1,721,062 research outputs found
Marian Ross Young Mitchell, Eleanor Maria James Young, and Emeline Free Young
No full textPortrait of Marian Ross Young Mitchell, Eleanor Maria James Young, and Emeline Free Young
Functional characterisation of aphid, Myzus persicae, nicotinic acetylcholine receptors and identification of a novel biogenic amine-gated ion channel from the honeybee, Apis mellifera
Get PDFNicotinic acetylcholine receptors (nAChRs) are cysteine-loop ligand-gated ion channels that are the targets of effective insecticides, including neonicotinoids and spinosad. The heterologous expression of nAChRs, in Xenopus laevis oocytes, has enabled the study of functional and pharmacological properties of these receptors by two-electrode voltage clamp electrophysiology.
Myzus persicae, the peach potato aphid, is a major global pest of multiple crop species. The nAChR subunits and several protein chaperones from Myzus persicae have been cloned. It was difficult to achieve robust and frequent expression of a nAChR consisting entirely of subunits from Myzus persicae with the chaperones RIC-3, UNC-50 and TMX3. However, use of the α1 subunit from Drosophila melanogaster allowed nAChRs containing Myzus persicae α3, α8 and β1 subunits to be expressed and characterised with an EC50 for acetylcholine of 123 µM. The Drosophila melanogaster α1 and Myzus persicae β1 subunits formed a functional nAChR with an EC50 for acetylcholine of 91.1 µM, upon which neonicotinoids acted as partial agonists.
The Apis mellifera, European honeybee, α5 subunit formed a homomeric nAChR in oocytes without any chaperones. This was sensitive to 0.1 μM α-bungarotoxin and responded to both acetylcholine and choline but with low affinity, as shown by EC50 values in the millimolar range (2.65 mM and 9.07 mM respectively). Further testing revealed that the α5 nAChR responded to dopamine (EC50 3.37 μM), 5-hydroxytryptamine (EC50 122 μM), octopamine (EC50 378 μM), tyramine (EC50 91.1 μM) and histamine (EC50 3.36 mM) but not to GABA, glycine or glutamate. Dopamine, 5-hydroxytryptamine, octopamine and tyramine all acted as superagonists relative to acetylcholine and had higher affinities than acetylcholine, as shown by EC50 values in the micromolar range, with dopamine having the highest efficacy and affinity. Histamine was a low-affinity, partial agonist. Phylogenetic analysis indicated that the non-Dipteran α5, including from Apis mellifera, form a distinct group from the Dipteran α5.
This thesis contributes to the rapidly growing field of knowledge gained from expressing insect nAChRs in heterologous systems. This is especially useful as a nAChR from a pest species has not been robustly expressed yet. The characterisation of a novel nAChR from the beneficial species, Apis mellifera, potentially indicates a new class of receptor, with unusual pharmacological properties
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
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
Randomised trial of cord clamping at very preterm birth: outcomes at 2 years
No full textObjective To report outcomes at 2 years corrected age for children of women recruited to a trial comparing alternative policies for timing of cord clamping and immediate neonatal care at very preterm birth. Design Parallel group randomised (1:1) trial. Setting Eight UK tertiary maternity units. Participants Two hundred and seventy-six babies born to 261 women expected to have a live birth before 32 +0 weeks' gestation. Interventions Deferred cord clamping (≥2 min) and immediate neonatal care with cord intact or immediate (≤20 s) clamping and immediate neonatal care after clamping. Main outcome measure Composite of death or adverse neurodevelopmental outcome at 2 years corrected age. Results Six babies born after 35 +6 weeks were excluded. At 2 years corrected age, outcome data were not available for a further 52 children, leaving 218 for analysis (115 deferred clamping, 103 immediate clamping). Overall, 24/115 (21%) children allocated deferred clamping died or had an adverse neurodevelopmental outcome compared with 35/103 (34%) allocated immediate clamping; risk ratio (RR) 0.61 (95% CI 0.39 to 0.96); risk difference (RD) -13% (95% CI -25% to -1%). Multiple imputation for missing data gave an RR 0.69 (95% CI 0.44 to 1.09) and RD -9% (95% CI -21% to 2%). Conclusions Deferred clamping and immediate neonatal care with cord intact may reduce the risk of death or adverse neurodevelopmental outcome at 2 years of age for children born very premature. Confirmation in larger studies is needed to determine the real benefits and harms. Trial registration number ISRCTN21456601.</p
When an external pilot is successful, should it be possible to transform it into an internal pilot by continuing recruitment into the full trial is ready? A case study of the cord pilot trial
No full textBackground: the Cord Pilot Trial recruited for one year at 8 sites to assess feasibility of a definitive UK trial, comparing timing of cord clamping for very preterm births. This was a complex study, funded as part of an NIHR programme for applied research. This paper will present and discuss our experience of trying to transform an external pilot into an internal pilot.Methods: at one year, recruitment was above target and other pre-specified feasibility criteria had been met. The TSC advised that recruitment should continue whilst funding for the full trial was sought, to maintain momentum, avoid loss of equipoise, and maximise efficiency. This was strongly supported by sites, endorsed by the DMC, and agreed with funder and sponsor.Results: a pathway for submission to NIHR HTA was agreed, as the usual research led call would require pilot sites to continue for 18 months. In view of the timescales, full trial preparation continued in parallel with grant submission. The full stage application was rejected, and the pilot trial therefore closed. A closure plan was agreed with sponsor and TSC, to allow sites to either close immediately, or to randomise women who had given consent if they remained eligible. Recruitment and compliance were maintained during phase 2.Conclusions: when an external pilot trial is successful, transforming it into an internal pilot by continuing into the full trial may maximise efficiency and value for money, but is a challenge to achieve
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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