Is Mini Beam Ready for Human Trials? Results of Randomized Study of Treating De-Novo Brain Tumors in Canines Using Linear Accelerator Generated Mini Beams.

The main challenge in treating malignant brain neoplasms lies in eradicating the tumor while minimizing treatment-related damage. Conventional radiation treatments are associated with considerable side effects. Synchrotron generated micro-beam radiation (SMBRT) has shown to preserve brain architecture while killing tumor cells, however physical characteristics and limited facility access restrict its use. We have created a new clinical device which produces mini beams on a linear accelerator, to provide a new type of treatment called mini-beam radiation therapy (MBRT). The objective of this study is to compare the treatment outcomes of linear accelerator based MBRT versus standard radiation treatment (SRT), to evaluate the tumor response and the treatment-related changes in the normal brain with respect to each treatment type. Pet dogs with de-novo brain tumors were accrued for treatment. Dogs were randomized between standard fractionated stereotactic (9 Gy in 3 fractions) radiation treatment vs. a single fraction of MBRT (26 Gy mean dose). Dogs were monitored after treatment for clinical assessment and imaging. When the dogs were euthanized, a veterinary pathologist assessed the radiation changes and tumor response. We accrued 16 dogs, 8 dogs in each treatment arm. In the MBRT arm, 71% dogs achieved complete pathological remission. The radiation-related changes were all confined to the target region. Structural damage was not observed in the beam path outside of the target region. In contrast, none of the dogs in control group achieved remission and the treatment related damage was more extensive. Therapeutic superiority was observed with MBRT, including both tumor control and the normal structural preservation. The MBRT findings are suggestive of an immune related mechanism which is absent in standard treatment. These findings together with the widespread availability of clinical linear accelerators make MBRT a promising research topic to explore further treatment and clinical trial opportunities.

Neurologic immune reconstitution inflammatory syndrome in HIV/AIDS: outcome and epidemiology.

OBJECTIVE: To characterize the immune reconstitution inflammatory syndrome in the nervous system (NeuroIRIS) among patients with HIV/AIDS. BACKGROUND: NeuroIRIS has been recognized as a complication of combination antiretroviral therapy (cART). METHODS: A retrospective analysis was performed of NeuroIRIS patients fulfilling diagnostic criteria and followed at the Northern or Southern Alberta (HIV) Clinics. A nested epidemiologic study was performed within a subset of patients in whom cART was started from 1999 to 2007. RESULTS: NeuroIRIS was diagnosed in seven patients initiating cART. All were men (median age, 35 years) and exhibited severe immunosuppression (median CD4(+) T cells, 30 cells/mm(3)). Four patients presented to the Southern Alberta Clinic, representing all NeuroIRIS cases among 461 patients in whom cART was initiated over an 8-year period (incidence 0.9%). New onset of neurologic deterioration (n = 4) or worsening of prior neurologic disabilities (n = 3) due to progressive multifocal leukoencephalopathy, toxoplasmic encephalitis, and cryptococcal meningitis occurred between 2 to 25 weeks after the initiation of cART. All patients demonstrated a robust increase in blood CD4(+) T-cell count in response to cART. A brain biopsy in one patient revealed inflammation and necrosis together with CD68(+) macrophage and CD8(+) T-cell infiltrates, which were also CD40 and CD154 immunoreactive. Two patients received corticosteroids as treatment for NeuroIRIS with an overall survival of 86%, while 14% exhibited fixed neurologic disabilities. CONCLUSIONS: Immune reconstitution inflammatory syndrome in the nervous system (NeuroIRIS) remains an uncommon complication of combination antiretroviral therapy (cART) but with a potentially poor outcome. Initiation of cART in very immunosuppressed patients requires close monitoring to manage NeuroIRIS in an expedient manner.

Subcortical middle cerebral artery ischemia abolishes the digit flexion and closing used for grasping in rat skilled reaching.

That rats reach for and grasp a food item using a single paw has prompted their use in neurobiological studies of skilled movements and modeling neural injury including middle cerebral artery stroke. Although motor system lesions have been shown to disrupt various qualitative aspects of the transport of a limb to a food target and withdrawal of the limb with the food, no lesion has been found to abolish digit flexion for grasping. Here, rats received unilateral transient middle cerebral artery ischemia that was restricted mainly to subcortical tissue of the forebrain (caudate-putamen, globus pallidus, and associated fibers) or a sham operation. Both paws were later trained and evaluated on skilled reaching using a rating scale for digit use. Middle cerebral artery rats did not flex and close their digits to grasp food when using their contralateral-to-lesion limb. The grasp impairment was not due to a failure to learn the task as middle cerebral artery rats used the ipsilateral limb as successfully as control rats and they were reinforced for reaching by raking food into the reaching box using an open paw. The impairment was also not due to an inability to move the digits, as they were flexed and closed in other phases of the reach. The paradigm should prove useful for further studies of rehabilitation in relation to the idea that digit closure may be controlled by the joint action of a number of neural systems that converge in the basal ganglia.

Embryonic intermediate filament, nestin, expression following traumatic spinal cord injury in adult rats.

Precursor cells in the ependyma of the lateral ventricles of adult mammalian brain have been reported in brain, and also in the spinal cord. The present study used antibody to the intermediate filament protein (nestin) as an immunohistochemical marker for neural stem cells and precursor cells in a rat model of spinal cord trauma. Male Sprague-Dawley rats (n=25) had a laminectomy at Thll-Thl2, and spinal cord contusion was created by compression with 30 g of force for 10 min. The rats were killed at 24 h, 1 week and 4 weeks after injury, and four levels of the spinal cord were examined: 5 mm and 10 mm, both rostral and caudal region to the injury center. Time- and region-dependent alterations of nestin immunoreactivity were analyzed. Revealed at 24 h post-injury, 5 mm rostral and caudal to the lesions, nestin expression was observed in ependymal cells and around the hemorrhagic and necrotic lesion located in dorsal spinal cord, peaking at 1 week after injury. Moreover, nestin expression was also observed in the white matter of ventral spinal cord, extending into arborizing processes centripetally from the pial surface toward the central canal. At 4 weeks after injury, nestin expression in ependyma decreased 10 mm from the injury site. But nestin expression in white matter increased dramatically with a 100-fold increase in nestin originating from the pial surface, and extension now to all the white matter. The latter was accompanied by glial fibrillary acidic protein positivity into very long arborizing processes, morphologically compatible with radial glia. The findings suggest two possible sources of precursor cells in adult mammalian spinal cord; ependyma of the central canal and subpial astrocytes. Subpial astrocytes may be associated with neural repair and regeneration after spinal cord injury.

Encephalopathy with staphylococcal endocarditis: multiple neuropathological findings.

BACKGROUND: Infective endocarditis is associated with serious neurological sequelae. OBJECTIVE: Here, we report a patient with Staphylococcus aureus endocarditis, secondary to congenital heart disease, with subacute onset of multiple neurological complications. RESULTS: Despite prompt antibiotic treatment with rapid sterilization of blood cultures, the patient died with brain herniation within 96 hours of admission. Neuropathological examination showed intraparenchymal hemorrhages, mycotic aneurysms, micro-abscesses and septic arteritis with accompanying infarction. Immunocytochemical studies revealed enhanced CD45 and GFAP immunoreactivity, together with adenosine A1 receptor detection on macrophages and microglia. CONCLUSIONS: Infective endocarditis is associated with multiple neuropathological lesions, which may contribute to its poor clinical outcome and activation of cells of monocyte-microglial lineage throughout the brain.

Non-pharmacologic (physiologic) neuroprotection in the treatment of brain ischemia.

Clinical trials for ischemic stroke have been characterized by a disappointing series of negative results, using a panoply of pharmacologic agents. This paper emphasizes five physiologic measures that can be taken to mitigate ischemic brain damage. These are (1) hypothermia, (2) insulin, (3) arterial hyperoxemia, (4) blood pressure control and (5) magnesium. Hypothermia is protective in both focal and global ischemia, even postischemically protecting against selective neuronal necrosis and infarction. The total equation for protection includes the (i) postischemic delay, (ii) depth, and (iii) duration of hypothermia. Insulin operates by lowering glucose levels to the normal range in focal ischemia. It is possible that very low glucose levels are detrimental in focal ischemia with paradoxical augmentation of the infarct size, and that spreading depression plays a role in this. Controlled arterial hyperoxemia seems effective experimentally in reducing infarct size, operating mechanistically by either a direct effect of oxygen, or vasoconstriction causing shunting of blood into the infarct, or both. Blood pressure is a critical determinant of infarct size, and raising blood pressure improves collateral blood flow and reduces stroke size. To be used clinically, however, hemorrhage must be ruled out. The most dramatic clinical effects of blood pressure are seen in aneurysm patients with vasospasm, where minor increases in blood pressure reverse temporary hemiparesis by reducing ischemia. Magnesium is likely the safest NMDA antagonist, with a long history of safe administration to pregnant women with eclampsia. There is potential interaction with insulin, in that magnesium causes hyperglycemia, which requires insulin to counteract it. Magnesium and insulin together have been shown effective in experimental brain ischemia. In the absence of safe and effective pharmacologic neuroprotection agents, clinical trials should be designed and launched to test these physiologic measures, singly and in combination, to reduce brain damage after ischemia.

Understanding and managing ischemic stroke.

Transient or permanent focal brain injury following acute thromboembolic occlusion develops from a complex cascade of pathophysiological events. The processes of excitotoxicity, peri-infarct depolarisation, inflammation, and apoptosis within the ischemic penumbra are proposed. While the translation of therapeutic agents from the animal models to human clinical trials have been disappointing, there remains an atmosphere of optimism as a result of the development of new diagnostic and therapeutic approaches, which include physiological, as opposed to pharmacological, intervention. This article provides an insight into the understanding of cerebral ischemia, together with current and future treatment strategies.

Hypoxia, hyperoxia, ischemia, and brain necrosis.

BACKGROUND: Human brains show widespread necrosis when death occurs after coma due to cardiac arrest, but not after hypoxic coma. It is unclear whether hypoxia alone can cause brain damage without ischemia. The relationship of blood oxygenation and vascular occlusion to brain necrosis is also incompletely defined. METHODS: We used physiologically monitored Wistar rats to explore the relationship among arterial blood oxygen levels, ischemia, and brain necrosis. Hypoxia alone (PaO2 = 25 mm Hg), even at a blood pressure (BP) of 30 mm Hg for 15 minutes, yielded no necrotic neurons. Ischemia alone (unilateral carotid ligation) caused necrosis in 4 of 12 rats, despite a PaO2 > 100 mm Hg. To reveal interactive effects of hypoxia and ischemia, groups were studied with finely graded levels of hypoxia at a fixed BP, and with controlled variation in BP at fixed PaO2. In separate series, focal ischemic stroke was mimicked with transient middle cerebral artery (MCA) occlusion, and the effect of low, normal, and high PaO2 was studied. RESULTS: Quantitated neuropathology worsened with every 10 mm Hg decrement in BP, but the effect of altering PaO2 by 10 mm Hg was not as great, nor as consistent. Autoradiographic study of cerebral blood flow with 14C-iodoantipyrine revealed no hypoxic vasodilatation during ischemia. In the MCA occlusion model, milder hypoxia than in the first series (PaO2 = 46.5 +/- 1.4 mm Hg) exacerbated necrosis to 24.3 +/- 4.7% of the hemisphere from 16.6 +/- 7.0% with normoxia (PaO2 = 120.5 +/- 4.1 mm Hg), whereas hyperoxia (PaO2 = 213.9 +/- 5.8 mm Hg) mitigated hemispheric damage to 7.50 +/- 1.86%. Cortical damage was strikingly sensitive to arterial PaO2, being 12.8 +/- 3.1% of the hemisphere with hypoxia, 7.97 +/-4.63% with normoxia, and only 0.3 +/- 0.2% of the hemisphere with hyperoxia (p < 0.01), and necrosis being eliminated completely in 8 of 10 animals. CONCLUSIONS: Hypoxia without ischemia does not cause brain necrosis but hypoxia exacerbates ischemic necrosis. Hyperoxia potently mitigates brain damage in this MCA occlusion model, especially in neocortex.

Electron microscopic evidence against apoptosis as the mechanism of neuronal death in global ischemia.

It has been repeatedly claimed that neuronal death in the hippocampal CA1 sector after untreated global ischemia occurs via apoptosis. This is based largely on DNA laddering, nick end labeling, and light microscopy. Delineation of apoptosis requires fine structural examination to detect morphological events of cell death. We studied the light and ultrastructural characteristics of CA1 injury after 5 min of untreated global ischemia in gerbils. To increase the likelihood of apoptosis, some ischemic gerbils were subjected to delayed postischemic hypothermia, a treatment that mitigates injury and delays the death of some neurons. In these gerbils, 2 d of mild hypothermia was initiated 1, 6, or 12 hr after ischemia, and gerbils were killed 4, 14, or 60 d later. Ischemia without subsequent cooling killed 96% of CA1 neurons by day 4, whereas all hypothermia-treated groups had significantly reduced injury at all survival times (2-67% loss). Electron microscopy of ischemic neurons with or without postischemic hypothermia revealed features of necrotic, not apoptotic, neuronal death even in cells that died 2 months after ischemia. Dilated organelles and intranuclear vacuoles preceded necrosis. Unique to the hypothermia-treated ischemic groups, some salvaged neurons were persistently abnormal and showed accumulation of unusual, morphologically complex secondary lysosomes. These indicate selective mitochondrial injury, because they were closely associated with normal and degenerate mitochondria, and transitional forms between mitochondria and lysosomes occurred. The results show that untreated global ischemic injury has necrotic, not apoptotic, morphology but do not rule out programmed biochemical events of the apoptotic pathway occurring before neuronal necrosis.

The effects of temperature and scopolamine on N-methyl-D-aspartate antagonist-induced neuronal necrosis in the rat.

The effects of temperature and scopolamine on dizocilpine maleate-induced neuronal necrosis in the rat cingulate/retrosplenial cortex, entorhinal/olfactory cortices and the dentate gyrus were studied. Mild, protracted hypothermia (48 h at a brain temperature of 34 degrees C), induced by a servo-controlled "exposure technique" in the awake female rat, significantly reduced dizocilpine maleate (5.0 mg/kg, i.p.)-induced neuronal death in the cingulate/retrosplenial and entorhinal/olfactory cortices seven days following drug administration. Scopolamine (0.25 mg/kg, i.p.), putatively neuroprotective [Olney J. W. et al. (1991) Science 254, 1515-1518], did not reduce injury in the cingulate/retrosplenial cortex of female rats following one injection, but did following two and three doses. Scopolamine had no significant effect in the other brain regions. A temperature elevation of only 1 degree C above baseline for 48 h in awake female rats increased dizocilpine maleate-induced damage. Finally, the sex differences in N-methyl-D-aspartate antagonist toxicity were replicated and extended to other structures, and found not to be due to temperature differences. Our data show that dizocilpine maleate neurotoxicity is temperature sensitive. Scopolamine treatment needed to be prolonged in order to reduce injury, and even then was only efficacious in one of three brain regions. The results underscore the importance of using neuronal necrosis in several brain regions as the endpoint and for the use of prolonged therapeutic interventions. Furthermore, given the potential hypothermic action of other putative neuroprotective drugs, a mechanistic re-evaluation of N-methyl-D-aspartate antagonist-induced injury is needed, with precise brain temperature measurement.

Characterization of postischemic behavioral deficits in gerbils with and without hypothermic neuroprotection.

