bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activation currents, sperm entry and surface contractions in ascidian eggs
Authors: Pecorella C. , Tosti E. , Kyozuka K. , Dale B. 
Published: September 2008

SummarySpermatozoa from the mollusc Ostrea edulis are capable of fusing to and entering de-chorionated ascidian eggs. During interaction they generate activation currents, comparable to the fertilisation currents induced by homologous spermatozoa. Activation currents are inward at − 80 mV, with a mean initial slope of 111 ± 124 pA/s for Ciona intestinalis eggs and 47 ± 25 pA/s for Phallusia mammillata eggs, while the mean peak currents are 2782 ± 1132 pA and 1523 ± 1668 pA, respectively. The fertilisation and activation currents reverse at a holding potential of 0 mV to + 20 mV, suggesting that oyster sperm and ascidian sperm gate the same channel precursor, a non-specific, large conductance channel described previously (Dale & DeFelice, 1984). In contrast to homologous fertilisation, the activation current is not followed by a polarised contraction of the egg surface, nor other signs of egg activation. Staining eggs with Hoechst 33342 after insemination shows the female nucleus and a single oyster sperm nucleus at the antipode. This suggests a specialised predetermined site at the vegetal pole for sperm entry. Homologous and heterologous spermatozoa delivered, in a large pipette, to localised areas of the egg surface generate fast inward currents of 200–2000 pA, but do not induce contraction of the egg surface. This shows that although channel precursors are located globally over the egg surface, channel activation does not necessarily trigger the contraction wave. Subsequent induction of both a fertilisation current and a contraction by homologous sperm added to the bath, implies a regionalised activation site with an accumulation of channel precursors and a ‘pacemaker’ for the initiation of the contraction wave.
Retention of hamster oolemma fusibility with spermatozoa after various enzyme treatments: a search for the molecules involved in sperm-egg fusion
Authors: Ponce Ruben H. , Yanagimachi Ryuzo , Urch Umbert A , Yamagata Tatsuya , lto Makoto 
Published: September 2008

SummaryThe plasma membrane (oolemma) of the hamster egg retains the ability to fuse with spermatozoa even after exhaustive treatment with proteases and glycosidases. In contrast, when mouse oolemma is treated with proteases, the ability of eggs to fuse with spermatozoa is reduced. In the present study, similar treatments effective in reducing fusibility in the mouse were reexamined in the hamster. Of the several enzymes and treatments tested, only trypsin in Ca2+-free medium significantly reduced the hamster oolemma's ability to fuse with spermatozoa. This is suggestive of a cadherin-like system of binding and fusion. When hamster oolemmae were treated with the same protease regimen that reduced fusibility of mouse oolemma for mouse spermatozoa, heterologous fusion of hamster oolemmae with mouse spermatozoa was reduced, without affecting the fusion of these oolemmae with hamster spermatozoa. These data suggest that a protease-sensitive oolemma molecule is of critical importance for mouse sperm-oolemma fusion but not for hamster sperm-oolemma fusion.
An ankryin-like protein in ascidian eggs and its role in the evolution of direct development
Authors: Jeffery William R. , Swalla Billie J. 
Published: September 2008

SummaryAn erythrochyte anti-ankryin antibody was used to investigate the presence and distribution of ankryin in eggs and embryos of ascidian species with different modes of development. In eggs of the indirect developerAscidia ceratodesanti-ankryin reacted with a 210 kDa polypeptide which has an electrophoretic mobility similar to the vertebrate ankryins. Immunofluorescence microscopy showed that the ankryin-like protein is co-distributed with the myoplasm throughout development. It is restricted to a thin layer under the plasma membrane in unfertilised eggs, undergoes ooplasmic segregation to the posterior pole of the zygote after fertilisation, and is distributed to the tail muscle cells during cleavage and embryogenesis. After gastrulation and neurulation, lower levels of the ankryin-like protein, presumably of zygotic origin, were observed in brain cells and in the apical margin of epidermal cells. The ankryin-like protein was also localised in the myoplasm in eggs and embryos of another indirect developing species,Halocynthia roretzi. The ankryin-like protein may link the cytoskeleton with the plasma membrane in ascidian eggs, as it does in vertebrate erythrocytes. In contrast toA. ceratodesandH. rorefzi, which are members of the families Ascidiidae and Pyuridae respectively, the pattern of ankryin-like protein expression was changed in five species in the family Molgulidae. These molgulid ascidians exhibit either indirect or direct development, and eggs of the direct developing species have lost or modified the myoplasm. The ankryir like protein was present in young oocytes but failed to persist during oogenesis and disappeared in mature eggs and embryos of these molgulid species. The change in ankryin-like protein expression may be a preadaptation for loss of the myoplasm and the evolution of direct development.
Non-plasmalemmal localisation of the major ganglioside in sea urchin eggs
Authors: Shogomori Hidehiko , Chiba Kazuyoshi , Kubo Hideo , Hoshi Motonori 
Published: September 2008

