bluuebunny/crossref_metadata_2025 huggingface dataset:
Positron Emission Tomography [15O]Water Studies with Short InterScan Interval for Single-Subject and Group Analysis: Influence of Background Subtraction
Authors: Chmielowska Jolanta , Coghill Robert C. , Maisog Jose-Marie , Carson Richard E. , Herscovitch Peter , Honda Manabu , Chen Robert , Hallett Mark
Published: November 2003

Use of short interscan interval [15O]water positron emission tomography (PET) studies reduces the overall study duration and may allow an increased number of scans for single-subject analysis of unique cases (e.g., stroke). The purpose of this study was to examine how subtraction of residual radioactivity from the previous injection (corrected scan) compared to nonsubtraction (uncorrected scan) in a PET short interscan interval (6 minutes) study affects single-subject and group data analysis using a motor activation task. Two currently widely used analytic strategies, Worsley's method and the SPM technique, were applied. Excellent agreement between activation maps obtained from corrected and uncorrected data sets was obtained both in single-subject analyses performed on data sets from the six normal subjects and three stroke (subcortical infarct) patients, and in group analysis (six normal subjects) within a particular statistical method. The corrected and uncorrected data were very similar in the (1) number of activated brain regions; (2) size of clusters of activated brain voxels; (3) Talairach coordinates of the activated region; and (4) t or Z value of the peak intensity for every significantly activated motor brain structure (both for large activations such as in motor cortex and small activations such as in putamen and thalamus). [15O]Water PET data obtained with a short interscan interval (6 minutes) produce similar results whether or not the background is subtracted. Thus, if injection dose and timing are constant, one can achieve the advantage of a short interscan interval without the added complexity of correcting for background radioactivity.
Cocaine Decreases Cortical Cerebral Blood Flow but Does Not Obscure Regional Activation in Functional Magnetic Resonance Imaging in Human Subjects
Authors: Gollub Randy L. , Breiter Hans C. , Kantor Howard , Kennedy David , Gastfriend David , Mathew R. Thomas , Makris Nikos , Guimaraes Alex , Riorden Jonn , Campbell Terry , Foley Mary , Hyman Steve E. , Rosen Bruce , Weisskoff Robert
Published: November 2003

The authors used functional magnetic resonance imaging (fMRI) to determine whether acute intravenous (IV) cocaine use would change global cerebral blood flow (CBF) or visual stimulation-induced functional activation. They used flow-sensitive alternating inversion recovery (FAIR) scan sequences to measure CBF and blood oxygen level-dependent (BOLD) sensitive T2* scan sequences during visual stimulation to measure neuronal activation before and after cocaine and saline infusions. Cocaine (0.6 mg/kg IV over 30 seconds) increased heart rate and mean blood pressure and decreased end tidal carbon dioxide (CO2). All measures returned to baseline by 2 hours, the interinfusion interval, and were unchanged by saline. Flow-sensitive alternating inversion recovery imaging demonstrated that cortical gray matter CBF was unchanged after saline infusion (–2.4 ± 6.5%) but decreased (–14.1 ± 8.5%) after cocaine infusion (n = 8, P < 0.01). No decreases were detected in white matter, nor were changes found comparing BOLD signal intensity in cortical gray matter immediately before cocaine infusion with that measured 10 minutes after infusion. Visual stimulation resulted in comparable BOLD signal increases in visual cortex in all conditions (before and after cocaine and saline infusion). Despite a small (14%) but significant decrease in global cortical gray matter CBF after acute cocaine infusion, specific regional increases in BOLD imaging, mediated by neurons, can be measured reliably.
Hypoglycemia, Hypoxia, and Ischemia in a Corticostriatal Slice Preparation: Electrophysiologic Changes and Ascorbyl Radical Formation
Authors: Pedersen Jens Z. , Bernardi Giorgio , Centonze Diego , Pisani Antonio , Rossi Luisa , Rotilio Giuseppe , Calabresi Paolo
Published: November 2003

Experimental and clinical data suggest that oxygen and/or glucose deprivation alters electrical transmission in the brain and generates free radicals, which may mediate neuronal death. We have analyzed the effects of oxygen and/or glucose deprivation on both excitatory transmission, by measuring field potential amplitude, and free radical production, by using electron spin resonance (ESR) spectroscopy, in a corticostriatal slice preparation. Combined oxygen and/or glucose deprivation (ischemia) lasting 10 to 20 minutes induced a long-term depression of field potential amplitude. The ascorbyl radical could only be detected in brain slices during the reperfusion-phase after 30 minutes of ischemia. It appeared in the early minutes after the washout of ischemic medium and remained stable throughout the reperfusion phase. This radical was never detected in the external medium. Ischemia induced only a slight, but progressive, release of lactate dehydrogenase (LDH) into the external medium during the reperfusion phase. In contrast, exposure of slices to hypoxia or hypoglycemia alone resulted in transient depression of field potential amplitude, and no generation of ascorbyl radicals was observed on reperfusion. We propose that the long-lasting loss of electrical signals is the early sign of neuronal damage during ischemia. On the other hand, ascorbyl radical formation may be considered an indicator of neuronal injury after prolonged energy deprivation.
Differentiation between Transient Ischemic Attack and Ischemic Stroke within the First Six Hours after Onset of Symptoms by Using 99mTc-ECD-SPECT
Authors: Berrouschot Jörg , Barthel Henryk , Hesse Swen , Köster Johannes , Knapp Wolfram H. , Schneider Dietmar
Published: November 2003

The aim of this study was to define the accuracy of 99mTc-ethyl cysteinate dimer-single photon emission computed tomography (99mTc-ECD-SPECT) in distinguishing transient ischemic attack from completed ischemic stroke at early stages after the onset of symptoms. In a prospective study we examined 82 patients within 6 hours after the onset of symptoms (neurologic deficit caused by middle cerebral artery ischemia) using both 99mTc-ECD-SPECT and computed tomography (CT). The follow-up was based on Scandinavian Stroke Scale (SSS) 24 hours and 5–7 days, as well as on CT 7 days, after the event. SPECT evaluation was performed both visually and using semiquantitative region-of-interest (ROI) analysis. According to visual SPECT analysis, on admission 59 of 82 patients had activity deficits in the symptomatic hemisphere. After 7 days, all these patients had neurologic symptoms (SSS 28 ± 12 points), caused by a cerebral infarction as evidenced with CT. Twenty-three of 82 patients displayed no early activity deficit despite clinical symptoms. None of these patients had neurologic symptoms after 7 days (indicating transient ischemic attack or prolonged reversible ischemic neurologic deficit). In the semiquantitative SPECT analysis, all patients had abnormal count densities in the respective ROI (activity <90% compared with the contralateral side). All patients with transient ischemia ( n = 23) had count rate densities more than 70% of the respective contralateral ROI, whereas all patients with subsequent infarction ( n = 59) had values < 70%. Use of 99mTc-ECD-SPECT allows transient ischemia to be distinguished from ischemic infarction using relative regional activity thresholds within the first 6 hours after onset of symptoms.
Cerebral Blood Flow Measurements by Magnetic Resonance Imaging Bolus Tracking: Comparison with [15O]H2O Positron Emission Tomography in Humans
Authors: Østergaard Leif , Johannsen Peter , Høst-Poulsen Peter , Vestergaard-Poulsen Peter , Asboe Helle , Gee Antony D. , Hansen Søren B. , Cold Georg E. , Gjedde Albert , Gyldensted Carsten
Published: November 2003

In six young, healthy volunteers, a novel method to determine cerebral blood flow (CBF) using magnetic resonance (MR) bolus tracking was compared with [15O]H2O positron emission tomography (PET). The method yielded parametric CBF images with tissue contrast in good agreement with parametric PET CBF images. Introducing a common conversion factor, MR CBF values could be converted into absolute flow rates, allowing comparison of CBF values among normal subjects.
Neural Activation of the Brain with Hemodynamic Insufficiency
Authors: Inao Suguru , Tadokoro Masanori , Nishino Masanari , Mizutani Nobuhiko , Terada Koichi , Bundo Masahiko , Kuchiwaki Hiroji , Yoshida Jun
Published: November 2003

Little is known about how ischemia affects hemodynamic responses to neural activation in the brain. We compare the effects of a motor activation task and a cerebral vasodilating agent, acetazolamide (ACZ), on regional cerebral blood flow (rCBF) in primary sensorimotor cortex (PSM) in six patients with major cerebral artery steno-occlusive lesions without paresis of the upper extremities. Quantitative rCBF was measured in all patients using H215 O autoradiographic method and positron emission tomography. The CBF was determined at rest, during a bimanual motor activation task, and 10 minutes after ACZ administration. With bimanual motor activation, rCBF increased significantly in both PSM compared with at rest ( P < 0.01 on lesion side, and P < 0.02 on contralateral side). However, rCBF did not increase after ACZ injection in the PSM on the lesion side, whereas rCBF increased significantly in the contralateral PSM after ACZ injection compared with the level at rest. This result suggests that despite a decreased hemodynamic reserve, there is a nearly normal flow response to neural activation, indicating that the mechanism of vasodilation responsible for perfusion change is different for acetazolamide and neural activation. The relations among neural activation, hemodynamic status, and cerebral metabolism in the ischemic stroke patients are discussed.
Optical Intrinsic Signal Imaging Responses Are Modulated in Rodent Somatosensory Cortex during Simultaneous Whisker and Forelimb Stimulation
Authors: Blood Anne J. , Toga Arthur W.
Published: November 2003

Optical intrinsic signal imaging(OIS) was used to investigate physiologic interactions between spatially and functionally distinct cortical somatosensory systems. The OIS response magnitude was evaluated after simultaneous stimulation of single whiskers and forelimb digits. Whisker C1 was deflected at a frequency of 10 Hz for 2 seconds while low- or high-intensity vibratory stimuli were applied to forelimb digits. The OIS responses to simultaneous whisker and forelimb stimulation were compared with lone whisker stimulated controls. Overall, addition of a second stimulus caused decreases in barrel cortex response magnitude. Three different response patterns were detected within individual trial sets. Modulation of barrel cortex evoked potentials provided evidence that changes in OIS responses observed here may be partially influenced by vascular responses to changes in neuronal activity. However, OIS responses in the barrel region during lone forelimb stimulation that were unaccompanied by evoked potentials suggested the possibility of independent vascular dynamic influences on response modulation. This study demonstrates that cortical responses at the level of primary sensory processing may be significantly influenced by activity in adjacent regions. Furthermore, it reveals that vascular and neuronal characteristics of interregional modulation do not co-localize and may produce responses in which one component increases while the other decreases.
Spreading Depression in Focal Ischemia: A Computational Study
Authors: Revett Kenneth , Ruppin Eytan , Goodall Sharon , Reggia James A.
Published: November 2003

When a cerebral infarction occurs, surrounding the core of dying tissue there usually is an ischemic penumbra of nonfunctional but still viable tissue. One current but controversial hypothesis is that this penumbra tissue often eventually dies because of the metabolic stress imposed by multiple cortical spreading depression (CSD) waves, that is, by ischemic depolarizations. We describe here a computational model of CSD developed to study the implications of this hypothesis. After simulated infarction, the model displays the linear relation between final infarct size and the number of CSD waves traversing the penumbra that has been reported experimentally, although damage with each individual wave progresses nonlinearly with time. It successfully reproduces the experimental dependency of final infarct size on midpenumbra cerebral blood flow and potassium reuptake rates, and predicts a critical penumbra blood flow rate beyond which damage does not occur. The model reproduces the dependency of CSD wave propagation on N-methyl-D-aspartate activation. It also makes testable predictions about the number, velocity, and duration of ischemic CSD waves and predicts a positive correlation between the duration of elevated potassium in the infarct core and the number of CSD waves. These findings support the hypothesis that CSD waves play an important causal role in the death of ischemic penumbra tissue.
Blood—Brain Barrier Phenylalanine Transport and Individual Vulnerability in Phenylketonuria
Authors: Möller Harald E. , Weglage Josef , Wiedermann Dirk , Ullrich Kurt
Published: November 2003

In vivo nuclear magnetic resonance spectroscopy can be used to measure intracerebral phenylalanine (Phe) concentrations in patients with phenylketonuria (PKU). Stationary levels, obtained under free nutrition, as well as time courses after an oral Phe load (100 mg/kg) were investigated in 11 PKU patients and were correlated with the individual clinical outcome. At blood levels around 1.2 mmol/L, brain Phe was 0.41 to 0.73 mmol/L in clinically “typical” patients, but less than 0.15 mmol/L in three untreated, normally intelligent, adult women. Kinetic investigations revealed higher transport Michaelis constants and lower ratios of the brain influx and consumption rates in these women than in the “typical” control patients ( Kt,app = 0.45 to 1.10 mmol/L versus 0.10 mmol/L; Tmax/νmet = 2.55 to 3.19 versus 7.8 to 14.0). Such variations seem to be major causative factors for the individual vulnerability to PKU.
Estimation of Component and Parameter Distributions in Spectral Analysis
Authors: Turkheimer Federico , Sokoloff Louis , Bertoldo Alessandra , Lucignani Giovanni , Reivich Martin , Jaggi Jurg L. , Schmidt Kathleen
Published: November 2003

A method is presented for estimating the distributions of the components and parameters determined with spectral analysis when it is applied to a single data set. The method uses bootstrap resampling to simulate the effect of noise on the computed spectrum and to correct for possible bias in the estimates. A number of bootstrap procedures are reviewed, and one is selected for application to the kinetic analysis of positron emission tomography dynamic studies. The technique is shown to require minimal assumptions about noise in the measurements, and its small sample properties are established through Monte-Carlo simulations. The advantages and limitations of spectral analysis with bootstrap resampling for deriving inferences for tracer kinetic modeling are illustrated through sample analyses of time-activity curves for [18F]fluorodeoxyglucose and [15O]-labeled water.
In Vivo Injection of [1-13C]Glucose and [1,2-13C]Acetate Combined with Ex Vivo13C Nuclear Magnetic Resonance Spectroscopy: A Novel Approach to the Study of Middle Cerebral Artery Occlusion in the Rat
Authors: Håberg Asta , Qu Hong , Haraldseth Olav , Unsgård Geirmund , Sonnewald Ursula
Published: November 2003

Astrocytes play a pivotal role in cerebral glutamate homeostasis. After 90 minutes of middle cerebral artery occlusion in the rat, the changes induced in neuronal and astrocytic metabolism and in the neuronal—astrocytic interactions were studied by combining in vivo injection of [1-13C]glucose and [1,2-13C]acetate with ex vivo13C nuclear magnetic resonance spectroscopy and HPLC analysis of amino acids of the lateral caudoputamen and lower parietal cortex, representing the putative ischemic core, and the upper frontoparietal cortex, corresponding to the putative penumbra. In the putative ischemic core, evidence of compromised de novo glutamate synthesis located specifically in the glutamatergic neurons was detected, and a larger proportion of glutamate was derived from astrocytic glutamine. In the same region, pyruvate carboxylase activity, representing the anaplerotic pathway in the brain and exclusively located in astrocytes, was abolished. However, astrocytic glutamate uptake and conversion to glutamine took place, and cycling of intermediates in the astrocytic tricarboxylic acid cycle was elevated. In the putative penumbra, glutamate synthesis was improved compared with the ischemic core, the difference appeared to be brought on by better neuronal de novo glutamate synthesis, combined with normal levels of glutamate formed from astrocytic glutamine. In both ischemic regions, γ-aminobutyric acid synthesis directly from glucose was reduced to about half, indicating impaired pyruvate dehydrogenase activity; still, γ-aminobutyric acid reuptake and cycling was increased. The results obtained in the current study demonstrate that by combining in vivo injection of [1-13C]glucose and [1,2-13C]acetate with ex vivo13C nuclear magnetic resonance spectroscopy, specific metabolic alterations in small regions within the rat brain suffering a focal ischemic lesion can be studied.
Estrogen Increases cGMP in Selected Brain Regions and in Cerebral Microvessels
Authors: Palmon Sally C. , Williams Megan J. , Littleton-Kearney Marguerite T. , Traystman Richard J. , Kosk-Kosicka Danuta , Hurn Patricia D.
Published: November 2003

