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https://www.readbyqxmd.com/read/28733991/ph-sensitive-amide-proton-transfer-effect-dominates-the-magnetization-transfer-asymmetry-contrast-during-acute-ischemia-quantification-of-multipool-contribution-to-in-vivo-cest-mri
#1
Yin Wu, Iris Yuwen Zhou, Dongshuang Lu, Emiri Manderville, Eng H Lo, Hairong Zheng, Phillip Zhe Sun
PURPOSE: To determine the origins of in vivo magnetization transfer asymmetry contrast during acute ischemic stroke, particularly in the diffusion lesion, perfusion lesion, and their mismatch using a middle cerebral artery occlusion rat model of acute stroke. METHODS: Adult male Wistar rats underwent multiparametric MRI of diffusion, perfusion, T1 , and amide proton transfer (APT) imaging at 4.7 T following a middle cerebral artery occlusion procedure. A multipool Lorentzian model, including the nuclear Overhauser effect, magnetization transfer, direct water saturation, amine and amide chemical exchange saturation transfer effects, was applied for Z-spectrum fitting to determine the sources of in vivo magnetization transfer asymmetry following acute stroke...
July 21, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28726131/detection-of-enzyme-activity-and-inhibition-during-studies-in-solution-in-vitro-and-in-vivo-with-catalycest-mri
#2
Sanhita Sinharay, Edward A Randtke, Christine M Howison, Natalia A Ignatenko, Mark D Pagel
PURPOSE: The detection of enzyme activities and evaluation of enzyme inhibitors have been challenging with magnetic resonance imaging (MRI). To address this need, we have developed a diamagnetic, nonmetallic contrast agent and a protocol known as catalyCEST MRI that uses chemical exchange saturation transfer (CEST) to detect enzyme activity as well as enzyme inhibition. PROCEDURES: We synthesized a diamagnetic MRI contrast agent that has enzyme responsive and enzyme unresponsive CEST signals...
July 19, 2017: Molecular Imaging and Biology: MIB: the Official Publication of the Academy of Molecular Imaging
https://www.readbyqxmd.com/read/28719589/an-excited-state-underlies-gene-regulation-of-a-transcriptional-riboswitch
#3
Bo Zhao, Sharon L Guffy, Benfeard Williams, Qi Zhang
Riboswitches control gene expression through ligand-dependent structural rearrangements of the sensing aptamer domain. However, we found that the Bacillus cereus fluoride riboswitch aptamer adopts identical tertiary structures in solution with and without ligand. Using chemical-exchange saturation transfer (CEST) NMR spectroscopy, we revealed that the structured ligand-free aptamer transiently accesses a low-populated (∼1%) and short-lived (∼3 ms) excited conformational state that unravels a conserved 'linchpin' base pair to signal transcription termination...
July 17, 2017: Nature Chemical Biology
https://www.readbyqxmd.com/read/28714513/in-vivo-evaluation-of-tumour-acidosis-for-assessing-the-early-metabolic-response-and-onset-of-resistance-to-dichloroacetate-by-using-magnetic-resonance-ph-imaging
#4
Annasofia Anemone, Lorena Consolino, Laura Conti, Francesca Reineri, Federica Cavallo, Silvio Aime, Dario Livio Longo
Dichloroacetate (DCA) can reverse the glycolytic phenotype that is responsible of increased lactate production and extracellular pH acidification in cancer cells. Magnetic resonance imaging-chemical exchange saturation transfer (MRI-CEST) pH mapping is a novel non-invasive imaging approach that can measure in vivo extracellular tumour pH. We examined whether MRI-CEST pH mapping can monitor in vivo changes in tumour acidosis for assessing treatment response to DCA. Cell viability and extracellular pH were assessed in TS/A breast cancer cells treated with 1-10 mM DCA for 24 h in normoxia or hypoxia (1% O2) conditions...
August 2017: International Journal of Oncology
https://www.readbyqxmd.com/read/28707688/probing-the-excited-state-chemical-shifts-and-exchange-parameters-by-nitrogen-decoupled-amide-proton-chemical-exchange-saturation-transfer-hn-dec-cest
#5
Qinglin Wu, Benjamin A Fenton, Jessica L Wojtaszek, Pei Zhou
CEST-NMR spectroscopy is a powerful tool for probing the conformational dynamics of macromolecules. We present a HN(dec)-CEST experiment that simplifies the relaxation matrix, reduces fitting parameters, and enhances signal resolution. Importantly, fitting of HN(dec)-CEST profiles enables robust extraction of exchange rates as well as excited-state chemical shifts and populations.
