bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional Reduction and Associated Cellular Rearrangement in SHRSP Rat Basilar Arteries Are Affected by Salt Load and Calcium Antagonist Treatment
Authors: Arribas Silvia M. , Costa Rosa , Salomone Salvatore , Morel Nicole , Godfraind Theophile , McGrath John C.
Published: November 2003

The stroke-prone spontaneously hypertensive rat (SHRSP) is a strain with high incidence of cerebrovascular accidents increased by salt-rich diet and decreased by calcium-antagonist treatment. In the SHRSP rat basilar artery the authors have previously shown reduced contractility and altered structure including regions of smooth muscle cell (SMC) disorganization, The aims of this study have been to analyze (I) the morphology of these abnormal regions, (2) the structural modifications responsible for the reduced function, and (3) the effect of salt and calcium-antagonist treatment on vascular structure and function, Wistar Kyoto and SHRSP rats, untreated or treated from week 8 through 14 with 1% NaCl or 1% NaCl + 1 ·kg−1·d−1 lacidipine, were used, Function was studied with wire myography, Structure was analyzed in fixed intact arteries with confocal microscopy, Basilar arteries from SHRSP rat showed (1) reduced contractility, (2) discrete foci of SMC disarray with altered proportion of adventitia to SMC, and (3) decreased SMC and increased adventitial cell number. Arteries from salt-loaded SHRSP rats showed a higher degree of SMC disarray and further reduction in contractility, Lacidipine treatment of salt-loaded rats significantly improved structure and function, These data suggest that vascular remodeling can provide an explanation for the observed reduction in vascular contractility of SHRSP rat basilar arteries and might show light on the effects of salt load and calcium-channel blockers in life span and the incidence of cerebrovascular accidents in SHRSP rats.
Quantitation of Extrastriatal D2 Receptors Using a Very High-Affinity Ligand (FLB 457) and the Multi-Injection Approach
Authors: Delforge Jacques , Bottlaender Michel , Loc'h Christian , Guenther Ilonka , Fuseau Chantal , Bendriem Bernard , Syrota André , Maziére Bernard
Published: November 2003

The multi-injection approach has been used to study in baboon the in vivo interactions between the D2 receptor sites and FLB 457, a ligand with a very high affinity for these receptors. The model structure was composed of four compartments (plasma, free ligand, and specifically and unspecifically bound ligands) and seven parameters (including the D2 receptor site density). The arterial plasma concentration, after correction for metabolites, was used as the input function, The experimental protocol, which consisted of three injections of labeled and/or unlabeled ligand, allowed the evaluation of all model parameters from a single positron emission tomography experiment In particular, the concentration of receptor sites available for binding ( B'max) and the apparent in vivo FLB 457 affinity were estimated in seven brain regions, including the cerebellum and several cortex regions, in which these parameters are estimated in vivo for the first time ( B'max is estimated to be 4,0 ± 1.3 pmol/mL in the thalamus and from 0.32 to 1.90 pmol/mL in the cortex), A low receptor density was found in the cerebellum ( B'max = 0.39 ± 0.17 pmol/mL), whereas the cerebellum is usually used as a reference region assumed to be devoid of D2 receptor sites, In spite of this very small concentration (1 % of the striatal concentration), and because of the high affinity of the ligand, we demonstrated that after a tracer injection, most of the PET-measured radioactivity in the cerebellum results from the labeled ligand bound to receptor sites, The estimation of all the model parameters allowed simulations that led to a precise knowledge of the FLB 457 kinetics in all brain regions and gave the possibility of testing the equilibrium hypotheses and estimating the biases introduced by the usual simplified approaches.
Which Linear Compartmental Systems Can Be Analyzed by Spectral Analysis of PET Output Data Summed over All Compartments?
Authors: Schmidt Kathleen
Published: November 2003

General linear time-invariant compartmental systems were examined to determine which systems meet the conditions necessary for application of the spectral analysis technique to the sum of the concentrations in all compartments. Spectral analysis can be used to characterize the reversible and irreversible components of the system and to estimate the minimum number of compartments, but it applies only to systems in which the measured data can be expressed as a positively weighted sum of convolution integrals of the input function with an exponential function that has real-valued nonpositive decay constants. The conditions are met by compartmental systems that are strongly connected, have exchange of material with the environment confined to a single compartment, and do not contain cycles, i.e., there is no possibility for material to pass from one compartment through two or more compartments back to the initial compartment. Certain noncyclic systems with traps, systems with cycles that obey a specified loop condition, and noninterconnected collections of such systems also meet the conditions. Dynamic positron emission tomographic data obtained after injection of a radiotracer, the kinetics of which can be described by any model in the class of models identified here, can be appropriately analyzed with the spectral analysis technique.
Cerebrovascular Hemodynamics and Ischemic Tolerance: Lipopolysaccharide-Induced Resistance to Focal Cerebral Ischemia is not Due to Changes in Severity of the Initial Ischemic Insult, but is Associated with Preservation of Microvascular Perfusion
Authors: Dawson Deborah A. , Furuya Kazuhide , Gotoh Jun , Nakao Yasuaki , Hallenbeck John M.
Published: November 2003

Lipopolysaccharide (LPS), administered 72 hours before middle cerebral artery (MCA) occlusion, confers significant protection against ischemic injury. For example, in the present study, LPS (0.9 mg/kg intravenously) induced a 31% reduction in infarct volume (compared with saline control) assessed 24 hours after permanent MCA occlusion. To determine whether LPS induces true tolerance to ischemia, or merely attenuates initial ischemic severity by augmenting collateral blood flow, local CBF was measured autoradiographically 15 minutes after MCA occlusion. Local CBF did not differ significantly between LPS- and saline-pretreated rats (e.g., 34 ± 10 and 29 ± 15 mL·100 g−1·min−1 for saline and LPS pretreatment in a representative region of ischemic cortex), indicating that the neuroprotective action of LPS is not attributable to an immediate reduction in the degree of ischemia induced by MCA occlusion, and that LPS does indeed induce a state of ischemic tolerance. In contrast to the similarity of the initial ischemic insult between tolerant (LPS-pretreated) and nontolerant (saline-pretreated) rats, microvascular perfusion assessed either 4 hours or 24 hours after MCA occlusion was preserved at significantly higher levels in the LPS-pretreated rats than in controls. Furthermore, the regions of preserved perfusion in tolerant animals were associated with regions of tissue sparing. These results suggest that LPS-induced tolerance to focal ischemia is at least partly dependent on the active maintenance of microvascular patency and hence the prevention of secondary ischemic injury.
Inhibition of Interleukin-1β Converting Enzyme Family Proteases (Caspases) Reduces Cold Injury-Induced Brain Trauma and DNA Fragmentation in Mice
Authors: Morita-Fujimura Yuiko , Fujimura Miki , Kawase Makoto , Murakami Kensuke , Kim Gyung Whan , Chan Pak H.
Published: November 2003

The authors examined the effect of z-VAD.FMK, an inhibitor that blocks caspase family proteases, on cold injury-induced brain trauma, in which apoptosis as well as necrosis is assumed to play a role. A vehicle alone or with z-VAD.FMK was administered into the cerebral ventricles of mice 15 minutes before and 24 and 48 hours after cold injury. At 24 hours after cold injury, infarction volumes in the z-VAD.FMK-treated animals were significantly smaller than infarction volumes in the vehicle-treated animals, and were further decreased at 72 hours (0.92 ± 1.80 mm3, z-VAD.FMK-treated animals; 7.46 ± 3.53 mm3, vehicle-treated animals; mean ± SD, n = 7 to 8). The amount of DNA fragmentation was significantly decreased in the z-VAD.FMK-treated animals compared with the vehicle-treated animals, as shown by terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling staining and DNA gel electrophoresis. By Western blot analysis, both the proform and activated form of interleukin-1β converting enzyme (caspase 1) were detected in the control brain, and the activated form showed moderate reduction after cold injury-induced brain trauma. These results indicate that caspase inhibitors could reduce cold injury-induced brain trauma by preventing neuronal cell death by DNA damage. The caspase family proteases appear to contribute to the mechanisms of cell death in cold injury-induced brain trauma and to provide therapeutic targets for traumatic brain injury.
A Potential Role for Erythropoietin in Focal Permanent Cerebral Ischemia in Mice
Authors: Bernaudin Myriam , Marti Hugo H. , Roussel Simon , Divoux Didier , Nouvelot André , MacKenzie Eric T. , Petit Edwige
Published: November 2003

The present study describes, for the first time, a temporal and spatial cellular expression of erythropoietin (Epo) and Epo receptor (Epo-R) with the evolution of a cerebral infarct after focal permanent ischemia in mice. In addition to a basal expression of Epo in neurons and astrocytes, a postischemic Epo expression has been localized specifically to endothelial cells (1 day), microglia/macrophage-like cells (3 days), and reactive astrocytes (7 days after occlusion). Under these conditions, the Epo-R expression always precedes that of Epo for each cell type. These results support the hypothesis that there is a continuous formation of Epo, with its corresponding receptor, during the active evolution of a focal cerebral infarct and that the Epo/Epo-R system might be implicated in the processes of neuroprotection and restructuring (such as angiogenesis and gliosis) after ischemia. To support this hypothesis, a significant reduction in infarct volume (47%; P < 0.0002) was found in mice treated with recombinant Epo 24 hours before induction of cerebral ischemia. Based on the above, we propose that the Epo/Epo-R system is an endogenous mechanism that protects the brain against damages consequent to a reduction in blood flow, a mechanism that can be amplified by the intracerebroventricular application of exogenous recombinant Epo.
Dynamics of Nitrotyrosine Formation and Decay in Rat Brain during Focal Ischemia-Reperfusion
Authors: Takizawa Shunya , Fukuyama Naoto , Hirabayashi Hisayuki , Nakazawa Hiroe , Shinohara Yukito
Published: November 2003

The purpose of this study was to establish the dynamics of nitrotyrosine (NO2-Tyr) formation and decay during the rise of NO2-Tyr in rat brain subjected to 2-hour focal ischemia-reperfusion, and to evaluate the role of inducible nitric oxide synthase in the rise. The authors first determined the half life of NO2-Tyr in rat brain at 24 hours after the start of reperfusion by blocking NO2-Tyr formation with NG-monomethyl-l-arginine and after the decay of NO2-Tyr by means of a hydrolysis/HPLC procedure. The values obtained were approximately 2 hours in both peri-infarct and core-of-infarct regions. Using the same hydrolysis/HPLC procedure, the ratio of nitrotyrosine to tyrosine from the 2-hour occlusion to as much as 72 hours after the start of reperfusion was measured in the presence and absence of aminoguanidine (100 mg/kg intraperitoneally twice a day). In the absence of aminoguanidine, the ratio of NO2-Tyr in the peri-infarct and core-of-infarct regions reached 0.95% ± 0.34% and 0.52% ± 0.34%, respectively, at 1 hour after the start of reperfusion, The elevated levels persisted until 48 hours, then declined, The peri-infarct region showed the highest percent NO2-Tyr level, followed by the core of infarct, then the caudoputamen, Aminoguanidine significantly reduced NO2-Tyr formation (up to 90% inhibition) during 24 to 48 hours, The authors conclude that inducible nitric oxide synthase is predominantly responsible for NO2-Tyr formation, at least in the late phase of reperfusion, These results have important implications for the therapeutic time window and choice of nitric oxide synthase inhibitors in patients with cerebral infarction.
Evidence of a Cerebrovascular Postarteriole Windkessel with Delayed Compliance
Authors: Mandeville Joseph B. , Marota John J. A. , Ayata C. , Zaharchuk Greg , Moskowitz Michael A. , Rosen Bruce R. , Weisskoff Robert M.
Published: November 2003

