Thesis (MSc)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: A 5 km cycling time trial (TT) demands high, sustained muscle power output and substantial oxidative and glycolytic energy delivery. The aims of this study were to firstly use the novel approach of using Peak Sustained Power Output (PSPO) as a predictor of cycling performance for variable fixed-workload testing and 5 km time trialing and whether oral creatine supplementation would affect 5 km time trial performance and metabolism. The effect of oral creatine supplementation with 20 g/day for 7 days on 5 km time trial performance and metabolism after a random-variable workload protocol (stochastic test) was investigated in a single-blind placebo controlled study. Thirteen trained male cyclists volunteered for the study that was approved by the University of Stellenbosch Research Ethics Committee. We hypothesized that Cr supplementation would affect time trial performance as well as the appearance of breakdown products of adenine nucleotides in the plasma. Baseline: the subjects' peak power output was measured and they underwent a baseline stochastic test followed immediately by a 5 km time trial (STI) and on a different day, a single 5 km time trial test (Tl) was undertaken. Study 1: In the following week the subjects repeated the stochastic test with 5 km time trial (ST2) and on a different day a 5 km time trial (T2). During T2 blood samples were taken at regular intervals as well as during recovery. A muscle biopsy was taken after T2 in the recovered state. The major performance predictors were the 5-km time trials (TTl and TT2) with a coefficient of variation between the thirteen trained male cyclists of 0.6%. The 5 km time trials in the fatigued state (STI and ST2) had a coefficient of variation of 0.7%. Results: There was a significant difference between 5 km TT performed fresh and 5km TT performed fatigued (P=0.0001). The decrement in time ranged between 1.0 sec to 38.0 sec. The relationship between two different high intensity endurance performance tests: PSPO and 5 km TT (TT mean) had a correlation ofr=-0.79 P<O.OI. The correlation between PSPO and the 5 km TT performed in the fatigued condition (ST mean) was r= -0.60 P<0.05. There was also a relationship between age and PSPO (F 0.73; P<0.05). Age showed a good negative relationship with TT mean (F- 0.71; P<0.05). Mass and PSPO were also correlated (FO.85; P<O.OI). Plasma lactate concentrations were significantly different from rest at all other time points P<O.OOOIup to 20 minutes post-exercise. Hypoxanthine (P<O.OOOI)and urate (P=O.05) concentrations were also significantly different from rest at all other time points. There was a significant change in plasma hypoxanthine concentrations over time (P<0.0001). There was a significant correlation between plasma lactate concentration at time 0 in recovery and % Myosin Heavy Chain (MHC) I (FO.59, P<0.05) and % MHC na (F -0.61, P<0.05). Area under the curve for hypoxanthine showed significant relationships of F -0.53 (P=O.05) and F 0.56 (P<0.05) respectively for %MHC I and %MHC ITa. Study 2 - Supplementation: following T2 the subjects received Cr or placebo powder containing sachets to be ingested 4 times daily for the next week with carbohydrate also provided. Post-supplementation testing: the subjects returned and conducted another variable fixedworkload test with 5 km time trial (ST3) as well as a single 5 km time trial (T3). They once again underwent the same blood sampling routine and had another muscle biopsy in the rested state. The average of ST1 and ST2 was used as the major measure for performance under fatigued conditions and TTmean. Results: there was a significant difference between 5 km TT performed fresh and 5 km TT performed fatigued (P=0.0001). Plasma lactate, hypoxanthine and urate samples were taken at the postloading 5 km time trial (TT3). The levels of these plasma metabolites were compared to the concentrations of those sampled at TT2 and between the creatine and placebo groups. The plasma hypoxanthine levels were significantly different from rest for both the creatine and placebo groups (P<0.0001). Plasma urate had significant change in concentrations over the time points (P<0.005). Another significant difference was found between the creatine and placebo groups for the pre-and post tests conducted (P<0.005). The creatine group showed a non-significant increase (7%) in mean total intramuscular creatine concentration. No significant differences were found in the mean values for total nucleotide concentration pre- and post loading in the creatine and placebo groups. Conclusions: The 5 km performance test resulted in high values for plasma lactate, hypoxanthine and urate, an indication of fatigue induced by this performance test. Oral creatine supplementation did not improve performance significantly in the variable fixedworkload protocol 5 km time trials or the individual 5-km time trials and had an effect on adenine nucleotide metabolism in both the variable fixed-workload protocol 5-km time trial and individual 5 km time trial performance tests. / AFRIKAANSE OPSOMMING: Die 5 km fietsry tyd toets (TT) verg hoëvolgehoue, spierkrag en wesenlike oksidatiewe en glikolitiese energie verskaffing. Die doelwitte van hierdie tesis was eerstens om 'n nuwe fietsergometer toets te ontwerp vir die voorspelling van kompetisie prestasie. Die toets was 'n veranderlike, voorafvasgestelde werkladingstoets (VVWT). Dit is vergelyk met 'n maksimale volgehoue kraguitsetingstoets (MVKT) en 'n 5 km TT. Daarna is bepaal ofkreatien supplementasie 'n effek sou hê op enige van hierdie oefeningstoetse of metabolisme tydens die 5 km TT. Die supplementasie eksperiment was 'n enkelblinde, plasebo-gekontroleerde studie ontwerp. Dertien manlike fietsryers het vrywilliglik deelgeneem. Resultate: Daar was 'n statisties betekenisvolle verskil tussen die 5 km TT wat vars onderneem is en die wat direk na die VVWT onderneem is (P=O.OOOl). Daar was ook 'n betekenisvolle korrelasie tussen die twee verskillende hoë intensiteit korttydsvak oefeningstoetse (r=-0.79 P<O.Ol vir TT en MVKT). Plasma laktaat konsentrasies was betekenisvol verhoog met vergelyking van die monsters geneem tydens rus en all ander onteledings tydspunte (P<0.0001) tot en met 20 minute na oefening. Hypoxantien (P<O.OOOl) en uraat (P=0.05) konsentrasies was ook betekenisvol verskillend van rus by alle ander tysdpunte. Daar was 'n betekenisvolle korrelasie tussen plasma laktaat direk na oefening en die % Myosien Swaarketting (MIlC) I (r=0.59, P<0.05) en % MHC ITa (r= - 0.61, P<0.05). Studie 2 - Na supplementasie was daar geen verskil in oefeningsprestasie nie maar wel in plasma metaboliet waardes van nie. Gevolgtrekkings: Die 5 km TT het baie hoë waardes vir plasma laktaat tot gevolg gehad, asook hypoxantien en uraat, 'n indikasie van die hoë mate van vermoeienis deur hierdie oefeningtoets berwerkstellig. Kreatine supplementasie kon nie oefeningsprestasie verbeter nie.

The thalamic reticular nucleus (TRN), and especially its caudal, sensory-related, half (cTRN), has been hypothesised for years to be at the very heart of thalamic sensory processing modulation, and attentional processes in particular. Very limited behavioural evidence is available, nonetheless, in support of such a functional attribution. In this thesis we carried out a series of investigations, combining immunocytochemical and lesion techniques with tests of behaviour, in order to examine the potential role of cTRN in attention and identify the attentional processes, if any, that it is more likely to contribute to. In chapter II, we looked at the Fos activation levels within modality-specific sectors of cTRN following attentive behaviours to stimulation of different modalities. We observed a selective activation of the visual sector of cTRN in visually attentive animals but not in tactilely attentive, yet visually stimulated, animals, thus demonstrating an involvement of that area in processes of visual attention. In chapter III we looked at the role of cTRN in cross-modal expressions of divided attention. We found that its removal, through neurotoxic lesioning, did not result in any behavioural costs with regard to the division of attention. Detriments in response accuracy, however, suggested that cTRN may be involved in stimulus processing enhancement operations, unrelated with the division of attention. Finally, in chapters IV and V, we looked at the effects of lesions of the visual sector of cTRN (TRNvis) on the ability to orient attention covertly within visual space. We found that the removal of TRNvis did not affect visual covert orienting behaviour, both when this is triggered by exogenous and endogenous means. Overall our results suggest that even though cTRN appears to be involved in some aspects of attention, it does not represent a necessary structure for the generation and operation of certain other forms of attention.

