‘Sensorimotor transformations’ are processes whereby sensory information is used to generate motor commands. One example is the ‘visuomotor map’ that transforms visual information about objects to motor commands that activates various muscles during grasping movements. In the first study we quantified the relative impact (or ‘weighting’) of visual and haptic information on the sensorimotor transformation and investigated the principles that regulates the weighting process. To do this, we let subjects perform a task in which the object seen (visual object) and the object grasped (haptic object) were physically never the same. When the haptic object became larger or smaller than the visual object, subjects in the following trials automatically adapted their maximum grip aperture (MGA) when reaching for the object. The adaptation process was quicker and relied more on haptic information when the haptic objects increased in size than when they decreased in size. As such, sensory weighting is molded to avoid prehension error. In the second study we investigated the degree to which the visuomotor map could be modified. Normally, the relationship between the visual size of the object (VO) and the MGA can be expressed as a linear relationship, where MGA = a + b * VO. Our results demonstrate that subjects inter- and extrapolate in the visuomotor map (that is, they are reluctant to abandon the linear relationship) and that the offset (a) but not the slope (b) can be modified. In the third study, we investigated how a ‘new’ sensorimotor transformation can be established and modified. We therefore replaced the normal input of visual information about object size with auditory information, where the size of the object was log-linearly related to the frequency of a tone. Learning of an audiomotor map consisted of three distinct phases: during the first stage (~10-15 trials) there were no overt signs of learning. During the second stage there was a period of fast learning where the MGA became scaled to the size of the object until the third stage where the slope was constant. The purpose of the fourth study was to investigate the sensory basis for the aperture adaptation process. To do that, the forces acting between the fingertips and the object was measured as the subjects adapted. Our results indicate that information about when the fingers contacts the object, that is, the ‘timing’ of contact, is likely to be used by the CNS to encode an unexpected object size. Since injuries and disease can affect the sensorimotor transformations that controls the hand, knowledge about how these processes are established and modified may be used to develop techniques for sensory substitution and other rehabilitation strategies.

The purpose of this study is to investigate the frequency and amplitude characteristics of vibration exposed to the bicycle and the rider as well as the features of the vibration transmission to the riders&amp / #8217 / body. The findings showed that, vibration transmission to the bicycle and the rider is effective in x-and z axis. As a result of increased roughness, effective frequency range shifted to lower frequencies between 15-30Hz at both saddle and stem. The severity of transmitted vibration to the bicycle was found to be considerably higher in road bike trials (up to 25 ms-2). The frequency range of the vibration exposure of the body parts were in between 0-30Hz and independent of the level of vibration transmission the peak values were within the range of 3-12Hz. As the acceleration magnitude increased depending on road roughness, normalized rms EMG values also increased up to 50% in forearm extensor muscles during MTB trials and in the flexor muscles during road bike trials. With respect to no vibration trials, rms EMG values increased in order to maintain the same force output. Vibration transmission to the body tends to be amplified with increased force production. Transmission values were found to be higher at lower frequencies. Since the magnitude and frequency of vibration is known to have some adverse effects on body functions such as impaired breathing pattern and increased muscle tone, vibration transmitted to the body might be considered to influence the riding comfort, controllability and overall health of the cyclist.

Disputats. Rheinische Friedrick-Wilhelms-Universität, 2002. / Haves kun i elektronisk udg.

Diabetes mellitus (DM) has become a global threat in developing and developed countries, where diabetic patients are more prone to cardiovascular complications, a condition called diabetic cardiomyopathy. Studies have shown a direct link between hyperglycaemia and an increase in the production of reactive oxygen species in cardiac cells leading to diabetic cardiomyopathy. This study tests oleanolic acid, a bioactive compound from the plant Syzigium aromaticum as an antioxidant which could have a potential role in management of DM. Aims i) To extract Oleanolic acid (OA) from Syzigium aromaticim, ii) Investigate the antioxidant effects of plant derived OA in an in-vitro model of hyperglycaemia induced oxidative stress. Methods The flower buds of the Syzigium aromaticim [(Linnaeus) Merrill & Perry] (Myrtaceae) plant (commonly called cloves) were used to isolate OA. The ethyl acetate solubles from the cloves were subjected to chromatographic fractionation to yield OA powder. Spectroscopic analysis was done using 1D and 2D 1H and 13C NMR techniques for the identification of the structure of the compound. This compound was then used in vitro to test for its antioxidative properties. H9C2 cardiac myoblasts were employed which were treated with normoglycaemic (5.5 mM) and hyperglycaemic (33 mM) glucose conditions. The cells were then treated with oleanolic acid to test for its antioxidant properties. We looked at a dose-dependent (0, 20, 50 μM) and time-dependent effects of OA treatment (6 and 24 hrs) following 48 hours glucose exposure. ROS levels were measured using H2DCF-DA fluorescence staining using microscopy and flow cytometry techniques for analysis. xviii Results Recrystallisation of the powder with ethanol and inspection of the 1 and 2- dimensional 1H- and 13C-NMR spectra of the compound with comparison to literature data confirmed OA molecular structure and IUPAC numbering similar to that of literature characterized and confirmed the structure of oleanolic acid. In cell specific data high glucose treatments on H9C2 cells showed increased ROS production (22 ± 6 % and 20 ± 7 % n= 3 p< 0.01) for 6 and 24 hrs treatments, respectively, compared to their normoglycaemic control groups. The 6 h OA treated group showed a decrease in ROS production with 26.6 ± 17.4 % for the 20 μM while for 50 μM there was a 37.7 ± 14.3% decrease. A ROS reduction trend was observed in the normoglycaemic group, but this was significant at 24 hrs with 46.8 ± 45.3% and 57.3 ± 9 % for both 20 and 50 μM treatments, respectively. The 24 hrs OA treated group showed a dose-dependent decrease in ROS with 50 μM more pronounced (80.7% ± 4.5 %). The 20 μM OA treatments also showed a 15.7 ± 19 % decrease in ROS. Discussion In the present study, we have evaluated the antioxidant effects of OA in vitro following extraction of the compound from Syzigium aromaticim. The oxidative stress induced by hyperglycaemia was attenuated by oleanolic acid and this also translated into decreased ROS suggesting its use as an antioxidant in alleviating cardiovascular complications associated with diabetes mellitus.

Since the discovery of mycotoxins in food, the thrust of biochemical and toxicological research has been carried out on animals which has proven to be uncoordinated and not easily extrapolated to humans. Over the last decade, there have been increasing pressures to review and reduce the use of animals in experimental toxicological studies. Consequently in this study aflatoxin B1 (AFB1), zearalenone (Zea) and their epoxide derivatives have been evaluated using in vitro assays. The HepG2, A549 and Hela cell lines were used for assessing the cytotoxicity, effects on cellular metabolism and sites of action of AFB1, Zea and their derivatives. The cytotoxicity of these mycotoxins was evaluated using the methylthiazol tetrazolium (MTT) reduction assay. Cells, treated with mycotoxins were prepared for transmission electron mlcroscopy (TEM), immunocytochemistry (ICC), scanning electron microscopy (SEM), confocal and light microscopy. From the cytotoxicity assay it was found that the epoxide derivatives were more toxic than the parent toxin when exposed to HepG2 cells with no significant differences in toxicity levels in A549 and Hela treated cells. Both epoxide derivatives displayed a regression of hepatoma cell proliferation at high doses (25ug/ml) while lower concentrations (<12.5ug/ml) enhanced cell growth. Microscopy analyses showed distinct cellular alterations. When exposed to AFB1 (12.5ug/ml) hepatoma cells showed prominent ultrastructural alterations such as areas of cytoplasmic lysis and increased numbers of secondary lysosomes while cells exposed to Zea (l2.5ug/ml) displayed numerous ovoid mitochondria and proliferation of rough endoplasmic reticulum which is indicative of enhanced protein synthesis. The presence of label in toxin treated cells is suggestive of the effects of these mycotoxins. Such cellular changes may lead to altered metabolism and cell function. / Thesis (M.Med.)-University of Natal, Durban, 1996.

