196,262 research outputs found
Sensing the lactic acid in probiotic yogurts using an L-lactate biosensor using a microdialysis fiber inserted in a flow analysis system. .
No full textLow potential detection of NADH with Prussian Blue bulk modified screen-printed electrodes and recombinant NADH oxidase from Thermus thermophilus
No full textA biosensor for the determination of the reduced coenzyme nicotinamide adenine dinucleotide (NADH) has been assembled using a recombinant enzyme NADH oxidase from Thermus thermophilus covalently immobilized on Prussian Blue bulk-modified screen-printed electrodes. Flow injection analysis (FIA) coupled with amperometric detection was used to detect NADH. Various parameters such as cofactor (FMN, flavin mononucleotide) concentration (2 mM), flow rate (0.35 mL/min), buffers (citrate-phosphate, phosphate and glycine-KOH), pH dependence (range 3.0-10.5), response time (12 s) and operational stability (120 injections) were evaluated and optimised. At pH 5.0, for which the biosensor showed the highest response, the detection and quantification limits were 1.1 x 10(-7) and 3.6 x 10-7 M, respectively, and the linear working range was comprised between 1 and 400 mu M. The proposed biosensor was stable for 2 months (preserved in 50 mM phosphate buffer, pH 6.8, at 4 degrees C). The possibility to co-immobilize glycerol dehydrogenase (GDH) and the NADH oxidase in order to measure glycerol, a key target analyte during the alcoholic fermentation of grapes, was also investigated. Different dilutions of a complex matrix such as wine were tested to assess the interferences, the probe recovery and stability. (c) 2006 Elsevier B.V. All rights reserved.[...
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
Interactions between the opioid and serotonin systems in chronic pain : quantitative live cell study by fluorescence cross-correlation spectroscopy (FCCS)
No full textChronic pain is a major health issue worldwide. It enacts considerable suffering on the affected individuals and significantly increases the societal burden, as it is the most common reason why individuals seek sick leave and ask for medical help. Pharmacotherapies for chronic pain are not satisfactory, and many patients, despite taking medications, do not find relief and end up using opioids. Long-term opioid use carries with it numerus adverse effects, including but not limited to opioid induced hyperalgesia (OIH), tolerance, dependence (addiction) and opioid-related deaths. OIH is defined as a state of nociceptive sensitization, i.e. a state of becoming more sensitive to painful stimuli when using opioids for a long time. Cellular and molecular mechanisms that underlie OIH are still not fully understood, and efficient treatment strategies that retain the analgesic effects of opioids, while reducing this negative side effect are therefore underdeveloped.Clinical studies in healthy subjects and patients with fibromyalgia, a chronic pain syndrome with abnormalities in cerebral opioid signaling, have implicated interactions between the mu-opioid (MOP) and the serotonin 1A (5-HT1A) receptors in descending pain modulatory circuits as important for chronic pain modulation. Preclinical studies have shown that co-treatment with 5-HT1A agonists reduces OIH, diminishes the rewarding effects of morphine and the development of opioid tolerance. They have also provided indirect evidence for the co-localization of MOP and 5-HT1A receptors in the same nerve terminals, and demonstrated that MOP and 5-HT1A synergistically inhibited GABA release in the periaqueductal gray (PAG), a structure that mediates opioid-based pain control. Based on these findings, it was proposed that MOP and 5-HT1A heterodimerization is a potential mechanism through which MOP- and 5-HT1A-mediated signaling pathways are interlinked. It is further hypothesized that MOP and 5-HT1A heterodimer formation alters cellular signaling and contributes to neuroplastic changes that, eventually, lead to sensitization of pronociceptive pathways at the organism level. However, while co-localization of MOP and 5-HT1A receptors in discrete brain and spinal cord regions is well documented, the existence of heterodimers between MOP and 5-HT1A receptors has, thus far, only been shown in one study, which relied on the use of co-immunoprecipitation and Bioluminescence Resonance Energy Transfer (BRET) to demonstrate that these heterodimer complexes could form.The primary objective of my PhD studies was to challenge the hypothesis that prolonged exposure to non-peptide opioids promotes heterodimer formation between MOP and 5-HT1A receptors, and that this effect can be abolished by co-treatment with 5-HT1A agonists. To this aim, cell lines of human and rat origin where genetically transformed to stably express physiologically relevant levels of MOP and 5-HT1A receptors tagged with spectrally distinct fluorescence reporters. Fluorescence Cross-Correlation Spectroscopy (FCCS), the dual color variant of the quantitative and nondestructive analytical technique called Fluorescence Correlation Spectroscopy (FCS), was used to characterize the receptor-receptor interactions in live cells. Additionally, confocal laser scanning microscopy (CLSM) was used to map the consequences of non-peptide opioid treatment on Ca2+ signaling dynamics and western blotting was applied to investigate signaling cross-talk via mitogen-activated protein kinases (MAPKs) p38 and the extracellular signal-regulated kinase (ERK1/2).The work presented in this thesis, summarized in papers I-V, has contributed to better understanding of important basic cellular and molecular mechanisms that underlie signal transduction and material uptake across the plasma membrane. In particular, the work presented in papers I-III focuses on cellular and molecular mechanisms that underlie the development of OIH. In Paper I, we have shown that prolonged exposure to non-peptide opioids facilitates heterodimer formation between MOP and 5-HT1A receptors in live cells expressing physiologically relevant receptor levels. The extent of receptor heterodimerization was found to be both, opioid-specific and dose-dependent. Furthermore, we have shown that different opioids differently affected second messenger pathways, as indicated by differences in Ca2+ signaling dynamics and differential activation of p38 and ERK1/2 MAPKs. In Paper II, we have shown that 5-HT1A agonists such as buspirone and three newly identified buspirone analogs: B2, B3 and B5, can effectively reverse MOP–5-HT1A heterodimerization, thus counteracting the aversive effects of morphine. Importantly, this study, which brought together molecular modeling, virtual screening and advanced experimental tests in live cells, may in the future lead to the development of new drugs that target MOP and 5-HT1A heterodimer formation. In paper III, we have quantitatively characterized using FCS/FCCS and PhotoActivated Localization Microscopy (PALM) the nanoscale lateral dynamics and spatial organization of wild type MOP and its naturally occurring isoform (MOPN40D). We have shown that this non-synonymous single-nucleotide polymorphism (SNP) in the OPRM1 gene encoding the MOP, which is known to confer pain- and substance abuse-specific phenotypes at the organism level, significantly affected the lateral dynamics and organization of MOPN40D at the nanoscale level. In particular, we found that MOP-containing domains were larger and more densely populated than the MOPN40D harboring domains, with a small fraction of molecules residing outside of nanodomains. The opposite was found for MOPN40D. Moreover, we found that cholesterol depletion dynamically regulated the partitioning of MOP but not of MOPN40D, and observed that MOP and MOPN40D differ with respect to opioid peptide-induced internalization, with MOP being readily internalized together with the opioid peptide upon stimulation with β-endorphin, whereas MOPN40D showed lower internalization propensity and was typically not internalized together with the opioid peptide. These apparently subtle differences at the nanoscale level may, at least in part, explain why differences with respect to opioid dependence and analgesia are observed at the organism level.Papers IV and V describe collaborative work where CLSM and/or FCS/FCCS were used to characterize translocation across the plasma membrane and cellular uptake. In Paper IV, we focus on substance delivery using cell-penetrating peptides as a vehicle. Using FCS/FCCS, we revealed the heterogeneity underlying self-assembly of cell-penetrating peptides and oligonucleotides, in this case small interfering RNA (siRNA), into large molecular complexes. We showed that peptide monomers, peptide self-aggregates and polydisperse peptide/cargo complexes coexist in solution and in live cell plasma membrane, which could explain why diverse cellular uptake mechanisms were simultaneously observed for cell-penetrating peptides-based delivery of cargo molecules. In Paper V, CLSM imaging was used to examine the role of α-Gal carbohydrate on protein uptake and degradation by immature monocyte-derived dendritic cells (iMDDCs), as a potential cellular and molecular mechanisms underlying the development of allergy to red meat. CLSM imaging revealed that presence of allergenic α-Gal epitopes on the protein surface significantly increases the uptake of the investigated model antigens, BSA-α-Gal and HSA-α-Gal, by in vitro cultured human iMDDCs, and showed that the taken up proteins are processed in endosomes.List of scientific papersI. Vlad Radoi, Gerd Jakobsson, Vinko Palada, Henrik Druid, Lars Terenius, Eva Kosek and Vladana Vukojević. Opioids differ in their capacity to induce heterodimer formation between the mu-opioid and the serotonin 1A receptors. [Manuscript]II. Vlad Radoi, Dimitar A. Dobchev, Vinko Palada, Mati Karelson, Eva Kosek and Vladana Vukojević. Busprione and its newly synthesized analogs hinder morphine induced heterodimer formation between the mu-opioid and the serotonin 1A receptors - A potentially new treatment strategy for opioid-induced hyperalgesia in chronic pain. [Manuscript]III. Rogacki MK, Golfetto O, Tobin SJ, Li T, Biswas S, Jorand R, Zhang H, Radoi V, Ming Y, Svenningsson P, Ganjali D, Wakefield DL, Sideris A, Small AR, Terenius L, Jovanović-Talisman T, Vukojević V. Dynamic lateral organization of opioid receptors (kappa, mu(wt) and mu(N40D)) in the plasma membrane at the nanoscale level. Traffic. 2018;19(9):690-709. https://doi.org/10.1111/tra.12582 IV. Vasconcelos L, Lehto T, Madani F, Radoi V, Hallbrink M, Vukojevic V, Langel U. Simultaneous membrane interaction of amphipathic peptide monomers, self-aggregates and cargo complexes detected by fluorescence correlation spectroscopy. Biochim Biophys Acta Biomembr. 2018;1860(2):491-504. https://doi.org/10.1016/j.bbamem.2017.09.024 V. Krstić Ristivojević M, Grundström J, Tran TAT, Apostolović D, Radoi V, Starkhammar M, Vukojević V, Ćirković Veličković T, Hamsten C, van Hage M. α-Gal on the protein surface affects uptake and degradation in immature monocyte derived dendritic cells. Scientific Reports. 2018;8(1):12684. https://doi.org/10.1038/s41598-018-30887-8 </p
Detection of NADH via electrocatalytic oxidation at single-walled carbon nanotubes modified with Variamine blue
No full textScreen-printed electrodes (SPEs) modified with Variamine blue (VB), covalently attached to the oxidized single-walled carbon nanotubes (SWCNTs-COOH), were developed and used as chemical sensors for the detection of the reduced nicotinamide adenine dinucleotide (NADH). The Variamine blue redox mediator was covalently linked to the SWCNTs-COOH by the N,N′-dicyclohexylcarbodiimide (DCC) and N-hydroxysuccinimide (NHS) chemistry. Infrared Fourier transform (FT-IR) spectroscopy revealed the presence of the amide bands situated at 1623 cm-1 (I band), 1577 cm-1 (II band) and 1437 cm-1 (III band) demonstrating the covalent linkage of Variamine blue to SWCNTs-COOH. The heterogeneous electron transfer rate, kobs., was 13,850 M-1 s-1, and the ks and α were 0.8 s-1 and 0.56, respectively. The pH dependence was also investigated. SPEs modified with Variamine blue by using the DCC/NHS conjugation method, showed a variation of -36 mV per pH unit. A successful application was the development of a lactate biosensor obtained by the immobilization of the l-lactate dehydrogenase on the NADH sensor. © 2007 Elsevier Ltd. All rights reserved
Simulation of thermal plant optimization and hydraulic aspects of thermal distribution loops for large campuses
No full textFollowing an introduction, the author describes Texas A&M University and its utilities system. After that, the author presents how to construct simulation models for chilled water and heating hot water distribution systems. The simulation model was used in a $2.3 million Ross Street chilled water pipe replacement project at Texas A&M University. A second project conducted at the University of Texas at San Antonio was used as an example to demonstrate how to identify and design an optimal distribution system by using a simulation model. The author found that the minor losses of these closed loop thermal distribution systems are significantly higher than potable water distribution systems. In the second part of the report, the author presents the latest development of software called the Plant Optimization Program, which can simulate cogeneration plant operation, estimate its operation cost and provide optimized operation suggestions. The author also developed detailed simulation models for a gas turbine and heat recovery steam generator and identified significant potential savings. Finally, the author also used a steam turbine as an example to present a multi-regression method on constructing simulation models by using basic statistics and optimization algorithms. This report presents a survey of the author??s working experience at the Energy Systems Laboratory (ESL) at Texas A&M University during the period of January 2002 through March 2004. The purpose of the above work was to allow the author to become familiar with the practice of engineering. The result is that the author knows how to complete a project from start to finish and understands how both technical and nontechnical aspects of a project need to be considered in order to ensure a quality deliverable and bring a project to successful completion. This report concludes that the objectives of the internship were successfully accomplished and that the requirements for the degree of Degree of Engineering have been satisfied
NADH screen-printed electrodes modified with zirconium phosphate, Meldola blue, and Reinecke salt. Application to the detection of glycerol by FIA
No full textBulk screen-printed electrodes (bSPEs) modified with zirconium phosphate (ZrP) and Meldola blue (MB) and by electrochemical deposition of a Reineckate film (bMBZrPRs-SPEs) have been constructed and used as NADH sensors. Cyclic voltammetric investigation of these bulk electrochemically modified screen-printed electrodes revealed stable catalytic activity in oxidation of the reduced form of the coenzyme nicotinamide adenine dinucleotide (NADH). Flow-injection analysis (FIA) coupled with amperometric detection confirmed the improved stability of the bMBZrPRs-SPEs (10(-4) mol L-1 NADH, %RSD=4.2, n=90, pH 7.0). Other conditions, for example applied working potential (+50 mV relative to Ag-AgCl), flow rate (0.30 mL min(-1)) and pH-dependence (range 4.0-10.0) were evaluated and optimized. A glycerol biosensor, prepared by immobilizing glycerol dehydrogenase (GDH) on the working electrode area of a bMBZrPRs-SPE, was also assembled. The biosensor was most stable at pH 8.5 (%RSD=5.6, n=70, 0.25 mmol L-1 glycerol). The detection and quantification limits were 2.8x10(-6) and 9.4x10(-6) mol L-1, respectively, and the linear working range was between 1.0x10(-5) and 1.0x10(-4) mol L-1. To assess the effect of interferences, and recovery by the probe we analyzed samples taken during fermentation of chemically defined grape juice medium and compared the results with those obtained by HPLC.[...
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