1,720,997 research outputs found
Utilizzo dei fibroblasti in coltura nella diagnostica biochimica delle malattie da accumulo lisosomale
No full textChange of ganglioside accessibility at the plasma membrane surface of cultured neurons, following Protein Kinase C activation
No full textWhile the mechanism of signal transduction across the plasma membrane from the exo- to the endoplasmic side has been extensively investigated, the possible return of messages back to the outer layer is less known. We studied the effect of protein kinase C activation on the ganglioside accessibility at the exoplasmic face of intact rat cerebellar granule cells in culture, using the enzyme sialidase as the probing molecule. Under the experimental conditions (1 milliunit/mL enzyme, 2 min incubation at 37 degrees C), only GT1b and GD1a gangliosides were partially affected by the enzyme (28.6 and 25.7% hydrolysis, respectively). After cell treatment with phorbol 12-myristate 13-acetate, inducing protein kinase C activation, GT1b and GD1a ganglioside susceptibility to sialidase was strongly decreased (8.6 and 15.9% hydrolysis, respectively). A reduction of ganglioside hydrolysis was also observed when protein kinase C activation was induced by cell treatment for 15 min with 100 mu M glutamate. On the contrary, accessibility did not vary when protein kinase C translocation was not effective (either in the absence of Ca2+ in the medium or using 1 mu M glutamate) or when the kinase activity was inhibited by staurosporine. These data suggest that following PKC activation, a key step of inbound transmembrane signaling, cell may dispatch outbound messages to the plasma membrane outer layer, changing the selective recognition and crypticity of glycolipids at the cell surface, possibly through a modulation of their segregation state
SPECIFIC GANGLIOSIDE CELL PROTEIN INTERACTIONS - A STUDY PERFORMED WITH GM1 GANGLIOSIDE DERIVATIVE CONTAINING PHOTOACTIVABLE AZIDE AND RAT CEREBELLAR GRANULE CELLS IN CULTURE
No full textThe incubation of cultured rat cerebellar granule cells with a photoreactive derivative of radiolabeled GM1 ganglioside, [H-3]GM1(N3), followed by illumination, led to the specific association of ganglioside to cell proteins. After 30 min of incubation only a few out of the cell proteins became radiolabeled. Two of these, at apparent molecular weights of 95 and 112 kDa, are interacting with the portion of associated ganglioside that is released by trypsin treatment; others, in the region between 31 and 44 kDa, are probably bound to molecules of ganglioside inserted into the outer membrane layer, thus showing that the ganglioside association to the cell surface is a selective phenomenon, involving specific proteins. Increasing the incubation time up to 24 h resulted in a larger number of radiolabeled proteins, probably as a consequence of the internalization and metabolic processing of administered [H-3]GM1(N3). In fact, photoreactive and radioactive metabolic derivatives of [H-3]GM1(N3) can also interact with a number of proteins. After 24 h incubation, some radioactivity was also associated to cytosolic proteins. Again in this case the interaction with proteins seems to be a specific process involving only a few out of the total cytosolic proteins
Lipid domains in the membrane : thermotropic properties of sphingomyelin vesicles containing GM1 ganglioside and cholesterol
No full textThe thermotropic behavior of palmitoylsphingomyelin vesicles containing GM1 ganglioside and cholesterol has been investigated by high-sensitivity differential scanning calorimetry. The thermograms exhibited by binary palmitoylsphingomyelin/GM1 mixtures are resolvable into two components. The relative contribution of the minor component, undetectable in the absence of ganglioside, to the total enthalpy and its transition temperature (>40 degrees C) increase with the concentration of the glycolipid embedded in the vesicles. These data suggest the occurrence of lateral phase separation and that more ordered, higher melting GM1 ganglioside-enriched domains are present within the sphingomyelin bilayer. Studies on binary sphingomyelin/cholesterol mixtures confirmed the known tendency of the sterol to decrease the total enthalpy of sphingomyelin, forming cholesterol-enriched domains. The thermograms exhibited by ternary sphingomyelin/ganglioside/cholesterol mixtures in variable proportions (up to 20% molar GM1 or