We have previously reported that exogenous and endogenous estrogen can amplify residual cerebral blood flow during experimental cerebral ischemia. Because estrogen has been linked to nitric oxide and cyclic guanosine monophosphate (cGMP) signaling in noncerebral tissue, we tested the hypothesis that long-term 17β-estradiol treatment increases basal cGMP in brain homogenates and cerebral microvessels in female rabbits. We also determined whether there are important baseline gender-specific differences in regional cGMP. Adult female rabbits were implanted with 17β-estradiol pellets, 10 mg (F10, n = 10) or 50 mg (F50, n = 13), and compared with untreated females (F, n = 19) and males with negligible estrogen (M, n = 19) (plasma 17β-estradiol levels of 4 ± 4 pg/mL in M, 7 ± 5 pg/mL in F, 141 ± 74 pg/mL in F10, and 289 ± 110 pg/mL in F50). Cyclic GMP was determined by radioimmunoassay in cerebellum, hypothalamus, caudate nucleus, hippocampus, and cortex. Cerebral microvessels were harvested from additional cohorts of untreated males and females or estradiol-implanted females (n = 6 per group). Basal cGMP was higher in F versus M only in cerebellum. Estrogen-induced increases in regional cGMP were prominent in hippocampus at all doses (M = 43 ± 26, F = 43 ± 21, F10 = 84 ± 24, F50 = 117 ±55 fmol/mg protein) and in cortex at the high dose (M = 78 ± 55, F = 88 ± 51, F10 = 69 ± 34, F50 = 143 ± 52 fmol/mg protein). Similarly, microvascular cGMP increased only in females treated with the 50 mg dose (M = 77 ± 13, F = 86 ± 25, F10 = 106 ± 35, F50 = 192 ± 88 fmol/mg protein). Therefore, 17β-estradiol increases cGMP content in parenchymal regions that are known physiologic targets for reproductive steroids but are also areas of selective vulnerability to ischemic insult. Further, high doses of estrogenic steroids could amplify cGMP signaling within the cerebral microvasculature.
Distribution Volume of Radiolabeled Large Neutral Amino Acids in Brain Tissue
Authors: Huang Sung-Cheng , Stout David B. , Yee Randa E. , Satyamurthy Nagichettiar , Barrio Jorge R.
Published: November 2003

Variations in the cerebellum to plasma ratio at late times in 6-[18F]fluoro-l-DOPA studies are shown to be consistent with competitive binding of large neutral amino acids for a common transporter in the blood—brain barrier and the stability of brain tissue large neutral amino acid level in the presence of plasma level changes. The distribution volume of an inert large neutral amino acid can be estimated from plasma and tissue large neutral amino acid levels and apparent half-saturation concentrations ( Km) of the transporter in the blood—brain barrier. Stability of brain large neutral amino acid levels is supported by literature findings and can be explained by high saturation of the large neutral amino acid transporter at physiologic conditions.
Attenuated c-fos mRNA Induction after Middle Cerebral Artery Occlusion in CREB Knockout Mice Does Not Modulate Focal Ischemic Injury
Authors: Hata Ryuji , Gass Peter , Mies Gunter , Wiessner Christoph , Hossmann Konstantin-Alexander
Published: November 2003

To elucidate the mechanism of ischemia-induced signal transduction in vivo, we investigated the effect of the targeted disruption of the α and Δ isoforms of the cAMP-responsive element-binding protein (CREB) on c-fos and heat-shock protein (hsp) 72 gene induction, Permanent focal ischemia was induced by occlusion of the middle cerebral artery of the CREB mutant mice (CREB(−/–), n = 5) and the wild-type mice (n = 6). Three hours after onset of ischemia, the neurologic score was assessed and pictorial measurements of ATP and cerebral protein synthesis (CPS) were carried out to differentiate between the ischemic core (where ATP is depleted), the ischemic penumbra (where ATP is preserved but CPS is inhibited), and the intact tissue (where both ATP and CPS are preserved). There were no significant differences in neurologic score or in ATP, pH, and CPS between the two groups, suggesting that the sensitivity of both strains to ischemia is the same. Targeted disruption of the CREB gene significantly attenuated c-fos gene induction in the periischemic ipsilateral hemisphere but had no effect on either c-fos or hsp72 mRNA expression in the penumbra. The observations demonstrate that CREB expression, despite its differential effect on c-fos, does not modulate acute focal ischemic injury.
Synergistic Protective Effects of Antioxidant and Nitric Oxide Synthase Inhibitor in Transient Focal Ischemia
Authors: Spinnewyn Brigitte , Cornet Sylvie , Auguet Michel , Chabrier Pierre-Etienne
Published: November 2003

Both nitric oxide synthase (NOS) inhibitors and free radical scavengers have been shown to protect brain tissue in ischemia-reperfusion injury. Nitric oxide and superoxide anion act via distinct mechanisms and react together to form the highly deleterious peroxynitrite. Therefore the authors examined the effects and the interaction between the NOS inhibitor, NG nitro-L-arginine (LNA) and the antioxidant/superoxide scavenger, di-tert-butyl-hydroxybenzoic acid (DtBHB) in the rat submitted to 2 hours of middle cerebral artery occlusion. Posttreatment was initiated 4 hours after the onset of ischemia and infarct volume was measured at 48 hours. The dose-related effect of LNA resulted in a bell-shaped curve: 15, 56, 65, and 33% reduction of total infarct for 0.03, 0.1, 0.3, and 1 mg/kg (intravenously [IV]) respectively and 11% increase in infarct volume for 3 mg/kg (IV). Whereas DtBHB (20 mg/kg; intraperitoneally [IP]) was ineffective, the dose of 60 mg/kg produced 65% protection in infarct volume. The combination of a subthreshold dose of LNA (0.03 mg/kg; IV) and DtBHB (20 mg/kg; IP) resulted in significant reduction (49%) in infarct volume. These results show that LNA and DtBHB act synergistically to provide a consistent neuroprotection against ischemic injury when administered 4 hours after ischemia. This suggests that nitric oxide and free radicals are involved and interact in synergy in ischemia-reperfusion injury.
An 18-Mer Peptide Fragment of Prosaposin Ameliorates Place Navigation Disability, Cortical Infarction, and Retrograde Thalamic Degeneration in Rats with Focal Cerebral Ischemia
Authors: Igase Keiji , Tanaka Junya , Kumon Yoshiaki , Zhang Bo , Sadamoto Yasutaka , Maeda Nobuji , Sakaki Saburo , Sakanaka Masahiro
Published: November 2003

It was previously reported that prosaposin possesses neurotrophic activity that is ascribed to an 18-mer peptide comprising the hydrophilic sequence of the rat saposin C domain. To evaluate the effect of the 18-mer peptide on ischemic neuronal damage, the peptide was infused in the left lateral ventricle immediately after occlusion of the left middle cerebral artery (MCA) in stroke-prone spontaneously hypertensive (SP-SH) rats. The treatment ameliorated the ischemia-induced space navigation disability and cortical infarction and prevented secondary thalamic degeneration in a dose-dependent manner. In culture experiments, treatment with the 18-mer peptide attenuated free radical-induced neuronal injury at low concentrations (0.002 to 2 pg/mL), and the peptide at higher concentrations (0.2 to 20 ng/mL) protected neurons against hypoxic insult. Furthermore, a saposin C fragment comprising the 18-mer peptide bound to synaptosomal fractions of the cerebral cortex, and this binding decreased at the 1st day after MCA occlusion and recovered to the preischemic level at the 7th day after ischemia. These findings suggest that the 18-mer peptide ameliorates neuronal damage in vivo and in vitro through binding to the functional receptor, although the cDNA encoding prosaposin receptor has not been determined yet.
The Reversible Change of GluR2 RNA Editing in Gerbil Hippocampus in Course of Ischemic Tolerance
Authors: Yamaguchi Kumiko , Yamaguchi Fuminori , Miyamoto Osamu , Hatase Osamu , Tokuda Masaaki
Published: November 2003

The ischemic tolerance is known to show protective effects on the neurons and the restricted Ca2+ influx through Ca2+ channels might be involved. In α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor, ribonucleic acid (RNA) editing of the GluR2 subunit determines receptor desensitization and Ca2+ permeability. The authors investigated the effect of ischemic tolerance on the messenger RNA editing of Q/R and R/G sites of GluR2 subunit in hippocampus. It was found that the rate of RNA editing in Q/R site showed no change (100% edited), whereas that in R/G site decreased significantly (83.3% normal editing level to 60.4%) at day 3 (preconditioning period) and returned to normal level at day 14 (after preconditioning period). Further investigation revealed that the decrease of editing rate in ischemic tolerance resulted mainly from the decrease of editing in CA1 area.
Matrix Metalloproteinases Increase Very Early during Experimental Focal Cerebral Ischemia
Authors: Heo Ji Hoe , Lucero Jacinta , Abumiya Takeo , Koziol James A. , Copeland Brian R. , del Zoppo Gregory J.
Published: November 2003

Microvascular integrity is lost during focal cerebral ischemia. The degradation of the basal lamina and extracellular matrix are, in part, responsible for the loss of vascular integrity. Matrix metalloproteinases (MMPs) may play a primary role in basal lamina degradation. By using a sensitive modification of gelatin zymography, the authors investigated the activity of MMP-2 and MMP-9 in frozen 10-µm sections of ischemic and nonischemic basal ganglia and plasma samples of 27 non-human primates after middle cerebral artery occlusion/reperfusion (MCAO/R) for various periods. The gelatinolytic activities were compared with parallel cell dUTP incorporation in the ischemic zones of adjacent sections. In the brain, the integrated density of MMP-2 increased significantly by 1 hour after MCAO and was persistently elevated thereafter. Matrix metalloproteinase-2 expression was highly correlated with the extent of neuron injury and the number of injured neurons (r = 0.9763, SE = 0.004, 2 P < 0.0008). Matrix metalloproteinase-9 expression only was significantly increased in subjects with hemorrhagic transformation. In plasma, only MMP-9 increased transiently at 2 hours of MCAO. These findings highlight the early potential role of MMP-2 in the degradation of basal lamina leading to neuronal injury, and an association of MMP-9 with hemorrhagic transformation after focal cerebral ischemia.
The Effect of the Nitric Oxide Synthase Inhibitor L-NMMA on Basal CBF and Vasoneuronal Coupling in Man: A PET Study
Authors: White Richard P. , Hindley Claire , Bloomfield Peter M. , Cunningham Vincent J. , Vallance Patrick , Brooks David J. , Markus Hugh S.
Published: November 2003

Nitric oxide (NO) regulates basal CBF. In a number of animal models NO has been implicated in the mediation of the regional changes in CBF (rCBF) that accompany neuronal activation (vasoneuronal coupling). However, some results in animal models have failed to confirm this finding, and the validity of extrapolation to man from animal data is uncertain. To determine the contribution of NO to basal global CBF and activation-induced changes in rCBF, the authors have performed quantitative H215O positron emission tomography (PET) studies before and after administration of the non-isoform-specific NO synthase inhibitor, NG-monomethyl-l-arginine (L-NMMA), in 10 healthy male volunteers. Learning a novel sequence of finger movements was used as a paradigm to induce regional frontal cortex activation. The effect of NO synthase inhibition on the magnitude and pattern of activation was determined. Resting global CBF fell from 33.3 ± 5.3 mL·100 g−1·min−1 at rest before L-NMMA, to 26.5 ± 7.7 mL·100 g−1·min−1 after L-NMMA ( P = 0.001). This fall was reversed by l-arginine administration. Learning sequential finger movements induced increases in rCBF in the left motor, right prefrontal, and bilateral premotor cortices. After NO synthase inhibition with L-NMMA, there was no change in this pattern of activation and no reduction in the magnitude of rCBF responses at the foci of maximal stimulation before and after L-NMMA. These findings confirm that NO production contributes to basal CBF regulation in man, but show that systemic NO synthase inhibition with L-NMMA does not impair regional vasoneuronal coupling.
In Vivo Determination of Absolute Cerebral Blood Volume Using Hemoglobin as a Natural Contrast Agent: An MRI Study Using Altered Arterial Carbon Dioxide Tension
Authors: Ulatowski John A. , Oja Joni M. E. , Suarez Jose I. , Kauppinen Risto A. , Traystman Richard J. , van Zijl Peter C. M.
Published: November 2003

The ability of the magnetic resonance imaging transverse relaxation time, R2 = 1/T2, to quantify cerebral blood volume (CBV) without the need for an exogenous contrast agent was studied in cats (n = 7) under pentobarbital anesthesia. This approach is possible because R2 is directly affected by changes in CBF, CBV, CMRO2, and hematocrit (Hct), a phenomena better known as the blood-oxygenation-level-dependent (BOLD) effect. Changes in CBF and CBV were accomplished by altering the carbon dioxide pressure, Paco2, over a range from 20 to 140 mm Hg. For each Paco2 value, R2 in gray and white matter were determined using MRI, and the whole-brain oxygen extraction ratio was obtained from arteriovenous differences (sagittal sinus catheter). Assuming a constant CMRO2, the microvascular CBV was obtained from an exact fit to the BOLD theory for the spin-echo effect. The resulting CBV values at normal Paco2 and normalized to a common total hemoglobin concentration of 6.88 mmol/L were 42 ±18 μL/g (n = 7) and 29 ±19 μL/g (n = 5) for gray and white matter, respectively, in good agreement with the range of literature values published using independent methodologies. The present study confirms the validity of the spin-echo BOLD theory and, in addition, shows that blood volume can be quantified from the magnetic resonance imaging spin relaxation rate R2 using a regulated carbon dioxide experiment.
Induction of Argininosuccinate Synthetase in Rat Brain Glial Cells after Striatal Microinjection of Immunostimulants
Authors: Heneka Michael T. , Schmidlin Andreas , Wiesinger Heinrich
Published: November 2003

The enzyme argininosuccinate synthetase (ASS) initiates the metabolic pathway leading from L-citrulline to L-arginine, the only physiological substrate of all isoforms of nitric oxide synthases. The presence of ASS in glial cells in vivo was investigated by immunohistochemical methods in a model of rat brain inflammation. Phosphate-buffered saline or a mixture of bacterial lipopolysaccharide and interferon-γ was injected into the left striatum, and animals were killed 24 hours later. Ipsilateral and contralateral sides of brain sections were incubated with an antiserum against ASS or antibodies against cell-specific markers. In the three areas examined, striatum, corpus callosum, and cortex, a strong induction of ASS immunoreactivity was observed in glial cells after injection of immunostimulants. A detailed quantitative analysis of double-stained sections revealed that ASS was almost exclusively expressed in reactive, ED1-positive microglial cells/brain macrophages in immunostimulant- or sham-injected ipsilateral sides of the sections. Furthermore, ASS/ED1 costaining was observed in perivascular cells. Colocalization of ASS with astroglial marker glial fibrillary acidic protein was given only occasionally after immunostimulation. ASS-positive neurons were detected in control and experimental animals; staining intensity was comparable in both cases. The results suggest that neurons express ASS constitutively, whereas the enzyme is induced in glial cells in response to proinflammatory stimuli. This finding is the first demonstration of an induction of a pathway auxiliary to generation of nitric oxide in brain in response to immunostimulants and provides new insight into neural arginine metabolism.
Altered In Vitro and In Vivo Flumazenil Binding in Human Epileptogenic Neocortex
Authors: Nagy Ferenc , Chugani Diane C. , Juhász Csaba , da Silva Ednéa A. , Muzik Otto , Kupsky William , Canady Alexa , Watson Craig , Shah Jagdish , Chugani Harry T.
Published: November 2003

In vitro and in vivo parameters of flumazenil (FMZ) binding were measured in spiking and nonspiking neocortex identified by intraoperative elcctrocorticography in epileptic patients who underwent cortical resection for seizure control. In vitro measures of receptor affinity (KD), number (Bmax) and laminar distribution for [3H]-FMZ binding in the epileptic focus (n = 38) were compared to nonspiking cortex from a subgroup of the patients (n = 12) and to tissue obtained from trauma patients (n = 5). The in vitro binding parameters were compared to in vivo [11C]-FMZ binding measured with positron emission tomography (PET) (n = 19). The Bmax was higher in the 38 spiking tissues as compared to the 12 nonspiking tissues ( P = .012). Paired comparison of spiking versus nonspiking binding in the 12 patients from whom nonspiking tissue was available showed increases in both KD ( P = .037) and Bmax ( P = .0047) in spiking cortex. A positive correlation was found between KD and Bmax values for 38 patients (r = 0.55, P < .0001), the magnitude of the KD increase being twice that of the Bmax increase. In addition, there was a significant correlation between the asymmetry indices of the in vivo FMZ binding on PET and in vitro KD of spiking cortex (n = 19, r = 0.52, P = .02). The laminar distribution of [3H]-FMZ showed increased FMZ binding in cortical layers V-VI in spiking cortex compared to nonspiking and control cortex. The increased receptor number in spiking cortical layers V-VI may be a compensatory mechanism to decreased GABAergic input. The increased Bmax in spiking cortex was accompanied by a larger decrease in the affinity of FMZ for the receptor suggesting that decreased FMZ binding in the epileptic focus measured with PET is due to a decrease in the affinity of the tracer for the receptor.
Early Training May Exacerbate Brain Damage after Focal Brain Ischemia in the Rat
Authors: Risedal Anette , Zeng RJinsheng , Johansson Barbro B.
Published: November 2003

