In the wild, when an animal is exposed to predators or harsh conditions, the stress response is often associated with fleeing behaviors, which are seen as increased locomotor behavior. Handling-stress procedures and intracerebroventricular (icy) injection of corticotropin-releasing factor (CRF) have both been shown to cause an increase in locomotor activity in roughskin newts (Taricha granulosa). The present experiments were designed to determine if icv administration of corticosterone (CORT) prevents stress-induced locomotor increases in activity, if it prevents CRF-induced increases in locomotor activity, and if the time-course and pharmacological specificity of the CORT effects on locomotor activity fit the model for intracellular or membrane receptors. In experiment 1, newts which had been injected with CORT or dexamethasone (DEX) received a standardized handling-stress procedure. Corticosterone administration was able to suppress the increase in locomotor activity in newts exposed to handling-stress at 20 minutes after administration. This effect was transient (no longer present at 2 hours after the injection) and not mimicked by DEX, a synthetic glucocorticoid that binds to intracellular and not membrane receptors. In experiments 2 and 3, either CORT or DEX was administered in the same icy injection with CRF. CORT suppressed CRF-induced locomotor activity in some cases, but this action of CORT seems to be context dependent. Results for DEX-injected newts were confounded the failure of CRF to induced significant increases in locomotor activity. There was variability in the effect of CRF on locomotor activity across seasons. Based on time-course and specificity, it appears that CORT can modulate locomotor activity in newts through mechanisms involving the membrane receptor. Variability in the effects of CRF on locomotor activity in newts suggests there may be seasonal differences in responses to stress. / Graduation date: 1998

Graduation date: 1994

The CERES-Wheat Crop Growth and Development model treats temperature, nitrogen and water stresses as limiting factors. For each day the model calculates a stress index for temperature, N and water, compares the magnitude of the indices, and then adjusts the calculated daily potential growth using the index of the most severe stress, while ignoring the other stresses. Under the conditions in Oregon, however, mild N and water stress will often be present together in about equal degree of stress. Some published results suggest that both stresses affect growth and yield under those conditions. Therefore, this work was undertaken to evaluate the combined effects of N and water stress on growth and development of wheat (Triticum aestivum L.). To make such an evaluation one must be able to control both N and water supplies to the plant and the response of the plant to these two variables must be measured at different growth stages. A system of imposing controlled plant water stress developed by Snow and Tingey (1985) was adapted and evaluated for its potential to impose controlled levels of both N and water stress to single wheat plants. Using a 12 mmol N and 4 cm pathlength as optimum N and water supply treatment, 2 mmol N and 12 cm pathlength and a 1 bar standard ceramic disc in the floral foam column as N and water stress treatments during tillering resulted in 15 % reduction in tillers/plant for limits to the N supply alone, a 39 % reduction for limits to the water supply alone, and a 52 % reduction when both stresses were imposed simultaneously. There was no effect of N or water supply treatments on the leaf appearance rate on the main stem, a measure of the rate of progress toward flowering. Both N and water supplies had a strong effect on tillers/plant which, in turn, affected plant biomass and its constituent parts. The effects were independent, suggesting that, to accurately model the wheat canopy development when both mild N and water stresses are present, both stresses must be considered. A 'law of minimum' concept as currently used in the CERES-Wheat model would not be an accurate model for the process of tillering. In an experiment where stress was imposed during flowering and grain-filling, the grain yield/plant varied significantly with both N and water supplies. The interaction between N and water treatments on grain yield was also significant and was due primarily to their significant interaction on mean kernel weight. The major determinant of grain yield was tillers/plant at harvest. Both N and water supplies affected kernels/ear and N stress caused a reduction of 12% in both fertile spikelets/ear and kernels/fertile spikelet. At an optimum water supply, the difference between the effect of optimum and medium N supply on grain yield was not significant but yield in low N supply was reduced by 54%. In the medium water supply, the grain yield at both medium and low N treatments were significantly lower than at optimum N supply. There was no significant difference in yield between N supply treatments in the low water supply treatments. Thus, under severe water stress, a 'law of minimum' concept appeared to be valid, but under less severe stress both N and water supply affected grain yield. The data on leaf water potential and leaf temperature showed that plants in low water supply treatments maintained consistently lower leaf water potential and higher leaf temperature than in optimum water supply treatment. / Graduation date: 1993

