Hematoma Removal, Heme, and Heme Oxygenase Following Hemorrhagic Stroke

The hemorrhagic strokes, intracerebral (ICH) and subarachnoid hemorrhage (SAH), often have poor outcomes. Indeed, the most common hemorrhagic stroke, ICH, has the highest mortality and morbidity rates of any stroke subtype. In this report, we discuss the evidence for the staging of red blood cell removal after ICH and the significance of control of this process. The protective effects of clinically relevant metalloporphyrin heme oxygenase inhibitors in experimental models of ICH and in superficial siderosis are also discussed. We also examine literature paradoxes related to both heme and heme oxygenase in various disorders of the central nervous system. Last, new data are presented that support the concept that heme, although primarily a pro-oxidant, can also have antioxidant properties.

Heme and iron metabolism: role in cerebral hemorrhage

Heme and iron metabolism are of considerable interest and importance in normal brain function as well as in neurodegeneration and neuropathologically following traumatic injury and hemorrhagic stroke. After a cerebral hemorrhage, large numbers of hemoglobin-containing red blood cells are released into the brain's parenchyma and/or subarachnoid space. After hemolysis and the subsequent release of heme from hemoglobin, several pathways are employed to transport and metabolize this heme and its iron moiety to protect the brain from potential oxidative stress. Required for these processes are various extracellular and intracellular transporters and storage proteins, the heme oxygenase isozymes and metabolic proteins with differing localizations in the various brain-cell types. In the past several years, additional new genes and proteins have been discovered that are involved in the transport and metabolism of heme and iron in brain and other tissues. These discoveries may provide new insights into neurodegenerative diseases like Alzheimer's, Parkinson's, and Friedrich's ataxia that are associated with accumulation of iron in specific brain regions or in specific organelles. The present review will examine the uptake and metabolism of heme and iron in the brain and will relate these processes to blood removal and to the potential mechanisms underlying brain injury following cerebral hemorrhage.

Protein oxidation and heme oxygenase-1 induction in porcine white matter following intracerebral infusions of whole blood or plasma

Spontaneous or traumatic intracerebral hemorrhage (ICH) in the white matter of neonates, children and adults causes significant mortality and morbidity. The detailed biochemical mechanisms through which blood damages white matter are poorly defined. Presently, we tested the hypothesis that ICH induces rapid oxidative stress in white matter. Also, since clot-derived plasma proteins accumulate in white matter after ICH and these proteins can induce oxidative stress in microglia in vitro, we determined whether the blood's plasma component alone induces oxidative stress. Lastly, since heme oxygenase-1 (HO-1) induction is highly sensitive to oxidative stress, we also examined white matter HO-1 gene expression. We infused either whole blood or plasma (2.5 ml) into the frontal hemispheric white matter of pentobarbital-anesthetized pigs ( approximately 1 kg) over 15 min. We monitored and controlled physiologic variables and froze brains in situ between 1 and 24 h after ICH. White matter oxidative stress was determined by measuring protein carbonyl formation and HO-1 gene expression by RT-PCR. Protein carbonyl formation occurred rapidly in the white matter adjacent to both blood and plasma clots with significant elevations (3- to 4-fold) already 1 h after infusion. This increase remained through the first 24 h. HO-1 mRNA was rapidly induced in white matter with either whole blood or plasma infusions. These results demonstrate that not only whole blood but also its plasma component are capable of rapidly inducing oxidative stress in white matter. This rapid response, possibly in microglial cells, may contribute to white matter damage not only following ICH, but also in pathophysiological states in which blood-brain-barrier permeability to plasma proteins is increased.

Minimally invasive therapy for intracerebral hematomas

The efficacy of surgical treatment of ICH remains unproven and controversial [40]. Although open surgery does not appear to improve the patient's outcome [2], less invasive methods of hematoma evacuation seem to show promising results in improving patient outcome and survival. To date, the only two clinical trials that have demonstrated benefit from surgical treatment over medical therapy for ICH have used minimally invasive techniques [27,38]. Randomized controlled clinical trials comparing minimally invasive surgical techniques versus best medical treatment are needed to determine the best management of ICH.

Experimental animal models of intracerebral hemorrhage

Experimental animal ICH models are able to reproduce the overall important pathophysiologic events documented in human ICH, including edema development, markedly reduced metabolism, and tissue pathologic responses. Thus, ICH models serve as an important tool for new understanding of the mechanisms underlying brain injury after an intracerebral bleed. Currently, ongoing studies in several laboratories using these models investigating secondary inflammatory responses as well as intracellular signaling and molecular events are expected to provide therapeutic targets for treating ICH. Future studies should also be directed at one aspect of ICH modeling that has received little attention--potential differences in the hemostatic systems and physical and biochemical properties of clots in animals that might make their susceptibility to aspiration and/or fibrinolytic drugs and rates of rehemorrhage different than in human beings. Also, future efforts should be directed toward the development of a model that mimics the pathophysiologic processes that lead to spontaneous ICH, progression of hemorrhage, and the recurrence of bleeding in human beings. This model would not only provide better understanding of the dynamic events leading to ICH and tissue injury but should also lead to the development of highly effective pharmacologic and surgical treatments.

Genomic responses of the brain to ischemic stroke, intracerebral haemorrhage, kainate seizures, hypoglycemia, and hypoxia

RNA expression profiles in rat brain were examined 24 h after ischemic stroke, intracerebral haemorrhage, kainate-induced seizures, insulin-induced hypoglycemia, and hypoxia and compared to sham- or untouched controls. Rat oligonucleotide microarrays were used to compare expression of over 8000 transcripts from three subjects in each group (n = 27). Of the somewhat less than 4000 transcripts called 'present' in normal or treated cortex, 5-10% of these were up-regulated 24 h after ischemia (415), haemorrhage (205), kainate (187), and hypoglycemia (302) with relatively few genes induced by 6 h of moderate (8% oxygen) hypoxia (15). Of the genes induced 24 h after ischemia, haemorrhage, and hypoglycemia, approximately half were unique for each condition suggesting unique components of the responses to each of the injuries. A significant component of the responses involved immune-process related genes likely to represent responses to dying neurons, glia and vessels in ischemia; to blood elements in haemorrhage; and to the selectively vulnerable neurons that die after hypoglycemia. All of the genes induced by kainate were also induced either by ischemia, haemorrhage or hypoglycemia. This strongly supports the concept that excitotoxicity not only plays an important role in ischemia, but is an important mechanism of brain injury after intracerebral haemorrhage and hypoglycemia. In contrast, there was only a single gene that was down-regulated by all of the injury conditions suggesting there is not a common gene down-regulation response to injury.

Rapid Nuclear Factor κB Activation and Cytokine and Heme Oxygenase-1 Gene Expression in Edematous White Matter After Porcine Intracerebral Hemorrhage

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Introduction: Lobar intracerebral hemorrhage (ICH) induces secondary events in perihematomal white matter including oxidative stress, edema and demyelination. Pro-inflammatory cytokines may play a role, since tumor necrosis factor-α (TNF-α)and interleukin-1β (IL-1β) induce vasogenic edema and TNF-α induces apoptosis in oligodendrocytes. Also, inhibition of heme oxygenase-1 (HO-1) reduces ICH-induced edema (Wagner et al. 2000). Since the oxidatively sensitive transcription factor, nuclear factor κB(NF-κB), regulates these genes, we hypothesize that NF-κB is activated and these mRNAs are expressed in perihematomal white matter early after ICH. Methods: We infused 2.5 ml of autologous blood into the frontal white matter of pentobarbital anesthetized pigs (N=12)and monitored and controlled physiologic variables. We froze brains in situ between 0.5 and 24 hrs post-ICH. We sampled tissue from perihematomal edematous and similarly located control white matter. Nuclear proteins were extracted for Western blotting (NF-κBp65 subunit) and for electrophoretic mobility shift assays (EMSA) and total RNA was extracted for RT-PCR. We used porcine-specific TNF-α, IL-1β, HO-1 and β-actin primers. Relative changes in densitometric data were normalized to β-actin. Results: NF-κB was activated at 30 min in edematous white matter and remained elevated during the 24 hrs following ICH. NF-κBp65 subunit levels were increased to 160±9% of control (mean±SD, N=3)in nuclear extracts between 0.5 and 2 hrs. A further significant (p<0.01) increase to 233±26% (N=3) occurred between 4 and 24 hrs. Including an inhibitor of NF-κB translocation in the infused blood prevented NF-κBp65 appearance in nuclear extracts. Increased NF-κB DNA binding activity (EMSA)was present at 2 hrs. Expression of TNF-α, IL-1β and HO-1 mRNAs were significantly (p<0.05) upregulated at 2 hrs (N=6) to 640±257%, 649±248% and 236±39% of control, respectively. Conclusion: Early NF-κB activation and cytokine and HO-1 gene expression may underlie delayed edema, DNA fragmentation and demyelination in perihematomal white matter after ICH.

Protein oxidation and enzyme susceptibility in white and gray matter with in vitro oxidative stress: relevance to brain injury from intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a devastating stroke sub-type with high mortality and morbidity. ICH frequently occurs in subcortical white matter generating hematomas that contain high heme iron levels. In this study, we examined the consequences of iron-induced oxidation (1-100 microM Fe2+ for 30 min. or 50 microM Fe2+ for 1-120 min.) on the activities of two oxidatively sensitive enzymes, creatine kinase (CK) and glutamine synthetase (GS), and on an oxidative stress marker, protein carbonyl formation, in porcine cerebral cortical white and gray matter. In vitro iron oxidation produced time and concentration dependent decreases in both CK [maximum decreases of 49.3+/-1.2% and 44.3+/-4.1% (average +/- SEM, N=3) for white and gray matter, respectively] and GS activities (maximum decreases of 16.9+/-1.7% and 13.2+/-1.0% for white and gray matter, respectively) and increases in protein carbonyl formation. Interestingly, protein carbonyl concentrations were significantly greater (p<0.05) in white vs. gray matter at 100 microM iron (30 min.) and 50 microM iron (120 min.). Additionally, CK and GS activities were lower for white versus gray matter at several time points and iron concentrations. It is our hypothesis that iron induced oxidative stress contributes to the pathogenesis of perihematomal brain injury following ICH.

Tin-mesoporphyrin, a potent heme oxygenase inhibitor, for treatment of intracerebral hemorrhage: in vivo and in vitro studies

Spontaneous intracerebral hemorrhage (ICH) is the stroke subtype with highest mortality and morbidity. ICH can also occur following traumatic brain injury and thrombolysis for ischemic stroke and myocardial infarction. Development of ICH-induced hemispheric edema can elevate intracranial pressure and cause death. In survivors, edema-related white matter injury can lead to life-long neurological deficits. At present, there are no scientifically proven treatments for ICH. Heme oxygenase products, particularly iron and bilirubin, can be toxic to cells. In cerebral ischemia models, metalloporphyrins that are potent heme oxygenase inhibitors, reduce edema and infarct size. Tin-mesoporphyrin (SnMP) is a neuroprotectant that has also been used clinically to treat hyperbilirubinemia. Presently, we tested the hypothesis that SnMP treatment would reduce edema development following experimental ICH. We produced hematomas in pentobarbital-anesthetized pigs (9-11 kg) by infusing autologous blood into the frontal white matter. To maximize tissue concentrations, SnMP (87.5 microM in DMSO) or DMSO (vehicle controls) was included in the infused blood. Pig brains were frozen in situ at 24 hrs. following ICH and hematoma and edema volumes were determined on coronal sections by computer-assisted image analysis. We also examined the effects of SnMP in vitro on ferritin iron release, the formation of iron-induced thiobarbituric acid reactive substances (TBARS) and initial clot formation and hemolysis. SnMP treatment significantly reduced intracerebral mass following ICH. This was due to significant decreases in hematoma (0.68+/-0.08 vs. 1.39+/-0.30 cc, vehicle controls p<0.025) and edema volumes (edema = 1. 16+/-0.33 vs. 1.77+/-0.31 cc, p<0.05). In vitro, SnMP did not stabilize ferritin iron against reductive release nor did it decrease iron-induced TBARS formation in brain homogenates. SnMP or DMSO added to pig blood did not alter clot weights. In conclusion, SnMP reduced intracerebral mass in an ICH model by decreasing both hematoma and edema volumes SnMP's mechanism of action is presently unknown but may involve its potent inhibition of heme oxygenase activity. SnMP's effect appears unrelated to ferritin iron release, antioxidant activity or initial clot formation. Since SnMP treatment could be brain protective following ICH, further investigations into neurological and neuropathological outcomes and as well as into its mechanism of action are warranted.

Hypoglycemic brain injury: potentiation from respiratory depression and injury aggravation from hyperglycemic treatment overshoots

Hypoglycemia can cause brain dysfunction, brain injury, and death. The present study seeks to broaden current information regarding mechanisms of hypoglycemic brain injury by investigating a novel etiology. The cat's high resistance to brain injury from hypoglycemia suggested that additional influences such as respiratory depression might play a facilitating role. Three groups of cats were exposed to fasting and insulin-induced hypoglycemia (HG; n = 6), euglycemic respiratory depression (RD; n = 5), and combined hypoglycemic respiratory depression (HG/RD; n = 10). The HG animals were maintained at <1.5 mmol (mean 1 mmol) serum glucose concentration for 2 to 6.6 hours. The respiratory depression was associated with PaO2 and PaCO2 values of approximately 50 mm Hg for 1 hour and of approximately 35 and approximately 75 mm Hg, respectively, for the second hour. Magnetic resonance diffusion-weighted imaging estimated brain energy state before, during, and after hypoglycemia. The hypoglycemic respiratory depression exposures were terminated either to euglycemia (n = 4) or to hyperglycemia (n = 6). Brain injury was assessed after 5 to 7 days of survival. Cats exposed to hypoglycemia alone maintained unchanged diffusion coefficients; that is, they lacked evidence of brain energy failure and all six remained brain-intact. Only 1 of 5 euglycemic RD but 10 of 10 HG/RD cats developed brain damage (HG and RD vs. HG/RD, P < 0.01). This difference in brain injury rates suggests injury potentiation by hypoglycemia and respiratory depression acting together. Three injury patterns emerged, including activation of microglia, selective neuronal necrosis, and laminar cortical necrosis. Widespread activation of microglia suggesting damage to neuronal cell processes affected all damaged brains. Selective neuronal necrosis affecting the cerebral cortex, hippocampus, and basal ganglia was observed in all but one case. Instances of laminar cortical necrosis were limited to cats exposed to hypoglycemic respiratory depression treated with hyperglycemia. Thus, treatment with hyperglycemia compared with euglycemia after hypoglycemic respiratory depression exposures significantly increased the brain injury scores (24 +/- 6 vs. 13 +/- 2 points; P < 0.05). This new experimental hypoglycemia model's contribution lies in recognizing additional factors that critically define the occurrence of hypoglycemic brain injury.

Stimulation of both aerobic glycolysis and Na(+)-K(+)-ATPase activity in skeletal muscle by epinephrine or amylin

Epinephrine and amylin stimulate glycogenolysis, glycolysis, and Na(+)-K(+)-ATPase activity in skeletal muscle. However, it is not known whether these hormones stimulate glycolytic ATP production that is specifically coupled to ATP consumption by the Na(+)-K(+) pump. These studies correlated glycolysis with Na(+)-K(+)-ATPase activity in resting rat extensor digitorum longus and soleus muscles incubated at 30 degrees C in well-oxygenated medium. Lactate production rose three- to fourfold, and the intracellular Na(+)-to-K(+) ratio (Na(+)/K(+)) fell with increasing concentrations of epinephrine or amylin. In muscles exposed to epinephrine at high concentrations (5 x 10(-7) and 5 x 10(-6) M), ouabain significantly inhibited glycolysis by approximately 70% in either muscle and inhibited glycogenolysis by approximately 40 and approximately 75% in extensor digitorum longus and soleus, respectively. In the absence of ouabain, but not in its presence, statistically significant inverse correlations were observed between lactate production and intracellular Na(+)/K(+) for each hormone. Epinephrine had no significant effect on oxygen consumption or ATP content in either muscle. These results suggest for the first time that stimulation of glycolysis and glycogenolysis in resting skeletal muscle by epinephrine or amylin is closely linked to stimulation of active Na(+)-K(+) transport.

