bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural studies of NMR detected lipids in myocardial ischemia
Authors: Evanochko William T. , Pohost Gerald M. 
Published: March 2007

AbstractLipid‐induced abnormalities in myocardial function have been implicated in a number of ischemic events including the accumulation of lipids in human myocardium following myocardial infarction. Although animal models have shown the source of these lipids to be triglycerides, the specific species involved has not been identified. In order to better understand the mechanism(s) defining this lipid accumulation, it follows that the identification of the lipids involved may be important in achieving this aim. Therefore, this study examined the use of NMR probes for delineating the biochemical makeup of the increased 1H NMR observed lipid signal following myocardial infarction. Specifically, the present study demonstrated the utility of the spin‐echo pulse sequence for the study of alterations in myocardial lipids following ischemic injury. Spin‐echo spectra allowed the analysis of subsets of lipids within the large lipid pool inherent in most myocardium. The analyses of the chemical shifts of the lipid resonances provided a simple yet powerful means for deducing lipid class associated with the ischemic injury and suggested the species arises predominantly from saturated lipids. The examination of the CH2/CH3 NMR ratio provided additional information regarding the species involved, however, because the spin‐echo technique was utilized, which may distort certain signal intensities, caution must be exercised in interpreting the specific species involved. With this in mind, a tentative assignment has been given to octanoic acid. Finally, a temperature dependence of the lipid signals was noted and determined to be unique for spin‐echo lipid. Although this dependence did not provide the necessary information regarding the gel‐to‐liquid crystal phase transition temperature which might aid in understanding the origin of the lipid species, it did determine that the species involved was only the spin‐echo observed lipid and that the dependence was reversible. Finally, the increase in signal intensity associated with the spin‐echo lipid signal at physiologic temperature may provide the necessary means to observe such species utilizing chemical shift imaging methods.
Optimization of magnetization transfer experiments for kinetic rate measurements
Authors: Taitelbaum Haim , Weiss George H. , Spencer Richard G. S. 
Published: March 2007

AbstractA framework is developed for optimizing magnetization transfer experiments for measuring first‐order rate constants of a two‐component exchange network. In the analysis the spin‐lattice relaxation time of the non‐saturated resonance is assumed to be known. However, we demonstrate that our work can also be applied to cases in which the spin‐lattice relaxation time falls within a physiologically reasonable range for this parameter. We provide an algorithm for the parameters permitting the experimenter to optimize the selection of measurement times in order to control the error in a worst‐case scenario. In addition, we compare the performance of the time‐dependent saturation experiment with an inversion experiment in this framework, finding that the former always leads to a more effective design.
Evaluation of liquid chromatography coupled with high‐field 1H NMR spectroscopy for drug metabolite detection and characterization: The identification of paracetamol metabolites in urine and bile
Authors: Spraul M. , Hofmann M. , Lindon J. C. , Farrant R. D. , Seddon M. J. , Nicholson J. K. , Wilson I. D. 
Published: March 2007

AbstractThe applicability of coupled reversed‐phase high performance liquid chromatography (HPLC)‐NMR spectroscopy for the detection and identification of paracetamol (N‐(4‐hydroxyphenyl)acetamide) and its sulfate, glucuronide and N‐acetylcysteinyl metabolites in the unprocessed biological fluids, human urine, rat urine and rat bile, is investigated. Analysis of these samples was performed by gradient HPLC elution and directly coupled 500 MHz 1H NMR spectroscopy detection using a combination of one‐ and two‐dimensional NMR methods in stopped‐flow mode. The stopped‐flow approach is demonstrated to be an efficient technique for identification of drug metabolites which have, for example, a UV‐chromophore. Stopped‐flow HPLC analysis with NMR detection is a viable technique and halting the chromatographic process several times during a run has a negligible effect on the separation and NMR characterization. The post‐acquisition data processing method of 'quantified maximum entropy' is shown to provide a means of improving the quality of spectra for minor components, thus aiding NMR resonance assignments.
Absolute quantitative proton NMR spectroscopy based on the amplitude of the local water suppression pulse. Quantification of brain water and metabolites
Authors: Danielsen E. R. , Henriksen O. 
Published: March 2007

AbstractQuantification in localized proton NMR spectroscopy has been achieved by various methods in recent years. A new method for absolute quantification is described in this paper. The method simultaneously rules out problems with B1 field inhomogeneity and coil loading, utilizing a relation between the locally optimized amplitude of a chemical shift selective water suppression pulse and the acquired signal. Validity and feasibility of quantification using the method of the water suppression pulse is demonstrated. Brain water and cerebral metabolites have been quantified in a study of 12 healthy volunteers. Localized proton NMR spectra were obtained from a region of primarily white matter in the occipital lobe. The observable water content in the NMR spectra was 0.685±0.025. The absolute metabolite concentrations were: [total choline]= 1.25±0.21 mM, [total creatine]= 6.71±0.59 mM and [NAA]= 9.15±0.74 mM. It is concluded that the quantification method is easily applied in vivo, and that the absolute concentrations obtained are similar to results in other studies except those relying on assumptions of the concentration of an internal reference. The advantage of the quantification method reported here is that it is independent of the assumptions needed for other methods.
Effects of high energy shock waves on tumor blood flow and metabolism: 31P/1H/2H nuclear magnetic resonance study
Authors: Smits Geert A. H. J. , Cornel Erik B. , van de Boogert Erik , Oosterhof Gosse O. N. , Debruyne Frans M. J. , Schalken Jack A. , Heerschap Arend 
Published: March 2007

AbstractThe effects of high energy shock waves (HESW) on tumor cell metabolism and tumor blood flow were studied in the NU‐1 kidney cancer xenograft by multinuclear 1H/2H/31P magnetic resonance spectroscopy. Tumor xenografts were exposed to 800 HESW using an experimental electromagnetic shock wave emitter based on the Siemens Lithostar Plus, which is used for clinical lithotripsy. Exposure of tumors to 800 HESW resulted in a temporary decrease of tumor blood flow (TBF) determined by the 2H NMR monitoring of the 2HO1H wash‐out after intratumoral injection. By concomitant recording of 31P and 1H NMR spectra, tumor pH, high‐energy phosphates and lactate levels were followed. Tumor treatment with HESW transiently resulted in acidification, ATP decrease, Pi increase and lactate increase. In contrast, HESW administration adjacent to the tumor did not significantly influence TBF, tumor pH, high‐energy phosphates or lactate levels, showing that the observed alterations are caused by an interaction of HESW and tumor tisue. The most likely explanation for these observations is that HESW administration causes local vascular malfunctioning followed by a reduction in oxygen and nutrient supply to the tumor which leads to a decreased aerobic energy metabolism. The results of this study may be used to aid the design of HESW‐based therapies.
Clinical proton spectroscopy–towards routine diagnostic use
Authors: Moser Ewald 
Published: March 2007

AbstractDespite 40 years of NMR spectroscopy and 10 years of in vivo spectroscopy in humans, the break‐even point for routine clinical diagnosis has not yet been reached. Obviously there are many factors that stimulate but also restrict the use of proton NMR spectroscopy in clinical routine.
Identification of ethanolamine in rat and gerbil brain tissue extracts by NMR spectroscopy
Authors: Smart S. C. , Fox G. B. , Allen K. L. , Swanson A. G. , Newman M. J. , Swayne G. T. G. , Clark J. B. , Sales K. D. , Williams S. C. R. 
Published: March 2007

AbstractSome NMR resonances which have previously been observed but not identified in mammalian brain tissue extracts have been shown to arise from ethanolamine. This conclusion is drawn from a systematic study of the perchloric acid extracts of rodent brain tissue in which several NMR experiments were used to assign the peaks unambiguously. The extraction procedure used in this work gave samples with highly reproducible spectra, and ethanolamine was observed in all our extract samples. A localized increase in the concentration of ethanolamine was seen in the spectra of extracts produced from a cerebral infarct induced by occlusion of the middle cerebral artery in the rat.
An experimental approach for dynamic rat liver observation in vivo and ex vivo by 31P localized MR spectroscopy for follow‐up of liver status at different steps of orthotopic transplantation–a feasibility study
Authors: Volk A. , Astarcioglu I. , Adam R. , Mispelter J. , Collet V. , Dimicoli J. L. , Bismuth H. 
Published: March 2007

AbstractAn experimental approach was evaluated to perform a follow‐up of rat liver transplantation by 31P spectroscopy. The approach is based on the use of an implanted surface coil attached to the liver and inductively coupled to the receiver/transmitter line by an external coupling loop. Spatial localization to the liver was performed by selective excitation and dephasing of spins in a slice between the implanted and the coupling coil, the slice being positioned on a proton image acquired prior to spectroscopy. Characteristics of the protocol were established on a phantom and in vivo on non‐transplanted rat livers indicating good localization and high signal‐to‐noise ratio. Preliminary results obtained on transplanted livers revealed a relation between evolution of the 31P spectrum and animal survival. As shown in separate experiments, the same technique also enabled easy acquisition of the 31P profile of livers stored at 4°C in University of Wisconsin solution. Therefore, the experimental approach described here opens up the possibility of measuring changes of the 31P profile on the same liver during the whole transplantation procedure, i.e., in the donor, during preservation and after transplantation, and comparing evolution of spectra with transplantation outcome.
Long‐term observation of in vivo31P nmr spectra in carbon tetrachloride‐intoxicated rabbit liver using implanted wireless surface coil
Authors: Morikawa Shigehiro , Inubushi Toshiro , Kito Kouichi , Amano Shigeru 
Published: March 2007

AbstractPhosphorus‐31 NMR spectra in rabbit liver were successively observed for more than 5 months in a chronic CCI4 intoxication model using implanted wireless surface coils. The quality of the obtained NMR spectra was satisfactory and there was sufficient time resolution to follow the dynamic changes that occurred during a fructose tolerance test. The implanted coil did not lead to any serious adverse effects such as infection or liver dysfunction. During an 18‐week administration of CCI4, the area of the phosphodiester peak significantly decreased. The ratio of Pi/β‐ATP was transiently elevated and gradually returned to the control level. In the fructose tolerance test, the increase in phosphomonoester and the decrease in Pi and β‐ATP after i.v. fructose loading were apparent, but the degrees in these changes became smaller during the CCI4 intoxication. This wireless surface coil was useful for consecutive and non‐invasive 31P NMR observations of the liver to follow chronically treated animal models over a period of several months.
Salicylate poisoning: Two‐dimensional J‐resolved NMR urinalysis
Authors: Maschke S. , Lhermitte M. , Azaroual N. , Vermeersch G. , Imbenotte M. , Leclerc F. 
Published: March 2007

AbstractIdentification of a case of acute salicylate intoxication using 300 MHz 1H NMR spectroscopy of a urine sample is reported. It has been achieved by using a combination of a one‐dimensional experiment with water presaturation and a two‐dimensional homonuclear J‐resolved experiment. By these means, lysine and the three major metabolites of acetylsalicylic acid have been assigned in the crude urine. The results are compared with those obtained at 600 MHz and with classical biochemical methods. The use of this method for routine diagnosis in biological analysis is discussed.
Preliminary observations of transverse relaxation rates obtained at 3 Tesla from the substantia nigra of adult normal human brain
Authors: Helpern J. A. , Gorell J. M. , Deniau J. C. , Welch K. M. A. , Ordidge R. J. 
Published: March 2007

AbstractThe transverse relaxation rates R2 and R*2 were measured at 3 T in the substantia nigra of the midbrain of adult normal human controls. The relaxation rate arising from magnetic inhomogeneities, R2′, was calculated from the relationship R*2=R2+R2′. No significant differences were found for any parameters between left and right side substantia nigral regions, however, a significant inverse correlation was found between R2 and R2′ (r=0.70, p=0.035). Water diffusion, in the presence of paramagnetic metal ions, may play a role in determining the relative contributions to reversible and irreversible transverse relaxation and may explain the inverse correlation demonstrated here.
A 31P NMR investigation into the effects of repeated vascular occlusion on uterine metabolites, intracellular pH and force, in vivo
Authors: Harrison Norma , Wray Susan , Larcombe‐Mcdouall Jacky B. 
Published: March 2007

AbstractLittle is known about the metabolic effects of ischaemia on high energy phosphates in vivo in smooth muscle. We have developed a method for reversibly occluding the uterine artery, which allows simultaneous measurement of uterine metabolites using 31P NMR spectroscopy, and intra‐uterine pressure, in vivo during ischaemia. We have investigated the effects of repeated ischaemia on metabolites, intracellular pH and contractions in anaesthetized rats. Occlusion produced an immediate drop in uterine blood flow and decreased contractions. Although contractions recovered upon reperfusion after both occlusions, the contractile activity was less after the second period of occlusion, suggesting less resistance after a prior ischaemic period. Significant falls in [ATP] and [phosphocreatine] and an increase in [Pi] occurred during both occlusions. These were all reversed within 30 min of reperfusion. There was a large drop in intracellular pH produced by occlusion, which was rapidly reversed upon reperfusion. The changes in metabolites and intracellular pH were similar during the repeated ischaemic period, to those occurring during the first ischaemic period suggesting no alteration in energy production or utilization had occurred, with prior exposure to ischaemia. The significance of these results to the functioning of the uterus in labour is briefly discussed.
1H MR visible lipids in colon tissue from normal and carcinogen‐treated rats
Authors: Brière Kathleen M. , Kuesel Annette C. , Ian Smith C. P. , Bird Ranjana P. 
Published: March 2007

AbstractMetabolic characteristics of colon mucosa, submucosa, muscularis and tumour specimens from four control (n = 105) and nine carcinogen (azoxymethane)‐treated (n = 91) Sprague‐Dawley rats were investigated by ex vivo 1H MRS. Ninety‐seven per cent of pure mucosa samples (n = 59) yielded spectra with narrow lipid resonances (chemical shift δ of ‐ (CH2)n‐, 1.3 ppm; linewidth at half‐height v1/2, 30‐50 Hz). Eighty‐two per cent of control mucosa samples with histologically proven submucosa contamination (n = 11) and 46% of control cross‐sections (containing mucosa, submucosa and muscularis; n = 57) yielded spectra with broad lipid resonances (δ ‐ (CH2)n ‐, 1.5 ppm; v1/2, 80‐100 Hz) identical to those of adipose tissue surrounding rat colon. Thirty per cent of tumour samples (n = 10) yielded spectra with narrow lipid resonances while 70% contained no significant amount of MR visible lipids. We conclude that (i) lipids giving rise to broad resonances are in the heterogeneously distributed adipocytes of submucosa, (ii) lipids giving rise to narrow resonances are within the mucosa in an unknown structural environment, and (iii) the type and distribution of lipids in human and rat colon are similar. Tumours contained significantly more taurine than pure control mucosa (n = 15; p<0.004) and pure mucosa containing aberrant crypt foci (putative preneoplasm, n = 36; p<0.002). Our results suggest that the rat colon is a good model for 1H MR investigations of human colon carcinogenesis.
Signal changes in gradient echo images of human brain induced by hypo‐ and hyperoxia
Authors: Rostrup E. , Larsson H. B. W. , Toft P. B. , Garde K. , Henriksen O. 
Published: March 2007

AbstractThe effect of hypoxia (inspired oxygen fraction, F1O2 of 10% and 16%) and hyperoxia (F1O2) of 100%) on gradient echo images of the brain using long echo times was investigated in six healthy volunteers (age 24‐28 years). Different flip angles were used with an F1O2 of 10% to assess the importance of saturation effects. The total cerebral blood flow was measured by a phase mapping technique during normoxia as well as hypoxia (F1O2 of 10% and 16%) and hyperoxia (F1O2 of 50% and 100%). High relative signal changes were found, independently of the flip angle, with F1O2 of 10%. With a flip angle of 40° the values of δR2* for cortical grey matter, central grey matter, white matter and the sagittal sinus were 0.79, 0.41, 0.26 and 3.00/s; with a flip angle of 10° the corresponding values were 0.70, 0.37, 0.24 and 3.15/s. The total cerebral blood flow increased by 41% during inhalation of 10% O2 and decreased by 27% during 100% O2; no flow changes were seen during moderate changes in F1O2. It is concluded that flow effects play a minor role for fMRI signal strength in this application since (i) they did not abolish the signal changes caused by changes in blood oxygenation during hyper‐ and hypoxia, (ii) the observed signal changes were closely related to the changes in arterial oxygen saturation during hypoxia and (iii) the signal changes were little affected by changing the flip angle from 40 to 10°.
Simultaneous recording of eeg, dc potential and diffusion‐weighted nmr imaging during potassium induced cortical spreading depression in rats
Authors: Busch Elmar , Hoehn‐Berlage Mathias , Eis Manfred , Gyngell Michael L. , Hossmann Konstantin‐Alexander 
Published: March 2007

AbstractElectrophysiological recording during in vivo NMR imaging for correlation of electrophysiological events with changes in NMR parameters has, until now, not been satisfactory. Here we present a method that uses specially prepared calomel electrodes for the continuous monitoring of both cortical steady potential and EEG during in vivo NMR imaging studies of experimental animal models. In order to demonstrate the reliability of this approach we elicited single episodes of cortical spreading depression in rats by intracortical potassium acetate injection, using an intracerebral micropipette. During the passage of DC potential shifts and associated reduction in EEG amplitude, hyperintense regions, reflecting the progression of cortical spreading depression over the cortex, were visible in diffusion‐weighted images of the rat brains. No susceptibility artifacts due to the electrodes and micropipette were visible in the NMR data. Thus, we have demonstrated under controlled experimental conditions, that electrophysiological recording with calomel electrodes can be performed simultaneously with diffusion‐weighted NMR imaging. The described method enables further NMR investigations of phenomena which are detectable by electrophysiology.
Diffusion coefficients of atp and creatine phosphate in isolated muscle: pulsed gradient 31p nmr of small biological samples
Authors: Hubley Mark J. , Moerland Timothy S. , Rosanske Richard C. 
Published: March 2007

AbstractMeasurements of the intracellular diffusion coefficients (Di) of ATP and creatine phosphate (PCr) in stable, isolated preparations of skeletal muscle were made by means of pulsed field gradient (PFG) 31P NMR. Experiments used a PFG NMR probe specifically designed for small, superfused biological samples. This provided a magnetic field gradient in the z axis of up to 195 G/cm with minimal eddy currents. DiATP and DiPCr in white (fast, glycolytic) skeletal muscle from goldfish (Carassius auratus) were determined to be 2.48±0.33 and 3.49±0.33 × 10−6 cm2/s, respectively, at 25°C and a diffusion time of approximately 19ms. For comparison with Di values, diffusion coefficients of ATP and PCr also were measured in solutions of ionic composition similar to that of fish muscle cytosol. The in vitro diffusion coefficients of ATP and PCr were 3.54±0.11 and 5.28±0.08 × 10−6cm2/s, respectively, at 25°C.
Water‐Suppressed one‐dimensional 1h nmr chemical shift imaging of the heart before and after regional ischemia
Authors: Balschi James A. , Hetherington Hoby P. , Pohost Gerald M. , Bradley Edwin L. 
Published: March 2007

AbstractThis study tests the hypothesis that brief periods of ischemia result in an increase in myocardial lipids during early reperfusion. We conducted 1H NMR spectroscopy to serially measure myocardial lipids before and after regional ischemia. Localized 1H NMR spectra (spatial resolution of 1.25mm) were obtained using a one‐dimensional chemical shift imaging technique. Two regions, the subendocardium and the subepicardium, were estimated by summing spectral areas from three slices (3.75 mm). Two groups of dogs that underwent a 45 min ischemia and 4 h reperfusion were studied: a group in which the myocardium beneath the surface coil underwent ischemia and reperfusion; and a group in which the ischemic event was distant from the tissue under the surface coil. Microsphere measurements showed significant blood flow reductions in the subepicardium and subendocardium in the ischemic zones during coronary occlusion. Flow returned to baseline values during reperfusion. In the ischemic zone group, the subendocardium, the triglyceride resonance areas decreased by 24% (p<0.05) during reperfusion. However, subepicardial triglyceride areas were unchanged. Subendocardial creatine areas were also unchanged. The non‐ischemic zone group subendocardial triglycerides decreased by 33% (p<0.05) following ischemia and reperfusion in the remote region. In contrast to the ischemic group, the subepicardial triglyceride resonance areas decreased by 42% (p<0.05). Subendocardial creatine areas were unchanged. These data show that triglycerides of the ischemic‐reperfused subendocardium do not increase during 4 h of reperfusion. Furthermore, they show that the triglycerides resonance areas of the non‐ischemic region decrease following remote ischemia and reperfusion. Decreases in the non‐ischemic region's triglycerides may reflect enhanced substrate demand resulting from increased work in that portion of the heart.