NMR and Time-Resolved Optical Studies of Brain Imaging

Abstract

My assignment in this symposium, as I see it, is to bridge the gap between non-invasive “whole body” technologies of NMR and time resolved spectroscopy, to give some perspective of what they do best, and where the future lies for the two technologies. The assignment has been made much more pleasant and less difficult because of the highly significant contributions of a number of my colleagues, particularly on NMR and time resolved spectroscopy, and my report here will emphasize those aspects that link the two technologies which might have been overlooked by my colleagues. Since the symposium focuses on oxygen in tissues, ³¹P NMR is of greatest interest and its ability to detect tissue oxygen relies upon the general equation for oxidative phosphorylation (Chance, et al., 1985; Chance, et al., 1986):

$$ 3ADP + 3P_i + 1/2O_2 + NADH + H^ + - - - - ^E - - - - > 3ATP + NAD^ + + H_2 O $$

((1))

in which oxygen is not just one of, but the key participant because its reduction to water gives the driving force for ATP synthesis. In brain, heart, and skeletal muscle (Chance, et al., 1985; Chance, et al., 1986), and more recently in transvected mice, by assuming Michaelis-Menten kinetics for oxidative phosphorylation (Chance and Williams, 1955) the effect of oxygen on the phosphocreatine (PCr)/inorganic phosphate (P_i) ratio is indicated by Eq. 2 Cr-kinase equilibrates a large pool of PCr with a smaller Creatine pool of ATP and permits the determination of ADP itself from the known equilibrium constant of the creatine kinase reaction. However, our interest is in detection of intracellular oxygen.