摘要:

AbstractNMR methods for measuring membrane transport rates rely in most cases upon there being a significant transmembrane difference in either the resonance frequency or the NMR relaxation times of the transported species. The first part of this review examines the various factors that can give rise to such differences in cell and vesicle suspensions. The second part provides an introduction to the theory of membrane transport measurements and describes the different ways in which transmembrane differences in NMR parameters have been exploited in monitoring both slow and fast membrane transport processes.

ISSN:0952-3480    

DOI:10.1002/nbm.1940030102

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractPhosphorus‐containing metabolites in normal human liver have been quantitated non‐invasively with31P magnetic resonance spectroscopy using surface coils. The location of the volume of interest (VOI) was defined by1H magnetic resonance imaging. Subsequently, a modified three‐dimensional localization technique (ISIS) was used to acquire31P magnetic resonance spectra from the VOI. To account for partial saturation produced by rapid signal averaging, the spin/lattice relaxation times (T1) of all hepatic phosphorus resonances were measured. The corrected resonance integrals were used to derive absolute molar concentrations for the following hepatic metabolites (mmol/kg wet weight): ATP, 2.0; inorganic phosphate, 2.1; phosphodiesters, 5.4; and phosphomonoesters, 0.9. These values are compared with previously reported values for humans using freeze‐clamping techniques, and provide a basis for comparison with studies of hepatic disease in this lab

ISSN:0952-3480    

DOI:10.1002/nbm.1940030103

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractA simple technique permitting long term31P magnetic resonance spectroscopy of cultured mammalian cells is described. Cells are encapsulated in calcium alginate gels and perfused with a new phosphate‐free medium designed for maintenance of high cell viability. Intracellular pH and β‐NTP/Piratios, studied in three cell types, remained stable over a 16–20 h NMR monitoring period. The techniques described may be useful for monitoring cell metabolism with a variety of cell

ISSN:0952-3480    

DOI:10.1002/nbm.1940030104

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractA decoupling structure using an additional LC resonant configuration for NMR transmit coils is analysed and the probe sensitivity of the receive coil with the decoupled transmit coil is calculated using simple circuit models. An adjustment‐free technique for the decoupling circuit under different loading conditions is proposed using the calculated results and demonstrated by experiments. The proposed method can simplify the probe operatio

ISSN:0952-3480    

DOI:10.1002/nbm.1940030105

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

摘要:

AbstractA research‐type 4 T whole‐body magnet, built by Siemens AG, Erlangen, FRG, was used to investigate magnetic resonance at high field strengths. Designs for head and body coils operating at 170 MHz are described. Proton images of the human head and body are degraded by dielectric resonances and penetration effects. The nature of the dielectric resonances was demonstrated in phantoms containing distilled and saline doped water. Radiation damping at 170 MHz generates secondary echoes after a spin echo sequence. This effect was observed in phantoms and with reduced amplitude in the human head. Hydrogen spectra of the human head were selected utilizing stimulated and spin echoes. The latter technique allows the volume size to be reduced to 1 cm3. Examples of brain tumors that have been routinely investigated with volumes of 8 cm3are given. Natural abundance carbon and phosphorus spectra of muscle and liver demonstrate the expected increase in spectral resolution and signal to noise ratio. Carbon spectra from the liver show the glycogen signal. Fluorine spectroscopy was used to study the time course of the absorption and emptying of a fluorinated antibiotic from the human stom

ISSN:0952-3480    

DOI:10.1002/nbm.1940030106

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY

ISSN:0952-3480    

DOI:10.1002/nbm.1940030101

出版商:John Wiley&Sons, Ltd.    

年代:1990

数据来源: WILEY