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

Graduation date: 1997

Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The radionuclide 75Se (T1/2= 119.8 days) decays to the stable isotope 75As by 100 % electron capture. Applications of this radioisotope include its use as a radiotracer in agricultural investigations and as a potential irradiation source in high-activity brachytherapy. The application of this isotope as a radiotracer in clinical studies has been limited due to a lack of availability of carrier-free 75Se. In this study the excitation functions for the production of carrier-free 75Se, other selenium radioisotopes and radiocontaminants produced via natBr(p,x) nuclear reactions were measured by the use of the stacked foil technique. Three separate stacks were assembled from aluminium and copper monitor foils and potassium bromide tablets. The latter were prepared by pressing KBr salt into tablets with a thickness of 200 mg/cm2 and a diameter of 20 mm, which are sandwiched between thin Al foils. The monitor foils, with a diameter of 19 mm, were punched from foil sheets. The stacks were irradiated at proton beam energies of 100.9 MeV, 66.8 MeV and 40.4 MeV respectively at the National Accelerator Centre cyclotron facility. After bombardment the KBr tablets were sealed in plastic bags to prevent the loss of any krypton isotopes produced. The gamma-ray spectra of the induced radioactivity in each of the target foils were recorded by means of a Ge-detector coupled with a SILENA 16-k multichannel analyser. The measured excitation functions for the above-mentioned isotopes are presented. Where applicable the cross-section values are compared with previously published values, while the others are presented as new data. Theoretical calculations by means of the computer code ALICE (IPPE) were also done for comparison. / AFRIKAANSE OPSOMMING: Die radionuklied 75Se (T1/2= 119.8 dae) verval deur 100 % elektronvangs na die stabiele isotoop 75As. Toepassings vir hierdie radioisotoop sluit in sy gebruik as 'n radiospoormiddel in landbou-ondersoeke en as 'n potensiële stralingsbron in hoë aktiwiteit bragiterapie. Die aanwending van hierdie isotoop as 'n radiospoorder in kliniese studies word egter beperk deur die gebrek aan beskikbaarheid van draer-vry 75Se. In hierdie studie is die opwekkingskrommes vir die produksie van draer-vry 75Se, ander selenium radioistope en radiokontaminante bepaal deur die natBr(p,x) kernreaksies te meet met behulp van die foelie-stapel metode. Drie verskillende stapels, bestaande uit aluminium- en koper-monitor foelies en kalium-bromied tablette, is saamgestel. Laasgenoemde is voorberei deur KBr sout saam te pers tot tablette met 'n dikte van 200 mg/cm2 en 'n deursnit van 20 mm en wat omsluit is met dun Al-foelies. Die monitor-foelies, met 'n deursnit van 19 mm, is gepons uit foelieplate. Die stapels is bestraal met protonbundels met energieë van onderskeidelik 100.9 MeV, 66.8 MeV en 40.4 MeV by die Nasionale Versneller Sentrum, Faure, se siklotron-fasiliteit. Na bombardering is die KBr tablette verseël in plastieksakkies om verliese van enige vervaardigde kripton isotope te verhoed. Die gamma-straal spektra van die geinduseeerde radioaktiwiteit in elke teiken is opgeneem met behulp van 'n Ge-detektor wat gekoppel was aan 'n SILENA 16-k multikanaal-analiseerder. Bogenoemde isotope se gemete opwekkingskrommes word aangebied. Waar van toepassing word die kansvlakwaardes vergelyk met vorige gepubliseerde waardes terwyl ander aangebied word as die eerste data bekend. 'n Vergelyking met die teoreties berekende kansvlakwaardes van die rekenaar kode ALICE (IPPE) word ook gedoen.

