摘要:

1-Methyladenine (1-MA) secreted from the follicle cells is the biological signal for meiosis reinitiation of starfish oocytes. The signal of-1-MA is transduced into cytoplasmic formation of maturation-promoting factor (MPF) that eventually induces a germinal vesicle breakdown (GVBD). Microinjection of pertussis toxin (PTX) inhibited 1-MA-induced GVBD inAsterina pectiniferaandAsterina (Patina) miniata.PTX-inhibition of GVBD was rescued by the injection of MPF into PTX-preinjected oocytes. Most of the PTX- and MPF-double injected eggs were fertilized and underwent cleavage, suggesting the presence of a GTP-binding protein (G protein) specific for 1-MA signal transduction. Indeed, plasma membrane preparations ofA. pectiniferaoocytes contained a G protein consisting of 39-kDa α, 37-kDa β, and 8-kDa γ subunits. The α subunit contained a site for ADP-ribosylation catalyzed by PTX. It was also recognized by antibodies specific for a common GTP-binding site of mammalian α subunits or a carboxy-terminal ADP-ribosylation site of mammalian inhibitory G protein (Gi) α subunits. Its gene was 74% and 83.7% identical to the rat Gi-2α gene in nucleotide and deduced amino acid sequences, respectively. The 39-kDa α subunit shared the common GTP-binding site of mammalian G protein α subunits and the PTX-catalyzed ADP-ribosylation site of mammalian Giα subunits as expected from the immunoreactivity. The oocyte membranes had apparently two forms of 1-MA receptors with high and low affinities. The high-affinity form was converted into the low-affinity one in the presence of a non-hydrolyzable analogue of GTP. The 39-kDa α subunit of starfish G protein was also ADP-ribosylated by cholera toxin only when 1-MA was added to the membranes. These results indicate that in starfish oocyte membranes, 1-MA receptors are functionally coupled with the 39-kDa PTX-substrate G protein that transduces the signal into the formation of a cytoplasmic factor (MPF) and eventually into the reinitiation of meiosis.

ISSN:0792-4259    

DOI:10.1080/07924259.1992.9672250

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Resumption of meiosis in starfish oocytes is induced by 1-methyladenine (1-MeAde) produced by ovarian follicle cells under the influence of a gonad-stimulating substance (GSS). With respect to 1-MeAde production by follicle cells of the starfish,Asterina pectinifera, (1) the action of GSS is initiated by a receptor mediated activation of G-proteins, resulting in the activation of adenylate cyclase and cyclic AMP (cAMP) formation; (2) 1-MeAde produced under the influence of GSS is not prestored within the follicle cells but is newly synthesized from a 1-MeAde precursor; (3) AMP plays an important role in the process of methylation during 1-MeAde biosynthesis induced by GSS.

ISSN:0792-4259    

DOI:10.1080/07924259.1992.9672251

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Methyl farnesoate (MF) is an unepoxidated form of juvenile hormone III, which controls reproduction in insects and appears to serve the same function in Crustacea. MF is synthesized by the mandibular organs (MOs) and has been found in the hemolymph of both females and males in more than 25 species of crustaceans. MF is most actively synthesized by females during vitellogenesis. MF appears to be an active gonadotropin since implants of MOs into non-reproductives will increase gonad indices. In males, high titers of MF are associated with large reproductive systems and aggressive mating behavior.

ISSN:0792-4259    

DOI:10.1080/07924259.1992.9672252

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Studies on the control of reproduction in crustaceans have, for the most part, dealt with the regulation of female reproduction. However, not a great deal of attention has been paid to cellular interactions of the neurohormones involved in this regulation. In this contribution recent data on inhibitory and stimulatory neuropeptides are discussed and reflections are made on their importance for further application-directed research. Attention is paid to: histophysiological events in the oocytes during vitellogenesis; biochemical aspects of the regulating neuropeptides and cytological localization of these neuropeptides in the neuroendocrine system. Opportunities for further research are identified and appraised in light of the knowledge reviewed.

ISSN:0792-4259    

DOI:10.1080/07924259.1992.9672253

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Structural aspects of insect pheromones, especially their hydrophobicity, prompted the examination of them byin vitroandin vivoexperiments as inhibitors of acetylcholinesterase. All 17 pheromones assayed in sufficient detail were reversible, competitive inhibitors of acetylcholinesterase:Kivalues ranged from 0.27 mM for frontalin to 9.3 mM for ipsenol, both aggregation pheromones. All seven pheromones assayed withTribolium castaneumimmobilised this species with an effect that was weakly dose-responsive over the range of concentrations tested. Concentrations eliciting 25% immobility (IC25) ranged from 2.0x103ppm for 3-methy 1–2-cyclohexenone to 2.0x104ppm forcis-7, cis-11-hexadecadien-1-yl acetate, both sex attractants. Such efficacies suggest that the pheromones tested would be effective as defence agents only in species living in a confined area, as under bark, or in aggregations.

