摘要:

AbstractAn extensive protocol for the study of tissue resonances of spin 3/2 nuclei is described. The roles of the most relevant multiple pulse experiments are indicated. Their theory is organized in terms of irreducible tensor operators and the pulse and quadrupolar relaxation transfer functions which relate them for atype cspectrum. A systematic approach to the interpretation of the temperature and/or magnetic field dependences of all six of the relaxation rate constants of the resonance of a single population of isolated spins in fast exchange, and giving rise to atype cspectrum, is presented. An experimental calibration and an application of this protocol are presented in an accompanying paper. The comprehensive method we describe has a number of practical benefits in the interpretation of the physiological spectra obtained from conventional one pulse experiments. A consideration of the appropriate transverse relaxation transfer function leads to an analytical expression for the heretofore empirical NMR visibility factor. This includes factors which account for relaxation during the receiver ‘dead’ time and relaxation during the pulse itself. Also, consideration of realistic transverse relaxation times likely to be observed in tissue leads to a reasonable strategy for the quantitative resolution and integration ofin vivospectra obtained in the presence of hyperfine shift reage

ISSN:0952-3480    

DOI:10.1002/nbm.1940040502

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe comprehensive approach described in the accompanying paper is illustrated here with the23Na signal of a concentrated solution of bovine serum albumin (BSA) in saline and the intracellular (Nai)23Na resonance of a dense suspension of Na+‐loaded yeast cells. We use frequency shift reagents to discriminate the latter from the extracellular resonance. We find that the Naisignal corresponds to that of an effective single population of Na+ions exhibiting a singletype cspectrum. This is true despite the fact that the yeast protoplasm is too large and too compartmentalized for a given Na+ion to sample its entirety on the relevant NMR timescale. Our results show clearly that, in addition to the decay of transverse magnetization, the recovery of longitudinal magnetization is biexponential. This is required for atype cspectrum but has not often been detected. The temperature dependence of the relaxation rate constants of the Nairesonance is not consistent with either a simple Debye process or a discrete exchange mechanism connecting two sites in the fast limit. We have fitted the data using an asymmetric continuous distribution of correlation times for the fluctuations of electric field gradients sensed by the Nainuclei. The analogous distribution function for the Na+in a 44% (w/w) BSA solution is quite similar to that of the Naiat the same temperature. This suggests that while the macromolecular environment of the Naiions is quite congested, it is also isotropic on quite a small spatial scale. Also, one can use the correlation time distribution function, obtained from fitting the relaxation data, to calculate a relaxometry curve. This is useful because experimental23Na relaxometry is difficult. The calculated curve may be a reasonable model for the mostly extracellular23Na resonance encounteredin viv

ISSN:0952-3480    

DOI:10.1002/nbm.1940040503

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractA MR spectroscopy method is described for the simultaneous discrimination and observation of sodium from the three compartments created by an intact cell monolayer. Results are reported for Madin Darby Canine Kidney (MDCK) cells, an epithelial‐like continuous cell line, cultured on Cytodex 1 microcarrier beads and perfused with medium containing 6 mM dysprosium (III) tripolyphosphate [Dy(TPP)72] as shift reagent. The sodium spectrum shows three resonances which are assigned to the shifted intrabead (basolateral) and extrabead (apical) pools and the unshifted intracellular pool. Ouabain inhibition of the Na+‐K+‐ATPase cellular pump mechanism was used to demonstrate the sensitivity of the method for monitoring intracellular sodium. The supported MDCK cells in this system remained viable after exposure for 5 h to medium containing Dy(TPP)72at a concentration of 6 mM, as determined by trypan blue dye exclusion and by comparison of the log growth rate and ability to form domes in subsequent generations of exposed cells vs unexposed con

ISSN:0952-3480    

DOI:10.1002/nbm.1940040504

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940040501

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY