Magnetic Resonance Characterization Research Articles

Two-dimensional longitudinal and transverse relaxation time correlation as a low-resolution nuclear magnetic resonance characterization of ancient ceramics

Longitudinal and transverse relaxation time correlation (T1-T2) is employed as a nuclear magnetic resonance noninvasive characterization tool for archeological ceramics. This paper is aimed at investigating whether the most relevant firing-induced changes in ceramics, including those involving pore space properties and paramagnetic mineral structures, could be used as markers of the firing process and therefore of ceramics themselves. Ancient ceramics are made up of naturally available clays, often rich in iron impurities, which undergo relevant modifications of pore distribution upon firing. The firing process also assists chemical and physical rearrangement of iron-bearing species, yielding mineral structures with different magnetic properties. That being so, T1-T2 maps are expected to show the interdependence between ceramic structure and firing technology. T1 and T2 distributions are basically proportional to pore-size distribution, but T2, which is also sensitive to magnetic susceptibility effects, may give information on the porous matrix composition as well. Such a methodology has first been employed on laboratory-prepared ceramic samples, with different paramagnetic compositions and controlled firing temperatures, in order to tackle the problem of model-ceramic selection. Then, the T1-T2 correlation approach has been used on medieval ceramic findings in order to get information about their thermal and compositional history. The information obtained by means of two-dimensional correlation maps proves coherent with archeological dating, thus illustrating the capabilities of this method.

Self-Assembling DNA Quadruplex Conjugated to MRI Contrast Agents

We report the preparation and magnetic resonance (MR) characterization of new MRI contrast agents based on gadolinium complexes conjugated to a self-assembling DNA quadruplex scaffold. As a single gadolinium-DOTA chelated DNA strand, the r(1) molar relaxivity is 6.4 mM(-1) s(-1) per Gd and increases to 11.7 mM(-1) s(-1) per Gd upon formation of a DNA quadruplex. Similar results were obtained when a gadolinium-DOTA dendrimer was conjugated to DNA, with the r(1) molar relaxivity increasing to 12.9 mM(-1) s(-1) per Gd upon the formation of DNA quadruplex, compared to that of 6.0 mM(-1) s(-1) for a single strand of gadolinium-DOTA dendrimer chelate. This yields an r(1) molar relaxivity of 154.8 and 46.8 mM(-1) s(-1) per DNA quadruplex based on DOTA dendrimer or monomer, respectively. Importantly, the DNA quadruplex scaffold is approximately 2.5 nm(3) in size, potentially enabling this type of contrast agent to be used for targeted delivery in vivo to detect specific cells or tissues, even behind intact blood vessels.

Nuclear magnetic resonance characterization of metabolite disorder in orange trees caused by citrus sudden death disease

Citrus sudden death (CSD) is a new disease of sweet orange and mandarin trees grafted on Rangpur lime and Citrus volkameriana rootstocks. It was first seen in Brazil in 1999, and has since been detected in more than four million trees. The CSD causal agent is unknown and the current hypothesis involves a virus similar to Citrus tristeza virus or a new virus named Citrus sudden death-associated virus. CSD symptoms include generalized foliar discoloration, defoliation and root death, and, in most cases, it can cause tree death. One of the unique characteristics of CSD disease is the presence of a yellow stain in the rootstock bark near the bud union. This region also undergoes profound anatomical changes. In this study, we analyse the metabolic disorder caused by CSD in the bark of sweet orange grafted on Rangpur lime by nuclear magnetic resonance (NMR) spectroscopy and imaging. The imaging results show the presence of a large amount of non-functional phloem in the rootstock bark of affected plants. The spectroscopic analysis shows a high content of triacylglyceride and sucrose, which may be related to phloem blockage close to the bud union. We also propose that, without knowing the causal CSD agent, the determination of oil content in rootstock bark by low-resolution NMR can be used as a complementary method for CSD diagnosis, screening about 300 samples per hour.

Complete multinuclear magnetic resonance characterization of a set of polyfluorinated acids and alcohols

A complete (1)H, (19)F, and (13)C NMR assignment of a homologous series of polyfluorinated acids and alcohols is reported. These assignments were obtained chiefly through single and multiple-bond (1)H-(13)C and (19)F-(13)C correlation experiments (HSQC, HMBC). (19)F NOESY experiments were required for assignment of two compounds with diastereotopic (19)F nuclei in the CF(2)chain of the molecule.

Cardiac and Liver Magnetic Resonance Characterization of Thalassemia Intermedia Patients: A Comparative Multicenter Study Versus Thalassemia Major Patients

Little is known about cardiac involvement in Thalassemia Intermedia (TI) using magnetic resonance imaging (MRI). Thus, we investigated myocardial and liver iron overload, myocardial fibrosis, biventricular function parameters and their inter-relationship in 60 TI using MRI. Then, we compared the data of 35 selected TI with age < 39 years with that of 60 Thalassemia Major (TM) patients matched for age. Myocardial Iron Overload (MIO) was assessed using a multislice multiecho T2* approach. Biventricular function parameters were measured quantitatively by cine images. Myocardial fibrosis was evaluated by late gadolinium-enhanced. MIO was present in the 22% of TI patients, more frequently (92%) with an heterogeneous distribution. TI patients with myocardial fibrosis (32%) showed significantly reduced left ventricular ejection fraction (LVEF) (P=0.01). No significant correlation was found between myocardial fibrosis and MIO. Figure shows a TI patient with no myocardial iron overload (all 16 segments and the mid-ventricular septum with T2* values > 20 ms) (A) and late enhancement (white arrows) in the antero-septal junction, in the infero-septal junction and in the mid-ventricular septum (B). In TI patients MIO was significantly lower respect to TM patients; conversely volumes, cardiac indexes, LVEF, bi-atrial areas, and liver iron overload were significantly higher. Myocardial fibrosis was comparable between the 2 groups. TI patients showed lower myocardial iron burden and more pronounced high cardiac output findings with myocardial fibrosis significantly associated to impaired heart function. These data seem to suggest using MRI also for TI patients and could place the basis to reconsider the current cardiological and haematological management in this population. [Display omitted]

Phosphorus in Poultry Litter and Soil: Enzymatic and Nuclear Magnetic Resonance Characterization

Knowledge of the P forms in poultry litter (PL) and their transformations in soil will help improve our understanding of the long‐term role of P in eutrophication. In this study, samples of PL and pasture soils with and without 20 yr of PL application were sequentially extracted to separate P into H2O, 0.5 mol L−1 NaHCO3, 0.1 mol L−1 NaOH, and 1 mol L−1 HCl fractions. After appropriate dilution and pH adjustment, the fractions were incubated in the presence of orthophosphate‐releasing enzymes. Cross‐examination of the solution 31P nuclear magnetic resonance spectra of the enzymatically treated and untreated fractions revealed that the peaks of organic P (Po) species of the enzymatically treated fractions became very weak or disappeared, confirming enzymatic hydrolysis of Po in the untreated fractions. Although the majority of P in the NaOH and HCl fractions of PL was in organic forms, these stable Po forms could be subjected to enzymatic hydrolysis after being applied to soil, an occurrence that was supported by the soil P data. Compared with soil without litter applied, 20 yr of PL application increased the pools of both labile and stable inorganic P in the soil; however, repeated application of PL did not lead to a significant accumulation of hydrolyzable Po in NaOH and HCl fractions, indicating that the stable Po must have been converted to other forms. The transformation of stable PL Po observed in this study could be an important mechanism for maintaining a balance between labile and immobile P in soils.

Zinc-Induced Formation of a Coactivator Complex Containing the Zinc-Sensing Transcription Factor MTF-1, p300/CBP, and Sp1

Herein, the mechanisms of transactivation of gene expression by mouse metal response element-binding transcription factor 1 (MTF-1) were investigated. Evidence obtained from coimmunoprecipitation assays revealed that exposure of the cells to zinc resulted in the rapid formation of a multiprotein complex containing MTF-1, the histone acetyltransferase p300/CBP, and the transcription factor Sp1. Down-regulation of endogenous p300 expression by small interfering RNA transfection significantly decreased zinc-dependent metallothionein I (MT-I) gene transcription without altering induction of zinc transporter 1 (ZnT1). MTF-1 independently facilitated the recruitment of Sp1 and p300 to the protein complex in response to zinc. Mutagenesis demonstrated that the acidic domain, one of three transactivation domains of MTF-1, is required for recruitment of p300 but not Sp1 as well as for zinc-dependent activation of MT-I gene transcription. Furthermore, mutation of leucine residues (L-->A) within a nuclear exclusion signal in the MTF-1 acidic domain impaired recruitment of p300 and zinc-dependent activation of the MT-I gene. Nuclear magnetic resonance characterization of an isolated protein fragment corresponding to the MTF-1 acidic region demonstrated that this region is largely unstructured in the presence and absence of excess stoichiometric amounts of zinc. This suggests that the mechanism by which MTF-1 recruits p300 to this complex involves extrinsic-zinc-dependent steps. These studies reveal a novel zinc-responsive mechanism requiring an acidic region of MTF-1 that functions as a nuclear exclusion signal as well as participating in formation of a coactivator complex essential for transactivation of MT-I gene expression.

Cardiovascular Magnetic Resonance Characterization of Mitral Valve Prolapse

This study sought to develop cardiovascular magnetic resonance (CMR) diagnostic criteria for mitral valve prolapse (MVP) using echocardiography as the gold standard and to characterize MVP using cine CMR and late gadolinium enhancement (LGE)-CMR. Mitral valve prolapse is a common valvular heart disease with significant complications. Cardiovascular magnetic resonance is a valuable imaging tool for assessing ventricular function, quantifying regurgitant lesions, and identifying fibrosis, but its potential role in evaluating MVP has not been defined. To develop CMR diagnostic criteria for MVP, characterize mitral valve morphology, we analyzed transthoracic echocardiography and cine CMR images from 25 MVP patients and 25 control subjects. Leaflet thickness, length, mitral annular diameters, and prolapsed distance were measured. Two- and three-dimensional LGE-CMR images were obtained in 16 MVP and 10 control patients to identify myocardial regions of fibrosis in MVP. We found that a 2-mm threshold for leaflet excursion into the left atrium in the left ventricular outflow tract long-axis view yielded 100% sensitivity and 100% specificity for CMR using transthoracic echocardiography as the clinical gold standard. Compared with control subjects, CMR identified MVP patients as having thicker (3.2 +/- 0.1 mm vs. 2.3 +/- 0.1 mm) and longer (10.5 +/- 0.5 mm/m(2) vs. 7.1 +/- 0.3 mm/m(2)) indexed posterior leaflets and larger indexed mitral annular diameters (27.8 +/- 0.7 mm/m(2) vs. 21.5 +/- 0.5 mm/m(2) for long axis and 22.9 +/-0.7 mm/m(2) vs. 17.8 +/- 0.6 mm/m(2) for short axis). In addition, we identified focal regions of LGE in the papillary muscles suggestive of fibrosis in 10 (63%) of 16 MVP patients and in 0 of 10 control subjects. Papillary muscle LGE was associated with the presence of complex ventricular arrhythmias in MVP patients. Cardiovascular magnetic resonance image can identify MVP by the same echocardiographic criteria and can identify myocardial fibrosis involving the papillary muscle in MVP patients. Hyperenhancement of papillary muscles on LGE is often present in a subgroup of patients with complex ventricular arrhythmias.

Selective isolation of in vitro phase II conjugates using a lipophilic anionic exchange solid phase extraction method

Identification, characterization and structure elucidation of human metabolites of drug candidates is crucial for the pharmaceutical industry to assess their activity against the therapeutic target of interest and potential toxicological effects. It often requires in vitro synthesis of microgram quantities of metabolites of interest with enzymatic preparations, pre-concentration of the reaction mixture by solid phase extraction (SPE), metabolite isolation using HPLC systems coupled to fraction collectors prior to nuclear magnetic resonance characterization. The method reported herein is a rapid and simple technique using solely off-line mixed phase anionic exchange lipophilic SPE cartridges to selectively isolate glucuronide and sulfate metabolites from their parent compound. This approach capitalizes on the p Ka differences between the parent compound, devoided of acidic moieties, and the negatively charged glucuronide and/or sulfate metabolites. Once loaded on the SPE cartridge, the incubation mixture is washed successively with a basic aqueous solution, methanol to elute the non-anionic parent compounds, and then with an acidic methanolic solution to protonate and recover the phase II conjugates. Over 100 μg (>95% purity) of 17α-ethynylestradiol-3-glucuronide and 6-gingerol-4′-glucuronide were successfully isolated using this technique, as well as glucuronide and a sulfate conjugates of 1-{4′-[(1 R)-2,2-difluoro-1-hydroxyethyl]biphenyl-4-yl}cyclopropanecarboxamide (DHBC) synthesized in-house. Their structures were confirmed by Ultra Performance Liquid Chromatography coupled to Quadrupole-Time of flight (UPLC-QTof) and nuclear magnetic resonance analysis.