Vaccines directed against the influenza virus become ineffective due to continuous mutation. An alternative approach might be to control replication at the genomic level by enzymatic methylation of the polymerase genes. Hence in this study, a method to locate and successfully isolate the H1N1 influenza A polymerase genes was investigated. The virus was cultured in chick embryos via the allantoic route using aseptic techniques. Following incubation, the allantoic fluid was isolated and washed to remove any contaminating blood cells. The allantoic fluid was checked for fungal and bacterial contamination using the blood agar test and the presence of the virus was established by the haemagglutination titration test. Viral particles were pelleted by ultracentrifugation. Electron microscopy verified the morphology and size of these viruses while immunofluorescence studies, using a monoclonal antibody, confirmed the influenza A strain. The ribose test verified the presence of RNA in the samples. Purified viral pellets were pooled and homogenised in buffer containing guanidine thiocyanate, mercaptoethanol and sarkosyl. The samples were incubated on ice before mechanical disruption of the virus. Viral RNA was isolated from the upper aqueous layer after a standard phenol/chloroform extraction procedure. RNA was quantified spectrophotometrically and purity assessed initially by the absorbance ratio readings at 260/280 nm. Electrophoresis of the RNA samples was performed together with RNA molecular weight markers on a 1.5% formamide agarose gel. Five bands were identified and the band containing the polymerase genes was size selected, located and excised. Purification of the polymerase genes from the agarose was achieved by using the BIO 101 RNAid kit. The three isolated polymerase RNAs were reverse transcribed using the Boehringer Mannheim cDNA synthesis kit. The results indicate that the H1N1 influenza virus was successfully grown and isolated from chick embryos. Absence of contamination and verification of viral presence at different stages of the study were indications that asepsis was successfully achieved. The RNA obtained was sufficient and suitable for cDNA synthesis. This cDNA may now be used for further molecular analysis and subsequent DNA methylation studies. Further, transfection studies may then be performed to determine, if any, the the expression of methylated and unmethylated cDNA. / Thesis (M.Med.)-University of Natal, 1992.

Aflatoxin B1 (AFB1) and Fumonisin B1 (FB1), potentially cytotoxic and carcinogenic mycotoxins are common contaminants of agricultural commodities in South Africa and thus could be detrimental to the human immune system. Many of the cytotoxic effects of AFB1 require its bioactivation to an epoxide, which will bind covalently to macromolecules to form protein and DNA adducts. Fumonisin B1 is a competitive inhibitor of sphingosine and sphinganine N aceyltransferase, which are key components in the pathways for sphingolipid biosynthesis. Accumulation of free sphingoid bases, which are both cytotoxic and mitogenic, could provide a plausible explanation for the toxicity and carcinogenicity of FB1. The cytotoxic effects of AFB1 and FB1 on normal human lymphocytes, individually and in combination were assessed using the methylthiazol tetrazolium (MTT) bioassay. Two different methods of treatment were used, the treatment of isolated normal human lymphocytes for 12, 24, 48, 72 and 96 hours and whole blood treated for 12 hours. Flow cytometry and fluorescent microscopy were used to determine whether AFB1 and FB1 (5uM and 50uM), individually or in combination, were capable of inducing apoptosis, necrosis or nuclear fragmentation in isolated lymphocytes and whole blood treated for 12 hours. DNA damage was evaluated using the comet assay. The results showed that AFB1routinely induced higher levels of cytotoxicity in isolated lymphocytes than FB1. In the combination treatment, the mitogenic properties of FB1 appeared to partially counteract the cytotoxic effect exerted by AFB1. When whole blood was treated with the same concentration and ratio of toxin, FB1 was shown to be more cytotoxic than AFB1. The combination treatment of whole blood was shown to be cytotoxic in a dose dependent manner. The toxins appeared to exert a greater cytotoxic effect, when treated in combination than individually at higher concentrations. Aflatoxin B1 induced increased levels of apoptosis and necrosis in isolated lymphocytes while treatment with the FB1 resulted in increased levels of apoptosis at both concentrations. Treatment with the combination also resulted in increased levels of apoptosis. The levels of apoptosis were reduced in whole blood lymphocytes when compared to isolated lymphocytes. However, treatment with AFB1 and FB1 resulted in increased levels of apoptosis. Both AFB1 and FB1 are capable of inducing nuclear fragmentation. Treatment with FB1 (5uM and 50uM) resulted in greater degree of fragmentation than AFB1. The most nuclear fragmentation was induced by the 5uM combination treatment. The 50uM combination treatment of isolated lymphocytes induced the most DNA damage. As both toxins are common contaminants and have been known to coexist, this could be a potential area of concern for public health. / Thesis (M.Med.)-University of KwaZulu-Natal, 2004.