Five minutes of global ischemia in gerbil results in delayed hippocampal CA1 neuronal degeneration, which is accompanied by working memory impairments and hyperactivity in novel environments. In this study, postischemic activity was characterized in familiar and in novel environments to determine whether hyperactivity was due to impaired spatial habituation or another form of motor hyperactivity. This study also determined whether 6-h delayed hypothermia, which reduces CA1 neuronal injury, would attenuate functional impairments. Gerbils were subjected to 5 min of normothermic ischemia or sham operation 2 days following implantation of brain temperature probes. One of two ischemic groups was cooled (>48 h) starting at 6-h postischemia. Locomotor activity in a familiar cage was measured for 6 days while activity in three novel environments was intermittently measured on days 4, 5 and 6. Open field behavior and working memory in a T-maze were also assessed. Untreated ischemia caused marked hyperactivity in the familiar cage on day 1, which reverted to near-normal by day 2. Nonetheless, these gerbils showed hyperactivity during novel environment sessions on days 4-6. This maze behavior, which predicted hippocampal CA1 injury, was not due to different habituation rates nor baseline hyperactivity. Conversely, open field sessions on day 8 revealed ischemic habituation rate deficits. Ischemia also impaired working memory in the T-maze. Delayed hypothermia, which reduced neuronal loss in the CA1 sector to 12% from 81%, reduced all functional impairments. Ischemic gerbils quickly developed spontaneous locomotion hyperactivity that returned to near-normal after 1 day. This motor hyperactivity did not explain the elevated activity found with delayed testing in novel environments. Regardless, only the open field test on day 8 revealed a habituation-like deficit.

Insulin, blood glucose levels, and ischemic brain damage.

Intensive efforts are presently directed toward developing pharmacologic therapy to protect the ischemic brain. Preclinical data from animal models indicate that insulin, already available for human use, may reduce damage in both global and focal ischemia. Two kinds of mechanisms may be involved: one in which insulin interacts directly with brain tissue and one in which insulin acts indirectly by reducing peripheral blood glucose levels. Animal data indicate that part of the former, direct mechanism is mediated by insulin-like growth factor-1 receptors. The direct effect appears to predominate in global ischemia. In focal ischemia, unlike global ischemia, the effect of insulin is predominantly via peripheral hypoglycemia, because neuroprotection is largely annulled by co-administration of glucose. The two clinical counterparts of global and focal ischemic models are, respectively, cardiac arrest encephalopathy and focal ischemic stroke. Insulin use in both of these clinical situations could be evaluated in clinical trials that attempt to reduce ischemic brain damage, because insulin has a long and safe history of human use in diabetes treatment.

Behavioral testing does not exacerbate ischemic CA1 damage in gerbils.

BACKGROUND AND PURPOSE: Previous research studying ablative lesions has suggested that functional use may exacerbate brain injury. If true, this would have considerable ramifications not only for the mechanistic understanding of neuronal injury but also for the clinical use of physiotherapy. In this report the hypothesis that behavioral use of brain tissue exacerbates ischemic hippocampal injury was tested. METHODS: Gerbils were subjected to sham operation or 5 minutes of normothermic ischemia. To produce borderline hippocampal CA1 injury and enhance susceptibility to exacerbation, 2 of 3 ischemic groups were cooled (>48 hours) beginning at 6 hours after ischemia. Increased use of the hippocampus was produced by a battery of tests involving 3 novel small mazes, a T maze, and an open field. One hypothermic group was not tested and served as a control. RESULTS: Behavioral testing failed to worsen ischemic damage since neuronal loss in the behaviorally tested and untested hypothermic groups was 12% and 8%, respectively, while that in the untreated ischemic group was 81% at a 1-month survival. Accordingly, protected CA1 cells tolerated the neuronal activity associated with behavioral testing. Concomitant with marked CA1 neuroprotection, a significant reduction in behavioral deficits with the hypothermic treatment was observed. Importantly, behavioral testing was found to transiently elevate brain temperature. CONCLUSIONS: CA1 neuronal survival was unaffected by behavioral testing or the associated mild fever. Hypothermia delayed for 6 hours provided sustainable CA1 neuroprotection.

Metastatic dermatofibrosarcoma protuberans mimicking meningioma.

Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive fibrohistiocytic tumor of intermediate malignancy with potential for local recurrences and with a small, but well recognized risk of distant metastases. We report a case of a 43-year-old Filipino male with an otherwise typical cutaneous DFSP followed 4 years later by a local recurrence of tumor with subsequent pulmonary metastasis at year 5, and 3 sequential central nervous system (CNS) metastases at years 5, 6, and 12 following the original diagnosis of DFSP. Recurrent and metastatic tumors showed areas of fibrosarcomatous change, high cellularity, high mitotic rate (10 - 15 per 10 high power fields), loss of CD34 expression, and aneuploidy. DFSP has not been previously reported to metastasize to the CNS. In addition, we report complex karyotypic aberrations within the metastasis, which have not been previously associated with DFSP. The dural-based location of the intracranial metastasis, together with the light- and electron-microscopic appearance, could cause diagnostic confusion with an anaplastic syncytial meningioma.

Molecular cloning of a novel potassium-dependent sodium-calcium exchanger from rat brain.

We have isolated a novel cDNA clone from rat cerebral cortex encoding a protein of 670 amino acids (NCKX2) that has significant similarity to the 1199-amino acid-long Na/Ca-K exchanger of bovine rod outer segment (NCKX1). NCKX2 transcripts are 10.5 kilobase pairs in length and are expressed abundantly in neurons throughout the brain and with much lower abundance in selected other tissues. The predicted topology of the rat NCKX2 protein is very similar to that of bovine NCKX1, beginning with a solitary transmembrane segment (M0), which is removed as a "signal peptide" in bovine NCKX1, an extracellular loop, a cluster of five transmembrane spanning segments (M1 to M5), a long cytoplasmic loop, and a final hydrophobic cluster (M6 to M11). Within the hydrophobic clusters, rat NCKX2 shares 80% identity and 91% similarity with bovine NCKX1. The two larger hydrophilic loops are much shorter in NCKX2 than in NCKX1, accounting largely for the difference in length between the two proteins, and are dissimilar in sequence except for a 32-amino acid stretch with 69% identity in the cytosolic loop. NCKX2 was epitope-tagged in the extracellular domain and was shown to be expressed at the surface of transfected HEK cells. Analysis of NCKX2 function by fluorescent imaging of fura-2-loaded transfected cells demonstrated that NCKX2 is a potassium-dependent sodium/calcium exchanger.

Structural neurotoxicologic investigation of the glycine antagonist 5-nitro-6,7-dichloroquinoxalinedione (ACEA-1021).

NMDA antagonists of glutamate have psychotomimetic side effects and structural side effects which have been shown to be lethal to CNS neurons in the cingulate and retrosplenial cortex of rodents, yet these compounds may reduce focal ischemic brain damage. This investigation used 38 Wistar rats to determine whether the structural toxicologic profile of a newly developed halogenated quinoxalinedione derivative, a pharmacologic antagonist of the glycine site on the NMDA receptor complex, is identical to that seen with MK-801. In the cingulate and retrosplenial cortex, examination of glutaraldehyde perfusion-fixed, plastic-embedded tissue 4 to 6 hours after intravenous administration of 10 mg/kg of the glycine antagonist 5-nitro-6,7-dichloroquinoxalinedione (ACEA-1021), no changes were seen by light or electron microscopy. At a dose of 30 mg/kg, neurons were seen containing 1 to 2 microns granules in perikarya and axons. Vacuolated neurons, as described in NMDA-antagonist neurotoxicity, were exceedingly rare, comprising only 4 in the entire study. Electron microscopy of the granulated profiles showed intracytoplasmic areas containing grouped mitochondria and lysosomes, located in neuronal perikarya, and rarely in myelinated axons. Neuronal necrosis was evaluated in formaldehyde perfusion-fixed, paraffin-embedded tissue at one week survival, and was absent. MK-801 5 mg/kg, in contrast, caused irreversible (necrotizing) neuronal changes. The results demonstrate that this glycine antagonist is devoid of lethal neurotoxicity, but causes a reversible alteration in a small proportion of cingulate and retrosplenial cortical neurons. Since previous studies have shown anti-ischemic efficacy of this compound in focal, but not global ischemia, it appears that the therapeutic profile of this antagonist of the strychnine-insensitive glycine site is similar, but the toxicologic structural profile is different, from NMDA receptor antagonists.

