[Electron microscopic and immunohistochemical studies of acute stages of severe brain injury in rats].

Few morphological studies on fluid-percussion experimental models using mechanically produced severe brain injury have been reported. This study was initiated to evaluate light and electron microscopic and immunohistochemical findings in severe brain injury models using rats. The experimental rats and the methods used were as described for a fluid-percussion model. Fluid-percussion models of traumatic brain injury produce injury rapidly by injecting fluid volumes into the epidural space of the temporal lobe. We used 5 rats which sustained various degrees of injury by high (7.0 atm), medium (5.6 atm) and low (3.5 atm) magnitudes of impact and sham control. The rats were sacrificed and perfused transcardially with buffer solution followed by 2.5% glutaraldehyde at intervals of 24 hours, 3 days, and 7 days, and there were normal and sham control groups. In this immunohistochemical study, monoclonal antibody to 70 kilodalton neurofilament subunit has been used in a standard Avidin-Biotin Complex Kit (DAKO). Microscopic findings of the animals revealed subarachnoid hemorrhage, lateral IIIrd ventricular hemorrhage, and rarefaction and petechial hemorrhage of the local contusional lesion. In the medium level injury, there was a marked petechial hemorrhage in the corpus callosum and subependymal area. In the high level injury, there was marked edema in the white matter of the ipsi and contralateral cerebral hemisphere, and multiple petechial hemorrhage in the brain stem and cerebellum. Microscopic findings in the corpus callosum, subependyma and brain stem in the vicinity of petechial hemorrhage revealed a large number of axonal swellings, but in these specimens only a few typical axonal retraction balls were seen using Bodian and immunohistochemical stains.(ABSTRACT TRUNCATED AT 250 WORDS)