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At least 91 records · Page 5Linked to original sources
PubMed1988

Characterization of 1-methyladenine binding in starfish oocyte cortices.

1-Methyladenine (1MeAde) is the naturally occurring maturation-inducing hormone of starfish oocytes. We have prepared a biologically active [3H]1MeAde of high purity and relatively high specific radioactivity. This ligand binds to cortices isolated from full-grown prophase-arrested oocytes of the starfish Asterina pectinifera. The binding of [3H]1MeAde to cortices was rapid and reached equilibrium in approximately 15 min. This is in excellent agreement with the hormone-dependent period required for the induction of oocyte maturation. Binding was maximal between pH 6.4 and 8.0 and diminished sharply above and below this range. Analysis of Scatchard plots of the equilibrium binding of [3H]1MeAde to cortices indicates the existence of a single class of binding site with a dissociation constant of 0.3 microM and a binding capacity of 0.02 fmol per cortex. Whereas biologically active analogs (1-benzyladenine, 1-ethyladenine) inhibited the specific binding of [3H]1MeAde by cortices, biologically inactive analogs (2-methyladenine, 3-methyladenine, 1,9-dimethyladenine, and 1-methylhypoxanthine) did not. These results suggest that the 1MeAde binding characterized herein is necessary for the maturational action of 1MeAde on starfish oocytes.

Adenine↗
PubMed2000

Evidence that fertilization activates starfish eggs by sequential activation of a Src-like kinase and phospholipase cgamma.

Recent evidence has indicated a requirement for a Src family kinase in initiating Ca(2+) release at fertilization in starfish eggs (Giusti, A. F., Carroll, D. J., Abassi, Y. A., Terasaki, M., Foltz, K. R., and Jaffe, L. A. (1999) J. Biol. Chem. 274, 29318-29322). We now show that injection of Src protein into starfish eggs initiates Ca(2+) release and DNA synthesis, as occur at fertilization. These responses depend on the phosphorylation state of the Src protein; only the kinase active form is effective. Like Ca(2+) release at fertilization, the Ca(2+) release in response to Src protein injection is inhibited by prior injection of the SH2 domains of phospholipase Cgamma. These findings support the conclusion that in starfish, sperm-egg interaction causes egg activation by sequential activation of a Src-like kinase and phospholipase Cgamma. Injection of the SH2 domain of Src, which inhibits Ca(2+) release at fertilization, does not inhibit Ca(2+) release caused by Src protein injection. This indicates that the requirement for a Src SH2 domain interaction is upstream of Src activation in the pathway leading to Ca(2+) release at fertilization.

Animals↗
PubMed1990

Cell-free translation systems prepared from starfish oocytes faithfully reflect in vivo activity; mRNA and initiation factors stimulate supernatants from immature oocytes.

Meiotic maturation stimulates a change in the translation of stored mRNAs: mRNAs encoding proteins needed for growth of oocytes are translated before meiotic maturation, whereas those encoding proteins required for cleavage are translated after meiotic maturation. Studies of translational regulation during meiotic maturation have been limited by the lack of translationally active cell-free supernatants. Starfish oocytes are ideal for preparing cell-free translation systems because experimental application of the hormone 1-methyladenine induces their maturation, synchronizing meiosis. We have prepared such systems from both immature and mature oocytes of starfish. Changes in protein synthesis rates and the specificity of proteins synthesized in these cell-free translation supernatants mimic those seen in vivo. Supernatants both from immature and mature oocytes have a high capacity to initiate new translation because 90% of the proteins made are newly initiated from mRNAs. Cell-free supernatants from mature oocytes have a much higher rate of initiation of translation than those from immature oocytes and use the 43S preinitiation complexes more efficiently in initiation of translation. Similarly, we have shown that mRNAs and initiation factors are rate limiting in cell-free translation systems prepared from immature oocytes. In addition, cell-free translation systems prepared from immature oocytes are only slightly, if at all, inhibitory to cell-free translation systems from mature oocytes. Thus, soluble inhibitors, if they exist, are rapidly converted by cell-free supernatants from mature oocytes. The similarities between translation in our starfish cell-free translation systems and in intact oocytes suggests that the cell-free translation systems will be useful tools for further studies of maturation events and translational control during meiosis.

Animals↗
PubMed1981

Nucleosomal structure of sea urchin and starfish sperm chromatin. Histone H2B is possibly involved in determining the length of linker DNA.

Comparison has been made between sea urchin and starfish sperm chromatin. The only protein by which chromatins from these sources differ significantly is histone H2B. Sea urchin sperm H2B is known to contain an elongated N-terminal region enriched in Arg. Analysis of the micrococcal nuclease digests of sea urchin and starfish nuclei in one- and two-dimensional electrophoresis has shown that sperm chromatin of both animals consists of repeated units similar in general features to those of rat thymus or liver. However, DNA repeat length in chromatin of sea urchin sperm (237 bp) is higher than that of starfish sperm (224 bp), while the core DNA length does not differ and is the same as in the chromatin of rat liver or thymus. A suggestion has been made that the N-terminal region of histone H2B is associated with the linker DNA and is responsible for the increased length of sea urchin linker DNA.

Amino Acids↗
PubMed1982

A protein in starfish sperm head which bundles actin filaments in vitro: purification and characterization.

From an extract of starfish sperm heads, a protein was purified using ammonium sulfate fractionation, Sephacryl S-300, hydroxyapatite and Whatman DE 52 columns. Co-sedimentability on low speed centrifugation of this protein with actin filaments was used as an index in the purification. This protein has a molecular weight of 57,000, as judged by SDS-polyacrylamide gel electrophoresis. It lowers the specific viscosity of an actin filament solution, although this effect is abolished under high ionic conditions such as 300 mM NaCl. Electron microscopic observation shows formation of actin filament bundles with a banding pattern of about 10 nm periodicity. Based on these results, we call this protein starfish sperm fascin. Changes in pH and Mg2+ or ATP concentration have no effect on the action of this sperm fascin. Neither the rate of actin polymerization nor that of depolymerization is affected by this protein. The bundles are depolymerized as well by actin-depolymerizing protein (Mabuchi, I. (1981) J. Biochem. 89, 1341-1344) purified from starfish eggs.

Actins↗
PubMed2003

Effect of organochlorine pesticides on maturation of starfish and mouse oocytes.

Methoxychlor, lindane, and dieldrin are organochlorine pesticides that have been described as altering different reproductive functions in mammals and in invertebrates. However, few data have been published concerning the effects these pesticides have on oocyte maturation and fertilization. The aim of this study was to determine whether these compounds could affect maturation of mouse and starfish oocytes. We observed that germinal vesicle breakdown (GVBD) in starfish oocytes was significantly inhibited by the pesticides. Furthermore, formation of the first meiotic spindle and extrusion of the first polar body were also altered in mouse as well as in starfish. Our results suggest that the three pesticides act on common intracellular targets in invertebrates as well as in vertebrates.

Animals↗
PubMed1983

Primary structure of histone H2A from gonads of the starfish Asterias rubens.

The complete amino acid sequence (124 residues) of histone H2A from gonads of the starfish Asterias rubens has been established from automated sequence analyses of large fragments obtained by staphylococcal protease digestion of histone H2A and by limited hydrolysis of H2A-H2B complex with mouse submaxillary gland protease and from structural studies of peptides generated by enzymatic hydrolyses of these fragments or of the protein. By comparison with calf homologous histone, the starfish histone H2A shows 5 deletions and 12 substitutions. Half of the substitutions are non-conservative. Microheterogeneities were found at positions 18, 40 and 50 and result in the existence of at least two variants of starfish gonad histone H2A.

Amino Acid Sequence↗
PubMed1992

The primary structure of the alpha subunit of a starfish guanosine-nucleotide-binding regulatory protein involved in 1-methyladenine-induced oocyte maturation.

Starfish-oocyte maturation induced by 1-methyladenine (MeAde) was inhibited by microinjection of pertussis toxin (PTX). The inhibition appeared to result from PTX-catalyzed ADP-ribosylation of a 39-kDa guanosine-nucleotide-binding regulatory protein (G protein) in the oocyte. These results strongly support the hypothesis that the MeAde-induced signals operate via a membrane receptor and are carried by the PTX-sensitive G protein. When PTX-injected oocytes were treated with dithiothreitol, 85% of them reinitiated meiosis, suggesting that dithiothreitol did not act on the MeAde receptor. We constructed a cDNA library from the immature ovary of starfish, Asterina pectinifera, and screened it with the cDNA of the alpha subunit of an inhibitory rat G protein (Gi-2). A positive cDNA clone contained an open reading frame of 1062 bases which had 74% identity with the rat Gi-2 cDNA. The deduced amino acid sequence was 85% and 89% identical to rat Gi-2 and rat Gi-1, respectively. The alpha subunit of the G protein purified from cortices of starfish oocytes was digested by trypsin and the resulting four peptides were microsequenced. Comparison of these amino acid sequences with the predicted one indicated that the isolated cDNA clone encoded the alpha subunit of the PTX-sensitive G protein in oocytes. The C-terminal sequence, KNNLKDCGLF, was identical to that of Gi, suggesting that the cysteine residue is the site of ADP-ribosylation.

