1,720,959 research outputs found
Identification and characterization of mature beta-hexosaminidases associated with human placenta lysosomal membrane
No full textHex (â-hexosaminidase) is a soluble glycohydrolase involved in glycoconjugate degradation in lysosomes, however its
localization has also been described in the cytosol and PM (plasma membrane). We previously demonstrated that
Hex associated with human fibroblast PM as the mature form, which is functionally active towards GM2 ganglioside.
In the present study, Hex was analysed in a lysosomal membrane-enriched fraction obtained by purification from
highly purified human placenta lysosomes. These results demonstrate the presence of mature Hex associated
with the lysosomal membrane and displaying, as observed for the PM-associated form, an acidic optimum pH.
When subjected to sodium carbonate extraction, the enzyme behaved as a peripheral membrane protein, whereas
Triton X-114 phase separation confirmed its partially hydrophilic nature, characteristics which are shared with the
PM-associated form of Hex. Moreover, two-dimensional electrophoresis indicated a slight difference in the pI of â-
subunits in the membrane and the soluble forms of the lysosomal Hex. These results reveal a new aspect of Hex
biology and suggest that a fully processed membrane-associated form of Hex is translocated from the lysosomal
membrane to the PM by an as yet unknown mechanism. We present a testable hypothesis that, at the cell surface,
Hex changes the composition of glycoconjugates that are known to be involved in intercellular communication and
signalling
Defective platelet beta-N-Acetyl hexosaminidase content and release in chronic myeloproliferative disorders
No full textBACKGROUND AND OBJECTIVES: Abnormalities of platelet function or structure are a hallmark of chronic myeloproliferative disorders (MPD). In vivo platelet activation with the release of alpha- and delta-granules in the circulation is one of the most frequently described alterations in MPD. Platelets contain and release upon activation also lysosomes, and in particular beta-N-acetylhexosaminidase (Hex). We have assessed whether the content and in vivo release of Hex of platelets from MPD patients is altered.
DESIGN AND METHODS: Twenty-three MPD patients were compared with 19 age- and sex-matched healthy controls. The activity of platelet beta-N-acetylhexosaminidase was measured in plasma, serum and in the capillary blood emerging from the skin wound inflicted for the measurement of the bleeding time. Lysosome integral membrane protein (LIMP or CD63), lysosome-associated membrane protein (LAMP-2 or CD107b) and P-selectin were evaluated by flow cytometry. Platelet aggregation in vitro and the release of beta-N-acetylhexosaminidase, ATP and beta-thromboglobulin were performed to study platelet reactivity.
RESULTS: Hex levels in plasma were significantly higher in MPD than in controls while the release of Hex in the bleeding time blood, i.e. at a localized site of in vivo platelet plug formation, was lower in MPD and the platelet content of Hex was reduced. These changes were accompanied by in vivo platelet activation. Finally, the isoenzymatic pattern of Hex was altered in platelets of MPD patients, with a reduced amount of the Hex A isoform as compared with controls.b
INTERPRETATIONS AND CONCLUSIONS: MPD patients present an altered platelet Hex content and release; prospective studies to assess whether altered platelet Hex is related to thrombotic/hemorrhagic complications and/or tissue fibrosis in MPD are warranted
Identification and characterization of a fully processed beta-hexosaminidase isoform associated to lysosomal membrane-52° Congresso SIB
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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
Expression of lysosomal proteases cathepsin D, B and L in fibroblasts from Alzheimer's disease patients
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