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Chemical exchange saturation transfer

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https://www.readbyqxmd.com/read/28544035/chemical-exchange-sensitive-mri-of-amide-amine-and-noe-at-9-4%C3%A2-t-versus-15-2%C3%A2-t
#1
Julius Juhyun Chung, Wonmin Choi, Tao Jin, Jung Hee Lee, Seong-Gi Kim
Chemical exchange (CE)-sensitive MRI benefits greatly from stronger magnetic fields; however, field effects on CE-sensitive imaging have not yet been studied well in vivo. We have compared CE-sensitive Z-spectra and maps obtained at the fields of 9.4 T and 15.2 T in phantoms and rats with off-resonance chemical-exchange-sensitive spin lock (CESL), which is similar to conventional chemical exchange saturation transfer. At higher fields, the background peak at water resonance has less spread and the exchange rate relative to chemical shift decreases, thus CESL intensity is dependent on B0 ...
May 22, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28526431/measurement-of-apt-using-a-combined-cert-arex-approach-with-varying-duty-cycles
#2
Zhongliang Zu, Hua Li, Junzhong Xu, Xiao-Yong Zhang, Moritz Zaiss, Ke Li, Mark D Does, John C Gore, Daniel F Gochberg
The goal is to develop an imaging method where contrast reflects amide-water magnetization exchange, with minimal signal contributions from other sources. Conventional chemical exchange saturation transfer (CEST) imaging of amides (often called amide proton transfer, or APT, and quantified by the metric MTRasym) is confounded by several factors unrelated to amides, such as aliphatic protons, water relaxation, and macromolecular magnetization transfer. In this work, we examined the effects of combining our previous chemical exchange rotation (CERT) approach with the non-linear AREX method while using different duty cycles (DC) for the label and reference scans...
May 17, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28501855/extracellular-ph-is-a-biomarker-enabling-detection-of-breast-cancer-and-liver-cancer-using-cest-mri
#3
Miaomiao Chen, Chaoying Chen, Zhiwei Shen, Xiaolei Zhang, Yanzi Chen, Fengfeng Lin, Xilun Ma, Caiyu Zhuang, Yifei Mao, Haochuan Gan, Peidong Chen, Xiaodan Zong, Renhua Wu
Extracellular pH (pHe) decrease is associated with tumor growth, invasion, metastasis, and chemoresistance, which can be detected by chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI). Here, we demonstrated that ioversol CEST MRI can be exploited to achieve pHe mapping of the liver cancer microenvironment. In in vitro studies, we firstly explored whether ioversol signal is pH-dependent, and calculated the function equation between the CEST effects of ioversol and pH values, in the range of 6...
April 25, 2017: Oncotarget
https://www.readbyqxmd.com/read/28497566/cest-mri-of-3-o-methyl-d-glucose-on-different-breast-cancer-models
#4
Michal Rivlin, Gil Navon
PURPOSE: To test the ability of chemical exchange saturation transfer (CEST) MRI of 3-O-methyl-D-glucose (3OMG) to detect tumors in several breast cancer models of murine and human origin, for different routes of administration of the agent and to compare the method with glucoCEST and with (18) FDG-PET on the same animals. METHODS: In vivo CEST MRI experiments were performed with a 7T Biospec animal MRI scanner on implanted orthotopic mammary tumors of mice before and after administration of 3OMG...
May 12, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28480619/rapid-and-simultaneous-measurement-of-phosphorus-metabolite-pool-size-ratio-and-reaction-kinetics-of-enzymes-in-vivo
#5
Sang-Young Kim, Wei Chen, Dost Ongur, Fei Du
PURPOSE: The metabolites phosphocreatine (PCr), adenosine triphosphate (ATP), and in-organic phosphate (Pi) are biochemically coupled. Their pool sizes, assessed by their magnetization ratios, have been extensively studied and reflect bioenergetics status in vivo. However, most such studies have ignored chemical exchange and T1 relaxation effects. In this work, we aimed to extend the T1nom method to simultaneously quantify the reaction rate constants as well as phosphorus metabolite pool size ratios under partially relaxed conditions...
May 8, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/28480589/quantification-and-tracking-of-genetically-engineered-dendritic-cells-for-studying-immunotherapy
#6
Amnon Bar-Shir, Lina Alon, Michael J Korrer, Hong Seo Lim, Nirbhay N Yadav, Yoshinori Kato, Arvind P Pathak, Jeff W M Bulte, Assaf A Gilad
PURPOSE: Genetically encoded reporters can assist in visualizing biological processes in live organisms and have been proposed for longitudinal and noninvasive tracking of therapeutic cells in deep tissue. Cells can be labeled in situ or ex vivo and followed in live subjects over time. Nevertheless, a major challenge for reporter systems is to identify the cell population that actually expresses an active reporter. METHODS: We have used a nucleoside analog, pyrrolo-2'-deoxycytidine, as an imaging probe for the putative reporter gene, Drosophila melanogaster 2'-deoxynucleoside kinase...
May 7, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28474409/amide-proton-transfer-cest-of-the-cervical-spinal-cord-in-multiple-sclerosis-patients-at-3t
#7
Samantha By, Robert L Barry, Alex K Smith, Bailey D Lyttle, Bailey A Box, Francesca R Bagnato, Siddharama Pawate, Seth A Smith
PURPOSE: The ability to evaluate pathological changes in the spinal cord in multiple sclerosis (MS) is limited because T1 - and T2 -w MRI imaging are not sensitive to biochemical changes in vivo. Amide proton transfer (APT) chemical exchange saturation transfer (CEST) can indirectly detect amide protons associated with proteins and peptides, potentially providing more pathological specificity. Here, we implement APT CEST in the cervical spinal cord of healthy and MS cohorts at 3T. METHODS: APT CEST of the cervical spinal cord was obtained in a cohort of 10 controls and 10 MS patients using a novel respiratory correction methodology...
May 5, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28470934/lanthanide-complexes-in-molecular-magnetic-resonance-imaging-and-theranostics
#8
Eva Toth, Sara Lacerda
Lanthanide complexes have attracted continuous attention in the biomedical field and today various imaging applications make use of their versatile magnetic and luminescence properties. In this minireview, we give insights into the mechanistic aspects that allow modulating the relaxation or chemical exchange saturation transfer (CEST) features, thus the MRI efficiency of paramagnetic lanthanide chelates in order to create agents that are capable of providing an MRI response as a function of a specific biomarker...
May 4, 2017: ChemMedChem
https://www.readbyqxmd.com/read/28435103/magnetization-transfer-contrast-and-chemical-exchange-saturation-transfer-mri-features-and-analysis-of-the-field-dependent-saturation-spectrum
#9
Peter C M van Zijl, Wilfred W Lam, Jiadi Xu, Linda Knutsson, Greg J Stanisz
Magnetization Transfer Contrast (MTC) and Chemical Exchange Saturation Transfer (CEST) experiments measure the transfer of magnetization from molecular protons to the solvent water protons, an effect that becomes apparent as an MRI signal loss ("saturation"). This allows molecular information to be accessed with the enhanced sensitivity of MRI. In analogy to Magnetic Resonance Spectroscopy (MRS), these saturation data are presented as a function of the chemical shift of participating proton groups, e.g. OH, NH, NH2, which is called a Z-spectrum...
April 21, 2017: NeuroImage
https://www.readbyqxmd.com/read/28433532/exci-cest-exploiting-pharmaceutical-excipients-as-mri-cest-contrast-agents-for-tumor-imaging
#10
Dario Livio Longo, Fatima Zzahra Moustaghfir, Alexandre Zerbo, Lorena Consolino, Annasofia Anemone, Martina Bracesco, Silvio Aime
Chemical Exchange Saturation Transfer (CEST) approach is a novel tool within magnetic resonance imaging (MRI) that allows visualization of molecules possessing exchangeable protons with water. Many molecules, employed as excipients for the formulation of finished drug products, are endowed with hydroxyl, amine or amide protons, thus can be exploitable as MRI-CEST contrast agents. Their high safety profiles allow them to be injected at very high doses. Here we investigated the MRI-CEST properties of several excipients (ascorbic acid, sucrose, N-acetyl-d-glucosamine, meglumine and 2-pyrrolidone) and tested them as tumor-detecting agents in two different murine tumor models (breast and melanoma cancers)...
April 20, 2017: International Journal of Pharmaceutics
https://www.readbyqxmd.com/read/28393130/oxidation-responsive-eu-ii-iii-based-multimodal-contrast-agent-for-magnetic-resonance-and-photoacoustic-imaging
#11
Lina A Basal, Yan Yan, Yimin Shen, E Mark Haacke, Mohammad Mehrmohammadi, Matthew J Allen
We report, for the first time, a multimodal, oxidation-responsive contrast agent for magnetic resonance imaging and photoacoustic imaging that uses the differences in the properties between Eu in the +2 and +3 oxidation states. The enhancement of contrast in T1-weighted magnetic resonance and photoacoustic imaging was observed in the +2 but not in the +3 oxidation state, and the complex is a known chemical exchange saturation transfer agent for magnetic resonance imaging in the +3 oxidation state.
March 31, 2017: ACS Omega
https://www.readbyqxmd.com/read/28384568/combination-of-a-crop-model-and-a-geochemical-model-as-a-new-approach-to-evaluate-the-sustainability-of-an-intensive-agriculture-system
#12
Gihan Mohammed, Fabienne Trolard, Marina Gillon, Anne-Laure Cognard-Plancq, André Chanzy, Guilhem Bourrié
By combining a crop model (STICS) and a geochemical model (PHREEQC), a new approach to assess the sustainability of agrosystems is proposed. It is based upon aqueous geochemistry and the stepwise modifications of soil solution during its transfer from the surface till aquifer. Meadows of Crau (SE France), irrigated since the 16th century, were field monitored (2012-2015) and modelled. Except for N, the mineral requirements of hay are largely covered by dissolved elements brought by irrigation water with only slight deficits in K and P, which are compensated by P-K fertilizers and the winter pasture by sheep...
October 1, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28375608/proton-transfer-driven-water-exchange-mechanism-in-the-na-solvation-shell
#13
Matti Hellström, Jörg Behler
Ligand exchange plays an important role for organic and inorganic chemical reactions. We demonstrate the existence of a novel water exchange mechanism, the "proton transfer pathway" (PTP), around Na(+)(aq) in basic (high pH) solution, using reactive molecular dynamics simulations employing a high-dimensional neural network potential. An aqua ligand in the first solvation (hydration) shell around a sodium ion is only very weakly acidic, but if a hydroxide ion is present in the second solvation shell, thermal fluctuations can cause the aqua ligand to transfer a proton to the neighboring OH(-), resulting in a transient direct-contact ion pair, Na(+)-OH(-), which is only weakly bound and easily dissociates...
April 14, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28374764/amide-proton-transfer-magnetic-resonance-imaging-in-detecting-intracranial-hemorrhage-at-different-stages-a-comparative-study-with-susceptibility-weighted-imaging
#14
Xiaoyue Ma, Yan Bai, Yusong Lin, Xiaohua Hong, Taiyuan Liu, Lun Ma, E Mark Haacke, Jinyuan Zhou, Jian Wang, Meiyun Wang
Amide proton transfer (APT) imaging is a noninvasive molecular magnetic resonance imaging (MRI) technique based on the chemical exchange-dependent saturation transfer mechanism. The purpose of this study was to investigate the diagnostic performance of APT MRI in detecting intracranial hemorrhage (ICH) at hyperacute, acute and subacute stages by comparing with susceptibility weighted imaging (SWI). APT MRI and SWI were performed on 33 included patients with ICH by using a 3-T MRI unit. A two-sided Mann-Whitney U test was used to detect differences in APT-weighted (APTw) and SWI signal intensities of ICH at hyperacute, acute and subacute stages...
April 4, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28370884/detecting-in-vivo-urokinase-plasminogen-activator-activity-with-a-catalycest-mri-contrast-agent
#15
Sanhita Sinharay, Christine M Howison, Amanda F Baker, Mark D Pagel
Urokinase plasminogen activator (uPA) promotes tumor invasion and metastasis. The monitoring of uPA activity using molecular imaging may have prognostic value and be predictive for response to anti-cancer therapies. However, the detection of in vivo enzyme activity with molecular imaging remains a challenge. To address this problem, we designed a nonmetallic contrast agent, GR-4Am-SA, that can be detected with chemical exchange saturation transfer (CEST) MRI. This agent has a peptide that is cleaved by uPA, which causes a CEST signal at 5...
