bluuebunny/crossref_metadata_2025 huggingface dataset:
Postischemic Steroid Modulation: Effects on Hippocampal Neuronal Integrity and Synaptic Plasticity
Authors: Krugers Harm J. , Maslam Suharti , Van Vuuren Sandra M. , Korf Jakob , Joëls Marian
Published: November 2003

Elimination of corticosteroids after ischemia, by removal of the adrenals, has been reported to preserve neuronal integrity later. To establish the therapeutic potential of this observation, the authors address two questions: first, whether clinically more relevant steroid manipulations after ischemia exert similar protective effects, and second, whether changes in synaptic functioning occur along with structural alterations. To test this, the authors treated animals immediately after hypoxia—ischemia with (1) the steroid synthesis inhibitor metyrapone, (2) the synthetic glucocorticoid receptor agonist dexamethasone, (3) the selective glucocorticoid antagonist RU 38486, or (4) corticosterone. Metyrapone, but none of the other compounds, attenuated the occurrence of seizures immediately after ischemia, Twenty-four hours after hypoxia—ischemia, CA1 hippocampal field potentials in response to stimulation of fibers were found to be reduced. The attenuation of synaptic transmission was partly prevented by metyrapone. None of the other experimental treatments influenced the impaired synaptic function, Gross morphologic analysis revealed no differences in the loss of neuronal structure between the experimental groups at this time point. Taken together, these data suggest that metyrapone preserves neuronal functioning despite loss of neuronal structure. The authors tentatively conclude that preventing the ongoing production of steroids shortly after ischemia can delay and attenuate the appearance of ischemia-related pathology.
Spectral Analysis of Arterial Blood Pressure and Cerebral Blood Flow Velocity during Supine Rest and Orthostasis
Authors: Chern Chang-Ming , Kuo Terry Bo-Jau , Sheng Wen-Yung , Wong Wen-Jang , Luk Yung-On , Hsu Li-Chi , Hu Han-Hwa
Published: November 2003

This study evaluates the effect of orthostasis on the low frequency (LF, 0.04 to 0,15 Hz) fluctuations in the blood flow velocity of the middle cerebral artery (MCAFV) in relation to its arterial blood pressure (ABP) equivalent to further define and quantify this relationship in cerebrovascular regulation. Spectral analysis was performed on 22 healthy subjects during supine rest and head-up tilt. The power in the LF range can be used to quantify the LF fluctuations, and four types of LF power data could be obtained for each individual: LF power of supine MCAFV, LF power of supine ABP, LF power of tilt MCAFV, and LF power of tilt ABP. By comparing LF power of MCAFV with LF power of ABP, two power ratios could be generated to describe the flow-pressure relationship during supine rest and head-up tilt, respectively, supine power ratio (LF power of supine MCAFV/LF power of supine ABP) and tilt power ratio (LF power of tilt MCAFV/LF power of tilt ABP). In addition, an index for dynamic autoregulation in response to orthostasis can be calculated from these two power ratios (tilt power ratio/supine power ratio). The authors found that this index was dependent on the extent of orthostatic MCAFV changes, and the dependency could be mathematically expressed ( r = 0.61, P = .0001), suggesting its involvement in cerebrovascular regulation. Moreover, these data further support the previous observation that the LF fluctuations of MCAFV might result from modulation of its ABP equivalent, and the modulation effect could be quantified as the power ratio (LF power of MCAFV/LF power of ABP). These observations could be an important step toward further insight into cerebrovascular regulation, which warrants more research in the future.
The Effect of Movement Amplitude on Activation in Functional Magnetic Resonance Imaging Studies
Authors: Waldvogel Daniel , van Gelderen Peter , Ishii Kenji , Hallett Mark
Published: November 2003

To evaluate the effect of movement amplitude on the “blood oxygen level-dependent effect,” the authors studied six normal subjects while they extended their index finger with two different amplitudes, Images were analyzed using SPM96, In five subjects, the signal intensity increase in the primary sensorimotor area was significantly greater with the larger amplitude movement. In other areas of interest (supplementary motor area, premotor cortex, insula, postcentral area, cerebellum), the large-amplitude movement often showed significant activation when the small-amplitude movement did not. The authors conclude that, in studies of the motor system, movement amplitude needs to be controlled.
The Cyclooxygenase-2 Inhibitor NS-398 Ameliorates Ischemic Brain Injury in Wild-Type Mice but not in Mice with Deletion of the Inducible Nitric Oxide Synthase Gene
Authors: Nagayama Masao , Niwa Kiyoshi , Nagayama Tomiko , Ross M. Elizabeth , Iadecola Costantino
Published: November 2003

The authors investigated the role of the prostaglandin-synthesizing enzyme cyclooxygenase-2 (COX-2) in the mechanisms of focal cerebral ischemia and its interaction with inducible nitric oxide synthase (iNOS). Focal cerebral ischemia was produced by permanent occlusion of the middle cerebral artery (MCA) in mice. Infarct volume was measured 96 hours later by computer-assisted planimetry in thionin-stained brain sections. The highly selective COX-2 inhibitor NS398 (20 mg/kg; intraperitoneally), administered twice a day starting 6 hours after MCA occlusion, reduced total infarct volume in C57BL/6 (–23%) and 129/SVeV mice (–21%), and ameliorated the motor deficits produced by MCA occlusion ( P < .05). However, NS398 did not influence infarct volume in mice with deletion of the iNOS gene ( P > .05). In contrast, the neuronal NOS inhibitor 7-NI (50 mg/kg; intraperitoneally), administered once 5 minutes after MCA occlusion, reduced neocortical infarct volume by 20% in iNOS −/− mice ( P < .05). NS398 did not affect arterial pressure, resting CBF or the CBF reactivity to hypercapnia in anesthetized iNOS null mice ( P > .05). The data suggest that COX-2 reaction products, in mouse as in rat, contribute to ischemic brain injury. However, the failure of NS398 to reduce infarct volume in iNOS null mice suggests that iNOS-derived NO is required for the deleterious effects of COX-2 to occur. Thus, COX-2 reaction products may be another mechanism by which iNOS-derived NO contributes to ischemic brain injury.
Hemodynamics and Metabolism in Stroke-Prone Spontaneously Hypertensive Rats before Manifestation of Brain Infarcts
Authors: Mies Günter , Hermann Dirk , Ganten Ursula , Hossmann Konstantin-Alexander
Published: November 2003

Genomic screening of hybrids from stroke-prone (SHR-SP) and stroke-resistant spontaneously hypertensive rats (SHR) identified a STR1 locus on the rat chromosome 1, which correlates with the susceptibility to cerebral stroke but not with hypertension. The authors examined whether this genetic abnormality is associated with hemodynamic or metabolic alterations in the brain that can be detected before the manifestation of brain infarction. Starting at 6 weeks of age, SHR-SP were fed with a salt-rich diet to accelerate arterial hypertension. At the age of 12 weeks, animals developed functional symptoms and were age-matched with symptom-negative SHR-SP to differentiate between presymptomatic and postsymptomatic changes. Brains were investigated by multiparametric imaging comprising quantitative double-tracer autoradiography of CBF and cerebral protein synthesis (CPS); bioluminescence imaging of regional ATP, glucose, and lactate content; and umbelliferone fluoroscopic imaging of tissue pH. None of the animals exhibited focal hemodynamic or biochemical abnormalities. In symptom-negative SHR-SP, global CBF was 1.1 ± 0.3 mL. g–1 · min–1, cortical CPS was 10.1 ± 3.1 nmol · g–1 · min–1, and cortical ATP, glucose, lactate, and pH levels were in the normal range. In SHR-SP with functional symptoms, ATP, glucose, and lactate levels also were normal, but tissue pH exhibited periventricular alkalosis, CBF was significantly reduced to 0.7 ± 0.2 mL · g–1 · min–1 ( P < 0.001), and cortical CPS was significantly reduced to 6.7 ± 2.1 nmol · g–1 · min–1 ( P < 0.001). The decline in brain perfusion of SHR-SP correlated significantly with both the severity of functional deficits and the decline of protein synthesis. Our observations demonstrate that SHR-SP had already developed functional symptoms before the manifestation of overt brain infarcts and that the symptoms are initiated by a decline in global CBF and cortical CPS. Genetic abnormalities in SHR-SP are associated with a diffuse vascular process that results in global decompensation of blood flow well before the onset of focal brain infarction.
A Transforming Growth Factor-β Antagonist Unmasks the Neuroprotective Role of This Endogenous Cytokine in Excitotoxic and Ischemic Brain Injury
Authors: Ruocco Antonio , Nicole Olivier , Docagne Fabian , Ali Carine , Chazalviel Laureut , Komesli Sylviane , Yablonsky Françoise , Roussel Simon , MacKenzie Eric T. , Vivien Deny , Buisson Alain
Published: November 2003

Various studies describe increased concentrations of transforming growth factor-β (TGF-β) in brain tissue after acute brain injury. However, the role of endogenously produced TGF-β after brain damage to the CNS remains to be clearly established. Here, the authors examine the influence of TGF-β produced after an episode of cerebral ischemia by injecting a soluble TGF-β type II receptor fused with the Fc region of a human immunoglobulin (TβRIIs-Fc). First, this molecular construct was characterized as a selective antagonist of TGF-β. Then, the authors tested its ability to reverse the effect of TGF-β 1 on excitotoxic cell death in murine cortical cell cultures. The addition of 1 μg/mL of TβRIIs-Fc to the exposure medium antagonized the neuroprotective activity of TGF-β 1 in N-methyl-D-aspartate (NMDA)-induced excitotoxic cell death. These results are consistent with the hypothesis that TGF-β 1 exerts a negative modulatory action on NMDA receptor-mediated excitotoxicity. To determine the role of TGF-β 1 produced in response to brain damage, the authors used a model of an excitotoxic lesion induced by the intrastriatal injection of 75 nmol of NMDA in the presence of 1.5 μg of TβRIIs-Fc. The intrastriatal injection of NMDA was demonstrated to induce an early upregulation of the expression of TGF-β 1 mRNA. Furthermore, when added to the excitotoxin, TβRIIs-Fc increased (by 2.2-fold, P < 0.05) the lesion size. These observations were strengthened by the fact that an intracortical injection of TβRIIs-Fc in rats subjected to a 30-minute reversible cerebral focal ischemia aggravated the volume of infarction. In the group injected with the TGF-β 1 antagonist, a 3.5-fold increase was measured in the infarction size (43.3 ± 9.5 versus 152.8 ± 46.3 mm3; P < 0.05). In conclusion, by antagonizing the influence of TGF-β in brain tissue subjected to excitotoxic or ischemic lesion, the authors markedly exacerbated the resulting extent of necrosis. These results suggest that, in response to such insults, brain tissue responds by the synthesis of a neuroprotective cytokine, TGF-β1, which is involved in the limitation of the extent of the injury. The pharmacologic potentiation of this endogenous defensive mechanism might represent an alternative and novel strategy for the therapy of hypoxic-ischemic cerebral injury.
Cerebral Functional Magnetic Resonance Imaging Activation Modulated by a Single Dose of the Monoamine Neurotransmission Enhancers Fluoxetine and Fenozolone during Hand Sensorimotor Tasks
Authors: Loubinoux Isabelle , Boulanouar Keder , Ranjeva Jean-Philippe , Carel Christophe , Berry Isabelle , Rascol Olivier , Celsis Pierre , Chollet François
Published: November 2003

Fluoxetine inhibits the reuptake of serotonin, and dextroamphetamine enhances presynaptic release of monoamines. Although the excitatory effect of both noradrenaline and dopamine on motor behavior generally is accepted, the role of serotonin on motor output is under debate. In the current investigation, the authors evidenced a putative role of monoamines and, more specifically, of serotonin in the regulation of cerebral motor activity in healthy subjects. The effects on cerebral motor activity of a single dose of fluoxetine (20 mg), an inhibitor of serotonin reuptake, and fenozolone (20 mg/50 kg), an amphetamine-like drug, were assessed by functional magnetic resonance imaging. Subjects performed sensorimotor tasks with the right hand. Functional magnetic resonance imaging studies were performed in two sessions on two different days. The first session, with two scan experiments separated by 5 hours without any drug administration, served as time-effect control. A second, similar session but with drug administration after the first scan assessed drug effects. A large increase in evoked signal intensity occurred in the ipsilateral cerebellum, and a parallel, large reduction occurred in primary and secondary motor cortices (P < 10–3). These results are consistent with the known effects of habituation. Both drugs elicited comparable effects, that is, a more focused activation in the contralateral sensorimotor area, a greater involvement of posterior supplementary motor area, and a widespread decrease of bilateral cerebellar activation (P < 10–3). The authors demonstrated for the first time that cerebral motor activity can be modulated by a single dose of fluoxetine or fenozolone in healthy subjects. Drug effects demonstrated a direct or indirect involvement of monoamines and serotonin in the facilitation of cerebral motor activity.
Behavioral Efficacy of Posttraumatic Calpain Inhibition is Not Accompanied by Reduced Spectrin Proteolysis, Cortical Lesion, or Apoptosis
Authors: Saatman Kathryn E. , Zhang Chen , Bartus Raymond T. , McIntosh Tracy K.
Published: November 2003

Administration of the selective calpain inhibitor AK295 has been shown to attenuate motor and cognitive dysfunction after brain trauma in rats. To explore mechanisms underlying the behavioral efficacy of posttraumatic calpain inhibition, we investigated histologic consequences of AK295 administration. Anesthetized Sprague-Dawley rats received lateral fluid percussion brain injury of moderate severity (2.2 to 2.4 atm) or served as uninjured controls. At 15 minutes after injury, animals were randomly assigned to receive a 48-hour infusion of either 2 mmol/L AK295 (120 to 140 mg/kg) or saline via the carotid artery. At 48 hours and 1 week after injury, spectrin fragments generated specifically by calpain were detected by Western blotting and immunohistochemistry, respectively, in saline-treated, brain-injured animals. Interestingly, equivalent spectrin breakdown was observed in AK295-treated animals when cortical and hippocampal regions were evaluated. Similarly, administration of the calpain inhibitor did not attenuate cortical lesion size or the numbers of apoptotic cells in the cortex, subcortical white matter, or hippocampus, as verified by terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphate nick-end labeling and morphology, at 48 hours after injury. These data suggest that an overt reduction in spectrin proteolysis, cortical lesion, or apoptotic cell death at 48 hours or 1 week is not required for behavioral improvements associated with calpain inhibition by AK295 after experimental brain injury in rats.
Overexpression of Copper and Zinc Superoxide Dismutase in Transgenic Mice Prevents the Induction and Activation of Matrix Metalloproteinases after Cold Injury-Induced Brain Trauma
Authors: Morita-Fujimura Yuiko , Fujimura Miki , Gasche Yvan , Copin Jean-Christophe , Chan Pak H.
Published: November 2003

Matrix metalloproteinases (MMPs), a family of proteolytic enzymes which degrade the extracellular matrix, are implicated in blood—brain barrier disruption, which is a critical event leading to vasogenic edema. To investigate the role of reactive oxygen species (ROS) in the expression of MMPs in vasogenic edema, the authors measured gelatinase activities before and after cold injury (CI) using transgenic mice that overexpress superoxide dismutase-1. A marked induction of pro-gelatinase B (pro-MMP-9) was seen 2 hours after CI and was maximized at 12 hours in wild-type mice. The pro-MMP-9 level was significantly lower in transgenic mice 4 hours ( P < 0.001) and 12 hours ( P < 0.05) after CI compared to wild-type mice. The activated MMP-9 was detected from 6 to 24 hours after injury. A mild induction of pro-gelatinase A (pro-MMP-2) was seen at 6 hours and was sustained until 7 days. In contrast, the activated form of MMP-2 appeared at 24 hours, was maximized at 7 days, and was absent in transgenic mice. Western blot analysis showed that the tissue inhibitors of metalloproteinases were not modified after CI. The results suggest that ROS production after CI may contribute to the induction and/or activation of MMPs and could thereby exacerbate endothelial cell injury and the development of vasogenic edema after injury.
Ischemic Brain Damage in Mice after Selectively Modifying BDNF or NT4 Gene Expression
Authors: Endres Matthias , Fan Guoping , Hirt Lorenz , Fujii Masazumi , Matsushita Kohji , Liu Xin , Jaenisch Rudolf , Moskowitz Michael A.
Published: November 2003

The neurotrophins and the tyrosine kinase (Trk) B receptor may play a protective role in the pathophysiology of cerebral ischemia. In this study, the authors investigated whether reducing endogenous expression of TrkB-binding neurotrophins modifies the susceptibility to ischemic injury after 1-hour middle cerebral artery occlusion followed by 23 hours of reperfusion in a filament middle cerebral artery occlusion model. Mice lacking both alleles for neurotrophin-4 ( nt4−/−) or deficient in a single allele for brain-derived neurotrophic factor ( bdnf+/−) exhibited larger cerebral infarcts compared to wild-type inbred 129/SVjae mice (68% and 91%, respectively, compared to controls). Moreover, lesions were larger (21%) in nt4−/− mice after permanent middle cerebral artery occlusion. Hence, expression of both NT4 and BDNF, and by inference the TrkB receptor, confers resistance to ischemic injury.
Identification of Thrombin Receptors in Rat Brain Capillary Endothelial Cells
Authors: Bartha Katalin , Dömötör Eszter , Lanza Francois , Adam-Vizi Vera , Machovich Raymund
Published: November 2003

Both thrombin and plasmin induce contraction of brain endothelial cells, which may increase capillary permeability thereby leading to disruption of the blood-brain barrier. Identification of thrombin receptors, as well as the influence of plasmin on their activation, in capillary endothelial cells and astrocytes are therefore essential for understanding injury-related actions of thrombin in the brain. Using the reverse transcriptase-polymerase chain reaction method, the present study shows that primary cultures of rat brain capillary endothelial (RBCE) cells and astrocytes derived from rat brain express two different thrombin receptors. The first is proteolytically activated receptor (PAR)-1, the receptor responsible for the vast majority of the thrombin's cellular activation functions; the second is PAR-3, a receptor described to be essential for normal responsiveness to thrombin in mouse platelets. In addition to these thrombin receptors, the mRNA (messenger RNA) for PAR-2, a possible trypsin receptor, was also identified. Functional significance of thrombin receptors was indicated by changes in [Ca2+]i in response to thrombin, as measured by FURA-2 fluorescence in RBCE cells. Thrombin as low as 4 nmol/L induced an abrupt increase in [Ca2+]i whereas, upon addition of active site-blocked thrombin or plasmin, [Ca2+]i remained unchanged. The [Ca2+]i signal attributable to thrombin was smaller in a low Ca2+-containing medium, indicating that an influx of Ca2+ from the extracellular medium makes a contribution to the overall [Ca2+]i rise. The amplitude of the transient [Ca2+]i signal was dependent on the concentration of thrombin, and repeated application of the enzyme caused an essentially complete and long-term desensitization of the receptor. The PAR-1 agonist peptide SFLLRN also elicited a transient increase in [Ca2+]i. After activation by SFLLRN, cells showed a diminished response to thrombin, but the response was not absent, indicating that PAR-3 might contribute to the generation of the [Ca2+]i signal. Pretreatment of RBCE cells with 100 nmol/L plasmin completely prevented [Ca2+]i rise attributable to thrombin. These data show that RBCE cells and astrocytes express at least two receptors for thrombin, PAR-1 and PAR-3, and probably both receptors are involved in thrombin-induced [Ca2+]i signals. Plasmin itself does not elevate [Ca2+]i but prevents the activation of receptors by thrombin.
Early Temporal Characteristics of Cerebral Blood Flow and Deoxyhemoglobin Changes during Somatosensory Stimulation
Authors: Silva Afonso C. , Lee Sang-Pil , Iadecola Costantino , Kim Seong-Gi
Published: November 2003

The close correspondence between neural activity in the brain and cerebral blood flow (CBF) forms the basis for modern functional neuroimaging methods. Yet, the temporal characteristics of hemodynamic changes induced by neuronal activity are not well understood. Recent optical imaging observations of the time course of deoxyhemoglobin (HbR) and oxyhemoglobin have suggested that increases in oxygen consumption after neuronal activation occur earlier and are more spatially localized than the delayed and more diffuse CBF response. Deoxyhemoglobin can be detected by blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI). In the present study, the temporal characteristics of CBF and BOLD changes elicited by somatosensory stimulation in rat were investigated by high-field (9.4 T) MRI. With use of high-temporal-resolution fMRI, it was found that the onset time of the CBF response in the somatosensory cortex was 0.6 ± 0.4 seconds (n = 10). The CBF changes occurred significantly earlier than changes in HbR concentration, which responded after 1.1 ± 0.3 seconds. Furthermore, no early increases in HbR (early negative BOLD signal changes) were observed. These findings argue against the occurrence of an early loss of hemoglobin oxygenation that precedes the rise in CBF and suggest that CBF and oxygen consumption increases may be dynamically coupled in this animal model of neural activation.
Dynamics of Regional Brain Metabolism and Gene Expression After Middle Cerebral Artery Occlusion in Mice
Authors: Hata Ryuji , Maeda Keiichiro , Hermann Dirk , Mies Günter , Hossmann Konstantin-Alexander
Published: November 2003

