Fiber optic surface fluorometry/reflectometry and 31-p-NMR for monitoring the intracellular energy state in vivo.

Various members of the respiratory chain exhibit different optical properties in the reduced and oxidized forms, thus enabling the non-invasive monitoring of various organs in vitro as well as in vivo. Since the pioneering work of Chance, Cohen, Jobsis and Schoener in 1962, many groups of investigators adopted their approach in monitoring NADH oxidation reduction states in vivo for the brain as well as for other body organs. In 1972, we introduced flexible, optical fibers into the surface fluorometry replacing the usual "rigid" optical system used by other groups. During the last decade, this technique has been developed, improved and applied to many experimental setups in brain research and very recently was combined with 31P NMR spectroscopy for the puppy and the adult dog brain in vivo. In our system, the effects of movement artifacts and changes in blood oxygenation are negligible while the effects of tissue absorption or blood volume changes are considerable and could be minimized by subtraction of the reflectance signal from that of the fluorescence (1:1 ratio) providing the corrected fluorescence signal.