While a great deal of research has been directed towards the phenomena of excess post exercise oxygen consumption (EPOC), the effect of thermal stress on EPOC is not well defined. To assess the effect of heat stress on EPOC, seven healthy, active subjects (4 female, 3 male; 23.9 ± 2.0 years of age) performed 4 trials: one control (quiet rest) and one exercise (45 minutes of cycling at 65% VO2max workload) trial in moderate (23° C, 50% humidity) and hot (35° C, 50% humidity) environments. Oxygen consumption (V02), heart rate (HR) and rectal temperature (RT) were assessed pre, during and post control or exercise. Subjects were monitored until post exercise VO2 had returned to within ±2% of baseline. EPOC was determined by subtracting baseline VO2 from total V02 during the post exercise period. During the first 15 minutes (acute) post exercise, a significant EPOC (p = 0.0019) was seen in both exercise conditions over both control conditions. During the slow phase (> 15 minutes post exercise to baseline), there was no significant difference between the hot control (HC), moderate exercise (ME), or hot exercise (HE) EPOC. Total time post exercise until baseline was achieved was 35, 44, and 51 minutes for HC, ME, and HE respectively. HR was significantly elevated in both exercise conditions. During the acute post exercise period, HR in HE was elevated above MC, ME and HC (p < 0.05). RT was elevated in both exercise conditions during and post exercise. The present data indicate that heat stress does not have a significant effect on the magnitude or duration of EPOC. / School of Physical Education

It has been suggested that children are less likely than adults to demonstrate a plateau in oxygen uptake (V02) at maximal exercise. However, there has been no direct comparison. Therefore, the purpose of this study was to compare boys and men in achievement of plateau as well as the secondary criteria for maximal effort: heart rate (HR), respiratory exchange ratio (RER), and blood lactate (BLa). Seventeen boys (10.7 ±v 0.6 yrs) and 21 men (22.5 ± 2.0 yrs) completed a practice exercise test and a graded exercise test in order to determine VO2max and achievement of the criteria. The men also completed a second graded exercise test at a faster speed to determine if speed may affect plateau achievement. Comparisons indicated that, except for the BLa criterion, men and boys have similar rates of achievement. In addition, speed does not seem to play a role in criteria achievement. However, due to a small sample size, these results should be viewed with caution. / School of Physical Education

o,o???-Dityrosine (dityrosine), an oxidation product of tyrosine produced by reaction between tyrosyl radicals, is becoming established as a biomarker of free radical oxidative protein damage in vivo. Attempts to measure dityrosine concentrations in various physiological and pathological systems have produced varied and often contradictory results. Dityrosine concentrations in urine, plasma, cerebrospinal fluid (CSF) and brain tissue varying over three orders of magnitude have been reported, together with inconsistent claims of significant dityrosine elevation in several ageing-related pathologies. Some of these findings have contributed to the implication of free radical activity in the pathology of several neurodegenerative disorders, vascular and ocular abnormalities and in phagocyte response to infection. The aim of this study was to test the hypothesis that dityrosine levels are elevated in ageing and ageing-related disease. The study also aims to determine the utility of dityrosine measurement as an index of oxidative damage, and elucidate possible explanations for the inconsistent levels reported. An assay for the quantification of dityrosine was developed using capillary HPLC with electrospray tandem quadrupole mass spectrometry (HPLC-MS/MS). The assay was highly specific for dityrosine and has the highest absolute sensitivity for dityrosine of any method reported to date, with a detection limit of 3 femtomoles of dityrosine on-column. Urine samples from volunteers of different age and from hospital patients with various pathologies were analysed. Plasma protein hydrolysates from control, Alzheimer???s and stroke subjects were analysed, together with hydrolysates of post mortem brain tissue from Alzheimer???s and control subjects. Urinary dityrosine level is elevated in states of acute infection and inflammation, but does not correlate with age or chronic disease. Protein dityrosine in four sections of Alzheimer???s brain was not significantly different from control sections. Dityrosine was present in human plasma and tissue proteins at approximately 5-35 residues per million tyrosine residues, and in normal urine at 5-25 micromol/mol creatinine or 20-200 nM. Most of the discrepancies in the literature relate to inadequate specificity of the analytical method. Interpretation of published data with critical appraisal of measurement technology specificity is essential in developing an accurate understanding of the role of free radicals in ageing and disease.

