1,720,972 research outputs found
Angiotensin II-stimulated collagen production in cardiac fibroblasts is mediated by reactive oxygen species
No full textOBJECTIVE:
The aim of the present study was to determine whether inhibition of reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H] oxidase and of various superoxide generating systems could affect the collagen production, the mRNA and protein expression of collagen types I and III in control and angiotensin II-treated cardiac fibroblasts.
METHODS:
Cardiac fibroblasts from passage 2 from normal male adult rats were cultured to confluency and incubated in serum-free Dulbecco's modified Eagle's medium for 24 h. The cells were then preincubated with(out) the tested inhibitors for 1 h and then further incubated with(out) angiotensin II (1 micromol/l) for 24 h. Collagen production was measured spectrophotometrically with picrosirius red as dye and with [3H]proline incorporation; collagen type I and III content by enzyme-linked immunosorbent assay and collagen type I and III mRNA expression by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). NAD(P)H-dependent superoxide anion production was assayed as superoxide dismutase-inhibitable cytochrome c reduction. Intracellular formation of reactive oxygen species was assessed with 2',7'-dichlorofluorescein diacetate as fluorescent probe.
RESULTS:
Angiotensin II stimulated the collagen production, the collagen I and III content and mRNA expression in cardiac fibroblasts, and apocynin, a membrane NAD(P)H oxidase inhibitor, abolished this induction. Rotenone, allopurinol, indomethacin, nordihydroguiaretic acid, ketoconazole and nitro-L-arginine (inhibitors of mitochondrial NAD(P)H oxidase, xanthine oxidase, cyclooxygenase, lipoxygenase, cytochrome P450 oxygenase and nitric oxide synthase, respectively) did not affect the angiotensin II-induced collagen production. Angiotensin II increased the NAD(P)H-dependent superoxide anion production and the intracellular generation of reactive oxygen species in cardiac fibroblasts, and apocynin abrogated this rise.
CONCLUSIONS:
Our data show that in adult rat cardiac fibroblasts the membrane-associated NAD(P)H oxidase complex is the predominant source of superoxide anion and reactive oxygen species generation in angiotensin II-stimulated adult cardiac fibroblasts. Inhibition of this NAD(P)H oxidase complex with apocynin completely blocked the angiotensin II-stimulated collagen production, and collagen I and III protein and mRNA expression
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
Effects of angiotensin II and insulin on ERK1/2 activation in fibroblasts from hypertensive patients
No full textBACKGROUND:
Insulin resistance, a frequent finding in hypertensive patients, leads to accelerated cardiovascular damage. It has been suggested that a crosstalk between angiotensin II and insulin signaling pathways may provoke insulin resistance, and may contribute to the development of cardiovascular damage. To identify a common pathophysiologic pathway between metabolic disorders and cardiovascular remodeling, we investigated the effect of angiotensin II and insulin on extracellular signal regulated kinases 1 and 2 (ERK1/2), isoforms of mitogen-activated protein kinases (MAPK) involved in cellular proliferation and extracellular matrix deposition.
METHODS:
Skin fibroblasts from normotensive subjects, insulin sensitive hypertensive subjects, and insulin resistant hypertensive subjects were cultured and used after four passages. The ERK1/2 expression and phosphorylation were measured by Western blot using specific antibodies, respectively anti-ERK1/2 and anti-pERK1/2. Expression of AT1 receptor for angiotensin II was determined by reverse transcriptase-polymerase chain reaction in real time.
RESULTS:
The ERK1/2 were similarly expressed in skin fibroblasts from all groups; ERK1/2 phosporylation evoked by angiotensin II was significantly higher in fibroblasts from hypertensive patients in comparison to normotensive subjects, but the increase was observed only in insulin resistant hypertensive subjects. The effect of insulin on ERK1/2 phosphorylation was not significantly different in the three groups. Treatment with the combination of insulin and angiotensin II increased ERK1/2 phosphorylation to a greater extent in comparison to the single agonists in normotensive subjects and in insulin sensitive but not in insulin resistant hypertensive subjects.
CONCLUSIONS:
Angiotensin II stimulated ERK1/2 activation is increased in insulin resistant hypertensive subjects, and it may play a role in the pathogenesis of insulin resistance and accelerated cardiovascular damage
RGS2 expression and aldosterone: renin ratio modulate response to drug therapy in hypertensive patients
Full text linkObjective RGS2 (regulators of G-protein signalling) is a negative regulator of G(alpha q) protein signalling, which mediates the action of several vasoconstrictors. Low RGS2 expression increases G-protein-coupled signalling in hypertensive patients. The aim of the present study was to correlate RGS2 expression in peripheral blood mononuclear cells (PBMs) with response to antihypertensive therapy in never-treated patients with essential hypertension.
Methods and design RGS2 expression was measured by real-time quantitative RT-PCR in peripheral blood mononuclear cells (PBMs) from 102 essential hypertensives. The diagnosis of essential hypertension was based on all clinically required tests, including the captopril suppression test. Antihypertensive treatment was given in accordance to international guidelines. End-point of the study was systolic blood pressure (BP) less than 140mmHg and diastolic BP less than 90mmHg with three or less different antihypertensive agents, which identified responders to treatment. Resistant hypertension was defined as the failure to control systolic and/or diastolic BP despite at least three different classes of antihypertensive agents, including a diuretic.
Results During follow-up, 85 (83%) patients reached the end point (responders). Resistant hypertensives (n=17, 17%) were older, had higher baseline BP, plasma aldosterone and aldosterone : renin ratio (ARR) and lower plasma renin activity than patients who reached the end point. RGS2 was negatively correlated to systolic BP at enrolment and significantly lower in PBMs from resistant hypertensives in comparison with patients that reached BP goal. According to logistic regression analysis, high RGS2 expression was predictor of reaching BP goal, whereas high ARR after captopril, age and systolic pressure at enrolment were predictor of resistant hypertension.
Conclusion RGS2 expression affects the response to antihypertensive treatment. Reduced RGS2 expression contributes to resistance to antihypertensive agents through poor negative feedback on the effects of aldosterone and of other vasoactive agents. J Hypertens 28: 1104-1108 (C) 2010 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins
- …