Adenine↗
PubMed1997

Association of calmodulin with nuclear structures in starfish oocytes and its role in the resumption of meiosis.

The resumption of meiosis in prophase-arrested starfish oocytes is induced by the hormone 1-methyladenine, which has been shown previously to induce a calcium transient in the nucleus which at this stage is called the germinal vesicle. This transient precedes the breakdown of the germinal vesicle (GVBD). Experiments were performed to establish whether nuclear calmodulin (CaM) was involved in the progression of the meiotic cycle. CaM antagonists, antibodies, and an inhibitory peptide corresponding to the CaM-binding domain of myosin-light-chain kinase have been injected into the nucleus of prophase-arrested starfish oocytes. The antagonists failed to affect the final response to 1-methyladenine, i.e. GVBD, although two antagonists delayed it, whereas the peptide inhibitor and the antibodies completely inhibited it. The antibodies suppressed the nuclear Ca2+ spikes that were shown by previous work to be induced by the photoreleasing of caged adenosine 3',5'-(cyclic)diphosphate ribose in the germinal vesicle. Immunofluorescence staining of isolated starfish oocyte nuclei with CaM antibodies showed CaM in the envelope and in the nucleolus. Immunogold labelling of oocytes revealed aggregates of CaM and of a 36-kDa protein, of the heterogeneous ribonucleoprotein particles (hnRNP), in electron-dense hnRNP in the nuclear matrix. 1-Methyladenine induced the disappearance of these hnRNP from the nucleoplasm and the translocation of CaM and the 36-kDa protein previously associated with them to the cytoplasm, prior to the breakdown of the nuclear envelope.

Adenine↗
PubMed2003

Metaphase I arrest of starfish oocytes induced via the MAP kinase pathway is released by an increase of intracellular pH.

Reinitiation of meiosis in oocytes usually occurs as a two-step process during which release from the prophase block is followed by an arrest in metaphase of the first or second meiotic division [metaphase I (MI) or metaphase II (MII)]. The mechanism of MI arrest in meiosis is poorly understood, although it is a widely observed phenomenon in invertebrates. The blockage of fully grown starfish oocytes in prophase of meiosis I is released by the hormone 1-methyladenine. It has been believed that meiosis of starfish oocytes proceeds completely without MI or MII arrest, even when fertilization does not occur. Here we show that MI arrest of starfish oocytes occurs in the ovary after germinal vesicle breakdown. This arrest is maintained both by the Mos/MEK/MAP kinase pathway and the blockage of an increase of intracellular pH in the ovary before spawning. Immediately after spawning into seawater, activation of Na+/H+ antiporters via a heterotrimeric G protein coupling to a 1-methyladenine receptor in the oocyte leads to an intracellular pH increase that can overcome the MI arrest even in the presence of active MAP kinase.

Adenine↗
PubMed1993

Association of p34cdc2/cyclin B complex with microtubules in starfish oocytes.

The microtubular cytoskeleton exhibits a dramatic reorganization, progressing from interphase radial arrays to a mitotic spindle at the G2/M transition. Although this reorganization has been suspected to be caused by maturation promoting factor (MPF: p34cdc2/cyclin B complex), little is known about how p34cdc2 kinase controls microtubule networks. We provide evidence of the direct association of the p34cdc2/cyclin B complex with microtubules in starfish oocytes. Anti-cyclin B staining of detergent-treated oocytes, isolated asters and meiotic spindles revealed fluorescence associated with microtubule fibers, chromosomes and centrosomes. Microtubules prepared from starfish oocytes were associated with cyclin B and p34cdc2 proteins. Microtubule-bound p34cdc2 and cyclin B were released from microtubules by a high-salt solution and possessed a complex form as shown by the adsorption to suc1-beads and by immunoprecipitation with the anti-cyclin B antibody. The p34cdc2/cyclin B complex associated to microtubules had high histone H1 kinase activity at meiotic metaphase. However, it was not necessary for the p34cdc2/cyclin B complex to be active for microtubule binding, as an inactive form in immature oocytes was also observed to bind to microtubules. The coprecipitation of suc1-column purified p34cdc2/cyclin B with purified porcine brain microtubules in the presence of starfish oocyte microtubule-associated proteins (MAPs) indicates that the association of p34cdc2/cyclin B with microtubules in vitro is mediated by MAPs.