The evolution of brain infarcts during permanent occlusion of the middle cerebral artery (MCA) was studied in mice using multiparametric imaging techniques. Regional protein synthesis and the regional tissue content of ATP were measured on adjacent cryostat sections at increasing intervals after vascular occlusion ranging from 1 hour to 3 days. The observed changes were correlated with the expression of the mRNA of hsp70, c-fos, c-jun, and junB, as well as the distribution of DNA double-strand breaks visualized by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling (TUNEL). One hour after MCA occlusion, the tissue volume with suppressed protein synthesis was distinctly larger than that in which ATP was depleted. With ongoing ischemia time, the ATP-depleted area gradually expanded and, within 1 day, merged with the region of suppressed protein synthesis. Expression of hsp70 mRNA occurred mainly in the penumbra (defined as the region of suppressed protein synthesis but preserved ATP), peaking at 3 hours after vascular occlusion. Expression of the immediate-early genes c-jun, c-fos, and junB increased both in the penumbra and the periinfarct normal tissue already at 1 hour after vascular occlusion, with slightly different regional and temporal patterns for each of these genes. DNA fragmentations were clearly confined to neurons; they appeared after 1 day in the infarct core (defined as the region of suppressed ATP) and never were detected in the penumbra. The late appearance of TUNEL after infarcts had reached their final size and the absence in the penumbra points against a major pathogenetic role of apoptosis. Permanent MCA occlusion in mice thus produces a gradually expanding infarct, the final size of which is heralded by the early inhibition of protein synthesis.
Graded Reduction of Cerebral Blood Flow in Rat as Detected by the Nuclear Magnetic Resonance Relaxation Time T2: A Theoretical and Experimental Approach
Authors: Gröhn Olli H. J. , Kettunen Mikko I. , Penttonen Markku , Oja Joni M. E. , van Zijl Peter C. M. , Kauppinen Risto A.
Published: November 2003

The ability of transverse nuclear magnetic resonance relaxation time, T2, to reveal acutely reduced CBF was assessed using magnetic resonance imaging (MRI). Graded reduction of CBF was produced in rats using a modification of Pulsinelli's four-vessel occlusion model. The CBF in cerebral cortex was quantified using the hydrogen clearance method, and both T2 and the trace of the diffusion tensor ( Dav = 1/3 TraceD) in the adjacent cortical tissue were determined as a function of reduced CBF at 4.7 T. A previously published theory, interrelating cerebral hemodynamic parameters, hemoglobin, and oxygen metabolism with T2, was used to estimate the effects of reduced CBF on cerebral T2. The MRI data show that T2 reduces in a U-shape manner as a function of CBF, reaching a level that is 2.5 to 2.8 milliseconds (5% to 6%) below the control value at CBF, between 15% and 60% of normal. This reduction could be estimated by the theory using the literature values of cerebral blood volume, oxygen extraction ratio, and precapillary oxygen extraction during compromised CBF. Dav dropped with two apparent flow thresholds, so that a small 11% to 17% reduction occurred between CBF values of 16% to 45% of normal, followed by a precipitous collapse by more than 20% at CBF below 15% of normal. The current data show that T2 can be used as an indicator of acute hypoperfusion because of its ability to indicate blood oxygenation level-dependent phenomena on reduced CBF.
Induction of Angiopoietin and Tie Receptor mRNA Expression after Cerebral Ischemia–Reperfusion
Authors: Lin Teng-Nan , Wang Chien-Kai , Cheung Wai-Mui , Hsu Chung-Yi
Published: November 2003

The angiopoietin/Tie receptor system may contribute to angiogenesis and vascular remodeling by mediating interactions of endothelial cells with smooth muscle cells and pericytes. The temporal expression of angiopoietin-1 (Angpo-1), angiopoietin-2 (Angpo-2), Tie-1, and Tie-2 mRNA was studied in a focal cerebral ischemia model in rats. The cDNA fragments obtained from reverse transcription polymerase chain reaction amplification were cloned and used as a probe to detect individual genes. Northern blot analysis showed a delayed increase of a 4.4-kb Angpo-1 transcript for up to 2 weeks after ischemia, eightfold higher than the values of the shamoperated controls. A biphasic expression of a 2.4-kb Angpo-2 transcript was noted, peaking at 24 hours (6.4-fold) and 2 weeks (4.6- fold) after ischemia. The expression of Tie-2 mRNA (4.3 kb), a receptor for Angpo-1, and Tie-1 mRNA (4.3 kb) also increased starting 24 hours after reperfusion and remained elevated for up to 2 weeks after ischemia. The temporal profiles of the expression of these genes were different from those of other angiogenic genes such as basic fibrobast growth factor/fibroblast growth factor receptor and vascular endothelial growth factor/vascular endothelial growth factor receptor and proteolytic enzymes (tissue-type plasminogen activator and urokinase plasminogen activator) and their inhibitors (plasminogen activator inhibitor-1). The expression patterns of these genes could be related to progressive tissue liquefaction and neovascularization after ischemia in this stroke model. Differential expression of these angiogenesis genes suggests the involvement of complex regulatory mechanisms that remain to be characterized.
Glutamate Does Not Mediate Acute Neuronal Damage after Spreading Depression Induced by O2/Glucose Deprivation in the Hippocampal Slice
Authors: Obeidat Akef S. , Jarvis Cathryn R. , Andrew R. David
Published: November 2003

This study argues that, in contrast to accepted excitotoxicity theory, O2/glucose deprivation damages neurons acutely by eliciting ischemic spreading depression (SD), a process not blocked by glutamate antagonists. In live rat hippocampal slices, the initiation, propagation, and resolution of SD can be imaged by monitoring wide-band changes in light transmittance (i.e., intrinsic optical signals). Oxygen/glucose deprivation for 10 minutes at 37.5°C evokes a propagating wave of elevated light transmittance across the slice, representing the SD front. Within minutes, CA1 neurons in regions undergoing SD display irreversible damage in the form of field potential inactivation, swollen cell bodies, and extensively beaded dendrites, the latter revealed by single-cell injection of lucifer yellow. Importantly, glutamate receptor antagonists do not block SD induced by O2/glucose deprivation, nor do they prevent the resultant dendritic beading of CA1 neurons. However, CA1 neurons are spared if SD is suppressed by reducing the temperature to 35°C during O2/glucose deprivation. This supports previous electrophysiologic evidence in vivo that SD during ischemia promotes acute neuronal damage and that glutamate antagonists are not protective of the metabolically stressed tissue. The authors propose that the inhibition of ischemic SD should be targeted as an important therapeutic strategy against stroke damage.
ALS-Linked Cu/Zn-SOD Mutation Impairs Cerebral Synaptic Glucose and Glutamate Transport and Exacerbates Ischemic Brain Injury
Authors: Guo Zhihong , Kindy Mark S. , Kruman Inna , Mattson Mark P.
Published: November 2003

Although degeneration of lower motor neurons is the most striking abnormality in amyotrophic lateral sclerosis (ALS), more subtle alterations may occur in the brain. Mutations in copper/zinc superoxide dismutase (Cu/Zn-SOD) are responsible for some cases of inherited ALS, and expression of mutant Cu/Zn-SOD in transgenic mice results in progressive motor neuron loss and a clinical phenotype similar to that of ALS patients. It is now reported that Cu/Zn-SOD mutant mice exhibit increased vulnerability to focal ischemic brain injury after transient occlusion of the middle cerebral artery. Levels of glucose and glutamate transport in cerebral cortex synaptic terminals were markedly decreased, and levels of membrane lipid peroxidation were increased in Cu/Zn-SOD mutant mice compared to nontransgenic mice. These findings demonstrate that mutant Cu/Zn-SOD may endanger brain neurons by a mechanism involving impairment of glucose and glutamate transporters. Moreover, our data demonstrate a direct adverse effect of the mutant enzyme on synaptic function.
Altered Expression of the Glutamate Transporter EAAC1 in Neurons and Immature Oligodendrocytes after Transient Forebrain Ischemia
Authors: Gottlieb M. , Domercq M. , Matute C.
Published: November 2003

Glutamate uptake is reduced during ischemia because of perturbations of ionic gradients across neuronal and glial membranes. Using immunohistochemical and Western blot analyses, the authors examined the expression of the glutamate transporters EAAC1, GLAST, and GLT-1 in the rat hippocampus and cerebral cortex 8 hours and 1 to 28 days after transient forebrain ischemia. Densitometric analysis of immunoblots of CA1 homogenates showed a moderate increase in EAAC1 protein levels early after the insult. Consistently, it was observed that EAAC1 immunostaining in CA1 pyramidal neurons was more intense after 8 hours and 1 day of reperfusion and reduced at later postischemia stages. A similar transient increase of EAAC1 immunolabeling was detected in layer V pyramidal neurons of the cerebral cortex. In addition, the authors observed that EAAC1 also was located in oligodendroglial progenitor cells in subcortical white matter. The number of EAAC1-labeled cells in this region was increased after 3 and 28 days of reperfusion. Finally, changes in GLAST and GLT-1 expression were not observed in the CA1 region after ischemia using immunohistochemical study or immunoblotting. Enhanced expression of EAAC1 may be an adaptive response to increased levels of extracellular glutamate during ischemia.
Serine Protease Inhibitors: Novel Therapeutic Targets for Stroke?
Authors: Vivien Denis , Buisson Alain
Published: November 2003

Although the thrombolytic activity of tissue-type plasminogen activator (t-PA) may be beneficial in the acute treatment of stroke, recent studies have suggested that this serine protease could also play a critical role in determining the extent of neuronal death after injury to the central nervous system (CNS). This hypothesis is based on several experimental results: t-PA-deficient mice are resistant to excitotoxic neuronal death induced by the intrahippocampal injection of kainate; the infarct volume induced by occlusion of the middle cerebral artery is reduced in t-PA knockout mice; and the intravenous injection of t-PA can under certain circumstances potentiate the infarct volume in animals subjected to middle cerebral artery occlusion.

In the CNS, the serine proteases have been identified to occur both in neurons and glial cells. Their enzymatic activity regulates the balance between the accumulation and the degradation of the extracellular matrix. They are involved in many physiologic functions, ranging from synaptic outgrowth during perinatal development to plasticity in adults. For instance, thrombin and t-PA are known to modulate neurite outgrowth and tissue remodeling in the early stages of development. In the adult brain, t-PA may contribute to the late phase of long-term potentiation and to the subsequent synaptic growth in the hippocampal mossy fiber pathway.

This balance between the degradation and accumulation of the extracellular matrix may also be integral to various pathologic processes involved in acute brain injury. For example, compounds that modulate the activity of serine proteases exhibit neuroprotective activity. Based on the above, numerous studies have focused on the production and modulation of the endogenously produced serine protease inhibitors, termed serpins, such as type 1 plasminogen activator inhibitor, neuroserpin, and protease nexin-1.

In the present review, we will discuss the need to distinguish between the potentially neurotoxic effects of t-PA and its beneficial effect on reperfusion. We will present data supporting the idea that the modulation of serine protease activity may represent a novel and efficient strategy for the treatment of acute cerebral injury in humans.
The Heat Shock Response Inhibits NF-κB Activation, Nitric Oxide Synthase Type 2 Expression, and Macrophage/Microglial Activation in Brain
Authors: Heneka Michael T. , Sharp Anthony , Klockgether Thomas , Gavrilyuk Vitality , Feinstein Douglas L.
Published: November 2003

