1,720,994 research outputs found
Isolation and characterization of an antifactor V antibody causing activated protein C resistance from a patient with severe thrombotic manifestations
No full textBlood. 2002 Jun 1;99(11):3985-92.
Isolation and characterization of an antifactor V antibody causing activated
protein C resistance from a patient with severe thrombotic manifestations.
Kalafatis M, Simioni P, Tormene D, Beck DO, Luni S, Girolami A.
Department of Chemistry, Cleveland State University, The Cleveland Clinic
Foundation, Cleveland, OH 44115, USA. [email protected]
A 44-year-old woman with a history of severe thrombotic manifestations presented
with a markedly reduced activated protein C-sensitivity ratio (APC-SR). DNA
sequencing of and around the regions encoding the APC cleavage sites in the
factor Va molecule excluded the presence of the factor VLeiden mutation and of
other known genetic mutations. No antiphospholipid antibodies were present in the
patient's plasma and both prothrombin time and activated partial thromboplastin
time were normal. The total immunoglobulin fraction was isolated from the
patient's plasma and found to induce severe APC resistance when added to normal
plasma and to factor V-deficient plasma supplemented with increasing
concentrations of factor V. Immunoblotting and immunoprecipitation experiments
with the total immunoglobulin fraction purified from the patient's plasma
demonstrated that the antibody recognizes factor V, is polyclonal, and has
conformational epitopes on the entire factor V molecule (heavy and light chains,
and B region). Thus, the immunoglobulin fraction interferes with the
anticoagulant pathway involving factor V. The inhibitor was isolated by
sequential affinity chromatography on protein G-Sepharose and factor V-Sepharose.
The isolated immunoglobulin fraction inhibited factor Va inactivation by APC
because of impaired cleavage at Arg306 and Arg506 of the heavy chain of the
cofactor. The isolated immunoglobulin fraction was also found to inhibit the
cofactor effect of factor V for the inactivation of factor VIII by the
APC/protein S complex. Our data provide for the first time the demonstration of
an antifactor V antibody not related to the presence of antiphospholipid
antibodies, which is responsible for thrombotic rather than hemorrhagic symptoms.
PMID: 12010798 [PubMed - indexed for MEDLINE
Clinical and laboratory expression of associated thrombophilic conditions (homozygous/heterozygous factor V Leiden mutation and heterozygous prothrombin variant 20210A) in an Italian family
No full textProthrombin variant 20210A is maintained to be a mild risk factor for venous thromboembolism (VTE). The association of this defect with other inherited thrombophilic conditions may result in an increased risk of developing VTE. In this article, a family is described in which prothrombin variant was associated with either homozygous or heterozygous factor V Leiden (FV Leiden) mutation. All family members except the proband were asymptomatic despite the presence and the severity of the underlying genetic defect(s). The proband, who carried homozygous FV Leiden mutation and heterozygous prothrombin variant, experienced recurrent VTE during pregnancies, whereas one brother, with the same defect, was asymptomatic. Mean prothrombin antigen and activity levels were higher in carriers of the prothrombin variant as compared with noncarriers. Thrombin generation was assessed in family members, in carriers of prothrombin variant or homozygous FV Leiden mutation and in a control group. Most of the family members presented with increased prothrombin fragment 1+2 levels possibly because of the presence of the FV Leiden mutation. Although it is conceivable that the co-inheritance of prothrombin variant and FV Leiden mutation may increase the risk of VTE, patients with these combined defects may remain asymptomatic. It is likely that acquired triggering conditions play a major role in determining VTE in carriers of a mild genetic predisposition. This has to be taken into account when recommendation for thromboprophylaxis is given
Asymptomatic homozygous nt 20210 G to A prothrombin polymorphism in two blood donors belonging to two different kindreds
No full textA protein S functional assay yields unsatisfactory results in patients with activated protein C resistance.
No full text
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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