SummaryM5 ganglioside (NeuGcα2–6Glcβl-' Cer) is the predominant glycosphingolipid in sea urchin eggs. Distribution of M5 ganglioside was studied in unfertilised and fertilised eggs of the sea urchinHemicentrotus pulcherrimusby indirect immunofluorescence microscopy. In the cortices of unfertilised eggs, anti-M5 antibody strongly stained the submembranous, polygonal and tubular network of endoplasmic reticulum that was revealed by a membrane-staining dye, DiIC18(3). In addition to the cortical network of endoplasmic reticulum, at least two morphologically distinct vesicles were positive to the antibody. In the cortices isolated from fertilised eggs 30 min after insemination, the antibody stained only a similar network of endoplasmic reticulum, presumably the one reconstructed 5–10 min after fertilisation. During mitosis the endoplasmic reticulum is known to aggregate within the asters of the mitotic apparatus. Indeed, the antibody stained the asters and (more strongly) the vesicular components attaching to the periphery of the mitotic apparatus.
In vivo parthenogenetic activation of ovulated oocytes in a marsupial, Sminthopsis crassicaudata
Authors: Anderson Rebecca , Breed William G. 
Published: September 2008

SummaryThe occurrence of in vivo parthenogenesis is documented for laboratory-bred individuals of the Australian dasyurid marsupial, Sminthopsis crassicaudata. About 30% of females that had been isolated from males for a greater period of time than the length of pregnancy were found, on dissection of their uteri, to have embryos present. The embryos were surrounded by a mucoid coat and shell membrane and at least the first two cleavage divisions occurred normally. After this time, however, unequal cleavage divisions appeared to result. The parthenogenesis that takes place may be initiated as a result of activation of ageing ovulated oocytes. Its frequent occurrence may prove useful in a study of maternal and paternal contributions to early embryonic development in this species.
Sperm penetration in parthenogenetic mouse embryos triggers a plasma membrane block to polyspermy
Authors: Maleszewski Marek , Bielak Anna 
Published: September 2008

SummaryMouse oocytes activated parthenogenetically do not generate a plasma membrane block against spermatozoa over the first three cell cycles. We show that they lose this fusibility spontaneously at the 8-cell stage. Insemination of 1-cell parthenogenetic embryos induces loss of fusibility earlier, at the 2-cell stage. This observation suggests that incorporation of the sperm cell membrane components into the oolemma may be responsible for the development of the membrane block.
A molecular screen for polar-localised maternal RNAs in the early embryo ofDrosophila
Authors: Ding Dali , Lipshitz Howard D. 
Published: September 2008

SummaryLocalised, maternally synthesised RNAs and proteins play an important role in an early animal embryogenesis. InDrosophila, genetic screens have recovered a number of maternal effect loci that encode localised products in the embryo. However, only a third ofDrosophila'sgenes have been genetically mutated. Consequently, we conducted a molecular screen for polar-localised RNAs in the earlyDrosophilaembryo in order to identify additional maternal molecules that carry out spatially restricted functions during early embryogenesis. Total RNA was purified from anterior or posterior poles cut off earlyDrosophilaembryos. These RNAs were used to construct directionally cloned anterior and posterior cDNA libraries which were used in a differential screen for cDNAs representing maternal RNAs localised to one or other pole of the embryo. Five such clones were identified, representingcyclinB RNA, Hsp83 RNA, 28SribosomalRNA,mitochondrial cytochrome c oxidase subunit oneRNA andmitochondrial 16S large ribosomalRNA. Mutations in the loci encoding these RNAs have not been recovered in genetic screens, confirming that our molecular approach complements genetic strategies for identifying maternal molecules that carry out spatially restricted functions in the early embryo. We consider the possible biological significance of localisation of each of these species of transcripts as well as the mechanism of their localisation, and discuss the potential use of our cDNA libraries in screens for rarer localised RNAs.
Fertilistion in sea urchins: how many different molecules are involved in gamete interaction and fusion?
Authors: Lennarz William J. 
Published: September 2008

SummaryIt has been established that fertilisation in the sea urchin involves binding of acrosome-reacted sperm to an egg cell surface receptor. The structure and function of receptor, as well as the possible involvement of other cell surface molecules in the binding, fusion and activation events, is discussed.
Confocal image analysis of spatial variations in immunocytochemically identified calmodulin during pollen hydration, germination and pollen tube tip growth inNicotiana tabacumL.
Authors: Tirlapur Uday K. , Scali Monica , Moscatelli Alessandra , Casino Cecilia Del , Cai Gianpiero , Tiezzi Antonio , Cresti Mauro 
Published: September 2008

SummaryUsing monoclonal anti-calmodulin antibodies in conjunction with confocal scanning laser microscopy we have analysed the spatial variations in the distribution pattern of calmodulin (CaM) during the sequential events of pollen hydration, germination and tube growth inNicotiana tabacum. These immunocytochemical observations have been complemented by immunochemical studies wherein the anti-calmodulin antibody raised against pea CaM recognises a polypeptide ofc.18 kDa in the pollen extracts. Digitisation of confocally acquired optical sections of immunofluorescence images reveals that in hydrated pollen a high level of CaM is consistently present in the region of the germinal apertures. Subsequently, with the onset of germination a high CaM concentration was found associated with the plasma membrane of the germination bubble and in the cytoplasm in its vicinity, while in the vegetative cytoplasm a weak diffuse and intense punctate signal was registered. CaM immunostain was also detected in association with the plasma membrane of the tube tips in both short and long pollen tubes. Furthermore, the cytosol of the tubes invariably manifested an apically focused CaM gradient. We were, however, unable to detect any vacuolar association of CaM in the older regions of the pollen tubes. Although punctate immunostain was obvious across the pollen tube numerous punctate structures were invariably present in the extreme tip. The possible implications of these findings in development of cell polarity, polarised growth, maintenance of calcium homeostasis and CaM interactions with other mechanochemical motor proteins in effecting propulsion of organelles during pollen hydration, germination and pollen tube growth are discussed.
In vitro fertilisation of maize by single egg and sperm cell protoplast fusion mediated by high calcium and high pH
Authors: Kranz Erhard , Lörz Horst 
Published: September 2008

SummaryWe present evidence for the fusion of isolated single maize egg and sperm cell protoplasts in a mannitol solution (400–430 mosmol/kg H2O) containing 0.05 M CaCl2 at pH 11.0, followed by cell division of the fusion products. These findings allow the performance of in vitro fertilisation of higher plants by combining single gametes as in lower plant and animal systems. Further, our findings open new avenues for investigating the basic mechanisms of adhesion and fusion of higher plant gametes and eventually for examining processes that inhibit polyspermy in higher plants.
Sperm-egg interaction in an Australian dasyurid marsupial with special refernce to changes in acrosomal morphology
Authors: Breed W.G 
Published: September 2008

SummaryThe morphology of the acrosome of spermatozoa an Australian daysyurid marsupial during in vivo fertilisation, as seen with the tranamission electron microscope, is described. In some spermatozoa close to the outer zona surface with largely intact acrosomes, eletron-demse struts between the inner and outer acrosomal membranes could be seen; in addition fusion between the outer acrosomal and overlying plasma membranes was sometimes evident. The zona matrix close to the acrosomal region of spermatozoa with heads party embedded within the zona pellucida was less electron-dense and more filamentous than elsewhere; perhaps indicative of local lytic activety. Nevertheless some of these spermatozoa at least had partly intact acrosomes with local regions of electron-dense bridges between the two acrosomal membranes. Spermatozoa with condensed chomatin were also observed within the egg cytoplsam some of which had membranes, vacuoles or close to the dorsal nuclear surface which could, in part, be acrosomal in orgin. These observations lend some support to the recent view, based on findings from an American species, that acrosomal changes of spermatozoa of some marsupials at the of fertillsation may be somewhat similar to those of eutherian mamals in spite of the considerable differences in gamete structure and design. How generally applicable these findings are to all marsupials remains, however, to be determined.
Cytogenetic studies of oocyte fusion products
Authors: Nogués Carme , Ponsà Montserrat , Egozcue Josep , Vidal Francesca 
Published: September 2008

SummaryWe describe for the first time the cytogenetic characteristics of mouse ‘embryos’ obtained by oocyte fusion (oocyte fusion products; OFP). Our results indicate that, after fusion, meiosis II is resumed correctly, with extrusion of two haploid polar bodies, and that metaphase synchronisation of the two haploid sets and chromosome segregation during the first cleavage are also normal.
Is the plasma membrane of the human oocyte reorganised following fertilisation and early cleavage?
Authors: Dale B. , Tosti E. , Iaccarino M. 
Published: September 2008

SummaryThe purpose of the present study was to determine whether the plasma membrance of the human oocyte is reorganised following fertlisation and during early cleavage. In order to characterise and localise the major sugar moieties on surface glycoporteins, oocytes and embroys were labelled with a range of flourescent lectins. Regional organisation of plasma membrane microvilli in oocytes and embryos was also studied using scanning electron microscopy (SEM). The plasma membrance of human oocytes, zygotes and early blastomeres stained strongly and homogeneously with concanavalin A andTriticum vulgarislectin (WGA), indicationg the presence of plasma membrance glycoconjugates with α-D-mannosyl residues, sialic acid and β-NAc-glucosaminyl groups. We did not observe regional domains in oocytes and zygotes, suggesting that the plasma membrane is not topographically reorganised following fertilisation. SEM shows the surface of the human zygote to be organised into short microvilli 0.2–3.0 μm in length and at a density of 5–20/μm2. In early cleavage stages the microvilli are shorter and less frequent (0.2–1.0 μm; 1–5/μm2); however, there is no evidence of polarisation at this level of organisation, at either stage of development. The surface of cell fragments, common in the human embryoin vitro, differs in having few microvilli and numerous cytoplasmic blebs. In conclusion, there are no obvious morphological signs of regionalisation in the plasma membrane of the human embryo before the 8-cell stage.
In vivostorage of XR family interspersed RNA inXenopusoocytes
Authors: Liu Chengyu , Smith L. Dennis 
Published: September 2008

SummaryInterspersed RNA is an abundant class of cytoplasmic poly(A)+RNA which contains repetitive elements within mostly heterogeneous single copy sequences. In spite of its quantitative importance in oocytes or eggs (two-thirds of the total poly(A)+RNA), very little is known about its synthesis, its interaction with other molecules, and its functional significance. Here, we analysed a prevalent family of interspersed RNa (XR family) duringXenopusoogenesis. We found that XR interspersed RNA, unlike extracted interspersed RNA, did not form RNA duplexesin vivo. Im small oocytes (stage III), XR RNA interacted with proteins forming rapidly sedimenting ribonucleoprotein particles (RNPs) with a median sedimentaion constant of 80S. However, towards the end of oogenesis (stage VI), these XR RNPs changed into smaller particles with a median sedimentaion constant of 40S. By analysing the proteins associated with XR RNA sequence, we have identified a 42 kilodalton protein in small oocytes, which was replaced by a 45 kilodalton protein at stage V of oogenesis.
Capacity of mouse oocytes to become activated depends on completion of cytoplasmic but not nuclear meiotic maturation
Authors: McConnell Joise M.L. , Campbell Liz , Vincent Caroline 
Published: September 2008

SummaryThe ability of mouse oocytes to become activated after exposure too the calcium ionophore A23187 has been investigated at different stages of meiotic maturation. The potential to respond to ionophore has been studied in relation to the time since resumption of meiotic maturation, the chromosomal conformation of the DNA within each cell and the protein synthetic profile of the maturing oocyte. Our studies demonstrate that when maturing oocytes from an MF1 strain of mice were treated with A23187 activation occured only in oocytes which had reached second meiotic metaphase (MII). However, development of the ability to respond to ionophore was not dependent on an orderly progression through normal chromosomal rearrangements such as separation at metaphase I (MI) and subsequent polar body extrusion, since there process could be prevented and the capacity to be activated became apparent in such oocytes at a time when control cells had reached MII. These data suggest that the ability to respond to ionophore depends on the development of a cytoplasmic or complex capable of monitoring the time since initiation of germinal vesicle breakdown. Metabolic radiolabelling of oocytes which were able to respond to calcium ionophore, even though they had been prevented from undergoing normal chromosomal rearrangements, showed them to be synthesising a group of proteins known as the 35 kDa complex.
Evaluation of a simple method for measuring the cellular DNA content of mouse oocytes and embryos, human fibroblasts and parthenogenetically activated human oocytes using a computerised image analysis system(Seescan)
Authors: Taylor Alison S. , Braude Peter R. 
Published: September 2008

SummaryWe report the use of a simple, reproducible, photocytometric method for measuring nuclear DNA content of DAPI-stained cells, using a computerised image analysis system: Seescan. As this technique is non-destructive and uses very short exposure to ultraviolet light, it can be used for either fixed or vital material. After correcting for any background cytoplasmic staining, the intensity of nuclear stain was measured by the Seescan and compared with that of control cells of known ploidy. Fixed material was found to stain more intensely than live material initially, but demonstrated a rapid loss of nuclear intensity over the first 90 min following removal from DAPI, after which the level plateaued. In contrast, live cells showed no change in nuclear intensity with time. The system was validated by measuring the DNA content of carefully timed mouse blastomeres, human fetal lung fibroblasts and parthenogenetically activated human oocytes. The results obtained were appropriate for the developmental stage or phenotypic appearance of each of the cell types measured.
Human oocyte cytometry and fertilisation rate after subzonal insemination
Authors: Wolf Jean Philippe , Bulwa Sylvie , Rodrigues Daniel , Jouannet Pierre 
Published: September 2008

SummaryThe cytometry of 545 oocytes was evaluated during subzonal insemination (SUZI; 85 attempts), on day 0 (egg retrieval and SUZI), day 1 and day 2(embryo transfer). On day 0, the egg and oolemma diameters (mean ± SD) were 164.0 ± 19.6 μm and 114.2±16.8 μ5m respectively.The zona thickness was 17.8± 13.4 μm and correlated with the oolemma diameter(r= 0.24,p< 0.001). The fertilisation rate was significantly lower for the smaller oocytes (less than 108 μm diameter) compared with the larger oocytes (over 108μm) (9.8% vs 21.2% respectively; p < 0.05). These was little variation in oocyte diameter according to nuclear status. However, oocyte diameter increased significantly between day 0 and day 1 (p< 0.001) for both fertilised and unfertilised oocytes. Six different indications for SUZI were investigated in detail: three with non-specific (normal and subnormal sperm within vitrofertilization failure, oligoasthenospermia) and three with specific sperm defects (flagellar dyskinesia, absence of outer dynein arms, antisperm antibodies). Oocytes from the non-specific defect groups had significantly smaller diameters than the others (p< 0.05). The mean fertilisation rate was related to the mean oolemma diameter for the groups with non-specific sperm defects and the group lacking dynein arms (LODA) (r= 0.91,p< 0.05). Eggs from the groups of patients with LODA and those with antisperm antibodies had thicker zona pellucida than others (p< 0.05). These findings suggest that in addition to nuclear criteria of maturity, the growth of oocytes is an important factor for fertilising ability. Insufficient development of the ooplasm may contribute to fertilisation failure, particularly when sperm with functional defects are used. In contrast, a thick zona pellucida may prevent sperm with specific anomalies such as LODA or antisperm antibodies from penetrating into the perivitelline space.
Xenopusinterspersed RNA families, Ocr and XR, bind DNA-binding proteins
Authors: Guttridge Katherine Ladner , Smith L. Dennis 
Published: September 2008

SummaryInterspersed RNA makes up two-thirds of cytoplasmic polyadenylated RNA inXenopusand sea urchin eggs.Although it has no known function, previous work has suggested that at least one family of interspersed RNA, XR, bindsXenopusoocyte proteins, and can influence the rate of translation. We have used twoXenopusrepeat families, Ocr and XR, to explore their protein binding abilities. Ocr RNA binds the same pattern of highly abundant oocyte proteins that XR RNA binds, which are believed to be messenger ribonucleoprotein (mRNP) particle proteins. In addition, we show that Ocr RNA binds the Oct-60 protein, a member of the POU-domain family of transcription factors found inXenopusoocytes. Using a 32 base pair sequence from the XR repeat in a DNA affinity column two proteins were isolated, 66KDa and 92KDa, that together form a complex with XR DNA. One of these proteins (92KDa) also binds XR RNA. We suggest that the role of at least a subset of interspersed RNAs in development may be to bind, and sequester in the cytoplasm, DNA-binding proteins until the end of oogenesis