Thesis (M.Ag.Sci. 1980) from the Department of Soil Science, University of Adelaide.

Thesis (Ph. D.)--University of Sydney, 2003. / Title from title screen (viewed Apr. 28, 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Dept. of Land, Water and Crop Sciences, Faculty of Agriculture, Food and Natural Resources. Degree awarded 2003; thesis submitted 2002. Includes bibliography. Also available in print form.

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A study was made to: i) determine the nature of acidity and buffering in acid soils of the Lower Fraser Valley of British Columbia, ii) evaluate and develop methods of predicting buffer capacities of these soils. Results of this study are described in a series of four papers, each describing different phases of this study. The Woodruff and Shoemaker, McLean and Pratt buffer methods proved to be unsuitable for use with these soils when compared to Ca(OH)₂ titration because the buffer pH depression was too small per unit lime requirement and there was considerable scatter about the regression calibration lime. Measurements of lime potential and corrected lime potential as well as pH were found to be significantly correlated with measures of exchangeable acidity but not with measures of pH-dependent acidity. The pH-dependent component of potential acidity was found to be highest for horizons highest in organic matter and in acid ammonium oxalate extractable Al and Fe. Regression equations derived for predicting buffer capacities explained the largest degree of variation of titrable acidity in the pH ranges below pH 5 and above pH 6. The model developed, combining these equations for prediction of buffer capacities to selected end pH values predicted buffer capacities as determined by a Ca(OH)₂ titration reasonably well. Comparison of NaOCl with H₂O₂ for oxidation of organic matter prior to acid ammonium oxalate extraction showed the former to be less destructive to sesquioxides, while at the same time as good or better for the oxidation of organic matter. Results of titrations of soils before and after oxalate extraction following treatment with NaOCl gave inconclusive results with respect to acidity due to the oxalate extractable component. This was due not to the method of removal of organic matter, however, but to uncertainties with respect to the nature of the exchange phase. / Land and Food Systems, Faculty of / Graduate

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The evaluation of changes during fermentation of heat-modified milk in connection with different fermentation temperatures was main goal of this thesis. Titrable acidity, active acidity and growth dynamics of bacteria strains - Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus were observed during fermentation process.

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BACKGROUND:The glycolytic nature of malignant tumors contributes to high levels of extracellular acidity in the tumor microenvironment. Tumor acidity is a driving force in invasion and metastases. Recently, it has been shown that buffering of extracellular acidity through systemic administration of oral bicarbonate can inhibit the spread of metastases in a mouse model for metastatic breast cancer. While these findings are compelling, recent assessments into the use of oral bicarbonate as a cancer intervention reveal limitations.METHODS:We posited that safety and efficacy of bicarbonate could be enhanced by dichloroacetate (DCA), a drug that selectively targets tumor cells and reduces extracellular acidity through inhibition of glycolysis. Using our mouse model for metastatic breast cancer (MDA-MB-231), we designed an interventional survival study where tumor bearing mice received bicarbonate, DCA, or DCA-bicarbonate (DB) therapies chronically.RESULTS:Dichloroacetate alone or in combination with bicarbonate did not increase systemic alkalosis in mice. Survival was longest in mice administered bicarbonate-based therapies. Primary tumor re-occurrence after surgeries is associated with survival rates. Although DB therapy did not significantly enhance oral bicarbonate, we did observe reduced pulmonary lesion diameters in this cohort. The DCA monotherapy was not effective in reducing tumor size or metastases or improving survival time. We provide in vitro evidence to suggest this outcome may be a function of hypoxia in the tumor microenvironment.CONCLUSIONS:DB combination therapy did not appear to enhance the effect of chronic oral bicarbonate. The anti-tumor effect of DCA may be dependent on the cancer model. Our studies suggest DCA efficacy is unpredictable as a cancer therapy and further studies are necessary to determine the role of this agent in the tumor microenvironment.

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