Zeitschriftenartikel: „Embryon ascidie“

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Dale, B., L. Santella und E. Tosti. „Gap-junctional permeability in early and cleavage-arrested ascidian embryos“. Development 112, Nr. 1 (01.05.1991): 153–60. http://dx.doi.org/10.1242/dev.112.1.153.

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Using the whole-cell voltage clamp technique, we have studied junctional conductance (Gj), and Lucifer Yellow (LY) coupling in 2-cell and 32-cell ascidian embryos. Gj ranges from 17.5 to 35.3 nS in the 2-cell embryo where there is no passage of LY, and from 3.5 to 12.2 nS in the later embryo where LY dye spread is extensive. In both cases, Gj is independent of the transjunctional potential (Vj). Manually apposed 2-cell or 32-cell embryos established a junctional conductance of up to 10 nS within 30 min of contact. Furthermore, since we did not observe any significant number of cytoplasmic bridges at the EM and Gj is sensitive to octanol, it is probable that blastomeres in the 2-cell and 32-cell embryos are in communication by gap junctions. In order to compare Gj in the two stages and to circumvent problems of cell size, movement and spatial location, we used cytochalasin B to arrest cleavage. Gj in cleavage-arrested 2-cell embryos ranged from 25.0 to 38.0 nS and remained constant over a period of 2.5 h. LY injected into a blastomere of these arrested embryos did not spread to the neighbour cell until they attained the developmental age of a 32- to 64-cell control embryo. Our experiments indicate a change in selectivity of gap junctions at the 32-cell stage that is not reflected by a macroscopic change in ionic permeability.

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Yoshida, S., Y. Marikawa und N. Satoh. „Posterior end mark, a novel maternal gene encoding a localized factor in the ascidian embryo“. Development 122, Nr. 7 (01.07.1996): 2005–12. http://dx.doi.org/10.1242/dev.122.7.2005.

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Ascidian embryogenesis is regarded as a typical ‘mosaic’ type. Recent studies have provided convincing evidence that components of the posterior-vegetal cytoplasm of fertilized eggs are responsible for establishment of the anteroposterior axis of the embryo. We report here isolation and characterization of a novel maternal gene, posterior end mark (pem). After fertilization, the pem transcript is concentrated in the posterior-vegetal cytoplasm of the egg and later marks the posterior end of developing ascidian embryos. Despite its conspicuous localization pattern, the predicted PEM protein shows no significant homology to known proteins. Overexpression of this gene by microinjection of synthesized pem mRNA into fertilized eggs results in development of tadpole larvae with deficiency of the anteriormost adhesive organ, dorsal brain and sensory pigment-cells. Lineage tracing analysis revealed that the anterior epidermis and dorsal neuronal cells were translocated posteriorly into the tail region, suggesting that this gene plays a role in establishment of anterior and dorsal patterning of the embryo. The ascidian tadpole is regarded as a prototype of vertebrates, implying a similar function of pem in vertebrate embryogenesis.

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Lambert, C. C. „Ascidian eggs release glycosidase activity which aids in the block against polyspermy“. Development 105, Nr. 2 (01.02.1989): 415–20. http://dx.doi.org/10.1242/dev.105.2.415.

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To ensure normal development, most animals have evolved a number of mechanisms to block polyspermy including prevention of binding to surface coats as well as sperm-egg fusion. Ascidian sperm bind to vitelline coat (VC) glycosides. In the genus Ascidia, N-acetylglucosamine (GlcNAc) is the ligand to which sperm bind. The number of sperm bound to the VC is biphasic following fertilization; sperm binding increases through the first minute or so, then abruptly declines. At fertilization, the eggs of Ascidia callosa, A. ceratodes, A. mentula, A. nigra and Phallusia mammillata release N-acetylglucosaminidase into the sea water (SW). This has been shown to inactivate VC GlcNAc groups, blocking the binding of supernumerary sperm and polyspermy in A. nigra. This block to polyspermy is inactivated by GlcNAc (2mM) or 150 mM-Na+ (choline substituted) SW. These treatments are not additive and therefore probably affect the same process. In A. callosa, fertilization in low Na+ SW causes a 60% decline in enzyme release and a similar increase in the number of sperm remaining on the VC at 4 min as well as a great increase in polyspermy. Thus the principal block to polyspermy in ascidian eggs involves the release of N-acetylglucosaminidase which appears to be Na+ dependent. Enzyme activity is found in the supernatant SW by 15 s after fertilization, suggesting that it is stored very near the egg surface. Histochemical staining of whole eggs and embryos shows loss of surface-associated enzyme activity following fertilization. Like other lysosomal enzymes this N-acetylglucosaminidase is mannosylated and has an acidic pH optimum.

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Tanaka-Kunishima, Motoko, Kunitaro Takahashi und Fumiyuki Watanabe. „Cell contact induces multiple types of electrical excitability from ascidian two-cell embryos that are cleavage arrested and contain all cell fate determinants“. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 293, Nr. 5 (November 2007): R1976—R1996. http://dx.doi.org/10.1152/ajpregu.00835.2006.

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Ascidian early embryonic cells undergo cell differentiation without cell cleavage, thus enabling mixture of cell fate determinants in single cells, which will not be possible in mammalian systems. Either cell in a two-cell embryo (2C cell) has multiple fates and develops into any cell types in a tadpole. To find the condition for controlled induction of a specific cell type, cleavage-arrested cell triplets were prepared in various combinations. They were 2C cells in contact with a pair of anterior neuroectoderm cells from eight-cell embryos (2C-aa triplet), with a pair of presumptive notochordal neural cells (2C-AA triplet), with a pair of presumptive posterior epidermal cells (2C-bb triplet), and with a pair of presumptive muscle cells (2C-BB triplet). The fate of the 2C cell was electrophysiologically identified. When two-cell embryos had been fertilized 3 h later than eight-cell embryos and triplets were formed, the 2C cells became either anterior-neuronal, posterior-neuronal or muscle cells, depending on the cell type of the contacting cell pair. When two-cell embryos had been fertilized earlier than eight-cell embryos, most 2C cells became epidermal. When two- and eight-cell embryos had been simultaneously fertilized, the 2C cells became any one of three cell types described above or the epidermal cell type. Differentiation of the ascidian 2C cell into major cell types was reproducibly induced by selecting the type of contacting cell pair and the developmental time difference between the contacting cell pair and 2C cell. We discuss similarities between cleavage-arrested 2C cells and vertebrate embryonic stem cells and propose the ascidian 2C cell as a simple model for toti-potent stem cells.

