No description available.

<p> Knowledge into uptake rate and interactions of the metals via the gastrointestinal tract of freshwater fish is vital, in order to provide tools to protect and to sustain aquatic biota. An in vitro stomach and gut sac technique was utilized to investigate uptake rates of essential metals (copper, zinc and nickel) and non-essential metals (cadmium, lead and nickel) at luminal concentrations of 50fJ.M via the gastrointestinal tract Metals had no effect on the fluid transport rates via the gastrointestinal tract except for copper at the stomach. The stomach emerged as small but important site for metal absorption and interaction. Essential metals were absorbed at approximately the same rate as nonessential metals via the gastrointestinal tract. Copper, zinc, nickel, silver, and lead showed statistical correlation between rate of absorption and mucus binding via gastrointestinal tract, an important first finding for the development of a Biotic Ligand Model (BLM) for the gastrointestinal tract of trout. </p> <p> There was an antagonistic effect of calcium on cadmium uptake at the stomach but not at the intestine. Zinc and calcium exhibited synergistic interaction at the stomach but no interaction at the intestine. These results showed the possibility of the transporters DMTl to mediate copper and cadmium uptake via the intestine; hZip 2 to mediate copper and zinc uptake at the stomach; and Mzip 4 or ZTLl to mediate zinc uptake via the gastrointestinal tract of trout. These results can be used to develop a BLM for the gastrointestinal tract of fish. </p> / Thesis / Master of Science (MSc)

Phosphorus (P) is an instrumental nutrient in numerous physiological processes, but can have detrimental environmental impact if fed in excess. Increased P intake in dairy cows leads to increased fecal excretion of P and a reduction in efficiency of use. Variability in P concentration or availability in feedstuffs can exacerbate P excretion. To investigate variability in P between and within feedstuffs, 170 feed samples (forages, concentrates, and by-products), were collected from across the U.S., classified by region fed, and analyzed for total P, inorganic P, and phytate. Forages contained a greater proportion of P in the inorganic form and less total P and phytate as compared to concentrates and by-products. The majority of total P (71.2, 81.8, and 81.9% of total P in forages, concentrates, and by-products, respectively) was associated with inorganic P and phytate. The enzyme phytase has been used successfully in swine and poultry nutrition, as a feed additive, to increase available P and reduce the need for supplemental inorganic P. An experiment was conducted to investigate the effect of phytase use and forage particle length, using a 2 x 2 factorial, on P availability in lactating dairy cows. Total P intake of the four diets was similar (P > 0.15). Total tract digestibility of total P tended (P < 0.10) to be reduced and total P excretion was increased (P < 0.05) with phytase supplementation. Milk fat yield, protein yield, 3.5% FCM, and ECM were increased (P < 0.05) with addition of exogenous phytase to the diet. This indicates that phytate may contain some anti-nutritional factors that reduce availability in other nutrients used for milk production. Variation in P compounds between feeds, and variation in P digestion and production performance with exogenous phytase suggests opportunity for improvement in prediction of P availability from feeds for lactating cows. / Ph. D.

Chlorophenols represent a class of organic contaminants that are commonly used and widely distributed in the environment. Adsorption to soils may inhibit the transport of these chemicals, while slow desorption rates can create a potential source for long-term contamination of groundwater supplies. Microbial degradation of these compounds may also play an important role in their environmental fate. The purpose of this study was to investigate how the processes of sorption, desorption, and biodegradation interact to affect the distribution of pentachlorophenol (PCP) and 4-monochlorophenol (4-MCP) in two soils with different soil organic matter (SOM) content. Batch soil microcosms were used to measure the sorption of both test compounds at three concentrations for each, exposed to two soils with different SOM levels. An ultrafiltration study was designed to quantify partitioning to dissolved organic matter (DOM), while batch desorption experiments were performed to measure chemical release from the soils. Finally, biodegradation experiments were carried out under aerobic conditions to evaluate microbial interactions with PCP and 4-MCP in both the liquid and solid phases. Sorption of both compounds was rapid, with 60-80% occurring within one day, but the process appeared to continue at a slower rate over several months. Statistical analysis showed that there were no differences in sorption due to SOM content or chemical concentration, for the two silty loam soils used in this study. Desorption followed a similar pattern of a fast and then a slow stage, and a significant difference was measured between the two soils. Higher levels of SOM resulted in slower desorption and a lower total release of the contaminants, but both soils retained a large percentage of unextractable compounds. Contact time was found to have the greatest effect on the amount of this nondesorbable fraction. The ultrafiltration study suggested that DOM polymerized into larger molecules after sufficient mixing time (3 months) in solution, which also increased the amount of 4c compounds that were bound to these humic substances. The biodegradation study suggested that natural soil microbes could utilize PCP and 4-MCP from both the liquid and solid phases, and that sorption to dissolved organics and colloidal matter could protect these chlorophenols from microbial degradation. Some data also indicated a possible correlation between desorption rates and bioavailability. / Master of Science

