Predicting outcomes after acute reperfusion therapy for basilar artery occlusion

BACKGROUND AND PURPOSE

Basilar artery occlusion (BAO) leads to high rates of morbidity and mortality, despite successful recanalization. The discordance between flow restoration and long-term functional status clouds clinical decision-making regarding further aggressive care. We sought to develop and validate a practical, prognostic tool for the prediction of 3-month favorable outcome after acute reperfusion therapy for BAO.

METHODS

This retrospective, multicenter, observational study was conducted at four high-volume stroke centers in the USA and Europe. Multivariate regression analysis was performed to identify predictors of favorable outcome (90-day modified Rankin scale scores 0-2) and derive a clinically applicable prognostic model (the Pittsburgh Outcomes after Stroke Thrombectomy-Vertebrobasilar (POST-VB) score). The POST-VB score was evaluated and internally validated with regard to calibration and discriminatory ability. External validity was assessed in patient cohorts at three separate centers.

RESULTS

In the derivation cohort of 59 patients, independent predictors of favorable outcome included smaller brainstem infarct volume on post-procedure magnetic resonance imaging (P < 0.01) and younger age (P = 0.01). POST-VB score was calculated as: age + (10 × brainstem infarct volume). POST-VB score demonstrated excellent discriminatory ability [area under the receiver-operating characteristic curve (AUC) = 0.91] and adequate calibration (P = 0.88) in the derivation cohort (Center A). It performed equally well across the three external validation cohorts (Center B, AUC = 0.89; Center C, AUC = 0.78; Center D, AUC = 0.80). Overall, a POST-VB score < 49 was associated with an 88% likelihood of favorable outcome, as compared to 4% with a score ≥ 125.

CONCLUSIONS

The POST-VB score effectively predicts 3-month functional outcome following acute reperfusion therapy for BAO and may aid in guiding post-procedural care.

Ultra-acute diagnostics for stroke: Large-scale implementation of prehospital biomarker sampling

OBJECTIVES

Blood-based biomarkers could enable early and cost-effective diagnostics for acute stroke patients in the prehospital setting to support early initiation of treatments. To facilitate development of ultra-acute biomarkers, we set out to implement large-scale prehospital blood sampling and determine feasibility and diagnostic timesavings of this approach.

MATERIALS AND METHODS

Emergency medical services (EMS) personnel of the Helsinki metropolitan area were trained to collect prehospital blood samples from thrombolysis candidates using a cannula adapter technique. Time delays, sample quality, and logistics were investigated between May 20, 2013 and May 19, 2014.

RESULTS

Prehospital blood sampling and study recruiting were successfully performed for 430 thrombolysis candidates, of which 50% had ischemic stroke, 14.4% TIA, 13.5% hemorrhagic stroke, and 22.1% stroke mimics. A total of 66.3% of all samples were collected during non-office hours. The median (interquartile range) emergency call to prehospital sample time was 33 minutes (25-41), and the median time from reported symptom onset or wake-up to prehospital sample was 53 minutes (38-85; n=394). Prehospital sampling was performed 31 minutes (25-42) earlier than hospital admission blood sampling and 37 minutes (30-47) earlier than admission neuroimaging. Hemolysis rate in serum and plasma samples was 6.5% and 9.3% for EMS samples, and 0.7% and 1.6% for admission samples.

CONCLUSIONS

Prehospital biomarker sampling can be implemented in all EMS units and provides a median timesaving of more than 30 minutes to first blood sample. Large prehospital sample sets will enable development of novel ambulance biomarkers to improve early differential diagnosis and treatment of thrombolysis candidates.

Symptomatic intracranial haemorrhage after thrombolysis with adjuvant anticoagulation in basilar artery occlusion

BACKGROUND AND PURPOSE

Our aim was to determine factors associated with symptomatic intracranial haemorrhage (sICH) in basilar artery occlusion patients treated with intravenous thrombolysis (IVT) and adjuvant anticoagulant therapy.

METHODS

A registry of 176 consecutive patients with angiography-proven basilar artery occlusion who received IVT with alteplase and heparin between 1995 to 2013 was assessed. Post-treatment sICH was evaluated with the European Cooperative Acute Stroke Study II criteria. Unfavourable outcome was defined as a modified Rankin Scale score of 3-6 at 3 months.

RESULTS

Twenty-four patients developed sICH (13.6%, sICH+), all of whom had unfavourable outcome and only two (8.3%) sICH+ patients survived. On admission, sICH+ patients more frequently had extensive ischaemic changes defined as posterior circulation Acute Stroke Prognosis Early CT Score (PC-ASPECTS) < 8 (50% vs. 27% in sICH-, P = 0.031) and lower platelet counts (183 vs. 218 E9/l; P = 0.011). They also had higher systolic blood pressure (SBP) (median 160 vs. 147 mmHg, P = 0.034) immediately after IVT. In multivariable regression analysis, lower platelet values [odds ratio (OR) 0.99, 95% confidence interval (CI) 0.97-0.996; P = 0.006], PC-ASPECTS < 8 on admission (OR 3.6, 95% CI 1.3-10.3; P = 0.017) and higher SBP after treatment (OR 1.03, 95% CI 1.01-1.05; P = 0.017) were independently associated with sICH. Ninety per cent of the sICHs occurred within 48 h from IVT/anticoagulation treatment. No differences in activated partial thrompoplastin times prior to or after the treatment were observed between sICH+ and sICH- patients.

CONCLUSIONS

The risk of sICH was largely determined by extension of ischaemic changes on admission computed tomography. Clinically relevantly, also higher post-thrombolytic SBP as described earlier and lower perithrombolytic platelet counts do increase the risk, a finding requiring confirmation in other patient series.

CT perfusion identifies increased salvage of tissue in patients receiving intravenous recombinant tissue plasminogen activator within 3 hours of stroke onset

BACKGROUND AND PURPOSE

In spite of the advent of thrombolytic therapy, CT-perfusion imaging is currently not fully used for clinical decision-making and not included in published clinical guidelines for management of ischemic stroke. We investigated whether lesion volumes on cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) maps predict final infarct volume and whether all these parameters are needed for triage to intravenous recombinant tissue plasminogen activator (rtPA). We also investigated the effect of intravenous rtPA on affected brain by measuring salvaged tissue volume in patients receiving intravenous rtPA and in controls.

MATERIALS AND METHODS

Forty-four patients receiving intravenous rtPA and 19 controls underwent CT perfusion (CTP) studies in the emergency department within 3 hours of stroke onset. Lesion volumes were measured on MTT, CBV, and CBF maps by region-of-interest analysis and were compared with follow-up CT volumes by correlation and regression analysis. The volume of salvaged tissue was determined as the difference between the initial MTT and follow-up CT lesion volumes and was compared between intravenous rtPA-treated patients and controls.

RESULTS

No significant difference between the groups was observed in lesion volume assessed from the CTP maps (P > .08). Coefficients of determination for MTT, CBF, and CBV versus follow-up CT lesion volumes were 0.3, 0.3, 0.47, with intravenous rtPA; and 0.53, 0.55, and 0.81 without intravenous rtPA. Regression of MTT on CBF lesion volumes showed codependence (R(2) = 0.98, P < .0001). Mean salvaged tissue volumes with intravenous rtPA were 21.8 +/- 17.1 and 13.2 +/- 13.5 mL in controls; these were significantly different by using nonparametric (P < .03) and Fisher exact tests (P < .04).

CONCLUSIONS

Within 3 hours of stroke onset, CBV lesion volume does not necessarily represent dead tissue. MTT lesion volume alone can be used to identify the upper limit of the size of abnormally perfused brain. More brain is salvaged in patients with intravenous rtPA than in controls.

Door to thrombolysis: ER reorganization and reduced delays to acute stroke treatment

The authors reorganized the emergency room (ER) by moving CT to the ER and streamlining triage by prenotification by emergency medical services (EMS), which reduced in-hospital delays and enhanced access to stroke thrombolysis. CT delay dropped from 1 hour 3 minutes +/- 14 minutes in 1999 to 7 +/- 2 minutes in 2004 (p < 0.0001). Door-to-needle time dropped from 1 hour 28 minutes +/- 7 minutes to 50 +/- 3 minutes (p < 0.001), while symptom-to-needle time dropped from 2 hours 44 minutes +/- 6 minutes to 2 hours 5 minutes +/- 4 minutes (p < 0.0001). From 23 patients in 1999, thrombolysis access was increased to 100 patients in 2004 and 183 patients in 2005.

Cerebral amyloid angiopathy in a 95+ cohort: complement activation and apolipoprotein E (ApoE) genotype

There is growing evidence that in Alzheimer's disease (AD) amyloid beta-protein (Abeta) triggers a chronic inflammatory reaction in cerebral amyloid plaques, including complement proteins. Abeta also accumulates cerebrovascularly in age- and AD-associated cerebral amyloid angiopathy (CAA). We investigated complement proteins in CAA in a population-based series using histological and immunohistochemical staining methods. The 74 subjects, aged 95 years or more, had undergone clinical neurological examination and apolipoprotein E (ApoE) genotyping. The brains had been studied for AD post-mortem, allowing us to relate the histopathological findings to clinical and genetic conditions. CAA with congophilic amyloid was found in 36/74 individuals (48.6%). The vascular amyloid deposits immunoreacted with antibodies to Abeta and complements 3d (C3d) and 9 (C9). The positivity in complement stains increased with growing severity of CAA (P = 0.001). The presence of CAA associated with ApoE epsilon4 (P = 0.0005) and overrepresentation of epsilon4 among those with moderate or severe vs. mild CAA (P = 0.03) was demonstrated. The presence of CAA associated with dementia (P = 0.01), which was contributed by both epsilon4+ (P = 0.02) and epsilon4- (P = 0.06) subjects. Our study shows that complement proteins are deposited in the affected vessels in Abeta-associated CAA. They may solely represent the cerebral Abeta- burden associated to inflammatory stimuli, or signal a contribution in the clearance of cerebral Abeta, thereby contributing to the events associated with evolution of clinical dementia. Our results demonstrate a strong association between CAA and ApoE epsilon4 as well as dementia and suggest that the contribution of CAA to dementia is largely independent of ApoE epsilon4.

Postischemic regulation of central histamine receptors

This study characterizes changes occurring in the central histaminergic system associated with ischemia-reperfusion pathology in the rat. Specifically, after a postocclusion time period of 48 h, we have analyzed histamine H(1) receptor mRNA expression, histamine H(2) receptor protein amount and binding densities, and histamine H(3) receptor mRNA expression and binding densities in brain regions that have been suggested to be selectively vulnerable to transient global ischemia, i.e. hippocampus, thalamus, caudate-putamen, and cerebral cortex. We found an increase in H(1) receptor mRNA expression in the caudate-putamen: given that ischemia reduces glucose uptake and H(1) receptor activation has been shown to decrease this effect, an increase of expression levels may result in mitigating tissue damage due to energy failure observed in ischemia. A decrease in H(2) receptor binding densities in the caudate-putamen was also observed; the ischemia-induced decrease in H(2) receptor protein was also detectable by Western blot analysis. This phenomenon may underlie the previously reported ischemia induced striatal dopamine release. H(3) receptor mRNA expression was increased in the caudate putamen of the postischemic brain but was decreased in the globus pallidus and the thalamus; in association with this, H(3) receptor binding densities were increased in the cortex, caudate-putamen, globus pallidus, and hippocampus. The upregulation of H(3) receptor ligand binding may be involved in the previously reported continuous neuronal histamine release. Our data suggest that central histamine receptor expression and ligand binding are altered in brain ischemia in distinct areas, and may participate in neuroprotection and/or ischemia-associated neuronal damage.

Brain diffusion changes in carotid occlusive disease treated with endarterectomy

BACKGROUND

Patients with unilateral high-grade carotid stenosis or occlusion have been reported to have more leukoaraiosis and ischemic lesions in ipsilateral than in contralateral cerebral hemisphere. The lesions alter apparent diffusion coefficient (ADC) values in diffusion-weighted MRI (DWI). The overall effects of carotid endarterectomy on ADC values have not yet been explored.

OBJECTIVE

S: To find out whether 1) average ADC (ADC(av)) values differed between hemispheres, 2) diffusion changes induced by carotid endarterectomy could be detected in brain tissue with serial DWI, and 3) patients with asymptomatic carotid stenosis differed from patients with a symptomatic stenosis.

METHODS

Forty-five patients (22 with asymptomatic carotid stenosis and 23 with symptomatic carotid stenosis) with unilateral high-grade carotid stenosis underwent DWI before carotid endarterectomy and 3 and 100 days afterward, and 45 age- and sex-matched healthy control subjects were imaged once. We evaluated ADC(av) values in normal-appearing gray and white matter, watershed regions (WsR), and thalamus.

RESULTS

ADC(av) values of ipsilateral white matter and WsR were higher than those of contralateral white matter and WsR, both being higher than in white matter and WsR of control subjects. After carotid endarterectomy, these differences were diminished, but the levels remained higher than in controls. ADC(av) values of gray matter and thalamus remained unaffected. Asymptomatic carotid stenosis and symptomatic carotid stenosis patient groups did not differ from each other.

CONCLUSIONS

Carotid stenosis has an effect on diffusion in the white matter of the ipsilateral hemisphere, and it is partly reversible by carotid endarterectomy. The finding may be associated with leukoaraiotic development ("preleukoaraiosis").

Adhesion molecule expression in symptomatic and asymptomatic carotid stenosis

BACKGROUND

Prior studies have suggested a central role for cellular adhesion molecules (CAMs) in the pathophysiology and symptoms of atherosclerotic carotid plaques (CPs).

OBJECTIVE

This study examined the role of CAMs in symptom generation in patients with advanced carotid artery disease.

METHODS

Ninety-two consecutive patients underwent carotid endarterectomy, six for both sides (54 symptomatic and 41 asymptomatic CPs). Intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), P-selectin, and E-selectin were immunostained in fresh-frozen CP specimens and examined semiquantitatively in the endothelium and intima-media. Plasma concentrations of soluble ICAM-1 and sVCAM-1 were analyzed by ELISA.

RESULTS

Endothelial expression of ICAM-1, VCAM-1, P-selectin, and E-selectin did not differ between symptomatic and asymptomatic CPs, but endothelial ICAM-1 was associated with serum sensitized C-reactive protein levels (p = 0.026). However, there was less ICAM-1 expression in the intima-media of the symptomatic CPs (p = 0.022), and there was a similar, but nonsignificant tendency for VCAM-1. Soluble ICAM-1 and soluble VCAM-1 were not associated with the symptom status.

CONCLUSIONS

In contrast to earlier studies, it was found that symptomatic carotid disease is not associated with increased expression of adhesion molecules in the endothelium of advanced carotid plaques or in circulation. Rather, there was less expression of adhesion molecules in the intima-media of symptomatic carotid plaques.

Differential expression of cytokines (IL-2, IFN-gamma, IL-10) and adhesion molecules (VCAM-1, LFA-1, CD44) between spleen and lymph nodes associates with remission in chronic relapsing experimental autoimmune encephalomyelitis

We have recently established chronic relapsing experimental autoimmune encephalomyelitis (CR-EAE) in SJL mice with a modified protocol. In this model, splenectomy aborts the relapsing-remitting course of the disease, and adoptive transfer of lymphocytes of the local draining lymph nodes (LNs) to naive recipients exacerbates the disease. Adoptive transfer of splenic cells converted acute EAE into CR-EAE in the naive recipients. In light of the different roles of the spleen and LNs in the evolution of CR-EAE, we examined by semiquantitative reverse-transcription polymerase chain reaction (RT-PCR) whether a differential mRNA expression profile of cytokines and cellular adhesion molecules (CAMs) in spleen versus LN was associated with relapse or remission in CR-EAE. All the cytokines tested (interleukin-1beta (IL-1beta), IL-2, IL-4, IL-7, IL-10, interferon-gamma (IFN-gamma)) as well as CAMs (ICAM-1, ICAM-2, VCAM-1, LFA-1 and CD44) were expressed at substantial levels in both spleen and LNs. Interestingly, disease remission was found to be associated with an increased mRNA expression of IL-2 and IFN-gamma in LNs and a decreased IL-10 mRNA level in the spleen. On the other hand, an increased mRNA expression of VCAM-1, LFA-1 and CD44 was observed in the spleens in comparison with that in LNs of mice, with remission. During relapses, mRNA expression of the tested molecules did not significantly differ between spleens and LNs. Our results suggest that a differential and polarized expression profile of certain cytokines and CAMs in spleen versus LN could provide molecular correlates of the cyclic pathogenesis of CR-EAE.

Evolution of cerebral tumor necrosis factor-alpha production during human ischemic stroke

BACKGROUND AND PURPOSE

Tumor necrosis factor-alpha (TNF-alpha) is detected in ischemic brain cells in experimental animal models and is believed to play an important role in apoptosis. However, the natural expression of TNF-alpha during human stroke is not known.

METHODS

We examined TNF-alpha immunohistochemistry and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) in brain samples of stroke victims (n=16) after variable survival (15 hours to 18 days). Systemic TNF-alpha content from a separate cohort including severe or lethal stroke cases (n=26) was also assayed.

RESULTS

Neuronal TNF-alpha was demonstrated from 0.6 to 5.4 days after the onset of stroke symptoms, peaking bilaterally during days 2 and 3. Bilateral glial TNF-alpha immunoreactivity was detected during the acute phase, with the astrocytic TNF-alpha expression dominating in later phases and persisting contralaterally to the infarct in more matured phases (17 to 18 days). Invading inflammatory cells were TNF-alpha immunopositive beginning on the third day. Besides, vascular wall structures showed immunoreactivity sporadically. TNF-alpha levels were mostly nondetectable in peripheral blood. TUNEL labeling and TNF-alpha staining overlapped, although not completely, during the first days.

CONCLUSIONS

The data support the hypothesis that TNF-alpha may be involved both in the acute propagation of inflammatory processes and cell death and possibly in the more delayed reconstitutive processes of human ischemic stroke.

Differential cellular expression of tumor necrosis factor-alpha and Type I tumor necrosis factor receptor after transient global forebrain ischemia

We examined the expression of tumor necrosis factor-alpha (TNF-alpha) and the Type I tumor necrosis factor receptor, (TNFR1), in relation to c-fos, a known regulator gene of immediate cellular responses, after an extended period of global ischemia. The number of TNF-alpha mRNA expressing cells peaked in most brain areas after 8 h of reperfusion. Significant increases in TNFR1 mRNA expression were evident in the cortex at 2 and 8 h of reperfusion and after 8 h of reperfusion in the CA3/CA4 region of the hippocampus. Transient neuronal c-fos mRNA expression preceded these responses. TNF-alpha immunoreactivity was seen in neurons>>>oligodendrocytes=perivascular cells=ependymal cells=vessel wall structures. After ischemia/reperfusion, increased TNF-alpha immunoreactivity was evident only in oligodendrocytes. TNFR1 immunoreactivity in sham brains manifested in bundles of cellular fibers of variable length and thickness. In post-ischemic brains, immunoreactivity in these cellular processes representing mainly astroglial extensions was suppressed at 2 h but recovered partially by 8 and 24 h of reperfusion. In contradiction, transient ischemia-induced TNFR1 immunoreactivity was observed in somas of large cortical neurons, in activated microglia/macrophages, perivascular and endothelial cells.Taken together, the increase in neuronal TNF-alpha mRNA appeared not to be followed by substantial translation to protein in the cerebral tissue after an extended period of global ischemia. However, there was increased neuronal TNFR1 immunostaining in conjunction with increased immunostaining for TNF-alpha in oligoglial elements, which suggests signaling to neurons by enhanced oligoglial TNF-alpha.

Splenectomy and adoptive cell transfer reveal a prominent role for splenic memory lymphocytes in the development of chronic relapsing experimental autoimmune encephalomyelitis

We previously reported that acute experimental autoimmune encephalomyelitis (EAE), induced by active immunization of SJL mice, could be converted into chronic relapsing EAE (CR-EAE) by a pretreatment with neuroantigen and killed mycobacteria 2 months earlier. This finding indicates that immune memory, established by the pretreatment, influences the subsequent EAE induction. The present study shows that splenectomy and lymphadenectomy, applied 1 week before the subsequent active immunization of the pretreated mice, efficiently abort the chronic nature of CR-EAE. Furthermore, we have found that adoptive transfer of lymphocytes from the spleen (but not of those from the local draining lymph nodes) of the pretreated mice to naive syngeneic recipients 1 week before the acute EAE-induction immunization results in the development of CR-EAE. On the other hand, the transfer of lymphocytes from the local draining lymph nodes aggravates the acute disease. These data support a critical role for immune memory of the previous suboptimal challenge in the development of chronic relapsing demyelinating disease.

The future of stroke treatment

The concept of the therapeutic window of opportunity in ischemic neuronal injury and understanding the necessity of well organized stroke services revolutionized the management of acute ischemic stroke during the last years of the second millennium. Thrombolysis with IV rt-PA within 3 hours from the onset of symptoms is an established therapy for selected patients. The challenge of stroke therapy at the outset of this millennium is how to translate basic pathophysiologic evidence of ischemic neuronal injury into novel neuroprotective therapies either independently or combined with thrombolysis. Great hopes are placed in identification of pivotal molecular events in ischemic brain tissue and design of effective pharmacological interventions to target them. Aggressive, invasive procedures are also being developed and therapies such as intra-arterial clot lysis, hemicraniectomy and mild hypothermia may improve the bleakest outcomes associated with the most severe forms of ischemic stroke, but their role must be rigorously evaluated. There is, however, no need to wait for future breakthroughs. The existing evidence strongly implies that good care of patients with stroke starts with organization of the entire stroke chain; from the prehospital scene, through the emergency room, to the stroke unit. Without structured stroke services no pharmacological or intervening therapy is likely to improve the outcome of the patient with a stroke.

Stanniocalcin: A molecular guard of neurons during cerebral ischemia

Stanniocalcin (STC) is a glycoprotein hormone originally found in bony fish, in which it regulates calcium/phosphate homeostasis and protects against hypercalcemia. The recently characterized human STC shows about 70% homology with fish STC. We previously reported a constitutive expression of STC in terminally differentiated neurons. Here, we show that exposure of human neural-crest-derived cell line Paju to hypercalcemic culture medium induced expression of STC. Treatment of Paju cells with recombinant human STC increased their uptake of inorganic phosphate. Paju cells expressing STC by cDNA transfection displayed increased resistance to ischemic challenge and to elevated intracellular free calcium induced by treatment with thapsigargin. An up-regulated and redistributed expression of STC was observed in neurons surrounding the core of acute infarcts in human and rat brains. Given that mobilization and influx of calcium is considered a main neurotoxic mechanism following ischemia, our results suggest that the altered expression of STC contributes to the protection of cerebral neurons against hypoxic/ischemic damage. Manipulation of the STC expression may therefore offer a therapeutic approach to limit the injury after ischemic brain insults.

Bilateral sphenoid wing metastases of prostate cancer presenting with extensive brain edema

A 76-year-old man insidiously developed diffuse neurological symptoms: cognitive decline, dysphagia, dysphasia and mental disturbance. Computed tomography of the cranium revealed widespread bilateral brain edema and symmetrical bilateral sphenoid wing hyperostosis. Adjacent to the hyperostosis that resembled skull base meningiomas, two separate parenchymatous temporal lobe lesions enhancing with contrast medium were observed. The patient had earlier been diagnosed to have prostatic carcinoma. Dexamethasone therapy resulted in discontinuation of the neurological symptoms. The diagnosis of metastasized adenocarcinoma of the prostate was confirmed histologically on autopsy after a sudden death from pneumonia. Intracranial metastases of prostate cancer may have a predilection site at the sphenoid wing, and can mimic a skull base meningioma. Intracranial spread of prostatic adenocarcinoma should be considered in elderly men as a treatable cause of gradual neurological deterioration, especially if cranial malignancy or hyperostosis is found.

Anti-ICAM-1 monoclonal antibody R6.5 (Enlimomab) promotes activation of neutrophils in whole blood

R6.5 (BIRR-1, Enlimomab), a murine IgG2a mAb to the human ICAM-1, inhibits leukocyte adhesion to the vascular endothelium, thereby decreasing leukocyte extravasation and inflammatory tissue injury. In initial clinical trials, R6.5 proved to be beneficial in reducing both disease activity in refractory rheumatoid arthritis and the incidence of acute rejection after kidney and liver allograft transplantations. However, adverse effects such as fever, leukopenia, or cutaneous reactions were not infrequent. We studied the effects of R6.5 on neutrophil function in whole blood samples ex vivo. Surprisingly, at the concentrations achieved in clinical trials, R6. 5 activated neutrophilic granulocytes, as indicated by a significant increase in expression of the adhesion molecule beta2-integrin CD11b, a concurrent decrease in L-selectin expression, and an enhancement of the oxidative burst activity. Neutrophil activation was not exerted by an anti-ICAM-1 mAb of the IgG1 isotype, by isotype-matched, irrelevant anti-2-phenyloxazolone mAb, or by F(ab')2 fragments of R6.5. Neutrophil activation was completely inhibited by soluble complement receptor type 1. We conclude that in whole blood, R6.5 activates resting neutrophils in a complement-dependent manner. This finding can explain, at least in part, the side effects associated with R6.5 therapy.

Cyclooxygenase-2 is induced globally in infarcted human brain

Cyclooxygenase (COX) catalyzes synthesis of prostanoids after liberation of arachidonic acid, an important biochemical sequela of cerebral ischemia that aggravates brain injury. We investigated expression of inducible COX-2 in infarcted human brains (symptom duration, 15 hours to 18 days) and found that COX-2 protein was present in both neuronal and glial cells throughout the brain in accord with infarct topography and duration. These results emphasize the global yet temporally regulated nature of COX-2 induction during focal ischemia in humans, clearly different from the circumscribed acute expression reported in experimental animal models. We speculate that early induction of COX-2 may fuel tissue damage through prostanoids and free radicals, and delayed induction in remote brain areas may promote reconstitutive processes in the face of tissue scarring and remodeling of the surviving neural networks.

Does glutamate mediate brain damage in acute encephalitis?

Cerebrospinal fluid (CSF) amino acid neurotransmitter concentrations in 23 patients with acute encephalitis were compared with those in patients with acute brain infarction, multiple sclerosis and controls. The concentration of glutamate was significantly higher in encephalitis (5.2+/-6.7 micromol/l) and stroke patients (9.6+/-14.2 micromol/l) than in MS patients (1.6+/-0.9 micromol/l) and controls (1.7+/-0.8 micromol/l; p < 0.001). The concentration of glycine was significantly higher in encephalitis (11.0+/-4.7 micromol/l) than in stroke (7.6+/-3.2 micromol/l) and MS patients (6.3+/-2.1 micromol/l) or controls (5.6+/-1.8 micromol/l; p < 0.002). Taurine levels were significantly lower in encephalitis patients than in the other groups (p = 0.04). The correlation of high glutamate levels with poor outcome was almost significant (Kendall tau 0.63, p = 0.06). Our observations suggest that exicitotoxic neurotransmission may play an important role in the series of events that lead to neuronal damage in encephalitis.

Tolerization against loss of neuronal function after ischemia-reperfusion injury

To investigate whether sublethal ischemia preserves neuronal function otherwise lost after stroke, anesthesized rabbits were subjected to clamping of abdominal aorta to cause lumbar spinal cord ischemia. An occlusion period of 12.5 min was followed 12 or 48 h later by a second occlusion for 30 min. When scored 24 h later for hindlimb function on a 0-6 scale, the rabbits that underwent tolerizing ischemia 12 h before infarction had better motor function (n = 7; 4.29+/-0.21,p < 0.0001) than sham-operated controls (n = 7; 1.00+/-0.27), but those infarcted at 48 h had mixed outcomes (n = 5; 2.20+/-0.21, ns). In correlation, the proportion of neurons with histological evidence of damage was lower in the tolerized rabbits (0.15+/-0.04) than in sham-operated controls (0.74+/-0.09, p < 0.001). We conclude that ischemic tolerance also improves neurological function of infarcted spinal cord and could be studied for clinical application.

Meningoencephalitis caused by Cryptococcus macerans

A case of meningoencephalitis caused by Cryptococcus macerans is described. The infection caused a severe form of epilepsy. Antifungal therapy based on fluconazol was successful in halting the disease process. The patient remained, however, unable to resume his job and previous activities.

Global forebrain ischemia results in differential cellular expression of interleukin-1beta (IL-1beta) and its receptor at mRNA and protein level

The mRNA expression of the proinflammatory cytokine interleukin-1beta (IL-1beta) has been shown to be induced in neural elements during ischemia. It is not clear which cells generate the IL-1beta mRNA and eventually synthesize IL-1 protein and which cells respond to this signaling by producing IL-1 receptors during ischemia. To clarify this question, rats were subjected to global ischemia by bilateral carotid occlusion and hypotension for 20 minutes, followed by reperfusion for 2 hours (n = 7), 8 hours (n = 7), or 24 hours (n = 7). Cryostat sections were hybridized using antisense oligonucleotide probes (30 dimer). Multiple cell markers were used in immunohistochemical staining to identify the cells expressing IL-1beta and IL-1R protein. The sham animals (n = 5) showed no or only a weak expression of IL-1R or IL-1beta mRNA. The number of IL-1beta mRNA-expressing cells was significantly increased by 2 hours of reperfusion in several brain areas including cortex (12-fold compared with sham) and caudate-putamen (14-fold), and was maximally increased in most hippocampal regions by 8 hours of reperfusion (mean +/- SD of positive cells/field versus sham equivalent being 37.9 +/- 12.3 versus 4.0 +/- 3.3; 30.6 +/- 9.0 versus 3.1 +/- 2.3; 41.3 +/- 17.5 versus 2.9 +/- 1.9; in CA1; CA2; CA3/CA4 regions of the hippocampus, respectively). IL-1beta mRNA signal was also intensified in the white matter areas. Changes in IL-1R mRNA were seen in the hippocampus (after 2 hours CA1: 16-fold; CA2: 17-fold; DG: 24-fold increase; and CA3/CA4: 10-fold increase after 8 hours), and the expression was prolonged especially in CA1 and CA2 regions up to 24 hours of reperfusion. The major cellular source of IL-1beta protein was glia (astrocytes, oligodendrocytes, microglia, and scattered perivascular macrophages/monocytes), while neurons and sporadic microvascular endothelia showed IL-1R immunoreactivity. The data suggest that neurons in discrete areas vulnerable for selective neuronal death, and possibly the vascular endothelium, are target cells for ischemia-induced glial IL-1beta production.

Microvascular perfusion during focal vasogenic brain edema: a scanning laser fluorescence microscopy study

Controversy exists about the effect of tissue edema on cerebral microcirculation. High spatial resolution is required for observation of extravasation and microcirculation during focal vasogenic edema formation. To study the relationship between tissue edema and perfusion, we developed a technique for simultaneous visualization of extravasation and microvessel perfusion in rats. Focal intracortical microvascular injury was generated with a 1-sec Nd-YAG laser pulse. Evans blue albumin (EBA) was infused 30 min before decapitation to study extravasation and FITC-dextran was injected 30 sec prior to decapitation to examine microvessel perfusion. Computerized scanning laser-excited fluorescence microscopy followed by high resolution image analysis permitted quantitative assessment of both parameters on single fresh-frozen brain sections. Studied at 30 min (3.66 +/- 0.15 mm), 2 hr (4.14 +/- 0.08 mm, P < .05), and 8 hr (4.69 +/- 0.18 mm, P < .01) after injury, the diameter of the circular, sharply demarcated zone of EBA-extravasation increased progressively. At 30 min, microvessels at a zone surrounding the area of EBA-extravasation contained 69 +/- 14% (P < .05) more fluorescent FITC-filling than in the control hemisphere, but the density of perfused microvessels was unchanged. At 2 hr, secondary tissue changes had already occurred in a zone surrounding the initial laser lesion. While severe reduction in the density (-76 +/- 13%, P < .05) of perfused microvessels was observed within 400 to 240 microm inside the border of EBA extravasation, perfusion indexes were normal despite the presence of extravasated plasma constituents within 0-80 microm from the border. In a narrow zone (80 microm) outside the border of extravasation, individual microvessels contained 34 +/- 9% (P < .01) less FITC-fluorescence than those in a homologous area of the uninjured contralateral hemisphere. This report demonstrates the feasibility of simultaneous measurement and high-resolution mapping of indices of microvascular perfusion (density, filling) and extravasated plasma constituents in damaged and intact brain areas. In this model, the presence of extravasated plasma constituents the size of proteins did not immediately influence indices of cortical microcirculation. However, microvascular perfusion may be perturbed surrounding such an area of advancing vasogenic edema formation.

Complement activation in the central nervous system following blood-brain barrier damage in man

The central nervous system (CNS) is virtually isolated from circulating immunological factors such as complement (C), an important mediator of humoral immunity and inflammation. In circulation, C is constantly inhibited to prevent attack on host cells. Since a host of diseases produce an abnormal blood-brain/cerebrospinal fluid (blood-brain/CSF) permeability allowing C protein extravasation, we investigated if C activation occurs in CSF in vitro and in CNS in vivo during subarachnoid hemorrhage (SAH) or brain infarction. After SAH (n = 15), the terminal complement complex (TCC) concentration on days 0 to 2 was higher in the CSF, 210 +/- 61 ng/ml, than in the plasma, 63 +/- 17 ng/ml, but null in the CSF of controls (n = 8) or patients with an ischemic stroke (n = 7). TCC was eliminated from the CSF after SAH (24 +/- 10 ng/ml on days 7 to 10). Incubation of normal human CSF with serum in vitro also activated the terminal C pathway. In 10 fatal ischemic brain infarctions, immunohistochemical techniques demonstrated neuronal fragment-associated deposition of C9 accompanied by neutrophil infiltration. We conclude that the C system becomes activated intrathecally in SAH and focally in the brain parenchyma in ischemic stroke. By promoting chemotaxis and vascular perturbation, C activation may instigate nonimmune inflammation and aggravate CNS damage in diseases associated with plasma extravasation.

Endothelial ICAM-1 expression associated with inflammatory cell response in human ischemic stroke

BACKGROUND

After focal brain ischemia, leukocytes adhere to the perturbed endothelium and are believed to aggravate reperfusion injury. Although ischemia-induced upregulation of endothelial adhesion molecules, intercellular adhesion molecule-1 (ICAM-1) and P-selectin, has been observed in experimental animals, the mechanism of cerebral leukocyte infiltration and thus therapeutic possibilities to reduce it in humans are uncertain.

METHODS AND RESULTS

We counted the granulocytes, mononuclear phagocytes, and the percentages of cerebral microvessels expressing ICAM-1 by applying immunohistochemistry on brain sections showing a variable degree of neuronal damage from 11 human subjects who died 15 hours to 18 days after ischemic stroke and from normal control brains. In infarcted regions, granulocytes were detected as early as at 15 hours after injury (11.3 versus 0.5 cells/mm2 in noninfarcted hemisphere); their amount exceeded 200 cells/mm2 by 2.2 days but was back to normal level at 6.3 and 8.5 days. Acute infarctions (0.6 to 8.5 days) harbored significantly more ICAM-1-stained microvessels (up to 97% of microvessels at 1.8 days) than the noninfarcted hemisphere (P < .001), although the noninfarcted hemisphere (1.8 to 6.3 days) also showed higher ICAM-1 expression than controls. In the absence of ICAM-1 upregulation, macrophages (> 200/mm2) were abundant in the core of neuronal damage at 17 and 18 days.

CONCLUSIONS

The striking upregulation of endothelial ICAM-1 expression, functioning in concert with chemotactic factors, may cause granulocyte infiltration during the first 3 days after stroke. This study may support the usage and timing of antibody infusions to block endothelial adhesion molecules in an attempt to reduce leukocyte-induced damage in stroke.

Heat-shock protein and C-fos expression in focal microvascular brain damage

Cortical brain damage was produced in rats by a focal pulse from a Nd-YAG laser, and evolution of the lesion was evaluated at 30 min, and 2, 8, and 24 h with respect to microvascular perfusion, blood-brain barrier (BBB) permeability, and expression of both the heat-shock/stress protein, hsp72, and the c-fos proto-oncogene transcription factor. A double-labeling fluorescence technique employing intravenously injected Evans blue albumin (EBA) and fluorescein-labeled dextran was used to map and measure BBB damage and microvascular perfusion in fresh frozen brain sections. Hsp72 and c-fos mRNAs were localized by in situ hybridization, and the respective proteins were identified by immunocytochemistry. Parallel sections were stained for glial fibrillary acidic protein and for routine histologic examination. Striking hsp72 mRNA expression was evident by 2 h in an approximately 300 microns wide rim surrounding an area of expanding BBB damage. Increased hsp72 mRNA was observed only in regions of preserved microcirculation, where the hsp72 protein was subsequently localized exclusively in the vasculature at 24 h after the insult. Hsp72-positive endothelial cells spanned the narrow margin between the lesion and histologically normal, glial fibrillary acidic protein (GFAP)-positive cortical tissue. There was no hsp72 expression in the area of subcortically migrating edema fluid. Inductions of c-fos mRNA and Fos protein were not strikingly evident around the focal brain lesion, but were observed transiently throughout the injured hemisphere at 30 min and 2.5 h, respectively, indicating that spreading depression was triggered by the focal injury. These results are in striking contrast to those previously obtained from studies of models of focal ischemic or traumatic brain injury, which are characterized by a complex pattern of glial and neuronal hsp72 expression in the periphery of an infarct, and which suggest that the tightly demarcated lesion produced by the Nd-YAG laser lacks these components of graded injury that are evident following other types of focal brain damage.

Antagonism of neutrophil adherence in the deteriorating stroke model in rabbits

Adhesion of leukocytes to the endothelium can occur in a few hours after the onset of ischemia, and the actions of leukocytes have been suggested to aggravate reperfusion injury. Adhesion is a prerequisite for the harmful leukocyte actions. Rapid mediation of leukocyte adhesion and aggravation of reperfusion injury can occur through production of platelet-activating factor (PAF). The authors hypothesized that prevention of leukocyte adhesion during ischemia reperfusion would have beneficial effects and that these effects might be enhanced by a PAF antagonist. To test this hypothesis, rabbits were anesthetized with pentobarbital and subjected to severe spinal cord ischemia (25 minutes) followed by 30 minutes of reperfusion, at which time either vehicle, antibody against the CD11/CD18 (anti-CD) leukocyte adhesion molecule (1 mg/kg), or the anti-CD and PAF antagonist, WEB 2086 (3 mg/kg), was administered intravenously and the animals were monitored for 6.5 hours. Using a score from 0 to 5, recovery of motor function was improved at 5.5 hours by the CD antibody (2.0 +/- 0.5 versus 0.4 +/- 0.2 in the six animals in the vehicle group, p < 0.05). No further improvement was induced by WEB 2086 in the six anti-CD treated animals (1.6 +/- 0.7). Spinal cord blood flow (laser Doppler flowmetry) at 6 hours was at the preischemic level in the control animals (-7% +/- 20%), but clearly increased in the anti-CD group (+73% +/- 29%, p < 0.5). The severity of blood-brain barrier damage in the spinal cord gray matter was decreased by the treatments. Extravasation of intravenously injected Evans blue albumin (EBA), measured by detection of EBA fluorescence, was reduced by approximately 50% in both treated groups (p < 0.05). The number of morphologically normal motor neurons in the lumbar anterior horns of the infarcted spinal cord showed protection in the seven animals in the anti-CD treated group at 6.5 hours: 12.7 +/- 1.7 versus 5.3 +/- 1.6 (vehicle), p < 0.05 without an additional effect by PAF antagonist 12.2 +/- 2.6 (anti-CD + WEB 2086). Our results suggest that ultraacute treatment of reperfusion injury based on special inhibition of leukocyte effects may be beneficial. Platelet-activating factor antagonism failed to enhance this therapeutic effect, which may suggest dependency on a common mechanism.

Laser-Doppler flowmetry in monitoring regulation of rapid microcirculatory changes in spinal cord

We established a rabbit model for continuous on-line monitoring of spinal cord microcirculation using laser-Doppler flowmetry (LDF). We tested the suitability of this model for studying rapid, nonequilibrium microcirculatory blood flow (BF) states induced by pharmacological treatments, hemorrhage, and asphyxia. Effective BF regulation was observed at systemic arterial pressure levels of 50 mmHg. Autoregulatory vasodilation began 1 min after the onset of severe hypotension, whereas more immediate vasodilation took place after asphyxia (hypercarbia). Pathological situations were studied in a simple model of spinal cord (SC) ischemia-reperfusion after 10 (n = 7) and 25 min (n = 7) of ischemia and 2 h of reperfusion. After 25 min of ischemia, delayed hypoperfusion (BF -35 +/- 7%, P less than 0.01) took place in association with tissue edema. LDF offered sensitive, stable, and reproducible estimates of microcirculation with high temporal resolution, thus permitting on-line evaluation of rapid, nonequilibrium BF responses and delayed states of spinal cord BF dysregulation.

Platelet-activating factor in stroke and brain injury

Platelet-activating factor, an endogenous phospholipid of proinflammatory, hemostatic, and vasoactive properties, is synthesized by neurons and in injured brain. Platelet-activating factor is released together with eicosanoids such as thromboxane A2, prostacyclin, and leukotrienes. Its effects in neurons are mediated through a specific receptor coupled to phospholipase C and phosphoinositol metabolism. The cerebrovascular effects of platelet-activating factor include disruption of the blood-brain barrier, edema formation, and vasospasm. It has also been described to possess direct toxicity to neuronal cells in culture. Discovery and development of several highly potent and selective antagonists to platelet-activating factor receptors facilitated experimental studies underscoring the role of this factor as an endogenous mediator in cerebral disorders, particularly cerebral ischemia and trauma. Significant biochemical, microvascular, functional, and behavioral recovery has been demonstrated using these antagonists in an array of experimental models of focal and global ischemia in the central nervous system (CNS). Clearly, studies of platelet-activating factor in experimental models of CNS ischemia and reperfusion injury open a new perspective on phospholipid metabolism in stroke and offer an exceptionally promising therapeutic prospect. Data supporting this factor as a mediator of specific pathological sequelae in stroke and neuroinjury are surveyed in this review. We discuss the mechanisms and significance of platelet-activating factor-mediated effects and propose directions for future studies.

Cortical microcirculation in a new model of focal laser-induced secondary brain damage

To study the causes of spatial and temporal evolution of progressive neuro-injury in focal brain ischemia, models with consistent lesion topography are required. In such models, continuous monitoring of the microcirculation in a penumbral area undergoing progressive damage could be possible. We used a fixed-pulse (1.0 s, 40 W) Nd-YAG laser (NYL) to produced discrete brain lesions in rats and monitored the cerebral blood flow (CBF) with laser-Doppler flowmetry (LDF) in nonirradiated areas directly adjacent to the maturing lesion. We also examined the time evolution of the lesion topography over a 4 day period. The lesion volume determined by histopathological methods increased from 3.1 +/- 0.5 to 4.5 +/- 0.5 mm3 (p less than 0.05) during the first 2 h. Simultaneously, LDF indicated severe hypoperfusion (-60 +/- 21%, p less than 0.01) at a zone (1 mm distance from the laser lesion) where progressive neuronal degeneration and increased tissue water content (80.0 +/- 3.3% versus 76.8 +/- 2.1% in normal tissue, n = 7, p less than 0.05) were also observed. At a 4 mm distance from the lesion, hyperemic CBF responses were observed, but no histopathological signs or edema. Secondary brain damage progressed up to 4 days (lesion volume of 6.0 +/- 0.7 mm3). The NYL-induced brain lesion produced a highly reproducible focal injury and progressive neuronal death in a spatial relationship with microcirculatory failure and edema formation. The model allows prospective study of tissue state at a discrete zone, which is separate from the initial injury, but susceptible to secondary brain damage.

Evidence for platelet-activating factor as a novel mediator in experimental stroke in rabbits

Platelet-activating factor is a potent mediator of inflammation, which has untoward effects on cerebrovascular and neural elements. While several investigators have reported attenuation of ischemic damage after treatment with antagonists of platelet-activating factor, no study has proved endogenous production of platelet-activating factor in ischemia of the central nervous system. We hypothesized that endogenous production of platelet-activating factor participates in the early pathologic manifestations of deteriorating stroke. In 12 rabbits, we found tissue levels of platelet-activating factor measured by the release of serotonin from washed platelets to be elevated by approximately 20-fold in spinal cord injured by 25 minutes of ischemia and 2 hours of reperfusion (2.80 +/- 0.98 ng/g) compared with that in normal spinal cord (0.15 +/- 0.06 ng/g, p less than 0.01). Given during ischemia to seven rabbits, 10 mg/kg i.p. of a highly selective and potent antagonist of platelet-activating factor (BN 50739) accentuated the early postischemic hyperemia and prevented the delayed hypoperfusion measured by on-line laser-Doppler flowmetry (-35 +/- 7% of baseline [n = 7] without versus 33 +/- 14% with treatment, p less than 0.01) and the edema formation measured as the increase in tissue water content (4.4 +/- 0.7% without [n = 6] versus 2.1 +/- 0.6% with [n = 7]treatment, p less than 0.05) after 2 hours of reperfusion. This neurochemical and pharmacologic evidence emphasizes a new perspective of ischemia-induced phospholipid degradation and suggests an important role for platelet-activating factor in the early manifestations of stroke.

Platelet-activating factor and progressive brain damage following focal brain injury

The effects of a platelet-activating factor (PAF) antagonist on brain edema, cortical microcirculation, blood-brain barrier (BBB) disruption, and neuronal death following focal brain injury are reported. A neodymium:yttrium-aluminum-garnet (Nd:YAG) laser was used to induce highly reproducible focal cortical lesions in anesthetized rats. Secondary brain damage in this model was characterized by progressive cortical hypoperfusion, edema, and BBB disruption in the vicinity of the hemispheroid lesion occurring acutely after injury. The histopathological evolution was followed for up to 4 days. Neuronal damage in the cortex and the hippocampus (CA-1) was assessed quantitatively, revealing secondary and progressive loss of neuronal tissue within the first 24 hours following injury. Pretreatment with the PAF antagonist BN 50739 ameliorated the severe hypoperfusion in 12 rats (increasing local cerebral blood flow from a mean +/- standard error of the mean of 40.5% +/- 8.3% to 80.2% +/- 7.8%, p less than 0.01) and reduced edema by 70% in 10 rats (p less than 0.05) acutely after injury. The PAF antagonist also reduced the progression of neuronal damage in the cortex and the CA-1 hippocampal neurons (decrease of neuronal death from 88.0% +/- 3.9% to 49.8% +/- 4.2% at 24 hours in the cortex and from 40.2 +/- 5.0% to 13.2% +/- 2.1% in the hippocampus in 30 rats; p less than 0.05). This study provides evidence to support progressive brain damage following focal brain injury, associated with secondary loss of neuronal cells. In this latter process, PAF antagonists may provide significant therapeutic protection in arresting secondary brain damage following cerebral ischemia and neurological trauma.

Increased cerebral lactate output to cerebral venous blood after forebrain ischemia in rats

Increased cerebral lactate levels are a well-known aspect of the sequelae of the metabolic derangements that follow cerebral ischemia. A new technique has recently become available to sample cerebral venous blood from the superior sagittal sinus on a long-term basis in conscious rats. We report the applicability of this method to assess serial biochemical responses to brain injury. Serum samples were obtained from the superior sagittal sinus, the common carotid artery, and the external jugular vein of nine anesthetized rats before and up to 7 days after 10 minutes of forebrain ischemia was produced by carotid occlusion and hypovolemic hypotension (mean arterial blood pressure 50 +/- 4 mm Hg). The cerebral venous-arterial difference in serum lactate concentration was increased for up to 3 hours after ischemia, while there was no significant change in the difference in serum lactate concentrations in the common carotid artery and the external jugular vein. This indicates an elevated output of lactate from brain tissue to blood, detectable only in the superior sagittal sinus, which underlines the usefulness of the technique. We observed a persistent elevation in brain lactate production after virtually complete recovery from the acute insult.

Effect of systemic platelet-activating factor (PAF) on the rabbit spinal cord microcirculation

Platelet-activating factor (PAF) is an endogenous phospholipid mediator with pro-inflammatory and vasoactive properties. Since PAF has been implicated in ischemic neuroinjury, we determined its effects on rabbit spinal cord microcirculation (SCM). Using laser-Doppler flow measurements, we monitored mean arterial pressure and SCM continuously on-line during and after i.v. infusion (1 min) of 0.5 nmol/kg of PAF (n = 20) and measured thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) in arterial blood 1.5 min after the infusion. Responses were compared to those after indometacin pretreatment (4 mg/kg, n = 11). During the infusion, spinal cord blood flow (SCBF) decreased by 14 +/- 5% (P less than 0.05) paralleling the systemic hypotensive changes (17 +/- 5%, P less than 0.01) with no changes in vascular resistance (SCVR). However, immediately after termination of PAF infusion, SCVR decreased by 17 +/- 5% (P less than 0.01) while SCBF rapidly recovered. Plasma levels of both TXB2 and 6-keto-PGF1 alpha were significantly elevated. TXB2 release was correlated with the degree of hypotension during the PAF infusion (r greater than 0.72; P less than 0.05) while 6-keto-PGF1 alpha release correlated well with the decrease in SCVR during the infusion period (r greater than 0.64; P less than 0.05). Indomethacin blocked both the hemodynamic events and the eicosanoid release induced by PAF. Our data suggest that PAF modulates SCM through eicosanoid-mediated mechanism.

Long-term sampling of cerebral venous blood in conscious rats

The mechanisms of secondary brain damage following cerebral ischemia or CNS trauma are still unknown. A variety of mediators, released by the injured brain, are held to be responsible for delayed neuronal cell damage. No technique is available yet for repeated sampling of cerebral venous blood (CVB) on a long-term basis, which allows to assess the neurobiochemical responses to brain injury chronically in conscious laboratory animals. This is a report on the establishment of a method to sample CVB from the superior sagittal sinus (SSS) for at least 7 days in conscious freely moving rats. The torcular was exposed for implantation of a catheter into the caudal SSS. Patency was preserved by perfusion with a nonsystemic dose of heparin by an Alzet osmotic pump and verified daily by aspirating of 0.5 ml CVB for blood analysis. No neuropathology was seen in histological examination. The rats appeared comfortable and without distress, and the transient weight loss was rapidly regained. The present model provides the opportunity to evaluate acute or chronic neurobiochemical responses to stroke, CNS trauma, or any other typ of brain injury in the conscious rat.

Validation of laser-Doppler flowmetry in measurement of spinal cord blood flow

Laser-Doppler flowmetry (LDF) is a non-invasive method for continuous on-line monitoring of microvascular blood flow. LDF has previously been validated with established methods in various tissues, yet its validity and resolution in the central nervous system (CNS) remain unclear. We compared LDF with the microsphere method (MS) using two independent laser probes placed on the dorsal lumbar spinal cord (L5 laminectomy) of anesthetized rabbits (n = 9). After base-line flow measurements, spinal cord blood flow (SCBF) was increased (up to 50%) with phenylephrine (10-80 micrograms.kg-1.min-1 iv) and decreased (up to 50%) with chlorisondamine (10 mg/kg iv) or other stimuli. The percentage changes of lumbar SCBF and vascular resistance (VR) from the base line obtained by LDF and MS excellently agreed (rBF = 0.86, rVR = 0.94, P less than 0.0001). LDF estimated also the absolute SCBF values parallel to MS (r = 0.77, P less than 0.001). In conclusion, the validity of LDF in estimating the SCBF and dynamic changes of BF and VR is confirmed. Therefore, LDF may prove useful for monitoring CNS microcirculation in normal or pathophysiological states.