Animals↗
PubMed2005

Increase in intracellular pH induces phosphorylation of axonemal proteins for activation of flagellar motility in starfish sperm.

Increased intracellular pH ([pH]i) activates dynein in sea urchin and mammalian sperm and induces activation of flagellar motility. It is thought that cAMP-dependent protein phosphorylation is associated with motility activation through increasing [pH]i, but little attention has been given to the cAMP-independent phosphorylation also induced by the [pH]i increase. The present study demonstrates that the increase in [pH]i in starfish sperm induces the phosphorylation of axonemal proteins and activation of flagellar motility independently of cAMP. Flagellar motility of intact sperm was activated when the [pH]i was raised by addition of NH4Cl. Histidine, which is known to activate motility of starfish sperm, also raised the [pH]i during the motility activation. In addition, motility of demembranated sperm flagella was activated in a pH-dependent manner without cAMP. These results indicate that in starfish sperm it is the increase in [pH]i that induces activation of flagellar motility. Moreover, phosphorylation of axonemal proteins (of molecular mass 25, 32 and 45 kDa) was observed during the pH-dependent and cAMP-independent motility activation of demembranated sperm. This suggests that the increase in [pH]i regulates flagellar motility via cAMP-independent phosphorylation of axonemal proteins.

Ammonium Chloride↗
PubMed1995

Distribution and action of SALMFamide neuropeptides in the starfish Asterias rubens.

The SALMFamides S1 and S2 are two structurally related neuropeptides that are present in starfish, and which share the C-terminal amino acid sequence SXLXFamide, where X is variable. To establish the distribution of S1 and S2 in starfish, we have raised antisera that recognise specifically the C-terminal pentapeptide sequence of either S1 or S2. Here we describe the production and characterisation of an S2-specific antiserum designated CLII. This antiserum, together with an S1-specific antiserum (BLII), has been used in a radioimmunoassay to measure S1 and S2 levels in extracts of body parts from the starfish Asterias rubens. High concentrations (250-400 pmol g-1) of both peptides were detected in the radial nerve cords of the nervous system and lower concentrations were detected in other body parts, including neuromuscular organs such as the tube feet, apical muscle and cardiac stomach. We have examined the pharmacological effects of S1 and S2 on the contractility of these three preparations. Neither S1 nor S2 influenced the tone of tube foot and apical muscle preparations but S2 caused relaxation of cardiac stomach preparations, antagonising the contracting action of acetylcholine.

Animals↗
PubMed2003

Genetic variation in northern Japanese populations of the starfish Asterina pectinifera.

The starfish Asterina pectinifera of the family Asterinidae is endemic Japanese species and commonly found in Japanese waters. In order to examine the degree of genetic variation and the maintenance mechanism of polymorphism within population, we studied the allozyme variation in five northern Japanese local populations of the starfish by electrophoresis. The species showed much higher genetic variability than many other shallow water echinoderms. Based on other allozyme studies and the ecological data, it was suggested that the high genetic variation of the starfish was closely related to the population size. Additionally, the relation between the degree of enzyme variation and the quaternary structure of enzymes was also examined, and the results suggested the close relation between the enzyme variability and functional constraints.

Animals↗
PubMed2004

Inhibitory effect of a SALMFamide neuropeptide on secretion of gonad-stimulating substance from radial nerves in the starfish Asterina pectinifera.

In starfish, the peptide hormone gonad-stimulating substance (GSS) secreted from nervous tissue stimulates oocyte maturation to induce 1-methyladenine (1-MeAde) production by ovarian follicle cells. The SALMFamide family is also known to an echinoderm neuropeptide. The present study examined effect of SALMFamide 1 (S1) on oocyte maturation of starfish Asterina pectinifera. Unlike GSS, S1 did not induce spawning in starfish ovary. In contrast, S1 was found to inhibit GSS secretion from radial nerves by treatment with high K+ concentration. Fifty percent inhibition was obtained by 0.1 mM S1. S1 did not have any effect on GSS- and 1-MeAde-induced oocyte maturation. Following incubation with a S1 antibody and subsequently with rhodamine-conjugated second antibody, neural networks were observed in ovaries. The networks were restricted mainly to their surface with little evidence of immunoreactivity inside the basement membranes. This indicates that neural networks are distributed in the ovarian wall. The result further suggests that S1 plays a role in oocyte maturation to regulate GSS secretion from the nervous system.