March 29, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28370655/detection-of-dt-diaphorase-enzyme-with-a-paracest-mri-contrast-agent
#16
Iman Daryaei, Kyle M Jones, Mark D Pagel
A responsive magnetic resonance (MRI) contrast agent has been developed that can detect the enzyme activity of DT-diaphorase. The agent produced different chemical exchange saturation transfer (CEST) MRI signals before and after incubation with the enzyme, NADH, and GSH at different pH values whereas it showed good stability in a reducing environment without enzyme.
May 11, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28370530/noninvasive-evaluation-of-renal-ph-homeostasis-after-ischemia-reperfusion-injury-by-cest-mri
#17
Dario Livio Longo, Juan Carlos Cutrin, Filippo Michelotti, Pietro Irrera, Silvio Aime
Acute kidney injury (AKI) in mice caused by sustained ischemia followed by reperfusion is associated with acute tubular necrosis and renal dysfunctional blood flow. Although the principal role of the kidney is the maintenance of acid-base balance, current imaging approaches are unable to assess this important parameter, and clinical biomarkers are not robust enough in evaluating the severity of kidney damage. Therefore, novel noninvasive imaging approaches are needed to assess the acid-base homeostasis in vivo...
March 29, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28358208/imidazole-appended-macrocyclic-complexes-of-fe-ii-co-ii-and-ni-ii-as-paracest-agents
#18
Patrick J Burns, Jordan M Cox, Janet R Morrow
The solution chemistry and solid state structures of the Co(II), Fe(II), and Ni(II) complexes of N,N'-bis(imidazole-2-ylmethyl)-4,10-diaza-15-crown-5 (HINO) are reported. The Co(II) and Ni(II) complexes of HINO are the first examples of paraCEST agents (paramagnetic chemical exchange saturation transfer) that feature exchangeable imidazole NH protons. The crystal structures of [Co(HINO)]CoCl4·H2O and [Fe(HINO)](CF3SO3)2 have the metal ions coordinated to four nitrogen and three oxygen donor atoms of the macrocyclic ligand in a distorted pentagonal bipyramidal geometry...
March 30, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28357518/longitudinal-relaxation-optimized-amide-1-h-cest-experiments-for-studying-slow-chemical-exchange-processes-in-fully-protonated-proteins
#19
Tairan Yuwen, Lewis E Kay
Chemical Exchange Saturation Transfer (CEST) experiments are increasingly used to study slow timescale exchange processes in biomolecules. Although (15)N- and (13)C-CEST have been the approaches of choice, the development of spin state selective (1)H-CEST pulse sequences that separate the effects of chemical and dipolar exchange [T. Yuwen, A. Sekhar and L. E. Kay, Angew Chem Int Ed Engl 2016 doi: 10.1002/anie.201610759 (Yuwen et al. 2017)] significantly increases the utility of (1)H-based experiments. Pulse schemes have been described previously for studies of highly deuterated proteins...
March 29, 2017: Journal of Biomolecular NMR
https://www.readbyqxmd.com/read/28346776/proton-exchange-in-a-paramagnetic-chemical-exchange-saturation-transfer-agent-from-experimental-studies-and-ab-initio-metadynamics-simulation
#20
Rodolphe Pollet, Célia S Bonnet, Pascal Retailleau, Philippe Durand, Éva Tóth
The proton-exchange process between water and a carbamate has been studied experimentally and theoretically in a lanthanide-based paramagnetic chemical exchange saturation transfer agent endowed with potential multimodality detection capabilities (optical imaging, or T1 MRI for the Gd(III) analogue). In addition to an in-depth structural analysis by a combined approach (using X-ray crystallography, NMR, and molecular dynamics), our ab initio simulation in aqueous solution sheds light on the reaction mechanism for this proton exchange, which involves structural Grotthuss diffusion...
March 27, 2017: Inorganic Chemistry
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