published_or_final_version / Sports Science / Master / Master of Science in Sports Science

published_or_final_version / Speech and Hearing Sciences / Master / Master of Science in Audiology

published_or_final_version / Sports Science / Master / Master of Science in Sports Science

published_or_final_version / Dentistry / Master / Master of Dental Surgery

published_or_final_version / Sports Science / Master / Master of Science in Sports Science

published_or_final_version / Speech and Hearing Sciences / Master / Master of Philosophy

Research suggests that, in individuals with carpal tunnel syndrome (CTS), low plasma pyridoxal 5'-phosphate (PLP) concentrations are related to an increased incidence and severity of symptoms associated with CTS. This study was designed to determine the relationship between plasma and red blood cell PLP concentrations and the severity and incidence of CTS symptoms. Thirty people with CTS were selected for a 9 month exercise study. Subjects were divided into either vitamin users or non-vitamin users based on supplement use data gathered at the beginning of the study. Blood was drawn at 1, 6 and 9 months. CTS symptoms questionnaires and health questionnaires were also administered at these intervals. The symptoms questionnaires were used to gather data on the frequency and nature of hand and wrist symptoms. Health questionnaires focused on vitamin supplement usage including frequency, amount and length of use. Mean plasma PLP, total plasma vitamin B6 and erythrocyte PLP concentrations were significantly higher in the sixteen vitamin users when compared to the fourteen non-vitamin users (p<0.001). While there was variation in plasma PLP and total plasma vitamin B6 over time, within each group, there were no significant changes in any of the status measures over the nine month period. Mean erythrocyte PLP concentration, in particular, was stable over time. In vitamin users, the intensity of pain, numbness and tingling was significantly higher when compared to non-vitamin users. In both groups, plasma PLP was negatively correlated with pain. This correlation reached statistical significance in vitamin users at month one and nine (p<0.01), but not at month six; a statistically significant correlation between these two variables was not found in non-vitamin users at any time point. Pain was also negatively and significantly correlated with plasma total vitamin B6 and erythrocyte PLP in vitamin users. No other symptoms were significantly correlated with the status measures. These results indicate that a higher vitamin B6 status may be related to a decrease in the severity of pain experienced by some individuals with CTS. / Graduation date: 1998

The purpose of this study was to examine the effect of extreme exercise on vitamin B-6 metabolism and urea nitrogen. Nine men and five women completed two 5-day trials; Trial 1 (T1) included a 50-km ultramarathon on day 4 and during Trial 2 (T2) subjects were "inactive" on day 4. During both trials, subjects consumed a diet providing men 2.0 and women 1.5 mg of vitamin B-6. With the exception of the ultramarathon, T1 activity was replicated during T2. Twenty four-hour urine collections were completed and blood was drawn pre-race (pre), mid-race (mid), post-race (post) and 60 minutes post race (P-60). On the inactive, day blood was drawn at the same intervals. Plasma was analyzed for pyridoxal 5'-phosphate (PLP), pyridoxal, 4-pyridoxic acid (4-PA), urea nitrogen (PUN), creatinine, albumin, glucose, and lactate concentration and alkaline phosphatase activity. Urine was analyzed for 4PA, creatinine, and total urinary nitrogen (TUN). During T1, compared to pre, plasma PLP concentration increased 17% at mid, decreased 5% by post, and 19% by P-60. During T2, plasma PLP concentration decreased 13% pre to P-60. During T1, plasma 4-PA concentration increased 135% and the percent dietary vitamin B-6 that was excreted as urinary 4-PA the day of the ultramarathon was higher than that excreted the day before and the day after. During T1, from pre to post mean PUN concentration increased 36.9%, and the average rate ofincrease from pre to mid, mid to post, and post to P60 was 0.5, 1.75, and 2 mg/dL/hour, respectively. During T1 on days 3, 4, and 5,88%, 100%, and 95% of nitrogen intake was excreted in the urine compared to 86%, 83%, and 84% for the same days during T2. The day of the ultramarathon, 24-hour TUN excretion was 2 g higher than the previous day. Extreme exercise of greater than six hours initially increases the plasma concentration of PLP but ultimately results in a significant decrease in plasma PLP, an increase in plasma 4-PA, and an increase in percent of dietary vitamin B-6 (as 4-PA) excreted in the urine. Additionally, the rate of change in PUN inoeases as duration increases. / Graduation date: 2001