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https://www.readbyqxmd.com/read/28321903/spin-lock-imaging-of-exogenous-exchange-based-contrast-agents-to-assess-tissue-ph
#1
Zhongliang Zu, Hua Li, Xiaoyu Jiang, John C Gore
PURPOSE: Some X-ray contrast agents contain exchangeable protons that give rise to exchange-based effects on MRI, including chemical exchange saturation transfer (CEST). However, CEST has poor specificity to explicit exchange parameters. Spin-lock sequences at high field are also sensitive to chemical exchange. Here, we evaluate whether spin-locking techniques can detect the contrast agent iohexol in vivo after intravenous administration, and their potential for measuring changes in tissue pH...
March 20, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28321227/co-expression-with-the-type-3-secretion-chaperone-cest-from-enterohemorrhagic-e-coli-increases-accumulation-of-recombinant-tir-in-plant-chloroplasts
#2
Jacqueline MacDonald, Sean Miletic, Typhanie Gaildry, Adam Chin-Fatt, Rima Menassa
Type 3 secretion systems (T3SSs) are utilized by pathogenic Escherichia coli to infect their hosts and many proteins from these systems are affected by chaperones specific to T3SS-containing bacteria. Toward developing a recombinant vaccine against enterohaemorrhagic E. coli (EHEC), we expressed recombinant T3SS and related proteins from predominant EHEC serotypes in Nicotiana chloroplasts. Nicotiana benthamiana were transiently transformed to express chloroplast-targeted Tir, NleA, and EspD from the EHEC serotype O157:H7; a fusion of EspA proteins from serotypes O157:H7 and O26:H11; and a fusion of epitopes of Tir (Tir-ep) from serotypes O157:H7, O26:H11, O45:H2, and O111:H8...
2017: Frontiers in Plant Science
https://www.readbyqxmd.com/read/28317074/probing-conformational-dynamics-in-biomolecules-via-chemical-exchange-saturation-transfer-a-primer
#3
Pramodh Valluruapalli, Ashok Sekhar, Tairan Yuwen, Lewis E Kay
Although Chemical Exchange Saturation Transfer (CEST) type NMR experiments have been used to study chemical exchange processes in molecules since the early 1960s, there has been renewed interest in the past several years in using this approach to study biomolecular conformational dynamics. The methodology is particularly powerful for the study of sparsely populated, transiently formed conformers that are recalcitrant to investigation using traditional biophysical tools, and it is complementary to relaxation dispersion and magnetization transfer experiments that have traditionally been used to study chemical exchange processes...
March 19, 2017: Journal of Biomolecular NMR
https://www.readbyqxmd.com/read/28283707/evaluating-the-cartilage-adjacent-to-the-site-of-repair-surgery-with-glycosaminoglycan-specific-magnetic-resonance-imaging
#4
Ulrich Koller, Sebastian Apprich, Benjamin Schmitt, Reinhard Windhager, Siegfried Trattnig
PURPOSE: The glycosaminoglycan (GAG) chemical exchange saturation transfer (CEST) imaging method (gagCEST) makes it possible to assess and quantify the GAG concentration in human cartilage. This biochemical imaging technique facilitates detection of the loss of GAG in the course of osteoarthritis. The gagCEST technique was used to analyse the perilesional zone (PLZ) adjacent to repair tissue after cartilage repair surgery, to determine whether there are biochemical changes present in the sense of degeneration...
March 10, 2017: International Orthopaedics
https://www.readbyqxmd.com/read/28273886/quantitative-chemical-exchange-saturation-transfer-cest-mri-of-glioma-using-image-downsampling-expedited-adaptive-least-squares-ideal-fitting
#5
Iris Yuwen Zhou, Enfeng Wang, Jerry S Cheung, Xiaoan Zhang, Giulia Fulci, Phillip Zhe Sun
Chemical Exchange Saturation Transfer (CEST) MRI is sensitive to dilute metabolites with exchangeable protons, allowing tissue characterization in diseases such as acute stroke and tumor. CEST quantification using multi-pool Lorentzian fitting is challenging due to its strong dependence on image signal-to-noise ratio (SNR), initial values and boundaries. Herein we proposed an Image Downsampling Expedited Adaptive Least-squares (IDEAL) fitting algorithm that quantifies CEST images based on initial values from multi-pool Lorentzian fitting of iteratively less downsampled images until the original resolution...
