bluuebunny/crossref_metadata_2025_split huggingface dataset:
31P NMR spectroscopy of the in vivo metabolism of an intracerebral glioma in the rat
Authors: Ross Brian D. , Higgins Robert J. , Boggan James E. , Knitteln Brian , Garwood Michael 
Published: March 2007

AbstractThe in vivo high‐energy phosphorus metabolic profile and pH of an experimental intracerebral C6 glioma in rats was examined using surface coil 31P NMR spectroscopy. Initially, phosphorus‐containing metabolites of the glioma were characterized by in vivo 31P surface coil spectroscopy of subcutaneously implanted tumors and by high‐resolution NMR studies of perchloric acid (PCA) extracts of both freeze‐clamped subcutaneous tumor tissue and cultured cells. These studies demonstrated that the C6 glioma has reduced levels of phosphocreatine (PCr) compared to the levels found in normal rat brain. Thus, reduced spectral PCr levels were useful as a metabolic indicator for monitoring the spatial selectivity of tumor metabolism distinct from that of adjacent normal brain tissue. To maximize 31P NMR signals from intracerebral tumors, tumor cells were stercotaxically placed superficially in the brain. Proton magnetic resonance imaging (1H MRI) was used to determine the size and location of the resultant brain tumors in order to preselect rats with large superficial tumors for spectroscopic study. 31P NMR spectra of the glioma tumors revealed a consistent reduction in the PCr/ATP ratio, an increase in the Pi/ATP ratio, and a slightly increased tissue pH. No correlation was found between levels of Pi/ATP and tumor pH in subcutaneous or intracerebral gliomas and the amount of necrosis as determined histologically. This study demonstrates that phosphorus metabolites of an experimental brain tumor in the rat can be monitored in vivo with minimal contributions from adjacent normal brain tissue metabolites using surface coil 31P NMR spectroscopy. © 1988 Academic Press, Inc.
31P NMR studies of the diabetic lens
Authors: Gonzalez R. Gilberto , Miglior Stefano , Von Saltza Ingrid , Buckley Lisa , Neuringer J. , Cheng Hong‐Ming 
Published: March 2007

AbstractPhosphorus‐31 (31P) nuclear magnetic resonance (NMR) spectroscopic analyses of the crystalline lens from the experimental diabetic rat were performed. Qualitative and quantitative alterations in the phosphorus‐31 NMR metabolic profile were observed over the course of 3 weeks after the induction of diabetes mellitus. Most striking was the appearance of two new, as yet unidentified, metabolites. These metabolites which resonate at 6.6 and 5.8 ppm were not detected in the normal lens. Compared to the normal lens, glycerol‐3‐phosphate (G3P) underwent an eightfold increase in concentration and phosphorylcholine decreased to one‐third its initial level. The phosphodiesters, glycerophosphorylcholine (GPC) and glycerophosphorylethanolamine (GPE), decreased to barely detectable levels. Oral treatment of the diabetic animal with an aldose reductase inhibitor resulted in the preservation of an essentially normal lens 31P NMR spectrum. Except for the changes observed in glycerol‐3‐phosphate, these alterations have not been previously reported and raise new questions about the metabolic consequences of diabetes mellitus and the dependence of these alterations on the action of a single enzyme, aldose reductase. © 1988 Academic Press, Inc.
Direct FLASH MR imaging of magnetic field inhomogeneities by gradient compensation
Authors: Frahm Jens , Merboldt Klaus‐Dietmar , Hänicke Wolfgang 
Published: March 2007

AbstractMR images based on gradient echoes are sensitive to artifacts caused by inhomogeneities of the static magnetic field. This paper describes the effects of local gradients in rapid FLASH MR images and presents a way of directly imaging affected areas. The idea is to compensate for signal losses due to mutual cancellation of dephased magnetizations by deliberate “misadjustments” of the refocusing part of the slice selection gradient. In contrast to conventional field imaging techniques no three‐dimensional data acquisition or subsequent Fourier analysis is required to obtain images at a particular gradient strength. Conventional as well as inhomogeneity compensated FLASH images have been obtained on phantoms and human heads using a 2.35‐T 40‐cm magnet and a 1.5‐T whole‐body system, respectively. © 1988 Academic Press, Inc.
Rapid line scan NMR angiography
Authors: Frahm J. , Merboldt K. D. , Hånicke W. , Gyngell M. L. , Bruhn H. 
Published: March 2007

AbstractThis paper describes a new technique for NMR angiography based on rapid line scan projection imaging and presaturation of stationary spins. The resulting line Scan angiograms are free from both misregistration artifacts common to subtraction methods and motion artifacts encountered in Fourier imaging. Moreover, line scan angiograms may be recorded within seconds and offer arbitrary fields of view as well as gradient zooming without problems due to aliasing. Three‐dimensional information is obtained by rotation of the read gradient axis generating multiple view angles. Experimental line scan angiograms of the forearms of healthy volunteers have been recorded using a Bruker 2.35‐T 40‐cm magnet. © 1988 Academic Press, Inc.
Detection of motion using B1 gradients
Authors: Karczmar G. S. , Tweig D. B. , Lawry T. J. , Matson G. B. , Weiner M. W. 
Published: March 2007

AbstractAn NMR method which makes use of a radiofrequency (RF) field gradient to detect diffusion, perfusion, or flow is demonstrated. The technique is analogous to the detection of motion using pulsed Bo gradients. The simplest form of the experiment is as follows: A spatially inhomogeneous RF field generated by a surface coil produces dispersal of magnetization in the YZ plane. After a delay, the RF field is applied with reversed phase to restore polarization along +Z, which is then sampled using an observe pulse or pulse sequence. If molecular motion occurs during the delay period the amplitude of Z magnetization will be. reduced. The lengths of the RF pulses and the delay period are varied so that the effects of relaxation, flow, and diffusion or perfusion can be distinguished. The present study demonstrates the use of this method to detect slow fluid flow. Advantages of this method include the availability of large RF gradients, and the avoidance of eddy currents. It is suggested that the method may have application to the study of perfusion and flow in vivo. © 1988 Academic Press, Inc.
Quantitative estimation of lactate in the brain by 1H NMR
Authors: Williams Stephen R. , Proctor Edward , Allen Kathryn , Gadian David G. , Crockard H. Alan 
Published: March 2007

Abstract1H NMR was used to detect lactate accumulation in the intact gerbil brain postmortem. The lactate concentration was estimated from the spectra by comparison to signals from N‐acetylaspartate, creatine + phosphocreatine, and water. The effects of T2, phase modulation, and solvent suppression were taken into account. The estimated concentrations were compared to determinations performed on the same brains after extraction. The lactate concentration estimated from the intact brain spectra was between 70 and 90% of the values determined in vitro, on the extracts, depending on the concentration standard used. If N‐acetylaspartate was used as the standard then the proportion of detected lactate (92%) was not significantly different from 100%. © 1988 Academic Press, Inc.
A one‐shot lactate‐editing sequence for localized whole‐body spectroscopy
Authors: McKinnon G. C. , Boesiger P. 
Published: March 2007

AbstractA pulse sequence is presented for performing localized lactate‐edited proton spectros‐copy in the whole‐body environment. The sequence is optimized for relatively low field strength (1.5‐T) clinical measurements. Characteristics of this method of lactate editing, which makes it more suitable for clinical applications than previous methods, include the following: The “one shot” nature of the method makes it relatively insensitive to patient motion; water suppression is high as all 90° pulses are binomial pulses; and very narrow band rf pulses, such as used in high‐field lactate‐editing sequences, but which are necessarily very long at low fields, are not required. Further, this lactate editing scheme can be very easily combined with localized spectroscopic measurements. © 1988 Academic Press, Inc.
31P NMR study of insulin effects on the isolated perfused rabbit urinary bladder
Authors: Fisher M. J. , Dillon P. F. 
Published: March 2007

AbstractInsulin stimulates hexose transport, intermediary metabolism, and cell growth and development. These effects are well‐documented in skeletal but not smooth muscle. 31P NMR spectroscopy was performed on rabbit urinary bladders (n=4) to characterize insulin's actions on smooth muscle. The bladder and its vasculature were surgically isolated from the animal and perfused with a PSS/red blood cell perfusate. After a control steady state was achieved (approx 1−2 h), insulin (0.100 mU/ml) was added to the perfusate. Relative levels of intracellular phosphorylated compounds, pH, and free Mg2+ were measured and compared to control values. Also, extracellular pH and fractional volume were assessed using phenylphosphonate, a 31P NMR extracellular pH and volume indicator. Insulin induced significant increases in PCr (16 ± 9%) at the expense of Pi, intracellular pH ( Δ 0.24 + 0.07 ), and fractional extracellular volume (49 ± 1%). Intracellular free Mg2+ and extracellular pH did not change. These results indicate that in situ smooth muscle is sensitive to physiological levels of insulin. In fact, insulin improves the energy state of smooth muscle cells and the overall tissue perfusion. © 1989 Academic Press, Inc.
Flow‐induced phase effects and compensation technique for slice‐selective pulses
Authors: Yuan Chun , Gullberg Grant T. , Parker Dennis L. 
Published: March 2007

