There is an increasing recognition that vascular disease risk is associated with a greater incidence of cognitive impairment and dementia. Such link is supported by the physiological observation that cerebral metabolism heavily relies on vascular supply of oxygen and energy substrates. Cerebral hypoperfusion which results from vascular dysfunction causes a mismatch between energy demand and supply and is associated with the pathological features of dementia, including the impairments of action potential generation and protein synthesis, glutamatergic excitotoxicity, and the deposition of cerebral amyloid-β proteins. In contrast, habitual aerobic exercise is an established strategy to ameliorate the risk factors for vascular disease and is increasingly recognized in improving cognitive function. Accordingly, the primary purpose of this dissertation study was to investigate whether the exercise-related improvement in cognitive function was attributable to ameliorated vascular function and risk factors for vascular disease. In order to address this as comprehensively as we could, both cross-sectional and interventional studies were conducted. The primary findings from the present study were as follows. In the cross-sectional study, a greater cognitive performance observed in endurance-trained adults was associated with higher levels of cerebral CO2 reactivity and brachial endothelium-dependent vasodilation and lower levels of central arterial stiffness and plasma insulin. In the interventional study, a 3-month aerobic exercise training intervention did not improve cognitive function although central arterial stiffness and brachial endothelium-dependent vasodilation made favorable changes. However, we found that the improvement in memory performance after aerobic exercise training was associated with the reduction in central systolic blood pressure. Taken together, a better cognitive performance observed in endurance-trained adults may not directly be attributable to greater vascular function because there were discrepant changes in cognitive and vascular functions after a 3-month aerobic exercise intervention. The correlation between the changes in memory performance and central systolic blood pressure is interesting but needs further investigation using a larger sample size. The discrepancy in the results between the cross-sectional and interventional studies could be explained by the duration of exercise training and/or the time it takes for the effect of improved vascular function to translate into cognitive function. / text

The copper smelting industry has under gone extreme change over the past three decades. These changes have reordered dramatically the demand for inputs and the way in which those inputs have been utilized. The stimulus for change has come from multiple sources, and chief among these stimuli has been the mandate to sharply curtail the atmospheric release of sulfur dioxide. Even though the total emissions were lower than those from steam generation of electricity and from the refinery and petro-chemical industry, the perceived local and regional impact of sulfur dioxide forced extreme changes in the utilization of fundamental inputs of capital, labor, energy and materials.This study attempts to analyze these input use changes by modeling the industry as a translog cost function and by generating a number of associated elasticities. In addition to the four basic inputs, the model includes as control variables output, and other variables that represent pollution abatement and technical change.The challenge of estimating a large model on a limited number of observations has delivered information that is more limited in scope than was originally desired. The proxy for technical change did not produce significant parameters and the pollution abatement proxy is limited in its participation in the results. The range of elasticities computed reveal a picture of an industry characterized by inelasticity, in general, labor and energy being part of the exceptions. The industry is found to be sensitive to output level in its degree of elasticity among inputs.The translog model is found to be an effective tool for industry analysis. The promise of detailed analytical information may be even greater at the firm level where data are more accurate and the number of observations far greater.

Aim: To determine the prognostic value of cardiopulmonary exercise testing (CPET) for major vascular surgery in South African patients. Methods: CPET has been used in Durban since October 2004 to predict cardiac risk for high-risk patients undergoing major vascular surgery. A submaximal 'anaerobic threshold' (AT) test was conducted on all high-risk patients. Patients were classified into two groups: 'low AT' where the oxygen consumption at the AT was <1 lml.kg^.min"1 for cycling or < 9ml.kg"1.mkf1 for arm cranking and 'high AT' when the patient surpassed these targets. Analysis of all in-hospital deaths following surgery was conducted by two independent assessors blinded to the CPET test result. Deaths classified as primarily 'cardiac in origin' have been used in this retrospective cohort analysis. Results: The AT measured during CPET was not a statistically significant pre-operative prognostic marker of cardiac mortality. However, the survivors of the patients with a 'low AT' may be identified by their response to increasing metabolic demand between 5 and 7 ml.kg^.min"1. Survivors were more dependent on increasing heart rate, while non-survivors were more dependent on oxygen extraction. When this information is added to the AT, CPET was the only test statistically associated with cardiac mortality, in comparison to Lee's Revised Cardiac Risk Index and the resting left ventricular ejection fraction which were not statistically associated with cardiac death. A hundred percent of patients with a positive test died of cardiac causes, while 11% of the patients with a negative test had cardiac deaths. The risk ratio associated with cardiac death following a positive test was 8.00 [95% CI 3.8-16.9]. The sensitivity was 0.25 [95% CI 0.04-0.64], the specificity was 1.00 [95% CI 0.90-1.00], the positive predictive value was 1.00 [95% CI 0.20-0.95] and the negative predictive value was 0.88 [95% CI 0.74-0.95]. Conclusions: CPET provides valuable prognostic information in our surgical population. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2007.

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1994. / Added t.p. with thesis statement inserted.

Thesis (Ph. D.). University of Lund. Depts. of Anasthesia and Clinical Physiology.

Thesis (doctoral)--Lund University, 1994. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Universitetet i Göteborg.

Thesis (doctoral)--Universitetet i Göteborg.

Thesis (doctoral)--Lund University, 1997. / Added t.p. with thesis statement inserted.