bluuebunny/crossref_metadata_2025 huggingface dataset:
1H NMR spectroscopic imaging of the monkey brain using binomial water suppression in a stimulated‐echo sequence
Authors: Richards Todd L.
Published: March 2007

A new proton, two‐dimensional pulse sequence for 1H NMR spectroscopic imaging (chemical shift imaging) was tested in phantoms and in the monkey brain. The pulse sequence consisted of one binomial chemically selective pulse and two spatially selective pulses in the stimulated‐echo sequence. The point‐spread function (which is influenced by k‐space filtering and the number of phase‐encoded steps) of a 1 mm source phantom was measured using a 16 X 16 spatial matrix and was found to have a FWHM of 10 mm (100 mm field of view) with very little rippling outside the main lobe. The binomial excitation profile was measured in order to correct the NMR intensity for the variable flip angles. Spectroscopic images were measured in the monkey brain with a 15 mm slice thickness and a 16 X 16 spatial matrix. Proton spectra derived from the brain contained sharp resonances of choline, creatine and N‐acetyl aspartate with minimal lipid contamination. Proton spectra derived from the subcutaneous fat and adipose tissue behind the eyes contained large lipid resonances.
A comprehensive approach to the analysis and interpretation of the resonances of spins 3/2 from living systems
Authors: Rooney William D. , Springer Charles S.
Published: March 2007

An extensive protocol for the study of tissue resonances of spin 3/2 nuclei is described. The roles of the most relevant multiple pulse experiments are indicated. Their theory is organized in terms of irreducible tensor operators and the pulse and quadrupolar relaxation transfer functions which relate them for a type c spectrum. A systematic approach to the interpretation of the temperature and/or magnetic field dependences of all six of the relaxation rate constants of the resonance of a single population of isolated spins in fast exchange, and giving rise to a type c spectrum, is presented. An experimental calibration and an application of this protocol are presented in an accompanying paper. The comprehensive method we describe has a number of practical benefits in the interpretation of the physiological spectra obtained from conventional one pulse experiments. A consideration of the appropriate transverse relaxation transfer function leads to an analytical expression for the heretofore empirical NMR visibility factor. This includes factors which account for relaxation during the receiver ‘dead’ time and relaxation during the pulse itself. Also, consideration of realistic transverse relaxation times likely to be observed in tissue leads to a reasonable strategy for the quantitative resolution and integration of in vivo spectra obtained in the presence of hyperfine shift reagents.
The molecular environment of intracellular sodium: 23Na NMR relaxation
Authors: Rooney William D. , Springer Charles S.
Published: March 2007

The comprehensive approach described in the accompanying paper is illustrated here with the 23Na signal of a concentrated solution of bovine serum albumin (BSA) in saline and the intracellular (Nai) 23Na resonance of a dense suspension of Na+ ‐loaded yeast cells. We use frequency shift reagents to discriminate the latter from the extracellular resonance. We find that the Nai signal corresponds to that of an effective single population of Na+ ions exhibiting a single type c spectrum. This is true despite the fact that the yeast protoplasm is too large and too compartmentalized for a given Na+ ion to sample its entirety on the relevant NMR timescale. Our results show clearly that, in addition to the decay of transverse magnetization, the recovery of longitudinal magnetization is biexponential. This is required for a type c spectrum but has not often been detected. The temperature dependence of the relaxation rate constants of the Nai resonance is not consistent with either a simple Debye process or a discrete exchange mechanism connecting two sites in the fast limit. We have fitted the data using an asymmetric continuous distribution of correlation times for the fluctuations of electric field gradients sensed by the Nai nuclei. The analogous distribution function for the Na+ in a 44% (w/w) BSA solution is quite similar to that of the Nai at the same temperature. This suggests that while the macromolecular environment of the Nai ions is quite congested, it is also isotropic on quite a small spatial scale. Also, one can use the correlation time distribution function, obtained from fitting the relaxation data, to calculate a relaxometry curve. This is useful because experimental 23Na relaxometry is difficult. The calculated curve may be a reasonable model for the mostly extracellular 23Na resonance encountered in vivo.
Characterization of a microcarrier cell culture system for 23Na MR spectroscopy studies
Authors: Shedd Suzanne F. , Spicer Leonard D.
Published: March 2007

A MR spectroscopy method is described for the simultaneous discrimination and observation of sodium from the three compartments created by an intact cell monolayer. Results are reported for Madin Darby Canine Kidney (MDCK) cells, an epithelial‐like continuous cell line, cultured on Cytodex 1 microcarrier beads and perfused with medium containing 6 mM dysprosium (III) tripolyphosphate [Dy(TPP)72] as shift reagent. The sodium spectrum shows three resonances which are assigned to the shifted intrabead (basolateral) and extrabead (apical) pools and the unshifted intracellular pool. Ouabain inhibition of the Na+ ‐K+ ‐ATPase cellular pump mechanism was used to demonstrate the sensitivity of the method for monitoring intracellular sodium. The supported MDCK cells in this system remained viable after exposure for 5 h to medium containing Dy(TPP)72 at a concentration of 6 mM, as determined by trypan blue dye exclusion and by comparison of the log growth rate and ability to form domes in subsequent generations of exposed cells vs unexposed controls.
Metabolite images of the human arm: Changes in spatial and temporal distribution of high energy phosphates during exercise
Authors: Nelson Sarah J. , Taylor June S. , Vigneron Daniel B. , Murphy‐Boesch Joseph , Brown Truman R.
Published: March 2007