The heat shock response (HSR) provides protection against stress-induced damage, and also prevents initiation of inflammatory gene expression via inhibition of NFκB activation. This article describes experiments demonstrating that the HSR prevents induction of nitric oxide synthase type 2 (NOS2) in rat brain. Twenty four hours after intrastriatal injection of lipopolysaccharide (LPS), IL-1β, and IFN-γ, NOS2 immunoreactive cells were detected in striatum, corpus callosum, and to a lesser extent in cortex. Induction of a HSR by whole body warming to 41°C for 20 minutes, done 1 day before LPS plus cytokine injection, reduced the number of NOS2-positive staining cells to background levels. Staining for ED1 antigen revealed that the HSR also suppressed microglial/brain macrophage activation in the same areas. Striatal injection of LPS and cytokines induced the rapid activation of NFκB, and this activation was prevented by prior HS, which also increased brain IκB-α expression. These results suggest that establishment of a HSR can reduce inflammatory gene expression in brain, mediated by inhibition of NFκB activation, and may therefore offer a novel approach to treatment and prevention of neurological disease and trauma.
Noninvasive Assessment of the Functional Neovasculature in 9L-Glioma Growing in Rat Brain by Dynamic 1H Magnetic Resonance Imaging of Gadolinium Uptake
Authors: van der Sanden Boudewijn P. J. , Rozijn Tom H. , Rijken Paul F. J. W. , Peters Hans P. W. , Heerschap Arend , van der Kogel Albert J. , Bovée Wim M. M. J.
Published: November 2003

Pathophysiologic parameters of the functional neovasculature and the blood-brain barrier of 9L-glioma in rat brain were measured noninvasively by dynamic 1H magnetic resonance imaging studies of gadolinium (Gd)-DTPA uptake. Changes of apparent [Gd-DTPA] uptake in time (CT[t]) were analyzed in a slice through the center of 10 9L-gliomas using fast T1 measurements. The distribution of the contrast agent was spatially correlated with the distribution of perfused microvessels as determined by immunohistochemical analysis. This method permits a distinction between perfused and nonperfused microvessels with a disrupted blood-brain barrier. In transverse slices of the whole tumor, a spatial correlation was observed between CT maps and the two-dimensional distribution of perfused microvessels. In the next step, Gd-DTPA uptake rates were spatially related to the perfused microvessel density (Np) or vascular surface area (Sp). In tumor voxels with perfused microvessels, a linear correlation was found between Gd-DTPA uptake rate constants (k values) and Np or Sp. No correlation was observed between k values and the total microvessel density. These are the first data that show a relation between Gd-DTPA uptake rates and parameters of the functional neovasculature in 9L-glioma growing in rat brain. Now that Gd-DTPA uptake studies can be related to parameters of the functional neovasculature, they may be used more efficiently as a prognostic tool before or during therapy.
Evidence for Coupling between Glucose Metabolism and Glutamate Cycling Using FDG PET and 1H Magnetic Resonance Spectroscopy in Patients with Epilepsy
Authors: Pfund Zoltán , Chugani Diane C. , Juhász Csaba , Muzik Otto , Chugani Harry T. , Wilds Ian B. , Seraji-Bozorgzad Navid , Moore Gregory J.
Published: November 2003

The purpose of this study was to examine the relation between glucose metabolism and glutamate concentration in the human brain, in both the normal and diseased state. Regional values of glucose metabolism measured with 2-deoxy-2[F-18]fluoro-D-glucose positron emission tomography (FDG PET) studies and single-voxel proton magnetic resonance spectroscopy (1H MRS) measurements of the glutamate/glutamine/γ-aminobutyric acid (Glx) tissue concentration were determined in multiple brain regions in 11 patients (5 girls and 6 boys, mean age 7.5 years) with medically intractable partial epilepsy. FDG PET and 1H MRS studies were performed in the interictal state in seven patients and in the ictal/periictal state in four patients. Regions of interest were identified in epileptic cortex (determined by intracranial and/or scalp electroencephalography) and in contralateral normal brain regions. Lower glucose metabolism and lower Glx concentrations were found in the epileptic focus than in the contralateral normal cortex in all seven patients examined in the interictal state, whereas higher glucose metabolism and higher Glx concentrations were observed in the epileptic focus in the four patients who had ictal/periictal studies. Significant correlations were found between the values of cerebral glucose utilization and Glx concentration in epileptic brain region, in nonepileptic brain regions, and in epileptic and nonepileptic regions combined. These results demonstrate a significant relation between glucose metabolism and glutamate/glutamine concentration in normal and epileptic cerebral cortex. This relation is maintained in both the interictal and ictal states.
ME3277, a GPIIb/IIIa Antagonist Reduces Cerebral Infarction without Enhancing Intracranial Hemorrhage in Photothrombotic Occlusion of Rabbit Middle Cerebral Artery
Authors: Kawano Ken-Ichi , Fujishima Kazuyuki , Ikeda Yasuhiko , Kondo Kazunao , Umemura Kazuo
Published: November 2003

GPIIb/IIIa antagonists are expected to have a beneficial effect on acute cerebral infarction, however, the occurrence of intracranial hemorrhage has not been as widely investigated. A rabbit focal thrombotic occlusion model of the middle cerebral artery was established by creating a photochemical reaction between green light and Rose Bengal. Hemorrhagic transformation was common in the area of cerebral infarction. Using this model, the effect of a GPIIb/IIIa antagonist, ME3277 (low dose, (L); 0.15 mg/kg + 0.125 mg/kg·h, middle dose, (M); 0.3 mg/kg + 0.25 mg/kg·h and high dose, (H); 0.6 mg/kg + 0.5 mg/kg·h), aspirin (20 mg/kg) and sodium ozagrel (thromboxane A2 synthase inhibitor, 1 mg/kg + 2 mg/kg·h) were evaluated. Drugs were intravenously administrated 30 minutes after the photochemical reaction for 24 hours. Aspirin inhibited the ex vivo platelet aggregation induced by arachidonic acid and collagen but not by adenosine diphosphate (ADP), while sodium ozagrel only inhibited the arachidonic acid-induced aggregation. ME3277 dose-dependently inhibited the platelet aggregation induced by all the inducers (approximately 60% in L, 80% in M, and 90% in H). At 24 hours of middle cerebral artery (MCA) occlusion, infarct volume was significantly reduced by aspirin and each dose of ME3277. These agents improved neurologic deficits, with ME3277 being more potent than aspirin. Sodium ozagrel did not alter the infarct volume nor neurologic deficits. No drug was found to worsen hemorrhage volume despite increasing bleeding time (2–3 fold) in the skin. In this model, the occluded artery was spontaneously recanalized and re-thrombosed frequently. One mechanism by which antiplatelet agents reduced infarct volume was inhibition of rethrombosis of the MCA. These results suggest that treatment with a GPIIb/IIIa antagonist is a useful intervention for acute cerebral infarction prolonging dose bleeding time to 3 times the basal value.
High Susceptibility to Cerebral Ischemia in GFAP-Null Mice
Authors: Nawashiro Hiroshi , Brenner Michael , Fukui Shinji , Shima Katsuji , Hallenbeck John M.
Published: November 2003

Astrocytes perform a variety of functions in the adult central nervous system (CNS) that contribute to the survival of neurons. Thus, it is likely that the activities of astrocytes affect the extent of brain damage after ischemic stroke. The authors tested this hypothesis by using a mouse ischemia model to compare the infarct volume produced in wild-type mice with that produced in mice lacking glial fibrillary acidic protein (GFAP), an astrocyte specific intermediate filament component. Astrocytes lacking GFAP have been shown to have defects in process formation, induction of the blood-brain barrier, and volume regulation; therefore, they might be compromised in their ability to protect the CNS after injury. The authors reported here that 48 hours after combined permanent middle cerebral artery occlusion (MCAO) and 15 minutes transient carotid artery occlusion (CAO) GFAP-null mice had a significantly ( P < 0.001) larger cortical infarct volume (16.7 ± 2.2 mm3) than their wild-type littermates (10.1 ± 3.9 mm3). Laser-Doppler flowmetry revealed that the GFAP-null mice had a more extensive and profound decrease in cortical cerebral blood flow within 2 minutes after MCAO with CAO. These results indicated a high susceptibility to cerebral ischemia in GFAP-null mice and suggested an important role for astrocytes and GFAP in the progress of ischemic brain damage after focal cerebral ischemia with partial reperfusion.
Heme Oxygenase-1 and Ferritin are Increased in Cerebral Arteries after Subarachnoid Hemorrhage in Monkeys
Authors: Ono Shigeki , Zhang Zhen-Du , Marton Linda S. , Yamini Baktiar , Windmeyer Emily , Johns Lydia , Kowalczuk Andrew , Lin George , Macdonald R. Loch
Published: November 2003

Hemoglobin is a key factor in the production of cerebral vasospasm. Metabolism of hemoglobin involves breakdown of heme by heme oxygenase (HO) and sequestration of the released iron in ferritin. We determined whether subarachnoid hemorrhage induces these proteins in cerebral arteries and, if so, in which cells they are produced. Whether the changes correlated with vasospasm also was investigated. Subarachnoid hemorrhage was created in monkeys, and vasospasm was assessed by angiography in cohorts of animals killed 3, 7, or 14 days after the hemorrhage. Ferritin and HO-1 messenger ribonucleic acid (mRNA) and protein were measured by competitive reverse transcription-polymerase chain reaction and Western blotting in hemorrhage-side and control-side cerebral arteries and brain tissue. The location of these proteins was determined by immunohistochemistry. There was significant vasospasm 3 and 7 days but not 14 days after subarachnoid hemorrhage. There were no significant changes in mRNA for HO-1 or ferritin in cerebral arteries or brain tissue at any time. There was a significant increase in HO-1 and ferritin protein in hemorrhage-side compared with control-side cerebral arteries at 3, 7, and 14 days. The increase in HO-1 protein was maximal at 3 days, whereas the increase in ferritin protein was maximal at 7 days. There was no detectable increase in HO-1 or ferritin protein in brain tissue at any time. Immunohistochemistry localized HO-1 protein and ferritin to cells in the adventitia of the arterial wall. We show that subarachnoid hemorrhage is associated with a significant increase in HO-1 and ferritin proteins in cerebral arteries that begins at least as early as 3 days after the hemorrhage and that persists for up to 14 days.
Selective Lutheran Glycoprotein Gene Expression at the Blood—Brain Barrier in Normal Brain and in Human Brain Tumors
Authors: Boado Ruben J. , Li Jian Yi , Pardridge William M.
Published: November 2003

The Lutheran (LU) glycoprotein was shown to be a specific marker of brain capillary endothelium, which forms the blood-brain barrier (BBB) in vivo. A 1.5 kb partial cDNA encoding the bovine LU was isolated from a bovine brain capillary cDNA library. Sequence analysis showed that the bovine and human LU had a 75% and 79% identity in the amino acid and nucleotide sequences, respectively. Northern blot analysis demonstrated a very high level of gene expression of the LU transcript in freshly isolated bovine brain capillaries, but no measurable LU mRNA in whole bovine brain. The high level of LU gene expression was maintained when bovine brain capillary endothelium was grown in tissue culture. Because many BBB specific genes are downregulated in tissue culture and in brain tumors, the expression of the LU mRNA and immunoactive LU protein was investigated in primary and metastatic human brain tumors. Immunocytochemistry of fresh frozen human brain and human brain tumors showed abundant immunostaining of brain capillary endothelium. Northern blot analysis showed the presence of LU transcripts in a panel of primary and metastatic human brain tumors. These studies demonstrated that the LU glycoprotein was a novel new marker of the BBB, and unlike other BBB specific genes, there was a persistent gene expression of the LU glycoprotein both in brain capillary endothelial cells grown in culture and in the endothelium of capillaries perfusing human brain cancer.