Browsing by Subject "Biological transport"
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Item Amino acid transport in the photosynthetic bacterium Chromatium vinosum(Texas Tech University, 1989-05) Kim, Young-aeNot availableItem Anions in hydrophobic environments: liquid-liquid extraction of sulfate and chloride, and membrane transport of chloride(2005) Eller, Leah Renee; Sessler, Jonathan L.The transport of an anion across a lipid bilayer or the extraction of an anion into organic solution requires the stabilization of a charged species in a hydrophobic environment. Due to the similar energetic barriers of both processes, liquid-liquid extraction can potentially be used as a model for membrane transport. Carrier species that can efficiently extract anions from aqueous solutions into solvents such as chloroform, can potentially be utilized to facilitate the diffusion of those anions across a lipid bilayer or cell membrane. The research presented here explores the relationship between liquid-liquid extraction and membrane transport behavior. Chapter 1 presents an introduction to the equilibria reactions that are involved in extraction, the structure of lipid bilayers and a description of liposome models of cell membranes. Chapter 2 details the partitioning analysis of sulfate using radiotracers. Chapter 3 explores the chloride extraction behavior of several pyrrole-based molecules using radiotracer analysis. Chapter 4 details the extensive studies of chloride transport across lipid bilayers using liposome model membranes.Item Cation/amino acid symports in the photosynthetic bacterium Chromatium vinosum(Texas Tech University, 1984-05) Cobb, K. AndreaNot availableItem Ion transport in photosynthetic purple bacteria(Texas Tech University, 1982-08) Davidson, Victor LesterNot availableItem Measurement of transient transport of hyperosmotic agents across cell membranes and resulting optical clearing using differential phase contrast optical coherence microscopy(2005) Rylander, Christopher Grady; Diller, K. R. (Kenneth R.)The response of tissue to hyper-osmotic agents is a reduction in light scattering and corresponding increase in optical clarity. “Tissue optical clearing” permits delivery of near-collimated light deeper into tissue potentially improving the capabilities of optical diagnostic and therapeutic applications. The overall objective of the proposed research is to characterize the mass transport of hyper-osmotic agents across cell membranes and the resulting optical clearing. To accomplish this task, a differential phase contrast optical coherence microscope (DPC-OCM) is configured to permit quantitative spaciotemporal optical path length (OPL) imaging of biological cell specimens. The first application of DPC-OCM is analyzing the intracellular dry mass of individual biological cells. Differences between normal and cancerous cell dry mass are investigated. Populations of normal and cancerous human dermal fibroblast cells and human prostate cells demonstrate a statistically significant difference in mean dry mass and mean en face area. Linear discriminant analysis yields a maximum of 79% accurate classification. The second application of DPC-OCM is use as a novel technique for determining cell membrane permeability parameters due to an osmotic chemical stimulus. Glycerol, a hyperosmotic agent, is perfused across an adherent layer of human keratinocytes, and the dynamic osmotic response of individual cells is imaged with DPC-OCM. A novel optical path length (OPL) mass transport model is devised relating chemical concentration to intrinsic refractive index and OPL. Hydraulic conductivity and solute permeability are determined by fitting the OPL mass transport model to transient OPL data collected with DPC-OCM. The final study investigates the mechanisms of optical clearing of cellular and collagenous tissue using hyperosmotic agents and evaporation. OCT and photographic images quantify optical scattering reduction between native and dehydrated tissue states. Air-drying optically clears tissue as effectively as the most successful hyperosmotic agent, glycerol. Tissue ultrastructural alterations due to dehydration are investigated using transmission electron microscopy. The Rayleigh-Gans model is used to simulate light scattering effects due to tissue ultrastructural alterations and measured refractive index excursion using DPC-OCM.Item Sodium-Dependent Transport in Chromatium Vinosum(Texas Tech University, 1981-08) Pettitt, Cynthia AnnNot Available.Item Speed and propagation of diffusive signals in spatially inhomogeneous membranes(2003) Martin, Douglas Stuart; Swinney, H. L., 1939-; Käs, Josef A.Item Strand replacement of plasmid R1162 and transport of MobA during conjugative transfer(2007-05) Parker, Christopher Todd, 1972-; Meyer, RichardR1162 is a broad-host range, mobilizable plasmid conferring resistance to streptomycin and sulfonamides. Efficient conjugative mobilization of R1162 requires three plasmid-encoded proteins: MobA, MobB and MobC. MobA binds plasmid DNA at the origin of transfer (oriT), nicks the subsequently transferred strand and ligates the ends of the strand after transfer into the recipient. The N-terminal region of this protein carries out this DNA processing. The C-terminal half is a primase required to initiate DNA synthesis at two single-stranded priming sites sites, oriL and oriR, during vegetative plasmid replication. The primase region of MobA is not necessary for DNA processing by the N-terminal part of the protein, however its role in strand replacement during conjugation is not clearly defined. This study demonstrates that R1162 can undergo multiple rounds of transfer from a single plasmid molecule. The presence of oriL increases the frequency of second-round transfer, presumably due to initiation of replacement strand synthesis at this site by R1162 primase in the donor. Priming at oriR by the primase region of MobA is required for efficient replacement strand synthesis in the recipient when the plasmid is transferred to Salmonella. When the plasmid is transferred into E. coli, the plasmid-encoded priming system is not required for strand replacement in the recipient, presumably due to a host-encoded mechanism capable of priming the transferred strand. Transport of MobA through the R751 conjugative pore was also investigated. The two domains of MobA can be transported to recipient cells independently of each other. However, MobB is required for the transport of either fragment. Two sites, named the R-site and the P-site, are located in the relaxase and primase domains of MobA, respectively, and make up part of the signals required for MobA transport. Unlike previously described type IV transport signals, domain structure is required for the MobA transport signals to be active.Item The effects of estrogen on the intestinal nutrient uptake in channel catfish(Texas Tech University, 2000-05) Tipton, Holly AnnOver the past two decades, a number of researchers have found that the gastrointestinal absorption of a diverse group of sugars, amino acids and ions can be modulated by the actions of specific hormones. Because steroids have also been found to increase the growth and food conversion efficiency in animals, interest in this area has grown. In this study, both the in-vitro (short-term) and in-vivo (long-term) effects of estrogen (E2) were studied on the intestinal transport of channel catfish. In conjunction with this overall experimental objective, a number of related projects ensued. The first of these, the discovery of putative Eo receptors (ER) in catfish intestine by immunocytochemistry, prompted the initial study of the effects of Ej on intestinal transport. Secondly, nutrient transport was characterized by assessing any differences seen between sexes using the everted sleeve technique. A tissue viability smdy was also performed to examine how long intestinal tissue remained viable in the in-vitro test system. Since catfish in this study varied in age from young (< 1 year) to three years of age, seasonal and developmental changes in the transport of the amino acid of interest, L-alanine, were followed. The results indicate that short-term (min-to-hours) and long-term (hours-todays) E2 treatments regulate nutrient uptake of the amino acid, L-alanine, in specific gut regions. Taken together, all the results indicate that age, endogenous E2 levels and E2 receptor expression may interact to determine E2's regulation of the channel catfish intestinal transport.