bluuebunny/crossref_metadata_2025_split huggingface dataset:
In vitro proton NMR study of collagen in human aortic wall
Authors: Vinée Philippe , Meurer Bernard , Constantinesco André , Kohlberger Bernd , Hauenstein Karl Heinz , Laubenberger Jörg 
Published: March 2007

AbstractThe authors relate the findings in the 1H solid state line shape (at 60 MHz) of human aortic walls (n = 12) in native state and after histologically controlled selective lysis of collagen and elastin. An analysis of the line shape shows a composite free induction decay (FID) consisting of a low amplitude (3‐7%) fast decaying component (T2 = 20 us) and a slow decaying one (T2 > 1 ms). The fast component is identified as the protons of the collagen macromolecules. The second moment computed from the experimental fast component of the FID is in agreement with published studies examining the motional characteristics of collagen by multinuclear NMR employing spin labeling. A theoretical second moment is computed for the collagen macromolecular backbone from the atomic positions in the superhelix. Comparison with the observed experimental values allows determination of the step angle (29°) of the fast rotational motion of the collagen strands along their long axis.
In vivo oxygen tension and temperature: Simultaneous determination using 19F NMR spectroscopy of perfluorocarbon
Authors: Mason Ralph P. , Shukla Himu , Antich Peter P. 
Published: March 2007

AbstractA novel technique is presented to measure in vivo simulataneously oxygen tension and temperature using 19F NMR spectroscopy of perfluorocarbon. This work examines the variation with oxygen tension (pO2) and temperature of the individual spin lattice relaxation rates (R1) of the 19F resonances of the perfluorocarbon emulsion Oxypherol‐ET. A linear relationship between R1 and pO2 is confirmed for all the resonances at any specific temperature in the range 27–50°C. Similarly, a linear relationship is determined between R1 and temperature at any specific pO2 in this temperature range. Each resonance behaves uniquely with respect to temperature and pO2 and consideration of 2 or more resonances uniquely defines pO2 and temperature simultaneously, and unambiguously. This concept is demonstrated in vivo in a murine tumor and perfused rat heart, where pO2 and temperature were both determined without prior knowledge.
Metabolic changes in activated T cells: An NMR study of human peripheral blood lymphocytes
Authors: Bental Michal , Deutsch Carol 
Published: March 2007

AbstractUsing NMR spectroscopy, we studied purified, human T lymphocytes in a serum‐free medium. Purified cells were entrapped inside agarose beads and induced to proliferate by the mitogens phorbol‐12‐myristate‐13‐acetate and ionomycin. T lymphocytes in standard culture and inside agarose beads exhibit comparable viability, and similar extent and kinetics of DNA synthesis and Interleukin‐2 secretion. 31P‐NMR revealed decreased phosphomonoester and increased phosphodiester content in cells stimulated for two days or longer. 13C‐glucose utilization and 13C‐lactate production rates showed that 85% of the utilized glucose was converted to lactate. 1H‐NMR spectra of the perfusing media indicated that lactate was also produced from substrates other than glucose or glycogen. Glucose accounted for 25% of the lactate produced by quiescent cells, and for 67% of lactate production by stimulated cells. Glycolysis was enhanced 6‐fold within the first 2 hours following stimulation, and 15‐fold by 48 or 96 h. Aerobic lactate production was increased 3‐fold by 48 h, with only a minor enhancement during the first 12 h of stimulation. Our results indicate a shift from mostly aerobic to mostly anaerobic lactate production in T lymphocytes within the first 90 min of the G0 to G1 transition during cell cycle progression.
In vivo NMR imaging and spectroscopic investigation of renal pathology in lean and obese rat kidneys
Authors: Bosch Coleen S. , Ackerman Joseph J. H. , Tilton Ronald G. , Shalwitz Robert A. 
Published: March 2007

AbstractDiabetic nephropathy is a major cause of end‐stage renal failure. While our understanding of the pathogenesis of nephropathy is incomplete, progressive glomerular injury appears to play a significant role in the decline of renal function. Proton NMR spectroscopy and imaging techniques were used to address changes in renal pathology associated with glomerular mesangial expansion in vivo in kidneys from spontaneously obese and lean (control) littermate Zucker rats. Fully functioning rat kidneys were surgically exposed and externalized for direct NMR signal detection via a coil placed around the organ. High‐resolution (78 μm in plane) proton images were obtained at 4.7 T magnetic field strength revealing fine structure within the well‐defined cortical and medullary regions. The obese rat kidney images were distinct in appearance from the lean kidney images and exhibited marked cortical expansion as well as increased overall kidney size. Enlargement of mean glomerular diameter was verified histologically in the obese kidneys as compared with the lean kidneys. Proton T1 and T2 relaxation times were determined from the entire kidney using standard spectroscopic techniques, and from specific regions within the kidney from multiple T1 and T2‐weighted images. Additionally, image contrast enhancement resulting from saturation transfer between protons in restricted‐mobility environments and mobile water protons within the kidney was investigated in the lean and obese rat kidneys using magnetization‐transfer imaging techniques. At the early stage of renal injury examined in this study, diseased and healthy kidneys could not be differentiated on the basis of relaxation times alone. The magnitude of saturation transfer obtained in cortical tissue in the lean and obese kidneys was also not statistically significantly different. However, the magnitude of saturation transfer achieved in the medullary tissue of obese kidneys was statistically significantly less than that achieved in lean kidneys.
Magnetization transfer characterization of hypertensive cardiomyopathy: Significance of tissue water content
Authors: Scholz Thomas D. , Ceckler Toni L. , Balaban Robert S. 
Published: March 2007

AbstractMagnetization transfer measurements offer the potential for specific noninvasive tissue characterization. The goal of the present study was to determine if changes in magnetization transfer would accompany the myocardial remodeling that occurs with hypertrophic cardiomyopathy. Using 40‐week spontaneously hypertensive rat (SHR) myocardium, T1, T2, and T1 in the presence of off‐resonance irradiation (T1sat) were found to be greater compared to Wistar‐Kyoto (WKY) controls. The pseudo‐first order rate constant of magnetization transfer (kfor) was less in 40‐week SHR compared with WKY while the ratio of equilibrium magnetization in the presence and absence of off‐resonance irradiation (Ms/M0) was not different. The extent to which observed interspecies differences in tissue water content affected these parameters was investigated by dehydrating normal and hypertrophic myocardium. Significant correlations found between tissue water content and T1, T2, T1sat and kfor, but not Ms/M0, suggested changes in tissue water dominated the observed interspecies differences in relaxation parameters. Thus, ventricular remodeling in hypertrophic cardiomyopathy does not alter magnetization transfer though the accompanying change in tissue water content influences water proton relaxation.
Field dependent transverse relaxation rate increase may be a specific measure of tissue iron stores
Authors: Bartzokis George , Aravagiri Manickam , Oldendorf William H. , Mintz Jim , Marder Stephen R. 
Published: March 2007

AbstractThe degree to which MRI magnet field strength affects measured transverse relaxation rates (R2) defines a measure termed the field dependent R2 increase (FDRI). We report here the results of in vivo and in vitro experiments that were conducted to evaluate whether FDRI is a potentially useful measure of tissue iron stores. T2 relaxation times were obtained using two clinical MRI instruments operating at 0.5 and 1.5 Tesla, and relaxation rates (R2) were calculated as the reciprocal of T2. The in vivo experiment measured R2 in human brain frontal white matter, caudate nucleus, putamen, and globus pallidus. The FDRI was very highly correlated with published brain iron levels for the four regions examined. The in vitro experiment measured R2 in agarose gel‐based phantoms containing physiologic forms and amounts proteins involved in iron storage and transport (ferritin, apoferritin, transferrin, and apotransferrin). Significant field dependence was observed only for the ferritin phantoms. The differences in the R2 values obtained at the two field strengths were striking, and were proportional to the ferritin levels of the phantoms. These studies suggest that FDRI may be a specific measure of tissue ferritin. The quantitative significance of the results to imaging and possible applications to the clinical investigation of pathologic states are discussed.
A perifusion loop‐gap resonator NMR probe for aerobic cell suspensions
Authors: Anderson Mark E. , Markley John L. , Arùs Carles , Chobanian Michael C. 
Published: March 2007

AbstractNMR studies of aerobic cell metabolism require that spectral data of high sensitivity and resolution be acquired from samples maintained under suitable conditions. The loop‐gap resonator 31P NMR probe described here was designed for investigations of highly aerobic‐dependent renal proximal tubules in an environment similar to those of conventional incubation flasks. The inherently higher sensitivity of the loop‐gap resonator design and associated circuitry made it possible to obtain adequate spectra in short periods of time with small amounts of sample. Cellular physiological properties of perifused aerobic renal proximal tubule cell suspensions in the loop‐gap resonator probe were found to be similar to equivalent tissue samples incubated in conventional flasks. Furthermore, the loop‐gap perifusion probe was found to provide useful 31P NMR spectra of the kidney tubule system after acquisition times as short as 3 min.
Diffusion in red blood cell suspensions: Separation of the intracellular and extracellular NMR sodium signal
Authors: van der Veen J. W. C. , van Gelderen P. , Creyghton J. H. N. , Bovée W. M. M. J. 
Published: March 2007

AbstractIt is shown that the signal of intracellular and extracellular sodium of red blood cells can be separated by a difference in diffusion. Comparison with proton diffusion experiments conducted in parallel showed that this difference was caused by restriction to the cell volume. The measured proton and sodium root mean square displacements agreed well with the cell dimensions. However, this experiment is limited to use in vitro by the required gradient strength.
A novel flow‐suppression technique using tailored RF pulses
Authors: Ro Y. M. , Cho Z. H. 
Published: March 2007

AbstractThe pulsatile nature of blood flow makes zipper‐like artifacts along the coding direction in the two‐dimensional Fourier transform NMR image. So far, spatial presaturation, one of the correction methods, is known to be effective in eliminating flow artifacts when the Fourier spin echo acquisition is employed. However, this method requires an additional RF pulse and a spoiling gradient for presaturation. Described in this paper is a new flow suppression technique, based on spin dephasing, using a set of tailored RF pulses. The proposed method does not require additional saturation RF pulses or spoiling gradient pulses, making it advantageous over other methods. In addition, the method is relatively robust to flow velocity. The proposed technique is equivalent to the existing flow saturation technique except that the elimination of the flow component is achieved by a pair of tailored 90–180° RF pulses in the spin echo sequence. The principle of the proposed method is the creation of a linear phase gradient within the slice along the slice selection direction for the moving material by use of two opposing quadratic phase RF pulses, i.e., 90° and 180° RF pulses with opposing quadratic phase distributions. That is to say, all the spins of the moving materials along the slice selection direction become dephased. Therefore, no observable signal is generated. Computer simulations and experimental results obtained using a 2.0‐T whole‐body imaging system on both a phantom and a human volunteer are also presented.
Susceptibility changes following bolus injections
Authors: Albert Mitchell S. , Haung Wei , Lee Jing‐Huei , Patlak Clifford S. , Springer Charles S. 
Published: March 2007

AbstractThe general mechanism of bulk magnetic susceptibility (BMS) induced MRI contrast following a bolus injection is elaborated. Combining radiolabeled tracer data for the first pass of a bolus injection through the human brain with the application of Wiedemann's law allows us to calculate the lower limit for the time course of the vascular BMS following the injection of any contrast agent. Superparamagnetic Iron oxide particles produce a much larger effect than any mononuclear Ln(III) che‐late. We also calculate the BMS changes occurring after a dilution bolus injection (of isosmolal physiological saline) subsequent to a prior slow infusion of an intravascular contrast agent. This technique bears some resemblance to the increasingly important approach that exploits changes in only the level of blood oxygenation. The calculation indicates that contrast changes after the dilution bolus injection are smaller than those following Ln(III) agent injections but larger than those due to changes in blood oxygenation and suggests a way to possibly enhance the latter. We present an In vivo study demonstrating the dilution bolus injection technique in the mouse brain, and that features its rapid repeatability. Extrapolation of these results to the human, however, indicates that the saline volumes required for venous injections, except possibly for cardiac studies, would be prohibitively large. Smaller, catheter‐delivered arterial bolus injections are feasible. We also suggest a method for using an agent bolus injection to measure the parenchymal BMS, and thus the iron content, of pathologically iron‐loaded tissue.
Quantitative interpretation of magnetization transfer
Authors: Henkelman R. Mark , Huang Xuemei , Xiang Qing‐San , Stanisz G. J. , Swanson Scott D. , Bronskill Michael J. 
Published: March 2007

