Activation Of Sea Urchin Eggs Research Articles

NH4Cl and other weak bases in the activation of sea urchin eggs.

NH4Cl and other weak bases in the activation of sea urchin eggs.

NH4Cl and other weak bases in the activation of sea urchin eggs (reply)

NH4Cl and other weak bases in the activation of sea urchin eggs (reply)

Mechanism of action of NH4Cl and other weak bases in the activation of sea urchin eggs.

EXPOSURE of unfertilised sea urchin eggs to NH4Cl and other weak bases such as procaine or nicotine results in the activation of some of the events which normally follow fertilisation, such as the acceleration of protein synthesis and the initiation of DNA synthesis1,2. The initial events of normal fertilisation, for example, the cortical reaction and respiratory burst, are bypassed. It has been shown that fertilisation triggers a Na–H ion exchange that results in an increase in the intracellular pH and a decrease in the pH of the surrounding seawater3. There is a similar acidification of the seawater and increase in intracellular pH when sea urchin eggs are exposed to NH4Cl or procaine. This led to the suggestion that the pH changes induced by weak bases were mediated by a mechanism similar to the Na–H ion exchange. However, it had been proposed that NH4Cl worked by a simple passive diffusion mechanism, where the uncharged species of weak base diffuses into the egg and picks up an H+ ion, resulting in an increase in the intracellular pH (ref. 4). The important distinction between these two mechanisms is that if weak bases are working by a passive diffusion mechanism, bypassing the Na–H ion exchange, then their action gives direct support to the hypothesis that an increase in the intracellular pH plays a part in the onset of biosynthetic activities after fertilisation. We show here that weak bases bypass the Na–H ion exchange, cause both the internal and external pH changes directly by their passive diffusion into the egg, and that the initial increase in the rate of protein synthesis is proportional to the amount of weak base entering the egg.

Cell nucleus negatively controls mitochondrial RNA synthesis in early sea urchin development

The removal of the nucleus highly stimulates the synthesis of mitochondrial RNA of parthenogenetic activated sea urchin eggs.

Intracellular pH and activation of sea urchin eggs after fertilisation.

The intracellular pH of the sea urchin embryo increases 0.3 pH units between 1 and 4 min after fertilisation. The increase in pH is required for initiating development. The increase results from an exchange of extracellular Na+ for intracellular H+.

Na is essential for activation of the inseminated sea urchin egg

The presence of at least 2.5 mM Na during the first several min after insemination is required for the activation of sea urchin eggs. Of those chemical species examined that exist entirely as cations, and which did not activate the unfertilized egg, only Li substitutes for Na. Ammonium and other amines, with pKa values between 9 and 10.8, in the complete absence of Na (a) can induce nuclear activation of unfertilized eggs, and (b) permit the development of the early fertilized egg through the stage that normally requires Na.

Relationship between release of surface proteins and metabolic activation of sea urchin eggs at fertilization.

Macromolecular components are released from sea urchin eggs when their metabolism is activated at fertilization or by incubation in ammonia. When the released material is dialyzed, concentrated, and added back to partially activated eggs the rate of protein synthesis is suppressed to the level of the unactivated egg. The surface proteins of the unfertilized eggs can be labeled with 125I by a lactoperoxidase procedure. When fertilized or activated with various parthenogenetic agents, 15-25% of the total labeled protein is released; most of the label is associated with a 150,000-dalton glycoprotein. The extent of metabolic activation, as assessed by measuring increased protein synthesis, is correlated with the amount of surface label released. Several other proteins are released during activation but are not labeled by the lactoperoxidase procedure in the intact cell. We have not yet identified which of these components is responsible for suppressing protein synthesis, nor do we know if any of the other metabolic changes of fertilization such as K+ conductance and DNA synthesis are also suppressed. We suggest that these released components are surface molecules involved in maintaining the low metabolic state occurring at the end of oogenesis and that removal of these components during fertilization results in the release of the suppression of the egg.

The activation of sea urchin eggs by the divalent ionophores A23187 and X-537A

The divalent ionophores A23187 and X-537A induce parthenogenesis in sea urchin eggs. This results from their ability to mobilize intracellular Ca 2+, which is implicated in both artificial parthenogenesis as well as the natural fertilization process. A23187 causes expulsion of cortical granules and elevation of the fertilization membrane within 0.5–9 min followed by an initiation of cell cleavage. The broader spectrum ionophore X-537A is less potent, but the production of cytoplasmic aberrations are more apparent. In contrast to the sperm-activated egg, the initial phase of ionophore induced activation is accompanied either by relatively insignificant changes in membrane resistance, or an increase.

Activation of sea-urchin eggs by a calcium ionophore.

Micromolar amounts of the divalent ionophore A23187 can activate echinoderm eggs. The activations by ionophore A23187 were examined in terms of membrane elevation, the program of membrane conductance changes, the respiratory burst, and the increases in protein and DNA synthesis which normally accompany activation by sperm. In all these respects activation by the ionophore was fairly normal although subsequent cleavage and embryonic development was limited. Ionophore A23187 activations of the cortex of Lytechinus pictus and Strongylocentrotus purpuratus eggs were compared in various ionic media and were found to be completely independent of the ionic composition of the external solution. Respiration and protein synthesis of L. pictus eggs in singly substituted ionic media also indicated that these activations were independent of external sodium, calcium, or magnesium. These results suggest that the ionophore acts by releasing intracellular Ca(++). Consistent with this interpretation is the finding that eggs preloaded with (45)Ca show a 20-fold increase in (45)Ca-efflux when activated by ionophore A23187 or fertilization. Measurements of the "free" and "bound" calcium and magnesium in homogenates of the unfertilized eggs show that most of the Mg(++) is already available in the soluble form, whereas Ca(++) is sequestered but available for release. We propose that both normal fertilization and ionophore activation affect the metabolism of the egg by releasing Ca(++) sequestered in intracellular stores.

Ca 2+-stimulated ATpase during the early development of parthenogenetically activated eggs of the sea urchin Paracentrotus lividus

A Ca 2+-stimulated ATPase shows fluctuations in the activity in parthenogenetically activated sea urchin eggs very similar to those described earlier for fertilized eggs. Besides activity peaks in the first part of a cell cycle the enzyme activity increases when the mitotic apparatus (MA) or MA-like structures like monasters or cytasters are formed. A possible function of the enzyme in the assembly of the MA is discussed.

Effect of various ionic compositions upon the membrane potentials during activation of sea urchin eggs

The membrane potentials of sea urchin ( Hemicentrotus pulcherrimus) eggs before and after fertilization and their changes during the membrane elevation induced by intracellular electrical stimulation were recorded in solutions of various ionic compositions. Upon fertilization, the membrane potential (−10 mV) depolarized and reversed polarity by a few mV, then gradually returned to a new steady level ranging between −50 and −60 mV. The activation potential is closely associated with a transient increase in the membrane permeability. The potential of the unfertilized egg is hyperpolarized by monovalent anions (Br −, Cl − and NO 3 −) and depolarized slightly by K +. In contrast, the membrane of the fertilized egg is markedly depolarized by K +. Suppression of depolarization associated with an increase of the membrane permeability was recorded in Na-free medium (Tris-HCl). The selective increase in permeability to monovalent anions is thought to alternate with the selective increase in permeability to K +through the mediation of a transient increase of Na +-permeability at the time of fertilization. No causal relationship between the membrane elevation and the depolarization was established because the breakdown of the cortical granules occurs without depolarization or an increase in membrane permeability.

Cytology and nucleic acid synthesis of parthenogenetically activated sea urchin eggs

Unfertilized eggs of Paracentrotus lividus activated with thymol and KCl can develop at least until the pluteus stage. Cytological studies showed that development of artificially activated eggs follows one of four different pathways: monaster formation, cytaster formation, haploid mitosis, or intranuclear chromosome replication. Cytospectrophotometric determination of DNA values from blastula nuclei indicated that parthenogenetic blastulae may contain either 1 n, 2 n or 4 n nuclei or they may be a mosaic regarding the ploidy of their nuclei. DNA synthesis in artificially activated eggs begins about 2.5 times later as compared to fertilized controls; its rate is about half that of fertilized eggs. The rate of RNA synthesis in activated eggs is similar, though somewhat lower, than in fertilized eggs. Parthenogenetically activated and fertilized eggs show a very similar uptake of thymidine and uridine.

The isolation and characterization of asters from artificially activated sea urchin eggs

1. 1. Asters produced in artificially activated eggs can be isolated by the same methods which have been used to isolate the mitotic apparatus from spermfertilized eggs. The methods described were the alcohol-digitonin and the sucrose-versene-dithiodiglycol methods. 2. 2. These isolated asters have similar solubility and stability properties as those of the mitotic apparatus. Isolated asters can be dissolved in Salyrgan (mersalyl acid) at pH 9, and in 0.53 M KC1 at pH ca 8. 3. 3. Ultracentrifuge analysis of SVD-isolated asters shows two peaks, with sedimentation velocities of 14 and 21. 4. 4. Electrophoresis of SVD-isolated asters shows two peaks; the major peak has a mobility of 1.04 × 10 −4 cm 2/volt sec, and the minor peak a mobility of 7.2 × 10 −5 cm 2/volt sec. 5. 5. Absorption spectra (UV) of solubilized SVD and digitonin-isolated asters show maxima at 260 mμ. 6. 6. ATPase analysis of dissolved asters gives an activity lower than that shown for the mitotic apparatus. 7. 7. Immunochemical identity has been found between isolated mitotic apparatus from sperm-fertilized eggs, and asters from artificially activated eggs.

THE PRESENCE OF CENTRIOLES IN ARTIFICIALLY ACTIVATED SEA URCHIN EGGS

THE PRESENCE OF CENTRIOLES IN ARTIFICIALLY ACTIVATED SEA URCHIN EGGS

On the incorporation of S35-methionine in artificially activated sea urchin eggs

Metionina-S35 e stata incorporata in uova vergini diParacentrotus lividus. In queste l'isotopo si trova per la piu gran parte nella frazione solubile in acido tricloracetico al 10%. Attivando le uova partenogeneticamente con acido butirrico si osserva una progressiva perdita di attivita di questa frazione ed una rapida incorporazione nei mitocondri. L'andamento del fenomeno e del tutto identico a quello gia descritto (Nakano eMonroy) nelle uova normalmente fecondate.

Fertilization and activation of sea urchin eggs in glass capillaries I. Membrane elevation and nuclear movements in totally and partially fertilized eggs

Psammechinus miliaris eggs were fertilized in glass capillaries of small diameter, the ends of which were sealed with drops of oil. Complete membrane elevation occurred on slightly elongated (cylindrical) eggs (110–140 microns) when these eggs were held stationary. Membrane elevation could be partially or totally inhibited by friction of the egg surface against the glass during sperm penetration. In eggs which had been elongated to a greater extent, the fertilization impulse failed to cover the entire egg surface, so that the egg was left only partially fertilized. The unfertilized portions of such eggs remained fertilizable, whereas the fertilized parts underwent the surface and interior changes associated with activation. Nuclear movements were observed in eggs in various degrees of elongation. The distance over which the egg and sperm nuclei must migrate in order to meet (penetration path plus copulation path) was varied by the manner of orientation of the eggs when drawn into the capillaries. The sperm nucleus penetrated a relatively constant distance from the surface (the penetration path) irrespective of the presence or position of the egg nucleus. These initial movements of the sperm nucleus were coincident with the growth of the sperm aster. Further movements of the two nuclei (copulation path) depended on the positions of the two nuclei and could be undertaken by either or both of the nuclei, which could exert a mutual attraction even when separated by a distance eight times as great as that in the normal spherical egg. The egg nucleus was unable to migrate when surrounded by unfertilized cytoplasm, but swelling and nuclear breakdown could occur. It is therefore believed that these latter phenomena were caused by diffusing substances.