Early overuse of a lesioned forelimb, induced by immediate immobilization of the intact forelimb after a cortical lesion, has been reported to increase tissue damage and delay functional recovery. To investigate if early training without immobilization of the intact forelimb could increase tissue loss and reduce recovery, the middle cerebral artery was ligated distal to the striatal branches in 25 male spontaneously hypertensive rats. Control rats were housed in standard cages, training rats were transferred to larger cages allowing various activities and received additional special training 1 hour a day starting either 24 hours or 7 days after the ligation. The rats were tested on a rotating pole, in a leg placement test, and in a water maze and they were killed 6 weeks after the ligation. Delayed training resulted in the best overall performance; however, both training groups performed better than standard rats on the rotating pole. The cortical infarct volume was larger in the early training group than in the other two groups ( P < .005), possibly related to increased glutamate release and peri-infarct cortical hyperexcitability.
Estrogen Reduces Leukocyte Adhesion in the Cerebral Circulation of Female Rats
Authors: Santizo Roberto , Pelligrino Dale A.
Published: November 2003

In this study the authors addressed the hypothesis that estrogen (i.e., 17β-estradiol) acts to repress leukocyte adhesion, The experiments involved comparing leukocyte adhesion in cerebral venules in vivo, in intact ovariectomized and 17β-estradiol-treated (100 μ/kg/day for 1 week) ovariectomized female rats using topical applications of the adhesion-promoting drug, phorbol 12-myristate 13-acetate (PMA), Adherent Rhodamine-6G-labeled leukocytes were viewed through a closed cranial window using intravital microscopy/videometry, Leukocyte dynamics were recorded at baseline and after each dose of PMA, The PMA was suffused (1.0 mL/min) at increasing concentrations (0,01, 0,1, and 1.0 μmol/L, 15 minutes at each level), A videotape record of each experiment was made for subsequent analysis of leukocyte adhesion, The data showed that the percentage venular area occupied by adherent leukocytes at baseline was significantly greater in the ovariectomized compared to the intact and 17β-estradiol—treated groups (12,2%, 3.4%, and 4,2% respectively), That relationship was maintained during PMA treatments to the extent that the percentage venular area occupied by adherent leukocytes increased to 26.4% in the untreated ovariectomized group compared to 14.4% and 11.3% in the intact and 17β-estradiol—treated groups, respectively, In conclusion, the authors found chronic estrogen depletion enhances leukocyte adhesion in the rat cerebral circulation. Estrogen repletion in such animals is accompanied by a significant reduction in leukocyte adhesion, These findings could, at least in part, account for the ischemic brain damage seen in ovariectomized versus intact females, and the restored neuroprotection observed upon 17β-estradiol treatment reported in earlier studies.
Gender Differences in Cerebral Blood Flow and Oxygenation Response during Focal Physiologic Neural Activity
Authors: Kastrup Andreas , Li Tie-Qiang , Glover Gary H. , Krüger Gunnar , Moseley Michael E.
Published: November 2003

Using functional magnetic resonance imaging techniques CBF and oxygenation changes were measured during sustained checkerboard stimulation in 38 right-handed healthy volunteers (18 men and 20 women). The average blood oxygenation level dependent (BOLD) contrast technique signal intensity change was 1.67 ± 0.6% in the group of male volunteers and 2.15 ± 0.6% in the group of female volunteers ( P < .05). Baseline regional CBF (rCBF) values in activated gray matter areas within the visual cortex were 57 ± 1 mL · 100 g−1 · min−1 in women and 50 ± 12 mL · 100 g−1 · min−1 in men, respectively ( P = .09). Despite a broad overlap between both groups the rCBF increase was significantly higher in women compared to men (33 ± 5 mL · 100 g−1 · min−1 versus 28 ± 4 mL · 100 g−1 · min−1, P < .01). The increase of rCBF was not correlated with the baseline rCBF (mL · 100 g−1 · min−1) (rs = 0.01, P = .9). Moreover, changes of rCBF were not correlated with changes in BOLD signal intensities (rs = 0.1, P = .7). Enhanced rCBF response in women during visual stimulation could be related to gender differences in visual physiology or may reflect gender differences in the vascular response to focal neuronal activation. Gender differences must be considered when interpreting the results of functional magnetic resonance imaging studies.
Group II Selective Metabotropic Glutamate Receptor Agonists and Local Cerebral Glucose use in the Rat
Authors: Lam Amy G. M. , Monn James A. , Schoepp Darryle D. , Lodge David , McCulloch James
Published: November 2003

