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Various Vascular Beds (various + vascular_bed)

Distribution by Scientific Domains

Medical Sciences	75%

Selected Abstracts

Arterial Myogenic Properties of the Spontaneously Hypertensive Rat

EXPERIMENTAL PHYSIOLOGY, Issue 5 2002
Jennifer M. Hughes
When subject to a transmural pressure gradient resistance arteries develop a spontaneous, intrinsically initiated contraction which varies according to the pressure stimulus and occurs in the absence of vasoconstrictor agonists. Such pressure-dependent active changes in vascular tone are indicative of the vascular myogenic response and contribute to autoregulation and the setting of total peripheral resistance and hence blood pressure regulation. The myogenic behaviour of blood vessels provides the background tone upon which other vasomotor influences act. Hypertension is associated with a raised vascular resistance and in this article the evidence for increased myogenic activity contributing to the raised vascular resistance is reviewed. Although there are some cases that provide evidence for exaggerated myogenic responsiveness in resistance arteries taken from hypertensive animals it is not possible to conclude that enhanced myogenic contractile responses within normal pressure ranges contribute to the raised total peripheral resistance. However, the myogenic tone of the resistance arteries of the various vascular beds is subject to differing modulatory influences in hypertensive animals and their normotensive controls which may contribute to the aetiology of hypertension. [source]

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]

In vitro and in vivo pharmacological characterization of the novel UT receptor ligand [Pen5,DTrp7,Dab8]urotensin II(4,11) (UFP-803)

BRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2006
Valeria Camarda
The novel urotensin-II (U-II) receptor (UT) ligand, [Pen5,DTrp7,Dab8]U-II(4,11) (UFP-803), was pharmacologically evaluated and compared with urantide in in vitro and in vivo assays. In the rat isolated aorta, UFP-803 was inactive alone but, concentration dependently, displaced the contractile response to U-II to the right, revealing a competitive type of antagonism and a pA2 value of 7.46. In the FLIPR [Ca2+]i assay, performed at room temperature in HEK293hUT and HEK293rUT cells, U-II increased [Ca2+]i with pEC50 values of 8.11 and 8.48. Urantide and UFP-803 were inactive as agonists, but antagonized the actions of U-II by reducing, in a concentration-dependent manner, the agonist maximal effects with apparent pKB values in the range of 8.45,9.05. In a separate series of experiments performed at 37°C using a cuvette-based [Ca2+]i assay and CHOhUT cells, urantide mimicked the [Ca2+]i stimulatory effect of U-II with an intrinsic activity (,) of 0.80, while UFP-803 displayed a small (,=0.21) but consistent residual agonist activity. When the same experiments were repeated at 22°C (a temperature similar to that in FLIPR experiments), urantide displayed a very small intrinsic activity (,=0.11) and UFP-803 was completely inactive as an agonist. In vivo in mice, UFP-803 (10 nmol kg,1) antagonized U-II (1 nmol kg,1)-induced increase in plasma extravasation in various vascular beds, while being inactive alone. In conclusion, UFP-803 is a potent UT receptor ligand which displays competitive/noncompetitive antagonist behavior depending on the assay. While UFP-803 is less potent than urantide, it displayed reduced residual agonist activity and as such may be a useful pharmacological tool. British Journal of Pharmacology (2006) 147, 92,100. doi:10.1038/sj.bjp.0706438 [source]

Most readily usable methods to measure ocular blood flow

ACTA OPHTHALMOLOGICA, Issue 2009
K GUGLETA
Purpose SIS Lecture. Methods Literature search. Results Ocular Blood Flow Research Association (OBFRA, recently merged with another organization - ISOCO, into one single Association for Ocular CDirculation - AOC) made a significant contribution to standardization of the blood flow measuring techniques in the field of ophthalmology. A consens was reached on the number of OBF measurements techniques that occured in the past decades. Particular emphasis was placed on the basic technology, specific parameters and interpretation, accuracy and reproducibility, field of clinical applications. Open questions were extensively discussed, limits of each technique clearly postulated. and a consensus statement put together for each of the technique involved. It encompassed techniques like color Doppler imaging, laser Doppler flowmetry (continuous as well as scanning LDF), laser Doppler velocimetry, Retinal Vessel Analyzer, combination of the vessel diameter measurement and the LDV, laser interferometry of the fundus pulsations amplitude, retinal oxymetry, measurements of the pulsatile component of the blood flow, blue field entoptic method and the newest - Doppler OCT. Conclusion There is no overwhelming measuring technique able to cover all the aspects of the research and the daily clinical routine. Various parameters and various vascular beds are involved, which makes the interpretation of the obtained results strenuous. Of particular importance is the capability of OBF measuring techniques to capture one dynamic feature of ocular circulation - its ability to regulate and to response to various challenges. It is widely believed that not the constantly reduced blood flow, but rather the lack of regulation thereof, leads to prevalent ocular diseases. [source]