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Venous Vessels (venous + vessel)

Distribution by Scientific Domains

Medical Sciences	50%
Life Sciences	50%

Selected Abstracts

Contribution of endothelium-derived hyperpolarizing factors to the regulation of vascular tone in humans

FUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 4 2008
Jeremy Bellien
Abstract Endothelium plays a crucial role in the regulation of cardiovascular homeostasis through the release of vasoactive factors. Besides nitric oxide (NO) and prostacyclin, increasing evidences show that endothelium-derived hyperpolarizing factors (EDHF) participate in the control of vasomotor tone through the activation of calcium-activated potassium channels. In humans, the role of EDHF has been demonstrated in various vascular beds including coronary, peripheral, skin and venous vessels. The mechanisms of EDHF-type relaxations identified in humans involved the release by the endothelium of hydrogen peroxide, epoxyeicosatrienoic acids (EETs), potassium ions and electronical communication through the gap junctions. The role of EETs could be particularly important because, in addition contributing to the maintenance of the basal tone and endothelium-dependent dilation of conduit arteries, these factors share many vascular protective properties of NO. The alteration of which might be involved in the physiopathology of cardiovascular diseases. The evolution of EDHF availability in human pathology is currently under investigation with some results demonstrating an increase in EDHF release to compensate the loss of NO synthesis and to maintain the endothelial vasomotor function whereas others reported a parallel decrease in NO and EDHF-mediated relaxations. Thus, the modulation of EDHF activity emerges as a new pharmacological target and some existing therapies in particular those affecting the renin,angiotensin system have already been shown to improve endothelial function through hyperpolarizing mechanisms. In this context, the development of new specific pharmacological agents especially those increasing EETs availability may help to prevent endothelial dysfunction and therefore enhance cardiovascular protection in patients. [source]

The Development of the Epicardium in the Sturgeon Acipenser naccarii

THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 10 2009
José M. Icardo
Abstract This article reports on the development of the epicardium in alevins of the sturgeon Acipenser naccarii, aged 4,25 days post-hatching (dph). Epicardial development starts at 4 dph with formation of the proepicardium (PE) that arises as a bilateral structure at the boundary between the sinus venosus and the duct of Cuvier. The PE later becomes a midline organ arising from the wall of the sinus venosus and ending at the junction between the liver, the sinus venosus and the transverse septum. This relative displacement appears related to venous reorganization at the caudal pole of the heart. The mode and time of epicardium formation is different in the various heart chambers. The conus epicardium develops through migration of a cohesive epithelium from the PE villi, and is completed through bleb-like aggregates detached from the PE. The ventricular epicardium develops a little later, and mostly through bleb-like aggregates. The bulbus epicardium appears to derive from the mesothelium located at the junction between the outflow tract and the pericardial cavity. Strikingly, formation of the epicardium of the atrium and the sinus venosus is a very late event occurring after the third month of development. Associated to the PE, a sino-ventricular ligament develops as a permanent connection. This ligament contains venous vessels that communicate the subepicardial coronary plexus and the sinus venosus, and carries part of the heart innervation. The development of the sturgeon epicardium shares many features with that of other vertebrate groups. This speaks in favour of conservative mechanisms across the evolutionary scale. Anat Rec, 2009. © 2009 Wiley-Liss, Inc. [source]

Intermediary Spleen Microvasculature in Canis familiaris, Morphological Evidences of a Closed and Open Type

ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 5 2003
G. Alexandre-Pires
Summary Numerous studies have been made regarding circulation via the red pulp of the spleen, and intense controversy surrounds the question as to whether or not endothelial continuity exists between arterial and venous vessels. Aware of this intense controversy, and in order to perform investigation over the spleen of dogs infected with a parasitic disease (future reports shall be done), the authors studied the vascularization of the normal dog spleen in order to define its normal pattern and evaluate the eventual changes of the circulation pattern under the parasitic condition. These studies led us to report, unequivocally, using complementary vascular replective techniques, that the normal dog's intermediary circulation is morphologically closed and of the open kind also. These findings are contrary to the thesis that defends the existence of a physiologically closed and morphologically open circulation in the dog spleen. Lymphatic vessels in the spleen of the dog are also demonstrated. [source]

Adrenergic mechanisms in canine nasal venous systems

BRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2003
Min Wang
We investigated the adrenergic mechanisms of the two venous systems that drain the nasal mucosa, thereby their exact role in eliciting nasal decongestion. The action of endogenously released noradrenaline and exogenous adrenergic agonists on different segments of the nasal venous systems, i.e. collecting (LCV, SCV) and outflow (SPV) veins of posterior venous system, collecting (ACV) and outflow (DNV) veins of anterior venous system and venous sinusoids of the septal mucosa (SM), were studied. In vitro isometric tension of the vascular segments was measured. Transmural nerve stimulation (TNS) produced constriction in ACV, DNV and SM, primary constriction followed by secondary dilatation in LCV and SCV and dilatation in SPV. Tetrodotoxin (10,6M) abolished all responses. Phentolamine (10,6M), prazosin (10,6M) and rauwolscine (10,7M) inhibited the constriction in all venous vessels. Propranolol (10,6M), atenolol (10,6M) and ICI 118,551 (10,6M) inhibited the relaxation in SPV but not in LCV and SCV. Phenylephrine and clonidine constricted whereas dobutamine and terbutaline relaxed all venous vessels dose-dependently. These results indicate ,1 -, ,2 -, ,1 - and ,2 -adrenoceptors are present in both venous systems. TNS causes constriction of anterior venous system, venous sinusoids and posterior collecting veins primarily via postjunctional ,2 -adrenoceptors but relaxation of posterior outflow vein equally via postjunctional ,1 - and ,2 -adrenoceptors. The combined action of the two adrenergic mechanisms can reduce nasal airway resistance in vivo by decreasing vascular capacitance and enhancing venous drainage via the posterior venous system. British Journal of Pharmacology (2003) 138, 145,155. doi:10.1038/sj.bjp.0705020 [source]