1,721,035 research outputs found
INVESTIGATIONS ON THE ACUTE EFFECTS OF NEUROPEPTIDES ON THE PITUITARY-ADRENOCORTICAL FUNCTION IN NORMAL AND COLD-STRESSED RATS .2. NEUROTENSIN AND NEUROMEDIN-N
No full textThe effects of a subcutaneous bolus injection of 2 micrograms neurotensin (NT) or neuromedin N (NMN) on the function of the hypothalamo-pituitary-adrenocortical axis were investigated in both normal and cold-stressed rats. The blood concentrations of ACTH, corticosterone (B) and aldosterone (ALDO) were measured by specific radioimmunoassays 1, 2 or 4 h after the neuropeptide administration. Cold stress enhanced plasma levels of ACTH, B and ALDO, and these rises lasted unchanged until 4 h. NT did not affect either basal or stress-stimulated plasma levels of ACTH and B, while it lowered the plasma ALDO concentration at 4 h in normal rats and increased it at 1 h in stressed animals. NMN did not change the basal plasma level of ACTH, but it did markedly raise blood levels of both B and ALDO; on the other hand, in cold-stressed rats NMN strongly depressed ACTH response and decreased B plasma concentration at 2 h, without evoking apparent changes in ALDO response. In light of these findings the following conclusions and hypotheses can be drawn and suggested: (i) NT and NMN, when administered at a relatively high dose, do not affect ACTH release in rats under basal conditions; (ii) NMN, but not NT, is able to prevent cold stress-induced stimulation of ACTH secretion, probably by inhibiting hypothalamic thermoregulatory centers; and (iii) NT and NMN exert direct adrenocortical antisecretagogue and secretagogue effects, respectively, which could explain the evident lack of correlation between the levels of circulating ACTH and the plasma concentrations of the main adrenal steroid hormones in both normal and stressed rats after neuropeptide administration
EVIDENCE THAT ENDOGENOUS VASOACTIVE-INTESTINAL-PEPTIDE (VIP) IS INVOLVED IN THE REGULATION OF RAT PITUITARY-ADRENOCORTICAL FUNCTION - IN-VIVO STUDIES WITH A VIP ANTAGONIST
No full textThe effect of a subcutaneous bolus injection of 2 micrograms magnitude of Ac,Tyr1,D-Phe2-GRF(1-29) amide, a specific VIP antagonist (VIP-A), on the hypothalamo-pituitary-adrenocortical (HPA) axis were investigated in both normal and ether- or cold-stressed rats. Blood concentrations of ACTH, aldosterone (ALDO) and corticosterone (B) were measured by specific RIA 1, 2 or 4 h after VIP-A injection. VIP-A administration to normal rats strikingly lowered the plasma concentration of ALDO, without significantly affecting those of ACTH and B. Ether and cold stresses notably raised the blood levels of ACTH, ALDO and B, and these rises lasted unchanged until 4 h. VIP-A did not affect the response of HPA axis to ether stress, but provoked a marked depression of that to cold stress. In light of these findings the following conclusions can be drawn: (i) endogenous VIP does not regulate HPA-axis function under basal conditions, but it plays a pivotal role in the mechanisms involved in the activation of HPA axis induced by cold exposure; and (ii) endogenous VIP exerts a tonic stimulatory action on ALDO secretion, probably by acting directly on the adrenal zona glomerulosa
The hyperplastic adrenal glands of chronically ACTH-administered rats display enhanced glucocorticoid secretory response to gastric inhibitory polypeptide
No full textGastric inhibitory polypeptide (GIP), a gastrointestinal hormone released after feeding, has been recently found to evoke a moderate glucocorticoid secretory effect in the rat. We have investigated whether a prolonged (from 1 to 3 weeks) infusion with ACTH changes the responsiveness of rat adrenal zonae fasciculata (ZF) and reticularis (ZR) to GIP. As expected, ACTH treatment caused hypertrophy of adrenals, rise in the plasma corticosterone concentration, and increase in the basal production of both corticosterone and cyclic-AMP by dispersed ZF/R cells. GIP evoked a net increase in corticosterone plasma concentration, and corticosterone and cyclic-AMP release by dispersed ZF/R cells in ACTH-untreated rats. ACTH infusion enhanced in vivo and in vitro adrenal responses to GIP in relation to the duration of treatment. The protein kinase A (PKA) antagonist H-89 abolished corticosterone response to GIP of ZF/R cells from either untreated and ACTH-treated rats. Autoradiography evidenced [125I]GIP binding sites in the ZF/R, and computer-assisted densitometry showed that their number significantly increased as a function of the duration of ACTH infusion. [125I]GIP binding was displaced by an excess of cold GIP, and unaffected by ACTH. Taken together, these findings suggest that prolonged ACTH treatment induces ZF/R cell glucocorticoid hyper-responsiveness to GIP in rats, probably through the up-regulation of adenylate cyclase/PKA-coupled GIP receptors
Role of adrenal renin-angiotensin system in the control of aldosterone secretion in sodium-restricted rats
No full textThis study examined the effect of the pharmacological manipulation of adrenal renin-angiotensin system (RAS) on aldosterone secretion from in situ perfused adrenals of rats kept on a normal diet and sodium restricted for 14 days. Neither the angiotensin-converting enzyme inhibitor captopril nor the nonselective angiotensin II receptor antagonist saralasin and the AT(1) receptor-selective antagonist losartan affected basal aldosterone output in normally fed rats. In contrast, they concentration dependently decreased aldosterone secretion in sodium-restricted animals, with maximal effective concentration ranging from 10(-7) to 10(-6) M. Captopril (10(-6) M), saralasin (10(-6) M), and losartan (10(-7) M) counteracted aldosterone response to 10 mM K(+) in sodium-restricted rats but not in normally fed animals. Collectively, these findings provide evidence that adrenal RAS plays a role in the regulation of aldosterone secretion, but only under conditions of prolonged stimulation of zona glomerulosa probably leading to overexpression of adrenal RAS
Cerebellin stimulates the secretory activity of the rat adrenal gland: in vitro and in vivo studies
No full textCerebellin is a 16-aminoacid peptide widely distributed in the central nervous system, where it exerts
neuromodulatory functions. Cerebellin is contained in human adrenal medulla, and it has been recently demonstrated
that cerebellin elicits catecholamine release by human adrenal in vitro. Aim of the present study was to ascertain
whether cerebellin affects adrenal function in the rat. Cerebellin concentration-dependently (from 10–9 to 10–7 M)
increased norepinephrine (but not epinephrine) and cyclic-AMP production by adrenomedullary tissue in vitro. The
norepinephrine response to 10–7 M cerebellin was blocked by the protein kinase (PK) A inhibitor H-89, but not by the
phospholipase C inhibitor U-73122 or the PKC inhibitor calphostin-C. Cerebellin did not affect aldosterone and
corticosterone secretion of dispersed zona glomerulosa and zona fasciculata-reticularis adrenocortical cells. Cerebellin
concentration-dependently (from 10–8 to 10–7 M) enhanced norepinephrine release by in situ perfused rat adrenals.
Cerebellin (10–7 M) also elicited a significant rise in aldosterone and corticosterone output, and this effect was annulled
by either the b1-adrenoceptor antagonist l-alprenolol or H-89. Collectively, the present findings allow us to conclude
that cerebellin 1) directly stimulates norepinephrine release via the adenylate cyclase/PKA-dependent signaling
pathway; and 2) indirectly enhances adrenocortical secretion in vivo, through a paracrine mechanism involving
medullary catecholamine release
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
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
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