T. M. Griffith

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We have developed a mathematical model of arterial vasomotion in which irregular rhythmic activity is generated by the nonlinear interaction of intracellular and membrane oscillators that depend on cyclic release of Ca2+ from internal stores and cyclic influx of extracellular Ca2+, respectively. Four key control variables were selected on the basis of the(More)
AIMS Our objective was to investigate whether pro-oxidant properties of ascorbic acid (AA) and tetrahydrobiopterin (BH(4)) modulate endothelium-dependent, electrotonically mediated arterial relaxation. METHODS AND RESULTS In studies with rabbit iliac artery (RIA) rings, NO-independent, endothelium-derived hyperpolarizing factor (EDHF)-type relaxations(More)
The effects of pharmacological interventions that modulate Ca(2+) homeodynamics and membrane potential in rat isolated cerebral vessels during vasomotion (i.e., rhythmic fluctuations in arterial diameter) were simulated by a third-order system of nonlinear differential equations. Independent control variables employed in the model were [Ca(2+)] in the(More)
We have investigated the role of vascular smooth muscle Ca2+ fluxes in the genesis of chaotic pressure oscillations induced by histamine in isolated resistance arteries from the rabbit ear. The responses exhibited distinct "fast" and "slow" components, with periods of 5-20 s and 1-5 min, respectively, which could be dissociated pharmacologically. The fast(More)
Chronic arsenic ingestion predisposes to vascular disease, but underlying mechanisms are poorly understood. In the present study we have analyzed the effects of short-term arsenite exposure on vascular function and endothelium-dependent relaxation. Endothelium-dependent relaxations, nitric oxide (NO) and endothelium derived hyperpolarizing factor(More)
We have shown that the patterns of vasomotion induced by histamine in isolated rabbit ear resistance arteries can be described in terms of iterative circle maps that model the dynamics of coupled nonlinear oscillators. Cyclopiazonic acid (CPA), an inhibitor of the sarcoplasmic reticulum Ca(2+)-adenosinetriphosphatase pump, consistently transformed chaotic(More)
Nonlinear mathematical techniques now make it possible to quantify the complexity of an irregular time series through calculation of a parameter known as fractal dimension. In the present study, we use such an analysis to provide evidence that histamine-induced pressure oscillations in an isolated rabbit ear resistance artery are generated by deterministic(More)
We have analyzed the contribution of membrane ion transport systems to chaotic vasomotion induced by histamine in isolated rabbit ear resistance arteries. Dynamic complexity was monitored as a fractal correlation dimension that provides an estimate of the minimum number of control variables contributing to an irregular time series and generally took a value(More)
We have explored the potential of an artificial neural network to capture the dynamics of chaotic temporal fluctuations in arterial pressure and flow. Model generated signals that simulate this ubiquitous physiological phenomenon in both form and complexity were used to train a Multilayer Perceptron (MLP) after first locating the optimum time delay to(More)
By using non-linear techniques to analyse irregular histamine-induced pressure oscillations in an isolated rabbit ear resistance artery, we have shown that the pressure oscillations are generated by deterministic rather than stochastic mechanisms. The average fractal dimension of the oscillations was between 2 and 3, thus implying that three (or more)(More)
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