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Contrast kinetics

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https://www.readbyqxmd.com/read/29777820/accuracy-and-precision-of-quantitative-dce-mri-parameters-how-should-one-estimate-contrast-concentration
#1
Nicole Wake, Hersh Chandarana, Henry Rusinek, Koji Fujimoto, Linda Moy, Daniel K Sodickson, Sungheon Gene Kim
INTRODUCTION: Pharmacokinetic parameters derived from dynamic contrast-enhanced MRI (DCE-MRI) data are sensitive to acquisition and post-processing techniques, which makes it difficult to compare results obtained using different methods. In particular, one of the most important factors affecting estimation of model parameters is how to convert MRI signal intensities to contrast agent concentration. The purpose of our study was to quantitatively compare a linear signal-to-concentration conversion (LC) as an approximation and a non-linear conversion (NLC) based on the MRI signal equation, in terms of the accuracy and precision of the pharmacokinetic parameters in T1 -weighted DCE-MRI...
May 16, 2018: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/29777430/the-artificial-humic-substance-hs1500-does-not-inhibit-photosynthesis-of-the-green-alga-desmodesmus-armatus-in-vivo-but-interacts-with-the-photosynthetic-apparatus-of-isolated-spinach-thylakoids-in-vitro
#2
Matthias Gilbert, Hanno Bährs, Christian E W Steinberg, Christian Wilhelm
Humic substances (HSs) can influence the growth and composition of freshwater phytoplankton assemblage. Since HSs contain many phenolic and quinonic moieties and cause growth reductions in eco-physiological field experiments, HSs are considered photosystem II herbicides. To test this specific mode of action in vivo and in vitro, respectively, we used intact cells of the green alga Desmodesmus armatus, as well as thylakoids isolated from spinach (Spinacia oleracea) as a model system for the green algal chloroplast...
May 18, 2018: Photosynthesis Research
https://www.readbyqxmd.com/read/29774983/mechanistic-insights-into-the-ni-catalyzed-reductive-carboxylation-of-c-o-bonds-in-aromatic-esters-with-co-2-understanding-remarkable-ligand-and-traceless-directing-group-effects
#3
Yan-Li Han, Bing-Yuan Zhao, Kun-Yao Jiang, Hui-Min Yan, Zhu-Xia Zhang, Wen-Jing Yang, Zhen Guo, Yan-Rong Li
The mechanism of the Ni0 -catalyzed reductive carboxylation reaction of C(sp2 )-O and C(sp3 )-O bonds in aromatic esters with CO2 to access valuable carboxylic acids was comprehensively studied by using DFT calculations. Computational results revealed that this transformation was composed of several key steps: C-O bond cleavage, reductive elimination, and/or CO2 insertion. Of these steps, C-O bond cleavage was found to be rate-determining, and it occurred through either oxidative addition to form a NiII intermediate, or a radical pathway that involved a bimetallic species to generate two NiI species through homolytic dissociation of the C-O bond...
May 18, 2018: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/29774904/investigating-subtle-4f-vs-5f-coordination-differences-using-kinetically-inert-eu-iii-tb-iii-and-cm-iii-complexes-of-a-coumarin-appended-1-4-7-10-tetraazacyclododecane-1-4-7-triacetate-do3a-ligand
#4
Anne Kathrine R Junker, Gauthier J-P Deblonde, Rebecca J Abergel, Thomas Just Sørensen
In order to reveal subtle differences between the solution chemistries of trivalent 4f and 5f elements, the physicochemical and photophysical properties of europium(iii), terbium(iii) and curium(iii) complexes formed with a 7-methoxy-coumarin appended 1,4,7,10-tetraazadodecane-1,4,7-triacid (DO3A) ligand were studied. All three complexes were found to be kinetically inert and exhibit stability constants similar to their 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) equivalents. The Cm(iii) and Eu(iii) complexes feature strong sensitised emission, while the triplet energy of the coumarin prohibits efficient sensitisation of the Tb(iii) analogue...
May 18, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29773906/spectrofluorimetric-quantification-of-antibiotic-drug-concentration-in-bacterial-cells-for-the-characterization-of-translocation-across-bacterial-membranes
#5
Julia Vergalli, Estelle Dumont, Jelena Pajović, Bertrand Cinquin, Laure Maigre, Muriel Masi, Matthieu Réfrégiers, Jean-Marie Pagés
The efficacy of antibacterial molecules depends on their capacity to reach inhibitory concentrations in the vicinity of their target. This is particularly challenging for drugs directed against Gram-negative bacteria, which have a complex envelope comprising two membranes and efflux pumps. Precise determination of the bacterial drug content is an essential prerequisite for drug development. Here we describe three approaches that have been developed in our laboratories to quantify drugs accumulated in intact cells by spectrofluorimetry, microspectrofluorimetry, and kinetics microspectrofluorimetry (KMSF)...
June 2018: Nature Protocols
https://www.readbyqxmd.com/read/29772172/an-unusual-salt-effect-in-an-interfacial-nucleophilic-substitution-reaction
#6
Shuheng Li, Milan Mrksich
This paper reports a kinetic characterization of the interfacial reaction of N-methylpyrrolidine with a self-assembled monolayer presenting an iodoalkyl group. SAMDI mass spectrometry was used to determine the extent of reaction for monolayers that were treated with a range of concentrations of the nucleophile for a range of times. These data revealed a second-order rate constant for the reaction that was approximately 100-fold greater than that for the analogous solution-phase reaction. However, addition of sodium iodide to the reaction mixture resulted in a seven-fold decrease in the reac-tion rate...
May 17, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29772085/ligand-induced-conformational-changes-in-hsp90-monitored-time-resolved-and-label-free-towards-a-conformational-activity-screening-for-drug-discovery
#7
Jörn Güldenhaupt, Marta Amaral, Carsten Kötting, Djordje Musil, Jonas Schartner, Matthias Frech, Klaus Gerwert
A detailed investigation of protein-ligand interactions is crucial during the early drug discovery process. However, most available techniques lack either structural or temporal resolution. In contrast, ATR-FTIR spectroscopy can monitor protein-ligand interactions label-free with high spatiotemporal resolution. Here we immobilize as example the heat shock protein HSP90 on an ATR-crystal. This protein is an important molecular target for drugs against several diseases including cancer. With our novel approach we investigated a ligand induced secondary structural change...
May 17, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29772028/randomized-phase-i-trial-hiv-core-003-depletion-of-serum-amyloid-p-component-and-immunogenicity-of-dna-vaccination-against-hiv-1
#8
Nicola J Borthwick, Thirusha Lane, Nathifa Moyo, Alison Crook, Jung Min Shim, Ian Baines, Edmund G Wee, Philip N Hawkins, Julian D Gillmore, Tomáš Hanke, Mark B Pepys
BACKGROUND: The failure of DNA vaccination in humans, in contrast to its efficacy in some species, is unexplained. Observational and interventional experimental evidence suggests that DNA immunogenicity may be prevented by binding of human serum amyloid P component (SAP). SAP is the single normal DNA binding protein in human plasma. The drug (R)-1-[6-[(R)-2-carboxypyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid (CPHPC, miridesap), developed for treatment of systemic amyloidosis and Alzheimer's disease, depletes circulating SAP by 95-99%...
2018: PloS One
https://www.readbyqxmd.com/read/29771727/modeling-gadoxetate-liver-uptake-and-efflux-using-dynamic-contrast-enhanced-magnetic-resonance-imaging-enables-preclinical-quantification-of-transporter-drug-drug-interactions
#9
Leonidas Georgiou, Jeffrey Penny, Glynis Nicholls, Neil Woodhouse, François-Xavier Blé, Josephine H Naish, Penny L Hubbard Cristinacce
OBJECTIVES: The aim of this study was to model the in vivo transporter-mediated uptake and efflux of the hepatobiliary contrast agent gadoxetate in the liver. The efficacy of the proposed technique was assessed for its ability to provide quantitative insights into drug-drug interactions (DDIs), using rifampicin as inhibitor. MATERIALS AND METHODS: Three groups of C57 mice were scanned twice with a dynamic gadoxetate-enhanced magnetic resonance imaging protocol, using a 3-dimensional spoiled gradient-echo sequence for approximately 72 minutes...
May 15, 2018: Investigative Radiology
https://www.readbyqxmd.com/read/29771701/dynamic-contrast-enhanced-ultrasound-identifies-microcirculatory-alterations-in-sepsis-induced-acute-kidney-injury
#10
Alexandre Lima, Tom van Rooij, Bulent Ergin, Michele Sorelli, Yasin Ince, Patricia A C Specht, Egbert G Mik, Leonardo Bocchi, Klazina Kooiman, Nico de Jong, Can Ince
OBJECTIVES: We developed quantitative methods to analyze microbubble kinetics based on renal contrast-enhanced ultrasound imaging combined with measurements of sublingual microcirculation on a fixed area to quantify early microvascular alterations in sepsis-induced acute kidney injury. DESIGN: Prospective controlled animal experiment study. SETTING: Hospital-affiliated animal research institution. SUBJECTS: Fifteen female pigs...
May 15, 2018: Critical Care Medicine
https://www.readbyqxmd.com/read/29771536/selective-removal-of-b800-bacteriochlorophyll-a-from-light-harvesting-complex-2-of-the-purple-photosynthetic-bacterium-phaeospirillum-molischianum
#11
Yoshitaka Saga, Keiya Hirota, Sayaka Matsui, Hitoshi Asakawa, Hiroshi Ishikita, Keisuke Saito
The selective removal of B800 bacteriochlorophyll (BChl) a from light-harvesting complex 2 (LH2) in purple photosynthetic bacteria is a clue about elucidation of the mechanism for the transfer of energy from these pigments to B850 BChl a and their roles in the LH2 protein structure. We demonstrated that the kinetics of the removal of B800 BChl a from two representative LH2 proteins derived from Phaeospirillum molischianum and Rhodoblastus acidophilus differed significantly, in contrast to the calculated binding enthalpy...
May 17, 2018: Biochemistry
https://www.readbyqxmd.com/read/29771515/the-link-between-membrane-composition-and-permeability-to-drugs
#12
Chi Hang Tse, Jeffrey Comer, Yi Wang, Christophe Chipot
Prediction of membrane permeability to small molecules represents an important aspect of drug discovery. First-principle calculations of this quantity require an accurate description of both the thermodynamics and kinetics that underlie translocation of the permeant across the lipid bilayer. In this contribution, the membrane permeability to three drugs, or drug-like molecules, namely, 9-anthroic acid (ANA), 2',3'-dideoxyadenosine (DDA) and hydrocortisone (HYL) are estimated in a pure 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) and in a POPC:cholesterol (2:1) mixture...
May 17, 2018: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/29771123/carotenoids-experimental-ionization-energies-and-capacity-at-inhibiting-lipid-peroxidation-in-a-chemical-model-of-dietary-oxidative-stress
#13
Olivier Dangles, Pascale Goupy, Michel Carail, Alexandre Giuliani, Denis Duflot, Catherine Caris-Veyrat
Carotenoids are important natural pigments and micronutrients contributing to health prevention by several mechanisms, including their electron-donating (antioxidant) activity. In this work, a large series of carotenoids, including 11 carotenes and 14 xanthophylls, has been investigated by wavelength-resolved atmospheric pressure photoionization mass spectrometry (DISCO line of SOLEIL synchrotron), thus allowing the experimental determination of their ionization energy (IE) for the first time. On the other hand, the carotenoids have been also investigated for their ability to inhibit the heme iron-induced peroxidation of linoleic acid in mildly acidic micelles, a simple but relevant chemical model of oxidative stress in the gastric compartment...
May 17, 2018: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/29766171/electron-donor-and-acceptor-functionalized-dithienylethenes-effects-of-charge-density-on-photochromic-properties
#14
Hao Wan, Haodong Xue, Yuan Ling, Yanjun Qiao, Yijing Chen, Gang Zhou
Electron-donating triphenylamine and/or electron-withdrawing pyromellitic diimide (PMDI) are functionalized on dithienylethene (DTE) and three novel photochromic materials have been designed and successfully synthesized. All the compounds display reversible photochromism due to the molecular switching between ring-closed isomers upon UV light irradiation and ring-open isomers upon exposure to visible light. Thus they can be applied as an anti-counterfeiting ink. Moreover, the study of the photoswitching kinetics reveals that both the ring-closing and ring-opening reactions are first-order reactions...
May 16, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29764146/contrast-between-the-mechanisms-for-dissociative-electron-attachment-to-ch-3-scn-and-ch-3-ncs
#15
Thomas M Miller, Albert A Viggiano, Nicholas S Shuman
The kinetics of thermal electron attachment to methyl thiocyanate (CH3 SCN), methyl isothiocyanate (CH3 NCS), and ethyl thiocyanate (C2 H5 SCN) were measured using flowing afterglow-Langmuir probe apparatuses at temperatures between 300 and 1000 K. CH3 SCN and C2 H5 SCN undergo inefficient dissociative attachment to yield primarily SCN- at 300 K (k = 2 × 10-10 cm3 s-1 ), with increasing efficiency as temperature increases. The increase is well described by activation energies of 0.17 eV (CH3 SCN) and 0.14 eV (C2 H5 SCN)...
May 14, 2018: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29762870/t-cells-and-ilc2s-are-major-effector-cells-in-influenza-induced-exacerbation-of-allergic-airway-inflammation-in-mice
#16
Bobby W S Li, Marjolein J W de Bruijn, Melanie Lukkes, Menno van Nimwegen, Ingrid M Bergen, Alex KleinJan, Corine H GeurtsvanKessel, Arno Andeweg, Guus F Rimmelzwaan, Rudi W Hendriks
Influenza virus infection is an important cause of severe asthma exacerbations, but it remains unclear how a Th1-mediated antiviral response triggers a prototypical Th2 disease. We investigated CD4+ T cells and group 2 innate lymphoid cells (ILC2s) in influenza virus-infected mice. We found that ILC2s accumulated in the lung rapidly after influenza virus infection, but the induction of IL-5 and IL-13 secretion was delayed and concomitant with T cell activation. In an influenza-induced exacerbation of allergic airway inflammation model we noticed an initial reduction of ILC2 numbers and cytokine production in broncho-alveolar lavage compared to chronic house dust mite (HDM)-mediated airway inflammation alone...
May 15, 2018: European Journal of Immunology
https://www.readbyqxmd.com/read/29760462/distinct-mechanisms-coordinate-transcription-and-translation-under-carbon-and-nitrogen-starvation-in-escherichia-coli
#17
Sukanya Iyer, Dai Le, Bo Ryoung Park, Minsu Kim
Bacteria adapt to environmental stress by producing proteins that provide stress protection. However, stress can severely perturb the kinetics of gene expression, disrupting protein production. Here, we characterized how Escherichia coli mitigates such perturbations under nutrient stress through the kinetic coordination of transcription and translation. We observed that, when translation became limiting under nitrogen starvation, transcription elongation slowed accordingly. This slowdown was mediated by (p)ppGpp, the alarmone whose primary role is thought to be promoter regulation...
May 14, 2018: Nature Microbiology
https://www.readbyqxmd.com/read/29757624/steric-control-of-the-rate-limiting-step-of-udp-galactopyranose-mutase
#18
Gustavo Pierdominici-Sottile, Rodrigo Cossio-P Eacute Rez, Isabel Da Fonseca, Karina Kizjakina, John J Tanner, Pablo Sobrado
Galactose is an abundant monosaccharide found exclusively in mammals as galactopyranose (Galp), the six-membered ring form of this sugar. In contrast, galactose appears in many pathogenic microorganisms as the five-membered ring form, galactofuranose (Galf). Galf biosynthesis begins with the conversion of UDP-Galp to UDP-Galf catalyzed by the flavoenzyme UDP-galactopyranose mutase (UGM). Because UGM is essential for the survival and proliferation of several pathogens, there is interest in understanding the catalytic mechanism to aid inhibitor development...
May 14, 2018: Biochemistry
https://www.readbyqxmd.com/read/29753488/gastric-digestion-of-milk-protein-ingredients-study-using-an-in-vitro-dynamic-model
#19
Xin Wang, Aiqian Ye, Quanquan Lin, Jianzhong Han, Harjinder Singh
The coagulation behavior and the kinetics of protein hydrolysis of skim milk powder, milk protein concentrate (MPC), calcium-depleted MPC, sodium caseinate, whey protein isolate (WPI), and heated (90°C, 20 min) WPI under gastric conditions were examined using an advanced dynamic digestion model (i.e., a human gastric simulator). During gastric digestion, these protein ingredients exhibited various pH profiles as a function of the digestion time. Skim milk powder and MPC, which contained casein micelles, formed cohesive, ball-like curds with a dense structure after 10 min of digestion; these curds did not disintegrate over 220 min of digestion...
May 9, 2018: Journal of Dairy Science
https://www.readbyqxmd.com/read/29753074/kinetic-and-stoichiometric-constraints-determine-the-pathway-of-h-2-o-2-consumption-by-red-blood-cells
#20
Florencia Orrico, Matías N Möller, Adriana Cassina, Ana Denicola, Leonor Thomson
Red blood cells (RBC) are considered as a circulating sink of H2 O2 , but a significant debate remains over the role of the different intraerythocyte peroxidases. Herein we examined the kinetic of decomposition of exogenous H2 O2 by human RBC at different cell densities, using fluorescent and oxymetric methods, contrasting the results against a mathematical model. Fluorescent measurements as well as oxygen production experiments showed that catalase was responsible for most of the decomposition of H2 O2 at cell densities suitable for both experimental settings (0...
May 9, 2018: Free Radical Biology & Medicine
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