bluuebunny/crossref_metadata_2025_split huggingface dataset:
A nuclear magnetic resonance investigation of the upper airways in ferrets. ii. contrast‐enhanced imaging to distinguish vascular from other nasal fluids
Authors: Reo Nicholas V. , Alexander Marise E. , Goel Rashmi 
Published: March 2007

AbstractProton magnetic resonance imaging (MRI), used in conjunction with the intravascular contrast agent albumin‐(Gd‐DTPA), provides a means to distinguish vascular fluids from other nasal fluids in the upper airways. Ferrets were given an intravenous dose of albumin‐(Gd‐DTPA) followed by an intranasal challenge with either histamine (HS) or methacholine (MC). An observed increase in image intensity indicates that HS and MC both cause an accumulation of fluids in the nasal turbinate region. The MRI data are also influenced by the presence of blood, which contains the contrast agent, and a clear distinction can be made between vascular fluids and other nasal fluids (i.e., cellular and glandular secretions). The results show that HS causes an increase in vascular fluids in the nasal turbinates while MC does not. This methodology represents a new means to investigate airway pharmacology and the pathophysiology associated with various pharmacological agents, allergens, or viral infections.
The design of liposomal paramagnetic mr agents: effect of vesicle size upon the relaxivity of surface‐incorporated lipophilic chelates
Authors: Tilcock Colin , Ahkong Quet Fah , Koenig Seymour H. , Brown Rodney D. , Davis Mark , Kabalka George 
Published: March 2007

AbstractThe 1/T1 NMRD profiles of lipid vesicles with the paramagnetic ion Gd attached via a chelate covalently linked to the membrane surface show a peak at approximately 20 MHz indicating that fluctuations of ∼10−8 contribute to the form of the dispersion profile. If the correlation time for fluctuations of the paramagnetic chelate on the membrane surface is much less than the correlation time for rotation of the lipid vesicle, it would be expected that the measured 1/T1 relaxation rate for solvent protons should be invariant with vesicle size above a certain minimum vesicle diameter. We show that this is indeed the case for vesicles in the size range 50 to 400 nm average diameter and discuss general design considerations for the preparation of vesicle‐associated MR contrast agents based upon paramagnetic chelates either trapped within the vesicle interior or attached to the membrane surface.
Characteristics of extracellular sodium relaxation in perfused hearts with pathologic interventions
Authors: Foy Brent D. , Burstein Deborah 
Published: March 2007

AbstractSodium spectroscopy and imaging sequences designed to emphasize fast T2 decay or the multiple quantum signal have previously demonstrated a high contrast between normal and pathologic tissue which may be due to changes in intracellular versus extracellular sodium distribution. Since alterations in the amount of signal with fast T2 decay have previously been shown to occur with changes in intracellular sodium content, this study investigated the fast T2 relaxation characteristics of extracellular sodium during pathologic interventions on nonsubmerged perfused rat hearts. T2 data on total sodium content were obtained while global ischemia (stopping all perfusate flow) and extracellular edema (due to long perfusion times) were induced in the heart. The data were fit to a biexponential, with Mf (T2f) the magnitude (time constant) of the fast component of decay. Mf increased significantly in both pathologies (to 319 ± 26%, n = 3, of baseline for ischemia and to 527 ± 284%, n = 3, of baseline for edema); the increase with edema was demonstrated to be due to extracellular sodium by intermittently perfusing the heart for a short period with shift reagent. When shift reagent was not used until the conclusion of the edema experiment, Mr increased to 169 ± 35% of baseline, also due mainly to extracellular sodium. T2f did not exhibit any trends with these experiments, with values ranging from 1.7 to 5.5 ms. We believe that these results indicate that compartmental sodium content will most likely not be quantifiable in pathologic states in the heart with relaxation‐based techniques. However, correlations between the pathologic state of the tissue and the sodium NMR signal obtained with pulse sequences or images that emphasize a particular aspect of relaxation may prove to be Useful.
Nuclear magnetic relaxation dispersion profiles of aqueous solutions of a series of gd(nota) analogs
Authors: Geraldes Carlos F. G. C. , Brown Rodney D. , Brucher Erno , Koenig Seymour H. , Sherry A. Dean , Spiller Marga 
Published: March 2007