Fertilization and activation of sea urchin eggs in glass capillaries III. Artificial activation and the fertilization impulse

Fertilization and activation of sea urchin eggs in glass capillaries III. Artificial activation and the fertilization impulse

Fertilization and activation of sea urchin eggs in glass capillaries II. Cortical changes and the fertilization impulse

Psammechinus miliaris eggs were fertilized in glass capillaries of small diameter, the ends of which had been sealed with drops of oil. As the diameter of the capillaries was decreased, the fertilization impulse (as detected by cortical granule breakdown and the dark-field color change) failed to extend over the entire surface of many of the eggs. In sixty-three cases of such partial fertilization in control and experimentally treated eggs, the area covered by the fertilization impulse was calculated. Stretching, straightening of the egg surface, and contact with the glass: three inseparable variables caused a reduction in the area affected by the impulse. Although glycine had no detectible effect on slightly stretched eggs, it considerably enhanced the inhibition due to greater stretching. Pretreatment of the eggs with ATP or periodate facilitated the passage of the impulse. The hypothesis of interior diffusion of an activating substance from the sperm is rejected on the grounds that the. cytoplasm of stretched mono- and dispermic eggs was not always entirely converted to the fertilized form although the cell volume was unchanged. The fertilization impulse is evidently accompanied by a structural change at the surface involving a decrease in cortical rigidity. This impulse is not an all-or-none phenomenon as evidenced by the appearance of an intermediate zone. Rate measurements and other considerations suggest a cortical chain reaction, which can be imagined as initiated by the activation of a certain number of units on the egg surface by the sperm. These units when activated are then able to activate others and so propagate the impulse. It is probable that high energy phosphate compounds can be used in the process and that the passage of the impulse is normally opposed by the presence of a carbohydrate inhibitor which can be destroyed by the action of periodate.

Ion Exchanges and Fertilization in Echinoderm Eggs

Previous articleNext article No AccessConference on Problems of General and Cellular Physiology Relating to Fertilization. IIIIon Exchanges and Fertilization in Echinoderm EggsEdward L. Chambers and Robert ChambersEdward L. Chambers Search for more articles by this author and Robert Chambers Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 83, Number 813Nov. - Dec., 1949 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/281605 Views: 3Total views on this site Citations: 20Citations are reported from Crossref PDF download Crossref reports the following articles citing this article:John D. Biggers, R. Michael Borland, R. Douglas Powers Transport Mechanisms in the Preimplantation Mammalian Embryo, (May 2008): 129–153.https://doi.org/10.1002/9780470720332.ch7Sheldon S. Shen, An-Li Sui K+ activity and regulation of intracellular pH in the sea urchin egg during fertilization, Experimental Cell Research 183, no.22 (Aug 1989): 343–352.https://doi.org/10.1016/0014-4827(89)90395-9David Epel An Ode to Edward Chambers: Linkages of Transport, Calcium and pH to Sea Urchin Egg Arousal at Fertilization, (Jan 1989): 271–284.https://doi.org/10.1007/978-1-4757-0881-3_14B. Ciapa, G. de Renzis, J. P. Girard, P. Payan Sodium-potassium exchange in sea urchin egg. I. Kinetic and biochemical characterization at fertilization, Journal of Cellular Physiology 121, no.11 (Oct 1984): 235–242.https://doi.org/10.1002/jcp.1041210129Bennett M. Shapiro, E.M. Eddy When Sperm Meets Egg: Biochemical Mechanisms of Gamete Interaction, (Jan 1980): 257–302.https://doi.org/10.1016/S0074-7696(08)61976-2Shun-ichi Miyazaki Fast polyspermy block and activation potential, Developmental Biology 70, no.22 (Jun 1979): 341–354.https://doi.org/10.1016/0012-1606(79)90032-0Laurinda A. Jaffe, Kenneth R. Robinson Membrane potential of the unfertilized sea urchin egg, Developmental Biology 62, no.11 (Jan 1978): 215–228.https://doi.org/10.1016/0012-1606(78)90103-3David Nishioka, Nicholas Cross THE ROLE OF EXTERNAL SODIUM IN SEA URCHIN FERTILIZATION11This work was supported by a grant from the National Science Foundation to Dr. D. Epel., (Jan 1978): 403–413.https://doi.org/10.1016/B978-0-12-217850-4.50039-3Kenneth R. Robinson Potassium is not compartmentalized within the unfertilized sea urchin egg, Developmental Biology 48, no.22 (Feb 1976): 466–472.https://doi.org/10.1016/0012-1606(76)90109-3Edward L. Chambers, Berton C. Pressman, Birgit Rose The activation of sea urchin eggs by the divalent ionophores A23187 and X-537A, Biochemical and Biophysical Research Communications 60, no.11 (Sep 1974): 126–132.https://doi.org/10.1016/0006-291X(74)90181-8R.Douglas Powers, Joseph T. Tupper Some electrophysiological and permeability properties of the mouse egg, Developmental Biology 38, no.22 (Jun 1974): 320–331.https://doi.org/10.1016/0012-1606(74)90010-4Joseph T. Tupper Inhibition of increased potassium permeability following fertilization of the echinoderm embryo: Its relationship to the initiation of protein synthesis and potassium exchangeability, Developmental Biology 38, no.22 (Jun 1974): 332–345.https://doi.org/10.1016/0012-1606(74)90011-6Joseph T. Tupper, R. Douglas Powers Changes in ion permeability and membrane potential during early echinoderm development: Electrophysiological and tracer-flux determinations, Journal of Experimental Zoology 184, no.33 (Jun 1973): 353–363.https://doi.org/10.1002/jez.1401840309Joseph T. Tupper Potassium exchangeability, potassium permeability, and membrane potential: Some observations in relation to protein synthesis in the early echinoderm embryo, Developmental Biology 32, no.11 (May 1973): 140–154.https://doi.org/10.1016/0012-1606(73)90226-1 Bibliography, (Jan 1973): 390–460.https://doi.org/10.1016/B978-0-12-285750-8.50018-0Robert David Allen, L. Jacobsen, J. Joaquin, L.F. Jaffe Ionic concentrations in developingPelvetia eggs, Developmental Biology 27, no.44 (Apr 1972): 538–545.https://doi.org/10.1016/0012-1606(72)90191-1R.M. IVERSON, GERALDINE H. COHEN Polysomes of Sea Urchins: Retention of Integrity, (Jan 1969): 299–313.https://doi.org/10.1016/B978-1-4832-2797-9.50020-0Hector Timourian, Paul C. Denny Activation of protein synthesis in sea-urchin eggs upon fertilization in relation to magnesium and potassium ions, Journal of Experimental Zoology 155, no.11 (Feb 1964): 57–70.https://doi.org/10.1002/jez.1401550105Albert Tyler, Alberto Monroy Changes in rate of transfer of potassium across the membrane upon fertilization of eggs of Arbacia punctulata, Journal of Experimental Zoology 142, no.11 (Oct 1959): 675–690.https://doi.org/10.1002/jez.1401420132F.H.N. Rudenberg The role of the jelly coat in the uptake of calcium by eggs of Arbacia punctulata before and after fertilization, Experimental Cell Research 4, no.11 (Jan 1953): 116–126.https://doi.org/10.1016/0014-4827(53)90194-3