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

Experiments were conducted to examine the role of dietary selenium (Se) and changes in antioxidant capacity during DMBA-induced mammary carcinogenesis. Weanling rats were fed graded amounts of Se in an AIN-76 diet, modified to approximate the amount and type of dietary fat consumed in Canada. Animals fed 3-4 ppm Se had a reduced tumor incidence but there was evidence of chronic Se toxicity. Low Se did not elevate tumor incidence. Thus, supplemental dietary Se did not offer any protection in reducing the incidence of cancer when rats were fed a diet representative of North American intakes of fat. Blood GSHPx activity was elevated in rats that remained free of tumors (NT group) compared to animals that would eventually develop tumors (WT group). SOD activity was reduced in WT and NT rats, but appeared to be related to carcinogen administration. These differences were observed before tumor development and over a wide range of Se intakes. WT rats excreted more $ sp{75}$Se compared to both control and NT rats. These changes, however, were not reflected in elevated lipid peroxidation. Thus, one of the protective mechanisms during carcinogenesis may be the capacity of the animal to elevate GSHPx activity.

No description available.

No description available.

Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In many parts of the world, soil is depleted of selenium (Se), leading to selenium-poor plants, animals and, therefore, humans. It was recognised that a study to examine the functionality of new products on the market to address this problem was required. The purpose of this research were threefold: to compare the effects of sodium selenite (NaSe) and organically bound selenium sources on small ruminant performance, to investigate the bioavailability of these Se sources, and analyse their influence on carcass characteristics, meat quality and antioxidant capabilities. Fourty growing Döhne Merino wethers from the Southern Cape region, a selenium-deficient area, were used for the study. The animals were all fed the same basal diet in the adaptation period and were then allocated to one of four treatment groups: Control (CT), inorganic selenium (IS), organically bound Se A (OSA) or B: (OSB). The period of supplementation was 90 days. This first study assessed the effect of the different Se sources on growth and Se bioavailability in the wethers. The wethers and the feed they consumed were regularly weighed to determine their growth and feed conversion rate (FCR) in the trial period. To gauge their Se level, blood samples were collected via jugular venipuncture at monthly intervals. The wool around the jugular was shorn and samples were collected on day 0 and day 90 for comparative Se level analysis. Liver, skeletal muscle and kidney samples were collected at day 90, directly after slaughter, to determine the Se level in these tissues. No effect could be reported in the growth and FCR of the wethers between the supplementation groups. For whole blood Se levels there was an effect in the early part of the study, with a greater increase in Se levels for the organically bound Se groups, but in the end no effect on whole blood levels could be seen between the different Se treatments. Neither could any difference between the inorganic Se and organic bound Se treatments be found in the liver – however, the total Se concentration of the wool, kidney and meat samples was greater in those animals offered organically bound Se when compared with those receiving a comparable dose of inorganic Se. The second study evaluated the antioxidant capabilities of the different Se supplements in the wethers. Blood samples were taken monthly for plasma collection to test for Glutathione peroxidase (GSH-Px) activity and total antioxidative capacity (TAC) with the oxygen radical absorbance capacity (ORAC) assay. Liver, skeletal muscle and kidney samples were collected at day 90, immediately after slaughter and measured for GSH-Px activity. With TAC, there was a significant effect for the treatment period between day 0 and day 90, however the treatments did not show any significant difference. No significant differences could be established between the different Se treatments for the GSH-Px analysis in any of the tissues. For the mean plasma values of the treatments no significant differences can be reported, but a significant difference was observed at day 30 in the contrast between the organically bound Se and the other treatment groups. The third study was to evaluate the quality and lipid oxidation of muscle from those wethers supplemented with different Se sources. Skeletal muscle samples were collected at day 90, directly after slaughter to determine this. No differences in the meat quality of the wethers could be detected between Se sources after the 90-day supplementation period. Lipid oxidation was measured by determining TBA reactive substances (TBARS) and once again no differences could be detected. Based on the results found in this investigation, it may be inferred that organically bound Se (OSA & OSB) supplementation will hold a number of advantages for small ruminants over inorganic Se supplementation. Animals fed the organically bound Se had reached adequate Se levels sooner on the organically bounded treatments than the inorganically bounded treated animals. The greater bioavailability of organically bounded Se over inorganic Se was proven by the increased Se levels in certain tissues and organs. Additionally, only the organically bounded Se could find a pathway to the wool, confirming that it was carried in an organic form (probably selenomethionine) in the body. Organically bound Se will therefore have a positive impact on small ruminant health and production, which will result in an indirect advantage for consumer health. / AFRIKAANSE OPSOMMING: Die grond in groot dele van die wêreld word selenium-arm en dit lei na selenium-arm plante, diere en mense. Dit is waargeneem dat ‘n studie wat kyk na die funksionaliteit van nuwe produkte op die mark om die probleem aan te spreek nodig is. Die doelwit van die studie was om verskillende selenium (Se) bronne te vergelyk en die uitwerking daarvan op klein herkouer prestasie te evalueer. Daar is gekyk na die biobeskikbaarheid, invloed daarvan op die karkas eienskappe en antioksidant vermoëns van die verskillende Se bronne. Veertig groeiende Dohne Merino-hamels van die Suid-Kaap-streek, 'n Se arm gebied is gebruik vir die studie. Die diere is almal dieselfde basale dieet gevoer in die aanpassing periode en dan toegeken aan een van vier behandelings: kontrole (CT), anorganiese Se (IS), organies gebinde Se A (OSA) of B: (OSB). Die tydperk van die aanvulling was 90 dae. In die eerste studie is gekyk na die effek van die verskillende bronne van Se op die groei en die biobeskikbaarheid daarvan aan die hamels. Die hamels en voer verbruik, is gereeld geweeg sodat hul groei en voer omset verhouding (VOV) in die proef tydperk te bepaal. Bloedmonsters is versamel deur middel van die jugulêre venipuncture vir die Se vlak bepaling daarvan. Lewer, skeletspier en nier monsters is versamel op dag 90, direk na die slagting vir die Se vlak bepaling. Die wol rondom die nekslagaar is geskeer en monsters is versamel op dag 0 en 90 vir Se vlak analise. Geen effek kan gerapporteer word vir die groei en VOV van die hamels tydens die aanvullings periode nie. Vir die bloed Se vlakke was daar 'n uitwerking in die vroeë deel van die studie, met 'n vinniger toename in Se vlakke vir die organies gebinde Se groepe, maar aan die einde kon geen effek gesien word tussen die verskillende Se behandelings nie. Geen verskil tussen die NaSe en organiese gebonde Se behandelings kon gevind word in die lewer nie. Die totale Se konsentrasie van die wol-, nier-en vleis