AbstractMagnetization transfer contrast (MTC) experiments using off‐resonance irradiation have been performed with an agar gel model by systematically varying offset frequency, amplitude of the RF irradiation and gel concentration. The experimental results are shown to be quantitatively modelled by a two‐pool system consisting of a liquid pool with a Lorentzian line shape and a small semisolid pool with a Gaussian lineshape. The fitted model yields physically realistic fundamental parameters with a T2 of the semisolid pool of 13 μs. Further analysis shows that the off‐resonance irradiation MTC experiment has significant limitations in its ability to saturate the semisolid pool without directly affecting the liquid component.
An asymmetric slice profile: Spatial alteration of flow signal response in 3d time‐of‐flight NMR angiography
Authors: Matsuda Tetsuya , Morii Isao , Kohno Fujimasa , Asato Reinin , Ikezaki Yoshikazu , Yoshitome Eiji , Sasayama Shigetake 
Published: March 2007

AbstractWe introduce an asymmetric slice profile technique, which alters the spatial response of the flow signal in 3D time‐of‐flight NMR angiography. By gradually increasing the flip angle from the inflow to the outflow portions of the slab, the inflow refreshment effect is distributed over a wide slab thickness. The asymmetric slice profile is simply produced by using a Gaussian RF excitation with an overlapping presaturation. The spatial distribution of steady flow signal in a phantom study demonstrated an essential agreement with a numerical simulation. 3D time‐of‐flight NMR angiography of volunteers' heads using this technique provided a smooth vascular depiction over a wide slab thickness.
Blood flow measurement using variable velocity encoding in the RR interval
Authors: Buonocore Michael H. 
Published: March 2007

AbstractVelocity‐encoded phase imaging using asynchronous gating requires input of a velocity encoding value to set the velocity sensitivity of the pulse sequence. The raw data interpolation and reconstruction scheme that the pulse sequence uses forces the encoding value to be constant throughout the RR interval. The sequence and the raw data interpolation scheme were modified to allow two velocity encodings during the RR interval. Two‐hundred cm/s encoding was used in systole, and 30 cm/s in diastole. Changing the encoding in diastole significantly improved the accuracy and precision of ascending aorta flow measurements.
Nonmagnetic hyperbaric chamber for in vivo NMR spectroscopy studies of small animals
Authors: Litt Lawrence , Xu Yan , Cohen Yoram , James Thomas L. 
Published: March 2007

AbstractA description is given of the design, construction, and initial use of a polycarbonate resin hyperbaric chamber for in vivo NMR spectroscopy studies of anesthetized, ventilated rats in a horizontal bore 4.7 Tesla magnet. The chamber and its associated equipment, initially used for hyperbaric studies of rats in states of extreme hypercapnia, are also well suited for conventional hyperbaric studies, such as those related to hyperbaric oxygen therapy, oxygen toxicity, and diving. Basic technical challenges that required innovations involved: a) preservation of magnetic field homogeneity; b) avoidance of a metallic chamber body that would overload gradient and RF coils; c) physiological monitoring; and, d) remote control and stabilization of electromagnetic and physiologic factors (especially ventilatory stability) during pressure changes. A small paramagnetic bulk magnetic susceptibility shift from chamber‐associated hyperbaric oxygen was observed when chamber oxygen tensions were only one atmosphere. High‐quality NMR imaging and spectroscopy were demonstrated during hyperbaric conditions.
Spatially localized 31P NMR measurements of longitudinal relaxation rates in the canine myocardium
Authors: Rath D. P. , Abduljalil A. M. , Robitaille P.‐M. L. 
Published: March 2007

AbstractFLAX‐ISIS spatial localization was combined with inversion recovery to enable the measurement of spatially localized T1 values. This approach was applied to the transmural determination of creatine phosphate longitudinal relaxation times in the canine myocardium. By examining five voxels spanning the left myocardial wall, we observed that transmural T1 values for creatine phosphate ranged from 3.61 = 0.20 in the endocardium to 4.00 ± 0.20 in the epicardium at 4.7 Tesla. As such, the canine myocardium exhibits no transmural variation in the T1 values of creatine phosphate. This simple approach can be extended to enable the in vivo measurement of transmural enzymatic rates.
Stability and nonreactivity of ergothioneine in human erythrocytes studied by 1H NMR
Authors: Rae Caroline D. , Sweeney Kimberley J. E. , Kuchel Philip W. 
Published: March 2007

AbstractThe N(CH3)3 resonance of ergothioneine in 1H spin‐echo Fourier transform (SEFT) NMR spectra of red blood cells is usually a large singlet and it has been common practice to use this apparently unchanging resonance as an intensity reference. Recently, Reglinski et al. (Magn. Reson. Med. 6, 217–223 (1988)) have questioned this practice, reporting changes seen in the resonance in response to oxidative stress induced by arsenicals. We propose that the changes in the ergothioneine resonance that were reported are artifacts due to alterations in osmolality and magnetic susceptibility induced by the addition of nonisotonic solutions to red blood cell suspensions. These factors change the specific intensity of the intracellular resonances of all compounds. Ergothioneine was observed not to take part in any chemical reactions with arsenicals in free solution or in intact erythrocytes, and we conclude that ergothioneine may still be used as an internal intensity reference in 1H SEFT NMR spectra, bearing in mind the above physical factors.
In vivo degradation of silicones
Authors: Garrido Leoncio , Pfleiderer Bettina , Papisov Mikhail , Ackerman Jerome L. 
Published: March 2007

Abstract29Si nuclear magnetic resonance (NMR) spectroscopy is applied to study the degradation of polysiloxanes (silicones) in vivo. Our results with animal models show that silicone migrates from the implant to the liver (29Si resonance at −20 ppm) and new silicon containing compounds form after the silicones are introduced into the rats. The new 29Si resonances in the chemical shift range of −40 to −85 ppm are related to hydrolyzed silicone, those at −90 to −115 ppm are indicative of the presence of silica (SiO2), and the peaks observed at −120 to −150 are related to high coordinated silicon complexes. These resonances are not present in the 29Si spectra of the silicones before implantation. Our findings demonstrate that silicones are not metabolically inert.
Transmural saturation transfer analysis of the creatine kinase system in the mammalian heart
Authors: Obitaille P.‐M. L. , Abduljalil A. , Rath D. , Zhang H. , Hamlin R. L. 
Published: March 2007

Abstract31P NMR spatial localization and saturation transfer techniques were combined to enable the transmural measurement of the forward creatine kinase (CK) rate (ATP:creatine N‐phos‐photransferase, EC 2.7.3.2.) in the in vivo canine myocardium. Five epicardial towards endocardial regions of the left ventricle (LV) were simultaneously examined using spatially localized voxels. Although intralefl ventricular CP/ATP ratios were constant, the pseudo first order rate constant (K′) and the forward creatine kinase rate (Rt) displayed a 61% variation across the LV wall. Because CK levels and calculated [ADP], [CP]and pH are transmurally invariant in the normal left ventricle, the observed changes in the Rt could not be explained by changes in the absolute levels of these substrates and of creatine kinase. In addition, because myocardial oxygen consumption rates are known to be higher in the endocardium, these results imply that forward creatine kinase rates are not directly related to oxidative phosphorylation rates.
Responses of myocardial high energy phosphates and wall thickening to prolonged regional hypoperfusion induced by subtotal coronary stenosis
Authors: Zhang J. , Path G. , Chepuri V. , Xu Y. , Yoshiyama M. , Bache R. J. , From A. H. L. , Uǧurbil K. 
Published: March 2007

AbstractThe response of the myocardium to prolonged or chronic ischemia may differ from the well documented changes that occur acutely subsequent to the onset of hypoperfusion. Therefore, we have examined in an instrumented canine model and using spatially localized spectroscopy to achieve transmural differentiation, the myocardial HEP and Pi levels as well as wall thickening in situ during prolonged ischemia induced by sustained coronary artery stenosis. The results demonstrate that subtotal coronary artery occlusion causes immediate and transmurally inhomogeneous decreases in the myocardial HEP content and increase in the Pi /CP ratio; however, during prolonged mild hypoperfusion, metabolic changes occur which lead to statistically significant recovery of CP (but not ATP) and disappearance of Pi despite the persistence of reduced blood flow and oxygen supply. Upon release of the occlusion, the previously ischemic muscle recovered blood flow, and some (but not all) of its preischemic contractile function without parallel changes in the HEP levels. It is concluded that normal HEP and Pi levels cannot be equated with either the absence of underperfusion or insensitivity of NMR spectroscopy to ischemia. Rather, it is imperative that both functional and spectroscopic measurements are performed simultaneously to distinguish between ischemic myocardium which is adapted versus unadapted to the hypoperfusion.