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Inorganic Phosphate Compartmentation in the Normal Isolated Canine Brain
Author(s) -
Gilboe David D.,
Kintner Douglas,
Anderson Mark E.,
Fitzpatrick James H.,
Emoto Sherrie E.,
Markley John L.
Publication year - 1993
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1993.tb03505.x
Subject(s) - nuclear magnetic resonance , spectral line , homogeneous , noise (video) , signal (programming language) , algorithm , magnetic resonance imaging , mathematics , analytical chemistry (journal) , physics , chemistry , computer science , combinatorics , artificial intelligence , medicine , radiology , chromatography , astronomy , image (mathematics) , programming language
In vivo 31 P magnetic resonance spectra of 16 isolated dog brains were studied by using a 9.4‐T wide‐bore superconducting magnet. The observed P i peak had an irregular shape, which implied that it represented more than one single homogeneous pool of P i . To evaluate our ability to discriminate between single and multiple peaks and determine peak areas, we designed studies of simulated 31 P i spectra with the signal‐to‐noise (S/N) ratios ranging from ∞ to 4.4 with reference to the simulated P i peak. For the analysis we used computer programs with a linear prediction algorithm (NMR‐Fit) and a Marquardt–Levenberg nonlinear curve‐fit algorithm (Peak‐Fit). When the simulated data had very high S/N levels, both methods located the peak centers precisely; however, the Marquardt‐Levenberg algorithm (M‐L algorithm) was the more reliable at low S/N levels. The linear prediction method was poor at determining peak areas; at comparable S/N levels, the M‐L algorithm determined all peak areas relatively accurately. Application of the M‐L algorithm to the individual experimental in vivo dog brain data resolved the P i peak into seven or more separate components. A composite spectrum obtained by averaging all spectral data from six of the brains with normal O 2 utilization was fitted using the M‐L algorithm. The results suggested that there were eight significant peaks with the following chemical shifts: 4.07, 4.29, 4.45, 4.62, 4.75, 4.84, 4.99, and 5.17 parts per million (ppm). Although linear prediction demonstrated the presence of only three peaks, all corresponded to values obtained using the M‐L algorithm. The peak indicating a compartment at 5.17 ppm (pH 7.34) was assigned to venous pH on the basis of direct simultaneous electrode‐based measurements. On the basis of earlier electrode studies of brain compartmental pH, the peaks at 4.99 ppm (pH 7.16) and 4.84 ppm (pH 7.04) were thought to represent interstitial fluid and the astrocyte cytoplasm, respectively.