Cardiovascular magnetic resonance characterization of a hamartoma in an asyntomatic child

Background The prevalence of primary cardiac neoplasms is approximately 0.3% and these masses should be distinguished from many of other primary and secondary processes that can occur in the heart. Further assessment of the left ventricular mass presents important clinical implications. Cardiovascular magnetic resonance was used. Clinical case An asyntomatic 12-year-old child was referred for cardiovascular magnetic resonance imaging to further assess a left ventricular mass found after an echocardiography, executed for assessment for sport activity. His past medical history was absolutely negative. The patient was in optimal state of health. The EKG showed an aspecific ST elevation. A hamartoma was diagnosed. A surgical approach was performed. After 7 days the patient is in good condition.

Solid-state nuclear magnetic resonance characterization of PE–PEG/silica hybrid materials prepared by microwave-assisted sol-gel process

Organic–inorganic hybrid materials were prepared by sol-gel processes starting from tetraethoxysilane (TEOS) and a triethoxysilane-terminated polyethylene–b-poly(ethylene glycol) copolymer (PE–PEG–Si). Curing of the initial reactant solution was carried out under different reaction conditions, and the materials so obtained were investigated by solid-state nuclear magnetic resonance (NMR). In particular, the molecular structure resulting from a conventional oven heating was compared with that obtained by unconventional microwave heating. The results highlighted that the extent of condensation reactions occurring over several hours under conventional heating is very similar to that resulting in 1 min under microwave heating. Additionally, 29Si–magic angle spinning (MAS) spectra showed that even though the overall extent of cross-linking in the inorganic network is only slightly affected by the thermal history of the sample, significantly different distributions of silicon sites can be present. 13C–CP/MAS selective spectra revealed the presence of PE “crystalline” domains within the organic phase, not detectable by differential scanning calorimetry (DSC). Finally, 1H–MAS spectra showed that different hydrogen-bond interactions are present in samples obtained under different curing conditions.

Steroidal isomers with uniform mass spectra of their per-TMS derivatives: Synthesis of 17-hydroxyandrostan-3-ones, androst-1-, and -4-ene-3,17-diols

In human sports doping control analysis most of the steroids are analyzed after enzymatic hydrolysis of the glucuronides as per-trimethylsilyl (TMS) derivatives applying gas chromatography–mass spectrometry (GC–MS). According to the recommendations of the World Anti-Doping Agency the identification of analytes should be based on retention time and on mass spectrometric characterization. This study shows that the bis-TMS derivatives of 16 specific C19 steroids, namely the stereoisomers of 5ξ-androst-1-ene-3ξ,17ξ-diol (8 isomers), androst-4-ene-3ξ,17ξ-diol (4 isomers), and 17ξ-hydroxy-5ξ-androstan-3-one (4 isomers), reveal very similar mass spectra. As a rule, when taking the retention times, which are provided as Kovac indices for all these isomers, into account, a restriction to two or three possible isomers is possible. Reliable identification should additionally include a comparison of the retention times of the analytes with the reference compounds measured concomitantly. In some cases standard addition may be appropriate. Due to the limited availability, the above mentioned isomers were synthesized by reduction of the corresponding α,β-unsaturated oxo steroids either with K-Selectride or by catalytic hydrogenation (Pd/C as catalyst). The products of the reactions were identified by means of nuclear magnetic resonance (NMR) characterization and by further reduction to the corresponding 5ξ-androstane-3ξ,17ξ-diols and GC–MS comparison with commercially available reference standards.