AbstractFlowing spins experience a time‐varying frequency during the application of slice‐se‐lective radiofrequency (RF) pulses. As a result the flowing spins accumulate phase relative to stationary spins as the spins are rotated toward the transverse plane. Using finite difference techniques to solve the Bloch equations for flowing spins, the phase of the transverse magnetization after a slice‐selective pulse was evaluated for varying flow velocities and for tip angles which ranged between 0° and 180°. The following results were obtained for constant slice thickness: (1) For a fixed tip angle, the phase varies nonlinearly with velocity. (2) For a fixed velocity, the phase varies nonlinearly with tip angle. For small tip angles the nonlinearity in the variation as a function of velocity is very small but increases for tip angles greater than 90° and becomes especially severe near 180°. A method is proposed to desensitize the phase of flowing spins during the application of slice‐selective pulses. The compensation scheme depends upon tip angle but is virtually independent of flow velocity. The technique was tested and verified with clinical images. © 1989 Academic Prcrs. Inc.
Pathways for the synthesis of sorbitol from 13C‐labeled hexoses, pentose, and glycerol in renal papillary tissue
Authors: Jans A. W. H. , Grunewald R.‐W. , Kinne R. K. H. 
Published: March 2007

AbstractSuspensions of rabbit renal papillary tissue were incubated with D‐[ 6‐13C]glucose, D‐[1‐13C]fructose, D‐[1‐13C] ribose, and [2‐13C]glycerol. The perchloric acid extracts of the above incubations were investigated with 13C NMR spectroscopy. All 13C‐labeled substrates give rise to 13C‐labeled D‐sorbitol. D‐[6‐13C]Glucose and D[1‐13C]fructose are converted directly into D‐sorbitol via the aldose reductase and sorbitol dehydrogenase pathway, respectively, whereas D‐[1‐13C] ribose and [2‐13C]glycerol give rise to labeling of the D‐glyceraldehyde pool which on its turn causes a labeling of D‐sorbitol. Label exchanges observed from incubations with glycerol and D‐ribose indicate that the pentose shunt plays a role in this synthesis of D‐sorbitol. © 1989 Academic Press, Inc.
Identification of a characteristic 31p NMR signal in acute experimental pancreatitis with the aid of 1H−31p correlated 2D measurements of intact pancreas
Authors: Kushnir T. , Kaplan O. , Askenasy N. , Navon G. 
Published: March 2007

AbstractTwo‐dimensional 1H–31P correlation spectroscopy and relaxation time measurements of intact diseased pancreas were performed in order to identify an unknown peak appearing at −0.18 ± 0.04 ppm in a31P NMR spectrum of taurocholate‐induced experimental acute pancreatitis in rats. The signal was identified as a solubilized lecithin taurocholate Complex. © 1989 Academic Press, Inc.
PEEP—A rapid chemical‐shift imaging method
Authors: Guilfoyle D. N. , Blamire A. , Chapman B. , Ordine R. J. , Mansfield P. 
Published: March 2007

AbstractThe phase‐encoded echo‐planar (PEEP) technique, a variant of echo‐planar imaging, is used to achieve simultaneous high‐speed spatial and chemical‐shift data acquisition. This technique is the 2DFT equivalent of the projection reconstruction echo‐planar method for chemical‐shift imaging. Examples of images and spectra obtained using the PEEP method are presented. © 1989 Academic Press, Inc.
Eigenimage filtering in MR imaging: An application in the abnormal chest wall
Authors: Haggar Allan M. , Windham Joe P. , Reimann David A. , Hearshen David O. , Froelich Jerry W. 
Published: March 2007

AbstractA postprocessing linear filter was applied to spin‐echo images on 10 patients with known or suspected chest wall invasion due to bronchogenic carcinoma. This technique known as eigenimage filtering allows selective feature extraction of suspected abnormali‐ties from conventional MR images. The final result is an image with marked increased contrast range through enhancement of a desired process (tumor) with suppression of an interfering process (e.g., normal surrounding tissue). This preliminary work demon‐strates the ease with which the technique may be implemented, the contrast enhancement obtained between the desired and the interfering feature in the final eigenimage, and its ability to correct for partial volume averaging effects. Also demonstrated are artifacts that can interfere with the interpretation of the eigenimage and a method for minimizing these artifacts in the final eigenimage. © 1989 Academic Press, Inc.
Low‐frequency restoration
Authors: Jackson John , Macovski Albert , Nishimura Dwight 
Published: March 2007

AbstractIn magnetic resonance imaging, if the object of interest is known to be spatially bounded within the image field‐of‐view. then the high‐intensity, low spatial frequencies can be determined by postprocessing. This allows the system receiver gain to be increased, thereby decreasing the quantization noise from the analog‐to‐digital converters. No imaging sequence modifications are required. © 1989 Academic Press. Inc.
High‐Flux Signals and Spatial Localization in High‐Resolution 1H Spectroscopy with Surface Coils
Authors: Bourgeois D. , Decorps M. , Remy C. , Benabid A. L. 
Published: March 2007

AbstractTo perform in vivo localized proton spectroscopy with water suppression, spin‐echo sequences, made of binomial pulses, are commonly used with surface coils. The frequency selective response to such a sequence is also spatially dependent, that is dependent on the sample shape and on the pulse angle adjustment. It is consequently pointed out in this paper that quantitative analysis for relative peak intensities may be strongly affected by the contribution of the high‐flux regions. In vivo proton spectroscopy of rat brain exemplifies this difficulty. It is shown that the use of selective prepulses to suppress high‐flux signals may be of poor efficiency depending on chemical shift, while the use of hard nonselective prepulses works for any chemical shift.
Relative contributions of chemical exchange and other relaxation mechanisms in protein solutions and tissues
Authors: Zhong Jianhui , Gore John C. , Armitage Ian M. 
Published: March 2007

AbstractTransverse relaxation times T2 of water protons were measured in 5% protein solutions and soaked rat liver in different static magnetic fields (0.15 to 11 T). Protein molecular weight varied between 1.4 and 480 kDa in solutions of yarying degrees of deuteration. The data obtained are analyzed in terms of a model system consisting of three phases of different relaxation characteristics: protein protons, hydration layer water protons, and bulk water protons. The contributions to relaxation due to hydrodynamic effects on water protons, cross relaxation between the hydration layer water protons and the protein protons, and chemical exchange between the hydration layer water protons and the bulk water protons are separately estimated. The experimental results indicate that the “hydrodynamic interactions” are about the same magnitude in rat liver and all the proteins studied, but the contribution of the cross relaxation differs by several orders in different protein systems. Fast chemical exchange between the hydration layer water and the bulk water causes considerable shortening of T2 at high magnetic fields for all the protein solutions and rat tissue studied. Selected samples were studied at different temperatures (2 13‐3 18 K) and with different intervals in the CPMG sequence. The rates of chemical exchange and fractional populations of different phases are determined, and the results obtained provide support for the model in which fast exchange among the different water phases is an important feature of the overall relaxation behavior.
On the use of double‐quantum coherence from an AX3 system (protons in lactate) for spectral editing
Authors: Nosel W. , Trimble L. A. , Shen J. F. , Allen P. S. 
Published: March 2007

AbstractThe suppression of water signals in in vivo proton spectra by means of multiple‐quanturn filtering can be brought about in several ways. This communication exposes the shortcomings of using purely subtractive filtering techniques to observe signals from metabolites that contain proton couplings of the form AX3.
Intrauterine fetal brain NMR spectroscopy: 1H and 31P studies in rats
Authors: Nakada Tsutomu , Kwee Ingrid L. , Suzuki Nobuyuki , Houkin Kiyohiro 
Published: March 2007

AbstractFetal brain metabolism was investigated in utero noninvasively using multinuclear nuclear magnetic resonance spectroscopy in rats at two representative prenatal stages: early (17‐18 days) and late (20‐21 days) stages. Phosphorus‐31 (31P) spectroscopy revealed that phosphocreatine is significantly lower in the early stage and increases to the level of early neonates by the late prenatal stage. Intracellular pH at the early stage was found to be strikingly high (7.52 ± 0.21) and decreased to a level similar to that of neonates by the late stage (7.29 ± 0.07). Phosphomonoester levels at both stages were similar to the values reported for early neonates. Water‐suppressed proton (1H) spectroscopy demonstrated a distinctive in vivo fetal brain spectral pattern characterized by low levels of N‐acetyl aspartate and high levels of taurine. High‐resolution proton spectroscopy and homonuclear chemical‐shift correlate spectroscopy of brain perchloric acid extracts confirmed these in vivo findings. In vitro 31P spectroscopy of acidified chloroform methanol extracts showed the characteristic membrane phospholipid profiles of fetal brain. The phosphatidylethanolamine (PE)‐to‐phosphatidylcholine (PC) ratio (PE/PC) did not show significant changes between the two stages at 0.40 ± 0.11, a value similar to that of early neonates. © 1989 Academic Press, Inc.
On the origin of paramagnetic inhomogeneity effects in blood
Authors: Brooks Rodney A. , Brunetti Arturo , Alger Jeffry R. , Chiro Giovanni Di 
Published: March 2007

AbstractHydrogen, sodium, and fluorine (added F‐) NMR spectra of venous and oxygenated blood were measured. The fluorine resonance was seen as a single peak in both samples, and all three resonances exhibited the same deoxy‐oxy shift. Because F‐ exchanges slowly across the red cell membrane, and because sodium is 95% extracellular, these results suggest that the intra‐extracellular field difference ΔB is less than 0.1 ppm. A small value of ΔB tends to rule out transmembrane exchange as an important contributor to relaxation in MRI of blood and hematomas. However, the broadening of the resonances with deoxygenation, by 0.3‐0.4 ppm, indicates that both intra‐ and extracellular gradients are of comparable and sufficient magnitude to produce the T2‐weighted hypointensity seen in clinical magnetic resonance images of hematomas at high fields. © 1989 Academic Press, Inc.
Phospholipid bilayer contribution to 31P NMR spectra in vivo
Authors: Murphy Elizabeth J. , Rajagopalan Bheeshma , Brindle Kevin M. , Radda George K. 
Published: March 2007

AbstractThe magnetic field‐dependent phosphodiester(PDE) signal found in 31PNMR spectra of liver and brain has been studied using saturation transfer and proton decoupling techniques. This PDE component, which accounts for as much as 45% of the signal in vivo, has been identified as primarily phospholipid bilayer with a small contribution from a motionally averaged macromolecule(S). © 1989 Academic Press, Inc.
Phosphorus‐31 magnetic resonance spectroscopy in humans by spectroscopic imaging: Localized spectroscopy and metabolite imaging
Authors: Twieg D. B. , Meyerhoff D. J. , Hubesch B. , Roth K. , Sappey‐Marinier D. , Boska M. D. , Gober J. R. , Schaefer S. , Weiner M. W. 
Published: March 2007

AbstractIn in vivo phosphorus magnetic resonance spectroscopy (MRS), spectroscopic imaging (SI) can be used as a flexible localization technique, producing spectra from multiple volumes in a single examination. Presented here are phosphorus SI studies of human organs in which a selective‐volume SI reconstruction was used rather than the usual array‐format SI reconstruction. A linear predictor technique was used to estimate the initial points of the free induction decay missing because of the delay needed for phase‐encoding gradients, significantly reducing the baseline artifacts which commonly complicate interpretation of SI spectra. In studies of heart, brain, liver, and kidney, the performance of SI was found to compare favorably with that of ISIS. SI phosphorus metabolite intensity images from a brain tumor patient were obtained at 2 X 2‐cm in‐plane resolution (with “slice” thickness of roughly 16 cm, determined by coil sensitivity) in 34 min, demonstrating the feasibility of obtaining clinically useful metabolite images in clinically reasonable examination times. © 1989 Academic Press, Inc.
T1ρ, dispersion imaging and volume‐selective Tlρ dispersion weighted NMR spectroscopy
Authors: Rommel E. , Kimmich R. 
Published: March 2007

AbstractPulse sequences which permit imaging and volume‐selective determination of parameters characterizing the frequency dependence of the spin‐lattice relaxation time in the rotating frame, T1ρ are presented. The contrasts are due to slowly moving macromolecules or paramagnetic contrast agents. In vivo test experiments were carried out with tumorous mice treated with a contrast agent. It is shown that the contrast effect is dramatically enhanced in T1ρ dispersion images compared with images weighted by any of the relaxation times. © 1989 Academic Press, Inc.
Real‐time MR fluoroscopic data acquisition and image reconstruction
Authors: Wright Ronald C. , Riederer Stephen J. , Farzaneh Farhad , Rossman Phillip J. , Liu Yu 
Published: March 2007

AbstractWe describe an experimental system for performing high‐speed reconstruction of MR image data acquired with a GRASS sequence. System characteristics are an image acquisition time of 627 ms, continuous image reconstruction at a rate of 6 images/s, and an image reconstruction time of 120 ms. The result is a system for performing MR imaging in real time. © 1989 Academic Press, Inc.