Neurotrauma, as in the case of traumatic brain injury, promotes protease over‐activation characterized by the select fragmentation of brain proteins. The resulting polypeptides are indicators of biochemical processes, which can be used to study post‐injury dynamics and may also be developed into biomarkers. To this end, we devised a novel mass spectrometry approach to characterize post‐injury calpain proteolytic processing of myelin basic protein (MBP), a biomarker of brain injury that denotes white matter damage and recovery. Our approach exceeds conventional immunological assays in its deconvolution of multiple protein isoforms, its absolute quantification of proteolytic fragments and its polypeptide selectivity. We quantified and characterized post‐injury proteolytic processing of all MBP isoforms identified in adult rat cortex. Further, the translation of calpain‐cleaved MBP into CSF was verified following brain injury. We ascertained that the exon‐6 sequence of MBP resulted in a characteristic shift in gel migration for intact and fragmented protein alike. We also found evidence for a second post‐TBI cleavage event within exon‐2 and for the dimerization of the post‐TBI 4.3 kDa fragment. Ultimately, the novel methodology described here can be used to study MBP dynamics and other similar proteolytic events of relevance to brain injury and other CNS processes.

Diagnosis and treatment of stroke and traumatic brain injury remain significant health care challenges to society. Patient care stands to benefit from an improved understanding of the interactive biochemistry underlying neurotrauma pathobiology. In this study, we assessed the power of neuroproteomics to contrast biochemical responses following ischemic and traumatic brain injuries in the rat. A middle cerebral artery occlusion (MCAO) model was employed in groups of 30-min and 2-h focal neocortical ischemia with reperfusion. Neuroproteomes were assessed via tandem cation-anion exchange chromatography-gel electrophoresis, followed by reversed-phase liquid chromatography-tandem mass spectrometry. MCAO results were compared with those from a previous study of focal contusional brain injury employing the same methodology to characterize homologous neocortical tissues at 2 days post-injury. The 30-min MCAO neuroproteome depicted abridged energy production involving pentose phosphate, modulated synaptic function and plasticity, and increased chaperone activity and cell survival factors. The 2-h MCAO data indicated near complete loss of ATP production, synaptic dysfunction with degraded cytoarchitecture, more conservative chaperone activity, and additional cell survival factors than those seen in the 30-min MCAO model. The TBI group exhibited disrupted metabolism, but with retained malate shuttle functionality. Synaptic dysfunction and cytoarchitectural degradation resembled the 2-h MCAO group; however, chaperone and cell survival factors were more depressed following TBI. These results underscore the utility of neuroproteomics for characterizing interactive biochemistry for profiling and contrasting the molecular aspects underlying the pathobiological differences between types of brain injuries.

Stable spike foci generated by weak penicillin solutions had a minimal area of distribution of 12.5 mm2. Two foci separated by 4 mm on the same gyrus were consistently dependent and simultaneous. An area of "positive surround" between the two spikes did not prevent dependency. This contradicts the hypothesis that "positive surround" prevents spreading of epileptiform discharges. Spike foci separated by 6 mm were almost always independent. Bursts of afterdischarges remained independent if the primary spikes were independent. Postafterdischarge suppression and spreading depression of Leao affected independent spike focus selectively. These experiments suggest that cross-talking between cortical columns is limited to column 1 to 2 mm apart.

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