Proton Nuclear Magnetic Resonance Characterization of Resins from the Family Pinaceae

Proton magnetic resonance spectra were recorded for solutions of resinous materials harvested from 82 species in seven genera of the gymnospermous plant family Pinaceae. Data were recorded in both one and two (COSY) dimensions. Approximately 11 peaks in the 1D spectra and 10 cross-peaks in the 2D spectra were present in almost all pinacean spectra, providing a familial diagnostic. Some 40 1D peaks or peak clusters and 60 2D cross-peaks or clusters were considered significant and are reported, when present, for all species. Whereas previous solid-state 13C data were diagnostic primarily at the family level, the patterns of 1D and 2D peaks may provide diagnostic information at the genus and species levels. These spectra constitute the first broad use of 1H NMR to study plant exudates in general and to provide taxonomic characterization in particular.

Natural Weathering Evaluation of LDPE‐Mango Starch Blends by Mechanical Properties and High Field NMR

AbstractThe low‐density polyethylene/mango starch blends were obtained and submitted a natural degradation. Their mechanical properties and structures changes were determined by tensile, low and high field nuclear magnetic resonance characterization after different weathering times. The exposition time and starch content could be correlated to the polymer matrix changes from void formation theories. The blend deformations were affected by the starch degradation time. The starch degradation, confirmed by nuclear magnetic resonance, could be able to form voids and improve the blends fragmentability at relative low weathering times.

Low- and high-resolution nuclear magnetic resonance (NMR) characterisation of hyaluronan-based native and sulfated hydrogels

Hyaluronan-based hydrogels were synthesised using different crosslinking agents, such as 1,3-diaminopropane (1,3-DAP) and 1,6-diaminohexane (1,6-DAE). The hydrogels were sulfated to provide materials (Hyal-1,3-DAP, Hyal-1,6-DAE, HyalS-1,3-DAP and HyalS-1,6-DAE) that were characterised by both high- and low-resolution nuclear magnetic resonance (NMR) spectroscopy. The 13C NMR spectra of the materials were analysed to identify, characterise and study the crosslinking degree of the hydrogels. The crosslinking degree was also determined by potentiometric titration and the effectiveness of the two techniques was compared. Measurements of longitudinal relaxation times (spin–lattice) and of NOE enhancement were used to study the mobility of the hydrogels. Low-resolution NMR studies allowed the determination of the water transport properties in the hydrogels. In addition, the swelling degree for the various hydrogels was calculated as a function of the longitudinal and transversal relaxation times of the water molecules. Lastly, the self-diffusion coefficients of the water in interaction with the four polysaccharides were measured by the pulsed field gradient spin echo (PFGSE) sequence.

13Carbon nuclear magnetic resonance characterization of ethylene–propylene–1-octadecene terpolymers and comparison with ethylene–propylene–1-hexene and 1-decene terpolymers

In this paper, we report the complete 13C NMR characterization of a set of ethylene–propylene–1-octadecene terpolymers obtained with the metallocenic system rac-ethylene bis-indenyl zirconium dichloride, using different comonomer ratios. A detailed study of 13C NMR chemical shifts, triad sequence distributions, monomer average sequence lengths and reactivity ratios for these terpolymers is presented. The incorporations of 1-octadecene were superior of those obtained using 1-hexene and 1-decene in the same conditions. Catalytic activities of terpolymers of ethylene–propylene and α-olefins (α-olefins:1-hexene, 1-decene and 1-octadecene) were compared showing that they increase with the amount of propylene in the feed.

Magnetic Resonance Imaging and Characterization of Spontaneous Lesions in a Transgenic Mouse Model of Tuberous Sclerosis as a Model for Endothelial Cell-Based Transgene Delivery

Tuberous sclerosis (TSC) is an autosomal dominant genetic disorder characterized by abnormalities in cellular migration, proliferation, and differentiation in many tissues. Benign hamartomas develop in multiple organs, believed to be caused by somatic mutation in addition to germ line mutation to cause loss of both alleles of either the TSC1 or TSC2 tumor suppressor gene, with resultant dysregulated growth due to loss of hamartin or tuberin function, respectively. This study focuses on detecting spontaneous lesions in a knockout mouse model of TSC2 by magnetic resonance imaging (MRI) and exploring the efficiency of introducing gene products into lesions, using transduced endothelial cells as gene vehicles. MRI was shown to be effective in detecting spontaneous lesions in multiple tissues as a means of assessing the prevalence of tumors. Tsc(2+/) heterozygous mice were screened at 12-24 months of age. MRI detected 100% of the renal lesions (cystadenomas, renal cell carcinomas) and 75% of the hepatic lesions (hemangiosarcomas), later identified by histology. Cell-mediated gene delivery was evaluated by immunohistochemical analysis of renal, hepatic, and lung lesions after intravenous delivery of MS1 mouse endothelial cells, transduced to express an enhanced form of green fluorescent protein (EGFP). Preliminary immunohistochemical analysis, using a polyclonal antibody to EGFP and a horseradish peroxidase-diaminobenzidine detection system, revealed these cells throughout liver, kidney, and lung sections from injected animals, organs that are frequently affected in TSC2 patients, as well as within the lesions themselves.

