bluuebunny/crossref_metadata_2025 huggingface dataset:
Saturation correction in human cardiac 31P MR spectroscopy at 1.5 T
Authors: van Dobbenburgh J. O. , Lekkerkerk C. , van Echteld C. J. A. , de Beer R.
Published: March 2007

This study was conducted to verify the validity of using saturation factors obtained from unlocalized 31P spectra containing both chest wall and heart muscle signals for correcting human heart muscle phosphocreatine/β‐adenosine triphosphate (PCr/β‐ATP) ratios. Saturation factors and T1 relaxation times were determined from 31 P magnetic resonance spectra of human chest wall and heart muscle simultaneously in healthy volunteers using one‐dimensional spectroscopic imaging in combination with a two‐dimensional ISIS sequence by using adiabatic 180° inversion and adiabatic 90° excitation pulses at 1.5 T. Blood corrected saturation factors for PCr/β‐ATP at a TR of 2.4s were significantly different in heart muscle and chest wall muscle, 1.30 ± 0.25 and 1.73 ± 0.31, respectively (p < 0.05). T1 values for PCr and β‐ATP in heart muscle were 4.28 ± 0.72 and 2.99 ± 0.52 and in chest wall muscle 6.82 ± 1.07 and 3.39 ± 0.48, respectively. The T1(PCr)/T1(β‐ATP) ratios in chest wall and heart muscle were not identical. The mean PCr/β‐ATP ratios in heart and chest wall muscle of six healthy volunteers were 1.23 ± 0.17 and 3.71 ± 0.53, respectively.
Investigation of broad resonances in 31P NMR spectra of the human brain in vivo
Authors: McNamara R. , Arias‐Mendoza F. , Brown T. R.
Published: March 2007

Broad resonances that lie underneath the familiar small molecule profile of in vivo 31P NMR spectra can make accurate spectral integration of these mobile phosphates difficult. The two major broad components are the phosphate contained in the hydroxyapatite in cranial bone and the phosphodiester moiety in partially mobile membrane phospholipids. They can be removed with post‐acquisition processing but this results in distortion of lineshapes and intensities and interferes with accurate quantitation. We have employed an off‐resonance saturation procedure to eliminate the bone resonance and isolate the signal from the membrane phospholipids by subtraction. Selective saturation of the phospholipid resonance increases the clarity of the sharp peaks downfield from the phosphocreatine peak. Selective saturation 3‐D chemical shift imaging techniques were used to create a localized phospholipid profile of the entire brain simultaneously. Monitoring localized phospholipid concentration may be important in studying demyelinating diseases.
Internal temperature calibration for 1H NMR spectroscopy studies of blood plasma and other biofluids
Authors: Farrant R. Duncan , Lindon John C. , Nicholson Jeremy K.
Published: March 2007

A method for temperature calibration of human blood plasma and cerebrospinal fluid (CSF) samples inside a high resolution NMR spectrometer is presented. This calibration is based on the temperature dependence of the chemical shift difference between the water signal and that from the H‐1 proton of endogenous α‐glucose or, in some circumstances, β‐glucose. This dependence can be fitted using a second‐order polynomial equation and functions for both human blood plasma and human CSF are given. Similar graphs could easily be generated for other fluids. The blood plasma calibration appears to be accurate to ±0.9 K in test samples. The use of the blood plasma calibration graph has also been evaluated using the 1H NMR spectra of CSF and shown to overestimate the CSF internal temperature by ca 1.3 K. This approach should have a general applicability to blood plasma and CSF samples from normal and pathological situations or from other species, because there are unlikely to be large changes in ionic strength or pH even in disease states. Knowledge of the exact internal temperature of plasma samples is likely to be of particular importance in the investigation of lipid and lipoprotein interactions because of the significant temperature dependence of lipid and lipoprotein NMR linewidths in such samples.
Non‐invasive measurement of steady‐state vitreous lactate concentration
Authors: Berkowitz Bruce A. , Bansal Navin , Wilson Charles A.
Published: March 2007

The cellular events leading to the proliferation of new preretinal blood vessels into the vitreous are unknown. It has been hypothesized that a metabolic trigger, such as increased lactate concentration, induces ambient growth factors to initiate this neovascularization. However, this hypothesis has not been tested in vivo because non‐invasive methods for measuring vitreous lactate concentration have not been available. In this study, we identified lactate as the dominant resonance in normal rabbit vitreous using a water‐suppressed, localized proton NMR method; negligible spectral contamination from lipid, alanine and threonine was demonstrated. The steady‐state vitreous lactate concentration in vivo was 11.3 ± 4 mM (mean ± SD, n = 7 eyes) which was not statistically different (p = 0.498) to the enzymatically determined lactate content in vitreous from a parallel group of animals [12.1 ± 0.6 mM (n = 6 eyes)]. Non‐invasive measurement of steady‐state vitreous lactate concentration using localized proton NMR represents the necessary first step in understanding the role of lactate in neovascularization.
Structural studies of NMR detected lipids in myocardial ischemia
Authors: Evanochko William T. , Pohost Gerald M.
Published: March 2007

Lipid‐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

A 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

The 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

Quantification 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

The 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

Despite 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

Some 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

An 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

Phosphorus‐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

Identification 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

The 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

Little 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

Metabolic 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

The 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

Electrophysiological 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

Measurements 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

This 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.
In vivo31p mrs: absolute concentrations, signal‐to‐noise and prior knowledge
Authors: Van Boogaart A. Den , Howe F. A. , Rodrigues L. M. , Stubbs M. , Griffiths J. R.
Published: March 2007

Absolute metabolite concentrations have been estimated for nucleoside triphosphate and Pi from in vivo 31P MR measurements using ISIS localization in a rat tumour model, and the results have been compared to those obtained from acid extracts of the tumours. The aim of the experiment was to assess the performance of four different spectral analysis techniques used for absolute quantitation. The spectral analysis techniques used were two frequency domain methods (peak area integration and Lorentzian fitting–FITSPEC) and two time domain methods (VARPRO and HLSVD). The spectra were acquired in blocks so that the degradation in performance of the four spectral analysis methods with decreasing signal‐to‐noise ratio (SNR) could be compared and referenced. This and the inclusion of a sophisticated method incorporating prior knowledge yields a more realistic and comprehensive protocol than previously published comparisons. The results suggest that VARPRO is the method of choice for quantitative analysis of tumour 31P MR spectra, giving the most reliable results at low SNR.
Determination of proton metabolite concentrations and relaxation parameters in normal human brain and intracranial tumours
Authors: Manton D. J. , Lowry M. , Blackband S. J. , Horsman A.
Published: March 2007

Quantitative proton spectroscopic studies were performed on 39 volunteers and 16 patients with intracranial tumours. Estimates of T2 were obtained in white matter, grey matter, cerebellum, astrocytomas and meningiomas; T1 was determined in white matter only. White matter values of T2 for trimethylamines, creatine and N‐acetyl aspartate (NAA) were 309±84, 195±41 and 369±124ms, respectively (mean±SD, n = 20). Metabolite concentrations in white matter were 2.0±0.4 m̈mol/g wet weight for trimethylamines, 7.3±1.1 for creatine and 11.4±1.4 for NAA. The mean concentrations of creatine and NAA in grey matter and all of three metabolites in cerebellum were greater than those in white matter. Tumour spectra were characterized by increased trimethylamines, reduced creatine and NAA and occasionally the presence of lactate. Meningiomas were further characterized by the presence of alanine. The mean T2 and concentration of trimethylamines in tumours was significantly greater than in normal brain. Creatine and NAA concentrations were decreased in all tumours. The longer T2 of trimethylamines and presence of alanine in meningiomas indicate that important differences exist in membrane and glucose metabolism within these tumours when compared to either astrocytomas or normal brain tissue.
Application of homonuclear decoupling to measures of diffusion in biological 31P spin echo spectra
Authors: Hubley Mark J. , Moerland Timothy S.
Published: March 2007