AbstractNuclear magnetic relaxation dispersion (NMRD) profiles and ESR linewidths have been measured for a series of neutral Gd3+ ‐triazamacrocyclic complexes and compared with previous data for the simplest member of the macrocyclic triaza series, Gd(NOTA), and for the widely studied linear triaza complex, Gd(DTPA)2‐. Water proton relaxivities and their temperature dependence were found to vary widely with the size of the triaza macrocycle and the identity of the side‐chain chelating groups. The number of rapidly exchanging water molecules directly coordinated to the Gd3+ ion (q) was found to vary from 2 to 4 for eight of the ten complexes examined and a linear relationship between the 50‐MHz relaxivity value and integral values of q is presented for this series of complexes. τs values derived from ESR linewidths for some of the complexes are in reasonable agreement with those derived from their NMRD profiles; however, those complexes which either tended to form aggregates in solution or gave evidence for multiple averaged solution structures showed broad, near Lorentzian linewidths which were clearly not dominated by the electron spin relaxation time (τs).
Changes in probe sensitivity during nmr spectroscopic studies of the perfused rat heart: a warning
Authors: Nédélec Jean‐François , Saunders John K. , Morris Paul , Clarke Kieran 
Published: March 2007

AbstractDuring NMR experiments on isolated, perfused rat heart, we observed a 57% change in probe sensitivity when the perfusion buffer surrounding the heart was replaced by either a low‐ionic‐strength mannitol solution or air and the heart was made ischemic. Such changes in sensitivity, should they go unrecognized, would result in substantial quantification errors.
A simple procedure for obtaining high‐quality nmr spectra of semiquantitative value from small tissue specimens: cervical biopsies.
Authors: Kuesel Annette C. , Kroft Thérèse , Saunders John K. , Préfontaine Michel , Mikhael Nadia , Smith Ian C. P. 
Published: March 2007

AbstractThe handling of small tissue biopsy samples (<100 μl) for NMR investigations poses special problems. Optimal and stable positioning of the samples within the sensitive volume of the radiopfrequency coil can be achieved by inserting the sample in a capillary. Methods for quantitation of the spectral information from samples requiring histological evaluation after the NMR experiment are discussed, in particular with respect to cervical biopsies.
NMR Venography Using the Susceptibility Effect Produced by Deoxyhemoglobin
Authors: Cho Z. H. , Ro Y. M. , Lim T. H. 
Published: March 2007

AbstractA new angiography technique using the susceptibility effect is proposed. Blood containing deoxyhemoglobin is more paramagnetic than surrounding tissue and thereby produces a susceptibility effect at blood‐tissue interfaces. By use of a specially tailored RF pulse, signals from normal tissues are suppressed while the signals from blood interfaces, where strong susceptibility‐induced fields are created, are enhanced. The design and characteristic behavior of the tailored RF pulse are discussed and experimental results obtained using both a phantom and a human volunteer with a 2.0‐T whole‐body NMR system are also presented.© 1992 Academic Press,Inc.
Phasing Spin‐Echo‐Acquired 31P Spectroscopic Images Using Complex Conjugate Data Reversal
Authors: Bourgeois Dominique , Deslauriers Roxanne 
Published: March 2007

AbstractA simple method has been developed for phasing 31P spectroscopic images acquired with short echo‐time (1–2 ms) spin‐echo sequences. The technique is based on reconstructing complete echoes in the time domain by the reversal of the complex conjugate of the data. After Fourier analysis, a magnitude reconstruction is used, which no longer broadens the lines. Advantages of the method compared to other phasing procedures are discussed.© 1992 Academic Press,Inc.
Feasibility of 19F Imaging of Perfluorochemical Emulsions to Measure Myocardial Vascular Volume
Authors: Judd Robert M. , Rottman Gerald A. , Forder John R. , Yin Frank C. P. , Blackband Stephen J. 
Published: March 2007

Abstract19F magnetic resonance images were obtained of the ventricular walls of isolated rabbit hearts perfused with a perfluorochemical (PFC) emulsion. Since the PFC is known to stay within the vascular space in normal myocardial tissue, the 19F signal should reflect myocardial vascular volume. 19F MRI of PFC emulsions represents a new investigational tool for the study of coronary vascular volume.© 1992 Academic Press,Inc.
Sodium Ion Transport in Rat Hearts during Cold Ischemic Storage: 23Na and 31P NMR Study
Authors: Askenasy Nadir , Vivi Antonio , Tassini Maria , Navon Gil 
Published: March 2007

AbstractThe success of heart transplantation is limited by the negative correlation between the length of the cold ischemic storage period and the quality of functional recovery. We use 23Na, 31P NMR spectroscopy, and hemodynamic parameters to describe temperature‐dependent changes in sodium influx and the concentration of phosphorus high‐energy compounds during different storage periods. Perfusion with Krebs—Henseleit solutions containing Dy(TTHA)3‐ permitted discrimination of intra‐ and extracellular sodium during cold ischemic storage. The 23Na NMR visibilities under the acquisition and processing parameters used in our experiments were 40 ± 4% for the intracellular compartment and 97 ± 11% for the extracellular compartment. At 4°C, the intracellular Na+ accumulation exceeded that observed at 15 and 22°C. The ATP and PCr depletion rates were much lower at 4°C and the left ventricular contractility was higher after longer periods of storage, as the storage temperature decreased. The intracellular Na+ concentration cannot serve as a marker for the postischemic recovery probability. The relative activity of the Na/K ATPase pumps is not correlated with the preservation success. However, intracellular sodium ion accumulation is a major factor in the time lag of the reperfusion recovery.© 1992 Academic Press,Inc.
Simultaneous Imaging of Proton and Fluorine at Moderate Field
Authors: Lou Th. , Briguet A. , Deguin A. , Desgoutte P. , Lapray C. 
Published: March 2007

AbstractSimultaneous imaging of proton and fluorine nuclei distributed in a unique sample has been performed by multiplexing the receiver coil's frequency for nmr signal acquisition. Implementation of the technique and modifications of a conventional spectrometer are described for operating at 0.13 T.© 1992 Academic Press,Inc.
Simultaneous measurement of intracellular and extracellular oxygen concentrations using a nitroxide‐liposome system
Authors: Glockner James F. , Norby Shong‐Wan , Swartz Harold M. 
Published: March 2007

AbstractThe concentration of oxygen within cells is important in many physiological and pathological processes, but such oxygendependent phenomena are generally studied as a function of the concentration of extracellular oxygen, due to a lack of suitable methods. Electron parmamagnetic resonance (EPR) oximetric techniques offer an attractive alternative to make such measurements. Previous EPR oximetric studies of extracellular‐intracellular oxygen gradients have been hindered, however, by the fact that separate samples, prepared in slightly different ways, were required for individual measurements of extracellular and intracellular oxygen concentrations. In this study we demonstrate a technique that allows simultaneous measurement of intracellular and extracellular oxygen concentrations in a single sample: extracellular measurement is achieved using positively charged nitroxides encapsulated in liposomes, while intracellular oxygen is determined using a membrane‐permeable nitroxide along with an extracellular broadening agent. Application of this system to the measurement of oxygen concentrations in suspensions of rat myoblast cells gave results which are consistent with nonsimultaneous measurements and which show substantial extracellular‐intracellular oxygen gradients in these rapidly respiring cells.
In vivo31P NMR studies of paraplegics' muscles activated by functional electrical stimulation
Authors: Levy M. , Kushnir T. , Mizrahi J. , Itzchak Y. 
Published: March 2007

AbstractThe bioenergetics of paralyzed muscles of spastic paraplegic patients under functional electrical stimulation (FES) was studied in vivo using 31P NMR. The protocol included rest, 3 min of induced tetanic isometric contraction through surface electrodes and 40 min of recovery. The continuous stimulation, the force recording and the 31P NMR measurements were sampled simultaneously inside the whole body imager. Normal values were found for the phosphorous metabolite ratios at rest. During contraction, prominent changes were detected including: a) accumulation of inorganic phosphate (P) accompanied by an unusually strong signal in the phosphomonoester (PME) region, b) phosphocreatine (PCr) decline, and c) a decrease in the intracellular pH. In the following recovery period the physiological state of the muscle was monitored and quantitated by 31P NMR. No metabolic and mechanical irreversible damage was detected in the paraplegics' muscles activated by FES under our experimental conditions.
A unified view of relaxation in protein solutions and tissue, including hydration and magnetization transfer
Authors: Koenig Seymour H. , Brown Rodney D. , Ugolini Raphael 
Published: March 2007

