bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of macromolecule resonances in the 1H NMR spectrum of rat brain
Authors: Behar Kevin L. , Ogino Takashi 
Published: March 2007

AbstractThe 1H NMR spectrum of the macromolecule fraction of rat brain cytosol was investigated following centrifugation and dialysis to remove low molecular weight metabolites and peptides (<3500 daltons). At least seven well resolved resonances were detected between 0.9 and 3.0 ppm in the 1H NMR spectrum of rat brain cytosol after dialysis, several of which cannot be observed in vivo due to overlap with N‐acetylaspartate, glutamate, glutamine, creatine, and yaminobutyric acid. Several cross‐peaks detected in 2D COSY spectra of the cytosolic macromolecule fraction coincided with those measured in a previous study of rat brain tissue in vitro and in situ (K. L. Behar, T. Ogino, Magn. Reson. Med. 17, 285 (1991)). Treatment of the cytosolic macromolecule fraction with a nonspecific protease permitted partial assignments of resonances in the 1H NMR spectrum to specific amino acids. Fractionation of the dialyzed cytosol of rat brain by gel filtration yielded qualitatively similar 1H NMR spectra for elution volumes corresponding to molecular masses from 12.5 kDa to over 100 kDa. The results indicate that many of the background nonmetabolite resonances observed in the 1H NMR spectrum of normal brain tissue arise from cytosolic proteins.
Quantification of tissue plasma volume in the rat by contrast‐enhanced magnetic resonance imaging
Authors: Kuwatsuru Ryohei , Shames David M. , Mühler Andreas , Mintorovitch Jan , Vexler Vladimir , Mann Jeffry S. , Cohn Frederic , Price David , Huberty John , Brasch Robert C. 
Published: March 2007

AbstractMagnetic resonance imaging enhanced with a macromolecular contrast medium (MMCM), albumin‐Gd‐DTPA, was used to estimate the plasma volume in vivo in the myocardium, lung, liver, and skeletal muscle of 10 normal rats. The plasma volumes of the same tissues in a parallel group of six rats were estimated in vitro by a conventional radioisotopic technique (111In‐transferrin). Plasma volumes of myocardium, lung, liver, and skeletal muscle estimated by the MR technique (μl plas. ia cc‐1 of tissue) were 101,109,163, and 11.0, respectively, while plasma volumes measured by the In‐transferrin radioisotope technique (mg plasma g‐1 of tissue) were 78.6, 215,143, and 11‐2, respectively. Assuming a ratio of densities of aerated lung to blood of 0.45 and of other tissues to blood of 1.0, correlation between the methods was excellent (R2 = 0.99) indicating that MR imaging enhanced with MMCM permits reliable in vivo estimation of tissue plasma volume in the rat.
Processing strategies for time‐course data sets in functional mri of the human brain
Authors: Bandettini Peter A. , Jesmanowicz A. , Wong Eric C. , Hyde James S. 
Published: March 2007

AbstractImage processing strategies for functional magnetic resonance imaging (FMRI) data sets acquired using a gradient‐recalled echo‐planar imaging sequence are considered. The analysis is carried out using the mathematics of vector spaces. Data sets consisting of N sequential images of the same slice of brain tissue are analyzed in the time‐domain and also, after Fourier transformation, in the frequency domain. A technique for thresholding is introduced that uses the shape of the response in a pixel compared with the shape of a reference waveform as the decision criterion. A method is presented to eliminate drifts in data that arise from subject movement. The methods are applied to experimental FMRI data from the motor—cortex and compared with more conventional image—subtraction methods. Several finger motion paradigms are considered in the context of the various image processing strategies. The most effective method for image processing involves thresholding by shape as characterized by the correlation coefficient of the data with respect to a reference waveform followed by formation of a cross‐correlation image. Emphasis is placed not only on image formation, but also on the use of signal processing techniques to characterize the temporal response of the brain to the paradigm.
MRI and MRS studies on the time course of rat brain lesions and the effect of drug treatment: Volume quantification and characterization of tissue heterogeneity by parameter selection
Authors: Pschorn Uwe , Körperich Hermann , Heymans Lothar , Subramanian Sankaran , Kuhn Winfried 
Published: March 2007

AbstractMagnetic resonance imaging has been used to follow the time course of lesions induced in the rat brain as an animal model for characterization of the volume of the lesion. The dispersion in spin‐spin relaxation has been used to characterize the nature of the brain lesion. Parameter selective estimation of T2 quantitative determination of the lesion sire and volume selective in vivo proton spectroscopy have been employed for the purpose. The work has been carried out on rats which were subject to lesioning by ibotenic acid as a model for excitotoxicity and also on rats which doses of ibotenic acid and subsequent doses of the NMDA antagonist drug MK 801 (dizocilpine). The time course of the progress of the lesions in untreated animals and the effect of neuroprotection by MK 801 was continuously monitored in all test animals. Further, a relatively new inhalation anesthetic agent, isoflurane, has been employed. A more logical and semiquantitative T2 bandwidth demarkation useful in distinguishing different degrees of lesioning from the onset and up to the ‘edema’ stage through penumbra (mild lesion), medium degree lesion and severe lesion has been proposed.
Spin‐lattice relaxation time measurement by means of a TurboFLASH technique
Authors: Blüml Stefan , Schad Lothar R. , Stepanow Boris , Lorenz Walter J. 
Published: March 2007

AbstractRapid measurements of in vivo proton spin‐lattice relaxation times (T1) in human tissues were performed by magnetic resonance imaging in a 1.5 T whole‐body super‐conducting MR scanner. The measurements employ serial TurboFLASH imaging (Snapshot‐FLASH) with scan times for a single experiment below 4 s. Using centric phase encoding order, an appropriate fitling of the T1‐parameter from images with minimum motion artifacts is possible. Comparative T1‐determination with a multipoint inversion recovery and spin‐echo technique was performed on phantoms containing Gd‐DTPA solutions with different T1‐values. We found a maximum deviation of 3.3% for T1 < 1100 ms and of 12.1% for 1100 ms < T1 < 1700 ms from the results obtained by the IR technique. In vivo measurements of T1‐relaxation times were performed in white and grey matter, cerebrospinal fluid, kidney, liver, spleen, muscle, and bone marrow, and yielded values that are in good agreement with reported data.
Apparent diffusion coefficient mapping of experimental focal cerebral ischemia using diffusion‐weighted echo‐planar imaging
Authors: Dardzinski Bernard J. , Sotak Christopher H. , Fisher Marc , Hasegawa Yasuhiro , Li Lirnin , Minematsu Kazuo 
Published: March 2007

AbstractDiffusion‐weighted, echo‐planar imaging (EPI) was used to map regional changes In the apparent diffusion coefficient (ADC) during experimental focal ischemia in the rat brain following permanent middle cerebral arterial occlusion (MCAO). Sixteen 64 × 64 diffusion‐weighted EPIs were acquired in 32 s with successively increasing amplitudes of the diffusion‐sensitive gradient pulses. A linear least‐squares regression algorithm was used to fit 15 of the 16 two‐dimensional matrices, on a pixel‐by‐pixel basis, to solve for the slope from which the ADC value was calculated. The correlation coefficient of the fit, R2 was used to filter the final ADC maps, and the ADCs were then scaled appropriately to be displayed in a 256 gray level format. Ranges (bins) of 0.05 × 10−3 mm2/s were then grouped and color coded to qualify and quantify the evolution of ischemia in the MCA territory. The percentage of area in the ischemic and contralateral hemispheres in seven ADC bins were calculated at 30, 60, and 120 min after MCAO for 10 animals and demonstrated a significant increase in ADC bins below 0.45 × 10−3 mm2/s and a decrease in bins above 0.50 × 10−3 mm2/s over the. The postmortem infarct area, as measured by TTC staining, was highly correlated with the portion of the ischemic hemisphere falling below ADC values of 0.55 × 10−3 mm2/s at 2 h after stroke onset. These studies suggest that focally ischemic brain tissue can be quantitatively subdivided according to ADC values and that ADC values below 0.55 × 10−3 mm2/s 2 h following ischemia highly predict infarction in a rat permanent occlusion stroke model.
Magnetic field distribution in models of trabecular bone
Authors: Ford J. Chetley , Wehrli Felix W. , Chung Hsiao‐Wen 
Published: March 2007

AbstractA magnetostatic model consisting of a tetragonal lattice of struts of diamagnetic material, mimicking vertebral trabecular bone, was developed. The model allows estimation of the magnetic field histogram within the lattice's unit cell as a function of geometric parameters. The field was computed analytically from the induced magnetic surface charge density on the faces of the struts. The contribution from the induced magnetic field to the effective transverse relaxation rate, R2 was obtained as the mean decay rate of the Fourier transformed histograms, for both fixed and randomly oriented lattices. The model predicts the field distribution to increase with both strut thickness and density, paralleling material density. Finally, significant changes in R2′ are predicted at constant material density, in that the field distribution widens with simultaneously increasing strut number density and decreasing strut thickness.
Identification of vascular structures as a major source of signal contrast in high resolution 2D and 3D functional activation imaging of the motor cortex at l.5T preliminary results
Authors: Lai S. , Hopkins A. L. , Haacke E. M. , Li D. , Wasserman B. A. , Buckley P. , Friedman L. , Meltzer H. , Hedera P. , Friedland R. 
Published: March 2007

AbstractWe have measured the T2* signal response associated with cortical activation due to finger motion at 1.5 Tesla. Both thin slice 2D and 3D images show signal intensity changes which vary from 2% to 32% depending on volunteer, echo time, slice thickness, and in‐plane resolution. The largest signal change occurred for the thinnest slices and highest resolution (2 mm3). This is consistent with reducing partial volume effects and a simple difference in phase between the intravascular signal and surrounding parenchyma. No inflow enhancement was seen on the 2D or 3D scans, confirming the nature of the signal difference for this approach was due to local field in‐homogeneity effects. Using 3D imaging, multiple effects can be seen simultaneously. With a 3D MRA method, it was possible to locate the vessel that was the source of the T2* behavior; it was in each case a vein on the surface of the cortical parenchyma.
Analysis of saturated phosphatidylcholine in amniotic fluid by 31P NMR
Authors: Pearce J. M. , Krone J. T. , Pappas A. A. , Komoroski R. A. 
Published: March 2007

AbstractA technique using solubilization with sodium cholate to resolve 31P NMR resonances of phospholipid molecular species was applied to amniotic fluid samples from 16 subjects. Gestational ages from 25 to 40 weeks were represented, and two subjects were sampled sequentially. Fitting of the partially resolved 31P NMR signal of phosphatidylcholine (PC) generated an estimate of percent disaturated acyl PC (%dsPC) which correlated more highly with gestational age than did several other potential indices of fetal lung maturation, such as the ratio of PC to inorganic phosphate from the solubilized spectra, or PC to sphingomyelin from extract spectra. In a few cases, enzyme‐catalyzed PC hydrolysis limited the precision, but did not appear to affect the accuracy, of the %dsPC estimates. Resolution of palmitoyl and oleoyl lyso‐PC species was observed for both the 1–and 2‐acyl isomers. Upfield shifts due to the presence of cis double bonds in the lone acyl chain of the lyso‐PCs were analogous to those observed for the diacyl PCs.
Differentiation of chronic lesions after stroke in stroke‐prone spontaneously hypertensive rats using diffusion weighted MRI
Authors: Takahashi M. , Fritz‐Zieroth B. , Chikugo T. , Ogawa H. 
Published: March 2007

AbstractApparent diffusion coefficients (ADCs) of tissue water were determined in chronic brain lesions of a rat stroke model, stroke‐prone spontaneously hypertensive rats and compared with histology. ADCs increased in the order control < edema < gliosis < cyst. The differences between individual groups were statistically significant. The increase in ADC is thought to mainly reflect a relative increase in the extracellular space in brain tissue. ADC values may be a clinically useful parameter for tissue characterization.
In Vivo proton spectroscopy and spectroscopic imaging of {1‐13C}‐g1ucose and its metabolic products
Authors: Van Zijl Peter C. M. , Scott Chesnick A. , Despres D. , Moonen Chrit T. W. , Rhiz‐Cabello J. , Van Gelderen P. 
Published: March 2007

AbstractMetaibolism of {1−13C}‐glucose was studied in situ in cat brain usinig gradient‐enhanced proton‐detected heteronuclear spectroscopy. Proton detection of {1−13C}‐glucose, {3−13C}−lactaite, 4−{13C}‐glutamine, 4−{13C}‐glutamate and the combined signals 2−{13C}‐glutamate/glutamine and 3−(13C}‐glutamate/glutamine was achieved, despite the fact that some of the associated proton resonances are close to the water signal. Two‐dimensional {1H‐13C}‐spectra demonstrate the possibility of in situ spectral assignment with 1H sensitivity and 13C resolution. Spectroscopic images of glucose and its metabolic products were also acquired, showing the possibility to study spatial dependence of metabolism.
Intracellular labeling of T‐cells with superparamagnetic contrast agents
Authors: Yeh Tzu‐Chen , Zhang Weiguo , Ildstad Suzanne T. , Ho Chien 
Published: March 2007

AbstractIsolated rat T‐cells have been labeled intracellularly, using endocytosis uptake of two superparamagnetic contrast agents, AquaMagl00 and BMS180549, which are both iron‐oxide particles coated with dextran. No deterioration of cell proliferation response to mitogen stimulation was observed alter labeling with either superparamagnetic contrast agent. AquaMag100 particles show aggregation and co‐precipitation in culture media for T‐cells. BMS180549 particles not only produce no observable aggregation or co‐precipitation, but also have a higher efficiency for labeling T‐cells than AquaPlag100. The efficiency of cell labeling was determined by measuring the decrease in the spin‐spin relaxation time of the water proton in cell samples containing 1 × 107 labeled T‐cells/milliliter of 2% w/w gelatin. After optimization of the labeling procedures, a shortening of the spin‐spin relaxation time by a factor of approximately 7 to 10 has been demonstrated. Under the present experimental conditions, the up‐regulation of low density lipoprotein receptor does not increase the labeling efficiency by endocytosis. Our results suggest that intracellular labeling of specific cell types can be achieved with good efficiency and the labeled cells can be detected by magnetic resonance imaging in rat testicles in vivo.
Experimental design of 31P MRS assessment of human forearm muscle function: Restrictions imposed by functional anatomy
Authors: Jeneson J. A. L. , van Dobbenburgh J. O. , van Echteld C. J. A. , Lekkerkerk C. , Janssen W. J. M. , Dorland L. , Berger R. , Brown T. R. 
Published: March 2007

AbstractThe restrictions imposed by the functional anatomy of the finger flexor muscles on the experimental design of 31P MRS assessment of human forearm muscle function employing surface coil localization and voluntary exercise were investigated. It was found that 31P MRS metabolic data of finger flexor muscle should be correlated with mechanical data of combined flexion of only the ring and little fingers, rather than all four fingers as has been commonly the case in previously reported studies.
Fast proton spectroscopic imaging using the sliced k‐space method
Authors: Norris David G. , Dreher Wolfgang 
Published: March 2007

AbstractThe use of one‐shot imaging methods for proton spectroscolpic imaging (1H‐SI) is examined. In particular the acquisition of Kx × Ky × Nt data points by means of Nt excitations, each acquiring a Kx, × Ky, k‐space slice, is advocated. A number of strategies for realising this experiment, and combining it with water suppression and volume‐selection are proposed. The practical implementation at 4.7 T for 1H‐Sl of the rat brain is described. Experimental results from a 32 × 32 spatial matrix with Nt = 64 are presented. Spectra obtained from volumes as low as 3.5 μl and within measuring times of as little as 3.8 min are shown. In these choline, creatine/phosphocreatine and N‐acetylaspartate are all clearly visible.
Simultaneous measurement of both lipid and lactate in isolated rat hearts by 1H NMR spectroscopy
Authors: Stewart Laura C. , Saunders John K. , Deslauriers Roxanne , Bourgeois Dominique , Nédélec Jean‐François J. 
Published: March 2007

AbstractMyocardial lipid and lactate levels are sensitive indicators of biochemical status: lipid levels have been shown to increase in response to high fat diets, disease or metabolic stress and elevated lactate levels are indicative of reduced oxygen supply. Selective measurement of lactate or lipid levels by 1H NMR is not straightforward since both the lactate methyl group and lipid methylene groups resonate at 1.3 ppm. We have overcome this difficulty by employing spectral editing techniques to observe both lipid methylene and lactate methyl resonances, and have measured lipid and lactate levels in perfused rat hearts during control perfusion and in response to metabolic stress. Lactate increased during ischemia and decreased during reperfusion, and the ischemia‐induced increase is inhibited by iodoacetate, as expected. In contrast, lipid levels increased during ischemia and remained elevated during reperfusion. Hearts from rats fed high fat diet show elevated lipid levels during control perfusion. Data obtained by 1H NMR are consistent with biochemical data, validating the technique.
31P transverse relaxation times of ATP in human brain in vivo
Authors: Jung Wulf‐Ingo , Widmaier Stefan , Bunse Michael , Seeger Uwe , Straubinger Klaus , Schick Fritz , Küper Klaus , Dietze Günther , Lutz Otto 
Published: March 2007

Abstract31P MRS examinations of the brain of 10 healthy volunteers were performed to determine T2 of the coupled ATP signals by use of the localized 90° ‐ TE/2 ‐ 2662 ‐ TE/2 ‐ acq frequency selective spin echo sequence for elimination of phase and intensity distortions. The T2 relaxation times obtained are much longer than usually assumed: γ‐ATP: 89 ± 9 ms; α‐ATP: 84 ± 6 ms; β‐ATP: 62 ± 3 ms.
A. functional MRI technique combining principles of echo‐shifting with a train of observations (PRESTO)
Authors: Liu Guoying , Sobering Geoffrey , Duyn Jeff , Moonen Chrit T. W. 
Published: March 2007

