1,720,974 research outputs found
Seminal plasma cobalamin significantly correlates with sperm concentration in men undergoing IVF or ICSI procedures
No full textMild hyperhomocysteinemia is caused by B vitamin deficiencies. We hypothesize that these biochemical derangements detrimentally affect spermatogenesis. Therefore, the aim of this study was to investigate the folate, cobalamin, pyridoxine, and homocysteine concentrations in blood and seminal plasma and the associations between these biomarkers and semen parameters in men participating in an in vitro fertilization or intracytoplasmic sperm injection program. From 73 men (median age [range]: 37 years [28-53]), blood and semen samples were obtained for the determination of serum and red blood cell (RBC) folate, serum total cobalamin, whole-blood pyridoxal-5'-phosphate, plasma total homocysteine (tHcy), and serum total testosterone. Semen analysis included sperm concentration, motility, and morphology according to World Health Organization criteria. The B vitamins and tHcy concentrations were significantly correlated in blood but not in seminal plasma. The serum and RBC folate concentrations were significantly correlated also with the total folate concentration in seminal plasma (r = .44; P < .001 and r = .39; P < .001, respectively). Likewise, the total cobalamin concentration in serum and seminal plasma was significantly correlated (r = .55; P = .001). Of interest is that the total cobalamin concentration in seminal plasma was significantly correlated with the sperm concentration (r = .42; P < .001). This is in contrast to the absence of significant associations between the other vitamins and tHcy in blood and seminal plasma and any of the semen parameters. These findings suggest that folate and cobalamin are transferred from the blood to the male reproductive organs and emphasize the role of cobalamin in spermatogenesis in human
Preconception folic acid treatment affects the microenvironment of the maturing oocyte in humans
No full textObjective: to investigate the influence of folic acid supplementation on the follicular fluid concentrations of folate and total homocysteine and their relationship to the diameter of the follicle.Design: observational study.Setting: tertiary referral fertility clinic at the Erasmus MC, University Medical Center, Rotterdam, The Netherlands.Patient(s): thirty-seven women undergoing IVF or intracytoplasmic sperm injection treatment.Intervention(s): no interventions other than routine stimulation treatment and the recommendation of folic acid supplementation.Main Outcome Measure(s): concentrations of folate and total homocysteine in monofollicular and pooled follicular fluid and the diameter of the follicle.Result(s): folic acid supplementation significantly increased folate and decreased total homocysteine concentrations in pooled follicular fluid. In monofollicular fluid, folate concentrations only were significantly increased in supplemented women. The total homocysteine concentration appeared to be significantly correlated with the diameter of the follicle (r = 0.27). Samples from single follicles were less prone to artifacts in the measurements of the folate and total homocysteine concentration.Conclusion(s): preconception folic acid supplementation significantly alters both folate and total homocysteine concentrations in follicular fluid. The correlation between the diameter of the follicle and total homocysteine concentration in follicular fluid warrants further investigation
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
The homocysteine pathway in human subfertility
Full text linkSubfertility, defined as at least one year of unprotected intercourse with the same partner
without conception, affects ten to fifteen percent of couples in the western world. Depending
on the duration of the subfertility, a female factor is the dominant cause of subfertility
in around 50%, a male factor in 20-26% and the cause is unexplained in 25-30%. In
most couples, subfertility is of multifactorial origin and should therefore be considered
as a complex disease. Whereas genetic causes are difficult to modulate, environmental
and lifestyle factors implicated in reproduction are potentially amendable to curative or
preventive measures. Worldwide, an increasing number of couples are treated by assisted
reproductive technology (ART) to achieve pregnancy. Currently, the chance of achieving
a clinical pregnancy is around 28-31% per started in vitro fertilization (IVF) cycle with
or without intracytoplasmic sperm injection (ICSI) in the Netherlands. The advantage of
the introduction of IVF and ICSI treatment is that it gives access to and information about
the direct environment of the gametes and early developing embryo. On the other hand,
IVF and ICSI treatment is introducing an artifactual endocrinologic milieu which may affect
the quality of the embryo. Whether concentrations of nutrients and enzymes change due
to ovarian hyperstimulation is unclear, but it has already been demonstrated that different
ovarian stimulation regimens increase the rates of embryo aneuploidy
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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