Ultra-early clot aspiration after lysis with tissue plasminogen activator in a porcine model of intracerebral hemorrhage: edema reduction and blood-brain barrier protection

OBJECT

Ultra-early hematoma evacuation (< 4 hours) after intracerebral hemorrhage (ICH) may reduce mass effect and edema development and improve outcome. To test this hypothesis, the authors induced lobar hematomas in pigs.

METHODS

The authors infused 2.5 ml of blood into the frontal cerebral white matter in pigs weighing 8 to 10 kg. In the treatment group, clots were lysed with tissue plasminogen activator ([tPA], 0.3 mg) and aspirated at 3.5 hours after hematoma induction. Brains were frozen in situ at 24 hours post-ICH and hematomal and perihematomal edema volumes were determined on coronal sections by using computer-assisted morphometry. Hematoma evacuation rapidly reduced elevated cerebral tissue pressure from 12.2+/-1.3 to 2.8+/-0.8 mm Hg. At 24 hours, prior clot removal markedly reduced hematoma volumes (0.40+/-0.10 compared with 1.26+/-0.13 cm3, p < 0.005) and perihematomal edema volumes (0.28+/-0.05 compared with 1.46+/-0.24 cm3, p < 0.005), compared with unevacuated control lesions. Furthermore, no Evans blue dye staining of perihematomal edematous white matter was present in brains in which the hematomas had been evacuated, compared with untreated controls.

CONCLUSIONS

Hematomas were quickly and easily aspirated after treatment with tPA, resulting in significant reductions in mass effect. Hematoma aspiration after fibrinolysis with tPA enabled removal of the bulk of the hematoma (> 70%), markedly reduced perihematomal edema, and prevented the development of vasogenic edema. These findings in a large-animal model of ICH provide support for clinical trials that include the use of fibrinolytic agents and ultra-early stereotactically guided clot aspiration for treating ICH.

Role of blood clot formation on early edema development after experimental intracerebral hemorrhage

BACKGROUND AND PURPOSE

Blood "toxicity" is hypothesized to induce edema and brain tissue injury following intracerebral hemorrhage (ICH). Lobar ICH in pigs produces rapidly developing, marked perihematomal edema (>10% increase in water content) associated with clot-derived plasma protein accumulation. Coagulation cascade activation and, specifically, thrombin itself contribute to edema development during the first 24 hours after gray matter ICH in rats. In the present study, we sought to determine whether blood clot formation is necessary for edema development by comparing intracerebral infusions of heparinized and unheparinized blood in pig (white matter) and in rat (gray matter). We also examined heparin's effect on thrombin-induced gray matter edema.

METHODS

In pigs, we infused autologous blood (with or without heparin) into the cerebral white matter to produce lobar hematomas and froze the brains in situ at 1, 4, or 24 hours after ICH. We determined hematomal and perihematomal edema volumes on coronal sections by computer-assisted morphometry. In rats, we infused either blood or thrombin (with or without heparin) into the basal ganglia and measured water, sodium, and potassium contents at 24 hours after ICH.

RESULTS

In pigs, unheparinized blood induced rapid (at 1 hour) and prolonged (24 hours) perihematomal edema (average volume, 1.29+/-0. 20 mL; n=6). No perihematomal edema was present following heparinized blood infusions (n=6). In rats, unheparinized blood produced significantly greater edema than heparinized blood infusions. As with whole blood, thrombin-induced gray matter edema at 24 hours was significantly reduced by coinjection of heparin.

CONCLUSIONS

After ICH, blood clot formation is required for rapid and prolonged edema development in perihematomal white and gray matter. Thrombin also contributes to prolonged edema in gray matter.

Stroke assessment: morphometric infarct size versus neurologic deficit

We presently examine the relation between histologic infarct size and neurologic deficit as endpoints and seek to clarify their sensitivity in defining stroke outcome. Neurologic deficits of 76 cats subjected to middle cerebral artery occlusion were assessed daily and correlated with the corresponding infarct sizes determined morphometrically after 2 weeks' survival. A five-item neurologic deficit score included the time elapsed until hemiparesis, and forced circling resolved (if ever), presence of impaired placing reactions and time elapsed until able to stand and being alert. We then evaluated the two endpoints' statistical powers to detect group differences using two sets of comparison groups. The neurologic deficit score correlated well with infarct size (r = 0.76, p < 0.001) and each of the individual deficit score components named above, in turn, correlated with decreasing power with infarct size. Even so, the number of study subjects required to achieve the same level of statistical significance in assessing group differences was two-fold greater when using the neurologic deficit than the infarct size data: Group sizes of eight and five animals were sufficient for significant infarct size differences while the groups needed be expanded to 15 and 10 animals to similarly achieve significant neurologic score differences. Thus, infarct size emerges as a more sensitive measure of stroke outcome than does the assessment of neurologic deficits.

Early metabolic alterations in edematous perihematomal brain regions following experimental intracerebral hemorrhage

OBJECT

The authors previously demonstrated, in a large-animal intracerebral hemorrhage (ICH) model, that markedly edematous ("translucent") white matter regions (> 10% increases in water contents) containing high levels of clot-derived plasma proteins rapidly develop adjacent to hematomas. The goal of the present study was to determine the concentrations of high-energy phosphate, carbohydrate substrate, and lactate in these and other perihematomal white and gray matter regions during the early hours following experimental ICH.

METHODS

The authors infused autologous blood (1.7 ml) into frontal lobe white matter in a physiologically controlled model in pigs (weighing approximately 7 kg each) and froze their brains in situ at 1, 3, 5, or 8 hours postinfusion. Adenosine triphosphate (ATP), phosphocreatine (PCr), glycogen, glucose, lactate, and water contents were then measured in white and gray matter located ipsi- and contralateral to the hematomas, and metabolite concentrations in edematous brain regions were corrected for dilution. In markedly edematous white matter, glycogen and glucose concentrations increased two- to fivefold compared with control during 8 hours postinfusion. Similarly, PCr levels increased several-fold by 5 hours, whereas, except for a moderate decrease at 1 hour, ATP remained unchanged. Lactate was markedly increased (approximately 20 micromol/g) at all times. In gyral gray matter overlying the hematoma, water contents and glycogen levels were significantly increased at 5 and 8 hours, whereas lactate levels were increased two- to fourfold at all times.

CONCLUSIONS

These results, which demonstrate normal to increased high-energy phosphate and carbohydrate substrate concentrations in edematous perihematomal regions during the early hours following ICH, are qualitatively similar to findings in other brain injury models in which a reduction in metabolic rate develops. Because an energy deficit is not present, lactate accumulation in edematous white matter is not caused by stimulated anaerobic glycolysis. Instead, because glutamate concentrations in the blood entering the brain's extracellular space during ICH are several-fold higher than normal levels, the authors speculate, on the basis of work reported by Pellerin and Magistretti, that glutamate uptake by astrocytes leads to enhanced aerobic glycolysis and lactate is generated at a rate that exceeds utilization.

Platelet glycoprotein receptor IIIa polymorphism P1A2 and ischemic stroke risk: the Stroke Prevention in Young Women Study

BACKGROUND AND PURPOSE

Platelet glycoprotein IIb/IIa (GpIIb-IIIa), a membrane receptor for fibrinogen and von Willebrand factor, has been implicated in the pathogenesis of acute coronary syndromes but has not been previously investigated in relation to stroke in young adults.

METHODS

We used a population-based case-control design to examine the association of the GpIIIa polymorphism P1A2 with stroke in young women. Subjects were 65 cerebral infarction cases (18 patients with and 47 without an identified probable etiology) 15 to 44 years of age from the Baltimore-Washington region and 122 controls frequency matched by age from the same geographic area. A face-to-face interview for vascular disease risk factors and a blood sample for the P1A2 allele and serum cholesterol were obtained from each participant. Logistic regression was used to estimate the odds ratio for one or more P1A2 alleles after adjustment for other risk factors.

RESULTS

Among cases and controls, the prevalence rates of one or more P1A2 alleles were 21% and 22% among blacks and 36% and 28% among whites, respectively. This genotype was significantly associated with hypertension only in black control subjects but otherwise not with any of the established vascular risk factors. The adjusted odds ratio for cerebral infarction of one or more P1A2 alleles was 1.1 (confidence interval [CI], 0.6 to 2.3) overall, 0.5 (CI, 0.1 to 7.1) among blacks, and 1.4 (CI, 0.5 to 3.7) among whites. For the cases with an identified probable etiology, the corresponding odds ratios were 3.0 (CI, 0.9 to 10.4) overall, 0.7 (CI, 0.1 to 7.1) among blacks, and 12.8 (CI, 1.2 to 135.0) among whites.

CONCLUSIONS

No association was found between the P1A2 polymorphism of GpIIIa and young women with stroke. However, subgroup analyses showed that the P1A2 polymorphism of GpIIIa appeared to be associated with stroke risk among white women, particularly those with a clinically identified probable etiology for their stroke. Further work with an emphasis on stroke subtypes and with multiracial populations is warranted.

Diagnostic bias in clinical decision making: an example of L-tryptophan and the diagnosis of eosinophilia-myalgia syndrome

OBJECTIVE

Eosinophilia-myalgia syndrome (EMS) has been defined as the clinical presentation of eosinophilia, severe myalgia, and the exclusion of other infectious/malignant illnesses. Since the case definition does not require exposure to L-tryptophan (LT), diagnostic bias would occur if a physician's decision to diagnose EMS were influenced by knowledge of LT use.

METHODS

A random sample of 813 physicians practising in the United States and Canada was obtained. Physicians were asked to provide diagnoses for 6 case vignettes having diverse resemblances to EMS. Six weeks later, participants were asked to provide diagnoses for a complementary series of cases described in identical text except for different data regarding LT use.

RESULTS

Physicians who responded (N = 227, 28%) were more likely to diagnose EMS when LT exposure was present compared to the same case without LT use. In the most striking difference, EMS was diagnosed by 48% of physicians when the case was described in a man using LT, but by only 8% of physicians for the same case without LT use. The McNemar bias ratios, which compare responses provided by physicians completing both series, ranged from 0.65 to 1.0.

CONCLUSION

These data indicate that the diagnosis of EMS may be biased by knowledge of LT. By showing the presence of diagnostic bias in clinical decision making, we suggest an important methodological problem that may arise in both clinical and research settings.

Lobar intracerebral hemorrhage model in pigs: rapid edema development in perihematomal white matter

BACKGROUND AND PURPOSE

The mechanisms underlying brain injury from intracerebral hemorrhage (ICH) are complex and poorly understood. To comprehensively examine pathophysiological and pathochemical alterations after ICH and to examine the effects of hematoma removal on these processes, we developed a physiologically controlled, reproducible, large-animal model of ICH in pigs (weight, 6 to 8 kg).

METHODS

We produced lobar hematomas by pressure- controlled infusions of 1.7 mL of autologous blood into the right frontal hemispheric white matter over 15 minutes. We froze brains in situ at 1, 3, 5, and 8 hours after hematoma induction and cut coronal sections of hematoma assessment, morphological brain examination, and immunohistochemical and water content determinations.

RESULTS

At 1 hour after blood infusion, "translucent" white matter areas were present directly adjacent to the hematoma. These markedly edematous regions had a greater than 10% increase in water content (>85%) compared with the contralateral white matter (73%), and this increased water content persisted through 8 hours. In addition, these areas were strongly immunoreactive for serum proteins. Intravascular Evans blue dye failed to penetrate into the brain tissue at all time points, demonstrating that this serum protein accumulation and edema development were not due to increased blood-brain barrier permeability.

CONCLUSIONS

Experimental lobar ICH in pigs models a prominent pathological feature of human ICH, ie, early perihematomal edema. Our findings suggest that serum proteins, originating from the hematoma, accumulate in adjacent white matter and result in rapid and prolonged edema after ICH. This interstitial edema likely corresponds to the low densities on CT scans and the hyperintensities on T2-weighted MR images that surround intracerebral hematomas acutely after human ICH.

Tyrosine and serine phosphorylation of dystrophin and the 58-kDa protein in the postsynaptic membrane of Torpedo electric organ

Dystrophin associates with a 58-kDa and an 87-kDa protein in the postsynaptic membrane of the Torpedo electric organ. We have previously shown that the 87-kDa protein is a major phosphotyrosine-containing protein in these membranes. Immunoprecipitation of the 87-kDa protein from phosphorylated postsynaptic membranes results in coimmunoprecipitation of additional phosphorproteins. These phosphorproteins are identified as dystrophin and the 58-kDa protein. Monoclonal antibodies to dystrophin and the 58-kDa protein immunoprecipitate phosphorylated forms of these proteins from postsynaptic membranes phosphorylated in vitro. Phosphoamino acid analysis reveals that dystrophin and the 58-kDa protein are phosphorylated on serine and tyrosine residues. In addition, both dystrophin and the 58-kDa protein are shown to be phosphorylated on tyrosine residues in vivo. These results suggest that the synaptic function of dystrophin and its associated proteins, the 58-kDa and 87-kDa proteins, may be modulated by tyrosine and serine protein phosphorylation.

Normoglycemia (not hypoglycemia) optimizes outcome from middle cerebral artery occlusion

We examined the effects of serum glucose concentration during middle cerebral artery (MCA) occlusion in the cat on death rates in animals that died from hemispheric edema and on infarct size in animals that survived. We occluded that MCA permanently in some groups and released the clip after 8 h in others. By injecting or infusing glucose solutions, saline, or insulin, we maintained six animal groups steadily either hyper-, normo-, or slightly hypoglycemic before and for 6 or 8 h after permanent or 8-h temporary MCA occlusion. Studies with these groups revealed a distinct optimal outcome with normoglycemic animals. In three additional groups, we altered the glycemia after permanent occlusion from hyper- to normo- or hypoglycemia and from normo- to hyperglycemia. Two of the three hypoglycemic groups (8-h reversible and permanent hyper- to hypoglycemic occlusions) yielded the worst outcomes in this study, with > 10x larger median infarcts than the best outcome group (normoglycemic permanent occlusion). Hyperglycemia also was detrimental and increased infarct size and mortality after permanent occlusion. Restoring the cerebral blood flow after 8 h of occlusion increased the death rate from hemispheric edema compared with a maintained occlusion. Following permanent MCA occlusion, converting from normo- to hyperglycemia or vice versa yielded outcomes intermediate between a sustained normo- or hyperglycemia. A regression analysis of the normo- and hyperglycemic groups and the two groups with glycemia altered after permanent occlusion showed a significant linear correlation between glycemia level at and 1 h after MCA occlusion and median infarct size.

Efficacious experimental stroke treatment with high-dose methylprednisolone

BACKGROUND AND PURPOSE

Recent studies reveal success in treating spinal cord trauma with early, high-dose methylprednisolone. As in spinal cord research, failure to find therapeutic effects with steroids in studies of acute stroke treatment may reflect institution of treatment too late and at too low dosage. We presently test the efficacy of stroke treatment with methylprednisolone administered early and at high doses using a cat temporary middle cerebral artery occlusion model.

METHODS

We occluded the middle cerebral artery for 4 hours in 24 pentobarbital-anesthetized cats. To enhance the probability of brain injury, we maintained the cats' serum glucose concentrations at high levels both during occlusion and for 6 hours afterward. Using a blinded, randomized study design, we treated 12 cats with methylprednisolone (30 mg/kg IV infused over 15 minutes starting 30 minutes after occlusion followed by 5.4 mg.kg-1.h-1 IV for the next 23 hours) and 12 control cats with vehicle. During and for 8 hours after occlusion, we monitored cerebral blood flow, brain and rectal temperatures, and multiple cardiovascular and blood compositional parameters. We assessed brain pathological outcome after animal survival for 4 days or after acute death from hemispheric edema.

RESULTS

Experimental and control animals showed similar early mortality rates (treated, 3/12; controls, 4/12). However, surviving methylprednisolone-treated cats (n = 9) showed a mean infarct size more than six times smaller than in the control animals (n = 8) (mean +/- SEM, 2.4 +/- 0.7% versus 15.6 +/- 6.2% of the ischemic territory, respectively; P < .05). The methylprednisolone-treated animals also showed less marked reduction in cerebral blood flow during ischemia than did the controls (mean +/- SEM, 58 +/- 5% versus 74 +/- 4%; P < .005).

CONCLUSIONS

Administering methylprednisolone at high doses early after onset of ischemia significantly reduces tissue injury in cats that survive 4 days of temporary middle cerebral artery occlusion. This improvement in outcome occurs in the setting of significant increases in ischemic cerebral blood flow. However, methylprednisolone treatment did not reduce hemispheric edema in animals that died early after temporary middle cerebral artery occlusion.