摘要:

AbstractData are presented from133Cs NMR studies on both excised andin situtissues from rats fed a regular diet and administered i.p. CsCl in aqueous solution for 6 to 14 days. Cesium is an NMR‐active potassium analog which accumulates in the intracellular spaces of tissues [Davieset al., Biochemistry27, 3547 (1988); Shehan, B.P.et al., Magn. Reson. Med.30, 573 (1993)]. Chemical shifts, relaxation properties, sensitivity and detectability of cesium in tissues were investigated. Consistent with previous reports, two resonances (representing intra‐ and extracellular cesium) were detected in blood. Only one resonance was detected in brain, kidney, and muscle tissue. Efforts to resolve intra‐ and extracellular components by T1and T2relaxation discrimination were not successful. Following i.p. administration, cesium accumulates intracellularly with a brain‐to‐cerebrospinal fluid concentration (μmol/g) ratio of 9:1 and a thigh muscle‐to‐plasma concentration ratio of 40:1. Considering the small extracellular volume in these tissues (ca 18% and 10%, respectively), the net content differences between intra‐ and extracellular cesium are approximately 40‐fold in brain and 360‐fold in muscle. The concentration ratio of cesium in brain to cesium in cerebrosinal fluid decreased to 3:1 1 h after death, indicating a relatively slow rate of leakage of cesium from the intra‐ to extracellular space in the face of bioenergetic failure. These data suggest that the cesium signal is dominated by the intracellularly located cesium and, thus, cesium may be useful as a probe of the intracellular environment despite an inability to resolve and directly observe distinct resonances from intra‐

ISSN:0952-3480    

DOI:10.1002/nbm.1940080502

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe analysis of crude tissue extracts by NMR has proven to be of use in the study of metabolism due to the non‐destructive and non‐selective character of the technique. Lists of1H and31P NMR assignments of phosphorus metabolites in water solution at specified pH and ionic composition are of large general value but their usefulness may be limited when analysing complex mixtures of metabolites at low concentrations. In this work we report on the use of gradient‐assisted proton detected multiple quantum1H and31P coherence experiments with selective pulses for the rapid and unambiguous assignments of some crowded regions in1H and31P spectra of crude extracts from rat liver. The amplitudes of the gradient episodes were calibrated to optimize the coherence transfer pathway between proton and phosphorus, and the delay for the evolution of the long‐range coupling was calculated from values of3JPHand4JPHranging from 1.4 to 7.5 Hz. Moreover, a selective 90° Gaussian pulse on the31P channel was introduced to increase the resolution in the F1‐domain and make the method even faster. The procedure was then applied to unambiguously assign the ID31P and1H spectra of perchloric acid extracts of rat livers that had been stimulated with phenylephrine, dBcAMP and glucagon and thus detect changes in the concentration of less abundant metabolites such as phosphoenolpyruvate, UDP‐glucose and AMP. The fact that the quantification of these metabolites by either31P and1H methods lead to different results is discussed, and the use of1H NMR spectroscopy for the quantification of phosphorus metabolites whose signal are too weak or poorly resolved in a31P spectrum

ISSN:0952-3480    

DOI:10.1002/nbm.1940080503

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractA series of ligands based upon 1,4,7‐triazacyclononane, containing variable numbers of acetate vs methylene‐phosphonate ester or methylenephosphinate sidechains, has been synthesized and characterized as possible31P NMR probes for monitoring [Mg2+]free. The diacetate monophosphinate and diacetate monophosphonate ester mixed ligands proved to have conditional (dissociation) constants at pH 7.4 in an appropriate range for measuring typical levels of intracellular [Mg2+]freeand binding selectivities for Mg2+over Ca2+that ranged from 1.4 to 6.8. The31P resonances of these ligands were well downfield of typical tissue phosphate metabolite resonances, and addition of Mg2+to any one of these ligands resulted in well‐resolved resonances for HL and MgL (where L = ligand), in slow chemical exchange. The chemical shift differences between the HL and MgL species varied from 2.1 to 2.6 ppm for three different ligands. The conditional Mg2+‐L binding constants were sensitive to pH in the physiological range, due to protonation of a single macrocyclic nitrogen at high pH (logK1values ranged from 10 to 12). However, given conditions that allow an independent assessment of pH (i.e., from the31P chemical shift of Pi), we show that accurateKDvalues can be estimated from the known thermodynamic stability constants (KMgL) and ligand protonation constants (K1). This makes these ligands potentially useful for monitoring [Mg2+]freeby31P NMR over a variety of solution conditions, even during conditions when the pH may be c

