Image Analysis: A New Tool in the Study of Mammalian Vascular Smooth Muscle Function

Wight, Marti (1990) Image Analysis: A New Tool in the Study of Mammalian Vascular Smooth Muscle Function. MSc(R) thesis, University of Glasgow.

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Abstract

The aim of this project was to develop a method to measure accurately dimensional changes in isolated blood vessel preparations using the technique of computerised on-line image analysis. A programme developed to study gut peristalsis was modified and refined for use by the image analyser (Magiscan) to study what effects various mechanical or chemical stimuli had on the dimensions of the vessels examined. Branch-free segments from both the arterial and venous sides of the circulation were set up under isotonic conditions with each vessel being subjected to a constant transmural pressure and longitudinal tension. The investigations involved looking at four different areas of vascular function: these were (1) postjunctional receptor populations in the rabbit small saphenous vein and saphenous artery, (2) the influence of the endothelium on contractile responses of the rabbit small saphenous vein and saphenous artery, (3) rhythmic activity in the rat thoracic aorta, rat portal vein and rabbit saphenous artery and finally (4) electrical field stimulation of the rabbit small saphenous vein. (1.1) Agonist and antagonist potency profiles indicate that the rabbit small saphenous vein has a heterogeneous postjunctional population of alpha1- and alpha2-adrenoceptors, the alpha2-adrenoceptors being the more dominant of the two in mediating constriction. (1.2) Agonist and antagonist potency profiles indicate that the rabbit saphenous artery also has a heterogeneous postjunctional population of alpha1- and alpha2-adrenoceptors. In this vessel though the alpha1-adrenoceptor is the dominant receptor mediating constriction. (1.3) The particularly high sensitivity to noradrenaline seen in both preparations may be due to the recruitment of a population of alpha2-adrenoceptors which is not revealed by other in vitro techniques. (2.1) Acetylcholine was able to relax noradrenaline-induced constrictions in both the rabbit small saphenous vein and saphenous artery. This relaxation, which was more pronounced in the vein, was presumably mediated via the release of EDRF from the endothelium. (2.2) Sodium nitroprusside, an endothelium-independent relaxant, was more effective than acetylcholine as a relaxing agent in both the artery and the vein. (2.3) Addition of haemoglobin, which blocks the action of EDRF, abolished or reduced the relaxation to acetylcholine in the artery and vein respectively. This provides further evidence for the existence of EDRF involvement in vascular function. (3.1) Rhythmic activity was seen in the rat portal vein and the rabbit saphenous artery, though in the artery only when the transmural pressure was reduced to venous levels. (3.2) No conclusive evidence was found for the presence of a propagated wave in either preparation. (4.1) Electrical field stimulation of the rabbit small saphenous vein caused a vasoconstriction which was evoked by neurally-released noradrenaline. (4.2) This constriction was shown to be more susceptible to rauwolscine than to prazosin, suggesting that the response was primarily via alpha2-adrenoceptors. (4.3) A small part of the response was resistant to addition of both antagonists, suggesting that either the antagonist concentrations were not high enough or that some other type of receptor was involved in the response. This study was not meant to be a comprehensive look at one particular aspect of vascular function. Instead a number of areas were examined to show where image analysis gave advantages over other in vitro techniques. Results have demonstrated image analysis to be a very sensitive and highly reproducible method for the isolated study of blood vessel function. In particular the technique mimics more closely the results found from in vivo studies. One example of this was the ease with which alpha2-adrenoceptors could be found both in vivo and when using image analysis but not when using other in vitro techniques.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Keywords: Physiology
Date of Award: 1990
Depositing User: Enlighten Team
Unique ID: glathesis:1990-78069
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 15:41
Last Modified: 30 Jan 2020 15:41
URI: http://theses.gla.ac.uk/id/eprint/78069

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