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Makabe, Kazuhiro W., Takeshi Kawashima, Shuichi Kawashima, Takuya Minokawa, Asako Adachi, Hiroshi Kawamura, Hisayoshi Ishikawa et al. „Large-scale cDNA analysis of the maternal genetic information in the egg of Halocynthia roretzi for a gene expression catalog of ascidian development“. Development 128, Nr. 13 (01.07.2001): 2555–67. http://dx.doi.org/10.1242/dev.128.13.2555.

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The ascidian egg is a well-known mosaic egg. In order to investigate the molecular nature of the maternal genetic information stored in the egg, we have prepared cDNAs from the mRNAs in the fertilized eggs of the ascidian, Halocynthia roretzi. The cDNAs of the ascidian embryo were sequenced, and the localization of individual mRNA was examined in staged embryos by whole-mount in situ hybridization. The data obtained were stored in the database MAGEST (http://www.genome.ad.jp/magest) and further analyzed. A total of 4240 cDNA clones were found to represent 2221 gene transcripts, including at least 934 different protein-coding sequences. The mRNA population of the egg consisted of a low prevalence, high complexity sequence set. The majority of the clones were of the rare sequence class, and of these, 42% of the clones showed significant matches with known peptides, mainly consisting of proteins with housekeeping functions such as metabolism and cell division. In addition, we found cDNAs encoding components involved in different signal transduction pathways and cDNAs encoding nucleotide-binding proteins. Large-scale analyses of the distribution of the RNA corresponding to each cDNA in the eight-cell, 110-cell and early tailbud embryos were simultaneously carried out. These analyses revealed that a small fraction of the maternal RNAs were localized in the eight-cell embryo, and that 7.9% of the clones were exclusively maternal, while 40.6% of the maternal clones showed expression in the later stages. This study provides global insights about the genes expressed during early development.

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Jeffery, William R., und Billie J. Swalla. „An ankryin-like protein in ascidian eggs and its role in the evolution of direct development“. Zygote 1, Nr. 3 (August 1993): 197–208. http://dx.doi.org/10.1017/s0967199400001477.

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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 developer Ascidia ceratodes anti-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 to A. ceratodes and H. 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.

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Serras, F., C. Baud, M. Moreau, P. Guerrier und J. A. M. Van den Biggelaar. „Intercellular communication in the early embryo of the ascidian Ciona intestinalis“. Development 102, Nr. 1 (01.01.1988): 55–63. http://dx.doi.org/10.1242/dev.102.1.55.

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We have studied the intercellular communication pathways in early embryos of the ascidian Ciona intestinalis. In two different series of experiments, we injected iontophoretically the dyes Lucifer Yellow and Fluorescein Complexon, and we analysed the spread of fluorescence to the neighbouring cells. We found that before the 32-cell stage no dye spread occurs between nonsister cells, whereas sister cells are dye-coupled, possibly via cytoplasmic bridges. After the 32-cell stage, dye spread occurs throughout the embryo. However, electrophysiological experiments showed that nonsister cells are ionically coupled before the 32-cell stage. We also found that at the 4-cell stage junctional conductance between nonsister cells is voltage dependent, which suggests that conductance is mediated by gap junctions in a way similar to that observed in other embryos.

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Nishikata, T., I. Mita-Miyazawa, T. Deno und N. Satoh. „Muscle cell differentiation in ascidian embryos analysed with a tissue-specific monoclonal antibody“. Development 99, Nr. 2 (01.02.1987): 163–71. http://dx.doi.org/10.1242/dev.99.2.163.

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Utilizing a muscle-specific monoclonal antibody (Mu-2) as a probe, we analysed developmental mechanisms involved in muscle cell differentiation in ascidian embryos. The antigen recognized by Mu-2 was a single polypeptide with a relative molecular mass of about 220 X 10(3). It first appeared at the early tailbud stage and continued to be expressed until the swimming larva stage. There were distinct and separate puromycin and actinomycin D sensitivity periods during the occurrence of the antigen, suggesting the new synthesis of the polypeptide by developing muscle cells. Embryos that had been permanently arrested with aphidicolin in the early cleavage stages up to the 32-cell stage did not express the antigen. DNA replications may be required for the antigen expression. Embryos that had been arrested with cytochalasin B in the 8-cell and later stages developed the antigen, and the number and position of the arrested blastomeres exhibiting the differentiation marker almost corresponded to those of the B4.1-line muscle lineage. Furthermore, in quarter embryos developed from each blastomere pair isolated from the 8-cell embryo, all the B4.1 as well as a part of b4.2 partial embryos expressed the antigen, while the a4.2 and A4.1 partial embryos did not show the antigen expression. These results may provide further support for the existence of cytoplasmic determinants for muscle cell differentiation in this mosaic egg.

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Wada, S., Y. Katsuyama und H. Saiga. „Anteroposterior patterning of the epidermis by inductive influences from the vegetal hemisphere cells in the ascidian embryo“. Development 126, Nr. 22 (15.11.1999): 4955–63. http://dx.doi.org/10.1242/dev.126.22.4955.

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Patterning along the anteroposterior axis is a critical step during animal embryogenesis. Although mechanisms of anteroposterior patterning in the neural tube have been studied in various chordates, little is known about those of the epidermis. To approach this issue, we investigated patterning mechanisms of the epidermis in the ascidian embryo. First we examined expression of homeobox genes (Hrdll-1, Hroth, HrHox-1 and Hrcad) in the epidermis. Hrdll-1 is expressed in the anterior tip of the epidermis that later forms the adhesive papillae, while Hroth is expressed in the anterior part of the trunk epidermis. HrHox-1 and Hrcad are expressed in middle and posterior parts of the epidermis, respectively. These data suggested that the epidermis of the ascidian embryo is patterned anteroposteriorly. In ascidian embryogenesis, the epidermis is exclusively derived from animal hemisphere cells. To investigate regulation of expression of the four homeobox genes in the epidermis by vegetal hemisphere cells, we next performed hemisphere isolation and cell ablation experiments. We showed that removal of the vegetal cells before the late 16-cell stage results in loss of expression of these homeobox genes in the animal hemisphere cells. Expression of Hrdll-1 and Hroth depends on contact with the anterior-vegetal (the A-line) cells, while expression of HrHox-1 and Hrcad requires contact with the posterior-vegetal (the B-line) cells. We also demonstrated that contact with the vegetal cells until the late 32-cell stage is sufficient for animal cells to express Hrdll-1, Hroth and Hrcad, while longer contact is necessary for HrHox-1 expression. Contact with the A-line cells until the late 32-cell stage is also sufficient for formation of the adhesive papillae. Our data indicate that the epidermis of the ascidian embryo is patterned along the anteroposterior axis by multiple inductive influences from the vegetal hemisphere cells and provide the first insight into mechanisms of epidermis patterning in the chordate embryos.

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Meedel, T. H., R. J. Crowther und J. R. Whittaker. „Determinative properties of muscle lineages in ascidian embryos“. Development 100, Nr. 2 (01.06.1987): 245–60. http://dx.doi.org/10.1242/dev.100.2.245.

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Blastomeres removed from early cleavage stage ascidian embryos and reared to ‘maturity’ as partial embryos often elaborate tissue-specific features typical of their constituent cell lineages. We used this property to study recent corrections of the ascidian larval muscle lineage and to compare the ways in which different lineages give rise to muscle. Our evaluation of muscle differentiation was based on histochemical localization and quantitative radiometric measurement of a muscle-specific acetylcholinesterase activity, and the development of myofilaments and myofibrils as observed by electron microscopy. Although the posterior-vegetal blastomeres (B4.1 pair) of the 8-cell embryo have long been believed to be the sole precursors of larval muscle, recent studies using horseradish peroxidase to mark cell lineages have shown that small numbers of muscle cells originate from the anterior-vegetal (A4.1) and posterior-animal (b4.2) blastomeres of this stage. Fully differentiated muscle expression in isolated partial embryos of A4.1-derived cells requires an association with cells from other lineages whereas muscle from B4.1 blastomeres develops autonomously. Clear differences also occurred in the time acetylcholinesterase activity was first detected in partial embryos from these two sources. Isolated b4.2 cells failed to show any muscle development even in combination with anterior-animal cells (a4.2) and are presumably even more dependent on normal cell interactions and associations. Others have noted an additional distinction between the different sources of muscle: muscle cells from non-B4.1 lineages occur exclusively in the distal part of the tail, while the B4.1 descendants contribute those cells in the proximal and middle regions. During the course of ascidian larval evolution tail muscle probably had two origins: the primary lineage (B4.1) whose fate was set rigidly at early cleavage stages and secondarily evolved lineages which arose later by recruitment of cells from other tissues resulting in increased tail length. In contrast to the B4.1 lineage, muscle development in the secondary lineages is controlled less rigidly by processes that depend on cell interactions.

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Cone, Angela C., und Robert W. Zeller. „Using ascidian embryos to study the evolution of developmental gene regulatory networks“. Canadian Journal of Zoology 83, Nr. 1 (01.01.2005): 75–89. http://dx.doi.org/10.1139/z04-165.

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Ascidians are ideally positioned taxonomically at the base of the chordate tree to provide a point of comparison for developmental regulatory mechanisms that operate among protostomes, non-chordate deuterostomes, invertebrate chordates, and vertebrates. In this review, we propose a model for the gene regulatory network that gives rise to the ascidian notochord. The purpose of this model is not to clarify all of the interactions between molecules of this network, but to provide a working schematic of the regulatory architecture that leads to the specification of endoderm and the patterning of mesoderm in ascidian embryos. We describe a series of approaches, both computational and biological, that are currently being used, or are in development, for the study of ascidian embryo gene regulatory networks. It is our belief that the tools now available to ascidian biologists, in combination with a streamlined mode of development and small genome size, will allow for more rapid dissection of developmental gene regulatory networks than in more complex organisms such as vertebrates. It is our hope that the analysis of gene regulatory networks in ascidians can provide a basic template which will allow developmental biologists to superimpose the modifications and novelties that have arisen during deuterostome evolution.

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Nishida, H. „Determinative mechanisms in secondary muscle lineages of ascidian embryos: development of muscle-specific features in isolated muscle progenitor cells“. Development 108, Nr. 4 (01.04.1990): 559–68. http://dx.doi.org/10.1242/dev.108.4.559.

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Muscle cells of the ascidian larva originate from three different lines of progenitor cells, the B-line, A-line and b-line. Experiments with 8-cell embryos have indicated that isolated blastomeres of the B-line (primary) muscle lineage show autonomous development of a muscle-specific enzyme, whereas blastomeres of the A-line and b-line (secondary) muscle lineage rarely develop the enzyme in isolation. In order to study the mechanisms by which different lines of progenitors are determined to give rise to muscle, blastomeres were isolated from embryos of Halocynthia roretzi at the later cleavage stages when conspicuous restriction of the developmental fate of blastomeres had already occurred. Partial embryos derived from B-line muscle-lineage cells of the 64-cell embryo (B7.4, B7.5 and B7.8) showed autonomous expression of specific features of muscle cells (acetylcholinesterase, filamentous actin and muscle-specific antigen). In contrast, b-line muscle-lineage cells, even those isolated from the 110-cell embryo (b8.17 and b8.19), did not express any muscle-specific features, even though their developmental fate was mainly restricted to generation of muscle. Isolated A-line cells from the 64-cell embryos (A7.8) did not show any features of muscle differentiation, whereas some isolated A-line cells from the 110-cell embryos (A8.16) developed all three above-mentioned features of muscle cells. This transition was shown to occur during the eighth cell cycle. These results suggest that the mechanism involved in the process of determination of the secondary-lineage muscle cells differs from that of the primary-lineage muscle cells. Interaction with cells of other lineages may be required for the determination of secondary precursors to muscle cells. The presumptive b-line and A-line muscle cells that failed to express muscle-specific features in isolation did not develop into epidermal cells. Thus, although interactions between cells may be required for muscle determination in secondary lineages, the process may represent a permissive type of induction and may differ from the processes of induction of mesoderm in amphibian embryos.

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Munro, Edwin M., und Garrett M. Odell. „Polarized basolateral cell motility underlies invagination and convergent extension of the ascidian notochord“. Development 129, Nr. 1 (01.01.2002): 13–24. http://dx.doi.org/10.1242/dev.129.1.13.

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We use 3D time-lapse analysis of living embryos and laser scanning confocal reconstructions of fixed, staged, whole-mounted embryos to describe three-dimensional patterns of cell motility, cell shape change, cell rearrangement and tissue deformation that accompany formation of the ascidian notochord. We show that notochord formation involves two simultaneous processes occurring within an initially monolayer epithelial plate: The first is invagination of the notochord plate about the axial midline to form a solid cylindrical rod. The second is mediolaterally directed intercalation of cells within the plane of the epithelial plate, and then later about the circumference of the cylindrical rod, that accompanies its extension along the anterior/posterior (AP) axis. We provide evidence that these shape changes and rearrangements are driven by active extension of interior basolateral notochord cell edges directly across the faces of their adjacent notochord neighbors in a manner analogous to leading edge extension of lamellapodia by motile cells in culture. We show further that local edge extension is polarized with respect to both the AP axis of the embryo and the apicobasal axis of the notochord plate. Our observations suggest a novel view of how active basolateral motility could drive both invagination and convergent extension of a monolayer epithelium. They further reveal deep similarities between modes of notochord morphogenesis exhibited by ascidians and other chordate embryos, suggesting that cellular mechanisms of ascidian notochord formation may operate across the chordate phylum.

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Wojciak, E., und W. Korohoda. „Ehrlich ascites tumour cells show tissue-specific adherence and modify their shape upon contact with embryonic fibroblasts and myotubes“. Journal of Cell Science 97, Nr. 3 (01.11.1990): 433–38. http://dx.doi.org/10.1242/jcs.97.3.433.

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Adhesiveness of Ehrlich ascites tumour (EAT) cells to glass, to mouse peritoneal membrane, living and aldehyde-fixed mouse embryo fibroblasts and chick embryo fibroblasts, myoblasts and myotubes was investigated. The ascitic EAT cells (and leukaemia L1210 cells) did not adhere to glass and peritoneum but readily adhered to embryo fibroblasts, myoblasts and myotubes. The attachment was followed by cell spreading and migration. Fixation of fibroblasts or myogenic cells with aldehydes did not prevent ascitic cells from attaching but reduced the rate of spreading. Only direct interaction of ascitic cells with embryo myoblasts or fibroblasts induced changes in tumour cell adhesiveness followed by cell spreading and locomotion. These results are discussed in relation to an observation that ascitic cells growing as a cell suspension intraperitoneally grow as a solid tumour when injected subcutaneously.

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Ohtsuki, Hisashi. „Statocyte and Ocellar Pigment Cell in Embryos and Larvae of the Ascidian, Styela plicata (Lesueur). (statocyte/ocellus/ascidian/embryo/larva)“. Development, Growth and Differentiation 32, Nr. 1 (Februar 1990): 85–90. http://dx.doi.org/10.1111/j.1440-169x.1990.00085.x.

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Ichbiah, Sacha, Fabrice Delbary, Alex McDougall, Rémi Dumollard und Hervé Turlier. „Embryo mechanics cartography: inference of 3D force atlases from fluorescence microscopy“. Nature Methods 20, Nr. 12 (Dezember 2023): 1989–99. http://dx.doi.org/10.1038/s41592-023-02084-7.

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AbstractTissue morphogenesis results from a tight interplay between gene expression, biochemical signaling and mechanics. Although sequencing methods allow the generation of cell-resolved spatiotemporal maps of gene expression, creating similar maps of cell mechanics in three-dimensional (3D) developing tissues has remained a real challenge. Exploiting the foam-like arrangement of cells, we propose a robust end-to-end computational method called ‘foambryo’ to infer spatiotemporal atlases of cellular forces from fluorescence microscopy images of cell membranes. Our method generates precise 3D meshes of cells’ geometry and successively predicts relative cell surface tensions and pressures. We validate it with 3D foam simulations, study its noise sensitivity and prove its biological relevance in mouse, ascidian and worm embryos. 3D force inference allows us to recover mechanical features identified previously, but also predicts new ones, unveiling potential new insights on the spatiotemporal regulation of cell mechanics in developing embryos. Our code is freely available and paves the way for unraveling the unknown mechanochemical feedbacks that control embryo and tissue morphogenesis.

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Ueki, Tatsuya, Kazuhiro W. Makabe und Noriyuki Satoh. „Isolation of cDNA Clones for Epidermis-Specific Genes of the Ascidian Embryo. (ascidian embryos/epidermal cells/specific gene expression/cDNA probes)“. Development, Growth and Differentiation 33, Nr. 6 (Dezember 1991): 579–86. http://dx.doi.org/10.1111/j.1440-169x.1991.00579.x.

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NISHIKATA, TAKAHITO, IZUMI MITA-MIYAZAWA und NORIYUKI SATOH. „Differentiation Expression in Blastomeres of Cleavage-Arrested Embryos of the Ascidian Halocynthia roretzi. (differentiation without cleavage/monoclonal antibodies/exclusive differentiation/ascidian embryo)“. Development, Growth and Differentiation 30, Nr. 4 (August 1988): 371–81. http://dx.doi.org/10.1111/j.1440-169x.1988.00371.x.

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Satoh, N. „Mechanisms of Specification in Ascidian Embryos“. Biological Bulletin 195, Nr. 3 (Dezember 1998): 381–83. http://dx.doi.org/10.2307/1543154.

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Satou, Yutaka, und Nori Satoh. „Developmental gene activities in ascidian embryos“. Current Opinion in Genetics & Development 9, Nr. 5 (Oktober 1999): 542–47. http://dx.doi.org/10.1016/s0959-437x(99)00012-x.

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Bates, William R. „Development of myoplasm-enriched ascidian embryos“. Developmental Biology 129, Nr. 1 (September 1988): 241–52. http://dx.doi.org/10.1016/0012-1606(88)90178-9.

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Negishi, Takefumi, Alex McDougall und Hitoyoshi Yasuo. „Practical tips for imaging ascidian embryos“. Development, Growth & Differentiation 55, Nr. 4 (24.04.2013): 446–53. http://dx.doi.org/10.1111/dgd.12059.

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MITA-MIYAZAWA, IZUMI, und NORIYUKI SATOH. „Mass Isolation of Muscle Lineage Blastomeres from Ascidian Embryos. (ascidian embryos/muscle lineage cells/mass isolation)“. Development, Growth and Differentiation 28, Nr. 5 (September 1986): 483–88. http://dx.doi.org/10.1111/j.1440-169x.1986.00483.x.

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Chenevert, Janet, Marianne Roca, Lydia Besnardeau, Antonella Ruggiero, Dalileh Nabi, Alex McDougall, Richard R. Copley, Elisabeth Christians und Stefania Castagnetti. „The Spindle Assembly Checkpoint Functions during Early Development in Non-Chordate Embryos“. Cells 9, Nr. 5 (28.04.2020): 1087. http://dx.doi.org/10.3390/cells9051087.

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In eukaryotic cells, a spindle assembly checkpoint (SAC) ensures accurate chromosome segregation, by monitoring proper attachment of chromosomes to spindle microtubules and delaying mitotic progression if connections are erroneous or absent. The SAC is thought to be relaxed during early embryonic development. Here, we evaluate the checkpoint response to lack of kinetochore-spindle microtubule interactions in early embryos of diverse animal species. Our analysis shows that there are two classes of embryos, either proficient or deficient for SAC activation during cleavage. Sea urchins, mussels, and jellyfish embryos show a prolonged delay in mitotic progression in the absence of spindle microtubules from the first cleavage division, while ascidian and amphioxus embryos, like those of Xenopus and zebrafish, continue mitotic cycling without delay. SAC competence during early development shows no correlation with cell size, chromosome number, or kinetochore to cell volume ratio. We show that SAC proteins Mad1, Mad2, and Mps1 lack the ability to recognize unattached kinetochores in ascidian embryos, indicating that SAC signaling is not diluted but rather actively silenced during early chordate development.

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Bates, William R., und Joan E. Mallett. „Anural development of the ascidian Molgula pacifica (Huntsman)“. Canadian Journal of Zoology 69, Nr. 3 (01.03.1991): 618–27. http://dx.doi.org/10.1139/z91-092.

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Molgula pacifica embryos exhibit anural development in which embryogenesis proceeds directly to the development of a juvenile, without the development of a tailed larva. The purpose of this study was to investigate the key events that are responsible for the development of M. pacifica juveniles. The results of the present investigation indicate that the timing and spatial rearrangements of the egg cytoplasm that occur after fertilization (termed ooplasmic segregation) are similar in M. pacifica eggs as compared with those that occur in typical urodele species. These observations suggest that the mechanism that is responsible for the urodele pattern of ooplasmic segregation was conserved during the evolution of anural species. The cleavage patterns displayed by M. pacifica embryos up to the eight-cell stage were similar to those exhibited by urodele embryos. However, gastrulation in M. pacifica embryos differed from the typical urodele mode of gastrulation. The mode of gastrulation exhibited by M. pacifica embryos is likely a consequence of their eggs containing a greater quantity of yolk than the less yolky eggs of species more commonly studied. In the second part of this investigation, ampullar development, structure, and function were studied. Two conclusions were made from these studies. First, the extracellular matrix materials comprising the tunic are secreted by the epidermal ampullar cells. Second, a shift in the timing of ampullar rudiment development in M. pacifica embryos suggests the possibility of a heterochronic mechanism of evolutionary change within the epidermal cell lineage.

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Nakatani, Y., R. Moody und W. C. Smith. „Mutations affecting tail and notochord development in the ascidian Ciona savignyi“. Development 126, Nr. 15 (01.08.1999): 3293–301. http://dx.doi.org/10.1242/dev.126.15.3293.

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Ascidians are among the most distant chordate relatives of the vertebrates. However, ascidians share many features with vertebrates including a notochord and hollow dorsal nerve cord. A screen for N-ethyl-N-nitrosourea (ENU)-induced mutations affecting early development in the ascidian Ciona savignyi resulted in the isolation of a number of mutants including the complementing notochord mutants chongmague and chobi. In chongmague embryos the notochord fails to develop, and the notochord cells instead adopt a mesenchyme-like fate. The failure of notochord development in chongmague embryos results in a severe truncation of tail, although development of the tail muscles and caudal nerve tracts appears largely normal. Chobi embryos also have a truncation of the tail stemming from a disruption of the notochord. However, in chobi embryos the early development of the notochord appears normal and defects occur later as the notochord attempts to extend and direct elongation of the tail. We find in chobi tailbud embryos that the notochord is often bent, with cells clumped together, rather than extended as a column. These results provide new information on the function and development of the ascidian notochord. In addition, the results demonstrate how the unique features of ascidians can be used in genetic analysis of morphogenesis.

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Takada, Norio, Jonathan York, J. Muse Davis, Brenda Schumpert, Hitoyoshi Yasuo, Nori Satoh und Billie J. Swalla. „Brachyury expression in tailless Molgulid ascidian embryos“. Evolution and Development 4, Nr. 3 (Mai 2002): 205–11. http://dx.doi.org/10.1046/j.1525-142x.2002.02004.x.

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Esposito, Rosaria, Hitoyoshi Yasuo, Cathy Sirour, Antonio Palladino, Antonietta Spagnuolo und Clare Hudson. „Patterning of brain precursors in ascidian embryos“. Development 144, Nr. 2 (19.12.2016): 258–64. http://dx.doi.org/10.1242/dev.142307.

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Mitani, Yasuo, Hiroki Takahashi und Nori Satoh. „Regulation of the muscle-specific expression and function of an ascidian T-box gene, As-T2“. Development 128, Nr. 19 (01.10.2001): 3717–28. http://dx.doi.org/10.1242/dev.128.19.3717.

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The Tbx6 T-box genes are expressed in somite precursor cells of vertebrate embryos and are essential for the differentiation of paraxial mesoderm. However, it is unclear how spatial regulation of the gene expression is controlled and how the genes function to promote muscle differentiation. The Tbx6-related gene As-T2 of the ascidian Halocynthia roretzi is first expressed very transiently in endodermal cells around the 32-∼44-cell stage, is then expressed distinctly and continuously in muscle precursor cells, and later in epidermal cells situated in the distal tip region of the elongating tail. We now show that inhibition of As-T2-mediated transcriptional activation by microinjection of As-T2/EnR into one-cell embryos resulted in suppression of the expression of the muscle-specific actin gene (HrMA4) and myosin heavy chain gene (HrMHC), but the injection did not affect the differentiation of endodermal cells or tail tip cells, suggesting that the primary function of As-T2 is associated with muscle cell differentiation. The 5′ flanking region of As-T2 contains two promoter modules that regulate its specific expression: a distal module that responsible for its specific expression in the tail, and a proximal module required for its muscle-specific expression. Around the proximal module, there are two putative T protein-binding motifs (TTCACACTT). Co-injection of an As-T2/lacZ construct with or without the T-binding motifs together with As-T2 mRNA revealed that these motifs are essential for autoregulatory activation of the gene itself. In addition, we found that the minimal promoter regions of HrMA4 and HrMHC contain T-binding motifs. Co-injection of HrMA4/lacZ or HrMHC/lacZ containing the T-binding motifs along with As-T2 mRNA revealed that As-T2 protein binds to these motifs to upregulate the gene activity. Taking into account the recent finding of maternal molecules for muscle differentiation, we propose a model for a genetic cascade that includes As-T2 as a regulator of muscle cell differentiation in the ascidian embryo.

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Jeffery, William R. „A gastrulation center in the ascidian egg“. Development 116, Supplement (01.04.1992): 53–63. http://dx.doi.org/10.1242/dev.116.supplement.53.

