125,495 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Small ribosomal subunits associate with nuclear myosin and actin in transit to the nuclear pores.
No full textWe have followed at high resolution theribosomal protein S6 entering the nucleus of HeLacells, stopping in some (not all) interchromatin granulesclusters and reaching, via Cajal bodies, the nucleolus.There, S6 is assembled with other proteins andrRNA into small ribosomal subunit (SSU), released inthe nucleoplasm, and exported through the nuclearpores. We show for the first time the spatial associationof nuclear myosin I (NMI) and actin with the SSUalready at the nucleolar periphery to the nuclear pore.A blockade of NMI or actin induces an upstreamaccumulation of the S6 protein en route to the nucleolus,and a temperature lower than normal influencesRNA export. Our data strongly suggest a functionalrelationship of SSU with NMI and actin. In our hypothesis,an active, myosin-driven movement of the smallribosomal subunit can be responsible for the exportof 10% of SSUs. This hypothesis is supported byultrastructural, immunofluorescence, and biochemicalanalyses. The currently accepted model for the subunitrelease suggests a diffusive, temperature-independentmechanism. However, the advantage of the doublemechanism would assure that the movement of a partof the subunits could be modulated, increased, ordecreased according to the needs of the cell at a specificmoment in the cell cycle.—Cisterna, B., Necchi, D.,Prosperi, E., Biggiogera, M. Small ribosomal subunitsassociate with nuclear myosin and actin in transit to thenuclear pores
Ultrastructural features of skeletal muscle in adult and aging Ts65Dn mice, a murine model of Down syndrome.
No full textPatients with Down syndrome (DS) suffer from muscle hypotonia and an altered motor coordination whose basic mechanisms are still largely unknown. Interestingly, they show muscle weakness like healthy aged subjects, suggesting possible similarity with sarcopenia: to test this hypothesis, the Ts65Dn mouse, a suitable animal model of DS, was employed. The fine structure of skeletal fibres of the quadriceps femoris muscle was analysed in adult (12 months) and aging (19 months) animals and their age-matched euploid controls by combining morphometry and immunocytochemistry at transmission electron microscopy. Results demonstrated structural alterations of mitochondria and myonuclei reminiscent of those observed in age-related sarcopenia, supporting the hypothesis that trisomy leads to an early aging of skeletal muscle consistent with the multi-systemic premature aging typical of DS
Transcription and splicing in the testis of mice fed on a genetically modified-soybean diet
No full textTranscription and splicing has been studied in the testis of mice fed on a genetically modified-soybean die
Ultrastructural and immunocytochemical study of skeletal muscles in a murine model of Down syndrome
No full textDown syndrome (DS) is a genetically-based disease which, in humans, affects about 1 over 700 newborns and is due to the presence of all or part of an extra chromosome 21. Among their several pathological traits, DS subjects suffer from an altered motor coordination but, although these difficulties in motility represent a serious problem in daily life, scarce data exist in the literature on skeletal muscles in DS. This is likely due to the obvious difficulties in obtaining bioptic material from patients with DS; however, this limitation may be partly overcome using suitable animal models. The Ts65Dn mouse bearing a trisomy for a segment of chromosome 16 (i.e. the homologue of human chromosome 21) is the most extensively studied murine model of DS since displays a remarkable number of phenotypic traits expressed in the human condition, including motor dysfunctions. By combining morphometry and immunocytochemistry at transmission electron microscopy, we examined the fine structure of skeletal myofibres, with particular attention to myonuclei, in adult and late adult Ts65Dn mice and their age-matched euploid controls, with the aim to evaluate the combined effect of DS and age on skeletal muscle. Our observations demonstrated in Ts65Dn mice an irregular arrangement of myofibrils and structural alterations of mitochondria, which often occurred in large clusters instead of being lined between myofibrils. In addition, myonuclei showed morphological modifications and changes in the amount of factors involved in RNA processing
"Entrada a la cisterna del conventual de Mérida"
No full text1 positivo en b/n 100x145 mmSignatura antigua R.395Entrada a la cisterna del conventual de MéridaUnidad documenta
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