-(S)-Alpha-phenyl-2-pyridine-ethanamine Dihydrochloride-, a low affinity uncompetitive N-methyl-D-aspartic acid antagonist, is effective in rodent models of global and focal ischemia.

[(S)-Alpha-phenyl-2-pyridine-ethanamine dihydrochloride] (ARL 15896AR) is a low affinity uncompetitive N-methyl-D-aspartic acid receptor antagonist that was tested in animal models of anoxia and ischemia. Pretreatment of rodents with ARL 15896AR extended survival time during exposure to hypoxia. With the rat four-vessel occlusion model of global ischemia (20 min), oral dosing commencing at reflow, resulted in significant protection of the CA1 hippocampal neurons. ARL 15896AR was, however, ineffective in the rat two-vessel occlusion model and in the gerbil models of forebrain ischemia, the latter due to an inability to attain suitable plasma levels. In the spontaneously hypertensive rat model of middle cerebral artery occlusion (MCAO) (2 hr plus 22 hr reflow), acute dosing with ARL 15896AR (i.p.) beginning from 30 min before or up to 1 hr post-MCAO significantly reduced cortical infarct volume. The ability of ARL 15896AR to influence infarct size, as well as functional correlates was examined in SHR after 90 min of MCAO. T2 weighted magnetic resonance images taken at 2 and 6 days post-MCAO revealed significantly smaller lesion sizes in the group receiving injections with ARL 15896AR beginning 30 min after occlusion. Spontaneously hypertensive rats were subsequently tested (30-42 days post-MCAO) and found to be deficient in skilled use of the forepaws (staircase test). The contralateral forepaw was most severely impaired, however, ARL 15896AR treatment prevented motor impairment in only the ipsilateral forepaw. Histopathological examination of cortical infarct size was unremarkable between treated and control rats. The findings indicate that ARL 15896AR exhibits neuroprotection in global and focal models of ischemia

Postischemic therapy with MK-801 (dizocilpine) in a primate model of transient focal brain ischemia.

The purpose of this study was to develop a primate model for assessing EEG, behavior and histology, and to test the effect of NMDA receptor blockade in transient focal ischemia. Squirrel monkeys (Saimiri sciureus) under halothane anesthesia were subjected to 110 min of transient focal ischemia (n = 15) by temporary clip occlusion of the MCA. An eight-lead EEG was recorded. Neurobehavioral testing was done in a subgroup of animals (n = 6). Brain temperature (37.5 degrees C) was monitored and controlled to avoid hypothermia or intergroup temperature differences, and blood pressure was regulated to 60 mmHg. The entire brain was subserially sectioned, and 52 standardized coronal sections encompassing the infarct were examined histologically 2 wk after the ischemia. Animals were randomized to receive either (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine (MK-801) 1 mg/kg of maleate salt or carrier solution, 20 min and again at 12 h after the onset of ischemia. Cingulate and retrosplenial cortex were examined for NMDA-antagonist-induced neuronal necrosis. No reduction, or trend toward reduction of neurobehavioral deficit was seen with MK-801. MCA occulsion reduced EEG power over the ischemic hemisphere. MK-801 appeared to cause brain activation, and globally increased power at several frequencies. MK-801 did not reduce infarction in either neocortex (p > 0.05) or striatum (p > 0.05). No selective neuronal necrosis was seen in the cingulate or retrosplenial cortex. We conclude that MK-801 given 20 min after the onset of transient ischemia offers no significant neuroprotective effect against either neurobehavioral deficit or ischemic infarction in this model of transient focal ischemia. Further experiments in unanesthetized animals are necessary to determine if MK-801-induced necrosis exists in the gyrencephalic brain, but the enhancement of primate brain electrical activity by MK-801 suggests that brain activation occurs in primates as it does in rodents.