摘要:

AbstractProton‐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, excellentB1homogeneity, 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 thePiresonance 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

ISSN:0952-3480    

DOI:10.1002/nbm.1940060302

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractA 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 by31P 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 thres

ISSN:0952-3480    

DOI:10.1002/nbm.1940060303

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractPhospholipid extracts of surgical tissue specimens from 18 patients, consisting of normal esophagus, distal esophageal tumor and normal stomach, were analyzed using31P 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 using31P N

ISSN:0952-3480    

DOI:10.1002/nbm.1940060304

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractChronic 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 withMycobacterium tuberculosis. High resolution1H 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 thatN‐acetylated compounds are slightly depleted in the disease. The results are discussed in relation to the biochemical interpretation of NMR spectra obtainedin vivofrom patients with multiple scle

ISSN:0952-3480    

DOI:10.1002/nbm.1940060305

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractShift‐reagent‐aided23Na NMR spectroscopy allows differentiation of the intracellular (Nai) and extracellular sodium (Na0) signals. The goal of the present study has been to develop a23Na NMR spectroscopic method to minimize the intensity of the shift‐reagent‐shifted Na0signal and thus increase Nairesolution. This is achieved by a selective inversion recovery (SIR) method which enhances the resolution between the Naiand Na0peaks in shift‐reagent‐aided23Na NMR spectroscopy. The application of SIR with Dy(TTHA), Tm(DOTP), or with low concentrations of Dy(PPP)2results in both good spectral resolution and physiologically acceptable contractile function in the isolated, perfused rat

ISSN:0952-3480    

DOI:10.1002/nbm.1940060306

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe 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 ofN‐methylN‐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

ISSN:0952-3480    

DOI:10.1002/nbm.1940060307

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe difficulties in quantitation ofin vivo31P spectra are exacerbated by the fact that, in general, coils with inhomogeneousB1fields are used within vivosamples. A general method for quantitation ofin vivo31P MRS results obtained with the ISIS localization method was developed using computer simulations. The simulation calculates the preparation of the sample magnetization throughout the sample by the ISIS pulse sequence, as well as the sensitivity of signal reception. The calculation accounts for both theB1field and theB0gradients applied to the sample. The sensitivity of the experiment is expressed by integration of the simulated signal over the sample, assuming a homogeneous sample. The primary advantage of this approach is that a separate localization experiment on a phantom of known concentration isnotrequired each time parameters of the localization experiment, such as dimensions or location of the localized volume, are altered. In addition, the simulations indicate the degree of contamination (signal from outside of the localized volume) that occurs, and provide a means of comparing different executions of the ISIS experiment. Experiments were performed on phantoms to verify the simulations, and experimental results on human brain and liver are reproduced to show that this approach provides reasonable estimates of metabolite levels in terms of molar concentrations.

ISSN:0952-3480    

DOI:10.1002/nbm.1940060308

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe 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 quant

ISSN:0952-3480    

DOI:10.1002/nbm.1940060309

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940060310

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940060301

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY