1,720,967 research outputs found
Paradoxical behaviour of lyophilised commercial control materials for CK and CK-MB assays after reconstitution at either 4°C or 24°C
No full textSignificant reduction of the bias among commercial immunoassays for lipoprotein(a) after use of a uniform calibrator
No full textDespite the increasing interest in the measurements of lipoprotein(a) (Lp(a)) in serum or plasma, at present there is no effective standardization for Lp(a) assays; the main problems to solve are represented either by the lack of a suitable primary standard or by the absence of a reliable and widely available reference method. A first step is hence the uniformity of calibration of different immunoassays. We calibrated three commercial immunoassays for Lp(a) (enzyme linked immunosorbent assay (ELISA), latex-enhanced immunonephelometric assay (LINA), and immunonephelometric assay (INA)) with either proprietary standards or purified Lp(a) material obtained with a rapid and simple procedure. Final results of purified Lp(a) calibration were reported in terms of protein Lp(a) mass whereas we were able to quantify the exact protein concentration of our purified lipoprotein. The uniformity of the calibration of the different assays led to a significant improvement of regression slopes (from 1.88 to 0.90 ELISA vs. LINA, from 1.45 to 0.95 ELISA vs. INA and from 1.27 to 0.96 INA vs. LINA) and correlation coefficients (from 0.990 to 0.994 ELISA vs. LINA, from 0.987 to 0.990 ELISA vs. INA and from 0.985 to 0.987 INA vs. LINA). Furthermore, the significant differences among Lp(a) values obtained after calibration with proprietary standards were minimized, becoming non-significant in two out of three cases. In conclusion, we demonstrated that a better agreement of Lp(a) values obtained with different commercial assays could be simply reached by uniformity of calibration and by employing standards with values accurately measured
Evidence that lipoprotein(a) is not an adhesive and proaggregating molecule for platelets in vitro
No full textBackground. Several studies demonstrated that Lp(a) play an important role in genesis and development of the atherosclerotic lesions. Nevertheless Lp(a) displays an adjunctive and exclusive thrombotic effect due to a supposed competition of the apo(a) protein moiety with plasminogen for activation and binding either to specific plasminogen receptors at the cell surface or to stabilized fibrin. Moreover, Lp(a), similarly to other lipoproteins, affects the functionality of platelets through its binding to cellular receptors, thus sensitizing platelets to a wide variety of stimulating agents. In the present study the potential role of Lp(a) in the adhesion and aggregation of human platelets was investigated. Methods. Lp(a) was purified from human plasma by lysine-Sepharose affinity chromatography and was used to coat the plastic surface of microplate wells where human platelets were incubated for 1 h in the absence and in the presence of the stimulants 10 mM ADP or 0.1 U/mL thrombin. Results. In this assay system, the adhesion of unstimulated platelets to 50 mug/mL Lp(a) was very low (3.8%), as was the adhesion to BSA (2.9 = %) and to fibrinogen (5.2%), while platelet adhesion was much higher (18.8%) when collagen was used as coating agent. Thrombin markedly increased the adhesion to BSA and to fibrinogen (19.7% and 23.3% respectively), while ADP increased the adhesion to fibrinogen but not to BSA 18.2% and 3.0% respectively). The adhesion of stimulated platelets to Lp(a) was very low (3.0% and 5.6% with ADP and thrombin respectively). Finally, Lp(a) at doses > 30 mug/mL inhibited both the adhesion of thrombin-stimulated platelets to fibrinogen or BSA and the ADP-induced aggregation in a dose-dependent fashion. Conclusion. From our results, we conclude that Lp(a) is not a physiological substrate for adhesion of platelets as we demonstrated that Lp(a) may behave as a potential anti-adhesive and anti-aggregating molecule. Therefore the athero-thrombotic potential of Lp(a) has to be explained by other mechanisms, at the inhibition of plasminogen activation
Urinary galactosyl-hydroxylysine in postmenopausal osteoporotic women: A potential marker of bone fragility.
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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
Age dependence of within-subject biological variation of nine common clinical chemistry analytes
No full textBackground: The knowledge of biological variation (BV) data is important for clinical decisions and as a basis for defining analytical quality specifications. However, in gene\xadrating reliable data of biological variation there are still some unsolved problems, such as age dependence. The aim of our work is to verify this aspect. Methods: Twenty-six subjects divided into three groups by age were studied. Blood samples were collected in lithium heparin tubes for four weeks at one week intervals, on the same day of the week (Tuesday) and at the same time of day (8-9 a.m.) by the same phlebotomist. They were analysed in duplicate for creatinine, urate, calcium, albumin, total cholesterol, high density lipoprotein (HDL) and low density lipoprotein (LDL)-cholesterol, triglycerides and iron. After outlier exclusion by Cochran\u2019s test, components of biological variation were calculated by ANOVA. The significance of the differences between results of the classes was also calculated with the Student\u2019s test (t-test) and the Fisher\u2019s test (F-test). Results: Excluding albumin, the group 3 results (age range from 78 to 98 years) showed significantly lower CV within subjects (CVW) than the other two groups. Conclusions: Our data seem to highlight the relevance of the age when choosing the reference subjects for biological variation studies. The level of within-subject biological variation of the elderly group may have been further reduced by the homogeneity of the group constituted by individuals living together in the same nursing home
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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