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The individual and combined anorexigenic effects of oxytocin and naltrindole in rodents
(The University of Waikato, 2026) Te Rire-McNeil, Shaun Toroa; Olszewski, Pawel K.; Head, Mitchell; Peters, Linda M.; Grainger, Megan N.C.; McGowan, Robert
Obesity is a characterized by excess body mass, and it reflects a failure to match energy intake to energy expenditure. Energy intake is regulated by a plethora of mechanisms, including the oxytocin (OT) and opioid systems, making both attractive targets for obesity pharmacotherapy. Initial studies utilizing OT and mu-opioid receptor antagonist naltrexone (NTX) suggest that combined targeting of OT and opioid signaling may enhance hypophagia. Thus far, there have no attempts to examine potential synergy between OT and delta opioid receptor blockers. The work presented in the current thesis was conceptualized to bridge this gap in knowledge by evaluating the anorexigenic potential of OT and naltrindole (NTI) when administered both individually and in combination. The literature describing OT effects on fat intake remains inconsistent. Macronutrient-focused studies that assess the anorexigenic effect of OT on fat consumption using liquid emulsions, most commonly Intralipid, report no suppression of intake. Conversely, studies which use solid high-fat foods more often report OT-induced hypophagia, despite not being designed to systematically test the influence of fat content. Therefore, in Specific Aim 1 of this thesis I systematically determined whether OT suppresses the consumption of solid fatty foods. Adult male rats received intraperitoneal (i.p.) OT (0.1–10.0 mg/kg) and were tested in no-choice and two-choice paradigms using solid mash diets providing 62%, 79%, or 91% of energy from fat; chow diets providing 10% or 60% of energy from fat; or a matrix-matched, cornstarch-rich control chow. The effect of fatty food consumption on neuronal activity was measured using c-Fos immunohistochemistry and c-Fos-OT double staining, where sated rats were either given small meals of 10% fat chow, 60% fat chow, or no food. In the single choice tests, OT reduced the consumption of the solid diets across a range of fat contents, and in the two-choice paradigm, OT-treated rats consumed less 60% fat chow than 10% fat chow compared to control animals. Consumption of 60% fat chow, but not 10% fat chow, increased activation of OT neurons in the PVN and SON and increased c-Fos immunoreactivity in multiple feeding-related regions. These findings demonstrate that OT suppresses intake of solid high-fat foods and help reconcile the discrepancy between Intralipid-based and solid-diet paradigms. In the context of the overarching aim of this thesis, our findings also indicate that conclusions about the anorexigenic effect of OT drawn from Intralipid intake data should be interpreted as specific to Intralipid, rather than assumed to generalise to dietary fat consumption more broadly. The literature lacks a consensus on how NTI affects sucrose intake. Prior reports frequently describe mixed or null effects of NTI on sucrose consumption, but these findings are commonly derived from paradigms in which animals are not habituated to sucrose and instead receive sucrose access in acute, ad hoc test sessions. For this reason, Specific Aim 2 of this thesis was to determine the effect of NTI, and by extension the role of DOR, on sucrose intake in rats that habitually consume sucrose solution. Adult male rats were habituated to daily 1 h access to sucrose solution for three weeks. Following habituation, rats received i.p. NTI (5 or 10 mg/kg) prior to their regular sucrose access period and sucrose intake was measured. We also assessed whether NTI altered deprivation-induced water intake or produced a conditioned taste aversion (CTA). Additionally, c-Fos immunoreactivity was assessed in rats with habitual sucrose access and in sucrose-naïve controls, with and without NTI treatment. NTI at 10 mg/kg reduced sucrose solution consumption independent of changes in thirst and without evidence of a CTA. Moreover, NTI induced changes in neuronal activity across a broader set of feeding-related regions in sucrose-habituated rats than in sucrose non-naïve rats. Together, these findings demonstrate that NTI can suppress sucrose intake once consumption is habitual, and that habituation is associated with a broader recruitment of central feeding-related mechanisms following NTI treatment. Of relevance to the overarching aim of this thesis, these results indicate that null effects of NTI observed under ad hoc sucrose access conditions should not be assumed to reflect NTI efficacy once sucrose intake is predictable and habitual. Finally, having established foundational knowledge of the individual effects of OT and NTI on intake in Specific Aims 1 and 2, we next examined their combined administration. Based on prior reports indicating that simultaneous targeting of OT and opioid signalling can produce stronger anorexigenic effects than either system alone, we tested OT and NTI in combination. We aimed to determine whether co-administration could overcome context-dependent limitations observed with each drug individually, including OT’s failure to suppress Intralipid intake and the dependence of NTI effects on habitual sucrose exposure. Specific Aim 3 of this thesis was to test whether the