1,720,961 research outputs found
Calcification mechanisms in native atherosclerotic arteries
No full textVascular Calcification, i.e., the ectopic accumulation of calcium phosphate salts in the vessel wall, is associated with atherosclerosis, aging, diabetes, and chronic kidney disease, which thusly contributes to increased cardiovascular morbidity and mortality. Previously considered to be a passive process, vascular calcification is now recognized as an active process similar to bone formation. However, the pathogenetic mechanisms involved in vascular calcification are particularly complex and remain inadequately understood, even though they impact significantly on patient prognosis as well as on the stenting placement and outcome of revascularization. Cellular, subcellular, genetic and molecular mechanisms have been proposed. Of particular importance is the role of the progenitor cells either resident in the vessel wall or circulating that are committed to an osteogenic program as well as transdifferentiation of vascular smooth-muscle cells. In addition, numerous evidences show that metastatic calcification is not as directly related to atherosclerosis as dystrophic is, indicating another mechanism of generation, involving additional metabolic pathways. A better understanding of the pathogenetic mechanisms corroborated with ultrastructural clues, as shown in the present review, will be essential for the development of new therapeutic strategies, in order to prevent and treat vascular calcification
Mechanisms of Arterial Calcification: The Role of Matrix Vesicles
No full textVascular calcification is related to vascular diseases, for example, atherosclerosis, and its comorbidities, such as diabetes and chronic kidney disease. In each condition, a distinctive histological pattern can be recognised that may influence technical choices, possible intra-operative complications, and procedure outcomes, no matter if the intervention is performed by open or endovascular means. This review considers the classification and initiating mechanisms of vascular calcification. Dystrophic and metastatic calcifications, Monckeberg's calcification, and genetic forms are firstly outlined, followed by their alleged initiation mechanisms; these include (a) ineffective macrophage efferocytosis; (b) ectopic osteogenesis driven by modified resident or circulating osteoprogenitors. As in physiological bio-mineralisation, active calcification starts with the deposition of cell derived matrix vesicles into the extracellular matrix. To substantiate this belief, an in depth ultra-structural documentation of hydroxyapatite crystal deposition on such vesicles is provided in an ex-vivo human vascular cell model. Revealing the vesicle composition and phenotype in normal and pathological vascular conditions will be essential for the development of new therapeutic strategies, in order to prevent and treat vascular calcification
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Considerations on the harvesting site and donor derivation for mesenchymal stem cells-based strategies for diabetes
No full textMesenchymal Stem Cells (MSCs) possess important characteristics that could be exploited in therapeutic strategies for Type 1 Diabetes (T1D) and for certain complications of Type 2 Diabetes (T2D). MSCs can inhibit autoimmune, alloimmune and inflammatory processes. Moreover, they can promote the function of endogenous and transplanted pancreatic islets. Furthermore, they can stimulate angiogenesis. MSC functions are largely mediated by their secretome, which includes growth factors, exosomes, and other extracellular vesicles. MSCs have shown a good safety profile in clinical trials. MSC-derived exosomes are emerging as an alternative to the transplantation of live MSCs. MSCs harvested from different anatomical locations (e.g. bone marrow, umbilical cord, placenta, adipose tissue, and pancreas) have shown differences in gene expression profiles and function. Data from clinical trials suggest that umbilical cord-derived MSCs could be superior to bone marrow-derived MSCs for the treatment of T1D. Autologous MSCs from diabetic patients may present abnormal functions. BM-MSCs from T1D patients exhibit gene expression differences that may impact in vivo function. BM-MSCs from T2D patients seem to be significantly impaired due to the T2D diabetic milieu. In this review, we highlight how the harvesting site and donor derivation can affect the efficacy of MSC-based treatments for T1D and T2D
Comparison of Quality of Life in Patients Undergoing Hemodialysis and Peritoneal Dialysis: a Systematic Review and Meta-Analysis.
Full text linkBACKGROUND/AIMS:
The increase in the survival rate of patients with chronic renal failure due to substitution treatment prompts an investigation of their quality of life (QoL), a key measure to evaluate the outcomes of chronic disease treatment. To determine whether hemodialysis or peritoneal dialysis provide a better QoL, a systematic meta-analysis was performed.
METHODS:
We searched through the database Cinahl, Medline, PubMed, Scopus and Proquest, including articles published from 2011 until June 2016. We selected articles that compared, through KDQOL-SF 1.3 or 36 questionnaires, QoL among patients undergoing hemodialysis and peritoneal dialysis. The data was collected using Excel Office, and t-test has been performed on independent samples to identify significant differences.
RESULTS:
Only some of the seven articles found significant differences between the two treatments. One of the studies showed a better QoL for peritoneal dialysis patients, while, on the contrary, two other studies support that the best QoL is in patients receiving hemodialysis. Another article displayed significant difference only for satisfaction in relation to care, better in patients on peritoneal dialysis, and for physical health, better in hemodialysis.
CONCLUSIONS:
The analysis has not led to a unanimous conclusion. Quantitative analysis showed that the only statistically significant difference between the QoL of patients on hemodialysis and peritoneal dialysis regards the effect of kidney disease, which happens to be better in patients undergoing peritoneal dialysis
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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