1,721,021 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Detection of testosterone esters in human plasma
No full textThe detection of testosterone misuse in sports is currently based on the urinary testosterone to epitestosterone ratio, although in some rare instances physiological or pathological conditions could compromise the application of this general criterion. The detection in the body of traces of the unchanged testosterone esters really ingested would offer unequivocal confirmation of testosterone administration In this work, the detectability of testosterone esters in humans was studied. Liquid-liquid extraction of human blood plasma and appropriate derivatization of nine testosterone esters are described. Different acyl (trifluoroacetyl, pentafluoropropionyl and heptafluorobutyryl) and trimethylsilyl derivatives were studied. The trimethylsilyl derivatives appear to be the best for screening purposes based on the characteristics of their mass spectra, with abundant molecular ions in the high-mass range. They also offered good conditions for tandem mass spectrometric analysis, needed to achieve the required sensitivity after oral administration of the drugs. The method was successful in the detection and determination of intramuscularly administered testosterone propionate and testosterone enanthate and orally ingested testosterone undecanoate
Non-targeted LC-MS based metabolomics analysis of the urinary steroidal profile
Get PDFThe urinary steroidal fraction has been extensively explored as non-invasive alternative to monitor pathological conditions as well as to unveil the illicit intake of pseudo-endogenous anabolic steroids in sport. However, the majority of previous approaches involved the a priori selection of potentially relevant target analytes. Here we describe the non-targeted analysis of the urinary steroidal profiles. The workflow includes minimal sample pretreatment and normalization according to the specific gravity of urine, a 20 min reverse phase ultra-performance liquid chromatographic separation hyphenated to electrospray time-of-flight mass spectrometry. As initial validation, we analyzed a set of quality control urines spiked with glucurono- and sulfo-conjugated steroids at physiological ranges. We then applied the method for the analysis of samples collected after single transdermal administration of testosterone in hypogonadal men. The method allowed profiling of approximately three thousand metabolic features, including steroids of clinical and forensic relevance. It successfully identified metabolic pathways mostly responsible for groups clustering even in the context of high inter-individual variability and allowed the detection of currently unknown metabolic features correlating with testosterone administration. These outcomes set the stage for future studies aimed at implementing currently monitored urinary steroidal markers both in clinical and forensic analysis
Synthetic isoflavones and doping: a novel class of aromatase inhibitors?
Get PDFIsoflavones are a group of flavonoids that may be of interest in sport doping because they can be used by athletes in the recovering periods after the administration of anabolic steroids, with the aim of increasing the natural production of luteinizing hormone (LH) and, consequently, the biosynthesis of endogenous androgens
Synthetic isoflavones and doping: A novel class of aromatase inhibitors?
No full textAnectodical information suggests that flavonoids may be widely used among athletes for their multiple biochemical and pharmacological effects. We have evaluated in vitro the effects of two synthetic isoflavones, methoxyisoflavone and ipriflavone, on the catalytic activity of human aromatase (CYP19), the enzyme catalyzing the conversion of androgens (ie, testosterone or androstenedione) to estrogens (ie, estradiol and estrone). The potential inhibitory effect was evaluated by measuring the rate of aromatization of testosterone, monitored by gas chromatography–mass spectrometry (GC–MS), both in the presence and in the absence of methoxyisoflavone or ipriflavone, comparing their effects with those of synthetic aromatase inhibitors (formestane, anastrozole, and aminoglutethimide) presently included in the list of prohibited substances and methods, and of natural flavonoids (chrysin, quercetin, and daidzein), that are known inhibitors of CYP19. The preliminary results of our in vitro study show that methoxyisoflavone and ipriflavone act as competitive inhibitors of aromatase, the degree of inhibition measured in vitro being of the same order of magnitude of that of the aromatase inhibitors commonly used in anti-estrogenic therapies. Our preliminary in vitro results indicate that, in principle, a sufficiently large intake of isoflavones could alter the kinetics of the dynamic equilibria between androgens and estrogens, suggesting their monitoring in doping control routine analysis
Multianalyte LC-MS-based methods in doping control: what are the implications for doping athletes?