December 2017: Scientific Reports
https://www.readbyqxmd.com/read/28272785/cest-imaging-of-fast-exchanging-amine-pools-with-corrections-for-competing-effects-at-9-4%C3%A2-t
#6
Xiao-Yong Zhang, Feng Wang, Hua Li, Junzhong Xu, Daniel F Gochberg, John C Gore, Zhongliang Zu
Chemical exchange saturation transfer (CEST) imaging of fast exchanging amine protons at 3 ppm offset from the water resonant frequency is of practical interest, but quantification of fast exchanging pools by CEST is challenging. To effectively saturate fast exchanging protons, high irradiation powers need to be applied, but these may cause significant direct water saturation as well as non-specific semi-solid magnetization transfer (MT) effects, and thus decrease the specificity of the measured signal. In addition, the CEST signal may depend on the water longitudinal relaxation time (T1w ), which likely varies between tissues and with pathology, further reducing specificity...
March 8, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28272761/accuracy-in-the-quantification-of-chemical-exchange-saturation-transfer-cest-and-relayed-nuclear-overhauser-enhancement-rnoe-saturation-transfer-effects
#7
Xiao-Yong Zhang, Feng Wang, Hua Li, Junzhong Xu, Daniel F Gochberg, John C Gore, Zhongliang Zu
Accurate quantification of chemical exchange saturation transfer (CEST) effects, including dipole-dipole mediated relayed nuclear Overhauser enhancement (rNOE) saturation transfer, is important for applications and studies of molecular concentration and transfer rate (and thereby pH or temperature). Although several quantification methods, such as Lorentzian difference (LD) analysis, multiple-pool Lorentzian fits, and the three-point method, have been extensively used in several preclinical and clinical applications, the accuracy of these methods has not been evaluated...
March 8, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28248966/a-magnesium-induced-triplex-pre-organizes-the-sam-ii-riboswitch
#8
Susmita Roy, Heiko Lammert, Ryan L Hayes, Bin Chen, Regan LeBlanc, T Kwaku Dayie, José N Onuchic, Karissa Y Sanbonmatsu
Our 13C- and 1H-chemical exchange saturation transfer (CEST) experiments previously revealed a dynamic exchange between partially closed and open conformations of the SAM-II riboswitch in the absence of ligand. Here, all-atom structure-based molecular simulations, with the electrostatic effects of Manning counter-ion condensation and explicit magnesium ions are employed to calculate the folding free energy landscape of the SAM-II riboswitch. We use this analysis to predict that magnesium ions remodel the landscape, shifting the equilibrium away from the extended, partially unfolded state towards a compact, pre-organized conformation that resembles the ligand-bound state...
March 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28244138/b1-inhomogeneity-mitigation-in-cest-using-parallel-transmission
#9
Desmond H Y Tse, Nuno Andre da Silva, Benedikt A Poser, N Jon Shah
PURPOSE: In order to benefit from the increased spectral bandwidth at ultrahigh field (UHF), the use of parallel transmission (pTx) to mitigate flip-angle inhomogeneity in chemical exchange saturation transfer (CEST) imaging is investigated. THEORY AND METHODS: A pTx basis pulse is homogenised by magnitude least-squares (MLS) optimization and expanded to form a frequency-selective saturation pulse for CEST. The pTx saturation pulse was simulated with a three-pool Bloch-McConnell equation to evaluate the impact of pTx on CEST contrast...
February 28, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28220538/on-bead-combinatorial-synthesis-and-imaging-of-europium-iii-based-paracest-agents-aids-in-identification-of-chemical-features-that-enhance-cest-sensitivity
#10
Jaspal Singh, Vineeta Rustagi, Shanrong Zhang, A Dean Sherry, D Gomika Udugamasooriya
The rate of water exchange between the inner-sphere of a paramagnetic ion and bulk water is an important parameter in determining the magnitude of the chemical exchange saturation transfer signal from paramagnetic CEST agents (paraCEST). This is governed by various geometric, steric, and ligand field factors created by macrocyclic ligands surrounding the paramagnetic metal ion. Our previous on-bead combinatorial studies of di-peptoid-europium(III)-DOTA-tetraamide complexes revealed that negatively charged groups in the immediate vicinity of the metal center strongly enhances the CEST signal...
