bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nuclear magnetic resonance imaging characterization of a rat mammary tumor
Authors: Osbakken Mary D. , Kreider John W. , Taczanowsky Pauline 
Published: March 2007

AbstractIntradermal injection (1 × 106 cells) of rat mammary adenocarcinoma (13762A) was made in the back skin in 12 rats. Tumor growth and characterization was followed with nuclear magnetic resonance imaging (NMRI) in 9 rats (3 rats died before completion of the study) at 3, 4, and 5 weeks after injection, using spin echo, inversion‐recovery, and calculated T1 techniques. Three rats were sacrificed after each of the three imaging periods for histological studies designed to distinguish solid tumor mass from necrosis. Qualitative NMR imaging T1 values increased as the tumors increased in size as evidenced by a progressive decrease in image intensity compared to the surrounding tissues on the T1 weighted images. Calculated T1 values also increased as the tumors aged (Week 3 = 0.3 ± 0.11; Week 4 = 0.45 ± 0.07; Week 5 = 0.42 ± 0.03). Planimetry of tumor areas on histological sections showed that as tumors increased in size, the ratio of necrotic area to solid tumor area increased (Week 3 = 0.3 ± 0.11; Week 4 = 0.45 ± 0.07; Week 5 = 0.51 ± 0.05). These findings indicate that the progressive increase in T1 observed on NMR images may be secondary to the increasing degree of necrosis, with a resultant change in water content and state. Thus, the range of T1 values observed in tumors of similar type may be due to change in tumor physiology and anatomy as tumor growth progresses. In conclusion, careful correlation of histological data with NMR image data is necessary before NMR imaging can be used to provide reliable noninvasive histological information concerning tumor pathology. © 1986 Academic Press, Inc.
Energetics of human muscle: Exercise‐induced ATP depletion
Authors: Taylor D. J. , Styles P. , Matthews P. M. , Arnold D. A. , Gadian D. G. , Bore P. , Radda G. K. 
Published: March 2007

AbstractThe energetics of human muscle have been investigated in vivo during and after fatiguing aerobic, dynamic exercise. Changes in cytoplasmic pH and concentrations of phosphocreatine, ATP and Pi were followed using 31P nuclear magnetic resonance spectroscopy. ATP was significantly depleted in 6 out of 12 experiments and in these 6 experiments decreased to 55 ± 5% of the pre‐exercise concentration. Depleted muscle had a lower phosphocreatine concentration (17 ± 5% of resting value) and lower pH (6.12 ± 0.04) than fatigued muscle in which ATP loss was not observed (26 ± 5% for phosphocreatine and 6.37 ± 0.09 for pH). The free energy of hydrolysis of ATP was not significantly different in the two groups and was also similar in exhausted and nonexhausted muscle. Loss of ATP was associated with altered recovery of the muscle: [phosphocreatine], [Pi], and pH returned more slowly to their pre‐exercise values and the initial rate of oxidative phosphorylation was diminished. The restitution of [ATP] to its pre‐exercise value was much slower than that of the other metabolites. © 1986 Academic Press, Inc.
Quantification of pulsatile flow in MRI by an analysis of T2 changes in ECG‐gated multiecho experiments
Authors: Mueller E. , Deimling M. , Reinhardt E. R. 
Published: March 2007

AbstractThe transport of magnetization by fluid flow through thin slices in MRI causes changes in the measured T2 relaxation time. This effect is used to compute velocity values at several different times relative to the cardiac cycle using data in ECG‐gated multiecho experiments which last a few minutes. © 1986 Academic Press, Inc.
A gross morphologic, histologic, hematologic, and blood chemistry study of adult and neonatal mice chronically exposed to high magnetic fields
Authors: Osbakken Mary , Griffith James , Taczanowsky Pauline 
Published: March 2007

AbstractSix sets of Charles River CD‐1 mice (3 sets of adults and 3 sets of offspring: 156 mice total) were raised for varying times (360 h over 1 month to 624 h over 3 months) in a 1.89‐T magnetic field. Each set was divided into 3 groups: control group raised in the animal facility (Control); control group raised in the magnet room but not in the magner (Magnet‐Controls); experimental group raised in the magnet (Magnet). At the end of each predefined exposure period, the mice were euthanized and studied. Body and organ weights were lower in 3 of 6 sets in the Magnet groups when compared to Control groups, but they were not significantly different from age matched, sex matched Magnet‐Controls. This seems to indicate that the decreased growth of mice was due to the laboratory envi‐ronment surrounding the magnet, when compared to the animal facility environment, rather than to magnetic field effects. No consistent differences were found in gross and microscopic morphology, hematocrit and white blood cell counts, plasma creatine phosphokinase, lactie dehydrogenase, cholesterol, tricylceride, or protein concentrations in Magnet groups compared to the two control groups. © 1986 Academic Press, Inc.
Two‐point T1 measurement: Wide‐coverage optimizations by stochastic simulations
Authors: Lin Max S. , Fletcher James W. , Donati Robert M. 
Published: March 2007

AbstractStochastic reliability of T1 measurement from image signal ratios is examined in the ideal case by stochastic simulations in the context of wide‐coverage optimizations. Precise measurements prove to be accurate, and accurate ones precise. Sign‐preserved inversion‐recovery (IR)/non‐IR techniques are the best ration method, reciprocal non‐IR/IR ones being equivalent, but inconvenient. Wide‐coverage optima are relatively unsharp. Suggested guidelines for covering the 150‐ to 1500‐ms T1 band are minimal relevant TE; T1 about 400 ms; effective repetition times about in the ratio, TR2(IR)/TR1 (non‐IR) = 2.5–3.0, and in a sum as long as possible up to about TR1 + TR2 = 3.5–4.0 s; signal‐averaging after and only after TR1 + TR2 has been lengthened to the said region. Also suggested are different guidelines for covering T1 bands, 120–1200 and 200–1800 ms. Typically, precisions and accuracies improve linearly or faster with increasing S/N and (S/N)2, respectively. Unnecessarily high pixel resolutions or thin slicings exact great penalties in accuracies. Progressively shortening TR1 eventually transforms a wide coverage into a sharp targeting with small potential gains in a narrow T1 locality and large compromises almost everywhere else. The simulations yield an insight into applicabilities of standard error propagation analyses in two‐point T1 measurement. © 1986 Academic Press, Inc.
Multipurpose NMR imaging using stimulated echoes
Authors: Matthaei D. , Frahm J. , Haase A. , Merboldt K. D. , Hänicke W. 
Published: March 2007

AbstractSTEAM (stimulated‐echo acquisition mode) imaging techniques recently introduced by the authors are demonstrated to provide a versatile tool for improving the parametric specificity in NMR imaging. Stimulated echoes can be excited by a sequence of at least three rf pulses with flip angles of 90° or less. The main characteristics of the STEAM method are based on the great functional flexibility of an imaging sequence comprising three rf pulses unequal to 180° and three intervals prior to acquisition of the data. Major advantages are the easy access to contiguous multiplanar images, to CHESS (chemical‐shift‐selective) images, and to T1 information. Moreover, the rf power deposition is considerably reduced as compared to spin‐echo NMR imaging sequences. Here first in vivo results on human extremities are presented including contiguous multislice images, multiple CHESS images, and spin‐lattice relaxation time images calculated from a series of simultaneously recorded T1‐weighted STEAM images. © 1986 Academic Press, Inc.
An in vivo31P NMR study of cerebral hypoxic hypoxia in rats
Authors: Litt Lawrence , González‐Méndez Ricardo , Weinstein Philip R. , Severinghaus John W. , Hamilton William K. , Shuleshko Julia , Murphy‐Boesch Joseph , James Thomas L. 
Published: March 2007

AbstractTwenty minutes of hypoxic hypoxia in five anesthetized rats reversibly reduced cerebral PCr and pH while ATP stayed constant. Complete metabolic and neurologic recovery occurred after oxygen was restored. Careful control of physiological parameters resulted in metabolite changes that were the same, within errors, in each animal. © 1986 Academic Press, Inc.
Metabolic consequences of anoxia in the isolated, perfused guinea pig heart: Anaerobic metabolism of endogenous amino acids
Authors: Brainard James R. , Hoekenga David E. , Hutson Judith Y. 
Published: March 2007

AbstractThe metabolic consequences of anoxia in the isolated, perfused guinea pig heart were examined by 13C NMR spectroscopy of 13C‐labeled metabolites in situ. Upon addition of [3‐13C]pyruvate to the perfusate during normoxic conditions, label is detected in several metabolites, including alanine (C3), glutamate (C2, C3, and C4), and aspartate (C2 and C3), reaching steady state levels 10–15 min after the labeled precursor reaches the heart. During anoxia, the label in glutamate and aspartate decreases and label appears in C2(3) of succinate. This real‐time observation demonstrates that in the isolated intact heart, anaerobic metabolism of the amino acids aspartate and glutamate to succinate occurs. These pathways, which were first noted to occur in skeletal muscle of diving mammals, may provide a mechanism supplemental to glycolysis for the production of nucleoside triphosphates during periods of anoxia. © 1986 Academic Press, Inc.
Improved formulae for signal amplitudes in repeated NMR sequences: Applications in NMR imaging
Authors: Sperber G. O. , Ericsson A. , Hemmingsson A. , Jung B. , Thuomas K.‐Å. 
Published: March 2007

AbstractAn improved formalism describing the dependence of the signal strength on relaxation times and spin densities in pulsed nuclear magnetic resonance experiments is presented. It is especially applicable to repetitive experiments such as occur in imaging applications. Essentially, it includes long‐time spin coherence effects not considered in the algorithms usually adopted. Also, some generalizations of classical concepts are made. Validity criteria are studied using numerical simulations. The algorithm assumes a relatively inhomogeneous main magnetic field, but the computer simulations indicate that the inhomogeneity normally present in magnetic resonance imagers is sufficient. The simulations also indicate that the field gradient pulses applied in the spatial encoding procedure do not necessarily interfere seriously with the validity of the formulae, but complicate the choice of optimal formula and may in some circumstances prevent the spin system from reaching a steady state. © 1986 Academic Press, Inc.
A proton relaxation enhancement investigation of the binding of fatty acid spin labels to human serum albumin
Authors: Slane Jean M. K. , Lai Ching‐San , Hyde James S. 
Published: March 2007

AbstractProton relaxation enhancement (PRE) values for fatty acid spin labels bound to human serum albumin have been investigated using the inversion‐recovery method at 24 MHz. At 0.1 mM protein concentration and a label‐to‐protein ratio of one‐to‐one, the PRE value for 12‐Doxylstearate‐albumin complex is 7.8 ± 2.3, whereas the PRE values for 5‐Doxylstearate and 16‐Doxylstearate‐albumin complexes are 1.5 ± 0.6 and 1.7 ± 0.7, respectively. Addition of 10‐fold excess of stearic acid reduced the PRE values nearly to 1, indicating that the strong enhancements arise from direct binding of fatty acid spin labels to human serum albumin. PRE values for all three labels exhibit maxima as a function of the label‐to‐protein ratio, suggesting multiple binding sites for fatty acid spin labels with labels in the tightest binding sites not resulting in the most effective relaxation. Based on the rates of reduction of ESR signal amplitudes by sodium ascorbate, the difference in PRE values for the three fatty acid spin labels bound to albumin is attributed to the difference in water accessibility of the nitroxide moieties at various positions along the acyl chain, being greater at the C‐12 position than at C‐5 or C‐16 position. The PRE value of 8 for 12‐Doxylstearate bound to human serum albumin indicates that this complex may be a suitable paramagnetic contrast agent for in vivo NMR imaging. © 1986 Academic Press, Inc.
Gd(DOTA): An alternative to Gd(DTPA) as a T1,2 relaxation agent for NMR imaging or spectroscopy
Authors: Magerstädt Michael , Gansow Otto A. , Brechbiel Martin W. , Colcher David , Baltzer Lars , Knop Richard H. , Girton Mary E. , Naegele Matthias 
Published: March 2007

AbstractMethods have been devised for obtaining gadolinium(III) complexes of the ligands NOTA (1, 4, 7‐triazacyclononane‐N, N′, N″‐triacetic acid), DOTA (1, 4, 7, 10‐tetraazacyclododecane‐N, N′, N″, N‴‐tetraacetic acid), TETA (1,4,8,11‐tetraazacyclotetradecane‐N, N′, N″, N‴‐tetraacetic acid), and DTPA (diethylenetriaminepentaacetic acid) as solids for use as pharmaceuticals. Their effectiveness as in vitro and in vivo contrast agents for NMR imaging or T1,2 relaxation agents for spectroscopy has been investigated. The Gd(DOTA) complex was shown to be a more stable alternative to Gd(DTPA) by serum stability studies and measurement of stability constants. Images of tumors grown in athymic mice were obtained by NMR after injection of Gd(DOTA) and Gd(DTPA). © 1986 Academic Press, Inc.
31P NMR measurements of T2 relaxation times of ATP with surface coils: Suppression of J modulation
Authors: Albrand J. P. , Foray M. F. , Decorps M. , Remy C. 
Published: March 2007

AbstractThe efficiency of selective refocusing pulses to suppress J modulation of spin echoes when using the surface‐coil technique has been investigated. 31P T2 values obtained for ATP by the HAHN spin‐echo method remain in good agreement when the standard refocusing pulse is replaced by selective pulses based on the DANTE excitation method. © 1986 Academic Press, Inc.
Tissue distribution and stability of metalloporphyrin MRI contrast agents
Authors: Lyon R. C. , Faustino P. J. , Cohen J. S. , Katz A. , Mornex F. , Colcher D. , Baglin C. , Koenig S. H. , Hambright P. 
Published: March 2007

AbstractMn(III), Fe(III), and Gd(III) complexes of tetrakis(4‐sulfonatophenyl)porphyrin (TPPS) and several other porphyrins were evaluated as potential MRI contrast agents. Based on consideration of relaxivity and stability properties in solution, Mn TPPS was found to be the compound of choice. At pH 7 the Gd and Mn complexes significantly enhanced the water proton relaxation rate, while the relaxivity of Fe TPPS exhibited a significant loss of relaxivity above pH 6 due to oxy‐dimer formation. Although GdTPPS exhibited the highest relaxivity in solution, this property was rapidly lost due to dissociation of the metal ion. By contrast MnTPPS remained stable in human plasma after incubation for 9 days. Upon intravenous injection into athymic mice bearing subcutaneous human colon carcinoma xenografts, MnTPPS provided enhanced relaxation of the tissue water in several excised mouse tissues, notably kidney, liver, and tumor. The results at a fixed field (0.25 T) and relaxation dispersion studies showed decreases in water relaxation rates with time for kidney and liver, but an increase for the tumor, with a maximum near 4 days at the highest dose used.
The flip‐angle effect: A method for detection of sodium‐23 quadrupole splitting in tissue
Authors: Joseph Peter M. , Summers Ronald M. 
Published: March 2007

AbstractA method is presented for the detection of quadrupole splitting in tissue, where the spectral line splittings are typically unobservable. The method used is a study of the rate of rotation of the flip angle as a function of radiofrequency (rf) amplitude. Our results with samples of skeletal muscle and cat brain indicate the absence of quadrupole splitting. © 1987 Academic Press, Inc.
In vivo31P NMR spectroscopy of agonist‐stimulated phosphatidylinositol metabolism in cat brain
Authors: Renshaw Perry F. , Schnall Mitchell D. , Leigh John S. 
Published: March 2007

AbstractAs a result of the agonist stimulation of muscarinic receptors, myc‐inositol‐1 ‐phosphate accumulates in the presence of millimolar lithium concentrations. This accumulation of myo‐inositol‐1 ‐phosphate can be detected by in vivo 31P NMR spectroscopy. Since myo‐inositol‐1‐phosphate is a breakdown product of phosphatidylinositol, this may provide a means of noninvasively monitoring phosphatidylinositol metabolism in vivo. © 1987 Academic Press, Inc.
Intracellular sodium and lithium NMR relaxation times in the perfused frog heart
Authors: Burstein Deborah , Fossel Eric T. 
Published: March 2007

AbstractWe have used a combination of a shift reagent and mathematical filtering or presaturation of the extracellular sodium resonance for the quantitative investigation of the intracellular sodium and lithium relaxation times in the perfused frog heart. While the T1 of the intracellular sodium was found to consist of a single‐exponential time constant (approximately 23 ms), the T2, was better fit as a double‐exponential decay with time constants of approximately 2 and 17 ms. However, the relative amplitudes of the two time constants in the T2 decay were found to be inconsistent with those which would be expected from a homogeneous pool of nuclei undergoing quadrupolar interactions. The relaxation times were not changed by a fivefold increase in the intracellular sodium level (due to perfusion with a ouabain‐containing buffer). The T1 and T2, of the intracellular lithium (after perfusion with lithium‐containing buffer) were both well fit by single exponentials (700‐ and 31‐ms time constants, respectively). © 1987 Academic Press, Inc.
Further improvement of high‐speed NMR flow‐velocity measurement using a differential phase‐encoding technique
Authors: Kim Y. S. , Mun C. W. , Jung K. J. , Cho Z. H. 
Published: March 2007

AbstractAn NMR imaging technique applicable to high‐velocity flow imaging is described. By subtraction of two phase images obtained by varying the flow‐encoding gradient, it is possible to extract much larger ranges of velocity components. This differential phase‐encoding technique is tested by experiments in a phantom as well as a human volunteer. © 1987 Academic Press, Inc.
31P NMR measurements of intracellular pH in erythrocytes: Direct comparison with measurements using freeze‐thaw and investigation into the influence of ionic strength and Mg2+
Authors: Petersen Aqqaluk , Jacobsen Jens Peter , Hørder Mogens 
Published: March 2007

AbstractThe pH‐dependent chemical shift behavior in 31P NMR spectroscopy of inorganic phosphate (P1) and methylphosphonic acid (MeP) in solutions of various composition at 37°C are presented. An ionic strength dependent lowering of the pKa. values of both P1 and MeP is observed. 3 mmol/liter Mg2+ did not affect the pH‐dependent chemical shift behavior of P1 and MeP in solutions containing 135 mmol/liter KCl and 5 mmol/liter NaCl. This finding: was reinforced by adding 5 mmol/liter 2,3‐diphosphoglycerate (2,3‐DPG) and 1.5 mmol/liter ATP to solutions with 3 mmol/liter Mg2+. The presence of these Mg+‐binding substances had no detectable effect on the chemical shift of P1 and MeP at various pH values The pH dependence of the chemical shift of MeP, P1 and 2,3‐DPG in oxygenated erythrolysates was compared to protein free model solutions. No significant differences could be detected for MeP and P1 whereas there was a change in the chemical shift of about 0.1–0.2 ppm for both phosphates in 2,3‐DPG. Finally intracellular pH estimated by 31P NMR were compared to pH measured by electrode in freeze‐thawed hemolysates. At an extracellular pH of 7.341 ± 0.045 (SD) (n = 6) the intracellular pH was 7.160 ± 0.014 (SD) by the freeze‐thaw procedure and 7.213 ± 0.027 (SD), 7.172 ± 0.029 (SD), and 7.152 ± 0.033 (SD) estimated by the chemical shift of MeP, and 3‐phosphorus and 2‐phosphorus of 2,3‐DPG, respectively. © 1987 Academic Press, Inc.
Three‐dimensional MRI microscopy of the normal rat brain
Authors: Johnson G. Allan , Thompson Morrow B. , Drayer Burton P. 
Published: March 2007

