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Subject: search.filters.subject.Hypothalamic-pituitary-adrenal axis

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    Ngā mea kōaro o ngā wā tamarikitanga, te taumahatanga o aua mea me ētahi mahi whakaora hinegaro mō ngā wāhine Māori = Adverse childhood experiences, HPA axis functioning and culturally enhanced mindfulness therapy among Māori women in Aotearoa New Zealand : a dissertation presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Psychology at Massey University, Palmerston North, New Zealand
    (Massey University, 2019) Ketu-McKenzie, Miriama Deborah
    Chronic health conditions such as obesity, type II diabetes, cardiovascular disease, depression and anxiety are prevalent among Māori women in New Zealand, as are adverse experiences in childhood and chronic stress. Recent studies have shown a link between adverse childhood experiences (ACEs) and chronic health problems later in life. Many of those studies propose that dysregulation in the stress response system - specifically the hypothalamic-pituitary-adrenal (HPA) axis - mediates that link. Cortisol is the primary corticosteroid released by the HPA axis and is commonly used as a biomarker for assessing HPA axis functioning. Mindfulness-Based Stress Reduction (MBSR) is a therapy that uses a range of breathing techniques, stretches, formal meditations and awareness exercises designed to help regulate the stress response by changing the way the brain manages and relates to stress. Due to its Eastern roots, MBSR therapy assumes an holistic view of health that mirrors some of the key concepts promoted in Te Ao Māori. This research tested the HPA axis functioning of eight adult Māori women who had experienced high ACEs, and explored associations between cortisol dysregulation, visceral obesity (a risk factor for many chronic health conditions) and psychological distress. This research also tested the clinical effectiveness and cultural responsiveness of an MBSR course that had been enhanced to suit a Māori audience. Participants provided pre, mid and post-treatment salivary cortisol samples that measured changes to their acute stress cortisol response, as well as changes to their daily cortisol slope, their cortisol awakening response and their overall cortisol levels. They also provided pre and post-treatment waist circumference measurements. Self-report data assessing depression and anxiety levels, PTSD levels, stress eating habits, perceived stress levels and mindful awareness levels, was collected, as was qualitative data in the form of pre and post-treatment interviews. The results indicated that culturally enhanced MBSR therapy was well received with this sample of Māori women and that the participants reported a wide range of benefits as a result of practicing mindfulness meditation.
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    Corticosterone responses to different stimuli and phenotypic plasticity in corticosterone responses in the kororā (little penguin, Eudyptula minor) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Physiology at Massey University, Manawatu, New Zealand
    (Massey University, 2018) Choi, MinSeo
    The overall aims of the research presented in this thesis were to compare in little penguins (Eudyptula minor) corticosterone concentrations following exposure to a variety of stimuli with corticosterone responses to handling, to investigate the relationship between corticosterone response to handling and corticosterone concentrations after exposure to different stimuli, and to examine plasticity in corticosterone responses. The study involved measurement of corticosterone concentrations in blood samples collected after a 15 min stimulus. Handling resulted in a greater mean plasma corticosterone concentration than all other stimuli. Plasma corticosterone concentrations in little penguins in nestboxes after the presentation of a novel object were greater than concentrations after the sound of dog barking and the sound of human talking. Corticosterone concentrations were higher in birds that were exposed to penguin alarm calls than birds exposed to human talking. Differences between mean corticosterone concentrations after human talking and dog barking, and between mean concentrations after the penguin alarm call and the novel object, were not significant. The mean concentration after human talking was the lowest and the mean concentration after novel object was the highest relative to responses to handling. Corticosterone concentrations after handling and concentrations after exposure to other stimuli were not correlated. A reaction norm revealed the existence of plasticity in corticosterone concentrations in little penguins. The reaction norm approach used to determine plasticity in this study did not allow for the quantification of the degree of plasticity. The findings of the present study have provided information about the way little penguins respond to different type of stimuli, whether responses to handling are similar to responses to other stimuli in the same bird, and show that the use of a reaction norm approach can provide useful information about plasticity in corticosterone responses to different stimuli in birds.
