xx, 65 leaves : graphs ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Agricultural Biochemistry, 1979

Protein has long been recognized as an essential dietary substance, necessary for the building and repair of body tissue. However, in recent years we have learned even more of the versatility of protein in body processes. In addition to the need of protein for growth and repair of tissue breakdown, protein compounds are now known to serve also as parts of hormones to regulate body processes, enzymes to digest foods, plasma albumin to maintain water balance and blood volume, globulins to resist infection, and hemoglobin to transport oxygen to the tissues. In times of food shortages, protein deficiency is more likely to occur than that of any other of the important dietary essentials. This is due to the fact that there is a shortage of the foods that furnish protein of high biological value, i.e., the proteins of meat, milk, eggs and cheese. At the present time, where food shortages exist, these foods are scarce and when available expensive. Because of this situation, research concerned with protein metabolism is especially significant today. Proteins differ from one another on the basis of the number and kind of amino acids of which they are made. Since there are nine (possibly 10) essential amino acids, that cannot be synthesized in the body in adequate amounts from other amino acids, they must be present in the food. These essential amino acids are found in protein of animal origin. Plant protein is good for supplementing other protein, but alone, it is inadequate for maintenance and growth in the body. With complete protein foods both scarce and expensive, a knowledge of the protein requirement, the factors that affect its utilization, and how the body needs are met are of prime importance. The protein requirement has been determined from the data obtained from protein (or nitrogen) balance experiments in man. However, due to the nature of the data and the many variable factors involved in the amino acid content of various dietaries, there have been disagreements as to the real requirement, some advocating a high intake, others suggesting a lower intake. Today a compromise of the two extremes is generally advocated. The National Research Council has suggested an adult protein allowance of 60 to 70 gm. per day, from a diet of mixed protein (both animal and plant foods). In view of the fact that the number of studies to determine the protein requirement of human beings has of necessity been small, this problem was originally undertaken to observe the effect of the variation of caloric intake on protein use by means of the nitrogen balance experiment. In developing a low protein diet for the above study, coffee was suggested by one of the subjects to make the diet more palatable. This raised the question of whether or not coffee might in some way affect protein utilization or nitrogen excretion. A search was made for data on this point. In reviewing the available literature it was found that workers between 1853 and 1912 had done some work on the effect of caffeine on the nitrogen in the urine of men and dogs, but their results were contradictory, and in most cases they had used varying and unspecified amounts of caffeine. Since that time this problem has apparently been neglected. In the hope of obtaining further information concerning the effect of coffee on nitrogen metabolism, this study was planned with the following purposes: To 1. Develop dietary and laboratory technique for the nitrogen balance experiment. 2. Attempt to reach the point of nitrogen equilibrium in subjects on a known protein and caloric intake. 3. Determine the effect, if any, of the ingestion of a known amount of coffee on the total nitrogen, urea and ammonia excretions. / Master of Science

In contrast to most teleost fish that are ammoniotelic, the gulf toadfish (Opsanus beta) is both facultatively ureogenic and ureotelic. In vivo pharmacological manipulations were used to show that lowering circulating cortisol levels or blocking glucocorticoid receptors (GR) enhanced both urea excretion and urea pulse size. These findings demonstrated that changes in pulsatile urea excretion in the toadfish are mediated by the permissive action of cortisol through GRs. Measurement of urea transport across isolated basolateral gill membranes revealed a cortisol-sensitive carrier mechanism. Cortisol infusion in vivo significantly reduced urea transport capacity, suggesting that cortisol inhibits the recruitment of urea transport proteins (UT) to the basolateral membrane to ultimately decrease the size of the urea pulse in toadfish. A 1.2 kb fragment of the upstream transcription start site for the toadfish urea transporter (tUT) gene was isolated and in silico analysis revealed the presence of several putative glucocorticoid response element (GRE) half sites. Toadfish provided with this regulatory sequence in a reporter gene construct showed increased reporter gene transcription driven by cortisol. The data indicated that cortisol-mediated upregulation of tUT mRNA by GREs may be necessary to maintain tUT activity. Four Rhesus (Rh) glycoproteins (Rhag, Rhbg, Rhcg1, Rhcg2) were isolated from toadfish; these sequences grouped with those of other vertebrates coding for membrane channels that transport ammonia. In vivo increases in circulating cortisol reduced branchial Rh glycoprotein expression and decreased ammonia excretion. These changes were accompanied by cortisol-induced increases in glutamine synthetase activity, an enzyme that captures ammonia for urea synthesis. Taken together, the data indicated that cortisol reduces the loss by branchial excretion of ammonia, instead favouring biochemical pathways that convert ammonia to urea. This thesis confirms that nitrogen excretion in toadfish is controlled and regulated in fashions unlike those in other teleosts. The results demonstrate the importance of the GR signaling pathway in mediating changes in both urea and ammonia transport through molecular mechanisms. As a whole, the data provide a new understanding of branchial nitrogen excretion in the gulf toadfish and enhance our evolutionary perspective of the integrated biological systems involved in nitrogen excretion in fish.

Fine tuning a nutritional strategy by incorporating dietary fibre (DF) in pig diets can help to improve gut health. Fermentation of DF, especially the soluble fraction, in pig intestines yields short-chain fatty acids (SCFA) and lactic acid, which have been found to improve gut health by favouring the growth of health-promoting bacteria such as <i>Lactobacilli</i> and <i>Bifidobacteria</i>, at the expense of pathogenic ones like <i>Clostridium</i> or <i>Salmonella</i>, which may enhance the health of host species. The presence of fermentable fibre in the pig diet can also contribute to reducing nitrogen (N) excretion, which can have a positive impact on the environmental footprint, one of the main concerns of a modern commercial pork production.<p> The overall objective of this thesis project was to evaluate the fermentation characteristics of a selection of feedstuffs in the pig intestines and their potential impact on the gut environment and nitrogen excretion. The evaluation was performed by executing two projects using both <i>in vitro</i> and in <i>vivo studies</i>.<p> The first project focused on the fermentation characteristics of hulless barley in comparison to hulled barley and oats and their effects on the gut environment, especially the production of fermentation metabolites. The rate of fibre fermentation in the intestines was first studied by means of an in vitro gas production technique. The results demonstrated that hulless barleys have higher fermentability and produce higher amounts of SCFA than hulled barley and oats. An experiment carried out on pigs confirmed that the fermentation of the soluble fibre fraction of hulless barley in the gut leads to increased production of SCFA and lactic acid, which in turn contribute to the growth of potentially beneficial microbiota and decrease potentially harmful bacteria, an indicator of improved gut health. This finding shows that gut health parameters may be modulated. Thus gut health could potentially be improved through feed formulation by a judicious selection of feed ingredients with specific fibre fractions, not only by the addition of isolated fibres, which is commonly recommended at present.<p> The second project was executed to study the effect of some feedstuffs differing in their DF and protein content on fermentation characteristics and N excretion in pigs. The feedstuffs included wheat bran, wood cellulose, peas, pea hulls, pea inner fibre, sugar beet pulp, flax seed meal and corn distiller's dried grains with solubles. The results showed that peas and pea fibre-based diets produced higher amounts of SCFA and reduced N excreted, compared to others. In a parallel <i>in vitro</i> study, fermentation characteristics and bacterial protein synthesis was also studied using the same feed ingredients. The findings of the <i>in vitro</i> study corraborated the results of the <i>in vivo</i> experiment. These studies showed that peas and pea fibres have the potential to be used in pig diets in order to gain gut health-benefits and reduce N excretion.<p> From this thesis, it can be concluded that sources and type of dietary fibre have a significant effect on the production of fermentation metabolites in the pig intestine and on N excretion. Among the feed ingredients studied, hulless barley and pea fibres seem to have the greatest potential to be included in pig diets as a source of fermentable fibre to modulate the gut environment, which in turn, extend possibly health-promoting properties and reduce N excretion from pigs. However, further research is needed to understand the specific health benefits of these fibre sources and to quantify the specific fibre components required to achieve these benefits.