Graduation date: 1991

Marine bioinvasion has been increasing exponentially due to intensive human activities. To manage the threats posed by marine bioinvasion, it is important to understand the key factors for invasion success. Stress tolerance is thought to play an important role in the invasion process, however, little is known of the nature of this tolerance, particularly whether stress tolerance is species- or population-specific. To determine this, laboratory experiments were conducted to investigate differential tolerance of populations of a cosmopolitan marine invasive mussel, Perna viridis, and whether stress tolerance can be altered through pre-selection of individuals. Comparisons were firstly made between two local P. viridis populations from the intertidal and subtidal zones to test if stress tolerance was population-specific. Individuals from the intertidal population had higher baseline heart rates, lower critical salinity values, Scrit, for cardiac activity and longer survival duration at low salinity than individuals from the subtidal population, supporting the presence of population level differences in stress tolerance. Mortality of P. viridis was also compared at sites in both their introduced range (Hong Kong) and native range (Indonesia) which revealed that individuals from the Hong Kong population were more stress tolerant than their native counterparts in Indonesia. Using the same experimental approach, the effect of pre-selection to stress (a prior pre-selection to hypoxia and a subsequent exposure to heat) showed that stress tolerance can be enhanced by pre-selection. The second part of this study investigated whether invasive mussels, Brachidontes variabilis and P. virdis, were more stress tolerant than the native, non-invasive, Septifer virgatus. Laboratory experiments compared the Scrit as well as critical temperature, Hcrit for cardiac activity. Mortality and byssus thread production were also measured in a factorial design with different combinations of temperature (16, 24 and 32 °C) and salinity (8, 16, 32 p.s.u) for 15 days. The two invasive mussels had a higher Hcrit and lower Scrit, which indicated a higher stress tolerance, than the non-invasive mussel. The mortality rate of P. viridis was faster than in B. variabilis and S. virgatus at 8 p.s.u. whereas S. virgatus was the only mussel that exhibited mortality in the medium hyposalinity (16 p.s.u.) and showed much slower byssus attachment than the invasive mussels, suggesting that the invasive mussels are more stress tolerant to heat and medium hyposalinity than the non-invasive species. Overall, stress tolerance proved to be higher in the invasive than non-invasive species and was also population-specific with higher stress tolerance in the invasive population, which may be attributed to the selection of more tolerant individuals during the invasion process. Such a process may occur when founding individuals successfully pass through an invasion process, which may increase the overall mean population-level of stress tolerance and explain why invasive species are generally more stress tolerant than native species. Thus stress tolerance plays an important role in invasion success and invasive species with high stress tolerance may be favoured by climate change, including ocean warming and increased precipitation, which may extend their current distribution range. / published_or_final_version / Biological Sciences / Master / Master of Philosophy

Protocols for the successful micropropagation of 'Queen Elizabeth' ('Q.E.') and 'Dick Koster' ('D.K.') roses were established, yielding a seven-ten fold multiplication rate per month. The effects of mechanically induced stress (MIS) (shaking stress) were evaluated on early establishment of greenhouse-grown 'Q.E.' and 'D.K.' rose cuttings and the ex vitro survival and hardiness of micropropagated 'Q.E.' plantlets. Shaking 'Q.E.' rose cuttings at 200 rpm for 30 min daily for 4 weeks during the rooting stage increased root length, dry weight and the root:shoot dry weight ratio. Similar shaking of 'D.K.' rose at 200 rpm for 15 min increased shoot fresh and dry weight and root length and dry weight. Prior to ex vitro acclimatization, plantlets shaken at 150 rpm for 15 min had reduced leaf dry weights. Those shaken at 200 rpm for 15 min had lower specific root water content but greater percent root dry matter. MIS was not directly implicated in improving ex vitro survival and hardiness of 'Q.E.' rose. (Abstract shortened by UMI.)