AbstractWe present a fast MRI technique sensitized to microscopic susceptibility effects. The method combines elements of echo‐shifted gradient‐recalled MR imaging (TE > TR) with the acquisition of multiple k‐space lines within a single TR‐period. The sequence results in a much reduced imaging time as compared with conventional gradient‐echo MRI methods. The feasibility of the method is demonstrated for susceptibility bolus tracking in the cat brain using an imaging time of 153 ms. The relative cerebral blood volume maps created with this method are comparable with those obtained with conventional methods.
Localized brain proton NMR spectroscopy in young adult phenylketonuria patients
Authors: Johannik K. , van Hecke P. , François B. , Marchal G. , Smet M‐H. , Jaeken J. , Breysem L. , Wilms G. , Baert A. L. 
Published: March 2007

AbstractLocalized proton magnetic resonance spectroscopy with short echo time (TE = 20 ms) was used to investigate biochemical changes in the cerebral white matter of 20 young adult patients (median 19 years) with phenylketonuria (PKU). Results were compared with those of a group of 12 age‐matched healthy volunteers (median 25 years). Concentrations of Nacetyl‐aspartate (NAA) and choline (Cho) relative to creatine (Cr) were unchanged. However, concentrations of inositol (Ins) relative to creatine were found to be significantly lower (P < 0.001) in the PKU patients (0.30 ± 0.09 versus 0.57 ± 0.17). Individual inositol concentrations did not correlate with age, diet, serum phenylalanine (Phe) levels or extent of pathological regions in the T,‐weighted images. The lack of correlation with individual data suggests that the decreased inositol concentration could be related to a metabolic deficiency during fetal development. No signal from the phenyl ring protons of phenylalanine was detected in the PKU patients (phenylalanine serum concentration ⩽ 1.27 mM), which suggests that concentration of phenylalanine may be lower in brain than in serum.
In vivo EPR studies of the metabolic fate of nitrosobenzene in the mouse
Authors: Fujii Hirotada , Zhao Baolu , Koscielniak Janusz , Berliner Lawrence J. 
Published: March 2007

AbstractWe report the first demonstration of EPR spectroscopy to study free radical reactions in live mice and excised muscle tissue resulting from the metabolism of nitrosobenzene. A broad three‐the EPR spectrum (aN = 11.6 G) appeared in the buttocks region of a mouse place in an L‐band loop gap resonator after intramuscular or intraperitoneal injection of 0.2 among nitrosobenzene. The signal intensity reached a maximum at 20 to 30 min and remained constant well beyond 2 h. If muscle tissue was dosed with nitrosobenzene and excised within 5 min, a similar three‐line X‐band EPR spectrum was obtained which was preceded by the rapid growth and subsequent decay of an EPR spectrum identical with that of the phenylhydronitroxide radical, which was presumably generated from reactions between nitrosobenzene and reducing agents in the blood or tissue such as NADH or ascorbic acid. A model system containing nitrosobenzene and unsaturated fatty acids (olive oil or animal fat) yielded an identical three‐line spectrum resulting from radical adducts of nitrosobenzene across the double bond. Overall, these results suggest that the most probable mechanism in vivo was nitrosobenzene covalently adding (“binding”) to polyunsaturated fatty acid clusters in fat or membranes.
Radioactive microsphere validation of a volume localized continuous saturation perfusion measurement
Authors: Walsh Edward G. , Minematsu K. , Leppo J. , Moore S. C. 
Published: March 2007

AbstractDetre et al. (Magn. Reson. Med. 23, 37–45 (1992)) and Zhang et al., (Magn. Reson. Med. 25, 362 (1992)) have recently demonstrated a technique for the measurement of regional cerebral blood flow (rCBF) based on the continuous saturation (or inversion) of the arterial blood supply to the brain in rats at 4.7 T. In the work reported here, we combined this technique with volume localized (PRESS) readouts to benefit from recording “perfusion” signals averaged over a larger volume, resulting in rapid acquisition of data with sufficient signal‐to‐noise ratio for application at 2.0 T. In 10 baseline flow measurements, the mean error between the NMR technique and the microsphere flow measurement was −1.5% with a standard deviation of 15.2%. For five measurements obtained with occlusion of the middle cerebral artery, the mean error was −32.4 ± 20.2%. Perfusion measurements from a single animal under hyper‐capnic conditions indicated that the NMR technique could underestimate rCBF at high flow rates. An error analysis of the NMR perfusion model is also presented, along with results for typical parameters encountered at 2.0 T.