In contrast to most teleost fish that are ammoniotelic, the gulf toadfish (Opsanus beta) is both facultatively ureogenic and ureotelic. In vivo pharmacological manipulations were used to show that lowering circulating cortisol levels or blocking glucocorticoid receptors (GR) enhanced both urea excretion and urea pulse size. These findings demonstrated that changes in pulsatile urea excretion in the toadfish are mediated by the permissive action of cortisol through GRs. Measurement of urea transport across isolated basolateral gill membranes revealed a cortisol-sensitive carrier mechanism. Cortisol infusion in vivo significantly reduced urea transport capacity, suggesting that cortisol inhibits the recruitment of urea transport proteins (UT) to the basolateral membrane to ultimately decrease the size of the urea pulse in toadfish. A 1.2 kb fragment of the upstream transcription start site for the toadfish urea transporter (tUT) gene was isolated and in silico analysis revealed the presence of several putative glucocorticoid response element (GRE) half sites. Toadfish provided with this regulatory sequence in a reporter gene construct showed increased reporter gene transcription driven by cortisol. The data indicated that cortisol-mediated upregulation of tUT mRNA by GREs may be necessary to maintain tUT activity. Four Rhesus (Rh) glycoproteins (Rhag, Rhbg, Rhcg1, Rhcg2) were isolated from toadfish; these sequences grouped with those of other vertebrates coding for membrane channels that transport ammonia. In vivo increases in circulating cortisol reduced branchial Rh glycoprotein expression and decreased ammonia excretion. These changes were accompanied by cortisol-induced increases in glutamine synthetase activity, an enzyme that captures ammonia for urea synthesis. Taken together, the data indicated that cortisol reduces the loss by branchial excretion of ammonia, instead favouring biochemical pathways that convert ammonia to urea. This thesis confirms that nitrogen excretion in toadfish is controlled and regulated in fashions unlike those in other teleosts. The results demonstrate the importance of the GR signaling pathway in mediating changes in both urea and ammonia transport through molecular mechanisms. As a whole, the data provide a new understanding of branchial nitrogen excretion in the gulf toadfish and enhance our evolutionary perspective of the integrated biological systems involved in nitrogen excretion in fish.

Fine tuning a nutritional strategy by incorporating dietary fibre (DF) in pig diets can help to improve gut health. Fermentation of DF, especially the soluble fraction, in pig intestines yields short-chain fatty acids (SCFA) and lactic acid, which have been found to improve gut health by favouring the growth of health-promoting bacteria such as <i>Lactobacilli</i> and <i>Bifidobacteria</i>, at the expense of pathogenic ones like <i>Clostridium</i> or <i>Salmonella</i>, which may enhance the health of host species. The presence of fermentable fibre in the pig diet can also contribute to reducing nitrogen (N) excretion, which can have a positive impact on the environmental footprint, one of the main concerns of a modern commercial pork production.<p> The overall objective of this thesis project was to evaluate the fermentation characteristics of a selection of feedstuffs in the pig intestines and their potential impact on the gut environment and nitrogen excretion. The evaluation was performed by executing two projects using both <i>in vitro</i> and in <i>vivo studies</i>.<p> The first project focused on the fermentation characteristics of hulless barley in comparison to hulled barley and oats and their effects on the gut environment, especially the production of fermentation metabolites. The rate of fibre fermentation in the intestines was first studied by means of an in vitro gas production technique. The results demonstrated that hulless barleys have higher fermentability and produce higher amounts of SCFA than hulled barley and oats. An experiment carried out on pigs confirmed that the fermentation of the soluble fibre fraction of hulless barley in the gut leads to increased production of SCFA and lactic acid, which in turn contribute to the growth of potentially beneficial microbiota and decrease potentially harmful bacteria, an indicator of improved gut health. This finding shows that gut health parameters may be modulated. Thus gut health could potentially be improved through feed formulation by a judicious selection of feed ingredients with specific fibre fractions, not only by the addition of isolated fibres, which is commonly recommended at present.<p> The second project was executed to study the effect of some feedstuffs differing in their DF and protein content on fermentation characteristics and N excretion in pigs. The feedstuffs included wheat bran, wood cellulose, peas, pea hulls, pea inner fibre, sugar beet pulp, flax seed meal and corn distiller's dried grains with solubles. The results showed that peas and pea fibre-based diets produced higher amounts of SCFA and reduced N excreted, compared to others. In a parallel <i>in vitro</i> study, fermentation characteristics and bacterial protein synthesis was also studied using the same feed ingredients. The findings of the <i>in vitro</i> study corraborated the results of the <i>in vivo</i> experiment. These studies showed that peas and pea fibres have the potential to be used in pig diets in order to gain gut health-benefits and reduce N excretion.<p> From this thesis, it can be concluded that sources and type of dietary fibre have a significant effect on the production of fermentation metabolites in the pig intestine and on N excretion. Among the feed ingredients studied, hulless barley and pea fibres seem to have the greatest potential to be included in pig diets as a source of fermentable fibre to modulate the gut environment, which in turn, extend possibly health-promoting properties and reduce N excretion from pigs. However, further research is needed to understand the specific health benefits of these fibre sources and to quantify the specific fibre components required to achieve these benefits.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references (leaves 80-89). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references (leaves 80-89). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 112-120). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 112-120). Also available on the Internet.