K. Shima

Mn-SOD and Bcl-2 Expression After Repeated Hyperbaric Oxygenation

To clarify the mechanism of ischemic tolerance induced by HBO, we investigated the effect of HBO on immunoreactivity to Bcl-2 and Bax, apoptosis-regulating protein, or Mn-SOD, a radical scavenging system, in the CA1 sector of the gerbil hippocampus. Pretreatment comprising, five sessions at 2 ATA (atmosphere absolute) every other day, but not that comprising, ten sessions at 3 ATA every day, caused significant increases in Bcl-2 and Mn-SOD immunoreactivity in the CA1 sector compared with in the sham pretreatment group. No significant differences in Bax immunoreactivity and neuronal density in the CA1 hippocampal neurons was observed between the groups. These results suggest that protection against mitochondrial alterations after ischemia through Mn-SOD and/or Bcl-2 expression is related to the ischemic tolerance induced by repeated HBO pre-treatment.

Alteration of gap junction proteins (connexins) following lateral fluid percussion injury in rats

Gap junctions are intercellular channels that mediate the cytoplasmic exchange of small hydrophilic molecules and are formed by a family of integral membrane proteins called connexins (Cxs). Cx43 is expressed predominantly in astrocytes, while Cx36 is expressed in neurons. In this study, we show alteration of Cx43 and Cx36 in the hippocampus after traumatic brain injury in rats. Adult male Sprague-Dawley rats were subjected to lateral fluid percussion injury of moderate severity. Brain coronal sections were used for immunohistochemistry with Cx43 and Cx36 antibodies. Cx43 immunoreactivity was increased in reactive astrocytes in the damaged hippocampus 24 hours after injury, and persisted for 72 hours. On the other hand, Cx36 immunoreactivity increased in CA3 neurons 1 hour after injury, and decreased later. These results indicate that gap junctions might participate in the pathophysiological process after traumatic brain injury.

Vascular endothelial growth factor expression in pituitary adenomas

Vascular endothelial growth factor (VEGF) is known to be a mediator of angiogenesis and vascular permeability. A cystic component and hemorrhage are often found in pituitary adenomas. In the present study we assess the VEGF expression based on immunohistochemical examinations in 48 pituitary adenomas. All the adenomas showed some VEGF immunoreactivity mainly in the cytoplasm of tumor cells. Of the 48 adenoma-cases, 16 cases had a strong VEGF immunoreactivity, 26 cases had a moderate one, and 6 cases had a weak one. On the MR images, a cystic component was found in 16 cases (33.3%), and a hemorrhage was found in 18 cases (37.5%). The VEGF immunoreactivity had a significant relationship with the cystic component but neither the hemorrhage, size, recurrence, or HE classification. These findings suggest that VEGF might play a potential role in the pathogenesis of cystic formation in pituitary adenomas.

Characteristic phosphorylation of the extracellular signal-regulated kinase pathway after kainate-induced seizures in the rat hippocampus

Extracellular signal-regulated kinase (ERK) pathways play a crucial role in cell growth and long-lasting neuronal plasticity. Several studies have shown that phosphorylated-ERK (p-ERK) significantly increases after kainic acid (KA) administration. However, little or no information is available about the spatial distribution of p-ERK after KA-induced seizures. We herein show that KA-induced seizures significantly increase p-ERK in both neurons and astrocytes in rat brain using Western blots and immunohistochemistry. A strong immunoreactivity for p-ERK was induced in the dentate hilar neurons and CA3 neurons 30 mins and 6 hrs after KA injection. In addition, immunoreactivity for p-ERK was seen in astrocytes 6 hrs after KA injection. 72 hrs after KA injection, all pyramidal neurons had died. These findings suggest that the ERK pathway participates in the KA-induced neurotoxicity in the rat hippocampus.

Hepatocyte growth factor reduces infarct volume after transient focal cerebral ischemia in rats.

Hepatocyte growth factor (HGF) was originally discovered as a powerful mitogen for hepatocytes. HGF functions both as a neurotrophic factor as well as an angiogenetic factor. Furthermore, HGF has an anti-apoptotic effect on vascular endothelial cells. The present study examined the neuroprotective effect of HGF after transient focal cerebral ischemia in rats, in which an anti-apoptotic and an angiogenetic effect of HGF was assumed to contribute to the reduction of the infarct volume. The intraventricular administration of human recombinant HGF (90 micrograms) significantly reduced the infarct volume after 120 minutes occlusion of both the right middle cerebral artery (MCA) and the bilateral common carotid arteries (CCAs). In a separate series of experiments, we investigated both the anti-apoptotic effect on neurons and the angiogenetic effect of HGF histopathologically. The number of survival neurons and vascular lumina in the HGF group were significantly higher than those in the vehicle group. A large number of TUNEL positive neurons were observed in the inner boundary of the infarct area in the vehicle group, whereas only a few TUNEL positive neurons were observed in a corresponding area in the HGF group. In the HGF group, Bcl-2 protein was obviously represented in survival neurons as well as in vascular endothelial cells and in glial cells subjected to ischemia. These data suggest that HGF prevents apoptotic neuronal cell death by upregulating the production of Bcl-2 protein and by an angiogenetic effect in the central nervous system which affected transient focal cerebral ischemia.

Pathophysiology and diagnosis of spontaneous intracranial hypotension.

