bluuebunny/crossref_metadata_2025 huggingface dataset:
The production, buffering and efflux of protons in human skeletal muscle during exercise and recovery
Authors: Kemp G. J. , Taylor D. J. , Styles P. , Radda G. K.
Published: March 2007

We show how quantitative information about proton handling in human skeletal muscle in exercise and recovery can be obtained by 31P MRS and illustrate this with data from metabolic disorders. Proton production, proton efflux and passive buffering can be distinguished by comparing changes in [phosphocreatine] and pH at the end of exercise and by calculating ATP turnover during ischaemic exercise and in the ‘natural experiment’ of myophosphorylase deficiency (McArdle's disease). We calculate the effective buffer capacity to be 20–30 mmol/L/pH unit (slykes), somewhat lower than published measurements made in vitro but similar to other values obtained in vivo. This analysis is applied to data from normal muscle and a variety of disease states to estimate proton efflux during recovery and ATP production during exercise: (i) proton efflux during recovery is pH‐dependent, reaching a 10 mmol/L/min at pH 6.2, and is increased in some cases of mitochondrial myopathy and in hypertension; (ii) glycogenolytic ATP production during exercise can reach 25 mmol/L/min in normal muscle and correlates approximately with [Pi] at the start of aerobic exercise and throughout ischaemic exercise; (iii) oxidative ATP production can reach 20–25 mmol/L/min and (as during recovery) correlates approximately with [Pi].
Absolute quantification and NMR visibility of glycogen in the isolated, perfused rat heart using 13C NMR spectroscopy
Authors: Garlick Pamela B. , Pritchard Ronald D.
Published: March 2007

NMR spectroscopy, possibly, does not detect 100% of large molecules such as glycogen (mol. wt = 107–109). Using both NMR and chemical quantification methods, we have, therefore, determined the NMR visibility of cardiac glycogen (defined as the ratio of the NMR value to the chemical value, expressed as a percentage) in the isolated, perfused heart. Rats (n = 7) were pretreated for 60 min with 0.2mg/kg isoproterenol (s.c.) to deplete their endogenous myocardial glycogen stores (mainly 12C). The hearts were then aerobically perfused (65 cm H2O, at 37 °C) in a double‐walled chamber (the annulus contained a standard), for 70 min with Krebs buffer plus 3.5 mM [13C]1‐glucose and 5 mM sodium acetate (natural abundance). From 70 to 175 min the sole substrate was natural abundance acetate (5 mM). 13C NMR spectra for glycogen quantification were acquired in two different ways; by applying 896, 90° pulses at 0.33 s intervals with 1H decoupling (‘fast’, practical spectra) and by applying 896, 90° pulses at 5 s intervals (‘slow’, impractical spectra). Hearts were then removed from the magnet, freeze‐clamped ( −196 °C) and analysed chemically. Cardiac glycogen, quantified from the ‘fast’ spectra (using conversion factors) and the ‘slow’ spectra was 16.8 ± 1.1 and 16.1 ± 1.8 (mean ± SEM) μmol glucosyl units/heart, respectively. After correction of the chemical value for the residual [12C]glycogen (determined from 1H NMR spectra of the extracted glycogen after hydrolysis), the NMR‐visibilities were calculated to be 101 ± 6 and 109 ± 7%, for the ‘fast’ and ‘slow’ spectra, respectively. We conclude that, despite its size, cardiac glycogen is 100% visible in NMR spectra of isolated rat hearts.
Quantitation of proton NMR spectra of the human brain using tissue water as an internal concentration reference
Authors: Barker Peter B. , Soher Brian J. , Blackband Stephen J. , Chatham John C. , Mathews Vincent P. , Bryan R. Nick
Published: March 2007

The use of cerebral water as an internal intensity standard for the quantitation of spatially localized proton spectra of the human brain is investigated. The method is validated on standard samples of N‐acetyl aspartate (NAA) and lactate, and possible sources of error are discussed. Using the STEAM pulse sequence, concentrations of choline, creatine and NAA in frontal lobe white matter are found to be 1.9±0.5, 10.6±1.3 and 16.6±2.3 μmol/g wet wt, respectively, in 10 normal volunteers. In the thalamus, the concentrations are 2.0±0.4, 11.6±2.0 and 17.2±1.3 μmol/g wet wt, respectively. Choline and creatine concentrations are in good agreement with conventional biochemical values: NAA concentrations are found to be three‐fold higher, suggesting overlap of the NAA signal with other compounds. Quantitation relative to tissue water is a convenient and rapid means of quantitating proton spectra of the human brain.
Design and application of NMR‐compatible bioreactor circuits for extended perfusion of high‐density mammalian cell cultures
Authors: Gillies R. J. , Galons J.‐P. , McGovern K. A. , Scherer P. G. , Lien Y.‐H. , Job C. , Ratcliff R. , Chapa F. , Cerdan S. , Dale B. E.
Published: March 2007

MR spectroscopy of cultured cells allows non‐invasive analyses of the metabolism of cells with specific phenotypes under defined conditions. This technique can be used to investigate the intracellular metabolism of cells or extended to critically evaluate phenomena observed by in vivo MRS. In this paper, a cell maintenance system is described which allows MR analyses with unparalleled spectral resolution, S/N and stability. This system consists of a 25 mm diameter hollow fiber bioreactor and a supporting circuit. The hollow fiber reactor was chosen because it yields a large filling factor which can be perfused through defined volumes. The fibers were 300 μm diameter microporous (0.2 μm) cellulose acetate/cellulose nitrate membranes with high porosity, which allow bulk convective flow throughout the extracapillary space. This flow (Starling flow) is necessary to disrupt steady‐state gradients in substrates and waste products. In many respects, the design of the supporting circuit is more important than the bioreactor itself, since it provides the reactor with the proper chemical and physical environment. Hence, this circuit can be applied to a variety of bioreactor configurations. The circuit consists of a hollow fiber oxygenator and a bleed‐and‐feed system housed in a temperature‐controlled cabinet. Culture of mammalian cells in this reactor yields 31P spectra which have excellent spectral and temporal resolution. At confluence, endogenous 31P line widths were typically <10 Hz (at 162 MHz) and well resolved spectra were obtained in <30 s.
Identification of scyllo‐inositol in proton NMR spectra of human brain in vivo
Authors: Michaelis Thomas , Helms Gunther , Merboldt Klaus‐Dietmar , Hänicke Wolfgang , Bruhn Harald , Frahm Jens
Published: March 2007

Scyllo‐inositol has been identified in proton NMR spectra of mammalian brain in vitro and in vivo. In contrast to myo‐inositol this isomer comprises six equivalent CH protons that yield a singlet resonance at a chemical shift of 3.35 ppm. 1‐D and 2‐D J‐resolved proton NMR studies (7.0 T) of perchloric acid extracts of brain tissues revealed different amounts of scyllo‐inositol in man, sheep, cow and rat. Absolute quantification of localized short‐echo time proton NMR spectra (2.0 T) of human brain in vivo resulted in scyllo‐inositol concentrations of 0.35±0.06 mM for white matter (n = 25), 0.43±0.11 mM for grey matter (n = 23) and 0.57±0.14 mM for cerebellum (n = 10). Evidence for a tight metabolic link to myo‐inositol was supported by a simultaneous variation of myo‐ and scyllo‐inositol in patients with various brain diseases.
Bulk magnetic susceptibility induced broadening in the 19F NMR of suspended leukemic cells
Authors: Adebodun Foluso , Post Jan F. M.
Published: March 2007

The relevance of bulk magnetic susceptibility (BMS) induced broadening to in vivo NMR studies of intact cells has been examined and the significance of the contribution of BMS difference to the resolution of intra‐ and extracellular resonances was demonstrated. BMS difference between intra‐ and extracellular compartments was found to limit the resolution of intra‐ and extracellular 19F resonances of fluoro compounds in leukemic cells.
Transmembrane 19F NMR chemical shift difference of fluorinated solutes in liposomes, erythrocytes and erythrocyte ghosts
Authors: Xu Arron S. L. , Waldeck A. Reginald , Kuchel Philip W.
Published: March 2007

In erythrocytes suspended in isotonic medium, a number of fluorinated anions showed well resolved 19F NMR resonances from the solute populations in the intra‐ and extracellular compartments; the intracellular resonances were shifted to higher frequency (low field). In addition 19F NMR resonances of extracellular solutes were shifted to higher frequency when bovine serum albumin was incorporated into the extracellular medium. The dependence of 19F NMR chemical shift on protein concentration was also demonstrated using resealed red cell ghosts and liposomes; in the presence of external hemoglobin, lysozyme and bovine serum albumin, the shift of the external resonances was to higher frequency. In addition, significant high frequency shifts of 19F NMR resonances were evident along with an increase of temperature. The results of the present study further support the contention that the principal physical basis for the shifts is the disruption of direct hydrogen bonds between 19F of the solutes and (primarily) solvent H2O by protein hydration. The ‘split peak’ phenomenon is of general importance in biological systems where a transmembrane protein‐concentration difference exists.
Biological applications for small solenoids: NMR spectroscopy of microliter volumes at high fields
Authors: Wiseman Robert W. , Moerland Timothy S. , Kushmerick Martin J.
Published: March 2007

In this paper we describe features of an NMR probe designed for the study of small, superfused muscles. We also present the results of an empirical study of the performance characteristics of several configurations of small solenoid coils, ca 2 mm diameter. Our data show that optimal use of the available volume of sample becomes the prime consideration in coil design at this scale. In contrast to large biological samples, for such small coils the equivalent resistance associated with the sample is minor relative to the resistance of the RF coil itself. Thus, substantial improvements in the S/N ratio can be obtained by adopting coil configurations that are inferior electrically, but which can sample a greater volume of tissue.
Effects of fish oil on phospholipid metabolism in human and rat liver studied by 31P NMR spectroscopy in vivo and in vitro
Authors: Dagnelie Pieter C. , Bell Jimmy D. , Cox I. Jane , Menon David K. , Sargentoni Janet , Coutts Glyn A. , Williams Steve C. R.
Published: March 2007

The effect of ω3 fatty acids on the metabolism of the normal liver was studied using 31P NMR spectroscopy. Human subjects were examined before and after 1, 3 and 7 days of supplementation with 50 mL fish oil per day (12 g ω3 fatty acids). 31P NMR spectra (1.6 T) revealed a significant increase in phosphodiester (PDE) to ATP ratios after 1 and 3 days of fish oil. After 7 days, [PDE]/[ATP] ratios at a TR of 1 s had returned to baseline levels, but [PDE]/[ATP] at a TR of 5 s appeared to remain high. Rats were fed diets containing 50% of the energy from fish oil or normal rat chow (controls) for 14 days. 31P NMR liver spectra in vivo (4.7 T) confirmed increased [PDE]/[ATP] in rats fed fish oil compared to controls, although the difference was only statistically significant at a TR of 1.5 s but not at a TR of 8s. 31P NMR spectra of rat liver extracts (8.7 T) suggested that increased concentrations of glycerophosphocoline and possibly glycerophosphoethanolamine were responsible for rising PDE levels in vivo. Phosphocholine (PC) concentrations were markedly reduced in rat liver after fish oil. The combined rise in glycerophosphocholine and reduction in PC would be consistent with a shift from the phospholipase C to the phospholipase A1/A2 pathway of phosphatidylcholine breakdown after fish oil consumption.
NMR spectroscopy of human post mortem cerebrospinal fluid: Distinction of Alzheimer's disease from control using pattern recognition and statistics
Authors: Ghauri Farida Y. K. , Nicholson Jeremy K. , Sweatman Brian C. , Wood John , Beddell Christopher R. , Lindon John C. , Cairns Nigel J.
Published: March 2007

1H NMR spectra have been measured at 500 and 600 MHz on 23 human cerebrospinal fluid samples obtained at autopsy from Alzheimer's disease patients and controls. The spectra at 500 MHz were quantified using 42 descriptors based on NMR peak heights and it was shown that differences between the two classes were apparent in the δ2.4–2.9 region. Remeasured at 600 MHz a detailed examination of this chemical shift range identified citrate, aspartate, N‐acetyl aspartate, methionine and glutamate in this region of the spectra. Principal components analysis showed that a separation of the two classes was possible and detailed statistics indicated that citrate level was the principal marker. Patient age and the interval between death and autopsy (parameters not closely matched between the two groups) were examined statistically to establish whether these might account for the citrate differences. Although they could possibly account for them to some extent, the relationship between citrate levels and disease state remained significant at p<0.05. The data invite a test of the importance of citrate levels in Alzheimer's disease using samples taken ex vivo.
Controllable graded cerebral ischaemia in the gerbil: Studies of cerebral blood flow and energy metabolism by hydrogen clearance and 31P NMR spectroscopy
Authors: Allen K. L. , Busza A. L. , Proctor E. , King M. D. , Williams S. R. , Crockard H. A. , Gadian D. G.
Published: March 2007

A technique for remotely controlling the degree of carotid artery occlusion in the gerbil model of cerebral ischaemia has been developed. The technique relies on manually adjustable nylon snares around the carotid arteries, in conjunction with a computer‐based monitoring system, to control the degree of occlusion. This has allowed us to determine the dependence of energy metabolism (as assessed by 31P NMR spectroscopy) on blood flow in greater detail than was possible in our previous studies. Data obtained show that energy changes first appear at flows of 25–30 mL/100 g/min, while at flows below 20 mL/100 g/min there is a major derangement of energy metabolism. The model was used to determine the sensitivity of cerebral energy metabolism to reduced cerebral blood flow under normothermic conditions and in mild hypothermia (30°C). Hypothermia had a protective effect in that energy metabolites were maintained at flows significantly below the normothermic threshold.
Experimental allergic encephalomyelitis raises betaine levels in the spinal cord of strain 13 guinea‐pigs
Authors: Preece N. E. , Baker D. , Butter C. , Gadian D. G. , Urenjak J.
Published: March 2007

Chronic relapsing experimental allergic encephalomyelitis, an animal model of multiple sclerosis, was induced in Strain 13 guinea‐pigs by subcutaneous injection of spinal cord homogenate and Freund's incomplete adjuvant supplemented with Mycobacterium tuberculosis. High resolution 1H NMR spectra of CNS tissue extracts indicated that the levels of choline metabolites, particularly betaine, were elevated in the spinal cord tissue, the principal site of lesion formation in this guinea‐pig strain. The spectra also show that N‐acetylated compounds are slightly depleted in the disease. The results are discussed in relation to the biochemical interpretation of NMR spectra obtained in vivo from patients with multiple sclerosis.
A comparative study of 1H NMR lineshape fitting analyses and biochemical lipid analyses of the lipoprotein fractions VLDL, LDL and HDL, and total human blood plasm
Authors: Ala‐Korpela M. , Hiltunen Y. , Jokisaari J. , Eskelinen S. , Kiviniitty K. , Savolainen M. J. , Kesäniemi Y. A.
Published: March 2007

The purpose of this work was two‐fold. In the first instance, 1H NMR spectra of the ultracentrifuged lipoprotein fractions (VLDL, LDL and HDL) from six volunteers with different clinical conditions were measured. The methylene regions of the experimental spectra were modelled in the frequency domain using non‐linear lineshape fitting analyses. In this way the resolvable Lorentzian component structures of the methylene regions of these lipoprotein fraction spectra could be determined. Second, the lipoprotein fraction analyses were used to construct simplified component structures, which interpreted the lipoprotein fraction spectra well, and were feasible to use in the total plasma spectra analyses. The considerable overlap problem of the resonances was properly handled in this way. The NMR‐based relative amounts of the lipoproteins (relative integrated intensities of the lipoprotein model signals) obtained were compared to the biochemically resolved relative molar percentages of the lipoprotein fractions and also of the lipid contents between the lipoprotein complexes. It was noticed that nearly all correlations were extremely good. Thus, it is suggested that the developed methodology could be used as a fast method to predict the relative amounts of the lipoproteins and also possibly the relative lipid contents between the major lipoprotein categories directly from the proton NMR spectrum of a total blood plasma sample. Furthermore, if internal or external reference for the integrated intensities of the proton NMR resonances were used, it should also be possible to obtain the absolute amounts of these quantities.
Pattern recognition of 31P magnetic resonance spectroscopy tumour spectra obtained in vivo
Authors: Howells S. L. , Maxwell R. J. , Howe F. A. , Peet A. C. , Stubbs M. , Rodrigues L. M. , Robinson S. P. , Baluch S. , Griffiths J. R.
Published: March 2007

Pattern recognition has been applied to the analysis of in vivo 31P NMR spectra. Using four different classes of tumour and three types of normal tissue, cluster analysis and artificial neural networks were successful in separating and classifying the majority of samples analysed. Although the phosphomonoester and Pi, regions appeared to be the most important spectral features, data representing the entire 31P spectrum were required for best separation of the tumour and tissue classes.
Quantitative analysis of 1H NMR detected proteins in the rat cerebral cortex in vivo and in vitro
Authors: Kauppinen Risto A. , Niskanen Timo , Hakumäki Juhana , Williams Stephen R.
Published: March 2007

Spectral editing experiments were used to quantify CH3 groups from macromolecular species in the chemical shift region from 1.2 to 1.4 ppm of rat cerebrum in vivo. Two peaks centred at 1.22 and 1.40 ppm were revealed when irradiation was positioned at 4.35 or 4.30 ppm. These peaks had lower saturation factors (1 vs. 1.72±0.10) than N‐acetyl aspartate (NAA) and shorter T2 [60±5.8 (1.22 ppm) and 51±2.2 (1.40 ppm) vs. 123±12 (NAA) ms]. The concentrations of the peaks at 1.22 and 1.40 ppm were calculated to be 0.65±0.09 and 1.37±0.18 mmol of CH3, equivalents/kg brain. Acid extract from cerebral corticies contained macromolecular peaks at the same chemical shifts with approximately the same area ratios to NAA as in vivo. These data show that the macromolecular peaks in the brain at TE>100 ms arise predominantly from proteins which are acid soluble. The assignment of macromolecular signals in the cerebral spectrum to a given polypeptide (thymosin β4 and histone H1) is discussed in the light of protein analyses of brain acid extracts.
in vivo assessment of mitochondrial functionality in human gastrocnemius muscle by 31P MRS. The role of pH in the evaluation of phosphocreatine and inorganic phosphate recoveries from exercise
Authors: Iotti S. , Lodi R. , Frassineti C. , Zaniol P. , Barbiroli B.
Published: March 2007

In this study we compared the kinetics of phosphocreatine (PCr) and Pi recovery, and their dependency on cytosolic pH in 38 normal individuals. Spectra were acquired during rest, work and recovery. A time resolution of 10 s was used to obtain detailed information. The kinetics of PCr and Pi recovery almost overlapped when the lowest value of cytosolic pH reached during recovery (termed the minimum pH) was <6.95, while they were completely dissociated when the minimum pH was >6.95. This result is interpreted as indirect in vivo evidence of the kinetic control exerted by ADP on mitochondrial oxidation. Our results represent a rationale for new experimental conditions to be used in clinical routine studies of pathologies due to primary or secondary mitochondrial malfunction.
The influence of medium formulation on phosphomonoester and UDP‐Hexose levels in cultured human colon tumor cells as observed by 31P NMR spectroscopy
Authors: Shedd Suzanne F. , Lutz Norbert W. , Hull William E.
Published: March 2007

High‐resolution 31P NMR spectroscopy at 11.7 T was used to examine the influence of medium formulation (medium and serum type, and concentrations of glucose and inositol) on the cellular phosphate metabolism of CX‐1 cells, a human colon cancer cell line derived from HT‐29 cells. Striking differences in the 31P spectra of harvested CX‐1 cells were observed. The largest variation was seen in the phosphocholine and UDP‐hexose levels (up to seven‐fold changes), with smaller differences in the levels of other phosphate metabolites. The major UDP‐hexose species were found to be UDP‐N‐acetylglucosamine and UDP‐N‐acetylgalactosamine (ca 2:1 ratio), which have been proposed in the literature to be markers of cell differentiation status. Medium‐induced alterations in metabolite levels were much greater than the normal variations seen in CX‐1 control samples grown under identical conditions. They even exceeded the characteristic differences observed between different human tumor cell lines grown under one set of culture conditions. The remarkable sensitivity of CX‐1 cellular phosphate metabolism to the culture environment has implications for the comparison of in vitro vs in vivo spectra, and for the interpretation of effects due to growth and therapy.
In vivo19F NMR studies of hyperthermia: Hydrophobic environments probed by halothane
Authors: Burt C. T. , Moore R. R. , Roberts M. F.
Published: March 2007

The steady‐state distribution of the general anesthetic halothane in different rat tissues, including a renal adenocarcinoma with and without hyperthermia treatment, has been evaluated by In vivo 19F NMR spectroscopy. The 19F spectra of halothane (which is a hydrophobic probe) from within tissue show differences in the partitioning between normal rat tissues and adenocarcinoma. Muscle, as a control tissue, exhibits a single large resonance around 0 ppm. However, the adenocarcinoma exhibits two slow‐exchanging resonances separated by 0.3 ppm with the one at the more hydrophobic chemical shift being more sensitive to hyperthermia treatment. The results from this tumor model suggest that 19F NMR spectroscopy may be useful first in detecting a change in hydrophobic environments using a lipophilic probe such as halothane, and secondly in monitoring the effects of hyperthermia, a treatment whose effectiveness may involve changes at the level of the plasma membrane. Under conditions of continuous delivery, a resonance which is not detected in the spectra of halothane in excised tissue appears 5 ppm downfield from the resonance for halothane localized in tissues. A rotating frame experiment is used to show that this resonance is derived from anesthetic absorbed on the tissue surface.
Growth and Magnetic Resonance Characteristics of Human Squamous Cell Carcinoma Xenografts Implanted with Cells Suspended in MatrigelTM
Authors: Czerski L. , Majors A. , Ng T. C. , Vijayakumar S. , Weichselbaum R.
Published: March 2007

Growth and magnetic resonance characteristics of a human squamous cell carcinoma SQ20B were studied in vivo as xenografts in nu/nu nude mice. Tumor cells injected subcutaneously in the flank using either MatrigelTM (MTG, an extract of basement membrane proteins) or growth medium (GM) as a vehicle were compared. Much higher tumor growth rates and cell density were observed with MatrigelTM than with GM implantation. Histology also showed that MTG implanted cells grew as vascularized solid tumors compared to GM tumors which formed cysts. As a result of increased cell density with the improved method, tumors as small as 0.3 cm3 provide high S/N magnetic resonance spectra which yield smaller standard deviations with fewer experiments.
Mapping of cerebral metabolites in rats by 1H magnetic resonance spectroscopic imaging. Distribution of metabolites in normal brain and postmortem changes
Authors: Higuchi Toshihiro , Fernandez Erik J. , Maudsley Andrew A. , Weiner Michael W.
Published: March 2007

The goal of this study was to examine metabolic differences between cortex and basal ganglia in normal rat brain and to determine postmortem changes using in vivo 1H magnetic resonance spectroscopic imaging at 300 MHz. The resonances observed were: choline, creatine+phosphocreatine, N‐acetyl aspartate (NAA), lactate (Lac), and three small resonances in the amino acid region which included resonances from aspartate + NAA (Asp), glutamine + NAA (Gln), and glutamate+GABA (Glu). A previously unassigned resonance was observed at 1.13 ppm in brain of rats anesthetized with pentobarbital. Spectroscopic images in normal brain demonstrated increased NAA and Gln and decreased Glu in cortex compared to basal ganglia. The major postmortem changes were an increase of Lac, Glu and Cho and a decrease of NAA and Asp. The rise in Lac was significantly higher in cortex than in basal ganglia.
Phospholipid metabolites, prognosis and proliferation in human breast carcinoma
Authors: Smith T. A. D. , Bush C. , Jameson C. , Titley J. C. , Leach M. O. , Wilman D. E. V. , McCready V. R.
Published: March 2007

The content of the phospholipid metabolites, phosphocholine, phosphoethanolamine, glycerophosphorylcholine and glycerophosphorylethanolamine was measured in chemical extracts from 46 human breast carcinoma using 31P NMR spectroscopy. Some patients had received therapy prior to tumour resection. The data were therefore stratified into two groups: (i) all tumours; and (ii) untreated tumours. Three indices of tumour proliferation i.e., mitotic index, Ki67 and S‐phase fraction were determined on tissue from the same tumours and were found not to correlate with the content of any of these metabolites. In addition oestrogen‐receptor status and density, tumour grade and DNA ploidy were obtained on some tumours. The phosphocholine content was higher in high grade tumours when compared with low grade tumours. There was no apparent relationship between DNA ploidy and the content of any of these metabolites. Glycerophosphorylcholine content of oestrogen‐receptor positive tumours correlated with receptor density. However, there was no significant difference between receptor positive and negative tumours in the content of any of the phospholipid metabolites measured.
Application of high field localised in vivo1H MRS to study biochemical changes in the thiamin deficient rat brain under glucose load
Authors: Rose S. E. , Nixon P. F. , Zelaya F. O. , Wholohan B. T. , Zimitat C. , Moxon L. N. , Crozier S. , Brereton I. M. , Doddrell D. M.
Published: March 2007

In vivo, volume‐selected 1H NMR spectroscopy employing the SPACE technique was used to monitor biochemical changes in the thiamin deficient rat brain in response to glucose loading. The concentrations of brain N‐acetylaspartate, glutamate/glutamine/γ‐aminobutyric acid, lactate and glucose differed significantly from those of control animals. The results are consistent with a metabolic block at the reaction catalyzed by the thiamin dependent enzyme α‐keto glutarate dehydrogenase soon after the onset of neurological symptoms of thiamin deficiency, and a further block at pyruvate dehydrogenase arising late in the course of thiamin deficiency.
In vivo31P MRS of experimental tumours
Authors: de Certaines J. D. , Larsen V. A. , Podo F. , Carpinelli G. , Briot O. , Henriksen O.
Published: March 2007

More than 50% of cancers fail to respond to any individual treatment and tumour follow‐up after treatment plays a major role in routine therapy planning and pharmacological research. Today, MRS is the only technological approach providing non‐invasive access to tumour biochemistry. Ten years ago, expectations were raised concerning 31P MRS as an exciting and promising technical approach to the study of tumours. However the expectations have not always come to fruition. How close are we now to seeing routine 31P NMR in clinical oncology? This review of the 127 published papers shows spectroscopy results in more than 150 experimental animal tumour models. These tumour/host/treatment systems provide us with a useful basis to evaluate the current state of the art, summarize the basic knowledge presently available, determine the key points underlying the present disappointment of some clinical oncologists and stimulate new basic research. The information collected concerns the discussion of the reliability of experimental models in oncology, the technical improvement of magnetic resonance technology and the monitoring of bioenergetic status, pH regulation and phospholipid metabolism in treated and untreated tumours. Recent advances (two‐thirds of the papers have been published in the last 5 years) seem to provide more optimistic perspectives than those generally accepted a few years ago, in the depressing period following early pioneering work.
Spin‐echo and gradient‐echo epi of human brain activation using bold contrast: A comparative study at 1.5 T
Authors: Bandettini Peter A. , Wong Eric C. , Jesmanowicz A. , Hinks R. Scott , Hyde James S.
Published: March 2007

In this study, Blood Oxygenation Level Dependent (BOLD) contrast in the detection of human brain activation was compared between spin‐echo and gradient‐echo echo‐planar sequences at 1.5 T. Time course series of spin‐echo and gradient‐echo images containing the primary motor cortex were collected during rest (no finger movement) and activation (finger movement). Each time course series was collected using a different TE. Resting and active state signal intensities at each TE were measured in identical regions in the motor cortex. From these data, resting and active state R2 (1/T2) and R (1/T) values were obtained. Across four subjects, brain activation produced an average R2 change of −0.16±0.02/s (±SE), and an average R change of −0.55±0.08/s. The average ΔR/ΔR2 ratio was 3.52±0.56. The average gradient‐echo/spin‐echo ratio of activation‐induced signal changes at the TE for maximal BOLD contrast for each sequence (TE≈T and T2) was calculated to be 1.87±0.40.
Functional MRI of CO2 induced increase in cerebral perfusion
Authors: Rostrup Egill , Larsson Henrik B. W. , Toft Peter B. , Garde Kim , Thomsen Carsten , Ring Poul , Søndergaard Lars , Henriksen Ole
Published: March 2007

The sensitivity of MR gradient echo imaging towards CO2 induced changes in cerebral blood flow was investigated in 10 normal subjects. The subjects were inhaling 5% and 7% CO2 and the experiments were carried out at 1.5T (n=6) and 2.0 T (n=5), allowing a comparison of field strengths. Additional experiments were carried out using a higher spatial resolution. The largest signal increases were noted in areas corresponding to larger vessels, but significant changes were also conspicuous in deeper cortical and central grey matter. The changes appeared linearly related to the arterial CO2 tension, within the range of PaCO2 studied. In white matter, the changes were not statistically significant.
Comparison of EPI gradient‐echo contrast changes in cat brain caused by respiratory challenges with direct simultaneous evaluation of cerebral oxygenation via a cranial window
Authors: Jezzard Peter , Heineman Frederick , Taylor Joni , Despres Daryl , Wen Han , Balaban Robert S. , Turner Robert
Published: March 2007

A gradient‐echo echo planar imaging (EPI) sequence has been used to generate images of cat brain during respiratory challenges. Direct spectrophotometric measurements have been made simultaneously in order to correlate the changes in oxygen saturation as measured by spectrophotometry with the image intensity changes seen in the gradient‐echo images. When blood volume remains approximately constant, as derived from the spectrophotometry data, good correlation is seen between calculated plots made of changes in the transverse relaxation rate, ΔR, and the oxygen saturation as measured by spectrophotometry for much of the time course of the respiratory challenges of anoxia, apnea and hypercapnia. In some cases, the correlation is poorer during the recovery periods of the apnea and anoxia challenges. Those lower correlations can often be accounted for by changes in blood volume, which also affects the NMR relaxation rate. These results contribute to the understanding of the image intensity changes seen during functional brain imaging studies in humans.
Brain or veinoxygenation or flow? On signal physiology in functional MRI of human brain activation
Authors: Frahm Jens , Merboldt Klaus‐Dietmar , Hänicke Wolfgang , Kleinschmidt Andreas , Boecker Henning
Published: March 2007

Stimulus‐related signal changes in functional MRI of human brain activation not only reflect associated adjustments of cerebral blood flow and oxygen consumption, but strongly depend on the MRI technique chosen and the actual experimental setting. A list of relevant parameters includes static field homogeneity of the magnet, MR pulse sequence and signal type, TE, TR, flip angle, gradient strengths, gradient waveforms, receiver bandwidth and voxel size. In principle, a local signal increase during functional activation may reflect a regional change in cerebral blood flow or deoxyhemoglobin concentration or both. This ambiguity was demonstrated using long TE FLASH MRI at high spatial resolution. Subsequently, experimental strategies were evaluated that either discriminate MRI effects in large vessels from those in the cortical microvasculature or separate changes in blood flow velocity from those in blood oxygenation. Examples comprise studies of the human visual and motor cortex.
Spatial patterns of functional activation of the cerebellum investigated using high field (4 T) MRI
Authors: Ellerman J. M. , Flament D. , Kim S.‐G. , Fu Q.‐G. , Merkle H. , Ebner T. J. , Ugurbil K.
Published: March 2007

Using single and multislice functional MRI at high field strength (4 T) we studied cerebellar activation in 12 subjects making a series of alternating wrist flexion and extension movements against constant inertial loads. Three spatial patterns of activation were observed: (i) parasagittal bands of activity localized primarily in the ipsilateral intermediate and lateral zones of the cerebellar hemispheres, (ii) medio‐lateral bands which in some subjects followed the contour of individual folia and (iii) fragmented regions of activation covering extensive areas of the cerebellum. Bilateral activation of the cerebellum was observed in all subjects with measurable activity. Mean statistically significant activation intensity ranged from 2.34 to 13.54% above baseline.
Inflow versus deoxyhemoglobin effects in bold functional MRI using gradient echoes at 1.5 T
Authors: Duyn Jeff H. , Moonen Chrit T. W. , van Yperen Gert H. , de Boer Ruud W. , Luyten Peter R.
Published: March 2007

Modified gradient‐echo MR techniques were applied to study the effects of inflow on functional brain imaging studies using visual and motor cortex stimulation. The results demonstrate that the large signal changes, seen in previously reported gradient‐echo studies at 1.5–2.0 T, are dominated by direct inflow effects, in particular when using a large flip angle and a thin slice. The findings suggest that inflow‐based functional imaging, along with Blood Oxygenation Level Dependent (BOLD) functional MRI, may play an important role in future research towards the functional organization of the human brain.
Comparison of diffusion‐weighted MRI with changes in cell volume in a rat model of brain injury
Authors: Verheul H. B. , Balazs R. , Berkelbach van der Sprenkel J. W. , Tulleken C. A. F. , Nicolay K. , Tamminga K. S. , van Lookeren Campagne M.
Published: March 2007

The precise mechanisms that underlie acute changes in tissue water diffusion following cerebral ischemia or related insults such as glutamate exposure remain unexplained, but it has been suggested that these may be caused by cell swelling due to water uptake. This study was undertaken to compare the changes observed in diffusion‐weighted MR images with changes in the cellular volume measured by electrical impedance in a model of N‐methyl‐D‐aspartate‐induced brain injury in perinatal rats. The results show that the temporal course of the intensity changes in the diffusion‐weighted images parallelled the progressive shrinkage of the extracellular space measured from the electrical impedance. After administration of the N‐methyl‐D‐aspartate antagonist MK‐801 the signal enhancement in the images was reversed, which paralleled the normalization of the extracellular space observed by the impedance measurements. It was estimated that the extracellular space decreased from 24 to 12% while the apparent diffusion coefficient of water decreased from 0.89×10−9 in normal tissue to 0.42×10−9 m2/s in tissue exposed to N‐methyl‐D‐aspartate. These data indicate that changes in tissue water diffusion are related to changes in cell volume.
pH and temperature effects on kinetics of creatine kinase in aqueous solution and in isovolumic perfused heart. A 31P nuclear magnetization transfer study
Authors: Goudemant J.‐F. , Elst L. Vander , Dupont B. , Van Haverbeke Y. , Muller R. N.
Published: March 2007

Phosphorylated metabolites concentrations and creatine kinase kinetics are measured by 31P NMR in solution and in isovolumic perfused rat hearts submitted to hypo‐ and hyperthermia as well as to acidosis (37°C). In the organ, temperature variation from 40 to 25°C induces an increase of phosphocreatine (PCr) stores, a decrease of Pi and ADP concentrations, but does not affect the ATP pool. Creatine kinase forward flux (Vfor) is gradually reduced when the temperature is lowered both in vitro and in perfused heart. In normothermic and hypothermic conditions, a relationship is found between cardiac performance (rate pressure product, RPP), Vfor and ATP synthesis estimated through the myocardial oxygen consumption rate (MVO2). At 40°C however, the RPP is reduced although both Vfor and MVO2 increase. In vitro experiments show an optimum pH of 7.7 for the forward creatine kinase reaction. In perfused heart submitted to acidosis, a decrease of PCr concentration is observed, whereas ATP and ADP contents remain unchanged. Heart creatine kinase flux increased as in hyperthermia. These high fluxes are attributed to the coupling of the creatine kinase reaction with energy consuming or producing reactions: the increase of energy demand related to non‐contractile processes could explain the high MVO2 and Vfor observed in those conditions.
High‐resolution one‐and two‐dimensional 1H MRS of human brain tumor and normal glial cells
Authors: Kotitschke Klaus , Jung Hans , Nekolla Stephan , Haase Axel , Bauer Albrech , Bogdahn Ulrich
Published: March 2007

Astrocytoma (WHO grade II, III), glioblastoma, malignant melanoma, and normal glial cell cultures, established from biopsies, were investigated by 1H MRS. At a 1H resonance frequency of 500 MHz (11.75 T) a high spectral resolution was achieved in 1D 1H spectra; in conjunction with 2D shift‐correlated (COSY) MRS, resonances of alanine, aspartate, choline, creatine, glutamate, glutamine, hypotaurine, myo‐inositol, phosphocreatine, phosphoryl‐ethanolamine, phosphoryl‐choline, lactate, lysine, N‐acetylaspartate, taurine, threonine and valine could be identified. T1 relaxation times for the most prominent compounds are presented. T1 values of lactate ranged between 450 ms and 850 ms. The intensity of the lactate signal revealed differences between individual spectra, but exhibited no correlation between different tumor specimens or degree of malignancy. It was shown that the lactate signal at 1.3 ppm is covered by peaks arising from threonine and fatty acids. The choline signal level varied among spectra of different tumors, among tumors with similar degree of malignancy, and within the same tumor. Further preliminary differences due to aspartate, inositol and glutamine/glutamate were found in 1D and 2D COSY spectra between normal glial cells as well as different tumors. These results indicate that some differences observed in in vivo spectra may be attributable to secondary macroscopic structural changes (hypoxia, necrosis) and not to tumor inherent characteristics. Further correlation between in vivo and in vitro spectroscopy is therefore required.
Characterization of a phosphonium analog of choline as a probe in 31P NMR studies of phospholipid metabolism
Authors: Szwergold Benjamin S. , Kappler Francis , Moldes Milagros , Shaller Calvin , Brown Truman R.
Published: March 2007

Tumors and transformed cells have been shown by 31P NMR to contain elevated concentrations of two phosphomonoesters, phosphorylcholine and phosphorylethanolamine, involved in phospholipid metabolism. In order to understand the biochemical basis for these phenomena new methods are needed to allow for analysis of the relevant metabolic pathways in intact cells. One such promising tool may be phosphonium‐choline, a 31P NMR‐visible analog of choline in which the trimethyl‐ammonium group of choline has been replaced with a trimethyl‐phosphonium moiety. As shown previously [Sim et al. Biochem. J. 154, 303 (1976)], this compound is non‐toxic and readily metabolized by cultured cells into phospholipids. In this paper we describe in greater detail some of the chemical and NMR spectroscopic properties of this material. Most significantly we show here that the chemical shift of phosphonium‐choline is sensitive to the phosphorylation state of the analog and that the phosphonium nucleus is NMR‐visible even after its incorporation into phospholipid. The unique properties of this analog should make it possible to use high‐field 31P NMR to follow the flux of phosphonium‐choline through the Kennedy pathway in intact perfused cells cultures.
Intracellular acidosis in murine fibrosarcomas coincides with ATP depletion, hypoxia, and high levels of lactate and total Pi
Authors: Vaupel P. , Schaefer C. , Okunieff P.
Published: March 2007

Bioenergetic and metabolic status of murine FSaII tumours were evaluated using 31P MRS, acid extracts (‘global’ techniques) and quantitative bioluminescence (‘microregional’ assay). Data obtained from s.c. tumours of varying sizes (44–600 mm3) have been correlated with the oxygenation status evaluated using O2‐sensitive needle electrodes. β‐NTP/Pi and phosphocreatine (PCr)/Pi ratios derived from 31P MRS were positively correlated to the median tissue pO2 values. pH declined during growth with intracellular acidosis being evident in tumours >350 mm3. Whereas lactic acid formation greatly contributed to this decline in small‐ and medium‐sized tumours, ATP hydrolysis and slowing down of the activities of pumps involved in pHi regulation seem to be major factors responsible for intracellular acidification in bulky tumours. PCr levels decreased at an early growth stage, whilst ATP concentrations dropped in bulky malignancies only, coinciding with a decrease in adenylate energy charge and a substantial rise in the levels of total Pi. MRS observable (mobile) Pi was consistently lower than [Pi] measured in acid extracts. On average, median pO2 values of ca 10 mmHg represent a critical threshold for energy metabolism. At higher median O2 tensions, levels of ATP, phosphomonoester and total Pi were relatively constant. This coincided with intracellular alkalosis or neutrality and stable adenylate ratios. On average, median pO2 values < 10 mmHg coincided with intracellular acidosis, ATP depletion, a drop in energy charge and rising Pi levels.
31P MRS of tumour metabolism in anaesthetized vs conscious mice
Authors: Sansom J. M. , Wood P. J.
Published: March 2007

The injectable anaesthetics Hypnorm/Hypnovel, chloral hydrate and etomidate, were examined for their effects on C3H/He mouse core temperature and on the in vivo 31P MR spectra of KHT and SCCVII/Ha transplantable tumours, compared with conscious mice gently restrained in jigs. Hypnorm/Hypnovel at 0.1 mL/mouse i.p. reduced core temperature by 6°C at 30 min after injection, returning to control levels by 100 min, but did not significantly alter the 31P MR spectra of either KHT or SCCVII/Ha tumours. Chloral hydrate at 300 mg/kg i.p. produced a 5°C fall in mouse core temperature, at 25 min after injection, again returning to control levels by 100 min. This agent increased the Pi/total ratio to 155% of control at 15 min after injection in the KHT tumour, and to 170% of control at 45 min in SCCVII/Ha. Etomidate at 25 mg/kg i.p. reduced mouse core temperature by 7.5°C by 20 min after injection, returning to only 84% of control by 100 min. This agent increased the Pi/total ratio by 260% in the KHT tumour 15 min after injection, without recovery to control values by 100 min. In SCCVII/Ha, a maximum increase in Pi/total of 360% was observed at 15 min after injection, with a return to control levels by 60 min. In addition, etomidate caused convulsions in the mice during the induction phase, and myoclonic jerking within 15 min of anaesthesia.
31P NMR in vivo study of the acute effects of different doses of γ‐radiation on rat brain phosphate metabolism
Authors: Semenova Nataly A. , Yushmanov Victor E. , Konradov Alexander A.
Published: March 2007

Changes in relative levels of brain phosphates and intracellular pH at selected time intervals after total γ‐irradiation of a rat at a single dose of 6.5 or 300 Gy were studied by 31P NMR in vivo. Irradiation yielded only minor changes in the spectra. Irradiation at a dose of 6.5 Gy caused a reversible decrease in Pi and an alkaline pH shift of 0.2 units after day 1, with no change in ATP. The signal, which consisted of α‐ATP, α‐ADP, NAD+/NADH and diphosphodiesters, declined after day 6, possibly due to a fall in NAD+/NADH concentration. Irradiation at a dose of 300 Gy led to an increase in ATP from 10 to 13% of total phosphates after day 1. Homeostasis of brain energy metabolism was characterized by the Z‐index (normalized sample correlation coefficients averaged over the correlation matrix for NMR‐measured phosphomonoesters, Pi, pH, phosphocreatine, γ‐ATP+β‐ADP,α‐ATP+α‐ADP+NAD+/NADH + diphosphodiesters and β‐ATP). The Z value rose from −0.18 ± 0.02 to −0.02 ± 0.02 by day 6 or from −0.19 ± 0.02 to −0.07 ± 0.02 by day 1 after irradiation at a dose of 6.5 or 300 Gy, respectively. This may indicate a pathological state of brain energetics as a system and a decrease in its stability.
13C NMR kinetic studies of the rapid stimulation of glucose metabolism by estrogen in immature rat uterus
Authors: Shinkarenko Leonid , Kaye Alvin M. , Degani Hadassa
Published: March 2007

Glucose metabolism in control and estrogen stimulated rat uteri was investigated using 13C NMR spectroscopy. By employing an NMR adapted perifusion system, and developing protocols and methods based on the application of [1‐13C]glucose labeling, it was possible to measure, with a temporal resolution of 10 min, the kinetics of glucose consumption, lactate production and 13C incorporation into glutamate, alanine and glycogen. In control immature rat uteri, under aerobic conditions, the rates (±SEM) of [1‐13C]glucose consumption and [3‐13C]lactate production were 24±2 and 7.5±0.5mmol/g wet weight/h. The rates of synthesis of [4‐13C]glutamate, [3‐13C]alanine and 13C labeling of glycogen at C1 of its glucose moieties were significantly lower and were in the range 0.3–0.6 mmol/g wet weight/h. Thus, ca 35% of the labeled glucose was accounted for by the glycolytic and other observed pathways. In vitro stimulation of the uteri by estrogen was found to increase significantly, within 1 h, glucose consumption by 80%, lactate production by 150% and glutamate and glycogen synthesis by 150%, in parallel to a rapid hormonal induction of mRNA for the brain type isozyme of creatine kinase.