Technical Requirements of Smooth Muscle Spectroscopy

Spectral quality is determined by a number of factors magnetic field strength, relaxation rates of the 

The relaxation rates of different nuclei are a function of the chemical nature of the compound and to a lesser extent of the field strength. The exponential time constant for relaxation, known as the Tj, determines how often the spin of the nucleus can be perturbed to generate the spectral signal. In most biological applications, Tj varies between 1 and 3 seconds. Collection of a fully relaxed spectrum requires about five Tj s. Signal-to-noise values can be improved by collecting more often, but the relative size of the peaks in such partially saturated spectra will not reflect the relative concentrations of the different peaks. In these cases, relative concentrations can be determined if the Tj values of the different peaks are known. 

Copyright 1996 by Academic Press, Inc. All rights of reproduction in any form reserved. 

Signal strength will increase linearly with the mass of the tissue. Smooth muscles vary considerably in size, from very small blood vessels to quite large bladder, intestinal, and uterine tissues. Using tissue that is as uniform as possible will enhance the reliability of the experiment. In the case of very small tissues, it is usually necessary to combine several samples to produce an acceptable signal within a reasonable time. 

Information on the concentration of ions bound to NMR visible peaks can be obtained from the position or chemical shift of the peak. In particular, the tissue pH can be obtained from the chemical shift of the Pj peak, and the free Mg + concentration can be measured from the position of the p-ATP resonance (Sec- 

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