Localized variations in metabolites in resting and exercising skeletal muscle have been studied using Chemical Shift Imaging (CSI) techniques to obtain 2‐D arrays of 31P NMR spectra from a slice through the human forearm. The excitation profile of the coil resulted in a slice thickness of ca 80 mm and the planar resolution of the CSI data corresponded to either 7, 10 or 14 mm. The metabolite information was represented both as 2‐D arrays of spectra and by constructing images of the spatial distribution of different metabolites. Correlation with the anatomy was clearly visualized by overlaying the metabolite images on the appropriate region of the corresponding proton images. At rest, significant variations in the intensity of Pi, phosphocreatine (PCr) and ATP were observed in different regions of the arm. Our planar spatial and temporal (1‐9 min) resolution was also sufficient to follow changes in Pi, PCr and pH in response to exercise. These changes were restricted to the exercising muscle and demonstrated heterogeneity both in the kinetics and magnitude of response between different muscles.
Detection of differential sensitivity to 5‐fluorouracil in ehrlich ascites tumour cells by 19F NMR spectroscopy
Authors: McSheehy P. M. J. , Maxwell R. J. , Griffiths J. R.
Published: March 2007

Quantitative analysis of extracts from two Ehrlich ascites tumour cell lines (Lettre cells) by 19F NMR in vitro demonstrated that one Lettre cell line (designated LLM) metabolized 30‐50% less 5‐fluorouracil to 5‐fluoronucleotides when compared to the other cell line (designated LHM). HPLC analysis of these cellular extracts showed a significant decrease in the concentration of the cytotoxic nucleotide 5‐fluorouridine triphos‐phate in LLM cells compared to LHM cells. No major differences could be observed in the 31P and 1H NMR spectra of the two cell lines. Growth inhibition studies in vitro demonstrated that LLM cells were less sensitive to 5‐fluorouracil than LHM cells. These results are consistent with the hypothesis that 19F NMR visible levels of 5‐fluoronucleotides can predict the cytotoxicity of the anti‐cancer drug 5‐fluorouracil.
Is cellular integrity responsible for the partial NMR invisibility of ATP in isolated ischemic rat liver?
Authors: Gallis Jean‐Louis , Delmas‐Beauvieux Marie‐Christine , Biran Marc , Rousse Nicole , Durand Thierry , Canioni Paul
Published: March 2007

The observability of nucleoside triphosphate (NTP) by 31P NMR spectroscopy was studied in the isolated rat liver during hypothermic perfusion and a subsequent 4‐h cold ischemia. The influence of hypothermia (4 deg.C) was examined because of its delaying effects on cell injury induced by the ischemic conditions. The viability of the liver after hypothermic ischemia was assessed by measuring the recovery of the βB‐NTP resonance after reperfusion. In 4‐h cold ischemic liver, recovery was found to be in the range of 90‐100% and consequently NTP visibility was studied under these conditions. Because the individual purine (or pyrimidine) NTPs are not distinguishable in the liver on the basis of their 31P NMR chemical shifts, the contributions of UTP and GTP were investigated by HPLC. The changes in liver NTP content measured either by NMR on isolated liver or by HPLC after perchloric acid extraction from the same organ are not significantly different. The total NTP level in normothermic perfused liver is 7.6±0.2 ±umol NTP/g liver dry wt as determined by NMR. In such a liver, ATP + GTP + UTP and ATP contents measured by HPLC are, respectively, 7.9±1.0 and 6.3±0.9 ±mol/g liver dry wt. This indicates that all NTP is detected by NMR and that a 20% contribution of the signal occurs from UTP + GTP. Under 4‐h cold ischemic conditions, NTP visibility remains unchanged, furthermore the UTP+GTP contribution reaches 32% of the whole NTP content. Further experiments in 6‐h cold ischemic livers show that βB‐NTP signals are at the limit of detection whereas the ATP+GTP+UTP level, measured by HPLC, still represents 20% of the basal value. This result suggests that NTP remains fully detectable by NMR in liver as long as cellular integrity is maintained.
Effect of pentoxiphylline on the recovery of the preserved rat liver: 31P NMR and ultrastructural studies
Authors: Ellermann J. , David H. , Lüning M. , Gewiese B. , Stiller D. , Römer T. , Plötz M. , Wolf K.‐J.
Published: March 2007

Hepatic failure often occurs following transplantation. This is primarily due to cold ischemia during preservation, warm ischemia during implantation, and finally reperfusion damage after transplantation and reflow. The possibility that this ischemia and reperfusion‐induced damage can be reduced by preischemic application of a xanthine derivative (pentoxiphylline) was examined using 31P NMR spectroscopy and electron microscopy (EM) studies of bioenergetic and ultrastructural changes in oxygenated erythrocyte‐perfused rat livers. EM illustrated that the hepatocytes and the mitochondria appeared to be relatively unaffected by cold preservation of the liver, whereas the endothelial cells lining the sinusoids became disrupted. After reperfusion, NMR spectroscopy showed a partial recovery of ATP levels, and EM indicated progressive mitochondrial injury. This progressive injury to the liver was probably due to endothelial cell damage which resulted in microcirculatory malfunction and free radical formation during reperfusion. Pentoxiphylline pretreated livers showed better preservation of the cell morphology and exhibited better ATP recovery than untreated livers. Pentoxiphylline is known to prevent the loss of precursors of ATP resynthesis by inhibiting AMP dephosphorylation during ischemia and improves the microcirculation via vasodilatory properties following ischemia. Thus, it is concluded that pentoxiphylline may ameliorate ischemia‐induced cell damage during transplantation.
Monitoring of the effects of dysprosium shift reagents on cell suspensions
Authors: Boulanger Yvan , Fleser Angelica , Amarouche Rabah , Ammann Hélène , Bergeron Michel , Vinay Patrick
Published: March 2007

