Laser Doppler flowmetry in non-human primate stroke studies: model refinement for pre-clinical development of cerebroprotective strategies.

BACKGROUND: Safety, feasibility, and efficacy trials in non-human primate stroke models are essential to the evaluation of experimental therapies and their translation to humans. Although Laser Doppler Flowmetry has been successfully employed in rodent stroke to continuously monitor cerebral blood flow, it has not been applied in primate studies. This investigation examined the utility of Laser Doppler Flowmetry in refining an existing baboon model of cerebral ischemia/reperfusion. METHOD: Continuous Laser Doppler Flowmetry monitoring was used, in non-human primates, to document local cerebral blood flow before, during, and after middle cerebral artery territory occlusion. In each baboon (n = 7) a single Doppler probe was placed into the left frontal cortex through a precoronal burr hole. Correlations between Laser Doppler Flowmetry values and latencies to Motor Evoked Potential dropout were compared using a linear regression model. FINDINGS: Placement of the Laser Doppler probe was easily accomplished in all animals. Laser Doppler Flowmetry tracings accurately documented blood flow changes that occurred with each technical manipulation during the procedure. Laser Doppler confirmed decreased perfusion that coincided both regionally and temporally with vessel occlusion. Depth of ischemia as measured by Laser Doppler Flowmetry was associated with Motor Evoked Potential dropout latencies for individual animals. CONCLUSIONS: Continuous, single probe Laser Doppler Flowmetry is a reliable method of documenting perfusion changes following middle cerebral artery territory occlusion in a baboon model of reperfused stroke. This advanced intraoperative monitoring technique may lead to more accurate evaluation of acute stroke therapies in pre-clinical trials.

Dehydroascorbic acid, a blood-brain barrier transportable form of vitamin C, mediates potent cerebroprotection in experimental stroke.

Neuronal injury in ischemic stroke is partly mediated by cytotoxic reactive oxygen species. Although the antioxidant ascorbic acid (AA) or vitamin C does not penetrate the blood-brain barrier (BBB), its oxidized form, dehydroascorbic acid (DHA), enters the brain by means of facilitative transport. We hypothesized that i.v. DHA would improve outcome after stroke because of its ability to cross the BBB and augment brain antioxidant levels. Reversible or permanent focal cerebral ischemia was created by intraluminal middle cerebral artery occlusion in mice treated with vehicle, AA, or DHA (40, 250, or 500 mg/kg), either before or after ischemia. Given before ischemia, DHA caused dose-dependent increases in postreperfusion cerebral blood flow, with reductions in neurological deficit and mortality. In reperfused cerebral ischemia, mean infarct volume was reduced from 53% and 59% in vehicle- and AA-treated animals, respectively, to 15% in 250 mg/kg DHA-treated animals (P < 0.05). Similar significant reductions occurred in nonreperfused cerebral ischemia. Delayed postischemic DHA administration after 15 min or 3 h also mediated improved outcomes. DHA (250 mg/kg or 500 mg/kg) administered at 3 h postischemia reduced infarct volume by 6- to 9-fold, to only 5% with the highest DHA dose (P < 0.05). In contrast, AA had no effect on infarct volumes, mortality, or neurological deficits. No differences in the incidence of intracerebral hemorrhage occurred. Unlike exogenous AA, DHA confers in vivo, dose-dependent neuroprotection in reperfused and nonreperfused cerebral ischemia at clinically relevant times. As a naturally occurring interconvertible form of AA with BBB permeability, DHA represents a promising pharmacological therapy for stroke based on its effects in this model of cerebral ischemia.

Serum S100B protein levels are correlated with subclinical neurocognitive declines after carotid endarterectomy.

OBJECTIVE: Carotid endarterectomy (CEA) is an effective means of stroke prevention among appropriately selected patients; however, neuropsychometric testing has revealed subtle cognitive injuries in the early postoperative period. The purpose of this study was to establish whether serum levels of two biochemical markers of cerebral injury were correlated with postoperative declines in neuropsychometric test performance after CEA. METHODS: Fifty-five consecutive patients underwent a battery of neuropsychometric tests 24 hours before and 24 hours after elective CEA. Two patients were excluded because of postoperative strokes. The pre- and postoperative serum levels of S100B protein and neuron-specific enolase for injured patients, defined as those who exhibited significant declines in neuropsychometric test performance (n = 12), were compared with the levels for uninjured patients (n = 41). RESULTS: There were no significant differences in the baseline S100B levels for the two groups. Injured patients exhibited significantly higher S100B levels, compared with uninjured patients, at 24, 48, and 72 hours after surgery (P < 0.05). There were no significant differences in neuron-specific enolase levels for injured and uninjured patients at any time point. CONCLUSION: These data suggest that subtle cerebral injuries after CEA, even in the absence of overt strokes, are associated with significant increases in serum S100B but not neuron-specific enolase levels. Analyses of earlier time points in future studies of subtle cognitive injuries and biochemical markers of cerebral injury after CEA may be revealing.

Postischemic cerebrovascular E-selectin expression mediates tissue injury in murine stroke.

BACKGROUND AND PURPOSE: Although the deleterious role of several proinflammatory mediators, including P-selectin, in reperfused stroke is well established, the role of E-selectin has not been fully characterized. METHODS: E-selectin mRNA expression was studied at 4, 10, and 24 hours after reperfusion with reverse transcription and polymerase chain reaction in mice (n=18) subjected to transient intraluminal middle cerebral artery occlusion (MCAO). Mice received intravenous injection with anti-E-selectin monoclonal antibody (10, 35, or 50 microg), nonimmune IgG, or vehicle immediately before MCAO and 90 minutes later (n=85). Others received anti-E-selectin antibody 3 or 6 hours after MCAO (n=32). Myeloperoxidase activity was measured in sham-operated mice and after 10 hours of reperfusion in saline-, nonimmune IgG-, or anti-E-selectin IgG-treated cohorts (n=17). Serial cerebral blood flow was measured with laser-Doppler flowmetry, and outcomes were assessed by neurological deficits and infarct volumes with the use of planimetric analysis of triphenyltetrazolium chloride-stained sections. RESULTS: Upregulated E-selectin expression occurred in the ischemic cerebral vasculature within 4 hours of reperfusion and persisted for 24 hours. Anti-E-selectin antibody increased ischemic cortical cerebral blood flow up to 2.6-fold (P:<0.05). In addition to dose-dependent reductions in neurological deficits (P:<0.05), mortality, and infarct volumes (P:<0.01 for 35 and 50 microg), anti-E-selectin treatment reduced cerebral neutrophil accumulation (P:<0.05) and was neuroprotective even if delayed until 3 hours after ischemia (P:<0. 05). CONCLUSIONS: These findings establish a functional role for E-selectin in the pathogenesis of tissue injury after cerebral ischemia and reperfusion and suggest that E-selectin blockade may be clinically useful in the treatment of reperfused stroke.

Severe pain confounds neuropsychological test performance.

There is little information on the effect of pain on neuropsychological test performance. We have undertaken this study to explore which tests are affected by pain, the magnitude of these changes, and other confounders of neuropsychological performance in a population of patients having spine surgery. Twenty-four elderly English speaking Caucasian patients (age > 60 years) were enrolled pre-operatively in this Institutional Review Board approved study. Pain scores using an 11-point Numeric Pain Intensity scale and performance on a neuropsychological battery (Controlled Oral Word Association, Rey Complex Figure, Trails A and B) were assessed at two times, before and one day after surgery. Scores were calculated using the standard algorithms and change scores were calculated by subtracting the baseline from follow-up scores. After surgery, performance on the Rey Complex Figure ( r = -0.577, p = 0.004) and Trails Part A (r = 0.527, p = 0.01) declined with increasing post-operative pain scores. Women reported higher pain scores post-operatively than men (p = 0.046), and performed worse than men for change in performance on Trails Part A (p = 0.027). These data suggest that pain can influence performance on certain cognitive tests, and that some gender differences in these effects may occur. Interpretation of performance measures should take into account possible effects of pain, although our understanding of pain effects and ability to predict them in individual people, currently are quite limited.

Transcranial Doppler monitoring during carotid endarterectomy: a technical case report.

We report a case involving a patient undergoing carotid endarterectomy in whom transcranial doppler monitoring demonstrated impaired cerebral blood flow during the initial dissection of the carotid artery, during cross-clamping of the carotid artery, and after the shunt was kinked inadvertently. Only when the carotid artery was cross-clamped were these ischemic changes also seen by electroencephalography. During the other episodes, the electroencephalography tracings demonstrated no detectable changes. This case illustrates the importance of using multiple modalities to determine the adequacy of cerebral blood flow and neuronal integrity.

Cigarette smoking and the development and rupture of cerebral aneurysms in a mixed race population: implications for population screening and smoking cessation.

BACKGROUND: Despite advances in the treatment of aneurysmal subarachnoid hemorhage (aSAH), major additional reductions in morbidity will require the identifications of unruptured aneurysms with a high propensity for bleeding. As screening the entire population is currently not cost-effective, risk factors for the presence of unruptured aneurysms must be identified, and if possible, these risk factors should be modified to reduce disease prevalence. METHODS: To examine whether cigarette smoking independent of arterial hypertension is a risk factor for the development of cerebral aneurysms rather than just being associated with aSAH and to determine whether smoking cessation decreases this risk, we conducted a case-control study comparing the prevalence and degree of smoking in a consecutive series of patients undergoing surgery for ruptured or unruptured aneurysm with age-, sex-, race-, and geographically matched control subjects culled from the New York Healthy Heart Study. RESULTS: Hypertension alone carries little additional risk for the development of ruptured or unruptured aneurysms. Smoking is a risk factor for not only aneurysmal subarachnoid hemorrhage (Relative Risk [RR]=2.83) but also aneurysm formation (RR=2.33). Coexistent hypertension increases the risk of smoking only minimally. Younger smokers are at threefold higher risk than middle-aged ones. Smoking cessation appears to reduce risk of aneurysmal rupture. The effect of smoking on aneurysm formation and rupture may be dose-dependent. CONCLUSIONS: Together these data suggest that smoking, independent of hypertension, plays a critical role in aneurysm development, especially in younger patients, but that physiological mechanisms exist for repair of the damage induced by this toxic insult if cessation is possible.

Matrix metalloproteinase-9 in cerebral aneurysms.

OBJECTIVE: Generalized disruption of arterial wall morphological changes in patients harboring cerebral aneurysms has been documented; however, little is known regarding the pathogenesis of these changes. To explore the role of the elastolytic gelatinase, matrix metalloproteinase-9 (MMP-9), levels of this enzyme in the wall of intracranial aneurysms were compared with those in both intracranial and extracranial arteries. The tissue levels of its major inhibitor, tissue inhibitor of metalloproteinase (TIMP), were measured in these tissues as well. The activity of MMP-9 in plasma was also evaluated. METHODS: The aneurysm wall was excised from three of six patients undergoing craniotomies for aneurysm clipping. A 1-cm segment of superficial temporal artery (STA) was obtained from each of six patients. Additional STAs were obtained from six patients in the control group who were undergoing craniotomies for nonvascular disease. An intracranial artery was also obtained from the anterior temporal neocortical resection of a patient undergoing a craniotomy for mesial temporal sclerosis. MMP-9 and TIMP levels were determined via Western blot analysis. Using substrate gel Zymography, MMP-9 plasma activity was determined for a separate cohort of patients with aneurysms (n = 6) and patients in the control group (n = 6). RESULTS: MMP-9 and TIMP levels in the aneurysm wall were markedly increased beyond levels in both extracranial arteries (STAs from patients with aneurysms and patients in the control group) and the intracranial artery. There were no differences in the levels of MMP-9 in the STAs of patients harboring aneurysms when compared with patients in the control group. Also, no differences were noted in plasma MMP-9 activity. CONCLUSION: Local rather than systemic perturbations in MMP-9 levels may contribute to the matrix disruption associated with cerebral aneurysms. This local up-regulation is not the result of TIMP down-regulation. The lack of increased systemic metalloproteinase activity precludes the use of plasma MMP-9 activity as a screening tool for presymptomatic aneurysms. However, local therapeutic modulation of MMP-9 activity may help arrest aneurysm progression.

The safety of intraoperative lumbar subarachnoid drainage for acutely ruptured intracranial aneurysm: technical note.

Recently, some concern has arisen regarding the safety of intraoperative spinal drainage for brain relaxation in aneurysm surgery, due to anecdotal association with both aneurysmal rebleeding and increases in symptomatic vasospasm. To address these concerns, we reviewed our experience with frequent spinal drainage and early surgery in 432 consecutive cases of surgically treated aneurysmal subarachnoid hemorrhage. Unless contraindicated by mass effect or associated pathology, all grade I-III patients referred within 14 days were treated with spinal drainage at surgery. In this cohort (n = 314), there were no cases of meningitis or nerve root injury. Only one case of intraoperative rebleeding could be associated with spinal drain placement (0.3%). In grade IV-V patients, 47% required preoperative ventriculostomy, and 11% were ineligible for spinal drainage due to mass effect. There were, however, no complications related to spinal drainage in the remaining 23 patients. Permanently-shunted hydrocephalus (8%) and symptomatic vasospasm (19%) were infrequent overall. When analyzed by grade, spinal drains were generally associated with equal or reduced incidence of these developments when compared to patients without spinal drainage. We conclude that brain relaxation can be safely and effectively obtained using intraoperative spinal drains during early aneurysm surgery.

Exacerbation of cerebral injury in mice that express the P-selectin gene: identification of P-selectin blockade as a new target for the treatment of stroke.

There is currently a stark therapeutic void in the treatment of evolving stroke. Although P-selectin is rapidly expressed by hypoxic endothelial cells in vitro, the functional significance of P-selectin expression in stroke remains unexplored. In order to identify the pathophysiological consequences of P-selectin expression and to identify P-selectin blockade as a potential new approach for the treatment of stroke, experiments were performed using a murine model of focal cerebral ischemia and reperfusion. Early P-selectin expression in the postischemic cerebral cortex was demonstrated by the specific accumulation of radiolabeled anti-murine P-selectin IgG, with the increased P-selectin expression localized to the ipsilateral cerebral microvascular endothelial cells by immunohistochemistry. In experiments designed to test the functional significance of increased P-selectin expression in stroke, neutrophil accumulation in the ischemic cortex of mice expressing the P-selectin gene (PS +/+) was demonstrated to be significantly greater than that in homozygous P-selectin-null mice (PS -/-). Reduced neutrophil influx was accompanied by greater postischemic cerebral reflow (measured by laser Doppler) in the PS -/- mice. In addition, PS -/- mice demonstrated smaller infarct volumes (5-fold reduction, P<.05) and improved survival compared with PS +/+ mice (88% versus 44%, P<.05). Functional blockade of P-selectin in PS +/+ mice using a monoclonal antibody directed against murine P-selectin also improved early reflow and stroke outcome compared with control mice, with reduced cerebral infarction volumes noted even when the blocking antibody was administered after occlusion of the middle cerebral artery. These data are the first to demonstrate a pathophysiological role for P-selectin in stroke and suggest that P-selectin blockade may represent a new therapeutic target in the treatment of stroke.

Elastin degradation in the superficial temporal arteries of patients with intracranial aneurysms reflects changes in plasma elastase.

