bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Cerebral White Matter Damage in Preterm Infants Using 1H and 31P Magnetic Resonance Spectroscopy
Authors: Robertson Nicola J. , Kuint Jacob , Counsell Serena J. , Rutherford Mary A. , Coutts Glyn A. , Cox I. Jane , Edwards A. David
Published: November 2003

The biochemical characteristics of white matter damage (WMD) in preterm infants were assessed using magnetic resonance spectroscopy (MRS). The authors hypothesized that preterm infants with WMD at term had a persisting cerebral lactic alkalosis and reduced N-acetyl aspartate (NAA)/creatine plus phosphocreatine (Cr), similar to that previously documented in term infants weeks after perinatal hypoxia–ischemia (HI). Thirty infants (gestational age 27.9 ± 3.1 weeks, birth weight 1122 ± 445 g) were studied at postnatal age of 9.8 ± 4.1 weeks (corrected age 40.3 ± 3.9 weeks). Infants were grouped according to the presence or absence of WMD on magnetic resonance (MR) images. The peak area ratios of lactate/Cr, NAA/Cr, myo-inositol/Cr, and choline (Cho)/Cr were measured from an 8-cm3 voxel in the posterior periventricular white matter (WM) using proton MRS. Intracellular pH (pHi) was calculated using phosphorus MRS. Eighteen infants had normal WM on MR imaging; 12 had WMD. For infants with WMD, lactate/Cr and myo-inositol/Cr were related ( P < 0.01); lactate/Cr and pHi were not ( P = 0.8). In the WMD group, mean lactate/Cr and myo-inositol/Cr were higher ( P < 0.001, P < 0.05, respectively) than the normal WM group. There was no difference in the NAA/Cr, Cho/Cr, or pHi between the two groups, although pHi was not measured in all infants. These findings suggest that WMD in the preterm infant at term has a different biochemical profile compared with the term infant after perinatal HI.
Noninvasive Assessment of Cerebral Oxygenation during Acclimation to Hypobaric Hypoxia
Authors: Dunn Jeff F. , Grinberg Oleg , Roche Marcie , Nwaigwe Casmiar I. , Hou Huagang G. , Swartz Harold M.
Published: November 2003

Factors regulating cerebral tissue Po2 (PtO2) are complex. With the increased use of clinical PtO2 monitors, it has become important to elucidate these mechanisms. The authors are investigating a new methodology (electron paramagnetic resonance oximetry) for use in monitoring cerebral PtO2 in awake animals over time courses of weeks. The authors used this to study cerebral PtO2 in rats during chronic acclimation to hypoxia predicting that such acclimation would cause an increase in PtO2 because of increases that occur in capillary density and oxygen carrying capacity. The average PtO2 between 7 and 21 days was increased by 228% over controls.
High Speed Diffusion Magnetic Resonance Imaging of Ischemia and Spontaneous Periinfarct Spreading Depression after Thromboembolic Stroke in the Rat
Authors: Kastrup Andreas , Neumann-Haefelin Tobias , Moseley Michael E. , de Crespigny Alex
Published: November 2003

Spontaneous episodes of transient cell membrane depolarization (spreading depression [SD]) occur in the surroundings of experimental stroke lesions and are believed to contribute to infarct growth. Diffusion-weighted imaging (DWI) is capable of detecting the water shifts from extracellular to intracellular space associated with SD waves and ischemia, and can make in vivo measurements of these two features on a pixel-by-pixel basis with good temporal resolution. Using continuous high speed DWI with a temporal resolution of 12 seconds over a period of 3 hours, the in vivo contribution of spontaneous SDs to the development of ischemic tissue injury was examined in 8 rats using a thromboembolic stroke model. During the observation period, the initial lesion volume increased in 4 animals, remained unchanged in 1 animal, and decreased in 3 animals (most likely because of spontaneous clot lysis). Irrespective of the lesion evolution patterns, animals demonstrated 6.5 ± 2.1 spontaneous SDs outside of the ischemic core. A time-to-peak analysis of apparent diffusion coefficient (ADC) changes for each SD wave demonstrated multidirectional propagation patterns from variable initiation sites. Maps of the time constants of ADC recovery, reflecting the local energy supply and cerebral blood flow, revealed prolonged recovery times in areas close to the ischemic core. However, repetitive SD episodes in the periinfarct tissue did not eventually lead to permanent ADC reductions. These results suggest that spontaneous SD waves do not necessarily contribute to the expansion of the ischemic lesion volume in this model.
Exogenous Aβ1–40 Reproduces Cerebrovascular Alterations Resulting from Amyloid Precursor Protein Overexpression in Mice
Authors: Niwa Kiyoshi , Carlson George A. , Iadecola Costantino
Published: November 2003

Transgenic mice overexpressing the amyloid precursor protein (APP) have a profound impairment in endothelium-dependent cerebrovascular responses that is counteracted by the superoxide scavenger superoxide dismutase (SOD). The authors investigated whether the amyloid-β peptide (Aβ) is responsible for the cerebrovascular effects of APP overexpression. Cerebral blood flow (CBF) was monitored by a laser—Doppler flowmeter in anesthetized-ventilated mice equipped with a cranial window. Superfusion of Aβ1–40 on the neocortex reduced resting CBF in a dose-dependent fashion (−29% ± 7% at 5 μmol/L) and attenuated the increase in CBF produced by the endothelium-dependent vasodilators acetylcholine (−41% ± 8%), bradykinin (−39% ± 9%), and the calcium ionophore A23187 (−37% ± 5%). Aβ1–40 did not influence the CBF increases produced by the endothelium-independent vasodilators S-nitroso-N-acetylpenicillamine and hypercapnia. In contrast, Aβ1–42 did not attenuate resting CBF or the CBF increases produced by endothelium-dependent vasodilators. Cerebrovascular effects of Aβ1–40 were reversed by the superoxide scavengers SOD or MnTBAP. Furthermore, substitution of methionine 35 with norleucine, a mutation that blocks the ability of Aβ to generate reactive oxygen species, abolished Aβ1–40 vasoactivity. The authors conclude that Aβ1–40, but not Aβ1–42, reproduces the cerebrovascular alterations observed in APP transgenics, Thus, Aβ1–40 could play a role in the cerebrovascular alterations observed in Alzheimer's dementia.
Reactive Oxygen Radicals in Signaling and Damage in the Ischemic Brain
Authors: Chan Pak H.
Published: November 2003

Reactive oxygen species have been implicated in brain injury after ischemic stroke. These oxidants can react and damage the cellular macromolecules by virtue of the reactivity that leads to cell injury and necrosis. Oxidants are also mediators in signaling involving mitochondria, DNA repair enzymes, and transcription factors that may lead to apoptosis after cerebral ischemia. Transgenic or knockout mice with cell- or site-specific prooxidant and antioxidant enzymes provide useful tools in dissecting the events involving oxidative stress in signaling and damage in ischemic brain injury.
Antisense Oligodeoxynucleotide to Inducible Nitric Oxide Synthase Protects against Transient Focal Cerebral Ischemia—Induced Brain Injury
Authors: Parmentier-Batteur Sophie , Bohme Georg Andrees , Lerouet Dominique , Zhou-Ding Li , Beray Virginie , Margaill Isabelle , Plotkine Michel
Published: November 2003

Nitric oxide (NO) has been suspected to mediate brain damage during ischemia. Here the authors studied the effects of an antisense oligodeoxynucleotide (ODN) directed against the inducible isoform of NO synthase (iNOS) in a model of transient focal cerebral ischemia in rats. Treatment consisted of seven intracerebroventricular injections of a phosphodiester/phosphorothioate chimera ODN (3 nmol each) at 12-hour intervals, and was initiated 12 hours before a 2-hour occlusion of the left middle cerebral artery and common carotid artery. Outcomes were measured three days after ischemia. When compared with animals treated with vehicle or an appropriate random non-sense control ODN sequence, the antisense treatment reduced the lesion volume by 30% and significantly improved recovery of sensorimotor functions, as assessed on a neuroscore. This effect was associated with a decrease in iNOS expression, as assessed by Western blot, a 39% reduction in iNOS enzymatic activity evaluated as Ca2+-independent NOS activity, and a 37% reduction in nitrotyrosine formation, reflecting protein nitration by NO-derived peroxynitrite. These findings provide new evidence that inhibition of iNOS may be of interest for the treatment of stroke.
Blood—Brain Barrier Genomics
Authors: Li Jian Yi , Boado Ruben J. , Pardridge William M.
Published: November 2003

The blood–brain barrier (BBB) is formed by the brain microvascular endothelium, and the unique transport properties of the BBB are derived from tissue-specific gene expression within this cell. The current studies developed a gene microarray approach specific for the BBB by purifying the initial mRNA from isolated rat brain capillaries to generate tester cDNA. A polymerase chain reaction–based subtraction cloning method, suppression subtractive hybridization (SSH), was used, and the BBB cDNA was subtracted with driver cDNA produced from mRNA isolated from rat liver and kidney. Screening 5% of the subtracted tester cDNA resulted in identification of 50 gene products and more than 80% of those were selectively expressed at the BBB; these included novel gene sequences not found in existing databases, ESTs, and known genes that were not known to be selectively expressed at the BBB. Genes in the latter category include tissue plasminogen activator, insulin-like growth factor-2, PC-3 gene product, myelin basic protein, regulator of G protein signaling 5, utrophin, IκB, connexin-45, the class I major histocompatibility complex, the rat homologue of the transcription factors hbrm or EZH1, and organic anion transporting polypeptide type 2. Knowledge of tissue-specific gene expression at the BBB could lead to new targets for brain drug delivery and could elucidate mechanisms of brain pathology at the microvascular level.
Brain Activation in Normal Subjects and in Patients Affected by Mitochondrial Disease without Clinical Central Nervous System Involvement: A Phosphorus Magnetic Resonance Spectroscopy Study
Authors: Rango Mario , Bozzali Marco , Prelle Alessandro , Scarlato Guglielmo , Bresolin Nereo
Published: November 2003

It remains unclear whether brain energetics is disturbed in patients with mitochondrial disease without clinical central nervous system involvement (MDW). The authors used the high temporal and spatial resolution phosphorus magnetic resonance spectroscopy (31P MRS) technique that they developed to study high energy phosphates (HEPs) and intracellular pH (pH) in the visual cortex of 9 normal subjects and 5 MDW patients with single mtDNA deletion at rest, during, and after visual activation. In normal subjects, HEPs remained unchanged during activation but rose significantly (by 17%) during recovery, and pH increased during visual activation with a slow return to rest values. In MDW patients, HEPs were within the normal range at rest and did not change during activation, but fell significantly (by 22%) in the recovery period; pH did not reveal a homogeneous pattern. In the brain of patients with MDW, energy balance remains normal until oxidative metabolism is intensively stressed, as during a postactivation phase. The heterogeneity of the physicochemical environment (that is, pH) suggests various degrees of subclinical brain involvement. The combined use of MRS and brain activation is fundamental for the study of brain energetics and may prove an important diagnostic tool in patients with MDW.
Radiolabeled Cholinesterase Substrates: In Vitro Methods for Determining Structure-Activity Relationships and Identification of a Positron Emission Tomography Radiopharmaceutical for In Vivo Measurement of Butyrylcholinesterase Activity
Authors: Snyder Scott E. , Gunupudi Neeraja , Sherman Phillip S. , Butch Elizabeth R. , Skaddan Marc B. , Kilbourn Michael R. , Koeppe Robert A. , Kuhl David E.
Published: November 2003

There is currently great interest in developing radiolabeled substrates for acetylcholinesterase and butyrylcholinesterase that would be useful in the in vivo imaging of patients with Alzheimer's disease. Using a simple in vitro spectrophotometric assay for determination of enzymatic cleavage rates, the structure-activity relationship for a short series of 1-methyl-4-piperidinyl esters was investigated. Relative enzymatic hydrolysis rates for the well-characterized 1-methyl-4-piperidinyl acetate, propionate, and i-butyrate esters were in agreement with literature values. The 4 and 5 carbon esters of 1-methyl-4-piperidinol were specific for butyrylcholinesterase and cleaved in the rank order n-valerate > n-butyrate >> 2-methylbutyrate, iso-valerate. These spectrophotometric results were also in agreement with in vitro hydrolysis rates in mouse blood and with in vivo regional retention of radioactivity in mouse brain of 11C-labeled analogs. Brain uptake and apparent enzymatic rate constants for 1-[11C]methyl-4-piperidinyl n-butyrate and n-valerate were calculated from in vivo measurements in M. nemistrina using positron emission tomography. Based on higher brain uptake of radioactivity and superior pharmacokinetics, 1-[11C]methyl-4-piperidinyl n-butyrate was identified as a new radiopharmaceutical for the in vivo measurement of butyrylcholinesterase activity.
Cavernous Sinus Ganglia are Sources for Parasympathetic Innervation of Cerebral Arteries in Rat
Authors: Bleys Ronald L. A. W. , Thrasivoulou Chris , Cowen Tim
Published: November 2003

Retrograde tracing and immunohistochemistry was used in rats to investigate whether the ganglia in the cavernous sinus contribute to cerebrovascular innervation. The cavernous sinus ganglia in rat include the cavernous part of the pterygopalatine ganglion (PGC) and small cavernous ganglia (CG). The tracers, fluorogold and fast blue, were applied to the middle cerebral artery in eight rats. After 1 to 4 days, the cavernous sinuses were dissected out and studied as whole mount preparations and sections. A moderate number of labeled neurons were visible in the ipsilateral PGC and CG. Furthermore, fibers in the cavernous nerve plexus and abducens nerve were labeled, suggesting that the pathway from the cavernous sinus ganglia to the cerebral arteries runs through the cavernous plexus and then retrogradely along the abducens nerve to the internal carotid artery. Selected sections were immunohistochemically stained for the cholinergic marker, vesicular acetylcholine transporter (VAChT). Most cells in the PGC and CG were VAChT-immunoreactive, some of which also contained tracer. It is concluded that in rat, the cavernous sinus ganglia, consisting of the PGC and small CG, contribute to parasympathetic cerebrovascular innervation and that the cavernous nerve plexus and abducens nerve are involved in the pathway from these ganglia to the cerebral arteries.
Peroxynitrite Reduces Vasodilatory Responses to Reduced Intravascular Pressure, Calcitonin Gene-Related Peptide, and Cromakalim in Isolated Middle Cerebral Arteries
Authors: DeWitt Douglas S. , Mathew Babu P. , Chaisson Jennifer M. , Prough Donald S.
Published: November 2003

Vasodilatory responses to progressive reductions in intravascular pressure or to calcitonin gene-related peptide (CGRP) or cromakalim were determined in rodent middle cerebral arteries (MCAs) before and after treatment with peroxynitrite (ONOO−). Middle cerebral artery diameters in isolated, pressurized MCAs were measured as intravascular pressure was reduced from 100 to 20 mm Hg in 20-mm Hg increments before and after inactive ONOO−, pH-adjusted ONOO−, or 10, 20, or 40 μmol/L ONOO− was added to the bath. In other MCAs, responses to CGRP (1 × 10−9 −5 × 10−8) or cromakalim (3 × 10−8 −8 × 10−7) were measured before and after the addition of 25 μmol/L ONOO−. Inactive ONOO− (n = 6, P = 0.40), pH-adjusted ONOO− (n = 6, P = 0.29), and 10 μmol/L ONOO− (n = 6, P = 0.88) did not reduce vasodilatory responses to reduced intravascular pressure. Middle cerebral arteries treated with 20 (n = 6, P < 0.0001) and 40 (n = 6, P > 0.0001) μmol/L ONOO− constricted significantly when intravascular pressure was reduced. Vasodilatory responses to CGRP or cromakalim were reduced by ONOO− ( P > 0.02, n = 6 and P > 0.01, n = 7, respectively). ONOO− had no effect on vasoconstriction in response to serotonin or vasodilation in response to KCl. These studies demonstrate that ONOO− reduces multiple cerebral vasodilatory responses.
Microglia/Macrophages Proliferate in Striatum and Neocortex but Not in Hippocampus after Brief Global Ischemia That Produces Ischemic Tolerance in Gerbil Brain
Authors: Liu Jialing , Bartels Matthew , Lu Aigang , Sharp Frank R.
Published: November 2003

The current study determined whether short durations of ischemia that produce ischemia-induced tolerance stimulate glial proliferation in brain. Adult male gerbils were injected with BrdU (50 mg/kg) and dividing cells were detected using immunocytochemistry after sham operations, 2.5 or 5 minutes of global ischemia, or ischemia-induced tolerance. The 2.5-minute ischemia and the ischemia-induced tolerance did not kill hippocampal CA1 pyramidal neurons, whereas the 5-minute ischemia did kill the neurons. At 4 days after 2.5-minute global ischemia, when cell proliferation was maximal, BrdU-labeled cells increased in striatum and in neocortex, but not in hippocampus. The majority of the BrdU-labeled cells were double-labeled with isolectin B4, showing that these dividing cells were primarily microglia or macrophages, or both. Similarly, BrdU-labeled microglia/macrophages were found in striatum and neocortex but not in hippocampus of most animals 4 days after ischemia-induced tolerance (2.5 minutes of global ischemia followed 3 days later by 5 minutes of global ischemia). No detectable neuronal cell death existed in striatal and cortical regions where the microglia/macrophage proliferation occurred. Though 3 of 7 animals subjected to 2.5 minutes of ischemia showed decreased myelin-associated glycoprotein (MAG) immunostaining and increased numbers of adenomatous polyposis coli-stained oligodendrocytes in lateral striatum, this did not explain the microglia/macrophage proliferation. Data show that ischemia-induced tolerance in the gerbil is associated with proliferation of microglia/macrophages in striatum and cortex but not in hippocampus. Because there is no apparent neuronal death, it is postulated that the microglia/ macrophage proliferation occurs in response to an unknown nonlethal injury to neurons or glia and may be beneficial.
Relation of Apparent Diffusion Coefficient Changes and Metabolic Disturbances after 1 Hour of Focal Cerebral Ischemia and at Different Reperfusion Phases in Rats
Authors: Olah Laszlo , Wecker Stefan , Hoehn Mathias
Published: November 2003

Changes in apparent diffusion coefficients (ADC) were compared with alterations of adenosine triphosphate (ATP) concentration and pH in different phases of transient focal cerebral ischemia to study the ADC threshold for breakdown of energy metabolism and tissue acidosis during ischemia and reperfusion. Male Wistar rats underwent 1 hour of middle cerebral artery occlusion without recirculation (n = 3) or with 1 hour (n = 4) or 10 hours of reperfusion (n = 5) inside the magnet, using a remotely controlled thread occlusion model. ADC maps were calculated from diffusion-weighted images and normalized to the preischemic value to obtain relative ADC maps. Hemispheric lesion volume (HLV) was determined on the last relative ADC maps at different relative ADC thresholds and was compared to the HLV measured by ATP depletion and by tissue acidosis. The HLVs, defined by ATP depletion and tissue acidosis, were 26.0% ± 10.6% and 38.1% ± 6.5% at the end of ischemia, 3.3% ± 2.4% and 4.8% ± 3.5% after 1 hour of reperfusion, and 11.2% ± 4.7% and 10.9% ± 5.2% after 10 hours of recirculation, respectively. The relative ADC thresholds for energy failure were consistently approximately 77% of the control value in the three different groups. The threshold for tissue acidosis was higher at the end of ischemia (86% of control) but was similar to the results obtained for ATP depletion after 1 hour (78% of control) and 10 hours (76% of control) of recirculation. These results indicate that the described relative ADC threshold of approximately 77% of control provides a good estimate for the breakdown of energy metabolism not only during middle cerebral artery occlusion but also at the early phase of reperfusion, when recovery of energy metabolism is expected to occur, or some hours later, when development of secondary energy failure was described.
Early c-Fos Induction after Cerebral Ischemia: A Possible Neuroprotective Role
Authors: Cho Sunghee , Park Eun-Mi , Kim Yoonseong , Liu Nian , Gal Judit , Volpe Bruce T. , Joh Tong H.
Published: November 2003

The role of c-Fos in neurodegeneration or neuroprotection after cerebral ischemia is controversial. To investigate whether early c-Fos induction after ischemia is associated with neuroprotection, rats were subjected to 10 minutes of transient forebrain ischemia and c-Fos expression was examined. Resistant dentate granule cells and neurons in CA2–4 displayed more robust immunoreactivity than vulnerable neurons in the CA1 region of hippocampus during early hours of reperfusion. By 6 hours after reperfusion, c-Fos immunoreactivity was greatly diminished in all areas of the hippocampus. Administration of N-acetyl-O-methyldopamine (NAMDA), a compound previously shown to protect CA1 neurons against ischemia, increased c-Fos immunoreactivity in the CA1 vulnerable region at 6 hours after ischemia and protected SK-N-BE(2)C neurons from oxygen glucose deprivation. Further in vitro study showed that NAMDA potentiated phorbol-12 myristate-13 acetate (PMA)-induced c-Fos expression, AP1 binding activity, and late gene expression determined by chloramphenicol acetyltransferase (CAT) activity from AP1 containing tyrosine hydroxylase promoter-CAT fusion gene in SK-N-BE(2)C neurons. In vivo and in vitro results showed that a neuroprotectant, NAMDA, in concert with another stimulus (for example, ischemia or PMA) up-regulates c-Fos expression and suggested that the early rise of NAMDA-induced c-Fos expression in vulnerable CA1 neurons may account for neuroprotection by means of up-regulating late gene expression for survival.
Positron Emission Tomography Compartmental Models
Authors: Gunn Roger N. , Gunn Steve R. , Cunningham Vincent J.
Published: November 2003

The current article presents theory for compartmental models used in positron emission tomography (PET). Both plasma input models and reference tissue input models are considered. General theory is derived and the systems are characterized in terms of their impulse response functions. The theory shows that the macro parameters of the system may be determined simply from the coefficients of the impulse response functions. These results are discussed in the context of radioligand binding studies. It is shown that binding potential is simply related to the integral of the impulse response functions for all plasma and reference tissue input models currently used in PET. This article also introduces a general compartmental description for the behavior of the tracer in blood, which then allows for the blood volume-induced bias in reference tissue input models to be assessed.
Interdependence of Regional and Global Cerebral Blood Flow during Visual Stimulation: An O-15-Butanol Positron Emission Tomography Study
Authors: Kemna Lars J. , Posse Stefan , Tellmann Lutz , Schmitz Thomas , Herzog Hans
Published: November 2003

The authors investigated the influence of variations in global cerebral blood flow (gCBF) on regional flow changes during visual stimulation. Global flow was varied using different end-expiratory CO2 values (Petco2) between 20 and 70 mm Hg. Visual stimulation was performed with a red LED-array flashing at 8 Hz. Blood flow was measured with O-15-butanol, continuous arterial blood sampling, and positron emission tomography (PET). Global flow changes surpassed the published values of O-15-H2O studies, better fitting the results of the inert gas technique (gCBF at 20, 40, and 70 mm Hg Petco2 ± SD was 31 ± 4, 48 ± 13, and 160 ± 50 mL 100 g−1 min−1, respectively). The relation between Petco2 and CBF in the current study was best described by an exponential rather than a linear function. At low Petco2, the activation-induced flow changes are moderately damped, whereas at high Petco2, they are nearly lost (ΔCBF (±SD): 52% ± 25%, 68% ± 22%, 16% ± 25% at Petco2 = 20, 40, 70 mm Hg, respectively).
Na+-K+-Cl− Cotransporter in Rat Focal Cerebral Ischemia
Authors: Yan Yiping , Dempsey Robert J. , Sun Dandan
Published: November 2003

In cultured neurons, the authors previously demonstrated that the Na+-K+-Cl− cotransporter is significantly stimulated by elevated extracellular potassium and glutamate, which are important factors in cerebral ischemic damage. These findings led the authors to hypothesize that stimulation of the cotransporter after ischemia might result in Na+, K+, and Cl− influx, and might contribute to neuron damage. In the current study, the authors investigated such a role of the Na+-K+-Cl− cotransporter in focal cerebral ischemia. Cerebral ischemia was induced by 2-hour occlusion of the left middle cerebral artery (MCA) and 24-hour reperfusion in male spontaneously hypertensive rats (SHRs). Immunocytochemical staining and immunoblotting revealed an up-regulation of expression of the cotransporter protein in neurons in cortex at 24 hours of reperfusion. Artificial cerebral spinal fluid (aCSF) or 100 μmol/L bumetanide (a cotransporter inhibitor) in aCSF were continuously microdialyzed through a microdialysis probe into left cortices throughout 2-hour MCA occlusion and 24-hour reperfusion. Compared with the aCSF-treated group, infarction volume was significantly reduced in the bumetanide-treated group (25%, P < 0.05). In addition, brain water content in the bumetanide-treated brains was decreased by 70% ( P < 0.05). These results strongly suggest that the Na+-K+-Cl− cotransporter may play an important role in cerebral ischemic neuronal damage.
Anatomic and Biochemical Correlates of the Dopamine Transporter Ligand 11C-PE2I in Normal and Parkinsonian Primates: Comparison with 6-[18F]Fluoro-L-Dopa
Authors: Poyot Thomas , Condé Françoise , Grégoire Marie-Claude , Frouin Vincent , Coulon Christine , Fuseau Chantal , Hinnen Françoise , Dollé Frédéric , Hantraye Philippe , Bottlaender Michel
Published: November 2003

Positron emission tomography (PET) coupled to 6-[18F]Fluoro-L-Dopa (18F-Dopa) remains the gold standard for assessing dysfunctionality concerning the dopaminergic nigrostriatal pathway in Parkinson's disease and related disorders. The use of ligands of the dopamine transporters (DAT) is an attractive alternative target; consequently, the current aim was to validate one of them, 11C-PE2I, using a multiinjection modeling approach allowing accurate quantitation of DAT densities in the striatum. Experiments were performed in three controls, three MPTP-treated (parkinsonian) baboons, and one reserpine-treated baboon. 11C-PE2I B′max values obtained with this approach were compared with 18F-Dopa input rate constant values (Ki), in vitro Bmax binding of 125I-PE2I, and the number of dopaminergic neurons in the substantia nigra estimated postmortem by stereology. In the caudate nucleus and putamen, control values for 11C-PE2I B'max were 673 and 658 pmol/mL, respectively, whereas it was strongly reduced in the MPTP-treated (B′max = 26 and 36 pmol/mL) and reserpine-treated animals (B′max = 338 and 483 pmol/mL). In vivo11C-PE2I B′max values correlated with 18F-Dopa Ki values and in vitro125I-PE2I Bmax values in the striatum and with the number of nigral dopaminergic neurons. Altogether, these data support the use of 11C-PE2I for monitoring striatal dopaminergic disorders and the effect of potential neuroprotective strategies.
Quantitative Comparison of the Bolus and Steady-State Methods for Measurement of Cerebral Perfusion and Oxygen Metabolism: Positron Emission Tomography Study Using 15O-Gas and Water
Authors: Okazawa Hidehiko , Yamauchi Hiroshi , Sugimoto Kanji , Takahashi Masaaki , Toyoda Hiroshi , Kishibe Yoshihiko , Shio Hideo
Published: November 2003

To evaluate a new simplified bolus method for measurement of cerebral perfusion and metabolism, the parametric images with that method were compared with those obtained from the conventional steady-state method with 15O-gas. The new method also provided images of arterial blood volume (V0), which is a different parameter from cerebral blood volume (CBV) obtained using a C15O technique. Seven healthy volunteers and 10 patients with occlusive cerebrovascular diseases underwent positron emission tomography (PET) scans with both methods. Three-weighted integration was applied to calculate regional cerebral blood flow (rCBF) and regional cerebral metabolic rate of oxygen (rCMRO2) in the bolus method. Global and regional CBF and CMRO2 in volunteers were compared between the two methods and used as control data. Regional values in patients also were evaluated to observe differences between the bilateral hemispheres. Both rCBF and rCMRO2 were linearly well correlated between the two methods, although global difference in CMRO2 was significant. The difference in each parametric image except for V0 was significant between the bilateral hemispheres in patients. The bolus method can simplify oxygen metabolism studies and yield parametric images comparable with those with the steady-state method, and can allow for evaluation of V0 simultaneously. Increase in CBV without a change in V0 suggested the increase might mainly be caused by venous dilatation in the ischemic regions.
Hydroxyfasudil, an Active Metabolite of Fasudil Hydrochloride, Relaxes the Rabbit Basilar Artery by Disinhibition of Myosin Light Chain Phosphatase
Authors: Nakamura Kensei , Nishimura Junji , Hirano Katsuya , Ibayashi Setsuro , Fujishima Masatoshi , Kanaide Hideo
Published: November 2003