July 14, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28686805/a-generalized-ratiometric-chemical-exchange-saturation-transfer-cest-mri-approach-for-mapping-renal-ph-using-iopamidol
#6
Yin Wu, Iris Y Zhou, Takahiro Igarashi, Dario L Longo, Silvio Aime, Phillip Zhe Sun
PURPOSE: To extend the pH detection range of iopamidol-based ratiometric chemical exchange saturation transfer (CEST) MRI at sub-high magnetic field and establish quantitative renal pH MRI. METHODS: Chemical exchange saturation transfer imaging was performed on iopamidol phantoms with pH of 5.5 to 8.0 and in vivo on rat kidneys (n = 5) during iopamidol administration at a 4.7 T. Iopamidol CEST effects were described using a multipool Lorentzian model. A generalized ratiometric analysis was conducted by ratioing resolved iopamidol CEST effects at 4...
July 7, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28686796/quesp-and-quest-revisited-fast-and-accurate-quantitative-cest-experiments
#7
Moritz Zaiss, Goran Angelovski, Eleni Demetriou, Michael T McMahon, Xavier Golay, Klaus Scheffler
PURPOSE: Chemical exchange saturation transfer (CEST) NMR or MRI experiments allow detection of low concentrated molecules with enhanced sensitivity via their proton exchange with the abundant water pool. Be it endogenous metabolites or exogenous contrast agents, an exact quantification of the actual exchange rate is required to design optimal pulse sequences and/or specific sensitive agents. METHODS: Refined analytical expressions allow deeper insight and improvement of accuracy for common quantification techniques...
July 7, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28653349/assignment-of-the-molecular-origins-of-cest-signals-at-2%C3%A2-ppm-in-rat-brain
#8
Xiao-Yong Zhang, Jingping Xie, Feng Wang, Eugene C Lin, Junzhong Xu, Daniel F Gochberg, John C Gore, Zhongliang Zu
PURPOSE: Chemical exchange saturation transfer effects at 2 ppm (CEST@2ppm) in brain have previously been interpreted as originating from creatine. However, protein guanidino amine protons may also contribute to CEST@2ppm. This study aims to investigate the molecular origins and specificity of CEST@2ppm in brain. METHODS: Two experiments were performed: (i) samples containing egg white albumin and creatine were dialyzed using a semipermeable membrane to demonstrate that proteins and creatine can be separated by this method; and (ii) tissue homogenates of rat brain with and without dialysis to remove creatine were studied to measure the relative contributions of proteins and creatine to CEST@2ppm...
June 26, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28647789/probing-slow-timescale-dynamics-in-proteins-using-methyl-1-h-cest
#9
Tairan Yuwen, Rui Huang, Lewis E Kay
Although (15)N- and (13)C-based chemical exchange saturation transfer (CEST) experiments have assumed an important role in studies of biomolecular conformational exchange, (1)H CEST experiments are only beginning to emerge. We present a methyl-TROSY (1)H CEST experiment that eliminates deleterious (1)H-(1)H NOE dips so that CEST profiles can be analyzed robustly to extract methyl proton chemical shifts of rare protein conformers. The utility of the experiment, along with a version that is optimized for (13)CHD2 labeled proteins, is established through studies of exchanging protein systems...
June 24, 2017: Journal of Biomolecular NMR
https://www.readbyqxmd.com/read/28644017/spectrally-undiscerned-isomers-might-lead-to-erroneous-determination-of-water-exchange-rates-of-paracest-eu-iii-agents
#10
Nevenka Cakić, Ben Tickner, Moritz Zaiss, David Esteban-Gómez, Carlos Platas-Iglesias, Goran Angelovski
We report a detailed study of the solution structure and water exchange rate of a Eu(III) complex with the cyclen-based ligand L(1), containing (S)-2-(2-acetamido)-3-(4-(trifluoromethyl)phenyl)propanoate pendant arms at positions 1 and 7 of the cyclen ring and acetylglycinate pendants at positions 4 and 10. The EuL(1) complex was characterized by a combination of NMR and luminescence spectroscopy and density functional theory (DFT) calculations. The chemical exchange saturation transfer (CEST) spectra obtained at different temperatures and saturation powers present a CEST signal attributed to the coordinated water molecule...