simultaneous targeting of OT receptors and DOR, through combined administration of OT and NTI, synergistically suppresses the consumption of liquid diets. Adult male mice received i.p. OT (0.1–3.0 mg/kg), NTI (3.0–10 mg/kg), or OT+NTI prior to 2 h access to saccharin, Intralipid, or sucrose solutions, and intake was measured. We also assessed post–water deprivation water consumption and characterised treatment-induced changes in neuronal activation in feeding-related regions using c-Fos immunohistochemistry. NTI, but not OT, reduced saccharin consumption, whereas OT+NTI produced a stronger reduction than NTI alone, consistent with a synergistic anorexigenic effect. In contrast, OT, but not NTI, reduced sucrose consumption, and neither drug alone nor the combination altered Intralipid intake. These intake outcomes occurred independent of changes in thirst. At the neuronal activation level, OT × NTI interactions were observed in the nucleus accumbens core and shell and in hypothalamic nuclei including the ventromedial and suprachiasmatic nuclei. Although combined treatment did not overcome the individual limitations observed for sucrose and Intralipid intake, the synergistic suppression of saccharin consumption is notable and extends evidence that combined targeting of OT and opioid signalling may hold promise for development of anorexigenic treatments. In summary, this thesis provides novel insights into the context-dependent anorexigenic actions of both OT and NTI, demonstrated by the efficacy of OT as an inhibitor of solid fatty food consumption but not Intralipid, and by the dependence of NTI-induced sucrose suppression on habitual consumption. Furthermore, this thesis provides additional evidence that simultaneous targeting of OT and delta opioid signalling can produce anorexigenic effects which extend beyond those achieved with single-drug treatment, as demonstrated by the synergistic suppression of saccharin intake observed with OT and NTI co-administration.
A video dataset of everyday life grasps for the training of shared control operation models for myoelectric prosthetic hands
(IEEE, 2024) Godoy, Ricardo V.; Guan, Bonnie; Dwivedi, Anany; Owen, Mahonri; Liarokapis, Minas
The control of high degree of freedom prosthetic hands requires high cognitive effort and has proven difficult to navigate particularly as prosthetic hands become more advanced. To reduce control complexity, vision-based shared control methods have been proposed. Such methods rely on image processing and/or machine learning to identify object features and classes and introduce a level of autonomy to the grasping process. However, currently available image datasets lack focus in the area of prosthetic grasping. Thus, in this paper, we present a new dataset capturing user interactions with a wide variety of everyday life objects using a fully actuated, human-like robot hand and an onboard camera. The dataset includes videos of over 100 grasps of 50 objects from 35 classes. A video analysis has been conducted, using established grasp taxonomies to compile a list of grasp types based on interactions of the user with the objects. The resulting dataset can be used to develop more efficient prosthetic hand operation systems based on shared control frameworks.
Amara
(The University of Waikato, 2026) Bojesen-Trepka, Guy Holton; Chidgey, Catherine; Slaughter, Tracey
Amara is a satirical reimagining of the Jesus story told from a God's-eye perspective. It lightly probes the myth of the virgin birth, miracles, Christianity’s departure from the teachings of Jesus, the notion of an omnipotent God, and what might happen if a Gen Z Messiah arrived in the age of DNA testing and rolling news. In an Australian relocation of the biblical Annunciation, Mary, soon to marry Joseph, becomes pregnant while claiming to be a virgin. Joseph tries to identify the father by collecting genetic samples from neighbours in the same apartment block. When this proves unsuccessful, and after being threatened by an antagonistic angel, Joseph abandons his search and accepts a bizarre alternative explanation: that Mary conceived while sunning her perineum on their balcony. Amara is born in a barn on 1 January 2000. Three girls, children of refugees, turn up with gifts after dreaming of her birth and become part of the family. A Catholic priest and a dogmatic parishioner become aware of a possible incarnation. While Joe is receptive to the priest's interest, Mary rebuffs his attempts to become involved, determined to protect Amara and give her a normal life. Joe and Mary have a second child, Joshua, and life is mostly suburban normal. As she grows, Amara reveals herself to be an extraordinary child, with an unusually close relationship with God. When Amara is ten, she disarms a knife-wielding man with a history of mental illness – an act that inexplicably restores his sanity. A journalist is assigned the story, and her investigation uncovers possible earlier miracles. The ensuing media interest prompts the return of the priest, parishioner and angel and makes normal life impossible for the family. A Catholic bishop sees an opportunity to deflect public attention from the growing scandal of institutional child abuse and offers sanctuary to the family at a retreat in the countryside. The submitted manuscript represents the first stage of a larger narrative following Amara from birth into adulthood.