Fasudil hydrochloride (AT877, hexahydro-1-(5-isoquinolinesulfonyl)-1H-1,4-diazepine hydrochloride, identical to HA1077) inhibits cerebral vasospasm after subarachnoid hemorrhage in experimental animals and humans. In the current study, the vasorelaxing mechanism of hydroxyfasudil, a hydroxylated metabolite of fasudil hydrochloride, was determined in the rabbit basilar artery. The effects of hydroxyfasudil on tension, intracellular Ca2+ concentration ([Ca2+]i), and phosphorylation of the myosin light chain were examined using the isolated and intact or permeabilized rabbit basilar artery without endothelium in vitro. In the intact rabbit basilar artery, hydroxyfasudil elicited a concentration-dependent relaxation of the artery precontracted with 1 nmol/L endothelin-1 (ET-1) plus 20 mmol/L KCl without any significant decrease in [Ca2+]i as determined by fura-2 microfluorometry (IC50: 5.1 ± 4.6 μmol/L). The relaxation induced by hydroxyfasudil was accompanied with dephosphorylation of the myosin light chain. In the permeabilized preparation, hydroxyfasudil inhibited the contraction induced by ET-1, guanosine 5′- O-(3-thiotriphosphate), or the catalytic subunit of rho-associated kinase, but it did not inhibit Ca2+-induced contraction under the condition of inhibited myosin light chain phosphatase. Hydroxyfasudil showed a greater relaxant effect under decreased adenosine triphosphate (ATP) levels. The present study indicated that hydroxyfasudil relaxes the rabbit basilar artery mainly by disinhibiting myosin light chain phosphatase through the inhibition of rho-associated kinase and that this effect depends on the intracellular ATP concentration.
Neuronal, but Not Microglial, Accumulation of Extravasated Serum Proteins after Intracerebral Hemolysate Exposure is Accompanied by Cytochrome c Release and DNA Fragmentation
Authors: Matz Paul G. , Lewén Anders , Chan Pak H.
Published: November 2003

Vasogenic edema after oxidative injury has been accompanied by intracellular accumulation of serum proteins and nuclear damage. This study sought to determine whether serum protein accumulation, along with other markers of brain injury, was present after exposure to intracerebral hemolysate, an oxidant model of intracerebral hemorrhage (ICH). Saline (n = 24) or hemolysate (n = 30) was injected into the caudate-putamen of adult Sprague-Dawley rats. Compared with saline, hemolysate deposition was associated with intracellular accumulation of serum proteins as evidenced by Evans blue uptake in neurons and microglia at 4 and 24 hours. Intracellular Evans blue colocalized with DNA fragmentation detected by nick end-labeling and whose presence was confirmed by gel electrophoresis. Immunoblots of cytosolic fractions confirmed cytochrome c release. Immunostaining established colocalization of cytosolic cytochrome c and intracellular Evans blue at 4 hours. At 24 hours, cytosolic cytochrome c was evident in astrocytes surrounding Evans blue-positive cells. Immunoblot analysis and immunostaining revealed HSP70 induction at 24 hours in regions adjacent to intracellular serum accumulation. Neuronal accumulation of extravasated serum proteins in this model of ICH was associated with cytochrome c release, DNA fragmentation, and cell death. Stress protein induction in adjacent regions suggested that vasogenic edema might have exacerbated cellular dysfunction and cell death after ICH.
Ornithine Decarboxylase Knockdown Exacerbates Transient Focal Cerebral Ischemia-Induced Neuronal Damage in Rat Brain
Authors: Rao Raghavendra Vemuganti L. , Dogan Aclan , Bowen Kellie K. , Dempsey Robert J.
Published: November 2003

Transient cerebral ischemia leads to increased expression of ornithine decarboxylase (ODC). Contradicting studies attributed neuroprotective and neurotoxic roles to ODC after ischemia. Using antisense oligonucleotides (ODNs), the current study evaluated the functional role of ODC in the process of neuronal damage after transient focal cerebral ischemia induced by middle cerebral artery occlusion (MCAO) in spontaneously hypertensive rats. Transient MCAO significantly increased the ODC immunoreactive protein levels and catalytic activity in the ipsilateral cortex, which were completely prevented by the infusion of antisense ODN specific for ODC. Transient MCAO in rats infused with ODC antisense ODN increased the infarct volume, motor deficits, and mortality compared with the sense or random ODN-infused controls. Results of the current study support a neuroprotective or recovery role, or both, for ODC after transient focal ischemia.
Targeting Expression of hsp70i to Discrete Neuronal Populations Using the Lmo-1 Promoter: Assessment of the Neuroprotective Effects of hsp70i In vivo and In vitro
Authors: Kelly Stephen , Bieneman Alison , Horsburgh Karen , Hughes David , Sofroniew Michael V. , McCulloch James , Uney James B.
Published: November 2003

