Oxides of manganese have received considerable attention lately, mainly because of the colossal magnetoresistance they exhibit. After a careful interpretation of the large body of available experimental results, the paramount importance of intrinsic inhomogeneities to the understanding of these materials, can no longer be ignored. A scenario, based on the competition between different ordered phases which are mixed by the intrinsic disorder, is proposed. Several quantities that follow from this scenario can be evaluated and are found to correspond to experiments. / Dissertation / PhD

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2001. / Includes bibliographical references (p. 143-146). / by Scott Rixner. / Ph.D.

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In 2015, private sector Department of Defense (DoD) contractors experienced decreasing profit margins by approximately 8% and an increase in estimated costs of approximately 250%. The purpose of this multicase study was to explore strategies used by business leaders of private sector contractors for DoD capacity-building projects to accurately estimate program costs to improve profitability. The target population for this study was business leaders of DoD capacity-building program contractors with successful experience improving cost-estimation processes and strategies in Southeast Asia and the former Soviet Union. The conceptual framework for this study was business process quality management with a supporting framework of game theory. The data collection process comprised semistructured virtual interviews and a review of government and corporate documents. The data analysis process consisted of compiling data, disassembling data, reassembling data into groups and themes, and interpreting data, including methodological triangulation. Through data analysis, 5 themes were identified: enhanced customer relationships, increasing ability to innovate, improved project awareness, acquisition policy and political environments, and identification of labor rates and pricing. The implications for social change include the potential for DoD private industry business leaders to develop business strategies that result in improved profitability, creating opportunities to increase local economic impact and wage scales for local employees, higher levels of employment, and increased local technical knowledge.

Antigen presenting cells (APCs) perform the essential task of integrating responses between the innate and adaptive immune system. Several approaches have been undertaken to manipulate the effects of APCs for therapeutic purposes. Panax notoginseng is a medicinal herb that is purported to possess a number of properties including modulation of the immune system. However, limited information exists on the effects and toxicities of this herbal on APCs. In this regard, we assessed the effects of Panax notoginseng on the fate and function of professional APCs in murine models using macrophages and dendritic cells (DCs). APCs were stimulated with the toll-like receptor ligands LPS, CpG and poly(I:C) and treated with notoginseng (0-200 ìg/ml). The LPS induced levels of the proinflammatory cytokine TNF-á, as well as the expression of accessory molecules MHC II, CD40 and CD86, were decreased dependent on notoginseng exposure time-points relative to LPS stimulation. LPS induced IL-1â, IL-6 and IL-12 production was also decreased with concurrent notoginseng treatment for 24 hours. Notoginseng decreased TNF-á and CD40 activation by CpG and poly(I:C), but had varied effects on the induction of IL-6 and CD86. Furthermore, treatment of APCs with ginsenosides Rb1 and Rg1 had differential effects on the production of TNF-á and IL-6. Phagocytosis of FITC-conjugated ovalbumin antigen by DCs was decreased by notoginseng. Furthermore, the uptake of FITC-conjugated modified LDL was reduced in notoginseng treated DCs. However, T cell proliferation in response to notoginseng treated-antigen-loaded DCs was not affected in vitro or in vivo. Mechanistically, notoginseng reduced nuclear levels of the transcription factor NFêB, but had no effect on glucocorticoid receptor activation. No immunotoxicities were observed with low dose notoginseng (660 ìg/kg) treatment of Balb/c mice in vivo. Collectively, our results indicate that notoginseng decreased inflammatory mediator production by APCs, without altering their ability to induce antigen specific CD 4+ T cell proliferation. Our research provides insight into the potential use of this herbal in the treatment of inflammatory diseases as a safe and effective complement to existing remedies.

