1,720,992 research outputs found
Dopamine DA-2 receptor sites in the rat renal cortex: a light microscope autoradiographic study.
No full textThe binding of the DA-2 receptor antagonist [3H]-spiroperidol, in the presence of appropriate concentrations of ketanserin to avoid the possible labelling of 5-HT-2 sites, was studied in sections of rat kidney using combined radioreceptor assay and light microscope autoradiography. [3H]-Spiroperidol was bound by sections of rat kidney in a manner consistent with the labelling of a single class of high affinity of DA-2 sites. Scatchard analysis of the binding isotherms showed a Kd value of 2.5 +/- 0.2 nmol/l and a Bmax value of 129.5 +/- 6.8 fmol/mg protein. Light microscope autoradiography, centered on the renal cortex, revealed the development of silver grains within cortical convoluted tubules. Silver grains were rather homogeneously distributed to both proximal and distal convoluted tubules, with no specific glomerular localization. These findings do not support the assumption of the existence of glomerular DA-2 receptors in the rat kidney
Radioligand binding and autoradiographic analysis of dopamine receptors in the human heart.
No full textThe effects of dopamine on the 3',5-'cyclic adenosine monophosphate (cAMP) generating system were analyzed in membrane particles from the human right and left cardiac ventricle. In addition, the pharmacological profile and the anatomical localization of dopamine receptors were assessed on frozen sections of human cardiac atrial or ventricular tissue. Dopamine increased cAMP levels, in a concentration-dependent manner, in membranes of the right and the left ventricle. These effects were abolished by the beta-adrenoceptor antagonist (-)-propranolol, but not by the D1 receptor antagonist SCH 23390 or by the non selective D1/D2 receptor antagonist haloperidol. No specific binding of the D1 receptor antagonist [3H]-SCH 23390 was noticeable within the atrial or ventricular portions of the heart examined using either radioligand binding or autoradiographic techniques. The D2 receptor antagonist [3H]-spiroperidol, in the presence of concentrations of ketanserin sufficient to block possible binding to 5-HT2 sites, was specifically bound to sections of human heart with a dissociation constant value of about 2.6 nmol/l. The highest density of [3H]-spiroperidol binding occurred in the right ventricle followed, in descending order, by the right atrium, the upper part of the left ventricle, the lower part of the left ventricle, the left atrium and the interventricular septum. The binding profile of [3H]-spiroperidol to sections of human heart was consistent with the labeling of dopamine D2 sites. Light microscope autoradiography revealed silver grains throughout the atrial and ventricular walls and these were frequently accumulated in clusters.(ABSTRACT TRUNCATED AT 250 WORDS
Pharmacological characterization and autoradiographic localization of dopamine receptors in human epicardial arteries.
No full textThe pharmacological properties and the anatomical localization of dopamine (DA) D1 and D2 receptor sites were studied in normal samples of the human right coronary and anterior interventricular arteries by assessing the effect of DA on the cyclic AMP generating system and by using combined radioreceptor binding and autoradiographic techniques. DA caused a concentration-dependent accumulation of cyclic AMP in membranes of right and anterior interventricular coronary arteries. This effect was antagonized by the selective D1 receptor antagonist SCH 23390 and by other DA receptor antagonists. D2 receptor responses negatively coupled to cyclic AMP generation were obtained by incubating membranes of coronary arteries with DA together with SCH 23390 or with D2 receptor agonists. This D2 effect was abolished by the selective D2 receptor antagonist (-)-sulpiride. [3H]SCH 23390 was bound to sections of the coronary arteries in a manner consistent with the labeling of D1 sites. Light microscope autoradiography revealed the localization of D1 sites in the medial layer of the coronary arteries. [3H]Spiroperidol, in the presence of ketanserin, was bound to sections of the coronary arteries in a manner consistent with the labeling of D2 sites. D2 receptor sites were located within the adventitia and the adventitial-medial border of the two arteries, and are probably prejunctional in nature. These findings indicate the existence of both D1 and D2 receptor sites in human right and anterior interventricular arteries. Moreover, they suggest that coronary vasodilation induced by DA or DA receptor agonists may be the result of a direct coronary vasodilatory activity
Structural variants of chromosome 9: a possibile association with hypogonadotropic hypogonadism
Full text linkWe report two cases of structural variations of chromosome 9 associated with hypogonadotropic hypogonadism and azoospermia in adolescent boys. One patient also had a partially imperforated urethral meatus. Histological examination revealed that both had hypotrophic and underdeveloped testes. There was no LH and FSH response to LH-RH stimulation nor was there any response to naloxone tests. Basal and HCG stimulated plasma testosterone values were below normal prepubertal levels. As the administration of gonadotrophins did not improve the clinical and hormonal findings, alternative androgen therapy was necessary to achieve secondary sexual characteristics. Although they reached a good level of androgenization, their testes were still very small and azoospermia remained, as confirmed by repeated semen analyses. A possible association between chromosome 9 polymorphisms and hypothalamo-pituitary axis abnormalities is suggested. It is hypothesized that structural variants of chromosome 9 are not unrelated occurrences. Furthermore, and in view of the fact that they can lead to a high risk of azoospermia and infertility, such variants call for clinical investigatio
Deep space transportation enhanced by 20 kW-Class Hall Thrusters
Full text linkDeep space is the new frontier for human exploration, with Moon and Mars identified as fundamental targets. Improving in-space transportation capabilities has been recognized as one of the critical enabler for sustainable and affordable space programs in Earth proximity and beyond. Envisioning the presence of future deep space infrastructures, cargo transferring becomes a major issue that can benefit from improvements in in-space propulsion technology. Electric propulsion could represent the turning point, thanks to the combination of new system architectures and technology advancements, e.g. cluster architecture and magnetic shielding, and improved capability of on-board power generation. High-power Hall Thrusters are considered the most promising solution for future space exploration, thanks to a favourable thrust to power ratio, higher than Gridded Ion Engines. Reusable platforms, based on Hall Thrusters, could represent a valid alternative to chemical-propelled spacecraft. These systems could be exploited to support human presence in deep space, delivering life support items and providing on-orbit servicing capabilities. In this paper, the typical mission analysis tools have been exploited to analyse the selected scenarios. The analysis highlights possible advantages achievable adopting high-power Hall Thrusters on board reusable platforms. Since the design of these spacecraft envisions the adoption of a 20 kW-class Hall Thruster string, the mass and power budgets are obtained for those subsystems that are most affected by this critical technology. Then, the feasibility of each scenario is assessed considering the needs defined not only by the traffic plan, in terms of loading/unloading cargo and transfer duration, but also by the peculiar mission and physical constraints. Last, the different platform design solutions are compared with respect to their electric propulsion configurations, in order to identify the possible commonalities in terms of architecture and technology, in line with the current trend of modularity and affordability
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
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