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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

The possible implication of selected Fusarium Mycotoxins in the aetiology of brain cancer.

Palanee, Thesla. January 2004 (has links)
The central nervous system is a potential site of action for the Fusarium mycotoxin Fumonisin B1 (FB1), and is exemplified in horses by the disease equine leukoencephalomalacia. Structurally resembling sphingoid bases, FB1 inhibits ceramide synthase, an enzyme involved in sphingolipid metabolism, leading to accumulation of free sphinganine (Sa) and sphingosine (So). This investigation focused on FB1, Sa, So and the Fusarium mycotoxins fusaric acid (FA), moniliformin (MaN), zearalenone (ZEA), deoxynivalenol (DON), and T-2 toxin (T2). Effects of the Fusarium mycotoxins and sphingoid bases on the N2a neuroblastoma cell line were assessed using the methylthiazol tetrazolium (MIT) and ApoGlow™ assays. The MIT assay revealed significant differences between the viability of N28 control cells and the cytotoxic effects of FB1 (p=0.001), So (p=1.1 x10-6 ), Sa (p=1.9x10-6 ), MON (p=0.002), DON (p=0.04) and ZEA (p=0.003) on N28 cells between 5-250µM. The cytotoxic effects of FA did not differ significantly from controls (p=0.1). The ApoGlow™ assay revealed that in N28 cells, FB1 at 8µg.ml-1, FA at 128µg.ml-1, and (FBI+FA) combined induced growth arrest at 2 and 4µg·ml-1. Assessment of the effects of FBI and FA on the Jurkat leukaemic suspension cell line revealed that FB1 induced apoptosis at 1.56,12.5 and 50µ.ml-1, growth arrest at 100, 200 and 800µg.ml-1 and proliferation at 400µg.mg-1. Fusaric acid induced proliferation at 1. 56µg.ml-1, apoptosis at 3.15µg.mrl, growth arrest at 100 and 200µg.mrl, and necrosis at 800µg.ml-1. Combined, (FB1+FA) induced apoptosis at 1.56, 3.15,12.5 and 800µg.ml-1. Flow cytometry and fluorescence microscopy revealed that mycotoxins, Sa and So induced varying levels of apoptosis and necrosis in N28 cells. Acridine orange and ethidium bromide staining facilitated discrimination between viable, apoptotic and necrotic cells. Transition of the mitochondrial transmembrane potential was measured using Rhodamine 123 with propidium iodide, and the dual emission potential sensitive stain JC-1. Changes in mitochondrial membrane potential and plasma membrane integrity were expressed as increases or decreases in fluorescence intensity. An increase in mycotoxin concentration from 50 to 200µM was usually paralleled by a decrease in J-aggregate formation, suggesting a decrease in the ?¦¥m. Staining with Rh 123/PI indicated at specific concentrations whether N28 cells were either late apoptotic or necrotic reflected by the levels of PI uptake. No dose dependant mechanism of cell death was established using either method, as fluctuations were evident. Immunolocalisation of T2, ZEA and FB1 within cellular organelles that exhibited ultrastructural pathology provided correlation between mycotoxin exposure and effects. Multinucleate giant cells and retraction of cellular processes were observed. At the electron microscope (EM) level, FB1 was immunolocalised within microsegregated and peripherally condensed nucleoli, the nucleoplasm, distorted mitochondria and dilated endoplasmic reticulum (ER). The capacity of cells to incorporate mycotoxins and effect cytological changes represents a major factor in the potential for initiation of malignant transformation. Exposure of N2a cells to FB1 for 72 hours increased intracellular free Sa and depleted complex sphingolipids. Using High Performance Liquid chromatography (HPLC), acid hydrolysis revealed reduction in Sa from a level of O.6±0.12µM in control cells, to 02±0.lµM in cells exposed to 50µM and lOOµM FB1. Base hydrolyses revealed increase in free Sa: So ratios from 0.52±0.2 in control cells, to 1.14±0.2 and 1.4±0.3 in cells exposed to 50 and l00µM FB1 respectively. The Sa: So ratio in the complete culture media (CCM) increased from 1. 7±0. 3 for control cells to 2.0±0.2 and 2.50±0.4 for cells exposed to 50 and lOOµM FB1 respectively. Correlation coefficients between Sa: So ratios to FB1 exposure in CCM (R=0.75) and within cells (R=0.85), imply that the free Sa: So ratio within cells appears to be a better biomarker for FB1-induced disruption of sphingolipid metabolism in vitro, than the Sa: So ratio in CCM. Optimisation of HPLC analytical procedures improved recovery of FB I from spiked human sera to 95.8% (n=15) and detection limits to -5ng.ml-1 at a signal to noise ratio of 5:1. Optimisation of methods for recovery of Sa and So from spiked sera, led to recoveries of 77.9% and 85.0%, for So and Sa respectively at levels of spiking with lOng per 500µl of serum. Matched sera Sa:So ratios and FB1 levels in brain cancer and non-cancer subjects in KwaZulu-Natal were determined using these optimised methods. Fumonisin B1 was detected in sera of non-cancer (76.7±62.2nM) and brain cancer subjects (l07.38±116nM). Mean serum Sa:So ratios of 21 non-cancer subjects was 1.7±0.7. There was no correlation (R=0.26) between these variables in non-cancer subjects. The mean serum FB1 level in brain cancer subjects was 107.4±116nM (range 10.5-298nM) (n=50) and the mean Sa:So ratio (n=50) was 1.9±1.7 (range 0.40-8.16). No correlation was found between these variables in the brain cancer subjects either (R = -0.23). Fumonisin B1 was irnmunolocalised in 49 of 76 brain tumour tissue samples analysed using immunohistochemistry (IHC). Thirty-eight of the 76 specimens had matched serum FBI levels and Sa: So ratios, and 23 of these were positive for FB1 presence. Although not significantly different (p=0.ll), the FBI sera levels in the cancer group with FBI within the tumour tissue had higher levels of FB1 in sera than the IHC FB1 negative group. Fumonisin B1 was localised within irregular profiles of nuclei, elongated and swollen mitochondria and ER. Immunolocalisation of FB1 within organelles in the brain showing ultrastructural cellular pathology suggests FBI may be implicated in the aetiology of human brain carcinogenesis. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2004.
42

