title: Effect of oxytocin on hunger discrimination

authors: Head, Mitchell Antony

subjects: Science & Technology

abstract: Centrally and peripherally administered oxytocin (OT) decreases food intake and activation of the endogenous OT systems, which is associated with termination of feeding. Evidence gathered thus far points to OT as a facilitator of early satiation, a peptide that reduces the need for a meal that has already begun. It is not known, however, whether OT can diminish a feeling of hunger, thereby decreasing a perceived need to seek calories. Therefore, in the current project, we first confirmed that intraperitoneal (i.p.) OT at 0.3–1 mg/kg reduces food intake in deprived and non-deprived rats. We then used those OT doses in a unique hunger discrimination protocol. First, rats were trained to discriminate between 22- and 2-h food deprivation (hungry vs. sated state) in a two-lever operant procedure. After rats acquired the discrimination, they were food-restricted for 22 h and given i.p. OT before a generalization test session. OT did not decrease 22-h deprivation-appropriate responding to match that following 2-h food deprivation, thus, it did not reduce the perceived level of hunger. In order to better understand the mechanisms behind this ineffectiveness of OT, we used c-Fos immunohistochemistry to determine whether i.p. OT activates a different subset of feeding-related brain sites under 22- vs. 2-h deprivation. We found that in sated animals, OT induces c-Fos changes in a broader network of hypothalamic and brain stem sites compared to those affected in the hungry state. Finally, by employing qPCR analysis, we asked whether food deprivation vs. sated state have an impact on OT receptor expression in the brain stem, a CNS “entry” region for peripheral OT. Fasted animals had significantly lower OT receptor mRNA levels than their ad libitum-fed counterparts. We conclude that OT does not diminish a feeling of hunger before a start of a meal. Instead OT's anorexigenic properties are manifested once consumption has already begun which is—at least to some extent—driven by changes in brain responsiveness to OT treatment in the hungry vs. fed state. OT should be viewed as a mediator of early satiation rather than as a molecule that diminishes perceived hunger.

text: Effect of oxytocin on hunger discrimination Centrally and peripherally administered oxytocin (OT) decreases food intake and activation of the endogenous OT systems, which is associated with termination of feeding. Evidence gathered thus far points to OT as a facilitator of early satiation, a peptide that reduces the need for a meal that has already begun. It is not known, however, whether OT can diminish a feeling of hunger, thereby decreasing a perceived need to seek calories. Therefore, in the current project, we first confirmed that intraperitoneal (i.p.) OT at 0.3–1 mg/kg reduces food intake in deprived and non-deprived rats. We then used those OT doses in a unique hunger discrimination protocol. First, rats were trained to discriminate between 22- and 2-h food deprivation (hungry vs. sated state) in a two-lever operant procedure. After rats acquired the discrimination, they were food-restricted for 22 h and given i.p. OT before a generalization test session. OT did not decrease 22-h deprivation-appropriate responding to match that following 2-h food deprivation, thus, it did not reduce the perceived level of hunger. In order to better understand the mechanisms behind this ineffectiveness of OT, we used c-Fos immunohistochemistry to determine whether i.p. OT activates a different subset of feeding-related brain sites under 22- vs. 2-h deprivation. We found that in sated animals, OT induces c-Fos changes in a broader network of hypothalamic and brain stem sites compared to those affected in the hungry state. Finally, by employing qPCR analysis, we asked whether food deprivation vs. sated state have an impact on OT receptor expression in the brain stem, a CNS “entry” region for peripheral OT. Fasted animals had significantly lower OT receptor mRNA levels than their ad libitum-fed counterparts. We conclude that OT does not diminish a feeling of hunger before a start of a meal. Instead OT's anorexigenic properties are manifested once consumption has already begun which is—at least to some extent—driven by changes in brain responsiveness to OT treatment in the hungry vs. fed state. OT should be viewed as a mediator of early satiation rather than as a molecule that diminishes perceived hunger.

year: 2019

title: The Formulation of Titanium - based Metal Feedstocks and the Fabrication of Parts using the Powder Injection Moulding Process