July 17, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28636798/a-ccpe-based-xenon-biosensor-for-magnetic-resonance-imaging-of-claudin-expressing-cells
#11
Anna Piontek, Christopher Witte, Honor May Rose, Miriam Eichner, Jonas Protze, Gerd Krause, Jörg Piontek, Leif Schröder
The majority of malignant tumors originate from epithelial cells, and many of them are characterized by an overexpression of claudins (Cldns) and their mislocalization out of tight junctions. We utilized the C-terminal claudin-binding domain of Clostridium perfringens enterotoxin (cCPE), with its high affinity to specific members of the claudin family, as the targeting unit for a claudin-sensitive cancer biosensor. To overcome the poor sensitivity of conventional relaxivity-based magnetic resonance imaging (MRI) contrast agents, we utilized the superior sensitivity of xenon Hyper-CEST biosensors...
June 2017: Annals of the New York Academy of Sciences
https://www.readbyqxmd.com/read/28627877/detection-and-quantification-of-hydrogen-peroxide-in-aqueous-solutions-using-chemical-exchange-saturation-transfer
#12
David Ryoo, Xiang Xu, Yuguo Li, Joel A Tang, Jia Zhang, Peter C M van Zijl, Guanshu Liu
The development of new analytical methods to accurately quantify hydrogen peroxide is of great interest. In the current study, we developed a new magnetic resonance (MR) method for noninvasively quantifying hydrogen peroxide (H2O2) in aqueous solutions based on chemical exchange saturation transfer (CEST), an emerging MRI contrast mechanism. Our method can detect H2O2 by its specific CEST signal at ∼6.2 ppm downfield from water resonance, with more than 1000 times signal amplification compared to the direct NMR detection...
July 5, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28602944/enhancing-sensitivity-of-ph-weighted-mri-with-combination-of-amide-and-guanidyl-cest
#13
Tao Jin, Ping Wang, T Kevin Hitchens, Seong-Gi Kim
Amide-proton-transfer weighted (APTw) MRI has emerged as a non-invasive pH-weighted imaging technique for studies of several diseases such as ischemic stroke. However, its pH-sensitivity is relatively low, limiting its capability to detect small pH changes. In this work, computer simulations, protamine phantom experiments, and in vivo gas challenge and experimental stroke in rats showed that, with judicious selection of the saturation pulse power, the amide-CEST at 3.6ppm and guanidyl-CEST signals at 2.0ppm changed in opposite directions with decreased pH...
June 7, 2017: NeuroImage
https://www.readbyqxmd.com/read/28590070/chemical-exchange-rotation-transfer-imaging-of-intermediate-exchanging-amines-at-2%C3%A2-ppm
#14
Zhongliang Zu, Elizabeth A Louie, Eugene C Lin, Xiaoyu Jiang, Mark D Does, John C Gore, Daniel F Gochberg
Chemical exchange saturation transfer (CEST) imaging of amine protons exchanging at intermediate rates and whose chemical shift is around 2 ppm may provide a means of mapping creatine. However, the quantification of this effect may be compromised by the influence of overlapping CEST signals from fast-exchanging amines and hydroxyls. We aimed to investigate the exchange rate filtering effect of a variation of CEST, named chemical exchange rotation transfer (CERT), as a means of isolating creatine contributions at around 2 ppm from other overlapping signals...
June 7, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28583638/a-phase-i-clinical-trial-of-the-knee-to-assess-the-correlation-of-gagcest-mri-delayed-gadolinium-enhanced-mri-of-cartilage-and-t2-mapping
#15
Wenbo Wei, Becky Lambach, Guang Jia, Christopher Kaeding, David Flanigan, Michael V Knopp
PURPOSE: Osteoarthritis (OA) is associated with the loss of glycosaminoglycan (GAG) during disease progression, which can be detected by glycosaminoglycan chemical exchange-dependent saturation transfer (gagCEST) MRI. Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) is considered one of the standard methods for GAG quantification in vivo. This Phase I study assessed the correlation between gagCEST MRI and dGEMRIC in determining cartilage GAG concentration. Standard T2 mapping was used as a comparator with the two other methods...
