1,720,983 research outputs found
Assessment of the conformational features of Vasoactive Intestinal Peptide in solution by limited proteolysis experiments
No full textThe structural features of vasoactive intestinal peptide (VIP) and of its Gln16-diaminopropane derivative (VIP-DAP) in solution were investigated by limited proteolysis experiments with trypsin and thermolysin. The proteolysis of the native peptide by both proteinases takes place near the residues in positions 12 and 21/22, suggesting that these amino acids are embedded in segments more flexible than the rest of the molecule. VIP-DAP appears to be more resistant to the proteolytic attack of trypsin, indicating that the derivatization in position 16 is able to stabilize the structure of the peptide. Moreover, the analysis of the mass spectra of the proteolytic mixtures supports the evidence that the derivatization is also able to protect Met17 against oxidation. From these data it can be concluded that VIP in solution under physiological conditions is characterized by the presence of segments with secondary structure, linked together by ‘‘hinge’’ regions that confer flexibility to the peptide, whereas VIP-DAP is embedded in a more rigid conformation, more suitable to receptor interaction
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
Different effect of a period of caloric restriction following treatment with a normal lipid or hyperlipidic diet in the experimental animal model: focus on mitochondrial dynamics proteins in the liver.
No full textIntroduction: An excess of the daily caloric intake facilitates accumulations of fat that leads to the development of obesity. Caloric restriction is the strategy used to restore body composition to optimal levels. Likewise, a period of hypo-nutrition following a balanced diet promotes nutritional deficiencies. Both conditions above described induce changes in the cellular metabolism to which the mitochondria actively participate. These organelles are very dynamic and undergo against continuous fusion and fission processes in correlation with their functionality.
Objectives: In this study were monitored the effects of a caloric restriction period, following treatments with normal or hyperlipidic diet, on mitochondrial dynamics in rat liver. Therefore, 4 experimental groups were constituted: N (control diet); HFD high fat diet); Nr (N + restriction); HFDr (HFD + restriction). Attention was focused on the main mitochondrial dynamics’ proteins, monitored by western blot: MFN2 (Mitofusin 2) and OPA1 (Optic atrophy type 1) as fusion markers; DRP1 (Dynamin-related protein 1) as a fission marker.
Results: The data show reduction of MFN2 and increase of DRP1 in the Nr group compared to N with variation of the high and low isoforms of OPA1, suggesting increase of the mitochondrial fission. In contrast, both MFN2 and DRP1 increase in the HFDr group compared to HFD. In this case, the data seem to suggest a beneficial effect of the restriction with a probable induction of the mitochondrial biogenesis. This mechanism, in fact, could make more the utilization of lipids mobilized by deposits in consequence to caloric restriction.
Conclusions: In conclusion, we can assume that a reduced caloric intake generates reorganization of the mitochondrial liver network by acting differently on the basis of the nutritional conditions prior to the hypocaloric regimen
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
Celiac autoantibodies to tissue transglutaminase modulate alpha-gliadin peptide 31-43 uptake by epithelial cells.
No full textAppropriate 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
The N-terminal 1-16 peptide derived in vivo from protein seminal vesicle protein IV modulates alpha-thrombin activity: potential clinical implications
No full textAnti-tissue transglutaminase antibodies activate intracellular tissue transglutaminase by modulating cytosolic Ca(2+) homeostasis
No full textAnti-tissue transglutaminase (tTG) antibodies are specifically produced in the small-intestinal mucosa of celiac disease (CD) patients. It is now recognized that these antibodies, acting on cell-surface tTG, may play an active role in CD pathogenesis triggering an intracellular response via the activation of different signal transduction pathways. In this study, we report that anti-tTG antibodies, both commercial and from a CD patient, induce a rapid Ca(2+) mobilization from intracellular stores in Caco-2 cells. We characterized the mechanism of Ca(2+) release using thapsigargin and carbonylcyanide-p-trifluoromethoxyphenylhydrazone, which are able to deplete specifically endoplasmic reticulum and mitochondria of Ca(2+), respectively. Our data highlight that both pathways of calcium release were involved, thus indicating that the spectrum of cellular responses downstream can be very wide. In addition, we demonstrate that the increased Ca(2+) level in the cells evoked by anti-tTG antibodies was sufficient to activate tTG, which is normally present as a latent protein due to the presence of low Ca(2+) and to the inhibitory effect of GTP/GDP. Herein, we discuss the importance of intracellular tTG activation as central in the context of CD pathogenesis
Gliadin Peptides Induce Tissue Transglutaminase Activation and ER-Stress through Ca(2+) Mobilization in Caco-2 Cells
No full textBACKGROUND:
Celiac disease (CD) is an intestinal inflammatory condition that develops in genetically susceptible individuals after exposure to dietary wheat gliadin. The role of post-translational modifications of gliadin catalyzed by tissue transglutaminase (tTG) seems to play a crucial role in CD. However, it remains to be established how and where tTG is activated in vivo. We have investigated whether gliadin peptides modulate intracellular Ca(2+) homeostasis and tTG activity.
METHODS/PRINCIPAL FINDINGS:
We studied Ca(2+) homeostasis in Caco-2 cells by single cell microfluorimetry. Under our conditions, A-gliadin peptides 31-43 and 57-68 rapidly mobilized Ca(2+) from intracellular stores. Specifically, peptide 31-43 mobilized Ca(2+) from the endoplasmic reticulum (ER) and mitochondria, whereas peptide 57-68 mobilized Ca(2+) only from mitochondria. We also found that gliadin peptide-induced Ca(2+) mobilization activates the enzymatic function of intracellular tTG as revealed by in situ tTG activity using the tTG substrate pentylamine-biotin. Moreover, we demonstrate that peptide 31-43, but not peptide 57-68, induces an increase of tTG expression. Finally, we monitored the expression of glucose-regulated protein-78 and of CCAAT/enhancer binding protein-homologous protein, which are two biochemical markers of ER-stress, by real-time RT-PCR and western blot. We found that chronic administration of peptide 31-43, but not of peptide 57-68, induces the expression of both genes.
CONCLUSIONS:
By inducing Ca(2+) mobilization from the ER, peptide 31-43 could promote an ER-stress pathway that may be relevant in CD pathogenesis. Furthermore, peptides 31-43 and 57-68, by activating intracellular tTG, could alter inflammatory key regulators, and induce deamidation of immunogenic peptides and gliadin-tTG crosslinking in enterocytes and specialized antigen-presenting cells
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