摘要:

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‐hum

ISSN:0952-3480    

DOI:10.1002/nbm.1940080202

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractElectrophysiological recording duringin vivoNMR imaging for correlation of electrophysiological events with changes in NMR parameters has, until now, not been satisfactory. Here we present a method that uses specially prepared calomel electrodes for the continuous monitoring of both cortical steady potential and EEG duringin vivoNMR imaging studies of experimental animal models. In order to demonstrate the reliability of this approach we elicited single episodes of cortical spreading depression in rats by intracortical potassium acetate injection, using an intracerebral micropipette. During the passage of DC potential shifts and associated reduction in EEG amplitude, hyperintense regions, reflecting the progression of cortical spreading depression over the cortex, were visible in diffusion‐weighted images of the rat brains. No susceptibility artifacts due to the electrodes and micropipette were visible in the NMR data. Thus, we have demonstrated under controlled experimental conditions, that electrophysiological recording with calomel electrodes can be performedsimultaneouslywith diffusion‐weighted NMR imaging. The described method enables further NMR investigations of phenomena which are detectable by electrophysiol

ISSN:0952-3480    

DOI:10.1002/nbm.1940080203

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

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 whether31P 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 similar31P NMR resonance ratios. BEX‐t and WIX‐t tumours showed significantly different31P NMR resonance ratios but similar fractions of cells in S‐phase. The31P 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 the31P 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 of31P NMR spectra recordedin vivoare probably of limited value in assessment of rate of cell proliferation in tumours and hence also in prediction of tumour treatment resi

ISSN:0952-3480    

DOI:10.1002/nbm.1940080204

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractMeasurements of the intracellular diffusion coefficients (Di) of ATP and creatine phosphate (PCr) in stable, isolated preparations of skeletal muscle were made by means of pulsed field gradient (PFG)31P NMR. Experiments used a PFG NMR probe specifically designed for small, superfused biological samples. This provided a magnetic field gradient in the z axis of up to 195 G/cm with minimal eddy currents. DiATPand DiPCrin white (fast, glycolytic) skeletal muscle from goldfish(Carassius auratus)were determined to be 2.48±0.33 and 3.49±0.33 × 10−6cm2/s, respectively, at 25°C and a diffusion time of approximately 19ms. For comparison with Divalues, diffusion coefficients of ATP and PCr also were measured in solutions of ionic composition similar to that of fish muscle cytosol. Thein vitrodiffusion coefficients of ATP and PCr were 3.54±0.11 and 5.28±0.08 × 10−6cm2/s, respectivel

ISSN:0952-3480    

DOI:10.1002/nbm.1940080205

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThis study tests the hypothesis that brief periods of ischemia result in an increase in myocardial lipids during early reperfusion. We conducted1H NMR spectroscopy to serially measure myocardial lipids before and after regional ischemia. Localized1H NMR spectra (spatial resolution of 1.25mm) were obtained using a one‐dimensional chemical shift imaging technique. Two regions, the subendocardium and the subepicardium, were estimated by summing spectral areas from three slices (3.75 mm). Two groups of dogs that underwent a 45 min ischemia and 4 h reperfusion were studied: a group in which the myocardium beneath the surface coil underwent ischemia and reperfusion; and a group in which the ischemic event was distant from the tissue under the surface coil. Microsphere measurements showed significant blood flow reductions in the subepicardium and subendocardium in the ischemic zones during coronary occlusion. Flow returned to baseline values during reperfusion. In the ischemic zone group, the subendocardium, the triglyceride resonance areas decreased by 24% (p<0.05) during reperfusion. However, subepicardial triglyceride areas were unchanged. Subendocardial creatine areas were also unchanged. The non‐ischemic zone group subendocardial triglycerides decreased by 33% (p<0.05) following ischemia and reperfusion in the remote region. In contrast to the ischemic group, the subepicardial triglyceride resonance areas decreased by 42% (p<0.05). Subendocardial creatine areas were unchanged. These data show that triglycerides of the ischemic‐reperfused subendocardium do not increase during 4 h of reperfusion. Furthermore, they show that the triglycerides resonance areas of the non‐ischemic region decrease following remote ischemia and reperfusion. Decreases in the non‐ischemic region's triglycerides may reflect enhanced substrate demand resulting from increased work in that portion of

ISSN:0952-3480    

DOI:10.1002/nbm.1940080206

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractAbsolute metabolite concentrations have been estimated for nucleoside triphosphate and Pifromin vivo31P MR measurements using ISIS localization in a rat tumour model, and the results have been compared to those obtained from acid extracts of the tumours. The aim of the experiment was to assess the performance of four different spectral analysis techniques used for absolute quantitation. The spectral analysis techniques used were two frequency domain methods (peak area integration and Lorentzian fitting–FITSPEC) and two time domain methods (VARPRO and HLSVD). The spectra were acquired in blocks so that the degradation in performance of the four spectral analysis methods with decreasing signal‐to‐noise ratio (SNR) could be compared and referenced. This and the inclusion of a sophisticated method incorporating prior knowledge yields a more realistic and comprehensive protocol than previously published comparisons. The results suggest that VARPRO is the method of choice for quantitative analysis of tumour31P MR spectra, giving the most reliable results at lo

ISSN:0952-3480    

DOI:10.1002/nbm.1940080207

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940080208

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940080201

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY