1,720,985 research outputs found
Insulin resistance in a large cohort of women with polycystic ovary syndrome: a comparison between euglycaemic-hyperinsulinaemic clamp and surrogate indexes
No full textSTUDY QUESTION: Could surrogate indexes identify insulin resistant individuals among women with polycystic ovary syndrome (PCOS)? SUMMARY ANSWER: Surrogate indexes may be able to rule in, but not rule out, insulin resistance in women with PCOS. WHAT IS KNOWN ALREADY: Insulin resistance is a typical finding of women with PCOS and most clinical information on this issue is based upon surrogate indexes of insulin resistance. However, data on the performance of these indexes in PCOS women are very limited. STUDY DESIGN SIZE, DURATION: A retrospective analysis of 406 women referred to our outpatient clinic for hyperandrogenism and/or menstrual dysfunction and submitted to hyperinsulinemic euglycaemic clamp between 1998 and 2015. PARTICIPANTS/MATERIALS, SETTING, METHODS: In total, 375 of these women had PCOS by the Rotterdam criteria and were included in the study. Six surrogate indexes of insulin sensitivity were calculated from glucose and insulin levels, either at fasting (homeostasis model assessment (HOMA), glucose/insulin (G/I) ratio and quantitative insulin sensitivity check index (QUICKI)) or after oral glucose load (Gutt, Stumvoll0-120 and Matsuda). MAIN RESULTS AND THE ROLE OF CHANCE: Overall, insulin resistance, as identified by the M-clamp value, was found in 74.9% of these women. The percentage was 59.3% in normal-weight vs 77.5% in overweight and 93.9% in obese subjects. All surrogate indexes were highly correlated with the M-clamp values. However, their ability to identify insulin resistant individuals was limited, in terms of sensitivity and especially in normal-weight subjects. ROC analysis showed similar performances of these indexes (AUC values 0.782-0.817). LIMITATIONS REASONS FOR CAUTION: Potential referral bias of PCOS patients may have caused overestimation of the prevalence of insulin resistance in these women. WIDER IMPLICATIONS OF THE FINDINGS: By using surrogate indexes many subjects with PCOS may be erroneously diagnosed as insulin sensitive, especially among normal-weight women. These indexes can be used to rule in, but not rule out, insulin resistance in PCOS
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
Attività enzimatiche glicometaboliche in linfomonociti di soggetti obesi con e senza diabete di tipo II: correlazione col binding e con la sensibilità insulinica in vivo.
No full textMononuclear leukocytes from obese patients with type II diabetes have reduced activity of hexokinase, 6-phosphofructokinase, and glucose-6-phosphate dehydrogenase.
No full textHyperinsulinemia amplifies GnRH agonist stimulated ovarian steroid secretion in women with polycystic ovary syndrome.
No full textContext: In vitro data show that insulin may enhance basal and LH-stimulated ovarian androgen secretion, particularly in theca cells from women with polycystic ovary syndrome (PCOS). However, in vivo studies gave inconsistent results.Objective: The objective of the study was to assess whether hyperinsulinemia affects in vivo ovarian steroid secretion and steroid metabolism.Design and Settings: This was a controlled cross-sectional study, conducted in a tertiary care academic center.Participants: Nine young PCOS women participated in the study.Intervention: Participants were submitted, in two separate days, to a GnRH agonist stimulation (buserelin 100 μg, sc), during a 17-h hyperinsulinemic (80 mU/m2 · min) euglycemic clamp and, as a control, during saline infusion. Adrenal steroid secretion was suppressed by dexamethasone.Main Measures: During both protocols, before and after GnRH agonist stimulation, serum insulin, gonadotropins, cortisol, progesterone, 17-hydroxyprogesterone, androstenedione, testosterone, estradiol, and urinary androgen metabolites were measured.Results: Insulin increased from 25.1 ± 13.3 to 341.5 ± 102.6 mU/liter during the clamp, whereas it did not significantly change during saline infusion. Baseline steroids and gonadotropins were similar in the two protocols. During hyperinsulinemia, GnRH agonist-stimulated serum progesterone and androstenedione were significantly higher than during saline infusion, and 17-hydroxyprogesterone was of borderline significance. Moreover, 24 h after GnRH agonist stimulation, testosterone was higher after hyperinsulinemia. Serum gonadotropins and estradiol response did not differ between the protocols. Urinary androgen metabolites excretion significantly increased after GnRH agonist stimulation, but the increase was similar during insulin and saline infusions.Conclusions: These in vivo data show that sustained hyperinsulinemia potentiates gonadotropin-stimulated ovarian androgen steroidogenesis. Insulin-induced increase in ovarian hormone secretion is not accompanied by an increased steroid metabolism
Effect on insulin clearance of different pharmacological treatments in women with polycystic ovary syndrome: a hypothesis-generative study
No full textPurpose: Impaired insulin clearance has been found in women with PCOS and contribute to generate hyperinsulinemia in these subjects. However, the mechanisms underlying this phenomenon remain unknown. The aim of this retrospective study was to explore if the heterogeneous treatments used in these patients to counteract their hormonal and metabolic alterations can also affect insulin clearance. Methods: Forty-seven women with PCOS were included in the study. They belonged to different experimental groups, submitted to treatments with the following drugs: GnRH-agonist (buserelin, n = 10), antiandrogens (spironolactone, n = 9), metformin (n = 18), or placebo (n = 10). Metabolic clearance rate of insulin (MCRI) and insulin sensitivity were measured by the hyperinsulinemic euglycemic clamp, performed before and after treatment. Insulin secretion was estimated by the HOMA β-index. Results: Treatments were associated, as expected, with different clinical effects. In ANOVA analysis, changes in MCRI significantly differed between treatment groups. In particular, metformin increased MCRI as compared with other treatments or placebo. Mediation analysis showed that about 25% of this effect of metformin was mediated by the concurrent BMI change, whereas it was not influenced by changes in peripheral insulin sensitivity or insulin secretion. Conclusion: The impairment of MCRI, which contributes to the hyperinsulinemia typical of PCOS, significantly improved after treatment with metformin. This effect was only partially explained by the reduction of BMI, whereas changes in insulin sensitivity did not show a mediation effect in this phenomenon, suggesting that other metformin-induced mechanisms are involved
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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