A pronounced temporal mismatch was observed between the responses of relative cerebral blood volume (rCBV) measured by magnetic resonance imaging and relative cerebral blood flow measured by laser—Doppler flowmetry in rat somatosensory cortex after electrical forepaw stimulation, The increase of relative cerebral blood flow after stimulus onset and decrease after stimulus cessation were accurately described with a single exponential time constant of 2.4 ± 0.8 seconds. In contrast, rCBV exhibited two distinct and nearly sequential processes after both onset and cessation of stimulation. A rapid change of rCBV (1.5 ± 0.8 seconds) occurring immediately after onset and cessation was not statistically different from the time constant for relative cerebral blood flow. However, a slow phase of increase (onset) and decrease (cessation) with an exponential time constant of 14 ± 13 seconds began approximately 8 seconds after the rapid phase of CBV change. A modified windkessel model was developed to describe the temporal evolution of rCBV as a rapid elastic response of capillaries and veins followed by slow venous relaxation of stress. Venous delayed compliance was suggested as the mechanism for the poststimulus undershoot in blood oxygen-sensitive magnetic resonance imaging signal that has been observed in this animal model and in human data.
Focal Ischemic Preconditioning Induces Rapid Tolerance to Middle Cerebral Artery Occlusion in Mice
Authors: Stagliano Nancy E. , Pérez-Pinzón Miguel A. , Moskowitz Michael A. , Huang Paul L.
Published: November 2003

In a process called ischemic preconditioning, a brief, sublethal ischemic insult protects tissue from subsequent, more severe injury. There have been no reports of rapidly induced ischemic preconditioning. The authors sought to develop a model of cerebral ischemic preconditioning in the mouse that can be applied to transgenic and knockout animals. They found that brief middle cerebral artery (MCA) occlusion only minutes before a severe ischemic insult can induce protection from that insult. Here the investigators describe a mouse model of preconditioning using intraluminal MCA occlusion as both the conditioning and the test stimulus. One or three 5-minute episodes of ischemia given 30 minutes before MCA occlusion for 1 or 24 hours (permanent occlusion) confer significant protection as assessed by infarct volume measurements 24 hours later.
Reduction of Cognitive and Motor Deficits after Traumatic Brain Injury in Mice Deficient in Poly(ADP-Ribose) Polymerase
Authors: Whalen Michael J. , Clark Robert S. B. , Dixon C. Edward , Robichaud Paul , Marion Donald W. , Vagni Vincent , Graham Steven H. , Virag Laszlo , Hasko Gyorgy , Stachlewitz Robert , Szabo Csaba , Kochanek Patrick M.
Published: November 2003

Poly(ADP-ribose) polymerase (PARP), or poly-(ADP-ribose) synthetase, is a nuclear enzyme that consumes NAD when activated by DNA damage. The role of PARP in the pathogenesis of traumatic brain injury (TBI) is unknown. Using a controlled cortical impact (CCI) model of TBI and mice deficient in PARP, the authors studied the effect of PARP on functional and histologic outcome after CCI using two protocols. In protocol 1, naïve mice (n = 7 +/+, n = 6 –/–) were evaluated for motor and memory acquisition before CCI. Mice were then subjected to severe CCI and killed at 24 hours for immunohistochemical detection of nitrated tyrosine, an indicator of peroxynitrite formation. Motor and memory performance did not differ between naïve PARP +/+ and –/– mice. Both groups showed nitrotyrosine staining in the contusion, suggesting that peroxynitrite is produced in contused brain. In protocol 2, mice (PARP +/+, n = 8; PARP –/–, n = 10) subjected to CCI were tested for motor and memory function, and contusion volume was determined by image analysis. PARP –/– mice demonstrated improved motor and memory function after CCI versus PARP +/+ mice ( P < 0.05). However, contusion volume was not different between groups. The results suggest a detrimental effect of PARP on functional outcome after TBI.
Bolus Injection versus Slow Infusion of [15O]Water for Positron Emission Tomography Activation Studies
Authors: Beason-Held Lori L. , Desmond Richard E. , Herscovitch Peter , Carson Richard E.
Published: November 2003

