The effects of postural threat on postural control among younger and older adults were examined. Fifteen younger (YA;8 females and 7 males; mean age 22.00 + 2.17 years) and fifteen older (OA; 10 females and 5 males; mean age 69.98 + 5.35 years) adults performed quiet standing and forward reaching under four conditions of postural threat. Postural threat was achieved by the manipulation of height (low(0.43m) and high (1.4m)) and stepping constraint (unconstrained (0.91m from the anterior edge of an elevating platform) or constrained (0m from the anterior edge of an elevating platform). Younger and older adults demonstrated conservative modifications to postural control that may reduce the likelihood of a fall in tenuous conditions. Interestingly, age-related differences emerged in the mechanism of achieving these accomodations to postural threat. Our findings indicate that older adults may adopt more proximal postural strategies under condtion of postural threat. The shift toward a more proximal postural strategies under conditions of postural threat. The shift toward a more proximal control of balance may reflect the age-related declines in the ability to control the movement of the trunk. Although these adaptations appear benefical to older adults, the possibility exists for detrimental consequences to postural recovery following a balance disturbance. / xi, 173 leaves : ill. ; 29 cm.

M.Sc. / Loss of quality occurs when tomatoes are stored for more than approximately 3-5 weeks at 12 °C. The most common disorders found in tomatoes during storage are colour development to an unacceptable shade of red, softening, shrivelling due to moisture loss, loss of flavour and fungal infections. Storage life of tomatoes is generally extended by storage under refrigeration. Further, extension of shelf life can be achieved by modified atmosphere packaging (MAP). This is done by sealing actively respiring produce in polymeric film packages to modify the 0, and CO, levels within the package atmosphere. Also, 1-methylcyclopropene (1-MCP) has been proven to be an effective postharvest treatment to prolong the storage life of tomatoes. In the present study four trails were conducted. In the first trial the effects of 1-MCP dosage rate and the colour stage of harvest on the quality of `Santa' tomatoes stored for 4 weeks at 12 °C were investigated. The results indicated that ripening related changes were delayed following 1-MCP treatment. 1-MCP treated fruit were firmer, had reduced TA losses, slower colour development, and reduced physiological disorders associated with long term storage. The stage of ripeness influenced the efficacy of 1-MCP on slowing down the tomato ripening process. 1-MCP was of little benefit for fruit treated at stage 4 of ripeness. In contrast, particularly when the 1-MCP dosage was high, 1-MCP markedly delayed ripening in fruit harvested at colour stage 2 and 3, but the quality attributes such as SSC were better in treated fruits harvested at stage 3. Relatively little difference was observed between 250 and 500 nL.L -I 1-MCP and thus 500 nL.Con fruit harvested at stage 3 of ripeness was used in the remaining experiments. Effects of MAP, 1-MCP and imazalil either as combined treatments or as single treatments were studied for their effect on the quality of tomatoes. Ripening related changes were delayed and loss of weight was significantly reduced following 1-MCP treatment and MA packaging in 17 gm thickness bags. Elevated CO, in MAP after a long storage period induced anaerobic metabolism with the generation of off-odurs and the proliferation of anaerobic microbes. Selected doses of imazalil (0, 0.5, 0.05, 0.005 and 0.0005 g.L.1 ) were evaluated for their effect on the fungal infections on tomato fruits. Imazalil at a rate of 0.005 g.L"' was found to reduce fungal infections by 50% when used in combination with MAP and 1-MCP. The combination of imazalil and MAP therefore appears to be the best treatment combination to facilitate export of 'Santa' tomatoes by sea. However, with regards to reducing the loss of TA, treatment with 1-MCP would be beneficial.

Tomatoes (Lycopersicon esculentum cv. Santa) are climacteric fruit that continue to ripen after harvest. Once the fruit are separated from the plant, the physiological reactions that control the ripening process are altered, so that tomato quality is altered. The earlier the stage of ripening at harvest, the larger the discrepancy between the tomatoes left to ripen on the plant and those harvested while still unripe. Quality is lost as the tomatoes lose moisture, firmness, nutrients and stored carbohydrates. Other aspects such as colour and flavour development and cell wall modifications also affect the quality of unripe harvested tomatoes. Environmental factors that affect the postharvest quality include the temperature, humidity and atmospheric conditions in which the tomatoes are stored. Hormonal manipulation (introducing or blocking ethylene) also has an effect on the final fruit quality. This research project concentrated on the changes that occur in quality during post harvest ripening. Comparisons were made on how different post harvest treatments and storage protocols influenced the quality and longevity of tomato fruit. The purpose of this study was to determine storage conditions that would prolong the shelflife of tomatoes so that they can be acceptable for consumption for up to 40 days after harvest. The best results were obtained from tomatoes that had not completely turned red at time of harvest. These tomatoes could maintain their acceptability best when they were stored at 12°C under controlled atmosphere conditions. 1-MCP treatment was also effective in limiting quality losses for up to a week after harvest, and avoiding exposure to ethylene gas can also be recommended. Heat treatment was not at all successful in improving the longevity of the fruit. / Prof. C.S. Whitehead

Thesis (Ph. D.)--Oregon State University, 1996. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

M.Sc. / The current study sought to investigate the relationship between stress and illness, while examining the effects of daily stressors, depression, hardiness, social support and coping skills on this relationship. The information gathered was then used to design a time and cost effective questionnaire to predict people prone to stress-related illness. This questionnaire has been called the Stress Fitness Scale. The subjects (n = 44) were split into three groups (healthy, ill, and neither ill nor healthy) according to their scores on Gurin's Psychosomatic Symptom List for non-parametric statistical analysis. Scores on the Hardiness Scale, Perceived Social Support Friends and Family, Beck Depression Inventory, COPE, Hassles and Uplifts Scale and Life Experiences were analysed and significant differences were found between the ill and healthy groups in all five areas using a Mann-Whitney U test. An intercorrelation matrix was performed and significant correlation was found between Stress Fitness and the other scales, although not for all the sub-scales. Many of these correlations corresponded with the differences found between the two groups using the Mann-Whitney U test. Item analysis was performed on the Stress Fitness Scale. Significant inter correlation was found for all the items of the Prone sub-scale, and all but three items of the Protect sub-scale. Although further research is necessary, from this limited study the Stress Fitness Scale appears to provide a time and cost effective way of predicting people prone to stress-related illness.

