1,721,655 research outputs found
Comparison of retinal nerve fibre layers between 11778 and 14484 mutations in Leber's hereditary optic neuropathy
No full textPurposeTo compare retinal nerve fibre layer (RNFL) thickness changes between mitochondrial DNA (mtDNA) mutations at nucleotides 11778 and 14484 in Leber's hereditary optic neuropathy (LHON) using optical coherence tomography (OCT).MethodsThirty LHON patients with mtDNA mutations at nucleotides 11778 or 14484 underwent full ophthalmologic examinations including Stratus OCT. Patients were divided into four groups according to disease duration (early6 months) and mtDNA mutation type (11778 and 14484), and their RNFL thicknesses were compared.ResultsAverage RNFL thickness in the early 11778 group was significantly greater than that in the early 14484 group (P=0.04). Average RNFL thickness in the late 11778 group was significantly less than that in the late 14484 group (P=0.02). Quadrant analysis of the superior, nasal, and inferior quadrant RNFL thickness in the late 11778 group showed more severe RNFL atrophy than in the late 14484 group (P=0.023, 0.015, 0.003, respectively).ConclusionsRNFL thickness was significantly increased in the early stage and decreased in the late stage in the 11778 group than in the 14484 group.Eye advance online publication, 27 February 2009; doi:10.1038/eye.2009.36.This work was supported by the Basic Research Program
of the Korean Science & Engineering Foundation
(Grant no. R01-2005-000-10875-0)
Evidence of active demyelination in a man with Leber's hereditary optic neuropathy mtDNA 14484 genotype
No full textLeber's hereditary optic neuropathy (LHON) is an inherited form of bilateral optic atrophy. The predisposing genotype is a mutation in mitochrondrial DNA. Three primary mutations have been classified to date (11778, 3460, 14484). A multiple sclerosis-like illness has been described in some patients with LHON. The majority of these reports have been in patients with the 11778 mutation, although focal peripheral neurological signs and magnetic resonance imaging (MRI) changes consistent with demyelination have been documented in patients with the 3460 and 14484 mutations. The case report below describes a man with MRI and cerebrospinal fluid (CSF) evidence of multiple sclerosis and the LHON mitochrondrial DNA mutation at base pair 14484. This case report is only the third of a patient with the mtDNA 14484 mutation and evidence of multiple sclerosis and the first with any mutation that shows advancing radiological disease. Recent case reports and theories of aetiology are reviewed.</p
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
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
Haplotype and phylogenetic analyses suggest that one European-specific mtDNA background plays a role in the expression of Leber hereditary optic neuropathy by increasing the penetrance of the primary mutations 11778 and 14484
No full textmtDNAs from 37 Italian subjects affected by Leber hereditary optic neuropathy (LHON) (28 were 11778 positive, 7 were 3460 positive, and 2 were 14484 positive) and from 99 Italian controls were screened for most of the mutations that currently are associated with LHON. High-resolution restriction-endonuclease analysis also was performed on all subjects, in order to define the phylogenetic relationships between the mtDNA haplotypes and the LHON mutations observed in patients and in controls. This analysis shows that the putative secondary/intermediate LHON mutations 4216, 4917, 13708, 15257, and 15812 are ancient polymorphisms, are associated in specific combinations, and define two common Caucasoid-specific haplotype groupings (haplogroups J and T). On the contrary, the same analysis shows that the primary mutations 11778, 3460, and 14484 are recent and are due to multiple mutational events. However, phylogenetic analysis also reveals a different evolutionary pattern for the three primary mutations. The 3460 mutations are distributed randomly along the phylogenetic trees, without any preferential association with the nine haplogroups (H, I, J, K, T, U, V, W, and X) that characterize European populations, whereas the 11778 and 14484 mutations show a strong preferential association with haplogroup J. This finding suggests that one ancient combination of haplogroup J-specific mutations increases both the penetrance of the two primary mutations 11778 and 14484 and the risk of disease expression
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