The vesicular glutamate transporter 1 (VGLUT1) is an important membrane protein located in glutamatergic synaptic vesicles. It is responsible for the storage and release of the excitatory neurotransmitter glutamate. VGLUT1 is a highly hydrophobic integral membrane protein with a molecular weight around 61 kD. The tertiary structure of VGLUT1 is still unknown. In our study, recombinant VGLUT1 was expressed in Pichia pastoris and purified using either a nickel chelating column or cobalt-coated Dynabeads. The HiTrapTM nickel chelating column proved to be more efficient in purification of recombinant VGLUT1 than Dynabeads. To study the physico-chemical properties and structure of VGLUT1 and advance our understanding of the membrane topology, FITC was used to modify VGLUT1 in solution. On average, 5.35 ¡À 1.10 lysines were labeled with FITC in each VGLUT1 molecule. Trypsin, endoproteinase Glu-C and Arg-C were used to digest FITC labeled VGLUT1 for mass spectrometry analysis. Mass spectrometry and other proteomics techniques were applied to identify labeled residues. Nine lysine residues were revealed to be labeled by FITC in total, among which 8 lysines (K10, K25, K140, K196, K272, K339, K378, and K507) are from native VGLUT1 and one is located at myc epitope (K569).

<p>This work describes the synthesis and initial characterization of the biological activity of a family of EAAT3 preferring inhibitors, L-&beta;-benzyl aspartate (L-&beta;-BA) and L-&beta;-BA derivatives. L-&beta;-BA and derivatives were initially synthesized in an approximate 2:1 ratio of diasteromers (threo:erythro), using base promoted enolate addition. Kinetic analysis of 3H-D-aspartate uptake into C17.2 cells expressing the hEAATs demonstrated that L-threo-&beta;-BA is the more potent diastereomer (Ki values of 9 µM for EAAT1, 10.0 µM for EAAT2 and 0.8 µM for EAAT3), acts competitively, and exhibits a 10-fold preference for EAAT3 compared to EAAT1 and EAAT2. Electrophysiological recordings of EAAT-mediated currents in Xenopus oocytes further identified L-&beta;-BA as a non-substrate inhibitor. Derivatives of L-&beta;-BA were prepared and characterized for the ability to inhibit 3H-D-aspartate uptake into hEAAT1-3 expressing C17.2 cells. Computational modeling and analysis of structure activity data suggest the area the aromatic moiety of L-&beta;-BA derivatives probe is 1) 3-dimentionally confined, 2) more tolerant of substitutions at the 3 and 5 positions than the 4 position, 3) at least partially distinct from the area probed by L-TBOA and 4) more accessible in the EAAT3 protein than EAAT1 and EAAT2. Computational modeling supports the pharmacological data and lends insight into the selectivity observed with L-&beta;-BA derivatives. Docking studies suggest that H-bonding interactions of L-&beta;-BA derivatives with key residues in the binding site position L-&beta;-BA analogues in a unique manner that is better tolerated in the EAAT3 protein than in the EAAT1 and EAAT2 proteins.</p>

<p>Glutamate transporters have a homotrimeric subunit structure with a large central water-filled cavity that extends partially into the plane of the lipid bilayer (Yernool et al., 2004). In addition to uptake of glutamate, the transporters also mediate a chloride conductance that is gated by Na+ and glutamate. Our data indicate that glutamate binding sites, transport pathways, and chloride channels reside in individual subunits in the trimer and function independently and that the anion channel is gated by alkali cations binding from either side of the membrane. We also investigated conformational changes during glutamate binding by incorporating a fluorescent probe into a site near the postulated external gate (HP2) of a mutant transporter that can bind but not transport L-Glu. Fluorescence changes were observed upon ligand binding that strongly depended on the number of subunits labeled; this suggests quenched fluorophore dimers form at the center of the trimer that are subject to HP2 loop closure upon substrate binding. This supports a model of gate motion that is also consistent with recent x-ray structural data (Boudker et al., 2007). Finally, we propose that the large aqueous central cavity in the trimeric complex (Yernool et al., 2004) may function to restrict the diffusion of molecules near the three ligand binding sites, resulting in an increase in the probability of rebinding.</p>