Get PDFOver the last 50 years, the list of doping
substances and methods has been progressively
expanding, being regularly reviewed
by the international antidoping authorities
(formerly the Medical Commission of the
International Olympic Committee, and afterward,
following its constitution in 1999, the
World Anti-Doping Agency [WADA]). New
substances/classes of substances have been
periodically included in the list, keeping the
pace with more advanced and sophisticated
doping trends. At present, and apart from
the prohibited performance enhancing and
masking methods (e.g., blood transfusions
and tampering strategies), the list comprises
several hundreds of biologically active substances,
with broad differences in their physicochemical
properties (i.e., molecular weight,
polarity and acid-basic properties) [1]. As a
consequence, the ‘one class – one procedure’
approach, which had been followed by nearly
all accredited antidoping laboratories worldwide
until the turn of the millennium, is no
longer sustainable. The need to minimize the
overall number of independent analytical procedures,
and, in parallel, to reduce the analytical
costs, stimulated the development of multitargeted
methods, aimed to increase the overall
ratio of ‘target analytes: procedure’ [2–6].
The above evolution has not always been
a straight forward process. The need to comply
with the WADA technical requirements
(both in terms of identification criteria and of
minimum required performance limits [7,8])
and with the reduction of the reporting time
(a constraint that becomes even more critical
during international sport events, where
the daily workload also drastically increases)
has imposed a thorough re-planning of the
analytical procedures.
The development of an antidoping analytical
method requires the appropriate knowledge
not only of the biophysicochemical
properties of the target analyte, but also of its
PK profile. Historically, immunological methods
and GC-based techniques were applied
in antidoping science, as preferential screening
methods for the detection of prohibited
substances, which were originally limited to
nonendogenous stimulants and narcotics. In
the 1980s, GC–MS became the reference analytical
platform for the detection and quantification
of the majority of the low molecular
weight doping substances [3–6]. In the following
two decades, with the inclusion in the
Prohibited List of new classes of low molecular
weight, hydrophilic, thermolabile, nonvolatile
analytes (including, but not limited to, glucocorticoids
and designer steroids) and simultaneously
of peptide hormones, scientists were
obliged to design, develop, validate and apply
techniques based on LC–MS/MS
Variations on the Author
Get PDF“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
Get PDFWe 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
Urinary excretion profiles of toremifene metabolites by liquid chromatography-mass spectrometry. Towards targeted analysis to relevant metabolites in doping control
No full textIn the present study, toremifene urinary excretion studies were evaluated in order to examine main metabolic reactions and to select target metabolites in doping control analysis. Urine samples from three female subjects were collected every 3 h for at least 15 days after the oral administration of a single dose of FarestonA (R) (60 mg). The elemental compositions of the compounds detected were determined by liquid chromatography-mass spectrometry using a time-of-flight system with accurate mass measurement. More detailed structure elucidation was obtained by monitoring the presence or absence of structure-specific ions, using product ion scan and neutral loss acquisition modes, whereas the metabolites urinary profiles were evaluated in selected reaction monitoring acquisition mode. The results showed that the main routes of phase-I modifications involved carboxylation of the chlorinated side chain, N-demethylation and hydroxylation in different positions. Fifteen metabolites were found in all subjects studied, most of them were detected for more than 10 days in the free, glucuronide and sulphate fractions, with a maximum of excretion generally after 9-22 and 34-47 h from drug administration. These metabolites can be divided in two groups: metabolites with the characteristic chlorine isotope pattern and metabolites without the characteristic chlorine isotope pattern. The most abundant and long-term compounds were the carboxylated metabolites followed by the hydroxylated metabolites. Their product ions originating after collision-induced dissociation were observed to occur prevalently in the dimethylaminoethoxy and in the chlorinated side chains. These structure-specific ions were used to design screening and confirmation procedures to positively identify toremifene administration in doping control analysis
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