bluuebunny/crossref_metadata_2025 huggingface dataset:
Cerebral metabolism of fluorodeoxyglucose measured with 19F NMR spectroscopy
Authors: Pouremad Reza , Wyrwicz Alice M.
Published: March 2007

Brain extracts from rats given various doses of 2‐fluoro‐2‐deoxy‐D‐glucose ranging from 20 to 300 mg/kg were examined with 19F NMR spectroscopy for fluorinated metabolic products and compared with the in vivo 19F spectra. Based on the analysis of these spectra and comparison with synthetic reference compounds, 2‐fluoro‐2‐deoxy‐D‐glucose 6‐phosphate and 2‐fluoro‐2‐deoxy‐D‐mannose 6‐phosphate were identified as the major metabolites present. 2‐Fluoro‐2‐deoxy‐D‐6‐phosphogluconate was detected only at high doses of 2‐fluoro‐2‐deoxy‐D‐glucose administered, along with non‐phosphorylated 2‐fluoro‐2‐deoxy‐D‐glucose and 2‐fluoro‐2‐deoxy‐D‐mannose. Small amounts of two other compounds, which were not identified, were also observed. Presence of the 2‐fluoro‐2‐deoxy‐D‐mannose 6‐phosphate is the result of 2‐fluoro‐2‐deoxy‐D‐glucose 6‐phosphate isomerization at the C2 position catalyzed by phosphoglucose isomerase. Results from the in vitro enzymatic reaction provide support for this hypothesis. Presence of 2‐fluoro‐2‐deoxy‐D‐mannose may be the result of 2‐fluoro‐2‐deoxy‐D‐glucose isomerization at the C2 position catalyzed by glucose isomerase or the result of the dephosphorylation of the 2‐fluoro‐2‐deoxy‐D‐glucose 6‐phosphate.
NMR estimation of protective effect of insulin on mouse liver with epinephrine‐induced metabolic lesions
Authors: Yushmanov Victor E. , Khristianovich Darya S. , Rozantseva Tatyana V. , Sibeldina Lili A.
Published: March 2007

In order to study the effects of epinephrine and insulin on liver metabolism, measurements of cellular phosphates and intracellular pH by 31PNMR, of glycogen by 13C NMR and of lactate by 1H NMR were performed in freshly dissected mouse liver at 0‐4 deg.C and in ethanolic liver extracts. The injection of epinephrine hydrochloride (0.1 mL of 0.1% solution i.p. per mouse) caused remarkable changes in liver metabolic profiles which were expressed most distinctly in 15‐30 min and could not be attributed solely to epinephrine‐induced hyperglycemia. Among these metabolic changes are falls in the levels of ATP and uridine diphosphate sugars by 60‐70%, possibly related to glycogen depletion, and intracellular acidification by 0.5 units attributed to the release of protons during hydrolysis of ATP rather than to accumulation of lactate in anaerobic glycolysis. Insulin injected prior to epinephrine (4 units i.p.) markedly suppressed epinephrine‐induced metabolic alterations, although the effect of the combination of insulin and epinephrine was not the sum of the separate effects of these hormones. The maximum protective effect of insulin was reached when insulin was injected 15 min prior to epinephrine. The results obtained demonstrate the applicability of NMR for evaluating the protective activity of modifiers at various extreme exposures.
23Na, 59Co and 2H NMR studies of experimental acute pancreatitis
Authors: Kushnir Tammar , Kaplan Ofer , Askenasy Nadir , Navon Gil
Published: March 2007

Multinuclear MR was applied to the study of experimental acute pancreatitis. A continuous increase, up to 700%, of total, NMR visible, sodium content was detected during the development of the disease through the edematous stage to necrosis. The effect of the elevation of sodium content is amplified by an increased 23Na NMR visibility during the disease. Interstitial and total water volume of pancreases were estimated using the distribution of Co(CN)36 and D2O, by 50Co and 2H NMR, respectively. In healthy pancreases the interstitial compartment was found to comprise 35% of the tissue volume. In the diseased pancreases the penetration volume of Co(CN)36 reached 90% of the total tissue volume, indicating extensive membrane injury. The time dependence of the 23Na NMR in the presence of the shift reagent Na7Dy(tripolyphosphate)2.3NaCl provided additional evidence of the increased permeability of the membranes in the diseased organs.
1H NMR characterization of normal human cerebrospinal fluid and the detection of methylmalonic acid in a vitamin B12 deficient patient
Authors: Commodari Fernando , Arnold Douglas L. , Sanctuary Bryan C. , Shoubridge Eric A.
Published: March 2007

1H NMR was used to analyze human cerebrospinal fluid (CSF) from a group of neurological disease controls and from a vitamin B12 deficient patient. The spectra were acquired at either 7.06 or 9.40 T at ambient temperature with CSF freeze dried and reconstituted in 2H2O. 3‐Trimethylsilyl propionate was used as an internal chemical shift and concentration reference. All of the CSF samples showed peaks for lactate, L‐alanine, acetate, glutamine, citrate, creatine/creatinine and sugar resonances. There was good agreement between the metabolite concentrations as determined by NMR with those obtained using conventional chemical methods. 1D and 2D 1H NMR techniques along with J‐coupling and T1 analysis were used to confirm the peak assignments. Methylmalonic acid could be detected and quantitated (ca 150 μM) in the CSF from the vitamin B12 deficient patient.
Biotransformation of 2‐fluoroaniline in rats studied by In Vivo19F NMR
Authors: Vervoort J. , Rietjens I. M. C. M. , Moonen C. T. W. , Von Kienlin M. , Despres D.
Published: March 2007

The present study describes results from an in vivo 19F NMR study on rats exposed to the xenobiotic compound 2‐fluoroaniline. Qualitative pharmacokinetics and the biotransformation of 2‐fluoroaniline were studied after exposure to 50 mg/kg body wt 2‐fluoroaniline. Accumulation and elimination of the parent compound in and from the liver of exposed animals were readily observed. Metabolites formed in the liver were shown to be efficiently excreted from the liver, as the amount of metabolites in this organ was always <10% of the maximum amount of the parent compound observed. In the bladder, rapid accumulation of 2‐fluoroaniline‐derived metabolites was detected. The metabolite pattern was shown to change in time, with the parent compound being dominantly present during the first hours of exposure. N‐acetylated products (4‐acetamido‐3‐fluorophenyl sulphate and 4‐acetamido‐3‐fluorophenyl glucuronide) were observed to accumulate more slowly in the bladder than the non‐acetylated products (4‐amino‐3‐fluorophenyl sulphate and 4‐amino‐3‐fluorophenyl glucuronide). Urine metabolite patterns obtained from the bladder in vivo were compared to those obtained during metabolic cage experiments.
The effect of intra‐tumour heterogeneity on the distribution of phosphorus‐containing metabolites within human breast tumours: An In Vitro study using 31P NMR spectroscopy
Authors: Smith T. A. D. , Glaholm J. , Leach M. O. , Machin L. , McCready V. R.
Published: March 2007

The concentration of phosphorus‐containing metabolites was determined in extracts of multiple samples from six human breast tumours and in samples from normal and inflamed breast tissue. The degree of lymphoid infiltrate, necrotic fraction and tumour cell and normal tissue fraction were determined on sections taken from each of the tumour samples. In four of the tumours there was a very high degree of variation between samples in the absolute concentration of metabolites. Three of these tumours showed a high degree of intra‐tumour variation in the distribution of tumour cells and of normal tissue. The other two tumours were relatively homogeneous with respect to both tumour cellularity and the distribution of phosphorus‐containing metabolites. Samples from normal breast tissue was found to contain only low concentrations of phosphorus‐containing metabolites. However one of the inflamed samples, which consisted predominantly of macrophages, contained high levels of such compounds. The effect of time delay between resection and freezing on the levels of metabolites in human breast tumours was also examined.
31P NMR and enzymatic analysis of cytosolic phosphocreatine, ATP, Pi and intracellular pH in the isolated working perfused rat heart
Authors: Dobson Geoffrey P. , Veech Richard L. , Passonneau Janet V. , Kobayashi Kumpai , Inubushi Toshiro , Wehrli Susanna , Nioka Shoko , Chance Britton
Published: March 2007

Hearts from fed male Wistar rats (200–350 g) were perfused at low and high workloads with Pi‐free Krebs‐Henseleit medium containing either 10 mM glucose or 10 mM glucose plus 15mU/mL insulin. The intracellular pH by 31P NMR ranged between 6.99 and 7.02 and agreed to within 0.1 pH unit of estimates calculated using enzymatically determined total tissue HCO3−/CO2 contents. At high work, where the tissue contents of phosphocreatine (PCr) and ATP were determined on the same heart as NMR areas (n = 16), the proportionality factors, defined as the 31P NMR area units divided by the total enzymatically determined tissue content (area units/μmol/g dry wt), were 112±8 for PCr, 99±4 for γ‐ATP, 138±9 for α‐ATP and 100±4 for β‐ATP. These values were normalized by taking β‐ATP as 100 area units/μmol/g dry wt. Since the proportionality factor for PCr and γ‐ and β‐ATP were not statistically different (p < 0.05), it was concluded that each was equally visible by 31P NMR and that no significant breakdown of PCr occurred during freezing or tissue acid extraction procedures. The cytosolic Pi estimated from NMR in glucose plus insulin perfused hearts at low and high work was 4.92±0.67 and 6.33±0.42 μmol/g dry wt. Using the near‐equilibrium expression of KCK/KG+G and the metabolite levels in heart extracts, the calculated cytosolic Pi was 13.08±1.83 and 16.17±3.08 μmol/g dry wt, respectively. The cytosolic NMR Pi in the glucose hearts was 8.42±1.0 and 8.42±0.75 μmol/g dry wt at low and high work and 12.08±1.58 and 27.20±4.20±μmol/g dry wt from near‐equilibrium estimates. The total tissue Pi measured enzymatically on freeze‐clamped hearts ranged from 18.0 to 26.42 μmol/g dry wt. The validity of using both the 31P NMR and the near‐equilibrium method for estimating cytosolic Pi in the heart was discussed.
Evidence that mitochondrial phosphate is visible in 31P NMR spectra of isolated, perfused rat hearts
Authors: Garlick Pamela B. , Soboll Sibylle , Bullock Gillian R.
Published: March 2007

We had previously found (P. B. Garlick, T. R. Brown, R. H. Sullivan and K. Ugurbil, J. Mol. Cell Cardiol. 15, 855–858 (1983)) that two peaks could be observed in the phosphate region of NMR spectra of isolated, perfused rat hearts. Upon valinomycin treatment, an increase in the peak at 2.8 ppm in the phosphate region (phosphocreatine set at −2.52 ppm) had been observed. We have now confirmed our hypothesis that this peak originates from the mitochondrial phosphate by: (i) determination of myocardial mitochondrial phosphate contents using density gradient centrifugation in non‐aqueous solvents; and (ii) quantitative electron microscopy of the heart tissue. Thus, we conclude that mitochondrial and cytosolic phosphate can be distinguished from each other in 31P NMR spectra of isolated, perfused rat hearts.
Classification of tumour 1H NMR spectra by pattern recognition
Authors: Howells S. L. , Maxwell R. J. , Griffiths J. R.
Published: March 2007

