Thesis (Ph. D.)--Georgia State University, 2008. / Title from file title page. Dabney W. Dixon, committee chair; Kathryn B. Grant, Jerry Smith, committee members. Electronic text (171 p. ; ill. (some col.)) : digital, PDF file. Description based on contents viewed June 23, 2008. Includes bibliographical references.

The emergence of multidrug resistance is a serious medical problem that has significantly affected the treatment of tumor cells and infectious diseases. This multidrug resistance phenotype is mediated by the action of a large family of membrane proteins that act as active transporters or energy driven efflux pumps in both of prokaryotic and eukaryotic cells. Most eukaryotic multidrug efflux pumps belong to the ATP binding cassette (ABC) family of transport proteins that include P-glycoprotein (P-gp1), Multidrug Resistance Associated Protein (MRP1), and Breast Cancer Resistance Protein (BCRP). In prokaryotic cells, Lactococcus lactis LmrA, a homolog of P-gp1, mediates drug resistance to antibiotics and cytotoxic drugs. The transport function of these proteins is facilitated by the hydrolysis of ATP. However, the mechanism by which these proteins bind to, and are able to transport structurally dissimilar drugs across the cell membrane remains poorly understood. In this thesis we have attempted to characterize the interactions of various ABC transporters (MRP1, BCRP, and LmrA) with structurally diverse drugs, using a well characterized photoreactive drug analogue of Rhodamine 123, [125I] iodoaryl azido-rhodamine 123 (IAARh123). In the case of MRP1 interaction with Rhodamine 123, it was of interest to determine the nature of MRP1 drug interactions. In that study, our results show that CHAPS (1-[(3-cholamidopropyl) dimethylamino]-1-propansulfate) and Brij35 inhibited the photolabeling of MRP1 with IAARh123, and this interaction occurred outside the lipid bilayer. These results were unexpected in light of previous results with another ABC transporter which also binds to Rhodamine 123. Consequently, we show that non-toxic concentrations of CHAPS and Brij35 potentiate the toxicity of two MRP1 substrates, vincristine and etoposide (VP16). In the second chapter, we have used IAARh123 to demonstrate for the first time that the BCRP mediates drug resi

No description available.

The study aims to provide information on efficiency opportunities on SCA's northbound cassettes. It has been made by examining the capacity utilization rate on the northbound cassettes on SCA's vessels for a period of two weeks. The cargo loaded in the ports of Rotterdam and Sheerness consists of external cargo of varying shape. The cargo is shipped northbound to Holmsund and Sundsvall. Measurements have been made on the cargo to the final destinations Sundsvall, Holmsund and Finland. The measurements have been used in a mathematical optimization model created to optimize the loading of the cassettes. The model is based on placing boxes in a grid where the boxes that are placed representing the cargo and the grids representing the cassettes. The aim of the model is to reduce the number of cassettes and thereby increase the capacity utilization rate. The study resulted in an increase in capacity utilization rate for both area and volume to all destinations. The overall improvement for all cassettes examined resulted in an increase in the area capacity utilization rate by 9.02 percentage points and 5.72 percentage points for the volume capacity utilization rate. It also resulted in a decrease of 22 cassettes in total on the four voyages that were examined which indicate that there are opportunities to improve the capacity utilization rate. The study also shows that the model can be used as a basis for similar problems.

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Advancing technology continually generates larger quantities of data at increasingly high transfer rates which fuels the need for instrumentation to take up the challenge of efficiently managing the collection of data. This defines the driving force behind the desire for increased channel capacity of PCM data formatters. By incorporating state-of-the-art Digital Signal Processing (DSP) technology coupled with high-performance Field Programmable Gate Arrays (FPGA), Inter-Coastal Electronics has designed the IF-810, a PCM data formatter. The IF-810 allows eight channels of PCM data, one voice channel and an InterRange Instrumentation Group (IRIG)-B channel to be combined and formatted for recording onto the TEAC RX-800 series recorders using a Hi8 8mm video cassette as the recording media. During playback, the IF-810 clocks the PCM data out using a reconstructed version of the input clock. With this unique design, the PCM data and clock outputs are input directly to a decommutator which eliminates the need for costly bit-synchronizers. This paper discusses the integration of the DSP, FPGA and buffering techniques into a low-cost and efficient multi-channel PCM data formatter that accommodates high data rate inputs, all without the need of a bit-synchronizer for decommutation.

by Wen-Liang Zhou. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (p. 125-144). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.

The Escherichia coli vitamin B12 transporter BtuCD-F is a type II importer belonging to the ABC transporter superfamily. Available data suggest both exporters and type I importers in the ABC superfamily employ similar transport mechanism in which the transmembrane (TMDs) are open to cytoplasm in the resting state, and ATP binding induces a major conformational change resulting in opening of the TMDs instead to the periplasm. However, the crystal structures of BtuCD from E. coli and recent EPR spectroscopy studies indicate that this type II importer employs a substantially different mechanism in which the TMDs are open to the periplasm in the resting state and to the cytoplasm after ATP binding. We have developed robust methods to study the conformation and transport mechanism of BtuCD-F reconstituted into lipid bilayers using single molecule fluorescence resonance energy transfer (smFRET) measurements. Fluorescent probes have been introduced at a variety of diagnostic sites, enabling smFRET to be used to measure distance changes in different conformational states as well as to observe the transitions between these states in real time. These data suggest that thermal fluctuations enable the transporter to explore different functional conformational states in the absence of ATP or other ligands. They also suggest that the ATP-bound state is indeed open to the cytoplasm and ATP binding/hydrolysis increases the rate of transition between open and closed states. Efforts are currently underway to observe the transport of vitamin B12 through a single BtuCD-F oligomer in real-time.

Philosophiae Doctor - PhD / Background: Extended-spectrum beta-lactamase-producing (ESBL) and carbapenemaseproducing Gram-negative bacilli showing resistance to cephalosporins and carbapenems respectively, have been reported from several countries globally and recently among Libyan combatants who have been transferred to European countries for advanced medical care. However, there is a lack of data about their presence in Misrata and in Libya in general. This is the first documented study aimed at investigating the prevalence and resistance mechanisms of ESBL and carbapenemase-producing K. pneumoniae isolates from Misrata. Materials and Methods: Two hundred Gram-negative bacillus isolates were collected and identified from hospitals and pathology laboratories in Misrata. Following antimicrobial susceptibility screening, those showing resistance to cephalosporin and carbapenem were tested for ESBL activity using the Modified double disc synergy test, Sensititer ESBL confirmatory MIC plates and MAST AmpC detection sets D52C and D68C. Carbapenemase activity was detected using RAPIDEC CARBA NP test, Modified Hodge test (MHT), carbapenem inactivation methods (CIM), carbapenem combined test (CCT), and by MAST carba puls set. ESBL and carbapenemases genes were detected using multiplex PCR. Results: K. pneumoniae was the predominant species (85/200) of the 14 species identified, with 56 (65.8%) showing carbapenem resistance, 16 (18.8%) were cephalosporin-resistant carbapenem-susceptible and 13 (15.2%) were susceptible to all antibiotics except ampicillin. OXA-48 was the only carbapenemase detected, with SHV, TEM and CTX-M group 1 found in almost all carbapenem and cephalosporin resistant K. pneumoniae. Rep-PCR analysis revealed multiple clones and some K. pneumoniae strains were genetically related or indistinguishable despite differences in ESBL genes or carbapenemase activity. Conclusion: The findings of this study show that carbapenemase- and ESBL-producing K. pneumoniae are prevalent in Misrata and emphasize the urgent need for optimized infection control and antibiotic stewardship programmes in the Libyan hospitals to prevent further spread of these organisms.

Chemotherapy is used in the treatment of cancer. Unfortunately, drugs often fail due to multidrug resistance (MDR) caused by P-glycoprotein (P-gp1or ABCB1) and the multidrug resistance-associated protein (MRP1 or ABCC1). These proteins bind and transport drugs out of cancer cells, thereby conferring MDR. / The second chapter of this thesis addresses an unexplained phenomenon that accompanies P-gp1 expression, collaterally sensitive to verapamil. The collective results of this work demonstrated that treatment of cells that over-express P-gp1 with verapamil induces apoptosis. Furthermore, the findings show that the ATPase activity of P-gp1 was activated by verapamil. The degree of ATPase activation was proportional to the level of apoptosis and the increased demand for ATP resulted in the production of reactive oxygen species (ROS). Finally, the production of ROS led to cell death mediated by apoptosis in that experimental model system. / Chapters three and four are devoted to understanding the binding characteristics of MRP1 with two of its physiological substrates, glutathione (GSH) and leucotriene C4(LTC4). Photoreactive derivatives of these substrates were synthesised to address this objective, IAAGSH and IAALTC4. Photolabelling and transport studies showed that these derivatives have similar binding characteristics as the native compounds. In addition, photolabelling of MRP1 occurred with a high specificity with both compounds. IAAGSH and IAALTC 4 were also used to determine the locations of GSH and LTC4 binding sites. This was accomplished using MRP1-variants containing hemagglutinin (HA) epitopes at specific locations in the amino acid sequence. Through photoaffinity labelling, immunoprecipitation, and trypsin digestion, a map of binding sites for IAAGSH or IAALTC4 was obtained. Both LTC4 and GSH bound to transmembrane (TM) regions 10-11 and 16-17 which have been previously implicated in drug binding. Furthermore, novel binding sites for both substrates were discovered. IAALTC4 photolabelled a novel site within the first five TMs (TMD0) of MRP1, whereas IAAGSH labelled two cytoplasmic regions (L1 and L0). These may represent specific binding sites for LTC4 and GSH. / The work within this thesis explores some of the biochemical characteristics of Pgp1 and MRP1 that are not directly related to drug resistance and may lead to new strategies in cancer treatment.

Dissertation (Ph.D.) -- University of Texas Southwestern Medical Center at Dallas, 2006. / Vita. Bibliography: p. 92-107.