Alan Stephenson

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Differences in prostaglandin H synthetase (PHS) activity in the substantia nigra of age- and postmortem interval-matched parkinsonian, Alzheimer's, and normal control brain tissue were assessed. Prostaglandin E2 (PGE2, an index of PHS activity) was higher in substantia nigra of parkinsonian brain tissue than Alzheimer's or control tissue. Incubation of(More)
In skeletal muscle, oxygen (O(2)) delivery to appropriately meet metabolic need requires mechanisms for detection of the magnitude of O(2) demand and the regulation of O(2) delivery. Erythrocytes, when exposed to a decrease in O(2) tension, release both O(2) and the vasodilator adenosine triphosphate (ATP). The aims of this study were to establish that(More)
The oxygen required to meet metabolic needs of all tissues is delivered by the erythrocyte, a small, flexible cell which, in mammals, is devoid of a nucleus and mitochondria. Despite its simple appearance, this 'bag of hemoglobin' has an important role in its own distribution, enabling the delivery of oxygen to precisely meet localized metabolic need. When(More)
Integration of the numerous mechanisms that have been suggested to contribute to optimization of O(2) supply to meet O(2) need in skeletal muscle requires a systems biology approach which permits quantification of these physiological processes over a wide range of length scales. Here we describe two individual computational models based on in vivo and in(More)
Adenosine triphosphate (ATP) release from rabbit erythrocytes occurs in response to deformation or reduced oxygen tension. A signal transduction pathway that relates these stimuli to ATP release has been proposed. This pathway includes the heterotrimeric G proteins, Gs and Gi, adenylyl cyclase, protein kinase A, and the cystic fibrosis transmembrane(More)
BACKGROUND Systems biology aims to understand biological systems on a comprehensive scale, such that the components that make up the whole are connected to one another and work through dependent interactions. Molecular correlations and comparative studies of molecular expression are crucial to establishing interdependent connections in systems biology. The(More)
The erythrocyte, a cell responsible for carrying and delivering oxygen in the body, has often been regarded as simply a vehicle for the circulation of hemoglobin. However, it has become evident that this cell also participates in the regulation of vascular caliber in the microcirculation via release of the potent vasodilator, adenosine triphosphate (ATP).(More)
Safety-critical embedded systems go through rigorous verification processes before being put into service. Verification is a major source of cost in the development process because of the rigour with which the verification is carried out. Most designs are subject to high levels of change traffic during development. This greatly increases the cost of the(More)
BACKGROUND Within erythrocytes (RBCs), cAMP levels are regulated by phosphodiesterases (PDEs). Increases in cAMP and ATP release associated with activation of β-adrenergic receptors (βARs) and prostacyclin receptors (IPRs) are regulated by PDEs 2, 4 and PDE 3, respectively. Here we establish the presence of cytosolic PDEs in RBCs and determine a role for(More)
The development of aviation engine control software is a prime example of a process in which the overriding concern is safety. In building such a complex system, change is inevitable. This paper discusses the aims of CONVERSE, an EPSRC-funded p r oject to investigate change management in safety-critical software development. The aim is to reduce the costs(More)