bluuebunny/crossref_metadata_2025 huggingface dataset:
α[C-11]Methyl-l-Tryptophan PET Maps Brain Serotonin Synthesis and Kynurenine Pathway Metabolism
Authors: Chugani Diane C. , Muzik Otto
Published: November 2003

α[C-11]Methyl-l-tryptophan (AMT) is an analog of tryptophan used with positron emission tomography for the measurement of serotonin synthesis in humans. Several attempts have been made to estimate the serotonin synthesis rate from plasma and brain kinetic data of AMT using the same model as that applied for the measurement of the glucose metabolic rate with 2-deoxyglucose. However, although AMT is similar to 2-deoxyglucose with regard to an irreversible pool of tracer uptake, there are important differences between the two tracers and how the model can be applied. These differences include transport at the blood-brain barrier and the presence of a large unmetabolized pool of AMT, precluding the method from providing the absolute serotonin synthesis rate. Despite this limitation, the unidirectional uptake rate constant (K-complex) values have been found to be stable within an individual, and the rank order of regional brain values for K-complex are consistent with the rank order for serotonin content in human brain. Furthermore, changes in K-complex with age, gender, and disease states are consistent with previously reported biochemical measurements of serotonin in brain tissue. The authors suggest, therefore, that the K-complex is an index of serotonin synthesis which they have termed the “serotonin synthesis capacity.” The authors argue that AMT is a useful tracer for study of serotonergic mechanisms, and under certain pathologic states, of metabolism by means of the kynurenine pathway.
Effect of JTP-2942, a Novel Thyrotropin-Releasing Hormone Analog, on Motor Deficits after Chronic Focal Cerebral Ischemia in Rats
Authors: Yonemori Fumihiko , Yamaguchi Tohru , Nakayama Hitoshi , Narita Koji , Hojo Shuntaro , Tamura Akira
Published: November 2003

To investigate the chronic effects of a novel thyrotropin-releasing hormone analog, JTP-2942 (Nα-[(1S, 2R)-2-methyl-4-oxocyclopentylcarbonyl]-l-histidyl-l-prolinamide monohydrate), on behavioral changes after stroke, the authors examined its effects on motor and neurologic deficits using a middle cerebral artery (MCA) occlusion model in rats. A left MCA was permanently occluded at a proximal site. From 1 week after occlusion, JTP-2942 was intravenously administered once a day for 4 weeks. Sensorimotor performance was evaluated weekly for 10 weeks after the occlusion. The ability of the rat to maintain its body position on an inclined plane and neurologic examination based on hemiparesis and abnormal posture were examined. After all behavioral examinations were completed, the degree of shrinkage of the left hemisphere was measured. The ability of MCA-occluded rats to maintain body position on an inclined plane in the left-headed position was significantly lower than that of sham-operated rats throughout the test period. JTP-2942 gradually improved this deficit dose dependently, and a dose of 0.03 mg/kg of JTP-2942 significantly improved performance to the levels of the sham-operated rats. Neurologic deficits were also observed in MCA-occluded rats. JTP-2942 also significantly improved these deficits dose dependently. On the other hand, CDP-choline (500 mg/kg, administered intravenously), a therapeutic agent for the disturbance of consciousness and hemiparesis after stroke, improved neurologic deficits but did not affect the motor deficits measured using the inclined plane. It is noteworthy that the effects of JTP-2942 on these deficits were observed 4 weeks after cessation of drug administration. Furthermore, there was no difference in the degree of shrinkage of the cerebrum among the MCA-occluded groups. In the present study, long-lasting improving effects of JTP-2942 on the impairment of motor and neurologic functions were observed in rats with MCA occlusion, which continued after cessation of drug administration and which were not attributable to a reduction in ipsilateral cerebral shrinkage. It is considered that the effect of JTP-2942 on functional recovery is attributable to the activation of substitutive functions such as neuronal reconstruction. These pharmacologic properties of JTP-2942 may be of interest for the treatment of patients with motor and neurologic deficits during the chronic or subacute phase of stroke.
Induction of Protein Kinase Cδ Subspecies in Neurons and Microglia after Transient Global Brain Ischemia
Authors: Koponen Susanna , Goldsteins Gundars , Keinänen Riitta , Koistinaho Jari
Published: November 2003

The delayed death of CA1 neurons after global brain ischemia is associated with induction of apoptosis genes and is inhibited by protein synthesis inhibitors, suggesting that the degeneration of CA1 pyramidal neurons is an active process that requires new gene expression. The transient global ischemia model has been extensively used to identify enzymes and other proteins underlying delayed neuronal cell death. The expression of protein kinase C (PKC) subspecies after 20 minutes of global brain ischemia produced by a four-vessel occlusion model in the rat was studied. From the multiple PKC subspecies studied, only PKCδ mRNA was significantly up-regulated in CA1 pyramidal neurons at 24 hours and in activated microglia at 3 to at least 7 days after ischemia. The induction of PKCδ mRNA was also found in the cortex at 8 hours and 3 days after ischemia. This cortical but not hippocampal induction was regulated by an α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid/kainate receptor antagonist, 6-nitro-7-sulfamobenzo[ f]quinoxaline-2,3-dione, and glucocorticoids. An N-methyl-d-aspartate receptor antagonist, MK-801, was without effect on the induction of PKCδ subspecies. The selective and prolonged induction of the PKCδ mRNA and protein first in CA1 pyramidal neurons and at a later stage in activated microglia suggests that the PKCδ isozyme may take part in regulation of the delayed death of CA1 neurons after transient global brain ischemia.
Cerebral Glucose Utilization and Glucose Transporter Expression: Response to Water Deprivation and Restoration
Authors: Koehler-Stec Ellen M. , Li Kang , Maher Fran , Vannucci Susan J. , Smith Carolyn B. , Simpson Ian A.
Published: November 2003

The relationship between local rates of cerebral glucose utilization (lCMRglc) and glucose transporter expression was examined during physiologic activation of the hypothalamoneurohypophysial system. Three days of water deprivation, which is known to activate the hypothalamoneurohypophysial system, resulted in increased lCMRglc and increased concentrations of GLUT1 and GLUT3 in the neurohypophysis; mRNA levels of GLUT1 and GLUT3 were decreased and increased, respectively. Water deprivation also increased lCMRglc in the hypothalamic supraoptic and paraventricular nuclei; mRNA levels of GLUT1 and GLUT3 appeared to increase in these nuclei, but the changes did not achieve statistical significance. Restoration of water for 3 to 7 days reversed all observed changes in GLUT expression (protein and mRNA); restoration of water also reversed changes in lCMRglc in both the neurohypophysis and the hypothalamic nuclei. These results indicate that under conditions of neural activation and recovery, changes in lCMRglc and the levels of GLUT1 and GLUT3 are temporally correlated in the neurohypophysis and raise the possibility that GLUT1 and GLUT3 transporter expression may be regulated by chronic changes in functional activity. In addition, increases in the expression of GLUT5 mRNA in the neurohypophysis after dehydration provide evidence for involvement of microglial activation.
Measurement of Striatal and Extrastriatal Dopamine D1 Receptor Binding Potential With [11C]NNC 112 in Humans: Validation and Reproducibility
Authors: Abi-Dargham Anissa , Martinez Diana , Mawlawi Osama , Simpson Norman , Hwang Dah-Ren , Slifstein Mark , Anjilvel Satish , Pidcock Justine , Guo Ning-Ning , Lombardo Ilise , Mann J. John , Van Heertum Ronald , Foged Christian , Halldin Christer , Laruelle Marc
Published: November 2003

To evaluate the postulated role of extrastriatal D1 receptors in human cognition and psychopathology requires an accurate and reliable method for quantification of these receptors in the living human brain. [11C]NNC 112 is a promising novel radiotracer for positron emission tomography imaging of the D1 receptor. The goal of this study was to develop and evaluate methods to derive D1 receptor parameters in striatal and extrastriatal regions of the human brain with [11C]NNC 112. Six healthy volunteers were studied twice. Two methods of analysis (kinetic and graphical) were applied to 12 regions (neocortical, limbic, and subcortical regions) to derive four outcome measures: total distribution volume, distribution volume ratio, binding potential (BP), and specific-to-nonspecific equilibrium partition coefficient ( k3/ k4). Both kinetic and graphic analyses provided BP and k3/ k4 values in good agreement with the known distribution of D1 receptors (striatum > limbic regions = neocortical regions > thalamus). The identifiability of outcome measures derived by kinetic analysis was excellent. Time-stability analysis indicated that 90 minutes of data collection generated stable outcome measures. Derivation of BP and k3/ k4 by kinetic analysis was highly reliable, with intraclass correlation coefficients (ICCs) of 0.90 ± 0.06 (mean ± SD of 12 regions) and 0.84 ± 0.11, respectively. The reliability of these parameters derived by graphical analysis was lower, with ICCs of 0.72 ± 0.17 and 0.58 ± 0.21, respectively. Noise analysis revealed a noise-dependent bias in the graphical but not the kinetic analysis. In conclusion, kinetic analysis of [11C]NNC 112 uptake provides an appropriate method with which to derive D1 receptor parameters in regions with both high (striatal) and low (extrastriatal) D1 receptor density.
Evaluation of Serotonergic Transporters using PET and [11C](+)McN-5652: Assessment of Methods
Authors: Buck Alfred , Gucker Pascale M. , Schönbächler Roland D. , Arigoni Michele , Kneifel Stefan , Vollenweider X. Franz , Ametamey Simon M. , Burger Cyrill
Published: November 2003

[11C](+)McN-5652 is an established positron emission tomography tracer used to assess serotonergic transporter density. Several methods have been used to analyze [11C](+)McN-5652 data; however, no evaluation of candidate methods has been published in detail yet. In this study, compartmental modeling using a one-tissue compartment model ( K1, k″2), a two-tissue compartment model ( K1 to k4), and a noncompartmental method that relies on a reference region devoid of specific binding sites were assessed. Because of its low density of serotonergic transporters, white matter was chosen as reference. Parameters related to transporter density were the total distribution volume DV″ (= K1/ k″2, one tissue compartment), DVtot (= K1/ k′1 (1 + k3/ k4), two tissue compartments), and Rv (= k′3/ k4, noncompartmental method). The DV″, DVtot, and Rv values extended over a similar range and reflected the known pattern of serotonergic transporters. However, all parameters related to transporter density were markedly confounded by nonspecific binding. With regard to K1, the one-tissue compartment model yielded markedly lower values, which were, however, more stable. The minimal study duration needed to determine stable values for the distribution volume was ∼60 minutes. The choice of the method to analyze [11C](+)McN-5652 data depends on the situation. Parametric maps of Rv are useful if no information on K1 is needed. If compartmental modeling is chosen, both the one- and the two-tissue compartment models have advantages. The one-tissue compartment model underestimates K1 but yields more robust values. The distribution volumes calculated with both models contain a similar amount of information. None of the parameters reflected serotonergic transporter density in a true quantitative manner, as all were confounded by nonspecific binding.
Assessment of Hemispheric Language Lateralization: A Comparison between fMRI and fTCD
Authors: Deppe Michael , Knecht Stefan , Papke Karsten , Lohmann Hubertus , Fleischer Helge , Heindel Walter , Ringelstein E. Bernd , Henningsen Henning
Published: November 2003

The cerebral blood flow velocity (CBFV) in the basal arteries during a word-generation task was assessed by functional transcranial Doppler ultrasonography (fTCD) and by functional magnetic resonance imaging (fMRI). The study investigates how event-related CBFV modulations in the middle cerebral artery (MCA) relate to regional cerebral blood flow (rCBF) changes. Both fMRI and fTCD were used in 13 subjects (7 men, 6 women, aged 21 to 44 years). The maximum difference of relative CBFV changes between the left and right MCA during the word-generation task was used as the language laterality index ( LIfTCD). For the fMRI examination during the nearly identical language task, the corresponding index was defined by LIfMRI = 100(NL − NR)/(NL + NR), where NL and NR refer to the numbers of voxels activated in the left and right hemisphere, respectively. The evoked CBFV changes expressed by LIfTCD and the corresponding laterality index, LIfMRI, estimated by fMRI showed a close linear relation (regression analysis: r = 0.95, p < 0.0001). The results of this study demonstrate that language-related velocity changes in the MCAs relate to rCBF increases in a linear fashion. Since the laterality indices assessed by fMRI and fTCD are in such close agreement both techniques can therefore be used in a complementary way.
Experimental Closed Head Injury: Analysis of Neurological Outcome, Blood–Brain Barrier Dysfunction, Intracranial Neutrophil Infiltration, and Neuronal Cell Death in Mice Deficient in Genes for Pro-Inflammatory Cytokines
Authors: Stahel Philip F. , Shohami Esther , Younis Firas M. , Kariya Karin , Otto Viviane I. , Lenzlinger Philipp M. , Grosjean Maurice B. , Eugster Hans-Pietro , Trentz Otmar , Kossmann Thomas , Morganti-Kossmann Maria C.
Published: November 2003

Cytokines are important mediators of intracranial inflammation following traumatic brain injury (TBI). In the present study, the neurological impairment and mortality, blood-brain barrier (BBB) function, intracranial polymorphonuclear leukocyte (PMN) accumulation, and posttraumatic neuronal cell death were monitored in mice lacking the genes for tumor necrosis factor (TNF)/lymphotoxin-α (LT-α) (TNF/LT-α−/−) and interleukin-6 (IL-6) and in wild-type (WT) littermates subjected to experimental closed head injury (total n = 107). The posttraumatic mortality was significantly increased in TNF/LT-α−/− mice (40%; P < 0.02) compared with WT animals (10%). The IL-6−/− mice also showed a higher mortality (17%) than their WT littermates (5.6%), but the difference was not statistically significant ( P > 0.05). The neurological severity score was similar among all groups from 1 to 72 hours after trauma, whereas at 7 days, the TNF/LT-α−/− mice showed a tendency toward better neurological recovery than their WT littermates. Interestingly, neither the degree of BBB dysfunction nor the number of infiltrating PMNs in the injured hemisphere was different between WT and cytokine-deficient mice. Furthermore, the analysis of brain sections by in situ DNA nick end labeling (TUNEL histochemistry) at 24 hours and 7 days after head injury revealed a similar extent of posttraumatic intracranial cell death in all animals. These results show that the pathophysiological sequelae of TBI are not significantly altered in mice lacking the genes for the proinflammatory cytokines TNF, LT-α, and IL-6. Nevertheless, the increased posttraumatic mortality in TNF/LT-α-deficient mice suggests a protective effect of these cytokines by mechanisms that have not been elucidated yet.
Development of an In Situ Mouse Brain Perfusion Model and its Application to mdr1a P-Glycoprotein-Deficient Mice
Authors: Dagenais Claude , Rousselle Christophe , Pollack Gary M. , Scherrmann Jean-Michel
Published: November 2003

An in situ mouse brain perfusion model predictive of passive and carrier-mediated transport across the blood-brain barrier (BBB) was developed and applied to mdr1a P-glycoprotein (Pgp)-deficient mice [ mdr1a(−/−)]. Cerebral flow was estimated from diazepam uptake. Physical integrity of the BBB was assessed with sucrose/inulin spaces; functional integrity was assessed with glucose uptake, which was saturable with a Km of ∼17 mmol/L and Vmax of 310 mmol · 100 g−1 · min−1. Brain uptake of a Pgp substrate (colchicine) was significantly enhanced (two- to fourfold) in mdr1a(−/−) mice. These data suggest that the model is applicable to elucidating the effects of efflux transporters, including Pgp, on brain uptake.
Rapid Tau Protein Dephosphorylation and Differential Rephosphorylation during Cardiac Arrest-Induced Cerebral Ischemia and Reperfusion
Authors: Mailliot Christel , Podevin-Dimster Valérie , Rosenthal Robert E. , Sergeant Nicolas , Delacourte André , Fiskum Gary , Buée Luc
Published: November 2003

The effects of cerebral ischemia/reperfusion on phosphorylation of microtubule-associated tau proteins were assessed in a canine model of cardiac arrest. As tau proteins are phosphorylated by kinases involved in different transduction signal pathways, their phosphorylation state is an excellent marker of neuronal homeostasis and microtubule dynamics. Canine brain tau proteins were characterized by immunoblotting using phosphorylation-dependent antibodies and antisera raised against different amino- and carboxy-terminal tau sequences. The present study reports a complete dephosphorylation of tau proteins during ischemia, which is shown by a higher electrophoretic mobility and the almost (if not total) disappearance of phosphorylation-dependent monoclonal antibody labeling. After 2-hour restoration of spontaneous circulation, a decrease in the electrophoretic mobility was observed, and after 24 hours of reperfusion, a full restoration of the phosphorylation was visualized using phosphorylation-dependent monoclonal antibodies directed against Ser/Thr-Pro sites. However, one particular phosphorylation site involved in tau binding to microtubules, located on Ser262/356, was never fully significantly rephosphorylated, suggesting that microtubule metabolism was still affected after 24 hours of reperfusion. Thus, the sequential and differential recovery of tau phosphorylation after ischemia followed by reperfusion is a useful marker with which to monitor neuronal integrity after brain ischemia.
Novel Characteristics of Glutamate-Induced Cell Death in Primary Septohippocampal Cultures: Relationship to Calpain and Caspase-3 Protease Activation
Authors: Zhao Xiurong , Newcomb Jennifer K. , Pike Brian R. , Wang Kevin K. W. , d'Avella Domenico , Hayes Ronald L.
Published: November 2003

Studies examined the phenotypic characteristics of glutamate-induced cell death and their relationship to calpain and caspase-3 activation. Cell viability was assessed by fluorescein diacetate and propidium iodide staining and lactate dehydrogenase release. Calpain and caspase-3 activity was inferred from signature proteolytic fragmentation of α-spectrin. Characterization of cell death phenotypes was assessed by Hoechst 33258 and DNA fragmentation assays. Exposure of septohippocampal cultures to 1.0, 2.0, and 4.0 mmol/L glutamate induced a dose-dependent cell death with an LD50 of 2.0 mmol/L glutamate after 24 hours of incubation. Glutamate treatment induced cell death in neurons and astroglia and produced morphological alterations that differed from necrotic or apoptotic changes observed after maitotoxin or staurosporine exposure, respectively. After glutamate treatment, cell nuclei were enlarged and eccentrically shaped, and aggregated chromatin appeared in a diffusely speckled pattern. Furthermore, no dose of glutamate produced evidence of internucleosomal DNA fragmentation. Incubation with varying doses of glutamate produced calpain and caspase-3 activation. Calpain inhibitor II ( N-acetyl-Leu-Leu-methionyl) provided protection only with a narrow dose range, whereas carbobenzoxy-Asp-CH2-OC( O)-2, 6-dichlorobenzene (Z-D-DCB; pan-caspase inhibitor) and MK-801 ( N-methyl-d-aspartate receptor antagonist) were potently effective across a wider dose range. Cycloheximide did not reduce cell death or protease activation.
Probability of Metabolic Tissue Recovery after Thrombolytic Treatment of Experimental Stroke: A Magnetic Resonance Spectroscopic Imaging Study in Rat Brain
Authors: Franke Claudia , Brinker Gerrit , Pillekamp Frank , Hoehn Mathias
Published: November 2003

The effect of thrombolytic therapy on metabolic changes was studied in rats submitted to thromboembolic stroke. Reperfusion was initiated at three different time points, 1.5, 3, and 4.5 hours after embolism (n = 3 each), by injection of recombinant tissue-type plasminogen activator (rt-PA). Recovery was observed during 5 hours of reperfusion using perfusion-weighted images and a two-dimensional 1H magnetic resonance spectroscopic imaging (MRSI) technique. Temporal evolution of the cerebral metabolites lactate and N-acetyl-aspartate (NAA) was determined. To analyze the chances of metabolic tissue recovery, the outcome of treatment, defined by a reversal of lactate concentration, was compared with the lactate intensity before treatment. In untreated animals (n = 4), clot embolism resulted in a drop of perfusion signal intensity in the occluded hemisphere followed by an increase of lactate concentration and a decrease of NAA that persisted throughout the observation period. Thrombolysis partially restored blood flow, but the mean lactate concentration decreased only slightly after successful lysis in animals treated 1.5 hours after embolism. If treatment was initiated later, no decline of lactate level was observed. Five hours after initiation of thrombolysis, the average tissue lactate amounted to 95 ± 6, 111 ± 17, and 139 ± 60% of the early ischemic value (40 minutes after embolization) if treatment began 1.5, 3, and 4.5 hours after embolism, respectively. The NAA level declined slightly but never showed a recovery after rt-PA treatment. In individual pixels, the probability of metabolic tissue recovery clearly declined with increasing lactate concentration before thrombolysis. Interestingly, this probability was independent of treatment delay, but the number of pixels with low lactate declined with increasing ischemia time. Potential clinical applications of MRSI include monitoring of therapeutic intervention as well as support for prognosis of outcome after rt-PA treatment.
Cyclic Adenosine Monophosphate Regulates the Expression of the Intercellular Adhesion Molecule and the Inducible Nitric Oxide Synthase in Brain Endothelial Cells
Authors: Balyasnikova Irina V. , Pelligrino Dale A. , Greenwood John , Adamson Peter , Dragon Serge , Raza Hassan , Galea Elena
Published: November 2003

The authors studied whether cyclic AMP (cAMP), a widespread regulator of inflammation, modulates the cytokine-mediated expression of the intercellular adhesion molecule, intercellular adhesion molecule-1 (ICAM-1), and the inflammatory nitric oxide synthase 2 (NOS-2), in primary and immortalized brain endothelial cell cultures (GP8.3 cell line). When measured by enzyme-linked immunosorbent assay (ELISA), ICAM-1 was constitutively expressed and was upregulated twofold by interleukin-1β, with no effect of interferon-γ. The NOS-2 activity, assessed by nitrite accumulation, was absent from untreated cultures but was induced by interleukin-1β and interferon-γ acting synergistically. Stimulation of cAMP-dependent pathways with forskolin or dibutyryl cAMP decreased ICAM-1 protein expression, whereas it increased NOS-2 protein expression. For both ICAM-1 and NOS-2, mRNA expression correlated with protein expression. Blockade of NOS activity with L-N-monomethylargiuine (L-NMMA) did not alter ICAM-1 expression, indicating that the nitric oxide released by NOS-2 did not cause the down-regulation of ICAM-1. Analysis of NFκB activation indicated that cAMP acted through a mechanism other than inhibition of nuclear translocation of NFκB. The authors conclude that cAMP modulates the expression of proinflammatory molecules in brain endothelium. This suggests that inflammatory processes at the blood-brain barrier in vivo may be regulated by perivascular neurotransmitters via cAMP.
Quantitative Assessment of Ischemic Pathology in Axons, Oligodendrocytes, and Neurons: Attenuation of Damage after Transient Ischemia
Authors: Valeriani Valerio , Dewar Deborah , McCulloch James
Published: November 2003

Axons and oligodendrocytes are vulnerable to cerebral ischemia. The absence of quantitative methods for assessment of white matter pathology in ischemia has precluded in vivo evaluation of therapeutic interventions directed at axons and oligodendrocytes. The authors demonstrate here that the quantitative extent of white matter pathology was reduced by restoration of cerebral blood flow after 2 hours of middle cerebral artery occlusion. Focal ischemia was induced in anesthetized rats by intraluminal thread placement, either transiently (for 2 hours) or permanently. At 24 hours after induction of ischemia, axonal damage was determined by amyloid precursor protein (APP) immunohistochemistry, and the ischemic insult to oligodendrocytes was assessed by Tau-1 immunostaining in the same sections. In adjacent sections, ischemic damage to neuronal perikarya was defined histologically. The hemispheric extent of axonal damage was reduced by 70% in the transiently occluded animals from that in permanently occluded animals. The volumes of oligodendrocyte pathology and of neuronal perikaryal damage were reduced by 62% and 58%, respectively, in the transiently occluded animals. These results demonstrate that this methodologic approach for assessing ischemic damage in axons and oligodendrocytes can detect relative alterations in gray and white matter pathology with intervention strategies.
L-Arginine Partially Restores the Diminished CO2 Reactivity after Mild Controlled Cortical Impact Injury in the Adult Rat
Authors: Golding Elke M. , Robertson Claudia S. , Bryan Robert M.
Published: November 2003

Using an open cranial window technique, the authors investigated the mechanisms associated with the suppressed CO2 reactivity after mild controlled cortical impact (CCI) injury in rats. The dilation of arterioles (n = 7) to hypercapnia before injury was 38 ± 12%, which was significantly reduced both at 1 hour (23 ± 15% dilation) and at 2 hours after injury (11 ± 19% dilation). In the presence of L-arginine (10 mmol/L topical suffusion, 300 mg/kg intravenous infusion), the dilation of pial arterioles (n = 6) to hypercapnia was partially restored to 30 ± 6% at 2 hours after injury. In the presence of the nitric oxide (NO) donor, S-nitroso- N-acetylpenicillamine (SNAP) (10−8 mol/L topical suffusion), the dilation of pial arterioles (n = 5) to hypercapnia remained diminished (5 ± 7%) at 2 hours after injury. The dilation of pial arterioles (n = 4) to hypercapnia also remained suppressed (5 ± 6%) with topical suffusion of the free radical scavengers, polyethylene glycol-superoxide dismutase (60 units/mL) and polyethylene glycol-catalase (40 units/mL). The authors have shown that L-arginine at least partially restores the diminished response to hypercapnia after mild CCI injury. Furthermore, these data suggest that the beneficial effects of L-arginine are mediated by a combination of providing substrate for NO synthase and scavenging free radicals.
Coupling of Neural Activation to Blood Flow in the Somatosensory Cortex of Rats is Time-Intensity Separable, but Not Linear
Authors: Ances Beau M. , Zarahn Eric , Greenberg Joel H. , Detre John A.
Published: November 2003

Changes in cerebral blood flow (CBF) because of functional activation are used as a surrogate for neural activity in many functional neuroimaging studies. In these studies, it is often assumed that the CBF response is a linear-time invariant (LTI) transform of the underlying neural activity. By using a previously developed animal model system of electrical forepaw stimulation in rats (n = 11), laser Doppler measurements of CBF, and somatosensory evoked potentials, measurements of neural activity were obtained when the stimulus duration and intensity were separately varied. These two sets of time series data were used to assess the LTI assumption. The CBF data were modeled as a transform of neural activity (N1–P2 amplitude of the somatosensory evoked potential) by using first-order (linear) and second-order (nonlinear) components. Although a pure LTI model explained a large amount of the variance in the data for changes in stimulus duration, our results demonstrated that the second-order kernel (i.e., a nonlinear component) contributed an explanatory component that is both statistically significant and appreciable in magnitude. For variations in stimulus intensity, a pure LTI model explained almost all of the variance in the CBF data. In particular, the shape of the CBF response did not depend on intensity of neural activity when duration was held constant (time-intensity separability). These results have important implications for the analysis and interpretation of neuroimaging data.
Influence of Blood Viscosity on Blood Flow in the Forebrain but Not Hindbrain after Carotid Occlusion in Rats
Authors: Lenz Christian , Frietsch Thomas , Fütterer Carsten , van Ackern Klaus , Kuschinsky Wolfgang , Waschke Klaus F.
Published: November 2003

That cerebral blood flow remains unchanged at an increased blood viscosity, as long as the vascular supply is not compromised, was tested. To induce a reduced blood supply of some parts of the brain and to keep the supply unchanged in others both carotid arteries were occluded in anesthetized, ventilated rats. By this procedure, blood supply to the rostral brain, but not to the brainstem and cerebellum, was compromised. Blood viscosity was increased by intravenous infusion of 20% polyvinylpyrrolidone (high viscosity group) or decreased by infusion of 5% albumin (low viscosity group). Cerebral blood flow was measured by the [14C]iodoantipyrine method in 50 complete coronal sections of the rostral brain and 22 complete coronal sections of the brainstem and cerebellum in each rat. In the high viscosity group, mean cerebral blood flow of the rostral brain was significantly lower (46 ± 7 mL/100 g−1 · min−1) than in the low viscosity group (82 ± 18 mL/100 g−1 · min−1). No differences could be observed in brainstem and cerebellum between both groups (162 ± 29 mL/100 g−1 · min−1 vs. 156 ± 18 mL/100 g−1 · min−1). Local analysis of cerebral blood flow in different brain structures of the coronal sections showed the same identical results; i.e., in 29 of the 31 brain structures analyzed in rostral brain, local cerebral blood flow was lower in the high viscosity group, whereas no differences could be observed in the 11 brain structures analyzed in the brainstem and cerebellum. It is concluded that under normal conditions cerebral blood flow can be maintained at an increased blood viscosity by a compensatory vasodilation. When the capacity for vasodilation is exhausted by occlusion of supplying arteries, an increased blood viscosity results in a decrease of cerebral blood flow.
Inflammatory Activation of Human Brain Endothelial Cells by Hypoxic Astrocytes In Vitro is Mediated by IL-1β
Authors: Zhang Wandong , Smith Catherine , Howlett Clare , Stanimirovic Danica
Published: November 2003

Leukocyte infiltration into the brain contributes to the development of ischemic brain damage and is mediated by endothelial/leukocyte adhesion molecules, cytokines, and chemokines released by ischemic brain cells. In this study, we provide evidence that human astrocytes (FHAs) subjected to in vitro hypoxia produce proinflammatory mediator(s) capable of up-regulating inflammatory genes, including intercellular adhesion molecule-1, interleukin (IL)-1β, tumor necrosis factor-α, IL-8, and monocyte chemotactic protein-1 (MCP-1) in human cerebromicrovascular endothelial cells (HCECs). FHAS were exposed to hypoxia in an anaerobic chamber for 4 hours, followed by reoxygenation for 24 hours. Astrocyte-conditioned media (ACM) collected from normoxic FHAS or FHAS subjected to hypoxia/reoxygenation were applied to HCEC cultures for 4 to 24 hours. Semiquantitative reverse transcription–polymerase chain reaction, immunocytochemistry, and enzyme-linked immunosorbent assay demonstrated up-regulation of intercellular adhesion molecule-1 in HCECs exposed to hypoxic ACM. A pronounced elevation in cytokine IL-1β and tumor necrosis factor-α, and chemokine IL-8 and MCP-1 mRNA, accompanied by increased release of immunoreactive cytokines and chemokines into cell media was observed in HCECs exposed to hypoxic ACM. Hypoxia/reoxygenation induced a transient (4 to 18 hours of reoxygenation) upregulation of IL-1β mRNA in FHAS and a two- to threefold increase in IL-1β levels secreted into ACM. Pretreatment of FHAS with 10 μmol/L dexamethasone inhibited both hypoxia-induced expression/secretion of IL-1β and the ability of hypoxic ACM to induce inflammatory phenotype in HCECs. The ability of hypoxic ACM to up-regulate inflammatory genes in HCECs was inhibited in the presence of IL-1 receptor antagonist (IL-1Ra) and by pretreating ACM with the blocking anti-IL-1β antibody. These findings strongly implicate IL-1β secreted by hypoxic astrocytes in triggering inflammatory activation of HCECs and thereby influencing inflammatory responses at the site of the blood-brain barrier.
Brain Injury and Cerebrovascular Fibrin Deposition Correlate with Reduced Antithrombotic Brain Capillary Functions in a Hypertensive Stroke Model
Authors: Ninomia Takashi , Wang Liang , Kumar S. Ram , Kim Anthony , Zlokovic Berislav V.
Published: November 2003

Hemostasis factors may influence the pathophysiology of stroke. The role of brain hemostasis in ischemic hypertensive brain injury is not known. We studied ischemic injury in spontaneously hypertensive rats in relation to cerebrovascular fibrin deposition and activity of different hemostasis factors in brain microcirculation. In spontaneously hypertensive rats subjected to transient middle cerebral artery occlusion versus normotensive Wistar-Kyoto (W-K) rats, infarct and edema volumes were increased by 6.1-fold ( P < 0.001) and 5.8-fold ( P < 0.001), respectively, the cerebral blood flow (CBF) reduced during middle cerebral artery occlusion (MCAO) by 55% ( P < 0.01), motor neurologic score increased by 6.9-fold ( P < 0.01), and cerebrovascular fibrin deposition increased by 6.8-fold ( P < 0.01). Under basal conditions, brain capillary protein C activation and tissue plasminogen activator activity were reduced in spontaneously hypertensive rats compared with Wistar-Kyoto rats by 11.8-fold ( P < 0.001) and 5.1-fold ( P < 0.001), respectively, and the plasminogen activator inhibitor-1 antigen and tissue factor activity were increased by 154-fold ( P < 0.00001) and 74% ( P < 0.01), respectively. We suggest that hypertension reduces antithrombotic mechanisms in brain microcirculation, which may enhance cerebrovascular fibrin deposition and microvascular obstructions during transient focal cerebral ischemia, which results in greater neuronal injury.
Functional Differentiation of Multiple Perilesional Zones after Focal Cerebral Ischemia
Authors: Witte Otto W. , Bidmon Hans-J. , Schiene Klaus , Redecker Christoph , Hagemann Georg
Published: November 2003

Transient and permanent focal cerebral ischemia results in a series of typical pathophysiologic events. These consequences evolve in time and space and are not limited to the lesion itself, but they can be observed in perilesional (penumbra) and widespread ipsi- and sometimes contralateral remote areas (diaschisis). The extent of these areas is variable depending on factors such as the type of ischemia, the model, and the functional modality investigated. This review describes some typical alterations attributable to focal cerebral ischemia using the following classification scheme to separate different lesioned and perilesional areas: (1) The lesion core is the brain area with irreversible ischemic damage. (2) The penumbra is a brain region that suffers from ischemia, but in which the ischemic damage is potentially, or at least partially, reversible. (3) Remote brain areas are brain areas that are not directly affected by ischemia. With respect to the etiology, several broad categories of remote changes may be differentiated: (3a) remote changes caused by brain edema; (3b) remote changes caused by waves of spreading depression; (3c) remote changes in projection areas; and (3d) remote changes because of reactive plasticity and systemic effects. The various perilesional areas are not necessarily homogeneous; but a broad differentiation of separate topographic perilesional areas according to their functional state and sequelae allows segregation into several signaling cascades, and may help to understand the functional consequences and adaptive processes after focal brain ischemia.
Ischemic Penumbra: Evidence From Functional Imaging in Man
Authors: Heiss Wolf-Dieter
Published: November 2003

The ischemic penumbra is defined as tissue with flow within the thresholds for maintenance of function and of morphologic integrity. Penumbra tissue has the potential for recovery and therefore is the target for interventional therapy in acute ischemic stroke. The identification of the penumbra necessitates measuring flow reduced less than the functional threshold and differentiating between morphologic integrity and damage. This can be achieved by multitracer positron emission tomography (PET) and perfusion-weighted (PW) and diffusion-weighted magnetic resonance imaging (DW-MRI) in experimental models, in which the recovery of critically perfused tissue or its conversion to infarction was documented in repeat studies. Neuroimaging modalities applied in patients with acute ischemic stroke—multitracer PET, PW-and DW-MRI, single photon emission computed tomography (SPECT), perfusion, and Xe-enhanced computed tomography (CT)—often cannot reliably identify penumbra tissue: multitracer studies for the assessment of flow and irreversible metabolic damage usually cannot be performed in the clinical setting; CT and MRI do not reliably detect irreversible damage in the first hours after stroke, and even DW-MRI may be misleading in some cases; determinations of perfusion alone yield a poor estimate of the state of the tissue as long as the time course of changes is not known in individual cases. Therefore, the range of flow values in ischemic tissue found later, either within or outside the infarct, was rather broad. New tracers—for example, receptor ligands or hypoxia markers—might improve the identification of penumbra tissue in the future. Despite these methodologic limitations, the validity of the concept of the penumbra was proven in several therapeutic studies in which thrombolytic treatment reversed critical ischemia and decreased the volume of final infarcts. Such neuroimaging findings might serve as surrogate targets in the selection of other therapeutic strategies for large clinical trials.
Involvement of Caspase-3 in Cell Death after Hypoxia–Ischemia Declines during Brain Maturation
Authors: Hu Bing R. , Liu Chun Li , Ouyang Yibing , Blomgren Klas , Siesjö Bo K.
Published: November 2003

The involvement of caspase-3 in cell death after hypoxia–ischemia (HI) was studied during brain maturation. Unilateral HI was produced in rats at postnatal day 7 (P7), 15 (P15), 26 (P26), and 60 (P60) by a combination of left carotid artery ligation and systemic hypoxia (8% O2). Activation of caspase-3 and cell death was examined in situ by high-resolution confocal microscopy with anti-active caspase-3 antibody and propidium iodide and by biochemical analysis. The active caspase-3 positive neurons were composed of more than 90% HI damaged striatal and neocortical neurons in P7 pups, but that number was reduced to approximately 65% in striatum and 34% in the neocortex of P15 pups, and approximately 26% in striatum and 2% in neocortex of P26 rats. In P60 rats, less than 4% of the damaged neurons in striatum and less than 1% in neocortex were positive for active caspase-3. Western blot analysis demonstrated that the level of inactive caspase-3 in normal forebrain tissue gradually declined from a high level in young pups to very low levels in adult rats. Concomitantly, HI-induced active caspase-3 was reduced from a relatively high level in P7, to moderate levels in P15 and P26, to a barely detectable level in P60 rats. The authors conclude that the involvement of caspase-3 in the pathogenesis of cell death after HI declines during neuronal maturation. The authors hypothesize that caspase-3 may play a major role in cell death in immature neurons but a minor role in cell death in mature neurons after brain injury.
Adenovirus-Mediated Gene Transfer to Human Cerebral Arteries
Authors: Khurana Vini G. , Smith Leslie A. , Weiler Deborah A. , Springett Margaret J. , Parisi Joseph E. , Meyer Fredric B. , Marsh W. Richard , O'Brien Timothy , Katusic Zvonimir S.
Published: November 2003

Gene therapy is being investigated as a putative treatment option for cardiovascular diseases, including cerebral vasospasm. Because there is presently no information regarding gene transfer to human cerebral arteries, the principal objective of this study was to characterize adenovirus-mediated expression and function of recombinant endothelial nitric oxide synthase (eNOS) gene in human pial arteries. Pial arteries (outer diameter 500 to 1000 μm) were isolated from 30 patients undergoing temporal lobectomy for intractable seizures and were studied using histologic staining, histochemistry, electron microscopy, and isometric force recording. Gene transfer experiments were performed ex vivo using adenoviral vectors encoding genes for bovine eNOS (AdCMVeNOS) and Escherichia coli β-galactosidase (AdCMVLacZ). In transduced arteries, studied 24 hours after exposure to vectors, expression of recombinant β-galactosidase and eNOS was detected by histochemistry, localizing mainly to the adventitia (n = 4). Immunoelectron microscopy localized recombinant eNOS in adventitial fibroblasts. During contractions to U46619, bradykinin-induced relaxations were significantly augmented in AdCMVeNOS-transduced rings compared with control and AdCMVLacZ-transduced rings ( P < 0.01; n = 6). The NOS inhibitor L-nitroarginine methylester (L-NAME) caused significantly greater contraction in AdCMVeNOS-transduced rings ( P < 0.001; n = 4) and inhibited bradykinin-induced relaxations in control and transduced rings ( P < 0.001; n = 6). The current findings suggest that in AdCMVeNOS-transduced human pial arteries, expression of recombinant eNOS occurs mainly in adventitial fibroblasts where it augments relaxations to NO-dependent agonists such as bradykinin. Findings from the current study might be beneficial in future clinical applications of gene therapy for the treatment or prevention of cerebral vasospasm.
Therapeutic Potential of Neurotrophic Factors and Neural Stem Cells Against Ischemic Brain Injury
Authors: Abe Koji
Published: November 2003

Development of neuronal and glial cells and their maintenance are under control of neurotrophic factors (NTFs). An exogenous administration of NTFs protects extremely sensitive brain tissue from ischemic damage. On the other hand, it is now known that neural stem cells are present in normal adult brain, and have a potential to compensate and recover neural functions that were lost due to ischemic stroke. These stem cells are also under control of NTFs to differentiate into a certain species of neural cells. Thus, the purpose of this review is to summarize the present understanding of the role of NTFs in normal and ischemic brain and the therapeutic potential of NTF protein itself or gene therapy, and then to summarize the role of NTFs in stem cell differentiation and a possible therapeutic potential with the neural stem cells against ischemic brain injury.
Cortical Death Caused by Striatal Administration of AMPA and Interleukin-1 is Mediated by Activation of Cortical NMDA Receptors
Authors: Allan Stuart M. , Rothwell Nancy J.
Published: November 2003

Striatal coadministration of interleukin-1β (IL-1β) with α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (S-AMPA) in rats results in widespread cortical cell death not caused by either treatment alone. This cortical damage was unaffected by cortical infusion of the AMPA-receptor antagonist NBQX. Cortical infusion of an NMDA-receptor antagonist D-AP5 significantly inhibited (57%; P < 0.05) cortical death, but had no effect on the local striatal death. Thus, cortical neuronal death induced by striatal S-AMPA and human recombinant interleukin-1β (hrIL-1β) is mediated by activation of NMDA receptors in the cortex. The authors propose that IL-1β actions on AMPA-receptor mediated cell death may involve the activation of polysynaptic pathways from the striatum to the cortex.
Activation of Specific Neuronal Circuits by Corticotropin Releasing Hormone as Indicated by c-fos Expression and Glucose Metabolism
Authors: Dubé Céline , Brunson Kristen , Nehlig Astrid , Baram Tallie Z.
Published: November 2003

The neuropeptide corticotropin releasing hormone (CRH) is the central nervous system (CNS) transducer of stressful stimuli. Endogenous CRH is released from neuronal terminals in several central nervous system regions—for example, amygdala and hypothalamus—during stress, and exogenous CRH administration mimics stress-related behaviors and hormonal patterns. However, whereas the role of endogenous CRH as a stress neuromodulator has been established, recent findings suggest that the peptide also functions to influence cognitive, emotional, and neuroimmune functions by modulating neuronal communication in a number of circuits. Although anatomic and pharmacologic approaches have provided evidence for this wider spectrum of CRH actions, the discrete regions and specific circuits activated by CRH have not been fully elucidated. In this article, the authors report on the use of two complementary methods to discern specific regions and cell groups activated by the administration of CRH. Glucose metabolism analysis provided quantitative measures of CRH-induced activation, but at a regional resolution; expression of the immediate early gene c-fos permitted a single cell resolution, but underestimated the neuroanatomic extent of CRH-induced activation. Overlapping regions activated using both methods delineated discrete cortical, limbic, and motor pathways. Importantly, cell groups activated by CRH included those possessing either or both members of the CRH receptor family, suggesting that both receptors may mediate the effects of the endogenous ligand. In summary, CRH activates a broad but selective array of neuronal structures belonging to cortical, limbic, and motor circuits. These findings indicate that stress-related release of this peptide may contribute to a spectrum of important modulations of CNS function.