AbstractProtein in water solution increases magnetic relaxation rates of solvent nuclei to an extent that depends on magnetic field strength and molecular weight. Koenig and Schillinger (J. Biol. Chem. 244, 3283 (1969)) showed that a small fraction of the water molecules in the first hydration shell, bound irrotationally with a residence lifetime in the range 01.1 to 10 us, would account for the phenomena. No experiments, as yet, have proven the existence of such long‐lived waters, nor yielded a value for their lifetime. Analogous measurements on solutions of both denatured and cross‐linked protein give data different from that of native protein, but much like results for tissue. By comparing proton and deuteron relaxation rates in solutions of native and cross‐linked protein, it is possible to demonstrate the existence of these relatively long‐lived waters; the data indicate that 1% of a monolayer of the waters of hydration of protein have lifetimes that cluster near 1 us and, it is argued, are held in place by multiple hydrogen bonds. Assigning shorter lifetimes for waters held by fewer bonds, it is possible to develop a unified view of relaxation of water nuclei in protein solutions and in tissue, and to relate it to recent crystallographic data on hydrated protein.
On the extracellular contribution to multiple quantum filtered 23Na NMR of perfused rat heart
Authors: Jelicks Linda A. , Gupta Raj K. 
Published: March 2007

AbstractWe investigated the contribution of extracellular Na+ to the multiple‐quantum filtered 23Na NMR signal of perfused rat hearts to determine if the presence of shift reagent Dy(PPPi)2 and inorganic phosphate were somehow responsible for the generation of extracellular multiple quantum coherence. Neither phosphate nor shift reagent caused an increase in the total multiple‐quantum filtered signal intensity or in the percent contribution from extracellular ions. On the contrary, addition of Dy(PPPi)2 actually decreased the total signal intensity from intra‐ and extracellular ions. Further addition of 1.5 mM Gd(PPPi)2 eliminated the extracellular contribution. These data indicate that the previously reported extracellular contribution in perfused hearts is a true contribution of extracellular ions, and not an artifact originating from their interaction with the shift reagent.
Carbon‐13 “magic‐angle” sample‐spinning nuclear magnetic resonance studies of human myelin, and model membrane systems
Authors: Husted Cynthia , Montez Bernard , Le Carl , Moscarello Mario A. , Oldfield Eric 
Published: March 2007

AbstractWe have obtained high‐field (11.7 Tesla), high‐resolution carbon‐13 solid‐state “magic‐angle” sample‐spinning nuclear magnetic resonance (NMR) spectra of a variety of phospholipids, sphingolipids, myelin and white matter samples, resolving and assigning over 40 resonances in the spectra of human and bovine myelin. The NMR results indicated no large spectral changes due to sample preparation, sample freezing, or brain location, and also no changes in myelin structure detectable via light microscopy, electron microscopy, thin layer chromatography, or sodium dodecyl sulfate‐polyacrylamide gel electrophoresis, attributable to the sometimes lengthy NMR data acquisition process. Human myelin and white matter chemical shift assignments were made based on 13C “magic angle” sample spinning (MAS) NMR spectra of individual model lipids, as well as on spectra of lipid mixtures. In all myelin samples there were essentially no features attributable to membrane proteins, with the exception of one small feature due to Cξ of Arg residues, primarily in the myelin basic proteins. The general similarity between the model lipid and intact myelin spectra suggested no major effects of protein on lipid mobility. We have also investigated human myelin samples as a function of developmental age (4,15, 48 months and adult), and our results showed only small changes in overall lipid composition, although there were significant decreases in lipid hydrocarbon chain unsaturation with age, as determined by computer line‐shape simulations of myelin and model compounds. The spectrum of an infant leukoencephalopathy myelin showed marked decreases in galactocerebrosides. Overall, the ability to resolve and assign over 40 resonances in the 13C MAS NMR spectra of myelin, and to detect changes as a function of development and disease, should provide a useful starting point for further more detailed studies of myelin membrane molecular motions, and function.
pH mapping in living tissues: An application of in vivo31P NMR chemical shift imaging
Authors: Morikawa Shigehiro , Inubushi Toshiro , Kito Kohichi , Kido Chie 
Published: March 2007

