Articles de revues : « Longitudinal relaxation enhancement »

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Shemesh, Noam, Jean-Nicolas Dumez et Lucio Frydman. « Longitudinal Relaxation Enhancement in1H NMR Spectroscopy of Tissue Metabolites via Spectrally Selective Excitation ». Chemistry - A European Journal 19, n^o 39 (3 septembre 2013) : 13002–8. http://dx.doi.org/10.1002/chem.201300955.

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Shmyreva, Anna A., Majid Safdari, István Furó et Sergey V. Dvinskikh. « NMR longitudinal relaxation enhancement in metal halides by heteronuclear polarization exchange during magic-angle spinning ». Journal of Chemical Physics 144, n^o 22 (14 juin 2016) : 224201. http://dx.doi.org/10.1063/1.4953540.

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Shemesh, Noam, Jens T. Rosenberg, Jean-Nicolas Dumez, Samuel C. Grant et Lucio Frydman. « Metabolic T1 Dynamics and Longitudinal Relaxation Enhancement In Vivo at Ultrahigh Magnetic Fields on Ischemia ». Journal of Cerebral Blood Flow & ; Metabolism 34, n^o 11 (10 septembre 2014) : 1810–17. http://dx.doi.org/10.1038/jcbfm.2014.149.

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Interruptions in cerebral blood flow may lead to devastating neural outcomes. Magnetic resonance has a central role in diagnosing and monitoring these insufficiencies, as well as in understanding their underlying metabolic consequences. Magnetic resonance spectroscopy (MRS) in particular can probe ischemia via the signatures of endogenous metabolites including lactic acid (Lac), N-acetylaspartate, creatine (Cre), and cholines. Typically, MRS reports on these metabolites' concentrations. This study focuses on establishing the potential occurrence of in vivo longitudinal relaxation enhancement (LRE) effects—a phenomenon involving a reduction of the apparent T1 with selective bandwidth excitations— in a rat stroke model at 21.1 T. Statistically significant reductions in Cre's apparent T1s were observed at all the examined post-ischemia time points for both ipsi- and contralateral hemispheres, thereby establishing the existence of LREs for this metabolite in vivo. Ischemia-dependent LRE trends were also noted for Lac in the ipsilateral hemisphere only 24 hours after ischemia. Metabolic T1s were also found to vary significantly as a function of post-stroke recovery time, with the most remarkable and rapid changes observed for Lac T1s. The potential of such measurements to understand stroke at a molecular level and assist in its diagnosis, is discussed.

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Bing, Shen, Hou Bo et Zhang Shibin. « Diagnostic Value of Gadolinium Delayed Enhancement Combined with Longitudinal Relaxation Time Quantitative Imaging for Myocardial Amyloidosis ». Journal of Medical Imaging and Health Informatics 11, n^o 7 (1 juillet 2021) : 1929–38. http://dx.doi.org/10.1166/jmihi.2021.3588.

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This article is based on the use of GE combined with longitudinal lag time to quantify cardiac MRI screening for amyloidosis autologous thousand-cell transplantation, combined with clinical routine risk stratification, method for risk assessment of patients with amyloidosis and monitor the patient’s evaluation of the efficacy after treatment. Cardiac involvement with systemic amyloidosis is of great significance for both treatment and prognosis assessment, and is essential for quantitative and qualitative diagnosis or objectively providing prognostic value. In summary, myocardial amyloidosis needs to be studied before heart failure. It is recommended that patients undergo routine cardiac MRI examination to comprehensively evaluate cardiac morphology, function, risk stratification, prognosis, and treatment guidance. Diagnosis based on a single modality has been replaced by a comprehensive multi-modality method, and there is sufficient evidence to show the potential value of cardiac. However, with the continuous improvement of quality and value in the medical field, the field of cardiac will inevitably develop. The predicted and baseline indexes of myocardial strain predicted cardiac remission were 0.96 and 0.79, respectively. When the predictive value of clinical routine indicators and cardiac indicators is analyzed using blood response as the evaluation standard, the reduction in end-diastolic volume/body surface area (P = 0.031) can predict complete haematological remission. Folded cross-validation test shows that the end-diastolic volume/body surface area reduction and the baseline index IgG combined with myocardial strain predict AUC of complete blood remission of 0.78 and 0.76, respectively. This study will also continue to follow up and increase the sample size to verify the current conclusions.

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Razanahoera, Aiky, Anna Sonnefeld, Geoffrey Bodenhausen et Kirill Sheberstov. « Paramagnetic relaxivity of delocalized long-lived states of protons in chains of CH₂ groups ». Magnetic Resonance 4, n^o 1 (16 février 2023) : 47–56. http://dx.doi.org/10.5194/mr-4-47-2023.

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Abstract. Long-lived states (LLSs) have lifetimes TLLS that can be much longer than longitudinal relaxation times T1. In molecules containing several geminal pairs of protons in neighboring CH2 groups, it has been shown that delocalized LLSs can be excited by converting magnetization into imbalances between the populations of singlet and triplet states of each pair. Since the empirical yield of the conversion and reconversion of observable magnetization into LLSs and back is on the order of 10 % if one uses spin-lock induced crossing (SLIC), it would be desirable to boost the sensitivity by dissolution dynamic nuclear polarization (d-DNP). To enhance the magnetization of nuclear spins by d-DNP, the analytes must be mixed with radicals such as 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPOL). After dissolution, these radicals lead to an undesirable paramagnetic relaxation enhancement (PRE) which shortens not only the longitudinal relaxation times T1 but also the lifetimes TLLS of LLSs. It is shown in this work that PRE by TEMPOL is less deleterious for LLSs than for longitudinal magnetization for four different molecules: 2,2-dimethyl-2-silapentane-5-sulfonate (DSS), homotaurine, taurine, and acetylcholine. The relaxivities rLLS (i.e., the slopes of the relaxation rate constants RLLS as a function of the radical concentration) are 3 to 5 times smaller than the relaxivities r1 of longitudinal magnetization. Partial delocalization of the LLSs across neighboring CH2 groups may decrease this advantage, but in practice, this effect was observed to be small, for example, when comparing taurine containing two CH2 groups and homotaurine with three CH2 groups. Regardless of whether the LLSs are delocalized or not, it is shown that PRE should not be a major problem for experiments combining d-DNP and LLSs, provided the concentration of paramagnetic species after dissolution does not exceed 1 mM, a condition that is readily fulfilled in typical d-DNP experiments. In bullet d-DNP experiments however, it may be necessary to decrease the concentration of TEMPOL or to add ascorbate for chemical reduction.

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Zhang, Yapeng, Jingjing Cheng et Wenzhong Liu. « Characterization and Relaxation Properties of a Series of Monodispersed Magnetic Nanoparticles ». Sensors 19, n^o 15 (2 août 2019) : 3396. http://dx.doi.org/10.3390/s19153396.

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Magnetic iron oxide nanoparticles are relatively advanced nanomaterials, and are widely used in biology, physics and medicine, especially as contrast agents for magnetic resonance imaging. Characterization of the properties of magnetic nanoparticles plays an important role in the application of magnetic particles. As a contrast agent, the relaxation rate directly affects image enhancement. We characterized a series of monodispersed magnetic nanoparticles using different methods and measured their relaxation rates using a 0.47 T low-field Nuclear Magnetic Resonance instrument. Generally speaking, the properties of magnetic nanoparticles are closely related to their particle sizes; however, neither longitudinal relaxation rate r 1 nor transverse relaxation rate r 2 changes monotonously with the particle size d . Therefore, size can affect the magnetism of magnetic nanoparticles, but it is not the only factor. Then, we defined the relaxation rates r i ′ (i = 1 or 2) using the induced magnetization of magnetic nanoparticles, and found that the correlation relationship between r 1 ′ relaxation rate and r 1 relaxation rate is slightly worse, with a correlation coefficient of R 2 = 0.8939, while the correlation relationship between r 2 ′ relaxation rate and r 2 relaxation rate is very obvious, with a correlation coefficient of R 2 = 0.9983. The main reason is that r 2 relaxation rate is related to the magnetic field inhomogeneity, produced by magnetic nanoparticles; however r 1 relaxation rate is mainly a result of the direct interaction of hydrogen nucleus in water molecules and the metal ions in magnetic nanoparticles to shorten the T 1 relaxation time, so it is not directly related to magnetic field inhomogeneity.

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Faas, Henryk M., James L. Krupa, Alexander J. Taylor, Francesco Zamberlan, Christopher J. Philp, Huw E. L. Williams, Simon R. Johnson, Galina E. Pavlovskaya, Neil R. Thomas et Thomas Meersmann. « Accelerated 19F·MRI Detection of Matrix Metalloproteinase-2/-9 through Responsive Deactivation of Paramagnetic Relaxation Enhancement ». Contrast Media & ; Molecular Imaging 2019 (28 février 2019) : 1–13. http://dx.doi.org/10.1155/2019/4826520.

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Paramagnetic gadolinium ions (GdIII), complexed within DOTA-based chelates, have become useful tools to increase the magnetic resonance imaging (MRI) contrast in tissues of interest. Recently, “on/off” probes serving as 19F·MRI biosensors for target enzymes have emerged that utilize the increase in transverse (T2∗ or T2) relaxation times upon cleavage of the paramagnetic GdIII centre. Molecular 19F·MRI has the advantage of high specificity due to the lack of background signal but suffers from low signal intensity that leads to low spatial resolution and long recording times. In this work, an “on/off” probe concept is introduced that utilizes responsive deactivation of paramagnetic relaxation enhancement (PRE) to generate 19F longitudinal (T1) relaxation contrast for accelerated molecular MRI. The probe concept is applied to matrix metalloproteinases (MMPs), a class of enzymes linked with many inflammatory diseases and cancer that modify bioactive extracellular substrates. The presence of these biomarkers in extracellular space makes MMPs an accessible target for responsive PRE deactivation probes. Responsive PRE deactivation in a 19F biosensor probe, selective for MMP-2 and MMP-9, is shown to enable molecular MRI contrast at significantly reduced experimental times compared to previous methods. PRE deactivation was caused by MMP through cleavage of a protease substrate that served as a linker between the fluorine-containing moiety and a paramagnetic GdIII-bound DOTA complex. Ultrashort echo time (UTE) MRI and, alternatively, short echo times in standard gradient echo (GE) MRI were employed to cope with the fast 19F transverse relaxation of the PRE active probe in its “on-state.” Upon responsive PRE deactivation, the 19F·MRI signal from the “off-state” probe diminished, thereby indicating the presence of the target enzyme through the associated negative MRI contrast. Null point 1H·MRI, obtainable within a short time course, was employed to identify false-positive 19F·MRI responses caused by dilution of the contrast agent.

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Baggiano, Andrea, Alberico Del Torto, Marco Guglielmo, Giuseppe Muscogiuri, Laura Fusini, Mario Babbaro, Ada Collevecchio et al. « Role of CMR Mapping Techniques in Cardiac Hypertrophic Phenotype ». Diagnostics 10, n^o 10 (29 septembre 2020) : 770. http://dx.doi.org/10.3390/diagnostics10100770.

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Non-ischemic cardiomyopathies represent a heterogeneous group of myocardial diseases potentially leading to heart failure, life-threatening arrhythmias, and eventually death. Myocardial dysfunction is associated with different underlying pathological processes, ultimately inducing changes in morphological appearance. Thus, classification based on presenting morphological phenotypes has been proposed, i.e., dilated, hypertrophic, restrictive, and right ventricular cardiomyopathies. In light of the key diagnostic and prognostic role of morphological and functional features, cardiovascular imaging has emerged as key element in the clinical workflow of suspected cardiomyopathies, and above all, cardiovascular magnetic resonance (CMR) represents the ideal technique to be used: thanks to its physical principles, besides optimal spatial and temporal resolutions, incomparable contrast resolution allows to assess myocardial tissue abnormalities in detail. Traditionally, weighted images and late enhancement images after gadolinium-based contrast agent administration have been used to perform tissue characterization, but in the last decade quantitative assessment of pre-contrast longitudinal relaxation time (native T1), post-contrast longitudinal relaxation time (post-contrast T1) and transversal relaxation time (T2), all displayed with dedicated pixel-wise color-coded maps (mapping), has contributed to give precious knowledge insight, with positive influence of diagnostic accuracy and prognosis assessment, mostly in the setting of the hypertrophic phenotype. This review aims to describe the available evidence of the role of mapping techniques in the assessment of hypertrophic phenotype, and to suggest their integration in the routine CMR evaluation of newly diagnosed cardiomyopathies with increased wall thickness.

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Rastrelli, Federico, Diego Frezzato, Ronald G. Lawler, Yongjun Li, Nicholas J. Turro et Alessandro Bagno. « Predicting the paramagnet-enhanced NMR relaxation of H 2 encapsulated in endofullerene nitroxides by density-functional theory calculations ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 371, n^o 1998 (13 septembre 2013) : 20110634. http://dx.doi.org/10.1098/rsta.2011.0634.

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We have investigated the structure and nuclear magnetic resonance (NMR) spectroscopic properties of some dihydrogen endofullerene nitroxides by means of density-functional theory (DFT) calculations. Quantum versus classical roto-translational dynamics of H 2 have been characterized and compared. Geometrical parameters and hyperfine couplings calculated by DFT have been input to the Solomon–Bloembergen equations to predict the enhancement of the NMR longitudinal relaxation of H 2 due to coupling with the unpaired electron. Estimating the rotational correlation time via computed molecular volumes leads to a fair agreement with experiment for the simplest derivative; the estimate is considerably improved by recourse to the calculation of the diffusion tensor. For the other more flexible congeners, the agreement is less good, which may be due to an insufficient sampling of the conformational space. In all cases, relaxation by Fermi contact and Curie mechanisms is predicted to be negligible.

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Surányi, Pál, Pál Kiss, Balazs Ruzsics, Brigitta C. Brott, Tamás Simor et Gabriel A. Elgavish. « Equilibrium signal intensity mapping, an MRI method for fast mapping of longitudinal relaxation rates and for image enhancement ». Magnetic Resonance Imaging 25, n^o 5 (juin 2007) : 641–51. http://dx.doi.org/10.1016/j.mri.2006.10.008.

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Querci, Leonardo, Inês B. Trindade, Michele Invernici, José Malanho Silva, Francesca Cantini, Ricardo O. Louro et Mario Piccioli. « NMR of Paramagnetic Proteins : 13C Derived Paramagnetic Relaxation Enhancements Are an Additional Source of Structural Information in Solution ». Magnetochemistry 9, n^o 3 (26 février 2023) : 66. http://dx.doi.org/10.3390/magnetochemistry9030066.

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In paramagnetic metalloproteins, longitudinal relaxation rates of 13C′ and 13Cα nuclei can be measured using 13C detected experiments and converted into electron spin-nuclear spin distance restraints, also known as Paramagnetic Relaxation Enhancement (PRE) restraints. 13C are less sensitive to paramagnetism than 1H nuclei, therefore, 13C based PREs constitute an additional, non-redundant, structural information. We will discuss the complementarity of 13C PRE restraints with 1H PRE restraints in the case of the High Potential Iron Sulfur Protein (HiPIP) PioC, for which the NMR structure of PioC has been already solved by a combination of classical and paramagnetism-based restraints. We will show here that 13C R1 values can be measured also at very short distances from the paramagnetic center and that the obtained set of 13C based restraints can be added to 1H PREs and to other classical and paramagnetism based NMR restraints to improve quality and quantity of the NMR information.

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Islam, Khairul, Manjurul Haque, Arup Kumar, Amitra Hoq, Fahmeed Hyder et Sheikh Manjura Hoque. « Manganese Ferrite Nanoparticles (MnFe2O4) : Size Dependence for Hyperthermia and Negative/Positive Contrast Enhancement in MRI ». Nanomaterials 10, n^o 11 (20 novembre 2020) : 2297. http://dx.doi.org/10.3390/nano10112297.

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We synthesized manganese ferrite (MnFe2O4) nanoparticles of different sizes by varying pH during chemical co-precipitation procedure and modified their surfaces with polysaccharide chitosan (CS) to investigate characteristics of hyperthermia and magnetic resonance imaging (MRI). Structural features were analyzed by X-ray diffraction (XRD), high-resolution transmission electron microscopy (TEM), selected area diffraction (SAED) patterns, and Mössbauer spectroscopy to confirm the formation of superparamagnetic MnFe2O4 nanoparticles with a size range of 5–15 nm for pH of 9–12. The hydrodynamic sizes of nanoparticles were less than 250 nm with a polydispersity index of 0.3, whereas the zeta potentials were higher than 30 mV to ensure electrostatic repulsion for stable colloidal suspension. MRI properties at 7T demonstrated that transverse relaxation (T2) doubled as the size of CS-coated MnFe2O4 nanoparticles tripled in vitro. However, longitudinal relaxation (T1) was strongest for the smallest CS-coated MnFe2O4 nanoparticles, as revealed by in vivo positive contrast MRI angiography. Cytotoxicity assay on HeLa cells showed CS-coated MnFe2O4 nanoparticles is viable regardless of ambient pH, whereas hyperthermia studies revealed that both the maximum temperature and specific loss power obtained by alternating magnetic field exposure depended on nanoparticle size and concentration. Overall, these results reveal the exciting potential of CS-coated MnFe2O4 nanoparticles in MRI and hyperthermia studies for biomedical research.

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Chan, Sammy H. S., Christopher A. Waudby, Anaïs M. E. Cassaignau, Lisa D. Cabrita et John Christodoulou. « Increasing the sensitivity of NMR diffusion measurements by paramagnetic longitudinal relaxation enhancement, with application to ribosome–nascent chain complexes ». Journal of Biomolecular NMR 63, n^o 2 (8 août 2015) : 151–63. http://dx.doi.org/10.1007/s10858-015-9968-x.

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Shemesh, Noam, Jean-Nicolas Dumez et Lucio Frydman. « Inside Cover : Longitudinal Relaxation Enhancement in1H NMR Spectroscopy of Tissue Metabolites via Spectrally Selective Excitation (Chem. Eur. J. 39/2013) ». Chemistry - A European Journal 19, n^o 39 (19 septembre 2013) : 12910. http://dx.doi.org/10.1002/chem.201390150.

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Pellico, Juan, Connor M. Ellis et Jason J. Davis. « Nanoparticle-Based Paramagnetic Contrast Agents for Magnetic Resonance Imaging ». Contrast Media & ; Molecular Imaging 2019 (5 mai 2019) : 1–13. http://dx.doi.org/10.1155/2019/1845637.

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Magnetic resonance imaging (MRI) is a noninvasive medical imaging modality that is routinely used in clinics, providing anatomical information with micron resolution, soft tissue contrast, and deep penetration. Exogenous contrast agents increase image contrast by shortening longitudinal (T1) and transversal (T2) relaxation times. Most of the T1 agents used in clinical MRI are based on paramagnetic lanthanide complexes (largely Gd-based). In moving to translatable formats of reduced toxicity, greater chemical stability, longer circulation times, higher contrast, more controlled functionalisation and additional imaging modalities, considerable effort has been applied to the development of nanoparticles bearing paramagnetic ions. This review summarises the most relevant examples in the synthesis and biomedical applications of paramagnetic nanoparticles as contrast agents for MRI and multimodal imaging. It includes the most recent developments in the field of production of agents with high relaxivities, which are key for effective contrast enhancement, exemplified through clinically relevant examples.

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Yu, Kaichao, Yousef Hamdan, Fuxian Wan, Yinxia Li, Kaixun Huang et Jinlan Zhou. « Synthesis, Relaxivity, and T1 Relaxation Enhancement of Binuclear Gadolinium(III) Complexes Based on DTPA or EDTA and Long-Chain Alkyl Esters of L-Lysine ». Australian Journal of Chemistry 60, n^o 3 (2007) : 218. http://dx.doi.org/10.1071/ch06214.

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Eight novel diamino-ester ligands were synthesized by amidation reaction of long-chain alkyl esters of l-lysine with diethylenetriamine pentaacetic acid monoanhydride or ethylenediamine tetraacetic acid monoanhydride. The corresponding dimeric Gd(iii) complexes were obtained by treating these ligands with GdCl3·6H2O. All ligands and complexes were characterized by 1H NMR, FT-IR, and elemental analysis. The longitudinal relaxation time (T1) was measured, and all relaxivity values (R1) of these dimeric Gd(iii) complexes are higher than that of Magnivest (Gd-DTPA). One of these complexes, possessing the highest relaxivity in the DTPA series, was chosen to test the acute toxicity and T1-weighted imaging. It was found that this dimeric Gd(iii) complex exhibits no acute toxicity, and offers highly enhanced MRI signal and increases intention time in the rat liver tissue compared to Magnivest.

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Ibrahim, Masooma, Thomas Rudszuck, Banan Kerdi, Steffen Krämer, Gisela Guthausen et Annie K. Powell. « Comparative NMR Relaxivity Study of Polyoxometalate-Based Clusters [Mn4(H2O)2(P2W1SO56)2]16− and [{Dy(H2O)6}2Mn4(H2O)2(P2W15O56)2]10− from 20 MHz to 1.2 GHz ». Applied Magnetic Resonance 51, n^o 11 (8 octobre 2020) : 1295–305. http://dx.doi.org/10.1007/s00723-020-01267-1.

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AbstractNuclear Magnetic Resonance relaxivities are a measure for the sensitivity of a contrast agent (CA), i.e. the potential of a paramagnetic moiety to enhance longitudinal and transverse relaxation of molecules in its near neighbourhood. The underlying mechanism is called Paramagnetic Relaxation Enhancement (PRE). The relaxivity, characterizing PRE, depends not only on the external applied magnetic field but also depends on numerous factors, such as number of coordinated water molecules, water exchange rate, rotational diffusion, first and second coordination hydration sphere, electronic and magnetic properties of paramagnetic centers and the molecular shape/size of the CA. Relaxation rates are usually normalized to the concentration of the contrast agent to provide the relaxivities. To investigate the influence of these factors on PRE of newly synthesized potential CA, two paramagnetic metals containing polyoxometalates (POMs) [Mn4(H2O)2(P2W15O56)2]16− (Mn4-P2W15) and [{Dy(H2O)6}2Mn4(H2O)2(P2W15O56)2]10− (Dy2Mn4-P2W15) were selected as models to be studied at 1H Larmor frequencies from 20 MHz to 1.2 GHz. Structurally, the POM Dy2Mn4-P2W15 is similar to the tetra-nuclear manganese(II)-substituted sandwich-type POM Mn4-P2W15, with the two coordinated DyIII cations acting as linkers connecting Mn4-P2W15 units, thus forming a 1D ladder-like chain structure based on sandwich-type rungs strung together by the dysprosium cations. This study shows that POM (Dy2Mn4-P2W15) is a promising CA at high magnetic fields and proves that the use of heterometallic clusters is an effective strategy to increase PRE due to the synergistic effects from different metal ions.

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Venu, Aiswarya Chalikunnath, Rami Nasser Din, Thomas Rudszuck, Pierre Picchetti, Papri Chakraborty, Annie K. Powell, Steffen Krämer, Gisela Guthausen et Masooma Ibrahim. « NMR Relaxivities of Paramagnetic Lanthanide-Containing Polyoxometalates ». Molecules 26, n^o 24 (10 décembre 2021) : 7481. http://dx.doi.org/10.3390/molecules26247481.

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The current trend for ultra-high-field magnetic resonance imaging (MRI) technologies opens up new routes in clinical diagnostic imaging as well as in material imaging applications. MRI selectivity is further improved by using contrast agents (CAs), which enhance the image contrast and improve specificity by the paramagnetic relaxation enhancement (PRE) mechanism. Generally, the efficacy of a CA at a given magnetic field is measured by its longitudinal and transverse relaxivities r1 and r2, i.e., the longitudinal and transverse relaxation rates T1−1 and T2−1 normalized to CA concentration. However, even though basic NMR sensitivity and resolution become better in stronger fields, r1 of classic CA generally decreases, which often causes a reduction of the image contrast. In this regard, there is a growing interest in the development of new contrast agents that would be suitable to work at higher magnetic fields. One of the strategies to increase imaging contrast at high magnetic field is to inspect other paramagnetic ions than the commonly used Gd(III)-based CAs. For lanthanides, the magnetic moment can be higher than that of the isotropic Gd(III) ion. In addition, the symmetry of electronic ground state influences the PRE properties of a compound apart from diverse correlation times. In this work, PRE of water 1H has been investigated over a wide range of magnetic fields for aqueous solutions of the lanthanide containing polyoxometalates [DyIII(H2O)4GeW11O39]5– (Dy-W11), [ErIII(H2O)3GeW11O39]5– (Er-W11) and [{ErIII(H2O)(CH3COO)(P2W17O61)}2]16− (Er2-W34) over a wide range of frequencies from 20 MHz to 1.4 GHz. Their relaxivities r1 and r2 increase with increasing applied fields. These results indicate that the three chosen POM systems are potential candidates for contrast agents, especially at high magnetic fields.

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Nagura, Kota, Yusa Takemoto, Fumi Yoshino, Alexey Bogdanov, Natalia Chumakova, Andrey Vorobiev, Hirohiko Imai et al. « Magnetic Mixed Micelles Composed of a Non-Ionic Surfactant and Nitroxide Radicals Containing a D-Glucosamine Unit : Preparation, Stability, and Biomedical Application ». Pharmaceutics 11, n^o 1 (19 janvier 2019) : 42. http://dx.doi.org/10.3390/pharmaceutics11010042.

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Metal-free magnetic mixed micelles (mean diameter: < 20 nm) were prepared by mixing the biocompatible non-ionic surfactant Tween 80 and the non-toxic, hydrophobic pyrrolidine-N-oxyl radicals bearing a D-glucosamine unit in pH 7.4 phosphate-buffered saline (PBS). The time-course stability and in vitro magnetic resonance imaging (MRI) contrast ability of the mixed micelles was found to depend on the length of the alkyl chain in the nitroxide radicals. It was also confirmed that the mixed micelles exhibited no toxicity in vivo and in vitro and high stability in the presence of a large excess of ascorbic acid. The in vivo MRI experiment revealed that one of these mixed micelles showed much higher contrast enhancement in the proton longitudinal relaxation time (T1) weighted images than other magnetic mixed micelles that we have reported previously. Thus, the magnetic mixed micelles presented here are expected to serve as a promising contrast agent for theranostic nanomedicines, such as MRI-visible targeted drug delivery carriers.

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Seshadri, Mukund, et Michael J. Ciesielski. « MRI-Based Characterization of Vascular Disruption by 5,6-Dimethylxanthenone-Acetic Acid in Gliomas ». Journal of Cerebral Blood Flow & ; Metabolism 29, n^o 8 (20 mai 2009) : 1373–82. http://dx.doi.org/10.1038/jcbfm.2009.68.

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The well-vascularized nature of gliomas has generated a lot of interest in antiangiogenic therapies. However, the potential of vascular disrupting agents (VDAs) against gliomas has not been investigated extensively. In this study, we examined the in vivo efficacy of the tumor-VDA 5,6-dimethylxanthenone-4-acetic acid (DMXAA) against gliomas. Contrast-enhanced magnetic resonance imaging (MRI) and diffusion-weighted MRI were used to characterize the vascular and cellular responses of GL261 and U87 gliomas to DMXAA treatment. Therapeutic efficacy was assessed by Kaplan-Meier survival analysis. Before VDA treatment, minimal enhancement was detected within the tumor in both models. Longitudinal relaxation rate ( R1 = 1/ T1) maps acquired 24 h after treatment showed marked extravasation and accumulation of the contrast agent in the tumor indicative of treatment-induced vascular disruption. Normalized change in relaxation rate (ΔR1) values of the tumor showed a significant increase ( P<0.01 GL261; P<0.05 U87) after therapy compared with baseline estimates. Mean apparent diffusion coefficient (ADC) values were significantly increased ( P = 0.015) 72 h after therapy in GL261 but not in U87 gliomas. Vascular disrupting agent therapy resulted in a significant ( P<0.01) increase in median survival in both models evaluated. The results highlight the potential of VDAs against gliomas and the utility of MRI in the assessment of glioma response to VDA therapy.

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Ma, Xiaohong, Shuang Wang, Longbin Hu, Shichao Feng, Zhiyuan Wu, Siyun Liu, Shaofeng Duan, Zhongwei Chen, Chunwu Zhou et Xinming Zhao. « Imaging Characteristics of USPIO Nanoparticles (<5 nm) as MR Contrast Agent In Vitro and in the Liver of Rats ». Contrast Media & ; Molecular Imaging 2019 (21 juillet 2019) : 1–9. http://dx.doi.org/10.1155/2019/3687537.

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Iron nanoparticles have an increasingly more and more important role in MR molecular imaging due to their novel magnetic and surface chemical properties. They provide new possibilities for noninvasive diagnosis and treatment monitoring, especially for tissues that are rich in macrophages. The smaller size and prolongation of the plasma half-life change the in vivo fate of ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles captured by liver in reticuloendothelial system (RES) or mononuclear phagocytic system (MPS). However, there is still a lack of MR imaging studies on the liver assessing USPIO nanoparticles <5 nm in size to reflect its absorption and clearance properties. In this study, we used MRI to study the in vitro phantom and in vivo rat liver imaging characteristics of USPIO nanoparticles (<5 nm). The results showed that USPIO nanoparticles (<5 nm) could potentially reduce longitudinal and transverse relaxation times and showed similar T1 relaxation rates compared with commercial gadolinium chelates. In addition, USPIO nanoparticles (<5 nm) in vivo demonstrated both positive (T1) and negative (T2) liver contrast enhancement in healthy rats’ liver. Furthermore, USPIO nanoparticles showed relatively good in vitro biocompatibility and fast clearance (within 45.17 minutes after intravenous injection) in the normal liver. Taken together, these data might inspire a new personalized and precise diagnostic tool and stimulate new applications for specific targeted molecular probes.

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Lopez-Ortiz, Fernando, et Rodrigo Jose Carbajo. « Applications of Polarization Transfer and Indirect Detection NMR Spectroscopic Methods Based on Phosphorus-31 in Organic and Organometallic Chemistry ». Current Organic Chemistry 2, n^o 2 (mars 1998) : 97–130. http://dx.doi.org/10.2174/1385272802666220127211106.

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This review will analyse state-of-the-art NMR experiments of polarization transfer and indirect detection based on phosphorus-31 and their applications in organic and organometallic chemistry. Triple resonance NMR spectroscopy based on phosphorus-31 as a source of signal intensity enhancement and/or detection, is currently a very well established tool in structural studies. Nowadays, improvements in NMR equipment allow to perform these pulse sequences on a routine basis. Initially, these techniques were developed to measure the chemical shift and coupling constants of insensitive nuclei scalarly coupled to phosphorus, but lacking a J coupling to protons. The main focus was devoted to metal nuclei of organotransition complexes, including the measurement of longitudinal relaxation times. This NMR methodology has been also very fruitful in providing structural information through 31P correlations with more common nuclei such as 6Li, 13C, 15N, and 110. Recent applications of phosphorus-detection cover the correlation of transition metal NMR parameters with chemical properties (catalytic activity, stability constants, reaction rates, etc.), of particular relevance to deduce structure-reactivity relationships.

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Li, Zhu, Jiali Jiang, Jianxiong Lyu et Jinzhen Cao. « Orthotropic Viscoelastic Properties of Chinese Fir Wood Saturated with Water in Frozen and Non-frozen States ». Forest Products Journal 71, n^o 1 (1 janvier 2021) : 77–83. http://dx.doi.org/10.13073/fpj-d-20-00069.

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Abstract In order to better understand the differences in orthotropic viscoelastic properties of Chinese fir (Cunninghamia lanceolata) in frozen and non-frozen states, the storage modulus (E′) and loss modulus (E″) of the longitudinal, radial, and tangential specimens were investigated under water-saturated conditions with temperatures ranging from −120°C (or 30°C) to 280°C. Results revealed that the order of magnitude in E′ for each orientation was consistent for temperatures below 0°C, while the anisotropy in E′ was reduced due to the enhancement effect of ice. Frequency-dependent γ-relaxation was observed at approximately −96°C for all orthotropic directions. A sharp discontinuity in E′ occurred at approximately 0°C for each specimen, together with the corresponding sharp peak in the E″ spectrum. Furthermore, the frozen free water had an effect on the orthotropic viscoelastic behavior in the water-saturated specimens within the range of −120°C to 280°C. Specimens with a frozen history leveled off at the initial temperature ramping phase for each orientation, while a frozen history reduced the decline in stiffness of the wood specimens. Similar to the variations in E′, the dramatic loss of water increased the complexity of the E″ values. The loss of free water also had a pronounced effect on the viscoelastic properties during the temperature ramping process. Thus, in the wood industry, it necessary to consider the variations in the orthotropic viscoelastic performance of specimens under water-saturated conditions during the water loss process.

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Yamada, Aki, Susumu Ohya, Masaru Hirano, Minoru Watanabe, Michael P. Walsh et Yuji Imaizumi. « Ca2+ sensitization of smooth muscle contractility induced by ruthenium red ». American Journal of Physiology-Cell Physiology 276, n^o 3 (1 mars 1999) : C566—C575. http://dx.doi.org/10.1152/ajpcell.1999.276.3.c566.

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The effects of ruthenium red (RuR) on contractility were examined in skinned fibers of guinea pig smooth muscles, where sarcoplasmic reticulum function was destroyed by treatment with A-23187. Contractions of skinned fibers of the urinary bladder were enhanced by RuR in a concentration-dependent manner (EC50 = 60 μM at pCa 6.0). The magnitude of contraction at pCa 6.0 was increased to 320% of control by 100 μM RuR. Qualitatively, the same results were obtained in skinned fibers prepared from the ileal longitudinal smooth muscle layer and mesenteric artery. The maximal contraction induced by pCa 4.5 was not affected significantly by RuR. The enhanced contraction by RuR was not reversed by the addition of guanosine 5′- O-(2-thiodiphosphate) or a peptide inhibitor of protein kinase C [PKC-(19—31)]. The application of microcystin, a potent protein phosphatase inhibitor, induced a tonic contraction of skinned smooth muscle at low Ca2+ concentration ([Ca2+]; pCa > 8.0). RuR had a dual effect on the microcystin-induced contraction-to- enhancement ratio at low concentrations and suppression at high concentrations. The relaxation following the decrease in [Ca2+] from pCa 5.0 to >8.0 was significantly slowed down by an addition of RuR. Phosphorylation of the myosin light chain at pCa 6.3 was significantly increased by RuR in skinned fibers of the guinea pig ileum. These results indicate that RuR markedly increases the Ca2+ sensitivity of the contractile system, at least in part via inhibition of myosin light chain phosphatase.

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Cerne, John W., Ashitha Pathrose, Roberto Sarnari, Manik Veer, Kelvin Chow, Kamal Subedi, Bradley D. Allen, Ryan J. Avery, Michael Markl et James C. Carr. « Left Ventricular Fibrosis Assessment by Native T1, ECV, and LGE in Pulmonary Hypertension Patients ». Diagnostics 13, n^o 1 (27 décembre 2022) : 71. http://dx.doi.org/10.3390/diagnostics13010071.

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Cardiac magnetic resonance imaging (MRI) is emerging as an alternative to right heart catheterization for the evaluation of pulmonary hypertension (PH) patients. The aim of this study was to compare cardiac MRI-derived left ventricle fibrosis indices between pre-capillary PH (PrePH) and isolated post-capillary PH (IpcPH) patients and assess their associations with measures of ventricle function. Global and segmental late gadolinium enhancement (LGE), longitudinal relaxation time (native T1) maps, and extracellular volume fraction (ECV) were compared among healthy controls (N = 25; 37% female; 52 ± 13 years), PH patients (N = 48; 60% female; 60 ± 14 years), and PH subgroups (PrePH: N = 29; 65% female; 55 ± 12 years, IpcPH: N = 19; 53% female; 66 ± 13 years). Cardiac cine measured ejection fraction, end diastolic, and end systolic volumes and were assessed for correlations with fibrosis. LGE mural location was qualitatively assessed on a segmental basis for all subjects. PrePH patients had elevated (apical-, mid-antero-, and mid-infero) septal left ventricle native T1 values (1080 ± 74 ms, 1077 ± 39 ms, and 1082 ± 47 ms) compared to IpcPH patients (1028 ± 53 ms, 1046 ± 36 ms, 1051 ± 44 ms) (p < 0.05). PrePH had a higher amount of insertional point LGE (69%) and LGE patterns characteristic of non-vascular fibrosis (77%) compared to IpcPH (37% and 46%, respectively) (p < 0.05; p < 0.05). Assessment of global LGE, native T1, and ECV burdens did not show a statistically significant difference between PrePH (1.9 ± 2.7%, 1056.2 ± 36.3 ms, 31.2 ± 3.7%) and IpcPH (2.7 ± 2.7%, 1042.4 ± 28.1 ms, 30.7 ± 4.7%) (p = 0.102; p = 0.229 p = 0.756). Global native T1 and ECV were higher in patients (1050.9 ± 33.8 and 31.0 ± 4.1%) than controls (28.2 ± 3.7% and 1012.9 ± 29.4 ms) (p < 0.05). Cardiac MRI-based tissue characterization may augment understanding of cardiac involvement and become a tool to facilitate PH patient classification.

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Lee, Dong-Han, Vinesh Vijayan, Pierre Montaville, Stefan Becker et Christian Griesinger. « Sensitivity Enhancement of Methyl-TROSY by Longitudinal1H Relaxation Optimization ». Journal of the Korean Magnetic Resonance Society 13, n^o 1 (20 juin 2009) : 15–26. http://dx.doi.org/10.6564/jkmrs.2009.13.1.015.

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Cerantola, S., S. Faggin, V. Caputi, V. Cortese, A. Bosi, D. Banfi, A. Rambaldo et al. « P044 Enteric dopaminergic pathways in mouse and human intestinal inflammation ». Journal of Crohn's and Colitis 16, Supplement_1 (1 janvier 2022) : i160—i161. http://dx.doi.org/10.1093/ecco-jcc/jjab232.173.

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Abstract Background Changes in dopamine beta-hydroxylase (DBH) and anomalies in dopaminergic machinery have been shown in inflammatory bowel disease (IBD) patients and related animal models. Thus, we aimed to evaluate the dopaminergic pathways in IBD patients as well as in a mouse model of dextran sodium sulphate (DSS)-induced ileitis. Methods Colon biopsies (CB) obtained from healthy volunteers (N=3) and matched-IBD patients (N=3), were used to evaluate DBH immunoreactivity by confocal microscopy. Male C57/Bl6 (8±2 weeks old; N=16 mice) received 1.5% DSS in drinking water for 5 days, then switched to regular drinking water for 3 days. Inflammatory cytokines (IL-1β, TNFα, IL-6) were measured to assess ileitis severity. Changes in ileal muscle tension were isometrically recorded following 30 μM dopamine or 30 μM SKF38393 (a dopamine receptor 1 (D1R) agonist) or 30 μM bromocriptine (a D2R agonist). Immunofluorescence distribution of Iba1 (a macrophage specific marker), D1R, DBH and dopamine transporter (DAT) were determined in longitudinal muscle-myenteric plexus whole-mount preparations (LMMPs) by confocal microscopy. D1R and D2R mRNA transcripts were evaluated by qRT-PCR. Results CB from IBD patients and LMMPs from DSS mice showed a significant increase of DBH immunoreactivity compared to healthy patients and sham mice (+25% [p<0.01], +20% [p<0.01], respectively). DSS treatment caused a significant increase of DAT and D1R immunoreactivity as well as D1R mRNA levels (+27% [p<0.05], +24% [p<0.05], +6-fold [p<0.05], respectively), accompanied by a significant reduction of dopamine-mediated relaxation (-27% [p<0.01]). SKF38393 determined a marked inhibitory response in ileal preparations from DSS mice compared to sham mice (+73% [p<0.01]), suggesting that dopamine responses are mainly mediated through D1R. A 2-fold increase of resident Iba1+ macrophages was observed in the myenteric plexus of DSS mice associated with a 2.9- and 1.5-fold enhancement of IL-6 and IL-1β mRNA levels, respectively. Conclusion Human colitis and mouse ileitis affect dopamine machinery in the enteric nervous system. Experimentally induced ileitis impairs dopaminergic neurotransmission altering D1R-mediated responses. These findings provide novel information on the involvement of dopaminergic pathways in IBD.

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Bellomo, Giovanni, Enrico Ravera, Vito Calderone, Mauro Botta, Marco Fragai, Giacomo Parigi et Claudio Luchinat. « Revisiting paramagnetic relaxation enhancements in slowly rotating systems : how long is the long range ? » Magnetic Resonance 2, n^o 1 (29 janvier 2021) : 25–31. http://dx.doi.org/10.5194/mr-2-25-2021.

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Abstract. Cross-relaxation terms in paramagnetic systems that reorient rigidly with slow tumbling times can increase the effective longitudinal relaxation rates of protons of more than 1 order of magnitude. This is evaluated by simulating the time evolution of the nuclear magnetization using a complete relaxation rate-matrix approach. The calculations show that the Solomon dependence of the paramagnetic relaxation rates on the metal–proton distance (as r−6) can be incorrect for protons farther than 15 Å from the metal and thus can cause sizable errors in R1-derived distance restraints used, for instance, for protein structure determination. Furthermore, the chemical exchange of these protons with bulk water protons can enhance the relaxation rate of the solvent protons by far more than expected from the paramagnetic Solomon equation. Therefore, it may contribute significantly to the water proton relaxation rates measured at magnetic resonance imaging (MRI) magnetic fields in the presence of slow-rotating nanoparticles containing paramagnetic ions and a large number of exchangeable surface protons.

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Yue, Huan, Ji Ae Park, Son Long Ho, Mohammad Yaseen Ahmad, Hyunsil Cha, Shuwen Liu, Tirusew Tegafaw et al. « New Class of Efficient T2 Magnetic Resonance Imaging Contrast Agent : Carbon-Coated Paramagnetic Dysprosium Oxide Nanoparticles ». Pharmaceuticals 13, n^o 10 (15 octobre 2020) : 312. http://dx.doi.org/10.3390/ph13100312.

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Nanoparticles are considered potential candidates for a new class of magnetic resonance imaging (MRI) contrast agents. Negative MRI contrast agents require high magnetic moments. However, if nanoparticles can exclusively induce transverse water proton spin relaxation with negligible induction of longitudinal water proton spin relaxation, they may provide negative contrast MR images despite having low magnetic moments, thus acting as an efficient T2 MRI contrast agent. In this study, carbon-coated paramagnetic dysprosium oxide (DYO@C) nanoparticles (core = DYO = DyxOy; shell = carbon) were synthesized to explore their potential as an efficient T2 MRI contrast agent at 3.0 T MR field. Since the core DYO nanoparticles have an appreciable (but not high) magnetic moment that arises from fast 4f-electrons of Dy(III) (6H15/2), the DYO@C nanoparticles exhibited an appreciable transverse water proton spin relaxivity (r2) with a negligible longitudinal water proton spin relaxivity (r1). Consequently, they acted as a very efficient T2 MRI contrast agent, as proven from negative contrast enhancements seen in the in vivo T2 MR images.

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Oude Engberink, Raoul D., Erwin L. A. Blezer, Erik I. Hoff, Susanne M. A. van der Pol, Annette van der Toorn, Rick M. Dijkhuizen et Helga E. de Vries. « MRI of Monocyte Infiltration in an Animal Model of Neuroinflammation Using SPIO-Labeled Monocytes or Free USPIO ». Journal of Cerebral Blood Flow & ; Metabolism 28, n^o 4 (14 novembre 2007) : 841–51. http://dx.doi.org/10.1038/sj.jcbfm.9600580.

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Magnetic resonance imaging (MRI) has been applied to visualize monocyte infiltration with the use of intravenously injected ultrasmall superparamagnetic iron oxide (USPIO). However, USPIO uptake in vivo remains elusive, and the heterogeneous enhancement patterns observed by MRI point to multiple pathophysiological events. This study focused on specific imaging of monocyte infiltration into the brain by transfusion of superparamagnetic iron oxide (SPIO)-labeled monocytes in a rat model of neuroinflammation, experimentally induced photothrombosis (PT). At day 5 after lesion induction, animals were transfused with SPIO-labeled monocytes (5 × 106 cells) or free USPIO (17 mg Fe/kg). MRI was performed 24, 72 and, 120 h later. To investigate temporal changes directly after intravenous USPIO administration, MRI was performed repeatedly up to 8 h. Relaxation measurements showed that rat monocytes were efficiently labeled in vitro using SPIO ( R2=12±0.9 s−1). After transfusion of SPIO-labeled monocytes, a significant increase in contrast enhanced area (340%±106%) in the PT lesion was observed not before 72 h. Contrast enhancement after USPIO injection increased up to 407%±39% at a much earlier point of time (24 h) and diminished thereafter. Repetitive MRI directly after USPIO injection showed significant contrast enhancement in the lesion within 2 h. Our study shows that MRI enables in vivo tracking of SPIO-labeled monocytes longitudinally. Moreover, our data suggest that contrast enhancement after injection of free USPIO does not primarily represent signals from peripherally labeled monocytes that migrated toward the inflammatory lesion. The use of SPIO-labeled monocytes provides a better tool to specifically assess the time window of monocyte infiltration.

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Papathanassoglou, Elizabeth D. E., Yoanna Skrobik, Kathleen Hegadoren, Patrica Thompson, Henry Thomas Stelfox, Colleen Norris, Louise Rose et al. « Relaxation for Critically ill Patient Outcomes andStress-coping Enhancement (REPOSE) : a protocol for a pilot randomised trial of an integrative intervention to improve critically ill patients’ delirium and related outcomes ». BMJ Open 9, n^o 1 (janvier 2019) : e023961. http://dx.doi.org/10.1136/bmjopen-2018-023961.

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IntroductionDelirium is a common complication of critical illness, associated with negative patient outcomes. Preventive or therapeutic interventions are mostly ineffective. Although relaxation-inducing approaches may benefit critically ill patients, no well-designed studies target delirium prevention as a primary outcome. The objective of this study is to assess feasibility and treatment effect estimates of a multimodal integrative intervention incorporating relaxation, guided imagery and moderate pressure touch massage for prevention of critical illness delirium and for related outcomes.Methods and analysisRandomised, controlled, single-blinded trial with two parallel groups (1:1 allocation: intervention and standard care) and stratified randomisation (age (18–64 years and ≥65 years) and presence of trauma) with blocking, involving 104 patients with Intensive Care Delirium Screening Checklist (ICDSC): 0–3 recruited from two academic intensive care units (ICUs). Intervention group participants receive the intervention in addition to standard care for up to five consecutive days (or until transfer/discharge); control group participants receive standard care and a sham intervention. We will assess predefined feasibility outcomes, that is, recruitment rates and protocol adherence. The primary clinical outcome is incidence of delirium (ICDSC ≥4). Secondary outcomes include pain scores, inflammatory biomarkers, heart rate variability, stress and quality of life (6 weeks and 4 months) post-ICU discharge. Feasibility measures will be analysed descriptively, and outcomes will be analysed longitudinally. Estimates of effects will be calculated.Ethics and disseminationThe study has received approval from the Human Research Ethics Board, University of Alberta. Results will inform the design of a future multicentre trial.Trial registration numberNCT02905812; Pre-results.

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Anuhya, Dayal, Ngwa Andin, Rutt Brian, Natarajan Arutselvan et Chang Edwin. « Better neural images by combining ultrahigh field strength MRI with innovative MRI sequences ». Journal of Neurology, Neurological Science and Disorders 8, n^o 1 (15 octobre 2022) : 007–17. http://dx.doi.org/10.17352/jnnsd.000047.

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Better MRI scanning technologies and protocols can provide insights into neurological disorders. In this review, we describe the basic concepts of MRI and, in the process, we convey to the reader the relevance of MRI as a high-resolution imaging modality of tissue structure and metabolism. We outline the main parameters for improving MRI resolution and sensitivity for the ultimate goal of optimizing the diagnosis of neurological diseases. A key to obtaining high-resolution images by MRI is the strength of the magnet’s external field strength (Bo). The higher the field strength, the better the signal-to-noise (SNR) of acquired signals. Hence, this results in improved sensitivity and resolution of the reconstructed images. This article recapitulates the advancement of MRI technology towards Ultra-High-Field Strength (UHF) apparatus and the consequent benefits in SNR. Other keys towards improving MRI images include deftly modifying the parameters of longitudinal magnetization relaxation time (T1), transverse magnetization relaxation time (T2), repetition times between radiofrequency (RF) pulses (TR), and the time of reading post-pulse (TE). Such parameters can be controlled through acquisition software associated with the MRI machines. The review profiles the cumulative efforts by researchers to complement UHF-MRI hardware with innovative RF pulse sequences protocols such as Diffusion Weighted Imaging (DWI), Pulse Gradient Spin Echo (PGSE), Oscillating Gradient Spin Echo (OGSE), Blood Oxygen Level Dependent (BOLD)-MRI and Arterial Spin Label (ASL)-MRI. Collectively, these advances in both MRI hardware and software have pushed the field to attain a mesoscopic level of resolution. Further enhancements in analyzing MRI images through Artificial Intelligence (AI) algorithms may advance resolutions beyond the mesoscopic stage and perhaps even toward the microscopic resolution of living tissue.

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OBERER, Monika, Klaus ZANGGER, Stefan PRYTULLA et Walter KELLER. « The anti-toxin ParD of plasmid RK2 consists of two structurally distinct moieties and belongs to the ribbon-helix-helix family of DNA-binding proteins ». Biochemical Journal 361, n^o 1 (17 décembre 2001) : 41–47. http://dx.doi.org/10.1042/bj3610041.

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NMR and CD spectroscopy have been used to characterize, both structurally and dynamically, the 82-amino-acid ParD protein of the post-segregational killing module of the broad-host-range plasmid RP4/RK2. ParD occurs as a dimer in solution and exercises two different control functions; an autoregulatory function by binding to its own promoter PparDE and a plasmid-stabilizing function by inhibiting ParE toxicity in cells that express ParD and ParE. Analysis of the secondary structure based on the chemical-shift indices, sequential nuclear Overhauser enhancements (NOEs) and 3JHα-NH scalar coupling constants showed that the N-terminal domain of ParD consists of a short β-ribbon followed by three α-helices, demonstrating that ParD contains a ribbon-helix-helix fold, a DNA-binding motif found in a family of small prokaryotic repressors. 15N longitudinal (T1) and transverse (T2) relaxation measurements and hetero nuclear NOEs showed that ParD is divided into two separate domains, a well-ordered N-terminal domain and a very flexible C-terminal domain. An increase in secondary structure was observed upon addition of trifluoroethanol, suggested to result from the formation of structured stretches in the C-terminal part of the protein. This is the first experimental evidence that the DNA-binding domain of ParD belongs to the ribbon-helix-helix fold family, and this structural motif is proposed to be present in functionally similar antidote proteins.

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Nadaud, Philippe S., Ishita Sengupta, Jonathan J. Helmus et Christopher P. Jaroniec. « Evaluation of the influence of intermolecular electron-nucleus couplings and intrinsic metal binding sites on the measurement of 15N longitudinal paramagnetic relaxation enhancements in proteins by solid-state NMR ». Journal of Biomolecular NMR 51, n^o 3 (9 août 2011) : 293–302. http://dx.doi.org/10.1007/s10858-011-9536-y.

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Lapinskas, Tomas, Chiodi Elisabetta, Chrysanthos Grigoratos, Ricardo Ladeiras-Lopes, GJ Fent, E. Abdul Rahman, Jonathan Rodrigues et al. « VIEWING ONLY POSTERS1323Evaluation of right ventricular transverse strain and strain rate in patients with acute ST-segment elevation myocardial infarction : a cardiac magnetic resonance feature tracking study1333Cardiac resynchronization in ischemic heart failure patients : a comparison between therapy guided by cardiac magnetic resonance imaging and 2D-speckle tracking echocardiography1338Cardiac magnetic resonance versus bisphosphonate scintigraphy for diagnosis of cardiac amyloidosis1341Strain relaxation index, a novel tagged MRI-derived diastolic function parameter, is impaired in metabolic syndrome1349Global Longitudinal Strain Predicts Chronic Myocardial Infarction in Patients with Normal Ejection Fraction1352Optimal Dose Of Dobutamine During Low-Dose Dobutamine Stress Echocardiography In Correctly Identify Viable Segments On Cardiovascular Magnetic Resonance1368Absolute wall thickening and left ventricular ejection fraction–a unifying theory of myocardial contraction and heart failure?1376Transient St Elevation in Acs Like Myocarditis1379Patients after Fontan with a “total cavopulmonary connection” Fontan modification develop more collateral flow compared to “old-fashioned” Fontan modifications1387A MRI–derived 3D patient specific model for fibrosis quantification in atrial fibrillation1391Scar burden and survival in patients with ischemic cardiomyopathy and poor LV ejection fraction1392Relation of inflammatory markers with myocardial and microvascular injury in patients with reperfused ST- elevation myocardial infarction1406Equivalence of segmented conventional and fast single-shot late gadolinium enhancement (LGE) techniques for1410Cardiac Mri Appearances of Tuberculosis - A Review of Varied Presentations in India1415Atheroma burden, cardiac remodelling and epicardial fat : A comparison between healthy South Asian and European adults using Whole Body Cardiovascular MR1418Symptomatic Ventricular Arrhythmias : Diagnostic Yield of Cardiac Magnetic Resonance1421CMR assessment of aortic stiffness in asymptomatic low risk patients with type 2 diabetes mellitus1436Shock index as a predictor of myocardial damage and clinical outcome in ST-elevation myocardial infarction1451Combined biomarker testing for the prediction of microvascular obstruction after primary percutaneous coronary intervention for acute ST-segment elevation myocardial infarction1452A novel oscillometric technique compared with cardiac magnetic resonance for the assessment of aortic pulse wave velocity in ST-segment elevation myocardial infarction1456Aorto-pulmonary collaterals evaluated by CMR is associated to reduced “effective” cardiac index late after Fontan palliation1458Evaluation of pulmonary transit time and Pulmonary Blood Volume with first-pass perfusion CMR imaging in adult with repaired Congenital Heart disease1459Prognostic value of the cardiac magnetic resonance as a predictor of improvement in ventricular function after TakoTsubo syndrome1462Diagnostic performance of ECG detection of left atrial enlargement in patients with arterial hypertension relative to the cardiac magnetic resonance gold-standard : impact of obesity1463Utility of cardiac magnetic resonance imaging for diagnosis of cardiac sarcoidosis and prediction of therapeutic effects in patients with complete heart block and implanted magnetic resonance-conditional pacemaker : A multicenter study1467Cardiac magnetic resonance late gadolinium enhancement in patients with genetic dilated cardiomyopathy14712.Left ventricular hypertrophy in hypertensive patients–comparison of Cardiac Magnetic Resonance and Echocardiographic analysis of morphological and functional LV-parameters1472Is Angiographic Perfusion Score assessed in patients with acute myocardial infarction correlated with Cardiac Magnetic Resonance infarct size and N-terminal pro-brain natriuretic peptide in 6-month follow-up1476Cardiac Magnetic Resonance Patterns of Left Ventricular Diastolic Function In Hypertrophic Cardiomyopathy1477Impact of platelet volume on thrombus burden and tissue reperfusion in patients with STEMI treated with primary angioplasty : MRI study1479Right ventricle systolic function assessment and its prognostic implications in cardiac amyloidosis1484Cardiac MRI - an important tool in the evaluation of multsystemic inflamatory diseases. An Erdheim-Chester Disease case report1485Predictive value of cardiac magnetic resonance for future adverse cardiac events in patients with ST-segment elevation myocardial infarction1486Time-to-treatment but not thrombectomy influence infarct size and microvascular obstruction in patients with acute ST-segment elevation myocardial infarction treated with primary coronary intervention1489Primary PCI versus Early Routine Post Fibrinolysis PCI for ST Elevation Myocardial Infarction1490Evaluation of ventricular function in Fontan patients undergoing feature tracking magnetic resonance strain1491Impacts of atrialized right ventricle and left ventricular displacement in Ebstein's anomaly on left ventricular function assessed by cardiovascular MRI1494Final diagnosis for patients presenting with chest pain, electrocardiographic changes or troponin rise and normal coronary arteries : insights from Cardiovascular MRI in our population1495Early Predictive Factors of LV Remodeling after STEMI ; Assessment by Coronary Angiogram and Cadiovascular Magnetic Resonance1497The Pathobiologic Mechanisms and the Prognostic Meaning of t wave Inversion in Acute Myocarditis. a Study Performed by Cardiac Magnetic Resonance1501The Influence of Left Atrial Function on Exercise Tolerance in Patients with Heart Failure and Preserved Ejection Fraction : A Cardiac Magnetic Resonance Feature Tracking Study1504Microvascular Obstruction in Patients with Anterior ST-Elevation Myocardial Infarction who Underwent Primary Percutaneous Coronary Intervention : Predictors and Impact on the Left Ventricular Function1508Histological Validation of ECV Quantification by Cardiac Magnetic Resonance T1 Mapping in Cardiac Amyloidosis1513Comparative Evaluation of Flow Quantification Across the Atrioventricular Valve in Patients with Functional Univentricular Heart After Fontan's Surgery and Healthy Controls : Measurement by 4D Flow Magnetic Resonance Imaging and Streamline Visualization1515Does arterial switch for d-transposition of the great arteries alter myocardial deformation of the ventricles?1527Accuracy of T1 Mapping by multi-professional CMR operators to predict myocardial infarct1531Detecting hypertensive heart disease : the additive value of cardiovascular magnetic resonance imaging1534Diagnostic Performance of Cardiac Magnetic Resonance Strain Parameters in Assesment of Myocardial Ischemia1535Relationships between left ventricular filling pressures and longitudinal dysfunction with myocardial fibrosis in uncomplicated hypertensive patients1539Predictive Clinical Factors of Tissue Damage Severity in Reperfused Acute Myocardial Infarction as Visualized by Cardiac Magnetic Resonance1541Which CMR derived parameter predicts better the need of invasive treatment in aortic coarctation?1543Contrast-enhanced magnetic resonance tomography in patients with supraventricular tachyarrhythmias1546Prognostic Value of CMR Imaging Biomarkers on Outcome in Peripheral Arterial Disease : a 6-year Follow-up Pilot Study1549Dobutamine-Stress-CMR in Young Adults after Arterial Switch Operation as Neonates1553Impact of posteromedial papillary muscle infarction on mitral regurgitation after ST-segment elevation myocardial infarction1556Role of cardiac magnetic resonance imaging in assessment of left ventricular hypertrophy1569Using intrinsic Cardiac Shear Waves to measure Myocardial Stiffness : Preliminary results from Patients with Heart failure with preserved Ejection Fraction1571Relationship of cerebrovascular reactivity and MRI pattern of carotid atherosclerotic plaque1577Feasibility study of an MR conditional pedal ergometer for cardiac stress MRI–preliminary results in healthy volunteers and patients with suspected coronary artery disease1581Pulmonary valve replacement for severe pulmonary stenosis has a positive effect on left ventricular remodeling1582The RV after cardiac surgery, more resilient than thought : multiparametric quantification shows altered rather than reduced function1584Usefulness of cardiovascular magnetic resonance to differentate coronary artery disease from non ischemic cardiomyoptathy in patients with heart failure1593What does CMR add to the ESC Risk Prediction Model to Assess the Occurrence of Sudden Cardiac Death in Patients with HCM?1597Detecting Progression of Diffuse Interstitial Fibrosis in Alstrom Syndrome1612Diffuse fibrosis in the ventricles of patients with transposition of great arteries late after atrial switch1631Utility of Cardiac Magnetic Resonance in the diagnosis and stratification of arrhythmic risk in patients with confirmed or suspected ventricular arrhythmias1635Size matters : pulmonary veins geometry by cardiac magnetic resonance imaging in atrial fibrillation patients1642How do the differences in Left Ventricular wall measurements from Echocardiography and CMR in patients with Hypertrophic Cardiomyopathy affect current Sudden Cardiac Death Risk Scores?1651Noninvasive assessment of intracardiac viscous energy loss in Fontan patients from 4D Flow CMR1653Behcet and Myocardial Infarction : A Rare Combination1328Impact of New Cerebral Ischemic Lesions On the Occurrence of Delirium after Transcatheter Aortic Valve Implantation1329Heart T2* assessment to measure iron overload using different software tools in patients with Thalassemia Major1332Hypertrabeculated Left Ventricle at Cardiac Magnetic Resonance Imaging : β-Thalassemia Major vs. Left Ventricular Non -Compaction Disease1335Aortic Regurgitation following Transcatheter Aortic Valve Implantation (TAVI) : a CMR Study of two prosthesis designs1336Incremental value of semi-quantitative evaluation of myocardium perfusion with 3T stress cardiac MRI1343Left ventricular morphological quantification with single shot and free-breathing SSFP cine imaging compared with standard breath-hold SSFP cine imaging1344Changes of cardiac iron and function during pregnancy in transfusion-dependent thalassemia patients1346Significant improvement of survival by T2* MRI in thalassemia major1350The impact of trans-catheter aortic valve implantation induced left-bundle branch block on cardiac reverse remodelling1351Value of magnetic resonance myocardial perfusion imaging in patients with indeterminate coronary computed tomography angiography results1353Gender differences in response to Transcatheter Aortic Valve implantation in patients with severe aortic stenosis assessed by feature tracking1354A qualitative assessment of first-pass perfusion bolus timings in the assessment of myocardial ischemia : A magnetic resonance study1355MRI prospective survey on cardiac iron and function and on hepatic iron in non transfusion-dependent thalassemia intermedia patients treated with desferrioxamine or non chelated1358Coronary Calcification Compromises Myocardial Perfusion Irrespective of Luminal Stenosis1359Non–contrast three–dimensional magnetic resonance imaging for pre–procedural assessment of aortic annulus dimensions in patients undergoing transcatheter aortic valve implantation1360“Systolic ventricularization” of the left atrium with bileaflet mitral valve prolapse : impact on quantification of mitral regurgitation1361CMR assessment of left ventricular remodeling 6 months after percutaneous edge-to-edge repair using Mitraclip1363Accuracy of Transthoracic Echocardiography (TTE) in comparison with Cardiac Magnetic Resonance (CMR)1374CMR for myocardial iron overload assessment : a new calibration curve from the MIOT project1381Can Speckle Tracking Imaging Reveal Myocardial Iron Overload in Thalassemia Major ? A Combined Echocardiography and Cardiac Magnetic Resonance Study1382Native myocardial T1 mapping in patients with pulmonary hypertension and age matched volunteers1384A Insidious Line Between Thalassemia Intermedia And Left Ventricular Non-Compaction Disease : The Role Of Cardiac Magnetic Resonance1388Pulmonary Artery : Ascending Aorta Diameter - An Important and Easily Measureable Prognostic Parameter1394Novel carotid artery ultrasound index–Extra-media thickness and a well-established cardiac magnetic resonance fat quantification method1403Validation of CMR-derived LVOT diameters against direct in-vivo measurements1409Early myocardial perfusion measured by CMR in acute myocardial infarction treated by primary PCI–a postconditioning study1420Assessment of paravalvular aortic regurgitation after transcatheter aortic valve implantation using cardiac magnetic resonance imaging : a comparative study with echocardiography and angiography1422Left atrial strain measured by feature tracking predicts left ventricular end diastolic filling pressure1426Validation of extracellular volume equation by serial cardiac magnetic resonance imaging measurements in patients with varying hematocrit1427Assessing diastolic function applying Cardiovascular Magnetic Resonance - comparison with the gold standard1475Role of Adenosine Stress Cardiac Mri in the Setting of Chronic Total Occlusion of Coronary Arteries1520Aortic Elasticity Indexes by Magnetic Resonance Predict Progression of Ascending Aorta Dilation1522Combined atrioventricular assessment of diastolic function by cardiac magnetic resonance1537Safety, image quality and clinical utility of cardiac magnetic resonance in patients with antiarrhythmic devices1538Usefulness of cardiac magnetic resonance to predict the need for surgical procedures in patients with mitral regurgitation1550Normal T1, T2, T2* and extracellular volume reference values in healthy volunteers at 3 Tesla cardiac magnetic resonance1551Comprehensive intra-ventricular myocardial deformation strain analysis in healthy volunteers : implications for regional myocardial disease processes1557Elastic properties changes of aorta in patients with dilatation of the ascending aorta evaluated by Magnetic Resonance1558The prevalence of active myocarditis assessed by cardiovascular magnetic resonance in patients with clinically suspected myocarditis1563Quantitative assessment of myocardial scar heterogeneity using texture analysis to risk stratify post–MI patients for ICD insertion1564Gender differences in exercise capacity and LV remodeling in response to pressure overload in aortic stenosis1572Myocardial wall stress as a novel CMR measure to assess cardiac function1573Feature tracking cardiac magnetic resonance to assess LV mechanics in pressure and volume overload1574Safety, feasibility and clinical impact of Cardiovascular Magnetic Resonance in patients with MR-conditional devices1576T1 Mapping at 1-Year Following Aortic Valve Replacement : Baseline Geometry Defines Magnitude of Fibrosis Regression1583Normal values of LV global myocardial mechanics using two and three-dimensional cardiovascular magnetic resonance1585Prediction of infarct transmurality in acute myocardial infarction based on cardiac magnetic resonance deformation analysis1595Measuring invasive blood pressure by catheters guided solely by Cardiovascular Magnetic Resonance by using a new guidewire without the need of a hybrid CMR-fluoroscopy suite1599Influence of active and passive cardiac implants on CMR image quality : results from a consecutive patient series1600Reproducibility of aortic 4D flow measurements in healthy volunteers1601An automatic approach to extract 4D flow hemodynamic markers : application in BAV-affected patients1602Global myocardial mechanics with 2 and 3-Dimensional cardiovascular magnetic resonance feature tracking in patients with myocarditis1603A CMR-based clinician-friendly assessment of in vivo left ventricle hemodynamics1604Reproducibility of left atrial strain using cardiovascular magnetic resonance myocardial feature tracking1605The severity of myocardial infarction in STEMI, determined by transmurality of infarct and infarct characteristics, impacts on myocardial T2 values1606MicroRNA as potential biomarkers of acute myocardial damage following STEMI1607Myocardial blush grade is associated with microvascular obstruction on CMR following STEMI16084D Flow CMR imaging : Comparison of conventional parallel imaging and variable density k-t acceleration1609In-vitro comparison of segmented-gradient-echo versus non-segmented echo planar imaging 4D Flow CMR : validation of flow volume and 3D vortex ring assessment1614Not just 2D but also 4D flow measurements in pulsatile phantom are accurate and reproducible1615Diffusion Tensor Imaging : Comparison of Hypertrophic Cardiomyopathy, Hypertension and Healthy Cohorts1624Impact of myocardial fibrosis measured by cardiac magnetic resonance imaging on reverse left ventricular remodelling after transcatheter aortic valve implantation1625Prosthetic valve regurgitation after transcatheter aortic valve implantation with new-generation devices compared to surgical aortic valve replacement–a cardiac magnetic resonance imaging flow measurement analysis1637Assessment of Aortic and Pulmonary Artery stiffness in Patients with COPD using Cardiac Magnetic Resonance1638Myocardial Mechanics implications using 2D Cardiovascular Magnetic Resonance in Aortic Regurgitation1639Delineation of myocardial infarction & ; viability by 12 lead ECG vs cardiac magnetic resonance1641Regional variation in native T1 values in normal healthy volunteers?1645Feasibility of myocardial strain assessment using tissue tracking at 3.0T CMR following ST-segment elevation myocardial infarction1648Diagnostic Impact of Cardiac Magnetic Resonance in patients with acute chest pain, troponin elevation and no significant angiographic coronary artery disease ». European Heart Journal – Cardiovascular Imaging 17, suppl 1 (mai 2016) : i37—i84. http://dx.doi.org/10.1093/ehjci/jew183.

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Kuzin, Sergei, Gunnar Jeschke et Maxim Yulikov. « Diffusion equation for the longitudinal spectral diffusion : the case of the RIDME experiment ». Physical Chemistry Chemical Physics, 2022. http://dx.doi.org/10.1039/d2cp03039j.

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Relaxation-induced dipolar modulation enhancement (RIDME) time trace shapes reveal linear scaling with the proton concentration in homogeneous glassy samples. We describe here an approximate diffusion equation-based analysis of such data,...

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Blystad, I., J. B. M. Warntjes, Ö. Smedby, P. Lundberg, E. M. Larsson et A. Tisell. « Quantitative MRI using relaxometry in malignant gliomas detects contrast enhancement in peritumoral oedema ». Scientific Reports 10, n^o 1 (22 octobre 2020). http://dx.doi.org/10.1038/s41598-020-75105-6.

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Abstract Malignant gliomas are primary brain tumours with an infiltrative growth pattern, often with contrast enhancement on magnetic resonance imaging (MRI). However, it is well known that tumour infiltration extends beyond the visible contrast enhancement. The aim of this study was to investigate if there is contrast enhancement not detected visually in the peritumoral oedema of malignant gliomas by using relaxometry with synthetic MRI. 25 patients who had brain tumours with a radiological appearance of malignant glioma were prospectively included. A quantitative MR-sequence measuring longitudinal relaxation (R1), transverse relaxation (R2) and proton density (PD), was added to the standard MRI protocol before surgery. Five patients were excluded, and in 20 patients, synthetic MR images were created from the quantitative scans. Manual regions of interest (ROIs) outlined the visibly contrast-enhancing border of the tumours and the peritumoral area. Contrast enhancement was quantified by subtraction of native images from post GD-images, creating an R1-difference-map. The quantitative R1-difference-maps showed significant contrast enhancement in the peritumoral area (0.047) compared to normal appearing white matter (0.032), p = 0.048. Relaxometry detects contrast enhancement in the peritumoral area of malignant gliomas. This could represent infiltrative tumour growth.

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Lin, Shangchao, Zhuangli Cai, Yang Wang, Lingling Zhao et Chenxi Zhai. « Tailored morphology and highly enhanced phonon transport in polymer fibers : a multiscale computational framework ». npj Computational Materials 5, n^o 1 (décembre 2019). http://dx.doi.org/10.1038/s41524-019-0264-2.

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AbstractAlthough tremendous efforts have been devoted to enhance thermal conductivity in polymer fibers, correlation between the thermal-drawing conditions and the resulting chain alignment, crystallinity, and phonon transport properties have remained obscure. Using a carefully trained coarse-grained force field, we systematically interrogate the thermal-drawing conditions of bulk polyethylene samples using large-scale molecular dynamics simulations. An optimal combination of moderate drawing temperature and strain rate is found to achieve highest degrees of chain alignment, crystallinity, and the resulting thermal conductivity. Such combination is rationalized by competing effects in viscoelastic relaxation and condensed to the Deborah number, a predictive metric for the thermal-drawing protocols, showing a delicate balance between stress localizations and chain diffusions. Upon tensile deformation, the thermal conductivity of amorphous polyethylene is enhanced to 80% of the theoretical limit, that is, its pure crystalline counterpart. An effective-medium-theory model, based on the serial-parallel heat conducting nature of semicrystalline polymers, is developed here to predict the impacts from both chain alignment and crystallinity on thermal conductivity. The enhancement in thermal conductivity is mainly attributed to the increases in the intrinsic phonon mean free path and the longitudinal group velocity. This work provides fundamental insights into the polymer thermal-drawing process and establishes a complete process–structure–property relationship for enhanced phonon transport in all-organic electronic devices and efficiency of polymeric heat dissipaters.

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Yan, Chengxi, Ruili Li, Xiaojuan Guo, Huan Yu, Wenhuan Li, Wenqiao Li, Meiji Ren, Minglei Yang et Hongjun Li. « Cardiac Involvement in Human Immunodeficiency Virus Infected Patients : An Observational Cardiac Magnetic Resonance Study ». Frontiers in Cardiovascular Medicine 8 (15 novembre 2021). http://dx.doi.org/10.3389/fcvm.2021.756162.

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Objectives: To investigate the subclinical imaging changes in terms of myocardial inflammation and fibrosis and to explore the risk factors associated with myocardial fibrosis by cardiac magnetic resonance (CMR) approach in a Chinese HIV/AIDS cohort.Methods: We evaluated myocardial function (cine), myocardial inflammation (T1, T2), and myocardial fibrosis (through extracellular volume fraction [ECV] and late gadolinium enhancement [LGE]) by a multiparametric CMR scan protocol in a total of 68 participants, including 47 HIV-infected individuals, who were divided into two groups: asymptomatic HIV (HIV+) (n = 30), and acquired immunodeficiency syndrome (AIDS) (n = 17), and 21 healthy controls.Results: HIV-infected patients had lower left (55.3 ± 6.5 vs. 63.0 ± 7.9%, P < 0.001) and right ventricular systolic function (35.9 ± 15.7 vs. 50.8 ± 9.3%, P < 0.001). Radial systolic strain (30.7 ± 9.3 vs. 39.3 ± 9.4%, P = 0.001), circumferential systolic strain (−17.5 ± 2.6 vs. −19.4 ± 2.7%, P = 0.008), and longitudinal systolic strain (−9.4 ± 5.7 vs. −12.8 ± 3.1%, P = 0.012) were also decreased in HIV. Native T1 relaxation time (1,337.2 ± 70.2 vs. 1,249.5 ± 47.0 ms, P < 0.001), ECV value (33.5 ± 6.2 vs. 28.5 ± 2.9 ms, P = 0.026), and T2 relaxation time (45.2 ± 3.5 vs. 42.0 ± 2.6 ms, P = 0.001) were higher in HIV-infected patients compared with controls. Myocardial fibrosis, predominantly in the mid-inferior wall, was detected in 24.4% of the HIV-infected patients. HIV+ had a significantly lower value of ECV [29.1 (26.1, 31.8) vs. 35.2 (31.8, 41.9) %, P < 0.001] and frequency of LGE [3/25 (8%) vs. 7/16 (43.8%), P = 0.014)] compared with AIDS. AIDS was associated with myocardial fibrosis.Conclusions: HIV-infected patients were associated with changes in myocardial function and higher rates of subclinical myocardial inflammation and fibrosis, which were more abnormal with greater severity of the disease. AIDS was associated with myocardial fibrosis, where the observations supported earlier initiation of antiretroviral therapy in the Chinese HIV/AIDS cohort.

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Gatterer, Constantin, Tim Wollenweber, Verena Pichler, Chrysoula Vraka, Gere Sunder-Plassmann, Max Lenz, Christian Hengstenberg et al. « Detection of sympathetic denervation defects in Fabry disease by hybrid [11C]meta-hydroxyephedrine positron emission tomography and cardiac magnetic resonance ». Journal of Nuclear Cardiology, 28 février 2023. http://dx.doi.org/10.1007/s12350-023-03205-7.

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Abstract Background Myocardial glycosphingolipid accumulation in patients with Fabry disease (FD) causes biochemical and structural changes. This study aimed to investigate sympathetic innervation in FD using hybrid cardiac positron emission tomography (PET)/magnetic resonance imaging (MRI). Methods and results Patients with different stages of Fabry disease were prospectively enrolled to undergo routine CMR at 1.5T, followed by 3T hybrid cardiac PET/MRI with [11C]meta-hydroxyephedrine ([11C]mHED). Fourteen patients with either no evidence of cardiac involvement (n = 5), evidence of left ventricular hypertrophy (LVH) (n = 3), or evidence of LVH and fibrosis via late gadolinium enhancement (LGE) (n = 6) were analyzed. Compared to patients without LVH, patients with LVH or LVH and LGE had lower median T1 relaxation times (ms) at 1.5 T (1007 vs. 889 vs. 941 ms, p = 0.003) and 3T (1290 vs. 1172 vs. 1184 p = .014). Myocardial denervation ([11C]mHED retention < 7%·min) was prevalent only in patients with fibrosis, where a total of 16 denervated segments was found in two patients. The respective area of denervation exceeded the area of LGE in both patients (24% vs. 36% and 4% vs. 32%). However, sympathetic innervation defects ([11C]mHED retention ≤ 9%·min) occurred in all study groups. Furthermore, a reduced sympathetic innervation correlated with an increased left ventricular mass (p = .034, rs = − 0.57) and a reduced global longitudinal strain (GLS) (p = 0.023, rs = − 0.6). Conclusion Hybrid cardiac PET/MR with [11C]mHED revealed sympathetic innervation defects, accompanied by impaired GLS, in early stages of Fabry disease. However, denervation is only present in patients with advanced stages of FD showing fibrosis on CMR.