In 1998, 30 juvenile elephants were captured in Botswana and transported to a holding facility in South Africa to be trained and sold to zoos and safari parks. The welfare of the 'Tuli Elephants' as they became known, became the source of acrimonious dispute between a number of conservation and animal groups. The case highlighted concerns over the welfare of elephants during capture, transport and confinement. Questions asked were: can an objective assessment of the effect on juvenile elephants on the removal from matriarchal group be made. This study was aimed to take an objective approach to assessing the welfare of captive juvenile elephants using behavioural and physiological methods of investigation. A behavioural study to identify indicators of stress was conducted in five groups of elephants subject to various husbandry systems. Thirteen behavioural indicators of stress were identified. A group of two elephants held in an enclosure 70 m2 that was devoid of mud and sand baths showed the highest number of behavioural indicators of stress. Elephants in larger enclosures with mud and sand baths showed fewer indicators of stress. The group able to range freely during the day showed the least number of stress¬related indicators. Conventionally the physiological assessment of adrenal responses to stress relies upon blood sample collection and the measurement of glucocorticoids but this is impossible without immobilisation or restraint that influences results. This study validated a recently established enzyme immunoassay (EtA) measuring faecal glucocorticoid metabolites in elephants. A preliminary investigation into the biological relevance of this non-invasive method was made for use in assessing welfare in elephants. Four juvenile elephants were injected i.m. with synthetic adrenocorticotrophic hormone (ACTH) (Synacthen, Novartis; 2.15 mg). Blood and faecal samples were collected over 4 hand 7 days respectively. Concentrations of serum cortisol and faecal cortisol metabolites were determined using immunoassay. Variability of basal and peak values in blood and faeces were observed among the elephants. After ACTH injection, serum cortisol concentrations increased by 400-700%. When compared to cortisol and corticosterone EIAs, 11-oxoaetiocholanolone EIA proved best suited to measure cortisol metabolites. Concentrations of faecal 11,17¬dioxoandrostanes increased by 570-1070% reaching peak levels after 20-25.5h. Samples left outside could be collected up to 8hrs after defecation without a significant effect on metabolite concentrations. A correlation between enclosure size, presence of stress-related behaviour and faecal 11,17 -DOAs was observed. Elephants kept in small enclosures exhibited more stress-related behaviour and had higher levels of glucocorticoid metabolites than those ranging in a larger area. The results of the study suggest that non-invasive faecal monitoring of glucocorticoid metabolites is useful in investigating adrenal activity in African elephants. / Dissertation (MSc)--University of Pretoria, 2002. / Companion Animal Clinical Studies / MSc / Unrestricted

No description available.

Experiments were conducted to explore physiological, pathological, and immunological aspects of stress in chickens. Mechanisms of habituation and their association with adrenal steroids were also studied. Degree of stress experienced during perinatal and neonatal stages was evaluated. In both stages, heterophilia and lymphopenia were noted and post-hatching heterophil to lymphocyte (H/L) ratios declined in a quadratic manner with age. Feed restriction elicited a similar stress response, as indicated by H/L ratios in dwarfs and normals with the effect of adapting to fasting having dissipated between 12 to 16 days. Resistance to Eimeria tenella infection was greater in normals than dwarfs, and for fasted than ad libitum fed chicks. Neither genotype nor feeding regimen had an effect on antibody response to SRBC. Frustration induced by thwarting of feeding resulted in a dramatic elevation in HIL ratios and conspicuous behavioral responses, suggesting responses to fasting may be physiologically and psychologically modulated. Provision of sand during feed withdrawal attenuated physiological responses, possibly via alteration of psychogenic components. An experiment was designed to evaluate the impact of mild feed restriction at several ages on heat tolerance. Normal chicks feed-deprived during the neonatal stage had lower H/L ratios, improved resistance to marble spleen disease and growth during heat treatment than those fed ad libitum or fasted at older ages. A companion experiment examined habituation and concomitantly the role of glucocorticoids in stress response. Neonatal fasting-induced stress responses without concurrent increases in adrenal steroidogenesis did not enhance ability of normal chicks to withstand high ambient temperatures. The hypothesis regarding modulatory roles of corticosteroids in neonatally-elicited adaptation was affirmed in a subsequent study. Feed withdrawal for 8 or 24 h at 36 days of age did not induce either H/L or plasma corticosterone response of chicks stressed early in life. In contrast, neither criterion provided evidence for adaptation to feed deprivation by neonates treated with an adrenal steroidogenesis blocker during the fast. corticosterone mediated inhibitory feedback regulation of the hypothalamic - pituitary - adrenal axis which down-regulates ACTH response was also evident. / Ph. D.

Water scarcity induced by drought, temperature, and salinity has plagued agricultural sustainability in recent years with unprecedented revenue losses, raising concerns for worldwide food security. Recent studies have revealed unique botanical response mechanisms to combat water related stress, namely the expression of proteins known as the dehydrins. Dehydrin proteins have been shown to serve various intracellular protective functions. The gene for a SK5 type dehydrin from the arctic plant Cerastium arcticum (CaDHN) was introduced into tobacco plants and water deficit tolerance was evaluated. Plants overexpressing CaDHN displayed improved tolerance to salt stress, but no improvement was observed under drought stress. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2015. / FAU Electronic Theses and Dissertations Collection