Pulsed field gradient (PFG) spin echo 31P NMR can be used to measure diffusion coefficients of phosphorus‐containing metabolites in vivo. In biological spin echo spectra, the ATP resonances are phase modulated by J‐coupling between the three phosphorus atoms. This phase modulation may severely decrease the apparent signal intensity of the ATP peaks. In this paper, we describe the use of homonuclear decoupling during spin evolution to suppress the effects of J‐coupling in biological spin echo spectra. Phosphorous spectra of ATP and creatine phosphate (PCr) in solution and goldfish (Carassius auratus) skeletal muscle demonstrate the effectiveness of homonuclear decoupling in improving the effective signal‐to‐noise ratio of ATP. In addition, diffusion coefficients of ATP and PCr determined in goldfish skeletal muscle show that PFG homonuclear decoupled spin echo (HDSE) NMR provides accurate measures of diffusion coefficients.
Inhibition of aldose reductase: 13C NMR studies in isolated peripheral nerve
Authors: Waterton John C. , Breen Seáan A. , Mirrlees Don J. , Sennitt Christopher M. , Carey Frank
Published: March 2007

We report 13C NMR measurements of the flux through aldose reductase in isolated rat sciatic nerve, and its inhibition by an aldose reductase inhibitor of the sulphonylnitromethane class. [1‐13C] galactose was used as substrate, and the rate of production of [1‐13C] dulcitol was measured. Quantitation required the use both of internal extracellular, and external, standards. The mean net forward flux (±S.D) was 20±11 nmol/(mL nerve water)/min (n = 10). In the presence of the inhibitor, flux was reduced significantly (p<0.001) to 13% of control. Since dulcitol is symmetrical, an estimate of the backward flux, to [6‐13C] galactose, is also possible; under our conditions, this was negligible.
In vivo and in vitro studies of cyclophosphamide chemotherapy in a mouse mammary carcinoma by 31P NMR spectroscopy
Authors: Street James C. , Mahmood Umar , Koutcher Jason A. , Matei Cornelia
Published: March 2007

The effect of cyclophosphamide on the metabolic profile of a mammary carcinoma implanted on the foot of mouse was studied by 31P NMR spectroscopy both in vivo and in perchloric acid extracts. The ratio nucleotide triphosphate: Pi was significantly elevated in cyclophosphamide treated tumours relative to untreated tumours after 96 h in vivo (p<0.05). Phosphocreatine: Pi was similarly elevated from 48 to 168 h (p<0.01). Resolution of the phosphomonoester peak into two distinct resonances allowed us to estimate the ratio of PME′ to phosphocholine (PC), where PME′ is a composite peak consisting, in part, of phosphoethanolamine (PE). PME′:PC was found to be significantly higher in treated animals relative to control animals in vivo (p<0.01 from 48 to 168h). Perchloric acid extract spectra suggest that the increase in PME′:PC was in part due to a decrease in PC concentration and also due to an increase in a previously unidentified resonance which was coresonant with PE. Extract data show that there was a significant increase in the concentration of the phosphodiesters, glycerophosphocholine (p<0.01) and glycerophosphoethanolamine (p<0.05) in treated relative to control tumours. The changes in the phosphomonoester resonances are qualitatively similar to previously described changes following radiation and suggest that they may be a marker of cell kill or lack of cell growth after antineoplastic therapy.
Gadolinium and dysprosium chelates of DTPA‐amide‐dextran: synthesis, 1H NMR relaxivity, and induced 23Na NMR shift
Authors: Chu Wen‐Jang , Elgavish Gabriel A.
Published: March 2007

In this study the conjugated macromolecular ligand, diethylenetriaminepentaacetic acid (DTPA)‐amide‐dextran, was synthesized by attaching DTPA to the dextran macromolecule (Mr∼6000) by a covalent amide bond. Subsequently, DTPA‐amide‐dextran was complexed with either of the two lanthanide metal ions dysprosium (Dy) or gadolinium (Gd). The paramagnetic 23Na NMR shift induced by Dy(DTPA‐amide‐dextran) and the relaxivity (ρi) induced by Gd(DTPA‐amide‐dextran) were characterized. Dy(DTPA‐amide‐dextran) induced a 25% larger 23Na NMR shift than that induced by Dy(DTPA). Neither the shift induced by Dy(DTPA‐amide‐dextran) nor the shift induced by Dy(DTPA) was affected by increasing levels of calcium ions in the solution. Gd(DTPA‐amide‐dextran) exhibited an in vitro ρi of 8.4 (mM s)−1 at a 0.23 T magnetic field and 9.3 (mM s)−1 at a 0.47 T magnetic field, thus indicating a positive magnetic field dependence.
31P NMR in vivo study of rat brain energy metabolism after frontal cortex injury. a method based on convoluted correlation matrices of the spectral data
Authors: Semenova Nataly A. , Konradov Alexander A. , Dubinsky Vladimir Z.
Published: March 2007

Disturbances of energy metabolism in rat brain after frontal lobectomy and post‐traumatic effects of monosialic ganglioside GM1 on brain energy metabolism were studied by 31P NMR in vivo. Frontal lobectomy caused the statistically significant reversible decrease of ATP and increase of ADP during the compensatory period. In a presence of GM, these post‐operational effects were not observed. The mean value of normalized correlation coefficients between NMR‐measured phosphomonoesters, Pi, pH, phosphocreatine, γ‐ATP +β‐ADP, α‐ATP+α‐ADP + NAD/NADH + diphosphodiesters and β‐ATP for a given group of animals (Z‐index) was used to estimate brain energetic status. It has been shown that the variation of the Z‐index correlates with the dynamics of locomotor activity during the compensatory period. The Z‐index increased by more than 100% for the subgroup with an increased moving activity and only by about 20% for the subgroup with a decreased activity. Moreover, the compositions of these subgroups were almost the same as those from the solution of the reverse task, i.e., the studied group was divided into two subgroups by the Z‐index. The Z‐index is proposed as a possible criterion of pathology detection in brain energetics.
Hypoglycemia prevents increase in lactic acidosis during reperfusion after temporary cerebral ischemia in rats
Authors: Sappey‐Marinier Dominique , Chileuitt Laureano , Weinstein Philip R. , Weiner Michael W. , Faden Alan I.
Published: March 2007

Sequential 31P and 1H MRS was used to measure cerebral phosphate metabolites, intracellular pH, and lactate in normoglycemic and hypoglycemic rats during 30 min of complete cerebral ischemia and 5.5 h of reperfusion. These results were correlated with brain levels of free fatty acids (FFAs), excitatory amino acids, cations, and water content at death. The lactate/N‐acetyl aspartate ratio was not significantly different between groups before or during occlusion. During reperfusion, the ratio was higher in normoglycemic rats from 3 to 85 min (p≤0.05), and recovery time was faster in hypoglycemic rats (29 vs 45 min; p = 0.04), suggesting reduced lactate production and faster recovery of aerobic metabolism. During occlusion, significant but comparable decrease of intracellular pH occurred in each group. Intracellular pH was higher in hypoglycemic rats at 140 min and 260 min of reperfusion. Water content, Na and K+ concentrations, and FFA and excitatory amino acid levels were not significantly different between groups, but hypoglycemic rats had less depletion of levels of Mg2+ (p=0.011). These results show that hypoglycemia has a limited but potentially beneficial effect on postischemic lactic acidosis.
On the use of 133Cs as an NMR active probe of intracellular space in vivo
Authors: Li Yi , Neil Jeff , Joseph Ackerman J. H.
Published: March 2007