ISSN:0792-4259    

DOI:10.1080/07924259.1992.9672254

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The influence of juvenile hormone (JH)-active chemicals on the settlement and metamorphosis of metatrochophore larvae of the polychaete annelidCapitellasp. I of theCapitellacomplex has been investigated. These studies demonstrate that JH-active chemicals are able to induce settlement and metamorphosis ofCapitellalarvae, and that these effects may possibly be mediated by protein kinase C induction. Evidence for the presence of JH-active compounds in marine sediments is also presented, suggesting that these chemicals may serve a natural role as chemical cues for settlement and metamorphosis forCapitellalarvae in the marine environment.

ISSN:0792-4259    

DOI:10.1080/07924259.1992.9672255

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Parthenogenesis following oocyte activation has been observed in a number of marine invertebrates, but the fate of parthenogenesis in bivalve mollusc embryos is unclear. We used the dwarf surf clam,Mulinia lateralis, to examine parthenogenetic development of KC1-activated oocytes using the polar body suppressing agents caffeine and heat or cytochalasin B. Development was followed by epifluorescence microscopy and flow-cytometric analysis using the DNA-specific fluorochrome DAPI. All agents suppressed polar body formation to some degree, putatively increasing the ploidy level and retaining a meiotic centrosome in the zygote; but the zygotes failed to develop normally. Failure of the zygotes to develop suggests that the meiotic centrosome is incapable of participating in mitosis in bivalves.

ISSN:0792-4259    

DOI:10.1080/07924259.1992.9672256

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The laser-scanning confocal microscope employed in conjunction with various specific agents and antibodies conjugated to fluorescent dyes reveals details of the actin scaffolding of developing oocytes and the nuclei of attendant cells. The employment of DNase I followed by anti-DNase I antibody has been particularly useful in revealing otherwise cryptic actin-containing structures. The cortical cytoskeleton of developing moth eggs was found to bind both poly (A)+RNA and RNA Pol II. Exposure to cytochalasin D disrupted the actin of the cortex, and at the same time caused redistribution of the proteins and RNA associated with the cytoskeleton. Cytochalasin also had dramatic effects on the structure of nuclei of nurse and follicle cells. Taken in context of the actin network in nuclei uncovered by DNase-anti-DNase treatment, these results suggest that actin plays a major structural and perhaps functional role in insect nuclei.

ISSN:0792-4259    

DOI:10.1080/07924259.1992.9672257

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A consequence of environmental and human health concerns arising from the use of toxic metals in marine antifouling coatings has been to recognise the need for a nontoxic alternative to fouling control. Recent research has focused on two approaches to this problem: the development of (a) foul-release coatings that work on the principle of either low surface free energy or coating ablation, and (b) coatings that incorporate a compound(s) that is nontoxic, or at least environmentally benign, that will deter fouling. Here we discuss the nature of the fouling problem and a new technology that is emerging to address it. The use of natural marine products and of analogues to these compounds holds considerable promise and is an area of intense research. It is recognized, however, that a melding of the technologies of foul-release and foul-deterrence may be required to develop broad spectrum, nontoxic antifouling coatings. This approach may more closely reflect antifouling strategies adopted by marine organisms that maintain a foul-free surface.

ISSN:0792-4259    

DOI:10.1080/07924259.1992.9672258

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The zebra mussel (Dreissena polymorpha) has spread rapidly in temperate fresh waters of North America since its introduction into the Great Lakes in 1985 or 1986. It attaches to hard substrates, forming layers, occluding water intakes, encrusting and killing native mussels, filtering algae in competition with other planktivores, and possibly interfering with fish spawning. It reproduces prolifically, suggesting that an approach to its control may be by controlling its reproduction. Previous literature suggests that spawning in bivalves is regulated by both environmental and internal chemical cues. A suggested sequence is that phytoplankton chemicals initially trigger spawning; chemicals associated with gametes provide a species-specific pheromonal positive feedback for spawning; and the response to environmental chemicals is mediated internally by serotonin (5-HT). The role of 5-HT in zebra mussels is under investigation. Both males and females can be induced to spawn by either injection or external application of 5-HT. The response can also be activated by 8-hydroxy-2-(di-n-propylamino)-tetralin, an agonist at 5-HT1Areceptors. HPLC analysis has detected 5-HT as the major biogenic amine in both male and female gonads. 5-HT immunocytochemistry demonstrates nerves containing serotonergic fibers innervating gonads of both males and females, with prominent varicosities surrounding the follicles in both sexes. A role of 5-HT in mediating spawning responses in zebra mussels is thus strongly supported. These studies have shown that reproductive behavior of zebra mussels can be modified by outside chemicals, a property that may be exploited for purposes of control.

ISSN:0792-4259    

DOI:10.1080/07924259.1992.9672259

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor