1,720,957 research outputs found
In vivo allograft rejection in a bony fish Dicentrarchus labrax (L.): Characterisation of effector lymphocytes
No full textLymphoid cell subpopulations involved in allograft
rejection in the teleost Dicentrarchus labrax were
characterised at the ultrastructural level and quantified by
using monoclonal antibodies against T- and B-lymphocytes.
T-cells positive for T-cell receptor β-chain (TcRβ)
were detected by reverse transcription/polymerase chain
reaction (RT-PCR) and in situ hybridisation by using RNA
probes for TcRβ. Flow cytometry detected a similar percentage
of T- and B-lymphocytes (around 17%) in the
leucocyte-enriched fraction from allografts. Two different
types of T-lymphocytes (DLT15-immunoreactive) infiltrating
the allografts were identified by cytomorphology: small
cells with high nuclear/cytoplasmic ratio and cells with a
higher cytoplasmic content. RT-PCR revealed a single band
(513 bp) corresponding to the TcRβ. In situ hybridisation
showed that TcRβ-positive cells in the grafted muscle fibres
were less numerous compared with DLT15-positive cells,
as evidenced in parallel sections, suggesting that cytotoxic
cells might express different TcR phenotypes. DLIg3-
immunoreactive Ig-producing lymphocytes had: 1) a high nuclear/cytoplasmic ratio or 2) a larger size similar to that
of pre-plasma cells (plasma cells lacked any membrane
labelling)
Ultrastructural study on the plical epithelium of the bursa of Fabricius in chick embryos: Influence of partial decerebration and hypophyseal allografts
No full textThe bursa of Fabricius of 18 day normal and partially decerebrated chick embryos, and partially decerebrated embryos bearing a hypophyseal allograft was analysed by scanning and transmission electron microscopy, focusing on the ultrastructural characterisation of the plical epithelium. The plicae of the normal bursa consist of interfollicular (IFE) and follicle associated epithelium (FAE). The FAE is composed of typical polygonal cells and is supported by a layer of epithelial cells which appears as a continuation of the corticomedullary epithelium. Bordering cells lie between the FAE and IFE. The IFE is composed of 4 cell types: (1) undifferentiated, (2) goblet, at various stages of maturity, (3) prismatic, and (4) globular light cells. Partially decerebrated embryos showed a gross impairment of plical epithelium development and the complex of FAE and IFE cells was largely undifferentiated. Partially decerebrated embryos with a hypophyseal allograft displayed the same cellular types as observed in controls, thus indicating a restored differentiation of plical epithelium. These findings suggest that the hypophysis affects the differentiation of plical epithelium during ontogenesis
Histological observations on lymphomyeloid organs of the Antarctic fish Trematomus bernacchii (Teleostei: Nototheniidae)
No full textLymphomyeloid organs of the Antarctic fish
Trematomus bernacchii were studied with the aim of
analysing some morphological aspects related to adap-
tation to low environmental temperature. The thymus of
T. bernacchii was flattened, incompletely lobated and
scarcely regionalised. It was filled by lymphoid elements
intermingled with stromal elements. The head kidney
appeared highly vascularised and mainly lymphopoietic.
The spleen appeared mainly erythropoietic, with scarcely
developed areas of white pulp
A study on the immune system of some Antarctic teleost species.
No full textSerum Ig from four different Antarctic fish species were studied. Morphological analysis of the thymus of Trematomus bernacchiii did not evidence appreciable difference with that of other teleosts.
Using a polyclonal antibody raised against sea bass Ig, cross-reactivity with H AND L chains of all species analysed was observed. An indirect ELISA was developed and detected the Ig concentrations in sera of the Antarctic species, using as standard sea bass Ig
Adaptation of fish lymphomyeloid organs to polar water
No full textLmphomyeloid organs of three common Antarctic fish species, Trematomus bernacchii, Trematomus nicolai and Chionodraco hamatus, were analysed. Contrary to species living in temperate sea water, the thymus of polar fishes were flattened, incompletely lobated and scarcely distinguishable by normal histology into cortical and medullary regions. Functional regionalisation, however, was suggested by differences in the sizes of thymocytes from the outer to the inner thymus zone. Another particularity was observed in the thymus of Trematomus species: next to lymphocytes, numerous erythroid cells circulated and differentiated in the parenchyma. Only two main types of epithelial cells could be found by cytological analysis: (i) limiting cells that surround the haematopoietic tissue and (ii) reticular cells that constitute the frame where the lymphoid and erythroid cells can proliferate and differentiate. The reticular cells could not be distinguished in cortical and medullary subtypes as observed in temperate-water fish. Numerous Hassall's corpuscles, probably with a scavenging role, were also observed in the thymus. The head kidney housed haematopoietic tissue, lacked any excretory tubules, and had a huge blood supply, characteristic of polar fish species. It appeared mainly lymphopoietic in C. hamatus but contemporary erythropoietic and lymphopoietic in Trematomus species. The ultrastructural analysis revealed the presence of both reticular and limiting epithelial cells. Reticular epithelial cells (REC) characteristically showed numerous vesicles with a granular content and cell debris. Numerous lymphoblasts, lymphocytes and plasma cells were observed among the REC. Erythropoiesis occurred in all polar species analysed, but in C. hamatus the erythroblasts did not differentiate because they had a fast senescence. The spleen appeared mainly erythropoietic, with scarcely developed areas of white pulp, in Trematomus species; the erythropoiesis was scarcely evident in C. hamatus. Small vascular ellipsoids showed numerous melano-macrophages in Trematomus, while large haematopoietic areas were organised around the capillaries in C. hamatus. Utrastructural analysis revealed, in all species examined, two main types of epithelial cells: reticular, close to the ellipsoids, and limiting-subcapsular, which surround the organ. A large blood supply and extended capillary frame were also observed in polar species. The possible adaptation of lymphoid organs to the low temperatures of polar water is discussed. © 2004 Taylor and Francis Ltd
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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