AbstractChemical shifts were extracted from in vivo3‐dimensional31P NMR CIS data and pH images were constructed. The images could spatilly resolve tissue pH ranging from 5.8 to 7.2 (with uncertainty of 0.11‐0.17 pH unit)in an ischemia‐reperfusion model of diabetic rat calf muscles.
In situ changes in purine nucleotide and n‐acetyl concentrations upon inducing global ischemia in cat brain
Authors: van Zijl Peter C. M. , Moonen Chrit T. W. 
Published: March 2007

AbstractSpectral changes upon death (global ischemia) were recorded in situ in cat cerebral cortex. A rapid signal loss of 10 ± 4% in the N‐acetyl resonance was observed (five cases), after which it remained constant for 1 h. For the first time signal changes are reported for low‐field resonances, which are assigned to adenosine/inosine and hypoxanthine.
RF pulse design using the inverse scattering transform
Authors: Buonocore Michael H. 
Published: March 2007

AbstractThe inverse scattering transform (IST) is a mathematical transformation that can be used to derive RF pulses from functions called continuous spectra describing the final state of the spin system. This paper reviews three seemingly unrelated numerical algorithms that have appeared in the literature, and shows that they are all derivable from the IST. When the continuous spectra are rational, the finite rank kernel method is used to convert the IST to a matrix equation that is easily solved. Another algorithm, equivalent to the so‐called “layer stripping” algorithm used in seismology, is derived by assuming that the spectra are Fourier series. Finally, the Shinnar‐Le Roux (SLR) algorithm is derived by assuming that the spectra are ratios of Fourier series. With proper interconversion between the rational, series, and ratio of series forms of the continuous spectra, these algorithms generate RF pulses with identical or nearly identical shapes and performance properties, and can be regarded as equivalent.
Some contrast agents in oilwell logging and in medical MRI
Authors: Brown Robert J. S. 
Published: March 2007

AbstractMagnetite particles and paramagnetic ion chelates are used as contrast agents in both nuclear magnetism logging of oilwells and in medical MRI. An analytic expression for reduction of T2 for free precession signal decay (or gradient echoes) by magnetite particles does not depend on diffusion and agrees with published Monte Carlo computations.
A knowledge‐based approach to minimize baseline roll in chemical shift imaging
Authors: Saeed Nadeem , Menon David K. 
Published: March 2007

AbstractA method has been developed to minimize baseline roll in chemical shift imaging (CSI). The technique is fully automated and employs knowledge based data processing in the frequency domain. The key feature of the algorithm is the computation of the “trough” and “ripple” components in the CSI data. The baseline roll can be regarded as an artifact that appears as a result of the summation of several sinc functions. Using prior knowledge, a mirror component corresponding to the artifact is created and added to the delayed spectrum. The method compensates for noise and zero‐order phase error when computing the roll artifact. The results obtained on implementing the baseline roll minimization procedure on simulated time‐delayed spectra indicated that the peak heights and areas were between 91% and 97% in magnitude when compared with the same peaks in the nondelayed spectra. The correction procedure was also assessed on clinical in vivo spectra. Nonlocalized 31P MR spectra of the liver were obtained with and without an acquisition delay of 2.1 ms, and the time delayed spectra subjected to the baseline minimization routine. Metabolite peak heights and areas in the corrected spectra were approximately 94% in magnitude when compared with the same peaks in the original nondelayed whole volume spectra. Implementation of the baseline minimization procedure on in vivo localized spectra with varying signal to noise ratios produced good results. It takes approximately 13 s to implement the baseline roll minimization procedure. In this paper, the technique will be referred to as BaseLine Artifact Suppression Technique (BLAST) routine.
Imaging time reduction through multiple receiver coil data acquisition and image reconstruction
Authors: Carlson J. W. , Minemura T. 
Published: March 2007

AbstractA technique is described for the simultaneous acquisition of MRI data using two independent receiver coils surrounding the same region of tissue, which enables the collection of data necessary for image reconstruction in a reduced number of phase‐encoded acquisitions. This results in a 50% reduction in minimum scan time and may be useful in time‐critical procedures. The algorithm and imaging procedures are described, and example images are shown that illustrate the reconstruction. Signal to noise is decreased by the square root of the time savings, making this technique applicable to cases in which the need to decrease minimum scan time outweighs the signal to noise penalty.