1,720,963 research outputs found
INTERACTION OF SCH-23390, A D-1-SELECTIVE ANTAGONIST, WITH THE ANTERIOR-PITUITARY D-2 RECEPTORS AND PROLACTIN SECRETION IN THE RAT
No full textThe affinity of the dopamine-1 (D-1) selective antagonist SCH 23390 (SCH) towards the dopamine-2 (D-2) receptor population present in the anterior pituitary (AP) was assessed in vitro and in vivo. [3H]Spiperone binding was used as biochemical marker for D-2 receptors in the rat AP and prolactin (PRL) was determined as a measure of the functional response to AP-D-2 blockade. SCH displayed weak activity in inhibiting [3H]spiperone binding in both AP and striatal membranes. The affinity was similar to that exhibited by sulpiride (μ molar range) but lower than that of haloperidol (HAL) (nmolar range). However inhibition of [3H]spiperone by SCH in the AP occurred in a biphasic manner indicating the existence of two D-2 sites with different affinity for the compound. SCH produced a transient and dose-dependent increase in plasma PRL levels when given by the subcutaneous (s.c.) route. A significant rise of PRL levels was observed only 30 min after the administration of high doses of SCH by the intraperitoneal (i.p.) route. SCH counteracted the inhibiting effect of apomorphine on PRL release and potentiated the stimulation effect of low doses of sulpiride on PRL secretion. The low affinity of SCH towards AP-D-2 receptors could be responsible for the small and short-lived increase in PRL secretion. This effect occurred at doses higher than those active in tests predictive for antipsychotic activity, which may depend directly on interaction with D-1 receptors. This study therefore indicates the threshold dose of SCH effective in stimulating the D-2 receptor in vivo thus providing a valuable tool to separate the effects of D-1 or D-2 receptors
Dopamine reuptake inhibitors and dopamine releasers : differential effect on plasma prolactin in the rat
No full textAdministration of diclofensine (5, 10 and 20 mg/kg ip) and CDCI (25 and 50 mg/kg ip), two potent inhibitors of dopamine (DA) reuptake, with virtually no DA releasing activity at the doses used, failed to alter either baseline plasma prolactin (PRL) or anterior pituitary DA concentrations in unanesthetized male rats. In contrast, nomifensine (5 and 10 mg/kg ip), a drug which induces both DA release and blockade of DA reuptake, lowered plasma PRL levels and increased anterior pituitary DA concentrations. The same effects were shared by diclofensine when administered at doses (45 and 100 mg/kg ip), reportedly capable of also affecting DA release. These data indicate that DA recapture into tuberoinflundibular DA nerve terminals does not play a major role in the removal of DA released into the hypophyseal portal system and that this mechanism is not operative in the inhibitory control of DA over PRL secretion
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
MECHANISMS SUBSERVING THE STIMULATORY AND INHIBITORY COMPONENTS OF GAMMA-AMINOBUTYRIC ACID-ERGIC CONTROL OF PROLACTIN SECRETION IN THE RAT
No full textRecently, the existence of a dual γ-aminobutyric acid (GABA)-ergic control of PRL secretion, one stimulatory exerted via the central nervous system, the other inhibitory, occurring at the level of the anterior pituitary (AP), has been envisioned. In the present study, new data are provided on the mechanisms subserving the peripheral inhibitory and central stimulatory components of GABA action on PRL release. In ovariectomized, estrogen-primed rats, iv injection of the specific peripheral GABA antagonist, bicuculline methiodide, completely blocked the inhibitory effect of muscimol (M), a specific GABA agonist, on the estrogen-induced plasma PRL rise. Direct instillation of ethanolamine-O-sulfate (EOS), a specific inhibitor of GABA transaminase (GABA-T), into the medial basal hypothalamus of freely moving male rats induced a clear-cut rise in hypothalamic and AP GABA concentrations and a striking lowering of baseline PRL levels. Intraventricular (IVT) administration of EOS (400 μg/rat) did not decrease GABA-T in the AP but only in the hypothalamus and the posterior lobe. M injected by the IVT route stimulated PRL release in unanesthetized male rats. Pretreatment with naloxone, a specific opiate receptor antagonist, or pilocarpine, a muscarinic receptor agonist, failed to impair the PRL-releasing effect of M, while blockade of cathecholamine synthesis by α-methylparatyrosine or their depletion by reserpine significantly inhibited it. In addition, IVT administration of M significantly reduced dopamine concentrations in the AP, a reliable indicator of tuberoinfundibular dopamine function. Pretreatment with 5,6-dihydroxytryptamine, a drug toxic to the serotoninergic (5-HT) system, failed to alter the PRL-releasing effect of M, while quipazine, a 5-HT receptor agonist, partially reduced the effect of M on PRL release. These data provide new information on the existence and mechanisms of action of two distinct components of GABA action on PRL secretion. It appears that 1) pituitary GABA receptors play a major role in the inhibition of PRL release induced by the peripheral administration of M; 2) the inhibitory effect of EOS injected into the mediobasal hypothalamus on PRL release results from an inhibition of GABA catabolism in a pathway which projects from the mediobasal hypothalamus to the median eminence and not from blockade of GABA-T in the AP gland; and 3) the central stimulatory component of GABA action acts via inhibition of the tuberoinfundibular dopamine system, without excluding the possibility of a participation of the 5-HT system
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
BIOCHEMICAL AND IMMUNOCHEMICAL STUDIES ON THE GABAERGIC SYSTEM IN THE RAT FALLOPIAN-TUBE AND OVARY
No full textγ-Aminobutyric acid (GABA) and glutamic acid decarboxylase (GAD) activities were measured in the ovary and the Fallopian tube of rats and compared with brain values. GABA levels in the Fallopian tube were about twice as high as in the brain, while in the ovary they represented only about 5% of the amino acid content of the CNS. In vitro decarboxylation of glutamate, measured via CO2 formation, occurred both in the Fallopian tube and in the ovary. These two organs contained, respectively, 10% and 1% of brain GAD activity. However, the actual formation of GABA from glutamate in a high-speed supernatant was detectable only in the Fallopian tube, where it represented about 5% of brain GAD activity. In contrast with the enzyme present in ovary, liver, anterior pituitary, and kidney, that in the Fallopian tube was quantitatively precipitated by a specific antiserum directed against rat neuronal GAD. Moreover, subcutaneous transplantation resulted in a quantitative decrease of both GABA levels and GAD activity in the Fallopian tube while no change occurred in the ovary and vagus nerve section induced a 50% decrease of GAD activity in the Fallopian tube, although GABA levels were not significantly altered. The findings suggest an extrinsic GABAergic innervation in the rat Fallopian tube but not in the ovary
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