This study was undertaken to determine whether immunoreactive atrial natriuretic peptide (irANP) concentrations in plasma and atrial tissue are altered in experimental diabetes mellitus (DM), and to compare the response of the DM and normal groups to exogenous administration of ANP. OM was induced by intraperitoneal injection of 45 mg/kg streptozotocin in male Sprague-Dawley rats. After three weeks of established OM (glucosuria and blood glucose> 250 mg/dl), plasma irANP levels were 149.6 ± 19.4 pg/ml in the OM group (n = 18) and 86.3 + 12.9 pg/ml in the normal group en = 12, P <0.01). Atrial tissue irANP levels were significantly lower in the OM group (38.1 ± 7.8 ng/mg, n = 7) than in the normal group (60.1 ± 1.3 ng/mg, n = 4, P < 0.02). In response to intravenous infusion of ANP (2.5 ug/kg prime, followed by 0.1 ug/kg/min for 30 minutes), urine flow rate and urine sodium and potassium excretion rates increased significantly in the normal group (n = 6, P < 0.05), while no significant responses were found in the OM group (n = 6). It is concluded that plasma levels of ANP are significantly elevated in streptozotocin-induced diabetes in rats, and that atrial tissue stores are significantly depleted in this diabetic model. In addition, the renal response to exogenously administered ANP appears to be diminished in streptozotocin-induced OM. / Master of Science

The purpose of the current thesis was twofold: (1) to examine various factors that might be contributing to age-related learning and memory deficits specifically related to the hippocampus, and (2) to validate our rat model of aging, employing a multilevel analysis. We found age-related deficits on both spatial and non-spatial hippocampus-dependent taks that were accompanied by structural alterations observed in vivo (volune, but not neuronal metabolic function) and post mortem (neuronal density and neurogenesis, but not synaptic or mitochondrial density). Furthermore, our results suggest that the observed hippocampal structural changes, named decreased volume and neurogenesis, predict learning and memory deficits, and both can be accounted for by neurogenic reduction. In addition, the above-mentioned pattern of age-related deficits closely resembles that seen in humans, suggesting the present rat version of aging to be a very useful model for investigating hippocampal aging in humans. / iii, 236 leaves : ill. (some col.) ; 29 cm.

Changes in postural stability following sensory manipulation were investigated among Parkinson's disease patients and healthy older adults. Sixteen Parkinson's disease patients (PD; mean age 68.2 + 2.7 years) and sixteen older adults (control; mean age 67.6 + 2.6 years) performed quiet standing trials that progressed through baseline, sensory manipulation, and reintegration. Postural control following visual deprivation was assessed following alternate removal and reinsertion of visual information. Postural recovery following sensory incongruence was assessed following the termination of visual, somatosensory, and visuosomatosensory incongruence. PD patients' balance was disrupted following visual deprivation, and was initially disrupted when visual information was returned. PD patients' pstural recovery was comparable to control subjects when sensory incongruence ended. These findings indicate that situations of visual deprivation in particular are initially disruptive for PD patients, and imply initial difficulty for sensory reorganization in these patients. Our results provide insight into environmental situations imposing greater fall risk among the parkinsonian population. / xii, 81 leaves ; 29 cm.

The effects of postural threat on gait initiation and steady state gait among Parkinson’s disease (PD) patients and age-matched adults were examined. Ten healthy adults (CTRL; mean age= 68.8 ± 8.4, range 56-80 years) and ten PD patients (PDOFF / ON ; mean age= 69.7 ± 10.3, range 54-81 years) initiated gait and continued with steady state walking along a walkway of two different height conditions. PD patients were first tested in a non-medicated state followed by testing in a medicated state. The results showed that gait initiation and steady state gait deficits inherent to PD are exacerbated in a postural threatening environment. As well, medication efficacy for overcoming parkinsonian deficits may be context dependent. These findings confirm the dynamic nature of movement deficits characteristic of parkinsonian patients and provide empirical evidence for specific environments that can create movement difficulties for people with PD. / x, 59 leaves : ill. ; 29 cm. --

This thesis investigates the role of the hippocampus in object memory. Currently, the role of the hippocampus in object recognition is unclear, with some studies demonstrating a delay-dependent impairment after hippocampal damage, others showing no impairment. The present thesis used the novel object recognition task and its variants to investigate various types of object memory in hippocampal lesion rats. In the first study, impairments were observed in discriminating object order and associating objects with contexts, while no impairment was observed in novel object recognition. In the second study, it was found that encountering another object shortly prior to or after encountering a target object impairs the recognition of the target object. In a control procedure, encountering a novel context either shortly before or after encountering the target object did not impair object recognition. In sum, in the absence of the hippocampus, object memory becomes vulnerable to interference, rendering rats unable to discern memories of multiple objects. The present thesis concludes that the hippocampus discriminates multiple objects via pattern separation. A stimulus-response model relating the role of the hippocampus to object memory is proposed. / vii, 150 leaves : ill. ; 29 cm. --