bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThe 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

AbstractHepatic 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

AbstractThe 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

AbstractTwo‐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

AbstractThe 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

AbstractThe 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

AbstractWe 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

Abstract31P 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

AbstractMeasuring 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

AbstractSeveral 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

AbstractThe 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

AbstractIn 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

AbstractIn 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

AbstractSpin 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

AbstractHuman 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

AbstractFormate 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

AbstractThe 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).