Claire B. Conboy

Noninvasive in vivo demonstration of 2-fluoro-2-deoxy-D-glucose metabolism beyond the hexokinase reaction in rat brain by 19F nuclear magnetic resonance spectroscopy

Abstract: The metabolism of 2‐fluoro‐2‐deoxy‐d‐glucose (FDG) in vivo was observed noninvasively in rat brain using “F nuclear magnetic resonance (NMR) spectroscopy following an intravenous injection of FDG (400 mg/ kg). At 3 h after infusion, four resonances with discrete chemical shifts were resolved. Chemical shift analysis of these resonances suggested the chemical identity of two of the resonances to be FDG and/or FDG‐6‐phosphate and 2‐fluoro‐2‐deoxy‐8‐phosphogluconolactone and/or 2‐fluoro‐2‐deoxy‐δ‐phosphogluconate. The chemical identities of the other two resonances remain to be elucidated. The present study indicates that the metabolism of FDG in vivo is more extensive than is previously recognized and demonstrates the feasibility of using 19F NMR spectroscopy to follow the 19F‐containing metabolites of FDG in vivo.

In vivo 19F-NMR study of halothane distribution in brain

Halothane distribution and elimination from rabbit brain was studied in vivo using 19F-NMR spectroscopy. Two exponential decay functions for the anesthetic were observed in the clearance curve. They are assigned to halothane in brain held in two distinct chemical environments characterized by different chemical shifts, and half-lives (25 and 320 min). A nonvolatile halothane metabolite with a half-life of several days was found to be present in rabbit brains. The in vivo results were corroborated by ex vivo experiments on excised brain tissue. Halothane was distributed in all of the major cell subfractions, whereas the metabolite was present predominantly in the cytoplasm.

A cylindrical-window NMR probe with extended tuning range for studies of the developing heart

Abstract Three matched cylindrical-window NMR probes were designed and constructed in graduated sizes (16, 25, and 30 mm) for neonatal, immature, and adult heart spectroscopy. The cylindrical probes were made of copper foil and had two symmetrical cylindrical conductive blades separated by openings subtending 90° arcs. The tuning range included both sodium-23 (52.9 MHz) and phosphorus-31 (81.0 MHz). The ability to tune to sodium-23 expedited shimming for phosphorus-31 experimental measurements. Standardization of phosphorus-31 spectra was achieved with an MDPA-filled capillary tube placed outside the cylindrical window. The finite element method was used to derive the electrical potential, magnetic field, and current densities. B1 field mappings showed uniformity throughout the usable areas, an attribute facilitating comparisons of spectra from hearts of different sizes. We summarize the current designs for low-inductance NMR probes of this type.

Conformational kinetics of methyl nitrite. I. NMR spectral evidence for statistical intramolecular vibrational redistribution

Pressure dependent rate constants for syn⇄anti conformational exchange in gaseous methyl nitrite and in gaseous methyl nitrite–CO2 mixtures have been obtained from line shape analyses of 1H NMR spectra. The pressure dependence of the exchange rates is consistent with a specific reaction rate constant of ∼1×109/s which agrees with RRKM calculations demonstrating that intramolecular vibrational redistribution is occurring at the statistical limit in methyl nitrite molecules with ∼12 kcal/mol of internal vibrational energy. At 12 kcal/mol methyl nitrite has a state density of ∼160/cm−1. These results indicate strong anharmonic and/or Coriolis coupling between vibrational levels. Bimolecular rate data for methyl nitrite and methyl nitrite–CO2 mixtures are consistent with a collisional efficiency βp for CO2 of 0.95(8) for activation of syn–anti conformational exchange at 258.8 K.

New NMR Probe Designs for Neonatal, Immature and Adult Heart Research with a Brief Review

We present three new radiofrequency probes for nuclear magnetic resonance (NMR) research with perfused rabbit hearts at different maturational ages. The objective of the double-tunable, cylindrical-window probe design was to achieve a highly homogeneous magnetic field throughout the 16, 25 or 30 mm diameter usable volume for consistency of comparison of measurements obtained from neonate, immature and adult rabbit hearts, respectively. This probe design tunes to 23-Sodium for rapid shimming and then, to 31-Phosphorus for measurements of pH and high energy phosphate metabolites. All three probes yielded excellent signal-to-noise ratios and radiofrequency operating characteristics. We introduce these new probes here in the context of a brief review of other state-of-the-art designs for in vitro and in vivo cardiovascular research.