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A gastrulation center is described in ascidian eggs. Extensive cytoplasmic rearrangements occur in ascidian eggs between fertilization and first cleavage. During ooplasmic segregation, a specific cytoskeletal domain (the myoplasm) is translocated first to the vegetal pole (VP) and then to the posterior region of the zygote. A few hours later, gastrulation is initiated by invagination of endoderm cells in the VP region of the 110-cell embryo. After the completion of gastrulation, the embryonic axis is formed, which includes induction of the nervous system, morphogenesis of the larval tail and differentiation of tail muscle cells. Microsurgical deletion or ultraviolet (UV) irradiation of the VP region during the first phase of myoplasmic segregation prevents gastrulation, nervous system induction and tail formation, without affecting muscle cell differentiation. Similar manipulations of unfertilized eggs or uncleaved zygotes after the second phase of segregation have no effect on development, suggesting that a gastrulation center is established by transient localization of myoplasm in the VP region. The function of the gastrulation center was investigated by comparing protein synthesis in normal and UV-irradiated embryos. About 5% of 433 labelled polypeptides detected in 2D gels were affected by UV irradiation. The most prominent protein is a 30 kDa cytoskeletal component (p30), whose synthesis is abolished by UV irradiation. p30 synthesis peaks during gastrulation, is affected by the same UV dose and has the same UV-sensitivity period as gastrulation. However, p30 is not a UV-sensitive target because it is absent during ooplasmic segregation, the UV-sensitivity period. Moreover, the UV target has the absorption maximum of a nucleic acid rather than a protein. Cell-free translation studies indicate that p30 is encoded by a maternal mRNA. UV irradiation inhibits the ability of this transcript to direct p30 synthesis, indicating that p30 mRNA is a UV-sensitive target The gastrulation center may function by sequestration or activation of maternal mRNAs encoding proteins that function during embryogenesis.

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Bates, William R. „Analysis of morphogenetic determinants in ascidian eggs and embryos by cytoplasmic deletion and microinjection“. Canadian Journal of Zoology 69, Nr. 11 (01.11.1991): 2811–18. http://dx.doi.org/10.1139/z91-396.

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The determination of cell fates in ascidian embryos is thought to be mediated primarily by factors localized in the cytoplasm. Morphogenetic factors were studied in ascidian eggs and early cleavage stage embryos by the partial deletion of blastomeres and by microinjection of sperm cells into anucleate, myoplasm-deficient egg fragments. In the first series of experiments, regions of blastomeres comprised of 20–30% of the volume of one blastomere were deleted from two- and four-celled embryos. Most of the embryos exhibited regulative capabilities, in that normal tadpole larvae developed from the operated embryos, irrespective of the deletion site. In a second series of experiments, the expression of endodermal alkaline phosphatase (AP) and muscle acetylcholinesterase (AchE) were tested in myoplasm-deficient egg fragments that were injected with sperm cells. After the unoperated controls had developed into tadpoles, myoplasm-deficient fragments injected with sperm cells were scored for their ability to express AP and AchE activity. Many of the myoplasm-deficient fragments that contained injected sperm cells expressed AP activity, whereas uninjected myoplasm-deficient fragments did not exhibit AP activity. When myoplasm-deficient fragments injected with sperm cells were tested for their ability to express AchE activity, none of the fragments expressed this muscle cell marker. Similar results were obtained using two species, Halocynthia roretzi and Styelaplicata. These results suggest that nuclear events are required for the expression of AP and that the myoplasmic region of the fertilized egg contains muscle cell determinants.

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Miyamoto, David M. „Formation of the notochord in living ascidian embryos“. Development 86, Nr. 1 (01.04.1985): 1–17. http://dx.doi.org/10.1242/dev.86.1.1.

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The dynamic behaviour of cells during formation of the notochord in the ascidian, Ciona intestinalis, was examined by means of Differential Interference Contrast (DIC) microscopy and time-lapse videorecording. The initial rudiment is formed in part as a consequence of the pattern of mitotic divisions as the blastopore shifts posteriorly. Vertical and horizontal rearrangements produce an elongate rod of disc-shaped cells stacked end to end. Further elongation is accompanied by a cell shape change. Some cell growth or swelling is indicated to occur later in development, but this growth appears to contribute mostly to an increase in the diameter, and only insignificantly to the length of the notochord. Intracellular vacuoles that appear around 13 h after fertilization increase in size and fuse at about 16 h to form intercellular ones. These in turn merge to form the central matrix core of the notochord at around 18 to 20 h. As the notochord elongates and cells change in shape, the basal surfaces bleb actively. This surface activity may be related to formation of the perinotochordal sheath.

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Tosti, E. „Gap junctional units are functionally expressed before first cleavage in the early ascidian embryo“. American Journal of Physiology-Cell Physiology 272, Nr. 5 (01.05.1997): C1445—C1449. http://dx.doi.org/10.1152/ajpcell.1997.272.5.c1445.

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Manually apposed ascidian zygotes established electrical communication within 50 min of fertilization and before cytokinesis. Junctional conductance between zygotes was 14.5 +/- 2.9 nS (n = 7), similar to that previously reported for ascidian two-cell-stage blastomeres, suggesting that zygotes and blastomeres express an equivalent number of gap junctional half-channels. Because puromycin at 400 microM does not inhibit the functional expression of these half-channels, they appear to be of maternal origin and their activation does not require protein synthesis. Loading zygotes with 500 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid or exposing zygotes to 10 microM of the calcium ionophore A-23187 shows that these half-channels are regulated by intracellular calcium, consistent with the behavior of these channels in adult tissues. The results show that gap junctional units are expressed in the ascidian at the zygote stage.

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Swalla, B. J., M. R. Badgett und W. R. Jeffery. „Identification of a cytoskeletal protein localized in the myoplasm of ascidian eggs: localization is modified during anural development“. Development 111, Nr. 2 (01.02.1991): 425–36. http://dx.doi.org/10.1242/dev.111.2.425.

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The myoplasm of ascidian eggs is a localized cytoskeletal domain that is segregated to presumptive larval tail muscle cells during embryonic development. We have identified a cytoskeletal protein recognized by a vertebrate neurofilament monoclonal antibody (NN18) which is concentrated in the myoplasm in eggs and embryos of a variety of ascidian species. The NN18 antigen is localized in the periphery of unfertilized eggs, segregates with the myoplasm after fertilization, and enters the larval tail muscle cells during embryonic development. Western blots of one-dimensional and two-dimensional gels showed that the major component recognized by NN18 antibody is a 58 × 10(3) Mr protein (p58), which exists in at least three different isoforms. The enrichment of p58 in the Triton X-100-insoluble fraction of eggs and its reticular staining pattern in eggs and embryos suggests that it is a cytoskeletal protein. In subsequent experiments, p58 was used as a marker to determine whether changes in the myoplasm occur in eggs of anural ascidian species, i.e. those exhibiting a life cycle lacking tadpole larvae with differentiated muscle cells. Although p58 was localized in the myoplasm in eggs of four urodele ascidian species that develop into swimming tadpole larvae, this protein was distributed uniformly in eggs of three anural ascidian species. The eggs of two of these anural species contained the actin lamina, another component of the myoplasm, whereas the third anural species lacked the actin lamina. There was no detectible localization of p58 after fertilization or segregation into muscle lineage cells during cleavage of anural eggs. NN18 antigen was uniformly distributed in pre-vitellogenic oocytes and then localized in the perinuclear zone during vitellogenesis of urodele and anural ascidians. Subsequently, NN18 antigen was concentrated in the peripheral cytoplasm of post-vitellogenic oocytes and mature eggs of urodele, but not anural, ascidians. It is concluded that the myoplasm of ascidian eggs contains an intermediate filament-like cytoskeletal network which is missing in anural species that have modified or eliminated the tadpole larva.

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Takahashi, H., K. Hotta, A. Erives, A. Di Gregorio, R. W. Zeller, M. Levine und N. Satoh. „Brachyury downstream notochord differentiation in the ascidian embryo“. Genes & Development 13, Nr. 12 (15.06.1999): 1519–23. http://dx.doi.org/10.1101/gad.13.12.1519.

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Bettoni, Rossana, Clare Hudson, Géraldine Williaume, Cathy Sirour, Hitoyoshi Yasuo, Sophie de Buyl und Geneviève Dupont. „Model of neural induction in the ascidian embryo“. PLOS Computational Biology 19, Nr. 2 (03.02.2023): e1010335. http://dx.doi.org/10.1371/journal.pcbi.1010335.

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How cell specification can be controlled in a reproducible manner is a fundamental question in developmental biology. In ascidians, a group of invertebrate chordates, geometry plays a key role in achieving this control. Here, we use mathematical modeling to demonstrate that geometry dictates the neural-epidermal cell fate choice in the 32-cell stage ascidian embryo by a two-step process involving first the modulation of ERK signaling and second, the expression of the neural marker gene, Otx. The model describes signal transduction by the ERK pathway that is stimulated by FGF and attenuated by ephrin, and ERK-mediated control of Otx gene expression, which involves both an activator and a repressor of ETS-family transcription factors. Considering the measured area of cell surface contacts with FGF- or ephrin-expressing cells as inputs, the solutions of the model reproduce the experimental observations about ERK activation and Otx expression in the different cells under normal and perturbed conditions. Sensitivity analyses and computations of Hill coefficients allow us to quantify the robustness of the specification mechanism controlled by cell surface area and to identify the respective role played by each signaling input. Simulations also predict in which conditions the dual control of gene expression by an activator and a repressor that are both under the control of ERK can induce a robust ON/OFF control of neural fate induction.

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Satou, Yutaka, Nori Satoh und Kaoru S. Imai. „Gene regulatory networks in the early ascidian embryo“. Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms 1789, Nr. 4 (April 2009): 268–73. http://dx.doi.org/10.1016/j.bbagrm.2008.03.005.

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Gallo, Alessandra. „Toxicity of marine pollutants on the ascidian oocyte physiology: an electrophysiological approach“. Zygote 26, Nr. 1 (13.12.2017): 14–23. http://dx.doi.org/10.1017/s0967199417000612.

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SummaryIn marine animals with external fertilization, gametes are released into seawater where fertilization and embryo development occur. Consequently, pollutants introduced into the marine environment by human activities may affect gametes and embryos. These xenobiotics can alter cell physiology with consequent reduction of fertilization success. Here the adverse effects on the reproductive processes of the marine invertebrate Ciona intestinalis (ascidian) of different xenobiotics: lead, zinc, an organic tin compound and a phenylurea herbicide were evaluated. By using the electrophysiological technique of whole-cell voltage clamping, the effects of these compounds on the mature oocyte plasma membrane electrical properties and the electrical events of fertilization were tested by calculating the concentration that induced 50% normal larval formation (EC50). The results demonstrated that sodium currents in mature oocytes were reduced in a concentration-dependent manner by all tested xenobiotics, with the lowest EC50 value for lead. In contrast, fertilization current frequencies were differently affected by zinc and organic tin compound. Toxicity tests on gametes demonstrated that sperm fertilizing capability and fertilization oocyte competence were not altered by xenobiotics, whereas fertilization was inhibited in zinc solution and underwent a reduction in organic tin compound solution (EC50 value of 1.7 µM). Furthermore, fertilized oocytes resulted in a low percentage of normal larvae with an EC50 value of 0.90 µM. This study shows that reproductive processes of ascidians are highly sensitive to xenobiotics suggesting that they may be considered a reliable biomarker and that ascidians are suitable model organisms to assess marine environmental quality.

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Corbo, J. C., M. Levine und R. W. Zeller. „Characterization of a notochord-specific enhancer from the Brachyury promoter region of the ascidian, Ciona intestinalis“. Development 124, Nr. 3 (01.02.1997): 589–602. http://dx.doi.org/10.1242/dev.124.3.589.

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We present evidence that the embryo of the ascidian, Ciona intestinalis, is an easily manipulated system for investigating the establishment of basic chordate tissues and organs. Ciona has a small genome, and simple, well-defined embyronic lineages. Here, we examine the regulatory mechanisms underlying the differentiation of the notochord. Particular efforts center on the regulation of a notochord-specific Ciona Brachyury gene (Ci-Bra). An electroporation method was devised for the efficient incorporation of transgenic DNA into Ciona embryos. This method permitted the identification of a minimal, 434 bp enhancer from the Ci-Bra promoter region that mediates the notochord-restricted expression of both GFP and lacZ reporter genes. This enhancer contains a negative control region that excludes Ci-Bra expression from inappropriate embryonic lineages, including the trunk mesenchyme and tail muscles. Evidence is presented that the enhancer is activated by a regulatory element which is closely related to the recognition sequence of the Suppressor of Hairless transcription factor, thereby raising the possibility that the Notch signaling pathway plays a role in notochord differentiation. We discuss the implications of this analysis with regard to the evolutionary conservation of integrative enhancers, and the subdivision of the axial and paraxial mesoderm in vertebrates.

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Bingham, B. L., und A. M. Reitzel. „Solar damage to the solitary ascidian, Corella inflata“. Journal of the Marine Biological Association of the United Kingdom 80, Nr. 3 (Juni 2000): 515–21. http://dx.doi.org/10.1017/s0025315400002216.

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The ascidian Corella inflata (Chordata, Ascidiacea) is common in many areas of Puget Sound, Washington, USA. However, it occurs only in habitats where it is protected from direct sunlight. Previous experiments with artificial lights showed that UV irradiation kills all life stages of this animal. The effects of natural sunlight exposure (measuring survival of adults, juveniles, larvae, and embryos) were compared. We partitioned the light spectrum to separate the effects of UVB, UVA, and visible light (PAR). Natural sunlight severely damaged C. inflata. Adults and juveniles died after 2-5 d. Exposed embryos failed to develop normally and larvae did not settle. As expected, UVB had significant effects, but pronounced effects were also seen when the animals were exposed to longer wavelengths alone (UVA and PAR). Thus, the distribution of C. inflata may be determined largely by exposure to light. Understanding the basic ecology of this species requires consideration of its vulnerability to sunlight damage and the effects of UVB, UVA, and PAR.

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Nishida, Hiroki. „Determination of Developmental Fates of Blastomeres in Ascidian Embryos“. Development, Growth and Differentiation 34, Nr. 3 (Juni 1992): 253–62. http://dx.doi.org/10.1111/j.1440-169x.1992.tb00014.x.

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Hikosaka, Akira, Takehiro Kusakabe, Noriyuki Satoh und Kazuhiro W. Makabe. „Introduction and Expression of Recombinant Genes in Ascidian Embryos“. Development, Growth and Differentiation 34, Nr. 6 (Dezember 1992): 627–34. http://dx.doi.org/10.1111/j.1440-169x.1992.tb00031.x.

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Akif Uzman, J., und William R. Jeffery. „Cytoplasmic determinants for cell lineage specification in ascidian embryos“. Cell Differentiation 18, Nr. 4 (Juni 1986): 215–24. http://dx.doi.org/10.1016/0045-6039(86)90053-9.

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Imai, Kaoru S., Hiroki Hikawa, Kenji Kobayashi und Yutaka Satou. „Tfap2andSox1/2/3cooperatively specify ectodermal fates in ascidian embryos“. Development 144, Nr. 1 (25.11.2016): 33–37. http://dx.doi.org/10.1242/dev.142109.

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Jeffery, W. R. „Requirement of cell division for muscle actin expression in the primary muscle cell lineage of ascidian embryos“. Development 105, Nr. 1 (01.01.1989): 75–84. http://dx.doi.org/10.1242/dev.105.1.75.

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The role of cell division in the expression of muscle actin and its relationship to acetylcholinesterase (AChE) development was examined in cleavage-arrested embryos of the ascidian Styela. Muscle actin expression was detected by two-dimensional gel electrophoresis of radioactively labelled proteins and by in situ hybridization with a cDNA probe, whereas AChE activity was assayed by enzyme histochemistry. In the majority of cases, muscle actin expression was first detected in embryos arrested after the 16-cell stage. Some embryos showed muscle actin expression after arrest at the 8-cell stage, however, muscle actin mRNA did not accumulate in embryos arrested at earlier cleavages. The cells that expressed muscle actin in 8- to 64-cell cleavage-arrested embryos belonged to the primary muscle lineage; secondary muscle cell precursors did not express muscle actin. Zygotic muscle actin mRNA appeared to accumulate with myoplasmic pigment granules in the perinuclear region of cleavage-arrested embryos, suggesting that the myoplasm may have a role in the organization of muscle cells. In contrast to muscle actin, AChE was detected in a small proportion of embryos treated with cytochalasin as early as the 1- or 2-cell stage, and most embryos treated with cytochalasin at later cleavages expressed this enzyme in some of their cells. Most primary muscle lineage cells expressed both muscle actin mRNA and AChE, however, some cells expressed only muscle actin mRNA or AChE. The results suggest that at least three cleavages are required for muscle actin expression and that muscle actin and AChE expression can be uncoupled in cleavage-arrested embryos.

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YOSHIDA, Shoko, und Noriyuki SATOH. „Mechanisms of muscle cell differentiation in the ascidian embryo.“ Seibutsu Butsuri 36, Nr. 3 (1996): 129–33. http://dx.doi.org/10.2142/biophys.36.129.

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Okamura, Yasushi, Haruo Okado und Kunitaro Takahashi. „The ascidian embryo as a prototype of vertebrate neurogenesis“. BioEssays 15, Nr. 11 (November 1993): 723–30. http://dx.doi.org/10.1002/bies.950151105.

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Hirose, Euichi, Ryuma Adachi und Koji Kuze. „Sexual reproduction of the Prochloron-bearing ascidians, Trididemnum cyclops and Lissoclinum bistratum, in subtropical waters: seasonality and vertical transmission of photosymbionts“. Journal of the Marine Biological Association of the United Kingdom 86, Nr. 1 (12.01.2006): 175–79. http://dx.doi.org/10.1017/s0025315406013002.

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The seasonality of sexual reproduction was studied in two Prochloron-bearing ascidians, Trididemnum cyclops and Lissoclinum bistratum, on a subtropical coral reef off Okinawajima Island, Japan. These colonial ascidians had testes and/or eggs/embryos from spring to summer. Embryos with tails occurred in summer. Whereas many photosymbiotic didemnids are thought to be sexually mature throughout the year in the tropics, sexual reproduction of the same species in subtropical waters may be limited to spring and summer. The subtropical winter may be too cold for gonad formation. A histological study of sexually mature colonies showed no Prochloron cells attached to ascidian larvae in the pre-hatch stage.

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Ferrari, Emma, Maria Concetta Eliso, Arianna Bellingeri, Ilaria Corsi und Antonietta Spagnuolo. „Short-Term Exposure to Nanoplastics Does Not Affect Bisphenol A Embryotoxicity to Marine Ascidian Ciona robusta“. Biomolecules 12, Nr. 11 (08.11.2022): 1661. http://dx.doi.org/10.3390/biom12111661.

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Plastic pollution is recognized as a global environmental threat and concern is increasing regarding the potential interactions of the smallest fragments, nanoplastics (1 µm), with either physical and chemical entities encountered in the natural environment, including toxic pollutants. The smallest size of nanoplastics (<100nm) rebounds to their safety associated with remarkable biological, chemical and physical reactivity that allow them to interact with cellular machinery by crossing biological barriers and causing damage to living beings. Recent findings on nanoplastic occurrence in marine coastal waters, including the Mediterranean Sea, leave open the question on their ability to act as a vector of other contaminants of emerging concerns (CECs) concomitantly released by wastewater treatment plants and reaching marine coastal waters. Here, we assess for the first time the role of non-functionalized polystyrene nanoparticles (PS NPs, 20 nm) as a proxy for nanoplastics (1 and 10 µg/mL) alone and in combination with bisphenol A (BPA) (4.5 and 10 µM) on Ciona robusta embryos (22 h post fertilization, hpf) by looking at embryotoxicity through phenotypic alterations. We confirmed the ability of BPA to impact ascidian C. robusta embryo development, by affecting sensory organs pigmentation, either alone and in combination with PS NPs. Our findings suggest that no interactions are taking place between PS NPs and BPA in filtered sea water (FSW) probably due to the high ionic strength of seawater able to trigger the sorption surface properties of PS NPs. Further studies are needed to elucidate such peculiarities and define the risk posed by combined exposure to BPA and PS NPs in marine coastal waters.

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HORI, Sawako, und Hiroki NISHIDA. „Sensory organ formation and the equivalence group in ascidian embryos.“ Seibutsu Butsuri 36, Nr. 3 (1996): 139–43. http://dx.doi.org/10.2142/biophys.36.139.

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