1,720,967 research outputs found
Increase of cross(auto)-reactive antibodies after immunization in aged mice: a cellular and molecular study
No full textAging in both humans and laboratory animals is often accompanied by an increase in autoreactive antibodies. Here we report that immunization with a bacterial antigen determined a marked increase of cross-reactive antibodies in aged but not in young mice. This phenomenon was observed in the aged individuals of two different mouse strains (Balb/c and C57BL/6) after a single injection of lyophilized vaccine from Streptococcus pneumoniae R36a (Pn) that express the immunodominant epitope phosphorylcholine (PC). These data were then confirmed by the analysis of cross-reactivity of anti-PC monoclonal antibody (mAb) generated from Pn-immunized young and aged Balb/c and C57BL/6 mice. Most of the anti-PC mAb from aged mice showed a broad spectrum of cross-reactivity with a panel of self and non-self antigens, while none of the mAb from young mice did so. We also showed that a genetic shift, in the VH/VL gene repertoire of anti-PC antibody, appeared to take place in aged mice and that aged mAb displayed a decrease in antibody affinity for the free hapten PC as compared to the young ones. We interpret these data as showing that immunization at advanced age may be linked to the production of cross-reactive antibodies and that this event may be related to the increased incidence of autoantibody in the age
Autologous anti-idiotypic antibody response is regulated by the level of circulating complementary idiotype
No full textLevel of circulating anti-idiotypic antibody determines the levels of autologous anti-idiotypic response following antigen delivery in viv
In vivo and in vitro study of the primary and secondary antibody response to a bacterial antigen in aged mice
No full textOne of the most important manifestations of aging in both humans and laboratory animals is a gradual decline in immune effectiveness. However, it is not clear as to how general is this decline. We here report that aged BALB/c mice showed no decline in the magnitude of the in vivo primary antibody response to phosphorylcholine (PC), an immunodominant epitope of the Streptococcus pneumoniae R36a (Pn). Often it appeared that aged mice responded better than young syngeneic mice. In contrast, the secondary antibody response had a different profile, with aged mice showing a marked decrease in PC-specific antibody. Further in vitro studies were conducted in order to determine the cause of the decline of the secondary antibody response in aging. We noted that B cells from young and aged donors, either primed or twice immunized with the antigen, when cultured without T cells and in the presence of antigen did not display any significant difference in their antibody response to PC. However, L3T4 cells from aged BALB/c mice, previously immunized twice with Pn, failed to augment the in vitro B cell response as compared to L3T4 cells from young mice. Moreover, we found that Lyt 2 cells from young and aged mice had no regulatory effects on the anti-PC response in vitro. Further in vivo experiments demonstrated that alteration of the idiotypic network may not be related to a decline in the secondary antibody response since two injections of the antigen are unable to elicit an anti-idiotypic antibody response in either young or aged mice. These data demonstrate that the decline of the anti-PC response after a secondary challenge with Pn is linked to defects in the T cell compartmen
Emergence of time-horizon invariant correlation structure in financial returns by subtraction of the market mode.
No full textWe investigate the emergence of a structure in the correlation matrix of assets' returns as the time horizon over which returns are computed increases from the minutes to the daily scale. We analyze data from different stock markets (New York, Paris, London, Milano) and with different methods. In addition to the usual correlations, we also analyze those obtained by subtracting the dynamics of the "center of mass" (i.e., the market mode). We find that when the center of mass is not removed the structure emerges, as the time horizon increases, from splitting a single large cluster into smaller ones. By contrast, when the market mode is removed the structure of correlations observed at the daily scale is already well defined at very high frequency (5 min in the New York Stock Exchange). Moreover, this structure accounts for 80% of the classification of stocks in economic sectors. Similar results, though less sharp, are found for the other markets. We also find that the structure of correlations in the overnight returns is markedly different from that of intraday activity
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
M cell: the main entrance of the mucosal immune system
No full textM cells are higly specialized cells within the follicle-associated epithelium (FAE) of the respiratory and intestinal tracts. They play a central role in the induction of the mucosal immune response by transporting antigens to the lymphoid tissue. In this way the immune system may encounter the limitless variety of antigens that enter the body through the gut and airways. Here we describe the structure and the function of intestinal M cells. In addition, controversial issues relating to the M cell biology, such as APC function and the origin of M cells within the FAE, are discussed
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
- …