Multi-grasp classification for the control of robot hands employing transformers and lightmyography signals
(IEEE, 2023) Godoy, Ricardo V.; Guan, Bonnie; Dwivedi, Anany; Shahmohammadi, Mojtaba; Owen, Mahonri; Liarokapis, Minas
The increasing use of smart technical devices in our everyday lives has necessitated the use of muscle-machine interfaces (MuMI) that are intuitive and that can facilitate immersive interactions with these devices. The most common method to develop MuMIs is using Electromyography (EMG) based signals. However, due to several drawbacks of EMG-based interfaces, alternative methods to develop MuMI are being explored. In our previous work, we presented a new MuMI called Lightmyography (LMG), which achieved outstanding results compared to a classic EMG-based interface in a five-gesture classification task. In this study, we extend our previous work experimentally validating the efficiency of the LMG armband in classifying thirty-two different gestures from six participants using a deep learning technique called Temporal Multi-Channel Vision Transformers (TMC-ViT). The efficiency of the proposed model was assessed using accuracy. Moreover, two different undersampling techniques are compared. The proposed thirty-two-gesture classifiers achieve accuracies as high as 92%. Finally, we employ the LMG interface in the real-time control of a robotic hand using ten different gestures, successfully reproducing several grasp types from taxonomy grasps presented in the literature.
Towards prosperity? Rural transformation in post-colonial Vanuatu
(The University of Waikato, 1993) Tapari, Budai; Cleary, Mark C.; Campbell, John; Bedford, Richard
This thesis examines the question of progress towards “prosperity” with particular reference to cash-generating activities of households in Nerenigman on Mota Lava in the Banks/Torres Local Government Region and the Longana area in East Ambae of the Ambae/Maewo Local Government Region. The assessment and comparison of post-colonial rural change in these areas is based on detailed anthropological research, and geographic and demographic theses published in the early 1980s by Rodman (1981) and Campbell (1985). These studies, together with results obtained from the 1979 population census, provide a baseline from which an examination of aspects of change in rural communities during the 1980s is conducted. The two areas were chosen as case studies to examine whether “balanced” rural development and prosperity had been achieved by the early 1990s. Rural villagers’ participation in cash-earning activities has meant that their subsistence mode of production has been modified and a path towards market-oriented farming established. Rural villagers in the study areas want development as measured in both tangible and intangible terms. In the study areas, this aspiration was evident through their participation in the capitalist economy. The presence of physical infrastructure such as schools, health centres, water supply systems and other capital assets villagers used for promoting development purposes, indicated their changing aspirations for Western-type consumer goods and services. In addition to the provision of the above services, the presence of commercial institutions such as co-operative stores, trade stores, commercial centres and banks were examples of facilities which were regarded as important for facilitating development. The villager’s access to these services has paved the way for their deepening integration into the modern cash economy. The evidence from this study suggests that opportunities for households to diversify and extend their sources of cash incomes on Mota Lava have been very limited since the independence of Vanuatu in 1980. There was little evidence that material living standards had improved much on the island. By comparison, the Longana area has shown evidence of increased levels of prosperity. There has been a significant change in the structure of the agricultural economy, from heavy dependence on copra in the 1980s to kava and livestock production which had become important sources of income by the early 1990s. While cultural values remain important attributes of ni-Vanuatu assessments of prosperity, most villagers expressed a real desire to participate in the capitalist system and to share some of the material benefits of that participation in the early 1990s. This study of cash-generating activities of households in the study areas serves to underline the nature and direction of change, which increasingly involves the integration of rural villagers into a capitalist economy.