Data are presented from 133Cs NMR studies on both excised and in situ tissues from rats fed a regular diet and administered i.p. CsCl in aqueous solution for 6 to 14 days. Cesium is an NMR‐active potassium analog which accumulates in the intracellular spaces of tissues [Davies et al., Biochemistry 27, 3547 (1988); Shehan, B.P. et al., Magn. Reson. Med. 30, 573 (1993)]. Chemical shifts, relaxation properties, sensitivity and detectability of cesium in tissues were investigated. Consistent with previous reports, two resonances (representing intra‐ and extracellular cesium) were detected in blood. Only one resonance was detected in brain, kidney, and muscle tissue. Efforts to resolve intra‐ and extracellular components by T1 and T2 relaxation discrimination were not successful. Following i.p. administration, cesium accumulates intracellularly with a brain‐to‐cerebrospinal fluid concentration (μmol/g) ratio of 9:1 and a thigh muscle‐to‐plasma concentration ratio of 40:1. Considering the small extracellular volume in these tissues (ca 18% and 10%, respectively), the net content differences between intra‐ and extracellular cesium are approximately 40‐fold in brain and 360‐fold in muscle. The concentration ratio of cesium in brain to cesium in cerebrosinal fluid decreased to 3:1 1 h after death, indicating a relatively slow rate of leakage of cesium from the intra‐ to extracellular space in the face of bioenergetic failure. These data suggest that the cesium signal is dominated by the intracellularly located cesium and, thus, cesium may be useful as a probe of the intracellular environment despite an inability to resolve and directly observe distinct resonances from intra‐ and extracellular spaces.
Detection and quantitation of phosphorus metabolites in crude tissue extracts by 1H and 31P NMR: use of gradient assisted 1H‐31P HMQC experiments, with selective pulses, for the assignment of less abundant metabolites
Authors: Pollesello Piero , Eriksson Ove , Geimonen Erika , Vittur Franco , Paoletti Sergio , Toffanin Renato
Published: March 2007

The analysis of crude tissue extracts by NMR has proven to be of use in the study of metabolism due to the non‐destructive and non‐selective character of the technique. Lists of 1H and 31P NMR assignments of phosphorus metabolites in water solution at specified pH and ionic composition are of large general value but their usefulness may be limited when analysing complex mixtures of metabolites at low concentrations. In this work we report on the use of gradient‐assisted proton detected multiple quantum 1H and 31P coherence experiments with selective pulses for the rapid and unambiguous assignments of some crowded regions in 1H and 31P spectra of crude extracts from rat liver. The amplitudes of the gradient episodes were calibrated to optimize the coherence transfer pathway between proton and phosphorus, and the delay for the evolution of the long‐range coupling was calculated from values of 3JPH and 4JPH ranging from 1.4 to 7.5 Hz. Moreover, a selective 90° Gaussian pulse on the 31P channel was introduced to increase the resolution in the F1‐domain and make the method even faster. The procedure was then applied to unambiguously assign the ID 31P and 1H spectra of perchloric acid extracts of rat livers that had been stimulated with phenylephrine, dBcAMP and glucagon and thus detect changes in the concentration of less abundant metabolites such as phosphoenolpyruvate, UDP‐glucose and AMP. The fact that the quantification of these metabolites by either 31P and 1H methods lead to different results is discussed, and the use of 1H NMR spectroscopy for the quantification of phosphorus metabolites whose signal are too weak or poorly resolved in a 31P spectrum is proposed.
Evolution of acute focal cerebral ischaemia in rats observed by localized 1H MRS, diffusion‐weighted MRI, and electrophysiological monitoring
Authors: Gyngell Michael L. , Busch Elmar , Schmitz Bernd , Kohno Kanehisa , Back Tobias , Hoehn‐Berlage Mathias , Hossmann Konstantin‐Alexander
Published: March 2007

Focal cerebral ischaemia was produced in 11 rats by permanent occlusion of the right middle cerebral artery (MCA) using a suture model modified to enable manipulation with the animals in situ in an NMR spectrometer. The development of the ischaemic insults and the resultant infarcts were observed for up to 6 h by localized 1H MRS and diffusion‐weighted MRI while performing continuous monitoring of electroencephalogram and extracellular DC potential. The ischaemic areas were depicted as regions of hyperintensity in the diffusion‐weighted images. Signals due to lactate became visible in the 1H spectra after MCA occlusion indicating the onset of anaerobic glycolysis. A depletion of N‐acetylaspartate was seen in all animals post‐occlusion. Transient or stepwise increases of lactate were observed to occur coincidentally with the events of spontaneous transient peri‐infarct depolarization detected by the electrophysiological measurements. Expansion of the ischaemic area delineated in the diffusion‐weighted images also accompanied peri‐infarct depolarizations. These observations are consistent with transient peri‐infarct depolarization playing a role in the growth of infarcts.
31P magnetic resonance spectroscopy as predictor of clinical response in human extremity sarcomas treated by single dose TNF‐α+ melphalan isolated limb perfusion
Authors: Sijens Paul E. , Dijk Pieter Van , Oudkerk Matthijs , Eggermont Alexander M. M.
Published: March 2007

Irresectable extremity sarcomas are large (grade II/III) tumors requiring amputation of the limb for local control. Limb salvage can be achieved by isolated limb perfusion (ILP) with tumor necrosis factor alpha (TNF‐α), interferon‐γ and melphalan. To obtain insight into the effects of single dose ILP on extremity tumors, phosphate metabolism was monitored by 31P magnetic resonance spectroscopy (MRS) using the chemical shift imaging (CSI) technique. 2D CSI was used in combination with a slice select gradient in the third dimension to obtain true 3D localization. Spectral maps obtained prior to ILP revealed reductions in phosphocreatine (PCr) level and increases in phosphomonoester (PME) and phosphodiester (PDE) in tumor compared with muscle tissue. ILP treated tumors showed highly divergent changes in Pi while PME decreased in all cases (n = 11). Tumor volume, unchanged on day 8 after ILP, was decreased by 58±29% (mean±SD) at 2 months. Linear regression analysis revealed correlation between the changes in tumor metabolites measured on day 8, with percent volume decrease (Pi: r=‐0.88, p<0.001) and percent necrosis at resection (PME: r=‐0.79, p‐0.01). Correlation between pretreatment spectra and effectiveness of ILP treatment was not found. It is concluded that a single ILP with TNF‐α+melphalan induced changes in tumor metabolite levels (measured on day 8) that reflect treatment efficacy. 31P MRS can thus provide information facilitating the decision as to when to remove tumor (residue) and, in the case where tumor remains inoperable, whether or not to apply additional therapy.
Quantification of biomedical NMR data using artificial neural network analysis: Lipoprotein lipid profiles from 1H NMR data of human plasma
Authors: Ala‐Korpela M. , Hiltunen Y. , Bell J. D.
Published: March 2007

Artificial neural network (ANN) analysis is a new technique in NMR spectroscopy. It is very often considered only as an efficient ‘black‐box’ tool for data classification, but we emphasize here that ANN analysis is also powerful for data quantification. The possibility of finding out the biochemical rationale controlling the ANN outputs is presented and discussed. Furthermore, the characteristics of ANN analysis, as applied to plasma lipoprotein lipid quantification, are compared to those of sophisticated lineshape fitting (LF) analysis. The performance of LF in this particular application is shown to be less satisfactory when compared to neural networks. The lipoprotein lipid quantification represents a regular clinical need and serves as a good example of an NMR spectroscopic case of extreme signal overlap. The ANN analysis enables quantification of lipids in very low, intermediate, low and high density lipoprotein (VLDL, IDL, LDL and HDL, respectively) fractions directly from a 1H NMR spectrum of a plasma sample in <1 h. The ANN extension presented is believed to increase the value of the 1H NMR based lipoprotein quantification to the point that it could be the method of choice in some advanced research settings. Furthermore, the excellent quantification performance of the ANN analysis, demonstrated in this study, serves as an indication of the broad potential of neural networks in biomedical NMR.