1,721,304 research outputs found
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
A SCID PATIENT RECONSTITUTED WITH HLA-INCOMPATIBLE FETAL STEM-CELLS AS A MODEL FOR STUDYING TRANSPLANTATION TOLERANCE
No full textWe studied a severe combined immunodeficiency (SCID) patient who received transplantations with completely HLA-mismatched fetal liver and thymus from two different donors. The patient is now 14 years old, healthy and shows normal immunoresponses to recall antigens. His T cells are of donor origin, whereas the monocytes, B cells, and natural killer (NK) cells are of the recipient. The successful immunological reconstitution raised questions as to how T and B cells could collaborate across an HLA barrier and how tolerance was achieved. We have shown that tetanus toxin-specific T cell clones isolated from this patient recognized this antigen in the context of host and not of donor HLA-DR, indicating that those cells were educated in the host environment, presumably the thymus. Despite this, an unexpectedly high frequency of host-reactive clones was found that could recognize MHC antigens of the host. It was particularly striking that CD8+ CTL clones were obtained that recognized class I MHC antigens on the host cells. Nevertheless, the patient did not show any sign of acute or chronic graft-versus-host disease (GVHD). These data indicated that no or only incomplete clonal deletion had taken place in this patient and suggest the presence of a peripheral suppressor mechanism. Thus far, we have no indication for the existence of suppressor T cells. Inasmuch as it was found that host-reactive T cells fail to produce IL-4, which is exceptional for CD4+ T cells, we are exploring the possibility that abnormal cytokine production patterns of host-reactive T cells are associated with suppression of these cells in vivo
CLONING OF A NOVEL CELL TYPE FROM HUMAN FETAL LIVER EXPRESSING CYTOPLASMIC CD3-DELTA AND CD3-EPSILON BUT NOT MEMBRANE CD3
No full textSeventeen-week human fetal liver cells cultured with a feeder cell mixture of irradiated PBL, irradiated JY cells (an EBV-transformed B cell line) and PHA contained a subpopulation of CD3- cells in addition to a major population of T cells with the mature phenotype. After 12 days in culture, CD3- CD16- cells were sorted and cloned by limiting dilution. Two representative clones, FL121 and FL125, were expanded and characterized. They shared the phenotype of CD2+CD3-CD4-CD5-CD6+CD16-CD56+. FL121 did not express CD8 whereas FL125 expressed CD8-alpha but not CD8-beta. Both clones were found to express cytoplasmic CD3-delta and CD3-epsilon-Ag while CD3- NK clones isolated from PBL were negative for them. These results indicate that FL121 and FL125 were committed to the T-cell lineage. Southern blot analysis showed that the TCR-beta-genes and the TCR-gamma-genes of these clones were in the germ-line configuration. The establishment of FL121 and FL125 may provide a novel insight into the earliest stage of T-cell development in man
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
A new mechanism of NK cell cytotoxicity activation: the CD40-CD40 ligand interaction.
No full textNK recognition is regulated by a delicate balance between positive signals initiating their effector functions, and inhibitory signals preventing them from proceeding to cytolysis. Knowledge of the molecules responsible for positive signaling in NK cells is currently limited. We demonstrate that IL-2-activated human NK cells can express CD40 ligand (CD-40L) and that recognition of CD40 on target cells can provide an activation pathway for such human NK cells. CD40-transfected P815 cells were killed by NK cell lines expressing CD40L, clones and PBL-derived NK cells cultured for 18 h in the presence of IL-2, but not by CD40L-negative fresh NK cells. Cross-linking of CD40L on IL-2-activated NK cells induced redirected cytolysis of CD40-negative but Fc receptor-expressing P815 cells. The sensitivity of human TAP-deficient T2 cells could be blocked by anti-CD40 antibodies as well as by reconstitution of TAP/MHC class I expression, indicating that the CD40-dependent pathway for NK activation can be downregulated, at least in part, by MHC class I molecules on the target cells. NK cell recognition of CD40 may be important in immunoregulation as well as in immune responses against B cell malignancies
CD40 expressed on thymic epithelial cells provides costimulation for proliferation but not apoptosis of human thymocytes
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