NAA identification and quantification

Typical high-resolution spectra obtained from extracts of acid-soluble metabolites from O-2A progenitors, immature oligodendrocytes and mature oligodendrocyte (grown in the presence and absence of CNTF) are shown in Figures 1 to 4.

Figures 1-4. Typically 107 - 108 cells were obtained for each extract. The protein content of samples ranged from 11.7 to 12.7 mg for O-2A progenitor cell extracts, from 3.4 to 14.5 mg in immature oligodendrocyte cell preparations, from 13.8 to 15.5 mg in CNTF treated mature oligodendrocytes, and from 8.8 to 14.1 mg for untreated mature oligodendrocytes. Spectra of (1) O-2A progenitors, (2) immature oligodendrocyte, (3 and 4) Mature oligodendrocyte with and without CNTF respectively.

Figures 1-4. Typically 107 - 108 cells were obtained for each extract. The protein content of samples ranged from 11.7 to 12.7 mg for O-2A progenitor cell extracts, from 3.4 to 14.5 mg in immature oligodendrocyte cell preparations, from 13.8 to 15.5 mg in CNTF treated mature oligodendrocytes, and from 8.8 to 14.1 mg for untreated mature oligodendrocytes. Spectra of (1) O-2A progenitors, (2) immature oligodendrocyte, (3 and 4) Mature oligodendrocyte with and without CNTF respectively.

These high field regions (0.5 - 4.5 ppm) contain signals from a variety of metabolites, including amino acids and related compounds, compounds involved in membrane biosynthesis (e.g. choline and choline-containing compounds) and compounds involved in intermediary metabolism (succinate and lactate). The metabolite of interest in the present study is the resonance assigned to NAA at 2.02 ppm, with reference to TSP. NAA was also identified and quantified using HPLC in the same samples. The O-2A progenitors expressed slightly lower levels of NAA then previously published data (15.1 ± 2.9 vs 21.1 ± 11.0 [mean ± SD] nmol/mg protein), whereas that for immature oligodendrocytes was similar (9.0 ± 4.1 vs 10.3 ± 5.4 [mean ± SD] nmol/mg protein).8, 9 NAA was also seen in both preparations of mature oligodendrocytes, with higher levels in the CNTF treated population (9.5 ± 1.5 in the untreated cells and 15.5 ± 1.8 in the CNTF treated oligodendrocytes [mean ± SD] nmol/mg protein). The levels of NAA seen in mature oligodendrocytes were comparable to those seen in a variety of neuronal cultures; cerebellar granule neurons 12.3 ± 2.6;9 cortical neurons 34.5 ± 3.7 and dorsal root ganglion neurons 15.6 ± 1.9 ([mean ± SD] nmol/mg protein).49 It is however uncertain whether NAA levels seen in these different cellular preparations is found in similar proportions in the individual cell-types in vivo. Meningeal cells derived from the meninges surrounding the cortex were grown as a control population of cells. These cells were cultivated and harvested under similar conditions as the other cell types. As expected no NAA was seen in extracts of these cells, which is in agreement with previously published data.8, 9 53

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