The synthesis of xanthone derivatives and their enzymatic conversion and inhibition of aflatoxin biosynthesis.

Gengan, Robert Moonsamy. January 1996 (has links)
The biosynthesis of Aflatoxin B1 (AFB1) has been the subject of conflicting speculation and numerous reviews. The currently accepted scheme for the aflatoxin pathway is based on data obtained from feeding studies using isotopically labelled precursors. In these studies the conversion of possible intermediate metabolites to AFBl by mutants of Aspergillus parasiticus illustrated their role as biogenetic precursors. Currently there is now agreement on the identity of most of the intermediate Illetabolites involved in the biosynthesis of AFB1. However, there is a lack of clarity on the details of AFB1 biosynthesis including the conversion of sterigmatocystin (ST) to AFB1 via the metabolite O-methylsterigmatocystin (OMST). There is no clear cut evidence of the metabolic role of OMST, i.e., either it is a compulsory intermediate or a shunt metabolite and hence part of a metabolic grid. In order to investigate this step in AFBl biosynthesis, ST was isolated from surface cultures of A. versicolor (M1101) and purified by silica gel column chromatography and repeated recrystallisation. Sterigmatocystin was characterised by thin layer chromatography (t.1.c.), low resolution mass spectrometry (M.S) and nuclear magnetic resonance spectroscopy (N.M.R). A series of seven derivatives of the free hydroxyl group of ST were synthesised by known chemical reactions, purified by silica gel column chromatography and characterised by high resolution mass spectrometry and proton nuclear magnetic resonance spectroscopy. A high pressure liquid chromatography (HPLC) method was developed using a fluorescence detector. The optimum parameters for the separation of the four major aflatoxins, namely AFBl, AFB2, AFGl and AFG2, using trifluoroacetic acid as the derivatising reagent, were obtained for a reversed phase Prodigy C18 column with a mobile phase of water: acetonitrile: isopropanol: acetic acid (8: 1: 0.5: 0.5, v/v). Feeding studies, using whole cells of A. parasiticus (WhI-11-105), showed that ST and the ST derivatives were converted to AFB1. A time courser study for the conversion of ST and selected ST derivatives to AFB1 indicated a decrease in the rate of conversion in the order: a-propyl sterigmatocystin (OPROST) > a-ethyl sterigmatocystin > a-methylsterigmatocystin > Sterigmatocystin> a-benzoyl sterigmatocystin (OBzST). It was apparent that the "enzyme" responsible for the conversion of the derivatives to AFB1 did not display a high degree of substrate specificity, since it was unable to recognize the difference between the various alkyl groups, either as ether or ester functional groups. An HPLC method was developed using a diode array detector. The optimum parameters for the separation of aflatoxin metabolites and the synthesised derivatives were obtained for a reversed phase Lichrosphere RP-I8 column with a 30 minute gradient elution program with water and acetonitrile as the mobile phase. Crude cell-free extracts were prepared by lyophilisation of the mycelia of A. parasiticus (Whl-11l-105) with phosphate buffer. The temperature and pH for the conversion of ST to AFB1, were found to be optimum at 28°C and 7.2, respectively. The addition of SAM (1.5 mM) and NADPH (1.5 mM) increased the conversion of ST to AFBl from 11.21 % to 27.10 %. A time course study with ST, OMST and OPROST showed that the rate of conversion to AFBl was close to linear for an incubation time of up to 60 minutes. Approximation of the reaction rate indicated a decrease in the order: OMST > ST > OPROST. This indicated that the time course reaction using whole cells was in part a measure of membrane permeability rather than substrate specificity. Molecular exclusion chromatography was used to separate enzymatic protein from primary and secondary metabolites, small biomolecules and indigenous co-factors (MW < 10 000) and the partially purified "enzyme" was concentrated by dialysis against solid sucrose. The "enzyme" was subjected to non-denaturing polyacrylamide gel electrophoresis and was found to be made of sub-units ranging from 58 kDa to over 200 kDa. Enzymatic investigations with ST, as substrate, indicated that OMST is a compulsory intermediate in the biosynthesis of AFBl. Also, enzymatic investigations of selected ST derivatives showed that the partially purified "enzyme" displayed relative specificity for these substrates, viz., OMST, OPROST and OBzST. Three xanthones, namely, 1-hydroxy-,6-dimethylxanthone, I-methoxy-3,6-dimethylxanthone and l-acetyl-3,6-dimethylxanthone were synthesised, purified and characterised spectroscopically. Whole cell studies of A. parasiticus (CMI 91019b) and A. parasiticus (Wh1-11-105) showed that these xanthones inhibited AFBl production to varying extents. Kinetic studies of cell-free extracts revealed that the 1-methoxy-3,6-dimethylxanthone derivative was a non-competitive inhibitor. The Michaelis Menten constant (Km) of approximately 5.60 uM (for OMST) was determined for a cell-free reaction at pH 7.2 and 28 QC. A Clark oxygen electrode was used to carry out oxygen consumption studies in a partially purified "enzyme" preparation. A calibration system was designed and the enzymatic conversion of OMST to AFB1 and NADPH consumption were monitored by HPLC and UV spectroscopy, respectively. From the results of these enzymatic reactions, the following stoichiometric relationship was determined: 2 mole oxygen consumed = 1 mole NADPH consumed = 1 mole AFB1 produced A tentative mechanism is discussed for the conversion of OMST to AFB1 which utilizes a monooxygenase and a dioxygenase. / Thesis (Ph.D.)-University of Natal, Durban, 1996.
43

The effects of vasopressin and oxytocin on methamphetamine : induced place preference behaviour in rats.

Subiah, Cassandra. 20 November 2013 (has links)
Methamphetamine is a highly addictive stimulant drug whose illicit use and resultant addiction has become an alarming global phenomenon. The mesolimbic dopaminergic system in the brain, originating in the ventral tegmental area and terminating in the nucleus accumbens, has been shown to be central to the neurobiology of addiction and the establishment of addictive behaviour. This pathway, as part of the reward system of the brain, has also been shown to be important in classical conditioning, which is a learnt response. This common pathway has supported theories suggesting addiction as a case of maladaptive associative learning. Within the modulation of learning and memory, the neurohypophyseal hormones vasopressin and oxytocin have been seen to play a vital role. Vasopressin exerts a long- term facilitatory effect on learning and memory processes. Studies have shown that the stress responsive AVP V1b receptor systems are a critical component of the neural circuitry underlying emotional consequences of drug reward. Oxytocin, on the other hand, has an effect on learning and memory opposite to that of vasopressin. Previous studies have shown that oxytocin caused a decrease in heroin self-administration, as well as attenuated the appearance of cocaine-induced hyperactivity and stereotyped behaviour. Therefore, we adopted a reinstatement conditioned place preference model to investigate whether a V1b antagonist or oxytocin treatment would cause a decrease in methamphetamine seeking behaviour. Behavioural findings indicated that methamphetamine induced a change in the place preference in the majority of our animals. This change in preference was not seen after vasopressin administration in the extinction phase. On the other hand, the change in place preference was enhanced during the reinstatement phase in the animals treated with oxytocin. Striatal dopamine levels were determined, as methamphetamine is known to increase dopamine transmission in this area. Results showed that rats that received both methamphetamine and oxytocin had significantly higher striatal dopamine than those that received oxytocin alone. Western blot analysis for hippocampal cyclic AMP response element binding protein (CREB) was also conducted as a possible indicator of glutamatergic NMDA receptor activity, a pathway that is important for learning and memory. The Western blot analysis showed no changes in hippocampal pCREB expression. Overall our data led us to conclude that methamphetamine treatment can change place preference behaviour in rats and that this change may be partially restored by vasopressin antagonism, but exaggerated by oxytocin. / Thesis (M.Med.Sc.)-University of KwaZulu-Natal, Westville, 2012.
44

