1,720,990 research outputs found
Kinin B-1 and B-2 receptors in pig vessels: characterization of two monoreceptor systems
No full textThe coronary artery and renal vein of the adult pig are sensitive and reliable monoreceptor systems for studying kinin receptors. The pig coronary artery with intact endothelium is highly sensitive to bradykinin (BK, pEC50 8.6), while being insensitive to the B1 receptor agonist, LysdesArg9BK. The tissue responds to BK with concentration-dependent relaxation, which is prevented by B2 receptor antagonists, particularly DArg[Hyp3, Thi5, DTic7, Oic8]BK (HOE 140, pKB 9.3), (E)-3-(6-acetoamido-3-pyridyl)-N-(N-{2, 4-dichloro-3-[(2-methyl-8-quinolinyl)oxy-methyl]phenyl}-N- methylaminocarbonyl-methyl)acrylamide (FR 173657), a new non peptide compound (pKB 9.3), while B1 receptor antagonists (e.g. Lys[Leu8]desArg9BK) are inactive. The order of potency of kinin-related peptides in this vessel is: LysBK > or = BK > [Hyp3]BK > [Aib7]BK, a sequence typical of a B2 receptor system. Antagonists such as HOE 140 and FR 173657, at high concentrations reduce the maximum effect of BK and thus behave as noncompetitive antagonists. The kinin B1 receptor was studied in the pig renal vein without endothelium and incubated for several hours in order to allow for the de novo formation of this functional site. After 7-8 h in vitro incubation, the vessel shows high sensitivity to LysdesArg9BK (pEC50 8.3) and is insensitive to BK. The pig renal vein responds to B1 receptor agonists with concentration-dependent contraction which maintains a stable plateau and is prevented by selective B1 receptor antagonists such as Lys[Leu8]desArg9BK (pKB 6.7). The most active antagonist has been found to be desArg9HOE 140 (pA2 7.6) which acts as competitive antagonist in this preparation. Some B2 antagonists (e.g. HOE 140) show weak (pKB 6.1) anti-B1 receptor activity while the non-peptide compound FR 173657 is inactive on the B1 receptor and therefore acts as a potent and selective kinin B2 receptor antagonist in the pig. The data obtained in this study allow us to compare the porcine B2 and B1 receptors with those of other species including man, and underline some interesting features that are unique to the porcine functional sites
Effects of vasoactive agents in healthy and diseased human saphenous veins
No full textAbstractPurpose: Smooth muscle reactivity is one of the factors involved in the pathogenesis of varicose veins. We investigated the myotropic effects of the 3 main vasoconstrictor agents—norepinephrine (NE), angiotensin II (Ang II), and endothelin-1 (ET-1)—in isolated human saphenous veins. Methods: Human saphenous veins were collected from 23 patients with primary chronic venous insufficiency who underwent elective varicose vein resections and who were stratified into the following 3 groups: group 1, 7 patients in clinical class 2; group 2, 9 patients in clinical classes 3 and 4; and group 3, 7 patients in clinical classes 5 and 6. Moreover, 6 patients who underwent arterial bypass grafting procedures represented the control group. The tissues were suspended in organ baths that contained Krebs solution, and their mechanical responses were measured isometrically. The cumulative concentration–response curves to Ang II, NE, and ET-1 were performed at 90-minute intervals in each tissue. Results: In the control tissues, NE, Ang II, and ET-1 induced concentration-dependent contractions with apparent affinities (pEC50, the negative logarithm to base 10 of the molar concentration of the agonist, which produces the 50% of the maximal effect) and maximal effects (maximum effect, g of contraction) that were equal to 7.06 ± 0.23, 8.53 ± 0.34, 7.63 ± 0.10, and 2.21 ± 0.33, 1.65 ± 0.31, 2.60 ± 0.77, respectively. Two main findings were evident in comparison of varicose veins with control tissues. First, the maximum effect that was evoked by all of the stimulants was reduced progressively with the increasing severity of the disease, which raised the third group to statistical significance for both NE and Ang II (P < .05). Second, a marked reduction of Ang II apparent affinity was already evident in tissues that were taken from patients in an early stage of the disease (P < .05). Conclusion: The demonstration of a significant reduction in Ang II and NE contractile activities and the important reduction of that of ET-1 in the diseased veins as compared with the control tissues extends the previous observations regarding the impairment of smooth muscle contractility in primary chronic venous insufficiency. Moreover, the dramatic reduction of Ang II affinity, which appears in an early stage of the disease, supports the hypothesis that such abnormality within the venous wall could play a role in the pathogenesis of primary varicose vein disease. (J Vasc Surg 1998;28:855-61.
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
Comparison of prazosin, terazosin and tamsulosin: Functional and binding studies in isolated prostatic and vascular human tissues
No full textBACKGROUND: Terazosin and tamsulosin are drugs currently used in the treatment of benign prostatic hypertrophy (BPH). The potency of these two alpha(1) receptor antagonists and that of prazosin to inhibit contractions induced by noradrenaline and the binding of [(3)H]-prazosin in human prostate and four different human arterial and venous vessels (saphenous and umbilical veins, renal and mesenteric arteries) was studied. METHODS: By bioassay and binding studies, we examined the receptor affinities of different alpha(1) receptor antagonists in different human tissues. RESULTS: pKb of terazosin, tamsulosin, and prazosin obtained in the prostatic tissues (8.15, 9.64, and 8.59, respectively) were not different from those obtained in the umbilical veins (8.07, 9.56, and 8.30, respectively), in the mesenteric artery (8.27, 10.29, and 9.01, respectively), renal artery (8.35, 10.13, and 8.76, respectively) and saphenous vein (7.8, 10.3, and 9.32, respectively). IC(50) (nM) of prazosin, terazosin, and tamsulosin obtained from binding studies in membrane preparations from prostate tissue were similar to those from umbilical veins, saphenous vein, and renal artery. CONCLUSIONS: All of the evaluated drugs showed similar selectivity for prostatic vs. vascular tissues. Thus, different clinical profiles of the present drugs should not result from their differential affinity for prostatic versus vascular alpha(1)-adrenoceptors. Copyright 2001 Wiley-Liss, Inc
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
In vitro characterization of FR 190997, the first non peptide B2 receptor agonist receptor binding and bioassay in the human umbilical vein
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
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
- …
