1,720,983 research outputs found
Sodium, interstitium, lymphatics, and hypertension - A tale of hydraulics
Full text linkBlood pressure is regulated by vascular resistance and intravascular volume. However, exchanges of electrolytes and water between intra and extracellular spaces and filtration of fluid and solutes in the capillary beds blur the separation between intravascular and interstitial compartments. Contemporary paradigms of microvascular exchange posit filtration of fluids and solutes along the whole capillary bed and a prominent role of lymphatic vessels, rather than its venous end, for their reabsorption. In the last decade, these concepts have stimulated greater interest in and better understanding of the lymphatic system as one of the master regulators of interstitial volume homeostasis. Here, we describe the anatomy and function of the lymphatic system and focus on its plasticity in relation to the accumulation of interstitial sodium in hypertension. The pathophysiological relevance of the lymphatic system is exemplified in the kidneys, which are crucially involved in the control of blood pressure, but also hypertension-mediated cardiac damage. Preclinical modulation of the lymphatic reserve for tissue drainage has demonstrated promise and also generated conflicting results thus far. A better understanding of the hydraulic element of hypertension and the role of lymphatics in maintaining fluid balance can open new approaches to prevent and treat hypertension and its consequences, such as heart failure
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
Role of Lymphatics in Renal Sodium Handling: Implications for Hypertension
Full text linkHypertension is the leading risk factor for cardiovascular diseases and strokes [1]. A portion of these patients exhibit SSHTN with high cardiovascular risk and are more difficult to pharmacologically control. The etiology of chronic hypertension includes renal immune cell accumulation and sodium retention. The lymphatic system maintains interstitial homeostasis and an expansion of lymphatic vessels is necessary to resolve inflammation. We have previously demonstrated that ecifically increasing renal lymphatic density prevents HTN in mice [2]. These mice, KidVD+, undergo kidney specific lymphangiogenesis through the overexpression of VEGF-D [3]. The HTN prevention in the KidVD mice is attributed to a common role for lymphatics: a reduction in renal immune cell numbers. We have recently identified that these mice with expanded renal lymphatics demonstrate increased sodium excretion [2]. The aim of this study is to identify the mechanism by which enhancement of renal lymphatics correlates with urinary Na+ excretion, and sensitivity to hypertensive stimuli. To improve the diagnostics and increase treatment efficacy, the mechanism of lymphatic expansion and Na+ retention within the kidney lymphatics may thus prove to be a potential therapeutic target for patients afflicted with SSHTN
Role of Lymphatic Endothelial Cell Caveolin-1 in Macromolecule Transport
Full text linkThe lymphatic system is a network of capillaries, vessels, and nodes that span the length of our entire body. Lymphatic capillaries uptake immune cells, fluid, and macromolecules from the interstitium and transport this lymph through vessels to lymph nodes for immune regulation and tissue fluid balance ultimately returning it to the blood vasculature. How fluid and solutes enter lymphatic capillaries has long been viewed as a passive paracellular mechanism in which macromolecules and fluid enter through valve-like openings in the loosely overlapped cell-cell junctions of lymphatic capillaries. Recent studies have demonstrated that lymphatic endothelial cells (LECs) may utilize pore formation with membrane caveolae as an active transcellular pathway to uptake macromolecules from the interstitium. Caveolin-1 is a protein required for the formation of caveolae and transcellular transport processes. We hypothesized that LECs utilize active caveolae to regulate lymphatic solute transport. To allow us to test our hypothesis, methods for primary LEC isolations and lymphatic vessel isolations had to be developed, established, and successfully tested. To test our hypothesis, we utilized a transgenic mouse carrying loxP sites flanking exon 3 of the Cav-1 gene. When crossed with mice expressing the enzyme Cre recombinase specifically in LECs, we generated mice lacking caveolin-1 in lymphatic endothelium, and, therefore, LECs incapable of forming caveolae. We utilized this mouse to identify changes in lymphatic uptake and transport of macromolecules over a range of sizes in vivo. We isolated and perfused lymphatic vessels from these mice to quantify changes in vessel permeability as a function of solute size. In vitro, LECs from these mice, were cultured into monolayers to demonstrate active barrier function to macromolecules. Our data thus identify mechanisms of lymphatic transport that actively regulate solute transport with implications in antigen transport and immune maintenance
Impact of Renal of Lymphatic Hyperplasia on Blood Pressure Regulation in Male Mice
Full text linkChronic high blood pressure, or hypertension, is identified as a risk factor for heart disease, stroke, and chronic kidney disease. The primary cause of most hypertension is increased peripheral vascular resistance that is controlled, in large part, by the kidney���s water handling. In the kidney, specific immune cell subsets and overall renal inflammation have both been identified as drivers of hypertension in preclinical models. Lymphatic vessels serve as a route of both fluid and immune cell clearance and their expansion, lymphangiogenesis, is necessary for the resolution of tissue inflammation. We hypothesized that by increasing renal lymphangiogenesis, renal inflammation would be reduced and blood pressure would be normalized during salt-sensitive hypertension. To investigate the role of renal immune cell trafficking in instances of blood pressure challenge, we employed a murine model of inducible renal lymphatic expansion. Mice expressing a lymphatic growth factor, vascular endothelial growth factor (VEGF)-D, under the control of a TRE-promoter were crossed with mice expressing a Kidney Specific Protein-regulated transactivator (rtTA). Upon administration of doxycycline, the rtTA-dox complex binds to the TRE promoter region, causing transcription of VEGF-D only in renal tubular epithelial cells. The resultant kidney-specific VEGF-D overexpression caused expansion of the existing renal lymphatic network in addition to generating de novo lymphangiogenesis in the cortex of ���Kid-VD��� mice. We then utilized the Kid-VD mouse model during an established rodent hypertension regimen of nitric oxide inhibition and high salt diet loading to identify the impact ��� through weekly blood pressure measures - and mechanism ��� by cellular, protein, and RNA analysis ��� of expanded renal lymphatics on blood pressure regulation. Lymphatic circulation may thus provide a new target for the treatment of chronic hypertension and its associated co-morbidities
- …