Magnetic resonance characterization of tumor microvessels in experimental breast tumors using a slow clearance blood pool contrast agent (carboxymethyldextran-A2-Gd-DOTA) with histopathological correlation

Carboxymethyldextran (CMD)-A2-Gd-DOTA, a slow clearance blood pool contrast agent with a molecular weight of 52.1 kDa, designed to have intravascular residence for more than 1 h, was evaluated for its potential to characterize and differentiate the microvessels of malignant and benign breast tumors. Precontrast single-slice inversion-recovery snapshot FLASH and dynamic contrast-enhanced MRI using an axial T1-weighted three-dimensional spoiled gradient recalled sequence was performed in 30 Sprague-Dawley rats with chemically induced breast tumors. Endothelial transfer coefficient and fractional plasma volume of the breast tumors were estimated from MRI data acquired with CMD-A2-Gd-DOTA enhancement injected at a dose of 0.1 mmol Gd/kg body weight using a two-compartment bidirectional model of the tumor tissue. The correlation between MRI microvessel characteristics and histopathological tumor grade was determined using the Scarff-Bloom-Richardson method. Using CMD-A2-Gd-DOTA, no significant correlations were found between the MR-estimated endothelial transfer coefficient or plasma volumes with histological tumor grade. Analysis of CMD-A2-Gd-DOTA-enhanced MR kinetic data failed to demonstrate feasibility for the differentiation of benign from malignant tumors or for image-based tumor grading.

Isolated Ventricular Non-Compaction in Adults With Idiopathic Cardiomyopathy: Cardiac Magnetic Resonance and Pathologic Characterization of the Anomaly

Non-compaction of the ventricular myocardium is an anomaly of myocardial morphogenesis that leads to persistence of the embryonic myocardium with an excessively prominent trabecular meshwork and deep intertrabecular recesses. This report describes 3 cases of isolated left ventricular non-compaction in adults leading to terminal heart failure. We describe their distinctive myocardial histopathology and prospective diagnosis by cardiac magnetic resonance imaging (CMR). Heart transplantation was the only treatment option for all 3 of these severely ill patients. Isolated ventricular non-compaction should be considered in patients with severe idiopathic cardiomyopathy whose symptoms appear in early adulthood, and consideration given for early transplantation. Non-invasive imaging with CMR can confirm the diagnosis.

Characterization of brain tumors by MRS, DWI and Ki-67 labeling index

With the advent of fast imaging hardware and specialized software, additional non-invasive magnetic resonance characterization of tumors has become available through proton magnetic resonance spectroscopy (MRS), hemodynamic imaging and diffusion-weighted imaging (DWI). Thus, patterns could be discerned to discriminate different types of tumors and even to infer their possible evolution in time. The purpose of this study was to investigate the correlation between MRS, DWI, histopathology and Ki-67 labeling index in a large number of brain tumors. Localized proton spectra were obtained in 47 patients with brain tumors who subsequently underwent surgery (biopsy or tumor removal). We performed MRS with short echo-time (30 ms) and metabolic values in spectra were measured using an external software with 25 peaks. In all patients who had DWI, we measured apparent diffusion coefficients (ADC) in the same region of interest (ROI) where the voxel in MRS was located. In most tumors the histological diagnosis and Ki-67 labeling index had been determined on our original surgical specimen. Cho/Cr, (Lip+Mm)/Cr, NAA/(Cho+Cr) and Glx/Cr indexes in MRS allowed discriminating between low- and high-grade gliomas and metastases (MTs). Likewise, absolute ADC values differentiated low- from high-grade gliomas expressed by Ki-67 labeling index. A novel finding was that high Glx/Cr in vivo MRS index (similar to other known indexes) was a good predictor of tumor grading.