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    The development of the corticosterone stress response of kororā (little penguin, Eudyptula minor) chicks in response to frequent handling : a thesis presented in partial fulfilment of the requirements of the degree of Master of Science in Physiology at Massey University
    (Massey University, 2018) Ogle, Shelley
    In birds, when a stressor is encountered, the hypothalamo-pitiutary-adrenal (HPA) axis is activated to produce the corticosteroid, corticosterone. The production of this hormone incites a flight or fight response in order to best avoid long-term damage from the stressor. However, prolonged or repeated exposure to high levels of corticosterone can have damaging behavioural and physiological effects. For this reason, high levels of the hormone should be avoided where possible in developing chicks. Chicks of altricial species in particular, seldom hatch with a highly functioning HPA axis so as to avoid these detrimental effects while their parents are still protecting them from major stressors such as predators, adverse weather and low food availability. Previously, studies have mapped the development of the HPA axis in a range of species or studied the effects of stress from a young age on future behavioural or physiological responses. This current study aimed to not only describe any adverse effects observed as a result of increased encounters with stressors but also track the development of the HPA axis in kororā (little penguin, Eudyptula minor) chicks. Kororā chicks from the Oamaru Blue Penguin Colony were selected from both available sites and grouped based on their age at the time of sampling, 2 weeks old, 4 weeks old and 6 weeks old and a further two groups were formed for chicks that were handled twice a week from 2 weeks of age until 4 weeks or 6 weeks at which point they were sampled. Blood sampling and handling and capture stress responses were done following a modified standard protocol of a blood sample at 0 mins, 15 mins and 30 mins at which point they were returned to their nest to avoid over or under heating depending on the age and weather. The chicks being exposed to frequent human interactions were weighed twice a week and also had their flipper length and beak width, length and depth measured to graph the growth rates and body condition indices which has never previously been done in penguin chicks. It was found that frequent interactions with people did not have a significant effect on the stress responses when comparing previously handled chicks with unhandled chicks of the same age and that the previously handled chicks developed their adult-like stress response at a similar age to those that had not been previously handled. With regards to body condition indices and growth rates, this study showed that the parents leave the nest just after body condition indices drop to the low point in the chicks’ development.
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    Corticosterone responses to stressors and the regulation of hypothalmic-pituitary-adrenal axis in Japanese quail : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physiology at Massey University, Palmerston North, New Zealand
    (Massey University, 2003) Chua, Wei-Hang
    Corticosterone is the major adrenal glucocorticoid in birds. It is secreted in response to stressors, with plasma concentrations typically rising to a peak within 10 to 15 minutes and then declining over 30 to 60 minutes once the stressor is removed. The increase in corticosterone is thought to help the animal to adjust to the stressor, although corticosterone may also inhibit the reproductive axis. The corticosterone response to a stressor varies between individuals, although the level of the hypothalamic-pituitary-adrenal axis at which this variation arises in birds has not been identified. The goals of this research were to determine in Japanese quail (Coturnix coturnix japonica): (1) the effects of corticosterone and of various stressors on sex steroid secretion; (2) corticosterone responses to 5, 10 or 15 min exposure to manual restraint and 15 min exposure to different stimuli; (3) quantifying individual variation in the corticosterone response; and (4) whether individual variation in the corticosterone response to stimuli used in goal 2 is regulated by differences in pituitary or adrenal sensitivity to corticotropin releasing factor (CRF) and adrenocorticotropic hormone (ACTH) respectively. A prolonged elevation in plasma corticosterone concentrations can inhibit reproduction. The effects of a short elevation in corticosterone are less understood, so the relationship between corticosterone and sex steroid secretion in quail was characterised by administering 1.2 mg corticosterone injections. Corticosterone treatment stimulated an increase in plasma corticosterone, while testosterone declined in both corticosterone-treated and control birds. Plasma LH was unaffected by challenge with corticosterone. Collectively, these data suggest that repeated handling associated with frequent blood sampling inhibited testosterone secretion directly at the testis. Corticosterone responses to a variety of novel stimuli were characterised. Manual restraint for 10 or 15 min caused a significant response whereas restraint for 5 min or less did not lead to an increase in corticosterone 15 minutes from the start of the stressor. Corticosterone responses to 15 min of mechanical restraint varied between birds whereas 15 min of manual restraint elicited a maximal plasma corticosterone response in all birds. Manual and mechanical restraint caused declines in plasma testosterone of a similar magnitude. There was more variation within than between birds in their corticosterone response to mechanical restraint. Despite this, the general pattern of the corticosterone response was repeatable for individuals. Quail with low or high plasma corticosterone responses to 15 minutes of mechanical restraint were injected intrajugularly with a dose of ACTH that stimulated a sub-maximal corticosterone response. The plasma corticosterone response to ACTH did not differ between birds with low or high corticosterone responses to mechanical restraint, indicating that variation in corticosterone responses to restraint did not arise at the level of the adrenal gland. A preliminary study showed that injections of ovine CRF stimulated corticosterone secretion. However, CRF did not consistently stimulate an increase in plasma corticosterone in these birds and hence it was not possible to determine if pituitary responsiveness to CRF differed between birds with low or high corticosterone responses to restraint. These results indicate that variation in the corticosterone response between individual Japanese quail arises above the level of the adrenal gland in the HPA-axis, and may occur at the pituitary gland or due to differences in activation of neural pathways in the brain.