Time-dependent increase in basic fibroblast growth factor protein in limbic regions following electroshock seizures.

Brief experimentally induced seizures have been shown to increase the expression of mRNA encoding basic fibroblast growth factor (FGF-2) in specific brain regions. However, the extent to which this change in mRNA affects the expression of FGF-2 protein in these brain regions has not been examined. In the present study, we exposed rats to brief non-injurious seizures to determine whether this treatment would lead to an increase in FGF-2 protein expression in selected brain regions. Because initial results indicated that the elevation of FGF-2 protein was not significant following acute seizure exposure, we examined both acute and chronic seizure treatment to determine whether FGF-2 protein expression could be increased under conditions of repeated seizures. Brief limbic seizures were induced by minimal electroconvulsive shock (ECS) given as daily treatments for 1 (acute) or 7 (chronic) days. FGF-2 protein was measured in hippocampus, rhinal cortex, frontal cortex, and olfactory bulb at 20, 48, and 72 h following the last seizure. No significant increases in FGF-2 protein were observed in any region following acute ECS. In the chronic ECS-treated groups, significantly elevated FGF-2-like immunoreactivity was found in the frontal and rhinal cortex as compared with the same regions from both control and acute ECS animals. Increases after chronic ECS were maximal at 20 h, and remained significantly elevated as long as 72 h. These increases were predominantly observed for the 24-kDa and 22/22.5-kDa FGF-2 isoforms. Because chronic ECS, which has been shown to be protective against neuronal cell death, induced significantly more FGF-2 immunoreactivity than did acute ECS, we suggest that FGF-2 expression may be an important substrate for the neuroprotective action of non-injurious seizures. A prolonged induction of the high molecular weight isoforms of FGF-2, as occurs after chronic ECS, may selectively reduce the vulnerability of certain brain regions to a variety of neurodegenerative insults.

Use of a portable CT scanner during resection of subcortical supratentorial astrocytomas of childhood.

The development of intraoperative imaging has made it possible to visualize shifting brain structures during surgery, and may allow greater intraoperative discrimination of normal and abnormal tissue. This may provide greater confidence to the neurosurgeon to proceed with a more extensive resection while decreasing postoperative morbidity. We investigated the intraoperative use of a portable CT scanner in the resection of 4 cases of supratentorial, subcortical astrocytomas of childhood to assess its usefulness in determining the endpoint of the dissection. We operated on 4 patients, ages 3-17, with astrocytomas. Three were thalamic, and 1 was based primarily in the caudate nucleus. The approach to the basal ganglia was transcallosal in 3 and transtemporal in 1. Specific observations on the intraoperative use of the portable CT scanner included its overall facility, any additional operative time required, the overall quality of the images, intraoperative decisions made based on the images and problems associated with its use. These observations are presented with a review of intraoperative imaging as it pertains to deep pediatric brain tumors. The CT scanner was helpful in limiting the dissection of the hypothalamic and midbrain regions and in localizing remaining abnormal tissue. The scans allowed informed decisions about leaving margins of the tumor which were adjacent to vital structures, but dit not prove to be a decisive factor in providing a complete resection. The following observations are worth noting: (1) average imaging time was 20 min per scan; (2) the extent and location of residual enhancing tumor was easily identified despite other materials in the surgical bed; (3) air/tissue interfaces limit resolution; (4) tumors retain contrast long enough to obtain multiple scans without additional dye, and (5) the cost profile of a mobile CT scanner is superior to that of a fixed intraoperative CT scanner.

Seroprevalence of hepatitis B and hepatitis C among rural emergency medical care personnel.

To identify the prevalence of serologic markers of hepatitis B and hepatitis C among rural prehospital providers, a prospective descriptive study was conducted of a rural county emergency medical services (EMS) system. Participants included 107 prehospital care providers: 102 EMT-Bs, 1 paramedic, and 4 law enforcement first responders. Blood samples taken from prehospital care providers were tested for hepatitis B surface antigen (HBsAg), antibody to HBsAg (HBsAb), antibody to hepatitis B core antigen (HBcAb), and antibody to hepatitis C (anti-HC). The 107 providers had a total of 635 years of EMS experience (5.93 years per subject). Three providers (3%) had received previous blood transfusions, 7 (7%) had worked in a metropolitan area, and 6 (6%) had multiple sexual partners prior to the study. No provider reported intravenous drug use or known homosexual or bisexual contact. Only one sample tested positive for hepatitis C antibody (anti-HC) and hepatitis surface antibody (HBsAb). Rural prehospital care personnel have a low prevalence (0.9%) of exposure to hepatitis B and hepatitis C. Despite this fact, continued vigilance should be maintained in preventing transmission of bloodborne illnesses.

The effects in vivo of hypoxia on brain injury.

To separately analyze the hypoxic component of hypoxic-ischemic encephalopathy, rats were prepared such that their paO2 was maintained at 20 mmHg while maintaining systemic arterial pressures. During the 20-min experiment, brain oxygen concentration and extracellular amino acid concentrations were monitored. At sacrifice, the brains were studied for morphologic evidence of injury by immunocytochemical staining for the non-constitutive stress protein HSP-72 or neuronal death by acid fuchsin staining. Oxygenated rats subjected to global ischemia were prepared for comparison. In these experiment, hypoxia resulted in no increase in extracellular glutamate concentration, and no morphologic injury was detected. Thus, hypoxia without ischemia is well tolerated by brain.

Mutations associated with amyotrophic lateral sclerosis convert superoxide dismutase from an antiapoptotic gene to a proapoptotic gene: studies in yeast and neural cells.

Familial amyotrophic lateral sclerosis (FALS) is associated with mutations in SOD1, the gene encoding copper/zinc superoxide dismutase (CuZnSOD). However, the mechanism by which these mutations lead to amyotrophic lateral sclerosis is unknown. We report that FALS mutant SODs expressed in yeast lacking CuZnSOD are enzymatically active and restore the yeast to the wild-type phenotype. In mammalian neural cells, the overexpression of wild-type SOD1 inhibits apoptosis induced by serum and growth factor withdrawal or calcium ionophore. In contrast, FALS-associated SOD1 mutants promote, rather than inhibit, neural apoptosis, in a dominant fashion, despite the fact that these mutants retain enzymatic SOD activity both in yeast and in mammalian neural cells. The results dissociate the SOD activity of FALS-associated mutants from the induction of neural cell death, suggesting that FALS associated with mutations in SOD1 may not be simply the result of a decrease in the enzymatic function of CuZnSOD. Furthermore, the results provide an in vitro model that may help to define the mechanism by which FALS-associated SOD1 mutations lead to neural cell death.

Increased expression of mRNA encoding calbindin-D28K, the glucose-regulated proteins, or the 72 kDa heat-shock protein in three models of acute CNS injury.

Changes at the level of gene expression are becoming an increasingly recognized component of the neuronal response to injury. We used Northern analysis and three in vivo models of central nervous system (CNS) injury in the rat to determine whether injury alters the expression of certain gene products related to cellular homeostasis. The three models included kainate (KA)-induced seizures, global ischemia, and lateral fluid percussion injury to the cerebral cortex. Animals were sacrificed at various times after injury, and total RNA was isolated from specific brain regions. Northern blots were hybridized with probes for calbindin-D28K, the 78 and 94 kDa glucose-regulated proteins (grp78, grp94), the inducible 72 kDa heat-shock protein (hsp72), and a control probe for the 18S ribosomal subunit. Results showed that mRNA for calbindin-D28K, grp78, and hsp72 increased in the hippocampus following seizures. Peak expression occurred 6-12 h after administration of KA, and returned towards baseline in most cases by 24 h. Changes in all four transcripts were seen in the hippocampus or cortex following global ischemia, although the return to baseline tended to exceed 24 h for the grps. In the trauma model, mRNA for hsp72 was increased in the cortex ipsilateral to the impact 12 h after injury. These results expand the repertoire of known changes in mRNA expression following CNS injury. The increases in hsp72 and grps indicate the occurrence of a generalized stress response. Furthermore, given the evidence that grp78 and grp94 are induced by calcium ionophores in vitro, and the potential role of calbindin-D28K in buffering cytoplasmic calcium, the changes observed in this study may represent a cellular response to perturbed calcium homeostasis that is known to occur in acute CNS injury.

