Rapid microglial activation induced by traumatic brain injury is independent of blood brain barrier disruption

Following CNS injury, microglia respond and transform into reactive species exhibiting characteristic morphological changes that have been termed "activated" or "ameboid" microglia. In an attempt to establish that microglial reactions induced immediately after injury are caused by intrinsic mechanisms rather than infiltration of blood and its constituents, oxygenized Ringer's solution was perfused into the cerebral circulation of rats so that the circulating blood could be eliminated prior to injury induction. Under artificial respiration, a catheter was inserted from the cardiac apex into the ascending aorta, and oxygenized Ringer's solution was immediately perfused with a pulsatile blood pump, resulting in wash out of the circulating blood from the brain within 1 min. Subsequently, a cortical contusion was induced in the unilateral parietal cortex using a controlled cortical impact (CCI) device. At 5 min following the injury, the brain was fixed by perfusion of fixative through the catheter and removed. Coronal vibratome sections were then processed for CR3 immunohistochemistry to examine the microglial activation. It appeared that microglial activation with both morphological transformation and an increase in CR3 immunoreactivity was induced throughout the hemisphere ipsilateral to the injury side exclusively, even in rats with elimination of circulating blood. The microglial reactions did not differ substantially from those observed in the control rats with extensive BBB disruption. The present results thus provide direct evidence that the microglial activation induced immediately after injury is independent of infiltration of circulating blood induced by concurrent BBB disruption.

Rapid and widespread microglial activation induced by traumatic brain injury in rat brain slices

In order to assess the role of circulating blood in early microglial activation after traumatic brain injury (TBI), controlled cortical impact injury was applied to adult rat brain slices (400 microm in thickness) and the microglial response was examined. The complement receptor (CR3) expression and morphological transformation of the microglia were evaluated by OX42 immunohistochemistry. At 5 min following injury, activated microglia with intense CR3 expression appeared throughout the hemisphere on the injured side. In contrast, the morphology and CR3 expression of the microglia on the contralateral side were indistinguishable from those of the resident ramified microglia seen in normal brains. At 30 min following injury, microglial activation was more pronounced on the injured side, while the microglia on the contralateral side still retained a ramified morphology. These results are consistent with our previous observations made in in vivo experiments, which indicate that, as the brain slice paradigm excludes variables arising from the circulating blood, the rapid and widespread microglial activation observed following TBI can not be attributed exclusively to the infiltration of blood-borne macrophages or molecules. Rather this activation is most likely caused by intrinsic mechanisms within the brain tissue, such as traumatic depolarization.

Peripheral-type primitive neuroectodermal tumor arising in the tentorium. Case report

The authors report the case of a peripheral primitive neuroectodermal tumor (PNET) arising in the tentorium in a 5-year-old boy who presented with frequent vomiting and mild palsy of the left abducent nerve. Following complete surgical excision of the tumor via a transpetrosal approach, the patient has thus far been disease free for 7 years. The tumor tissue was composed of small cells with uniform round nuclei and minimal identifiable cytoplasm. Homer-Wright rosettes were frequently observed. Immunohistochemical studies demonstrated a positive reaction to HBA-71, which recognizes the cell surface glycoprotein p30/32, a product of the MIC2 gene. Both the clinical and immunohistochemical characteristics of this tumor are consistent with a diagnosis of peripheral PNET, which is genetically distinct from the more common intracranial PNET.

Regeneration of dorsal column axons after spinal cord injury in young rats

In contrast to previous reports denying the occurrence of axonal regeneration of the dorsal column (DC) projections, here we demonstrate for the first time that marked regeneration occurs spontaneously after transection in infant rats. Transection was made sharply so as to produce edema-free lesions without subsequent formation of either scars or cysts. Transganglionic labeling of axons revealed that regenerated axons ascended in the normal tract in a manner similar to normal projections as a tightly-packed fasciculus and terminated densely in the nucleus gracilis. The present study indicates that failure of regeneration of DC axons is due to neither intrinsic deficiency of regrowth potential nor globally-inhospitable axonal environment but rather the local conditions of the lesion site.