The effects of two widely used paramagnetic shift reagents for cationic NMR, dysprosium tripolyphosphate [Dy(PPP)27−] and dysprosium triethylenetetramine hexaacetate [Dy(TTHA)3−], on the cell structure of dog and human erythrocytes, dog kidney cortical tubules and rat hepatocytes were investigated. The effect of shift reagents on cell integrity was monitored by measuring the hematocrit values for erythrocytes, by measuring the lactate dehydrogenase (LDH) release and by electron microscopy for cortical tubules and hepatocytes. The quantitation of the dyprosium penetration inside cells was accomplished by atomic absorption, atomic emission and neutron activation. More severe effects were observed with Dy(PPP) than with Dy(TTHA)3−, and were dependent on the divalent cation concentration and on the shift reagent concentration. Very serious cell damage was observed after 60 min incubation in the presence of 10 μmol Dy(PPP)/mL suspension at low or high divalent cation concentration. The situation was improved at 5 μmol Dy(PPP)27−/mL suspension especially at high divalent cation concentration (2.5 mM). Incubation with Dy3+, PPP5− or Dy(TTHA)3− caused little or no structural effects but dysprosium was found to penetrate slowly inside tubules with Dy(TTHA)3−. Both Dy3+ and Dy(PPP) penetrated rapidly inside cells. Dysprosium was found to bind to the isolated cytosol but not to isolated membranes, eliminating the possibility of extracellular membrane binding.
Two‐dimensional 1H spectroscopic imaging for evaluating the local metabolic response to focal ischemia in the conscious rat
Authors: Peres Michel , Bourgeois Dominique , Roussel Simon , Lefur Yann , Devoulon Philippe , Remy Chantal , Barrere Bertrand , Decorps Michel , Pinard Elisabeth , Riche Danièle , Benabid Alim‐Louis , Seylaz Jacques
Published: March 2007

Two‐dimensional 1H spectroscopic imaging and magnetic resonance imaging were used to study focal ischemia induced by middle cerebral artery occlusion in rats. A water suppressing spin‐echo sequence was used at 4.7 T. Phase encoding during the spin‐echo delay (TE = 272 ms) yielded an 8 × 8 array of 35 μL voxels. The injured area of the brain had a higher lactate level and markedly lower N‐acetyl aspartate, creatine and choline levels than did the non‐ischemic regions. The spectroscopic imaging data clearly showed the localization of the infarct, which agreed well with both magnetic resonance imaging and the histological data obtained post‐mortem. This study demonstrates the potential usefulness of combining magnetic resonance imaging and 1H spectroscopic imaging for studying animal models of stroke, and indicates the suitability of the technique for further pharmacological approaches.
Visibility of phospholipids in 31P NMR spectra of human breast tumours in vivo
Authors: Lowry Martin , Porter David A. , Twelves Christopher J. , Heasley Philippa E. , Smith Michael A. , Richards Michael A.
Published: March 2007

The aims of this study were two‐fold: to characterize the in vivo 31P NMR spectrum of human breast tumours by identifying the metabolites contributing to each peak; and to demonstrate changes in the detectability of the phosphodiester (PDE) peak at varying field strengths. This was achieved by obtaining 31P spectra from 23 patients in vivo at 1.5 T and also of 11 perchloric acid (PCA) extracts and 3 chloroform‐methanol (CM) extracts of tumour biopsy samples at 9.4 T. In spectra acquired in vivo the percentage areas for each peak were: phosphomenoester (PME), 15%; Pi, 11%; PDE 35%; phosphocreatine, 5%; γ‐NTP, 11%; α‐NTP, 11% and β‐NTP, 12% of the total spectral area. PCA extracts showed the PME peak to be > 70% phosphorylethanolamine whilst the PDE peak included almost equal proportions of glycerophosphorylethanolamine and glycerophosphorylcholine. CM extracts of tumours revealed additional metabolites in the PDE region suggesting that the large PDE peak observed in vivo could arise mainly from phospholipids. Spectra of human breast tumour xenografts examined in vivo at both 1.9 T and 9.4 T confirmed that the presence of a large PDE peak in vivo was a function of field strength. Further experiments with microsomal membranes from rat mammary tumours at 1.5 and 9.4 T demonstrated that phospholipids are more clearly visible at the lower field strength due to a substantial decrease in linewidth.
1H NMR properties of N‐acetylaspartylglutamate in extracts of nervous tissue of the rat
Authors: Holowenko Dedeshya , Peeling James , Sutherland Garnette
Published: March 2007

The 1H NMR spectrum of the putative neurotransmitter dipeptide N‐acetylaspartylglutamate (NAAG) is described, along with its identification in acid extracts of tissues of the central and peripheral nervous systems of the rat. The N‐acetyl methyl resonance of NAAG (2.058 ppm) is close to that of N‐acetylaspartate (NAA, 2.022 ppm), a prominent signal in 1H NMR spectra of the brain. The tissue concentration of NAAG is such that resonances of NAAG do not contribute greatly to 1H NMR spectra of the brain, except in studies of the brain stem or thalamus. In the spinal cord and peripheral nerves the level of NAAG is similar to that of NAA, and NAAG is a major metabolite contributing to the 1H NMR spectrum. The implications of these observations for 1H NMR spectra in vivo are discussed.
Brain metabolism and blood flow in acute cerebral hypoxia studied by NMR spectroscopy and hydrogen clearance
Authors: Allen Kathryn , Busza Albert L. , Crockard H. Alan , Gadian David G.
Published: March 2007

We have developed a reliable, reproducible model of hypoxia in the gerbil. 1H and 31P NMR spectroscopy demonstrates that cerebral energy metabolism is very resistant to hypoxia. Cerebral blood flow (measured by hydrogen clearance) began to increase when the arterial oxygen tension (paO2) was reduced to 40–50 mm Hg, and there was no change in phosphorus metabolites or lactate until paO2 was below 40 mm Hg. In 50% of the animals lactate increased prior to any change in the phosphorus metabolites or intracellular pH, suggesting that 1H NMR may be more sensitive than 31P NMR at detecting hypoxic or ischaemic changes. The calculated rate of oxygen delivery at a time when phosphorus energy metabolism becomes impaired is similar in both hypoxia and ischaemia (ca 4 mL/100 g/min). We suggest that the critical factor in ischaemia is the reduction in oxygen supply, rather than the accumulation of toxic metabolites, such as lactate.
Assessment of magnesium concentrations by 31P NMR in vivo
Authors: Halvorson H. R. , Vande Linde A. M. Q. , Helpern J. A. , Welch K. M. A.
Published: March 2007

31P NMR spectra obtained in vivo reveal the presence of a few reasonably well defined chemical species, namely, ATP, orthophosphate (Pi), and, in brain, phosphocreatine. The chemical shifts of these resonances respond to changes in concentrations of ions such as H+ and Mg2+ in a manner that depends on both the chemical shifts intrinsic to individual complexes and the formation or binding constants for the several complexes. Values of the appropriate formation constants are well established in the literature. We have derived estimates of the chemical shifts intrinsic to the individual complexes by analyzing high resolution spectra of solutions whose composition brackets the domain of physiological relevance. This provides information sufficient to estimate intracellular concentrations of H+ and Mg2+ from chemical shifts seen with in vivo spectra. The primary finding is an estimate of 0.3 mM for the concentration of free magnesium in human brain. Differing values are obtained from other tissues.
Perfluorocarbon temperature measurements using 19F NMR
Authors: Berkowitz Bruce A. , Handa James T. , Wilson Charles A.
Published: March 2007

Measuring the T1 of the fluorine resonances of perfluorocarbons (PFC) is a unique method for monitoring oxygen tension in vivo. However, because T1 is also temperature sensitive, error in the pO2 determination due to animal‐to‐animal temperature variation may arise. Pathophysiologic conditions, such as ischemia, where temperature is not known a priori may also introduce error. Thus, measuring the PFC temperature is clearly desirable in order to correct for tissue temperature variations during the pO2 determination. Because the fluorine chemical shift of various fluorinated compounds has a significant temperature dependence, we evaluated the effect of temperature on the chemical shift of the fluorine resonances of perfluorotributylamine (FTBA). A linear relationship was found between chemical shift and temperature in vitro. In addition, the relative FTBA chemical shifts were essentially independent of pO2. Chemical shift temperature measurements in vivo, obtained from a 10 μL FTBA bubble in the preretinal vitreous space of the rabbit eye, were in good agreement (±0.5 °C) with thermocouple measurements from the same location. Good agreement between the NMR determined temperature and core body temperature was also found. The implication of such temperature measurements for the ultimate accuracy of the pO2 determination based on PFC T1 measurements is discussed. To the best of our knowledge, this report describes the first absolute temperature measurement in vivo by NMR.
Comparison of double and zero quantum NMR editing techniques for in vivo use
Authors: van Dijk J. E. , Mehlkopf A. F. , Bove W. M. M. J.
Published: March 2007

Several multiple quantum editing techniques for in vivo proton NMR are discussed and compared using simulated and experimental data. Extensions of these techniques for improved editing are given. Relative S/N ratios, modulation characteristics, metabolite selectivity, B0 and B1 inhomogeneity and motion effects are considered. Frequency selective read pulses can be used for signal enhancement and lipid suppression. Extra suppression of undesired signals can be obtained with a two‐shot t1 cycle which gives good results for both the zero and double quantum sequences. These sequences give at most 50% signal intensity and lipid suppression factors of ca 2000 and 7000, respectively. A sequence which selects zero and double quantum coherences yields 100% signal intensity but only gives a good lipid suppression factor (7000) in combination with phase cycling. It is shown that the multiple quantum modulation can be used to obtain specific metabolite editing. Corrections can be made for the effects of B0 inhomogeneity on the multiple quantum coherences; B1 inhomogeneity affects the investigated multiple quantum sequences in about the same way and decreases the volume of interest. In vivo measurements show the good performance of the proposed zero and double quantum sequences for lactate.
19F NMR studies of enflurane elimination and metabolism
Authors: Preece N. E. , Challands J. , Williams S. C. R.
Published: March 2007

The elimination and metabolism of enflurane, a fluorinated ether anaesthetic, was studied by 19F NMR in vivo in both rat liver and brain as well as human body fluids. In the liver of thiobarbitone‐anaesthetized rats the half‐life for enflurane following exposure to 0.15% (v/v) for 30 min was 76 min but this could be decreased to 39 min by pretreatment of the animals with isoniazid (0.1% in the drinking water for 7 days), an agent known to enhance enflurane metabolism. In these animals the major organic metabolite difluoromethoxy difluoroacetate (DFMDFA) was also detected by 19F NMR in vivo. This metabolite was detected along with fluoride ion in rat and human urine and plasma by high resolution 19F NMR. Human urine also contained signals from a probable DFMDFA conjugate and unexpectedly from trifluoroacetate.
In vivo and in vitro31P magnetic resonance spectroscopy of focal hepatic malignancies
Authors: Cox I. Jane , Bell Jimmy D. , Peden Carol J. , Iles Richard A. , Foster Christopher S. , Watanapa Prasit , Williamson Robin C. N.
Published: March 2007