Animals↗
PubMed2006

Sponge systematics by starfish: predators distinguish cryptic sympatric species of Caribbean fire sponges, Tedania ignis and Tedania klausi n. sp. (Demospongiae, Poecilosclerida).

Tedania ignis (Duchassaing and Michelotti, 1864), the fire sponge, is common throughout the tropical western Atlantic, and is a popular species for studies of ecology, larval biology, and chemistry. T. ignis is readily consumed by seagrass-dwelling starfish, and so finding sponges similar to this species in a seagrass meadow provoked closer scrutiny. A variety of ecological, morphological, and molecular traits consistently and unambiguously distinguish T. ignis from a cryptic sympatric congener, here described as Tedania klausi, n. sp. Starfish that consume T. ignis reject T. klausi, and angelfish consume T. klausi less quickly. In Belize, T. ignis individuals transplanted to a seagrass meadow inhabited by T. klausi were consumed by starfish, and individuals of T. klausi transplanted to a mangrove-lined creek in which T. ignis flourishes, died. In Panama, many individuals of T. klausi were diseased in May 2004, while adjacent individuals of T. ignis were unaffected. Spicule types are the same in the two forms, and sizes overlap; but within individuals, the relative sizes of styles and tylotes differ in a pattern that distinguishes the two forms. Comparison of DNA sequences for mitochondrial cytochrome c oxidase subunit I (COI) revealed that 8 single nucleotide mutations consistently differ between the two forms regardless of habitat (seagrass vs. mangrove) and geographically separated sites (Belize vs. Panama).

Animals↗
PubMedDate not supplied

[Polyclonal antibodies, labeling radial nerve cells of the starfish Asterias amurensis].

The results of preliminary studies suggest that the cytoskeletal fraction of the radial nerve of the starfish Asterias amurensis contained a 32 kDa protein, which is tissue specific. This protein was isolated from the radial nerve by preparative electrophoresis and used as an antigen for raising polyclonal antibodies. When testing these antibodies on sections of the starfish tissues, it was shown that they interact only with the proteins present in the radial nerve cells. A conclusion was drawn that the raised antibodies may be used as a cell marker when studying regeneration of the nervous system in starfish.

Animals↗
PubMed1986

Stereospecific induction of starfish oocyte maturation by (8R)-hydroxyeicosatetraenoic acid.

Oocyte maturation (meiosis reinitiation) in starfish is induced by the natural hormone 1-methyladenine. This induction of meiotic divisions can be triggered also by four fatty acids: 5,8,11-20:3; 5,8,11,14-20:4 (arachidonic acid); 6,9,12,15-20:4; 5,8,11,14,17-20:5, all other fatty acids being completely inactive. This maturation triggered by eicosanoids occurs in the micromolar range and is facilitated by the presence of calcium. A variety of arachidonic acid derivatives (esters, epoxides, etc.) and metabolites (cyclooxygenase and lipoxygenase products) has been tested; the biological activity is restricted to 8-hydroxyeicosatetraenoic acid (8-HETE), other mono- and poly-HETEs being completely inactive. Maturation triggered by 8-HETE occurs around 10 nM and is insensitive to the presence of calcium. 8-HETE methyl ester and 8-hydroperoxyeicosatetraenoic acid are able to induce maturation at higher concentrations. Both (8S) and (8R) stereoisomers have been tested; the biological activity is strictly restricted to the (8R) isomer. 8-HETE triggers a complete maturation, i.e. maturation-promoting factor appearance, germinal vesicle breakdown, emission of the polar bodies, and formation of a female pronucleus. (8R)-HETE, but not (8S)-HETE, triggers the typical decrease in cyclic AMP concentration induced by 1-methyladenine and the burst of protein phosphorylation associated with maturation. Starfish oocytes oxidize exogenous arachidonic acid into 8-HETE and other HETEs. 8-HETE was identified, after high pressure liquid chromatography purification, by gas chromatography mass spectrometry. Furthermore, it was found that the starfish oocytes only produce the (8R)-HETE isomer. This highly stereospecific induction of oocyte maturation by (8R)-HETE suggests that this fatty acid, or a very closely related fatty acid, may play a role in the transduction of the 1-methyladenine message at the plasma membrane level.

Animals↗