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Kim, Eugene, Davide Di Censo, Mattia Baraldo, Camilla Simmons, Ilaria Rosa, Karen Randall, Clive Ballard et al. « In vivo multi-parametric manganese-enhanced MRI for detecting amyloid plaques in rodent models of Alzheimer’s disease ». Scientific Reports 11, n^o 1 (14 juin 2021). http://dx.doi.org/10.1038/s41598-021-91899-5.

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AbstractAmyloid plaques are a hallmark of Alzheimer’s disease (AD) that develop in its earliest stages. Thus, non-invasive detection of these plaques would be invaluable for diagnosis and the development and monitoring of treatments, but this remains a challenge due to their small size. Here, we investigated the utility of manganese-enhanced MRI (MEMRI) for visualizing plaques in transgenic rodent models of AD across two species: 5xFAD mice and TgF344-AD rats. Animals were given subcutaneous injections of MnCl2 and imaged in vivo using a 9.4 T Bruker scanner. MnCl2 improved signal-to-noise ratio but was not necessary to detect plaques in high-resolution images. Plaques were visible in all transgenic animals and no wild-types, and quantitative susceptibility mapping showed that they were more paramagnetic than the surrounding tissue. This, combined with beta-amyloid and iron staining, indicate that plaque MR visibility in both animal models was driven by plaque size and iron load. Longitudinal relaxation rate mapping revealed increased manganese uptake in brain regions of high plaque burden in transgenic animals compared to their wild-type littermates. This was limited to the rhinencephalon in the TgF344-AD rats, while it was most significantly increased in the cortex of the 5xFAD mice. Alizarin Red staining suggests that manganese bound to plaques in 5xFAD mice but not in TgF344-AD rats. Multi-parametric MEMRI is a simple, viable method for detecting amyloid plaques in rodent models of AD. Manganese-induced signal enhancement can enable higher-resolution imaging, which is key to visualizing these small amyloid deposits. We also present the first in vivo evidence of manganese as a potential targeted contrast agent for imaging plaques in the 5xFAD model of AD.

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Wang, Xiaoming, Shiwei Guo, Zhiqian Li, Qiang Luo, Yan Dai, Hu Zhang, Yun Ye, Qiyong Gong et Kui Luo. « Amphiphilic branched polymer-nitroxides conjugate as a nanoscale agent for potential magnetic resonance imaging of multiple objects in vivo ». Journal of Nanobiotechnology 19, n^o 1 (9 juillet 2021). http://dx.doi.org/10.1186/s12951-021-00951-z.

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Abstract Background In order to address the potential toxicity of metal-based magnetic resonance imaging (MRI) contrast agents (CAs), a concept of non-metallic MRI CAs has emerged. Currently, paramagnetic nitroxides (such as (2,2,5,5-tetramethylpyrrolidine-1-oxyl, PROXYL), (2,2,6,6-tetramethylpiperidine-1-oxide, TEMPO), etc.) are being extensively studied because their good stability and imaging mechanism are similar to metal-based contrast agents (such as Gd3+ chelate-based clinical CAs). However, a lower relaxivity and rapid in vivo metabolism of nitroxides remain to be addressed. Previous studies have demonstrated that the construction of macromolecular nitroxides contrast agents (mORCAs) is a promising solution through macromolecularization of nitroxides (i.e., use of large molecules to carry nitroxides). Macromolecular effects not only increase the stability of nitroxides by limiting their exposure to reductive substances in the body, but also improve the overall 1H water relaxation by increasing the concentration of nitroxides and slowing the molecular rotation speed. Results Branched pDHPMA-mPEG-Ppa-PROXYL with a high molecular weight (MW = 160 kDa) and a nitroxides content (0.059 mmol/g) can form a nanoscale (~ 28 nm) self-assembled aggregate in a water environment and hydrophobic PROXYL can be protected by a hydrophilic outer layer to obtain strong reduction resistance in vivo. Compared with a small molecular CA (3-Carboxy-PROXYL (3-CP)), Branched pDHPMA-mPEG-Ppa-PROXYL displays three prominent features: (1) its longitudinal relaxivity (0.50 mM− 1 s− 1) is about three times that of 3-CP (0.17 mM− 1 s− 1); (2) the blood retention time of nitroxides is significantly increased from a few minutes of 3-CP to 6 h; (3) it provides long-term and significant enhancement in MR imaging of the tumor, liver, kidney and cardiovascular system (heart and aortaventralis), and this is the first report on nitroxides-based MRI CAs for imaging the cardiovascular system. Conclusions As a safe and efficient candidate metal-free magnetic resonance contrast agent, Branched pDHPMA-mPEG-Ppa-PROXYL is expected to be used not only in imaging the tumor, liver and kidney, but also the cardiovascular system, which expands the application scope of these CAs. Graphical abstract

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Wong, C. Y. « P873 A rare and potentially treatable cause of left ventricular hypertrophy ». European Heart Journal - Cardiovascular Imaging 21, Supplement_1 (1 janvier 2020). http://dx.doi.org/10.1093/ehjci/jez319.517.

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Abstract Introduction A 67-year-old man was referred for care of "asymptomatic hypertrophic cardiomyopathy". He did not have hypertension. No significant positive family history could be elicited. Electrocardiogram showed sinus rhythm with voltage criteria of left ventricular hypertrophy (LVH). Outside Transthoracic Echocardiogram (TTE) reported normal ejection fraction with asymmetric septal hypertrophy without outflow obstruction. He was put on observation for few years and was not any treatment. On first encounter in our clinic, physical examination including skin and eye assessment, and laboratory tests including renal function were unremarkable. Procedure TTE was repeated in our clinic showing normal left ventricular size with ejection fraction 55%, and impaired diastolic relaxation. There was asymmetric septal hypertrophy with septal thickness 2.1 cm (Figure A). There was mild systolic anterior motion of mitral apparatus and mild mitral regurgitation, without resting or Valsalva provoked outflow obstruction. Global longitudinal strain was -7.7% with most prominent abnormalities seen at apex, mid to basal anteroseptal and anterior wall (Figure B). Further assessment by Cardiac MRI showed similar asymmetric septal wall thickening. Late gandolinium enhancement study demonstrated patchy fluffy hyperenhancement of the mid wall of the basal to mid anteroseptal segment, and mid to apical anterior segment, suggestive of myocardial fibrosis (Figure C1 and C2). Dried spot blood was sent to Taiwan for enzyme study which revealed partial acid alpha-galactosidase A deficiency. Further genetic study detected a mutation of Hemizygous NM_000169.2(GLA):c.640-801[G > A] at intron 4. Finally endomyocardial biopsy was done which confirmed the cardiac involvement of Fabry disease (Figure D, myelin body shown under electron microscopy). This gentleman was referred for consideration of Enzyme Replacement Therapy (ERT). Discussion Fabry disease is an X-linked glycolipid storage disease with accumulation of globotriaosylceramide in lysosomes in multiple cell types throughout the body leading to various organ involvement. Cardiac manifestations include unexplained LVH, valvular regurgitation, conduction abnormalities etc. It occurs in up to 0.3-5% of patients with hypertrophic cardiomyopathy. Fabry disease should be considered as a differential diagnosis in all men with sporadic or non-autosomal dominant transmission of unexplained LVH, since treatment with ERT is available which may reduce LVH and improve myocardial function, although any impact on long term outcome has not yet been established. Conclusion This case illustrated a rare but potentially treatable cause of hypertrophic cardiomyopathy. Myocardial strain imaging should be integrated in routine TTE study for assessment of unexplained left ventricular hypertrophy. Multi-modality imaging and multi-specialty approach help in identifying patients of cardiac variant of Fabry disease who may benefit from ERT. Abstract P873 Figure.

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Pavon, A., M. Guglielmo, D. Arangalage, M. Bonanni, G. Angelini, V. Paiocchi, L. Leo et al. « Additional value of CMR feature tracking parameters for the evaluation of the risk of complex ventricular arrhythmias and sudden cardiac death in patients with Mitral Valve Prolapse ». European Heart Journal - Cardiovascular Imaging 23, Supplement_1 (1 février 2022). http://dx.doi.org/10.1093/ehjci/jeab289.372.

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Abstract Funding Acknowledgements Type of funding sources: None. Background Mitral valve prolapse (MVP) with mitro-annular disjunction (MAD) has been associated with complex ventricular arrhythmias (c-VA) and sudden cardiac death (SCD) but risk stratification in this subset of patients remains insufficiently characterized. The aim of this study was to investigate the association between deformation parameters assessed by feature tracking (FT) cardiac magnetic resonance (CMR) in patients with MVP and MAD (MVP-MAD) and c-VA and/or SCD. Methods We included 23 patients (47 ± 13 years; 43 % males) with MVP-MAD, of whom 17 (74 %) presented with c-VA and 6 (26%) with SCD, as well as 20 age- and sex-matched controls (50 ± 18 years; 57% males). All patients underwent CMR with assessment of MAD length, late gadolinium enhancement (LGE), extracellular volume (ECV), global and regional longitudinal (LS), and circumferential strain (CS). RATIO-CS was defined as the ratio between regional CS in the basal inferolateral and mid-inferolateral walls (fig.1). Results In MVP-MAD patients, non-ischemic LGE of the LV inferior and inferolateral wall was observed in 21 patients (50%). As compared to controls, MVP-MAD patients showed lower global LS (-18.7 ±4.1 vs -24.7 ± 5.7 p < 0.001), higher native T1 relaxation time and ECV of the left ventricle (LV) inferolateral wall (1104 ± 63ms vs 1083 ± 66ms p < 0.029 and 0.31 ± 0.03 vs 0.27 ± 0.04 p 0.003), lower CS and LS of the LV mid and inferolateral segments (p < 0.005). Logistic univariate regression analysis showed an increased risk of c-VA in case of LGE presence (OR: 9.52 [2.28-39.7] p = 0.002), a high number of LV segments with LGE (OR: 1.78 [1.21-2.63] p = 0.004), GLS (OR: 1.58 [1.21-2.07] p < 0.001), decreased inferolateral mid ventricular wall CS (OR: 1.41 [1.16-1.72] p < 0.001), decreased basal and mid-ventricular inferolateral wall LS (OR: 1.11 [1.00-1.23] p = 0.047 and OR: 1.62 [1.22-2.13] p < 0.001 respectively), increased native T1 times (OR: 1.01 [1.00-1.02] p = 0.039), increased ECV of the basal infero-lateral wall (OR: 4.93e + 07 [1.22-1.98e + 15] p = 0.047) and decreased RATIO-CS (OR: 7.48 [1.87-30.00] p = 0.005) (table 1). In multivariate analysis the presence of a lower LS in the basal inferolateral wall remained an independent predictor of c-VA (OR: 1.62 [1.22-2.13.00] p = 0.0007) and RATIO-CS remained an independent predictor of SCD (OR: 7.73 [1.78-33.60] p = 0.006). Conclusion Lower inferolateral LS and RATIO CS are respectively associated with c-VA and SCD in MVP-MAD patients. FT may provide additional value for risk stratification on top of standard CMR parameters in this subset of patients. Abstract Figure. fig.1 Abstract table 1

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