<p>Pulmonary fibrosis involves the invasion of lung tissue with fibrotic, scar tissue and affects roughly five million people total worldwide. Fibrotic development in the lung has several causes, including chronic inflammatory diseases, infections, medical compounds, and environmental agents. There is no known cure for the disease, but only therapies to improve quality of life. Scar tissue formation must be targeted in order to begin to provide any type of cure for fibrotic diseases. In this study, asbestos was used to induce pulmonary fibrosis in a mouse model and gene expression studies were then performed to identify potential candidate genes involved in asbestos response. One gene with the potential to regulate the fibrotic response is SPARC (secreted protein acidic and rich in cysteine), a matricellular protein involved in tissue repair, extracellular matrix (ECM) regulation, cellular proliferation, and cellular adhesion. The goal of this project was to determine the role of SPARC in fibrosis development after asbestos exposure, specifically targeting how lack of SPARC expression can influence collagen production. I hypothesize that SPARC is a necessary component involved in the fibrotic response to asbestos through an influence on collagen deposition in the lung. I have found that the expression of SPARC is increased in the lungs of C57Bl/6 wild-type mice exposed to asbestos. This increase in expression correlates to higher collagen deposition in the lung. The absence of SPARC in these treated mice resulted in a reduction of the level of collagen deposition back to baseline. To determine the therapeutic potential of these findings, SPARC expression was reduced by small interfering RNA (siRNA) in wild-type mice already suffering from fibrosis. Collagen deposition in the fibrotic mice that received the SPARC siRNA vector showed a significant decrease in collagen accumulation when compared to those that did not receive the vector. Overall, these results indicate that expression of SPARC is a significant step in the development of lung fibrosis through the modulation of collagen deposition and therefore, SPARC may be a potential therapeutic target.</p>

Learning and memory formation are invaluable processes in human life; however, the cellular mechanisms that control these phenomena are largely unknown. Synaptic plasticity, which is the ability of the synapse between two neurons to change in strength based on activity, is believed to be a key process in the formation of memories and learning. Endocannabinoids (eCB) have recently emerged as important modulators of synaptic plasticity but their precise roles and mechanisms are not well understood and many contradictions exist in the current literature. We have investigated the roles of eCBs and their primary receptor, the CB1 receptor, in the central nervous system using electrophysiological recordings in rodent hippocampus. We find that a moderate frequency 10 Hz stimulation protocol produces long-term potentiation (LTP) that is modulated by eCBs in both mice and rats; but surprisingly, the roles played by eCBs differ greatly between species. In rats, 10 Hz LTP requires CB1 receptor activation, as it is completely abolished by the CB1 antagonists AM251 and SR141716. Unlike theta burst stimulation (TBS) induced LTP, 10 Hz LTP does not require NMDA receptor activation. However, it is prevented when both NMDA and group1 mGluR receptors are blocked. The 10 Hz LTP is also independent of GABAergic synaptic inhibition, suggesting it is a novel form of excitatory synaptic plasticity mediated by the eCB system in hippocampus. In mice, we find that CB1 has an inhibitory effect on 10 Hz induced LTP. When the receptor is genetically removed in CB1 (-/-) mice or pharmacologically blocked wild type mice, 10 Hz LTP is greatly facilitated. Similar to TBS LTP, 10 Hz LTP in mice is NMDA receptor mediated. Also, the ability to achieve successful long-term depression (LTD) is decreased in CB1 (-/-) mice; yet, the magnitude of successful LTD is not changed. Together, this data supports a role for the CB1 receptor in inhibiting the induction of LTP with moderate stimulation protocols in mice, while in rats CB1 activation is required for 10 Hz LTP. Overall, our data supports that eCBs are crucial modulators of synaptic plasticity, although the roles they play may differ among species.