Metallophthalocyanine complexes containing non-transition metals are very useful as sensitizers for photodynamic therapy, a cure for cancer that is based on visible light activation of tumour localized photo sensitizers. Excited sensitizers generate singlet oxygen as the main hyperactive species that destroy the tumour. Water soluble sensitizers are sought after for the convenience of delivery into the body. Thus, phthalocyanine (pc), tetrapyridinoporphyrazines (tppa) and tetramethyltetrapyridinoporphyrazines (tmtppa) with non-transition central metal atoms of Ge, Si, Sn and Zn were studied. First was the synthesis of these complexes, followed by their characterisation. The characterisation involved the use of ultraviolet and visible absorption spectroscopy, infrared spectroscopy, nuclear magnetic resonance spectroscopy, electrochemical properties and elemental analysis. Photochemical properties of the complexes were then investigated. Photolysis of these macrocycles showed two processes; -reduction of the dye and photobleaching, which leads to the disintegration of the conjugated chromophore structure of the dye. Photobleaching is the reductive quenching of the excited state of the sensitizers. The intensity of the quenching decreased progressively from tmtppa, tppa to pc metal complexes with photobleaching quantum yields, 6.6 x 10.5⁻¹, 1.8 x 10.5⁻¹ and 5.4 x 10⁻⁶ for Zntmtppa, Zntppa and Znpc, respectively. Efficiency of singlet oxygen sensitization is solvent dependent with very different values obtained for the same compound in different solvents, for example, 0.25 and 0.38 were observed as singlet oxygen quantum yields for Gepc complex in DMSO and DMF respectively. In DMSO the efficiency of ¹O₂ generation decrease considerably from pc to tppa and finally tmtppa. In water Getmtppa exhibits much higher singlet oxygen quantum yield, hence promising to be effective as a sensitizer for photodynamic therapy.

A series of structurally related BODIPY dyes were synthesised and characterised. Their photophysical properties were studied in order to determine whether they would be suitable candidates for use as photosensitisers in the photodynamic therapy (PDT) treatment of cancer. The synthesis of two highly fluorescent BODIPY cores was achieved via the acid-catalysed condensation of a pyrrole and a functionalised aldehyde. In order to promote intersystem crossing, and hence improve the singlet oxygen generation of these dyes, bromine atoms were added at the 2,6-positions of the BODIPY core. These dibrominated analogues showed good singlet oxygen quantum yields, and excellent photostability in ethanol. In order to red-shift the main spectral bands of the BODIPY dyes towards the therapeutic window, vinyl/ styryl groups were introduced at the 3-, 5-, and 7-positions via a modified Knoevengal condensation reaction. The addition of vinyl/ styryl groups to the BODIPY core caused an increase in fluorescence quantum yield as well as a decrease in singlet oxygen quantum yield with respect to the dibrominated analogues. However, two of the red-shifted BODIPY dyes still showed moderate singlet oxygen quantum yields. The use of BODIPY dyes in nonlinear optics (NLO) was explored. The nonlinear optical characterisations and optical limiting properties of a series of 3,5-dithienylenevinylene BODIPY dyes were studied, both in dimethylformamide (DMF) solution and when embedded in poly(bisphenol A carbonate) (PBC) as thin films. The 3,5-dithienylenevinylene BODIPY dyes showed typical nonlinear absorption behaviour, with reverse saturable absorption (RSA) profiles, indicating that they have potential as optical limiters. The second-order hyperpolarizability (Y), and third-order nonlinear susceptibility (/m[/(3)]) values are also reported for these dyes. The optical limiting values of one of the BODIPY dyes in solution, and two of the BODIPY-embedded PBC films, were below the maximum threshold of 0.95 J-cm-2. The effect of addition of substituents on the electronic structure of the BODIPY dyes was investigated using TD-DFT calculations. The calculated trends closely followed those determined experimentally.