ISSN:0952-3480    

DOI:10.1002/nbm.1940080504

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractFocal cerebral ischaemia was produced in 11 rats by permanent occlusion of the right middle cerebral artery (MCA) using a suture model modified to enable manipulation with the animalsin situin an NMR spectrometer. The development of the ischaemic insults and the resultant infarcts were observed for up to 6 h by localized1H MRS and diffusion‐weighted MRI while performing continuous monitoring of electroencephalogram and extracellular DC potential. The ischaemic areas were depicted as regions of hyperintensity in the diffusion‐weighted images. Signals due to lactate became visible in the1H spectra after MCA occlusion indicating the onset of anaerobic glycolysis. A depletion ofN‐acetylaspartate was seen in all animals post‐occlusion. Transient or stepwise increases of lactate were observed to occur coincidentally with the events of spontaneous transient peri‐infarct depolarization detected by the electrophysiological measurements. Expansion of the ischaemic area delineated in the diffusion‐weighted images also accompanied peri‐infarct depolarizations. These observations are consistent with transient peri‐infarct depolarization playing a role in the gro

ISSN:0952-3480    

DOI:10.1002/nbm.1940080505

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractIrresectable extremity sarcomas are large (grade II/III) tumors requiring amputation of the limb for local control. Limb salvage can be achieved by isolated limb perfusion (ILP) with tumor necrosis factor alpha (TNF‐α), interferon‐γ and melphalan. To obtain insight into the effects of single dose ILP on extremity tumors, phosphate metabolism was monitored by31P magnetic resonance spectroscopy (MRS) using the chemical shift imaging (CSI) technique. 2D CSI was used in combination with a slice select gradient in the third dimension to obtain true 3D localization. Spectral maps obtained prior to ILP revealed reductions in phosphocreatine (PCr) level and increases in phosphomonoester (PME) and phosphodiester (PDE) in tumor compared with muscle tissue. ILP treated tumors showed highly divergent changes in Piwhile PME decreased in all cases (n = 11). Tumor volume, unchanged on day 8 after ILP, was decreased by 58±29% (mean±SD) at 2 months. Linear regression analysis revealed correlation between the changes in tumor metabolites measured on day 8, with percent volume decrease (Pi: r=‐0.88, p<0.001) and percent necrosis at resection (PME: r=‐0.79, p‐0.01). Correlation between pretreatment spectra and effectiveness of ILP treatment was not found. It is concluded that a single ILP with TNF‐α+melphalan induced changes in tumor metabolite levels (measured on day 8) that reflect treatment efficacy.31P MRS can thus provide information facilitating the decision as to when to remove tumor (residue) and, in the case where tumor remains inoperable, whether or not to apply ad

ISSN:0952-3480    

DOI:10.1002/nbm.1940080506

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractA robust method for fast lactate imaging is presented using a combination of a lactate editing sequence and a one‐shot imaging experiment. The lactate editing method is based on manipulation of the phase of the lactate CH3signal viaJ‐modulation. This is applied as a preparation experiment to the U‐FLARE imaging sequence. Phantom experiments are presented in which the quality of water and lipid suppression is established. Edited lactate images with a spatial resolution of 3 m̈L and total measuring time of 15.8 min are shown. These were obtained from a hemispherical ischemia in the gerbil brain. The images are compared with diffusion‐weighted wate

ISSN:0952-3480    

DOI:10.1002/nbm.1940080507

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940080508

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940080501

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY