Thesis (Ph. D.)--University of Wisconsin--Madison, 1923. / Typescript. With this is bound: The action of selenium oxychloride upon ethylene, propylene, butylene and amylene / By Carl E. Frick. Reprinted from Journal of the American Chemical Society, Vol. XLV, no. 7 (July 1923), p. [1795]-1800. Includes bibliographical references.

"June 2004" / Includes bibliographical references. / 1 v. : ill., maps ; 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, School of Agriculture and Wine, Discipline of Plant and Pest Science, 2004

Selective isolation protocols of selenium (Se) species integrated to Se specific atomic absorption spectroscopy (AAS) detection were developed and optimized for Se speciation in food supplements, including selenized yeasts. By ultrafiltration, 69.18% of Se in the extract was found as a low molecular weight soluble form, the remaining 30.82% was bound to high molecular weight components. After a cation-exchange chromatography of the ultrafiltrate, 3.77% of the Se in the extract was found in the aqueous washings of the column indicating the presence of free inorganic anions of Se; the 65.41% of Se retained on the column corresponded to the free organic Se cations. The limit of detection for the HPLC-THG-AAS system was 1.85 ng of Se. Se was shown to be widely distributed over all the proteins with one sharp peak corresponding to the free forms of Se. Four major peaks were found at MW $>$ 250 000 Da (15.97% of Se recovered), between 102 330 and 117 490 Da (7.06%), between 48 977 and 53 703 Da (12.71%) and close to the dye migration band (17.25%). / Selective isolation and HPLC-AAS protocols were also developed and optimized for the determination of free organic forms e.g. selenomethionine (SeMet), selenocystine (SeCystine) and inorganic forms of selenium in aqueous solutions, and in complex matrices such as nutritional supplements and mixtures of free amino acids. The selenoamino acid in alkaline solution was first derivatized with 1-fluoro-2,4-dinitrobenzene. After removal of excess of reagent by partitioning with diethyl ether, the N-dinitrophenyl (DNP)-derivatized selenoamino acid was acidified and extracted with diethyl ether. Inorganic Se(IV) was extracted from the acidic aqueous phases by complexation with 1,2-phenylenediamine, forming a piazselenol. Se derivatives were determined selectively by HPLC-THG-AAS. A selective chromatographic mechanism based on $ pi$-electron interactions was optimized using a silica stationary phase derivatized with p-nitrophenyl moieties. Co-injections of DNP-SeMet, DNP-SeCystine and piazselenol save retention times of 3.7, 4.0 and 4.9 min, respectively, using a methanolic mobile phase containing 1.5% triethylamine and 0.013M acetic acid. Primary analytical validation parameters including stability, linearity and limits of detection were obtained using purified DNP-SeMet, DNP-SeCystine and piazselenol standards which were characterized by $ sp1$H-, $ sp{13}$C- and $ sp{77}$Se-NMR analysis and/or fast atom bombardment MS techniques. The calibration graphs for sequential dilutions of these Se standards were linear and the limits of detection from the resultant calibration graphs were 17 ng, 0.21 ng and 18.53 ng of Se, respectively. The purified DNP-SeMet and DNP-SeCystine were found to be photosensitive. The recovery of SeMet, SeCystine and inorganic Se from the stock solutions and/or nutritional supplements was virtually quantitative. In the presence of a 500-fold excess of other amino acids, the recovery of SeMet and SeCystine (96.1 $ pm$ 3.9% and 98.08 $ pm$ 4.2%, respec

No description available.

Graduation date: 1997

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Leaves vi, ix and 167 are blank. Typescript. Includes bibliographical references (leaves 173-174). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Leaves vi, ix and 167 are blank. Typescript. Includes bibliographical references (leaves 173-174). Also available on the Internet.

Seven species of marine phytoplankters assigned to different taxonomic divisions were tested for toxic responses to two different molecular species of selenium known to be prevalent in seawater, selenite and selenate. Selenate proved to be more toxic than selenite, although severe toxicity was only observed at high concentrations (10⁻² and 10⁻³ M) of both selenate and selenite. At these concentrations, growth was completely or severely inhibited in most species tested. In some of the species that remained viable, both the percentage of motile cells and their swimming speed were drastically reduced. Scanning electron microscopy revealed that, under these circumstances, Dunaliella tertiolecta cells possessed much shorter flagella compared to the controls, while those that became non-motile lacked flagella altogether. Despite these striking alterations in both growth and morphology, cells of Amphidinium carterae, Dunaliella tertiolecta and Pavlova lutheri showed, after prolonged exposures, signs of adaptation to high selenium concentrations. Lower concentrations of selenium were generally non-toxic and frequently even stimulatory to growth. These observations suggest that for meaningful inferences on selenium toxicity both the concentration range and the length of the studies must be considered and the potential for adaptation to high selenium concentrations taken into consideration. The main ultrastructural and physiological changes in cells of Dunaliella tertiolecta, Pavlova lutheri and Amphidinium carterae treated with selenite or selenate involved the cell coat, mitochondria, chloroplasts as well as the respiratory and photosynthetic rates. Other changes were observed in the nucleus, lipids, vacuoles, nitrogen and carbon contents, but these showed greater variability among the microalgae studied. The major alterations suggested that energy transducing systems were severely affected by selenium toxicity. These led to significant decreases or even elimination of storage products which were indicative of severe shortage in energy and produced major reductions in growth. These occurred later upon exposure to the toxicant and coincided with the loss of cell coat material, suggesting that the shedding of cell surface material might play a major role in the detoxification and adaptation of the microalgae to toxic concentrations of selenium. / Science, Faculty of / Botany, Department of / Graduate

Bioavailability of selenium (Se) in processed tuna and wheat products was studied in humans and rats. The protein source of the rat diets was torula yeast with Se supplied by either raw, precooked or canned tuna, or whole wheat flour, bread or bran. Sodium selenite was used as a control. Each Se source was fed at three levels; 0.05, 0.10 and 0.15 ppm. Using increase in glutathione peroxidase (GSH-Px) activity in various tissues of rats as an indicator of bioavailabiiity, no difference was seen among the three tuna products or among the three wheat products tested. However, significantly lower GSH-Px activity was found in the combined tuna groups as co»pared to the combined wheat groups, suggesting that the Se an wheat was more available than that in tuna. Se concentration m four rat tissues (Liver, Kidney, Whole blood and muscle) was also measured. A significant increase in the liver Se content of rats fed canned tuna over those fed raw or precooked tuna was observed. Since this did not correspond with an increase in GSH-Px activity it was concluded that it did not represent increased bioavaiiability of canned tuna. In the human experiment, eight young men ate controlled diets where the Se was supplied by either whole wheat bread or canned tuna for two week periods. The Se content of the tuna diet was 331.5 ug/day and the bread diet was 354 ug/ day. No difference was observed in whole blood GSH-Px or Se due to the tuna or bread diets but this may be due to the short time period. No significant difference in excretion of Se was observed in the balance study. On the tuna diet, the subjects excreted 72.7% of the Se consumed and on the bread diet they excreted 70.4%. / Graduation date: 1982

No description available.