Chol) displayed, on increasing the content of either the sterol or the ganglioside, features addressable to sphingomyelin/cholesterol (peaks centered at temperature 140 degrees C, decrease of enthalpy) or to sphingomyelin/GM1 mixtures (peaks centered at a temperature >40 degrees C), respectively. This trend was confirmed by deconvolution analysis, showing that the thermograms are resolvable into components addressable to GM1-enriched and to cholesterol-enriched domains. Taken all together, the results shout that the architectural features of sphingomyelin bilayers are strongly dependent on the presence of GM1 ganglioside and cholesterol, whose presence is leading to the formation of separate, GM1-enriched and cholesterol-enriched distinct domains. Ganglioside-sphingomyelin and sphingomyelin-cholesterol, together with mutual ganglioside-ganglioside, interactions could contribute to maintain a network of bonds extending to proteins, forming specialized membrane domains, such as caveolae, or others, whose experimental clues are the glycolipid-enriched detergent-insoluble fractions that can be isolated from cell membranes
PATTERNS OF ENDOGENOUS GANGLIOSIDES AND METABOLIC PROCESSING OF EXOGENOUS GANGLIOSIDES IN CEREBELLAR GRANULE CELLS DURING DIFFERENTIATION IN CULTURE
No full textThe qualitative and quantitative pattern of endogenous gangliosides and the routes of metabolic processing of exogenous GM1, H-3 labeled in the sphingosine moiety (Sph-H-3 GM1) were studied in cerebellar granule cells during differentiation in vitro. During the first 7-8 days in culture the ganglioside content markedly increased, and the qualitative pattern showed, in percentage terms, a drastic decrease of GD3 and a marked increase of GD2, O-Ac-GT1b, O-Ac-GQ1b and GQ1b. After pulse with (Sph-H-3) GM1, at all the investigated days in culture, different radiolabelled lipids were formed indicating that taken up exogenous GM1 was degraded and that its catabolic fragments, and partly GM1 itself, were used for biosynthetic purposes; moreover radioactive water was measured in the culture medium during chase indicating that labelled sphingosine underwent also degradation. The uptake of exogenous GM1 and the extent of its metabolic processing per cell unit increased during differentiation: a) GM2 was the major metabolic product and was relatively more abundant at 2 than 7 days in culture; b) the percentage of metabolites of biosynthetic origin over total metabolites increased during differentiation, especially at the short pulse times; c) among the metabolities of anabolic origin sphingomyelin equalled gangliosides at 2 days, whereas it was largely overcome by gangliosides at 7 days in culture; d) at 4 and 7 days in culture a radioactive substance, not yet identified, was present, whereas no trace of it was found at 2 days. In conclusion, cerebellar granule cells in culture feature a different pattern of endogenous gangliosides and display different ability to metabolically process exogenous GM1 ganglioside in the undifferentiated and fully differentiated stage
Ganglioside lateralization in the brain of female rats
No full textThe ganglioside composition of the cerebral hemispheres of young and adult rats of either sex has been herein assessed for the first time, In females, the total ganglioside content at any age, the content of GM1, GD1a, and GD1b at 8 days, and the content of GM1, GD1b, GT1b, and GQ1b at 60 days were higher in the right than in the left hemisphere, In males, no difference was observed, Concerning the ceramide moiety, a difference was displayed by C18:1 long-chain base in GD1a, whose proportion was-higher in the left than in the right hemisphere of females aged 8 days, The comparison between homolateral hemispheres of rats of different sex revealed several differences, On average, in 8-day-old animals, the content of gangliosides was higher in females than in males, At 60 days the amount of gangliosides was on average lower in females than in males, even if with some exception, The data obtained with the current investigation show the existence of a ganglioside lateralization in rat brain, exclusively in females, and almost entirely at charge of the oligosaccharide portion, Moreover, age dependent changes of ganglioside pattern and content show a dependence on brain lateralizatio
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
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