Intraoperative monitoring of jugular bulb oxygen saturation in patients with moyamoya disease

The jugular bulb oxygen saturation (SjO2) and end-tidal carbon dioxide (ETCO2) were monitored continuously during surgery in six cases of Moyamoya disease who had demonstrated multiple episodes of transient ischemic attacks (TIAs) and/or fluctuating neurological deficits preoperatively. The arterial carbon dioxide tension (PaCO2) levels were also measured repeatedly at predetermined interval. In two cases (group H), the ETCO2 was controlled at hypercapnic levels during surgery (45.5 +/- 1.5 mmHg) and the remaining four (group N) were operated on in a normocapnic state (39.0 +/- 2.0 mmHg). The group H patients demonstrated high levels of SjO2 ranging from 72 to 85%, indicative of excessive hyperemia. One of the group H patients demonstrated mild and transient motor weakness postoperatively. The group N patients demonstrated normal levels of SjO2 ranging from 66 to 78%. All the patients in both groups demonstrated fluctuations in SjO2 levels in clear positive correlation with spontaneous changes in PaCO2 levels. The present findings indicated that: (1) Global carbon dioxide reactivity of cerebral perfusion is well preserved in patients with Moyamoya disease; and (2) hypercapnia in these patients often causes excessive hyperemia. The occurrence of postoperative neurological deficits in association with such an excessive hyperemia suggests that hyperapnia during surgery is not always beneficial. Intraoperative monitoring of SjO2 is useful for maintaining cerebral perfusion within the optimum range.

Transplantation of polymer-encapsulated fetal hippocampal cells into ischemic lesions of adult rat hippocampus

In a previous study we demonstrated that fetal hippocampal cells, when transplanted into ischemic lesions of the adult rat hippocampus, can survive in large numbers in the host brain and show the innervation of the transplants by cholinergic fibers originated from the host brain. The present study was undertaken in an attempt to elucidate the hypothesis that the fiber connections forming synapses between the transplanted fetal neurons and the host brain play an important role in the survival of the transplanted cells. We transplanted the polymer-encapsulated fetal hippocampal cells prepared from E17-18 rat fetuses into the ischemic lesions in the adult rat hippocampus at which the CA1 pyramidal cells selectively died, and examined both histochemically or immunohistochemically for their survival and the expression of the synaptic vesicle protein, synaptophysin, and dendritic cytoskeltal protein, microtubule-associated protein 2 (MAP 2) within them. In addition, the cholinergic fibers originated from the host brain were examined by acetylcholine esterase (AChE) histochemistry. The results demonstrated that the polymer-encapsulated hippocampal cells could survive in the brain; however, the number of surviving cells markedly decreased following the transplantation, whereas no host-derived cholinergic fibers penetrated the polymer membrane of the capsules following the transplantation. In the cluster of surviving cells, only slight synaptophysin expression and no extensive growth of the dendrites were detected. The present results indicate that the direct contact between the host brain tissue and the transplant play an important role in the survival of such allografted neurons.

Role of excitatory amino acid-mediated ionic fluxes in traumatic brain injury

One major event taking place at the moment of traumatic brain injury in neuronal cells is the occurrence of massive ionic fluxes across the plasma membrane, which can be referred to as traumatic depolarization (TD). Unlike spreading depression, TD can occur over wide brain areas simultaneously. Furthermore, recovery from TD often takes far longer than recovery from ionic perturbation elicited by the passage of a single wave of spreading depression. Neuronal cell damage caused by ischemic brain injury is also initiated by massive ionic fluxes, termed anoxic depolarization. The occurrence of similar ionic events in these two forms of brain injury may account for the genesis of diffuse ischemia-like damage without actual episodes of hypoxia or ischemia in traumatic brain injury. We review the data indicating that excitatory amino acids (EAA) may play a vital role in producing TD, and that such EAA-mediated ionic perturbation is responsible for a number of posttraumatic events including subcellular metabolic dysfunction and cellular responses such as microglial activation and astrocytic transformation. TD may represent one of the most important mechanisms of diffuse neuronal cell dysfunction and damage associated with traumatic brain injury.

The temporal and spatial activation of microglia in fiber tracts undergoing anterograde and retrograde degeneration following spinal cord lesion

The role of microglia in the response to CNS injury is not fully understood. We characterized the temporal activation of microglia in the adult spinal cord following a lesion that severed the axons of the dorsal columns and corticospinal tract at T8. Two days after lesion, microglia in the severed T4-T5 fasciculus (f.) gracilis were ameboid and expressed intense OX42 and increased class I major histocompatibility complex (MHC) antigen (OX18) immunoreactivities. No activated microglia were seen in the intact f. cuneatus or the corticospinal tract. Five days postlesion, OX42 immunoreactivity was slightly decreased in the f. gracilis, and OX18 expression was slightly enhanced. By 12 days postlesion, OX42 and OX18 immunoreactivities were near control levels. At L1-L2, activated microglia with increased OX18 expression were restricted to the corticospinal tract and were maximal 5 days postlesion, returning to near control levels by 12 days postlesion. In the medulla, enhanced OX42 and OX18 immunoreactivities were seen in the nucleus (n.) gracilis, but not the n. cuneatus, at 2 days postlesion. At 5 days postlesion, OX42 immunoreactivity was markedly decreased, but class I MHC antigen expression was still enhanced. GFAP immunoreactivity increased only in the n. gracilis and remained elevated 2-12 days postlesion. Microglial activation is an early lesion-induced event in the CNS, and activated microglia may play a role in mediating the regenerative capacity of injured CNS axons.

Altered acidic and basic fibroblast growth factor expression following spinal cord injury

In normal spinal cord, acidic fibroblast growth factor (aFGF) immunoreactivity was localized in the cytoplasm of ventral motor neurons and sensory fibers in the dorsal columns. Basic FGF (bFGF) immunoreactivity was restricted to astrocyte nuclei and the cytoplasm of a few neurons in the intermediate gray matter. Spinal cord lesions resulted in complete destruction of the dorsal columns at T8. Two days postlesion, aFGF immunoreactivity was increased in ventral motor neurons and was now seen in intermediate gray matter neurons. Acidic FGF was not detected in the lesioned fasciculus gracilis at T4-5, but markedly increased in the fasciculus cuneatus. At L1-2, aFGF-immunoreactive fibers in the fasciculus gracilis also increased. This aFGF immunostaining was maintained 5 and 12 days postlesion. A lesion-induced loss of aFGF immunoreactivity in the nucleus gracilis suggests that aFGF is anterogradely transported in ascending sensory fibers. Two days postlesion, glial fibrillary acidic protein immunoreactivity increased at the lesion site, as well as at T4-5 and L1-2, with no change in bFGF staining. Five days postlesion, increased bFGF immunoreactivity appeared at the edge of the cystic cavity and the dorsal columns at T4-5 in both the nucleus and the cytoplasm of reactive astrocytes, and was increased at 12 days postlesion. The differential cellular, temporal, and spatial expression of aFGF and bFGF following spinal cord lesion suggest they subserve distinct roles in the response to CNS injury.

Magnetic resonance imaging of xanthomatous meningioma

A case of meningioma with extensive xanthomatous metaplasia occurring in the left frontal convexity of a 37-year-old woman is reported. The tumour was demonstrated as a hypodense mass with minimal enhancement on CT. Our findings suggest that magnetic resonance imaging may provide a clue to the diagnosis of meningiomas with extensive xanthomatous metaplasia when CT is less specific.

Temporal pattern of survival and dendritic growth of fetal hippocampal cells transplanted into ischemic lesions of the adult rat hippocampus

Cell suspensions obtained from the fetal hippocampus were transplanted into the adult rat hippocampus at 1 or 4 weeks after transient forebrain ischemia. Only when the ischemia induced death of most of the CA1 pyramidal cells of the host hippocampus and transplantation was performed at 1 week after the ischemia, did a large number of transplanted cells survive and the most extensive dendritic growth was demonstrated by microtubule-associated protein 2 immunohistochemistry. The dendrites of the cells located in the ventral part were oriented ventrally, lining up similarly to the parallel arrangements of apical dendrites of normal CA1 pyramidal cells. These findings suggest that certain forms of trophic factors, which appear to occur in association with the presence of free terminals of afferent fibers during the earlier period after ischemic insult, are involved in the survival of and dendritic growth from transplanted hippocampal cells.

Survival and fibre outgrowth of neuronal cells transplanted into brain areas associated with interstitial oedema

The influence of interstitial oedema on the survival of fetal raphe cells transplanted into serotonin (5-HT)-denervated rats and the fibre outgrowth from these cells was investigated. Fetal raphe cells were transplanted into the corpus callosum in which long-lasting interstitial oedema had been induced by intracisternal kaolin injection. The 5-HT and 5HIAA levels in the corpus callosum were restored to their maximum within 5-6 weeks post-transplantation regardless of whether interstitial oedema was induced or not. Furthermore, it was appeared that the presence of interstitial oedema even facilitated fibre growth as demonstrated by the 5-HT immunohistochemistry and the restoration of the 5-HT and 5-HIAA levels in brain areas distant from the transplantation sites. These results imply favourable effects of interstitial oedema on the survival of transplanted raphe cells and their fibre outgrowth.