In positron emission tomography studies using bolus injection of [15O]water, activation responses reflect underlying CBF changes during a short time (15 to 20 seconds) after arrival of the bolus in the brain. This CBF sensitivity window may be too short for complex activation paradigms, however, particularly those of longer duration. To perform such paradigms, we used a slow infusion method of tracer administration to lengthen the CBF sensitivity window. The present study was designed to determine if this slow infusion technique yields similar results to a bolus injection with a short activation task involving memory for faces. When analyzed using statistical parametric mapping, scanning durations of either 90 or 120 seconds and a 90-second slow infusion schedule produced very similar results to a standard 60-second scan collected after bolus injection, indicating that statistically similar brain activation maps can be produced with the two infusion techniques. This slow infusion approach allows for increased flexibility in designing future studies in which a short CBF sensitivity window is a limiting factor.
Dynamic In Vivo Measurement of Erythrocyte Velocity and Flow in Capillaries and of Microvessel Diameter in the Rat Brain by Confocal Laser Microscopy
Authors: Seylaz Jacques , Charbonné Robert , Nanri Kazunori , Von Euw Dominique , Borredon Josiane , Kacem Kamel , Méric Philippe , Pinard Elisabeth
Published: November 2003

A new method for studying brain microcirculation is described, Both fluorescently labeled erythrocytes and plasma were visualized on-line through a closed cranial window in anesthetized rats, using laser-scanning two-dimension confocal microscopy, Video images of capillaries, arterioles, and venules were digitized off-line to measure microvessel diameter and labeled erythrocyte flow and velocity in parenchymal capillaries up to 200 μm beneath the brain surface, The method was used to analyze the rapid adaptation of microcirculation to a brief decrease in perfusion pressure, Twenty-second periods of forebrain ischemia were induced using the four-vessel occlusion model in eight rats, EEG, arterial blood pressure, and body temperature were continuously controlled, In all conditions, labeled erythrocyte flow and velocity were both very heterogeneous in capillaries, During ischemia, capillary perfusion was close to 0, but a low blood flow persisted in arterioles and venules, while EEG was flattening, The arteriole and venule diameter did not significantly change, At the unclamping of carotid arteries, there was an instantaneous increase (by about 150%) of arteriole diameter. Capillary erythrocyte flow and velocity increased within 5 seconds, up to, respectively, 346 ± 229% and 233 ± 156% of their basal value, No capillary recruitment of erythrocytes was detected, All variables returned to their basal levels within less than 100 seconds after declamping, The data are discussed in terms of a possible involvement of shear stress in the reperfusion period.
Multiple Microvascular and Astroglial 5-Hydroxytryptamine Receptor Subtypes in Human Brain: Molecular and Pharmacologic Characterization
Authors: Cohen Zvi , Bouchelet Isabelle , Olivier André , Villemure Jean-Guy , Ball Rita , Stanimirovic Danica B. , Hamel Edith
Published: November 2003

Physiologic and anatomic evidence suggest that 5-hydroxytryptamine (5-HT) neurons regulate local cerebral blood flow and blood-brain barrier permeability. To evaluate the possibility that some of these effects occur directly on the blood vessels, molecular and/or pharmacologic approaches were used to assess the presence of 5-HT receptors in human brain microvascular fractions, endothelial and smooth muscle cell cultures, as well as in astroglial cells which intimately associate with intraparenchymal blood vessels. Isolated microvessels and' capillaries consistently expressed messages for the h5-HT1B, h5-HT1D, 5-HT1F, 5-HT2A but not 5-HT7 receptors. When their distribution within the vessel wall was studied in more detail, it was found that capillary endothelial cells exhibited mRNA for the h5-HT1D and for the 5-HT7 receptors whereas microvascular smooth muscle cells, in addition to h5-HT1D and 5-HT7, also showed polymerase chain reaction products for h5-HT1B receptors. Expression of 5-HT1F and 5-HT2A receptor mRNAs was never detected in any of the microvascular cell cultures. In contrast, messages for all 5-HT receptors tested were detected in human brain astrocytes with a predominance of the 5-HT2A and 5-HT7 subtypes. In all cultures, sumatriptan inhibited (35–58%, P < .05) the forskolin-stimulated production of cyclic AMP, an effect blocked by the 5-HT1B/1d receptor antagonists GR127935 and GR55562. In contrast, 5-carboxamidotryptamine induced strong increases (≥ 400%, P < .005) in basal cyclic AMP levels that were abolished by mesulergine, a nonselective 5-HT7 receptor antagonist. Only astroglial cells showed a ketanserin-sensitive increase (177%, P < .05) in IP3 formation when exposed to 5-HT. These results show that specific populations of functional 5-HT receptors are differentially distributed within the various cellular compartments of the human cortical microvascular bed, and that human brain astroglial cells are endowed with multiple 5-HT receptors. These findings emphasize the complex interactions between brain serotonergic pathways and non-neuronal cells within the CNS and, further, they raise the possibility that some of these receptors may be activated by antimigraine compounds such as brain penetrant triptan derivatives.
Delayed Hypovolemic Hypotension Exacerbates the Hemodynamic and Histopathologic Consequences of Thromboembolic Stroke in Rats
Authors: Dietrich W. Dalton , Prado Ricardo , Pravia Cristina , Zhao Weizhao , Ginsberg Myron D. , Watson Brant D.
Published: November 2003

Abnormalities in cerebrovascular reactivity or hemodynamic reserve are risk factors for stroke. The authors determined whether hemodynamic reserve is reduced in an experimental model of thromboembolic stroke. Nonocclusive common carotid artery thrombosis (CCAT) was produced in rats by a rose bengal-mediated photochemical insult, and moderate hypotension (60 mm Hg/30 min) was induced 1 hour later by hemorrhage. Alterations in local cerebral blood flow (lCBF) were assessed immediately after the hypotensive period by 14C-iodoantipyrine“ autoradiography, and histopathologic outcome was determined 3 days after CCAT. Compared to normotensive CCAT rats (n = 5), induced hypotension after CCAT (n = 7) led to enlarged regions of severe ischemia (i.e., mean lCBF < 0.24 mL/g/min) in the ipsilateral hemisphere. For example, induced hypotension increased the volume of severely ischemic sites from 16 ±4 mm3 (mean ± SD) to 126 ± 99 mm3 ( P < 0.05). Histopathologic data also showed a larger volume of ischemic damage with secondary hypotension (n = 7) compared to normotension (22 ± 15 mm3 versus 5 ±5 mm3, P < .05). Both hypotension-induced decreases in lCBF and ischemic pathology were commonly detected within cortical anterior and posterior borderzone areas and within the ipsilateral striatum and hippocampus. In contrast to CCAT, mechanical ligation of the common carotid artery plus hypotension (n = 8) did not produce significant histopathologic damage. Nonocclusive CCAT with secondary hypotension therefore predisposes the post-thrombotic brain to hemodynamic stress and structural damage.
Blood—Brain Barrier Transport and Protein Binding of Flumazenil and Iomazenil in the Rat: Implications for Neuroreceptor Studies
Authors: Videbæk Charlotte , Ott Peter , Paulson Olaf B. , Knudsen Gitte M.
Published: November 2003

The calculated fraction of receptor ligands available for blood–brain barrier passage in vivo (favail) may differ from in vitro (feq) measurements. This study evaluates the protein–ligand interaction for iomazenil and flumazenil in rats by comparing feq and favail. Repeated measurements of blood–brain barrier permeability for two benzodiazepine antagonists were performed in 44 rats by the double-indicator technique. Cerebral blood flow was measured by intracarotid Xe-injection. The apparent permeability–surface product (PSapp) was measured while CBF or bolus composition was changed. Comparison of PSapp obtained in the absence and presence of 5% albumin in the injectate yielded favail, whereas feq was measured by equilibrium dialysis. Iomazenil and flumazenil favail was 62% and 82%, respectively, whereas feq was significantly lower, 42% and 61%. The PSapp for iomazenil and flumazenil increased significantly by 89% and 161% after relative CBF increases of 259% and 201%, respectively. The results demonstrate that application of feq in neuroreceptor studies underestimates the plasma input function to the brain. Model simulations render possible that the differences between favail and feq as well as the effect of CBF on PSapp can be caused by capillary heterogeneity.
Quantification of δ-Opioid Receptors in Human Brain with N1′ -([11C]Methyl) Naltrindole and Positron Emission Tomography
Authors: Smith Justin S. , Zubieta Jon-Kar , Price Julie C. , Flesher John E. , Madar Igal , Lever John R. , Kinter Christopher M. , Dannals Robert F. , Frost J. James
Published: November 2003

The regional binding of N1′ -([11C]methyl)naltrindole (MeNTI), a selective δ-opioid antagonist, was studied in healthy human subjects with positron emission tomography (PET). After the bolus intravenous administration of high specific activity [11C]MeNTI, PET was performed over 90 minutes. Arterial plasma samples were obtained during the scanning period and assayed for the presence of radiolabeled metabolites. The data were analyzed with various kinetic (two-and three-compartment models, Patlak graphical analysis) and nonkinetic (apparent volume of distribution and activity at a late scanning time) approaches. This tracer showed irreversible binding characteristics during the scanning period used. The results of the analyses also were compared with the density and distribution of δ-opioid receptors in the human brain in vitro. Additionally, computer simulations were performed to assess the effects of changes in receptor binding and tracer transport changes on the perceived binding parameters obtained with the models. A constrained three-compartment kinetic model was demonstrated to be superior to other quantification models for the description of MeNTI kinetics and quantification of δ receptor binding in the human brain with 11C-labeled MeNTI.
Increased Cytokine Release from Peripheral Blood Cells after Acute Stroke
Authors: Ferrarese Carlo , Mascarucci Paolo , Zoia Chiara , Cavarretta Rosella , Frigo Maura , Begni Barbara , Sarinella Federica , Frattola Lodovico , De Simoni Maria Grazia
Published: November 2003

Cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-α can play pathogenetic or protective roles in stroke. They are increased in the brain after experimental ischemia and in the CSF of patients with stroke. However, their presence in the periphery is still controversial. To determine the source and time-course of cytokines in blood of stroke patients, IL-6 and TNF-α release from blood cells and serum levels were determined in 40 patients on days 1 through 2, 4, 10, 30, and 90 after stroke. Twenty healthy age-matched volunteers were used as controls. IL-6 and TNF-α release from stimulated blood cells was increased in stroke patients, compared to controls. A peak response (+224%) was observed at day 4 for IL-6, while TNF-α release was largely and significantly increased (about three-fold compared to controls) from day 1 to 2 until day 90 after stroke. The increase in IL-6 release was significantly higher in ischemic, compared to hemorragic strokes, at days 1 and 4. Circulating IL-6 was increased at each time point. The ischemic processes in the CNS induces a long-lasting activation of IL-6 and TNF-α production in peripheral blood cells, which are a major source of serum cytokines after stroke.
Adventitial Expression of Recombinant Endothelial Nitric Oxide Synthase Gene Reverses Vasoconstrictor Effect of Endothelin-1
Authors: Onoue Hisashi , Tsutsui Masato , Smith Leslie , O'Brien Timothy , Katusic Zvonimir S.
Published: November 2003

The present study was designed to determine the effect of recombinant endothelial nitric oxide synthase (eNOS) gene expression on reactivity of canine basilar arteries to endothelin-1 (ET-1). Experiments were performed ex vivo. The arteries were exposed (30 minutes at 37°C) to adenoviral vectors encoding eNOS gene (AdCMVeNOS) or β-galactosidase reporter gene (AdCMVβ-Gal). Twenty-four hours after transduction, transgene expression was evident mainly in the vascular adventitia. Rings of control (nontransduced), AdCMVβ-Gal- and AdCMVeNOS-transduced arteries with and without endothelium were suspended for isometric tension recording. Levels of guanosine 3′,5′ -cyclic monophosphate (cGMP) were measured by radioimmunoassay. During contractions to uridine 5′-triphosphate, ET-1 (10−10 to 3×10−9 mol/L) caused further increase in tension in control and AdCMVβ-Gal-transduced arteries. In contrast, ET-1 caused concentration-dependent relaxations of AdCMVeNOS-transduced arteries. The relaxations to ET-1 in AdCMVeNOS-transduced arteries were endothelium-independent They were abolished by NG-nitro-L-argininemethyl ester or by chemical treatment of adventitia with paraformaldehyde before gene transfer. ET-1 (10−9 mol/L) significantly increased intracellular cGMP levels in AdCMVeNOS-transduced arteries without endothelium. In arteries transduced with AdCMVeNOS, higher concentrations (10−9 to 3×10−8 mol/L) of ET-2 also caused relaxations, whereas ET-3 and sarafotoxin, a selective ETB receptor agonist, did not produce any relaxations. The relaxations to ET-1 in AdCMVeNOS-transduced arteries were strongly reduced by BQ-123 (10−7 mol/L), an ETA receptor antagonist, but were not affected by BQ-788 (3×10−7 mol/L), an ETB receptor antagonist These results suggest that genetically modified adventitia can produce nitric oxide and cause relaxations in response to ET-1 via activation of ETA receptors. Our findings support a novel concept that successful transfer and expression of recombinant eNOS gene can lead to a qualitative change in responsiveness to vasoconstrictor substances.
Expression of Tumor Necrosis Factor-Alpha and Intercellular Adhesion Molecule-1 after Focal Cerebral Ischemia in Interleukin-1β Converting Enzyme Deficient Mice
Authors: Yang Guo-Yuan , Schielke Gerald P. , Gong Chao , Mao Ying , Ge Hai-Liang , Liu Xiao-Hong , Betz A. Lorris
Published: November 2003

Interleukin-1β (IL-1β) is expressed after cerebral ischemia and blocking its action reduces subsequent ischemic brain injury. However, the mechanisms by which IL-1β affects ischemic brain are not understood. To investigate the role of IL-1β in regulation of tumor necrosis factor-alpha (TNF-α) and intercellular adhesion molecule-1 (ICAM-1) during focal cerebral ischemia, the authors studied mutant mice deficient in the IL-1 converting enzyme (ICE) gene (ICE knockout [KO] mice). Ninety-four adult male ICE KO and wild-type mice underwent 3, 6, 12, and 24 hours of permanent middle cerebral artery occlusion using the suture method. Expression of TNF-α and ICAM-1 protein in ischemic brain was examined using immunohistochemistry and Western blot analysis. Neither ICE KO nor wild-type mice had significant differences in CBF and body temperature measurements during the ischemic procedure. TNF-α expression increased in the ipsilateral hemisphere after 3 hours of occlusion, peaked at 12 hours and decreased at 24 hours of ischemia in both ICE KO and wild-type mice. ICAM-1 immunohistochemistry showed that the number of ICAM-1–positive vessels in the ischemic hemisphere was reduced in ICE KO mice ( P < .05). Western blot analysis showed that ICAM-1 protein expression was significantly attenuated in the ipsilateral hemisphere in the ICE KO mice, which paralleled the immunohistochemistry results, The authors' results indicate that TNF-α expression is increased in both ICE KO and wild-type mice suggesting that TNF-α expression is not related to or upregulated by IL-1β. ICAM-1 expression is significantly reduced in the ICE KO mice suggesting that IL-1β plays an important role in the upregulation of adhesion molecules during focal cerebral ischemia.
Survival- and Death-Promoting Events after Transient Cerebral Ischemia: Phosphorylation of Akt, Release of Cytochrome C, and Activation of Caspase-Like Proteases
Authors: Ouyang Yi-Bing , Tan Ying , Comb M. , Liu Chun-Li , Martone M. E. , Siesjö Bo K. , Hu Bing-Ren
Published: November 2003

Release of cytochrome c (cyt c) into cytoplasm initiates caspase-mediated apoptosis, whereas activation of Akt kinase by phosphorylation at serine-473 prevents apoptosis in several cell systems. To investigate cell death and cell survival pathways, the authors studied release of cyt c, activation of caspase, and changes in Akt phosphorylation in rat brains subjected to 15 minutes of ischemia followed by varying periods of reperfusion. The authors found by electron microscopic study that a portion of mitochondria was swollen and structurally altered, whereas the cell membrane and nuclei were intact in hippocampal CA1 neurons after 36 hours of reperfusion. In some neurons, the pattern of immunostaining for cyt c changed from a punctuate pattern, likely representing mitochondria, to a more diffuse cytoplasmic localization at 36 and 48 hours of reperfusion as examined by laser-scanning confocal microscopic study. Western blot analysis showed that cyt c was increased in the cytosolic fraction in the hippocampus after 36 and 48 hours of reperfusion. Consistently, caspase-3–like activity was increased in these hippocampal samples. As demonstrated by Western blot using phosphospecific Akt antibody, phosphorylation of Akt at serine-473 in the hippocampal region was highly increased during the first 24 hours but not at 48 hours of reperfusion. The authors conclude that transient cerebral ischemia activates both cell death and cell survival pathways after ischemia. The activation of Akt during the first 24 hours conceivably may be one of the factors responsible for the delay in neuronal death after global ischemia.
Quantification of [11C]FLB 457 Binding to Extrastriatal Dopamine Receptors in the Human Brain
Authors: Olsson Hans , Halldin Christer , Swahn Carl-Gunnar , Farde Lars
Published: November 2003