authors: Ewart, Paul Douglas

subjects: Binder

abstract: Development of a profitable titanium industry for New Zealand will not come about without innovative technologies. Plastic injection moulding has long held a place in NZ manufacturing to produce large quantities of complex parts and holds the key to such innovation.
Titanium metal parts were fabricated by injection moulding titanium based metal powder feedstock followed by a debinding process and subsequent sintering. The fabrication process in its entirety was investigated in four distinct steps. Feedstock formulation involved combining the metal powders with various carrier components. Injection moulding enabled the shaping of the feedstock into geometries approximating the final part. Debinding being the process whereby the carrier/binder system is removed from the part to create a powder compact retaining the required geometry. Sintering being the final step where the metal powders are consolidated into a fully dense metal part of net shape.
The feedstock binder consisted of water soluble polyethylene glycol that reduced feedstock viscosity, improved particle wetting, aided greenpart shape retention and eliminated toxic solvents in debinding. Carnauba wax and bees wax aided dispersion, lubricated particles, were safe to handle and better for the environment (than petroleum waxes). Their low melt temperatures aided removal during thermal debinding and supported residue elimination.
By optimising the ratio of water soluble, wax and polyolefin binder components (3: 2: 1 respectively) for melt flow and pellet formation, greenparts defect free with uniform particle distribution were made. The optimal binder system proved suitable for titanium alloy and irregular shape pure titanium powders (hydride-de-hydride). Increasing powder loading (wP = (0.60 to 0.65)) had no appreciable effect on viscosity while enabling feedstock with good uniformity and pellet formation. Dimensional change was not affected by uniformity of the feedstock however molecular weight, volume and dispersion of binder components affected interparticular distances. Low processing temperatures reduced disruption to part geometry, benefitted particle bonding and helped retain handling strength.
The use of low temperatures for thermal debinding (t = 250 °C) enabled removal of the binder below the temperatures that facilitate interstitial diffusion and oxide/carbide formation, although part thickness, mass and overall volume effected the processing time. A strong correlation was seen between handling strength of the greenparts and defects, such as non-uniform density distribution and cracking after sintering.
Sintering was essential to produce the final part and showed that a binder free brownpart was not the only criteria for eliminating impurities. The furnace atmosphere must remain free from contamination to eliminate transfer back to the parts. This was addressed using an argon sweep gas, however, the design and efficacy of the system was considered inadequate. Decomposition products need to be removed quickly from the furnace as they evolve before impurities from the sweep gas diffuse back into the parts during the extended duration at sinter temperatures (t = 1300 °C).
The combination of an optimised titanium feedstock and the use of a low temperature thermal debinding technique produced a consolidated MIM part of relatively large dimensions. The parts were seen to have uniform microstructure throughout the cross-section with density comparable to that of MIM standards. In difference to the literature, a high powder loading (φp = 0.65) of HDH powders was used and shown to be readily mouldable. The higher powder loading also eliminate separation defects and shape distortions evident using lower amounts of powder.

text: The Formulation of Titanium - based Metal Feedstocks and the Fabrication of Parts using the Powder Injection Moulding Process Development of a profitable titanium industry for New Zealand will not come about without innovative technologies. Plastic injection moulding has long held a place in NZ manufacturing to produce large quantities of complex parts and holds the key to such innovation.
Titanium metal parts were fabricated by injection moulding titanium based metal powder feedstock followed by a debinding process and subsequent sintering. The fabrication process in its entirety was investigated in four distinct steps. Feedstock formulation involved combining the metal powders with various carrier components. Injection moulding enabled the shaping of the feedstock into geometries approximating the final part. Debinding being the process whereby the carrier/binder system is removed from the part to create a powder compact retaining the required geometry. Sintering being the final step where the metal powders are consolidated into a fully dense metal part of net shape.
The feedstock binder consisted of water soluble polyethylene glycol that reduced feedstock viscosity, improved particle wetting, aided greenpart shape retention and eliminated toxic solvents in debinding. Carnauba wax and bees wax aided dispersion, lubricated particles, were safe to handle and better for the environment (than petroleum waxes). Their low melt temperatures aided removal during thermal debinding and supported residue elimination.
By optimising the ratio of water soluble, wax and polyolefin binder components (3: 2: 1 respectively) for melt flow and pellet formation, greenparts defect free with uniform particle distribution were made. The optimal binder system proved suitable for titanium alloy and irregular shape pure titanium powders (hydride-de-hydride). Increasing powder loading (wP = (0.60 to 0.65)) had no appreciable effect on viscosity while enabling feedstock with good uniformity and pellet formation. Dimensional change was not affected by uniformity of the feedstock however molecular weight, volume and dispersion of binder components affected interparticular distances. Low processing temperatures reduced disruption to part geometry, benefitted particle bonding and helped retain handling strength.
The use of low temperatures for thermal debinding (t = 250 °C) enabled removal of the binder below the temperatures that facilitate interstitial diffusion and oxide/carbide formation, although part thickness, mass and overall volume effected the processing time. A strong correlation was seen between handling strength of the greenparts and defects, such as non-uniform density distribution and cracking after sintering.
Sintering was essential to produce the final part and showed that a binder free brownpart was not the only criteria for eliminating impurities. The furnace atmosphere must remain free from contamination to eliminate transfer back to the parts. This was addressed using an argon sweep gas, however, the design and efficacy of the system was considered inadequate. Decomposition products need to be removed quickly from the furnace as they evolve before impurities from the sweep gas diffuse back into the parts during the extended duration at sinter temperatures (t = 1300 °C).
The combination of an optimised titanium feedstock and the use of a low temperature thermal debinding technique produced a consolidated MIM part of relatively large dimensions. The parts were seen to have uniform microstructure throughout the cross-section with density comparable to that of MIM standards. In difference to the literature, a high powder loading (φp = 0.65) of HDH powders was used and shown to be readily mouldable. The higher powder loading also eliminate separation defects and shape distortions evident using lower amounts of powder.