February 21, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28209897/host-cell-attachment-elicits-posttranscriptional-regulation-in-infecting-enteropathogenic-bacteria
#11
Naama Katsowich, Netanel Elbaz, Ritesh Ranjan Pal, Erez Mills, Simi Kobi, Tamar Kahan, Ilan Rosenshine
The mechanisms by which pathogens sense the host and respond by remodeling gene expression are poorly understood. Enteropathogenic Escherichia coli (EPEC), the cause of severe intestinal infection, employs a type III secretion system (T3SS) to inject effector proteins into intestinal epithelial cells. These effectors subvert host cell processes to promote bacterial colonization. We show that the T3SS also functions to sense the host cell and to trigger in response posttranscriptional remodeling of gene expression in the bacteria...
February 17, 2017: Science
https://www.readbyqxmd.com/read/28192930/mitochondria-targeted-and-intracellular-biothiol-triggered-hyperpolarized-129-xe-magnetofluorescent-biosensor
#12
Qingbin Zeng, Qianni Guo, Yaping Yuan, Yuqi Yang, Bin Zhang, Lili Ren, Xiaoxiao Zhang, Qing Luo, Maili Liu, Louis-S Bouchard, Xin Zhou
Biothiols such as gluthathione (GSH), cysteine (Cys), homocysteine (Hcy), and thioredoxin (Trx) play vital roles in cellular metabolism. Various diseases are associated with abnormal cellular biothiol levels. Thus, the intracellular detection of biothiol levels could be a useful diagnostic tool. A number of methods have been developed to detect intracellular thiols, but sensitivity and specificity problems have limited their applications. To address these limitations, we have designed a new biosensor based on hyperpolarized xenon magnetic resonance detection, which can be used to detect biothiol levels noninvasively...
February 9, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28179167/mri-and-mrs-of-the-human-brain-at-magnetic-fields-of-14t-to-20t-technical-feasibility-safety-and-neuroscience-horizons
#13
Thomas F Budinger, Mark D Bird
The three goals of this paper are: 1) to evaluate the improvements in technology for increasing magnetic flux density (magnetic field) to 14T in the next few years and eventually to 20T; 2) to highlight neuroscience opportunities enabled by these advances; and, 3) to evaluate the physiological and biophysical effects associated with MRI at very high performance levels. Substantial recent advances in magnet technology including superconductor developments enable neuroscience goals that are not obtainable at contemporary magnetic fields...
February 5, 2017: NeuroImage
https://www.readbyqxmd.com/read/28111824/on-the-transmit-field-inhomogeneity-correction-of-relaxation-compensated-amide-and-noe-cest-effects-at-7%C3%A2-t
#14
Vitaliy Khlebnikov, Johannes Windschuh, Jeroen C W Siero, Moritz Zaiss, Peter R Luijten, Dennis W J Klomp, Hans Hoogduin
High field MRI is beneficial for chemical exchange saturation transfer (CEST) in terms of high SNR, CNR, and chemical shift dispersion. These advantages may, however, be counter-balanced by the increased transmit field inhomogeneity normally associated with high field MRI. The relatively high sensitivity of the CEST contrast to B1 inhomogeneity necessitates the development of correction methods, which is essential for the clinical translation of CEST. In this work, two B1 correction algorithms for the most studied CEST effects, amide-CEST and nuclear Overhauser enhancement (NOE), were analyzed...
January 23, 2017: NMR in Biomedicine
https://www.readbyqxmd.com/read/28096269/differentiation-between-radiation-necrosis-and-tumor-progression-using-chemical-exchange-saturation-transfer
#15
Hatef Mehrabian, Kimberly L Desmond, Hany Soliman, Arjun Sahgal, Gregory J Stanisz
PURPOSE: Stereotactic radiosurgery (SRS) is a common treatment used in patients with brain metastases and is associated with high rates of local control, however, at the risk of radiation necrosis. It is difficult to differentiate radiation necrosis from tumor progression using conventional MRI making it a major diagnostic dilemma for practitioners. This prospective study investigated whether chemical exchange saturation transfer (CEST) was able to differentiate these two conditions. MATERIALS & METHODS: Sixteen patients with brain metastases who had been previously treated with SRS were included...
January 17, 2017: Clinical Cancer Research: An Official Journal of the American Association for Cancer Research
https://www.readbyqxmd.com/read/28075559/one-component-supramolecular-filament-hydrogels-as-theranostic-label-free-magnetic-resonance-imaging-agents
#16
Lye Lin Lock, Yuguo Li, Xinpei Mao, Hanwei Chen, Verena Staedtke, Renyuan Bai, Wang Ma, Ran Lin, Yi Li, Guanshu Liu, Honggang Cui
Gadolinium (Gd)-based compounds and materials are the most commonly used magnetic resonance imaging (MRI) contrast agents in the clinic; however, safety concerns associated with their toxicities in the free ionic form have promoted the development of new generations of metal-free contrast agents. Here we report a supramolecular strategy to convert an FDA-approved anticancer drug, Pemetrexed (Pem), to a molecular hydrogelator with inherent chemical exchange saturation transfer (CEST) MRI signals. The rationally designed drug-peptide conjugate can spontaneously associate into filamentous assemblies under physiological conditions and consequently form theranostic supramolecular hydrogels for injectable delivery...
January 24, 2017: ACS Nano
https://www.readbyqxmd.com/read/28035783/separating-dipolar-and-chemical-exchange-magnetization-transfer-processes-in-1-h-cest
#17
Tairan Yuwen, Ashok Sekhar, Lewis E Kay
An amide (1) H-Chemical Exchange Saturation Transfer (CEST) experiment is presented for studies of conformational exchange in proteins. The approach, exploiting spin-state-selective magnetization transfer, completely suppresses undesired NOE-based dips in CEST profiles so that chemical exchange processes can be studied. The methodology is demonstrated with applications involving proteins that interconvert on the millisecond timescale between major and invisible minor states, and accurate amide (1) H chemical shifts of the minor conformer are obtained in each case...
December 30, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/28012297/balanced-steady-state-free-precession-bssfp-from-an-effective-field-perspective-application-to-the-detection-of-chemical-exchange-bssfpx
#18
Shu Zhang, Zheng Liu, Aaron Grant, Jochen Keupp, Robert E Lenkinski, Elena Vinogradov
Chemical exchange saturation transfer (CEST) is a novel contrast mechanism and it is gaining increasing popularity as many promising applications have been proposed and investigated. Fast and quantitative CEST imaging techniques are further needed in order to increase the applicability of CEST for clinical use as well as to derive quantitative physiological and biological information. Steady-state methods for fast CEST imaging have been reported recently. Here, we observe that an extreme case of these methods is a balanced steady-state free precession (bSSFP) sequence...
December 8, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/27987233/imaging-extracellular-lactate-in-vitro-and-in-vivo-using-cest-mri-and-a-paramagnetic-shift-reagent
#19
Lei Zhang, André F Martins, Yuyan Mai, Piyu Zhao, Alexander M Funk, M Veronica Clavijo Jordan, Shanrong Zhang, Wei Chen, Yunkou Wu, A Dean Sherry
Overproduction of lactate is a hallmark of cancer, yet a method to quantitatively measure lactate production by cancer cells is not straight-forward. Chemical exchange saturation transfer magnetic resonance imaging (CEST MRI) can potentially be used to image lactate but the small difference in chemical shift of the lactate -OH proton and water proton resonances make it challenging. Like other spectroscopic methods, CEST MRI cannot discriminate intracellular lactate from extracellular lactate. Herein, we demonstrate a relatively simple way to shift the lactate -OH proton resonance far away from water by addition of the paramagnetic shift reagent, EuDO3A, while retaining the CEST properties of lactate itself...
February 3, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27980128/nor-sass-norwegian-sonothrombolysis-in-acute-stroke-study-randomized-controlled-contrast-enhanced-sonothrombolysis-in-an-unselected-acute-ischemic-stroke-population
#20
Aliona Nacu, Christopher E Kvistad, Halvor Naess, Halvor Øygarden, Nicola Logallo, Jörg Assmus, Ulrike Waje-Andreassen, Kathinka D Kurz, Gesche Neckelmann, Lars Thomassen
BACKGROUND AND PURPOSE: The NOR-SASS (Norwegian Sonothrombolysis in Acute Stroke Study) aimed to assess effect and safety of contrast-enhanced ultrasound treatment in an unselected acute ischemic stroke population. METHODS: Patients treated with intravenous thrombolysis within 4.5 hours after symptom onset were randomized 1:1 to either contrast-enhanced sonothrombolysis (CEST) or sham CEST. A visible arterial occlusion on baseline computed tomography angiography was not a prerequisite for inclusion...
February 2017: Stroke; a Journal of Cerebral Circulation
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