1,721,005 research outputs found
Reduced aerobic metabolic efficiency in postischemic myocardium dysfunction in rats: role of aging.
No full textAge-related effects of platelet activating factor (PAF) in the isolated perfused rat heart.
No full textPlatelet Activating Factor (PAF) is a phospholipid that has been implicated as an
important mediator of anaphylactic cardiac dysfunction and involved in the toxic
effects of the ischaemia-reperfusion process. In the elderly, these phenomena are
thought to be exaggerated by the age-related changes in response to several
chemical factors and myocardial ischaemia. We evaluated the effects of PAF
(acetyl-o-alkyl-l-phosphatidylcholine) on left ventricular systolic (LVSP) and
diastolic (LVDP) pressure, coronary flow rate (CFR) and heart rate (HR) in adult
(6 months, AH) and senescent (24 months, SH) rat hearts. The perfusion of PAF
(10(-8), 10(-7) and 10(-6) M) induced a concentration-related reduction of LVSP,
CFR and HR and a linear increase in LVDP. Contractile modifications were more
pronounced in senescent hearts: LVSP decreased (P < 0.01) and LVDP increased with
respect to younger animals (P < 0.01 vs. AH). This negative inotropic effect was
also present in electrically paced hearts. PAF produced conduction arrhythmias
ranging from second-degree atrio-ventricular conduction block to cardiac
standstill both in adult and senescent hearts; at a higher dose (10(-6) M),
cardiac standstill appeared after 96.5 +/- 15.3 s in adult hearts and after 45.5
+/- 17.6 s in senescent hearts (P < 0.01). Lyso-PAF did not modify while specific
PAF antagonist compounds CV-3988 inhibited all electromechanical responses both
in adult and senescent hearts. These data suggest that age influences the effect
of PAF on contractile parameters, coronary flow and conduction arrhythmias by acting on receptors, whose function is unaffected by age
Arrhythmogenic age-related effects of lysophosphatidylcholine in the rat heart.
No full textVentricular arrhythmias are the most common cause of death among patients with coronary artery disease; this is more evident in the elderly, who tend to have
more severe coronary artery disease and age-dependent modifications of cardiac electrophysiology. Lysophosphoglycerides, which accumulate in the ischemic
myocardium, are responsible for oscillatory after-potentials and may contribute to the development of ventricular arrhythmias. The aim of this study was to
examine the effects of lysophosphatidylcholine (5 x 10(-5) M) in the absence or presence of epinephrine (10(-6) M) in isolated, perfused hearts from adult (6-12 months old) and senescent (24 months old) rats. Rat hearts (30/group) were randomly divided into four groups each of which included hearts of 6, 12 and 24-month old rats. The groups comprised a control group, a group treated with epinephrine, a group treated with lysophosphatidylcholine and a group treated
with both epinephrine and lysophosphatidylcholine. Analysis of arrhythmias indicated a linear correlation between epinephrine- and lysophosphatidylcholine-induced ventricular arrhythmias and age. The incidence of
arrhythmias was higher in the hearts treated with epinephrine and lysophosphatidylcholine together than in those treated with either substance separately (p less than 0.01). The results indicate that age influences the
arrhythmogenic action of lysophosphatidylcholine, and that epinephrine contributes to this effect
Dipyridamole echocardiography as a useful and safe test in the assessment of coronary artery disease in the elderly
No full textWe prospectively studied the sensitivity, specificity, feasibility, and safety of high-dose dipyridamole echocardiography, compared to exercise electrocardiography in 130 subjects (67 younger and 63 elderly patients) referred for angiographic
evaluation of suspected or proven coronary artery disease. Sensitivity, specificity, and feasibility of dipyridamole echocardiography were respectively 75.5%, 100%, and 88.0% in younger patients and 82.9%, 100%, and 79.4% in elderly patients (P = NS). The sensitivity of exercise electrocardiography was 72.7% in young and 66.6% in elderly patients (P = NS); specificity 66.0% vs 60.0% (P = NS); feasibility 83.6 vs 63.5 (P = 0.05). Forty-nine younger and 38 elderly patients performed both tests. Sensitivity of dipyridamole echocardiography compared to exercise electrocardiography was 76.2% vs 73.8% in young patients and 83.3% vs 70% in the older group (P = NS). The feasibility of the two tests was significantly different in the elderly group only (dipyridamole echocardiography 79.4% vs exercise electrocardiography 63.5%; P less than 0.01). The incidence of side effects during dipyridamole echocardiography was similar in the two groups, except for dyspnea which was observed in 20% of older and 5% of younger patients
(P less than 0.05). Our data demonstrate that the dipyridamole test combined with
echocardiographic monitoring of regional myocardial contractility may be considered a valid non-invasive method for evaluating coronary artery disease in the elderly and that this test is a satisfactory alternative to the exercise stress test
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
Modificazioni elettro-meccaniche indotte dal fattore di attivazione piastrinico (PAF) nel cuore di ratto isolato e perfuso: effetto dell’invecchiamento
No full textEffetto dell’invecchiamento sulla risposta emodinamica e metabolica alla stimolazione della glutatione perossidasi nel cuore di ratto isolato e perfuso
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
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