M.Sc. / Developments in the catchment area of the Olifants River, such as poor agricultural practices and overgrazing, caused increased amounts of erosion material to enter the river. This leads to the silting up of the Phalaborwa Barrage, situated in the river, on the border of the Kruger National Park. Because of the occasional flushing of the Barrage, in order to retain storage capacity, the Olifants River inside the Kruger National Park is subjected to very high sediment loads. This has led to poor water quality and subsequent fish mortalities. The objective of this study was therefore to investigate the possible effects of silt loads released from the Barrage on the survival of selected life stages of Oreochromis mossambicus. Silt was collected from the Phalaborwa Barrage, and the silt/fish interaction was invesigated under controlled laboratory conditions. Oreochromis mossambicus was exposed to various silt concentrations for different exposure periods to determine the LC50 and sub-lethal concentration ranges. After determination of sub-lethal values, 0. mossambicus was exposed to these concentrations to determine whether they have any effects on the oxygen consumption and selected haematological parameters of exposed fish. Lethal levels for suspended sediment are interrelated with age differences of the fish, particle size of the suspended sediment and concentration. Increased suspended sediment disrupted activity and respiratory patterns, changed orientation responses and ultimately resulted in the death of the fish. The gills and the opercular cavities of the dead fish were usually clogged with a thick layer of mucus and silt. The laboratory experiments revealed that LC5 0 values for 0. mossambicus ranged from 26,78 to 54,20g silt/1 for larvae, 35,10 to 39,20g silt/1 for juveniles and 32,93 to 35,43g silt/1 for adult fish. The larval stage was generally less tolerant of suspended silt than juveniles and adults. Sub-lethal levels for adult fish ranged from 0 to 27g silt/l, where no mortalities occurred. Exposure of adult fish to sub-lethal concentrations of silt did alter routine oxygen consumption by causing increased rates (9 to 330% from initial) of oxygen consumption. This indicates that sub-lethal levels of suspended silt concentrations result in an increase in oxygen consumption by the fish due to an increase in metabolic rate associated with increased activity and stress. Silt exposure Exposure of adult fish to sub-lethal silt concentrations (<20g silt/l) resulted in increases in haemotocrit, red blood cell counts, white blood cell counts and blood glucose concentrations, but decreases in haemoglobin and mean corpuscular volume when compared to that for the control fish. These differences became more apparent as the silt exposure concentration increased with statistically significant differences (P<0.05) between most of the selected

This study was undertaken to determine and compare the rates of oxygen consumption and carbon dioxide elimination during normal and hyperventilated breathing at progressive work rates. Three subjects stepped at 18, 24, 30, 36 and 40 steps per minute on an eighteen inch bench for a duration of ten minutes or until exhaustion. All exercises were performed inside a 6,900 liter closed circuit respirometer. The volume of each subject obtained from hydrostatic weighings was subtracted from the chamber volume as was the volume of the bench. Net volume was corrected to STPD. The respirometer was equipped with Beckman oxygen and carbon dioxide analyzers, an internal cooling system as well as wet and dry thermocouples on three sides . Oxygen and carbon dioxide concentrations were continuously analyzed and automatically recorded against time. A resting metabolic rate was established prior to each work task. Completion of the exercise was followed by a fifteen minute recovery period. Curves of cumulative oxygen consumption (VO₂) and carbon dioxide elimination (VCO₂) were plotted against time. By determining the gradients of these curves at different points it was possible to plot the corresponding velocity curves [formula omitted]. The acceleration curves [formula omitted] were derived from the velocity curves. An IBM computer program was used to determine the velocity and acceleration values. When compared to normal breathing, hyperventilating at the higher work loads increases the VO₂ and VCO₂ during the early phase of exercise. This is generally followed by decreased VO₂ during the recovery period. There are well defined differences in the derivative curves between normal and hyperventilated breathing. Implications for athletic performance are indicated. Derivative curves of oxygen consumption and carbon dioxide elimination appear to be highly individual. Their use as a fitness criterion is indicated. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

The 2 in VO2 is in subscript. / Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Please see fulltext for abstract / AFRIKAANSE OPSOMMING: Sien asb volteks vir opsomming

Thesis (MPhil (Physiological Sciences))--University of Stellenbosch, 2006. / The responses of central systems to oxygen deprivation have been well characterised while adaptations in peripheral systems, such as skeletal muscles, have presented confounding variations. Several reasons for these discrepancies are purported, amongst them being the duration of exposure to hypoxia and variations in fibre composition. Moreover, in real-life high altitude situations there may be a combination of factors which have the ability to modify or alter the effect of hypoxia. This study investigates the effect of short duration hypoxia per se on substrate utilisation in different types of skeletal muscles.

The enzyme Methionine sulfoxide reductase A (MsrA) repairs oxidized proteins, and may act as a scavenger of reactive oxygen species (ROS), making it a potential therapeutic target for age-related neurodegenerative diseases. The anoxia-tolerant turtle offers a unique model to observe the effects of oxidative stress on a system that maintains neuronal function following anoxia and reoxygenation, and that ages without senescence. MsrA is present in both the mitochondria and cytosol, with protein levels increasing respectively 3- and 4-fold over 4 hours of anoxia, and remaining 2-fold higher than basal upon reoxygenation. MsrA was knocked down in neuronally-enriched cell cultures via RNAi transfection. Propidium iodide staining showed no significant cell death during anoxia, but this increased 7-fold upon reoxygenation, suggesting a role for MsrA in ROS suppression during reperfusion. This is the first report in any system of MsrA transcript and protein levels being regulated by oxygen levels. / by Lynsey Erin Bruce. / Thesis (M.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.