OBJECTIVE: alpha 1-Antitrypsin (AAT) and alpha 2-macroglobulin (AMG) are elastase inhibitors that bind the enzyme and reduce measured levels of free elastase. It was recently demonstrated that some patients with intracranial aneurysms have significantly elevated plasma elastase (PE) levels. Although this elevation is unrelated to plasma AAT, it is unknown whether abnormal AAT phenotypes or reduced AMG levels play a role. Moreover, the pathological significance of this elevation is not understood. METHODS: Plasma from 24 patients with aneurysms (ruptured, n = 15; unruptured, n = 9) and 10 age-matched patients who comprised a control group was analyzed for PE and AMG levels by enzyme-linked immunosorbent assay and for AAT phenotype by isoelectric focusing. Sections of superficial temporal temporal artery obtained from these patients at the time of surgery were examined for evidence of elastin degradation by using a van Gieson stain, with scoring on a nine-point quantitative scale. RESULTS: Patients with aneurysms showed significantly elevated PE levels (119 +/- 28 versus 17 +/- 7 micrograms/ml, P < 0.05), but AMG levels were not decreased. AAT phenotypic abnormalities were observed in 10% (2 of 20) of the patients with aneurysms, but this was not different from the expected population incidence (7%). Elastin degradation scores were significantly higher in patients with aneurysms than in patients control group (4.26 +/- 0.54 versus 1.21 +/- 0.43, P < 0.05). In addition, patients with higher elastase levels (> 80 micrograms/ml) demonstrated 55% higher degradation scores than did those with lower elastase levels (< 80 micrograms/ml). CONCLUSION: These data suggest that high PE levels may play a role in systemic arterial elastin degradation seen in patients with intracranial aneurysms. These data also support the contention that elevated elastase levels are not the result of decreased protease inhibitor levels. Although PE levels were significantly higher for the entire group of patients with aneurysms, this assay has relatively low sensitivity for predicting the presence of unruptured aneurysms. Additional study is necessary to determine whether serum elastase levels greater than 80 micrograms/ml, in the setting of other risk factors, are useful in identifying asymptomatic patients for additional screening.

Giant posterior fossa cystic craniopharyngiomas presenting with hearing loss. Report of three cases and review of the literature.

BACKGROUND: Autopsy studies and recent reviews report that 4% of craniopharyngiomas have posterior fossa extension at initial operation, and 12% subsequently develop this extension during their course. However, only two patients in the literature have been shown to present with deafness, which preceded the more typical suprasellar signs and symptoms of increased intracranial pressure, endocrine disturbance, altered mentation, and visual deterioration. METHODS: The authors report three cases of giant cystic posterior fossa craniopharyngioma initially presenting in childhood with either unilateral or bilateral deafness. These cases are presented, the literature on posterior fossa craniopharyngioma is reviewed, and staged operative management is discussed. RESULTS: Despite being rarely reported, 10% to 20% of giant cystic craniopharyngiomas with posterior fossa extension at presentation may have unilateral or bilateral deafness as their first symptom. Deafness as a presenting symptom is much less common in patients presenting with recurrent tumors in this location than with primary tumors. Pterional or bifrontal craniotomy is appropriate for management of the parasellar component and should be undertaken first when visual symptoms are present. Suboccipital craniectomy is appropriate for management of the posterior fossa component and should be undertaken first when brain stem compressive symptoms make it necessary. Skull-base techniques may have value in certain settings, but patient's morbidity when using these techniques must be carefully considered. CONCLUSIONS: Our results indicate that staged operations with the goal of achieving gross total resection can yield excellent results. Adjuvant radiation is indicated for those with residual tumor seen on magnetic resonance imaging (MRI), but in young children without residual tumors by MRI, we prefer to follow carefully with serial scans. Since the loss of hearing in children can compromise language development, we suggest referral of these children to a specialist in language rehabilitation.

Intramedullary spinal cord metastasis: report of three cases and review of the literature.

BACKGROUND: Intramedullary spinal cord metastasis is rare; but it is being encountered with increasing frequency. Optimal treatment after diagnosis remains controversial. METHODS: In the last 3 years, we have encountered three cases of intramedullary metastasis presenting as focal mass lesions with minimal systemic evidence of cancer. We present our results in these patients and review the literature in an effort to more optimally define both the natural course of this disease, as well as a potential subset of patients who might benefit from more aggressive treatment. RESULTS: With the availability of more sensitive imaging techniques, these tumors are being diagnosed with increasing frequency. Magnetic resonance imaging is sensitive, but nonspecific, in distinguishing intramedullary spinal cord metastases from primary cord tumors. Urgent biopsy is often necessary prior to definitive treatment. Radiation with chemotherapy significantly prolongs survival. Radical subtotal resection may offer additional quality survival, especially in cases of metastatic melanoma with an occult primary. CONCLUSIONS: Regardless of treatment, many patients survive less than 1 year. Intramedullary spinal cord metastasis is a devastating condition, but with appropriate diagnosis and aggressive treatment, selected patients may have substantially increased survival.

Management of spinal epidural hematoma after tissue plasminogen activator. A case report.

STUDY DESIGN: This case report illustrates a patient with a spontaneous epidural hematoma after tissue plasminogen activator therapy who presented 10 days after the incident with a resolving Brown-Sèquard syndrome. OBJECTIVES: The treatment of this patient involves the principles of conservative follow-up directed by an improving examination and an understanding of the pathophysiology of coagulopathy-induced spontaneous epidural bleeds. SUMMARY OF BACKGROUND DATA: The use of tissue plasminogen activator therapy for thrombolysis in patients with early acute myocardial infarction is becoming increasingly routine. Use is limited most significantly by bleeding complications. Recently, several groups have drawn attention to the neurologic complications associated with intracranial hemorrhage after tissue plasminogen activator therapy. Spontaneous spinal epidural hemorrhage has, by comparison, received little attention. The authors report the second case in the literature and the first without a history of antecedent trauma. METHODS: The onset of the painful myelopathy in this patient was missed in the acute setting because of low suspicion. When the diagnosis was made, coadministered heparin had already been discontinued without reversal, and the patient's examination had already improved. Careful follow-up by neurologic examination and magnetic resonance imaging was obtained without spinal angiography being performed. RESULTS: The patient regained his prehemorrhage neurologic status, experienced no further bleeding, and his coronary ischemia remained subclinical. CONCLUSIONS: Spinal epidural hemorrhage secondary to thrombolytic therapy is becoming increasingly common. Urgent surgical decompression is generally warranted to preserve neurologic function. In cases where the deficit is minimal or resolving, a conservative approach may be warranted with magnetic resonance imaging but not angiographic follow-up.

Mild hypothermia reduces penumbral glutamate levels in the rat permanent focal cerebral ischemia model.

Although the cerebroprotective effects of hypothermia in focal models of ischemia are undisputed, the underlying mechanisms of this protection are still subject to much controversy. To analyze whether mild hypothermia attenuates glutamate levels in the penumbra surrounding permanent focal infarcts, extracellular glutamate concentration was analyzed bilaterally by microdialysis 20 minutes before to 120 minutes after a middle cerebral artery occlusion (MCAO) in rats. Normothermic animals (n = 11) had a baseline glutamate concentration of 1.14 +/- 0.40 mumol/ml (standard error of the mean) before the MCAO. Extracellular glutamate levels increased gradually after vessel occlusion to peak at 10.1 +/- 1.45 mumol/ml 80 minutes after the MCAO. This level gradually decreased to 5.72 +/- 1.67 mumol/ml by 120 minutes. Hypothermic animals (n = 11) had a baseline glutamate concentration of 1.73 +/- 0.83 mumol/ml before the MCAO. Extracellular glutamate levels increased after vessel occlusion but stabilized at 3.47 +/- 1.37 mumol/ml 30 minutes after the MCAO and remained stable until completion of the experiment. There were no significant differences in cortical blood flow between the normothermic and hypothermic groups at any time during the experiment. Infarct volumes, expressed as a percentage of the volume of the right (ipsilateral) hemisphere, were 19.8 +/- 2.16% in the normothermic group and 13.0 +/- 1.42% in the hypothermic group (P < 0.02). Although the normothermic penumbral glutamate levels began to increase immediately after the MCAO, they did not peak until 80 minutes after occlusion. In contrast, the normothermic core glutamate levels peaked within 30 minutes after the MCAO. Glutamate diffusion from the core region to the penumbra might account for this delay. Hypothermic cerebroprotection might involve a reduction in the pool of potentially diffusable glutamate in the core region but have little direct effect on glutamate release in the penumbra.

