1,720,997 research outputs found
Hereditary and acquired protein S deficiencies are associated with low TFPI levels in plasma.
No full textJ Thromb Haemost. 2010 Feb;8(2):294-300. Epub 2009 Nov 30.
Hereditary and acquired protein S deficiencies are associated with low TFPI
levels in plasma.
Castoldi E, Simioni P, Tormene D, Rosing J, Hackeng TM.
Department of Biochemistry, CARIM, Maastricht University, Maastricht, the
Netherlands. [email protected]
BACKGROUND: Protein S and tissue factor pathway inhibitor (TFPI) act together in
down-regulating coagulation.
OBJECTIVE: To investigate the TFPI/protein S system in hereditary and acquired
protein S deficiency.
METHODS: Plasma antigen levels of protein S and full-length TFPI were determined
in heterozygous type I protein S-deficient individuals (n=35), patients on oral
anticoagulant treatment (OAT) (n=29), oral contraceptive (OC) users (n=10) and
matched controls. Thrombin generation was determined using calibrated automated
thrombography.
RESULTS: Full-length TFPI levels were lower in type I protein S-deficient
individuals (76.8+/-33.8%) than in age- and sex-matched controls (128.0+/-59.4%,
P<0.001). Among protein S-deficient individuals with thrombosis, those on OAT had
not only lower total protein S levels (25.7+/-8.2% vs. 54.7+/-8.2%, P<0.001), but
also lower full-length TFPI levels (52.6+/-15.0% vs. 75.4+/-22.9%, P=0.009) than
those not on OAT. Similarly, OC users had lower protein S (73.8+/-11.5% vs.
87.9+/-10.8%, P=0.005) and full-length TFPI levels (73.7+/-27.7% vs.
106.4+/-29.2%, P=0.007) than non-users. When triggered with tissue factor, plasma
from protein S-deficient individuals generated 3-5-fold more thrombin than
control plasma. The difference was only partially corrected by normalization of
the protein S level, full correction requiring additional normalization of the
TFPI level. Protein S-immunodepletion experiments indicated that free protein S
and full-length TFPI form a complex in plasma, and the protein S/TFPI interaction
was confirmed by surface plasmon resonance analysis.
CONCLUSIONS: Full-length TFPI binds to protein S in plasma and is reduced in
genetic and acquired protein S deficiency. The concomitant TFPI deficiency
substantially contributes to the hypercoagulable state associated with protein S
deficiency.
PMID: 20002538 [PubMed - indexed for MEDLINE
Thrombin generation-based assays to measure the activity of the TFPI-protein S pathway in plasma from normal and protein S-deficient individuals.
No full textSimilar hypercoagulable state and thrombosis risk in type I and type III proteinS-deficient individuals from mixed type I/III families.
No full textHaematologica. 2010 Sep;95(9):1563-71. Epub 2010 Apr 26.
Similar hypercoagulable state and thrombosis risk in type I and type III protein
S-deficient individuals from families with mixed type I/III protein S deficiency.
Castoldi E, Maurissen LF, Tormene D, Spiezia L, Gavasso S, Radu C, Hackeng TM,
Rosing J, Simioni P.
Department of Biochemistry, Maastricht University P.O. Box 616, 6200 Maastricht,
The Netherlands. [email protected]
BACKGROUND: Protein S, which circulates in plasma in both free and bound forms,
is an anticoagulant protein that stimulates activated protein C and tissue factor
pathway inhibitor. Hereditary type I protein S deficiency (low total and low free
protein S) is a well-established risk factor for venous thrombosis, whereas the
thrombosis risk associated with type III deficiency (normal total and low free
protein S) has been questioned.
DESIGN AND METHODS: Kaplan-Meier analysis was performed on 242 individuals from
30 families with protein S deficiency. Subjects were classified as normal, or
having type I or type III deficiency according to their total and free protein S
levels. Genetic and functional studies were performed in 23 families (132
individuals).
RESULTS: Thrombosis-free survival was not different between type I and type III
protein S-deficient individuals. Type III deficient individuals were older and
had higher protein S, tissue factor pathway inhibitor and prothrombin levels than
type I deficient individuals. Thrombin generation assays sensitive to the
activated protein C- and tissue factor pathway inhibitor-cofactor activities of
protein S revealed similar hypercoagulable states in type I and type III protein
S-deficient plasma. Twelve PROS1 mutations and two large deletions were
identified in the genetically characterized families.
CONCLUSIONS: Not only type I, but also type III protein S deficiency is
associated with a hypercoagulable state and increased risk of thrombosis. These
findings may, however, be restricted to type III deficient individuals from
families with mixed type I/III protein S deficiency, as these represented 80% of
type III deficient individuals in our cohort.
PMCID: PMC2930959
PMID: 20421270 [PubMed - in process
Type III protein S deficiency is associated with a hypercoagulable state and an increased risk of venous thrombosis
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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