Positron emission tomography (PET) has hitherto been used to examine D2 dopamine receptor binding in the striatum, a region with a high density of receptors. Research has been hampered by the lack of suitable radioligands for detection of the low-density D2 dopamine receptor populations in the limbic and cortical dopamine systems that are implicated in the patophysiology of schizophrenia. [11C]FLB 457 is a new radioligand with the very high affinity of 20 pmol/L (Ki) for the D2 and D3 dopamine receptor subtypes. This study in eight healthy subjects was designed to evaluate the suitability of [11C]FLB 457 for quantification of extrastriatal D2/D3 dopamine receptors. PET-data were acquired in the three-dimensional mode and the arterial input function was corrected for labeled metabolites. The standard three-compartment model and four derived approaches were applied to calculate and compare the binding potentials. Besides the striatum, conspicuous radioactivity was found in extrastriatal regions such as the thalamus, the anterior cinguli, and the temporal and frontal cortices. The time activity curves could be described by the three compartment model. The different approaches gave similar binding potential values and the rank order between regions was consistent with that found in vitro. The short time of a PET measurement using [11C]FLB 457 (63 minutes) seemed not to be sufficient for reliable determination of the high binding potential in the striatum. These results are of principal importance because they show the potential for PET quantification of minute receptor populations in the human brain.
Phosphorylation of c-Jun and Its Localization with Heme Oxygenase-1 and Cyclooxygenase-2 in CA1 Pyramidal Neurons after Transient Forebrain Ischemia
Authors: Matsuoka Yasuji , Okazaki Mitsuhiro , Zhao Heng , Asai Satoshi , Ishikawa Koichi , Kitamura Yoshihisa
Published: November 2003

Accumulating evidence on the molecular and cellular basis of ischemiaireperfusion-induced neurodegeneration suggests that oxidative stress is involved. Heme oxygenase (HO) and cyclooxygenase (COX) play physiologically important roles in the CNS. Conversely, HO and COX also can increase oxidative stress. Recent studies suggest that c-Jun phosphorylation is an important step in some forms of stress-induced neuropal apoptosis. In this study, the authors tried to clarify the association of HO and COX with c-Jun phosphorylation. Inducible forms of HO and COX (HO-1 and COX-2, respectively) were transiently induced in CA1 pyramidal neurons after ischemia. c-Jun also was induced in pyramidal neurons throughout the hippocampal formation, but its phosphorylation was limited to CAL In contrast, these molecules were constitutively expressed at low levels. Most (84%) of the CA1 pyramidal neurons examined expressed HO-1, COX-2, or both, and such expression showed good co-localization with c-Jun phosphorylation. These results suggest the following: (1) c-Jun phosphorylation was associated with ischemia/reperfusion-induced neuronal apoptosis; (2) HO-1 and COX-2 were induced in CA1 pyramidal neurons, which undergo cell death; and (3) most CA1 pyramidal neurons expressed HO-1, COX-2, or both, which strongly suggests that these are candidates for neuron killers.
Temporal Profile and Cellular Localization of Interleukin-6 Protein after Focal Cerebral Ischemia in Rats
Authors: Suzuki Shigeaki , Tanaka Kortaro , Nogawa Shigeru , Nagata Eiichiro , Ito Daisuke , Dembo Tomohisa , Fukuuchi Yasuo
Published: November 2003

Although interleukin-6 (IL-6) has various neuroprotective effects against cerebral ischemia, the topographic distribution and cellular source of IL-6 after cerebral ischemia remain unclear. In the current study, the localization of IL-6 protein was immunohistochemically examined in rats after 3.5, 12, 24, and 48 hours of reperfusion after 1.5 hours of middle cerebral artery occlusion. Middle cerebral artery occlusion was induced by the intraluminal suture method. The specificity of the anti–IL-6 antibody used in the current study was confirmed by Western blot analysis and an immunoabsorption test. To identify the cellular source, lectin histochemical study and immunohistochemical study with microtubule-associated protein-2, ED1, and glial fibrillary acidic protein also were carried out. The sham group did not show any clear IL-6 immunoreactivity. After 3.5 hours of reperfusion, IL-6 immunoreactivity was first detected on the reperfused side, and it was upregulated, especially in the periinfarct region, after 24 hours of reperfusion. Also, IL-6 was expressed after 3.5 hours of reperfusion in the contralateral cerebral cortex and bilateral hippocampi. Double staining showed that the cells containing IL-6 were neurons and round-type microglia, not astrocytes. The current findings suggest that IL-6 expression in ischemically threatened neurons and reactive microglia is closely associated with brain tissue neuroprotective mechanisms against cerebral ischemia.
Neuroprotection by Estrogens in a Mouse Model of Focal Cerebral Ischemia and in Cultured Neurons: Evidence for a Receptor-Independent Antioxidative Mechanism
Authors: Culmsee Carsten , Vedder Helmut , Ravati Alexander , Junker Vera , Otto Dörte , Ahlemeyer Barbara , Krieg Jürgen-Christian , Krieglstein Josef
Published: November 2003

Estrogens have been suggested for the treatment of neurodegenerative disorders, including stroke, because of their neuroprotective activities against various neurotoxic stimuli such as glutamate, glucose deprivation, iron, or β-amyloid. Here, the authors report that 17β-estradiol (0.3 to 30 mg/kg) and 2-OH-estradiol (0.003 to 30 mg/kg) reduced brain tissue damage after permanent occlusion of the middle cerebral artery in male NMRI mice. In vitro, 17β-estradiol (1 to 10 μmol/L) and 2-OH-estradiol (0.01 to 1 μmol/L) reduced the percentage of damaged chick embryonic neurons treated with FeSO4. In these primary neurons exposed to FeSO4, the authors also found reactive oxygen species to be diminished after treatment with 17β-estradiol (1 to 10 μmol/L) or 2-OH-estradiol (0.01 to 10 μmol/L), suggesting a strong antioxidant activity of the estrogens that were used. Neither the neuroprotective effect nor the free radical scavenging properties of the estrogens were influenced by the estrogen receptor antagonist tamoxifen. The authors conclude that estrogens protect neurons against damage by radical scavenging rather than through estrogen receptor activation.
Identification of Genes Differentially Expressed in Canine Vasospastic Cerebral Arteries after Subarachnoid Hemorrhage
Authors: Onda Hideaki , Kasuya Hidetoshi , Takakura Kintomo , Hori Tomokatsu , Imaizumi Tada-Atsu , Takeuchi Toshiyuki , Inoue Ituro , Takeda Jun
Published: November 2003

To understand the molecular processes of continuous vasospasm of cerebral arteries after subarachnoid hemorrhage, mRNA differential display and screening of cDNA expression array were performed to identify genes that are differentially expressed in vasospastic arteries of canine two-hemorrhage models. The expression levels of 18 genes were found to be upregulated, and those of two genes to be down-regulated. Of these, 12 represent known genes or homologues of genes characterized previously, and the other eight genes are not related to any sequences in the databases. The known genes include five upregulated inflammation-related genes encoding monocyte chemotactic protein-1, cystatin B, inter-α-trypsin inhibitor family heavy chain-related protein, serum amyloid A protein, and glycoprotein 130, suggesting that inflammatory reaction may be involved in the development of cerebral vasospasm. The upregulation of three known genes encoding stress-related proteins of vascular endothelial growth factor, BiP protein, and growth-arrest and DNA-damage–inducible protein may be involved in possible cell survival in the damaged arteries. A full-length cDNA for the unknown clone DVS 27, whose expression was most highly upregulated, was isolated from the cerebral artery cDNA library by hybridization. Characterization of these genes should help to clarify the molecular mechanism of continuous cerebral vasospasm after subarachnoid hemorrhage.
Determination of Oxygen Extraction Ratios by Magnetic Resonance Imaging
Authors: Oja Joni M. E. , Gillen Joseph S. , Kauppinen Risto A. , Kraut Michael , van Zijl Peter C. M.
Published: November 2003

The oxygen extraction ratio (OER) of a tissue describes the interplay between oxygen delivery and consumption and, as such, directly reflects the viability and activity of any organ. It is shown that OER can be quantified using a single magnetic resonance imaging observable, namely the relaxation time T2 of venous blood draining from the tissue. This principle is applied to study local OER changes in the brain on visual stimulation in humans, unambiguously demonstrating a mismatch between changes in blood flow and oxygen metabolism on activation.
Effects of Tissue Type Plasminogen Activator in Embolic versus Mechanical Models of Focal Cerebral Ischemia in Rats
Authors: Meng Wei , Wang Xiaoying , Asahi Minoru , Kano Tsuneo , Asahi Kazuko , Ackerman Robert H. , Lo Eng H.
Published: November 2003

Tissue type plasminogen activator (tPA) can be effective therapy for embolic stroke by restoring cerebral perfusion. However, a recent experimental study showed that tPA increased infarct size in a mouse model of transient focal ischemia, suggesting a possible adverse effect of tPA on ischemic tissue per se. In this report, the effects of tPA in two rat models of cerebral ischemia were compared. In experiment 1, rats were subjected to focal ischemia via injection of autologous clots into the middle cerebral artery territory. Two hours after clot injection, rats were treated with 10 mg/kg tPA or normal saline. Perfusion-sensitive computed tomography scanning showed that tPA restored cerebral perfusion in this thromboembolic model. Treatment with tPA significantly reduced ischemic lesion volumes measured at 24 hours by >60%. In experiment 2, three groups of rats were subjected to focal ischemia via a mechanical approach in which a silicon-coated filament was used intraluminally to occlude the origin of the middle cerebral artery. In two groups, the filament was withdrawn after 2 hours to allow for reperfusion, and then rats were randomly treated with 10 mg/kg tPA or normal saline. In the third group, rats were not treated and the filament was not withdrawn so that permanent focal ischemia was present. In this experiment, tPA did not significantly alter lesion volumes after 2 hours of transient focal ischemia. In contrast, permanent ischemia significantly increased lesion volumes by 55% compared with transient ischemia. These results indicate that in these rat models of focal cerebral ischemia, tPA did not have detectable negative effects. Other potentially negative effects of tPA may be dependent on choice of animal species and model systems.