Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2001. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Title from PDF of title page (University of Missouri--Columbia, viewed on Mar. 15, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. J. David Robertson. Vita. Includes bibliographical references.

An ionic gradient source and a complimentary transport system regulates the flow of ions across a cell membrane. The major objective of the research focused on analyzing kinetic data to better understand the zinc transport mechanism. This study examined passive diffusion as a possible mode for zinc transport by using a liposome model system. There is a connection between bilayer fluidity (packing order of fatty acids) and rates of diffusion and this was evaluated by choosing lipids that vary with chain length and the degree of saturation or unsaturation. Zinc diffusion kinetics were monitored by observing spectral differences in the visible region of the spectrum in order to determine optimal wavelengths for the calculation of rate constants. The final objective was to calculate a permeability coefficient for each type of liposome and to make comparisons to the permeability of zinc into hepatocytes which has a permeability coefficient of about 1 X 10-7 cm/s. All liposomes used were phosphatidylcholine based. The values of the permeability coefficients for the liposomes used in this project were comparable to permeability in hepatocytes which suggest the potential importance of passive diffusion as a means for transporting biological zinc. / Department of Chemistry

The mechanism of zinc transport has been investigated in red cells from normal humans, lampreys, sheep, sickle cell anaemia patients and in bovine chondrocytes. In all the cell types investigated except for lamprey red cells, zinc transport is mainly via the anion exchanger (band 3), which accounts for over 80% of total measured zinc uptake, when the medium contains no zinc binding ligands. Zinc uptake via the band 3 pathway is stimulated by the presence of bicarbonate (5mM) and inhibited by treatment with DIDS or SITS (10andmu;M). This anion-dependent mechanism represents the major route for zinc transport across the cell membrane in vitro. The presence of the zinc binding ligands albumin and histidine in the media greatly reduced the uptake of zinc via the anion exchanger due to the decrease in free zinc concentration. Histidine, in addition to its chelating effect, shows a specific facilitating effect on zinc uptake in all the cell types. This stimulating effect of histidine was stereospecific (significantly different between L-, and D-histidine) in red cells from normal humans and sickle cell anaemia patients, but not in red cells from lampreys, sheep, and bovine chondrocytes. Evidence from all cell types strongly suggests that the stimulus is due to the cotransport of zinc and histidine via the histidine transport systems, which are system L, and y* in normal human and sickle red cells; a non-stereospecific L-like system in lamprey red cells and bovine chondrocytes; system C or unknown specific histidine transporter in sheep red cells. The amino acid linked zinc uptake may represent a physiologically significant mechanism for zinc transport into cells.

Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on January 3, 2008) Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--Ohio University, June, 2005. / Title from PDF t.p. Includes bibliographical references (p. 77-88)

Folate supplementation at a level of 15 to 35 mg per week is routinely prescribed for many chronic hemodialysis patients in B.C. In recent studies involving these levels of folate supplementation, RBC folate concentrations ranged from near the upper limit of normal to 1.5 times this upper limit. Initially there was research suggesting that high dose folate supplementation impaired zinc absorption but more recent studies refute this hypothesis. A beneficial effect of high dose folate supplementation is lowering of plasma homocysteine levels. This may be desirable since the homocysteinemia observed in chronic renal failure patients may be a factor in their commonly occurring premature vascular disease. The present study addressed folate needs on a nutritional basis but did not investigate folate's effect on homocysteine levels. The study involved chronic hemodialysis patients and was designed to: 1. assess whether patients consuming the Recommended Nutrient Intake for folate, require a folate supplement to maintain normal folate stores; 2. assess whether patients receiving a supplement of 5 mg of folate per day will have RBC folate levels exceeding the upper limit of the normal range; 3. compare serum zinc concentrations (and in some cases hair zinc levels as well) of patients receiving no zinc supplement or a 22.5 mg per day zinc supplement, to each other and to normal values; 4. assess whether a supplement of 5 mg of folate per day is associated with impaired zinc status; 5. in the event that a 5 mg per day folate supplement is associated with impaired zinc status, assess whether a supplement of 22.5 mg of zinc per day is associated with an improvement in zinc status; and 6. determine average daily energy, protein, folate and zinc intakes of patients. A 2x2 factorial quasiexperimental design was employed. The study included 21 clinically stable chronic hemodialysis patients between the ages of 25 and 69, who were receiving folate and/or zinc supplements at certain specific levels. Subjects were entered into treatment groups based on the following folate/zinc supplementation levels: no folate, no zinc; no folate, 22.5 mg zinc/day; 5 mg folate/day, no zinc; 5 mg folate/day, 22.5 mg zinc/day. Folate status was assessed using RBC folate concentration. Serum zinc concentration was measured in all subjects. Hair zinc level was determined in 6 of the zinc-supplemented subjects. A food frequency questionnaire was developed to determine dietary folate and zinc intakes. Subjects kept 3 day food records so average daily energy and protein intakes could be determined. Study results indicated no significant difference in protein intake (g/kg b.w.) or energy intake (expressed as a percent of requirement) among the four treatment groups. Differences in dietary folate intakes among the four treatment groups as well as between zinc-supplemented and non zinc-supplemented subjects, were not significant (p≤0.05). Mean dietary folate intake for all study subjects was 4.2 ug/kg b.w. RBC folate concentration was normal in both treatment groups receiving no supplemental folate. In contrast, the RBC folate concentration for both folate-supplemented groups was approximately 6.5 to 7 times the upper limit of the normal range. The difference between RBC folate concentration for folate supplemented and unsupplemented groups was highly significant (p<0.00001) and remained so when analysis of covariance was done with number of months of folate supplementation as the covariate. RBC folate levels did not differ significantly between zinc-supplemented and unsupplemented groups (p≤0.05). Differences in dietary zinc intakes among the four treatment groups as well as between zinc-supplemented and non zinc-supplemented subjects were not significant (p≤0.05). Mean dietary zinc intake for all study subjects was 9.39 mg/day. Serum zinc levels were below normal in both treatment groups receiving no supplemental zinc. The 22.5 mg zinc, no folate group had a serum zinc concentration near the lower limit of the lower range while that in the 22.5 mg zinc, 5 mg folate group was slightly below normal. When all zinc supplemented subjects were combined, serum zinc concentration was just within the normal range. Hair zinc analysis was conducted in a subgroup of 6 zinc-supplemented subjects and a group of non zinc-supplemented healthy controls. Hair zinc level was significantly higher in the zinc-supplemented subjects than in the controls (p≤O.01). In conclusion, folate supplementation does not appear to be required on a nutritional basis in clinically stable chronic hemodialysis patients not receiving medications known to affect folate status, who are consuming a diet providing a minimum of 1 g of protein per kg b.w. and 4.6 ug of folate per kg b.w. The low serum zinc concentrations observed in both zinc-supplemented and non zinc-supplemented patients may have been due to a shift of zinc from serum to other "zinc pools" in the body as reported in the literature. / Land and Food Systems, Faculty of / Graduate

Thesis: M.S., Massachusetts Institute of Technology, Department of Nutrition and Food Science, 1980 / Bibliography: leaves 78-81. / by Mary Ann O'Neil. / M.S. / M.S. Massachusetts Institute of Technology, Department of Nutrition and Food Science