1H spectra of tumours or normal tissues, which include signals from all hydrogen‐containing metabolites, are too complex for the human eye to interpret. We have studied 58 1H spectra from perchloric acid extracts of three normal tissues (liver, kidney and spleen) and five rat tumours (GH3 pituitary, fibrosarcoma, Morris Hepatomas 7777 and 9618a and Walker carcinosarcoma). Instead of editing them or quantifying individual metabolites, we have used statistical pattern recognition techniques to classify them into groups. This automatic, objective method differentiated spectra from normal and malignant rat tissue biopsies, and from different types of cancer. It seems likely that this technique can be applied to human tissues and thus used for cancer diagnosis.
Identification of lactate, threonine and alanine in rat thymus and tumorigenic lymphoid cells using 1H 2‐D COSY NMR spectroscopy
Authors: Tang Hailun L. , Buist Richard J. , Rixon Raymond H. , Whitfield James F. , Smith Ian C. P.
Published: March 2007

One‐ and two‐dimensional 1H NMR spectra were obtained for normal murine thymus and malignant lymphoma tissue, as well as for the supernatant fractions from high speed centrifugal separations. Crosspeaks in the two‐dimensional spectra resembled those reported by others for adenocarcinoma and leukemic lymphoblast cells, assigned tentatively to the carbohydrate fucose. However, for the present systems, spectral analysis and the spectral response to addition of known compounds led to assignment of the crosspeaks as follows: 1.33–4.12 ppm, lactate anion; 1.33–4.26 ppm, threonine; 1.48–3.78 ppm, alanine. Differences between the NMR data for the normal and malignant specimens were only in the relative intensities of the peaks. No peaks characteristic of fucose were found in spectra of cytosol, tissue or membrane lipids. Thus, the NMR data for malignant lymphoma cells are significantly different from those for adenocarcinoma and leukemic lymphoblasts. The NMR characteristics of different types of cancer cell must be individually determined.
Quantitative magnetic resonance spectroscopy by optimized numerical curve fitting
Authors: Webb S. , Collins D. J. , Leach M. O.
Published: March 2007

A technique is reported for generating the quantitative area under selected peaks within a 31P NMR spectrum. A numerical iterative method generates the fitted curve so as to minimize the RMS deviation between the fit and the experimental data. The curve is constructed from elemental grains of spectral density (“spexels”), each of which represents an elemental Lorentzian distribution, where the centre frequency and line width of the spexel may be varied within predetermined limits. This provides a fit that in principle is not restricted to a Lorentzian model. The method allows peak areas to be estimated, including the case of overlapping peaks. The method has been tested using simulated spectra containing six overlapping spectral lines each of known amplitude (ranging from 367 to 661 mV) and area; together with additional Gaussian noise with a standard deviation ranging from 30 to 646 mV. The results of fitting both unfiltered and filtered spectra were compared. The variation of quality of fit with spectral noise and filtering has been evaluated. In all cases, the method fitted the peak amplitudes to within 1% of the simulated value. The optimization processes provide an excellent non‐linear spectrum filtering algorithm. Provided the noise in the spectra did not exceed ca 400 mV, prefiltered data could be adequately fitted.
A two‐point volume localized T1 measurement sequence for in vivo spectroscopy using a surface coil
Authors: Yongbi N. M. , Leach M. O. , Payne G. S. , Collins D. J.
Published: March 2007

A technique for obtaining T1 values from well localized regions using surface coils and with a clinically practicable measurement time is described. The method uses a two‐point Inversion‐Recovery/Saturation‐Recovery (IR/SR) sequence in conjunction with the image‐selected in vivo spectroscopy localization scheme. T1 values are obtained by comparing the ratio of peak areas with those in a pre‐computed look‐up table. The method was tested by measuring the T1s of six calibrated water phantoms doped with different concentrations of gadolinium. This indicated an accuracy of 3% for T1 values in the range 400‐1500 ms. 31P spectra and T1 values of Pi, phosphocreatine and α‐, β‐ and γ‐NTP metabolites from the calf muscle of healthy volunteers were obtained with the sequence employing Bi‐insensitive excitation pulses and a surface coil. The T1 values fall within the range of published values obtained by other techniques.
General features of systemic effects of murine leukemias on phosphate metabolism in liver studied by 31P NMR
Authors: Yushmanov Victor E. , Khristianovich Darya S. , Rozantseva Tatyana V. , Sibeldina Lili A.
Published: March 2007

31P NMR was used to study the systemic effects of a tumor on a host organism by monitoring the phosphate metabolite content in freshly excised mouse liver at 0–4°C and in ethanolic liver extracts of animals suffering from La, L1210 and P388 leukemias and Ehrlich ascites tumor (EAT). The progression of murine leukemia is characterized by increases in the intensities of the resonances of Pi and phosphomonoesters (PME), in particular, phosphorylethanolamine, in liver; phosphodiester (PDE) signals increase two‐ to four‐fold during the period of rapid tumor growth and decline to undetectable levels in the terminal stage. There were no reliable alterations detected in the ATP content and intracellular pH throughout the course of the leukemia. The kinetics of intracellular phosphates are similar in various kinds of leukemia but quite different in EAT. The reduction of inoculum causes the appearance of maxima in the Pi and PME profiles in the latent period of La leukemia, but the profiles of liver PDE considered from the end of the latent period are independent of inoculum. Possible mechanisms for the changes in PDE concentrations and their biochemical role are discussed. NMR spectroscopy of liver may be used to indirectly monitor the progression of tumors unavailable for direct NMR assay.
31P NMR spectroscopy of a xenografted hypopharynx carcinoma: Effects of tumor growth and treatment with cisplatin on the tumor phosphorus metabolism, histology and cytokinetics
Authors: Tausch‐Treml Robert , Baumgart Frank , Ziessow Dieter , Köpf‐Maier Petra
Published: March 2007

A xenografted hypopharynx carcinoma growing subcutaneously in nude mice was studied by in vivo 31P NMR spectroscopy during uninfluenced growth and following treatment with cisplatin (CDDP). Parallel to the NMR experiments, the cytokinetic and histological changes in the tumor were investigated. The most significant change in the growing tumor was a decline in the level of phosphocreatine (PCr), whereas the tumor pH did not change. Following treatment with CDDP (4, 8 and 12 mg/kg), a dose‐dependent decrease in the level of phosphomonoesters (PME) took place, whilst no dose dependence could be observed for the increase of PCr. the pH shifted to alkaline only after administration of the highest CDDP dose. Tumor cytokinetics revealed a cell arrest at the G1/S boundary 24 h after chemotherapy. At this time, the histological sections showed a dilatation of capillaries, whereas first necroses appeared on day 3. The proliferative activity of the tumor showed a sharp decline 24 h after CDDP application, followed by a revival of cell proliferation that was proportional to the dose applied between days 5 and 7. This increase in proliferative activity was paralleled by a marked increase in the PME/phosphodiesters ratio. Thus, in the tumor investigated the PME were the best indicators of tumor response to therapy. A precise correlation between the cytokinetic data and the re‐energization of the tumor was not possible because histological changes, which may contribute to improved tumor energy status took place at the same time.
Quantitation of metabolites in NMR spectra from isolated tissues, using 14N spectroscopy and nitrate to determine tissue volume
Authors: Wray S. , Wilkie D. R.
Published: March 2007

Quantification of metabolites is a goal of many biomedical NMR studies. To obtain absolute measurements of metabolite concentrations is often both difficult and time‐consuming. In this paper a method for determining metabolite concentrations directly is described and validated. It is applicable to studies of amphibian muscles, and with suitable precautions, to other isolated organs and tissues. The method is based upon using 14N NMR and nitrate‐containing solutions to determine what fraction (F) of the sensitive volume of the RF coil is occupied by tissue. As the concentration of nitrate is known it can be used to calibrate other 14N metabolites in the tissue. Moreover, once F is determined, it can be used to calibrate metabolites in spectra from other nuclei e.g., 31P or 31C. All that is required is that a spectrum from a standard for that nucleus is obtained. Thus this method does not require any “internal” (intrinsic to the tissue) standard, and is extremely quick and simple to use.
31P NMR spectroscopy of perinatal hypoxic‐ischemic brain damage: A model to evaluate neuroprotective drugs in immature rats
Authors: William Gerald D. , Palmer Charles , Roberts Rebecca L. , Heitjan Daniel F. , Smith Michael B.
Published: March 2007

Cerebral energy metabolism can be measured non‐invasively in unanesthetized neonatal rats with 31P NMR spectroscopy. Using this technique, serial changes in high energy phosphates were determined from the right cerebral hemispheres of 7 day postnatal rat pups during a hypoxic‐ischemic insult known to produce focal brain injury. During 3 h of hypoxia‐ischemia the concentration of ATP dropped to 33±8% of prehypoxic (baseline) levels, phosphocreatine (PCr)/Pi decreased from 1.5±0.51 to 0.16±0.06, while pH decreased nominally by 0.2 units. After 2.5 h of recovery in air, ATP returned to 75±10% of baseline levels, PCr/Pi rose to 1.1±0.28, and pH returned to its normal value of 7.16±0.06. This model was used to test the efficacy of the adenosine deaminase inhibitor, 2‐deoxycoformycin (DCF) as a potential neuroprotective drug. The data for the drug‐ and saline‐treated populations were analyzed by integrating ATP and Pi/PCr levels over specific time intervals, expressing it relative to baseline levels, and modeling it with cubic splines. Pretreatment with 500 μg/kg DCF shows a small, but statistically significant, preservation of both ATP and phosphorylation potential during hypoxia and initial recovery. Brain water content (edema) at 42 h recovery was apparently associated with both mean ATP and mean Pi/PCr in the last 2 h of hypoxia‐ischemia. When ATP fell below 70% of baseline, brain edema was evident at 42 h of recovery. This methodology is suitable for extension to human infants.
Depth selective quantification of phosphorus metabolites in human calf muscle
Authors: Dunn J. F. , Kemp G. J. , Radda G. K.
Published: March 2007

We have used phase modulated rotating frame imaging, a depth selective NMR technique, in conjunction with two methods of calibration, in order to determine the feasibility of quantifying phosphorus compounds in selected regions of a biological sample. In one method, we related peak areas obtained from a sample to the peak area of an external reference located within the receiver coil, previously calibrated against a standard. In the second method we measured peak areas from a standard separately and related them directly to the area of the sample peak. We examined the calf muscles of male volunteers, positioning the coil to obtain signal mainly from the gastrocnemius in the shallow slices and soleus in the deep slices. The concentrations of Pi, phosphocreatine and ATP (in mmol/kg tissue) were 3.0±0.5, 18±2 and 4.8±0.2 at 2 cm depth (mean±SD; n = 5). These results are similar to published biopsy data. A comparison with published values obtained from other NMR quantification methods suggests that, while it is possible to obtain consistent results within one laboratory, it is not currently possible to obtain similar results between laboratories. This is evident from the fact that different laboratories report different phosphocreatine/ATP ratios, indicating that the techniques are limited by variations in the processes of data collection and peak area measurement.
Application of time‐domain fitting in the quantification of in vivo1H spectroscopic imaging data sets
Authors: de Beer R. , van den Boogaart A. , van Ormondt D. , Pijnappel W. W. F. , den Hollander J. A. , Marien A. J. H. , Luyten P. R.
Published: March 2007

Time‐domain model function fitting techniques were applied to improve the reconstruction of metabolite maps from the data sets obtained from in vivo 1H spectroscopic imaging (SI) experiments. First, residual water‐related signals were removed from the SI data sets by using SVD‐based linear time‐domain fitting based upon the HSVD (State Space) approach. Second, peak integrals of the metabolites of interest were obtained by quantifying the proton spin‐echoes of the voxels by means of non‐linear time‐domain fitting based upon the maximum likelihood principle. Third, in order to save computational time, interpolation of the metabolite images (from size 32 × 32 to 128 × 128) was performed in the image‐domain by applying one‐dimensional cubic splines. It was found that the residual water signals can be almost completely removed from the SI data sets by applying the linear HSVD fitting method. Furthermore, it was found that voxel dependency of certain NMR parameters (e.g., variations of the spin‐echo offset frequencies and/or phase factors) can be accounted for automatically by applying the non‐linear time‐domain fitting technique. For that purpose it appeared to be essential to employ prior knowledge of the NMR spectral parameters.
Phosphorus metabolite characterization of human prostatic adenocarcinoma in a nude mouse model by 31P magnetic resonance spectroscopy and high pressure liquid chromatography
Authors: Kurhanewicz John , Dahiya Rajvir , Macdonald Jeffrey M. , Jajodia Prahalad , Chang Lee‐Hong , James Thomas L. , Narayan Perinchery
Published: March 2007

A series of experiments were conducted to identify and quantify the phosphorus metabolites of DU 145 xenografts (a human prostatic adenocarcinoma cell line grown in nude mice) using 31P MRS and HPLC. The 31P spectral characteristics of DU 145 xenografts were compared to perfused DU 145 cells and to in situ human prostatic adenocarcinomas. These studies demonstrated that both DU 145 xenografts and perfused DU 145 cells exhibited reduced levels of phosphocreatine relative to spectra of in situ human prostatic adenocarcinomas. Elevated levels of phosphomonesters (PMEs) were observed in 31P spectra of both DU 145 xenografts and in situ human prostatic adenocarcinomas. The major components of the PME resonance of DU 145 xenografts were identified as phosphocholine and phosphoethanolamine. High levels of diphosphodiesters (DPDEs) were consistently observed for both DU 145 xenografts and perfused DU 145 cells, but were absent in 31P spectra of in situ primary human adenocarcinomas. In agreement with spectroscopic results, high pressure liquid chromatographic analyses of human tissue removed at surgery contained insignificant amounts of DPDEs while DU 145 xenografts had high levels of DPDEs consisting mainly of uridine‐5′‐diphospho‐N‐acetylgalactosamine (22.4 nmol/mg protein) and uridine‐5′‐diphospho‐N‐acetylglucosamine (7.4 nmol/mg protein).
An assessment of 31P MRS as a method of measuring pH in rat tumours
Authors: Stubbs M. , Bhujwalla Z. M. , Tozer G. M. , Rodrigues L. M. , Maxwell R. J. , Morgan R. , Howe F. A. , Griffiths J. R.
Published: March 2007

The contribution of extracellular components to the measurement of pHMRS of a variety of rat tumours (nitrosomethyl urea induced mammary tumours, GH3 prolactinomas, Hepatoma 9618a, UA hepatomas and Walker sarcomas) has been assessed. Acid extractable Pi was between 2.6 and 12.5 μmol/g wet wt depending on tumour type, and of this 53±4.8% (mean ± SEM) was MRS‐visible. The Pi content of tumour exudate was 2–3 mM, of interstitial fluid (sampled from a micropore chamber incorporated within a tumour) 1.7 mM, and of blood plasma 1.95 mM. The mean extracellular volumes of the tumours, measured by distribution of 3H2O and [14C]inulin, were 49‐55% depending on tumour type and were at least twice that found in normal liver. Calculations suggested that for most tumours with an extracellular volume not exceeding 55%, at least 65% of the Pi(MRS) signal was derived from intracellular Pi, and thus that pHMRS is a measure of pHi. For each tumour type, pHMRS was measured both in “pulse‐acquire” mode at 1.9T which may include signals from surrounding tissue, and in localized mode at 4.7 T where the signal came uniquely from tumour tissue. The steady state pHMRS was either neutral or on the alkaline side of neutrality (pH range 7.04–7.37). Raised lactate content and decreased buffering capacity (compared to normal tissues) accompanied these neutral to alkaline pH values. The extracellular pH of all the tumour types was found to be significantly lower than pHi when calculated from the distribution of lactate across the plasma membrane ([lactate−]out/[lactate−]in = [H+]in/[H+]out) by the method of Veech [Veech, R. L. NMR Biomed. 4, 53–58 (1991)] whereas in control tissue (liver) the extracellular pH was higher, as would be expected.
Effect of hypoglycemia on changes of brain lactic acid and intracellular pH produced by ischemia
Authors: Nagai Y. , Naruse S. , Weiner M. W.
Published: March 2007

Previous investigators have attributed the fall of brain intracellular pH (pHi) produced by ischemia to accumulation of lactic acid. The goal of the present experiments was to examine the hypothesis that the acidosis produced by cerebral ischemia is due to accumulation of lactic acid. The present experiments inhibited lactic acid production by lowering glucose availability using insulin‐induced hypoglycemia. The adverse effects of hypoglycemia were prevented by the prior elevation of β‐hydroxybutyric acid and acetoacetic acid induced by a high lipid diet. Brain pHi and lactic acid were measured by 31P and 1H NMR. The results showed that insulin‐induced hypoglycemia markedly inhibits production of lactic acid, but has no effect on brain pHi during ischemia. These findings suggest that, at least under some conditions, the acidosis produced by cerebral ischemia is not due to accumulation of lactic acid.
A 15N NMR study of in vivo cerebral glutamine synthesis in hyperammonemic rats
Authors: Kanamori Keiko , Parivar Farhad , Ross Brian D.
Published: March 2007

Rats were given intravenous 15NH4+ infusion at a rate of 2.2 or 5.5 mmol/h/kg body wt to induce hyperammonemia, as animal models of hepatic encephalopathy. Its effect on cerebral amino acid metabolism was studied in vivo by 15N NMR spectroscopy at 20.27 MHz for 15N. Cerebral [γ‐15N]glutamine (present at a tissue concentration of 4–9 μmol/g) and [α‐15N]glutamate/glutamine (6 μmol/g) were clearly observed in living rats within 9‐18 min. In portacaval‐shunted rats, final cerebral [γ‐15N]glutamine concentrations were higher than those in controls after the same infusion period, presumably because decreased 15NH removal in the liver led to increased 15NH3 diffusion into the astrocytes. In control rats, cerebral [γ‐15N]glutamine pool increased at a rate of 1.7 μmol/h/g when blood ammonia concentration was 0.8 mM. 15N enrichment in γ‐15N was 71%. From these observations, in vivo activity of glutamine synthetase in rat brain was estimated to be 3.5 μmol/h/g. Comparison with reported optimum in vitro activity suggests that in situ concentrations of some substrates and cofactors limit the activity of glutamine synthetase in vivo.
Relaxation times and concentrations of 7Li in the brain of patients receiving Lithium therapy
Authors: Kushnir T. , Itzchak Y. , Valevski A. , Lask M. , Modai I. , Navon G.
Published: March 2007

The present study describes a protocol for the determination of in vivo absolute molar concentrations of Li+ in the human brain using a double tuned 1H/7Li surface coil. The protocol follows the method of Thulborn and Ackerman [J. Mag. Reson. 55, 357–371 (1983)] where the ratio of the signal intensities of 7Li and 1H in the brain is compared to the same ratio in a phantom containing known concentrations of Li+. The 7Li T1 values in the brains of five patients receiving lithium therapy were measured. The average result was T1 = 3.5±0.25s. The phantom solution was adjusted to have this T1 value. The protocol was applied for eight bipolar patients receiving lithium therapy. The average ratio of brain to serum lithium molar concentration was found to be 0.59±0.12.
An assessment of artefacts in localized and non‐localized 31P MRS studies of phosphate metabolites and pH in rat tumours
Authors: Howe F. A. , Stubbs M. , Rodrigues L. M. , Griffiths J. R.
Published: March 2007

UA hepatomas, GH3 prolactinomas and N‐methyl‐N‐nitrosourea‐induced mammary tumours, which were subcutaneously grown in rats, have been studied by 31P MRS using non‐localized pulse‐acquire, image selected in vivo spectroscopy (ISIS) and one‐dimensional chemical shift imaging (1‐D CSI) techniques. Comparisons have been made with measurements from acid extracts of these tumour types and surrounding tissues (i.e., muscle and skin). Since muscle containing high concentrations of phosphocreatine (PCr) is often found adjacent to the tumour, we have compared the ratio of the PCr to γ‐NTP peaks in the spectra with the same ratio calculated from the acid extract data, and have used deviations between the two sets of data to assess the discrimination of the MRS localization technique to signals from the tissue surrounding the tumour. Extract data showed an average NTP content of 1.25 μmol/g wet wt for all three tumour types. PCr (at 0.42 μmol/g wet wt), was significant only in the GH3 prolactinoma whereas it was negligible in the other tumour types (<0.1 μmol/g wet wt). There was good agreement between the ISIS PCr/γ‐NTP ratio and the extract data for all tumours. However, the 1‐D CSI data showed an unexpectedly large contamination of the tumour spectrum with PCr signals from the skin which was shown by subsequent phantom experiments to be due to the curved geometry of tumour and skin rather than Fourier bleed. In pH measurements by MRS it was found that biological variability was greater than the effects of artefacts (due to either the chemical shift artefact in the ISIS technique or partial volume effects) in the localization technique. An average pH of 7.2 was observed for all tumours. By initially comparing data from different localization schemes with that from chemical extracts potential sources of error have been highlighted and show that phantom studies alone are not sufficient to fully assess the accuracy of localized MRS data.
1H NMR spectroscopy of colon tumors and normal mucosal biopsies; elevated taurine levels and reduced polyethyleneglycol absorption in tumors may have diagnostic significance
Authors: Moreno Angel , Rey Mercé , Montane Josep M. , Alonso Juli , Arús Carles
Published: March 2007

Twenty‐three pairs of normal mucosa and colonic adenocarcinoma biopsy specimens have been examined in this pilot study by 1H NMR spectroscopy at 9.4 T to determine whether it was possible to find spectral malignancy markers. The 3.2 ppm (trimethylamine‐containing compounds)/0.9 ppm (methyl of fatty acids) resonance intensity ratio in water suppressed spectra, proposed by other authors as a malignancy marker, results in our hands, using resonance areas, in partial overlap between tumor and mucosa values, which reduces its diagnostic value. Furthermore, we have found that submucosa contamination could mask the normal mucosa pattern and artifactually decrease the 3.2/0.9 ppm, ratio value by increasing the 0.9 ppm resonance due to the known triglyceride content of normal submucosa. On the other hand, we have observed in the Hahn spin‐echo spectra of intact biopsies resonances arising from taurine and exogenous polyethyleneglycol (PEG). Their assignment and quantification has been carried out in perchloric acid extracts of the tissue biopsies. The taurine (3.4 ppm)/creatine (3.0 ppm) area ratio produced an excellent discrimination between normal mucosa and tumour groups while the PEG (3.7 ppm)/creatine (3.0 ppm) area ratio presented a large overlap, although it was clearly higher in the mucosae than in the tumors for paired samples. These two NMR observable parameters are in our hands highly discriminating and are accordingly proposed as malignancy markers in tissue biopsies although their possible utility for in vivo studies remains to be demonstrated.
Effect of acute and chronic hyponatremia on blood‐brain barrier function in the rat
Authors: Adler Sheldon , Williams Donald , Verbalis Joseph G.
Published: March 2007

To study whether acute or chronic hyponatremia alters blood‐brain barrier (BBB) permeability, rats made hyponatremic by constant desmopressin acetate infusion were studied by NMR spectroscopy and imaging. On constant volume ventilation and nitrous oxide, acute (1‐ and 2‐day) and chronic (7‐ and 14‐day) hyponatremic and normonatremic controls were infused with 0.25 M HCI. Despite reducing blood pH by at least 0.35 in <50min, brain pH, measured by 31P NMR, was unaffected in any group. As a second test of BBB function, gadolinium‐DTPA (Gd‐DTPA) was injected intravenously in these five groups. Coronal slice 1H NMR images obtained before and after Gd‐DTPA showed image intensity changes in multiple areas outside brain, but neither control nor hyponatremic rats showed any differences in cortex, white matter or cerebellum. To ascertain whether the threshold for BBB disruption was altered, hypertonic mannitol (1.5, 2.0 or 3.0 mL) was injected rapidly into one internal carotid artery and pre‐ and post‐Gd‐DTPA images obtained. In both control and hyponatremic rats only the largest dose caused detectable Gd‐DTPA leakage into brain. Thus, BBB function appears intact in both acute and chronic hyponatremia since neither H+ nor GD‐DTPA penetrated the barrier and resistance to mannitol disruption was unaffected by hyponatremia.
Non‐linear regression and variance ratio analysis of time based NMR data
Authors: Endre Zoltan H. , Duggleby Ronald G.
Published: March 2007

Biomedical NMR experiments rely frequently on data obtained sequentially over time. A method is presented for analysis of time based NMR data, which allows modelling of continuous and discontinuous functions to observed intensity changes by non‐linear regression and which uses variance ratio analysis to compare these models statistically. The method eliminates many of the usual problems in the parametric analysis of experimental values obtained at discrete time points and of comparison of the coefficients of model functions which require unsubstantiated assumptions about the distribution of parameters and ignore internal correlations which may exist between such parameters. The variance ratio method is illustrated for multiple time courses obtained with 23Na NMR of perfused rat kidney undergoing hypoxic perturbation in the presence of different treatments.
Simultaneous 31P NMR spectroscopy and laser doppler flowmetry of rat brain during global ischemia and reperfusion
Authors: Kloiber O. , Miyazawa T. , Hoehn‐Berlage M. , Hossmann K.‐A.
Published: March 2007

The relationship between blood flow and metabolism was studied in halothane‐anaesthetized, normothermic rats submitted to 30 min global ischemia by four‐vessel occlusion. Phosphocreatine (PCr), ATP, intracellular pH and intracellular magnesium (pMg) were measured by 31P NMR spectroscopy, and blood flow by laser Doppler flowmetry. Prior to ischemia the PCr/ATP ratio of fully relaxed spectra was 2.4±0.3, intracellular pH was 7.26±0.15 and pMg was 3.26±0.13. Vascular occlusion led to complete cessation of blood flow in four out of eight rats, and to incomplete ischaemia (< 10% of control) in the other four animals. During vascular occlusion EEG flattened and energy metabolism broke down in all but one animal with a residual blood flow of 8% of control. pH declined to 6.70±0.08. The speed of electrophysiological and metabolic recovery after 30 min ischemia varied considerably from animal to animal. Variability depended mainly on the recirculation delay (i.e., the interval from vascular release to normalization of blood flow) but was independent of residual blood flow during ischemia, pre‐ischemic glucose, ischemic or post‐ischemic acidosis, or the degree of post‐ischemic hypoperfusion. After 3 h recirculation PCr and intracellular pH returned to normal but pMg was slightly increased, and ATP was reduced by up to 50% in all animals except the rat with incomplete breakdown of energy metabolism during ischemia. The dissociation between PCr and ATP is attributed to a loss of total adenylate, the severity of which depends on the quality of post‐ischemic recirculation. The data refute the hypothesis that the quality of post‐ischemic metabolic recovery depends mainly on the severity of tissue acidosis but stress the importance of post‐ischemic haemodynamic factors for the speed and quality of brain resuscitation.
An in vivo31P MRS study of patients with liver cirrhosis: Progress towards a non‐invasive assessment of disease severity
Authors: Munakata T. , Griffiths R. D. , Martin P. A. , Jenkins S. A. , Shields R. , Edwards R. H. T.
Published: March 2007

Fourteen patients with liver cirrhosis of differing severity participated in a one‐dimensional chemical shift imaging 31P MRS study of the liver. Patients were divided into two groups according to the severity of their liver disease using Child's classification and the aminopyrine breath test (AB test). Seven normal volunteers without liver disease acted as controls. The phosphomonester (PME) peak in normal subjects was 4.77% (95% confidence interval, CI: 4.11–5.42) of total phosphorus. The PME peak was significantly elevated in both mild cirrhosis [5.80% (95% CI: 5.46–6.14), p=0.0051, vs normal subjects] and severe cirrhosis [9.64% (95% CI: 8.71–10.57), p=0.0002, vs normal subjects and p=0.001, vs mild cirrhosis]. There was a significant negative linear correlation (r=0.88, p<0.01) of PME with the percentage dose of 14CO2 excreted over 2 h in the AB test. pH values in patients with mild cirrhosis [7.45 (95% CI: 7.35–7.55)] but not severe cirrhosis [7.36 (95% CI: 7.25–7.47)] were significantly elevated (p=0.04) compared to normal subjects [7.29 (95% CI: 7.17–7.41)]. Comparison of the peak area of PME at TR = 0.5 s against that using TR = 5.0 s in cirrhotic liver suggested no reduction in T1 of phosphorus metabolites in cirrhosis. A relationship between the severity of liver cirrhosis and a relative increase in PME was demonstrated and this was not due to a reduction of T1. This study highlights the clinical potential of 31P MRS as a non‐invasive means of assessing the severity of liver cirrhosis.
Proton‐decoupled 31P chemical shift imaging of the human brain in normal volunteers
Authors: Murphy‐Boesch Joseph , Stoyanova Radka , Srinivasan Ravi , Willard Tamela , Vigneron Daniel , Nelson Sarah , Taylor June S. , Brown Truman R.
Published: March 2007

Proton‐decoupled, 31P three‐dimensional (3‐D) chemical shift imaging (CSI) spectra have been acquired from the entire human brain using a new dual tuned resonator. The resonator operates in quadrature mode to provide improved sensitivity, excellent B1 homogeneity, and reduced power deposition at both frequencies. Proton‐decoupled and fully NOE enhanced, 31P spectra were acquired from normal volunteers using Waltz‐4 proton decoupling with continuous wave bi‐level excitation applied through a second radio frequency channel. Well resolved peaks in the phosphomonoester (PME) and phosphodiester regions were obtained from non‐localized FIDs and spectra localized with 3‐D CSI without processing for resolution enhancement. pH measurements made over large regions of the brain using the Pi resonance show no significant variations (6.9±0.02) for a single individual. The improved spectral resolution and sensitivity of the PME resonances results in more well defined metabolite images of the PME peak region.
Esophageal cancer phospholipid characterization by 31P NMR
Authors: Merchant Thomas E. , de Graaf Peter W. , Minsky Bruce D. , Obertop Huug , Glonek Thomas
Published: March 2007

Phospholipid extracts of surgical tissue specimens from 18 patients, consisting of normal esophagus, distal esophageal tumor and normal stomach, were analyzed using 31P NMR. The prominent phospholipids detected in these tissues included cardiolipin (CL), phosphatidylethanolamine plasmalogen, phosphatidylethanolamine (PE), phosphatidylserine (PS), sphingomyelin (SPH), phosphatidylinositol (PI), phosphatidylcholine plasmalogen and phosphatidylcholine (PC). Very small quantities of the phospholipids lysophosphatidylcholine, phosphatidic acid, phosphatidylglycerol, and an uncharacterized phospholipid at −0.13 δ also were detected in some of the 54 tissue specimens analyzed. The mean relative concentrations of these phospholipids, in mole percentages of total detected phosphorus, were determined from the acquired spectra and used to differentiate among the three tissue groups. The relative concentrations of the following phospholipids differed significantly (p<0.001) among the respective tissue groups: normal esophagus vs esophageal tumor, PS, SPH, PI, PC; normal esophagus vs normal stomach, CL, PE, PS, SPH; esophageal tumor vs normal stomach, CL, PE. Membrane phospholipids implicated in modulating the growth and metastases of tumors of epithelial origin can be profiled to discriminate among normal esophagus, distal esophageal tumor and normal stomach using 31P NMR.
A selective inversion recovery method for the improvement of 23Na NMR spectral resolution in isolated perfused rat hearts
Authors: Simor Tamás , Kim Sung K. , Chu Wen‐Jang , Pohost Gerald M. , Elgavish Gabriel A.
Published: March 2007

Shift‐reagent‐aided 23Na NMR spectroscopy allows differentiation of the intracellular (Nai) and extracellular sodium (Na0) signals. The goal of the present study has been to develop a 23Na NMR spectroscopic method to minimize the intensity of the shift‐reagent‐shifted Na0 signal and thus increase Nai resolution. This is achieved by a selective inversion recovery (SIR) method which enhances the resolution between the Nai and Na0 peaks in shift‐reagent‐aided 23Na NMR spectroscopy. The application of SIR with Dy(TTHA), Tm(DOTP), or with low concentrations of Dy(PPP)2 results in both good spectral resolution and physiologically acceptable contractile function in the isolated, perfused rat heart model.
The effect of oestrogen ablation on the phospholipid metabolite content of primary and transplanted rat mammary tumours
Authors: Smith T. A. D. , Baluch S. , Titley J. C. , Ormerod M. G. , Eccles S. , Tombs A. J. , Leach M. O. , Griffiths J. R. , McCready V. R.
Published: March 2007

The concentration of phospholipid metabolites was determined in chemical extracts from two types of rat mammary tumours and compared with proliferation data (S‐phase fraction). One of the tumours was an oestrogen‐sensitive transplanted tumour. In this tumour the concentration of phosphocholine (PC) and glycerophosphorylcholine (GPC) correlated strongly with the S‐phase fraction but not with the number of cells actively synthesizing DNA. Oestrogen ablation resulted in tumour regression. Regressing tumours contained less PC and more GPC than those actively growing. The other tumour was induced in rats by intravenous administration of N‐methyl N‐nitrosourea. Phosphoethanolamine (PE), PC and GPC levels were not associated with the S‐phase fraction in this tumour. Oestrogen ablation resulted in tumour regression. There was no significant difference between the regressing and growing tumours in PE, PC or GPC content.