Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Theses (Ph. D.)--Marshall University, 2004. / Title from document title page. Includes abstract. Document formatted into pages: contains xiv, 175 p. Bibliography: p. 149-162.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Andras Z. Szeri, Dept. of Mechanical Engineering. Includes bibliographical references.

No description available.

Human red blood cell ghosts were prepared by a modification of the procedure of stepwise hemolysis (57). EDTA (1.0 mM) was included in the washing procedure to remove endogenous ATP and divalent cations. Ghosts resealed with appropriate amounts of ATP, calcium and magnesium were found to have Mg+Ca-ATPase activity and linearity was maintained up to thirty minutes. Active calcium transport could be studied in these ghosts by measuring the change ln the cellular concentration of calcium over time by atomic absorption spectrophotometry. Variation in the concentration of calcium in the loading medium resulted in an activation of Mg+Ca-ATPase and two peaks were evident on the activation curve. The high and low affinity Mg+Ca-ATPase were maximally stimulated at 0.25 and 5.0 mM calcium in the loading medium,respectively. The velocity of calcium transport was also found to be dependent on the concentration of calcium in the loading medium and was activated over the concentration range of 0.1 to 5.0 mM calcium. A change in the concentration of cellular calcium was not evident in the absence of added ATP. In contrast to the activation of Mg+Ca-ATPase two peaks were not obtained, and the activation curve had a sigmoidal appearance. Comparison of the calcium activation curves of Mg+Ca-ATPase and calcium transport revealed, a similarity in the shape and position of the low affinity part of the Kg+Ca-ATPase and calcium transport activation curves. A stoichiometry of two (Ca :ATP) was obtained, in the low affinity activity range. Ruthenium red (0.05 to 0.4 mM) selectively inhibited the low affinity Mg+Ca-ATPase and inhibited calcium transport over the same concentration range to a similar degree. Both low affinity Mg+Ca-ATPase and calcium transport were inhibited by external ruthenium red with an I₅₀ of 0.2 mM. Propranolol, qulnidine and quinine (10⁻⁵ to 10⁻³M) were found to be Ineffective in stimulating or Inhibiting Mg+Ca-ATPase when added to the Internal and external aspects of the ghosts. Manganese, added to the loading medium over a wide concentration range, was unable to substitute for calcium in activating Mg+Ca-ATPase. External divalent cations calcium and magnesium further increased Mg+Ca-ATPase activities when added to the external medium. Maximal stimulation occurred at a concentration of approximately 3.0 mM and calcium was almost twice as effective as magnesium. / Pharmaceutical Sciences, Faculty of / Graduate

No description available.

No description available.

Another family of organic anion transporters, the multi-drug resistant-associated-protein (MRP) is another subject of my study. Reverse transcription PCR and immunohistochernistry showed that MRP1 is expressed by the basal cells. MRP1 was cloned from the rat epididymis and expressed in HEK cells with a view to delineate its functions. HEK cells expressed with MRP1 showed little accumulation of calcein-AM compared to cells not expressed with the protein, or cells expressed with the protein but treated with MK571, an inhibitor of MRP1. This ability of MRP1 to eliminate calcein-AM from the cells was competitively reduced by verapamil, omeprazole, lonidamine or methotrexate, all are pharmacological agents commonly used for diverse clinical conditions. These results indicate that MRP1 is a multi-specific drug transporter. Freshly isolated basal cells also excluded verapamil and this effect was blocked by MK571. / In summary, my work has focused on the expression, distribution and functions of two major organic anion transporters, OAT1 and MRP1 thought to be the molecular entities involved in the transport of organic substances across the epididymal tubule. This membrane- and cell-specific placement of the two organic anion transporters that have different substrate specificity and mediate counter flows of substrates offer a mechanism whereby organic substance entry into the epididymis can be 'filtered'. Having low substrate specificity, OAT1 indiscriminately brings into the cells a diverse spectrum of organic anions, some of which might be useful organic substances that nourish spermatozoa, while others could be sperm toxicants. By virtue of the drug-specific MRP1, basal cells expel some of these toxicants from the epididymis. In this way, basal cells play a protective role. They prevent access of foreign substances to spermatozoa stored in the epididymis. This hypothesis is speculative albeit an attractive one. Further work is required to lay the experimental groundwork for this hypothesis. / The functions of OAT1 in the rat epididymis were studied by measuring the secretion (basal-to-apical) of PAH by epididymal epithelia in culture. The transport exhibited non-genomic up-regulation and down-regulation by PKA and PKC, respectively. These short-term regulations are not unlike those reported for the kidney OAT1 and are thought mediated through agonists-stimulated MAPK, PLA2 or COX-1 pathway. Since COX-1 has previously been shown to be exclusively present in the basal cells, it is conceivable that organic anion transport by the principal cells is regulated by the basal cells in the manner that principal cell Cl- secretion is regulated by the basal cells. / The nature of my work is to study the way by which organic substances cross the blood-epididymis barrier. My work is inspired by the anatomical and functional analogies between the epididymis and the kidney tubule. In the latter, elimination of toxic metabolites and foreign substances are known to occur through arrays of membrane proteins uniquely adapted to transport cationic and anionic organic substances across membranes. My work is to unravel the role of organic anion transporters in the epididymis using a combination of molecular biology and cellular physiology techniques carried out on cultured epithelia as well as on freshly isolated cells from the rat epididymis. / Using RT-PCR and Western Blot analysis, I identified the expression of organic anion transporter genes, OAT1, OAT2 and OAT3 mRNA in the rat epididymis. Immunohistochemistry revealed that OAT1 protein is present in the basal side of the principal cells of both the corpus and cauda epididymidis. OAT3 is seen in the lamina propria and blood vessels but not on the principal or other epithelial cells. Immunohistochemistry, however, failed to detect OAT2 protein. OAT1 was cloned from the rat cauda epididymidis using standard cloning techniques and verified by gene sequencing. Functional studies of the cloned protein expressed in human embryonic kidney (HEK) cells revealed similarities between the rat epididymal OAT1 and kidney OAT1 in that both transporters take up para-aminohippurate (PAH) into cells with similar kinetics and efficacy. Rat epididymal OAT1 was able to take up the anti-fertility drug, lonidamine. / Leung Chi Ting Gideon. / "October 2006." / Adviser: P. Y. D. Wong. / Source: Dissertation Abstracts International, Volume: 68-09, Section: B, page: 5678. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 122-143). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (p. 147-155).