Procedural and strain-related variables significantly affect outcome in a murine model of focal cerebral ischemia.

The recent availability of transgenic mice has led to a burgeoning number of reports describing the effects of specific gene products on the pathophysiology of stroke. Although focal cerebral ischemia models in rats have been well described, descriptions of a murine model of middle cerebral artery occlusion are scant and sources of potential experimental variability remain undefined. We hypothesized that slight technical modifications would produce widely discrepant results in a murine model of stroke and that controlling surgical and procedural conditions could lead to reproducible physiological and anatomic stroke outcomes. To test this hypothesis, we established a murine model that would permit either permanent or transient focal cerebral ischemia by intraluminal occlusion of the middle cerebral artery. This study provides a detailed description of the surgical technique and reveals important differences among strains commonly used in the production of transgenic mice. In addition to strain-related differences, infarct volume, neurological outcome, and cerebral blood flow appear to be importantly affected by temperature during the ischemic and postischemic periods, mouse size, and the size of the suture that obstructs the vascular lumen. When these variables were kept constant, there was remarkable uniformity of stroke outcome. These data emphasize the protective effects of hypothermia in stroke and might help to standardize techniques among different laboratories to provide a cohesive framework for evaluating the results of future studies in transgenic animals.

Cerebral protection in homozygous null ICAM-1 mice after middle cerebral artery occlusion. Role of neutrophil adhesion in the pathogenesis of stroke.

Acute neutrophil (PMN) recruitment to postischemic cardiac or pulmonary tissue has deleterious effects in the early reperfusion period, but the mechanisms and effects of neutrophil influx in the pathogenesis of evolving stroke remain controversial. To investigate whether PMNs contribute to adverse neurologic sequelae and mortality after stroke, and to study the potential role of the leukocyte adhesion molecule intercellular adhesion molecule-1 (ICAM-1) in the pathogenesis of stroke, we used a murine model of transient focal cerebral ischemia consisting of intraluminal middle cerebral artery occlusion for 45 min followed by 22 h of reperfusion. PMN accumulation, monitored by deposition of 111In-labeled PMNs in postischemic cerebral tissue, was increased 2.5-fold in the ipsilateral (infarcted) hemisphere compared with the contralateral (noninfarcted) hemisphere (P < 0.01). Mice immunodepleted of neutrophils before surgery demonstrated a 3.0-fold reduction in infarct volumes (P < 0.001), based on triphenyltetrazolium chloride staining of serial cerebral sections, improved ipsilateral cortical cerebral blood flow (measured by laser Doppler), and reduced neurological deficit compared with controls. In wild-type mice subjected to 45 min of ischemia followed by 22 h of reperfusion, ICAM-1 mRNA was increased in the ipsilateral hemisphere, with immunohistochemistry localizing increased ICAM-1 expression on cerebral microvascular endothelium. The role of ICAM-1 expression in stroke was investigated in homozygous null ICAM-1 mice (ICAM-1 -/-) in comparison with wild-type controls (ICAM-1 +/+). ICAM-1 -/- mice demonstrated a 3.7-fold reduction in infarct volume (P < 0.005), a 35% increase in survival (P < 0.05), and reduced neurologic deficit compared with ICAM-1 +/+ controls. Cerebral blood flow to the infarcted hemisphere was 3.1-fold greater in ICAM-1 -/- mice compared with ICAM-1 +/+ controls (P < 0.01), suggesting an important role for ICAM-1 in the genesis of postischemic cerebral no-reflow. Because PMN-depleted and ICAM-1-deficient mice are relatively resistant to cerebral ischemia-reperfusion injury, these studies suggest an important role for ICAM-1-mediated PMN adhesion in the pathophysiology of evolving stroke.

