1,720,957 research outputs found
Egg-matrix for large-scale single-step affinity purification of plant lectins with different carbohydrate specificities
No full textHen eggs represent an easily available and inexpensive source of glycoproteins expressing a variety of sugars. Egg glycoproteins
might therefore be exploited to purify by affinity chromatography carbohydrate-binding proteins (lectins) with different specificities.
A method to generate an affinity matrix from hen eggs is described. The matrix was assayed for its ability to purify in a single step
biologically active phytohemagglutinin, wheat germ agglutinin, lentil lectin, and peanut agglutinin. Milligrams of purified lectins per
gram of matrix was obtained, with the only exception of peanut agglutinin that was not efficiently retained into the affinity column.
Hen egg chromatography is a relatively simple, fast, and reproducible method to purify high amount of plant lectins
Active soybean lectin in foods: quantitative determination by ELISA using immobilised asialofetuin
No full textA recently described immunoenzymatic method for the quantitative determination of biologically active lectins in unknown
samples has been adapted to measure the concentration of active soybean lectin (SBA) in foodstuffs. The method was developed by
using purified SBA to build up reference standard curves and to determine the specificity and the sensitivity of the assay. Detectable
amounts of soybean lectin were found in soy-based edible products such as hamburger, milk and sprouts and they have been
compared to those determined in standard hemagglutination tests. Particular attention has been given to SBA quantitation in soy
sprouts as a function of germination time. SBA was not degraded during germination although the hamagglutination activity of
sprout extracts rapidly decreased. SBA expression was modulated during the first 10 days of germination, a time period spanning
that used to produce soy-sprouts for alimentary purposes
Temperature-dependent decay of wheat germ agglutinin activity and its implications for food processing and analysis
No full textA recently-described immunoenzymatic (ELISA) method for the quantitative determination of biologically-active wheat germ
agglutinin (WGA) in unknown samples has been applied to measure the concentration of active WGA in raw and cooked wheatderived
foodstuffs. The method exploits the binding specificity of WGA to ovalbumin as a first step followed by identification of
bound lectin with polyclonal antibodies. Purified WGA was used to obtain calibration curves. Detectable amounts of WGA were
found in raw foodstuffs and wheat flours, whilst variable amounts of agglutinin were found in wholemeal pasta probably as a
consequence of thermal inactivation during food processing. The thermal gradient gel electrophoresis (TGGE) technique was
therefore applied to analyse the thermal stability of WGA. The biological activity of WGA decreased as a function of heating
temperatures and time of exposure to thermal treatment in an S-shaped fashion with an inflection point around 65 C. As a
consequence, WGA might represent a biochemical ‘‘indicator’’ allowing one to determine the thermal treatment undergone by
wheat-derived foods during processing
Studies on the joint cytotoxicity of Wheat Germ Agglutinin and monensin
No full textWheat Germ Agglutinin (WGA) cytotoxicity has been studied using two human leukemia cell lines, Molt3 and K562, and human
peripheral blood mononuclear cells (PBMC). In spite of similar binding at the cell surface, WGA was found to promote cell death to
a different extent in Molt3, K562 and PBMC and to induce different death events leading to apoptosis in Molt3 and either apoptosis
and necrosis in K562 cells and PBMC. In Molt3 but not in K562 cells, WGA cytotoxicity could be potentiated 66–200 fold by 50 nM
monensin, a carboxylic ionophore that perturbs the intracellular trafficking of endocytosed molecules. Synergism between the
cytotoxic activities of WGA and monensin was demonstrated in Molt3 cells by comparing non toxic, or slightly toxic, doses of
WGA and monensin alone or in combination.
These results show that the cytotoxic effect of WGA is dependent on internalisation events which may differ among the cell lines
used. WGA and monensin can enter the human diet being a component of wheat germ and an antibiotic used for zootechnic reasons
in the bioindustry, respectively. These data reveal the synergistic effect between two dietary molecules, otherwise per se toxic at much
higher concentrations, with possible implications for human and animal health
Effects of dietary wheat germ deprivation on the immune system in Wistar rats: a pilot study
No full textBioactive molecules that can gain access to body tissues through the gastrointestinal tract may interact with immune
regulatory circuits and effector functions. Among these are plant lectins, such as wheat germ (WG) agglutinin, which constitute
common components of the human diet and target the immune system on a daily basis. Dietary bioactive molecules might be
considered as immunomodulatory signals. To investigate the possible effects on the immune system of the long-term absence of
such signals, two groups of rats were fed on a diet containing or deprived of WG. The WG-deprived diet induced a state of
functional unresponsiveness in lymphocytes from primary and secondary lymphoid organs, as evaluated by in vitro stimulation
with T cell mitogen phytohemoagglutinin (PHA) and B cell mitogen lypopolysaccarides (LPS). The unresponsive state of the
immune cells could be reversed by injection of antigen emulsified in oil with inactivated mycobacteria (complete Freund’s
adjuvant, CFA) Dietary signals can thus interact with the immune system possibly influencing its shaping during ontogenesis
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
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