摘要:

AbstractMRS offers unique possibilities for non‐invasive studies of biochemistry in the human brainin vivo. A growing body of evidence suggests that proton MRS may contribute to the clinical evaluation of a number of pathologies including ischaemia, tumours, epilepsy, metabolic and neuropaediatric disorders. In most cases results are expressed as ratios between metabolite signals obtained at certain experimental conditions. Presenting the results as metabolite signal ratios may lead to misinterpretation because such alterations can be due to changes in the content of either one of the metabolites or both, or may simply be due to changes in relaxation behaviour. Absolute quantitation of metabolite concentrations is therefore warranted. A number of studies using single volume proton MRS indicate that absolute quantitation of metabolite concentration is possible with respect toN‐acetyl aspartate (NAA), total creatine, choline containing compounds, (Cho) and inositols (Ins). Internal standards (unsaturated water signal) as well as external standards have been used for signal calibration. Quality control with respect to signal linearity with concentration or with size of selected volume, selection efficiency, outer volume depression and signal contamination is essential for validation of the measurements. Furthermore, corrections for the influence of relaxation behaviour are necessary. The results published so far indicate that the concentrations of NAA, total creatine, Cho and Ins in mmoles (kg wet weight)−1range between 8.2 and 17.2, (mean 10.2), 5.9 and 11.6 (mean 7.2), 1.1 and 2.0 (mean 1.5) and 3.9 and 8.1 (mean 6.1), respectively. So far only a limited number of clinical studies has been published including studies of acute stroke, multiple sclerosis and Alzheimer's disease. The results are promising and encourage further exploitation of the utility of quantitative proton MRS in clinical pra

ISSN:0952-3480    

DOI:10.1002/nbm.1940080402

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of cyclophosphamide on the metabolic profile of a mammary carcinoma implanted on the foot of mouse was studied by31P NMR spectroscopy bothin vivoand in perchloric acid extracts. The ratio nucleotide triphosphate: Piwas significantly elevated in cyclophosphamide treated tumours relative to untreated tumours after 96 hin vivo(p<0.05). Phosphocreatine: Piwas similarly elevated from 48 to 168 h (p<0.01). Resolution of the phosphomonoester peak into two distinct resonances allowed us to estimate the ratio of PME′ to phosphocholine (PC), where PME′ is a composite peak consisting, in part, of phosphoethanolamine (PE). PME′:PC was found to be significantly higher in treated animals relative to control animalsin vivo(p<0.01 from 48 to 168h). Perchloric acid extract spectra suggest that the increase in PME′:PC was in part due to a decrease in PC concentration and also due to an increase in a previously unidentified resonance which was coresonant with PE. Extract data show that there was a significant increase in the concentration of the phosphodiesters, glycerophosphocholine (p<0.01) and glycerophosphoethanolamine (p<0.05) in treated relative to control tumours. The changes in the phosphomonoester resonances are qualitatively similar to previously described changes following radiation and suggest that they may be a marker of cell kill or lack of cell growth after antineoplastic

ISSN:0952-3480    

DOI:10.1002/nbm.1940080403

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this study the conjugated macromolecular ligand, diethylenetriaminepentaacetic acid (DTPA)‐amide‐dextran, was synthesized by attaching DTPA to the dextran macromolecule (Mr∼6000) by a covalent amide bond. Subsequently, DTPA‐amide‐dextran was complexed with either of the two lanthanide metal ions dysprosium (Dy) or gadolinium (Gd). The paramagnetic23Na NMR shift induced by Dy(DTPA‐amide‐dextran) and the relaxivity (ρi) induced by Gd(DTPA‐amide‐dextran) were characterized. Dy(DTPA‐amide‐dextran) induced a 25% larger23Na NMR shift than that induced by Dy(DTPA). Neither the shift induced by Dy(DTPA‐amide‐dextran) nor the shift induced by Dy(DTPA) was affected by increasing levels of calcium ions in the solution. Gd(DTPA‐amide‐dextran) exhibited anin vitroρiof 8.4 (mM s)−1at a 0.23 T magnetic field and 9.3 (mM s)−1at a 0.47 T magnetic field, thus indicating a

ISSN:0952-3480    

DOI:10.1002/nbm.1940080404

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractDisturbances of energy metabolism in rat brain after frontal lobectomy and post‐traumatic effects of monosialic ganglioside GM1on brain energy metabolism were studied by31P NMRin vivo. Frontal lobectomy caused the statistically significant reversible decrease of ATP and increase of ADP during the compensatory period. In a presence of GM, these post‐operational effects were not observed. The mean value of normalized correlation coefficients between NMR‐measured phosphomonoesters, Pi, pH, phosphocreatine, γ‐ATP +β‐ADP, α‐ATP+α‐ADP + NAD/NADH + diphosphodiesters and β‐ATP for a given group of animals (Z‐index) was used to estimate brain energetic status. It has been shown that the variation of the Z‐index correlates with the dynamics of locomotor activity during the compensatory period. The Z‐index increased by more than 100% for the subgroup with an increased moving activity and only by about 20% for the subgroup with a decreased activity. Moreover, the compositions of these subgroups were almost the same as those from the solution of the reverse task, i.e., the studied group was divided into two subgroups by the Z‐index. The Z‐index is proposed as a possible criterion of pathology

ISSN:0952-3480    

DOI:10.1002/nbm.1940080405

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSequential31P and1H MRS was used to measure cerebral phosphate metabolites, intracellular pH, and lactate in normoglycemic and hypoglycemic rats during 30 min of complete cerebral ischemia and 5.5 h of reperfusion. These results were correlated with brain levels of free fatty acids (FFAs), excitatory amino acids, cations, and water content at death. The lactate/N‐acetyl aspartate ratio was not significantly different between groups before or during occlusion. During reperfusion, the ratio was higher in normoglycemic rats from 3 to 85 min (p≤0.05), and recovery time was faster in hypoglycemic rats (29 vs 45 min; p = 0.04), suggesting reduced lactate production and faster recovery of aerobic metabolism. During occlusion, significant but comparable decrease of intracellular pH occurred in each group. Intracellular pH was higher in hypoglycemic rats at 140 min and 260 min of reperfusion. Water content, Na and K+concentrations, and FFA and excitatory amino acid levels were not significantly different between groups, but hypoglycemic rats had less depletion of levels of Mg2+(p=0.011). These results show that hypoglycemia has a limited but potentially beneficial effect on postischemic lactic acido

ISSN:0952-3480    

DOI:10.1002/nbm.1940080406

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940080407

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940080408

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940080409

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940080410

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940080401

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY