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(2022) Cao, JunThesisThis thesis focuses on the development and applications of magnetic resonance electrical properties tomography (MREPT), which is an emerging imaging modality to noninvasively obtain the electrical properties of tissues, such as conductivity and permittivity. Chapter 2 describes the general information about human research ethics, MRI scanner, MR sequence and the method of phase-based MREPT implemented in this thesis. Chapter 3 examines the repeatability of phase-based MREPT in the brain conductivity measurement using balanced fast field echo (bFFE) and turbo spin echo (TSE) sequences, and investigate the effects of compressed SENSE, whole-head B_1 shimming and video watching during scan on the measurement precision. Chapter 4 investigates the conductivity signal in response to short-duration visual stimulus, compares the signal and functional activation pathway with that of BOLD, and tests the consistency of functional conductivity imaging (funCI) with visual stimulation across participants. Chapter 5 extends the use of functional conductivity imaging to somatosensory stimulation and trigeminal nerve stimulation to evaluate the consistency of functional conductivity activation across different types of stimuli. In addition, visual adaptation experiment is performed to test if the repetition suppression effect can be observed using funCI. Chapter 6 explores if resting state conductivity networks can be reliably constructed using resting state funCI, evaluates the consistency of persistent homology architectures, and compares the links between nodes in the whole brain. Chapter 7 investigates the feasibility of prostate conductivity imaging using MREPT, and distinctive features in the conductivity distribution between healthy participants and participants with suspected abnormalities.
Metabolic and behavioural effects of cafeteria diet-induced maternal obesity on rat offspring: Impact of postweaning diet(2023) Seyed Tajaddini, AynazThesisMuch evidence indicates that maternal obesity programs a range of complications in offspring, highlighting the need to identify beneficial interventions. The present thesis examined if the programmed effects of maternal obesity on offspring are exacerbated by exposure to a high-fat, high-sugar ‘Cafeteria’ (Caf) diet and investigated the effects of a healthy diet intervention in adulthood. The first study examined whether a diet switch intervention could reverse the adverse effects of an unhealthy postweaning diet in male and female rat offspring born to dams fed standard chow or a high-fat, high-sugar, Caf diet. Weanling offspring from Caf dams were smaller and lighter, yet had more retroperitoneal (RP) fat, particularly in males. Maternal obesity enhanced the impact of postweaning Caf exposure on adult (14-week-old) body weight, RP fat, liver mass and plasma leptin in males but not females. Maternal Caf diet significantly increased relative expression of ACACA and Fasn in male and female weanling liver, whereas PPARα was increased in males from Caf dams. Hepatic CPT-1 expression was reduced in adult males from Caf fed dams. The results underline the sex-specific detrimental effects of maternal obesity on offspring; maternal obesity exacerbated the obesogenic phenotype produced by postweaning Caf diet in male, but not female offspring. A subset of rats from this first cohort were maintained on their postweaning diets until 22 weeks of age, when postweaning Caf groups were switched to chow for a further 5 weeks. Switching from Caf to chow in adulthood suppressed energy intake below groups maintained on chow. Consequently, body weight and adiposity fell in switched groups, but remained significantly higher than chow-fed controls. The diet switch improved a deficit in place recognition memory observed in Caf-fed groups, with no significant change over time in chow-fed groups. Importantly, the effects of the switch did not differ between offspring born to chow or Caf-fed dams. Thus, in these older adult offspring a healthy dietary intervention led to benefits regardless of prior exposure to maternal obesity. To complement these data, our second study investigated if the programming effects of maternal obesity were aggravated by offspring exposure to a Caf diet when introduced in adulthood. Male and female offspring from lean and obese dams were weaned onto chow until 9 weeks of age; siblings were then either continued on chow or switched to Caf diet for 5 weeks. Offspring from Caf dams were smaller than those from chow dams at birth, and exhibited greater adiposity, plasma glucose and leptin levels at weaning in both sexes. Offspring of Caf dams exhibited elevated liver triglyceride content at weaning but no significant changes in the liver antioxidant enzymes GPx, SOD, and CAT. The switch to Caf diet elevated body weight and fat mass, with more pronounced effects in females than males. As in our first study, adult males (14 week old) from Caf-fed dams exhibited increased body weight, adiposity, and plasma insulin and leptin levels relative to offspring from chow dams. In female offspring, only RP fat mass and plasma insulin were increased by maternal obesity. Moreover, there were behavioural effect of maternal obesity (reduced anxiety-like behaviour) on offspring. Thus, the effects of maternal Caf diet exposure were absent until a cafeteria diet challenge in adulthood, indicating that Caf diet-induced maternal obesity programs a latent vulnerability to obesogenic diet exposure in offspring, particularly in males. Further studies are needed to investigate the beneficial effects of reprogramming strategies such as healthy diet intervention in offspring, which are likely to be influenced by the duration, timing and mode of intervention.
Developing and evaluating a culturally adapted internet-delivered mindfulness intervention for Indonesian university students experiencing psychological distress(2023) Listiyandini, Ratih ArruumThesisPsychological distress is prevalent among university students worldwide, including in Low-and-middle income countries, such as Indonesia. Considering its promising scalability, a culturally relevant Internet-delivered mindfulness intervention has potential to treat psychological distress among Indonesian university students. However, there is no previous research into the development and impact of culturally relevant internet-delivered mindfulness interventions for Indonesian university students, leaving a gap in the research literature. The current thesis aims to: a) develop a culturally adapted internet-delivered mindfulness intervention and evaluate its relevancy for Indonesian university students; b) assess its feasibility and acceptability in a pilot open trial, and c) investigate its effectiveness for treating distress among Indonesian students in a randomised controlled trial. To achieve the thesis objectives, the systematic cultural adaptation framework proposed by Barrera and colleagues (2006; 2013) was employed as a guiding framework for culturally adapting an Australian internet-delivered mindfulness program to be more relevant for Indonesian university students. The development of a culturally adapted internet-delivered mindfulness intervention was achieved through two studies using mixed-methods approach. Study 1 was an online cross-sectional survey of Indonesian students’ openness and preferences toward an internet-delivered mindfulness program. Study 2 engaged Indonesian university students, as well as mindfulness or mental health experts in focus group discussions, structured interviews, and the completion of cultural relevancy questionnaires. The purpose of Study 2 was to gain feedback on an initial version of the culturally adapted program. These studies showed that an internet-delivered mindfulness intervention is relevant for Indonesian university students, but some adjustments needed to be made to enhance its cultural suitability and engagement. Based on these studies, an Indonesian counsellor-guided internet-delivered mindfulness program, called PSIDAMAI (Program Intervensi Mindfulness Daring Mahasiswa Indonesia) was developed. Subsequently, Study 3 assessed the feasibility, acceptability, and preliminary clinical outcomes of counsellor guided PSIDAMAI using a pre-post open trial study design. Study 3 showed that PSIDAMAI was feasible, acceptable, and associated with significant improvements in psychological distress between baseline and post-treatment, with good completion rates (70%). In Study 4, the clinical efficacy of PSIDAMAI was tested in a randomized controlled trial using a wait-list control group as a comparator. Study 4 found that PSIDAMAI was more effective at improving psychological distress compared to the wait-list control group with medium to large between-group effect sizes. The improvements were maintained up to one-month follow-up. In summary, the thesis is the first to demonstrate evidence that a culturally adapted internet-delivered mindfulness intervention is relevant, acceptable, feasible, effective, and has positive impacts for Indonesian university students’ mental health. Thus, strategies for wider implementation within the Indonesian higher education mental health system are now needed.