1,720,977 research outputs found
Adrenergic regulation of vascular smooth muscle tone in calf digital artery
No full textRadioligand binding studies and functional assays on isolated smooth muscle preparations were performed in order to obtain a biochemical and functional characterization of the beta-adrenoceptor (beta-AR) subtypes involved in regulation of the smooth muscle relaxation of the calf's common digital artery. The results indicate that the common digital artery possesses two beta-AR populations (40% beta(1) and 60% beta(2)) and the beta(2)-subtype appears to predominate as far as function is concerned. Only the beta(2)-AR agonists clenbuterol and fenoterol caused dose-related relaxant effects, antagonized by propranolol, when tested in preparations precontracted both with PGF(2alpha) (1.4 x 10(-5) m) and noradrenaline (1.2 x 10(-6) m). In noradrenaline precontracted preparations the beta(1)-AR selective agonists dobutamine and xamoterol caused vasodilation which was not antagonized by (+/-)propranolol. While the functional relaxant effects of dobutamine may be attributed to its potent competitive alpha-AR blocking activity, further investigations are required to explain the effect of xamoterol. The vasodilator effect of (+/-)isoproterenol was irregular. The recorded contractile effects, mainly at dosages greater than 10(-6) m, suggest the loss of drug selectivity for beta-AR and alpha-AR activation. Indirect evidence indicates that the alpha-adrenoceptor (alpha-AR) population in this tissue which produces a strong contraction is functionally dominant over the beta-AR, suggesting limited therapeutic benefit for beta-AR drugs to control blood flow disorders in the calf's distal limb
Effects of mepartricin on estradiol and testosterone serum levels and on prostatic estrogen, androgen and adrenergic receptor concentrations in adult rats
No full textThe effects induced by oral administration of 0, 5 and 20 mg of meparticin kg-1 of body weight for 28 days (group 1, 2 and 3, respectively) upon prostatic estrogen, androgen, α1- and β-adrenergic receptor concentrations and on estradiol and testosterone serum levels in adult male rats were studied. The effects produced by mepartricin treatments on the weight and dimension of the gland were investigated. Both mepartricin dosages induced significant decreases (P< 0.05) of the absolute and relative weights and of the dimensions of the prostate. A significant dose-dependent decrease (P<0.05) in estradiol serum levels was observed in treated rats, whereas no significant modifications were found in testosterone serum levels. As far as prostatic steroid receptor concentrations were concerned, a significant (P<0.05) decrease in estrogen receptor number was observed in both treated groups, whilst a significant increase (P<0.05) of androgen receptor concentrations was recorded only in rats treated with 20 mg mepartricin kg-1. Conversely, a dose-dependent up-regulation of both prostatic α1- and β-AR was found. Data obtained suggest that the prostatic α1-AR expression may be strongly influenced by estrogen deprivation (mepartricin treatment), therefore the combination of estrogen suppression (mepartricin) and adrenergic suppression (α1-AR blockers) may be suggested as a possible pharmacotherapeutic strategy for the treatment of benign prostatic hyperplasia
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
Modifications of receptor concentrations for adrenaline, steroid hormones, prostaglandin F-2 alpha and gonadotropins in hypophysis and ovary of dairy cows with ovarian cysts
No full textReceptor concentrations for adrenaline, steroid hormones, PGF(2 alpha), LH and FSH were measured in the hypophysis and ovary of dairy cows with ovarian cysts and the results were compared with those of healthy animals. Significant modifications were found in all receptor concentrations, either between follicular and luteal structures or between the hypophyseal and ovarian receptorial status. The correlations between catecholaminergic and steroidal systems have already been demonstrated, particularly those existing between p-adrenoceptors and steroid hormone receptors. Particular attention has been given to the possibility that a derangement in neurogenic inputs may be at the basis of some ovarian pathologies. The results of the present study suggest that the modifications of the ovarian and hypophyseal receptorial status of healthy and affected cows could play an important role in the pathogenesis of ovarian cysts
Beta-adrenoceptors involved in subcutaneous adipose tissue lipolysis in food-producing animals
No full textRegolazione ß-adrenergica della muscolatura liscia longitudinale e circolare dell’ileo del cavallo
No full textDifferences between longitudinal and circular smooth muscle in ß-adrenergic control of motility of isolated equine ileum
No full textOBJECTIVE:
To identify beta-adrenoceptor subtypes involved in motility inhibition of circular and longitudinal smooth muscle layers of equine ileum.
SAMPLE POPULATION:
Isolated strips of equine ileum circular smooth muscle and membrane preparations from circular and longitudinal muscle layers.
PROCEDURE:
Functional assays of circular muscle preparations and radioligand binding assays and measurements of cAMP production in smooth muscle membranes from circular and longitudinal layers.
RESULTS:
Selective beta-adrenergic agonists exerted inhibitory effects on circular muscle preparations. Binding studies of cell membranes indicated that the density and distribution of 3 beta-adrenoceptor subtypes did not differ between longitudinal and circular muscle layers. Measurement of cAMP production in membrane preparations of longitudinal and circular muscle after selective beta-stimulation confirmed presence of the 3 adenylate cyclase-coupled beta-adrenoceptor subtypes; however, preparations from the 2 layers had differing cAMP production efficacy.
CONCLUSIONS:
The data may partly explain the differing functional responses between circular and longitudinal muscle preparations.
CLINICAL RELEVANCE:
Findings support the important role of beta-atypical adrenoceptors in the inhibitory regulation of equine ileum motility
INVESTIGATIONS ON THE STEREOSELECTIVE ACTION OF ISOXSUPRINE ON ALFA AND BETA ADRENOCEPTORS IN EQUINE COMMON DIGITAL ARTERY
No full textThe affinity and functional effects of isoxsuprine enantiomers were investigated to determine the enantiospecificity of the β-agonistic and α-blocking effects. Functional assays on isolated smooth muscle preparations from equine common digital artery were performed to determine the apparent affinity (pD2) and intrinsic activity (α(E)) of (-)erythro-isoxsuprine (αS, βR, γR) and (+)erythro-isoxsuprine (αR, βS, γS). The affinity of two enantiomers for the different adrenoceptor types was studied by radioligand binding assays on membrane preparations from the same tissue: using (-)[3H]CGP12177 and [3H]prazosin. On noradrenaline-precontracted artery preparations (-)isoxsuprine was markedly more potent than(+)isoxsuprine in dilating preparations, indicating that the laevorotatory enantiomer has a very high apparent affinity for α-adrenoceptors. Binding studies confirmed that (-)isoxsuprine has a higher affinity than (+)isoxsuprine for α-adrenoceptors, while the (+) isomer competes for β-adrenoceptors with an affinity similar to that of propranolol. As described for other β-phenylethylamines, the two isoxsuprine enantiomers studied have different efficacies for α- and β-adrenoceptors and the effects of the commercially available mixture of stereoisomers therefore depend on the density and functional importance of the adrenoceptor types present in the tissue studied
- …
