchin eggs.2. Exocytosis is prevented by including a variety of polymers of different chemical composition and molecular weight in the sea water surrounding the eggs. Inhibition is complete at a polymer osmolality of 250 mosmol/kg.3. The increase in membrane capacitance which occurs during exocytosis and which corresponds to the fusion of secretary granules with the plasma membrane is not substantially altered by inhibitory concentrations of polymer.4. In the absence of the ions present in sea water, these polymers inhibit exocytosis at an osmolality of 950 mosmol/kg. 5. Calcium, magnesium and sodium ions reduce the polymer osmolality required to prevent exocytosis. 6. A comparison of the effects of monovalent and divalent ions indicates that the divalent ions bind to and stabilize the secretary granule contents.7. These results demonstrate that polymers prevent exocytosis by preventing dispersal of the granule contents once fusion of the secretary granule with the plasmalemma has occurred. The ions present in sea water do not promote dispersal, rather, they hinder it. The contribution of ionic fluxes to granule swelling during exocytosis is discussed.

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Secretory functions of egg cortical granules in fertilization and development: A critical review

Cited by 214 publications

References 283 publications

U.V. Irradiation Inhibits The Electrical Block to Polyspermy in Echinoderms*

U.V. Irradiation Inhibits The Electrical Block to Polyspermy in Echinoderms*

Secretion of phenolic bodies following fertilisation inDurvillaea potatorum(Durvillaeales, Phaeophyta)

Inhibition of secretory granule discharge during exocytosis in sea urchin eggs by polymer solutions.

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