BACKGROUND Spontaneous intracranial hypotension (SIH) has become a well-recognized syndrome. However, diagnosis of SIH is still challenging. The problem with SIH is that the precise mechanism of cerebrospinal fluid (CSF) leakage remains largely unknown and there is no definite diagnostic criterion in the imaging. METHODS The clinical findings of our ten cases and 301 literature reports on SIH were investigated in a retrospective analysis to clarify the pathophysiology of CSF leakage, correlate the findings of imaging studies and determine the most adequate diagnostic criteria. RESULTS The events precede symptoms of SIH were categorized as traumatic, secondary and strictly spontaneous (62%). The location of the spinal CSF leak remains undetectable in approximately 50% of cases reported. In 93% of patients, the CSF leakage sites were detected at the cervical or thoracic level of the spine. On recent MRI studies, 88% of patients showed spinal epidural fluid collections that most likely represent CSF leakage. MR myelography using heavily T2-weighted fast-spin-echo sequence can clearly demonstrate the site of CSF leakage. Although numerous treatment options are available, none of the treatments have been evaluated by randomized clinical trials. In 48% of papers, autologous epidural blood patch (EBP) was the treatment of choice in patients who have failed initial conservative management. Forty-nine percent of patients showed relief of symptoms after up to three repeated EBPs. CONCLUSION We propose new diagnostic criteria of SIH to avoid misdiagnosis.

A role of glial fibrillary acidic protein in hippocampal degeneration after cerebral trauma or kainate-induced seizure

Astrocytes perform a variety of functions in the adult central nervous system (CNS). Recent evidence suggests the robust upregulation of glial fibrillary acidic protein (GFAP) after CNS insult. However, little is known about the role of GFAP in the hippocampal degeneration after brain injury. We herein compared the GFAP knockout (KO) and wild type (WT) mice on the histological and behavioral outcome in response to cerebral trauma or kainic acid (KA)-induced seizure. Although all KO mice showed hippocampal CA3 neuronal degeneration. WT mice did not show any neuronal degeneration in CA3 subfield at 72 hrs after trauma. Thereafter, KO mice showed a higher susceptibility to KA-induced seizures and an increased number of pyknotic CA3 neurons 72 hrs after KA administration. These results indicate that GFAP plays a crucial role in the hippocampal neurodegeneration after CNS insult.

Evaluation of spontaneous intracranial hypotension: assessment on ICP monitoring and radiological imaging.

We describe two recent cases of spontaneous intracranial hypotension. A 38-year-old woman developed a severe postural headache. Magnetic resonance imaging (MRI) showed marked dural enhancement. Histopathological findings of dural biopsy showed numerous dilated vessels in the dura, rather than hypertrophic change. Lumber CSF pressure was 5 cmH 2 O and RI cisternography suggested CSF leakage. A 58-year-old woman with postural headache and vertigo had bilateral subdural haematoma associated with diffuse dural enhancement on MRI. Lumber CSF monitoring confirmed persistent low pressure ranging from 0‘5 cm H 2 O. MRI myelography revealed multiple CSF pouches along the whole spinal axis. CSF leakage was demonstrated on Radioisotope (RI) cisternography. Both cases described in this report were diagnosed as spontaneous intracranial hypotension caused by CSF leakage from spinal meningeal diverticula and were successfully treated by intravenous Factor XIII administration.

Blood-Brain Barrier, Cerebral Blood Flow, and Cerebral Plasma Volume Immediately After Head Injury in the Rat

The purpose of the present study was to determine blood-brain barrier (BBB) permeability, regional cerebral blood flow (rCBF) and regional cerebral plasma volume (rCPV) in the period immediately after head injury, and thereby to evaluate the effects of vascular factors in the pathophysiology of traumatic brain injury. Male Sprague-Dawley rats (350-450 g) anesthetized with 1.0-1.5% halothane were subjected to an impact acceleration closed head injury at the moderate level. BBB permeability (n = 5), rCBF (n = 8) and rCPV (n = 9) were measured by quantitative autoradiographic techniques using 14C-alpha-aminoisobutyric acid (AIB), 14C-iodoantipyrine and 14C-sucrose, respectively. Intravenous administration of each radiotracer was simultaneous with the traumatic impact. At 10 min after injury, BBB permeability, the transfer constant for AIB, was less than 0.1 ml/kg/min for all regions except for those with a relatively leaky BBB. At 30 s after injury, a significant and heterogeneous increase in rCBF was observed at 9 subcortical regions (p < 0.05). RCPV increased significantly in the frontal cortex, parietal cortex, thalamus, and hypothalamus (p < 0.05). In our closed head injury model without severe hypertension, BBB disruption did not occur immediately after trauma. Vascular responses in the period immediately after trauma may result from the derangement of cerebral autoregulation.

MRI analysis of hydrocephalus associated with acoustic neurinoma.

We investigated the hydrocephalus in 24 patients associated with acoustic neurinoma. We found the high incidence of homo-lateral ventricular dilatation to the side of the acoustic neurinoma. Utilizing magnetic resonance imaging, the diameter of the tumor parallel to the pyramidal bone, diameter of the tumor perpendicular to the pyramidal bone, grade of the 4th ventricle deviation, and the shape of the tumor (round or oval) were analyzed. Ten (42%) of the 24 patients with acoustic neurinoma were found to have hydrocephalus. Seven (70%) of the 10 patients with hydrocephalus exhibited asymmetrical lateral ventricle dilatation: in all cases the lateral ventricle in the hemisphere homolateral to the acoustic neurinoma was larger than that of the contralateral side. The hydrocephalus was not related to the grade of the 4th ventricle deviation but rather to the diameter of the tumor parallel to the pyramidal bone (p < 0.01). The diameter of the tumor parallel to the pyramidal bone was also related to the asymmetrical lateral ventricular dilatation (p < 0.05).