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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Role of the L-arginine-nitric oxide pathway in vascular smooth muscle
No full textThis brief overview discusses the ability of mediators associated with vascular injury, such as interleukin-1 β and tumour necrosis factor α, to activate vascular smooth muscle cells to produce nitric oxide or a related donor of nitric oxide. The cytokines cause the synthesis of nitric oxide synthase(s), which catalyzes the conversion of L-arginine to nitric oxide and L-citrulline. The production of nitric oxide can be modulated by factors produced by vascular cells and formed elements of the blood (e.g. platelet-derived growth factor, transforming growth factor β), but also those generated at sites of vascular injury from inactive precursors circulating in the blood (e.g. thrombin, plasmin). The production of nitric oxide by vascular smooth muscle cells may contribute to the homeostasis of blood vessels at sites of injury. In particular, nitric oxide may prevent the local development of vasospasms, unwanted proliferation of smooth muscle cells, and also help to control coagulation and the formation of the thrombus.link_to_subscribed_fulltex
SIN-1 stimulates the production of cyclic GMP but not cyclic AMP in porcine aortic endothelial cells
No full textThe purpose of the present investigations was to determine whether or not SIN-1, a metabolite of molsidomine that spontaneously releases nitric oxide, stimulates the production of adenosine-3',5'-cyclic monophosphate (cyclic AMP) and of guanosine-3',5'-cyclic monophosphate (cyclic GMP) in endothelial cells. All experiments were performed on first or second passage cultured porcine aortic endothelial cells. SIN-1 induced a time- and concentration-dependent accumulation of cyclic GMP but not of cyclic AMP. The production of cyclic GMP evoked by SIN-1 but not evoked by human α-natriuretic polypeptide was inhibited by treatment of the cells with either methylene blue (an inhibitor of soluble guanylate cyclase) and hemoglobin (a scavenger of nitric oxide). These data suggest that SIN-1 enhances the activity of soluble guanylate cyclase, which in turn induces the accumulation of cyclic GMP in endothelial cells. This response is probably due to the spontaneous release of nitric oxide, which is a potent activator of soluble guanylate cyclase.link_to_subscribed_fulltex
Inhibitors of calmodulin impair the constitutive but not the inducible nitric oxide synthase activity in the rat aorta
No full textThe possibility that calmodulin inhibitors impair the constitutive but not the inducible nitric oxide synthase(s)-mediated inhibitions of tone was investigated in the rat aorta. The endothelium-dependent relaxations evoked by acetylcholine, ATP and the calcium ionophore A23187 (which are mediated by the constitutive nitric oxide synthase) were inhibited by calmodulin inhibitors [calmidazolium, W-7 and (N-(6-aminohexyl)-5-chloro-1-naphthalene- sulfonamide, hydrochloride, fendiline] and by an inhibitor of nitric oxide synthase, nitro L-arginine. Nitro L-arginine but not calmidazolium reduced the inhibitory influence of the endothelium on the concentration-contraction curves evoked by phenylephrine. Treatment of aortic rings without endothelium with interleukin-1β inhibited the contractions to phenylephrine by inducing nitric oxide synthase activity. Nitro L-arginine but not calmidazolium restored the contractility of the aortic rings. The relaxations evoked by a donor of nitric oxide, 3-morpholino-sydnonimine, were minimally affected by calmidazolium and nitro L-arginine. The basal tissue content in, and the production of, guanosine 3',5' cyclic monophosphate evoked by acetylcholine in rings with endothelium were inhibited by calmidazolium and nitro L- arginine. The production of cyclic GMP evoked by interleukin-1β in rings without endothelium was inhibited by nitro L-arginine but not by calmidazolium. These observations indicate that calmodulin inhibitors inhibit the constitutive but not the inducible nitric oxide synthase(s) in the rat aorta.link_to_subscribed_fulltex
Variations on the Author
Get PDF“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
Get PDFWe 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
L-Arginine evokes both endothelium-dependent and -independent relaxations in L-arginine-depleted aortas of the rat
No full textThis study was designed to investigate the effects of L-arginine (the substrate for the formation of endothelium-derived nitric oxide) in vascular tissues. Rat aortic rings, with or without endothelium, were suspended in organ chambers for the measurement of isometric tension; they were contracted with phenylephrine (10-6 M). After a short incubation period (0.5 hour) in physiological salt solution, L-arginine induced minor changes in both types of rings. In contrast, when the incubation time was increased (2, 4, 6, and 8 hours), L-arginine evoked concentration- and time-dependent relaxations in aortic rings both with and without endothelium. The relaxations were larger in rings with endothelium. The presence of L-arginine (10-3 M) in the incubation medium inhibited subsequent relaxations evoked by the amino acid. The concentration-relaxation curves associated with acetylcholine in rings with endothelium and the curves associated with Sin-1, a spontaneous donor of nitric oxide, in rings with or without endothelium were slightly but significantly shifted to the right after a 6-hour incubation. Nitro-L-arginine (3 x 10-5 M) and methylene blue (3 x 10-7 M) attenuated the relaxations evoked by L-arginine in rings both with and without endothelium. Other basic amino acids (D-arginine, L-homoarginine, L-citrulline, L-lysine, and L-ornithine; all tested at 10-3 M) either had no effect or induced small relaxations and did not affect the response to L-arginine. These observations suggest that L-arginine specifically and stereoselectively relaxes aortic rings with and without endothelium, probably by restoring the endogenous pool of the amino acid, which is likely depleted by prolonged incubation. Since the relaxations in response to L-arginine are inhibited by nitro-L-arginine in rings both with and without endothelium, the present experiments demonstrate that both the endothelial cells and the vascular smooth muscle possess biochemical pathways converting L-arginine to nitric oxide.link_to_subscribed_fulltex
L-arginine evokes relaxations of the rat aorta in both the presence and absence of endothelial cells
No full textThe effect of L-arginine [the substrate for the formation of nitric oxide (NO) in endothelial cells] on the reactivity of isolated vascular preparations was studied. Rings of rat aorta, with or without endothelium, were suspended in organ chambers for the measurement of isometric force. After various incubation periods in physiological salt solution (37°C, 95% O2 and 5% CO2), they were contracted with phenylephrine (10-6 M) before the addition of cumulative concentrations of L-arginine. L-Arginine evoked only minor changes in tension in preparations incubated for 0.5 h. However, when the incubation period was longer than 2 h, the amino acid evoked concentration- and time-dependent relaxations in preparations both with and without endothelium. The relaxations evoked by L-arginine were impaired by nitro-L-arginine and methylene blue. Other basic cationic amino acids (D-arginine, L-homoarginine, L-citrulline, L-lysine, and L-ornithine) evoked only small or no relaxations in both types of preparations. These observations demonstrate that L-arginine stereoselectively and specifically relaxes the rat aorta whether or not it contains the endothelium; this response depends on the duration of the prior incubation of the rings in physiological salt solution. The relaxations are impaired by inhibitors of both the formation and the action of NO, demonstrating that the endothelial cells and the vascular smooth muscle of the rat aorta possess an L-arginine - NO pathway(s) associated with relaxation.link_to_subscribed_fulltex
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