Twenty-one women, lifelong residents of Xichang County, Sichuan Province, China, an area of very low soil selenium (Se), received tablets containing either 100 μg Se daily as Se-enriched yeast (+Se) or no additional Se (-Se), throughout the last trimester of pregnancy and the first three months of lactation. Diet was analyzed using diet recalls and proximate analysis of mixed diet samples. Milk and plasma samples were analyzed for Se content, glutathione peroxidase activity, and fatty acid profile and plasma alone was analyzed for vitamin E content and lipid peroxidation. At parturition and three months after delivery, milk and plasma Se levels and plasma GPx activities were significantly higher in the +Se women than the -Se women. Milk GPx activity did not change significantly with supplementation. Plasma vitamin E was not different between the treatment groups at either time. Plasma lipid peroxidation levels (TBARS) were significantly higher in the supplemented women at both time points. Fatty acid profiles at delivery and three months after delivery were similar in both plasma and milk between the two groups. The data suggest that this level and length of supplementation, when given to pregnant women of very low Se status, are not adequate to influence the fatty acids in milk. / Graduation date: 2000

The reproductive success of leatherback turtles (Dermochelys coriacea) is typically the lowest of the seven sea turtle species. Why this vital rate is decreased has remained unanswered for nearly a century. Recently, detailed postmortem examination of leatherback hatchlings identified muscular pathologies that suggested possible selenium deficiency. High bodily burdens of mercury compounds are associated with selenium depletion. Selenium is a necessary detoxifying nutrient that itself can be toxic at elevated concentrations. Mercury compounds are toxicants with no known biological function. High bodily concentrations of mercury can be detrimental to marine organismal health, reproduction and survival, both directly and indirectly through inducing selenium depletion. The goals of this dissertation are to evaluate several related hypotheses to explain low leatherback nest success. ... Because leatherbacks take in high volumes of prey, high tissue concentrations of mercury and selenium can result. This study provides the first evidence that chemical contaminants may explain low reproductive success in leatherback sea turtles. / by Justin R. Perrault. / Thesis (Ph.D.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.