It is known that different-sized blood vessels performs different functions within the circulation. Analysis of the literature suggests that there are diameter-dependent differences in the characteristics of neuronal regulation of arterial smooth muscle tone. The experiments described in this thesis were designed to investigate this by systematically studying the neuronal control of arterial tone in three sizes of artery using the rat mesentery as a model vascular bed. The role of purinergic transmission was of particular interest. My experiments show that ,-meATP and suramin are far less potent in large arteries than in smaller vessels. Contractions evoked by brief trains of nerve stimulation are mainly purinergic in small and medium-sized arteries but almost entirely adrenergic in large arteries. Investigations of the sources of calcium for contraction revealed that blockade of L-type calcium channels has very little effect on agonist or nerve-evoked contractions. Inhibition of calcium-induced calcium release also caused hardly any reduction of contractile responses. Despite the pharmacological differences observed in whole tissue experiment, immunohistochemical analysis showed no substantial differences in the expression pattern of P2X receptor isoforms in the three sizes of artery. Electrophysiological experiments indicate that P2X current densities are broadly similar in all arteries, and in contrast to contraction studies, currents were always suramin sensitive. In addition, all post-junctional responses to P2X receptor agonist are abolished in vas deferens from P2X1-deficient mice. The two main conclusions that can be drawn from my data are i) purinergic transmission is more important in sympathetic nerve-mediated control of arterial tone in small arteries which are crucial in blood pressure regulation ii) almost all the calcium required for smooth muscle contraction is provided by calcium entry through the P2X receptor channel. This may have important implications for the treatment of hypertension.

No description available.

No description available.

Orally administered non-steroidal anti-inflammatory drugs (NSAIDs) are routinely used in the management of several rheumatic disorders. However, one of the major drawbacks to their use has been the severity of the adverse reactions, in particular the gastro-toxicity associated with oral administration. Topical formulations of NSAIDs were introduced in an attempt to overcome the systemically mediated gastro-toxic effects of oral delivery. It was claimed that topical delivery localised the drug at the site of action and therefore reduced the gastro-toxic effects. These claims were investigated, using carrageenan-induced rat paw oedema arid U.V.- induced erythema models of inflammation. The aim of this study was to determine whether the topical NSABD formulations under investigation produced their beneficial effects locally or systemically, and if topical delivery afforded any benefits with regard to gastro-toxicity. Following topical administration of the NSAID the drug did not remain localised within the tissue and the plasma drug levels achieved were comparable to those produced orally. Hence the number of lesions observed after topical administration were not significantly different to those caused by oral administration. In carrageenan-induced rat paw oedema plasma drug levels appeared to be a critical factor in producing a beneficial anti-inflammatory effect. However, in U.V.-induced erythema tissue drug levels relate to significant anti-inflammatory activity. Therefore, it can be concluded that the topical NSAID formulations under investigation appear to have both systemically arid locally mediated anti-inflammatory effects and that they do not afford any benefits in terms of reducing gastro-toxic effects. The site of action is probably dependent upon the type of end-point inflammatory response (oedema or erythema) and the mediators responsible for the inflammatory response.

Background: Statin-use and the adoption of healthy lifestyle choices are important components of cardiovascular disease prevention. The nature of the relationship between the former and the latter, and the influence of personal and social factors on this relationship remains unclear. Aim: This research aimed to examine whether statin-use influences the adoption of healthy dietary and exercise choices by changing the way people think of high cholesterol as a risk factor for cardiovascular disease in the context of their social world. Methods: Questionnaires were used to compare the dietary and exercise behaviours; perceptions of high cholesterol; and perceived future risk of cardiovascular disease of statin users and non-statin users recruited in Nigeria and in the UK. In-depth interviews were conducted in each country to explore between group differences and the influence of social factors on statin-use, adoption of a healthy lifestyle choices; perceptions of high cholesterol, future cardiovascular disease risk and availability of social support. Results: A similar proportion of the 148 participants recruited from Nigeria and the 89 participants recruited from the UK reportedly adopted a low-fat diet, 69% and 70% respectively. Reported adoption of healthy exercise behaviours was much lower and notably different between the country samples, 16% and 32% respectively. Statin-use was found to influence the adoption of healthy lifestyle choices in 3 ways: it was found to encourage, hinder, and work alongside the adoption of healthy lifestyle choices. The adoption of healthy lifestyle choices was also influenced by cause-control perceptions, gender, and social factors such as location, preferences and demands of other people, and societal norms such as body image ideals. Conclusion: Statin-use influenced the adoption of healthy lifestyle choices in 3 different ways. Dietary changes were preferred to exercise changes. Illness perceptions and preferences of the individual and their social world influenced statin-use and the adoption of healthy lifestyle choices.

In this thesis, new applications of microdosing were explored in two clinical trials. Methods were developed for the separation and quantification of 14C-labelled analytes in human plasma using two-dimensional HPLC and accelerator mass spectrometry (AMS). Caffeine, midazolam, tolbutamide and fexofenadine were quantified in plasma after administration of a 14C-labelled cassette microdose to human volunteers via a HPLC-AMS recovery constant method. Mean accuracy for all analytes was within 13% of the measured plasma concentration with precision of <20% CV, meeting recommended acceptance criteria for HPLC-AMS assays. Complete resolution of each analyte was demonstrated by two-dimensional HPLC. Pharmacokinetic data obtained after cassette microdose administration were in close agreement with those previously obtained after administration of therapeutic doses. Co-administration of the cassette microdose with known inhibitors of metabolism enzymes and transporters resulted in a significant (p<0.01) increase in the area under the concentration-time curve from time zero to infinity (AUC0-∞) for caffeine (x8.2), midazolam (x11.7), fexofenadine (x3.2) and tolbutamide (x1.8, p<0.05). Administration of a combined 11C and 14C-labelled verapamil microdose allowed distribution in the brain to be monitored by PET imaging, while simultaneously obtaining plasma pharmacokinetics by AMS. The separation of 14C-verapamil by two-dimensional HPLC and AMS analysis resulted in the individual pharmacokinetics of R- and S-verapamil being consistent with those reported after therapeutic doses. In addition, a significant difference in pharmacokinetic data obtained for the two enantiomers clearly showed the preferential clearance of S-verapamil. Data were accurate within 12% of the true value with precision of <18% CV. Pharmacokinetic data obtained after PET analysis were consistent with those obtained during AMS analysis, proving the concept of combining the two techniques in clinical studies and enabling maximum information to be achieved from one single study.

Systematic reviews can provide timely, reliable evidence on which to make informed decisions. In order to make balanced decisions, information is not only needed on the benefits of an intervention, but also on its adverse effects. Yet few systematic reviews incorporate adverse effects data in their analysis. There is currently a lack of guidance on how to identify adverse effects data, this may impede systematic reviewers. This thesis helps address this situation by evaluating and optimising the methods for retrieval of research evidence for systematic reviews of adverse effects. The first stage of this programme of research critically reviews the methodological literature relating to the retrieval and inclusion of adverse effects data, including aspects such as the impact of study design (for example RCTs and cohort studies), database search strategies (for example in MEDLINE and EMBASE), sources of data (including database and non-database sources), publication status and funding status. Second, the results of a survey of the literature searching methods used in 849 systematic reviews of adverse effects are presented. Data were collated on aspects such as sources searched, search strategy design and the standard of reporting of the methods used. The reviews are published over a 17 year time period (1994-2011) thus enabling time trends analysis. The methods used in these systematic reviews of adverse effects are also compared with those reported in surveys of other types of reviews. Further potentially relevant evidence is incorporated to address gaps identified in the literature. A detailed analysis is provided of the contribution of different sources of data for adverse drug reactions using 58 included studies from a case study systematic review. The same case study systematic review is then used to measure the performance of adverse effects search filters in MEDLINE and EMBASE. Finally 242 included papers from a series of 26 systematic reviews are evaluated to strengthen the evidence base regarding adverse effects search filters and to assess individual adverse effects search terms in MEDLINE, EMBASE, and Science Citation Index (SCI). The strengths and weaknesses of the analyses are discussed and implications for practice and guidance presented along with recommendations for future research.

Streptokinase (SK), expressed by Lancefield Group A, C and G β-haemolytic Streptococci and Staphylocoagulase (SCG), expressed by S. aureus, are bacterial virulence factors which belong to a family of proteins known as Zymogen-activator and adhesion proteins (ZAAPs). SK and SCG are responsible for the non-proteolytic activation of plasminogen and prothrombin, respectively. Understanding of SK activity is exclusively based on the Group C (GCS) S. equisimilis H46a SK, a 'clot buster' or thrombolytic used in the treatment of Myocardial Infarction (MI), which exhibits no fibrin specificity. SK is the most used thrombolytic worldwide. Here, detailed kinetic studies in purified assay systems explored the mechanistic variation between a recombinant H46a SK (rSK H46a) and a Group A Streptococcal SK (M1GAS), most typically isolated in invasive human infection. This work demonstrates a fibrin specific mechanism for M1GAS SK and proposes a kinetic model for M1GAS SK plasminogen activation, to compliment the 'Trigger and Bullet' hypothesis for H46a SK by Bock and colleagues. This work has relevance to the use of SK variants, with enhanced fibrin specificity, for improvement of thrombolytic therapies. Cardiovascular diseases such as myocardial infaraction and ischaemic stroke are significant casues of mortality, particularly in the developing world. Access to Alteplase, an expensive recombinant tPA and the only licensed treatment for stroke, is limited and there is interest in the use of SK for this purpose. Furthermore, microbial resistance is an increasing health burden, as demonstrated by programs such as the Longitude prize. Exploring the mechanisms of bacterial virulence factors at the molecular level such as this could provide rationale for the development of much-needed new antimicrobial technologies.

No description available.

No description available.