Browsing by Subject "effects"
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Item Effects of Cardiorespiratory Fitness on Serum Ferritin Concentration and Type 2 Diabetes: Evidence from the Aerobics Center Longitudinal Study (ACLS)(2008-05-01) Le, Tuan D.; Sejong Bae; Karan Singh; Steven BlairLe, Tuan D., Effects of Cardiorespiratory Fitness on Serum Ferritin Concentration and Type 2 Diabetes: Evidence from the Aerobics Center Longitudinal Student (ACLS). Doctor of Public Health (Clinical Research). May 2008, 114 pp., 12 tables, 8 figures, bibliography, 68 titles. Recent studies suggest that an elevated serum ferritin concentration is considered an independent factor associated with increased risk of type 2 diabetes and cardiorespiratory fitness (CRF) is inversely associated with diabetes. Using secondary data from Aerobics Center Longitudinal Study at the Cooper Institute, Dallas, Texas, the author explored the association between serum ferritin levels and diabetes, CRF and diabetes, and the effect of CRF on the association between serum ferritin levels and diabetes. A cross-sectional study and a longitudinal cohort study were used. In the cross-sectional study, an increased CRF level found to be associated with a decreased serum ferritin concentration and a lowered prevalence of type 2 diabetes. Participants with high ferritin levels and high triglyceride levels were 1.89 and 1.57 times more likely to have diabetes respectively. Overweight or obese individuals were 1.35 to 1.40 times more likely to have diabetes. Participants with a family history of diabetes were 3.69 times more likely to have diabetes. Participants in the highest CRF quintile levels were 40% and 15% less likely to have type 2 diabetes among persons with normal and high blood glucose, respectively. In the prospective cohort study, it was found that serum ferritin might predict the development of type 2 diabetes in males and high serum ferritin concentration levels. The incidence rate among males increased with serum ferritin quartile (ptrend [less than] 0.05). A reduction of serum ferritin concentration was associated with a reduction of diabetes risk in those participating in physical activity. It suggests physicians might use patients' serum ferritin concentrations as a marker for predicting risk for new-onset diabetes and patients should be encouraged to participate in physical activities.Item Endurox R4® & Gatorade®: Effects of Recovery Drinks After Prolonged Glycogen-Depleting Exercise(1999-06-01) Williams, Michael Brandon; Raven, Peter B.; Smith, Michael; Shi, XiangrongWilliams, Michael B., Endurox R4® & Gatorade®: Effects of Recovery Drinks After Prolonged Glycogen-Depletion Exercise. Master of Science (Biomedical Sciences, Integrative Physiology), June, 1999, 73 pp., 2 tables, 18 figures, references. Purpose: Eight high-fit (bicycle Vo2max=62.4 ± 1.10 ml·kg-1·min-1) male cyclists, aged 28.4±1.65 yrs, performed a two-hour endurance bicycle exercise to achieve depletion of skeletal muscle and liver glycogen. During recovery, Endurox R4 Recovery Drink®, or Gatorade®, was ingested to investigate their relative restorative capacities to enable further exercise. Methods: Each subject performed two days of testing: one for each drink presented in random order. On each testing day, the twelve-hour fasted subject performed a two-hour cycling exercise bout at 75% VO2max followed by one to three five-minute sprints at 85% VO2max. At the end of the exercise blood glucose concentrations were 3.98±0.138 mmol/L. A four hour recovery period ensued in which the subject was given 24-ounces of the recovery drink. A performance test at 85% VO2max to exhaustion was then conducted. Ventilatory responses were collected breath-to-breath, while venous blood samples were measured for oxidation products, glucose and insulin concentrations. Results: The recovery phase showed significant increases in both plasma glucose and serum insulin following Endurox R4 Recovery Drink® ingestion as compared to Gatorade®. There was a significant increase in time to exhaustion (+55%) following Endurox R4 Recovery Drink® during the performance ride compared to Gatorade®. Final oxidation products following Endurox R4 Recovery Drink® ingestion were significantly decreased as compared to Gatorade® ingestion, in that Thiobarbituric Acid Reactive Substrates (T-BARS) were significantly decreased. Conclusions: These data indicate that the Endurox R4 Recovery Drink®, when compared to Gatorade®, significantly enhanced recovery from glycogen-depleting exercise. In addition, Endurox R4 Recovery® Drink decreased the formation of final oxidation products, when compared to Gatorade®.Item The Effects of Elevated Glucose Upon Na+/K+-ATPase in Bovine Retinal Pigment Epithelial Cells(1994-12-01) Crider, Julie Y.; Thomas Yorio; John Lane; Edward OrrCrider, Julie Y., The Effects of Elevated Glucose Upon Na+/K+-ATPase in Bovine Retinal Pigment Epithelial Cells. Doctor of Philosophy (Biomedical Sciences, Pharmacology), December, 1994, 154 pp., 14 tables, 31 illustrations, bibliography, 288 titles. Bovine retinal pigment epithelial (RPE) cells were cultured under 1, 4.5 and 10 g/l glucose conditions in order to characterize the effects of hyperglycemia upon Na+/K+-ATPase. Functional activity of Na+/K+-ATPase was measured as ouabain-sensitive Rb+ uptake. 3H ouabain was used to assess binding characteristics of Na+/K+-ATPase. The major contributors to rubidium (mRb+) uptake activity were the ouabain-sensitive Na+/K+-ATpase and a bumetanide-sensitive NA+/K+/Cl- cotransporter. Dose response curves for ouabain and bumetanide produced IC50 values for 86Rb+ uptake of 60-100 nM and 120 nM, respectively. At elevated glucose concentrations, the aldose reductase inhibitor (ARI) AL-1576 stimulated 86Rb+ uptake upon chronic treatment. A sensitive new nonradioactive Rb+ uptake assay was developed which utilized suppressed conductivity detection and provided several advantages over the radioactive method. The average ouabain IC50 value was confirmed to be 100nM and was not significantly affected by elevated glucose concentrations. The bumetanide sensitive component was responsible for approximately 30% of Rb+ uptake at all glucose concentrations. Potassium efflux out of the cells was observed that was sensitive to the Na+/K+/Cl- cotransport inhibitor bumetanide. Elevated glucose appeared to increase Rb+ transport through potassium channels was also reduced Rb+ uptake indicating a decrease in Na+/K+-ATPase activity. Bovine RPE cells exposed to both high glucose and AL-1576 for one month showed mild stimulation of Rb+ uptake compared to the activity in high glucose alone. Ouabain and strophanthidin inhibition of 3H ouabain binding, in bovine RPE cells, appeared to be unaffected by hyperglycemia. The average IC50 values for these compounds were 5.02 x 10^-8 M, respectively. The results of this study indicate that Na+/K+-ATPase activity in bovine RPE is decreased by hyperglycemic state, and can be stimulated by treatment with an aldose reductase inhibitor administered from the onset of the hyperglycemic insult.Item The Effects of Hyperlipidemia and Hypoglycemia on Myocardial Contractile Function and Oxygen Utilization During Coronary Hypoperfusion(1998-08-01) Hart, Bradley Joe; Downey, H. Fred; Mallet, Robert T.; Smith, Michael B.Hart, Bradley Joe, The Effects of Hyperlipidemia and Hypoglycemia on Myocardial Contractile Function and Oxygen Utilization During Coronary Hypoperfusion Master of Science (Biomedical Sciences), August, 1998, 85 pp., 1 table, 5 figures, references, 51 titles. This study was designed to determine the effects of elevated fatty acid and lowered glucose concentrations on myocardial contractile function and substrate selection during hypoperfusion. Coronary perfusion pressure (CPP) was lowered in the left anterior descending coronary artery of open-chest anesthetized dogs. Glucose uptake, fatty acid uptake, and percent segment shortening (%SS) were determined with normal arterial FFA concentrations (Group 1) or with elevated concentrations (Groups 2 and 3). When glucose was removed by dialysis in Group 3, FFA uptake increased and glucose uptake decreased relative to Group 1 at 40 mmHg CPP (p [less than] 0.05). Oxygen consumption significantly increased (p [less than] 0.05); however, %SS was unchanged. Thus, although the myocardium switches from fatty acid to glucose metabolism to increase oxygen utilization efficiency during hypoperfusion, blocking this switch does not contribute to a further decrease in myocardial contractile function.Item The Involvement of D1 and D2 Dopamine Receptors in Cocaine Self-Administration(1996-06-01) Peltier, Rachel; Michael Forster; Patricia A. Gwirtz; Thomas YorioPeltier, Rachel L., The Involvement of D1 and D2 Dopamine Receptors in Cocaine Self-Administration. Doctor of Philosophy (Biomedical Sciences), June 1996, 195 pp. introduction, 6 chapters, discussion, bibliography, 91 titles. D1 and D2 dopamine receptor subtypes have been implicated in producing the reinforcing properties of cocaine. Chronic exposure to cocaine produces tolerance to its reinforcing effects in rats trained to self-administer cocaine. The time between cocaine reinforcers (ISRT) is directly related to dose. A three-point dose-response curve (0.125, 0.25 and 0.5 mg/inj) for cocaine self-administration is obtained during a single test session, allowing determination of optimal tolerance effects of cocaine (20 mg/kg/8 hr/7 days; IP) as demonstrated by a shift of the curve to the right. To test if pharmacokinetic factors contribute to the development of tolerance to the reinforcing properties of cocaine (20 mg/kg/8hr/7days; IP), cocaine and benzoylecgonine (metabolite) were measured in the plasma and brains of rats given a challenge injection of cocaine (2.0 mg/kg; I.V.). Chronic cocaine did not reduce the concentration of cocaine must be due to pharmacodynamics changes. Acute pretreatment with either the direct dopamine agonists d-amphetamine (0.32-3.2 mg/kg) or methamphetamine (1.0 mg/kg) did not consistently change cocaine self-administration. Chronic high-dose treatment with d-amphetamine and methamphetamine produced cross-tolerance to the reinforcing effects of cocaine but apomorphine (0.32-3.2 mg/kg) did not. In contrast, acute pretreatment with dopamine antagonists; flupentixol (mixed D1 and D2, 0.032-1.0 mg/kg), SCH23390 (specific D1, 0.0032-0.32 mg/kg), or eticlopride (specific D2, 0.0032 -3.2 mg/kg); dose-dependently decreased the reinforcing effects of cocaine (ISRT). Chronic treatment with mixed of D1 antagonists (flupentixol, 3.2 mg/kg/12 hr/5 days; or SCH23390, 0.25 mg/kg/12 hr/7 days) produced sensitization to the reinforcing effects of cocaine, but the D2 antagonist eticlopride (0.25 mg/kg/12 hr/7 days) produced cross-tolerance to the reinforcing effects of cocaine. In summary, both the D1 and D2 receptor subtypes seem to be involved in the acute effects of cocaine; however, the development of tolerance to cocaine appears to involve only the D1 receptor subtype.