AbstractMagnetic resonance imaging techniques have been developed to enable imaging of the live rat brain with thin (1.2‐mm) slices and microscopic pixels (115 × 115 μm). Signal‐to‐noise ratios high enough to realize the microscopic resolution are obtained with of coils designed for the subject and through the use of three dimensional Fourier spin warp imaging. The technique yields 16 contiguous slices. Correlation with fixed pathologic specimens enables unequivocal identification of gray and white matter structures in the brain of a live 200‐g rat. Structures clearly visible in the MR images include Ammon's horn, the hypothalamus, corpus callosum and substantia nigra, as well as a number of brainstem nuclei. © 1987 Academic Press, Inc.
Noninvasive evaluation of effects of an aldose reductase inhibitor in rat brain by 19F FDG NMR spectroscopy
Authors: Nakada Tsutomu , Kwee Ingrid L. 
Published: March 2007

AbstractThe inhibitory effects of an aldose reductase inhibitor, sorbinil (Pfizer, NY), on cerebral glucose metabolism were investigated noninvasively in rat brain using 19F nuclear magnetic resonance (NMR) spectroscopy and 2‐fluoro‐2‐deoxy‐D‐glucose (2‐FDG). Sorbinil given orally in the daily recommended doses (25 mg/kg) for man for the treatment of diabetic complications inhibited 2‐FDG flux into the aldose reductase sorbitol (ARS) pathway, demonstrated as a reduction in the intensity of the ARS index resonance as well as an increase in the resonance area ratio between the pentose monophosphate shunt (PMS) and ARS index resonances (PMS/ARS ratio). Spatial metabolite mapping using rotating frame one‐dimensional zeugmatography indicated that the inhibitory effect is spatially nonspecific. The present study is the first direct noninvasive observation of the effects of a pharmacological agent on cerebral enzymatic activities. © 1987 Academic Press, Inc.
The effect of moderate blood alcohol levels on T1 and T2 relaxation times in the brains of normal volunteers
Authors: Logsdail Stephen , Miller David , Macmanus David , Johnson Glyn , Lolin Yvette , O'Gorman Patrick 
Published: March 2007

AbstractT1 and T2 measurements of the brains of six human volunteers did not change in the presence of moderate blood alcohol levels. © 1987 Academic press, Inc.
The effects of finite sampling in spin‐echo or field‐echo magnetic resonance imaging
Authors: Haacke E. M. 
Published: March 2007

AbstractThe artifacts associated with finite sampling in magnetic resonance imaging are shown to be significant when the ratio of half the sampling time, Ts/2, to transverse relaxation time, T2 is on the order of unity or greater. For both symmetric and asymmetric sampling, these artifacts include enhanced high spatial frequency image intensity (bright edges), induced systematic noise, loss of resolution, and changes in phase. Simple filtering of the raw data does not remove the problem in tissues with positiondependent T2 values. An exact deconvolution method is described to remove these problems associated with finite position‐dependent T2 values. © 1987 Academic Press, Inc.
NMR spectroscopy of heterogeneous solid‐liquid mixtures. Spin grouping and exchange analysis of proton spin relaxation in a tissue
Authors: Sobol W. T. , Pintar M. M. 
Published: March 2007

AbstractAn attempt to resolve the complicated proton NMR signal of a heterogeneous material is presented. Lung tissue is used to illustrate the approach to this problem, which is based on resolving the total proton magnetization into components according to their relaxation times. This procedure is utilized at both low and high magnetic fields. These results are then correlated and analyzed for the effect of exchange between spin groups. For example, the total proton NMR signal of lung tissue is shown to arise from three interacting proton groups: protons on solid macromolecules, bound water protons, and bulk water protons. The dynamics of water is modeled to satisfy the dispersivity and the values of the relaxation parameters obtained considering the effect of exchange. It is proposed that this approach is generally applicable. © 1987 Academic Press, Inc.