May 2017: European Journal of Radiology
https://www.readbyqxmd.com/read/28569374/quantitative-pulsed-cest-mri-at-a-clinical-3t-mri-system
#16
Julia Stabinska, Tom Cronenberg, Hans-Jörg Wittsack, Rotem Shlomo Lanzman, Anja Müller-Lutz
OBJECTIVES: The goal of this study was to quantify CEST related parameters such as chemical exchange rate and fractional concentration of exchanging protons at a clinical 3T scanner. For this purpose, two CEST quantification approaches-the AREX metric (for 'apparent exchange dependent relaxation'), and the AREX-based Ω-plot method were used. In addition, two different pulsed RF irradiation schemes, using Gaussian-shaped and spin-lock pulses, were compared. MATERIALS AND METHODS: Numerical simulations as well as MRI measurements in phantoms were performed...
May 31, 2017: Magma
https://www.readbyqxmd.com/read/28566586/b1-power-optimization-for-chemical-exchange-saturation-transfer-imaging-a-phantom-study-using-egg-white-for-amide-proton-transfer-imaging-applications-in-the-human-brain
#17
Yuki Kanazawa, Yasutaka Fushimi, Naotaka Sakashita, Tomohisa Okada, Yoshiki Arakawa, Mitsue Miyazaki
The chemical exchange saturation transfer (CEST) effect on an egg white (EW) suspension was investigated for optimization of magnetization transfer (MT) power (B1,rms) and pH dependency with the addition of lactic acid. Applying a higher MT pulse, B1,rms, Z-spectrum shows higher asymmetry and the magnetisation transfer ratio (MTR)asym signal increases to around 1-3.5 ppm, indicating a higher CEST effect. Amide proton transfer (APT) at 3.5 ppm shows a signal elevation in MTRasym with the application of higher B1,rms power and high pH...
May 31, 2017: Magnetic Resonance in Medical Sciences: MRMS
https://www.readbyqxmd.com/read/28558795/non-caloric-sweetener-provides-magnetic-resonance-imaging-contrast-for-cancer-detection
#18
Puneet Bagga, Mohammad Haris, Kevin D'Aquilla, Neil E Wilson, Francesco M Marincola, Mitchell D Schnall, Hari Hariharan, Ravinder Reddy
BACKGROUND: Image contrast enhanced by exogenous contrast agents plays a crucial role in the early detection, characterization, and determination of the precise location of cancers. Here, we investigate the feasibility of using a non-nutritive sweetener, sucralose (commercial name, Splenda), as magnetic resonance imaging (MRI) contrast agent for cancer studies. METHODS: High-resolution nuclear-magnetic-resonance spectroscopy and MR studies on sucralose solution phantom were performed to detect the chemical exchange saturation transfer (CEST) property of sucralose hydroxyl protons with bulk water (sucCEST)...
May 30, 2017: Journal of Translational Medicine
https://www.readbyqxmd.com/read/28547862/mri-evaluation-of-regional-and-longitudinal-changes-in-z-spectra-of-injured-spinal-cord-of-monkeys
#19
Feng Wang, Zhongliang Zu, Ruiqi Wu, Tung-Lin Wu, John C Gore, Li Min Chen
PURPOSE: In principle, MR methods that exploit magnetization transfer (MT) may be used to quantify changes in the molecular composition of tissues after injury. The ability to track such changes in injured spinal cord may allow more precise assessment of the state of neural tissues. METHODS: Z-Spectra were obtained from the cervical spinal cord before and after a unilateral dorsal column lesion in monkeys at 9.4T. The amplitudes of chemical exchange saturation transfer (CEST) and nuclear Overhauser enhancement (NOE) effects from multiple proton pools, along with nonspecific semisolid MT effects from immobile macromolecules, were quantified using a five-peak Lorenzian fitting of each Z-spectrum...
May 25, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28526431/measurement-of-apt-using-a-combined-cert-arex-approach-with-varying-duty-cycles
#20
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
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