The novel mGluR agonist L Y354740 and a related analogue LY379268 are selective for mGluR2/3 receptors and are centrally active after systemic administration. In this study, rates of local cerebral glucose use were measured using the [14C]2-deoxyglucose autoradiographic technique to examine the functional consequences of their systemic administration in the conscious rat. Both LY354740 (0.3, 3.0, 30 mg/kg) and LY379268 (0.1, 1.0, 10 mg/kg) produced dose-dependent changes in glucose use. After LY354740 (3.0mg/kg), 4 of the 42 regions measured showed statistically significant changes from vehicle-treated controls: red nuclei (−16%), mammillary body (−25%), anterior thalamus (−29%), and the superficial layer of the superior colliculus (+50%). An additional 15 regions displayed significant reductions in function-related glucose use ( P < .05) in animals treated with L Y354740 (30 mg/kg). LY379268 (0.1, 1.0, 10 mg/kg) produced changes in glucose metabolism in 20% of the brain regions analyzed. Significant increases ( P < .05) in glucose use were evident in the following: the superficial layer of the superior colliculus (+81 %), locus coeruleus (+57%), genu of the corpus callosum (+31%), cochlear nucleus (+26%), inferior colliculus (+20%), and the molecular layer of the hippocampus (+14%). Three regions displayed significant decreases: mammillary body (−34%), anteroventral thalamic nucleus (−28%), and the lateral habenular nucleus (−24%). These results show the important functional involvement of the limbic system together with the participation of components of different sensory systems in response to the activation of mGluR2 and mGluR3 with LY354740 and LY379268.
Kinetic Modeling of N-[11C]Methylpiperidin-4-yl Propionate: Alternatives for Analysis of an Irreversible Positron Emission Tomography Tracer for Measurement of Acetylcholinesterase Activity in Human Brain
Authors: Koeppe Robert A. , Frey Kirk A. , Snyder Scott E. , Meyer Phillipp , Kilbourn Michael R. , Kuhl David E.
Published: November 2003

N-[11C]Methylpiperidin-4-yl propionate ([11C]PMP) is a substrate for hydrolysis by acetylcholinesterase (AChE). This work evaluates kinetic analysis alternatives for estimation of relative AChE activity using dynamic positron emission tomography (PET) studies of [11C]PMP. The PET studies were performed on three groups of subjects: (1) 12 normal volunteer subjects, aged 20 to 45 years, who received a single intravenous injection of 16 to 32 mCi of [11C]PMP; (2) six subjects, aged 21 to 44 years, who received two 16-mCi injections of [11C]PMP (baseline and visual stimulation, respectively); and (3) five subjects, aged 24 to 40 years, who received two 16-mCi injections separated by 200 minutes (baseline and after a 1-hour constant infusion of 1.5 mg of physostigmine, respectively). Dynamic acquisition consisted of a 17-frame sequence over 80 minutes. All analysis methods were based on a first-order kinetic model consisting of two tissue compartments with the parameter k3‘ representing PMP hydrolysis, being the index of AChE activity. Four different schemes were used to estimate k3: (1) an unconstrained nonlinear least-squares fit estimating blood—brain barrier transport parameters, K1 and k2, in addition to the hydrolysis rate constant k3; (2) and (3), two methods of constraining the fit by fixing the volume of distribution of free tracer (DVfree); and (4), a direct estimation of k3 without use of an arterial input function based on the shape of the tissue time—activity curve alone. Results showed that k3 values from the unconstrained fitting and no input methods were estimated with similar accuracy, whereas the two methods using DVfree constraints yielded similar results. The authors conclude that the optimal analysis method for [11C]PMP differs as a function of AChE activity. All four methods gave precise measures of k3 in regions with low AChE activity (~10% coefficient of variation in cortex), but surprisingly, with unconstrained methods yielding estimates with lower variability than constrained methods. In regions with moderate to high AChE activity, constrained methods were required to yield meaningful estimates and were superior to the unconstrained methods.
Direct Evidence of in Vivo Nitric Oxide Production and Inducible Nitric Oxide Synthase mRNA Expression in the Brain of Living Rat during Experimental Meningitis
Authors: Suzuki Yasuhiro , Fujii Satoshi , Tominaga Teiji , Yoshimoto Takashi , Fujii Shigemoto , Akaike Takaaki , Maeda Hiroshi , Yoshimura Tetsuhiko
Published: November 2003

To detect endogenous nitric oxide (NO) produced in a rat bacterial meningitis model, the authors applied an electron paramagnetic resonance (EPR) NO-trapping technique. Iron complex with N,N-diethyldithiocarbamate were used as a trapping agent. Experimental meningitis was induced by a mixture of lipopolysaccharide and interferon-γ. Sequential changes of NO formation under meningitis were observed in rat brain tissue by using X-band (9 GHz) EPR spectroscopy, and endogenous NO was detected in the head of a living rat with a 700-MHz EPR system. Inducible NO synthase mRNA expression in the brain tissues also was proven by using a reverse transcriptase-polymerase chain reaction technique.
Measurement of the Tricarboxylic Acid Cycle Rate in Human Grey and White Matter in Vivo by 1H-[13C] Magnetic Resonance Spectroscopy at 4.1T
Authors: Mason Graeme F. , Pan Jullie W. , Chu Wen-Jan , Newcomer Bradley R. , Zhang Yantian , Orr Roger , Hetherington Hoby P.
Published: November 2003

13C isotopic labeling data were obtained by 1H-observed/13C-edited magnetic resonance spectroscopy in the human brain in vivo and analyzed using a mathematical model to determine metabolic rates in human grey matter and white matter. 22,5-cc and 56-cc voxels were examined for grey matter and white matter, respectively. When partial volume effects were ignored, the measured tricarboxylic acid cycle rate was 0.72 ± 0.22 (mean ± SD) and 0.29 ± 0.09 μmol min–1 g–1(mean ± SD) in voxels of ∼70% grey and ∼70% white matter, respectively. After correction for partial volume effects using a model with two tissue compartments, the tricarboxylic acid cycle rate in pure grey matter was higher (0.80 ± 0.10 mol min–1 g–1; mean ± SD) and in white matter was significantly lower (0.17 ± 0.01 μmol min–1 g–1; mean ± SD). In 1H-observed/13C-edited magnetic resonance spectroscopy labeling studies, the larger concentrations of labeled metabolites and faster metabolic rates in grey matter biased the measurements heavily toward grey matter, with labeling time courses in 70% grey matter appearing nearly identical to labeling in pure grey matter.