The purpose of this research was to further test a stable isotope based approach as a more reliable in vivo method to determine amino acid bioavailability from a variety of ingredients. The method was used to assess feather meal (FM), blood meal (BM), soybean meal (SBM), and a rumen protected amino acid (RPAA). An abomasal infusion of raw EAAs (isoleucine, leucine and methionine) and an abomasal infusion of sodium caseinate were used as control treatments to test the accuracy of the technique. The isotope-based results were then compared to in situ, in vitro and in vivo test results. The isotope-based technique provided AA bioavailability values for five non-essential AA and seven essential AA. The raw EAA infusion had the greatest AA recovery in plasma with an estimated absorbed RUP value of 93.4± 7.35% followed by the casein infusion (86.7 ± 4.81%), SBM (54.8 ± 5.19%), FM (52.7 ± 4.81%) and BM (47.5 ± 4.81%). The RPAA treatment had the lowest bioavailability at 9.9 ± 12.73%. Numerically, SBM supplied the most absorbable EAA of the 4 feed ingredients, but was not significantly different from that of BM and FM. Simply based on the control treatments in this research (raw EAA and casein), this isotope method was a more accurate method in determining AA bioavailability values with relatively low standard errors. Ingredients are exposed to all aspects of natural digestive processes and the method is able to determine AA appearance in the blood with no use of in situ or in vitro measurements. / Master of Science

Yes / Hot melt extrusion has been used to produce a solid dispersion of the thermolabile drug artemisinin. Formulation and process conditions were optimised prior to evaluation of dissolution and biopharmaceutical performance. Soluplus®, a low Tg amphiphilic polymer especially designed for solid dispersions enabled melt extrusion at 110ºC although some drug-polymer incompatibility was observed. Addition of 5% citric acid as a pH modifier was found to suppress the degradation. The area under plasma concentration time curve (AUC0-24hr) and peak plasma concentration (Cmax) were four times higher for the modified solid dispersion compared to that of pure artemisinin. / EPSRC grant no (EP/J003360/1) and UKIERI: UK-India Education and Research Initiative (TPR 26).

Two times are critical for the horse ¾ the first few days of its life and the last few moments of a race. Vitamin E is critical in regard to immune competence in the first and antioxidant status in the latter. Studies conducted at the Middleburg Agricultural Research and Extension (MARE) Center include the development of horse feeds that replace sugar and starch with fat and fiber. The previous fat source of the pasture supplement under development was corn oil, which contains much vitamin E, was replaced with a cereal by product, which contains relatively little. Vitamin E has been studied in horses to a limited degree but not in grazing Thoroughbreds, thus the MARE Center gave me the opportunity to study vitamin E in Thoroughbred mares and foals. Middleburg is located in the Blue Ridge Mountains on Northern Virginia close to the site of one of the toughest endurance races in the world. This allowed me the opportunity to study vitamin E and antioxidant status in the horse during endurance racing. Initial studies of vitamin E supplementation to mares during the last trimester of gestation were disconcerting with no changes in serum concentrations of a-tocopherol (vitamin E). Studies conducted during the post-partum period revealed evidence of responses to vitamin E supplementation, as increased a-tocopherol concentrations were observed in mares' milk and in foal serum. Foals are born with virtually no circulatory antibodies and the supplementation of a synthetic form of vitamin E to mares demonstrated an increased passive transfer of immunoglobulins to foals. Natural vitamin E has shown a greater bioavailability than synthetic forms, in other species and was tested here at the MARE Center on mares. A greater passive transfer of immunoglobulins was observed with natural vitamin E supplementation compared with the synthetic forms, with immunoglobulin M concentrations in foal serum remaining higher for a longer period after birth compared to foals of non-supplemented mares. The transfer of a-tocopherol via the milk was also increased in concentration and duration in mares supplemented with natural vitamin E. Bioavailability of five oral forms of vitamin E (3 natural and 2 synthetic) were tested and one natural form was also administered intravenously so that clearance of vitamin E could be used to calculate the efficiency of absorption of the oral forms. Efficiency of absorption for oral treatments was not determined because of the slow turnover time of the intravenously administered vitamin E, which confounded all subsequent baseline serum a-tocopherol concentrations. Of the salvageable data, serum a-tocopherol concentrations were higher in grouped treatments at 9 and 12 h post dosing. Lipid fractions revealed possible insufficient absorption of the oral doses of vitamin E and possibly tissue saturation following intravenous doses of vitamin E. Serum concentrations of a-tocopherol were generally higher following natural forms of oral vitamin E administration. As vitamin E is the most important antioxidant in cells, it is often supplemented to endurance horses competing in 80 and 160 km races. Vitamin E protects lipid cell membranes from peroxidation by free radicals, which are increased during strenuous exercise resulting in oxidative stress. The antioxidant status of horses is severely tested during endurance racing and so a study was conducted to monitor changes in circulating antioxidants during three endurance races. Interesting novel findings in the horse were the maintenance of serum a-tocopherol and the depletion of erythrocyte glutathione and plasma ascorbate during two 80 km and one 160 km races. Associations were found between increased muscle cell enzyme leakage and decreased antioxidant status during endurance exercise and although associations do not prove a causation of oxidative stress, they do provide motivation to search for a cause and it is tempting to propose that oxidative stress damaged muscle cell membranes in endurance horses. Further, these findings propose a connection between muscle cell damage and a new form of exertional rhabdomyolysis (ER) that has been observed in endurance horses, where oxidative fibers are damaged compared to the typical glycolytic fiber damage associated with known forms or ER. An increased understanding of vitamin E utilization in the horse will improve the health and welfare of all horses, but especially newborn foals and the athletic endurance horses. / Ph. D.

Experiments were performed with naphthalene and a-naphthol to compare the processes involved in the sorption of a polycyclic aromatic hydrocarbon (PAH) and its metabolite, respectively, and to assess the bioavailability of these two compounds adsorbed to two sandy soils with different organic carbon contents. Adsorption conditions were varied to estimate the extent that biologically-mediated and chemically-induced oxidative coupling, and rate-limited diffusive processes contributed to the apparent irreversible adsorption of these compounds. The purposes of this research were to: (1) investigate the processes which cause the irreversible adsorption of organic contaminants to soil~ (2) gauge the impact that these different adsorption processes have on the bioavailability of sorbed contaminants; and, (3) evaluate the environmental significance of these processes in soils and the subsurface. This dissertation has been prepared as three separate articles for publication in peer reviewed journals. The first article serves as a literature review in evaluating the significance of oxidative coupling reactions in soil and subsurface environments. This review concludes that oxidative coupling of organic contaminants may be important in soils and could be stimulated as a viable remediation strategy. For subsurface systems oxidative coupling appears much more limited, however, engineered systems could be developed to enhance this process. The second article presents experimental results used to quantify the individual processes involved in the irreversible adsorption of naphthalene and a-naphthol. This article concludes that both biological and chemical catalysts are important in promoting irreversible adsorption reactions, and that once the partial oxidation of a PAH occurs, oxidative coupling can become a significant process affecting contaminant fate. The third and final article examines the effect of different adsorption processes on the subsequent bioavailability of sorbed naphthalene and anaphthol, and concludes that the biodegradation of naphthalene and α-naphthol adsorbed to both the soils tested was controlled by the rate of desorption and the reversibility of the adsorption process. / Ph. D.

No description available.

Mineral binding capacity of rice bran, oat hull, soy bran, wheat bran, peanut, apple, tomato, and barley fiber were investigated. Defatted fibers were analyzed for ash, protein, acid detergent fiber, and lignin. The fibers were washed with 1% HCl and Acid washed samples were studied for their mineral binding ability. The minerals tested were zinc, copper, and magnesium. Analysis of acid washed samples showed that most of the original minerals had been stripped from the fiber. In most of the fibers studied, the order of binding was copper > zinc > magnesium. Among the eight fibers studied, oat hull and apple fiber had the lowest consistent binding capacity for the three minerals investigated. This in vitro binding study has been run to duplicate intestinal condition of pH 6.8.