year: 2015

title: The Development and Evaluation of a Cultural Competency Training Programme for Psychologists Working with Māori: A Training Needs Analysis

authors: Waitoki, Waikaremoana

subjects: Māori

abstract: The purpose of this study was to develop and evaluate a cultural competency training programme for clinical psychology students to work with Māori consumers.  A pilot programme (study 1) was developed from the international and national cultural competency and bicultural training literature.  Following the pilot, it was identified that the programme could be made more robust by conducting a second study the training needs analysis using the critical incident technique.  Study two was conducted with 30 experienced clinical psychologists who had worked with Māori clients.
  
The training needs analysis sought to identify the awareness, knowledge and skills (AKS) that the experienced psychologists used in their practice with Māori.  An unexpected finding from study two was that the psychologists used distinctly Māori-cultural practices incorporating Māori tikanga and Māori knowledge with their clients even though they had little or no bicultural course content in their clinical training.  The data from the pilot programme, and the training needs analysis were used to refine the final workshop.  
The workshop was delivered to two university sites over a two-day period using intern clinical psychologist.  The programme evaluation had three components: (1) analysis of pre and post programme questionnaires; (2) analysis of the retrospective questionnaires (3) and an analysis of a participant’s case report on a Māori consumer. 
The themes that evolved from this research are that the critical incident technique is a useful way of identifying bicultural training material that would otherwise go unnoticed.  In relation to training evaluation, there is a real need to develop meaningful measures of bicultural competency acquisition for clinical students.  The finding advances the proposition that a distinct Māori psychology exists that could potentially challenge the relevance of Western psychology for Māori.  
A contextual theme underpinning bicultural training programmes is that training and practice occurs against the backdrop of Pākehā dominance in all aspects of academia and society. Consequently, there is a need to find a balance between Māori and Western psychological knowledge.  Future uses of this research will be in developing and evaluating bicultural training programmes, developing appropriate measures of cultural competency acquisition and assessing the potential for a distinct Māori psychology.

text: The Development and Evaluation of a Cultural Competency Training Programme for Psychologists Working with Māori: A Training Needs Analysis The purpose of this study was to develop and evaluate a cultural competency training programme for clinical psychology students to work with Māori consumers.  A pilot programme (study 1) was developed from the international and national cultural competency and bicultural training literature.  Following the pilot, it was identified that the programme could be made more robust by conducting a second study the training needs analysis using the critical incident technique.  Study two was conducted with 30 experienced clinical psychologists who had worked with Māori clients.
  
The training needs analysis sought to identify the awareness, knowledge and skills (AKS) that the experienced psychologists used in their practice with Māori.  An unexpected finding from study two was that the psychologists used distinctly Māori-cultural practices incorporating Māori tikanga and Māori knowledge with their clients even though they had little or no bicultural course content in their clinical training.  The data from the pilot programme, and the training needs analysis were used to refine the final workshop.  
The workshop was delivered to two university sites over a two-day period using intern clinical psychologist.  The programme evaluation had three components: (1) analysis of pre and post programme questionnaires; (2) analysis of the retrospective questionnaires (3) and an analysis of a participant’s case report on a Māori consumer. 
The themes that evolved from this research are that the critical incident technique is a useful way of identifying bicultural training material that would otherwise go unnoticed.  In relation to training evaluation, there is a real need to develop meaningful measures of bicultural competency acquisition for clinical students.  The finding advances the proposition that a distinct Māori psychology exists that could potentially challenge the relevance of Western psychology for Māori.  
A contextual theme underpinning bicultural training programmes is that training and practice occurs against the backdrop of Pākehā dominance in all aspects of academia and society. Consequently, there is a need to find a balance between Māori and Western psychological knowledge.  Future uses of this research will be in developing and evaluating bicultural training programmes, developing appropriate measures of cultural competency acquisition and assessing the potential for a distinct Māori psychology.

year: 2012