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The behavioural and neurological effects of excessive sucrose intake overlap with those of abused drugs, suggesting that sucrose bingeing should be categorized with addictive disorders. Behaviorally, a primary characteristic of drug addiction is compulsive responding, manifested as an inability to inhibit drug intake despite negative consequences. We examined whether excessive sucrose self-administration produces these behavioural patterns using a validated rat model of sucrose bingeing (Avena et al., 2008) and investigated potential neurophysiological correlates with brain slice electrophysiology. Rats (n = 8-16 per group) received 12 or 24 hour access to a 10% sucrose solution and food, while control groups received food only or a 0.1% saccharin solution with food, each day for 28 days. Sucrose/saccharin/food consumption and weight were recorded daily. Compulsive responding for sucrose was assessed one or 28 days after the final self-administration session using a conditioned suppression paradigm. Persistent responding in the presence of a cue (tone) predicting a negative outcome (0.5 mA footshock) was used as a measure of compulsive responding. Only rats given 12-hour access to sucrose developed a binge pattern of intake, in which solution consumption increased dramatically during the first hour of each session. This group also developed compulsive responding for sucrose, exhibiting a reduced conditioned suppression effect following both one day and 28 days of abstinence. At a neural level, there was a switch in direction (from reduction to enhancement) in dopaminergic (DA) modulation of GABA synaptic transmission in the oval bed nucleus of the stria terminalis (ovBNST) of rats that developed a binge pattern of sucrose intake. This switch was similar to that recently observed in rats displaying enhanced motivation to self-administer cocaine. Therefore, excessive intermittent sucrose consumption produces compulsive responding and this shift from controlled to compulsive intake may involve the same neural mechanisms that underlie excessive cocaine self-administration. / Thesis (Master, Psychology) -- Queen's University, 2012-09-28 09:28:10.705

To gain an understanding of the transcriptional regulation of sucrose transport and metabolism in wheat and to examine their relationships with dry matter accumulation in seeds, this study has characterized the expression patterns of two sucrose transporters (TaSUT1 and TaSUT2) and two sucrose synthase (TaSuSy1 and TaSuSy2) genes in five spring wheat cultivars at different seed developmental stages. Cultivar ‘AC Andrew’ with higher TaSUT1 and TaSuSy2 transcript abundance particularly during the early grain filling stage, exhibited higher dry grain weight than other cultivars. The result, overall, suggests the significance of coordinated expression between TaSUT1 and TaSuSy2 for grain growth. This study also demonstrated the seed specificity of high molecular weight glutenin promoter subunit Dy10, which can be used as an important tool to drive the expression of any sucrose and starch related genes specifically in wheat grains to further our understanding of carbon partitioning and/or increase wheat starch yield.

To gain an understanding of the transcriptional regulation of sucrose transport and metabolism in wheat and to examine their relationships with dry matter accumulation in seeds, this study has characterized the expression patterns of two sucrose transporters (TaSUT1 and TaSUT2) and two sucrose synthase (TaSuSy1 and TaSuSy2) genes in five spring wheat cultivars at different seed developmental stages. Cultivar ‘AC Andrew’ with higher TaSUT1 and TaSuSy2 transcript abundance particularly during the early grain filling stage, exhibited higher dry grain weight than other cultivars. The result, overall, suggests the significance of coordinated expression between TaSUT1 and TaSuSy2 for grain growth. This study also demonstrated the seed specificity of high molecular weight glutenin promoter subunit Dy10, which can be used as an important tool to drive the expression of any sucrose and starch related genes specifically in wheat grains to further our understanding of carbon partitioning and/or increase wheat starch yield.

NMR studies of water oxygen-17 relaxation in aqueous sucrose and lysozyme solutions have been carried out to investigate the interactions of water with sucrose and lysozyme. The effect of sucrose and lysozyme concentration on water oxygen-17 relaxation has been studied in detail. The dependence of relaxation on frequency and pH has also been analysed. The existing model, describing the relaxation of water oxygen-17 in aqueous protein solutions suggested by Halle in 1981, is tested to see whether it gives a true representation. It is found that at low concentrations of sucrose and lysozyme, the experimental data give good agreement with the model. However, at saturated sucrose concentration the agreement is not so good. An extra contribution to the transverse relaxation rate is seen. A possible explanation for the extra contribution to the transverse relaxation rate at high sucrose content is discussed. The effect of ionic charge on oxygen-17 relaxation in lysozyme solutions is also investigated. It is observed that both the ionic charge of lysozyme as well as lysozyme aggregation strongly affect the relaxation of water oxygen-17. A method for analysing the experimental data for water oxygen-17 relaxation in aqueous sucrose and lysozyme solutions using Halle's model is presented and employed to calculate the various parameters of the model. The relaxation and chemical shift of calcium-43 in simple calcium salts, calcium acetate and calcium ascorbate have been studied as a function of concentration and pH. The complexation of calcium to sucrose and to lysozyme has also been investigated. In almost all cases, a significant calcium-43 chemical shift has been detected. The direct measurement of complexation and binding of calcium by relaxation time and chemical shift measurements has been of particular interest.

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Thesis (Ph.D.)--Tufts University, 2001. / Adviser: Robin B. Kanarek. Submitted to the Dept. of Psychology. Includes bibliographical references (leaves 99-122). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph.D.)--Tufts University, 2004. / Adviser: Robin B. Kanarek. Submitted to the Dept. of Psychology. Includes bibliographical references (leaves 138-162). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (MSc)--University of Stellenbosch, 2007. / Bibliography. Also availale via the Internet.

Thesis (MSc)--University of Stellenbosch, 2008. / Bibliography. Also availabe via the Internet.