1,721,204 research outputs found
Univacuolar refractile hemocytes from the tunicate Ciona intestinalis are cytotoxic for mammalian erythrocytes in vitro
No full textA discontinuous, Percoll density gradient was used to separate hemocyte populations from the hemolymph of Ciona intestinalis. Hemocytes from each band were examined for their frequency, morphology, and cytotoxic activity against rabbit and sheep erythrocytes; results were expressed as a percentage of hemolysis. Statistical analysis revealed that only the 'univacuolar' granulocytes from Band 5, which contain a vacuole of refractile material, were cytotoxic. Cytotoxic activity was inhibited by sphingomyelin. For the first time in tunicates, lytic activity against erythrocytes was assessed by an assay based on plaque-forming cells. Plaques of lysis were revealed against rabbit erythrocytes but not against sheep erythrocytes
Prophenoloxidase activating system in tunicate hemolymph
No full textThe activation sequence and related factors of the prophenoloxidase activating system in crustaceans was compared with the equivalent system in tunicates. Both solitary and colonial ascidians present in their hemolymph a copper-dependent phenoloxidase activity that may be inhibited by tropolone and phenylthiourea. Carbohydrates are able, to various extents, to trigger proPO system which requires serine protease cleavage for activation to phenoloxidase (PO). In some ascidians, hemocytes called ≪morula cells≫ show PO activity, while in Ciona intestinalis the ≪univacuolar refractile granulocytes≫ are positive after cytochemical staining with L-dopa. The relationships between proPO system and defence reactions (opsonic, cytotoxic) of ascidians are discussed. © 1996 Taylor & Francis Group, LLC
Spermatocyte chromosomes in some species of the family Aplysiidae (Gastropoda, Opisthobranchia).
No full textThe inflammatory Response of Urochordata : The basic process of the Ascidians' innate immunity
No full textAscidians form a widespread marine invertebrate group and are heterogeneous in terms of the taxonomic groups’ evolutionary lineages. The ascidian genomes lack significant homologies for rearranging genes of the vertebrate adoptive immunity. Genome analysis, gene sequencing, and transcriptional profiling have allowed us to disclose upregulation of innate immunity genes and cell labeling with riboprobes and antibodies has identified hemocyte types in tunic and pharynx inflammatory responses. Lymphocyte-like cells are stem cells and their immunocompetence has been proposed. Granulocyte types (compartment/morula cells) and hemocytes with large granules/vacuoles (compartment/morula cells) are mature cells expressing and releasing inflammatory components. LPS stimulates gene families of innate immune receptor homologs of the mammalian counterparts, as well as immune regulatory genes, during inflammatory responses. Proinflammatory components are involved in allogeneic reactions, and nonself and missing-self recognitions may be proposed. The findings on Ig-like domains contained in chitin-binding proteins (VCBPs) indicate the ancestral origin of vertebrate adaptive immunity and show that relevant genetic circuitry was already in place in the common ancestor of the protochordates and vertebrates. On the other hand, ascidians share with the other invertebrates the prophenoloxidase system that produces melanin and is involved in the inflammatory cytotoxic mechanism. The peroxinectin gene is also upregulated. Damage signals could be proinflammatory, but there are difficulties in assessing this that presumably could be examined during larva metamorphosis. Findings indicate that genetic circuitries relevant for vertebrate innate immunity were already in place in the common ancestor of the protochordates and vertebrates
Phenoloxidase characterization in vacuolar hemocytes from the solitary ascidian Styela plicata
No full textPhenoloxidase (PO) activity was shown in lysates of Styela plicata hemocytes assayed spectrophotometrically by means of L-Dopa oxidation without divalent cations. Trypsin and chymotrypsin pretreatment and preincubation with microbial lipopolysaccharides significantly activated PO, whereas laminarin or zymosan were ineffective. Soybean trypsin inhibitor, tropolone, and phenylthiourea, but not benzamidine, were inhibitors. Finally, hemocytes were separated by a discontinuous Percoll density gradient to determine which cells were active. PO activity was demonstrated, by both biochemical and cytochemical assays, in the separated fraction enriched mainly with the globular granulocytes called morula cells. © 1995 by Academic Press, Inc
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Evolution of the complement system: ancient molecules and new evidences from tunicates
No full textThe complement system is a key player in innate immunity but, recently, it is becoming even more evident that complement plays also important roles in adaptive immunity.
Components of the human complement system possess unique domain structures and are classified in protein families: C3, factor B (Bf), mannan-binding protein-associated serine protease (MASP), C6 and factor I (If) family.
These complement families probably derive from exon shuffling, which created the unique domain structures of each family, and gene duplication and subsequent functional divergence, which increased the number of members in each family. Accumulating information on the complement system of vertebrates indicates that these gene duplications, which played a pivotal role in establishing the classical and the lytic pathway, occurred in jawed vertebrates. In contrast, information on complement genes of invertebrate chordates is limited and, so far, only the ascidians, such as Ciona intestinalis and Halocinthia roretzi, and the cephalochordate Branchiostoma floridae have an almost complete set of the complement gene families: C3-, Bf-, MASP-, and C6-like genes.
In the present work we demonstrate the presence of C6-, C3-, MASP-, MBL- and Bf-like genes in the colonial ascidian Botryllus schlosseri and the enhanced transcription after zymosan infection, which indicates their involvement in the ascidian immunity. The observation of a transcribed C6 gene suggest that the presence of the lytic pathway predates the appearance of the vertebrates. We are now carrying out new investigation to demonstrate a complement-related lytic activity in B. schlosseri
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