Cardiopulmonary exercise testing for high-risk South African surgical patients.

Biccard, Bruce M. January 2007 (has links)
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.
45

Oxidative stress of tissue in hypertensive rats.

Govender, Melvin M. January 2006 (has links)
Oxidative stress, resulting from an antioxidant/free radical imbalance, is considered to be an important etiologic factor in the patho-physiological changes associated with salt sensitive hypertension. An important unresolved issue in hypertension research is the mechanism for organ damage during the development of the syndrome. Reactive oxygen species (ROS) such as the superoxide radical (02) , hydrogen peroxide (H202), and the hydroxyl radical (OH), may playa critical role in the pathogenesis of hypertension by targeting the very tissue that is responsible for regulating blood pressure, during the hypertensive state. Thus, this study was undertaken to evaluate the antioxidant and free radical status in the DSS rat strain, which has been shown to be an excellent model of salt sensitive hypertension. The antioxidant status was evaluated on the basis of the vascular superoxide dismutase (SOD) and glutathione peroxidase (GPx) levels, and the free radical status was evaluated on the basis of the plasma H20 2 concentration. The levels of malonyldialdehyde (MDA), which is a bio-marker for lipid peroxidation was used to determine the level of oxidative stress in the kidney, liver and brain. The kidney and liver were also subjected to an induced free radical mediated lipid peroxidation, by exposing the tissue to increasing known concentrations of H202 (2.5mM - 15mM). The level of lipid peroxidation was used to assess the tissues antioxidant buffering capacity to an induced free radical "attack". The results have shown that the DSS strain may have a compensatory increase in vascular SOD levels, to counter an increase in 02-. SOD levels were significantly lower during salt loading. The GPx levels were significantly lower in the DSS strain, and showed a slight increase during salt loading. The results demonstrate that the DSS strain has a compromised antioxidant status compared to the DSR strain. The plasma H202concentration displayed non-significant changes in the DSS strain, however salt loading did result in a non-significant increase in the plasma H202 concentration in the DSS strain. The GPx : HZ02 ratio, demonstrated an inadequate increase in GPx levels during salt loading to neutralise this non-significant increase in HzOz concentration. The kidney showed an increased level of in vivo lipid peroxidation, which could implicate increased tissue damage, and thus confirm the kidney as being a target organ during the hypertensive state. The liver and brain showed non-significant differences in the level of in vivo lipid peroxidation and are therefore thought not to be target tissue in the hypertensive state. The kidney displayed a decreased antioxidant buffering capacity to the induced free radical "attack", thereby demonstrating the tissue's decreased ability to neutralise an increased free radical level. Although the liver displayed a "normal" level of in vivo lipid peroxidation, it also displayed a decreased antioxidant buffering capacity to an induced free radical "attack", showing that the liver is able to cope with in vivo free radical levels, but at higher free radical levels, its loses its ability to quench a free radical "attack" and thereby minimise lipid peroxidation. The in vivo lipid peroxidation levels of the kidney, liver and brain have shown that tissues have varying abilities to cope with tissue oxidative stress, and behave differently, in their free radical quenching abilities. These results have shown that a compromised free radical and antioxidant status results in oxidative damage to the tissue responsible for regulating blood pressure. / Thesis (M.Med.Sc.)-University of KwaZulu-Natal, Westville, 2006.
46

The effects of nerve stimulation on pacemaking activities of biological tissues.

Bhagat, Chotoo Ichharam. January 1973 (has links)
The effects on the cardiac cycle length of stimulating the vagus nerves with single supramaximal electrical shocks depended upon when they were stimulated during the cycle. A maximum prolongation of the cardiac cycle was obtained when the vagi were stimulated 167 msec (SD±64) after the peak of an electrocardiogram P wave. The interval between a P wave and the subsequent vagal stimulation was called Pl-St interval. Pl-St(max) was the Pl-St interval at which maximum prolongation of the cardiac cycle occurred. Pl-St(max) increased significantly (p (0.001) with longer cardiac cycles. When the Pl-St intervals were shorter or longer than 167 msec (SD±64) the effects of vagal stimulation were less. The latent period for the effects of vagal stimulation was 195 msec (SD±32) The latent period also increased significantly (p(O.Ol) with longer cardiac cycles. The rise time of the vagal effect, obtained by subtracting (Pl-St(max)+ latent period) from the control cardiac cycle length, was 124 msec (SD+31) and occurred between Pl-St intervals of 167 msec (SD±64) and 291 msec (SD±70). The rise time did not vary with cardiac cycle length (p) 0.1), but the magnitude of the maximum response to vagal stimulation was inversely proportional to rise time (p <. 0.02). The peak response to vagal stimulation must have occurred when the vagal effects pegan somewhere in the middle of diastolic depolarization of the pacemaker cells in the S-A node. The reasons for this were discussed. The half-decay time for the effects of vagal stimulation was 210 msec (SD±102). The slope of the curve relating the prolongation of the cardiac cycle length to Pl-St is positive at Pl-St intervals less than 167 msec (SD±64) and negative at Pl-St intervals between 167 msec (SD±64) and 291 msec (SD±90). The positive slope ranged from 0.13 to 0.48 with a mean of 0.23. The paradoxical responses of the S-A node to vagal inhibitory input obtained by Reid (1969), Levy et al (1969)and Dong and Reitz (1970) would be explained by the dependence of the cardiac cycle length upon the time of arrival of vagal stimulus in relation to the previous P wave and upon the slope of the curve relating the prolongation of the cardiac cycle length to Pl-St interval being positive and between zero and two at Pl-St intervals less than 167 msec (SD±64. The effects of single shock stimulation of the vagus nerves persisted for 3.890 sec (SD+l.255)7 the number of cardiac cycles involved varied between 5 and 11. The duration of the effects of vagal stimulation did not depend upon when during the cardiac cycle the vagi were stimulated. A "dip" in the response to vagal stimulation was present in all the experiments. The possibility of the "dip" phenomenon being due to simultaneous stimulation of the sympathetic fibres in the vago-sympathetic trunk was ruled out. It is suggested that the "dip" phenomenon may be due to transient accumulation of K+ in the interstitial fluid surrounding the pacemaker cells in the S-A node.There was no paradoxical response of the smooth muscle in the distal colon of the adult rabbit when the frequency of sympathetic inhibitory input was continuously increased. A paradoxical response in the frequency but not in the size of the contraction of the smooth muscle was obtained when the sympathetic nerves were stimulated with bursts of stimuli, each burst consisting of 5-40 impulses, 10 msec apart. One may conclude from this that the delay of the next spontaneous contraction but not the inhibition of the size of smooth muscle contraction is dependent upon the arrival time of a burst of stimuli during a contraction cycle. This was confirmed in an experiment when the sympathetic nerves were stimulated with single bursts of stimuli applied at different times during the contraction cycle. It is unlikely that such a paradoxical response would occur under physiological conditions as this would require the natural sympathetic efferent discharges to the smooth muscle to occur in regular bursts, each burst consisting of impulses at a high frequency. Stimulation of the sympathetic nerves at 3, 5, 10 and 25 PPS caused an inhibition of the size and frequency of smooth muscle contraction in the distal colon of the newborn rabbit. Assuming that the cholinergic fibres are excitatory there is therefore no evidence for the sympathetic fibres to the distal colon being cholinergic in the newborn rabbit. This is contrary to Burn's (1968) report of the sympathetic fibres being motor and cholinergic to the small intestinal smooth muscle in the newborn rabbit.The heart rate increased rapidly at the onset of exercise and then more gradually over the rest of the exercise period. The initial increase in the heart rate during exercise was not affected by adrenergic blockade but the subsequent increase in heart rate was significantly reduced by adrenergic blockade. Hence the increase in heart rate at the onset of exercise is due primarily to a decrease in the cardiac vagal efferent discharge, whereas the subsequent increase in heart rate is due to both a further decrease ln vagal discharge and an increase in sympathetic discharge to the S-A node. In almost all the sub jects there was initially a rapid decline in the heart rate in the post-exercise period, but subsequently the heart rate returned to resting levels in a variety of ways. These were classified into 5 types. Of particular interest to the present study was the Type V pattern of heart rate change. This was characterised by an increase in heart rate of 6 beats or more per minute during the post-exercise period, with or without superimposed arrhythmia. The Type V pattern may be the equivalent of the paradoxical responses to inhibitory input demonstrated in animal experiments i.e. an increase in the heart rate with increasing vagal stimulation frequency. Type V pattern occurred more frequently at mild exercise levels (4 out of 14) than at moderate exercise level (lout of 14) and also more frequently in adrenergic blocked individuals (11 out of 28) than in control subjects (5 out of 28) It is suggested that the sympathetic effects on the P-R interval and arterial baroreceptor modulation of vagal efferent discharge protect again st the occurrence of paradoxical responses to vagal inhibitory input. They may do so by confining the vagal discharge to the rise time of vagal effect during the cardiac cycle. On the other hand the Type V pattern in p-adrenergic blocked individuals may be due to a decrease in the vagal discharge, in which case Type V pattern would not be a paradoxical response. The changes in minute ventilation in the post-exercise period were also variable. Besides a gradual decline in minute ventilation there were also gradual increases and sudden increases and decreases in minute ventilation. These may represent a form of paradoxical response to increasing inhibitory input and decreasing excitatory input to the respiratory neurones in man. However, all the changes in minute ventilation could also be explained by fluctuating excitatory and inhibitory neural input to the respiratory neurones. / Thesis (MD)-University of Natal, Durban, 1973.
47

The physicality of the self

Turp, Maggie January 2003 (has links)
The submitted publications address aspects of 'The Physicality of the Self from a psychoanalytic perspective and in so doing extend the remit of psychoanalytic thinking. Conscious and unconscious investment of personal meaning in physical exercise, body-oriented behaviour and physical dimensions of experience and communication is explored through presentation and discussion of clinical case examples and infant observation material. The embodied nature of our being is identified as an issue of key significance in psychoanalysis, where unconscious communication, much of which is non-verbal, is a central concern of both theory and practice. Ways of conceptualising psychosomatic disturbance are discussed, whether the disturbance emerges in physical symptoms without apparent organic underlay or in disturbed body-oriented behaviour such as eating disorders and self-injury. With regard to clinical practice, the central significance of receptivity to unconscious communication and capacity for containment (Bion 1962) is reaffirmed. The therapist's 'use of body' as part of the 'use of self Is discussed with particular reference to somatic communication in the transference - countertransference matrix. The primary context for the work is a contemporary object relations framework. The perspective on embodiment or'indwelling' developed by D. W. Winnicott and the post- Kleinian concept of 'psychic skin' are of particular Importance. The disciplines of philosophy, psychology, neuroscience and sociology constitute a secondary, broader, context and inform the discussion of changing perspectives on 'mind', 'body', 'health' and'illness'. A'continuum' model of self-care and self-harm is developed. The acronym 'cashas' is introduced to refer to 'culturally accepted self-harming acts/activities', behaviours which occupy a border area between good enough self-care and clinically relevant self-harm. Drawing on clinical material and research Involving practitioner discussion of clinical vignettes, arguments are advanced for the relevance and clinical usefulness of the 'continuum' model.
48

Physiological and psychological responses of patients with chronic fatigue syndrome to regular physical activity

Fulcher, Kathy January 1997 (has links)
No description available.
49

Measurement and prediction of the hemodynamic effects of passive leg elevation /

Kazan, Samira M., January 1900 (has links)
Thesis (M.App.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 114-145). Also available in electronic format on the Internet.
50

Depression and bone mineral density

Govender, Catherine Olly January 2008 (has links)
Thesis (MSc. (Physiology)--Faculty of Health Sciences) - University of Pretoria, 2008. / Includes bibliographical references.

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