In vivo 31 P magnetic resonance spectroscopy (MRS) was undertaken in 28 healthy adult individuals and 32 patients with hepatic malignancies of varying histology, using chemical shift imaging techniques. The mean peak area ratio (total range) of phosphomonoester (PME) to phosphodiester (PDE) in the health adult group was 0.23 (0.15–0.41). The mean (total range) PME/PDE ratio of the total patient group was 0.68 (0.15–2.38), which was significantly elevated (P < 0.001) compared to the mean of the healthy adult group. Liver biopsies, obtained at operation, were analysed using high‐field in vitro MRS techniques in order to identify the contributions of aqueous‐soluble metabolites to the multicomponent PME and PDE in vivo signals. Concentrations of phosphorylethanolamine (PE), phosphorylcholine (PC), glycerophosphorylethanolamine (GPE) and glycerophosphorylcholine (GPC) were measured. The in vitro spectrum of six samples of liver of normal histological appearance all showed a similar pattern of PE, PC, GPE and GPC. The in vitro spectrum of seven liver tumours of differing histology all showed an increase in PE and PC signals and a decrease in GPC and GPE signals. The in vitro results were compared with in vivo findings in five patients. The increase in PME/PDE observed in vivo represented, in part, an increase in PE and PC in the PME region and a decrease in GPE and GPC in the PDE region.
An in vivo19F NMR study of isoflurane elimination as a function of age in rat brain
Authors: Chen M. , Olsen J. I. , Stolk J. A. , Schweizer M. P. , Sha M. , Ueda I.
Published: March 2007

In vivo 19F NMR at 4.7 T has shown that the biphasic elimination of the vapor anesthetic isoflurane from rat brain is ca 15% slower in old (23‐24 months) animals compared with young (5–6 months) animals. The fast kinetic component has a t1/2 of ca 7–9 min and the slow event, 100–115 min. Gas chromatographic measurement of arterial blood elimination displays age attenuation to the same extent, although a monophasic kinetic process (6–7 min). The slow wash‐out from brain is thought to involve elimination from intracranial fatty tissue as postulated by others in rabbit brain. Longitudinal relaxation time measurements show monoexponential recovery and essentially identical values for young (1.09+0.11 s) and old (1.04±0.09s) animals. For dipalmitoylphosphatidylcholine vesicles the monoexponential recovery also suggests rapidly exchanging averaged homogeneous lipid environments for the anesthetic, but the longer T1s (2.75±0.25 s) imply less restricted mobility compared with brain. Single T2 values were obtained in vivo, indicating either a single compartment or rapid exchange between multiple environments. These measurements were inconsistent, undoubtedly as a result of B1 inhomogeneity. The age‐attenuated elimination kinetics for isoflurane are consistent with poorer cardiopulmonary function, whereas the T1 data suggest similar environments for the anesthetic in young and old brain tissue.
Threshold voltages for hyperbolic secant inversion pulses
Authors: Payne Geoffrey S. , Leach Martin O.
Published: March 2007

Spin inversion produced by hyperbolic secant RF pulses is independent of pulse amplitude once a threshold value is exceeded. A semi‐empirical formula for these pulses has been derived by application of analytical solutions to the Bloch equations. This predicts the required coil voltages for inversion as a function of inversion bandwidth and side‐to‐width parameter μ, based on knowledge of a reference voltage for the loaded coil. The voltage required is shown to increase linearly with bandwidth but to fall with the μ, approximately as (1/μ)0·4. Experimental confirmation is presented, and factors affecting choice of pulse parameters are discussed.
In vivo1H, 31P‐{1H} and 13C‐{1H} magnetic resonance spectroscopy of malignant histiocytoma and skeletal muscle tissue in man
Authors: Bachert Peter , Bellemann Matthias E. , Layer Günter , Koch Thomas , Semmler Wolfhard , Lorenz Walter J.
Published: March 2007

Human tumor and skeletal muscle tissue was studied by means of in vivo 1H, 31P, and 13C MRS. The examinations were performed with a 1.5 T whole‐body MR scanner equipped with a second RF system. Localized 1H and broadband proton‐decoupled 31P and 13C MR spectra were obtained in measurement times of 5, 10 and 33 min, respectively, from a malignant fibrous histiocytoma in a patient and from gastrocnemius muscle tissue in healthy volunteers. Proton decoupling enhanced the sensitivity (via the nuclear Overhauser effect) and the information available from in vivo 31P and 13C MR spectra significantly. The most information was obtained from 1H‐decoupled 31P spectra. Observation of more than one spin species allows peak assignments to be verified mutually. The spectral data of the histiocytoma differ largely from that of muscle tissue and show a tumor with elevated pH value, normal level of nucleoside 5′‐triphosphates, and high level of compounds involved in phospholipid turnover. The multinuclear in vivo MRS experiment may allow the non‐invasive observation of almost the complete pathway of phospholipid synthesis and degradation in intact human tissue.
Quantitation of metabolites in human blood serum by proton magnetic resonance spectroscopy. A comparative study of the use of formate and TSP as concentration standards
Authors: Kriat Mostafa , Confort‐Gouny Sylviane , Vion‐Dury Jean , Sciaky Martine , Viout Patrick , Cozzone Patrick J.
Published: March 2007

Formate has been evaluated as an alternative standard to quantitate human serum metabolites in 1H NMR spin‐echo spectra. The comparison between added formate and 3‐(trimethylsilyl) 3,3,3,3‐tetradeutero‐propionic acid (TSP) shows that, unlike TSP, formate does not interact with serum macromolecules. Transverse and longitudinal proton relaxation times have been measured on several serum metabolites, in the presence of ammonium chloride. With the exception of glucose, values of metabolite concentrations derived from Hahn spinecho spectra recorded on serum containing 15.4 mM exogenous formate as a standard, are in excellent agreement with the results of biochemical and chromatographic assays, after correction for differential relaxation effects. This approach can be readily used for quantitation of metabolites from blood serum (and eventually other physiological fluids) in normal and in pathological situations not involving disorders of endogenous formate metabolism.
Direct absolute quantification of metabolites in the human brain with in vivo localized proton spectroscopy
Authors: Hennig J. , Pfister H. , Ernst T. , Ott D.
Published: March 2007

The absolute concentrations of the three major brain metabolites observable by in vivo proton spectroscopy—N‐acetylaspartate(NAA), creatine and phosphocreatine (Cr and PCr) and choline (Cho)—have been measured at four standardized localizations in 34 healthy volunteers by in vivo localized proton spectroscopy using an external reference sample. The results show that the concentration of Cr and PCr as observed by in vivo MRS (5–6 mmol/L) is lower than that measured by other methods. The results are concordant with the hypothesis, that the Cr and PCr resonance as observed by proton spectroscopy is due mainly to PCr, whereas Cr remains invisible by being attached to a larger molecule. It is also demonstrated, that Cr and PCr is higher in the cerebellum than in the cerebrum, whereas NAA remains constant within the margin of error (8–9 mmol/L).
Experimental characterization of the ISIS technique for volume selected NMR spectroscopy
Authors: Keevil S. F. , Porter D. A. , Smith M. A.
Published: March 2007

As clinical applications of MRS grow in number and complexity, there is a need for standardized methods for characterizing the performance of volume selection techniques. The results are presented of a thorough evaluation of a particular implementation of ISIS performed using a procedure which forms the basis of the method adopted by the European Community Concerted Action on MRS and MRI. We have found that ISIS localization is optimal when the volume of interest is slightly smaller than the region we wish to study. Contamination with extraneous signal has little T1 dependence so long as TR > T1, and the detection pulse angle is 90°. However, a poorly optimized detection pulse results in T1‐weighted contamination unless TR > 3T1. In the clinical context, this corresponds to a different degree of contamination for each peak in the spectrum. Adiabatic detection pulses were used in an attempt to overcome this problem without resorting to unacceptable TR values, but these were found to function less well than properly optimized rectangular pulses, even if the power was increased above the level determined by the system for B1 insensitivity. These detailed results pertain only to our system, but illustrate the importance of performing similar measurements as part of clinical spectroscopy programmes at other centres.
A gating 31P NMR method triggered by pulses for cardiac pacing
Authors: Tanaka Kunio , Honda Hajime , Akita Nobuyuki
Published: March 2007

A new gating NMR technique triggered by pulses for the cardiac pacing of isolated, perfused rat heart is described. This technique is suitable for obtaining spectra at the same positions over the cardiac cycle with the same RF pulse repetition time and with constant heart rate. Accordingly, each recovered magnetization level at these positions during the cycle can be kept constant. It also allows a qualitative analysis of the myocardial energy level during the cycle under the condition of the same or different cardiac workload (rate pressure product, HR X LVP). This method was used to observe cyclical changes in the concentration of adenosine triphosphate (ATP), phosphocreatine (PCr), Pi, and in pH during the cardiac cycle, and confirmed that the levels of ATP and PCr showed reversible decreases, and Pi showed an antiphasic increase at the peak systole. On the other hand, no significant changes in pH were noted during the cardiac cycle. This pacing‐gated technique is an improvement over other gated NMR techniques triggered by the blood pressure or by ECG traces.
Localized proton NMR spectroscopy of experimental gliomas in rat brain In Vivo
Authors: Gyngell M. L. , Hoehn‐Berlage M. , Kloiber O. , Michaelis T. , Ernestu R.‐I. , Hörstermann D. , Frahm J.
Published: March 2007

Experimental brain tumors produced in rats (n = 10) by stereotactic implantation of cells from the F98 anaplastic glioma clone into the right caudate nucleus were studied in vivo using localized proton NMR and in vitro using high‐resolution proton NMR, bioluminescent imaging of lactate, ATP and glucose distributions, and fluorescent imaging of regional pH. In vivo spectra from normal brain contralateral to the tumor regions showed resonances assignable to N‐acetyl aspartate (NAA), creatines, choline‐containing compounds, myo‐inositol, glutamate and glucose in a pattern similar to those obtained from normal anaesthetized rats. In vivo tumor spectra were characterized by the almost complete absence of NAA, a substantial reduction of total creatine and glucose, and an increase of cholines. Based on the in vitro spectra the increase of the myo‐inositol signal observed in vivo was mainly attributed to glycine. Histological examination as well as bioluminescent and fluorescent imaging indicated two stages of tumor development, i.e., solid vital tumors and tumors with necrosis. However, there was no consistent relationship between proton NMR observations and tumor development.
Absolute quantification of 31P liver metabolites in rat using an external reference and a surface spoiling magnetic field gradient
Authors: De Bisschop Elke , Luypaert Robert , Annaert Guido , Coremans Jean , Osteaux Michel
Published: March 2007

A simple method for measuring absolute concentrations of 31P metabolites in rat liver using an external reference is described. It neutralizes systematic errors due to conductive losses by calibration of the matching capacitor and selects liver signals via an electrically driven, surface spoiling magnetic field gradient. The technique avoids the chemical shift problems associated with linear field gradient localization methods at 4.7 T and allows combinaton with the double standard method for absolute metabolite concentration determination. Application of the method to the in vivo measurement of the absolute concentrations of ATP and Pi in eight rat livers yields results that are in good agreement with literature values. Absolute phosphomonoester concentrations were also obtained, but no literature data were available.
A new high sensitivity 19F probe for labeling cysteine groups of proteins
Authors: Kalbitzer Hans Robert , Rohr Gerhard , Nowak Ewa , Goody Roger S. , Kuhn Winfried , Zimmermann Erbert
Published: March 2007

A novel iodoacetamide label 4‐perfluoro‐tert‐butyl‐phenyliodoacetamide (PFP) containing nine fluorine atoms in equivalent positions has been synthesized. It provides a homogeneous 19F NMR resonance line which can be detected with high sensitivity when coupled to proteins. As an example, the sulfhydryl groups of actin have been labeled with PFP; <100 nmol of this medium sized protein (corresponding to 2.5 mL of a 40μM solution) can be detected easily in a single scan at 470 MHz.
Comparison of pH measurements made using 31P NMR and a fibreoptic pH meter
Authors: Jayasundar Rama , Hall Laurance D. , Bleehen Norman M.
Published: March 2007

The objective of this study was to compare pH measurements made in biological samples using 31P NMR (pHNMR) with those made with a novel, dye‐based fibreoptic pH measurement system (pHF), which is compatible with use in electromagnetic fields without field perturbation. Using protein‐free model solutions, pHNMR was calibrated against pHF, giving a correlation coefficient of 0.969 and a mean difference (± SD) between pHNMR and pHF of 0.037±0.054 over the pH range 6.8–7.7. Further calibration of pHNMR with pHF was carried out for human red blood lysates and then pHNMR was compared with pHF for whole, packed red blood cells over the pH range 7.0–7.8. Values for pHNMR, the intracellular pH, were consistently lower than for pHF, the extracellular pH, by a mean (±SD) of 0.15±0.02 units. A close correlation of extracellular pHNMR with pHF was demonstrated for a blood sample exhibiting two Pi peaks, over the pH range 7.03–7.71. We conclude that concurrent use of NMR and the fibreoptic pH meter provides a reliable method of simultaneous measurement of intracellular and extracellular pH in biological systems.
Chemical exchange in tissue extracts revisited: Bicarbonate and deuterium isotope effects on 31P resonances of phosphoethanolamine and phosphocreatine
Authors: Bezabeh Tedros , Ackerman Joseph J. H.
Published: March 2007

It is not sufficiently appreciated that chemical exchange can markedly affect the appearance of 31P tissue extract NMR spectra. In addition to the commonly recognized 31P chemical shift effects of divalent metal cation (e.g. Mg2+) binding upon ATP resonances, multiple resonances for phosphoethanolamine (PE) and phosphocreatine (PCr) are observed under certain conditions of pH, temperature, and D2O and bicarbonate concentrations. In the presence of bicarbonate ion (commonly used to neutralize acidic extractions) carbamate formation causes a second 31P resonance for PE to appear. This effect has been described previously for 13C and 1H amino acid resonances in tissue extracts [Sherry et al. J. Magn. Reson. 89, 391––398 (1990)]. The observation of a splitting of the PCr 31P resonance in aqueous solutions containing D2O has been recently ascribed to proton scalar coupling but was described earlier in an underappreciated report [Kupriyanov et al. Biochem. Biophys. Res. Comm. 114, 1117–1125 (1983)] as due to a deuterium isotope effect. These effects, carbamate formation and deuterium isotope shift, are verified herein to cause marked shifts in PE and PCr 31P resonances. The dependence upon experimental parameters is explored.
Aqueous shift reagents for high‐resolution cation NMR. VI. Titration curves for in vivo23Na and 1H2O MRS obtained from rat blood
Authors: Albert Mitchell S. , Huang Wei , Lee Jing‐Huei , Balschi James A. , Springer Charles S.
Published: March 2007

Frequency shift/concentration calibration curves applicable to the use of shift reagents (SRs) for in vivo 23Na MRS studies can be obtained from experiments with whole blood. Here, they are reported for titrations of rat blood with the SRs DyTTHA3− and TmDOTP5−. There are a number of considerations that must be made in order to derive accurate calibration curves from the experimental data. These include the effects of bulk magnetic susceptibility (BMS, since the SRs are paramagnetic), the effects of water flux (since addition of the SR stock solution to blood renders the plasma hyperosmotic), and the consequences of restricted distribution of the SR anion in the erythrocyte suspension. We give in some detail the BMS shift theory that obtains in this case and show also how it applies to excised perfused organ as well as in vivo studies. Also, we report significant effects of adjuvant Ca2+ additions in the TmDOTP5−titrations. These are very important to the successful use of this SR in vivo. Finally, our considerations of BMS lead naturally to an understanding of its manifestations in the shifts of the 1H2O resonance frequencies of cell suspensions and tissues induced by SRs. Since these are being increasingly reported, and often misinterpreted, we devote an experiment and some discussion to this subject. We show that this phenomenon cannot be used to quantitatively discriminate intra‐ and extracellular 1H2O signals.
In vivo19F nuclear magnetic resonance of a monofluorinated neuroleptic in the rat
Authors: Günther Ulrich , Albert Klaus
Published: March 2007

In vivo 19F NMR measurements of the fluorinated neuroleptic melperone [4′‐fluoro‐4‐(4‐methylpiperidino)‐butyrophenone hydrochloride] in the rat brain were performed using a geometrically optimized surface coil at 4.7 T. It was possible for the first time to detect a signal of a monofluorinated neuroleptic drug with a time resolution of 30 min after i.p. application. The kinetic time course of the investigated neuroleptic melperone was recorded over 6 h and showed that the half‐life in the rat brain is 4.3 h. The total amount of drug and its metabolites in the brain was estimated to be 50 μM. the chemical shift of the 19F NMR signal shows the same upfield shift relative to that in aqueous solution as has been reported for trifluorinated neuroleptic drugs.
Energy cost of twitch and tetanic contractions of rat muscle estimated in situ by gated 31P NMR
Authors: Foley Jeanne M. , Meyer Ronald A.
Published: March 2007

The phosphagen cost of maximal isometric twitch and tetanic contractions in rat gastrocnemius muscle was measured in situ by 31P NMR with acquisitions gated to precise time points after a brief (< 10 s) burst of contractions. Alteration of twitch stimulation frequency did not affect the energy cost per contraction. Pooled results of four twitch rates from 1 to 8 Hz produced an average cost of 0.257±0.012 μmol ATP/g/twitch. This value was compared with the initial twitch cost estimated from the time zero derivative of an exponential fit of averaged scan phosphocreatine (PCr) data from a previous study of 8 min of contraction in situ at 0.75 Hz. Agreement of the two estimates validates the use of the fitting/derivative method to assess energy cost and confirms the monoexponential character of the PCr time course. Evaluation of muscle pH changes demonstrated that all ATP use during the brief twitch contraction bouts could be accounted for by PCr hydrolysis. Results also showed a brief delay in onset of PCr recovery, consistent with the response time of oxidative systems. Tetanic contractions of 100 ms duration at 100 Hz required 2.17±0.07 μmol ATP/g muscle/contraction, in general agreement with estimates reported using a variety of other methods.
Quantitative 31P MRS of the normal adult human brain. Assessment of interindividual differences and ageing effects
Authors: Longo R. , Ricci C. , Palma L. Dalla , Vidimari R. , Giorgini A. , den Hollander J. A. , Segebarth C. M.
Published: March 2007

The characteristics of the 31P MR spectra from a large central volume in the brain of 47 healthy adults (aged 25–85 years) were assessed. Spectral parameters were estimated by means of a time‐domain fitting technique. Statistical uncertainties of the estimates were determined by means of the Cramer‐Rao theory and minimized by introducing a priori knowledge into the fitting procedure. Age‐dependency of the spectral parameters was assessed by means of linear regression. Significant differences between individuals were established for some parameters. A significant age‐dependency (p⩽0.001) of ca 20% over the age range considered was found for the intensity of the phosphocreatine resonance line.
Graphic‐aided study of metabolic modifications of plasma in cancer using proton magnetic resonance spectroscopy
Authors: Vion‐Dury J. , Favre R. , Sciaky M. , Kriat M. , Confort‐Gouny S. , Harlé J. R. , Grazziani N. , Viout P. , Grisoli F. , Cozzone P. J.
Published: March 2007

Proton high‐resolution MRS of human plasma allows the rapid detection, on the same spectrum, of many compounds originating from different metabolic pathways. In this paper, we illustrate the modifications of the plasma metabolic profiles recorded by proton NMR spectroscopy in different classes of cancers. These modifications can be easily monitored with graphic aids such as ‘star plots’ which define for each type of cancer a particular pattern describing the most altered metabolic pathways. By using ‘star plots’ three types of metabolic patterns have been distinguished: (i) the ‘inflammatory’ pattern characterized by an increase of glycosylated moieties of glycoproteins; (ii) a ‘lipid modified’ pattern, characterized by various modifications occurring mainly in the lipid moieties detected by MRS; and (iii) a pattern which is often observed in sarcomas and mainly characterized by an alteration in the N‐acetyl glucosamine/N‐acetyl neuraminic acid ratio. This study demonstrates the ability of proton MRS of plasma to rapidly detect the occurrence of metabolic modifications brought about by cancer evolution or therapy.
Control of phosphocreatine resynthesis during recovery from exercise in human skeletal muscle
Authors: Kemp G. J. , Taylor D. J. , Radda G. K.
Published: March 2007

Information about the control of mitochondrial function in skeletal muscle in vivo can be obtained from the relationship between the rate of mitochondrial oxidation and the intracellular concentrations of phosphorus metabolites, although the analysis is complicated by the constraints imposed by the creatine kinase equilibrium. The rate of phosphocreatine (PCr) recovery after exercise measured by 31P MRS is an estimate of net oxidative ATP synthesis. Analysing such data from normal and abnormal human muscle, we show that the approximately exponential recovery kinetics of ADP and PCr imply that the rate of PCr resynthesis has a hyperbolic dependence on [ADP] but remains approximately linear with respect to the concentration of orthophosphate (Pi) and therefore also [PCr] and [creatine]. Both kinds of relationship are consistent with experimental data from exercising animal muscle and also with data from isolated mitochondria which suggest kinetic control of mitochondrial ATP synthesis of [ADP]. These relationships are altered in proven mitochondrial disease. This analysis offers a way to quantify mitochondrial function and its abnormalities in vivo.