bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of intracellular pH in neuronal and glial tumour cells, studied by multinuclear NMR spectroscopy
Authors: Flögel Ulrich , Willker Wieland , Leibfritz Dieter 
Published: March 2007

AbstractThe effect of extracellular pH (pHe) on intracellular pH (pHi) and cellular metabolism was examined by multinuclear NMR spectroscopy of cells in vivo and in vitro. A decrease in pHe from 7.4 to 6.4 led to a significant drop in pHi, in both neuronal and glial tumour cells, as detected by in vivo 31P NMR of cells embedded in basement membrane gel threads. A more than 50% decrease in both the phosphocreatine (PCr) level and derivatives of glycolysis (i.e., glycerol 3‐phosphate) was observed, concomitantly to the fall in pHi. A 50% decrease in intracellular lactate levels was seen in in vivo 1H NMR spectra under these conditions. Reperfusion with fresh medium (pHe 7.4) resulted in the full recovery of pHi, simultaneously with an increase in both PCr and intracellular lactate back to their control levels. Perchloric acid and lipid extract measurements confirmed the observations made by in vivo 31P and 1H NMR spectroscopy and further showed a decrease both in tricarboxylic acid cycle activity and phospholipid synthesis. The data revealed no significant differences between the neuronal and glial tumour cells investigated. pHi measurements in the presence of inhibitors of the various pH regulatory mechanisms showed that the Na+/H+ exchanger, the carbonic anhydrase and at least one of the bicarbonate‐transport systems are involved in pH regulation of both cell types. The results suggest that Na+/H+ exchange is the preferred mechanism by which both neuronal and glial cells regulate their pHi after extracellular acidification.
Mobile lipids and metabolic heterogeneity of brain tumours as detectable by Ex Vivo1H MR spectroscopy
Authors: Kuesel Annette C. , Donnelly S. Maureen , Halliday William , Sutherland Garnette R. , Smith Ian C. P. 
Published: March 2007

AbstractTo examine metabolic heterogeneity in primary brain tumour, multiple biopsies (one to five per tumour) from four benign meningiomas, five acoustic schwannomas, eleven glial tumours and five medulloblastomas were each subdivided into one to five samples (total = 194) and investigated using ex vivo 360 MHz 1H MR spectroscopy with histopathological correlation. Low amounts of mobile lipids were detected in meningothelial meningiomas and medulloblastomas, high amounts in some or all samples of all other tumours. The differences in non‐lipid metabolites between different tumour types were less marked, with the exception of the medulloblastomas, which had high amounts of N‐acetyl aspartate and cholines. The amount of mobile lipid correlated with Antoni type B areas in schwannomas and necrosis in a high grade giant cell tumour. The amount of lipid varied significantly from sample to sample in a grade 2 astrocytoma and grade 4 astrocytoma samples with 0–5% necrosis but did not correlate with the site in the tumour or histopathological characteristics. The metabolic heterogeneity occurred on a spatial scale at least as small as the size of the MR samples, i.e., ≤60 mg. These results suggest that the detection of metabolic heterogeneity and mobile lipids may have importance for the design of clinical studies.
1H NMR spectroscopic characterization of perchloric acid extracts from breast carcinomas and non‐involved breast tissue
Authors: Gribbestad Ingrid S. , Petersen Steffen B. , Fjøsne Hans E. , Kvinnsland Stener , Krane Jostein 
Published: March 2007

AbstractHigh‐resolution 1H NMR spectra were obtained from perchloric acid extracts of breast tumor specimens and adjacent non‐involved tissue. Two‐dimensional shift‐correlated and homonuclear J‐resolved spectroscopy were used to identify coupled resonances in the spectra. Chemical shifts, multiplicities and spin‐spin coupling constants of several non‐resolved resonances in the one‐dimensional spectra could be determined by the two‐dimensional methods. Several differences in the metabolite content of the two types of extracts were established. The spectra of extracts from non‐involved tissue were dominated by signals from glucose and other carbohydrates, while most of the tumors had very low or no detectable levels of glucose. High concentrations of lactate, taurine and succinate, an increase of the phosphocholine level, and a very low phosphocreatine level were characteristic findings in the 1H spectra of tumor extracts. The variation in the level of myo‐inositol follows the variation in glucose for the two types of tissue. Scyllo‐inositol was for the first time observed in the NMR spectra from breast tissue. Uridine 5′‐diphospho‐N‐acetylglucosamine and uridine 5′‐diphospho‐N‐acetylgalactosamine have been identified and there is an increased level of these two hexoses in the tumor tissue. These results provide insight into breast tumor metabolism, by simultaneously detecting a large number of metabolites and demonstrate the potential for using 1H NMR spectroscopy for studying different metabolic pathways in breast tumors. At the same time they provide useful information for interpretation of in vivo 1H NMR spectra of breast tumors.
Comparison of calibration strategies for the in vivo determination of absolute metabolite concentrations in the human brain by 31P MRS
Authors: Buchli Reto , Martin Ernst , Boesiger Peter 
Published: March 2007

AbstractCerebral concentrations of phosphorus metabolites can be assessed non‐invasively by 31P MRS provided the metabolite signals are calibrated with the signal of a standard of known concentration. The reliability of the concentration estimates depends mainly on the strategy of calibration. Three strategies were compared by assessing the concentrations both in a test dummy and in the brain of volunteers. The first strategy utilized tissue water as an internal heteronuclear concentration standard. The second and third strategies used a phosphorus solution as an external homonuclear standard; this solution was either put into a reference bottle placed on top of the head or into a simulation phantom measured instead of the head. Localization was always achieved with the ISIS pulse sequence. The two external homonuclear strategies achieved a higher accuracy (mean error ≈5%) and reproducibility (mean SD ≈8%) of the concentration estimates than the internal heteronuclear strategy (mean error ≈11%; mean SD ≈15%).
Decrease in brain choline‐containing compounds following a short period of global ischemia in gerbils as detected by 1H NMR spectroscopy in vivo
Authors: Kuhmonen Johanna , Sivenius Juhani , Riekkinen Paavo J. , Kauppinen Risto A. 
Published: March 2007

AbstractCerebral metabolism was studied in the postischaemic gerbil brain using surface coil 31P and 1H NMR spectroscopy. The ratio of choline‐containing compounds (Cho) to total creatine (Cr) in the brain decreased from 0.46 ± 0.02 to 0.32 ± 0.02 by the fifth day following exposure to 5 min of global ischaemia and it remained at this low level for at least 19 days. The amounts of cerebral Cho as quantified by 1H NMR in vivo were 1.70 ± 0.15 and 1.09 ± 0.22 mmol/kg in control and postischaemic animals, respectively. The T2 of Cho was longer in the postischaemic cerebral cortex than in the control one. N‐acetyl aspartate (NAA) as determined by 1H NMR in vivo did not differ in the two animal groups. High‐resolution 1H NMR of acid‐extracted brain cortices showed a decrease in total Cho (glycerophosphocholine, phosphocholine and choline) by 31%, but no changes in NAA, total creatine, taurine and myo‐inositol, in the brain cortex seven days postischaemia relative to control animals. The decrease in acid extractable Cho was mainly due to the drop in glycerophosphocholine concentration. 31P NMR indicated normal energy state and phosphomonoester/phosphocreatine (PCr) and phosphodiester/PCr ratios in the in vivo brain 7 days postischaemia. Silver impregnation did not reveal neuronal degeneration but immunohistochemical staining showed a number of glial fibrillary acidic protein expressing astrocytes as indicators of reactive gliosis in the postischaemic cerebral cortex. These data show, for the first time, that a 1H NMR decrease in Cho metabolites takes place as a consequence of brief ischaemic episode even in the absence of obvious neuronal degeneration.
1H‐2H exchange in the perfused rat liver metabolizing [3‐13C]alanine and 2H2O as detected by multinuclear NMR spectroscopy
Authors: Moldes Milagros , Cerdán Sebastian , Erhard Peter , Seelig Joachim 
Published: March 2007

AbstractThe exchange of individual protons of hepatic metabolites against the solvent deuterons has been investigated in perfused rat liver. Livers from starved rats were perfused for 20 min with a 10 mM solution of unlabeled or 3‐13C‐labeled L‐alanine in Krebs Ringer bicarbonate buffer, with or without 50% deuterium oxide (2H2O). High resolution 13C NMR analysis of deuterium‐induced isotopic shifts and of 2H‐13C couplings revealed a differential 1H‐2H exchange depending on the chemical nature of the metabolite and on the site of 13C labeling. [3‐13C]Aspartate isotopomers showed similar 2H/1H ratios in the C3 and in the C2 carbons while [2‐13C]aspartate isotopomers had much smaller 2H/1H ratios in the C2 than in the C3 carbons. Similarly, [2‐13C]glutamate isotopomers had 2H/1H ratios significantly smaller in the C2 than in the C3 carbon. These results suggest that the hydration‐dehydration reactions of the citric acid cycle, which result in exchange at the C3 carbons of aspartate and glutamate, approach equilibrium with the perfusate faster than the aminotransferases of aspartate and alanine, which induce exchange at the C2 carbons of these amino acids. Taken together, the results obtained are consistent with a heterogeneous solvent exchange environment in the perfused liver.
Comparative NMR study of a differentiated rat hepatoma and its dedifferentiated subclone cultured as spheroids and as implanted tumors
Authors: Ronen S. M. , Volk A. , Mispelter J. 
Published: March 2007

AbstractH4IIEC3 (H4), a differentiated rat hepatoma line and H5, its dedifferentiated subclone, were investigated as proliferating spheroids and as implanted subcutaneous tumors in juvenile rats. H4 cells formed tight, round spheroids whereas H5 cells formed loose, grape‐like structures. 31P MR spectra showed that phosphocreatine was present in H5 spheroids but not in H4 spheroids or tumors. [13C]Lactate production from [13C]glucose, with no detectable uptake of [13C]alanine, indicated that energy production in H5 spheroids was primarily via glycolysis. No [13C]glucose utilization was detected in H4 spheroids, but uptake of alanine and accumulation of labeled lactate, glutamate and glutamine indicated oxidation via the tricarboxylic acid (TCA) cycle. Tumors of H4 cells were well perfused, unlike tumors of H5 cells which were highly necrotic. Following i.v. infusion with [13C]alanine, [13C]lactate and glutamate, evidence of oxidation via the TCA cycle, were observed in H4 tumors. Thus the results obtained by 31P and 13C MRS correlated with the differentiation state of H4 and H5 spheroids and tumors.
Healthy and infarcted brain tissues studied at short diffusion times: The origins of apparent restriction and the reduction in apparent diffusion coefficient
Authors: Norris David G. , Niendorf Thoralf , Leibfritz Dieter 
Published: March 2007

AbstractThe significance of NMR water diffusion measurements performed at short diffusion times (<10 ms) for brain tissue is examined. An apparent restriction to diffusion for both healthy and cytotoxically edematous tissue is shown: cytotoxic edema lengthens the diffusion time at which this phenomenon is visible. The dramatic reduction in apparent diffusion coefficient (ADC) observed in the core of cytotoxic edema is explained in terms of the enclosure of extracellular water in non‐contiguous pockets in conjunction with the shift of water from the extra‐to the intracellular space. The model presented provides an explanation for the ADC reduction without recourse to changes in the cell membrane permeability to water, or unrealistic values for the extra‐ and intracellular diffusion coefficients.
Dysfunctional activation of subcortical nuclei in palatal myoclonus detected by high‐resolution MRI
Authors: Boecker H. , Kleinschmidt A. , Weindl A. , Conrad B. , Hänicke W. , Frahm J. 
Published: March 2007

AbstractMagnetic resonance images that were sensitized to changes in cerebral blood oxygenation state demonstrated dysfunctional activation of the dentate nuclei, the left inferior olivary nucleus and the left red nucleus in a 56‐year‐old patient with palatal myoclonus. These findings represent the first demonstration of movement‐related activation of cerebellar, brainstem and midbrain nuclei in a single subject and at a spatial resolution comparable to that of anatomic MR images.
19F NMR magnetization transfer between 5‐FBAPTA and its complexes. An alternative means for measuring free Ca2+ concentration, and detection of complexes with protein in erythrocytes
Authors: Gilboa Haggai , Chapman Bogdan E. , Kuchel Philip W. 
Published: March 2007

AbstractThe 19F NMR Ca2+‐indicator molecule 5,5'‐difluoro‐1,2‐bis(o‐aminophenoxy)ethane‐N,N,N′,N′‐tetraacetic acid (5‐FBAPTA) was used in a procedure that enhances its range of applications to measuring free Ca2+ concentrations in buffer solutions and human erythrocytes. Even if the signal from the Ca‐5‐FBAPTA complex was not visible, the concentration of the complex could be calculated from saturation transfer spectra. This was demonstrated with well characterized buffer solutions in vitro and shown to also apply to concentrated haemolysates. The analysis required a precise estimate of the dissociation rate constant of the complex; this was found to be 295/s at 37°C and the corresponding association rate constant was 4.1×108 L/mol/s. These values differ from those obtained previously in different buffer conditions and by two different NMR methods. A series of spectra were acquired from haemolysates containing 5‐FBAPTA, in which saturating irradiation was applied at a frequency that was progressively off‐set from the carrier frequency. Saturation transfer to the free 5‐FBAPTA was seen from irradiation at frequencies different from that of Ca‐5‐FBAPTA, thus suggesting the presence of complexes with proteins.
Localized T2 measurements using an OSIRIS–CPMG method. Application to measurements of blood oxygenation and transverse relaxation free of diffusion effect
Authors: Girard F. , Poulet P. , Namer I. J. , Steibel J. , Chambron J. 
Published: March 2007