The incidence of sudden death during or after squash play has become a source of concern. In order to screen for coronary artery disease, exercise stress testing has been advocated, by the American College of Sports Medicine (1986), for those at or above the age of 45 already exercising or before embarking on exercise. Eighteen veteran squash players (mean age 49 ± 3 yr) took part in the study. Heart rate response was monitored throughout a squash match and for an hour after play. ECG changes were monitored for one hour after squash play. Mean heart rate, throughout playing time was 148 ± 16 beats per minute (range 118 - 168 bpm), representing 86.7% of Predicted Maximum Heart Rate (PMHR). Mean maximal heart rate was 169 ± 14 bpm (range 141 - 186 bpm), representing 98.8% of PMHR. Thus squash represents a very high intensity activity for these players. On subsequent ECG monitoring, no abnormalities were detected. The results of this study confirm that squash is an extremely high intensity sport and that even veteran players play at a level close to their maximal. This level of play did not provoke subsequent cardiac arrhythmias in this small group of players, contrary to an earlier study that reported arrhythmias in one third of a group of younger players in the post match period. / Thesis (M.Med.Sc.)-University of Natal, 1997.

No abstract available. / Thesis (M.Sc.)-University of Durban-Westville, 1990.

Due to the lack of morphological data on prepubertal Indian male soccer players in South Africa, this study was undertaken on ninety male prepubertal subjects. The subjects were divided into three groups of thirty subjects each: Experienced "E" (those playing organized soccer for more than two years), beginners "8" (those playing organized soccer for less than two years) and sedentary "S" (those not participating in organized soccer). All subjects were measured according to Heath - Carter anthropometric somatotype methods. Fitness tests comprising power and strength tests (vertical jump height and standing broad jump) and muscle endurance tests (push - ups and sit - ups) were also done. The three groups were first compared to each other and then to available international data. There were no statistical differences among the three groups for: height, weight, age, triceps, subscapular, suprailiac, calf and total skinfolds, humerus and biceps girth, ectomorphy, mesomorphy and endomorphy, suggesting a general homogenicity between groups. For fitness tests the "E" group performed significantly better than the others for standing broad jump and sit - ups (p = 0.005 and p = 0.036 respectively). For push - ups the "8" and "E" were significantly better than the "S" group, (p = 0.013, for "8" versus "S" group), indicating that in soccer muscle strength and explosive strength are important. The lack of difference between the groups for anthropometric criteria in this study may be explained by the experienced players' inadequate training. Other factors may include the lack of parental involvement, inadequate knowledge on fitness aspects and poor training methods. Furthermore, the sedentary group may be participating in unorganized activities which renders them at a level similar to the experienced group. Data on non - Indian South African junior players is required to help us understand the lack of significant Indian talent in the National team. Other factors such as diet, cultural differences, training methods, level of coaching, environmental factors and sport facilities need investigation and be addressed if we want to see an improvement in the South African Indian soccer players. / Thesis (M.Med.Sc.)-University of Natal, Durban, 1997.