1,720,967 research outputs found
A new multiphasic buffer system for benzyldimethyl-n-hexadecylammonium chloride polyacrylamide gel electrophoresis of proteins providin efficient stacking
No full textAcidic PAGE systems using cationic detergents such as benzyldimethyl-n-hexadecylammonium chloride (16-BAC) or CTAB have proven useful for the detection of methoxy esters sensitive to alkaline pH, resolving basic proteins such as histones and membrane proteins. However, the interesting phosphate-based system suffered from poor stacking, resulting in broadened bands and long running times. Therefore, a new 16-BAC PAGE system based on the theory of moving boundary electrophoresis with properties comparable to the classical SDS-PAGE system was designed. As a result a new multiphasic analytical 16-BAC PAGE system providing efficient stacking and significantly shorter running times is presented here. It is based on acetic acid and methoxyacetic acid as common ion constituents. This PAGE system takes advantage of the additional counterstacking, effect due to a cross boundary electrophoresis system resulting from the selected buffer constituents. Furthermore, the concentration of 16-BAC was optimized by determining its previously unknown CMC. Due to efficient focusing of the introduced tracking dye, methyl green, termination of electrophoresis can now be more easily followed as compared to the Schlieren line
Presynaptic alpha-synuclein aggregates, not Lewy bodies, cause neurodegeneration in dementia with Lewy bodies
No full textLewy bodies, the pathological hallmark of dementia with Lewy bodies (DLB), are large juxtanuclear inclusions of aggregated alpha-synuclein. However, the small number of cortical Lewy bodies relative to the total neuron count does not correlate with the extent of cognitive impairment. In contrast to dopaminergic neurons in Parkinson's disease, nerve cell loss is usually less prevalent in the cortex of DLB, suggesting a different mechanism of neurodegeneration. Because antibodies used for immunodetection per se do not generally differentiate the aggregated from the physiological and monomeric isoform of alpha-synuclein, we developed the paraffin-embedded tissue (PET) blot and the protein aggregate filtration (PAF) assay for the sensitive and selective detection of alpha-synuclein aggregates in tissue slides and brain homogenates, respectively. In contrast to common immunohistochemistry, the PET blot detected an enormous number of small alpha-synuclein aggregates, which, in contrast to the few Lewy bodies, may explain the cognitive impairment in DLB. Using the PAF assay, we demonstrate that the absolute majority of alpha-synuclein aggregates are located at presynaptic terminals, suggesting a severe pathological impact on synaptic function. Indeed, parallel to the massive presynaptic accumulation of alpha-synuclein aggregates, we observed significant synaptic pathology with almost complete loss of dendritic spines at the postsynaptic area. Our results provide strong evidence for a novel concept of neurodegeneration for DLB in which synaptic dysfunction is caused by presynaptic accumulation of alpha-synuclein aggregates. This concept may also be valid for Parkinson's disease
Selective detection, quantification, and subcellular location of α-synuclein aggregates with a protein aggregate filtration assay
No full textParkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy are caused by α-synuclein aggregates. At present, there is no good biochemical method defining α-synuclein aggregates formed in vivo versus oligomers as a means to investigate α-synuclein aggregation and its mechanisms of neurodegeneration. A simple method, therefore, for the selective and sensitive detection of α-synuclein aggregates suited for screening purposes would be useful. Since in contrast to prions a proper detection of α-synuclein aggregates by Western blot analysis is difficult, we developed a protein aggregate filtration (PAF) assay. It takes advantage of the inherent insolubility of aggregated α-synuclein using microfiltration to separate it from soluble isoforms. For the first time, this assay even makes quantitative comparisons possible. We describe how the PAF assay can be applied to human brain tissue and animal and cell culture models, as well as used as a screening method for the subcellular location of α-synuclein aggregates. Since it detects the pathological isoform instead of surrogate markers, the PAF assay may have also potential in diagnosis of PD and DLB
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
Modulation of L-type voltage-gated calcium channels by recombinant prion protein
No full textThe prion protein (PrPC) has a primary role in the pathogenesis of transmissible spongiform encephalopathies. Here we analysed in detail the effect of recombinant PrPC and N- and C-terminal fragments of PrPC on the whole-cell current amplitude through voltage-gated calcium channels (VGCCs) of cultured wild-type cerebellar granule cells. With the application of full-length recombinant PrPC (50-500 nm), a highly significant reduction of the whole-cell current amplitude was observed in a dose-dependent manner. Amplitude reduction was abolished when cells were pre-incubated with nifedipine, a specific blocker of voltage-gated L-type calcium channels. N-terminal PrP fragments also led to a dose-dependent reduction of the maximal current amplitude, whereas a C-terminal fragment did not affect the current amplitude. These data demonstrate that nanomolar concentrations of PrPC modulate L-type VGCCs in mouse cerebellar granule cells, an effect that is dependent upon the copper-binding amino-terminal domain of PrPC
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
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