Visualization by mass spectrometry of 2-dimensional changes in rat brain lipids, including N-acylphosphatidylethanolamines, during neonatal brain ischemia.
ABSTRACT Spatial synthesis of N-acyl-phosphatidylethanolamines (NAPEs) and N-acylethanolamines (NAEs) during ischemia-reperfusion in neonatal rats has been investigated and compared to the spatial degradation of other phospholipids. Ischemia was induced in anesthetized Wistar P7 rat pups by left middle cerebral artery electrocoagulation combined with a transient and concomitant occlusion of both common carotid arteries. Pups were sacrificed after 24 and 48 h. Sham-treated animals were sacrificed after 48 h. The frozen brains were sliced and subjected to desorption electrospray ionization imaging mass spectrometry. There was a remarkable increase in the levels of many species of NAPEs in the whole injured area at both time points, and a clear but minor increase in selected NAEs. In the ischemic area, the sodium adducts of phosphatidylcholine and of lyso-phosphatidylcholine accumulated and the potassium adduct of phosphatidylcholine disappeared, indicating breakdown of the Na(+)/K(+) pump. Free fatty acids, e.g., arachidonic and docosahexaenoic acids, tended to be more abundant in the periphery than in the center of the ischemic area and showed different spatial distribution. NAPEs are synthesized in the whole ischemic area where the cells seem to be dead and other phospholipids are degraded. Free fatty acids can be found in the periphery of the ischemic area.
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ABSTRACT: Easy ambient sonic spray ionization (EASI) and desorption electrospray ionization (DESI) were used for imaging of a number of samples, including sections of rat brain and imprints of plant material on porous Teflon. A novel approach termed Displaced Dual-mode Imaging was utilized for the direct comparison of the two methods: Images were recorded with the individual rows alternating between EASI and DESI, yielding a separate image for each technique recorded under perfectly similar conditions on the same sample. EASI works reliably for imaging of all samples, but the choice of spray solvent and flow rate is more critical in tissue imaging with EASI than with DESI. The overall sensitivity of EASI is, in general, slightly lower than that of DESI, and the representation of the dynamic range is different in images of the two techniques for some samples. However, for abundant compounds, EASI works well, resulting in images of similar quality as DESI. EASI can thus be used in imaging experiments where the application of high voltage is impractical or undesirable. The present study is in its nature also a comparison of the characteristics of the two techniques, showing results also applicable for non-imaging work, with regards to sensitivity and experimental conditions.Journal of the American Society for Mass Spectrometry 08/2012; 23(10):1670-8. · 3.59 Impact Factor