Design and testing of a probe for simultaneous collection of optical fluorescence and (31)P nuclear magnetic resonance spectra in vivo

An optical fluorescence spectrometer for measurement of intracellular calcium concentration and a double-tuned 31P/1H radio frequency coil were constructed to allow for simultaneous measurement of optical fluorescence and 31P nuclear magnetic resonance (NMR) spectra. The combination of these modalities not only increases the amount of information which can be learned from a single experiment since NMR sensitive and fluorescence sensitive variables may be monitored together, but also reduces subject and treatment variability since only a single experiment is performed. The utility of this technique was demonstrated by simultaneously measuring intracellular calcium concentration (via optical fluorescence) and high-energy phosphate metabolic state (via NMR spectroscopy) in the in vivo, in situ heart of the western painted turtle Chysemys picta bellii. This species is interesting to comparative cardiac physiologists because of its remarkable tolerance to prolonged and severe hypoxia. Additionally, techniques including the use of appropriately designed coil arrays were investigated as a means to maximize the signal-to-noise ratio over a particular volume of interest in an NMR experiment.