Transgenic technology provides a powerful means of studying gene regulation and specific gene function with complex mammalian systems. In this study, the authors exploited the specific and discrete neuronal expression pattern mediated by promoter 1 of the Lmo-1 gene to study the neuroprotective effects of the inducible form of heat shock protein 70kD (hsp70i) in primary hippocampal cultures in a mouse model of global cerebral ischemia. Targeting expression of hsp70i to hippocampal neurons protected these cells significantly from toxic levels of glutamate and oxidative stress (for example, exposure to 10 μmol/L free iron produced a 26% increase in lactate dehydrogenase release from neurons cultured from wild-type mice, but a 7% increase in neurons cultured from hsp70i transgenic mice). Bilateral carotid occlusion (25 minutes) produced significantly less neuronal damage in the caudate nucleus and posterior thalamus in hsp70i transgenic mice than in wild-type littermates (for example, 21% ± 9.3% and 12.5% ± 9.0% neuronal damage in lateral caudate nucleus of wild-type and hsp70i transgenic mice, respectively, P < 0.05). The current study highlights the utility of targeted expression of transgenes of interest in cerebral ischemia and demonstrates that expression of hsp70i alone is sufficient to mediate the protection of primary neurons from denaturing stress and that expression of human hsp70i in vivo plays crucial role in determining the fate of neurons after ischemic challenge.
Imaging Human Mesolimbic Dopamine Transmission with Positron Emission Tomography: I. Accuracy and Precision of D2 Receptor Parameter Measurements in Ventral Striatum
Authors: Mawlawi Osama , Martinez Diana , Slifstein Mark , Broft Allegra , Chatterjee Rano , Hwang Dah-Ren , Huang Yiyun , Simpson Norman , Ngo Kim , Van Heertum Ronald , Laruelle Marc
Published: November 2003

Dopamine transmission in the ventral striatum (VST), a structure which includes the nucleus accumbens, ventral caudate, and ventral putamen, plays a critical role in the pathophysiology of psychotic states and in the reinforcing effects of virtually all drugs of abuse. The aim of this study was to assess the accuracy and precision of measurements of D2 receptor availability in the VST obtained with positron emission tomography on the high-resolution ECAT EXACT HR+ scanner (Siemens Medical Systems, Knoxville, TN, U.S.A.). A method was developed for identification of the boundaries of the VST on coregistered high-resolution magnetic resonance imaging scans. Specific-to-nonspecific partition coefficient (V3″) and binding potential (BP) of [11C]raclopride were measured twice in 10 subjects, using the bolus plus constant infusion method. [11C]Raclopride V3″ in the VST (1.86 ± 0.29) was significantly lower than in the dorsal caudate (DCA, 2.33 ± 0.28) and dorsal putamen (DPU, 2.99 ± 0.26), an observation consistent with postmortem studies. The reproducibility of V3″ and BP were appropriate and similar in VST (V3″ test–retest variability of 8.2% ± 6.2%, intraclass correlation coefficient = 0.83), DCA (7.7% ± 5.1%, 0.77), DPU (6.0% ± 4.1%, 0.71), and striatum as a whole (6.3% ± 4.1%, 0.78). Partial volume effects analysis revealed that activities in the VST were significantly contaminated by counts spilling over from the adjacent DCA and DPU: 70% ± 5% of the specific binding measured in the VST originated from D2 receptors located in the VST, whereas 12% ± 3% and 18% ± 3% were contributed by D2 receptors in the DCA and DPU, respectively. Thus, accuracy of D2 receptor measurement is improved by correction for partial voluming effects. The demonstration of an appropriate accuracy and precision of D2 receptor measurement with [11C]raclopride in the VST is the first critical step toward the use of this ligand in the study of synaptic dopamine transmission at D2 receptors in the VST using endogenous competition techniques.
Relation of Cerebral Energy Metabolism and Extracellular Nitrite and Nitrate Concentrations in Patients after Aneurysmal Subarachnoid Hemorrhage
Authors: Sakowitz Oliver W. , Wolfrum Sebastian , Sarrafzadeh Asita S. , Stover John F. , Dreier Jens P. , Dendorfer Andreas , Benndorf Götz , Lanksch Wolfgang R. , Unterberg Andreas W.
Published: November 2003

In a prospective clinical investigation on neurochemical intensive care monitoring, the authors' aim was to elucidate the temporal profile of nitric oxide metabolite concentrations—that is, nitrite and nitrate (NOx)—and compounds related to energy-metabolism in the cerebral interstitium of patients after aneurysmal subarachnoid hemorrhage (SAH). During aneurysm surgery, microdialysis probes were implanted in cerebral white matter of the vascular territory most likely affected by vasospasm. Temporal profiles of NOx were analyzed in a subset of 10 patients (7 female, 3 male, mean age = 47 ± 14 years). Microdialysis was performed for 152 ± 63 hours. Extracellular metabolites (glucose, lactate, pyruvate, glutamate) were recovered from the extracellular fluid of the cerebral parenchyma. NOx was measured using a fluorometric assay. After early surgery, SAH patients revealed characteristic decreases of NOx from initial values of 46.2 ± 34.8 μmol/L to 23.5 ± 9.0 μmol/L on day 7 after SAH ( P < 0.05). Decreases in NOx were seen regardless of development of delayed ischemia (DIND). Overall NOx correlated intraindividually with glucose, lactate, and glutamate ( r = 0.58, P < 0.05; r = 0.32, P < 0.05; r = 0.28, P < 0.05; respectively). After SAH, cerebral extracellular concentrations of NO metabolites decrease over time and are associated with concomitant alterations in energy-or damage-related compounds. This could be related to reduced NO availability, potentially leading to an imbalance of vasodilatory and vasoconstrictive factors. On the basis of the current findings, however, subsequent development of DIND cannot be explained by a lack of vasodilatory NO alone.
Glutamate, NMDA, and AMPA Induced Changes in Extracellular Space Volume and Tortuosity in the Rat Spinal Cord
Authors: Vargová Lýdia , Jendelová Pavla , Chvátal Alexandr , Syková Eva
Published: November 2003

Glutamate release, particularly in pathologic conditions, may result in cellular swelling. The authors studied the effects of glutamate, N-methyl-d-aspartate (NMDA), and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) on extracellular pH (pHe), extracellular potassium concentration ([K+]e), and changes in extracellular space (ECS) diffusion parameters (volume fraction α, tortuosity λ) resulting from cellular swelling. In the isolated spinal cord of 4-to 12-day-old rats, the application of glutamate receptor agonists induced an increase in [K+]e, alkaline-acid shifts, a substantial decrease in α, and an increase in λ. After washout of the glutamate receptor agonists, α either returned to or overshot normal values, whereas λ remained elevated. Pretreatment with 20 mmol/L Mg++, MK801, or CNQX blocked the changes in diffusion parameters, [K+]e and pHe evoked by NMDA or AMPA. However, the changes in diffusion parameters also were blocked in Ca2+-free solution, which had no effect on the [K+]e increase or acid shift. The authors conclude that increased glutamate release may produce a large, sustained and [Ca2+]e-dependent decrease in α and increase in λ. Repetitive stimulation and pathologic states resulting in glutamate release therefore may lead to changes in ECS volume and tortuosity, affecting volume transmission and enhancing glutamate neurotoxicity and neuronal damage.
Cationic Polymer and Lipids Augment Adenovirus-Mediated Gene Transfer to Cerebral Arteries In vivo
Authors: Toyoda Kazunori , Nakane Hiroshi , Heistad Donald D.
Published: November 2003

Adenovirus-mediated gene transfer to blood vessels is relatively inefficient because binding of adenovirus to vessels is limited. The authors have reported that incorporation of cationic polymer and lipids with adenovirus augments gene transfer to blood vessels ex vivo. In this study, the authors determined whether complexes of adenovirus and cations improve efficiency of gene transfer in vivo. Poly-l-lysine, lipofectamine, or lipofectin was complexed with adenovirus encoding β-galactosidase. Optimum ratios of the cations per adenovirus were determined by gene transfer to fibroblasts. After injection of the adenovirus into the cisterna magna of anesthetized rabbits, transgene activity was greater in the adventitia of intracranial arteries and meninges after injection of the complexes than adenovirus alone. Thirty minutes after application of adenovirus with the cations, binding of adenovirus to fibroblast cells in vitro or the basilar artery in vivo (by Southern blot analysis) was augmented, which suggests that enhanced binding of virus contributes to augmentation of transgene expression. Thus, cationic polymer and lipids improve transgene expression in intracranial arteries, primarily in the adventitia, after adenovirus-mediated gene transfer in vivo. This strategy may be applicable to studies of gene transfer and eventually for gene therapy.
Apoptotic and Antiapoptotic Mechanisms after Traumatic Brain Injury
Authors: Keane Robert W. , Kraydieh Susan , Lotocki George , Alonso Ofelia F. , Aldana Phillip , Dietrich W. Dalton
Published: November 2003

Caspase and inhibitor of apoptosis (IAP) expression was examined in rats subjected to moderate traumatic brain injury (TBI) using a parasagittal fluid-percussion brain insult (1.7 to 2.2 atm). Within 1 hour after injury, caspase-8 and −9, two initiators of apoptosis, were predominantly expressed in superficial cortical areas adjacent to the impact site and in the thalamus. Caspase-3, an effector caspase, was evident at 6 hours throughout the traumatized cerebral cortex and hippocampus. Moreover, the authors observed that XIAP, cIAP-1, and cIAP-2, members of the IAP family, were constitutively expressed in the brain. Colocalization of XIAP-immunolabled cells with cell-specific markers indicated that XIAP is expressed within neurons and a subpopulation of oligodendrocytes. Immunoblots of brain extracts revealed that the processed forms of caspase-8, −9, and −3 are present as early as 1 hour after trauma. The appearance of activated caspases corresponded with the detection of cleavage of XIAP into fragments after injury and a concomitant increase in the levels of cIAP-1 and cIAP-2 in the traumatized hemispheres. The current data are consistent with the hypotheses that caspases in both the extrinsic and intrinsic apoptotic pathways are activated after moderate TBI and that IAPs may have a protective role within the brain with alterations in levels and cleavage of IAPs that contribute to cell death in this setting.
Delayed, but Marked, Expression of Apolipoprotein E is Involved in Tissue Clearance after Cerebral Infarction
Authors: Kitagawa Kazuo , Matsumoto Masayasu , Kuwabara Keisuke , Ohtsuki Toshiho , Hori Masatsugu
Published: November 2003

Clearance of infarct tissue would be an important process for tissue repair after a stroke. Delayed clearance may hamper reconstitution of the blood–brain barrier and glial boundary formation. Recent growing evidence has indicated that apolipoprotein E (APOE), a major apoprotein, plays an important role in lipid transport and homeostasis in the brain. The tissue in the infarction contains abundant lipids must be removed for tissue clearance. In the current study, the authors investigated APOE expression after focal ischemia and the functional role of APOE in tissue clearance using APOE-knockout mice. Expression of APOE was delayed, but marked, in immunohistochemistry and immunoblotting 7 days after permanent focal ischemia. Macrophages were found to express APOE in the infarct center. Infarct size was similar after focal ischemia between wild-type and APOE-knockout mice, although there was no APOE protein expression in knockout mice. However, clearance of infarct tissue 2 weeks after ischemia was significantly delayed in APOE-knockout mice compared with wild-type mice. The current study supports current thinking that APOE is a key molecule for tissue remodeling in the brain. Clearance of damaged tissue may be one of the important functions of APOE in the brain.