AbstractThis work presents a new method allowing localized T2 measurements, based upon the OSIRIS scheme. A train of 180° pulses is applied after the OSIRIS preparation cycle, recording directly the transverse magnetization decay. The method was verified for two nuclei, 1H and 19F, with phantoms and in vivo on rats. The accuracy of the T2 values is discussed, as well as possible applications of the OSIRIS‐CPMG method to proton transverse spin relaxation measurements, free of diffusion effects, and to non‐invasive in vivo blood oxygenation measurements, through the use of an emulsion of perfluorooctylbromide, a blood substitute containing fluorine.
Investigation of the 1H NMR visibility of lactate in different rat and human brain cells
Authors: Kotitschke Klaus , Schnackerz Klaus D. , Dringen Ralf , Bogdahn Ulrich , Haase Axel , von Kienlin Markus 
Published: March 2007

AbstractIn recent years, 1H MRS has been used in a number of studies to measure the lactate content of brain, and it is generally assumed that the methyl resonance at 1.3 ppm reflects the total amount of lactate present in the tissue. However, reduced NMR visibility of lactate has recently been reported for blood, heart and skeletal muscle as well as for bacteria. We have assessed the NMR visibility of lactate in cultures of human and rat brain cells, comparing the concentrations measured by NMR and by biochemical methods. Contributions of fatty acids have been eliminated using their different relaxation behavior. We found approximately 30% of the lactate to be undetectable by NMR in the studied cell cultures. While the mechanism partially masking lactate in 1H spectra is not yet understood, the potential invisibility of some pools of lactate to NMR may greatly affect the interpretation of brain spectra.
Transmural distribution of 2‐deoxyglucose uptake in normal and post‐ischemic canine myocardium
Authors: Yoshiyama Minoru , Bache Robert J. , Merkle Hellmut , Garwood Michael , Ugurbil Kamil , Zhang Jianyi , Arthur H. L. 
Published: March 2007

AbstractThis investigation was performed to determine (i) whether 31P spatially localized 31P NMR spectroscopy could be utilized to determine the transmural distribution of 2‐deoxyglucose (2DG) uptake in the in vivo canine heart and (ii) whether transmural 2DG uptake would be affected by a preceding ischemic insult. 2DG was infused and the accumulation of 2‐deoxyglucose‐6‐phosphate (2DGP) was monitored (by means of spatially localized 31P NMR) in control hearts, in pharmacologically hyperperfused hearts, and in hearts subjected to four (5 min) occlusions of the left anterior descending coronary artery. Myocardial blood flow was measured with radioactive microspheres. In control hearts, subendocardial (ENDO) 2DGP contents were significantly higher than those in the subepicardium (EPI) being 3.8±0.3 and 2.2±0.2 m̈mol/g, respectively; the ENDO/EPI ratio of 2DGP was 1.70±0.21. During hyperperfusion blood flow increased approximately four‐fold but 2DGP accumulation was not altered. ATP levels in post‐ischemic myocardium were significantly decreased (ENDO more than EPI) and 2DGP accumulation in each layer was increased (p<0.01 vs control); however, the ENDO/EPI ratio of 2DGP was not altered. 2DG infusion induced a marked elevation of blood insulin and norepinephrine levels. These data demonstrate that in the presence of high blood levels of 2DG and insulin: (i) 2DGP accumulation can be measured in the in vivo canine heart; (ii) in normal hearts 2DG uptake is more pronounced in the inner layers of the left ventricular wall (this transmural 2DG uptake gradient is not due to subendocardial hypoperfusion); and (iii) 2DG uptake is greater in the post‐ischemic heart but the ENDO/EPI gradient of 2DG uptake is not altered indicating that the more severe ischemic insult in the subendocardium does not result in a disproportionate increase in 2DG uptake in that region of the myocardium. Although 2DG uptake patterns in this model most probably reflect those of glucose (at comparable glucose and insulin levels), quantitative extrapolations with regard to the rate of glucose uptake are not possible from the present data.
Experimental allergic encephalomyelitis in non‐human primates: mri and mrs may predict the type of brain damage
Authors: Richards T. L. , Petersen K. , Heide A. C. , Cluff J. , Alvord E. C. , Rose L. M. , Peterson J. , Cosgrove S. , Petersen R. 
Published: March 2007

AbstractVolume‐localized proton spectroscopy and T2‐weighted MRI were performed on 23 monkeys with experimental allergic encephalomyelitis (EAE). The purpose of this study was to determine the relationships between temporal changes in lesion activity (measured on T2‐weighted MRI), MRS [N‐acetyl aspartate (NAA), creatine (CR), choline (CHO)], and the histologic definition of disease determined post‐mortem. Animals were scanned in the same areas of the brain once a week before and after sensitization to myelin basic protein (BP). Histologic lesion types were predicted by a combination of preceding MRI and MRS measurements. Acutely fatal EAE lesions were large and monophasic as visualized by MRI, and increased CHO (p<0.02, n=16) and CHO/CR ratio (p<0.001, n = 16) were detected by MRS at disease onset. Chronic EAE lesions were preceded by multiple inflammatory attacks as visualized by MRI and consistently low levels of NAA (p<0.02, n = 13) and NAA/CR (p<0.01, n = 13) which occurred after the initial attack. MRI negative brain regions (from animals that were sensitized to BP) were associated with low CHO/CR (p<0.1, n = 5). The temporal correlation of MRI lesion activity and absolute MRS proton metabolites shows promise for predicting the subsequent duration and histologic type of lesions in EAE in non‐human primates.
31P nmr spectroscopy studies of phopholipid metabolism in human melanoma xenograft lines differing in rate of tumour cell proliferation
Authors: Lyng Heidi , Olsen Dag R. , Rofstad Einar K. , Petersen Steffen B. 
Published: March 2007

AbstractThe concentration of phospholipid metabolites in tumours has been hypothesized to be related to rate of cell membrane turnover and may reflect rate of cell proliferation. The purpose of the study reported here was to investigate whether 31P NMR resonance ratios involving the phosphomonoester (PME) or phosphodiester (PDE) resonance are correlated to fraction of cells in S‐phase or volume‐doubling time in experimental tumours. Four human melanoma xenograft lines (BEX‐t, HUX‐t, SAX‐t, WIX‐t) were included in the study. The tumours were grown subcutaneously in male BALB/c‐nu/nu mice. 31P NMR spectroscopy was performed at a magnetic field strength of 4.7 T. Fraction of cells in S‐phase was measured by flow cytometry. Tumour volume‐doubling time was determined by Gompertzian analysis of volumetric growth data. BEX‐t and SAX‐t tumours differed in fraction of cells in S‐phase and volume‐doubling time, but showed similar 31P NMR resonance ratios. BEX‐t and WIX‐t tumours showed significantly different 31P NMR resonance ratios but similar fractions of cells in S‐phase. The 31P NMR resonance ratios were significantly different for small and large HUX‐t tumours even though fraction of cells in S‐phase and volume‐doubling time did not differ with tumour volume. None of the 31P NMR resonance ratios showed significant increase with increasing fraction of cells in S‐phase or significant decrease with increasing tumour volume‐doubling time across the four xenograft lines. Consequently, the PME and PDE resonances of 31P NMR spectra recorded in vivo are probably of limited value in assessment of rate of cell proliferation in tumours and hence also in prediction of tumour treatment resistance caused by rapid cell proliferation.
Chemotherapy‐associated changes in 31P MRS spectra of sera from patients with multiple myeloma
Authors: Kuliszkiewicz‐Janus M. , Baczynski S. 
Published: March 2007

Abstract31P NMR spectra were obtained from sera of 22 healthy volunteers and 20 patients with multiple myeloma at the time of diagnosis and repeated up to five times during therapy. All spectra consisted of a Pi peak (used as a reference peak) and two peaks from phospholipids (PL): one peak due to phosphatidylethanolamine and sphingomyelin (PE + SM) and a second peak due to phosphatidylcholine (PC). Prior to therapy, peak intensities of the phospholipids were low relative to Pi. During therapy leading to remission, the resonance from PL progressively increased to approximate the spectral pattern seen in normal sera. By contrast, in non‐responders an opposite trend was noted: the intensities of the phospholipid peaks became progressively reduced or remained unchanged. Long‐term follow‐up studies showed a good correlation between this 31P MRS evaluation of sera and the response of the disease to the therapy. In addition to the correlation with tumor response, our studies also show significant correlations between area, intensities of peaks of PE + SM, PC, and the concentrations of high‐density lipoprotein (HDL) (correlation coefficients 0.46, 0.43, 0.59, respectively; p<0.001). We found that the concentration of HDL in serum of patients with multiple myeloma was significantly reduced. In individuals responding to therapy HDL levels increased to the point where there were no statistically significant differences between them and healthy volunteers. In patients not responding to therapy, HDL concentration did not increase. In summary, analysis of plasma lipids by MRS offers a convenient method for establishing a blood lipid profile in patients with haematological malignant disease and offers yet another modality for assessing patient response to therapy in multiple myeloma.