Brain acidosis induced by hypercarbic ventilation attenuates focal ischemic injury.

Intracellular calcium toxicity appears to play a major role in cell death during cerebral ischemia. Such calcium enters the cell mainly through the N-methyl-D-aspartate subclass of the postsynaptic glutamate receptor. Increased extracellular hydrogen ion concentration has been shown recently to reduce N-methyl-D-aspartate-activated divalent cation currents. Therefore, we studied the effect of induced brain acidosis, via hypercarbic ventilation, as a potential therapeutic modality in focal cerebral ischemia. Brain acidosis reduced infarct volume in a biphasic manner, with maximal protection at approximately brain pH 6.8. The effect was lost at pH 6.5, presumably due to the effect of acidosis on glial glutamate uptake.

Prior ischemic stress protects against experimental stroke.

We studied the possible role of prior ischemic stress as a protective mechanism against cerebral infarction in rats. Two brief periods of global cerebral ischemia, separated by 24 h, did not cause cell death in brain, but did produce neuronal stress, as demonstrated by induction of the nonconstitutive 72 kDa heat shock protein (HSP72). Forty-eight hours later, animals subjected to prior ischemia had smaller infarct from permanent middle cerebral artery occlusion than did sham-operated controls. These findings support an association between ischemia-induced stress, HSP72 induction, and attenuation of injury from subsequent focal cerebral ischemia.

Reduction of glutamate release and protection against ischemic brain damage by BW 1003C87.

BW 1003C87, 5-(2,3,5-trichlorophenyl)-2,4-diaminopyrimidine ethane sulphonic acid, has been tested for its in vitro and in vivo effects on glutamate release in rat brain tissue, and for its cerebro-protective action in two rodent models of cerebral ischemia. In rat brain slices the release of glutamate evoked by veratrine is inhibited by BW 1003C87 (IC50 = 1.6 microM). In anaesthetised rats with microdialysis probes implanted in the dorsal hippocampus the increase in extracellular glutamate evoked by veratrine is markedly reduced by co-infusion of BW 1003C87, 100 microM. In anaesthetised rats with microdialysis probes implanted in the cortex and the caudate nucleus ipsilateral to a middle cerebral artery (MCA) occlusion the increase in dialysate glutamate concentration seen in the first 2 h following MCA occlusion is markedly attenuated by the prior administration of BW 1003C87, 20 mg/kg i.v. In rats subjected to 10 min of bilateral common carotid artery occlusion the loss of CA1 pyramidal neurons (assessed 7 days later) is reduced by administration of BW 1003C87 (20 mg/kg i.v., at the time of ischemia and 4 h later). The volume of cortex showing infarction 72 h after unilateral MCA occlusion is reduced by treatment with BW 1003C87 (20 mg/kg, i.v., beginning 5 min after occlusion). Inhibition of glutamate release may provide a therapeutic approach in cerebral ischemia as well as in epilepsy.

The temporal profile of 72-kDa heat-shock protein expression following global ischemia.

The potential role of the nonconstitutive 72-kDa heat-shock protein (HSP72) in selective neuronal vulnerability to ischemia was studied in rats subjected to graded global ischemia. Immunocytochemistry using a monoclonal antibody against HSP72 was performed on tissue collected after 24 hr of reperfusion. The appearance of HSP72 immunoreactivity correlated in a graded fashion with those regions known to be selectively vulnerable in ischemia. That is, HSP72 was induced in only hilar interneurons and CA1 pyramidal cells following brief ischemia. After intermediate durations of ischemia, HSP72 was expressed in the CA3 neurons and cortical layers 3 and 5, and after the longest intervals, HSP72 appeared in dentate granule cells. Heat-shock protein expression preceded cell death (assessed with acid fuchsin staining) in all regions. This temporal profile suggests that the capability of neurons to express HSP72 is unlikely to account for selective vulnerability of different brain regions following ischemia; its role in neuroprotection during ischemic injury in vivo remains unknown.