Mild hypothermia and MK-801 have similar but not additive degrees of cerebroprotection in the rat permanent focal ischemia model.

Although not the sole factor, glutamate-mediated excitotoxicity is accepted as a major mechanism of ischemic neuronal damage. MK-801 and mild hypothermia, two cerebroprotective modalities, which have been documented to alter glutamatergic action, were tested in the rat middle cerebral artery occlusion (MCAO) model simulating permanent focal ischemia. We administered normothermic (37 degrees C) animals with either MK-801 (1.0 mg/kg 30 min before MCAO or 2.5 mg/kg 30 min before, immediately after, 4 hours, and 8 hours after MCAO) or saline vehicle (30 min before MCAO). Mildly hypothermic (33 degrees C) animals were administered either MK-801 (1.0 mg/kg) or saline vehicle 30 minutes before MCAO. Mild hypothermia was induced over a 20-minute period before MCAO in hypothermic animals. All animals were killed 24 hours after MCAO; their brains were sectioned and stained with 2,3,5-triphenyltetrazolium chloride and their infarct volumes were calculated. In normothermica animals given 1.0 mg/kg and multidose 2.5-mg/kg intraperitoneal injections of MK-801, the infarct volumes (as a percentage of right hemispheric volume) were 16.8 +/- 3.5% and 16.3 +/- 3.0%, respectively. These infarct volumes were significantly different (P < 0.05; single-variable analysis of variance) from the normothermic, drug-free control (26.8 +/- 1.9%), but not significantly different from each other. Analysis of the data using a nonparametric test (Kruskal-Wallis; P = 0.02) confirmed the same significant differences in infarct size. The infarct volumes from the mildly hypothermic groups were not different (1 mg/kg of MK-801, 15.5 +/- 2.3% and saline control, 15.4 +/- 1.1%).(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesic effects of intrathecally-administered 3 alpha-hydroxy-5 alpha-pregnan-20-one in a rat mechanical visceral pain model.

Recent studies in animals have demonstrated that the steroid, 3 alpha-hydroxy-5 alpha-pregnan-20-one (3A5P), is a potent analgesic when given intracerebroventricularly. Several studies in humans report that spinal steroids are effective in the treatment of chronic low-back pain when given in combination with morphine. The spinal antinociceptive effect of steroids, in particular a progesterone metabolite has not been studied in a visceral pain model. The experiments in the following study were designed to test, first, if the intrathecally-administered (i.t.) steroid, 3A5P, has analgesic properties in a mechanical visceral nociceptive assay, and second, if the intrathecal coadministration of this steroid and morphine is more effective than either therapy alone. Our mechanical visceral pain model (VPM) consists of a chronic indwelling duodenal balloon catheter implanted in the rat. The balloon is inflated to elicit a writhing response. Protection values are defined as the percentage of rats in each group which did not writhe. In this model, 3A5P was found to provide a dose-independent, though significant (p less than 0.01), antinociception when administered alone (33-67% protection vs. 0-25% for controls). Yet, protection offered by the coadministration of 3A5P and morphine (79%) was not significantly greater than that offered by morphine alone (85%). Unlike a dose and time-dependent response observed in a thermal cutaneous nociceptive assay, the antinociception of 3A5P was not dose-dependent when challenged with a mechanical visceral noxious stimulus.