Biomedical subjects
Publications and source records attributed to W M Bovee.
A method is described to selectively measure lactate in vivo using proton zero quantum coherence techniques. The signal from lipids is eliminated. A surface coil and additionally slice selective localization are used. The resulting spectra demonstrate the good performance of the method.
Using in vivo 1H NMR spectroscopy (1H MRS) and biochemical analysis, the effects of hyperammonemia on cerebral function were studied in three rat models: acute liver ischemia (LIS), administration of urease (UREASE) and administration of methionine sulfoximine (MSO). By means of localization in three dimensions signals were obtained exclusively from the cerebral cortex. Specially developed lineshape correction and fitting methods were used to quantitate the MRS signals. The following concentration changes were observed; a decrease in glutamate and (phospho)choline for all the models; an increase in glutamine in the LIS and UREASE model but a decrease in the MSO model; a marked increase in lactate in the LIS and UREASE group; a tendency to a decrease in N-acetylaspartate in all the models. These changes agree well with the changes in the post-mortem biochemically determined cerebral cortex glutamine and glutamate concentrations. Estimated absolute 1H MRS metabolite concentrations agree well with those obtained by other techniques; cerebral cortex glutamate, however, is underestimated by about 35% by NMR. The present data support the hypothesis that hyperammonemia is associated with a decreased availability of glutamate for neurotransmission.
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Methods developed for in vivo 1H-NMR spectroscopy are evaluated and applied using conscious rats. Good quality 1H-spectra of the brain are obtained using a surface coil and a spin echo pulse sequence with the binomial 1-1 and 2-2 water suppression pulses. However, comparing spectra from various rats with each other the water and lipid signals, which cause spectral overlap problems, may differ while the other spectral peaks agree well. Spatially one- and two-dimensional 1H spectroscopic imaging of the rat brain shows that the former signals stem from distinct spatial regions localized close to the rf coil. From a spectroscopic image, a spectrum over a limited spatial region is constructed in which the water signals are strongly reduced, the lipid signals are eliminated and lactic acid can be observed clearly simultaneously with other metabolites.
Evaluating the response of tumours to therapy promises to become one of the major applications of in vivo phosphorus (31P) nuclear magnetic resonance spectroscopy. Decreases in the levels of organic phosphates in favour of inorganic phosphate (Pi) as occur in murine tumours after hyperthermia treatment, can be quantified by the ratio ATP/Pi. In this study the relationship between the time of heating (15, 30 and 60 min) and the temperature (43 and 44 degrees C) was investigated in mice with NU-82 tumours by considering the changes in ATP/Pi ratio as a function of both variables. After 30 min treatment at 43 degrees C the percentage decrease in ATP/Pi ratio was similar to that observed after 15 min at 44 degrees C (42 +/- 9 vs. 48 +/- 9); after 60 min at 43 degrees C the decrease was similar to that after 30 min at 44 degrees C (75 +/- 7 vs. 74 +/- 4). These results give further evidence for the validity of a current working definition of thermal dose: thermal dose = t integral of 0 2T-43 dt. In addition this study shows that in vivo 31P NMR spectroscopy can be a useful means for assessment of thermal dose.